Patent Document

BACKGROUND OF THE INVENTION 
     This invention relates generally to refrigeration and more specifically to a cooler which creates and maintains frost on articles cooled thereby, particularly in conditions where there is low moisture content in the ambient air. 
     Articles which must be or are most preferably kept cold, such as containers of a beverage, are frequently sold from a cooler directly accessible by the consumer. One example of such a beverage is beer, particularly as sold in glass bottles. These coolers may appear in the refrigeration isle of a supermarket or other store, or elsewhere as a point of sale display. Merchandising refrigerated articles in the summer or in locations where the weather is hot is significantly aided by conveying a consumer concept that the beverage is very cold. Conventionally, signage is used which conveys in words and/or illustrations that the products contained within are kept cold. However, such representations do not provide direct visualization to the consumer of the actual temperature of the containers. 
     One way providing the consumer with direct evidence that the temperature of the beverage within the container is cold, is the presence of frost on the exterior of the container. The existence of frost on the bottle immediately conveys to the consumer the concept that the product contained inside is kept cold. It is known to provide frosted glasses or other containers for receiving liquid. Generally, a wetted container is placed in an temperature controlled cooler environment where the temperature of the container is quickly dropped causing the moisture to freeze as ice on the exterior of the container. If the controlled ambient air has a sufficient moisture content, there will not be a problem in maintaining such ice or frost on the containers. However, in some situations where the ambient air has low moisture content, such as in dry or elevated regions, it is difficult to achieve or maintain the frost. Moreover, the presence of substantial moisture in the cooler can cause operating problems for the refrigeration equipment. Still further where the containers carry a liquid, it is necessary to achieve frosting without causing the liquid to freeze. Generally, for glass bottles containing beer, the exterior temperature of the bottle is maintained between about −4° C. and −7.5° C. 
     SUMMARY OF THE INVENTION 
     Among the several objects and features of the present invention may be noted the provision of a cooler which achieves and maintains a frost on articles held by the cooler; the provision of such a cooler which provides additional moisture to the interior of the cooler for condensing on the articles; the provision of such a cooler which maintains the frost on the articles during defrost of a cooling coil in the cooler; the provision of such a cooler which inhibits the circulation of warm air within an article holding zone; the provision of such a cooler which controls delivery of moist air to the article holding zone and maintains the cooler within a desired temperature operating range; the provision of such a cooler which inhibits icing of the cooling coil; the provision of such a cooler which voltage protects its components; and the provision of such a cooler which is self-contained. 
     Generally, a cooler of the present invention comprises an insulated cabinet defining a product zone for holding the articles to be cooled. A cooling coil constructed and arranged for receiving a coolant therethrough removes heat from the product zone in the cabinet and a fan circulates air over the cooling coil and through the product zone in the cabinet. A water vapor source in fluid communication with the product zone delivers water vapor to the zone for condensing on the articles as frost. A controller to control flow of coolant through the cooling coil, operation of the fan and operation of the water vapor source, is configured to automatically conduct a defrost mode of the cooling coil to melt any frost thereon, and to restart a cooling mode of the coil at termination of the defrost mode. The controller delays operation of the fan after restarting the cooling mode following defrost until the cooling coil has reached a preselected temperature so that the circulation of air temperature though the cabinet will not adversely affect frost on the articles. 
     In another aspect of the invention, a cooler for cooling articles and maintaining frost on the articles generally comprises a cabinet, cooling coil, fan, and water vapor source as set forth above. A controller is capable of controlling flow of coolant through the cooling coil, operation of the fan, and operation of the water vapor source to deliver water vapor into the cabinet for condensing on the articles as frost. The controller is configured to prevent operation of the water vapor source until after the product zone has been cooled to a pulldown temperature. 
     In a further aspect of the invention, a cooler for cooling articles and maintaining frost on the articles generally comprises, a cabinet having a product zone, cooling coil and fan as described above. A water vapor source in fluid communication with the product zone delivers water vapor to the product zone for condensing on the articles. The water vapor source comprises a heater for heating water to form a vapor and piping extending from the heater at least partially within the insulated wall of the cabinet and having an outlet opening into the product zone. 
     In still another aspect of the present invention, a cooler for cooling articles and maintaining frost on the articles generally comprises, a cabinet having a product zone, cooling coil and fan as described above. A water vapor source in fluid communication with the product zone for delivers water vapor to the product zone for condensing on the articles. The water vapor source comprises a heater for heating water to form a vapor and piping extending from the heater and having an outlet opening into the product zone. The outlet is located downstream from the cooling coil and fan within the flow of air circulated by the fan. 
     In another aspect of the present invention, a cooler for holding and cooling articles generally comprises a cabinet defining a cooled area in which articles can be held. A cooling coil is disposed for cooling the cooled area, and a fan circulates air over the cooling coil and through the cooled area. The cooler further includes a compressor for compressing refrigerant, a condenser for removing heat from compressed refrigerant, a control for controlling operation of the compressor, and a temperature sensor for detecting the temperature of the cooled area of the cabinet. A voltage sensor detects voltage of a power source to which the cooler can be connected. The control is configured to operate in a normal mode to turn on and off the compressor in response to the temperature of the cooled area detected by the temperature sensor and to operate in an override mode to prevent the compressor from being turned on when the voltage sensor detects that the voltage of the power source is below a predetermined minimum start voltage. 
     Other objects and features of the present invention will be in part apparent and in part pointed out hereinafter. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective of a cooler of the present invention in the form of a merchandiser having a door in an open position with a product shelf (for holding bottles) exploded from the merchandiser; 
     FIG. 2 is a fragmentary rear perspective of the merchandiser showing a water vapor delivery device; 
     FIG. 3 is a schematic, fragmentary cross section of an upper portion of the merchandiser; 
     FIG. 4 is a perspective of a controller and LED display of the merchandiser; 
     FIG. 5 is a diagrammatic plan view of the controller illustrating controller inputs and outputs; 
     FIG. 6 is a schematic illustration of the controller; 
     FIG. 7 is a flow chart illustrating general operation of the controller; and 
     FIGS. 8A-8D are a more detailed flow chart of the operation of the controller. 
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, and in particular to FIG. 1, a frosted bottle merchandiser (broadly, “cooler”) constructed according to the principles of the present invention is designated generally at  9 . The merchandiser comprises a cabinet (generally indicated at  11 ) defining a substantially rectangular interior refrigerated product zone  13  and product mounting shelves  15  for holding articles containing a consumable liquid, such as bottles B of beer. The cabinet  11  includes an outer shell  17  and an inner shell  19 , between which is located insulation  21  (FIG.  3 ). A representative one of the shelves  15  has been exploded from the cabinet  11  in FIG.  1  and has a wire frame construction including plural channels  23  for holding separate rows of bottles B extending in a front to back direction of the cabinet  11  to the thereby optimize air circulation through product zone  13 . A door  25  pivotally mounted on the cabinet can be closed to seal off an open front of the cabinet, or opened to access the product zone  13  in the cabinet  11  to remove or load bottles B. Although in the preferred embodiment the invention is a merchandiser  9 , it is not necessary for a cooler of the present invention to be of the type which is used in a display area of a supermarket or other store, or otherwise to be accessible by the end consumer. Moreover, the articles may be other than beverages or consumables of any type without departing from the scope of the present invention. 
     In the illustrated embodiment, the frosted bottle merchandiser  9  is self-contained, having a compressor  29  located in a lower compartment  31  of the cabinet  11 , an evaporator  33  (FIG. 3) located in an upper compartment  35  above the product zone  13 , and a condenser  39  mounted on the rear wall (FIG. 1) of the cabinet. As such, the merchandiser  9  can be connected to an electrical power source for operation without any other plumbing or electrical connection. The compressor  29  is piped together with the evaporator  33  (broadly, “cooling coil”) and condenser  39  in a conventional vapor compression refrigeration circuit. The compressor  29  forces liquified refrigerant (broadly, “coolant”) from the condenser  39 , through an expansion valve or capillary tube (not shown) into the evaporator  33  where the refrigerant absorbs heat and is vaporized. The vaporized refrigerant returns to the compressor  29  where it is compressed to high pressure and temperature and delivered back to the condenser  39  where the rejection heat load is removed to the condensation temperature of the refrigerant. Other conventional vapor phase system components, such as a receiver (not shown), may be present. It is to be understood that the merchandiser  9  need not be self-contained, as either or both of the compressor  29  and condenser  39 , and/or a control device may be located remotely from the cabinet  11 . Moreover, it is envisioned that secondary cooling or other types of cooling (not shown) may also be used without departing from the scope of the present invention. 
     As shown in FIG. 3, the evaporator  33  is positioned in the upper compartment  35  of the merchandiser  9  defined by upper, side and rear walls of the cabinet  11 , a lower evaporator drip pan  41  and an angled duct member  42  defining a front plenum chamber  43  with a discharge opening  44 . A fan  45  mounted in the upper compartment  35  of the cabinet  11  pulls air from the product zone  13  through a rear air opening behind the drip pan  41  and across the evaporator  33  for removing heat from the air. The cooled air passes through the fan  45  to the front discharge opening  44  where the cold air is discharged to circulate downwardly through the product zone  13  containing the bottles B. The discharge opening  44  preferably extends laterally of the cabinet  11  across the front above the product zone  13  and the flow of air is indicated generally by arrows in FIG.  3 . It will be clear that other air control means may be used to promote even air distribution through the product zone  13 . Thus it may be seen that air is circulated by the fan  45  through the cabinet  11  for evenly cooling the bottles B on all shelves  15  in the cabinet. A defrost heater  47  is provided for defrosting the evaporator  33  and a pan heater  49  is provided for heating the drip pan  41  to facilitate removal of frost from the evaporator coil and keeping the pan from becoming blocked with ice during defrost. In the illustrated embodiment, the heaters  47 ,  49  are controlled on the same circuit  51  (i.e., so both are simultaneously active or inactive, as shown in FIG.  6 ), but it is envisioned that they could be separately controlled. For example in one embodiment, the evaporator heater  47  is controlled by a microcontroller (described hereinafter) to be on, during a defrost cycle, while the drip pan heater  49  may be energized constantly. In another embodiment, an alternate form of defrost, such as hot gas, can be employed. 
     The merchandiser  9  of the present invention is equipped with a water vapor source, indicated generally at  55 , to generate moisture in the air inside the cabinet  11 , as needed to form and maintain a coating of frost on the bottles B. As shown in FIG. 2, the water vapor source  55  comprises a reservoir tank  57  exteriorly mounted on the back side of the cabinet  11  for containing water. A lid  59  covering the open top of the tank  57  has a ports  61  for filling the tank. A central opening  63  in the lid  59  receives a submersible heater  65  into the tank  57  extending down into the water contained in the tank (FIG.  3 ). In the illustrated embodiment, the heater  65  is a 700W heater, but may be of a different power. When energized, the heater  65  heats up the water in the tank to percolate a constant water vapor at the top of the tank. A fitting  67  in the central opening  63  of the lid  59  connects a flexible hose  69  to the tank  57  and allows water vapor to pass out of the tank into the hose. The flexible hose  69  extends upward and bends to attach to another fitting  71  at the rear wall of the cabinet  11  for connection to a moisture distribution duct  73  located between the outer and inner shells  17 ,  19  of the cabinet  11  within the insulation  21 . The insulation  21  helps to reduce heat loss and condensation within the duct  73 . An outlet duct section  75 , including an elongate outlet  77  extends downwardly into the upper cooling compartment  35 . The duct section  73  is inclined to help keep any water condensate from dripping into the upper compartment  35  when the heater  65  is turned off. 
     The outlet  77  is located downstream from the evaporator  33  and fan  45 , with respect to the direction of air flow through the upper compartment  35 . The outlet  77  of the outlet section  75  is also angled toward the front of the merchandiser  9 , away from the evaporator  33  and fan  45 . By this arrangement moisture is entrained in the cold air circulated by the fan  45  and delivered throughout the product zone  13  and over the bottles B, where moisture is desired, before being recirculated back to the evaporator  33  and fan, where moisture is not desired. Thus, optimum moisture condensation on the bottles B is achieved before the air returns to the evaporator  33  and icing of the evaporator is significantly reduced to provide optimum effectiveness of the refrigeration system. In the illustrated embodiment, the moisture distribution system includes the flexible hose  69 , straight duct section  73  and outlet section  75  collectively constitute “piping”. 
     Referring now to FIGS. 4-6, a controller of the merchandiser  9  indicated generally at  81  includes a housing  83  adapted for convenient mounting as on the door  25  of the merchandiser. The controller  81  comprises a microcontroller  85  connected by a ribbon cable  84  to an LED display  86  mounted in the cabinet  11  for viewing the internal temperature and other information, as will be described hereinafter. The microcontroller  85  includes a sensor input for receiving signals from a temperature sensor  87  positioned to detect the air temperature within the product zone  13  of the cabinet  11 . A second input is connected to a set point switch  89  operable to select the air temperature set point for the product zone  13 . In the illustrated embodiment, the merchandiser  9  can be set for −6° C. or −4° C. set point operation. The lower set point may be used in summer or hotter regions, while the higher set point is acceptable for winter or colder regions. A third input is attached to a infrared (IR) receiver  91  used to initiate or terminate defrost, as will be more fully described, by a command external of the microcontroller  85 . The command may be given through a hand held IR control  92 . A fourth input is connected to a door switch  93  which is opened or closed in correspondence with the position of the door  25 . The controller  81  also has a connection for attachment to a power supply  95  (FIG. 5) powering operation of the controller and the LED display  86 . The microcontroller  85  further includes outputs for independently controlling the evaporator and drip pan heaters  47 ,  49 , the compressor  29 , the fan  45  and the vapor generating heater  65 . 
     Referring now to FIG. 6, is may be seen that the input from the temperature sensor  87  is amplified by an amplifier (A) and converted by an analog-to-digital converter (ADC) to a digital signal for manipulation by the microcontroller  85 . A reset circuit  96  is operable to reset the microcontroller  85  as necessary. A voltmeter  97  is in electrical communication with the power source to which the merchandiser  9  is connected for reading the voltage of the power source for the reasons discussed hereinafter. Based on the various inputs, the microcontroller  85  is programmed to operate various control circuits, including the single defrost circuit  51  controlling both the evaporator heater  47  and the drip pan heater  49 , through drivers. A steam circuit  101  operates the heater  65  of the water vapor source  55 , a fan circuit  103  operates the fan  45  and a compressor circuit  105  operates the compressor  29 . The door switch  93  is operable to cause the microcontroller  85  to open the fan circuit  103  to shut off the fan  45  when the door  25  is open. 
     The operation of the controller  81 , (i.e. microcontroller  85 ), and the merchandiser  9 , is now described with reference to FIGS.  7  and  8 A- 8 D. The general operation of the controller  81  is illustrated in FIG. 7 to include initially a system checks routine  107  in which parameters are initialized and operating conditions are checked. Certain steps of the system checks routine  107  are repeated throughout operation of the microcontroller program, as will be described, while others are not. The program proceeds from the system checks to any of three general operating functions (remote defrost initiate/terminate routine  109 , defrost routine  111  or temperature check routine  113 ) depending upon the conditions. If the appropriate signal is received, the controller  81  can initiate defrost (i.e., cause the program to move to defrost routine  113 ) or terminate an ongoing defrost of the merchandiser  9  by way of remote defrost initiate/terminate routine  109 . This is useful both to check operation upon initial installation of the merchandiser  9  and to diagnose problems or verify operation of the merchandiser at some later time. Assuming no special circumstance exists, the controller  81  proceeds to the temperature check routine  113  by comparing the temperature measured by the sensor  87  with the set point. If the temperature is within a bounded range of the set point, the controller  81  proceeds back to the system checks routine  107 . Of course upon start up, the temperature of the product zone  13  is higher than the upper end of the set point range so that the controller  81  will first proceed to a cooling routine  115 . The cooling routine will activate the compressor circuit  105  and the fan circuit  103 , after certain delay periods have expired, to cool and circulate air through the product zone  13  of the merchandiser cabinet  11 . 
     At certain predetermined times or under certain conditions specified hereinafter, the defrost routine  111  is carried out. Defrost is conducted until such time as the temperature of the product zone  13  measured by the sensor  87  exceeds a prescribed upper limit, or a defrost timer times out. An important feature of the present invention is that upon leaving defrost, the fan  45  is delayed after the compressor  29  begins to operate so that warm air will not be circulated through the product zone  13  to protect the frost formed on the bottles B. Also, the fan  45  is not run during defrost for the same reason. Further, defrost will be terminated if the temperature in the product zone  13  rises to a point which threatens the frost on the bottles B. The evaporator heater  47  and drip pan heater  49  are activated by closing the circuit  51  during defrost to heat the evaporator  33  and the drip pan  41 . 
     Activation of the water vapor source  55  pursuant to a frosting routine  117  to provide moisture in the form of steam to the product zone  13  of the cabinet  11  occurs only after the product zone has been pulled down, that is, the temperature in the product zone measured by the sensor  87  has fallen below the lower end of the set point range so that the compressor  29  is shut off. In the illustrated embodiment, the range is ±1.5° C. from the set point (−4° C.), but other set points and ranges may be employed. Frosting will not be initiated by the frosting routine  117  unless the temperature measured in the case is below a certain predetermined minimum frosting initiation temperature. Further, frosting can be terminated after it is started if the measured temperature of the product zone  13  rises above a maximum frosting temperature, which is a temperature above the upper end of the set point range. If conditions for initiating frosting are satisfied, the controller  81  causes the heater  65  to be energized so long as the compressor  29  is running. A frosting timer  118  permits frosting to be carried out for a predetermined period of time (e.g., 40 minutes). Thereafter, frosting is not permitted to activate for another period of time (e.g., 40 minutes). Cycling of the frosting function in this manner assists in reducing icing of the evaporator  33  while maintaining frost on the bottles B. 
     Reference is made to FIGS. 8A-8D for a more specific understanding of the operation of the controller  81 . When the merchandiser  9  is first installed or restarted, the microcontroller  85  begins the operating program with an initialize parameters function  121  setting the initial values of certain parameters used in the remainder of the program. The set point is retrieved as the last set point stored by the microcontroller  85 , which may be for example −4° C. The microcontroller  85  is also placed in a cooling mode. Other parameters are set as follows: 
     
       
         
               
               
             
           
               
                   
               
             
             
               
                 refrigeration cycle timer = 0 
                 compressor delay = 90 seconds 
               
               
                 fan delay = 0 
                 pulldown = LOW 
               
               
                 defrost timer = 0 
                 temperature protection −5° C. = ON 
               
               
                 frosting timer = 0 
                 fan flag = HI 
               
               
                 compressor flag = HI 
               
               
                   
               
             
          
         
       
     
     The meaning of these parameters will be explained hereinafter. In the next step, the microcontroller  85  makes certain that all relays are open, i.e., so that the compressor  29 , fan  45 , evaporator and drip pan heaters  47 ,  49  and water vapor source heater are all inactive as the program begins. The program is now prepared to enter its main operating sections. 
     The system checks routine  107  includes features to protect the compressor  29  (and other electrically powered parts of the merchandiser which are controlled by the microcontroller  85 ) from starting if the voltage from the power source (e.g., utility power or a local generator) is not within specification. The microcontroller  85  receives a signal from the voltmeter  97  (see FIG. 6) which is representative of the voltage of the power source. At a voltage decision block  123  (FIG. 8A) the program compares the measured voltage with a minimum start voltage stored in the microcontroller  85 . Examples of a minimum start voltage are 115 volts for a 127 volt standard power and 198 volts for 220 volt standard power. Of course, the minimum start voltages will depend upon the particular equipment being powered, and can be other than described without departing from the scope of the present invention. If the minimum acceptable start voltage is not present, the program enters a loop in which it will re-examine the measured power source voltage to determine if it is above the minimum start voltage. The program will not proceed until the minimum start voltage is detected so that the compressor  29  and other electrical components of the merchandiser  9  cannot be activated under conditions which could damage or materially reduce their life or maintenance cycle. 
     Once the minimum start voltage has been detected at block  123 , the program proceeds to check for a change in the temperature set point. For example, and as stated above, the merchandiser may have two set points, −4° C. and −6° C. The set point may be changed by the user through the set point switch  89  in the merchandiser  9  (FIG.  6 ). In a set point change decision block  125 , the program determines whether the switch has been changed from one position to the other since the last time the switch position was read. If the switch has been moved, the new set point is shown on the LED display  86  of the merchandiser  9 . The temperature as measured by the temperature sensor  87  is read, and the microcontroller  85  checks at block  127  to determine if the sensor is operating. If not, the controller  81  causes the display  86  to show the alarm or malfunction symbol “99” on the LED display and the program loops back to open the relays, until such time as the presence of an operating sensor is detected. If the sensor  87  is functioning properly, the program of the microcontroller  85  proceeds to update the temperature shown on the LED display  86 . 
     The remote defrost initiate/terminate routine  109  is available, upon detection of a IR signal from a remote control  92 . The remote control can be an IR transmitter provided to a refrigeration installation and/or repair technician. Other types of remote controls, such as RF or hardwired Internet controls could also be used. If the signal is detected by the IR receiver  91 , the microcontroller  85  first verifies at verification block  129  that the signal corresponds to a preset code to prevent inadvertent initiation or termination of the defrost cycle. If the signal does not satisfy the code (i.e. is not found to be a command signal at decision block  131 ), the program returns to its ordinary sequence of operation. However if the signal is verified, the microcontroller  85  will check the mode of operation at decision block  133 , which has been initially set to cooling mode, as noted above. The mode will be changed to defrost mode so that in due course, the defrost routine  111  will be entered. However, in the event the mode of operation had already been changed to defrost mode (such as in the subsequent operation of the merchandiser  9 ), the mode would be changed back to cooling mode. Thus it may be seen that receipt of a signal from the remote control  92  is operable to initiate defrost or to terminate defrost, depending upon the present mode of operation of the microcontroller  85 . 
     If no signal is received by the IR receiver, the program queries whether the microcontroller  85  is in the cooling mode or the defrost mode at decision block  135  (FIG.  8 B). The microcontroller  85  was placed in the cooling mode when the parameters were initialized at block  121 . Assuming no IR signal has been detected to change the mode to defrost, the program increments the refrigeration cycle timer. The next decision block  137  compares the value of the refrigeration cycle timer with the time allotted between initiation of defrost, which in the illustrated embodiment is four hours. Upon start-up of the merchandiser  9 , four hours will not have passed, so the program continues on to inquire at block  139  if the compressor delay, which was initialized at 90 seconds, has counted down to zero. The answer will be no, so the program passes through a step of decrementing the compressor delay and then return to the systems checks routine  107  (more specifically, to voltage decision block  123 ). If the voltage falls below a preset minimum after operation of the compressor  29  has begun, the microcontroller  85  will shut down the compressor. 
     The program will loop back to the same decision block  139  until the compressor delay reaches zero. This will allow some time to make sure that the power source voltage is settled within specification before the compressor  29  can be energized. Eventually, the compressor delay reaches zero and the program proceeds to the temperature check routine  113 . At the high end temperature range decision block  141 , the microcontroller  85  compares the temperature of the product zone  13  measured by the sensor  87  against the set point plus 1.5° C. Where the set point is −4° C., the high end of the temperature range is −2.5° C. The temperature of the product zone  13  in the merchandiser  9  will be greater than −2.5° C. when the merchandiser is first plugged in so the program will leave the temperature check routine  113  and continue on at “E” (FIG. 8C) in the cooling routine  113  at function block  143  to turn on the compressor  29 . In the same block  143 , the microcontroller  85  causes a portion of the LED display  86  to flash, which indicates that the compressor  29  is running. The compressor flag is also reset from its initial value to LOW. The program then checks the fan delay at block  145 , the significance of which will be explained hereinafter in the context of pull down after defrost. However, as an initial matter the fan flag has been set to HI (i.e., “high”) so the program turns on the fan  45  at function block  147 . 
     The frosting routine  117  will not be implemented at this early stage. Although the frosting timer  118  is incremented at block  149 , when the program reaches a temperature protection decision block  151  (FIG. 8D) it will proceed to reset the frosting timer to zero (block  153 ) because the temperature of the product zone  13  in the merchandiser  9  will not have fallen to −5° C. However even if the measured temperature in the product zone  13  is less than −5° C., the frosting routine  117  will not be entered because the product zone has not been pulled down to the lowest end of its temperature range (i.e., −5.5° C.). In other words, unless the compressor  29  has been shut off once, frosting cannot be initiated. The parameter pulldown was initially set to LOW (meaning pulldown not yet achieved) which prevents the onset of frosting at decision block  155 . Under either circumstance, the program proceeds from the frosting timer reset block  153  via “B” which returns the program to the system checks routine  107  (block  123 ). 
     The program will follow the same steps until such time as the temperature of the product zone  13  is reduced to −2.5° C. (or below). The program will proceed from block  141  (FIG. 8B) to a low end temperature range decision block  157  where the measured temperature is compared with the low end of the range (i.e., −5.5° C.). Assuming for purposes of this description that the merchandiser  9  has just been activated, the temperature will be less than −2.5° C. and greater than −5.5° C. for some time, so the program will proceed at “D” back to the cooling routine  115 . The compressor flag has been set to LOW so the answer at decision block  159  (FIG. 8C) is “no” and the program keeps the compressor  29  and fan  45  operating to continue cooling the product zone  13 . Again the frosting routine  117  will not be entered because either the temperature will not be less than −5° C. (FIG. 8D, block  151 ), or because the pulldown flag continues to be LOW (block  155 ) because the compressor  29  has yet to shut off one time. 
     Assuming normal operation of the merchandiser  9 , the temperature in the product zone  13  will eventually fall below −5.5° C. so that the answer at the low temperature end range decision block  157  will be “yes” (FIG.  8 B). The pulldown flag is still set to LOW so the program proceeds from decision block  161  to reset the refrigeration cycle timer and the frosting timer to zero. Immediately following, the pulldown flag is reset to HI, because the merchandiser  9  has achieved refrigeration pulldown of the product zone  13 . Additionally, the compressor  29  is turned off and the compressor flag is set to HI. The compressor delay is reset to 90 seconds (preventing short cycling), and the portion of the LED display  86  stops flashing. The temperature protection −5° C. is turned on. The program once again returns to the system checks routine  107  and proceeds in a loop (at block  139 ) until the compressor delay times out. After the delay has expired, the program proceeds to the temperature check routine  113 . If the temperature remains below the low end of the set point range (i.e., below −5.5° C.) the program cycles back to the system checks routine  107  at “B”. However, because pulldown has been achieved and the pulldown flag is set to HI, the refrigeration cycle timer and frosting timer will not be reset to zero. It is noted that the frosting timer will not have been incremented during the period of the compressor delay. 
     The product zone  13  will warm up due to inherent product heat loads, and ambient conditions around the merchandiser, i.e. as heat exchange from the bottles B of beer is absorbed by the air, as ambient heat penetrates the outer and inner shells  17 ,  19  and insulation  21  of the merchandiser cabinet  11  and as the door  25  is opened to access the bottles. Eventually, when the program reaches low end temperature range decision block  157  (FIG.  8 B), the measured temperature will have risen above −5.5° C. and the program will proceed at “D” to the cooling routine  115 . However, the cooling routine will not be entered because the compressor flag has been set to HI when the compressor  29  was shut off so the program returns (at “C” in FIG. 8C) to block  123 . Thus, the compressor  29  will not be turned on until the measured temperature exceeds the upper end of the set point temperature range. The operation of the cooling routine  115  is substantially the same when the temperature rises again above −2.5° C. It is noted that the frosting routine  117  will not be immediately entered when the compressor  29  is started again because the temperature protection −5° C. is on at the temperature of the product zone  13  will initially be in excess of that (block  151 ). 
     Once pulldown is achieved and the compressor  29  operates for a second time to cool the product zone  13  of the merchandiser  9 , it is possible to enter the frosting routine  117 . When the temperature drops below −5° C., the program proceeds at temperature protection decision block  151  (FIG. 8D) to make certain that the compressor  29  is running (block  163 ) and that pulldown has been achieved (block  155 ). The temperature protection block  163  prevents frosting from being initiated where the temperature in the refrigerate product zone  13  has risen rapidly or cannot be relatively constantly maintained. However, in the circumstances described, both of these conditions would be satisfied and the microcontroller  85  turns on the steam at block  165  by closing the circuit  101  for the heater  65  of the water vapor source  55 . The temperature protection −5° C. will have been turned off at block  167  so subsequent the initiation, frosting may continue at temperatures in the product zone  13  above −5° C. It will be seen that once the temperature protection is turned off at block  167 , the next time the program reaches temperature protection status decision block  169 , the −5° C. temperature check steps (i.e., block  151 ) is skipped. Steam generated by the water vapor source  55  enters the merchandiser  9  for condensing on the bottles B as frost. The program cycles back via “B” to block  123  in the systems check routine  107 . 
     Under normal operating conditions, the program will cycle back to “H” in FIG. 8D, each time incrementing the frosting timer  118  at block  149  in FIG.  8 C. Unless other terminating conditions (to be discussed) are met, the program will continue cycling in this manner so that the heater  65  continues to operate to generate steam for frosting the bottles B. The steam introduces heat into the refrigerated product zone  13  so that even though the compressor  29  is running, the temperature will ordinarily not go below the lower end of the set point temperature range (i.e., below −5.5° C.). It is noted that frosting will continue only so long as the compressor  29  is on (block  163 ). The size of the compressor  29  and set point temperature range are selected so that appropriate conditions for operation of frosting for a selected duration are most likely to occur in normal operation. Eventually when the program gets to a frosting timer decision block  171  (FIG.  8 D), the frosting timer  118  will be greater than 40 minutes. The program then proceeds to decision block  173  where it is inquired whether the frosting timer  118  has exceeded 80 minutes. The times “40 minutes” and “80 minutes” were selected after testing the merchandiser  9  described, but could be other than these particular times without departing from the scope of the present invention. It will be understood that through these steps, frosting is operated (all other things being equal) on a 40 minutes on and 40 minutes off basis. Limiting operation in this manner helps to prevent the evaporator  33  and fan  45  from becoming iced too rapidly in the presence of the additional moisture supplied by the water vapor source  55 . However, operation of the water vapor source  55  is sufficient to keep the bottles B frosted. 
     In any event, the answer to the query at decision block  173  will initially be “no” as the frosting timer  118  will not have been incremented to 80 minutes. The microcontroller  85  then turns off the heater  65  at function block  175  so that steam is not generated. The program will continue to operate to cool the product zone  13  on demand as described above. However, frosting will not be activated because the frosting timer is greater than 40 minutes and less than or equal to 80 minutes. When the frosting timer reaches a value greater than 80 minutes, the program at block  177  resets the frosting timer to zero, which will again allow frosting to occur upon satisfaction of the other conditions previously described. 
     Under certain conditions frosting will be terminated prior to the frosting timer  118  reaching 40 minutes. Each time the program cycles through the frosting routine  117  an inquiry is made at decision block  179  whether the temperature in the product zone  13  of the merchandiser  9  is less than or equal to −2° C. As with all of the temperatures and time periods, this value is believed to be optimal for the particular case and product (beer bottles B), but may be other than described without departing from the scope of the present invention. If the temperature is greater than −2° C., the program inquires at block  181  whether the steam has been turned on twice. In other words has the microcontroller  85  recorded the heater  65  being turned on, then being turned off and thence being turned on again. If frosting has been initiated only once, the program turns the temperature protection 5° C. back on (it will have been turned off at block when the steam is turned on). This will cause the microcontroller  85 , by operation of decision block  151  and function block  175  to turn off the steam (or will prevent the steam from being turned on if frosting has not yet been initiated). Thus, if the temperature in the merchandiser  9  gets two degrees above the set point temperature while frosting is ongoing, frosting will be terminated. The heater  65  of the water vapor source  55  cannot be turned on again until the temperature in the product zone  13  again falls below −5° C. while the compressor  29  is running. 
     However at block  181  if the steam has been turned on twice, the microcontroller  85  will be put into the defrost mode at block  183  and the heater  65  will be de-energized to stop the flow of steam into the merchandiser  9 . When the program cycles back around to the system checks routine  107  (block  123 ), the existence of the defrost mode is detected at block  135  (FIG. 8B) and the microcontroller  85  puts the merchandiser  9  into defrost, the operation of which is to be described. If the temperature in the merchandiser  9  is above −2° C. after the merchandiser has been operating a sufficiently long time for the steam to have been turned on twice, this indicates that the evaporator  33  has probably iced to the point where cooling is materially affected. For this reason, the program causes the microcontroller  85  to begin a defrost of the evaporator  33 . 
     Referring now to FIGS. 8B and 8C, the operation of the defrost routine  111  will be more specifically described. As mentioned previously, defrost may be initiated at decision block  135  if the microcontroller  85  detects that the defrost mode is present under non-standard conditions, such as when the evaporator  33  has iced prematurely or defrost is remotely activated. If no unusual conditions exist, defrost will be initiated on the preset time cycle, such as every four hours. At decision block  137 , the program compares the refrigeration cycle timer against the four hour time limit. If the refrigeration cycle timer is greater than four hours, the program first checks if pulldown at decision block  185  has been achieved (i.e., pulldown=HI). If not, the refrigeration cycle timer is reset to zero and no defrost occurs. 
     Assuming pulldown has been achieved (or that the program detected the defrost mode at block  135 ), the program asks at block  187  whether the conditions of the temperature of the product zone  13  being in excess of 20° C. and the defrost timer being less than 20 minutes are both satisfied. Upon first entering defrost, the answer will be “yes” so that defrost is then initiated by turning on the defrost heaters  47 ,  49 , turning off the compressor  29  and fan  45  and causing a portion of the LED display  86  to hold in a constantly on position. The defrost timer is incremented and the program returns to the system checks routine  107 . Unless defrost is terminated by a signal from the remote control, the program will continue to move through the defrost routine  111  in the manner described until the temperature in the product zone  13  exceeds 20° C. or the defrost timer exceeds 20 minutes. The provision of a temperature termination of defrost protects the bottles B from exposure to temperatures which would rapidly melt the frost on the bottles. 
     When the defrost timer reaches or exceeds 20 minutes or the product zone temperature reaches or exceeds 20° C., the answer at decision block  187  in the defrost routine  111  will be “no”. At this time the program proceeds through “F” to blocks  189 , the defrost heaters  47 ,  49  are turned off, the portion of the LED display  86  is turned off and the defrost timer is reset to zero. In addition, the pulldown is set to LOW and temperature protection −5° C. is turned on. Thus, in order for frosting to be activated after defrost has occurred, pulldown will have to be achieved and the temperature in the product zone  13  will need to be less than −5° C., in the same way as when the merchandiser  9  was first turned on. Thus, the refrigerated condition of the product zone  13  is allowed to be substantially stabilized before warm steam is again introduced. Importantly, compressor and fan delays of 30 seconds and 120 seconds, respectively, are set. The difference in delay times is provided to protect the frost on the bottles B from exposure to warm air circulating through the product zone  13 . At the end of defrost, the evaporator  33  will be relatively warm. The temperature of the product zone  13  will be such that cooling will almost certainly be demanded at decision block  141  and the compressor  29  will be turned on (after the 30 second delay). However, if the fan  45  were allowed to come on simultaneously with the compressor  29  it would be circulating air over a still warm evaporator  33 , causing the air to be warmed rather than cooled. Instead, the compressor  29  is allowed to operate for 90 seconds during which time the evaporator  33  becomes cold again. Only then is the fan  45  permitted to turn on (decision block  145 ) for circulating air over the evaporator  33  and through the product zone  13 . 
     Thus it may be seen that the several objects are achieved and other advantageous results attained by the present invention. The merchandiser  9  protects its electrical components (particularly compressor  29 ) against damage caused by improper power supply voltage. The merchandiser  9  provides moisture to create and maintain frost on products held in the merchandiser. The merchandiser  9  is controlled to protect the frost by limiting defrost time and inhibiting circulation of warm air. Moreover, icing is minimized by limiting the time steam is introduced into the merchandiser  9  and also be providing for termination of the steam under conditions which indicate icing may be occurring. 
     When introducing elements of the present invention or the preferred embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. 
     As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Technology Category: 2