Form - 2
THE PATENTS ACT, 1970
COMPLETE SPECIFICATION (SECTION 10)
"A PARTICULAR CONSTRUCTION OF SECONDARY ISOLATING CONTACTS IN 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:-

Technical Filed
The present invention relates to "A PARTICULAR CONSTRUCTION OF SECONDARY ISOLATING CONTACTS IN CIRCUIT BREAKERS" which is aimed at achieving high modularity so that various accessories provided in the circuit breaker can be easily added/replaced.
Background art
Circuit breakers for low voltage generally find application in the current range of below & upto 6400A. These Circuit Breakers are available in Fixed & Drawout versions. Drawout version facilitates easy maintenance and installation.
For drawout Circuit Breakers, a chamber like unit, henceforth called Cradle, fixed in the panel, is generally additionally required, through which current carrying parts of the circuit breaker get connected in sliding/plug-in way. Power circuit, which handles current as per the ampere rating of circuit breaker (<=6300Amp), has one arrangement; while various accessories viz. Closing release, shunt release, electrical charging device, auxiliary switch etc. which form part of control circuit have an independent arrangement (generally through SICs). The current of control circuits is of the order of upto 10 Amperes.
The arrangement for control circuit has to be suitable for as many accessories as are present in modern day circuit breakers. The number varies from twenties to sixties or so.
Drawout circuit breakers can assume three different positions:
1. " Service" position; where power as well as control circuit is connected. This is the position when circuit breaker is in operation.
2. "Test" position; where power circuit is disconnected but control circuit is connected. In this position, the circuit breaker can be tested for proper functioning of all protective devices without switching/carrying main power.
3. "Isolated" position; when control circuit is also disconnected.
Electrical micro switches are generally mounted in the cradle which sense the position of circuit breaker in cradle.
The arrangement for control circuit is required in line with the accessories chosen by different users & hence needs to be independently modular.
Many a time, because of process interlocking requirements, few control circuits need to be connected only in service/test position.

The constructions available generally meet only basic definition but not the modularity/circuit breaker position sensing/process interlocking needs.
The present invention effectively meets all these requirements in unique way.
Disclosure of the invention
The present invention relates to particular construction of contacts for connection of control circuit which is called as Secondary Isolating Contacts (abbreviated as SICs). The basic SIC module consists of the minimum possible i.e. ONE. Hence as less as one SIC can be provided in our circuit breaker. This construction is thus called a unipolar construction.
One SIC consists of one breaker SIC & one cradle SIC. The breaker SIC slides over the cradle SIC thus providing the desired connection.
In circuit breaker, many accessories are added by the user at a later date. In our construction, when such an accessory is added, the corresponding SIC(s) can be added without disturbing previously present SIC(s).
Similarly, when any accessory needs replacement, the corresponding SIC(s) can be withdrawn without disturbing other SIC(s).
The cradle SIC(s) construction is such that it provides contact in Service + Test + Isolated position or any one position or combination of any two or all three positions, as desired.
Brief description of the accompanying drawings
Figure 1 shows four different varieties of Cradle SIC(s) contacts (1a, 1b, 1c & 1d)
Figure 2a & 2b show details of Cradle SIC insulated housing.
Figure 3. shows assembly of conducting strip & Cradle SIC insulated housing.
Figure 4. shows stack of cradle SIC(s).
Figure 5a & 5b show fixation details of cradle SIC & cradle SIC mounting
member.
Figure 6a, 6b & 6c show details of breaker conducting contact & Breaker
insulated housing.
Figure 7a & 7b show fixation details of conducting contact & Breaker SIC
insulated housing.
Figure 8. shows stack of Breaker SIC(s).
Figure 9a & 9b show fixation details of Breaker SIC & Breaker SIC mounting
member.
Figure 10 shows a complete SIC.

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.
Figure 1 explains the particular constructions of conducting strip of Cradle SIC(s) which are explained here: All position (1a), Only Isolated position (1b), Only Test position (1c), Only Service position (1d). Similarly, more combinations viz. Test + Service, Test + Isolated, etc. can be derived from this concept as variations.
Reference is now invited to Figure 2a & 2b, which illustrates the cradle SIC(s) insulated housing (4) is designed such that front & rear side of it (4F & 4R) dovetail constructions (47 & 46) with the help of which two insulated housing can be clubbed together without using fastener just by sliding onto each other. Likewise many SIC(s) can be clubbed together to get desired number of contacts (99a, 99b, 99c and so on ref. fig. 10)
As further illustrated in Figure 3 wire terminals (2 & 3) are fitted on projection (41) in insulated housing (4 - Ref. fig. 2a). Holes (11) provided on copper strips (1a, 1b, 1c & 1d- ref. fig. 1) fit into corresponding pips (45) on insulated housing (4). Specially constructed surfaces (12) of the copper strip trap between surfaces (21 & 22) of wire terminals (2 & 3) & wall construction (44) of insulated housing. This assembly thus obtained in Fig. 3 is identified as "Cradle SIC".
The cradle SIC(s) obtained this way (99) are illustrated in fig 4.
Fig 5a & 5b illustrates mounting of Cradle SIC(s) (99}. The cradle SIC(s) by virtue of their projection construction (42) are directly fixable on Cradle SIC mounting member (7); which in turn sits firmly on Cradle of circuit breaker. They trap at
locations (7a, 7b, 7c, , 7n). Projection (43) traps against surface (71) of
Cradle SIC mounting member (7). Thus a cradle SIC can be readjjy added[or deleted to the cradle SIC stack wjthout disturbing the neighboring SIC(s). A Cradle SIC insulated housing (4- ref.Fig. 2) encloses last Sic conducting strip to prevent this probable electrically live part from the danger of exposure.
For completion of electrical circuit, every Cradle SIC (99) has corresponding Breaker SIC (100 - ref, fig. 7a). Slot (81 - ref. fig. 6a) in conducting contact (8) fits on corresponding'profile (93 -ref. fig. 6c) in breaker SIC moulded housing (9). Wall (82 - ref. fig. 6a) of conducting contact (8) rests against wire terminal (101 ref. fig. 7a). As shown in Fig 7b breaker SIC insulated housing (9) has dovetail constructions (91 & 92) on its front & rear side (9F & 9R). Hence two or more Breaker insulated housings (9) can be clubbed together without using any fastener just by sliding onto each other as illustrated in fig. 8. A number of Breaker SIC(s) can be clubbed together to get desired number of contacts.

With the help of projection construction (94 - Ref. Fig. 6c), Breaker SIC(s) are directly fixable on Breaker SIC mounting member (6 - -Ref. Fig. 9a & 9b); at
locations (6a, 6b, 6c, , 6n). Fig 8 shows the clubbed together Breaker SIC(s)
and Fig 9a & 9b shows the Breaker SIC(s) on the mounting plate. Thus a Breaker SIC can be readily added or deleted to the breaker SIC stack without cjisfurbing the neighboring SIC(s). As shown in figure 10, this design of SIC(s) provides continuity between breaker SIC(s) (100a, 100b, 100c) & Cradle SIC(s) (99a, 99b, 99c) by sliding action. The breaker SIC(s) (100a, 100b, 100c) conducting contact slides on the conducting strip of Cradle SIC(s) (99a, 99b, 99c).
When an air circuit breaker is in ISOLATED position, assembly (99) with Isolated
position Cradle SIC(s) design (1b) comes in contact with Breaker SIC (100a,
100b, 100c, ) (i.e. surface (83) of Breaker SIC copper contact (8).
Similarly when air circuit breaker is in TEST position, assembly (99) with Test position Cradle SIC(s) construction (1c) makes contact with surface (83). Likewise, in SERVICE position, service position Cradle SIC(s) construction (1d) makes contact with surface (83). All position cradle SIC(s) construction (1a) remains connected throughout the travel of breaker i. e from ISOLATED to SERVICE position.
Further, by virtue of possibility of these arrangements, aptly called programming, control wiring scheme can be designed with high flexibility using any or all arrangements (i. e programs).

We Claim
A particular construction of control contacts, called secondary isolating contacts {called SIC(s)}, the basic module consists of the minimum possible i.e. ONE, hence as less as one SIC can be provided, this construction is thus called a unipolar construction which gives high modularity; & can provide continuity in Service or Test or Isolated position or any combination thereof and hence are called programmable SIC(s), & any one or more SIC can be added or removed without disturbing the remaining arrangement.
Dated this 28th day of August, 2001
Deepak Mehr'a (Agent for Applicant)