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Browse Prior Art Database

AUTOMATED BEARING PRELOAD MEASUREMENT

IP.com Disclosure Number: IPCOM000026225D
Original Publication Date: 1990-Dec-31
Included in the Prior Art Database: 2004-Apr-05
Document File: 8 page(s) / 427K

Publishing Venue

Xerox Disclosure Journal

Abstract

All non-separable ball bearings are manufactured with a small clearance between the balls and the raceways. Clearance is carefully controlled so that when a radial ball bearing is subject to axial load, optimum angles of contact between the balls and raceway are formed. The ability of the bearing to support axial load depends on the contact angles formed.

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Page 1 of 8

XEROX DISCLOSURE JOURNAL

AUTOMATED BEARING PRELOAD Proposed Classification MEASUREMENT U.S. C1.318/696 Robert J. Kleckner
Aron Sereny
John J. Ricciardelli

Int. C1. H02k 37/00

Fig. 1

I I

SHAFT DEFLECTION Fig. 2

XEROX DISCLOSURE JOURNAL - Vol15 No 6 November/December 1990 401

AXIAL

LOAD

Fa

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Page 2 of 8

AUTOMATED BEARING PRELOAD MEASUREMENT(Cont'd)

NUMERIC DISPLAY

DUAL- LI M IT

AMP wlh

Yes 1\

Ye5

Fig. 3

402 XEROX DISCLOSURE JOURNAL - Vol15 No 6 November/December 1990

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Page 3 of 8

AUTOMATED BEARING PRELOAD MEASUREMENT(Cont'd)

70 -\ - 42

46 42

- .-

-

I

24

XEROX DISCLOSURE JOURNAL - Vol15 No 6 NovembedDecember 1990 403

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Page 4 of 8

AUTOMATED BEARING PRELOAD MEASUREMENT(C0nt'd)

All non-separable ball bearings are manufactured with a small clearance between the balls and the raceways. Clearance is carefully controlled so that when a radial ball bearing is subject to axial load, optimum angles of contact between the balls and raceway are formed. The ability of the bearing to support axial load depends on the contact angles formed.

The same diametrical clearance produces an axial endplay that may or may not be tolerable to the bearing user. For example, in a chain sprocket drive it is acceptable to operate a pair of radial ball bearings with a small clearance. In precision applications, such as a machine tool spindle or an optical scanner, the clearance results in unacceptable shaft wobble. One eliminates clearance and improves running accuracy by axial preloading.Figure 1 shows a pair of face- to-face preloaded bearings A and B with a measuring force F, applied to the end of the shaft 12 nearest the shoulder 14. Shaft deflection 8 is simultaneously measured. When F is less than the preload the measured stiffness, AF/AS, is approximately the bearing stiffness. When F is large, bearing-B is no longer in contact with the shoulder and AFlA6 drops to approximately the stiffness of the wave washer 16.

In practice, both the bearing stiffness and the wave washer stiffness are non- linear. Assuming that the stiffness values are linear for small displacements about the equilibrium position, the following force-displacement relationship can be found from static equilibrium of the shaft

P+6K= < 6K-6 > kb+F c11

where

P is the axial preload K is the equivalent stiffness, defined by:

K= 1

(l/k + l/kb) r21

k is the stiffness of the wave washer kb is the stiffness of one bearing

6~ is the value of shaft deflection at which bearing-B loses contact with the shoulder.

404 XEROX DISCLOSURE JOURNAL - Vol15 No 6 NovembedDecember 1990

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Page 5 of 8

AUTOMATED BEARING PRELOAD MEASUREMENT(Cont'd)

Note that the term in pointed brackets is nonexistent for values of 6 which reduce it to a negative value. Thus, if the two stiffness values and one displace...