Patent ID: 6907728

Claim:
A load sensing hydraulic system comprising two pump means, at least one hydraulic fluid consumer, and a pressure balance circuit, wherein; in the case of no demand from the consumers, hydraulic fluid flows from each of the pump means through the pressure balance circuit and to tank; in the case of a demand from the consumers for hydraulic fluid at a flow rate less than or equal to the flow rate provided by the first pump means, hydraulic fluid from the first pump means flows to the consumers, and hydraulic fluid from the second pump means flows to tank; and in the case of a demand from the consumers for hydraulic fluid at a flow rate greater than the capacity of the first pump means, hydraulic fluid from both pump means flows to the consumers; wherein the pressure balance circuit includes a pair of valve blocks, each of the valve blocks including a spring biased valve, and wherein the outputs of the first and second pumps are each connected to a respective one of the valve blocks on the upstream side of the spring biased valve, and wherein each valve block includes at least one control input, the pressure at the control input working against the spring to open the valve, and wherein the control input for the second valve block senses the demand for hydraulic fluid on the first pump means, and wherein the flow of hydraulic fluid from the second pump means is diverted from tank to the consumers when the control signal indicates that the demand from the consumers is greater than the capacity of the first pump means; and wherein the control input to the second valve block is connected to the hydraulic line from the first valve block to tank; and wherein the hydraulic line includes a check valve.