Abstract:
A method includes sensing an exposure of a refrigerated compartment of a vending machine to ambient air and, in response, sensing an initial temperature of the refrigerated compartment. The method also includes, responsive to sensing the exposure to ambient air, selecting a procedure from a plurality of procedures according to the sensed initial temperature, and controlling a refrigeration system of the vending machine using the selected procedure during an initial period. The method may include sensing a current temperature of the vending machine and, once the refrigerated compartment reaches a second predetermined temperature, controlling the refrigeration system according to the sensed current temperature, monitoring an operational characteristic of a compressor of the refrigeration system, and performing a defrost procedure according to the monitored operational characteristic.

Description:
CROSS-REFERENCE TO RELATED APPLICATION AND CLAIM OF PRIORITY 
       [0001]    The present application is related to U.S. Provisional Patent Application No. 61/195,160, filed Oct. 3, 2008, entitled “DEFROST STRATEGY”. Provisional Patent Application No. 61/195,160 is assigned to the assignee of the present application and is hereby incorporated by reference into the present application as if fully set forth herein. The present application hereby claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 61/195,160. 
     
    
     TECHNICAL FIELD OF THE INVENTION 
       [0002]    The present application relates generally to refrigerated vending machines and, more specifically, to an apparatus and method for vending machine defrosting. 
       BACKGROUND OF THE INVENTION 
       [0003]    During operation of a refrigeration system of a refrigerated vending machine, water vapor in the air may condense on the cooling elements (or coils) within the vending machine cabinet. Such condensation may freeze on the coils, and the resulting ice may inhibit the heat transfer from the cooling system to products contained within the vending machine. This reduced heat transfer may increase operating costs and decrease efficiency, and reduce product cooling. Moreover, if ice builds up within the unit, it may interfere with other components of the refrigeration system or vending machine and lead to mechanical failure. 
         [0004]    Defrosting may be performed by temporarily removing all products from the vending machine cabinet, turning off power to the unit, leaving the doors to the unit open, and waiting for the ice to melt, and draining it appropriately. The defrosting process may be sped up by mechanical removal of ice, or by the introduction of gentle heat into the cabinet. For example, placing a pan of hot water in the vending machine and closing the vending machine may be an effective method. In addition, using a fan to blow room temperature air over the built-up ice may also speed up the melting process, as well as help to evaporate moisture from damp surfaces. 
         [0005]    This process can be time consuming and labor intensive. Perishable products may require refrigeration during such a defrosting process. Determining when a defrost cycle is needed may require regular physical inspection of the machine. 
       SUMMARY 
       [0006]    In one embodiment, a method includes sensing an exposure of a refrigerated compartment of a vending machine to ambient air. In response, the method further includes sensing an initial temperature of the refrigerated compartment, selecting a procedure from a plurality of procedures according to the sensed initial temperature, and controlling a refrigeration system of the vending machine using the selected procedure during an initial period. 
         [0007]    In another embodiment, a vending machine includes a controller, a temperature probe, and a refrigeration system. The temperature probe and the refrigeration system are communicatively coupled to the controller. The controller senses an exposure of a refrigerated compartment of a vending machine to ambient air. In response, the controller also senses an initial temperature of the refrigerated compartment, selects a procedure from a plurality of procedures according to the sensed initial temperature, and controls a refrigeration system of the vending machine using the selected procedure during an initial period. 
         [0008]    In yet another embodiment, a method includes sensing an opening of a door of a refrigerated compartment of a vending machine and, in response, sensing an initial temperature of the refrigerated compartment. The method also includes, in response to sensing the opening of the door and during an initial period, operating a compressor of a refrigeration system of the vending machine in cycles of activation and deactivation, where the compressor is activated and deactivated for predetermined lengths of time that are selected according to whether the initial temperature of the vending machine is above a predetermined temperature. 
         [0009]    Before undertaking the DETAILED DESCRIPTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term “controller” means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts: 
           [0011]      FIG. 1  illustrates a block diagram of a vending machine according to an embodiment of the disclosure; 
           [0012]      FIG. 2  is a state diagram of initial refrigeration control of a vending machine according to an exemplary embodiment of the disclosure; and 
           [0013]      FIG. 3  is a state diagram of refrigeration control for temperature maintenance and defrosting of a vending machine according to an exemplary embodiment of the disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]      FIGS. 1 through 3 , discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged vending machine. 
         [0015]      FIG. 1  illustrates a block diagram of a vending machine  100  according to an embodiment of the disclosure. The vending machine  100  includes a vending machine controller (VMC)  102  that operates to control functions of the vending machine  100 . Such functions may include vending, payment, and refrigeration functions. In some embodiments, the control functions of the controller  102  may be implemented in a single microcontroller or microprocessor. In other embodiments, the control functions of the controller  102  may be distributed across a plurality of microcontrollers or microprocessors. 
         [0016]    The vending machine includes a temperature probe  104  that is communicatively coupled to the VMC  102 . The temperature probe  104  is located in a position within the vending machine  100  that enables the temperature probe  104  to sense a temperature that is representative of the temperature of products stored in the vending machine  100 . For example, such a location may be in a product compartment of the vending machine  100  in which products are stored, or in a return air duct for air returning from the compartment to be chilled. 
         [0017]    The vending machine  100  also includes a refrigeration system  106  that controls the temperature of the product compartment of the vending machine  100 , in which products are stored. In the refrigeration system  106 , a refrigerant is compressed in a compressor  108 . The compressed refrigerant is cooled in condenser coils and then passes through an expansion device. The low pressure refrigerant flows through evaporator coils before returning to the compressor. An evaporator fan  110  pulls air from the product compartment over the evaporator coils and pushes chilled air back into the product compartment. The compressor  108  and the evaporator fan  110  are communicatively coupled to the VMC  102 , which controls their operation. In some embodiments, the temperature probe  104  may be located in a position that that enables the temperature probe  104  to sense a temperature of the evaporator coils. 
         [0018]    Typically, the product compartment of the vending machine  100  is accessible via a door for restocking products. The vending machine  100  further includes a door sensor communicatively coupled to the VMC  102 . The door sensor  112  provides an indication of whether the door is open or closed. 
         [0019]    The vending machine  100  also includes a cumulative clock  114  that is communicatively coupled to the VMC  102 . The VMC  102  controls the cumulative clock  114  by resetting its value to zero, starting it without changing its value, stopping it, and reading its current value. The VMC  102  may use the cumulative clock  114  to determine a cumulative length of time that the compressor  108  has been activated by starting and stopping the cumulative clock  114  whenever the VMC  102  activates and deactivates, respectively, the compressor  108 . 
         [0020]      FIG. 2  illustrates a state diagram  200  of initial refrigeration control of a vending machine according to an exemplary embodiment of the disclosure. Often, the door that provides restocking access to the product compartment of the vending machine  100  comprises an entire sidewall of the compartment. As a result, a significant quantity of unchilled outside air may enter the compartment when the door is opened. 
         [0021]    The introduction of outside air and unchilled products to the product compartment during restocking may cause the temperature within the compartment to rise. Furthermore, condensation may build up on products and surfaces inside the product compartment that are below the dew point. Similarly, when power is turned off to the vending machine  100 , the refrigeration system  106  stops functioning and the temperature within the product compartment increases. 
         [0022]    When the door is closed or the power is turned back on, the vending machine  100  enters an initial mode during which the VMC  102  operates the refrigeration system  106  to quickly bring the temperature within the product compartment to a desired operating temperature. This initial mode is illustrated in  FIG. 2 . From any state of the state diagram  200 , when the door is opened, the VMC  102  enters a Door Open/Power Off state  202 . Similarly, when power is first applied to the vending machine, the VMC  102  enters the Door Open/Power Off state  202 . 
         [0023]    When the door sensor  112  indicates that the door is closed, the VMC  102  moves from state  202  to either a Reload state  204  or an Initial Pulldown state  206 , according to an initial temperature in the product compartment, as sensed by the temperature probe  104 . If the initial temperature is less than 73 degrees Fahrenheit, the state of VMC  102  changes to the Reload state  204 . If the initial temperature is greater than or equal to 73 degrees Fahrenheit, the state of VMC  102  changes to the Initial Pulldown state  206 . 
         [0024]    In both the Reload state  204  and the Initial Pulldown state  206 , the VMC  102  controls the refrigeration system  106  according to scripted actions that include cycles of activating and deactivating the compressor  108 , which are explained in more detail below. In either the Reload state  204  or the Initial Pulldown state  206 , if the VMC  102  determines that the temperature probe  104  has reached a predetermined temperature set point, the state of the VMC  102  changes to a Steady State Temperature state  210 . 
         [0025]    In some embodiments, the predetermined temperature set point is 35 degress Fahrenheit. In other embodiments, the predetermined temperature set point is 37 degress Fahrenheit. While particular predetermined temperature set points have been described, it will be understood that in still other embodiments, other predetermined temperature set points may be utilized. In yet other embodiments, the predetermined temperature set point may be set by an operator of the vending machine  100 . 
         [0026]    If the VMC  102  completes the scripted actions in the Reload state  204  and the temperature probe  104  has not reached the predetermined temperature set point, then the state of the VMC  102  changes to a Reload Pulldown state  208 . In the Reload Pulldown state  208 , the VMC  102  again controls the refrigeration system  106  according to scripted actions, which are explained in more detail below. While in the Reload Pulldown state  208 , if the VMC  102  determines that the temperature probe  104  has reached the predetermined temperature set point, the state of the VMC  102  changes to the Steady State Temperature state  210 . 
         [0027]    In the Reload State  204 , the VMC  102  controls the refrigeration system  106  according to the following script of actions. As indicated above, if at any time during the performance of this script the VMC  102  determines that the temperature probe  104  has reached the predetermined temperature set point, the state of the VMC  102  changes to the Steady State Temperature state  210 . 
         [0028]    Reload state  204  Script:
       1. Activate (turn on) the evaporator fan  110 .   2. Wait two minutes.   3. Activate (start) the compressor  108 .   4. Wait forty-five (45) minutes.   5. Deactivate (stop) the compressor  108 . The evaporator fan  110  stays activated (running).   6. Wait three minutes.   7. Start the compressor  108 .   8. Wait forty-five (45) minutes.   9. Stop the compressor  108 . The evaporator fan  110  stays running.   10. Wait two minutes.   11. Start the compressor  108 .   12. Wait forty-five (45) minutes.   13. Stop the compressor  108 . The evaporator fan  110  stays running.   14. Wait two minutes.       
 
         [0043]    Initial Pulldown state  206  Script:
       1. Turn on the evaporator fan  110 .   2. Activate (start) the compressor  108 .   3. Wait FirstIPCompressorOnTime.   4. Deactivate (stop) the compressor  108 . The evaporator fan  110  stays activated (running).   5. Wait four minutes.   6. Start the compressor  108 .   7. Wait SecondIPCompressorOnTime.   8. Stop the compressor  108 . The evaporator fan  110  stays running.   9. Wait ten minutes.   10. Start the compressor  108 .   11. Wait SecondIPCompressorOnTime.   12. Stop the compressor  108 . The evaporator fan  110  stays running. The evaporator fan  110  stays running.   13. Wait twenty minutes.       
 
         [0057]    In some embodiments the FirstIPCompressorOnTime is 7 hours and the SecondIPCompressorOnTime is 6 hours. In other embodiments, which may be used with a smaller vending machine, the FirstIPCompressorOnTime and the SecondIPCompressorOnTime are both 5 hours. 
         [0058]    Reload Pulldown state  208  Script:
       1. Turn on the evaporator fan  110 .   2. Activate (start) the compressor  108 .   3. Wait RPCompressorOnTime.   4. Deactivate (stop) the compressor  108 . The evaporator fan  110  stays activated (running).   5. Wait FirstRPCompressorOffTime.   6. Start the compressor  108 .   7. Wait RPCompressorOnTime.   8. Stop the compressor  108 . The evaporator fan  110  stays running.   9. Wait SecondRPCompressorOffTime.   10. Start the compressor  108 .   11. Wait RPCompressorOnTime.   12. Stop the compressor  108 . The evaporator fan  110  stays running.   13. Wait ThirdRPCompressorOffTime.       
 
         [0072]    In some embodiments:
       the RPCompressorOnTime is six hours,   the FirstRPCompressorOffTime is eight minutes,   the SecondRPCompressorOffTime is twelve minutes, and   the ThirdRPCompressorOffTime is twenty minutes.       
 
         [0077]    In other embodiments, which may be used with a smaller vending machine:
       the RPCompressorOnTime is five hours,   the FirstRPCompressorOffTime is twelve minutes,   the SecondRPCompressorOffTime is twelve minutes, and   the ThirdRPCompressorOffTime is twenty minutes.       
 
         [0082]    While particular compressor on times and compressor off times for two embodiments have been described, it will be understood that in still other embodiments, other compressor on times and compressor off times may be utilized. While three compressor on-off cycles have been described for the two embodiments shown, it will be understood that more or fewer compressor on-off cycles may be used in any or all of the Reload state  204 , the Initial Pulldown state  206 , or the Reload Pulldown state  208 . 
         [0083]      FIG. 3  illustrates a state diagram  300  of the Steady State Temperature state  210 , which provides refrigeration control for temperature maintenance and defrosting of a vending machine according to an exemplary embodiment of the disclosure. In some embodiments, while in the Steady State Temperature state  210 , the VMC  102  maintains a temperature of the product compartment of the vending machine  100  within a range of temperatures. As described with reference to  FIG. 3 , the Steady State Temperature state  210  is entered when the temperature probe  104  has reached a predetermined temperature set point. Upon entering the Steady State Temperature state  210 , the VMC  102  enters a state  302 , deactivating the compressor  108 , setting the cumulative clock  114  to zero, and leaving the evaporator fan  110  activated. 
         [0084]    After two minutes, the VMC  102  enters a state  304 . In the state  304 , the temperature probe  104  is monitored and the compressor  108  is started and stopped according to the current temperature as sensed by the temperature probe  104 . Specifically, when the compressor  108  is stopped and the temperature probe exceeds the predetermined temperature set point by a predetermined hysteresis amount, the compressor  108  and the cumulative clock  114  are started. In some embodiments, the hysteresis amount is 2.7 degrees Fahrenheit. When the compressor  108  is running and the temperature probe falls below the predetermined temperature set point, the compressor  108  and the cumulative clock  114  are stopped. In the state  302 , the evaporator fan  110  is running both when the compressor  108  is activated and deactivated. 
         [0085]    As described in the state  302 , the predetermined temperature set point and the hysteresis amount define a range of temperatures where the temperature set point is at the low end of the range. In other embodiments, the VMC  102  may start the compressor  108  when the temperature probe  104  exceeds the temperature set point and stop the compressor  108  when the temperature probe falls below the temperature set point by more than the hysteresis amount. In such embodiments, the temperature set point is at the high end of the range of temperatures defined by the predetermined temperature set point and the hysteresis amount. In still other embodiments, the predetermined temperature set point and the hysteresis amount may be combined to define a range with the temperature set point in any desired position relative to the range. In still further embodiments, the hysteresis amount may be larger or smaller than 2.7 degrees Fahrenheit. 
         [0086]    After thirty-six (36) hours, the VMC  102  enters a state  308 . In the state  308 , the temperature probe  104  is monitored and the evaporator fan  110  is started and stopped along with the compressor  108 , according to the current temperature as sensed by the temperature probe  104 . Control of the compressor  108  and the cumulative clock  114  according to the current value of the temperature probe  104  is the same as that described for the state  304 . 
         [0087]    In either the state  304  or the state  308 , if a predetermined defrost trigger is reached, the VMC  102  will enter a state  306  or a state  310 , respectively. In both the state  306  and the state  310 , the VMC  102  performs a defrost function by turning off the compressor  108 , while leaving the evaporator fan  110  running. After fifteen minutes, the VMC  102  returns from the state  306  to the state  304 , or from the state  310  to the state  308 . 
         [0088]    In some embodiments, the defrost trigger is a total accumulated time that the compressor  108  has been activated since a last previous defrost cycle or since last entering the Steady State Temperature state  210 . While in the state  304  or the state  306 , the VMC  102  starts and stops the cumulative clock  114  when starting and stopping, respectively, the compressor  108 . When the length of time measured by the cumulative clock  114  exceeds 180 minutes, the defrost trigger is reached and either the state  306  or the state  310  is entered to perform a defrost cycle. When the defrost cycle is completed, the VMC  102  resets the cumulative clock  114  to zero, returns to the state  304  or the state  306 , and resumes starting and stopping the cumulative clock  114  when starting and stopping, respectively, the compressor  108 . 
         [0089]    In other embodiments, the defrost trigger is a number of activations of the compressor  108  since a last previous defrost cycle or since last entering the Reload state  204 . While in the state  304  or the state  306 , the VMC  102  increments a counter each time the compressor  108  is started. When the counter value reaches  20 , the defrost trigger is reached and either the state  306  or the state  310  is entered to perform a defrost cycle. When the defrost cycle is completed, the VMC  102  resets the counter to zero, returns to the state  304  or the state  306 , and resumes counting activations of the compressor  108 . 
         [0090]    In still other embodiments, both the total accumulated time that the compressor  108  has been activated and the number of activations of the compressor  108  are monitored. The defrost trigger may be reached when the first of 180 minutes of activation or 20 activations is reached, and a defrost cycle performed. When the defrost cycle is completed, both the cumulative clock  114  and the activation counter are reset to zero. 
         [0091]    It the embodiment described with reference to  FIG. 2  and  FIG. 3 , the cumulative clock  114  tallies only time that the compressor  108  is activated while in the Maintain Temperature mode  210 . In another embodiment, the cumulative clock  114  also tallies time that the compressor  108  is activated while in one or more of the Reload state  204 , the Initial Pulldown state  206 , or the Reload Pulldown state  208 . In such an embodiment, the cumulative clock  114  is reset to zero each time the compressor  108  is stopped when the temperature probe  104  is above the predetermined temperature set point. When the compressor  108  is started, the cumulative clock  114  is started. Thus, if the temperature probe  104  reaches the predetermined temperature set point VMC  102  and changes to the Maintain Temperature mode  210 , any final period that the compressor  108  was running will be included in the total time count accumulated by the cumulative clock  114 . 
         [0092]    Although the present disclosure has been described with an exemplary embodiment, various changes and modifications may be suggested to one skilled in the art. It is intended that the present disclosure encompass such changes and modifications as fall within the scope of the appended claims. For example, while temperatures have been expressed in Fahrenheit in this disclosure, it will be understood that in other embodiments temperature measurements may be made in Centigrade or another suitable temperature scale.