GB849128A - Improvements in apparatus for magnetically holding work pieces or other articles - Google Patents

Abstract

849,128. Magnetic work-holders. SYKES, A. E. June 17, 1959 [March 17, 1958], No. 8463/58. Class 60. A magnetic work-holder comprises a plate or block 10 having means for magnetically holding work thereon and a plurality of plungers 37, Fig. 3, which protrude from the work-engaging face at different parts thereof; in combination with fluid-pressure operated means for securing the plunger in a position in which they make contact with the work. The plate 10 may be flat or may have a profiled working surface contoured to correspond approximately to the shape of a workpiece ; it may be separate or an integral part of a magnetic chuck. The selfadjusting plungers 37 are spring-loaded to bear against the work-piece as it is placed in position and are looked by fluid-pressure to form rigid support so that when the plate is energised the plungers will prevent the work from being distorted at points where gaps exist between the work and the surface of the plate. The adaptor plate 10, Fig. 2, has inserted at spaced intervals transversely extending pole-piece 13 either permanent or electro-magnetic, and a plurality of plunger-receiving pockets 14 arranged in rows and connected by bores 15, alternate bores having linking connections 17 at their outer ends with adjacent bores to provide a continuous pressure channel through the plate from an inlet 20 to the group of plunger sprockets at the remote end. Each plunger 37, Fig. 3, is supported by a spring 41 within a.thinwalled cylinder 34 having flanges 32, 33 pressed into the plate 10. Ring seals 35, positioned by a split cylindrical distance-piece 36, form pressuretight seals. The head 38 of each plunger is surrounded by a flexible washer 39, the periphery of which engages a recess 40 in the mouth of the cylinder. Fluid pressure is applied simultaneously by a screw-jack 26 to the cylinder walls 34 to grip the plungers until a pre-determined pressure is reached, as indicated by the extent to which a spring-loaded indicator 27 projects from a casing 23. Alternative methods of housing and sealing the plungers in the plate are described. In one modification, the spring 41 is omitted, the plunger being moved upwardly by the resilient washer 39 and/or by the attraction of the work-piece for a plunger of magnetic material ; the plunger may alternatively be locked by fluid pressure from within as described in Specification 802,278.