GB540354A - Improvements in electrical apparatus of the eddy current type - Google Patents

Abstract

540,354. Electromagnetic couplings. WINTHER, M. P. Sept. 28, 1940, No. 14674. Convention date, May 4, 1940. [Class 35] In eddy current apparatus, such as an electromagnetic clutch, noiseless cooling is effected by forming the eddy-induced drum on its outer surface with a number of ribs surrounded by an outer cover in such a way that cooling air enters the spaces between the ribs at the edge of the drum and leaves them through a space between the edge of the cover and the periphery of the drum. Means for demountably coupling the apparatus so as to allow for disalignment of the driven member are also described. The doublytruncated eddy drum 5 of the clutch shown in Fig. 1 is carried by and spaced at 9 from a carrier 2 on the driving shaft 1 and is doubly coned on its outer surface which, as shown in Fig. 3, is formed with close-set milled-out ribs 63. The edges 11, 13 of the carrier 2 and a cover 15 at the other end, together with layers of binding wire 53 in grooves on the periphery of the ribs, enclose the channels between the ribs as far as the central openings 47, between which cooling air is flung out centrifugally after being entrained through the openings 22 in the magnetic spider 23 which carries the inducing member. This consists of magnetic rings 25 clamped to the annular yoke on either side of the magnetizing coil 29 and having teeth 27, Fig. 3, analogous to those shown in Specification 533,725. In an alternative form, Fig. 8, the air ducts consist of sinuous grooves formed by annular ribs 75, 81 on the exterior and interior surfaces of the eddy drum 5 and cover plates 77, 79 respectively. The binding wire may be applied, as shown in detail in Fig. 5, by placing its end first in a sawcut 67 across one of the ribs, hammering over the slot, passing the wire next through oblique cuts which are then hammered up 69, 71 in two ribs, winding it under tension in the groove around all the ribs and anchoring it at its other end similarly in hammered up slots. When several layers of wire are used their, ends are anchored in this way in fibs symmetrically chosen around the periphery of the drum. A single layer of metal tape may replace the binding wire. To allow for disalignment between the driving and driven shafts 1, 39, Fig. 1, the rotor 23 is attached to an intermediate shaft 35 and is mounted on a spherical bearing 31. The shaft 35 is coupled to the driven shaft by a clutch consisting of rounded teeth 91, 92 between which are convolutions of a leaf spring 95 within a cover 93 carried by the clutch member 89. A spring-pressed pin 90 forces the teeth 91, 92 into engagement with the leaf spring to reduce noise. The shaft 35 may be easily removed by removing the bolts 97 from the hub and moving the shaft back to clear the centering shoulder 36.