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Ruland jaw couplings for servo motors

12 February 2021

Zero-backlash jaw couplings from Ruland have high dampening capabilities, can accommodate all forms of misalignment, and are highly customisable.

They are well-suited for servo motors that are often used in precise positioning applications found in semiconductor, solar, medical and robotics.

Each application that uses a servo motor will have different performance requirements such as rpm, torque, and misalignment. It may be challenging for a motor manufacturer or integrator to specify one coupling that can satisfy all these requirements. Zero-backlash jaw couplings are a three-piece design comprised of two lightweight aluminium hubs and an elastomeric insert “spider.” The spider is available in three durometers: 98 Shore A for the highest torque, 92 Shore A for a balance of stiffness and compliance, and 85 Shore A for the highest dampening capabilities. Inch, metric, keyed, and keyless hubs with clamp or set screw hardware can be combined to fit user shaft requirements. This combination of options within an outer diameter gives motor manufacturers and integrators the ability to choose one coupling envelope with hundreds of different standard combinations allowing coupling performance to match application requirements.

Ruland uses a proprietary curved jaw profile on the hub tenons that press fit with the spider to ensure zero-backlash operation. Standard jaw couplings found elsewhere on the market have a straight jaw design that introduces backlash and makes them less suitable for servo motor systems. In the event of spider failure, the hub tenons of Ruland jaw couplings will interlock to continue power transmission. This feature is useful in servo motor applications where abrupt stops can cause damage to sensitive system components. The user can safely shut down the application and replace the spider, restoring full system capabilities at a lower cost relative to other coupling styles that require complete replacement of the coupling.

Ruland zero-backlash jaw couplings have a balanced design for reduced vibration at higher speeds, a critical feature in servo motor applications with high acceleration and deceleration curves. They are available in bore sizes from 1/8 inch to 1-1/4 inch and 3mm to 32mm. All Ruland jaw couplings are carefully manufactured in Ruland’s Marlborough, MA factory from bar stock sourced from select North American mills. Stainless steel hubs and a spider with a centre hole are available on request.

Jaw couplings are part of Ruland’s motion control coupling product line which also includes beam, bellows, controlflex, disc, oldham, and slit couplings. 3D CAD files, full product specifications, and installation videos are available on

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