Feature Clutches, brakes & couplings
inaccurate data readings or damage. The centre disk will also act as a torque limiter during overload to protect more expensive machinery components. When the disk fails, it breaks cleanly and does not allow any transmission of power.
Oldham coupling
zero-backlash, or nylon for shock absorption and noise reduction. Ideal for many light duty industrial and high tech applications, oldham couplings are electrically isolating due to the non-conductive material of the centre disk. This prevents electri- cal current from being passed to delicate instruments which can cause
‘High tech applications in industries such as medical, semiconductor, solar, packaging and printing require precision components to maintain a high degree of accuracy and repeatability. The shaft coupling is an important component of such systems’
Zero-backlash jaw couplings The jaw coupling is also a three piece design comprised of two aluminium hubs and an elastic element called the ‘spider’. Made of an advanced polyurethane material, the spider provides dampening of impulse loads, minimising shock to the servo motor and other sensitive equipment. Available from Ruland in three durometers, the spider allows the user to tailor the performance of the jaw coupling, such as torsional stiffness, misalignment, and dampening require- ments, to their application. For added customisation, metric and inch hubs (set screw, clamp style, keyed, or keyless) are interchange- able and can be combined into a single coupling. The jaw couplings feature a curved profile hub which press fits onto the spider assuring zero-backlash opera- tion for high tech applications.
Products to improve double clutch transmissions
A new series of products have been launched by SKF to improve the performance, reliability and lifespan of double clutch transmissions. The Double Clutch Bearing Set and clutch support angular contact ball bearing can resist high temperatures and loads. The Bearing Set is used to decouple the engine from the gearbox for gear changing. The two bearing units can be used in dry or wet clutch applications, and are compact and lightweight. The internal bearing geometry has been optimised to minimise contact pressure and to be able to carry the high loads associated with double clutch transmissions. Selected materials have been used for the bearing
cage, grease and seals (for dry clutches), to withstand the increased temperatures in such transmissions. The design includes self-alignment and radial guiding of the bearings plus support possibili- ties for actuations by mechanical fork contact or hydraulic piston. The clutch supports angular con- tact ball bearing guides and locates the clutch driving plate as it transfers loads from the engine to the gearbox. SKF
T: 01582 496433
The curved jaw profile concentrates the forces to the centre of the spider’s limbs, improving the effectiveness of the elastomer material. Raised contact points on the spider limbs help main- tain proper spacing between the two hubs, assuring electrical isolation and full angular misalignment capabili- ties. Jaw couplings are considered fail safe because the jaws of the two hubs interlock for direct power transmis- sion if the spider was to fail, allowing the application to be safely shut down for maintenance.
Ruland couplings are available in the UK from Techdrives.
Ruland
www.ruland.com
Techdrives T: 01234 321320
www.techdrives.co.uk
Enter 208 Enter 209
Curved jaw coupling
‘Super-sized’ couplings
Enter 210 Braking solution for arduous environments
Now available from Techdrives is the compact INTORQ BFK471 brake, which delivers torque up to 1500Nm. This is a spring applied design that is normally engaged, and is released by applying a DC voltage. It is available with either one or two rotating discs with corresponding rated torques of 750/1500 Nm. Both have an outside diameter of only 333mm and a maximum bore size of 65mm. The brake has manual release which is said to be both smooth and efficient with low applied force. There is an option for mechanically locking the lever in a ‘brake-off’ position.
The brake has a zinc plated casing and nitrided friction surfaces, providing a UL recognised enclosure rating of IP66, suitable for jetted water. The brakes can therefore be used for dockside machinery, cranes, ships’ winches and general outdoor applications including bulk handling conveyors. The internal air gap for the BFK471, which is a measure of wear, can be easily measured in-situ using a check bore hole. As an option a non- contacting sensor can be fitted to monitor the wear and the brake operation. Where ambient temperatures are particularly low, typically below -20˚C, a heating element can be added. Techdrives
www.techdrives.co.uk 16 Enter 211
Robust couplings for extremely large and challenging applications are now available from Zero Max. The customised high torque CD couplings measure up to 20in in diameter, handling 78,000 Nm peak torque. With torsional stiffness of 419,000 Nm/DEG and continuous torque of 39,000 Nm, these have angular mis- alignment capacity of 1.5˚ with axial misalignment of 6.5mm and parallel misalignment of 0.24mm. Designed around the composite
centre disc, super-sized CD couplings are said by the company to perform at these peak torques in the most hostile operating environments – from extreme cold to hot weather conditions: -57˚C to + 121˚C.
Applications include drive trains, gear boxes and generators, providing trouble-free operation in sea water and abrasive desert sand conditions. Zero-Max
www.zero-max.dk Enter 212
OCTOBER 2012 Design Solutions
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