GB1004694A - Improvements in or relating to percussion drilling apparatus - Google Patents

Abstract

1,004,694. Boring earth, &c. MISSION MANUFACTURING CO. Sept. 13, 1961 [Sept. 19, 1960; Dec. 5, 1960], No. 32915/61. Heading E1F. [Also in Division B4] Percussion drilling apparatus comprises an anvil 11 (Fig. 3) at one end of a body 9, an inlet 27 (Fig. 2A) for pressure fluid at the other end of the body, a tubular member 13 extending from the inlet to a discharge duct 21 in the anvil, separate passages 22, 25 in the member communicating with the inlet and the discharge duct respectively, an inlet port 28 in the member communicating with the passage 22, a hammer piston 12 having a recess 45 forming valving means directing fluid from the port 28 to the opposite ends of the body, and a discharge port 29 in the member communicating with the discharge duct. The invention is adapted for "down-the-hole" drilling, the tool being mounted at the end of a rotatable string of drill pipe through which pressurized fluid (air) is supplied to the inlet 27 of the tool. Before the bit contacts the hole bottom the anvil which is rotatable with the tool body 9 drops so that its shoulder 65 is supported on body shoulder 66 to expose port 19a of the member 13. Fluid escaping from the port 28 in the member 13 passes through the recess 45, recesses 33, 34 in the member 13, and port 19a to discharge through the duct 21 and the bit, the hammer not reciprocating. When the bit rests on the bottom of the hole the anvil is positioned as shown in full lines (Fig. 3), the port 19a is closed, and fluid from port 28 is supplied below the hammer until it rises a distance when the shoulder 56 engages tube shoulder 36 to cut off air supply from port 28 to below the hammer, an exhaust port 14 in the body not being obstructed by the hammer. The fluid below the hammer expands and the hammer travels a distance B when an exhaust port 29 in the member 13 is opened, the hammer moving a further short distance under its inertia. After the port 14 is closed by the hammer, a hammer shoulder 55 passes a tube shoulder 37 so that fluid from the port 28 passes through recesses 45, 31, 32 to above the hammer, the supply of air continuing whilst the hammer travels a distance C when the port 28 is closed by the shoulder 56. The change above the hammer is compressed as the hammer moves a distance D and the hammer is returned under this compression until the port 28 is uncovered to supply more fluid during the part C of the hammer's travel. During the travel E the fluid at the top of the hammer expands until the shoulder 57 clears the port 14 and the space above the hammer is exhaust. Fluid is then supplied below the hammer to repeat the cycle. A port 26, or a separate duct, provides for a continuous by-pass of fluid for removing debris. In a modification the tubular member comprises a tubular structure with an outer sleeve-and the space above the hammer is connectable to a pressure chamber according to Specification 1,004,696.