1. An improved frost free refrigerator to store food items comprising of an uninterrupted cooling system wherein the system comprising of a fan mounted in lower refrigerator compartment operating on a battery in case of power failure, which pumps the cold air to refrigerator compartment by using cooling of frost on evaporator coils, food stored in freezer and cool pack in freezer, and a temperature sensor mounted in the cold air path.

2. An improved frost free refrigerator as claimed in claim 1, wherein the fan is DC fan mounted in return path/in discharge path.

3. An improved frost free refrigerator as claimed in claim 1 or 2, wherein in case the DC fan is mounted in cold air discharge path, the air flow circulation direction by freezer fan in normal mains power operation and the air flow by the fan on battery in case of power failure remain same.

4. An improved frost free refrigerator as claimed in claim 1 or 2, wherein in case the DC fan is mounted in return air flow path, the air flow circulation direction by freezer fan in normal mains power operation and the air flow by said fan on battery in case of power failure are reverse to each other.

5. An improved frost free refrigerator as claimed in any of the preceding claims, wherein the temperature sensor is such as NTC thermistor to sense the freezer compartment temperature and signals the control circuit.

6. An improved frost free refrigerator as claimed in any of the preceding claims, wherein the cool pack is made of phase change material to store the cooling therein, which is mounted in freezer compartment.

7. An improved frost free refrigerator as claimed in any of the preceding claims, comprising of module of light integrated with electronic control circuit such as herein described wherein the module switches over to battery power automatically from mains power in case of power failure.

8. An improved frost free refrigerator to store food items substantially as herein described with reference to the accompanying drawings.

FIELD OF INVENTION
This invention relates to an improved frost free type Refrigerator used to store the food items. The refrigerator continues to cool the refrigerator compartment even if the mains power fails/ is disconnected for several hours and keeps the food fresh for longer duration.
BACKGROUND OF THE INVENTION
At present the refrigerator having two thermally insulated compartments (Freezer and refrigerator sections) fitted with hermetically sealed compressor based refrigeration cycle system. When the refrigerator is connected to mains AC power supply, it starts cooling the refrigerator. In case, the power supply fails for few hours (eg: no power for 2-8 hrs duration), the refrigerator compartment temperature starts increasing (warming) due to cooling loss through thermal insulation and usage.
The basic construction and cooling operation is described herein below to explain the existing technology.
FROST FREE REFRIGERATOR WORKING:
Referring to figure - 1 explaining the various parts used in refrigerator for its basic function.
The cooling generated at evaporator using the conventional refrigeration cycle principle wherein the refrigeration cycle consists of compressor, condenser coil, evaporator coil, drier and refrigerant.

The cooling generated at evaporator coil is circulated in the whole refrigerator using a fan mounted in freezer compartment. The cold air is circulated through the ducts as shown in the figure.
As mentioned above, the Top mount Frost free refrigerators cooling is carried out by forced airflow using a fan mounted in freezer compartment. The cold air from evaporator coil is circulated in refrigerator and freezer by this fan as long as electrical power is available and maintains the desired temperature inside the refrigerator.
In case of mains power failure condition (several hours very common in India), the refrigerator lower compartment temperature starts increasing rapidly due to stoppage of cold air circulation from freezer section and food gets spoilt.
OBJECTS OF THE INVENTION
The primary object of the present invention is to provide an improved frost free type Refrigerator used to store the food items which is simple in construction.
Another object of the present invention is to provide an improved frost free type Refrigerator used to store the food items which is efficient.
Further object of the present invention is to provide an improved frost free type Refrigerator which uses freezer cooling to cool the Refrigerator compartment by extra battery operated fan in case of AC mains power failure.

STATEMENT OF INVENTION
According to this invention, there is provided an improved frost free refrigerator to store food items comprising of an uninterrupted cooling system wherein the system comprising of a fan mounted in lower refrigerator compartment operating on a battery in case of power failure, which pumps the cold air to refrigerator compartment by using cooling of frost on evaporator coils, food stored in freezer and cool pack in freezer, and a temperature sensor mounted in the cold air path.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings and wherein:
Fig. 1 shows: top mount frost free refrigerator air flow and cooling system.
Fig. 1A shows: electronic control system block diagram. Fig. 2 shows: DC fan mounting in cold air duct discharge point. Fig. 3 shows: modified air flow and new power backup cooling subsystem. Fig. 4 shows: refrigerator air flow system.

DETAIL DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS:
The present invention discloses an improved frost free type refrigerator comprising of a fan mounted in return or discharge path, which runs on a rechargeable battery, a temperature sensor mounted in the cold air path to sense the freezer compartment temperature, which sends the signal to control circuit and a LED module of white light integrated with electronic control circuit.
Referring to fig. 1A, wherein the refrigerator comprising of following components:-
DC fan motor: A DC fan is mounted in return path/in discharge path. It sucks the cold air from frosted evaporator coils and freezer storage cooling, when the main freezer fan is in off condition due to power failure. Then, it throws the cold air in the lower compartment (Refrigerator compartment), maintains cooling and keeps the food fresh for longer period.
Rechargeable battery: It gets charged (store electrical energy) while mains is available and supplies the power to DC extra fan in case of mains power not available. The battery type and voltage level can be selected as per backup duration and life expectancy requirement.
Temperature sensor: It is a temperature sensor for example NTC thermistor. This is mounted in the cold air path to sense the cold air temperature. It is used to sense the freezer compartment temperature and send the signal to control circuit.

ON/Off switch: It is On/off control switch for user to select or deselect the DC fan operation in case of power failure. If switch is Off, the fan remains in off condition and if switch is selected as ON , the fan starts working on battery in case of power failure by automatic switching on battery.
LED indicator: It is a signal LED used to indicate the switch position (On/off) to the user. LED glows when switch is On.
Electronic control circuit: It is an electronic circuit using a DC power supply and semiconductor logic circuit for the following functions:
a) Proper charging and discharging of battery control.
b) Power On/Off control for DC fan as per mains On or Off. If mains AC power available, it keeps the fan off and switches On the DC fan on battery power in case of mains power failure.
c) Stops the DC fan if freezer temperature exceeds (warming) a cut off
temperature limit.
Electronic control reference logic table: Following table explains the control logic of various electric parts used in different conditions for reference:
(Table Removed)

Wiring Harness: This is the wiring harness used to make the electrical circuit connectivity between electrical parts in the refrigerator.
Cool Pack (Phase change material solution): The cool pack is made of PCM (Phase change material) to store the cooling therein. The cool pack is mounted in freezer compartment. It absorbs the cooling when refrigerator is cooled down while operating on mains AC power. Whereas the stored coolness is pumped by battery operated DC fan mounted into lower refrigerator compartment in case of mains AC power failure.
LED white light module: The LED module of white light is also integrated with electronic control circuit. The purpose of white light is to illuminate the refrigerator inside when the refrigerator door is opened. This operates on mains power when mains power available and it switches over to battery power automatically in case of power failure.
WORKING PRINCIPLE: This refrigerator is provided with an extra fan mounted in lower refrigerator compartment which starts operating on a small battery in case of power failure and pumps the cold air to refrigerator compartment. The fan uses the cooling of frost available on evaporator coils, the food stored in freezer and Cool pack (Phase change material used to store cooling) used in freezer.
This way, it helps in maintaining the cooling in refrigerator lower compartment and keeps the food fresh for longer duration. The concept of the present invention is an unique and very useful for the places of longer power cuts. Further, it provides a better cooling appliance compared to existing refrigerators. The battery backup can be set according to the requirement.

The DC fan can be mounted typically in following two different ways (as shown in figures).
A) Cold Air discharge path:
B) Return Air Flow path:

A) Cold Air discharge section: Reference may be made to fig. 2. If the extra DC fan is mounted in cold air discharge path, the air flow circulation direction by freezer fan in normal mains power operation and the airflow by extra fan on battery in case of power failure remain same. The suitable Fan mounting location is in refrigerator lower compartment near air entry point flow path from freezer to Refrigerator lower compartment.
B) Return Air Flow section: Reference may be made to fig. 3. If the extra DC fan is mounted in return air flow path (as shown in figure), the air flow circulation direction by freezer fan in normal mains power operation and the airflow by extra fan on battery in case of power failure are reverse to each other. '
The DC fan mounting is as per refrigerator structure requirement. The important aspect is to use the DC fan to pump the cold air from freezer to refrigerator lower compartment to cool it in case of mains power failure.
Further, reference may be made to fig. 4.

The main aspects of invention are as follows:
1) Use of freezer cooling to cool the Refrigerator compartment by extra battery operated fan in case of AC mains power failure.
2) Optimization and selection of DC fan and battery combination to minimize the cost and maximize back up time.
3) The combination of Cool pack with battery operated fan system to circulate the cool pack cooling to Refrigerator compartment.
4) Mounting of DC fan in two different ways given hereinbelow:

(A) DC Fan mounting in Refrigerator lower compartment's return air path. (The air flow cycle is in reverse direction by battery operated DC fan in case of power failure)
(B) DC fan mounting in refrigerator lower compartment in the cold air entry and pumping the airflow in same direction as in case of normal functioning on mains supply.

5) Use of cooling stored on evaporator coil in the form of frost for refrigerator compartment in case of power failure.
6) Fan mounting on top side of Refrigerator to ease the cold air flow downward to minimize the DC fan and battery capacity.
7) Use of battery operated LED lighting inside Refrigerator along with battery operated DC fan system in case of power failure.
8) Use of NTC temperature sensor to control the battery operated fan operation to limit the temperature rise in freezer compartment.
It is to be noted that the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present invention, which is further set forth under the following claims:-

WE CLAIM;
1. An improved frost free refrigerator to store food items comprising of an uninterrupted cooling system wherein the system comprising of a fan mounted in lower refrigerator compartment operating on a battery in case of power failure, which pumps the cold air to refrigerator compartment by using cooling of frost on evaporator coils, food stored in freezer and cool pack in freezer, and a temperature sensor mounted in the cold air path.
2. An improved frost free refrigerator as claimed in claim 1, wherein the fan is DC fan mounted in return path/in discharge path.
3. An improved frost free refrigerator as claimed in claim 1 or 2, wherein in case the DC fan is mounted in cold air discharge path, the air flow circulation direction by freezer fan in normal mains power operation and the air flow by the fan on battery in case of power failure remain same.
4. An improved frost free refrigerator as claimed in claim 1 or 2, wherein in case the DC fan is mounted in return air flow path, the air flow circulation direction by freezer fan in normal mains power operation and the air flow by said fan on battery in case of power failure are reverse to each other.
5. An improved frost free refrigerator as claimed in any of the preceding claims, wherein the temperature sensor is such as NTC thermistor to sense the freezer compartment temperature and signals the control circuit.
6. An improved frost free refrigerator as claimed in any of the preceding claims, wherein the cool pack is made of phase change material to store the cooling therein, which is mounted in freezer compartment.
7. An improved frost free refrigerator as claimed in any of the preceding claims, comprising of module of light integrated with electronic control circuit such as herein described wherein the module switches over to battery power automatically from mains power in case of power failure.
8. An improved frost free refrigerator to store food items substantially as herein described with reference to the accompanying drawings.