Claims:WE CLAIM:

1. A moulded case low voltage current limiting circuit breaker comprising
a plurality of fixed contacts disposed across from each other;
a rotary moving contact assembly comprising a single break moving contact (11), pivotably coupled to a plurality of side plates (12) on either side, and configured to electrically couple and decouple the fixed contacts, said moving contact (11) having a first substantially linear edge (41) and a second substantially arcuate shaped edge (42), said side plates (12) having a first substantially semi-circular edge (51) so as to receive a fixed pin (21), a substantially U-shaped edge (52) so as to receive a floating pin (22), said fixed pin (21) and floating pin (22) are coupled by means of extension springs (23), wherein the floating pin is configured to move along said first edge (41) and said second edge (42) of the moving contact (11) during different states of operation of the circuit breaker.

2. The circuit breaker as claimed in claim 1, wherein the moving contact (11) is pivotably coupled to the side plates (12) by rivet pins (13).

Dated this 30th day of March 2019

Abhishek Sen
IN/PA Reg No: 980
Of S. MAJUMDAR & CO.
(Applicant’s Agent)

, Description:F O R M 2

THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)

1. Title of the invention –

CURRENT LIMITING BREAKER WITH IMPROVED CONTACT RESET PERFORMANCE FOR MECHANISM

2. Applicant(s)

(a) NAME : LARSEN & TOUBRO LIMITED

(b) NATIONALITY: An Indian Company.

(c) ADDRESS: L & T House, Ballard Estate, P.O. Box: 278,
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 INVENTION

The present invention relates to the field of protection devices in general, more particularly to circuit breakers, involving a current limiting molded case circuit breaker.

BACKGROUND

In modern current limiting molded case circuit breakers, the moving contacts will react to fault currents without even waiting for fault sensing module to trigger the mechanism to open the rotating shafts to break the circuit. These moving contacts will repel open fully, get locked in the process so that no re-closure of moving contact will happen and also eventually start the current interruption process. Normally, breaker after interruption process will be brought to operating condition by mechanism which invariably received the fault signal from the sensing module. Current limiting breakers have an advantage over conventional breakers in form of less structural and thermal stress to devices located in the downstream.
Generally, repulsion of the moving contact is based on electromagnetic forces generated on the contacts due to the current flow. Contact opening is restrained up to some current threshold to enable breaker application in high starting inrush current loads. Repelling contacts have another feature of locking which significantly enhances the interruption performance and the purview of the invention is about how the locking being achieved.
Reference has been made to US5313180, disclosing movable contact bridge of a molded case limiting circuit breaker is supported by a bar by a system of springs enabling opening with electrodynamic repulsion. The contact bridge cooperates with stationary contacts rigidly secured to current input conductors in the shape of half-loops. An anvil is adjoined to the rear of the stationary contacts to increase the closing impact effect of the contact bridge and prevent contact resistance dispersions. The anvil is made of ferromagnetic material increase the magnetic field for blowout of the arc to the extinguishing chambers. In overall, it relates to the arrangement of the moving contact in the rotor assembly, engagement of the moving contact with stationary contact and the anvil used in the stationary contact which serves the dual purpose of supporting stationary contact and also enhances electromagnetic forces during contact repulsion.
Reference has been made to KR20130020070A, which teaches a movable contactor assembly for a molded case circuit breaker is provided to improve the performance of a breaker by reducing the number of a frictional surface for obstructing a trip and a current-limiting operation. This invention relates to braid less rotor assembly of the circuit breaker, claims are made for the method of engaging the moving contact with the stationary arm and way in which the cam is used for the contact mechanism to achieve repel and locking action.
Reference has been further made to US7394032B2, teaching an electrodynamically tilting contact system for power circuit breakers includes an actuating shaft segment, a rotary contact bridge pivotally mounted therein and contact force springs that form components of a tilting snap-action mechanism, which holds the rotary contact bridge in a repulsed position after an electrodynamically effected repulsion of fixed contacts. Two rockers, while serving as an additional component of the tilting snap-action mechanism, are mounted on the rotary contact bridge in a manner that enables them to tilt. The contact force springs are supported between the actuating shaft segment and the rockers, whereby the spring longitudinal axes, the tilting axes of the rockers, and the rotational symmetry axis of the rotary contact bridge are located in the tilting point plane of the tilting snap-action mechanism. The rotary contact bridge is mounted in the actuating shaft segment via a bearing pin and an elongated hole bearing whose longitudinal axis, together with the tilting point plane, forms an at most, acute angle perpendicular to the bearing pin.
In the prior art, some of the technical problems faced are conventional compression or extension spring with dead center contact mechanism will bound to have high reset forces for breaker mechanism. Conventional compression spring contact system requires minimum two extra components to hold the compression spring and to perform its intended action. Extension spring with dead center mechanism will have high stress accumulation in hook as well as the body of the spring. Thermoset shaft is needed to take care of the thermal stresses built up in the conventional contact system.
To overcome aforementioned problems, thus there is a need for a moulded case low voltage current limiting circuit breaker configured to reduce the reset burden of the breaker mechanism and enhance the reliability of the product by eliminating thermoplastic components abutting the internal current carrying parts.

SUMMARY OF THE INVENTION

The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.
An object of the present invention is to provide a moulded case low voltage current limiting circuit breaker.
An object of the present invention is to reduce the reset burden of a moulded case low voltage current limiting circuit breaker mechanism and enhance the reliability of the product by eliminating thermoplastic components abutting the internal current carrying parts.
An object of the present invention is to provide a moulded case low voltage current limiting circuit breaker having cam navigation profile in the moving contact and support is provided for the moving pin by the metal plates, notable deviation is that cam being on the copper reduces friction and enhances faster movement.
In accordance with an aspect of the present disclosure, is to provide providing a moulded case low voltage current limiting circuit breaker comprising a plurality of fixed contacts disposed across from each other, a rotary moving contact assembly comprising a single break moving contact, pivotably coupled to a plurality of side plates on either side, and configured to electrically couple and decouple the fixed contacts, said moving contact having a first substantially linear edge and a second substantially arcuate shaped edge, said side plates having a first substantially semi-circular edge so as to receive a fixed pin, a substantially U-shaped edge so as to receive a floating pin, said fixed pin and floating pin are coupled by means of extension springs, wherein the floating pin is configured to move along said first edge and said second edge of the moving contact during different states of operation of the circuit breaker.

Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The above and other aspects, features and advantages of the embodiments of the present disclosure will be more apparent in the following description taken in conjunction with the accompanying drawings, in which:
Figure 1 illustrates an exploded view of the rotor assembly in accordance to the invention.
Figure 2 illustrates a front view with extension spring position in accordance to the invention.
Figure 3 illustrates the ON, FLIP, repelled state of the assembly in accordance to the invention.
Figure 4 illustrates the profile of moving contact in accordance to the invention.
Figure 5 illustrates the profile of side plate in accordance to the invention.
Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure. Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the present disclosure as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and constructions may be omitted for clarity and conciseness.
The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the present disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustration purpose only and not for the purpose of limiting the present disclosure as defined by the appended claims and their equivalents.
It is to be understood that the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a component surface" includes reference to one or more of such surfaces.
All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which various embodiments belong. Further, the meaning of terms or words used in the specification and the claims should not be limited to the literal or commonly employed sense, but should be construed in accordance with the spirit of the disclosure to most properly describe the present disclosure.
The terminology used herein is for the purpose of describing particular various embodiments only and is not intended to be limiting of various embodiments. As used herein, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising" used herein specify the presence of stated features, integers, steps, operations, members, components, and/or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, members, components, and/or groups thereof. Also, Expressions such as "at least one of," when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.
The present disclosure will now be described more fully with reference to the accompanying drawings, in which various embodiments of the present disclosure are shown. The present disclosure may, however, be embodied in many different forms and should not be construed as being limited to the various embodiments set forth herein, rather, these various embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the present disclosure. Furthermore, a detailed description of other parts will not be provided not to make the present disclosure unclear. Like reference numerals in the drawings refer to like elements throughout.
The subject invention lies in providing a moulded case low voltage current limiting circuit breaker comprising a plurality of fixed contacts disposed across from each other, a rotary moving contact assembly comprising a single break moving contact (11), pivotably coupled to a plurality of side plates (12) on either side, and configured to electrically couple and decouple the fixed contacts, said moving contact (11) having a first substantially linear edge (41) and a second substantially arcuate shaped edge (42), said side plates (12) having a first substantially semi-circular edge (51) so as to receive a fixed pin (21), a substantially U-shaped edge (52) so as to receive a floating pin (22), said fixed pin (21) and floating pin (22) are coupled by means of extension springs (23), wherein the floating pin is configured to move along said first edge (41) and said second edge (42) of the moving contact (11) during different states of operation of the circuit breaker. The moving contact (11) is pivotably coupled to the side plates (12) by rivet pins (13).
In this present invention, as illustrated in Fig.1 the moving contact assembly comprises of a single break moving contact connected through braid to terminal. The rotor assembly consists of a moving contact assembly pivoted by pins to the side plates. The side plates are held together by two pins other than pivot pin which are riveted.
As shown in Fig.2, two extension springs are connected between fixed pin in the top and floating pin in the bottom, wherein the floating pin moves in the slot provided in the side plates. Ideally, the moving contact has three states to it, i.e., ON (the initial state of the assembly), FLIP (point at which the spring is stretched to the maximum length) and Repelled (final stop position in the assembly after repelling).
When the breaker is in open condition, the contact system will be there in the ON condition as shown in Fig. 3. And when the breaker is switched ON (closed condition), the moving contact rotates to certain degree as desired and defined for required contact pressure, a position between the ON and FLIP condition.
When the moving contact faces higher repulsion force induced by faulty current, the moving contact will start rotating towards the FLIP condition, which is also the dead center condition of the spring. And the spring faces higher stress in this condition only. And in the present design, the spring stresses are limited to around 70% of the maximum permissible stress, thereby maintaining the reliability of the spring. This is an intermediary position not a stable condition. Eventually, it shifts to the third, repelled condition, the second stable condition, where the moving contact will rest until it was brought back to the initial condition (ON condition).
During the fault condition, the breaker mechanism will receive a TRIP signal from the tripping module, initiating the TRIP operation. During the TRIP operation, the breaker mechanism should reset the contact system back to its initial condition. And the profile of the Contact system is designed in such a way that the resetting forces are minimal and can reset multiple poles at a time without any burden to the mechanism. While resetting the contact system, the contact system will shift from Repelled condition to FLIP condition to ON condition.
Side plate and its assembly called as core of the structure is enclosed by covers on both sides. Covers serve two purpose, viz., shielding and hinging the assembly to the cassette. Fitment of the covers to the core of the assembly is established through the snap fit.
The profile A of the moving contact as shown in Fig. 4 is designed in such a way that the repulsion force generated by the contact system flips the moving contact easily, reducing the stresses on the springs and helps during the resetting of flipped contacts by breaker mechanism with ease.
The profile B of the side plate as shown in Fig. 5 is made as a slot which allows the floating pin to move in a guided manner allowing the contact to get flipped.
Some of the non-limiting advantages of the present invention are:
a) Extension spring with CAM profile in the moving contact have reduced the breaker mechanism reset force.
b) Use of extension spring instead of conventional compression spring contact system has eliminated the requirement for plastic spring holders in the assembly which are otherwise exposed high temperature of the internal current carrying parts.
c) Making the shaft’s core structure metal has obviated the need for thermoset component.
d) Constant contact pressure realization at contact joint because of replacing deformation prone thermoplastic spring holders.

Although moulded case low voltage current limiting circuit breaker has been described in language specific to structural features, it is to be understood that the embodiments disclosed in the above section are not necessarily limited to the specific methods or devices described herein. Rather, the specific features are disclosed as examples of implementations of moulded case low voltage current limiting circuit breaker.