Adjustable bypass valve to effect steering limits in booster power steering system

摘要

A bypass vavle arrangement extends fixedly from the end wall of a double acting cylinder through the radial wall of a booster piston with a sliding sealed fit to block bypass flow between the pressure chambers at opposed faces of the piston between desired limits of piston travel. Bypassing of such flow from one chamber to another effects a pressure drop from the pressurized chamber to the chamber being exhausted to limit the pressure driving force on the piston and thus effect a desired limit or extent of piston travel and of the connected steering mechanism. The invention provides for such bypass flow by means of flow passages spaced on opposite sides of a central valve body portion which passages are of a length to span the radial wall through which the valve body has passed when the piston has reached a certain point of its travel in either direction. A particular point of novelty resides in the adjustability of the bypass valve means so as to predetermine the point at which bypass effect takes place so that desired limits of travel of the piston are thus determined, such adjustment being made from the exterior of the cylinder at one end thereof. A further feature resides in the provision of a bushing having axial play through which the valve body passes and which bushing is pressure actuated to cut off bypass flow at either limit of piston travel so that rapid reversed direction steering under pressure can be effected with no need for manual force at the steering wheel to effect pressure build up.