Claims:
1. A moulded case circuit breaker comprising:
a housing enclosing within
a rotary operating mechanism, ROM (13), operably coupled to a contact system (5), wherein the contact system (5) is adapted to rotate a fork lever (14) to engage and disengage one or more moving contacts (9) from one or more fixed contacts (10) to open and close a circuit.

2. The circuit breaker as claimed in claim 1, wherein the fork lever (14) is a spring-loaded fork lever and said lever (14) is coupled to a ROM handle (7) of the ROM, by means of a rack (6), to facilitate toggling and rotating of an upper link (17) to indicate open or closed state of the contact system (5).

3. The circuit breaker as claimed in claim 2, wherein the circuit breaker comprises a latch link (16) operably coupled to the upper link (17), to facilitate rotation and disengagement of the one or more moving contacts (9) from the one or more fixed contacts (10), during a trip condition and bring the ROM handle to a trip position.

4. The circuit breaker as claimed in claim 3, wherein the circuit breaker comprises a primary actuator (4) mounted on a shaft of the contact system (5) operably coupled to a secondary actuator (3) mounted on a chassis (8) and the secondary actuator (3) is further coupled to a stopper link (1) mounted inside the housing of the ROM (13), wherein the primary actuator, the secondary actuator and the stopper link (1) move in synchronization during an ON-OFF condition of the circuit breaker.

5. The circuit breaker as claimed in claim 4, wherein the circuit breaker comprises a pin (7b) embedded in the ROM handle (7) which when operably pushed downwards, through a single matching hole (13a) in the housing of the ROM (13) exposes the slot where lock can be inserted, during normal operating conditions.

6. The circuit breaker as claimed in claim 5, wherein the one or more moving contacts (9) gets welded to the one or more fixed contacts (10) to restrict the movement of the shaft of the contact system (5), during over-current or fault conditions,
wherein the rotation of the latch link (16) exerts a force on the shaft of the contact system (5) through the upper link (17) and lower links to rotate the shaft of the contact system (5) from over-travel position to just-touch position, to break the weld,
wherein if the weld is strong and does not break with the force applied by the latch link (16), then the weld will restrict further motion of the shaft of the contact system (5), the upper link (17) and the latch link (16), to keep the ROM handle (7) in on position and indicate that the circuit is still closed.

7. The circuit breaker as claimed in claim 6, wherein the ROM handle (7) is adapted to rotate a few degrees on application of a torque to switch off the circuit breaker, and the rack (6) will interfere with the stopper link (1), to prevent further motion of the rack (6) and disallow the ROM handle (7) to reach the OFF position,
on releasing the ROM handle (7), the fork lever (14) is adapted to make the ROM handle (7) to return to ON position, and
the pin (7b) inside the ROM handle (7) cannot be pushed down as there will be no matching hole in the housing of the ROM (13).
, Description:
FIELD OF THE INVENTION
Embodiments of the invention in general relate to rotary operated mechanism, ROM of a Moulded Case Circuit Breaker, MCCB, and more particularly, to positive indication and off padlock prevention when electrical contacts of a circuit breaker are welded. When electrical contacts of circuit breakers weld due to over-current it is imperative to prevent the off-padlock of indicator knob by not allowing it to reach the “OFF” position.

BACKGROUND OF THE INVENTION
Circuit Breaker is a mechanical switching device capable of making, carrying and breaking currents. Under normal circuit conditions it will make the circuit, carry current for a specified time and break the circuit under specified abnormal circuit conditions.

Circuit Breakers are employed for current interruption. More particularly Circuit Breakers are utilized to protect instruments from damage during adverse conditions prevailing during the operation of the circuit in which 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 system.

When release senses abnormal conditions, it gives Trip command to the mechanism so that the latter opens the circuit.

This current interruption happens when a set of movable electrical contacts are separated from their respective fixed contacts by means of an operating mechanism.

During certain abnormal conditions like overcurrent it is possible that one or many from the set of electrical contacts get welded to each other i.e. movable contacts get welded to their respective fixed contacts.

Under such conditions when the release issues the trip command, 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 means of a ROM, he should not be able to padlock the handle in off position. This is achieved by preventing the handle from reaching the ‘OFF’ position.

The present invention talks of a method by which if the weld remains unbroken, the operating handle of ROM cannot be padlocked in “OFF” position. The handle will be stopped by means of interference between two components. This will not let the handle move further even with the application of three times the normal torque required to switch off the MCCB. On removal of this applied torque the handle will return to the “ON” position thereby depicting the true condition of the contacts and the circuit.

Reference is being made to US5296664A, disclosing an arrangement of links such that during contact welded conditions the links will prevent the lever from moving to the OFF position. The ROM when used to operate this lever will have an indirect stop through the lever. So, it is an indirect method of stopping the ROM wherein a complicated arrangement of some links sense the contact condition and then interfere with the lever, thereby stopping the ROM. ROM therefore has no direct interaction with the contact system. Such indirect method is less reliable owing to its complexity. Also, any misalignment of the links can lead to malfunction and prevent the intended function from happening. Furthermore, it uses a number of components as part of building the link work between the contacts and the ROM.

Thus, there is a dire need for an arrangement, where all the requisite functions can be achieved in a more simplistic and direct way and by using fewer components in comparison to the above invention. The ROM directly takes feedback from contact system about the circuit condition (welded / not welded, close / open). Direct linking with 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.

According to one aspect of the present invention, a moulded case circuit breaker comprising a housing enclosing within it a rotary operating mechanism, ROM, operably coupled to a contact system, wherein the contact system is adapted to rotate a fork lever to engage and disengage one or more moving contacts from one or more fixed contacts to open and close a circuit has been provided. The circuit breaker comprises a latch link operably coupled to the upper link, to facilitate rotation and disengagement of the one or more moving contacts from the one or more fixed contacts, during a trip condition and bring the ROM handle to a trip position. The circuit breaker further comprises a primary actuator mounted on a shaft of the contact system operably coupled to a secondary actuator mounted on a chassis and the secondary actuator is further coupled to a stopper link mounted inside the housing of the ROM. The primary actuator, the secondary actuator and the stopper link move in synchronization during an ON-OFF condition of the circuit breaker. The circuit breaker comprises a pin embedded in the ROM handle which when operably pushed downwards, through a single matching hole in the housing of the ROM exposes the slot where lock can be inserted, during normal operating conditions. The one or more moving contacts gets welded to the one or more fixed contacts to restrict the movement of the shaft of the contact system, during over-current or fault conditions, and the rotation of the latch link exerts a force on the shaft of the contact system through the upper link and lower links to rotate the shaft of the contact system from over-travel position to just-touch position, to break the weld. If the weld is strong and does not break with the force applied by the latch link, then the weld will restrict further motion of the shaft of the contact system, the upper link and the latch link, to keep the ROM handle in on position and indicate that the circuit is still closed. Under these faut conditions, the ROM handle is adapted to rotate a few degrees on application of a torque to switch off the circuit breaker, and the rack will interfere with the stopper link, to prevent further motion of the rack and disallow the ROM handle to reach the OFF position,
on releasing the ROM handle, the fork lever is adapted to make the ROM handle to return to ON position, and the pin inside the ROM handle cannot be pushed down as there will be no matching hole in the housing of the ROM.

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 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 a schematic of a rotary operated mechanism and contact system in ON position, according to an embodiment of the present invention.

Figure 2 illustrates rotary operated mechanism and contact system in OFF position, according to an embodiment of the present invention.

Figure 3 illustrates rotary operated mechanism and contact system in welded position, according to an embodiment of the present invention.

Figure 4 illustrates a sectional view of rotary operated mechanism and contact system in ON Position, according to an embodiment of the present invention.

Figure 5 illustrates a sectional view of rotary operated mechanism and contact system in OFF Position, according to an embodiment of the present invention.

Figure 6 illustrates a sectional view of rotary operated mechanism and contact system in OFF Position, according to an embodiment of the present invention.

Figure 7 illustrates positions of handle indicating ON, TRIP and OFF position, according to an embodiment of the present invention.

Figure 8 illustrates a sectional view of rotary operated mechanism and contact system in Welded Position, according to an embodiment of the present invention.

Figure 9 illustrates an isometric view of rotary operated mechanism handle, according to an embodiment of the present invention.

Figure 10 illustrates an isometric view of rotary operated mechanism housing, according to an embodiment of the present 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 moulded case circuit breaker comprising a housing enclosing within a rotary operating mechanism, ROM (13), operably coupled to a contact system (5), wherein the contact system (5) is adapted to rotate a fork lever (14) to engage and disengage one or more moving contacts (9) from one or more fixed contacts (10) to open and close a circuit.

According to an embodiment of the present invention, A Rotary Operating Mechanism 13 switches the contact system 5 through a rack 6 which rotates the fork lever 14 to engage and disengage the moving contact 9 with fixed contact 10 to close and open the circuit respectively. The ROM handle 7 is rotated clockwise, when in OFF as shown in figure 7, to switch ON the MCCB and anti-clockwise, when in ON as shown in figure 7, to switch OFF the MCCB. As the extension spring loaded fork lever 14 is rotated by means of a rack 6 connected to ROM handle 7 it reaches the toggle point of upper link 17 on to which the other end of extension spring is loaded. This rotates the upper link 17 and when upper link 17 crosses the toggle point of the fork lever 14 it toggles the fork lever 14 and the ROM handle 7 to indicate the state of the contact system 5 viz. Close or Open. The upper link 17 is connected to lower links on either side which in turn are connected to moving contact shaft 5. Hence the motion of upper link 17 rotates the moving contact shaft 5 to open and close the circuit.

When trip command is issued the latch link 16 is disengaged causing it to rotate anti-clockwise. This rotation causes upper link 17 and thereby lower links to rotate and disengage the moving contact 9 from fixed contact 10. As the upper link 17 rotates during trip it crosses the toggle point of fork lever 14 and brings the ROM handle 7 to trip position, as shown in figure 7.

A primary actuator 4 mounted on shaft 5 is a connection between secondary actuator 3, mounted in chassis 8, and shaft 5. The primary actuator 4 moves the secondary actuator 3 up when switched ON and down when switched OFF. The stopper link 1 mounted inside ROM housing 13 and connected to secondary actuator 3 rotates anti-clockwise when the secondary actuator 3 moves up and rotates clockwise when secondary actuator 3 moves down.

During normal operating conditions, when the ROM handle 7 is rotated from ON to OFF, the fork lever 14 will first cross the toggle point of upper link 17 causing it to rotate and disengage the moving contact 9 and fixed contact 10 and take the moving contact shaft 5 to OFF position. This will rotate the stopper link 1 in anti-clockwise direction as the secondary actuator 3 moves down. This rotation of upper link 17 will then make the extension spring to cross the toggle point of fork lever 14 and take the fork lever 14 and rack 6 to OFF position and the ROM handle 7 will indicate OFF. A pin 7b embedded in the ROM handle 7 can now be pushed downwards, through a single matching hole 13a in ROM housing 13 to expose the slot where lock can be inserted, as shown in figure 6.

During overcurrent or other fault conditions if moving contact 9 gets welded to fixed contact 10 it will restrict the rotation of moving contact shaft 5 beyond just-touch position when trip command is issued by the release and the mechanism trips. During tripping the rotation of latch link 16 will exert a force on moving contact shaft 5 through upper link 17 and lower links to rotate the moving contact shaft 5 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 16 then the weld will restrict further motion of moving contact shaft 5 and thereby of upper link 17 and latch link 16. As upper link 17 does not rotate enough to cross the toggle point of fork lever 14, fork lever 14 and ROM handle 7 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 torque to rotate ROM handle 7 in anti-clockwise direction, it will rotate a few degrees. After which the rack 6 will interfere with the stopper link 1, as shown in figure 3 & 8. This interference will prevent further motion of rack 6 and this will not allow the ROM handle 7 to reach the OFF position. On releasing the ROM handle 7 the fork lever 14 will make the ROM handle 7 to return to ON position as the fork lever’s 14 toggle point was not crossed on account of upper link 17 not being able to rotate beyond the toggle point of fork lever 14. Since the ROM handle 7 does not reach the OFF position, the pin 7b inside the ROM handle 7 cannot be pushed down as there will be no matching hole in the ROM housing 13.

In an exemplary implementation, during normal switching operations the rack 6 connected to ROM handle 7 do not interfere with the stopper link 1 mounted inside ROM housing 13. The pin 7b can be pushed down and lock inserted. When the contacts are welded, the rack 6 interfere with stopper link 1 as the ROM handle 7 is rotated and prevent it from reaching the OFF position. Even an application of three times the torque required to switch off the breaker during normal operation does not take the ROM handle 7 to OFF position and hence the lock could not be inserted. On releasing the applied torque to rotate the ROM handle 7, it returns to ON position and indicates the true state of the circuit.

Some of the non-limiting advantages of the positive indication and off padlock prevention during contacts welded condition in rotary operated mechanism of moulded case circuit breakers are:

1. All the requisite functions can be achieved in a more simplistic and direct way and by using fewer components.
2. The ROM directly takes feedback from contact system about the circuit condition (welded / not welded, close / open).

Although positive indication and off padlock prevention during contacts welded condition in rotary operated mechanism of moulded case circuit breakers 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 positive indication and off padlock prevention during contacts welded condition in rotary operated mechanism of moulded case circuit breakers.