Tripping mechanism for semiautomatic and automatic firearms

Abstract: The invention relates to a tripping mechanism for semiautomatic and automatic firearms with a closed-type bolt carriage and which can be used for either single shot firing mode and automatic firing mode. The mechanism has a ser (4) slideably fitted on the trigger between the oscillating pivot (5) and a resting plane (6a) formed on the trigger, away from said pivot. The sear is stressed by a spring (11) which normally pushes it towards the hammer to interact with the latter, is susceptible to translation with the trigger when it is operated and is also susceptible to a longitudinal sliding on the trigger in one direction due to spring (11) and in the opposite direction due to the hammer at least during the engagin in armed position phase, as well as the balancing phase between oscillanting pivot (5) and resting plane (6a).

Description: The present invention relates to semiautomatic and automatic firearms with a closed-type bolt carriage and more particularly regards a tripping mechanism for suche firearms especially for machine guns according to the preamble of claim 1. Such a mechanism is well-known in practice. An object of the present invention is to supply a tripping mechanism for firearms with a new conception and execution and which permits the firearm to be used both in single shot firing mode and in automatic, continuos firing mode, by changing over the mechanism from one condition to the other through a selector cam rod which also acts as a safety rod and with the help of a lever placed on the side of the hammer which is designed to delay the percussion action of the hammer in order to ensure the closure of the obturator beforehand. Another object of the invention is to supply a tripping mechanism of a simpler construction than the ones known so far, formed from a limited number of components and which is reliable due to this simplicity. The here proposed tripping mechanism is fitted onto an underguard which is insertable in the trip box of a semiautomatic or automatic firearm with an open bolt and is characterized in what is claimed in at least claim 1. Further details of the invention will appear clearer following the description with references being made to the attached drawings regarding an embodiment for the release mechanism. In said drawings: Fig. 1 shows the trippings mechanism in a "ready to fire" static situation and in relation to the bolt carriage of the firearm in a closed position; Fig. 2 is a similar view to the one in Fig.1, but with the device in a position a moment before the releasing of the hammer in the single shot firing mode; Fig. 3 is a view as in Fig.2, but at the moment when the hammer is released; Fig. 4 shows the mechanism with the hammer as released and in an intermediate position of its movement towards the firing pin; Fig. 5 shows the mechanism with the hammer in a position of percussion on the firing pin for the shooting of an ammunition; Fig. 6 shows the mechanism in an intermediate recocking phase of the bolt carriage which returns to the opening position after the shooting of each ammunition; Fig. 7 shows the mechanism the moment before the engaging of the hammer by the sear; Fig. 8 shows the mechanism at the moment when the hammer engages to the sear and whilst the trigger still pressed; Fig. 9 shows the mechanism with the hammer in a percussion position as in Fig.5, but in an automatic firing mode; Fig. 10 shows the mechanism in the automatic firing mode at the moment of the releasing of the automatic firing lever with the bolt carriage in a backing phase; Fig. 11 is a view of the bolt carriage and of the hammer ind direction of the arrows XI-XI in Fig.10; Fig. 12 is a view from above of the bolt carriage and of the hammer; Fig. 13 is a similar view to the one in Fig.10, but with the bolt carriage completely backwards; Fig. 14 shows the mechanism at the moment the automatic firing lever begins sliding on the bolt carriage; Fig. 15 is a view in the direction of the arrows XV-XV in Fig.14; and Fig. 16 is a similar view to the one in Fig.13, but with a bolt carriage as closed. The tripping mechanism (100) is fitted onto an underguard (101) which in insertable in the trip box (not shown) of a firearm such as a machine gun. The firearm has a barrel, of which only the axis (102) is indicated, and a bolt carriage (1) carrying a firing pin (2) only partially shown and already known. The bolt carriage (1) is movable in a known way from a forward position (A) of closure/percussion of ammunition in the barrel to a backward position (B) of aperture/armament and vice versa. In particular, it should be noted that the bolt carriage (1) has a sloped plane (H) on its lower part, at the lever of the back end of the firing pin (2). The sloped plane (H) is angled from the top to the bottom, from the back towards the front of the bolt carriage itself and has a split (1b) aligned to the firing pin (2) in its back part. The tripping mechanism (100) comprises a percussion hammer (3), a sear (4), a trigger (6) and a safety camshaft. The hammer (3) is fitted onto the underguard (101) through a rotating axle (3a) for its angular movements towards and away from the firing pin (2) on the bolt carriage (1) respectively in the percussion and armament positions. The hammer (3) has an arming tooth (3b) on its top which is designed to interact with a release tooth (4a) integral to the sear (4) for the stopping of the hammer in its armed position. The hammer (3) is also stressed by a spring (12) placed between a spring holder rod (7) and a spring guide housing (8) and is designed to move the hammer to its percussion position on the firing pin (2) when it is released from the sear (4). The spring holder rod (7) and the spring guide housing (8) are aligned and whilst the rod (7) is pivoted (7a) to an intermediate part of the hammer (3) , the spring guide housing (8) is pivoted (8a) to the underguard (101) so that the two elements (7,8) can vary their position depending on the position and rotation of the hammer. The sear (4) is fitted as a slide which is susceptable to longitudinal movements on the trigger (6) and is normally pushed forwards towards the hammer (3) through a sear spring (11) placed between the sear itself and a pin (11a) fixed to the underguard (101). The base of the sear (4) rests on a plane (6a) which is formed on the trigger. The trigger (6) is pendulum fitted on the underguard (101) through an oscillating pivot (5) and is stressed by a spring (9). This spring normally tends to move and keep the trigger (6) in a forward inactive position, that is to say at rest, whilst it loads when the trigger is operated. It should be noted that the oscillating pivot (5) of the trigger (6) is found in a split (4b) formed on the top fo the sear (4). This is so that the pivot can alternately interact with the sides of said split (4b) in order to limit the longitudinal sliding of the sear and also to engage with a step (4c) on the bottom of said split so as to determine a balancing of the sear following its longitudinal movements and to fovour the engaging of the hammer in the armed position by the sear. The safety camshaft (10) is transversally fitted in the underguard (101) behind the trigger (6). It can be rotated through a safety lever (10a) and can be stopped in three different positions (with reference to the lever): a safety position "S"; a single shot firing position "I"; an automatic firing position "R". In the intermediate part of such a safety camshaft (Fig.2) there is a portion with a cylindrical surface (10s) and two flattenings or depressions (10i,10r) of different depths. By rotating the camshaft (10) in the above mentioned positions it is possible to turn the cylindrical surface portion (10s) or one or the other of the two flat surfaces (10i,10r) towards the trigger in order to secure the firearm or to respectively choose whether to use the firearm for single shot firing mode or automatic firing mode, the flat surfaces (10i,10r) allowing for a different backwards movement of the trigger when operated. Finally an automatic firing lever (14) is fitted in a recessed position on the side of the hammer (3). Said lever (14) oscillateds on an intermediate pivot (14a) and has a head (14b) designed to interact with the lower plane (G) of the bolt carriage (1) and a tail (14c) designed to rest against the hammer. A spring (15) normally tends to move the lever (14) by the head (14b) outwards, outside the profile of the hammer. The movement is delimited on the other side by the tail (14c) which rests against the hammer.The lever is returned to the position inside the hammer profile because of a bevel (1a) formed at the tree end (back) of the bolt carriage, on one side with respect to the trajectory of the hammer, that is to say on one sine of the split (1b) of said bolt carriage. Fig.1 of the drawings show the tripping mechanism in a static "ready to fire" situation. Thus, the tooth (3b) of the hammer (3), is engaged to the sear tooth (4a) of the sear (4); the bolt carriage is moved forwards in the closed position (A); the trigger (6) is at rest and the safety camshaft (10) is rotated in the single shot firing mode "I". In such conditions, the sear (4) is kept in a balanced position through its contact with the plane (6a) of the trigger, by the resting of the front side and the bottom (4c) of its split (4b) against the oscillating pivot (5) of the trigger (6) and, obviously, by the force exerted on it by the hammer through the coupled teeth (3b,4a). The hammer (3) is thus ready to be released for the percussion action on the firing pin (2) which is on the bolt carriage (1). Such a release of the hammer occurs by voluntarily operating the trigger (6) according to the arrow "C" shown in Figs. 2 and 3. When the trigger (6) is operated, it rotates on the pivot (5) and moves the sear (4); the hammer (3), which is engaged with the sear tooth (4a), slightly rotates downwards according to the arrows in Fig. 2. This rotation of the hammer (3) causes a further compression of the spring (12) whilst the rotation of the trigger (6) causes a further loading of the spring (9). When the trigger (6) is pressed (Fig. 3) but is not yet engaged on the safety shaft, the sear (4) disengages the hammer (3). The spring (12) pushes the hammer (3) which rotates towards the obturator (1); but there still remains a space "X" between the trigger (6) and the flat surface (61), (single shot firing mode) of the safety camshaft (10). When the trigger is completely pressed it stops against said flat surface (6i), (the least deep), whilst the rotating hammer slides against the sear (4), (Fig.4), in its first movement phase and then abandons the sear in order to move towards the firing pin. In this situation the sear is subject to: a forward translation towards the hammer because of the relative spring (11); a forward balancing as the pivot (5) of the trigger comes into contact whit the step (4c) on the bottom of the split of the sear; a stopping as the back side (V) of said split rests against the pivot (5). Fig.5 shows the mechanism with the hammer released in the percussion position on the firing pin (2) on the bolt carriage (1) for the firing of ammunition in the barrel; the trigger is always operated through voluntary pressure. The automatic firing mode lever (14) on the side of the hammer (3), in contact with the bevel (1a) on the bolt (1) returns into the profile of the hammer. Following the firing of ammunition, the bolt carriage moves backwards towards the opening position (B) causing the rotation of the hammer towards the sear (4) through the sloped plane (H). Figs. 6, 7 and 8 show the rearmament sequence of the hammer. In Fig. 6 the hammer comes into contact with the sear pushing it back in opposition to the action of the spring (11). When pushed by the hammer (Fig. 7), the sear (4) makes composite movements, firstly rotating forwards (anti-clockwise in Fig. 7) with respect to the pivot of the trigger and then translating towards the back. These movements are forced from the top by the pivot (5) resting on the step (4c) and from the bottom by the sear resting (J) on the plane (6a) of the trigger. The sear (4) is then in an unstable position which resets as soon as the tooth (3b) of the hammer goes under the tooth (4a) of the sear (4), Fig. (8). In this condition the sear (4) translates forwards when pushed by the spring (11) until it rests (V) against the pivot of the trigger and into the engaging position of the hammer as soon as the bolt carriage, which has finished the contrary stroke, returns forwards in the closed position (Fig. 1). The firing of another single shot will it then only be possible by releasing the trigger and then pressing it once more. For the automatic firing mode, it is first of all necessary to rotate the safety camshaft (10) in the "R" position where its automatic firing flat surface (10r), which is the deepest, is turned towards the trigger. The firing of a first shot and the releasing sequence of the hammer from the sear take place in a similar way as described in relation to Figs. 1-4. Fig. 9 shows the mechanism for an automatic firing mode where the operated trigger (6) is moved against the automatic firing flat surface (10r) of the safety camshaft (10) and where the hammer (3) is in a percussion position on the firing pin (2) of the bolt carriage (1), obviously in the closed position (A). When the trigger (6) rests against the said flat surface (10r) the sear (4) never intercepts the hammer (3) because it is at a "T" distance out of the trajectory of the hammer. The hammer thus rotates backwards when pushed by the bolt carriage which returns to the open position (B) and then forwards towards the firing pin when the bolt carriage goes in the closed position (A) for firing a second shot, a thrid shot, etc. in sequence as long as the trigger is pressed. Fig. 10 shows the mechanism once again in the automatic firing mode and during the phase in which the bolt carriage (1) slides with the relative sloped plane (H) on the hammer (3) rotating it backwards while returning to the position (B), (Fig. 13), after the firing of ammunition. In the same Fig. 10 and more particularly in Fig. 11 the moment of the release of the automatic firing lever (14) is also shown, that is to say the moment in which such a lever disengages from the split (1b) of the bolt carriage at "Z" when pushed by the relative spring (15). Thus, the head (14b) of the automatic firing lever (14) protrudes from one side of the hammer (3), (Fig. 15) in order to interact with the lower plane (G) of the bolt carriage on one side of the split (1b). This phase is also reproduced in Fig. 14 where the bolt carriage has already inverted its direction of movement in order to return towards the closed position. During its return to closure, the lower plane (G) of the bolt carriage slides on the automatic firing lever thus keeping the hammer in an armed position until the bolt carriage is actually in ten closed position (A). Only at this point (Figs. 16 and 17) does the automatic firing lever result as being disengaged from said plane (G) so the hammer can rotate towards the firing pin. Following this rotation, the automatic firing lever (14) returns inside the profile of the hammer after coming into contact whith the bevel (1b), as also occurs in single shot firing mode. This allows the hammer to go into the split (1b) of the bolt carriage and to reach the firing pin. This is so as long as the trigger remains operated, but as soon as the trigger is released, the sear returns to the intercepting and stopping position of the hammer thus interrupting the automatic firing mode. Thus, the sear selects either single shot firing mode and automatic firing mode by either going closer to or moving further away from the hammer. The automatic firing lever on the side of the hammer helps to delay the percussion action of the hammer until the bolt carriage is securely closed.

Claims: A tripping mechanism for semiautomatic and automatic firearms with a closed-type bolt carriage for either single shot firing mode and automatic, continuos firing mode, comprising:a hammer (3) fitted on a rotation axle and movable away from and towards a firing pin on the bolt carriage, the hammer being movable away from the firing pin in an armed position by the bolt carriage and towards the firing pin by a spring: a sear (4) designed to engage the hammer in said armed position at least for the single shot firing mode; a trigger (6) fitted on an oscillating pivot, designed to control said sear (4) and stressed by a spring in a normal rest position; a rotating camshaft (10) which acts as a safety catch for the firearm and for selecting single shot firing mode and automatic firing mode, characaterized in that the sear (4): is slideably fitted on the trigger between the oscillating pivot (5) and a resting plane (6a) formed on the trigger away from said pivot; is stressed by a spring (11) to be normally pushed towards the hammer in an intermediate position with the latter; is susceptible to translation with the trigger when the trigger is operated; is also susceptible to slide longitudinally on the trigger in one direction through said spring (11) and in the opposite direction through the hammer at least during the engaging phase in the armed position and to balance between said oscillating pivot (5) and said resting plane (6a). Tripping mechanism as claimed in claim 1 and wherein the bolt carriage has a split (1b) in its back part which is aligned to the firing pin, has a resting plane (G) in its lower part at least on one side of said split and has a sloped plane (H) descending from the back towards the front at the same height of the firing pin, whereby the hammer (3) is fitted with and automatic firing lever (14) in a recessed position of one side of the hammer, in that said automatic firing lever (14) oscillates on an intermediate pivot and has a head (14b) designed to protude from the profile of the hammer and to interact with said lower resting plane (G) of the bolt carriage and has a tail designed to rest against the hammer in order to limit the protusion of the head of the automatic firing lever from the hammer, in that said automatic firing lever (14) is stressed by a spring (15) which tends to keep said head normally protruding from the hammer, and in that the back end of the bolt carriage has a bevel (1a) on one side of the split (1b) which interacts with said head of the automatic firing lever to return it inside the profile of the hammer when the hammer moves towards the firing pin and the bolt carriage is closed. Tripping mechanism as claimed in claim 1, characterized in that the sear (4) has a sear tooth (4a) turned towards and interagent with an arming tooth (3b) which is integral with the hammer for engagin the hammer in the armed position when the trigger is in a resting position. Tripping mechanism as claimed in claim 1, characterized in that the oscillating pivot (5) of the trigger extends in a split (4b) formed at the top of the sear (4), in that said split has two sides which alternately rest against said pivot to allow for the longitudinal sliding of the sear on and relative to the trigger in one direction and the other, and in that the bottom of said split (4) has a step (4c) which is interagent with said pivot in order to cause the balancing of the sear during the longitudinal movement of the sear itself and during the operating of the hammer in the arming phase.

Inventors: BERETTA PIER GIUSEPPE, BERETTA, PIER GIUSEPPE
Applicants: BERETTA ARMI SPA, FABBRICA D'ARMI P.BERETTA S.P.A.
Application year: 1992
Main classification: F41A19
IPC codes: F41A19