GB749328A - Fluid actuated reciprocatory prime mover - Google Patents

Abstract

749,328. Percussive rock drilling apparatus. HUGHES TOOL CO. Dec. 28, 1953 [May 1, 1953], No. 35999/53. Class 85 [Also in Group XXIX] A well drill in which the cutting action is provided by the rotation of an earth boring bit and the simultarieous application of impacts to the bit, is fully fluid-actuated in its reciprocatory move ments. Flushing fluid is supplied through a sleeve 15 to a chamber 23 in the interior of a piston 10 reciprocable in a housing 5. An annular piston head 20 is reciprocable in a chamber 16 formed between the housing and the sleeve 15, ports 17 providing access to the exterior of the housing, and a chamber 23<SP>1</SP> is provided below the piston head. A valve 25 is provided in the chamber 23 and comprises a ring 38 fixed to a stem 26 and a valve head 27. At the commencement of a power stroke the valve head 27 is held upon a seat ring 32 by the excess of upward force acting on the ring 38 over the downward force on the head 27, the upper side of the ring being in communication with the chamber 16 and hence subject to the pressure outside the housing, and the lower side of the valve head 27, and the chamber 23<SP>1</SP>, being open to the exterior of the housing through a bore in the piston and drill bit 14. The piston is thus moved downwardly and the valve 25 is held on the seat 32 until the ring 38 clears the sleeve 15, whereupon the valve 25 is moved downwardly by the pressure on its head 27 to seat the head on a seat ring 33. The piston continues to travel downwardly under its own momentum until the bit hits bottom. The fluid then passes between the head 27 and the seat ring 32 into the chamber 23<SP>1</SP> and the piston is moved upwardly. The valve 25 is held in its lower position until after the ring 38 has entered the spare between the sleeve 15 and the wall of the piston. When the piston head 20 has cleared a shoulder 19 of the sleeve, the differential pressure between the upper and lower sides of the ring 38 raises the valve, and the next power stroke is begun. The distance that the piston moves upwardly after clearing the shoulder 19 may be altered by modifying or changing the sleeve 15 in order to compensate for the use of different fluids and differing rates of supply of the actuating fluid. A passage 41 in the valve 25 is open at all times to allow the passage of the flushing fluid. In a modification the piston terminates in a hammer collar co-o<SP>p</SP>erating with an anvil bushing attached to the bit.