FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention. - PRESSURE ACTUATED FUSE BLOWN INDICATION SYSTEM
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:

FIELD OF THE INVENTION
The present invention relates to an improved indication system used for displaying the blown status of a fuse whenever a fuse has cleared a fault due to occurrence of any surge voltage, surge current, overload condition and the like. More particularly, the invention is concerned about pressure actuated fuse blown indication system which provides a visual indication of the blown out status of the fuse.
BACKGROUND AND THE PRIOR ART
A fuse clears a fault by utilizing the excessive current flowing through the fuse links. The excessive current flowing through the fault creates a huge amount of heat. The fuselinks are designed in such a way that this excessive heat results in melting down of the fuselink and thus the fault is cleared. This whole process happens inside an enclosed ceramic body and is not visible from outside.
US5153553 discloses a fuse having a rated current for protecting electric or electronic circuitry comprises a body having a blow chamber. A fusible element is contained within the body and extends through the blow chamber. A contact is disposed on the body electrically connected to the fusible element for making an electrical connection between the fuse and the circuitry. The blow chamber is sealed around the fusible element so that thermal energy in the fusible element can increase within the blow chamber for causing the element to open when an elevated current is applied to the element. The blow chamber is sufficiently sealed around the element for retaining a pressure created therewithin by vaporization of a portion of the element; that pressure is sufficient to cause an arc produced by fusion of the element to extinguish. The body is of sufficient strength to contain the pressure within the blow chamber for allowing the fuse to fail gracefully. Thermal conductive cement is disposed about the entire fusible element without the blow chamber for preventing the fusible element

from opening without the blow chamber before opening within the blow chamber. However, it was not known from the prior art that visual indication of blown out status of a fuse can be provided by means of a pressure actuating means.
US5946495 discloses an apparatus for use in a power distribution system including an assembly with a support having an electrically conductive portion and an arm pivotally mounted to the first support for movement between a closed position and an open position. The arm has a conductive portion which is adapted to be electrically connected to one of a power source and a load and which is spaced from the conductive portion of the support both when the arm is in its closed position and when the arm is in its open position. The assembly further includes a spring biasing the arm to its open position, and a fuse electrically connected between the conductive portion of the arm and the conductive portion of the support. The fuse retains the arm in its closed position against the bias of the spring. When current flow causes the fuse to blow, the spring biases the arm to its open position thereby providing a visual indication that there is no current path from the source to the load. Though visual indication of blown out fuse is mentioned in the prior art, it was not known that pressure inside the fuse chamber can be used as an actuating means for visual indication of the blown out fuse.
The prior art documents though teaches visual indication of blown out fuse, was complex in construction and not cost effective.
Thus in order to have an appropriate visual indication of the blown status of the fuse in case of surge voltages, surge currents, overload and the like, there is a need to provide for an improved fuse blown indicating system which is simple in construction and cost effective an indicator is used on the outside body visible to the user.

OBJECTS OF THE INVENTION
One object of the present invention is to overcome the disadvantages/drawbacks of the prior art.
A basic object of the present invention is to provide a pressure actuated fuse blown indication system.
These and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.
SUMMARY OF THE INVENTION
One aspect of the present invention is to provide an improved indication system for
indicating blown status of fuse, said system comprising :
fuse body;
plurality of end plates fixed at predetermined position at both ends of said fuse body;
and
indicating means screwably fixed to said end plates;
wherein said indicating means comprising diaphragmatic valve means, wherein said
valve means having thickness such that it will pop out almost instantaneously when
there is excess pressure inside said fuse body.
DETAILED DESCRIPTION OF THE INVENTION
The present invention describes a novel system for indication of blown status of the fuse. The invention is based upon the concept of pressure developed inside the fuse body in case of fault clearing situation. The ceramic body of the fuse contains fuselinks, silica crystals and some trapped air. When a fault occurs, excessive current

passes through the fuselinks. This excessive current produces large amounts of heat resulting into melting of fuselinks and fusion of some silica crystals. This large amount of heats results into expansion of the entrapped air and thus increasing the pressure inside the fuse body. This increase in pressure can be used to pop out/operate a diaphragm based indicator valve screwed to the fuse end plates.
The present invention utilizes the pressure developed inside the ceramic fuse body during clearing of a fault. Depending upon the amount of excessive current flowing in the fuselinks, heat will be generated. This heat will melt the fuselinks and some of the silica crystals present inside the body will fuse. This heat will cause an expansion of the entrapped air present in the fuse body. This expansion of air will result into an increase in the pressure inside the body. This pressure will find a way out into the diaphragm based indicator valve screwed to the fuse end plates. The thickness of the diaphragm layer is calculated in such a way that it will pop out because of the excess pressure inside the fuse body. The diaphragm lid is hinged to the diaphragm based indicator valve. Thus it will remain there in pop-out condition thus indicating the blown-out state of the fuse. Thus a very simple yet effective method of indication of the fuse having cleared the fault can be obtained.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The drawings illustrate one preferred embodiment presently contemplated for carrying out the invention. In the drawings:
Fig 1: shows the overall schematics of a fuse using this present invention. Fig 2: shows another view of the fuse.
Fig 3: shows the front view of the diaphragm based indicator valve. Fig 4: shows another view of the diaphragm based indicator valve.

Fig 5: shows the cross-sectional view of the diaphragm based indicator valve.
Fig 6: shows the cross-sectional view of the fuse integrated with diaphragm based
indicator valve.
Fig 7: shows the detailed view of the assembly of diaphragm based indicator valve
(1) with End plate (2)
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig 1: This figure describes the overall schematics of a fuse using this present invention. The figure comprises of End Plates (2) and the new diaphragm based indicator valve (1) screwed to the fuse end plates.
Fig 2: This figure shows another view of the fuse. It comprises of Fuse Knives (3) and Fuse Body (4).
Fig 3: This figure shows the front view of the diaphragm based indicator valve.
Fig 4: This figure shows another view of the diaphragm based indicator valve.
Fig 5: This figure shows the cross-sectional view of the diaphragm based indicator valve. It consists of Diaphragm Lid (2c). Hinge Point (2a), Threaded surface (2b) and passage for pressurized gases (2d).
Fig 6: This figures shows the cross-sectional view of the fuse integrated with diaphragm based indicator valve.
Fig 7: This figure shows the detailed view of the assembly of diaphragm based indicator valve (1) with End plate (2).

ADVANTAGES
Assembly is resistant to shock and vibrations. Easy of assembly. Reduced no. of components. Increased reliability of operation. Long term reliability
Although the invention is described with various specific embodiments, it will be obvious for a person skilled in the art to practice the invention with modifications. However, all such modifications are deemed to be within the scope of the claims and true spirits of the present invention. It is also to be understood that the following claims are intended to cover all of the generic and specific features of the present invention described herein and all the statements of the scope of the invention which as a matter of language might be said to fall there between.

WE CLAIM
1. An improved indication system for indicating blown status of fuse, said
system comprising :
fuse body;
plurality of end plates fixed at predetermined position at both ends of said
fuse body; and
indicating means screwably fixed to said end plates;
wherein said indicating means comprising diaphragmatic valve means,
wherein said valve means having thickness such that it will pop out almost
instantaneously when there is excess pressure inside said fuse body.
2. System as claimed in claim 1 wherein said valve means comprising diaphragm lid hinged to said valve means.
3. System as claimed in claim 1 wherein said valve means comprising passage means for release of pressurized gases.
4. System as claimed in claim 1 wherein said valve means comprising threaded surface.
5. System as claimed in claim 1 further comprising plurality of fuse knives.

6. An improved indication system for indicating blown status of fuse as herein substantially described and illustrated with the accompanying drawings.