FORM 2
THE PATENT ACT 1970 &
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION:
"Door Interlock for Module in MCC switchboard"
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
Electrical & Automation North Wing, Gate 7, Level 0, Powai Campus, Saki Vihar Road, Mumbai 400 072, INDIA
3. PREAMBLE TO THE DESCRIPTION:
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.

Door Interlock for Module in MCC switchboard
Filed of the invention
This invention related to the interlock of the closed door system for motor control center (MCC).
Background of the invention
In closed door system, it is desirable that system cannot be operated at without closed door condition.
In draw-out feeders of a Switchboard (particularly motor control center-MCC) have been three operating position (Service, Test, Isolation). When Power Contacts and Auxiliary contacts both are engaged it is called as 'service' position. When power contacts are engaged and auxiliary contacts are disengaged it called as 'Test' condition. When both contacts are disengaged it is called as 'Isolation' condition. These three distinct positions of the feeders or module in closed door operated module are achieved by using mechanism. Mechanism has to be operated to achieve service, test, and isolation position. In closed door operated module mechanism is operated through control fascia. By this interlock, it is ensured that module can be operated only in closed door condition. From safety points of view, module should not operate at open door condition.
This interlock server two purpose, 1) it does not allow operator to operate module (mechanism) at open door condition. Operators cannot access the mechanism at that condition. 2) It provides the safety to the operator, from internal arc and short circuit, by preventing open door operation of the module.
In today's scenario module is movable and it is mounted on the tray, is stationary. Service, Test and Isolation positions are marked on the tray at predefined distance.

Power contacts and auxiliary contacts are fixed on rear side of the module. To achieve three positions of module, front door of the switchboard module is to be opened and the module is moved physically. This open door operation is very dangerous to the operator.
So, now a day's closed door operation is preferred compare to open door operation. Service, Test and Isolation Position of the module are achieved without moving the module and with closed-door position. To achieve this racking mechanism is used. At closed door position, for operating the module mechanism handle is used. It is inserted into the control facia and mechanism bracket, and engaged with the mechanism shaft. From safety point of view, it is very necessary to ensure that module should not be operated at open door condition. This is one of the safety features of closed door operated module.
The power/auxiliary contacts in module are not rigidly fixed to the module frame, which is necessary for the movement of contacts without moving the module with respect to the module door. The racking mechanism in the module racks out or racks in Power and auxiliary contacts to achieve Service, Test and Isolation positions. In this case module is not moving, only power and auxiliary contacts moves and door is also closed. The movement of power contact and auxiliary contact is done by module mechanism. This closed door operation is required for safety of operator. To ensure only closed door operation, some interlocks required, which does not allow accessing the module mechanism.
There is need to provide a door interlock for module in MCC switchboard, which does not allow operator to operate module (mechanism) other than closed door condition and unsure that at open door condition, module cannot be operates, thereby providing safety to operator from dangerous effect of open door operation.
Objects of the present invention

Object of the present invention is to provide a door interlock for module in MCC switchboard, which does not allow operator to operate the module at open door condition.
Another object of the present invention is to provide a door interlock for module in MCC switchboard, which ensures safety to an operator from dangerous effect of open door operation.
Yet another object of the present invention is to provide a door interlock for module in MCC switchboard, which allow operator to operate module at only when door is closed.
Summary of the invention
According to the present invention there is provided a door interlock assembly for modular MCC boards to restrict access in open door condition, the assembly comprising:
a door pusher disposed perpendicular against the door, the door pusher having a slant slot thereover;
a interlock lever disposed perpendicularly with respect to the door pusher and over a mechanism bracket, the interlock lever having
a projection slideabely disposed in the slant slot of the interlock
lever,
an opening for pivoting the interlock lever with the mechanism
bracket for oscillating thereof, and
a first and second slots are provided for guiding and restricting the
oscillating motion of the interlock lever; and a spring disposed on the door pusher and restrained against the mechanism bracket for pushing the door pusher away from the mechanism bracket for accessing the

mechanism shaft for operation in closed condition thereby preventing sticking of spark.
Brief description of the figures
Figure 1 shows an internal view illustrating a door interlock assembly of a MCC switchboard in accordance with the present invention in unlocked position;
Figure 2 shows an outer view of a MCC switchboard in accordance with the present invention in unlocked position;
Figure 3 shows an internal view illustrating a door interlock assembly of a MCC switchboard in accordance with the present invention in locked position;
Figure 4 shows an outer view of a MCC switchboard in accordance with the present invention in locked position;
Figure 5 shows a perspective view of an door pusher in accordance with the present invention;
Figure 6 shows a perspective view of an interlock lever in accordance with the present invention;
Figure 7 shows a perspective view of an interlock spring in accordance with the present invention; and
Figure 8 shows a perspective view of a rivet in accordance with the present invention.

Detail 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.
Referring now figures 1, 2, 3 & 4, various views of a door interlock assembly (100) for module in MCC switchboard in accordance with the present invention. The door interlock mechanism (100) includes a door pusher (1) (refer figure 5) , an interlock lever (2) (refer figure 6), an interlock spring (3) (refer figure 7), a mechanism bracket (4), a MS rivet (5) (refer figure 8), a mechanism shaft (6) and a Door (7).
The door pusher (1) pushes his interlock pusher with the door (7) is closed. When the door (7) is opened the door pusher (1) comes out. For module (mechanism) operation, the door pusher (1) should be pushed. Further, the interlock lever (2) has a round portion. The round portion of the interlock lever (2) is inserted in a slot (la) of the door pusher (1). The slot is design such a way that with the linear movement of pusher, lever can rotate along the mechanism shaft. So, this slot converts the linear movement of pusher to rotational movement of lever.
When the open door (7) are in open condition the door pusher (1) blocks the mechanism access. It has rotational movement. The interlock lever (2) is riveted with mechanism bracket. The interlock lever (2) has a first slot (2a) and a second slot (2b). The movement of the lever is restricting by this slot. In pusher, lever mounting slot is design such that with the inside movement of pusher, lever can rotates anti-clockwise direction. When door opens, the door pusher (1) comes out and the interlock lever (2) rotates clockwise direction refer figures 3 & 4.

The interlocking spring (3) is assembled with the door pusher (1). When door is closed the interlocking spring (3) compressed. When door open the interlocking spring (3), which helps the door pusher (1) to come out and the interlock lever (2) to block the mechanism access.
The door pusher (1), the interlock lever (2), the interlock spring (3) are mounted on the mechanism Bracket (4). The mechanism Bracket (4) has the opening to access the mechanism. It is mounted with module mechanism, by which module are operated. The interlock lever (3) is riveted with the mechanism bracket with the MS rivets (5). The rivets (5) have steps configured there over, on which the interlock lever (2) can rotate.
Further, to operate module the shaft (6) has to be rotated. The mechanism bracket (4) is mounted with a Module mechanism. For operating mechanism, handle is required. For insertion of handle in mechanism shaft opening is given in this bracket (4). At open door condition lever (2) is block this handle insertion opening in the mechanism bracket (4). This interlock lever (2) is riveted with mechanism bracket (part 4). The interlock lever (2) and the door pusher (1) are assembled in such a way that with the liner movement of the door pusher (1), the interlock lever (2) rotates along the mechanism shaft. This round portion of the interlock lever (2) is inserted in the slot (la) of the door pusher (1). The slot (la) of the door pusher (1) is design such a way that with the movement of the door pusher (1), the interlock lever (2) rotates.
In open door condition, the door pusher (1) comes out of the module and the interlock spring (3) is in expanding condition. The interlock lever (2) is connected to the pusher (part 1) is in front of mechanism shaft opening. So, for operation of the mechanism shaft (6) is not accessible. So, the module position cannot be changed. As shown in Figure 3.

In closed door condition, the door inside surface pushes the door pusher (1). As, the interlock lever (2) is attached with the door pusher (1), it rotates such that shaft opening at the bracket (4) is cleared. As shown in figure 4. That that condition, module shaft are accessible. Module position can be change. In the door pusher (1), the interlock lever (2) mounting the slot is design such that with the inside movement of the door pusher (1), the interlock lever (2) can rotates anti clockwise direction. The interlock lever (2) also has the first slot (2a & 2b). The movement of the interlock lever (2) is restricting by these slots (2a & 2b). The door pusher (1) slot profile design such that, when door fully closed than only the interlock lever (1) fully cleared the shaft opening. Pusher (part 1) slot and the interlock lever (2) slots are related with each other, so that with the full movement of the door pusher (1), the interlock lever (3) can rotate fully.
At closed door condition, as the door pusher (1) is pressed, the interlock spring (3) is compressed. When the door is open the interlock spring (3) try to get back its original condition, it pushes the door pusher (1). Then the door pusher (1) comes out automatically, as pusher moves lever also rotates in clock-wise direction and block the shaft opening at the mechanism bracket (4). As shown in figure 3.
So, this interlock ensures that at open door condition module cannot be operated. To operate module interlock pusher has to be pressed. This ensures operate safety.
It should be understood that the present invention is not to be limited by the exact details of the illustrated embodiment. However, it is to be taken as the preferred example of the invention and that various changes may be resorted to by a person skilled in the art without departing from the spirit of the invention or the scope of below mentioned claims. Also, the terminologies used herein are for the purpose of description and should not be regarded as limiting.

We Claim:
1. A door interlock assembly for modular MCC boards to restrict access in open door condition, the assembly comprising:
a door pusher disposed perpendicular against the door, the door pusher having a slant slot thereover;
a interlock lever disposed perpendicularly with respect to the door pusher and over a mechanism bracket, the interlock lever having
a projection slideabely disposed in the slant slot of the interlock lever,
an opening for pivoting the interlock lever with the mechanism bracket for oscillating thereof, and
a first and second slots are provided for guiding and restricting the oscillating motion of the interlock lever; and
a spring disposed on the door pusher and restrained against the mechanism bracket for pushing the door pusher away from the mechanism bracket for accessing the mechanism shaft for operation in closed condition thereby preventing sticking of spark.