Differential pressure vortex sensor

• US 4,475,405 A
• Filed: 03/12/1982
• Issued: 10/09/1984
• Est. Priority Date: 03/12/1982
• Status: Expired due to Term

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Corpron, Gary P., Pagel, Roy E.
• Primary Examiner(s): Goldstein, Herbert
• Application Number:
  US06/357,472
• Time in Patent Office: 942 Days
• Field of Search: 73/715-721, 73/861.22, 73/861.24
• US Class Current: 73/861.24
• CPC Class Codes: G01F 1/3259 for detecting fluid pressure oscillations

Abstract

A differential pressure sensor (10) adapted specifically for use with vortex shedding flowmeters which can be used in small spaces, uses a bending beam (60) for providing an electrical signal proportional to differential pressures between two oppositely facing diaphragms (40A, 40B). The diaphragms deflect under differential pressure and cause the beam (60) to be bent. The diaphragms have low mass and have a support structure (43) between them, carrying spring clips (50) which load one end of the bending beam (60). The other end of the bending beam (60) is then supported so it cantilevers from its mounting or support (61, 62) and upon movement of the diaphragms under differential pressure the beam (60) will bend. The signal can be derived by using a bending element made of a piezoelectric "bimorph" beam, which provides a voltage output as it bends, a strain gauge sensor on a beam, or an optical sensor, such as a fine fiber which deflects and provides an optical output may be used, as well as similar devices. Preferably, the sensor is a piezoelectric bimorph beam because of the direct electrical signals provided, which result from bending of the beam (60).

Claims

1. A vortex flowmeter having a body forming a housing, the body having first and second surfaces which are subjected to pressure differentials representative of flow, separate diaphragm means positioned on the body and facing in the directions of said first and second surfaces respectively, for deflecting in response to pressure differentials at the first and second surfaces, fluidly isolated bore means defined in part by the separate diaphragm means, means in said bore means for transmitting deflecting motion of the separate diaphragm means caused by differentials in pressure on the separate diaphragm means comprising a tubular member having end faces engaging the respective separate diaphragm means and carrying compression loads between the diaphragm means, a beam member positioned in said bore means and extending laterally from the tubular member and having one end mounted with respect to said body at a location spaced from the means for transmitting deflecting motion, an opposite end of said beam member being coupled to the tubular member to thereby bend said beam member responsive to the movement of the tubular member as the separate diaphragm means deflect.

2. The flowmeter of claim 1, including means to couple the opposite end of the beam member to the tubular member comprising motion transmitting element means receiving the end portion of the beam member, and permitting sliding removal and replacement of the beam member in lateral direction from the tubular member.

3. The flowmeter of claim 1 wherein said bore means includes a laterally extending bore section in which the beam member is positioned, said flowmeter being adapted to be mounted in a fluid conduit, and having a portion sealingly mounted on the fluid conduit and opening to the exterior thereof, said bore section opening to the exterior of the fluid conduit to permit said beam member to be removed and replaced from the exterior of said fluid conduit.

4. A differential pressure sensor comprising a housing having first and second surfaces which are, in use, subjected to pressure differentials responsive to flow, a first bore in said housing having ends open to and providing a passageway between said first and second surfaces, separate diaphragm means comprising at least portions of said first and second surfaces, respectively and closing the ends of said first bore, a second bore opening to said first bore between said diaphragm means and extending outwardly from the first bore, said bores being closed to isolate said bores from fluid in which the sensor is used, bending motion sensing means mounted on said housing at location spaced from the first bore and communicating through said second bore to said first bore, a lightweight compression carrying tubular spool mounted in the first bore for carrying compression loads tending to move the diaphragm means toward each other, said tubular spool having end surfaces for supporting the respective diaphragm means and said tubular spool moving in the first bore as the separate diaphragm means both deflect in the same direction for transmitting motion signals from said diaphragm means, and means coupling the bending motion sensing means to the tubular spool to bend the bending motion sensing means and provide an output signal when differential in pressures cause said separate diaphragm means to deflect and move the tubular spool.

5. The apparatus as specified in claim 4 wherein said bending motion sensing means comprises a beam member extending through said second bore and having an end movable in the first bore to result in bending of the beam member to provide an output signal, said tubular spool having an aperture therein to permit the end of the beam member to extend into the interior of the tubular spool, and the means coupling being carried by the tubular spool.

6. The apparatus as specified in claim 5 wherein said housing comprises a portion of a vortex generating flowmeter and said first and second surfaces and the diaphragm means are generally parallel to the flow direction, and means upstream from said housing to cause pressure differentials to be present adjacent the first and second housing surfaces.

7. The apparatus as specified in claim 4 wherein said separate diaphragm means comprise a pair of thin flexible wall diaphragms hermetically sealed relative to the housing.

8. The apparatus as specified in claim 4 wherein said beam member comprises a piezoelectric bimorph beam.

9. A differential pressure sensor for use in connection with a vortex flowmeter comprising a vortex generating body having generally parallel spaced side surfaces which are generally parallel to the direction of flow to be measured, the differential pressure sensor comprising a housing portion having a first bore, a pair of deflectable diaphragms for hermetically sealing said first bore at the opposite ends of the first bore, the diaphragms having outer surfaces opening to the respective side surfaces of a vortex generating body in use so as to be subjected to vortices formed in the flow past the vortex flowmeter, a counterbore formed in said housing and extending laterally from said first bore and extending to the exterior of the housing portion, said first bore and counterbore both being fluidly isolated from the fluid which is to be measured for flow, tubular compression carrying means in said first bore having opposite end surfaces engaging both of said diaphragms for supporting said diaphragms from movement toward each other and moving in the first bore in response to deflecting motions of the diaphragms in unison caused by differential pressure being present on the outer surfaces of the respective diaphragms, and motion sensing means mounted in said counterbore responsive to movements of said tubular compression carrying means including means to provide a signal as a known function of the motions of said tubular compression carrying means from a reference rest position.

10. The differential pressure sensor specified in claim 9 wherein said means to sense motion comprises a beam member mounted on said flowmeter at a first end thereof and having a free end cantilevered from its mounting and extending through said counterbore and into said first bore and the means to transmit engaging the free end of said beam member and causing bending of said beam member when the diaphragms shift under differential pressures.

11. The differential pressure sensor of claim 9 wherein the counterbore opens to a larger diameter bore portion in the housing at a position spaced from the first bore and has a mounting head, said motion sensing means comprising a beam having one end mounted on the mounting head and the other end coupled to the tubular compression carrying means, said mounting head fitting into the larger diameter bore portion, and means to clamp the mounting head relative to the housing with the mounting head within the larger diameter bore portion.

12. The differential pressure sensor of claim 11 and means forming an interlocking key and keyway to orient the mounting head in only one position in the larger diameter bore portion.

13. A vortex flowmeter having a body forming a housing having first and second surfaces which are subjected to pressure differentials, separate diaphragms forming continuations of said first and second surfaces respectively, for deflecting in response to pressure at the first and second surfaces, means in said housing for transmitting deflecting motion of the diaphragms caused by differentials in pressure on the separate diaphragms comprising a pair of flat springs each coupled to one of the diaphragms, so each spring moves, respectively, with its respective diaphragm, a beam member having one end mounted on said body spaced from the means for transmitting deflecting motion, an opposite end of said beam member extending to position between the springs, said springs each having portions extending toward and bearing against the opposite end of the beam member to thereby cause said beam member to bend when differential in pressures at the first and second surfaces cause said diaphragms to deflect.

14. A differential pressure sensor for use in connection with a vortex flowmeter comprising a vortex generating body having a portion forming a housing, said body having generally parallel spaced side surfaces which are generally parallel to the direction of flow to be measured, a first bore formed through said housing and opening to said parallel side surfaces, a pair of deflectable diaphragms hermetically sealing said first bore adjacent the opposite ends of the first bore whereby the diaphragms have outer surfaces responsive to vortices formed in the flow past the vortex flowmeter body, a counterbore formed in said housing and extending laterally from said first bore, a beam member having a first end mounted with respect to said housing and having a free end cantilevered from its mounting and extending through said counterbore and into said first bore, said beam being bendable to permit the free end to move, a tubular spool member slidably mounted in the first bore and having opposite end flanges, each of said flanges resting against a respective one of said diaphragms, an opening in said tubular spool member, the free end portion of said beam member passing through said opening, and spring means carried by said tubular spool member and engaging the free end portion of said beam member to resiliently transmit motions in opposite directions from a reference rest position of the diaphragms to the free end portion of said beam member as the diaphragms deflect in unison responsive to differentials in pressure on the outer surfaces of the diaphragms.

15. The differential pressure sensor as specified in claim 14 wherein said spool member has mechanical elements fixed to said diaphragms and to the end flanges to support the end flanges on said diaphragms, respectively.

16. A differential pressure sensor for use in connection with a vortex flowmeter comprising a vortex generating body having a portion forming a housing, said body having generally parallel spaced side surfaces which are generally parallel to the direction of flow to be measured, a first bore formed through said housing and opening to said parallel side surfaces, deflectable diaphragms hermetically sealing said first bore at the opposite ends of the first bore whereby the diaphragms have outer surfaces subjected to vortices formed in the flow past the vortex flowmeter, a counterbore formed in said housing and extending laterally from said first bore and extending to the exterior of the body, said bores being fluidly isolated from the fluid which is to be measured for flow, a pair of leaf spring members, each leaf spring being positioned in the first bore and mechanically coupled to one of said diaphragms and extending from the respective diaphragm toward the center of the first bore, said leaf spring members moving in response to deflecting motions of the diaphragms in unison caused by differential pressure being present on the outer surfaces of the respective diaphragms, and sensing means responsive to said means to transmit, located in said counterbore, including means to provide a signal as a known function of the unison motions of said diaphragms from a reference rest position, said sensing means comprising a beam member mounted on the body at a first end and having a free end cantilevered from the first end and extending through said counterbore and into the first bore, said leaf type spring members being mechanically moved upon deflection of said diaphragms from a rest position under differential pressure, said leaf spring members providing a spring force resiliently clamping the free end of said beam member to cause the beam member to bend as the diaphragms move in unison.