GB500934A - Improvements in feeding devices for rock drills - Google Patents

Abstract

500,934. Percussive drills. MOSS, E. W. (Ingersoll-Rand Co.) July 26, 1938, No. 22272. [Class 124] In a feeding device for a fluid actuated rock drill comprising a pair of relatively reciprocable members, one having opposed pressure surfaces in pressure chambers in the other member,.and including a main valve with an actuating surface which is manually operated in one direction to supply fluid to advance and operate the drill and is automatically operated in the other direction to interrupt and reverse the feeding device when the latter is fully extended, an automatic valve is displaceably mounted on one of the members within one of the pressure chambers so as to be displaced with respect to the said member to admit pressure fluid to the actuating surface at the end of the feeding operation and thereby operate the main valve in the other direction. In the form shown, a feeding device comprises a stationary cylinder 27 containing a piston 28 with opposed differential pressure surfaces 29, 30 and connected by a rod 31 to a rock drill 21. Pressure fluid is supplied by a conduit 41, secured to a plate 36, into the bore 40 of a throttle valve 39 in a chamber 38, the valve having a stem 42 manually actuated by a lever 43 to the open position. The valve 39 has a port 45 to register with a passage 44 which supplies the fluid to the rock drill 21. A port 47 connects the bore 40 to a part-annular groove 46 which may register simultaneously with two passages 48, 49. The passage 48 opens into a chamber 50 in the rod 31 and a passage 51 therefrom leads to pressure chamber 52. The passage 49 connects with a tube 53 which leads to an enlarged pressure chamber 54. The passages 48, 49 may be opened to the atmosphere through a groove 71 in the valve 39, the groove 71 connecting with a longitudinal groove 72 and an exhaust port 73 in the plate 36. The latter is also provided with a piston chamber 55 accommodating a swing piston 56, which is keyed on the stem 42, and formed with an exhaust port 60 and an air vent 61. Pressure fluid is conveyed to the pressure surface 62 of piston 56 by a passage 63, tube 64, and a port 65 associated with the pressure chamber 52, the pert 65 normally being closed by a valve 66 and a spring 67, a flange 69 on the valve 66 abutting against a shoulder 68 on the rod 31. When the feeding device is fully extended the flange 69 engages a head 70 on the cylinder 27, the valve 66 is moved, and the port 65 communicates with the pressure chamber 52. The valve 39 is thereby rotated, through the intermediary of the piston 56, until the groove 46 is out of register with the passage 49, the pressure in the chamber 54 is reduced, and the pressure in the chamber 52 retracts the piston 28. The passage 49 also connects with a passage 77 which leads to a passage 76 in a rotatable handle 74 on the drill, and it may be connected to the atmosphere by means of a port 78, a valve 79, and a pivoted lever 80. By this means pressure within the chamber 54 may be relieved when the drill encounters soft strata in the rock.