GB739494A - A new or improved polishing machine - Google Patents

Abstract

739,494. Polishing turbine blades. GARRINGTONS, Ltd. July 26, 1954 [April 28, 1953], No. 11659/53. Class 60. A machine for polishing a gas turbine blade or similar elongated workpiece 14 comprises a chuck 26 for releasably supporting the workpiece, a pair of relatively-displaceable polishing body supports 13 disposed on opposite sides of the workpiece and each resiliently supporting a polishing body, and means for relatively reciprocating the chuck 26 and supports 13 in the direction of length of the workpiece, relatively reciprocating these members in a second direction substantially along the major axis of cross-section of the workpiece, and traversing the workpiece relatively to the support for the entire length of the workpiece to be polished. The supports 13 are carried on two arms 15 pivoted on a slide 11 which is traversed by a feed screw 12; the two arms are urged together by a spring 16 and can be withdrawn by a handoperated cam 17. Each support consists of a bracket of inverted channel shape in which is mounted by means of a bolted pressure plate 21, Fig. 2, a rubber block 19. The inwardly projecting portion of each block is provided with a series of horizontal slits 20 and supports an abrasive strip 24 which is clamped at its ends between the block and adjacent parts of the bracket and pressure plate. The inner faces of the blocks may be flat or of convex or concave form to conform to the shape of the blade being polished. The chuck 26 pivots freely on an arm 27 which, to provide the longitudinal reciprocation of the blade between the polishing bodies, is oscillated from a driven shaft 32 through a connecting rod 31 and pivoted lever 29; the pivot 30 of the lever 29 also carries a forked arm 3 which is connected by a link 37 with the arm 27 and urged by a spring 36 into contact with a cam 34 mounted on the end of the feed screw 12. By means of this mechanism, the workpiece is reciprocated at relative high frequency in its longitudinal direction, traversed for the full length to be polished by manual operation of the feed screw 12 and, through the medium of the cam 34 as the feed screw is turned, caused to reciprocate in the vertical direction at a small frequency and amplitude; during this operation the pivoted mounting of the chuck 26 permits the blade to turn in accordance with its twist. For polishing a blade embodying an edge, such as a profile edge, at least one of the supports 13 is arranged so that its associated abrasive strip 24 extends partially around, and resiliently engages, the edge. The Provisional Specification describes also the opposed faces of the supports 13 as being of L- form so as to provide a shallow recess in which the blade is received for engagement by the abrasive strips.