Patent ID: 7770696

Claim:
An energy recovering system of a hydraulic lift device for a battery operated industrial truck which is provided with a lift cylinder for lifting a lift means, an electric motor driven by a battery power source, a hydraulic pump for supplying pressurized working fluid to said lift cylinder to lift said lift means, and a control valve disposed between said lift cylinder and said hydraulic pump, whereby when said lift means lowers in a state the pressurized working oil is not being supplied to said lift cylinder the pressurized working fluid is returned from said lift cylinder to a working fluid reservoir tank by downward force exerting on the pressurized working fluid in said lift cylinder, wherein a hydraulic motor is disposed in a working fluid recovering path through which the pressurized working fluid returns from said lift cylinder via said control valve so that said hydraulic motor is driven by the pressurized working fluid returning through said working fluid recovering path, and said hydraulic motor is connected to said electric motor with a one-way clutch with which torque transmission is possible only from said hydraulic motor to said electric motor, wherein said electric motor serves both as an electric motor for driving the hydraulic pump and as an electric generator driven by the hydraulic motor for recovering energy, said hydraulic pump is driven by said hydraulic motor when the lift means is raised, while said electric motor and said hydraulic pump are driven by said hydraulic motor via the one-way clutch when the lift means is lowered.