The hydraulic oil forms a certain pressure by the vane pump, and enters the lower end of the hydraulic cylinder through the oil filter, explosion-proof electromagnetic reversing valve, throttle valve, hydraulic control check valve and balance valve, so as to make the piston of the hydraulic cylinder move upward and lift the heavy objects. The return oil at the upper end of the hydraulic cylinder returns to the oil tank through the explosion-proof electromagnetic reversing valve, and its rated pressure is adjusted through the overflow valve, and the reading value of the pressure gauge is observed through the pressure gauge.
The piston of the hydraulic cylinder moves downward (i.e. the weight drops). The hydraulic oil enters the upper end of the hydraulic cylinder through the explosion-proof electromagnetic directional valve, and the return oil at the lower end of the hydraulic cylinder returns to the oil tank through the balance valve, hydraulic control check valve, throttle valve and explosion-proof electromagnetic directional valve. In order to make the weight drop stably and brake safely and reliably, a balance valve is set on the oil return circuit to balance the circuit and maintain the pressure so that the lowering speed is not changed by the weight. The flow is adjusted by the throttle valve to control the lifting speed. In order to make the brake safe and reliable and prevent accidents, a hydraulic control check valve, i.e. a hydraulic lock, is added to ensure the safety of self-locking when the hydraulic pipeline bursts accidentally. The overload sound control alarm is installed to distinguish overload or equipment failure.