Patent Publication Number: US-6668815-B1

Title: Self-aligning paintball gun barrel assembly with optional bore size adapter

Description:
FIELD OF THE INVENTION 
     The present invention is directed generally to paintball guns; and, more particularly, to a self-aligning multi-part paintball gun barrel assembly. 
     BACKGROUND OF THE INVENTION 
     Pneumatic paintball guns launch fluid-filled projectiles by controlling the release of compressed gas from the gun. The fluid-filled projectiles, variously denominated as shooting capsules, marking pellets, and paintballs (hereinafter generically referred to as “paintballs”) are generally made of a fragile shell filled with biodegradable “paint.” When a competitor or other object is hit with a paintball, the shell ruptures and the paint is released onto and marks the target, thereby providing evidence of the hit. 
     As can be appreciated, it is desirable to have a pneumatic paintball gun that provides accurate and consistent aiming. However, this has proved somewhat problematic in the prior art due, at least in part, on variations in the paintballs themselves. Although the shell of a paintball ideally has a diameter of 0.68 inches, paintballs in practice have varying diameters. Real paintballs typically vary from between 0.65 to 0.70 inches, due to variations among manufacturers and other factors, such as ambient weather conditions. 
     Separately, it has proven desirable to have paintball gun barrels formed of two or more pieces connected in series that may be disassembled in order to make storage and transport easier. Because such arrangements typically have two parts, a shank portion that attaches to the paintball gun body and a muzzle portion that attaches to the distal end of the shank, these arrangements are commonly referred to as “two-piece” paintball gun barrels. When the two pieces of the barrel are designed to be connected via a simple threaded connection, as is typical, one problem that commonly arises is providing good alignment between the bores of the two portions. This is due to the very tight dimensional control needed to size the features appropriately and to keep the bores concentric with the threads on the mating ends of the two barrel pieces. If the two bores are not concentric where they meet, a lip may be formed in the combined barrel bore that has a tendency to rupture the skin of the paintballs while the paintballs are being fired through the barrel, leading to obviously poor performance and user dissatisfaction. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a paintball gun barrel assembly. The paintball gun barrel assembly includes a muzzle portion that removably couples to a shank assembly. The shank assembly is adapted to mate to a paintball gun body and has an internal first bore therethrough and a first angled surface on an output end thereof substantially concentric with the first bore thereat. The muzzle portion has a second bore, an output end, and an input end; the input end having a second angled surface substantially concentric with the second bore. Mating the muzzle to the shank assembly causes the respective angled surfaces to inter-engage and thereby causes the first bore at the output end of the shank assembly to substantially align with the second bore at the input end of the muzzle. Thus, the shank assembly and the muzzle are self-aligning with respect to each other. 
     In some embodiments, the shank assembly includes an insert housing with a first removable bore tube insert. The insert housing is adapted to mate to the paintball gun body and has a longitudinal internal passage. The bore tube is adapted to removably fit in the internal passage of the insert housing. The first angled surface and the first bore are associated with the bore tube. With the first bore tube disposed in the insert housing and the insert housing mated to the muzzle portion, engaging the first angled surface with the second angled surface causes the first bore at the output end of the first bore tube to substantially align with the second bore at the input end of the muzzle portion. Thus, in these embodiments, the bore tube portion of the shank assembly and the muzzle are self-aligning with respect to each other. 
     In other embodiments of the present invention, a plurality of different size bore tubes may be used, each having a different internal bore diameter but the same outer dimensions. With such an arrangement, a user may readily change the effective bore diameter of shank assembly to accommodate different sizes of paintballs. The user need only remove the muzzle by unscrewing it from the shank assembly, slide the first bore tube out from the insert housing, insert a new bore tube into the insert housing, and reattach the muzzle. Note that no special alignment process is needed, as the muzzle and bore tubes are self-aligning. Further, the entire barrel bore size change process can be accomplished without removing the insert housing from the gun body. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows one embodiment of the paintball gun barrel assembly of the present invention mated to a paintball gun body. 
     FIG. 2 shows one embodiment of the paintball gun barrel assembly of the present invention. 
     FIG. 3 shows an exploded view of the components of FIG.  2 . 
     FIG. 4 is a partial cross-sectional view of the coupling between the muzzle and the shank assembly of FIG.  2 . 
     FIG. 5 shows an exploded view of another embodiment of the present invention including two different sized bore tubes. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As illustrated in FIG. 1, a paintball gun, generally designated  10 , is shown with a barrel assembly  30  according to the present invention. The gun  10  may take any form known in the art, and typically includes a main gun body  12  having a trigger  14 , a magazine  16 , and an air hose  18  connected to a supply of pressurized air. Relevant to the present discussion, the main gun body  12  typically includes an internally threaded orifice leading to its firing chamber; the gun barrel assembly  30  of the present invention is intended to mate to the gun body  12  via this threaded orifice. As the other details of the paintball gun  10  are not necessary for understanding the present invention by one of ordinary skill in the art, they are omitted for brevity. Examples of suitable paintball guns are available commercially from Worrgame Products of Corona, Calif. and WDP of Birmingham, England. 
     The gun barrel assembly  30  attaches to the main gun body  12 . The gun barrel assembly  30  includes a muzzle portion  40  distal from the gun body  12  and a shank assembly  60  connecting the muzzle portion  40  to the gun body  12 . Referring to FIGS. 2-4, the muzzle portion  40  (or simply “muzzle”) is generally elongate with a bore  42  running therethrough along a longitudinal axis  44 . As illustrated, the distal portion of the muzzle  40  may include a plurality of holes and/or flarings as known in the art. The proximal portion of the muzzle  40  includes external threads  46 , an external shoulder  48 , and an angled surface  50 . The external shoulder  48 , which is disposed distal to the threads  46 , provides a stop for a optional seal  49 , such as an elastomeric O-ring. The angled surface  50  is disposed at the input end of the bore  42  of the muzzle  40 , and takes the form of a ring around the entry to the bore  42 . Accordingly, the bore  42  may be described as having a chamfered entry. Of course, the angular surface  50  need not be a flat surface, but this may be advantageous; indeed a flat surface at an inward angle in the range of 5°-60°, and more particularly of approximately 10-15°, may be most advantageous. The angled surface  50  and the bore  42  should be concentric about the longitudinal axis  44 . As is explained further below, the muzzle  40  releasably couples to the shank assembly  60 , such as via a threaded coupling comprising threads  46 . 
     The shank assembly  60  connects the muzzle  40  to the main gun body  12 . The shank assembly  60  of FIG. 3 includes insert housing  70  and a bore tube  90 . The insert housing  70  acts as the main support for the shank assembly  60 , and is adapted to mate to the paintball gun main body  12 . The insert housing  70  has a longitudinal internal passage  72 , external threads  80  on its proximal end, internal threads  78  on its distal end, and may optionally include a viewing window  82 . The internal passage  72  extends the length of the insert housing  70 , from the proximal face  76  to the distal face  78 . The internal passage  72  advantageously includes a shoulder  73 , such as where a larger diameter inner wall extending from the distal face  78  meets a smaller diameter inner wall extending from the proximal face  76 . 
     The bore tube  90  is a generally elongate body having a longitudinal bore  92  disposed along a longitudinal axis  94  that extends from an input end  96  to an output end  98 . The output end  98  of the bore tube  90  includes an angular surface  100  that takes the form of a ring about the exit from the bore tube  90 . Thus, the bore tube  90  may be said to have a chamfered exit. Once again, the angular surface  100  need not be a flat surface, but a flat surface at an outward angle of approximately 10-15° may be most advantageous. Further, it should be noted that the angular surface  50  of the muzzle  40  and the angular surface  100  of the bore tube  90  should be complimentary, so that the two angular surfaces  50 , 100  may engage one another. The angular surface  100  and the bore  92  of the bore tube  90  should be concentric about the longitudinal axis thereof  94 . The external portion of the bore tube  90  may advantageously include an outwardly extending shoulder section  102  located slightly toward the input end  96  from the angular surface  100 . It is intended that this shoulder section  102  be spaced from the input end  96  of the bore tube  90  such that when the shoulder section  102  of the bore tube  90  engages the corresponding shoulder  73  on the insert housing  70 , the input end  96  of the bore tube  90  is flush with the proximal face  76  of the insert housing  70 . 
     Advantageously, the bore tube  90  removably fits within the internal passage  72  of the insert housing  70 , with the insertion of the bore tube  90  being from the direction of the distal face  74  towards the proximal face  76 . As such, the outer dimensions of the bore tube  90  should be sized accordingly. However, the outer dimensions of the bore tube  90  should advantageously be sized as large as possible while still maintaining a sliding fit within the insert housing  70 , so that the internal walls of the insert housing  70  provide radial support for the bore tube  90 . In addition, the outer surface of the bore tube  90  may include one or more grooves  104  for accepting corresponding optional collars  106 , such as common O-rings, to provide a small amount of friction to help slightly retain the bore tube  90  within the insert housing  70  during assembly and disassembly, while still allowing the output end  98  of the bore tube  90  to radially float somewhat within the insert housing  70 . There may be one seal  106 , preferably located towards the end nearest the muzzle portion  40 , or there may be a plurality of seals  106  disposed in spaced relation to one another, if desired. 
     The barrel assembly  30  of FIGS. 3-4 allows for self-alignment of the bore tube  90  with the muzzle  40 , thereby allowing for lower cost production of “two-piece” barrels. The user slides the bore tube  90  into the insert housing  70  from the distal face  74  of the insert housing  70 , with the input end  96  inserted first. When inserted fully, the angled surface  100  of the bore tube  90  disposed towards the distal face  74  of the insert housing  70 . The muzzle  40  is then attached to the insert housing  70 , and screwed into place. The displacement of the muzzle  40  towards the insert housing  70  during the screwing process causes the angled surface  50  of the muzzle  40  to engage the angled surface  100  of the bore tube  90 . As the muzzle  40  becomes fully threaded in place, the shoulder section  102  on the bore tube  90  engages the corresponding shoulder  73  in the internal passage  72  of the insert housing  70 . As such, the distal portion of the bore tube  90  is trapped between the shoulder  73  of the insert housing  70  on one side and the angled surface  50  of the muzzle  40  on the other, resulting in firm engagement of the respective angled surfaces  50 , 100 . Because the bore tube  90  is allowed to float very slightly within the insert housing  70 , the engagement of the angled surfaces  50 , 100  causes the longitudinal axis  44  of the muzzle  40  and the longitudinal axis  72  of the bore tube  90  to become aligned, thereby self-aligning the bores  42 , 92  of the muzzle  40  and the bore tube  90 . 
     The gun barrel assembly  30  of the present invention may include one or more additional bore tubes  120 . The various bore tubes  90 , 120  should have the same outer dimensions, but may advantageously have bores of different inner diameters. With such an arrangement, a user may readily change the effective bore size of shank assembly  60  to accommodate different sizes of paintballs. The user need only remove the muzzle  40  by unscrewing it from the shank assembly  60 , slide the first bore tube  90  out from the insert housing  70 , insert a new bore tube  120  into the insert housing  70 , and reattach the muzzle  40 . Note that no special alignment process is needed, as the muzzle  40  and bore tubes  90 , 120  are self-aligning. Further, notice that the entire process can be accomplished without removing the insert housing  70  from the gun body  12 . 
     To aid in distinguishing the various sizes of bore tubes  90 , 120 , and identifying the one currently in use, the different (bore) sizes of bore tubes  90 , 120  may be color coded, with the color visible through the viewing window  82  on the insert housing  70 . For instance, bore tubes  90  with an inner diameter of 0.660 inches may be colored red, bore tubes  120  of inner diameter 0.663 inches may be orange, bore tubes  120  with an inner diameter of 0.700 inches may be blue, and so forth. Of course, the various bore diameters of the bore tubes  90 , 120  should not be larger than the diameter of the bore  42  of the muzzle  40 , so that the paintball does not encounter an inwardly extending lip and rupture inside the barrel assembly  30 . 
     The gun barrel assembly  30  of the present invention may be sold as separate components, such as a shank assembly  60  alone for a user that already owns a muzzle  40 , or as a collection or kit of an insert housing  70 , a muzzle  40 , a plurality of different size bore tubes  90 , 120 , and an optional carrying case (not shown). 
     One embodiment of the paintball gun barrel assembly  30  of the present invention include a muzzle portion made from 6061-T6 aluminum, with an insert housing  70  made from  303  stainless steel with a 0.748 inch diameter internal passage  72  (upstream from shoulder  73 ) and a shoulder  73  of 0.805 inches, and a bore tube  90  made from 6061-T6 aluminum and approximately six inches long, with an outer diameter upstream from the shoulder  102  of 0.7465 inches and a shoulder  102  of 0.803 inches. The angled surfaces  50 , 100  may be approximately 11.5° by {fraction (3/16)} inch chamfer. The overall length of the barrel assembly may be generally about twelve to sixteen inches. 
     The discussion above has assumed that the shank assembly  60  and muzzle  40  of the barrel assembly  30  mate via a threaded coupling (e.g., threads  46 , 78 ). However, a threaded coupling, while advantageous, is not required. Indeed, any form of coupling between the two parts  30 , 60  known in the art may be used, including a bayonet-type coupling, etc. 
     In addition, the discussion above has assumed that the shank assembly  60  comprises at least two parts—an insert housing  70  and a distinct bore tube  90 . However, the self-aligning aspects of the present invention may also be realized with an alternate gun barrel assembly embodiment using a single-piece shank assembly  60  that does not include a bore tube  90  removable from an insert housing  70  but with the two parts  70 , 90  instead integrally formed into a single part. Such a shank assembly  60  would still have a bore  92  and a angled surface  100  on the distal end thereof. The mating of the shank assembly  60  to a muzzle portion  40  would cause the respective angled surfaces  50 , 100  to engage and thereby align the bore  92  of the shank assembly  60  at the output end thereof with the bore  42  of the muzzle  40  at the input end thereof. Of course, it should be realized that changing bore sizes of the shank assembly  60  in such an arrangement may require replacement of the existing shank assembly with a new shank assembly with a different size of bore  92 . 
     The present invention may, of course, be carried out in other specific ways than those herein set forth without departing from the essential characteristics of the invention. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.