FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)


TITLE OF THE INVENTION Improved Cooling System for IC Engine
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. Deepak S, Kulkarni and Mr. V R Jalgaonkar
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


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FIELD OF INVENTION
This invention relates to cooling system used in IC engines. More particularly, it deals with provision of bypass arrangement for thermostat used in cooling system. Such a bypass is useful in protecting the engine from overheating and consequential damage to the engine.
BACKGROUND OF THE INVENTION
Automotive cooling systems primarily extract the heat from the engine and maintain the engine at optimum temperature. The cooling systems are also fitted with thermostat which operates as a thermal switch. Thermostat is used to achieve engine operating temperature faster. Thermostat is also useful in maintaining the desired operating temperature during engine operation. When the engine cooling temperature starts exceeding the normal operating temperature, the thermostat starts opening and thus allowing the coolant to flow through the radiator where it gets cooled. Thermostat is a two-way valve, which receives coolant from the engine. When the coolant temperature is low, the engine coolant is circulated back to the engine and when the coolant is warm the bypass path is closed and the coolant is circulated through the radiator where it gets cooled. During the engine operation the recirculation mode is in operation for a limited period and the thermostat open duration is for significantly long period
If, the thermostat is faulty, the coolant flow through the radiator does not take place. Such a situation leads to engine overheating. The bypass provided in the present day thermostats is not adequate in that it may save the engine from complete seizure but damage to parts like Cylinder head gasket, cylinder head, Piston and rings cannot be avoided. Typically, the cost of the engine is at least 200-400 times the cost of the thermostat. Hence, it is worthwhile to provide a bypass path for the coolant and safeguard the engine from overheating.
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As shown in figure 1 the conventional cooling system of the internal combustion engine comprises of an engine (11) having an upper water cooling line (12). The upper water cooling line carries the coolant from the engine to the radiator (13). The thermostat (14) is placed between the engine (11) and the radiator (13). A bypass line (15) is taken from the thermostat to the coolant pump (16). The coolant pump (16) circulates the coolant through the engine when the engine is started. Initially when the engine coolant temperature is low, the thermostat remains closed and it blocks the coolant flow through the radiator and the coolant is re-circulated into the engine. This helps in faster engine warm up. As, the engine coolant temperature rises further, the thermostat opens and the bypass line is closed. This results in coolant flow through the radiator, thereby cooling the engine coolant. The functioning of the conventional engine cooling system primarily depends on proper opening of the thermostat.
PRIOR ART
US 5361980 teaches a fail safe thermostat valve for controlling the flow of coolant to an engine. This prior art fail-safe thermostat valve has, in addition to a thermostat element that expands and contracts to open and close the valve, a fusible element that supports an elevated plate that holds two springs. One spring holds the valve plate in its normally closed position. When the thermostat element fails, the fusible element melts and allows the second spring to force the elevated plate away from the valve seat and pull valve plate away from the valve seat as well. Thus, when the thermostat element fails, the valve will remain permanently open until it can be replaced.
US 4942849 teaches a system for converting the failure mode of a motor vehicle type thermostat whereby a secondary cooling fluid passage, connected in parallel to the primary (thermostat controlled) cooling fluid passage is established. The bypass valve means of the secondary passage is normally open and is closed only when the motor
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vehicle ignition is started. If the control for the primary passage malfunctions, a thermocouple interrupts the circuit that holds said bypass valve closed, thus allowing cooling fluid to flow through said secondary passage.
US 4981260 teaches a thermostat adapted for use in a cooling system of an engine designed to operate between minimum and maximum operating temperatures is partially constructed from a meltable material that has a controlled melting point at the maximum operating temperature of the engine. If the thermostat fails to allow coolant to flow from the engine to a radiator, thereby causing the temperature of the engine to rise beyond its maximum operating temperature, the meltable portions of the thermostat are melted by coolant, resulting in a path for the coolant to flow from the engine and to the radiator.
It is evident from the above referred documents that the bypass thermostat arrangement proposed has bypass as an integral part of the thermostat. Hence, if there is a mechanical malfunction (spring damage, clogging etc.), the bypass is also affected.
The working of bypass depends more upon a mechanism of which spring action is a major part. Hence even after the fusible disc melts and if the spring does not operate the bypass will not work.
In the arrangement proposed in US 4,942,849, the parallel path is operated by an electromechanical valve. In this case also the operation of the bypass depends upon the second action.
In the arrangement proposed in US 4,981,260 the bypass does not allow the full flow of the engine coolant as the bypass flow area is less than main coolant flow area.
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In all of the above referred patents there is no clear indication to the driver of the vehicle regarding malfunction of the thermostat and opening of the bypass. This will delay the corrective action.
The present invention addresses the above drawbacks such that -
The bypass is located at a different place
The bypass is independent of the thermostat hardware and is solely dependent on melting
of fusible disc.
The bypass provides full flow.
The bypass gives a positive indication to the driver regarding thermostat malfunction
without any delay.
OBJECTS OF INVENTION
The main object of this invention is to provide the cooling system for the engine which is failsafe.
Yet another object of this invention is to provide an add-on type and replaceable bypass path for thermostat in coolant circuit.
Yet another object of this invention is to provide a bypass path for the thermostat that comes into action only if the thermostat malfunctions and the engine tends to overheat.
Yet another object of this invention is to provide bypass which is as efficient as primary cooling circuit and alerts the driver to take corrective action by giving proper alarm.
Yet another object of the present invention to provide cooling system that is simple in construction and is cost effective.
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BRIEF DESCRIPTION OF INVENTION
The present invention aims at an improved cooling system for an internal combustion engine. The bypass path in accordance with the present invention is normally a closed type valve, which positively opens in case of engine overheat. It is provided between the engine and the radiator. The bypass is fitted with a thermally fusible disc that melts at a predetermined temperature. Since the melting point of metal and an alloy is repeatable point the operation is positive. The melting point of the fusible disc is decided based on the engine and the application.
The fusible disc is of one time use and needs to be replaced after an overheat incident. In addition an indication is provided to the driver of the vehicle indicating when the fusible disc has melted. The indication is provided through an electrical lamp which is operated through a circuitry of which the fusible disc is an electrically conductive part. This indication gives warning in advance and thus ample time to the driver to take necessary corrective action and thus protect the engine.
BRIEF DESCRIPTION OF DRAWINGS
The sketches showing details of the arrangement of components for a thermostat bypass device are given herewith
Figure 1 shows the conventional cooling system of the vehicle.
Fig. 2 shows the cooling system in accordance with the present invention..
Fig 3 shows constructional details of the fusible alloy type thermostat bypass proposed in
the present invention.
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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 Fig. 2 an improved cooling system in accordance with this invention comprises of an engine (11) having an upper coolant line (12) which carries the coolant from the engine. The thermostat (14) is placed between the engine (11) and the radiator (13). A bypass line (15) is taken from the thermostat (14) to the coolant pump (16). The coolant pump (16) circulates the coolant through the engine (11) when started. In addition, a second bypass line (20) is provided for the thermostat (14). The second bypass line (20) connects the upstream of upper water cooling line (12) and the radiator (13) bypassing the thermostat assembly. The second bypass line (20) houses a fusible disc (21) that melts when the engine coolant tends to overheat. The melting point of the fusible disc (21) (which depends upon the material composition) lies between full opening temperature of the thermostat (upper tolerance) and the boiling point of the engine coolant under engine operating pressures. In the event of engine overheating on account of thermostat malfunction, the fusible disc (21) melts providing a bypass for the engine coolant upto the radiator (13). Since the diameter of thermostat line (first bypass line) and the second bypass line are nearly equal, this arrangement provides a full flow bypass. The fusible alloy disc (21) is connected electrically by electrical wires (22) into an electric circuit. The electrical circuit also comprises of an electric warning lamp provided on the dashboard (not shown). When the fusible disc (21) melts on account of engine overheat the electric circuit opens which causes the overheat warning indicator lamp to glow. When the fusible disc (21) melts, the bypass path remains continuously open which is failsafe position. The fusible disc (21) needs to be replaced after the lamp glows. However, even if it is not replaced the engine is still protected from the overheat since the bypass fails in open condition.
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As shown in the Fig 3 the fusible disc type thermostat bypass device comprises of a tube
(21) having a provision (31) for holding the fusible alloy disc (32). The fusible alloy disc rests on an O-ring support (33) on either side to protect it from mechanical damage and coolant leakage. The fusible alloy disc is also connected electrically by electrical wires
(22) into the circuit which operates a lamp when the fusible disc melts and the electrical circuit opens providing a warning signal to the driver. The composition of the fusible alloy is decided by the temperature at which the disc is required to melt and open the bypass passage. The dimensions of the disc are decided from strength and heat transfer point of view. The assembly of the bypass tube is installed in the upper water cooling line bypassing the conventional thermostat.
Advantages
An improved cooling system of the present disclosure comprises a fusible disc providing
a bypass for the thermostat circuit.
An improved cooling system of the present disclosure solely depends on melting of
fusible disc in response to engine coolant temperature.
An improved cooling system of the present disclosure provides full flow path for the
coolant in the event of engine over heating.
An improved cooling system of the present disclosure provides a warning to the driver in
case of engine over heating on account of thermostat malfunction.
An improved cooling system of the present disclosure is simple and cost effective.
The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purpose of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such
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modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.

WE CLAIM
1. An improved cooling system for an internal combustion engine comprising:
a coolant line extending from an engine to a radiator for carrying coolant from the engine;
a thermostat located at a predetermined position on said coolant line between the engine and the radiator;
a first bypass line between the thermostat and a coolant pump for circulating the coolant through the engine during engine start-up condition;
a second bypass line connecting the upstream of the coolant line and the radiator, thereby bypassing the thermostat;
a meltable fusible disc housing means provided in the second bypass line, which comprises a fusible disc adapted to melt to provide a bypass for the engine coolant from the engine upto the radiator upon engine overheating and failure of the thermostat.
2 The system as claimed in Claim 1, wherein the coolant flow capacity to said
coolant line and said second bypass line is nearly equal, thereby allowing full flow of the coolant.
3. The system as claimed in claim 1, wherein the fusible disc housing means comprises a tube having a provision for holding the fusible disc.
4. The system as claimed in claim 3, wherein the said fusible disc rests on O-ring supports for protection from mechanical damage and coolant leakage.
5. The system as claimed in any one of the preceding claims, wherein the said fusible disc is connected to an electric circuit, adapted to open when the said fusible disc melts on account of engine overheat causing an overheat warning indicator lamp to glow.
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6. The system as claimed in Claim 1, wherein the material composition of said fusible disc is selected suitably in accordance with the temperature at which the said disc is required to melt to open the said second bypass line.
7. The system as claimed in claim 1, wherein the second bypass line remains continuously open in a failsafe mode on failure of said thermostat.
8. The system as claimed in claim 1, wherein constructional features of said fusible disc are based on strength and heat transfer factors and is of use-and-throw type .
9. An internal combustion engine with an improved cooling system as claimed in claims 1 to 8.
10. An improved cooling system for an internal combustion engine as described hereinabove with reference to figures 2 and 3 .
Dated this 15th day of July 2008
TATA MOTORS LIMITED By their Agent & Attorney
(Karuna Goleria) of DePENNING & DePENNING
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