| 摘要 |
PURPOSE:To facilitate replacement of broken shear pin by making a shear pin insertion hole and a coupling moving pin hole through upper and lower coupling members, then inserting a moving pin through the coupling moving pin hole and rotary driving an upper device. CONSTITUTION:Upper and lower coupling members have flange sections 15a, 15b provided with shear pin insertion hole 18 fitted with bushes 11a, 11b at joint end portions. A shear pin 7 has threaded pin removing portions 8a, 8b at the opposite ends thereof, where a flange 12 having diameter larger than that of the insertion hole 18 is provided to one threaded portion while a nut 12b is screwed over the other threaded portion 8a in order to prevent falling of the shear pin 7. A constricted portion 13 is formed in the center of the shear pin 7 so that the shear pin 7 is sheared at the portion 13. Furthermore, circular grooves 17 are formed in flange sections 15a, 15b in order to protect endfaces of the bushes 11a, 11b from damage upon breaking of the shear pin 7. |
