Patent GB-738383-A (GB)
Title: Manual and power actuated steering gear
IPC: B62D5/06
Filed: 1952-06-06
Abstract: 738,383. Fluid-pressure servomotors; pressure-relieving devices for fluids; valves. GEMMER MANUFACTURING CO. June 6, 1952 [July 2, 1951], No. 14331/52. Class 135. A power-assisted vehicle steering-gear comprises a hydraulic pump I<SP>2</SP>, Figs. 7, 12, discharging through a spring-loaded by-pass valve N which maintains a substantially constant rate of flow despite variations in speed of the pump, branches I<SP>5</SP>, I<SP>6</SP> connected to the outer ends of cylinders D, D<SP>1</SP> containing pistons H, H<SP>1</SP> which abut a lever B<SP>3</SP> on a shaft B carrying a drop arm B<SP>2</SP> connected to the road wheels, and valves K, K<SP>1</SP> controlling return lines I<SP>7</SP>, I<SP>8</SP>, I<SP>4</SP> to a reservoir I<SP>1</SP>, the valves being operated by lateral displacement about a spherical bearing F<SP>1</SP> of a section F of the steering column caused by the torque reaction between gear-wheels G, G<SP>1</SP> mounted, respectively, on the steering column section F and on a shaft G<SP>2</SP> carrying a worm C meshing with a worm-wheel B<SP>1</SP> on the shaft B. The sections E<SP>1</SP>, F of the steering column are interconnected by a tongue and slot with an interposed rubber &c. element F<SP>5</SP> and the valves are actuated by a block L rotatably mounted on the section F and engaged by a roller L<SP>1</SP> to maintain the gear-wheels G, G<SP>1</SP> in mesh. The valves K, K<SP>1</SP> normally permit restricted communication of each line I<SP>7</SP>, I<SP>8</SP> with the line I<SP>4</SP> through a passage a', Fig. 6, and parallel passages a<SP>5</SP> controlled by lands b<SP>4</SP>. When the block L is moved, e.g. towards the valve K, Fig. 7, the restriction in the line I' is increased and that in the line I<SP>8</SP> decreased, the resulting pressure changes in the cylinders D, D<SP>1</SP> causing the pistons, H, H<SP>1</SP>, to move to the right. These pressure changes are also transmitted through the branches I<SP>5</SP>, I<SP>6</SP> to a valve O causing a valve member 0 which is normally centralized by a resilient arm O<SP>7</SP>, to move towards the branch which is at lower pressure thereby reducing the flow to the corresponding cylinder D or D<SP>1</SP> and increasing the flow to the other cylinder to increase the pressure difference acting on the pistons H, H<SP>1</SP>. The pressures in the lines I<SP>7</SP>, I<SP>8</SP> are transmitted to the outer ends of the valves K, K<SP>1</SP> to provide " feel." In a modification, a separate pump is employed for the supply to each of the cylinders D, D<SP>1</SP>. In a further modification, the pump is connected to the two cylinders D, D<SP>1</SP>, through valves K<SP>2</SP>, K<SP>3</SP>, Fig. 8, similar to the valves K, K<SP>1</SP> and also operated by the block L. The arrangement is such that the initial movement of the block L partially operates the valves K, K<SP>1</SP> whereupon the pressure differences set up enable the valves K <SP>2</SP>, K<SP>3</SP> to be operated to control the flow to the cylinders D, D<SP>1</SP> in like manner to the valve O of Fig. 7. After the valves K<SP>2</SP>, K<SP>3</SP> are fully displaced the operation of the valves K, K<SP>1</SP> is completed. Pressure relieving devices for fluids.-To absorb pulsations in the delivery from the pump a device comprising telescopically engaged tubular elements P, P<SP>1</SP>, Fig. 10, loaded by a tension spring P<SP>4</SP> is fitted in the pump delivery line. Valves; actuation retarding.-Outward movement of the valves K is checked by fluid in a chamber b<SP>9</SP>, Fig. 6, from which it can escape only through a restricted opening R<SP>1</SP>. A check valve R opens to permit unimpeded movement in the opposite direction. In a modification, an additional restricted passage is controlled by movement of the valve K to provide a progressive retardation and the check valve also carries an additional ball check valve opening in the same direction.