Abstract:
A thermocouple assembly for measuring the temperature of a pipe, comprises a pipe clamp having a pair of dissimilar metal strips mounted therein to contact a pipe held in the pipe clamp. A thermocouple reading instrument is connected to the metal strips to indicate the temperature of the pipe.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates to measuring the temperature of fluids in a pipe. Refrigeration and air conditioning technicians need temperatures of fluids in pipes for proper adjustment. If they can get the temperature of the pipe itself, in most cases that&#39;s good enough. 
         [0002]    Many companies supply products that include various mechanisms and technologies to get the temperature of the pipe. These include beaded thermocouples with a Velcro strap, thermistors in a ‘clothespin’ style clamp, and several different methods of using thermocouples in a plastic clamp. 
         [0003]    There are primarily two thermocouple techniques used for pipe clamps. One is to weld the individual thermocouples to a metal plate, and then mechanically press the metal plate against the pipe. The thermocouple delivers a voltage proportional to somewhere between that delivered by the two junctions to the plate. 
         [0004]    To accommodate a wider variety of pipes, the plate has to be “V” or “U” shaped. If the plate is a “V,” at best there are two line-shaped contacts. Most of the contacting force for big pipes is on one plate, while the contacting force for the little pipe is on the other plate, with the varying force creating thermal conducting problems, since conductivity varies with the force applied. 
         [0005]    Beyond that, the impediments to speed and accuracy with this technique are many, including that the plate dissipates heat to the environment easily due to big area of contact with ambient air. The contact point with the plate may be far from the thermocouple junctions; the contact spot changes as the jaws of the clamp get wider; the contact spot size may be small; the plate may absorb a lot of heat; the force between the contact plate and the pipe vary causing varying thermal conductance and the plate mounting mechanism (usually tabs) offers a path for heat to the environment. In addition, with any kind of clamp that has pivoting arms (like scissors or salad grabbers) the angle of the jaws vary as the clamp opens and closes, causing contact spot variability. 
         [0006]    The other technique is to push a thermocouple junction made of ribbons of thermocouple material up against the pipe directly. This solves most of the problems of the plate, but is less rugged and more costly. 
       SUMMARY OF THE INVENTION 
       [0007]    This invention provides a third thermocouple technique that uses thermocouple rails. Eliminating the plate and pressing thermocouple material (rails) up against the pipe directly provides a very fast response and an accurate reading. Its principle of operation is similar to that of the plate thermocouple device with the difference being the absence of a plate. 
         [0008]    The plate, the contact spots, the weld locations, and the distance between the welds and the contact spot cause all the problems with the plate design. The rail design according to the present invention eliminates the problems associated with plate thermocouple devices by making the pipe itself the intermediary metal. The elegance of the present invention is that the contact spot is the thermal junction. The electrical junction that measures temperature is at exactly the same temp as the contact spot, because they are the same spot. Readings are much faster and more accurate than can be obtained using prior above-referenced thermocouple devices. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a functional block diagram showing the use of a prior art plate-type thermocouple device to measure the temperature of a pipe; 
           [0010]      FIG. 2  is a functional block diagram showing the use of a thermocouple device according to the present invention to measure the temperature of a pipe; 
           [0011]      FIG. 3  illustrates a thermocouple device according to the present invention that includes a clamp and a thermocouple wire assembly associated with the clamp; 
           [0012]      FIG. 4  illustrates half of the clamp of  FIG. 3  with thermocouple wires connected to corresponding thermocouple rails; 
           [0013]      FIG. 5  illustrates thermocouple wires from the thermocouple wire assembly connected to corresponding thermocouple rails; 
           [0014]      FIG. 6  illustrates a thermocouple device according to the present invention being used with a small diameter pipe; 
           [0015]      FIG. 7  illustrates a thermocouple device according to the present invention being used with a large diameter pipe; 
           [0016]      FIG. 8  is a perspective view of a second embodiment of a thermocouple clamp device according to the present invention that includes a pair of thermocouple slats that comprise thermocouple contacts; 
           [0017]      FIG. 9  is a perspective view of a pair of wires connected to the thermocouple slats of  FIG. 8 ; 
           [0018]      FIG. 10  is a side elevation view showing the thermocouple device of  FIG. 8  being used with a small diameter pipe; 
           [0019]      FIG. 11  is a side elevation view showing the thermocouple device of  FIG. 8  being used with a large diameter pipe; 
           [0020]      FIG. 12  is a perspective view showing the thermocouple device of  FIG. 8  showing the thermocouple slats spaced apart to form an open circuit configuration; 
           [0021]      FIG. 13  s a perspective view showing the thermocouple device of  FIG. 8  showing the thermocouple slats spaced apart to form a closed circuit configuration; and 
           [0022]      FIG. 14  is a perspective view showing the thermocouple slats in contact with an electrical conductor. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    Referring to  FIG. 1 , a prior art thermocouple device  10  is arranged to measure the temperature of an electrically conducting pipe  12 . The thermocouple device  10  includes a first thermocouple wire  14  that extends between a thermocouple  16  and a voltmeter adjustable  18 . The thermocouple  16  is connected to the underside (as seen in  FIG. 1 ) of a metal plate  18  by any convenient means such as welding or soldering. A second thermocouple wire  20  extends between the voltmeter  18  and a thermocouple  22  that is also connected to the underside of the metal plate  18 . Temperature measurements using the thermocouple device  10  involve exerting pressure on the plate  18  to bring the thermocouples  16  and  22  into contact with the pipe  12 . The temperature of the pipe  12  may then be determined by the voltage difference between the two thermocouples  16  and  22 . 
         [0024]      FIG. 2  illustrates a thermocouple device  26  according to the present invention. A first thermocouple wire  28  extends between a thermocouple  30  and a voltmeter  32 . The thermocouple  30  is connected to a first rail  34  that extends across the pipe  12 . A second thermocouple wire  36  extends between the voltmeter  32  and a thermocouple  38  that is connected to a second rail  40  that is spaced apart from the rail  34 . The thermocouples  30  and  38  are formed of dissimilar metals. The rails  34  and  40  are formed of the same metal as the corresponding thermocouples  30  and  38 . The thermocouple wires  28  and  36  are formed of the same metal as their corresponding rails  34  and  40 . 
         [0025]      FIGS. 3, 4, 6 and 7  show the thermocouple device  26  according to the present invention mounted in a pipe clamp  42  that includes clamp halves  44  and  46 . A thermocouple wire assembly  48  extends between the handles of the pipe clamp  42  to a location between the clamp jaws. 
         [0026]    As best shown in  FIG. 5 , the separate thermocouple wires  28  and  36  extend out of the thermocouple wire assembly  48  and are connected to the thermocouples  30  and  38 , respectively. The rails  34  and  40  may be parallel and arranged to extend transversely across the pipe  12 . Alternatively, the rails  34  and  40  may be arranged such that space between the ends  34   a  and  40   a  differs from the space between the ends  34   b  and  40   b . Having the rails  34  and  40  formed so that different distances between the corresponding ends are beneficial when the surface of the pipe  12  is dirty or corroded. The rails  34  and  40  may be placed in contact under pressure from the clamp  42  with the pipe  12 . Rotating the clamp through a small angle about the pipe causes the rails  34  and  40  to plough away material on the surface of the pipe  12  so that the rails  34  and  40  and the thermocouples  32  and  38  make good thermal contact with the pipe  12 . 
         [0027]    Bringing the rails  34  and  40  into thermal contact with the pipe  12  creates two thermocouple junctions where each of the rails  34  and  40  contacts the pipe  12 . A voltage is produced between the thermocouple junctions in accordance with the well-known thermoelectric effect. This voltage is processed to determine the temperature of the pipe. 
         [0028]    The rails  34  and  40  may arranged at an angle relative to one another so that a wide range of pipe sizes may be measured using the same mechanical pivot style clamp  42  as shown in  FIGS. 6 and 7 . The angles of the rail  34  and  40  may be is such that the ends of the rails  34  and  40  closest to the outer end of the clamp  42  are slanted so that the largest pipe size is still pushed to the ‘throat’ of the clamp (doesn&#39;t ‘spit’ the pipe out). The inside end portions of the rails  34  and  40  are then angled to push the smallest pipe towards the jaw opening (doesn&#39;t ‘swallow’ the small pipe). 
         [0029]    The rails  34  and  40  allow the pipe clamp  42  to be pulled toward the pipe  12  as the clamp  12  applies pressure to the pipe  12 . This enables the clamp to have both more stability and higher resistance to coming off the pipe, or a lighter spring that is less expensive and easier to use. With the plate design, any ‘cocking’ of the installed pipe clamp in direction of the pipe causes the plate to be lifted off the pipe, with the contact spot only on the edge, thermally far away from the junction. 
         [0030]    Referring to  FIGS. 8 and 9 , a clamp thermocouple device  50  includes two thermocouple slats  62  and  64  of K-type thermocouple material having widths of about 5mm mounted in jaws  58  and  60 . If a metal pipe ( FIGS. 10 and 11 ) is in the jaws  58  and  60  forming an electrical and thermal contact to both slats  62  and  64 , the two junctions create a voltage that may be read as a temperature. The difference between the thermocouple clamp device  50  and the embodiment of the invention described with reference to  FIGS. 3-7  is that the metal thermocouple contacts in the thermocouple device  50  extend from side to side (parallel to the pipe) instead of front to back (perpendicular to the pipe). A wire assembly  66  includes thermocouple wires  67  and  68  that are connected to the thermocouple slats  62  and  64 , respectively. 
         [0031]      FIG. 12  is a perspective view showing the thermocouple device  50  of  FIG. 8  showing the thermocouple slats spaced apart to form an open circuit configuration. 
         [0032]      FIG. 13  s a perspective view showing the thermocouple device  50  of  FIG. 8  showing the thermocouple slats  62  and  64  spaced apart to form a closed circuit configuration. 
         [0033]      FIG. 14  is a perspective view showing the thermocouple slats  62  and  64  in contact with an electrical conductor.