Patent GB-1444402-A (GB)
Title: Electromagnetic lifting device
IPC: B65H29/30
Filed: 1973-11-02
Abstract: 1444402 Lifting magnets KOHAN SENDAN KIKAI CO Ltd 2 Nov 1973 [14 Sept 1973] 50958/73 Heading H1P Magnetic device for successively lifting steel sheets from a pile comprises an electromagnet body 12 suspended from a cable 20 attached to lugs by sling chains. The body 12 has a magnetic poleface 23 and a pair of casings 24, 26 spaced along opposite sides to contain non-magnetic gap setting members 28, 29 extensible therefrom by toggles simultaneously actuated by a solenoid 30 and connecting rod 32 for each adjacent pair (Figs. 1, 3, 5). The toggle mechanism 34 (Fig. 5) of casing 24 comprises links 36, 38 pivoted together at 35. Link 36 is pivoted at 40 to one end of gap setting member 28, and link 38 is pivoted at 50 to an adjustable fixture 48 on the top of casing 24, with a perpendicular arm 52 carrying counterweight 54. Solenoid 30 in adjacent casing 61 has coil 62 with axial iron plunger 64 therein operating rod 68 sliding in end member 68 to act perpendicularly to links 36, 38 over endpiece 74. A similar toggle mechanism 134 in casing 26 is operatively connected to the other such mechanism by the adjustable connecting rod 32 abutting links 36, 38 and the similar links of mechanism 134. In operation the lifting magnet is energized and the gap setting members 28, 29 are spaced off by gap h from the poleface 23 such that the magnetic force attracts the top sheet only (Fig. 3) for lifting; during which coil 62 of solenoid 30 is energized by the instructions of a timer 92 on the electromagnet body so as to displace the link members 36, 38 of each toggle and retract the gap setting members flush with the pole. The effect is to increase the attractive force on the sheet during lifting. The gap h is adjustable by the fixing assemblies 48 attaching the toggles to the tops of casings 24, 26 to be small for thick sheets and larger for thin sheets. Stops 88 of the casings 26 and the length of the connecting rod adjust the retraction of the gap setting members 28, 29. For detachment of the metal sheet by de-energization of electromagnet body 12 solenoid 30 is de-energized and the counterweights restore link members to detach the sheet and prepare for lifting the next. In a modification (Figs. 6, 7, 8, not shown) the sides of the electromagnet body are vertically grooved to retain slidable non-magnetic gap setting plates with projections fitting the grooves and castellated lower edges. A reversible motor on the electromagnet is coupled through worm gear to a transverse shift driving eccentrics engaging rectangular openings of the gap setting plates. The motor is controlled to project the plates a critical gap distance below the lower face of the magnet for lifting and thereafter to retract the plates and eliminate the gap, which is adjustable by varying the angle of rotation of the eccentrics.  In a further modification (Figs. 9, 10, 11, not shown) plural non-magnetic gap setting members are vertically slidable in guides spaced along the sides of the electromagnet body which are protruded and retracted by a worm geared drive motor through a threaded shaft traversing plural sliding blocks each with pins engaging fork members, which rotate eccentric discs bearing on the heads of the respective gap setting members, whose gap is adjustable by altering the rotational angle of the eccentric discs.