Forward-reverse drive control providing automatic braking

Claim 1

In combination: a control valve assembly comprising a housing having high (126), transfer (110), and low (114, 116) pressure chambers; a common bore intersecting the chambers; individual valve bores in communication with the transfer and low pressure chambers and with plural service passages (84, 86, 88, 90) in said housing; first and second range selector valve elements (F1F2, R2R1) each shiftably disposed in a different one of the individual valve bores, said valve elements being movable selectively from a position interconnecting the low pressure chamber and the service passages to discrete operating positions at once interconnecting the transfer chamber and selected service passage and interconnecting the low pressure chamber and the unselected service passages; a dump valve element (CD) shiftably disposed in said common bore and having an undisplaced, satisfied position interconnecting the transfer and high pressure chambers and a displaced, dump position interconnecting the transfer and low pressure chambers; means including pressure movable control means (104, 124) carried by the dump valve element for shifting same selectively to make available high pressure to, or to dump the pressure from, the transfer passage and the selected service passage; utilization means for said control valve assembly comprising a vehicle supported for rolling movement on a horizontal surface; a run detector dump (22) connected to the vehicle to sense its direction of rolling movement and having a directionalized pump output; means including a desired direction selector (20) for controlling application of the pump output in two paths to said pressure movable means carried by the dump valve element each opposing and balancing the other so that said element takes an undisplaced, satisfied position when the direction in which the vehicle is rolling as sensed by the pump is the desired direction; said application means including the desired direction selector comprising valving including a neutralizable operator operated valve (20) effective to communicate pump output to an unopposed, valve element displacing, pressure movable means carried by the dump valve element when the direction in which the vehicle is rolling as sensed by the pump is undesired; said dump valve element having means including a control device therefor (138 or 122) effective to restore the dump valve element to the undisplaced, satisfied position, when the pump output falls to or below a predetermined reduced value indicative that rolling of the vehicle in the undesired direction has reached a substantial standstill; a brake operating cylinder for brakes carried by the vehicle; and a communication between the brake operating cylinder and said transfer chamber to make available high pressure to, or to dump the pressure from, the cylinder for automatically holding the brakes set when the direction in which the vehicle is rolling as sensed by the pump is the undesired direction, or for automatically holding the brakes released both when the direction in which the vehicle is rolling as sensed by the pump is the desired direction and also when the direction in which the vehicle is rolling as sensed by the pump is the undesired direction in the event that the pump output is at or below said predetermined reduced value.