GB1212975A - Improvements in or relating to percussive tools - Google Patents

Abstract

1,212,975. Percussive tools. BRITISH STEEL PILING CO. Ltd. 18 Jan., 1968 [19 Jan., 1967], No. 2831/67. Heading B4C. [Also in Division E1] A percussive tool operable by a compressible fluid comprises a differential area ram piston 6 reciprocable in a cylinder 2 having at least one fluid port at each opposite end region, a valve 30 for alternately connecting one port 26 to a fluid supply line 41 and effecting communication between the ports, the other port being spaced from the associated end of the cylinder, and exhaust ports 28. As illustrated the tool is a pile driver or extractor and the fluid is air. In operation compressed air admitted via the line 41 causes the differential valve piston 46 to move to the position shown. The line 41 then communicates with the port 26, and the piston is forced upwardly. When the exhaust ports 28 are closed by the piston, the air above the piston is compressed and when the pressure of that air reaches 45 lb./sq. inch the valve piston is displaced downwardly thus permitting the ports to communicate. The piston still continues to rise under its inertia thus raising the pressure of the air in the region of the cylinder above the piston and closes the port associated with the inlet conduit 24 before the air pressure above the piston is sufficient to reverse the piston motion. During downward movement the air pressure falls to 46 lb./sq. inch when the ports 28 are uncovered, thereby releasing air under pressure and-allowing the valve piston to be displaced by compressed air to the position shown. The piston stem 12 strikes an anvil block 22 which is attached to the cylinder by a resilient wire strap passing through aperture 21a. For raising or extracting a pile the tool is inverted and attached to a pile by wire bridles in which case the hammer piston is in an end position opposite to that shown. In order to commence reciprocation of the hammer piston, compressed air is admitted via conduit 48 and one-way valve 49 to the cylinder to raise the piston 6 until ports 28 are uncovered whereupon operation of the tool will commence.