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
A locking mechanism for moveable contact assembly of a manually operated circuit breaker.
APPLICANT
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR
Joshi Pradeep & Chitnis Prashant of S2 Division, Switchgear Complex, Crompton Greaves Limited, A3, Ambad, Nashik, Maharashtra, India, 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 a locking mechanism for a moveable contact assembly of a manually operated circuit breaker.
BACKGROUND OF THE INVENTION
Manually operated circuit breakers are generally provided with a handle protruding outside of the circuit breaker framework, the handle being actuated by an operator for rotation from an 'isolated' position to a 'contact' position. Rotation of the handle, in turn provides a rack-in or rack-out motion to a rotatable shaft that provides a to-fro motion to the moveable contacts of a circuit breaker to provide an 'isolation' or a 'contact position with the stationary contact of the circuit breaker. The circuit breakers are usually placed side by side within a cabinet having a panel, the handles being well exposed on the face of the panel and made accessible for control wherever needed so that the status of any individual circuit breakers be at all time visible, before or after being set in 'isolation', or 'contact' positions.
It is desired that the moveable contact remain in 'isolation' position and be prevented from the stationary contact due to any accidental movement of the handle and the rotatable shaft. One

skilled in the relevant arts can readily appreciate such a requirement, especially during maintenance operation of circuit breakers. Accidental contact between the stationary and movable contacts may result in high current flow through the circuit breaker causing hazardous threat to human life. To overcome this and several other disadvantages the proposed invention is disclosed herewith.
OBJECTS OF THE INVENTION
An object of the invention is to provide a locking mechanism to firmly restrict a moveable contact assembly of a manually operated circuit breaker in an isolation position.
DETAILED DESCRIPTION OF THE INVENTION
In accordance with the invention, a locking mechanism to firmly restrict a moveable contact assembly of a manually operated circuit breaker in an isolation position. The mechanism comprising of a castell lock-key fixed to a framework supporting the moveable contact assembly and a rectangular plate and an arc plate secured fixedly on a rotatable shaft to define an enclosure, wherein the rotatable shaft when rotated extends a traversable motion to the moveable contact assembly and a circular motion to the rectangular plate and the arc plate. The castell lock-key when actuated in the 'isolation' position releases a protruding member which engages in the enclosure, thereby firmly restricting the traversable motion of the moveable contact assembly.

Several aspects of the invention are described below with reference to examples for illustration. It should be understood that numerous specific details, relationships, and methods are set forth to provide a full understanding of the invention. One skilled in the relevant art, however, will readily recognize that the invention can be practiced without one or more of the specific details, or with other methods, etc. In other instances, well known structures or operations are not shown in detail to avoid obscuring the features of the invention.
The following is a detailed description of the invention with reference to the accompanying drawings, in which;
Figure 1 is an isometric view illustrating the locking mechanism according to a preferred embodiment of the present invention in which the key is in actuated position,
Figure 2 is an isometric view illustrating the locking mechanism according to a preferred embodiment of the present invention in which the key is not actuated.
Figure 1 shows an isometric view of the locking mechanism with the key in an actuated position. The locking mechanism is shown containing a castell lock-key I, shaft 2, rectangular plate 3, arc plate 4. Handle 5 can rotate a rotatable shaft 6 to keep the moveable contacts in a 'contact' or an 'isolated3 position. A rack-in movement of the rotatable shaft 6 leads to a 'contact' between the moveable and the stationary contacts (not shown) of a circuit breaker,

while a rack-out movement leads to an 'isolation' of the moveable contacts assembly (not shown). A castell lock-key 1 is shown fixed to the framework of the circuit .breaker. A manual operation of the handle can extend a traversable motion (rack-in or rack-out) to the rotatable shaft 6 through a gear arrangement 7 and place the moveable contacts in 'contact' or 'isolated' positions respectively. Rectangular plate 3 and arc plate 4 are extended proportional circular motion in clockwise or anti-clockwise direction for a corresponding rotating motion extended on the rotatable shaft. The rectangular plate 3 and arc plate 4 are securely arranged with each other by screws such that they provide for an enclosing space. The castell lock-key 1 when actuated releases a protruding shaft 2 in to this enclosing space thereby preventing any further movement of the rotatable shaft and thus limiting the to-fro motion of the moveable shaft. A manual operator can release the shaft by actuating the castell lock-key 1 (turning the key) in an 'isolated' position to prevent any further movement of the moveable contact assembly by accidental movement of the handle 5.
Figure 2 is an isometric view illustrating the locking mechanism according to a preferred embodiment of the present invention in which the castell lock-key 1 is not in an actuated position. The rotatable shaft 6 and related gear arrangement 7 is shown covered by a protecting cover 8. The castell lock-key 1 when not actuated causes the protruding shaft 2 to be held inside the framework of the circuit breaker .The rectangular plate 3 and arc plate 4 can freely rotate about their central axis without being obstructed by the protruding shaft 2.

We Claim,
1. A locking mechanism to firmly restrict a moveable contact assembly of a circuit breaker in an isolation position, the mechanism comprising of:
a casteil lock-key fixed to a framework supporting the moveable contact assembly; and
a rectangular plate and an arc plate secured fixedly on a rotatable shaft to define an enclosure, wherein the rotatable shaft when rotated extends a traversable motion to the moveable contact assembly and a circular motion to the rectangular plate and the arc plate;
wherein the castle lock-key when actuated in the isolation position releases a protruding member which engages in the enclosure, thereby firmly restricting the traversable motion of the moveable contact assembly.
2. The locking mechanism of claim 1, wherein the protruding member is a shaft.