GB847394A - Improvements relating to magnetic workholders - Google Patents

Abstract

847,394. Permanent magnets. PANTON, J. R., and WEBB, A., [trading as PANTON & WEBB]. Sept. 10, 1958 [Sept. 10, 1957], No. 28586/57. Class 35. [Also in Group XXIII] A magnetic work-holder comprises a work-holding surface made up compositely of a plurality of spaced pole pieces 1a, 1b, alternate pieces 1a making one series and the remaining pieces 1b another series, and switch means to rotate at least one permanent magnet from positions wherein the work-holding surface is rendered operative and inoperative respectively. The pole pieces are in the form of rectangular rhombic, trapezoidal, triangular, circular or polygonal laminations of magnetic material separated by laminations 2 of non-magnetic material; the thickness of the laminations may or may not be the same. The laminations are provided with a circular hole 4 of the same diameter as the magnet 12 which is cylindrical with flat, chordal surfaces 15, 16 and poles N, S located adjacent the arcuate surfaces 13, 14 thereof. The holes 4 in the laminations 1a are enlarged to the right, as shown at 6, and those in the laminations 1b enlarged to the left, as shown at 8. With the magnet in the bores with the chordal surfaces vertical, each arcuate surface of the magnet transmits flux to the laminations 1a and 1b, the flux path thus being internal of the laminations and the work-holding surface inoperative. When the magnet is rotated, say clockwise, 90 degrees, the N pole of the magnet is only in contact with, and therefore transmits flux to, the laminations 1b and the S pole of the magnet is only in contact with, and therefore transmits flux to, the lamination 1a and the work-holding surface is operative, the flux path being completed by a workpiece held on the surface. The longitudinal sides of the workholder are also operative and the lower surface may be made operative by removal of a non- magnetic base 3. More than one bore may be provided in the laminations for a plurality of magnets and two magnets each provided with a rectangular extension 30 at one end disposed in each bore with the projections abutting each other and engaging a slot in a disc 33 which has diametrically opposed keyways 34 co-operating with projections 35 on a pinion 36. A handle 37 which is on a spindle having a pinion 38 engaging racks 43 is movable through 180 degrees to displace the racks which are connected to further racks 42 engaging the pinion 36 to rotate the magnets through 90 degrees; the racks are provided with adjustable stops. The magnets in each bore may be operated independently from those in the other bores. The surface of the work-holder may be flat, V-shaped or have a concave depression.