FORM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention - SAFETY LOCKING ASSEMBLY FOR SWITCHING
DEVICES

2. Applicant(s)
(a) NAME :
(b) NATIONALITY:
(c) ADDRESS :

LARSEN & TOUBRO LIMITED
An Indian company
L & T House, Ballard Estate, Mumbai 400 001, State of Maharashtra, India

3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
The present invention relates to an interlocking assembly for use in switching devices/circuit breakers. More particularly, the invention relates to an interlocking assembly for switching devices adapted to lock actuation of one switching device when the other is in ON state. The mechanical interlocking assembly of the invention comprises a unique non force-transferring mechanism implying that force due to switching ON of one of the devices is not transferred to the driveshaft or any other internal component of the other device.
BACKGROUND AND THE PRIOR ART
Generally, industries have a backup system for power generation / distribution, which is used when the main power source is discontinued, so that, the critical operations will continue by the help of backup power source, like generator or inverter. Thus there is a need to have a device which will have two power supplies i.e. main power supply and backup power supply at input side of the switch and one output power supply for the load, further these input power supplies must have complete electrical isolation from each other, and only one power supply should get connected to a load at a time.
However, foremost requirement for having two switching devices/circuit breakers in one assembly is that when


one of the switching devices is in operation, the other switching device cannot be made ON. For the above purpose it is required to provide interlocking provision between the two switches such that the switches can be operated one at a time i.e. when one switch is in ON state the other will remain in OFF state and vice versa. In the existing interlocking mechanisms for switching devices it has been found that that most of the mechanism are unable to provide desired interlocking between the switches and sometimes both the switches were made to operate in the same state i.e. ON state. This type of malfunctioning or sometimes intentional/accidental switching on of both the switches at the same time endangers the circuit health and also negatively affects the equipments connected the circuit. The aforesaid problems have been proved to be serious for generation/distribution of power in the industries and therefore there is exits a need to provide for an interlocking assembly which could provide reliable interlocking of the switching device such that only one of the two switching devices/circuit breakers can be made ON at a time.
US6031193 describes an interlock for first and second tandemly aligned circuit breaker switches which respectively have first and second external operating handles thereon oriented such that the operating handles are disposed away from each other when the switches are OFF and towards each other when the switches are ON. The interlock includes a substantially inflexible control member movably and retainably


mounted relative to the switches. The control member has first and second stops, each of the stops being disposed between the operating handles for engagement therewith. The control members are constructed and arranged such that pushing the first operating handle from an OFF to an ON position pushes the second operating handle from an ON to an OFF position. The control member also includes guide structure for guiding the control member along a central groove defined by the existing structure of the switches. However, no non force transferring mechanism is found in this prior art.
US6777628 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. However, no non force transferring mechanism is found in this prior art.


US6617533 describes an interlock for two circuit breakers, with the circuit breakers configured in the same electrical circuit and with each circuit breaker having a cross bar and contact assembly. The interlock comprises a pivot pin mounted a spaced distance from the two circuit breakers. An interlock yoke having two ends, with a notch proximate each end of the yoke and the yoke is coupled to the pivot pin. A first operator rod having a first end is configured to engage the cross bar and contact assembly of one circuit breaker and has a second end configured to engage the notch of the yoke. A second operator rod having a first end is configured to engage the cross bar and contact assembly of the other circuit breaker and has a second end configured to engage the notch of the yoke. When one operator rod is moved by the cross bar and contact assembly of one circuit breaker, that operator rod pivots the yoke, causing the other operator rod to block the operation of the other circuit breaker. However, no non force transferring mechanism is found in this prior art.
Thus there is a need to provide for an interlocking assembly for switching devices/circuit breakers adapted to lock actuation of one switching device when the other is in ON state.
The present inventors have found that a unique design of interlocking mechanism with the component means integrated in a manner can provide a non force


transferring mechanism by which improved and reliable
interlocking can be achieved between the switching
device. This would enable in operating only one switch
at a time.
OBJECTS OF THE INVENTION
Accordingly, one object of the present invention is to overcome the problems/disadvantages of the prior art.
Another object of the present invention is to provide a interlocking assembly for switching devices/circuit breakers for locking actuation of one switching device when the other is in ON state.
Another object of the present invention is to provide a mechanical interlocked switching device arrangement for certain pre-ordained configurations of the states of the switching device.
Yet another object of the present invention to provide a non force-transferring mechanism.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided an interlocking assembly for switching devices/circuit breakers adapted to lock actuation of


one switching device when the other is in ON state, said assembly comprising:
mounting plate defining to be a base for supporting said switching devices/circuit breakers (1 and 2) and other components of the assembly;
interlocking arrangement located on said base, said arrangement comprising lever means rotatably fixed on the base, slider link juxtaposed to said lever means in a manner that rotating movement of said lever operatively establishes contact with said slider „link whereby said link is enabled to perform linear motion;
actuator means for actuating said lever means and slider link, said actuator means communicate with driveshaft of the switch so as to transfer force from driveshaft to lever means;
bracket means mounted on said base, said bracket means accommodating actuator means for the other switch 2, said actuator means having single degree of freedom to move, said bracket means having plural substantially circular holes so as to allow slider link to get disposed in the holes after being actuated by lever means whereby movement of said actuator means of switch 2 is obstructed
wherein said actuator means of switch 2 acting
substantially vertical to slider link thereby not
transferring any force to change the state of switch 1;
and


wherein when switch 2 is in ON state with the actuator means of switch means covering substantially whole length of said bracket means, actuation of switch 1 is obstructed by the actuator means of switch 2 in substantially perpendicular direction whereby no force is transferred to change state of switch 2.
The other objects and advantages of the present invention will be apparent from the description provided hereinbelow with reference to the accompanying figures.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 illustrates the assembly of two switching devices/circuit breakers
Figure 2 illustrates the rear exploded view of the interlocking assembly
Figure 3 illustrates the initial condition of the
switching device where in switching device 1 (breaker
1) is in OFF position and switching device 2 (breaker
2) is in ON position
Figure 4 illustrates the configuration of the switching device


where in switching device 1 (breaker 1) is in ON position and switching device 2 (breaker 2) is in OFF position
Figure 5 illustrates the alternate arrangement where in interlocking mechanism is mounted on the front side of switching devices.
DETAILED DESCRIPTION OF THE ACCOMPANYING FIGURES
The present invention relates in general to safety device for two mechanically interlocked switching devices/circuit breakers. The two multi-pole switching devices/circuit breakers say normal device and alternate device are mounted on a common mounting plate provided with lever means and shaft arrangement, which forms the fundamental mechanical interlocking mechanism. The actuators take actuation directly or indirectly from the mechanism, or any component linked thereto, of respective devices.
The characteristics of a mechanically interlocked system as pertains to switching devices, is that it uses mechanical means to achieve an arrangement which allows only certain pre-ordained configurations of the states of the switching devices. As pertains to the present scenario, the number of switching devices is limited to two and the pre-ordained configuration is that the two devices cannot be brought to the ON condition simultaneously. Any other possible


configuration of the states of the switching devices is allowed. Thus, when one of the switching devices is in the ON condition, the other cannot be switched ON.
In the course of the description of the operation of the mechanical interlocking system, it is assumed that the direction facing from the mechanism towards the switching devices, and perpendicular to the face of the base plate is the upward direction.
The directional assignment is applicable only to the arrangement as shown in figures 1 to 5. This arrangement has been used for illustrative purposes and for the description and explanation of the operation of the mechanism. However, the actual implementation of the mechanism can be done in any different suitable orientation, as defined by space constraints and suitability of component of switching device for deriving actuation from.
In the present invention, the aforementioned condition is achieved by means of the lever and slider link arrangement. When one of the actuators is depressed (assuming that this actuator is the one in contact with the lever), consequent to the corresponding device switching ON, the lever rotates about its axis, pushing the slider link so that it obstructs the path of the other actuator, should it be attempted to switch ON the corresponding device subsequently. Otherwise, if firstly the device corresponding to the actuator near the slider link is switched ON, the actuator obstructs


the path of the slider link, so that the motion of the other actuator is hindered, effectively disallowing the switching ON of the other device.
Figure 1 shows the assembly of two switching devices/circuit breakers, normal device (1) and alternate device (2), each of which have two positions, ON and OFF, indicating the continuity or discontinuity, respectively, of the circuit. These are mounted on a base plate (3) and fixed thereon and stationary in relation to it. These devices . are mechanically interlocked so that both of them cannot be in the ON position simultaneously. It can be considered, for illustrative purposes, that the normal device is connected to a utility power supply and the alternative device is connected to a backup supply. Hence, it becomes obvious, the necessity of the mechanical interlock, which renders the two supplies mutually exclusive, preventing a short circuit.
Figure 2 shows a rear view of the interlocking assembly. The actuators (4) & (5) are shown in the figure. Actuator (5) has single degree of freedom to move inside a bracket means (11) . The actuators take actuation from the drive shaft of the switching devices. They are confined by the base plate in such a manner that in the course of operation, they can perform only vertical motion. Also shown is the Lever (6), which maintains contact with the actuator (4), and connects it to the mechanism. The lever is hinged at a point on its body as shown, so that it is restricted to


perform rotational motion about an axis perpendicular to its body. The lever is hinged by means of the C-bracket (12), which is fixed on the base plate and is held stationary thereon. The lever maintains contact with the Slider link (7). The slider link is essentially a rod, with a small arm protruding from it at one end of its body, perpendicular to it. The rod and arm assembly is rigid and is confined by the L-bracket (14) and the C-bracket in such a manner that it can only perform translational motion along the length of its body. The rotational motion about an axis along its own body is restricted, in the normal course of operation, by the channel formed by the C-bracket. Further, the slider link is provided with a stopper washer, fastened to its body at a suitable position, so as to hold a spring (10), which provides the restoring means for the mechanism. The slider link is confined in the direction perpendicular to the face of the base plate, by means of its positioning so that its body passes through the hole provided in the L-bracket. Further, as can be seen in the figure, a U-bracket (11) is fixed on the base plate, and is held stationary with respect to it. The hole provided in the U-bracket is positioned so that, in the course of operation of the mechanism, the slider link is able to move freely through it. The U-bracket also provides the housing for the actuator (5). This also houses the restoring means for the said actuator. The assembly has two supporting screws (13), which locate a support plate (8), in such a way that it can engage fully with the actuator, and can move along the supporting screws with the vertical


motion of the actuator. Provided along with the screws are two springs (9), which are placed co-axially with the shaft of the supporting screws. These engage with the support plate and form the restoring means for the actuator.
As pertains to the working of the mechanical interlocking system, the demonstration is made of the two mutually exclusive states of operation: one in which the normal device is ON with the alternate device OFF, the other in which the alternate device is ON with the normal device OFF.
When the normal device is ON, as shown in figure 3, the actuator (4), is lowered, and depresses the long arm of" the lever. This forces the lever to rotate about its hinge point, which, by means of the protruding tip on the small arm, pushes the slider link away from its initial position, towards the U-bracket, thus compressing the spring on the slider link. Now, it has been assumed that the alternate device is OFF, which implies that the actuator (5) and support plate assembly is in an elevated position, so that the hole in the U-bracket is unobstructed. Thus, the slider link moves through the hole and positions itself below the support plate. Now, when the alternate device is attempted to be switched ON, the driveshaft pushes the actuator down, which tries to push the support plate downwards, which is obstructed by the slider link rod, and thus, the alternate device cannot be switched ON.


Further, to understand the function of the restoring spring provided on the slider link, if the normal device is switched OFF, the driving force of the driveshaft is removed, which renders the actuator incapable of holding the lever in the inclined position, which, in turn, removes the force it was exerting on the slider link. In the absence of any opposing force, the spring, which was compressed due to the motion of the lever, provides the force which pushes the slider link, by means of the stopper washer, to its original position.
On the other hand, when the alternate device is in the ON condition, the actuator (5) is lowered, and the support plate compresses the springs, placed on the shaft of the supporting screws, by means of the force provided by the drive shaft. This arrangement effectively obstructs the hole on the U-bracket, thus disallowing the motion of the slider link through the U-bracket. Hence, when the normal device is tried to be switched ON, by the process described above, the slider link attempts to pass through the hole in the U-bracket, but is obstructed by the actuator. Hence, the normal device cannot be switched ON.
Again, if the alternate device is switched OFF, the compressed springs (9) will provide the restoring force, required to move the actuator and support plate assembly to the initial position.


The invention has been described in a preferred form only and many variations may be made in the invention which will still be comprised within its spirit. The invention is not limited to the details cited above. The components herein described may be replaced by its technical equivalence and yet the invention can be performed. The structure thus conceived is susceptible of numerous modifications and variations, all the details may furthermore be replaced with elements having technical equivalence. In practice the materials and dimensions may be any according to the requirements, which will still be comprised within its true spirit.


WE CLAIM
1. An interlocking assembly for switching devices/circuit breakers adapted to lock actuation of one switching device when the other is in ON state, said assembly comprising:
mounting plate defining to be a base for supporting said switching devices/circuit breakers (1 and 2) and other components of the assembly;
interlocking arrangement located on said base, said arrangement comprising lever means hinged on the base, slider link juxtaposed to said lever means in a manner that rotating movement of said lever operatively establishes contact with said slider link whereby said link is enabled to perform linear motion;
actuator means for actuating said lever means and slider link, said actuator means communicate with driveshaft of the switch so as to transfer force from driveshaft to lever means;
bracket means mounted on said base, said bracket means accommodating actuator means for the other switch 2, said actuator means having single degree of freedom to move, said bracket means having plural substantially circular holes so as to allow slider link to get disposed in the holes after


being actuated by lever means whereby movement of said actuator means of switch 2 is obstructed
wherein said actuator means of switch 2 acting substantially vertical to slider link thereby not transferring any force to change the state of switch 1; and
wherein when switch 2 is in ON state with the actuator means of switch means covering substantially whole length of said bracket means, actuation of switch 1 is obstructed by the actuator means of switch 2 in substantially perpendicular direction whereby no force is transferred to change state of switch 2.
2. Assembly as claimed in claim 1 wherein lever means comprises rounded projection adapted to generate sliding motion for the slider link.
3. Assembly as claimed in claim 1, wherein the bracket associated with switch 2 is substantially U shaped.
4. Assembly as claimed in claim 4, wherein the bracket comprises
(i) support plate means;
(ii) Screw means holding said support plate means; and


(iii) Spring means mounted on said screw means so as to offer resilient motion to the said support plate means.
5. Assembly as claimed in any of the preceding claims further comprising .such arrangement so as to provide single degree of freedom to the slider link.
6. Assembly as claimed in any of the preceding claims further comprising a substantially support bracket means adapted to provide rotational movement of the lever.
7. Assembly as claimed in claim 1, wherein the slider link further comprises spring means adapted to generate restoring force to restore interlocking mechanism to initial position on completion of operation.
8. An interlocking assembly for switching devices/circuit breakers as substantially herein described and illustrated with reference to accompanying figures.



ABSTRACT
SAFETY LOCKING ASSEMBLY FOR SWITCHING DEVICES
The present invention relates to an interlocking assembly for switching devices to lock actuation of one switching device when the other is in ON state. The assembly comprises mounting plate (3) for supporting said switching devices, interlocking arrangement located on the plate. The interlocking arrangement comprises lever means (6) rotatably fixed on the plate (3), slider link (7), actuator means (5), bracket means (11) accommodating actuator means (5) for the other switch 2. Bracket means (11) allow slider link (7) to get disposed in the holes whereby movement of said actuator means (5) of switch 2 is obstructed such that no force is transferred to change the state of switch 1. When switch 2 is in ON state actuation of switch 1 is obstructed by the actuator means (5) of switch 2 such that no force is transferred to change state of switch 2.
Figure 2