Techdrives now has a complete range of universal joints for machinery applications available via its website. Suiting shaft diameters from 6-50mm, these universal joints permit much greater angular misalignments than flexible couplings; a single universal joint can accommodate up to 45 degrees, whereas flexible couplings typically accept only 1-3 degrees. The Techdrives range includes single, double and telescopic universal joints with the majority available from stock.
The selection process begins with the type of bearings. A single universal joint is constructed with a central 'spider' block connecting a pair of yoked hubs. These three main parts are connected by pins spaced at 90 degrees. At low speeds plain bearings, constructed by hardening and precision grinding the rubbing parts, are the best option because 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 is often necessary. At higher speeds sealed needle roller bearings are the best option and these are recommended for speeds from 1000-3000rpm.
There is a further choice from three different designs. Single universal joints can run with angles up to 45 degrees 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 90 degrees. Even here a matching of speed is not guaranteed; it is necessary for input and output shafts to be parallel in order to achieve this.
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 while torque is being transmitted.
Techdrives offers single, double and telescopic universal joints in both plain and needle roller types. Most options are available from stock. Dimensions are to DIN 808 with the older DIN 808/7551 being available on request. In most cases hubs are prepared for pinning to the shafts, but keyway versions are also stocked.
Follow the link for more information and a selection guide for Techdrive's range of universal joints.