Hydraulic levelling apparatus for automotive vehicles and shut-off valve for the same

Claim 1

In a levelling apparatus for an automotive vehicle having an engine, a hydraulic suspension element interposed between the sprung and the unsprung masses of the vehicle, resilient means biasing said element in a direction to move said masses vertically away from each other, a feed conduit, a return conduit, and control valve means interposed between said element and said feed and return conduits for connecting said element to said feed and return conduits respectively in response to changes in the vertical spacing of said masses, the improvement which comprises: a. a shut-off valve arrangement including 1. a plurality of port means for connecting the valve arrangement to respective conduits for flow of fluid between the valve arrangement and said conduits, said port means including pressure port means, feed port means, return port means, and drain port means, 2. first valve means operatively interposed between said pressure port means and said drain port means and responsive to a flow of fluid from said pressure port means toward said drain port means for moving toward a closing position in which said first valve means seals said pressure port means from said drain port means, and thereafter responsive to higher pressure at said pressure port means than at said drain port means for maintaining the closing position thereof, 3. second valve means operatively interposed between said return port means and said drain port means, 4. yieldably resilient means biasing said second valve means toward a closing position in which said second valve means seals said return port means from said drain port means, 5. motion transmitting means interposed between said first and second valve means for moving each of said valve means away from the closing position thereof in response to movement of the other valve means into the respective closing position, 6. third valve means interposed between said pressure port means and said feed port means; and 7. yieldably resilient means biasing said third valve means toward a closing posItion in which said third valve means seals said feed port means from said pressure port means, but adapted to yield when the fluid pressure at said pressure port means exceeds the fluid pressure at said feed port means by a predetermined amount; b. a pressure pump having an intake and a pressure discharge; c. a container adapted to hold hydraulic fluid; d. a suction conduit connecting said intake to said container; e. a pressure conduit connecting said pressure discharge to said pressure port means; f. a drain conduit connecting said drain port means to said container, 1. said engine being drivingly connected to said pump, 2. said feed conduit being connected to said feed port means, and 3. said return conduit being connected to said return port means; and g. a body of hydraulic fluid substantially filling said element, said feed conduit, said return conduit, and said control valve means.