GB1310528A - Hydraulic servomotor arrangements - Google Patents

Abstract

1310528 Vehicle power steering HOBOURNEATON MFG CO Ltd 23 July 1970 [25 July 1969] 37607/69 Heading B7H A power assisted steering mechanism comprises a servomotor having a double acting piston 26 with unequal effective areas and a servo valve plunger or spool 33 controlling pressure fluid to the motor and having opposite surfaces in permanent communication with respective faces of the servo piston 26, the ratio of the effective areas of the servo piston and of the plunger surfaces being equal. The piston-rod 24 is flexibly anchored to the chassis of the vehicle and two lugs (76), Fig. 2 (not shown) on a tubular casing 13 have the ends of steering track arms (not shown) pivotally connected to them. A pitman stud 37 has the end of a pitman arm secured to it. Slots 44, 45 formed in an end member 14 allow movement of the stud which is pivotally connected to the spool 33. Movement of the spool 33 by the stud to the right cuts off communication between grooves 63 and 71 and pressure fluid flows from supply pipe (75) to cylinder space 65 to cause the cylinder 12 and tubular casing 13 to move to the right. Fluid displaced from cylinder space 56 flows to chamber 71 into recess 72 and to a reservoir. Pressure in chamber 61 rises resulting in the spool 33 returning to its central position. Movement of the spool 33 to the left by the pitman arm cuts off communication between grooves 71 and 72 and pressure fluid is applied to both cylinder spaces 56, 65 to cause cylinder 12 to move to the right owing to the unequal areas of piston 26. In a similar manner movement of the spool to the left produces a restoring force tending to return the spool to its central position.