Ring Keeps Bearings in Vacuum Housing

The Kirby Company, a division of Scott Fetzer, has produced commercial and industrial vacuum cleaning devices for nearly a century. As with any market, cost containment and product reliability are the cornerstones of survival.

During the development of the G5, the latest in Kirby's line of upright vacuums, engineers even worked with scientists at NASA's Lewis Research Center in Cleveland, OH, to develop a quieter, more stress-resistant fan for the unit. However, they were faced with the problem of mounting a precision steel ball bearing in a molded plastic housing on the commutator end of the motor. (The Kirby design uses a single motor for driving the fan and other functions.) Adding to the dilemma were motor operating temperatures near 100°C and a typical motor speed between 15,000 and 16,000 rpm. Failure to adequately retain the bearing could eventually lead to the bearing's outer race spinning free in the housing, leading to brush damage, excessive vibration and possible destructive failure of the motor.

The Kirby engineers solved the problem by using a corrugated steel shim made by USA Tolerance Ring. Each ring is made from 301 stainless steel, with a Rockwell rating of 41-45. The corrugations allow for generous molding tolerances, and they expand and contract to keep bearings in place, even under temperature extremes. Besides acting as a vibration damper, the ring also provides adequate security of the outer bearing race in housings that might be slightly out of round.

USA Tolerance Ring proposed to Kirby a modified version of the standard ring for installation on the end of the motor that attaches to the fan. The bearing on this end uses a standard retainer and clip. The modified ring would perform better than a standard type to withstand the particular rotational stresses that the bearing is exposed to during operation.

--RM

For more information, contact:

USA Tolerance Rings, Sullivan Way, PO Box 7509, West Trenton, NJ 08628-0509. 877-865-7464. Circle 227.

The Kirby Company, 4750 West 160th St., Cleveland, OH 44135. 800-437-7170.
Circle 421.