Power plants – Pressure fluid source and motor – Having distinct cooling or lubricating structure
Patent
1980-09-29
1982-10-19
Michalsky, Gerald A.
Power plants
Pressure fluid source and motor
Having distinct cooling or lubricating structure
60464, 91419, 91431, 91438, 91464, 180132, F15B 1304
Patent
active
043543510
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates generally to a fluid circuit and more particularly to a steering circuit having continuous flow therethrough to keep the oil in the lines warm in cold weather conditions.
2. Background Art
In the use of vehicles in extremely cold environments, as for example when the vehicles are used in Alaska during the winter, the hydraulic fluid in a steering circuit or in other circuits may increase in viscosity to a magnitude sufficient to make the system slow to respond. One particular location at which the hydraulic fluid can easily become excessively viscous is in the relatively long conduits which provide the fluid pathway between the steering control valve and the hydraulic cylinder which actuates the steering mechanism. During extended operation without utilizing the steering function, the fluid in these long conduits can cool to a value at which the pump pressure is slow to move the viscous fluid in the conduit upon actuation of the steering valve.
One useful circuit for solving such a problem is disclosed in U.S. Pat. No. 4,059,042 issued Nov. 22, 1977 to J. W. Bridwell and George H. Miner III. This patent sets up a circuit wherein fluid is trickled through the hydraulic lines connecting the brake or clutch control valve with its respective hydraulic actuator when that actuator is not being powered in one direction or another. The circuit is not, however, in any way sensitive to the actual work condition of the hydraulic actuator, i.e., to whether or not the hydraulic actuator is, in reality, acting against a load. Instead, actuation is responsive to physical movement of the clutch or brake pedal which serves to mechanically push a control valve into a position to deactivate the trickle flow through the long lines when the brake or clutch is activated, and to reactivate the trickle flow when the brake or clutch is deactivated. Such mechanical parts can conceivably hang up, due to friction, wear, or the like, in incorrect positions, thus causing undesirable deactuation of the trickle flow when such is desirable.
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, an improvement is provided in a fluid circuit having a pressurized fluid source, a fluid actuator and a directional control valve selectively positionable in first (closed) and second (open) positions and being connected to receive pressurized fluid from the source. The circuit includes circulating means for circulating fluid from the valve to the actuator in response to positioning of the valve in the second position and flowing means for flowing pressurized fluid into and from the circulating means. The improvement comprises logic means for preventing operation of the flowing means in response to positioning of the valve in the second position and to the pressure of the fluid in the circulating means exceeding a selected level.
An improved circuit as set out above has the advantage that it is automatically actuated in response to load sensed by the circuit and is not dependent upon positioning of a lever or other mechanical member, but only positioning of the control valve. Flow is provided through the long hydraulic lines which connect the control valve with a fluid actuator ensuring that the fluid passing through such lines is kept warm in cold weather conditions. In accordance with one preferred embodiment of the invention, flow through the lines connecting the control valve to the actuator can be terminated when the fluid temperature is sufficiently high. In another embodiment, means can be provided for cooling the fluid which is flowing through the hydraulic lines which connect the control valve to the fluid actuator during warm weather, thus allowing a relatively viscous oil, such as SAE-10 hydraulic oil, to be utilized on an all year round basis without the need to dilute with additives.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates, schematically, one embodiment of
REFERENCES:
patent: 2688313 (1954-09-01), Bauer
patent: 2742878 (1956-04-01), Glenny et al.
patent: 3401605 (1968-09-01), Born
patent: 3865514 (1975-02-01), Lonnemo
patent: 4043419 (1977-08-01), Larson et al.
patent: 4059042 (1977-11-01), Bridwell et al.
patent: 4179981 (1979-12-01), Yedu
Caterpillar Tractor Co.
Michalsky Gerald A.
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