coaxially through the locking limit 40 and aligns with the through holes 313 in the shafts 31 the annular hole 42 is formed in the outside surface of the locking limit 40 and communicates with the rod hole 41 the retaining ball 43 is mounted movably in the annular hole 42 and is able to partially enter the rod hole 41 and the locking shaft cavity 15 the spring 44 is mounted between the bottom of the cavity extension 14 and the bottom of the locking limit 40 to keep the locking limit 40 from dropping the shackle 50 is u shaped is mounted in the dial core cavity 13 and the cavity extension 14 and has a mounting end 51 a locking end 52 and a positioning protrusion 53 the mounting end 51 is mounted slidably and rotatably through the through holes 313 in the shafts 31 is mounted in the rod hole 41 of the locking limit 40 and has a recess 511 the recess 511 is bowl like and corresponding to the retaining ball 43 the locking end 52 corresponds to and selectively aligns with the locking recess 17 and the locking hole of the card clamp 20 with reference to fig7 and 8 is mounted slidably and detachably in the locking recess 17 and is extending through and positioned securely in the locking recess 17 and the locking hole of the.