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

Interlocking Assembly for Switchboard Panel Door
Field of the invention
The present invention relates to an electrical switching device and more particularly, to an interlocking assembly for a switchboard panel door for locking with a circuit breaker.
Background of the invention
An electrical circuit breaker is defined as a unit designed to carry, make and break current and protect the equipments connected in an electrical circuit from abnormal conditions like overload, under-voltage, short circuit and the like. The circuit breaker is commonly used as an electrical switching device.
There are two popular versions of the circuit breakers namely, a fixed type and a draw-out type. In the draw-out type, the breaker is removed without dismantling terminals, in order to facilitate maintenance and secure stability. Unlike fixed breakers, draw-out breakers are housed inside a cradle or cassette. The draw-out breakers are racked-in and out from the cradle. The circuit breakers are generally placed inside an electrical switchboard panel having a door. While the breaker is in use that is while conducting current through main contacts or power contacts, the panel door should remain closed. To achieve this, a locking element that provides inter-latching between the panel door and the circuit breaker is used.
In the draw-out type of circuit breaker, positions of the breaker with respect to the cradle are normally defined as 'Disconnected/Isolated', 'Test' and 'Connected/ Service'. In the draw-out type of breaker, the breaker is racked-in by use of a detachable crank from 'Disconnected' position to 'Test position' and then to 'Connected' position and racked out in the reverse order.

When the breaker is racked-in to the 'Test' position, control circuit contacts of the , breaker and the cradle gets connected. When the breaker is completely racked- in to 'Connected' position, the breaker terminals are in contact with the cradle terminals through jaws. In this condition, both the main/power circuit and the control circuit are connected. When the breaker is completely racked-out that is to 'Disconnected' position, both the main circuit and the control circuit are disconnected. In the 'Test' position, the main/power circuit is not connected but the control circuit is connected.
In previous arts, an apparatus was designed for interlocking the switchboard panel door with an interlock component mounted on the cradle that used to work in 'Connected' position that is the apparatus was designed to interlock the panel door , with thQ circuit breaker only in 'Connected' position.
Accordingly, there exists a need to provide an interlocking assembly for a switchboard panel door that overcomes the drawbacks of the prior art.
Objects of the invention
An object of the present invention is to lock a switchboard panel door with a draw-out type of circuit breaker in a 'Test' position.
Another object of the present invention is to provide enhanced safety to an . operator.
Summary of the invention
Accordingly, the present invention provides an interlocking assembly for a switchboard panel door for locking with a draw-out type of circuit breaker. The interlocking assembly comprises a cradle component, an actuating link, a stopper and a panel door component.

The cradle component includes a front top cross bar and a flat link. The flat link is a spring loaded flat link. The flat link includes a hook shaped portion on a front side thereof and a subcomponent attached to the flat link. The subcomponent is mounted on the front top cross bar and includes a limb/leg for supporting the flat link. The leg/limb remains freely suspended in the 'Disconnected' position of the draw-out type of circuit breaker. The actuating link is mounted on a housing of the draw-out type of circuit breaker and capable of pushing the leg/limb of the subcomponent of the cradle component. The stopper is mounted on the front top cross bar of the cradle component. The panel door component includes a cavity that gets anchored with the hook shaped portion of the flat link.
When the draw-out type of circuit breaker starts travelling from a 'Disconnected' position towards a Test' position, the actuating link pushes the leg/limb causing complete rotation and resting of the flat link on to the stopper thereby causing the front hook shaped portion of the flat link to get anchored in the cavity of the panel door component and get latched to achieve an interlocking, and when the draw-out type of circuit breaker reaches to a 'Connected' position, as the flat link is already rotated and inserted inside the panel door component, the panel door remains latched with the draw-out type of circuit breaker till in the 'Connected' position.
Brief description of the drawings
Figure 1 shows a side view of an interlocking assembly for a switchboard panel door, in accordance with the present invention;
Figure 2 shows a perspective view of the interlocking assembly for the switchboard panel door of figure 1;
Figure 3 shows the interlocking assembly for the switchboard panel door in an 'Isolated/Disconnected' position;

Figure 4 shows the interlocking assembly for the switchboard panel door in a Test' position; and
Figure 5 shows the interlocking assembly for the switchboard panel door in a
'Connected' 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 interlocking assembly for a switchboard panel door for locking with a draw-out type of circuit breaker. The interlocking assembly starts functioning just before a 'Test' position is reached and continues to be in a locked position till reaches to a 'Connected' position while doing rack-in operation of the draw-out type of circuit breaker. The switchboard panel door gets locked with the draw-out type of circuit breaker in the 'Test' position as well as in the 'Connected' position and the switchboard panel door remains closed.
The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description.
In a draw-out type of circuit breaker (not numbered), the draw-out type of circuit breaker (hereinafter "the circuit breaker") is supported on a rail assembly (120) (Refer figure 1) or any equivalent draw-out assembly that is an integral part of a cradle assembly (150) (Refer figure 3). The cradle assembly (150) consists of a cradle (not shown), a base plate (not shown), a racking assembly (not shown), a

pair of side plates (not shown) for guiding the circuit breaker and the rail assembly (120). Racking operation is accomplished by the racking assembly mounted on the base plate. The rotation of a detachable crank (not shown) causes the circuit breaker to move in or out of the cradle depending upon the direction of rotation of the crank that is whether a rack-in or a rack-out operation. When a racking handle (not shown) is rotated in a clockwise direction, the circuit breaker is racked in that is from 'Disconnected' - 'Test' - 'Connected' position. On the other hand, when the racking handle is rotated in a counter clock wise direction, the circuit breaker is racked-out that is from 'Connected' to 'Test' to 'Disconnected' position.
Referring to figures 1-5, an interlocking assembly (100) for a switchboard panel door (not shown) for locking with the circuit breaker in accordance with the present invention is shown. Specifically, the interlocking assembly (100) is designed for the switchboard panel door for locking with the draw-out type of circuit breaker in the Test' position.
The interlocking assembly (100) comprises a cradle component (20), an actuating link (40), a stopper (60) and a panel door component (80).
The cradle component (20) includes a flat link (10) and a front top cross bar (12). The flat link (10) includes a hook shaped portion (4) on a front side (not numbered) thereof and a subcomponent (8). In an embodiment, the flat link (10) is . a spring loaded flat link. The subcomponent (8) is attached to the flat link (10) (herein after 'the spring loaded flat link (10)') and mounted on the front cross bar (12). The subcomponent (8) includes a limb/leg (6). The limb/leg (6) supports the flat link (10). The limb/leg (6) is freely suspended in an initial position that is 'Disconnected' position of the circuit breaker as shown by an arrow "A" in figure 3.
The actuating link (40) is mounted on a housing (200) (Refer figure 2) of the circuit breaker. In an embodiment, the actuating link (40) is suitable for left as

well as right hinged panel door.
The stopper (60) is mounted on the front top cross bar (12) of the cradle component (20) and supports the cradle component (20). The panel door component (80) is positioned on the switchboard panel door. The panel door component (80) includes a cavity (70). The cavity (70) anchored in the hook shaped portion (4) of the flat link (10).
Referring again to figures 1-5, during the rack-in operation, as the crank is rotated in the clockwise direction, the circuit breaker starts travelling from the 'Disconnected position towards a cradle (not shown) that is away from an operator (not shown) causing the actuating link (40) to move inside the cradle. As the circuit breaker approaches towards the 'Test' position, the actuating link (40) starts pushing the leg/limb (6) of the subcomponent (8). As the leg/limb (6) is pushed further, the spring loaded flat link (10) of the cradle component (20) supported on the limb/leg (6) starts rotating downwards. Just before the circuit breaker reaches the Test' position, the leg/limb (6) is further pushed by the actuating link (40) that in turn causes the spring loaded flat link (10) to rotate completely thereby resting on to the stopper (60) mounted on the front top cross bar (12). This causes the front hook shaped portion (4) of the spring loaded flat link (10) to get anchored in the cavity (70) of the panel door component (80) and gets latched as shown by an arrow "B" in figure 4. Even after forceful effort door is not opened and thus interlocking is achieved.
On further rotation of the crank in the clockwise direction, the circuit breaker travels further and reaches to the 'Connected' position. As the spring loaded flat link (10) is already rotated and inserted inside the panel door component (80), the panel door remains latched with the circuit breaker till in the 'Connected' position as shown by an arrow "C" in figure 5.

On the counter clockwise rotation of the crank, the circuit breaker is racked-out from the 'Connected' position to the 'Test' position and further to the 'Disconnected' position. Till the circuit breaker reaches to the 'Test' position from the 'Connected' position, the spring loaded flat link (10) remains latched with the switchboard panel door. On further travel from the 'Test' position to the 'Disconnected' position, the leg/limb (6) keeps on rotating upwards as the , actuating link (40) travel towards the operator. Just after the circuit breaker leaves the Test' position, the actuating link (40) leaves contact with the leg/limb (6) of the subcomponent (8) and undergoes complete upward rotation thereby pushing out the front hook shaped portion (4) of the spring loaded flat link (10) from the cavity (70) of the panel door component (80). This result in the front hook shaped portion (4) to get de-latched as shown by the arrow "A" in figure 3.
Advantages of the invention
1. The interlocking assembly (100) resolves the problem of delayed actuation of door interlock's cradle component mentioned in the prior art. Advanced . actuation provides locking of the switchboard panel door with the circuit breaker before the 'Test' position is reached while racking-in and locking of the switchboard panel door with the circuit breaker till the 'Test' position is left while racking-out.
2. The interlocking assembly (100) provides enhanced electrical safety by locking the switchboard panel door with the circuit breaker in both the Test' and the 'Connected' positions wherein the control circuit and the power circuit respectively are electrically 'live'.
3. The interlocking assembly (100) is suitable for both left hinged and right .
hinged panel doors.
4. The interlocking assembly (100) assures an enhanced safety to an operator.

5. The interlocking assembly (100) avoids use of any external lock from outside the panel door.
6. The actuating link (40) facilitates the interlocking assembly (100) to function in 'Test' position of the circuit breaker and makes the cradle component (20) to lock the switchboard panel door in the 'Test' position.
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. An interlocking assembly (100) for a switchboard panel door for
locking with a draw-out type of circuit breaker, the interlocking assembly (100)
comprising:
a cradle component (20) having
a front top cross bar (12). and
a flat link (10) having a hook shaped portion (4) on a front side thereof and a subcomponent (8) attached to the flat link (10), the subcomponent (8) mounted on the front top cross bar (12), the subcomponent having a limb/leg (6) for supporting the flat link (10);
an actuating link (40) mounted on a housing (200) of the draw-out type of circuit breaker, the actuating link (40) being capable of pushing the leg/limb (6) of the subcomponent (8) of the cradle component (20);
a stopper (60) mounted on the front top cross bar (12) of the cradle component (20); and
a panel door component (80) having a cavity (70), the cavity (70) being capable of anchoring the hook shaped portion (4) of the flat link (10),
wherein, when the draw-out type of circuit breaker starts travelling from a 'Disconnected' position towards a 'Test' position, the actuating link (40) pushes the leg/limb (6) causing complete rotation and resting of the flat link (10) on to the stopper (60) thereby causing the front hook shaped portion (4) of the fiat link (10) to get anchored in the cavity (70) of the panel door component (80) and get latched to achieve an interlocking, and when the draw-out type of circuit breaker reaches a 'Connected' position, as the flat link (10) is already rotated and inserted inside the panel door component (80), the panel door remains latched. with the draw-out type of circuit breaker till in the 'Connected' position.
2. The interlocking assembly (100) as claimed in claim 1, wherein the
flat link (10) is a spring loaded flat link.

3. The interlocking assembly (100) as claimed in claim 1, wherein the leg/limb (6) remains freely suspended in the 'Disconnected' position of the draw-out type of circuit breaker.