Field of the Invention
This invention relates to flow meters, and in particular, to manufacturing flow meters comprised of flow tubes made of a fluoropolymer substance.
Problem
It is known to use Coriolis effect mass flow meters to measure mass flow and other information pertaining to materials flowing through a pipeline as disclosed in U.S. Pat. Nos. 4,491,025 issued to J. E. Smith, et al. of Jan. 1. 1985 and Re. 31,450 to J. E. Smith of Feb. 11, 1982. Flow meters have one or more flow tubes of a straight, curved or in-egular configuration. Each flow tube has a set of natural vibration modes, which may be of a simple bending, torsional, or twisting type. Each material filled flow tube is driven to oscillate at resonance in one of these natural modes. The natural vibration modes are defined in part by the combined mass of the flow tubes and the material within the flow tubes. If desired, a flow meter need not be driven at a natural mode.
Material flows into the flow meter from a connected material source on the inlet side. The material is directed through the flow tube or flow tubes and is delivered to a material receiver connected to the outlet side.
A driver applies force to oscillate the flow tube. When there is no material flow, all points along a flow tube oscillate with an identical phase. As the material begins to flow, Coriolis accelerations cause each point on the flow tube to have a different phase with respect to other points on the flow tube. The phase on the inlet side of the flow tube lags the driver; the phase on the outlet side leads the driver. Pick-offs are placed on the flow tube to produce sinusoidal signals representative of the motion of the flow tube. The phase difference between the two pick-offs signals is proportional to the mass flow rate of the material flow.
It is known to use flow meters having different flow tube configurations. Among these configurations are single tube, dual tube, straight tube, curved tube, and flow tubes of irregular configuration. iVIost of the flow meters are made of metal such as aluminum, steel, stainless steel and titanium. Glass flow tubes are also known.

Positive attributes of Titanium in these types of flow meters are its high strength and low coefficient of thermal expansion (CTE). A negative attribute of Titanium is its cost of manufacturing. A Titanium flow meter is difficult and expensive to produce.
The prior art also suggests plastic flow tubes and plastic flow meters. This includes prior art where the entire flow meter is plastic or only the flow tube is formed of plastic. Much of this prior art merely contains an assertion that a flow meter may be made of various materials such as steel, stainless steel, titanium or plastic.
This prior art is not extensive so far as concerns the disclosure of a plastic Coriolis flow meter that can accurately output information over a range in operating conditions including temperature. This prior art is not extensive so far as concems the disclosure of manufacturing a Coriolis flow meter that has a plastic flow tube.
The mere substitution of a plastic flow tube for a metal flow tube will produce a structure that looks like a flow meter. However, the structure will not function as a flow meter to generate accurate output information over a useful range of operating conditions. The mere assertion that a flow meter could be made out of plastic teaches nothing beyond the abstraction that plastic can be substituted for metal in a Coriolis flow meter. It does not teach how a plastic flow meter can be manufactured to generate accurate information over a useful range of operating conditions.
Perfluoroalkoxyethlene (PFA) is one type of plastic mentioned for use in a flow meter. U.S. Pat. No. 5,918,285 to Vanderpol discloses use of PFA for a flow tube. This suggestion regarding the use of PFA is incidental and the patent discloses no information regarding how a flow meter having a PFA flow tube could be manufactured to generate accurate flow information.
U.S. Pat. No. 5,403.533 to Dieter Meier discloses a flow tube lined with PFA. Unfortunately, the flow tube material and the PFA liner have different themnal properties. This causes the PFA liner to disengage from the flow tube creating leaks and performance problems. The manufacturing process for lining the metal flow tubes with PFA is also extremely costly.
PFA is very chemically inert and has very low surface energy. This makes PFA very difficult to bond to other objects using common adhesives. One way to

^ — ^.wwiofii IS 10 Change the surface chemistry of PFA by chemical etching. Etching the surface of PFA provides for much stronger bonds using adhesives.
However, even though etching provides a stronger bond with PFA, bonding PFA to other objects must be carefully done to create a strong bond. The following considerations should be taken into account to create a strong bond: the type of adhesive used, the gap between the PFA and another object, whether there is complete coverage of the gap with the adhesive, whether the adhesive cures properly, the condition of the surface of the PFA, and the condition of the surface of the other object. Unfortunately, there is currently no convenient way to bond PFA to other objects to build a flow meter.
Typical Coriolis flow metens as described above are manufactured out of metal. Metalls fairly easy to manufacture with using current machining and welding technologies. A Coriolis flow meter is comprised of one or more metal flow tubes. Most Coriolis flow meters require that the ends of a flow tube be secured to achieve the desired dynamic characteristics of a vibrating tube. The flow tube is generally held in a fixed position at its ends by manifolds, brace bars, or some other stmcture. The flow tube is affixed to a manifold by welding the flow tube to the manifold. A driver and pick-offs are also affixed to the flow tube. One example of the driver and the picle applied to the flow tube and an inner surface of the tube opening of the first leg. .'he tube opening of the second leg has a diameter slightly larger than the flow tube to create a gap between tube opening of the second leg and the flow tube.
The adhesive opening of the second leg provides access to the gap so that adhesive may be applied to the flow tube and an inner surface of the tube opening of the second leg.

The following illustrates a method that a manufacturer may use to build the flow meter described above. First, the manufacturer orientates the tube opening of the first leg, the adhesive opening of the first leg, and the flow tube on a horizontal plane. The manufacturer positions a tip of an adhesive applicator in the adhesive opening of the first leg to access the gap proximate an outer surface of the flow tube and the inner surface of the tube opening of the first leg. The manufacturer introduces an amount of adhesive in the gap. Due to the surface energies of the outer surface of the flow tube and the inner surface of the tube opening of the first leg, the adhesive is drawn into the gap due to capillary action or wicking. When the adhesive reaches the ends of the tube opening, the wicking stops and forms a unifomi and symmetric fillet. The manufacturer then allows the adhesive to cure. The manufacturer performs the same operation to affix the flow tube to the tube opening of the second leg. The adhesive openings provide an easier and better way to bond the flow tube to the base of the flow meter.
One embodiment of the fixture apparatus comprises a first section and a second section. The fixture apparatus is configured to secure a flow tube of a flow meter during manufacturing of the flow meter. The first section includes a first tube opening portion on an end of the first section. The second section includes a second tube opening portion on an end of the second section. The end of the first section and the end of the second section are configured to fit adjacent one another.
When placed adjacently, the first section and the second section fonm a fixture block. The fixture block includes a tube opening formed from the first tube opening portion and the second tube opening portion. The tube opening is for holding the flow tube of the flow meter during manufacturing.
A securing means secures the first section and the second section to the base of the flow meter. The securing means aligns the tube opening of the fixture block with the tube openings of the base of the flow meter. That way, the flow tube can be secured to the base of the flow meter.
The fixture apparatus also includes an alignment means for affixing a driver component and a pick-off component to the flow tube.
One embodiment of the method of testing the alignment of a driver and a pick-off on a flow tube of a flow meter is as follows. To test the alignment, the

manufacturer vibrates the flow tube at one or more drive frequencies using the driver. The manufacturer uses a processing system to receive pictc-off signals from the pick-offs. The pick-off signals represent a vibrating frequency of the flow tube. The processing system processes the pick-off signals and signals representing the drive frequencies to determine a frequency response. The processing system identifies unacceptable alignment of the driver and the pick-offs on the flow tube based on the frequency response.
One embodiment of the method for manufacturing flow tubes made from a fluoropoiymer substarice is provided below. The manufacturer extrudes a flow tube from an extruding system. The flow tube is made from a fluoropoiymer substance, . such as PFA. The flow tube comes out of the extruder at a temperature that is higher than room temperature. The manufacturer cuts a section of the flow tube. The manufacturer then secures the section of the flow tube to hold the longitudinal shape of the section straight as the section cools down. When the flow tube has cooled and is straight, the manufacturer packages the section of flow tube to maintain the straight shape of the section.
The invention includes one or more aspects that are provided beiow.
One aspect of the invention is a method of assembling a Corioiis flow meter, comprising:
providing a flow meter structure having a base and two legs, where the two legs are attached to the base and are in a spaced apart relationship, the two legs each having a cylindrical opening through the leg, where the two cylindrical openings are aligned in a co-axial relationship;
providing a flow tube having an outer diameter, where the outer diameter is configured to flt into the. two cyiindrica! openings In the two legs while leaving a predefined gap;
placing the flow tube into the two cylindrical openings where a section of the flow tube extends between the two legs, and where the flow tube creates two predefined gaps between the outer diameter of the flow tube and the inner diameter 3f the two openings;
inserting an adhesive in the two predefined gaps.
Preferably, the method where the adhesive is inserted into each predefined lap through an adhesive opening in each leg, where each adhesive opening

intersects and is perpendicular to the cylindrical opening in each leg and where the axis of the two adhesive openings are in essentially the same plane and where the adhesive openings and the cylindrical openings are held in a horizontal orientation while the adhesive is inserted.
Preferably, the method where the outer surface of the flow tube is etched in at least one of a plurality of attachment areas whereby an attachment area is an area where the flow tube is attached to another surface.
Preferably, the method where the etching is done using a sodium naphthalene etchant.
Preferably, the method where the section of the flow tube extending between the two legs is held in an essentially straight configuration while the inserted adhesive cures.
Preferably, the method where the section of the flow tube extending between the two legs is held in an essentially straight configuration by providing a fixture block where providing the fixture block comprises:
providing a first section having a first tube opening portion on an end of the first section; and
providing a second section having a second tube opening portion on an end of said second section, said end of said second section adapted to fit adjacent to said end of said first section to form a fixture block, said fixture block having tube opening formed from said first tube opening portion and said second tube opening portion, said fixture block adapted to fit between said first leg and said second leg of said base.
Preferably, the method where providing the fixture block further comprises:
providing a driver opening extending from a surface of said fixture block and ntersecting said tube opening of said fixture block; and
providing at least one pick-off opening extending from said suirface of said ixture block and intersecting said tube opening of said fixture block.
Preferably, the method where the providing fixture block further comprises:
providing an alignment means adapted to fit in said openings of said fixture ilock and extend from said surface of said fixture block to an area adjacent said jbe opening of said fixture block.

Preferably, the method where providing the fixture block further comprises;
providing a securing means adapted to secure said first section and said second section to said base of said flow meter to align said driver opening of said fixture block with a driver opening in said base and to align said at least one pick-off opening of said fixture block with at least one pick-off opening in said base.
Preferably, the method where the flow tube is made of perfluoroalkoxyethlene (PFA).
Preferably, the method where the flow tube is made of polytetrafluoroethylene (PTFE).
Preferably, the method where the adhesive comprises a cyanoacrylate adhesive.
Preferably, the method further comprising:
providing a plurality of components configured to attach to the section of the flow tube extending between the two legs;
aligning the plurality of components to a predefined set of locations along the flow tube;
attaching the plurality of components to the flow tube using the adhesive.
Preferably, the method where at least one of the plurality of components is a driver.
Preferably, the method where at least one of the plurality of components is a pickoff.
Preferably, the method further comprising:
testing the position of the plurality of components by vibrating the flow tube using at least one of the plurality of components to drive the vibration and using at • least one of the plurality of components to sense the vibration of the flow tube.
Preferably, the method further comprising:
adjusting the predefined locations for the plurality of components based of the result of the tested positions.
Preferably, the method further comprising:
manufacturing the provided flow tube by extruding a section of the flow tube wherein the extmded section of flow tube has a temperature above room temperature;

securing the section of extruded flow tube to hold the longitudinal shape of the flow tube straight as the flow tube cools.
Description of the Drawings
These and other advantages and features of the present invention may be better understood in connection with a reading of the following detailed description thereof in connection with the drawings in FIGS. 1-15.
FIG, 1 discloses a perspective view of a flow meter in an example of the invention.
FIG. 2 is a top view of the flow meter of FIG. 1.
FIG. 3 is a front view of the flow meter of FIG. 1.
FIG. 4 is a cross-sectional view taken along lines 4-4 of the flow meter in FIG. 2.
FIGS. 5-7 illustrate a flow meter having adhesive openings in a base of the flow meter in an example of the invention.
FIGS. 8-13 illustrate a fixture apparatus for manufacturing flow meters in an example of the invention.
FIG. 14 illustrates a method of testing the alignment of a driver and pick-offs on a flow tube of a flow meter in an example of the invention.
FIG. 15 illustrates a method for manufacturing flow tubes made from a fluoropolymer substance in an example of the invention.
Detailed Description
FIGS. 1-15 and the following description depict specific examples to teach those skilled in the art how to make and use the best mode of the invention. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations from these

Preferably, said alignment means includes a lip on one end that is larger than a diameter of said driver opening of said fixture block, said lip adapted to allow said alignment means to extend into said driver opening a certain distance.
Another aspect of the invention comprises a method of using said fixture apparatus to affix said flow tube to said base of said flow meter, the method characterized by the steps of:
inserting said flow tube through said tube opening of said first leg and said tube opening of said second leg;
aligning said first section and said second section of said fixture apparatus to enclose said flow tube between said first tube opening portion and said second tube opening portion;
fastening said first section to said second section to fomn said fixture block;
securing said fixture block to said base;
introducing an amount of adhesive in a gap between an outer surface of said flow tube and said inner surface of said tube opening of said first leg; and
introducing said amount of adhesive in a gap between said outer surface of said flow tube and said inner surface of said tube opening of said second leg.
Preferably, said adhesive comprises a cyanoacrylate adhesive.
Preferably, said flow tube is made of perfluoroalkoxyethlene (PFA).
Preferably, said base is made of stainless steel.
Preferably, the method further comprises selecting said adhesive based on a viscosity of said adhesive.
Preferably, the method further comprises controlling a relative humidity of an environment surrounding said flow meter to cure said adhesive.
Preferably, the method further comprises controlling a temperature of said flow meter to cure said adhesive.
Preferably, the method further comprises etching said outer suri'ace of said flow lube prior to introducing said adhesive.
Preferably, the method further comprises etching said outer surface of said flow tube using a sodium naphthalene etchant.
Preferably, the method further comprises cleaning said outer surface of said flow tube prior to introducing said adhesive.

Preferably, the method further comprises roughening said inner surface of said tube opening of said first leg and said inner surface of said tube opening of said second leg prior to introducing said adhesive.
Preferably, the method further comprises cleaning said inner surface of said tube opening of said first leg and said inner surface of said tube opening of said second leg prior to introducing said adhesive.
Preferably, cleaning said inner surface of said tube opening of said first leg and said inner surface of said tube opening of said second leg comprises washing said inner surface of said tube opening of said first leg and said inner surface of said tube opening of said second leg with acetone in an ultrasonic bath.
Preferably, the method further comprises selecting a size of said gap between said outer surface of said flow tube and said inner surface of said tube opening of said first leg based on a viscosity of said adhesive, a surface energy of said outer surface of said flow tube, and a surface energy of said inner surface of said tube opening of said first leg.
Preferably, the method further comprises selecting said amount of said adhesive based on a speed of curing.
Preferably, the method further comprises applying an accelerator to said adhesive to accelerate curing of said adhesive.
Another aspect of the invention comprises a method of using said fixture apparatus to affix a driver component of said driver to said flow tube of said flow meter, the method characterized by the steps of:
attaching said driver component to said alignment means;
applying an adhesive to a surface of said driver component;
inserting said driver component through said driver opening of said fixture block using said alignment means; and
contacting said adhesive on said surface of said driver component to said flow tube using said alignment means.
Preferably, said adhesive comprises a cyanoacrylate adhesive.
Preferably, said driver component comprises a magnet.
Preferably, the method further comprises allowing said adhesive to cure and removing said alignment means from said driver opening of said fixture block.
13

Preferably, the method further comprises controlling a relative humidity of an environment surrounding said flow meter to cure said adhesive.
Preferably, the method further comprises controlling a temperature of said flow tube and said driver component to cure said adhesive.
Preferably, the method further comprises etching said outer surface of said flow tube prior to applying said adhesive.
Preferably, the method further comprises cleaning said outer surface of said flow tube prior to applying said adhesive.
Preferably, the method further comprises cleaning said surface of said driver component prior to applying said adhesive.
Preferably, the method further comprises applying an accelerator to said adhesive to accelerate curing of said adhesive.
Another aspect of the invention Is a method of using said fixture apparatus to affix a pick-off component of said at least one pick-off to said flow tube of said flow meter, the method characterized by the steps of:
attaching said pick-off component to said alignment means;
applying an adhesive to a surface of said pick-off component;
inserting said pick-off component through said pick-off opening of said fixture block using said alignment means; and
contacting said adhesive on said surface of said at least one pick-off component to said flow tube using said alignment means.
Preferably, said adhesive comprises a cyanoacrylate adhesive.
Preferably, said pick-off component comprises a magnet.
Preferably, the method further comprises allowing said adhesive to cure and removing said alignment means from said at least one pick-off opening of said fixture block.
Preferably, the method further comprises controlling a relative humidity of an environment surrounding said flow meter to cure said adhesive.
Preferably, the method further comprises controlling a temperature of said flow tube and said pick-off component to cure said adhesive.
Preferably, the method further comprises etching said outer surface of said flow tube prior to applying said adhesive.

Preferably, the method further comprises cleaning said outer surface of said flow tube prior to applying said adhesive.
Preferably, the method further comprises cleaning said surface of said pick-off component prior to applying said adhesive.
Preferably, the method further comprises applying an accelerator to said adhesive to accelerate curing of said adhesive.
Another aspect of the invention is a method of manufacturing flow tubes made from a fluoropolymer substance that are substantially straight, wherein a flow tube is extruded from an extruding system, the method characterized by the steps of:
cutting a section of said flow tube, wherein said flow tube has a temperature above room temperature;
securing said section of said flow tube to hold the straight longitudinal shape of said section of said flow tube straight as said section cools down from said temperature; and
packaging said section of said flow tube to maintain the longitudinal shape of said section of said flow tube.
Preferably, said flow tube is made of perfluoroalkoxyethlene (PFA).
Preferably, the method further comprises etching said section of said flow tube before packaging said section of said flow tube.
Preferably, the method further comprises storing said section of said flow tube to avoid exposing said section of said flow tube to light.
Preferably, the method further comprises storing said section of said flow tube at a constant temperature.
Another aspect of the invention is a method of testing an alignment of a driver and at least one pick-off on a flow tube of a flow meter comprised of a base, said flow tube made from a fluoropolymer substance, said driver for vibrating said flow tube, and said at least one pick-off for detecting movement of said vibrating flow tube, said driver and said at least one pick-off are affixed to said flow tube with an adhesive, the method comprising:
vibrating said flow tube at at least one frequency using said driver,
receiving pick-off signals from said at least one pick-off, said pick-off signals represent a vibrating frequency of said flow tube;
the method characterized by the steps of:

l>

processing said pick-off signals and signals representing said at least one frequency to determine a frequency response; and
indicating an unacceptable alignment of said driver and said at least one pick-off on said flow tube based on said frequency response.
Preferably, the method further comprises indicating an unacceptable axial alignment of said driver and said at least one pick-off if said frequency response includes a second bending mode.
Preferably, the method further comprises indicating an unacceptable lateral alignment of said driver and said at least one pick-off if said frequency response includes a first torsion mode.
Description of the Drawings
These and other advantages and features of the present invention may be better understood in connection with a reading of the following detailed description thereof in connection with the drawings in FIGS. 1-15.
FIG. 1 discloses a perspective view of a flow meter in an example of the invention.
FIG. 2 is a top view of the flow meter of FIG. 1.
FIG. 3 is a front view of the flow meter of FIG. 1.
FIG. 4 is a cross-sectional view taken along lines 4-4 of the flow meter in FIG. 2.
FIGS. 5-7 illustrate a flow meter having adhesive openings in a base of the flow meter In an example of the Invention.
FIGS. 8-13 illustrate a fixture apparatus for manufacturing flow meters in an example of the invention.
FIG. 14 illustrates a method of testing the alignment of a driver and pick-offs on a ftow tube of a flow meter in an example of the invention.
FIG. 16 illustrates a method for manufacturing flow tubes made from a fluoropolymer substance in an example of the invention.
Detailed Description
FIGS. 1-15 and the following description depict specific examples to teach those skilled in the art how to make and use the best mode of the invention. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations from these

examples that fall within the scope of the invention. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the invention. As a result, the invention is not limited to the specific examples described below, but only by the claims and their equivalents. Description of FIG. 1
FIG. 1 is a perspective view of a first possible exemplary embodiment of the invention and discloses a flow meter 100 having a flow tube 102 inserted through legs 117,118 of base 101. Picl. oy mis means, the process material delivered by supply tube 104 is -received by inlet 405 of flow tube 102. The process material flows to the right through flow tube 102 to fixed body 111 of connector 109 where the outlet 406 of flow tube 102 is flush with the end of stub 413. This sealabty affixes the end 408 of tube 106 to connector 109 and to the outlet 406 of flow tube 102. The other connectors 107 and 110 of FIG. 1 are identical to those described for the details of connectors 108 and 109 on FIG. 4. A Flow meter with Adhesive Openings - FIGS. 5-7
FIGS. 5-7 illustrate an example of flow meter 500 in an example of the invention. Flow meter 500 is comprised of U-shaped base 552, flow tube 501, driver D, and pick-offs LPO and RPO as shown in FIG. 5. For the invention, flow meter 500 does not have to include U-shaped base 552. Flow meter 500 could include a V-shaped based or any other type of base, which are all within the scope of the invention. Flow tube 501 is made from a fluoropolymer substance. Examples of fluoropolymer substances are perfluoroalkoxyethlene (PFA), polytetrafluoroethylene (PTFE), and fluorinated ethylene polymer (FEP). U-shaped base 552 could be made of stainless steel. Driver D and pick-offs LPO and RPO are affixed to flow tube 501.
U-shaped base 552 of flow meter 500 is comprised of leg 517 and leg 518. Leg 517 and leg 518 are parallel to one another. Leg 517 includes tube opening 502 and adhesive opening 504. Adhesive opening 504 is shown as centered on leg 517, but adhesive opening 504 could be positioned closer to one side or the other. Tube opening 502 and adhesive opening 504 are positioned to intersect one another in leg 517. Leg 518 includes tube opening 512 and adhesive opening 514. Adhesive opening 514 is shown as centered on leg 518, but adhesive opening 504 could be positioned closer to one side or the other. Tube opening 512 and adhesive opening 514 are positioned to intersect one another in leg 518. Tube opening 502 and tube opening 512 are on the same axis.
Flow tube 501 passes through tube opening 502 and tube opening 512. rube opening 502 has a diameter slightly larger than flow tube 501 to create a gap 06 between tube opening 502 and flow tube 501. FIG. 6 is a cross-sectional view f leg 517 that illustrates tube opening 502, adhesive opening 504, and gap 506. dhesive opening 504 provides access to gap 506 so that adhesive may be applied

to outer surface 510 of flow tube 501 and inner surface 508 of tube opening 502. Tube opening 512 of FIG. 5 has a diameter slightly larger than flow tube 501 to create a gap 516 between tube opening 512 and flow tube 501. Adhesive opening
514 provides access to gap 516 so that adhesive may be applied to outer surface 510 of flow tube 501 and inner surface 515 of tube opening 512. The adhesive bonds flow tube 501 to inner surface 508 of tube opening 502 and inner surface
515 of tube opening 512.
Flow meter 500 operates substantially the same as flow meter 100 described in FIGS. 1-4. Flow meter 500 receives a flow of process material. The process material travels through flow tube 501. Driver D vibrates flow tube 501 at a resonant frequency. Piclpening 515 of leg 518 in FIG. 5. The manufacturer aligns first half section 802 nd second half section 804 on U-shaped base 552. The manufacturer abuts end 13 of first section 802 to end 915 of second section 804 to enclose flow tube 501 stween flrst tube opening portion 912 and second tube opening portion 914 to rm fixture block 1000. The manufacturer fastens first section 802 to second

section 804. The manufacturer may secure fixture block 1000 to U-shaped base 552 using securing means 806. The manufacturer introduces an amount of adhesive in gap 506 between outer surface 510 of flow tube 501 and inner surface 508 of tube opening 502 of leg 517. The adhesive could be a CA. The manufacturer could introduce the adhesive through an adhesive opening, such as adhesive opening 504 as shown in FIGS. 6-7. The manufacturer also introduces an amount of adhesive in gap 516 between outer surface 510 of flow tube 501 and inner surface 515 of tube opening 514 of leg 518.
This method may incorporate the factors considered to produce a stronger bond as described above. In particular, the method could further include selecting the type and amount of adhesive used, preparing of the surfaces being bonded, controlling the humidity of the air when the adhesive is curing, controlling the temperature of the surfaces when the adhesive is curing, and selecting an optimal gap size.
The following is an example of a method of using fixture apparatus 800 to affix a driver component 1212 of driver D to flow tube 501. The manufacturer attaches driver component 1212 to alignment means 1206. Attaching in this sense does not mean that the driver component 1212 is necessarily secured to alignment means 1206. Driver component 1212 could just be set on an end of alignment means 1206. The manufacturer applies an adhesive to a surface of driver component 1212. The adhesive could be a CA. The manufacturer inserts driver component 1212 through opening 402 and driver opening 1202 using alignment means 1206. FIG. 13 shows alignment means 1206 fully inserted into opening 402 and driver opening 1202. The manufacturer contacts the adhesive on the surface of driver component 1212 to flow tube 501 using alignment'means 1206. Lip 1208 prevents alignment means 1206 from pushing driver component 1212 too far and damaging flow tube 501. The manufacturer lets the adhesive cure. The manufacturer then removes alignment means 1206 from opening 402 and driver opening 1202.
This method may incorporate the factors considered to produce a stronger bond as described above. In particular, the method could further include selecting the type and amount of adhesive used, preparing of the surfaces being bonded, controlling the humidity of the air when the adhesive is curing, controlling the

temperature of the surfaces when the adhesive is curing, and selecting an optimal gap size.
The following is an example of a method of using fixture apparatus 800 to affix a pick-off component 1214 of pick-offs LPO and RPO to flow tube 501. The manufacturer attaches pick-off component 1214 to alignment means 1206. Attaching in this sense does not mean that the pick-off component 1214 is necessarily secured to alignment means 1206. Pick-off component 1214 could just be set on an end of alignment means 1206. The manufacturer applies an adhesive to a surface of pick-off component 1214. The adhesive could be a CA. The manufacturer inserts pick-off component 1214 through opening 404 and pick-off opening 1204 using alignment means 1206. FIG. 13 shows alignment means 1206 fully inserted into opening 404 and pick-off opening 1204. The manufacturer contacts the adhesive on the surface of pick-off component 1214 to flow tube 501 using alignment means 1206. Lip 1208 prevents alignment means 1206 from pushing pick-off component 1214 too far and damaging flow tube 501. The manufacturer lets the adhesive cure. The manufacturer then removes alignment means 1206 from opening 404 and pick-off opening 1204.
Driver component 1212 and pick-off component 1214 could be magnets. Driver D and pick-offs LPO and RPO are commonly magnet-coil systems. Therefore, alignment means 1206 is made of a non-magnetic material, such as brass.
This method may incorporate the factors considered to produce a stronger >ond as described above. In particular, the method could further include selecting ie type and amount of adhesive used, preparing of the surfaces being bonded, antrolling the humidity of the air when the adhesive is curing, controlling the smperature of the surfaces when the adhesive is curing, and selecting an optimal jp size. sthod of Testing Driver and Pick-off Alignment - FIG. 14
FIG. 14 illustrates a method for testing the alignment of a driver and pick-offs a flow tube of a flow meter in an example of the invention. This method could used to test how accurate a manufacturing process is in affixing driver nponents and pick-off components to a flow tube of a flow meter. For instance, f a flow meter manufacturer uses fixture apparatus 800 in FIGS. 8-13 to affix

driver component 1212 and pick-off components 1214 to flow tube 501, the manufacturer could use this method to test the quality of fixture apparatus 800. Reference numbers for FIG. 14 are in parenthesis below.
To test a flow meter, the manufacturer vibrates the flow tube at one or more drive frequencies using the driver (1402). The manufacturer may vibrate the flow tube over a spectrum of frequencies to achieve more favorable results. The manufacturer uses a processing system to receive pick-off signals from the pick-offs (1404). The pick-off signals represent a vibrating frequency of the flow tube. The processing system processes the pick-off signals and signals representing the drive frequencies to determine a frequency response (1406). The processing system identifies unacceptable alignment of the driver and the pick-offs on the flow tube based on the frequency response (1408).
For instance, if the alignment of the driver and the pick-offs is good, then the frequency response includes only the first and third bending modes of the flow tube. If the frequency response includes a spike in a second bending mode of the flow tube, then this indicates a poor axial alignment of the driver and the pick-offs. The processing system would indicate to the manufacturer that the axial alignment is unacceptable. If the frequency response includes a spike in a first torsion mode of the flow tube, then this indicates a poor lateral alignment of the driver and the pick-off. The processing system would indicate to the manufacturer that the lateral alignment is unacceptable. The degree of misalignment of the flow tube, driver, or pick-offs is proportional to the leakage onto the second bending mode and the first torsional mode. Those skilled in the art will understand what the first, second, and third bending modes and the first torsion mode of the flow tube are. Therefore, an explanation will be left out for the sake of brevity.
Based on the information from the frequency response, the manufacturer can detemnine the quality of the flow tubes being built. The manufacturer can also use the information to change fixture apparatus 800 or some other component of' the manufacturing process. Method of Manufacturing Flow Tubes - FIG. 15
FIG. 15 illustrates a method for manufacturing flow tubes made from a fluoropolymer substance in an example of the invention. As described in the background, flow tubes from flow tube manufacturers often have a curved shape.

The flow tube manufacturers can use this method to produce straight flow tubes. Reference numbers for FIG. 15 are in parenthesis below.
The manufacturer extrudes a flow tube from an extruding system (1502). The flow tube is made from a fiuoropoiymer substance, such as PFA. The flow tube comes out of the extruder at a temperature that is higher than room temperature. The manufacturer cuts a section of the flow tube (1504). The manufacturer then secures the section of the flow tube to hold the longitudinal shape of the section straight as the section cools down (1506). For instance, the manufacturer could clamp the section to a flat surface to straighten the flow tube. The manufacturer could also put the flow tube in some type of mold to straighten the flow tube. When the flow tube has cooled and is straight, the manufacturer packages the section of flow tube to maintain the straight shape of the section (1508). The manufacturer could put the flow tube in some type of packaging mold to keep the flow tube straight during storage or shipping.
The manufacturer could also etch the section of said flow tube before packaging the section. This could be very convenient for the manufacturer of the flow meter. The manufacturer could store the section of flow tube in a special kind of packaging to avoid exposing the section of flow tube to light to avoid degrading the etched surface. The manufacturer could also store the section of flow tube in a controlled environment to keep the section at an ambient temperature. Both of hese steps help to maintain integrity of the etched surface of the flow tuhR

WE CLAIM :
1. A method of assembling a Coriolis flow meter, comprising:
providing a flow meter structure having a base (522) and two legs (517, 518), where the two legs are attached to the base and are in a spaced apart relationship, the two legs each having a cylindrical opening (502, 512) through the leg, where the two cylindrical openings are aligned in a co-axial relationship;
providing a flexible fluoropolymer flow tube (510) having an outer diameter, where the outer diameter is configured to fit into the two cylindrical openings (502, 512) in the two legs while leaving a predefined gap;
placing the flexible fluoropolymer flow tube (102) into the two cylindrical openings where a section of the non-rigid flow tube extends between the two legs, and where the flow tube creates two predefined gaps between the outer diameter of the flow tube and the inner diameter of the two openings;
inserting an adhesive in the two predefined gaps;
holding the outer surface of the section of the flexible fluoropolymer flow tube extending between the two legs in an essentially straight configuration while the inserted adhesive cures.
2. The method as claimed in claim 1 where the adhesive is inserted into each predefined gap through an adhesive opening (504, 514) in each leg, where each adhesive opening intersects and is perpendicular to the cylindrical opening (502, 512) in each leg (517, 518) and where the axis of the two adhesive openings are in essentially the same plane and where the adhesive openings and the cylindrical openings are held in a horizontal orientation while the adhesive is inserted.
3. The method as claimed in claim 1 where the outer surface of the flow tube is etched in at least one of a plurality of attachment areas whereby an attachment area is an area where the flow tube is attached to another surface.

4. The method as claimed in claim 3 where the etching is done using a sodium naphthalene etchant.
5. The method as claimed in claim 1 where the section of the flow tube extending between the two legs is held in an essentially straight configuration by providing a fixture block (1000) where providing the fixture block comprises:
inserting a first section (802) between said first leg and said second leg of said base where the first section has a first tube opening portion on an end of the first section; and
inserting a second section (804) between said first leg and said second leg of said base where the second section has a second tube opening portion (914) on an end (915) of said second section, said end of said second section adapted to fit adjacent to said end of said first section to form a fixture block (1000), said fixture block having a tube opening (1101) formed fi-om said first tube opening portion and said second tube opening portion, and where the flow tube is held in the tube opening portion of said fixture block.
6. The method as claimed in claim 5 where providing the fixture block (1000) further
comprises:
providing a driver opening (1202) extending from a surface of said fixture block and intersecting said tube opening (1101) of said fixture block where a driver is attached to said flow tube using said driver opening; and
providing at least one pick-off opening (1204) extending from said surface of said fixture block and intersecting said tube opening of said fixture block where at least one pick-off is attached to said flow tube using said at least one pick-off opening.
7. The method as claimed in claim 6 where the providing fixture block further comprises:
providing an alignment means (1206) adapted to fit in said openings of said fixture block
(1000) and extend from said surface of said fixture block to an area adjacent said tube opening (1101) of said fixture block where the alignment means is used to hold the driver and the at least
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one pick-off in an aligned position with respect to the flow tube while being attached to the flow tube.
8. The method as claimed in claim 6 where providing the fixture block further comprises: providing a securing means (806) adapted to secure said first section (802) and said second section (804) to said base (552) of said flow meter (500) to align said driver opening (1202) of said fixture block (1000) with a driver opening in said base and to align said at least one pick-off opening (1204) of said fixture block with at least one pick-off opening in said base and using said securing means to secure said first section and said second section to said base.
9. The method as claimed in claim 1 where the flow tube is made of perfluoroalkoxyethlene (PFA).
10. The method as claimed in claim 1 where the flow tube is made of polytetrafluoroethylene (PTFE).
11. The method as claimed in claim 1 where the adhesive comprises a cyanoacrylate adhesive.
12. The method as claimed in claim 1 comprising:
providing a plurality of components configured to attach to the section of the flow tube extending between the two legs;
aligning the plurality of components to a predefined set of locations along the flow tube; attaching the plurality of components to the flow tube using the adhesive.
13. The method as claimed in claim 12 where at least one of the plurality of components is a
driver.
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14. The method as claimed in claim 12 where at least one of the plurality of components is a pickoff.
15. The method as claimed in claim 12 comprising:
testing the position of the plurality of components by vibrating the flow tube using at least one of the plurality of components to drive the vibration and using at least one of the plurality of components to sense the vibration of the flow tube.
16. The method as claimed in claim 15 comprising:
adjusting the predefined locations for the plurality of components based of the result of the tested positions.
17. The method as claimed in claim 1 comprising:
manufacturing the provided flow tube by extruding a section of the flow tube wherein the extruded section of non-rigid flow tube has a temperature above room temperature;
securing the section of extruded flow tube to hold the longitudinal shape of the flow tube straight as the flow tube cools.