| 摘要 |
<p>A device for recording the number of strokes during a tennis or similar hitting game is mounted in a tennis racket, hockey stick or the like. The device comprises a cylinder 1 having both ends sealed by covers 2, 3 and a movable piston 4 disposed in the cylinder and maintained in a rest position in the centre of the cylinder by springs 5,6. Depending upon the magnitude of the hitting force and the side of the racket or stick which hits the ball, the piston 4 will temporarily move to one end of the cylinder and engage a contact 7 or 8 to establish an electrical connection for energizing a counter 11 or 12. <IMAGE></p> |
