FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003 COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention: IMPROVED INTERLOCK ASSEMBLY FOR
A SWITCHING DEVICE IN MOTOR CONTROL CENTER
2. Applicants):
(a) NAME : LARSEN & TOUBRO LIMITED
(b) NATIONALITY : An Indian Company
(c) ADDRESS : 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:

TECHNICAL FIELD OF THE INVENTION
This invention relates generally to an arrangement for circuit protection. More particularly, the present invention relates to an improved interlock assembly for a switching device in motor control center to prevent manual error and hazardous situation during racking operation, withdrawals and insertion of module. This invention finds its application in Motor Control Center, Switchboard where any Short Circuit Protection Device (SCPD) or switching device is mounted in module Chassis.
BACKGROUND AND THE PRIOR ART
Switchboard or Motor control centre consists of panels, which having a vertically arranged compartments. These compartments are called module chassis. Module chassis are open to a front face of the cabinet. In the module chassis all the electrical equipments are mounted. Module chassis are two type fixed and draw-out. In draw-out feeders of a Switchboard (particularly motor control center-MCC) there are three operating position (Service, Test, and Isolation). In Service Position both power Circuit and Auxiliary Circuit is connected, and in Test position only power Circuit is connected and Auxiliary Circuit is disconnected. In case of isolated position both power and Auxiliary circuit is disconnected.
During normal operating condition, module remains in service condition and Switching Device remains in 'ON' condition. At that operating condition, if module position is changed from Service to Test condition, then there will be chances of Flash-over or arcing in both incoming and outgoing power contact. For preventing arcing during module operation Switching Device should be is in 'OFF' condition.
Some of the prior arts in the present field of invention are as follows:
US4659884 provides a safety interlock switching device for protecting equipment, which assures the switching-off of the dangerous operating condition in the opened position of the protecting

equipment, and comprises a housing, a toggle lever provided with a pivotably mounted locking lever which has two dead center points and has a cam surface which cooperates with a respective cam surface of an actuating element rigidly mounted on the protective hood and insertable into the housing. A switch is provided which actuates the toggle lever. The toggle lever and the switch are positioned in the housing of the switching device. The housing has an insertion opening into which the actuating element is insertable. In one dead center position of the toggle lever, the locking lever and the actuating element interlock with each other, and in the other dead center position the dangerous operating condition is switched off by the switch, and the actuating element with the protective hood are released.
This is not similar to the present invention as it is a safety interlock switching device for protecting equipment, where interlock mechanism and switching device mounted on a housing, which assures the switching-off of the dangerous operating condition in the opened position of the protecting equipment, where as present interlock assembly is not part of Switching device. It is a part of MCC module, which assures "OFF" condition of switching device during module operation (changing module position from service to test or isolate and vice-versa) and withdrawal of the module from the panel.
US7411139 provides a system comprising a breaker interlock device adapted to mechanically couple a handle of a first circuit breaker to a handle of a second circuit breaker, said breaker interlock device is adapted for said first circuit breaker to be adjacent to said second circuit breaker, said breaker interlock device is adapted for said first circuit breaker and said second circuit breaker to be in a side-by-side orientation, said breaker interlock device comprising: a first ear adapted to clipably attach said breaker interlock device to at least said first circuit breaker; a second ear adapted to clipably attach said breaker interlock device to at least said second circuit breaker; a clip adapted to snapably attach said breaker interlock device to said first circuit breaker and/or said second circuit breaker; and a boomerang-shaped latch adapted to contact said handle of said first circuit breaker and said handle of said second circuit breaker, said boomerang-shaped latch adapted to resist motion of said handle of said first circuit breaker from an OFF first position to an ON second position unless said handle of said second circuit breaker is in an OFF position.

This is a breaker interlock device, between the two circuit breakers mounted side by side. This interlock comprise a breaker interlock device adapted to mechanically resist switching a handle of a first circuit breaker from an OFF position to an ON position when a handle of a second circuit breaker is in an ON position, wherein the first circuit breaker is adjacent to the second circuit breaker. But our interlock is for MCC module, where only single switching device is involved.
US6329615 provides an interlock device using locks to prevent manual actuation of a switch having a handle inlet, and to allow the switch to be actuated manually in a certain sequence of operations determined by using keys for the locks, thereby enabling the switch to pass from a first switching position to a second switching position, the device comprising a first lock and a second lock each operable by means of at least one key capable of being withdrawn from the corresponding lock or of being engaged in said lock only when the lock is in its locked position, a set of cams whose rotation is tied to actuation of the switch and which act on the bolts of said locks to prevent the first lock from being operated so long as the second switch is not in its second switching position and to prevent the second lock being operated by its key as soon as the second switch no longer occupies its first switching position, both locks being disposed in such a manner that their respective bolts, when in the advanced position, close the handle inlet of the switch, the bolt of the first lock being in its retracted position and the bolt of the second lock being in its advanced position when the switch is in its first switching position.
This invention relates to generator circuit in electricity producing station, such as gas turbine installations. This interlock allows the switches to be operated manually in certain sequence of operation determined by keys for the locks. It ensures the operation of the switches in certain sequence.
US5642256 provides an interlock mechanism in a motor control unit for preventing the motor control unit from being engaged with current carrying bus bars within an enclosure when a handle disposed on the motor control unit is in an ON position, the handle controls a switching device disposed in the motor control unit, the interlock mechanism interacts with the switching

device and automatically engages when the control unit is connected to the current carrying bus bars whereby preventing the motor control unit from being disengaged from the current carrying bus bars once the control unit becomes engaged with the current carrying bus bars and the handle is moved to the ON position.
This interlock prevents the motor control unit from being engaged or disengaged with current carrying bus bars within an enclosure when a handle disposed on the motor control unit is in an ON position. This objective is similar to our invention. But, in our invention it also ensures that when switching device is in ON condition, motor control unit or module chassis cannot be withdrawn from the enclosure. Also the method of achieving this interlock is completely different from ours. In our interlock a lever which attached with switching device, converts rotational motion to linear motion to ensure that motor control unit or module chassis cannot be withdrawn from the enclosure.
US5019676 provides a removable control unit of a motor control center that has an auxiliary operator handle linked to a molded case circuit breaker handle for control of the circuit breaker externally of the motor control center cabinet. An interlock slide bar is driven by the auxiliary handle to an extended position to block removal of the unit with the circuit breaker in the ON condition, and follows the handle by gravitational force to a withdrawn position upon movement of the handle to an OFF condition of the circuit breaker, the slide bar abutting a fixed stop prior to the handle reaching the OFF condition to separate the handle from the slide bar in the OFF condition. A spring carried on the interlock slide bar is engaged by the handle to effect driving engagement, compression of the spring occurring only as the handle is nearly in the ON condition.
To achieve that, the present invention provides an interlocking arrangement that ensures OFF position of switching device during draw-out of module from panel. This interlock help prevent unforced manual error and hazardous situation during withdrawals and insertion of module. It only ensures the withdrawals and insertion of module when circuit breaker is in "OFF" condition applicable for draw-out module.

But in the present invention, apart from this it also prevents the operation of the module from service to test and isolate position or vice-versa, keeping module is in inside of the enclosure. Also the method of achieving this interlock is completely different from ours. In this interlock assembly a lever which attached with switching device, converts rotational motion to linear motion to ensure that motor control unit or module chassis cannot be withdrawn from the enclosure.
OBJECTS OF THE INVENTION
A basic object of the present invention is to prevent module operation when Switching Device is in 'ON' condition.
Another object of the present invention is to prevent unforced manual error and hazardous situation during withdrawals and insertion of module if switching device is in 'ON' condition.
Yet another object of the present invention is to prevent arcing during module operation.
These and other advantages of the present invention will become readily apparent from the following detailed description read in conjunction with the accompanying drawings.
SUMMARY OF THE INVENTION
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.
There is provided an arrangement for circuit protection.

According to one aspect of the present invention, there is provided an improved interlock assembly for a switching device in motor control center to prevent manual error and hazardous situation during withdrawals and insertion of module, said assembly comprising an interlock guiding plate configured to guide movement of a switching device interlock plate; an interlock lever attached to a switching device shaft; an interlock lever fixing bracket having profile in conformance to cross section of said switching device shaft; a control facia slider; an interlock locking plate configured to prevent opening of said control fascia slider during switching device ON condition; an interlock plate connected to an interlock lever, said interlock plate adapted to move substantially vertically and inserted into module tray during switching device ON condition; wherein said interlock plate connected with interlock lever and mounted such that 90° rotation of a handle shaft of said switching device adapted to provide a rotation of+45° to -45° of said interlock lever and vice versa in 360° quadrant system; this interlock lever design such a way that with the angular rotation of the switching device shaft, the movement of the interlock plate will be almost linear direction, wherein said switching device interlock plate inserted into a tray means fixed to a panel thereby preventing withdrawal of said module from said panel when said switching device is in ON condition.
Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The following drawings are illustrative of particular examples for enabling methods of the present invention, are descriptive of some of the methods, and are not intended to limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description.
Fig 1 illustrates the Switching Device in 'OFF' condition.

Fig 2 illustrates internal arrangement when the Switching Device is in 'OFF' condition.
Fig 3 illustrates the Switching Device in 'ON' condition.
Fig 4 illustrates internal arrangement when the Switching Device is in 'ON' condition.
Fig 5 (a) illustrates interlock guiding plate.
Fig 5 (b) illustrates interlock lever.
Fig 5 (c) illustrates SCPD interlock lever fixing bracket.
Fig 5 (d) illustrates SCPD interlock guiding plate.
Fig 6 (a) illustrates SCPD interlock plate.
Fig 6 (b) illustrates control facia slider.
Fig 6 (c) illustrates short circuit protection device (SCPD) shaft device.
Fig 6 (d) illustrates switching device.
Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure.

Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.
DETAILED DESCRIPTION OF THE INVENTION
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.
The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
It is to be understood that the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.
By the term "substantially" it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

Accordingly the present invention provides a method to avoid racking operation of feeder module when Switching Device is in 'ON' condition. It also prevents the operation of mechanism (i.e. the mechanism by which Service, Test, Isolation of the Module is achieved), when Switching Device is in 'ON ' condition.
In Fig. 1 when Switching Device is in 'OFF' condition, at that time module feeder position (i.e. Service, test, Isolation) can be change by operating mechanism and module can be draw-out from the panel. But, when Switching Device is in 'ON' condition (Fig.3) module position cannot be change, because at that time mechanism Handle can't be inserted in the Control Fascia. This is due to Switching Device interlock bracket that prevents the opening of Control Fascia Slider.
Moreover When the Switching Device is in 'ON' condition, the interlock plate is also inserted into Tray (fixed with panel), that prevent Pull out (withdrawal) of module from panel. In 'OFF' condition of the switching device, the interlock plate is removed from the tray slot that enables the withdrawal of the module from the panel.
The main components of the arrangement are as follows:
• Interlock guiding plate (1) that guides Switching Device interlock plate during up-down movement of the plate.
• Interlock lever (2), fixed with Switching Device shaft.
• Interlock lever fixing bracket (3) that changes according to changes of Switching Device shaft cross-section and shape.
• Interlock locking plate (4) that prevents the opening of control fascia slider during Switching Device 'ON' condition.
• Interlock plate (5) that move vertically (up-down). During Switching Device 'ON' condition, it is inserted into module tray.
• Control fascia slider (6), by moving this, mechanism handle is inserted into mechanism shaft.
• Switching Device Shaft (7).
• Short Circuit Protection Device (SCPD) or Switching Device (8).

This invention helps us to ensure that when Switching Device is in ON condition, module cannot be draw-out from panel and state of the module position (e.g. Service, Test, and Isolation) cannot be changed.
In fig.l, interlock lever (2) rotate with Switching Device Shaft. One interlock plate (5) is connected with interlock lever. With interlock plate (5) one locking bracket (4) is fixed. Interlock lever is mounted in such a way that, with the 90° rotation of Switching Device Handle shaft (7), lever rotation will be +45° to-45° and vice versa in 360° quadrant system for almost linear rotation of interlock plate.
When Switching Device is in 'OFF' position interlock plate is inside the module and interlock locking bracket is above the mechanism control fascia slider (6). At that time module can be removed from panel or mechanism can be operated by opening the mechanism control fascia slider (6). When Switching Device is in 'ON' position interlock plate is moving downward direction and inserted into tray which is fixed with panel. So module cannot be removed (Draw-out) from panel. With the movement of interlock plate, locking bracket is also moved in downward direction, comes to the front of control fascia (mechanism) slider. It prevents the opening of the slider.
The present invention ensures that withdrawal of module and operation of module take place only when Switching Device is in 'OFF' condition. It also avoids the possibility of Arcing during module operation (i.e. Service to Test and Vice-versa) and Withdrawal of module from panel.
This interlock depends upon the Switching Device handle shaft and it actuates when Switching Device handle rotates. Switching Device handle rotation is angular rotation, but this interlock moves in linear direction. For achieving almost linear rotation of the interlock plate , with angular rotation of Switching Device handle, shaft fixing Leaver is made such that with the 90° rotation of Switching Device handle, Lever rotates +45° to -45° in 360° quadrant and vice-versa during 'ON' and 'OFF' operation of Switching Device.

Lever is fixed with Switching Device Handle Shaft. It varies with shaft cross-section and shape. The variation of Lever is minimized by making uniform lever, only changing one simple bracket depending on shaft. It also solves the problem of inventory of different type complicated lever according to variation Shaft.
Although the embodiments herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the embodiments herein with modifications. However, all such modifications are deemed to be within the scope of the claims.
It is also to be understood that the following claims are intended to cover all of the generic and specific features of the embodiments described herein and all the statements of the scope of the embodiments which as a matter of language might be said to fall there between.

WE CLAIM:
1. An interlock assembly for a switching device in motor control center to prevent manual error and hazardous situation during racking operation, withdrawals and insertion of module, said assembly comprising:
an interlock guiding plate configured to guide movement of a switching device interlock plate;
an interlock lever attached to a switching device shaft;
an interlock lever fixing bracket having profile in conformance to cross section of said switching device shaft;
a control facia slider;
an interlock locking plate configured to prevent opening of said control fascia slider during switching device ON condition;
an interlock plate connected to an interlock lever, said interlock plate adapted to move substantially vertically and inserted into module tray during switching device ON condition;
wherein said interlock plate connected with interlock lever and mounted such that 90° rotation of a handle shaft of said switching device adapted to provide a rotation of +45° to -45° of said interlock lever and vice versa in 360° quadrant system for almost linear rotation of interlock plate.
wherein said switching device interlock plate inserted into a tray means fixed to a panel thereby preventing withdrawal of said module from said panel when said switching device is in ON condition.

2. Assembly as claimed in claim 1 wherein a switching device interlock bracket configured to prevent opening of said control fascia slider thereby preventing insertion of racking mechanism handle into the control fascia.
3. Assembly as claimed in claim 1 wherein said mechanism handle inserted to said mechanism shaft by moving said control facia slider.
4. Assembly as claimed in claim 1 wherein said interlock plate having a locking bracket fixed thereto.
5. An improved interlock assembly for motor control center to prevent manual error and hazardous situation during racking operation, withdrawals and insertion of module as herein described and illustrated with reference to accompanying drawings.