Commonly used self-sealing pressure type hydraulic seals are mainly ○-shaped sealing rings, circular sealing rings and square sealing rings, etc. They have the advantages of simple structure, easy manufacturing, low cost, etc. Therefore, they are widely used in hydraulic transmission systems. Dynamic sealing element and static sealing element. Their installation in the seal groove usually produces a 10-25% radial compression deformation and creates a high initial contact stress on the sealing surface, thus preventing leakage of pressure-free liquid. The
When the hydraulic cylinder is in operation, the pressure liquid squeezes the self-sealing pressure-type hydraulic seal to further deform it and generate a large pressure with the pressure of the liquid on the sealing surface, strictly speaking, it should be the pressure. Increases and increases the additional contact stress and together with the initial contact stress prevents the leakage of the pressure fluid. However, when the working pressure is greater than 10 MPa, in order to prevent a part of the synthetic rubber self-sealing pressure-type hydraulic seal from being squeezed into the seal gap and cut in the reciprocating motion of the hydraulic cylinder to cause leakage, it is necessary to seal the pressure in the synthetic rubber. A synthetic resin retaining ring, such as a nylon retaining ring, a polyacetal retaining ring, and a filled PTFE retaining ring, is provided on each pressure side of the tight type hydraulic seal. The Since the synthetic rubber self-sealing compaction type hydraulic seal has a large compression deformation during operation, the static seal friction resistance of the hydraulic seal is particularly large, and is usually more than double the dynamic frictional resistance thereof. Such large static friction resistance in certain low-pressure hydraulic transmission systems is bound to cause undesirable phenomena such as low-pressure crawling and operational difficulties. This is the reason why the self-sealing compact hydraulic seal is used as a small dynamic seal alone.