Patent ID: 7430860

Claim:
A hydraulic system comprising: (a) a variable displacement main pump; (b) a hydraulic motor; (c) a closed loop hydraulic circuit, including first and second leg portions, operatively interconnecting said main pump and motor; (d) a pair of one-way check valves positioned between the first and second leg portions of the circuit; (e) a charge pump within said circuit, having a single outlet line connected to said circuit, said charge pump providing a flow of fluid into the closed loop hydraulic circuit from a reservoir within the circuit, the circuit configured such that all of the flow of fluid from the charge pump, and only the flow of fluid from the charge pump, passes through the pair of one-way check valves; (f) a shuttle valve having a neutral position in which first and second orifices of said shuttle valve are in fluid communication with said first and second leg portions respectively, said first and second orifices providing fluid flow to said low pressure relief valve when said shuttle valve is in the neutral position, said first and second orifices being sized so as to allow substantially a full flow of said charge pump to said low pressure relief valve when said shuttle valve is in the neutral position; and (g) wherein all of the fluid flow from the shuttle valve is directed to the low pressure relief valve.