Machine Design
Low Weight and Low Inertia Make for Energy-Saving Torque Couplings for Shafts

Low Weight and Low Inertia Make for Energy-Saving Torque Couplings for Shafts

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Engineers at R+W America, Bensenville, Ill. (, have redesigned the SL Series of torque limiters so that they have less mass and inertia, which translates into energy savings, higher throughput rates, less downtime, and consistent performance.

The Series relies on a proven spring-loaded detent subsystem and a previously patented preload for zero backlash. And coupling weight has also been painstakingly reduced by 50%. For example, a conventional torque limiter rated to disengage at 160 Nm typically has a mass of 1.3 kg and a 1.6 × 10-3 kgm2 moment of inertia. The SL version’s mass is 370 gm and its moment of inertia is 0.8 × 10-3 kgm2.

The company cut weight by redesigning the springs and making components smaller. The four sizes of couplings in the Series have torque settings ranging from 5 to 700 Nm, bore diameters from 0.5 to 2.250 in., and include rigid flange, bellows couplings, and elastomer coupling configurations. They operate in temperatures from –22 to 248°F, and handle over 10,000 disengagements, depending on rotational speed. The SLN clamping and SLP keyway (shown) use flanges to attach to sprockets, sheaves, pulleys, and gears, and have dual bearings to support belt and chain tension. The SL2 bellows coupling and SLE servo insert coupling mount in-line between independently supported shafts. All limiters are field adjustable and come with English and metric bores.

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