FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
Trip trigger for a circuit breaker
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTORS
Rajgopal Shivdas Desale and Vishal Vijay Bagade of Crompton Greaves Ltd, S3 Division, Switch gear complex, Nashik 422010, Maharashtra, India
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed

FIELD OF THE INVENTION
The present invention relates to a trip trigger for a circuit breaker. More specifically, the present invention relates to a trip trigger disposed in a latching contact with a latch in tripped and un-tripped positions.
BACKGROUND OF THE INVENTION
A circuit breaker comprises a trip trigger which is displaceable between a tripped and an un-tripped position to effect opening and closing of contacts of the circuit breaker. The trip trigger is releasably latchable in the tripped and un-tripped positions by a trip holding latch which comprises a latch lever and a roller fixedly disposed at an end of the latch lever. The latch lever is pivotally movable between positions corresponding to the tripped and un-tripped positions and. the roller is disposed in a latching contact with the trip trigger in said positions.
In existing trip triggers, during the un-tripped position, the roller is releasably held against a latch surface of the trigger. The latch surface has a surface area just enough to maintain a point of contact with the roller. In the tripped position, the roller is releasably held on a roller retaining surface perpendicularly adjacent to the latch surface. When the trip trigger moves from the untripped position to the tripped position, the roller displaces from the latch surface to the roller retaining surface and vice versa.
However, there is a disadvantage associated with such type of trip triggers. The trigger contact area available to the roller for making a latching contact in the untripped position is just enough to maintain a point of contact. Thus, there is a possibility of slipping of the roller from the latch surface and move towards the roller

retaining surface. When the roller moves towards the roller retaining surface on its own, the circuit breaker trips and the contacts are opened. Thus, the contacts of the circuit breaker are opened, even when they are required to be closed.
To avoid slipping of the roller from the latch surface, a trip trigger may be made with a larger latch surface. However, the trip trigger is a solid body, increasing the size of latch surface results in increment in overall size and weight of the trip trigger. If the size and weight is increased, then the force required to actuate the trip trigger increases, thereby increasing the effort and costs involved.
Therefore, there is a need for a trip trigger in which a larger contact area is available to a latch roller for making a latching contact in the untripped position, without significantly increasing the cost, weight, and size of the trip trigger.
OBJECTS OF THE INVENTION
An object of the invention is to provide a trip trigger in which a larger contact area is available to a latch roller for making a latching contact in the untripped position, without significantly increasing the cost, weight, and size of the trip trigger.
DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION
Various embodiments of the present invention provide a trip trigger for a circuit breaker, the trip trigger being displaceable between a tripped and an un-tripped position to effect opening and closing of contacts of the circuit breaker and being releasably latchable in the tripped and untripped positions by a trip holding latch which comprises a latch lever and a roller fixedly disposed at an end of the latch lever, the latch lever being pivotally movable therewith between positions

corresponding to the tripped and un-tripped positions and the roller disposed in a latching contact with the trip trigger in said positions, the trip trigger comprising a primary arm and an auxiliary arm pivotally connected together in a scissor like arrangement, each of the primary and auxiliary arms having a first end and a second end disposed at opposite sides of a pivot point, the first ends of said arms being connected to each other by a spring and the second ends disposed in parallel and slidable over each other along an axis substantially parallel to axis of the spring, the second end of the auxiliary arm overlapping the second end of the primary arm and having a top portion which extends beyond a top edge of the second end of the primary arm when the spring is in neutral position, the spring being compressible for relatively sliding the second ends for coinciding top edges of both the second ends, the second end of the auxiliary arm having an outer surface for retaining the roller in a latching contact in the untripped position and the primary arm having a roller retaining surface disposed adjacent to respective top edge for releasably holding the roller in the tripped position.
Preferably, the first end of the auxiliary arm is triggerable by an actuating mechanism for displacing the trip trigger from the tripped to the untripped position.
Preferably, the coinciding of the top edges of the second ends facilitates the roller to move from the outer surface to the roller retaining surface and vice versa.
Preferably, the auxiliary arm is made up of a thin sheet of metal.
Preferably, the second end of the auxiliary arm has a surface area greater than that of the second end of the primary arm.
These and other aspects, features and advantages of the invention will be better understood with reference to the following detailed description, accompanying

drawings and appended claims, in which,
Fig.l is a front view of a portion of a circuit breaker including a trip trigger in an un-
tripped position in accordance with an embodiment of the present invention;
Fig.2 is a front view of a portion of a circuit breaker including a trip trigger in the
tripped position in accordance with an embodiment of the present invention;
Fig.3 is a perspective view of the trip trigger in accordance with an embodiment of the
present invention;
Fig.4 is a perspective view of auxiliary arm of the trip trigger in accordance with an
embodiment of the present invention;
Fig. 5 is an exploded view of a trip trigger and a roller of the holding latch disposed in
a latching contact in an un-tripped position in accordance with an embodiment of the
present invention;
Fig. 6 is an exploded view of a trip trigger and a roller of the holding latch disposed in
a latching contact in an intermediate position in accordance with an embodiment of
the present invention; and
Fig. 7 is an exploded view of a trip trigger and a roller of the holding latch disposed in
a latching contact in a tripped position in accordance with an embodiment of the
present invention.
Referring to Figs.l and 2. the circuit breaker 100 comprises a trip trigger 1, a trip coil 2, a trip holding latch 3, a lever 4, a cam 5, a ratchet 6, a closing holding latch 7, a closing trigger 8, a closing coil 9. a trip spring 10, and a closing spring 11.
The trip trigger 1 is displaceable between a tripped and an un-tripped position to effect opening and closing of the contacts (not shown in the figure) of the circuit breaker 100. An actuating mechanism such as the trip coil 2 actuates the trip trigger 1

to move from an un-tripped position to a tripped position. In both the tripped and un-tripped positions, the trip trigger 1 is releasably latchable by the trip holding latch 3, which comprises a latch lever 31 and a roller 32 fixedly disposed at an end of the latch lever 31. The latch lever 31 is pivotally mounted in a housing of the circuit breaker 100 and is movable between positions corresponding to the tripped and untripped positions. The roller 32 is disposed in a latching contact with the trip trigger 1 in said positions. The trip holding latch 3 is coupled to a lever 4 rotatably mounted in the housing, which is coupled to the contacts (not shown in the figure) of the circuit breaker 100.
The lever 4 is also coupled to the cam 5, which is rotatably mounted on the ratchet 6. The rotation of the lever 4 and the cam 5 causes charging and discharging of the trip spring 10 and the closing spring 11. The cam 5 and the ratchet 6 are operably coupled to the closing holding latch 7 which releasably latches the closing trigger 8. The closing trigger 8 is actuated by the closing coil 9.
Referring to Fig. 1, the roller 32 is disposed in a latching contact with an outer surface 33 of the trip trigger 1 in the un-tripped position. Referring to Fig. 2, when the trip coil 2 pushes the trip trigger 1, the trip trigger 1 rotates in clockwise direction, sliding the roller 32 in anticlockwise direction towards the outer surface 34 for resting thereon. The sliding of the roller 32 towards the outer surface 34 causes the latch lever 31 to rotate in clockwise direction and free itself from the latching contact with the lever 4. The rotation of the latch 3 causes the lever 4 to rotate in anticlockwise direction leading to discharging of the trip spring 10 and opening of the contacts. The rotation of the lever 4 in anticlockwise direction causes the cam 5 to rotate in clockwise direction leading to charging of the closing spring 11.

Referring to Figs.3 and 4, the trip trigger 1 comprises a primary arm 12 and an auxiliary arm 13 pivotally connected to each other at a pivot point 14 in a scissor like arrangement. The primary arm 12 comprises a first end 121 and a second end 122 disposed at opposite sides of the pivot point 14. Similarly, the auxiliary arm 13 comprises a first end 131 and a second end 132 disposed at opposite sides of the pivot point 14. The inner surfaces of the first ends 121 and 131 are connected by a biasing member such as a spring 15. The second ends 122 and 132 are disposed in parallel and relatively slidable over each other along an axis substantially parallel to axis of the spring 15.
The second end 122 comprises a top edge 123 and a bottom edge 124, and the second end 132 comprises a top edge 133 and a bottom edge 134. The second end 132 has a breadth similar to that of the second end 122, however has a length greater than that of the second end 122. Thus, the second end 132 has a greater surface area than the second end 122 and therefore, completely overlaps the second end 122.
The second end 132 has the outer surface 33 and the primary arm 12 has a roller retaining surface 34 disposed adjacent to the top edge 123. When the spring 15 is in neutral position, the second end 132 has a top portion 135 which extends beyond the top edge 123. The spring 15 is compressible to relatively slide the second ends 122 and 132 such that the top edges 123 and 133 coincide with each other and the top portion 135 is no more visible in the compressed position of the spring 15.
Referring to Fig. 5, in the untripped position of the trigger 1, the spring 15 is in neutral position and the roller 32 is disposed in a latching contact with the outer surface 33. The outer surface 33 provides an increased contact surface area to the

roller 32 as compared to corresponding surface of the second end 122 and therefore, prevents sliding of the roller 32 from the outer surface 33 to the surface 34.
Referring to Fig. 6, an outer surface 136 of the first end 131 may be pushed by the trip coil 2 for displacing the trigger 1 from the untripped position to the tripped position. When the outer surface 136 is pushed by the trip coil 2, the trigger 1 rotates in clockwise direction, and in an intermediate position, the spring 15 compresses and the top portion 135 moves downwards, facilitating the coinciding of the top edges 123 and 133 and the roller 32 to slide towards the roller retaining surface 34.
Referring to Fig.7, in the tripped position of the trigger 1, the roller 32 rests on the roller retaining surface 34 and is releasably held therein. The spring 15 regains its neutral position and the top portion 135 regains its original position. The time in which the spring regains its position is sufficient to enable sliding of the roller 32 from the outer surface 33 to the outer surface 34 or vice versa.
In various embodiments of the present invention, the primary arm 12 may be an existing trip trigger and the auxiliary arm 13 may be a thin sheet of metal mounted on the primary arm 12. The auxiliary arm 13 is light weight, inexpensive, easy to manufacture and is an addon feature without much of design change. The auxiliary arm 13 provides a larger contact area 33 to the latch roller 32 in the untripped position. Due to larger contact area 33 in the untripped position, there is a decrease in the probability of slipping of the roller 32 from the outer surface 33 towards the surface 34. The auxiliary arm 13 provides benefit of non-slippage of the roller 32 in the untripped position without requiring additional energy during actuation of the trigger 1.

Although the invention has been described with reference to a specific embodiment, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiment, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can be made without departing from the scope of the invention as defined in the appended claims.

We claim:
1. A trip trigger for a circuit breaker, the trip trigger being displaceable between a tripped and an un-tripped position to effect opening and closing of contacts of the circuit breaker and being releasably latchable in the tripped and untripped positions by a trip holding latch which comprises a latch lever and a roller fixedly disposed at an end of the latch lever, the latch lever being pivotally movable therewith between positions corresponding to the tripped and un-tripped positions and the roller disposed in a latching contact with the trip trigger in said positions, the trip trigger comprising:
a primary arm and an auxiliary arm pivotally connected together in a scissor like arrangement, each of the primary and auxiliary arms having a first end and a second end disposed at opposite sides of a pivot point, the first ends of said arms being connected to each other by a spring and the second ends disposed in parallel and slidable over each other along an axis substantially parallel to axis of the spring, the second end of the auxiliary arm overlapping the second end of the primary arm and having a top portion which extends beyond a top edge of the second end of the primary arm when the spring is in neutral position, the spring being compressible for relatively sliding the second ends for coinciding top edges of both the second ends, the second end of the auxiliary arm having an outer surface for retaining the roller in a latching contact in the untripped position and the primary arm having a roller retaining surface disposed adjacent to respective top edge for releasably holding the roller in the tripped position.

2. The trip trigger as claimed in claim 1, wherein the first end of the auxiliary arm is triggerable by an actuating mechanism for displacing the trip trigger from the tripped to the untripped position.
3. The trip trigger as claimed in claim 1, wherein the coinciding of the top edges of the second ends facilitates the roller to move from the outer surface to the roller retaining surface and vice versa.

4. The trip trigger as claimed in claim 1, wherein the auxiliary arm is made up of a thin sheet of metal.
5. The trip trigger as claimed in claim 1, wherein the second end of the auxiliary arm has a surface area greater than that of the second end of the primary arm.