GB1260285A - Pressure fluid operated tool - Google Patents

Abstract

1,260,285. Safety arrangement in a pressure fluid-operated tool. N. B. PARSON, and S. M. ROSE. 16 Jan., 1969 [18 Jan., 1968; 9 April, 1968], Nos. 2892/68 and 16901/68. Heading B4C. A pneumatically-operated tool including a piston 53 and a blade 49, for driving a fastener, e.g. a nail or staple, or to which a tool kit is connected, a chamber 2 connected with a source of compressed air, and a differential piston-type valve member 21 comprises means for preventing operation of the tool unless it is held against a work surface. The means includes a duct 43 and conduit 42 joining the chamber 2 and the nose 40 of the tool, a duct 37, 38 joining the nose and a chamber 35, sealing members 46, 47, and a spool valve 32. The conduit 42 may have a ball valve (as shown) which is unseated upon application of the tool to a work surface or a manuallyoperable valve. In operation, when the tool is pressed against a work surface compressed air passes via duct 43, conduit 42 and duct 37, 38 to move the spool valve upwardly, thus opening chamber 22 to atmosphere via ducts 27, 28 and 33. The valve member 21 is thus raised from its seating on apertured disc 18 and compressed air acts on the upper surface of the piston. The space below the piston is initially open to atmosphere via gap 50. When the space is closed to atmosphere the air below the piston is compressed until the piston abuts a resilient buffer 10, in which position compressed air passes via annular valve member 56 into space 4 and via apertures 55 into the space below the piston. Withdrawal of the tool from the work surface causes the spool valve to return to its initial position thus opening the chamber 22 to the chamber 2 and closing the chamber 22 to atmosphere. The valve member 21 is thus moved downwardly to seat against the disc 18 and to open the space above the piston to atmosphere via ducts 14, 15. The piston 53 is then returned to its initial position, by air therebelow. When a bit is attached to the blade 49, the tool includes means providing a succession of pressure impulses to the piston whilst the tool is pressed against a work surface.