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14/01/2010
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A range of universal joints for machinery applications is available on the Techdrives website. Suiting shafts from 6 to 50mm, these universal joints allow much higher angular misalignments than flexible couplings.
 A single universal joint can accommodate up to 45º whereas flexible couplings typically accept only 1 to 3º. The Techdrives range includes single, double and telescopic universal joints with the majority being available from stock.
The selection process begins with the type of bearings. A single universal joint is constructed with a central block between two yoked hubs.
The three main parts are connected by pins spaced at 90º. At low speeds plain bearings, constructed by hardening and precision grinding the rubbing parts, are the best option as they give lower cost and a better resistance to peak loads. However, they do tend to shed their lubricant and a grease filled rubber gaiter will often be necessary. At higher speeds sealed needle roller bearings are the best option and these are recommended from 1000 to 3000r/min.
There is a further choice from three different designs. Single universal joints can run with angles up to 45º but the output speed will vary cyclically four times per revolution. In some cases such as hand winding this may not be a problem, but continuously running machines will often use two single joints installed at equal and opposite running angles to achieve an exact match of speeds.
An alternative is a double universal joint that can transmit torque through up to 90º. Even here a matching of speed is not guaranteed. It is necessary for input and output shafts to be parallel in order to achieve it.
Telescopic universal joints are designed for machinery where modules are set statically, for example guides on a packaging machine. Sliding of the internal splines is not normally possible whilst transmitting torque loads.
Techdrives offers single, double and telescopic universal joints in both plain and needle roller versions. Most options are from stock. Dimensions are to DIN808 with the older DIN808/7551 being available on request. In most cases hubs are prepared for pinning to the shafts, but keyway versions are also stocked.
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Author
Chris Shaw
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