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 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 screw structure (10) is provided for male and female threads (14) having at least one thread (14) extending helically along a cylindrical support member (12) in spaced thread turns. A root portion (22) extends between adjacent thread (14) turns and has a curvature defined by a portion of an ellipse (24) for providing improved stress reduction during periods of severe loading.

Abstract: A core drilling mechanism in an elongate housing is rotated from a vertical storage position to a horizontal operable position. This permits the transport downhole of a drilling mechanism of sufficient longitudinal dimension to drill a core sample of substantial length perpendicular to the borehole sidewall. A fixed slotted plate and hydraulically actuated rotatable drive plate control the motion of the drilling mechanism, which is stored vertically for descent and ascent, and rotated 90-degrees and moved outward for core drilling. After a core sample is drilled, the drilling mechanism is tilted upward to break off the core, and then returned to its vertical storage position.