Patent Publication Number: US-7213359-B2

Title: Additional safety device for sear mechanism for firearms

Description:
This application is a continuation in part of Ser. No. 10/390,939, now U.S. Pat. No. 6,769,208, filed Mar. 18, 2003, which claims the priority of Italian Application Serial No. MI2002A 000623, filed Mar. 26, 2002. 

   BACKGROUND OF THE INVENTION 
   (1) Field of the Invention 
   The present invention refers to a new additional safety device for a sear mechanism for firearms. 
   (2) Description of Related Art 
   In general, the field of portable, semi-automatic or automatic firearms foresees different solutions for the sear mechanism, which comprises a mobile element which holds the hammer in the cocking position. 
   Following the voluntary pulling of the trigger, the mobile element frees the hammer and allows it to hit against a firing pin under the thrust of a preloaded elastic element. 
   Such a mobile element can be realized, for example as a sear or as a sear pawl, pivoted at a fixed part of the body of the firearm and biased by an elastic element. To carry out its function such a mobile element is thus engaged with both the trigger and with the hammer. 
   Such a mobile sear element constitutes a delicate detail of the sear mechanism, since it is stressed mechanically and has a complex form, and it is thus generally made from metal. 
   Since the hammer and the sear element are equipped with additional engagement teeth, due to problems of wear of the interfacing contact surfaces, the hammer must also necessarily be made from metal. 
   A purpose of the present invention to provide an improved sear mechanism for firearms. U.S. patent application Ser. No. 10/390,939, which is incorporated herein by reference describes a sear mechanism which is adaptable for use in the present invention. 
   Hereafter specific reference shall be made to a rifle, even though that which is object of the invention can be applied to all firearms, including side-by-side, semi-automatic, rifled and military firearms, etc. 
   Moreover, given that the invention is intended for experts in the field of firearms, it the detailed description of the structure and operation of a firearm, in particular of a rifle like the one described is omitted. This description is set forth to point out the functions of the parts of a firearm which are the subject matter of the technical problem which is the basis of the invention. 
   BRIEF SUMMARY OF THE INVENTION 
   The invention provides a sear mechanism for firearms comprising a sear box  12 , a trigger  15  mounted in said sear box  12  on a rotation pin  18  which is acted upon by an elastic return element  25 , and having a hammer  16  mounted in said sear box  12  on a pin of the hammer  31  and upon which acts an elastic thrust element  33 , said hammer  16  being equipped with a mounting tooth  40  for engaging sear tooth  41 , and a breechblock carrier  13  carrying a firing pin  14 , and comprising a sear device  17  controlled by said trigger  15  which said hammer  16 , motion between a cocking position A in engagement with said sear tooth  41  and a striking position B against said firing pin  14 , wherein said sear tooth  41  is fixed and integral with said sear box  12 , said hammer pin  31 , is in engagement with a slot  32  of said sear box  12  said sear device  17  comprises at one end an engagement element  43  mounted on said hammer pin  31  said pin being adapted to cause said hammer pin to advance in said slot  32 , said motion between said cocking position A and said striking position B of said hammer  16  comprising an initial translation step and a subsequent rotary step under the action of said elastic thrust element  33 , said sear device  17  being connected at an opposite end thereof to said trigger  15 , and including an additional safety device which comprises an interposing element  60  which is slidably mounted below the firing pin latch  43  in a housing having a first inclined plane element  63  and a second inclined plane element  63 A which are arranged between lateral walls  62  to form a seat  61  which holds element  60  in a first position where it does not interfere with the operation of the firing pin latch  43  but allows said element  60  to move into a position where it prevents the pin latch  43  from moving downwardly to disengage hammer  16 . 
   The additional passive safety device prevents the hammer  16  from being accidentally released by the disengagement of sear tooth  41  from mounting tooth  40  by an impact force or unforeseen vibration. The passive safety device comprises an interposing element  60  which is slidably mounted below the firing pin latch  43  in a housing having a first inclined plane element  63  and a second inclined plane element  63 A which are arranged between lateral walls  62  to form a seat  61  which holds element  60  in a first position where it does not interfere with the operation of the firing pin latch  43  but allows said element  60  to move into either a forward position ( FIG. 3A ) or rearward position ( FIG. 4A ) where it prevents the pin latch  43  from moving downwardly to disengage hammer  16 . 
   The additional passive safety device prevents the hammer from releasing accidentally and firing under the action of inertial forces acting along the direction of the longitudinal axis of the barrel due to sudden acceleration. Thus, if the firearm is dropped and either end strikes an object, the interposing element  60  will move along one of the inclined plane elements along the longitudinal axis of the firearm to prevent the firing pin latch  43  from becoming disengaging the hammer  16 . 
   Accordingly, it is a primary object of the present invention to provide an additional passive safety device that is automatically activated under impact conditions that may cause the firing pin latch to disengage but is not activated during the normal handling and firing of the firearm. 
   Another object of the present invention is to provide a sear mechanism which is lighter and may be made of elements which comprise a plastic material. 
   Another object of the invention is to permit the use of a low actuation force to activate the trigger and provide a structure which is not subject to excessive wear. 
   It is also an object of the invention to provide a safer design which is simple to assemble and provides greater cost-effectiveness in manufacturing. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       FIG. 1  is an exploded perspective view of a sear mechanism for firearms, that shows a sphere as the additional safety device; 
       FIG. 2  is an enlarged top view of the additional safety device for a sear mechanism of the present invention; 
       FIG. 3  is a section side view of the sear mechanism in cocking position A, and of the additional safety device with its sphere in a forward position over an inclined element for preventing movement of the firing pin latch and hammer; 
       FIG. 3A  is an enlarged section side view of a portion of  FIG. 3  which corresponds to the dotted circle in  FIG. 3 ; 
       FIG. 4  is a side section side view of the sear mechanism and of the additional safety device with its sphere in a backward position over an inclined element for preventing movement of the firing pin latch and hammer ; 
       FIG. 4A  is an enlarged section side view of a portion of  FIG. 4  which corresponds to the dotted circle in  FIG. 4 . 
       FIG. 5  is a section side view of the sear mechanism in a position with the firing pin unlocked and of the additional safety device with its sphere in a neutral position in the seat, between the two inclined elements of the additional safety device; 
       FIG. 5A  is an enlarged section side view of a portion of  FIG. 5  which corresponds to the dotted circle in  FIG. 5 . 
       FIG. 6  is a section side view of the sear mechanism with the hammer in striking position B, and of the additional safety device with its sphere in a neutral position in the seat between the two inclined elements that descend to the bottom of the additional safety device; 
       FIG. 6A  is an enlarged section side view of a portion of  FIG. 6  which corresponds to the dotted circle in  FIG. 6 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   As shown in  FIG. 1 , the sear mechanism  10  for firearms comprises a sear box  12 , which can be inserted in the structure of a firearm, for example in the stock or fore-end. 
   The firearm comprises a well known breechblock carrier  13  carrying a firing pin  14 , as partially shown in  FIGS. 3–6 . 
   On the sear box  12  are mounted a trigger  15 , a hammer  16  and a sear device  17  which when controlled by trigger  15 , releases the hammer  16  from a cocking position A in engagement on sear box  12  and a striking position B against the firing pin  14 . As shown in  FIGS. 1–6 , the trigger  15  is mounted at the sear box  12  through a rotation pin  18 , housed in a hole  19 , so as to be protruding below the front part of the sear box  12 . 
   The trigger  15  consists of an upper forked portion  20  mounted straddling an abutment rib  21  of the sear box  12 . A connection pin  24 , to which the sear device  17  is hinged, is applied to the upper forked portion  20  of the trigger. In the sear mechanism  10 , described only as an example, the sear device  17  is hinged in offset position and forward with respect to the rotation pin  18 . 
   In the cocking position A and in the striking position B of the hammer, the pin  24  is respectively in abutment with an upper surface portion  22  or a lower surface portion  23  of the rib  21 . 
   An elastic return element  25  acts on the trigger  15 . This elastic return element may be a spring, which takes the trigger  15  back to rest position when it is released after firing. 
   In the proposed embodiment, the return spring  25  also ensures the return into rest position of the sear device  17  hinged to the trigger  15 . 
   The return spring  25  is made up of a first end  27 , arranged in abutment on a breechblock locking lever  26 , of a first winding  28 , arranged around the rotation pin  18  of the trigger, of a second winding  29 , arranged around the connection pin  24  between the sear device  17  and the trigger  15  and of a second end  30 , arranged in abutment on the sear device  17 . 
   The hammer  16  is mounted at a rear portion of the sear box  12  through a pin of the hammer  31 , housed in a slot  32  arranged in such a sear box  12 . 
   An elastic thrusting element  33  acts on hammer  16 , which, in the example shown, consists of a spring made up of two windings  34 , which are symmetrical with respect to a middle plane  35  of the sear box  12  and are arranged on housing sleeves  36  of the hammer pin  31 , which protrude from the side of the hammer  16 . 
   The preloaded thrust spring  33  is equipped with two ends  37 , bound to the sear box  12 , and with a bridge portion  38  between the windings  34 , positioned in abutment on a mobile lower face  39  of the hammer  16 . 
   In the cocking position A, the hammer  16  is held by a fixed sear tooth  41 , realised integral with the sear box  12  and matching a mounting tooth  40  arranged on a rear wall of the hammer  16 . 
   Since the sear tooth  41  is fixed, it is possible to make it from plastic, thus allowing plastic to also be used for the hammer. The mass of the sear mechanism is thus substantially reduced whilst still ensuring low wear conditions between the interfacing contact surfaces. 
   The sear device  17  of the mechanism for firearms  10  is hinged at one of its front ends to the trigger  15  and is equipped at the opposite end with an element for engagement with the pin of the hammer  31 . 
   As shown in  FIGS. 1 to 6 , the sear device  17  consists of a first translating connection lever  42  and a second rototranslating firing pin latch  43 , coupled together through matching engagement means. 
   The connection lever  42 , which has a variously shaped profile, has a perforated front end  44  and is hinged to the connection pin  24  in a lateral position with respect to the trigger  15 . In a central portion  45  the connection lever  42  extends next to the inner wall of the sear box  12  and in the rear part has an arm  46 , arranged in the middle plane  35  of the sear box  12  and extending downwards, carrying a U-shaped engagement element  47 . 
   The firing pin latch  43 , also operating in the middle plane  35  and fitted onto the pin of the hammer  31 , constitutes the engagement element with the pin of the hammer suitable for causing it to advance in the slot  32 . For such purpose the hammer  16  is equipped with a groove  48  in the middle plane to avoid movement interference. 
   The firing pin latch  43  consists of three tailpieces which extend downwards, upwards and backwards. 
   A tapered lower tailpiece  49  constitutes the engagement element matching the U-shaped engagement element  47  of the connection lever  42 . 
   An upper intervention tailpiece  50 , extending diagonally towards the front part of the sear box  12 , frees the firing pin  14  inside the breechblock  13  when it is pressed against a latch  51  of the firing pin  14 . Finally, the firing pin latch  43  is equipped with a rear tailpiece  52 , carrying a safety catch  53  in engagement in an opening  54  of the rear wall of the sear box  12 . 
   The sear mechanism  10  has an initial cocking position A ( FIG. 3 ), in which the trigger  15  is in rest position and the hammer  16  is held by the fixed sear tooth  41 , following the voluntary pulling of the trigger  15  in the direction of the arrow F, the trigger rotates with a pivot in its rotation pin  18 , causing the advance through translation of the first connection lever  42 . The connection lever  42  gives the firing pin latch  43  motion which is initially rotational and then translational. 
   Indeed, since the matching engagement means between the connection lever  42  and the firing pin latch  43  offset at the bottom with respect to the pin of the hammer  31 , the firing pin latch  43  is initially made to rotate about the pin of the hammer  31 . 
   The upper intervention tailpiece then goes into abutment against the latch  51  of the firing pin  14  and presses it releasing the motion of the firing pin  14  in the breechblock  13 . 
   When the sear mechanism  10  is in an unlocking position of the firing pin C, shown in  FIG. 5 , the further rotary motion of the firing pin latch  43  is prevented. The connection lever  42  then pulls the firing pin latch  43  into translational advancing motion which also involves the hammer  16 , the pin  31  of which advances in the slot  32 , which allows for translational movement of pin  31 . 
   The mounting tooth of the hammer  40  is then released from the fixed sear tooth  41  and, thrusted by the preloaded spring  33 , goes into the striking position B ( FIG. 6 ). 
   The motion of the hammer  16  between the cocking position A and the striking position B is therefore made up of an initial translation step and a subsequent rotary step under the action of said elastic thrust spring  33 . 
   The trigger  15 , released, returns into the starting position through the effect of the return spring  25 , which also resets the initial position of the sear device  17 . 
   The sear mechanism  10 , according to the proposed embodiment, when it is in cocking position A, is equipped with a safety device which prevents the firing of an accidental shot following hard knocks, such as those generated by the use of the firearm to knock down an obstacle, or in the case of the firearm itself being falling to the ground. 
   Indeed, the translational movement of the pin of the hammer  31  and of the hammer  16  itself to free the mounting tooth  40  from the fixed sear tooth  41  is prevented by the safety catch  53  of the firing pin latch  43 , which is in engagement in the opening  54  of the sear box  12 . 
   Only by pulling the trigger  15  is it possible to cause the rotation of the rear tailpiece  52  carrying the safety catch  53 , which releases it from the opening  54  of the sear box  12 , allowing the subsequent translational movement of the firing pin latch  43  and thus of the hammer  16 . 
   The sear mechanism for firearms which is subject of the present invention has the advantage of making possible the elimination of the sear connecting lever to hold the hammer in cocking position. 
   The fact that the hooking of the mounting tooth of the hammer to a fixed tooth of the sear box has been foreseen advantageously allows the hammer to be made from plastic, making the structure substantially lighter. Indeed, due to problems of wear of the interfacing contact surfaces, the hammer can be made from plastic only if the sear tooth is also made from plastic. 
   Moreover, the sear mechanism, object of the present invention, has a simplified structure, consisting of a low number of components, which advantageously allows a great cost-effectiveness of construction and simplicity of assembly to be obtained. 
   The firearm comprises a breechblock carrier  13  carrying a firing pin  14 , only partially represented in  FIGS. 3 to 6  and already known. 
   On the sear box  12  are mounted a trigger  15 , a hammer  16  and a sear device  17  which, when controlled by the trigger  15 , gives the hammer  16  motion between a cocking position A in engagement on the sear box  12  and a striking position B against the firing pin  14 . 
   The additional safety device of the invention provides a passive safety device that is activated by sudden acceleration or sudden impact loads on the firearm without any intervention of the user of the firearm. 
   When the firearm is subjected to sudden acceleration which results in an impact such as is caused by the dropping of a firearm on a hard surface, inertial forces may be generated which may cause the moveable parts to move and cause the disengagement of the firing pin latch  43  from the opening  54  of the sear box  12 . The hammer  16 , being held in place in this condition only by the elastic return element  25 , may be released and strike the firing pin which can cause an accidental firing. 
   As shown in  FIGS. 1 to 6 , the additional safety device of the sear mechanism, comprises an interposing element  60  housed in a seat  61  of the sear box  12  under the rear tailpiece  52  of the safety catch  53 . In a preferred embodiment, for example shown in  FIG. 1  and in the enlarged detail of  FIG. 2  the interposing element  60  is a sphere and the seat  61  comprises lateral containment walls  62  and  62 A which are arranged parallel to each other along the longitudinal axis of the firearm. The distance between the lateral walls  62  and  62 A is slightly greater than the sphere&#39;s diameter. The inclined plane elements  63  and  63 A are arranged between the lateral walls  62  facing each other and are inclined to converge towards one another at the bottom of the seat  61 . The inclined plane elements  63  and  63 A are spaced by a distance less than the sphere&#39;s diameter to form a seat  61  which is a constriction between the inclined plane elements  63  and  63 A having an open bottom as shown in  FIG. 4A .  FIG. 3A  shows sphere  60  in a forward position which sphere  60  would assume if translational movement were induced by sudden acceleration caused by dropping the firearm on its muzzle (not shown).  FIG. 4A  shows sphere  60  in a rearward position which sphere  60  would assume if translational movement were induced by sudden acceleration caused by dropping the firearm on its butt end (not shown).  FIG. 5A  shows sphere  60  in a neutral position which sphere  60  would assume when the firearm was held in a substantially level position (not shown).  FIG. 6A  shows sphere  60  in a neutral position which sphere  60  would assume when the firearm has just been fired as shown by the hammer  16  in contact with firing pin  14 . 
   The sphere  60  moves in response to sudden high impact forces (inertial forces) which also act on safety catch  53 . The inertial force causes sphere  60  to move along the inclined plane elements  63 ,  63 A into position under the rear tailpiece  52  of the safety catch  53  to prevent the safety catch  53  from moving downwardly under the influence of inertial forces. After the termination of the application of an inertial force, caused by sudden acceleration, only gravity acts on the sphere  60  which is free to move according to the orientation of the firearm. For example, the gravitational forces applied to sphere  60  by moving the firearm, e.g. from the horizontal position to a non-horizontal position cause the sphere  60  to move out of the neutral position under the tailpiece  52 . During normal firing, when the trigger activates the firing mechanism, the safety catch  53  is rotated and the rear tailpiece  52  shifts the sphere  60  downwardly towards the bottom of the seat  61 , i.e. in the neutral position where it does not interfere with the firing operation where it does not interfere with the firing operation. 
     FIG. 5A  shows the terminal edges  65  and  65 A of inclined plane  63  and  63 A as having a substantially flat profile that provides support points  66  and  66 A as shown in  FIG. 4A  that provide a stop for sphere  60 . 
   When inertial forces are directed either towards the front or towards the rear part of the firearm, the sphere slides or translates respectively over the front inclined plane element  63  or rear inclined plane element  63 A ( FIGS. 3 and 4 ) interposing itself between the rear tailpiece  52  of the safety catch  53  and the sear box  12 . Any downward movement of the firing pin latch  43  which could cause release of the hammer  16  is therefore prevented. 
   When the firearm is handled for firing, the sphere  60  is housed in an opening  64  on seat  61  ( FIGS. 5 and 6 ) and does not interfere with the downward movement of the firing pin latch  43 . Seat  61  is formed by the spaced opening defined by inclined planes  63  and  63 A. 
   While the preferred embodiment of the interposing element  60  is a sphere or ball of a material which may be metal or plastic, it is possible to use other spherically shaped elements which can exhibit translational or rotational movement in response to sudden acceleration caused by impact loading. These spherically shaped elements may comprise rounded objects of varying geometries that can be slidably mounted in opening  64  on the bottom of seat  61 . Further, cylinders or rollers as well as sliding wedges may be provided as interposing elements.