FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION:
"A Knob Interlock for Horizontally Adjacent 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. O. 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.

A Knob Interlock for Horizontally Adjacent Breakers
Field of the invention
The present invention relates to an interlocking device for MCCB, more particularly, it relates to an interlocking device, which can be used for MCCBs with rotary operating knob to ensure that at least any one of the interlocked breakers remains in OFF condition at all times.
Background of the Invention
There are various types of mechanical interlocks available for switching devices. Walking beam type interlock can be used for only two switching devices, out of which only one switching device can be kept ON at one time. It includes a pivoting rocker arm and a linkage assembly associated with each switching device. This interlocking device enables only mounting of breakers in a fixed prescribed distance. Interlock using key locks is also available. Cable type Interlock system is used if there is a need for variable distance between the switching devices. Another type of interlock is using sliding bar arrangement fitted on switching devices. It prevents simultaneous closing of two switching devices by arresting the motion of operating knobs of the interlocked breakers by virtue of its geometry.
PRIOR ART:
US 6043439 dated March 28 2000, describes an apparatus for interlocking horizontally adjacent first and second circuit breakers and preventing the circuit breakers from simultaneously being in a closed operating position. The circuit breakers each have a pivotable actuating handle movable between a closed position which is proximal to the other circuit breaker, and a open position which is distal to the other circuit breaker. A housing lies between the first and second

circuit breakers and an interlock bar is slidably retained in the housing. In operation, the interlock bar is slidable between a first position where the interlock bar prevents the first circuit breaker handle from pivoting into the closed position and a second position where the interlock bar prevents the second circuit breaker handle from pivoting into the closed position. If the interlock bar is in the first position and the handle of the second circuit breaker is in the closed position, the handle of the second circuit breaker prevents the interlock bar from being moved into the second position. To move the interlock bar into the second position, the user must move the handle of the second circuit breaker into the open position. Once the handle of the second circuit breaker is in the open position, the interlock bar can be moved into the second position and the handle of the first circuit breaker may be closed. While the interlock bar is in the second position and the handle of the first circuit breaker is in the closed position, the handle of the first circuit breaker prevents the interlock bar from being moved into the first position.
US 6777628 B2 dated August 17 2004, describes a device for interlocking at least two single- or multipole circuit breakers, of which:-a first circuit breaker, suitable to be fixed to a mounting plate of the first and second circuit breakers; ~a second circuit breaker, suitable to be fixed by virtue of fixing means to the first bracket and to be supported thereby;~an interlocking element, provided with a contoured body that is operatively coupled to the second bracket so that it can move with respect to it, the interlocking element being suitable to be rigidly connected to the second bracket, by virtue of locking means, in a chosen position in which it interacts operatively with at least the first opening/closure lever in a condition that corresponds to the opening of the first circuit breaker, preventing its movement and preventing the circuit breakers from being closed simultaneously.
US 5814777 dated Sep 29 1998, describes A cable interlock system for preventing at least two circuit breakers from being closed at the same time, comprising 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.
US 4827089 dated May 2 1989, describes 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.
Disadvantages of the prior art:
1. Interlocking between switching devices of different rating are not possible in most of the other type of interlocks.

2. Taking output from the shaft of the breaker may possibly create a hindrance towards achieving desired contact pressure or opening velocity of the breaker mechanism.
3. Walking beam type of interlocking disrupts bottom mounting accessories like plug-in, withdraw-able mechanism etc.
4. External space requirement behind the breakers for walking beam type of interlocks.
5. Getting input from shaft of breakers for walking beam type of mechanism is tougher.
6. Walking beam type of interlocking doesn't offer padlocking feature. So unauthorized operation of breakers is not prevented.
7. Extra protrusion are required which extends out of the breaker to give shaft actuation as the input. This consumes more space and makes flush mounting impossible.
8. Extra components or profile modification of shaft is required to get actuation.
OBJECTS OF THE INVENTION:
Object of the invention is to provide a knob interlock for horizontally adjacent breakers, which ensures the knob position of interlocked breakers in desirable state.

Yet another object of the invention is to provide a knob interlock for horizontally
adjacent breakers, which ensures that shaft rotation is properly arrested. .
One more object of the invention is to provide a knob interlock for horizontally adjacent breakers, which does not affect mechanism operating characteristics.
Further object of the invention is to provide a knob interlock for horizontally adjacent breakers, which does not require cutout for getting input for interlocking.
Another object of the invention is to provide a knob interlock for horizontally adjacent breakers, which with minor modification can achieve inter-frame interlocking.
Yet another object of the invention is to provide a knob interlock for horizontally adjacent breakers, which does not requires addition of extra components and modification of existing ones to get the input for the breaker.
One more object of the invention is to provide a knob interlock for horizontally adjacent breakers, which does not require any extra mounting provisions.
Yet another object of the invention is to provide a knob interlock for horizontally adjacent breakers, which has optional padlock to ensure that unauthorized operation of breakers is prevented.
One more object of the invention is to provide a knob interlock for horizontally adjacent breakers, which is easy assemble on site.
Summary of the invention
According to the present invention there is provided a knob interlock for two circuit breakers disposed adjacent to each other. The knob interlock two supports

(2 & 3) and a slider solid bar (1). The supports (2 & 3) are disposed on the respective circuit breaker. The slider solid bar (1) is slidably disposed over the two supports (2 & 3). Further, the slider solid bar (1) has a slot for facilitating sliding of the slider solid bar (1). A bent portion is configured on the slider solid bar (1) to configure a knob (7) and another bent with two holes (5) for providing padlocking. Also, a hole (6) is configured on either support (2 & 3) disposed towards the two holes (5) for insert and lock with the padlock (8). Therefore, the two supports (2 & 3) and the slider solid bar (1) enables in maintaining one of the circuit breaker in "ON" position at a time.
Brief description of the drawings
Figure 1 shows a one line industrial diagram interlocked two breakers;
Figure 2 shows an exploded view of the knob interlock in accordance with the present invention;
Figure 3 and Figure 4 interlocked circuit breaker in ON and OFF position respectively.
Figure 5 shows a perspective view of the interlocked circuit breaker;
Figure 6 shows another perspective view of the interlocked circuit breaker with padlock, and
Figure 7 shows yet another perspective view of the interlocked circuit breaker with padlock.

Detail description of the invention
For a thorough understanding of the present invention, reference is to be made to the following detailed description, including the appended claims, in connection with the above-described drawings. Although the present invention is described in connection with exemplary embodiments, the present invention is not intended to be limited to the specific forms set forth herein. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but these are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present invention. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
The present invention is related to interlock mechanism for switching devices. Restricting operation of circuit breakers is common to prevent unintended operation of individual interlocked breakers which may result in catastrophic effects. Limiting of 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.
To better understand the necessity of interlocking three breakers, consider the following one line diagram as shown in figure 1, this is the typical case in many industries. Here two sources S1, S2 are used to power the load L at two different conditions, power supply from the distribution line and power from the diesel generator.
The load L should be powered by any one of the sources at any time. Therefore any one of the switches, A and B will be allowed to close at any instant. If both of them are closed at the same time, dead shot of S1 & S2 will occur. So if SI is active, say power is provided by EB, A is closed and B is in open. If S1 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 equipment
The invention disclosed here is a fixed distance interlock assembly to prevent simultaneous closure of two switching devices (4) as shown in figure 2. The assembly comprises of two similar supports (2 & 3), each mounted on to the breaker using mounting holes and a sliding solid bar (1), which slides on the two supports. The solid bar (1) is provided with slots to facilitate sliding and is bent at one edge to serve as a knob (7).
The knob on the circuit breakers (4) is of rotary type which facilitates the opening and closure of the circuit breaker. Here the knob position - 45° inclination to ground represents OFF position of the breaker and 135° inclination to ground position represents ON position of the circuit breaker. Clockwise rotation of the knob for 90° makes it move from OFF state to ON state.
Referring again to figure 3 and 4, the supports (2 & 3) on both of the circuit breakers (4) are sheet metals bent to the required shape. They are mounted on to the MCCB using the mounting holes and the bends ensure that the slider motion is properly constrained and as per requirement. The support at right end (3) is provided an extra bend with a hole (6) - provision for a padlock (6), if required.
The sliding component (1) is a bent sheet metal which slides between the supports (2 & 3). It is allowed only sliding motion above the breakers (4), properly constrained by the supports (2 & 3). A bend is given in the top part of the slider to serve the function of a knob (7), It also has an additional bend at one end with two holes (5) for providing padlocking feature if required.
Upon to the interlock assembly, the switching devices (4) are mounted and then the entire assembly is fixed on to the panel board at the prescribed distance.

The slider (1) aligned properly, by virtue of its shape, will allow knob of only one of the breaker to rotate full 90 degrees. It ensures that at every instant only one breaker can be switched ON, For switching on any one of the interlocked breakers (4), the slider (1) needs to be moved towards the extreme and then the knob be operated. And if the user wants to switch ON the other breaker, the initial breaker need to be brought to OFF position, then the slider (1) moved to the opposite extreme and then switching ON the required breaker.
The assembly is arranged in such a way that it allows closing only any one of the two breakers (4) possible at all the times. Switching ON two breakers is not at all possible. But both may be permitted to remain in OFF condition simultaneously. Hence desirable interlocking between the breakers is achieved. The following table shows the possible combinations.

A B
0 0
J 0
0 1
Here '1' represents ON state of breaker; '0' represents OFF state of breaker
Working
Consider initially both the interlocked breakers (4) are in OFF position. Let left side breaker represented as a breaker A and the right side one as a breaker B. In this position closing of any switch (A or B) is possible. Both the knobs are having a 45° inclination to the ground. The knob has to make a 90 degree clockwise rotation to go from OFF to ON position.

Now for switching ON breaker A, ensure that the slider (1) is moved to the extreme edge of A (max left motion in our case). This position of the slider (1) will allow knob rotation of breaker A. Now the breaker can be operated to achieve ON position. The slider (1) by its geometry will now prevent the possibility of rotation of breaker B and thus unintended closure of the breaker B is avoided. In the current scenario, slider (1) is aligned in such a way that it's one end will be staying in touch with the knob of breaker B. Even if the user wishes to switch breaker B also to ON position, slider profile will block the knob rotation of breaker B and thereby ensure interlocking.
For turning ON breaker B under any circumstances, the operator has to first turn OFF the closed switch A, move the slider (1) to the other extreme and then move on to the switch B to turn it ON.
The provision for padlocking may be used if the user wishes to do so. For retaining the desirable position of slider (1) and preventing unauthorized operation of breakers (4), the user can use an external padlock (8). In current case, say Breaker A is remaining in closed position, the slider (1) will be aligned in a position such that hole in slider (5) and the hole in support (6) are in line. Now the user can insert a padlock (8) through the holes inline and retain the position and prevent unauthorized usage.
For using the breaker B under any circumstances, the user has to remove the padlock (8) from the position, close the breaker A, move the slider (1) to the opposite extreme and then switch on breaker B. This position of the slider will make another hole in slider (5) and the hole in support aligned in a line (6). This is also pad Iockable for the user.
The interlock setup with one breaker in ON position and the position retained using padlock is shown in Figure5. The interlock setup with the next breaker in ON position and the position retained using padlock is shown in Figure 6.

Advantages of the invention
This invention solves the existing problem of interlocking knob operation of MCCB s with rotary actuation.
The actuation happens at the top of the MCCB thereby giving a clear visual indication.
This invention does not constraint the type of switching devices whether it is withdraw-able or plug-in type. It can be applicable to any type.
There is no component that interacts with the shaft of the breaker which may affect the contact pressure or opening velocity of the mechanism.
This invention can be applicable to 3 pole or 4 poles or combination of 3 pole and 4 pole switching devices
The invention is capable of giving interlocking between switching devices of different rating, with slight modification in the component dimensions.
This invention is a different approach to achieve interlocking between switching devices.
This invention ensures that the knob rotation itself is properly blocked with addition of no extra components to the breaker.
The interlock is fully contained on the top of the MCCB thereby reducing any space requirement behind the breaker.

This invention is a different approach to achieve interlocking between two breakers. It uses a solid slider to interlock breakers having rotary actuation. It is not like existing approach; which gives only interlocking arrangement for toggle type of knobs.
Since the relative alignment of interlocked breakers is the only constraint for proper functionality, the breakers as a set could be arranged either horizontal or vertical.
This interlocking mechanism consists of three components that can be fitted to breaker easily at last. This invention does not require any modification in the switching devices to fit with. The components can be easily assembled to switching devices. This ensures easy site installation by customer.
The actuation for interlocking is taken from rotary knob of the MCCBs. So there is no impact on the mechanism characteristics like opening velocity, contact pressure etc.
An extra provision for padlocking is provided to facilitate the user to go for the feature to prevent unauthorized use, if required.
Since the input is provided by an existing component, the addition of an extra component or rework of any component is eliminated.
The invention uses less number of components for the actuation to happen, all of which are sheet metal make. So it eases out manufacturing lead time and reduces cost.
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, and 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 omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present invention.

We Claim:
1. A knob interlock for two circuit breakers disposed adjacent to each other, the knob interlock comprising:
two supports (2 & 3) disposed on the respective circuit breaker;
a slider solid bar (1) slidably disposed over the two supports (2 & 3), the slider solid bar (1) having a slot for facilitating sliding of the slider solid bar (1), a bent portion to configure a knob (7) and another bent with two holes (5) for providing padlocking; and
a hole (6) configured on either support (2 & 3) disposed towards the two holes (5) for insert and lock with the padlock (8),
wherein the two supports (2 & 3) and the slider solid bar (1) enables in maintaining one of the circuit breaker in "ON" position at a time.