Abstract: A top head drive cooling system is provided for an earth drilling machine of the type having a mast, a top head drive assembly mounted for movement along the mast, a quill included in the top head drive assembly, and an electric motor for rotating the quill. This cooling system includes an air duct mounted to the mast and defining a slot extending along the mast. The slot is sealed by a pair of flexible resilient lips which bridge the slot, and a blower is situated at ground level to blow cooling air into the air duct. A conduit is provided on the top head drive assembly, and the conduit extends between the lips into the air duct and conducts air from the air duct to the electric motor. The portion of the conduit which extends into the air duct is preferably tapered at both ends in order to provide a sliding seal against the lips. A position measuring system is coupled to the conduit and is positioned within the air duct.

Abstract: A top head drive assembly for a drilling machine includes a wrench assembly used to make up and break out threaded connections. This wrench assembly is mounted for axial movement on rails of the top head drive assembly, and is positioned immediately under the quill. The top head drive assembly also includes a tubular support assembly which includes slip type inserts for supporting a string of down hole tubulars. This support assembly can be pivoted out of alignment with the drilling axis or can be locked in alignment with the drilling axis. A plurality of centering elements are mounted under the support assembly and are movable to center the upper end of a tubular for insertion into the tubular support assembly. Preferably, both the top head drive assembly load beam and the support beam of the support assembly are formed of box sections having converging side plates and internal diagonal brace plates which transmit downward forces on the beam into forces tending to cause the side plates to diverge.