A fixed base comprises an upper cover comprising an outer canister a top plate and a sidewall. The sidewall encircles the top plate to form a receiving room. An inner canister penetrates the receiving room and is attached to the top plate, which comprises a wall. At least one hatch is defined in the wall, and is connected to the receiving room. A positioning component is set inside the surface of the top plate. A limitation frame comprises a frame body, a connecting block, and a positioning block. The positioning block is slidably connected to the positioning component. At least one groove opposite the hatch is defined in the wall of the frame body, and comprises a sliding groove and a fixing groove connecting with the sliding groove. The fixed base further comprises a driver and a trigger switch.