FORM 2
THE PATENTS ACT, 1970
COMPLETE SPECIFICATION
(See Section 10)
DUAL MODE DOOR INTERLOCK FOR SWITCHING
DEVICES numbered as dated
INVENTORS:
1. CHANDRAKANT PATIL
APPLICANT:
LARSEN & TOUBRO LIMITED
L&T House, Ballard Estate, P.O. Box No. 278,
Mumbai, 400 001, Maharashtra
INDIA.

DUAL MODE DOOR INTERLOCK FOR SWITCHING DEVICES
A) TECHNICAL FIELD
[0001] The present invention generally relates to an interlocking mechanism used for interlocking a mechanical switch mounted inside the panel/enclosure with the panel/enclosure door. More specifically it relates to a dual mode interlock for electrical switching device such as molded case circuit breaker, changeover switches with the panel door.
B) BACKGROUND OF THE INVENTION
[0002] Switching devices such as circuit breaker, switch fuses, changeovers and like are generally used to provide protection against over current, under voltage supply and or line leakages to the end product. These electrical switching devices typically have two operating handle positions corresponding to status of the separable contacts. For example, these positions include an ON position, in which the separable contacts are closed and an OFF position in which the contacts are open. Some switching devices have a third position which corresponds to a tripped condition in which the contacts are tripped open.
[0003] Switching devices are usually installed in an enclosure so that the entire control and distribution network arranged in the form of metallic sheets and/or cable wires are housed


inside the enclosure. All the operating means are arranged outside the enclosure to prevent an access to the high voltage sections to eliminate the generation of a potential hazard. It is often desirable or essential that the settings of the switching devices remain undisturbed during a maintenance operation. Unauthorized or inadvertent changing of the position of these breakers could result in unwanted interruptions to service or operations and serious damage to an electrical apparatus, or even serious harm to a person. For example, accidental actuation of a circuit breaker might result in electrocution or shock to a workman performing electrical work or repair on equipment downstream from the circuit breaker.
[0004] The operating means hence forth called as handle are mounted outside the enclosure and are connected by means of a connector shaft to the device located inside the enclosure. Thus when a handle is operated from outside the enclosure, the motion is directly transmitted to the operator resulting in a change of state of the operator. The safety standards may require the provision for interlocking enclosed electrical switchgear and control devices. The interlocks are desirable to permit the access to the interior of an enclosure only when the control devices therein are in OFF state or to permit operation of the control devices to an ON state only when the door of the enclosure is in particular condition.
[0005] The prior art (US4806710) discloses an interlock for an electrical equipment enclosure where in the interlock prevents the switch from being closed when the door is not latched and includes a drive/latch member carried by the door and a locking member carried by the enclosure which cooperate to retain the drive/latch in a position to prevent the door from being opened when the switch is in the closed position.


[0006] The prior art (US4074091) discloses an operating mechanism for enclosed switchgear having defeater interlock. The operating mechanism permits access to and/or operation of enclosed switchgear only under designated conditions. It permits opening of the enclosure door only when switchgear within the enclosure is in an off or other wise safe state, and which permits actuation of the switchgear to an on state only when the door is closed.
[0007] The prior art (US4405844) discloses a door interlock for electrical apparatus. It includes a switch with in the enclosure; it permits the door of the enclosure to be opened only if the electrical apparatus is in a predetermined condition, such as switch closed. The interlock prevents the switch from being re-closed as long as the door is open. A latch holds the door closed if the switch is closed, if the door is locked closed by a door lock, or if both conditions obtain. If the switch is opened while the door is locked closed by the door lock, the latch continues to latch the door closed.
[0008] Apparatus presently available are providing door interlocking in ON and OFF state of the breaker. Door interlocking in OFF state is possible when it is padlocked that is door interlocking and padlocking happens at the same time. Sometimes there are requirement on the field that when the switch is padlocked with door mounted handle to avoid actuation; door opening should be possible to access the switch for maintenance.
[0009] Thus none of the prior art discloses a mechanism to have an option for interlocking as well as not interlocking the door when the switch is in OFF condition. Hence there is a need to develop a flexible dual mode door interlocking system for switching devices to allow the opening of the door during the locking of the switch with the door to enable access to


the switch for maintenance, when the switch is in off condition. Also there is a need to open the door when the switch is in ON condition.
C) OBJECT OF THE INVENTION
[0010] The primary object of the present invention is to provide a dual mode door interlock system for switching devices for interlocking electrical switching device such as molded case circuit breaker, switch disconnector, changeover switches with the enclosure/panel door.
[0011] Another object of the present invention is to provide a dual mode door interlocking system to provide an option for interlocking as well as for not interlocking the door of the housing, when the switch is in OFF condition.
[0012] Yet another object of the present invention is to provide a dual mode door interlocking system for the switching devices to ensure door interlocking operation during the ON condition of the switch, opening of the door during the ON condition of the switch using a simple tool, auto-restoration of the door during the ON condition of the switch and optional door interlocking facility in the OFF condition of the switch.
[0013] Yet another object of the present invention is to provide a dual mode door interlocking system for switching devices with a simplified handle assembly. A single internal component sliding plate is designed in such a way that is achieves all the features of interlocking in OFF/ON, defeating in ON, autorestoration.


[0014] Yet another object of the present invention is to develop a dual mode door interlocking system provided with simple mechanism of sliding plate to achieve the door interlocking operation with a handle assembly.
[0015] Yet another object of the present invention is to develop a dual mode door interlocking system for switching device to padlock the actuating handle without performing the door interlocking operation to restrict the actuation of switch by unauthorized person and there by enabling the maintenance person to access the switch mounted inside the panel board.
[0016] These and other objects and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.
D) SUMMARY OF THE INVENTION
[0017] The abovementioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.
[0018] The various embodiments of the present invention provide a provision for interlocking a mechanical switch mounted inside the panel/enclosure with the panel/enclosure door. The purpose of the invention is to develop a flexible door interlocking system wherein the door opening is possible to access the switch for maintenance when the switch is padlocked. While padlocking the actuating handle mounted


on the panel door, operator have the flexibility to have padlock with interlocking of the panel door or have padlock without interlocking of the panel door.
[0019] According to one aspect, the present invention provides a configuration and arrangement to get door interlocking in ON state, Defeating only with use of tool, autorestoration of the door, optional door interlocking in OFF state of the switch. It uses a novel mechanism for interlocking, defeating and autorestoration of the switch with the panel/enclosure door.
[0020] An interlocking assembly according to the embodiment of the present invention consist of a Handle which is screwed to coupler, through the E-plate. The handle assembly is simple and uses minimum components; it uses a sliding plate concept to achieve interlocking of the mechanical switch inside the panel, with the panel door. The Handle assembly is mounted on the panel door with screws and the switch is mounted inside the panel. In OFF state of the switch, the shaft pin is vertical and for off state of handle, slot in the coupler is always vertical. Keeping the handle in OFF state would engage the shaft with the coupler slot in the handle assembly, thus switch can be operated with the handle.
[0021] If either handle assembly or shaft is not in the desired position, there will not be any engagement between the two, thus prohibiting/preventing the wrong indication of switch position on the handle or unintentional nondesired operation of the switch. Thus the arrangement ensures OFF position of the handle for OFF state of the switch and ON position of the handle for ON state of the switch.


[0022] According to the embodiment of the present invention a handle assembly includes a locking tag hinged in the handle with a pin. A Locking tag is rested on the padlock lever, which is inserted in to the hole provided on the handle. A Sliding plate, loaded with the spring slides along the slots provided on the escutcheon (E) plate. Pip on the sliding plate protrudes out of the E-plate and a Shroud cover is click fitted on to the E-plate. The entire handle assembly is fitted on the panel or enclosure door using Screws. The door of the panel board or enclosure can be opened to access switch mounted inside the enclosure.
[0023] The mechanism simplifies the assembly of the actuating handle. It contains only one component to perform door interlocking in ON, defeating of interlocking and autorestoring in ON, door interlocking in OFF. Thus actuating handle can be padlocked to restrict actuation of switch by unauthorized person, without door interlocking, thereby facilitates maintenance person to access the switch mounted inside the panel board. However if it is required that nobody should able to open the panel door when padlocked in OFF state, then door can be interlocked with the switch.
[0024] The above concept can be extended to the changeover switches where there are two ON states and one OFF state of the handle without addition of any extra component.
[0025] These and other objects and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.


E) BRIEF DESCRIPTION OF THE DRAWINGS
[0026] The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:
[0027] FIGURE.l shows an exploded perspective view of a handle assembly in a dual mode door interlocking system for the switching devices according to one embodiment of the present invention.
[0028] FIGURE.2 illustrates a back side view of the handle assembly mounted on the panel door in a dual mode door interlocking system according to one embodiment of the present invention.
[0029] FIGURE.3 illustrates a sectional side view of a handle in the handle assembly in the dual mode door interlocking system according to one embodiment of the present invention, indicating the movement of the pip in the handle assembly to interlock the door.
[0030] FIGURE.4 illustrates a sectional side view and a bottom view of a handle in the handle assembly in the dual mode door interlocking system according to one embodiment of the present invention, indicating the rotation of the locking tag, movement of the padlock lever to interlock the door in OFF state, top view indicates place to insert padlock for padlocking.


[0031] FIGURE.5 illustrates a sectional view of a handle assembly in the dual mode door interlocking system according to one embodiment of the present invention, indicating the opening of the door in ON state by defeating the door interlocking with a tool.
[0032] FIGURE.6 illustrates a sectional view of a handle assembly in the dual mode door interlocking system according to one embodiment of the present invention. It shows autorestoration mechanism.
[0032] FIGURE.7 shows padlock insertion.
[0033] Although specific features of the present invention are shown in some drawings and not in others. This is done for convenience only as each feature may be combined with any or all of the other features in accordance with the present invention.
F) DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0034] In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which the specific embodiments that may be practiced is shown by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and it is to be understood that the logical, mechanical and other changes may be made without departing from the scope of the embodiments. The following detailed description is therefore not to be taken in a limiting sense.


[0035] The various embodiments of the present invention provide a provision for interlocking a mechanical switch mounted inside the panel/enclosure with the panel/enclosure door. The purpose of the invention is to develop a flexible door interlocking system wherein the door opening is possible to access the switch for maintenance when the switch is padlocked. While padlocking the actuating handle mounted on the panel door, operator have the flexibility to have padlock with interlocking of the panel door or have padlock without interlocking of the panel door.
[0036] A handle assembly according to the embodiment of the present invention includes a handle portion, a coupler, E-plate, locking tag, padlock lever, sliding plate and a shroud cover. A Handle is screwed to coupler, through the E-plate. For off state of handle, slot in the coupler is always vertical. A Locking tag is hinged in the handle with a pin. A Locking tag is rested on the padlock lever, which is inserted in to the hole provided on the handle. A Sliding plate, loaded with a spring slides along the slots provided on the E-plate. A Pip on the sliding plate protrudes out of the E-plate and a shroud cover is click fitted on to the E-plate. The entire handle assembly is fixed on the panel door using screws.
[0037] The Handle assembly is mounted on the panel door with screws and switch is mounted inside the panel. In off state of the switch, the shaft pin is vertical. Keeping the handle in OFF state will engage the shaft with the coupler slot in the handle assembly, thus switch can be operated with the handle. If either handle assembly or shaft is not in the desired position, there will not be any engagement between the two, thus prohibiting/preventing the wrong indication of switch position on the handle or unintentional non desired operation of the switch. Thus the arrangement ensures OFF


position of the handle for OFF state of the switch and ON position of the handle for ON state of the switch.
[0038] Accordingly the embodiments of the present invention provides a configuration and arrangement to get door interlocking in ON state, Defeating only with use of tool, autorestoration of the door, optional door interlocking in OFF state of the switch. It uses a novel mechanism for interlocking, defeating and autorestoration of the switch with the panel/enclosure door.
[0039] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description of the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.
[0040] FIG.l shows the exploded view of the components in the handle assembly. Assembly consist of Handle (3) which is screwed to coupler (2), through the E-plate (1). For off state of handle, slot in the coupler is always vertical. Locking tag (7) is hinged in the handle (3) with pin (8). Locking tag is rested on the padlock lever (6), which is inserted in to the hole provided on the handle. Sliding plate (9), loaded with the spring (4) slides along the slots provided on the E-plate. The Pip on the sliding plate protrudes out of the E-plate. A Shroud cover (10) is click fitted on to the E-plate (1). Screw 11 and 12 are provided to fix the handle


assembly on the panel door. The entire handle assembly is mounted on the panel door with screws (11) and (12) and switch is mounted inside the panel.
[0041] FIG.2 illustrates a handle assembly mounted on the panel door with screws (11) and (12) and the switch mounted inside the panel. As shown in the figure the shaft pin is vertical in OFF state of the switch. Keeping the handle in OFF state will engage the shaft with the coupler slot in the handle assembly, thus switch can be operated with the handle. If either handle assembly or shaft is not in the desired position, there will not be any engagement between the two, thus prohibits wrong indication of switch position on the handle or unintentional non desired operation of the switch. Thus the arrangement ensures OFF position of the handle for OFF state of the switch and ON position of the handle for ON state of the switch.
[0042] FIG.3 illustrates a method for door interlocking in OFF state of the switch by using a handle assembly. Door interlocking in OFF state of the switch ensures interlocking of the switch with the door in OFF position of the handle. As shown in the figure, for door interlocking in OFF state, pip on the sliding plate (9), protruding out of the E-plate (1) is pressed with the finger. It causes movement of the sliding plate along the guide ways in the E-plate. Keeping it pressed and simultaneously rotating the locking tag (7) drives the padlock assembly (6) and sliding plate (9) is held in this position. At this position shaft pin is blocked by the sliding plate as shown in FIG.3, Thus preventing the shaft from coming out of the handle assembly and consequently interlocks the door with the switch, as handle assembly is mounted on the door and shaft is fixed on the switch unit. The handle assembly is


manufactured in such a way that the maximum of three padlocks can be inserted in the locking tag (7).
[0043] FIG.4 illustrates a top and side view of the rotation of locking tag to drive the padlock assembly. For door interlocking in OFF state, pip on the sliding plate (9), protruding out of the E-plate (1) is pressed with the finger. It causes movement of the sliding plate along the guide ways in the E-plate. Keeping it pressed and simultaneously rotating the locking tag (7) as shown in the figure.4 drives the padlock assembly (6) and sliding plate (9) held in this position. At this position shaft pin is blocked by the sliding plate, thus preventing the shaft from coming out of the handle assembly and consequently interlocks the door with the switch, as handle assembly is mounted on the door and shaft is fixed on the switch unit.
[0044] FIG.5 illustrates a configuration and arrangement to get door interlocking in ON state, Defeating by using a tool and autorestoration of the door. When the switch unit is switched ON with the handle, shaft pin on the shaft gets blocked under the sliding plate. Thus handle assembly, consequendy door on which handle is mounted gets interlocked with the switch unit. To open the door in ON state of the switch unit, sliding plate pip is pushed with the pin as shown FIG.5. Pushing the pip with the finger will not cause sufficient movement of the sliding plate (9) for defeating, thus as per standard safety requirements sliding plate pip has to be pushed with a Pin for defeating the door in ON state. Pushing the sliding plate will release the shaft pin through the slots provided on the sliding plate, thus door can be opened.


[0045] After opening the door in ON state, it can be closed just by pushing the door. When door is pushed to close, conical shape of shroud (10) guides the shaft in the coupler (2), further the shaft pin slides along the inclided surface on the sliding plate which pushes the sliding plate and engages with the coupler. As sliding plate is spring loaded it comes back to the original position.
[0046] FIG.6 illustrates guiding of the shaft in the coupler. After opening the door in ON state, it can be closed just by pushing the door. When door is pushed to close, conical shape of shroud (10) guides the shaft in the coupler (2), further the shaft pin slides along the inclined surface on the sliding plate which pushes the sliding plate and engages with the coupler. As sliding plate is spring loaded it comes back to the original position. Padlock insertion is shown in FIG.. 7.
[0047] Thus the various embodiments of the present invention provide a provision for interlocking a mechanical switch mounted inside the panel/enclosure with the panel/enclosure door. It provides a flexible door interlocking system wherein the door opening is possible to access the switch for maintenance when the switch is padlocked. While padlocking the actuating handle mounted on the panel door, operator have the flexibility to have padlock with interlocking of the panel door or have padlock without interlocking of the panel door.
[0048] The present invention provides a novel mechanism for interlocking, defeating and autorestoration of the switch with the panel/enclosure door. Accordingly it provides a configuration and arrangement to get door interlocking in ON state, Defeating only with use


of tool, autorestoration of the door, optional door interlocking in OFF state of the switch. The handle assembly is simple and uses minimum components; it uses a rotating plate concept to achieve interlocking of the mechanical switch inside the panel, with the panel door.
[0049] The mechanism also simplifies the assembly of the actuating handle. It contains only one component to perform door interlocking in ON, defeating of interlocking and autorestoring in ON, door interlocking in OFF. Thus actuating handle can be padlocked to restrict actuation of switch by unauthorized person, without door interlocking, thereby facilitates maintenance person to access the switch mounted inside the panel board. However if it is required that nobody should able to open the panel door when padlocked in OFF state, then door can be interlocked with the switch. The above concept can be extended to the changeover switches where there are two ON states and one OFF state of the handle without addition of any extra component.
[0050] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will


recognize that the embodiments herein can be practiced with modification within the spirit and scope of the appended claims.
[0051] Although the invention is described with various specific embodiments, it will be obvious for a person skilled in the art to practice the invention with modifications. However, all such modifications are deemed to be within the scope of the claims.
[0052] It is also to be understood that the following claims are intended to cover all of the generic and specific features of the present invention described herein and all the statements of the scope of the invention which as a matter of language might be said to fall there between.




CLAIMS
WHAT IS CLAIMED IS:
1. A dual mode door interlocking system for switching device, the system comprising:
a handle assembly mounted on a door panel enclosing a housing provided to
accommodate a switching device;
a handle unit provided in the said handle assembly coupled to the switching device to
move a switch unit to ON position or OFF positions;
a locking tag hinged to the handle unit;
a sliding plate which slides in the slots provided in the E-plate
wherein the sliding plate is provided with a pip so that the pip is activated to open
the door, when the switch unit is interlocked with the handle in ON position and
same pin is pushed with finger for interlocking in OFF state.
2. The system according to claim 1, wherein the handle assembly further comprises:
a drive shaft;
a coupler;
a escutcheon (E) plate;
a sliding plate;
a pad lock lever; and
a shroud cover.


3. The system according to claim 1, wherein the handle is screwed to the coupler through the E plate.
4. The system according to claim 2, wherein the drive shaft is coupled to the switch
unit.
5. The system according to claim 2, wherein the E plate is provided with slots.
6. The system according to claim 2, wherein the sliding plate is provided with a spring.
7. The system according to claim 2, wherein the sliding plate is moved along the slots provided in the E- plate.
8. The system according to claim 2, wherein the locking tag is rested on the padlock lever, wherein when locking tag is rotated, it pushes the padlock lever in to the E-plate.
9. The system according to claim 1, wherein the locking tag is provided to receive a pad lock that is used to lock the handle at a given position.
10. The system according to claim 8, wherein the desired position is a switch ON position.
11. The system according to claim 8, wherein the desired position is a switch OFF position.


12. The system according to claim 2, wherein the shroud cover is click fitted on the E plate.
13. The system according to claim 1, wherein the pip is provided on the sliding plate to protrude outwardly.
14. The system according to claiml, wherein the pip is pressed to move the sliding plate along the slots in the E plate to permit or prevent the movement of a shaft to permit or prevent the movement of the switch unit.
15. The system according to claim 1, wherein the pip is kept pressed and the locking tag is rotated to drive a pad lock lever and to move the sliding to prevent the movement of the shaft from the handle assembly to interlock the door with the switch unit.
16. The system according to claim 1, wherein the pip is pushed with a tool to move the



ABSTRACT
The embodiments of the present invention provide a dual mode door interlocking system for switching devices to enable the opening of the door both in switch ON and OFF condition using a single component. The handle is provided with a pip which is activated to move a drive shaft to prevent or permit the opening of the door during the switch ON or OFF condition. The system uses a pip and a pin to close or open the door during the interlocking of the handle with the switch.


Date: Match.2008. RAKESH PRABHU
Place: Bangalore. Counsel for the Applicant