Claims:WE CLAIM:

1. A circuit breaker comprising:
a housing (A3);
at least one fixed conductor (A1) mounted in said housing (A3); and
at least one separable conductor (A22) operatively coupled to an operating mechanism (A4), said mechanism configured to engage or disengage said separable conductor (A22) from said fixed conductor (A1), said mechanism comprising lever means (A41) coupled to a plurality of links (A45, A46), said links (A45, A46) being operatively coupled to a drive shaft (A21) to selectively move along a path between an ON position in which said separable conductor (A22) is closed by said operating mechanism (A4) and an OFF position in which said separable conductor (A22) is opened by said operating mechanism (A4),
wherein said drive shaft (A21) is operatively coupled to said lever means (A41) and is configured to restrict disengaging of the at least one separable conductor (A22) from the at least one fixed conductor (A1) and retracting of the operating mechanism (A4) to OFF position when said separable conductor (A22) is welded closed.

2. The circuit breaker as claimed in claim 1, wherein the operating mechanism (A4) comprises of an upper link (A45) and at least one lower link (A46), said upper link coil (A45) being coupled to said lever means (A41) by extension spring means (A44), said lower link (A46) being operable coupled to said upper link (A45) on either side.

3. The circuit breaker as claimed in claim 1, wherein the operating mechanism (A4) comprises a latch link (A42) operatively coupled to said upper link (A45), said latch link (A42) configured to rotably engage said upper link (A45) so as to disengage the said separable conductor (A22) from said fixed conductor (A1).

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 –

CIRCUIT BREAKER WITH POSITIVE ISOLATION INDICATION FOR OFF PROTECTION

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 circuit breakers in general, more particularly to circuit breakers having mechanisms which prevent movement of the circuit breaker operating handle to the off position if the contacts are welded closed.

BACKGROUND

Circuit Breaker is an electro-mechanical switching device capable of making, carrying and breaking currents also known as over current protective device. Under normal circuit conditions it will make the circuit closed, carry current for a specified time and breaks the circuit under specified abnormal circuit conditions.
Circuit Breaker is employed for current interruption. More particularly MCCBs are utilized to protect instruments from damage during adverse conditions prevailing during the operation of the circuit in which molded case circuit breaker is employed. During adverse conditions like short circuit, the current rises to an alarmingly high level. This high current may cause damage to the parts in the electrical system. Hence during these conditions, the circuit has to be opened to protect the parts after the breaker.
A circuit breaker can be manually opened and closed, as well as automatically opened to protect conductors or equipment’s from damage caused by excessive heating due to over current in abnormal conditions such as overload or short-circuit.
It is possible under certain abnormal conditions like overcurrent it is possible that one or many from the set of electrical conductors get welded to each other i.e. movable conductor get welded to their respective fixed conductor. Under these circumstances, the trip device of the circuit breaker described can respond to the overload condition by de-latching the latchable mechanism. it is required that the operating mechanism either break the weld and indicate trip via its indication means or if the weld is strong and cannot be broken then the indicator means should indicate “ON” even though the release has issued the trip command.
Also under such circumstances if a user tries to switch off the MCCB by operating the mechanism, either manually or other operating mechanisms, he should not be able to take the lever to its “OFF” position provided the weld is still not broken.
Reference has been made to US5296664A, teaching a positive off mechanism for a circuit breaker which includes a pair of positive off levers slide able in slots in the side plates and extendable into the path of the operating handle to prevent movement of the handle to the off position when the contacts are welded closed. The positive off levers are actuated by positive off links pivotally mounted to the side plates and coupled to the positive off levers by “dog bone” connections. The positive off links in turn are actuated by the toggle mechanism of the circuit breaker which collapses to open the contacts during normal circuit breaker operation, but which remains erect when the contacts are welded closed.
To overcome aforementioned problems, there is a need which is satisfied by the present invention which is directed to a method by which if the weld remains unbroken, the operating lever cannot be taken to “OFF” position. The drive shaft helps in achieving positive isolation i.e. when breaker contacts were welded or closed the drive shaft will prevent the breaker operating handle to the OFF position. All the requisite functions can be achieved in a more simplistic way and by using fewer components in comparison to the existing circuit breakers. Simple and fewer components ensure robust and reliable way of achieving the requisite functions.
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 circuit breaker with positive isolation indication for OFF protection.
In accordance with an aspect of the present disclosure, is to provide a circuit breaker comprising a housing, at least one fixed conductor mounted in said housing and at least one separable conductor operatively coupled to an operating mechanism, said mechanism configured to engage or disengage said separable conductor from said fixed conductor, said mechanism comprising lever means coupled to a plurality of links, said links being operatively coupled to a drive shaft to selectively move along a path between an ON position in which said separable conductor is closed by said operating mechanism and an OFF position in which said separable conductor is opened by said operating mechanism, wherein said drive shaft is operatively coupled to said lever means and is configured to restrict disengaging of the at least one separable conductor from the at least one fixed conductor and retracting of the operating mechanism to OFF position when said separable conductor is welded closed.

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 side view of a full Circuit Breaker with Mechanism drive shaft assembly in accordance to the invention.
Figure 2 illustrates the operating mechanism and the contact system in ON state in accordance to the invention.
Figure 3 illustrates the operating mechanism and contact system in OFF state in accordance to the invention.
Figure 4 illustrates the operating mechanism switching to OFF state when contact system is in welded condition 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 circuit breaker comprising a housing (A3), at least one fixed conductor (A1) mounted in said housing (A3) and at least one separable conductor (A22) operatively coupled to an operating mechanism (A4), said mechanism configured to engage or disengage said separable conductor (A22) from said fixed conductor (A1), said mechanism comprising lever means (A41) coupled to a plurality of links (A45, A46), said links (A45, A46) being operatively coupled to a drive shaft (A21) to selectively move along a path between an ON position in which said separable conductor (A22) is closed by said operating mechanism (A4) and an OFF position in which said separable conductor (A22) is opened by said operating mechanism (A4), wherein said drive shaft (A21) is operatively coupled to said lever means (A41) and is configured to restrict disengaging of the at least one separable conductor (A22) from the at least one fixed conductor (A1) and retracting of the operating mechanism (A4) to OFF position when said separable conductor (A22) is welded closed.
The operating mechanism (A4) comprises of an upper link (A45) and at least one lower link (A46), said upper link coil (A45) being coupled to said lever means (A41) by extension spring means (A44), said lower link (A46) being operable coupled to said upper link (A45) on either side. The operating mechanism (A4) further comprises a latch link (A42) operatively coupled to said upper link (A45), said latch link (A42) configured to rotably engage said upper link (A45) so as to disengage the said separable conductor (A22) from said fixed conductor (A1).
The present invention is addressed to a circuit breaker for rapidly cooling and extinguishing an arc, and describes a method by which if the breaker’s electrical conductors under some circumstance got welded and the weld remains unbroken, then the operating lever fork cannot be taken to “OFF” position. The lever fork will interfere with driveshaft which will not let the lever fork move further even with the application of three times the normal force required to switch off the MCCB. And on removal of this force the lever will return to the “ON” position thereby depicting the true condition of the contacts and the circuit.
The embodiments are described with reference to a circuit breaker, but the present invention may be implemented on any electrical device that has electrical contact system that can be opened and closed.
As best seen in FIG. 1, side view of a circuit breaker assembly A. Circuit breaker is designed to quickly cool and quench an arc. Circuit breaker, having a fixed conductor assembly A1 which can be mounted directly to a housing A3 or may be mounted inside the housing A3 along with drive shaft assembly A2, generally connected to the line, or the incoming supply, however, this electrical conductor can also be connected to the load. Circuit breaker has a moving conductor assembly A21 movable with respect to the fixed conductor Assembly A1 generally is connected to the load, or the equipment drawing power, however, this electrical conductor may be connected to the line or the load. An operating mechanism A4 is used to switch the contact system by engaging and disengaging the moving contact A22 with fixed conductor A11 to close and open the circuit. The fork lever A41 is rotated anti-clockwise, when in OFF as shown in figure 3, to switch ON the MCCB and clockwise, when in ON as shown in figure 2, to switch OFF the MCCB. As the extension spring A44 loaded fork lever A41 is rotated it reaches the toggle point of an upper link A45 on to which the other end of extension spring A44 is loaded. This rotates the upper link A45 and when upper link A45 crosses the toggle point of the fork lever A41 it toggles the fork lever A41 to indicate the state of contact system viz. Close or Open. The upper link A45 is connected to lower links A46 on either side which in turn are connected to moving drive shaft A21. Hence the motion of upper link A45 rotates the moving drive shaft A21 to open and close the circuit.
When trip command is issued the latch link A42 is disengaged causing it to rotate anticlockwise, this rotation causes upper link A45 and thereby lower links A46 to rotate and disengage the moving conductor A22 from fixed conductor. As the upper link A45 rotates during trip it crosses the toggle point of fork lever A41 and brings it to trip position.
During overcurrent if moving conductor A22 gets welded to fixed conductor A11 it will restrict the rotation of moving Drive shaft A21 beyond just-touch position, when trip command is issued by the TM release A23 and the mechanism trips. During tripping, the rotation of latch link A42 will exert a force on moving drive shaft A21 through upper link A45 and lower links A46 to rotate the moving Drive shaft A21 from over-travel position to just-touch position and then will try to break the weld. However, if the weld is strong and does not break with the force applied by latch link A42 then the weld will restrict further motion of moving drive shaft A21 and thereby of lower links A46, upper link A45 and latch link A42. As upper link A45 does not rotate enough to cross the toggle point of lever fork A41, fork will remain in ON position and indicate that the circuit is still closed.
In this condition if a user tries to switch off the breaker by applying a force to rotate fork lever A41 in clockwise direction, it will rotate a few degrees. After which the drive shaft A21 stopper feature will interfere with leaver fork A41. This interference will prevent further rotation of fork and won’t allow it to reach the off position. On releasing the force applied to rotate the fork it will return to ON position as it’s toggle point was not crossed on account of upper link A45 not being able to rotate beyond the toggle point of fork lever A41.
During normal operating conditions, when the fork is rotated from ON to OFF, it will first cross the toggle point of upper link causing it to rotate and disengage the moving conductor and fixed conductor and take the moving drive shaft A21 to OFF position. This rotation of upper link will then make the extension spring A44 to cross the toggle point of lever fork A41 and take the fork to OFF position.
Some of the non-limiting advantages of the present invention are:
a) No additional components needed to achieve the positive isolation indication for off protection.
b) Direct interaction of fork lever and contact drive shaft without any intermediate links.
c) Easy and fast assembly on account of no extra components.
d) Robust and reliable operations.

Although circuit breaker with positive isolation indication for off protection 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 circuit breaker with positive isolation indication for off protection.

List of parts/components:

• A - Breaker assembly
• A1- Fixed conductor assembly
• A11- Fixed conductor
• A12- Arc runner
• A2- Drive shaft assembly
• A21-Drive shaft
• A22-Moving conductor
• A23-TM Release assembly
• A3- Housing
• A4- Mechanism assembly
• A41-Lever Fork
• A42-Latch link
• A43-Latch Bracket
• A44- Extension spring
• A45-Upper link
• A46-Lower link