Abstract:
In one embodiment, a sight tube flowmeter is formed of a plurality of fluoropolymer components welded together to form a unitary flowmeter body. The components can comprise a PFA upright sight tube having two end portions, a flow conduit extending therethrough and two fitting portions that are uniquely welded onto each end of the sight tube, and a fluoropolymer float device movable to various positions within the flow conduit depending on the flow level of the fluid flowing therethrough. The float device can be of conventional design or for those flowmeter embodiments where low fluid flow rates are to be measured, an elongate float can be utilized. The floats and, in particular, a designated portion thereof, are visible through the sight tube to provide visual indication of the position, and thus the flow rate of fluid flowing through the flowmeter. In addition, alternative embodiments include the implementation of the unique sight tube and elongate float design in conventional flowmeters.

Description:
RELATED APPLICATIONS  
       [0001]     This is a divisional of U.S. Patent Application filed May 28, 2002, entitled “Fluoropolymer Flowmeter” and assigned Ser. No. 10/156,449, which in turn claims the benefit of the contents and filing date of U.S. Provisional Patent Application filed May 25, 2001, entitled “Injection Molded and Welded Fluoropolymer Flow Meters” and assigned Ser. No. 60/293,672, and Provisional Patent Application filed Mar. 15, 2002, entitled “Low Flow Rate Fluoropolymer Flowmeter” and assigned Ser. No. 60/364,774, with all of said applications being incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates generally to fluid flowmeters, and more particularly, to a substantially unitary-bodied fluoropolymer flowmeter capable of employing various component and float configurations.  
       BACKGROUND OF THE INVENTION  
       [0003]     Flowmeters are utilized in many different industries to measure and control the flow of various fluids. Flowmeters generally utilize moveable float members in the fluid flow stream for the measurement of pressure drops across an orifice in the fluid flow stream. These flowmeters generally have electrical circuits and readouts that provide highly accurate measurements of flow rates. Due to their complexity, reliability and maintenance are issues, as is cost. A mechanically simple and highly reliable flowmeter utilizes an upright tube that allows for visual gauging of volumetric flow rates through the monitoring of marked indicia on the sight flow tube itself, or other connection means. The sight tube will have a pair of fittings at each end of the sight tube for connection to and insertion into a fluid flow circuit. A “float” is denser than the fluid being measured, is visible through the sight tube, and rises up the tube as the flow rate increases. The flow rate is visually indicated by the position of the float in the sight tube. Typical floats are generally shaped as balls, spherical objects, and other non-elongate members designed to move freely in the sight tube or to be guided along a guide rod securely mounted within the sight tube. Such conventional float designs generally function sufficiently in measuring medium to high fluid flow rates through a flowmeter. However, in certain industries, such as semi-conductor processing, low and ultra-low fluid flow rates are often required during processing. The measurement of these reduced flow rates through a fluid flowmeter must be accurately indicated to ensure processing efficiency and precision.  
         [0004]     Even known float assemblies in the industry having a generally elongate float, which are designed to meter low fluid flow rates, are deficient. Referring to  FIG. 2  in particular, a prior art flowmeter  210  having a tapered elongate float  217  and sight tube  212  system is utilized wherein the float  217  is guided through guides  214 ,  216 . This system is intended to meter low fluid flow rates. The float  217  comprises a tapered section  218  that ends approximately central to the float  217  at a ledge  222 . Lateral float movement is controlled with the use of bottom guides  216  and top guides  214 . The taper of the float  217  increases from one end proximate the guides  216  to the ledge  222 . As the float  217  is forceably moved upward with fluid pressure through the sight tube  212 , it progresses upward until the ledge  222  engages the top guides  214 . With a reduction in fluid flow, the float  217  returns downward until being stopped by the tapering effect of the tapered section  218 . Such a system has an innate drawback in that stopping of the float  217  with the tapered section  218  within the bore or channel of guides  216  can cause an undesirable wedging effect. This innate characteristic is particularly unacceptable when measuring low flow rates. Namely, the tapered section  218  can become measurably stuck within the guides  216  such that a higher level of flow is required to initiate forceable movement of the float  217  within the tube  212 . Since low flow rates are the focus of such a flowmeter, this can serve to decrease reliability and accuracy, especially for the periods of fluid flow prior to dislodging of the wedged float  217 . In fact, this may completely prevent fluid flow metering for ultra-low fluid flows through the flowmeter  210 .  
         [0005]     In the processing of semi-conductor wafers into integrated circuits, highly corrosive, ultra-pure fluids, such as hydrochloric, sulfuric and hydrofluoric acid, are in extreme temperature ranges and are utilized. These fluids not only damage traditional flowmeter materials, but they additionally impose significant health risks for personnel exposed to the fluids during the manufacturing process. Moreover, the equipment and materials in contact with these ultra-pure fluids must not contaminate or add impurities to the fluids.  
         [0006]     Thus, semi-conductor processing applications require flowmeter construction providing accurate fluid flow measurements at varying fluid flow rates, while at the same time utilizing highly inert materials that withstand the potential damaging effects of these corrosive fluids, that do not contaminate the fluids, and that tolerate the broad temperature ranges. Moreover, the design of such flowmeters must minimize fluid leakage pathways.  
         [0007]     Prior art flowmeters have addressed the problems associated with the use of corrosive fluids in flowmeters by using highly inert corrosive-resistant plastics in the construction of components of the flowmeters. Fluoropolymers such as perfluoroalkoxy resins (PFA), polytetrafluoroethylenes (PTFE), and ethylenetetrafluoroethylenes (ETFE) are plastics that are suitable for use with these corrosive fluids. The translucent-transparency characteristics of thin-walled PFA is typically utilized in the construction of the sight tube of these flowmeters.  
         [0008]     U.S. Pat. No. 5,672,832 (the &#39;832 patent) is an example of a flowmeter device where fluoropolymers are utilized. This specific device discloses a fluoropolymer housing flowmeter that places two cavities in the flow tube region where pressure sensors are placed for accurately measuring fluid flow rates. The rectangular housing and cover for this invention are constructed of non-translucent PTFE and the cover is mounted to the housing with screws, with a gasket positioned in between the two in an attempt to minimize fluid leakage.  
         [0009]     U.S. Pat. Nos. 5,078,004, 5,381,826, and 5,549,277 are examples of fluoropolymer flowmeters utilizing sight tubes where a limited portion of the flowmeter is made of PFA material. In such flowmeters, the centrally located sight tube can be machined from PFA, with additional fitting components machined from PTFE, or other non-translucent materials, which are connected directly to the ends of the sight tube, or connected in series with those parts that do have a direct association with the PFA sight tube. Generally, each of these components are attached to each other and/or the sight tube via threaded portions.  
         [0010]     These currently available fluoropolymer flowmeter devices, whether they be conventional sight tube flowmeters or other flowmeters, contain disadvantages centering mainly around the materials used and the methods of assembly.  
         [0011]     Generally fluoropolymers, particularly PTFE, are not conducive to injection molding processes. As a result, in the known commercial sight tube fluoropolymer flowmeters, such as the device shown in  FIG. 1 , each component is machined to obtain the desired shapes, tolerances, and the requisite threaded connections. Machining adds very significant labor costs to the production of the devices and, to the extent possible, should be avoided. Moreover, multi-component flowmeter assemblies utilizing threaded portions present potential fluid leakage pathways. The possibility of fluid leakage is increased with each non-unitary connection between components. For instance, in  FIG. 1 , the flowmeter  200  includes at least a first fitting  202 , and a second fitting  204  that are threadably attached, at threaded portions  208 , to the tapered sight tube  206 , thus increasing the potential for unacceptable leakage. Further, the sight tube  206  is likely constructed of translucent PFA, while the fittings  202 ,  204  are constructed of a material such as PTFE.  
         [0012]     Ideally, flowmeters, particularly those utilized in handling corrosive-caustic fluids, should have a minimum number of non-unitary connections that do utilize the process of threadingly joining molded flowmeter components, namely the fittings to the sight tube.  
         [0013]     The manufacturing process for the so-called unitary-bodied flowmeters constructed of conventional plastics generally involves the affixation of a plug or cap to a body portion. The affixation processes known for these conventional plastic sight tube flowmeters involve adhesive bonding and ultrasonic welding. Ultrasonic welding involves vibrating or oscillating a first plastic component with respect to a second plastic component that it is in engagement with the first plastic component. Such welding is not effective for joining tubular end portions. Moreover, due to the “slippery” nature of fluoropolymers, forms of vibrating or oscillating bonding is not realistic. Similarly, adhesives do not work on fluoropolymers, and would only add potential contaminants which must be avoided in semi-conductor processing applications.  
         [0014]     Although PFA is substantially more expensive then PTFE (perhaps 10-15 times as expensive) it is considered to have great advantages over PTFE. Namely, PFA is cleaner, providing less contaminants than PTFE. Further, and unlike PTFE, PFA can be injection molded and homogeneously joined with like materials.  
         [0015]     Homogeneously joining by welding separate fluoropolymers components, such as PTFE, is essentially impossible. In comparison, PFA components may be welded together utilizing non-contact heating as disclosed in U.S. Pat. No. 4,929,293, assigned to Fluoroware, Inc., also the owner of the instant application. It is believed that these welding techniques have never, before this invention, been utilized in association with the manufacture of a fluoropolymer flowmeter.  
         [0016]     All of the discussed prior art falls short of adequately addressing the unique accuracy, purity, and low fluid flow needs of the semi-conductor processing industry. The prior art does not address the need for coupling the benefits PFA offers in resisting corrosion with the advantages a unitary-bodied component construction advances with regard to leakage prevention and reduced manufacturing and assembly costs.  
       SUMMARY OF THE INVENTION  
       [0017]     The embodiments of the flowmeter of the present invention substantially solve the problems innately present with conventional fluid flowmeters. These needs are addressed by introducing a corrosive-resistant flowmeter made of a material such as PFA where reliability and effectiveness are increased while manufacturing costs can be reduced in one embodiment by utilizing a unitary-bodied component construction. Further, the a functional component design that enables accurate and efficient readings and indications of reduced fluid flow rates.  
         [0018]     In one embodiment, a sight tube flowmeter is formed of a plurality of fluoropolymer components welded together to form a unitary flowmeter body. The components can comprise a PFA upright sight tube having two end portions, a flow conduit extending therethrough and two fitting portions that are uniquely welded onto each end of the sight tube, and a fluoropolymer float device movable to various positions within the flow conduit depending on the flow level of the fluid flowing therethrough. The float device can be of conventional design or for those flowmeter embodiments where low fluid flow rates are to be measured, an elongate float can be utilized. The floats and, in particular, a designated portion thereof, are visible through the sight tube to provide visual indication of the position, and thus the flow rate of fluid flowing through the flowmeter. In addition, alternative embodiments include the implementation of the unique sight tube and elongate float design in conventional flowmeters not having a unitary-bodied configuration.  
         [0019]     At least one of the fittings may include a valve assembly to control the flow rate of the fluid. The invention also includes the process of manufacturing the flowmeter, in particular the steps of injection molding PFA components and welding the PFA components to form a unitary flowmeter body. In one embodiment of the process the components are welded using a noncontact heater to melt the PFA portions to be welded, wherein the portions are then brought into contact with each other and held until the PFA cools and solidifies. A curing step involving baking at least one of the PFA flowmeter components on a jig, may also be added.  
         [0020]     A feature and advantage of an embodiment of the invention is that the entire flowmeter body can be of a unitary construction. Threaded connections between the sight tube and the sight tube end connections are eliminated. This minimizes potential leakage pathways, lessens potential hazards to personnel, and lowers manufacturing costs.  
         [0021]     A further feature and advantage of an embodiment of the invention is that machining of component parts of the flowmeter is substantially, or even entirely, eliminated. This, in turn, can lower labor and manufacturing costs, and the end cost of the flowmeter.  
         [0022]     Yet another feature and advantage of an embodiment of the invention is that the body is manufactured entirely of PFA which is cleaner and exposes the metering process to less contamination. This is essential in the semiconductor processing field.  
         [0023]     Still another feature and advantage of an embodiment of the invention is that the entire body can be measurably translucent. Translucent characteristics provide for increased visibility of the component positions such as a valve member and float, and provide increased visibility of any contaminants that may be present within any portion of the flowmeter.  
         [0024]     A further feature and advantage of an embodiment of the invention is that it can be an injection molded flowmeter that is inert and chemically resistant to the chemicals utilized in semiconductor wafer processing.  
         [0025]     Yet another feature and advantage of an embodiment of the invention is that the design of the elongate float coupled with the shape and construction of the conduit within the sight tube cam permit an increase in metering accuracy for low and ultra-low fluid flow rates through the flowmeter.  
         [0026]     Another feature and advantage of an embodiment of the invention is that the sight tube and elongate float design of the present invention can be implemented in those conventional flowmeters that are not unitary-bodied to increase measurement of low and ultra-low fluid flow rates.  
         [0027]     Still another feature and advantage of an embodiment of the invention is that the welding of multiple components or parts together to form a unitary-bodied flowmeter can increase the possibilities and efficiencies of adjusting and modifying the structural configuration of the three main weldable components of the flowmeter. Modifications can be efficiently focused on only those components where it is needed such that molding and manufacturing processes for the entire flowmeter are not unnecessarily disrupted or altered. For instance, design and functional changes can be narrowly directed to the sight tube and float assembly if desired. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]      FIG. 1  is a view of a prior art flowmeter;  
         [0029]      FIG. 2  is cross-sectional view of a prior art float assembly employed in a prior art flowmeter;  
         [0030]      FIG. 3  is a cross-sectional view of one embodiment of a unitary-bodied fluoropolymer flowmeter in accordance with the present invention;  
         [0031]      FIG. 4  is a cross-sectional view of one embodiment of a valveless unitary-bodied fluoropolymer flowmeter in accordance with the present invention;  
         [0032]      FIG. 5  is a side view of one embodiment of a valveless unitary-bodied fluoropolymer flowmeter in accordance with the present invention;  
         [0033]      FIG. 6  is a an exploded view of one embodiment of a unitary-bodied fluoropolymer flowmeter in accordance with the present invention;  
         [0034]      FIG. 7  is a cross-sectional view of one embodiment of a unitary-bodied fluoropolymer flowmeter in accordance with the present invention;  
         [0035]      FIG. 8  is a cross-sectional view of one embodiment of a unitary-bodied fluoropolymer flowmeter in accordance with the present invention;  
         [0036]      FIG. 9  is a cross-sectional view of one embodiment of a unitary-bodied fluoropolymer flowmeter in accordance with the present invention;  
         [0037]      FIG. 10  is an exploded view of one embodiment of a unitary-bodied fluoropolymer flowmeter in accordance with the present invention;  
         [0038]      FIG. 11  is a view of a mold for injection molding fluoropolymer flowmeter components;  
         [0039]      FIG. 12  is a schematic view illustrating baking an injection-molded fluoropolymer component;  
         [0040]      FIG. 13  illustrates an apparatus for non-contact welding fluoropolymer components;  
         [0041]      FIG. 14  is a perspective view of a fluid flow rate calibration jig;  
         [0042]      FIG. 15  is a perspective view of a fluid flow rate calibration jig. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0043]      FIG. 3  shows one embodiment of a unitary-bodied flowmeter  12  in accordance with the present invention. The flowmeter can be a welded assembly of injection molded fluoropolymer plastic components, generally PFA components or fluoropolymers having translucent qualities, wherein at least two of the three main body components are joined through a compactable welding process. Other fluoropolymer plastics are also envisioned for component and part use in the flowmeters in accordance with the present invention. For example, but not for limiting purposes, PTFE, ETFE, and other plastics are envisioned. The translucent characteristics of the preferred fluoropolymers can vary in the degree to which it is translucent, such that translucent characteristics permit gauging of a float device within the sight tube, as will be discussed in detail herein.  
         [0044]     Referring to  FIGS. 3-10 , flowmeter  10  generally comprises the joining of at least two of three main body components into a unitary flowmeter body  12 . Unitary-bodied can mean the joining two of the three main body components to the third component through a weldment bond (discussed herein) such that two of components are initially molded as one piece. For instance, one molded piece could comprise of the second fitting  18  and sight tube  16 , with the first fitting  14  being later welded or otherwise joined with the available end of the sight tube  16 . It is preferred that at least one of the three main body components is constructed of a translucent fluoropolymer for preferred embodiments.  
         [0045]     The three main body components are first fitting  14 , sight tube  16 , and second fitting  18 . Once each component is positionally joined to properly form the unitary flowmeter body  12 , as will be explained in detail, body conduit  20  is formed which provides a flow channel beginning with and running through first fitting  14 , continuing through sight tube  16 , and running through and out of the end of second fitting  18 .  
         [0046]     First fitting  14  generally comprises an entering end  22  and an exiting end  24 . In one embodiment, these ends  22 ,  24  are generally in a perpendicular relationship to each other. A first fitting conduit  26  defines an inner bore of some diameter within first fitting  14 , traveling along the longitudinal axis of first fitting  14  for the entire distance beginning with entering end  22  and ending with exiting end  24 . First fitting conduit  26  results in first fitting openings  28  at each end  22 ,  24  of first fitting  14 . Known fittings, connectors, and other devices known to one skilled in the art for connecting to sight tubes and other components of flowmeters are envisioned for first fitting  14 .  
         [0047]     In one embodiment, as shown in  FIGS. 3-4 , sight tube  16  comprises a generally cylindrical tube with first fitting end  30  and second fitting end  32 . The sight tube  16  has a tube conduit  34  running through it so that an inner bore of some diameter generally larger than the inner diameters of first fitting conduit  26  and second fitting conduit  52  is defined. Tube conduit  34  traverses the longitudinal axis of sight tube  16  for the entire distance of sight tube  16  so that sight tube openings  42  are formed at each of the ends  30 ,  32 . The diameter of tube conduit  34  can gradually taper the distance of the tube conduit  34 . It is preferred that the diameter at second fitting end  32  is larger than the diameter at first fitting end  30 . While preferred embodiments are generally cylindrical with visual gauging characteristics, other shapes and constructions for the tube  16  are envisioned without deviating from the unitary characteristic of the flowmeter in accordance with the embodiments of the present invention.  
         [0048]     As shown in  FIGS. 5-6 , the outer surface of sight tube  16  can comprise flow indicia  44 . This flow indicia  44  generally consists of molded or etched marks depicting specific volumetric flow rate information for use in visual gauging.  
         [0049]     In another embodiment, as shown in  FIGS. 7-9 , sight tube  16  can comprise a generally hourglass-shaped tube with a first fitting end  30 , and second fitting end  32 . Sight tube  16  has a tube conduit  34  running through it to permit fluid flow communication between the first fitting  14  and the second fitting  18 . The conduit  34  is generally divided into three fluid flow channels or conduits: an entry conduit  36 , an exit conduit  38 , and an intermediate narrowed channel  40 . The portion proximate the center of the hourglass sight tube  16  and the inner tube conduit  34  defines a division between the entry conduit  36  and the exit conduit  38  and defines the intermediate narrowed channel  40 . The intermediate narrowed channel  40  serves as the communication channel between the conduits  36 ,  38  and is some size smaller in diameter and cross-section than conduits  36 ,  38 . Preferably, the diameter of entry conduit  36  gradually tapers such that the diameter at the portion of the conduit  36  proximate the first fitting end  30  is larger than the diameter proximate the intermediate channel  40 . The diameter of the exit conduit  38  is substantially consistent along its length, with only a diameter increase or tapered effect at the end  32 ,  38  connectable to and in communication with the second fitting  18 . Similarly, the diameter or cross-section of intermediate channel  40  is generally consistent along its entire length, but could be varied. Tube conduit  34  traverses the longitudinal axis of sight tube  16  for the entire distance of sight tube  16  through conduit/channels  36 ,  38 ,  40  such that a continuous fluid flow path is established and sight tube openings  42  are formed at each of the ends  36 ,  38 .  
         [0050]     As best shown in  FIG. 10 , the outer surface of the hour-glass shaped sight tube  16  also comprises flow indicia  44 . This flow indicia  44  generally consists of molded or etched marks depicting specific volumetric flow rate information for use in visual gauging.  
         [0051]     For each of the preferred embodiments, second fitting  18  generally takes the form of a T-shaped fitting comprising entering end  46 , exiting end  48 , and valve end  50 . Entering end  46  is generally perpendicular to exiting end  48  and valve end  50  with exiting end  48  and valve end  50  sharing a common linear plane, with the shared linear plane intersecting the linear plane of entering end  46  so that the longitudinal axis of entering end  46  is nearly positioned at the center of the distance between the far ends  48 ,  50 . Second fitting  18  has a second fitting conduit  52  traversing the longitudinal axis of second fitting  18  so that an inner bore of some diameter is defined. Second fitting conduit  52  traverses the entire distance of entering end  46 , exiting end  48 , and valve end  50  so that second fitting conduit  52  begins at entering end  46  and traverses toward the herein described plane intersection where it opens into and is one continuous shared channel with the portion of second fitting conduit  52  traversing the entire distance between exiting end  48  and valve end  50 . Known fittings, connectors, and other devices known to one skilled in the art for connecting to sight tubes and other components of flowmeters are envisioned for first fitting  14 . In certain embodiments, such as the flowmeters shown in  FIGS. 4-5 , regardless of the sight tube and float assembly configurations, the flowmeter  10  can be constructed without a valve device.  
         [0052]     In those embodiments having a valve device, second fitting conduit  52  at valve end  50  can define valve member opening  54 . Valve member opening  54  can be internally threaded some distance from valve end  50  inward toward exiting end  48 . This threading is designed for receiving a threaded valve assembly  56 . Such valve devices are best shown in  FIGS. 3 , and  6 - 9 .  
         [0053]     Valve assembly  56  comprises valve shaft  58 , and valve top portion  60 . Valve shaft  58  comprises a first end portion  62 , a valve member  64 , and can have a threaded portion  66 . Valve top portion  60  affixes to the first end  62  via a valve aperture  68  in valve top portion  60  which traverses some longitudinal distance not equal to the entire length of the valve top portion  60 . In an embodiment having external threading, threaded portion  66  is capable of threadably engaging internal threading in second fitting  18  such that the assembly  56 , and particularly the valve member  64 , can be adjustably moved in and out of the opening  54 . Other means of moving such a valve member  64  in and out of such an opening known to one skilled in the art are also envisioned.  
         [0054]     The valve member  64  portion can include a valve needle protrusion  70  or extension shaped for insertion in and out of compatible area of the opening  54  with the relative linear movement of the valve assembly  56 . The valve needle  70  can be tapered or non-tapered, depending on the sealing performance desired, and the particular manufacturing requirements or limitations.  
         [0055]     Generally, in those flowmeters  10  utilizing a valve assembly, valve top portion  60  is affixed to valve shaft  58  via a snapping means, as shown best in  FIGS. 3 , and  7 - 9 . The snapping means comprises the valve shaft  58 , valve shaft groove  72 , valve top portion  60 , and valve top groove  74 . Valve shaft groove  72  is located distal the valve needle  70  end of the shaft  58 , begins some distance inward from the end opposite to the valve needle  70  end, and travels the entire outer circumference of the shaft with the recess of valve shaft groove  72  recessed into the shaft  58  some distance. Valve top groove  74  is located at the end of valve aperture  68  and is designed to receive valve shaft groove  72  of valve shaft  58  so that the valve shaft  58  and valve top portion  60  become interlocked in a rotationally limiting manner.  
         [0056]     Alternative embodiments can use other means of affixing valve top portion  60  to the valve shaft  58 . These alternative embodiments can include fasteners such as screws or bolts. Single piece molding of valve top portion and valve shaft portion together is also an available embodiment. As stated, yet other embodiments can exclude any valve assembly at all.  
         [0057]     Various known or inventive float assemblies can be employed with the flowmeter of the present invention. For instance, a spherical float or an elongate float and corresponding assemblies can be employed without deviating from the spirit and scope of the present invention.  
         [0058]     For those flowmeter embodiments utilizing a spherical float  78 , as shown in  FIGS. 3-6 , float assembly  76  is contained within sight tube  16 . Such a float assembly  76  comprises spherical float  78 , guide rod  79 , and resting apertures  81 . Spherical float  78  further comprises a float bore  83  that intersects substantially the center of float  78  and defines the receiving channel for insertion of the guide rod  79 . The diameter of float bore  83  is some size larger than the outside diameter of guide rod  79 . Guide rod  79  is generally a small diameter cylindrical rod with a first and second end. The outside diameter of guide rod  79  is significantly smaller than the diameter of tube conduit  34 . Guide rod  79  centrally traverses the entire distance of the tube conduit  34  of sight tube  16 , traversing completely through float bore  83 . Guide rod  79  is rested securely in its final assembled position when the first and second ends of guide rod  79  travel into and rest within resting apertures  81 . Resting apertures  81  can be located within an area inside the first fitting conduit  26  and second fitting conduit  52 . The inside diameter of resting apertures  81  are some size larger than the outside diameter of guide rod  79  so that selective insertion and removal of guide rod  79  from resting apertures  81  is possible.  
         [0059]     For those flowmeter embodiments utilizing an elongate float  80 , referring primarily to  FIGS. 7-10 , float assembly  76  is within sight tube  16  at the completed assembly of flowmeter  10 . Float assembly  76  generally comprises an elongate float  80 , and at least one float guide stop  84 . The float  80  preferably has a circular cross-section, but can also take on a myriad of other shapes, such as triangular, rectangular, oval, variations thereof, and the like. The elongate float  80  is preferably tapered for some length of the float  80 . Generally, the float  80  is tapered such that the diameter or cross-section of the float  80  gradually increases until it reaches an integrated float flange  82 . The flange can have bores, notches, or like features to enable fluid flow through a portion of the flange  82  to control the movement sensitivity of the float  80 . While the flange  82  is generally cylindrical, it can take on various other shapes as well. In one embodiment the flange  82  is located at an end of the float  80 , as shown in  FIGS. 8-10 . In another embodiment, the flange  82  is located proximate the center portion of the float  80 , but can be located anywhere along the length of the float  80 , as shown in  FIG. 7 . The outside diameter, or the cross-section, of the float  80  at the widest or largest portion is substantially smaller than that of either conduit  36 ,  38  but is minimally smaller than the width or cross-section of channel  40 .  
         [0060]     The float guider  84  can take the form of at least one guide  86  and/or at least one guide stop  88 . The guides  86  can be rectangular, oval, circular, spherical or a myriad of other shapes. The guides  86  can include a plurality of bores to permit fluid flow, as shown in  FIG. 10 . The guide stops  88  are preferably of a T-shaped cross-section and can also include a plurality of guide stop bores  92  to permit fluid flow, as best shown in the cross-section view of  FIG. 9 . The T-shaped form is substantially defined by the extension of a guide stop protrusion  94 . The stop protrusion  94  can be of varying lengths.  FIG. 9  shows an embodiment implementing a relatively long stop protrusion  94 . Mounting needs and locations for the guide stops  88  and a litany of other factors will influence the length. A receiving bore  96  is generally included which is some size larger than the diameter of the portion of the float  80  it is designed to receive. The receiving bore  96  generally traverses the longitudinal axis of the stop protrusion  94  to completely penetrate the guide stop  88 . The diameter of the stop protrusion  94  is generally smaller than the diameter or cross-section of the flange  82  such that contact or abutment of the flange  82  against the proximate end of the stop protrusion  94  will limit the upward movement of the float  80  within exit conduit  38 .  
         [0061]     In one embodiment, as shown best in  FIGS. 8-9 , there are a plurality of float guiders  84  within the sight tube  16 . In particular, two guides  86  having a guide bore  90  are fixed within the entry conduit  36 , and a single guide stop  88 , with or without a protrusion  94 , is fixed within the exit conduit  38 . Both guide/stops  86 ,  88  can be fixed at the end of the corresponding conduits  36 ,  38 , or fixed some distance inward of the ends  30 ,  32 . Alternatively, there can simply be one guide  86 , with at least one bore shaped and located such that it is capable of receiving the float  80  and restricting lateral movement in much the same manner as if two guides were implemented. The flange  82  is preferably located at a region proximate one end of the float  80  with such an embodiment, with said end of the float  80  being greater in cross-section or diameter than the distal end. The largest diameter cross-section of the float  80  at the tapered end is still some size smaller than the diameter of channel  40  to facilitate free movement through the channel  40 . The diameter or cross-section of the flange is larger than that of the proximate portion of the float  80  to limit upward movement against the stop  88 , and the protrusion  94  in particular.  
         [0062]     If there are a plurality of guides  86 , then they are fixedly spaced some distance from each other such that a guide channel  98  is created. The portion of the float  80  traveling within this channel distance is small enough so that it can move freely without binding or wedging, while at the same time limiting lateral movement of the float  80  within the entry conduit  36 .  
         [0063]     In another embodiment, as best shown in  FIG. 7 , a single guide stop  88  is utilized and fixed within the exit conduit  38 . Movement of the float  80  is significantly limited to a region within conduit  38 , and thus lateral movement within conduit  36  is not a concern, and a guide  86  may not be needed. Accordingly, the flange  82  is located some distance along the float  80  away from the ends. Preferably, the flange  82  is proximate the center region of the float  80  in such an embodiment. At a lower region of the float  80 , the tapering gets smaller as it moves away from the flange  82 , while the cross-section of the float  80  remains substantially constant for the region approaching the opposite end or upper region above the flange  82 . The tapered end below the flange  82  at its largest diameter is still some size smaller than the diameter of channel  40 . The non-tapered end of the float  80  in this embodiment is generally sized smaller than the receiving bore  96  of the guide stop  88  and can be moved in and out of the bore until stopped by contact with the flange  82  against the guide stop protrusion  94 .  
         [0064]     While the elongate float  80  described herein has been described with a unitary-bodied flowmeter, the elongate float and sight tube components and configurations detailed are also envisioned for use with conventional flowmeters.  
         [0065]     Referring generally to the processes shown in  FIGS. 11-13 , a process of manufacture of one embodiment of the unitary-bodied flowmeter in accordance with the present invention involves the following steps: first, designated PFA, or similarly at least translucent fluropolymer, components used in the manufacturing of the flowmeter  10  are injection molded in a mold  100  with a retractable insert  102 . This injection molding process permits the construction and shaping of thin PFA tubular components in order to achieve the desired result with regard to component translucence, which is particularly important with respect to the sight tube  16 . Each of the three body components  14 ,  16 ,  18  can be molded separately to be welded as described herein, or at least two of the components can be molded as a single component to be welded with the final component.  
         [0066]     Following the injection molding process, each designated PFA component is baked in an oven  103  at a temperature range of approximately 300° F. to 500° F., forming the PFA components into their final sizes and construction for joining to form the final unitary-bodied flowmeter  10 . The PFA components can shrink substantially during the baking process. This injection molding and baking can be adjusted greatly with various jigs and other manufacturing processes and tools. As stated, various component configurations and combinations can be implemented. Further, component  14 ,  16 ,  18  shapes and sizes can be altered or re-designed while still leaving the remaining components untouched. This allows focused re-configuration to reduce manufacturing costs. For instance, if the manufacturer is desirous of changing only the configuration of the sight tube  16 , such a change can be made without altering the configurations of the fittings  14 ,  18 .  
         [0067]     Referring to  FIG. 13 , once the components have been properly injection molded and baked, final joining of the components into a unitary-bodied fluoropolymer flowmeter  10  is possible. Generally, at least two of the three main body components,  14 ,  16 ,  18  are non-contact welded together creating a weldment bond  104 . For instance, first fitting end  30  of sight tube  16  can be non-contact welded to exiting end  24  of first fitting  14 , creating a weldment bond  100 . Further, second fitting end  32  of sight tube  16  can be non-contact welded to entering end  46  of second fitting  18 . Details of such non-contact welding are found in U.S. Pat. No. 4,929,293 which is incorporated herein by reference. In addition, other non-contaminating techniques and methods of bonding the fluoropolymer components known to one skilled in the art can be employed as well.  
         [0068]     Referring primarily to  FIGS. 13-14 , the non-contact welding and manufacturing process for one spherical float  78  embodiment is shown. Float assembly  76  for the spherical float  78  embodiment is calibrated prior to the joining or welding of second fitting  18  to a previously joined assembly of first fitting  14  and sight tube  16 . Spherical float  78  is positioned in the juncture of first fitting  14  and sight tube  16  so that float  78  rests at the resting aperture  81  integral to first fitting conduit  26 . A calibration guide rod  112  is positioned through the float into the guide rod aperture  81  of first fitting  14  so that it extends upwardly. A calibration fitting  114  engages the top opening of sight tube  16 . The calibration guide rod  112  is received by the fitting  114 . The calibration fitting  114  is temporarily sealingly attached to sight tube  16  and is removed upon completion of the calibration process.  
         [0069]     Fluid, typically water, is forced into entering end  22  of first fitting  14 , traveling through first fitting conduit  26  and into the tube conduit  34  of sight tube  16  where it forces float  78  up guide rod  112  some distance depending on the applied flow rate. Spherical float  78  is replaced with others of different size, shape, or weight until the desired flow readings are obtained consistent with actual flow rates provided by calibration circulator  106 .  
         [0070]     Once calibration readings are ideal, the calibration fixture  114  and guide rod  112  are removed, guide rod  79  is inserted through aperture  81  in place of the calibration guide rod  112 , and aperture  81  is sealed by heating and pinching the boss  110 .  
         [0071]     Referring primarily to  FIGS. 13 and 15 , the non-contact welding and manufacturing process for an elongate float  80  embodiment is shown. Assembly  76  is generally calibrated prior to the joining of second fitting  18  to the already joined assembly of first fitting  14  and sight tube  16 .  
         [0072]     Fluid, typically water, is forced into entering end  22  of first fitting  14 , traveling through first fitting  14  and into sight tube  16  where it forces float  80  up body conduit  20 . Float  80  is replaced with others of different size, shape, or weight until the desired flow readings are obtained consistent with actual flow rates provided by calibration circulator  106 . Various low and ultra-low rates can be easily metered with such precision calibration. Once calibration readings are ideal, the calibration fixture is removed. In addition, aperture  108  is generally sealed by heating and pinching the boss  110 .  
         [0073]     With calibration complete, on either float assembly embodiments, the next step generally consists of joining second fitting  18  and sight tube  16  by non-contact welding second fitting end  32  of sight tube  16  to entering end  48  of second fitting  18 . However, as stated herein, it is envisioned that non-contact welding could be implemented to attach or bond only two of the three main body components  14 ,  16 ,  18 . Completion of the assembly and calibration processes results in the final flowmeter body  12  assembly with body conduit  20  consisting of a continuous flow channel beginning with entering end  22  of first fitting  14 , continuing through sight tube  16 , and running through and out of exiting end  48  opening of second fitting  18 .  
         [0074]     During operation of the flowmeter  10  having a generally elongate float  80 , fluid is introduced into entering end  22  of first fitting  14 . As the fluid traverses through the conduit  26  into conduit  34  it puts anti-gravitational pressure on float  80 , which has a gravitational bias. The vertical force of the fluid consequently moves float  80  upward closer to second fitting  18 . In preferred elongate float embodiments having a flange, the flange  82  begins in an initial seat or rest position against the region where the upper portion of channel  40  and the lower portion of conduit  38  join. In this initial seated position, the flange  82  substantially closes off fluid communication through channel  40 , and thus measurably restricts fluid from entering into conduit  38  from conduit  36 . In conventional flowmeter float designs, a relatively significant amount of vertical fluid force is needed to counter the gravitational bias of the float. In the present invention, however, the fluid flow required to move the float  80  is significantly reduced. This is possible because of the initial closed position of the flange  82  against the channel  40  and the narrowing distance provided by the narrow channel  40 . Fluid force builds up rather easily behind the flange  82  since there is substantially no room between the float  80  and the proximate walls of the channel  40 . This reduced fluid travel space coupled with the inability of the fluid to travel past the blockage created by the flange  82  creates a highly sensitive configuration where fluid metering of low fluid flow is possible. Fluid pressure behind the flange  82  and channel  40  is easily created despite low or ultra low fluid flows.  
         [0075]     As the low flowing fluid builds up within the channel  40  and against the flange  82 , the float  80  will move correspondingly. Because of the relative narrowness of the channel  40 , and the reduced size of conduit  38  in comparison to conduit  36 , fluid pressure on the float  80  will continue despite consistent low or ultra-low fluid flow rates within the body conduit  20  even after the flange  82  has moved some distance upward beyond its initial seated position against the opening of channel  40 . Once the vertical force of the fluid is equal to that of the gravitational bias of float  80 , vertical movement will stabilize. If not, movement of the float  80  upward will continue until the flange  82  abuts the guide stop  88 , or protrusion  94 . The distance between the flange  82  in its resting position, and the protrusion  94  can be adjusted by altering the length of the conduit  38 , adjusting the length of the protrusion  94 , the fixed location of the guide stop  88 , and like techniques and configurations. Indications of the fluid flow rates can be measured by metering a portion of the float  80  against the marked or etched indicia  44  on the sight tube  16 . Preferably, flow rates can be measured according to the alignment of the flange  82  in relationship to the indicia  44 . Needed adjustments to fluid flow rates can be made based on the obtained flow readings.  
         [0076]     During operation of the flowmeter  10  employing a generally spherical float  78 , fluid is introduced into entering end  22  of first fitting  14 . As the fluid traverses through the body conduit  20  into tube conduit  34  it puts and anti-gravitational pressure on float  78  which has a gravitational bias. The vertical force of the fluid consequently moves float  78  along guide rod  79 , moving float  78  closer to second fitting  18 . Once the vertical force of the fluid is equal to that of the gravitational bias of float  78 , vertical movement will stabilize. Flow rate readings during this stabilization period can be made according to flow indicia  44 . Needed adjustments to fluid flow rates can be made based on the obtained flow readings.  
         [0077]     Although the invention hereof has been described by way of example of preferred embodiment, it will be evident that other adaptations and modifications may be employed without departing from the spirit and scope thereof. The terms and expressions employed herein have been used as terms of description and not of limitation; there is no intent of excluding equivalents and it is intended that the description cover any and all equivalents that may be employed without departing from the spirit and scope of the invention.