Patent Publication Number: US-9845517-B2

Title: Sub-zero treatment device

Description:
TECHNICAL FIELD 
     The present invention relates to a sub-zero treatment device capable of cooling a steel material such as a machine component to a low temperature of 0° C. or lower, thereby improving the performance such as the hardness and the toughness of the steel material. 
     This application is the U.S. national phase of International Application No. PCT/JP2014/056503 filed Mar. 12, 2014 which designated the U.S. and claims priority to Japanese Patent Application No. 2013-060698, filed Mar. 22, 2013, the entire contents of each of which are hereby incorporated by reference. 
     BACKGROUND ART 
     Sub-zero treatments in which steel materials such as machine components are cooled to low temperatures of 0° C. or lower are used conventionally to improve the performance such as the hardness and the toughness of the steel materials. 
     One known sub-zero treatment method is a low-temperature atmospheric method in which the atmosphere inside a cooling tank housing a cooling target object is cooled using a refrigerator or liquid nitrogen or the like, thereby cooling the cooling target object. 
     Patent Document 1 discloses a sub-zero treatment device (see  FIG. 12 ) used in performing the above sub-zero treatment. 
       FIG. 12  is a cross-sectional view illustrating a schematic outline of a conventional sub-zero treatment device. 
     As illustrated in  FIG. 12 , a sub-zero treatment device  100  disclosed in Patent Document 1 has a cooling tank  102 , a refrigerant inlet passage  103 , a liquid refrigerant inlet valve  104 , a temperature controller  105 , an agitation fan  108 , and a baffle plate  109 . 
     The cooling tank  102  is formed from an insulating material, and has an internal treatment space. An exhaust port  102 A is provided in a side wall of the cooling tank  102 , and penetrates through the side wall. When the pressure inside the cooling tank  102  increases due to evaporation of the liquid nitrogen (the liquid refrigerant), the exhaust port  102 A externally exhausts a portion of the nitrogen gas from inside the cooling tank  102  to a location outside the cooling tank  102  in order to ensure that the pressure is maintained within a prescribed pressure range. 
     The refrigerant inlet passage  103  is connected to a liquid nitrogen supply source not shown in the drawing. When the liquid refrigerant inlet valve  104  (the valve provided in the refrigerant inlet passage  103 ) is opened, the refrigerant inlet passage  103  supplies liquid nitrogen into the cooling tank  102 . 
     The temperature controller  105  measures the temperature inside the cooling tank  102 , and adjusts the degree of opening of the liquid refrigerant inlet valve  104  based on the result of the measurements. 
     The agitation fan  108  is housed inside the cooling tank  102 . The agitation fan  108  converts the liquid nitrogen to a mist and diffuses the mist through the interior of the cooling tank  102 , as well as agitating the low-temperature nitrogen gas (low-temperature gas) inside the cooling tank  102 . 
     The baffle plate  109  is housed inside the cooling tank  102 , and is disposed between the agitation fan  108  and the cooling target object  101 . The baffle plate  109  has a suction port and blowout ports. The baffle plate  109  has the function of enhancing the agitation action of the agitation fan  108 . 
     PRIOR ART LITERATURE 
     Patent Documents 
     Patent Document 1: Japanese Patent (Granted) Publication No. 3,946,796 
     DISCLOSURE OF INVENTION 
     Problems to be Solved by the Invention 
     However, when the low-temperature nitrogen gas is discharged externally from the cooling tank  102  through the exhaust port  102 A that penetrates through a side wall of the cooling tank  102 , as is the case in the sub-zero treatment device  100  disclosed in Patent Document 1, temperature irregularities tend to occur inside the cooling tank  102 . 
     If temperature irregularities occur inside the cooling tank  102  in this manner, then the cooling of the cooling target object  101  tends to lack uniformity, and fluctuations occur in the quality of the cooling target object  101 . 
     Further, depending on the position in which the exhaust port  102 A is provided within the side wall of the cooling tank  102 , the low-temperature nitrogen gas may be exhausted through the exhaust port  102 A before contributing satisfactorily to the cooling of the treatment space, and therefore a large amount of the liquid refrigerant is required for cooling the cooling target object  101 . 
     Accordingly, the present invention has an object of providing a sub-zero treatment device that is capable of uniformly cooling a cooling target object and reducing the amount of liquid refrigerant used for cooling the cooling target object. 
     Means for Solving the Problems 
     In order to achieve the above object, the present invention provides: 
     (1) a sub-zero treatment device containing: a cooling tank composed of a cooling tank main body formed from a base plate and first to fourth side walls, and a lid, the cooling tank having a cooling target object mounting chamber in which a cooling target object is mounted, and a fan housing chamber that is connected to the cooling target object mounting chamber; a baffle member, disposed inside the cooling tank so as to separate the cooling target object mounting chamber and the fan housing chamber, and having a suction port for guiding the atmosphere of the cooling target object mounting chamber into the fan housing chamber, and blowout ports for guiding the atmosphere of the fan housing chamber into the cooling target object mounting chamber; an agitation fan housed in the fan housing chamber in a position opposing the suction port, the agitation fan converting a liquid refrigerant supplied to the fan housing chamber into a mist or a low-temperature gas, as well as agitating the atmosphere inside the cooling tank; and an exhaust member, extending from a through-hole provided in the cooling tank main body through to the interior of the cooling target object mounting chamber, and having an exhaust port; wherein the first to fourth side walls are disposed so as to surround the outer peripheral edge of the base plate and contact the lid, thereby forming an internal space inside the cooling tank, the exhaust port is disposed in an exhaust port positioning space located in the cooling target object mounting chamber within the internal space, such that if the orthogonal height between the surface of the base plate on the side of the internal space and the surface of the lid on the side of the internal space is deemed H, then the exhaust port positioning space is a space composed of a portion reaching an orthogonal distance of H/2 from the surface of the lid on the side of the internal space, and a transverse width of the exhaust port positioning space, which is the width in a direction orthogonal to the aforementioned height and parallel to the baffle member having the suction port, is equal to the maximum value for the transverse width of the suction port in a direction orthogonal to the aforementioned height and parallel to the baffle member having the suction port, with the center of the transverse width of the exhaust port positioning space coinciding with the center of the transverse width of the suction port. 
     Further, the present invention also provides: 
     (2) the sub-zero treatment device disclosed in (1), wherein the exhaust port is disposed in the exhaust port positioning space located between the cooling target object and the baffle member. 
     Furthermore, the present invention also provides: 
     (3) the sub-zero treatment device disclosed in (1) or (2), wherein the exhaust member has an exhaust member main body, and the exhaust member main body is positioned so that the exhaust port faces toward the lid. 
     Moreover, the present invention also provides: 
     (4) the sub-zero treatment device disclosed in (3), wherein the exhaust member main body is a circular cylindrically shaped pipe, and when the exhaust member is cut along a surface that passes through the exhaust port in a direction orthogonal to the direction of extension of the exhaust member main body, the exhaust port has a central angle, formed by connecting the two edges of the exhaust port with the center of the exhaust member main body, that is not more than 90°. 
     Further, the present invention also provides: 
     (5) the sub-zero treatment device disclosed in (1), wherein the exhaust member has a water drain hole that is formed facing toward the base plate. 
     Furthermore, the present invention also provides: 
     (6) the sub-zero treatment device disclosed in any one of (1) to (5), wherein the baffle member has at least one plate-like member having a uniform thickness, and the suction port and the blowout ports penetrate through the same plate-like member. 
     Moreover, the present invention also provides: 
     (7) the sub-zero treatment device disclosed in any one of (1) to (5), wherein the baffle member has a first plate-like member that faces the agitation fan, and second and third plate-like members disposed orthogonally relative to the first plate-like member, the suction port penetrates through the first plate-like member, and the blowout ports penetrate through the second and third plate-like members. 
     Effects of the Invention 
     In the sub-zero treatment device of the present invention, by providing an exhaust member which has an exhaust port and extends from a through-hole provided in the cooling tank that forms the cooling target object mounting chamber through to the interior of the cooling target object mounting chamber, and positioning the exhaust port in an exhaust port positioning space, which is the space located in the upper half of the cooling target object mounting chamber and having a width in the transverse direction that is equal to the maximum value for the width in the transverse direction of the suction port, temperature fluctuations in the atmosphere inside the cooling target object mounting chamber can be suppressed even when a low-temperature gas (the gasified liquid refrigerant) is discharged through the exhaust port to a location outside the cooling tank. 
     As a result, the cooling target object can be cooled uniformly (or in other words, fluctuations in the quality of the cooling target object can be suppressed). 
     Further, because exhausting of the low-temperature gas through the exhaust port before the gas can contribute satisfactorily to the cooling of the treatment space can be suppressed, the amount of the liquid refrigerant used in cooling the cooling target object can be reduced. 
     In other words, the sub-zero treatment device of the present invention is capable of uniformly cooling a cooling target object and reducing the amount of liquid refrigerant used for cooling the cooling target object. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view illustrating the external appearance of a sub-zero treatment device according to a first embodiment of the present invention. 
         FIG. 2  is a diagram for explaining the structural components of the sub-zero treatment device housed inside the cooling tank main body illustrated in  FIG. 1 , and is a plan view of the cooling tank illustrated in  FIG. 1  viewed through the lid illustrated in  FIG. 1  along the direction A. 
         FIG. 3  is a diagram for explaining the structural components of the sub-zero treatment device housed inside the cooling tank main body illustrated in  FIG. 1 , and is a diagram of the inside of the cooling tank illustrated in  FIG. 1  viewed through the first side wall illustrated in  FIG. 1  along the direction B. 
         FIG. 4  is a cross-sectional view along the line C-C of the exhaust member and the third side wall of the cooling tank main body illustrated in  FIG. 2 . 
         FIG. 5  is a diagram of the through-hole illustrated in  FIG. 4  and the third side wall located around the periphery of the through-hole, viewed along the direction D in  FIG. 4 . 
         FIG. 6  is a diagram of the exhaust member illustrated in  FIG. 4 , viewed along the direction E in  FIG. 4 . 
         FIG. 7  is a cross-sectional view along the line G-G of the exhaust member illustrated in  FIG. 4 . 
         FIG. 8  is a diagram for explaining a sub-zero treatment device according to a modification of the first embodiment, and is a plan view of the sub-zero treatment device viewed through the lid of the sub-zero treatment device. 
         FIG. 9  is a diagram for explaining a sub-zero treatment device according to a second embodiment, and is a plan view of the sub-zero treatment device viewed through the lid of the sub-zero treatment device. 
         FIG. 10  is a diagram illustrating the second plate-like member of the baffle member illustrated in  FIG. 9 , viewed along the direction M in  FIG. 9 . 
         FIG. 11  is a cross-sectional view along the line N-N of the exhaust member, the third side wall of the cooling tank main body, and the second plate-like member of the baffle member illustrated in  FIG. 9 . 
         FIG. 12  is a cross-sectional view illustrating a schematic outline of a conventional sub-zero treatment device. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Embodiments of the present invention are described below in detail with reference to the drawings. The drawings used in the following description are provided to assist the description of the structures of the embodiments of the present invention, but the size, thickness, and dimensions and the like of the various illustrated components may differ from the dimensional relationships found in the actual sub-zero treatment devices. 
     First Embodiment 
       FIG. 1  is a side view illustrating the external appearance of a sub-zero treatment device according to a first embodiment of the present invention.  FIG. 2  is a diagram for explaining the structural components of the sub-zero treatment device housed inside the cooling tank main body illustrated in  FIG. 1 , and is a plan view of the cooling tank illustrated in  FIG. 1  viewed through the lid illustrated in  FIG. 1  along the direction A. 
     Accordingly, the lid  36  that is one of the structural components of the sub-zero treatment device  10  of the first embodiment is omitted in  FIG. 2 . 
       FIG. 3  is a diagram for explaining the structural components of the sub-zero treatment device housed inside the cooling tank main body illustrated in  FIG. 1 , and is a diagram of the inside of the cooling tank illustrated in  FIG. 1  viewed through the first side wall illustrated in  FIG. 1  along the direction B. Accordingly, the first side wall  39 - 1  that is one of the structural components of the sub-zero treatment device  10  of the first embodiment is omitted in  FIG. 3 . 
     Further, structural portions that are the same in  FIG. 1  to  FIG. 3  are labeled with the same reference signs. 
     As illustrated in  FIG. 1  to  FIG. 3 , the sub-zero treatment device  10  of the first embodiment includes a cooling tank  13 , a through-hole  14 , a temperature sensor  16 , a temperature controller  18 , a refrigerant supply line  21 , a refrigerant supply portion  23 , a liquid refrigerant inlet valve  24 , a baffle member  25 , an agitation fan  27 , a rotational axis  28 , a rotational drive device  29 , and an exhaust member  31 . 
     The cooling tank  13  has a cooling tank main body  35  and the lid  36 . The cooling tank main body  35  has a base plate  38  and first to fourth side walls  39 - 1  to  39 - 4 . 
     The first to fourth side walls  39 - 1  to  39 - 4  are positioned so as to surround the outer peripheral edges of the rectangular base plate  38 . The bottom edges of the first to fourth side walls  39 - 1  to  39 - 4  are integrated with the base plate  38 . 
     The first and second side walls  39 - 1  and  39 - 2  are positioned facing each other. Similarly, the third and fourth side walls  39 - 3  and  39 - 4  are positioned facing each other. 
     The first and second side walls  39 - 1  and  39 - 2  are integrated with the adjacent third and fourth side walls  39 - 3  and  39 - 4 . 
     The lid  36  contacts the top edges of the first to fourth side walls  39 - 1  to  39 - 4 . As a result, a rectangular cuboid-shaped or cubic internal space (a space including a cooling target object mounting chamber  43  and a fan housing chamber  45 ) is formed inside the cooling tank  13 . 
     The cooling tank  13  includes the cooling target object mounting chamber  43  and the fan housing chamber  45 . The cooling target object mounting chamber  43  and the fan housing chamber  45  are separated by the baffle member  25 . A cooling target object  11  is mounted inside the cooling target object mounting chamber  43 . 
     The through-hole  14  is provided so as to penetrate through the third side wall  39 - 3 . The through-hole  14  is positioned within a space on the third side wall  39 - 3  that is located in the upper half of the height H of the cooling target object mounting chamber  43 , and positioned between the cooling target object  11  and the baffle member  25 . The shape of the through-hole  14  may, for example, be a circular cylindrical shape (see FIG.  4  and  FIG. 5 ), but the present invention is not limited to any particular shape. For example, a quadrangular prism-shaped through-hole  14  may also be used. 
     The height H refers to the distance along the orthogonal between the surface of the base plate on the side of the internal space (namely, the upper surface) and the surface of the lid on the side of the internal space (namely, the lower surface), and the space located in the upper half of the height H of the cooling target object mounting chamber  43  refers to the space, within the internal space inside the cooling tank, from the lower surface of the lid down to an orthogonal distance of H/2 below the lower surface. 
     The temperature sensor  16  is disposed with a tip section  16 A positioned inside the fan housing chamber  45 . The temperature sensor  16  is connected electrically to the temperature controller  18 . The temperature sensor  16  transmits data relating to the temperature of the fan housing chamber  45  to the temperature controller  18 . 
     A thermocouple or the like can be used as the temperature sensor  16 . In such a case, the tip section  16 A is the hot junction point. 
     The temperature controller  18  is provided outside the cooling tank  13 . The temperature controller  18  is connected electrically to the temperature sensor  16  and the liquid refrigerant inlet valve  24 . Data relating to the prescribed temperature range for the fan housing chamber  45  (for example, −80° C. to −70° C.) is stored in advance in the temperature controller  18 . 
     Based on the data relating to the prescribed temperature range for the fan housing chamber  45  (for example, −80° C. to −70° C.), and the data transmitted from the temperature sensor  16  (specifically, the data relating to the actual measured temperature of the fan housing chamber  45 ), the temperature controller  18  adjusts the degree of opening of the liquid refrigerant inlet valve  24  (including the states of fully open and fully closed) to ensure that the temperature of the fan housing chamber  45  falls within the prescribed temperature range. 
     One end of the refrigerant supply line  21  is connected to a liquid refrigerant supply source (not shown in the drawings) disposed outside the cooling tank  13 , and the other end is connected to the refrigerant supply portion  23  disposed inside the fan housing chamber  45 . An example of the liquid refrigerant supply source (not shown in the drawings) is a source which supplies liquid nitrogen as the liquid refrigerant. 
     The refrigerant supply portion  23  is positioned inside the fan housing chamber  45 . The refrigerant supply portion  23  is used for supplying the liquid refrigerant that has been transported through the refrigerant supply line  21  to the side surface of the agitation fan  27 . 
     The liquid refrigerant inlet valve  24  is a solenoid valve, and is provided in the refrigerant supply line  21 . The liquid refrigerant inlet valve  24  is connected electrically to the temperature controller  18 . 
     The liquid refrigerant inlet valve  24  is used for controlling whether or not the liquid refrigerant is supplied to the refrigerant supply portion  23 , and adjusting the supply rate of the liquid refrigerant supplied to the refrigerant supply portion  23 . 
     The liquid refrigerant inlet valve  24  supplies the liquid refrigerant to the inside of the fan housing chamber  45  when the temperature inside the fan housing chamber  45  rises and breaches the prescribed temperature range (for example, −80° C. to −70° C.). 
     The baffle member  25  is disposed inside the cooling tank  13  so as to separate the cooling target object mounting chamber  43  and the fan housing chamber  45 . 
     The baffle member  25  has a plate-like member  47 , a suction port  48 , and first and second blowout ports  49 - 1  and  49 - 2 . The plate-like member  47  is a member of uniform thickness. 
     The top edge of the plate-like member  47  contacts the lower surface  36   a  of the lid  36  (namely, the surface on the side of the internal space), and the bottom edge of the plate-like member  47  contacts the upper surface  38   a  of the base plate  38  (namely, the surface on the side of the internal space). 
     Further, one edge of the plate-like member  47  in the transverse direction contacts the inside surface of the third side wall  39 - 3 , and the other edge of the plate-like member  47  in the transverse direction contacts the inside surface of the fourth side wall  39 - 4 . 
     The suction port  48  is provided so as to penetrate through a portion of the plate-like member  47  (specifically, the central portion of the plate-like member  47 ) opposing the agitation fan  27  housed inside the fan housing chamber  45 . 
     In other words, the suction port  48  and the first and second blowout ports  49 - 1  and  49 - 2  are provided within the same plate-like member  47  of uniform thickness. 
     It is particularly preferable that the suction port  48  and the first and second blowout ports  49 - 1  and  49 - 2  are formed so that the surface area of each opening does not decrease through the interior of the plate-like member  47 , but is rather a constant surface area through the entire thickness direction of the plate-like member  47 . 
     The suction port  48  is a through-hole that is used for guiding the atmosphere of the cooling target object mounting chamber  43  toward the fan housing chamber  45 . 
     The shape of the suction port  48  may, for example, be a similar shape to the outer shape  27 A of the agitation fan  27 . The size of the suction port  48  is set to substantially the same size as the outer shape  27 A of the agitation fan  27 . 
     In the present invention, the expression that the size of the suction port  48  is substantially the same as the outer shape  27 A of the agitation fan  27  means that the diameter of the suction port  48  is within a range from 0.9 to 1.1 times the diameter of the agitation fan  27 . 
     The first blowout port  49 - 1  penetrates through a portion of the plate-like member  47  located between the suction port  48  and the third side wall  39 - 3 . The first blowout port  49 - 1  can be formed, for example, as a through-slot (slit) that extends in a direction from the base plate  38  toward the lid  36 . 
     The second blowout port  49 - 2  penetrates through a portion of the plate-like member  47  located between the suction port  48  and the fourth side wall  39 - 4 . The second blowout port  49 - 2  is formed with the same shape as the first blowout port  49 - 1 . If the side wall  39 - 3  is deemed the right side and the side wall  39 - 4  is deemed the left side, then the baffle member  25  is formed with a shape having left-right symmetry. 
     The first and second blowout ports  49 - 1  and  49 - 2  are used for guiding the atmosphere inside the fan housing chamber  45  toward the cooling target object mounting chamber  43 . 
     In the example shown in  FIG. 3 , the first and second blowout ports  49 - 1  and  49 - 2  are illustrated as through-slots that extend along the vertical direction of the plate-like member  47 , but the shape of the first and second blowout ports  49 - 1  and  49 - 2  and the number of blowout ports are not limited to this particular example. Further, the shapes of the first and second blowout ports  49 - 1  and  49 - 2  may also be different from each other. 
     For example, a line or a plurality of lines of circular or rectangular through-hole portions may be provided in the plate-like member  47  as the first and second blowout ports  49 - 1  and  49 - 2 , and the sizes of those through-hole portions may differ. 
     Alternatively, rectangular or oval-shaped through-slots may be positioned along either the transverse direction or the longitudinal direction of the plate-like member  47 , and the sizes of those through-slots may differ. 
     The agitation fan  27  is disposed inside the fan housing chamber  45 , in a location opposing the suction port  48 . The agitation fan  27  is connected to one end of a rotational axis that penetrates through the second side wall  39 - 2 . As a result, the agitation fan  27  is located inside the fan housing chamber  45  in a rotatable state. A sirocco fan or the like may be used as the agitation fan  27 . 
     The agitation fan  27  converts the liquid refrigerant supplied from the side of the agitation fan  27  into a mist or a low-temperature gas, and also agitates the atmosphere inside the cooling tank  13 . 
     As a result, the atmosphere of the cooling target object mounting chamber  43  sucked through the suction port  48  disperses to the sides behind the agitation fan  27 , and the atmosphere of the fan housing chamber  45  is fed into the cooling target object mounting chamber  43  through the first and second blowout ports  49 - 1  and  49 - 2 . 
     The rotational axis  28  penetrates through the second side wall  39 - 2 . One end of the rotational axis  28  is connected to the agitation fan  27 , and the other end, which is located outside the cooling tank  13 , is connected to the rotational drive device  29 . 
     The rotational drive device  29  is provided outside the cooling tank  13 . The rotational drive device  29  rotates the agitation fan  27  via the rotational axis  28 . A motor or the like can be used as the rotational drive device  29 . 
       FIG. 4  is a cross-sectional view along the line C-C of the exhaust member and the third side wall of the cooling tank main body illustrated in  FIG. 2 .  FIG. 5  is a diagram of the through-hole illustrated in  FIG. 4  and the third side wall located around the periphery of the through-hole, viewed along the direction D in  FIG. 4 .  FIG. 6  is a diagram of the exhaust member illustrated in  FIG. 4 , viewed along the direction E in  FIG. 4 . In  FIG. 5 , the exhaust member illustrated in  FIG. 4  is omitted. 
     As illustrated in  FIG. 2  to  FIG. 4  and  FIG. 6 , the exhaust member  31  has an exhaust member main body  55 , an exhaust port  56  and a water drain hole  57 . 
     The exhaust member main body  55  is a cylindrical member, one end of which is open. The open end of the exhaust member main body  55  is inserted in the through-hole  14  provided in the third side wall  39 - 3 . The outer diameter of the exhaust member main body  55  is the same as the inner diameter of the through-hole  14 . 
     In the state where the exhaust member main body  55  is inserted in the through-hole  14 , the exhaust member main body  55  extends from the through-hole  14  into the interior of the cooling target object mounting chamber  43 , with the other end of the exhaust member main body  55  positioned in an exhaust port positioning space  59 . 
     The exhaust port positioning space  59  is a space located in the upper half of the cooling target object mounting chamber  43 , and is a space having a width in the transverse direction that is equal to the maximum width in the transverse direction of the suction port  48  (the diameter of the suction port  48  in the case shown in  FIG. 3 ). 
     If the distance in an orthogonal direction between the lower surface  36   a  of the lid  36  and the upper surface  38   a  of the base plate  38  is deemed the height H of the cooling target object mounting chamber  43 , then the aforementioned space located in the upper half is defined as the space, within the internal space inside the cooling tank, from the lower surface  36   a  of the lid  36  down to an orthogonal distance of H/2 below the lower surface. Further, the transverse direction of the exhaust port positioning space  59  and the transverse direction of the suction port  48  refer to the direction orthogonal to the aforementioned height and parallel to the baffle member  25 . 
     Furthermore, the expression that the exhaust port positioning space  59  has a width in the transverse direction that is equal to the maximum width in the transverse direction of the suction port  48  (the diameter of the suction port  48  in the case shown in  FIG. 3 ) means that, within the internal space inside the cooling tank, the center of the transverse width of the exhaust port positioning space coincides with the center of the maximum transverse width of the suction port, and that these widths in the transverse direction are equal. 
     There are no particular limitations on the outer shape of the surface of the exhaust member main body  55  orthogonal to the direction of extension, and the shape may be circular or rectangular or the like.  FIG. 6  illustrates one example in which the exhaust member main body  55  is a pipe having a circular cylindrical shape (in which the outer shape of the exhaust member main body  55  is circular). 
       FIG. 4  describes one particular example in which the exhaust member main body  55  is inserted into the through-hole  14 , but the inner diameter of the exhaust member main body  55  and the inner diameter of the through-hole  14  may be set to the same size, and the exhaust member main body  55  then secured to the cooling tank  13  without inserting a portion of the exhaust member main body  55  into the through-hole  14 . 
     When the liquid refrigerant is supplied to the fan housing chamber  45  and the pressure inside the cooling tank  13  increases, the exhaust port  56  has a function of adjusting the pressure inside the cooling tank  13  so that it satisfies a prescribed pressure range by discharging a portion of the low-temperature gas (the gasified liquid refrigerant) through the exhaust member main body  55  to a location outside the cooling tank  13 . 
     The exhaust port  56  is provided at the opposite end of the exhaust member main body  55  from the end that is connected to the through-hole  14 . As a result, the exhaust port  56  is positioned inside the cooling target object mounting chamber  45  in a location distant from the first to fourth side walls  39 - 1  to  39 - 4  of the cooling tank  13 . 
     In this manner, by positioning the exhaust port  56  in the exhaust port positioning space  59 , which is the space located in the upper half of the cooling target object mounting chamber  43  having a width in the transverse direction that is equal to the maximum width in the transverse direction of the suction port  48  (the diameter of the suction port  48  in the case shown in  FIG. 3 ), a low-temperature gas flow is generated along the centerline inside the cooling target object mounting chamber  43  flowing from the side wall  39 - 1  toward the side wall  39 - 2 , and by positioning the exhaust port  56  within this flow, drift is eliminated and the cooling target object can be cooled uniformly (or in other words, fluctuations in the quality of the cooling target object  11  can be suppressed). 
     Further, the low-temperature gas located near the first side wall  39 - 1 , the third side wall  39 - 3  and the fourth side wall  39 - 4 , which does not contribute significantly to the cooling of the cooling target object mounting chamber  43 , can be prevented from being discharged from the exhaust port  56 , and therefore the amount of liquid refrigerant used for cooling the cooling target object  11  can be reduced. 
     In other words, the cooling target object  11  can be cooled uniformly, and the amount of liquid refrigerant used for cooling the cooling target object  11  can be reduced. 
     The exhaust port  56  is preferably disposed so that the entire exhaust port  56  is located inside the exhaust port positioning space  59 , but similar effects can be achieved even when only a portion of the exhaust port  56  is located inside the exhaust port positioning space  59 . 
     Further, if the exhaust port  56  is disposed in a space located in the lower half of the cooling target object mounting chamber  43  (namely, the space within the internal space inside the cooling tank from the upper surface  38   a  of the base plate  38  to an orthogonal distance of H/2 above the upper surface), then low-temperature gas that is still capable of satisfactorily contributing to the cooling of the cooling target object mounting chamber  43  is recovered, and therefore, as described above, it is necessary that the exhaust port  56  is disposed in the space located in the upper half of the cooling target object mounting chamber  43 . 
     The exhaust member main body  55  has the exhaust port  56  provided in the opposite end from the end connected to the through-hole  14 , with the opening of the exhaust port  56  facing the lid. By providing the exhaust port  56  facing the lid, the low-temperature gas of lower temperature that has sunk to the bottom of the cooling tank  13  must flow around the exhaust member main body  55  to reach the exhaust port  56 , meaning the cold energy can be used effectively without wastage. For example, if the exhaust port  56  in the exhaust member main body  55  were to open toward the side wall  39 - 1  of the cooling tank, then low-temperature gas fed into the cooling tank in the horizontal direction could be readily suctioned through the exhaust port  56  prior to circulation within the cooling tank  13 , resulting in cold energy wastage. 
     As illustrated in  FIG. 7 , when the exhaust member  31  is cut along a surface that passes through the exhaust port  56  in a direction orthogonal to the direction of extension of the exhaust member main body  55 , the exhaust port  56  preferably has a central angle θ, formed by connecting the two edges  56 A and  56 B of the exhaust port  56  with the center of the exhaust member main body  55 , that is not more than 90°. This enables the amount of the low-temperature gas suctioned through the exhaust port  56  to be set appropriately, meaning the cold energy of the low-temperature gas can be used with minimal waste. 
     As illustrated in  FIG. 2  and  FIG. 4 , the water drain hole  57  penetrates through the exhaust member main body  55 , and is located on the opposite side from the exhaust port  56 , namely on the side facing the base plate  38  of the cooling tank  13 . 
     When the temperature inside the cooling tank  13  reaches a temperature within the prescribed temperature range, and the supply of the liquid refrigerant is stopped, the atmosphere outside the cooling tank  13  can enter via the exhaust member main body  55  (or in other words, the exhaust member  31 ), and sometimes the moisture within the external atmosphere condenses and freezes inside the exhaust member main body  55 , blocking the inside of the exhaust member main body  55 . 
     Accordingly, by providing the water drain hole  57  in the exhaust member main body  55  in a position beneath the exhaust port  56 , the accumulation of moisture inside the exhaust member main body  55  can be suppressed, meaning blockages inside the exhaust member main body  55  (or in other words, the exhaust member  31 ) can also be suppressed. 
     In the sub-zero treatment device of the first embodiment, by providing the exhaust member  31 , which includes the exhaust port  56  and extends into the interior of the cooling target object mounting chamber  43  from the through-hole  14  provided in the third side wall  39 - 3  constituting the cooling target object mounting chamber  43 , and positioning the exhaust port  56  within the exhaust port positioning space  59 , which is the space located in the upper half of the cooling target object mounting chamber  43  having a width in the transverse direction that is equal to the maximum width in the transverse direction of the suction port  48  (the diameter of the suction port  48  in the case shown in  FIG. 3 ), temperature fluctuations in the atmosphere inside the cooling target object mounting chamber  43  can be suppressed even when low-temperature gas (low-temperature gas not contributing to the cooling of the cooling target object mounting chamber  43 ) is discharged through the exhaust port  56 . 
     As a result, the cooling target object  11  can be cooled uniformly (or in other words, fluctuations in the quality of the cooling target object  11  can be suppressed). 
     Further, because exhausting of the low-temperature gas through the exhaust port  56  before the gas can contribute satisfactorily to the cooling of the cooling target object mounting chamber  43  can be suppressed, the amount of the liquid refrigerant used in cooling the cooling target object  11  can be reduced. 
     In other words, the sub-zero treatment device  10  of the first embodiment is capable of uniformly cooling the cooling target object  11  and reducing the amount of liquid refrigerant used for cooling the cooling target object  11 . 
     The first embodiment was described using an example in which the through-hole  14  was provided in the third side wall  39 - 3 , but the through-hole  14  may be provided anywhere in the cooling tank  13  that constitutes the cooling target object mounting chamber  43 , provided that the exhaust port  56  can be positioned in the exhaust port positioning space located between the cooling target object  11  and the baffle member  25 . 
     Specifically, the through-hole  14  may also be provided in any one of the first side wall  39 - 1 , the fourth side wall  39 - 4  and the lid  36  instead of the third side wall  39 - 3 . 
       FIG. 8  is a diagram for explaining a sub-zero treatment device according to a modification of the first embodiment, and is a plan view of the sub-zero treatment device viewed through the lid of the sub-zero treatment device. 
     In  FIG. 8 , those structural portions that are the same as the sub-zero treatment device  10  of the first embodiment illustrated in  FIG. 2  are labeled with the same reference signs. Further, in  FIG. 8 , for the sake of convenience, the lid of the sub-zero treatment device according to this modification of the first embodiment (namely, the lid  36  illustrated in  FIG. 1 ) is omitted. 
     As illustrated in  FIG. 8 , with the exception of having different installation positions for the through-hole  14  and the exhaust member  31 , the sub-zero treatment device  65  according to this modification of the first embodiment has the same structure as the sub-zero treatment device  10  of the first embodiment. 
     In the sub-zero treatment device  65  according to this modification of the first embodiment, the through-hole  14  is provided in the third side wall  39 - 3  in a position close to the first side wall  39 - 1 , so that the exhaust port  56  is disposed within the exhaust port positioning space  59  in a position between the cooling target object  11  and the first side wall  39 - 1 . 
     The sub-zero treatment device  65  according to this modification of the first embodiment, having the type of structure described above, is able to achieve similar effects to the sub-zero treatment device  10  of the first embodiment. 
     Second Embodiment 
       FIG. 9  is a diagram for explaining a sub-zero treatment device according to a second embodiment, and is a plan view of the sub-zero treatment device viewed through the lid of the sub-zero treatment device. 
     In  FIG. 9 , those structural portions that are the same as the sub-zero treatment device  10  of the first embodiment illustrated in  FIG. 2  are labeled with the same reference signs. Further, in  FIG. 9 , for the sake of convenience, the lid of the sub-zero treatment device  70  according to the second embodiment (namely, the lid  36  illustrated in  FIG. 1 ) is omitted. 
     As illustrated in  FIG. 9 , with the exception of replacing the baffle member  25  that constitutes part of the sub-zero treatment device  10  of the first embodiment, and the cooling target object mounting chamber  43  and fan housing chamber  45  separated by the baffle member  25  with a baffle member  71 , and a cooling target object mounting chamber  81  and fan housing chamber  82  separated by the baffle member  71  respectively, the sub-zero treatment device  70  according to the second embodiment has the same structure as the sub-zero treatment device  10 . 
     The baffle member  71  has an angular U-shape when viewed in plan view. The bottom edge of the baffle member  71  contacts the upper surface  38   a  of the base plate  38 , and the upper edge contacts the lower surface of the lid, which is not shown in the drawing. 
     As a result, the baffle member  71  separates the inside of the cooling tank  13  into the cooling target object mounting chamber  81 , which is located inside the baffle member  71  and has a rectangular cuboid shape, and the fan housing chamber  82 , which is located outside the baffle member  71  and has a shape that appears as an angular U-shape when viewed in plan view. 
     The baffle member  71  has a first plate-like member  72 - 1 , a second plate-like member  72 - 2 , and a third plate-like member  72 - 3 . 
     The first plate-like member  72 - 1  is disposed between the agitation fan  27  and the exhaust member  31 . 
     The first plate-like member  72 - 1  is positioned parallel to the first side wall  39 - 1 . The first plate-like member  72 - 1  includes the suction port  48  that opposes the agitation fan  27 . 
       FIG. 10  is a diagram illustrating the second plate-like member of the baffle member illustrated in  FIG. 9 , viewed along the direction M in  FIG. 9 . 
     As illustrated in  FIG. 9  and  FIG. 10 , the second plate-like member  72 - 2  is disposed inside the cooling tank  13  near the third side wall  39 - 3 , in an orientation parallel to the third side wall  39 - 3 . One of the edges in the transverse direction of the second plate-like member  72 - 2  is integrated with the first plate-like member  72 - 1 , and the other edge in the transverse direction contacts the inside surface of the first side wall  39 - 1 . 
     The second plate-like member  72 - 2  has a first blowout port  74 - 1  and an exhaust member insertion hole  76 . The first blowout port  74 - 1  is provided so as to penetrate through the lower portion of the second plate-like member  72 - 2 . The first blowout port  74 - 1  has the function of guiding the atmosphere of the fan housing chamber  82  into the cooling target object mounting chamber  81 . 
       FIG. 11  is a cross-sectional view along the line N-N of the exhaust member, the third side wall of the cooling tank main body, and the second plate-like member of the baffle member illustrated in  FIG. 9 . In  FIG. 11 , structural portions that are the same as those in  FIG. 9  and  FIG. 10  are labeled with the same reference signs. 
     As illustrated in  FIG. 9  to  FIG. 11 , the exhaust member insertion hole  76  is provided so as to penetrate through the second plate-like member  72 - 2  in a location opposing the through-hole  14 . The exhaust member  31  is inserted through the exhaust member insertion hole  76 . 
     As illustrated in  FIG. 9 , the third plate-like member  72 - 3  is disposed inside the cooling tank  13  near the fourth side wall  39 - 4 , in an orientation parallel to the fourth side wall  39 - 4 . One of the edges in the transverse direction of the third plate-like member  72 - 3  is integrated with the first plate-like member  72 - 1 , and the other edge in the transverse direction contacts the inside surface of the first side wall  39 - 1 . 
     The third plate-like member  72 - 3  has a second blowout port  74 - 2 . The second blowout port  74 - 2  is provided so as to penetrate through the lower portion of the third plate-like member  72 - 3  in a location opposing the first blowout port  74 - 1 . 
     The second blowout port  74 - 2  has the same shape as the first blowout port  74 - 1 . 
     Furthermore, the second blowout port  74 - 2  has the same function as the first blowout port  74 - 1 . 
     In the example shown in  FIG. 9  and  FIG. 10 , the first and second blowout ports  74 - 1  and  74 - 2  are illustrated as through-slots that extend along the transverse direction of the plate-like members  72 - 2  and  72 - 3  respectively, but the shape of the first and second blowout ports  74 - 1  and  74 - 2  and the number of blowout ports are not limited to this particular example. Further, the shapes of the first and second blowout ports  74 - 1  and  74 - 2  may also be different from each other. 
     For example, a line or a plurality of lines of circular or rectangular through-hole portions may be provided in the plate-like members  72 - 2  and  72 - 3  as the first and second blowout ports  74 - 1  and  74 - 2 , and the sizes of those through-hole portions may differ. 
     Alternatively, rectangular or oval-shaped through-slots may be positioned along either the transverse direction or the longitudinal direction of the plate-like members  72 - 2  and  72 - 3 , and the sizes of those through-slots may differ. 
     The sub-zero treatment device  70  of the second embodiment, having the type of structure described above, is able to achieve similar effects to the sub-zero treatment device  10  of the first embodiment. 
     Although preferred embodiments of the invention have been described above in detail, the present invention is in no way limited by these specific embodiments, and various modifications and alterations can be made without departing from the scope of the present invention defined in the appended claims. 
     INDUSTRIAL APPLICABILITY 
     The present invention can be applied to a sub-zero treatment device that is capable of uniformly cooling a cooling target object and reducing the amount of liquid refrigerant used for cooling the cooling target object. 
     DESCRIPTION OF THE REFERENCE SIGNS 
     
         
           10 ,  65 ,  70 : Sub-zero treatment device 
           13 : Cooling tank 
           14 : Through-hole 
           16 : Temperature sensor 
           16 A: Tip section 
           18 : Temperature controller 
           21 : Refrigerant supply line 
           23 : Refrigerant supply portion 
           24 : Liquid refrigerant inlet valve 
           25 ,  71 : Baffle member 
           27 : Agitation fan 
           28 : Rotational axis 
           29 : Rotational drive device 
           31 : Exhaust member 
           35 : Cooling tank main body 
           36 : Lid 
           38 : Base plate 
           38   a : Upper surface 
           39 - 1 : First side wall 
           39 - 2 : Second side wall 
           39 - 3 : Third side wall 
           39 - 4 : Fourth side wall 
           43 ,  81 : Cooling target object mounting chamber 
           45 ,  82 : Fan housing chamber 
           47 : Plate-like member 
           48 : Suction port 
           49 - 1 ,  74 - 1 : First blowout port 
           49 - 2 ,  74 - 2 : Second blowout port 
           55 : Exhaust member main body 
           55 A: Center 
           56 : Exhaust port 
           56 A,  56 B: Edge 
           57 : Water drain hole 
           59 : Exhaust port positioning space 
           72 - 1 : First plate-like member 
           72 - 2 : Second plate-like member 
           72 - 3 : Third plate-like member 
           76 : Exhaust member insertion hole 
         H: Height 
         θ: Central angle