FEATURE CLUTCHES, BRAKES & COUPLINGS W
ith their excellent kinematic properties and torsional stiffness,
Huco Dynatork’s flexible membrane couplings (Flex M) and bellows couplings (Flex B, K and Ni) are not only suitable for servo drives but also satisfy the criteria for highly dynamic position and velocity control systems. However, while bellows couplings have the greater torsional stiffness, the flexible membrane, or disc coupling, has the more tolerant flexural system and features a dynamically balanced construction. So what are the design and performance criteria governing their selection? The couplings are beneficial where
torsional stiffness is a critical parameter and when the backlash-free life requirement is beyond that of a sliding contact type coupling. Typically, they serve applications with speeds of above 5,000 rpm and when rotation is continuous or the duty cycle exceeds 50%. A Flex M or bellows type is ideal in
applications where a coupling with axial compliance is needed to protect fragile bearings from thrust loads and where environmental conditions favour an all- metal product. These are best suited to applications where there is little risk of alignment errors exceeding prescribed limits during initial installation or on subsequent replacement of a motor or encoder. The Flex M is characterised
by thin metallic membranes pressed from spring quality stainless steel that acts as pivotal media. These are attached alternately to the drive and driven members and provide flex to compensate for misalignment. Any torque is resolved to simple tensile stresses as no secondary forming operations are involved in the coupling’s manufacture. There are three versions available:
• Single stage (highest torsional rigidity) • Double stage
COUPLING UP:
Operating principles and application solutions
Flexible membrane and bellows couplings offer
specific performance features that enable their use in a range of applications. Huco Dynatork looks into the operation of these servo class solutions
long and stretched – and each offers different characteristics. 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, up to 25,000rpm. Flex K couplings have bonded hubs. The scope of this design,
in terms of size and geometry, provides Huco Dynatork with greater opportunity to design and
manufacture customised solutions. Flex Ni, meanwhile, is the popular
A variety of couplings are available from Huco Dynatork
• Double stage with spacer (highest axial compensation). Typical applications for these are in
machine tools, robots, centrifuges, turbines and dynamometers.
COUPLING TYPES The Flex B and Flex K stainless steel bellows couplings are available in three standard configurations – short,
electro-deposited nickel version of the bellows coupling, typically used in drives for sensitive instruments such as encoders, dynamometers and switches. Nickel bellows couplings accommodate a high degree of axial, angular and 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.
Huco Dynatork T: 01992 501900
www.huco.com
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