GB1275812A - A compressed-air percussion tool - Google Patents

Abstract

1275812 Pneumatic tools KARL SCHMIDT GmbH 16 Oet 1969 [22 Nov 1968] 50937/69 Heading B4C A pneumatic tool, e.g. for dressing castings, comprises a main piston 1 reciprocable in a cylinder 9 mounted within a compressed air chamber 10, a valve 2 connected by a tubular shaft 6 to -an auxiliary piston 7, a spring 8 normally urging the valve into closing relationship with the upper end of the cylinder, means for releasably holding the mainpiston 1 in an initial position at the upper end of the cylinder, and means for creating a suction in the cylinder space above the main-piston 1 when the valve is in its lowermost position and the main piston 1 is in a driven position. In operation, compressed air supplied via pipe 20 forces auxiliary piston 7 against bias of spring 8 and the valve moves away from the cylinder. The main piston is then -driven on a working stroke. When supply via pipe 20 is terminated, -the valve 2 closes the cylinder, the space above the main piston is vented via ports 18, 19 and duct 17, and compressed air acting through ports 12, 13 initially forces a piston valve 16 downwardly, and then passes through a nozzle 14. Suction is thus induced in the space above the main piston in the piston valve, which is returned to its initial position. The-piston valve is contacted by the main piston during its-return stroke, and the piston valve closes communication between the nozzle 14 and ports 12, 13. The main piston may be held in its initial position by magnets or as shown by a spring ring 3. The main piston includes a plastics jacket 22 consisting of individual rings 23, 24.