Patent GB-1248782-A (GB)
Title: Open chamber breech mechanism
Inventor: DARDICK DAVID
IPC: F41A9/27
Filed: 1968-09-03
Abstract: 1,248,782. Automatic ordnance; cartridges. TRW Inc. 3 Sept., 1968 [31 Aug., 1967], No 41908/68. Headings F3A and F3C. An open chamber breech mechanism 10 for a gun comprises a breech frame 14 having a carrier 22 rotatably mounted in a chamber 16 thereof, a bore 20 opening into the chamber 16 and a lateral infeed opening through the breech frame 14 into the chamber 16. The carrier 22 contains a firing chamber 30 which opens laterally through the circumference of the carrier such that the firing chamber 30 can be rotated into register with the infeed opening to be loaded and into a firing position wherein the firing chamber is closed by the breech frame and communicates with the bore 20. A firing means 43 is provided and an automatically operated carrier actuating means to rotate the carrier through the loading and firing positions. In the construction shown the firing means comprises a spring loaded firing pin 118 which is cocked during rotation of the carrier after loading by a cam follower 122 thereof working in a cam track of the breech frame 14. The firing pin 118 is urged forward by its spring loadings as the firing chamber comes into alignment with the bore 20, that is when the cam follower 122 co-operates with a longitudinally directed portion of the cam track (Fig. 9, not shown). The firing pin 118 may be held in its cocked position by a manually retractable stop pin 128 which can be locked in its inoperative state by a latch 132. The carrier is rotated during the recoil and counter-recoil strokes of the barrel 18 and breech frame 14 in a gun cradle 34. To this end the carrier actuating means comprises a spring loaded cam follower 84 mounted on the cradle 34, which follower 84 cooperates with a cam track (Figs 10, 11, 12 not shown) provided on the cylindrical face of the carrier. The cam assembly causes the carrier to oscillate such that the firing chamber moves from the firing position to the infeed position and if the ammunition is of the cased variety the firing chamber moves through an ejection position in a direction away from the two aforesaid positions before returning to the infeed position (Figs 2, 3, 4, not shown). The carrier is held by a manually actuated latch (Fig. 5, not shown) in the infeed position and when the latch is disengaged the carrier is rotated to the firing position by a spring 40. With the cam follower 84 manually disengaged from the corresponding cam track the carrier can be oscillated by means of a handle 140 which is disconnected when the gun is allowed to operate automatically. In a modification (Figs 14, 15, not shown) the manually actuated latch is replaced by an automatic latch which is disengaged from the carrier by a piece of ammunition being loaded into the firing chamber. The ammunition which is substantially triangular in cross-section is fed to the infeed opening from a hopper (Figs 1,2, not shown). The gun is provided with counter recoil means 36 and shock absorbers and is mounted on a carriage (Fig. 1, not shown) for training and elevation, the forward wheels of the carriage being raisable to allow a firing pad to engage the ground. In a further embodiment the carrier is provided with four equispaced firing chambers and is connected to a cam follower disc on which are mounted four cam followers (Figs 15 to 18, not shown). Diametrically opposed cam followers co-operate with cam tracks formed in the gun cradle on recoil and counter-recoil such that the carrier is rotated one step at a time to bring the firing chamber successively through the loading, firing and ejection position. The spring loaded firing pin is actuated at each step by a firing cam rotatably fixed with the carrier and cam follower disc. In a third embodiment (Figs 19 to 22, not shown) a cam follower is provided on a gas operated piston to oscillate the carrier through its positions. A rack is provided on the rod of the piston such that the carrier can be rotated by a handle through a pinion. A spring loaded, floating piston may be interposed between the source of the explosion gases and the aforesaid gas operated piston, the spring operating between the two pistons (Fig. 23, not shown).