GB813308A - A new or improved permanent-magnetic chuck - Google Patents

Abstract

813,308. Magnets. HAGOU METAALWARENFABRIEKEN N.V. Nov. 8, 1957 [Dec. 8, 1956], No. 34879/57. Class 35. [Also in Group XXIII] A magnetic workholder comprises a body member 3, Fig. 2, which incorporates a plurality of permanent magnets 5, presents at its upper surface elongated pole faces of alternate polarity and is slidable relative to a top plate 4 which has its upper surface formed from a plurality of soft-iron or like bars 11 of smaller width and spacing than the pole faces of the member 3 and separated from each other by narrow strips of non- ferro-magnetic material 12, and its lower surface formed from a plurality of soft iron or like strips 15 of the same width and spacing as the pole faces of the member 3. The body member 3 is constructed of the permanent magnets 5, which have their north poles uppermost, and soft iron or like bars 6 alternately arranged and separated from each other by aluminium spacers 7, the whole being clamped together by bolts 8. A soft iron or like plate 9 is secured to the base of the array which is slidable in an aluminium casing 1 between operative and inoperative positions. In the operative position, as shown in Fig. 2, the magnets and bars are aligned with the soft iron strips 15 secured to the top plate 4 which, in turn, is secured to the casing 1 and consists of the soft iron bars 11 and non-ferro-magnetic strips 12 clamped together between end blocks 13<SP>1</SP> by bolts 13. The narrow width of the bars 11 which may be straight or of zig-zag or other suitable shape, form an upper surface of narrow pole surfaces and enables small workpieces of little height to be securely held on the top plate. In the inoperative position, the array is moved half the pitch distance between the poles to the right so that the strips 15 bridge the space between the magnets 5 and bars 6 to substantially remove the magnetic force at the surface of the plate 4. In a modification, the strips 15 and bars 11 are replaced by rectangular blocks of the same width as the strips and having longitudinal vertical grooves cut approximately two thirds deep from the upper surface of the blocks and filled with non-ferro-magnetic material, the blocks being separated by a soft iron bar and non-ferro-magnetic strips. In a further modification, the strips 15 and bars 11 are replaced by groups of two or more profiled bars having a lower web portion 19, Fig. 4, and flange portion 20, the groups being separated by soft iron bars 11 and the intervening spaces filled with a non-ferro-magnetic material.