CLIAMS:1. A lockable safety shutter for enclosure of withdrawal type air circuit breaker comprising:
at least one pair of shutter doors configured to slidably open when said air circuit breaker is pushed into said enclosure, and automatically close when said withdrawal type air circuit breaker is pulled out;
at least one locking mechanism configured to lock at least one pair of shutter doors after said withdrawal type air circuit breaker is pulled out, wherein said at least one locking mechanism is configured to put a padlock, and wherein said padlock locks said at least one locking mechanism configured on said at least one pair of shutter doors.
2. The safety shutter of claim 1, wherein said safety shutter has a modular construction having a plurality of locking mechanisms, wherein said safety shutter is configured on each phase such that said plurality of locking mechanisms correspond to different phases and are simultaneously locked by said padlock.
3. The safety shutter of claim 1, wherein a single locking mechanism covers multiple pairs of shutter doors pertaining to multiple phases.
4. The safety shutter of claim 1, wherein said at least one pair of shutter doors is configured with at least one corresponding pair of actuating means such that when said air circuit breaker is pushed in, said at least one corresponding pair of actuating means slides open to allow said air circuit breaker to make contact with live parts.
5. The safety shutter of claim 4, wherein said at least one corresponding pair of actuating means is configured such that it diverges towards its upper end.
6. The safety shutter of claim 4, wherein said at least one locking mechanism comprises at least one window, each window corresponding to said at least one pair of shutter doors, and wherein said at least one window comprises one or more stepped slots, wherein each stepped slot corresponds to said at least one corresponding pair of actuating means.
7. The safety shutter of claim 6, wherein said stepped slot comprises a wider section and a narrower section, and wherein said stepped slot is configured to allow engagement of said at least one locking mechanism with said at least one corresponding pair of actuating means through the wider section, and wherein upon engagement, said at least one locking mechanism holds the said at least one corresponding pair of actuating means at the narrower section.
8. The safety shutter of claim 1, wherein said at least one locking mechanism is configured with at least one pair of projections, wherein said at least one pair of projections is configured to sit adjacent to outer edge of said at least one pair of shutter doors when said at least one locking mechanism is placed on said safety shutter for purpose of locking.
9. The safety shutter of claim 1, wherein said at least one locking mechanism is configured with pair of complimentary steps at its two ends such that when at least two locking mechanisms are configured on at least two corresponding adjacent safety shutters, locking mechanism on one side holds said locking mechanism on the other side in its position.
10. The safety shutter of claim 1, wherein said at least one locking mechanism is configured with a guiding pin that helps during assembly of said at least one locking mechanism with said at least one safety shutter and provides additional locking.
,TagSPECI:TECHNICAL FIELD

[1] The present disclosure generally relates to circuit protection devices used in power supply circuits. In particular, it relates to an air circuit breaker. More specifically, the present disclosure relates to a locking device for safety shutter of an air circuit breaker.
BACKGROUND

[2] The background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[3] Circuit breakers are incorporated in a power supply circuit for protection against potential damage that may be caused to electrical circuit and connected load by potentially damaging occurrences such as but not limited to overvoltage, short-circuit etc. Circuit breakers are designed to detect such potentially dangerous conditions and operate to disconnect the load automatically. After a fault has been diagnosed and rectified, circuit breaker can be either manually or remotely reset and power supply circuit can resume its normal operations/ functioning. They can also be used to isolate the connected load from power supply that may become necessary for various reasons such as maintenance.
[4] Circuit breakers are designed according to their operating environment and intended purpose. They come in many different sizes and shapes. Circuit breakers are also of many different types. The present disclosure pertains to Air Circuit Breakers (ACB) of which there are two types namely, fixed type and extractable or withdrawal type. Fixed types of Air Circuit Breakers are standalone and need no external enclosure for their operations. In extractable or withdrawal type of Air Circuit Breakers, which the present disclosure relates to, the circuit breaker is housed inside an external frame or enclosure that encases the circuit breaker within in such a way that the circuit breaker can be switched off and extracted from within the enclosure for maintenance without removing the termination of bus bars. In extractable/ withdrawal type of circuit breakers, electrical connection between the circuit breaker and external enclosure is maintained with the help of array of movable and flexible contacts. Array of flexible contacts are fixed to the enclosure and remain energized even when the breaker is disconnected and is in withdrawn position. Thus, flexible contacts carry the system potential.
[5] ACBs generally have a safety shutter that provides safety by avoiding any unintentional access to live parts such as flexible contacts in the enclosure, thereby avoiding resultant potential hazard that can occur to maintenance engineer or any other workmen in the vicinity of installation. However, safety shutters are not foolproof if tampered with, and therefore purpose of safety can be better served if these shutters can be locked in closed position in order to prevent any possibility of unauthorized access.
[6] In state of art arrangements, a separate actuation link extending from the safety shutter is provided, which when pressed by the circuit breaker rear housing, opens the shutters to provide access to moving contacts of circuit breaker to make contact with flexible contacts to facilitate completion of circuit. The actuating link when pulled and padlocked prevents the opening of safety shutter.
[7] The prior art suffers from drawbacks such as fitment of the locking arrangement is done on individual phases separately and therefore is not user friendly. Further, fitment of locking arrangement is not smooth and performance after fitment is not effective.
[8] There is therefore a need for locking mechanism for shutters of ACBs that locks all the phases simultaneously, can be assembled/disassembled easily, and whose performance after locking is satisfactory and fool proof.
[9] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
[10] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
[11] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[12] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[13] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.
OBJECTS OF THE INVENTION

[14] It is an object of the present disclosure to enhance safety for the maintenance personnel working on air circuit breakers.
[15] It is an object of the present disclosure to provide safety shutters for withdrawal type air circuit breakers that can be locked to avoid any chance of their unintentional opening.
[16] It is an object of the present disclosure to provide safety shutters for withdrawal type air circuit breakers that are modular.
[17] It is an object of the present disclosure to provide a mechanism to lock shutters of a withdrawal type Air Circuit Breaker.
[18] It is an object of the present disclosure to provide a locking mechanism that is modular.
[19] It is an object of the present disclosure to provide a locking mechanism that inspite of being modular can lock shutters of all phases at the same time.
[20] It is an object of the present disclosure to provide a locking mechanism for safety shutters that can be easily and reliably assembled / disassembled from the air circuit breaker.
[21] It is an object of the present disclosure to provide a padlock feature in the safety shutter locking mechanism of an Air Circuit Breaker so that it cannot be opened by an unauthorized person thus enhancing safety and making it fail safe.
SUMMARY

[22] Aspects of the present disclosure generally relate to a safety device for withdrawal type air circuit breakers that incorporate shutters in their enclosure to close openings that provide access to live flexible contacts so as to prevent accidental contact with the live contacts.
[23] In an aspect, the present disclosure provides safety shutters for withdrawal type air circuit breakers that can be locked to avoid any chance of their unintentional opening. The safety shutter disclosed in the present disclosure is modular type in which one shutter can be used on one phase and each of the phases can have identical safety shutter.
[24] In an aspect, the present disclosure provides for locking mechanism for shutters of a withdrawal type ACB so that it is not possible to unintentionally open the shutters – an act that can be hazardous for maintenance personnel working on the Air Circuit Breakers – thus ensuring safety. In an aspect, locking mechanism disclosed in the present disclosure is also modular type and a number of identical locking mechanisms can be used to lock different phases.
[25] In another aspect, the present disclosure provides a locking mechanism that, inspite of being modular, locks all phases of the ACB simultaneously at the same time thus saving time in assembly.
[26] In another aspect, locking mechanism disclosed in the present disclosure can be locked with a padlock to secure locking and make it failsafe. In an aspect, only one padlock can lock locking mechanism of all phases simultaneously.
[27] Various objects, features, aspects and advantages of the present disclosure will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like features.
BRIEF DESCRIPTION OF DRAWINGS

[28] The diagrams are for illustration only, which thus are not a limitation of the present disclosure, and wherein:
[29] FIG. 1(a) illustrates an exemplary perspective view of a safety shutter of a withdrawal type ACB in accordance with embodiments of the present disclosure.
[30] FIG. 1(b) illustrates an exemplary pair of actuating means configured on shutter doors in accordance with embodiments of the present disclosure.
[31] FIG. 2(a) illustrates an isometric view of an exemplary safety shutter locking mechanism for locking of safety shutters in accordance with embodiments of the present disclosure.
[32] FIG. 2(b) illustrates front view of an exemplary safety shutter locking mechanism for locking of safety shutters in accordance with embodiments of the present disclosure.
[33] FIG. 3 illustrates a perspective view of an exemplary padlock in accordance with an embodiment of the present disclosure.
[34] FIG. 4(a) illustrates an exemplary perspective view with safety shutter locking mechanism positioned on safety shutters of all three phases in accordance with an embodiment of the present disclosure.
[35] FIG. 4(b) illustrates an exemplary close up view of locking mechanism indicating seating of one end of locking mechanism on safety shutter in accordance with an embodiment of the present disclosure.
[36] FIG. 5 illustrates an exemplary view of enclosure of air circuit breaker with two safety shutter locking mechanisms positioned to lock all three phases and both upper and lower rows of shutter doors in accordance with an embodiment of the present disclosure.
[37] FIG. 6 illustrates an exemplary alternate design for safety shutter locking mechanism in accordance with an embodiment of the present disclosure.
DETAILED DESCRIPTION

[38] Unless the context requires otherwise, throughout the specification and claims which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.”
[39] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
[40] As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
[41] The headings and abstract of the disclosure provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.
[42] Reference will now be made in detail to the exemplary embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.
[43] The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.
[44] Embodiments of the present disclosure generally relate to a safety device for withdrawal type Air Circuit Breakers. In an aspect, the present disclosure provides for a safety shutter for enclosure of withdrawal type ACB that is modular and can be configured on enclosure to cover one phase. The safety shutter incorporates features that can be used to position a locking mechanism such that these shutters cannot be opened unintentionally.
[45] In an embodiment, the present disclosure provides a locking mechanism that can lock shutters of a withdrawal type Air Circuit Breaker, thereby preventing their unintentional or accidental opening that can be hazardous and may lead to electrocution of maintenance persons working on enclosure of the ACB.
[46] In an embodiment of the present disclosure, the disclosed locking mechanism is modular such that it can be used for one safety shutter covering one phase of ACB or multiple safety shutters covering a number of phases of ACB. In an aspect, the disclosed locking mechanism, despite being modular, can lock all the phases of the ACB simultaneously at the same time, and thus does not involve locking of individual phases, making it easier and faster to lock the shutters.
[47] In yet another embodiment, locking mechanism of the present disclosure incorporates feature that can be used to put a padlock so that only a person authorized to open the lock can do so, thereby further enhancing the safety and making it fool proof. In an aspect only one padlock is used to lock all phases simultaneously.
[48] In an embodiment an alternate configuration of single piece locking mechanism that can lock all phases is also disclosed.
[49] FIG. 1(a) illustrates a perspective view of a safety shutter 100 of withdrawal type Air circuit breaker. Depicted therein is a shutter that can cover back of enclosure that corresponds to one of the phases. It incorporates plurality of pair of shutter doors 102 each pair having two doors. The exemplary figure FIG. 1(a) has 6 pairs of shutter doors 102, with three doors being configured in each row of the two rows 150-1 and 150-2.The upper row 150-1 and lower row 150-2 correspond to top and bottom terminal adapters of the ACB respectively. The shutter doors 102,as depicted, can remain in shut position under force of springs 104, thereby covering the flexible contacts configured on enclosure behind the shutter. There can be two springs for each door positioned at two ends - upper and lower ends of the door 102. The doors, when actuated by suitable means, can slide sideways to provide access to flexible contacts with which moving contact configured on ACB can establish electrical connectivity thereby energizing the ACB.
[50] The safety shutter 100 can be configured with a hook 106 and a slot 108 at its top side and bottom side respectively as means to fix it with rear of circuit breaker enclosure, details of which shall be explained in subsequent paragraphs. Safety shutter 100 can also incorporate two padlock brackets 110,each corresponding to each row 150-1 and 150-2 of shutter doors 102, configured for insertion of padlock after positioning of locking mechanism to prevent opening of shutter doors 102 by an unauthorized person.
[51] In an embodiment, each shutter door 102 can be configured with actuating means 112 that can help to slide shutter doors 102 sideways to open them when actuated by suitably configured actuating means that would normally be positioned on ACB. There can be a plurality of pairs of lugs with each pair comprising two actuatingmeans112 positioned adjacent to each other on two shutter doors 102 that comprise a pair. In the exemplary safety shutter depicted in FIG. 1(a), two pairs of actuatingmeans112 have been shown on each pair of shutter doors.
[52] FIG. 1(b) illustrates an exemplary pair of actuatingmeans112 configured on shutter doors 102 that comprise a pair. As depicted, actuating means112 can be V shaped diverging towards their upper end such that combined upper width 202 of pair of actuating means112 at their upper end is more than their combined lower width 204 at their root/lower end. In an embodiment, these diverging V shaped actuating means 112 can be additionally used to position shutter locking mechanism such that the shutter doors cannot be opened unintentionally.
[53] In an embodiment, safety shutter 100 is modular in design with each safety shutter 100 covering one phase, wherein, for a multi-phase system, a number of such safety shutters can be used adjacent to each other, depending upon the number of poles to cover all phases. Alternatively, if situation (such as a multi pole ACB being used for single pole application) so demands, shutters not covering all the phases can also be used along with its locking mechanism with shutter and locking mechanism being equally effective.
[54] FIG. 2(a) illustrates an exemplary perspective view of a set of safety shutter locking mechanism 200. The figure depicts three locking mechanisms 202, each covering one of the safety shutters 100 corresponding to one phase. In practice, number of locking mechanisms 202 in a set 200 can be same as the numbers of shutters covering different phases. However, as would be apparent from subsequent description, it is also possible to use only one or more than one locking mechanisms 202 irrespective of number of shutters with equal effectiveness to ensure safety of shutter to which it is configured. Locking mechanism 202 can be of rectangular cross section with various elements for locking configured on it along its length. Locking mechanism 202 can include locking windows 204 that can be configured to hold pairs of actuating means112 of a pair of shutter doors 102 so as to lock them in closed position. The locking mechanism 202 can also incorporate a plurality of pair of projections 206 that can be configured to sit adjacent to outer edge of shutter doors 102 when the locking mechanism 202 is placed on safety shutter 100 for purpose of locking the safety shutter 100.
[55] In an embodiment, plurality of pairs of projections 206 - each pair having two projections - can be spaced so as to hold a pair of shutter doors 102 between them so as to prevent them from sliding outwards. Number of pairs of projections 206 in a locking mechanism can be same as number of pairs of shutter doors 102 in a safety shutter 100. The exemplary locking mechanism 202 depicted in figure 2(a) is configured with three sets of projections 206 to hold three sets of doors configured in each row150-1 and 150-2 of the exemplary safety shutter 100.
[56] In an embodiment, one end of locking mechanism 202 (left side in the exemplary locking mechanism 202) can be configured with a guiding pin 208 that can be helpful during assembly of the locking mechanism 202 with the safety shutter 100 and can also provide additional locking. Other end of the locking mechanism 202 can incorporate a padlock lug 210 that can be configured to suitably engage with padlock bracket 110 of safety shutter 100 to provide means for putting a padlock so that locking mechanism 202 can be removed only by a person who is authorized to do so.
[57] In an embodiment, locking mechanism 202 can incorporate a pair of complimentary steps 212 and 214 at its two ends such that when two locking mechanisms 202 are placed on adjacent safety shutters 100, locking mechanism 202 on right side holds down the other locking mechanism 202 that is placed on left side as depicted at 216. Thus, in a situation where more than one locking mechanisms 202 are to be placed on a number of safety shutters 100 corresponding to different phases, the exemplary locking mechanisms 202 can be configured on safety shutter 100 on extreme left first and thereafter adjacent one in sequence. In similar embodiment, removal of locking mechanisms 202 can be done starting from right extreme onwards.
[58] FIG. 2(b) illustrates an exemplary front view of a set of safety shutter locking mechanism 200 having three locking mechanisms 202, one for each safety shutter 100 corresponding to three phases. Depicted therein are details of an exemplary window 204 that has been configured to engage with a pair of actuating means112 of a pair of shutter doors 102. The window 204 can incorporate two slots, one each on upper and lower side, where each of these slots can be stepped having a wider section 218 and a narrower section 220. The wider section 218 and narrower section 220 can be configured to have a smooth slide fit with combined upper width 202 of pair of actuating means112 at their upper end and their combined lower width 204 at their root/lower end respectively. In an embodiment, pair of two slots, one each on upper and lower side of window 204 can be configured to hold a separate pair of actuating means112 configured on one pair of shutter doors 102.
[59] In an embodiment, locking mechanisms 202 can be fitted on safety shutter 100 by inserting wider section 218of window 204 around combined upper end of pair of actuating means112, pushing it towards bottom/root of pair of actuating means112 and thereafter pushing locking mechanism 202 down so that narrower section 220 of window 204 engages with combined lower width 204 of actuating means112. Locking mechanisms 202 can thus prevent opening of corresponding shutter doors 102 by holding their actuating means112 within narrower section 220 of slot in window 204. Above described locking of shutter doors 102 can be an additional locking in addition to locking of shutter doors 102 by pairs of projections 206 as explained in earlier paragraph.
[60] In another embodiment, engagement of window 204 with pair of actuating means 112 can prevent accidental or unintentional removal of locking mechanism. As is apparent, removal of locking mechanism 202 from shutter can require above mentioned two steps repeated in reverse order. Such an engagement can thus prevent accidental or unintentional removal of locking mechanism as it requires a conscious and deliberate two step action.
[61] In an embodiment, safety can be further enhanced by providing means to ensure that nobody other than one authorized to remove locking mechanism 202, can do so. The requirement can be met by means to configure a padlock such as one depicted in FIG. 3 on the locking mechanism 202. It may be noted that lock depicted in FIG. 3 is only exemplary and any other type of lock such as number lock; electronic lock etc. can be used to securely lock the locking mechanism 202.PadlockLug 210 incorporated on locking mechanism 202 can align with padlock bracket 110 of safety shutter 100 and both these lugs can be configured with slots to insert a padlock 300 and lock the locking mechanism 202 so that none other than one holding key or combination number as the case may be of padlock 300 can open and remove locking mechanism 202, making the locking system of the present disclosure failsafe.
[62] FIG. 4(a) illustrates an exemplary view 400 of a set of safety shutters 100 along with sets of safety shutter locking mechanism 200 positioned on three phases in accordance with embodiments of the present disclosure. Depicted therein are two sets of safety shutter locking mechanism 200 configured on each of upper row 150-1 and a lower row 150-2 corresponding to top and bottom terminal adaptors of the ACB respectively. The figure also depicts window 204 holding pair of actuating means112 of middle pair of shutter door 102 in narrower section220 of its slot. Each of these sets of safety shutter locking mechanism 200 can be configured on set of safety shutters 100 covering all phases of ACB, starting from left side placing one locking mechanism 202 at a time that involves aligning wider section 218 of slot on window 204 of locking mechanism 202 with pair of actuating means112 of middle shutter door 102, pushing the locking mechanism 202 towards bottom/root of pair of actuating means112 and thereafter pushing locking mechanism 202 down such that a narrower section 220 of slot on window 204 engages with pair of actuating means112. Simultaneous to above while the locking mechanism 202 is being pushed down, three pairs of projections 206 of locking mechanism 202 can engage with outer sides of each pair of shutter doors 102 thereby locking each pair of the shutter doors of respective row150-1 and 150-2 and phase. In an embodiment if situation demands, only one locking mechanism 202 can be placed on one safety shutter 100 covering one phase and a padlock placed between padlock lug 210 of locking mechanism 202 and padlock bracket 110 of safety shutter to secure locking and make it fail safe.
[63] In an alternate embodiment involving locking of more than one safety shutter 100 covering more than one phase, safety shutter 100 pertaining to next phase on right side can be configured with locking mechanism 202. During placement of next locking mechanism 202, step 212 configured on its left end can engage with step 214 of locking mechanism 202 placed earlier on left side thereby preventing upward movement of locking mechanism 202 placed earlier. As upward movement of locking mechanism 202 is necessary to disengage it from pair of actuating means112, locking mechanism 202 placed earlier cannot be removed without first removing right side locking mechanism 202. After last of the locking mechanism 202 has been configured on last of the safety shutter 100 a padlock 300 can be placed between padlock lug 210 of last locking mechanism 202 and padlock bracket 110 of last safety shutter 100 that can ensure that last of the locking mechanism 202 cannot be removed without opening of padlock 300. Since any other locking mechanism 202 placed on left side cannot be removed without first removing right side locking mechanism 202, above placement can ensure that safety shutters pertaining to all phases of ACB are securely locked in failsafe manner.
[64] FIG. 4 (b) illustrates a close up view depicting engagement of guiding pin 208 of locking mechanism 202 with a slot451configured on safety shutter 100 The pin 208 can be helpful during assembly of the locking mechanism 202 with the safety shutter 100 as it is pushed down for engaging the narrower section 220 of window 204 with pair of actuating means112 and can also provide additional sideways locking.
[65] FIG. 5 illustrates an exemplary enclosure 500 of withdrawal type ACB assembly configured with plurality of safety shutters 100 and Safety Shutter Locking Mechanisms 200 in accordance with embodiments of the present disclosure. The exemplary enclosure 500 comprises of three phases each covered by a safety shutter 100 and set of three safety shutters 100 secured with two sets of Safety Shutter Locking Mechanisms 200 – one securing each row 150-1 and 150-2 of shutter doors 102. Each of the safety shutters 100 can be assembled with back panel of enclosure 500 by means of hook 106 of safety shutters 100 that can be inserted around a crosspiece 502 on top of back panel of the enclosure 500.Bottom of the safety shutters 100 can be fixed to bottom horizontal crosspiece 504 of the enclosure 500 by means of suitable screws through slot 108 of safety shutters 100.
[66] FIG. 6 illustrates an alternate configuration of locking mechanism 600 in accordance with an embodiment of the present disclosure. In alternate configuration locking mechanism 600 can be of one piece construction covering all phases. The exemplary locking mechanism 600 is configured to cover four safety shutters 100 corresponding to four pole application with each safety shutters 100 comprising of rows 150-1 and 150-2 of three pairs of shutter doors 102. In another embodiment, windows can be configured to hold only one pair of actuating means112 of a pair of shutter doors 102 and accordingly window 602 incorporates only one stepped slot configured in the same way as in earlier embodiment with wider section 218 and narrower section 220. In another embodiment there can be a window 602 for each pair of shutter doors 102 and some of these can be placed in the lower part of locking mechanism 600 such as window 604. The exemplary locking mechanism 600 can incorporate four pins 606 to guide locking mechanism 600 in corresponding slot 451 configured on safety shutters 100 during assembly. It can incorporate a lug 608 at center to put a padlock 300 for secure and failsafe locking.
[67] The present disclosure has been described generally in relation to Air Circuit Breakers used with three phase 3 pole power supply circuits. However this design can be suitably modified and adopted for Air Circuit Breakers used with three phase 4 pole power supply circuits.
[68] The present disclosure is not restricted to the particular embodiment shown in the drawings or as described above. Thus, for example, Safety Shutter Locking Mechanism of the present disclosure can be used with the Circuit Breakers of all types of switch gears.
[69] As used herein, and unless the context dictates otherwise, the term "coupled to" is intended to include both direct coupling (in which two elements that are coupled to each other contact each other) and indirect coupling (in which at least one additional element is located between the two elements). Therefore, the terms "coupled to" and "coupled with" are used synonymously. Within the context of this document terms "coupled to" and "coupled with" are also used euphemistically to mean “communicatively coupled with” over a network, where two or more devices are able to exchange data with each other over the network, possibly via one or more intermediary device.
It should be apparent to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims. Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refers to at least one of something selected from the group consisting of A, B, C …. and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.
ADVANTAGES OF THE INVENTION

[70] The present disclosure enhances safety for the maintenance personnel working on air circuit breakers.
[71] The present disclosure provides safety shutters for withdrawal type air circuit breakers that can be locked to avoid any chance of their unintentional opening.
[72] The present disclosure provides safety shutters for withdrawal type air circuit breakers that are modular.
[73] The present disclosure provides a mechanism to lock shutters of a withdrawal type Air Circuit Breaker.
[74] The present disclosure provides a locking mechanism that is modular.
[75] The present disclosure provides a locking mechanism that despite of being modular can lock shutters of all phases at the same time.
[76] The present disclosure provides a locking mechanism for safety shutters that can be easily and reliably assembled / disassembled from the air circuit breaker.
[77] The present disclosure provides a padlock feature in the safety shutter locking mechanism of an air circuit breaker so as to enhance the safety and make it fail safe by preventing opening of locking mechanism by an authorized person.