Expanded – threaded – driven – headed – tool-deformed – or locked-thr – With means to indicate application of predetermined... – Axially deformable member or portion
Reexamination Certificate
2000-07-11
2002-07-30
Saether, Flemming (Department: 3627)
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
With means to indicate application of predetermined...
Axially deformable member or portion
C411S013000, C411S014000
Reexamination Certificate
active
06425718
ABSTRACT:
FIELD OF THE INVENTION
This invention relates in general to direct tension indicating and maintaining washers and in particular to direct tension indicating and maintaining washers that maintain bolt tension and/or indicate when the proper bolt tension has been achieved.
DISCUSSION OF THE PRIOR ART
The present invention is an improvement to commonly-assigned U.S. Pat. No. 5,931,618 issued Aug. 3, 1999 to Wallace et al. hereby incorporated by reference herein. Referring to
FIGS. 10-13
, the prior art device comprises a direct tension indicating washer
60
having bumps
12
. As bolt
50
is tightened, the head of bolt
50
squeezes bumps
12
flat against surface
10
. An indicating material
64
, such as colored silicone compound, is deposited in indentations beneath bumps
12
(see FIG.
11
). Thus, as bumps
12
become flattened, so do the indentations, causing the indicating material to squeeze out through channels
62
from beneath direct tension indicating washer
60
and the bolt head as shown in
FIG. 13
, providing an immediately visible indication that a desired bolt minimum tension has been reached.
There are, however, applications which a single known bolt tension is insufficient. For example, sometimes it is desirable to know that a bolt has be tensioned to within a specified range. In this circumstance, it would be desirable to know not just that a bolt has been tensioned beyond a specific minimum, but that it has not been tensioned too far, i.e., beyond a maximum allowable tension.
Additionally, there are some bolting applications where the bolt must be tightened to two specific tensions. For example, a lower tension may be needed for pre-assembly conditions and “running in” of the machine or equipment, and then a higher tension for service life.
SUMMARY
The limitations of the prior art noted above are overcome by providing a direct multi-tension indicating washer that extrudes indicating material of varying colors depending on the compression force applied to it. The direct multi-tension indicating washer has a first and second surface having respective bumps and indentations. The compression force on the washer is equal to the tension in the bolt which has been inserted through the washer. The indentations in the second surface are filled with a solid extrudable colored material. By making at least a first bump taller than at least a second bump, the first bump will compress before the second bump, causing it to extrude the color material in its corresponding indentation before the second bump does the same as the tension in the bolt is increased. By making the material under the first bump a different color than the material under the second bump, an operator can determine which of two desired tensions the bolt has reached.
In use, an operator merely tightens the bolt passing through the washer or a nut threaded onto the bolt until the bolt reaches a first desired tension as indicated by the extruded material of the first color, such as green. An intervening step is performed at the first bolt tension, if required. Then, the operator continues to tighten the bolt or nut until the bolt reaches a second desired tension as indicated by the extruded material of the second color, such as red.
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Herr John A.
Wallace Ivan Wayne
Applied Bolting Technology Products Inc.
Cantor & Colburn LLP
Saether Flemming
LandOfFree
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