GB630533A - Improvements in clutches for conveying or preventing rotary motion - Google Patents

Abstract

630,533. Electromagnetic clutches. ROBERTSON, Ltd., D. R., and SAMPIETRO, A. C. Sept. 5, 1947, No. 24564. [Class 35] [Also in Group XXIV] An electromagnetically engaged jaw tooth clutch has baulking means preventing engagement until its coaxial members are synchronized, comprising interlaced field polepieces of opposite polarity, which, when substantial relative rotation exists, set up eddy currents in the armature thereby developing a demagnetizing flux opposing the magnetizing flux created by the exciting winding, and so reducing the excitation that the members remain disengaged. As synchronism is approached, the eddy currents decrease and the magnetizing flux becomes sufficiently strong to overcome a disengagement biassing means and effects engagement. Applied to a two-speed planetary overdrive gear, Fig. 1, comprising the output shaft 11 of a gear-box 10, a driven member 12 rigid with an annulus gear 15, pinions 14 on a planet carrier 13 fast on the shaft 11, and a hollow shaft 16 having a sun pinion 17 and splines 18, overdrive is effected by locking stationary the shaft 16. A coaxial armature 25, mounted on a sleeve 24 splined to the shaft 16, is biassed to the disengaged position by a helical compression spring 29. The surrounding field comprises a hollow ring 30 containing a winding 33 and having in its bore two rings of interlaced polepieces 31, 32 which set up eddy currents when the armature rotates above a predetermined speed. As ' stand still is approached, the force exerted by the field overcomes that of the spring 29 and the sleeve 24 moves axially to engage a stationary splined ring 23. Direct free-wheel and bi-directional drive effected by a wedging roller 21 and by the engagement of splines 18 and 19 prospectively. The invention is also applied to the conventional back-to-back pair of synchromesh clutches as used in automobile change-speed transmission gearing. In this case slip rings are dispensed with by having a two-part field, a stationary member carrying the coil and a rotating member constituting a polar inductor, the poles being cylindrically disposed. Direct current excitation is used, but low-frequency alternating current may be used in conjunction with a homopolar field.