Historical Document · 1969
Wilhelm Ketterer's H&K trigger-mechanism patent, filed 18 December 1967 and issued 27 May 1969. The HK PSG1 dive cites it for the G3-family fire-control group.
May 27, 1969 w. KETTERER 3,446,] 14 TRIGGER MECHANISM FOR AUTOMATIC FIREARMS Filed Dec. 18, 1967 Ville/m li’efiteei BY INVENTOR ' v‘m' ATTORNEYS United States Patent 0 ice 1 3,446,114 ‘TRIGGER MECHANISM FOR AUTOMATIC FIREARMS 3,44 6,1 14 Patented May 27, 1969 2 utterly uncontrollable advance of the breech block and the ?ring of a shot. This is a source of considerable danger. Wilhelm Ketterer, Oberndorf-Lindenhof, Germany, as The invention has as its object to avoid these dis Filed Dec. 18, 1967, Ser. No. 691,288 advantages of the known arrangement and to provide a trigger mechanism ensuring that the catch lever comes signor to Heckler & Koch GmbH Claims priority, applicatioill (icirmany, Dec. 20, 1966, 6 3 into full engagement with the breech block so that un intentional advance of the breech block is safely elimi~ nated. This problem is solved according to the invention US. Cl. 89-140 8 Claims by mounting on the same pivot with the trigger a back 10 ing plate adapted to be rotated relative to the trigger through a smaller angle than the angle of rotation of ABSTRACT OF THE DISCLOSURE Int. 01. File 5/00 A trigger mechanism for automatic ?rearms employ the trigger, preloading the backing plate in the direction of trigger motion and providing the same with two sectors ing a hammer ?ring device, having a means for convert of different radii separated by a steep ?ank, and providing ing both from semi-automatic to full-automatic ?ring the catch lever at its end located in the trigger box with and, simultaneously, from closed bolt to open bolt op a hook-shaped lug engaging the larger-radius sector of eration, including a catch lever which, when the ?rearm the backing plate with the trigger pulled, until it comes is in an automatic ?ring mode, projects into the passive within reach of the smaller-radius sector of the backing movement of the breech block, catching and holding the plate carried along by the trigger when the latter is re breech block in its rearward position, and further in 20 leased and drops abruptly onto said last-mentioned sector. cluding a driving member for displacing the catch lever Thus, in the trigger mechanism according to the in from its normal position. vention the catch lever does not follow the trigger move ment when the trigger is released, but is maintained by the backing plate in the position in which its end is out 25 This invention relates to a trigger mechanism for auto side of the path of movement of the breech block, until matic ?rearms having a changeover device to change the driving member for displacing the catch lever pro both from semi-automatic to full-automatic ?ring and vided on ‘the trigger has been displaced clear of the simultaneously, from ?ring from closed bolt position to catch lever su?iciently for the catch lever to return to its ?ring from open bolt position, said mechanism being dis normal position without being prevented therefrom by posed in a trigger box and comprising a catch lever which 30 said driving member. Only then is the catch lever released in its normal position, with the weapon set for automatic by the backing plate so that, under the action of its load ?ring, projects into the path of movement of the breech ing spring, it can be returned abruptly to its normal block, catching and holding the later in its rearmost posi position. The spring and the mass have been selected tion, the trigger of said mechanism being provided with so that the speed at which the catch lever moves to its a driving member for displacing said each lever from 35 normal position is high compared to that of the breech its normal position. block, whereby it is ensured that the catch lever reaches A trigger mechanism of this type for a weapon of the its normal position under any circumstances and comes pin ?ring type is known, in which two side rollers are ino full engagement with the breech block when the provided on the trigger and engaged by an arm of the latter is caught. In this manner, the aforementioned catch lever under the action of a spring, provided the danger is completely eliminated. When the trigger is catch lever has been released by the safety roll when operated, the driving member provided on the same setting the weapon for automatic ?ring. The arrange comes into engagement with the catch lever to displace ment is such that when the trigger is pulled, the end of the same without the backing plate changing at once the trigger projecting into the path of movement of the its position. Only when the catch lever has been lifted breech block is displaced from said path of movement su?iciently for its hook-shaped lug to slide off the ?ank whereas when the trigger is released, the catch lever fol between the two sectors of the backing plate is the back lows the trigger and reenters the path of movement of ing plate, which until then has remained at rest, rotated the breech block and then catches the latter to terminate by its loading spring so that the larger-radius sector of a burst. This known arrangement has the disadvantage that the movements of the catch lever, which follows the movements of the trigger, are relatively slow compared to the movement of the breech block. This is why the the ‘backing plate backs up the hook-shaped lug of the cat-ch lever. This has the added advantage that the posi tion of the trigger, once the weapon has been released, is no longer very critical because any burst released is interrupted only when the trigger is released suf?ciently to be close to its normal position. The long distance catch lever can assume any position when the breech which the trigger has to travel in the direction of its block comes into catching position so that the possi normal position before a burst is interrupted has the bility exists for the engaging surfaces on the catch lever advantage that the trigger need not be maintained at and the breech block to barely overlap. When the trigger all costs in a rearmost position but can perform certain is further released, the catch lever will not continue to come into engagement with the breech block, as it is 60 movements under the in?uence of the recoil movements maintained in its position by friction between the breech of the weapon, without the burst being thereby inter rupted unintentionally. block and its catching surface, said friction being very hgh due to the heavy pressure exerted by the closing In a preferred embodiment of the invention, the trigger spring. This involves the risk of this insu?icient engage and the backing plate are coupled to each other by a ment between the breech block and the catch lever being pin-and-slot connection, the slot in the backing plate released by any vibrations that may be set up, causing enabling the necessary movement relative to the trigger 3,446,114 3 to be performed. The backing plate is conveniently loaded by a leg spring encircling its pivot, said leg spring having the advantage of permitting a large spring travel despite its relatively small space requirement. In a preferred embodiment of the invention, a known trigger mechanism of the hammer ?ring type is employed, 4 helical compression spring 5 supported against the trigger box 1. The hammer 2 is maintained in the position shown in the drawing by a trigger lever 6 engaging with its nose 7 a corresponding detent 8 on the outer surface of the hammer. The trigger lever 6 is pivotably supported on the same pivot 9 as the trigger 10 and is moreover mov the catch lever and the backing plate being additionally able in the directions indicated by the dual arrow 11. incorporated therein. A trigger mechanism of the hammer It is forced in the direction of the surface of the hammer ?ring type generally offers the possibility of releasing the 2 by a roller 13 mounted on the legs of a spring 12. trigger precisely at the moment when the breech block 10 Moreover, a spring (not shown) tends to hold the trigger has passed by the end of the catch lever, while a detent provided on the hammer is still within reach of the trigger lever 6 in its left-hand position as shown in the drawing. When the trigger 10 is operated to ?re a shot, the rear lever. In this case, the hammer can still be caught while nose 14 is carried along by the lug 15 provided on the the breech block is moving forward to introduce a car trigger 10 so that the trigger lever 6 is rotated counter 15 tridge into the barrel which has run hot during ?ring. In clockwise as shown in the drawing and its nose 7 is moved order to eliminate this possibility, in the preferred embodi out of the detent 8. The hammer 2 can then strike for ment of the invention the detent on the hammer and ward and release a shot in known manner. The catching the trigger lever are associated so that the detent will pawl 16 whose transverse web coacts with another detent come within reach of the trigger lever to be caught by 18 on the hammer 2 releases the hammer 2 in known the latter if when the weapon is being cocked, the hammer 20 manner only when the release lever 19 has been forced is rotated beyond the position in which it engages in its downwards by the advancing breech block. The construc cocked position the under side of the breech block. The tion and function of the trigger device described thus hammer is rotated beyond the said position due to its far are known so that they need not be discussed in inertia when during the return travel of the breech block detail. it is moved at high speed. By this it is ensured that the 25 greater The trigger device shown in the drawing includes fur hammer can be caught only during the return travel but ther a catch lever 21, which is pivotably supported near not during the forward movement of the breech block. its upper end on a pivot 22 and disposed in such a man This eliminates the possibility of a cartridge being fed ner that, in the position shown, its upper end 23 projects into the cartridge chamber of a barrel that has run hot out of the trigger box 1 and into the path of movement 30 during ?ring, without said cartridge being ?red by means of the breech block, whereas its end 24 located within the of the hammer and/or ?ring pin, so that the danger of trigger box extends to a point adjacent the pivot 9 of the spontaneous ?ring is eliminated and maximum safety in trigger 10 and is provided with a hook-shaped lug 25 ex handling the weapon is ensured. Thus, the catching 0f tending substantially radially of the pivot 9 and at the the hammer by the trigger lever depends on the condi same time, approximately tangentially of the circle around tion that the hammer is cocked at high speed, such as is the pivot 22 of the catch lever 21. The latter is loaded by done by the returning breech block upon the ?ring of a a leg spring 26 disposed on the pivot 22 of said catch lever, cartridge. If however, the weapon is cocked by hand, the said spring 26 tending to maintain the end 23 of the lever breech block is moved at a low speed which does not in the path of movement of the breech block. In the posi suffice to throw the hammer beyond the aforementioned 40 tion shown, a breech block would be maintained in its position. In order to avoid operating errors due to this rearmost position by the end 23 of the catch lever 21. In arrangement, a further embodiment of the invention pro order to have a weapon ?ring from closed bolt position for vides a sprung projection on the hammer near the free semi-automatic ?ring, a lug 28 is provided on the safety end thereof, said projection projecting above the surface roll 27, said lug enabling the catch lever 21 to be rotated of the hammer facing towards the breech block and hav clockwise su?iciently for its end 23 to clear the path of ing an end face disposed approximately perpendicularly movement of the breech block when changing to semi to the path of movement of the breech block and facing automatic ?ring. Consequently, the breech block retained towards the latter. Because of this projection, when en by the catch lever when the weapon is set for full-auto gaged by the breech block the hammer is rotated through matic ?ring, is released when changing to semi-automatic a wider angle than corresponds to the position in which it ?ring so that it will feed a cartridge and move into its engages the under side of the breech block. Therefore, it 50 locked position. can be caught positively by the trigger lever even when With the weapon set for full-automatic ?ring as illus trated in the drawing, the catch lever 21 is displaced from cooking the weapon by hand or when shooting cartridges the position shown by a lug 29 when the trigger is pulled, having an insu?icient charge. However, since the projec said lug 29 being provided on an arm 30 connected to the tion is spring loaded, the hammer can engage the under side of the breech block immediately upon snapping home 55 trigger 10. Further, a backing plate 31 is rotatably sup ported on the pivot 9 mounting the trigger 10, said back in the trigger lever. The projection can be de?ned in ing plate being provided with a relatively large-radius sec simple manner by the nose of a pull-over lever supported tor 32 and a considerably smaller-radius sector 33. The pivotally on the hammer, said pull-over lever having its backing plate 31 is loaded by a leg spring 34, which tends pivot disposed closer to the end of the hammer than its end face and being maintained by a spring in a rest 60 to swivel the backing plate counterclockwise as shown in position in which its nose extends through a recess in the surface of the hammer facing towards the breech block. The invention is described and illustrated more particu the drawing, that is, in the same direction in which the trigger 10 is operated. Inserted in the plate 31 is a pin 35 engaging an arc-shaped slot 36 in the trigger 10, said slot being concentric with the pivot 9. The pin 35 and the slot 36 are so arranged that the backing plate 31 is main larly in conjunction with the accompanying drawing which 65 tained in the position shown against the action of its spring shows an embodiment of the invention. The ?gure shows diagrammatically a longitudinal sec tion of a trigger mechanism according to the invention, 34 when the trigger is released. In this case, the hook shaped lug on the inner end of the catch lever 21 engages over the nose 37, said nose being limited by the ?ank be~ parts unimportant to the invention having been omitted. tween the larger-radius sector 32 and the smaller-radius The trigger mechanism shown in the drawing is de 70 sector 33 of the backing plate 31. When the trigger 10 of the mechanism shown is op signed for weapons with hammer ?ring and comprises a erated, the lug 29 of the trigger comes into engagement on trigger box 1 in which all parts of the trigger device are and displaces the catch lever 21. The backing plate 31 accommodated. Said parts comprise a hammer 2 sup remains at ?rst in the position shown, in which its nose ported pivotably on a pivot 3 and loaded by a pressure 75 37 engages the hook-shaped lug 25 of the catch lever 21. fork 4, said pressure fork being under the action of a 5 3,446,114 The slot 36 is of sufficient length to enable the trigger 10 to swivel. If then, the catch lever 21 has been rotated su?’iciently for the hook-shaped lug 25 to release the nose 37 of the backing plate, said backing plate is swivelled counterclockwise abruptly by the spring 34 to the extent permitted by the slot 36. It then backs up with its larger diameter sector 32 the hook-shaped nose 25 on the catch lever 21 so that said lever cannot return to its initial posi tion. In this position, the end 23 of the catch lever is clear of the path of movement of the breech block so that 6 of the pull-over lever 41, the hammer 2 is rotated ad ditionally by an amount corresponding to the height of the end face 44, until the breech block slides over the nose 43 of the pull-over lever 41 thereby rotating it against the action of the spring 45 su?'iciently for the nose 43 to disappear substantially in the recess in the ham mer 2. In this manner, an additional swivel motion is ac complished, whereby the detent 8 comes within reach of the nose 7 of the trigger lever 6. This additional swivel motion, however, takes place only during the return the latter can advance unimpeded. Also, the lug 15 pro 10 and not during the advance of the lbreech block so that vided on the trigger 10 has displaced the trigger lever 6 the safety feature provided by the aforementioned a-r clear of the detent 8 on the hammer 2 so that automatic ?ring results. rangement of the detent 8 and the nose 7 is fully main tained. Nevertheless, troublefree operation of the weapon If the automatic ?ring is to be interrupted and the 15 is ensured even when ?ring ammunition whose propelling trigger 10 is released, the catch lever 21 remains in its force is insu?icient and when loading the weapon by position last described, as it is backed up by the plate 31, hand. although the lever is released by the lug 29. Only after The invention can he applied not only to trigger mecha the trigger 10 has been swivelled clockwise through a nisms of the hammer ?ring type, but for example also considerable angle is the pin 35 on the backing plate 31 20 to mechanisms of the pin ?ring type. carried along by the end of the slot 36 so that now the backing plate 31 is rotated together with the trigger 10. What I claim is: 1. A trigger mechanism for automatic ?rearms having If then, the nose 37 of the backing plate slides off the a changeover device to change both from semi-automatic hook-shaped lug 25 on the catch lever 21, the latter is re to full-automatic ?ring and simultaneously from ?ring turned abruptly into the initial position shown by the 25 from closed ‘bolt position to ?ring from open ‘bolt posi spring 26. The lug 29 provided on the trigger 10 does not tion, said mechanism ‘being disposed in a trigger box and hamper this movement of the catch lever so that the speed comprising a catch lever which in its normal position, of this movement depends exclusively on the force of the with the ?rearm set for automatic ?ring, projects into spring 26. Consequently, this movement can take place the path of movement of the breech block, catching and rapidly and vigorously enough to positively move the holding the latter in its rearmost position, the trigger of catch lever 21 to the position shown, even if the breech said mechanism being provided with a driving ‘member for block when releasing the catch is positioned directly for displacing said catch lever from its normal position, wardly of the end 23 of the lever. In this manner it is characterized in that on the same pivot (9) as the trig ensured that the end 23 of the catch lever fully engages ger (10), a backing plate (31) is supported, said back the breech block so that the latter cannot come loose ing plate being able to ‘be rotated relative to said trig 35 under the action of vibrations and move forward unin ger through a smaller angle than the angle of rotation tentionally. of said trigger, that said backing plate is preloaded in In order to ensure that the hammer 2 cannot ‘be caught the direction of motion of the trigger and has two sectors by the trigger lever '6 with the breech block advancing (32 and 33) of different radii separated by a steep ?ank, when the trigger 10 is released, to prevent a cartridge 40 and that said catch lever (21) at its end located in the being introduced without being ?red into the barrel heated trigger box (1) has a hook-shaped lug (25), said lug en by automatic ?ring, the length of the trigger lever 6, its gaging the larger-radius sector (32) of said backing plate range of movement in the directions indicated by the dual arrow 11 and the position of the detent 8 on the hammer 2 are tuned to each other so that even with the trigger 10 released, the detent 8 will come within reach of the nose when the trigger has been pulled, until it comes within reach of the smaller-radius sector (33) of the backing plate carried along ‘by the trigger when the latter is re leased and drops abruptly on to said last-mentioned 7 of the trigger lever 6 only if the hammer 2 is rotated sector. much farther than to its position of engagement on the 2. A mechanism as claimed in claim 1, characterized under side of the breech block, during whose return move in that said trigger (10) and said backing plate (31) are ment the hammer is cocked. Rather, the hammer 2 must 50 swing beyond said position under the in?uence of its inertia, to come into engagement with the nose 7 of the trigger lever 6. This swinging movement is ensured at the high speeds encountered when ?ring normal ammunition. It may happen, however, that when defective ammuni 55 tion is fed the breech block will not return su?iciently for the hammer 2 to swing over with its detent 8 to within reach of the catch lever 6, and when the weapon is cocked by hand, the speeds are not reached that would produce such swinging movement. In order to ensure even in this case that the detent 8 engages the nose 7 of the trigger lever, a pull-over lever 41 is pivotally sup coupled to each other by a pin-and-slot connection (35, 36). 3. A mechanism as claimed in claim 1, characterized in that said backing plate (31) is loaded by a leg spring (34) encircling the pivot (9) thereof. 4. A mechanism as claimed in claim 1, characterized in that the ?ank provided on the backing plate (31) and the hook-shaped lug (25) on the catch lever (21) ex tend substantially in the direction of motion of said hook-shaped lug. 5. A trigger mechanism as claimed in claim 1, further comprising a hammer ?ring means. 6. A mechanism as claimed in claim 5 having a sprung trigger lever (6) and on the hammer, a detent (8) for ported on a pivot 42 at the free end of the hammer 2. Said pull-over lever 41 has a nose 43 which penetrates said trigger lever, characterized in that said detent (8) through a corresponding recess in the hammer 2 and has 65 and said trigger lever (6) are arranged so that the detent an end face 44 facing towards the breech block, and comes within reach of and can be caught by the trigger which is substantially vertically positioned on the path lever only when the hammer (2) as the weapon is being of movement of the breech block when the hammer is cocked is rotated beyond the position in which it en cocked. The pivot 42 is disposed closer to the end of the gages the under side of the breech block in its cocked con hammer 2 then the end face 44, and the lever 41 is 70 dition. loaded by a spring 45, which maintains the lever 41 in a 7. A mechanism as claimed in claim 6, characterized rest position in which its nose 43 projects above the in that a sprung projection (41) is provided on said surface 46 of the hammer 2 facing towards the breech hammer (2) near its free end, said projection projecting block. When the breech block during its return move beyond the surface (46) of the hammer facing towards ment runs up with its back face against the end face 44 the breech block and having an end face (44) disposed 7 3,446,114 approximately perpendicularly to the path of movement of the breech block and facing towards the latter. 8 References Cited FOREIGN PATENTS 5/1964 Great Britain. 8. A mechanism as claimed in claim 7, characterized 999,514 in that said projection is formed by the nose (43) of a pull-over lever (41) pivotally supported on said hammer, 5 BENJAMIN A. BORCHELT, Primary Examiner. the pivot of said pull-over lever being disposed closer to the end of said hammer (2) than the latter’s end face STEPHEN C. BENTLEY, Assistant Examiner. (44) and said pull-over lever (41) being held by a spring (45) in a rest position in which its nose (43) extends through a recess in the surface (46) of the hammer fac89—l43 ing towards the breech block. 10 US. Cl. X.R.