Delayed governor cutoff valve

Claim 1

A delayed governor cutoff valve system for use in connection with a hydraulic control system for a multiple speed ratio power transmission, said hydraulic control system comprising, a source of fluid pressure; first valve means for providing a constant fluid pressure from the source to first and second conduits; hydraulic governor means in fluid communication with the first conduit and operably connected to a transmission output member for producing a plurality of hydraulic governor pressure signals that are functionally related in magnitude to the speed of the output member; a plurality of automatic selector valves in fluid communication with the governor; each automatic selector valve operable upon receiving a pressure signal from the governor to select and initiate a different speed ratio change; said delayed governor cutoff valve system comprising, a cutoff valve interposed between the governor and the automatic selector valves; said valve having a housing defining a longitudinal bore; a spOol assembly slidably received in the housing bore and movable to a first position to permit fluid communication between the governor and the automatic selector valves and movable to a second position to block communication between the governor and the automatic selector valves; a first end of the housing bore defining a first chamber in fluid communication with the second conduit so that a first end of the cutoff valve spool is subjected to the constant fluid pressure supplied through the second conduit; a second end of the housing bore defining a second chamber receiving a second end of the cutoff valve spool; third conduit means interconnecting the second chamber with a transmission control assembly; a normally closed one-way check valve in the third conduit; a fourth conduit straddled about the one-way check valve and having flow restricting means therein; said transmission control assembly normally supplying pressure fluid through the third and fourth conduits at a pressure value which is higher than the constant fluid pressure in the first chamber of the cutoff valve so that the cutoff valve spool is normally biased to an open position which permits fluid communication between the governor and the automatic selector valves; said delayed governor cutoff valve system operable in response to a drop in fluid pressure in the third conduit below the constant fluid pressure in the second conduit to cause the one-way check valve to open and the cutoff valve spool to move to a closed position which blocks fluid communication between the governor and the automatic selector valves until such time as the pressure in the third conduit exceeds the constant fluid pressure in the second conduit.