FORM 2
The Patents Act 1970
(39 of 1970)
&
The Patent Rules 2003
COMPLETE SPECIFICATION
(See Section 10 and rule 13)
TITLE OF THE INVENTION:
SWITCH GEAR ASSEMBLY WITH A BIMETAL SNAP ACTION
DISC
APPLICANT:
LARSEN & TOUBRO LIMITED
L&T House, Baiiard Estate, P.O. Box No. 278,
Mumbai, 400 001, Maharashtra
INDIA.
PREAMBLE OF THE DESCRIPTION:
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

A) TECHNICAL FIELD
[0001] The present invention generally relates to switch gears and particularly relates to a bimetallic snap action disc that is used in the switch gears for detecting abnormal rise in temperature.
B) BACK GROUND OF THE INVENTION
[0002] Switch gears are the mechanical switching devices capable of making, carrying and breaking currents under normal circuit conditions and also making, carrying for a specified time and breaking currents under specified abnormal circuit conditions.
[0003] In the existing technique, during an abnormal circuit conditions there is a tremendous amount of heat generated within the circuit. Further due to the heat generated in the circuit, a n abnormal rise in the temperature is found. The abnormal rise in temperature in the circuit may not be detected in the existing technique, which results in the breakage of the circuit. Further the life of the switch gears also decrease due to an abnormal increase in temperature.
[0004] Further in the existing technique, the abnormal temperature rise detection is current dependent and detects abnormal conditions in the load due to which the fault condition detected in the switchgear products may vary and further the switchgear product may be damaged.[0005] Furthermore, an abnormal rise in temperature can also prove to be dangerous to the user, who, unaware of the excessive heat generated on the unit may cause harm to himself by operating/touching the switchgear device.

[0006] Another technique discloses that a plurality of components is used to detect the temperature and bring down the temperature in the circuit breaker. Further due to the plurality of components used in the circuit breaker, the maintenance cost also increases.
[0007] The bimetal snap action disc is composed of thermostat metal which is pre-tensioned to dishing or doming. When it is subjected to heat due to temperature rise, the thermal stresses generated cause the disc to snap to the opposite concave due to bimetal action. This action of the bimetal can be used to detect abnormal rise in temperature by connecting it to an electronic/electrical circuit.
[0008] Thus there is a need for a bimetallic snap action disc that is used in the circuit breakers for detecting abnormal rise in temperature.
[0009] The above mentioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.
C) OBJECT OF THE PRESENT INVENTION
[0010] The primary object of the present invention is to provide a bimetallic snap action disc that is used in the switchgear for detecting an abnormal rise in temperature.
[0011] Another object of the present invention is to provide safety to the users of switch gear products.
[0012] Yet another object of the present invention is to generate a visual display indicating an abnormal rise in temperature.

[0013] Yet another object of the present invention is to generate an electrical signal to indicate an abnormal rise in temperature by connecting the micro switch to the electronic circuit.
D) SUMMARY OF THE INVENTION
[0014] The various embodiments of the present invention provide a bimetallic snap action disc mounted on a switch gear device in the assernbly. The assembly includes the switch gear device, two or more terminals, a hollow tube mounted on the terminals, a bimetallic snap action disc stuck on the periphery of the tube, a micro switch and a display load. The bimetallic snap action disc detects an abnormal rise in temperature in the switch gear device when subjected to a temperature and the disc snaps to the opposite concave indicating the abnormal rise in the temperature through a display. Additionally / alternately, the snap action during abnormal temperature rise can be used to actuate a micro-switch which, in turn, can offer an electrical signal for operating the further circuit.
[0015] According to one embodiment of the present invention, the abnormal rise in temperature is indicated when the temperature exceeds the predefined actuating temperature range.
[0016] According to one embodiment of the present invention, the bimetal snap action disc is composed of a thermostat metal.
[0017] According to one embodiment of the present invention, the disc snaps to the opposite concave with a force due to bimetal action.
[0018] According to one embodiment of the present invention, the force that the disc snaps is used to operate at least one of a micro switch and an electronic device.

[0019] According to one embodiment of the present invention, the snap action of the disc from one concave to the other can also be used to have mechanical actuation that will be finally connected to a visual, non-electrical indicator.
[0020] According to one embodiment of the present invention, the bimetallic snap action disc detects a fault condition by without damaging the switchgear device and the detection is based on the temperature.
[0021] According to one embodiment of the present invention, the micro switch is connected to an external circuit with a display load for displaying the fault condition in the switchgear device.
[0022] According to one embodiment of the present invention, the abnormal rise in temperature is indicated through the display load such as a bulb and a Light emitting device.
[0023] According to one embodiment of the present invention, the abnormal rise in temperature is indicated by raising an alarm.
[0024] These and other objects and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.
E) BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:
[0026] FIG. 1 illustrates the perspective view showing the assembly and method of placement of Bimetal snap disc on a Switch disconnector fuse terminal, according to one embodiment of the present invention.

[0027] FIG. 2 illustrates the snapshot of an image with the snap action disc, according to one embodiment of the present invention.
[0028] FIG. 3 illustrates the snapshot of an image with the snap action disc, according to another embodiment of the present invention.
[0029] Although the specific features of the present invention are shown in some drawings and not in others. This is done for convenience only as each feature may be combined with any or all of the other features in accordance with the present invention.
F) DETAILED DESCRIPTION OF THE INVENTION
[0030] In the following detailed description, a reference is made to the accompanying drawings that form a part hereof, and in which the specific embodiments that may be practiced is shown by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and it is to be understood that the logical, mechanical and other changes may be made without departing from the scope of the embodiments. The following detailed description is therefore not to be taken in a limiting sense.
[0031] The various embodiments of the present invention provide a bimetallic snap action disc mounted on a switch gear device in the assembly. The assembly includes the switch gear device, two or more terminals, a hollow tube mounted on the terminals, a bimetallic snap action disc stuck on the periphery of the tube, a micro switch and a display load. The bimetallic snap action disc detects an abnormal rise in temperature in the switch gear device when subjected to a temperature and the disc snaps to the opposite concave indicating the abnormal rise in the temperature through a display.

[0032] FIG. 1 illustrates the perspective view showing the assembly and method of placement of Bimetal snap disc on a Switch disconnector fuse terminal, according to one embodiment of the present invention. The assembly includes a Switchgear device 102, a front housing of the switch gear device 104, a plurality of terminals 106, and a hollow tube 108. A bimetallic disc is stuck on the periphery of the hollow tube 108 in the dish 110 and dome 112 condition. The bimetallic disc is stuck on the periphery of the tube so as to allow a snapping of the disc when an actuating temperature is reached. The assembly further includes a micro switch 114, a source 116 a display load 118, and a resistor 120.
[0033] The hollow tube 108 is placed onto the terminals 106 of the switchgear device 102. The switch gear device 102 is also known as the switch disconnector Fuse (SDF). The bimetal action disc is stuck on the periphery of the hollow tube 108 and the bimetallic snap action disc is stuck on the tube such that the snapping of the disc is allowed when the actuating temperature is reached.
[0034] Further the assembly includes the micro switch 114 with a stiff bent metal strip where the stiff bent metal strip is placed in the vicinity of the bimetallic disc. The micro switch 114 is connected to the simple resistor 120. A temperature of 110°C is measured at the terminals 106 of the switchgear device 102 in normal conditions. Further during abnormal conditions the temperature in the assembly rises above 110° C at the terminals of the switch gear device 102. The bimetal snap action disc is composed of thermostat metal that is pre-tensioned to dishing or doming.
[0035] The bimetallic snap action disc has a predefined actuating temperature range of 60 to 70°C. However, depending upon the requirement, snap disc of other temperature range can also be used. When the snap action disc in the switch gear device 102 is subjected to a temperature of the predefined actuating temperature range of 60 to 70°C, then the disc snaps to the opposite concave. The disc snaps to the opposite concave due to thermal stresses generated and the abnormal rise in temperature is indicated through a

display or by an audio such as an alarm. The snapping of discs action is reversible and the doming snaps back into dishing on cooling of the switch gear device. The temperature at the terminals 106 is much higher than the actuating temperature of the disc due to which the disc is placed at some distance away from the terminals 106.
[0036] For instance, consider a hollow tube of 10 mm used for the experiment. When the temperature at the terminals 106 during abnormal conditions reaches the temperature range of 120°C-130°C, then the temperature is sensed by the bimetal snap action disc. The temperature range is within the threshold limit of the disc due to which it leads to flipping of the disc. The force with which the disc snaps is used to operate a micro switch 114 or any other electronic device. The force with which the disc flips is measured and found to be 0.7 Kg. This is equivalent to a 0.7Kg load that is applied by the disc. The force is then used to switch the micro switch 114 that is kept in the vicinity of the disc. The micro switch JJ4 is connected to an external circuit with a lighting load such as a bulb or a light emitting device (LED) that lights up and indicates the fault condition in the circuit. Alternately, the micro-switch can also cut-off other pre-defined circuitry which, in turn, can cut-off the electric current through the said switchgear.
[0037] FIG. 2 illustrates a snapshot of an image with the snap action disc, according to one embodiment of the present invention. FIG. 3 illustrates the snapshot of an image with the snap action disc, according to another embodiment of the present invention. While with respect to FIG. 2 and FIG. 3, the thermal stresses generated in the circuit causes the disc 202 and 302 to snap to the opposite concave due to bimetal action. The snapping of discs action is reversible and the doming snaps back into dishing on cooling on the switch gear device. The force that the disc snaps is used to operate a micro switch 114. The micro switch 114 is then connected to an electronic circuit to generate a visual or audio display indicating an abnormal rise in temperature.

G) ADVANTAGES OF THE INVENTION
[0038] The present invention provides a bimetallic snap action disc that is temperature dependent and detects fault condition without the switchgear product getting damaged. The present invention provides a method of advanced detection and prevention for abnormal rise in temperature in the switchgear products. The method further detects abnormal conditions in the switchgear device itself, thereby preventing any damage to the product as well as protecting other equipment down the line.
[0039] 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.
[0040] 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.

CLAIMS
What is claimed is:
1. A switch gear assembly comprising:
a switch gear device;
a plurality of terminals;
a hollow tube mounted on the plurality of terminals;
a bimetallic snap action disc stuck on the periphery of the tube;
a micro switch; and
a display load;
Wherein the bimetallic snap action disc snaps to an opposite concave during an
abnormal rise in temperature in the switch gear device and indicating the rise in
temperature through a display / electrical signal.
2. The assembly of claim 1, wherein the abnormal rise in temperature is indicated when the temperature exceeds a predefined actuating temperature range.
3. The assembly of claim 1, wherein the bimetal snap action disc is composed of a thermostat metal.
4. The assembly of claim 1, wherein the disc snaps to the opposite concave with a force due to bimetal action.
5. The assembly of claim 4, wherein the force created during the disc snap is used to operate at least one of a micro switch and an electronic / electrical device.
6. The assembly of claim 1, wherein the bimetallic snap action disc detects a fault condition based on the temperature.
7. The assembly of claim 1, wherein the micro switch is connected to an external circuit with a display load for displaying the fault condition in the switchgear device.

8. The assembly of claim 1, wherein the abnormal rise in temperature is indicated through the display load.
9. The assembly of claim 8, wherein the display is at least one of a bulb and a Light emitting device.
10. The assembly of claim l, wherein the abnormal rise in temperature is indicated by raising an alarm.