Abstract:
A method of operating a refrigerated merchandiser. The refrigerated merchandiser includes a case that defines a product display area, and at least one door that provides access to the product display area. The method includes sensing a parameter of an ambient environment adjacent the case, delivering a signal indicative of the sensed parameter to a controller, and determining a duty cycle using the controller based on the signal indicative of the sensed parameter. The method also includes detecting a change in the sensed parameter using the controller, interrupting the duty cycle by initiating a clearing interval using the controller in response to the controller receiving the signal indicative of the change in the sensed parameter, and clearing condensation from the door during the clearing interval.

Description:
RELATED APPLICATIONS 
       [0001]    This patent application claims priority to U.S. Patent Application Ser. No. 60/870,152, filed Dec. 15, 2006, the entire contents of which are hereby incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    The present invention relates to a control system for a refrigerated merchandiser that heats a glass door of the merchandiser to eliminate condensation on the glass door. More particularly, the present invention relates to a control system for a refrigerated merchandiser that initiates a heating process for a glass door of a refrigerated merchandiser using a controller in response to a change in a position of the glass door. 
         [0003]    Existing refrigerated merchandisers display fresh and frozen food product in a product display area, and include glass doors to provide visibility of the food product and product accessibility to consumers. Often, condensed moisture accumulates on the exterior surface of the cold glass, which obscures viewing of the product in the merchandiser. The moisture in the relatively warm ambient air of the store can condense on the outside surface of the glass door. Similarly, moisture can condense on the cold inside surface of the glass door when the door is opened. Without heating, the condensation on the outside and inside of the glass door does not clear quickly and obscures the food product in the merchandiser. Long periods of obscured food product caused by condensation may detrimentally impact sales of the food product. 
         [0004]    Some glass doors include a resistive coating or semi-conductive film (e.g., tin-oxide) adhered or affixed to the glass door to remove condensation and fog. The resistive coating supplies heat to the glass door via current flow through the coating caused by a supply of electrical potential or electricity from the merchandiser. Typically, the heat applied to the glass door is controlled by a controller based on a duty cycle. These duty cycles are varied between an “on” state (i.e., heat applied to the glass door) and “off” state to regulate the time that heat is applied to the glass door, and are generally defined by the percentage of time that the duty cycle is in the “on” state. 
         [0005]    Some merchandisers employ a knob or other manual control that can be used by an operator to set the percentage of time that the duty cycle is in the “on” state based on the experience of the operator. Other existing merchandisers include a sensor to sense parameters of the ambient environment surrounding the merchandiser (e.g., humidity, temperature). A controller is in electrical communication with the sensor, and determines a duty cycle to remove condensation from the glass door based on the sensed parameters. 
         [0006]    Typically, sensors of conventional control systems are attached to the merchandiser at a relatively large distance from the glass door and the refrigerated product display area (e.g., on an exterior wall of the merchandiser, on a wall adjacent the merchandiser) to avoid an adverse impact on the sensed parameters caused by infiltration of relatively cold, dry air when the glass door is opened. However, placement of conventional sensors at relatively long distances from the glass door limits the effectiveness of the sensor to accurately measure ambient conditions adjacent the glass door. As a result, the duty cycle determined by the controller may not be adequate to clear the glass door because insufficient heat may be supplied by the resistive coating. Insufficient heat applied to the glass door can cause poor dissipation of condensation and fog. Similarly, inaccurate measurements by the sensor may cause the controller to supply too much heat to the glass door, resulting in increased energy costs. 
         [0007]    Existing control systems regulate heat applied to glass doors based on a predetermined duty cycle. These control systems supply electrical potential to the glass door based on the predetermined time that the duty cycle is in the “on” state. The time that the duty cycle is in the “on” state is regulated to limit energy use by the merchandiser. Once the duty cycle enters the “off” state, no electrical potential is supplied to the glass door. When the glass door is opened during the predetermined time that the duty cycle is in the “off” state, condensation may readily form on the interior and/or exterior of the glass door. 
         [0008]    Conventional control systems cannot eliminate condensation that forms on the glass door when the duty cycle is in the “off” state. Instead, heat is applied to the glass door to remove condensation only when the duty cycle is in the “on” state. As such, the duty cycle regulated by conventional control systems can adversely affect elimination of condensation from the glass door due to a relatively long period of time between the glass door being opened and the duty cycle entering the “on” state. The inability of existing control systems to actively remove condensation from glass doors in response to formation of condensation allows condensation to remain on the glass doors for a long time, and detrimentally impacts the viewability of the food product. 
         [0009]    Similarly, conventional control systems cannot compensate for multiple door openings that occur in a relatively short period of time to adequately clear condensation and fog from the glass doors. For example, when multiple door openings occur and the duty cycle is in the “off” state (i.e., no heat applied to the glass door), condensation can accumulate on the glass door. The condensation is not removed by the control system until the duty cycle enters the “on” state. Depending on the duty cycle, a relatively long period of time can elapse between the last of the multiple door openings and entry of the duty cycle into the “on” state. As a result, the glass door can remain obscured by condensation for a relatively long time. 
       SUMMARY 
       [0010]    In one embodiment, the invention provides a method of operating a refrigerated merchandiser that includes a case that defines a product display area, and at least one door that provides access to the product display area. The method includes sensing a parameter of an ambient environment adjacent the case, delivering a signal indicative of the sensed parameter to a controller, and determining a duty cycle using the controller based on the signal indicative of the sensed parameter. The method also includes detecting a change in the sensed parameter using the controller, interrupting the duty cycle by initiating a clearing interval using the controller in response to the controller receiving the signal indicative of the change in the sensed parameter, and clearing condensation from the door during the clearing interval. 
         [0011]    In another embodiment, the invention provides a method of operating a refrigerated merchandiser that includes a case that defines a product display area, and at least one door that provides access to the product display area. The method includes sensing a parameter of an ambient environment adjacent the case, determining a duty cycle using the controller based on the signal indicative of the sensed parameter, detecting the occurrence of a door event of the door in response to the door moving between a first position to a second position, interrupting the duty cycle by initiating a clearing interval using the controller in response to the door event, and clearing condensation from the door during the clearing interval. 
         [0012]    In yet another embodiment, the invention provides a refrigerated merchandiser that includes a case and at least one door coupled to the case. The case defines a product display area and includes a casing that has at least one mullion defining an opening that is in communication with the product display area. The door provides access to the product display area and substantially encloses the product display area, and includes a glass member that has a conductive film. The refrigerated merchandiser also includes at least one sensor and a controller. The sensor is positioned adjacent the door, and is in communication with the opening to detect a door event of the door and to generate a signal indicative of the door event. The controller is in communication with the sensor to receive a signal indicative of the door event from the sensor, and is further in communication with the conductive film to initiate a clearing interval to clear condensation from the door in response to the signal indicative of the door event. 
         [0013]    Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a perspective view of an exemplary refrigerated merchandiser that includes a plurality of doors and a control system. 
           [0015]      FIG. 2  is a perspective view of the doors and a casing of the refrigerated merchandiser of  FIG. 1 . 
           [0016]      FIG. 3  is an enlarged front view of the refrigerated merchandiser of  FIG. 1 , including a sensor of the control system coupled to the casing adjacent a closed door. 
           [0017]      FIG. 4  is an enlarged perspective view of the refrigerated merchandiser of  FIG. 1 , including the sensor attached to the casing adjacent an open door. 
           [0018]      FIG. 5  is a schematic view of one embodiment of a process of the control system for determining a clearing interval for the doors. 
           [0019]      FIG. 6  is a schematic view of another embodiment of a process of the control system for determining a clearing interval for the doors. 
           [0020]      FIG. 7  is a perspective view of the sensor of  FIG. 3  attached to the casing. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
         [0022]      FIG. 1  shows a refrigerated merchandiser  10  for displaying food product (not shown) available to consumers in a retail setting (e.g., a supermarket or grocery store). The refrigerated merchandiser  10  includes a case  14  that has a base  18 , side walls  22 , a case top  26 , and a rear wall  30 . At least a portion of a refrigeration system (not shown) can be located within the case  14  to refrigerate the food product. The area partially enclosed by the base  18 , the side walls  22 , the case top  26 , and the rear wall  30  defines a product display area  34 . The food product is supported on shelves  38  within the product display area  34 . 
         [0023]    The case  14  includes a casing  42  adjacent a front of the merchandiser  10 .  FIG. 2  shows that the casing  42  includes vertical mullions  46  that define openings  50  to allow access to food product stored in the product display area  34 . The mullions  46  are spaced horizontally along the case  14  to provide structural support for the case  14 . Each mullion  46  is defined by a structural member that can be formed from a non-metallic or metallic material. The mullions  46  are substantially hollow, and can be filled with insulating foam (not shown). In some constructions, a light assembly  54  may be attached to a surface of the mullions  46  adjacent the product display area  34  to illuminate the food product. 
         [0024]    As illustrated in  FIGS. 1 and 2 , the case  14  further includes doors  58  pivotally attached to the casing  42  using upper and lower hinge assemblies  62 . Each door  58  is positioned over a respective opening  50  to allow access to the food product in the product display area  34 . A handle  66  is positioned along an edge of the door  58  to move the door  58  between an open position and a closed position. 
         [0025]    Each door  58  includes a door frame  70  and a glass member  74 . The door frames  70  can be formed from materials (e.g., polyurethane) that have relatively low thermal conductivity for minimizing thermal losses. In other constructions, the door frame  70  may be formed from other suitable material capable of supporting the glass member  74  (e.g., aluminum, steel, composites, etc.). 
         [0026]    One glass member  74  is secured to each door  58  by a respective door frame  70  to allow viewing of the food product from outside the case  14 . In some constructions, the glass member  74  may include three panes of glass. In other constructions, the glass member  74  may include more or fewer than three glass panes (e.g., one pane of glass, four panes of glass). Generally, multiple panes of glass are spaced apart from each other and held in generally parallel, face-to-face positions relative to each other by the door frame  70 . In some constructions, one or more of the glass panes may include a low-emissivity coating. 
         [0027]    Condensation generally forms on a surface of the glass member  74  when the temperature of the surface is lower than a dew point of air that is in contact with the surface. Condensation is a result of a combination of surface temperature and moisture in the surrounding air. Thus, condensation can form on an interior surface of the glass member  74  after the door  58  has been opened due to exposure of the generally cold interior surface to generally warm ambient conditions. Similarly, condensation can form on an exterior surface of the glass member  74  when the temperature of the exterior surface is below the dew point of the ambient air. 
         [0028]    In the illustrated construction, an electrically conductive film or resistive coating (not shown) is adhered to the interior surface of each glass member  74 . The conductive film is generally transparent to minimize interference with viewing the food product stored in the product display area  34 . In some constructions, the conductive film may be adhered to the exterior surface of the glass member  74 , or alternatively, to the interior surface and the exterior surface. 
         [0029]      FIG. 1  shows that the merchandiser  10  further includes a control system that has a sensor  86  attached to each mullion  46 , and a controller  90  in electrical communication with the merchandiser  10  and each sensor  86  via sensor leads  91  ( FIG. 7 ). The sensors  86  are located on the mullions  46  so that the sensors  86  are in communication with the openings  50  to detect when one or more doors  58  are opened and closed. The sensors  86  are also in electrical communication with the controller  90  to deliver signals indicative of the door positions to the controller  90 . In the construction illustrated in  FIG. 7 , each sensor  86  is positioned substantially within the mullions  46  behind a mullion cover  87 , and is in communication with the openings  50  via a hole  88  in each mullion  46 . Each hole  88  generally faces outward from the mullion  46  into the opening  50 . In this construction, an insulating washer  89  can be used to secure each sensor  86  to the mullions  46 . In other constructions, the sensors  86  can be adhered to a surface of the mullions  46 . In still other constructions, the sensors  86  can be attached to the door frames  70  adjacent an edge of the doors  58 . 
         [0030]    In some constructions, the sensors  86  are positioned adjacent the doors  58  and in communication with ambient air to detect one or more parameters of an environment surrounding the refrigerated merchandiser  10 . In these constructions, the sensors  86  are defined as environmental sensors, and can include a temperature sensing element and/or a humidity sensing element (not shown) to detect a temperature and humidity of the environment surrounding the merchandiser  10 . In other constructions, the sensors  86  can sense other environment parameters. Generally, the sensors  86  indirectly sense when one or more of the doors  58  are closed based on the sensed parameter (e.g., temperature and/or humidity). The temperature and humidity of the ambient air can be sensed by the sensors  86  at a predetermined time interval (e.g., one minute, two minutes, etc.), or alternatively, the measurements can be made continuously. In some constructions, the sensors are the SHT1x and SHT7x sensors provided by SENSIRION, which are described in the attached Appendix. In other constructions, the sensor  86  may detect other ambient conditions. 
         [0031]    In other constructions, the sensor  86  can be defined as a door switch sensor that is positioned adjacent each door  58  to detect a position of the door  58  (i.e., opened and closed). In these constructions, a different sensing device (not shown) can be coupled to the case  14  to detect various conditions of the ambient environment. 
         [0032]    The controller  90  is in electrical communication with the conductive film through the case  14  to regulate current through the conductive film ( FIG. 1 ) based on the signals received from the sensors  86 . The current is passed through the conductive film, which heats the glass member  74  to remove condensation. The controller  90  is a microcontroller that can be attached to the merchandiser  10  in any suitable location (e.g., the base  18 , on the case top  26 , etc.). Alternatively, the controller  90  may be remotely located from the merchandiser  10 . 
         [0033]      FIGS. 5 and 6  show that the controller  90  determines a duty cycle or pulse width modulation period  94  to regulate heat applied to the glass member  74  based on the conditions of the ambient environment. In constructions that include the sensors  86  defined as environmental sensors, the signals indicative of the conditions of the ambient environment are delivered by the sensors  86  to the controller  90  to establish the duty cycle  94 . In constructions that include the sensors  86  defined as door switch sensors, the additional sensing device can deliver signals indicative of the conditions of the ambient environment to the controller  90 . 
         [0034]    In some constructions, the control system can include one or more sensors  86  to detect ambient conditions of the environment, which send signals indicative of the conditions to the controller  90  for determining the duty cycle  94  for every door  58 . In these constructions, the duty cycle  94  is the same for each door  58 . In other constructions, the control system can include multiple sensors  86 , with one sensor  86  attached to the case  14  adjacent each door  58  to independently regulate the duty cycle  94  for the respective door  58 . In these constructions, the duty cycle  94  for one door  58  can be the same or different from the duty cycle  94  for the remaining doors  58  in a refrigerated merchandiser  10  that includes multiple doors  58 . 
         [0035]    The duty cycle  94  is operated by the controller  90  over a predetermined time duration (e.g., 10 minutes), and is varied by the controller  90  between an “on” state  98  and an “off” state  102  to limit energy consumption of the case  14 . In some constructions, the duty cycle  94  can be varied between a first “on” state that corresponds to a first amount of electrical potential, and a second “on” state that corresponds to a second amount of electrical potential that is larger than the first amount of electrical potential. In other words, the duty cycle  94  in these constructions increases the electrical potential from a first electrical potential to a second, increased or higher electrical potential relative to the first electrical potential to remove condensation and fog from the glass member  74 . After the glass member  74  is cleared, the amount of electrical potential can be decreased from the second electrical potential to the decreased or lower first electrical potential. 
         [0036]    The predetermined time duration represents one complete duty cycle  94 , i.e., the time needed for the duty cycle  94  to cycle through one “on” state  98  and one “off”  102  state. The duty cycle  94  is operated for a first predetermined time in the “on” state  98  (e.g., 4 minutes), and is operated for a second predetermined time in the “off” state  102  (e.g., 6 minutes). When the duty cycle  94  is in the “on” state  98 , heat is applied to the glass member  74  through the conductive film to remove or inhibit condensation. When the duty cycle  94  is in the “off” state  102 , current no longer flows through the conductive film and no heat is applied to the glass member  74 . 
         [0037]      FIGS. 5 and 6  show the duty cycle  94  beginning in the “off” state  102 . In other constructions, the duty cycle  94  may begin in the “on” state  98 . The controller  90  renews the duty cycle  94  in response to expiration of the predetermined time duration. The duty cycle  94  is generally defined by the percentage of time that heat is applied to the glass member  74  (i.e., the first predetermined time relative to the time period defined by one complete duty cycle  94 ). For example, a forty percent duty cycle  94  for a predetermined time duration of ten minutes results in the duty cycle being operated in the “off” state  102  for six minutes (i.e., the first predetermined time), and operated in the “on” state  98  for four minutes (i.e., the second predetermined time). Thus, a relatively small percentage duty cycle  94  (e.g., 10 percent) corresponds to a relatively short second predetermined time, and a relatively large percentage duty cycle  94  (e.g., 90%) corresponds to a relatively long second predetermined time. 
         [0038]    The controller  90  operates the duty cycle  94  in the “on” state  98  for the first predetermined time to clear condensation from the glass member  74 . The first predetermined time is generally a function of the temperature and humidity differential between the refrigerated product display area  34  and the ambient environment. When the differential is relatively large, a longer first predetermined time is needed to clear the condensation from the glass member  74 . When the differential is relatively small, a shorter first predetermined time is adequate to remove or inhibit condensation from the glass member  74 . 
         [0039]    In operation, the control system periodically senses conditions of the environment to determine the duty cycle  94 . The controller  90  receives the signals indicative of the temperature and humidity from the sensor  86 , or alternatively from the sensing device. The duty cycle  94  repeats indefinitely to periodically apply heat to the glass member to inhibit condensation on the interior and exterior surfaces of the glass member  74 . 
         [0040]    Each sensor  86  delivers a signal indicative of a door event  106  to the controller  90  when one or more doors  58  are opened. In other constructions, the door event  106  may be defined by one or more doors  58  in the closed position. The controller  90  selectively initiates a clearing interval  110  in response to the signal indicative of the door event  106 . The clearing interval  110  is defined by a predetermined period of time (e.g., 1 minute, 90 seconds, 2 minutes, etc.) that heat is applied to the glass member  74  to remove or inhibit condensation. In other words, the current flows through the conductive film to heat the glass member  74  when the controller  90  initiates the clearing interval  110 . 
         [0041]    In some constructions, the control system initiates the clearing interval  110  simultaneously for each door  58  of a multiple door refrigerated merchandiser  10  without regard to which door  58  experiences the door event  106 . In these constructions, when a door event  106  is detected by one or more sensors  86  for a corresponding number of doors  58 , the clearing interval  110  is initiated for every door  58 . In other constructions, the control system can initiate the clearing interval  110  independently for each door  58  of a multiple door refrigerated merchandiser  10 . In these constructions, the controller  90  separately initiates the clearing interval  110  and overrides the duty cycle  94  for each door  58  that has experienced the door event  106  independent from the remaining doors  58  that have not experienced a door event  106 . The controller  90  continues to regulate condensation on the remaining doors  58  using the determined duty cycle  94 . 
         [0042]      FIG. 5  shows one embodiment of the control system that selectively initiates the clearing interval  110  based on the humidity sensed by the sensor  86 . The controller  90  establishes a baseline humidity value based on signals from the sensor  86  indicative of the humidity of the ambient environment. The baseline measurements are generally determined on a rolling average of the sensed humidity over a period of time, and indicate an average of the ambient humidity that can be compared with subsequent measurements by the sensor  86 . In other constructions, the control system selectively initiates the clearing interval  110  based on the temperature sensed by the sensor  86 . In these constructions, the controller  90  establishes a baseline temperature value based on signals from the sensor  86  indicative of the temperature of the ambient environment. The baseline measurements are generally determined on a rolling average of the sensed temperature over a period of time, and indicate an average of the ambient temperature that can be compared with subsequent measurements by the sensor  86 . In still other constructions, the control system can selectively initiate the clearing interval  110  based on the temperature and humidity sensed by the sensor  86 , or alternatively, other parameters sensed by the sensor  86 . Generally, the controller  90  establishes a baseline humidity value and/or temperature value based on signals from the sensor  86  indicative of the temperature and/or humidity of the ambient environment. 
         [0043]    Placement of the sensor  86  in close proximity to the glass members  74  subjects the sensors  86  to refrigerated air when the door  58  is opened to access the food product. When the door  58  is open, the sensor  86  detects the relatively cold, dry air from the product display area  34  rather than the ambient conditions outside the case  14 . The measurements of the cold, dry air by the sensor  86  are delivered to the controller  90 , and are compared with the baseline measurements. 
         [0044]    As illustrated in  FIG. 5 , the controller  90  determines the existence of a door event  106  based on the parameter (e.g., temperature, humidity, etc.) of the ambient environment sensed by the sensor  86 . Refrigerated air flows outward from the product display area  34  when the door  58  is opened, which decreases the temperature and humidity of the air adjacent the sensors  86 . In some constructions, a relatively large humidity differential results when the refrigerated air sensed by the sensor  86  is compared by the controller  90  with the baseline humidity. Similarly, a relatively large temperature differential can result when the refrigerated air sensed by the sensor  86  is compared by the controller  90  with the baseline temperature. After the relatively large humidity and/or temperature differential is determined by the controller  90 , the controller  90  discards the measurements of the refrigerated air made by the sensor  86  to avoid changing the duty cycle  94  in response to the refrigerated air. 
         [0045]    Absent a door event  106 , the controller operates the duty cycle  94  without interruption by the clearing interval  110 . The controller  90  determines the existence of the door event  106  based on the relatively large humidity differential and/or temperature differential caused by refrigerated airflow adjacent the sensor  86 . When the door event  106  occurs, the controller  90  interrupts or overrides the duty cycle  94  and initiates the clearing interval  110  to remove or inhibit condensation on the glass member  74 . As illustrated in  FIG. 5 , the controller  90  restarts the duty cycle  94  after the clearing interval  110  is complete (i.e., the predetermined period of time has elapsed). In other constructions, the controller  90  may restart the duty cycle  94  at the point where the duty cycle  94  was interrupted by the clearing interval  110 . 
         [0046]      FIG. 6  shows another embodiment of the control system that initiates the clearing interval  110  in response to a door event  106  based on the signal from the door switch sensor  86 . The duty cycle  94  operates normally and without interruption when a door event  106  is not detected by the controller  90  (i.e., the door  58  remains closed). When the door  58  is opened, the signal indicative of the door event  106  is delivered to the controller  90  by the door switch sensor  86 . As discussed with regard to  FIG. 5 , the controller  90  interrupts or overrides the duty cycle  94  and initiates the clearing interval  110  in response to the signal indicative of the door event  106  to remove or inhibit condensation on the glass member  74 . The controller  90  restarts the duty cycle  94  after the clearing interval  110  is complete (i.e., the predetermined period of time has elapsed). In some constructions, the controller  90  may restart the duty cycle  94  at the point where the duty cycle  94  was interrupted by the clearing interval  110 . In other constructions, the clearing interval  110  may be initiated in response to the closing of the door  58  as sensed by the door switch sensor  86 . In still other constructions, the clearing interval  110  may be initiated after a predetermined lapse of time after the door  58  is opened or closed as detected by the sensor  86 . 
         [0047]    The control system determines the existence of the position of the doors  58  such that heat is applied to the glass members  74  immediately or very soon after the doors  58  move between open and closed positions. Initiation of the clearing interval  106  in response to door events  106  quickly removes or inhibits condensation on the glass members  74 . Once the clearing interval  106  is complete, the control system returns to normal operation. 
         [0048]    Various features and advantages of the invention are set forth in the following claims.