FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION (See section 10 and rule 13)
1. TITLE OF THE INVENTION:
"Modified coupling arrangement of Drive Shaft Assembly For Circuit Breaker
For Contact Support"
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
Electrical & Automation North Wing, Gate 7, Level 0, Powai Campus. Saki Vihar Road, Mumbai 400 072, INDIA
3. PREAMBLE TO THE DESCRIPTION:

COMPLETE
The following specification particularly describes the invention and the manner in which it is to be
performed.

Modified coupling arrangement of Drive Shaft Assembly For Circuit Breaker
For Contact Support
Field of invention
The present invention relates to a circuit breaker, and more particularly, to a circuit breaker with multiple electric poles having integral mono-block drive shaft assembly.
Background of the invention
Generally, a circuit breaker typically serves two basic purposes, firstly as a switching device i.e. switching ON-OFF during normal operating conditions for the purpose of operation and maintenance. Secondly, as a protecting device i.e. tripping or isolating by breaking the contacts interrupting the fault current during abnormal conditions such as short-circuit, overload and under voltage.
Conventionally, the circuit breaker consists of one or more electric poles. The numbers of electric poles are determined by the application as a single pole circuit breaker, two pole circuit breaker, three pole circuit breaker, four pole circuit breaker, five pole circuit breaker and so on. Each pole is made up of a contact system and each contact system consists of a moving contact, a pair of fixed contacts, a pair of arc chutes assembly and insulated drive shaft to rotate the moving contact to make connection and disconnection of current during ON'-OFF operation. The insulated drive shaft along with the moving contacts is connected mechanically to the actuation mechanism of respective circuit breaker.
In circuit breakers containing two or more poles, the insulated drive shaft (hereinafter referred as "the IDS") of each pole combines to form an improved drive shaft arrangement. An improved drive shaft arrangement is responsible to engage and transmit the actuation command from mechanism or any other driving

member in any form engaged or connected and mechanically meshed by any means like gear or link or fasteners and likes to the moving contact of each and
every pole.
A US Patent No. 6960731 discloses a mechanism, wherein the drive shafts are assembled with an extra component known as coupler between the poles, which increases the number of components to achieve the required functions. In this solution, the number of components increases with the number of poles in the circuit breaker. With this, there is a rotational lag that is developed inherently due to the number of components in engagement. Moreover, this clearly has a negative impact on manufacturing and operating costs of the circuit breaker.
Another US Patent No. 5479143, discloses drive shafts assembled having motion transmitted by means of a metal coupler. Provision of the metal coupler causes potential danger of short-circuiting if not shielded or isolated properly during assembly.
Still another European Patent EP0555158 Bl and US Patent 6084489 discloses that IDS of one pole is coupled together with other pole IDS by means of additional interconnection components such as bars or pins throughout the entire length of the shaft, so as to allow to transmit motion among the various poles of the circuit breaker. A conducting bar or pin running throughout the entire length between various poles may cause short-circuiting which is very dangerous.
In the above mentioned prior art patents, the rotational lag occurs due to the cumulative tolerance that sums up between members of relatively moving components. The rotational lag causes the low contact pressure in the poles at the extreme ends, thereby affecting the performance of the breaker.
Accordingly, there exists a need to provide a integrated drive shaft assembly which overcomes drawbacks of the prior art.

Objects of the invention
An object of the present invention is to provide a drive shaft assembly with reduced rotational lag.
Another object of the present invention is to reduce potential danger of short-circuiting if the metal coupling of the prior art drive shafts are not shielded or isolated properly during assembly.
Summary of the invention
Accordingly, the present invention provides a drive shaft assembly for a circuit breaker having at least two electric poles. The drive shaft assembly includes a plurality of insulated drive shafts. Each insulated drive shaft of the plurality of insulated drive shafts is placed axially with respect to other insulated drive shafts of the plurality of insulated drive shafts. Further, an end cap is configured on each axial end of the insulated drive shaft of the plurality of insulated drive shafts. The end cap provided is with moving contact assembly therein. The end cap includes a male projection and female projection configured thereon. The male and female projections includes a first opening provided thereon. Further, a joining means provided on any one of the male and female projection for joining the plurality of insulated drive shafts. A covering member provided on the joining means to provide even surfaces and smooth resting of the insulated drive shafts on the electric poles, wherein the male projection of one insulated drive shaft of the plurality of drive shafts engages with the female projection of other insulated drive shaft thereby locking the plurality of insulated drive shafts to form the drive shaft assembly.
Brief description of the drawing

Figure 1 and 2 illustrates an exploded view of the drive shaft assembly of the circuit breaker, in accordance with present invention.
Figure 3, 4 and 5 illustrates an assembled view of the drive shaft assembly of figure 1 and 2.
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 embodiments.
Accordingly, the present invention provides a drive shaft assembly for circuit breaker for contact support with reduced rotational lag. The drive shaft assembly reduces potential danger of short-circuiting which occurs in case a metal coupling of the prior art drive shafts when not shielded or isolated properly during assembly.
Referring now to figure 1 to 5 , there is shown an a drive shaft assembly of a circuit breaker (100), in accordance with present invention. Specifically, figure 1 and 2 shows exploded view of the drive shaft assembly (100) and figure 3, 4 and 5 shows the assembled view of the drive shaft assembly (100) (hereinafter 'the assembly (100)').
The assembly (100) includes a plurality of insulated drive shafts (10). For the purpose of explanation, the assembly (100) is shown to include three insulated drive shafts (10a, 10b and 10c). Each insulated drive shaft (hereinafter the IDS) (10a, 10b and 10c) includes inner elements along with moving contact assembly. The IDS (10a, 10b and 10c) are placed axially with respect to each other.

Each IDS (10a. 10b and 10C ) includes an end cap (20) configured on each axial end thereof. The plurality of insulated drive shafts (10) are placed axially so that the end cap (20) of each IDS (10a, 10b and 10c) face each other. Specifically, the end cap (20) is provided with moving contact assembly therein.
The end cap (20) includes a male projection (30) and female projection (40) configured thereon. Specifically, the male projection (30) of one IDS, for example the IDS (10a) is capable of being engaged with the female projection (40) of the other IDS, for example the IDS (10b) and so on. The male projection (30) and female projections (40) includes mechanical actuation links capable of passing therethrough. Further, the male projection (30) and female projections (40) includes a opening (42) provided thereon. In an embodiment, the opening (42) is of any profile provided in an axis perpendicular to the IDS (10a, 10b and 10c) engagement direction. The opening (42) arrest all degrees of movement when the male projection (30) on one IDS. for example, the IDS (10a) and the female projection (40) for example, the IDS (10b) engages each other.
The male projection (30) and female projections (40) further includes a joining means (44) provided on any one of the male projection (30) and female projections (40) for joining the plurality of insulated drive shafts (10), as shown in figure 4. In an embodiment, the joining means (44) in an opening capable of accommodating mechanical or physical means therein for joining the plurality of insulated drive shafts (10). Specifically, the joining means (44) is provided in mutually perpendicular direction of the IDS (10a, 10b and 10c). In an embodiment, the opening (42) and the joining means (44) may be used alone or can be used in combination. The coupled plurality of insulated drive (10) shafts by means of the joining means (44) are provided with a cap (46) to avoid uneven surfaces and smooth resting on the contact system poles of the circuit breaker. This avoids friction during transmission of rotational movement.

Specifically, figure 2 shows IDS (10a, 10b and 10c) arrangement to form sub¬assembly (70), wherein the male projection (30) of one IDS (10a) engages with the female projection (40) of other IDS (10b). The male projections (30) and female projections (40) are locked in its position to arrest all degrees of movement through opening (42). Further figure 3, shows the drive shaft assernbiy (100) constructed depending on the number of poles required wherein one more IDS (10a, 10b and 10c) joins with the sub-assembly. Furthermore, figure 5 shows the multi-pole assembled IDS (10a, 10b and 10c), which acts as a mono-block type integral arrangement, wherein the individual pole drive combined acts as a single unit avoiding engagement errors and lag during transmission.
Advantages of the present invention
1. The assembly (100) provides a mono-block type integral construction of insulated drive shafts.
2. The assembly (100) reduces rotational lag by constraining the relative movement of the end caps.
3. The assembly (100) provides a uniform contact pressure.
4. The assembly (100) reduces the die complexity, reduce number of dies and standardization of components.
5. The assembly (100) provides an improved performance and tool life.
6. The assembly (100) leads in reduction in manufacturing and assembly time
and cost, wherein one component can be used to construct multi-pole drive shaft.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others skilled in the art to best utilize the present invention and various

embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the spirit or scope of the present invention.

We claim
1. A drive shaft assembly for a circuit breaker having at least two electric
poles, the drive shaft assembly comprising:
a plurality of insulated drive shafts, each insulated drive shaft of the plurality of insulated drive shafts placed axially with respect to other insulated drive shaft of the plurality of insulated drive shafts;
an end cap configured on each axial end of the insulated drive shaft of the plurality of insulated drive shafts, the end cap provided with moving contact assembly therein, the end cap having a male projection and female projection configured thereon;
an first opening provided on the male and female projections;
a joining means provided on any one of the male and female projection for joining the plurality of insulated drive shafts; and
a covering member provided on the joining means to provide even surfaces and smooth resting of the insulated drive shafts on the electric poles,
wherein the male projection of one insulated drive shaft of the plurality of drive shafts engages with the female projection of other insulated drive shaft thereby locking the plurality of insulated drive shafts to form the drive shaft assembly.
2. The drive shaft assembly as claimed in claim 1, wherein the male
projection and female projections includes mechanical actuation links capable of
passing therethrough.