Patent Application
20060179870
1. Field of Invention
The present invention relates to a food refrigeration appliance and, more particularly, to a food refrigeration appliance that includes a power back up system that utilizes cold air from a freezer compartment to keep food stored in a refrigerator compartment below a predetermined temperature during a temporary power outage.
2. Description of Related Art
Most food refrigeration appliances in use today include a food refrigeration compartment and a freezer compartment. Food stored in the food refrigeration compartment is kept slightly above, but near, the freezing point of water to retard the activity of bacteria and delay the onset of spoilage. The freezer compartment is kept well below the freezing point of water, typically about 0° F., which allows for the virtual indefinite storage of many food items. Milk, for example, can be safely stored in a refrigeration compartment for about two weeks, but can be safely stored in the freezer compartment for months.
Food refrigeration appliances use the evaporation of a compressed refrigerant gas to absorb heat. The compressed refrigerant gas becomes a liquid that evaporates at an extremely low temperature, so it can create temperatures below the freezing point of water inside the freezer compartment and the food refrigeration compartment. A compressor compresses the refrigerant gas, which raises the pressure and temperature. Heat-exchanging coils, typically disposed outside the refrigerator allow the refrigerant to dissipate the heat of pressurization. As the refrigerant cools, it condenses to form a liquid that flows through an expansion valve. When the liquid flows through the expansion valve, the liquid refrigerant moves from a high-pressure zone into a low-pressure zone. Expansion causes evaporation, which allows the refrigerant to flowing through coils inside the freezer compartment and the food refrigeration compartment absorb heat, making it cold. Fans help move air adjacent to the coils through the compartments.
The compressors in most food refrigeration appliances are powered by an external electrical alternating current (AC) power source. When this external power is interrupted, such as during a power outage, refrigeration ceases. Once refrigeration ceases, the temperature inside the food refrigeration compartment rises. If the power outage is sufficiently long in duration, the food will be exposed to a risk of spoilage.
If the refrigerator door is not opened, a typical refrigerator will maintain the temperature within the food refrigeration compartment for a period of four to six hours during a power outage. After that period of time has elapsed, food stored within the food refrigeration compartment will begin to spoil. Milk, for example, will begin to develop bacteria within two hours when exposed to temperatures in excess of 40° F.
A freezer compartment, on the other hand, will typically hold the temperature for about 24 to about 48 hours during a power outage, assuming the freezer door is not opened. The food stored within the freezer compartment may begin to defrost, but typically does not begin to spoil during this time.
Power outages occur for many reasons. Most often, power outages are temporary events caused by inclement weather. Most power outages are brief. It has been observed that 67% of power interruptions last five minutes or less. Sustained interruptions account for 33% of outages, where the average duration of a sustained outage is about 106 minutes. In most prolonged instances, power is restored within 9 to 12 hours.
However, in recent times, a spate of hurricanes and other circumstances have created power blackouts that resulted in sustained periods of time in which refrigerators could not function. It has been determined that such extended blackouts result in out-of-pocket expenses of $2 billion for consumers for food spoilage and consumable goods such as candles, flashlight batteries and prepared food, i.e. in restaurants.
75% of American homeowners experienced a power outage in 2000. 99% experienced a power outage between 1996 and 2000. In 2000, the average metro homeowner experienced 2.9 outages, while non-metro homeowners experienced more. The average duration of the longest blackouts in 2000 was 16.8 hours. 10% of American consumers plan to buy a portable generator, which cost in a range between $399 and $1199.
In the event of a sustained or extended outage, it is known that milk will begin to develop bacteria and spoil within two hours if exposed to temperatures above 40 degrees. A typical food refrigeration appliance cannot hold this temperature within a food refrigeration compartment for periods extending beyond 4 to 6 hours, depending on ambient temperature in the kitchen. A freezer compartment It would be highly desirable to have a food refrigeration appliance that could keep food stored in a refrigerator compartment below a predetermined temperature during a temporary power outage.
The difficulties and drawbacks of previous-type systems are overcome by the food refrigeration appliance of the present invention including a freezer compartment for storing food at a first temperature below the freezing point of water and a refrigeration compartment for storing food at a second temperature above the freezing point of water. A duct is provided between the freezer compartment and the refrigeration compartment. A fan is used for moving air through the duct from the freezer compartment to the refrigeration compartment. A battery supplies power to the fan when electrical power from an external source is interrupted during a power outage.
The foregoing and other features of the invention are hereinafter more fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the present invention may be employed.
A typical food refrigeration appliance, i.e. a “refrigerator,” includes a freezer compartment and a separate refrigerator compartment, which may be subdivided into smaller specific purpose compartments. The freezer compartment is for storing food at one or more temperatures below the freezing point of water in order to maintain food items in a frozen state for extended periods of time. The refrigerator compartment is for storing food at one or more temperatures slightly above the freezing point of water but temperatures at which bacteria is actively cultured, to maintain freshness of food and beverage items to be consumed in the near term.
Specific reference is now be made to the figures, where it is appreciated that like reference numerals refer to like elements. The three most common types or configurations of refrigerators are shown in
The freezer compartments 12a, 12b and 12c are respectively closed by a standard freezer door 22a, 22b and 22c. The refrigerator compartments 14a, 14b and 14c are respectively closed by a standard refrigerator door 24a, 24b and 24c. It is to be understood that these doors 22a, 22b, 22c, 24a, 24b and 24c are hinged so as to allow a user to open them along a pivotal axis, as is common in the art. These doors 22a, 22b, 22c, 24a, 24b and 24c may also include shelving for retaining additional food items within the freezer compartment 12a, 12b and 12c or the refrigerator compartment 14a, 14b and 14c when the door 22a, 22b, 22c, 24a, 24b and 24c is closed. The freezer compartment 12a, 12b and 12c and refrigerator compartments 14a, 14b and 14c are retained within a respective cabinet 20a, 20b and 22c. The cabinet 20a, 20b and 22c and the doors 22a, 22b, 22c, 24a, 24b and 24c are preferably thermally insulated to maintain a cold temperature within the compartments 12a, 12b, 12c, 14a, 14b and 14c defined by them.
As shown
As indicated in
It will be appreciated that the refrigerator 10a shown in
Refrigerators operate normally only when a constant supply of power, typically alternating electrical current, is received from an external source such as a standard home electrical outlet or the like. This external power source is required to drive the compressor 30 and the fan 40. In the event of a power outage, the compressor and fan cease to operate, and refrigeration to both the freezer compartment and the refrigerator compartment therefore ceases. In the event of an external power failure, the insulated cabinet 20a, 20b and 20c can keep the freezer compartment 12a, 12b and 12c relatively cold for about 24 to about 48 hours, especially when the freezer compartment is loaded with frozen food items, which serve as a thermal ballast. However, the refrigeration compartment 14a, 14b and 14c tends to warm up more quickly than the freezer compartment in the event of a power outage, particularly when the refrigerator is in a warm ambient environment such as is typical in a home. The temperature within the refrigerator compartment of a conventional refrigerator typically rises above 40° F. within about 2 hours after a power failure or outage.
The present invention serves to prolong the time during which the temperature within the refrigerator compartment is maintained below a desired temperature, and thus also serves to protect the food and beverage items stored in the refrigerator compartment from spoiling for a significantly longer period of time than would otherwise occur with a conventional refrigerator. The present invention provides a battery backup system that selectively energizes a fan to move cold air from the freezer compartment through the duct into the refrigerator compartment. This extends the period during which the refrigerator contents can be maintained at a sufficiently cold temperature to retard food spoiling. Depending upon various factors, which are discussed below, the present invention can maintain the temperature in the refrigerator compartment below a desired temperature for a period of twenty hours or more in the event of an external power failure.
The present invention provides a battery backup system 50 for supplying electrical power to the fan 40 when electrical power from the external source is interrupted during a power outage. A battery 52 supplies power to the fan 40, which moves air through the duct 42 from the freezer compartment to the refrigeration compartment. The air within the freezer compartment is cooled by the food items and other frozen items in or adjacent to the freezer compartment, and thus the fan transfers cold air from the freezer compartment to the refrigerator compartment, as needed, to maintain the temperature of the food items stored in this compartment below a temperature at which spoilage is likely to occur. The battery 52 can be of any desired size, but preferably is large enough and has sufficient capacity to supply power to the fan for at least about 20 hours of operation. Batteries and systems containing batteries suitable for use in the invention can be purchased from Emerson Network Power's Liebert Division.
The battery backup system 50 also preferably comprises a thermostat 46, which can be set to control the operation of the fan 40 during a power outage. In the preferred embodiment, the thermostat 46 is mounted within the refrigeration compartment 14a, 14b and 14c. The thermostat 46, which may be the same as or different from a thermostat used to control the temperature of the refrigeration compartment during the normal operation of the refrigerator using an external power source, preferably includes a switch that closes to send power to the fan 40 when the thermostat 46 senses that the temperature within the refrigerator compartment exceeds a desired set temperature, and opens to stop sending power to the fan 40 when the thermostat 46 senses that the temperature within the refrigerator compartment has fallen below the desired set temperature. It will be appreciated that the thermostat 46 can also include a sensor that sends a signal to a microprocessor control device incorporated into the battery backup system 50, which controls operation of the fan 40.
The backup power system 50 may further comprise thermal ballast elements 54, which assist in the maintenance of cooling in the event of a power outage. The thermal ballast elements 54 can be one or more freezer packs maintained within the freezer compartment 12a, 12b and 12c. It will be appreciated that frozen food items can serve as thermal ballast in the event of a power outage.
In order to insure that the battery 52 is adequately charged in the event of an external power failure, the present battery backup system 50 preferably further comprises a battery charger 56 for recharging and maintaining the charge of the battery 52 using power from the external source. The battery charger 56 is preferably connected to the same power connection 58 that operates the fan 40 under normal conditions such that sufficient charging of the battery 52 can occur when the external power source is functioning properly. The battery backup system 50 also preferably comprises an inverter 60 for switching the electrical power to operate the fan 40 from the external source to the battery 52 during a power outage.
The components comprising the battery backup system 50 can be arranged in a variety of ways. In one embodiment, which is generally shown in
In another embodiment of the invention, which is generally shown in
In yet another embodiment of the invention, which is shown in
The following example is intended only to illustrate the invention and should not be construed as imposing limitations upon the claims.
Measurements were performed using a 22 Cu. Ft. Side-by-Side Refrigerator-Freezer. Model ED2VHGXMQ00 sold by Whirlpool Corporation. An 8-channel DATA PAQ data logger was used to sample interior temperatures during testing. An emergency backup lighting unit with a 20-hour battery was used as a power source. Typical freezer temperatures during use are about 0 to −5 degrees F., while a typical refrigerator temperature was about 35 to 37 degrees F. During testing, the refrigerator compartment was filled with cans of soda, bottles of water and other beverages and the freezer was packed with 66 pounds of bagged ice.
Without using the power backup system according to the invention, as shown in
The temperature did not rise above 40 degrees F. in the refrigerator compartment during any test until the battery was completely discharged and the fan ceased operation. Therefore, it is concluded that the temperature could be maintained in the refrigerator compartment for a much longer time than 17 hours if sufficient battery power was available, and at least until substantial thawing of the freezer contents occurred. It will be appreciated that the length of time during which the refrigerator compartment could be kept below a predetermined temperature in the event of a power failure would depend on variables such as the volume of frozen items stored in the freezer compartment (i.e., the extent of the thermal ballast), the end-user's freezer temperature setting, the ambient temperature of the room in which the refrigerator is stored and the number of times that the refrigerator or freezer doors were opened.
Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and illustrative examples shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.
