GB1237892A - - Google Patents

Abstract

1,237,892. Impacting apparatus. F. C. F. EVENNETT. 9 June, 1969 [17 June, 1968], No. 28734/68. Heading B4C. [Also in Divisions F1 and F2] Apparatus for applying vibrations to an associated apparatus, for oscillating a shaft about its axis, or for applying impacts to a tool comprises a cylinder a, and a piston b reciprocable in the cylinder. The chamber at each end of the cylinder has an exit openable and closable by a valve member, the valve members being so connected that when one exit is open the other is closed. A chamber f within the length of the piston and bounded by the piston and cylinder is in constant communication with a fluid supply port e and, via passages g, h, m, with the end chambers. The piston itself effects movement of the valve members. As illustrated the apparatus is a pneumatic drill and includes a tool holder d defining one end of the cylinder. The valve members o<SP>1</SP>, o<SP>2</SP> are interconnected by a tie-rod p. In the condition shown, the piston will move under air pressure in end chamber-” towards end cap c and will engage valve member o<SP>1</SP> to close exit l and open exit q. The piston will then move in the opposite direction. Annular chamber r coacts with an annular projection s on the piston to provide an air cushion. A resilient packing t is provided to absorb blows delivered by the piston to the tool holder. Reciprocation of the piston is controlled by adjustment of a sleeve valve u. Instead of the tool holder the cylinder a may be closed at its bottom end by an end cap similar to end cap c. The apparatus when so constructed will be used to impart vibrations to an associated apparatus to which it is connected, e.g. a sand sifter. Alternatively the piston may include a gear rack adapted to mesh with a gear mounted on a shaft passing through the cylinder wall so as to oscillate the shaft about its axis.