Couplings for dynamic positioning and velocity control systems

Huco (Altra Industrial Motion)visit website


Huco Dynatork is promoting its range of Flex M shaft couplings. When specifying a coupling for any driveline, speed, inertia, bearing load, shaft misalignment, torque capacity and space constraint all need to be taken into account, and a servo application is no different in this regard.

A servo-class coupling needs to be able to maintain high signal integrity. This is particularly important in a closed loop or velocity-controlled system where the coupling can have the effect of reducing the resonant frequency. A coupling with high torsional stiffness is vital in this instance.

When the emphasis is on performance, a stiffer coupling is needed to reduce setting times, improve positional accuracy and raise the upper limit of dynamic performance.

The Flex M, the flexible membrane or disc coupling, provides the highest performance in the Huco Dynatork range. These products feature thin pressed steel membranes that act as pivotal members. Torque is resolved to simple tensile stresses in opposing segments of the membranes.

The company claims that these couplings have near-infinite life, and have a dynamically balanced construction which makes them suitable for applications requiring high rotational speed and high-level motion integrity.

Three versions of the Huco Dynatork Flex M couplings are available – single stage (highest torsional rigidity), double stage, and double stage with spacer (highest axial compensation). Typical applications for these products are in machine tools, robots, centrifuges, turbines and dynamometers.

Whilst Flex M has the more tolerant flexural system, Huco Dynatork Flex B and Flex K bellows couplings have the greater torsional stiffness. These stainless steel bellows couplings are available in three standard configurations – short, long and stretched – each with different characteristics to provide a wide choice for designers seeking high performance in precision motion systems.

Huco Flex B flexible bellows are attached to the hubs by a swaging technique that overcomes the uncertainties of bonding or soldering. The convolutions are torsionally rigid but elastic in the lateral and longitudinal planes. This type of bellows coupling is limited to a peak torque of 12.5Nm and rated for continuous uni- and bi-directional rotation and when dynamically balanced rotation can be up to 25,000rpm. Flex K couplings have bonded hubs. The scope of this design, in terms of size and geometry, enables Huco Dynatork to design and manufacture customised products.

Electrodeposited nickel version

Flex Ni is the electrodeposited nickel version of the Huco Dynatork bellows coupling, typical used in drives for sensitive instruments such as encoders, dynamometers and switches. Nickel bellows couplings accommodate a high degree of axial, angular or parallel misalignment through the flexure of their convolutions. These are formed by the electrolytic deposition of nickel to produce a stress-free and uniform, closely-controlled wall thickness.

For further details about the Flex shaft couplings range, visit

18 September 2012

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