FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION (See section 10 and rule 13)
1. TITLE OF THE INVENTION:
"Miniature Circuit Breaker"
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,
L&T House, Ballard Estate, P. 0. Box: 278, Mumbai 400 001, India
3. PREAMBLE TO THE DESCRIPTION:
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.

MINIATURE CIRCUIT BREAKER
Field of the invention
The present invention relates to a circuit breaker and more particularly, to a miniature circuit breaker.
Background of the invention
Miniature circuit breaker is an automatically operated electrical switch designed
to protect an electrical circuit from damage caused by an overload or a short circuit. The basic function of the miniature circuit breaker is to detect a fault condition and by interrupting continuity, to immediately discontinue electrical flow. A welding group is a current carrying path of the miniature circuit breaker.
Drawbacks of the prior art
1. Inconsistent thermal performance
2. Division of current due to parallel path affecting magnetic performance
3. Welding heat to weld existing double layer coil with other components is higher
4. Welding joint is not strong and welding is difficult.
Accordingly, there exists a need to provide a miniature circuit breaker that overcomes the drawbacks of the prior art.
Objects of the invention
An object of the present invention is to provide a series path of current to flow through a miniature circuit breaker against the parallel path.

Another object of the present invention is to give a consistent thermal performance.
Summary of the invention
Accordingly, the present invention provides a miniature circuit breaker. The miniature circuit breaker comprises a housing, a box clamp, an U-frame, an arc runner frame, a moving contact, a fixed contact, a coil welded to the box clamp, a bimetal joined to the U-frame, a first braided wire connected to the bimetal, a second braided wire, a knob and a pair of din clips. The coil is a rectangular coil acting as a solenoid and responsible for magnetic performance of the miniature circuit breaker. The bimetal is responsible for thermal performance of the miniature circuit breaker. Current flows from the U-frame to the moving contact through the second braided wire and further moves from the moving contact to the fixed contact when the miniature circuit breaker is turned ON thereby providing a series path for the current to flow through the miniature circuit breaker.
Brief description of the drawings
Figures 1-2 show a block diagram of a miniature circuit breaker, in accordance with the present invention; and
Figure 3 shows a side view of a welding group of the miniature circuit breaker
of figure 1.
Detailed description of the 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.
The present invention provides a miniature circuit breaker. The miniature circuit breaker comprises a welding group that provides a series path of current to flow through the miniature circuit breaker against the parallel path.
The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the
following description.
Referring to figures 1-3, a miniature circuit breaker (hereinafter "the MCB (200)") in accordance with the present invention is shown. The MCB (200) comprises a housing (10), a box Clamp (20), an U-frame (30), an arc runner frame (40), a moving contact (50), a fixed contact (not numbered), a coil (60), a bimetal (70), a first braided wire (80), a second braided wire (90), a knob (100) and a pair of din clips (110). In an embodiment, the box clamp (20), the coil (60), the first braided wire (80), the bimetal (70), the U-Frame (30), the arc runner frame (40), the second braided wire (90) and the moving contact (50) forms a welding group (not numbered) of the MCB (200). Specifically, the present invention relates to the welding group of the 63A MP MCB.
The arc runner frame (40) closes a circuit of the U-frame (30). The arc runner frame (40) is connected to the U-frame (30) and carries very small amount of current. The U-frame (30) is connected to the bimetal (70) from one side and carries current to the second braided wire (90). The second braided wire (90) is spot welded to the U-frame (30) to carry current to the moving contact (50). Whenever the MCB (200) is switched ON the moving contact (50) connects with the fixed contact to complete the current path in the device.

The box clamp (20) is used for termination purpose and assembles with a screw (not shown) and a terminal (not shown). The box clamp (20) is welded to the coil (60) through the spot welding. In an embodiment, the coil (60) is a rectangular coil. The coil (60) is welded to the first braided wire (80) through the spot welding and connects to the box clamp (20). The coil (60) acts as a solenoid and responsible for magnetic performance of the MCB (200). The first braided wire (80) is connected to the bimetal (70) and acts as a connecting link between the coil (60) and the bimetal (70). The bimetal (70) is joined to the U-frame (30) through the spot welding. The bimetal (70) is responsible for thermal performance of the MCB (200) and carries current to the U-frame (30). The knob (100) is a toggle switch used for switching ON and OFF the MCB (200). The pair of din clips (110) is used for mounting the MCB (200) on a din rail (not shown).
Referring again to figures 1-3, in an operation, the current flows from the U-frame (30) to the moving contact (50) through the second braided wire (90). The current then moves from the moving contact (50) to the fixed contact when the MCB (200) is turned ON thereby providing a series path for the current to flow through the jMCB (200).
Advantages of the invention
1. The present invention provides series path of current to flow through the MCB (200) against the parallel path and there is no division of current due to series path of the current.
2. The welding group is accommodated in the existing housing (10) and a cover (not shown) with few modifications hence saving cost and time of manufacturing.
3. The welding group gives a consistent thermal performance.
4. The parts of the welding group are easy to weld and give strong joints with less heat generation.
5. Less rejection in thermal calibration.

6. Ease of welding due to elimination of multi-components joint at the same place.
7. Maintaining the hardness of components, safeguarding them against excess heat of multiple joint welding at the same place.
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, and 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 omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present invention.

We Claim:
1. A miniature circuit breaker (200) comprising a housing (10), a box clamp (20), an U-frame (30), an arc runner frame (40). a moving contact (50), a fixed contact, a coil (60) welded to the box clamp (20), a bimetal (70) joined to the U-frame (30), a first braided wire (80) connected to the bimetal (70), a second braided wire (90), a knob (100) and a pair of din clips (110), the miniature circuit breaker (200) characterized in that current flows from the U-frame (30) to the moving contact (50) through the second braided wire (90) and further moves from the moving contact (50) to the fixed contact when the miniature circuit breaker (200) is turned ON thereby providing a series path for the current to flow through the miniature circuit breaker (200).
2. The miniature circuit breaker (200) as claimed in claim 1 characterized in that the coil (60) is a rectangular coil acting as a solenoid and responsible for magnetic performance of the miniature circuit breaker (200).
3. The miniature circuit breaker (200) as claimed in claim 1 characterized in that the bimetal (70) is responsible for thermal performance of the miniature circuit breaker (200).