By the motor drive pump, high pressure oil into the valve block P cavity, the 1 to the A cavity through the one-way valve output, into the lift cylinder, so that the operating platform slowly rising. Depending on the load, the relief valve 2 is set to work under pressure, can prevent overload or overpressure. The operation platform falls, open solenoid valve 4, the lifting cylinder on the load platform under the gravity, the hydraulic oil flow to the A into the valve chamber, a one-way valve 1 closed due to reverse, hydraulic oil only through the solenoid valve to open the 4, the adjustable throttle valve 3, O cavity into the fuel tank, then the operation platform slowly decline.
