The new backlash-free torque overload protection

Torque Limiters and Safety Couplings without any risk!
courtesy of R+W America

Zero backlash Torque Limiters and Safety Couplings for a secure overload protection

In consideration of economic aspects limiting torques is a continuous challenge when developing torque limiters as an overload protection coupling. The new generation of the zero-backlash torque limiters has been designed for being used in power-transmission and servo applications. Important requirements such as being backlash-free, short reaction times and long service life have been further optimized. The constructive benefit is ensured through fast availability of applications after a crash.

For limited installations

The development and optimization of the well established backlash-free torque limiter series SK offers the appropriate element for various applications. The transmittable torques can be surely defined and set. Even in regard to restricted space of installation, the couplings correspond to the latest state-of-the-art.

Areas of applications of the torque limiters from 0.1 to 2,800 Nm can be found in any branch of general mechanical engineering.

Highly dynamic drives are being protected by the use of preset torque limiters. When the overload occurs the torque limiters immediately disengages in milli seconds. The movement of the actuation ring is sensed and used to control and switch off the machine. Immediate availabillity of the machine after re-engaging of the torque limiter is assured. Die neue Kompaktserie der Sicherheitskupplungen

Increased economic efficiency

Optimized disc springs and materials adapted to the use of the coupling enable the compact and reliable design, better performance and less weight. Also a long service life and maintenance and wear free use should be taken into account when choosing couplings.

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

The size of the torque limiter has been reduced by approx. 1/3 compared to other available products. Less mass needs to be separated in case of a crash due to the reduced weight and a smaller technical diameter.

When comparing the facts, the user finds out that R + W develops and delivers the most compact torque limiters.

A great variety

The advantage of ball detent design torque limiters is the separation of the drive and the driven unit in milliseconds in case of an overload. Easy handling and their reliability is a further advantage

Machine designs with little installation space or hardly accessible areas do however often require special solutions. The R+ W range facilitates the choice by means of sort of a modular concept. The hub type that is appropriate for the application is chosen and combined for its purpose of use.

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.

Poor manufactured couplings may cause pulsating radial forces onto the rotational axle during operation. schwingungsgedämpfte Sicherheitskupplungen

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

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 protect 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 provides 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 compromises 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 disengagement torque requested by the customer. Once installed, the disengagement value can easily be changed.

The torque area is radially engraved on the adjustment nut. An outstanding feature is an easy radial adjustment which clearly facilitates adjustment of the coupling. Due to the positive stop of the adjustment nut, the safety function of the coupling is allways assured.

For each torque limiting coupling model there are four different function systems available:

single position = re-engaging automatically in the same position (360°)

multi-position = re-engaging in several positions per revolution

full disengagement = contact free separation, must be re-engaged manually

load holding = no disengagement possible, controllable via inductive switch

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

Conclusion about Torque Limiters

Above all in the highly productive series production, for example with shift work, machine down times cause high loss of production costs which inevitably result 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 time, consequential damages will be minimized. And the price of the coupling can be considered as being relatively low when comparing it to later arising follow-up costs.

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