Flow control valve

Claim 1

A flow control valve for use in cooperation with first, second, and third fluid lines associated with a fluid pressure source, comprising: a valve body defining an internal bore and first and second end portions, the first, second, and third lines individually communicating with the bore; a valving spool disposed in the bore and reciprocable therein toward the first end portion and away from the second end portion, and toward the second end portion and away from the first end portion; the valving spool defining passage means; the valving spool being movable to a first position wherein the first and second lines are in communication with each other through the passage means, with the valving spool substantially blocking off the third line therefrom; the valving spool being movable to a second position wherein there is substantially no communication between any of the first, second, and third lines, the valving spool substantially blocking each of these lines off from the others; the valving spool being movable to a third position wherein the second and third lines are in communication with each other through the passage means, with the valving spool substantially blocking off the first line therefrom; first resilient means disposed within the bore adjacent the first end portion for urging the valving spool toward said third position; a single retainer member disposed within the bore between the second end portion and the valving spool, and positioned to contact the valving spool so that movement of the retainer member away from the second end portion moves the valving spool toward its first position; the retainer member being configured to contact a stepped portion defined by the valve body as part of the bore when moved away from the second end portion to determine, with the first resilient means, upon such contact, the second position of the valving spool; second resilient means disposed within the bore adjacent the second end portion for urging the retainer member away from the second end portion and providing such force, in relation to the first resilient means, to normally position the valve spool in its second position; the valving spool being movable to its first position from the second position against the resiliency of the first resilient means, the valving spool being movable to its third position from the second position against the resiliency of the second resilient means, but being relatively stably held in said second position; means for selectively moving the valving spool to its first position; and means for selectively moving the valving spool to its third position.