Claims
- 1. In a Coriolis flowmeter:
a flow tube for receiving a material flow; a balance bar coupled by a brace bar means to said flow tube; a driver that vibrates said flow tube and said balance bar in phase opposition at a drive frequency substantially equal to the resonant frequency of said flow tube with material flow; said vibrations and said material flow are jointly effective for inducing Coriolis deflections of said flow tube; pick off means coupled to said flow tube that generate signals representing information pertaining to said material flow in response to said said Coriolis deflections; said Coriolis flow meter further comprises: at least one rib element on said balance bar that raises the resonant frequency of lateral vibrations of said balance bar.
- 2. The Coriolis flowmeter of claim 1 characterised in that said at least on rib is integral to said balance bar.
- 3. The Coriolis flow meter of claim 2 in which said at least one rib element is on a side of said balance bar and oriented parallel to the longitudinal axis of said balance bar.
- 4. The Coriolis flow meter of claim 2 in which said at least one rib element comprises a pair of ribs positioned on sides of said balance bar and oriented parallel to the longitudinal axis of said balance bar.
- 5. The Coriolis flow meter of claim 4 in which said balance bar includes voids; and
said ribs increase the cross sectional area of said balance bar in a portion of said balance bar proximate said voids to increase axial stiffness of said balance bar and resist the tensile and compressive forces axially exerted on said balance bar whenever said flow tube attempts to change in length.
- 6. The Coriolis flow meter of claim 2 characterized in that said Coriolis flowmeter further comprises:
a hole in said balance bar for receiving a magnet of said driver; and a first mounting element integral to said balance bar that enables the attachment of a coil of said driver to said balance bar.
- 7. The Coriolis flow meter of claim 6 in which said first mounting element that enables said attachment of said drive coil includes:
an axially center element on said balance bar; and a flat surface on said center element having a center opening that enables said drive magnet to protrude through said center opening into said drive coil.
- 8. The Coriolis flow meter of claim 6 further comprising:
a second mounting element integral to said balance bar that enables the attachment of said pick off means to said balance bar.
- 9. The Coriolis flow meter of claim 8 in which said second element that enables said attachment of said pickoffs includes a flat surface having an opening in said balance bar that facilitates the attachment of said pick off means to said balance bar.
- 10. The Coriolis flow meter of claim 2 further comprising:
an element integral to said balance bar that lowers the resonant frequency of said balance bar towards that of said material filled flow tube.
- 11. The Coriolis flow meter of claim 10 in which said element that lowers said resonant frequency of said balance bar comprises elements of increased flexibility integral to said balance bar.
- 12. The Coriolis flow meter of claim 11 in which said element that increases the flexibility of portions of said balance bar comprises voids in said balance bar on each axial side of said center portion of said balance bar.
- 13. The Coriolis flow meter of claim 1 further comprising:
an element integral to said balance bar that causes the vibration amplitude of said balance bar to be less than the vibration amplitude of said flow tube.
- 14. The Coriolis flow meter of claim 1 further comprising:
an element integral to said balance bar that lowers the second bending frequency of said balance bar to make the calibration factor of said Coriolis flowmeter independent of density of said flowing material.
- 15. The Coriolis flow meter of claim 1 characterized in that said brace bar means defines separate brace bars each of which is integral with said balance bar at different ends of said balance bar;
each brace bar is a circular member having a center opening for receiving said flow tube and having a surface perpendicular to the longitudinal axis of said balance bar.
- 16. A method of fabricating a balance bar for a Coriolis flowmeter comprising the steps of:
forming said balance bar as an elongated member having a radial center opening adapted to receive a flow tube, forming brace bars integral to said balance bar and having a center opening at each end of said elongated member, forming at least on void in said balance bar; forming at least one rib element integral to said balance bar to raise the lateral vibration frequency of said balance bar, said at least one rib element comprises ribs on the sides of said balance bar and oriented parallel to the longitudinal axis of said balance bar, and said ribs include elements that increase the cross sectional area of said balance bar in areas proximate said at least one voids that offset the tensile and compressive forces axially exerted on said balance bar whenever said flow tube attempts to change in length.
- 17. The method of claim 16 further including the steps of:
forming a first mounting element integral to said balance bar to enable the attachment of a driver to said balance bar, said first mounting element defines an axially center element on said balance bar and forming a flat surface on said center element having a center opening that enables said attachment of said driver to said balance bar.
- 18. The method of claim 17 further including the steps of:
forming a second mounting element integral to said balance bar that enables the attachment of said pick off means to said balance bar, said second element includes a flat surface having an opening in said balance bar to facilitate the attachment of said pick off means to said balance bar.
- 19. The method of claim 18 further including the steps of:
forming an element integral to said balance bar to lower the resonant frequency of said balance bar towards that of said material filled flow tube; said element that lowers said resonant frequency of said balance bar comprise elements of increased flexibility integral to said balance bar; said element that increases the flexibility of portions of said balance bar comprises cutout portions defining voids in said balance bar on each axial side of said center portion of said balance bar; said element that lowers the second bending frequency of said balance bar also makes the calibration factor of said Coriolis flowmeter independent of density of said flowing material.
- 20. The method of claim 19 further including the steps of:
forming an element integral to said balance bar that causes the vibration amplitude of said balance bar to be less than the vibration amplitude of said flow tube.
- 21. The method of claim 16 characterized in that said steps of forming include forming a mold having:
a cavity that defines an elongated member of said balance bar having a radial center opening adapted to receive a flow tube, a cavity that defines brace bars integral to said balance bar and having a center opening at each end of said elongated member, a cavity that defines at least on void in said balance bar; a cavity that defines at least one rib element integral to said balance bar to raise the lateral vibration frequency of said balance bar, said at least one rib element comprises ribs on the sides of said balance bar and oriented parallel to the longitudinal axis of said balance bar, and said ribs include elements that increase the cross sectional area of said balance bar in areas proximate said at least one voids that offset the tensile and compressive forces axially exerted on said balance bar whenever said flow tube attempts to change in length, said method of forming including the further steps of: filling said cavities with molten material to form said balance bar; and extracting said formed balance bar from said mold.
- 22. The method of claim 17 characterized in that said steps of forming include the step of forming a mold having:
a cavity that defines a first mounting element integral to said balance bar to enable the attachment of a driver to said balance bar, said first mounting element defines an axially center element on said balance bar and a flat surface on said center element having a center opening that enables said attachment of said driver to said balance bar.
- 23. The method of claim 18 characterized in that said steps of forming include the step of forming a formed having:
a cavity that defines a second mounting element integral to said balance bar that enables the attachment of said pick off means to said balance bar, said second element includes a flat surface having an opening in said balance bar to facilitate the attachment of said pick off means to said balance bar.
- 24. The method of claim 19 characterized in that said steps of forming include the step of forming a mold having:
a cavity that defines an element integral to said balance bar to lower the resonant frequency of said balance bar towards that of said material filled flow tube; said element that lowers said resonant frequency of said balance bar comprise elements of increased flexibility integral to said balance bar; said element that increases the flexibility of portions of said balance bar comprises cutout portions defining voids in said balance bar on each axial side of said center portion of said balance bar; said element that lowers the second bending frequency of said balance bar also makes the calibration factor of said Coriolis flowmeter independent of density of said flowing material.
- 25. The method of claim 20 characterized in that said steps of forming include the step of forming a mold having:
a cavity that defines an element integral to said balance bar that causes the vibration amplitude of said balance bar to be less than the vibration amplitude of said flow tube.
- 26. The method of claim 20 including the step of filling said cavities with material to constitute said balance bar.
CROSS REFERENCE TO A RELATED APPLICATION
[0001] This application is a divisional of U.S. patent application Ser. No. 09/345.078 titled “Balance Bar for a Coriolis Flowmeter” and filed on Jun. 30, 1997. The referenced application is hereby incorporated by reference as if the referenced application were included in this application.
Divisions (1)
|
Number |
Date |
Country |
Parent |
09345078 |
Jun 1999 |
US |
Child |
09916793 |
Jul 2001 |
US |