Patent Publication Number: US-2022228825-A1

Title: Firearm Having Reciprocable Breech Cover

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 16/924,537, filed Jul. 9, 2020, which application is based upon and claims benefit of priority to U.S. Provisional Application No. 62/885,837, filed Aug. 13, 2019, both applications being hereby incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to firearms and features for providing access to the breech end the firearm&#39;s barrel. 
     BACKGROUND 
     A bottom ejection type shotgun features a spring biased, forked elevator that functions to both chamber and eject shells. The forked elevator spreads during the termination of travel of the bolt during the feeding cycle. Cam surfaces on the bolt pass the end of the elevator. The spring bias of the elevator assures compliant contact with the width of the bolt after it has “snapped over” the cams surfaces. The cam surfaces contact the ends of the elevator during the aft travel of the bolt (the ejection cycle), lifting the elevator to the ejection position. 
     In bottom ejection type shotguns, once fed onto the elevator, a shell must complete the chambering and ejection cycle in order to be removed from the gun. However, if the shell is damaged (due to manufacturing issues or during shotgun operation), and the nature of the damage is such that chambering cannot be accomplished, the shell will not be able to be removed, rendering the shotgun inoperative. (If the shell is resting on top of the elevator, it cannot be pulled through the elevator). 
     There is clearly a need to provide access to the breech of bottom ejection shotguns to ensure that ammunition feed malfunctions can be cleared quickly without the need to disassemble the weapon. 
     SUMMARY 
     The invention concerns a firearm. An example firearm according to the invention comprises a receiver. A barrel is mounted on the receiver. The barrel has a breech end. A butt stock is movably mounted on the receiver adjacent to the breech end of the barrel. A cover is mounted on the butt stock. A portion of the cover extends toward the breech end of the barrel. The butt stock is movable between a closed position, wherein the portion of the cover is positioned in overlying relation to the breech end of the barrel, and an open position, wherein the portion of the cover is positioned in spaced relation away from the breech end of the barrel, thereby exposing the breech end. 
     An example embodiment further comprises a guide rail mounted on the receiver proximate to the breech end of the barrel. The guide rail projects from the receiver toward the butt stock. The butt stock is slidably mounted on the guide rail. The butt stock defines a cavity for receiving the guide rail in sliding relationship. A slot is positioned in the guide rail and extends lengthwise therealong. A pin is mounted on the butt stock and extends transversely to the guide rail. The pin extends through the slot for limiting sliding motion of the butt stock along the guide rail. 
     An example firearm according to the invention may further comprise a latch mounted on the butt stock. The latch has a hook movable between an engaged position engaged with the receiver and thereby preventing motion of the butt stock relatively thereto, and a disengaged position not engaged with the receiver and thereby permitting motion of the butt stock relatively thereto. By way of example the hook engages the receiver via engagement with the guide rail. In another example embodiment the latch comprises a rotation axis affixed to the butt stock. The rotation axis is oriented transversely to the guide rail. A first leg extends from the rotation axis. The hook is mounted on the first leg distal to the rotation axis. A second leg extends from the rotation axis. A spring acts between the butt stock and the second leg for biasing the hook into the engaged position. A button is movably mounted on the butt stock. The button comprises an action surface engageable with the second leg of the latch and a contact surface for manual manipulation of the button. A return spring acts between the button and the butt stock for biasing the contact surface away from the second leg. Further by way of example, the button is slidably movable relatively to the butt stock. 
     By way of example, the firearm according to the invention may comprise a shotgun having a bullpup configuration. An ammunition elevator may be mounted on the butt stock. 
     Another example firearm according to the invention may comprise a receiver. A barrel is mounted on the receiver. The barrel has a breech end. A butt stock is mounted on the receiver adjacent to the breech end of the barrel. A cover is mounted on the butt stock. A portion of the cover extends toward the breech end of the barrel. The cover is movable between a closed position wherein the portion of the cover is positioned in overlying relation to the breech end of the barrel, and an open position wherein the portion of the cover is positioned in spaced relation away from the breech end of the barrel, thereby exposing the breech end. 
     A further example of a firearm according to the invention comprises a guide rail mounted on the receiver proximate to the breech end of the barrel. The guide rail projects from the receiver toward the butt stock. The butt stock is slidably mounted on the guide rail. By way of example the butt stock defines a cavity for receiving the guide rail in sliding relationship. In this example a slot is positioned in the guide rail and extending lengthwise therealong. A pin is mounted on the butt stock and extending transversely to the guide rail. The pin extends through the slot for limiting sliding motion of the butt stock along the guide rail. An example embodiment may further comprise a latch mounted on the butt stock. The latch has a hook movable between an engaged position engaged with the receiver and thereby preventing motion of the butt stock relatively thereto, and a disengaged position not engaged with the receiver and thereby permitting motion of the butt stock relatively thereto. The hook engages the receiver via engagement with the guide rail in this example. 
     In an example embodiment the latch comprises a rotation axis affixed to the butt stock. The rotation axis is oriented transversely to the guide rail. A first leg extends from the rotation axis. The hook is mounted on the first leg distal to the rotation axis. A second leg extends from the rotation axis. A spring acts between the butt stock and the second leg for biasing the hook into the engaged position. Further by way of example, a button is movably mounted on the butt stock. The button comprises an action surface engageable with the second leg of the latch and a contact surface for manual manipulation of the button. A return spring acts between the button and the butt stock for biasing the contact surface away from the second leg. In an example embodiment the button is slidably movable relatively to the butt stock. 
     An example firearm according to the invention may comprise a shotgun having a bullpup configuration. Such an example may comprise an ammunition elevator mounted on the butt stock. 
     A further example firearm may comprise a hinge connecting the cover to the butt stock. The hinge defines an axis of rotation. The cover is rotatable about the axis between the closed position and the open position. An example may further comprise a spring acting between the butt stock and the cover for biasing the cover into the open opposition. A latch is mounted on the firearm. The latch engages the cover for holding the cover in the closed position. By way of example the latch is mounted on the receiver. In a further example the cover is slidably mounted on the butt stock. The cover is slidably movable relatively to the butt stock between the open and the closed positions. An example embodiment further comprises a cam track mounted on either the butt stock or the cover. The cam track extends in a direction defining sliding motion of the cover relatively to the butt stock. A cam follower is mounted on either the butt stock or the cover. The cam follower engages the cam track and guides the sliding motion of the cover between the open and the closed positions. 
     The invention also encompasses a method of clearing an ammunition feed malfunction of a firearm having a butt stock engaged with a receiver. A barrel is mounted on the receiver. The barrel has a breech end. In an example embodiment the method comprises:
         moving the butt stock out of engagement with the receiver thereby exposing the breech end of the barrel;   removing ammunition from the receiver proximate to the breech end of the barrel;   moving the butt stock back into engagement with the receiver.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of an example shotgun having a reciprocal breech cover according to the invention; 
         FIG. 2  is an exploded isometric view of the shotgun shown in  FIG. 1 ; 
         FIG. 3  is a partial cut-away view illustrating an ammunition feed malfunction in the shotgun shown in  FIG. 1 ; 
         FIG. 4  is a partial cut-away view illustrating an ammunition feed malfunction in the shotgun shown in  FIG. 1 ; 
         FIG. 4A  is a partial cut-away view of a portion of the shotgun shown in  FIG. 4  on an enlarged scale; 
         FIG. 5  is a partial cut-away view of the shotgun shown in  FIG. 1  with the breech cover in an open position; 
         FIG. 6  is an isometric view of another example embodiment of a shotgun according to the invention; and 
         FIG. 7  is an isometric view of another example embodiment of a shotgun according to the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a firearm, in this example, a self-defense shotgun  10  having a bullpup configuration. Example shotgun  10  comprises a receiver  12  which includes an upper receiver  14  and a lower receiver  16 . Lower receiver  16  houses the fire control group  18  including a trigger  20  and its associated mechanisms (not shown). As shown in  FIG. 2 , upper receiver  14  houses the firearm&#39;s action  22 , in this example a pump action, represented by the movable fore-end  24 , hammer  26  and breech bolt  28 . Also mounted on the upper receiver  14  are tubular ammunition magazines  30  and a barrel  32  beneath a barrel shroud  34  vented for cooling. Barrel  32  has a breech end  34  which is engaged by the breech bolt  28  as the shotgun is cycled out of and into battery when the fore-end  24  is moved toward and away from the breech end  34  as shown in  FIG. 4 . 
       FIGS. 1 and 2  also show a butt stock  36 , in this example embodiment, movably mounted on the receiver  12  adjacent to the breech end  34  of the barrel  32 . A cover  38  is mounted on the butt stock  36 . A portion  40  of the cover  38  extends toward the breech end  34  of the barrel  32 . As shown in a comparison of  FIGS. 4 and 5 , the butt stock  36  is movable between a closed position ( FIG. 4 ) wherein the portion  40  of cover  38  is positioned in overlying relation to the breech end  34  of the barrel  32 , and an open position ( FIG. 5 ) wherein the portion  40  of cover  38  is positioned in spaced relation away from the breech end  34  of the barrel  32 , thereby exposing the breech end. 
     As shown in  FIG. 2 , motion of the butt stock  36  is enabled by mounting it on a guide rail  42 . Guide rail  42  is mounted on the receiver  12  proximate to the breech end  34  of the barrel  32 . The guide rail  42  projects from the receiver  12  toward the butt stock  36 , and the butt stock is slidably mounted on the guide rail. The butt stock  36  defines a cavity  44  for receiving the guide rail  42  in sliding relationship. A slot  46  is positioned in the guide rail  42  and extends lengthwise along it. A retaining pin  48  is mounted on the butt stock and extends transversely to the guide rail  42 . Pin  48  extends through the slot  46  and limits sliding motion of the butt stock  36  along the guide rail  42 . The pin and slot combination also retains the butt stock  36  to the receiver  12 . As shown in  FIGS. 3 and 4 , the butt stock  36  is held in the closed position by a latch  50  mounted on the butt stock. In this example embodiment, the latch has a hook  52  movable between an engaged position ( FIG. 3 ) engaged with the receiver  12 , and a disengaged position ( FIG. 4 ) not engaged with the receiver. When hook  52  is in the engaged position, motion of the butt stock  36  relatively to the receiver is prevented, and when the hook is in the disengaged position, motion of the butt stock relatively to the receiver is permitted. In this example embodiment the hook  52  engages the receiver indirectly via engagement with an opening  54  in the guide rail  42 . 
     An example latch  50  is shown in detail in  FIG. 4A . The example latch comprises a rotation axis  56  defined by a pin  58  affixed to the butt stock  36 . The rotation axis  56  is oriented transversely to the guide rail  42 . A first leg  60  extends from the rotation axis  56 . The hook  52  is mounted on the first leg  60  distal to the rotation axis  56 . A second leg  62  also extends from the rotation axis  56 . A spring  64  acts between the butt stock  36  and the second leg  62  for biasing the hook  52  into the engaged position shown in  FIG. 3 . Latch  50  also comprises a button  66  movably mounted on the butt stock  36 . As shown in  FIG. 4A , button  66  comprises an action surface  68  engageable with the second leg  62 , and a contact surface  70 , for manual manipulation of the button. A return spring  72  acts between the button  66  and the butt stock  36  for biasing the contact surface  70  away from the second leg  62 . In this example embodiment the button  66  is slidably movable relatively to the butt stock  36 . 
     As shown in  FIG. 2 , an ammunition elevator  74  is also mounted on the butt stock  36 . In this example embodiment, the ammunition elevator  74  comprises a fork  76  which pivots about a pivot axis  78  oriented transversely to the guide rail  42 . The pivoting motion of fork  76  is controlled by the shotgun&#39;s action  22  and presents ammunition released from the magazines  30  to the breech end  34  of barrel  32  as described below. 
     If a bullpup shotgun is to be compatible with ambidextrous use then ejection of a spent shell is advantageously from the bottom of the firearm, as in the example shotgun  10 . However, a complication arises with bottom ejecting shotguns if there is an ammunition misfeed. The misfeeding shell is typically above the elevator and therefore is almost impossible to clear from the action, as the elevator blocks any such attempt. It would be advantageous to be able to easily remove a shell which does not chamber or does not chamber properly, and to that end the example shotgun  10  disclosed herein features the reciprocable cover  38  mounted on the butt stock  36 . 
     Operation of the reciprocable cover  38  is described with reference to  FIGS. 3, 4 and 5 . As shown in  FIG. 3 , the fore-end  24  has been pulled toward the breech end  34  of barrel  32 . This fore-end motion pivots the elevator fork  76  clockwise about its pivot axis  78  and also releases a shell  80  from the ammunition magazine  30  onto the pivoted fork. The user then attempts to chamber the shell  80  by pushing the fore-end  24  away from the breech end  34  and place the action back into battery. This fore-end motion will pivot the fork counterclockwise allowing the shell to be presented for chambering. However, shell  80  will not chamber, for example, because the hull of the shell is bulged due to an improper crimp. The fore-end  24  cannot be pushed away from the breech end  34  to force the action  22  back into battery, nor can the misfed shell  80  be ejected by cycling the fore-end again. However, the misfed shell  80  may be cleared by moving the butt stock  36  out of engagement with the receiver  12 , which also moves cover  38  and elevator  74 , and thereby exposes the breech end  34  of the barrel  32 . As shown in  FIGS. 4 and 4A , with the “weak hand” still on the fore-end  24 , the button  66  is depressed using the “strong hand” formerly holding the pistol grip  82 . Force applied to the contact surface  70  of the button  66  causes the action surface  68  to engage the second leg  62  of latch  50  and pivot it clockwise about rotation axis  56 . This also causes the first leg  60  to pivot about rotation axis  56  and thereby disengage hook  52  from opening  54  in the guide rail  42 . With the hook  52  disengaged, the butt stock  36  and, consequently, cover  38  and elevator  74 , are now free to move along guide rail  42 . As shown in  FIG. 5 , the strong hand pulls the butt stock  36  away from the receiver  12 , the motion of the butt stock being halted by engagement between the retaining pin  48  and the end of slot  46  in guide rail  42 . The butt stock  36  is thus moved from the closed position ( FIG. 4 ), wherein the cover portion  40  is in overlying relation to the breech end  34  of the barrel  32 , to the open position ( FIG. 5 ), wherein the portion  40  of cover  38  is positioned in spaced relation away from the breech end  34  of the barrel  32 . The breech end  34  is now exposed and accessible, allowing the misfed ammunition (shell  80 ) to be manually removed from the receiver  12  proximate to the breech end  34  of the barrel  32  using the strong hand. Once the shell  80  has been removed the butt stock  36  is moved back into engagement with the receiver  12  ( FIG. 3 ), the spring biased hook  52  again engaging opening  54  in guide rail  42  and securing the butt stock and cover  38  to the receiver  12 . 
       FIG. 6  shows another example embodiment of a firearm, again, a bullpup shotgun  84  according to the invention. Shotgun  84  comprises a hinge  86  connecting the cover  38  to the butt stock  36 . Hinge  86  defines an axis of rotation  88  about which the cover  38  rotates between the closed position and the open position (shown). It is advantageous to bias the cover  38  into the open opposition using a spring  90  acting between the butt stock and the cover. A latch  92 , mounted on the firearm  84 , engages the cover for holding the cover in the closed position. In this example embodiment the latch  92  is mounted on the receiver  12  and engages a tab  94  projecting from the cover  38 . 
     Another example firearm embodiment  96  is shown in  FIG. 7  wherein the cover  38  is slidably mounted on the butt stock  36 . The cover  38  is slidably movable relatively to the butt stock  36  between the open (shown) and the closed positions. In this example embodiment, a cam track  98  is mounted on either the butt stock  36  or the cover  38 . The cam track extends in a direction shown by arrow  100  which defines the sliding motion of the cover  38  relatively to the butt stock  36 . One or more cam followers  102  are also mounted on either the butt stock  36  or the cover  38 , the cam followers  102  engaging the cam track  98  which guides the sliding motion of the cover between the open and the closed positions. In this example the cam track  98  comprises a groove  104  recessed within the butt stock  36  and the cam followers comprise pins  106  mounted on the cover  38  and projecting into the groove  104 . It is advantageous to duplicate the cam track and cam follower arrangement on the opposite side of cover  38  to provide controlled motion of the cover  38  between the open and closed positions. 
     Shotguns having reciprocable breech covers according to the invention are expected to improve the operation and reliability of such weapons.