Structural form and sealing mechanism of hydraulic seals
Commonly used self-sealing compression hydraulic seals are mainly ○-shaped sealing rings, circular sealing rings, square sealing rings, etc. They have the advantages of simple structure, easy manufacturing, and low cost, so they are widely used in hydraulic transmission systems. Dynamic sealing elements and static sealing elements. They usually produce 10-25% radial compression deformation when installed in the sealing groove, and produce high initial contact stress on the sealing surface, thereby preventing the leakage of unpressurized liquid. When the hydraulic cylinder is working, the pressure liquid squeezes the self-sealing compression hydraulic seal, causing it to further deform and generate a large pressure on the sealing surface along with the pressure liquid. Strictly speaking, it should be pressure. The additional contact stress increases due to the increase, and together with the initial contact stress, prevents the leakage of pressure liquid. However, when the working pressure is greater than 10 MPa, in order to prevent part of the synthetic rubber self-sealing compression hydraulic seal from being squeezed into the sealing gap and being cut off during the reciprocating motion of the hydraulic cylinder, causing leakage, the synthetic rubber self-sealing pressure seal must be Each tight hydraulic seal is provided with a synthetic resin retaining ring on the pressure side, such as a nylon retaining ring, a polyoxymethylene retaining ring and a filled polytetrafluoroethylene retaining ring. Since synthetic rubber self-sealing compression hydraulic seals have large compression deformation during operation, their static friction resistance is particularly large, usually more than twice its kinetic friction resistance. Such large static friction resistance will inevitably cause undesirable phenomena such as low-pressure crawling and operating difficulties in some low-pressure hydraulic transmission systems. This is why self-sealing compression hydraulic seals are very small and can be used alone as dynamic seals. Lip seal At present, the hydraulic combination seals commonly used in hydraulic cylinders of hydraulic machinery and equipment in ceramic factories are mainly composed of ○-shaped sealing rings, square sealing rings, U-shaped sealing rings, Y-shaped sealing rings, YX-shaped sealing rings and other special-shaped hydraulic sealing rings. Made up of superimposed V-shaped sealing ring The sealing performance of the V-shaped sealing ring is better. The number of sealing rings used can be determined according to the working pressure. Usually, the adjustment of the gland must be used to compensate for the wear of the sealing ring. Its fatal weakness is the complex structure, which usually requires It consists of three parts: a support ring, a sealing ring and a pressure ring. Its friction resistance is large and increases with the increase of the working pressure and the number of sealing rings. Therefore, V-shaped sealing rings are only suitable for hydraulic cylinders with low movement speed and high working pressure. U-shaped sealing ring The U-shaped sealing ring has better sealing performance, but it is very easy to roll when used alone. Therefore, it needs to be used in conjunction with a tin bronze support ring. Its friction resistance is large and increases with the increase of working pressure. Therefore, U-shaped sealing rings are only suitable for hydraulic cylinders with low working pressure or low movement speed. Y-shaped sealing ring The Y-shaped sealing ring relies on its open lip to be close to the sealing surface to maintain the seal. It can usually be used alone. It has good sealing performance, small friction resistance, good pressure resistance, good working stability and long service life. long. Therefore, the Y-shaped sealing ring is suitable for use in hydraulic cylinders with high-speed voltage transformation, large bore, and large stroke. YX-shaped sealing ring YX-shaped sealing ring is a Y-shaped sealing ring whose cross-section height to width ratio is greater than 2 and the working lip is not equal in height to the non-working lip. It is divided into YX-shaped sealing ring for hole and YX-shaped sealing ring for shaft. Their sealing performance is the same. , In addition to having all the advantages of the Y-shaped sealing ring, the YX-shaped sealing ring will never roll when used alone, further improving its pressure resistance and working stability. Therefore, YX-shaped sealing rings are particularly suitable for use in high-pressure, high-speed pressure change and fast-moving hydraulic cylinders. Self-sealing tight hydraulic seals: Lip seals, like self-sealing compression hydraulic seals, produce high initial contact stress on the sealing surface based on their own deformation, preventing the leakage of pressureless liquid. When the hydraulic cylinder is working, the pressure liquid squeezes and expands its sealing lip, making it close to the sealing surface, resulting in a higher additional contact stress that increases with the increase in pressure of the pressure liquid, and together with the initial contact stress, prevents the pressure Liquid leakage. The commonly used combined seals in hydraulic cylinders are mainly bud rings, Glyph rings and Stereo seals. 1: bud-shaped circle The bud ring is usually composed of a synthetic rubber ○-shaped sealing ring and a cloth-covered rubber Y-shaped sealing ring. It is similar to self-sealing compression hydraulic seals and self-sealing tight hydraulic seals, lip type Like the seal, its own deformation produces a high initial contact stress on the sealing surface, preventing the leakage of pressureless liquid. When the hydraulic cylinder is working, the pressure liquid always squeezes and expands the sealing lip of the Y-shaped sealing ring through the elastic deformation of the ○-shaped sealing ring, making it close to the sealing surface and generating a higher pressure that increases with the increase of the pressure of the pressure liquid. Additional contact stress, together with the initial contact stress, prevents leakage of pressure fluid. 2:Gelai circle The grated ring is usually composed of a synthetic rubber ○-shaped sealing ring and a polytetrafluoroethylene-filled square sealing ring. It can be divided into a hole grated ring and a shaft grated ring, but its sealing The function is the same. According to its own deformation, it generates a high initial contact stress on the sealing surface to prevent the leakage of pressureless liquid. When the hydraulic cylinder is working, the pressure liquid squeezes the square seal ring to the maximum extent through the elastic deformation of the ○-shaped seal ring, making it close to the sealing surface, resulting in higher additional contact stress that increases with the increase in pressure of the pressure liquid, and Together with the initial contact stress, leakage of pressure fluid is prevented. ３：Stefon Stereo seals are usually composed of synthetic rubber ○-shaped sealing rings and special-shaped rectangular-trapezoid sealing rings filled with polytetrafluoroethylene. Like Glyph rings, they can be divided into hole seals and shaft seals. The sealing function and sealing mechanism of the Stereo seal are the same as those of the Glyph ring, but it only has a one-way sealing function. Self-sealing tight hydraulic sealing ring: lip sealing ring, the lip contact area that closely fits the sealing surface is small, which can produce greater compression deformation and obtain better sealing effect. But it is easy to wear, and its sealing effect is significantly reduced after wear. If a ○-shaped sealing ring is used in combination with it, that is, when the seal is combined, even after the lip is worn, because the synthetic rubber ○-shaped sealing ring has greater elasticity, it It will force the lip of the lip seal ring to be close to the sealing surface, generating sufficient surface contact stress to achieve the sealing effect. The friction resistance is small, the work is smooth, and it is easy to assemble and repair. Therefore, at present, hydraulic seals widely used in fully automatic hydraulic brick presses, daily ceramic products, plate and disc isostatic molding machines, and medium-pressure grouting and high-pressure grouting sanitary ceramic molding machines are almost all combination seals. Such as the Gelai circle and the Ste circle.
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