FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION (See section 10 and rule 13)
1. TITLE OF THE INVENTION:
"Moving Contact Arrangement for Switchgears"
2. APPLICANT:
(a) NAME: Larsen & Toubro Limited
(b) NATIONALITY: Indian Company registered under the
provisions of the Companies Act-1956.
(c) ADDRESS: Larsen & Toubro Limited
Electrical & Automation North Wing, Gate 7, Level 0, Powai Campus, Saki Vihar Road, Mumbai 400 072, INDIA
3. PREAMBLE TO THE DESCRIPTION
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.

Moving Contact Arrangement for Switchgears
Field of invention
The present invention relates to switchgear and more particularly to a circuit breaker. More particularly, the present invention relates to arrangement of current path of an air circuit breaker. It suggests an improved flexible conductor and finger portion in a single arrangement in current path having Low watt loss and reduces the number of components required for assembly of the same for circuit breaker. The flexible conductor preferable comprised of flexible sheet of conductive material arranged in a stack.
The present invention arrangement relates to the circuit breaker having a current path structure includes a plurality of electrically conductive members arranged as a laminate.
Background of the invention
Circuit breakers are electrical devices that are installed in an electrical circuit to allow the connection and disconnection of the circuit from the power source. Circuit breaker are commonly known as interrupters that opens and closes to stop and start the flow of electrical current to the electrical circuit.
Current path of Circuit breaker interrupters are comprised of a number of components that are manually assembled using fasteners or with the help of brazing. The Complexity of the current path of the circuit breaker tends to increase the manufacturing cost. In addition to that the Mechanical joints formed by the assembly tend to increase the resistance of current path of circuit breaker.

This resistance leads to increase in temperature that can adversely impact performance rating of the circuit breaker.
1) PATENT NO.- US 5,530,216
The above invention relates to a flexible connector for connecting a movable contact to a fixed electrical terminal. Although the following description relates to the vacuum interruption system, Our invention relates more particularly to arrangement of current path of a switchgear. It suggests an improved flexible conductor and finger portion in a single arrangement in current path having Low watt loss and reduces the number of components required for assembly of the same for circuit breaker.
' 2) PATENT NO.- US 2010/0072044 Al (Closest Prior Art)
The above mentioned closest prior art describes about the "Circuit breaker with Unitary Current path" However the design of the present invention differs in shape of the moving contact portion , material saving and conductivity with the help of moving contact cover of Mild steel. Present moving contact portion is of width 9 mm and it is not able to accommodate a pin of Diameter 10.1 mm so this moving contact cover of unique shape is attached to moving contact portion in such a way , that the 10.1 mm diameter pin goes through both moving contact portion and cover, this moving contact cover is also serves the purpose to protest the moving contact portion to delaminate.
1) In first aspect the arcing contact system (68) is attached to the moving contact system (56) by a screw shown in the above US patent '044.
2) There is no such arrangement given in the US patent application for protecting the solidified conductive sheet or finger portion during short circuit. During short circuit test high amount of heat and forces generate in the circuit breaker. There is provision which provides extra protection against these forces.

3) In US patent application '044 the profile of the moving contact is made more than 15 mm (approximately) particularly to incorporate the pin of diameter more than 10 mm. there is no provision to incorporate the same pin of Dia 10 mm in the Moving contact of width 9 mm.
4) In the US patent application they have shown the unitary current path comprising of Arcing contact, Moving contact portion, braid portion and bottom terminal portion as single unit.
Object of present invention
Object of present invention is to provide an arrangement which can replace the finger and braid arrangement by a single structure.
Yet another object of present invention is to a providing energy efficient yet performance matching arrangement over the existing one.
Summary of the invention
According to the present a moving contact circuit breaker for protecting electric circuit, the circuit breaker comprising:
a fixed contact secured in a housing of the circuit breaker and connected electrically to a top cradle terminal;
a fixed arcing contact configured over and connected to the fixed contact;
a flexible contact flexibly disposed in the housing of the circuit breaker and connected to a bottom cradle terminal, characterized in that the flexible contact having,
a plurality of finger members extending from the flexible contact, the flexible member secured in the housing of the circuit breaker, the flexible member capable of providing arcuate motion to the flexible contact;

a moving contact button disposed on each of the finger member and opposite to the fixed contact, the moving contact button enable to close the circuit when in contact with the fixed contact;
a flexible arcing contact disposed over the distal portion of each if the finger member, above the moving contact button and opposite to fixed arching contact; and
a finger cover with holes disposed over each of the flexible member for protecting the finger member from short circuit and for strengthening thereby quenching the arc during separation of fixed and moving contacts.
Description of the drawings of present invention
Figure 1 shows a side view illustration of an embodiment of a circuit breaker having a current path in open contact condition;
Figure 2 shows a side view illustration of the arrangement of current path in circuit breaker;
Figure 3 shows a complete current path assembly of the circuit breaker;
Figure 4 shows an isometric" view of complete current path assembly of the circuit breaker;
Figure 5 shows front view of finger and flexible portion with arcing contact of the circuit breaker;
Figure 6 shows a perspective view of finger and flexible portion with arcing contact of the circuit breaker;
Figure 7 shows the side view of current path having solidified electrically conductive sheets in movable portion;

Figure 8 shows a perspective view of current path having solidified electrically conductive sheets in movable portion;
Figure 9 shows an arcing contact and rivets for joining arcing contact to movable portion (finger); and
Figure 10 shows side view and schematic view of finger cover.
Detailed description of present invention
The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.
This new current path structure comprised of a flexible portion which acts as a braid and a movable portion which acts as a finger. The braid portion of the plurality of individual electrically conductive sheets are stacked in a laminate arrangement and the finger portion of electrically conductive sheets are solidified to each other. With the help of electrically conductive laminate arrangement, we have achieved less number of components and joints in current path which result in decrease in resistance and low watt loss.
A current path structure for a circuit breaker is provided. The current path structure includes a top terminal portion, fixed contact, moving contact, a movable portion and a bottom terminal portion.
The present invention will now be explained in more detail hereafter.
The circuit breaker is the device used in protection of electric systems. Whenever
a fault occurs in the line it is the duty of nearest circuit breaker to isolate the

healthy section of the line from faulty one and thus protect the healthy line from fault.
Circuit breaker has three main parts:
A mechanism, a current path and an arcing chamber.
Mechanism of circuit breaker causes the motion of moving contact towards fixed
contact and thus the contact between fixed and moving part is established.
Current path elements of circuit breaker carries current when circuit breaker is on i.e. in no fault condition. It breaks the electric supply by opening contact in case of faults. While the arcing chamber quenches the arc which is produced during separation of fixed and moving contacts.
The current path should have minimum length and joints to decrease its cost and electrical energy loss (watt loss).
In prior art, as described above has many components which in the suggested art are eliminated. This innovation suggests arrangement which eliminate the need of joining of the braid to the movable portion (finger).
Fig.l shows the side view illustration of an embodiment of a circuit breaker having a current path in open contact condition. The circuit breaker a flexible contact (15) and a fixed contact (16). The flexible contact (15) and the fixed contact (16) are shown in open position. The circuit breaker is generally arranged to open under abnormal operating conditions, such as short circuit. The circuit breaker further includes an interrupter portion that is arranged to move between a closed state, where current flows from power source to load and open state where the flow of electrical power ceases. The interrupter part of a circuit breaker comprises of, a fixed contact (16), a flexible contact (15), a moving portion or finger (26), a braid or flexible contact (3). The interrupter is coupled to a mechanism that includes component to move the contact arm from a closed to an open position. The flexible contact includes a flexible contact (3), a moving

contact button (15), a flexible arching contact (1), and a finger cover (2) with hole (17).
Further, the fixed contact is secured in a housing of the circuit breaker and connected electrically to the top cradle terminal (10). The fixed arcing contact (4) is configured over and connected to the fixed contact (3). The flexible contact (3) is flexibly disposed in the housing of the circuit breaker and connected to a bottom cradle terminal (11).
The flexible contact (3) having a plurality of finger members (26) extending therefrom. The flexible contact (3) is secured in the housing of the circuit breaker and is capable of providing arcuate motion to the flexible contact (3). The moving contact button (15) is disposed on each of the finger member (26) and opposite to the fixed contact (4), the moving contact button enables closing of the circuit when in contact with the fixed contact (4). The flexible arcing contact (1) is disposed over the distal portion of each if the finger member (26), above the moving contact button (15) and opposite to the fixed arching contact (1). The finger cover (2) with holes (17) disposed over each of the flexible contact (3) for protecting the finger member (26) from short circuit and for strengthening thereby quenching the arc during separation of fixed and moving contacts.
Referring now to figure 2, the operation of the circuit breaker will be described. The circuit breaker is coupled to the electrical circuit at the inlet terminal and the outlet terminal which are enclosed within the housing. The current path structure includes top cradle terminal (10), top holder (8), top breaker terminal (6), arcing contact (4), fixed contact (16), moving contact button (15), finger or movable member, finger cover (2), the flexible contact (3), the bottom breaker terminal (7), the bottom holder (9), the bottom cradle terminal (11). The finger member (26) includes a contact button tip together form the contact arm assembly.

During operation the circuit breaker moves between a closed position in which moving contact (15) touches the fixed contact button (16). To improve the performance and minimizes the resistance and watt loss of the circuit breaker, the exemplary embodiment uses a single joint current path structure. The flexible contact (3) is joined with the bottom breaker terminal (7) with the help of screws. This current path structure uses a single component to form the finger or movable portion (26), and the flexible contact (3) as illustrated in figure 3-6. As will be discussed in more detail below, in the exemplary embodiment. The current path structure is formed from a laminate assembly of electrically conductive sheets, such as of copper for example, where the material for finger member (26) and flexible portion (3) is contiguous, meaning formed from the single piece of material. The finger member (26) is solidified by the application of heat and pressure and the flexible contact (3) remains in the laminate form.
To improve the performance and minimizes the resistance and watt loss of the circuit breaker, the exemplary embodiment uses a single joint current path structure. The current path structure has finger or movable portion (26), and the flexible contact (3) as a single component as illustrated in figure 7-8. In this embodiment, plurality of sheets made from an electrically conductive material are stacked in a laminate arrangement. In this embodiment, the sheets are 0.035 mm thick and there are 125 sheets are in the laminate. A force is applied to the finger member (26), of the whole arrangement for the solidification of the conductive sheets. Coincident with the application of the pressure, heat is added to the finger member (26), causing the conductive sheets to weld together. The heat and pressure used in this process are sufficient to join the sheets and solidify the finger member (26). Once the finger portion (26) is solidified, the current path structure has essentially solid ends, with the flexible portion (3) remaining as a laminate as illustrated in figure 4. Additional subsequent machining operation in the finger portion (26) may also performed, this operation may include the recess which is made for riveting arcing contact (1). Additional subsequent machining operation is also performed in flexible portion (3). These operations may include the

forming of holes (21, 22) to connect the bottom breaker terminal (7) to the flexible portion (3) by screws.
Referring now to figure 6, arcing contact (1) is attached to the finger portion by riveting (rivet 13). Figure 9 shows the side view of an arcing contact. Arcing contact (1) plays a major role during short circuit test. The slanted side (30) is very important and facilitates commutation during short circuit and the pip (28, 29) on the other side used to attach contact spring which are very essential to maintain the contact force. We can also use brazing method to join the arcing contact (1) to the slot (23, 24, 25) of the finger member (26) of the current path. Hole (31 , 27) in the arcing contact (1) should be aligned with the hole (19,20) in finger member (26) for the riveting. As shown in figure 6, we are using a finger cover (2) of mild steel to protect the solidified conductive sheet or finger portion (26) during short circuit. During short circuit test high amount of heat and forces generate in the circuit breaker, this MS finger cover provides extra protection against these forces. Another function of finger cover (2) to strengthen the hole (17) provided in the finger member (26). This finger portion hole (18) will be covered by finger cover hole (17) so that it will hold a pin which is very important for the commutation point of view in short circuit test.
Advantages of the present invention
1. Simplified arrangement of current path elements, easy to assemble and maintenance.
2. The material used is less and only simple manufacturing processes (like bending, punching) involved in manufacturing all current path elements thus the arrangement is very cost effective.
3. The number joints in current path reduced and the contact pressure at holder improved by forming two parallel conductors carrying current in

same direction. Thus with the help of suggested arrangement the power losses and temperature rise reduced significantly.
4. The arcing contact (16) is fixed by means of brazing and riveting by both sides, with the help of brazing and riveting we are able to reduce the size of the flexible contact (3).
5. The finger cover (2) made of mild steel protects the solidified conductive sheet or finger portion during short circuit. During short circuit test high amount of heat and forces generate in the circuit breaker, this MS finger cover provides extra protection against these forces.
6. The profile of the flexible contact (3) has a finger cover (2) to incorporate the same pin of Diameter 10 mm in the Moving contact of width 9 mm.
7. The flexible contact (3) and bottom cradle terminal (II) are two different parts,
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the spirit or scope of the present invention.

We Claim:
1. A moving contact circuit breaker for protecting electric circuit, the circuit
breaker comprising:
a fixed contact secured in a housing of the circuit breaker and connected electrically to a top cradle terminal;
a fixed arcing contact configured over and connected to the fixed contact; a flexible contact flexibly disposed in the housing of the circuit breaker and connected to a bottom cradle terminal, characterized in that the flexible contact having,
a plurality of finger members extending from the flexible contact, the flexible member secured in the housing of the circuit breaker, the flexible member capable of providing arcuate motion to the flexible contact;
a moving contact button disposed on each of the finger member and opposite to the fixed contact, the moving contact button enable to close the circuit when in contact with the fixed contact;
a flexible arcing contact disposed over the distal portion of each if the finger member, above the moving contact button and opposite to fixed arching contact; and
a finger cover with holes disposed over each of the flexible member for protecting the finger member from short circuit and for strengthening thereby quenching the arc during separation of fixed and moving contacts.
2. The moving contact circuit breaker for protecting electric circuit as claimed in claim 1, wherein the finger cover is made of mild steel.
3. The moving contact circuit breaker for protecting electric circuit as claimed in claim 1, wherein the holes on the finger cover enables to hold a pin.

4. The moving contact circuit breaker for protecting electric circuit as claimed in claim 1, wherein the arc contact is braced to a slot and holes on the flexible member.
5. The moving contact circuit breaker for protecting electric circuit as claimed in claim 1, wherein the finger members are made of electrically conducting sheets.
6. The moving contact circuit breaker for protecting electric circuit as claimed in claim 1, wherein the finger member are solidified by the application of heat and pressure and the flexible contact remains in the laminate form.