| 摘要 |
1,255,924. Cocking mechanism for guns. DEFENCE, SECRETARY OF STATE FOR. 29 Nov., 1967 [29 Nov., 1966], No. 53472/66. Heading F3C. A cocking mechanism for a gun incorporates a shaft 1 rotatably mounted in bearings 3, 4 carried by the gun cradle 5 and having two intersecting screw-threads, one a right-handed thread 6 of fairly slow pitch and the other a lefthanded thread 7 of twice that pitch. Mounted on the shaft 1 and restrained against rotation by engagement with a guideway 18 in the cradle 5 is a slide 19 which constitutes a retractor member and carries a forwardly extending hook member 20 for engaging a forward facing surface on the breech ring 21 of the gun 22 which can, thereby, be pulled rearwardly with the other recoiling parts of the gun. A hollow, cylindrical boss 23 formed on the slide 19 houses a cylindrical " half-nut " 24 having a raised thread portion 25 which locates in the grooves of the shaft's screw-threads. At each end of the screwthreaded part of the shaft 1 is a collar 26, 27 shaped to form a cam surface 28, 29 respectively, such that its engagement with the thread portion 25 will cause the " half-nut " 24 to turn about its axis and to be diverted from one screw-thread of the shaft 1 to the other. Starting from the rest position, clockwise rotation of a handle 8 mounted to the rear of the shaft 1 will cause the " half-nut " 24 to travel rearward along the screw-thread 6, carrying the slide 19 and the recoiling parts of the gun rearward against the action of the recoil return spring 30 to perform the required cocking action. At the rear end of the shaft 1 the "half-nut" 24 is caused to rotate so that the thread portion 25 is diverted into the thread 7. The recoiling parts then run out forwardly under the action of the spring 30 while the shaft 1 free-wheels relative to the handle 8 by way of a pawl-and-ratchet 17. During a firing sequence, the cocking action is performed by the recoil movement of the gun after firing the previous round. At the start of a firing sequence, however, the abovedescribed manual cocking action is performed. Various types of thread-engaging member other than a " half-nut " may be used, one example being a pair of nuts mating respectively with the two screw-threads on the shaft, with clutch means, reversible by contact with a bush at the end of its travel, for locking one or other of the nuts, according to the direction of motion, against rotation relative to the retractor member. |
