Patent Publication Number: US-7219508-B2

Title: Evaporator assembly for cold tables and method for refrigerating cold tables

Description:
The application claims priority to copending U.S. Provision Patent Application No. 60/555,065, filed on Mar. 22, 2004, titled SLOPED COIL EVAPORATOR, the disclosure of which is hereby incorporated in its entirety by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention pertains to commercial cold tables of the type used in the food service industry. More particularly, this invention pertains to evaporator assemblies utilized for refrigerating cold tables. 
     Commercial cold tables are utilized in the food service industry to provide means for chilling containers of food that are exposed to ambient air from above. Commercial cold tables often comprise a refrigerated interior air chamber that is accessible by more or more hinged doors. The air chamber is typically refrigerated using an evaporator assembly. The top of the air chamber is bounded by a plurality of serving containers that can be selectively removed and replaced. Thus, while food placed in the serving containers is exposed to the ambient air, refrigerated air within the air chamber cools the serving containers and thereby chills the food in the containers. The refrigerated air chamber of a cold chamber is often also utilized to store containers of food for future use. 
     The safety guidelines and requirements related to the use of cold tables have changed over time and have resulted in the need to achieve lower average temperatures of the food placed in the serving containers. However, many cold tables are unable to achieve these lower temperatures due to the limitations imposed by their evaporator assemblies that refrigerate their air chambers. The evaporator assemblies utilized in older cold tables often comprised a housing, one or electric fans, and an evaporator coil. Older evaporator assemblies were typically configured such that the fans drew air into the housing of the evaporator assembly from above the evaporator coil and forced such air out of the housing in the opposite direction through the evaporator coil. To increase the ability of such evaporator assemblies to cool the exposed food containers, some evaporator assemblies have been modified by reversing the direction of the electric fan(s) such that air is drawn into the housing through the evaporator coil and is discharged from the housing by the fan(s). As result of this modification, air circulation within the air chamber is reversed and the coldest air in the air chamber is closer to the exposed serving containers, thereby allowing the cold table to achieve lower temperatures of food within the exposed serving containers. 
     Along with the advantages of the modified evaporator assemblies discussed above came several disadvantages. One such disadvantage is that the evaporator coil of such a modified evaporator assembly has an increased tendency to freeze-up. This is because the reversed air circulation flow direction creates a suction force on the condensation that accumulates on the convection fins of the evaporator coil. This suction force prevents the condensation from draining off evaporator coil and often results in the evaporator coil freezing-up. 
     Another disadvantage of the modified evaporator assemblies discussed above is that drawing air into the housing from beneath the fans has a tendency to draw debris, such as lettuce and other foods that are stored within the air chamber, into the evaporator coil. Such debris often clogs the convection fins of the evaporator coil and thereby reduces the cooling capacity of the evaporator assembly. 
     The present invention overcomes the above-mentioned disadvantages associated with prior art evaporator assemblies. Furthermore, the present invention enhances the efficiency of cold table evaporator assemblies by directing the coldest air within the air chamber directly toward the exposed serving containers. 
     SUMMARY OF THE INVENTION 
     The inventors of the present invention have developed a new evaporator assembly for use in connection with cold tables. The new evaporator assembly incorporates several design features that each improve the performance of the evaporator assembly. 
     In a first aspect of the invention, an evaporator assembly is configured and adapted for use within a cold table and comprises a housing, an evaporator coil, and at least one electric fan. The housing defines a interior cavity of the evaporator assembly and comprises a mounting portion that is configured and adapted to support the housing from a vertical wall of the cold table. The housing also comprises first and second air passageways that each connect the interior cavity of the evaporator assembly to an environment external to the evaporator assembly. The evaporator coil comprises a plurality of convection fins, each of which has opposite first and second perimeter edges. The first edges of the convection fins are generally coplanar and define a first plane of the evaporator coil. Likewise, the second edges of the convection fins are also generally coplanar and define a second plane of the evaporator coil. The evaporator coil is fixed in orientation with respect to the housing in a manner such that the first plane of the evaporator coil is inclined from vertical and horizontal when the housing is supported from the vertical wall of the cold table via the mounting portion of the housing. The fan is configured and adapted to draw air from the environment external to the evaporator assembly through the evaporator coil and into the interior cavity of the evaporator assembly via the first air passageway in a manner such that the air passes through the first and second planes of the evaporator coil. The fan is also configured and adapted to expel air from the interior cavity of the evaporator assembly into the environment external to the housing via the second air passageway in a manner such that the air has an upward vertical velocity component and a horizontal velocity component as it is expelled into the environment external to the evaporator assembly. 
     In a second aspect of the invention, a cold table comprises and interior air chamber and an evaporator assembly. The interior air chamber is bound by at least one generally vertical wall. The evaporator assembly comprises a housing, an evaporator coil, and an electric fan. The evaporator assembly is mounted to the wall of the cold table. The housing defines an interior cavity of the evaporator assembly and comprises first and second air passageways that each connect the interior cavity of the evaporator assembly to the interior air chamber of the cold table. The evaporator coil comprises a plurality of convection fins, each of which has opposite first and second perimeter edges. The first edges of the convection fins are generally coplanar and define a first plane of the evaporator coil. Likewise, the second edges of the convection fins are generally coplanar and define a second plane of the evaporator coil. The first plane of the evaporator coil is inclined with respect to the wall. The fan is configured and adapted to draw air from the interior air chamber of the cold table through the evaporator coil and into the interior cavity of the evaporator assembly via the first air passageway in a manner such that the air passes through the first and second planes of the evaporator coil. The fan is also configured and adapted to expel air from the interior cavity of the evaporator assembly into the interior air chamber of the cold table via the second air passageway. 
     In yet another aspect of the invention, a method of refrigerating a cold table comprises steps of providing a cold table, mounting an evaporator coil to the cold table, and circulating air within the cold table. The step of providing a cold table occurs in manner such that the cold table has an interior air chamber. The step of mounting the evaporator coil to the cold table occurs in a manner such that the evaporator coil is inclined. The step of circulating air within the interior air chamber of the cold table occurs in a manner such that the air is circulated through the evaporator coil in a manner drawing heat out of the air and into the evaporator coil to thereby cool the air within the interior air chamber of the cold table. 
     While the principal advantages and features of the invention have been described above, a more complete and thorough understanding of the invention may be obtained by referring to the drawings and the detailed description of the preferred embodiment, which follow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front elevation view of the preferred embodiment of an evaporator assembly in accordance with the invention. 
         FIG. 2  is a rear elevation view of the evaporator assembly shown in  FIG. 1 . 
         FIG. 3  is top plan view of the evaporator assembly shown in  FIGS. 1 and 2 . 
         FIG. 4  is a cross-sectional view of the evaporator assembly shown in  FIGS. 1–3 , taken about the line  4 — 4  shown in  FIG. 3 . 
         FIG. 5  is a side elevation view of the evaporator assembly shown in  FIGS. 1–4  positioned within an cold table, and is shown from within the interior air chamber of the cold table. 
     
    
    
     Reference characters in the written specification indicate corresponding items shown throughout the drawing figures. 
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION 
     A preferred embodiment of an evaporator assembly in accordance with the invention is depicted in  FIGS. 1–5  and is indicated by the reference numeral  20 . In general, the evaporator assembly  20  comprises a housing  22 , an evaporator coil  24 , and one or more electric fan(s)  26 . 
     The housing  22  of the evaporator assembly is preferably formed of sheet metal and preferably comprises a top portion  28 , a front portion  30 , a rear portion  32 , a bottom portion  34 , and opposite side portions  36 . The top portion  28  of the housing  22  is preferably planar and is preferably horizontally oriented. The front portion  30  of the housing  22  preferably comprises a vertical planer portion  38  and an inclined planar portion  40  adjacent and above the vertical planer portion. The top of the inclined planar portion  40  of the front portion  30  of the housing  22  is preferably coterminous with the top portion  28  of the housing. The rear portion  32  of the housing  22  is preferably planar and vertically oriented, and is also preferably coterminous with top portion  28  of the housing. The bottom portion  34  of the housing  22  is generally horizontal with its rear most edge  46  turned upwards, and is preferably coterminous with the vertical planer portion  38  of the front portion  30  of the housing. Additionally, the bottom portion  34  of the housing  22  is preferably spaced vertically below and horizontally in front of the rear portion  32  of the housing. Each of the side portions  36  of the housing  22  is preferably planar and vertically oriented, and is preferably coterminous with each of the top  28 , front  30 , rear  32 , and bottom  34  portions of the housing. The top  28 , front  30 , rear  32 , bottom  34 , and side portions of the housing  22  define and bound an interior air cavity  42  of the evaporator assembly  20  therebetween. 
     The housing  22  also comprises a plurality of openings. The space between the lower edge  46  of the rear portion  32  of the housing  22  and the rear edge  46  of the bottom portion  34 , and between the side portions  36 , creates an evaporator coil opening  48 . Preferably, two circular fan openings  50  extend through the through the inclined planer portion  40  of the front portion  30  of the housing  22 . A drain opening  52  preferably extends through the bottom portion  32  of the housing  22 . One or more electrical pass-through opening(s)  54  preferably extends through either of the side portions  36  of the housing  22 . Finally, one or more refrigerant line opening(s)  56  preferably extend(s) through either of the side portions  36  of the housing  22 . 
     The evaporator coil  24  is preferably a standard off-the-shelf slab type evaporator coil. The evaporator coil  24  comprises a serpentine refrigerant line  58  and a plurality of closely spaced convention fins  60 . The convection fins  60  are typically similar in size and shape to each other and each comprises opposite first  62  and second  64  perimeter edges. The first edges  62  of the convection fins  60  are generally coplanar and define a first plane of the evaporator coil  24 . Likewise, the second edges  64  of the convection fins  60  are also generally coplanar and define a second plane of the evaporator coil  24 . The convections fins also comprise opposite top  66  and bottom  68  perimeter edges that are coterminous with and perpendicular to the first  62  and second  64  edges of the evaporator coil  24 . 
     The evaporator coil  24  is preferably positioned within the housing  22  of the evaporator assembly  20  in an inclined orientation immediately adjacent the evaporator coil opening  48 . A plurality of fasteners  70  secure the evaporator coil  24  to the housing  22 . The opposite ends  72  of the refrigerant line  58  of the evaporator coil  24  preferably extend through the refrigerant line opening(s)  56  of the housing  22 . Preferably, grommets  72  or mastic material can be utilized to block the passage of any air through the refrigerant line opening(s)  56 . 
     The electric fans  26  are preferably off-the-shelf fans of the type typically used in evaporator assemblies. Each fan  26  is preferably positioned within the housing  22  adjacent one of the fan openings  50  that extend through the inclined planar portion  40  of the front portion  30  of the housing. A pair of fasteners  74  preferably sandwich the inclined planar portion  40  of the housing  22  between each one of the fans  26  and a fan grill  76  that covers the fan opening  50  on the exterior of the housing. As such, it should be appreciated that each fan  26  is inclined in a manner such that its axis of rotation is normal to the inclined planar portion  40  of the front portion  30  of the housing  22 . An electrical junction box  78  is preferably attached to housing  22  and the fans  26  are preferably wired to the junction box. 
     The evaporator assembly  20  is preferably installed in a cold table  80  as shown in  FIG. 5 . The evaporator assembly  20  may be utilized as a replacement for a previously installed evaporator assembly or as a component part of a newly produced cold table. Regardless, the installation procedure is generally the same in either case. The evaporator assembly  20  is preferably mounted to the rear vertical wall  82  of the cold table  80  beneath the serving containers  84 . This is preferably done using threaded fasteners (not shown) that extend through the rear portion  32  of the housing  22  and into the vertical wall  82  of the cold table  80 . Thus, the rear portion  32  of the housing  22  acts a mounting portion for securing the evaporator assembly  20  to the cold table  80 . However, it should be appreciated that other techniques for securing the evaporator assembly  20  to the cold table  80 , such as using brackets, adhesives, or other types of fasteners, could be employed. 
     During the installation of the evaporator assembly  20  in the cold table  80 , refrigerant lines from the compressor and condenser (not shown) of the cold table are connected to the refrigerant line  58  of the evaporator coil  24 . Although not shown, it should be appreciated that other refrigeration components, such a solenoid valve and an expansion valve, can be attached to the refrigerant lines either inside or outside of the housing  22  of the evaporator assembly  20 . 
     Additionally, a electrical power supply line  86  is preferably inserted through the electrical pass-through opening  54  of the housing  22  where it is then electrically connected to the fans  26  via the junction box  78 . If applicable, one or more addition power supply lines may also pass through the housing  22  of the evaporator assembly  20  for controlling an internal refrigerant solenoid or other control mechanisms. Finally, a drainage tube  88  is attached to the drain opening  52  of the bottom portion  34  of the housing  22 . The drainage tube  88  is preferably routed to a drain outside of the cold table  80 . 
     During operation, the evaporator assembly  20  circulates and refrigerates the air within the air chamber  90  of the cold table  80 . The fans  26  of the evaporator assembly  20  draw air from the air chamber  90  of the cold table  80  into the interior air cavity  42  of the evaporator assembly  20  through a first air passageway that extends through the evaporator coil opening  48  of the housing  22  and the evaporator coil  24 . As this occurs, the fans  26  also discharge air from within the interior air cavity  42  of the evaporator assembly  20  back out into the air chamber  90  of the cold table  80  through another air passageway that extends through the fan openings  50  of the housing  22  and the fan grills  76 . The general direction of air flow circulation through the evaporator assembly  20  is represented by arrows in  FIG. 5 . 
     Various aspects of the configuration of the evaporator assembly  20  are advantageous over prior art cold table evaporator assemblies. One such aspect is the inclined orientation of the evaporator coil  24 . This inclination facilitates the drainage of condensation. In particular, it should be appreciated that as gravity pulls the condensation on the convection fins  60  downward, the condensation tends to be channeled by cohesion tension along the first edges  62  and bottom edges  64  of the convention fins, and down to the intersections of such edges. By channeling all of the condensation to a single corner of the convection fins  60 , the gravity acting on the condensation is able to overcome the cohesion tension that resists the separation of the condensation from the convection fins. Thus, the condensation is able to drip off of the evaporator coil  24  where it then accumulates on the bottom portion  34  of the housing  22  and ultimately drains from the housing via the drainage tube  88 . With prior art non-inclined evaporator coils, condensation only gathers together after reaching the bottom of the convection fins and therefore slowly moves down the fins. Moreover, condensation reaching the bottom edge of a convection fin of a non-inclined evaporator coil evenly disperses across the length of the bottom edge, thereby increasing the cohesion tension and allowing the evaporator coil to carry more water. Thus, it should be appreciated that the inclination of the evaporator coil  24  of the evaporator assembly  20  disclosed herein facilitates the drainage of condensation from the convection fins  60  and thereby reduces the occurrence of evaporator coil freeze-up. 
     Another beneficial aspect of the evaporator assembly  20  of the preferred embodiment relates to the inclination of inclined planar portion  40  of the front portion  30  of the housing  22  and of the fan(s)  26 . This inclination causes the air discharged from the interior air cavity  42  of the evaporator assembly  20  to exit the evaporator assembly with an upward vertical velocity component and a horizontal velocity component (as depicted by the arrow indicated by reference numeral  92 ). As such, the discharged air, which is the coolest air in the air chamber  90  of the cold table  80 , flows directly toward the serving containers  84 , and thereby lowers the temperature of the serving containers and any food therein beyond what the temperature would otherwise be. 
     Yet another beneficial aspect of the evaporator assembly  20  of the preferred embodiment relates to how circulated air is drawn into the interior air cavity  42  of the evaporator assembly. Notably, the evaporator coil opening  48  of the housing  22  faces the rear vertical wall  82  of the cold table  82 . Thus, air drawn into the interior air cavity  42  of the evaporator assembly  20  is drawn from the area of the air chamber  90  that lies between the evaporator coil opening  48  and the rear vertical wall  82  of the cold table  80  (as depicted by the arrow indicated by reference numeral  94 ). Thus, debris such as food parcels from food items  96  placed in the cold table  80  for storage are less likely to be sucked into the evaporator coil  24  of evaporator assembly  20 . Additionally, the housing  22  prevents items pushed beneath the evaporator assembly  20  from damaging the evaporator coil  24  and shields the evaporator coil from debris dropped from above as serving containers  84  are removed and replaced during normal use of the cold table  80 . 
     While the present invention has been described in reference to a specific embodiment, in light of the foregoing, it should be understood that all matter contained in the above description or shown in the accompanying drawings is intended to be interpreted as illustrative and not in a limiting sense and that various modifications and variations of the invention may be constructed without departing from the scope of the invention defined by the following claims. For example, the evaporator assembly and variation thereof may be utilized in refrigerators and freezers other than cold tables. Thus, other possible variations and modifications should be appreciated. 
     Furthermore, it should be understood that when introducing elements of the present invention in the claims or in the above description of the preferred embodiment of the invention, the terms “comprising,” “including,” and “having” are intended to be open-ended and mean that there may be additional elements other than the listed elements. Similarly, the term “portion” should be construed as meaning some or all of the item or element that it qualifies.