Patent Publication Number: US-8991088-B1

Title: Folding buttstock for firearms with recoil assemblies contained within the buttstock

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application Ser. No. 61/561,249 entitled “FOLDING BUTTSTOCK FOR FIREARMS WITH RECOIL ASSEMBLIES CONTAINED WITHIN THE BUTTSTOCK” filed on 17 Nov. 2011. 
    
    
     BACKGROUND OF THE INVENTION 
     Compactly storing a firearm is a challenge. This is especially the case for firearms such as M-16/AR-15/AR-10 types which have mechanisms that use direct gas impingement. Many M-16 type weapons have a direct gas impingement system, and could benefit from being able to fold the stock; however, suitable mechanisms permitting a folding stock in a direct gas impingement system have not been developed. 
     Folding stocks are known. US Patent Application No. 2010/0307042 shows a modular firearm stock system which includes a foldable butt stock assembly. U.S. Pat. No. 7,966,761 shows an automatic or semiautomatic rifle with a folding stock. Similarly, US Patent Application No. 2011/0131857 shows an automatic or semiautomatic rifle with a folding stock which is the same as in U.S. Pat. No. 7,966,761. U.S. D636,834 shows simply a folding firearm stock without internal details. US Patent Application No. 2010/0212206, and U.S. Pat. Nos. 7,827,721 and 7,673,412 show folding stock assemblies that do not accommodate any mechanisms. U.S. Pat. No. 7,418,797 shows another simple foldable rifle stock which has an added adjustable cheek pad. These foldable butt stock assemblies simply function as foldable stocks and do not accommodate any actuation. 
     Firearms which incorporate hinges are also known. U.S. Pat. No. 7,802,392 teaches tactical firearm systems, and methods of manufacturing same, which includes a modular locking hinge having two parts that attach modular components; however, the hinge does not appear to be used for a foldable stock. U.S. Pat. No. 6,591,533 shows a locking hinge used with a folding shoulder rest for a paintball gun which basically is analogous to a rifle stock for a handgun. 
     Direct gas impingement systems in M-16 type weapons bleed combustion gas from the barrel and convey it through a hollow tube back to the weapon&#39;s upper receiver. The gas from the tube pushes rearward on the bolt carrier assembly that rides within the upper receiver. The rearward push on the bolt carrier assembly, and attached bolt, cause the assembly to move rearward. The rear of the bolt carrier assembly bears against a recoil buffer and associated spring which are contained within the buffer tube, buttstock, or a receiver extension. When the bolt travels rearward, it compresses the buffer spring; it is this force combined with the weight of the buffer which slows, and then stops, the bolt carrier assembly&#39;s rearward movement. The direction of movement then reverses, and the carrier assembly travels forward again, back into battery. 
     SUMMARY OF THE INVENTION 
     The present invention is a folding buttstock for firearms with recoil assemblies contained within the buttstock or equivalent. The buffer and recoil spring are retained within a buffer tube of the buttstock so the stock can fold. The innovation provides a device that bisects the buffer tube by providing a hinge therebetween. In operation, the buffer and buffer spring may be retained within the buttstock when the buttstock is folded back. The bolt carrier is not physically attached to the buffer and recoil spring, but instead, the bolt carrier and buffer spring merely bear against each other. The present invention is described by way of a buttstock with a shoulder rest; however, weapons that only have a rearward extending buffer tube without the shoulder rest are included. 
     Folding stocks are desirable on firearms because they make them easier to store and transport. There are no folding stocks available for conventional M-16 style rifles and pistols which utilize direct gas impingement. The present design retains the buffer and spring within the folded stock, and makes it possible to have an M-16 style rifle with a folding stock. A folding stock assembly which contains the buffer and buffer spring within the folded portion of the stock for a firearm that uses a direct gas impingement system. 
     To actuate the bolt carrier assembly and related appurtenances, in this style of firearm, there is a recoil buffer (weighted cylinder) and spring which are contained within a buffer tube. The buffer tube forms part of such weapon&#39;s buttstock, and extends therefrom towards the muzzle end of the weapon. The buffer travels within the buffer tube in response to the recoil of the weapon upon firing. 
     A manually operated hinge release mechanism may be used to both allow hinge movement operation and to activate or actuate the system which retains the buffer within the butt stock. Additionally, these two operations could utilize separate controls whereby one controls the hinge opening/closing and the other controls the mechanism used to retain the buffer/spring within the buttstock. A manually operated mechanism is utilized to lock the buffer tube hinge closed, or straight, position so that the weapon may be operated. Further, retainer devices may be utilized to hold the buffer tube in an open, or folded, position. 
     These and other aspects of the present invention will become readily apparent upon further review of the following drawings and specification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features of the described embodiments are specifically set forth in the appended claims; however, embodiments relating to the structure and process of making the present invention, may best be understood with reference to the following description and accompanying drawings. 
         FIG. 1A  shows a side view of an alternative embodiment of the current design with the buffer retained in the buttstock buffer tube. 
         FIG. 1B  shows a side view of an alternative embodiment of the current design with the buffer free to move into the forward buffer tube. 
         FIG. 1C  shows a side view of folding buttstock according to alternative embodiment of the current design. 
         FIG. 1D  shows a front view of the retainer mechanism in position to retain the buttstock buffer tube. 
         FIG. 1E  shows a front view of the retainer mechanism in position to permit the buffer and spring to move into the forward buffer tube. 
         FIG. 2  is a top view of the embodiment shown in  FIGS. 1A and 1B , which demonstrates the hinged attachment. 
         FIG. 3A  shows a partially exploded side view of an alternative embodiment of the current design with the buffer retained in the buttstock buffer tube. 
         FIG. 3B  show side views of an alternative embodiment of the current design with the buffer and buffer spring unrestrained. 
         FIG. 4A  shows a side view of the prior art weapon having a buttstock with the buffer and buffer spring forward. 
         FIG. 4B  shows a side view of the prior art weapon having a buttstock with the buffer and buffer spring backwards into the buttstock. 
         FIG. 5A  shows a side view of an alternative embodiment of the current design with the buffer retained in the buttstock buffer tube. 
         FIG. 5B  shows a side view of an alternative embodiment of the current design with the buffer and buffer spring unrestrained. 
         FIG. 6A  shows a side view of an alternative embodiment of the current design with the buffer retained in the buttstock buffer tube. 
         FIG. 6B  shows a side view of an alternative embodiment of the current design with the buffer and buffer spring unrestrained. 
         FIG. 7A  shows an alternative design of a retainer mechanism using a pivot pin in which the buffer is retained in the buttstock buffer tube. 
         FIG. 7B  show an alternative design of retainer mechanism using a pivot pin in which the buffer and buffer spring are unrestrained. 
         FIG. 8  shows an alternative design of retainer mechanism using v-spring in which the buffer is retained in the buttstock buffer tube. 
         FIG. 9A through 9F  show alternative designs of mechanism used to mate the collars to the buffer tubes. 
         FIGS. 10A through 10G  show alternative hinge and closure mechanisms according to alternative embodiments of the present design. 
         FIG. 11A  shows an elevated environmental side view of a folded buttstock disposed on a weapon according to an alternative embodiment of the present design. 
         FIG. 11B  shows an elevated environmental rear view of a folded buttstock disposed on a weapon according to an alternative embodiment of the present design. 
         FIGS. 11C and 11D  show details of the retainer mechanism  26  in the embodiments of  FIGS. 11A and 11B . 
     
    
    
     Similar reference characters denote corresponding features consistently throughout the attached drawings. 
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     A folding stock assembly  12  contains a buffer tube folding mechanism  24 , an embodiment of which is shown in  FIGS. 1A ,  1 B and  1 C, with a buffer  14  and a buffer spring  16  disposed within a buffer tube  28  within the folded portion of the stock  18  for a firearm  20  that uses a direct gas impingement system. A buffer tube folding mechanism  24  is provided which has first and second collars  30  and  32 , hingedly attached to one another, with openings therethrough. A buffer retainer  26  is shown if  FIGS. 1D and 1E  to retain the buffer  14  therein.  FIG. 1A  in greater detail shows, a buffer tube  28  of a buttstock  18  is attached to the rear hinge block, which is the first collar  30 . The buffer retainer  26 , shown in  FIGS. 1A ,  1 B,  1 D, and  1 E, has a plunger  36  is contained in the collar  30  just below the opening therethrough, and the plunger  36  is pushed upward by plunger spring  38  when the collars  30  and  32  are not closed. The plunger  36  protrudes into opening of the collar  30  and prevents the buffer  14  and spring  16  from falling out. 
     When the collars  30  and  32  are closed for use as shown in  FIG. 1B , the retainer actuator  40  engages plunger  36  and pushes it downward due to the angled opening  42  in the plunger  36 . Actuator  40  may have a roller tip or other means of reducing friction (not shown) when it contacts plunger  36 . Plunger  36  may also have bearings where it is engaged by actuator  40 . Additionally, the plunger  36  may have bearings on its exterior to reduce the friction when it moved up/down within its opening. The opening  42  through which plunger  36  moves may also have bearings. 
     The first collar  30  is shown in  FIGS. 1A and 1B  as threading into a first receiver  44 . A modified standard lock ring  48  is shown with a hole threaded through  50  to accept a screw (not shown for clarity) which will prevent the first collar  30  from rotating. There are many other possible methods for preventing the collars  30  and  32  from rotating. 
       FIG. 1C  shows that the first collar  30  may have a standard buffer tube  28  of buttstock  18  installed using the conventional lock ring  48  with a castle nut  52 . Other methods would also work and these elements have generally been omitted from the other figures for the sake of clarity. Additionally, the first collar  30  may be connected to the lower receiver  54  in several different ways. The second collar  32  may contain an integral threaded tube which would screw into the lower receiver in the same manner as a standard buffer tube  28  or it may utilize a separate threaded tube which would thread into both the lower receiver  54  and the second collar  32 . If necessary to help the threads index such that the second collar  32  aligns properly with the lower receiver  54 , then a spacer or spacers of variable thickness could be used in place of or to augment a lock ring  56 . 
       FIG. 2  is essentially a top view of the elements shown in  FIGS. 1A and 1B , except that it also shows a hinge  22 . The elements are shown in both their folded and unfolded positions. A weapon  20  has a folding stock assembly  12  with a buffer  14  and a buffer spring  16  retainable within the folded buttstock  18 . The buttstock  18  folds laterally on hinges  22 , as demonstrated in  FIG. 2 , connected on the side thereof. 
     The innovative design described in this application retains the buffer  14  and recoil spring  16  within the folded buttstock  18  in the first collar  30  on the buffer tube  28  of the buttstock  18 . There are alternative ways to retain the buffer  14  and recoil spring  16  within a folded buttstock  18 , each blocking the opening at the first collar  30  retaining the buffer  14 .  FIGS. 3A and 3B  show an alternative retainer mechanism  26  that is biased upwards to block the motion of the buffer  14 . The retainer mechanism  26  is actuated by closing the collars  30  and  32  whereupon the retainer  26  is withdrawn permitting unhindered movement of the buffer  14  and spring  16 .  FIG. 3A  shows a different arrangement to actuate the plunger  36  which utilizes a connecting rod  58  and a bellcrank  60 . When the stock  18  is folded to the side, the bellcrank spring  38  moves within the recess shown, and pushes the connecting rod  58  and plunger  36  upward. This retains buffer  14  and spring  16  within the buffer tube  28  of the buttstock  16 .  FIG. 3B  shows that when the stock is unfolded to the rear, the actuator  40  presses on the bellcrank  60  which causes it to pivot as shown. This puts tension on connecting rod  58  and pulls plunger  36  downward, thereby allowing the buffer  14  and buffer spring  16  to move unhindered to bear against the bolt carrier assembly (not shown). 
     Note that all the previous figures show a protrusion from the plunger  36  at the six o&#39;clock position into the buffer tube  28  of the buttstock  18  which retains the buffer  14  and spring  16  when the stock  18  is folded. Note that there is a recess in the conventional bolt carrier assembly  34  which allows the bolt carrier assembly  34  to pass over the protrusion and into the buffer tube  28  of the buttstock  18 . The buffer  14  does not have such a recess and therefore cannot pass over the buffer retainer  26 . 
     Conventional wisdom had deemed it impossible for known M-16 style weapons which are shown in  FIGS. 4A and 4B  to have a folding buttstock  18 . The various embodiments of the present design work because the bolt carrier  34  is not physically attached to the buffer  14  and recoil spring  16 . Instead, the bolt carrier  34  and buffer spring  16  merely bear against each other. When the weapon  20  discharges and the bolt carrier mechanism  34  is actuated, it is pushed partially into the buffer tube  28  of the buttstock  18  thereby forcing the buffer  14  rearward and compressing the buffer spring  16 . After the spring  16  stops the rearward motion of the buffer  14  and bolt carrier assembly  34 , it forces them forward and reloads the weapon  20 . 
     The design of the present invention system is applicable to other weapons beyond the M-16 family of firearms, and is not limited to those style weapons. Indeed, any weapon which contains part of its operating mechanism within the buttstock could potentially benefit from the present design. When the stock  18  is folded, the bolt carrier  34  may still travel rearward and protrude from the weapon  20 , but is prevented from falling out by the charging handle and lower receiver. 
     The same methods which are used to retain the buffer  14  and spring  16  assembly within the buttstock  18  are adapted to retain the bolt carrier  34  deeper within the weapon&#39;s receiver and prevent much of its rearward movement. This may be accomplished automatically upon folding/unfolding the stock  18  or with some assistance from the user. Another approach to retaining the bolt carrier  34  assembly deeper within the receiver is to pull the trigger after the stock is folded open after ensuring that the weapon is unloaded. This would allow the hammer to pivot forward and retain the bolt carrier assembly  34  completely forward within the upper receiver. 
     Yet another approach to retaining the bolt carrier assembly  34  deeper within the receiver is a simple plug made from plastic, rubber or a similar material. It could be easily inserted by the user and removed before the stock is unfolded. A variation of this would be two plugs which could be joined together by a string, rubber band, or similar material. One would fit into the receiver as described above and the other would fit into the first collar  30  in folded buttstock  18 . These would also serve to keep dirt and other contaminants out of the operating mechanisms. 
     In operation, the user retracts the charging handle to move the carrier and buffer rearward while compressing the buffer spring  16 . Once the buffer  14  has been moved rearward so that it is within the first collar  30 , also called the rear hinge block  30  in the examples, the hinge  22  would be opened and the retainer  26  would rise to retain the buffer  14  within the buttstock  18 . The stock  18  is then completely folded and the user gives a slight push forward to the bolt carrier assembly  34 . Alternatively, the user could push the built-in forward assist on the upper receiver, as is well known. 
     Unfolding the stock  18  simply entails the user closing the hinge  22 . The internal workings of the design can be timed to retract the retainer mechanism  26  and release the buffer  14  and spring  16  assembly to move forward once the buttstock  18  was adequately closed. Alternately, the retainer mechanism  26  for the buffer  14  and spring  16  could be made to require a specific manual input from the user other than simply closing the stock  18 . 
     The stock shown in the drawings folds to the left side, but the design is applicable to all directions including the right (ejection port) side, over the top, or under toward the magazine. A lower receiver which incorporates the elements necessary to allow an integral folding stock mechanism may also be used. The design would allow the use of existing AR-15 stocks or buffer tubes, but other designs could be created. The hinge blocks and mechanism could cause a slight increase in the distance between the rear of the bolt carrier assembly when it is battery and the inside rear of the buttstock or buffer tube. This would create less pre-load on the buffer spring and could affect the weapon&#39;s functionality. To offset this distance, a spacer could be added to the rear of the buffer spring. Alternately, the spacer could be located on the buffer itself. A longer buffer spring or one with a modified spring rate could also be created to perform the same function, as could a modified buffer. A shorter butt stock or buffer tube would serve the same purpose. The design could incorporate a safety mechanism that would prevent the weapon from discharging if the stock is folded 
       FIGS. 5A through 5B  show an embodiment of a hinge and retainer mechanism according to an alternative embodiment of the current design.  FIGS. 5A  and  5 B show another embodiment which utilizes an arm  60  which rotates forward and rearward. When the stock  18  is folded to the side as in  FIG. 2 , the arm  60  is held in the forward position by a torsion spring  62 . A compression spring similar to  38  in  FIGS. 1A ,  1 B,  1 D,  1 E,  3 A, and  3 B could also be used. When the stock  18  is unfolded to the rear, the actuator  40  rotates arm  60  rearward and releases the buffer  14  and spring  16 . 
       FIGS. 5A and 5B  also show a different folding mechanism  24 . In this configuration, the second collar  32  overlaps the first collar  30  when the stock  18  is unfolded. This may add rigidity to the system and may also keep foreign material out of the system. This configuration could be applied to the other embodiments as well. 
       FIGS. 6A through 6C  show an embodiment of a hinge and retainer mechanism according to an alternative embodiment of the current design. This embodiment utilizes an arm  64  which rotates forward and rearward. When the stock  18  is folded as in  FIG. 2 , the arm  64  is held in the forward position by a torsion spring  66  which must be strong enough to overcome the forward force exerted by the buffer spring  16 . A compression spring  38  similar as used elsewhere could also be used instead of the torsion spring  66  and other spring types may also work satisfactorily, as is well known. When the stock  18  is unfolded to the rear as in  FIG. 6B , the actuator  40  rotates arm  64  rearward and releases the buffer  14 . 
       FIGS. 7A and 7B  shows an alternative design of retainer mechanism  26  using a v-spring  68  with a tip  72  attached thereto, although a flat spring or leaf spring would suffice. When the stock  18  is folded to the side, the v-spring  68  expands and its tip protrudes into the first collar  30  of the buffer tube  28  which retains the buffer  14  and spring  16 . When the stock  18  is unfolded for use, the actuator  40  on the second collar  32  compresses the spring. The v-spring  68  must be strong enough to overcome the forward force exerted by the buffer spring  16 . 
     Pivot pins, torsion springs, leaf springs, tension springs, and compression springs are also usable according to various embodiments of the present design, and all are designated by the numeral  68  hereafter.  FIG. 8  shows an alternative design of retainer mechanism using a pivot pin.  FIG. 8  shows an embodiment that utilizes a v-spring  68  with a tip  72  which protrudes into the first collar  30  adjacent the buffer tube  28  when the stock  18  is folded. When the stock  18  is unfolded to the rear, the v-spring  68  is compressed by the opening and notch  70  in the second collar  32  which lowers the tip  72  and releases the buffer  14  and spring  16 . A roller or ball bearing  74  as well as other types of bearings may be used to reduce the friction between the v-spring  68  and the notched opening  70 . Additionally, the v-spring  68  may be depressed by an actuator  40  protruding from the first collar  30 , as shown in  FIGS. 7A and 7B , instead of an opening and notch  70  within the second collar  32 . When the stock  18  is unfolded for use, the opening  70  on the second collar  32  is configured to pinch the spring  68  which retracts the tip  72  from within the first collar  30  adjacent the buffer tube  28  allowing the buffer  14  and spring  16  to move forward to meet the carrier  34 . 
       FIGS. 9A through 9F  show an alternative design of a collar  31  (either the first collar  30  or the second collar  32 ) to mate with the adjacent parts of the buffer tube  28  to form a single buffer tube  28  with the folding mechanism  24  when unfolded. When the stock  18  is folded, the collet release ring  80  is not in contact with the collet fingers  82 . The collet fingers  82  which are attached to a collet ring  84  are springy and their normal state is contracted such that they protrude into the open interior diameter of the buffer tube  28 . This effectively reduces the diameter and prevents the buffer/spring (not shown) from moving forward and exiting the first collar  30 . When the buttstock  18  is unfolded, the collet release ring  80  puts pressure on the collet fingers  82  and flexes them outward, away from the inner diameter of the buffer tube  28 . This increases the effective diameter and allows the buffer and spring assembly (not shown) to move forward. Note that four collet fingers  82  are shown, but more or fewer could also be used. Additionally, the collet fingers  82  could have tips  84  which would protrude and create a shoulder which would offer more positive retention of the buffer/spring. 
     Closer details of the hinge and retainer mechanisms are depicted throughout for reference only; numerous alternative designs of hinges are well known.  FIGS. 10A through 10E  show a hinge mechanism  22  for a folding buffer tube  28  according to alternative embodiments of the present design. The mechanism  22  may be adapted to accommodate either a folding buttstock  18  which retains part of the firearm&#39;s operating system within the buttstock  18 , or it may accommodate a folding buttstock  18  that does not retain any of the firearm&#39;s  20  operating system within the buttstock  18 . 
       FIGS. 10A through 10C  show the device with the buttstock  18  locked into the folded position by the outboard detent ball  90 . The plunger rod  92  is spring  94  loaded and has cutouts  96  with ramps that apply upward force to the detent balls  98  until the plunger rod  92  is depressed, at which time it slides toward the hinge  22  exposing the detent balls  98  to cutouts  96  within the plunger rod  92 . At this point, the collars  30  and  32  can be rotated about the hinge  22  to fold or unfold the buffer tube  28 . When the unit has been rotated 90 degrees +/− about the hinge  22 , and the plunger rod  92  is released by the user, the detent balls  98  will be pushed upward by the plunger rod  92  and into cutouts  100  within the first collar  30 . Releasing pressure from the plunger rod  92  will cause it to be forced outward by the plunger return spring  94  which will again push the detent balls upward into the cutouts  100  in the first collar  30 . Note that the unit could be structured such that the detent balls are contained within the second collar  32  instead of the first collar  30 . 
     When the plunger rod  92  is depressed, the plunger return spring  94  becomes compressed into a recess within the plunger rod  92 . The plunger rod  92  slides linearly within the first collar  30  inside a cutout partially depicted for clarity as  102 . An alternative version of the plunger rod  92  which could be used, and operates as follows: wherein the rod is still circular, but only has the recesses for the detent balls on top. It may have a folding lever that protruded from the end. When the lever is rotated, it would rotate the plunger rod and either cam the detent balls upward or release them. If desired, this may be linked to the apparatus which retains buffer  14  within the buttstock  18 . 
     The cutouts  96  within the plunger rod  92  could surround the around the entire circumference of the plunger rod  92 , as shown in  FIGS. 10F and 10G . The hinge pin  22  penetrates an opening in the plunger rod  92  which is large enough so the hinge pin  22  does not interfere with the movement of the plunger rod  92 . Instead of individual cutouts  100  within the first collar  30 , a single v-shaped cut could be created along the length of the first collar&#39;s  30  hinge block  106  in  FIG. 10B . The opening  104  would accommodate movement of the bolt carrier group through the first and second collars  30  and  32 , and into the buffer tube  28  if used on an M-16/AR-15 type weapon system. 
       FIGS. 10D through 10E  show the unit with the stock unfolded to the rear. In  FIG. 10D , the detent balls  98  are shown being pushed upward into the first collar  30  by the plunger rod  92  which locks the first and second collars  30  and  32  together. In  FIG. 10E , the detent balls  98  are shown as being located downward, inside the second collar  32  as if the plunger rod  92  is being depressed. This would free the collars ( 30  and  32 ) to rotate about the hinge. 
       FIGS. 11A and 11B  show an environmental view of an example folding stock assembly  12 , and a weapon  20  having a folding stock assembly  12  in a folded position.  FIGS. 11C and 11D  show the operation of the retainer mechanism  26  used in the example of  FIGS. 11A and 11B .  FIG. 11C  shows the retainer mechanism  26  is position to retain the buffer  14  and spring  16 . 
     It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.