FORM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention: IMPROVED AUTOMATIC CHANGEOVER MECHANISM FOR FUSE TESTING AND A METHOD THEREOF
2. Applicant(s):
(a) NAME : LARSEN & TOUBRO LIMITED
(b) NATIONALITY: An Indian Company.
(c) ADDRESS: L & T House, Ballard Estate, Mumbai 400 001,
State of Maharashtra, India
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed:

TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to a mechanism and method for fuse testing. More particularly the invention relates to an improved automatic changeover mechanism for use in fuse testing adapted to reduce testing time and providing a precise result and a method thereof.
BACKGROUND AND THE PRIOR ART
In the conventional way of doing fuse test, the test current is passed through low voltage current source (A) for a short duration. This helps in heating the fuse elements. Before the fuse blows a changeover is done manually (C) and current is fed from a rated voltage source (B) as shown in figure 1.
US 2553436 discloses a fuse testing apparatus for testing fuses of the type which includes arming mechanism operated by centrifugal force, comprising means for rotating the fuse, means under control of the arming means for generating a series of electrical impulses responsive to rotation of said fuse at uniform speed and means for determining if pulses are generated or not while the fuse is rotating, said generating means including a light source, and reflecting means for producing flashes of light from said source and transmitting them over a path adapted to be interrupted by operation of said arming means.
The drawback of conventional system is that it draws more power, more time consuming and less accurate. Thus there is a need to overcome the problems of the prior art. Therefore, the present inventors have developed an improved automatic changeover mechanism for use in fuse 15 test that would reduce testing time and bringing more precise results. It would also save carbon foot print and contributing towards green earth, we propose an automatic changeover scheme.

OBJECTS OF THE INVENTION
A basic object of the present invention is to overcome the disadvantages/drawbacks of the known art.
Another object of the present invention is to provide an improved automatic changeover mechanism for use in fuse 15 test
Another object of the present invention is to provide an improved automatic changeover mechanism adapted to reduce testing time and bringing more precise results.
Another object of the present invention is to provide a method for automatic changeover in fuse testing adapted to reduce testing time and providing a precise result.
Yet, another object of the present invention is to provide an improved automatic changeover mechanism adapted to save carbon foot print and contribute towards green earth.
These and other advantages of the present invention will become readily apparent from the following detailed description read in conjunction with the accompanying drawings.
SUMMARY OF THE INVENTION
There is provided a mechanism and method for fuse testing.

According to one embodiment of the present invention, there is provided improved automatic changeover mechanism for use in fuse testing adapted to reduce testing time and providing a precise result, said mechanism comprising a voltage source passing a test voltage for a short duration; a logic circuitry for sensing excess current, said circuitry providing actuation signal for automatic changeover; a rated voltage source providing rated constant current on getting actuation signal from said logic circuitry.
Other embodiment of the present invention provides a method for automatic changeover in fuse testing adapted to reduce testing time and providing a precise result, said method comprising the steps of: passing a test voltage for a short duration using a voltage source; sensing excess current using a logic circuitry and providing actuation signal for automatic changeover; providing rated constant current through a rated voltage source on getting actuation signal from said logic circuitry.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
In the appended drawings;
Fig 1 illustrates a conventional mechanism of doing fuse test.
Fig 2 illustrates an improved automatic changeover mechanism for use in fuse 15 test
Fig. 3 illustrates a flow diagram of how the mechanism functions

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The following drawings are illustrative of particular examples for enabling methods of the present invention, are descriptive of some of the methods, and are not intended to limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description.
Reference is first invited to Fig 1 where a conventional mechanism for fuse testing is shown.
Fig. 2 provides a mechanism for fuse testing in accordance with the present invention.
The invented system is thus an improved automatic changeover mechanism for use in fuse testing adapted to reduce testing time and providing a precise result.
DETAILED DESCRIPTION OF THE INVENTION
Accordingly in the present invention there is provided an improved automatic changeover mechanism for use in fuse 15 test. The test current will be passed through low voltage current source (A) for a short duration as in conventional scheme. Before the fuse blows a logic circuit will sense and automatic change over actuates (C) and current starts flowing from a rated voltage source (B).
With manual change over, correct fusing time is difficult to achieve. The fuse may blow while low voltage source in feeding the current to the unit under test. If changeover (from low voltage to high voltage) is done too early it may take longer

duration to blow the fuse. This result in wastage of test fuses, wrong results obtained and the time required in conducting these repeat operations.
As the current passes through any test sample, its resistance increases. A constant current source maintains this current. For a fuse, just before fusing the rate of rise of resistance is very high. A servo controlled current source receives fast pulses for maintaining the test current. This fast pulses can be used to actuate a logic circuit which will in turn do the changeover (C) from low voltage source (A) to rated voltage source(B),when it is actually required as shown in figure 2.
ADVANTAGES:
1. Reducing testing time.
2. More precise results.
3. Saving carbon foot print.
4. Contributing to green earth.
Although the embodiments herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the embodiments herein with modifications. However, all such modifications are deemed to be within the scope of the claims.
It is also to be understood that the following claims are intended to cover all of the generic and specific features of the embodiments described herein and all the statements of the scope of the embodiments which as a matter of language might be said to fall there between.

WE CLAIM
1. An improved automatic changeover mechanism for use in fuse testing, said
mechanism comprising:
a voltage source passing a test voltage for a short duration;
a logic circuitry for sensing excess current, said circuitry providing actuation signal for automatic changeover;
a rated voltage source providing rated constant current on getting actuation signal from said logic circuitry.
2. Mechanism as claimed in claim 1 wherein said current source is substantially a low voltage source.
3. Mechanism as claimed inn claim 1 wherein said voltage source is a servo controlled source.
4. Mechanism as claimed in claim 1 wherein said logic circuit providing for automatic changeover from said current source to said rated voltage source.
5. A method for automatic changeover in ruse testing, said method comprising the steps of: passing a test voltage for a short duration using a voltage source; sensing excess current using a logic circuitry and providing actuation signal

for automatic changeover; providing rated constant current through a rated voltage source on getting actuation signal from said logic circuitry.
6. Method as claimed in claim 5 wherein said automatic changeover is performed from said current source to said rated voltage source.
7. An improved automatic changeover mechanism for use in fuse testing as herein described and illustrated with reference to accompanying drawings.
8. A method for automatic changeover in fuse testing as herein described and illustrated with reference to accompanying drawings.