Patent Publication Number: US-6698128-B2

Title: Adjustable bore paint ball gun

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to paint ball guns of the type usually used in recreational activities. More directly, the invention relates to a gun barrel with an adjustable diameter for use in projecting paint ball pellets with a compressed gas. 
     Paint ball guns are generally used for target shooting or for recreation where individuals, or teams, fire paint balls or pellets at each other in an effort to simulate combat, or war. In operation, a paint ball is deposited into a compression chamber of the paint ball gun. By pulling the trigger on the gun, the user unleashes a short blast of compressed gas (generally carbon dioxide) that propels the paint pellet out of the compression chamber, through the barrel of the gun, and out of the muzzle. To maximize the force of the compressed gas on the paint ball, the bore of the barrel of the paint ball gun should slightly compress or be close in diameter to the diameter of the paint pellet. However, a barrel with a bore that is too small for the paint pellet will require extra energy to dislodge the pellet from the barrel slowing it down or in extreme circumstances, causing it to become lodged in the barrel or causing the pellet to break apart while traveling down the barrel. Conversely, a barrel with a bore much larger than the paint pellet will allow the compressed gas to leak around it, reducing the force of the gas upon the pellet, resulting in a slower muzzle velocity and less range. 
     Paint pellets are produced by many different manufacturers and vary in their spherical diameters. As traditional paint ball guns have a barrel that is not adjustable, some paint pellets may not fire effectively because of the differing spherical diameters. 
     It has been known to compensate for spherical deviation of paint pellets by using removable barrels that can be replaced with barrels of differing bore sizes. This is achieved, in the prior art, by the addition of a quick disconnection mechanism. Such a paint ball gun barrel is disclosed in U.S. Pat. No. 6,273,080 to D. Sullivan, Jr. incorporated herein by reference. A quick disconnect barrel system, however, requires the user to carry numerous barrels of differing bore diameters to ensure availability of a bore properly matching the size of the paint pellets to be fired. 
     It has also been known to use interchangeable bore sleeves of varying diameter or to use pins with a spring loaded tension to position the paint pellet in the barrel of the gun. The pins are placed around the interior of the barrel at 3 or 4 locations. However, as the pins provide only point contact, compressed gas may be lost around the paint pellet by traveling between the pellet and the inner wall of the barrel. 
     SUMMARY OF THE INVENTION 
     In one embodiment of the present invention, a barrel for a paint ball gun having an adjustable bore is provided. The barrel includes an adjustment mechanism that compresses an inner-bore sleeve to numerous diameters, allowing the paint ball gun to fire paint pellets of different sizes. 
     The adjustment mechanism is capable of adjusting the inner diameter of the barrel without having to remove the barrel from the paint ball gun. In one embodiment of the invention, rotation of an outer collar around the barrel is sufficient to alter the diameter of the barrel. 
     One embodiment of the invention includes a resilient inner-bore sleeve capable of springing back to a larger diameter whenever the compression force is removed. The inner-bore sleeve should be sufficiently resilient to continually return to its initial rest dimensions, thereby ensuring the same maximum barrel diameter may always be achieved by the adjustable bore barrel. 
     With the present invention, the user is able to accurately set the diameter of the bore without having to carry replacement barrels, attachments, or measuring devices. Any one of numerous well known alignment mechanisms may be used to allow the user to accurately set the diameter of the bore. The alignment mechanisms allow the user to set the bore diameter for more efficient utilization of the compressed air charge of the gun during firing. Furthermore, the alignment mechanisms allow the user to experiment in the use of different types of paint pellets enabling the user to compare various brands and various sizes without the need to purchase additional paint ball guns. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a perspective view of a paint ball gun including a barrel with an adjustable bore. 
     FIG. 2 shows an exploded perspective view of the embodiment of the present invention shown in FIG.  1 . 
     FIG. 3 shows a perspective view of an embodiment of an inner-bore sleeve shown in FIG.  2 . 
     FIG. 3A is a side view of the inner-bore sleeve of FIG.  3 . 
     FIG. 3B is an end view of the inner-bore sleeve of FIG.  3 . 
     FIG. 4 shows a perspective view of an embodiment of a barrel body shown in FIG.  2 . 
     FIG. 4A is a longitudinal cross-sectional view of the barrel body taken along line  4 A— 4 A of FIG.  4 . 
     FIG. 5 is a cross-sectional view of one embodiment of an outer sleeve taken along line  5 — 5  in FIG.  2 . 
     FIG. 6 shows a cross-sectional view of another embodiment of an outer sleeve. 
     FIG. 7A is a cross-sectional view of the adjustable barrel assembly taken along line  7 — 7  in FIG. 1 showing the barrel in the largest bore setting. 
     FIG. 7B is a cross-sectional view of the adjustable barrel assembly taken along line  7 — 7  in FIG. 1 as would appear when being moved between settings. 
     FIG. 7C is a cross-sectional view of the adjustable barrel assembly taken along line  7 — 7  in FIG. 1 showing the barrel in the smallest bore setting. 
     FIG. 8 is a front view of an embodiment of a retaining ring shown in FIG.  1 . 
     FIG. 8A is a side view of the retaining ring shown in FIG.  8 . 
     FIG. 9 is a longitudinal cross-sectional view of the barrel assembly taken along line  9 — 9  in FIG. 1 showing a flange of the inner-bore sleeve retained by the barrel body and a barrel extension. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With respect first to FIG. 1, a paint ball gun generally indicated by the numeral  10  is shown. Paint ball gun  10  includes an adjustable barrel generally indicated as  12 , a muzzle or barrel extension  24 , and a main body portion  26 . 
     As shown in FIG. 2, the adjustable barrel  12  includes an inner-bore sleeve  14 , a barrel body  16 , an outer sleeve or collar  18 , a plurality of force elements  20  and a retaining ring or stop spacer  22 . In one embodiment of the invention, inner-bore sleeve  14 , barrel body  16 , outer sleeve  18 , retaining ring  22  and barrel extension  24 , all share an identical longitudinal axis  28 . 
     FIGS. 3,  3 A, and  3 B show one embodiment of inner-bore sleeve  14 , including a longitudinal slit  30  and a flange  31 . In one embodiment, inner-bore sleeve  14  is manufactured from an aluminum composite and has a smooth inner-bore  32 . In addition, inner-bore sleeve  14  has an at-rest diameter  15 . At-rest diameter  15  is the diameter that inner-bore sleeve  14  will naturally hold when no compressing force is exerted upon it. However, when a compressing external force is exerted upon inner-bore sleeve  14 , the width of longitudinal slit  30  decreases, and inner-bore sleeve  14  compresses, reducing the diameter. 
     Flange  31  is located at one end of the inner-bore sleeve  14 . Flange  31  has an outer diameter that is larger than the outer diameter of inner-bore sleeve  14  for use in assembly of the adjustable barrel in a manner discussed below. 
     Referring now to FIGS. 4 and 4A, the barrel body  16  is shown. Barrel body  16  has a generally cylindrical shape around longitudinal axis  28 . Barrel body  16  includes barrel threads  34 , gun threads  36 , a bearing surface  37  adjacent the gun threads, and a plurality of openings  38 . A shoulder  39  is located on the interior of barrel body  16  adjacent barrel threads  34 . In one embodiment of the invention, the gun threads  36  are male threads sized to mate with female threads (not shown) in the main body portion  26  of gun  10  for securing the assembled adjustable barrel  12  thereto. It should be noted that the gun threads  36  may be female if necessary to complement the threads of the main body portion  26 . 
     Barrel threads  34  are located on the end of barrel body  16  opposite gun threads  36 . Barrel threads  34  may be either male or female threads with the choice being arbitrary as long as the type of threads chosen mate for attachment with threads on barrel extension  24 . The embodiment shown in FIG. 4 depicts barrel threads  34  as female threads. An embodiment as shown in which the barrel threads  34  and the gun threads  36  are each of different type, i.e., one being male and one being female, allows the user to make a quick distinction as to which end is the barrel threads  34  and which end is the gun threads  36  without the need for marking the barrel. 
     In the embodiment shown, the barrel openings  38  are elongated holes through the barrel body  16  of sufficient size and shape as to allow force elements  20  to pass through the barrel body  16 , yet limit movement of the force elements, in a manner described below. 
     Referring again to FIG. 2, one embodiment of the force elements  20  that may be utilized in the present invention is shown. The force elements  20  are roller pins made from a hard plastic or metallic material and positioned in such a position that the longitudinal axes of the pins are generally parallel to the longitudinal axis  28  of the adjustable barrel  12 . 
     Referring to FIGS. 2 and 5, outer sleeve  18  has a generally hollow cylindrical shape. In one embodiment, outer sleeve  18  is cast or machined from a metallic material such as aluminum. Outer sleeve  18  includes an outer surface  40 , an inner surface  42 , a plurality of recesses generally indicated at  44 , and rotational stops  50 . Outer sleeve  18  may also include marking indicators  52  for indicating the setting of the adjustable barrel  12  as is described more fully below. The recesses  44  vary in depth to allow distinct barrel diameter adjustments in the manner described below. In the arrangement of FIG. 2, recesses  44  extend in a longitudinal manner generally parallel to axis  28  allowing for the reception of the roller pins  20 . In this embodiment, outer sleeve  18  has four similar quadrants. Each quadrant is separated by a rotational stop  50 . Each quadrant has five recesses  44   a - 44   e  varying in depth from the shallowest recess  44   a  to the deepest recess  44   e.    
     Referring now to FIGS. 8 and 8A, retaining ring  22  is shown in detail. In one embodiment, retaining ring  22  is generally made from a metallic or hard plastic material and is generally shaped as a circular ring. FIG. 8A shows a side view of retaining ring  22  including a screw hole  33 . Screw hole  33  is generally a threaded through hole allowing receipt of a small screw (not shown) or similar means used to hold retaining ring  22  after being positioned on the adjustable barrel  12 . In this embodiment, the retaining ring  22  includes three screw holes  33  located near the center of the width of the retaining ring and spaced at approximately 120° around the circumference. Of course, any number of screw holes  33  may be used to fix retaining ring  22  on the adjustable barrel  12 . 
     As can be seen in FIGS. 2 and 9, barrel extension  24  has a threaded end  56  for attachment to the barrel body  16 , a flange  58 , and a distal end  60 , where paint pellets exit the paint ball gun  10 . Distal end  60  may include slits or other ornamentation as shown which do not affect the functionality of the gun. 
     The main body portion  26  includes a handle  62  having a trigger  64 . Along the top of main body portion  26  is an indexing line  66  that is generally aligned along longitudinal axis  28  for use as an indexing indicator for the adjustable barrel  12   
     To assemble paint ball gun  10 , inner-bore sleeve  14  is inserted into barrel body  16  with the flange  31  located at the end of the barrel body configured to receive barrel extension  24 . Barrel extension  24  is then screwed into the barrel body  16  to hold the inner-bore sleeve  14  in place by clasping flange  31  between the threaded end  56  of barrel extension  24  and shoulder  39  of barrel body  16  (FIG.  9 ). Force elements  20  are then inserted into the openings  38  of the barrel body  16 . The force elements  20  are precluded from going all the way through openings  38  because they contact inner-bore sleeve  14  which is inside the barrel body. Outer sleeve  18  is then slipped over this subassembly holding the force elements  20  in position. Outer sleeve  18  is secured in position with retaining ring  22 , by tightening the screws (not shown) extending through holes  33  onto bearing surface  37  of barrel body  16 . 
     Referring now to FIGS. 7A-7C, the arrangement of these components is displayed in a sectional view. Generally, force elements  20  are compressed between inner surface  42  of outer sleeve  18  and the exterior of inner-bore sleeve  14 . Outer sleeve  18  and inner-bore sleeve  14  limit the movement of force elements  20  radially inward or outward from the longitudinal axis  28 , but the force elements can roll around the circumference of the inner-bore sleeve  14  in the openings  38  of the barrel body  16 . The openings  38  are of sufficient size to allow the force elements  20  to pass freely through the openings while still maintaining the circumferencial position of the force elements. It should also be noted, the spacing of openings  38  corresponds to the spacing between like sized recesses  44   a - 44   e  between each quadrant of outer sleeve  18 . 
     Once the adjustable barrel  12  is assembled, gun threads  36  are generally of a standard type allowing replacement of standard paint ball gun barrels with the improved adjustable barrel  12  disclosed herein. An operator with a standard barrel may unscrew and remove the standard barrel from a standard paint ball gun and then attach the disclosed adjustable barrel  12 . This feature allows many standard paint ball guns currently on the market to fire paint ball ammunition pellets of varying diameters without the need to purchase a new paint ball gun for installation of adjustable barrel  12 . 
     To operate the adjustable barrel assembly  12 , an operator may rotate the outer sleeve  18  around the longitudinal axis  28  to adjust the diameter of the inner-bore sleeve  14  to optimize the fit of the paint pellet in the barrel. In order to set the desired inner-bore sleeve  14  diameter, the operator must supply a rotational force upon the outer sleeve  18  sufficient to rotate it, causing force members  20  to ride against the inner surface  42 . The operator would then continue rotation until the desired diameter of inner-bore sleeve  14  is achieved. It should also be appreciated that a certain amount of resistance is encountered when rotating outer sleeve  18  until force elements  20  roll out of the recesses  44  into which they are seated such that the set diameter tends to remain fixed until purposely changed by the operator. Outer surface  40  may be contoured in a manner such that the operator may obtain a better grip on the outer sleeve  18  to facilitate rotation of the outer sleeve  18  around the longitudinal axis  28 . 
     In operation, the plurality of recesses  44   a - 44   e  of outer sleeve  18  form an adjustment means in combination with the force elements  20  and barrel body  16  for adjusting the diameter of the inner-bore sleeve  14 . Recesses  44  are shaped to receive force elements  20  as shown. Outer sleeve  18  is relatively inflexible compared to inner-bore sleeve  14 , causing the diameter of inner-bore sleeve  14  to become smaller as the force elements  20  are moved from a deeper to a more shallow recess  44 . Likewise because of the resilient nature of inner-bore sleeve  14  when the force elements are moved from a more shallow to a deeper recess  44 , the diameter of inner-bore sleeve will expand and increase. 
     As the diameter of the inner-bore sleeve  14  is determined by the distance between the force elements  20  and the longitudinal axis  28 , the depth of the recesses  44  is directly proportional to the diameter of the inner-bore sleeve  14 ; i.e. the greater the depth of the recess that force elements are in, the larger the diameter of the inner-bore sleeve  14 . 
     The use of recesses  44  allows for a plurality of distinct settings to be chosen by the operator. In the embodiment shown in FIGS.  5  and  7 A- 7 C, outer sleeve  18  may be rotated approximately 90° about longitudinal axis  28 , as contact between force elements  20  and stops  50  will prevent further rotation. Also, in this embodiment the five recesses  44   a - 44   e  in each quadrant provide five distinct diameter settings for inner-bore sleeve  14 . In FIG. 7A, adjustable barrel assembly is shown with the force elements  20  and the deepest recesses  4   e  providing the largest diameter bore setting for paint ball gun  10 . In FIG. 7B, the roller elements are shown as they would appear when moving the adjustable barrel from one setting of bore diameter to another. It should be noted, that at this transition point, the diameter of inner-bore sleeve  14  is smaller than when the force elements are located in any of the recesses and correspondingly, longitudinal slit  30  is narrowest at these transition points. In FIG. 7C, adjustable barrel  12  is shown with the force elements in the shallowest recess  44   a  providing the smallest diameter bore setting for inner-bore sleeve  14 . It is possible for an operator to determine which recess the force elements are indexed in by the alignment of marking indicators  52  on outer sleeve  18  with the indexing line  66  on the main body portion  26  of gun  10 . The indexing line  66  on main body portion  26  may be a notch or marking of a different color designed to give the operator a reference point. The marking indicators  52  on the outer sleeve  18  correspond to various settings for the diameter of the inner-bore sleeve  14 . The marking indicators may be numbers or lines and may be inscribed, painted, or marked in any of a number of well known methods upon the outer surface  40  of the outer sleeve  18 . 
     As is apparent from the foregoing, the inner-bore sleeve  14  is the controlling diameter with which the paint ball pellet will travel within the barrel  12  of paint ball gun  10 . As such, the ability to compress inner-bore sleeve  14  determines the adjustability of the adjustable barrel  12 . Therefore, any embodiment of inner-bore sleeve  14  which allows for compression in a manner similar to that shown in FIG. 2 may be substituted in this invention. For example, a spiral spring shaped inner-bore sleeve  14  with an inner diameter that may be reduced upon exertion of external forces toward the longitudinal axis  28  may be readily substituted for the inner-bore sleeve  14  with longitudinal slit  30 . 
     However, it is believed that an advantage is gained when using an inner-bore sleeve  14  with a longitudinal slit  30 . Generally, paint ball pellets (not shown) are round, plastic containers filled with paint that explode upon impact with an opponent, dispersing the paint contained therein. In competition, it is advantageous to have a gun that fires straight and for the greatest distance, enabling the user to shoot at targets while staying out of range from their weapons. It is believed that longitudinal slit  30  has the effect of decreasing the rotation of the paint balls fired from paint ball gun  10 , thereby increasing the distance and speed of the ball. Further, this also increases the accuracy of the gun as less rotation of the paint ball pellet equates to straighter flight. In addition, it is believed that a paint gun  10  using the adjustable barrel  12  of the present invention may be adjusted to shoot the same distance as a standard gun by using a lower gas charge, thereby increasing the number of shots that may be taken with one carbon dioxide canister load. 
     In another embodiment of the invention, ball bearings (not shown) may be used as the force elements  20  in place of the roller pins. The ball bearings may be round metallic or hard plastic spheres capable of providing the force necessary to compress the inner-bore sleeve  14 . Although the recesses  44  may be of any shape to hold the diameter of the inner-bore sleeve  14  constant, when the force elements  20  are ball bearings, it is desired that the recesses  44  located within the inner surface  42  be complimentary to the shape of the ball bearings. This helps to ensure the operator will have an increased level of repeatability when adjusting the diameter of the inner-bore sleeve  14 . 
     Although any shaped force elements, capable of withstanding the crush force on the inner-bore sleeve may be used in the invention, generally, it is desirable to minimize the friction of force elements  20  against the inner-bore sleeve  14  unless a configuration such as shown in FIG. 6 as described below is used for the outer sleeve. In addition to the force elements  20  discussed above, which rotate with respect to inner-bore sleeve  14 , it is anticipated that other force elements capable of sliding along the outer surface of the inner-bore sleeve  14  may be substituted. An advantage to the use of a sliding force element is that the need for recesses  44  may be eliminated as the friction of the force element itself may be sufficient to hold the outer collar  18  in position when adjusting the diameter of the inner-bore sleeve  14 . A drawback to the use of sliding force elements  20  is that, over time, wear may occur on the outer surface of the inner-bore sleeve  14  and on the inner surface of the outer sleeve  18 , along with wear to the actual force element itself. A wearing in any of these three components may affect the accuracy of the settings. In addition, wear may increase the presence of particulate matter in the inner-bore sleeve  14  with particulates from the force elements  20  breaking free and slipping into the bore. 
     Referring now to FIG. 6, another embodiment of the outer sleeve is depicted and referred to by the designation  18   a . This embodiment includes a plurality of rotational stops  50  and a substantially smooth inner surface  42   a . Inner surface  42   a  slopes from a distance closer to the longitudinal axis  28  to a distance farther from the longitudinal axis  28 . Further, each portion of inner surface  42   a  located between the stops  50  has substantially the same shape and slope. This embodiment differs from the above described embodiment depicted in FIG. 5 in that it allows for gradual adjustment of the barrel diameter in the manner described below, as opposed to indexed movement. In this embodiment, the operator may set the inner-bore to any of an infinite number of diameters. In the embodiments shown, stops  50  are all the same distance from longitudinal axis  28 . However, with this arrangement, the operator may sacrifice some repeatability when selecting the diameter as there is no indexing means provided. 
     From the foregoing, it should be readily apparent that the inner surface  42  may be of any shape which has portions differing in distance from the longitudinal axis  28  to provide the varying diameter on inner-bore  14 . For example, an inner surface  42  including protrusions (not shown) in place of the recesses  44  may be used to further compress the force elements  20 , decreasing the diameter of the inner-bore sleeve  14 . It is also contemplated that the invention may be accomplished with the use of an integral force element  20  by providing a camming surface (not shown) on the exterior surface of inner-bore sleeve  14 . A mating cam surface on the outer sleeve  18  could then be used to adjust the diameter of the bore by directly compressing or allowing inner-bore sleeve  14  to return to its at-rest diameter when the outer sleeve is rotated. The two embodiments of the outer sleeve  18  disclosed above are merely meant to serve as illustrative examples of configurations that may be used for inner surface  42 . 
     Although the present invention is shown and described in detail above, the same is for purposes of example only and is not intended to limit the scope of the invention. Numerous changes and variations to the disclosed embodiment will be readily apparent to those skilled in the art without departing from the invention. Accordingly, the scope of the present invention is to be limited only by the terms of the claims.