GB728829A - Improvements in and relating to distributing valve mechanisms for devices having pistons operated by compressed air - Google Patents

Abstract

728,829. Engine distributing valves; valve gear. BOHLER & CO., AKT.-GES., GEB. April 10, 1952 [April 11, 1951], No. 9197/52. Class 122 (2). In a distributing valve mechanism for devices having pistons operated by compressed air, particularly impact tools, in which two annular valve a, b slide one within the other the compressed air is supplied during the working stroke of the piston through two annular gaps and during the return stroke through only one annular gap. The valve a has a cylindrical part c which is slidable within a cylindrical part d of the valve b and controls a port g therein. During the working stroke as shown in Fig. 1 the valves are slid into each other as closely as possible, the valve a bearing on a seat s and compressed air flows between the valve a and a seat m and between the valve b and a seat n to the cylinder space above the piston to force the latter downwards; air below the piston being exhausted to atmosphere through a passage e, annular groove f, port g, and annular groove h. Towards the end of its working stroke the piston first uncovers a port communicating with a passage p leading via passages q, r to cavities i, k in the internal end surfaces of the valves a, b, and then immediately after uncovers its exhaust port. Since the passage p is of relatively small diameter the - pressure of the air acting on the valves a, b to press them together falls before that in the cavities i, k and the valves a, b are thereby forced apart so that valve a bears on seat m and valve b on seat n and port g is closed. Compressed air then flows between valve a and seat s and through passage e to the cylinder space below the piston to urge the latter upward on its return stroke. When the air above the piston is sufficiently compressed it causes the valves to slide into each other again and the cycle recommences.