Patent GB-1516228-A (GB)
Title: Sealing means on or for a breech block
IPC: F41A3/74
Filed: 1976-11-22
Abstract: 1516228 Breech block sealing means DIEHL 22 Nov 1976 [5 Dec 1975] 48592/76 Heading F3C A wedge type breech block carries a stressing bolt which is slidable or rotatable on the block to press, via a radially moving member or members, a sealing ring against a sealing face of the cartridge chamber. In a first embodiment (see Fig. 1) a wedge type breech block 4 carries a longitudinally slidable bolt 26 having an electric firing mechanism 32, 33. The bolt is reciprocable by a lever 6, which also acts to move the wedge into place, and carries a ring 55 supported by resilient webs 56 from its front end. The ring has a frusto conical outer surface 53 which engages radially movable balls 61 of a bearing carried in a recess in the front of the bolt. The balls also engage the frusto conical rear surface 61 of a sealing ring 52, axially movable in the recess and co-operable with a ring 3 of the cartridge chamber 2. The lever 6 acts to move the bolt through a lever 17, pivoted at 19, and a lever 18, which co-operates with the lever 17 and which carries teeth 27 and a lug 28. Teeth 27 act to move the bolt whilst lug 28 acts, through a lever 30, to move the firing mechanism relative to the bolt. In use the lever 6 is pivoted to the position A shown in Fig. 1 to locate the breech against the chamber. Further movement of the lever 6 from position A to E has no further effect upon the wedge due to the shape of the upper part of the cam way 11 of the wedge but actuates through cam surface 8 a roller 21 of lever 17. Lever 17 is rotatable anticlockwise which in turn rotates lever 18 clockwise which moves the bolt to the rear. Movement of the bolt to the rear first causes the ring 55 to engage the balls to forward the sealing ring 60 into contact with ring 3 and then causes, by further pressure on the balls by the ring 55, the ring 60 to be pushed hard against the ring 3 thereby pre-stressing it. The amount of pre-stressing in ring 3 can be controlled by controlling the distance the ring 55 moves during the prestressing stage. This distance is controlled by altering the depth of the recess by locating various shims between the base 50 of the recess and a shoulder 51 on the bolt. Whatever shim is used, seating of the base 50 on the shoulder is ensured by adjustment of the pivot point of lever 18 through a threaded bolt 20, which adjustment alters the end points of travel of the bolt. After firing the bolt is forwarded by reverse movement of levers 6, 17, 18, contact of roller 21 with the lever 6 being ensured after the stress has been relieved from the ring 60 by a return cam 22 on the lever 17. In a second embodiment (see Fig. 3) the bolt is rotatably mounted on the wedge and is rotated via levers 6 and 17 by a two armed lever 74 having teeth engaging a sprocket 80 mounted on the rear of the bolt. The position of the bolt and thus the amount of pre-stressing in the ring 60 is coarsely controlled by a set of shims 84 interposable between the sprocket and a shoulder on the wedge 4. The front end of the bolt carries a gear 86 turning threads which co-operate with a ring 87 prevented from rotating by a pin 89. The ring in turn co-operates with balls 61 as in the first embodiment and the balls co-operate with a sealing ring 60. In use, rotation of the bolt moves the ring 87 backwardly to effect the required movement and pre-stressing of the ring 60. Fine adjustment of the pre-stressing is effected by a turnbuckle type arrangement 77, 78 interposed between levers 74 and 17. In a third embodiment (see Fig. 5) the ring 87 is replaced by a ring 96 which co-operates with a radially expansible thrust transmitting ring 90, the balls being dispensed with.