Patent Publication Number: US-6990764-B2

Title: Shotgun attachment

Description:
BACKGROUND OF THE INVENTION 
   This invention relates to attachments for a shotgun, and in particular to an attachment for use with the muzzle end of a shotgun barrel. 
   It is known to provide choke tubes as attachments for a shotgun barrel. In fact, many shotgun barrels have an internal thread formed in the barrel at the muzzle end, and a shoulder stop, so that a permanent or removable choke tube(s) may be threaded onto the barrel, through the use of a fine thread, such that the choke tube is threaded into the barrel until a first end of the choke tube engages and seats against the shoulder as described in U.S. Pat. No. 6,052,935. The choke tube may have an interior configuration to modify a pattern of the shot that are released from the shotgun shell when it is fired. This interior configuration may include a narrowing or a widening of the internal diameter interior of the choke tube, and may also include abrupt steps or pins that protrude into the inner passage of the choke tube to engage the wad of the shotgun shell. For example, U.S. Pat. No. 2,092,649 shows such a choke tube. It is also known to provide a semiannular rib in conjunction with a nozzle to cause wad retardation by imparting a spin to the wad as it progresses down the nozzle. U.S. Pat. No. 3,045,379 also discloses these features. It is also known to provide conventional chokes on a shotgun muzzle, which offer a constriction or a constriction followed by an expansion to adjust the spray pattern. These restrictions can also slow down a wad traveling down the barrel but they apply radial forces to the shot pellets, thereby distorting the resulting pattern. U.S. Pat. Nos. 5,452,535 and 6,128,846 disclose the use of projecting pins or rings to engage the shot wad, and also the use of other attachments to the choke tube to further condition the shot pattern. U.S. Pat. No. 5,317,825 discloses an attachment to a choke tube to reduce recoil. 
   The sole means of attachment of these internal choke tubes is the meshing of the fine thread of the interior of the barrel and the exterior of the choke tube. This provides only a single point of attachment and this attachment is secured only by snugging the seating of choke tube against the shoulder on the inside of the barrel. U.S. Pat. No. 6,052,935 attempts to overcome the problem associated with the required fine threads, that is, the need to rotate the choke relative to the barrel through a large number of turns by using discontinuous threads. However, this requires precise machining of both the internal portion of the shotgun barrel, i.e., the “bore” and the choke tube, and also requires precise rotational alignment between the two parts upon assembly. 
   This single point of attachment, in a cantilevered fashion, is subject to loosening due to vibrations occurring during the firing of the shotgun, from recoil, internal pressure and also the passage of the shot charge, wad and propelling gasses, if the choke tube is not continuously checked for tightness, a hazardous condition resulting from a loose tube could result. The tube can loosen from its proper position in the bore, by way of the backing-out of its threads or else by lateral vibration and movement. The resulting hazards may include the failure of the choke-tube-to-bore gas seal, the deformation of the dimensions of choke tube, the threads and the bore of the barrel, which can occur with catastrophic result. The instability of such cantilevered seating of the tube also negatively affects the pellet patterning efficiency and consistency of the shotgun choke tube even when properly seated. 
   U.S. Pat. No. 5,317,825 discloses an attachment for the exterior of a choke tube, however this attachment is to reduce recoil and it is not described in this patent to use the attachment to stabilize or prevent the loosening of the choke tube relative to the barrel. 
   It would therefore be an improvement in the art if there were provided a means for securing the attachment of the choke tube, or other attachment for a shotgun barrel that would minimize or prevent the unwanted loosening and lateral instability of the choke tube or attachment. 
   Further, since the choke tube or other attachment for the shotgun barrel must be made by utilizing the fine threads on the interior of the shotgun barrel, the attachment process is time consuming because the attachment requires many revolutions of the choke tube or attachment until the end of the choke tube or attachment seats against the shoulder. In some instances, particularly in law enforcement and military use, shotguns are used for different applications that require installing different attachments to the muzzle end of the barrel of the shotgun, where the weight-bearing strength and the overall stability of the tube within the bore and time for changing between different attachments may be at a premium. 
   It would therefore be an improvement in the art if there were provided a means for attaching various attachments, in a stable and secure manner to a shotgun barrel, and to be able to do so in a less time consuming manner than utilizing the fine threaded attachment arrangement provided on the interior of the shotgun barrel. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a means for securing the attachment of the choke tube, or other attachment for a shotgun barrel, that would prevent the unwanted loosening of the choke tube or attachment. 
   It is also an object of the present invention to provide a means for attaching various attachments, in a secure manner, to a shotgun barrel, in a less time consuming manner than utilizing the fine threaded attachment arrangement provided on the interior of the shotgun barrel. 
   These objects are inventively achieved in one embodiment where a locking arrangement for a shotgun choke is provided, wherein the shotgun choke comprises a cylindrical tube having a first external threaded portion at one end for threadingly engaging an internal thread in a shotgun barrel which is spaced inwardly of a muzzle end of the shotgun barrel and which firmly seats that first portion of the tube to the bore and seals it. Also, a lateral notch, slot or other device may be located at the opposite or forward end of the exposed tube beyond the muzzle end of the shotgun barrel, so as to permit the tube&#39;s internal seal and threads to be initially firmly seated and tightened. The stabilizing locking arrangement comprises a second external threaded portion on the choke cylindrical tube, which second portion will remain exposed beyond the muzzle end of the shotgun barrel when the choke is fully threaded into engagement with the bore of the said shotgun barrel. An internally threaded ring is provided which is sized to be threadingly carried on an outside of the choke and to engage the second external threaded portion of the choke such that the ring can be threaded onto the choke tube until it tightly and abuttingly securely engages the muzzle end of the shotgun barrel, providing an additional seating point adding to the longitudinal, lateral and axial security, seat and stability of the choke tube. 
   The objects are inventively achieved in a further embodiment where a tube and ring assembly for use with a shotgun barrel is provided comprising a cylindrical tube with a first externally threaded portion at one end for threadingly engaging an internal thread in the shotgun barrel which is spaced inwardly of a muzzle end of the shotgun barrel, and a second externally threaded portion which will remain exposed beyond said muzzle end of said shotgun barrel when said tube is fully threaded into engagement with said shotgun barrel. An internally threaded ring is also provided which is sized to be threadingly carried on an outside of the tube and to engage the second externally threaded portion of the tube such that the ring can be threaded onto the tube. 
   Other embodiments provide additional features of the invention as described in greater detail below. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a longitudinal sectional view of an end portion of a shotgun barrel in which the present invention can be utilized and including a longitudinal sectional view of an embodiment of the invention as it is being assembled onto the shotgun barrel; 
       FIG. 2  is a longitudinal sectional view of an end portion of a shotgun barrel in which the present invention can be utilized and including a longitudinal sectional view of an embodiment of the invention as it is locked onto the shotgun barrel; 
       FIG. 3  is a side elevational view of the ring; 
       FIG. 4  is an end elevational view of the ring; 
       FIG. 5  is a longitudinal sectional view of an end portion of a shotgun barrel in which the present invention can be utilized and including a longitudinal sectional view of an embodiment of the invention with an elongated ring as it is locked onto the shotgun barrel; 
       FIG. 6  is a longitudinal sectional view of an end portion of a shotgun barrel in which the present invention can be utilized and including a longitudinal sectional view of an embodiment of the invention with an elongated and constricting ring as it is locked onto the shotgun barrel; 
       FIG. 7  is a longitudinal sectional view of an end portion of a shotgun barrel in which the present invention can be utilized and including a longitudinal sectional view of an embodiment of the invention with an elongated and expanding ring as it is locked onto the shotgun barrel; 
       FIG. 8  is a longitudinal sectional view of an end portion of a shotgun barrel in which the present invention can be utilized and including a longitudinal sectional view of another embodiment of the invention as it is locked onto the shotgun barrel. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  shows, in a partial, longitudinal sectional view, a locking and stabilizing arrangement  20  for a shotgun choke  22 , wherein the shotgun choke comprises a cylindrical tube  24  having a first external threaded portion  26  at or near a first end  28  for threadingly engaging an internal thread  30  in a shotgun barrel  32  which is spaced inwardly of a muzzle end  34  of the shotgun barrel. The choke  22  may also include a surface feature  33  on an interior surface  31  thereof in the form of projecting pins, a step, a gradual decrease in diameter, or other known construction to impede wad movement or condition the shot pattern achieved by the choke  22 . For example, without limitation, the choke may be similar to those described in U.S. Pat. Nos. 5,452,535 and 6,128,846, the disclosures of which are incorporated herein by reference. As is well known, the shotgun barrel  32  has an internal seat or shoulder  35  adjacent to the internal thread  30  against which the first end  28  of the choke  22  will abut and seal when the choke is fully engaged with the barrel. A surface feature  37  may be applied to the choke  22  to assist in rotating the choke relative to the barrel  32 . For example, a slot may be provided to be engaged by a tool. A roughened or non-circular outer circumferential surface may also be provided to enhance manual or tool assisted tightening of the choke  22  on the barrel  32 . 
   The locking and stabilizing arrangement  20  comprises a second external threaded portion  36  on the choke cylindrical tube  24 . The second portion  36  remains exposed beyond the muzzle end  34  of the shotgun barrel  32  when the choke  22  is fully threaded into engagement with the shotgun barrel and may or may not extend a short distance into the barrel. An internally threaded ring  38  is provided which is sized to be threadingly carried on an outside  40  of the choke  22  and to engage the second external threaded portion  36  of the choke  22 , such that the ring  38  can be threaded onto the choke until the ring abuttingly engages the muzzle end  34  of the shotgun barrel  32  as shown in  FIG. 2 . When the ring  38  is snugged up against the muzzle end  34  of the shotgun barrel  32 , a second point of attachment, securement and stabilization of the choke  22  to the barrel  32  is achieved. This helps to stabilize the choke  28 , to make it less susceptible to vibration and loosening relative to the barrel  32 , and the ring  38  acts as a jam nut to prevent the inadvertent loosening of the choke from the barrel. 
   The ring  38  itself can have a variety of constructions and may simply be an internally threaded ring as shown in  FIG. 1 , or it may be of a “lock nut-type” of construction as is known, with internal features to hold the ring in place on the threads  36 . For example, such a ring  38  may be good for only a one-time use and then discarded and replaced, or may be of the multiple use type. Also, the ring  38  may be a “double ring” type of construction, with one of the rings being a lock ring, such as a split ring, as is known. Further, the ring may be provided with other locking or retarding devices or arrangements, such as one or more set screws drilled and tapped into the ring radially. Once the ring is rotated into position, the set screw(s) can be tightened against the exterior surface of the choke  22  so that the ring  38  will not be able to back off from its engagement with the muzzle  34 . 
   Thus, the ring  38  prevents the forward-rear, lateral and longitudinal vibration and movement of the choke  22 , which is no longer only attached in a cantilevered fashion. This additional locking and stabilizing ring, over time, protects the gun barrel  32  and its threads  30 , and the choke  22 , from wear, mutilation and possible failure which could be caused by motion of the choke relative to the barrel (work hardening) and keeps the choke more securely and firmly aligned in its proper “directly straight ahead” position within the bore of the barrel. This will make the gun more accurate and the pattern distribution more even. Further, the use of the locking and stabilizing ring  38  protects the internal dimensions of the tube, the rear skirt seal  35 , and any internal pattern conditioning wad-retarding devices  33  from being work-hardened out of round or being directly contacted by the shot charge metal and thereby marred, mutilated or worn-away. If a choke  22  were to tilt slightly in the barrel  32 , it would allow and direct the shot metal to collide with an bear directly upon the internal protrusions, pins, etc.  33 , which could cause them to be eroded. Further, tube tilt could cause the rear seating skirt to become off-center, and to thus protrude slightly into the bore itself, and the path of the approaching shot column. If a shotgun shell were to be fired after such a condition occurs, internal bore pressures could increase to a point which might cause the choke and barrel to separate or to cause the barrel to rupture, either of which would be costly and dangerous. 
   In an embodiment of the invention, as shown in  FIGS. 1 and 2 , the ring  38  may have an axial length  41  that is shorter than a protruding portion  42  of the choke  22  that carries the second threaded portion  36 , such that when the ring is threaded onto the choke and into engagement with the muzzle end  34 , a free end  43  of the choke will extend beyond the ring in a direction away from the muzzle. In an embodiment, the axial length  41  of the ring  38  is less than ¼ th  of an inch (6 mm), while in other embodiments, the axial length  41  is greater than ¼ th  of an inch (6 mm). For example, the axial length  41  may be longer than a length of the exposed threads  36  so that the ring will also function as a protection for the threads. An entire interior length of the ring  38  may be threaded, or only a portion of the length. 
   In an embodiment of the invention, the ring  38  has a round outer circumference  46 . In some embodiments the ring  38  has an outer surface configuration  48  which enhances manual manipulation of the ring. For example, as shown in the embodiment of  FIG. 3 , the outer circumference  46  is knurled. In another embodiment, as shown in  FIG. 4 , the outer circumference  46  has a non-circular configuration, which preferably is a regular polygonal shape, such as a square or hexagonal shape. 
   In an embodiment of the invention, as shown in  FIG. 5 , the ring  38  has an axial length  41  greater than the protruding portion  42  of the choke  22 , such that when the ring is threaded onto the choke and into engagement with the muzzle end  34 , the ring will extend beyond the choke in a direction away from the muzzle. 
   In an embodiment of the invention, as shown in  FIG. 6 , the ring  38  incorporates a pattern-conditioning element  50  on an interior portion  52  thereof. As shown in  FIG. 6 , the pattern-conditioning element  50  comprises a constriction  54  of an interior diameter  56  of the ring  38  along its axial length  41 . As shown in  FIG. 7 , the pattern-conditioning element  50  comprises an expansion  58  of the interior diameter  56  of the ring  38  along its axial length  41 . 
   As shown in  FIGS. 1 and 2 , the second external threaded portion  36  has a thread pitch courser than the fine thread pitch of the first external threaded portion  26 . This means that the ring  38  will move axially a greater distance for each revolution of the ring on the choke  22  than the axial distance the choke will move for each revolution of the choke relative to the shotgun barrel  32 . Thus, a given axial length of the ring  38  can be captured on the second threaded portion  36  with fewer rotations of the ring relative to the choke  22  than are required to capture the same axial length of the choke on the shotgun barrel at the first threaded portion  26 . This allows the ring  38  to be quickly assembled onto the choke  22  and to be moved into a snug engagement with the muzzle end  34  of the shotgun barrel  32 . For example, it may take  20  full rotations of the choke  22  (taking up to a minute) to fully seat in the shotgun barrel, but only two full rotations of the ring  38  (taking only a few seconds to be snugged up against the muzzle  34 . 
   In a further embodiment of the invention, the second external threaded portion  36  has a thread of opposite hand compared to the first external threaded portion  26 . Thus, as either the ring  38  or the choke  22  is vibrated to rotate in one rotational direction, the other will be further tightened by such rotation and hence will prevent the loosening of the choke tube. 
   In a further embodiment of the invention, as illustrated in  FIG. 8 , the locking arrangement may be used in combination with a cylindrical tube  70  other than a choke tube. That is, the tube  70  may not have any pattern conditioning elements or features, and may merely be a continuation of the inner diameter of the shotgun barrel. In this embodiment, the invention comprises a tube and ring assembly  72  for use with the shotgun barrel  32  comprising the cylindrical tube  70  with a first externally threaded portion  74  at a first end  76  for threadingly engaging the internal thread  30  in the shotgun barrel which is spaced inwardly of the muzzle end  34  of the shotgun barrel. A second externally threaded portion  78  is provided which remains exposed beyond the muzzle end  34  of the shotgun barrel  32  when the tube  70  is fully threaded into engagement with the shotgun barrel. An internally threaded ring  80  is provided which is sized to be threadingly carried on an outside  82  of the tube  70  and to engage the second externally threaded portion  78  of the tube such that the ring can be threaded onto the tube until the ring abuttingly engages the muzzle end  34  of the shotgun barrel  32 . 
   The ring  80  may have all of the aspects of the ring  38  described above, that is, it may have an axial length lesser or greater than an exposed axial length of the tube  70 , it may have an outer surface configuration that enhances manual manipulation or rotation of the ring, and it may incorporate a pattern conditioning element or some other feature. 
   In this embodiment, the tube  70  may be used to protect the internal threads of the shotgun barrel, if no pattern conditioning is desired, or the tube may function as a carrier platform for the ring, wherein the ring has functional elements desirable for use with the shotgun. 
   A surface feature  84  may be applied to the tube  70  to assist in rotating the tube relative to the barrel  32 . For example, a slot may be provided to be engaged by a tool. A roughened or non-circular outer circumferential surface may also be provided to enhance manual or tool assisted tightening of the tube  70  on the barrel. 
   Thus, the present invention provides a novel method of locking a tube  28 ,  70  to a shotgun barrel  32  comprising the steps of inserting the tube into the shotgun barrel, rotating the tube relative to the shotgun barrel to engage a threaded connection  26 ,  30 ,  74  between the tube and the shotgun barrel, continuing the relative rotation between the tube and the shotgun barrel until the tube abuttingly engages and seals with an internal step  35  in the shotgun barrel, positioning a ring  38 ,  80  around an exterior  40 ,  82  of the tube, rotating the ring relative to the tube to engage a threaded connection  36 ,  78  between the tube and the ring, and continuing the relative rotation between the tube and the ring until the ring abuttingly engages a muzzle end  34  of the shotgun barrel. 
   It is to be understood that any of the ring configurations or features can be used with any of the tubes shown in the various figures in various combinations. 
   Although the present invention has been described with reference to a specific embodiment, those of skill in the art will recognize that changes may be made thereto without departing from the scope and spirit of the invention as set forth in the appended claims. 
   As is apparent from the foregoing specification, the invention is susceptible of being embodied with various alterations and modifications which may differ particularly from those that have been described in the preceding specification and description. It should be understood that I wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of my contribution to the art.