Patent Publication Number: US-11022386-B2

Title: Firearm breech cover interlock

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims benefit of priority to U.S. Provisional Application No. 62/886,997, filed Aug. 15, 2019, which application is hereby incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to interlock mechanisms to prevent discharge of firearms. 
     BACKGROUND 
     Reciprocable covers overlying the breech of a breach loaded weapon are useful to allow ammunition feeding malfunctions to be cleared by providing access to the breech and parts of the weapon&#39;s action by simply moving the cover to expose the breech and action. When using a reciprocable cover overlying the action of a breech loading firearm such as a shotgun, it is prudent to provide a means preventing firing of the shotgun when the cover is in an open position exposing the action. When the fire control group of the firearm is remote from the cover, as is the case for a “bullpup” configuration, fire control disconnection is impractical. For a firearm such as a bullpup shotgun, it would be advantageous to provide a mechanical interlock which prevents the action from returning to battery (thus preventing discharge of the shotgun) while the cover remains in an open position. 
     SUMMARY 
     The invention concerns an interlock for coordinating motion of a breech cover assembly relatively to a breech of a firearm with a position of a fore end of the firearm. The breech cover assembly is movable between a first position overlying the breech and a second position not overlying the breech. The fore end is movable between a first position placing the firearm in battery and a second position placing the firearm out of battery. In an example embodiment the interlock comprises a latch mountable on the breech cover assembly. The latch is movable with the assembly relatively to the breech. An action bar has first and second ends oppositely disposed. The action bar defines a longitudinal axis between the ends. The action bar is movably mountable on the firearm. The first end of the action bar is attachable to the fore end and the second end comprises a catch. The catch is engageable with the latch when the fore end and the breech cover assembly are each in the first positions respectively. Engagement between the catch and the latch prevents motion of the breech cover assembly into the second position while the firearm is in battery. Motion of the fore end into the second position disengages the catch and the latch from one another thereby permitting motion of the breech cover assembly into the second position not overlying the breech when the firearm is out of battery. 
     By way of example, the latch is pivotably mountable on the breech cover assembly. In a specific example the latch may further comprise a spring biasing the latch into engagement with the catch. In an example embodiment the latch comprises a first hook and the action bar comprises a second hook positioned proximate to the second end of the action bar. The first hook is engageable with the second hook. Further by way of example the first hook comprises a first engagement surface oriented angularly with respect to the longitudinal axis and the second hook comprises a second engagement surface oriented angularly with respect to the longitudinal axis. The first engagement surface contacts the second engagement surface when the hook engages the catch. The first engagement surface has a first orientation angle and the second engagement surface has a second orientation angle. In an example embodiment the first and second orientation angles are complementary to one another. 
     By way of further example the action bar may comprise a ramp surface positioned proximate to the catch. The ramp surface engages the latch upon relative motion between the action bar and the latch. 
     The invention also encompasses a firearm. In an example embodiment the firearm comprises a receiver. A barrel is mounted on the receiver. The barrel has a breech. An action is positioned within the receiver. A fore end is mounted on the receiver and is movable between a first position placing the action in battery and a second position placing the action out of battery. A breech cover assembly is mounted on the receiver. The breech cover assembly is movable between a first position overlying the breech and a second position not overlying the breech. 
     An interlock coordinates motion of the breech cover assembly relatively to the breech with a position of the fore end. In an example embodiment the interlock comprises a latch mounted on the breech cover assembly and movable therewith relatively to the breech. An action bar has first and second ends oppositely disposed. The action bar defines a longitudinal axis between its ends. The action bar is movably mounted on the firearm. The first end of the action bar is attached to the fore end and the second end comprises a catch. The catch is engageable with the latch when the fore end and the breech cover assembly are each in the first positions respectively. Engagement between the catch and the latch prevents motion of the breech cover assembly into the second position while the firearm is in battery. Motion of the fore end into the second position disengages the catch and the latch from one another thereby permitting motion of the breech cover assembly into the second position not overlying the breech when the firearm is out of battery. 
     In an example embodiment the latch is pivotably mounted on the breech cover assembly. Further by way of example, a spring bias the latch into engagement with the catch. In an example embodiment the latch comprises a first hook and the action bar comprises a second hook positioned proximate to the second end of the action bar. The first hook is engageable with the second hook. By way of further example the first hook comprises a first engagement surface oriented angularly with respect to the longitudinal axis and the second hook comprises a second engagement surface oriented angularly with respect to the longitudinal axis. The first engagement surface contacts the second engagement surface when the hook engages the catch. 
     By way of example the first engagement surface has a first orientation angle and the second engagement surface has a second orientation angle. The first and second orientation angles may be complementary to one another in an example embodiment. Further by way of example the action bar may further comprise a ramp surface positioned proximate to the catch. The ramp surface engages the latch upon relative motion between the action bar and the latch. 
     In an example embodiment the breech cover assembly comprises a buttstock mounted on the receiver. The buttstock is movable toward and away from the breech. The latch is mounted on the buttstock. A cover is also mounted on the buttstock. In an example embodiment the latch is pivotably mounted on the buttstock. In a further example a spring acts between the buttstock and the latch for biasing the latch into engagement with the catch. 
     An example firearm according to the invention may comprise a shotgun. Further by way of example, the shotgun may have a bullpup configuration. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of an example firearm having an example breech cover interlock according to the invention; 
         FIG. 2  is a partial sectional side view of the firearm shown in  FIG. 1  with the firearm&#39;s action in battery; 
         FIG. 2A  is a partial sectional side view of a portion of the firearm shown in  FIG. 2  on an enlarged scale; 
         FIG. 3  is a partial sectional side view of the firearm shown in  FIG. 1  with the firearm&#39;s action out of battery; 
         FIG. 3A  is a partial sectional side view of a portion of the firearm shown in  FIG. 2  on an enlarged scale; 
         FIG. 4  is a partial sectional side view of the firearm shown in  FIG. 1  having a breech cover in an open position; 
         FIG. 4A  is a partial sectional side view of a portion of the firearm shown in  FIG. 4 ; 
         FIG. 5  is a partial sectional side view of the firearm shown in  FIG. 1  illustrating closing of a breech cover; 
         FIG. 5A  is a partial sectional side view of a portion of the firearm shown in  FIG. 5  on an enlarged scale; 
         FIG. 6  is a partial sectional side view of the firearm shown in  FIG. 1  illustrating manipulation of a breech cover for take down of the firearm; 
         FIGS. 6A, 6B and 6C  are sectional side views of a portion of the firearm shown in  FIG. 6  on an enlarged scale. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows an example embodiment of a firearm according to the invention, in this example a shotgun  10 . Shotgun  10  comprises a receiver  12  which houses the firearm&#39;s action  14 . As is well understood, action  14  includes the various mechanisms such as the bolt, ammunition feed cut-offs, and the ammunition elevator (not shown) which receive a round of ammunition from a magazine, chamber the round in a barrel, lock the bolt with the barrel breech, fire the round, extract and eject the spent cartridge during the firing cycle of such breech loading weapons. Receiver  12  also houses the fire control group  16  which comprises components such as the sear, trigger, hammer, and firing pin (not shown) which cooperate with the action  14  to fire the round. Shotgun  10  has a “bullpup” configuration in which the action  14  is located behind the fire control group  16 . A barrel  18  is mounted on the receiver  12 . Barrel  18  has a muzzle end  20  and a breech  22 . Two tubular ammunition magazines  24  (right magazine shown) are mounted below the barrel  18  side by side. A fore end  26  is mounted on receiver  12  beneath the magazines  24  and the barrel  18 . The fore end  26  engages the action  14  and is manually movable between a first position (shown) which places the action  14  “in battery” (bolt locked with the breech, ready to fire) and a second position “out of battery” (bolt unlocked, breech open, see  FIG. 3 ) to work the action  14  during operation of the firearm as is well understood for pump action shotguns. A breech cover assembly  28  is also mounted on the receiver  12 . In this example embodiment the breech cover assembly  28  comprises a butt stock  30  on which a cover  32  is mounted. Breech cover assembly  28  is movable between a first position in which the cover  32  overlies the breech  22  (shown) and a second position wherein the cover does not overlie the breech (see  FIG. 4 ). 
       FIGS. 2 and 2A  shows an example breech cover interlock  34  for coordinating motion of the breech cover assembly  28  relatively to the breech  22  with the position of the fore end  26 . In this example the interlock comprises a latch  36  mounted on the breech cover assembly  28  and movable therewith relatively to the breech  22 . Interlock  34  further comprises an action bar  38  having a first end  40  which is attached to the fore end  26 . A second end  42  of the action bar is oppositely disposed from the first end and comprises a catch  44 . Action bar  38  defines a longitudinal axis  46  between its ends  40  and  42 . The action bar  38  is movably mounted on the firearm and moves along a longitudinal axis  46  defined between its first and second ends  40  and  42 . Latch  36  is advantageously pivotably mounted on the buttstock  30  via a pivot pin  48  to permit breakdown of the shotgun  10  as described below. A spring  50  acts between the buttstock  30  and the latch  36  for biasing the latch into engagement with the catch  44 . 
     As shown in  FIG. 2A , the latch  36  of the example embodiment comprises a first hook  52  and the action bar  38  comprises a second hook  54  positioned proximate to its second end  42 . The first and second hooks  52  and  54  are engageable with one another. Engagement between the hooks is advantageously effected by contact between a first engagement surface  56  on the first hook  52  and a second engagement surface  58  on the second hook  54 . To provide positive mechanical engagement between the hooks  52  and  54  the engagement surfaces  56  and  58  are oriented angularly with respect to the longitudinal axis  46  of the action bar  38 . In the example embodiment the first engagement surface  56  has a first orientation angle  60  and the second engagement surface has a second orientation angle  62 . The first and second orientation angles  60  and  62  are advantageously complementary to one another to permit reliable engagement and disengagement of the latch  36  and the catch  44 . Practical orientation angles  60  and  62  may range from about 45° to about 60° although other values of the orientation angles are of course feasible. Action bar  38  may further comprise a ramp surface  64  positioned proximate to the catch  44 . Ramp surface  64  engages the latch  36  upon relative motion between the action bar  38  and the latch, and the spring  50  maintains the latch in contact with the action bar during cycling of the shotgun&#39;s action, as shown by a comparison of  FIGS. 2 and 3 . In  FIG. 2  the action  14  is in battery, in  FIG. 3  the action is out of battery as indicated by the positions of the fore end  26  in each Figure. In  FIG. 2  (in battery) the hooks  52  and  54  are engaged and any motion of cover  32  is prevented; in  FIG. 3  (out of battery) the hooks are not engaged and the spring  50  maintains the hook  52  in contact with the action bar  38  as shown in  FIG. 3A  so that when the action is returned to battery ( FIG. 2 ) during cycling of the action the hooks  52  and  54  reliably engage one another. 
     In operation, as shown starting with  FIG. 2 , the breech cover interlock  34  maintains the breech cover assembly  28  in the first position, with cover  32  overlying the breech  22  of barrel  18  when the fore end  26  is in its first position, fully forward toward the muzzle end  20  of barrel  18 . With the fore end  26  fully forward, action  14  is locked in battery and the shotgun  10  is ready to fire if a live round is chambered within the barrel  18 . Motion of the breech cover assembly  28  toward its second position (cover  32  not overlying breech  22 ) independent of the fore end  26  is prevented by engagement between latch  36  mounted on the buttstock  30  and the catch  44  of the action bar  38  (see also  FIG. 2A ), whose first end  40  is attached to the fore end  26  and therefore only moves when the fore end moves. 
     If access to the breech  22  is desired, for example, to clear a malfunction, then, as shown in  FIGS. 3 and 3A , the action  14  is unlocked from battery by moving the fore end  26  away from the muzzle end  20  of barrel  18 . Action bar  38 , being attached to the fore end  26 , moves with it, thereby disengaging catch  44  from the latch  36 . As shown in detail in  FIG. 3A , the latch  36  is maintained in contact with the action bar  38  by the biasing action of spring  50  and rides up the ramp surface  64  of the action bar (see  FIG. 2 ), pivoting about pin  48 . Motion of the action bar  38  disengaging the catch  44  from the latch  36  establishes a separation distance  66  between the engaging portions of the latch and the catch. In this example embodiment the separation distance  66  is between the respective engagement surfaces  56  and  58  of the first and second hooks  52  and  54 . 
     As shown in  FIG. 4 , with action  14  no longer in battery and with a separation distance between the latch  36  and the catch  44 , the breech cover assembly  28  may be moved into its second position wherein the cover  32  is not overlying the breech  22 . As shown in  FIG. 4A , the separation distance  66  is reduced by motion of the breech cover assembly relative to the receiver  12 . In a practical embodiment, the butt stock  30  comprising the breech cover assembly may be attached to the receiver  12  with a separate locking mechanism (not shown) from the breech cover interlock  34 . 
     Breech cover assembly  28  may be returned to its first position overlying the breech  22  in two ways. The buttstock  30  may be pushed back into overlying relation with the breech  22  independently from motion of the fore end  26 , or, as shown in  FIGS. 5 and 5A , the fore end  26  can be pushed toward the muzzle end  20  of barrel  18  (compare positions of fore end  26  in  FIGS. 4 and 5 ). Action bar  38  moves with the fore end  26  and the catch  44  on the action bar thereby engages the latch  36  on the buttstock  30  and draws the buttstock back into the first position with the cover  32  overlying the breech  22  (see  FIG. 2 ). In either case, the buttstock  30  may again engage the aforementioned separate locking mechanism attaching it to receiver  12 . The breech  22  is thus covered as the action  14  is driven into battery to chamber a live round as the fore end  26  moves toward the muzzle end  20  of the barrel  18  as shown in  FIGS. 1 and 2 . 
       FIGS. 6, 6A, 6B and 6C  illustrate steps necessary to take down the shotgun  10  having an interlock  34  according to the invention. For take down it is necessary to disengage the latch  36  from the catch  44 . Disengagement is effected using a disassembly tool  68 . As shown in  FIGS. 6 and 6A , the tool  68  is inserted through an opening  70  in the buttstock  30 . Opening  70  is positioned so that the tool  68  engages the latch  36 . As shown in  FIG. 6B , upon engagement between the tool  68  and the latch  36 , force applied to the tool pivots the latch against the force of its biasing spring  50 , separating the latch from the catch  44 . When the latch  36  and catch  44  respectively comprise first and second hooks  52  and  54  as in this example, it is advantageous to provide some separation between the first and second engagement surfaces  56  and  58  to permit ready separation of the latch from the catch when desired. The spring  50  however otherwise reliably biases the latch  36  into engagement with the catch  44  to ensure proper contact between the engagement surfaces  56  and  58  during operation of the shotgun  10  as described above. As shown in a comparison of  FIGS. 6B and 6C , with the latch  36  held out of alignment with the catch  44  ( 6 B) the breech cover assembly  28  may be moved away and separated from the receiver  12  provided that the aforementioned separate locking mechanism which otherwise holds the assembly  28  to the receiver  12  is also actuated. Provision is also made for ease of reattachment of the breech cover assembly  28  to the receiver  12  through the use of first and second lead-in surfaces  72  and  74  positioned respectively on the first and second hooks  52  and  54 . Each lead-in surface is positioned on its respective hook on an opposite side to the hook&#39;s engagement surface and each is angularly oriented with respect to the longitudinal axis  46  such that when the breech cover assembly  28  is again engaged with the receiver  12  the interaction between the lead-in surfaces  72  and  74  will cause the latch  36  to pivot about pin  48  and clear the catch  44 . Once the breech cover assembly is positioned so that the first and second hooks  52  and  54  are no longer in contact the biasing spring  50  pivots the latch  36  so that the engagement surfaces  56  and  58  of the hooks are again in facing relation as shown in  FIG. 6A . 
     It is expected that the use of a breech cover interlock according to the examples disclosed herein will improve the operation of breech loading firearms.