GB572007A - Improvement in and relating to a permanent magnet chuck or work holder - Google Patents

Abstract

572,007. Magnetic chucks. SIMMONS, F. L. May 21, 1943, No. 8137. [Class 60] [Also in Group XXXV] In a magnetic chuck of the kind having a work-supporting plate 14, Figs. 1 and 2, oomprising two sets of alternately arranged polepieces 12, 13 of opposite polarity, and wherein the operating magnet or magnets 10, 11 may be disconnected from the polepieces to facilitate removal of the work-piece from the supporting plate, the effects of leakage flux, which would interfere with the removal of the work-piece, are reduced by the provision of one. or more non-magnetic slides, such as 40, 46 carrying magnetic blocks 42 which are arranged to bridge the sets of polepieces, as shown in Fig. 2, when the magnets are disconnected from the polepieces. When the chuck is operative, the blocks 42 register with the polepieces, as shown in Fig. 1, and polar ridges 18-all of the same polarity-on the upper surface of the magnets are in contact with the polepieces 12, the polepieces 13 being connected to polar ridges 19 of the opposite polarity on the lower face of the magnet through the side plates 15 and baseplate 16 of the chuck which are of magnetic material. The base-plate has ridges 27 corresponding with the ridges 19 and the grooves 28 between them are filled with Babbitt metal, as also are the spaces 26 surrounding the polepieces 13 which are of less depth than the polepieces 12. Disconnection of the magnet from the polepieces is effected by a crank 36, rotation of which through 180 degrees moves the magnets by means of an eccentric pin 33 and cam plate 30, into a position where the polar ridges 18, 19 register with the Babbitt metal-filled spaces 26, 28. The slides 40, 46 are operated by movement of the magnets through a lost-motion connection provided by lugs 43, 44 depending from the slides into one of the channels 20 between adjacent polar ridges 18 of the magnets. When the chuck is to be out of use for a time, the slide may be used as a keeper for the magnets by returning the crank through 90 degrees so-that the parts then occupy the positions shown in Fig. 3 and a closed magnetic circuit is formed. In a modified construction, the magnet structure comprises three spaced magnets arranged side by side with the upper surface of the outer magnets of opposite polarity to the central magnet, the side plates of the chuck being of non-magnetic material. In this construction, the magnets may be stationary and have flat upper and lower surfaces, connection and disconnection of the upper surfaces with the polepieces of the work-supporting plate being effected by a movable pole-plate arranged between the under surface of the work-supporting plate and the magnetic and non-magnetic sections. U.S.A. Specification 2,286,238 is referred to.