GB1095550A - - Google Patents

Abstract

1,095,550. Power steering. CLARK EQUIPMENT CO. Nov. 29, 1966 [Dec. 27, 1965], No. 53292/66. Heading B7H. A motor vehicle two-axle power steering system comprises a pair of hydraulic cylinders 28 operatively connected through their piston rods 34 with the front wheels 12 which are steeringly inter-connected by a tie bar 38, and a pair of hydraulic cylinders 44 operatively connected by their piston rods 50 with the rear wheels 16 with which is associated a tie bar 56. The hydraulic circuit includes a pump 62 and a flow control device 70 maintaining a constant flow and pressure in a supply line 72 to a steering control-unit 78 operated by the steering wheel 84. Opposite ends of the cylinders 28 are interconnected as shown and there are supply/return lines 80, and 90, the latter being connected by a valve 88 with a line 82 in the position shown in Fig. 1. In this position, the front wheels only are steered, pressure fluid being directed to one of lines 80 or 82 according to the direction of steer and returned through the other. A mechanical latch device may be provided for the rear wheels. A rod @2 is connected to a follow-up mechanism in the control unit 78. The opposite ends of the rear cylinders 44 are interconnected as shown, and the supply/return lines 98 and 100 are connected to the valve 88 as shown. When the latter is put in the position of Fig. 1A and a steering motion is obtained by pressure being applied in the line 80, the front wheels will be turned to the right, and the fluid displaced from the cylinders 28 is transmitted through the lines 90 and 98 to the cylinders 44 whereby the rear wheels 16 are turned to the left. Fluid displaced from the cylinders 44 returns through the lines 100, 82. For a turn in the opposite direction, pressure fluid is directed through the lines 82 and 100 to the rear cylinders 44, the front cylinders 28 being consequentially operated through the lines 98, 90, the fluid displaced returning through the line 80. The rear wheels may be set for a sideways movement with the valve 88 in the position of Fig. 1A, and locked in this position by returning to the position of Fig. 1, so that the vehicle may be steered for a " crabwise " movement. In a modification (Fig. 3), a single hydraulic cylinder acting upon one wheel only is provided for each pair of wheels, the other wheel being turned through the tie rod. In this modification, the rear wheels are steered when the control valve is in the position for steering one pair only, and the vehicle may have four wheel steering in contrary and "crabwise" directions in a manner corresponding to the first embodiment.