Sandvik Rock Tools, Inc.

Galloway Trust

David Mildren

Robert F Kane

Faisal J Yousef

Joel Ham

A driver sub and a case for enclosing a piston chamber of a percussion drill are threadedly connected by respective identical male and female screw threads. Each of the identical male and female screw threads includes a root portion, the shape of which is defined by portions of two axially overlapping ellipses interconnected by a flat.

Screw thread structure for percussion drill driver sub and case

A thread coupling comprises two interconnected screw threads. Each of the screw threads has a root portion shaped as a portion of an ellipse. With respect to one of the threads having such a shape, the major axis of the ellipse is longer than that of the other thread.

Screw thread coupling

A screw thread structure includes a root portion, the shape of which is defined by portions of two axially overlapping ellipses interconnected by a flat.

Growing community of inventors

Houston, TX, United States of America

David Mildren