Measuring and testing – Fluid pressure gauge – Bourdon
Reexamination Certificate
1999-10-05
2001-10-02
Oen, William (Department: 2855)
Measuring and testing
Fluid pressure gauge
Bourdon
Reexamination Certificate
active
06295876
ABSTRACT:
FIELD OF THE INVENTION
The field of art to which the invention relates comprises post-assembly linearity adjustment for pressure gauges having a spring suspended movement.
BACKGROUND OF THE INVENTION
Pressure gauges of the type having the combination of a Bourdon tube and a spring suspended movement commonly provide for span adjustment that establishes accurate beginning and end points over the pressure range of the indicia scale. Otherwise, such gauges are generally deficient in not providing for linearity adjustment along the intermediate points between the ends.
National standard ASME B-40.1 establishes the standard of accuracy by which the suspended movement type gauges can qualify for “grade A” or closer accuracy. In accordance therewith, pointer rotation is required to be closely tailored to conform with the placement of increments shown on the dial face. Prior attempts toward linearizing have required special, costly, and impractical design changes of the segment gear. Further, any adjustment could only be effected with some degree of disassembly as with the case removed, rendering it necessary to conduct a final inspection for accuracy after complete re-assembly of all gauge components. Such added operations have heretofore made linearity adjustment impractical from a product cost standpoint.
DESCRIPTION OF THE PRIOR ART
Commercial forms of pressure gauges of the spring suspended movement type are disclosed, for example, in U.S. Pat. Nos. at 4,055,085; 4,246,796 and 4,444,057 each incorporated herein by reference. The spring suspended movement or amplifier thereof is mounted onto the free end of a Bourdon tube for floating conjoint movement therewith. A remotely connected link wire actuator extends into the motion path to define a pivot axis for a hinged gear sector arm of the amplifier. In pivoting about the actuator axis, the sector arm operably drives a rotatable output shaft supporting a pointer or the like opposite a graduated dial face. In a typical construction, a superficial form of linearity of the instrument is preset during manufacture. This has consisted generally of presetting the height of the amplifier above the stem to match generally the operating characteristics of the Bourdon tube without regard to variations in operating characteristics as may be contributed elsewhere. This has been effected by vertical positioning of the actuator link to a desired but arbitary height prior to the link being securely staked to the stem.
The foregoing however, has contributed to gross inaccuracies in linearity since the gauge does not become operable for calibration until after staking of the link wire. Once staking has been completed, it has not been readily possible heretofore to alter the predisposed relationship that might contribute to operationally enhanced linearity.
Despite recognition of the foregoing, a ready solution therefore has not heretofore been known.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to provide a novel pressure gauge having a suspended movement readily capable of post assembly calibration for linearity.
It is a further object of the invention to effect the previous object by allowing for post assembly link displacement defining the pivot axis of the suspended movement.
It is a still further object of the invention to effect the previous objects by low cost features enabling linearity settings over the operational span of the pressure gauge.
SUMMARY OF THE INVENTION
This invention relates to pressure gauges of the type having a suspended movement. More specifically, the invention relates to such a pressure gauge in which the suspended movement is capable of post operational calibration for linearity so as to enhance indicia accuracy of the gauge readout.
In accordance with the invention, the gauge is of a suspended movement type as exemplified by the disclosure of U.S. Pat. No. 4,246,796 mentioned supra. The gauge is comprised of a Bourdon tube that internally communicates with an inlet socket extending outward of the gauge case or housing and into which fluid to be pressure monitored is received. The suspended movement is secured to the free end of the Bourdon tube and includes a sector arm pivotally supported by the distal end of an elongated link. Unlike the prior art in which the link is staked securely in place during initially assembly, the link hereof is only secured more casually in place with a controlled resistance that enables external post-assembly displacement of the link. Normal calibration is first performed using the equipment, and procedure recommended in the American National Standard ASME B40.1 section 6. Data collected during this procedure will indicate the amount of linearity adjustment required in order to improve the accuracy grade of the gauge being tested. By then displacing the link appropriately as necessary, changes in the linearity of pointer indication is achieved accurately in response to pressure input. The result is to effect enhanced linear accuracy of the gauge readout thereafter.
Enabling such linearity adjustment is a lateral recess in the gauge stem located about the under end of the link. While using a commercially available calibrator mechanism, linearity adjustment is effected by using a small pliers or other suitable hand tool having its nose extending inward of the recess to grip the under end of the link. This affords leverage for the tool so that the link can be displaced rectilinearly parallel to the stem axis until optimum linearity is achieved. The effect of displacing the link in this manner is to alter the location of the axis about which the sector arm of the movement is pivoted so as to cause enhanced linear accuracy over the operational range of the instrument to be achieved. Thereafter the link can be more firmly secured if desired.
As a consequence of the foregoing, a simple, yet effective structural feature enables not only enhanced accuracy of the gauge per se but at the same time enables compliance with the National Standard ASME B 40.1 for effecting a product upgrade in the marketplace.
The above noted features and advantages of the invention as well as other superior aspects thereof will be further appreciated by those skilled in the art upon reading the detailed description that follows in conjunction with the drawings.
REFERENCES:
patent: 4055085 (1977-10-01), Wetterhorn
patent: 4246796 (1981-01-01), Wetterhorn
patent: 4444057 (1984-04-01), Wetterhorn
Dresser, Inc.
Jenkens & Gilchrist P.C.
Oen William
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