Hybrid propellant electromagnetic gun system

Abstract

A hybrid gun device composed of two barrels (1,10) that accept energy from combustion of standard propellant (6), one barrel (10) being operative to produce a high intensity electric current to add accelerating energy to a projectile (7) in the second barrel (1) and at least one coil (8) stage to convert energy between electrical and kinetic to cause the projectile (7) to be launched at hypervelocity.

Claims

1. A hybrid gun for firing a projectile that is at least partly electrically conductive, said gun comprising: a main gun portion having a proximal end and a distal end, and a first longitudinal bore extending between said ends and open at both ends, for receiving the projectile, an auxiliary gun portion having a proximal end and a distal end, and a second longitudinal bore extending between said ends, open at said proximal end and closed at said distal end; a driver body of electrically conductive material installed in, and movable along, said second longitudinal bore, said driver body being normally retained at said proximal end of said auxiliary gun portion; a breech block enclosing a space for containing a propellant and communicating with said proximal ends of said first and second longitudinal bores; and an electromagnetic energy transfer circuit coupled between said auxiliary gun portion and said main gun portion and including inductors that transfer kinetic energy from said driver body to the projectile following detonation of the propellant.

2. The hybrid gun of claim 1, wherein each of said gun portions comprises a respective barrel part along which said electromagnetic energy transfer circuit is disposed, said respective barrel parts being made of a material that is substantially transparent to electromagnetic radiation.

3. The hybrid gun of claim 2, wherein said material that is substantially transparent to electromagnetic radiation is a dielectric material.

4. The hybrid gun of claim 3, wherein said dielectric material is a carbon composite material.

5. The hybrid gun of claim 1, wherein each said gun portion comprises a main barrel part and an extension barrel part, said second barrel part of each said gun portion being made of a material that is substantially transparent to electromagnetic radiation.

6. The hybrid gun of claim 5, wherein said material that is substantially transparent to electromagnetic radiation is a dielectric material.

7. The hybrid gun of claim 5, wherein said dielectric material is a carbon composite material.

8. The hybrid gun of claim 5, wherein said electromagnetic energy transfer circuit comprises at least one pair of coils including a decelerator coil positioned along said extension barrel part of said auxiliary gun portion, and an accelerator coil positioned along said extension barrel part of said main gun portion.

9. The hybrid gun of claim 8, wherein said electromagnetic energy transfer circuit further comprises a current source connectable to said decelerator coil to supply a seed current to said decelerator coil.

10. The hybrid gun of claim 9, wherein said electromagnetic energy transfer circuit further comprises a switching network connected to said coils and having a first switching state in which the seed current is supplied to said decelerator coil and a second switching state in which said coils are connected together in series.

11. The hybrid gun of claim 5, further comprising a detent element in said bore of said auxiliary gun component that temporarily holds said driver body at said proximal end of said auxiliary gun portion.

12. The hybrid gun of claim 1, wherein said electromagnetic energy transfer circuit comprises at least one pair of coils including a decelerator coil positioned along said extension barrel part of said auxiliary gun portion, and an accelerator coil positioned along said extension barrel part of said main gun portion.

13. The hybrid gun of claim 12, wherein said electromagnetic energy transfer circuit further comprises a current source connectable to said decelerator coil to supply a seed current to said decelerator coil.

14. The hybrid gun of claim 13, wherein said electromagnetic energy transfer circuit further comprises a switching network connected to said coils and having a first switching state in which the seed current is supplied to said decelerator coil and a second switching state in which said coils are connected together in series.

15. The hybrid gun of claim 1, further comprising a detent element in said bore of said auxiliary gun component that temporarily holds said driver body at said proximal end of said auxiliary gun portion.

16. The hybrid gun of claim 15, wherein said main gun portion has a vent communicating with said bore to permit escape of propellant gas from said bore.

17. The hybrid gun of claim 1, wherein said main gun portion has a vent communicating with said bore to permit escape of propellant gas from said bore.

18. The hybrid gun of claim 1, further comprising a single body of propellant material disposed in said space enclosed by said breach block.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a longitudinal-sectional view of one embodiment of the invention, which will be housed in a suitable gun mount.

(2) FIG. 2 is a first longitudinal-sectional view of the embodiment of the invention as illustrated in FIG. 1, which illustrates driver deceleration and projectile acceleration during firing of the gun.

(3) FIG. 3 is a second longitudinal-sectional view of the embodiment of the invention as illustrated in FIG. 1, which illustrates driver deceleration and projectile acceleration during firing of the gun.

(4) FIG. 4 is a schematic view of the electrical components according to the invention, which will be housed in a suitable position adjacent to the gun.

(5) FIG. 5 is a schematic of propellant action and electrical functions according to the invention.

(6) FIGS. 6a to 6c show the operating sequence of an exemplary coil circuit according to the invention, which acts to supply current to the acceleration coils.

(7) FIG. 7 is a pictorial showing one form of construction of components according to the present invention.

(8) FIG. 8 is a diagram of one exemplary embodiment of circuitry for operating a hybrid gun device according to the invention.

(9) FIG. 9 is a circuit diagram of a circuit embodiment of the invention associated with three coil sets.

DETAILED DESCRIPTION OF THE INVENTION

(10) The basic components of a hybrid gun device for launching projectiles according to the invention are shown in FIGS. 1-4. The device includes a main barrel with breech, auxiliary barrel with breech, cartridge case of propellant, driver mass, projectile, deceleration and acceleration coils stages, an electrical switching network, and an external electrical source unit to supply a starting current for the coil stages along the auxiliary barrel.

(11) As shown, the main gun portion of the system has a main barrel 1, a breech section 2 that houses the main barrel 1, a breechblock 3, a main barrel hollow core, or bore, 4 open at both ends, and a main barrel extension 5. The hollowed volume of the breech section 2 is filled with propellant 6. The main barrel breech 2 contains a projectile 7. Surrounding main barrel extension 5 are acceleration coil stages 8 and projectile position sensors 52. In addition, connected to the breech section 2 is an auxiliary breech section 9 to which auxiliary gun barrel 10 is attached. Auxiliary barrel 10 contains an auxiliary barrel hollow core, or core, 11 closed at its distal, or outlet, end. Attached to the end of the auxiliary barrel 10 is an auxiliary barrel extension 12 that contains a residual velocity absorber 13. The auxiliary barrel extension 12 is equipped with vent slots 14. Auxiliary barrel 10 contains driver mass 15 and driver positioning detent 16. The auxiliary barrel extension 12 has attached deceleration coil stages 17 and driver position sensors 51. The main barrel breech 2 and auxiliary breech 9 have an internal orifice 18 that leads from the barrel breech 2 to the interior hollow of auxiliary breech 9. Main barrel 1 and main barrel extension 5 are connected by barrel collar 19. Each coil 17 is coupled to a respective coil 8, as shown in FIG. 6.

(12) Auxiliary barrel 10 and auxiliary barrel extension 12 are also connected by barrel collar 19, which simply maintains the desired positioning between the barrels. Barrel collar 19 also connects main barrel 1 to auxiliary barrel 10. Main barrel 1 and main barrel extension 5 may not have the same diameter and length as auxiliary barrel 10 and auxiliary barrel extension 12. The main barrel 1 contains venting slots 50 for venting of gaseous products associated with combustion of propellant 6.

(13) Detent 16 is a semi-locking mechanism to hold the driver in place initially when the chamber has no pressure in it. It basically is at least one thin solid body (two are shown in FIG. 1) having parallel opposed sides and shaped at the side facing radially inwardly, the detent surface, to facilitate retention of driver 15 at the proximal, or rear, end of barrel 10. The, or each, detent slides radially in a cavity of mating size cut into the gun breech. Its narrow length extends along the longitudinal axis of barrel 10. According to one embodiment, its radial dimension may be 8 times its narrow length and its circumferential dimension may be 4 times its narrow length. There may be several such detents located about the gun barrel circumference.

(14) The, or each, detent 16 can move only in the radial direction. The, or each, cavity receiving a detent 16 contains a coil spring (not shown) whose coil axis is radial. The spring bears against the radially outwardly facing side of detent 16 to urge the detent radially inwardly. The cavity may have a depth about equal to one-half the radial dimension of the detent to seat the detent into the cavity. When retained by detent(s) 16, driver 15 is not free to move down the gun barrel.

(15) However, a small taper is placed on the half of the detent surface that faces the breech end of the barrel. When combustion pressure acts on the base of driver 15, significant pressure must build up before the component of force acting on the detent due to the inclination of the tapered surface in the outward radial direction can overcome the spring force and allow the force due to pressure to move the detent(s) outward radially, thus freeing the driver to move longitudinally under the effect of the pressure from the propellant combustion. After the driver leaves the vicinity of the detent(s) and after propellant gases have left the barrel, the detent(s) will move inward due to the force of the spring.

(16) To return the driver(s) to the initial position (shown in FIG. 1) requires a means to lift the detent. One method could be to place a taper on the detent surface that faces the muzzle end of the barrel so that the driver's motion upon return will impact that tapered surface with sufficient force to retract the detent and allow the driver(s) to return to its starting position. With the driver(s) in starting position, the force of the spring moves the detent into a groove that may be cut in the driver body.

(17) In operation, propellant 6 is ignited and upon combustion creates high pressure within the hollow of main breech 2 and orifice 18. The combustion pressure is applied to the base of projectile 7 and to driver 15, which accelerates projectile 7 in main barrel hollow core 4 and driver 15 in auxiliary barrel hollow core 11. Pressure produced by combustion of propellant 6 is sufficient to overcome semi-locking detent 16. As projectile 7 moves from initial position 20 to intermediate position 21 and driver 15 moves from position 22 to position 23, combustion of propellant 6 produces gases 24 that fill main barrel hollow core 4 and auxiliary barrel hollow core 11 up to the base of projectile 7 and the base of driver 15. When projectile 7 reaches position 21 and driver 15 reaches position 23, the acceleration phase of projectile 7 and driver 15 due to combustion of propellant 6 comes to an end. As projectile 7 passes by venting slots 50, combustion gases 24 are released to the region surrounding the gun system.

(18) With completion of the first acceleration phase by propellant gases 24, projectile 7 at projectile position 21 approaches the vicinity of main barrel coil stages 8 located along main barrel extension 5, where a second phase of projectile acceleration begins. Also, driver 15 located at position 23 reaches the vicinity of auxiliary barrel coil stages 17 along auxiliary barrel extension 12 where deceleration of driver 15 begins.

(19) Driver 15 decelerates as it passes through auxiliary coil stages 17 and arrives at near zero velocity at driver position 25. Should any small residual velocity of driver 15 exist at driver position 25, residual velocity absorber 13 acts to bring driver 15 to rest. Ambient air that initially filled hollow core 11 ahead of driver 15 is vented through vent slots 14 as driver 15 moves to position 25. Deceleration of driver 15 in auxiliary barrel coil stages 17 generates electrical energy that is sequentially applied to main barrel coil stages 8. Projectile 7, passing through main barrel coil stages 8 to projectile position 26, is accelerated by main barrel coils stages 8 to a velocity beyond that acquired at projectile position 21. The projectile acceleration taking place within the final stage or stages of coil stages 8 can be altered by changing applied current so that a velocity correction is made to projectile 7.

(20) After projectile 7 exits main barrel extension 5, residual propellant gases 24 that have not been vented by venting slots 50 can exit the muzzle of main barrel extension 5. Exit of propellant gases 24 through venting slots 19 and the muzzle of main barrel extension 5 ultimately reduces pressure in main barrel hollow core 4 and auxiliary barrel hollow core 11 to ambient conditions.

(21) A small reversed electrical current applied to auxiliary coil stages 17 provides a restoring force that moves driver 15 from driver position 25 back to the initial position 22 of driver 15 in advance of the next shot.

(22) An alternate means of restoring driver 15 to position 22 uses a small amount of stored gases from propellant gases 24 that are subsequently injected into space between driver position 25 and absorber 13 together with a means for temporarily closing vent slots 14. Breechblock 3 is opened and a new projectile 7 and charge of propellant 6 is loaded into the main barrel breech 2. Breechblock 3 is closed and propellant 6 is ready to be ignited for another shot.

(23) Referring to FIG. 4, external low-level power source 27 connects electrically and conductively to deceleration coil stages 17 through source cable 28. Deceleration coil stages 17 connect to switching network 29 through power cable 30 while electrical output from switching network 29 connects to acceleration coil stages 8 through output cable 31. Source cable 28, power cable 30, and output cable 31 may contain multiple wires such that power source 27 and switching network 29 can supply sequenced electrical pulses to decelerator coil stages 17 and accelerator coil stages 8.

(24) FIG. 5 shows a schematic of propellant action and electrical functions that take place sequentially during gun firing. At 100, the signal to fire the gun is produced and acts to initate, at 101, supply of a seed current to the decelerator coil of at least the first coil set initiate, at 103, delay of an ignition signal to the projectile cartridge case primer. At 105 the propellant is ignited and the projectile receives its initial acceleration. At 107, the driver interacts with successive decelerator coils. At 109, high current is sent to each successive accelerator coil and, at 111, the projectile undergoes successive supplemental accelerations.

(25) FIG. 6 give one example of a circuit that produces electrical pulses to accelerate projectile 7. The circuit is comprised of battery 32 representing power source 27, capacitor 33, a single decelerator coil represented by decelerator inductor 34, decelerator coil resistance as decelerator coil resistor 35, a single accelerator coil given as accelerator coil inductor 36, and an accelerator coil resistance represented by accelerator resistor 37. Circuit switches include power switch 38, decelerator coil switch 39, and accelerator coil switch 40. Coil 34 corresponds to coil 17 and coil 36 corresponds to coil 8.

(26) In operation, as shown in FIG. 6a, capacitor 33 is electrically charged from battery 32 when initially open switch 38 is subsequently closed forming an initial circuit that contains only the battery 32 and capacitor 33. Switch 39 and switch 40 are open to prevent current from flowing in the remainder of the circuit during the time taken to fully charge capacitor 33.

(27) Then, as shown in FIG. 6b, after capacitor 33 is sufficiently charged, switch 38 is opened while switch 39 is closed, which creates an intermediate circuit that includes capacitor 33, inductor 34, and resistor 35. In this circuit state, electrical current is discharged from capacitor 33 into decelerator coil inductor 34 and decelerator coil resistor 35. Current flow through decelerator coil inductor 34 establishes a magnetic field 41 within the decelerator coil inductor 34. As driver 15 enters decelerator coil inductor 34, circuit inductance is reduced, driver 15 is decelerated, and the current rises, which flows back into capacitor 33 producing a high level of energy stored in capacitor 33. Direction of current flow within the decelerator coil inductor 34, the established magnetic field 41, and current induced in metallic driver 15 develop decelerating forces that act on driver 15.

(28) Then, as shown in FIG. 6c, after an increment of velocity is lost from the driver by entering decelerator coil 36, a final circuit state is established that connects capacitor 33 with accelerator coil inductor 36 and accelerator coil resistor 37 by closing switch 41 and opening switch 39. Current flow through the accelerator coil inductor 36 develops a magnetic field 42 within accelerator coil inductor 36. The direction of current flow in the final circuit, direction of magnetic field 42 and induced current in the projectile 7 develops accelerating forces acting on projectile 7. After initial, intermediate, and final circuits complete assigned functions, all switches are returned to positions of the initial circuit in advance of the next shot.

(29) Exemplary materials for the above described components may include conducting metals such as copper or aluminum for projectile 7, driver 15, wires for inductor 34 and inductor 37. The projectile 7 may have an outer sheath of high conductivity metal to accommodate induced currents. Main barrel 1, main barrel breech 2, auxiliary barrel breech 9, auxiliary barrel 10, breechblock 3, and collar 19 are composed gun barrel steel or other high strength metal, while main barrel extension 5 and auxiliary barrel extension 12 are composed high strength wound glass or carbon filament composites or other material transparent to magnetic fields. Electrical components to include cables, circuitry, and coils use high conductivity metals such as copper. The absorber 13 is composed of spring steel or suitable energy absorbing material. Propellant 6 can be of any suitable type known to those skilled in the art.

(30) FIG. 7 is essentially a pictorial view of an exemplary embodiment of the invention equipped with, by way of example, 10 coil sets. This embodiment will be operated in the manner disclosed herein with reference to the other figures.

(31) FIG. 8 illustrates one example of circuitry for operating a hybrid gun device according to the invention. This is composed essentially of a component 200 that produces a signal to fire the gun, typically in response to actuation of a trigger mechanism, and a plurality of circuit units, each connected to control a respective one of the coil sets that are spaced apart along the barrels.

(32) Each circuit unit is composed of a switching network 202, 202′, driver position sensor 51, 51′, and projectile position sensor 52, 52′. Each network 202, 202′ contains a respective control logic module 210, 210′, a respective power actuator A, A′, and a respective power actuator B, B′. Each actuator A contains switches 38 and 39 (FIG. 6) and each actuator B contains switch 40 of its associated coil set.

(33) While FIG. 8 shows two circuit units, it will be understood embodiments of the invention will have a number of circuit units equal to the number of coil sets with which the gun is equipped, one circuit unit for each coil set.

(34) Each circuit unit is constructed to route current to the respective decelerator coil and accelerator coil at proper times.

(35) A respective driver position sensor 51 is located near each decelerator coil stage along auxiliary barrel extension 12 and a respective projectile position sensor 52 is located near each acceleration coil stage along barrel extension 5. Sensors 51 and 52 are located upstream of their associated coils. Each storage capacitor 33, 33′ may be located on or near to the hybrid gun system with suitable electrical cables connecting to power actuators A and B, deceleration coils 34, and acceleration coils 36.

(36) Each control logic module is composed of multiple transistors connected respectively to the firing unit and position sensors 51 and 52 such that signals received from the sensors cause the transistors to apply current to respective solenoids, which actuate switches 38, 39, 40, in the desired sequence.

(37) In operation, a signal to fire the gun is sent from component 200 to the control logic modules, which in turn instruct power actuator A to close switch 38 of each coil set to connect the storage capacitor to an outside low-level power source representing battery 32.

(38) This action charges storage capacitors 33 initially.

(39) As driver 15 approaches a deceleration coil 34, a signal is sent by the driver position sensor 52 to the control logic module to open switch 38 within the power actuator A to the outside power source and close switch 39 within the power actuator A to connect the storage capacitor 33 to decelerator coil 34. This action applies seed current to the decelerator coil 34 and creates magnetic field 41 that retards the moving driver 15 and generates a high level of current.

(40) Subsequently, the generated current flows back into storage capacitor 33 since switch 39 between decelerator coil 34 and the capacitor 33 is closed. After storage capacitor 33 has received nearly all the charge generated by the passage of driver 15 through decelerator coil 34, the control logic module instructs power actuator A to disconnect the storage capacitor from decelerator coil 34, i.e., to open switch 39.

(41) As projectile 7 reaches the proper position with respect to accelerator coil 36, projectile position sensor 51 sends a signal to the control logic module to instruct actuator B to connect the storage capacitor to accelerator coil 36, by closing switch 40. Flow of current from the storage capacitor through accelerator coil 36 creates magnetic field 42 that accelerates projectile 7.

(42) After a suitable delay, the control logic module may require that switch 40 connecting storage capacitor 33 to acceleration coil 36 be opened at a time when storage capacitor 33 retains a small amount of charge to provide seed current to the next coil stage through the power actuator A of the next coil stage, for example. This will be explained more fully below in the description of the embodiment shown in FIG. 9.

(43) The process of alternately charging the storage capacitor by decelerator coils, and in turn having the storage capacitor supply current to accelerator coils, is repeated sequentially from the first coil stage to successive coil stages wherein driver 15 undergoes successive decelerations and projectile 7 undergoes successive accelerations.

(44) Control logic module 210, 210′ is an electronic device powered by a low-level power source represented by battery 32 that supplies power to the power actuators A and B when instructed to do so. The control logic module consists of many three-terminal transistors that can produce output current on two output terminals in response to a voltage change placed on the third terminal. The driver position sensor 51 and projectile position sensor 52 provide the voltage change when the driver 15 or projectile 7 passes by the respective sensor. The manner of constructing the control logic modules will be readily apparent to those skilled in the art.

(45) Sensors 51 and 52 may each consist typically of a single or few turn coil wound about the barrels, or Rogowski coils, located at appropriate positions along the auxiliary barrel extension 12 or barrel extension 5, respectively. The two transistor output terminals are connected to a solenoid within power actuator A or B that powers a mechanical switch that corresponds to switches 38, 39, 40. The mechanical switch connects the storage capacitor 33 to battery 32, deceleration coil 34, or acceleration coil 36 at appropriate times. When the transistor produces no output current, a particular switch remains in the open position and therefore does not connect any of the indicated components. When the transistor produces output current, a particular switch within the power actuator is closed to connect the storage capacitor 33 to one of the discussed components. The number of such transistors required includes one for the switch connecting battery 32 to capacitor 33, and corresponding others to connect the storage capacitor 33 to decelerator coil 34 and accelerator 36 coil that are included in the system.

(46) FIG. 9 shows a variant of the circuitry for controlling the coil sets. Three coil sets are shown with the switches to send current to and from the three decelerator coils and to three switches to send current to the accelerator coils. Switching may be controlled by circuitry of FIG. 8, except that only one capacitor will be provided to send seed current to each decelerator coil in sequence.

(47) Driver position sensors #1, #2 and #3 correspond to sensors 51, projectile position sensors #1, #2 and #3 correspond to sensors 52, decelerator coils #1, #2 and #3 correspond to coils 34 accelerator coils #1, #2 and #3 correspond to coils 36, switches 1d, 2d, 3d correspond to switches 39 and switches 1d, 2d, 3d correspond to switches 39 and switches 1a, 2a, 3a correspond to switches 40.

(48) Each coil set and its associated switches are controlled by a respective set of position sensors.

(49) Initially, all switches are open. Then, the capacitor is charged, as shown in FIGS. 6 and 9 and as previously described, by closing the switch provided between the power source and the capacitor upon production of a signal to fire the gun. During function of each of the coil sets, only one switch is closed at a time and each coil set is operated independently.

(50) To start a switching network, driver 16 approaches decelerator coil #1. Driver position sensor #1 senses that the driver is about to pass through decelerator coil #1, in response to which a signal is sent, e.g., from power actuator A in FIG. 8, to close switch 1d to supply power from the capacitor to decelerator coil #1 to initially energize the coil and create a low-level magnetic field.

(51) As driver 15 passes through decelerator coil #1, a large current is developed in decelerator coil #1 that passes through closed switch 1d to the capacitor to recharge the capacitor, now to a very high level of electrical charge.

(52) After that, switch 1d is opened, and the capacitor is not connected to anything.

(53) Then projectile position sensor #1 senses that the projectile is in the proper position relative to accelerator coil #1 to begin the projectile acceleration process. At that point the projectile position sensor #1 produces a sensing signal to the associated actuator (e.g., power actuator B in FIG. 8) to send power to the solenoid of switch 1a to close switch 1a. Now, only accelerator coil #1 is connected to the capacitor. The capacitor can now send the stored energy to accelerator coil #1, which creates a high intensity magnetic field within accelerator coil #1 to accelerate the projectile.

(54) After the projectile has been accelerated, but before all energy has been drained from the capacitor, switch 1a is opened under control of the associated power actuator.

(55) Now all switches are open so the capacitor is not connected to anything.

(56) Shortly thereafter, driver position sensor #2 senses that the driver is now close to decelerator coil #2 and thus sends a signal to cause the associated power actuator (e.g., power actuator A′ in FIG. 8) to close switch 2d. With switch #2d closed, the capacitor furnishes seed current to decelerator coil #2 to create a low-level magnetic field in preparation for generation of high current in decelerator coil #2 as the driver passes therethrough. That high level current flows back into the capacitor since it is connected to decelerator coil #2 by switch 2d. Once the driver and decelerator coil #2 have completed the storing of high energy in the capacitor, switch 2d is opened so that nothing is connected to the capacitor at this point.

(57) Meanwhile projectile position sensor #2 senses that the projectile has advanced to the proper position relative to accelerator coil #2, to be accelerated. Thus, projectile position sensor #2 signals the associated power actuator (e.g., power actuator B′ in FIG. 8) to close switch 2a. Closing of switch 2a applies current to accelerator coil #2 and the projectile receives another increment of acceleration. Before all the energy is dumped from the capacitor, switch 2a is opened so that some residual change remains to provide seed current to decelerator coil #3. The entire process is repeated for each coil set in the system.

(58) While the description above refers to particular embodiments of the present invention, it will be understood that many modifications may be made without departing from the spirit thereof. For example, multiple coils are used to improve efficiency of the electro-mechanical system and as such many coil sets can be used beyond the three stages shown herein. The accompanying claims are intended to cover such modifications as would fall within the true scope and spirit of the present invention.

(59) The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

REFERENCES

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