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: SPLIT KNOB ASSEMBLY FOR TRIP ALARM CONTACT IN MINIATURE CIRCUIT BREAKER

2. Applicant(s):

(a) NAME : LARSEN & TOUBRO LIMITED
(b) NATIONALITY : An Indian Company
(c) ADDRESS : L & T House, Ballard Estate, 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:

A) TECHNICAL FIELD

The present invention generally relates to miniature circuit breakers (MCB) and particularly to miniature circuit breakers with trip alarm contact (TAC) used in a domestic as well as industrial purposes. The present invention more particularly relates to a split knob assembly mechanism for restricting the movement of the knob in the trip alarm contact in the miniature circuit breaker.

B) BACK GROUND OF THE INVENTION

Miniature circuit breakers are the mechanical switching devices capable of making, carrying, and breaking currents under normal circuit conditions and also making, carrying for a specified time, and breaking currents under specified abnormal conditions. A miniature circuit breaker basically consists of a pair of separable contacts and an interrupting medium. The function of the contacts is to conduct the electrical current when the breaker is closed and withstand the arcs while interrupting. Generally, the electrical contacts have a stationary part and a moving part. By bringing the moving contact to touch the stationary contact, the electric current flow through the circuit and the miniature circuit breaker is closed. By driving the moving contact away from the stationary contact, an electric arc develops in the circuit and by quenching the electric arc, the current stops flowing to the circuit and the miniature circuit breaker gets opened.

In any kind of miniature circuit breaker (MCB) or switching device, the operating mechanism plays a very crucial role. The module width of low voltage miniature circuit breaker is very less and hence the mechanism should be compact. The trip alarm contact (TAC) is a type of accessory used along with MCBs to indicate the status of the MCB in case of a fault. The MCB can operate during erroneous system conditions like over currents and short-circuits, but can also be operated routinely as a part of operating cycle (ON to OFF or vice versa) whereas the TAC operates only in case of fault conditions and not otherwise.

In the existing techniques, the number of linkages present in a switching device’s operating mechanism is more thereby making the movement of the operating mechanism quite slow. Also due to larger no of components, the structure of the assembly is quite complex and difficult. Due to larger size of components, it is difficult to incorporate the mechanism in half width modules.

Hence there exists a need to provide a mechanism for switching devices to restrict the movement of the knob in ON position. There also exists a need to provide a mechanism which is compact with reduced number of components to restrict the movement of the knob.

The above mentioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.

C) OBJECT OF THE PRESENT INVENTION

The primary object of the present invention is to provide an interlocking mechanism for restricting the movement of the knob in the trip alarm contact miniature circuit breaker.

Another object of the present invention is to provide an interlocking mechanism to restrict the movement of knob in ON position in a low voltage miniature circuit breaker.

Another object of the present invention is to provide an interlocking mechanism with a split knob design in the trip alarm contact miniature circuit breaker to restrict the movement of knob in ON position in a low voltage miniature circuit breaker.

Yet another object of the present invention is to provide an interlocking mechanism for which is compact in size.

D) SUMMARY OF THE INVENTION

The various embodiments of the present invention provide a trip alarm contact assembly with a split knob assembly for a miniature circuit breaker to restrict the switching of the knob from ON position to OFF position. The trip alarm contact assembly for a miniature circuit breaker comprises a split knob assembly which includes a first knob, a second knob and a first torsion spring arranged between the first knob and the second knob. The first knob includes a dimple/grooves profile to secure the first torsion spring between the first knob and the second knob so that when the first knob is switched from an ON position to OFF position, the second knob operation is restricted. The first knob is arranged exterior to the second knob.

According to one embodiment of the present invention, the trip alarm contact assembly with a split knob assembly for a miniature circuit breaker further comprises a housing to enclose the knob assembly, a second torsion spring inserted between the housing and the second knob, a fixed contact assembly, an actuating link assembly, a U-pin, an actuating link, a connecting link connected to the actuating link, a pivot assembly, a lock lever connected to the pivot assembly and a pin.

According to one embodiment of the present invention, the split knob assembly is connected to the U-pin connecting the connecting link and the lock lever. The pin connects the connecting link with the actuating link. The actuating link is connected to a coupling link which in turn is connected to the fixed contact assembly and a moving contact assembly.

According to one embodiment of the present invention, the assembly is adapted to operate in at least one of a reset condition, a fault condition and a manual switching from ON to OFF condition.

According to one embodiment of the present invention, the split knob assembly transmits a force provided by an user to the coupling link connected to the fixed contact assembly and the moving contact assembly through the connecting link which in turn will change the state of trip alarm contact from an OFF condition to an ON condition during a reset condition of the trip alarm contact assembly.

According to one embodiment of the present invention, the miniature circuit breaker is adapted to clear the fault which in turn changes the status of the trip alarm contact during the fault condition.

According to one embodiment of the present invention, an operating mechanism of the miniature circuit breaker and the trip alarm contact assembly are internally connected.

According to one embodiment of the present invention, a pivot pin connects the output of the miniature circuit breaker to the trip alarm contact pivot assembly.

According to one embodiment of the present invention, for resetting the trip alarm contact from OFF to ON position, the miniature circuit breaker knob is operated to turn ON the miniature circuit breaker in case of no fault and once miniature circuit breaker is switched ON then the trip alarm contact is switched ON.

According to one embodiment of the present invention, the pivot and the knob assembly are arranged such that the first knob and the second knob of the trip alarm contact are arranged in same direction such that the user switches the first knob from an ON position to an OFF position during a fault condition.

According to one embodiment of the present invention, the pivot and the knob are arranged such that the first knob and the second knob of the trip alarm contact are arranged in different directions such the mechanism does not change the state from ON to OFF until a fault condition occurs during a manual switching from ON to OFF condition.

These and other objects and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.

E) BRIEF DESCRIPTION OF THE DRAWINGS

The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:

FIG. 1 illustrates a cross sectional view of the miniature circuit breaker with a trip alarm contact in an OFF position, according to one embodiment of the present invention.

FIG. 2 illustrates a cross sectional view of the miniature circuit breaker with trip alarm contact in ON position, according to one embodiment of the present invention.

FIG. 3 illustrates an exploded perspective view of the trip alarm contact assembly, according to one embodiment of the present invention.

FIG. 4 illustrates an exploded perspective view of a split knob assembly, according to one embodiment of the present invention.

FIG. 5 illustrates a front view of the trip alarm contact mounted on the miniature circuit breaker, according to one embodiment of the present invention.

FIG. 6 illustrates an exploded perspective view of the pivot linkages between the trip alarm contact and the miniature circuit breaker, according to one embodiment of the present invention.

FIG. 7 illustrates an exploded front perspective view of the knobs and pivot arrangement of the trip alarm contact and the miniature circuit breaker in ON Position, according to one embodiment of the present invention.

FIG. 8 illustrates an exploded front perspective view of the knobs and pivot arrangement of the trip alarm contact and the miniature circuit breaker in OFF Position, according to one embodiment of the present invention.

Although the specific features of the present invention are shown in some drawings and not in others. This is done for convenience only as each feature may be combined with any or all of the other features in accordance with the present invention.

F) DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description, a reference is made to the accompanying drawings that form a part hereof, and in which the specific embodiments that may be practiced is shown by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and it is to be understood that the logical, mechanical and other changes may be made without departing from the scope of the embodiments. The following detailed description is therefore not to be taken in a limiting sense.

The various embodiments of the present invention provide a trip alarm contact assembly with a split knob assembly for a miniature circuit breaker to restrict the switching of the knob from ON position to OFF position. The trip alarm contact assembly for a miniature circuit breaker comprises a split knob assembly which includes a first knob, a second knob and a first torsion spring arranged between the first knob and the second knob. The first knob includes a dimple profile or grooves to secure the first torsion spring between the first knob and the second knob so that when the first knob is switched from an ON position to OFF position, the second knob operation is restricted. The first knob is arranged exterior to the second knob.

According to one embodiment of the present invention, the trip alarm contact assembly with a split knob assembly for a miniature circuit breaker further comprises a housing to enclose the knob assembly, a second torsion spring inserted between the housing and the second knob, a fixed contact assembly, an actuating link assembly, a U-pin, an actuating link, a connecting link connected to the actuating link, a pivot assembly, a lock lever connected to the pivot assembly and a pin.

According to one embodiment of the present invention, the split knob assembly is connected to the U-pin connecting the connecting link and the lock lever. The pin connects the connecting link with the actuating link. The actuating link is connected to a coupling link which in turn is connected to the fixed contact assembly and a moving contact assembly.

According to one embodiment of the present invention, the assembly is adapted to operate in at least one of a reset condition, a fault condition and a manual switching from ON to OFF condition.

According to one embodiment of the present invention, the split knob assembly transmits a force provided by an user to the coupling link connected to the fixed contact assembly and the moving contact assembly through the connecting link which in turn will change the state of trip alarm contact from an OFF condition to an ON condition during a reset condition of the trip alarm contact assembly.

According to one embodiment of the present invention, the miniature circuit breaker is adapted to clear the fault which in turn changes the status of the trip alarm contact during the fault condition.

According to one embodiment of the present invention, an operating mechanism of the miniature circuit breaker and the trip alarm contact assembly are internally connected.

According to one embodiment of the present invention, a pivot pin connects the output of the miniature circuit breaker to the trip alarm contact pivot assembly.

According to one embodiment of the present invention, for resetting the trip alarm contact from OFF to ON position, the miniature circuit breaker knob is operated to turn ON the miniature circuit breaker in case of no fault and once miniature circuit breaker is switched ON then the trip alarm contact is switched ON.

According to one embodiment of the present invention, the pivot and the knob assembly are arranged such that the first knob and the second knob of the trip alarm contact are arranged in same direction such that the user switches the first knob from an ON position to an OFF position during a fault condition.

According to one embodiment of the present invention, the pivot and the knob are arranged such that the first knob and the second knob of the trip alarm contact are arranged in different directions such the mechanism does not change the state from ON to OFF until a fault condition occurs during a manual switching from ON to OFF condition.

FIG. 1 illustrates a cross sectional view of the miniature circuit breaker with trip alarm contact in OFF position, according to one embodiment of the present invention. The trip alarm contact assembly includes, a split knob assembly 1 assembled in the housing 11. The torsion spring with higher force inserted in-between the housing 11 and the second knob of the split knob assembly 1. The fixed contact assembly 6 and actuating link assembly 7 are then assembled in the housing 11. The other mechanism components U-pin 2, the connecting link 3, the actuating link 4, the lock lever 5, the pivot 8 and the pin 9 are assembled as shown in FIG. 1. The contact spring (compression) is than placed in-between the actuating link 4 and the housing 11 which helps in delivering the required contact pressure. The whole assembly is then closed with the help of a cover.

The split knob assembly 1 is connected to the u-pin 2 which is then connected to the connecting link 3 and the lock lever 5. The connecting link 3 is connected to the actuating link 4 with the pin 9. The lock lever 5 is connected to the pivot assembly 8. The actuating link 4 is then connected to the coupling link 10 which in turn is connected to the fixed contact assembly 7 and the moving contact assembly 6. The output of the moving contact assembly 6 indicates the contact position (normal or changeover) of the trip alarm contact. The FIG. 1 shows the miniature circuit breaker with trip alarm contact in OFF position. The trip alarm contact operates only in case of fault conditions and not otherwise.

FIG. 2 illustrates a cross sectional view of the miniature circuit breaker with trip alarm contact in ON position, according to one embodiment of the present invention. The trip alarm contact assembly includes, a split knob assembly 1 assembled in the housing 11. The torsion spring with higher force inserted in-between the housing 11 and the second knob of the split knob assembly 1. The fixed contact assembly 6 and actuating link assembly 7 are then assembled in the housing 11.

The split knob assembly 1 is connected to the u-pin 2 which is then connected to the connecting link 3 and the lock lever 5. The connecting link 3 is connected to the actuating link 4 with the pin 9. The lock lever 5 is connected to the pivot assembly 8. The actuating link 4 is then connected to the coupling link 10 which in turn is connected to the fixed contact assembly 7 and the moving contact assembly 6. The output of the fixed contact assembly 7 and the moving contact assembly 6 is used to indicate the contact position (normal or changeover) of the trip alarm contact. The contact spring (compression) is placed in-between the actuating link 4 and the housing 11 which helps in delivering the required contact pressure. The whole assembly is then closed with the help of a cover. The FIG. 2 shows the miniature circuit breaker with trip alarm contact in ON position. The trip alarm contact will operate only in case of fault conditions and not otherwise.

FIG. 3 illustrates an exploded perspective view of the trip alarm contact mechanism, according to one embodiment of the present invention. The trip alarm contact assembly includes, the split knob assembly 1 is assembled in the housing 11 and the torsion spring with higher force is inserted in-between the housing 11 and the second knob of the split knob assembly 1. The split knob assembly 1 is then connected to the u-pin 2 which is then connected to the connecting link 3 and the lock lever 5. The connecting link 3 is connected to the actuating link 4 with the pin 9. The lock lever 5 is connected to the pivot assembly 8. The contact spring (compression) is placed in-between the actuating link 4 and the housing which helps in delivering the required contact pressure. The whole assembly is then closed with the help of a cover.

FIG. 4 illustrates an exploded perspective view of the split knob assembly, according to one embodiment of the present invention. The split knob assembly 1 includes a first knob 1a, a second knob 1b and a torsion spring 12. The first knob 1a is assembled with the second knob 1b and the torsion spring 12 is inserted between them. The first knob 1a includes a slotted profile to secure the torsion spring 12 in the first knob 1a which restrict the movement of the torsion spring 12 once the torsion spring 12 is secured between the first knob 1a and the second knob 1b. The design of the split knob assembly 1 is adapted to restrict the operation of the second knob 1b when the user accidentally or purposefully tries to operate the first knob 1a from ON position to OFF position.

FIG. 5 illustrates a front view of the trip alarm contact mounted on the miniature circuit breaker, according to one embodiment of the present invention. As shown in FIG. 5, the trip alarm contact assembly 13 is mounted on the miniature circuit breaker 14 in such a manner that there is no physical contact between the miniature circuit breaker and the trip alarm contact assembly 13 apart from the trip alarm contact pivot 8 the miniature circuit breaker pivot 16. The trip alarm contact knob 1 and the miniature circuit breaker knob 15 are not connected to each other. The miniature circuit breaker 14 should be switched ON first then the trip alarm contact 13 is switched ON. But the user is allowed to reset the trip alarm contact 13 before turning the miniature circuit breaker 14 to ON position easily.

FIG. 6 illustrates a front perspective view of the pivot linkages between the trip alarm contact and the miniature circuit breaker, according to one embodiment of the present invention. The trip alarm contact 13 includes the split knob assembly 1 which includes a first knob 1a and a second knob 1b and the pivot assembly 8 which includes a pivot 8a and a pivot pin 8b as shown in FIG. 6. The miniature circuit breaker includes a miniature circuit breaker knob 16 and the miniature circuit breaker pivot 16 as shown in FIG. 6.

The mechanisms of miniature circuit breaker 14 and the trip alarm contact 13 are connected internally by the pivot 8a. The miniature circuit breaker 14 is designed such that the pivot 16 only move in case of fault condition and for normal operation there is no pivot movement. Thus, the output of miniature circuit breaker pivot 16 is connected to the trip alarm contact pivot 8a by a pivot pin 8b. When fault occurs the NO (normally open) and NC (normally closed) contact position of the trip alarm contact 13 changes which then produces a sound or visual indication to the user that the miniature circuit breaker 14 has been operated due to fault present in the system.

For resetting the trip alarm contact 13 (OFF to ON operation) the miniature circuit breaker knob 15 is operated first, if there is no fault present in the system than only the miniature circuit breaker14 will turn ON. Once the miniature circuit breaker is switched ON then the trip alarm contact 13 is switched ON.

The miniature circuit breaker 14 and trip alarm contact 13 are mounted in such a manner that they have no physical contact with each other apart from the trip alarm contact pivot 8 and the miniature circuit breaker pivot 16. Both the trip alarm contact knob 1 and the miniature circuit breaker knob 15 are not connected to each other as shown in FIG. 5, as the user should switch ON the miniature circuit breaker 14 first and then turn the trip alarm contact 13 from OFF position to ON position. But the user is allowed to reset the trip alarm contact 13 before turning the miniature circuit breaker 14 to ON position easily. Both the trip alarm contact knob 1 and the miniature circuit breaker knob 15 are in same direction so it is easy for the user to switch the miniature circuit breaker 14 from ON position to OFF position.

FIG. 7 illustrates a front perspective view of the knob assembly and pivot arrangement of the trip alarm contact and the miniature circuit breaker in an ON Position, according to one embodiment of the present invention. The mechanisms of miniature circuit breaker 14 and the trip alarm contact 13 are connected internally by the pivot 8a, such that the pivot 16 of the miniature circuit breaker 14 will only move in case of fault and for normal operation it will not have any movement. Thus, the output of miniature circuit breaker pivot 16 is connected to trip alarm contact pivot 8a by a pivot pin 8b. When fault occurs the NO (normally open) and NC (normally closed) contact position of the trip alarm contact 13 will change which will give a buzzer or visual indication to the user that the miniature circuit breaker 14 has been operated due to fault present in the system.

For resetting the trip alarm contact 13 i.e. from OFF position to ON position, the miniature circuit breaker knob 15 is operated first. If there is no fault present in the system, than only the miniature circuit breaker 14 will turn ON and once miniature circuit breaker 14 is switched ON then the trip alarm contact 13 is switched ON.

FIG. 8 illustrates a front perspective view of the knobs and pivot arrangement of the trip alarm contact & miniature circuit breaker in an OFF Position, according to one embodiment of the present invention. The operating mechanism of the miniature circuit breaker 14 and the trip alarm contact 13 are connected internally by the pivot 8a, such that the pivot 16 of the miniature circuit breaker 14 move during a fault condition and for normal operation, there is no pivot movement. The output of miniature circuit breaker pivot 16 is connected to trip alarm contact pivot 8a by a pivot pin 8b. When fault occurs the NO (normally open) and NC (normally closed) contact position of the trip alarm contact 13 changes. The change in contact position of the trip alarm contact 13 provides a sound indication or visual indication to the user that the miniature circuit breaker 14 has been operated due to a fault present in the system.

When the user accidentally or purposefully tries to switch the knob 1 of the trip alarm contact from ON to OFF position, the user is unable to do that because the knob assembly 1 consists of first knob 1a and the second knob 1b which are inter linked with the help of the torsion spring 12 as shown in FIG. 4. In this case the first knob 1a will move but will not latch the mechanism since its force value is lower than the second spring force so the first knob 1a will rotate but will be unable to latch the mechanism. Both the trip alarm contact knob 1 and the miniature circuit breaker knob 15 are not in same direction so the mechanism will not switch OFF on its own (change its state from ON to OFF) until a fault occurs in system. FIG. 8 shows the fault condition where the first knob 1 and the second knob 15 of the trip alarm contact 13 and the miniature circuit breaker 14 are in OFF position.

Although the invention is described with various specific embodiments, it will be obvious for a person skilled in the art to practice the invention with modifications. However, all such modifications are deemed to be within the scope of the claims.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the present invention described herein and all the statements of the scope of the invention which as a matter of language might be said to fall there between.

G) ADVANTAGES OF THE INVENTION

The trip alarm contact of the present invention prevents the user from accidently switching of the trip alarm contact from ON position to OFF position.

The trip alarm contact of the present invention provides a compact arrangement with less number of components to restrict the movement of knob in ON position.

The split knob arrangement in the trip alarm contact assembly of the present invention restricts the movement of knob assembly from ON to OFF position and only allow the knob assembly to be moved from OFF to ON position.

The split knob arrangement in the trip alarm contact assembly of the present invention provides a buzzer sound or a visual indication only in case of fault and not under any condition which can be caused intentionally or unintentionally.

The split knob arrangement in the trip alarm contact assembly of the present invention can be easily used in half module width i.e. 9mm as the components are quite small and less in number.

The actuating and the latching mechanism of the present embodiments are quite simple and easy to assemble.

WE CLAIM:

1. A split knob assembly for a trip alarm contact assembly in a miniature circuit breaker, the assembly comprising:
a first knob;
a second knob; and
a first torsion spring arranged between the first knob and the second knob;
wherein the first knob includes a dimpled profile to secure the first torsion spring between the first knob and the second knob, when the first knob is switched from an ON position to OFF position, thereby restricting operation of the second knob.

2. The assembly according to claim 1, wherein the first knob is arranged exterior to the second knob.

3. The assembly according to claim 1, further comprises:
a housing to enclose the knob assembly;
a second torsion spring inserted between the housing and the second knob;
a fixed contact assembly;
an actuating link assembly;
a U-pin;
an actuating link;
a connecting link connected to the actuating link;
a pivot assembly;
a lock lever connected to the pivot assembly; and
a pin.

4. The assembly according to claim 1, wherein the split knob assembly is connected to the U-pin connecting the connecting link and the lock lever.

5. The assembly according to claim 1, wherein the pin connects the connecting link with the actuating link.

6. The assembly according to claim 1, wherein the actuating link is connected to a coupling link which in turn is connected to the fixed contact assembly and a moving contact assembly.

7. The assembly according to claim 1, wherein the assembly is adapted to operate in a reset condition.

8. The assembly according to claim 1, wherein the assembly is adapted to operate in a fault condition.

9. The assembly according to claim 1, wherein the assembly is manually switched from ON to OFF condition.

10. The split knob assembly according to claim 1, wherein the connecting link transmits a force provided by an user to the coupling link connected to the fixed contact assembly and the moving contact assembly to change a state of trip alarm contact from an OFF condition to an ON condition during a reset condition of the trip alarm contact assembly.

11. The split knob assembly according to claim 1, wherein the miniature circuit breaker is adapted to clear the fault which in turn changes the status of the trip alarm contact during the fault condition.

12. The assembly according to claim 1, wherein an operating mechanism of the miniature circuit breaker and the trip alarm contact assembly are internally connected.

13. The assembly according to claim 1, wherein a pivot pin connects the output of the miniature circuit breaker to the trip alarm contact assembly.

14. The assembly according to claim 1, wherein the miniature circuit breaker knob is operated to turn ON the miniature circuit breaker for resetting the trip alarm contact from OFF to ON position, in case of no fault and then the trip alarm contact is switched ON after the miniature circuit breaker is switched ON.

15. The assembly according to claim 1, wherein the first knob and the second knob are arranged in same direction such that the user switches the first knob from an ON position to an OFF position during a fault condition.

16. The assembly according to claim 1, the first knob and the second knob are arranged in different directions such that the trip alarm contact mechanism does not change the state from ON to OFF until a fault condition occurs during a manual switching from ON to OFF condition.