Form - 2
THE PATENTS ACT, 1970
COMPLETE SPECIFICATION (SECTION 10)
COMBINATION-HOUSING FOR CIRCUIT BREAKERS
LARSEN & TOUBRO LIMITED
L&T House, Ballard Estate,
Mumbai -400 001,Mharashtra State, India
An Indian company duly registered and incorporated under
Company's Act, 1956.
22 NOV 2004
The following specification particularly describes and ascertains the nature of the invention and the manner in which it is to be performed:-

GRANTED
ORIGINAL
668/MUM/2001
13 Jul 2001

Technical field
This invention relates to a housing combination for circuit breakers which can be co-ordinated between various housing for lower & higher ratings by simple replacing side inserts of the mould.
Background art
Circuit Breakers for low voltage application, with air as an inten-upting medium, find application in the current range of below and upto 6300A.
Due to rising demands for higher & higher breaking capacities, poles of all modem circuit breakers are generally enclosed in an insulated housings.
These insulated housing have to be mechanically very strong to be able to withstand electrodynamic forces generated when short circuit of the order of 100, 000 Amp or higher takes place. Also, these housings have to withstand temperature generated due to heat in normal running. In addition, arcing faults are also required to be withstood by them.
Unsaturated polyesters, which are the thermosetting materials with requisite glass contents, are the only stable materials available for such applications. Compressions moulding technology is almost invariable made use of for manufacturing such housings.
The tool size of housings required for ratings 4000A & beyond is a challenge to manufacturing and hence is not commonly a one-piece component.
A large number of manufactures either conclude their product range below 4000A or else resort to open construction. Also exist some designs where two smaller housings are joined in manners which result in non-uniform terminal distributions. Also there are designs on unipolar construction, but product maintenance & life enhancements are compromised.
Our invention effectively & economically overcomes these shortcomings:
Disclosure of the invention
In our invention, the co-ordination is done between various housing for lower & higher ratings.
The lower rating (indicated as M) comprises of a front housing & a rear housing. The higher rating (indicated as N) is conceived in two halves, henceforth called left half & right half. Since the housing arrangements fundamentally are made up

of front housing & rear housing, hence it now results into Left Front Half, Right Front Half, left Rear Half & Right Rear Half.
The two halves of front housings are such that when left & right halves are placed together & bolted, the combination is just like a single piece.
The design of rear housings is however made in a different manner. Since a joined set of rear housing complete with current carrying parts called pole assembly would be too heavy to assemble in shop & also when replacing pole assemblies, our design is such that they can be individually assembled, still resulting in an arrangement same as if made integrally.
Since the two halves differ only at the end wall, it becomes possible as well as economical to make two halves as also the parts of frame for rating M from the same mould by merely replacing inserts.
Brief descriDtion of the drawings
Figure 1-(i) shows front view of Front Housing of frame for rating A. Figure 1-(ii) shows front view of Left Front Housing of frame for rating B. Figure 1-(iii) shows front view of Right Front Housing of frame for rating C.
Figure 2 shows front view of all the above overlapped.
Figure 3 shows the dovetail construction built in corresponding left & right housings.
Figure 4 shows isometric view of Left Front Housing & Right joined together.
Figure 5 shows isometric view of front housing joined, rear left housing joined but rear right housing still open.
Description of the preferred embodiment
The invention will now be described with the help of above referred drawings, which are non-restrictive examples. They are duly marked with appropriate numerals for convenient reference.
As can be seen from figure 1 & 2 the housing design is such that other than the end walls (10), (11) and (12), all other features are identical. Most significantly, the overall width (B) of right side end wall of Left Housing (6LF) & overall width (C) of Left side end wall of Right Housing (7RF) is less than overall width (A) of either end wall of Housing (5F) of frame for rating M. Further, the dovetail construction (1) (2) & (3) of Left Housing (6LF) & con-espondingly (4) (5) & (6) of Right Housing (7RF) as shown in Figure 3 are such designed that when joined.

the total outward construction & dimension is same as in other in-between inter-pole walls.
The dovetail construction (1) (2) & (3) and correspondingly (4) (5) & (6) in the Left (6LF & 6LR) corresponding Right components (7RF & 7RR) ensures that once placed correctly, the components become inseparable side-wise even without screws.
The total wall thickness (T) between two poles is quite limited; of the order of 20mm or so & carving dovetails (1, 2, 3, 4, 5 & 6) as well as screw (8) fixing arrangement in this room is a matter of skill and engineering. The assembly has to be rigid & strong so as to withstand the forces generated during short circuits.
As shown in Figure 4, the Left housing (6LF) and Right housing (7RF) are joinable by a set of screws (8) and hence it is a simple assembly.
The design of rear combination housing (6LR & 7RF), though principally the same, is made such that they are fastenable onto the front housing assembly (6LF +7RF) one after the other. This is exhibited in Figure 5. Hence, in assembled situation, the construction & hence terminal pitch dimension (D), wiring lengths, etc. are uniform throughout. At the same time, for assembly in factory as well as maintenance/replacement by user, modularity is exploitable to a greater extent in case of Rear combination-Housing {6LR+7RR).

CLAIM:
Combination-housings for circuit breakers wherein the front housing comprises of left front half & right front half { 6LF & 7RF ref in fig (5)} are joinable by simple fasteners, resulting in an integral front housing, likewise the rear housing comprises of left rear half & right rear half {6LR & 7RR ref in fig (5)} the said rear housing which cany the pole assemblies, joinable in series, resulting in an integral & uniformly pole pitched rear housing assembly {as ref in fig (5)}, the said rear housing facilitates modularity for assembly / disassembly/ easy replacement of the pole assemblies, the said housing i.e. front housing for lower rating, left front & right front housing for higher rating can be derived from same mould as for lower rating likewise for rear housing by simple replacing side inserts of the mould.
Dated this 13th of July 2001.
Deepak Mehra (Agent for Applicant)