A transistor and a fabrication method thereof, and in particular, a technique for compatibly improving reduction of an ON-state voltage and reduction of a turn-off time. First and second emitter layers are selectively formed in isolation from each other on a surface of a base layer 3, and a channel region 6 opposed to a gate electrode 8 through a gate insulating film is formed therebetween. In an ON state, a base current I.sub.b is supplied from a base electrode, while a prescribed gate voltage is applied to the gate electrode. The first and second emitter layers couple with each other and function as a single emitter layer, whereby the ON-state voltage becomes a low value of about the same degree as a bipolar transistor. When bringing a device into an OFF state, supply of the base current I.sub.b is stopped while a zero (or negative) voltage is applied to the gate electrode. Consequently, coupling between the first emitter layer and the second emitter layer is canceled, whereby a second collector current I.sub.c2 which is a component of a main current passing through the second emitter layer rapidly attenuates similarly to a MOS.

1. Field of the Invention
The present invention relates to a transistor and a method of fabricating the same, and more particularly, it relates to an improvement for compatibly improving an output characteristic and an OFF characteristic.
2. Discussion of the Background
In general, a MOSFET (hereinafter simply referred to as MOS) has been mainly employed in a region having a rated voltage of not more than 200 V and a bipolar transistor (hereinafter simply referred to as BIP) or an insulated gate bipolar transistor (hereinafter simply referred to as IGBT) has been employed in a region of at least 300 V in various types of power transistors (power transistors). The respective ones of the conventional MOS, BIP and IGBT are now described.
FIG. 37 is a sectional view showing the structure of the conventional MOS. This MOS 151 corresponds to an example of the so-called vertical MOS. As shown in FIG. 37, an n.sup.- layer 172 is formed on an N.sup.+ layer 171 in the MOS 151, and p-type base layers 173 are selectively formed in an upper surface part of the n.sup.- layer 172 by diffusing a p-type impurity. Further, n-type source regions 174 are selectively formed in upper surface parts of the base layers 173 by diffusing an n-type impurity. The source layers 174 are partially arranged in single base layers 173, and the impurity concentrations thereof are set higher than the n.sup.- layer 172.
A gate oxide film 177 is formed on an exposed surface of the n.sup.- layer 172 and exposed surfaces of the base layers 173 held between the n.sup.- layer 172 and the source layers 174, and a gate electrode 178 made of polysilicon is formed further on this gate oxide film 177. Parts of the base layers 173 opposed to the gate electrode 178 through the gate oxide film 177 function as channel regions 176.
A source electrode 180 is formed on the exposed surfaces of the base layers 173 excluding the channel regions 176, i.e., upper surfaces of regions held between the source layers 174. The source electrode 180 and the gate electrode 178 are typically isolated from each other by an interlayer isolation film 179. Further, a drain electrode 182 is formed on an exposed surface of the N.sup.+ layer 171. These source electrode 180 and drain electrode 182 form a pair of main electrodes functioning as paths of a main current.
This MOS 51 operates as follows: First, a drain voltage V.sub.DS of prescribed magnitude is applied between the drain electrode 182 and the source electrode 180, so that the side of the drain electrode 182 is positive. When applying a gate voltage V.sub.GE (i.e., turning on a gate) exceeding a gate threshold voltage V.sub.GE (th) between the gate electrode 178 and the source electrode 180 so that the side of the gate electrode 178 is positive in this state, the p-type channel regions 176 are inverted to an n type and n-type channels are formed in the channel regions 176. Consequently, the n.sup.- layer 172 and the source layers 174 conduct with each other, whereby the drain electrode 182 and the source electrode 180 conduct with each other. Namely, the MOS 151 enters an ON state.
Then, when inverting the gate voltage V.sub.GE from the positive value to the value of zero or a negative (reverse bias) value (i.e., turning off the gate) in the state applying the drain voltage V.sub.DS, the channel regions 176 having been inverted to the n type return to the original p type. Consequently, the n.sup.- layer 172 and the source layers 174 are disconnected from each other, whereby the drain electrode 182 and the source electrode 180 are disconnected from each other. Namely, the MOS 151 enters an OFF state.
FIG. 38 is a sectional view showing the structure of the conventional BIP. In this BIP 152, an n.sup.- layer 202 is formed on an N.sup.+ layer 201, and a p-type base layer 203 is formed on an upper surface of the n.sup.- layer 202 by diffusing a p-type impurity. Further, an n-type emitter layer 204 is selectively formed in an upper surface part of the base layer 203 by diffusing an n-type impurity. The impurity concentration of the emitter layer 204 is set higher than the n.sup.- layer 202.
An emitter electrode 210 and a base electrode 211 are formed on exposed surfaces of the emitter layer 204 and the base layer 203 respectively, and a collector electrode 212 is formed on an exposed surface of the N.sup.+ layer 201. The collector electrode 212 and the emitter electrode 210 function as a pair of main electrodes.
This BIP 152 operates as follows: First, a collector voltage V.sub.CE of prescribed magnitude is applied between the collector electrode 212 and the emitter electrode 210 so that the side of the collector electrode 212 is positive. When supplying a base current from the base electrode 211 in this state, the diffusion potential of the base layer 203 is relaxed or canceled. Consequently, the collector electrode 212 and the emitter electrode 210 conduct with each other. Namely, the BIP 152 enters an ON state.
Then, when stopping supply of the base current in the state applying the collector voltage V.sub.CE, the diffusion potential of the base layer 203 revives. Consequently, the collector electrode 212 and the emitter electrode 210 are disconnected from each other. Namely, the BIP 152 enters an OFF state.
FIG. 39 is a sectional view showing the structure of the conventional IGBT. In this IGBT 153, an N.sup.+ buffer layer 311 is formed on a p.sup.+ layer 301, and an n.sup.- layer 302 is formed on the N.sup.+ buffer layer 311. Further, p-type base layers 303 are selectively formed in an upper surface part of the n.sup.- layer 302 by diffusing a p-type impurity. In addition, n-type emitter layers 304 are selectively formed in upper surface parts of the base layers 303 by diffusing an n-type impurity. The emitter layers 304 are partially arranged in single base layers 303, and the impurity concentrations thereof are set higher than the n.sup.- layer 302.
A gate oxide film 307 is formed on an exposed surface of the n.sup.- layer 302 and exposed surfaces of the base layers 303 held between the n.sup.- layer 302 and the emitter layers 304, and a gate electrode 308 made of polysilicon is formed further on this gate oxide film 307. Parts of the base layers 303 opposed to the gate electrode 308 through the gate oxide film 307 function as channel regions 306.
An emitter electrode 310 is formed on exposed surfaces of the base layers 303, i.e., upper surfaces of regions held between the emitter layers 304. The emitter electrode 310 and the gate electrode 308 are electrically isolated from each other by an interlayer isolation film 309. A collector electrode 312 is formed on an exposed surface of the p.sup.+ layer 301. These emitter electrode 310 and collector electrode 312 form a pair of main electrodes functioning as paths for a main current.
As hereinabove described, the IGBT 153 has such a structure that the N.sup.+ layer 201 is just replaced with a two-layer structure formed by the p.sup.+ layer 301 and the N.sup.+ buffer layer 311 in the MOS 151.
This IGBT 153 operates as follows: First, a collector voltage V.sub.CE of prescribed magnitude is applied between the collector electrode 312 and the emitter electrode 310 so that the side of the collector electrode 312 is positive. When applying a gate voltage V.sub.GE exceeding a gate threshold voltage V.sub.GE (th) (turning on a gate) so that the side of the gate electrode 308 is positive, the p-type channel regions 306 are inverted to an n type and n-type channels are formed in the channel regions 306.
Through these channels, electrons are injected from the emitter electrode 310 into the n.sup.- layer 302. The p.sup.+ layer 301 and the n.sup.- layer 302 (including the N.sup.+ buffer layer 311) are forward-biased by the injected electrons, and holes are injected from the p.sup.+ layer 301. Consequently, the resistance of the n.sup.- layer 302 remarkably lowers, and a large main current flows from the collector electrode 312 to the emitter electrode 310. Namely, the IGBT 153 enters an ON state. Thus, the IGBT 153 lowers the resistance of the n.sup.- layer 302 by injection of the holes from the p.sup.+ layer 301.
Then, when inverting the gate voltage V.sub.GE from the positive value to the value of zero or a negative (reverse bias) value (turning off the gate) in the state applying the collector voltage V.sub.CE, the channel regions 306 having been inverted to the n type return to the original p type. Consequently, the injection of the electrons from the emitter electrode 310 into the n.sup.- layer 302 stops. Following this, the injection of the holes from the p.sup.+ layer 301 into the n.sup.- layer 302 also stops. Thereafter the electrons and the holes having been stored in the n.sup.- layer 302 (including the N.sup.+ buffer layer 311) escape toward the collector electrode 312 and the emitter electrode 310 respectively, or disappear by coupling with each other. Thus, the IGBT 153 enters an OFF state.
As hereinabove described, each of the MOS 151, the BIP 152 and the IGBT 153 controls the main current in response to the voltage or the current applied to a control electrode (i.e., the gate electrode or the base electrode).
These three types of transistors had characteristics described below. FIG. 40 is a graph showing output characteristics of these three types of transistors with rated voltages in the range of about 200 V to about 500 V. Referring to FIG. 40, the horizontal axis corresponds to the voltages (i.e., the collector voltages V.sub.CE) between the pairs of main electrodes, and the vertical axis corresponds to the main currents. In the MOS 151, an ON-state voltage rises when the main current increases. Further, such a point that the magnitude of the main current is small as compared with the remaining transistors is characteristic.
In the IGBT 153, the main current is large, while such a characteristic is recognized that an ON-state voltage in the low current range is large. On the other hand, the BIP 152 exhibits such a characteristic that the main current is large and moreover an ON-state voltage is low. Namely, it can be said that the BIP 152 is most excellent in relation to the output characteristics.
FIG. 41 is a graph showing turn-off characteristics of the three types of transistors similarly with rated voltages in the range of about 200 V to about 500 V. Referring to FIG. 41, the horizontal axis corresponds to elapsed times, and the vertical axis corresponds to the magnitude of the main currents in the process of transition from ON states to OFF states. In the BIP 152 which is most excellent in the output characteristics, the turn-off time lengthens to about 10 times the MOS 151. Comparing the MOS 151 and the IGBT 153 with each other, there is no large difference although the turn-off time of the MOS 151 is short to some extent.
As hereinabove described, there has been such a problem that the ON-state voltages are high in the MOS and the IGBT, and there has been such a problem that the turn-off time is long in the BIP among the conventional three types of power transistors. A transistor whose ON-stage voltage is low, which is simultaneously excellent in turn-off characteristic has not been known in general.

Transistor and method of manufacturing the same


A vacuum cleaner inlet door lighting device for illuminating the area directly in front of a vacuum cleaner wall mounted inlet. The lighting device includes LED's operated upon the opening of a rotatable door have a directional pattern for optimum illumination. The LED's are mounted behind the rotatable door to cause illumination when the rotatable door is open. In an alternative embodiment the LED's are remotely mounted using fiber optic cabling for direction of the light when the rotatable door is opened. When the rotatable door opens the area in front of the wall mounted inlet is illuminated so that the dirt and debris can be seen while being pushed into the collection container. When the rotatable door is closed, the illumination is turned off.

Vacuum cleaning systems are a modern convenience and used in most all homes, offices and commercial establishments. These systems generally utilize a unitary centrally located station containing a vacuum supply coupled to a collection receptacle and a plurality of conduits which interconnect various parts of the structure to the central station. The conduits can either terminate in a hose adapter coupling enabling each area to be cleaned by inserting the hose assembly into a hose coupling or terminate with an inlet door where debris can be drawn into the vacuum supply system.
Central vacuum systems with wall mounted inlet doors are in the prior art. For instance, U.S. Pat. No. 5,504,967 discloses a combined inlet structure and switching device for a central vacuum system which includes an inlet housing having top, bottom and side walls defining a vacuum inlet chamber and a front with a dirt receiving opening. An aperture located in the top wall and can be connected to a pipe leading to a central vacuum source. A closure member is movable between first and second positions in order to close or open the aperture. A foot operated actuator is connected to the housing and is able to pivot the closure member between the first and second positions. A spring biases the closure member towards the first position and operates when the actuator is pressed in one direction. When the closure member is moved to the second position, it will remain there unless the actuator is pressed in another, opposite direction. There is also a switch mechanism responsive to movement of the actuator for opening and closing an electrical circuit connected to the central vacuum source.
U.S. Pat. No. 5,279,016 discloses a suction inlet for a central vacuum system of a building which includes a housing mounted on the floor of the building thereby defining a slot along the floor. The slot can be opened and closed and simultaneously a vacuum duct connected to the housing is opened and closed by a plug member. When the plug and the slot are opened, a switch actuates the central vacuum system to draw air into the housing through the slot across the floor so that dust, dirt and debris on the floor can simply be swept into the slot and drawn away.
U.S. Pat. No. 6,292,977 discloses a vacuum fitting for connection to a remote source of vacuum, such as a central vacuum system. The vacuum fitting comprising a main body mountable to a fixed structure. The main body includes an inlet opening and an outlet opening; an openable closure is mounted to the main body and is moveable between an open position and position covering the inlet opening; a latch member is selectively positionable to keep the closure in said covering position when positioned between the main body and the closure and to permit said closure to move to an open position when not positioned between said main body and the closure; and a biaser to urge the closure to an open position. A switch is also provided to initiate the remote source of vacuum, such as a central vacuum system, when the closure is moved to the open position by the biaser.
U.S. Pat. No. 6,108,858 discloses a waste receptacle for a vacuum cleaning system. The waste receptacle is a floor mounted sweeping suction inlet is provided with a rotatable door that carries a user-activated portion by which the rotatable door may be opened by contact from a foot. The vacuum source can be turned-on automatically by opening the rotatable door by the presence of a door-activated electrical switch. An adapter converts the floor-mounted vacuum opening to a standard circular opening for receiving a vacuum hose and wand.
U.S. Pat. No. 6,158,080 discloses improvements in the operation and design of wall-mounted recessed vacuum cleaner systems. The disclosed invention incorporates an extremely compact motor design which enables the filtering debris receptacle to be arranged directly over the motor housing. The vacuum system of the disclosed invention includes an upper containment compartment and a lower evacuation compartment. The containment compartment houses an air filtering and residue collecting receptacle, e.g. a vacuum bag assembly, which may incorporate HEPA filtration characteristics.
U.S. Pat. No. 7,580,281, issued to the inventor of the present invention, discloses an improved wall-mounted recessed vacuum cleaner system which incorporates vibration dampening mounts between the motor and the outer housing, air channels within the housing to smooth air flow and reduced number of parts to significantly reduce the noise level during operation. The vacuum cleaner system incorporates an extremely compact housing and motor design with a filtering debris receptacle arranged directly over the motor compartment.
What is lacking in the art is an improved lighting system for illuminating the area in front of wall mounted inlet doors.

Vacuum cleaner inlet door lighting device


There is provided a cleaning apparatus for a surface of a sheet steel capable of satisfactorily removing scale from a surface of a sheet steel before, for example, hot rolling. Waters (42a, 46a) are ejected from nozzles (42, 46), with an ejection pressure of 100 kg/cm.sup.2, a flow rate of 60 liters/minute and an ejection angle of 20.degree. with respect to normal of the surface (32a) of the sheet steel, toward a downward-stream end with respect to a carrying direction. On the other hand, waters (44a, 48a) are ejected also from nozzles (44, 48), with the same ejection pressure, flow rate and ejection angle as those of the nozzles (42, 46), but different in the ejecting direction. That is, waters (44a, 48a) are ejected toward an upward-stream end with respect to the carrying direction. In other words, waters (42a, 44a, 46a, 48a) are ejected from the nozzles (42, 44, 46, 48) alternately in opposite directions as to an upward-stream end with respect to said carrying direction and a downward-stream end with respect to said carrying direction.

In manufacture of a hot-rolled sheet steel, usually, a slab is charged into a heating furnace in an oxidizing atmosphere to be heated with a temperature within a range of 1100.degree.-1400.degree. C. extending over several hours. The heated slab is hot-rolled repeatedly by a rolling machine extending over a plurality of number of times so that a predetermined thickness thereof is obtained. A high temperature heating extending over several hours causes scale to be created on a surface of the slab. If the scale is subjected to a hot rolling process in such a state that the scale does not sufficiently break away, the scale will encroach on the surface of the slab and as a result remains as a scale defect. The scale defect on the surface of the slab remarkably damages a surface nature. In addition, the scale defect will become a starting point of cracks in a bending processing or the like. These will be a cause of serious damage to quality of products. In view of this matter, hitherto, there are proposed several ways to prevent an occurrence of scale defects on a slab surface (a sheet steel surface). As one of the ways, there is known a scheme in which a water jet descaling apparatus (hereinafter, referred to as a descaler) for ejecting water at a pressure, for example, about 100-150 kg/cm.sup.2 is disposed in a direction (a width direction of a sheet steel) which intersects substantially perpendicularly to a carrying direction of the sheet steel, and high pressure water is ejected from the descaler toward a surface of the sheet steel to separate and remove scale created on the surface of the sheet steel.
In general, according to the scheme as mentioned above, there are provided a plurality of arrays of the descaler each being equipped with a plurality of nozzles in a longitudinal direction thereof (a width direction of a sheet steel) to eject water toward the surface of the sheet steel. In order to prevent scale removed by water ejected from the respective nozzles from entering a rolling machine which is installed at the downward-stream end with respect to the carrying direction of the sheet steel, water is ejected from the descaler of each of the arrays toward the upward-stream end with respect to the carrying direction of the sheet steel. By the way, water ejected from the descaler disposed at the downward-stream end with respect to the carrying direction toward the upward-stream end with respect to the carrying direction flows on the surface of the sheet steel up to a collision area in which water ejected from the descaler disposed at the more upward-stream end with respect to the carrying direction than the noticed descaler collides with surface of the sheet steel. Hence, water ejected from the descaler disposed at the more upward-stream end with respect to the carrying direction than the noticed descaler does not collide directly with surface of the sheet steel, but collides once with water ejected from the descaler disposed at the more downward-stream end with respect to the carrying direction and flowing on the surface of the sheet steel. As a result, water ejected from the descaler disposed at the more downward-stream end with respect to the carrying direction serves as a cushion, so that an impact force of water ejected from the descaler disposed at the more upward-stream end with respect to the carrying direction to the surface of the sheet steel will be reduced. Thus, this will be a cause of such a problem that it is difficult to implement a sufficient descaling.
Further, as another method of the scale eliminating ways, there is proposed a method (refer to Japanese Patent Laid Open Gazette No. 502113/1984) in which as shown in FIG. 21, water 14a is ejected from a cooling header 14 disposed at the upward-stream end with respect to the carrying direction 12 of a sheet steel 10 toward the upward-stream end with respect to the carrying direction, while water 16a is ejected from a cooling header 16 disposed at the downward-stream end with respect to the carrying direction 12 toward the downward-stream end with respect to the carrying direction, and thus water 14a ejected from the cooling header 14 disposed at the upward-stream end flows on a surface of the sheet steel, as shown by arrow 14b, toward the upward-stream end with respect to the carrying direction, while water 16a ejected from the cooling header 16 disposed at the downward-stream end flows on the surface of the sheet steel, as shown by arrow 16b, toward the downward-stream end with respect to the carrying direction, whereby water ejected from the cooling header 14 and water ejected from the cooling header 16 do not interfere with each other on the surface of the sheet steel so as to collide directly with the surface of the sheet steel.
According to the method described in the Gazette referenced above, while water ejected from the cooling header 14 and water ejected from the cooling header 16 do not interfere with each other on the surface of the sheet steel, water ejected from each of a plurality of nozzles disposed on a single cooling header will be emitted with a spread. Hence, waters ejected from adjacent nozzles will interfere with each other on the surface of the sheet steel. A state of the interference of water on a surface of a sheet steel will be explained referring to FIG. 22. FIG. 22 is a typical illustration showing on a plan view basis the state of the interference.
To perform a descaling, there is a need to cause water to have a collision extending over overall width of the sheet steel 10 being transported in the carrying direction 12. Consequently, water is emitted from the respective nozzle in such a manner that collision areas 20 and 22, in which waters emitted from the adjacent nozzles disposed on a single descaler (not illustrated) collide with a sheet steel surface 10a, partially overlap. While it is desired that the overlapped area is as narrow as possible, usually, the nozzles are arranged in such a manner that the overlapped area having 5 mm-10 mm in a direction of a sheet steel width is formed, since spread of the collision areas 20 and 22 will be varied owing to a variation in a distance between the sheet steel 10 and the nozzles, which variation caused by a variation in thickness of the sheet steel 10, and a spread of the collision area differentiates owing to an error in manufacture of nozzles.
In the overlapping area, water-to-water ejected from the mutually adjacent nozzles collide with each other, so that the collision force is reduced. Consequently, it is difficult to sufficiently remove scale. In order to provide a narrower overlapping area, there is considered a scheme in which as shown in FIG. 23, collision areas 24 and 26 for waters ejected from the mutually adjacent nozzles are staggered with respect to the carrying direction 12, and waters are ejected from the respective nozzles toward the upward-stream end with respect to the carrying direction 12. However, since water ejected toward the upward-stream end with respect to the carrying direction 12 will be emitted with a spread, water in the collision area 24 will be spread on the sheet steel surface 10a toward the upward-stream end with respect to the carrying direction 12. Thus, a part of waters serves as a cushion for water ejected to the collision area 26. As a result, in the area shown by an arrow 28, it may be considered that water ejected from the nozzle does not collide directly with the sheet steel surface. Thus, there is a fear such that scale in this area can not be sufficiently removed.
In order to solve the problem as mentioned above, there is considered a scheme in which the respective nozzles are arranged at sufficient intervals with respect to the carrying direction, and before water ejected from a nozzle spreads up to a collision area in which said water will collide with water ejected from another nozzle, said water is removed from a sheet steel surface. However, this method involves undesired problems in operation, such that it is needed to provide a space for installation of nozzles arranged at sufficient intervals with respect to the carrying direction, and conditions of descaling or cooling conditions by descaling are different owing to variance in temperature conditions on the sheet steel surface with which waters ejected from the respective nozzles arranged at sufficient intervals with respect to the carrying direction collide.
By the way, the quality of separativeness of scale in removal of scale is largely affected by the operational conditions such as water pressure of a descaler, and in addition the nature of scale, that is, composition and structure of scale and the like. Specifically, it is known that a primary scale created on a steel, which is large in the Si (silicon) content, is very difficult to be separated. The reason why such scale is very difficult to be separated is that when the steel, which is large in the silicon content, is oxidized through high-temperature heating, Si contained in the steel is subjected to the selective oxidization to form 2FeO.SiO.sub.2 (fayalite) which is large in thermal plasticity, so that a sub-scale layer possessing such a characteristic structure that the interface with the steel is complicated is formed. A heat treatment of the steel containing, for example, Si not less than 0.1% increases remarkably an amount of the sub-scale mentioned above. This sub-scale cannot be easily removed, as mentioned above. Thus, an infinite number of scale defects remains on a surface of a product after a rolling process. This will be a cause of a remarkable degradation of commercial value of products. Further, it happens that the secondary scale, which will be formed after a removal of the primary scale, does not break away by the above-mentioned method of ejecting high pressure water. Hence, this is in danger of an occurrence of scale defects.
As a technique to solve the foregoing problem, Japanese Patent Publication No. 1085/1985 discloses "a descaling method at hot rolling for a steel containing Si in which when a slab consisting of a steel containing 0.10-4.00% of Si is subjected to a hot rolling process to produce a hot-rolled sheet steel, descaling by a high pressure water jet of 80-250 kg/cm.sup.2 is practiced not less than 0.04 seconds in a cumulative time during a rolling period of time in which a cumulative draft reckoning from a starting point of time of rolling is not less than 65% and an ingot piece temperature is 1000.degree. C. Further, Japanese Patent Laid Open Gazette No. 238620/1992 discloses "a descaling method in which when a difficult-separative scale of steel species is subjected to a hot rolling process to produce a hot-rolled sheet steel, a high pressure water spray, given by a collision pressure per unit spraying area between 20 g/mm.sup.2 and 40 g/mm.sup.2 and a flow rate between 0.1 liters/min.multidot.mm.sup.2 and 0.2 liters/min.multidot.mm.sup.2, is ejected on a surface of the sheet steel prior to a finishing rolling.
As a nozzle for separating and removing difficult-separative scale, Japanese Patent Laid Open Gazette No. 261426/1993 proposes "a descaling nozzle in which an rectifying liquid flow channel is arranged on a longitudinal basis". In this Gazette, it is disclosed that the use of the descaling nozzle having a rectifier may increase the collision force comparing with the conventional nozzle, and thus it is effective for the difficult-separative scale of steel species.
However, according to the technique disclosed in Japanese Patent Publication No. 1085/1985 among the above-mentioned prior arts, there is a need to ensure a high FET (Finisher Entry Temperature), such as 1000.degree. C. or more, and thus it is obliged to extract the sheet steel at high temperature. This involves such problems that unit requirement gets worse, and scale is increased. And in addition, the high temperature such as 1000.degree. C. or more causes various restrictions in draft and descale time. This will be a cause of a complicated work in rolling.
According to the technique disclosed in Japanese Patent Laid Open Gazette No. 238620/1992, the collision pressure and flow rate of the high pressure water spray are defined to separate scale by an instantaneous collision force. In this technique, it is considered that the separative amount of scale depends on the collision pressure of the high pressure water spray. This concept has been described in detail in a paper "Collision pressure at the time of high pressure water descaling in hot rolling" appearing in a publication "Iron and Steel", 77(1991), Vol. 9. This paper discloses that consideration of variations in thermal expansion caused by a quenching action for scale with high pressure water and the minimum collision pressure for separating scale created on the various kinds of steels permits descaling to be satisfactorily performed. However, according to the technique as mentioned above, while most of the scale components are separated, a scale component having such a structure that scale encroaches on a ground metal will not be removed and thus remains. Hence, even after rolling, the scale defect referred to as a red scale remains. There arises the problems that such a scale defect becomes remarkable as the Si content is increased.
The above-mentioned Japanese Patent Laid Open Gazette No. 261426/1993 discloses structure and performance of the descaling nozzle equipped with the rectifier, but fails to disclose a method of the use in a hot rolling factory, for instance, the optimum distance between the nozzle and the sheet steel surface.
As a method of removing scale created on a surface of sheet steel, there is disclosed a method in which a liquid is ejected from a nozzle with a supplying pressure between 1000 Kg/cm.sup.2 and 10000 Kg/cm.sup.2 so that droplets formed in a droplet stream area of the liquid collide with a surface of a sheet steel, thereby removing scale (refer to Japanese Patent Laid Open Gazette No. 138815/1992). However, according to the method referenced above, since the supplying pressure of the liquid is not less than 1000 Kg/cm.sup.2, there arises the problems that this method is unfavorable in economy and maintenance of facilities for supplying liquid.
In view of the foregoing, it is an object of the present invention to provide cleaning method and cleaning apparatus which may be preferably used, for example, when scale is removed from a surface of a sheet steel before a hot rolling process.

Cleaning method and cleaning apparatus for surface of sheet steel


The present invention describes a method for determining whether an individual is suffering from cancer by determining a parameter representing the TIMP-1 concentration in body fluid samples from the individual.

Colorectal cancer is the fourth most frequent cancer in the Western world, with about 160,000 new cases yearly in the US. Forty to 50% of all colorectal cancer patients will be diagnosed with early stage disease (Dukes' stage A or B). Most of these patients with early stage colorectal cancer can be cured by surgery alone. Thus, risk of recurrence is closely related to stage of disease at time of primary surgery, with about a 10% relapse rate in Dukes' stage A and 25-30% in Dukes' stage B. Patients with Dukes' stage C colorectal cancer have a five-year relapse rate of 70% following surgery and are offered adjuvant chemotherapy. Following relapse, the risk of dying of the disease is significant. Thus, one way to improve survival is to increase the number of patients being diagnosed with early stage disease. Screening for colorectal cancer has been shown to improve survival, however, current tests suffer from a lack of compliance, from low sensitivity, and from the need for strict dietary restrictions. Thus, the development of new and improved tests for the early detection of colorectal cancer is needed.
Thus, 30-40 percent of patients who have undergone a complete resection of a colorectal malignancy will experience relapse with metastatic disease, which is usually fatal. Thus, hundreds of thousands of people with resected CRC are candidates for surveillance, as it is a commonly held clinical view that early detection of metastases and metachronous disease by relevant surveillance regimens may allow for interventions with the aim of improving overall survival, disease-free survival and quality of life.
The majority of recurrences of CRC occur within 5 years, and usually within 3 years following surgery. A tremendous effort has been put into the establishment of effective tests for the detection of recurrent disease at a stage when intervention is not futile. Carcinoembryonic antigen (CEA) tests, colonoscopies, chest x-rays, liver function tests, complete blood cell counts, fecal occult blood tests, computerized tomography (CT), ultrasonography, magnetic resonance (MR) and positron emission tomography (PET) are all methods that have been extensively reported on for the postoperative surveillance of CRC. Unfortunately, the results from randomised studies of such monitoring of CRC patients have varied widely and demonstrated minimal efficacy (Schoemaker, Gastroent, 1998; Ohlsson, Dis Col Rec, 1995; Makela, Arch Surg, 1996; Kjeldsen, Int J Color Dis, 1997). As a result hereof, considerable variation in clinical follow-up practice is evident (Virgo KS, Ann Surg, 1995) and expenses for 5-year follow-up of CRC patients have differed from $561 to $16,492 per patient (Virgo, JAMA, 1995).
The American Society of Clinical Oncology (ASCO) has recommended against the use of liver function tests, fecal occult blood tests, complete blood counts, pelvic imaging, CT scanning and chest x-rays as means for regular postoperative monitoring of CRC. However, it was recommended that postoperative measurement of serum CEA is performed every 2 to 3 months for ≧2 years in patients with stage II or III disease where resection of liver metastases is clinically indicated (Benson, JCO, 2000). Of note, however, is the fact that approximately 30 percent of all CRC recurrences do not produce CEA (Safi, Cancer Detect Prev, 1993). Thus, it was stressed by the ASCO that new surveillance methods for the detection of CRC recurrences are needed (Benson, JCO, 2000). This statement has gained further weight as recent data has shown that chemotherapy of metastatic CRC can improve short-term survival and often improve the quality of life (Cunningham, Lancet, 1998) and that treatment of asymptomatic CRC yields better results than postponing treatment until the disease has become symptomatic (Nordic Gastr Tumor Adj Group, JCO, 1992).
Because metastatic disease is the main cause of cancer patient morbidity and mortality, molecules involved in the regulation of tumor invasion and metastasis are attractive as potential diagnostic/prognostic/monitoring targets. It is well established that proteolytic enzymes produced by cancer cells or by cells in the tumor stroma are involved in extracellular tissue degradation, leading to cancer cell invasion and metastasis. A number of enzymes have been associated with this process, the most thoroughly investigated being the metalloproteinases, such as the collagenases and stromelysins, and the serine proteases such as plasmin. Recently, data have been published indicating that these molecules, free or bound in complexes, are released from tumor tissue and find their way into the circulation.
Matrix metalloproteinases (MMP's) play a pivotal role in cancer growth and spread, contributing to enzymatic degradation of the extracellular matrix (Liotta et. al., 1991; Stetler-Stevenson et. al., 1993; MacDougall & Matrisian, 1995). The naturally occurring inhibitors of MMP's, tissue inhibitors of MMP's (TIMP's), form tight 1:1 stoichiometric complexes with the activated forms of the MMP's (Welgus et. al., 1985; Kleiner et. al., 1993), thereby inhibiting the catalytic activity of these enzymes (Stetler-Stevenson et. al., 1996; Goldberg et. al., 1992; Birkedal-Hansen et. al., 1993). While the balance between the matrix-degrading properties of MMP's and the inhibitory effect of TIMP's is closely regulated under normal physiological conditions (Matrisian, 1992; Thorgeirsson et. al., 1993; Birkedal-Hansen et. al., 1993), this balance might be disrupted in malignant tissue.
A number of enzyme-linked immunoassays for the detection of TIMP-1 (Kodama et. al., 1989; Cooksley et. al., 1990; Clark et. al., 1991) and TIMP-2 (Fujimoto et. al., 1993) have been described. These assays have been applied to body fluids, e.g. serum, plasma, amniotic fluid, cerebrospinal fluid, urine, but the number of samples tested has not been sufficient to establish normal ranges for TIMP levels in healthy individuals (Kodama et. al., 1989; Clark et. al., 1991). Furthermore, none of these assays have been sufficiently validated for technical performance or for clinical use. We have recently described and validated an ELISA for the quantitation of total TIMP-1 in plasma samples, and using this assay we could demonstrate that healthy blood donors have a very narrow range of total plasma TIMP-1 (Holten-Andersen et. al., Br. J. Cancer 1999). We have also recently developed and validated an ELISA for the quantitation of uncomplexed TIMP-1 in plasma (Holten-Andersen et. al., manuscript submitted)
In a study by Mimori et. al. (Mimori et. al., 1997) in which tumor tissue levels of TIMP-1 mRNA were studied in patients with gastric carcinoma, high tumor/normal tissue ratios of TIMP-1 mRNA were found to be associated with increased invasion and poor prognosis and Guillem et. al., (Proc Annu Meet Am Assoc Cancer Res; 34:A466, 1993) suggest a possible correlation between TIMP-1 RNA levels and poorly differentiated, invasive colorectal cancers. However, TIMP-1 protein levels in sera from prostate cancer patients and healthy donors (Baker et. al., 1994) showed a high degree of overlap. Similarly, a separate study of plasma from prostate cancer patients and healthy donors showed no difference in TIMP-1 levels between the two groups (Jung et al., 1997).
We have recently published that preoperatively measured plasma levels of total TIMP-1 show highly significant association with colorectal cancer patient survival, i.e. patients with high TIMP-1 levels had a significantly shorter survival than those patients with low TIMP-1 levels (Holten-Andersen et. al., Clin. Cancer Res, 2000).
Furthermore, Nauro et. al., (J. Urol, vol. 1, no 3, September 1994, pp 228-231) found that serum TIMP-1 levels are significantly higher in metastatic bladder cancer patients compared to a healthy control group, whereas no results were presented about the TIMP-1 levels of pre-metastatic bladder cancers. TIMP-1 measurements in urine have also been described as being useful in the diagnosis of other cancers such as bladder cancer, liver cancer and renal cancer (Japanese patent application no. 8-136548). In none of these studies a correlation between the TIMP-1 level of patients with early stage bladder cancers and the TIMP-1 level of patients with cystitis have been included.
Measurements of TIMP-1 levels have also been shown to be useful in diagnosing diseases of the nervous system as described in U.S. Pat. No. 5,324,634.
Studies of TIMP-1 complexed with MMP-9 in plasma of patients with advanced gastrointestinal and gynaecological cancer (Zucker et al., 1995) demonstrated significantly higher levels in blood samples from cancer patients with metastatic disease compared to healthy control individuals, and that patients with high levels of TIMP-1:MMP-9 complex had a shorter survival (Zucker et. al., 1995 and U.S. Pat. No. 5,324,634). However, this study did not include measurements of total or free TIMP-1, only the complex between TIMP-1 and one of the up to now approximately 24 identified MMP's. Furthermore, in this study, no differences in complex levels were found between patients with breast cancer and healthy donors. Also, this study did not include patients with early stage cancer.

Tissue inhibitor of matrix metalloproteinases type-1 (TIMP-1) as a cancer marker and postoperative marker for minimal residual disease or recurrent disease in patients with a prior history of cancer

Abstract: The present invention furthermore describes a method for determining whether an individual is suffering from minimal residual disease or recurrent cancer after being treated for the primary cancer by determining a parameter representing the post-operative TIMP-1 concentration in body fluid samples from the individual. In addition, the invention describes the additive effect of combined post-operative measurements of plasma TIMP-1 and serum CEA.


Pedicle screws that can include a pedicle screw body, housing, plurality of clamps, rod, and set screw are disclosed herein. The clamps may be positioned side by side inside the lower portion of the housing. When the rod and set screw are provided in the housing, the set screw applies a force on the rod and the rod engages the plurality of clamps, causing the clamps to frictionally engage a head of the pedicle screw between the clamps.

1. Field of the Invention
Disclosed herein are pedicle screws related to the field of orthopedic surgery. More particularly, certain embodiments disclosed herein relate to a pedicle screw and methods of use.
2. Description of the Related Art
Spinal fusion encompasses a surgical technique in which two or more vertebrae are connected together. This technique may be used for multiple indications, including abnormal spinal curvature (e.g., scoliosis) and weakening or injuring of the vertebrae or spinal disc.
In some instances, this process is accomplished and/or supplemented using a plurality of screws implanted into the pedicle of adjacent vertebrae and joined together by a series of one or more rods. The pedicle screw may have an enlarged head that interfaces with a housing having a corresponding cavity, thus allowing for a range of polyaxial articulation between the screw and the housing. After the pedicle screw is implanted into bone, a rod may be placed in the housing, and a set screw may delivered into engagement with the housing, applying a downward force on the rod to hold the assembly together. This downward force is also supposed to cause engagement of the head of the pedicle screw relative to the housing, to thereby fix the position of the pedicle screw relative to the housing and prevent disengagement. However, prior pedicle screw designs may not provide sufficient force to hold the pedicle screw relative to the housing to fix their relative locations and/or prevent disengagement.

This patent is subject to a terminal disclaimer.

Pedicle screws and methods of using the same


The portable multi-use self-defense device can include a trigger; a housing; two or more canisters, said canisters containing at least one of gas and liquids; and an engagement mechanism coupled to said trigger and to said canisters, said engagement mechanism being capable of actuating the discharge of the at least one of gas and liquids from the two or more canisters substantially simultaneously.

Conventional self-defense devices use a single system or combination of systems to deter potential assailants. The systems utilizing a combination of systems have different mechanisms for activating each system. Valuable time may be wasted in preparing to use one of the systems on a device. For example, a user may have to push multiple buttons on different ends a device to enable both systems at once. The elimination of this wasted time may mean the difference between safely avoiding a dangerous situation. Therefore, a device that incorporates time-saving features is needed to provide a safer self-defense device.


Embodiments relate to a horizontal type bipolar junction transistor element (BJT) and a CMOS image sensor having the same to form a photodiode. In embodiments, the bipolar junction transistor as well as collector current may flow uniformly in a horizontal direction, which may increase the entire amount of current. In embodiments, large current gain may be obtained. In embodiments, a bipolar junction transistor element with various current gains can be manufactured.

An image sensor may be a semiconductor device to convert an optical image into an electrical signal. An image sensor may be a charge coupled device (CCD), where individual metaloxide-silicon (MOS) capacitors may be located adjacent each other and may store charge carriers and may further transfer them. Alternatively, an image sensor may be a CMOS (complementary MOS) image sensor, which may adopt a switching manner. A CMOS device may include as many MOS transistors as a number of pixels. A CMOS device may include, as peripheral circuits, a control circuit and a signal processing circuit, and may sequentially detect outputs using such circuits.
A CMOS image sensor may implement images by forming a photodiode and a MOS transistor in a unit pixel and detecting the signals in the switching manner.
In a related art process of manufacturing a CMOS image sensor, an NPN element may be manufactured by applying a CMOS process to an epi-layer.
FIG. 1 is a drawing illustrating a related art horizontal type NPN bipolar junction transistor element and FIG. 2 is a drawing illustrating a cross section of the horizontal type NPN bipolar junction transistor element shown in FIG. 1.
Referring to FIGS. 1 and 2, the horizontal type NPN bipolar junction transistor element may include shallow trench isolation (STI) area 160, which may be a device isolating area, on P-type semiconductor substrate 100 and may include P-well 112 and N-well 110.
N-type emitter E, P-type base B, and N-type collector C may be formed in P-well 112, and a N-type guard ring (N-ISO) may be formed in N-well 110 and may space P-well 112 from the peripheral thereof.
STI area 160 may be formed between emitter E and base B and between collector C and the N-type guard ring (N-ISO) and may partition each area.
Each upper layer of emitter E, base B, and collector C area may be formed with emitter contact area 126 and collector contact area 130, where a high concentration of N-type ionss may be implanted, and base contact area 128, where P-type ionss may be implanted. An upper layer of the N-type guard ring (N-ISO) area may be formed with a guard ring contact area where a high concentration of N-type ions may be implanted.
Emitter contact area 126, collector contact area 130, base contact area 128, and the N-type guard ring (N-ISO) area may each contact metal electrodes 133a, 133b, 133c, and 133d.
The P-well may be formed with the emitter and the collector together, which may allow for the electrons implanted from the N-type emitter E to flow to the N-type collector C, and may form horizontal collector current IC in a normal active mode.
However, the ratio of base current IB to collector current IC in the bipolar junction transistor element BJT, that is, IC/IB may be referred to as a common emitter current gain (beta), and may be an important specification that may determine DC performance of the element.
There may be a problem that the current gain of the horizontal type bipolar junction transistor (BJT) element in the related art may be small because the base layer may be wide. For example, the current gain of a horizontal type bipolar junction transistor (BJT) element may be smaller than that of a vertical type bipolar junction transistor element in which current may flow vertically.
Moreover, since the current flow may be non-uniform in view of a element structure, it may be difficult to expect and model current.

Bipolar junction transistor and CMOS image sensor having the same


Optimal design method and apparatus for synchronous digital circuits by retiming through selective flipflop positioning and electronic circuit configuration produced by executing the method. The method is for designing a synchronous digital electronic circuit that comprises cells and clocked flipflops interconnected by nets and running at a predetermined clock period, operates as follows. First, uniform-directedly as starting from any cell for any sub-path emanating therefrom its associated delay is accumulated. Next, if for such sub-path the accumulation result exceeds a predetermined integer number of clock periods. The sub-path in question is signalled for subsequent provision with such integer number of flipflops and its accumulation is terminated. Finally, all elementary cell-to-cell connections are provided with flipflops in minimal accordance with said signalling. The invention is particularly advantageous with large circuits such as used in digital video processors and with small clock periods.

The invention relates to a method for designing a synchronous digital electronic circuit that comprises cells and clocked flipflops interconnected by nets and running at a predetermined clock period, through selective positioning of said flipflops, wherein any cell of the circuit imparts to a path between an input/output pair of the cell a respective signal delay, and wherein in-circuit paths imparting a total delay above said clock period are being provided with at least one flipflop. If the granularity considered in the design of the circuit is fine, a cell or node may be an essentially unclocked combinatorial element. In case of coarser granularity a node may comprise one or more clocked elements, or broader, sequentially operating elements. Moreover, the relevance of the clocked element may depend on the actual signal path through the node considered, as will be explained hereinafter. A method according to the preamble has been described in the paper `Retiming Synchronous Circuitry` by Ch. E. Leiserson and J. B. Saxe, published in Algorithmica '91 pp. 5-35. Especially the introduction of Digital Signal Processing (DSP) for video signals has increased the requirements for signal throughput, which would in fact necessitate putting flipflops closer to each other, in terms of the number of interposed cells. A particular technique in the reference is repositioning of the flipflops or "retiming" to enhance the performance, and in particular, allowing for higher clock frequencies. A subset or special case of retiming is pipelining. These two techniques will be discussed hereinafter. According to the reference, circuit latency is not increased. The reference operates by setting up matrices of inter-cell signal delays and providing flipflops to all inter-cell paths that show a delay time that is larger than one clock period. Subsequently, the flipflops are subjected to retiming or shifting. However, the solving of the many conditions is not efficient for large circuits, inter alia, because of the lengthy path that may interconnect an arbitrary pair of cells, and the great number of such conditions in view of the great number of cells.


Multilayer meltblown fibrous webs, as well as apparatus and methods of forming the webs. The webs are produced on a rotating collector that also moves parallel to its longitudinal axis. The webs are thus formed in a helical process, and the resulting tubular web is separated in a direction parallel to a helix angle. By separating the tubular web in a direction parallel to the helix angle, a flat multilayer meltblown fibrous web is provided that allows for incorporation of feathered edges formed during the article""s manufacture.

The present invention pertains to multilayer meltblown fibrous webs, methods of manufacturing such webs, and apparatus for manufacturing multilayer meltblown fibrous webs.
The manufacture of meltblown fibrous webs has been discussed in many references, including, Wente, Van A., Superfine Thermoplastic Fibers, 48 Industrial Eng. and Chem. 1342-46 (1956); Report No. 4364 of the Naval Research Laboratories, published May 25, 1954, entitled Manufacture of Superfine Organic Fibers, by Wente, V. A., Boone, C. D., and Fluharty, E. L.; and U.S. Pat. No. 3,971,373 to Braun.
In making meltblown fibrous webs, a thermoplastic polymer or resin is commonly extruded through a row of small, side-by-side orifices into a high velocity gaseous stream that attenuates the emerging material into fibers. The gaseous stream creates turbulence that randomly entangles the fibers to form a coherent nonwoven web on a collector. The collector may be a moving flat belt or rotating cylindrical screen or drum. The resulting nonwoven web is transferred from the collector to a temporary storage roll.
Known processes have a couple drawbacks, namely, they can produce significant waste as a process by-product and they can produce non-uniformities across the web.
Waste (also referred to as weed) is commonly produced at the web edges when manufacturing meltblown fibrous webs. The waste or weed results because the web edges are typically xe2x80x9cfeatheredxe2x80x9d, meaning the edges taper off and do not have the same weight and density as the central portion of the web. The feathering stems from fiber dispersal at the web edges. To eliminate this variation in weight and density, the web edges typically are trimmed off and then discarded as waste, while the central portion of the web is retained for further processing. The wasted material adds to processing costs, especially when in-line web processing is desired.
Known meltblown fibrous webs are typically mono-layer webs that, by definition, have only a single layer. Mono-layer meltblown fibrous webs often suffer from non-uniformities over their cross-web dimension due, for example, to variations in orifice diameter. The variations in orifice diameter can cause non-uniform fiber deposition that, in turn, causes variations in the basis weight in the cross-web dimension. The basis weight is the weight per unit area of the mono-layer web, and it is commonly adjusted by varying the polymer extrusion rate or the collector speed or both. For example, if a higher basis weight web is desired, the collector speed can be reduced and/or the extrusion rate can be increased. Conversely, if a lower basis weight web is desired, the collector speed can be increased and/or the extrusion rate can be decreased.
One approach to overcoming variations in basis weight include laminating multiple webs together using agents such as adhesives or resins and/or by physical processing such as welding. The variations in the multiple webs then preferably average out the non-uniformities such that the minimum acceptable basis weight is achieved over the entire laminated web. One disadvantage to this approach is that some areas of the web can have an excessive basis weight and hence unnecessary amounts of web material. The unnecessary material, as well as the laminating agents and/or processing needed to laminate the webs to form the multi-web products adds to production costs and increases complexity. Furthermore, the agents and/or welds used to laminate the layers can adversely affect the resulting articles"" conformability and flexibility.
Attempts to employ tubular fibrous web processes to achieve a flat web have typically involved forming the tubular meltblown fibrous web and compressing the tube to obtain a flat web without feathered edges. Alternatively, the tubular web may be slit longitudinally so that the tube is opened, thereby producing a flat web with two machine-cut edges. Two such approaches are described in U.S. Pat. Nos. 3,909,174 (Blair et al.) and 4,032,688 (Pall). A disadvantage of these processes is that variations in web thickness may often be helical in nature. As a result, slitting the web longitudinally often causes banded variations in the web density, which variations are located at an angle, commonly referred to as a xe2x80x9cbias angle,xe2x80x9d with respect to the web centerline.
The present invention is directed to overcoming the noted drawbacks in known methods for making meltblown fibrous webs. In one aspect, the present invention provides a new apparatus for manufacturing a meltblown fibrous web. The new apparatus includes (i) a collector that has a generally cylindrical forming surface and (ii) a source that is capable of directing meltblown fibers at the forming surface. The generally cylindrical forming surface can rotate about a longitudinal axis and can simultaneously move parallel to the longitudinal axis, such that a selected point on the forming surface can move in a helical pattern about and along the longitudinal axis from a first end of the collector to a second end of the collector. The helical pattern defines a helix angle relative to the longitudinal axis. The apparatus also includes (iii) a separator that can separate a tubular meltblown fibrous web formed on the forming surface in a direction generally parallel to the helix angle. The separator thus converts the tubular meltblown fibrous web into a non-tubular or flat meltblown fibrous web.
In a second aspect, the present invention provides a method of manufacturing a meltblown fibrous web using a collector having a generally cylindrical forming surface. The forming surface is rotated about a longitudinal axis and simultaneously moves longitudinally in the direction of the longitudinal axis such that a selected point on the forming surface moves in a helical pattern about and along the longitudinal axis from a to first end of the collector to a second end of the collector. The helical pattern defines a helix angle relative to the longitudinal axis. Meltblown fibers are directed at the forming surface as the forming surface rotates and moves longitudinally, such that a tubular meltblown fibrous web is formed on the forming surface. The tubular meltblown fibrous web is then separated along a direction generally parallel to the helix angle to convert the tubular meltblown fibrous web into a non-tubular or flat meltblown fibrous web.
In a third aspect, the present invention provides a multilayer meltblown fibrous web that has a plurality of interconnected layers that contain meltblown fibers. At least one of the fiber-containing layers has a feathered edge. The web also has two separated edges. The feathered edge is located between the separated edges, and the separated edges and the feathered edge are generally parallel to each other. The multilayer meltblown fibrous web may be used in a variety of articles such as filters for masks or respirators.
The multilayer meltblown fibrous webs of the present invention are produced on a collector having a forming surface in the general shape of a cylinder where the forming surface rotates about the longitudinal axis of the cylinder. While the forming surface rotates as such, it is simultaneously advanced parallel to and along the longitudinal axis. As a result, any particular point on the forming surface moves along a helical path during web manufacture.
A meltblown fiber source is directed at the forming surface along at least a portion of the longitudinal length of the collector, thereby forming a layer of meltblown fibers on the forming surface. The forming surface typically completes at least one rotation about the longitudinal axis in the time required to advance the forming surface along the length of the meltblown fiber source. Where the forming surface completes two or more rotations in the time required to advance the forming surface along the length of the collector, a multilayer tubular web is built-up on the forming surface.
Because the forming surface rotates about the longitudinal axis while simultaneously advancing parallel to the longitudinal axis, the feathered edges in each layer of meltblown fibers are formed in a helical pattern on the cylindrical forming surface.
A separator is used to separate the tubular meltblown fibrous web in a direction oriented at an oblique angle relative to the longitudinal axis of the cylindrical forming surface. That oblique angle is equal to the helix angle formed by the feathered edges during manufacture of the meltblown fibrous web. The flat meltblown fibrous web formed after separating the tubular multilayer meltblown fibrous web along the helix angle includes two separated edges that have a thickness substantially the same as the thickness of the remainder of the web and does not require trimming or further processing before use of the web in other processes.
By separating the tubular multilayer meltblown fibrous web in a direction generally parallel to the helix angle to produce a flat multilayer meltblown fibrous web, variations in the density or weight of the meltblown fibrous web caused by the feathered edges are parallel to the edges of the formed flat web. This is in direct contrast with known tubular meltdown fibrous webs that are slit longitudinally, causing the feathered edges to cross the web at a bias angle with respect to the flat web centerline.
The meltblown fibrous webs of the present invention are different from known webs because of their multilayer composition in which the feathered edges are incorporated into the web and are disposed generally parallel to the web""s separated edges. Because the meltblown fibrous articles are commonly formed from multiple layers of meltblown fibers, variations in basis weight contributed by the feathered edges can be significantly reduced. The web layers that terminate in feathered edges form only a fraction of the overall basis weight of the web as a whole. In addition, any variations in the basis weight contributed by non-uniformities across the die or dies used to form the articles may also be reduced because of the multilayer nature of the articles. The helical nature of the process will naturally displace those variations over the width of the web such that they will not typically be aligned throughout the web thickness. Because the process causes the feathered edge to be included in the resulting web, the invention is advantageous in that it eliminates waste production stemming from the previous need to remove the feathered edge from the product.
These and other features and advantages of the meltblown fibrous webs, apparatus for manufacturing them, and methods for manufacturing them are discussed below in more detail.
In reference to the invention, the following terms are defined as set forth below:
xe2x80x9ccollectorxe2x80x9d means an apparatus that is capable of collecting meltblown fibers;
xe2x80x9cfeathered edgexe2x80x9d means the portion of a meltblown fibrous web layer in which the density and basis weight of the web tapers off due to fiber dispersal;
xe2x80x9cforming surfacexe2x80x9d means that portion of a collector on which meltblown fibers are deposited after exiting a meltblown fiber source;
xe2x80x9chelical patternxe2x80x9d means a pattern formed in the shape of helix, in other words, similar to the path followed by the threads of a screw;
xe2x80x9chelix anglexe2x80x9d means the angle formed by the helical pattern relative to a plane perpendicular to the longitudinal axis;
xe2x80x9cinterconnected layersxe2x80x9d means meltblown fiber layers that are connected to each other by, for example, fiber entanglement between fibers in the different layers, an agent introduced to connect the layers (for example, a resin, adhesive, etc.), and/or processing (for example, pin, welding, etc.);
xe2x80x9cintermediate layerxe2x80x9d means a meltdown fiber layer located between the first and second layers of a multilayer meltblown fibrous web;
xe2x80x9clongitudinal axisxe2x80x9d means the central axis about which the cylindrical forming surface rotates;
xe2x80x9cmachine directionxe2x80x9d means the direction of travel of the forming surface during formation of a tubular meltblown fibrous web;
xe2x80x9cmeltblown fiber layerxe2x80x9d and its variations means a nonwoven fibrous structure that contains meltblown fibers and possibly other ingredients formed on a collector or other surface during one pass past a source of meltblown fibers;
xe2x80x9cmeltblown fibrous webxe2x80x9d means a nonwoven fibrous structure that contains meltblown fibers and possibly other ingredients and that has sufficient integrity to be handlable by itself as a mat; and
xe2x80x9cseparated edgexe2x80x9d means an edge of a multilayer meltblown fibrous web that is physically separated from another edge of the web by any suitable method, for example, slitting, tearing, etc.


A centrally-folded and centrally-thickened ridge cover is formed from sheet shingle material by repeatedly back folding the material on itself to provide a thickened central portion for the ridge cover. The thickened central portion is disposed intermediate of a lower and an upper portion of the ridge cover. A plurality of inscribed transverse grooves are impressed into the work piece of sheet shingle material, to insure that the work piece folds at desired locations to form the back folds and thickened central portion of the finished ridge cover. A method of effecting the desired folding of a ridge cover work piece is also disclosed.

1. Field of the Invention
The present invention relates to a low-cost, durable and highly aesthetic high-profile ridge cover made of sheet roofing material, and to a method of making the ridge cover. This high-profile ridge cover is appropriately used for roofing, and is effective to improve the aesthetics of a shingle roof.
2. Description of the Related Art
A conventional inorganic asphalt composition ridge cover is known in accord with U.S. Pat. No. RE 36,858, owned by the assignee of the present application.
Manufacturing a ridge cover according to the U.S. Pat. No. RE 36,858 patent requires that an elongate strip or ribbon of sheet roofing material be partially cut through in the outline of the individual workpieces which will become ridge covers. Within the outline of each ridge cover workpiece, a T-shaped slit is formed by partially cutting through the work piece. Also, a plurality of transverse slits are formed along the length of the T-shaped slit in order to insure that the work piece will fold on itself at the locations of these transverse slits. The outlining, forming of the T-shaped slit, and forming of the plural transverse slits are all done while the individual workpieces are still part of the elongate strip of sheet roofing material. These cutting or slitting operations are performed by training the elongate strip about a roller having outwardly disposed knife edges protruding an appropriate distance above the roller surface, and in the shape of the slits to be formed. These knife edges are a high maintenance item in the manufacturing operation, and a reduction or elimination of the use of these knife edges for slitting operations would be an important improvement in the manufacturing of such folded ridge covers.

Folded high-profile ridge cover, and method of making


This invention relates to a method of manufacturing a wind turbine blade and a wind turbine blade thereof. A central core element and a plurality of side core elements are sandwiched between first layers and second layers of a first fibre material. The central core element is spaced apart from the side core elements to form a first and a second recess. This sandwich structure is then impregnated with a first resin and cured in a first step. Layers of a second fibre material of a first and a second main laminate are laid up in the first and second recesses. The first and second main laminates are then impregnated with a second resin and cured in a second step.

It is well-known that wind turbine blades for modern wind turbines have become larger and heavier in an effort to increase the energy production from the wind turbine. This is achieved by increasing the aerodynamic profile of the wind turbine blades and thus increasing the blade length. Increasing the size of the wind turbine blade also increases the aerodynamic and static loadings on the wind turbine blade, which in turn also requires larger and heavier hubs and nacelle main frames in order to transfer these loadings to the wind turbine tower.
For larger wind turbine blades, larger blade moulds are needed in order to manufacture the blade shell parts of these large wind turbine blades. This in turn increases the amount of materials needed to manufacture the blade shell and the load carrying structure arranged within the blade shell, thereby, further increasing the total manufacturing costs and time.
The wind turbine blade may be manufactured by laying up layers of a laminate of a fibre material in a blade mould, optionally after a gel coating have been applied to the moulding surface. Optionally, a core material may be arranged between a first set of layers of fibre material and a second set of layers of fibre material to form a sandwich structure. A resin is then introduced into the fibre material and the optional core material, and finally cured to form a first blade shell part with a desired aerodynamic profile. The process is then repeated for a second blade shell part. The two cured blade shell parts may then be joined together via an adhesive. The outer surfaces, optionally only the glue lines, of the blade shell may be worked into their finished shape and then coated to form the finished wind turbine blade.
EP 2934857 A2 discloses a two-step manufacturing process, wherein layers of a fibre material are initially laid up on the moulding surface after which core elements, trailing edge reinforcements and leading edge reinforcements are laid up. Further layers of fibre material are then laid up over the core elements and the trailing and leading edge reinforcements. A resin is then introduced and cured. A continuous main laminate of the wind turbine blade is afterwards arranged in a continuous recess formed by the core elements. The main laminate is then attached to the pre-cured blade part, e.g. by introducing a resin which is then cured.
EP 3086924 A1 discloses a single-step manufacturing process, wherein first layers of a fibre material and then core elements are initially laid up on the moulding surface. After which, layers of a first and a second main laminate are arranged in a first recess and a second recess formed by the core elements. Second layers of a fibre material are finally laid up over the core elements and further over the first and second main laminates. A resin is then introduced and cured. Permeable fabrics are further arranged on both sides of each main laminate in order to facilitate the resin flow into each main laminate.
EP 2788176 A1 discloses an alternative manufacturing process, wherein multiple blade shell portions are pre-manufactured separately using manufacturing moulds and then joined together in a joining mould. A pre-cured central portion comprises a central core element, a main laminate and further a first side core element located on each side of the central core element is initially placed in the joining mould. Other pre-cured portions comprising second side core elements are subsequently placed in the joining mould and then joined to each first core element using a vacuum infusion. Alternatively, the second side core elements may be laid up directly in the joining mould and then infused and cured.
EP 3099471 A1 discloses a two-step manufacturing process where layers of a first fibre material is laid up in a mould, infused with a first resin and then cured. Subsequently, layers of a second fibre material is laid up on the cured structure and infused with a second resin. The infused second fibre material is finally cured to form an integrated wind turbine blade.
EP 1162058 A1 discloses a manufacturing process of a composite structure having a hollow core material sandwiched between layers of a fibre-reinforced material, wherein resin can be infused uniformly and quickly due to the shape of the core material.

Wind turbine blade and a method of manufacturing the wind turbine blade

LM WINDPOWER INTERNATIONAL TECHNOLOGY II APS


A system and method of controlling clearance in a turbomachine includes adjusting the machine case cooling air in response to the difference between the desired clearance and the actual clearance. An accurate estimate of the actual clearance is made with a real time mathematical model on-board engine controller. The model computes thermal growth of the turbomachine components each with a difference equation derived from a closed form solution to the 1st order differential equation obtained through the application of 1st law of thermodynamics. The resulting equation is conveniently formulated in terms of equivalent time constant and steady state growth both correlated with thermo-physical characteristics of multiple fluid streams exchanging heat with the component. The solution is applied over a time step of the control software. Approximating coefficients are strategically placed in the model to allow calibration of the model to a particular version of the engine hardware.

The present invention generally relates to a system and method of clearance control of motor or engine fan blades, and more particularly relates to a system and method of determining thermal growth of motor or engine parts to thereupon control the clearance of motor or engine fan blades.
The knowledge and control of radial growth of turbo-machinery components has long been a stumbling block on the way to achieving higher efficiency and stability levels demanded by the designers of gas turbine engines, pumps and compressors. This undesirable situation is driven in part by lack of reliable, accurate and affordable sensors for measuring radial growth. Alternatively, the radial growth can be computed using a mathematical model that relates growth to various turbo-machine measured and otherwise obtained parameters. Numerous attempts were made in the past to devise such an algorithm. However, none of the known algorithms delivered required steady state and transient accuracy, ability to calibrate the equations to high fidelity data and formulation suitable for implementation in a digital computer.
Imperfect control of the clearance between a turbine engine fan blade and case results in either the clearance being too loose or the clearance being too tight resulting in excessive rubs. In either instance, imperfect clearance results in loss of performance (e.g. engine efficiency, thrust) and/or violation of the engine operating limits (e.g. exhaust gas temperature overshoot) and/or reduced compressor stability. Standard practice has been to design a clearance control system to prefer loose clearance over fight clearance which may also result in damage to the blades and case. Some engines such as, for example, the PW4000 use an open loop clearance control system that sacrifices significant performance in comparison with a xe2x80x9cperfectxe2x80x9d clearance control system. Other engines such as, for example, the V2500 use a closed loop system that relies on crudely modeled clearances and therefore sacrifices less performance, but still falls short of ideal clearance control.
Improved accuracy and reliability in estimating tip clearances will also enable the clearance control system to be active during those parts of an airplane mission that are more likely to experience abrupt changes in operating conditions. For example, a typical active clearance control system is traditionally deactivated during airplane takeoff where tip clearances are particularly hard to predict due to rapidly changing engine operating conditions. This approach worked well in the past for the cases where takeoff constituted a relatively small portion of the overall airplane mission and the engine stability margins were conservatively high. In contrast, takeoff fuel economy gains importance for the engines designed for short haul aircraft applications such as, for example, PW6000 designed for A318 application. The ability to deploy active clearance control during takeoff also increases the exhaust gas temperature margin which otherwise diminishes with increased clearance, and helps to avoid clearance induced stability loss. Thus, it is desirable to further improve clearance control accuracy to, in turn, improve engine performance while maintaining all operating limits, compressor stability and ensuring reliable rub-free operation throughout the airplane mission
The principal difficulty in modeling clearances for a closed loop system resides in modeling the thermal growths of the engine components, not in modeling the mechanical strains which are relatively easy to calculate. Thermal growths are far more difficult to model because the physical configurations of the engine components and the multiple time varying influences to which those components are subjected (i.e., throttle transients, multiple fluid streams of different and time varying temperatures, flow rates, etc.) complicate the problem of modeling the heat transfer and energy storage phenomenon.
In view of the foregoing, it is a general object of the present invention to provide a system and method of clearance control that overcomes the above-mentioned drawbacks.
In one aspect of the present invention a method of controlling clearance in a turbomachine between blades and a wall adjacent to and opposing tips of the blades includes adjusting air flow adjacent to the wall in response to the difference between the desired clearance and the actual clearance. Due to lack of suitable sensors, an accurate and reliable estimate of the actual clearance is made with a real time, mathematical model running, on-board engine controller. As part of the clearance calculation the subject model computes thermal growth of the turbomachine components and their subcomponents with a difference equation derived from a closed form solution to the 1st order differential equation obtained through the application of the 1st law of thermodynamics. The component is treated as being made of uniform material with given average specific heat and mass while at uniform temperature throughout the volume. The heat transfer phenomenon is modeled as a sum of a finite number of heat transfer processes taking place over the entire area of the component interface with the known gas turbine fluid streams. Each heat transfer process is characterized by a local average heat transfer coefficient, contact surface area and fluid temperature. The solution is defined over a time step of the control software assuming either step or ramp input and is expressed in terms of equivalent time constant, steady state growth and a set of approximating coefficients. The steady state growth is calculated as a weighted average of the growths due to thermal exchange with fluid streams of varying temperatures, flow rates and thermo-physical properties. The weighting is accomplished with performance parameters that are first formed as functions of the local fluid stream area of contact, the local heat transfer coefficient, the total component mass and the component average specific heat. Then, recognizing that these characteristics are impractical to define for a specific component or its subcomponents, the performance parameters are correlated with the measured and otherwise synthesized engine characteristics such as shaft speeds, pressures and temperatures. Finally, the inverse of the equivalent time constant is calculated as a sum of the same performance parameters.
In a second aspect of the present invention, a system for controlling clearance in a turbomachine between blades and a wall adjacent to and opposing tips of the blades includes adjusting air flow adjacent to the wall in response to the difference between the desired clearance and the actual clearance. Due to lack of suitable sensors, an accurate and reliable estimate of the actual clearance is made with a real time, mathematical model running, on-board engine controller. As part of the clearance calculation the subject model computes thermal growth of the turbomachine components with a difference equation derived from a closed form solution to the 1st order differential equation obtained through the application of the 1st law of thermodynamics. The component is treated as being made of uniform material with given average specific heat and mass while at uniform temperature throughout the volume. The heat transfer phenomenon is modeled as a sum of a finite number of heat transfer processes taking place over the entire area of the component interface with the known gas turbine fluid streams. Each heat transfer process is characterized by a local average heat transfer coefficient, contact surface area and fluid temperature. The solution is defined over a time step of the control software assuming either step or ramp input and is expressed in terms of equivalent time constant, steady state growth and a set of approximating coefficients. The steady state growth is calculated as a weighted average of the growths due to thermal exchange with fluid streams of varying temperatures, flow rates and thermo-physical properties. The weighting is accomplished with performance parameters that are first formed as functions of the local fluid stream area of contact, the local heat transfer coefficient, the total component mass and the component average specific heat. Then, recognizing that these characteristics are impractical to define for a specific component, the performance parameters are correlated with the measured and otherwise synthesized engine characteristics such as shaft speeds, pressures and temperatures. Finally, the inverse of the equivalent time constant is calculated as a sum of the same performance parameters.
In a third aspect, a gas turbine engine system comprises an engine including case and disk with blades rotatable within the case. Means are provided for controlling clearance in a turbomachine between blades and a wall adjacent to and opposing tips of the blades to adjust air flow adjacent to the wall in response to the difference between the desired clearance and the actual clearance. Due to lack of suitable sensors, an accurate and reliable estimate of the actual clearance is made with a real time, mathematical model running, on-board engine controller. As part of the clearance calculation the subject model computes thermal growth of the turbomachine components with a difference equation derived from a closed form solution to the 1st order differential equation obtained through the application of the 1st law of thermodynamics. The component is treated as being made of uniform material with given average specific heat and mass while at uniform temperature throughout the volume. The heat transfer phenomenon is modeled as a sum of finite number of heat transfer processes taking place over the entire area of the component interface with the known gas turbine fluid streams. Each heat transfer process is characterized by a local average heat transfer coefficient, contact surface area and fluid temperature. The solution is defined over a time step of the control software assuming either step or ramp input and is expressed in terms of equivalent time constant, steady state growth and a set of approximating coefficients. The steady state growth is calculated as a weighted average of the growths due to thermal exchange with fluid streams of varying temperatures, flow rates and thermo-physical properties. The weighting is accomplished with performance parameters that are first formed as functions of the local fluid stream area of contact, the local heat transfer coefficient, the total component mass and the component average specific heat. Then, recognizing that these characteristics are impractical to define for a specific component, the performance parameters are correlated with the measured and otherwise synthesized engine characteristics such as shaft speeds, pressures and temperatures. Finally, the inverse of the equivalent time constant is calculated as a sum of the same performance parameters.
An advantage of the present invention is that the thermal growths of turbomachine components and its sub-components may be accurately and reliably determined for subsequent use in the estimation of actual clearance of a turbomachine which is a required element in closed loop active clearance control schemes such as one typically employed in a turbine case cooling.
A second advantage of the present invention is that an accurate numerical technique, namely a closed form solution to the governing differential equation applied over time step of control software is employed to implement 1st order dynamics of the thermal growth.
A third advantage is that the effect of multiple fluid streams is accounted for in the calculation of both steady state and transient characteristics of the thermal growth.
A fourth advantage is the allowance of finite order dynamics to be implemented as the sum of 1st order dynamic elements. Thus, to model a component of complex geometry and heat transfer phenomenon the component can be subdivided into a finite number of sub-components each modeled with a 1st order dynamic element.
A fifth advantage is the use of approximating coefficients to allow for calibration against high fidelity models and test data, and to facilitate the model traceability to a specific set of turbomachine hardware which may be changing through the operational life of the machine.
A sixth advantage is that the physics-based model increases chances of sensible results outside the machine operating envelope.

System and method of controlling clearance between turbine engine blades and case based on engine components thermal growth model


An automotive air bag assembly including a tethering element providing shape definition across the air bag. The tethering element may be seamed to itself or to other tethering elements by an attachment seam to reduce the effective operative length of the tethering element and to move the axis of rotation for the air bag rearward. The attachment seam is adapted to separate upon development of adequate pressures within the air bag.

It is well known to provide an air bag assembly including an inflatable air bag cushion for protecting the occupant of a transportation vehicle. In an automotive vehicle such air bag assemblies are typically located within the hub of the steering wheel and in a recess in the vehicle instrument panel for protection of the vehicle occupants seated in opposing relation to such assemblies. Additional air bag assemblies may be located within the seats and/or door panels for protection of the occupants during a side impact event. It is also known to utilize inflatable curtain-like structures for deployment from the structural pillars or roofline of the motor vehicle so as to promote restraint and protection of the vehicle occupant during a roll-over event.
Air bag assemblies typically include an inflatable cushion in fluid communication with a gas emitting inflator. Upon sensing predetermined vehicle conditions, such as a certain level of vehicle deceleration, the inflator discharges a fixed amount of inflator gas thereby forcing the air bag into a deployed position. The inflator gas occupies the available volume within the air bag cushion thereby forcing the air bag cushion to expand outwardly to the extent permitted by its construction. As inflation gas enters the air bag cushion the pressure within the cushion is increased. As the occupant comes into contact with the expanded air bag cushion, the inflator gas is forced out of the cushion thereby dissipating the kinetic energy of the occupant achieving a so-called "ride down" effect.
Traditional air bag cushions tend to project outwardly away from their storage positions in a substantially straight line during the initial stages of inflation. In a so called "top mount" or "mid mount" design, this directional projection may cause the cushion to first travel in a generally upward direction away from the air bag exit opening and against the windshield. After this initial outward projection during the latter stages of inflation such cushions assume their final inflated design profile causing them to rotate downwardly in covering relation to portions of the instrument panel below the air bag exit opening.
In order to provide additional control over the inflation characteristics of the air bag cushion it has been suggested to utilize tethering elements in the form of straps or webs extending between surfaces of the air bag cushion. These straps or webs may be released from a first restrained operative length to a second extended operative length as the depth of the air bag cushion is increased. A system incorporating such extensible tethering straps is illustrated and described in U.S. Pat. No. 5,489,119 to Prescaro et al. the contents of which are incorporated by reference as is fully set forth herein.

Air bag cushion including break-away tethers


A service methodology based on distribution of secured content, such as, movies, music, games, information and the like, whereby revenue may be generated for premier and pay-per-use access to the secured content. The service is manifested by the combination of a video disk reader, controller and authorization center. A service provider, for instance, locks up a movie on a video disk for which a premier event viewing date and time may be defined and which the provider may then directly distribute, in advance of the premier event, to potential consumers. Each consumer may purchase the right to view the movie once for a certain fee, for example $5.00, through online access from the controller to the authorization center, but the single viewing will only be allowed by the controller on or after the premier event. Thereafter, the consumer pays for viewing of the movie on a pay-per-use basis or over a defined window of time, perhaps for reduced fee, such as $1.00. Moreover, the online authorization process makes it possible to track consumer preferences at the authorization center, and as an alternative to the online payment processing, smart cards may be utilized for such.

The present invention relates, generally, to distribution of secured prerecorded content and, in particular, to a method and an apparatus for enabling access, dependent upon timed availability, to the secured content provisioned on a storage medium,
It is known to distribution in bulk (i.e., mass distribution) software packages. Such packages generally comprise a software application in encrypted format on a CD-ROM which is distributed in advance to potential consumers who would either have none or limited use of the software application. Each consumer desiring full use or access thereto typically is required to place a voice call to a 1-800 number and purchase, via credit card, from the distributor a password (decryption) key that is capable of unlocking the encrypted software. A decryption utility which is supplied with the package and executed by the consumer on a personal computer prompts for the key, responsive to which the consumer enters the key and subsequently is allowed to copy the software application onto a disk. Alternatively, the software package may execute functionality to invoke an online connection, when the computer includes a modem, with an automated authorization center from which the key may be downloaded to the computer.
The above distribution technique is limited in its ability to generate revenue from the software package, specifically, to receipt of a single payment for unrestricted use of the software application.
In U.S. Pat. Nos. 4,827,508 to Shear and 5,010,571 to Katznelson, systems for metering access to encrypted data in the form of a database provisioned on a CD-ROM are disclosed. Briefly, in Shear or Katznelson, a CD-ROM containing an encrypted database of interest to a user is distributed typically at nominal cost or at no cost. The user terminal includes a CD-ROM reader, and a remote cryptographic control unit which is provided with stored cryptographic keys needed to access to the database. The amount of actual data use, i.e. the retrieval and decryption of data from the CD-ROM, is metered locally and recorded as a stored data usage record. The charge for data access may be either in accordance with the amount of data decrypted, or in accordance with price information recorded in the respective data headers of each individual data packet.
The local stored data usage record is reported by telephone modem from the remote user terminal to a cryptographic operations center. Each remote cryptographic control unit has a stored user secret key, unique to that user terminal. Communication between the user terminal and the cryptographic operations center is protected by encryption under the user secret key, which is stored in a secure memory in the cryptographic control unit. The user secret key for each user is also stored in the cryptographic operations center. When a remote user terminal calls in and identifies itself, the cryptographic operations center looks up the corresponding user secret cryptographic user key, which is then used to secure the subsequent communication data exchange between the remote user terminal and the cryptographic operations center. Also stored in the cryptographic operations center are the various cryptographic keys corresponding to the available CD-ROM database titles. The user secret key is also used to secure the delivery of secret database keys from the cryptographic operations center to the user terminal for a desired CD-ROM database. After the data usage report is successfully uploaded to the cryptographic operations center, the user is then billed for the actual database usage based on the content of the uploaded data usage report. Thus, rather than being required to purchase an entire CD-ROM database, the user pays only for the amount of data actually used or decrypted from the CD-ROM.
It is, therefore, apparent that more flexible and alternative capabilities to unlock secured prerecorded content whereby revenue generation from distribution thereof is expanded are desirable. Shear or Katznelson provide such capabilities on the basis of measuring actual use of the content. Capabilities based on timed availability to the secured content is a further alternative.

Timed availability of secured content provisioned on a storage medium