GB905525A - Improvements in rock drills - Google Patents

Abstract

905,525. Percussive tools. INGERSOLL-RAND CO. Feb. 17, 1961 [Feb. 29, 1960], No. 6029/61. Class 124. [Also in Group XXVI] In a fluid-actuated tool comprising a casing 10, a piston 14 reciprocable in the casing, an implement 22 actuated by the piston, and valve means 28 to distribute fluid to either end of the piston, the piston moves rearwardly away from the implement slower than it moves forwardly towards the implement. Fluid is supplied to the tool through a hose 26, the flow being controlled by a valve 24. The valve 28 slides in a cage 46, fluid from the hose passing to the interior of the cage and valve 28 through ducts 27. Fig. 1 shows the moving parts of the tool at the beginning of a working cycle and after the piston has delivered a blow to an anvil 20 interposed between piston and implement. The valve 28 is in its forward position permitting fluid to flow through ports 44, an undercut 48 and a duct 74 to move the piston slowly rearwardly because of the small area of the ports 44. After the piston has passed a duct 69 part of the fluid in the bore 12 from the duct 74 will discharge through ducts 69, 68, 66, undercuts 52, 50 and exhaust 76 to further decrease the piston speed. At the end of the piston's rearward stroke the fluid rearward of the piston is discharged through ducts 67, 70 before being brought to rest on a cushion of trapped fluid. As the piston is moving rearwardly fluid flows through the ports 42, 58 into a cavity 62 to apply pressure slowly to a surface 36 on the valve 28, the resultant pressure being slightly greater than the opposing pressure on a surface 40 so that the valve is forced rearwardly. When the valve 28 has moved rearwardly, fluid from the space 37 (Fig. 2) is vented by a duct 80, and fluid flows through ducts 66, 70 to give the piston its initial forward movement. The piston is then moved forwardly by fluid from the duct 67, fluid being exhausted from the bore in front of the piston by duct 74, undercuts 48, 50 and exhaust 76. After the duct 65 has been uncovered during the forward movement of the piston, sone of the fluid flows through ducts 65, 64 into the cavity 62 to move the valve 28 to its forward position after the piston strikes the anvil and the cycle is complete.