GB1310194A - Hydraulic fluid actuated percussion tool - Google Patents

Abstract

1310194 Hydraulically actuated percussive tools ATLAS COPCO AB 16 June 1971 [16 June 1970] 28128/71 Heading B4C [Also in Division B3] An hydraulic fluid e.g. oil actuated percussive tool comprises a cylinder a hammer piston reciprocable in the cylinder and defining therewith two variable volume for receiving hydraulic fluid means for alternately connecting one or the one and the other of the chambers to a source of pressurized hydraulic fluid and to draw an accumulator converted to the one of the chambers and loaded by a spring and means for automatically loading the spring in proportion to the pressure of the hydraulic fluid supplied to the tool. In operation of the tool illustrated fluid supplied via conduit 43 (with the valve in the illustrated position) passes to the chamber 25 to urge the hammer piston 12 on its working stroke to apply an impact via an anvil 24 to a drill rod 19 which can be rotated by hydraulic motor 20 and which can receive flushing fluid via connection 23, and valve 42 is held in its illustrated position by fluid passing through conduit 59 and acting on surface 58. When the piston portion 14 passes the port of conduit 57 fluid passes from the chamber 25 to act on surface 55 of the valve 42 and force the valve 42 to the left thus connecting the supply conduit 43 to the chamber 34 to effect braking stopping and the return stroke of the piston and connecting the chamber 25 to drain via conduit 48. The valve is held in its leftmost position by fluid passing through conduit 61 and action on surface 60. During the braking of the piston on its working stroke excess fluid passes to the accumulator 38 and this fluid is returned to the chamber 37 during the return stroke. When the chamber 34 is connected to conduit 56 via a selected one of conduits 56a (the appropriate conduit 56a is selected by varying the position of a pin 63 thus the piston stroke can be varied), the valve 42 will be returned to its illustrated position and the chamber 25 will be connected to the supply conduit 43 to effect braking stopping and the working stroke of the piston. The accumulator 30 will store fluid during this reversal of the piston's movement. If the piston on its return stroke passes groove 25 its motion will be reversed by fluid trapped in chamber 25 and by an accumulator 32. On the working stroke over travel of the piston, due to a "no-load" condition or absence of the drill rod, will be cushioned by fluid trapped in the chamber 34 and slight leakage past piston portion 13. In an alternative embodiment (Fig. 5 not shown) fluid is constantly fed to one chamber (34) and a second chamber (25) is alternately connected by means of slide valve (79) to a supply conduit (43) and to exhaust. An accumulator (30) operable in the manner of accumulator 30 of the embodiment of Fig. 4 is connected to the second chamber.