DESC:FIELD OF THE INVENTION
The present invention relates to a contact locking mechanism with variable toggling point and a method of locking moving contacts.

BACKGROUND OF THE INVENTION
A circuit breaker is a mechanical switching device, 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 circuit conditions such as those of short circuit (Short circuit is an accidental or intentional connection, by a relatively low resistance or impedance, of two or more points in a circuit which are normally at different voltages)
The main function of any electrical switching apparatus is to carry the rated current. Therefore the current carrying capacity of any circuit breaker is so important that if the unit fails to carry the rated current it will cause damage to itself as well as to the electrical equipment to which it is protecting.
Circuit breakers have three positions corresponding to the status of the separable contacts. For example, these positions would include an ON position, in which the separable contacts are closed, an OFF position in which the contacts are open and Trip position in which the contacts are tripped open.
These circuit breakers / switching devices are usually installed in an enclosure so as to have all the control and distribution network laid in form of metallic sheets and or cable wires inside and all operating means from outside so as to prevent access to high voltage and thus a potential hazard.
When a circuit breaker is in ON condition and a short circuit fault condition arises, high amount of fault current flows through the circuit and in response to this the circuit breaker tries to move the separable contacts to open position after sensing the fault condition through short circuit sensing mechanism (such as magnetic arrangement). The time taken from a fault condition initiation and the fault current being interrupted by circuit breaker determines the let through energy / arc energy passed by the circuit breaker to the downstream equipments. A circuit breaker is said to be more efficient when the let through energy is minimal.
Let through energy of circuit breaker depends on many parameters, one among them being the time for opening of the contacts from closed condition. The short circuit sensing mechanism of circuit breaker involves mechanical elements in between and thus takes a definite time before giving a trip open signal to the contacts thus increasing the let through energy.
Short circuit conditions involves high amount of fault current levels which induces high repulsive forces between suitably arranged current carrying contacts. Thus if the contacts can be locked in the repelled open position, the let through energy can be reduced substantially. This improves life of the equipments and systems connected downstream and greatly reduce the hazardous conditions which can damage the downstream equipments.
Thus many of the circuit breakers use such locking systems for contact locking under short circuit conditions. Further, efficiency of a contact locking system is measured by the velocity it can induce to the contacts once they have repelled open. It is also important to have the desired contact force in the ON condition, i.e. when the separable contacts are in closed condition.
In traditional / present circuit breakers additional moving components having complex cam profile is used to achieve contact locking. This reduces the efficiency of the locking mechanism as there is some amount of energy lost in overcoming friction. Friction also gets added to the amount of heat generated at the surfaces in contact. It also increases wear and tear of the parts, thereby reducing the overall life of the system. Also, there will be variation in the contact force over a period of time due to such wear and tear.
It is also desirable to make the contacts move faster once it crosses the toggling position resulting in faster cut-off of fault current increasing the current limiting capability of the circuit breaker. It is also very important to achieve optimum contact force in the ON condition to keep the potential drop at the contact buttons to the minimum. However, in present cases shown above the contacts do not move after toggling due friction between sliding component and drive shaft
These and other limitations and needs of the conventional mechanisms necessitate an improved contact locking mechanism. Such a locking mechanism has been disclosed herein which overcomes the limitations over and above the improvements and flexibility provided additionally.
The present invention relates to contact locking mechanism with optimum components with an inbuilt feature to flip–flop without having any component with complex cam profile for flip-flop. This invention enhances the velocity of contact system during toggling during fault clearance by circuit breaker while reducing let through energy. Hence the life of circuit breaker against short circuit fault clearance is improved.
Following are the features and benefits of the invention:
1. Main objective/benefit of the present invention is the component with simple cam profile to reduce friction for movement
2. Another benefit is the higher velocity of moving contact even while toggling resulting in faster cut-off of fault current increasing the current limiting capability of the circuit breaker.
3. Consistency in the contact force throughout the life of the system
Here are some Patents on mechanism which also talks about Contact Locking. All the locking mechanisms shown here are of only single point moving type.
US 5633483 US 5874699 US 7217895 US 5844455 US 4539538
However, the mechanisms described in the aforesaid patents are different from the mechanism of the present invention.

OBJECTS OF THE INVENTION
One object of the invention is to overcome the disadvantages/drawbacks of the prior art.
A basic object of the present invention is to provide a contact locking mechanism with variable toggling point.
Another object of the present invention is to provide a method of locking moving contacts.
These and other advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.

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.
In an aspect of the present invention, there is provided a contact locking system for a circuit breaker; said system comprising:
a contact arrangement comprising a moving contact and a fixed contact;
a rotating drive shaft for providing rotation to said moving contact;
at least two extension spring(s) for providing a contact force to said contact arrangement; and
a braid block brazed to said moving contact;
wherein said system provides a flip-flop movement of said contact arrangement during toggling during fault clearance by said circuit breaker, thereby reducing let through energy and enhancing the life of said circuit breaker against fault clearance.
In an aspect of the present invention, there is provided a method of locking contact(s) in circuit breaker, said method comprising steps of:
rotating a moving contact pivoted on a shaft about a pivot pin in upward direction, when a fault occur(s) in said circuit breaker,
changing a load line by pulling said pin pivoted in said moving contact in a new position facilitating repelling of said moving contact by extension of a spring , therefore crossing a toggling point,
releasing spring energy by said spring, when said toggling point is crossed,and
locking of said moving contact with said fixed contact.
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 following drawings are illustrative of particular examples for enabling methods of the present invention, are descriptive of some of the methods, and are not intended to limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description.
Figure 1 shows the front view (Contacts in ON condition)
Figure 2 shows the front view with hidden lies (Contacts in ON condition)
Figure 3 shows the front view in (Contacts in repelled open condition)
Figure 4 shows the front view (Contacts in ON & Repelled open condition)
Figure 5 shows the Isometric view (Contacts in ON condition)
Figure 6 shows the Isometric view (Contacts in Repelled open condition)
Figure 7 shows the exploded front view
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 numerals are used to depict the same or similar elements, features and structures.

DETAILED DESCRIPTION OF THE PRESENT INVENTION
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention 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 embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are 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 invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention 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.
By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.
Accordingly, present invention provides a contact locking mechanism with variable toggling point and a method of locking moving contacts.
This invention talks about a contact locking mechanism with minimal components with an inbuilt feature to flip–flop without having any component with complex cam profile for flip-flop. This feature enhances the velocity of contact system during toggling during fault clearance by circuit breaker as the friction required for additional component is reduced
This invention is incorporated with the better velocity of contacts separation during toggling during fault clearance by circuit breaker reducing let through energy and at the same time it enhances the life of circuit breaker against short circuit fault clearance.
Locking system disclosed herein is shown in Figure 1 to Figure 7. Please refer the exploded view of locking system in Figure 7. It consists of a rotating member of the circuit breaker mechanism, called as drive-shaft 2 to which the upper contact 1 is pivoted at pin 5. This upper contact has an elliptical shaped hole instead of conventional round hole. Rotation of this driveshaft will cause upper moving contacts to come in contact with the lower contacts and thereby it completes the electrical circuit. Braid block 3 is brazed to upper contact 1. Two nos. of tension springs are used to achieve contact pressure / contact force. One end of extension Spring 4 is placed on the pin 6 pivoted on driveshaft and the other end of spring is placed on pin 7 which is pivoted on upper contact This spring exerts force on upper contact
Figure 5 & 6 shows the 3D view of the arrangement from the front end of the driveshaft for a single pole of the circuit breaker. For multiple poles, multiple such assemblies will be used side by side using a common connecting driveshaft across all the poles.
The working of the invention is shown in Fig 1 to 4 with different positions. These are the positions in which the moving contact cannot go further down or up since it stops on the driveshaft.
When the fault occurs, there is an upward force on the Upper contact 1 thereby it will rotate about the pivot pin 5. This movement of the contact will cause extension of the tension spring 4. These extended springs will try to pull the pin pivoted in the upper contact to a new location thus changing the load / force line. This load / force line will now get shifted to a new location. This location is nearer to the toggling axis as compared with the original location. This makes the upper contact to repel much early than the previous case.
As soon as the toggling point is crossed, the extension springs will release their energy, thus the springs which are extended to its maximum deflection reaches an equilibrium state by reducing its length and releasing energy in the process to rotate the upper contact and it will rotate the upper contact in upward direction till it stops over mechanism. If the repulsion force on the upper contact is less than contact pressure / contact force offered by extension springs, then the toggling will not occur and contact will not get locked and the moving contact will again come to it ON position.
Once the moving contact gets locked, it is brought back to the normal condition when the circuit breaker protection system subsequently trips the mechanism due to fault. When the signal is given, the driveshaft rotates in the upward direction. The moving contact then comes in contact with the cover / top portion of the circuit breaker and experiences a reaction force in the downward direction in a way as to make the moving contact cross the toggling position. Once the moving contact crosses the toggling position, it goes to the normal position by virtue of the force exerted by the extension spring. Therefore, process of unlocking of moving contact is just the opposite of the locking process.
The extension spring is used to flip–flop without having any complex component with cam profile for flip-flop. This invention is incorporated with the better velocity of contacts separation during toggling during fault clearance by circuit breaker reducing let through energy and at the same time it enhances the life of circuit breaker against short circuit fault clearance.
Since moving contact moves after toggling without repulsive force, there is faster energy release by the spring after toggling, resulting in higher velocity of moving contact. This results in faster cut-off of fault current increasing the current limiting capability of the circuit breaker.
Toggling position is that instant at which the pivot pin at upper contact hinge 5, pivot pin at drive-shaft 6 and sliding pin in upper contact 7 come in the same line during repulsion.
The orientation of the spring load line is fixed on various parameters by design. The effectiveness of the toggling position is decided by the closeness of the toggling position to the ON position. Since, in such case the amount of rotation required by the moving contact to reach the toggling position and gets locked will be lesser. In present invention the spring load line gets shifted during repulsion which helps early toggling. This will reduce the let through energy of the mechanism to the downstream equipments.
However it will reduce the contact force between the moving and fixed contacts in the breaker due to lesser angle between toggling axis with respect to spring load line. In order to achieve the same contact force with toggling position closer to the ON position, higher load spring can be used. This will ensure the required contact pressure at lower currents and will repel & lock only after the pre-defined threshold level.
The present invention relates to contact locking mechanism with minimum components without complex cam profile for flip-flop.
This invention is incorporated with the velocity of contacts separation while toggling during fault clearance by circuit breaker reducing let through energy and at the same time it enhances the life of circuit breaker against short circuit fault clearance.
With increasing demand of green product, it is imperative for everyone to
a. Reduce the consumption of raw material by reducing the number of components used.
b. Reduce the energy / power lost in the device
c. Use the material that requires least energy to produce it ,CLAIMS:1. A contact locking system for a circuit breaker; said system comprising:
a contact arrangement comprising a moving contact and a fixed contact;
a rotating drive shaft for providing rotation to said moving contact;
at least two extension spring(s) for providing a contact force to said contact arrangement; and
a braid block brazed to said moving contact;
wherein said system provides a flip-flop movement of said contact arrangement during toggling during fault clearance by said circuit breaker, thereby reducing let through energy and enhancing the life of said circuit breaker against fault clearance.
2. The system as claimed in claim 1, wherein said moving contact (s) is (are) pivoted to said drive shaft using a pin.

3. The system as claimed in claim 1, wherein said moving contact (s) having an elliptical shaped hole.

4. The system as claimed in claim 1, wherein one end of said extension spring is connecting to a pin pivoted on said driveshaft and other end of said spring is connecting to a sliding pin pivoted on said upper moving contact, thereby exerting a force on said moving contact(s).

5. The system as claimed in claim 1, wherein said moving contact rotates about a pivot pin due to an upward force on said moving contact, when a fault occur(s) in said circuit breaker.

6. The system as claimed in claim 5, wherein rotation of said moving contact facilitates extension of said spring, therefore changing a load line by pulling said pin pivoted in said moving contact in a new position facilitating repelling of said moving contact, by crossing a toggling point.

7. The system as claimed in claim 7, wherein said spring releasesspring energy to facilitate rotation of said moving contact, when said toggling point is crossed, therefore is providing locking of said moving contact with said fixed contact.

8. The system as claimed in claim 1, wherein said shaft rotates in upward direction, when trip signal is provided to said circuit breaker.

9. The system as claimed in claim 9, wherein rotation of said shaft in upward direction providing a force to said moving contact in downward direction, therefore said moving contact crossed said toggling point thereby providing unlocking of said contact(s).

10. The system as claimed in claim 1, wherein said moving contact is in normal position as a result of the force exerted by said extension spring, when said contact crossed said toggling point.

11. The system as claimed in claim 1, wherein said toggling point is the point, when said pivot pin at said moving contact hinge , said pivot pin at said shaft and said sliding pin in said moving contact are in the same line during repulsion.

12. A method of locking contact(s) in circuit breaker, said method comprising steps of:
rotating a moving contact pivoted on a shaft about a pivot pin in upward direction, when a fault occur(s) in said circuit breaker,
changing a load line by pulling said pin pivoted in said moving contact in a new position facilitating repelling of said moving contact by extension of a spring , therefore crossing a toggling point,
releasingspring energy by said spring, when said toggling point is crossed,
locking of said moving contact with said fixed contact.

13. The method as claimed in claim 1, wherein a shaft rotates in upward direction, when trip signal is provided to said circuit breaker.

14. The method as claimed in claim 13, wherein said shaft rotates in upward direction, when trip signal is provided to said circuit breaker.

15. The method as claimed in claim 14, wherein rotation of said shaft in upward direction providing a force to said moving contact in downward direction, therefore said moving contact crossed said toggling point thereby providing unlocking of said contact(s).

16. The method as claimed in claim 15, wherein said moving contact is in normal position as a result of the force exerted by said extension spring, when said moving contact crossed said toggling point.

17. The method as claimed in claim 13, wherein said toggling point is the point, when said pivot pin at said moving contact hinge , said pivot pin at said shaft and said sliding pin in said moving contact are in the same line during repulsion.

18. The method as claimed in claim 13, wherein said moving contact (s) pivoted to said shaft using a pin.

19. The method as claimed in claim 13, wherein said moving contact (s) is provided with an elliptical shaped hole.

20. The method as claimed in claim 13, wherein one end of said extension spring is connecting to a pin pivoted on said driveshaft and other end of said spring connecting to a sliding pin pivoted on said upper moving contact, thereby exerting a force on said moving contact(s).