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Torque limiters combine millisecond disengagement with zero backlash design

21 September 2016

R+W torque limiting couplings from Drive Lines feature a pre-loaded ball detent design that eliminates backlash.

The design also ensures a much faster operation, separating the drive and driven elements in milliseconds in the event of an overload. 

Backlash can be a particular problem in torque limiting clutches. In a standard design, when torque is applied there is a mechanical deformation of the various elements of the coupling. When the torque limiting function is engaged, the stresses are first relieved and then applied to opposite sides of the components, resulting in a reversed angular motion, or backlash.

R+W couplings have always been renowned for their low or zero backlash performance. With the latest spring loaded ball detent design, zero backlash is guaranteed and the repeatability of the preset disengagement torque is significantly improved, especially when compared with a slip clutch. The patented operational principle assures reliable and safe protection against overload, even with heavy loads.

Optimised disc springs and materials specially selected for use within torque limiting couplings ensure a compact and highly reliable design with guaranteed performance. The more compact design means lower overall weight and smaller diameter, aiding machine builders who want to downsize their systems while also improving the torque limiting performance through a reduced separation masses. Typical disengagement time is 1-2msec, faster than with larger units.

The R+W development team also focus on providing a longer service life and maintenance free operation. To this end, there is very little wear while running disengaged and very low residual friction in general (2-5 percent).

The R+W torque limiting coupling range is mainly spread over the SK and ST series of safety couplings. Available in sizes from 0.1Nm to 2,800Nm, the SK series torque limiting clutches offer protection from rotating inertia as well as motor torque, with precise torque overload protection. The SK series offers a number of mounting options, including conical clamping bushes, clamping hubs or keyway mounting for indirect drives, and with the addition of bellows couplings or elastomer couplings for direct drives. There are also the SL (Superleggera) range of compact, low inertia couplings where space and weight saving are important factors.

The SK series are capable of providing overload protection wherever rotation and overload exist. Typical applications will include machine tools, packaging machinery, conveyors and feeders, metal forming equipment, test stands, pump drives, assembly systems and converting equipment.

For heavier duty applications where a zero backlash design is critical, R+W ST series torque limiting couplings are available in sizes from 2,000Nm to 165,000Nm. 

Combining precise overload protection with easily adjustable disengagement torque in a compact design, the ST Series provide a simple zero maintenance solution. Typical applications include timber processing machinery, bulk materials handling, tunnel boring machinery, industrial shredders, rotary test stands, extruder drives and wastewater scraper drives.

The complete ST range offers variants with keyway mounting or conical clamping ring for indirect drives, or with keyway mounting with either electric coupling or crown gear coupling for direct drives.

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