Cylindrical telescopic kelly-bar apparatus.

摘要

A kelly-bar apparatus includes, for example, an inner kelly-bar 50, a second kelly-bar 60 and an outer kelly-bar 70. These kelly-bars are relatively telescopically operable and torque is transmitted from outside to inside. When the second and outer kelly-bar are in a contracted position, they are supported by a spring 31 on a spring support 54 fixed to the inner kelly-bar. The bottom end of a torque transmitting projection of the inner kelly-bar is fitted into and welded to the spring support. The spring support is fixed onto an engagement member formed integrally with the inner kelly-bar. In addition, a stop member 74 for preventing the second kelly-bar from coming away from the outer kelly-bar projects from the inner periphery of the outer kelly-bar at a location above the torque transmitting portion.