Patent GB-1501853-A (GB)
Title: Differential pressure piston combustion chamber system for the production of propellant gases
IPC: F41A1/04
Filed: 1969-07-28
Abstract: 1501853 Gun with hypergolic propellants MESSERSCHMITT-BOLKOW GmbH 28 July 1969 [21 Aug 1968] 37857/69 Heading F3C A differential pressure piston combustion chamber system for the production of propellant gases from fluid media, particularly hypergolic propellant components, and especially for firearms, is characterized in that the piston is driven by a force in addition to that due to the combustion chamber pressure at the commencement of its working stroke. As shown, in a system in which this additional force is provided by a gas cushion between the front limiting surface of the combustion chamber housing 1 and the piston 2, the latter consists of a piston head 3, an internal part 4 with guide tube 5, and an external part 6 with annular part 7, and slides in the housing 1 to which a firearm barrel is attached. Two storage containers 8, 9 for the liquid fuel and oxidizer are connected via external ducts 10, 11 and internal ducts 12, 13 with annular feed chambers 14, 15. Within the internal piston part 4 and guide tube 5, an injection ram consisting of a draw rod 16 pulled in the direction Y by a draw spring (not shown) and a control disc 17 may slide to and fro. A swirl chamber 18 for the fuel, with an injection orifice 19, is provided inside the draw rod and disc. Tangential apertures 20 lead to the chamber 18 and are supplied from an annular chamber 21 with fuel, the chamber 21 being connected with the feed chamber 14 via a feed bore 22. From the feed chamber 15 for the oxidizer, injection bores 23 lead to the end face of the piston 2, the injection orifices 23a being covered by the disc 17 when this is in its rearward position. In addition, the apertures 20 do not then coincide in position with the annular chamber 21. The housing 1 contains control bores 25, 26 which are opened or closed by a control piston 27 or by a control bush 28. When the piston 2 is performing its forward motion, X, the annular piston part 7 from the line a forwards compresses the air enclosed between the front piston surface 31 and the shoulder surface 29 integral with the housing 1. The piston 2 is thereby brought to a halt and then driven back in the direction Y, during the initial phase of its working stroke, and the propellant components forced from the feed chambers 14, 15 through the orifices 19, 23a into the combustion chamber 33. The ram 16, 17 is in an open position which it assumes as a result of its own inertia when the piston 2 reverses. The components undergo a hypergolic reaction, the pressure in the chamber 33 increasing and driving the piston 2 back, resulting in the injection of the remaining quantities of propellant components in the feed chambers 14, 15. For the damping of the return motion and the initial acceleration of the forward motion of the piston 2, air is compressed by the annular part 7 between the rear piston surface 32 and the shoulder surface 30 integral with the housing 1. In place of the gas cushions, annular springs (Fig. 2, not shown) may be used. Alternatively (Fig. 3, not shown) the additional force may be provided by an outside pressure source. The pressure gases occurring as a result of the combustion drive outwards a projectile 41 introduced into the barrel by a loading device.