Patent Publication Number: US-10323895-B2

Title: Universal adapter end cap for a firearm

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 15/395,706, filed Dec. 30, 2016, which claims the benefit of U.S. Provisional Application No. 62/273,121, filed on Dec. 30, 2015. The entire teachings of the above applications are incorporated herein by reference. 
    
    
     BACKGROUND 
     Shotgun barrels often include a choke tube at the distal (i.e., shot-expelling) end. The typical shotgun choke tube is inserted into the barrel to constrict the shotgun&#39;s shot charge as the shot charge leaves the muzzle, thereby modifying the spread of the shot charge on its way to a target. For example, a choke tube with more constriction provides for a denser shot pattern at longer range, and a less constrictive choke tube would provide for a less dense shot pattern. Typical shotgun coke tubes screw into the muzzle of the barrel and enable multiple constrictions to be used on the same barrel by changing one choke tube for another. 
     SUMMARY 
     There exists a need for a device enabling a shotgun operator to carry an additional choke tube on the body of a shotgun. Typical pump-action and semi-automatic shotguns include a magazine tube positioned under the barrel to store the additional ammunition cartridges with an end cap threaded onto the distal end of the magazine. Prior art end caps simply serve to close the end of the shotgun magazine and secure an internal spring. Additionally, some prior art end caps may also secure the firearm&#39;s barrel assembly to the lower receiver and/or magazine tube. Embodiments of the present invention include a universal adapter end cap having a first end configured to be threaded onto the end of a shotgun magazine and a second end adapted to secure an accessory (e.g., a choke tube) to the shotgun. Accordingly, embodiments enable an operator to stow and carry a second unused choke tube, or any other accessory at the end of the shotgun magazine. 
     Some embodiments of the universal adapter end cap include a threaded opening that enables a choke tube to be threaded into the threaded opening. Some embodiments provide threads constructed from flexible material to enables both threading and push insertion of the choke tube into the universal adapter end cap. 
     An example embodiment is a universal adapter end cap for a magazine of a firearm, comprising a first end having a threaded opening adapted to secure the universal adapter end cap to a corresponding threaded end of the magazine of the firearm, and a second end opposite to the first end, the second end having an accessory interface adapted to secure to the firearm a corresponding interface of an accessory via the universal adapter end cap. The firearm may be any type of firearm with a magazine having (or being adaptable to have) a threaded end where the universal adapter end cap may be attached. According to some embodiments, the firearm may be a shotgun, and the threaded opening may be adapted to replace an end cap of the shotgun magazine. The accessory, for non-limiting example, may be a shotgun choke tube, and the corresponding threaded end of the shotgun choke tube may be adapted to thread the choke tube into a barrel of a shotgun. 
     In some embodiments, the threaded opening of the first end is a first threaded opening and the accessory interface of the second end comprises a second threaded opening having a depth along the second direction, where the depth enables the corresponding threaded end of the choke tube to be inserted into the second threaded opening. In some embodiments, the accessory interface of the second end is a threaded opening, with the threads of the second threaded opening being constructed from a pliable material enabling both push-insertion and pull-removal of an accessory (e.g., a choke tube). The second end may be constructed from a pliable material, and the accessory interface is an opening enabling both push-insertion and pull-removal of the accessory (e.g., choke tube). The pliable material may enable accessories of a range of diameters to be inserted into the second end, based on, for example, a durometer of the pliable material and an inner diameter of the opening of the second end. 
     According to some embodiments, enabling both push-insertion and pull-removal of an accessory allows the user of the firearm to quickly and easily insert and remove accessory from the universal adapter end cap at the distal end of the firearm. This makes the accessory more accessible to the user of the firearm than if the accessory were stored in a pouch or pocket. 
     In yet another embodiment, the accessory interface of the second end defines an opening and an inner surface of the opening includes one or more pliable interface features. The pliable interface features may protrude from the inner surface and enables both push-insertion and pull-removal of the accessory (e.g., choke tube). The one or more pliable interface features may be pliable inserts adapted to be removably coupled to the inner surface. The one or more pliable interface features may be threaded to accept the corresponding threads of the accessory (e.g., choke tube). The one or more pliable interface features may be flexible bands suspended in the opening and adapted to be deflected by the accessory (e.g., choke tube) upon insertion of the accessory, the deflection of the flexible bands providing an interface fit against the accessory. The one or more pliable interface features may be one or more flexible toroidal gaskets positioned in corresponding circumferential grooves on the inner face of the opening. 
     In some embodiments, the accessory interface of the universal adapter end cap defines an opening with an inner surface, the inner surface including one or more press fit detents. The one or more press fit detents protruding from the inner surface and enabling both push-insertion and pull-removal of the accessory. 
     In some embodiments, the threaded opening is a first threaded opening facing in a first direction, the accessory interface is a second threaded opening of the second end, and the corresponding interface of the accessory is a corresponding threaded end of the accessory, with the second threaded opening facing in a second direction, the second direction being opposite to the first direction. The first and second ends may be first and second ends of a main body, and the main body may be constructed from a material selected from the group consisting of: metal, rubber, polymer, or glass filled nylon. The accessory may be selected from the group consisting of: a choke tube, flashlight, bipod, storage container defining storage space, first-aid/survival kit, ammunition, duck caller, weight or laser sight. 
     The universal adapter end cap may further include a coupling interface between the first and second ends, the coupling interface removably coupling the second end to the first end, and thereby enable a two-part construction of the universal adapter end, with the second end being interchangeable for different accessories or, for example, different choke tube sizes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing will be apparent from the following more particular description of example embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating embodiments of the present invention. 
         FIG. 1A  is an illustration of a typical pump-action or semi-automatic shotgun with an end cap and a choke tube. 
         FIG. 1B  is an illustration of a choke tube being inserted into the distal end of a shotgun barrel. 
         FIG. 2  is an illustration of an adapter end cap embodiment having interior threads configured to accept the mating threads of a choke tube. 
         FIG. 3  is an illustration of an adapter end cap embodiment having a two-part construction with a distal end having interior threads constructed from a pliable material. 
         FIG. 4  is an illustration of an adapter end cap embodiment having pliable interior fitting features for interfacing with the external surface of a choke tube. 
         FIG. 5  is an illustration of an adapter end cap embodiment having an insert including interface fitting protrusions adapted to secure a choke tube by forming an interference fit against the external surface of the choke tube. 
         FIG. 6A  is an illustration of an adapter end cap embodiment having an insert including interface fitting protrusions positioned parallel to the length of the adapter end cap. 
         FIG. 6B  is an illustration of the front view of an adapter end cap embodiment including interface fitting protrusions positioned parallel to the length of the adapter end cap. 
         FIG. 7  is an illustration of an adapter end cap embodiment having interior press fit ball detents for interfacing with the external surface of an accessory. 
         FIGS. 8A-8E  are illustrations of an example adapter end cap embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A description of example embodiments of the invention follows. 
       FIG. 1A  shows a typical pump action or semi-automatic shotgun  100  profile, the shotgun  100  having a rear stock  102 , trigger  104 , barrel  106 , muzzle  108 , choke tube  110  (dashed lines), fore-end  112 , and magazine tube  114  capped at the distal end by an end cap  116 . 
     In operation, the choke tube  110  is threaded into the muzzle  108  of the barrel  106  and can be removed by a user with a hand or a wrench. The removal of the choke tube  110  is an operation that can be done prior to using the shotgun  100  or while using the shotgun  100 , between discharges. Additionally, the end cap  116  is threaded onto the end of the magazine tube  114 , and typically secures one end of a spring inside the magazine tube. 
       FIG. 1B  shows a typical shotgun barrel  106  and choke tube  110 , with the choke tube  110  partially inserted into the barrel  106  and not yet threaded into corresponding interior threads  107  of the barrel  108 . The threads  111  of the choke tube  110  may be positioned in the middle of the choke tube  110  (as shown) or may also be at the proximal end (the end of the choke tube  110  first inserted into the barrel  108 ), depending on the manufacturer&#39;s design choice in locating the internal threads  107 . Typically, each individual manufacturer requires a different corresponding choke tube  110  design. 
       FIG. 2  is an illustration of an example adapter end cap embodiment  200  having interior threads  202  configured to accept mating threads an accessory (e.g., choke tube). The example adapter end cap embodiment  200  has a proximal end  204  configured to thread onto the end of a shogun magazine tube  114  (replacing a typical end cap  116 ) and a distal end  206  configured to accept an accessory (e.g., shotgun choke tube  110 ). The distal end  206  includes an opening facing away from the proximal end  204  and includes interior threads  202  enabling a choke tube  110  to be threaded into the adapter end cap  200 . 
     In operation, a user replaces the shotgun&#39;s end cap  116  ( FIG. 1A ) with the adapter end cap  200  of  FIG. 2 , thereby enabling the user to attach an accessory (e.g., second choke tube) to the adapter end cap  200  and carry the attached accessory in an easy-to-reach location on the shotgun  100 .  FIG. 2  also shows a front view of the adapter end cap  200 , illustrating the circular shape of the exterior of the adapter end cap  200  and the interior threads  202  in the distal end  206  of the adapter end cap  200 . 
       FIG. 3  is an illustration of an adapter end cap embodiment  300  having a two-part construction with a distal end  300   b  and interior threads  302  constructed from a pliable material.  FIG. 3  shows an adapter end cap  300  constructed from two different materials. The proximal end  300   a  is constructed from a durable and hard material, such as metal or ballistic nylon and the distal end  300   b  is constructed from a pliable material, such as rubber or a flexible polymer. The distal end  300   b  also includes an opening with interior threads  302  configured to accept an accessory (e.g., shotgun choke tube  110 ). In operation, the pliable material of the distal end  300   b  enables a user to either thread an accessory (e.g., choke tube  110 ) into the interior threading  302  or simply push-fit the accessory (e.g., choke tube  110 ) into the opening of the distal end  300   b . The pliable material also enables accessories of slightly larger or smaller diameters, or with different thread patterns, to be secured by an interface fit against the inner threads  302 . 
     Additionally, the distal end  300   b  of the adapter end cap  300  may be constructed as a separate part to be removably coupled to the proximal end  300   a , thereby enabling a user to swap the distal end  300   b  part for a separate distal end (not shown) of a different size or material, or for a separate distal end (not shown) having a different accessory attachment configuration. 
       FIG. 4  is an illustration of an adapter end cap embodiment  400  having pliable interior fitting features  402  for interfacing with the external surface of an accessory (e.g., choke tube  110 ).  FIG. 4  shows an adapter end cap  400  where the interior of the distal opening  404  includes three grooves  406  holding three pliable gasket rings  408 . The pliable gasket rings  408  are positioned to accept an accessory (e.g., choke tube  110 ) that is push-fit into the distal opening  404  of the adapter end cap  400 . It should be understood that other numbers and dimensions of pliable gasket rings  408  may alternatively be employed. 
     In operation, the pliable gasket rings  408  are deflected by the outer surface of the accessory (e.g., choke tube  110 ) as it is inserted into the adapter end cap  400 , and the deflection of the pliable gasket rings  408  creates an interface fit between the adapter end cap  400  and the accessory (e.g., choke tube  110 ). Additionally, by choosing the properties of the pliable gasket rings  408 , such as the durometer and thickness, the adapter end cap  400  may accept a wide range of accessories) by being able to interface fit against a range of exterior diameters of the accessories. 
       FIG. 5  is an illustration of an adapter end cap embodiment  500  having an insert  502  including interface fitting protrusions  504  perpendicular to the length of the adapter end cap  500  and are adapted to secure an accessory (e.g., choke tube  110 ) by forming an interference fit against the external surface of the accessory (e.g., choke tube  110 ).  FIG. 5  shows an adapter end cap embodiment  500  having a distal opening  508  with a pliable insert  504  secured inside the distal opening  508  and forming the circumferential surface of the distal opening  508 . The pliable insert  502  includes one or a plurality of interface fitting protrusions  504  projecting into the volume of the distal opening  508 . The interface fitting protrusions  504  are configured to create an interface fit with choke tube  110 , as shown inserted into the adapter end cap  500 . 
     In operation, a user can swap the pliable insert  502  for one of a different material or internal diameter, for example, to accept accessories of various external diameters or to improve performance in different environments by choosing a material suited to perform in a given environment, such as hotter and colder temperatures. Additionally, the removability of the pliable insert  502  enables a user to easily swap out a worn-out pliable insert  502  for a new one, or clean the pliable insert  502  and distal opening  508  after repeated use of the adapter end cap  500  accumulates grease or grit in the distal opening  508 . 
       FIG. 6A  is an illustration of an adapter end cap embodiment  600  having an insert  602  including interface fitting protrusions  604  parallel to the length of the adapter end cap  600  and are adapted to secure an accessory (e.g., choke tube  110 ) by forming an interface fit against the external surface of the accessory (e.g., choke tube  110 ).  FIG. 6A  shows an adapter end cap embodiment  600  having a distal opening  608  with a pliable insert  602  secured inside the distal opening  608  and forming the circumferential surface of the distal opening  608 . The pliable insert  602  includes one or a plurality of interface fitting protrusions  604  projecting into the volume of the distal opening  608 . The interface fitting protrusions  604  are configured parallel along the length of the opening with the height of the protrusions  604  increasing further into the distal opening  608 . Alternatively, the height of the protrusions  604  may be uniform throughout the length of the distal opening  608 . In some embodiments, the interface fitting protrusions  604  are made of pliable material, and as the accessory is inserted, the protrusions  604  create an interface fit with the accessory. It should be understood that other numbers and dimensions of pliable protrusions  604  may alternatively be employed. 
     Because the diameter of the distal opening  608  gradually decreases from the distal end  610   a  toward the proximal end  610   b , the adapter end cap  600  is able to accept accessories of various external diameters. In operation, the user pushes the accessory into the distal opening  608  until the accessory is held firmly in place. The accessory can then be removed by pulling the accessory out of the distal opening  608 . This enables the user to quickly and easily insert and remove the accessory from the adapter end cap  600 , without the need to thread and unthread the accessory into the adapter end cap  600 . 
       FIG. 6B  is an illustration of the front view of the adapter end cap embodiment  600  including the interface fitting protrusions  604 . According to some embodiments, the protrusions  604  may be rectangular and run from the front of the distal end  610   a  toward the proximal end  610   b  of the adapter end cap  600 . 
       FIG. 7  is an illustration of an adapter end cap embodiment  700  having one or more interior press fit ball detents  702  for interfacing with the external surface of an accessory.  FIG. 7  shows an adapter end cap  700  in which the interior of the distal opening  708  includes six press fit ball detents  702 . Six press fit ball detents  702  are shown as an example; it is understood that the adapter end cap  700  may have any number of press fit ball detents  702  to interface with the external surface of an accessory (e.g., a choke tube). According to some embodiments, the press fit ball detent  702  may be held in cylindrical cavities  704  inside the adapter end cap  700 . The ball detents may be pressed toward the distal opening  708  by springs  706 . The ball detents  702  may be comprised of any type of material including metal, plastic, rubber, nylon, or any pliable material. 
     As an accessory is inserted into the distal opening  708 , pressure is exerted onto the external surface of the accessory by the press fit ball detents  702 . The pressure exerted onto the accessory holds the accessory in the distal opening  708  of the adapter end cap  700  in a manner enabling a user to easily push the accessory into the distal opening  708  for storage and pull the accessory out of the adapter end cap  700 . In some embodiments, the accessory may have corresponding grooves or holes for the ball detents  702  to rest in, creating a stronger grip between the adapter end cap  700  and the accessory. It should be understood that other numbers, dimensions, and placements of press fit ball detents  702  may alternatively be employed. 
       FIGS. 8A-8E  are illustrations of an example adapter end cap embodiment  800 .  FIG. 8A  is an isometric view of the example adapter end cap embodiment  800 . According to this embodiment, the adapter end cap  800  has shape similar to a prolate spheroid with indents  802  around the outside of the adapter end cap  800 . The indents  802  provide a user extra grip for threading the adapter end cap  800  onto and off of a firearm magazine.  FIG. 8A  shows the distal end  810   a  and the distal opening  808  at the top of the adapter end cap  800 , and the proximal end  810   b  at the bottom of the adapter end cap  800 . 
       FIG. 8B  is a semitransparent side view of the adapter end cap  800 .  FIG. 8B  shows the distal opening  808  for accepting the accessory and the threads  812  at the proximal end  810   b  for accepting a firearm magazine tube. 
       FIG. 8C  is a top view of the adapter end cap  800 ,  FIG. 8D  is a side view of the adapter end cap  800 , and  FIG. 8E  is a bottom view of the adapter end cap  800 . 
     While this invention has been particularly shown and described with references to example embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.