Abstract:
A magazine attachment/detachment mechanism ( 10 ) is equipped with; protrusions ( 11   a,    11   b ) extending downward from a receiver ( 2 ); and an attachment/detachment unit ( 12 ) that is movably attached to the protrusions ( 11   a,    11   b ) and that attaches a magazine ( 3 ) to the receiver ( 2 ) in a detachable manner. The attachment/detachment unit ( 12 ) attaches/detaches the magazine ( 3 ) to/from the receiver ( 2 ) by moving between a securing position that secures the magazine ( 3 ) and a release position that releases the magazine ( 3 ). Thus, the magazine ( 3 ) is attached directly to the receiver ( 2 ), so deviation from the design value for the attachment height of the magazine ( 3 ) with respect to the receiver ( 2 ) can be reduced. Accordingly, it is possible to prevent defects in the chambering of cartridges without reducing the strength of the receiver ( 2 ).

Description:
TECHNICAL FIELD 
     The present invention relates to a magazine look for attaching and detaching a magazine with respect to a firearm receiver. Further, the present invention relates to a portable firearm which is provided with such a magazine lock. 
     BACKGROUND ART 
     An automatic portable firearm is provided with a magazine in which a number of cartridges are held. The magazine is usually attached to the bottom side of the firearm receiver at the rear part of the barrel. It is desirable that the magazine can be attached and detached with respect to the portable firearm to quickly reload the cartridges. In this case, the portable firearm, as shown in PLT 1, is provided with a magazine lock. 
     CITATIONS LIST 
     Patent Literature 
     PLT 1: U.S. Pat. No. 5,899,013 
     SUMMARY OF INVENTION 
     Technical Problem 
     The cartridges in the magazine are biased upward by a spring and abut against the top part of the magazine. In a so-called “bolt action” system, a bolt is slid forward in the firearm receiver to push the cartridge at the topmost part of the magazine to the muzzle side whereby the cartridge is loaded into the chamber for firing. If the height of attachment of the magazine to the firearm receiver is low, the contact area of the bolt and cartridge becomes smaller, so the bolt cannot push the cartridge at the topmost part of the magazine and in turn the cartridge jams. 
     As the method of holding a large number of cartridges in a magazine, the system called the “double column-double feed” system is known. In the double column-double feed system, as shown in  FIG. 14 , two columns of cartridges are alternately stacked in the magazine in a partially overlapping state. The cartridges of the different columns are alternately fed from the magazine into the chamber. With this system, the dead space in the magazine can be made smaller, so the magazine can hold more cartridges. 
     However, with the double column-double feed system, the center of the bolt and the center of a cartridge are offset in the direction vertical to the stacking direction of the cartridges (left-right direction of  FIG. 14 ), so the contact area between the bolt and the cartridge becomes smaller. For this reason, a cartridge easily jams, so the allowable deviation of the height of attachment of the magazine to the firearm receiver from the design value is smaller. 
     Usually, at the time of assembly, the firearm receiver and a trigger guard are attached to the stock. In other words, the trigger guard is positioned with respect to the firearm receiver via the stock. In the magazine lock which is described in PLT 1, the magazine is attached to the trigger guard by a lever and pin which are arranged before and after the magazine. Therefore, the magazine is positioned with respect to the firearm receiver via the trigger guard and stock. For this reason, the height of attachment of the magazine to the firearm receiver can deviate from the design value by the amounts of tolerance of the parts of the stock and trigger guard. As explained above, if the height of attachment of the magazine with respect to the firearm receiver is low, a cartridge can jam. 
     If, to prevent jamming of a cartridge, strictly limiting the tolerances of the parts of the stock and trigger guard, the unit costs of the parts of the stock and trigger guard will increase. Further, if setting a threshold value of the height of attachment of the magazine to the firearm receiver and separating out defective products in the assembly process of the portable firearm, the man-hours required will increase and therefore the manufacturing costs will increase and the mass production effect will fall. 
     As another method for preventing jamming of a cartridge, it is known to provide a projection at the bottom part of the bolt so as to make the contact area of the bolt and the cartridge increase. In this case, it is necessary to provide a groove for the passage of the projection of the bolt at the inside surface of the firearm receiver. This causes the thickness of the firearm receiver to decrease and in turn causes a drop in the strength of the firearm receiver. The firearm receiver also has the role of receiving the recoil when a cartridge is fired. For this reason, if the strength of the firearm receiver is low, it is not possible to use high powered rounds like magnum rounds, so the types of cartridges which can be used become limited. Further, a special bolt at which the projection is provided and a special firearm receiver at which the groove is provided become necessary, so the firearm receiver and bolt and in turn the portable firearm become more expensive. 
     The present invention was made in consideration of the above situation and has as its object the provision of a magazine lock which decreases the deviation of the height of attachment of the magazine to the firearm receiver from the design value and thereby can prevent a cartridge from jamming without causing a decline in the strength of the firearm receiver. 
     Solution to Problem 
     In a first aspect of the present invention, there is provided a magazine lock which comprises projections which extend downward from a mesh firearm receiver and lock parts which are movably attached to the projections and attach and detach a magazine with respect the firearm receiver, wherein the lock parts move between a fastening position where they fasten the magazine and a release position where they release the magazine so as to attach and detach the magazine. Note that the firearm receiver side of the magazine lock is defined as the “top” side of the magazine lock, while the opposite side from the firearm receiver along the short direction of the bash firearm receiver is defined as the “bottom” side of the magazine lock. 
     In the first aspect of the present invention, preferably the magazine is a double column-double feed type of magazine. 
     In the first aspect of the present invention, preferably the lock parts include two engagement members which engage with the front side and rear side of the magazine. 
     Note that the muzzle side of the firearm receiver is defined as the “front” side of the magazine lock, while the opposite side from the muzzle along the longitudinal direction of the breech fire rm receiver is defined as the “rear” side of the magazine lock. 
     In the first aspect of the present invention, preferably the magazine lock further comprises a link mechanism which links the two engagement members, and the link mechanism makes the two engagement members simultaneously move between the fastening position and the release position. 
     In a second aspect of the present invention, there is provided a portable firearm which is provided with a magazine lock of the first aspect of the present invention. 
     In the second aspect of the present invention, preferably the portable firearm includes a trigger guard which is positioned with respect to the magazine lock via the stock and firearm receiver, and the trigger guard has an access hole which enables the lock part to be directly accessed from the bottom side of the trigger guard. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to provide a magazine lock which can reduce the deviation of the height of attachment of the magazine to the breech firearm receiver from the design value and thereby prevent a cartridge from jamming without lowering the strength of the firearm receiver, 
     Below, the present invention will be much more sufficiently understood from the description of the preferred embodiments of the present invention and the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a partial perspective view of a portable firearm which is provided with a magazine lock according to the present invention. 
         FIG. 2  is a partial front view of a portable firearm which is provided with a magazine lock according to the present invention. 
         FIG. 3  is a partial plan view of a portable firearm which is provided with a magazine lock according to the present invention. 
         FIG. 4  is a front view of a portable firearm according to the present invention. 
         FIG. 5  is a disassembled perspective view of part of a portable firearm according to the present invention. 
         FIG. 6  is a cross-sectional view along the line X-X of  FIG. 3 . 
         FIG. 7  is an enlarged view of a part A of  FIG. 6 . 
         FIG. 8  is an enlarged view of a part B of  FIG. 6 . 
         FIG. 9  is a disassembled perspective view of a magazine lock according to the present invention. 
         FIG. 10  is a perspective view which shows a rear side of a magazine. 
         FIG. 11  is a perspective view which shows a front side of a magazine. 
         FIG. 12  is a perspective view of a magazine in which cartridges are held. 
         FIG. 13  is a front view of a magazine in which cartridges are held. 
         FIG. 14  is a cross-sectional view along the line Y-Y of  FIG. 13 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Below, referring to the attached drawings, an embodiment of the present invention will be explained. Further, in the attached drawings, the same components are assigned the same reference notations. 
     First, referring to  FIG. 1  to  FIG. 5  and  FIG. 12  to  FIG. 14 , the mechanism by which a cartridge which is held in the magazine is loaded into the chamber for firing will be briefly explained. 
       FIG. 1  to  FIG. 3  are respectively a partial perspective view, a partial front view, and a partial plan view of a portable firearm  1  which is provided with a magazine lock  10  according to the present invention (see  FIG. 9 ).  FIG. 1  and  FIG. 2  show a firearm receiver  2 , a magazine  3  which is attached by the magazine lock  10  to the bottom side of the firearm receiver  2 , and a trigger guard  4  which is arranged so as to surround the bottom part of the magazine  3 . Details of the magazine lock  10  will be explained later. 
       FIG. 4  is a front view of a portable firearm  1  according to the present invention. In  FIG. 4 , as an example of the portable firearm  1 , a rifle  1  is shown. The firearm receiver  2  is arranged at the rear of the barrel  5 . The magazine  3  is attached to the bottom side of the firearm receiver  2  and is held inside a stock  6 . The trigger guard  4  is attached to the stock  6  and is positioned with respect to the magazine lock  10  via the stock  6  and firearm receiver  2 . Note that, as shown in  FIG. 2  and  FIG. 4 , in the Description, the muzzle  7  sides of the portable firearm  1  and firearm receiver  2  are defined as the “front” sides of the portable firearm  1  and magazine lock  10 , while the sides opposite to the muzzle  7  along the longitudinal direction of the portable firearm  1  and firearm receiver  2  are defined as the “rear” sides of the portable firearm  1  and magazine lock  10 . Further, the firearm receiver  2  sides of the portable firearm  1  and magazine lock  10  are defined as the “top” sides of the portable firearm  1  and magazine lock  10 , while the sides opposite to the firearm receiver  2  along the short direction of the portable firearm  1  and firearm receiver  2  are defined as the “bottom” sides of the portable firearm  1  and magazine lock  10 . 
       FIG. 5  is a disassembled perspective view of part of the portable firearm  1  according to the present invention. As shown in  FIG. 5 , the magazine  3  can be detached from the body of the portable firearm by the magazine lock  10 . By doing this, an empty magazine and another magazine in which cartridges are loaded can be switched, so a large number of cartridges can be quickly reloaded. 
       FIG. 12  and  FIG. 13  are respectively a perspective view and front view of a magazine  3  in which cartridges  8  are held.  FIG. 14  is a cross-sectional view along the line Y-Y of  FIG. 13 . The system of holding cartridges  8  which is shown in  FIG. 12  to  FIG. 14  is called a “double column-double feed” system. In the double column-double feed system, as shown in  FIG. 14 , two columns of cartridges  8  are alternately stacked in the magazine  3  in a partially overlapping state. The cartridges  8  of the different columns are alternately fed from the magazine  3  into the chamber. With this system, the dead space in the magazine  3  can be made smaller, so the magazine  3  can hold more cartridges  8 . 
     In a so-called “bolt action” system, a bolt  9  is slid forward in the firearm receiver  2  to push the cartridge  8  at the topmost part of the magazine  3  to the muzzle  7  side whereby the cartridge  8  is loaded into the chamber for firing. The shape of the bolt  9  is shown best in  FIG. 5 . A user can operate a handle  91  of the bolt  9  to make the bolt  9  move back and forth inside the firearm receiver  2 . When the bolt  9  is slid forward in the firearm receiver  2  and passes over the magazine  3 , as shown in  FIG. 14 , the bolt  9  and the cartridge  8  at the topmost part inside the magazine  3  come into contact, so the cartridge  8  at the topmost part is pushed by the bolt  9  and loaded from the magazine  3  to the chamber. After that, in the magazine  3 , a cartridge  8  of a different column from the cartridge  8  which was loaded is biased upward by a spring  31  which is set at the bottom part of the magazine  3  and abuts against the top part  32  of the magazine  3 . 
     After the cartridge is fired, the handle  91  is operated to make the bolt  9  retract whereby the spent round is ejected. If again sliding forward the bolt  9 , the other cartridge  8  at the topmost part in the magazine  3  is loaded into the chamber. In this way, by back and forth motion of the bolt  9 , it becomes possible to continuously fire rounds without hand loading a cartridge  8  into the magazine  3  each time. 
     Next, the magazine lock  10  according to the present invention will be explained in detail. 
       FIG. 6  is a cross-sectional view along the line X-X of  FIG. 3 .  FIG. 9  is a disassembled perspective view of the magazine lock  10 . As shown in  FIG. 6  and  FIG. 9 , the magazine lock  10  is provided with projections  11   a ,  11   b  which extend downward from the firearm receiver  2  and lock parts  12  which are movably attached to the projections  11   a  and  11   b  and attach and detach the magazine  3  with respect to the firearm receiver  2 . The lock parts  12 , as explained later, can move between a fastening position where they fasten the magazine  3  with respect to the firearm receiver  2  and a release position where they release the magazine  3 . Due to this, the magazine  3  can be attached and detached with respect to the firearm receiver  2 . The projections  11   a ,  11   b , as shown in  FIG. 1 , are fastened to the firearm receiver  2  by bolts  30  in this embodiment, but may also be formed integrally with the firearm receiver  2 . 
     In the present invention, the magazine  3  is directly fastened by the magazine lock  10  to the firearm receiver  2 . Due to this, in the present invention, the tolerance of the parts of the stock  6  and trigger guard  4  does not affect at all to the height of attachment of the magazine  3  with respect to the firearm receiver  2 . Therefore, it is possible to make the deviation of the height of attachment of the magazine  3  with respect to the  14  firearm receiver  2  from the design value decrease. For this reason, even if the magazine  3  is a double column-double feed system magazine, there is no need to provide a projection of the bolt  9  and a groove of the firearm receiver  2 . Therefore, it is possible to prevent a cartridge  8  from jamming without causing the strength of the firearm receiver  2  to decrease. Due to this, the portable firearm can use high powered rounds like magnum rounds as cartridges  8 . 
     The lock parts  12  include two engagement members  12   a ,  12   b  which respectively engage with a front side and rear &amp;de of the magazine  3 .  FIG. 10  and  FIG. 11  are respectively perspective views which show the rear side and front side of the magazine  3 . At the rear side of the magazine  3 , a hole  33  is provided for the rear side engagement member  12   b  to engage with, while at the front side of the magazine  3 , a projecting part  34  is provided for the front side engagement member  12   a  to engage with. As shown in  FIG. 6 , the two engagement members  12   a ,  12   b  respectively engage with the front side projecting part  34  and the rear side hole  33  of the magazine  3 , whereby the magazine  3  is fastened with respect to the firearm receiver  2 . By fastening the both sides of the front side and the rear side, compared with fastening one side of the front side or the rear side, the magazine  3  can be fastened more strongly with respect to the firearm receiver  2 . Due to this, after attachment of the magazine  3 , the magazine  3  is kept from descending from the firearm receiver  2  due to vibration etc. Note that, the engagement parts of the magazine  3  may both be holes or projecting parts or may be other shapes such as recesses. 
       FIG. 7  and  FIG. 8  are respectively enlarged views of the part A and part B of  FIG. 6 . In  FIG. 7  and  FIG. 8 , the engagement members  12   a ,  12   b  which have been made to move to a release position where they release the magazine  3  are shown by broken ones. As shown in  FIG. 7  and  FIG. 8 , the two engagement members  12   a ,  12   b  respectively move between the fastening position (solid lines) where they fasten the magazine  3  and the release position (broken lines) where they release the magazine  3  and thereby can attach and detach the magazine  3  with respect to the firearm receiver  2 . Note that the mode of movement of the engagement members  12   a ,  12   b  is not limited to rotational motion such as in the embodiment and may also be translational motion. 
     As shown in  FIG. 2  and  FIG. 9 , the magazine lock  10  is preferably further provided with a link mechanism  20  which links the two engagement members  12   a ,  12   b . The link mechanism  20  can, by the later explained configuration, make the two engagement members  12   a ,  12   b  simultaneously move between the fastening position and the release position. By doing this, it is possible to make only the one engagement member  12   a  move and thereby easily detach the magazine  3 . 
     Below, the link mechanism  20  will be explained in detail. 
     As shown in  FIG. 9 , the link mechanism  20  is provided with two elongated links  21   a ,  21   b  which link the two engagement members  12   a ,  12   b , two pins  22   a ,  22   b  which serve as rotation center axes for the engagement members, and two sets of connecting members  23   a ,  23   b  which connect the links  21   a ,  21   b  with the engagement members  12   a ,  12   b . The connecting members  23   a ,  23   b  are provided with guide bars  24   a ,  24   b  which extend inside the engagement members  12   a ,  12   b  and the projections  11   a ,  11   b , collars  25   a ,  25   b  which receive the guide bars  24   a ,  24   b  outside of the projections  11   a ,  11   b , and two snap rings  26   a ,  26   b  which fasten the two ends of the guide bars to the link. At the projections  11   a ,  11   b , holes  110   a ,  110   b  through which the pins  22   a ,  22   b  pass, long holes  111   a ,  111   b  through which the guide bars  24   a ,  24   b  pass and which limit the range of movement of the engagement members  12   a ,  12   b , and bolt holes  112   a ,  112   b  through which the bolts  30  pass are provided. The engagement members  12   a ,  12   b  are also provided with holes  120   a ,  120   b  through which the pins  22   a ,  22   b  pass and holes  121   a ,  121   b  through which the guide bars  24   a ,  24   b  pass. The front side pin  22   a  and guide bar  24   a  and the rear side pin  22   b  and guide bar  24   b  are arranged at the top and bottom facing each other. More specifically, at the front side, the pin  22   a  is arranged at the bottom side from the guide bar  24   a , while at the rear side, the pin  22   b  is arranged at the top side from the guide bar  24   b . Due to this configuration, as explained later, the front side engagement member  12   a  and the rear side engagement member  12   b  simultaneously rotate in opposite directions due to the link mechanism  20 . 
     The engagement members  12   a ,  12   b  are respectively attached to the projections  11   a ,  11   b  to be able to rotate about the pins  22   a ,  22   b . As shown in  FIG. 1 , the bottom part of the front side engagement member  12   a  can be accessed from the access hole  41  of the trigger guard  4 . For this reason, the front side engagement member  12   a  can be rotated by a finger from the bottom of the trigger guard  4 . 
     As shown in  FIG. 8 , if pushing down the front side engagement member  12   a , the front side engagement member  12   a  rotates together with the guide bar  24   a  clockwise about the pin  22   a , so disengages from the projecting part  34  of the magazine  3 . At this time, the links  21   a ,  21   b  which are fastened to the guide bar  24   a  move forward. Next, as shown in  FIG. 7 , the guide bar  24   b  which is fastened to the links  21   a ,  21   b  rotates together with the rear side engagement member  12   b  about the pin  22   b  counterclockwise. Due to this, the rear side engagement member  12   b  is disengaged from the hole  33  of the magazine  3 . Therefore, the link mechanism  20  can make the two engagement members  12   a ,  12   b  move simultaneously between the fastening position and the release position. Further, if, in the state with the palm of the hand placed below the magazine  3 , the finger of the same hand is used to push down the front side engagement member  12   a  through the access hole  41  of the trigger guard  4 , the detached magazine  3  can be received by the palm of the hand. Therefore, the link mechanism  20  can be used to quickly detach the magazine  3  by a single hand. 
     Next, the method of attaching another magazine in which cartridges have been loaded after the empty magazine is detached will be explained. A magazine  3  is pushed into the body of the portable firearm by the palm of the hand from below the trigger guard  4 . In that state, the front side engagement member  12   a  is pushed upward by a finger of the same hand through the access hole  41  of the trigger guard  4 . If doing this, the two engagement members  12   a ,  12   b  are rotated from the release position to the fastening position. At this time, the front side engagement member  12   a  and the rear side engagement member  12   b  respectively engage with the projecting part  34  and hole  33  of the magazine, so the magazine  3  is fastened with respect to the firearm receiver  2 . Therefore, the link mechanism  20  enables the magazine  3  to be quickly attached by a single hand. 
     The present invention has been explained based on a specific embodiment, but a person skilled in the art could make various changes, corrections, etc. without departing from the and concept of the present invention. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1 . portable firearm (rifle) 
               2 . firearm receiver 
               3 . magazine 
               31 . spring 
               32 . top part 
               33 . hole 
               34 . projecting part 
               4 . trigger guard 
               41 . access hole 
               5 . barrel 
               6 . stock 
               7 . muzzle 
               8 . cartridge 
               9 . belt 
               91 . handle 
               101 . magazine lock 
               11   a ,  11   b . projections 
               110   a ,  110   b . holes 
               111   a ,  111   b . long holes 
               112   a ,  112   b . bolt holes 
               12 . lock part 
               12   a ,  12   b . engagement members 
               120   a ,  120   b . holes 
               121   a ,  121   b . holes 
               20 . link mechanism 
               21   a ,  21   b . links 
               22   a ,  22   b . pins 
               23   a ,  23   b . connecting members 
               24   a ,  24   b . guide bars 
               25   a ,  25   b . collars 
               26   a ,  26   b . snap rings 
               30 . bolt