DESC:TECHNICAL FIELD OF THE INVENTION
The present invention relates to a motor control center unit and more particularly, to safety shutter assembly mechanism which automatically closes off access to bus bars for preventing accidental contact with terminals or contacts. This safety shutter assembly mechanism reduces the risk of inadvertent electrical contact by a technician installing, operating, withdrawing or removing MCC units / modules / feeders / buckets from the enclosure.

BACKGROUND AND THE PRIOR ART
A Motor control center is a multi-compartment steel enclosure to perform various protection, monitoring and control functions in industrial environment. In such motor control centers, three-phase or three-phase plus neutral electric power is fed from main conductors. Within the motor control center enclosure, internal electric power is fed from mains to the horizontal and vertical bus conductors called bus bars.
In motor control center various switchgear, control devices, protective circuit devices, programmable logic controllers, motor drives and so forth are housed in a large enclosure that may be sub-divided into compartments. These compartments are generally draw-out units, typically known as feeders or modules or drawers or buckets. The modules contain electrical components such as one or more circuit breakers, starters, overload protectors, indicating lamps, auxiliary devices. The vertical bus bars distribute power to these compartments.
The vertical bus bars are often mounted on a completely insulated housing and barriers to prevent accidental personal contact. The motor control center units are generally draw-out types and racked-in and racked-out of the control center enclosure to facilitate maintenance, testing and installation. This requires making and breaking of contact between the contact device/ stab assembly/ or jaw assembly and the bus-bars. This in turn requires access opening in the barriers at regular intervals.

MCC unit has 3 different positions service, test and isolation. In service condition moving draw out contacts are engaged with stationary contacts mounted on vertical bus bar or vertical bus bar itself. In test and isolation position both the contacts are disengaged.
When draw-out unit is in service position, there is complete safety, and no possibility of contact with the bus bars. But when the draw-out unit is completely withdrawn from the compartment, the vertical bus bars are clearly visible through the contact opening in the barrier.
Various shutter arrangements for preventing access to the bus bars when the draw-out unit is racked out are available. Safety shutter is a mechanism which isolate live conductor like vertical bus bars from functional unit like module when it is not in service position.
When draw-out unit is in test or isolation position, safety shutter assembly is in closed condition. When the draw-out unit is racked in the enclosure or panel or switchboard or motor control center, the safety shutter slowly starts opening. It opens completely when the unit comes to service condition and moving draw-out contacts are engaged with stationary current carrying contacts or conductor.
The movement of safety shutter mainly depends on the movement of draw-out unit, when motor control center unit is being racked out, the safety shutter starts closing the stationary power contact or terminal or conductor. This assures complete safety of personnel who is installing or working on this draw-out unit. The person will never see live contact even if unit is in isolation position since safety shutter becomes the barrier between live contact and functional unit. Vice versa it will allow engaging contacts when unit is being racked in.
Further while doing research on the existing patented technologies, the inventors have come across few prior patent documents which are cited herein are US 4722693, US 5343355, US 6047873, US 7067747, US 7887346, US 4038585, US 4417108, US 4565908, US 4688144, US 5654871, US 7869194 and US 8248761. However, none of the prior art teaches mechanism as disclosed in the present document.
The present invention aims at providing Automatic shutter operating mechanism that will close on its own as draw-out unit in contact with the bus bars is removed from the enclosure, without any action being taken by an operator and automatically open the shutter as the unit is inserted back into the enclosure to make contact with the bus bars.

OBJECTS OF THE INVENTION
One object of the invention is to overcome the disadvantages/drawbacks of the prior art.
A basic object of the present invention is to provide an assembly mechanism which automatically closes off access to bus bars for preventing accidental contact with terminals or contacts.
Another object of the present invention is to provide a safety shutter assembly mechanism which reduces the risk of inadvertent electrical contact by a technician installing, operating, withdrawing or removing MCC units / modules / feeders / buckets from the enclosure.
These and other advantages of the present invention will become readily apparent from the following detailed description taken 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.
In an aspect of the present invention, there is provided a shutter assembly for a bus bar fixed contacts in a motor control center, said assembly comprising:
a shutter actuation lever facilitate automatic opening of a shutter barrier of said motor control center;
a spring means with bent end(s) connected in said shutter actuation lever for bringing said actuation lever in normal position during closing of said shutter barrier;
a padlock latch assembled in said actuation lever using a latch pin for padlocking said shutter assembly from operating said shutter barrier;
wherein said shutter assembly mechanism provides a automatic opening and closing of said shutter barriers therefore reducing access to said bus bar(s) for preventing accidental contact with the bus-bar(s) fixed contact and a draw out contact(s).

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 to Fig. 5 show different views of an MCC assembly and working of shutter assembly mechanism.
Fig. 6 and Fig. 7 show different parts of the shutter assembly mechanism like Shutter actuation lever, spring, padlock latch and latch pin.
Fig. 8 to Fig. 15 show different features of shutter actuation lever along with entire shutter assembly mechanism of the present invention.
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 numerals 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, present invention provides a shutter assembly for a bus bar fixed contacts in a motor control center for automatically closes off access to the bus bar(s), therefore preventing accidental contact with the bus-bar(s) fixed contact and draw out contact(s).
Construction of the assembly mechanism of the present invention is explained with reference to the accompanying figures.
a) Shutter assembly mechanism (Part 5) can be characterized as consisting of four parts; Part 51 (Shutter actuation lever), Part 52 (spring), part 53 (padlock latch) & Part 54 (latch pin) as shown in Fig. 6 & Fig. 7
b) Fig. 1 to Fig. 5 shows different views of an MCC assembly and working of shutter assembly mechanism.
c) Part 1 is a motor control center (MCC) unit also called as bucket or module or feeder or draw-out unit. Part 1 is a movable component and is racked-in and racked-out of the MCC compartment using guides or rails mounted on the sides.
d) Part 1 generally contains electrical components such as one or more circuit breakers, starters, overload protectors, indicating lamps, auxiliary devices (not shown).
Part 1 has a horizontal frame known as chassis on which draw-out contact device (Part 9) are mounted for giving incoming electrical supply to the unit. Part 1 also has a vertical frame member on which the same draw-out contact device (Part 9) are mounted for giving outgoing electrical supply to the load side of the units.
e) Incoming electrical supply to the unit is fed through Part 2 known as bus bars (vertical). From these bus bars the supply is fed through Part 3 known as bus bar fixed contact. When the withdrawable unit is racked-in and racked-out the said contact device (Part 9) makes and breaks the supply with this Part 3 (fixed contact).
f) When the withdrawable chassis or unit (Part 1) moves inside the motor control center, the rod/pin attached below this chassis also traverse along the cam trajectory to open the safety shutter barrier. This feature facilitate automatic opening of the shutter as the unit is inserted back into the enclosure to make contact with the bus bars. Spring (Part 52) is used to positively bring the shutter actuation lever to its normal position when the draw-out unit is racked out from the MCC frame. The shutter mechanism will close on its own as draw-out unit in contact with the bus bars is removed from the enclosure, without any action being taken by an operator.

g) Padlock latch (Part 53) which rotates around latch pin (Part 54), and gets locked when lifted on to the supporting tray (Part 8), can be used to padlock (Part 10) the entire shutter assembly mechanism from operating the safety shutter barrier (Part 4). This assures complete safety of personnel who is installing or working on this draw-out unit.

h) Fig. 4 shows the safety shutter barrier assembly consisting of Part 41 (shutter housing) and Part 42 (shutter flap).

i) Fig. 5 clearly indicates the movement of MCC unit and safety shutter assembly mechanism.

j) Fig. 8 to Fig. 15 shows the different features of shutter actuation lever (Part 51) along with entire shutter assembly mechanism (Part 5) as listed above in novelties.

Novel constructions feature of the present assembly:
· A shutter assembly mechanism (Part 5) is relatively simple and having few parts.
· The operation of shutter assembly mechanism does not depend upon the force of gravity.
· The shutter actuation system does not include bulky & complex components such as cams, chains, sprockets, metal levers and the like.
· The shutter actuation lever (part 51) is plastic in nature with rigid structure to take care of the loads.
· The shutter actuation lever is very compact with no extension of the mechanism above the draw-out unit chassis frame.
· Padlock latch (Part 53) which rotates around latch pin (Part 54), and gets locked when lifted on to the supporting tray (Part 8), can be used to padlock (Part 10) the entire shutter assembly mechanism from operating the safety shutter barrier (Part 4). This assures complete safety of personnel who is installing or working on this draw-out unit. The person will never see live contact even if unit is in isolation position since safety shutter becomes the barrier between live contact and functional unit, and added safety is provided with padlocking the safety shutter assembly mechanism.
· Cam trajectory (51A) facilitates the conversion from translational movement in ‘Y’ direction to ‘X’ direction. This is required to open the safety shutter barrier to enable the draw-out contact device (Part 9) to make contact with bus-bar fixed contacts (Part 3). (Refer Fig. 5)
· When the withdrawable chassis or unit (Part 1) moves inside the motor control center, the rod/pin attached below this chassis also traverse along the cam trajectory (51A) to open the safety shutter barrier. The profile of shutter actuation lever (51) is such that it forms a ‘V’ shaped construction with the help of 2 limbs, and this functions as a self spring for moving the safety shutter barrier. So to open the barrier extra spring is not required. This feature facilitate automatic opening of the shutter as the unit is inserted back into the enclosure to make contact with the bus bars. (Refer Fig. 9)
· Spring (Part 52) is used to positively bring the shutter actuation lever to its normal position when the draw-out unit is racked out from the MCC frame. The shutter mechanism will close on its own as draw-out unit in contact with the bus bars is removed from the enclosure, without any action being taken by an operator.
· Spring (Part 52) is engaged into shutter actuator lever using a special slot or hook (51M) provided. (Refer Fig. 14)
· After assembly of spring the ends of the spring are bent, to restrict the spring from coming off the shutter actuation lever. (Refer Fig. 6 & Fig. 7)
· A very unique Triangular shaped rib structure (51B) is provided on the back side of shutter actuation lever. This is a crisscross rib pattern, making the lever highly rigid in nature to give more strength. (Refer Fig. 10)
· Very special click-fit structures (51C & 51D) are provided to mount the safety shutter assembly mechanism onto the supporting tray (Part 8) (Refer Fig. 11 & Fig. 4). Once assembled onto the tray, this can’t be removed by hand, ensuring the positive assembly.
· A very unique rest area (51E) for spring (Part 52) is provided, so that the spring doesn’t fall down from the safety shutter assembly. There are 2 rest
areas provided on the bottom side of right limb and left limb of the V-shaped construction of lever. Additionally 2 areas are provided beneath conical hangar (51G) along the circular peripheral edges. (Refer Fig. 12)
· A special conical hangar (51G) is provided for spring on the top side of V-shaped construction at the circular profile to protect the spring from outside exposure. This also acts as a guard for spring, and which will also prevent the spring from coming out of the actuation lever or coming up. (Refer Fig. 12)
· Additionally 2 traps (51F) are provided, each on the top side of the V-shaped limbs, to prevent the movement of the spring in upward direction. (Refer Fig. 12)
· A slot (51H) is provided for assembling padlock latch (Part 53) in shutter actuation lever (Part 51). This is done by inserting latch pin (Part 54) through the holes provided on lever as well on padlock latch. (refer Fig. 13)
· A special feature called scoop for padlock (51K) is provided for easy lifting of the padlock latch (Part 53) and easy gripping for putting the padlock (Part 10) (Refer Fig. 13)
· Arc shaped rib (51N) structure is provided on shutter actuation lever (Part 51) to strengthen the cam trajectory portion. (Refer Fig. 15) ,CLAIMS:1. A shutter assembly mechanism for a bus bar fixed contacts in a motor control center, said mechanism comprising:

a shutter actuation lever facilitate automatic opening of a shutter barrier of said motor control center;

a spring means with bent end(s) connected in said shutter actuation lever for bringing said actuation lever in normal position during closing of said shutter barrier;

a padlock latch assembled in said actuation lever using a latch pin for padlocking said shutter assembly from operating said shutter barrier;

wherein said shutter assembly mechanism provides a automatic opening and closing of said shutter barriers therefore reducing access to said bus bar(s) for preventing accidental contact with the bus-bar(s) fixed contact and a draw out contact(s).

2. The mechanism as claimed in claim 1 further comprising a drawable unit of the motor control center, said unit being racked inside said motor control center, a pin connected below said drawable unit essentially transverse along a cam trajectory of said actuation lever for opening said shutter barrier, thereby enabling a draw-out contact device for making contact with said bus-bar(s) fixed contact of said motor control center.

3. The mechanism as claimed in claim 1 and claim 2, wherein when said drawable unit is racked out from said motor control center, said shutter barrier is closed by the movement of said spring connected to said actuation lever which bring said actuation lever in normal position.

4. The mechanism as claimed in claim 1 further comprising at least click-fit structure on said actuation level for mounting said assembly on a supporting tray of said motor control center.

5. The mechanism as claimed in claim 1, wherein said shutter actuation lever is made up of plastic.

6. The mechanism as claimed in claim 1 and claim 2, wherein said actuation lever is substantially V-shaped having a left limb and a right limb, acting as a self spring facilitating automatic opening of said shutter barrier (s) when said drawable unit of said motor control center inserted into said motor control center to make contact with the bus bar(s).

7. The mechanism as claimed in claim 1, wherein said spring is fixed in a slot provided on said actuation lever having at least two hook(s).

8. The mechanism as claimed in claim 1, wherein said padlock latch rotates around said latch pin and gets locked when lifted on to said supporting tray.

9. The mechanism as claimed in claim 1, wherein a conical hangar is provided on top side of V-shaped construction of said actuation lever at its circular profile preventing said spring from coming out of said actuation lever.

10. The mechanism as claimed in claim 1, wherein an arc shaped rib structure is provided on shutter actuation lever (Part 51) to strengthen the cam trajectory portion.

11. The mechanism as claimed in claim 1, wherein said actuation lever having at least two trap(s) on top side of said V-shaped limb(s) of said actuation lever for preventing movement of said spring in upward direction.

12. The mechanism as claimed in claim 1, wherein a scoop on said actuation lever is provided for lifting and gripping for putting said padlock latch in a slot, said slot is provided for assembling said padlock latch on said actuation lever.

13. The mechanism as claimed in claim 1, wherein said cam trajectory facilitates conversion from translational movement of said actuation lever in ‘Y’ direction to ‘X’ direction during opening of said shutter barrier.