Clamping device for clamping strings of stringing machine for sport rackets

A clamping device for stringing a machine, comprising:

• a slide member, a positioning device, a control device and a rail, the rail adapted to be located at a top of the stringing machine and a slot defined in the rail, the positioning device located at an end of the slide member and a tube located at the other end of the slide member, an extension of a clamping device inserted into the tube, the control device located between the positioning device and the tube;
• the control device including a pin, a ring-shaped member and a knob, the ring-shaped member engaged with the slide member and the pin pivotably connected with the ring-shaped member, the pin pivotably connected with the knob, an annular space defined in a top of the ring-shaped member and a torsion spring received in the annular space, two ends of the torsion spring connected to the slide member and the knob respectively, and
• the knob having a pin hole defined in an underside thereof and the slide member having a pivotal hole, the tube including an engaging section and a receiving section, the engaging section inserted into an insertion hole and a lower end of the engaging section being in contact with a top of the slide member, the receiving section having a positioning pin and a spring which biases the positioning pin so as to move the positioning pin axially, the tube having a slit which is located in the receiving section, the slide member having an insertion slot which communicates with the pivotal hole, the insertion slot extending to an underside of the knob, the positioning pin including a piece and an insertion member, the piece received in the receiving section and the insertion member engaged with the insertion slot, the piece and the insertion member being connected with each other by a connection portion which is pivotably engaged with the slit, the knob being secured by inserting the insertion member into the pin hole.