Abstract:
In one aspect of the invention a drywell includes a heated receiver for receiving a temperature probe. The receiver has upper and lower ends and an inner shield positioned around the receiver to define a first air channel extending between the upper and lower ends. A flow plate is positioned above the upper end of the receiver and extends outwardly from the receiver. The flow plate defines a plate opening positioned over the receiver opening and has a lower surface sloping away from the receiver with distance above the receiver. A blower positioned below the lower end of the receiver induces air flow through the air channel. The lower surface of the flow plate directs the air flow away from the temperature probe.

Description:
TECHNICAL FIELD 
       [0001]    This invention relates to drywell calibrators and, more particularly, to cooling systems for drywell calibrators. 
       BACKGROUND OF THE INVENTION 
       [0002]    It is typical for thermometers and thermal switches to be calibrated using a drywell. Drywells may include a receiver in which a thermometer or thermal switch is inserted. A heating element and temperature sensor are in thermal contact with the receiver such that the temperature within the receiver may be accurately set. The set temperature of the drywell may then be compared to the readout temperature of the thermometer or the switching temperature of a thermal switch to determine its accuracy. In some uses, a reference thermometer is inserted within the receiver along with the thermometer or switch being calibrated, and the readout of the reference thermometer is used for calibration purposes. 
         [0003]    A ventilation system cools the housing in which the receiver is mounted in order to avoid damage to the housing and electronic components of the drywell. The ventilation system typically directs air upward through the drywell in order to avoid excessive heating of a support surface. Often, the vented air heats the probe to the point that it can no longer be comfortably or safely handled by an operator. 
         [0004]    Some operators will wrap foil around the probes to reduce heating of the probe. Others will put a set of baffle plates having an opening for the probe on top of the drywell. The plates are expensive to manufacture and complicate set-up and storage of the drywell. In use, the plates may become hot and unsafe for use. Inasmuch as they are not contained within the housing of the drywell, operators risk burns from handling the plates. The plates also interfere with proper venting of the drywell  10 . Improper venting causes variation from the calibrated operating condition of the drywell resulting in measurement errors. Improper venting may also damage heat sensitive components. 
         [0005]    In view of the foregoing it would be an advancement in the art to provide an improved method for venting a drywell to avoid heating the probe. 
       SUMMARY OF THE INVENTION 
       [0006]    In one aspect of the invention a drywell includes a receiver for receiving a temperature probe. The receiver has upper and lower ends and an inner shield positioned around the receiver to define a first air channel extending between the upper and lower ends. A heating element is positioned in thermal contact with the receiver to heat the receiver to a specified temperature. A flow plate is positioned above the upper end of the receiver and extends outwardly from the receiver. The flow plate defines a plate opening positioned over the receiver opening and has a lower surface sloping away from the receiver with distance above the receiver. A blower positioned below the lower end of the receiver induces air flow through the air channel. The lower surface of the flow plate directs the air flow away from the temperature probe. A housing may surround the inner shield to define a second air channel therebetween. The blower may induce air flow through the second air channel. The air flow from the first and second channels mixes above the upper end of the receiver. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is an isometric view of a drywell in accordance with an embodiment of the present invention. 
           [0008]      FIG. 2  is a side cross sectional view of a drywell in accordance with an embodiment of the present invention. 
           [0009]      FIG. 3  is a front elevation view of a drywell in accordance with an embodiment of the present invention. 
           [0010]      FIG. 4  is a top plan view of a flow plate and inner shield in accordance with an embodiment of the present invention. 
           [0011]      FIG. 5  is a front elevation view of a flow plate in accordance with an embodiment of the present invention. 
           [0012]      FIG. 6  is a side elevation view of a flow plate in accordance with an embodiment of the present invention. 
           [0013]      FIG. 7  is a top plan view of a plate shaped for deformation into a flow plate in accordance with an embodiment of the present invention. 
           [0014]      FIG. 8  is a side cross sectional view of a drywell illustrating airflow within the drywell in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0015]    Referring to  FIG. 1 , a drywell  10  according to an embodiment of the invention may include a housing  12 . A vent plate  14  may be secured near the top of the housing  12  and permit air to flow out of the drywell  10 . The vent plate  14  defines an aperture  16  positioned over a receiver  18 . The receiver  18  includes one or more apertures  20  sized to receive the probe  22  of a thermometer, thermal switch, or the like. In use, the temperature of the receiver  18  is elevated to a specified temperature in order to test the thermal response characteristics and accuracy of the device being tested. A heating element in thermal contact with the receiver  18  may be used to control the temperature of the receiver  18 . 
         [0016]    The drywell  10  may include a control module  24  secured thereto. Alternatively, the control module  24  is remote from the drywell  10  and coupled to the drywell  10  by wires or other communication means. The control module  24  may include an interface  26  for interacting with the drywell  10 . The interface  26  may include a display  28 , input buttons  30 , and ports  32  for coupling thermometers, thermal switches, and the like to the control module  24  for testing. 
         [0017]    Referring to  FIGS. 2 and 3 , in some embodiments, the receiver  18  is substantially cylindrical and is inserted within a heater  34 . An inner shield  36  may be positioned around the heater  34  and receiver  18  and define an air channel  38 . In the illustrated embodiment, the inner shield  36  includes sides  40   a - 40   d  arranged to form a box around the heater  34 . A fan  42  may be positioned below the inner shield  36  to induce airflow  44  up through the air channel  38 . The walls  40   a ,  40   c  may include flared portions  46  to guide airflow from the fan  42  into the air channel  38 . In the illustrated embodiment, only walls  40   a ,  40   c  are flared. However, in some embodiments each of the walls  40   a - 40   d  includes flared portions  46 . 
         [0018]    A flow plate  48  is positioned over the receiver  18  and includes one or more sloped lower surfaces  50 . The lower surfaces  50  preferably slope outwardly from the receiver  18  with vertical distance from the upper end of the receiver  18 . The lower edges of the lower surfaces  50  may be located immediately above the upper end of the receiver  18 . However, in a preferred embodiment the lower surface  50  does not touch the receiver  18  or the heater  34 . 
         [0019]    In the illustrated embodiment, the lower surface  50  projects across the air channel  38  and includes a portion at an angle  52  relative to a vertical direction  54  extending between the upper and lower ends of the receiver  18 . The angle  52  may be effective to cause airflow  44  to be directed away from the probe  22  sufficiently to overcome convective effects that would tend to draw hot air toward the probe  22 . In one embodiment, the angle  52  is between about 25 and 45 degrees. In another embodiment, the angle  52  is between about 30 and 40 degrees. In the preferred embodiment, the angle  52  is about 35 degrees. The flared upper portions  56  may be angled such that the distance  58  between the flared upper portions  56  and the lower surface  50  is substantially constant over a substantial area of the flared upper portions  56  and the lower surface  50 . Maintaining a substantially constant distance  58  may beneficially reduce back pressure as the airflow  44  passes between the lower surface  50  and the flared upper portions  56 . In an alternative embodiment, the distance  58  increases with upward distance from the receiver such that the airflow  44  encounters a slightly divergent channel. The walls  40   a ,  40   c  may include vertical portions  59  adjacent the flared upper portions  56 . The vertical portions  59  may advantageously limit the amount of hot air directed at an operator. 
         [0020]    In some embodiments, an outer shield  60  is positioned around the inner shield  36  and defines an outer air channel  62 . The outer shield  60  may include sides  64   a ,  64   b  to which the inner shield  36  secures. In one embodiment the sides  64   a ,  64   b  include a lower flared portion  72 . A gap  68  may be present between the lower flared portion  72  and the lower flared portion  46  of the inner shield  36  such that there is some airflow  70  around the outside of the inner shield  36 . The sides  64   a ,  64   c  may further include upper flared portions  74 . The upper flared portions  74  may have a substantial area thereof substantially parallel to the upper flared portion  56  of the sides  40   a ,  40   c.    
         [0021]    Referring to  FIG. 4 , in some embodiments, the flow plate  48  includes a central plate  76  positioned above the receiver  18 . The central plate may include an aperture  78  proximate the center thereof. In the illustrated embodiment the aperture  78  has a diameter approximately that of the cylindrically shaped receiver  18 . An area  80  surrounding the aperture  78  may be substantially continuous, without apertures or other perforations therein. The area  80  may extend from the aperture  78  a distance  82  horizontally across the air channel  38 . In some embodiments, the distance  82  is equal to about 30 to 60 percent of the width of the air channel  38 . In a preferred embodiment, the area  80  extends across about 45 to 55 percent of the air channel  38 . 
         [0022]    Referring to  FIGS. 5 and 6 , while still referring to  FIG. 4 , the sloped lower surfaces  50  may be formed by flanges  84  extending downwardly from the central plate  76  and inwardly toward the receiver  18 . The flanges  84  are angled relative to the central plate  76  at an angle  86 . In one embodiment, the angle  86  is between about 45 and 65 degrees. In another embodiment, the angle  86  is between about 52 and 58 degrees. In a preferred embodiment, the angle  86  is about 55 degrees. 
         [0023]    Supports  88  may be secured to the central plate  76  between the flanges  84  and secure the central plate  76  to the inner shield  36 . In the illustrated embodiment, the supports  88  extend from the corners of the central plate  76 . Tabs  92  may be secured to the supports  88  and be insertable within apertures in the sides  40   a ,  40   b  to retain the flow plate  48 . In the illustrated embodiment, the tabs  92  are inserted within the vertical portions  59  of the sides  40   a ,  40   b , adjacent the flared upper portion  56 . The tabs  92  may be narrower than the supports  88  such that the apertures in the walls  40   a ,  40   b  may be sized to receive the tabs  92  but prevent insertion of the supports  88 . 
         [0024]    In some embodiments the supports  88  vertically offset the central plate  76  a distance  94  from a point of securement to the inner shield  36 . For example, in the illustrated embodiment, the supports  88  are angled relative to the tabs  92  and central plate  76  such that the tabs  92  are offset vertically below the central plate  76 . In some embodiments, the offset distance  94  is equal to about 20 to 60 percent of the vertical extent  96  of the lower surfaces  50 . In another embodiment, the offset distance  94  is equal to about 40 to 55 percent of the vertical extent  96 . 
         [0025]    In the illustrated embodiment, the tabs  92  are secured to the walls  40   a  and  40   b . The supports  88  therefore extend from the central plate to the walls  40   a  and  40   b  and reduce the amount of airflow outwardly from the walls  40   a  and  40   b . As is apparent in  FIG. 5 , airflow  98  incident on the supports  88  is directed laterally, relative to the walls  40   a ,  40   b . Inasmuch as the wall  40   a  faces the control module  24 , the arrangement disclosed reduces the amount of hot air directed at the operator of the drywell  10 . Referring to  FIG. 7 , in some embodiments, the central plate  76 , flanges  84 , supports  88 , and tabs  92  are formed in a monolithic steel plate that is bent into the shapes of  FIGS. 4 ,  5 , and  6 . 
         [0026]    Referring to  FIG. 8 , airflow through the drywell  10  may occur as illustrated. The airflow  44  passing between the inner shield  36  and the heater  34  is redirected by the lower surface  150  such that it is directed away from the probe  22 . The airflow  44  mixes with the cooler airflow  70  from between the inner shield  36  and the housing  12 . Inasmuch as the airflow  44  is moving at a higher velocity than the surrounding air, it will have lower pressure and may tend to induce airflow  100  away from the probe  22 , further reducing heating of the probe  22 . A combined airflow  102  is therefore directed away from the probe  22  and includes a mixture of cooler airflows  100  and  70  to reduce the temperature of the airflow  44 . 
         [0027]    Although the present invention has been described with reference to the disclosed embodiments, persons skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. Such modifications are well within the skill of those ordinarily skilled in the art. Accordingly, the invention is not limited except as by the appended claims.