FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION (See section 10 and rule 13)
1. TITLE OF THE INVENTION:
"Assembly for Mechanically Interlocking Two 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. 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.

Assembly for Mechanically Interlocking Two Circuit Breakers
Field of the invention
The present invention relates generally to an interlock device for circuit breaker, and more particularly, to a flexible interlock assembly for two circuit breakers to ensure closing of one of the interlocked circuit breakers to be remained in OFF condition at all time.
Background of the invention
Generally, mechanical interlocking is provided outside a circuit breaker as an accessory. Further, the mechanical interlocking is provided as an external system to mechanically interlock motion of two circuit breakers. In changeover applications, the mechanical interlocking is used so that when one circuit breaker operates, the circuit breaker hinders the operation of other circuit breaker even when switching signal is provided to the other circuit breaker externally.
For example, two power sources S1, 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 S1 and S2 occurs. 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 load.

Various types of the interlocks have been described in the prior art. Walking beam type interlocks are applicable for two switching devices, out of which only one switching device is ON at any time. The interlock includes a pivoting rocker arm and a linkage assembly associated with each switching device. The interlocking enables only mounting of breakers in a fixed prescribed distance. Another type of interlock used in the prior art is a sliding bar arrangement fitted on switching devices that prevents simultaneous closing of two switching devices by arresting the motion of operating knobs of the interlocked breakers. Cable type interlock systems are used if there is a need for variable distance between the switching devices.
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.
Another US Patent 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.
However, numerous drawbacks are observed from the mechanical interlock of the prior art which are illustrated as follows:
1. Existing walking beam concept prevents the flexible mounting of circuit breakers reducing the flexibility.
2. Different components are to be used for interlocking both fixed and plug-in type of the circuit breakers.
3. Sliding bar type interlocking setup which is usually mounted on the front fascia of the circuit breaker interrupts the mounting of external accessories on the circuit breaker.
4. Interlock kit mounted below the circuit breaker increases effective depth in the circuit breaker mounting.
5. Cable type interlocking in the operating knobs disrupts the use of accessories that are to be mounted on top of the circuit breaker.
6. Extra protrusions are required which extends out of the circuit breaker to give shaft actuation as the input consuming more space and makes flush mounting impossible.

7. Any interlocking setup taking input from the knob disrupts the possibility of automation by denying the use of electrical operating mechanism (hereinafter referred as 'EOM') on the circuit breaker.
Accordingly, there exists a need to provide a flexible interlock system for for two 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 allow frequent changing of position of the circuit breakers.
Yet another object of the present invention is to reduce the extra depth requirement in mounting the circuit breakers.
Still another object of the present invention is to reduce the number of manufacturing process, and simplify the processing of the components.
Further object of the present invention is to lessen extra depth requirement in mounting of the circuit breakers.
Another object of the present invention is to facilitate the use of same components for both fixed and plug-in versions of circuit breakers.
Yet another object of the present invention is to provide easy site assembly at the customer end.
Summary of the invention

Accordingly, the present invention provides an assembly for mechanically interlocking two circuit breakers for preventing simultaneous closure of the two circuit breakers. Each circuit breaker includes a connecting pin capable of aligning cassettes and shafts thereof. Further, each circuit breaker includes a spacer aligned to the shaft of the circuit breaker for receiving a rotary motion input signal from the shaft. The assembly comprises a base plate disposed on the circuit breaker, and an actuator removably coupled with the spacer. The actuator is capable of receiving actuation from the spacer thereby converting the rotatory motion of the spacer to a linear motion. Further, the assembly includes a coupler hinged on the base plate, wherein the coupler capable of being rotated with the sliding motion of the actuator. Furthermore, the assembly includes a cable anchored to the base plate and connected to the coupler, wherein the cable connects couplers of the two circuit breakers for transferring motion therebetween. Wherein, when one circuit breaker of the of the two circuit breakers is switched ON, the shaft rotates thereby giving input to the actuator through the spacer, which in turn transfers the input to the coupler, the input is further transmitted through the cable to a coupler of other circuit breaker via the cable thereby blocking the motion of a spacer of other circuit breaker and blocking the shaft rotation of the other circuit breaker.
Brief description of the drawings
Figure I shows schematic drawing of interlocking concept of circuit breakers:
Figure 2 shows an exploded view of an assembly for mechanically interlocking two circuit breakers, in accordance with the present invention;
Figure 3 shows an exploded view of the assembly of figure 2;
Figure 4 shows an arrangement of all components of the assembly of figure 2;

Figure 5 shows the assembly of figure 2 in ON position;
Figure 6 shows a side view the assembly of figure 2 in ON position;
Figure 7 shows the assembly of figure 2 in OFF position; and
Figure 8; shows a side view the assembly of figure 2 in the 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 an assembly for mechanically interlocking two circuit breakers to prevent simultaneous closure of two circuit breakers. Each circuit breaker includes an assembly connected by a 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. Restricting operation of the circuit breaker is common method to prevent unintended operation of an individual interlocked circuit breaker which may 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.
Referring to figure 2 and 3, an exploded view of an assembly for mechanically interlocking two circuit breakers is shown. The present invention discloses the assembly (50) for mechanically interlocking two circuit breakers that prevents

simultaneous closure of two circuit breakers. Each circuit breaker (100) includes a connecting pin (not shown) capable of aligning cassettes, shafts thereof (not shown) and a spacer (60) aligned to the shaft of the circuit breaker for receiving a rotary motion input signal from the shaft. Specifically, the spacer (60) is positioned in between the cassette of the circuit breaker (100) using the connecting pin. More specifically, the spacer (60) sits between the cassettes of the circuit breaker (100) at the two extreme ends of the circuit breaker (100). The spacer (60) is an integral component of the operating mechanism of the circuit breaker (100) that facilitates the actuation to the assembly (50).
The connecting pin 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 through the spacer (60) as the assembly (50) operates.
The assembly (50) in each of the circuit breaker (100) includes a base plate (15). an actuator (20), a coupler (30) and a cable (40). The base plate (15) is disposed on the circuit breaker (100). The base plate (15) is a sheet metal bent to a required shape so as to mount all the components of the assembly (50) to the circuit breaker in addition to other components of the circuit breaker (100). The base plate (15) is secured to the circuit breaker (100) by any securing means known in the art, for example, nut and bolt.
The actuator (20) is a moulded plastic component removably coupled with the spacer (60). The actuator (20) is configured on the base plate (15) and slidably secured thereto. The actuator (20) is capable of rotating along with the orientation of the shaft of the circuit breaker (100). The actuator (20) receives the actuation from the connecting pin. The actuator (20) moves in a smooth motion in a slot provided in the base plate (15).

Specifically, the actuator (20) is configured to have a pair of pin (20b) on a side adaptably coupled with the spacer (60) thereon to receive a rotary motion input signal from the shaft and one another pin (20a) on other side adapted to rotate with the shaft rotation of the circuit breaker (100). The actuator (20) converts the rotary motion of the spacer to a linear motion. The pair of pin (20b) is designed to ensure that the actuator can be easily assembled to the spacer (60). The pin (20a) on other side provides an input/a motion signal to the coupler (30).
The coupler (30) is a blanked sheet metal component with holes at either ends. The coupler (30) adaptably configured to receive the input from the actuator (20). The coupler (30) includes a first hole, a second hole and a third hole. The first hole adaptably hinges the coupler onto the base plate (15). The coupler (30) is capable of being rotated with the sliding motion of the another pin (20a) of the actuator (20). The second hole facilitates to secure the cable (40) in the assembly (50). The third hole is capable of being rotated with the sliding motion of the another pin (20a) of the actuator (20) which allows the rotary motion of the first shaft to be transferred to the second shaft therefrom. The third hole in the present embodiment is an oblong shaped hole.
The cable (40) is a flexible type Bowden cable that is used to transmit mechanical force or energy by the movement of an inner cable 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 (40) have threads and lock nuts as fixing means. Fixing means of the flexible Bowden cable (40) is made of steel. The ends of the flexible Bowden cable (40) are assembled to the couplers of the two circuit breakers.
The flexible Bowden cable (40) includes a first end and a second end adapted to secure a cable head (42) to the coupler (30). The flexible Bowden cable (40) fixing end is secured to the base plate (10) by means of threads and lock nuts

and adjusted for required free play. The cable head (42) and is connected to the coupler (30) of the two circuit breakers (100) for transferring motion therebetween. The assembly (50) includes a cable holder (46) anchored to the base plate (15) using fixing means to transmit a mechanical force in between the two assembly (50) of the each circuit breaker (100).
Similarly, all the components such as the base plate (15), the actuator (20), and a coupler (30) are assembled on other circuit breaker (not shown) of the two circuit breaker, except the cable (40) which is common to both circuit breakers and connects the coupler (30) of both the circuit breakers. Connecting the cable (40) to each coupler of the circuit breakers completes the interlock assembly (50). Now a force applied vertically down on any one of the coupled actuators (30) causes the corresponding motion of the other actuator.
Each of the circuit breaker (100) is mounted onto the base plate (15) using mounting holes and the knock-out means in a housing (10a) adaptably assembled to uptake the input and provide easy assembly of the actuator (20). The actuator (20) is adaptably assembled such that only rotation with respect to the shaft rotation of either the circuit breaker (100) is allowed. The knock-out means provided in the housing (10a) is such that once it is defeated. The actuator (20) can be properly assembled to the spacer (60) allowing to rotate freely. Two holes exactly matching the outer dimensions of the two pins (20b) in the actuator (20) is provided in the spacer (60) by default. Upon assembling the actuator (20) in the holes, any further movement in the circuit breaker (100) shaft causes a corresponding movement in the actuator (20).
The coupler (30) is hinged to the base plate (15) after aligning the actuator's pin (20a) in the slot provided. The cable's fixing end is secured to the base plate (15) by means of the threads and lock nuts facilitating adjustment for required free play. The cable head (62) is finally secured onto the coupler (30) using the cable holder (46). The two breakers are assembled in a similar manner to obtain

uniformity. The spacer (60) provides facility to adaptably connect the first circuit breaker and the second circuit breaker using the cable (40). Upon applying a force on any one of the coupled actuators (20) results in the corresponding motion (rotation) of the other actuator (20) transferred through the cable (40).
Referring to figure 3, an exploded view of the interlock assembly is shown. Upon assembling of the assembly (50) on the circuit breakers, the interlock assembly is fixedly secured on to a panel board (not shown) as per positions specified by the customer/user. The flexible Bowden cable (40) is used for interlocking which ensures that the required degree of flexibility in mounting is provided.
Referring to figure 4-8, an arrangement of all components and operation of the assembly (50) is shown. When one circuit breaker (100) of the of the two circuit breakers is switched ON, the shaft rotate thereby giving rotary motion to the actuator (20) through the spacer (60), which in turn transfers the rotary motion to the coupler (30). The rotary motion is further transmitted through the flexible Bowden cable (40) to a coupler (not shown) of other circuit breaker (not shown) thereby blocking the motion of a spacer (not shown) of other circuit breaker and blocking the shaft rotation of the other circuit breaker.
Further, change in knob (80) position of the circuit breaker (100) also changes the relative position of actuators (20) in the assembly (50) of each circuit breaker using the rotary motion from spacers (60) and thereby controls the shaft rotation of the other circuit breaker.
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. The assembly (50) is designed such that switching ON two breakers at the same time is not at

all possible, but both may be permitted to remain in OFF condition simultaneously. Hence desirable interlocking between two breakers is achieved.
The following table shows the possible combinations

First circuit breaker (10)(A) Second circuit breaker (10){B)
0 0
1 0
0 1
Where 1 represents ON state of breaker; '0' represents OFF state of breaker
Initially in the first condition the first circuit breaker (A) and the second circuit breaker (B) are in OFF position. In this first position closing of any switch (A or B) is possible.
In a second condition, in case the first circuit breaker A is to be closed, the knob (80) is turned to a predefined angle. The turning movement of knob (80) facilitates the rotation of the shaft of the first circuit breaker A and thereby rotating the spacer (60) coupled with the first shaft. The actuator (20) rotates in accordance with the spacer (60) that transmits the rotary motion to the coupler (30) via the another pin (20a) on the other side of the actuator (20). The coupler (30) further rotates in accordance to the signal with respect to hinge point. Further, the coupler (30) rotates in clockwise direction which facilitates the cable head (62) resting in the cable holder (46) to be pulled away thereby pulling the cable (40) anchored to the base plate (15).
Further, the movement of the cable (40) thereby results counter-clockwise directional (left side) rotation the coupler (30) positioned in the second circuit breaker B. The rotation of the coupler (30) ensures that the actuator (20) is

coupled in extreme left position, thereby hindering the rotation of the spacer (60) in the second circuit breaker B. The blocked motion of the spacer (60) thereby further blocks rotation of the shaft to prevent unintended operation of the second circuit breaker B from moving to ON position.
If operator/user wishes to turn ON the second circuit breaker B under any circumstances, the operator has to first turn OFF the closed first circuit breaker A. and then move on to the second circuit breaker B to turn it ON.
Advantages of the invention
1. The assembly (50) solves the existing problem of fixed inter breaker distance in walking beam type of mechanical interlocking.
2. The assembly (50) is applicable to both is fixed or plug-in type.
3. The assembly (50) uses flexible cable; hence placing switching devices anywhere within the reach of cable is possible. The assembly (5) avoids any constrain to the customer to keep the breakers at a distance specified by the manufacturer allowing frequent changing of position of the switching devices possible.
4. The assembly (50) uses a component that already exists in the circuit breaker (J00) ruling out the requirement of any extra components in the circuit breaker for facilitating interlocking.
5. The assembly (50) adaptably applicable to 3 pole or 4 poles or combination of 3 pole and 4 pole switching devices.
6. The assembly (50) facilitates getting actuation from the right hand side of the circuit breaker enabling compatibility with all external accessories mounted on the front portion of the breakers like extended rotary operating handle and the like.
7. The assembly (50) ensures complete blockage of the shaft rotation avoiding use of any extra components to the breaker.

8. The assembly (50) uses less number of components for the actuation hence eases out manufacturing lead time and reduces cost.
9. The assembly (50) provides a different approach to achieve interlocking between switching devices.
10. 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.
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. An assembly for mechanically interlocking two circuit breakers for preventing simultaneous closure of the two circuit breakers, each circuit breaker having a connecting pin capable of aligning cassettes and shafts thereof, and further having a spacer aligned to the shaft of the circuit breaker for receiving a rotary motion input signal from the shaft, the assembly comprising:
a base plate disposed on the circuit breaker;
an actuator removably coupled with the spacer, the actuator being capable of receiving actuation from the spacer thereby converting the rotary motion of the spacer to a linear motion;
a coupler hinged on the base plate, the coupler being capable of being rotated with the sliding motion of the actuator; and
a cable anchored to the base plate and connected to the coupler, wherein the cable connects couplers of the two circuit breakers for transferring motion therebetween;
wherein, when one circuit breaker of the of the two circuit breakers is switched ON, the shaft rotates, thereby giving input to the actuator through the spacer, which in turn transfers the input to the coupler, and the input is further transmitted through the cable to a coupler of the other circuit breaker, thereby blocking the motion of the spacer of the other circuit breaker and blocking the shaft rotation of the other circuit breaker.
2. The assembly as claimed in claim 1, wherein the actuator includes a pair of pins on a side thereof for coupling with the spacer and another pin on other side thereof adapted to convert the rotary motion of the spacer into a linear motion.

3. The assembly as claimed in claim 1, wherein the base plate includes a cable holder for securing a cable head of the cable.