elasticity of the contact tab 301 itself may cause failure after frequently use thereof referring to an embodiment illustrated in fig2 the present embodiment provides a more reliable preferred implementation in which the trigger assembly generally includes a trigger 4 and an elastomer 5 both of which are arranged together with the safety switch 3 on the same side of the inner pipe 1 the safety shift structure on the inner pipe 1 is the receiving groove 101 for accommodating the trigger 4 in this arrangement the inner pipe 1 is slidably connected with the pipe sleeve 2 which generally encases at least the relevant portion of the inner pipe 1 and the inner pipe 1 with a long size can pass through the pipe sleeve 2 and slide therein the safety switch 3 is arranged inside the pipe sleeve 2 and is fixedly connected to the pipe sleeve 2 the contact tab 301 has one end fixedly connected with the safety switch 3 and the other end being a free end the body of the switch is further arranged with a contact thereon which can be contacted and pressed for on off control when the free end of the contact tab 301 is pressed it is certain that a.