Delrin bearings operate smoothly, silently and maintenance-free

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Spyraflo 10mm diameter self-clinching, self-aligning Delrin bearings have been used to mount retractable TV screens in the ceilings of luxury tour buses.

A TV company had a market requirement to mount flat-screen HDTVs using a retractable design mounted in the ceiling of luxury tour buses. However, there were several key application criteria that needed to be satisfied. For safety reasons, the Department of Transportation imposes severe limits on the amount of additional weight that can be added to the roof of a bus. In addition there were two crucial design criteria: the raising and lowering mechanism had to operate silently and be maintenance-free.

The weight issue became even more of a factor when the tour operator, for easy passenger visibility, insisted on several screens per bus. The designers were faced with tough problems: how to produce a suitable mechanism that met the stringent application requirements and yet be robust enough to withstand the rigours of a bus environment. The weight limitation stipulated the use of 16-gauge sheet steel for the mounting of the raising and lowering mechanism. It was critical that the bearings could be securely mounted without the risk of shaking loose during the travelling lifetime of the bus.

A study of bearing types found that very few came near to fulfilling these requirements, being either too large, too heavy, noisy, or difficult to install or align. Finally the engineers selected 10mm diameter self-clinching, self-aligning Delrin bearings from Spyraflo, with four of these required per assembly. The final result was a TV monitor that raised and lowered speedily, silently and, despite there being ultimately multiple screens in the bus ceiling, the weight was kelp below the DOT threshold.

Self-clinching is a mounting technique used by fastener manufacturers in applications where, if the bearing is pressed into non-precision holes, the panel material cold-flows into the bearing retainer, thereby creating an extremely secure mounting. Spyraflo is claimed to be unique in using this mounting method for bearings. The +/-5 degree self-aligning capability compensates for misaligned mounting holes, which are a fact of life when punching, bending and welding sheet steel chassis and ensures smooth running shafts with no stick-slip.

Micromech is the UK and Eire distributor for Spyraflo bearings.

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