Abstract:
A system for enabling the measurement of a temperature in a furnace ( 30, 48 ) using a pyrometer ( 38 ) that includes a pallet support ( 32, 52 ) for supporting a pallet ( 40, 50 ) a given distance (c) above a furnace floor ( 31 ) and a pyrometer target ( 10, 60, 80 ) that includes a support member ( 12, 62, 82 ) and a target member ( 14, 68 ) separable from said support member ( 12, 62, 82 ) where the support member ( 12, 62, 82 ) has a height less than the given distance (c).

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention is directed toward a system for and method of enabling the measurement of a temperature in a furnace using a pyrometer, and more specifically, toward a system for enabling the measurement of a temperature in a furnace using a pyrometer which system includes a pyrometer target having a target member separable from a support member and to a method of using the pyrometer target in a furnace. 
       BACKGROUND OF THE INVENTION 
       [0002]    Optical pyrometers are commonly used to measure temperatures in environments that are too hot to be measured by other temperature measuring devices such as thermometers and thermocouples. Some materials, including graphite and various metals, change color as they are heated, and therefore the temperature of a material can be estimated from the observed color. An optical pyrometer detects the color of an object being heated or the color of a surface in a furnace and correlates this color with a particular temperature. The optical pyrometer is generally mounted at a location where temperatures are not extreme and focused on a portion of a furnace or a material being treated in a furnace to measure color. Some furnaces, for example, may include windows through which a pyrometer can view the color of a material therein. In this manner, very high temperatures can be measured without exposing a measuring device to extreme conditions. 
         [0003]    The color measured by a pyrometer is dependent on the material being heated. Therefore, if the pyrometer is focused on a product being processed in a furnace, the relationship between color and temperature for each product processed must be known. To avoid this difficulty and obtain consistent temperature measurements, the pyrometer may be aligned with either a target made of a known material or with a specific portion of a furnace so that repeatable temperature measurements can be obtained. 
         [0004]    Some furnace arrangements lend themselves to the mounting of a pyrometer target on a wall of the furnace where the target can remain without interfering with product loading and unloading. Other known furnaces, however, have limited interior space, and therefore any pyrometer target used must be placed in the furnace after the product is loaded into the furnace and removed from the furnace before the product can be removed from the furnace. In one known process, materials to be processed are placed on a pallet, the pallet is placed on a support table having rollers, and the pallet is rolled from support table rollers onto rollers in a furnace. A large and therefore heavy graphite door is placed between the furnace door and the pallet, and the graphite door is then used as a pyrometer target. Smaller targets can be used, but the target must still generally have a large enough targeting area to allow a pyrometer to be readily aimed thereat and be tall enough to provide a temperature reading in a central portion of a furnace away from the furnace floor and to be visible through a window in a furnace door or wall. Since pyrometer targets may be made from dense materials such as steel or graphite, suitable targets are difficult to move. This increases the time required for loading and unloading a furnace and increases the likelihood of worker injury. It would therefore be desirable to provide a system and method for enabling the measurement of a temperature in a furnace that includes a relatively easy to use pyrometer target. 
       SUMMARY OF THE INVENTION 
       [0005]    These problems and others are addressed by the present invention, a first feature of which is a system for enabling the measurement of a temperature in a furnace using a pyrometer which system includes a pallet support for supporting a pallet a given distance above a furnace floor and a pyrometer target comprising a support member and a target member. The target member is separable from the support member, and the support member has a height less than the given distance. 
         [0006]    Another feature of the invention is a method of enabling a temperature measurement in a furnace using a pyrometer that involves providing a pallet support in the furnace for supporting a pallet a given distance above a floor of the furnace and providing a pyrometer target comprising a support member and a target member separable from the support member. The pyrometer target has a height greater than the given distance, and the support member has a height less than the given distance. The support member is placed in the furnace, and a pallet is moved into the furnace over the support member and onto the pallet support. After moving the pallet over the support member, the pyrometer target is placed on the support member, and a pyrometer is directed at the pyrometer target member. 
         [0007]    Yet another feature of the invention is a system for enabling the measurement of a temperature in a furnace using a pyrometer that includes a pallet support comprising a plurality of rollers for supporting a pallet a given distance above a furnace floor and a pyrometer target. The pyrometer target includes a support member having an upper surface and a height less than the given distance and a target member separable from the support member and comprising a base member supported by the support member upper surface and a targeting portion supported by the base member. A thickness of the base member is selected to be less than or equal to the difference between the given distance and a height of the support member. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    These aspects and features of embodiments of the invention will be better understood after a reading of the following detailed description of embodiments of the invention together with the accompanying drawings wherein: 
           [0009]      FIG. 1  is a perspective view of a pyrometer target comprising a target member and a support member; 
           [0010]      FIG. 2  is a front elevational view of a system comprising a first embodiment of a pallet support in a furnace supporting a pallet together with the pyrometer target of  FIG. 1 ; 
           [0011]      FIG. 3  is a sectional elevational view taken along line III-III of  FIG. 2 ; 
           [0012]      FIG. 4  is second embodiment of a pallet support in a furnace supporting a pallet together with the pyrometer target of  FIG. 1 ; 
           [0013]      FIG. 5  is a side elevational view of a second embodiment of a pyrometer target; 
           [0014]      FIG. 6  is a side elevational view of a third embodiment of a pyrometer target; and 
           [0015]      FIG. 7  is a flow chart illustrating a method according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Referring now to the drawings, wherein the showings are for the purpose of illustrating preferred embodiments of the invention only and not for the purpose of limiting same,  FIG. 1  illustrates a pyrometer target  10  that comprises a support member  12  and a target member  14 . Support member  12  has a bottom surface  16  and a top surface  18  and a height equal to the distance between bottom surface  16  and top surface  18 . Target member  14  comprises a base member  20 , a targeting portion  22 , and a spacer  24  spacing targeting portion  22  from base member  20 . In this embodiment, the width of targeting portion  22  is greater than the width of spacer  24 . Also in this embodiment, support member  12  and target member  14  are formed from graphite, and base member  20 , targeting portion  22  and spacer  24  are interconnected in a manner suitable for joining graphite elements. Targeting portion  22  in this embodiment is square, but the invention is not limited to the use of a square targeting portion. Targeting portion  22  should be large enough to permit a pyrometer to be aimed at the targeting portion, but small enough so as to avoid unnecessarily increasing the weight of target member  14 . Likewise, the size and shape of spacer  24  is based on the required location of targeting portion  22  relative to a furnace in which it is used and the location of a pyrometer that will be aimed at targeting portion  20 . 
         [0017]      FIGS. 2 and 3  illustrate a furnace  30  that includes a floor  31  and first and second pallet supports  32  on floor  31  which each comprise a plurality of support rollers  34  for supporting a pallet, such as pallet  40 , in furnace  30 . Pallet  40  may be formed, for example, of a sheet of graphite large enough and strong enough to support the weight of articles (not shown) that are to be moved into furnace  30 . Pallet supports  32  are configured to support pallet  40  a given distance c above the floor of the furnace. A pyrometer  38  for use with pyrometer target  10  is illustrated in  FIG. 3 . 
         [0018]    To use pyrometer target  10  to measure the temperature of furnace  30 , support member  12  is placed on the floor  31  of furnace  30  between first and second pallet supports  32 , preferably toward the front or loading side of furnace  30 . After this initial placement, support member  12  can be left in furnace  30  for multiple process cycles. Support member  12  could alternately be permanently attached to the floor  31  of furnace  30 , but greater flexibility of furnace use is provided if support member  12  is removable from furnace  30 . With support member  12  in place, a pallet  40 , supporting articles (not shown) to be treated, is moved into furnace  30  over support member  12  and onto rollers  34  of first and second pallet supports  32 . Prior to entering furnace  30 , pallet  40  may, for example, be supported by a support table (not shown) which may be moved to the furnace entrance with pallet  40  generally level with pallet supports  32  so that the pallet  40  can be kept generally level while being rolled off the support table and onto rollers  34  of first and second pallet supports  32 . 
         [0019]    Because support member  12  has a height less than given distance c between the bottom of pallet  40  and the floor  31  of furnace  30 , pallet  40  can move over and past support member  12  and onto pallet supports  32 . The support table may, for example, have a height about the same as the given distance c so that a pallet  40  on the support table can move in the plane of the pallet from the support table into furnace  30 . This relationship between the given distance or clearance c and the height of support member  12  allows a portion of pyrometer target  10  to remain in furnace  30  between uses. 
         [0020]    With pallet  40  positioned in furnace  30 , target member  14  of pyrometer target  10  is placed on support member  12 . The combined height of support member  12  and target member  14  is greater than the given distance c. Base member  20  of target member  14  may be large enough to stably support target member  14  on support member  12 ; however the size and weight of target member  14  can be reduced by making base member  20  smaller than necessary for stable support and positioning an end of base member  20  under pallet  40  to that pallet  40  will help limit the movement of base member  20  and hold target member  14  in an upright position. Thus, the thickness of base member  20  should be slightly less than the difference between given distance c and the height of support member  12 . With target  10  in this position, pyrometer  38  can be aimed at targeting portion  22  to determine the temperature of targeting portion  22  and hence the temperature of furnace  30 . To remove the pallet from the furnace, the process is reversed Much of the mass of pyrometer target  10 , namely, the amount represented by support portion  12 , can be left in the furnace  30  between process cycles, and therefore the mass of the target member  14  that must be moved between process cycles is kept relatively low. A second pyrometer target can be used at the other end of pallet  40 , and more than one pallet  40  may be loaded in furnace  30  during a furnace cycle without exceeding the scope of the present invention. 
         [0021]    The above embodiment is useful in a furnace  30  that includes pallet supports  32 . If pallet supports  32  are not present in a furnace, such as furnace  48  illustrated in  FIG. 4 , a second embodiment of the present invention may be used. In this embodiment, a pallet  50  is mounted on or attached to movable pallet supports  52  which include rollers  54 . Pallet  50  is supported on pallet supports  52  and rollers  54  to provide a given distance c between the bottom of pallet  50  and the surface on which rollers  54  roll. In this manner, pallet  50  with articles (not shown) supported thereon, can be rolled into and removed from furnace  48  without requiring the removal of pyrometer target support member  12  (which has a height less than the given distance c). Pyrometer target  14  is retained on support member  12  and used as described above in connection with the first embodiment. 
         [0022]      FIG. 5  illustrates a different embodiment of a pyrometer target that can be used in a manner similar to the pyrometer target  10  described above. Pyrometer target  60 , illustrated in  FIG. 5 , includes a pyrometer support member  62  having a bottom  64  and a top  66  that includes an opening  67 . A pyrometer target member  68  includes a targeting portion  70  and a spacer  72  for spacing targeting portion  70  from support member  62 . Spacer  72  is placed in opening  67  to support target member  68  in support member  62 . The height of support member  62 , the distance between bottom  64  and top  66 , is less than the given distance c between the bottom of a pallet supported in a furnace and the floor of the furnace. Pyrometer target  60  can therefore used in a similar manner as pyrometer target  10  discussed above with support member  62  placed into a furnace before a pallet is moved into the furnace and target member  68  is inserted into support member  62  after a pallet has cleared the support member  62  and moved into place in the furnace. 
         [0023]      FIG. 6  illustrates a further embodiment of a pyrometer target. Pyrometer target  80  includes a support member  82  having a bottom  84 , a top  86  and a projection  88  projecting along top  86  having a projection top  88 . The distance between bottom  84  and projection top  88  is less than given distance c, allowing a pallet to clear support member  82  when moving into and out of a furnace. Projection  86  is configured to engage a portion of the base member  20  of a pyrometer target member  14  to help hold target member  14  on support member  82 . 
         [0024]      FIG. 7  outlines a method according to an embodiment of the present invention that includes a step  90  of providing a pallet support in a furnace for supporting a pallet a given distance above a floor of the furnace, a step  92  of providing a pyrometer target comprising a support member and a target member separable from the support member, the pyrometer target having a height greater than the given distance and the support member having a height less than the given distance, a step  94  of placing the support member in the furnace and a step  96  of moving a pallet into the furnace over the support member and onto the pallet support. The method further includes a step  98  of after moving the pallet over the support member, placing the pyrometer target on the support member and a step  100  of directing a pyrometer at the pyrometer target member. 
         [0025]    The present invention has been described herein in terms of several embodiments. Additions and modifications to these embodiments will become apparent to those skilled in the relevant arts upon a reading of the forgoing disclosure. It is intended that all such obvious additions and modifications form a part of the present invention to the extend that they fall within the scope of the several claims appended hereto.