HK1165545A - Manufacturing flow meters having a flow tube made of a fluoropolymer substance - Google Patents

Description

Manufacture of flowmeters having flow tubes made of fluoropolymer substances

The present invention is a divisional application of a patent application having the same name as that of patent application No. 02823508.8 and having an international filing date of 2002, 11/19/2002.

Technical Field

The present invention relates to flow meters, and more particularly to the manufacture of flow meters including flow tubes made of fluoropolymer substances.

Background

It is known to use coriolis effect mass flowmeters to measure mass flow and other information about material flowing through a pipeline, as described in U.S. patent 4491025 to j.e.smith et al, 1 st 1985 and re.31450 to j.e.smith, 11 st 1982. These meters have one or more flow tubes that are not straight, curved, or irregularly configured. Each flow tube has a set of natural vibration modes that may be simple bending, torsional or torsional types. Each material filled flow tube is driven to resonate in one of these natural modes. The natural vibration modes are determined in part by the combined mass of the flow tube and the material within the flow tube. The flow meter need not be driven in the natural mode if desired.

Material flows into the flow meter from a source of material connected on the inlet side. The material passes through one or several other flow tubes and flows to a material receiver attached to the exterior of the flowmeter.

The driver provides a force for vibrating the flow tube. When there is no material flow, all points along the flow tube vibrate with the same phase in the first bending mode of the flow tube. Coriolis accelerations cause each point on the flow tube to have a different phase than other points on the flow tube. The phase on the inlet side of the flow tube lags the driver and the phase on the outlet side leads the driver. A sensor is disposed on the flow tube for generating a sinusoidal signal representative of the motion of the flow tube. The phase difference between the two sensor signals is divided by the vibration frequency to obtain a delay proportional to the mass flow of the material flow.

It is known to use flow meters having different flow tube configurations. Among these structures are single tubes, double tubes, straight tubes, bent tubes and irregularly configured flow tubes. Most flow meters are constructed of metals such as aluminum, steel, stainless steel, and titanium. Glass flow tubes are also known.

The advantageous properties of titanium in these types of flow meters are its high strength and low Coefficient of Thermal Expansion (CTE). A disadvantageous property of titanium is its metallic nature and manufacturing costs. In addition, titanium flow meters are difficult and expensive to manufacture.

The prior art also proposes plastic flow tubes and plastic flow meters. Where the entire meter is plastic or only the flow tube is plastic. Many of these prior art techniques merely include inferences that the flow tubes can be made from steel, stainless steel, titanium, or plastic.

These prior art techniques, which have so far been directed to coriolis plastic flow meters, are not extensive. Coriolis flowmeters can accurately output information over a range of operating conditions including temperature. These prior art techniques, which have heretofore been directed to coriolis plastic flowmeters having plastic flow tubes, are also not extensive.

Merely replacing the metal flow tubes with plastic flow tubes would create the structure of the flowmeter. However, this structure cannot accurately output information as a flow meter in the range of the operation state. Merely asserting that the flow meter may be made of plastic does not teach beyond the concept of replacing metal with plastic in a coriolis flow meter. It does not teach how plastic flow meters can be manufactured to produce accurate output information over a range of operating conditions.

Perfluoroalkoxyethylene (PFA) is a plastic that can be used in flow meters. The use of PFA to make flow tubes is suggested in U.S. patent 5918285 to Vanderpol. This proposal is incidental to the Vanderpol patent in that it does not disclose information on how to manufacture a flowmeter having a PFA flow tube for generating accurate flow information.

PFA lined flow tubes such as disclosed in U.S. patent 5403533 to Dieter Meier. However, the flow tube material and the PFA liner have different thermal properties. This causes the PFA liner and flow tube to come off creating leakage and performance problems. The process of manufacturing lined metal flow tubes using PFA is also extremely expensive.

The prior art also suggests plastic flow tubes and plastic flow meters. These prior art techniques include the entire meter being plastic and wherein only the flow tube is made of plastic. Most of this prior art relates to metal flow meters and contains only one assertion that the flow meter can be made of various materials such as steel, stainless steel, titanium or plastic. This prior art does not disclose a plastic coriolis flowmeter that can accurately output information over a range of operating conditions, including temperature.

Replacing a metal flow tube with a plastic flow tube only would result in a structure that looks like a flow meter. However, this configuration does not provide a flow meter to produce accurate output information over a useful range of operating conditions. It is only considered as an assertion that the flow meter can be made of plastic, which makes no sense except to say that plastic can replace metal. It does not teach how to manufacture a plastic flow meter to produce accurate information over a useful range of operating conditions.

A problem in some applications is that a typical coriolis flowmeter can contaminate the process material. This is undesirable for systems in which ultra-high purity material must be provided to the consumer application by means of a flow meter. This is the case in the manufacture of semiconductor chips, which require the use of process materials that are free of contaminants, including ions migrating from the tubes in the path of the process stream. In such applications, the flow tube may be a source of contamination. The metal walls of the flow tube may release ions in the process stream. The released ions can cause the chips on the semiconductor wafer to become defective. The same is true for glass flowtubes, which can release lead ions from the glass to the process stream. The same is true for flow tubes constructed of conventional plastics.

Disclosure of Invention

The above and other problems are solved and a need in the art is met by the present invention which discloses an improved flow meter using a flow tube made of a fluoropolymer substance, a fixture for manufacturing a flow meter having a flow tube made of a fluoropolymer substance, a method for manufacturing a straight flow tube made of a fluoropolymer substance, and a method for detecting driver and sensor alignment on a flow tube.

The improved flow meter advantageously has an adhesive opening machined into the base of the flow meter into which adhesive is injected to bond the flow tube to the base. The adhesive openings allow for a better effective area of attachment between the flow tube and the base, which results in a strong bond. The adhesive openings also make the process of the flowmeter easier.

The fixing device advantageously fixes the flow tube on the fixed axis during the manufacturing process. Securing the flow tube by a securing device may make it easier for a flowmeter manufacturer to attach the flow tube to the base of the flowmeter. The fixture also allows the driver and sensor to be more easily bonded to the flow tube. The fixture also helps to properly align the driver and sensor on the flow tube. The fixture also serves to straighten the flow tube and minimize or eliminate curvature in the active or vibrating portion of the flow tube.

The method of detecting the alignment of the driver and transducer on the flow tube advantageously provides a quality control check to the flowmeter manufacturer. The flowmeter manufacturer can easily and conveniently determine the accuracy of the manufacturing process. The flowmeter manufacturer can also identify problems in the manufacturing process and determine what adjustments need to be made.

The method for manufacturing a straight flow tube made of a fluoropolymer substance advantageously helps the flow tube manufacturer to manufacture a more accurate flow meter. When a straight flow tube is desired, a meter manufacturer can easily and conveniently receive the straight flow tube directly from a flow tube manufacturer who acts as a supplier and defines the straightness requirements for the flow tube specification. The flowmeter manufacturer does not have to straighten the flow tube prior to manufacturing the flowmeter. The flowmeter manufacturer need not face the challenge of manufacturing flowmeters with locally bent flowtubes.

One embodiment of the improved flow meter is a flow meter comprising a base, a driver, a transducer, and a flow tube. The driver and sensor are attached to the flow tube. The base of the flowmeter includes a first column and a second column. The first post includes a tube opening and an adhesive opening and the second post includes a tube opening and an adhesive opening. The flow tube extends through the tube opening of the first column and the tube opening of the second column. The tube opening and the adhesive opening on the first column intersect and lie in approximately the same plane in the first column so that the tube opening and the adhesive opening of the first column are simultaneously horizontally positioned. The tube opening and the adhesive opening on the second column intersect and lie on approximately the same plane in the second column, so that the tube opening and the adhesive opening of the second column are positioned horizontally at the same time.

The tube opening of the first column is slightly larger in diameter than the flow tube, thereby forming a gap between the tube opening of the first column and the flow tube. The adhesive opening of the first column provides an access port into the gap for applying adhesive to the flow tube and the inner surface of the tube opening of the first column. The tube opening of the second column is slightly larger in diameter than the flow tube, thereby forming a gap between the tube opening of the second column and the flow tube.

The adhesive opening of the second column provides an access port into the gap for applying adhesive to the interior surfaces of the flow tube and the tube opening of the second column.

The following describes a method that a manufacturer can use to manufacture a flowmeter as described above. First, the manufacturer orients the tube opening, the adhesive opening, and the flow tube in a horizontal plane. The manufacturer positions the tip of the adhesive applicator in the adhesive opening and into the gap so as to be adjacent the outer surface of the flow tube and the inner surface of the tube opening of the first post. The manufacturer introduces a certain amount of adhesive into the gap. Due to the surface energy of the outer surface of the flow tube and the inner surface of the tube opening of the first post, the adhesive is drawn into the gap by capillary action or wicking. When the adhesive reaches the open end of the tube, wicking ceases and a uniform and symmetrical strip of packing is formed. The manufacturer then cures the adhesive in the gap. The manufacturer performs the same operation to attach the flow tube to the tube opening of the second column. The adhesive openings provide an easy and better way to bond the flow tube to the base of the flow meter.

One embodiment of a fixation device includes a first section and a second section. The fixture is configured to define a flow tube of the flow meter during manufacture 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 segment and the end of the second segment are configured to fit adjacent to each other. When adjacently arranged, the first section and the second section form a fixation block. The fixation block includes a tube opening formed by a first tube opening portion and a second tube opening portion. The tube openings are used to hold the flow tubes of the flow meter during the manufacturing process. The securing device secures the first section and the second section to a base of the flow meter. The fixture aligns the tube opening of the fixture block with the tube opening of the base of the flow meter. In this way, it is fixed to the base of the flowmeter.

The fixture also includes alignment means for attaching the driver component and the sensor component to the flow tube.

One embodiment of a method of detecting alignment of a driver and a sensor on a flow tube of a flow meter is as follows. To detect the alignment condition, the manufacturer vibrates the flow tube at one or more drive frequencies through the use of a driver. The manufacturer receives sensor signals from the sensors using a processing system. The sensor signal is representative of the vibration frequency of the flow tube. A processing system processes the sensor signal and the signal representative of the drive frequency to determine a frequency response. The processing system identifies an unacceptable alignment of the driver and the sensor on the flow tube based on the frequency response.

One embodiment of a method of making a flow tube made of a fluoropolymer substance is provided below. The manufacturer squeezes the flow tube through a squeezing system. The flow tube is made of a fluoropolymer substance, such as PFA. The temperature of the flow tube exiting the extruder is above room temperature. The manufacturer cuts a section of the flow tube. The manufacturer then secures the flow tube section to keep the longitudinal shape of the section straight as the section cools. As the flow tube cools and straightens, the manufacturer encapsulates the section of the flow tube so as to maintain the straight shape of the section.

The invention includes one or more of the following aspects.

One aspect of the invention is a method of assembling a coriolis flow meter comprising:

providing a flowmeter structure having a base with two posts, wherein the two posts are in spaced apart relation, the two posts each having a cylindrical opening therethrough and an adhesive opening intersecting the cylindrical opening, the two cylindrical openings being aligned in a coaxial relation;

providing a non-rigid flow tube having an outer diameter and made of fluoropolymer, wherein the outer diameter is configured to fit into the two cylindrical openings in the two columns while leaving a predetermined gap;

providing a driver and at least one sensor connected to the flow tube;

placing a non-rigid flow tube into the two cylindrical openings, wherein a section of the non-rigid flow tube extends between the two posts and the non-rigid flow tube forms two predetermined gaps between an outer diameter of the non-rigid flow tube and an inner diameter of the two openings;

inserting adhesive into the two predetermined gaps between the outer diameter of the non-rigid flow tube and the inner diameter of the two cylindrical openings by extending the tip of the adhesive applicator into the adhesive opening using the adhesive applicator;

a mounting block is used to maintain the section of non-rigid flow tube extending between the two posts in a substantially straight configuration when the inserted adhesive cures.

Preferably, in the method, each adhesive opening is perpendicular to the cylindrical opening in each post, and the adhesive opening and the cylindrical opening remain in a horizontal orientation when adhesive is inserted.

Preferably, in the method, the outer surface of the non-rigid flow tube is etched.

Preferably, in the method, the etching is performed using a sodium naphthalene etchant.

Preferably, in the method, providing the anchor block by providing an anchor block such that the section of the non-rigid flow tube extending between the two legs remains in a generally straight configuration comprises:

inserting a first section having a first tube opening portion on an end thereof between the first and second posts of the base; and

inserting a second section between the first and second legs of the base, the second section having a second tube opening portion on an end of the second section, the end of the second end adapted to mate adjacent to the end of the first section to form a fixture block, the fixture block having a tube opening formed by the first and second tube opening portions, the non-rigid flow tube being retained in the tube opening portion of the fixture block.

Preferably, in the method, providing the fixed block further includes:

providing a driver opening extending from a surface of the fixed block and intersecting the tube opening of the fixed block, said driver attached to the non-rigid flow tube using the driver opening; and

at least one sensor opening is provided that extends from the surface of the fixed block and intersects the tube opening of the fixed block, the at least one sensor being attached to the non-rigid flow tube using the at least one sensor opening.

Preferably, in the method, providing the fixed block further includes:

an alignment device is provided that is adapted to fit in the driver opening of the fixed block and extends from the surface of the fixed block to an area near the tube opening of the fixed block, the alignment device for maintaining the driver and the at least one sensor in an aligned position relative to the non-rigid flow tube when attached to the non-rigid flow tube.

Preferably, in the method, providing the fixed block further includes:

providing a fixture securing the first section and the second section to the base of the flow meter to align the driver opening of the fixture block with the driver opening in the base and to align the at least one sensor opening of the fixture block with the at least one sensor opening in the base, with the fixture securing the first section and the second section to the base.

Preferably, in the method, the non-rigid flow tube is made of Perfluoroalkoxyethylene (PFA).

Preferably, in the method, the non-rigid flow tube is made of Polytetrafluoroethylene (PTFE).

Preferably, in the method, the adhesive comprises a cyanoacrylate adhesive.

Preferably, the method further comprises:

aligning the driver and at least one sensor along the non-rigid flow tube at a predetermined set of positions; and

the driver and at least one sensor are attached to the non-rigid flow tube using an adhesive.

Preferably, the method further comprises: the non-rigid flow tube is vibrated by using the driver to drive vibration and sensing the vibration of the flow tube using at least one sensor, thereby detecting alignment of the driver and the at least one sensor.

Preferably, the method further comprises:

based on the result of the detected position, a predetermined alignment of the driver and the at least one sensor is adjusted.

Preferably, the method further comprises:

with an extruder, wherein the extruded non-rigid flow tube exiting said extruder has a temperature above room temperature;

securing the extruded section of the non-rigid flow tube to maintain the longitudinal shape of the non-rigid flow tube straight as the non-rigid flow tube cools, thereby manufacturing the provided flow tube.

Drawings

These and other advantages and features of the invention will be better understood by reading the following detailed description in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of a first embodiment of the present invention;

FIG. 2 is a top view of the embodiment of FIG. 1;

FIG. 3 is a front view of the embodiment of FIG. 1;

FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 2;

FIGS. 5-7 illustrate a flow meter having adhesive openings in the base of the flow meter of an embodiment of the invention;

8-13 illustrate a fixture for manufacturing a flow meter in an embodiment of the invention;

FIG. 14 illustrates a method of detecting alignment of a driver and a sensor on a flow tube of a flow meter in an embodiment of the invention; and

FIG. 15 illustrates a method of making a flow tube from a fluoropolymer substance in an embodiment of the invention.

Detailed Description

Fig. 1-15 and the following detailed description depict specific examples to teach those skilled in the art the best mode of carrying out the invention. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those of ordinary skill 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. Therefore, the present invention is not limited to the specific embodiments described below, but is defined by the appended claims and equivalents thereof.

Description of FIG. 1

FIG. 1 is a perspective view of a first possible embodiment of the invention, disclosing a flow meter 100 comprising a flow tube (flow tube)102 inserted through posts 117, 118 of a base 101. Pickoffs LPO and RPO and driver D are connected to flow tube 102. The flow meter 100 receives a process material flow from a supply pipe 104 and extends the flow to a flow pipe 102 through a connector 108. The flow tube 102 is vibrated at its resonant frequency with material flow by means of the driver D. The resulting coriolis deflections are detected by pickoffs LPO and RPO, which provide signals representative of the coriolis deflections to meter electronics 121 via conductors 112 and 114. The meter electronics 121 receives the sensor signals, determines the phase difference therebetween, and provides output information regarding material flow to application circuitry, not shown, via output path 122.

The material flows through flow tube 102 and through tube 106. Tube 106 again directs the flow of material through return tube 103 to exit tube 105 via connector 107, and exit tube 105 provides the flow of material to the user application. The user application may be a semiconductor processing device. The process material may be a semiconductor slurry that is supplied to the surface of the semiconductor wafer to form a flat surface. The PFA (perfluoroalkoxyethylene) material used in the flow tube shown in fig. 1 ensures that the process material is free of impurities, which may be, for example, ions transferred from the walls of the metal flow tube or the glass flow tube.

In use, the flow tube 102 has a narrow diameter that approximates the diameter of a soda straw and weighs negligible, for example 0.8 grams, which excludes the weight of the magnet. The magnets associated with pickoffs LPO, RPO and driver D have a mass of about 0.2 grams, and thus the total mass of flow tube 102, attached magnets and process material is about 2 grams. The vibrating flow tube 102 has a dynamic unbalanced structure. The base 102 is heavy, weighing approximately 12 pounds. This provides a ratio of the mass of the base to the mass of the material filled flow tube approximately equal to 3000 to 1. The base of such a large mass is sufficient to absorb the vibrations generated by the dynamically unbalanced flow tube 102 with material flow.

Connectors 107, 108, 109 and 110 connect the pipes 104, 105 and 106 to the ends of the flow pipe 102 and the return pipe 103. The details of these connectors are shown in figure 4. The connector has a securing portion 111 that includes threads 124. The movable portion of the connector 107 and 110 is threaded onto the external thread 124 in order to connect its respective tube to the fixed body of the connector of which the fixed portion 111 is a part. These connectors connect the tubes 104, 105 and 106 to the ends of the flow tube 102 and return tube 103 in a similar manner to known copper-tube flared connectors. Fig. 4 shows further details of the connector. The temperature sensor RTD senses the temperature of the return tube 103 and transmits a signal representative of the sensed temperature to the meter electronics 121 via path 125.

Opening 130 extends from a surface on post 117 through flow tube 102 and from a surface on post 118 through flow tube 102. Opening 130 provides a location for injecting an adhesive to secure flow tube 102 to post 117 and 118. A set screw is threaded into opening 130 to hold flow tube 102 in place.

Description of FIG. 2

Fig. 2 is a top view of the flow meter 100 of fig. 1. Each of the pickoffs LPO and RPO and the driver D includes a coil C. Each of these elements also includes a magnet attached to the bottom of the flow tube 102, as shown in fig. 3. Each of these elements also includes a base, such as 143 for driver D, and a thin strip of material, such as 133 for driver D. The thin material strip may comprise a printed circuit board to which the coil C and its winding terminals are fixed. The transducer LP0 and RPO also have respective base elements 142, 144 and thin strips 132, 134 secured to the tops of the base elements. This configuration facilitates the installation of the driver or sensor by the steps of: gluing the magnet M to the underside of the PFA flow tube, gluing the coil C to the printed wiring board 133 (for the driver D), positioning the opening in the coil C around the magnet M, moving the coil C upward so that the magnet M fully enters the opening in the coil C, then positioning the base element 143 under the printed wiring board 133 and bolting these elements together so that the bottom of the base 143 is attached to the surface of the heavy base 116. Fig. 12-13 illustrate a system and method for attaching the driver D and pickoffs LPO, RPO to the flow tube 102.

Figure 2 shows the external threads 124 of the connectors 107-110. The internal details of each of these elements are shown in fig. 4. Opening 132 receives conductors 112, 113 and 114. The opening 126 receives the conductors 112, 113, 114. The meter electronics shown in fig. 1 are not shown in fig. 2 to simplify the figure. It should be understood, however, that conductors 112, 113, 114 extend through opening 126 and, in turn, through passageway 123 shown in fig. 1 to meter electronics 121 shown in fig. 1.

Description of FIG. 3

Fig. 3 shows pickoffs LPO, RPO and driver D, which include a magnet M attached to the bottom of flow tube 102 and a coil C attached to the bottom of each element LPO, RPO and driver D.

Description of FIG. 4

Fig. 4 is a sectional view taken along line 4-4 of fig. 2. Fig. 4 discloses further details of all the elements and connectors 108, 109 of fig. 3. Fig. 4 also discloses openings 402 and 404 in the base 101. The top of each of these openings extends to the lower surface of the bottom of the pickoffs LPO, RPO and driver D. Also shown in fig. 4 are a coil C and a magnet M associated with each of these elements. The meter electronics 121 shown in fig. 1 are not shown in fig. 3 and 4 for simplicity. Element 405 in connector 108 is the inlet of flow tube 102; element 406 in connector 109 is the outlet of flow tube 102.

The fixing body 111 of the connector 108 comprises external threads 409 which screw into mating threads located in the element 401 of the base 101 in order to connect the connector 111 to the element 401 of the base 101. The fixing body 111 of the connector 109 on the right is similarly assembled and connected to the element 401 located on the base 101 by means of the screw thread 409.

Fixed body 111 of connector 108 also includes a threaded portion 124 that threadably receives a movable portion 415 of connector 108. The connector 109 is similarly assembled. Fixed body 111 of connector 108 also includes on its left side a tapered stub 413 which, together with movable element 415, acts as a counterbore joint to force the right end of input tube 104 over tapered stub 413 of fixed portion 111. This forms a press fit that sealingly secures the flared opening of the supply tube 104 to the tapered stub portion 413 of the fixed portion 111 of the connector. The inlet 405 of the flow tube 102 is positioned within the connector securing portion 111 and is flush with the face 425 of the stub 413. In this manner, process material provided by the supply pipe 104 is received by the inlet 405 of the flow pipe 102. The process material flows through the flow tube 102 to the right to the stationary body 111 of the connector 109 where the outlet of the flow tube 102 is flush with the end of the stub 413. This allows the end 408 of the tube 106 to be sealingly attached to the connector 109 and to the outlet 406 of the flow tube 102. The other connectors 107 and 110 of fig. 1 are the same as the connectors 108, 109 of fig. 4 in detail.

Flowmeter with adhesive openings-fig. 5-7

Fig. 5-7 show an example of a flow meter 500 in an embodiment of the invention. As shown in fig. 5, flow meter 500 includes a U-shaped base 522, flow tube 501, driver D, and pickoffs LPO, RPO. With the present invention, flow meter 500 need not include U-shaped mount 522. It is within the scope of the present invention that flow meter 500 may include a V-shaped seat or any other form of seat. Flow tube 501 is made of a fluoropolymer substance. Examples of fluoropolymer substances are Perfluoroalkoxyethylene (PFA), Polytetrafluoroethylene (PTFE), and Fluorinated Ethylene Polymer (FEP). The U-shaped mount 522 may be made of stainless steel. Driver D and pickoffs LPO, RPO are attached to flow tube 501.

The U-shaped base 522 of flow meter 500 includes a post 517 and a post 518. The post 517 and the post 518 are parallel to each other. The post 517 includes a tube opening 502 and an adhesive opening 504. The adhesive opening 504 is shown in the center of the post 517, but the adhesive opening 504 may be located near one side or the other. The tube opening 502 and the adhesive opening 504 may be positioned to intersect each other in the post 517. The post 518 includes a tube opening 512 and an adhesive opening 514. The adhesive opening 514 is shown as being located in the center of the post 518, but the adhesive opening 514 may be located near one side or the other. The tube opening 512 and the adhesive opening 514 may be positioned to intersect each other in the column 518. Tube opening 502 and tube opening 512 are located on the same axis.

Flow tube 501 passes through tube opening 502 and tube opening 512. The diameter of tube opening 502 is slightly larger than the diameter of flow tube 501 so that a gap 506 is formed between tube opening 502 and flow tube 501. FIG. 6 is a cross-sectional view of the post 517, showing the tube opening 502, the adhesive opening 504, and the gap 506. Adhesive opening 504 provides access to gap 506 for the application of adhesive to outer surface 510 of flow tube 501 and inner surface 508 of tube opening 502. Tube opening 512 is shown in fig. 5 as having a diameter slightly larger than the diameter of flow tube 501 so that a gap 516 is formed between tube opening 512 and flow tube 501. Adhesive opening 514 provides access to gap 516 for the application of adhesive to outer surface 510 of flow tube 501 and to 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.

The operation of the flow meter 500 is substantially the same as the operation of the flow meter 100 shown in fig. 1-4. The flow meter 500 receives a process stream. The process material flows through flow tube 501. Driver D causes flow tube 501 to vibrate at a resonant frequency. Transducers LPO, RPO are also attached to flow tube 501. The pickoffs LPO, RPO detect the coriolis deflections generated by the flow of process material in the flow tube 501 and generate signals indicative thereof. The signal is transmitted to meter electronics (not shown) that processes the signal.

The method used by the manufacturer to bond flow tube 501 to tube opening 502 and tube opening 512 in flow meter 500 is described below. First, the manufacturer orients tube opening 502, adhesive opening 504, and flow tube 501 in a horizontal plane. Referring to fig. 7, the manufacturer positions tip 724 of adhesive applicator 722 in adhesive opening 504 into gap 506 so as to be adjacent to outer surface 510 of flow tube 501 and inner surface 508 of tube opening 502. It should be understood that the adhesive applicator 722 shown in fig. 7 is not vertical. The adhesive opening 504, the tube opening 502, and the flow tube 501 are on a horizontal plane, and the adhesive applicator 722 is thus inserted horizontally into the adhesive opening 504. One example of an adhesive applicator 722 is an EFD micro-dispenser model 1500 XL-CA. The micro-dispenser was set to 3PSI and had a 3ml syringe and a half inch long needle of 0.006 inch Teflon substrate. The manufacturer introduces an amount of adhesive 720 into gap 506 between outer surface 510 of flow tube 501 and inner surface 508 of tube opening 502. Adhesive 720 may be a Cyanoacrylate Adhesive (CA). An example of a CA is superbond 420 manufactured by Loctite.

Due to the surface energy of outer surface 510 and inner surface 508, adhesive 720 is drawn into gap 506 by capillary action or wicking. The arrows in fig. 7 indicate this wicking action. Wicking acts on approximately 100% of the active area of the gap 506. By horizontally positioning tube opening 502, adhesive opening 504, and flow tube 501, adhesive 720 is not subjected to hydrostatic pressure. Thus, adhesive 720 fills gap 506 due to wicking and is not subject to hydrostatic forces. When the adhesive 720 reaches the end of the tube opening 502, wicking ceases and a uniform and symmetrical strip of packing is formed. The manufacturer causes the adhesive 720 to cure in the gap 506.

The manufacturer then orients tube opening 512, adhesive opening 514, and flow tube 501 in a horizontal plane. This level may be the same level as described above so that tube opening 102 and tube opening 112 are connected to flow tube 501 simultaneously. The manufacturer positions tip 724 of adhesive applicator 722 in adhesive opening 514 into gap 516 so as to be adjacent to outer surface 510 of flow tube 501 and inner surface 515 of tube opening 512. The manufacturer introduces a quantity of adhesive 720 into gap 516 between outer surface 510 of flow tube 501 and inner surface 515 of tube opening 512. Due to the surface energy of the outer surface 510 and the inner surface 515, the adhesive 720 is drawn into the gap 516 by capillary action or wicking. By horizontally positioning tube openings 512, adhesive openings 514, and flow tube 501, adhesive 720 is not subjected to hydrostatic pressure. Thus, adhesive 720 fills gap 516 due to wicking and is not subject to hydrostatic forces. When the adhesive 720 reaches the end of the tube opening 512, wicking ceases and a uniform and symmetrical strip of packing is formed. The manufacturer causes the adhesive 720 to cure in the gap 516. After the adhesive is applied, set screws may be threaded into adhesive openings 504 and 514 to further hold flow tube 501 in place.

Adhesive openings 504 and 514 advantageously provide easy, adequate, and efficient access to gaps 506, 516 for bonding flow tube 501 to inner surfaces 508, 515.

Adhesive strength

The strength and quality of the bond between the flow tube 501 and the tube openings 502, 512 is dependent on the type and amount of adhesive used, the preparation of the bonded surfaces, the air humidity at which the adhesive cures, the surface temperature at which the adhesive cures, and the gap size between the bonded surfaces.

Selection of adhesives

The manufacturer may select the type of adhesive based on its viscosity. The viscosity of the adhesive affects the extent to which the adhesive wicks in the gaps 506, 516. The preferred viscosity range for the adhesive is 2-110 centipoise. The amount of adhesive used depends on the strength required for bonding, the speed of curing, and the ease of manufacture.

Surface preparation

To form a strong bond, the outer surface 510 of flow tube 501, the inner surface 508 of tube opening 502, and the inner surface 515 of tube opening 512 should be suitably prepared. Preparation of the surfaces 510, 508, 515 may be performed prior to adhesive application. As described in the background, flow tube 501 is made of a fluoropolymer substance, such as PFA, which has a very low surface energy. This makes it difficult for the adhesive to bond to flow tube 501. The following method allows the manufacturer to form a strong bond with the outer surface 510 of flow tube 501. Prior to assembling flowmeter 500, the manufacturer etches the exterior surface 510 of flow tube 501. The manufacturer uses a sodium naphthalene etchant to etch the outer surface 510. Examples of naphthyl sodium etchants are ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. It will be appreciated by those of ordinary skill in the art that the supplier of flow tube 501 may etch outer surface 510 and thus the manufacturer need not do so. Subsequently, the manufacturer cleans the outer surface 510. The manufacturer cleans the outer surface 510 with an ethanol solution.

Inner surface 508 of tube opening 502 and inner surface 515 of tube opening 512 may be similarly prepared. Assume for the U-shaped mount 522 that it is made of stainless steel. The manufacturer makes the tube openings 502, 512 unsmooth. The optimum surface roughness is about 64 microinches RMS (root mean square value). In the general case, the inner surfaces 508, 515 have a surface roughness sufficient to achieve a secure bond when the tube openings 502 and 512 in the U-shaped base 522 are machined by the manufacturer. The manufacturer then removes oil and other substances by cleaning the interior surfaces 508 and 515. The manufacturer may then clean the interior surfaces 508, 515 by scrubbing the interior surfaces 508, 515 with acetone in an ultrasonic bath. The manufacturer may also clean the ethanol bearing inner surfaces 508, 515 prior to applying the adhesive.

Humidity and temperature

Humidity and temperature affect how the adhesive cures. To form a stronger bond, the manufacturer may control the manufacturing environment of the flow meter 500. Adhesives such as CA (cyanoacrylate adhesive) are moisture-containing adhesives. Moisture is required on the outer surface 510 of flow tube 501 and the inner surfaces 508, 515 of tube openings 502, 512 so that adhesive 720 cures properly. Thus, when the adhesive 720 cures, the manufacturer can control the relative humidity of the environment surrounding the flow meter 500. When the adhesive 720 is cured, the relative humidity can be maintained at 40-60%. If the relative humidity is too low, an adhesive accelerator may be used to aid in the curing of the adhesive. The manufacturer may also control the temperature of the environment surrounding the flow meter 500 or control the temperature of the components of the flow meter 500 being bonded. The temperature is set at greater than 23 degrees celsius.

Size of the gap

The size of the gaps 506, 516 is important for bond strength. The size of gaps 506, 516 can be selected based on the viscosity of the adhesive used, the ease of application, the quality of the adhesive active area, and the surface energy of outer surface 510 of flow tube 501 and inner surfaces 508, 515 of tube openings 502, 512. Acceptable gap sizes range from 0.001 to 0.02 inches. If the gap is too small, wicking of the adhesive is inhibited and the adhesive effective area is insufficient. If the gap is too large, the adhesive cannot move by wicking and does not fully cure. The optimum gap for the gaps 506, 516 is about 0.0035 inches to form a strong bond.

Fastening device-figures 8-13

Fig. 8-13 illustrate a fixture in an embodiment of the invention. The fixture 800 is configured to secure a flow tube of a flow meter (e.g., flow meter 500) during manufacture of the flow meter. Referring to fig. 5, fixture 800 may be used to hold flow tube 501 in place so that flow tube 501 is bonded to tube opening 502, tube opening 512, driver D, and pickoffs LPO, RPO.

As shown in fig. 8-9, the fixture 800 includes a first section 802 and a second section 804. The first and second sections 802, 804 may be made of polyoxymethylene resin or stainless steel. The first section 802 includes a first tube opening portion 912 on an end 913 of the first section 802. The second section 804 includes a second tube opening portion 914 on an end 915 of the second section 804. The end 913 of the first segment 802 and the end 915 of the second segment 804 are configured to mate adjacent to each other.

Fig. 10-11 show a first segment 802 adjacent to a second segment 804. When adjacently arranged, the first section 802 and the second section 804 form a fixed block 1000. Mounting block 1000 includes a tube opening 1101 formed by a first tube opening portion 912 and a second tube opening portion 914, as shown in FIG. 9. Tube opening 1101 is used to hold flow tube 501 of flow meter 500 during manufacturing. Tube opening 1101 is slightly larger than the diameter of flow tube 501. The mounting block 1000 is configured to fit between the post 517 and the post 518 of the U-shaped base 552. The length of the fixation block 1000 is approximately the distance between the inner surface of the post 517 and the inner surface of the post 518.

The fixture 800 also includes a fixture 806. Fixtures 806 secure first section 802 and second section 804 to a U-shaped base 552 of flow meter 500. Fixture 806 aligns tube opening 1101 with tube openings 502, 512 of U-shaped base 552. The securing device 806 may be a bolt, screw, clamp, pin, or any other fastening device.

The fixture 800 further includes a fastening device 810, the fastening device 810 connecting the first section 802 to the second section 804. The fastening device 810 may be a bolt, screw, clamp, pin, or any other fastening device.

The fixture 800 implements the following functions. Fixture 800 forces flow tube 501 to be straight so that flow tube 501 does not bend. Fixture 800 positions flow tube 501 and holds flow tube 501 so that flow tube 501 is aligned with tube openings 502, 512. Fixture 800 also positions and supports flow tube 501 so that driver components and sensor components are attached to flow tube 501.

Fig. 12-13 illustrate another embodiment of a fixture 800 in an example of the invention. The fixture 800 includes a driver opening 1202. Driver opening 1202 extends from the surface of fixture block 1000 and intersects tube opening 1101 of fixture block 1000. In this example, the U-shaped base 552 also includes an opening 402. The driver opening 1202 is located on the same axis as the opening 402 of the U-shaped base 552. Securing device 806 secures fixture block 1000 to U-shaped base 552 such that opening 402 of U-shaped base 552 is aligned with driver opening 1202 of fixture block 1000.

The fixture 800 also includes a sensor opening 1204. Sensor opening 1204 extends from the surface of fixture block 1000 and intersects tube opening 1101 of fixture block 1000. In this example, the U-shaped base 552 also includes an opening 404. The sensor opening 1204 is located on the same axis as the opening 404 of the U-shaped base 552. Fixture 806 secures fixture block 1000 to U-shaped base 552 such that opening 404 of U-shaped base 552 is aligned with sensor opening 1204 of fixture block 1000.

Fig. 12-13 show driver opening 1202 and sensor opening 1204 on the bottom side of fixture 800. Driver opening 1202 and sensor opening 1204 are aligned with openings 402 and 404 of U-shaped base 552. The driver opening 1202 and/or the sensor opening 1204 may be located on a top side of the fixture 800. In this case, the U-shaped base 552 need not have openings 402 and 404.

Fixture 800 also includes alignment means 1206. Alignment means 1206 is configured to fit in opening 402 of U-shaped base 552 and in driver opening 1202 of fixture block 1000. Alignment means 1206 extends from the surface of fixture block 1000 to an area near tube opening 1101 of fixture block 1000. Alignment means 1206 includes a lip 1208 on one end that is larger than the diameter of opening 402 or driver opening 1202. Lip 1208 allows alignment means 1206 to extend a particular distance into opening 402 or driver opening 1202. Lip 1208 stops alignment means 1206 before the tip of alignment means 1206 comes into contact with flow tube 501. This prevents alignment means 1206 from damaging flow tube 501.

The following is an example of a method of using fixture 800 to hold flow tube 501 while flow tube 501 is bonded to U-shaped base 552. The manufacturer inserts flow tube 501 through tube opening 502 of column 517 and tube opening 515 of column 518 shown in fig. 5. The manufacturer aligns the first half section 802 and the second half section 804 on the U-shaped base 552. The manufacturer brings end 913 of first section 802 and end 915 of second section 804 into abutment so as to enclose flow tube 501 between first tube opening portion 912 and second tube opening portion 914, thereby forming mounting block 1000. The manufacturer secures the first section 802 to the second section 804. The manufacturer may use fixture 806 to secure fixture block 1000 to U-shaped base 552. The manufacturer introduces an amount of adhesive into the gap 506 between the outer surface 510 of the flow tube 501 and the inner surface 508 of the tube opening 502 of the post 517. The adhesive may be CA. The manufacturer may introduce adhesive through an adhesive opening, such as adhesive opening 504 shown in fig. 5-7. The manufacturer may also introduce a quantity of adhesive into the gap 516 between the outer surface 510 of the flow tube 501 and the inner surface 515 of the tube opening 514 of the post 518.

This method incorporates the considerations of making a strong bond as described above. In particular, the method also includes selecting the type and amount of adhesive used, preparation of the bonded surface, controlling the air humidity at which the adhesive cures, controlling the surface temperature at which the adhesive cures, and selecting the optimal gap size.

The following is an embodiment of a method of attaching driver component 1212 of driver D to flow tube 501 using fixture 800. The manufacturer attaches driver component 1212 to alignment means 1206. The attachment at this point does not mean that driver component 1212 must be secured to alignment means 1206. Driver assembly 1212 is simply disposed on the end of alignment means 1206. The manufacturer applies adhesive to the surface of the driver component 1212. The adhesive may be CA. The manufacturer inserts driver subassembly 1212 through opening 402 and driver opening 1202 by using alignment means 1206. Fig. 13 shows alignment means 1206 fully inserted into opening 402 and driver opening 1202. The manufacturer contacts flow tube 501 with adhesive on the surface of driver component 1212 through the use of alignment means 1206. Lip 1208 prevents alignment means 1206 from pushing driver assembly 1212 too far and damaging flow tube 501. The manufacturer causes the adhesive to cure. The manufacturer then removes alignment means 1206 from opening 402 and driver opening 1202.

This method incorporates the considerations of making a strong bond as described above. In particular, the method also includes selecting the type and amount of adhesive used, preparation of the bonded surface, controlling the air humidity at which the adhesive cures, controlling the surface temperature at which the adhesive cures, and selecting the optimal gap size.

The following are embodiments of a method of attaching pickoff components 1214 of pickoffs LPO, RPO to flow tube 501 using fixture 800. The manufacturer attaches sensor component 1214 to alignment device 1206. Attachment at this point does not mean that sensor component 1214 must be secured to alignment means 1206. Sensor elements 1214 are simply disposed on the ends of alignment means 1206. The manufacturer applies an adhesive to the surface of the sensor component 1214. The adhesive may be CA. The manufacturer inserts sensor component 1214 through opening 404 and sensor opening 1204 using alignment means 1206. Fig. 13 shows alignment means 1206 fully inserted into opening 404 and sensor opening 1204. The manufacturer contacts flow tube 501 with adhesive on the surface of sensor component 1214 by using alignment means 1206. Lip 1208 prevents alignment means 1206 from pushing sensor component 1214 too far and damaging flow tube 501. The manufacturer causes the adhesive to cure. The manufacturer then removes alignment means 1206 from opening 404 and sensor opening 1204.

The driver component 1212 and the sensor component 1214 may be magnets. The driver D and the pickoffs LPO, RPO are typically magnet-coil systems. Accordingly, alignment means 1206 is made of a non-magnetic material, such as brass.

This method incorporates the considerations of making a strong bond as described above. In particular, the method also includes selecting the type and amount of adhesive used, preparation of the bonded surface, controlling the air humidity at which the adhesive cures, controlling the surface temperature at which the adhesive cures, and selecting the optimal gap size.

Method of detecting driver and sensor alignment-FIG. 14

FIG. 14 illustrates, in an exemplary form of the invention, a method for detecting alignment of a driver and a sensor on a flow tube of a flow meter. The method can be used to test the accuracy of a manufacturing process that attaches driver components and sensor portions to a flow tube of a flow meter. For example, after a manufacturer of the flow meter uses the fixture 800 shown in fig. 8-13 to attach the driver component 1212 and the sensor component 1214 to the flow tube 501, the manufacturer may use this method to detect the quality of the fixture 800. The reference numerals of fig. 14 are in parentheses below.

To test the flow meter, the manufacturer vibrates the flow tube at one or more drive frequencies using the driver (1402). The manufacturer can vibrate the flow tube in the frequency spectrum to achieve more beneficial results. The manufacturer receives sensor signals from the sensors using the processing system (1404). The sensor signal is representative of the vibration frequency of the flow tube. A processing system processes the sensor signal and the signal representative of the drive frequency to determine a frequency response (1406). The processing system identifies an unacceptable alignment of the drive and the sensor on the flow tube based on the frequency response (1408).

For example, if the alignment of the driver and sensor is good, the frequency response includes only the first and third bending modes of the flow tube. If the frequency response includes a spike in the second bending mode of the flow tube, it indicates that the axial alignment of the driver and sensor is poor. The processing system may indicate to the manufacturer that the axial alignment is unacceptable. If the frequency response includes a spike in the first torsional mode of the flow tube, it indicates that the lateral alignment of the driver and sensor is poor. The processing system may indicate to the manufacturer that the lateral alignment is unacceptable. The degree of misalignment of the flow tube, driver, and sensor is proportional to the losses of the second bending mode and the first torsional mode. Those of ordinary skill in the art will understand the meaning of the first, second, third bending modes and first torsional mode of the flow tube. And thus a detailed description is omitted herein for the sake of simplicity.

Based on the information of the frequency response, the manufacturer can determine the quality of the constructed flow tube. The manufacturer may also use this information to change the fixture 800 or some other component in the manufacturing process.

Method of manufacturing flow tubes-figure 15

FIG. 15 illustrates, in exemplary form, a method for making a flow tube made of a fluoropolymer substance. As described in the background, flow tubes provided by flow tube manufacturers are generally curvilinear in shape. Flow tube manufacturers can use this method to make straight flow tubes. The reference numerals of fig. 14 are in parentheses below.

The manufacturer squeezes the flow tube (1502) through a squeezing system. The flow tube is made of a fluoropolymer substance, such as PFA. The temperature of the flow tube exiting the extruder is above room temperature. The manufacturer cuts a section of the flow tube (1504). The manufacturer then secures the flow tube section to keep the longitudinal shape of the section straight when the section cools down (1506). For example, the manufacturer may clamp the section to a flat surface to straighten the flow tube. The manufacturer can also place the flow tube in other forms of molds to straighten the flow tube. As the flow tube cools and straightens, the manufacturer encapsulates the section of flow tube so as to maintain the straight shape of the section (1508). The manufacturer can place the flow tube in other forms of packaging molds to keep the flow tube straight during shipping or storage.

The manufacturer may also etch the section of the flow tube prior to packaging the section. This is very convenient for the manufacturer of the flowmeter. The manufacturer can store the flow tube section in a special type of package to avoid exposure of the flow tube section to light, thereby preventing degradation of the etched surface. The manufacturer may also maintain the flow tube section in a controlled environment to maintain the section at ambient temperature. Two of these steps can maintain the integrity of the etched surface of the flow tube.

Claims (15)

1. A method of assembling a coriolis flow meter, comprising:

providing a flowmeter structure having a base (522) with two posts (517, 518), wherein the two posts are in spaced apart relation, the two posts each having a cylindrical opening (502, 512) therethrough and an adhesive opening intersecting the cylindrical openings, the two cylindrical openings being aligned in coaxial relation;

providing a non-rigid flow tube (510) having an outer diameter and made of fluoropolymer, wherein the outer diameter is configured to fit into the two cylindrical openings (502, 512) in the two columns while leaving a predetermined gap;

providing a driver and at least one sensor connected to the flow tube;

placing a non-rigid flow tube (102) into the two cylindrical openings, wherein a section of the non-rigid flow tube extends between the two posts and the non-rigid flow tube forms two predetermined gaps between an outer diameter of the non-rigid flow tube and an inner diameter of the two openings;

inserting adhesive into the two predetermined gaps between the outer diameter of the non-rigid flow tube and the inner diameter of the two cylindrical openings by extending the tip of the adhesive applicator into the adhesive opening using the adhesive applicator;

a mounting block is used to maintain the section of non-rigid flow tube extending between the two posts in a substantially straight configuration when the inserted adhesive cures.

2. The method of claim 1, wherein each adhesive opening is perpendicular to the cylindrical opening (502, 512) in each post (517, 518), and the adhesive opening and the cylindrical opening remain horizontally oriented when adhesive is inserted.

3. The method of claim 1 wherein the outer surface of the non-rigid flow tube is etched.

4. The method of claim 3, wherein etching is performed using a sodium naphthalene etchant.

5. The method of claim 1, wherein providing a mounting block (1000) by providing the mounting block such that the section of the non-rigid flow tube extending between two legs remains in a generally straight configuration comprises:

inserting a first section (802) between the first and second posts of the base, the first section having a first tube opening portion on an end of the first section; to know

Inserting a second section (804) between the first and second legs of the base, the second section having a second tube opening portion (914) on an end (915) of the second section, the end of the second end adapted to mate adjacent to the end of the first section to form a fixture block (1000), the fixture block having a tube opening (1101) formed by the first and second tube opening portions, the non-rigid flow tube retained in the tube opening portion of the fixture block.

6. The method of claim 5, wherein providing a fixed block (1000) further comprises:

providing a driver opening (1202) extending from a surface of the fixed block and intersecting the tube opening (1101) of the fixed block, said driver being attached to the non-rigid flow tube using the driver opening; and

at least one sensor opening (1204) is provided extending from the surface of the fixed block and intersecting the tube opening of the fixed block, the at least one sensor being attached to the non-rigid flow tube using the at least one sensor opening.

7. The method of claim 6, wherein providing the fixed block further comprises:

an alignment means (1206) is provided, the alignment means adapted to fit in the driver opening of the fixed block (1000) and extending from the surface of the fixed block to an area near the tube opening (1101) of the fixed block, the alignment means for maintaining the driver and the at least one sensor in an aligned position relative to the non-rigid flow tube when attached to the non-rigid flow tube.

8. The method of claim 6, wherein providing a fixed block further comprises:

-providing a fixing means (806) for fixing the first section (802) and the second section (804) to the base (552) of the flow meter (500) such that the driver opening (1202) of the fixture block (1000) is aligned with a driver opening in the base and such that said at least one sensor opening (1204) of the fixture block is aligned with at least one sensor opening in the base, by means of said fixing means for fixing said first section and said second section to said base.

9. The method of claim 1, wherein the non-rigid flow tube is made of Perfluoroalkoxyethylene (PFA).

10. The method of claim 1, wherein the non-rigid flow tube is made of Polytetrafluoroethylene (PTFE).

11. The method of claim 1, wherein the adhesive comprises a cyanoacrylate adhesive.

12. The method of claim 1, further comprising:

aligning the driver and at least one sensor along the non-rigid flow tube at a predetermined set of positions; and

the driver and at least one sensor are attached to the non-rigid flow tube using an adhesive.

13. The method of claim 12, further comprising: the non-rigid flow tube is vibrated by using the driver to drive vibration and sensing the vibration of the flow tube using at least one sensor, thereby detecting alignment of the driver and the at least one sensor.

14. The method of claim 13, further comprising:

based on the result of the detected position, a predetermined alignment of the driver and the at least one sensor is adjusted.

15. The method of claim 1, further comprising:

with an extruder, wherein the extruded non-rigid flow tube exiting said extruder has a temperature above room temperature;

securing the extruded section of the non-rigid flow tube to maintain the longitudinal shape of the non-rigid flow tube straight as the non-rigid flow tube cools, thereby manufacturing the provided flow tube.