4-Inch Rubber Coupling

A 4-inch rubber coupling is a flexible mechanical device designed to connect two rotating shafts, accommodating misalignment, reducing vibration, and transmitting torque efficiently in industrial machinery. The "4-inch" specification refers to the outer diameter of the coupling’s rubber element, which is typically paired with metal hubs (often made of cast iron or steel) that attach to the shafts via keyways or set screws. This size makes it suitable for medium-duty applications, such as connecting motors to pumps, conveyors, or compressors, where torque requirements range from 500 to 3,000 Nm.

The rubber element, usually made of nitrile rubber (NBR) or ethylene propylene diene monomer (EPDM), is the core component. NBR offers excellent oil resistance, making it ideal for machinery in automotive or hydraulic systems, while EPDM excels in high-temperature environments (up to 150°C) and resistance to weathering, suitable for outdoor equipment. The rubber is molded into a flexible spider or sleeve shape with grooves that allow axial, angular, and radial misalignment—up to 0.5mm axially, 1.5° angularly, and 0.3mm radially—without transferring excessive stress to the connected shafts.

Installation and maintenance are straightforward: the metal hubs are mounted on the shafts, and the rubber element is sandwiched between them, often secured with bolts or clamps. The rubber’s elasticity dampens vibration and reduces noise, protecting sensitive components like bearings and gears from premature wear. Unlike rigid couplings, 4-inch rubber couplings do not require precise shaft alignment, simplifying installation in field applications. They also act as a torque limiter, as the rubber can deform or shear under extreme overload, preventing damage to expensive machinery. Regular inspection of the rubber element for cracks, hardening, or wear is recommended, with replacement intervals typically ranging from 12 to 24 months depending on operating conditions.

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