GB1034415A - Improvements in power assisted steering gear for motor vehicles - Google Patents

Abstract

1,034,415. Steering vehicles. ZAHNRADFABRIK FRIEDRICHSHAFEN A.G. April 2, 1963 [April 4, 1962], No. 13060/63. Heading B7H. An overload valve is arranged between the fluid inlet and return passages in a powerassisted steering control valve. The steering gear may comprise a worm and nut which actuates a piston 9 formed with a rack 14 which engages a pinion 15 through which the drop arm 18 is rotated, the pressure fluid being directed to one side or the other of piston 9 under the control of an axially moving spool valve 20, there being a supply passage 38 and return passage 45 through the valve housing connected with a reservoir 44 and pump 37. In a cross bore 50 between the passages, there is provided a valve member 51 having an enlarged head formed with a shoulder 64, the member 51 being urged to the right by a spring 55, and having an axial bore 61 and radial bores 56. The return passage 45 is completed by an annulus 59 formed in the cross bore. The ends of member 51 and its shoulder 64 are acted upon by the pressures of the fluid in the supply and return bores respectively, the excess force to the left, due to the larger dimension, being balanced by the spring. Upon an increase in pressure. however, the force of the spring will be overcome and the pressure fluid will discharge to reservoir through the radial bores 56. In modifications, Fig. 2, there is provided a spring-loaded ball valve 70 between the supply and return passages 38 and 45 and, Fig. 3, a radial passage through the valve member 51 is closed by a spring-loaded ball valve 97 so as to be effective against a rise in pressure in the opposite direction.