Compact and efficient safety coupling for aviation equipment

SL2 with clamping hub for direct drives

SLP with keyway mounting transmits torques of 10 to 700 Nm depending on series

A leading manufacturer of aircraft and aviation equipment inquired about a safety coupling for an intelligent lifting device in mobile cabins for transport and service work. The goal: Reduction of mass and moments of inertia combined with a compact design.  Depending on the aircraft model, a release torque of between 40 and 135 Nm is required, with a maximum overall length of 30mm and a maximum overall weight of 200g.  Finally, this torque limiter was to be integrated into a scissor lift in the smallest possible space.  The company opted for the innovative lightweight safety coupling from the clutch specialist R+W Antriebselemente. The SLP Series, size 30 safety coupling was adapted to meet an additional customer requirement.  The unit needed to provide overload protection with a sealed design, in order to protect it from liquids and dirt and so that it can be used in any weather conditions.

Compact clutch series TORQLIGHT SL

The TORQLIGHT SL series, developed by R + W in collaboration with technical universities, is the ideal solution for such demanding applications. It combines high-tech materials with unique coatings in a lightweight, compact, and powerful design. This torque limiter runs backlash-free thanks to the proven spring-loaded ball-locking principle, thus ensuring even greater safety. The SL series consists of high-tech materials with a unique coating that achieves a weight reduction of up to 60% compared to the standard series. For example, the SLP series, size 30 has a torque capacity of up to 135 Nm, a dead weight of just 200g, and a mass moment of inertia of 0.1 * 10-3 kgm². Thanks to the special machining of the base body and mounting flange, this safety coupling reacts within milliseconds with a repeat accuracy of +/- 5 %. The ratio of torque capacity to physical dimensions and weight makes the TORQLIGHT safety couplings truly unique on the global market.

Modular design principle for even greater precision

In addition to the choice of special materials, R+W achieved further weight reduction by intelligently compressing the individual components - without affecting the service life or accuracy. The custom disc springs developed for R+W, in combination with a further development of the ball-locking principle, lead to a torque increase of up to 40%. Thanks to the functional principle of the R+W spring-loaded safety couplings, the required backlash-free operation and high torsional spring stiffness are achieved over the entire service life of the coupling. Blocking elements (balls) are braced in pairs against each other in their conical detents. The specially developed disc springs with a special characteristic curve, enable precise torque overload protection and very fast reaction times. Only after exceeding the set disengagement torque does the coupling start to move. The balls then leave their rest position and the torque flow is interrupted; residual friction is reduced to zero. The drive balls do not move while seated inside their corresponding detent, which avoids clutch wear during normal operation when the pre-set disengagement torque has not be reached.  The reduction of the spring force during disengagement and the lightweight switch ring help reduce the wear forces to a minimum. Changes to the disengagement torque setting as a result of environmental factors, as can often occur in the case of friction disc slip clutches, was not an option.

Safety in four versions

Currently, R+W offers five standard models of the TORQLIGHT lightweight series.  Depending on the mounting situation, a customer can request the SL unit with clamping ring or keyway mounting for indirect drives, e.g. for connecting to pulleys or sprockets. Two other models have been designed for direct drives. These are equipped with a clamping hub and compensate for shaft misalignments. Customers can choose between a version with a torsionally stiff metal bellows coupling or with a vibration-damping elastomer insert. The various series are currently available in single or multi-position automatic re-engagement configurations.  

The angle synchronous version (single-position) snaps back into place after rotating exactly 360°, due to a special arrangement of holes in the base body. The number of balls and detents in the base body are designed in such a way that the coupling continues to work safely and wear-free after re-engagement. This ensures that the drive train is absolutely synchronous. The multi-position version works according to the same principle. However, here the detents are placed at symmetrical angular distances over the entire base body, so that re-engagement takes place after 30°, 45°, 60°, 90° or 120°. Additional engagement angles can be set at the factory depending on customer requirements.  Each model is available in four sizes: 30, 60, 150 and 300. Disengagement torque settings can vary from 5Nm up to 700Nm.  

Individual customisation made easy

Customers can also adapt their safety couplings individually to their needs. The modular design of the SL series allows a wide range of combinations. All safety couplings come set to a requested disengagement torque value at our factory in Klingenberg.  Thanks to the new construction, the disengagement torque setting can also be modified in the field- the torque range is marked on the adjustment nut, providing assistance when changing the torque setting. The function system and performance of the unit will not change with slight adjustments to the disengagement torque value.

In order to protect the safety coupling when used in very dusty environments or environments where it may come into contact with liquids or aggressive cleaning agents, R + W has achieved a design that seals the internal component. This also ensures that no grease can escape from the coupling. The design completely integrates all components in one housing and offers a special seal.  The specifically developed O-ring is inserted into the base body of the coupling and completed covered by an extended actuation ring. This solution protects the sealed safety coupling from all external influences and can even be used in clean room environments.

TORQLIGHT sets new standards

With the development of the new lightweight safety couplings, R+W is setting new standards in drive technology. The modular payload concept with flexible design allows aerospace customers to combine their individual application needs with maximum safety. The lightweight, compact, and powerful TORQLIGHT SL model series opens a new chapter in the field of safety couplings, allowing them be used in completely new application areas.