Measuring and testing – Vibration – By mechanical waves
Reexamination Certificate
2000-11-09
2002-04-30
Williams, Hezron (Department: 2856)
Measuring and testing
Vibration
By mechanical waves
C073S587000, C073S659000, C073S660000
Reexamination Certificate
active
06378373
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a bearing analysis system, and more specifically, to a computerized bearing analysis system capable of operating at high-speeds to test the bearing at its normal operational levels.
2. Discussion of the Related Art
Anderonmeter machines are typically used for vibration or noise analysis of precision ball bearings, and particularly those used in high-speed dental handpieces. The Anderonmeter machine generally operates at speeds of at least 200 times lower than the actual operating speeds of a bearing in a high-speed dental handpiece. The Anderonmeter machine operates by spinning a test bearing on a test rig, and applying or touching a reading needle to the outer ring of the test bearing to produce an acoustic output. An operator uses a set of headphones to listen to the acoustic output to detect any unusual noises during the test.
Because Anderonmeter machines operate at speeds far less than the actual operating speeds for which the bearings are designed, the data collected with the Anderonmeter machines often do not represent the real vibrational characteristics of the bearings used in a real-world application. For example, bearing vibrations analyzed at a rotation speed of 1,800 revolutions-per-minute (rpms), the typical rotation speed of an Anderonmeter machine, do not provide complete information regarding the bearing in a real-world application. In a high-speed bearing for use in dental applications, for example, the operational rotation speed may range from approximately 350,000 to 500,000 rpms. This testing methodology is analogous to testing a race car at 5 miles-per-hour (mph) and then assuming that the race car will perform as well at 200 mph.
A number of factors influence the vibrational behavior of a bearing at different speeds. Centrifugal forces are an important factor, and at speeds of 350,000 to 500,000 rpms, the centrifugal forces are high. For example, each one millimeter (mm) steel ball of a small dental bearing rotating at 500,000 rpms presses against the outer ring of a bearing with approximately 1.5 pounds (lbs.) of force. These forces greatly influence the operational nature of the bearings, not to mention the lubricants utilized within the bearings. Therefore, a tremendous advantage is to be gained by being able to test bearings at their high operational speeds because many characteristics may be measured incorrectly at lower test speeds.
Additionally, with an Anderonmeter machine, because an operator listens using a set of headphones, human error may contribute to inaccurate readings, and the data collected may not be consistent from one operator to another.
Another method to measure for vibrations or noise of a high-speed bearing is to directly measure the roundness and finish of the raceway (the groove in which the balls rest) with a measuring needle. Although the quality of the raceway is a strong determinator of smooth and quiet operation of the high-speed bearing, it is not the only determinant. Therefore, measuring the raceway quality alone is not sufficient to predict how a high-speed bearing will operate.
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New Hampshire Ball Bearings, Inc.
Saint-Surin Jacques
Williams Hezron
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