Patent GB-879089-A (GB)
Title: Trigger mechanism for automatic firearms
IPC: F41A19/46
Filed: 1960-07-25
Abstract: 879,089. Trigger mechanisms for automatic firearms. FRANCHI, S.p.A., LUIGI. July 25, 1960 [Aug. 5, 1959], No. 25858/60. Classes 92 and 119. Relates to a trigger mechanism for automatic firearms provided with a change-fire mechanism and having a reciprocating breech bolt 20 Figs. 1, 2 carrying a firing pin 21 which is actuated by a pivotal hammer 17. According to the invention a slow rate of fire is achieved by the provision of a delay mass 18 pivoted at 12 co-axially with the hammer 17 and urged forwardly by a push rod 23 and spring 25 towards the breech bolt 20, the delay mass 18 being locked in the rearward position during recoil by a spring urged pawl 32 which engages a tooth 18b on the mass 18. The pawl 32 is fixed to a lever arm 33 cooperating with an unlocking lever 35 pivoted also at 12 and adapted to engage a cam 36 on the bolt 20 immediately before closure thereof, which cam moves the lever 35 to disengage the pawl 32 from the tooth 18b, thus unlocking the delay mass 18. The hammer 17 carries a pin 26 on which is pivotally mounted one end of another spring-urged push rod 27 which, like the rod 23, freely passes through an opening in the trigger casing 10, the arrangement of pivot 12, pin 26 and the opening in the back plate 10 forming a toggle link, such that in the position of the pin 26 as shown in Fig. 1, the spring 28 on the rod 27 tends to swing the hammer clockwise, while in the raised position of the pin 26, as shown in Fig. 2, the hammer tends to swing anti-clockwise. The hammer 17 carries a lateral finger 17b protruding into the path of the mass 18, the arrangement being such that towards the end of the forward movement of the mass 18, a surface 30 on the mass 18 meets the finger 17b and swings the hammer forwardly to take the pin 26 across the dead-centre position, thus permitting the spring 28 to swing the hammer towards the firing pin 21. A trigger 40 and a sear 41 are pivoted on a pin 16, the trigger having a rear arm 44 co-operating with a charge-fire selector 45 comprising a rotatable pin with a diametral incut 46. The sear 41 is formed with an elongated slot 47 through which the pin 16 passes thus permitting a pivotal motion and also a motion of translation. The sear is urged forwardly by a spring-pressed plunger 50 housed in the body of the trigger. As soon as the deadcentre position is passed and the hammer swings forwardly, a hammer tooth 17c engages an arm 41a of the sear 41 and the latter recedes against the action of the plunger 50 and comes to rest in the position shown in Fig. 2 and the trigger mechanism is cocked. In the "safe" position- Fig. 1, the trigger arm 44 bears against the cylindrical part of the selector 45, thus locking the trigger. By turning the selector to the position shown in Fig. 2 the trigger arm 44 partially penetrates into the cut 46 and by pulling the trigger 40, a trigger tooth 51 engages the rear arm 41b of the sear and rotates the sear until the hammer tooth 17c disengages from the sear arm 41a and the spring 28 swings the hammer 17 against the firing pin. Simultaneously the sear 41 slides forwardly under the action of the plunger 50 thus removing the rear arm 41b from the path of the tooth 51. On firing the breech bolt recoils, cocking is effected and the hammer notch 17c strikes against the arm 41a moving back the sear, the rear arm of which slides on a step 52 and comes to rest against but below the tooth 51 locking the hammer. To fire another shot, the trigger must be released, thus allowing the sear 41 to slide backwards to the position shown in Fig. 2 when firing can then be effected. For continuous fire the selector 45 is further rotated to the position shown in Fig. 4. There the trigger arm 44 can penetrate completely into the cut 46 and in this condition the sear 41 is tilted by the trigger step 52 so as to remove the front arm 41a of the sear away from the path of the hammer tooth 17c and the hammer will not be stopped by the sear so long as the trigger remains pulled.