Accumulators serve two purposes, when moving at low speeds. ① The required flow rate of the hydraulic pump, the flow rate of the hydraulic pump, and the flow rate of the pump are stored in the energy storage. When the flow rate of the hydraulic pump requiring a large flow rate is sucked, the fluid is discharged from the device to make up for the insufficient flow of the hydraulic pump. ②When the machine stops but still needs to maintain a certain pressure, the hydraulic pump can be stopped and the energy of the system can be compensated by the accumulator to maintain the pressure of the system. The accumulator can also use the pressure pulsation of the hydraulic pump or absorb the hydraulic shock pressure generated in the system. The pressure in the accumulator can be generated by compressed gas, heavy hammer or spring. Correspondingly, the accumulator is divided into gas type, heavy hammer type and spring type. The gas in the energy device is in direct contact with the liquid, the bottom contact type, its structure is simple, and the capacity is large, but it is easy to mix gas in the liquid, and it is often used on hydraulic presses. For isolation, the bladder has a large volume and small changes in the carrying capacity. It is often used to absorb dynamic pulsation. The weight change function equivalent system is often used in the middle and for energy storage.