Importance

Loading Importance Indicators...

Abstract

A device in rock or earth drilling apparatus for rotary drilling including an axially stationary chuck (21) and an axially movable chuck (27) which is rotated by a reversible pressure fluid driven rotary motor (32) having a pressure fluid supply conduit for each direction and which is moved forwards and backwards by a reversible pressure fluid driven feed motor (17) having a pressure fluid supply conduit (18, 19) for each direction, the chucks being actuated to withdraw from or insert in a drill hole a drill string (23) composed by a number of threaded string elements and (are also actuated) to make or break the joints between the string elements. One of the pressure fluid supply conduits (18 or 19) of the feed motor is connected to one of the pressure fluid supply conduits (37 or 36) of the rotary motor (32) via a conduit (100), so that when breaking or making the joint between two string elements gripped by the two chucks (21, 27) the feed motor will be actuated to move the axially movable chuck (27) relatively to the stationary chuck (21) in a direction to decrease the pressure on the threads accomplished by the weights of the axially movable chuck and devices (such as 32) connected thereto. A suitable illustration is FIG. 3.

Loading the Abstract Image...

First Claim