GB877437A - Improvements relating to eddy current coupling or braking devices - Google Patents

Abstract

877,437. Eddy current couplings and brakes. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Oct. 2, 1959 [Oct. 3, 1958], No. 31685/58. Class 35. In an eddy current device, shown in Fig. 1 as a brake comprising relatively rotatable, relatively axially movable primary and secondary members 1, 5 disposed one within the other, the primary member 1 carries a permanent magnet structure 6 defining a ring of alternate N and S poles 8 and the secondary member 5 carries axially off-set main and secondary elements 3, 4 of which the former when opposite the magnet ring affords a return path for the magnet flux and includes rotationally fast with the secondary member 5 a cylindrical electrically conductive part which provides a circulating path for torque transmitting induced eddy currents, whilst the secondary element 4 when axially moved to a position opposite the magnet ring instead of the main element 3 also affords a flux return path but is so constituted as not to transmit torque between the members. This constitution comprises laminating the element 4 and mounting it on bearings 17 so as to be freely rotatable, The conductive part may be either the magnetic body 12 itself affording the flux return path or a copper coating 15 thereon, and the coating may have a graded thickness in the axial direction to produce optimum braking characteristics. Guides 11 permit the axial movement and prevent rotation of the member 1. The axial movement may be controlled by a face cam 18 and linkage 19 driven through reduction gearing 20 by the shaft 5, and may control the rate of decent of nuclear reactor control rods reference being directed to Specification 832,694. In the Fig. 3 embodiment, the solid or laminated body 21 affording the flux return path of the main secondary element is rotatable on bearings 22 to reduce inertia. In modifications, the device may form a coupling in which both members are rotatable, the rotor member 3, 4, 5 may be axially movable instead of the stator 1, and the stator 1 may carry the secondary elements 3, 4 whilst the shaft 5 carries the magnets 6.