FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION [See section 10 and rule 13)
1. TITLE OF THE INVENTION:
Rotor Shaft Assembly for Circuit Breaker
2. APPLICANT:
(a) NAME: Larsen &Toubro Limited
(b) NATIONALITY: Indian Company registered under the
provisions of the Companies Act-1956.
(c) ADDRESS: LARSEN & TOUBRO LIMITED,
L&T House, Ballard Estate, P. 0. Box: 278, Mumbai 400 001, India
3. PREAMBLE TO THE DESCRIPTION:
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.

Rotor Shaft Assembly for Circuit Breaker
Field of the invention
The present invention relates to circuit breakers, and more particularly to a moving contact of the circuit breaker.
Background of the invention
Currently, all molded case circuit breaker have a rotor/drive shaft which rotates and switches the electrical circuit. The shaft construction of the presently available circuit breaker uses an open shaft construction or partially closed shaft construction.
For example, US Patent No. 5310971 as shown in figure la , US Patent No. 6870112 as shown in figure lb, US Patent No. 6262642 as shown in figure lc, and US Patent No. 6965292 as shown in 1d shows open shaft construction and partially open shaft construction.
During short circuit, a moving contact in the shaft starts rotating due to repulsion forces produced by electromagnetic interaction during the short circuit. Simultaneously, an arc is produced between a fixed contact and a moving contact.
For rotation of the moving contact with respect to the shaft, there has to be an opening in the shaft with slot length depending on degree of rotation of the moving contact. However, during arcing, hot gases and the arc products are produced which may enter inside the shaft thereby damaging components like

springs and pins inside the shaft. An open shaft construction of the prior art increases the chance of standing arc because of lesser insulation between the fixed contact and the moving contact.
Accordingly, there exists a need to provide a shaft assembly for a circuit breaker which overcomes the abovementioned drawbacks.
Object of the invention
An object of the present invention is to protect components inside of a shaft of a circuit breaker from getting damaged due to arcing of contacts.
Another object of the present invention is to reduce erosion of the moving contact.
Yet another object of the present invention is to reduce the let through energy by insulating arc from bare moving contact, so the quicker quenching of arc.
Still another object of the present invention is to prevent the pop out of end caps of the shaft/rotor.
Summary of the invention
Accordingly, the present invention provides a rotor shaft assembly for a circuit breaker. The rotor shaft assembly comprises a moving contact capable of removabely connecting to a fixed contact thereby forming any one of closed and open condition therebetween. The rotor shaft assembly further includes a spring arranged between spring holders. The spring is capable of providing

pressure for maintaining the connection between the moving contact and the fixed contact. Furthermore, the rotor shaft assembly includes one or more pin members for aligning the moving contact and the spring. Characterized in that, the moving contact is enclosed within a sleeve which insulates the moving contact and provides a barrier between the moving contact and other components of the rotor shaft assembly.
Brief description of the drawings
Figures la, lb, lc and 1d shows a shaft construction of the prior art;
Figure 2 shows a circuit breaker assembly with fixed contacts and moving contact in closed condition;
Figure 3 shows a circuit breaker assembly with the fixed contacts and moving
contact in open condition;
Figure 4 shows a rotor assembly/drive shaft of the circuit breaker;
Figure 5 shows the rotor assembly/drive shaft of the circuit breaker with a sleeved moving contact housed therein.
Figure 6 shows a bare moving contact of the circuit breaker;
Figure 7 shows a sleeved moving contact of the circuit breaker, in accordance with the present invention; and
Detailed description of the invention

The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiment.
Referring to figure 2 to 1, there is shown a rotor shaft assembly (100) of a circuit breaker and various components thereof. Specifically, figure 4 and 5 shows the rotor shaft assembly (100] (hereinafter 'the assembly (100)'). The assembly (100) includes a moving contact (10), a spring (not shown) arranged within spring holders, and pin members for aligning the moving contact (10) and the spring within housing of the assembly (100).
The moving contact (10) is capable of removabely connecting to fixed contacts (20). The fixed contacts (20) are housed within the circuit breaker housing. The moving contact (10) forms any one of closed and open condition therebetween.
Specifically, figure 2 shows a circuit breaker assembly with the fixed contacts (20) and the moving contacts (10) in closed condition. The fixed contacts (20) and the moving contact (10) are designed in such a way that during short circuit conditions, an electromagnetic force acts between the moving contact (10) and the fixed contacts (20). The electromagnetic force rotates the-moving contact (10) and brings the moving contact (10) to repelled position as shown in figure 3. Specifically, figure 3 shows a circuit breaker assembly with the fixed contacts (20) and the moving contacts (10) in open condition. The moving contact (10) is supported by the spring.

Specifically, the spring is arranged between spring holders for providing pressure for maintaining the connection between the moving contact (10) and the fixed contacts (20).
Characterized in that, the moving contact (10) is enclosed within a sleeve (12). The sleeve (12) insulates the moving contact (10) and provides a barrier between the moving contact (10) and other components of the assembly (100). Specifically, figure 6 shows the moving contact (10) without a sleeve, and figure 7 shows the moving contact (10) with a sleeve (12).
In an embodiment, the sleeve (12) is made of an insulating material with fire retardant properties. The insulating materials are well known in the art and same are being used here. In another embodiment, the sleeve (12) is formed on the moving contact (10) by any one of fluidized base coating, powder coating, and heat shrinking process. The sleeve (12) thickness may be varied upon the design requirement.
As shown in figure 3, when the moving contact (10) moves to the repelled position, arcing happens and as a result of which arc products and hot gases are produced. The sleeve (12) of the moving contact (10) provides insulation for the moving contact (10) from the arcing products and hot gases.
The sleeve (12) of the moving contact (10) protects other internal components housed in the assembly (100) which come in direct contact with the current carrying component i.e. the moving contact (10). Also, during normal operating condition when heat is being produced by current carrying conductor i.e. the moving contact (10), the sleeve (12) protects the surrounded plastic parts.

Further, during short circuit condition, the sleeve (12] of the moving contact (10) prevents erosion of the moving contact (10) end caps which results in end cap popping out and at the end malfunctioning of the circuit breaker.
Also during the short circuit condition, if the moving contact (10) is not sleeved/covered, then chances of arc jumping on the moving contact (10) is high and it delays the arc quenching and calls off high IΛ2t value. The sleeved moving contact (10) prevents delaying of the arc quenching and helps in preventing recovery voltage build up, in results faster quenching of the arc and lesser IΛ2tvalues,
Further, the sleeve (12) on the moving contact (10) increases life of the circuit breaker and performance of the circuit breaker becomes more reliable in abnormal conditions.
Advantages of the invention
1. The assembly (100) ensures the reliability of the circuit breaker performance in abnormal/faulty conditions by preventing moving contact erosion during high current arc.
2. The assembly (100) insulates other internal components of the rotors from current carrying conductor in normal and abnormal operating conditions, so prevents damage of internal components form arc and excess heat.
The foregoing object the invention is accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiment.

Detailed descriptions of the preferred embodiment are provided herein; however, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure, or matter. The embodiments of the invention as described above and the methods disclosed herein will suggest further modification and alterations to those skilled in the art. Such further modifications and alterations may be made without departing from the spirit and scope of the invention.

We Claim:
1. A rotor shaft assembly for a circuit breaker, the rotor shaft
assembly comprising;
a moving contact capable of removabely connecting to a fixed contact thereby forming any one of closed and open condition therebetween;
a spring arranged between spring holders, the spring capable of being providing pressure for maintaining the connection between the moving contact and the fixed contact; and
one or more pin members for aligning the moving contact and the spring, characterized in that,
the moving contact is enclosed within a sleeve which insulates the moving contact and provides a barrier between the moving contact and other components of the rotor shaft assembly.
2. The rotor shaft assembly as claimed in claim 1, wherein the sleeve is made of an insulating material with fire retardant properties
3. The rotor shaft assembly as claimed in claim 1, wherein the sleeve is formed on the moving contact by any one of fluidized base coating, powder coating, heat shrinking process, and moulded component.