GB1322493A - Drilling machines - Google Patents

Abstract

1322493 Rock drills VICTOR PRODUCTS (WALLSEND) Ltd 8 Sept 1970 [9 June 1969] 22529/69 Heading B3C A rock and like drilling machine comprises an hydraulic motor 10, for rotating the drill rod, and an hydraulic ram 12 for feeding the rod, a torque sensor 152 sensitive to the pressure of fluid supplied to motor 10 so as to sense the torque on the drill rod, and a thrust control valve 150 which controls the flow of hydraulic fluid to the ram in response to the pressure sensed, and which is able to reverse the fluid pressure being supplied to the ram if the torque on the drill rod exceed a predetermined value P. Hydraulic fluid is supplied at P and splits into lines 25, 26, 27. In the operative positions of three-position reversing valves 14, 16, the fluid passes along line 27 and by a line 18 to sump 19. Flow along line 26 is interrupted by valve 14, and flow along line 25 passes through thrust control device 150, and hence to a line 20, where the flow is interrupted by valve 16. Flow along line 26 passes to motor 10, back along line 28, and thence via device 150, to sump 19. Flow along line 20 passes to ram 12, back along line 29, and thence via device 150 to sump 30. Device 150 includes a three-position spool 151 which is maintained in its mid position, as shown, during normal operation of the drilling machine, by a balance of forces between the torque sensor 152 and a manually adjustable spring 153. Should the thrust become excessive sensor 152 gradually moves spool 151 so that its reverse-flow position b becomes progressively operative. This first causes a gradual throttling of the flow along lines 25, 20, to ram 12, and then shuts it off completely. Further movement of the spool starts the reverse flow, which is throttled less and less as the torque rises further, leading to an increasing reversal of the thrust applied by ram 12 to the drill rod. To prevent the ram from being starved of fluid when there is little or no load on motor 10, sensor 152 responds to the reduced pressure in line 24, and allows spring 153 to move spool 151 towards the a position so as to throttle the return flow from motor 10. Therefore the pressure in line 24 cannot fall below the value determined by spring 153.