Historical Document · 1966
Kenzo Iwashita's Howa patent (Japanese priority 28 June 1963; filed 16 April 1964; patented 22 February 1966) for the straight-line hammer rate reducer that slows the Type 64 rifle's cyclic rate. The Type 64 dive's source for the mechanism.
Feb. 22, 1966 KENZQ [WASHITA 3,236,154 MECHANISM FOR REDUCING THE RATE OF FIRE IN _ _ AUTOMATIC FIRING ARMS Flled Apr1l 16, 1964 4 Sheets-Sheet 1 F l G. I SLIDE 5} I 2 BACK RFJUR“ I, g FIRE HAMMER ‘ GE BACK "swat" NM“ m _. 1; BA Ck 2h _____ __I DWELL 3h Ty; RENR“ < E ‘ HAMMER FIRE Feb. 22, 1966 KENZO lwAsHn-A 3,235,154 MECHANISM FOR REDUCING THE RATE OF FIRE IN AUTOMATIC FIRING ARMS Filed April 16, 1964 . Y- I0 I 22 4 Sheets-Sheet 2 Feb. 22, 1966 KENZQ lwAsHlTA 3,236,154 MECHANISM FOR REDUCING THE RATE OF FIRE IN AUTOMATIC FIRING ARMS Filed April 16, 1964 4 Sheets-Sheet 5 Feb. 22, 1966 KENZO lWASHlTA 3,236,154 ’ MECHANISM FOR REDUCING THE RATE OF FIRE IN AUTOMATIC FIRING ARMS Filed April 16, 1964 4 Sheets-Sheet 4 United States Patent 0 ” ICC 3,236,154 Patented Feb. 22, 1966 1 2 3,236,154 until a dead point is reached, a receiver in which said Kenzo Iwashita, Chikusa-ku, Nagoya-shi, Japan, assignor to Howa Kogyo Kabushiki Kaisha, Nagoya-shi, Japan, stop and being capable of having inserted therethrough MECHANISM FOR REDUCING THE RATE OF FIRE IN AUTOMATIC FIRING ARMS a joint-stock company of Japan Filed Apr. 16, 1964, Ser. No. 360,297 Claims priority, application Japan, June 28, 1963, 38/ 33,081 3 Claims. (Cl. 89—128) The present invention'relates to mechanism for reduc ing the rate of ?re in automatic ri?es and more particu-‘ larly to an improved arrangement of trigger, sear and hammer, slide, ?ring pin and recoil spring are arranged, a receiver tail containing the hammer spring, a hammer substantially all of said hammer when the same is re tracted, a sear adapted to lock the hammer in the retracted position, a trigger for triggering the hammer at said re tracted position, a sear lock mounted for pivotal move ment, a front projection on the sear lock adapted to be displaced downwardly at the termination of the return of said slide, a rear projection on said sear lock adapted to displace ‘upwardly the forward end of said sear when the front projection is displaced downwardly thereby releas ing the hammer, a scar lock spring urging said sear lock adjustably selecting one of fully automatic ?ring, short 15 to normally displace said front projection upwardly, a connector pivoted to the sear lock at the pivotal mounting or single ?ring and no ?ring operations. hammer components, as well as additional mechanism for In automatic arms, it is most important to provide. them with excellent automatic ?ring accuracy so that these arms are required to ‘be equipped with mechanisms which can provide such a feature. This is necessary for arms constructed for ?ring both single shot and a number of shots in rapid succession as well as for those constructed for only sustained ?re, but the following factors, are con sidered to be important in designing arms which have 25 excellent ?ring accuracy as well as other desirable charac teristics. Firstly, it is necessary to prolong insofar as possible the interval between the ?rst shot and the second shot. Thus, for example, in a conventional fully automatic ri?e having a normal rate of ?re of from 700 to 800‘ shots or rounds per minute, it is desirable to reduce this rate as low as for the sear lock for adapting the ?re arm to any state of continuous shot, single shot and safety, means de?ning a trigger chamber in which chamber is enclosed said trigger, sear lock, sear lock spring and connector, the arrangement being such that when the hammer retracts together with the slide by ?ring, the recoil spring returns the slide upon the same reaching its rear end with the hammer being locked by the sear and the sear lock ac tuated by the slide when the slide reaches its forward breech locking location for releasing the locking of the hammer whereby the hammer is urged toward the ?ring pin by the force of the hammer spring to strike the ?ring pin, the locking end of the sear being positioned at the rear portion of the receiver so as to make a substantial portion of the hammer retract into the receiver tail there by lengthening the advancing distance of the hammer be tween the releasing position of the hammer from the sear possible, for example to 400K to 500 shots per minute. If this reduction is possible, better ?ring accuracy can be and the striking position and the weight of the hammer attained. being such as to decrease the advance velocity of the Secondly, the mechanism should be so constructed that hammer between the position where the hammer is re—' the motions of a reciprocating member, such as a slide, leased from the sear and the position where the hammer and a ?ring mechanism, such as a hammer, etc., may be strikes the ?ring pin. well balanced and smooth and that these components can The characteristic features of the present invention will reciprocate in as straight a line as possible. With this 40 become apparent from the following description taken construction, any moment that is caused by the mechanism in connection with the accompanying drawings,»in ‘which itself and which tends to de?ect the barrel axis can be eliminated, thereby resulting in excellent ?ring accuracy. drawings like members are designated by like reference characters, and in which: Thirdly, it is necessary to utilize a mechanism which FIG. 1 shows an operation diagram of a mechanism can reduce the recoil energy of the weapon itself. This 45 feature can be satisfactorily attained by increasing the weight of the rifle or by applying a muzzle brake. It is one of the objects of this invention to provide a noval mechanism which can ful?l the above mentioned ?rst and second features by a single mechanism. A further object of this invention is to provide a novel mechanism which is quite simple, but can operate ac curately without any trouble, reduce the rate of ?re, and embodying this invention; FIG. 2 shows an operation diagram of a mechanism employed in the conventional weapon for reducing the rate of ?ring thereof; 7 FIG. 3 is a view in longitudinal section, partly broken away, illustrating the arrangement of all members of- a mechanism constructed according to this invention; FIGS. 4 and 5 are sectional views respectively showing relative positions of the ‘respective members for automa eliminate any moment that tends to disturb the main tic ?ring operations with FIG. 4 showing the state of tenance of the aim. 55 readiness before the trigger is actuated by the shooter, The above and other objects and advantages of the and FIG. 5 the state wherein the trigger has been actuated; present invention have been attained by’ a mechanism for FIGS. 6 and 7 are sectional views respectively showing reducing the rate of ?re in automatic ri?es of the type the relative positions of the respective members for single comprising a ?ring pin, a hammer, a chamber for the shot ?ring operation with FIG. 6 showing the statepofr hammer, a hammer spring associated therewith for ac 60 readiness, and FIG. 7 the state wherein the trigger has tuating the hammer to strike the ?ring pin, a slide, a been actuated; i recoil spring for said slide, said slide together with said FIG. 8 is a similar view illustrating the safety condition hammer being guided in the hammer chamber for ad of the mechanism of FIG. 3; vance movement in a straight line towards the ?ring pin, FIG. 9 is an exploded view of a trigger and its asso< means for retracting the hammer together with the 'slide 65 ciated members of the mechanism of FIG. 3; and 3,236,154. 3 4 FIG. 10 is a side view partly in elevation and partly case as described in connection with FIG. 2, although the in cross section illustrating the mutual relation of a trigger and a sear when they are engaged in the mechanism of FIG. 3. In order to indicate fully the features of this invention, it seems necessary to describe them in comparison with those of the conventional mechanism by referring to the operation diagrams illustrated in FIGS. 1 and 2 of the mined by the velocity of the slide at the time when it strikes the actuator, the rearward strokes of the slide are not always the same in the practical ?ring operation. Thus, the veloctiy of the slide at the time when it strikes accompanying drawing. extent of the rearward movement of the actuator is deter the actuator varies substantially. Accordingly, the recip rocating time of the actuator and the force imparted to the slide lock by the actuator also vary substantially, Referring now FIG. 2, in the conventional mechanism 10 thereby causing irregularities in the ?ring intervals. In a slide is pushed backwardly by gas pressure or other some cases the slide lock fails to release the slide. motive force after one shot has been ?red. Near the end In accordance with this invention, since the forward of the backward stroke, the slide strikes the head of an movement of the slide causes the hammer to move freely actuator to cause it to retract while compressing a spring in the forward direction, there is no possibility of func positioned behind the actuator until it stops at a balance 15 tional failure as described hereinbefore. Moreover, as point. Thereafter, the spring acts to push the actuator in the time necessary for the hammer to advance is constant the forward direction. due to constant stroke of the hammer and constant force On the other hand, the slide begins its forward move of the hammer spring, the ?ring intervals are very regular. ment from the stroke end thereof under the action of a Another outstanding feature of the mechanism con recoil spring, but it is locked by a slide lock at the initial 20 structed according to the principle of this invention is stage of its forward movement. However, as the actuator that the respective members thereof are completely free advances to release the slide lock at the end of its forward from any disarrangement even when the ri?e is subjected stroke the slide again begins to advance forwardly to to an abnormal shock. In conventional mechanism, how charge the succeeding cartridge into the ?ring chamber ever, there are frequent cases in which the safety lock is just before the end of its stroke, thus completing the 25 caused by such shock to become ineffective even when it breech lock. is originally set to operate. According to this invention It will be understood by those skilled in the art that the such a defect is obviated by designing the sear so as to periods of the above described forward and rearward minimize the tendency to affect the locking function motions of the actuator have the effect of prolonging the thereof or to rotate it about the axis of its pivot pin even interval between successive shots. In the mechanism of 30 when an impact from the outside is applied to the weapon the type described above, a hammer is generally pivotally in any direction and by interlocking the hammer and the mounted in a trigger housing so that the hammer will be sear in a hook fashion. pushed back at its head by the slide at the initial stage of the retracting stroke thereof to be rotated around a In addition to providing such a reliable safety mecha nism, it is a further feature of this invention to provide a pivot pin while moving backwardly until it is locked by 35 novel single shot mechanism. In order to provide this single shot feature the mecha a sear. As the slide advances, the hammer is released from the sear immediately after completion of the breech nism is constructed so that actuation of the trigger by locking operation and then advances over a relatively ?nger will cause ?ring of the ?rst cartridge, and immedi short distance while rotating under the action of a hammer ately thereafter the slide will retract and then advance to spring until it strikes the rear end of a ?ring pin to effect 40 charge the next cartridge into the ?ring chamber. Even the next ?ring. In contrast, as can be clearly noted from FIG. 1, with if the shooter continues to hold the trigger, subsequent ?ring is prevented, and when the shooter releases the the mechanism of this invention, as soon as the slide trigger it is permitted to return to its initial position, so reaches the dead point of its backward movement the slide is returned to the original position by the recoil spring that only when the shooter actuates the trigger again, the thus completing the charging of the next cartridge. The hammer which is pushed back by this slide to move next shot is ?red. In the mechanism of this invention only two members, namly, trigger and a sear, are utilized for this purpose, and the above mentioned objects can be attained by using a special contact position between the sear and the near the dead point of its backward stroke, thus being prevented from returning. When the forward movement 50 trigger. Referring now to FIG. 3 which illustrates one embodi of the slide caused by the recoil spring and the breech locking operation are completed, the action of the sear ment of this invention, there is shown a reciprocating mass 1 including a slide and a bolt (not shown) adapted .is interrupted, whereby the hammer becomes free to move. to charge and remove a cartridge, not shown, in the man Thus, the hammer is advanced from the position 211 to ner well known in the art. A ?ring pin 2 is arranged in the position 3h (FIG. 1) along a relatively long straight a conventional manner. Within a trigger housing 4, a distance until, ?nally, the position 3h is reached, at which linearly at the same speed as the slide is held by a sear point the hammer strikes a ?ring pin, thus resulting in the trigger 3 is pivotally mounted by a pivot pin 5, said trig ger being biased in the counterclockwise direction, as next ?ring. Thus, it will be obvious that, with this con viewed in the drawing, by a trigger spring 6 acting there struction, increase in the ?ring interval should be obtained by the interval of travel 2h—3h. This .is a distinct differ 60 upon through a trigger pusher 7. Also, a scar 8 is mounted within the housing 4 by means of an elongated ence in comparison with the operation provided by the slot 8a and a pin 9 passing therethrough. The sear 8 conventional mechanism, described in connection with is biased toward the left upper side by a scar spring 10 dis FIG. 2. posed below the pin 9, so that the rear extension 8f of A further outstanding feature of the mechanism of this the sear 8 will be rotated in the clockwise direction until invention is that the motion of the hammer is rectilinear. it is engaged by the lower surface 11 of the receiver R. This means that a mechanism incorporating the ?rst fea‘ A hammer 12 is constructed so that it will retract to ture involves the second feature also. It will be clear gether with the slide 1 but will advance independently of that the construction in which the hammer is adapted to the forward movement of the slide. In the receiver tail R’, strike a ?ring pin during its motion along a straight line between the hammer 12 and a hammer spring 13 is inter can greatly minimize any moment that may cause dis posed a hammer spring stop 14 provided with a shaft 14a turbance of the aim of the weapon when compared with the conventional construction wherein the hammer is about which the spring 13 is wound. The stop and shaft rotated to hit the ?ring pin. ‘In various weapons, a more important objective is to minimize any tendency for functional failures. In the are inserted in the receiver tail R’ so as to slide there through. A hook shaped projection 12a is formed on the fore end of the hammer 12. 3,236,154 7 of the scar and the inclined surface 30 of the trigger 3, and the angle (3 between a line passing through the latter point of contact and through the axis of the pin 5 which supports the trigger and the inclined surface 30 so that these angles satisfy the following equations, where 95 represents the angle of rotation of the trigger around the pin 5 when actuated by the shooter. By so selecting these angles the shock imparted to the trigger 3 through the rear end of the sear can be greatly reduced, so that only a very small impact is transmitted to the ?nger of the shooter while the sear 8 is maintained in the automatic ?ring position. It was found that best results can be obtained by making 8 shock from the outside. Thus, this invention provides a novel mechanism of high utility without the possibility of any trouble, which mechanism is also capable of reducing the rate of ?re and greatly improving the ?ring accuracy. Although a speci?c embodiment has been disclosed to illustrate the invention, it will be evident that various modi?cations and variations can be made within the scope of this invention. It, therefore, is to be understood that within the scope of the appended claims, the inven tion may be practiced otherwise than as speci?cally de scribed. What is claimed is: 1. A mechanism for reducing the rate of ?re in auto matic ?re arms, particularly automatic ri?es of the type comprising a ?ring pin, a hammer, a chamber for the hammer, a hammer spring associated therewith for actu ating the hammer to strike the ?ring pin, a slide, a recoil spring for said slide, said slide together with said hammer Finally, it is necessary to maintain the safety condition even when the mechanism is subjected to an unexpected shock from the outside, for example, hard knocking. Of course, such a shock will impart moments in abnormal directions to various members constituting the mech anism, and it is the ‘best approach to maintain the safety condition to decrease to a minimum this effect caused by said shock. being guided in the hammer chamber for advance move ment in a straight line towards the ?ring pin, means for retracting the hammer together with the slide until a dead point is reached, a receiver in which said hammer, slide, ?ring pin and recoil spring are arranged, a receiver tail containing the hammer spring, a hammer stop and being capable of having inserted therethrough substantially all of said hammer when the same is retracted, a sear adapted to lock the hammer in the retracted position, a trigger for triggering the hammer at said retracted position, a sear According to this invention the slot 8a is so machined lock mounted for pivotal movement, a front projecion as to position the pin 9 substantially at the center of grav 30 on the sear lock adapted to be displaced downwardly at ity of the sear 8 when -it is displaced to the right under the termination of the return of said slide, a rear projec the ‘bias of the hammer spring 13. By this construction tion on said sear lock adapted to displace upwardly the the sear 8 is positively prevented from rotating about the forward end of said sear when the front projection is pin 9 by an impact imparted thereto by unexpected displaced downwardly thereby releasing the hammer, a ‘strong outside shock. Even the slightest tendency for 35 sear lock spring urging said sear lock to normally dis such a rotation can be precluded by providing slightly in place said front projection upwardly, a connector pivoted clined engaging surfaces between the projection 12a on to the sear lock at the pivotal mounting for the sear lock the hammer 12 and the projection Sr: of the sear as best for adapting the ?re arm to any state of continuous shot, shown in FIG. 10, These inclined engaging surfaces can single shot and safety, means de?ning a trigger chamber positively prevent not only unexpected ?ring in the case 40 in which chamber is enclosed said rigger, sear lock, sear of the trigger being slightly pulled inadvertently, but also accidental ?ring caused by impact due to dropping of the ri?e and other causes. In addition to the various features described herein above, it can be easily observed from the drawing that the stroke ofV-the hammer 12 is very long and is rectilinear, which is an important factor in reducing the ?ring rate, because a longer stroke requires a longer time for traverse. Moreover, with reference to the hammering mass, the effective hammering mass is the sumof the mass of the hammer 12, that of the hammer spring stop 14 including that of shaft 14a since the hammer stop and shaft advance as a unitary component in the ?ring operation. Further more, it is possible to design the dimensions of the ham lock spring and connector, the arrangement being such that when the hammer retracts together with the slide by ?ring, the recoil spring returns the slide upon the same reaching its rear end with the hammer being locked by the sear and the sear lock actuated by the slide when the slide reaches its forward breech locking location for re leasing the locking of the hammer whereby the hammer is urged toward the ?ring pin by the force of the hammer spring to strike the ?ring pin, the locking end of the sear being positioned at the rear portion of the receiver so as to make a substantial portion of the hammer retract into the receiver tail thereby lengthening the advancing dis tance of the hammer between the releasing position of the hammer from the scar and the striking position and mer spring 13 and its biasing force with ample surplus 55 the weight of the hammer being such as to decrease the margin, which insures more reliable ?ring operations. advance velocity of the hammer between the position With a rotatably hinged hammer commonly utilized in where the hammer is released from the sear and the posi conventional arms, the force acting upon it will act in a tion where the hammer strikes the ?ring pin. direction to create a torque tending to swing the weapon, whereas according to the construction according to this invention the hammer is arranged to travel along a straight line. For this reason, not only the ?ring accuracy of the automatic ?ring weapons can be remarkably im proved, but also damage to the ?ring pin can also be effectively prevented. The various outstanding features of this invention de scribed hereinabove are contributed by the fact that the mechanism is constituted by a very small number of com 2. The mechanism as claimed in claim 1, in which the assemblage including the sear and trigger combined with the sear lock includes a scar lock pin constituting the pivotal mounting for the sear lock, said connector having at one end thereof an open slot, a fixed pin received in said open slot, said sear lock spring being de?ned by a 65 leaf spring, and an eccentric pin carried by said connector for being positioned at any desired angle whereby adjust ing of such latter pin adapts the ?re arm for continuous ‘ ?ring, single shot ?ring and safety. ponent members, that the respective members are disposed 3. The mechanism as claimed in claim 1, in which in ample spaces to give them su?icient rigidity, that the 70 the assemblage including the sear and trigger combined striking function of the hammer is made positive by the with the sear lock further includes a sear pin, a scar spring travel hereof along a straight line, that the interval of ?r biasing the sear, a trigger pin pivotally supporting the ing is prolonged due to a relatively long hammer, and that trigger, a trigger pusher element operably associated with the respective members are mounted in Well-balanced con the trigger and a trigger spring, said trigger and sear hav dition to be free of adverse effect due to any abnormal 75 ing contacting portions so designed that during squeezing 3,236,154 5 6 For making possible automatic ?ring, a sear lock 19, having a projection 19a disposed to be pushed down by the returning motion of the slide 1, is connected, by a pin any movement of the slide 1, as can be clearly understood by comparing FIGS. 4 and 6. Means for providing this feature will be described hereinbelow by referring to 20, to a connector 16 which in turn is supported in the FIG. 9. More speci?cally, this means comprises a connector 16 trigger housing 4 by a pivot pin 18, a projection 19b on the end opposite to said projection 19a being normally urged in the counterclockwise direction by a leaf spring 21. When this projection 19b and the fore end projection having an open slot 16a at its one end for receiving a transversal pin 17 secured to the trigger housing 4. The opposite end of the connector 16 is held by an eccentric pin 18 forming an extension of a pin 18a journaled in the 8d of the sear 8 are in the same phase, the rotation of the sear lock 19 in the clockwise direction induces the 10 side walls of the ‘trigger housing 4. Thus, by manipulat ing the pin 18, the connector 16 can be positioned at any rotation of the sear 8 in the counter-clockwise direction, desired angle. When the eccentric pin 18 is positioned in the extreme righthand position (FIGS. 4 and 5), the which, of course, is induced by contact between the pro jection 19b against the projection 8d. When these pno mechanism is set for the continuous automatic ?ring oper to the right, as viewed in the drawing, along the elongated 15 ation, whereas, when it is positioned in the extreme left opening 8a such a transmission of motion does not occur. hand position (FIG. 8), the vertical end face 16b of the connector 16 abuts the front vertical surface of the trig The sear 8 is formed to have a pointed edge 81) and a ger 3, thus causing it to become inoperative. In other lower surface 80, and the trigger 3 is provided with an inclined surface 3c, the purpose of which will be described words, ‘such an abutment serves as a safety device. In intermediate positions, that is, when the pin 18 is later. adjusted to position the connector 16 in a slightly inclined In FIG. 4, the hammer 12 is shown in its position when it is locked by the sear 8. This state of locking is quite position with its lefthand end depressed downwardly as stable, owing to a lock fashioned joint between the rear shown in FIGS. 6 and 7, the pin 20 is shifted to the left projection 8c of the sear 8 and the projection 12a on the together with the sear lock 19. This brings the curved hammer 12, which cannot be disengaged by any abnor surface 19c on the left side of the projection 1911 into mal shock imparted from the outside. contact with the left side wall of an opening 22 of the When actuated by ?nger, the arm 3a of the trigger 3 receiver. By suitably selecting the con?guration of the jections are out of phase, or when the sear 8 is displaced engages the lower surface 80 of the sear 8 to push it up wardly, thereby to rotate the sear 8 in the counter-clock wise direction around the pivot pin 9 to release the ham mer 12. surfaces of these engaging members, the projection 19a can be prevented from deeply entering into the opening 30 22. In other words, the projection 19a can be maintained Thus, the hammer 12 is advanced rapidly un out of contact with the slide 1. der the bias of the hammer spring 13 to strike the ?ring pin 2, thereby ?ring cartridge, not shown, at the end of its forward stroke. Gas pressure produced as a result of ?ring causes the slide 1 and the hammer 12 to retract until the hammer 12 is locked by the sear 8, as shown in FIG. 5. It will be understood that the slide 1 is returned by a recoil spring, not shown. As the slide 1 depresses the projec tion 19a of the sear lock 19, the opposite projection 1%, 40 which is now in the same phase as the projection 8a’ of the sear 8 as shown in FIG. 5, rotates the sear 8 in the Concurrently therewith, the projections 19b and 8d are brought into out-of~phase relation so that they will not engage each other. This renders completely inactive the sear lock 19 which operates for the automatic ?ring operation, and ?ring can be carried out only by the trigger 3. This is the condi tion for the single shot operation. As shown in the drawing, a suitable buffer 15 is pro vided at the upper left side of the trigger housing 4 and as has been pointed out hereinabove, it will be understood that the slide 1 is returned to its righthand position by a conventional recoil spring, not shown. Another feature of the mechanism embodying this in counter-clockwise direction to release again the hammer 12, thus repeating the ?ring in the same manner as above vention is the capability of holding the sear 8 in a state described. At this stage of the ?ring operation, the pivot for automatic ?ring operation without relying upon any pin 9 of the sear 8 is at the righthand end of the slot 85!, additional mechanism, this feature being provided by suit but, upon release of the trigger 3, the edge 8b disengages from the inclined face 3c, whereby the hammer 12 pushes the sear 8 to the right until the pin 9 reaches the lefthand end of the slot 8a, thus bringing the projections 8d and 19b into an out-of-phase relation. As a result, even when the projection 19a is depressed by the slide 1, the projection 1% does not raise the projection 8d, thus as suring continuous locking of the hammer to prevent fur there ?ring operation. Since the mechanism of this invention is constructed as described hereinabove, after the slide 1 and the ham mer 12 have retracted to their dead points, only the hammer 12 is prevented from advancing forwardly at a point 111, FIG. 1, whereas the slide 11 is permitted to ad ably shaping the trigger 3 and the sear 8 so as to come in to direct contact. More particularly, the sear 8 is biased to rotate clockwisely around the pin 9 by a spring 10 while the hammer spring 13 urges the sear 8 to the right. Of course, the force of the hammer spring 13 is much greater than that of the spring 10. This means that unless a suitable means is used to prevent the sear from moving to the right, it is impossible to provide automatic ?ring op eration. Accordingly, in this invention, it is necessary for designing the trigger 3 so that the sear is positively held against the strong hammer spring 13, the shooter is per mitted to hold the trigger in its actuated position, and when released by the shooter, the trigger is positively re 60 turned to its released position under the action of the vance to a point 211. At this point 2h, where this advance trigger spring 6 transmitted thereto through the trigger is terminated, the sear 8 unlocks the hammer 12. It will pusher 7. These requirements conflict with each other, so be noted that a relatively long time interval is required that, if the trigger is shaped to fully satisfy the former to permit the hammer 12 to reach a point 311 in order requirement the latter requirements cannot be ful?lled. to reduce the rate of ?re. 65 On the contrary, if the trigger 3 is shaped to satisfy the As can be clearly observed from the accompanying latter requirement, there will be caused a dangerous con drawings, a relatively large space is provided for the dition wherein the sear 3 is ‘displaced to the right, as strokes of the hammer 12 which is constructed to recipro shown in FIG. 3, even when the trigger 3 is maintained cate linearly along the longitudinal axis of the ?rearm. in its actuated state. This contributes to providing a recoiling effect with al 70 Accordingly, in order to simultaneously satisfy said most no effect with respect to the center of gravity of con?ctiing requirements, this invention contemplates se the ?rearm, thus effectively improving the ?ring accuracy. lecting the angle a (FIG. 10) between a line passing As shown in FIGS. 6 and 7, for single shot operation, the projection 19a of the sear lock 19 is kept in a position such that the projection is not affected in any way by through the point of contact between the hook 8e on the sear 8 and the projection 12a of the hammer 12, and through the point of contact between the pointed edge 8b 3,236,154 9 10 of the trigger the sear is kept in continuous ?ring position With the trigger returning to idle position upon the re- 1,573,655 2,909,100 2/1926 10/1959 604,348 7/1948 162156 of the trigger. FOREIGN PATENTS References Cited by the Examiner 1,561,756 Sutter _____________ __ 89—130 Kenn?fléy-T?ylm‘ ----- 89-140 5 G ma tB 't ' . n am UNITED STATES PATENTS EARL M. BERGERT, Primary Examiner. 11/1925 FRED C. MATTERN, JR., Examiner. Tucker ____________ __ 89—142