GB1177765A - Improvements in or relating to Devices for Applying Hammer Blows to a Body - Google Patents

Abstract

1,177,765. Percussive tools. H. BRIDEN. 3 Aug., 1967 [5 Aug., 1966], No. 35181/66. Heading B4C. [Also in Division F1] Anhydraulically-actuated reciprocating hammer, e.g. for breaking rock, cutting metals, actuating extrusion dies or driving piles, comprises a hammer member 19 supplied to a driving piston 21 moved on its leftward stroke by hydraulic pressure and on its rightward stroke by gas or spring pressure stored driving the leftward stroke and acting through piston 26 and a liquid column. Reciprocation is controlled by a slide valve 31 which is moved to its hammer-extracting position by system pressure acting through a piston and cylinder and a snap-action lever system, Figs. 5 to 8 (not shown), and to its hammer driving position by a push rod 34 engaged by the hammer at the end of its retracting stroke. Valve 31 controls hydraulically-actuated valves 255 and 216. In the positions shown, the hammer is on its return stroke with the right-hand side of piston 21 connected to pressure via passages 24, chamber 25 and valves 216 and 255 and the left-hand side of piston 21 connected to exhaust via chamber 23 and the valves. During the return strokeÀ piston 21 contacts the pistonrod of a piston 28 which cushions the impact, pistons 21 and 28 then continuing to move with an accumulator piston 26 to pressurize gas in a chamber 16, or a spring or springs. The return movement continues until the hammer triggers valve 31 through rod 34; valve 31 then reverses valve 255, which cuts off chamber 25 from pressure, except for a restricted connection 62, cuts off chamber 23 from exhaust, and causes valve 216 to move to the left to connect chamber 25 to chamber 23. The stored pressure in chamber 16 then acts on piston 26 to drive the hydraulic fluid out of chamber 25 into chamber 23 to move piston 21 and the hammer on the forward stroke. The rod 211 of piston 26 also displaces the fluid in chamber 23, so that piston 21 moves much faster than piston 26, until hammer 19 strikes the head 4 of the tool-driving shaft, Fig. 2 (not shown). If the energy of the impact is not completely absorbed by the workpiece, the shaft and hammer are brought to rest by piston and cylinder assemblies 7, 8 operating in two stages and connected to an accumulator piston 15 in chamber 16 via chamber 11; and also connected to the pressure supply via restriction 12. A plate valve 18 restricts return flow from piston 15 to pistons 7. When rod 34 is released by the hammer, valve 31 is returned to its position shown and reverses the actuating pressure connections to valve 255. Reversal of valve 255 is delayed by a flow restriction 218 in valve 31. When valve 255 has returned to its position shown, it connects chamber 23 to exhaust chamber 25 to pressure and causes valve 216 to close the connection between chambers 23 and 25 for the return stroke of the hammer. In Figs. 9 and 10 (not shown), piston 21 is coupled to hammer 19 by a connecting rod incorporating part-spherical joints and cushioning means, the piston being a fluidtight fit in its cylinder without seals. The hammer and drive assembly is mounted in a housing for axial movement, the housing incorporating hydraulic jacks for advancing the assembly to engage the workpiece, a valve being actuated by the assembly when fully advanced, to stop the drive and return the assembly to its starting position, Figs. 11 and 17 (not shown). Hydraulic piston and cylinder assemblies are engaged by the assembly at the end of its advancing movement to bring it to rest. The housing may be pivotally mounted on a ramoperated arm of a vehicle, Fig. 1 (not shown). A control circuit is described Fig. 17 (not shown).