Abstract: A top drive system with a plurality of top drive modules, which are configured to be quickly exchanged. The top drive modules may include any or all of the following: a main body module, a gearbox module, a drive motor module, a pipe handler module, an upper fluid module, a lower well control valve module, a block interface module, a retract system interface frame module, a cooling system module, a work platform guard module, and a quill saver sub module. Alternatively, the top drive may comprise a first top drive and a second top drive which are configured to be quickly exchanged.

Abstract: An apparatus is disclosed for handling a tubular segment, coupling the tubular segment with a tubular string, and handling the tubular string in a well bore. The apparatus has a tubular engagement assembly, which connects to a drive shaft of a top drive. The tubular engagement assembly has a self-engaging ball and taper assembly that releasably engages the tubular segment. When the tubular engagement assembly connects to the drive shaft and the ball and taper assembly engages the tubular segment, any rotation in the drive shaft results in rotation of the tubular segment. This rotation allows the tubular segment to engage the tubular string.

Abstract: A down-the-hole hammer drill having a reverse circulation system which conducts pressurized air downwardly to a lower cutting face of a drill bit. The air travels across the cutting face and upwardly through a central exhaust passage. The air is conducted to the cutting face through longitudinal and lateral passages in the bit which are kept isolated from the environment surrounding the bit so that no appreciable amount of pressurized air can escape, and so that the passages do not become clogged with dirt. The drill bit comprises upper and lower pieces. Upper sections of the longitudinal passages are formed in the upper piece, and lower sections of the longitudinal passages are formed in the lower piece.

Abstract: 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.

Abstract: A percussion drill includes a reciprocating piston surrounded by a cylindrical casing. Disposed at opposite ends of the cylindrical casing are replaceable hollow cylindrical wear sleeves. The wear sleeves are mounted within recesses formed in the outer surface of the casing. Each wear sleeve has a thickness equal to the depth of its respective recess. A longitudinal inner end of each wear sleeve is spaced longitudinally from an end surface of the recess, and a flexible seal is situated between those opposing ends. The wear sleeves can be replaced after being worn by the abrasive environment encountered in the hole being drilled. The wear sleeves may be formed of a more wear resistant material than the casing.

Abstract: 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.

Abstract: 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.