FORM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention.- IMPROVED SHAFT COUPLING ARRANGEMENT FOR A MOULDED CASE CIRCUIT BREAKER
2. Applicant(s)
(a) NAME : LARSEN & TOUBRO LIMITED
(b) NATIONALITY: An Indian Company.
(c) ADDRESS: L & T House, Ballard Estate, Mumbai 400 001,
State of Maharashtra, India
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed:

TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to circuit breakers and more particularly to an improved shaft coupling arrangement for a moulded case circuit breaker.
BACKGROUND AND THE PRIOR ART
In circuit breakers with cassette construction (meaning each pole of breaker consists of a separate cassette), the mechanism drives the central pole. The motion is transmitted to adjacent poles through coupling arrangement of shaft.
Fig 1 to 4 shows different philosophies of shaft coupling presently in use. In Fig 1 and Fig 2, a separate coupler is used between the two shafts to couple them together. For efficient transfer of torque from centre pole to side poles, it is better to have minimum number of joints. In the philosophy using separate coupler, there are two joints between each shaft coupling. Fig 2 and 3 uses a coupling philosophy where long pins are used for coupling between shafts. The pins pass through the shafts, thus holding it together and permits motion transfer.
The main disadvantages of using pins for motion transmission are
1. Pins have to be completely insulated inside the shaft, as they can cause short circuit between adjacent poles if not insulated properly.
2. Provision of insulated pins through the shaft reduces the space for contact movement inside the shaft.

Although generally used the conventional arrangement has lots of disadvantages due to use of pins as provided above. The present invention therefore provides an improved shaft coupling arrangement for a moulded case circuit breaker.
OBJECTS OF THE INVENTION
One object of the present invention is to overcome the disadvantages/drawbacks of the prior art.
Another object of the present invention is to provide an improved shaft coupling arrangement for use in moulded case circuit breakers.
These and other advantages of the present invention will become readily apparent from the following detailed description read in conjunction with the accompanying drawings.
SUMMARY OF THE INVENTION
There is provided an improved shaft coupling arrangement for use in a moulded case circuit breaker.
According to one embodiment of the present invention, there is provided arrangement comprising a protrusion provided on either side of a shaft facilitating coupling between poles.
Other embodiment of the present invention provides arrangement adapted to couple a male protrusion from one shaft to a female protrusion on other shaft.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig 1 to 4 shows different philosophies of shaft coupling presently in use.
Fig 5 shows the two sides of the proposed shaft coupling arrangement
Fig 6 shows the exploded view of the shafts in 3 pole arrangement.
Fig 7 shows the exploded view of 3 pole cassette construction
Fig 8 shows the 3 poles coupled together.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The following drawings are illustrative of particular examples for enabling methods of the present invention, are descriptive of some of the methods, and are not intended to limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description.
Reference is first invited to Fig I where the conventional arrangement of shaft coupling is shown. In Fig 1 and Fig 2, a separate coupler is used between the two shafts to couple them together. Fig 1 to 4 shows different philosophies of shaft coupling presently in use.
Fig.5 shows the sides of the shaft having coupling arrangement built on it.
Fig. 6 shows the different shafts separately.

Fig. 7 shows three pole cassette constructions in exploded form.
Fig. 8 shows the three poles coupled together in accordance with the present invention.
The invention therefore provides an improved shaft coupling arrangement for a moulded case circuit breaker.
DETAILED DESCRIPTION OF THE INVENTION
Accordingly in the present invention as shown in fig. 5, the sides of the shaft (503) itself have coupling arrangement built on it. The coupling arrangement comprises Y profile feature both male and female such a male protrusion (502) on one of one shaft component can be coupled into female Y profile feature. When two poles are coupled together, the male side from one shaft gets connected with the female side of the adjacent shaft. The clearances can be decided based on the tightness of the joint required. The Y profile feature comprises limbs having angle of about 120 degrees between each other.
Though one particular shape is shown in this case, the shape of the protrusions on male and female side can be chosen depending on the conditions present in the breaker. In fig.5, the hole for coupling mechanism with the shaft is shown. This calls for the type of profile to be provided on the shafts.
The main advantages of this philosophy are:
1. It avoids extra components in the form of connecting pins and extra coupler.
2. It reduces the number of joints from shaft to shaft from 2 to 1.

3. It reduces the risk of failure during short circuit which is possible in case of connecting pins.
4. It provides increased space for contacts inside the shaft as against the shaft with through pins.
Although the embodiments herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the embodiments herein with modifications. However, all such modifications are deemed to be within the scope of the claims.
It is also to be understood that the following claims are intended to cover all of the generic and specific features of the embodiments described herein and all the statements of the scope of the embodiments which as a matter of language might be said to fall there between.

WE CLAIM
1. An improved shaft coupling arrangement for a moulded case circuit breaker,
said arrangement comprising:
plural shaft components;
wherein each of the said shaft components comprising a substantially Y-profile feature provided on either side of said shaft (503) facilitating coupling between adjacent shafts and poles; and
wherein said Y-profile feature on one side of said shaft is a male protrusion (502) and on other side of said shaft is a female protrusion (501).
2. Arrangement as claimed in claim 1 wherein said arrangement is adapted to couple shafts of adjacent poles said male protrusion (502) from one shaft to said female protrusion (501) on other shaft.
3. Arrangement as claimed in claim 1 wherein said coupling arrangement of shaft adapted to provide transmission of motion to adjacent pole shafts.
4. Arrangement as claimed in claim 1 wherein said Y-profile feature comprising limbs having an angle of about 120 degree from each other.
5. A shaft coupling arrangement for a moulded case circuit breaker as herein described and illustrated with reference to the accompanying drawings.