GB1010692A - Improvements in or relating to means for limiting mechanical vibrations in electrical apparatus - Google Patents

Abstract

1,010,692. Screw and nut gearing. BRITISH OXYGEN CO. Ltd. June 20, 1962 [July 3, 1961], No. 23717/62. Heading F2Q. To prevent the separation of mating surfaces in screw-and-nut gearing and thereby limit vibration in electrical apparatus wherein the screw-and-nut gearing effects relative displacement of parts to vary some electrical characteristic, the screw mating surfaces are inclined 15 to 50 degrees to the screw axis so as to have a wedging action and are subjected to a non-reversing axial electromagnetic force arising from operation of the apparatus. The electromagnetic force is augmented by a mechanical, such as spring, force. The thread may be of V form or, since only one flank is load-supporting, a buttress thread loaded on its "back" flank may be used. The screw-and-nut gearing may move a coil or set of coils or a stack of laminations relative to another set of coil or coils in a variable reactance transformer, such as a welding transformer, or a stack of laminations relative to a choke coil to adjust the impedance of a welding choke. In the moving coil welding transformer shown, a coil support 29 is integral with a nut 31 engaging a lead screw 10 which carries a handle 28, is mounted in a housing 27 and, to contain vibrations transmitted thereto, is adjustably, resiliently constrained in the axial direction by cup springs 17 arranged between adjusting nuts and lock nuts 23, 25 and washers 22 abutting thrust races 16. The support nut 31 has spaced threaded portions 33, 34 for stability. A helical spring 36 is interposed between the support nut 31 and an abutment nut 37. Both nuts 31, 37 are prevented from rotation by guides 38, 39 so as to maintain the same relative spacing during rotation of the lead screw 10 and thereby maintain the spring compression constant.