LOCKING DEVICE FOR A TOOL WITH TELESCOPICALLY DISPLACEABLE PARTS

摘要

A locking device for a tool with telescopically displaceable parts such as the various tools including a drilling jar used in the deep-well drilling art comprises thickened spindle portion (1) and a sleeve portion (2) with a displaceable sleeve (11) displaceable therein to and away from an axial abutment (17). The thickening of the spindle portion provided by a rigid tapered sleeve (3) with tapered end surfaces (5 and 6) and the sleeve (11) within the sleeve portion with an internal tapered surface (12) are coupled via locking balls (19) disposed for radial movement in an annular cage 20 between the rigid and displaceable sleeves 3 and 11. The sleeve (11) is held by an axial spring (16) in such a position that the balls come to lie axially between the axial abutment (17) and a region of the tapered sleeve (3) having a larger diameter and thereby form a constriction to the passage of the sleeve (3) of the spindle portion (11). This constriction can only be passed when the spindle and tapered sleeve (3) is pulled axially with an overload force sufficient to impress a radial force on the balls (19) which in turn forces an axial displacement of the internal tapered sleeve (11) disposed in the sleeve portion until the balls move radially sufficiently to allow passage of the larger diameter of the sleeve (3) and spindle to pass.