Abstract:
The present invention is a joint assembly that enables the rapid and precise self-alignment of two portions of a pool cue. The joint assembly comprises a bushing and a pin, one coupled to each of the two cue portions, the bushing and the pin coupling in the normal male-female fashion to connect the pool cue portions. The bushing has a closed base to prevent glue from leaking into the bushing when the bushing is fastened to a portion of the pool cue. The interior of the bushing comprises a threaded region proximate to the closed base with a tapered portion where the threaded region meets a smooth bore region, and an angled entrance region between the bore region and the opening of the bushing. The pin is fastened to another portion of the pool cue and comprises a threaded head portion to engage the threaded region of the bushing.

Description:
Pool cues are commonly provided in two pieces that must be connected to assemble the pool cue for play. Typically, this connection is accomplished by means of a joint assembly comprising a pin portion and bushing portion, one located on each of the two pieces, to enable a standard type male-female coupling when the two portions are screwed together. 
     The most common joint pin and bushing on a pool cue, consists of a fully threaded pin that is screwed into a fully threaded (internal and external threads) brass insert. Aligning the two parts while trying to screw a two-piece pool cue together can be frustrating. If the two parts are not perfectly aligned, damage can be done when attempting to start the pin into the bushing, even to the extent of stripping the threads on one or both of the parts involved. 
     Joint assembly pins are commonly made of stainless steel and the bushings are made of brass. The stainless steel pins are made on a thread-rolling machine, but this method results in joint pins of variable tolerances and this makes it impossible to maintain a precision fit between the joint pins and bushings. The difficulty of maintaining precision fit is compounded when joint screws and brass inserts are made by different manufacturers. Among the problems involved is variation in the pitch on the threads between the joint pin and bushing. As a result, joint pins and bushings are not easily interchangeable between pool cues. Manufacturers of pool cues are thus currently unable to get joint pins and bushings that are reliably precision-fitting and interchangeable. 
     Lack of precision joint-assembly may result in several problems. Improper alignment of the portions of a joint can result in the stripping of the threads. Improper alignment also results in the two pieces of a pool cue being out of true and the pool cue being sub-optional for playing pool. It is also more difficult to accomplish assembly of the two pool cue pieces resulting in time wasted and frustration on the part of the user. 
     Some joint pin and bushing assemblies currently on the market attempt to accomplish a more precise alignment. However, they remain somewhat difficult to assemble and are relatively costly. They also have other flaws such as a bushing portion that allows glue to enter the interior of the bushing during assembly causing corruption of the joint assembly. 
     The present invention is directed to overcoming these limitations by providing an improved pool cue joint assembly that is self-aligning and that allows rapid and precise assembly of pool cue portions. 
     BRIEF SUMMARY OF THE INVENTION 
     The joint assembly of the present invention is for use with pool cues comprising at least two pieces. The joint assembly is comprised of a bushing portion and a pin portion that are sized and structured to enable a typical male-female coupling when the joint is assembled. A precision alignment and fit of the bushing and pin is established by sizing and structuring the mating components so that a simultaneous close fit is achieved at two points: (1) where the nose of the pin meets an interior tapered region of the bushing located just prior to the internal threaded region of the bushing, and (2) where the smooth alignment portion of the pin first meets the smooth inner bore of the bushing. The bushing has a closed base to prevent glue from leaking into the bushing when the bushing is fastened to a portion of the pool cue. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The accompanying drawings are provided to illustrate the principles of the invention only and are not necessarily drawn to scale. In the accompanying drawings: 
     FIG. 1 a  is a side view of an embodiment of the pool cue detailing the joint assembly at the area where two portions of the pool cue are coupled together. 
     FIG. 1 b  is a side view of an embodiment of the pool cue without the joint assembly at the area where two portions of the pool cue are coupled together. 
     FIG. 2 is a side view of the bushing with labels referencing the actual dimensions of one embodiment thereof. 
     FIG. 3 is a side view of the pin with labels referencing the actual dimensions of one embodiment thereof. 
     FIG. 4 is a side view of a joint protector for the bushing on one portion of the pool cue. 
     FIG. 5 is a side view of a joint protector for the pin on one portion of the pool cue. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now specifically to the Figures, in which identical or similar parts are designated by the same reference numerals throughout, a detailed description of the present invention is given. It should be understood that the following detailed description relates to the best presently known embodiment of the invention. However, the present invention can assume numerous other embodiments, as will become apparent to those skilled in the art, without departing from the appended claims. 
     Referring to FIG. 1 a  and FIG. 1 b,  pool cue  10  is depicted as comprising a first cue portion  12  (here shown as the lower butt of a pool cue) and a second cue portion  14  (here shown as an upper pool cue shaft) joined together by a joint assembly  11 . 
     Joint assembly  11  comprises a pin  15  fastened to the first cue portion  12  and a bushing  13  fastened to the second cue portion  14 . Assembly of pool cue  10  is attained when pin  15  and bushing  13  join in a typical male-female coupling to connect the first and second cue portions ( 12  and  14 ) in a precise alignment. Though a pool cue typically comprises two portions, a butt and a shaft, the joint assembly  11  may be applied to join any number of portions in pool cues comprising more than two portions. 
     Bushing  13  has a sidewall  34  defining an open anterior end and an opening  35 , and a closed posterior end defining a base  24 . The base is closed to prevent glue from entering the open interior portion of the bushing  13  when it is fastened to the second cue portion  14 . 
     The sidewall  34  of the bushing  13  has an exterior surface  33  and an interior surface  32 . The exterior surface  33  has a posterior threaded portion  16  and an anterior slightly threaded portion  25 , the threads of the anterior portion  25  being less dense than those of the posterior portion  16 . The second cue portion  14  (see, FIG. 1 b ) has a centered threaded bore  40  extending inwardly along a longitudinal axis from a center end face  41 . The posterior and anterior threaded portions ( 16  and  25 ) of the exterior surface of bushing  13  (FIG. 1 a ), are adapted to securely locate the bushing  13  in the threaded bore  40  of the second cue portion  14  by screwing and gluing them together. 
     The interior surface  32  of the sidewall  34  comprises a posterior threaded region  23 , a smooth bore region  17  anterior thereto, and an angled entrance region  37  between the bore region  17  and the opening  35 . The threaded region  23  also forms a smooth tapered region  22  where it joins the bore region  17 . 
     Pin  15  comprises a smooth truncated nose portion  21 , atop a threaded head portion  18  at an anterior end of the pin  15 , a threaded tail portion  20  at the posterior end and a smooth middle portion  19  located between the head portion  18  and the tail portion  20 . 
     The first cue portion  12  (see, FIG. 1 b ) has a centered threaded bore  30  extending inwardly along a longitudinal axis from a center end face  31 . The tail portion  20  (FIG. 1 a ) is threaded and thereby adapted to securely locate the pin  15  in the threaded bore  30  (FIG. 1 b ) of the first cue portion  12  by screwing and gluing them together. The remaining nose  21  and head  18  portions and a part of the middle portion  19  extend outward from the first cue portion  12 . 
     The middle portion  19  (FIG. 1 a ) is smooth and functions in aligning the pin  15  with the bushing  13 . The head portion  18  is threaded and topped by a nose portion  21  that is smooth, truncated and tapers to form a slightly pointed tip at the terminus of the pin  15 . 
     The first and second portions of the cue ( 12  and  14 ) are connected when the head portion  18  of the pin  15  is inserted through opening  35  of the bushing  13  and slid into its smooth bore  17 . The angled entrance  37  and smooth bore  17  regions of the bushing  13  serve to guide the nose  21  of pin  15  into the bushing  13 . When the nose  21  meets the tapered region  22  of bushing  13 , the smooth middle portion  19  of pin  15  is simultaneously in contact with the smooth bore region  17  of bushing  13 . Furthermore, the middle portion  19  of the pin  15  and the smooth bore region  17  of the bushing  13  are sized to accomplish a close fit (generally, within 0.0003 inches) when the two are coupled. 
     The result of the simultaneous contact of nose  21  and smooth middle portion  19  of pin  15  with the tapered region  22  and smooth bore region  17  of the bushing  13 , respectively, together with the sizing for a close fit, is a precise alignment prior to the engagement of their respective threaded regions ( 18  and  23 ). This precision fit at two points prevents side play (looseness). When the first and second portions of cue  10  are screwed together by coupling of the bushing  13  and pin  15 , first and second portions of the pool cue  10  align precisely. 
     Threading may be easily and flawlessly accomplished thereafter because of the precise alignment achieved at insertion of the pin  15  into the bushing  13 . The precise alignment of bushing  13  and pin  15  results in an assembled pool cue that is straight and true. Precise alignment also avoids cross threading and the stripping of threads that often accompanies attempts to couple bushing  13  and pin  15  when they are misaligned. The number of turns required to assemble the two cue portions are minimized. Approximately two to three turns are required for the two cue portions to be fully assembled and threaded. The precise alignment of pool cue portions  12  and  14  furthermore eliminates unwanted noise when hitting a cue ball with pool cue  10  and assures efficient energy transfer from second cue portion  14  to the first cue portion  12 . 
     Referring now to FIG. 2, the specifications of an embodiment of bushing  13  are depicted. Though precise measurements are given in the following, they are meant to provide a guide to the general proportions of the present invention only. 
     The smooth interior bore  17  of bushing  13  has an internal diameter ID 1  of 0.323 inches, and a length L 6  of 0.440 inches. The smooth bore  17  is preceded by the short angled entrance region  37  with walls at a 45° angle A 1  for ease of entrance of the pin  15 . ID 1  is followed by a tapered region  22  with a 63° angle A 2  with a length L 7  of 0.060 inches, followed by the threaded region  23  of {fraction (5/16)}-14 threads per inch (TPI) with a major pitch internal diameter ID 2A  of 0.308 inches and a minor pitch internal diameter ID 2B  of 0.252 inches and a length L 8  of 0.368 inches. ID 2  is followed by an unthreaded smooth basal portion  39  with an internal diameter ID 3  of 0.250 inches with a length L 9  of 0.125 inches, which then extends on its external surface at an angle A 3  of 130° to the base  24  of the bushing  13  which is a length L 10  of 0.030 inches. L 10  is followed by a solid area with the length L 11  of 0.032 inches to the end of the bushing  13 . 
     The bushing  13  has an optional outer should  38  with a diameter OD 1  of 0.488 inches with a radius R 1  of 0.1 inches, and a length L 1  of 0.048 inches, followed by a smooth area on the shoulder  38  with a length L 2  of 0.077 inches. The shoulder  38  is an optional component of the bushing  13 . 
     The bushing  13  has an outer diameter OD 2  of 0.441 inches +/− 0.001 with an area threaded {fraction (7/16)}-14 TPI to a depth of only 0.010 inches to allow for glue and a length L 3  of 0.340 inches, followed by a threaded major pitch outer diameter OD 3A  of 0.434 inches,  {fraction (7/16)}-14  TPI, with a minor pitch outer diameter OD 38B  of 0.364 +/− 0.001, and a length L 4  of 0.420 inches, for securing the bushing to the second cue portion  14 ; then extends at an angle A 4  of 71° and a length L 5  of 0.170 inches which terminates at the external base end of the bushing with an outer diameter OD 4  of 0.325 inches. The bushing  13  has an overall length L 13  of about 1.055 inches. 
     FIG. 3 depicts an embodiment of the pin  15  in which the tip of the nose portion  21  has a 0.112 perimeter of arc with a radius R 20  of 0.135 inches followed by a 0.211 perimeter of arc with a radius R 21  of 0.450 inches and a length L 20  of 0.215 inches, threaded head portion  18  of {fraction (5/16)}-14 TPI with a major pitch outer diameter OD 21A  of 0.3075 +/− 0.0005 inches and a minor pitch outer diameter OD 21B  of 0.263 +/− 0.0005 inches, with a length L 21  of 0.270 inches, followed by a 65° angle A 22  with a length L 22  of 0.075 inches, followed by a smooth unthreaded middle portion  19  with an outer diameter OD 23  of 0.3225 +/− 0.0003 inches, and a length L 23  of 0.800 inches, followed by a threaded tail portion  20  of {fraction (5/16)}-14 TPI with a major pitch outer diameter OD 24A  of 0.307 +/− 0.0005 inches and a minor pitch outer diameter OD 24B  of 0.262 +/− 0.0005 inches, with a length L 24  of 1.073 inches, followed by an unthreaded outer diameter OD 25  of 0.205 inches and a length L 25  of 0.087 inches. The pin  15  has an overall length L 26  of abot 2.520 inches. 
     FIG. 4 depicts a bushing joint protector  150  which can be coupled to bushing  13  to protect bushing  13  against damage while the pool cue  10  is disassembled. Bushing joint protector  150  depicts an embodiment in which the tip of a nose portion  127  has a 0.112 perimeter of arc with a radius R 120  of 0.135 inches followed by a 0.211 perimeter of arc with a radius R 121  of 0.450 inches and a combined length L 120  of 0.215 inches, a threaded head portion  118  of {fraction (5/16)}-14 TPI with a major pitch outer diameter OD 121A  of 0.3075 +/− 0.0005 inches and a minor pitch outer diameter OD 121B  of 0.263 +/− 0.0005 inches, with a length L 121  of 0.335 inches, followed by a smooth unthreaded middle portion  128  with an outer diameter OD 123  of 0.3225 +/− 0.0003 inches, and a length L 123  of 0.375 inches, followed by an interior width of shoulder groove IW 123  of 0.560 inches with a depth D 126  of 0.150 inches, followed by an end knob  129  with a length L 124  of 0.455 inches (excluding the shoulder groove) and an outer diameter OD 122  of 0.855 inches. Bushing joint protector  150  has an overall length L 126  of 1.380 inches, whereas, threaded head portion  118  mates with interior threaded region  23  of bushing  13  so that bushing joint protector  150  can be screwed to bushing  13 . 
     FIG. 5 depicts an embodiment of a pin joint protector  160  which can be coupled to pin  15  to protect the mating end of a the shaft. Pin joint protector  160  has a smooth interior bore  137  with an internal diameter ID 132  of 0.323 inches, and a length L 130  of 0.440 inches. The smooth bore  137  is followed by a tapered region  138  with a 63° angle A 131  with a length L 131  of 0.060 inches, followed by a threaded region  139  of {fraction (5/16)}-14 threads per inch (TPI) with a major pitch internal diameter ID 133A  of 0.308 inches and a minor pitch internal diameter ID 133B  of 0.252 inches and a length L 132  of 0.368 inches, which mates with threaded head portion  18  of pin  15 . Threaded region  139  is followed by an unthreaded smooth area  141  with an internal diameter ID 134  of 0.250 inches with a length L 133  of 0.125 inches, which then extends at an angle A 132  of 130° to the base  140  of pin joint protector  160  which is a length L 134  of 0.037 inches. Unthreaded smooth area  141  is followed by a solid area  142  with the length L 137  of 0.045 inches to the end of the pin joint protector  160 . The pin joint protector  160  has an overall length L 136  of 1.075 inches, an inside length L 135  of 1.030 inches, and an outer diameter OD 132  of 0.855 inches. 
     Bushing and pin joint protectors  150  and  160  are preferably made out of acetyl, but alternatively, can be made of other suitable materials such as steel, aluminum, brass, wood, and the like.