Pneumatically operated projectile launching device

Information

  • Patent Grant
  • 6637421
  • Patent Number
    6,637,421
  • Date Filed
    Tuesday, September 24, 2002
    22 years ago
  • Date Issued
    Tuesday, October 28, 2003
    21 years ago
Abstract
An electronically-operated pneumatic launching device preferably includes a gun-shaped body having a trigger. A bolt preferably permits a projectile to be loaded into a chamber during a loading operation. The bolt can be configured to be opened by the application of pneumatic force. A valve is preferably located in the body and selectively supplies compressed gas from a compressed gas source to the chamber during a firing operation. An electrical circuit is also preferably arranged in the body to initiate the firing operation of the paintball gun in response to actuation of the trigger.
Description




BACKGROUND OF THE INVENTION




The current invention consists of a device for launching a projectile using pneumatic force. Guns using pneumatic force to propel a projectile are well known. In particular, it is well known to use pneumatic force to fire a fragile spherical projectile containing a colored, viscous substance (known as a “paintball”) which bursts upon impact with a target. However pneumatically operated guns used in paintball applications (as well as existing pneumatically operated guns in general) suffer from several deficiencies affecting the accuracy of the shot which are eliminated by the present invention.




Existing pneumatically operated guns invariably use a spring mechanism in some fashion to aid in generating the propellent force necessary to fire the projectile at the desired velocity from the gun. The use of a spring creates a non-linear transformation of energy from a pneumatically stored potential form into kinetic acceleration of the projectile, since the spring releases continuously less energy as it expands from its maximum deformation to its undeformed natural state. In the case of any flexible projectile in general and particularly in the case of paintballs, this non-linear transformation of energy causes some deformation in the shape of the projectile that alters the ballistic forces created upon it in flight, adversely affecting the accuracy with which the projectile can be fired to strike its intended target. The adverse ballistic effects stemming from projectile deformation are particularly felt at the low projectile-velocities required in paintball applications for player safety. Given the spring forces used in the existing state of the art, it is necessary to fire a paintball at the highest pneumatic pressures possible in order to eliminate these adverse ballistic effects. This has caused development of a thicker paintball shell to eliminate paintball breakage within the firing chamber of the gun. This increased thickness has in turn created a problem with paintball breakage as it impacts its target. To eliminate all of these problems without sacrificing player safety, it has become necessary in paintball applications to find a way to minimize projectile deformation at low pneumatic pressure levels, in order to permit the accurate sighting and firing of a low velocity shot.




The present invention solves all of these problems by eliminating the use of spring mechanisms in the transfer of energy to the projectile during the launching sequence. The invention uses a launching sequence which results in only the application of pneumatic force to the projectile. This creates a linear change in the amount of energy that is applied to the projectile as the pneumatically stored energy undergoes expansion and decompression upon release. This in turn minimizes the physical deformation of the projectile during the launching sequence, increasing the accuracy of the shot. In paintball applications, this linear application of force contributes greatly to increased accuracy, since a non-linear transfer of force at the low pressures required to limit paintball velocities to safe levels exaggerates the adverse ballistic effects on the paintball, due to its low velocity.




The accuracy of the present invention has been proven through testing at the projectile velocity levels used in paintball applications. Ten shot clusters from a conventional hand held paintball gun that is fired from a target distance of 60 yards typically exhibits an average maximum inaccuracy of 15 inches for projectile velocities in the 290 to 300 feet per second range. The same conventional paintball gun shot under the same conditions from a rigid mount typically exhibits an average maximum inaccuracy of 10 inches. In contrast, the present invention exhibited an average maximum inaccuracy of less than 8 inches when fired from a hand held position, and an average maximum inaccuracy of 4 inches when rigidly mounted.




The invention also provides increased aiming accuracy through the use of a cam shaped trigger and electrical switch arrangement to initiate the projectile launching sequence. This arrangement minimizes the pull force necessary to engage the switch by contact with the trigger, due to the mechanical advantage provided by the transfer of force through the cam. This in turn minimizes the amount of hand and arm movement experienced upon pulling the trigger, which increases firing accuracy.




Finally, the present invention also provides a significant accuracy advantage over all prior art spring-loaded guns at all pneumatic operating pressures, due to the minimized recoil experienced after a shot is fired. Typical spring-loaded guns exhibit greater recoil than does the invention, due to the non-linear reaction forces created on the gun body by the expansion of the spring. In contrast, the elimination of spring loading in the present invention eliminates these non-linear forces, minimizing the amount of recoil experienced and thus allowing greater accuracy over all types of existing spring-loaded gun designs in the firing of a shot.




Accordingly, it is an object of the present invention to provide a projectile launching device that uses only pneumatic force to propel a projectile.




It is also an object of the present invention to provide a projectile launching device for use in the recreational and professional sport of paintball that uses only pneumatic force to propel the paintball.




It is also an object of the present invention to provide a projectile launching device which can be aimed and fired with greater accuracy than all types of spring-loaded guns at all pneumatic operating pressures.




It is also an object of the present invention to provide a projectile launching device for use in the recreational and professional sport of paintball which can be aimed and fired with greater accuracy than existing paintball guns at low pneumatic operating pressures.




It is also an object of the present invention to provide a projectile launching device that uses electro-pneumatic control to release the pneumatic force that propels the projectile.




It is also an object of the present invention to provide a projectile launching device for use in the recreational and professional sport of paintball that uses electro-pneumatic control to release the pneumatic force that propels the projectile.




SUMMARY OF THE INVENTION




The pneumatically operated projectile launching device is preferably comprised of three principal elements: a body which houses and interconnects all of the pneumatic components and also houses the electrical power source, a grip mounted to the body which includes an electrical switch that activates a launching sequence, and an electrical control unit housed within both the body and the grip which directs flow between the pneumatic components to load, cock and fire the gun.




The body preferably contains a plurality of bores in communication with each other including a bore containing and distributing pressurized gas, a bore containing a compressed gas storage chamber and mechanisms for filling the storage chamber with gas and releasing gas from the storage chamber to fire the projectile, and a bore containing mechanisms for loading and launching the projectile. The electrical control unit preferably includes an electrical power source which activates an electrical timing circuit when the electrical switch is closed, and two electrically operated pneumatic flow distribution devices which are sequentially energized by the electrical timing circuit to enable the loading of a projectile for launching and to release compressed gas from the storage chamber to fire the projectile, respectively.




Before the initiation of a launching sequence the compressed gas storage chamber is filled with compressed gas while the projectile launching mechanism is disabled. Filling of the compressed gas storage chamber is preferably accomplished automatically by actuation of the compressed gas filling mechanism. When the electrical switch is closed to initiate the launching sequence the projectile is first loaded into the launching mechanism by electrical timing circuit actuation of the first electrically operated pneumatic flow distribution device. The projectile is then fired when the electrical timing circuit actuates the second electrically operated pneumatic flow distribution device to release gas from the compressed gas storage chamber into the launching mechanism.




The present invention eliminates the use of spring mechanisms in the transfer of energy to the projectile during the launching sequence. The invention uses a launching sequence which results in only the application of pneumatic force to the projectile. This creates a linear change in the amount of energy that is applied to the projectile as the pneumatically stored energy undergoes expansion and decompression upon release. This in turn minimizes the physical deformation of the projectile during the launching sequence, increasing the accuracy of the shot. In paintball applications, this linear application of force contributes greatly to increased accuracy, since a non-linear transfer of force at the low pressures required to limit paintball velocities to safe levels exaggerates the adverse ballistic effects on the paintball, due to its low velocity.




The accuracy of the present invention has been proven through testing at the projectile velocity levels used in paintball applications. Ten shot clusters from a conventional hand held paintball gun that is fired from a target distance of 60 yards typically exhibits an average maximum inaccuracy of 15 inches for projectile velocities in the 290 to 300 feet per second range. The same conventional paintball gun shot under the same conditions from a rigid mount typically exhibits an average maximum inaccuracy of 10 inches. In contrast, the present invention exhibited an average maximum inaccuracy of less than 8 inches when fired from a hand held position, and an average maximum inaccuracy of 4 inches when rigidly mounted.




The invention also provides increased aiming accuracy through the use of a cam shaped trigger and electrical switch arrangement to initiate the projectile launching sequence. This arrangement minimizes the pull force necessary to engage the switch by contact with the trigger, due to the mechanical advantage provided by the transfer of force through the cam. This in turn minimizes the amount of hand and arm movement experienced upon pulling the trigger, which increases firing accuracy.




Finally, the present invention also provides a significant accuracy advantage over all prior art spring-loaded guns at all pneumatic operating pressures, due to the minimized recoil experienced after a shot is fired. Typical spring-loaded guns exhibit greater recoil than does the invention, due to the non-linear reaction forces created on the gun body by the expansion of the spring. In contrast, the elimination of spring loading in the present invention eliminates these non-linear forces, minimizing the amount of recoil experienced and thus allowing greater accuracy over all types of existing spring-loaded gun designs in the firing of a shot.











BRIEF DESCRIPTION OF THE DRAWINGS




FIG. (


1


) is a side view of the pneumatically operated projectile launching device.




FIG. (


1


A) is a side view of the pneumatically operated projectile launching device.




FIG. (


2


) is a rear view of the pneumatically operated projectile launching device.




FIG. (


3


) is a top view of the body of the pneumatically operated projectile launching device.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT




The pneumatically operated projectile launching device is preferably comprised of three principal elements: a body which houses and interconnects all of the pneumatic components and also houses the electrical power source; a grip mounted to the body which includes a trigger and an electrical switch that activates the launching sequence; and an electrical control unit housed within both the body and the grip which directs flow between the pneumatic components to load, cock and fire the gun.




As shown in FIG. (


2


), the body preferably has three cylindrical pneumatic bores with axes that are preferably parallel to the longitudinal axis of the gun body


40


. The gun body


40


can be made of materials suitable in the art for withstanding the force of the launching sequence such as metal or plastic. The first bore


1


contains compressed gas and is preferably sealed by a removable fitting


5


which is removed to inject the gas. The first bore


1


is preferably in communication with the second bore


2


and the third bore


3


through a series of ported passageways


6




a


and


6




b


, respectively, bored through the interior of the gun body


40


. As shown in FIG. (


3


), the second bore


2


houses the compressed gas storage chamber


11


, the compressed gas filling mechanism


12


and the compressed gas releasing mechanism


13


. The third bore


3


is also preferably in communication with both the first bore


1


and the second bore


2


through a series of ported passageways


6




b


and


6




c


, respectively, bored through the interior of the gun body


40


. As shown in FIG. (


1


), the third bore


3


houses the projectile loading mechanism


14


and the projectile launching mechanism


15


.




As shown in FIG. (


3


), the compressed gas storage chamber


11


is bordered by the interior walls of the second bore


2


and by the compressed gas filling mechanism


12


on one end and by the compressed gas releasing mechanism


13


on the end opposite the compressed gas filling mechanism


12


. The compressed gas storage chamber


11


is filled with compressed gas from the first bore


1


by means of the interconnections


6




a


between the first bore


1


and the second bore


2


when the compressed gas filling mechanism


12


is actuated. The compressed gas storage chamber


11


releases stored gas to the projectile launching mechanism


15


by means of the interconnections


6




c


between the second bore


2


and the third bore


3


when the compressed gas releasing mechanism


13


is actuated.




As shown in FIG. (


3


), the compressed gas filling mechanism


12


preferably consists of a valve


16


with a metallic or plastic conically or spherically shaped plug


17


which is normally shut against a metallic, plastic, or rubber conically or concavely shaped seat


18


by the loading of a spring


19


when the compressed gas filling mechanism


12


is not in its actuated position. The plug


17


is attached to a second end


20




b


of a metallic or plastic rod-shaped mechanical linkage


20


which opens the valve


16


by compressing the spring


19


when the compressed gas filling mechanism


12


is in its actuated position to create a flow path for compressed gas from the first bore


1


to the compressed gas storage chamber


11


.




As shown in FIG. (


3


), the mechanical linkage


20


passes through the compressed gas storage chamber


11


and has a first end


20




a


which is attached to the compressed gas releasing mechanism


13


. The compressed gas releasing mechanism


13


preferably consists of a metallic or plastic cylindrical piston


21


which slides along the longitudinal axis of the second bore


2


in a space adjacent to the compressed gas storage chamber


11


. A second end


21




b


of the piston


21


is adjacent to the compressed gas storage chamber


11


and is connected to the first end


20




a


of the mechanical linkage


20


. The second end of the piston


21




b


has a flexible O-ring seal


23


made of rubber or other suitable synthetic sealing materials such as polyurethane that prevents gas leakage out of the compressed gas storage chamber


11


. Compressed gas from the first bore


1


is applied to the second end of the piston


21




b


to actuate the compressed gas releasing mechanism


13


by unseating the O-ring


23


sealing the compressed gas storage chamber


11


to allow stored gas to be released from the compressed gas storage chamber


11


into the projectile launching mechanism


15


by means of the interconnections


6




c


between the second bore


2


and the third bore


3


. The piston


21


contains a notched area


22


adjacent to the O-ring


23


that provides a surface for applying compressed gas pressure from the first bore


1


to unseat the O-ring


23


and actuate the compressed gas releasing mechanism


13


.




The piston


21


has a first end


21




a


opposite the compressed gas storage chamber


11


which is subjected to pneumatic pressure to actuate the compressed gas filling mechanism


12


by transmitting through the mechanical linkage


20


a compression force on the spring


19


that opens the valve


16


. The opening in the valve


16


is formed when the plug


17


is separated from the seat


18


to create a flow path for compressed gas from the first bore


1


to the compressed gas storage chamber


11


by means of the interconnections


6




a


between the first bore


1


and the second bore


2


. Compressed gas from the first bore


1


is applied to the first end of the piston


21




a


to open the valve


16


and actuate the compressed gas filling mechanism


12


. The first end of the piston


21




a


also contains a flexible O-ring seal


24


which prevents actuating pressure leakage into the compressed gas storage chamber


11


when the compressed gas filling mechanism


12


is actuated.




As shown in FIG. (


1


), the third bore


3


of the gun body


40


houses the projectile loading mechanism


14


and the projectile launching mechanism


15


. The projectile loading mechanism


14


preferably consists of a metallic or plastic cylindrical piston


25


which slides along the longitudinal axis of the third bore


3


. The projectile launching mechanism


15


preferably consists of a metallic or plastic cylindrical bolt


26


which also slides along the longitudinal axis of the third bore


3


and which has a port


27


for receiving released gas from the compressed gas storage chamber


11


to propel a projectile


41


from the gun body


40


. The bolt


26


is connected to the piston


25


by a metallic or plastic rod-shaped mechanical linkage


28


, which moves the bolt


26


to receive the projectile


41


by gravity loading from the projectile feed mechanism


29


when the projectile loading mechanism


14


is actuated.




The projectile loading mechanism


14


is actuated when compressed gas from the first bore


1


is applied by means of the interconnections


6




b


between the first bore


1


and the third bore


3


to a first end


25




a


of the piston


25


which is attached to the mechanical linkage


28


. This compressed gas acts against the piston


25


and the mechanical linkage


28


to drive the bolt


26


back to the cocked position which enables the loading of a projectile


41


into engagement with the bolt


26


from the projectile feed mechanism


29


. The subsequent release of stored gas from the compressed gas storage chamber


11


through the bolt port


27


will drive the projectile


41


from the gun body


40


. After the launching sequence has been completed compressed gas is applied from the first bore


1


to a second end


25




b


of the piston


25


opposite the mechanical linkage


28


to disable the bolt


26


from receiving a projectile


41


by driving the bolt


26


to the shut position.




The second principal element is the grip, shown in FIG. (


1


). The grip is mounted to the body and preferably houses three principal components, a handle


7


, a trigger


8


and an electrical switch


30


. The handle


7


can be made of any suitable material such as metal or plastic and is preferably shaped with a hand grip to allow the gun to be held in a pistol-like fashion. The metallic or plastic trigger


8


is attached to the handle


7


and preferably has a leading edge shaped to be pulled by two fingers with a cam shaped trailing edge to engage the electrical switch


30


. A trigger guard


9


which prevents accidental trigger displacement is preferably attached to the trigger


8


. A spring


10


preferably returns the trigger


8


to a neutral position after the electrical switch


30


has been contacted to initiate a launching sequence. The electrical switch


30


is preferably a two-pole miniature switch which contains a plunger


31


loaded by a spring


32


.




As shown in FIG. (


1


), the third principal element is the electrical control unit which is housed within both the body and the grip. The electrical control unit preferably consists of an electrical timing circuit


34


housed in the handle


7


along with two electrically operated 3-way solenoid valves


35


and


36


housed in the gun body


40


and an electrical battery power source


33


housed in a fourth bore


4


of the gun body


40


. The electrical timing circuit


34


is a network of electronic components that includes two solid state integrated circuit timers which control the launching sequence by sending energizing pulses to the solenoid valves


35


and


36


which function as electrically operated pneumatic flow distribution mechanisms. When actuated the solenoid valves


35


and


36


pass compressed gas flow from the first bore


1


and when not actuated the solenoid valves


35


and


36


operate to vent gas from the pressurized area. Upon initiation of the launching sequence the electrical timing circuit


34


energizes each solenoid valve


35


or


36


separately in a timed sequence to ensure that each solenoid valve


35


or


36


either passes or vents pressurized gas at the appropriate time within the launching sequence to propel a projectile


41


from the gun body


40


.




DETAILED DESCRIPTION OF OPERATION




Before the initiation of a launching sequence the introduction of compressed gas into the first bore


1


will preferably automatically cause pneumatic pressure to be applied to the first end of piston


21




a


to cause gas flow from the first bore


1


to the compressed gas storage chamber


11


through actuation of the compressed gas filling mechanism


12


as described above. Simultaneously pneumatic pressure will preferably automatically be applied to the second end of piston


25




b


driving the bolt


26


to the shut position to disable the loading of a projectile


41


. When these conditions are met the compressed gas storage chamber


11


is charged with the bolt


26


closed and the gun is ready for the initiation of a launching sequence.




A launching sequence is preferably initiated when the electrical switch


30


completes a circuit between the electrical power source


33


and the electrical timing circuit


34


as the cam shaped trailing edge of the trigger


8


contacts the plunger


31


to compress the spring


32


. When contact is made the electrical power source


33


energizes the electrical timing circuit


34


which first sends an energizing pulse to actuate the first solenoid valve


35


. When actuated the first solenoid valve


35


passes pressurized gas flow to the first end of piston


25




a


to actuate the projectile loading mechanism


14


by driving the bolt


26


back to the cocked position and to enable the loading of a projectile


41


into engagement with the bolt


26


from the projectile feed mechanism


29


. The electrical timing circuit


34


then sends an energizing pulse to actuate the second solenoid valve


36


which then passes pressurized gas flow to the second end of piston


21




b


to actuate the compressed gas releasing mechanism


13


. Simultaneously the first solenoid valve


35


returns to its non-actuated position to vent the first end of piston


25




a


. This venting in combination with the actuation of the compressed gas releasing mechanism


13


allows the stored gas released into the bolt port


27


from the compressed gas storage chamber


11


to drive the projectile


41


from the gun body


40


.




After the launching sequence has been completed pneumatic pressure is again preferably automatically applied to the second end of piston


25




b


to drive the bolt


26


shut. Similarly pneumatic pressure is again preferably automatically applied to the first end of piston


21




a


to actuate the compressed gas filling mechanism


12


to re-pressurize the compressed gas storage chamber


11


as described above.




The launching sequence may then be repeated as many as nine times per second. The volume of the compressed gas storage chamber


11


and the bore interconnections


6


are preferably sized to produce projectile velocities in the 290 to 300 feet per second range at an operating gas pressure of approximately 125 pounds per square inch gauge pressure. However, the 1.5 cubic inch volume of the compressed gas storage chamber


11


and the 0.0315 square inch area of the bore interconnection orifices


6


will allow operation of the preferred embodiment at gas pressures of up to 175 pounds per square inch gauge pressure. As will be obvious to one skilled in the art, these parameters may be varied in order to allow for a differing operating gas pressure or projectile velocity.




While presently preferred embodiments have been shown and described in particularity, the invention may be otherwise embodied within the scope of the appended claims.



Claims
  • 1. An electronically-operated pneumatic launching device comprising:a gun-shaped body including a trigger; a bolt for loading a projectile into a chamber during a loading operation, wherein said bolt is configured to be opened by the application of a pneumatic force; a valve located in the body and configured to selectively supply compressed gas from a compressed gas source to the chamber during a firing operation; and an electrical circuit arranged in the body for initiating the firing operation of the launching device in response to actuation of the trigger.
  • 2. A device according to claim 1, wherein the pneumatic force to open the bolt is applied to a first end of a pneumatic mechanism, and wherein the pneumatic mechanism is coupled to the bolt through a mechanical linkage.
  • 3. A device according to claim 2, wherein the bolt is configured to be closed by the application of pneumatic force to a second end of the pneumatic mechanism.
  • 4. A device according to claim 1, wherein said electrical circuit comprises an electronic solenoid configured to receive a signal from an electrical timing circuit to initiate the firing operation.
  • 5. A device according to claim 4, wherein the electronic solenoid is part of a solenoid valve configured to route compressed gas to a pneumatically-controllable actuator to open the valve to cause compressed gas from the compressed gas source to enter the firing chamber during the firing operation.
  • 6. A device according to claim 5, wherein the actuator is a pneumatic mechanism configured to be moved by operation of the solenoid valve.
  • 7. A device according to claim 1, further comprising:one or more solenoid valves configured to electro-pneumatically control a movement of the bolt for loading the projectile into the firing chamber based on an electronic signal from the electrical circuit; and wherein said one or more solenoid valves are further configured to control an opening of the valve to cause compressed gas to enter the firing chamber from the compressed gas source based on an electronic signal from the electrical circuit.
  • 8. A device according to claim 7, further comprising:a pneumatic mechanism configured to receive compressed gas from the one or more solenoid valves and to vent compressed gas through the one or more solenoid valves to operate the pneumatic mechanism; the pneumatic mechanism communicating with the bolt via a mechanical linkage; and wherein operation of the pneumatic mechanism controls movement of the bolt.
  • 9. A device according to claim 7, further comprising:a compressed gas storage chamber configured to lie in a fluid path between the compressed gas source and the firing chamber to store compressed gas for the firing operation; a pneumatic mechanism configured to receive compressed gas from the one or more solenoid valves and to vent compressed gas through the one or more solenoid valves to operate the pneumatic mechanism; and wherein said pneumatic mechanism is configured to open the valve to release compressed gas from the compressed gas storage chamber into the firing chamber.
  • 10. An electronic circuit board for controlling the device of claim 1.
  • 11. An electrically-controllable pneumatic projectile launching device, comprising:a body comprising a trigger; a bolt configured to be opened by the application of a pneumatic force; and an electronic circuit board mounted in the body, wherein the electronic circuit board initiates a launching operation based on trigger actuation.
  • 12. A device according to claim 11, further comprising:an electronic valve located in the gun body and configured to receive and selectively distribute compressed gas; and a pneumatic mechanism located in the gun body, wherein movement of a piston in the pneumatic mechanism is controlled by selective distribution of compressed gas through the electronic valve based on electrical signals from the electronic circuit board.
  • 13. A device according to claim 12, wherein:the piston is mechanically coupled to the bolt; and the pneumatic mechanism is configured to operate the bolt.
  • 14. A device according to claim 12, wherein the pneumatic mechanism is configured to operate a firing valve to launch a projectile from the device.
  • 15. A pneumatically operated projectile launching device, comprising:a body which houses and interconnects pneumatic components and an electrical power source of the device; a grip mounted to the body, said grip comprising a trigger and an electrical switch that activates a launching sequence of the device; and an electrical control unit housed within the body, the grip, or both, said electrical control unit configured to direct a flow of compressed gas between the pneumatic components to load and fire the device.
  • 16. A device according to claim 15, wherein the electrical control unit comprises a solenoid valve.
  • 17. A device according to claim 16, wherein the device is loaded by directing compressed gas through the solenoid valve to an end of a pneumatic mechanism to open a bolt, wherein the pneumatic mechanism is mechanically coupled to the bolt.
  • 18. A device according to claim 16, wherein the device is fired by directing compressed gas through the solenoid valve to an end of a pneumatic mechanism to open a firing valve.
  • 19. A device according to claim 15, comprising:a power supply connection configured to receive power from a power supply; an electrical timing circuit configured to receive electrical power through the power supply connection and to initiate a launching sequence of the device in response to actuation of a trigger; and at least one solenoid valve configured to receive one or more electronic pulses from the electrical timing circuit to launch a paintball from the paintball gun.
  • 20. An electrical control unit according to claim 19, wherein the at least one solenoid valve comprises two three-way solenoid valves.
Parent Case Info

This application is a continuation of U.S. patent application Ser. No. 09/490,735 (now U.S. Pat. No. 6,474,326), filed Jan. 25, 2000, which is a continuation of patent application Ser. No. 08/586,960 (now U.S. Pat. No. 6,035,843), filed Jan. 16. 1996.

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Continuations (2)
Number Date Country
Parent 09/490735 Jan 2000 US
Child 10/254891 US
Parent 08/586960 Jan 1996 US
Child 09/490735 US