Hydraulic transmission is to use liquid as the working medium to control the energy transfer by using the pressure of the liquid. Hydraulic transmission systems are widely used, such as: rail-type freight elevators, fixed scissor lifts, mobile lifting platforms, aluminum alloy lifting platforms, etc. Compared with other transmission methods, hydraulic transmission has its unique advantages:
1) The weight per unit of power is light, that is, a larger force and torque can be obtained with a lighter equipment weight. For example, the force-to-weight ratio of a hydraulic cylinder is about 100 times larger than that of a DC motor; compared with a general DC motor, a medium-power hydraulic motor has a torque-to-inertia ratio of 1020 times and a power-to-weight ratio of 810 times. Therefore, the hydraulic transmission has a compact structure, light weight, and a large power-to-weight ratio. Using the hydraulic transmission, the lifting platform can easily obtain a large driving force and torque;
2) Due to its small size and light weight, it has small inertia and can start and brake quickly. For example, it takes a few seconds to start a medium-power electric motor, while it only takes about 0.1s to start a hydraulic motor of considerable power. Therefore, the use of hydraulic transmission is easy to realize the smooth and frequent starting, stopping, reversing or shifting of the lifting platform;
3) Stepless speed regulation can be conveniently carried out during the operation of the freight elevator; the speed regulation range is large, and the low speed performance is good.
