Abstract:
A flowmeter of the thermal type, having a heated flow-sensing element and a temperature-sensing reference element, the elements constructed and arranged to be installed in a pressurized pipe. The flowmeter has one probe with the heated element and a separate second probe with the reference element. The probes are constructed and arranged to pass through the pipe wall in separate through-holes. There is a mounting structure such as a split ring that is adapted to be mounted to the pipe. Two valves operatively coupled to separate locations of the mounting structure, where one probe passes through each valve and into the pipe.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation in part of and claims priority of application Ser. No. 13/916,119, filed on Jun. 12, 2013, which itself claims priority of two Provisional patent applications: application Ser. No. 61/715,904, filed on Oct. 19, 2012, and application Ser. No. 61/722,833 filed on Nov. 6, 2012. The disclosures of these three applications are incorporated herein by reference. 
     
    
     FIELD 
       [0002]    A thermal flowmeter designed for easy installation in a pressurized compressed-air pipe. 
       BACKGROUND 
       [0003]    Thermal flowmeters operate on the well-known thermal principal by which one element is heated and maintained warmer than a second element; the amount of heat required to maintain the temperature difference is a measure of the fluid mass velocity. The two elements are normally built into a single probe. When the flowmeter is to be installed into a pressurized pipe, the probe is inserted through a valve into the pipe. The probe has a relatively large diameter and so a large hole, typically ⅝ inch in diameter or larger, must be drilled in the pipe. The force exerted by the compressed air on a drill entering the pipe is sufficient to require specialized equipment to restrain the drill. 
       SUMMARY 
       [0004]    The subject flowmeter operates on the thermal principal by which one element is heated and maintained warmer than a second element, the amount of heat required to maintain the temperature difference being a measure of the fluid mass velocity. The two elements can be separated and placed in small probes that can be inserted into the pipe through small holes that are easily drilled in the pipe. The flowmeter thus can be installed in a pipe that is in service. 
         [0005]    The currently preferred embodiment of the flowmeter includes a split ring suitable for clamping around a pipe affixed to a mounting plate, two valves contained within the mounting plate, a removable seal plate configured to affix to the mounting plate and seal around the probes, and an assembly including the probes and electronics to measure, report and display flow, that assembly configured to latch to the mounting plate. It may also include a removable drill guide and filter assembly for use during installation. There may be a drill bit having a long shank and a short flute that is used during installation. 
         [0006]    To install this example of the flowmeter on a pipe containing compressed air, the user first clamps the split ring to the pipe, next drills two holes into the pipe through the valves, closing the valves as the user retracts the drill bit, then installs the seal plate to provide seals around the probes when they are installed, and then installs the probe and electronics assembly by inserting the probes through the valves into the pipe and latching the assembly into place. The user then connects power to the meter and it will display flow. 
         [0007]    In another example of the invention, the flowmeter may include a split ring suitable for clamping around a pipe, two valves mounted on the ring, mounting fittings, two probe assemblies, an electronic enclosure that is electrically connected to the probe assemblies and containing electronics to measure, report and display flow, and a removable drill guide and filter assembly for use during installation. There may be a drill bit having a long shank and a short flute that is used during installation. 
         [0008]    To install this example of the flowmeter on a pipe containing compressed air, the user clamps the split ring to the pipe, and then installs each probe by drilling a hole in the pipe through the corresponding valve, partially withdrawing the drill so that chips vent into the filter, closing the valve, and then inserting the probe through the valve and securing it in place. The user then connects power to the meter and it will display flow. 
         [0009]    All examples of the flowmeter may further include a drill guide and filter assembly adapted to be releasably coupled to the mounting fitting. The drill guide and filter assembly may include a drill guide assembly with a longitudinal opening that is adapted to receive a drill bit. The drill guide and filter assembly may further include a filter that is fluidly coupled to the opening at a coupling location. The longitudinal opening may be larger below the coupling location than it is above the coupling location. The flowmeter may further include an O-ring that forms a seal between the mechanical structure and the pipe, where the O-ring is separated from the path of the drill by a solid barrier. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    Other objects, features and examples will occur to those skilled in the art from the following description and the accompanying drawings, in which: 
           [0011]      FIG. 1  is an overall view of one example of a flowmeter mounted on a section of pipe. 
           [0012]      FIG. 2  is an end view, partially in section, showing the probe assemblies inserted through the mounting fittings, the valves and the ring into the pipe. 
           [0013]      FIG. 3  is an enlarged sectional view showing the O-ring gasket surrounding one of the probes and compressed between the ring and the pipe. 
           [0014]      FIG. 4  is a side view of the mounting fitting. 
           [0015]      FIG. 5  is a top view of the probe assembly. 
           [0016]      FIG. 6  is a sectional side view of the probe assembly. 
           [0017]      FIG. 7  is a sectional side view of the drill guide and filter assembly. 
           [0018]      FIG. 8  is an illustration of the relation between the length of the flute of the drill and the dimensions of the other components. 
           [0019]      FIGS. 9A-9E  show the sequence of steps in the installation of the device of  FIG. 1 . 
           [0020]      FIG. 10  is an overall view of a second example of the flowmeter. 
           [0021]      FIG. 11  is an angled view of the base assembly  FIG. 12  is partial section view through the base assembly. 
           [0022]      FIG. 13  is an angled view of one of the valves. 
           [0023]      FIG. 14  is an angled view of one of the latches. 
           [0024]      FIGS. 15A and 15B  are two angled views of the seal plate, showing the top and bottom surfaces. 
           [0025]      FIG. 16  is an angled view of the top assembly. 
           [0026]      FIG. 17  is an angled view of the drill guide assembly. 
           [0027]      FIGS. 18A-18E  show the sequence of steps in installing the second example of the flowmeter. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    The disclosure includes a flowmeter of the thermal type designed for installation in a compressed-air line under pressure. The flowmeter can be used to sense the flow of compressed air. The flowmeter has a heated element and an unheated element. The heated and unheated elements can be in separate probes, and the probes are adapted for insertion through valves into a pipe. Accordingly, the required holes in the pipe are small and the attendant apparatus is compact, facilitating installation and allowing installation in a pipe that is in use carrying compressed air. 
         [0029]      FIG. 1  is an overall view of one example of the disclosed flowmeter  100 . A control enclosure  101  is mounted on a split ring  110  by bracket  103  which can include provisions (not shown) for the enclosure to be rotated to accommodate horizontal or vertical pipes. The control enclosure includes a display  104  and a cable  105  receiving power from an outside source. The control enclosure is connected to probe assemblies  106 ,  107  by cables  108 ,  109 . Split ring  110  clamps to the pipe  102 . 
         [0030]      FIG. 2  is an end view showing the mounting of the probes. An appropriate mechanical mounting structure such as a split ring  110 , typically made of aluminum, is clamped to pipe  102  by cap screws (not shown). The mounting structure could be something other than a split ring, e.g., a metal part affixed to the pipe by a band clamp or another type of clamp. Ball valves  203 ,  204  are threaded into the mounting structure in tapped holes  205 ,  206 . These valves are preferably ⅛-inch pipe size, brass with stainless-steel balls, and with a male thread on one end and a female thread on the other. Other types of valves could be used, e.g., slide valves, plug valves or gate valves. Threaded into the valves are mounting fittings  207 ,  208 , and affixed to these are probe assemblies  106 ,  107 . Optional safety cables  211 ,  212  prevent ejection of the probe assemblies from the meter. 
         [0031]      FIG. 3  is an enlarged sectional detail of the area where one of the probes enters the pipe. The probe  301  exits the male thread  302  at the base of the valve and passes through a close-fitting hole  303  in the ring  110 . This hole constrains the motion of the probe. O-ring  305  in groove  306  forms a seal between the ring and the pipe  102 . A wall of metal  308  separates the O-ring from the hole through which the drill passes to protect the O-ring when the hole in the pipe is being drilled. 
         [0032]      FIG. 4  shows one of the mounting fittings  207  which screw into the tops of the valves. It is typically made of aluminum or brass. It has a pipe thread  309  at its base to fit the thread in the valve, a raised circular portion  402  at the center of its top surface to center the drill guide, two socket head cap screws  403 ,  404  in threaded holes to engage the two parts that will, in succession, mount on it, and a drilled hole (not shown) in its center, slightly larger than the diameter of the drill that will pass through it. 
         [0033]      FIG. 5  is a top view of one of the probe assemblies  106 . The base portion  501 , typically made of aluminum, has a small hole in its center,  502  to receive the probe. Wires  503  from the probe pass through a space  504  at the center of the base portion and exit through one side as a cable  108 . Two curved, slotted holes,  506 ,  507  are shaped to receive the cap screws  403  and  404  in  FIG. 4  when the probe is inserted into the mounting fitting turned at an angle, and to engage them when it is rotated to its normal position. An enlarged-head projection (e.g., a knob)  508  provides for the attachment of a safety cable (not shown) to prevent the probe assembly from being ejected during or after assembly. 
         [0034]      FIG. 6  is a partial sectional view of one probe assembly  106 . It includes the probe  301  whose body is typically a stainless-steel tube, with a thermally-conductive tip  602  containing an RTD (not shown) and surrounded by the tube but exposed at the end. Thermal contact between the tip and the tube is provided by thermally-conductive epoxy, thermally-conductive silicone, or a similar material. Where the probe enters the base piece  603 , it is held in place by epoxy or a similar adhesive (not shown) and surrounded by an O-ring  311  set in a groove  605 . 
         [0035]      FIG. 7  is a sectional view of drill guide and filter assembly  700 . The drill guide portion  710  may be made of aluminum, brass or steel. It has curved, slotted holes  701 ,  702  similar to those in the probe base to engage the cap screws in the mounting fitting. A hole  703  through the long axis of the portion  710  will receive the drill bit, while a circular recess  704  in the base will center it on the mounting fitting. The filter portion  705  is a commercially-available compressed-air muffler that is suitable for filtering particles from the air as well as muffling sound. It typically has a ⅛-inch male pipe-thread connection. It screws into a threaded hole  706  in the drill guide portion and connects to the hole  703  at the center of that portion at location  707 . The diameter of the portion of hole  703  below location  707  is substantially larger than that of the drill bit, providing free passage of air from the flute of the drill to the muffler and space to collect chips from drilling, while the diameter of the portion of hole  703  above location  707  is essentially equal to the diameter of the drill bit, to inhibit the escape of air and metal chips. 
         [0036]      FIG. 8  illustrates the assembly of the parts for drilling and the length of the flute of the drill bit. The drill guide assembly  700  is shown mounted to the mounting fitting  207  which in turn is mounted on the valve  203  and the valve in turn is mounted on the split ring  110 . Drill bit  805  is shown next to these assembled parts for clarity. The parts must be dimensioned so that the tip of the drill  808  can be above the top surface of the ball  809  of the valve  203  while the flute  806  is within the drill guide portion  210 . 
         [0037]      FIGS. 9A-9E  (representing STEP  1  through STEP  5 , respectively) illustrate the process of installing one of the probes in a pipe under pressure. The valve  203  and the mounting fitting  207  are supplied installed in the ring  110 , and are held in place together and to the ring with epoxy, so as to control the depth of insertion of the probes into the pipe which is important to the accuracy of the meter. As shown in  FIG. 9A , the user first securely clamps the ring  110  to the pipe  102  and affixes the drill guide  710  to the mounting fitting  207  and tightens the screws to secure it in place. Then, using drill guide assembly  700  and a long drill bit with a short flute  805 , the user drills the hole in the pipe. (Gloves and full-face protection must be worn during this process.) Once the hole is drilled, air will flow from the inside of the pipe along the drill, through the valve, through the mounting fitting (the hole in which is slightly larger than the drill bit), and through the lower portion of the drill guide (where the hole is substantially larger than the drill bit) and into the filter. This flow of air will reduce the likelihood of chips from the drilling operation entering the pipe. 
         [0038]    As shown in  FIG. 9B , the user next retracts the drill bit to the point at which the top of the flute of the drill bit is within the drill guide. Air will then rush into the filter, taking most of the chips from the drilling operation with it. As shown in  FIG. 9C , the user next withdraws the drill a short additional distance such that the bit is free of the valve, closes the valve via valve handle  215 , removes the drill and removes the drill guide and filter assembly. 
         [0039]    As shown in  FIG. 9D , the user then inserts the probe assembly  106  into the mounting fitting  207 . A safety cable  211  is connected from the split ring to the knob at this time to prevent the probe assembly from being pushed out of the hole by air pressure when the valve is opened. Gripping the probe assembly firmly, the operator then opens the valve, presses the probe the rest of the way through the valve and into the pipe, and rotates the probe assembly in order to engage the screws in the probe base. He then tightens the screws. The installed probe is shown as  FIG. 9E . 
         [0040]    Referring to  FIG. 1 , the user repeats the process for the second probe assembly  107  and connects power to the device through electrical cable  105 . The device will then display flow of compressed air in the pipe. 
         [0041]      FIG. 10  is an overall exploded view of a second example of the disclosed flowmeter  1000  showing its key components separated from each other. This example is the currently preferred embodiment. The base assembly  1010 , consisting of split ring  1020  and attached base plate  1030  mount on a pipe. The seal plate  1040  is mounted on the base assembly after holes are drilled in the pipe. The top assembly  1050 , consisting of top bracket  1060 , mounting plate  1070 , control enclosure  1080  and two probes  1090  and  1100 , is then latched to the base assembly with the probes projecting through drilled holes into the pipe. 
         [0042]      FIG. 11  is an angled view of base assembly  1010 . Split ring  1020  clamps around the pipe using screw holes  2010  and bolts (not shown). A gasket (not shown) seals between the ring and the pipe. Base plate  1030 , attached and sealed to split ring  1020 , contains quarter-turn valves  2020  and  2030 , intersected by through holes  2040  and  2050  which are parallel and extend through base plate  1030  and split ring  1020 . Spring-loaded latches  2060  at both ends of the base plate engage top bracket  1060 . The movement of the latches is limited by shoulder screws  2070  and  2080 . Locating pins  2090  and  2100  engage recesses  6050  and  6060  ( FIG. 15B ) in seal plate  1040 . Slotted holes  2110 ,  2120  locate pins  4010  in the quarter-turn valves (see  FIG. 13 ). Socket head cap screws  2130  and  2140  (with enlarged heads) are used to secure the drill guide and the seal plate. 
         [0043]      FIG. 12  is a section view through split ring  1020 , base plate  1030  and valves  2020  and  2030  in closed and open positions, respectively. Seal pieces  3010  and  3020 , made of a soft, slippery material such as polytetrafluoroethylene, are pressed into the base plate and form a seal around the valves and against the base plate. Drill bushings  3030  and  3040 , typically made of hardened steel and pressed into the split ring with a suitable retaining compound to ensure a seal, guide the drill bit as it enters the pipe. Such guidance is needed because the drill bit enters the wall of the pipe at a slight angle to the perpendicular. O-rings  3050  and  3060  seal between the drill bushings and the seal pieces. 
         [0044]      FIG. 13  is an angled view of one of the quarter turn valves  2020 . Valve  2030  may be identical. The valves may be made of stainless steel. Pin  4010  locates the valve within base plate  1030  and limits its rotary motion. Handle  4020  allows the user to turn the valve and indicates the position of the valve. Hole  4030  is made slightly larger than the drill bit, to avoid interference while minimizing the space in which chips can accumulate. Grooves  4040  and  4050  accommodate O-rings (not shown) to provide a redundant seal against leakage along the valve stem. 
         [0045]      FIG. 14  is an angled view of latch  2060 . Hole  5010  is made to seat a spring (not shown) which provides movement to the latch. Threaded hole  5020  is used in conjunction with shoulder screw  2080  for limiting the movement of the latch and locking it in place. As shown in  FIG. 11 , latch  2060  protrudes through opening  7020  in bracket  1060 . See  FIG. 16 . 
         [0046]      FIGS. 15A and 15B  show top and bottom angle views respectively of seal plate  1040 . The seal plate provides seals around the probes outside of the valves and it allows these seals to be installed after the holes are drilled in the pipe, so that the seals will not be damaged as the holes are drilled. O-rings  6010  and  6020 , on the underside of the seal plate, form the seals around the probes and also seal between the seal plate and the base plate  1030 . The seal plate engages cap screws  2130  and  2140  in slotted holes  6030  and  6040 . Pins  2090  and  2100  engage recesses  6050  and  6060  in the seal plate in order to locate it accurately in relation to base plate  1030 . 
         [0047]      FIG. 16  is an angled view of top assembly  1050 , including control enclosure  1080 , mounting plate  1070 , top bracket  1060  and probes  1090  and  1100 . The control enclosure is electrically connected to the probes and contains electronic circuitry to sense and display flow. The top bracket includes holes  7010  and  7020  which engage the latches ( 2060 , not shown here). Mounting plate  1070  and top bracket  1060  include provision (not shown, but such as a spring-loaded latch) to permit the control enclosure to be rotated 90 degrees from the position shown to facilitate application to horizontal or vertical pipes. The electronics are typically powered by a wall-plug supply and cable (not shown). 
         [0048]      FIG. 17  is an angled view of drill guide  8000 . The drill guide minimizes noise by directing the escaping fluid through muffler  8010  while simultaneously collecting the chips from the drilling process. Muffler  8010  is a commercially-available muffler of a type used for exhausts from compressed-air tools. It has a threaded connection for mounting. An O-ring seal (not shown) contained by drill-guide screw  8020  prevents leakage out of the drill guide along the shaft of the drill bit. To adapt drill guide  8000  to base plate  1030 , slots  8030  and  8040  permit the drill guide to be placed over cap screws  2130  and  2140  and slid to align with one probe hole and then the other. 
         [0049]      FIGS. 18A-18E  (representing STEP  1  through STEP  5 , respectively) show the step-by-step installation process consisting of steps  1 - 5 .  FIG. 18A  shows drill guide  8000  mounted onto base assembly  1010 . Slots allow for sliding for proper alignment with each probe hole. The drill guide is slid to one end of its range of movement and the cap screws are tightened. The drill bit is inserted through the drill guide, past the open slide valve, and up against the application pipe. The user drills through the wall of the pipe. In  FIG. 18B , the user extracts the drill bit just beyond the slide valve, then closes the valve and completely removes the drill bit. During the time between the drilling of the hole and the closure of the valve, air flows along the flutes of the drill bit and into the muffler, carrying most or all of the chips from drilling with it. The drill guide seal inhibits or prevents air from escaping along the stem of the drill. The flute of the drill bit should be shorter than the distance between the valve and the drill guide seal, so that the valves can be closed without air and chips escaping along the flute of the drill. The user then closes the valve and then completely removes the drill.  FIGS. 18A and 18B  are performed for each probe hole. The drill guide is then removed; the cap screws are loosened but remain in place. 
         [0050]    In  FIG. 18C , the user fits seal plate  1040  over the cap screws, slides it into place with pins  2090  and  2100  engaging recesses  6050  and  6060 , and tightens the cap screws. 
         [0051]      FIG. 18D  prepares for the top assembly to be inserted into the pipe. The user inserts the probes beyond the O-rings on the underside of the seal plate and as far as the closed valves. 
         [0052]    In  FIG. 18E , the user opens the two valves and presses the top assembly into place, with the probes projecting into the pipe. The two latches engage the cutouts in the upper bracket, holding the top assembly in place. The user then tightens the locking screws to ensure that the latches will not become disengaged. When power is connected to the electronic enclosure, the meter will display flow. 
         [0053]    Features of the claimed invention may be shown in some drawings and not others, and may not all be shown in the same drawing. The examples above support but do not limit the claims.