AN IMPROVED AUTO RESET MECHANISM FOR A CIRCUIT
BREAKER FIELD OF THE INVENTION
[0001] The present invention generally relates to circuit breakers and more particularly embodiments of the invention relates to an improved auto reset mechanism for a circuit breaker.
PRIOR ART [0002] A circuit breaker is normally introduced in an electrical network to protect conductors or equipment from damage caused by excessive temperature due to over current in abnormal conditions such as overload or short-circuit In order to be able to protect the equipments from damage, there should be an efficient and quick means for opening and closing of contact system in a circuit breaker. In conventional type MCCBs, breaker will feature three position in the top cover near the knob to show ON, OFF and TRIP. The knob is placed over the fork of the operating mechanism. When the knob indicates ON it means the breaker is ON i.e., the current path is closed. Similarly, the position of the knob indicates the state of the circuit breaker.
[0003] According to standards, the top position of the knob, if the breaker is placed vertically or the longest distant position of the knob away from the operator, if the breaker is mounted horizontally is marked as ON POSITION. The other extreme end in both cases is marked as the OFF POSITION. The TRIP position of the knob will be somewhere near to the centre. In conditions of overload and/or short circuit, the release on the circuit breaker delivers the TRIP signal to the. Upon receiving the trip signal, the breaker opens the circuit and the knob goes to the trip position to show the operator that a fault has occurred in the system. However, the circuit breaker cannot be turned ON without resetting the breaker. Normally, resetting of the breaker is done by moving the knob (fork) to the OFF position from the TRIP position. This movement loads the mechanism spring and now enables the turning ON of the breaker.
[0004] However, there is a need for a mechanism that can provide an auto reset mechanism without the need for manual intervention. There are reset mechanisms

known to be available in the prior art that provide an auto reset mechanism utilizing electronic circuits. This adaptation adds another component to the circuit breaker thereby increasing the development and maintenance costs. Hence, there is a need for an auto reset mechanism provides an efficient reset mechanism without the need to incorporate additional external components.
OBJECT OF THE INVENTION [0005] It is an object of the invention to provide an improved auto reset mechanism for a circuit breaker. More particularly, it is an object of the invention to provide an adjustable link mechanism that can adapted for turning ON and OFF or resetting the circuit breaker.
BRIEF DESCRIPTION OF THE DRAWINGS [0006] So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to various embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. [0007] Figure 1 shows the outline diagram of the auto reset mechanism according to an embodiment of the invention.
[0008] Figure 2 shows the formation of dead centre according to an embodiment of the invention.
[0009] Figure 3 shows the outline diagram of alignment of members of the auto reset mechanism during the OFF condition of the Circuit breaker according to an embodiment of the invention.
[0010] Figure 3 a shows the line diagram of the alignment of members of the auto reset mechanism during the OFF condition of the Circuit breaker according to an embodiment of the invention
[0011] Figure 4 shows the outline diagram of alignment of members of the auto reset mechanism during the ON condition of the Circuit breaker according to an embodiment of the invention.

[0012] Figure 4a shows the line diagram of the alignment of members of the auto
reset mechanism during the ON condition of the Circuit breaker according to an
embodiment of the invention.
[0013] Figure 5 shows the outline diagram of the trip mechanism coupled to the
reset mechanism according to an embodiment of the invention.
[0014] Figure 6 shows the outline diagram of alignment of members of the auto
reset mechanism during the TRIP condition of the Circuit breaker according to an
embodiment of the invention.
[0015] Figure 6a shows the line diagram of the alignment of members of the auto
reset mechanism during the TRIP condition of the Circuit breaker according to an
embodiment of the invention.
DETAILED DESCRIPTION OF INVENTION [0016] Various embodiments of the invention provide an improved auto reset mechanism for a circuit breaker. More particularly, embodiments of the invention provide an improved adjustable link mechanism to trigger ON and reset the contact system of the circuit breaker. The invention and its embodiments shall be described in detail herein below.
[0017] Figure 1 shows the outline diagram of the auto reset mechanism according to an embodiment of the invention. The auto reset mechanism comprises of a fork 1; an actuating link 3 to move the contact; a spring 2 coupled at one end to the actuating link and at the other end to the fork; a trip lever 4 connected to the actuating link 3 and at least one reset link 6, coupled at one end to the fork and at the other end to the actuating link. The dead centre 5 of the circuit breaker is reached when the upper spring point (fork), trip lever-link point and the lower spring point get aligned along a straight line as shown in Figure 2 The reset link member 6 has an elongated slot at one end adapted for slidably locating itself with respect to a support member positioned on the trip lever and a slot for coupling the reset link to both the fork and the trip lever [0018] Circuit Breaker in OFF position.
[0019] Figure 3 shows the arrangement of the members of the auto reset mechanism according to an embodiment of the invention. In the OFF position of

the circuit breaker, the position of the fork is at OFF position and the spring is contracted. The actuating link is situated along the axis of the dead centre. The elongated slot provided on the reset link is locked at its distal position on to the pin provided on the trip lever arm. This position of the trip lever arm does not alter the trip assembly. Figure 3a shows the line diagram of the alignment of members of the auto reset mechanism during the OFF condition of the Circuit breaker according to an embodiment of the invention. In the figure, O'A shows the position of the fork during OFF position. 0"PS represents the position of the trip lever in relation to the fork. PQT is the position of the actuating link that couples to the moving contact of the circuit breaker represented by X'OXRR'. The position of the reset link BCC in relation the fork, the trip lever and the contact system is as shown. The dotted line represented by the O'A' indicates the maximum degree of freedom of the fork and the dotted line represented by O'X' represents the maximum degree of freedom of the moving contact. [0020] Circuit Breaker in ON position.
When the fork 1 is moved towards ON position as shown in Figure 4, the pin from the trip lever 4 is pushed down as the fork advances, so that it can be latched. The reset link 6 will be along the direction of the fork. Now the mechanism can be switched ON when the fork point crosses the dead centre 5. The elongated slot provided in the reset link enables the link to set its position along the direction of the fork without altering the position of the trip lever or the actuating link. Figure 4a shows the line diagram of the alignment of members of the auto reset mechanism during the ON condition of the Circuit breaker according to an embodiment of the invention.
[0021] Circuit Breaker at TRIP condition:
[0022] Figure 5 shows the elements of the trip mechanism coupled to the reset mechanism. The mechanism comprises of a trip plate 7, latch plate 8, latch pin with two ends wherein a first end is located on the latch plate and the other end is adapted to fit into a countersunk hold, a button 10 with an actuator and a torsion spring 9. A countersunk hole 12 is provided to retain the pin within the hole and enable movement of the pin. The torsion spring 9 is placed in such a way that one

end of it pushes the latch pin away from the mechanism and the other end pushes the trip plate away from the mechanism. The profile of the trip plate is in such a way that it can slide over the latch plate. When the release senses the abnormality, it pushes the trip plate towards the mechanism. As the torsion spring force is comparatively low the trip plate moves towards the mechanism. As the other end of the torsion spring is trying to push the latch pin in the opposite direction, the trip plates slides down on the surface of the latch plate. Once the trip plate moves down completely, the latch plate moves back and gets locked. As the latch plate moves back, the latch pin also moves back along with it, thus the trip lever is released. [0023] During resetting, the trip button 10 is pushed down. An actuating rod, which connects the button with the reset mechanism will touch the latch plate 7. Hence when the button is pushed down, this actuating rod pushes the latch plate 7 towards the mechanism such that the latch plate slides and goes below the trip plate. As the torsion spring always pushing the trip plate away from the mechanism, the trip plate 8 will slide over and rise above the latch plate, thus locking the latch plate.
[0024] Before the trip lever 4 comes down, the reset mechanism is ready. The latch pin will be positioned in such a way that when the trip lever comes down it will move over the latch pin, pushing it back in the slot available in the latch plate. On the other end of the latch pin, torsion spring is acting against this movement. Once the trip lever slides and goes passed the latch pin, the spring force will bring the latch pin to its original position. Then the trip lever is locked as the further downward movement is locked by the fork movement and its upward movement is locked by the latch pin. The resetting of the trip lever is achieved before the fork reaches the dead centre. The trip lever's pin simply runs in the slot of the reset link without affecting the trip lever's position during normal ON and OFF operation. [0025] The invention as illustrated by the diagrams and as described herein in detail provides an improved adjustable link mechanism adapted for auto reset of the circuit breaker. The invention advantageously reduces the need to bring the fork to OFF position in order to reset the contact system of the circuit breaker. Hence, embodiment of the invention advantageously provides a mechanism to

reset the circuit breaker on the way when the knob is moved to ON position. Further, the invention also provides a safety mechanism to indicate the TRIP condition of the circuit breaker.
[0026] The foregoing description of the invention has been set for merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to person skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.

We claim:
1. An improved auto reset mechanism for a circuit breaker, the circuit breaker
having a fixed contact and a moving contact, said reset mechanism
comprising:
a fork;
ii. an actuating hnk
iii. a spring coupled to the actuating Ink and the fork; iv. a trip lever connected to the actuating link; and V. at least one reset link coupled to the fork at one end and the
actuating link such that the moving contact is brought to
reset position.
2. An auto reset mechanism of claim 1, wherein the reset link member comprises an elongated slot adapted at one end for slidably locating itself with respect to a support member positioned on the trip lever.
3. An auto reset mechanism of claim 1, wherein the reset link member comprises an elongated slot adapted at the other end for slidably locating itself with a slot for coupling the reset link to both the fork and the trip lever.
4. An auto reset mechanism of claim 1, wherein the trip lever pin is configured to slide through the slot of the reset link.
5. An auto reset mechanism of claim 1, further wherein the trip lever is coupled to activate a trip mechanism, the said mechanism comprising
i. a trip plate;
ii. a latch plate coupled to the trip plate; iii. a latch pin with two ends wherein a first end is located on
the latch plate and the other end is adapted to fit into a
countersunk hole, iv. a trip button adapted to lockable release the latch plate; V. a torsion spring configured to push at first end the latch pin
away from the mechanism and at the other end to push the
trip plate away from the mechanism.


6. An auto reset mechanism of claim 1, wherein the slidable movement of the
trip lever pin along the slot of reset link member does not alter the trip
position of the trip lever.
7. An auto reset mechanism of claims 1 -6 as illustrated by the diagrams and
as described in detailed description.
8. A circuit breaker having an auto reset mechanism as claimed in claims 1-7,
wherein the contact system of the said circuit breaker is a single break
contact system.
9. A circuit breaker having an auto reset mechanism as claimed in claims 1-7,
wherein the contact system of the said circuit breaker is a double break
contact system.

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