GB354040A - Improvements in or relating to power transmission by electromagnetic means - Google Patents

Abstract

354,040. Electromagnetic clutches ; transmitting mechanical power. MURPHY, J., Coolfadda Mills, Bandon, Co. Cork, and BRENNAN, J., 80, Highfield Road, Rathgar, Co. Dublin. July 23, 1930, No. 22244. [Classes 35 and 38 (iv).] In an electromagnetic power transmission apparatus comprising an armature and a field magnet, the speed ratio of the driving and driven shafts is rendered automatically variable by mounting one or both members of the clutch upon spiral or screw thread mountings so as to be axially movable. In Fig. 1, the armature a is screw-threaded at e on the driving shaft b and can move axially against a spring f bearing against a sleeve b<11> fixed to the shaft. If the shaft b accelerates in the direction of the arrow, the armature will lag and will move to the right so that the field effect thereon is varied. The driven field magnet c accordingly will tend to run at constant speed. The field winding and armature are connected in series. In a modification, Fig. 4, the driving shaft b is screw-threaded at g in an armature a and the driven shaft d is threaded in a second armature a<1>, both threads being left-hand. Springs h, k normally maintain the armatures in the weak field positions. Acceleration of the shaft b in the direction of the arrow causes the armature a to move into the stationary field c, and the armature a<1> moves into the field c<1> when exerting its maximum torque on the shaft d. To enable the armature a<1> to move axially in either direction of rotation, the shaft d<1> is threaded in a sleeve l which is itself oppositely-threaded in the armature. The spring k may react on the armature a instead of on the fixed collar on the shaft d, in which case the armature a is fully positioned in the field c and the spring h and screw-thread g are arranged for inverse operation. The armature a also may be mounted on a slidable key so that when in the maximum field it will be moved outwards by inward movement of the armature a<1>. The armatures and field coils are all connected in series and a double pole change-over switch is provided to reverse the current through the armature a<1> whereby the driven shaft can be started, stopped or reversed by means of the switch.