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 Stroke adjustment mechanism for a circuit breaker APPLICANT
Crompton Greaves Limited, CG House. Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company INVENTOR
Ravindra Vanji Sonje, Vishal Vijay Bagade, Himanshu Chadrakant Joshi of Crompton Greaves Ltd, S3-Technology Department, Switchgear Complex, Ambad, Nasik-422010, Maharashtra, India,all Indian Nationals
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 stroke adjustment mechanism for a circuit breaker. more particularly to adjusting distance between movable and fixed contacts of the circuit breaker in an open position.
BACKGROUND OF THE INVENTION
In circuit breaker operation, stroke is the distance moved by a movable contact towards a fixed contact from an open position to a closed position and wipe is the distance moved by the movable contact towards the fixed contact from a contact touch position to the closed position. If the distance setting between the two contacts in an open position is above desired stroke, the mechanical parts of pole unit assembly may break during a switching operation, Whereas, if the distance setting is below the desired stroke, there may be overheating of contacts when a current is passed through the circuit breaker.
Therefore, the distance between the movable and fixed contacts in the open position is required to be set according to the desired stroke/wipe. Conventionally, there exists a jack arrangement which manually adjusts the distance between the circuit breaker contacts in an open position. The existing jack arrangement is disposed in a circuit breaker housing and comprises a jack, one end of which is operably attached to a mechanical linkage of the movable contact and other end rests on a crossbar of the housing. A force is applied to the jack through a handle for moving the movable contact relative to the fixed contact.

However, there are many disadvantages associated with the existing jack arrangement. The crossbar of the existing jack arrangement is bulky and lot of effort is required to fix it at the required position in the housing. Further, there is high possibility of slippage of jack from crossbar. Further, a high manual force for rotating the handle is applied from a height of 2 meter from the ground, which is difficult and cumbersome.
OBJECTS OF THE INVENTION
An object of the invention is to provide a mechanism for adjusting stroke of a circuit breaker
Another object of the invention is to provide a stroke adjustment mechanism which is simple in construction, reliable and has less components
Yet another object of the invention is to provide a stroke adjustment mechanism which requires less manual efforts
DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION
According to the invention, there is provided a stroke adjustment mechanism disposed within a housing of a circuit breaker. The stroke adjustment mechanism comprises a lead screw, an outer end of the lead screw being threadly engaged to a nut disposed outside the housing, the nut being rotatable by a handle to cause horizontal slidable movement of the lead screw in the housing; and an auxiliary lever pivotally connected to an inner end of the lead screw and rigidly connected to an operating lever of the circuit breaker, the auxiliary lever and the operating lever being adapted

to rotate in same direction about a common axis of rotation, the rotation of the operating lever actuating movement of the movable contact relative to a fixed contact.
Preferably, the inner end of the lead screw comprises a hole for engaging with a hole of the auxiliary lever through a pin.
Preferably, the nut has hexagonal cross section and internal square threads matching with external square threads of the lead screw.
Preferably, the auxiliary lever is rigidly connected to a center of the operating
lever.
Preferably, the rotation of the nut causes the lead screw to slide, thereby actuating the rotation of the auxiliary lever and subsequently of the operating lever. causing the movable contact to move relative to the fixed contact.
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 1 is a schematic view of a stroke adjustment mechanism disposed within a housing of a circuit breaker in accordance with an embodiment of the present invention.

Referring to Fig.l, the housing 1 comprises an existing operating mechanism of the circuit breaker and a stroke adjustment mechanism connected to the operating mechanism.
The operating mechanism of the circuit breaker comprises an operating lever 2. an adjuster rod 3, a pulley 4, and a link member 5. The operating lever 2 is pivotally connected to the adjuster rod 3 which is pivotally connected to the pulley 4. The pulley 4 is pivotally connected to the link member 5 which is connected to a movable contact.
The operating lever 2 is essentially a two arm lever, one arm of which is pivotally attached to the adjuster rod 3 and the other arm is operably connected to a spring load. Under normal circuit breaker operation, the operating lever 2 rotates due to changes in spring load. The rotation of the operating lever 2 actuates movement of the adjuster rod 3, which is transferred to the link member 5 via the pulley 4. The movement of the link member 5 actuates movement of the movable contact relative to a fixed contact.
The stroke adjustment mechanism comprises a lead screw 6. an auxiliary lever 7, a nut 8. a bearing 9, a housing support angle 10 and a rotatable handle 11.
The lead screw 6 consists of external threads at an outer end 12 and a flat portion with a hole 13 at an inner end 14. The outer end 12 of the lead screw 6 is threadly engaged to the nut 8 disposed outside the housing 1. The nut 8 is rotatable by the handle 11 such as a spanner to cause horizontal slidable movement of the lead

screw 6 in the housing 1. The bearing 9 is disposed between the lead screw 6 and the nut 8 for minimizing the friction between (he nut 8 and the housing 1. It may be noted that the nut 8 and bearing 9 are screwed on the housing support angle 10 of the housing 1. In an exemplary embodiment of the present invention, the nut 8 has cylindrical shape, hexagonal cross section and internal square threads matching with external square threads of the lead screw 6.
The inner end 14 of the lead screw 6 is pivotally connected to the auxiliary lever 7. In an exemplary embodiment of the present invention, the hole 13 of the lead screw 6 engages with a hole at an end of the auxiliary lever 7 through a pin. which may be of cylindrical in shape and has circular cross section.
The auxiliary lever 7 is rigidly connected to the operating lever 2 such that the auxiliary lever 7 and the operating lever 2 rotate in same direction about a common axis of rotation. In an exemplary embodiment, the auxiliary lever 7 is rigidly connected to the center 15 of the operating lever 2.
Operationally, a rotational force may be exerted on the nut 8 by the handle 11 for rotating it thereof. The rotation of the nut 8 causes the lead screw 6 to horizontally slide either towards or away from the housing support angle 10. The horizontal sliding movement of the lead screw 6 causes the auxiliary lever 7 to rotate, which in turn causes the operating lever 2 to rotate, thereby actuating the movement of the movable contact relative to the fixed contact. Thus, rotation of the nut 8 by the handle 11 directly controls the closing and opening of the movable and fixed contacts and adjusts stroke thereof.

In an exemplary embodiment of the present invention, a rotational force for rotating the handle 11 may be applied at a height of 0.5m from ground when the circuit contacts are opened. The rotation of nut 8 in clockwise direction causes the lead screw 6 to slide towards the housing support angle 10, which in turn rotates the auxiliary lever 7 in clockwise direction. The rotation of the auxiliary lever 7 in clockwise direction rotates the operating lever 2 in clockwise direction, which in turn causes the adjuster rod 3 to move upward and the pulley 4 to rotate anticlockwise, thereby causing the link member 5 to move upwards and move the movable contact towards the fixed contact. Thus, in the open position, the desired distance befween the movable contact and the fixed contact is set using the stroke adjustment mechanism.
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 stroke adjustment mechanism disposed within a housing of a circuit breaker
comprising:
a lead screw, an outer end of the lead screw being threadly engaged to a nut disposed outside the housing, the nut being rotatable by a handle to cause horizontal slidable movement of the lead screw in the housing: and
an auxiliary lever pivotally connected to an inner end of the lead screw and rigidly connected to an operating lever of the circuit breaker, the auxiliary lever and the operating lever being adapted to rotate in same direction about a common axis of rotation, the rotation of the operating lever actuating movement of a movable contact relative to a fixed contact.
2. The stroke adjustment mechanism as claimed in claim 1, wherein the inner end of the lead screw comprises a hole for engaging with a hole of the auxiliary lever through a pin.
3. The stroke adjustment mechanism as claimed in claim 1, wherein the nut has hexagonal cross section and internal square threads matching with external square threads of the lead screw.
4. The stroke adjustment mechanism as claimed in claim 1, wherein the auxiliary lever is rigidly connected to a center of the operating lever.
5. The stroke adjustment mechanism as claimed in claim 1, wherein the rotation
of the nut causes the lead screw to slide, thereby actuating the rotation of the

auxiliary lever and subsequently of the operating lever, causing the movable contact to move relative to the fixed contact.