Lenkeinrichtung,insbesondere fuer schwere Fahrzeuge

1,264,140. Hydrostatic steering mechanism. DANFOSS AS. 5 May, 1969 [3 May, 1968], No. 22801/69. Heading B7H. Hydrostatic steering mechanism comprises a steering motor 2 which is part of a secondary hydrostatic system including a control unit 13 actuated by the motor 6 of a primary system having a control unit 5 actuated by a steering wheel 1. Each control unit 5, 13 includes a control valve and a metering device. The motor 6 may be a rotary motor; and the systems preferably incorporate step-up means which increase the amount of fluid passed to the steering motor 2 for each revolution of the steering wheel 1. Such means may be an hydraulic amplifier in the primary hydrostatic system or a mechanical step-up gear on the input side of the metering device of the secondary control unit 13. The metering device of the secondary control unit 13 may be an orbital gear pump having a displacement per revolution equal to the total volume of the displacement chambers therein multiplied by the number of gear teeth, or the metering devices in both control units 5, 13 may be rotary piston pumps with volume step-up means. Separate feed pumps 4, 14 feed the two hydrostatic systems from a common reservoir 21. One-way valves 24, 25 connect the first system to the second so that the steering motor 2 can be operated from the primary control unit 5 should the feed pump 14 be inoperative, a oneway valve 26 preventing reverse flow through the inoperative pump. If the feed pump 4 is inoperative the motor 6 is operable by manual actuation of the metering device in the primary control unit 5. Fig. 2 shows a unitary assembly 20 incorporating the primary motor 6 and the secondary control unit 13. The motor 6 comprises a rotatable eccentric ring gear 29 and a gear 28 mounted on a shaft 27. The metering device of the control unit 13 comprises an orbital gear 38 and a fixed gear ring 40, and the control valve comprises inner and outer rotatable valve sleeves 45, 46. The inner valve sleeve 46 is coupled to the shaft 27 by a pin 47, and the outer valve sleeve 45 drives the orbital gear 38 through a pin 48 and a wobble shaft 49. The-pin 48 engages a larger bore 51 in the inner valve sleeve 46 so that the sleeves are coupled with provision for limited relative rotation, and spring means 50 urge the sleeves into a predetermined neutral position. Ports 57, 58 in the outer valve sleeve 45 co-operate with grooves 63, 64 in the inner valve sleeve 46 to control fluid flow to the steering motor 2, an