GB799411A - Improvements in or relating to lifting magnets - Google Patents

Abstract

799,411. Magnetic lifting devices. NEILL & CO. (SHEFFIELD), Ltd., J. Jan. 9, 1957 [Jan. 26, 1956], No..2559/56. Class 78 (4). [Also in Group XXXV] A lifting magnet comprises a permanent magnet 18 movably mounted so that its flux may be directed into and out of a magnetic circuit which includes at least two pole pieces 2, 6, 1 separated by non-magnetic material 7, 8 and any magnetic load not shown bridging the pole pieces, and a mechanism operated by relative vertical movement of a suspending member when the magnet is lifted from a support alternately to move the permanent magnet to energize and de-energize the lifting surface 4, 5 formed by the pole pieces. As shown, the mechanism comprises a sleeve 27 urged downwardly by a spring 30 and bearing a rack 34, Fig. 3, meshing with a pinion 35 borne on a shaft 36 and rotatably coupled thereto by a ratchet 39 ... 42. The shaft 36 also has a crank pin 43, Fig. 4, slidable in a slot 44 in a lever 45 pivoted at 46 and carrying pivotally at 47 lugs 20 secured to the upper pole piece 15 of two annular pole pieces 14, 15 secured by bolts 19 to the annular permanent magnet 18 which may comprise a number of segments. When the whole magnet is resting on a load to be lifted initial lifting effort on an eye 28 raises stem 27 relatively to the whole magnet and through the gearing 34, 35 and mechanism 43, 45, 20 lowers the magnet assembly 14, 15, 18 so that pole piece 14 enters a recess 13 of pole piece 6 whereby the magnet 18 energizes the lifting surface 4, 5 via the pole pieces 14, 6, the load, two parallel circuits comprising a housing part 1 and the core 2, and the pole piece 15. The load may then be moved, and during the final stage of subsequent lowering the stem is reset by spring 30. The next lifting effort raises the magnet assembly 14, 15, 18 whereby its flux passes through only the parallel circuits of part 1 and core 2, and the load is left deposited. A handle 51 indicates the position of the magnet assembly and has a mechanism providing for manual movement of the assembly. In another embodiment, not shown, a key and keyway and a cam and follower replace the rack and pinion and the ratchet and crank respectively; also, the pole piece faces have annular complementary grooves and the stem has a bellows to exclude foreign matter. The Provisional Specification refers to the magnet having spaced segmental lower poles partial rotation of which effects holding or release of the load.