Unique coupling offers best of both worlds

A coupling has been developed that has a unique design that offers design engineers both radial flexibility and high torsional stiffness. Dean Palmer reports Genuine innovation in the world of couplings is pretty rare these days. But UK-based couplings manufacturer Huco has developed a unique design of coupling that combines the torsional stiffness of a straight beam coupling with the lateral flexibility of its helical counterpart. At a recent meeting at Huco's headquarters in Hertford, the company's joint managing director David Lockett told Eureka: "High torsional stiffness and good radial flexibility have, until now, been mutually exclusive characteristics of couplings. Whilst a straight beam coupling provides high torsional stiffness, it offers poor flexibility and exerts substantial side forces on bearings. Conversely, a helical beam has great flexibility but is torsional-soft. So choosing the right coupling for the job inevitably involves a degree of trade-off between the two." Huco's new coupling offers designers the best of both worlds. By employing new 'Step-Beam' technology, the 'Torq-Link' coupling combines the torsional stiffness of a straight beam coupling with the radial flexibility of a helical cut coupling. But there's more. According to Lockett, the new coupling "offers double the torque capacity of the equivalent helical beam coupling and far greater torsional stiffness". The device is relatively low cost too. Torq-Link was a joint development effort between Huco and a US-based designer (who must remain nameless) and the really clever thing about the coupling is that it can be moulded in one piece. Huco does all the moulding at its Hertford site. This means the coupling can be manufactured in large quantities to economic advantage. The standard version is moulded from polymer (a nylon variant), which can withstand temperatures up to 150°C and nano-filled models will be available for additional toughness. Huco has also supplied a PEEK version for use in a high voltage capacitor. Other polymer and composite materials are currently being assessed. Initially, three of the most popular sizes will be available - 13mm, 19mm and 25mm with standard bores of 3mm to 12.7mm. Other sizes will follow later this year as standard, although special bore sizes are available now. All couplings are supplied with clamp fixing or set screw. As far as applications and target markets are concerned, with its high accuracy and low inertia, the new coupling is ideal for driving encoders or for applications that require electrical isolation and corrosion resistance. Huco has also been busy preparing a brand new guide for design engineers to help them select the correct coupling for their application. The 'Designer's Guide to Precision Shaft Couplings' is a handy, pocket-sized publication designed to make the lives of design engineers that little bit easier. It gives them the opportunity to create the perfect combination of coupling and application, whether to compensate for misalignment or to ensure high precision positioning in sophisticated control systems. The guide contains conversion factor tables and useful guides to help predict misalignment; how to select the ideal coupling; selecting couplings for true, angular misalignment and zero misalignment; selecting for axial compliance; and selecting for torsional stiffness and torque capacity. More details from www.huco.com