CROSS-REFERENCE TO RELATED APPLICATION AND CLAIM OF PRIORITY
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.
FIELD OF THE INVENTION
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The present application relates generally to refrigerated vending machines and, more specifically, to an apparatus and method for vending machine defrosting.
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OF THE INVENTION
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.
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.
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.
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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.
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.
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.
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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
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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:
FIG. 1 illustrates a block diagram of a vending machine according to an embodiment of the disclosure;
FIG. 2 is a state diagram of initial refrigeration control of a vending machine according to an exemplary embodiment of the disclosure; and
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.
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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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.