A spark plug includes a ceramic insulator having an engagement portion, and a metallic shell provided around the ceramic insulator and having a protrusion. The protrusion has a diameter-decreasing portion, which seats on the engagement portion via an annular seat packing. On a cross section including an axial line, θs>θp is satisfied, where θp represents an acute angle (°) between a straight line orthogonal to the axial line and the contour of the engagement portion, and θs represents an acute angle (°) between a straight line orthogonal to the axial line and the contour of the diameter-decreasing portion. In the aforementioned cross section, Hvo>Hvi is satisfied, where Hvo represents the Vickers hardness (Hv) of the seat packing at the midpoint of a first line segment, and Hvi represents the Vickers hardness (Hv) of the seat packing at the midpoint of a second line segment.

A spark plug is attached to a combustion apparatus of an internal combustion engine or the like, and is employed for ignition of an air-fuel mixture in a combustion chamber. Generally, a spark plug includes an insulator having an axial hole extending in the direction of an axial line; a center electrode inserted into a forward portion of the axial hole; a metallic shell provided around the insulator; and a ground electrode which is provided at the forward end of the metallic shell and which provides a gap in combination with the center electrode. The metallic shell has, on an inner wall thereof, an annular protrusion which projects inwardly in a radial direction and whose center coincides with the axial line. The insulator is inserted in the metallic shell and crimped thereto by means of a rear end portion of the metallic shell bended through application of a load to the rear end portion, such that an engagement portion provided at the forward end of the insulator seats on a diameter-decreasing portion (i.e., a rear side surface) of the protrusion. An annular plate packing is provided between the engagement portion and the diameter-decreasing portion for the purpose of improving the gas-tightness therebetween (see, for example, Japanese Patent Application Laid-Open (kokai) No. H10-289777).

Spark plug, and production method therefor


An IVR operative for voice communication with a telephone network and a data network and including a VoiceXML interpreter The VoiceXML interpreter being operative to provide a streaming audio output to the data network.

Telephones offer an effective means of enabling not only two-way conversations among individuals and groups of individuals, but also one-way broadcasts from a single host to many participants In a typical two-way conversation, two individuals may utilize a telephone network for a two-way conversation. The first individual may directly communicate voice over the telephone network to a second individual and vice versa
A more sophisticated method of two-way conversation is the telephone conference In a telephone conference, groups of individuals may coordinate a conferencing session in which bi-directional conversation is enabled through the use of mixing technologies Each of the members of the group typically connects to a central mixing, service that transmits the conversation to each member Telephone conferences enhance the ability of groups of individuals to communicate with each other.
A third popular utilization of the telephone is telephone broadcasts. As opposed to bi-directional two-way communication, telephone broadcasts provide a mechanism for a single host to communicate to multiple participants. Telephone broadcastilne, is particularly useful for distance learning, where students who cannot physically attend a lecture can hear the lecture broadcast over the telephone
Ogdon et al in U.S. Pat. No. 6,161,137 entitled "Method and system for providing a presentation on a network", describe a method of telephone and video broadcasting in which interactive and/or real-time presentations may be broadcast to multiple participants Each participant may have access to a data communication network eg the Internet, and/or a telephony network for voice communication In Ogdon et al the participants access a broadcast that originates from content servers, such as steaming web servers
Recently, with the advent of the Internet, another method for enabling multiple participants to converse has emerged Internet conference calls have become an increasinly popular and effective means of communication
There are many conference call services available through the Internet and telephone, such as Spiderphone.com, Inc Spiderphone's system provides advanced conferencing features, such as the ability to view a list of who is participating in the conference through a web browser and to send web pages, PowerPoint files or any other suitable types of file to conference participants.
One of the challenges facing developers of telephony applications is to determine a suitable application environment. VoiceXML has recently emerged as a standard in the field. VoiceXML is a markup language which enables VoiceXML web server platform developers to make information accessible to telephone users in the same manner that regular web servers provide information to web users

Broadcasting and conferencing in a distributed environment


Disclosed herein are a light emitting module and a lighting device that may be used for a display application or a lighting application. The light emitting module includes an electrode layer including a plurality of blocks that are insulated from each other by an electrode separating line; and one or more light emitting elements mounted on the electrode layer so as to be electrically connected to any one block of the blocks of the electrode layer and a neighboring block, respectively, wherein the blocks have another neighboring block disposed in a first direction and still another neighboring block disposed in a second direction, based on any one block of the blocks while having the electrode separating line formed to be bent more than once at a predetermined interval therebetween so that heat generated from the light emitting elements is emitted through the blocks.

Field
The present invention relates to a light emitting module and a lighting device, and more particularly, to a light emitting module and a lighting device that may be used for a display application or a lighting application.
Description of the Related Art
A light emitting diode (LED) refers to a kind of semiconductor device capable of implementing light having various colors by configuring a light emitting source by forming a PN diode of a compound semiconductor. The above-mentioned light emitting element has advantages that it has a long lifespan, it may be miniaturized and lightened, and it may be driven at a low voltage. In addition, since the above-mentioned LED has impact resistance and vibration resistance, does not need a preheating time and a complex driving, and is mounted in various forms on a substrate or a lead frame to be then packaged, it may be modularized in various applications and may be applied to a backlight unit, a variety of lighting devices, or the like.

Light emitting module and lighting device


A turbocharger for supercharging an internal combustion engine includes: a bearing housing which accommodates a bearing supporting a rotational shaft of the turbocharger; an oil discharge port for discharging lubricant oil stored in an internal space of the bearing housing; an air pocket formed in the oil discharge port or an oil discharge pipe connected to the oil discharge port; and a communication flow passage which brings the air pocket and the internal space into communication.

A known turbocharger drives a compressor coupled to a rotational shaft, and thereby supercharges an internal combustion engine. The rotational shaft of the turbocharger is supported rotatably by a bearing accommodated in a casing. The bearing supporting the rotational shaft is housed in a bearing housing, and the bearing housing is supplied with lubricant oil from an oil pan or the like, which lubricates each component.
The lubricant oil used for the bearing is returned to the oil pan, via an oil discharge pipe from an oil discharge port disposed below the bearing housing. Herein, depending on the operation state of the turbocharger, if the internal pressure of the bearing housing, from which the lubricant oil is discharged, becomes lower than the internal pressure of the oil pan, to which the lubricant oil is discharged, discharge of the lubricant oil to the oil pan may become hindered. In case discharge of the lubricant oil is hindered as described above, the amount of lubricant oil accumulated in the bearing housing increases, and the liquid surface of the lubricant oil rises. Then, lubricant oil may leak outside from the gap of the bearing housing (the bearing housing is configured to receive a rotational shaft, and thus has some gap in the vicinity of the rotational shaft in particular). If lubricant oil leaks to the compressor housing side housing the compressor in particular, the lubricant oil enters the combustion chamber of the internal combustion engine with intake air, which may produce white smoke or cause degraded oil substances to adhere and accumulate, causing a decrease in the performance of the internal combustion engine.
To solve the above problem, Patent Document 1 discloses providing an air guide pipe which brings a bearing housing from which lubricant oil is discharged and an oil pan to which lubricant oil is discharged into communication, to equalize the internal pressure of the bearing housing and the internal pressure of the oil pan and promote discharge of lubricant oil.

MITSUBISHI HEAVY INDUSTRIES ENGINE & TURBOCHARGER, LTD.


A zipper closure for a polymeric package includes a plurality of profile members on a first polymeric surface, where one and not more than one of these plurality of profile members is colored differently from the remaining profile members on the same polymeric surface. The differently colored profile members provide a visual reference for properly orienting the zipper closure to the polymeric packaging during manufacture.

Flexible polymeric packages may be used to hold a variety of products. Such products may be a variety of edible food products such as cheese, meat, crackers, sugar, powdered sugar, flour, salt, and baking soda, or non-food products such as laundry detergent, sand, medical supplies, and other products. Resealable packages are convenient because they can be closed and resealed to preserve and contain the enclosed contents. Resealable packages are also advantageous because they help prevent food products from spoiling and may be opened and closed multiple times.
Zipper closures are often employed to allow a polymeric package to be sealed and re-sealed. These closures are required to both seal the package tightly so that the contents do not leak or spoil, while at the same time allow the closure to be opened and closed without excessive force. To accomplish this, a zipper closure may be designed so that the seal formed by the zipper closure is more secure in the direction facing the contents of the package than the seal is in the direction facing away from the contents of the package. This arrangement allows the package to be opened by the user with a relatively small amount of effort, but also ensures that the package contents are adequately contained against accidental opening.
A problem arises, however, in the manufacture of polymeric packages where the zipper closure must have a certain orientation relative to the rest of the package. Zipper closures are typically provided on a production line as a rolled strip of material. The operator feeds this material into a machine that attaches the zipper closure strip to the rest of the polymeric package. The proper orientation of the zipper closure can be difficult to determine reliably. The features that cause the zipper closure to have a greater sealing force in one direction than the other are not such that they are readily perceptible to the operator. Because of this lack of easy perceptibility, the machine operator may misfeed the zipper closure strip into the manufacturing machinery, causing the resulting package to have sealing forces that are the opposite of that desired. Namely, a misfed zipper closure would result in a package where a greater force is required by the user to open the package and a lesser force seals the contents of the package. It is therefore desired that a zipper closure be configured so that the manufacturing machine operator can reliably and readily feed the zipper closure strip into the machinery in the correct orientation.


A multi-position valve for dispensing fluid and providing continuous fluid flow through the valve assembly. The multi-position valve assembly including an inlet port, an outlet port, and a return port leading to a fluid chamber. The multi-position valve assembly further includes a closure assembly for selectively directing fluid through the valve assembly. The closure assembly is operatively connected with some type of linear actuator, such as an air cylinder, for selectively moving the closure assembly and placing the multi-valve assembly between a closed position, a partially-open position, and a fully-open position. When in the closed position, the closure assembly directs fluid flow through a return flow path leading to the return port, while blocking the fluid flow to the outlet port. When in the partially-open position, the closure assembly directs fluid flow through both the return flow path and a first outlet flow path leading to the outlet port. When in the fully-open position, the closure assembly directs fluid flow through both a first and a second outlet flow path leading to the outlet port, while blocking fluid flow to the return port. The air cylinder is detachably connected to the valve to provide for repair and replacement.

Certain fluid dispensing processes require valve assemblies capable of providing both accurate control of the amount of fluid being dispensed and continuous flow of fluid through the valve assembly. One example of such a fluid dispensing process is the dispensing of dye. Continuous flow of dye and other similar fluids through a valve assembly is necessary to prevent fluid stagnation in the valve assembly during time intervals when there is a reduced amount of fluid being dispensed from the valve assembly. Fluid stagnation in the valve assembly can decrease the quality of the fluid being dispensed by allowing the fluid to harden, separate or settle.
Prior art valve assemblies used for dispensing dye maintain a continuous and constant flow through the valve assembly by providing a return or recirculation port. The return port allows fluid to be continuously pumped through the valve assembly so as to eliminate the occurrence of a reduced flow condition which can cause a hardening or settling of the fluid. At least a portion of the fluid entering valve assemblies of the prior art is always recirculated through the return port.
One important disadvantage of the above-discussed valve assemblies of the prior art is that the ability of these valve assemblies to rapidly dispense large volumes of fluid is reduced by the continuous circulation of fluid through the return port. Because a portion of fluid flow passing through the valve assembly is continuously recirculated through the return port, the fluid rate at which the valve assembly is capable of dispensing fluid is limited.
Another problem of prior art valve assemblies capable of recycling fluid is the inability to efficiently replace and repair individual components of the valve assembly.

Multi-position valve apparatus having a return port


A process is disclosed for producing an optical active alkoxybenzonitrile derivative in which process a benzonitrile derivative is subjected to condensation reaction with an optical active alcohol.. A process is also disclosed for producing an optical active alkoxy benzoic acid derivative in which process a benzonitrile derivative is subjected to condensation reaction with an optical active alcohol and the reaction product thus derived is hydrolyzed.. In these processes conversion of an optical active alcohol to tosylate or halide is not required and thus it is possible to produces producing an optical active alkoxybenzonitrile derivative and an optical active alkoxy benzoic acid derivative in a simple and inexpensive manner.

1. Field of the Invention
This invention relates to a process for the production of optical active alkoxybenzonitrile derivatives and optical active alkoxybenzoic acid derivatives which have utility as medicines, materials for liquid crystal or intermediates thereof.
2. Prior Art
It has been known that an optical active alkoxybenzonitrile having an optical active alkoxy group bonded through an oxygen atom to benzonitrile at the 4 position finds extensive use for materials of liquid crystal and medicines. However, there has not been developed a method for synthesizing such optical active compounds which can be utilized universally in a simple manner.
Williamson Method is known for synthesis of compounds having ether bonds as well as alkoxybenzonitrile in which method alkoxide is reacted with alkylhalide or alkyltosylate. However, the synthesis of an optical active alkoxybenzonitrile using this method accompanies a problem that an optical active alkylhalide and alkyltosylate used as a starting material can not be mass-produce in an inexpensive manner and particularly the former is susceptible to reduced optical purity. Furthermore, this synthesis method involves another problem that if an optical active secondary alkylhalide or alkyltosylate is used as a starting material the resulting compound is attached with a risk of reduction in optical purity depending upon kinds of the secondary alkyl groups and the reaction conditions because the reaction of Williamson method progresses in S.sub.N 2 reaction system and in this connection the asymmetric center becomes the reaction center.
On the other hand, Williamson Method is employed also for synthesizing an optical active alkoxy benzoic acid having an alkyl group bonding through an oxygen atom to the 4-position of benzoic acid by reacting 4-hydroxybenzoic acid or the ester thereof and an optical active alkylhalide or alkyltosylate under basic conditions. For instance, in a publication entitled "Liquid Crystals" 16.299 (1994), there is reported a method for synthesizing an optical active alkoxy benzoic acid by reacting tosylate derived from a variety of optical active secondary alcohol with methyl 4-hydroxy benzoic acid and hydrolyzing the resulting methyl alkoxybenzoate. However, the products derived from the method also encounter reduction of optical purity and involve with a problem that the preparation of an optical active alkyltosylate used as a starting material requires much expenditure.

Process for producing an optically active compound


A media player and a method for operating a media player are disclosed. A media program is able to substantially immediately begin playing after a media play selection has been made. Through intelligent operation, the media program is able to start playing even before the media program has been substantially or completely loaded from disk storage into semiconductor memory (i.e., cache memory). Additionally, the media program can be loaded into semiconductor memory through use of a background process without disturbing the playing of the media program. Further, if desired, the disk storage is able to be aggressively “powered off” when not being accessed, thereby enhancing battery life when being battery-powered.

1. Field of the Invention
The present invention relates to media devices and, more particularly, to playing of media on media devices.
2. Description of the Related Art
Media players are becoming more popular these days. Of particular popularity are portable media players such as MP3 players or DVD players. Media players operate to play media items for their user that are stored within the media players. The media items are most commonly audio items (e.g., songs) but could also be video items (e.g., DVDs). Typically, an MP3 player will store various audio items internally on a storage disk. When the user makes a selection to play one of the stored audio items, the audio item must first be loaded into semiconductor memory (i.e., Random-Access Memory) before the audio item begins to be played. Unfortunately, the delay in reading the rather large file for the audio item is unsatisfactory to users who are anxious to hear the audio item they have already selected to be played. Thus, there is a need for improved techniques for media players to play media items.

Media player with instant play capability


A cable for monitoring a tubular structure. The cable comprising a fiber optic bundle arranged for simultaneously sensing a plurality of parameters along a length of the tubular structure that the cable is interfaced with.

In the oil and gas industry there are certain installations in which various connections and conduits are necessary. In the subsea domain, for example, subsea hydrocarbon production systems using sea surface facilities of any sort require petroleum fluids to flow from the seabed to the surface through various connections and conduits. Such connections and conduits, also referred to herein as tubular structures or pipe structures, may include any combination of rigid, semi-flexible or flexible risers, flowlines, flexible pipes and umbilicals.
Due to the various forces acting on these tubular structures, for example as the sea surface rises and falls with waves and tides and the facilities are moved vertically, laterally and rotationally, such structures are subject to structural failure due to fatigue. Additional damage may occur in the form of corrosion, erosion, or blockage which can be caused by the interior deposition of one or more of the flow components (such as wax, hydrates, asphaltenes, scales, etc.).
In the surface operating domain, whether onshore or offshore for example, pipe structures may experience structural failure due to periodic installation and disassembly, or jarring from high pressure fluid flow.
Accordingly, there is a need to monitor the condition of such pipe structures for effective operation so that remedial measures may be taken before such structural failure occurs.
WO2009087371 discloses a monitoring system for use in floating production installations such as those used in offshore oil and gas production. The disclosure teaches a continuous optical fiber distributed sensor installed as part of a flexible (or partially flexible) pipeline, wherein the sensor provides a distributed measurement of temperature and/or strain.


The invention is an amusement device comprising a control arm generally in the form of a stick and a rolling toy in the form of a wheel. The stick is used to move the wheel in various directions. The inventive portion of the device lies in a series of grooves in the wheel and a corresponding series of grooves in the bottom, or blade, of the control arm. The use of the grooves enables one to efficiently and quickly control the speed and movement of the wheel.

1. Field of the Invention
The invention relates to the field of wheel and stick type toys where a stick resembling, say a hockey stick, is used to propel a wheeled device. More particularly, the stick portion and the wheel portion of the amusement device come with notched or grooved surfaces in each in order to more easily control the speed and direction of the wheel.
2. Description of the Prior Art
There are amusement devices that use a stick or a blade in order to control a device in the form of a tire or a ball that is manipulated by the stick. However, there are none that applicant is aware of that have a series of grooves cross wise across both the wheel and the stick in order for the two to work together more efficiently.


A method of producing glucosamine hydrochloride from chitin by grinding the chitin to a very fine size and digestion with concentrated hydrochloric acid. The glucosamine hydrochloride is decolorized with activated charcoal, washed with ethanol and assayed by pH titration with a base.

The present invention relates to methods of preparing glucosamine hydrochloride from chitin or chitinaceous material.
Glucosamine hydrochloride (GHCl) is an amino sugar which is incorporated into the structure of body tissues. It comprises about 80% glucosamine, a compound helpful in maintaining joint health in individuals suffering from degenerative conditions such as arthritis. When orally ingested, it is selectively taken up by joint tissues to exert beneficial effects. Glucosamine may also have other therapeutic effects such as antiviral, anti-cancer, anti-aging, immune boosting or cholesterol lowering activity.
GHCl may be obtained by hydrolysis and deacetylation of chitin, a polymer of N-acetyl glucosamine or by the hydrolysis of chitosan with hydrochloric acid. It is desirable if such processes are efficient in both time and cost, and produce high-purity product with good yield. As well, it would be advantageous to provide a quick, simple and accurate method of assaying GHCl to be used in conjunction with a method of producing GHCl.
The present invention is directed to a method of producing glucosamine hydrochloride from chitin or chitinaceous material, said method comprising the steps of: (a) grinding the chitin or chitinaceous material to less than about xe2x88x9220 mesh; (b) digesting the chitin with prewarmed, concentrated HCl, by mixing the chitin with the HCl, and heating to about 95xc2x0 C. to produce a slurry; (c) cooling the slurry to room temperature and filtering the precipitate; (d) dissolving the precipitate in water and with activated charcoal at room temperature; (e) filtering the solution and discarding the solids; (f) evaporating the solution to recover GHCl solids; (g) washing the solids with ethanol and filtering the solids/ethanol mixture to separately recover both the solids and the ethanol; and (h) drying the solids.
In another aspect, the invention may comprise a method of producing glucosamine hydrochloride from chitin or chitinaceous material, said method comprising the steps of: (a) hydrolysing the chitin in hydrochloric acid; (b) precipitating the glucosamine hydrochloride; (c) separating the precipitated glucosamine hydrochloride and redissolving it in water; and (d) assaying for GHCl by pHmetric titration.
In another aspect, the invention may comprise a method of assaying GHCl in solution comprising the step of measuring the amount of base necessary to raise the pH of the solution to a pre-determined value and corresponding the amount of base to an amount of GHCl. The base may be sodium hydroxide.

Preparation of glucosamine hydrochloride


A variable ratio power transmission in the form of a gear box is described, in which the gear ratio of the input and output shafts can be varied continuously between a maximum and a minimum. The power transmission comprises a first bevel wheel (40) rotatably mounted in connection with a U-shaped member (32) on a first axis (34). The U-shaped member (32) is pivotable about the axis (34) and is coupled to the bevel wheel (44) via a sprag clutch (36). Hence, pivoting movement of the U-shaped member (32) in a first direction about the axis (34) results in a torque being applied via the sprag clutch (36) to the bevel wheel (44), whereas pivoting movements of the U-shaped member (32) in the opposite direction has no effect via the sprag clutch (36) on rotation of the bevel wheel (44). A second bevel wheel (50) is also coupled to the U-shaped member (32) via a second sprag clutch (38) which operates in the reverse direction to that of the first sprag clutch (36). An actuating member (52) is mechanically coupled to the U-shaped member (32) via a rotational coupling (63). Rotation of actuating member (52) about a second axis (60) produces an orbital motion of the rotational coupling (63) which in turn produces an oscillating pivoting movement of the U-shaped member (32) about the first axis (34). By varying the radius of orbit of the rotational coupling (63) the angle through which the U-shaped member (32) pivots can be varied, so that an output torque transmitted via the bevel wheels (44, 50) can be varied independently of an input torque applied to the actuating member (52).

Fundamentally the function of a gear box is to change the speed from that of an input shaft to that of an output shaft whilst allowing the transmission of torque between the shafts. Typically gear boxes comprise several gear clusters or gear trains that can be coupled to each other in various configurations to give selected gear ratios of the input and output shafts.
One of the disadvantages of most conventional gear boxes is that the gear ratios that can be selected are fixed at certain preselected ratios that may or may not be optimum to derive maximum torque from the engine or other drive source. In motor vehicles it is desirable to maintain the internal combustion engine at an optimum speed, both from the point of view of fuel economy and to obtain maximum torque. Likewise, it is preferable to maintain the speed of certain types of electric motors within a prescribed RPM range in order to develop maximum torque efficiency. However this is not possible with a conventional gearbox and a compromise is made using preselected gear ratios.
Another disadvantage of most conventional gear boxes is that they are generally bulky and occupy a considerable volume in the drive train. A still further disadvantage of most conventional gear boxes is that the load must be disconnected when changing gears and when starting the engine or motor driving the load.
The present invention was developed with a view to providing a variable ratio power transmission that is able to overcome one or more of the above-noted disadvantages of the prior art.


A radio frequency bridge, useful for measuring complex values of an unknown impedance or associated complex reflection coefficient and VSWR value, which comprises an rf source, a novel asymmetrical bridge, a measuring device (comprising two logarithmic amplifiers, a difference amplifier and a phase detector), a computing device and a display or interface device. The complex impedance may be any two terminals of a general N-port network not to exclude an antenna with or without feed-line. The invention is more accurate than prior art when measuring complex impedance values having magnitudes from approximately five ohms to an upper value limited only by the dynamic range of the logarithmic amplifiers, normally greater than 4000 ohms. It has the great advantage of maintaining constant measuring accuracy over a wide measuring range and can be designed to operate over very wide bandwidths.

1. Field of Invention
This invention relates to electronic bridge networks as used for the measuring of complex electrical impedance values comprising resistive (real) and reactive (imaginary) components.
2. Description of Prior Art
FIG. 1 illustrates a bridge configuration that is most commonly used in low cost radio frequency (rf) bridge based measuring instruments. Instruments of this type determine the complex electrical impedance magnitude (|ZX|) and the associated reflection coefficient magnitude (|xcfx81|) for the complex impedance value being measured. Magnitude values for the real (RX) and unsigned reactive (XX) components as well as Voltage Standing Wave Ratio (VSWR), as taught by Paul""s seminal U.S. Pat. No. 2,323,076 (1940), are then derived.
Referring to FIG. 1, Vsource is an alternating current (a.c.) voltage source at a frequency of interest for the measurement. ZX is a complex impedance whose value is unknown and having, in general, both resistive (real) and reactive (imaginary) components. ZX may be any two terminals of a general N-port network, not to exclude an antenna with or without feed-line. RO may, in general, be any value but is normally selected to be equal to a standard characteristic impedance, typically 50 or 75 ohms resistive. Voltages |VD|, and |V1| are indicated by measuring devices M1 and M2 respectively, simple a.c. voltmeters with magnitude determination only. Also, measuring devices M3 and M4, simple a.c. voltmeters with magnitude determination only, indicate voltages |VBxe2x88x92V2| and |V2| respectively. It follows that a computing device (not illustrated) could utilize the four measured values of FIG. 1 to calculate the following useful quantities:
Complex Impedance Magnitude=|ZX|=RO|V2|/(|VBxe2x88x92V2|),
Voltage Across the Horizontal Bridge Diagonal=|VD|=|V2xe2x88x92V1|,
Reflection Coefficient Magnitude=|xcfx81|=|(ZXxe2x88x92RO)/(ZX+RO)|=|VD|/|V1|,
Voltage Standing Wave Ratio (VSWR)=(1+|xcfx81|)/(1xe2x88x92|xcfx81|),
Resistive Component of ZX=RX={(|ZX|2+RO2)(1xe2x88x92|xcfx81|2)}/ {f2RO(1+|xcfx81|2)} and
Unsigned Reactive Component of ZX=XX=(|ZX|2xe2x88x92RX2)xc2xd
where |ZX|, RO, |xcfx81|, VSWR, RX, and XX are real unsigned numbers.
BACKGROUND-LIMITATIONS OF THE PRIOR ART
Measuring accuracy and bandwidth for the circuit of FIG. 1 are primarily limited by measuring devices M1 through M4, the accuracy and purity of the resistive bridge elements and stray inductances, capacitances and resistances associated with the physical embodiment of FIG. 1. The measuring devices depicted in FIG. 1 as M1 through M4 typically comprise rf detection (rectification) diodes, in series with an appropriately valued capacitor, connected between the measurement nodes as illustrated in FIG. 2 and contribute to measuring error in several ways.
In FIG. 2, voltages |VD|, |V1|, |VBxe2x88x92V2| and |V2| are developed across four capacitors, C1 through C4, respectively, after being detected by diodes D1 through D4, respectively. Not shown in FIG. 2, the detected voltages may be indicated on simple direct current (d.c.) voltmeters or converted to a digital format with an Analog to Digital Converter (ADC) for processing. The best embodiment of rf diodes D1 through D4 is based on zero bias schottky or back (tunnel) diodes, special diodes perfected for use as small signal radio frequency detectors. Even the best embodiment for the rf diodes will exhibit detection inaccuracies due to non-linear diode forward conduction characteristics, especially at small voltage levels normally experienced across the bridge horizontal diagonal (|VD|=|V2xe2x88x92V1|). When detecting small voltage levels, the non-linear diode characteristics cause dead zones where no useful voltage is detected thus causing measurement drop-outs. Variations of the diode junction voltages, induced by ambient temperature fluctuations, will further add to inaccuracies in detected voltages. Forward d.c. biasing of the diodes as well as compensation for the above cited errors, in the computing device for determining |ZX|, |xcfx81|, VSWR, RX or unsigned XX, provides some improvement but accuracy is still severely limited for low VSWR measurements and for measuring of |ZX| values near RO.
Referring again to FIG. 2, a second measuring limitation of the prior art is the loading effect and resulting measurement distortion and accuracy degradation caused by the measuring device being connected in parallel with the various bridge sides. This alters the effective value of the bridge resistances, RO, and even the value of the impedance being measured, ZX, in a nonlinear manner difficult to characterize for compensation purposes.
A further limitation of the prior art is the inability to determine a sign for the derived reactive component of the complex impedance being measured. Attempts have been made in prior art to overcome this shortfall by detecting a relative phase difference between (VBxe2x88x92V2) and V2 as shown in FIG. 2. Unfortunately, connecting a phase detector across the impedance being measured produces further unwanted loading and attendant measurement distortion and accuracy degradation.
Prior art measuring accuracy of |ZX| values, due to the above limitations, is typically xc2x110% to xc2x135% for VSWRs of 2:1 or less with nominal measuring ranges of 5 to 1000 ohms. Multiple instruments are required to cover the 1 to 500 MHz frequency range and coverage above 500 MHz is not generally available. A typical ambient operating temperature range is 10 to 35 degrees Centigrade.
BACKGROUND-OBJECT AND ADVANTAGES
Accordingly, several objects and advantages of the new invention are:
(a) to provide a low-cost complex rf impedance measuring capability with improved accuracy compared to prior art,
(b) to provide a low-cost complex rf impedance measuring capability with increased bandwidth compared to prior art,
(c) to provide a low-cost complex rf impedance measuring capability with increased measuring range compared to prior art,
(d) to provide an rf bridge in which there is negligible loading of the unknown impedance being measured by the measuring device,
(e) to provide an rf bridge capability that is linear in response from low to high values of measured quantities without the dead zones associated with attempted detection of voltages below diode thresholds commonly found in prior art,
(f) to increase rf bridge measuring accuracy, compared to prior art, over wider ambient temperature variations,
(g) to provide for nullification of measuring device capacitive loading effects on the rf bridge and
(h) to provide an rf bridge capability with constant measuring accuracy over a wide measuring range.
Further objects and advantages of the invention will become apparent from a consideration of the drawings and ensuing description.
My invention, a radio frequency bridge, useful for measuring complex values of an unknown impedance or associated complex reflection coefficient and VSWR value, comprises an rf source, a novel asymmetrical bridge, a measuring device (comprising two logarithmic amplifiers, a difference amplifier and a phase detector), a computing device and a display or interface device. The complex impedance may be any two terminals of a general N-port network not to exclude an antenna with or without feed-line. The invention is more accurate than prior art when measuring complex impedance values having magnitudes from approximately five ohms to an upper value limited only by the dynamic range of the logarithmic amplifiers, normally greater than 4000 ohms.
Referring again to FIG. 3, the invention employs a novel asymmetrical bridge with a measuring device, improved over prior art, to increase accuracy, bandwidth and measuring range. It has the great advantage of maintaining constant measuring accuracy over a wide measuring range. The bridge is a wide band design for complex impedance measuring, implemented in a manner to minimize bridge associated stray inductances, capacitances and resistances. The bridge may be frequency compensated, over a wide range of frequencies, to nullify the effects of the measuring device""s logarithmic amplifier input capacitance.
A computing device can provide a complex value (magnitude and phase angle) as well as real values for the resistive and signed reactive component for the complex impedance being measured. A complex value for the associated reflection coefficient and a real VSWR value can also be calculated as well as other desired quantities. All computed quantities are either displayed on a display device or interfaced for subsequent processing or display.

Wide-band ratiometric radio frequency bridge


A laser transmitter device includes a laser light source, first and second optical elements, and first and second detection elements. The first optical element has a first optical characteristic with wavelength dependency, whose light transmissivity or reflectivity shows a monotone increase or decrease within a wavelength range over channels. The second optical element has a second optical characteristic with wavelength dependency, whose transmissivity or reflectivity changes in a cycle corresponding to intervals of the channels or two times the intervals. The first detection element detects an intensity of light emitted from the laser light source and coming via the first optical element, and generates a first electric signal reflecting the first optical characteristic. The second detection element detects an intensity of light emitted from the laser light source and coming via the second optical element, and generates a second electric signal reflecting the second optical characteristic.

1. Field of the Invention
The present invention relates to a laser transmitter device, and more particularly to a technique for locking the wavelength of light emitted from a laser light source for optical communication at a predetermined wavelength.
2. Description of the Related Art
As a method of increasing the capacity of optical communication, a DWDM (Dense Wavelength-Division Multiplexing) method is known. Since DWDM optical communication has advantages in that, e.g., it can effectively utilize properties of optical fibers in terms of broad band and large capacity, it is considered as a promising method, and research and development thereof proceed. Light sources used in DWDM optical communication are required to output laser light with a plurality of different wavelengths. The wavelengths have to be set at wavelengths decided for respective channels based on a recommendation from ITU-T (International Telecommunication Union—Telecommunication Standardization Section).
For example, in the case of a conventional DWDM optical communication system, which performs wavelength multiplex of 32 wavelengths, it is provided with 32 semiconductor lasers for oscillating laser light with wavelengths different from each other, or 32 wavelength-tunable lasers, which can change their oscillation wavelengths by adjusting the laser temperature or driving current. DFB (Distributed Feedback) lasers or DBR (Distributed Bragg Reflector) lasers are used as the wavelength-tunable lasers.
Particularly, where wavelength-tunable lasers are used, it is possible to reduce the number of kinds of semiconductor lasers used as ordinary-use light sources and preparatory light sources in a light source system for DWDM optical communication. For example, in a DWDM optical communication system with 32 wavelengths, if one semiconductor laser is used for one wavelength, it is necessary to use 64 semiconductor lasers in total, consisting of 32 ordinary-use light sources and 32 preparatory light sources. On the other hand, if wavelength-tunable semiconductor lasers each being capable of oscillating 8 wavelengths are used, only 4 kinds of lasers suffice the preparatory light sources.
Each of these semiconductor lasers has a diffraction grating whose pitch or the like is designed to oscillate single mode laser light with a predetermined wavelength in a steady state, but it is not always locked at the predetermined wavelength. For example, at the startup, the semiconductor laser normally does not oscillate at the predetermined wavelength. Even in the steady state, there are certain fluctuations. Accordingly, any wavelength-tunable laser capable of oscillating a plurality of wavelengths suffers the phenomena described above, and thus it is necessary to stabilize it at an aimed one of predetermined wavelengths.
As described above, in DWDM optical communication, the oscillation wavelength of each semiconductor laser has to be set at a predetermined channel wavelength with high accuracy. Since the oscillation wavelength of each semiconductor laser varies with time, a wavelength monitor function is added to keep the oscillation wavelength constant.
FIG. 32 is a view showing the internal structure of a CW (continuous-wave) laser transmitter device (module) with a conventional wavelength monitor function built therein. This device 10 includes a DFB laser (light source) 11, an FP (Fabry-Perot) filter 16, monitor PDs (Photo Diode) 17 and 34, and so forth. These members are mounted, through a carrier 18, on a Peltier element 19 for temperature control. Light emitted forward from the DFB laser 11 focuses on an optical fiber 14 through lenses 12 and 13.
Light emitted backward from the DFB laser 11 in the reverse direction relative to the optical fiber 14 passes through a lens 15 and is divided into two parts by a beam splitter 32. One of the light outputs divided by the beam splitter 32 passes through an FP filter 16 and is incident on a monitor PD 17, which outputs an electric current in accordance with reception light intensity. The FP filter 16 is designed to have an FSR (Free Spectral Range) equal to the channel intervals in DWDM optical communication. The other of the light outputs divided by the beam splitter 32 is directly incident on a monitor PD 34.
For example, the DFB laser (wavelength-tunable laser) 11 is assigned to 4 channels ch1 to ch4 with wavelength intervals of 100 GHz (about 0.8 nm) based on an ITU-T recommendation. The DFB laser 11 oscillates light with a wavelength corresponding to one of 4 channels, while its temperature being controlled by the Peltier element 19.
The output current of the monitor PD 17 is used by a controller (wavelength lock control circuit (AFC)) 21 to adjust the temperature of the Peltier element 19, so as to control the oscillation wavelength of the DFB laser 11 to be constant. On the other hand, the output current of the monitor PD 34 is used by a controller (output control circuit (APC)) 36 to adjust the current fed to the DFB laser 11, so as to control the intensity of the optical output of the DFB laser 11 to be constant. Each of the controllers 21 and 36 is formed of, e.g., an MPU (Microprocessor Unit) for control.
FIG. 33 is a graph showing the wavelength dependency of the output current Ipd of the monitor PD 17 in the laser transmitter device shown in FIG. 32. In FIG. 33, the horizontal axis denotes the DFB laser oscillation wavelength, and the vertical axis denotes the monitor output current. The output current Ipd periodically changes with the wavelength, in the same cycle as the channel intervals, because it reflects the transmission characteristic of the FP filter 16. In this conventional example, when the output current Ipd takes on a target value X0, the oscillation wavelength coincides with one of the channel wavelengths.
FIG. 34 is a view for explaining a wavelength control operation in the laser transmitter device shown in FIG. 32. In this wavelength control operation, the temperature of the DFB laser 11 is controlled by the Peltier element 19 so that the output current Ipd takes on the target value X0. The controller 21 receives the output current Ipd, and, when the output current Ipd is larger than the target value X0 (a point Ja in FIG. 34), it controls the oscillation wavelength to be longer. Conversely, when the output current Ipd is smaller than the target value X0 (a point Jb in FIG. 34), it controls the oscillation wavelength to be shorter. As a consequence, the output current Ipd is always kept at the target value X0, i.e., the oscillation wavelength of the DFB laser 11 is stabilized at an aimed channel wavelength.
FIG. 35 is a graph showing the wavelength dependency of the output current Ipd of the monitor PD 17, in a case where the increase and decrease in a control parameter for the oscillation wavelength (such as temperature) is controlled in reverse between the even-numbered channels and odd-numbered channels, so that the size of the channel intervals can be halved. In this case, for example, the DFB laser 11 is assigned to 8 channels ch0 to ch7 with wavelength intervals of 50 GHz (about 0.4 nm) based on an ITU-T recommendation. The FP filter 16 is designed to have an FSR equal to two times the channel intervals in DWDM optical communication.
In the control method shown in the FIG. 35, when the oscillation wavelength of the DFB laser 11 is tuned to (stabilized at) an even-numbered channel, the controller 21 performs a wavelength control operation, as follows. Specifically, when the DFB laser 11 starts up, the controller 21 receives an instruction to tune the wavelength at the even-numbered channel. If the output current Ipd is larger than the target value X0, the controller 21 controls the oscillation wavelength to be longer. If the output current Ipd is smaller than the target value X0, the controller 21 controls the oscillation wavelength to be shorter.
In the control method shown in the FIG. 35, when the oscillation wavelength of the DFB laser 11 is tuned to (stabilized at) an odd-numbered channel, the controller 21 performs a wavelength control operation in reverse to that described above, as follows. Specifically, when the DFB laser 11 starts up, the controller 21 receives an instruction to tune the wavelength at the odd-numbered channel. If the output current Ipd is larger than the target value X0, the controller 21 controls the oscillation wavelength to be shorter. If the output current Ipd is smaller than the target value X0, the controller 21 controls the oscillation wavelength to be longer.
However, in either case of using the control method shown in FIG. 33 or 35, when the DFB laser 11 starts up, it does not necessarily oscillate at a predetermined wavelength. Besides, the controller 21 controls the oscillation wavelength on the basis only of comparison in the magnitude relationship between the monitor current Ipd and target value X0. Furthermore, the transmission characteristic of the FP filter (such as an etalon) 16 relative to the wavelength shifts with the temperature change of the filter 16. As a consequence, the control of tuning the oscillation wavelength of the DFB laser 11 to a predetermined wavelength suffers problems described later.
Under the circumstances, there are demands for a laser transmitter device, which can reliably tune the oscillation wavelength of a laser light source for optical communication to a predetermined wavelength.


Disclosed is a hydraulic circuit for a pipe layer, in which the generation of hydraulic shock in equipment is prevented when an operating device or a moving device is finely operated during combined work in a pipe-laying operation mode. The hydraulic circuit for a pipe layer according to the present invention comprises a main control valve having a straight traveling valve and controls a discharged flow of a hydraulic pump by a negative flow control system, wherein the hydraulic circuit comprises: an unloading valve which linearly controls the closing of a passage of a flow that flows to a hydraulic tank from a center bypass passage of a hydraulic pump when an operating device or a moving device is finely operated during combined work; a pilot valve which is linked with a straight traveling valve, and supplies signal pressure corresponding to an operation signal of the moving device or the operating device to the unloading valve; and an operation mode switch valve which is switched during the combined work, and respectively supplies pilot signal pressure to the straight traveling valve, the pilot valve, and a valve spool which is installed on a downstream side of the center bypass passage of the hydraulic pump.

The above negative flow control system refers to a system in which when a pilot signal pressure generated from a pilot signal pressure-generating means installed at the downstream side of a center bypass path is high at the upstream side of the center bypass path, a discharge flow rate of a variable displacement hydraulic pump is controlled to be decreased whereas when the pilot signal pressure generated from a pilot signal pressure-generating means is low at the upstream side of the center bypass path, the discharge flow rate of the variable displacement hydraulic pump is controlled to be increased.
A conventional hydraulic circuit for a pipe layer in accordance with the prior art as shown in FIG. 1 includes:
first and second variable displacement hydraulic pumps (hereinafter, referred to as "first and second hydraulic pumps") P1 and P2 and a pilot pump P3, which are configured to be connected to an engine 1;
one or more first control valves 3, 4 and 5 installed in a center bypass path (cbp) 2 of the first hydraulic pump P1 and configured to be shifted to control a flow direction and a flow rate of a hydraulic fluid that is supplied to a left traveling motor and a first work apparatus (or a swing motor, a winch motor, or the like);
one or more second control valves 7 and 8 installed in a center bypass path 6 of the second hydraulic pump P2 and configured to be shifted to control a flow direction and a flow rate of a hydraulic fluid that is supplied to a right traveling motor and a second work apparatus (or a boom cylinder or the like);
a straight traveling valve 9 installed at the upstream side of the center bypass path 6 of the second hydraulic pump P2, and configured to be shifted by a pilot signal pressure Pi from the pilot pump P3 to cause the hydraulic fluid discharged from the first hydraulic pump P1 to be distributed and supplied to the control valves 3 and 7 for the left and right traveling motors and to cause the hydraulic fluid discharged from the second hydraulic pump P2 to be distributed and supplied to the control valves 4, 5 and 8 for the first and second work apparatuses to thereby prevent one-way traveling when a combined operation mode for simultaneously driving the work apparatus and a traveling apparatus is selected;
an unloading valve 10 configured to be shifted by the pilot signal pressure that shifts the straight traveling valve 9 so that when the unloading valve is opened, the straight traveling valve 9 is shifted to prevent an overload from occurring in the center bypass paths 2 and 6 of the first and second hydraulic pumps P1 and P2;
one or more pilot valves 10 and 11 configured to release an unloading function of the unloading valve 10 when any one of the control valves 4, 5 and 8 for the work apparatuses and the control valves 3 and 7 for the traveling motors is driven in a shift mode in which the straight traveling valve 9 is shifted;
an operation mode switching valve 13 configured to be shifted in response to an electrical signal applied thereto from the outside when a combined operation mode for simultaneously driving the work apparatus and the traveling apparatus is selected to cause the pilot signal pressure from the pilot pump P3 to be supplied to the straight traveling valve 9 and the pilot valves 11 and 12, respectively; and
a first shuttle valve 14 configured to control a swivel angle of a swash plate (a) of the first hydraulic pump P1 by a pressure selected from among a pilot signal pressure Pi1 supplied to the pilot valve 12 and a pressure at the downstream side of the center bypass path 2 of the first hydraulic pump P1, and a second shuttle valve 15 configured to control a swivel angle of a swash plate (b) of the second hydraulic pump P2 by a pressure selected from among a pilot signal pressure Pi2 supplied to the pilot valve 12 and a pressure at the downstream side of the center bypass path 6 of the second hydraulic pump P2.
In the drawings, a non-explained reference numeral 24 denotes cbp spools respectively installed at downstream sides of the center bypass paths 2 and 6, and a non-explained reference numeral 16 denotes a main control valve (MCV).
The operation of a hydraulic circuit for a pipe layer to which the negative flow control system as constructed above will be described hereinafter with reference to the accompanying drawings.
The hydraulic fluids discharged from the first hydraulic pump P1 and the second hydraulic pump P2 are dividedly supplied to the main control valve (MCV) 16 and the unloading valve 10 via the center bypass paths 2 and 6, respectively. The unloading valve 10 is not used in an excavation operation mode of the equipment, but is used when a pipe-laying operation (PL) mode signal is activated.
In the pipe-laying operation mode, when the operation mode switching valve 13 is shifted, the straight traveling valve 9 is shifted to a state shown in FIG. 1 by the pilot signal pressure supplied to a port Ts (referring to a signal pressure port formed at the main control valve 16 to shift the straight traveling valve 9) from the pilot pump P3
As a result, a part of the hydraulic fluid discharged from the first hydraulic pump P1 is supplied to the control valve 3 via the center bypass path 2 to drive the left traveling motor. At the same time, a part of the hydraulic fluid discharged from the first hydraulic pump P1 is supplied to the control valve 7 through the shifted straight traveling valve 9 via the center bypass path 2 and a flow path 25 to drive the right traveling motor.
On the other hand, a part of the hydraulic fluid discharged from the second hydraulic pump P2 is supplied to the control valves 4 and 5 via the center bypass path 6, the straight traveling valve 9, and the flow path 26 to drive the first work apparatus (or a swing motor or the like). At the same time, a part of the hydraulic fluid discharged from the second hydraulic pump P2 is supplied to the control valve 8 via the center bypass path 6 and the flow path 27 to drive the second work apparatus (or a boom cylinder or the like).
As described above, when the operation mode switching valve 13 manipulated by an operator during the pipe-laying operation, the straight traveling valve 9 is shifted by the pilot signal pressure supplied from the pilot pump P3 to cause the hydraulic fluid discharged from the first hydraulic pump P1 to be distributed and supplied to the left and right traveling motors and the hydraulic fluid discharged from the second hydraulic pump P2 to be distributed and supplied to the work apparatus (or a boom cylinder or the like).
Therefore, in the pipe-laying operation mode, when the work apparatus and the traveling apparatus are driven simultaneously, the traveling speed can be prevented from being changed abruptly due to a difference in a load occurring in the work apparatus or the traveling apparatus
In the meantime, a signal pressure (40 kg/cm2) is applied to the unloading valve 10 from the pilot valve 12 to open the unloading valve 10 by the signal pressure supplied to the pilot valve 12 through a signal line 17 connected to the port Ts. At the same time, the signal pressures of the outlet ports A1 and A2 of the pilot valve 12 are supplied to the ports Pi1 and Pi2 of the via the signal lines 18 and 19 after passing through the first and second shuttle valves 14 and 15 installed at the downstream side of the pilot valve 12, respectively. As a result, the swivel angles of the swash plates (a and b) of the first and second hydraulic pumps P1 and P2 is controlled by the regulators R1 and R2 to minimize the discharge flow rate of the first and second hydraulic pumps P1 and P2.
In addition, the hydraulic fluid of signal lines 20 and 21 discharged from the main control valve 16 is set to be introduced into the first and second shuttle valves 14 and 15 to minimize the discharge flow rate of the first and second hydraulic pumps P1 and P2.
This state is defined as a neutral state of the pipe-laying operation mode.
In this case, in the neutral state of the pipe-laying operation mode, when signals (i.e., a manipulation signal by an attachment control joystick and a manipulation signal by a travel control pedal) of attachment switching devices (for example, a hoist winch (HW), a swing (SW), a boom (BM) and a circuit in which the ports PS1 and PS2 are indicated) 30 and 40 is activated, the pilot valve 12 is shifted with Pi1 by the hydraulic fluid (having a pressure of 40 k/cm2 or so) applied at the port PS2 (or PS1) of the attachment switching device 40. At the same time, the valve spools (or cbp spools) 24 of the main control valve 16 are shifted through the signal line 20.
When the valve spools 24 are shifted, respectively, the hydraulic fluid introduced into the main control valve 16 from the first hydraulic pump P1 and supplied to the hydraulic tank T, and the hydraulic fluid introduced into the main control valve 16 from the second hydraulic pump P2 and supplied to the hydraulic tank T are blocked, respectively.
When the pilot valve 12 is shifted, the hydraulic fluid of the port Ts is blocked at the pilot valve 12, and the hydraulic fluid of the port Pil disappears while flowing along a tank line 22 from the port A1 by the shifted pilot valve 12. In this case, the pressure applied to the first shuttle valve 14 at the downstream side of the port A1 also disappears simultaneously. As a result, when the pressure of the signal line 19 is reduced to cause the pressure of the port Pil of the first hydraulic pump P1 to be reduced to maximally control the discharge flow rate of the first hydraulic pump P1. At the same time, when the valve spools 24 of the main control valve 16 are shifted, the hydraulic fluid of a signal line 23 of the main control valve 16 is blocked and thus the pressure of the port Pil of the first hydraulic pump P1 is reduced via the first shuttle valve 14 to maximally control the discharge flow rate of the first hydraulic pump P1. At this time, the hydraulic fluid flowing to the hydraulic tank T from the port P1 of the unloading valve 10 is blocked.
On the other hand, when a signal of the attachment switching device (for example, BM or SW) 30 is activated, the attachment switching device 30 is connected to the Pi2 of the pilot valve 12 to shift the pilot valve 12 to the left on the drawing sheet. At this same time, the pressure of the port A2 of the pilot valve 12 and the pressure of the port Pil of the pilot valve 11 nearly disappear. The port A1 of the pilot valve 11 and the port Pil of the unloading valve 10 are connected to the tank line 22, and thus the pressures of the port A1 of the pilot valve 11 and the port Pil of the unloading valve 10 disappear. In this case, the ports P2 and T of the unloading valve 10 are blocked. At the same time, the pressure of the port A2 of the pilot valve 12 disappears, and thus the pressure of the signal line disappears so that the discharge flow rate of the second hydraulic pump P2 is controlled to be discharged maximally. At this time, the maximally discharged hydraulic fluid is supplied to each attachment switching device.
In the meantime, the unloading valve 10 of a poppet type controls the flow rate of the hydraulic fluid in an ON/OFF manner by the pilot signal pressure applied from the outside. In other words, even if the pilot signal pressure of 1-40 kg/cm2 is supplied to the ports Pi1 and Pi2 of the unloading valve 10, the flow rate is controlled in the ON/OFF manner. Therefore, when the unloading valve 10 is closed, a cross-sectional area of the closed aperture of a flow path is abruptly reduced to bring about a hydraulic shock (see FIG. 2(a)). As a result, it can be found that even if a low pilot signal pressure is applied to the unloading valve 10, the flow rate of the hydraulic fluid discharged from the first hydraulic pump P1 and the second hydraulic pump P2 is suddenly increased (see FIG. 2(b)).
As described above, when the attachment is finely manipulated by a pilot check type unloading system in the pipe-laying operation mode, the center bypass path is blocked by the poppet closing of the unloading valve. For this reason, the conventional the hydraulic circuit for a pipe layer entails a problem in that the discharge flow rate of the hydraulic pumps is controlled to the maximum in terms of the characteristics of the negative flow control system to cause the pressure to rise due to the excessive flow rate of the hydraulic fluid discharged from the hydraulic pump, leading to generation of chattering.


The lowest metering port in the suction feed pipe of an accumulator is located such that a residual liquid storage volume is created which is at least 20% of the total volume available for liquid storage without overflowing into the suction feed pipe.

In an inactive air conditioning, heat pump, or refrigeration system, refrigerant tends to condense and collect at cool and/or low locations in the system. For the range of indoor and outdoor temperatures encountered in many systems during the off-portions of their cycles, the compressor is often the coolest part of the system for some period of time. As a result, considerable liquid refrigerant may collect in both suction-side and discharge-side portions of the compressor, possibly degrading compressor reliability in several ways.
Liquid refrigerant that collects in the compressor oil sump dilutes the oil, reducing its ability to lubricate compressor bearings and other moving parts when the compressor is started. Liquid that condenses on the suction side of a compressor may be drawn into the compression mechanism at start-up and wash away lubricating oil films normally present on moving parts. Liquid that condenses on the suction side may also be delivered directly or indirectly into the compressor oil sump at start-up, thereby diluting oil with the possible consequences described above.
Because of the affinity between refrigerants and many of the lubricants used therewith, refrigerant may also migrate to, and dissolve into, the oil over time even when the compressor is not any cooler than other portions of the system, thereby contributing to oil dilution and attendant loss of lubricating ability. This phenomenon makes it very desirable to maintain a minimum oil charge amount-to-refrigerant charge amount ratio that will help ensure that the oil will have adequate lubricating quality even in the most diluted state. For the start-up transients of many typical systems using presently available refrigerants and oils, experimentation and field experience have resulted in an approximate guideline that the oil charge amount should be at least about 30 to 40% of the refrigerant charge amount.
To mitigate these problems a number of design approaches may be employed, one of which is a refrigerant accumulator. An accumulator is commonly used to collect liquid refrigerant on the suction-side of the compressor and then meter its flow rate to the compressor compression mechanism and/or oil sump at start-up. A typical accumulator consists of an inlet pipe, a volume for storing liquid, a suction feed pipe that provides a passage for refrigerant gas to enter the compression mechanism or oil sump, and a circuitous flow path. The circuitous flow path is interposed between inlet pipe and inlet of suction feed pipe to divert liquid refrigerant, entering via the inlet pipe, away from the inlet of the suction feed pipe and into the storage volume, aided by the action of gravity. Often the circuitous flow path is created using a baffle in which holes or passages that allow the passage of refrigerant are vertically misaligned relative to the inlet of the suction feed pipe. Other arrangements that do not use a baffle are also possible, such as vertical misalignment of inlet pipe and suction feed pipe inlet, for example.
At start-up, low pressure caused by the action of the compression mechanism tends to vaporize any liquid refrigerant residing in the liquid storage volume and draws the vapor towards the compression mechanism via the suction feed pipe. Converting the liquid refrigerant to vapor in this manner helps avoid the washing of oil films and/or dilution of sump oil that might otherwise occur if liquid refrigerant were allowed to enter the compression mechanism or sump directly.
In practice, a small amount of liquid still may still enter the compression mechanism and/or sump via one or more "bleed holes" or metering ports located in the suction feed pipe and connecting its passage with the storage volume. A metering port is necessary to prevent accumulation of oil that normally circulates through the system with refrigerant in small percentages. Upon reaching the accumulator inlet pipe via piping connecting the evaporator and accumulator, oil may be in any or all of several forms. Oil may arrive as a film on interior walls, pushed along by the flow of refrigerant vapor. Oil may also arrive in mixture with or solution with liquid refrigerant. Some oil may also be entrained in refrigerant vapor as a mist. The circuitous path used to divert liquid refrigerant into the storage volume is also effective in diverting oil into the storage volume. Additionally, when oil enters the accumulator as a mist entrained in refrigerant vapor, the circuitous path requires changes in flow velocity and direction and may enhance flow impingement with some of the accumulator's internal solid surfaces. These tend to cause some portion of any oil entrained in the flowing refrigerant vapor to become separated out, where it flows to and collects at the bottom of the accumulator as a consequence of gravity.
Without a least one metering hole, over time the accumulator storage volume might become filled with separated oil. As accumulator storage volumes are typically a considerable fraction of oil sump volumes, and may exceed oil sump volumes, the resulting reduction of oil level in compressor sump could very well result in eventual failure by loss of lubrication. To minimize the amount of residual oil that may be prevented from returning to the compressor sump, at least one metering port is conventionally located near the bottom of the accumulator storage volume. In instances where an immiscible or partially miscible oil is used, metering ports are located at several elevations along the suction feed pipe of the accumulator. In this way, oil or an oil-rich mixture of oil and refrigerant floating on top of liquid refrigerant can be fed into the suction feed pipe. For these cases, at least one metering port is still located near the bottom of the storage volume to minimize the amount of residual oil that may be trapped in the accumulator when no liquid refrigerant is present. The lowest practical location of a metering hole in conventional accumulators is determined by manufacturing process and assembly tolerances. Typically, a metering hole may be located such that, for the worst-case assembly, trapped residual liquid volume may be a fraction of a fluid ounce in a small accumulator to as much as about a fluid ounce (30 cc) in a large accumulator. In conventional accumulators, trapped residual liquid volumes are on the order of a few percent to, in extreme cases, perhaps as much as 10% of the accumulator liquid storage volume.
When the storage volume contains liquid refrigerant, the metering port allows liquid refrigerant to flow into the suction feed pipe as well as oil. Accumulators can still be effective as long as the metering port is correctly sized and the amount of liquid refrigerant entering the accumulator does not exceed its storage capacity. If the metering port is too large, then, during operation with liquid refrigerant entering the accumulator, the flow rate of liquid refrigerant metered into the suction feed pipe may exceed rates required for reliable operation. If the metering port is too small or the accumulator storage capacity is too small for the system refrigerant charge, then liquid refrigerant may overflow the inlet of the suction feed pipe. If this happens, the rate of liquid flow to the compression mechanism and/or oil sump could be substantially increased. As this liquid is predominantly liquid refrigerant, washing of oil films from moving parts and/or dilution of oil in the sump may result.
As mentioned earlier, another effective and desirable approach is to design the compressor oil sump to hold an amount of oil that is at least about 30 to 40% of the system refrigerant charge amount, and preferably greater. Trends in system design are making this increasingly difficult and costly, however. Increasingly, consumer preference is towards systems with longer refrigerant connection lines and multiple indoor units serviced by a single outdoor unit and compressor. Both of these trends may result in systems with increased refrigerant charge amounts.
Redesigning compressor shells to increase oil sump volume may be costly, particularly insofar as these increases may exceed the capabilities of existing capital equipment. Simply adding additional oil to compressors without changing the volumes of their sumps may also be undesirable. The resulting increase in oil level may cause increased oil circulation rates due to impingement by moving parts or entrainment in discharged gas. Increased oil circulation rate, in turn, could degrade performance of heat transfer surfaces, thereby causing a loss of system efficiency.
If additional oil storage could be provided in a cost-effective manner in a compressor component that refrigerant may enter and leave, the oil to refrigerant ratio of the system could be increased without increasing the storage capacity of the oil sump. Further, if this additional oil storage could be provided in the suction accumulator, then during those times when primarily liquid refrigerant would otherwise be delivered to the compressor, a mixture of liquid refrigerant and oil would be delivered, having much better lubricating ability than liquid refrigerant. After oil has left the accumulator in this manner, a subsequent period of normal operation would allow the liquid separating mechanisms inherent in suction accumulators to replenish the oil stored in the accumulator, thereby allowing the additional oil stored in the accumulator to perform its functions repeatedly during the life of the system.


A system and method of separation of therapeutic components from blood. The system includes a dual member centrifuge and a disposable single use fluid transfer set. The set includes an elongated flexible separation chamber having an input port, a separated component output port and a residual fluid output port. The input port and the separated component output ports are located at opposite ends of the elongated separation chamber. The centrifuge includes a receiving chamber with a selectively formed annular slot therein. The separation chamber is positioned in the annularly shaped slot and rotated at a predetermined rotational velocity. Fluids such as whole blood flows through the separation chamber and are separated into various therapeutic components such as platelet rich plasma and residual concentrated red blood cells. Platelet rich plasma can be drawn off as the separated therapeutic component. An alternate two part transfer set provides for highly efficient platelet pheresis. The platelet rich plasma is separated from the residual red blood cells in a first part. The platelet rich plasma flows into the second part and is separated into platelet poor plasma and platelets. The platelet poor plasma can be drawn off and returned to a donor or collected. The platelet concentrate can then be accumulated in a separate container.

The collection of blood from volunteer donors has become a very successful and very refined activity. The development of single needle, single use, disposable blood collection sets has provided a safe, relatively inexpensive and donor comfortable medium for use in the blood collection process. Such sets have made possible large-scale collection of blood from volunteer donors at sites such as church halls, schools or offices which might be remote from medical facilities. The availability of volunteer donors is important in that such donors tend to be relatively healthy. In addition, they provide a potentially much larger reservoir of donatable blood than is available from the available group of paid donors.
In recent years, processing of whole blood from a donor has come to routinely include separating the blood into therapeutic components. These components include red blood cells, platelets and plasma. Various techniques and apparatus have been developed to facilitate the collection of whole blood and the subsequent separation of therapeutic components therefrom
The collection of platelets or plasma from volunteer donors, as opposed to the collection of whole blood, has not been nearly as successful. As a result, much of the plasma now collected comes from paid donors, as opposed to volunteer donors. It would be very desirable to be able to upgrade the collection of plasma so that it becomes a volunteer based activity to a much greater extent than it is currently.
Various methods are known for the collection of platelets or plasma. For example, a unit of blood can be drawn from a human donor in a conventional fashion and accumulated in a blood bag or other standard collection container. This unit of blood can then be processed by a centrifuge to separate the plasma from the other components of the blood unit. The separated platelets and plasma can subsequently be removed from the blood bag. Although allowing all blood components to be harvested, this process has the disadvantage that the donor must internally replace the complete unit of blood from which the plasma was extracted. The replacement process can take 6 to 12 weeks during which time the donor cannot again give blood. Further, this process yields only a small portion of available plasma/donor.
In a modification of the above system, plasmapheresis can be performed by centrifugation at the time of donation. The non-plasma portion of the blood is then returned to the donor immediately. While this process allows more frequent donation, often as frequently as once per week, the blood is physically separated from the donor for centrifugation.
Such physical separation is undesirable because of the cost and complexity of systems and procedures that have been developed to minimize the risk of error when several donors are being processed simultaneously. In addition, physical separation of the blood from the donor could potentially raise concerns in the collection staff of exposure to infectous agents in the collected blood if fluid drips or leaks occur.
Separation systems in which the accumulated whole blood is not physically separated from the donor are also known. These can be either batch or continuous systems.
One continuous centrifuge based system is disclosed in Judson et al. U.S. Pat. No. 3,655,123 entitled "Continuous Flow Blood Separator." The system of the Judson et al. patent uses two needles, an outflow needle and an inflow needle. Whole blood is drawn from a donor via the outflow needle. The whole blood fills a buffer bag. Blood from the buffer bag drains, under the force of gravity into a centrifuge. The system of the Judson et al. patent uses the centrifuge to separate blood components. The plasma can be collected in a container. The red blood cells can be returned to the donor via the inflow needle.
Various systems are known that utilize annular separation chambers for plasma pheresis. For example, U.S. Pat. No. 4,531,932 to Luppin et al. entitled Centrifugal Plasmapheresis Device discloses a system which incorporates a centrifuge with a rotating annular rotor. A centrally located rotating seal couples stationary fluid flow lines to the rotating rotor.
Whole blood is drained from a donor, passed through the rotating seal and subjected to separating rotational forces in the rotating rotor. Separated plasma is drawn off and concentrated whole blood cells are passed back through the rotating seal and returned to the donor.
Related types of systems which incorporate rotatable, disposable annular separation chambers coupled via rotary seals to stationary tubing members are disclosed in U.S. Pat. Nos. 4,387,848; 4,094,461; 4,007,871; and 4,010,894.
One consideration in the processing of whole blood is the requirement that the processing take place under sterile conditions. A second consideration is the requirement that processing take place so as to maximize storage life. Unless the processing takes place within a single sealed system, the permitted storage duration and usable lifetime of the blood components is substantially shortened. Components processed within a sealed system can be stored for four to six weeks or longer before use. On the other hand, whole blood or components thereof must be used within 24 hours if the system seal is broken.
To promote the desired ends of sterile processing within a single sealed system, a family of dual member centrifuges can be used to effect cell separation. One example of this type of centrifuge is disclosed in U.S. Pat. No. RE 29,738 to Adams entitled "Apparatus for Providing Energy Communication Between a Moving and a Stationary Terminal."
As is now well known, due to the characteristics of such dual member centrifuges, it is possible to rotate a container containing a fluid, such as a unit of donated blood and to withdraw a separated fluid component, such as plasma, into a stationary container, outside of the centrifuge without using rotating seals. Such container systems can be formed as closed, sterile transfer sets.
The Adams patent discloses a centrifuge having an outer rotatable member and an inner rotatable member. The inner member is positioned within and rotatably supported by the outer member.
The outer member rotates at one rotational velocity, usually called one omega, and the inner rotatable member rotates at twice the rotational velocity of the outer housing or two omega. There is thus a one omega difference in rotational speed of the two members. For purposes of this document, the term "dual member centrifuge" shall refer to centrifuges of the Adams type.
The dual member centrifuge of the Adams patent is particularly advantageous in that, as noted above no seals are needed between the container of fluid being rotated and the non-moving component collection containers. The system of the Adams patent, provides a way to process blood into components in a single, sealed, sterile system wherein whole blood from a donor can be infused into the centrifuge while the two members of the centrifuge are being rotated.
An alternate to the apparatus of the Adams patent is illustrated in U.S. Pat. No. 4,056,224 to Lolachi entitled "Flow System for Centrifugal Liquid Processing Apparatus." The system of the Lolachi patent includes a dual member centrifuge of the Adams type. The outer member of the Lolachi centrifuge is rotated by a single electric motor which is coupled to the internal rotatable housing by belts and shafts.
U.S. Pat. No. 4,108,353 to Brown entitled "Centrifugal Apparatus With Oppositely Positioned Rotational Support Means" discloses a centrifuge structure of the Adams type which includes two separate electrical motors. One electric motor is coupled by a belt to the outer member and rotates the outer member at a desired nominal rotational velocity. The second motor is carried within the rotating exterior member and rotates the inner member at the desired higher velocity, twice that of the exterior member.
U.S. Pat. No. 4,109,855 to Brown et al. entitled "Drive System For Centrifugal Processing Apparatus" discloses yet another drive system. The system of the Brown et al. patent has an outer shaft, affixed to the outer member for rotating the outer member at a selected velocity. An inner shaft, coaxial with the outer shaft, is coupled to the inner member. The inner shaft rotates the inner member at twice the rotational velocity as the outer member. A similar system is disclosed in U.S. Pat. No. 4,109,854 to Brown entitled "Centrifugal Apparatus With Outer Enclosure".
Centrifuges of the type disclosed in the above identified Brown et al. and Brown patents can be utilized in combination with a sealed fluid flow transfer set of the type disclosed in U.S. Pat. No. 4,379,452 to DeVries. The disclosure of the DeVries patent is incorporated herein by reference. The set of the DeVries patent incorporates a blood collection container that has a somewhat elongated shape similar to those of standard blood collection sets. One embodiment of this combined system is the CS3000 cell separator system marketed by Travenol Laboratories, Inc.
The CS3000 incorporates a dual member centrifuge in combination with a sealed set of the type disclosed in DeVries. This is a continuous system that requires the donor to receive two needle punctures. Such systems have been extensively used in blood centers for plasma and platelet pheresis.
The CS3000 is a large and expensive unit that is not intended to be portable. Further, the DeVries type transfer sets are quite complex to install .and use. They are also an order of magnitude more expensive than a standard, multi-container blood collection et.
further alternate to the Adams structure is illustrated in U.S. Pat. No. 4,530,691 to Brown entitled "Centrifuge With Movable Mandrel." The specification and figures of this Brown patent are hereby incorporated by reference herein. The centrifuge of this latter Brown patent also is of the Adams-type. However, this latter centrifuge has an exterior member which is hinged for easy opening. When the hinged upper section is pivoted away from the bottom section, it carries the rotatable inner member along with it.
The inner member supports a receiving chamber with a spring biased mandrel which continually presses against a sealed, blood containing container positioned within the receiving chamber. The system of this latter Brown patent also discloses the use of two separate electric motors to rotate the inner and outer members. The motors are coupled to a control system.
There thus continues to be a need for methods and related apparatus of platelet or plasmapheresis which can readily be used with volunteer donors at various temporary locations. This method and related apparatus should be usable by technicians with a level of skill commensurate with the level of skill now found at volunteer-based blood collection centers. Further, both the method and related apparatus should be readily portable to locations such as churches or schools where blood collection centers are temporarily established. Preferably the apparatus will be essentially self-contained. Preferably, the equipment needed to practice the method will be relatively inexpensive and the blood contacting set will be disposable each time the plasma has been collected from a single donor.

Centrifugation system having an interface detection surface


The invention relates to an improved process which, starting from 2-cyclopenten-1-ones substituted in the 3-position, gives a high yields of 1,3-dialkylcyclopentadienes which can be directly metallated and reacted to give the corresponding 1,3-dialkylcyclopentadienyl-transition metal complexes.

Owing to the wide variety of possible uses of the abovementioned transition metal complexes as catalysts in organic synthesis and, in particular, in the polymerization of olefins, the efficient industrial preparability of sandwich complexes which are disubstituted on the cyclopentadienyl radicals has become increasingly important (EP-A-O 128 045, EP-A-O 366 290, EP-A-O 283 739, EP-O 582 480, U.S. Pat. No. 4,874,880).
The preparation of such compounds is known in principle. The procedure according to equation (1) can generally be used for this purpose, ##STR1## where M can be Li, MgCl or MgBr;
R and R.sup.1 are identical or different and each is an alkyl or aryl radical. PA1 M' is a metallating agent; PA1 M.sup.1 is a transition metal; PA1 X is Cl, Br or I; PA1 m is the oxidation state of M.sup.1 ; and PA1 n.ltoreq.m. PA1 C.sub.1 -C.sub.20 substituted and unsubstituted, alkyl, alkenyl, cycloalkyl, aryl and arylalkyl radicals; PA1 X is Cl, Br or I; PA1 M' is a metallating agent such as Li, Na, K, NaH, KH, or Li alkyl; PA1 M.sup.1 is a transition metal such as Sc, Ti, Zr, Hf, Fe, V or Cr; PA1 X.sup.1 is Cl, Br or I; PA1 m is the oxidation state of M.sup.1 ; and PA1 n.ltoreq.m. PA1 M.sup.1 is a transition metal such as Sc, Ti, Zr, Fe, V or Cr; PA1 X.sup.1 is Cl, Br or I; PA1 m is the oxidation state of M.sup.1 ; and PA1 n.ltoreq.is m;
A disadvantage of this procedure was that after the reaction of 3-alkylcyclopenten-1-ones with Grignard compounds or lithium alkyls, the resulting alkoxide (2) first had to be hydrolyzed by means of water and isolated as alcohol (3) before, upon separate catalytic dehydration and work-up, the desired 1,3-dialkylcyclopentadiene component (4) was then obtained, and compound (3) could only be used for the further reaction after separate drying (Tetrahedron 1965, 21, 2313; Chem. Ber. 1976, 109, 329; J. Organomet. Chem., 1991, 417, 9).
It was therefore an object of the invention to simplify the reactions I., II. and III. (equation (1)) to such a degree as to provide a process which allows, in one reaction without isolation of the intermediates, the synthesis in high yields of 1,3-disubstituted cyclopentadienes which can then be reacted to give the corresponding transition metal complexes, e.g. according to equation (2): ##STR2## wherein Cp denotes cyclopentadienyl;

Process for preparing 1 3-disubstituted cyclopentadienyl ligands and transition metal complexes thereof


An implantable cardiac device includes electrodes for sensing and pacing the heart, and optionally, defibrillation electrodes. The IECG with a noise component sensed in the heart is processed to derive raw sense signals indicative of whether the sensed QRS complexe's range is outside a certain range. This range is dynamically adjusted to compensate for the noise component. Preferably this range is defined by a threshold signal generator which generates a threshold signal including a first part which varies dynamically in accordance with a preset criteria and a second part which is at least equal to the peak amplitude of the noise.

A. Field of Invention
This invention pertains to implantable cardiac devices (ICDs) such as pacemakers, and more particularly to such devices with means for distinguishing ambient electronic noise from arrhythmic cardiac behavior such as abnormally fast heart beats so as to provide appropriate and reliable therapy to a patient even in the presence of low level continuous noise, caused for example by electrical interference.
B. Description of the Prior Art
Typically ICDs monitor a patient's heart condition by sensing the Intra Cardiac Electrogram (IECG), a voltage that occurs when the cardiac muscle depolarizes at the beginning of each heart contraction. The IECG is sensed by one or two electrodes placed in or near the heart, where it appears as a voltage waveform which is normally referred to as the QRS complex. The IECG QRS complex during normal heart beats has an amplitude of about 15 to 25 mV and a broad frequency spectrum in the range of about 40 to 70 Hz. There are numerous systems in the prior art that detect the QRS complex by amplifying the IECG signal, filtering it to reduce noise and then detecting the QRS complex with an amplitude threshold detector. The threshold detector may have a fixed threshold or adapt the threshold to the changing amplitude of the signal.
A problem with this method of detecting cardiac activity is that because of its low amplitude and particular spectral characteristics, the IECG can be corrupted by ambient signals such as noise or artefact from natural and artificial sources. Common sources of such ambient signals include electromyographic noise from skeletal muscles near the electrodes, contact noise from intermittent contact in the electrode circuit (either the electrode wiring or between the electrode and heart muscle as the heart moves) and radiated or induced voltages from voltage lines and other external power sources. These ambient signals appear as waveforms with an amplitude and frequency content similar to the QRS complex and thus may confuse the sensing system of the ICD and cause incorrect therapy to be applied to the patient. This problem is compounded by the nature of the IECG of some arrhythmias, in particular, ventricular fibrillation, which has a lower amplitude (0.2 to 5 mv), higher rate (300 to 400 beats/min.) and lower frequency content than the normal IECG.
A common method used in many pacemakers to resolve this problem is referred to as the noise sensing window. This method takes advantage of the fact that even the fastest natural heart rates result in signals which follow a QRS complex by at least 300-400 ms. Accordingly, a noise window is designated as a window typically 100-120 ms after a QRS complex is sensed. Any signals sensed in this window are assumed to be noise.
A variation of this method is described in U.S. Pat. No. 4,173,230 to Digby entitled "Noise Elimination and Refractory Period Control In Demand Pacemakers" where a combination of filters and refractory periods are used to reduce the effect of noise.
Another noise detection method is described in U.S. Pat. No. 4,694,931 to Beck entitled "Sampled Data Sense Amplifier." The device disclosed therein searches for discontinuities in the background level of the sensed signal, and therefore ignores any noise if it is continuous and uniform.
U.S. Pat. No. 5,395,393 discloses a noise elimination method using variable amplifier thresholds.
These prior art noise detection systems have inherent problems of their own. One such problem exists if the noise level is near the detection threshold, or is of variable amplitude. In this situation, the detection is intermittent, thus providing a variable classification of noise that may lead to intermittent or indeterminate delivery of therapy to the patient. Additionally, these systems fail to work effectively when used for arrhythmia detection where an arrhythmia maybe of sufficiently high rate to cause a valid detection to fall in the noise window.
The problem of these systems misclassifying ventricular fibrillation (VF) as noise is significant. This is because the IECG for VF is highly variable and can have short intervals that have very similar characteristics to sine waves induced of by conventional power lines. This is of major consequence to patients with ICDs which require fast and accurate diagnosis of VF for the ICD to effectively save their lives from this lethal arrhythmia.
Other schemes among automatic sensing threshold, such as for example in my co-pending U.S. application Ser. No. 700,730 filed Aug. 13, 1996, entitled APPARATUS AND METHOD OF NOISE CLASSIFICATION IN AN IMPLANTABLE CARDIAC DEVICE, now U.S. Pat. No. 5,702,495. However, these schemes are very sensitive to noise at low heart rate. Moreover, these schemes are also very sensitive to noise during the asystole.
Some implantable cardiac devices are shown in U.S. Pat. No. 5,048,521 and 5,111,816.

Apparatus with noise classification in an implantable cardiac device by using an amplifier with a variable threshold