Motors: expansible chamber type – Plural relatively movable or rigidly interconnected working... – Separate valve means actuatable by a common nonmanual...
Patent
1982-10-25
1986-10-28
Hershkovitz, Abraham
Motors: expansible chamber type
Plural relatively movable or rigidly interconnected working...
Separate valve means actuatable by a common nonmanual...
91529, 13759616, F15B 1100
Patent
active
046191879
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates generally to a fluid control system for selectively controlling the actuation of two independent actuators and more particularly to such a system which prevents operation of the actuators if the controls are affected by contaminates.
BACKGROUND ART
One control arrangement for a single speed transmission having independently actuatable forward and reverse clutches has a control valve with a pair of directional spools for selectively actuating the clutches. Each of the directional spools are moved to a position for actuating the associated clutch by venting pressurized fluid from a chamber at one end of the associated spool through a solenoid valve. The solenoid valve is normally spring biased to the closed position to cause the chamber to become pressurized and is moved to the open or venting position upon energizing the coil thereof.
One of the problems encountered with such control arrangement is that if one of the clutches is partially engaged due to a leaky solenoid valve caused by contaminates, the partial engagement would cause slippage and serious damage to the clutch.
The present invention is directed to overcoming one or more of the problems as set forth above.
DISCLOSURE OF THE INVENTION
In one aspect of the present invention. A fluid control system for selectively controlling actuation of a pair of actuators comprises a reservoir; a pump connected to the reservoir; a control valve having a bore, a pair of directional spools slidably positioned in the bore, a common actuating chamber defined in the bore between one end of each of the directional spools, and first and second actuating chambers each being defined in the bore at the other end of each of the directional spools, said common actuating chamber being in fluid communication with said pump, each of the directional spools being movable between a first position at which the pump is in communication with one of the actuators and a second position at which said one of the actuators is in communication with the reservoir, the directional spools being arranged in the bore so that only one of the directional spools is moved to its first position when one of the first and second actuating chambers is pressurized; orifice means for communicating said pump with said first and second actuating chambers; and control means for selectively pressurizing said first and second actuating chambers.
The problem caused by a leaky solenoid valve is solved by the use of a pair of normally open solenoid valves controlling a pair of directional spools having a common actuating chamber defined in the bore between the directional spools and by having the directional spools adapted to abut one another so that only one of the clutches can be engaged when one solenoid valve is actuated or to prevent operation of the clutches if the normally open solenoid valves are affected by contaminates.
BRIEF DESCRIPTION OF THE DRAWINGS
The sole FIGURE is a schematic of the embodiment of the present invention with portions shown in cross section.
BEST MODE FOR CARRYING OUT THE INVENTION
Referring now to the drawing, a fluid control system is generally indicated by the reference numeral 10 and selectively controls actuation of two independent actuators 12,14. The actuators in the embodiment shown are forward and reverse clutches, respectively, of the type which are engaged by fluid pressure directed thereto and disengaged when the pressurized fluid is vented therefrom. The pump control system 10 includes a reservoir 16, a pump 18 connected to the reservoir, and a control valve 20 connected to the output of the pump 18 through a branched pressure conduit 22 and to the reservoir 16 through a drain conduit 24. A pair of motor conduits 26,28 connect the control valve 20 with the forward and reverse clutches 12,14, respectively. A relief valve 30 is connected to the pressure conduit 22 to control the fluid pressure level in a conventional manner.
The control valve 20 includes a valve body 32 having a bore 34 therein. A pair of directiona
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Blake William W.
Coutant Alan R.
Burrows J. W.
Caterpillar Inc.
Hershkovitz Abraham
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