devices for use in training baseball pitcher trainees to throw a curve ball , such as an over hand or “ 6 / 12 ” curve ball , and methods of their use are disclosed herein . the devices include a cover capable of holding a ball and capable of being gripped by a trainee . the devices also include a counterweight , which allows the trainee to detect readily the spin on the device after the trainee has thrown the device . the counterweight may be separate from the cover and attached to the cover by a connecting portion . alternatively , the counterweight and cover form a single composite structure . in such embodiments , the counterweight is positioned at one portion of the cover so that the device has an asymmetric distribution of weight when a ball is inside the cover . the counterweight may have sufficient mass on its own to affect the spin of the device when the device is thrown by the trainee . alternatively , the counterweight may require the addition of a weighted object to properly affect the spin of the device when the device is thrown by the trainee . in such embodiments , the counterweight includes a slit or hole into which a weighted object can be inserted . the weighted object may be an object of any shape or size that provides appropriate mass to the device . the counterweight may itself be a cover capable of holding a ball , and the weighted object may be a ball . as shown in fig1 , one embodiment of the invention is a sleeve for encapsulating two selected balls to form a baseball training assembly . sleeve 10 includes first ball cover member 20 , second ball cover member 30 , and optional connecting member 60 . the first and second ball cover members can be identical or different . first ball cover member 20 includes a slit or hole 40 through which a first ball ( not shown ) can be introduced into the interior space of the first ball cover member . similarly , second ball cover member 300 includes slit or hole 50 through which a second ball ( not shown ) can be introduced into the interior space of the second ball cover member . the interior spaces of the first and second ball cover members may be continuous with each other , or they may be physically separated . the first and second ball cover members are joined by connecting member 60 . in this embodiment , the counterweight member is a second ball cover member attached to the first ball cover member by a connecting by a connecting member , and the weighted object is a second ball . it will be understood , however , that the invention is not limited by the this example and encompasses other embodiments . for example and without limitation , the counterweight member need not be a ball cover member ; the weighted object need not be a ball ; the counterweight need not accommodate a weighted object ; and the counterweight member need be attached to the ball cover member by a connecting member . the sleeve can be formed as a single piece , for example by injection molding , or it can be formed by joining separately formed pieces , such as by gluing or heat welding . preferably , the sleeve or its component pieces are formed from an elastic polymer ( an elastomer ) or rubber material whose elasticity and thickness are adjusted to provide the desired extensibility , hardness , and weight . for example , the elastomer may be polyurethane , polyurea , silicone , and polyvinyl chloride . in a preferred embodiment , the sleeve is sufficiently elastic so as to allow the user to insert and remove balls through the slits or holes , and conforms to the balls tightly enough to keep them in place during use , including during the stresses encountered during pitching practice . however , if the sleeve is formed from separate pieces , the connecting member may be made of a different , less elastic material to keep the relative positions of the first and second ball fixed . optionally , the outer surface of the sleeve can possess a baseball stitching pattern . as used herein , a baseball stitching pattern can be a texture , molded - on imitation baseball threads , or actually sewn - on threads ( see structure 80 in fig2 ) so as to improve the feel and realism for the user compared to throwing an actual baseball . the height of the threads on a real baseball can vary according to the regulations of the league for which the baseball is designed , for example , little league , high school , college , or professional . consequently , the height of the baseball stitching pattern on the surface of the sleeve can vary as well . for example , the stitching pattern may have a height of less than about 0 . 1 cm , 0 . 2 cm , 0 . 3 , cm , 0 . 4 cm , 0 . 5 cm , 0 . 6 cm , 0 . 7 cm , 0 . 8 cm , 0 . 9 cm , or 1 . 0 cm . the stitching pattern may be in contrasting color to the color of the cover . the stitching pattern may contain thread , string , or traditional leather ( e . g ., horsehide or cowhide ) strips attached to give the outer surface of the device the look and feel of an actual baseball . the stitching pattern may cover the entire sleeve or may cover only the ball cover member portion . the ball cover member is essentially spherical and hollow and has the approximate size of a regulation baseball . for example , when a ball cover member contains a ball , i . e ., is “ loaded ,” it may have circumference of not less than 9 inches and not more than 9 . 25 inches , or , in certain embodiments , within +/− 1 %, 2 %, 3 %, 5 %, 7 %, 10 %, 20 %, 30 %, or 50 % thereof . the counterweight member may also be essentially spherical . alternatively , it may be any other shape that allows the device to spin when thrown by the trainee . in certain embodiments , the ball cover member is about the size of a regulation baseball , while the counterweight member is smaller . the connecting member can vary in shape , size , and conformation as desired . in some embodiments , the connecting member fills much of the space between the two ball cover members to provide a more aerodynamic shape . the invention also encompasses an assembly in which the sleeve contains a ball in the ball cover member . in some embodiments , the assembly also includes a weighted object contained within the counterweight member . in some embodiments , the weighted object is also a ball . if present , the ball inserted into the counterweight member may be the same as or different from the ball in the ball cover member . any type of ball that fits within the ball cover member may be used . balls that are commonly available for other sporting purposes may be used with the device , provided that they fit within the device . for example , a tennis ball , golf ball , handball , squash ball , racquetball , lacrosse ball , or field hockey ball may be inserted into the device . alternatively , the device may be used with balls made specifically for use with the device . for example , balls can contain particular materials , such as rubber , plastic , string , yarn , cork , cotton , or leather . balls can be custom - made to a particular size , for example , having a circumference of about 3 - 4 inches , 4 - 5 inches 5 - 6 inches , 6 - 7 inches , 7 - 8 inches , or 8 - 9 inches . in embodiments in which balls are used as weighted objects , the balls can be fabricated as pairs so that one ball can be inserted into the ball cover and the other ball can be inserted into the counterweight member . balls can paired so that the two balls are the same size or so that one ball is larger than the other . balls in pairs can be matched by color so that the balls in a matched pair have the same color but balls of different pairs have different color . balls in pairs can also be matched by weight so that the sum of the weights of the two balls in every pair is the same but the relative weights between the first and second ball in each pair is different . for example , first ball and second ball of each matched pair can have weight ratios ( expressed as percentages of total weight ) of 50 / 50 , 60 / 40 , 70 / 30 , 80 / 20 , 90 / 10 , and 95 / 5 . an important aspect of the invention is the total weight of the assembly , which is the sum of the weights of the sleeve , ball , and , if present , weighted object . for the device to provide a pitching experience with the device that accurately simulates pitching with a real baseball , it is desirable that the total weight of the assembly is as close as possible to the weight of a real baseball . under rule 1 . 09 of major league baseball ( mlb , see www . mlb . com / mlb / official_info / index . jsp ), a baseball must weigh not less than 5 ounces and not more than 5 . 25 ounces . therefore , in embodiments of the invention , the total weight of assembly , is within +/− 1 %, 2 %, 3 %, 5 %, 7 %, 10 %, 20 %, 30 %, or 50 % of the official mlb weight range of a baseball . another important aspect of the invention is the distribution of weight within the assembly . for assemblies that include a ball and weighted object , e . g ., a first ball and second ball , the distribution of weight within the assembly is affected by the relative weights of the ball and weighted object , e . g ., first ball and second ball . the ball , e . g ., first ball , fits into the ball cover member , which is gripped by the trainee during use . the weighted object , e . g ., second ball , fits into the counterweight member , which serves to highlight the rotation of the assembly and thus provide information on the trainee &# 39 ; s pitching technique . for a novice trainee , it is desirable to have significant fraction of the weight of the assembly come from the weighted object , e . g ., second ball . as the trainee &# 39 ; s technique becomes more developed , however , it is advantageous to have more of the weight contained within the ball cover member and thus come from the ball , e . g ., the first ball . consequently , in some embodiments , the sleeve is provided with matched pairs of ball and weighted object , e . g ., first ball and second ball , such that total weight of each matched pair is the same but the relative weights between the ball and weighted object , e . g ., first ball and second ball , in each matched pair differs . for example , a set of matched pairs may include a ball and weighted object , e . g ., first ball and second ball , having weight ratios ( expressed as percentages of total weight ) of 50 / 50 , 60 / 40 , 70 / 30 , 80 / 20 , 90 / 10 , and 95 / 5 , or any subset of matched pairs having these weight ratios . the devices of the invention can be used to train a baseball pitcher to throw a curve ball . when the device , ball , and , if present , weighted object are assembled , the trainee grips the ball cover member and imparts a spin on the assembly with the throwing motion . the spin on the portion containing the ball cover and ball imposes a centrifugal force on the counterweight , which rotates around the portion containing the ball cover and ball . due to the size of the counterweight , its rotation is readily visible to the trainee . in embodiments that include a weighted object , the relative difficulty of imparting and detecting the proper spin on the assembled device varies depending on the relative weights of the ball and weighted object . consequently , it can be advantageous for trainees to use an assembly in which the weight ratio between the ball and weighted object is adapted for their skill level . a novice can benefit from assembly in which the ball and weighted object have approximately equal weights , i . e ., a weight ratio ( expressed as percentages of total weight ) of 50 / 50 . in contrast , a more advanced trainee can benefit from an assembly with a higher weight ratio , which contains more of its weight in the portion containing the ball cover and ball and therefore more closely approximates the feel of throwing an actual baseball . thus , the devices of the invention can be used in training methods that entail ( 1 ) allowing a trainee to throw an assembly having a particular weight ratio between ball and weighted object for a period , e . g ., as measured by number of pitches or by units of time , e . g ., minutes , hours , days , weeks , months , etc ., so that the trainee can master the spin with that particular assembly , and then ( 2 ) repeating the exercise with an assembly having a different weight ratio between ball and weighted object , e . g ., a higher weight ratio . the process can be performed iteratively until the trainee is ready to graduate from a training device to a real baseball .
a training device for use by a pitcher in practicing throwing a curve ball and a method for using the training device is described .