Balance valve and balance circuit of hydraulic cylinder
Generally speaking, in the hydraulic control system of hydraulic gate hydraulic hoist, in order to prevent the gate which moves vertically or rotates around the horizontal axis from falling because of its own weight, the hydraulic element which produces a certain back pressure can be set on the downlink circuit of the hydraulic cylinder piston to prevent the gate from falling freely, or to slow down the acceleration and decline of the gate due to its own weight. This kind of circuit is called the balance circuit.
The common balance circuit is generally composed of one-way sequence valve or one-way throttle valve with liquid control one-way valve. The balance circuit composed of one-way sequence valve runs smoothly, but because of the leakage of sequence valve, the piston will drop slowly during long stay, so it is only suitable for hydraulic system with small weight of supporting gate and short residence time. Although the balance circuit composed of one-way throttle valve and liquid-controlled one-way valve has small leakage and good locking performance, because of the inherent flow-load characteristics of throttle valve itself, the speed of hoist is greatly affected by the change of load, and even vibration will occur when the load changes greatly. Therefore, both of these balance circuits have shortcomings.
Hydraulic speed limit balance valve (also known as one-way cut-off speed regulating valve or deceleration valve, brake valve) is a kind of load balancing valve with overspeed automatic regulation function, which combines the advantages of the above two, overcome their respective shortcomings, which can not only make the working parts run smoothly, but also has good locking performance, which is suitable for the mechanism with large power, load change and stable decline and long time locking.
In addition, the hydraulic control speed-limiting balance valve can also be used to prevent the horizontal hydraulic cylinder from causing the motion speed out of control when it is subjected to sudden reverse load during operation, so that the motion speed of the actuator is not affected by the sudden change of load size and direction, and it is always running smoothly at the pre-set speed, which is a function not available by the conventional balance valve.
The hydraulic speed limit balance valve has the advantages of rapid reaction, reliable action and convenient installation. It has been used in metallurgical machinery, papermaking industry machinery, road bridge lifting mechanism and other hydraulic equipment at home and abroad, and this balance valve has also been used in some gate hoist in China.