Load sensing hydraulic system

A load sensing hydraulic system comprising first and second pump means, at least one hydraulic fluid consumer and a pressure balance circuit, wherein the pressure balance circuit includes a three position valve including at least one input and at least one output, an output of the first pump means and an output of the second pump means each being connected to a respective input of the valve, the valve being connected to and receiving a switching signal from a load sensing line, and the at least one output of the valve directing hydraulic fluid from the pump means to the or each consumer or to tank, characterized in that:

• in the case of no demand from the consumer a pressure balance is established with the valve in the first position, such that 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 a pressure balance is established with the valve in the second position, such that 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 a pressure balance is established with the valve in the third position, such that hydraulic fluid from both pump means flows to the consumers.