Patent GB-770684-A (GB)
Title: Improvements in or relating to electrical power transmission system
IPC: B62D5/02
Filed: 1954-09-24
Abstract: 770,684. Electric follow-up systems. HUPP CORPORATION. Sept. 24, 1954 [Sept. 29, 1953], No. 27641/54. Class 40 (1). [Also in Group XXXI] In a power transmission system comprising resiliently coupled driving and driven members, a pair of driving elements power driven through a pair of electromagnetic clutches in series with the parts of a rheostat on opposite sides of a normally central contact arm, apply a torque to the driven member the magnitude and sense of which depends on the relative energization of the clutches which is controlled by the relative positions of the driving and driven members to which the rheostat winding and contact arms are connected so that the driven member followup movements of the driving member. In the power-assisted steering mechanism shown in Fig. 1 motion is communicated from the steering wheel 122 to steering column 119 through the resilient coupling shown. Member 123 on the steering wheel engages a pair of pins 125 (only one visible in Fig. 1) resiliently urged against it by springs 126 abutting flanges on a plate 121 fixed to steering column 119. The initial tension of the springs is adjustable by the adjustable nuts shown. Consequently the wheel is angularly displaced relative to the column an amount proportional to the resistance offered by the road surface. The displacement is converted into a displacement of moving contact 105 of rheostat 104, the body 118 of which is fixed to plate 121, via sector 117 fitted on the wheel and pinion 115<SP>1</SP>. An extension 175 of the contact arm forms with segments 172, 173 a switch in series with motor 92 which is therefore operative whenever turning effort is applied to the steering wheel. The motor drives shaft 93 on which pinions 96, 97 engaging crown wheel 98 are free to rotate. Weak equal torques are continuously applied to the pinions through magnetic clutches 89, 91, e.g. of the magnetic particle type, the windings of which are in series with the parts of the rheostat winding between contact 105 and ends 107, 108 respectively and with battery 113. Consequently with no torque applied to the steering wheel balanced torques act on wheel 98 which through the gearing shown moves the track rods and hence the steering column. When the steering wheel is turned the distribution of current in the two clutch windings is altered thus causing a resultant torque to be applied to crown wheel 98 in such a direction as to make the steering column follow up the movement. The rheostat windings may be shaped so as to give a linear or any other relationship between the power assistance and the turning effort at the steering wheel. Member 123 moves in an elongated slot 124 in plate 121 so that should the power fail it engages plate 121 to steer the car directly. Similarly if the power assistance is inadequate direct engagement will again occur but in this case the maximum available power assistance will be sustained. In an alternative system (Figs. 6 and 7, not shown) motor 92 is replaced by a shaft driven off the engine via a belt and pulley system which includes a releasable coupling to allow unassisted steering with the engine stopped. In this case shaft 99 drives the steering column direct through a pair of bevel wheels one of which is mounted on the column and a similar arrangement may be used in Fig. 1. U.S.A. Specification 2,587,377 is referred to.