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U-Cup

Categories : Rubber Products & Parts

U-Cups (U-rings) are versatile lip seals, named after their characteristic "U"-shaped cross-section. They are specifically engineered for reciprocating applications and serve as primary seals in hydraulic and pneumatic cylinders. Key Performance Benefits Pressure-Energized Sealing: The U-shape enables the sealing lips to expand against the hardware surface under system pressure. As the pressure increases, the sealing force proportionally grows, ensuring a reliable seal. Dual-Purpose Design: U-Cups function effectively as Rod Seals (preventing external leakage) and Piston Seals (preventing internal bypass between cylinder chambers). Optimized Friction: The lip geometry provides a secure seal with minimal contact area, reducing heat generation and mechanical wear during operation. Synergy with Back-up Rings High-Pressure Integrity: For systems operating above 5 MPa (50 bar), pairing a U-Cup with a back-up ring is essential to prevent material extrusion into clearance gaps. Structural Support: The back-up ring stabilizes the U-Cup in dynamic applications, particularly when large extrusion gaps or high-speed cycles are present. Common Industry Materials Polyurethane (PU): Offers superior abrasion resistance and high shear strength, ideal for heavy-duty hydraulic systems. Nitrile (NBR): Standard choice for pneumatic cylinders and lower-pressure environments. PTFE / POM: Often used for back-up rings to provide high-hardness support.