The sport rackets, such as the tennis rackets or badminton rackets, have an enclosed head with strings located within the head and the tension of the strings can effectively hit the balls and the players control the direction that the balls fly partially by the tension of the strings. The tension of the strings is formed by the pulling forces applied to the strings. In order to control that all of the strings have the precise tension, the stringing process is made by using the stringing machine.
There are a pair of holding members for holding the head of the racket before stringing, as shown in FIGS. 1 and 2, the positioning device for holding member of the conventional stringing machine comprises a guide board 2 fixed on the top board 1 of the stringing machine and the guide board 2 has an elongate slot 202 defined axially in the guide board 20. The base 4 of the holding members 3 is connected to the top of the guide board 2 and a bottom board 402 is connected to the hollow portion of the lower part of the base 4. The bottom board 402 has two pins 404 extending from the underside thereof and engaged with the guide slot 202. A bolt 5 extends from the underside of the top board 1 and the guide slot 202 and is cooperated with a washer 504. By rotating the head 502 of the bolt 5 to loose the bolt 5, the base 4 can be moved along the guide slot 202. When the base 4 is moved to a desired position, the bolt 5 is tightened to position the holding members 3 so that the head of the rackets of different brands can be held.
The heads of the rackets of different brands have different sizes and shapes, so that the distance between the holding members 3 may be varied according to the different heads of rackets. Therefore, the holding members 3 cannot be set at a fixed position due to the different sizes of the heads of rackets. In order to save space, the holding members 3 are moved toward each other when not in use, so that the users have to release and tighten the bolts repeatedly to set the holding members 3 between the operation status and the non-operation status. This wastes time for the users.
The present invention intends to provide a positioning device for the holding member to improve the shortcoming of the conventional one.