Form – 2 THE PATENTS ACT, 1970
COMPLETE SPECIFICATION (SECTION 10)
AN IMPROVED WAY TO INTERFACE POLE-MAECHANISM CONNECTION 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 field
This invention relates to "AN IMPROVED WAY TO INTERFACE POLE-MECHANISM CONNECTION IN CIRCUIT BREAKERS". This is aimed at enhancing the useful life of circuit breakers by simplifying the replacement of moving contacts at the end of its electrical life in minimum downtime & with minimum efforts & skill.
Background
Circuit Breakers for low voltage application, operating in air as interrupting medium, in the current range of below and upto 6300A are expected to have a decent mechanical life; of the order of 20,000 operations. However, the current switching parts, by virtue of the severity of current which they need to handle, are unable to match this life electrically. Either the circuit breakers are discarded at the end of their electrical life, in which case the full mechanical life is not fully utilized, or the current switching parts are replaced & the product is put back in service.
A number of designs presently available are such that current switching parts are not easily replaceable at the user's end. This necessitates sending the product back to manufacturer's premises/service centers or else requisitioning specialists from the supplier.
Prior Art
Some designs, which offer ease of replacement, need expensive parts or high manufacturing/assembly skills.
Yet another way to achieve is by way of complex driving arm of mechanism shaft.

Yet another way of achieving pole replacing is by attaining pole cage design, this however necessities use of bolted joins & copper part & thus weakness in electrical parts.
Our invention aims at providing effective, innovative & economic solution for above listed shortcomings.
Disclosure of the invention
One of the objects of the present invention is to provide easy replacement of moving contacts of current switching device, henceforth called "Main Contact Assembly".
Main contact assembly comprises of 1) Fix contact assembly & 2) Moving contact assembly. Circuit breaker generally has 3-4 poles; R, Y, B respectively. Each pole comprises of one no. of Fix contact assembly & Moving contact assembly. Fix contact assembly is generally easy to replace in most available designs & is not the subject of invention here. Entire current switching device is housed in an insulated housing made up of two parts - named front cover & rear cover.
Moving contact assembly comprises, assembly of spring-loaded set of contacts hinged at their lower ends and coupled together with the help of single pin. Circuit breaker is in service i.e carrying current only when Fix contact assembly & Moving contact assembly are in contact with each other; that completes the electrical circuit (current carrying path).
To move this moving contact assembly with desired velocity & make contact with Fix contact assembly & to retain it in the same position with maintaining desired pressure between two contact surfaces of Fix contacts & Moving contacts, equal to or more force is require from the

other side; hence Moving contact assembly is connected to a Mechanism through it's driving arm & in turn through connector assembly.
Connector assembly comprises 3 parts 1) male connector, 2) female connector & 3) Locking stud to lock them. Both male & female connectors are made up of insulating & tough material. Locking stud locks male connector & female connector & can be assembled / removed from top; which is essential since access to Moving contact assembly is only from top. Male part of connector assembly remains permanently attached to common pin passing through no. of spring loaded Moving contacts. The front cover has openings through which the driving arm of the mechanism drives the connector assembly. Depending on making & breaking of moving contact assembly with Fix contact assembly driving arm of mechanism has two well-known stable positions known as - OPEN & CLOSED.
For easy Moving contact assembly replacement, the two covers forming housing have to be always separated but the most important pre-requirement is easy disconnection of moving contact assembly from the driving arm. Similarly, after new moving contact assembly is housed, equally easy re-connection is needed after the two covers; front cover & rear cover, are fastened.
In our design, for disconnecting moving contact assembly, once the circuit breaker is totally disconnected from the main power supply i.e it is not electrically live in any way, is first brought in CLOSED position i.e Moving contact assembly is in contact with Fix contact assembly. This makes the Locking stud head accessible from top of the housing, which has opening from top but is covered with arc-chute used for arc quenching at the time of short circuit, when circuit breaker is in service. Hence to access this Locking stud one need to remove the arc-chute first. The same Locking

stud is not accessible from top of housing in OPEN position of driving arm of mechanism, hence it is require to bring driving arm of mechanism in it's CLOSED position to remove Locking stud. Once the driving arm of mechanism is brought to it's CLOSED position, Locking stud can be removed easily with the help of a normal screw-driver.
Once the Locking stud is withdrawn; then the driving arm of mechanism is brought in OPEN condition because in CLOSED position of driving arm of mechanism i.e circuit breaker, it is not possible to separate two connectors since there is no place to move the Moving contact assembly at rear side. Hence the two pieces of connector assembly get disengaged because of removing of Locking studs only when the driving arm of mechanism is brought to it's OPEN position. In the present invention the aforesaid housing can be easily separated and the moving contact assembly(ies) can be dislodged with the rear cover.
For re-connection, the rear cover carrying the Moving contact assembly(ies) is fastened with the front cover, when the driving arm of mechanism is in OPEN mode.
Female connector has a projection at it's bottom, which rests on the designed surface provided in Front cover when the driving arm of mechanism is in OPEN position. In the same position Moving contact assembly & hence projection in male connector which because of smaller projection at it's bottom sits in desired orientation; can be moved manually & aligned / partially inserted in the cavity to adapt the same. Subsequently when the mechanism is brought to it's CLOSED position; this partially inserted male connector gets fully inserted in the cavity provided in female connector to adapt the same. Further the Locking stud can be aligned with hole in female connector first & then can be locked with the nut provided in male connector because of external threads on the Locking stud.

The locking stud is consequently inserted & the two connector pieces become inseparable. The complete Moving contact assembly replacement is thus achieved in very easy way.
Brief description of the drawings
Figure 1 shows partial side sectional view of a circuit breaker without arc-chute, when the driving arm of mechanism, hence circuit breaker is in CLOSED position.
Figure 2 shows partial side sectional view of a circuit breaker with arc-chute, when the driving arm of mechanism, hence circuit breaker is in OPEN position.
Figure 3 shows yet another partial side sectional view when female connector is sitting in the specifically designed position & male connector is ready to negotiate its entry.
Figure 4 shows exploded isometric view of the two parts of connector & the locking stud.
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.
We shall first describe the disconnection of an already supplied & electrically expired Moving contact assembly (8).

As shown in Figure 1, First bring the driving arm (6a) of mechanism, hence circuit breaker in CLOSED position, the head (4) of Locking stud (1) having suitable cut (4a) to adapt a screwdriver, connecting female connector (2) & male connector (3); is accessible from top opening in housing assembly made by joining front cover (6) & rear cover (7); hence can be removed by common tools like screwdriver.
Once the Locking stud (1) is taken out, driving arm of mechanism is brought to it's OPEN position, which is essential to separate male connector (3) & female connector (2), since there is no space to move Moving contact assembly (8) at rear side in rear cover (7) in it's CLOSED position as can be seen from FIG.1; the bolts (5) which fasten the front cover (6) and rear cover (7) are loosened & removed & the rear cover (7) is pulled out along with Moving contact assembly (8) & Fix contact assembly (8a).
For re-connection, the rear cover (7) duly fitted with new Moving contact assembly(ies) (8) is fastened with the front cover (6). For re-connection it is essential to bring the driving arm (6a) of mechanism i.e circuit breaker in OPEN condition first; to facilitate initial entry of male connector (3) in the cavity (2b) provided in female connector (2).
As shown in Figure 3, once the driving arm (6a) of mechanism is brought to OPEN condition, by virtue of the specially designed profile (9) of front cover (6) & specially designed profile (10) of female connector (2), the female connector (2) sits in the designed position. Similarly, due to the co-ordinated design of profile (11) of male connector (3) & design of profile (12) of Moving contact assembly (8), male connector (3) which restricts the complete rotation of male connector & (3) i.e. it doesn't get any access at it's rear side & hence sits in a desired orientation . A mild guidance to projection (3b) in male connector (3) attached to Moving contact assembly

(8) ensures partial entry of male connector (3). If in this position of female connector (2) & male connector (3); the circuit breaker is brought to it's CLOSED position, then the complete entry of male connector (3) takes place because of the design.
Male connector (3) has circular cavity (3a) in it & a threaded nut trapped in it to adapt threaded Locking stud (1). Also, female connector (2) carries a through circular cavity (2a) in it; which once male connector (3) gets fully inserted in female connector (2), axis of cavity (3a) in male connector (3) gets aligned with the axis of cavity (2a) in female connector (2); hence clears the path of Locking stud (1) once entered in the cavity (2a) in female connector (2) from top. Once male connector (3) gets fully inserted in the cavity (2a) in female connector (2); the Locking stud (1) is re-engaged & locked from top. This completes the Moving contact assembly (8) replacement.

We Claim
1. An Improved way to interface pole-mechanism connection in Circuit Breakers wherein the moving contact assembly (8) is connected to the main driving arm of mechanism; to achieve two positions of circuit breaker i.e. driving arm of mechanism, CLOSED & OPEN position, this moving assembly connected to driving arm (6a) of mechanism with the help of a connector assembly, the said connector assembly comprises of locking stud, female and male connector; wherein the female connector (2) comprises bearing hole having a cavity (2b), chamfer, the said cavity made of two different diameters, wherein the male connector (3) comprises bearing hole having a projection (3b), locking stud (1) to lock the said connectors.
2. An Improved way to interface pole-mechanism connection in Circuit Breakers as claimed in claim 1 having Female connector (2) with a bearing hole around which it is hinged on driving arm of mechanism (6a); having a cavity (2b) with a chamfer at it's entry to facilitate easy entry of male connector (3);
3. An Improved way to interface pole-mechanism connection in Circuit Breakers as claimed in claim 1 & 2 female connector (2) having another cavity (2a) made of two different diameters smaller diameter to adapt locking part of locking stud (1) & bigger diameter against which collar of Locking stud (1) stops & decides final position of Locking stud (1); gets aligned with a cavity (3a) in male connector (3) & thus gets access to Locking stud (1) with a collared head (4);
4. An Improved way to interface pole-mechanism connection in Circuit Breakers as claimed in claim 1,2 & 3 female connector (2) having designed projection (10) at it's lower end which stops against the

designed profile (9) in front cover (6) & hence sits in desired orientation at the time of insertion of male connector (3).
5. An Improved way to interface pole-mechanism connection in Circuit Breakers as claimed in claim 1, Male connector (3) with a bearing hole around which it is hinged on Moving contact assembly (8); having a projection (3b) at it's front end which enters partially in the cavity (2b) in female connector (2) when the driving arm of mechanism (6a) is in CLOSED position & once the driving arm (6a) of mechanism is brought to it's OPEN position gets fully inserted in the same.
6. An Improved way to interface pole-mechanism connection in Circuit Breakers as claimed in claim 1 & 5 a male connector (3) having a cavity (3a) in projection (3b) with a threaded nut trapped in it, which when gets aligned with the cavity (2a) in female connector (2).
7. An Improved way to interface pole-mechanism connection in Circuit Breakers as claimed in claim 1, 5 & 6 male connector (3) having designed profile (11) at it's lower end, which stops against the designed profile (12) in Moving contact assembly (8) & hence sits in desired orientation at the time of insertion in the cavity (2b) provided in female connector (2).
8. An Improved way to interface pole-mechanism connection in Circuit Breakers as claimed in claim 1 having Locking stud (1) with; smaller diameter with external threads on it to get locked once fitted & larger diameter to decide the final position of the stud which unites the pole connectors; also easily accessible from top when circuit breaker is in CLOSED condition, and is thus easy to fit / remove.

9. An Improved way to interface pole-mechanism connection in Circuit Breakers as claimed in claim 1 & 8 having Locking stud (1) having a cutout suitable to adapt standard available screwdriver for removing/assembling the same in CLOSED / OPEN position of driving arm (6a) of mechanism respectively.
10. An Improved way to interface pole-mechanism connection in Circuit Breakers as claimed in claim 1 to 9 substantially as herein described with reference to the accompanying specification and drawing.