Liquid Propellant Weapon System

1. Field of the Invention

This invention relates to weapon systems employing a liquid propellant, and particularly to such systems wherein the propellant is continuously pumped into the combustion chamber as the projectile advances along the firing bore.

2. Prior Art

Weapon systems providing traveling charge effects on projectiles, or rockets, or other systems are listed in my earlier patent U.S. Pat. No. 4,069,739 issued on Jan. 24, 1978. In that patent I disclose a recoilless gun having a cased, preloaded cartridge. The cartridge has a burstable diaphragm and an annular piston for continuously pumping liquid into the combustion chamber as the projectile advances along the firing bore. Such weapon systems are also listed in U.S. Pat. No. 4,043,248, issued to M. J. Bulman et al on Aug. 23, 1977. In that patent Bulman et al disclose an annular piston for continuously pumping liquid into a forward combustion chamber and into an aft combustion chamber as the projectile advances along the firing bore.

In most of the prior art liquid propellant guns, a relief valve is required to prevent the flow of liquid propellant through the injection orifices during the filling operation. Conventional spring loaded poppets can be utilized, but achieving a large liquid flow area requires a large number of poppets. Design complexities arise and structural integrity is difficult to maintain.

The use of nested rings in heart valves or compressor valves is shown in U.S. Pat. Nos. 3,134,399, issued to A. Deminger et al on May 26, 1964; 3,378,029, issued to D. E. Lee on Apr. 16, 1968; 3,536,094, issued to F. E. Manley, Jr. on Oct. 27, 1970; 3,898,999, issued to J. D. Haller on Aug. 12, 1975; and 3,999,898, issued to W. Chomczyk et al on Dec. 28, 1976.

An object of this invention is to provide an improved liquid propellant gun having an annular piston whose head is also a massive relief valve for providing a relatively high rate of flow therethrough.

A feature of this invention is the provision of a liquid propellant gun having an annular piston whose head is formed of nested rings to provide a relatively high rate of flow from the aft face of the head to the forward face of the head.

These and other objects, advantages and features of the invention will be apparent from the following specification thereof taken in conjunction with the accompanying drawing in which:

FIG. 1 is a view in side elevation in longitudinal cross-section of a gun embodying this invention, showing the arrangement of parts before charging the gun with liquid propellant;

FIG. 2 is a view similar to FIG. 1 showing the arrangement of parts during charging the gun with liquid propellant;

FIG. 3 is a view similar to FIG. 1 showing the arrangement of parts after charging and ready to fire;

FIG. 4 is a view similar to FIG. 1 showing the arrangement of parts during firing;

FIG. 5 is a detail schematic view illustrating the basic concept of the construction of the differential piston of the gun of FIG. 1 utilizing chevron rings and a central piston rod;

FIG. 6 is a view similar to FIG. 5 showing the arrangement of parts permitting flow of liquid propellant through the head of the piston;

FIG. 7 is a detail schematic view of another embodiment of the piston using a sleeve in lieu of a central piston rod;

FIG. 8 is a detail schematic view of yet another embodiment of the piston utilizing flat surface rings;

FIGS. 9 and 10 are detail schematic views of still another embodiment of the piston utilizing interrupted lug chevron rings;

FIG. 11 is a view similar to FIG. 9 showing the arrangement of parts permitting flow through the head of the piston;

FIG. 12 is a detail schematic view of even another embodiment of the piston utilizing interrupted lug flat rings;

FIG. 13 is a view similar to FIG. 12 showing the arrangement of parts permitting flow through the head of the piston;

FIG. 14 is a schematic view of a first control rod technique; and

FIG. 15 is a schematic view of a second control rod technique.

FIGS. 1 through 4 illustrate a liquid propellant recoilless gun utilizing a differential piston embodying this invention. The gun consists of a breech assembly 8 having a chamber 10 in which a projectile 12 is received before firing, and a thrust reaction system 14 behind the projectile chamber 10. A gun barrel 16 is fixed to the breech assembly forward of the projectile chamber. The projectile chamber 10 is here shown as formed in a rotating block 18 with a forward annular seal 20 and an aft annular seal 22. A projectile feed system 24 supplies projectiles in sequence to the projectile chamber 10. The thrust reaction system 14 includes a sleeve piston 26 having a concentric ring injector system 28 as its piston head or forward end. The embodiment of the injector system here shown utilizes interlocking lug or spline teeth to retain the rings nested and to limit the relative motion between adjacent rings. The sleeve piston 26 is supported by and slides with respect to a central pedestal 30. The pedestal is fixed by a plurality of radial struts 32 on the longitudinal axis of the recoil nozzle 34 of the thrust reaction system. The pedestal includes a plurality of passageways 36 for supplying liquid propellant to a pumping chamber 38 disposed between the piston head 28 and the forward end of the pedestal, and a check valve 40. The check valve includes a head 41 which is coupled by a tubular stem 42 to a piston 44 which operates in a cylinder 46. The pedestal also includes a passageway 48 for providing liquid pressure into the cylinder aft of the piston. A helical compression spring 50 is disposed in the cylinder forward of the piston. The pedestal further includes a control rod 52 disposed within the central longitudinal bore of the check valve, whose forward end is coupled to the injector system 28 and whose aft end is fixed to a piston 54 which operates in a cylinder 56 having a forward stop 58, and a passageway 60 for providing fluid pressure into the cylinder 56 forward of the piston 54. An ignition system 62 opens into a combustion chamber 64 which is disposed aft of the projectile chamber 18 and forward of the injector system 28. The ignition system may be any suitable means for supplying hot, high pressure gas to initiate the regenerative piston action, such as a replaceable pyrotechnic system, or metering in a small quantity of liquid propellant and igniting it as shown in U.S. Pat. No. 3,763,739, issued to D. P. Tassie on Oct. 9, 1973.

The injector system 28 serves both as the head of a differential piston and as a poppet valve. During the firing portion of the gun cycle the injection system must pass liquid propellant from the pumping chamber into the combustion chamber. During the remainder portion of the gun cycle such passage must be barred.

FIG. 5 illustrates a first embodiment of the injector system comprising a concentric ring construction. The concentric ring piston head is carried on a central piston rod 100. The head is comprised of a series of rings, each having a forward facing chevron valve seat 102 and an aftward facing chevron valve seat 104, as shown in my earlier patent, U.S. Pat. No. 3,782,241, issued Jan. 1, 1974. The arrangement permits the aft surface of the head to be flat and imperforate when the rings are nested. Each ring also has an annular, forward shoulder 106 with a plurality of longitudinal holes 108 therethrough, disposed in an annular row, and an aft shoulder 110. An annular compression spring 112, shown schematically, is disposed between the shoulder 106 of each spring and the shoulder 110 of the next adjacent spring. Each spring biases the outboard ring aft relative to the nextmost inboard ring, to force the adjacent valve seats into contact. Wavy washers, gas filled O-rings or Belleville washers may be utilized. A nut 114 fixes the innermost ring to the piston rod 100. Each ring may contain any desired number and type of injection holes 108.

In operation, as fluid enters to the aft or left face of the piston head as shown in FIG. 5, the springs hold the valve seats closed as shown. The springs must be strong enough to withstand filling pressure without allowing the rings to separate. The springs must be preloaded to do this. After ignition, pressure on the forward or right face of the head generates sufficiently high force to overcome the preloading forces on the springs, and the rings begin to separate, spacing apart the valve seats, to permit the liquid propellant to flow through these spaces and out the injection holes. When full flow is established, the piston head assumes the configuration shown in FIG. 6.

FIG. 7 illustrates a second embodiment of the injector system utilizing an outer sleeve 200 as the retention member, in lieu of the central piston rod 100 of FIG. 5. The angle of the valve seats 102, 104 is the mirror image of those shown in FIG. 5, and the shoulders 106, 110 are outwardly directed. The operation of the sleeve system is similar to that of the central rod system of FIG. 5. The advantage of the sleeve piston is the fact that the ring circumference increases as the cumulative load transmitted from ring to ring also increases. The strength of the ring to ring engagement is easier to maintain. In the central rod piston, by contrast, the largest cumulative load must be terminated at the smallest diameter, that of the rods.

FIGS. 5 and 7 have shown rings having chevron or conical sealing surfaces. If the aft surface of the piston head can be stepped rather than flat, then rings having flat sealing surfaces 302, 304 may be utilized as in the third embodiment shown in FIG. 8.

The rings shown in FIGS. 5, 7 and 8 are not separable, and the annular shoulder 106 has to be joined to its respective ring as the assembly of rings and springs is built up. This is accomplished, for example, by mutually threading the shoulder and the ring, or by brazing. An alternative is to have rings utilizing shoulders defined by spaced apart lugs, wherein the lugs of one shoulder will pass through the spaces or lacunae of the adjacent shoulder and then can be rotated to interlock.

FIGS. 9 and 10 illustrate a fourth embodiment of the injector system utilizing a central piston rod 400 and rings having lugs 402 and lacunae 404. Two rings out of a plurality are shown nested. The lugs and lacunae are formed as spline or gear teeth. While the lacunae may never be narrower than the lugs which they pass, they may be wider. The lacunae serve as the injection holes and the rate of flow of the liquid propellant is a function of their cross-sectional area. The rings are centrally engaged and then rotated one-half pitch and then locked by a pin 406 through a bore 408 which passes through both rings. The pin is fixed to one ring and is free in the other ring, to permit relative longitudinal movement, as shown in FIG. 11.

FIGS. 12 and 13 illustrate a fifth embodiment of the injector system utilizing a central piston rod 500 and flat rings 501 having lugs and lacunae.

By varing the cross-sectional area of the injection bores and the spring force in each ring, a progressive or sequentional opening of the flow passageways can be achieved. Thus, flow can be gradually increased as pressure increases. A small "squirt" of fluid for ignition can be developed by having one spring quite weak behind a few holes.

As shown in FIG. 14, a control technique can replace the individual springs in controlling the position of the concentric rings during fill and firing. The springs are eliminated, and the control rod permits accurate metering of the liquid propellant charge by providing a stop to end the travel of the rings. The control rod 502 is held aft by pneumatic, hydraulic or even propellant pressure behind its piston head 504 in a cylinder 506. The nested ring elements 508, including the inner element 510 which is fixed to the forward end of the rod, and the outermost element 512 which extends as a sleeve piston into a cylinder 514 whose aft end is vented to atmospheric pressure, serve as the injector, differential pressure, piston head. The transverse cross-sectional area of the sleeve element 512 provides the major difference between the cross-sectional area of the front or combustion chamber face of the head and the cross-section area of the aft or pumping chamber face of the head. The transverse cross-sectional area of the rod 502 provides a minor difference. When the propellant enters through the check valve 516, the center element tends to remain aft, holding all of the other nested elements aft. The pressure of the entering propellant opposes the force provided by the piston head 504, to seat the nested elements even more firmly in a sealed interrelationship. When the total force on all of the elements exceeds the hold back force of the piston head, the nested element assembly will begin to move forwardly. The hold back force must still be great enough to hold all of the elements together. Too low a hold back force could allow some or all of the elements to separate. Actually the hold back force has to exceed the sum of inertia and friction forces on all of the elements except the center one to prevent premature opening of the assembly. When the control rod reaches its forward limit, pressure can remain on indefinitely. The filled piston will remain waiting for chamber pressure to start the firing action. Damping will be provided as the piston approaches its forward limit.

A similar control technique can be applied to conventional piston construction with a center rod 600, as shown in FIG. 15. Here the major difference in cross-sectional areas is provided by the center rod 600, and the minor difference by the control rods 602.

In both of the arrangements shown in FIGS. 14 and 15, it will be noted that during the injection stroke, as the injector head moves aft reducing the volume of the pumping chamber under the influence of the difference in pressures on the front and aft faces of the injector head, after the sleeve element 514 or the rod 600 has reached its aft limit of travel, the differential pressure on the ring elements will cause these elements to nest tightly, sealing up the injector head.

It will be appreciated that the disclosed concentric ring element construction provides a relatively simple construction without the need for separate poppets, to provide an injector, differential pressure, piston head which can be sealed during the filling of the pumping chamber, and yet has a generous flow orifice area during the injection stroke. The disclosed control rod technique eliminates the need for individual return spring between the ring elements, provides damping at the end of the filling stroke, and provides an easy method of metering the propellant charge into the pumping chamber.