Patent Publication Number: US-10330407-B2

Title: Bolt stop buffer device in gun

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a 371 application of the International PCT application serial no. PCT/JP2015/079289, filed on Oct. 16, 2015. The entirety of each of the above-mentioned patent applications is hereby incorporated by reference herein and made a part of this specification. 
     TECHNICAL FIELD 
     The present invention relates to a bolt stop buffer device in a gun including a bolt member which is disposed in a gun body so as to be movable forward and rearward, which moves rearward in response to gas pressure generated by bullet shooting so as to compress a bolt spring, and which moves forward in response to release of the compressed pressure so as to perform bullet loading, and a bolt stop which stops forward movement of the bolt member. 
     BACKGROUND ART 
     The bolt stop is disposed in many guns having a bolt which compresses a spring (simply, referred to as the bolt spring in this document) acting on the bolt in response to a gun operation, and which moves forward in response to the released pressure. An automatic loading firearm which is so-called assault rifle includes this mechanism. In this type of gun, the bolt moves forward so as to load a bullet. After last bullet shooting, the bolt stops by colliding with the bolt stop in order to notify a user that the bullets are all shot. This operation of collision and stop is repeatedly performed every time the bullets are all shot. 
     Therefore, every time the bolt collides with the bolt stop, a strong impact is applied to the bolt stop. Consequently, metal fatigue is likely to occur, thereby causing damage to the bolt stop in the worst case. In a case of a real gun, this problem has been pointed out for a long time. However, at the present time, no idea can be found about what kind of remedial measures has to be planned. That is, it is not possible to find a recognizable gun in which damage prevention measures are planned for the bolt stop. 
     Even if the related art is examined, an intended result cannot be obtained. For example, through a text search site of the Japanese Patent Office, only 3 search results are obtained by using the bolt stop as a keyword. One of the results relates to an internal combustion engine, and the other two results are also irrelevant to an aspect of the bolt stop which is an object of the present invention. Japanese Unexamined Patent Application Publication No. 2010-025501 discloses an invention of a mechanical power supply stop device in an electric gun according to an application of the present applicant, and the bolt stop is referred to in the description. However, the disclosed electric gun imitates a real gun as a component. In fact, the disclosed electric gun only has a reset function. The other remaining one result in PCT Japanese Translation Patent Publication No. 2000-508051 discloses an invention relating to a bolt firing pin locking device of a firearm. In the description with reference to  FIG. 2 , there is a phrase such as “a bolt  14  can move rearward as far as a slight distance until a stop wall  25 W comes into contact with a bolt stop surface  31   f ”, and a phrase such as “the bolt  14  is pressed against a bullet C by a large reaction spring (not illustrated) linked to the bolt  14  via a circular column  35 ” is described at the end of the sentence. However, these phrases in the description indicate that the impact applied to the bolt stop by the bolt is not an issue. 
     Furthermore, after US Patent Publications are examined by using the bolt stop as the keyword through a site of the US Patent and Trademark Office, approximately 10 results are obtained. Among these results, two inventions relating to the bolt stop of the firearm are found. In the two inventions, US2010/0275485A1 discloses an invention relating to the bolt stop employing a both-handed type so that the bolt stop can be used for a left-handed person, similarly to a right-handed person. In addition, US2005/0183310A1 discloses an invention in which a magazine is attached and detached in association with the bolt stop. Both of these do not disclose that the impact of the bolt is regarded as a problem. 
     CITATION LIST 
     Patent Literature 
     [PTL 1] Japanese Unexamined Patent Application Publication No. 2010-025501 
     [PTL 2] PCT Japanese Translation Patent Publication No. 2000-508051 
     [PTL 3] US2010/0275485A1 
     [PTL 4] US2005/0183310A1 
     SUMMARY OF INVENTION 
     Technical Problem 
     The present invention is made in view of the above-described circumstances, and an object thereof is to provide a bolt stop buffer device in a gun which is unlikely to be damaged and which ensures improved durability by buffering impacts of a bolt member, even if the impacts are repeatedly applied to a bolt stop. In addition, another object of the present invention is to detect that bullets are completely shot, to disengage the bolt stop from the bolt member when a magazine is replaced and reloaded, and to detect bullet absence in response to the disengagement. According to the present invention, while a function to replace and reload the magazine is maintained, it is possible to absorb the impacts applied by forward movement of the bolt member. 
     Solution to Problem 
     According to the present invention, in order to solve the above-described problem, there is provided a gun including a bolt member that is disposed in a gun body so as to be movable forward and rearward, that moves rearward in response to gas pressure generated by bullet shooting so as to compress a bolt spring, and that moves forward in response to release of the compressed pressure so as to perform a bullet loading operation, and a bolt stop that stops forward movement of the bolt member. The bolt stop has engagement means for engaging with the bolt member which moves forward to reach the engagement means after last bullet shooting, and includes buffer means for buffering an impact force applied to the bolt stop due to the engagement so as to act on the bolt stop. 
     A target of the gun to which a bolt stop buffer device according to the present invention is applied is a gun which uses gas generated using explosive combustion caused by bullet shooting as a pressure source. A main purpose of the bolt member is as follows. The bolt member moves rearward in response to gas pressure. At that time, the bolt member performs a discharge operation for removing a cartridge from a bullet loading chamber, and a bullet loading operation for a bullet into the bullet loading chamber. More specifically, as an example, the bullet loading operation includes an operation for closing a gun chamber by converting forward movement of the bolt into rotational movement. In addition, the bolt stop holds the bolt member to stay at a rearward movement position, thereby notifying a user that a magazine is emptied. Accordingly, the user can quickly reload the magazine. 
     The bolt stop according to the present invention has a function to stop the bolt member which moves forward to reach the bolt stop after last bullet shooting. That is, the bolt stop has engagement means for engaging with the bolt member which moves forward to reach the engagement means after the last bullet shooting, and includes buffer means for buffering an impact force applied to the bolt stop due to the engagement so as to act on the bolt stop. In this case, as a minimum configuration requirement, the bolt stop includes the engagement means for engaging with the bolt member, and the buffer means acts on the bolt stop. If this requirement is satisfied, the present invention is established. Therefore, as a matter of course, other requirements can be added to the present invention. The bolt member moves rearward in response to the gas pressure generated by bullet shooting so as to compress the bolt spring, and moves forward in response to the release of the compressed pressure so as to perform a bullet loading operation. The bolt member causes the impact to be buffered. 
     In addition, the present invention preferably adopts the following configuration. The gun body has bullet absence detection means for detecting the presence or absence of a bullet to be supplied to a bullet loading unit in response to a gun operation. The bullet absence detection means detects bullet absence. In this manner, the bullet absence detection means includes a link mechanism which enables the engagement means to engage with the bolt member by causing the bolt stop configuring a bolt stop mechanism to protrude into a track when the bolt member moves forward and rearward. 
     The bolt stop may include the bolt stop mechanism that receives an impact of the bolt member which moves forward to reach the bolt stop mechanism and transmit the impact to the buffer means, between the bolt member and the buffer means. It is desirable that the buffer means includes an elastic member that is elastically deformed by the transmitted impact. According to this configuration, the elastic member is disposed in a rear stage of the bolt stop mechanism. However, the buffer means has only to act on the bolt stop. Accordingly, the above-described form is consistently applied to a case of using the bolt stop mechanism. 
     In addition, it is desirable to adopt a configuration as follows. The bolt stop configuring the bolt stop mechanism has a long hole in a forward-rearward direction where a shaft disposed on the gun body side is located, and is disposed so as to be movable in a range of the long hole and rotatable around the shaft. In addition, it is preferable to adopt the following configuration. The engagement means includes an engagement portion disposed in the bolt member and an engagement pair portion disposed in the bolt stop, and is disposed so as to configure an acute angle in a forward movement direction of the bolt member. According to this configuration, reliable engagement is expected. However, in a case where the above-described configuration of the acute angle is not appropriate, there is room for adopting a configuration of a right angle or an obtuse angle. 
     This type of gun includes a so-called gun dedicated to single shooting and a switching gun for repeated shooting and single shooting. However, the present invention is applicable to any one of both of these. In a case of the switching gun for repeated shooting and single shooting, if shooting is repeatedly performed, bullets decrease fast, and the magazine is frequently replaced. The frequency of impacts received by the bolt stop increases. Therefore, impact buffering according to the present invention is more effectively used. 
     Advantageous Effects of Invention 
     The present invention is configured and operated as described above. Accordingly, the impact of the bolt member which is applied to the bolt stop can be absorbed and buffered by the buffer means, and the bolt member can resist the repeated impacts. Accordingly, it is possible to provide the bolt stop buffer device in the gun which is unlikely to be damaged and which ensures improved durability. In addition, according to the present invention, the bolt stop member is disengaged from the bolt member when the magazine is replaced and reloaded after detecting that bullets are completely shot. In this manner, while a function to detect the bullet absence and to replace and reload the magazine is maintained, it is possible to absorb the impact applied by forward movement of the bolt member. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a longitudinal sectional view for describing an example of an assault rifle to which a bolt stop buffer device is applied in a gun according to the present invention. 
         FIG. 2A  and  FIG. 2B  are enlarged views illustrating a main portion of the device,  FIG. 2A  is a longitudinal sectional view for describing the main portion, and  FIG. 2B  is a sectional view taken along line IIB-IIB in  FIG. 2A . 
         FIG. 3A  and  FIG. 3B  relate to an operation of the device,  FIG. 3A  is a longitudinal sectional view for describing a state before last bullet shooting, and  FIG. 3B  is a longitudinal sectional view for describing a state where a bolt member intermediately moves rearward after the last bullet shooting. 
         FIG. 4A  and  FIG. 4B  also relate to an operation of the device,  FIG. 4A  is a sectional view for describing a state where the bolt member moves rearward to the maximum, and  FIG. 4B  is a sectional view for describing a state where the bolt member starts to move forward. 
         FIG. 5A  and  FIG. 5B  relate to an operation of the device,  FIG. 5A  is a sectional view for describing a state indicating a forward movement position of a bolt stop member, and  FIG. 5B  is a sectional view for describing a state where the bolt stop member is move rearward in a range of a long hole by a buffer spring. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, the present invention will be described in more detail with reference an illustrated embodiment. A bolt stop buffer device in a gun according to the present invention is applicable to various guns having a bolt stop which stops a bolt member. The illustrated embodiment relates to an assault rifle, and includes configurations which are indispensable for detailed description of the present invention. 
     A gun G illustrated in  FIG. 1  includes a shooting device  10  for shooting a bullet in a gun body, and includes a barrel portion  11  disposed in a front portion of the shooting device  10 , a movable body portion  21  for a blowback bolt carrier  15  which is disposed in a rear portion of the shooting device  10 , and a magazine loading unit  26  disposed in a lower portion of the shooting device  10 , respectively. A rear portion of the barrel portion  11  has a bullet loading chamber  12  in which a cartridge C having a bullet (warhead) B is loaded, and a front portion of the barrel portion  11  has an outlet  13  for removing gas generated by bullet shooting from the inside of the barrel. The bullet in a case where bullet loading is referred means a so-called ball cartridge (live cartridge) which is integrated with the cartridge C before shooting. 
     One end side of a gas tube  14  disposed outside the barrel is connected to the above-described outlet  13 , and the other end side of the gas tube  14  extends rearward to reach the inside of the gun body. The gas tube  14  is disposed so as to be connectable to and detachable from a front end portion of a bolt carrier key  16  which is movable forward and rearward integrally with a bolt carrier  15 . As described above, the bolt carrier  15  is disposed on the gun body side so as to be movable forward and rearward. The bolt carrier  15  moves rearward in response to gas pressure generated by bullet shooting so as to compress a bolt spring  24 , and moves forward in response to release of the compressed pressure so as to perform a bullet loading operation. 
     The bolt carrier  15  has a longitudinally elongated and substantially rod-shaped form, and a bolt  20  is disposed in a shaft core portion of the rod-shaped form so as to be movable forward and rearward. The bolt carrier key  16  communicates via a duct  17  with a cylindrical bore  18  in which the bolt  20  moves forward and rearward. Gas generated by the bullet shooting is guided rearward of a piston-shaped pressure receiving portion  19  of the bolt  20  which slides inside the bore  18 . A firing pin (firing pin, refer to  FIG. 2A  and  FIG. 2B )  20   a  which hits a blasting cap of the cartridge C is incorporated in the shaft core portion of the bolt  20  so as to be movable forward and rearward. In the present embodiment, the bolt carrier  15  having the bolt  20  incorporated therein is called a bolt member. A structure of the bolt employs various types other than the illustrated structure. The present invention is applicable to any type of the gun, as long as the bolt moves rearward in response to the gas pressure generated by the bullet shooting so as to compress the bolt spring and moves forward in response to the release of the compressed pressure so as to perform the bullet loading operation. 
     A movable body portion  21  is disposed in the rear of the bolt carrier  15 , and the movable body portion  21  has a casing  22  attached to the gun body and a movable shaft  23  disposed therein. The movable shaft  23  is disposed inside the casing  22  so as to be movable forward and rearward, and is configured to be connected to a rear end of the bolt carrier  15  in a shaft head  23   a . In the drawing, the reference numeral  24  represents a bolt spring, and the bolt spring  24  biases the movable shaft  23  in a forward movement direction, thereby finally bringing the bolt carrier  15  in a shooting preparation state. In addition, the bolt spring  24  functions as means for relaxing recoil shock by receiving the bolt carrier  15  during a rearward movement operation. 
     A trigger mechanism to be included in the gun according to the present invention is common to that of the assault rifle, and the operation is also the same as the general operation. Accordingly, a schematic configuration will be described below, and detailed description will be no longer continued. That is, a configuration is adopted as follows. The reference numeral  25  represents a trigger for the operation. Through the operation, a locked state of a hammer (not illustrated) is released, thereby hitting the above-described firing pin (firing pin)  20   a . According to this configuration, the blasting cap of the bullet loaded in the bullet loading chamber  12  is hit, thereby leading to the bullet shooting. 
     A magazine  30  is located in a lower portion of the shooting device  10 . The magazine  30  is detachably attached to the magazine loading unit  26  disposed in the lower portion of the gun body. The ball cartridge is supported by a follower  27  incorporated therein, and is pressed up to an empty space  29  (refer to  FIG. 4A  and  FIG. 4B ) in the rear of the bullet loading chamber illustrated in  FIG. 4A  and  FIG. 4B  and subsequent drawing by the follower spring  28 . 
     The bolt stop buffer device in the gun according to the present invention is illustrated in detail as an embodiment in  FIG. 2A  and  FIG. 2B . The bolt stop buffer device according to the embodiment has a configuration including the bolt carrier  15  which is compressed by the gun operation so as to move forward in response to the release of the bolt spring  24 , and the bolt stop  31  which stops the above-described forward moving bolt carrier  15 . Particularly, the embodiment has a configuration in which the operation of the bullet absence detection means  33  causes the bolt stop  31  to protrude into a track X in which the bolt carrier  15  moves forward and rearward. The configuration is adopted so that the impact applied when the bolt carrier  15  moving forward and the bolt stop  31  collide with each other is absorbed using the buffer means  40 . 
     The above-described follower  27  fulfills a role of detecting that the last bullet B is shot. That is, the follower  27  is installed inside the magazine  30 , and rises as the follower spring  28  compressed by the bullet (ball cartridge) is stretched by a resilient force thereof. The follower  27  hits the lower side of the bolt carrier  15 , and stops. Thereafter, if the bullet B is shot and the bolt carrier  15  moves rearward, the follower  27  rises. The follower  27  engages with a relay member  32  connected to the bolt stop  31  in a rear end portion  27   a . Therefore, the follower  27  and the relay member  32  configure the bullet absence detection means  33 . 
     A rear end portion  27   a  of the follower  27  engages with and presses up one end portion  32   a  in the relay member  32  with the bolt stop  31 , and causes the bolt stop  31  to protrude into the track X in which the bolt carrier  15  moves forward and rearward. The follower  27  and the relay member  32  configure a link mechanism for allowing the bullet absence detection means  33  and the bolt stop  31  to communicate with each other. 
     The above-described relay member  32  engages with the bolt stop  31  configuring a bolt stop mechanism  35 . That is, the other end portion  32   b  of the relay member  32  engages with the bolt stop  31  in a groove-shaped engagement portion  31   a . Therefore, if bullet absence is detected by the bullet absence detection means  33 , bullet absence information indicating that the bullets B to be loaded in the bullet loading chamber  12  are all shot is sequentially transmitted to the bolt stop  31  by the bullet absence detection means  33 . 
     Referring to  FIG. 2B , the relay member  32  is illustrated as a member extending to the left and right of the gun body. The relay member  32  is pivotally supported in the gun body by a shaft  32   c  disposed on the left side of the gun body, and is disposed so that a right side portion (crank-shaped portion in  FIG. 2A  and  FIG. 2B ) is movable upward and downward by the rotation around the shaft. In addition, the relay member  32  has an operation unit  32   d  appearing on the left side of the gun body in the upper portion of the shaft  32   c . A spring  32   e  is operated in the lower portion thereof, thereby causing the relay member  32  to return to a fixed position. In this manner, the bolt stop  31  (to be described later) is pressed down. 
     A long hole  31   b  is formed in a forward-rearward direction of the bolt stop  31 , and the bolt stop  31  is pivotally supported on the gun body side by the shaft  34  so as to be capable of oscillating. Therefore, the bolt stop  31  is movable as much as a stroke amount inside the long hole  31   b , and is rotatable around the shaft  34 . As a result of this configuration, the link mechanism causes the engagement pair portion  31   c  side of the bolt stop  31  to rise via the relay member  32 , and enables the bolt stop  31  to protrude into the track X in which the bolt carrier  15  moves forward and rearward. 
     The bolt carrier  15  is disposed in the engagement portion  15   a  as one engagement means  36 , and this engagement portion  15   a  is configured so as to be capable of engaging with an engagement pair portion  31   c  disposed in the above-described bolt stop  31  as the other engagement means  36  (refer to  FIG. 4A  and  FIG. 4B ). In particular, the engagement portion  15   a  and the engagement pair portion  31   c  according to the embodiment are disposed to serve as inclined portions configuring an acute angle in the forward movement direction of the bolt carrier  15 . In a configuration in which the bolt stop  31  is pivotally supported by the shaft  34  in the long hole  31   b  in the forward-rearward direction, the inclination of the engagement portion  15   a  and the engagement pair portion  31   c  can eliminate unstable engagement which may occur in a case where the engagement portion  15   a  and the engagement pair portion  31   c  is set to form a right angle. Forming the engagement means  36  to have the acute angle in the forward movement direction is merely one means in this embodiment. If the conditions for the engagement between the bolt carrier  15  and the bolt stop  31 , for example, mass, speed, and a material of the members involved in the engagement are different from each other, a form of using a right angle or an obtuse angle may be selected within a conceivable range. 
     The buffer means  40  acts on the bolt stop  31 . The buffer means  40  according to the embodiment has a buffer link  37 , a buffer shaft  39  incorporated in the buffer link  37  so as to be movable to an attachment portion  38  on the gun body side in the forward-rearward direction, and a buffer spring  41  which pressurizes the buffer shaft  39  forward. The above-described buffer link  37  is pivotally supported on the gun body side by the shaft  37   b  so as to be capable of oscillating. One end engages with a front engagement portion  31   d  of the bolt stop  31 , and the other end engages with the tip of the buffer shaft  39 . Accordingly, at the time of the collision caused by the forward movement of the bolt carrier  15 , the impact applied by the bolt stop  31  moving in a gunpoint direction is transmitted to and absorbed by the buffer means  40 . 
     The relay member  32  and the bolt stop  31  are arrayed side by side in a direction from the gunpoint toward the gunstock. Accordingly, when moving forward, the bolt carrier  15  collides with the bolt stop  31  of the bolt stop mechanism  35 . However, the relay member  32  has a structure which does not come into contact with the bolt carrier  15 , and has a structure which comes into contact with the bolt stop  31  even if the bolt stop  31  moves to the maximum. Accordingly, the relay member  32  does not come into direct contact with the relay member  32 . The bolt stop  31  engages with the shaft  34  in the long hole  31   b . Accordingly, the bolt stop  31  is movable in the maximum length range of the long hole  31   b . When the bolt stop  31  moves to the maximum, the other end portion  32   b  of the relay member  32  is brought into a state of further entering a groove portion  31   a  of the bolt stop  31 . 
     With regard to the bolt stop buffer device in the gun according to the present invention configured in this way,  FIG. 3A  illustrates a state before the last bullet (ball cartridge) is finally shot in the bullet loading unit  12 . If the bullet B is shot by operating a trigger  25 , the barrel is fully filled with gas generated by the bullet shooting, and the pressure flows from the gas tube  14  into the bore  18  of the bolt carrier  15 . The bolt carrier  15  is moved rearward, thereby performing a so-called discharge operation in which the bolt spring  24  is compressed and the cartridge C is pulled out from the bullet loading chamber  12  ( FIG. 3B ). 
     If there is no more bullet (ball cartridge) in the magazine  30 , the bolt carrier  15  moves rearward to the maximum rearward movement position ( FIG. 4A ). In the magazine  30 , the resilient force the follower spring  28  causes the follower  27  to be pressed up to the empty space  29  near the rear portion of the bullet loading unit  12 , and the follower  27  reaches the highest position. As the follower  27  rises, a pressing-up force acts on the relay member  32  engaging with the rear end portion  27   a  of the follower  27  in one end portion  32   a.    
     The relay member  32  engages with the bolt stop  31  in the other end portion  32   b  and the groove portion  31   a . If the rising of the follower  27  is transmitted, the bolt stop  31  is rotated around the shaft  34 , and is rotated counterclockwise in  FIG. 4A . As a result, the engagement pair portion  31   c  located in the upper portion of the bolt stop  31  protrudes into the track X. 
     After the bolt carrier  15  moves rearward to the maximum rearward movement position, the bolt carrier  15  is caused to move forward by a released accumulation force of the bolt spring  24 . The engagement portion  15   a  disposed as one engagement means  36  in the bolt carrier  15  engages with the engagement pair portion  31   c  disposed in the above-described bolt stop  31  as the other engagement means  36  ( FIG. 4B ). 
     If the bolt carrier  15  further moves forward, the bolt stop  31  is carried forward by the engagement means  36 . Accordingly, the position of the shaft  34  is changed so as to relatively move from the front end to the rear end of the long hole  31   b  ( FIG. 5A ). While the bolt stop  31  moves as described above, the bolt stop  31  presses the buffer link  37  engaging with the front engagement portion  31   d  against one end portion, and the other end portion presses the tip portion of the buffer shaft  39  engaging therewith against the elastic force of the buffer spring  41 . Therefore, the impact applied by the bolt stop  31  moving in the gunpoint direction is absorbed by the buffer means  40  during the collision caused by the forward movement of the bolt carrier  15 , and the bolt carrier  15  is gently stopped. 
     Subsequently, the bolt stop  31  is pressed rearward by the elastic force of the buffer spring  41 , and the bolt carrier  15  also moves rearward to the position in  FIG. 4B , thereby completing the operation of the buffer device ( FIG. 5B ). Furthermore, a magazine attachment/detachment device is operated so as to replace the magazine. The operation unit  32   d  of the relay member  32  is pressed or the bolt carrier  15  is moved rearward using a charging handle (not illustrated). In this manner, the front portion of the bolt stop  31  is lowered, and the engagement means  36  is disengaged. As a result, the bullet (ball cartridge) is reloaded, and the gun chamber is brought into a closed state. 
     In the bolt stop buffer device in the gun according to the present invention, the bolt stop  31  which stops the bolt carrier  15  is indirectly buffered by the buffer means  40 , and the damage is prevented. In this manner, the gun can be protected so that sudden malfunction does not occur. In addition, the device according to the present invention maintains a function to detect the bullet absence indicating that the bullets B are all shot, and to replace and reload the magazine. 
     The operation of the bolt stop buffer device according to the present invention is performed as described above. Even in a case of general guns such as the assault rifle, the bullet is reloaded by replacing the magazine, and the bolt carrier  15  is operated by operating a handle (not illustrated). In this manner, the bullet is loaded, and the gun chamber is closed. Accordingly, there is no difference between the general guns and the gun to which the device according to the present invention is applied. Therefore, the device according to the present invention can be incorporated into the existing guns, and thus, it is possible to buffer the impact of the bolt when the gun is operated.