An LD module having a spot-size conversion LD for emitting a beam of a small aperture angle, an optical fiber or a waveguide and a lens for converging the LD beam to the fiber or the waveguide.

1. Field of the Invention
This invention relates to an LD (laser diode) module, in particular, a low-cost, small-sized and high-performance LD module which is utilized in optical communication systems.
This application claims the priority of Japanese Patent Application No.2000-147867 filed on May 19, 2000 which is incorporated herein by reference.
2. Description of Related Art
FIG. 1 shows a prior art LD module 1 which is sealed in a vertical metal case. This is one of the most prevalent LD modules at present. The transmitting (LD) module 1 has a metallic package. A circular metal stem 2 has a pole 3 erected near the center. An LD (laser diode) 4 is bonded on a side of the pole 3. A top incidence type PD 5 is mounted with a light receiving surface upward at the center of the stem 2. A cylindrical metal cap 6 is welded on the stem 2 for covering the LD 4 and the PD 5. The cap 6 has a top opening 7 for guiding the LD light outward.
A metallic cylindrical lens holder 8 is welded outside of the cap 6 upon the stem 2 for supporting a lens 9 just above the LD 4. A conical ferrule holder 10 is further welded upon the lens holder 8 for maintaining a ferrule 12 at an axial hole. The ferrule 12 holds an end of an optical fiber 11. The LD 4 emits light from both ends in both directions. The LD light has a wide aperture with wide diverging angles. Front light emitted from the front end is converged and guided by the lens 9 to the end of the fiber 11. The front light is signal light. The ends of the fiber and the ferrule are ground slantingly for prohibiting the light reflected at the end from returning to the LD and inducing instability of the LD oscillation. Such a metal packaged three dimensional LD module is still in prevalent, influential use at present. The metal case can hermetically seal the LD chips or the PD chip completely. The metal package prevents corrosive water or oxygen from invading into the package. The hermetic seal protects the module from oxidization or corrosion of the chips, the patterns or the wires. The metal case brings about a long lifetime and high reliability to the module. The metal package is a standardized one which reduces the part cost. The prior LD module of FIG. 1 is still an excellent one.
Further, prevalence of the optical networks strenuously requires lower-cost and smaller-size optoelectronic modules than the metal packaged modules. An improvement of LD modules is a purpose of the present invention. The Inventors are interested in the structure of LDs (laser diodes). Conventional LD modules have commonplace, cheap LD chips having a uniform emission stripe with a constant width w and a constant thickness d extending in the longitudinal direction (z-direction). The emission stripe means a spatially-restricted, active layer which makes laser light by the stimulated emission induced by an electric current injection. FIG. 2 shows a schematic structure of a conventional LD chip for showing only the active layer (stripe) clearly in a perspective view. This is a simple Fabbry-Perrow laser diode. The LD generates light power by inducing light by the injected current, amplifying the light in-phase by the repetitions of propagation in the stripe and reflections at the ends (mirrors) and leaking a part of the amplified light out of the (half-mirror) end. Some sophisticated LDs have light waveguides with a periodical saw-teeth shape upon the stripes for selecting the wavelength more strictly. The shape of the stripe itself is the uniform stripe same as the cheap one of FIG. 2.
For example, an LD emitting 1.3 xcexcm wavelength light has a 300 xcexcm length, a 300 xcexcm width and a 100 xcexcm thickness. The active layer (emission stripe) of the LD chips has e.g., a 1.2 xcexcm width, a 0.2 xcexcm thickness and a 300 xcexcm length (cavity length). The active layer is otherwise called a xe2x80x9ccavityxe2x80x9d, a xe2x80x9cstripexe2x80x9d, an xe2x80x9cemission stripexe2x80x9d or a xe2x80x9cresonatorxe2x80x9d. All the terms signify the same matter. In the prior LD chip in FIG. 2, the width and the thickness of the active layer are constant in the full length. The length of the stripe determines the wavelength of the emitted light. The width and the thickness determine the aperture of the light. The LD light disperses in a wide angle. The aperture angle of the light emitted from the stripe is about 30 degrees to 40 degrees. The wide beam spread is one of the drawbacks of the current LDs. The LD wide beam dispersion sometimes induces difficulties.
An optical fiber consists of a core and a cladding. The core has a 10 xcexcm diameter in a single-mode fiber for the 1.3 xcexcm band light. The cladding has a 125 xcexcm diameter. The LD active layer (w=1.2 xcexcm, d=0.2 xcexcm) is smaller than the fiber core (10 xcexcm) in section. But almost all of the LD light escapes from the fiber and dissipates in vain due to the wide dispersion (30xc2x0 to 40xc2x0) of the LD light, even if the fiber is brought into direct contact with the LD without gap. A lens, therefore, is indispensable for the coupling of an LD to a fiber.
FIG. 1 denotes the lens 9 of converging the dispersing LD light into the end of the fiber 11 for joining the fiber 11 to the LD 4 on an optimum condition. The LD module 1 utilizes a spherical lens having convex spherical curves on both surfaces as converging optics. Sophisticated LD modules employ aspherical lenses for enhancing the coupling efficiency further. Inexpensive LD modules use a ball lens for facilitating the assembly and reducing the cost. In any cases, the three-dimensional structure LD modules require converging optics.
The solid-structured LD module of FIG. 1 is encapsulated in a metal package of a 5.6 mm outer diameter. The LD 4 is a common cheap chip with a uniform stripe as denoted in FIG. 2. An active layer 14 is shown in a chip 13 in a perspective view. As described before, the inexpensive commonplace LD chips have the uniform active layer having a constant breadth w and a constant thickness d. The uniform stripe forgives the light dispersing in a wide aperture. LD modules require converging optics for coupling the LD to the fiber. The converging optics is a ball lens, a spherical lens or an aspherical lens. Low-power, inexpensive modules adopt ball lenses for joining the LD to the fiber.
A ball lens is inexpensive but has large aberration. The aberration prevents the ball lens from heightening the coupling efficiency up to the maximum. Conventional ball lenses allow the LD driving current of about 30 mA to produce an output power of 0.2 mW to 0.5 mW at another fiber end. Thus, the ball lens convergence optics are mainly employed for low-power, low-cost, low-speed and short-range optical communication networks.
On the contrary, high-power, long-range optical communication networks require aspherical lenses for the convergence optics. Aspherical lenses can suppress all kinds of aberration to low levels. The use of the aspherical lens enables the same 30 mA LD driving current to make a 1 mW to 2 mW output power at another fiber end. The coupling efficiency is enhanced several times by the aspherical lens. Aspherical lenses, however, are expensive. The aspherical lenses are used in mainstream fiber cable lines or equipment in central stations.
The ball lens optics and the aspherical lens optics are chosen by the criterion whether the module should be a low-cost, low-power one or a high-cost, high-power one. One purpose of the present invention is to provide a low-cost, high-power, small-size, high-value added LD module. Another purpose of the present invention is to provide an inexpensive ball-lens converging LD module with as high power as the expensive aspherical lens converging LD module. A further purpose of the present invention is to provide an inexpensive ball lens LD loaded module with higher coupling efficiency than the conventional ball lens loaded LD module.
Preparatory descriptions are required for showing the idea of the present invention. A novel type of laser diode has been proposed for coupling the LD to a fiber without convergence optics. The new LD is called a xe2x80x9cspot-size converted laser diodexe2x80x9d. The new SSC-LD has an advantage of eliminating convergence optics from the coupling between an LD and an optical fiber. The present invention is not directed to an improvement of SSC-LDs but to an improvement of LD modules. But the present invention makes use of the novel SSC-LD. The SSC-LDs are not well known even in the skilled.
The SSC-LD is now described before starting the description of the present invention. In short, the SSC-LD has a tapered end stripe produced by reducing the width or the thickness for enlarging the output beam size. Since the LD enlarges the spot size, the LD is called xe2x80x9cspot size convertedxe2x80x9d LD. In spite of the term xe2x80x9cconvertedxe2x80x9d, the SSC-LD does not reduce the beam size but only increases the beam spot size. There are two kinds of the SSC-LDs. One is a width-narrowing SSC-LD, which is called a xe2x80x9chorizontally-taperedxe2x80x9d SSC-LD. The other is a thickness-reducing SSC-LD, which is named a xe2x80x9cvertically-taperedxe2x80x9d SSC-LD.
FIG. 3 shows a vertically-tapered SSC-LD. An LD chip 13 has an active layer 14 with a reducing thickness d toward the front end. The width w of the stripe is constant along the axial line. A coordinate is defined to be z=0 at the rear end, z=L at the front end and z=L1 at the starting point of the taper (0 less than L1 less than L). L is the length of the LD. (Lxe2x88x92L1) is the length of a tapering portion 15 of the active layer 14. The top-tapered SSC-LD gives the stripe the width w(z) and the thickness d(z) as functions of z,
0xe2x89xa6zxe2x89xa6L w(z)=wo,xe2x80x83xe2x80x83(1)
0xe2x89xa6zxe2x89xa6L1 d(z)=do,xe2x80x83xe2x80x83(2)
L1xe2x89xa6zxe2x89xa6L d(z)=doxe2x88x92xcex1(zxe2x88x92L1),xe2x80x83xe2x80x83(3)
xcex1 greater than 0, doxe2x88x92xcex1(Lxe2x88x92L1) greater than 0.xe2x80x83xe2x80x83(4)
Here, a is an inclination angle of the tapered end of the stripe. Inequality (4) signifies a definite thickness at the front end (z=L). The narrowing active layer cannot enclose the light completely and allows the light to leak from the active layer. The leak of the light power out of the stripe layer increases the beam diameter. The (beam) spot size is enlarged by the tapered stripe. Since the sectional area is enlarged, the dispersion angle of the beam is reduced to the contrary. The beam spot size is inversely proportional to the beam dispersion angle. The reduction of the dispersion angle is important for the SSC-LDs.
FIG. 4 shows a horizontally-tapered SSC-LD. The thickness d of the active layer is constant. The breadth w is narrowed toward the front end. A coordinate is defined to be z=0 at the rear end, z=L at the front end and z=L2 at the starting point of the taper (O less than L2 less than L). L is the length of the LD. (Lxe2x88x92L2) is the length of a tapering portion 16 of the active layer 14. In the horizontally-tapered SSC-LD, the stripe 14 has the width w(z) and the thickness d(z) as functions of z,
0xe2x89xa6zxe2x89xa6L d(z)=do,xe2x80x83xe2x80x83(5)
0xe2x89xa6zxe2x89xa6L2 w(z)=wo,xe2x80x83xe2x80x83(6)
L2xe2x89xa6zxe2x89xa6L w(z)=woxe2x88x92xcex2(zxe2x88x92L2),xe2x80x83xe2x80x83(7)
xcex2 greater than 0, woxe2x88x92xcex2(Lxe2x88x92L2) greater than 0.xe2x80x83xe2x80x83(8)
Here, xcex2 is a reduction angle of the tapered sides of the stripe. Inequality (8) signifies a definite width at the front end (z=L). The narrowing active layer induces insufficient enclosure of the light. The leak of the light from the active layer enlarges the beam spot size. The increase of the spot size reduces the beam spreading angle. Both the SSC-LDs (FIG. 3 and FIG. 4) have a function of reducing the beam spreading angle.
The SSC-LD is not an entirely novel device but is not well known for the skilled in art yet. The fact requires some description of the SSC-LD. Conventional LDs emit small size spot beams with large dispersion angles. A lens is indispensable for the prior LD modules with the conventional LDs. The use of the lens, however, raises the part cost, the assembling cost and the package cost. Elimination of the lens enables the LD module to reduce the cost. The purpose of contriving the SSC-LD is to eliminate the lens form LD devices.
It is desired to combine an optical fiber to an LD without lens. Small dispersion of the LD beam seems to be sufficient for the non-lens coupling between the fiber and the LD. In fact, the LD stripe has a small breadth (1.21 xcexcm) and a small thickness (0.21 xcexcm). Someone may suppose that the direct touching of the fiber to the LD would introduce the LD light into the fiber with high efficiency. But it is not true. The excess size difference between the fiber and the LD impedes the introduction of the LD beam into the fiber. If the beam size of the laser is enlarged up to the size of the fiber core, the coupling efficiency will be raised.
If the waveguide of the LD is narrowed, the power of localizing the light power within the waveguide is weakened. The decline of localizing the light power into the waveguide core allows the light power to pervade outside of the waveguide of the LD stripe. The diffused light power will enhance the coupling efficiency between the LD and the fiber. The SSC-LD with the narrowed stripe (waveguide) aims at enhancing the coupling efficiency by enlarging the LD beam spot size near the fiber core size through the narrowed stripe. Thus, such a laser diode is called a spot-size converted laser diode (SSC-LD). An increase of the spot size (beam diameter) will invite a decrease of the aperture of the beam. The narrow aperture will enable the LD to introduce the light power into the fiber with high efficiency without converging lens.
The SSC-LD with the narrow stripe end was invented from the idea of decreasing the aperture angle by increasing the beam (spot) size through the narrowness of the stripe. The end of the active stripe is sharpened for decreasing the aperture angle of the emission beam in the improved LD as shown in FIG. 3 and FIG. 4. Various contrivances have been suggested for improving the SSC-LDs.
{circle around (1)} Japanese Patent Laying Open No.9-61652, xe2x80x9cA semiconductor waveguide and a method of making samexe2x80x9d, proposes a tapered waveguide and an improved LD having a tapered waveguide as an active stripe. The single tapered waveguide can convert the spot size by coupling to a conventional laser diode (LD).
{circle around (2)} Japanese Patent Laying Open No.11-220220, xe2x80x9cA semiconductor laser and a method of making samexe2x80x9d, suggests an LD having an active layer with a narrowing width, as shown in FIG. 4. The narrowing angle xcex2 of inequality (8) is less than 0.14 degree. The narrowing width enables the LD to generate a narrow aperture beam.
{circle around (3)} Yoshio Itaya, Toshihiko Sugie, Mitsuo Yamamoto, xe2x80x9cSpot-size converted lasers (SSC-LD)xe2x80x9d, Technical Report of IEICE (The Institute of Electronics, Information and Communication Engineers), OPE95-140, LQE95-134(1996-2), p31, makes SSC-LDs on a two-inch InP wafer. The SSC-LD has a 600 xcexcm length and a 300 xcexcm width. The active layer (emission stripe) is gradually reduced from 1.5 xcexcm to 0.3 xcexcm. The SSC-LD is coupled to a light waveguide without lens. The coupling loss is 1.2 dB to 2.5 dB. The coupling loss is sufficiently small.
{circle around (4)} Y. Inaba, M. Kito, M. Ishino, T. Chino, T. Nishikawa, T. Uno, Y. Matsui, xe2x80x9c1.3 xcexcm tapered-active-stripe laser with low threshold and high slope efficiencyxe2x80x9d, Technical Report of IEICE (The Institute of Electronics, Information and Communication Engineers), EMD97-43, CPM97-81, OPE97-59, LQE97-55(1997-08), p81, proposes SSC-LDs having a active layer with a narrowing width. The tapering width of the active layer is 0.61 xcexcm at the front end and 1.6 xcexcmxcx9c2.6 xcexcm at the rear end. Various SSC-LDs having a variety of tapering angles are made. The SSC-LDs are coupled to a fiber without lens. The coupling efficiency is measured by changing the distance between the SSC-LD and the fiber end. The maximum coupling efficiency is xe2x88x924.7 dB at an optimum distance. The range of xc2x13 xcexcm from the optimum distance obtains coupling efficiency of higher than xe2x88x924.7 dB. The coupling efficiency of the conventional LDs to fibers is xe2x88x929 dB at the highest. Thus the SSC-LD obtains an extra increase of 4 dB of coupling efficiency in comparison to the conventional LDs.
{circle around (5)} Yoshio Itaya, Osaake Nakajima, Mitsuru Naganuma, Mitsuo Fukuda, Kiyoyuki Yokoyama, Hiromu Toba, xe2x80x9cOptical Semiconductor Devices for Hybrid Modulesxe2x80x9d, NTT RandD, vol.46, No.5, 1997, p487-490, proposes a spot-size converter laser diode (SSC-LD) having a tapering active stripe layer with a reducing thickness end. The thickness of the active layer is 0.3 xcexcm in the oscillating region but is reduced to 0.1 xcexcm at the front end. The active layer has a constant width of 1.5 xcexcm. The half width angle of the emission aperture of the laser is 6 degrees to 9 degrees. The full aperture angle is 12 degrees to 18 degrees. In the conventional laser diodes with a constant stripe, the beam aperture is 30 degrees to 40 degrees. The SSC-LD succeeds in confining the LD beam within about a half angle of the conventional LD aperture.
{circle around (6)} xe2x80x9cLight/microwave semiconductor application technologyxe2x80x9d, Science Forum Corporation published Feb. 29, 1996, first print, first copy, p165, xe2x80x9cDigital Communication Devicesxe2x80x9d, takes a review of the spot-size conversion laser diodes. The report says that the conventional LDs emit wide beams with an aperture angle of 33 degrees but the SSC-LDs make narrow beams of a 9 degree aperture angle. The review writes that the loss of the non-lens coupling is about 10 dB for the conventional LDs and about 4 dB for the SSC-LDs.
{circle around (7)} Japanese Patent Laying Open No.2-195309, xe2x80x9cPhotocoupling devicexe2x80x9d, proposes a passive device with the spot-size conversion function. The device has a substrate with width-varying waveguides having the spot-size conversion function. Instead of coupling a fiber to another fiber with a lens, the invention employs the proposed SSC-waveguide for coupling a fiber to another fiber. An increase of the core width w results in a reduction of the beam size (spot size) in the waveguide. A decrease of the core width w invites an increment of the beam size. The fibers are coupled by the light waveguide having a narrow core intermediate part and wide core ends. The wide core ends enhance the coupling efficiency through the reduction of the beam sections at both ends.
{circle around (8)} Nobuaki Hiraguri, Kazuo Shiraishi, xe2x80x9cCoupling characteristics between integration-oriented lensed fibers and LD""s with narrow beam divergencexe2x80x9d, Technical Report of IEICE (The Institute of Electronics, Information and Communication Engineers), EMD97-44, CPM97-82, OPE97-60, LQE97-56(1997-08), p87, proposes a ball-lensed fiber coupling to the SSC-LD (LD""s with narrow beam divergence) with high coupling efficiency. The fiber is called a xe2x80x9cball-lensed fiberxe2x80x9d since it has an end being shaped in a ball lens. A fiber is ball-lensed by melting an end of the fiber by oxygen-hydrogen flame. The molten glass makes a ball at the end by the surface tension. The balled end is cooled into a ball lens. This report employs and compares coreless lensed fibers and GI lensed fibers.
The coreless fiber means a fiber without the core-cladding structure. The core-cladding structure is rather an obstacle when the fiber is changed to be a lens at the end. Thus, the special convenient coreless fiber is employed. An object fiber is a conventional single mode fiber having a core of a 10 xcexcm diameter and a cladding of a 125 xcexcm diameter enclosing the core. The coreless fiber of a 125 xcexcm diameter is made of the same material as the cladding of the single mode fiber. A 1 mm long coreless fiber is fused with a single mode fiber. The coreless end is heated by the oxygen-hydrogen flame into a ball lens.
The GI fiber is a graded-index fiber having a core of continually decreasing refractive index in the radial direction down to the refractive index of the cladding at the boundary. Both the ball-lensed coreless fiber and the ball-lensed GI fiber can be coupled to the SSC-LD with small coupling loss.
However, the coupling by the ball-lensed fibers has some drawbacks. It is difficult to fuse a short, tiny fiber to an end of a narrow single-mode fiber. The end is melted into a ball lens by the oxygen-hydrogen flame. The process depends upon an accident. The diameter of the ball lenses is a stochastic variable. It is difficult to make ball lensed fibers with the predetermined size. The tolerance of the positioning of the end is excessively narrow. It takes much time to align the fiber and the laser diode. The device consisting of the ball lensed fiber and the SSC-LD is a sophisticated device but is not suitable for mass-production. It will be an expensive device. This device aims only at the direct coupling of the fiber to the SSC-LD. The proposal makes the ball lens at the end of the fiber for improving the direct coupling.
The prior art of the SSC-LDs has been described. This invention can be applied to any kinds of the SSC-LDs.
The direct coupling to a fiber is the sole purpose of the SSC-LDs. Thus, the prior SSC-LDs have been stuck either directly to the end of a light waveguide as shown in FIG. 5 or directly to the end of an optical fiber as shown in FIG. 6.
FIG. 5 is a plan view of a horizontally-tapering SSC-LD 18 and a light waveguide 20. The SSC-LD 18 has an active layer 14 having a horizontally narrowing part 16. The light waveguide 20 has a core 21 with a higher refractive index than the cladding parts. The core 21 is coupled to the tapering front end 16 of the SSC-LD 18. The SSC-LD 18 is directly joined to the waveguide 20 without lens. The light made in the parallel active layer 14 by the injected current is enlarged in the tapering portion 16 in spot size but is diminished in aperture angle. The narrow aperture angle allows the LD light to enter the core 21 of the light waveguide 20 with high efficiency.
FIG. 6 is a vertically sectioned view of a vertically-tapering SSC-LD 19 and an optical fiber 22. The SSC-LD 19 has an active layer 14 having a vertically narrowing part 15. The fiber 22 has a core 23 with a higher refractive index than the cladding parts. The core 23 is coupled to the tapering front end 15 of the SSC-LD 19. The SSC-LD 19 is directly joined to the fiber 22 without lens. The light made in the parallel active layer 14 by the injected current is enlarged in spot size but is diminished in aperture angle in the tapering portion 15. The narrow aperture angle allows the LD light to enter the core 23 of the fiber 22 with high efficiency.
The SSC-LDs have been contrived for coupling to a fiber or a waveguide with a small NA (Numerical Aperture) with high coupling efficiency. The SSC-LD dispenses with a lens for coupling with the fiber or the waveguide. The small aperture angel prevents the LD beam from dispersing out of the waveguide or the fiber. The omission of lens is the most important object of the SSC-LDs. The skilled believes there is no room for a lens in the coupling between the SSC-LD and the fiber/waveguide. xe2x80x9cNon-lens couplingxe2x80x9d is the most conspicuous character of the SSC-LDs.
On the contrary, the conventional LD module as shown in FIG. 1 has an LD which emits a wide aperture angle (30 degrees to 40 degrees) beam. The converging lens 9 is indispensable in the LD module. The lens 9 is a ball lens, a spherical lens or an aspherical lens which is chosen in accordance with the purpose or performance.
In the conventional LD modules (transmission modules), the choice of a ball lens or an aspherical lens depends upon the low-power/low-cost or the high-power/high-cost. Namely, low-cost and low-power LD modules have cheap ball lenses. High-cost/high-power LD modules are equipped with sophisticated aspherical lenses in the prior optoelectronic devices. One purpose of the present invention is to provide a low-cost ball-lens LD module which can generate light power as high as the conventional high-cost aspherical lens LD modules. Another purpose of the present invention is to provide an aspherical lens LD module which can generate stronger light power than the conventional high-cost aspherical lens LD modules.
The present invention proposes an LD module having a spot-size conversion LD with a narrow beam aperture angle (of 10 degrees to 20 degrees), a light guide medium (a fiber or a waveguide) and a lens for converging the LD light to an end of the light guide medium. The novelty lies in the coupling of an SSC-LD and a lens.
The spot-size conversion laser diodes have been known to the skilled, as described hitherto. The module of a conventional LD and a lens shown in FIG. 1 is also known to the skilled. The present invention proposes a new coupling of an SSC-LD and a lens which will be obtained from FIG. 1 by replacing the conventional LD by the SSC-LD. In short, the present invention suggests an assembly of (SSC-LD+lens) instead of (LD+lens).
The SSC-LDs have been developed and investigated for eliminating the converging lens. The skilled in art believes that there is no probability of interposing a lens between the SSC-LD and the fiber. In any cases, the SSC-LDs have been directly coupled to the fibers or the waveguides.
The Inventors hit an idea of applying positively the converging optics (lens) to the spot-size conversion laser diode which can do without lens.
Instead of joining the SSC-LD directly to the medium (fiber/waveguide), this invention tries to couple the SSC-LD via a lens to the medium (fiber/waveguide). Namely, the module of the present invention is an air-gaped coupling system consisting of an SSC-LD, a lens and a medium which are separated by air gap.
The aperture angle of the beam emitted from the SSC-LD is so narrow that even a ball lens is nearly free from spherical aberration. The SSC-LD enables a cheap ball lens to converge almost all the LD rays. The present invention can introduce higher power into the medium than the conventional LD module as shown in FIG. 1. This is an important feature which will be later described in detail.
The rate of the LD spot size to the fiber/waveguide core is reduced to about a half. The length of the module can be shortened.
If a cap having a lens as shown in FIG. 1 is employed, the LD module is completely hermetically sealed, which raises the reliability of the LD module. The metal package which is a standardized inexpensive metal case can be used. Thus, the present invention can give a low-cost, high-power LD module.
The advantages of the present invention are described here. The present invention succeeds in raising the LD/medium coupling efficiency by 50% to 100% by employing the SSC-LD emitting a beam of a wide spot size and a narrow aperture angle.
Lower injection current produces the same light power as the conventional module of FIG. 1. The present invention saves the current and alleviates the electric power consumption. The low driving current prolongs the lifetime of the laser and enhances the reliability of the module.
Inherently, the SSC-LDs have been developed for the purpose of removing the converging lens and directly coupling the medium to the LD. Any persons have believed in the lensless, direct coupling of the SSC-LD to the medium. The Inventors have first noticed the excellent indirect lens-used coupling of the SSC-LD to the medium.


Disclosed is a method for producing an alcohol from a lactone or a carboxylic acid ester, which enables to produce an alcohol from a lactone or a carboxylic acid ester under relatively mild conditions with high yield and high catalytic efficiency. This method also enables to produce an optically active alcohol from an optically active lactone or an optically active carboxylic acid ester. Specifically disclosed is a method for producing an alcohol by hydrogen reducing a lactone or a carboxylic acid ester in the presence of a catalyst containing ruthenium and a phosphine compound represented by the following general formula (1):

There have been many reports on the method for producing an alcohol by hydrogenating a lactone or a carboxylic acid ester, with various catalysts and reaction modes. Patent Documents 1 to 3 and Non-Patent Document 1 describe hydrogenation reactions of lactones and carboxylic acid esters in fixed bed or liquid phase suspension systems. Patent Documents 4 to 6 and Non-Patent Documents 2 and 3 describe hydrogenation reactions of esters in the liquid phase, using ruthenium complexes that are formed from a ruthenium compound and an organic phosphine compound. Furthermore, methods for producing optically active alcohols by hydrogenating optically active carboxylic acids, are described in Patent Documents 7 and 8, and Non-patent Document 4.    Patent Document 1: JP-A No. 51-8203    Patent Document 2: DE3217429A1    Patent Document 3: JP-A No. 58-216131    Patent Document 4: JP-A No. 2001-247499    Patent Document 5: JP-A No. 2004-300131    Patent Document 6: JP-W No. 2005-524704    Patent Document 7: JP-W No. 2002-501817    Patent Document 8: JP-W No. 2002-501935    Patent Document 9: WO2006/106483    Patent Document 10: WO2006/106484    Non-Patent Document 1: Org. React., 1954, 8, 1    Non-Patent Document 2: J. Chem. Soc. Chem. Commun., 1980,    Non-Patent Document 3: Angew. Chem. Int. Ed., 2006, 45, 1113    Non-Patent Document 4: Adv. Synth. Cat., 2001, 343, 802

Method for producing alcohol by hydrogenating lactone and carboxylic acid ester in liquid phase

Abstract: wherein R1 represents a spacer; R2, R3, R4, R5, R6 and R7 independently represent a hydrogen atom, an alkyl group having 1-12 carbon atoms, an aryl group or a heterocyclic group; and R8, R9, R10, R11, R12 and R13 independently represent an alkyl group having 1-12 carbon atoms, an aryl group or a heterocyclic group.


A watch saddle for providing ventilation and spacing between a user's wrist and a wristwatch.

1. Field of the Invention
The present invention relates to a watch saddle. The watch saddle has particular utility in connection with providing ventilation and spacing between a user's wrist and a wristwatch.
2. Description of Related Information
A wristwatch typically comprises a roughly circular body having a face, a crystal, a crown, and a backplate. A digital watch may comprise one or more buttons rather than a crown. The wristwatch body is typically held in place on the wrist by a strap and buckle combination (or a continuous band) that is attached to the edges of the watch body that correspond to the twelve o'clock and six o'clock edges of the face. The face of the watch is directed away from the user's wrist when the watch is worn.
In the past, the backplate of a watch typically rested against the user's wrist. This constant contact with the user's wrist was responsible in the past for inducing heat retention, friction, and sweat under the backplate. Besides causing some discomfort to the user, sweat can have an unpleasant odor and can attract dirt to the watch. The moisture may also rust the backplate or the watch mechanism. It is desirable therefore to provide ventilation and spacing means between a user's wrist and a watch body so as to both reduce sweating and to reduce the likelihood that sweat will come into contact with the backplate.
In addition to inducing sweat, wristwatches that lay flat against the wrist may impede access to the crown or control buttons, and may impede full wrist motion. In addition, where a wristwatch is flat against the wrist, the hardware connecting the body to the strap is immediately adjacent to the wrist and can trap wrist hair. It is desirable therefore to provide spacing means between the wrist and the watch body.
Wristwatches today are as much a fashion accessory as a time-telling means, and as a result, cumbersome or unattractive ventilation or spacing means would be a great disadvantage. Thus, any mechanism employed for the aforementioned purposes would preferably complement the overall appearance of the watch.
Any mechanism employed for the aforementioned purposes should be flexible to allow a secure fit with a variety of watches. The mechanism should also have sufficient contact area with a user's wrist so as not to concentrate forces into a small area thereof. Because the user may wish to remove the mechanism, after playing a sport for example, the mechanism should be easy to install and remove. Consequently, a mechanism permanently affixed to the watch by cement, rivets or the like would be undesirable. Finally, the mechanism should enjoy the advantages of a one-piece design.
A need exists, therefore, for a one-piece watch saddle, for ventilating and spacing the body of a wristwatch, that features economy and simplicity of design, that will accommodate a variety of watches, that is easy to install and remove, that is quiet and secure when installed, and whose appearance does not detract from the overall appearance of the watch.


Apparatus for cleaning the outer surface of a pipeline (10, 10B, 10C) including a self propelled carriage (28, 28B, 28C) supported on the pipeline for movement. A housing (30, 30B, 30C) forms an enclosed cleaning chamber about the pipeline and the cleaning material along with entrained waste material removed from the pipeline may be conveyed by a suitable conduit (40) from a discharge opening in the bottom of the housing (30, 30B, 30C) for separation of the cleaning material and waste material and return of the separate water to the housing in a recirculation system. The embodiment of FIGS. 11-15 is particularly adapted for use with high pressure water and includes a plurality of nozzle units (91C) mounted externally on the housing (30C) with each unit (91C) having a hydraulic fluid drive motor (96C) operatively connected to a nozzle (94C) for pivoting of the nozzle (94C) back and forth in an arcuate path. High pressure water is supplied to a tube or tubular shaft (90 C) connected to the nozzle (94C). An embodiment of FIG. 16 illustrates a fixed installation for the cleaning apparatus with the pipe being moved through the apparatus for cleaning.

This invention relates to an apparatus and method for cleaning a pipeline, and more particularly to such a method and apparatus for cleaning the outside of the pipeline including a self propelled carriage moving along the pipeline.
Heretofore, apparatus has been provided including a self propelled carriage or vehicle, such as shown in U.S. Pat. No. 4,603,516 for cleaning the outside of pipe or pipeline as the self propelled carriage moves along a pipeline while supported thereon. Cleaning the outside of pipe removes loose rust, scale and dirt, to prepare the pipe for the subsequent application of a coating material on the outer surface of the pipe to minimize corrosion and prolong the service life of the pipe. In some instances, the pipe may be wrapped with an outer lining material containing an inner coating material for contacting the outer cleaned surface of the pipe. Normally abrasive particles, such as hard shot particles or grit, have been thrown by centrifugal force from an impeller wheel or the like against the outside of the pipe for cleaning the pipe. Particularly where hard shot particles of a uniform size were used previously, a relatively smooth clean outer surface of pipe was provided. The terms "pipe" and "pipeline" are interpreted herein as being the same.
It is desirable to have a roughness on the outer surface of the pipe to provide a strong bond between the pipe and coating. The roughness increases the surface area of the pipe in contact with the coating for "anchoring" the coating on the pipe. Such an increased area bond is particularly needed upon an expansion of the pipe resulting from pressure or temperature increases to maintain the bonding contact between the pipe and coating. The greater the roughness, the stronger the bond between the pipe and coating particularly for shearing stresses. An enclosed blast chamber or housing on a self propelled carriage travelling along the pipe has been utilized previously but such carriages have been relatively complex for carrying blast wheels or impellers and for assembly on and disassembly off the pipe.
Oftentimes, high pressure water is utilized for the cleaning of pipe. For example, as shown in U.S. Pat. No. 5,092,357 dated Mar. 3, 1992, a self propelled apparatus travels along a pipeline and discharges high pressure water from rotating water jets or nozzles for cleaning the outer surface of the pipeline. As shown in U.S. Pat. No. 4,552,594, a self propelled vehicle discharges high pressure water from nozzles mounted on a frame which oscillates as the apparatus moves along the pipeline for cleaning the outer surface of the pipeline.
An enclosed chamber or housing is normally provided on a travelling carriage of the pipe cleaning apparatus for maintaining the high pressure water or other cleaning material in an enclosed volume about the pipe. However, the carriages heretofore for supporting the housing and discharge nozzles for assembly on and disassembly off the pipe have been relatively complex. It is noted that in some instances a non-uniform cleaning of the pipe has been obtained as the distance of the nozzles to the outer periphery of the pipe varies substantially throughout the movement or stroke of the nozzle resulting in the water jets striking the outer periphery of the pipe at different velocities at different portions of the stroke. Thus, a non-uniform cleaning action may be obtained.

Apparatus and method for cleaning a pipeline


A package including a flanged tray and a wrapper surrounding it. The tray typically contains a foodstuff such as a pie. The wrapper is formed of a rectangular, unitary blank of paperboard which is folded and wrapped aroung the tray, the wrapper being folded to the form of a tube with the tray therein. The wrapper includes two oppositely located latching flaps (24) whose free edges (28) are curved so as to match the curvature of the tray. The curved or arcuate latching flaps are initially folded downwardly more than 90 degrees from the plane of the blank. Other portions (16, 18) of the blank are bent upwardly along respective transverse fold lines (23), causing the arcuate latching flaps to bow inwardly and beneath the flanges of a tray (32) and contact the tray flanges (34). Portions (16, 18) of the wrapper are then folded beneath and on the sides of the tray and ends (17) are overlapped and glued together to finish the package. If the tray is rectangular instead of round or oval, the free edges (28) of the flaps (24) are straight.

This invention relates to a wrapper and more particularly for a paperboard wrapper for forming a package having a flanged tray, such as a pie tray.
The art is aware of wrappers for trays, the wrapper being in the general form of a paperboard blank wrapped around a flanged tray, such constructions usually having tabs or flaps to engage either the flange of the tray or the tray itself to inhibit movement of the tray with respect to the wrapper. The resultant package includes a generally rectangular sleeve or tube, open at both ends, with the tray positioned centrally thereof and held in place by flaps, flanges, or gussets.
While satisfactory for the purpose intended, such known flanged tray wrappers suffer the disadvantage of complexity, with their attendant need for cut flaps, panels or gussets.


A surgical apparatus for hair removal surgery includes an extraction module, a visualization component and a bridging component. The extraction module includes independently controllable coring and clipping devices. The visualization component acts to align a target hair follicle with the extraction module. The extraction module also includes at least one independently controllable suction port. The instrument also includes a dissection module having a tissue separating device.

The present disclosure relates to an instrument that may be used for Hair Restoration Surgery (HRS) or any subdermal tissue removal procedure without altering the integrity of the overlying skin surface. The surgical method of donor follicle removal in HRS is based on the principal of "donor dominance", wherein the region of the scalp in which the hair is destined to persist throughout a person's lifetime, known as the "donor area" will continue to grow in the same fashion, when transplanted to the "recipient area", or the scalp zone of non-permanent hair growth.
Original HRS techniques included the excision of large punch grafts from the donor area and transplantation to the recipient area. Utilization of these large grafts was necessary in order to ensure hair survival after transplantation. Smaller grafts, or implantation into smaller recipient sites, were often not feasible due to the low graft viability secondary to decreased blood perfusion of transplanted grafts. While this large-graft method enabled transplanted graft growth within the recipient area, the grafts often had an unnatural, "pluggy" appearance, and the punched-out scars in the donor area left an unattractive buckshot-type pattern in the back of a patient's head.
To overcome these methodical and aesthetic shortcomings of many original HRS techniques, an alternative method for donor hair harvesting was proposed: the strip harvest technique. This alternative approach involved the following procedural steps: removing a strip of hair-follicle bearing skin from the donor region, suturing the donor wound closed, dissecting out each individual follicle or cluster of follicles (a.k.a. a "follicular unit", FU), and transplanting each individual FU separately in the recipient area. Each FU may contain one or more individual hair follicles and can be defined based on the naturally-occurring arrangement of a bulb region. An FU may be classified based on its caliber and the quantity of hairs it contains as a single-haired FU, a fine-single-haired FU, a double-haired FU, a fine double-haired FU, a triple-haired FU, or a follicular family containing four or more intact hair follicles.
The approach, known as "micrografting" or "follicular unit transplanting" (FUT), helped to create a more natural and less "pluggy" appearance in the recipient area than that resulting from the large grafts. Furthermore, this new approach left only a linear scar in the donor area, rather than a more obvious buckshot pattern.
In order to achieve a maximum number of grafts via the "micrografting" technique, many patients requested wider donor strip removal which would, in turn, yield more donor hair follicles. A consequence of this more aggressive approach is that patients are increasingly left with relatively large (2-10 mm) and obvious linear scars in the donor portion of their head. To reduce or eliminate this aesthetically displeasing result, a process known as Follicular Unit Extraction (FUE) was developed. In FUE, each individual follicular unit is meticulously punched out from the donor area with a small biopsy punch, and then transplanted into the recipient area. This differs from the original approach to HRS in that FUE involves the transfer of only individual FU's, rather than large (4-5 mm) punch grafts.
However, several disadvantages persisted with the advent of FUE: a high percentage (up to 40%) of hairs are transected (thus, limiting their survival), a moth-eaten scarring pattern often still remains (though to a lesser degree than seen with the original, larger punch grafts) from where FUs are extracted, and a considerable number of patients (up to 30%) are not candidates for FUE based on their hair characteristics (e.g. light color or considerable and unpredictable curl beneath the skin surface) that present undue challenges for the surgeon.
The technique described herein allows for: 1) the isolation of an intact hair follicle with maximal tissue (both dermal and subcutaneous) surrounding the stem cell-containing portion of the follicle without traumatizing the overlying skin surface; and 2) eliminates the stigma of any apparent scar in the donor area from which the hair is harvested.
A challenge associated with extracting/harvesting tissue that includes essential portions beneath the skin surface often pertains to determination of the location, depth, and position of the desired tissue. Without cutting or altering the integrity of the overlying skin surface, obtaining the desired tissue segment beneath the skin is especially difficult. In order to overcome these challenges, a device is disclosed herein to enable a user to 1) manipulate a visualization device located outside of the skin surface to identify a target tissue, and 2) harvest tissue located beneath the skin surface based on the information provided by the visualization device. Movement of the visualization device and the internal issue extraction device are directly tied to the movements of the operator performing each movement outside of the skin surface.
Without cutting or altering the overlying skin surface, the design described herein enables a precisely-controlled extraction/harvest of desired tissue that accounts for the borders of the desired tissue, the angle and direction of the tissue (e.g. hair follicle) as it is positioned beneath the skin surface, and the depth of penetration of the desired tissue all while effectively avoiding inclusion of undesirable surrounding tissue in the harvest or injuring vital vessels or nerve plexes in the process.
The direct association between the visualization/manipulation of a probe located outside of the body and the extraction/harvesting module located within the body that approaches, but does not directly touch, the outerlying probe enables this unique achievement.

This patent is subject to a terminal disclaimer.


Disclosed is a micro fan. The micro fan comprises a hub rotatably mounted to a shaft, and a plurality of blades radially formed on a circumferential outer surface of the hub, wherein each blade has an airfoil-shaped cross-section which generates lift force larger than drag force; and wherein, when assuming that one end of the airfoil-shaped cross-section of each blade, which is rounded at a predetermined radius, is a leading edge, the other end of the airfoil-shaped cross-section of each blade is a trailing edge, a straight line which connects the leading edge and the trailing edge with each other is a chord line, a thickness center line between the leading edge and the trailing edge is a mean line, and an inclination angle of the chord line with respect to a parallel line which is drawn from the leading edge is a blade angle, a blade angle at a root of the blade which is adjacent to the hub is about 24.degree.-34.degree., a blade angle at a tip of the blade which is adjacent to a duct of the micro fan is about 18.degree.-28.degree., and a span twist angle which is represented by a difference between the blade angles at the root and the tip is 2.degree.-12.degree. of helical twist.

1. Field of the Invention
The present invention relates to a micro fan, and more particularly, the present invention relates to a micro fan in which each blade has an airfoil-shaped cross-section and is applied with a helical twist by twisting at a predetermined angle a span between a root and a tip of the blade, to generate optimum volume flow rate and wind pressure when the blade is rotated, thereby improving rotational efficiency and reducing electric power consumption and rotation noise.
2. Description of the Related Art
Generally, a micro fan is mainly used in a limited space such as in a notebook computer or a personal computer, for cooling and dissipating driving heat existing in a driving device such as a micro-processor or a VGA card, which generates heat upon driving. In these days, it is the norm to use a single rotation type axial flow fan having a small size as a micro fan.
A micro fan is directly locked to a micro-processor or is independently attached to an inside structure in a notebook computer or the like. At this times due to the fact that capacity and speed of a CPU for respective driving devices are multiplied while a personal computer trends toward miniaturization of its components, because load capacity is rapidly raised, heat of a high temperature is generated.
This driving heat generated in the CPU can cause driving failure due to overheating when it is not properly cooled and can induce damage to main components of the computer, thereby resulting in a breakdown of the entire computer.
Accordingly, while cooling of a CPU, which is not considered as a crucial subject in the past, comes recently in the limelight as an important task which cannot be passed over, a CPU cooling fan which is used at the present stage, reveals a technical limitation by which it cannot perform a sufficient cooling function.
On the other hand, when performing a cooling function by using a micro fan, a method for increasing volume flow rate of the fan can be implemented. Volume flow rate of a fan is determined by various factors such as blade size, blade configuration, running rpm, etc., and specifically, because it is used in a fixed space, problems which can result from spatial limitations, electric power consumption and noise generation must be essentially dealt with.
Accordingly, a micro fan must be designed such that energy loss due to separation of flowing air is prevented, noise is reduced, flow loss between an inlet and an outlet of a blade is minimized and a static pressure rise is maximized, whereby a high performance of the micro fan can be accomplished.
Specifically, it was found through various experiments that most fan noise is caused by variables including rpm, gap between a blade tip and a duct, the number of blades, chord length, camber, the sweep of a blade, etc.
FIG. 1 is a front view illustrating a structure of a conventional micro fan which is generally used in these days. The drawing reference numeral 1 denotes a hub which is fastened to a shaft and is integrally rotated therewith, the drawing reference numeral 2 represents a plurality of blades which are integrally formed on a circumferential outer surface of the hub 1, and the drawing reference numeral 3 depicts a duct which surrounds the hub 1 and the plurality of blades 2 from the outside and guides air flow through a gap defined between the blade and the duct.
The hub 1 is a rotating member of a motor of the micro fan. A magnet is attached inside the hub 1, and if electric power is supplied to the hub 1, by an interaction between a stator coil being a fixed member and the magnet, the hub 1 is rotated.
The plurality of blades 2 function to supply outside air to a micro-processor while being integrally formed on the circumferential outer surface of the hub 1 and being integrally rotated therewith.
The duct 3 is placed radially outward of the blades 2, surrounds the blades 2, and performs a function of a guider which guides air sucked by the blades 2 into the micro-processor.
FIG. 2 is an enlarged partial plan view illustrating a blade configuration of the micro fan of FIG. 1. The blade 2 of the conventional micro fan has a configuration of a circular arc having a cross-section which is curved upward, and possesses one end which is coupled to the hub 1 and the other end which is inclined downward.
On the other hand, the duct 3 which is separated by a fine gap from an outer circumference of the blade 2 and surrounds the plurality of blades 2, has a lower part which is integrally connected with the fixed member of the motor and is locked to the micro-processor by a separate fastening means such as a screw.
Specifically, as seen in FIG. 1 a fine guide gap 3a which is defined between the outer circumferences of the blades 2 and an inner circumference of the duct 3 performs a function of a guider which guides smoothly outside air sucked by the blade 2 into the micro-processor.
Accordingly, if the hub 1 begins to rotate as electric power is supplied to the motor, the plurality of blades 2 which are integrally formed with the hub 1 are rotated, and outside air is sucked into the micro fan by pressure differentials between surfaces of the blades 2, to be supplied to the micro-processor.
The air flow is effected by the fact that, by a surface contour of the blade 2 which is curved upward, pressure is abruptly reduced inside rather than outside the surface of the blade 2 when the blade 2 is integrally rotated with the hub 1 and according to this, air flows from a point of high pressure toward a point of low pressure.
However, because most micro fans which are used in these days are manufactured only for the purpose of sucking air from the outside, a configuration of the blade 2 is designed in a simple way. Namely, while volume flow rate of the fan is determined by blade size, blade configuration, running rpm, etc., the cross-section of the blade 2 which is applied to the conventional micro fan has a simple configuration as shown in FIG. 2 in which both ends of a lower surface being a straight line are connected with each other by a circular arc having a predetermined radius, a blade angle which is an inclination angle of the blade 2 with respect to the hub is the same at a root and a tip of the blade 2, a camber ratio which is a ratio of a maximum height difference between the lower surface and a thickness center line to a length of the lower surface is about 10% which is a somewhat large value, and a chord line length is the same at the root and the tip of the blade 2.
If the plurality of blades 2 which are integrally coupled to the hub 1 are driven, when observing at various rpms, that is, at 8500 rpm, 9500 rpm and 10500 rpm, variations in wind pressure of the blades depending upon variations in volume flow rate which is generated by the micro fan, performance characteristics which are given in TABLE 1 are obtained.
TABLE 1 Wind Pressure (mmAq) Wind Pressure (mmAq) Volume Flow Rate 8500 9500 10500 Volume Flow Rate 8500 9500 10500 (cmm) rpm rpm rpm (cmm) rpm rpm rpm 0 1.4306 1.6943 2.2725 0.017 0.3564 0.4684 0.655 0.001 1.3435 1.6129 2.1748 0.018 0.3357 0.4476 0.6426 0.002 1.2357 1.497 2.0445 0.019 0.3191 0.4228 0.6343 0.003 1.1444 1.385 1.9223 0.02 0.2734 0.4103 0.6135 0.004 1.0449 1.2813 1.8042 0.021 0.2361 0.3688 0.5845 0.005 0.9495 1.1818 1.6984 0.022 0.178 0.3315 0.5638 0.006 0.85 1.0822 1.5592 0.023 0.1241 0.2776 0.5264 0.007 0.7712 0.9785 1.4472 0.024 0.0661 0.2237 0.4974 0.008 0.6675 0.8831 1.3186 0.025 0 0.178 0.4476 0.009 0.5804 0.7919 1.2067 0.026 0.1075 0.3896 0.01 0.5057 0.7048 1.0864 0.027 0.0536 0.3232 0.011 0.4435 0.6094 0.991 0.028 0 0.2651 0.012 0.4145 0.5555 0.8707 0.029 0.1863 0.013 0.4103 0.5223 0.7919 0.03 0.1158 0.014 0.4062 0.5099 0.7421 0.031 0.0412 0.015 0.3979 0.4933 0.6882 0.032 0 0.016 0.3813 0.485 0.6758 0.033
On the other hand, FIG. 3 is a graph which is made using performance characteristics as given in TABLE 1.
From the performance characteristic variations given and illustrated in the TABLE 1 and the FIG. 3, respectively, it is to be readily understood that the more volume flow rate is decreased, the more wind pressure of the micro fan is increased, and the more volume flow rate is increased, the more wind pressure of the micro fan is decreased.
Also, it is to be readily understood that these wind pressure characteristic variations are effected also depending upon rpm of the blade.
On the other hand, as can be seen from TABLE 1 and FIG. 3, when wind pressure is decreased by the increase in volume flow rate, a surging phenomenon in which air flow is unstabilized occurs at a point where wind pressure reduction slope is changed from an abrupt one to a gradual one. By this, there is caused a problem in that fan driving efficiency is deteriorated.
This is because a stall which retards a performance characteristic occurs when wind pressure is abruptly varied. If a hub ratio is increased, air supplying performance characteristics reveal a tendency that highest pressure is increased, a slope of a driving region is steepened and a depth of the stall is deepened.
Accordingly, due to the fact that desired cooling efficiency cannot be achieved by the conventional micro fan, overheating of a device is caused, and in order to cope with this problem, a motor having larger load capacity must be used for increasing rotating force of the micro fan.
Further, since vortex flow is structurally generated at the tip which is the outer circumference of the blade, separation of air flow is brought about, and a peripheral flow field is disturbed by the separation of air flow, whereby performance of the micro fan is impaired and noise is increased.
On the other hand, because a micro-processor of a high capacity and a high speed which have been recently developed must provide a more shortened processing time, a proper cooling cannot be implemented by the conventional blade configuration. Due to this aspect, the development of a fan blade which can satisfy the above condition has drawn considerable attention with increasing demand.


An alloy steel having particular utility for roll caster shells used in the direct casting of molten aluminum to sheet, consisting essentially of, in weight %, 0.25-0.45% C, 1.75-3.75% Cr, 0.75-2.5% Mo, 0.35 to 0.8% V, 0.4-1% Mn, greater than 0.4-1% Ni, 0.02% max P, 0.02% max S, up to 0.35% Si and balance essentially Fe. Roll caster shells fabricated from the steel have excellent toughness and ductility at room temperature to enable a greater shrink-fit with the core. The shells also have good resistance to heat checking. The excellent properties are provided by a controlled amount of Mo.sub.2 C and VC as well as limiting the amount of C in solution.

The present invention relates to ferrous compositions which may be used for roll shells, a component of steel caster rolls which are used to strip cast aluminum alloys. The shells have excellent resistance to heat checking at higher shrink-fit stresses between the shells and the water cooled cores.
Molten aluminum at about 675.degree. C. is directly cast to strip between two water cooled rolls each composed of a roll shell (hoop or sleeve) which has been shrink-fitted on a water cooled core. The rolls arc driven rotationally in opposite directions and the distance between them determines the thickness of the cast strip. The cast strip solidifies in contact with the rolls. The main function of the shells is to contain and extract heat from the molten aluminum to control the solidification and provide a good aluminum cast surface.
The shells must have excellent mechanical properties such as high strength and toughness since the rolls arc subjected to stresses caused by separating forces and roll drive forces during casting. The shells will also have to withstand the mechanical stress due to the shrink-fit between the shells and the water cooled cores. Additionally, the shell surfaces will continuously expand and contract during the cyclic temperatures developed during casting. This cyclic stress developed on the surfaces will contribute to the initiation and propagation of any cracks or defects formed during casting. Therefore, the rolls must also possess good resistance to thermal fatigue.
Thermal fatigue is caused by any variation in temperature which generates a change in dimension. If a material is heated homogeneously, the uniform temperature change will bring a change in volume but no stress. However, a temperature gradient in the material causes stress to occur in relation to the thermal gradient. When the shell surface contacts the molten aluminum, the surface temperature rapidly increases while the bulk of the shell is cooled by thermal transfer from the water cooled core. The stress levels reached will exceed the compressive yield strength of the steel and result in plastic deformation of the shell surface while in contact with the molten aluminum. When that portion of the shell moves away from the molten aluminum, it rapidly decreases in temperature and will contract causing high surface tensile stresses. Numerous cycles of this type will eventually cause mechanical fatigue and cracking when the ductility is exhausted. After a number of hours of casting, the surfaces of any roll shells will develop heat checking patterns or surface cracks which grow deeper into the shells and eventually mark the cast strip. These defects may also cause complete failure of the roll shells if allowed to grow excessively large. Periodic reconditioning of the shells is to be expected. Typically, reconditioning will remove up to about 0.15 inches (3.8 mm) of the shell thickness.
Resistance to heat checking and cracking is generally associated with a low coefficient of thermal expansion, high thermal conductivity, high elevated temperature yield strength, high elevated temperature ductility and a low modulus of elasticity. This combination of properties is difficult to attain and attempts to improve one of these properties has usually resulted in a sacrifice in one or more of the other properties.
The shells must also have good mechanical properties at room temperature because of the many stresses introduced during machining and reconditioning. Good ductility and toughness are very important to avoid brittleness during grinding and handling which could cause further cracking.
U.S. Pat. No. 4,409,027 (assigned to Armco Inc.) used a ferritic alloy composition for the roll shell which consisted essentially of, in weight %, about 0.53 to about 0.58% C, about 0.4 to about 1% Mn, 0.1 to 0.2% Si, about 0.02% max P, about 0.02% max S, about 0.45 to about 0.55% Ni, 1.5 to 3.0% Cr, 0.8 to 1.2% Mo, 0.3 to 0.5% V and balance essentially iron.
Stresses which are greater than the yield strength and tensile in nature will produce heat checks or cracks by a thermal fatigue mechanism when cyclic yielding or plastic flow occurs. A hysteresis loop can be plotted representing the accumulation of plastic damage during each cycle for the circumferential stresses perpendicular to the longitudinal cracks in the roll shell surface. In prior an chromium-molybdenum steels, the number of cycles to failure is about 10.sup.4 if the extent of plastic deformation per cycle is about 0.001 inch per inch or slightly less. High carbon levels were required to provide hardness, strength and resistance to localized softening which resulted from the distribution of carbon in the microstructure. Molybdenum and vanadium were increased to form carbides which increased the elevated temperature strength. By increasing the elevated temperature yield strength by 50-100%, the service life was increased three-fold if the elevated temperature ductility was maintained. This patent found that increasing the elevated temperature yield strength more than compensated for the loss in thermal expansion, modulus of elasticity and conductivity when improving the resistance to checking.
In the equation set forth in U.S. Pat. No. 4,409,027 for total thermal strain [thermal strain (.epsilon..sub.t)=.alpha..DELTA.T where .alpha. is the coefficient of thermal expansion and .DELTA.T is 1150.degree. F. which represents the difference between the maximum roll surface at 1250.degree. F. and the minimum roll surface temperature of 100.degree. F.], the total strain is assumed to be the sum of elastic and plastic components: EQU .epsilon..sub.t =.epsilon..sub.elastic +.epsilon..sub.plastic =.sigma.y/E +.epsilon..sub.plastic
where .sigma.y is the yield strength in tension and E is the elastic modulus
Thus, the elastic component of the strain is represented by the yield strength in tension divided by the elastic modulus. In the case of a steel having a yield strength of 200,000 psi at room temperature, .epsilon..sub.elastic =.epsilon.y/E=200,000/30.8.times.10.sup.6 psi-6.49.times.10.sup.-3 in/in. If the yield strength is decreased by 50% at elevated temperatures, such as 1250.degree. F., the .epsilon..sub.elastic =.epsilon.y/E=100,000/24.times.10.sup.6 psi=4.16.times.10.sup.-3 in/in.
Where the total strain is equal to or greater than twice the elastic strain, to account for the compression and tension portion of elastic reaction, then plastic flow is possible in both the compression and tension ends of the cycle. With a 50% decrease in yield strength to 100,000 psi, 2.times..epsilon..sub.elastic =2.times.4.16.times.10.sup.-3 =8.32.times.10.sup.-3 in/in. The plastic component then becomes .epsilon..sub.plastic =.epsilon..sub.t -2.times..epsilon..sub.elastic =8.0.times.10.sup.-4 in/in.
Consequently, a plastic flow of about 0.001 inch per inch per cycle is possible, which would indicate a potential exhaustion of plasticity and failure in 10.sup.4 to 10.sup.5 cycles.
The calculations are believed to support the belief that the high elevated temperature yield strength of the steel causes a much greater percentage of the thermal expansion and contraction to occur in the elastic region. This minimizes the plastic reaction and results in much greater resistance to heat checking. Maintenance of the high ductility of the steel at a higher yield strength insures a retarded crack growth rate once heat checking does occur.
While the roll shell of this patent had good elevated temperature strength, the material did not have good toughness and ductility at room temperature which is required for a higher shrink-fit to minimize slippage between the shell and core. Improving the toughness would also allow the material to withstand the handling required during grinding to remove heat checks and resist the propagation of cracks.
A standard alloy used for roll caster shells referenced in U.S. Pat. No. 4,409,027 comprised 0.53-0.58% C, 0.45-0.65% Mn, 0.2-0.3% Si, 0.4-0.5% Ni, 1-1.2% Cr, 0.45-0.55% Mo, 0.1-0.15% V, 0.02% max P, 0.02% max S and balance essentially Fe.
Another alloy referenced in U.S. Pat. No. 4,409,027 as an Al die casting alloy had 0.3-0.4% C., 0.2-0.4% Mn, 0.8-1.2% Si, 4.75-5.5% Cr, 1.25-1.75% Mo, 0.8-1.2% V and balance Fe. It was discussed as being expensive and difficult ti process.
U.S. Pat. No. 4,802,528 (assigned to Chavanne-Ketin) produced forged casings for continuous casting aluminum from an alloy steel having 0.3-0.36% C, 0.3-0.6% Mn, 0.15-0.45% Si, less than 0.4% Ni, 2.8-3.4% Cr, 0.85-1.25% Mo, 0.1-0.3% V, 0.02max P, 0.02% max S, 0.3% max Cu, and balance essentially Fe. This alloy reduced the carbon content from previous alloys to improve ductility and toughness. While sacrificing some thermal conductivity, the grade of steel is stated to have a surprising improvement in resistance to thermal fatigue cracking. This patent studied the mechanical and thermal cycles of the roll during shrink-fitting and casting of aluminum. The roll shell has mechanical stress related to roll production which produces circumferential tensile stress and longitudinal stress and it has operating stress from torsion due to the driving torque and bending stress due to separating forces during casting. The thermal stresses relate to the difference in temperature between the inner cooled core of the roll and the temperature of the molten aluminum which cause the roll shell to exceed the elastic limit of the steel which causes plastic deformation. The cooling of the roll causes the deformation to start to disappear but the shell can not return to its original position because of the plastic deformation in compression. The return to the low temperature will cause the elastic limit to be exceeded in tension and result in plastic deformation. This cycle of deformation of thermal origin will cause fatigue of the surface and result in the initiation and subsequent propagation of microcracks. One of the essential properties demanded of the roll shell is the resistance to thermal fatigue.
An alloy referenced in U.S. Pat. No. 4,802,528 used for roll caster shells had 0.53-0.57% C, 0.9-1.3% Cr, 0.4-0.6% Mo, 0.1-0.2% V, 0.7-0.9% Mn, 0.4-0.7% Ni and 0.2-0.4% Si, 0.02% max P, 0.02% max S and balance essentially Fe.
Another alloy referenced in U.S. Pat. No. 4,802,528 used for roll caster shells had 0.53-0.58% C, 1.5-3% Cr, 0.8-1.2% Mo, 0.3-0.5% V, 0.4-1.0% Mn, 0.45-0.55% and 0.1-0.2% Si, 0.02% max P, 0.02% max S and balance essentially Fe.
U.S. Pat. No. 4,861,549 (assigned to National Forge Company) disclosed a ferritic steel preferably containing 0.45-0.49% C, 1.20-1.50% Ni, 0.90-1.00% Mn, 1.20-1.45% Cr, 0.010% max P, 0.80-1.00% Mo, 0.002% max S, 0.15-0.20% V, 0.15-0.35% Si, up to 0.08% rare earth metals and balance Fe. The steel was designed for roll shells to cast aluminum sheets. The steel was stated to have good resistance to heat checking and cracking when subjected to extreme heat stresses in repeated thermal cycles. Rare earth elements were added to avoid temper embrittlement.
Prior attempts to provide good elevated temperature yield strength for reducing heat checking and craze cracking have also increased the room temperature yield strength. This has an adverse effect on the ductility and shrink-fit process. High carbon was used to provide solution strengthening for elevated temperature strength but this made the steel brittle at room temperature and had an adverse effect on toughness.
Even though some improvements in service life were obtained for the rolls used to strip cast aluminum alloys, there is still a need for further improvement in order to increase production and improve the quality of the aluminum strip. There is also a need to increase the shrink-fit between the shell and the core of the roll without adding excessively to stresses in the shell. This allows for less slippage of the shell over the core during casting. Prior roll shell alloys had chemistries balanced to provide good high temperature properties and were less concerned with room temperature properties which are critical for shrink-fit and machining properties.


A stray magnetic field suppression system for use in a CRT image display suppresses a stray magnetic field that emanates from the horizontal deflection coil of a beam-deflecting yoke which is energized by sawtooth waveform pulses from a horizontal oscillator. The system comprises two series-connected magnetic coil assemblies in conjunction with a capacitor and activated by the sawtooth waveform pulses. The capacitor serves to integrate the pulses, enabling the suppression system to form an effective field for suppressing a stray magnetic field when the magnetic coil assemblies are interposed in the path of the stray magnetic field on opposite sides of the yoke.

This invention relates to cathode ray tube image displays, hereafter simply called "CRT's," and is addressed to means for suppressing stray magnetic fields emitted by such systems. More particularly, the objective is to suppress such emissions to a level below that established by a recognized standard. The invention is applicable to both monochrome and color CRT image displays in which the viewer may be in close proximity to the faceplate, such as the viewers of visual display terminals and television sets.
The present invention had its origin in the concern over the possible detrimental effects of stray magnetic fields on the physiology of the viewers. Testing for such fields in visual display terminals is described in a publication of the National Board for Measurement and Testing (MPR) of Sweden entitled "Test Methods for Visual Display Units: Visual Ergonomics and Emission Characteristics." MPR 1990:8 1990-1991, Boras, Sweden. This standard is known as "MPR-2." The subject of stray magnetic fields is also covered by the IEEE Transactions on Electromagnetic Compatibility, a periodic publication of the IEEE Electromagnetic Compatibility Society.
As is known, the primary source of stray magnetic fields in CRT's is the yoke. The yoke is an electromagnetic device that causes an electron beam to scan a raster on the CRT viewing screen in both the horizontal and vertical directions. Monochrome CRT's utilize a single electron beam. CRT's displaying color images typically utilize three beams, one for energizing each of the red, green and blue light-emitting phosphors on the viewing screen. In this disclosure, reference is made to only a single beam CRT, with the understanding that its content applies as well to multiple-beam CRT's.
Essentially, a yoke consists of two pairs of coils, one of which deflects the electron beam in the horizontal direction, and the other in the vertical direction. The two pairs of coils appear as dual radiating magnetic dipoles. The present invention is directed to the suppression of stray magnetic fields produced by the horizontal deflection yoke coils.
The coils are energized by a horizontal oscillator and a vertical oscillator. The horizontal oscillator provides a train of pulses having a frequency of 15,750 Hz in monochrome television sets, a frequency of 15,734.26 Hz in color television sets, and frequencies of up to 150 kHz in some visual display terminals. The pulses are routed to the horizontal winding of the yoke.
FIG. 1A depicts the general configuration of the sawtooth waveform pulse emitted by a horizontal oscillator. The activation of prior art stray magnetic field suppression devices has been accomplished by the inverted sawtooth waveform pulse indicated in FIG. 1B, which is essentially a mirror-image of the horizontal oscillator waveform of FIG. 1A. The inverted pulse depicted is used to energize prior art stray field suppression devices such as the device disclosed in U.S. Pat. No. 4,709,220 to Sakane et al.
Known solutions to the problem of suppressing stray magnetic fields typically involve some shielding combined with field cancellation techniques. The techniques have taken the form of additional field generating coils in series connection with the horizontal deflection windings of the yoke. The disadvantage of this approach is that higher pulse voltages are required to drive the windings. As a result, a major redesign of the circuits of the horizontal oscillator and the power supplies has been required.
The stray magnetic field that emanates from the beam-deflecting yoke of CRT is depicted diagrammatically in FIG. 2. A CRT 10 is enclosed in a cabinet 12. A beam-deflecting yoke 14 is indicated as encircling the neck 16 of CRT 10. By the variance of its magnetic fields, yoke 14 provides for the horizontal and vertical deflection of an electron beam emitted by an electron gun 18 that is enclosed in neck 16 of CRT 10.
The stray magnetic field that emanates from the horizontal deflection coil of the yoke 14 is indicated as being composed of two loops, a first loop 22 and a second loop 24, both of which extend beyond the perimeter of the cabinet 12. The clockwise direction of the stray magnetic field indicated by first loop 22 that extends into the frontal area 26 of cabinet 12 is indicated by arrows 28 and 30. The counter-clockwise direction of the stray magnetic field indicated by second loop 24 that extends into the rearward area 32 of cabinet 12 is indicated by arrows 34 and 36.
The suppression of the stray magnetic field by a stray field suppression system is indicated diagrammatically in the form of two loops 38 and 40 running in paths opposite to the respective paths of the stray fields indicated by loops 22 and 24. The stray field represented by first loop 22, shown as rotating in a clockwise direction indicated by arrows 28 and 30, is opposed by the third loop 38, in which arrows 41 and 42 indicate that the stray field suppressing third loop 38 lies in a counterclockwise direction. Similarly, the stray field indicated. by second loop 24 is opposed by the fourth loop 40, and arrows 44 and 46 indicate that the direction of the fourth loop 40 lies in a clockwise direction.
The measurement of the strength of the magnetic field emitted by the yoke 14 of the CRT 10 is indicated in FIGS. 3 and 4. The value measured is the rms (root mean square) of the strength of the field according to the formula for the rms value of periodic waveforms: ##EQU1##
FIG. 3 is a three-dimensional view of the three planes of the system along which the field is measured: a top plane 48, a middle plane 50 (also shown by FIGS. 2 and 4) and a bottom plane 52. The distance 54 between the planes is preferably 0.3 meter.
With reference to FIG. 4, measurements are made from the center 54 of the cabinet 12. Center 54 is in coincidence with the horizontal center line 56 of CRT 10. The distance R, or radius, in meters between the center 54 of the cabinet 12 and the perimeter of the three planes 48, 50 and 52 is determined by the formula R=L/2+0.5 m, where L is the front-to-back dimension of the cabinet 12.
FIG. 4 also depicts the points of measurement 58 of the strength of a stray magnetic field on each of the three planes 48, 50 and 52. Measurements on each plane are taken every 22.5 degrees. As sixteen measurements are taken in each plane, the total number of measuring points is forty-eight.
The range of stray field intensity among CRT image displays of various sizes and types was found to be 70 to 150 nT (nanoTesla). Measurements at the measurement points on planes 48, 50 and 52 disclosed a range of 40 to 150 nT. The Swedish MPR-2 standard specifies a maximum of 25 nT. The strength of a stray magnetic field is determined by means of a meter capable of measuring the rms value of low frequency magnetic fields; that is, fields in the frequency range of 2,000 Hz to 400 kHz. The meter must have a dynamic range of 0.01 uT to 10,000 uT. The measurement cycle includes measurement of the strength of stray magnetic field, its frequency and its polarization. A suitable instrument is Magnetic Field Meter 1000 manufactured by Combinova AB, Bromma, Sweden. The United States representative of this company is Ergonomics, Inc., Southhampton, Pa.
A feasible system for the resolution of the problem of stray magnetic fields must provide for stray field suppression well below the established standard, and do so with minimum interference with existing circuits, and with minimum power consumption. Also, the system must be simple and inexpensive to manufacture and install. The present invention meets these and all other requirements.

Stray magnetic field suppresser for CRT image displays


A graphic data encoding method and apparatus generating a bitstream by encoding a header having at least one piece of first information determined in consideration of a predetermined graphic profile from among multiple pieces of encodable first information; and encoding a payload having at least one piece of second information determined in consideration of the predetermined graphic profile from among multiple pieces of encodable second information. A graphic data decoding method and apparatus decode the generated bitstream. Irrespective of the functions that can be performed by the graphic data encoding apparatus and the functions that can be performed by the graphic data decoding apparatus, the graphic data decoding apparatus, which is in accordance with a graphic profile, can completely restore a 3D mesh model described in the bitstream generated by the graphic data encoding apparatus that is satisfactory to the graphic profile.

1. Field of the Invention
The present invention relates to graphic data, and more particularly, to compression and decompression of the graphic data.
2. Description of the Related Art
3-dimensional (3D) mesh models expressed in 3D by a plurality of vertices and faces formed by the vertices are widely used in various multimedia application fields, such as 3D games, 3D modeling, animation, etc. Various methods of encoding and decoding model data of such a 3D mesh model are suggested. Bitstreams, which are generated by encoding using various methods, may have different formats. Accordingly, a method of completely decoding a bitstream irrespective of an encoding method used to generate the bitstream is required.

Method and apparatus for encoding/decoding graphic data


Methods and apparatus for high speed location determinations are disclosed. An example apparatus includes at least two coils arranged along a zone of interest to generate a magnetic field, and a sensor to measure a change in the magnetic field associated with the at least two coils as an object of interest moves within or into the zone of interest. The example apparatus also includes a processor to determine a position of the object of interest based on the measured change.

In sporting events, such as hockey or soccer for example, an object of interest and/or sport implement such as a ball or a puck plays an important role in determining an outcome of a game. For example, whether a puck travels across a goal line is an important determination in hockey. However, the speed at which the puck travels (e.g., 100 miles per hour (mph)) can make this important determination very difficult based on visuals. For example, video replays captured by high-speed cameras are subject to occlusion, blurring and/or unclear/obstructed viewing angles that can that can make location determination of the puck difficult for scoring determinations.
Some known systems utilize magnets and/or magnetic fields to determine a location of a soccer ball near a goal line.
The figures are not to scale. Instead, to clarify multiple layers and regions, the thickness of the layers may be enlarged in the drawings. Wherever possible, the same reference numbers will be used throughout the drawing(s) and accompanying written description to refer to the same or like parts. As used in this patent, stating that any part is in any way positioned on (e.g., positioned on, located on, disposed on, or formed on, etc.) another part, means that the referenced part is either in contact with the other part, or that the referenced part is above the other part with one or more intermediate part(s) located therebetween. Stating that any part is in contact with another part means that there is no intermediate part between the two parts.


The present disclosure relates to improved processes for treating acid gases to remove acid gas components therefrom. Processes in accordance with the present invention include preparing a calcium silicate hydrate sorbent in the form of a semi-dry, free-flowing powder, and treating the gas with the powdery sorbent, such as by injecting the sorbent into a stream of the gas. The powdery sorbents may be prepared by slurrying/drying or pressure hydration techniques. Examples disclosed herein demonstrate the utility of these processes in achieving improved acid gas-absorbing capabilities in both lab-scale and pilot plant studies. Additionally, disclosure is provided which illustrates preferred plant design configurations for employing the present processes using conventional dry sorbent injection equipment. Retrofit application to existing plants is also addressed.

1. Field of the Invention
The present invention relates to processes for reducing the level of acid gas components (e.g. sulfur oxides) from acid gases. In particular, the invention relates to use of semi-dry calcium silicate hydrates in the form of free-flowing powders for removal of sulfur oxides (SO.sub.2 /SO.sub.3) and/or other acid gases such as hydrogen chloride (HCl), hydrogen fluoride (HF) and hydrogen bromide (HBr) from flue gases resulting from combustion of solid/liquid fuel or waste.
2. Description of the Related Art
Coal represents one of the most bountiful sources of energy in the world today. For example, it has been estimated that the known coal reserves in the U.S. alone could supply sufficient energy for domestic consumption for several hundred years. Unfortunately much of this coal contains high levels of sulfur which, when the coal is burned, is released into the atmosphere, generally in the form of sulfur dioxide. One of the most serious environmental problems associated with such sulfur emissions is the generation of atmospheric sulfuric acid, resulting in so-called "acid rain."
Attempts at controlling sulfur dioxide emissions from coal burning plants have led to the development of a number of advanced systems and processes for flue gas desulfurization. Fluidized-bed combustion, furnace lime injection, and flue gas desulfurization are some of the examples. In these processes, limestone and/or lime has been used as a sorbent which forms primarily calcium sulfate at a temperature above 700.degree. C.
Fluidized bed combustion (FBC) and scrubbers for flue gas desulfurization (FGD) represent two of the more promising advanced processes for power generation. FBC relates to the combustion of coal with limestone particles as the bed material, and has received increasing attention as a promising and versatile technology for clean power generation. Equally promising has been FGD, wherein sulfur-reactive sorbents are employed to remove sulfur from flue gases prior to their venting into the atmosphere. In developing the technologies for FBC and FGD, a search for sorbents more effective than limestone and/or lime, especially ones which are amenable to recycle, has been a challenging task.
Flue gas desulfurization by the means of spray dryer absorber and bag filter or electrostatic precipitator has recently received much attention. In the spray dryer/bag filter system, flue gas is contacted with a fine spray of an aqueous solution or slurry of a reactive alkali (typically lime), with SO.sub.2 removal and drying occurring simultaneously. The sulfur dioxide is absorbed into the water droplet during the constant rate period of drying until it shrinks to the extent that the particles touch each other. During the following falling rate period, the remaining water diffuses through the pores of agglomerated particles until the solids establish pseudo-equilibrium with the humid environment of spray dryer.
The third stage of drying may be called the second-falling rate period. Any drying/mass transfer during this period is limited by the diffusion of moisture from within tightly packed particles. The first two stages take place exclusively in the spray dryer. The majority of pseudoequilibrium period occurs in the duct joining spray dryer and bag filter and in the bag filter itself. Since not all moisture is removed from the solids in the spray dryer, the remaining moisture promotes further removal of SO.sub.2 in the bag filter. Therefore the total SO.sub.2 removal in the system is a sum of removal in the spray dryer and bag filter.
The recycle of product solids is among the options that have been tested to increase the utilization of reagent. Numerous reports indicate that recycle of product solids and fly ash results in substantial improvement of reagent utilization and SO.sub.2 removal. This option provides a higher Ca(OH).sub.2 concentration in the slurry feed at the same Ca(OH).sub.2 stoichiometry (moles of Ca(OH).sub.2 fed to the system/moles of SO.sub.2 in the feed gas). In one pilot plant, increasing the recycle ration (g solids recycled/g fresh Ca(OH).sub.2) from 6:1 to 12:1 increased SO.sub.2 removal in the spray dryer from 70% to 80% at stoichiometry 1.0 (Blythe et al., 1983, Proceedings: Symposium or Flue Gas Desulfurization, Vol. 2, NTIS PB84-110576). In another installation, recycle tests gave 10 to 15% more SO.sub.2 removal at stoichiometry 1.5 (Jankura et al., presented at the Eighth EPA/EPRI Symposium on Flue Gas Desulfurization, New Orleans, La., 1983).
Another option enhancing lime utilization uses the recycle of both solids captured downstream in the spray dryer and solids from the baghouse. However, removal does not appear to be significantly different when either spray dryer solids or fabric filter solids are employed as the recycled material. At stoichiometry 1.0 the removal increased from 53% when no recycle was employed to 62% with 0.5:1 recycle ration. When ash content in the feed slurry increased from 5% to 20%, SO.sub.2 removal in the spray dryer increased from 80% to 92% for stoichiometry 1.6 (Jankura et al., 1983).
U.S. Pat. No. 4,279,873, to Felsvang et al., relates several experiments investigating the effects of fly ash recycle and proved it to be beneficial for SO.sub.2 removal in a spray dryer. It was found that substantially higher removal of SO.sub.2 may be achieved when recycling the fly ash and Ca(OH).sub.2 than when recycling Ca(OH).sub.2 alone. Corresponding efficiencies for stoichiometry 1.4, 500 ppm inlet SO.sub.2, and comparable solids concentration were 84% and 76%, respectively. For the same stoichiometry and SO.sub.2 concentration, removal was only 67% for the simple once-thru process. At low SO.sub.2 concentration and high recycle ratios, over 90% removal was achieved even at extremely low stoichiometries. At 548 ppm SO.sub.2, 25:1 recycle, 0.76 stoichiometry and at 170 ppm SO.sub.2, 110:1 recycle, 0.39 stoichiometry, SO.sub.2 removal was 93.8% and 97.8%, respectively.
Removal efficiencies up to 65% were reported with a slurry of highly alkaline (20% CaO) fly ash only (Hurst and Bielawski, Proceedings: Symposium on FGD, EPA-600/981-019b, 853-860, 1980). In another experiment, 25% SO.sub.2 removal was achieved when spraying slurried fly ash collected from a boiler burning 3.1% sulfur coal (Yeh et al., Proceedings: Symposium on Flue Gas Desulfurization, EPRI CS-2897, 821-840, 1983). A weak trend was found in a study of 22 samples of fly ashes that a slurry with a higher total slurry alkalinity tended to have a higher SO.sub.2 capture (Reed et al., Environ. Sci. Technol., 18, 548-552, 1984).
Flue gas desulfurization by dry injection of a calcium-based sorbent such as lime into the flue gas downstream of economizer or air preheater has been a very attractive concept because of its technical simplicity and low capital cost requirement. In the dry injection procedures known in the art, lime powder, when used as sorbent, has to be very dry (i.e., containing less than about 5% water by weight) to stay in the free-flowing state for solids handling and dry injection. If the moisture content of the lime is increased above this level, it becomes a wet, sticky lime having a tendency to cake and cause soaling and plugging problems. However, the dry lime sorbent is not reactive toward SO.sub.2 unless the surface moisture is increased. Thus, for effective SO.sub.2 removal using a dry lime sorbent, the flue gas must typically be humidified by evaporation of atomized water droplets, thereby increasing the moisture content and the sorbent reactivity.
A large vessel may be required to provide adequate mixing and residence time to achieve sufficient flue gas humidification. Without such a vessel, water evaporation would be limited and the resulting duct scaling and plugging would present problems in operation. It should be noted that even after the flue gas is adequately humidified for efficient SO.sub.2 removal (to an approach to saturation temperature of 5.degree. to 30.degree. C.), the reactivity of injected lime is still low. Usually less than 20% utilization of the lime injected as expected, thereby wasting more than 80% of the sorbent. Therefore, there is a need for a reactive sorbent which can be handled by conventional dry solids injection equipment and yield high utilization.
Calcium silicate hydrates have heretofore presented problems when used as a sorbent for spray drying methods of flue gas desulfurization. As a relatively high humidity (5.degree. to 30.degree. C. approach to saturation temperature) has to be maintained in the spray dryer for effective desulfurization, and the hydrates cannot be adequately dried at high humidity (probably due to their water retention characteristics and agglomerating tendencies when slurried), operating problems such as wet deposition and scaling in the spray dryer vessel typically occur.
Calcium silicate hydrates have been shown to be a reactive sorbent for SO.sub.2 removal when injected dry into a pre-humidified flue gas stream. However, the sorbent preparation procedure for dry injection involves drying a calcium silicate slurry to produce the dry sorbent, which is a very energy intensive process. Therefore, there is a need to improve the sorbent preparation process to reduce or eliminate the drying requirement and decrease the production cost.
In the foregoing discussion, emphasis has been upon SO.sub.2 removal for several reasons: (1) sulfur oxides are one of the more difficult acid gases to control, and (2) sulfur oxide emissions nationwide are substantially greater than other acid gases. Generally, in order of decreasing reactivity toward alkali materials, the acid gases (compounds which exhibit acid behavior when mixed with water) are (HF/HBr/HCl SO.sub.3), SO.sub.2, CO.sub.2, NO.sub.2. Thus, it is believed that for any acid gases which are more reactive than SO.sub.2, the potential for significant control by calcium silicates is at least as great as for SO.sub.2. Hence, the remaining discussions will refer to acid gases meaning any individual gas, or combination of gases, which are as reactive or more reactive than SO.sub.2.

Processes for removing acid components from gas streams

Board of Regents, The University of Texas System


The present invention discloses intersexual heterozygous Phycomyces strains. These strains show an improved .beta.-carotene productivity and an increased stability when compared with both the wild type and heterokaryotic Phycomyces strains. The present invention also discloses a method for obtaining Phycomyces transformants without using selection markers. Furthermore, a process is provided for manufacturing .beta.-carotene comprising the use of intersexual heterozygous Phycomyces strains in a submerged culture.

In the late fifties and early sixties Mucorales strains, in particular Blakeslea trispora, Choanephora cucurbitarum and Phycomyces blakesleeanus have been studied in order to develop a fermentation process for the production of carotenoids. Wildtype strains of these fungi accumulate carotenoids, in particular .beta.-carotene. However, the amounts that can be obtained with pure cultures are insignificant for commercial production.
.beta.-carotene is a lipid-soluble yellow chemical with provitamin A and reportedly with anticancer activities. Various applications in the food, feed, cosmetics, chemicals and pharmaceutical industries are reported.
Several processes that increase the .beta.-carotene production are based on the co-cultivation of strains of opposite mating type, (+) or (-). The interaction between mycelia of opposite mating types leads the formation of trisporic acids and to enhanced .beta.-carotene accumulation. Co-Is cultivation of Blakeslea trispora strains of opposite mating type in a batch-type fermentation process was developed by Hesseltine and Anderson (U.S. Pat. No. 2,865,814 and U.S. Pat. No. 2,890,989). Up to pilot-plant scale the process looked a promising way to produce .beta.-carotene. .beta.-Ionone was added to stimulate .beta.-carotene production of the two strains within the fermentor. In later years this process was optimized by several industrial companies. Numerous other additives have been used to stimulate the .beta.-carotene accumulation. However, these developments no longer were pursued as it became clear that these processes could not compete on a cost-price level with chemical processes to manufacture .beta.-carotene on an industrial scale.
Nowadays only in the former USSR a plant is in use to produce .beta.-carotene from Blakeslea trispora. Agricultural waste-products are used as raw materials for the fermentation and the .beta.-carotene obtained is used as a feed-additive.
Meanwhile academic research focussed on the biochemistry and regulation of .beta.-carotene biosynthesis using the filamentous fungus Phycomyces blakesleeanus as a convenient model system. The synthesis of .beta.-carotene in Phycomyces is subject to strict metabolic regulation. Mutations of the regulatory genes may overcome this strict regulation. Classical mutation experiments resulted in the development of strains with a strongly increased .beta.-carotene productivity even in the absence of stimulatory factors. Wildtype Phycomyces strains in the dark contain about 50 .mu.g .beta.-carotene per gram dry weight of biomass. Regulatory single mutants have been found to contain up to 6 mg .beta.-carotene/g dry weight. Double mutants have been isolated which contain over 10 mg .beta.-carotene per gram dry weight.
Phycomyces blakesleeanus is a filamentous fungus with hyphae containing no transverse cell walls (septa), thus the whole mycelium may be viewed as a single collective cell or coenocyte containing millions of nuclei. Unlike other fungi the hyphae never fuse together. Therefore, fusion can only be achieved by using artificial methods such as protoplast fusion or microsurgery or by transplantation of structures of the sexual cycle (T. Ootaki in Phycomyces, E. Cerda-Olmedo and ED Lipson eds. (1987), CSH Laboratory Press, 345-349; T. Suarez et al., Ibid 351-353). Reproduction of the fungus can take place either through a sexual cycle involving zygospores and germspores or by vegetative reproduction (Phycomyces, E. Cerda-Olmedo and E. D. Lipson eds., (1987) CSH Laboratory Press, 2).
The germspores that are the meiotic products of the mating process of two strains of opposite mating type and the resulting mycelia are usually homokaryotic, i.e. all their nuclei are genetically identical, however a few heterokaryotic germspores are formed spontaneously even in normal crosses. As a consequence some of the germspores give rise to intersexual heterokaryons which contain a mixture of (+) and (-) nuclei.
Such heterokaryons are morphologically different from the normal mycelia. The mycelia show a bright color due to the increased accumulation of .beta.-carotene and characteristic structures, so-called pseudophores, are formed.
The maintenance and propagation of intersexual heterokaryons is difficult since the nuclei show a clear tendency to segregate leading to sectors of mycelia having nuclei of one mating type only. The construction of intersexual heterokaryotic strains, wherein both the nuclei contain a recessive lethal mutation, to minimize the segregation of nuclei, has been the strategy by which F. J. Murillo Araujo et al. (U.S. Pat. No. 4,318,987) have succeeded to construct superproducing strains. These strains which can be described as stabilized intersexual heterokaryons of deregulated mutants were found to produce .beta.-carotene up to 25 mg/g dry weight.
However, even with these recessive lethal mutations, controlling the nuclear ratio to a certain extent, the intersexual heterokaryotic strains are not optimally suited for .beta.-carotene production. These intersexual heterokaryotic strains grow much worse than wild type strains and moreover they seldom or never sporulate.