Power plants – Pressure fluid source and motor – Having condition responsive control in a system of distinct...
Reexamination Certificate
1999-02-25
2001-03-27
Ryznic, John E. (Department: 3753)
Power plants
Pressure fluid source and motor
Having condition responsive control in a system of distinct...
C060S486000, C060S422000
Reexamination Certificate
active
06205781
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to fluid control systems, and more particularly, to a system including a valve arrangement operable for selectively, controllably supplying pressurized fluid to a work element of the system from at least two pressurized fluid sources depending on load conditions on the pressurized fluid sources.
BACKGROUND ART
In fluid control systems having a plurality of work elements, such as a fluid control system on a bucket loader having work elements including a lift actuator for lifting the bucket and a tilt actuator for tilting the bucket, it is common practice to provide the work elements with pressurized fluid from a single pressurized fluid source by interconnecting the work elements in parallel. However, if the work elements are operating under greatly different pressure conditions, because they are linked hydraulically in parallel, fluid flow from the pressurized fluid source will tend to follow the path of least resistance to the lower pressure work element, resulting in less fluid supply to the higher pressure work element and poor operability thereof.
As an attempted remedy to this problem, an operator can try to find a modulation point for the lower pressure work element wherein fluid flow thereto is sufficiently restricted such that adequate fluid supply to the higher pressure element will be available. However, when such modulation point is found, it has been observed that both work elements will slow down and otherwise suffer from poor operability, due to the shared fluid supply.
In some applications, the fluid system will include an additional pressurized fluid source such as a steering pump that is idle or under-utilized when the above discussed work elements such as the lift and tilt actuators are being operated. Thus, it would be desirable to have the capability to direct pressurized fluid flow from the idle or under-utilized source to one of the working elements to improve the operability of the working elements.
Accordingly, the present invention is directed to overcoming one or more of the problems and achieving the results as set forth above.
DISCLOSURE OF THE INVENTION
In one aspect of the present invention, a fluid control system including a valve arrangement operable for selectively, controllably supplying pressurized fluid to a work element of the system from at least two pressurized fluid sources depending on load conditions on the pressurized fluid sources is disclosed. The valve arrangement is operable for directing pressurized fluid from the first pressurized fluid source to the work element when a first or low load condition is present on the first pressurized fluid source and directing pressurized fluid from the second pressurized fluid source to the work element when a second or high load condition greater than the first load condition is present on the first pressurized fluid source and a low load condition is present on the second pressurized fluid source, such that operability of the work element and other work elements supplied by the pressurized fluid sources is maintained.
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Burrows J. W.
Caterpillar Inc.
Haverstock Garrett & Roberts
Ryznic John E.
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