Seal for a joint or juncture – Seal between fixed parts or static contact against... – Contact seal for a pipe – conduit – or cable
Reexamination Certificate
1997-08-08
2001-12-04
Knight, Anthony (Department: 3626)
Seal for a joint or juncture
Seal between fixed parts or static contact against...
Contact seal for a pipe, conduit, or cable
C277S616000, C285S379000
Reexamination Certificate
active
06325390
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to sealing arrangements for vacuum flanged tubing connections and like components and more particularly to an O-ring positioning and holding fixture for ISO-NW type vacuum flanged tubing or components.
BACKGROUND OF THE INVENTION
Prior art vacuum flange O-ring centering rings are typically constructed from aluminum or stainless steel, and are designed to hold an elastomeric O-ring in position during the assembly and use of ISO-NW vacuum sealing flanges for tubing connections. Such centering rings only function to hold the O-ring in position for sealing to the flat sealing surfaces of the flanges and to prevent the O-ring from moving inward when gas pressure inside the tubing is lower than the gas pressure outside the tubing.
Two major shortcomings are associated with prior art centering ring designs. The shortcoming has to do with the diameter of the inner surface of the centering ring not matching the diameter of the inner surface of typical vacuum tubing and like components with ISO-NW vacuum flange connections. This shortcoming produces a stepped inner surface at the tubing (or component) connection. The stepped inner surface produces a turbulent gas flow effect, known as sudden expansion and/or sudden contraction (Vena contracta). The viscous flow of gases through this type of tubing connection will have turbulent flow with eddy current flow and total gas flow losses. This shortcoming can cause gas phase reactions, condensation, and premature clogging in some types of machinery gas piping.
The other shortcoming associated with prior art centering ring designs has to do with their “straight edge” outer surface design. The outer annular side surface of present centering rings are perpendicular to the annular face surfaces of the ring. This produces a 90 degree ring shoulder which mates with the counter bore area of the sealing flange. The 90 degree ring shoulder of prior art centering ring designs require the sealing surfaces of the sealing flanges to be aligned nearly parallel with each other when assembling the centering ring and the vacuum tubing, to prevent binding.
Accordingly, a need exists for an improved vacuum flange O-ring centering ring that substantially eliminates the turbulent gas flow and binding problems of prior art vacuum flange O-ring centering ring designs.
SUMMARY
A fixture for centering and holding an elastomeric O-ring in position between vacuum sealing flanges during assembly and use thereof, comprising an annular body defining an outer surface and O-ring holding means disposed on the outer surface for holding an elastomeric O-ring. The outer surface of the annular body defines a beveled surface portion which enables the fixture to be inserted between the vacuum sealing flanges during assembly thereof without any substantial binding.
One aspect of the invention involves the beveled surface portion tapering inwardly from the O-ring holding means, wherein the beveled surface portion tapers inwardly at an angle of approximately 10 degrees as measured from a reference line which is perpendicular to the O-ring holding means.
Another aspect of the invention involves a second beveled surface portion defined on the outer surface of the fixture. The second beveled surface portion tapers inwardly from a second side of the O-ring holding means at an angle of approximately 10 degrees as measured from as measured from a reference line which is perpendicular to each of the sides of the O-ring holding means.
In still another aspect of the invention, the annular body defines a cylindrical inner surface and each of the sealing flanges defines a cylindrical inner surface of a predetermined diameter, the inner surface of the annular body having a diameter which is substantially identical to the predetermined diameter to substantially prevent turbulent gas flow effects.
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QF Hardware—Catalog pp. 6-1 and 6-3, by Kurt J. Lesker Company.
ITT Manufacturing Enterprises Inc.
Knight Anthony
Patel Vishal
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