Patent GB-623804-A (GB)
Title: Improvements relating to trigger mechanisms for firearms
IPC: F41A19/24
Filed: 1946-01-30
Abstract: 623,804. Smallarms. KEENE, S. I. Jan. 30, 1946, No. 3050. [Class 119] A trigger mechanism for a firearm includes a sear 18 adapted to engage with a cocking- piece, means comprising an arm 28 and a member 44 which restrain the sear from releasing the cocking-piece, and selecting means adjustable to cause either the arm or the member to restrain the sear from releasing the cocking- piece except upon release after retraction or upon retraction, respectively, of a fingerretractable trigger. In the construction shown, the breech-bolt 2 has a notch 16 for engagement by the sear 18 which is pivoted at 19 and is under the action of a spring 20. The sear has a vertical slot for the passage of the trigger 7 which is pivoted to the sear at 22 and which carries a slidable pin 23 urged by a spring into contact with the upper wall of the trigger chamber. The trigger passes also through a vertical slot in a member 26 which is pivoted at 27 to the arm 28 which moves about a fixed pivot 29. A spring around pivot 27 tends to open out members 27, 28, and a spring 33 tends to move arm 28 clockwise so that a shoulder thereon moves under a projection 32 on the sear. The member 26 is slotted at 40 for the passage of a pin 100 on the trigger, and carries the member 44 in the form of a spring-controlled pivoted block which can be engaged by a shoulder 93 on the trigger and which can cooperate with the rear end of the sear as described below. Beneath the member 26 is a lever 52 which has a limited longitudinal movement on its pivot 53, and which can be moved longitudinally by a pin 71, Fig. 5, on a hand lever fixed on a sleeve 60 in the trigger guard. A cross-bar 50 on the lever is urged upwardly by a spring towards the member 26. Action.-To permit firing by the " triggerrelease " method, the low cam face 80, Fig. 10, is brought to face the arm 28, thus letting member 26 move to the rear so that block 44 moves clear of the sear and also letting the upper part of the arm to engage beneath the projection 32 of the sear. In addition, lever 52 is moved forwardly so that its rear end 56 may be moved upwards by the marksman's middle finger into the recess shown, thus causing cross-bar 50 to press upwards on member 26. On pressing the trigger, the member 26 will move upwardly when pin 100 can move into a recess 41 of the slot 40. When the trigger is released, this pin will bear in the recess, and the spring 24 on pin 23 will cause the trigger to move forwards carrying member 26 with it until eventually this member has caused arm 28 to disengage the projection 32 on the sear, when firing takes place. For compression firing with a hair trigger action, the intermediate cam surface 82 is operative, this surface permitting arm 28 to move clear of the sear projection 32, and permitting member 26 to move forwards so that a small part of 44 is under the sear, thus preventing the sear nose 17 from releasing the breech-bolt. When the trigger is pulled its movement is first resisted only by the spring 24, but when the shoulder 93 on the trigger meets the block 44 there is a noticeable increase in the resistance. Further retraction of the trigger causes block 44 to swing clear of the sear and the accumulated power in spring 24 effects the release of the sear from the sear notch in the breech-bolt. When cam surface 81 is effective, parts 26 and 44 move forwards still further and as a result a longer travel of the trigger is needed to move the block 44 clear of the sear to effect firing. Specification 601,594 is referred to.