GB908883A - Improvements in rock drills - Google Patents

Abstract

908,883. Percussive tools. INGERSOLLRAND CO. Feb. 21, 1961 [Feb. 29, 1960], No. 6385/61. Class 124. [Also in Group XXVI] A fluid-actuated tool comprises a casing 30 having a chamber 32, a sleeve 34 reciprocable in the chamber, a piston 36 reciprocable in the sleeve, and an implement 40 having an end extending into the casing to be actuated by the piston. Fluid is supplied to a distribution chamber 46 through a hose 44 and valve 42, and is discharged from the chamber 32 through an exhaust 48. An anvil 38 interposed between piston and implement is slidable in a retainer 57. The wall 50 of the chamber 32 has exhaust ports 58, 60, 62, 64 connected to the exhaust, and inlet ports 66, 68, 70 connected with the distribution chamber. The sleeve has inlet ports 74 and inlet and outlet ports 76, 78. A chamber 84 between the wall and sleeve is constantly connected to the distributing chamber through the ports 68, the pressure on shoulder 90 constantly urging the sleeve forwardly towards the implement. Fig. 1 shows the position of the elements of the tool at the beginning of a working cycle and immediately after the piston has struck the anvil, fluid then being supplied to the interior of the sleeve through ports 66, 76 to force the sleeve rearwardly against the pressure on the shoulder 90. As the sleeve moves rearwardly the fluid entering the sleeve halts the rebound of the piston and returns it to contact the anvil. Further rearward of the sleeve to the position shown in Fig. 8 opens ports 74 (connected to the inlet ports 70) to move the piston rearwardly, the fluid above the piston being exhausted through ports 76, 60. The speed of the sleeve decreases since the inlets 66 are closed, the sleeve finally stopping its rearward motion when the ports 58 are partially closed. The sleeve is urged forwardly by the pressure on the shoulder, and by the pressure of fluid from the port 70 on the foot 116 of the sleeve. As the sleeve is moved forwardly to the position shown in Fig. 10, the piston continues to move rearwardly fluid being supplied through ports 70, 78 to move the piston. The pistons final rearward movement within the sleeve is cushioned by fluid trapped at the end of the sleeve. As the sleeve continues to move forwardly, the ports 78 are connected to the exhaust port 62 so that the resilience of the cushion starts the piston to move forwardly within the sleeve to open the ports 76 to drive the piston from the position shown in Fig. 13 to the position shown in Fig. 1 to end the cycle. The rearward stroke of the piston is slower than the forward stroke since ports 70 are smaller than ports 66. In the event of the implement striking a soft spot the piston is cushioned by compressing fluid in the sleeve below the ports 74. The anvil is prevented from striking shoulder 110 of the retaining by fluid supplied to a chamber 100. Vibration caused by the moving elements of the tool is prevented from being transferred to the casing by the fluid in the chamber 84.