Patent GB-445734-A (GB)
Title: Rotary automatic breech mechanism for generating combustion products under pressure
IPC: F41A9/26
Filed: 1935-01-18
Abstract: 445,734. Generating pressure gases from explosives. COFFMAN, R. A., 4733, Center Avenue, Pittsburg, U.S.A. Jan. 18, 1935, No. 1724. [Class 92 (ii)] [See also Group XII] Apparatus for developing and delivering under pressure combustion products generated by the firing of cartridges containing a combustible material such as a mixture of nitroglycerine and nitro-cellulose grains and applicable to starting mechanism for internal-combustion engines comprises a magazine 12, Fig. 8, providing a plurality of cylinders 11 for receiving cartridges 13, the cylinders being adapted to engage successively a seat on an extension 9, Fig. 4, of a barrel member 5 which conducts the generated gases to the point of utilization, means to ignite the cartridges, means operated by a portion of the pressure generated to press the cylinder into leak-proof engagement with its seat and means, also operated by a portion of the pressure generated, for moving the magazine so as to bring another cylinder into operative position. The extension 9 opens into an enlarged portion 8 of a barrel forming the combustion chamber. Some of the gases generated act on a piston 14 working in an extension 15 of the barrel and connected to a head 17 which is connected at its ends to rods 18 and 19, Fig. 3, the former extending along the outside of the magazine and the latter extending axially through the magazine. The rods are connected at their other ends by a breech block 20 carrying an electric firing pin 21 for the cartridges. Pressure on the piston 14 thus acts to press the firing pin into engagement with the cartridge and the cylinder on to its seating on the extension 9. The block is pivotally mounted on the rod 18 and is held down by a thumb nut 28 screwing on to the rod 19. A transversely screw-threaded lug 33, Fig. 3, receives a screw-threaded sleeve 34 surrounding the rod 19 and between the lug 33 and a shoulder 36 on the sleeve is held a circular plate 35 having an annular channel 35a, Fig. 8, lined with asbestos or other fireproof material 44 which supports the open ends of the cylinders 11. The magazine consists of a hub 41 and radial web 42 rotatably mounted on the sleeve 34. When a cartridge is fired, another portion of the gases generated passes to the rear of a piston and moves forward a piston rod 48 against the action of a spring 50, the rod carrying with it a slide 53 having two cam surfaces 54 and 55. The surface 54 controls the vertical position of a pin 56. On the forward stroke of the rod 48 the pin is moved upwardly and acts firstly through a lever 59, pawl 60 and teeth 63 on the hub 41 to rotate the magazine and secondly through a lever 72 to compress a spring 71 so that when another cylinder has been brought into operative position over the extension 9, a lock rod 68 is sprung into one of a series of openings 69 in the web 42 to hold the magazine in position. On the rearward stroke of the piston rod the pin 56 is lowered and springs 65 and 71 operate to release the lock rod and to move the pawl 60 so as to engage the next tooth of the rack 63. The apparatus also includes a dashpot 75, Fig. 7, having a tubular piston rod 76 carrying at its outer end an oscillatory latch plate 101. A block 48a carried by the piston rod 48 on its outward stroke moves past this latch but on the return stroke under the action of the spring 50 it engages the latch and moves the piston of the dashpot. This has the effect of slowing up the return of the piston rod 48 and the rearward movement of the cam surface 54 until a tail 103 of the latch 101 has been rotated by an inclined plate 104 out of engagement with the block 48a. The circuit for the firing of the charge can be completed only by the depression of a rod 95 by the dashpot piston rod at the end of its forward or return stroke. During the return of the rod 48 another latch, carried by the block 48a, engages a cam disc 105 mounted on the barrel, causing the disc to move inwardly a piston rod 108, Fig. 11, operating in a cylinder 109 and forming an exhaust valve for the barrel thus allowing scavenging by the escape of unburnt gases. The other cam surface 55 of the slide 53 serves to free the fired cartridge from engagement by the firing pin and to relieve the pressure on the breech block prior to a rotation of the magazine, the cam acting on the tail 115 of a rocking member 116 mounted in a block 117 secured to the rod 19. Specification 444,172 is referred to.