referring initially to fig1 , a training bat is shown , generally designated 10 , which includes a handle 12 connected to a barrel 14 . the bat 10 may be made of wood or metal or composite materials and may be a conventional bat altered in accordance with present principles . as shown in fig1 , visible indication can be provided on the barrel 14 of the barrel 14 being swung in a preferred swing plane described by the arc 16 at or greater than an acceptable speed as it passes through an imaginary vertical line 18 intersecting a preferred location in the arc , typically just in front of a home plate 20 next to which a batter in training typically would stand ( fig1 assumes a right - handed swing ). the visible indication , however is not provided if the barrel 14 passes through the imaginary vertical line 18 at less than the acceptable speed . in the embodiment shown in fig1 , the visible indication is a flash of light generated by a source of light such as one or more lamps . in the non - limiting embodiment shown , plural light emitting diodes ( led ) 22 are mounted on the surface of the barrel 14 for operation to be shortly disclosed . fig2 - 4 show non - limiting details of one preferred implementation of the bat 10 . cross - referencing fig2 - 4 , a channel 24 extends into the barrel 14 from the end 26 of the barrel 14 . preferably , the channel is located coaxially with the long axis of the bat 10 . a cap 28 covers the open end of the barrel as shown . at the closed end of the channel , a disk - shaped stationary magnet 30 is located . if desired , a first disk - shaped spacer 32 may be positioned in the channel to abut the stationary magnet 30 . in the non - limiting implementation shown , a hollow , typically plastic tube 34 with a closed end is then advanced into the channel closed end first . to fixedly hold these components within the channel 24 , epoxy 36 may be deposited in the channel 24 as shown . at least one second spacer 38 having a thickness “ t ” ( fig4 ) is positioned within the tube 34 against its closed end . as perhaps best shown in fig4 , the spacer 38 may be centrally formed with a hub 40 , and the hub 40 protrudes toward and may be receivable in an interference fit with a channel 42 of an otherwise disk - shaped movable magnet 44 . the pole of the movable magnet 44 facing the stationary magnet 30 is the opposite polarity of the pole of the stationary magnet 30 that faces the movable magnet 44 , so that the magnets attract . the magnets may be , without limitation , neodymium magnets or iron magnets . it may now be appreciated that the magnetic attraction between the magnets 30 , 44 ( aided if desired by the frictional fit between the hub 40 and channel 42 of the movable magnet 44 ) holds the movable magnet in the housed position shown in fig2 . it may be further appreciated that when sufficient centrifugal force is imposed on the movable magnet 44 toward the end of the bat , i . e ., when the bat is swung at sufficient speed , the magnetic attraction is overcome and the movable magnet 44 rapidly slides down the tube 34 toward the end of the bat to the swung position shown in fig3 . it may be still further appreciated that the separation force needed to move the movable magnet 44 to the swung position depends on the strength of the magnetic attraction in the housed position and , hence , on the thickness “ t ” of the spacer 38 . the thickness “ t ” thus may be established to establish the bat speed at which the magnet 44 moves to the end of the bat . to this end , several spacers 38 of varying thickness may be provided , and the user can select thicker spacers ( and hence lower separation bat speeds ) for younger batters and thinner spacers ( and hence higher separation bat speeds ) for older batters . or , multiple spacers of the same thickness may be provided , and the user simply inserts as many spacers as are required to achieve the desired separation bat speed . insertion of the desired spacer or spacers 38 is easily done by removing the cap 28 from the barrel to expose the open end of the tube , removing the movable magnet , inserting into the tube ( and / or removing from the tube ) spacers 38 as desired , inserting the movable magnet back into the tube , and re - engaging the cap with the barrel . a wire coil 46 surrounds the tube 34 and is electrically connected to the leds 22 , which advantageously are mounted in a depression 48 in the surface of the barrel 14 and surrounded by a transparent material such as transparent epoxy . accordingly , when the magnet 44 passes through the coil 46 , an electrical signal is temporarily induced in the coil 46 , temporarily energizing the leds 22 to cause them to appear to flash briefly . since no energy need be stored in , e . g ., a battery , the bat 10 need contain no source of electrical power apart from the electrical power generated by the movable magnet 44 moving through the coil 46 . completing the description of fig2 - 4 , the cap 28 holds a shock absorbing pad 50 that is contacted by the movable magnet 44 when the movable magnet 44 reaches the swung position shown in fig3 to generate audible and tactile feedback signals to a person swinging the bat . as shown , the cap 28 can have male threads 52 that engage a complementarily threaded passage in the barrel 14 , or the end of the barrel 14 may be externally threaded to engage an internal female thread structure of an alternate cap 28 . other means including set screws may be provided to hold the cap 28 onto the end of the bat . with the non - limiting example embodiment described above , development of a short , powerful swing by a batter is facilitated . specifically , embodiments of the invention help develop muscular coordination for the short swing by only giving positive feedback if the swing has produced the centripetal acceleration necessary to produce the centrifugal force required to release the magnet through the coil . once bat speed is maximized , momentum carries the bat at that speed through the remainder of the swing . in addition to producing maximum bat speed , the short swing also requires substantially less time to move the bat from the ready position to the hitting zone , giving more time to react to pitch location , and requires less movement to orient the swing plane to the pitch location . practicing with the present bat helps train the batter to generate the maximum bat speed of which that batter is capable , and to do so with optimum plate coverage , bat orientation , swing plane , and body position . if any of those factors are absent , the leds will not flash in the proper location , or will not flash at all . while the particular training bat with visual feedback of proper swing is herein shown and described in detail , it is to be understood that the subject matter which is encompassed by the present invention is limited only by the claims . for example , means other than the stationary magnet may be used to urge the movable magnet toward the housed position , including a spring or elastic band affixed at one end to the channel and at the other end to the movable magnet , with or without a latch mechanism to maintain the magnet in the housed position . or , the stationary magnet can be omitted and a frictional fit between the spacer hub and movable magnet channel exclusively used to hold the magnet in the housed position .
a training baseball bat has an internal movable magnet that accelerates to the end of the bat when swung at a fast enough speed . as the magnet moves it passes through a coil that is connected to one or more leds so that the leds momentarily flash as the magnet moves through the coil . a stationary magnet can be used to hold the movable magnet until sufficient centrifugal force is imparted by the swing to overcome the magnetic holding force . spacers can be provided to establish a distance between the magnets as needed to establish a desired swing speed at which centrifugal force overcomes the magnetic attraction .