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	request details	Key Considerations for choosing Shaft Couplings
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The problem is well known: no appropriate drive elements for a new machine. One of the general requirements in mechanical and plant engineering is more focused on reliable and compact components. In addition, manufacturers of machine tools, industrial robots, and general machine design have considerably higher expectations of shaft couplings, not only in consideration of these demands but also in consideration of installation space, which is getting smaller and smaller. R+W Antriebselemente offers some advice on key factors to take into consideration when choosing industrial couplings.

Properties
Special requirements and features for shaft couplings with damping properties can be subdivided into different categories. There are different tasks to be fulfilled depending on the area of application. Basically the following is included:

• Connection of two rotating shafts
• Transmission of torque
• Compensation of shaft misalignments, especially radial, angular, and axial
• Damping and influence of rotary movements, especially intermittent losses and vibration problems
• Good hysteresis loops and reduced wear
• Compact style and easy assembly
• Performance of high speeds of up to 20,000 rpm in precisely balanced execution
• Application in explosion-proof plants in accordance with the new Atex 95/137 guidelines
• Coupling hubs in different materials, covering high-strength aluminium, steel and stainless steel. Any surface treatment is available as desired.

Concept adapted to dynamic requirements
The elastomer coupling Servomax has been developed for being used in highly dynamic servo axes. The elastomer insert consists of polyurethane and is able to compensate axial, lateral and angular misalignment and dampens vibrations and impact due to its elasticity. During operation of machines with frequent impact, alternating and vibration load, the high damping capacity can have a positive effect on the service life of the connected motors and controllers.

The customer may choose elastomer inserts of different hardness. There is a choice of Shore hardness 80 A, 98 A, and 64 D. Polyurethanes are preferred materials for elastomer inserts. They are most resistant against oils, greases, gas, and many solvents. With the basic assortment, torques of 2 to 1600Nm and shaft diameters of 5 to 80mmcan be achieved.

Telescopic shafts with elastomer couplings
The safe and economic connection of long distances between shaft ends is a real problem for most of the designers. Easy assembly is a further demand when spanning long distances. R+W introduces a new product for this, the adjustable telescopic shaft with elastomer coupling. The telescopic design of the intermediate tube allows for an easy adjusting of the length. Split hubs with elastomer inserts have been chosen for an easy assembly so that the line shaft may easily be integrated in existing systems as a complete unit.

There are line shafts of up to 1,100Nm and up to 4m length available. An intermediate bearing to support the shaft is not needed.

Design and calculation criteria via R+W Software
A special software helps to determine the most critical values of the application. The values obtained there provide detailed information on the elastic deformation, critical resonant speed, torsional stiffness of the complete shaft, angle of turn, weight, mass moments of inertia and possible compensation of misalignment. The maximally admissible radial misalignments directly depends on the length of the line shaft. This calculation software which has been especially developed by R+W helps the user to make his decision.

Highly dynamic intermediate shafts are increasingly being used in the entire mechanical and plant engineering area. Areas of application especially exist in gantries, connection of linear guides, palletising and packaging robots.

Overload protection with dampening properties
In order to achieve an additional damping property with backlash-free torque limiters, R+W has developed another series of elastomer couplings from the existing compact series. One of the remarkable features of these couplings is precision. Easy, axial mounting of the coupling is guaranteed.

Due to the patented functional system the couplings remain backlash-free and torsionally rigid during the entire service life. A spring loaded ball detent design of the torque limiter helps to achieve an exact overload protection while having short actuation times. Only when exceeding the set torque, will the coupling disengage. The elastomer torque limiter ES2 is optionally available as single-position, multi-position, load-holding, or full disengagement type and covers torques of up to 800Nm.

Easy assembly after alignment of the shafts due to split hubs
The exact alignment of two shafts regarding the radial and angular misalignment is of utmost importance to the service life and wear of shaft couplings. Radial misalignment directly influences the smoothness of running of the entire drive unit. When using split hubs, the alignment is even easier. The drive and the driven unit can be mounted and aligned prior to the assembly of the coupling. After the alignment, the coupling can simply be installed radially and tightened. An installation and assembly instructions is enclosed with the delivered products.

Couplings according to the Atex 95/137 directory
The new generation of explosion-proof couplings has already been manufactured in the design and production phase in compliance with the fundamental requirements of the new ATEX directory.

The explosion safety is confirmed for zone 1 and zone 2. Special marking of the couplings shows the manufacturer's name, type of equipment, and production date, production number for continuous documentation and traceability. In addition, an operating and maintenance instruction is required and delivered with every ATEX registered coupling.

R+W Antriebselemente welcomes the opportunity to offer some further advice on considerations for choosing industrial shaft coupling solutions specific to your needs.

Published: Nov 2004 by R+W Antriebselemente GmbH