To increase performance and speed in machine and plant construction, components are becoming increasingly smaller and lighter. A coupling manufacturer has also recognized this trend toward miniaturization and offers whole product families.

The R+W company as manufacturer of couplings offers a wide range of miniature couplings: The current portfolio covers a torque range from 0.01 to 10 Nm with diameters from 1.0 to 28.0 mm. The company has developed the smallest coupling, the Model FK1 Microflex, for micro-applications in the field of medicine and measurement technology. With a length of 9 mm and an external diameter of 5.5 mm, it is available for shaft diameters up to 1.5 or 2 mm The slotted flexible segment of the coupling is made of polyamide. In this way the development engineers achieved a certain degree of flexibility of the coupling, which a the same time compensates for lateral, axial and angular shaft misalignment. The coupling is clamped by a slotted radial set screw and a stainless steel hub. If a more rigid design of the application is required, miniature couplings with tombac bellows can be used. R+W achieves high smoothness and very accurate measurement results due to the concentricity of the bores. These couplings are used for example in micropumps or manipulators. The smallest possible outside diameter is 6.5 mm with a total length of 14 mm .

Metal bellows couplings

Miniature metal bellows couplings transmit only low torques - their primary task is exact transfer of the angle of rotation. In the MK product series, R+W offers a variety of solutions for connection to pulse generators, measuring and control systems or small servo drives. Here a high degree of torsional stiffness while at the same time maintaining flexibility as well as the exact transmission of the angle and the torque is an important criterion. These two properties are achieved by the use of a metal bellows as compensation and transmission element. Accurate assembly of the coupling is crucial in order to fully exploit the technical characteristics of the couplings and to compensate for shaft misalignment without transmission errors. Each individual miniature coupling is therefore mounted on a mandrel.
The product portfolio of the Ecoflex® miniature metal bellows couplings also includes the Economy model. This is designed for nominal torques of up to 3 Nm and bore diameters from 3 to 12.7 mm. The coupling can be used in a temperature range of -40°C to +200°C by employing a special jointing method for the hub connection. This version is used for example in encoders and projects with high volumes, in which a cost-optimized solution coupled with quality is called for.
Thanks to their high level of precision and manufacturing quality, the miniature metal bellows couplings with blind mate connection and radial set screws or clamping hubs of the MK4 and MK5 series are suitable for exact angle transmission in measurement, control and regulation systems. They are able to compensate for all three types of misalignment with low restoring forces. With the blind mate connection, but backlash-free principle, preset encoders for example can simply be pushed onto the already mounted drive unit. Mounting bores on intermediate flanges are not required and assembly times are reduced.
The high-speed coupling of the MKS series has been developed for high-speed applications up to 120,000 rpm. These speeds can be achieved by the concentric construction of the individual components, such as the coupling hub with tapered male connection as well as standard balancing of Q 2.5 quality. The miniature metal bellows couplings of the MKS series are used in micropumps, for example.

Elastomer and plastic couplings

Miniature couplings are also available in the area of vibration damping couplings. The user can select from elastomer couplings of the Servomax® and the Ecolight® product lines. While the hubs of the Servomax elastomer miniature couplings are made from high-strength aluminium, the hubs of the Ecolight® series are manufactured from rigid, fibre-reinforced plastic. This ensures high power density with compact dimensions. To adapt the coupling to the respective application requirements, both series are available with different Shore hardnesses of the elastomer insert.

Safety couplings

If a coupling is used to protect against torque overload, the miniature version of the SK series can be used. These safety couplings guarantee safe overload protection at a disengagement torque of only 0.1 Nm and bore diameters from 3 mm. In the event of a torque overload, possibly caused by a machine collision, the backlash-free safety couplings disengage in milliseconds and separate the input and output side. This avoids costly downtime and repair costs. After eliminating the overload, the system can be put into operation again in the shortest possible time.
With the ESL model, R+W also provides an economy version in this area. The safety part of this elastomer coupling is made from high-strength steel, while the drive balls are made from hardened steel. The coupling hub is made of high-strength aluminium and the elastomer insert from a wear-free plastic. This coupling is mainly used in applications with high volumes, such as reverse vending systems.

Special Solutions

R+W has also added a number of special solutions to its wide range of miniature couplings. These are tailored to the specific requirements of customers according to the application. Here the engineers and developers have access to many years' experience in the design and construction of special couplings.

Jörg Stang, Sales Manager


R+W America

1120 Tower Lane

Bensenville, IL 60106


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