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US 5,664,477 AGranted
Control system for a hydraulic circuit
AssigneeCaterpillar Inc.
InventorDouglas W. Koehler
Life of this patent
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AssigneeCaterpillar Inc.
InventorDouglas W. Koehler
Estimating the term…
A control system is provided for use in a hydraulic system to provide a simple arrangement with a limited number of elements that bypasses the system flow in the event of an electrical malfunction in the system and further allows other hydraulic circuits to operate even if one or more of the hydraulic circuits have experienced an electrical malfunction. The subject arrangement uses an electro-hydraulic fluid flow control valve mechanism in conjunction with directional valve mechanisms that have at least three functional positions and are controlled by associated electrically controlled displacement control mechanisms in response to receipt of electrical signals from an electrical controller. In the event of an electrical malfunction, each of the directional valve mechanisms are spring biased to one of its extreme positions in the absence of an electrical signal to the associated electrically controlled displacement control mechanisms and the electro-hydraulic fluid flow control valve mechanism bypasses all of the fluid from a source of pressurized fluid to a reservoir. With the directional valve mechanisms of one hydraulic circuit in their spring biased extreme positions, the electrical signal to the electro-hydraulic fluid flow control valve mechanism can be re-instated and the other hydraulics can be operated.
A control system adapted for use in a hydraulic system including a reservoir, a source of pressurized fluid connected to the reservoir, a hydraulic circuit having an actuator with first and second fluid ports, first and second directional valve mechanisms each having at least three positions and being connected between the source of pressurized fluid and the respective ones of the first and second fluid ports of the actuator, and an input controller operative to output an electrical signal to an electrical controller that is proportional to a desired input, the control system comprising:
A method of controlling individual hydraulic circuits in a hydraulic system in the event of an electrical malfunction in one of the hydraulic circuits, the hydraulic system including a reservoir, a source of pressurized fluid connected to the reservoir, an electro-hydraulic fluid flow control mechanism operative to control the flow of fluid from the source of pressurized fluid to the hydraulic circuits in response to an electrical signal, at least two hydraulic circuits each having an actuator with first and second fluid ports, first and second directional valve mechanisms each having at least three positions and being controlled by respective electrically controlled displacement control mechanism and connected between the source of pressurized fluid and the respective ones of the first and second fluid ports of the actuator, and an input controller operative to output an electrical signal to an electrical controller that is proportional to a desired input, the method comprising the steps of:
Dependencies are inferred from the claim text.