Title of Invention

MECHANICAL INTERLOCK SYSTEM OF THREE AIR CIRCUIT BREAKERS

Abstract A mechanical interlock system of three air ciruit breakers for safety of equipment and personnel by achived simultaneous closing of all the three ACBs. This mechanism can be achieved by clutch cables connected between the commanding shaft & the ACBs.
Full Text Form - 2
THE PATENTS ACT, 1970 (39 of 1970)
COMPLETE SPECIFICATION (Section 10; rule 13)
"MECHANICAL INTERLOCK SYSTEM OF THREE AIR 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:-

Title: Mechanical interlock system of Three Air Circuit Breakers
Field of the Invention: The present invention relates to a mechanical interlocking system for air circuit breakers and in particular to a group of three Air Circuit Breakers (henceforth abbreviated as ACBs) by using clutch cables, wherein the clutch cables are connected between commanding shaft and the trip shaft of the circuit breaker, which deter closing of all the three ACBs at a time.
Background of the invention:
It is known that in continuous process industries, the power interruptions for longer time is not acceptable, are fed by two independent power sources. Both power sources are connected to bus bars through one circuit breaker in each. This ACB is normally called "Incomer". Total load of the industry is distributed between two bus bars.
A third ACB is inserted between two bus bars to connect them in case of failure of any one-power source. The third ACB is known as "Bus Coupler" and it remains open in normal condition. In case if any one power supply fails, the "Incomer" breaker of the power supply is Switch Off and "Bus Coupler" is switched ON to connect both bus bars. The mechanical interlock ensures that at any given point of time maximum two ACBs can be switched on.
It is known that the mechanical interlocks cannot prevent closing of all three ACBs when closing commands are given at the same time. Additionally if any cable connected between ACB fails (breaks) the mechanical interlock becomes ineffective and it allows all the three ACBs to close at a time. Due, to which the basic purpose of interlocking is not achieved, hence these interlocks are not reliable.
Object of the invention
It is thus the basic object of the invention for safety of equipment and personnel. The safety can be achieved by avoiding simultaneous closing of all the three ACBs. The mechanical interclock system is operated in such a way that if one or more cables connected between the ACBs fail; it will not allow all the three ACBs to close at a time. (This is a unique feature of the interlock)
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Yet another object of the invention is when closing commands to all three breakers are given simultaneous in any situation it will deter closing of all the three ACBs at a time.
Yet another object of fhe invention is free arrangement of Circuit Breakers in all the direction since this mechanical interlock also operates successfully with longer than 2 m Clutch Cable.
Summary of the Invention
Thus according to the basic aspects of the present invention is to provide mechanical interlock system of three ACBs comprising: -
a actuator shaft mounted on the cradle, which rotates in Anti-clockwise direction when Circuit Breaker changes its state from OFF to ON, and vice verse. This anti¬clockwise direction of the actuator shaft is achieved by rotation of the main shaft of the circuit breaker and rotation in reverse direction is achieved by springs anchored on crank of actuator shaft.
Likewise first ends of two clutch cables are anchored on the crank assembly of actuator shaft of ACB (1)and
the second ends of the same are anchored on the crank assembly of trip shaft of ACB (2) & (3) and vice verse in case of ACB (2) & (3). Two return springs are also anchored on the Crank assembly of actuator shaft so that Crank assembly of actuator shaft pulls the two cables when it rotates in clockwise direction and the same is reversed when actuator shaft rotates in anti clockwise direction. Whereas Crank assembly of trip shaft rotates in anti¬clockwise direction when any one clutch cable is pulled from its first end.
This Trip shaft as mentioned above is mounted on the cradle and it directly actuates the tripping mechanism of the ACB when it rotates in clockwise direction.
If the tripping command is activated of (1) or (2) or (3) ACB, then under such circumstances the ACB can not be closed because the tripping command supersedes the closing command.
Description of the preferred embodiments
FIG. 1 shows diagrammatically and in sideview, three ACBs mechanically interlocked using clutch cables. (ACB"s in OFF Condition) FIG. 2 shows the detail of ACB (2) of FIG. 1 (OFF Condition)

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FIG. 3 shows ACB (1) in ON condition.
FIG. 4 shows ACB (1) and ACB (3) in ON condition and it"s effect on ACB (2).
Breakers with means of mutual locking are of known design and functioning, so that only the parts essential to the invention will be described below.
From FIG.l may be observed a possible arrangement of three Circuit Breakers (1), (2), and (3) having means of mechanical interlocking. (4), (5) are mounting plates for cables, which remains common in all the breakers. The mounting plates are mounted on side plate (1) of ACB (1) and fixed using screws.
Operation of central ACB (2) is explained here as an example.
One end of spring (19) is anchored on side plate of ACB (2) and other end is connected on crank assembly of trip shaft (9).
One ends of spring (18) is connected to mounting plate (4) and the other end is connected to crank assembly of actuator shaft (8).
Ends of the cables (14), (15) are connected to crank assembly of the actuator shaft (8) and the same cables are anchored on mounting plate (4) of Circuit Breaker-2 using nuts. The another end of the cable (14) is connected to crank assembly of trip shaft (7) and anchored on mounting plate (5) of ACB (1) and another end of the cable (15) is connected to crank assembly of trip shaft (11) and anchored oif mounting plate (5) of ACB (3).
Cranks (8) & (9) rotates with respect to their Heinz points (22) & (23) respectively.
Cranks assemblv of actuator shafts (8) sea%es the status of the circuit breaker (2) and
rotates in clockwise direction when the Circuit Breaker (2) changes its state from ON to
OFF.
The movement of crank assembly of actuator shaft (8) is transferred to Crank assembly of
trip shaft (7) of ACB (1) and Crank of trip shaft (11) of ACB (3) through clutch cables
(14) and (15) respectively.
Crank of trip shaft (9) rotates in clockwise direction to activate trip command of ACB (2). After that ACB (2) can not be switched ON.
One ends of clutch cables (13) and (16) are connected to crank of trip shaft (9) and other ends of the cables are connected to crank assembly of actuator shaft (6) of ACB (1) and crank assembly of actuator shaft (10) of ACB (2).
Operation of the mechanical interlocking system is been explained with examples as follows.

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Example 1
ACB (1) is switched on the Crank assembly of actuator shaft (6) rotates in anti¬clockwise direction and remains in the position shown in Fig-3. The rotation of Crank assembly of actuator shaft (6) releases the pulling forces from the cables (12) and (13).
Although the cables (12) and (13) connected to Crank assemblies of trip shaft (11) and (9) becomes free,the Crank assemblies of trip shaft (11) and (9) remains in its original position as it was in Fig-1. Because, the cable (15) [Connected between Crank assembly of trip shaft (11) and Crank assembly of actuator shaft (8)] and cable (16) [Connected between Crank assembly of trip shaft (9) and Crank assembly of actuator shaft (10)] give pulling force to Crank assemblies of trip shaft (9) and (11).
Example 2
ACB (3) is switched on the Crank assembly of actuator shaft (10) rotates in anti¬clockwise direction and remains in the position shown in Fig-4. The rotation of Crank assembly of actuator shaft (10) releases the pulling forces from the cables (16) and (17). With this action in the system the Crank assemblyjpf trip shaft (9) also routes in clockwise direction because both cable (16) and (13) have become free and do not give "pulling Also the spring (19) pulls the Crank assembly of trip shaft (9). This movement of Crank assembly of trip shaft (9) results into locking of ACB (2).
It is thus possible by way of above invention to provide simple/safe & cost effective mechanical interlock system for Circuit Breakers in particular to a group of three ACBs. The mechanical interlock system is operated in such a way that if one or more cables fail; it will not allow all the three ACBs to close at a time. The mechanism also deters closing of all the three ACBs at a time even if the closing commands for all three ACBs are given simultaneous in any situation.

We Claim
1. A mechanical interlock system to prevent closing of three air circuit breakers at a time
comprising:
three actuator shafts (6, 8 & 10) located on first (ACB 1), second (ACB 2) and third (ACB 3) circuit breakers respectively such that in the first circuit breaker actuator shaft (6) being mounted on a cradle (1) and rotating in anti-clockwise direction when the circuit breaker changes its state from OFF to ON, vice versa;
three springs (18) wherein one end of each connected to mounting plate (4) of three ACBs (1,2 & 3) and the other end of each anchored on crank assembly of actuator shaft (6, 8 & 10) respectively, said springs being adapted to pull said actuator shafts (6, 8 & 10) providing rotation in clockwise direction;
three pairs of clutch cables operatively connecting the three ACBs such that each ACB will have two pairs of clutch cables connected to other two ACBs such that when one end of a pair of clutch cable is connected to mounting plate and crank assembly of the actuator shaft of same ACB, other ends of same clutch cables are connected to crank assembly of the trip shaft and mounting plate of another two ACBs such that the clutch cables are pulled with the rotation of the actuator shaft.
2. A mechanical interlock system as claimed in claim 1, wherein the said actuator shaft rotates in clockwise direction when the ACB changes its state from ON to OFF.
3. A Mechanical interlock system as claimed in claim 1, said trip shafts rotate in anti¬clockwise direction when circuit breaker (ACB 1) changes its state from ON to OFF, and in clockwise direction when the vice versa.
4. A mechanical interlock system of air circuit breakers substantially as herein described with reference to the accompanying drawings.

Documents:

444-mum-2004-abstract(12-08-2004).doc

444-mum-2004-abstract(12-08-2004).pdf

444-mum-2004-cancelled pages(13-04-2004).pdf

444-mum-2004-claims(granted)-(12-08-2004).doc

444-mum-2004-claims(granted)-(12-08-2004).pdf

444-mum-2004-correspondence(12-08-2004).pdf

444-mum-2004-correspondence-(ipo)-(27-05-2004).pdf

444-mum-2004-form 1(13-04-2004).pdf

444-mum-2004-form 19(13-04-2004).pdf

444-mum-2004-form 2(granted)-(12-08-2004).doc

444-mum-2004-form 2(granted)-(12-08-2004).pdf

444-mum-2004-form 3(13-04-2004).pdf

444-mum-2004-power of authority(13-04-2004).pdf


Patent Number 210701
Indian Patent Application Number 444/MUM/2004
PG Journal Number 43/2007
Publication Date 26-Oct-2007
Grant Date 08-Oct-2007
Date of Filing 13-Apr-2004
Name of Patentee LARSEN & TOUBRO LIMITED
Applicant Address L & T HOUSE, BALLARD ESTATE, MUMBAI-400 001
Inventors:
# Inventor's Name Inventor's Address
1 RITESHKUMAR TULSIDAS PATEL LARSEN & TOUBRO LIMITED, ELECTRICAL SECTOR (EBG), SWITCGEAR DESIHN & DEVELOPMENT CENTRE, POWAI WORKS (E), SAKI VIHAR ROAD, MUMBAI-400 072.
PCT International Classification Number H01H9/26
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA