Patent Publication Number: US-8118693-B2

Title: Practice bat

Description:
PRIORITY CLAIM 
     This application claims the benefit of U.S. Provisional Patent Application 61/163,707 filed 26 Mar. 2009 for PRACTICE BAT. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an article of manufacture used for practicing batting technique. 
     SUMMARY OF THE INVENTION 
     A practice bat includes an elongated shaft having a free sliding region. In an embodiment, the free sliding region is followed by a first damping region followed by a second damping region. A slider and a damper substantially surround the shaft. The slider is moved from the free sliding region toward a free end of the shaft when the shaft is swung from a handle end, the damper is pushed toward the free end of the shaft when it is impacted by the slider and the damper dissipates slider kinetic energy and tends to bring the slider to rest. The resting position of the damper relative to markings on the shaft in the first damping region is operative to indicate swing quality. 
     In another embodiment a practice bat comprises an elongated shaft, the shaft having a gripping region and a free sliding region. A bumper is fixed to the shaft adjacent to the free sliding region and an end stop is fixed to a distal end of the shaft. A carrier assembly including a carrier tube and a replica sports ball circumferentially engages the carrier tube and the carrier tube has a cylindrical section and a rim at one end, the rim having an outer diameter greater than that of the cylindrical section. The carrier tube circumferentially engages the shaft free sliding region. The carrier assembly is operative to translate along the shaft in response to inertial forces, the motion of the carrier tube being limited by the bumper and the end stop. Gripping and swinging the shaft causes the carrier assembly to move along the shaft free sliding region, the carrier tube to strike the end stop, the ball to break free from the carrier tube, the ball to pass over the end stop, and the ball to take flight. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is described with reference to the accompanying figures. These figures, incorporated herein and forming part of the specification, illustrate embodiments of the present invention and, together with the description provide examples enabling a person skilled in the relevant art to make and use the invention. 
         FIG. 1  is a perspective view of a practice bat in accordance with the present invention. 
         FIG. 2  is a perspective exploded view of parts of the practice bat of  FIG. 1 . 
         FIG. 3  is a first side view of a portion of the practice bat of  FIG. 1 . 
         FIG. 4  is a second side view of a portion of the practice bat of  FIG. 1 . 
         FIG. 5  is an electrical diagram of a circuit of the practice bat of  FIG. 1 . 
         FIG. 6A  is a cross-section of a portion of the practice bat of  FIG. 1 . 
         FIG. 6B  is an illustration of two relevant diameters of the practice bat of  FIG. 1 . 
         FIG. 7A  illustrates a second practice bat in accordance with the present invention. 
         FIG. 7B  illustrates the practice bat of  FIG. 7A  with the carrier assembly in a second position. 
         FIG. 7C  illustrates the practice bat of  FIG. 7A  with the carrier assembly in a third position. 
         FIG. 8  is an exploded view of the parts of the practice bat of  FIG. 7A . 
         FIG. 9  is an exploded view of a third practice bat in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The disclosure provided in the following pages describes examples of several embodiments of the invention. The designs, figures, and description are non-limiting embodiments of the invention. Other embodiments of the disclosed device may or may not include the features described herein. Moreover, disclosed advantages and benefits may apply to only certain embodiments of the invention and should be not used to limit the disclosed inventions. 
       FIG. 1  shows a perspective view  100  of a practice bat in accordance with the present invention. An elongated shaft  102  has a handle end  103  and an opposed free end  105 . Near the handle end, a shaft gripping region  118  is located between an end knob  104  and a first bumper  110  that is spaced apart from the end knob. A slider  106  that substantially encircles the shaft is located between the first bumper and a damper ring  112  and is free to move therebetween. 
       FIG. 2  shows an exploded view  200  of parts of the practice bat of  FIG. 1 . In an embodiment, an end stop  108  is fitted to the shaft  102  near the free end  105 . Embodiments of the end stop having differing weights attributable to one or more of end stop dimensions, material density and end stop attachments provides a means for adjusting a bat dynamics during a swing, for example during batter training or batter warm-up. 
     In various embodiments, suitable means known to persons of ordinary skill in the art are used to fix or removably fix the end stop  108  to the shaft  102 . Such means include pins such as roll pins  204  passing through the shaft and the end stop (as shown), similarly situated screws, similarly situated bolts, interference fits, use of adhesives, screw threads within a bore of the end piece and mating screw threads on the interfacing region of the shaft, spring loaded fasteners, other fasteners and other similar means. Where an end stop  108  is used, some embodiments include a second bumper  114  encircling the shaft  102  and abutting the end stop. 
     The end knob  104  is fitted to the shaft in a manner similar to that used for the end stop. In some embodiments, the end knob is fixed to the shaft using a pin such as a roll pin  206  passing through the shaft  102  and the end knob (as shown). 
     The shaft  102  may be made of any suitable rigid material including wood and metallic materials commonly used for ball sports bats known by persons of ordinary skill in the art. In an embodiment the shaft is tubular. In an embodiment the shaft has a hollow portion  305  (see  FIG. 3 ). In other embodiments, the shaft is solid such as is common for a wooden baseball bat. 
     The damper  112  may be made of any material suited for interacting with the shaft  102  to resist relative motion therebetween. For example, one or more synthetic and natural materials are used in various embodiments including rubbers, plastics, corks, woods, and similar materials. Further, one or more rubbers such as butyl, ethylene propylene diene monomer, fluorocarbon, silicon, vulcanized, non-vulcanized and resilient rubbers are used in some embodiments. In an embodiment, the damper is an O-Ring made from a suitable elastomer such as one of the rubbers mentioned above. In various embodiments using O-Rings, the O-Ring cross-sectional shape is circular, arced or prismatic. 
     The first and second bumpers  110 ,  114  may be made of any material suited for being impacted by the slider  106 . For example, one or more synthetic and natural materials with shock resistant characteristics are used in various embodiments including rubbers, plastics, corks, woods, and resilient materials. In particular, one or more plastics including PVC, ABS, HDPE, acetal resin such as DuPont Delrin® and resilient plastics are used in some embodiments. Further, one or more rubbers such as butyl, ethylene propylene diene monomer, fluorocarbon, silicon, vulcanized, non-vulcanized and resilient rubbers are used in some embodiments. In an embodiment, the bumpers are O-Rings made from a suitable elastomer such as one of the elastomers mentioned above. 
     The slider  106  may be made of any material suited for sliding on a shaft subjected to swinging motions and suited for impacting the above described bumpers  110 ,  114 . In various embodiments, the slider is made from one or more of the materials suited for making bumpers and metallic materials such as alloys and/or compounds of aluminum, steel, copper, stainless steel, titanium and other suitable metals. For example, a multipart slider having a metallic body extending between plastic end pieces is used in an embodiment. In another embodiment, a plastic damper such as a PVC tube is used. 
     In some embodiments, the slider  106  includes an anti-friction material at a slider end-face  130  for minimizing the coefficient of friction between the end-face and the damper  112 . Persons of ordinary skill in the art will understand that suitable anti-friction materials are chosen in relation to the selected damper material. In various embodiments, one or more antifriction materials containing Teflon®, silicon, nylon, polyethylene, inorganic lubricants, organic lubricants and the like is used. In some embodiments, one or both of the damper and the slider are made from one or more of these antifriction materials. 
     The knob  104  may be made of any material suited to rigorous use associated with a practice bat. These materials include the materials of construction of the bumpers  110 ,  114  listed above. The end stop  108  may be made of any material suited to rigorous use associated with a practice bat, fitment to the shaft  102  and impacts caused by the slider  106 . These materials include the materials of construction of the bumpers listed above. 
     Along the length of the practice bat l 1  there is a gripping region  118 , a free sliding length or region l 2  is followed by a first damping length or region l 3 . In an embodiment, a second damping length or region l 4  follows the third damping length. Within the free sliding length, the slider  106  typically moves along the shaft  102  without being impeded by the damper ring  112 . Within the first damping length, a damper ring will, if present, impede movement of the slider as the slider must push the damper ring as it translates along the first damping length toward the free end  105 . Within the second damping length, a damper ring will, if present, impede movement of the slider as the slider must push the damper ring as it translates along the second damping length toward the free end. 
     In an embodiment, the first damper length l 3  includes one or more indicators  211   a - e  for indicating position along the length of the shaft  102 . For example, in the embodiment shown there are five indicators  211   a - e  in the form of marks such as marks made with colorants or pigments, deformations, embedments or the like. As shown in the figure, the marks encircle the shaft in the form of a continuous ring. In another embodiment, the marks are discontinuous such that they do not form a continuous ring around the shaft but take, for example, the form of discrete points or arc-like segments. 
     In an embodiment, the first bumper  110  encircles the shaft and a holding means tends to prevent movement of the bumper relative to the shaft. In some embodiments, a holding means includes a shallow circular groove  202  in the shaft in which the bumper is seated; here, a peripheral portion of the bumper protrudes above the outer surface of the shaft. In other embodiments, the holding means includes one or more of mechanical fasteners and adhesives. 
       FIG. 3  shows a first side view  300  of a portion of the practice bat of  FIG. 1 . Here, the slider  106  is shown spaced apart from the end stop  108  and abutting the damper ring  112  that is between the free end of the shaft  105  and an indicator mark  116 . 
       FIG. 4  shows a second side view  400  of a portion of the practice bat of  FIG. 1 . Here, the slider  106  is shown abutting the damper ring  112  and the damper ring is shown abutting the end stop  108 . 
     In an embodiment, an electric annunciator  304  for providing signals to a user of the practice bat is provided. Suitable annunciators include devices providing visible, audible, tactile and other signals  402  perceptible by a user of the practice bat  100 . Devices providing visible signals include lamps, lights, light emitting diodes, filament devices, plasma devices, laser devices and other known devices for visible signaling. Devices providing audible signals include buzzers, horns, speakers, mechanical devices, piezoelectric devices and other known devices for aural signaling. Devices providing tactile signals include buzzers, electrical stimulators, thermal stimulators, motion stimulators, piezoelectric devices and other known devices for tactile signaling. 
     Where an electric annunciator  304  is used, some embodiments have no damper ring  112 . Other embodiments relocate the damper ring  112   a  to abut the bumper  114  to avoid a need to reposition the damper ring after one or more swings. 
     In an embodiment, the practice bat  100  includes an electrical circuit including the annunciator  304 . For example,  FIG. 5  is an electrical diagram  500  of a circuit of the practice bat of  FIG. 1 . As can be seen, the annunciator  304  is actuated when a pushbutton  302  of the switch  301  closes the circuit and energy from an energy storage element such as a battery  506  flows through interconnecting electrical conductors such as wires or printed circuits  508 ,  510 ,  512  to the annunciator. 
     In various embodiments having an elastomeric damper, the damper slows the impacting slider  106  when, among other things, the damper drags on the shaft and/or the damper rolls on the shaft. In an embodiment, the shaft surface material and finish and the damper material are chosen to provide a suitable coefficient of friction and contact force for slowing the slider due to frictional drag between the damper and the shaft. Contact force is determined here by, among other things, the elasticity of the damper material, the thickness of the damper material and the unstretched inner diameter of the damper. 
     Where it is desired to prevent rolling of the damper  112  on the shaft  102 , a damper having a prismatic cross-section such as a rectangular or triangular cross-section may be chosen. Here, the damper tends to stop the slider&#39;s motion relative to the shaft when, among other things, a stick-slip interaction between the shaft and the damper causes cyclic damper flexing and, among other things, conversion of kinetic energy to heat as a result of losses including mechanical hysteresis losses. 
     Where rolling of the damper  112  on the shaft  102  is desirable, embodiments having a damper with a circular cross section may be chosen. In such an embodiment the damper slows the slider by, among other things, cyclic flexing. 
       FIG. 6   a  is a cross-section  600   a  of a portion of the practice bat shaft. Shown here is the slider  106  encircling the shaft  102  and abutting an elastomeric damper  112  having a substantially circular cross-section. Positions C 1 , C 2  and C 3  indicate successive positions of the damper as it is forced along the shaft by a translating slider  106 . At position C 1 , a point “x” on the periphery of the damper is in contact with the shaft as indicated by rotational arrow “n 1 .” At position C 2 , the point “x” on the periphery of the damper is directly opposite the shaft due to rotation indicated by arrow “n 2 .” At position C 3 , the point “x” on the periphery of the damper is again in contact with the shaft as indicated by arrow “n 3 .” 
       FIG. 6   b  illustrates two diameters, “d 1 ” and “d 2 ”  600   b . Diameter “d 1 ” corresponds to the substantially unflexed fibers of the damper at peripheral location “x” and at position C 1 . Diameter “d 2 ” corresponds to the substantially flexed fibers of the damper at the peripheral location “x” at position C 2 . Therefore, it is seen that cyclic flexure of a substantially circular damper  112  results when the damper rolls on the shaft. Here, the damper tends to stop the slider&#39;s motion relative to the shaft when, among other things, a rolling interaction between the shaft and the damper causes cyclic damper flexing and, among other things, conversion of kinetic energy to heat as a result of losses including mechanical hysteresis losses. 
     Use of the practice bat  100  is typified by a swinging motion resulting when a user grasps the gripping region  118  and swings the bat as if to make contact with a sports ball such as a baseball. As described below, the practice bat provides users and others with an indication of a batter&#39;s swing quality. 
     Before the swing, the damper  112  is located at a first damper position “z” that is spaced apart from the second damper by a length l 0  (see  FIG. 1 ). When preparing to swing, the practice bat  100  is raised such that it&#39;s free end  105  points generally upward and the slider  106  rests against the first bumper  110 . During the swing, the slider is subjected to forces causing it to move toward the free end. Upon contacting the damper, the slider forces the damper toward the free end. The slider comes to rest when it pushes the damper against the second bumper  114  or, earlier, if the kinetic energy of the slider is dissipated by, among other things, the damper before the damper strikes the second bumper. 
     In  FIG. 3 , the position of the damper  112  and abutted slider  106  indicate that swing forces have caused the slider to push the damper toward the free end of the practice bat  105 . Here, the slider has not reached its end point at position “u.” In  FIG. 4 , the position of the damper  112  and the abutted slider  106  indicate that applied swing forces have been sufficient to cause the slider to push the damper into contact with the second bumper  114 . In this case, the slider has reached its end point at position “u.” 
     As will be appreciated by persons of ordinary skill in the art, selection of the initial damper position “z” to increase l 0  also increases the work required to move the damper to the end point “u.” Therefore, it is seen that l 0  may be selected by a user or a user&#39;s coach to accommodate the user&#39;s ability, a particular practice exercise or a similar training goal. 
     Embodiments of the practice bat  100  provide signals useful for training the user. In an embodiment, the slider  106  and shaft  102  are of contrasting colors such that the position of the slider with respect to the shaft is observable during a swing or a portion of a swing. An example exercise using this feature is attempting to force the slider to position “u” at the instant the free end of the practice bat  105  reaches the desired location for striking a ball. 
     As discussed above, selection of l 0  will influence the swing dynamics and in particular how much swinging force a user must impart to the practice bat to achieve the desired result. For example, l 0  can be adjusted to match the strength of a particular player and/or in a program aimed at enhancing a player&#39;s strength. In addition, selecting “z” to coincide with a particular position indicator on the shaft  211   a - e  allows a repeatable practice regime to be established, monitored and adjusted for a particular player. 
     To emphasize the slider reaching position “u,” some embodiments utilize audible devices to provide a signal. In an example, the damper  112  and second bumper materials are chosen to provide an audible signal resulting from their mechanical impact. In another example, an electrical annunciator provides an audible signal when a pushbutton  302  of an electrical switch  301  is depressed by interaction with the damper  112  and slider  106 . In yet other embodiments, electrical devices producing visible and/or tactile signals are used to indicate a location of the slider. 
     In various embodiments, the practice bat  100  has either a removable end stop  108  and second bumper  114  or it does not utilize these parts. Such bats have no position “u” where the slider  106  stops due to contacting the second bumper or the end stop. A swinging force sufficient to cause the slider to push the damper off the shaft  102  results in the slider taking flight. This feature can be used to train a player&#39;s swing and in cases to emphasize swing technique for directing the flight path of the ball struck by the bat. 
       FIG. 7A  shows a second practice bat in accordance with the present invention  700 A. An elongated shaft  702  has a handle end  704  and an opposed free end  705 . Near the handle end, a shaft gripping region  718  is located between an end knob  703  and a bumper  710  that is spaced apart from the end knob. A carrier assembly  720  is engaged with a free sliding region of the shaft  716 . 
     The carrier assembly includes a carrier tube  722  and a ball, sports ball or replica of a sports ball  728 . The carrier tube includes a cylinder  726  for engaging the shaft  716  and a ball retaining rim  724  fixed to one end of the cylinder. Notably, the cylinder and rim may be a single part or multiple parts. In various embodiments, the ball is one or more of solid, hollow, thin walled, smooth surfaced, and perforated. 
       FIG. 8  shows an exploded view  800  of parts of the practice bat of  FIG. 1 . In particular, the ball carrier assembly  720  is shown with the ball  728  removed from the carrier tube  722 . The ball has a through bore  802  with an internal diameter ID 1 . The carrier tube cylinder  726  has an outside diameter OD 1 . 
     In an embodiment, there is a loose fit between the ball&#39;s bore ID 1  and the carrier tube cylinder&#39;s outer diameter OD 1 . For example, the ball&#39;s bore is about 0.1% to 5% larger than the carrier tube cylinder&#39;s outer diameter. And, in an embodiment, there is an interference fit between the ball&#39;s bore ID 1  and the carrier tube cylinder&#39;s outer diameter OD 1 . For example, the ball&#39;s bore is about 0.1% to 1% smaller than the carrier tube cylinder&#39;s outer diameter. In some embodiments  885  (see  FIG. 8 ), the carrier tube cylinder  726  has ridges  881  engaged by projections  883  from the bore  802  of the ball. 
     In various embodiments, the ball  728  is hollow and in various embodiments the ball is solid. The ball has a borehole  802  for receiving the shaft  716 . For example, a thin-walled hollow ball such as a WIFFLE® ball is used in some embodiments. 
     In an embodiment, an end stop  708  is fitted to the shaft  702  near the free end  705 . The end stop has a through bore  709  for receiving the shaft  716  and an outer diameter shown as OD 2 . End stop outer diameter OD 2  is equal to or less than the inner diameter of the ball ID 1 . Embodiments of the end stop having differing weights attributable to one or more of end stop dimensions, material density, and end stop attachments provide a means for varying bat swing dynamics, for example during batter training or batter warm-up. 
     In various embodiments, suitable means known to persons of ordinary skill in the art are used to fix or removably fix the end stop  708  to the shaft  702 . Such means include a knob that is integral with the shaft  920  and a knob that is fastened to the shaft. Fastening means include pins such as roll pins  730  passing through the shaft and the end stop (as shown in  FIG. 7A ), similarly situated screws, similarly situated bolts, interference fits, use of adhesives, screw threads within a bore of the end piece and mating screw threads on the interfacing region of the shaft, spring loaded fasteners, other fasteners and other similar means. 
     The end knob  704  is fitted to the shaft in a manner similar to that used for the end stop. In some embodiments, the end knob is fixed to the shaft using a pin such as a roll pin  732  passing through the shaft  702  and the end knob (as shown in  FIG. 7A ). 
     The shaft  702  may be made of any suitable rigid material including wood and metallic materials commonly used for ball sports bats known by persons of ordinary skill in the art. In an embodiment the shaft is tubular. In other embodiments, the shaft is solid such as is common for a wooden baseball bat. 
     In some embodiments, a damper (see for example  FIG. 1 ) encircles the shaft  716  between the carrier assembly  720  and the end stop  708 . The damper  112  may be made of any material suited for interacting with the shaft  102  to resist relative motion therebetween. For example, one or more synthetic and natural materials are used in various embodiments including rubbers, plastics, corks, woods, and similar materials. Further, one or more rubbers such as butyl, ethylene propylene diene monomer, fluorocarbon, silicon, vulcanized, non-vulcanized and resilient rubbers are used in some embodiments. In an embodiment, the damper is an O-Ring made from a suitable elastomer such as one of the rubbers mentioned above. In various embodiments using O-Rings, the O-Ring cross-sectional shape is circular, arced or prismatic. 
     The bumper  710  and the end stop  708  are preferably made from a material suited for being impacted by the carrier tube  722 . In some embodiments, the bumper and or end stop material is selected to enhance impact sounds when the bumper or end stop is struck by the carrier tube. In an embodiment, the bumper is made from a metal such as steel or aluminum. In other embodiments one or more synthetic and natural materials with shock resistant characteristics are used including rubbers, plastics, corks, woods, and resilient materials. In particular, one or more plastics including PVC, ABS, HDPE, acetal resin such as DuPont Delrin® and resilient plastics are used in some embodiments. Further, one or more rubbers such as butyl, ethylene propylene diene monomer, fluorocarbon, silicon, vulcanized, non-vulcanized and resilient rubbers are used in some embodiments. 
     The carrier tube  722  may be made of any material suited for sliding on a shaft subjected to swinging motions and suited for impacting the above described bumper  710  and end stop  708 . In various embodiments, the slider is made from one or more of the materials suited for making bumpers and metallic materials such as alloys and/or compounds of aluminum, steel, copper, stainless steel, titanium and other suitable metals. In some embodiments the carrier tube is made from a polymer such as a plastic. Suitable plastics include thermoplastic elastomers, PVC, ABS, and HDPE materials. 
     The knob  704  may be made of any material suited to rigorous use associated with a practice bat. These materials include the materials of construction of the bumper  710  listed above. The end stop  708  may be made of any material suited to rigorous use associated with a practice bat, fitment to the shaft  702  and impacts caused by the slider carrier tube  722 . These materials include the materials of construction of the bumpers listed above. 
     Along the length of the practice bat there is a gripping region  718  denoted by length l 1  and a free sliding region denoted by length l 2 . The carrier assembly  720  is free to move along the free sliding region. The ball  728  is movable with respect to the carrier tube cylinder  726  in response to inertial forces such as swing forces. 
     Use of the practice bat  700 A is typified by a swinging motion resulting when a user grasps the gripping region  718  and swings the bat as if to make contact with a sports ball such as a baseball. As described below, the practice bat provides users and others with an indication of a batter&#39;s swing quality. 
     Before the swing, the carrier assembly  720  is located adjacent to the bumper  710 . When preparing to swing, the practice bat  700 A is raised such that it&#39;s free end  705  points generally upward and the carrier assembly  720  rest against the bumper  710 . During the swing, the carrier assembly is subjected to forces causing it to move toward the free end  705 . 
       FIG. 7B  shows the carrier assembly with ball in a second position  700 B. Here, the carrier assembly has moved along the free sliding region of the shaft  716  through length l 2 . When a front face of the carrier tube cylinder  804  strikes a mating face of the end stop  806 , the inertia of the sports ball  728  overcomes the interference fit and/or latching action between the ball and the carrier tube cylinder. Now moving relative to the carrier tube cylinder, the ball passes over the end stop. 
       FIG. 7C  show the ball  708  in a third position  700 C. Here, the ball has passed completely over the end stop and is no longer restrained by a coupling to the bat shaft  702 . Free of the bat shaft, the ball takes flight and travels in a direction pointed to by the shaft at the moment the ball leaves the shaft. 
     Embodiments of the practice bat  700 A provide signals useful for training the user. In an embodiment, the carrier assembly  720  and shaft  702  are of contrasting colors such that the position of the carrier with respect to the shaft is observable during a swing or a portion of a swing. 
     To emphasize the carrier assembly  720  reaching the end stop  708 , some embodiments utilize audible devices to provide a signal. In an example, the carrier tube  726  and end stop materials are chosen to provide an audible signal resulting from their mechanical impact. In another example similar to that shown in  FIG. 3  above, an electrical annunciator provides an audible signal. In yet other embodiments, electrical devices producing visible and/or tactile signals are used to indicate a location of the carrier assembly. 
       FIG. 9  shows an exploded view of a third practice bat in accordance with the present invention  900 . This bat is similar to the bat shown in  FIG. 7A  above, the most significant difference being the lack of a carrier assembly  720 . 
     An elongated shaft  920  has a handle end  924  and an opposed free end  922 . Near the handle end, a shaft gripping region  926  is located between an end knob  904  and a bumper  910  that is spaced apart from the end knob. In various embodiments, either or both of the bumper and the end knob are integral with the shaft. In yet other embodiments, either or both of the bumper and the end knob are not integral with the shaft. 
     A ball  928  is for engaging the shaft  920 . The ball has a through bore  902  with an internal diameter ID 3 . A free length of the shaft  916  with an outer diameter OD 3  is for mating with the through bore of the ball. In various embodiments, the ball is one or more of solid, hollow, thin walled, smooth surfaced, and perforated. For example, a thin-walled hollow ball such as a WIFFLE® ball is used in some embodiments. 
     In an embodiment, there is a loose fit between the ball&#39;s bore ID 3  and the shaft outer diameter OD 3 . For example, the ball&#39;s bore is about 0.1% to 5% larger than the shaft outer diameter OD 3 . And, in an embodiment, there is an interference fit between the ball&#39;s bore ID 3  and the shaft&#39;s outer diameter OD 3 . For example, the ball&#39;s bore is about 0.1% to 1% smaller than the shaft&#39;s outer diameter OD 3 . 
     In various embodiments, suitable means known to persons of ordinary skill in the art are used to fix or removably fix the knob  904 . Such means include a knob that is integral with the shaft  920  and a knob that is fastened to the shaft. Fastening means include pins such as roll pins  730  passing through the shaft and the end stop (as shown in  FIG. 7A ), similarly situated screws, similarly situated bolts, interference fits, use of adhesives, screw threads within a bore of the end piece and mating screw threads on the interfacing region of the shaft, spring loaded fasteners, other fasteners and other similar means. 
     The shaft  702  may be made of any suitable rigid material including wood and metallic materials commonly used for ball sports bats known by persons of ordinary skill in the art. In an embodiment the shaft is tubular. In other embodiments, the shaft is solid such as is common for a wooden baseball bat. 
     The bumper  910  is preferably made from a material suited for interfacing with the ball  928 . In an embodiment, the bumper is made from a metal such as steel or aluminum. In other embodiments one or more synthetic and natural materials are used including rubbers, plastics, corks, woods, and resilient materials. In particular, one or more plastics including PVC, ABS, HDPE, acetal resin such as DuPont Delrin® and resilient plastics are used in some embodiments. Further, one or more rubbers such as butyl, ethylene propylene diene monomer, fluorocarbon, silicon, vulcanized, non-vulcanized and resilient rubbers are used in some embodiments. 
     The knob  704  may be made of any material suited to rigorous use associated with a practice bat. These materials include the materials of construction of the bumper  710  listed above. 
     Along the length of the practice bat there is a gripping region  926  and a free sliding region  916 . The ball  928  is free to move along the free sliding region in response to inertial forces such as swing forces. 
     Use of the practice bat  900  is typified by a swinging motion resulting when a user grasps the gripping region  926  and swings the bat as if to make contact with a sports ball such as a baseball. As described below, the practice bat provides users and others with an indication of a batter&#39;s swing quality. 
     Before the swing, the ball  928  is located adjacent to the bumper  910 . When preparing to swing, the practice bat  900  is raised such that its free end  922  points generally upward and the ball rests against the bumper  910 . During the swing, the ball is subjected to forces causing it to move toward the free end  922 . 
     While the batter&#39;s swing is in progress, the ball  928  moves away from the bumper  910 , along the bat&#39;s free sliding region  916 , and toward the bat&#39;s free end  922 . Near the end of the batter&#39;s swing, the ball passes over the bat&#39;s free end and takes flight, generally traveling in a direction pointed to by the shaft at the moment the ball leaves the shaft  920 . 
     Embodiments of the practice bat  900  provide signals useful for training the user. In an embodiment, the ball  928  and the shaft  920  are of contrasting colors such that the position of the carrier with respect to the shaft is observable during a swing or a portion of a swing. 
     While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. It will be apparent to those skilled in the art that various changes in the form and details can be made without departing from the spirit and scope of the invention. As such, the breadth and scope of the present invention should not be limited by the above-described exemplary embodiments, but should be defined only in accordance with the following claims and equivalents thereof.