GB785246A - Improvements in or relating to magnetic chucks or clamping devices and methods of manufacturing such devices - Google Patents

Abstract

785,246. Printing surfaces. HERZER, A. E. Aug. 9. 1955 [Aug, 12, 1954, Nov. 29, 1954], No. 22935/55. Class 100(2) A magnetic chuck or clamping device comprises a base at least one outer surface of which formed as a work holding surface and having one or more longitudinally extending bore of circular cross section therethrough, a rotatable magnet assembly in the bore(s) consisting of at least one flat bar permanent magnet mounted in non-magnetic guiding means of circular crosssection which engage the walls of the bore(s) and ensure that an air gap of unitform width all round the bore is provided for the pole faces of the magnet and means for rotating the magnet assembly engaging at least one end thereof. As shown in Fig. 5, the magnetic holder or clamp comprises a base 1 of magnetizable material in which longitudinal and transverse grooves have been cut and in which rest flat bars 4 also of magnetizable material, the spaces between the bars and the base being filled with non-magnetic material. Bores 6 are provided in the base 1 such that the bars 4 form part of the wall of the bores and into these bores are inserted permanent magnets 7, 8 the poles of which are aligned vertically when the magnet is the position shown at 7, so that a printing surface may be held on the block, but which are aligned horizontally when the magnet is in the position shown at 8 so that no force is then exerted on the printing surface which may then be moved or replaced. The magnets are held in the bores by means of cylindrical coupling parts 24 (Fig. 13) of non- magnetic material having 'slits 25 into which the magnets are inserted. The magnets have slots 21 therein into' which fit head pieces 23 having bolts 22 which fit into bores in the coupling pieces 24. An end coupling piece is provided having a portion of reduced diameter provided with means for the insertion of a tool for rotating the magnet. The magnets in all the bores may be rotated simultaneously as shown in Fig. 18.. On the end coupling pieces are mounted toothed wheels 30, 31. 32 which co-operate with toothed racks 33, 34, so that when one magnet is rotated the racks cause rotation of the other magnets. The racks are held in position by a suitable cover plate attached, to the base plate 1. Instead of the coupling pieces 24 a single cylindrical holder may be used having longitudinal slots therein for accommodating the magnet. The bores 6 may be provided in a cylindrical base in which case, the magnets are rotated in unison by turning a toothed wheel 41 (Fig. 21) which meshes with a toothed segment 44 the outer surface of which meshes with the toothed wheels 40-40<SP>1111111 </SP>associated with the magnets. The wheels 40-40<SP>1111111</SP> also mesh with a fixed toothed rim 42 on the cylinder. The turning of the magnets is limited by a stop device 45. Alternatively, (Fig. 22), instead of the gear wheels 40-40<SP>1111111</SP>, wheels 46-46<SP>1111</SP> having stop arcs 47 and 48, and grooves 49 are provided. A pin 54 on a wheel 51 actuated by a gear wheel 55, cooperates with grooves 49. Normally, turning of the wheels 46-46<SP>1111</SP> is prevented by engagement of the arcs 47, 48 on the rim of the wheel 51, but in the region of the pin 54 the wheel 51 is provided with an arcuate hollow 52. Thus as the wheel 51 is rotated the magnets are sequentially moved from an inoperative to an operative position. In a further embodiment, the grooves in the base plate 61 (Fig. 27) in which the bars 64 are located may be dovetailed, the bars 64 having dovetailed portions 65 which fit into the grooves. Strips 66-69 of non- magnetic material are inserted into the spaces between the grooves and the bar portions 65. the remaining spaces being filled with further non-magnetic material.