FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003


COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE OF THE INVENTION
An Air Cooler for Automobiles
APPLICANTS
TATA MOTORS LIMITED, an Indian company
having its registered office at Bombay House,
24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
INVENTORS
Mr. Dattatraya R. Katkar and Mr. Deepak S. Kulkarni
both Indian nationals
of TATA MOTORS LIMITED,
an Indian company having its registered office
at Bombay House, 24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India

PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner
in which it is to be performed


FIELD OF INVENTION
This invention relates to air conditioning arrangement for automobiles. More particularly, it relates to an add on type air conditioning system making use of a freezing mixture as a refrigerant fluid.
BACKGROUND OF THE INVENTION
Rapid growth of economy coupled with growth in industry has resulted in growth in automotive population. Increase in per capita income has changed the luxury into a necessity for example air conditioning, power steering have become essential features of vehicles now. In tropical countries like India the need of air conditioning (cooling) is felt even more. The current technology automotive air conditioners derive power required for their operation from the engine. This arrangement has the following disadvantages. -
i) It consumes the power produced by the engine
ii) It reduces the pickup of the vehicle.
iii) Increases the fuel consumption.
This makes the air conditioning less attractive for diesel engines and more so for small vehicles where the engine power is limited. Secondly, conventional air conditioners also do not cater to the requirement of providing the air conditioning when the engine is not running. In case of present air conditioners the engine must be run at all the times at least at high idle to operate the air conditioner. The present invention deals with a device that provides the cooling of air without absorbing any power from the engine. Thus retaining the vehicle performance intact. This has higher significance in Indian context and in case of light and small vehicles wherein these features are preferably required and without any deterioration in vehicle performance at marginal extra cost
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PRIOR ART
US patent 2841964 teaches a method relating to new and useful improvements and structural modifications in air coolers which are fully self contained and portable. The air cooler is provided with a compartment to receive crushed ice. Dry ice or any other suitable cooling medium. Through air passages are provided inside through the ice compartment. It also comprises of an electric fan which is powered by a portable battery. These constructional features makes it self contained, portable and suitable for indoor as well as outdoor applications
It is evident from the above patents that the first idea makes use of ice or other suitable substance to provide air cooling. In this case improvements and refinements in air coolers are incorporated for making it a portable and compact device. However it suffers from the drawbacks of inadequate heat transfer area . Similarly, when the ice melts, the contact area is reduced lowering the cooling performance.
The present invention aims at overcoming the above mentioned drawbacks and provide a compact and efficient air cooling device for automobiles that will not directly derive the power from the engine.
THEORY OF FREEZING MIXTURE
Freezing mixture is a mixture that produces the cooling effect due to mixing of two substances. Most common freezing mixture is ice and sodium chloride. When the Ice is mixed with sodium chloride, the mixture finally results in formation of a sodium chloride solution . This solution has lower free energy and higher entropy. The free energy change is converted into cooling effect. Thus, the net cooling effect is higher than the latent heat of ice alone. Secondly, the Ice sodium chloride solution provides a temperature of -20 deg C. Thus the freezing mixture provides an additional temperature difference for heat transfer and higher cooling effect. This
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provides faster cooling and prolonged cooling effect. The increment is cooling effect is by 25% and the increase in driving force is by ~ 50%.
The theory freezing mixture is well known and documented sufficiently. The present invention deals with the cooling of passenger compartment cooling of an automobile using a freezing mixture.
OBJECT OF THIS INVENTION
The main object of this invention is to provide an air conditioning system for automobiles that does not consume power from the engine.
Yet another object of this invention is to provide a device and arrangement that augments for air conditioning of the vehicles that does not deteriorate the performance of the vehicle during its use.
Yet another object of this invention is to provide a device and arrangement that augments for air conditioning of the vehicles that does not add any parasitic losses due to its installation.
Yet another object of this invention is to provide a device and arrangement that augments for air conditioning of the vehicles that does not increase the cooling load on the vehicle.
Yet another object of this invention is to provide a device and arrangement for air cooling of vehicles having an environmental friendly refrigerating medium.
SUMMARY OF INVENTION
The present invention deals with use of freezing mixture as a refrigerating medium
for generating the cooling effect which is further used for providing air conditioning
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in the passenger compartment. Ice crush and salt are stored on board separately. The ice crush is stored in an insulated vessel. When the air conditioning is needed, the mixture of ice crush and salt is added into the freezing mixture heat exchanger. The ice crush is stored in an insulated box and stored away from heat and direct sunlight. Typical storage capacity is such that the ice crush should be sufficient for 3 to 4 hrs of operation. The air blower forces the air over the freezing mixture heat exchanger and the air gets cooled as passes over the finned tubes containing the freezing mixture. As the ice melts a salt solution is formed. This salt solution is collected at the bottom and subsequently drained out. Ice crush and sodium chloride are replenished periodically. The further air handling arrangement of the air conditioning system remains similar to the conventional air conditioning system. This is a batch type of system. The feeding of freezing mixture to the heat exchanger tubes is done manually or through an electric motor controlled by the timer.
BRIEF DESCRIPTION OF DRAWINGS
The sketches showing details of the arrangement of components for a freezing mixture air cooling system for automobiles.
Figure 1 shows the constructional details of the of the freezing mixture heat
exchanger in accordance with the current invention.
Figure 2 shows the freezing mixture heat exchanger having feeder arrangement in
accordance with the current invention.
Figure 3 shows the constructional details of the retainer plate
Figure 4 shows the details of the drive arrangement for the feeder screw.
Figure 5 shows the details of the overall arrangement of freezing mixture heat
exchanger.
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DESCRIPTION OF PREFFERED EMBODIMENTS
Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting the same.
As shown in figure 1 the freezing mixture air cooling system (10) heat exchanger comprises of a top header (1) wherein the freezing mixture is stored initially. An opening is provided to top header to feed the freezing mixture. The heat exchanger core tubes (2) run down from the top header. These tubes carry the freezing mixture from top header. Fins (3) are provided around the heat exchanger tubes which enhance the heat transfer. A conical funnel (4) converges from the top header to the core tube, thus all the ice fed into the top header is distributed to individual core tubes. This arrangement ensures complete utilization of freezing mixture. The bottom header (5) receives the molten solution from the heat exchanger tubes. The molten salt solution is collected into the bottom header. A retainer plate (6) holds the freezing mixture (which is in solid state ) in its position inside the core tubes, prevents it from directly falling into the bottom header and allows only the liquid droplets to drip down and get collected into the bottom header. The drain storage (7) tank stores all the solution which is finally drained periodically. A solenoid operated valve (8) is provided in the connection from bottom header to drain tank. This allows the salt solution to be retained into the bottom header and drained out after a predetermined time interval. Thus the leftover cooling effect from the solution can also be extracted. The operation of the solenoid valve (8) is controlled by a timer or by a microprocessor based electronic controller.
Figure 2 shows yet another version of freezing mixture heat exchanger. The
construction of the heat exchanger remains similar to figure 1. In addition, a feed
screw shaft (11) is provided at the entry of the core tubes. It is helical in nature.
One shaft is provided in each core tube. These shafts facilitate the entry of the
freezing mixture into the core tube. The shafts are rotated periodically by an
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electrical motor (12) which is operated by a timer or by an electronic controller. A pair of bevel gears (13) is used to provide the drive for individual feeder screw. The feeder screw arrangement improves feeding of core tubes. The operation of the feed screw (11) and the solenoid valve (8) is controlled by a timer or by a microprocessor based electronic controller.
Fig.3 shows the constructional details of the retainer plate. The retainer plate (6) comprises of a flat plate having small drain holes (14). Multiple holes are drilled on the retainer plate at a distance equal to the pitch of the core tubes.
Fig. 4 shows the details of the bevel gear drive arrangement for the feed screw shaft. The horizontal shaft (15) is driven by the electric motor (12). A pair of bevel gears (13) comprises of gear (16) which is mounted on horizontal shaft (15) and gear (17) which is mounted on vertical shaft (18). This gear pair converts the horizontal rotational motion into vertical rotational motion of the feeder screw. The feeder screw is attached to the vertical shaft (18). This mechanism provides drive to the feeder screw.
Fig.5 shows the overall arrangement of components of the freezing mixture air cooling system. The heat exchanger assembly (10) is mounted inside an air flow duct (20). The heat exchanger assembly is mounted in such a way that the storage portion and the drive arrangements remain out of the air flow duct and the bottom header is remains inside the air flow duct. This arrangement facilitates the ice feeding and also enables the extraction of the cooling effect from the solution contained in the bottom header. The feed screw shafts in the second row get the drive from belt (21) operated by toothed gears (22), (23) attached at the end of the first and the second row of the shafts respectively. The blower (24) circulates the air over the heat exchanger.
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WE CLAIM:
1) An air cooling system for vehicles comprising
a heat exchanger assembly to hold a freezing mixture, said heat exchanger assembly comprising:
a freezing mixture storage portion;
a plurality of funnel-shaped openings converging from bottom of said storage portion to a plurality of core tubes located downwardly from said storage portion to enable said freezing mixture to travel downwardly from said storage portion through the said core tubes;
said core tubes supported on a retainer plate and liquidly connected to a bottom portion;
said bottom portion configured to be connected to a drain storage tank; said heat exchanger assembly being placed in front of a blower means to enable the air from said blower means to pass around the said tubes of said heat exchanger and thereby get cooled.
2) The system as claimed in claim 1, wherein said core tubes are provided with
fins to enhance heat transfer.
3) The system as claimed in claim 1, wherein said retainer plate has a plurality of holes for draining of molten liquid from the core tube into the bottom portion and said holes are provided at a distance equal to the pitch of the core tubes.
4) The system as claimed in claim 1, wherein a solenoid valve is fitted between the bottom portion and the drain storage tank to allow draining of molten liquid from the bottom portion into the drain storage tank at a predetermined time interval.
5) The system as claimed in claim 4, wherein the operation of said solenoid valve is controlled by a timer or by a microprocessor based electronic controller.
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6) The system as claimed in claims 1 to 4, wherein feed screw shafts are provided at the entry of one or each of the said core tubes to facilitate the entry of the freezing mixture into the core tube, said shafts driven periodically by electrical motor operated by a timer or by an electronic controller.
7) The system as claimed in claim 6, wherein said screw shaft is a helical screw shaft and drive arrangement are used to provide the drive for individual feeder screw shafts.
8) The system as claimed in claim 7, wherein said drive arrangement comprises
of a first bevel gear mounted on a horizontal shaft and a second bevel gear mounted
on a vertical shaft said first and second bevel gears configured to convert the
horizontal rotational motion from the electrical motor into vertical rotational motion
of the feeder screw.
9) The system as claimed in any one of the preceding claims wherein the
freezing mixture is preferably a mixture of ice and sodium chloride.
10) The system as claimed in any one of the preceding claims, wherein said heat
exchanger assembly is positioned inside an air flow duct such that the storage
portion and the drive arrangement are out of the air flow duct and the bottom
portion is inside the air flow duct.
Dated this 21st day of August 2008

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