Patent ID: 8720606
Filing Date: 2014-05-13
Classification: E21B

Abstract:
1. A locking mechanism for locking an insertable device relative to an outer tube of a ground drill, the locking mechanism comprising: at least one latch, which is arranged to releasably retain the insertable device in a substantially fixed axial position relative to the outer tube, wherein the locking mechanism comprises a cam and a cam follower, which are arranged to control a radial position of the latch, wherein the cam presents a withdrawal surface, against which the cam follower is arranged to slide to cause the latch to withdraw to unlock the insertable device from the outer tube, the withdrawal surface extending from a first end of the cam to a second end of the cam, wherein the cam follower is movable along the withdrawal surface from the first end of the cam, closest to the pivot axis, to the second end of the cam, farthest away from the pivot axis, wherein the withdrawal surface at the second end of the cam is closer to the first longitudinal edge than at any other point along the cam, and wherein the withdrawal surface is continuously curved between the first end of the cam and the second end of the cam.