FORM 2
THE PATENT ACT 1970
&
T
he Patents Rules, 2003
COMPLETE SPECIFICATION (See section 10 and rule 13)
1. TITLE OF THE INVENTION:
"Flexible Mechanical Interlock Assembly for Circuit Breakers"
2. APPLICANT:
(a) NAME: Larsen & Toubro Limited
(b) NATIONALITY: Indian Company registered under the
provisions of the Companies Act-1956.
(c) ADDRESS: LARSEN & TOUBRO LIMITED.
L&T House. Ballard Estate. P. 0. Box: 278. Mumbai 400 001, India
3. PREAMBLE TO THE DESCRIPTION:
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.

Flexible Mechanical Interlock Assembly for Circuit Breakers
Field of the invention
The present invention provides an interlocking for circuit breakers, and more particularly, to a flexible mechanical interlock assembly for circuit breakers for preventing simultaneous closure of two circuit breakers in an industrial application.
Background of the invention
Restricting operation of circuit breakers is common to prevent unintended operation of individual interlocked circuit breakers which result in catastrophic effects. Limiting of the circuit breaker operation from OFF to ON. is desirable in situations where multiple power sources are used to supply power to a limited number of energy consuming devices.
For example, two power sources SI. S2 are used to power a load L at two different conditions, i.e. the power supply from distribution line and the power from the diesel generator as shown in figure 1. Generally, the load L should be powered by any one of the power sources SI and S2 at any time. Therefore, any one of the circuit breakers A and B will be allowed to close at any instant. If both of them are closed at the same time, dead shot of SI and S2 occurs. So if SI is active, say power is provided by EB. A is closed and B is in open. If SI fails, EB turns off and diesel generator powers the unit. Now, A is opened and B is allowed to close. This explains the necessity of having mechanical interlock in places where two separate power sources are used to give input to same load.
There are various types of mechanical interlocks available for the circuit breakers. A walking beam type interlock is applicable for only two circuit breakers, out of which only one switching device is ON at any time. The walking beam type interlock includes a pivoting rocker arm and a linkage assembly associated with each circuit breaker. This interlocking enables only mounting of the circuit breakers in a fixed prescribed

distance. Another type of interlock is using sliding bar arrangement fitted on the circuit breaker. It prevents simultaneous closing of the two circuit breakers by arresting the motion of operating knobs of the interlocked circuit breakers. Interlock using key locks is also available. The cable type interlock system is used if there is a need for variable distance between the switching devices
US Patent No. 5814777 discloses a cable interlock system ibr preventing at least two circuit breakers from being closed at the same time. The system comprises a first circuit breaker having a first operating handle, wherein the first operating handle is adapted to close or open the first circuit breaker, a second circuit breaker having a second operating handle, wherein the second operating handle is adapted to close or open the second circuit breaker, a first mounting bracket that is attached or secured to or otherwise associated with the first circuit breaker, a first lever arm movably attached or secured to or otherwise associated with the first mounting bracket, a second mounting bracket that is attached or secured to or otherwise associated with the second circuit breaker, a second lever arm movably attached or secured to or otherwise associated with the second mounting bracket, a cable assembly having one end adapted to be connected to the first lever arm of the first mounting bracket and having another end adapted to be connected to the second lever arm of the second mounting bracket, wherein said cable assembly and the first lever arm and the second lever arm operate together so as to prevent the first operating handle and the second operating handle from both being in the closed position.
Another US Patent No. 5726401 discloses a cable interlock system is provided for preventing at least two circuit breakers from both being closed. The system comprises a first circuit breaker assembly comprising a first main contact, a first cross bar, a first cross bar plunger, a first transfer assembly and a first operating handle, wherein the first operating handle is adapted to close or open the first circuit breaker assembly, and wherein the first cross bar plunger is adapted to contact the first cross bar, and wherein the first transfer assembly is adapted to move the first cross bar plunger; a second circuit breaker assembly comprising a second main contact, a second cross bar. a second cross bar plunger, a second transfer assembly and a second operating handle.

wherein the second operating handle is adapted to close or open the second circuit breaker assembly, and wherein the second cross bar plunger is adapted to contact the second cross bar. and wherein the second transfer assembly is adapted to move the second cross bar plunger; a cable assembly having one end adapted for association with the first transfer assembly and having another end adapted for association with the second transfer assembly, wherein the one end of the cable assembly and the first transfer assembly cooperate with the first cross bar and the first cross bar plunger, and the another end of the cable assembly and the second transfer assembly cooperate with the second cross bar and the second cross bar plunger so as to prevent the first main contact and the second main contact from both being closed.
Yet another US Patent 4827089 discloses a molded case circuit breakers connected to two different sources of power within an industrial application are interlocked to prevent one circuit breaker from being turned on while the other circuit breaker is already on. The circuit breakers include a molded plastic crossbar arranged for rotation within the circuit breaker enclosure. The interlock arrangement consists of a pivoted bell crank assembly including a pair of pivotally mounted insulative posts on either end of the bell crank. A corresponding cam integrally formed on the circuit breaker crossbar is in interference with one of the upstanding posts when the circuit breaker is in the "OFF" position and is out of interference with the upstanding post when the circuit breaker is in its "ON" condition.
Deficiencies of the prior art
1. Existing walking beam interlocking system doesn't allow the flexible mounting of the circuit breakers.
2. In cable type interlocking, the operating knobs disrupts the use of accessories that are to be mounted on top of the circuit breaker,
3. in molded case circuit breakers, getting input from shaft for modular type of circuit breakers is tougher.

4. Extra protrusion are required which extends out of the circuit breaker to give shaft actuation as the input. This consumes more space and makes flush mounting impossible.
5. Extra components or profile modification of shaft is required to get actuation.
6. Interlocking circuit breakers of slightly different ratings is not possible.
Accordingly, there exists a need to provide a interlocking mechanism for the circuit breakers which overcomes the drawbacks of the prior art.
Objects of the invention
An object of the present invention is to provide flexible mounting of circuit breakers in any location in an industrial application.
Another object of the present invention is to reduce use of accessories for interlocking the circuit breakers.
Another object of the present invention is to make interlocking between breakers of different ratings possible.
Yet another object of the present invention is to block shaft rotation with addition of no extra components to the circuit breaker.
Summary of the invention
Accordingly, the present invention provides a flexible mechanical interlock assembly for preventing simultaneous closure of two circuit breakers. Each circuit breaker comprises a through pin capable of aligning cassettes and shafts thereof. The flexible mechanical interlock assembly for each circuit breaker comprises a base plate disposed on the circuit breaker. Further, the assembly includes an actuator configured on the base plate. The actuator is capable of sliding up and down with respect to orientation of a

shaft of the circuit breaker, wherein the actuator receives the actuation from a through pin. Furthermore, the assembly includes a coupler hinged on the base plate. The coupler is capable of being rotated with the sliding motion of the actuator. Moreover, the assembly include a flexible Bowden cable anchored to the base plate and connected to the coupler of the two circuit breakers for transferring motion there between. Wherein force applied to switch the circuit breaker makes the shaft thereof to rotate thereby giving input to the actuator through the through pin which in turn transfers motion to the coupler and the coupler transmits the motion to a coupler of the other circuit breaker via flexible Bowden cable which then actuates actuator of the other circuit breaker thereby blocking the shaft rotation of the second interlocked breaker. The coupler is hinged so that cable pull is standardized irrespective of the rating and size of the circuit breaker. This facilitates inter-frame interlocking compatibility.
Brief description of the drawings
Figure 1 shows schematic drawing interlocking concept of circuit breakers;
Figure 2 shows an exploded view of a flexible mechanical interlock assembly, in accordance with the present invention:
Figure 3 shows arrangement of components of the flexible mechanical interlock assembly of.figure 2;
Figure 4 shows a right side view of the circuit breaker with the flexible mechanical interlock assembly in ON position: and
Figure 5 shows a right side view of the circuit breaker with the flexible mechanical interlock assembly in OFF position.

Detailed description of the invention
The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art. techniques and approaches are overcome by the present invention as described below in the preferred embodiments.
The present invention provides a flexible mechanical interlock to prevent simultaneous closure of two circuit breakers. The assembly comprises of two similar sub assemblies with four components each connected by an external cable component. The assembly provides flexible mounting of the circuit breakers in any location in an industrial application. Further, the assembly reduces use of accessories for interlocking the circuit breakers. Also the assembly allows interlocking between breakers of different ratings.
Referring now to figure 2 and 3 there is shown a flexible mechanical interlock assembly (50) (hereinafter referred to as The assembly (5Q)r) for preventing simultaneous closure of two circuit breakers. Each circuit breaker (100) of the two circuit breakers comprises a through pin (60) capable of aligning cassettes and shafts thereof. The through pin (60) provides actuation to the assembly (50) and serves two main purposes in the circuit breaker (100). One is to align all the cassettes and shafts of the circuit breaker (100) and second one is to transfer the shaft rotation between all connected shafts as the assembly (50) operates.
The assembly (50) for each circuit breaker (100) comprises a base plate (10). an actuator (20), a coupler (30). and a flexible Bowden cable (40).
The base plate (10) is disposed on the circuit breaker (100). The base plate (10) is a sheet metal bent to a required shape so as to mount all the components of the assembly (50) lo the circuit breaker in addition to other components of the circuit breaker (100). The base plate (10) is secured to the circuit breaker (100) by any securing means known in the art. for example, such as nut and bolt.

The actuator (20) is configured on the base plate (10) and slidably secured thereto. The actuator (20) is capable of sliding up and down with respect to orientation of the shaft of the circuit breaker (100). The actuator (20) receives the actuation from the through pin (60). The actuator (20) moves in a smooth motion in a slot provided in the base plate (10). Further, the actuator (20) includes an pin (22) which helps the actuator (20) to properly slide within the slot. This ensures that the actuator (20) motion is properly constrained. Specifically, the actuator (20) slides perfectly in the space between cassettes, through the slot in the housing of the circuit breaker (100) and gets a signal from the through pin (60).
The coupler (30) is hinged on the base plate (10). The coupler (30) is capable of being rotated with the sliding motion of the actuator (10).
The flexible Bowden cable (40) is anchored to the base plate (10) and is connected to the coupler of the two circuit breakers for transferring motion therebetween. The Bowden cable's (40) fixing end is secured to the base plate (10) by means of threads and lock nuts and adjusted for required free play. Head (42) of the flexible Bowden cable (40) is coupled to the coupler (30). The flexible Bowden cable (40) is a type of flexible cable used to transmit mechanical force or energy by the movement of an inner cable (most commonly of steel or stainless steel) relative to hollow outer cable housing. The housing is generally of composite construction, consisting of a helical steel wire, often lined with plastic, and with a plastic outer sheath. Both ends of the flexible Bowden cable have threads and lock nuts as fixing means. Fixing means of the cable is made of steel. The ends of the flexible Bowden cable (40) are assembled to the couplers of the two circuit breakers.
Similarly, all the components such as the base plate (10), the actuator (20). and a coupler (30) are assembled on other circuit breaker (not shown) of the two circuit breaker, except the flexible Bowden cable (40) which is common to both circuit breakers and connects the coupler (30) of both the circuit breakers. Connecting the flexible Bowden cable (40) to each coupler of the circuit breakers completes the

interlock assembly (M)). Now a force applied vertically down on any one of the coupled actuators (30) causes the corresponding motion of the other actuator.
Upon assembling of the interlock assembly (50) on the circuit breakers, the entire assembly is fixed on to the panel board as per positions specified by the customer.
The force applied to switch the circuit breaker (100) makes the shaft to rotate thereby giving input to the actuator (20) through the through pin (60). This motion is transferred to coupler (30) and then transmitted between couplers of the two circuit breakers via the flexible Bowden cable (40) and finally as an input to the actuator of the other circuit breaker. This block the shaft rotation of the second interlocked circuit breakers (100) through the through pin of the other circuit breaker, Accordingly, any changes in circuit breaker (100) knob position also changes the relative position of actuators (20) in the two sub modules by using the input from through pin (60). and thereby controlling the shaft rotation of the circuit breakers (100).
The assembly (50) is arranged in such a way that the assembly (50) allows closing only any one of the two breakers possible at all the times. Switching ON two circuit breakers is not at all possible. But both the circuit breakers may be permitted to remain in OFF condition simultaneously. Hence, desirable interlocking between the two breakers is achieved. The following table shows the possible combinations.

A 8
0 0
1 0
0 1
Here T represents ON state of the circuit breaker: '0' represents OFF state of the circuit breaker.
Consider initially both the interlocked the circuit breakers are in OFF position. In this position closing of any the circuit breaker (A or B) is possible.

When the circuit breaker A is closed, then the shaft of the A rotates thereby rotating the through pin (60) coupled with it. This will give the actuator (20) an input to move down. The actuator (20) transfers the signal to the coupler (30) via actuator pin (22) and the coupler (30) rotates in accordance to the signal with respect to its hinge point. As the coupler (30) is rotating in counter clockwise direction, the head (42) of the flexible Bowden cable (40) that is resting on the coupler (30) is pulled away thereby pulling the entire flexible Bowden cable (40) anchored to the base plate (30).
In the switch B. due to the movement of the flexible Bowden cable (40). the coupler is pulled near to the anchor point and so it rotates in clockwise direction. This gives the actuator an input to move up into the circuit breaker A through space provided between the cassettes. Mow the actuator of the circuit breaker B is positioned so as to block the rotation of shaft of circuit breaker B by blocking it's through pin (60). Since the shaft rotation is blocked, the unintended operation of the circuit breaker B is prevented while breaker A is made to ON. The coupler (30) is hinged in such a way that the cable pulled is standardized irrespective of rating and frame size. Thus it is possible even to interlock circuit breakers of different ratings.
For turning ON the circuit breaker B under any circumstances, the operator has to first turn OFF the closed circuit breaker A. and then move on to the switch B to turn it ON. Specifically, figure 4 shows a right side view of the circuit breaker with interlock in ON position and figure 5 shows a right side view of the circuit breaker with the interlock in OFF position.
Advantages of the invention
1. The assembly (50) provides flexible cable which replaces the solid shaft of the usual
walking beam mechanism and assures flexibility in mounting breakers in the panel
board.
2. The assembly (50) do not have constraints regarding the orientation of the circuit
breaker arrangement in the switch board as arranging the circuit breakers in the board

either horizontal or vertical is possible and that too arrangement in different modules of the circuit breaker is permitted.
3. The assembly (50) can be lilted to any circuit breaker easily without modification in the circuit breaker.
4. The actuation for interlocking of the two circuit breakers is provided by through pins in a shaft of circuit breakers whose primary function is to couple the shaft rotation in all cassettes of the breaker. This solves the problem of getting direct input from the shaft.

5. The actuation for interlocking of the two circuit breakers happens at the base of circuit breaker thus facilitating flush mounting.
6. The assembly (50) provides flexibility in mounting the two circuit breakers in location of an industrial application.

7. The assembly (50) may be used for fixed, withdraw-able or plug-in type of circuit breaker
8. The assembly (50) may be used for 3 pole. 4 poles and combination of 3 pole and 4 pole circuit breakers.
9. The assembly's (50) actuation input is provided by an existing component, and therefore addition of an extra component or rework of any component is eliminated.

10. The assembly (50) requires less number of components for the actuation to happen, which eases out manufacturing lead time and reduces cost
11. The assembly (50) makes it possible to interlock breakers of different ratings
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and

obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the spirit or scope of the present invention.

We claim
1. A flexible mechanical interlock assembly for preventing simultaneous
closure of two circuit breakers, each circuit breaker comprising a through pin capable of
aligning cassettes and shafts thereof, the flexible mechanical interlock assembly for
each circuit breaker comprises
a base plate disposed on the circuit breaker;
an actuator configured on the base plate, the actuator capable of sliding up and down with respect to orientation of a shall of the circuit breaker, wherein the actuator receives the actuation from a through pin;
a coupler hinged on the base plate, the coupler capable of being rotated with the sliding motion of the actuator; and
a flexible Bowden cable anchored to the base plate and connected to the coupler, wherein the flexible Bowden.cable connects couplers of the two circuit breakers for transferring motion therebetween.
wherein force applied to switch a circuit breaker of the two circuit breakers makes the shaft to rotate thereby giving input to the actuator through the through pin which in turn transfers motion to the coupler and the coupler transmits the motion to a coupler of the other circuit breaker via flexible Bowden cable which then actuates actuator of the other circuit breaker thereby blocking the shaft rotation of the second interlocked breaker.
2. The flexible mechanical interlock assembly as claimed in claim 1. wherein base plate includes a slot therein for movement of actuator therethrough.
3. The flexible mechanical interlock assembly as claimed in claim 1. wherein the actuator includes a pin for ease of movement thereof within the slot of the base plate.

4. The flexible mechanical interlock assembly as claimed in claim 1,
wherein the flexible Bowden cable includes a head lor securing 10 the coupler.