Appliance of Science in Motor Bearing Mounts

In almost every appliance, whether it is a washing machine, dishwasher or refrigerator, the electric motor creates or is subjected to noise and vibration, and this presents one of the biggest failure modes in the white goods industry today. Finding a convenient and dependable method for mounting bearings in motors presents a difficult challenge, particularly in these severe operating conditions.

'Tolerance rings provide a simple and cost-effective way of addressing this challenge', says Stuart Kelly, Appliance Product Manager at Rencol.

Rencol has developed an innovative, yet simple, cost-effective and reliable, motor bearing mount that overcomes all of these problems.The tolerance ring acts as a spring fastener between the bearing and housing.This allows the tolerance on the housing to be relaxed significantly, since the spring characteristics of the ring compensate, so less costly 'as moulded' parts can be used.

In similar way, the tolerance ring provides compensation for differential thermal expansion between the bearing and housing. Additionally, the sprung nature of the coupling in the assembly reduces or even eliminates the adverse effects of minor radial or axial misalignment.

'In service, the key benefit of tolerance rings is undoubtedly their reliability but they can offer other useful advantages', explains Kelly.'They are excellent, for example, at dampening vibration and helping with noise reduction'.'This can be particularly important in equipment operating at high rotational speeds, or in high-quality appliances where near-silent operation is a prerequisite'.

Mounting methods for bearings are many and diverse, with a simple interference fit still used in many applications.Although seemingly simple, this conventional mounting method has many shortcomings, not least of which is that it relies on costly precision machining of the bearing housings.

It is also intolerant of misalignment, thermal expansion and prolonged high levels of vibration.For this reason, alternative mounting methods have been developed, including the use of O-rings, circlips, screws and plastic cups.Unfortunately, all of these techniques add to assembly cost and complexity without providing a comprehensive solution.

Rencol will demonstrate the new mount and highlight the key benefits of its spring metal fasteners to the appliance industry at Domotechnica in Cologne, Germany from 18th to 21th February 2008.

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