Form - 2
THE PATENTS ACT, 1970
COMPLETE SPECIFICATION (SECTION 10)
"AN IMPROVED FRONT COVER 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.
The following specification particularly describes and ascertains the nature of the invention and the manner in which it is to be performed: -
GRANTED
2-11-2004

Technical Field
This invention relates to an improved front coyer for an circuit breaker adapted for effective installation of front features/main operating mechanism. More particularly, the improved cover is aimed at improving the space utilization and optimize control wiring in the panel when Circuit breakers of different Frame sizes are mounted in a panel.
Background art
Circuit Breakers for low voltage application are generally available for current range from 630 Amp or lower to 6300Amp; with intermediate common ratings of 800Amp, lOOOAmp, 1250Amp, 1600Amp, 2000Amp, 2500Amp, 3200Amp, 4000Amp and 5000Amp. Almost all designs available are such that these intermediate ratings are covered in three or four basic sizes, commonly referred to as frame sizes. While different currents result in different volumes of conducting path, all other user interactive features (henceforth called Front features) of circuit breakers viz. Main operating mechanism, Charging handle, push buttons, indications & protection settings are normally manageable in same volume. These are generally arranged on the front of the circuit breaker so that they are available projecting out of the panel door in which the circuit breakers are housed.
Also, most modern circuit breaker designs are such that within these three or four frame sizes, only width changes while height & depth remains more or less the same. Also, popular panels widths are such that it can normally accommodate circuit breakers of upto 4000 Amp ratings. However, most common ratings are in the lower ratings. Hence, panels of higher widths are only generally used even for smaller width circuit breakers.
The unutilized width can be used very effectively if the smaller circuit breakers are placed intelligently on one side. At the same time, in a panel where circuit breakers of different ratings are mounted one below the other, it is desired that Front features appear perfectly one below the other, i.e. symmetrically aligned.

Most modern circuit breakers with box construction do not mount Front Features at any fixed distance from any end may be because of various technological difficulties in mounting the main operating mechanism, resulting into loss of effective panel space by way of its segregation in two parts.
In all designs where box construction is used & which is the latest practice currently, the main operating mechanism (which actually decides the placement of all front features) mounting is required to be extremely rigid on Front Cover for successful design. Most designs depend on one or more of the inside walls for directly fixing the Main mechanism. Since wall location generally varies in different frame sizes, so does the main mechanism & therefore the Front features.
In some designs, the wall location is made constant by creating more & non-equal number of pockets for poles of different poles. Therein, while constant distance is achieved for Front Features, irregular terminal pitch & other customer inconveniences are noticeable.
Statement of Invention
According to the present invention there is provided an improved front cover for an circuit breaker adapted for effective installation of front features/main operating mechanism comprising:
- plurality of tunnels formed in the front cover by carving out the said tunnels across the width of the front cover;
- a plurality of rigid strips provided in each of the tunnels adapted for mounting of the said front features/main operating mechanism, at a constant distance from one end of the cover,

the rigid strips being additionally adapted for mounting other front features on their extending lengths till the end of the widths of front cover such that the front ' cover is insert free.
Disclosure of the invention
In our design, the main current carrying parts popularly called poles are contained in a big insulating box made up of thermosetting compound. The front covers of the insulating box of all frame sizes are newly designed such that two or more strong steel strips are rigidly mountable on the front cover at suitable identical locations. These strips vary in length and their own mounting locations from frame to frame. Main operating mechanism & other front features, on the other hand are mounted on these strips at a constant distance from one end.
These steel strips are additionally used for mounting most front features; this thus helps to make the front cover free of inserts. This makes the front cover molding simpler & the front cover is more environment friendly for disposal at the end of the product life.
Brief description of the drawing
Figure 1 shows three frames of circuit breakers of a typical family which differ in width due to different rating & front features are at random location from either end.
Figure 2 shows how they are normally mounted in a common panel.
Figure 3 shows three frames of circuit breaker of our newly designed family.
Figure 4 shows how they are mounted in a common panel
Figure 5a shows the front cover & figure 5b shows the metallic mounting strip
Figure 6 shows the front cover on which three (here) metallic strips are mounted.

Figure 7 shows isometric view of a typical frame of circuit breaker with overall shroud removed. Hence main mechanism, which needs to be rigidly fixed, can be seen, besides other front features.
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 is evident from Figure 1 and Figure 2, to be able to align the front features viz. Charging Handle (1) etc. on door, the smaller frame is mounted such that the unutilized space (2) in panel (3) gets randomly divided on either side. It is known that a number of other electrical devices e.g. contactors, push buttons, relays etc. are generally always required with a circuit breaker. The unutilized available space is made use of for mounting these devices. Due to space becoming non-contiguous, the mounting & wiring of these devices (5) is not as comfortable as in case of Figure 4 due to design as shown in Figure 3.
As shown in figure 5a, Front cover (6) is designed such that three tunnels (7) are carved across the whole width of the front cover in such a way that the front cover is not made deeper than required by internal pole & arc chute assemblies, which are mounted in any circuit breaker.
Also, it is known that main mechanism (8) fastening has to be quite rigidly made on the front cover (6) & also it should not cause excessive stress on front cover (6) when circuit breaker (13) is closed. This is achieved by fastening the metallic strips with the front cover through hardware trapped in the thickness of the walls and at the specially designed ends.

The main operating mechanism (8) is then mounted at the desired fixed location (say "c") from one end (from RHS here).
The thickness of the metallic strips (9,10,11) is sufficient to engage sufficient number of threads of screws, which are used to fasten the main operating mechanism, so that the load appearing when closing the circuit breaker is adequately borne by the metallic strips.
The metallic strips (9,10,11) are also made use of for locating the bearings (12) at ends & at intermediate locations. Similarly, protection device (14) is also mounted on the strips.

WE CLAIM:
1. An improved front cover for an circuit breaker adapted for effective installation of front features/main operating mechanism comprising:
- plurality of tunnels formed in the front cover by carving out the said tunnels across the width of the front cover;
- a plurality of rigid strips provided in each of the tunnels adapted for mounting of the said front features/main operating mechanism, at a constant distance from one end of the cover,
the rigid strips being additionally adapted for mounting other front features on their extending lengths till the end of the widths of front cover such that the front cover is insert free.
Dated this 29th day of April 2001

DEEPAK MEHRA AGENT FOR APPLICANT