Patent ID: 6401842
Filing Date: 2002-06-11
Classification: E21B

Abstract:
An apparatus for drilling a borehole in the earth, comprising:a housing having a front end and a rear end, a shaft extending through said housing, said shaft being rotatable relative to said housing and movable longitudinally between forward and rearward positions relative to said housing, said shaft having a front end for receiving a drill means, an annular cam located in said housing, said annular cam being rotatable relative to said housing, a groove formed in said annular cam and which extends between rearward and forward positions, a cam follower being located in said groove of said annular cam, means for preventing rotation of said cam follower relative to said housing, said cam follower being movable longitudinally relative to said annular cam, moving means for moving said cam follower relative to said annular cam, said cam follower being movable longitudinally in said groove relative to said annular cam to rotate said annular cam to cause said cam follower to be moved to different positions in said groove, said cam follower being movable rearward in said groove to said rearward position of said groove by said moving means, said cam follower being movable forward in said groove from said rearward position of said groove by said moving means.