COMPILE AFTER PROVISIONAL
LEFT ON 23/8/06
THE PATENTS ACT, 1970
COMPLETE SPECIFICATION
Section 10
"An Incubator To Maintain The Selected Temperature Of Liquid Reagents"
Span Diagnostics Limited., an Indian company, of 173-B, New Industrial Estate, Udhna,
Surat-394210, India
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

FIELD OF INVENTION
This invention relates to an incubator to maintain the selected temperature of the liquid reagents.
BACKGROUND
Conventional incubators shown in fig 1 & 2A, consists of a rectangular aluminium block (1) having holes (2) on the top to hold test tubes containing liquid reagents. The said rectangular block (1) is provided with a temperature sensor (4) on the side. Printed Circuit Board - PCB (6) having an electronic circuit was placed below the heating element (5). The said PCB and heating elements were placed below the rectangular block holding test tubes containing liquid reagents. When the electronic circuit in the PCB (6) is switched on, it will switch on the heating element (5), which in turn will heat the rectangular aluminium block (1) and the liquid reagents in the test tubes. The sensor (4) on one side of the aluminium block will sense the temperature inside the said block. If the temperature in the rectangular aluminium block exceeds the desired temperature the sensor will sense the temperature, switch off the electronic circuit in the PCB, and thereby disconnect the heating element. The drawbacks of this instrument are:
a) The weight of the rectangular block is more for holding given number of test tubes.
b) The rectangular aluminium block occupies more space and thereby increases the overall size of an instrument.
c) Since overall design is bulky and requires more space, the manufacturing cost is also more.
d) The Power consumption is also more.
e) The sensor (4) is provided on one side of the rectangular block and hence it is not equidistant from holes made on the rectangular block.

Hence, when larger face of the rectangular block dissipate more heat to the ambient as compared to the smaller face of the rectangular block, there lies a minima! difference of temperature gradient between two adjacent faces and that is not sensed by this position of the sensor. Accordingly, the various liquid reagents provided in the test tubes in said rectangular block have variable temperature for a long period.
Another conventional incubators shown in fig 2 & 2A, also consists of a rectangular aluminium bLock(1) having holes (2) on the top to hold test tubes. A PCB (6) having an electronic circuit is connected to the heating element (5). A temperature sensor (4) is placed on said heating plate (3).The said rectangular block is placed on heating plate (3) when the electronic circuit in the PCB (6) is switched on, it will switch on the heating element (5), which in turn heat the heating plate and rectangular aluminium block to maintain the desired temperature of the liquid reagents in the test tubes. Since sensor is built on the heating plate (3), it will sense the temperature of the heating plate and subsequently the temperature of rectangular aluminium block. The drawbacks in this instrument are:
a) The weight of the rectangular block is more for holding given number of test tubes.
b) The rectangular aluminium block occupies more space and thereby increases the overall size of an instrument.
c) Since, overall design is bulky and requires more space, the manufacturing cost is also more.
d) The Power consumption is also more
e) Whenever there is improper or loose contact between the heating plate (3) and the block (1) on the plate (3) and / or the sensor (4) the instrument will not be able to maintain the liquid reagents at the desired temperatures.
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f) Additional heating plate is used which adds in the cost and weight of the instrument
The object of this invention is to maintain the liquids at a desired temperature in the incubators with increased efficiency (i.e reduction in power consumption) by reducing the mass of the block for holding same number of test tubes and to provide compact design with economical price.
To achieve said objective, this invention provides an incubator to maintain the selected temperature of liquid reagent comprising:
- a round aluminium block having holes to hold test tubes containing liquid reagents,
- a PCB having an electronic circuit is placed below the heating element to switch on the said heating element,
- said, PCB heating element and copper foil are placed below said round aluminium block, and
- a temperature sensor which is placed at the center of said round aluminum block through PCB, the heating element and copper foil such that the sensor is at a equidistance from the test tubes in the round aluminium block from the holes in the same pitch circle diameter, to sense the temperature accurately and switch off or on the electronic circuit inside the PCB automatically.
The advantages in using the round aluminium block are:
- The mass of round block used is less as compared to the
conventional rectangular block for holding same number of test tubes
(i.e 24 no of 12.5mm). The mass reduction as compared to
conventional rectangular block is approximately 15-20%.
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- In case of round block the heat dissipation will be uniform from all sides as compared to the conventional rectangular aluminium block. This helps in maintaining uniform temperature through out the round block.
- Round shape has allowed in making. the design of instrument more compact as compared to instrument with conventional rectangular block.
- The heating plate is replaced (Material :- Aluminium, size about 3.-6mm thick) by means of a very thin copper foil (size about 0.03-0.1mm). This, we reduces the overall weight of the instrument. Moreover, by using copper foil, maximum heat from heating element is transferred to the round aluminium block. The reason is copper being very good conductor of heat as compared to aluminium. Here, the copper foil dissipates almost all the heat absorbed by it from the heating element to the round aluminium block. !t saves the power
- loss, which would otherwise, being wasted, in heating the thick aluminium plate. This is one of the important factor in power saving. This reduces the power consumption to as low as 45-90% of the presently available incubators.
- By using the round aluminium block and we positioning the sensor at
' the center of the round block; results in that all the test tubes. in same
pitch circle diameter are equidistant from the temperature sensor. Thereby, sensor will be able to sense the temperature of the reagents in the test tubes more accurately as compared to the conventional rectangular block.
- Moreover black anodized the round aluminium as black body, by its
property is a good heat absorber, it (round aluminium block) regains
the heat what ever is supplied to it rather than dissipating it to the
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environment as compared to the conventional silver anodized Rectangular aluminium block. This is a good heat dissipater.
- By compounding above points, a compact design of the incubator is achieved, which has less power consumption and economy in manufacturing.
The invention will now be described with reference to the accompanying drawings.
Figure 1 shows the conventional rectangular aluminium block incubator having temperature sensor on one side without heating plate
Figure 2 shows the conventional rectangular aluminium block incubator wherein the temperature sensor on the heating plate
Figure 2A shows the conventional rectangular aluminium block having holes for holding the test tubes used in figures 1 & 2
Figure 3 shows the round aluminium block incubator with a temperature sensor at the center, according to this invention.
Figure 3B shows the round aluminium block having holes for holding the test tubes.
Figure 4 shows the complete incubator with round aluminium block having holes for holding the test tubes and its other components
Referring to the drawings, the incubator according to this invention is shown in figure 4. It may be seen from the figure 3 that PCB (6) having electronic circuit, heating element (5) and copper foil (7) are placed below the round aluminum block (8). Sensor (4) is placed at the center of the round aluminium block and goes into the aluminium block to sense the
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temperature of the round aluminium block. The said sensor(4) is at the center of the round aluminum block, which is equidistant from the holes (2) in the same pitch circle diameter to hold the test tubes placed in the round aluminum block, as shown in figure 3B and sense the temperature accurately.
The test tubes containing liquid reagents, which are to be incubated, are kept in the holes provided in the "Round Aluminum Block." This Aluminum block is heated by means of heating resistors / elements, which are located below the block.
Technical specifications of the incubator are mentioned below: TECHINCAL SPECIFICATIONS

1 Temperature Selection Range (Room Temperature +3° C to 70u C (Minimum is 20° C)
2 Temperature Accuracy ±0.2˚C
3 Warm up time (approximate, for glass tubes) For37uC - 20min For 54° C - 30min For 70° C - 40min
4 Display Resolution 0.2UC
5 Timer Selection 1 to 999 minutes
6 Incubator Block Hole specification Diameter - 89mm x 45 mm (Variable) 24 holes of 12.5 mm diameter (Variable)
7 Power Requirement 230 V AC, 50W
8 Fuse Requirement 1A, Fast blow, Glass fuse
g Dimensions Approx. 210 mm x 140 mm x 75 mm
10 Weight Approx. 1.785 Kgs.
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DESCRIPTION
Before operating the said incubator, ensure that the incubator is kept on dry and flat surface and ambient temperature is within range of 20°C to 35°C. Initially when the power is switched "ON," instrument displays the existing temperature of the round block, which is being sensed by the sensor. This sensor senses the value of temperature in the form of resistance. This sensed resistance value is sent to the voltage divider circuit. By using the voltage divider rule this change in resistance of sensor is converted into voltage. The converted voltage is then fed to Analogue to digital converter, which gives digital output of voltage. This voltage is further sent to pre programmed microcontroller for comparison and further action of controlling the associated devices like heating resistors and display. Initially when the incubator is switched on, then the temperature will be more or less equal to the ambient temperature. At this stage, the heating resistor/ elements (5) are in "OFF" condition. In order to start the heating of block we need to set the temperature which atleast +3°C to the displayed temperature.
The temperature can be set by pressing the "TEMP" key and using the arrow keys for incrementing or decrementing the value as shown in figure (4). After setting the temperature, display blinks for 10 times, then the buzzer beeps once to indicate that the microcontroller of the instrument memorizes the new set temperature. Display starts showing the existing temperature of the incubator block. Now the memorized temperature is compared with the existing temperature in the programmed microcontroller in conjunction with other electronic circuitry. If the temperature of the block is less than the set temperature then, the signal is sent to the heating resistors / element (5) through the PCB (6), electronic circuit as explained above, and the heating resistors / elements are switched ON. As a result the heating resistors / elements generate the heat. The generated heat is then transferred to the block via thin Copper foil (size about 0.2 to 0.5mm) (7) by the phenomenon of conduction & convection. Copper foil is used as copper being the very good conductor of heat, it transfers maximum amount of heat
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from the heating resistors to the round aluminium block uniformly at its base. This heated round aluminum block (8) transfers the heat to the test tubes and they in turn heat the liquid / Reagent filled in them.
In order to heat the liquid to desired temperature the temperature of the round aluminum block (8) is. to be controlled by means of temperature sensor.
The temperature of the round aluminum block is controlled by means of an electronic circuit, which involves "TEMPERATURE SENSOR (4)." The sensor senses heat and sends the resistance data to the electronic circuit / PCB (6), which in turn, process the resistance values and convert them into comparison base and sends the corresponding signal for ON OFF action of the heating resistors /element{5). i.e. whether the heating resistor /element (5) should remain "ON" or "OFF" for that particular moment. And .this depends upon the difference between the temperature attained and the temperature set. This process is continuous as long as the Instrument is kept "ON." And as a result the liquid in the test tubes remains at the desired temperature.
From above, it can be concluded that if sensor works properly or if it gives the correct information then the Instrument will respond properly. And for proper control it is necessary to position the sensor at a place from where it can get the best result. Hence, the position of sensor plays a vital role in controlling the temperature of Aluminum block.
The sensor is located right at the center of the block & within the block rather than below the heating plate or at the periphery of the Aluminum block as described in the conventional incubators. So here Sensor comes in direct contact with the aluminum block and as a result it provides the best possible data to the electronic circuit. This provides better control over the temperature of the block.
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Moreover, black anodized the round aluminium block, which helps in storing the heat supplied to it rather than transferring the same to the ambient temperature, as a result the amount of heat loss is less. Also, the block being round, the surface area which is responsible for heat transfer to ambient is @15 % less as compared to conventional rectangular block.
EXAMPLE
1) To Accommodate 24 holes of 12.5mm Dia in Rectangular Block
Dimensions of Rectangular block are= 72mm X 98mm X 45mm
Therefore, Area of Rectangular Block= 7056 Sqmm
To Accommodate 24 holes of 12.5mm Dia in Round Block
Dimensions of Round block is = 89.5 mm Dia X 45mm
Therefore, Area of Round Block = 6288.046 Sqmm
From this, it can be concluded we that round block requires less space, material as well as mass. As aresult overall size of the instrument gets reduced and subsequently the overall raw material cost comes down. The round block can be manufactured more easily as compared to rectangular block.
2) Presently available Instruments in market have a power consumption = @100-150Watt, whereas the present designed Instrument have a Power Consumption = 35Watt Max.
3) Approximate Weight of the conventional rectangular aluminium block is @540 gm, which is having dimensions as 72mm X 98mm x 45mm.
Approximate Weight of the round aluminium block is @450 gm, which is having dimensions as 89.5mm Dia & 45mm height. This is also one of the advantages derived by converting the rectangular block to round.
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We Claim
1. An incubator to maintain the selected temperature of liquid reagents comprising:
- a round aluminum block which is black anodised having holes to
hold test tubes containing liquid reagents,
- a PCB having an electronic circuit is placed below the heating element to switch on the said heating element,
- said PCB, heating element and copper foil are placed below the said round aluminum block, and
- a temperature sensor which is placed at the center of said round aluminum block through PCB, the heating element and copper foil such that the sensor is at a equidistance from the test tubes in the round aluminium block from the holes jn the same pitch circle diameter, to sense the temperature accurately and switch off or on the electronic circuit inside the PCB automatically.

2. An incubator as claimed in claiml, wherein round aluminium block is having 24 holes to hold test tubes containing liquid reagents in three different pitch circle diameter.
3. An incubator such as herein described and exemplified with reference to drawings.
Dated this 22nd. of August, 2006.

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ABSTRACT
An incubator to maintain the selected temperature of liquid reagents comprising:
- a round aluminum block which is black anodised having holes to
hold test tubes containing liquid reagents,
a PCB having an electronic circuit is placed below the heating element to switch on the said heating element,
- said PCB, heating element and copper foil are placed below the said round aluminum block, and
- a temperature sensor which is placed at the center of said round aluminum block through PCB, the heating element and copper foil such that the sensor is at a equidistance from the test tubes in the round aluminium block from the holes in the same pitch circle diameter, to sense the temperature accurately and switch off or on the electronic circuit inside the PCB automatically.