Torque Limiters / Safety Couplings:
The new backlash-free overload protection

For limited installations

The further development and optimization of the already well established backlash-free Torque Limiter series SK has brought about an appropriate design for each application. The transmittable torques can be accurate defined and set. Even in regard to restricted installation space now, the couplings represent the latest state-of-the-art. 

Areas of applications of the Torque Limiters ranging from 0.1 to 2,800 Nm can be found in any type of mechanical engineering.

Increased economic efficiency

Optimized disc springs and materials adapted to the use of the coupling allow for the compact and reliable design, better performance and wer mass. Also a long service life and maintenance free operation are importtant consierations when selecting couplings.

Smaller couplings combined with a higher torque density additionally result in a cost advantage due to smaller dimensioning.

On average the size of the Torque Limiter has been reduced by approx. 1/3 compared to other available products. This results in a reduced separation of masses in case of a crash due to the reduced weight and a smaller technical diameter.

A great variety

The advantage of ball detent design Torque Limiters is the separation of the drive and the driven elements in milliseconds in case of an overload. Easy handling reliability are further advantages.

Machine designs with little installation space or difficult to access areas do however often require special solutions. The R+ W range facilitates the easy modification by means of a modular concept. The hub type that is appropriate for the application is selected and integrated for the ideal design.

The press-fit principle that has been developed by R+W uses the axial spring force of the metal bellows to pre-tension a tapered male part into the corresponding counter-piece slightly axially. An axial pre-tensioning of the metal bellows of only 0.2 millimeters assures the absolutely backlash-free torque transmission. The self-adjusting tapered segment guaranties a wear and maintenance-free operation.   

Torque limiters with damping Properties

R+W has designed and launched a new overload protection with damping Properties. This combines the known elastomer couplings with a torque limiting portion.

Between the safety element with clamping hub and the other coupling half, there is an elastomer insert made of thermoplastic polyurethane (TPU) absorbing the drive vibrations. Owing to its elasticity, it is able to compensate axial, angular and lateral misalignment, vibrations, and impacts. During operation in machines with frequent impact, change or vibration load, its high damping capacity can have a positive effect on the service life of the connected aggregates. This however only applies to first-quality couplings which consist of individual elements showing the necessary truth of running and concentricity of the bores.

Choice of different Shore hardness

There is a choice of elastomer inserts with different Shore hardness 98 A, 64 D, and 80 A.  The inserts are calibrated most precisely in order to ensure perfect mounting of the coupling. The otherwise usual, but high pretension of the inserts is thus reduced and the assembly is much easier. If on the other hand the inserts are pressed in at too high pretension, the radial forces occurring with lateral misalignment on the shafts will increase. In addition, there is the risk of too much inner heating of the inserts because of increased flexing work.

Made of special steel, even completely sealed

For applications in the food area it is mostly required to oftect the coupling against aggressive cleaning detergents , liquid media, or dirt. Sealed couplings are also used in clean-room technology and in very dusty applications. A complete sealing that is optionally offered by R+W avoids leaking grease and at the same time penetration of coupling damaging substances. This solution ofvides all the sealing elements integrated in one component. An O-ring is inserted in the base element of the coupling and covered by an extended Actuation ring. This system makes sure that the external dimensions of the coupling stay the same.  Costly solutions where the coupling was sealed with a housing are therefore unnecessary

Nitrocarburizing, oxidizing, or nickel-plating is possible for steel types. Aluminum can be anodized, other materials and surfaces can be offered on request.

Function of the patented R+W prinziple

R+W’s patented operational principle guarantees reliable and safe protection against overload even with heavy loads. Due to the spring loaded ball detent design of the coupling high repeating accuracy of the preset disengagement torque is reached and continuous operation is ensured when using a ball detent design Torque Limiter vs. a slip clutch. Overload protection does not allow any comofmises in regard to reliability and quality of the individual components although Torque Limiters are always designed for an economic use. R + W conceived a solution which stands out.

Function always assured

At the factory the Torque Limiters are adjusted to the exact disengagement torque requested by the customer. After installation the disengagement value can easily be changed to siut actual requirements.

The torque adjustment range is engraved on the adjustment nut. An outstanding feature opf the R+W design is an easy radial adjustment which clearly facilitates adjustment of the coupling. Due to the positive stop on the adjustment nut, disengagement of the coupling is allways assured.

For each coupling model there are four different function systems available:
single position = attempting re-engagement automatically in the same position (360°)
multi-position = attempting re-engagement in several positions per revolution
full disengagement = complete load separation, must be re-engaged manually
load holding  = no disengagement occurs but an external sensor can be instantly triggered

With these four function systems R+W offers a solution for every application.

Conclusion

Most importantly in mass production situations, machine down time causes high loss of Production which inevitably results in rising unit costs. When using a Torque Limiter, which separates driving force and driven force in milliseconds and is thus fully operable after a very short period of time, consequential damages will be minimized. The price of the coupling can be considered as being relatively very low when compared to the cost of down time.

If you wish to receive more information on this Product please do not hesitate to contact R+W Antriebselemente GmbH at phone:
+49-9372-9864-0 or via email at info@rw-kupplungen.de