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 composition for use as a sealant or coating for concrete block walls is disclosed which includes water soluble silicate, water, fibers, clay and limestone, wherein the limestone accelerates the drying of the composition. The fibers used may be non-allergenic fibers such as polyethylene or polypropylene fibers. A method of using the sealant composition also is disclosed.

Abstract: A percussion tool assembly, such as a rock drill assembly, with a new and useful split retaining ring for maintaining the drill bit in the drill assembly. The split retaining ring has a Belleville spring-like profile to enable the split retaining ring to deflect resiliently when the drill bit is driven into engagement with the split retaining ring. The split retaining ring functions as a conventional retaining ring and also as a shock absorber to absorb surplus energy not completely used in the drilling of rock or other strata.

Abstract: A percussion drill comprises a drill bit and a reciprocable hammer piston for imparting blows to the bit. Pressurized air is supplied to the piston for reciprocating the piston. Some of the air is by-passed to an exhaust passage and is exhausted ahead of the bit for removing cuttings. An indexable choke valve is disposed in the exhaust passage for regulating the amount of air which is exhausted. The choke valve comprises a portion of a valve carrier which carries a check valve at its rear end. The valve carrier is rotatable to produce an indexing of the choke valve. The valve carrier is insertable in a front-to-rear direction into a central opening of a rear sub and is secured to the rear sub by a pin which also holds the choke valve in selected positions of adjustment.

Abstract: A down-hole percussion drilling tool supplied with compressed air includes a piston reciprocated in an enclosed cylinder against a bit. A spool is continuously reciprocated in a valve chamber by a pilot fluid pressure supply, tapped from the compressed air from a major air flow passage to either a first or a second feed passage. Compressed air conducted through the first feed passage accelerates the piston toward the bit and compressed air conducted through the second feed passage accelerates the piston away from the bit. The continuous reciprocation of the spool is independent of the position of the piston relative to the cylinder.

Abstract: A rock drilling bit comprises a steel body defining a cutting face with hard material inserts press-fitted into preformed openings in the cutting face. The inserts have ends extending outwardly of the cutting face which perform the actual drilling or cutting operation. The face surface of the body is case hardened except for narrow continuous bands about each insert opening. A method particularly suited for forming the case hardened cutting face is also disclosed.

Abstract: In a percussion drilling tool, a bit is connected to a drill motor through a mating spline connection. External splines on the bit engage internal splines in the drill motor and have respective load bearing faces disposed in a plane extending radially outwardly from central axes. The splines also include a crest land, and a root land. When the splines are in an abutting centered position, there is a uniform radially measured outer clearance between the external spline crests and the internal spline roots, and a uniform radially measured inner clearance between the external spline roots and the internal spline crests. The outer clearance is less than the inner clearance to prevent abrasive damage below the root diameter of the bit resulting from axial relative movement so that the external spline crests will engage the associated internal spline roots while continually maintaining a spacing between the external spline roots and the internal spline crests.

Abstract: The present invention relates to a seat protector device of the type which may be employed with drill rods for transmission of thrust from a driving member to a driven member. More specifically, the invention relates to an improved drill rod system for earth drilling where the rod also provides an axial passageway for a fluid to carry drill cuttings away from the cutting area. The seat protector device of the present invention may be detachably inserted between one or more drill rod sections and/or between one of the drill rods and the drill bit and/or between one of the drill rod members and the driving chuck for transmitting thrust load forces while simultaneously reducing damage and/or wear between the component parts.