GB844999A - Improvements in or relating to permanent magnetic chucks - Google Patents

Abstract

844,999. Magnetic chucks. HAGOU METAALWARENFABRIEKEN N. V. April 24, 1959 [April 24, 1958], No. 14057/59. Class 60. A magnetic chuck comprises upper and lower plates 16, 18 which are relatively movable from a first, work-holding, to a second, work-releasing position, at least one of the plates having a plurality of permanent magnets 28 adapted to co-operate with flux-conducting means 34 on the other plate to provide a work-holding circuit when in the first position, Fig. 2, and to neutralize the flux when in the second position and one of the plates being provided with at least one inclined cam surface 42 extending in the direction of relative movement for co-operation with a ball or roller 40 carried by the other plate so as to effect separation of the plates during relative movement of the plates from the first to the second position. The permanent magnet elements 28, 34, which may be of a partly ceramic material, are polarized in the direction generally parallel to the plane of the upper surface of the plate 16, like poles opposing those of adjacent elements. They are separated by space-bars 20, 36, of soft iron and are preferably provided with wearing-strips of non- magnetic material e.g. stainless steel. The spacer-bars are held in a frame comprising non- magnetic side and central members 22, 32, 24, 26. The two plates 16, 18 are contained within a non-magnetic housing 10 to which the upper plate 16 is attached whilst the lower plate 18 is movable within the side walls in the direction of polarization, to the extent of one pole-pitch. Springs 19 are provided to retain the plates in contact when the like poles of the elements 28, 34 are opposed. When moved towards the workreleasing position of the resulting attraction, the unlike poles is lessened by the action of the wedge-like cam members 38 riding on the followers 40. A second inclined face 44 allows the faces to contact again when a distance of one pole-pitch has been traversed by the lower plate 18. In the modification shown in Fig. 4, the direction of magnetism of the permanent magnets 62 is normal to the work contacting surface of the upper plate 50. Soft iron members 52 and 64 are separated by non-magnetic strips 54, 66, the whole being held together by draw-bolts 56, 68. The upper plate 50 is secured to a casing 58 of non-magnetic material, e.g. aluminium, whilst the lower plate 60 is allowed longitudinal freedom of movement during which cam-faces 78 engage rollers 76 to separate or close the contacting faces of the two plates. Springs, such as 19 of Fig. 2, may be used below the flux return member 70 to hold the separated lower plate from the bottom of housing 58.