Claims:1. An improved door interlock assembly for an enclosure housing electrical switching apparatus, said enclosure including a frame having a first and second sides for supporting said electrical switching apparatus and a panel door (2) for controlling access to said electrical switching apparatus housed therein, said door interlock assembly comprising:
a panel door slider link (29) positioned on the door (2) and operably coupled to a trip slider link (15), said slider link (15) engages with a main trip actuator link (18) to move therewith;
a trip input link (13) operably coupled to the main actuator link (18), said input link (13) is guided by support link (11) and operably coupled to a trip actuator (7), said trip actuator being coupled to a trip shaft (5) to move therewith;
a panel door locking link (30) positioned on the door (2) and operably coupled to a coupler link (14), said link (14) is coupled to a pole shaft (12) of said electrical switching apparatus to operably engage an actuator (26), to disable and enable door (2) opening when switching apparatus is in ON and OFF condition.

2. The door interlock assembly as claimed in claim 1, wherein electrical switching apparatus is a draw out type circuit breaker (3), a fixed type circuit breaker (3) and the like.

3. The door interlock assembly as claimed in claims 1 or 2, comprises a mounting plate (25) on either cradle side plate (3a) in case of draw out type circuit breaker or on breaker housing (9) right side in case of fixed type circuit breaker, said mounting plate assembly comprising different linkages to actuate tripping command and disable breaker to ON/close when door (2) is open.

4. The door interlock assembly as claimed in claim 3, wherein the coupler link (14) is rotatably coupled to a locking link (22) to enable locking between said door locking link (30) and said locking link (22), said locking link (22) mounted on the mounting plate (25).

5. The door interlock assembly as claimed in claim 1, wherein the main trip actuator link (18) is mechanically coupled to move along the cam profile of the trip slider link (15) and a guide roller (21).

6. The door interlock assembly as claimed in claim 1, wherein the trip input link (13) is coupled to a slide link (10), said slide link (10) is operably coupled to a trip actuator slider so as to give rotational movement to the trip actuator (7).

7. The door interlock assembly as claimed in claim 6, wherein the trip actuator is further coupled to an anti-pumping link (6) so as to disable the switching ON said electrical switching apparatus when door (2) is open.

8. The door interlock assembly as claimed in claim 1, wherein a locking link (22) is coupled to an actuator pin (27), said actuator pin (27) being functionally engaged by the actuator (26) to disable door (2) opening when said switching apparatus is in ON condition.
, Description:FIELD OF INVENTION
The present invention relates to electrical protection devices in general, more particularly to door interlocking mechanism for circuit breakers for controlling access to the circuit breakers housed within an enclosure having a door.

BACKGROUND

Electrical transmission and distribution employs a device known as Circuit breaker; a kind of which known as “Air Circuit breaker” is customarily used in Low Voltage Power distribution systems. It is used to carry, make & break current in low-voltage, high current applications. Two types of circuit breakers are there one is fixed and other is draw- out. Draw out type Air Circuit breakers comprises of cradle assembly which used to carry breaker and can move and hold the breaker in four critical positions of any circuit breaker that is “connected”, “test”, “disconnect” and “maintenance”. Typical advantage of the draw out breaker is that is helps in frequent maintenance of circuit breaker and one can provide interlocked earthling and testing of breaker; it also helps in easy replacement of circuit breaker.
Air circuit breaker typically is mounted with switchboard panel where it is connected with electrical incoming supply and subsequent distribution of load to downstream equipment. Different switchgear products are assembled along with air circuit breaker in different enclosed compartment. Panel door is provided as part of panel assembly to access air circuit breaker, where it can be closed during normal operation of the air circuit breaker and opened during any maintenance activity.
In panel door closed condition; breaker can be moved in or out in any of the position i.e. “connected”, “test”, “disconnect”. For any maintenance work on the breaker, panel door needs to be opened to remove breaker into “maintenance” position from cradle assembly mounted on panel support system.
Different safety interlocks with panel becomes crucial when taking breaker into any maintenance work or into operations condition. In existing door interlock system/mechanism, when breaker moves into “connected” position, panel opening is not permissible. There is defeat mechanism provided which can be operated using special tool and door can be opened in “Connected” position.
In existing system when panel door is open, it allows ON-OFF operations of circuit breaker. The same condition allows any unsafe operations. There is no interlock of ON-OFF operation of circuit breaker and panel opening condition. Further locking of panel door with air circuit breaker is only available in Draw out type circuit breaker in connected position. In addition, locking is not depended of ON state of breaker. When circuit breaker is in “connected” position, panel door can be opened in case of fixed type breaker, thereby making existing system limited to only draw out type air circuit breaker.
Thus the above mentioned existing interlock mechanism has limitations and disadvantages and calls for an improvement in the design to provide extra safety feature.

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.
An object of the present invention is to provide an improved door interlocking mechanism for circuit breakers for controlling access to the circuit breakers housed within an enclosure having a door.
An object of the present invention is to provide an improved door interlocking mechanism for both fixed type and draw out type circuit breakers for controlling access to the circuit breakers housed within an enclosure having a door.
In accordance with an aspect of the present disclosure, is to provide an improved door interlock assembly for an enclosure housing electrical switching apparatus, said enclosure including a frame having a first and second sides for supporting said electrical switching apparatus and a panel door for controlling access to said electrical switching apparatus housed therein, said door interlock assembly comprising a panel door slider link positioned on the door and coupled to a trip slider link, said slider link engages with a main trip actuator link to move therewith, a trip input link operably coupled to the main actuator link, said input link is guided by support link and operably coupled to a trip actuator, said trip actuator being coupled to a trip shaft to move therewith, and a panel door locking link positioned on the door and operably coupled to a coupler link, said link is coupled to a pole shaft of said electrical switching apparatus to operably engage an actuator, to disable and enable door opening when switching apparatus is in ON and OFF condition.

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 above and other aspects, features and advantages of the embodiments of the present disclosure will be more apparent in the following description taken in conjunction with the accompanying drawings, in which:
Figure 1 illustrates an overview of Air circuit breaker mounting on panel in accordance to the invention.
Figures 2-4 illustrate overview of breaker mounted mechanism linkages from different positions in accordance to the invention.
Figure 5 illustrates an overview of Interlock mechanism assembly on circuit breaker cradle in accordance to the invention.
Figures 6 illustrates Interlock condition in panel close condition in accordance to the invention.
Figure 7 illustrates Interlock condition in panel door open condition in accordance to the 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 numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the present disclosure 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 various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and constructions may be 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 present disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustration purpose only and not for the purpose of limiting the present disclosure 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. Thus, for example, reference to "a component surface" includes reference to one or more of such surfaces.
All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which various embodiments belong. Further, the meaning of terms or words used in the specification and the claims should not be limited to the literal or commonly employed sense, but should be construed in accordance with the spirit of the disclosure to most properly describe the present disclosure.
The terminology used herein is for the purpose of describing particular various embodiments only and is not intended to be limiting of various embodiments. As used herein, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising" used herein specify the presence of stated features, integers, steps, operations, members, components, and/or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, members, components, and/or groups thereof. Also, Expressions such as "at least one of," when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.
The present disclosure will now be described more fully with reference to the accompanying drawings, in which various embodiments of the present disclosure are shown. The present disclosure may, however, be embodied in many different forms and should not be construed as being limited to the various embodiments set forth herein, rather, these various embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the present disclosure. Furthermore, a detailed description of other parts will not be provided not to make the present disclosure unclear. Like reference numerals in the drawings refer to like elements throughout.
The subject invention lies in providing a door interlock mechanism with additional safety feature. If the switchboard panel door is open, it does not allow circuit breaker to get ON/Close. It does not allow to open the switchboard panel door when the circuit breaker is closed/ON state (i.e. connected with electrical supply). The abovementioned safety features are applicable to both Fixed and Draw out type circuit breaker, thus ensuring safe condition of any operation in any door open condition and eliminating any hazardous condition when panel door is open. Locking of panel door when breaker is closed ensures that it is completely isolated from electrical circuit. It also actuates continuous tripping command when door is open which makes this feature dual safe.
In a Draw out type of circuit breaker, positions of breaker with respect to cradle are normally defined as ‘Disconnected’, ‘Test’ and ‘Connected’. When breaker is completely racked in i.e. in ‘Connected’ position, breaker terminals are in contact with cradle terminals through cradle jaws in the ‘Connected’ position. In this condition, both Power (main) circuit and control circuit are connected and the breaker can be switched ON. When the breaker is completely racked out i.e. in ‘Disconnected’ position, both main circuit and control circuit are disconnected. In the ‘Test’ position, Power (main) circuit is not connected but control circuit is connected. The breaker can also be drawn out to ‘Maintenance’ position where it can be lifted off the cradle for servicing and maintenance activities.
The present invention relates to switchgear application wherein, the objective of the invention is to provide different safety interlock between both Fixed or Draw out type circuit breaker and switchboard panel door. It aims to ensure safety of operator when breaker is Closed/ON and panel door is open.
According to an exemplary embodiment of the present invention, an improved door interlock assembly for an enclosure housing electrical switching apparatus, said enclosure including a frame having a first and second sides for supporting said electrical switching apparatus and a panel door (2) for controlling access to said electrical switching apparatus housed therein, said door interlock assembly comprising a panel door slider link (29) positioned on the door (2) and operably coupled to a trip slider link (15), said slider link (15) engages with a main trip actuator link (18) to move therewith, a trip input link (13) operably coupled to the main actuator link (18), said input link (13) is guided by support link (11) and operably coupled to a trip actuator (7), said trip actuator being coupled to a trip shaft (5) to move therewith, and a panel door locking link (30) positioned on the door (2) and operably coupled to a coupler link (14), said link (14) is coupled to a pole shaft (12) of said electrical switching apparatus to operably engage an actuator (26), to disable and enable door (2) opening when switching apparatus is in ON and OFF condition.
In typical switchboard panel assembly, air circuit breaker (3) is rigidly mounted on panel structure (1). All the respective electrical connection is connected to air circuit breaker (3). Air circuit breaker (3) is enclosed with panel door (2). In the present invention, function of actuating tripping command in panel door (2) open condition is achieved through mechanism mounted on breaker housing (9) and other parts mounted on cradle side plate (3a) in case of draw out type breaker and in case of fixed type breaker it is mounted on breaker housing (9). Function of taking inputs for ON/Close or OFF/Trip command is taken from coupler link (14) assembly on pole shaft (12). Pole shaft (12) is rigidly connected to main contact and used for ON and OFF operation of circuit breaker. Panel slider link (29) is assembled on panel door (2) and used for defeating ON command when door is open. Panel locking link (30) is assembled on panel door (2) and used in locking panel door (2) when circuit breaker is close/ON. Mounting plate (25) is mounted on cradle side plate (3a) and has two sub-assembly mounted on it.
In panel door open condition:
When panel door (2) is opened for any maintenance work, panel slider link (29) releases actuation of Trip slider link (15) and due to slider-reset spring (17) it moves towards panel door (2) with guide on slider support pin (16). In the same condition, main trip actuator link (18) moves along with cam profile of Trip slider link (15) and guide roller (21). Also, locking link rest spring (24) gives forces to upward direction. In this condition main trip actuator link (18) actuate trip input link (13) and gives anti-clockwise rotation to it. Trip inputs link is supported and guided by support link (11). Further to that, its rotation gives upward movement to slide link (10) on which trip actuator slider (8) is connected rigidly. Trip actuator slider (8) gives anti-clockwise rotational movement to trip actuator (7) which is directly connected to Trip shaft (5).
In addition, anti-clockwise rotational movement of trip actuator (7) gives push command to anti-pumping link (6), which defeats ON/Close command thus disabling breaker to ON when door is open. Ultimately, above condition gives tripping command to breaker and defeats ON/Close when panel door (2) is in open condition.
In panel door close condition:
When panel door (2) is in close condition, panel slider inputs link (29) pushes the trip slider link (15) which moves main trip actuator link (18) downwards and defeats any tripping command given through trip input link (13). It enables normal function of breaker ON and OFF operations. When breaker gets ON/Close, coupler link (14) assembled on pole shaft (12) moves in the anti-clockwise direction. In this condition, it moves actuator (26) in upward direction, which is guided on actuator pin (27). Simultaneously it moves locking link (22) in anti-clockwise direction, which is rotated at hinge of locking link support pin (23). Thus, it is locked with panel locking link (30).
Above locking condition disables panel door (2) opening when circuit breaker is in ON/Close condition. When breaker is OFF/Trip, locking between panel locking link (30) and locking link (22) gets unlocked which enables panel door to open when breaker is in OFF/Trip condition.
Some of the non-limiting advantages of the present invention are:
a) Panel door cannot be opened when circuit breaker is Close/ON
b) It does not allow closing/ON of Circuit breaker when Door is open.
c) Ensure safety when Door is open keeping circuit breaker always open/OFF.
d) Ensure safety when breaker is ON/Close keeping door closed.
e) Applicable to both fixed and draw out type air circuit breaker.
f) Double safety by actuating the TRIP command as well as the defeating the CLOSE command when door is open.
g) Status of the breaker derived from pole shaft directly connected to contacts through welded links thus, ensuring the reliability of the status (ON/OFF) perceived.
h) Suitable for site retrofitting
i) Provision also provided such that the interlock assembly becomes non-functional if needed by the user.

Although an improved door interlock assembly for an enclosure housing electrical switching apparatus has been described in language specific to structural features, it is to be understood that the embodiments disclosed in the above section are not necessarily limited to the specific methods or devices described herein. Rather, the specific features are disclosed as examples of implementations of an improved door interlock assembly for an enclosure housing electrical switching apparatus.

List of parts/components:

1- Panel Structure
2- Panel Door
3- Air circuit breaker Cradle
3a-Cradle Side plate
4-Breaker
5-Trip shaft
6-Antipumping Link
7-Trip actuator
8-Trip actuator slider
9-Breaker housing
10-Slider link
11-Support link
12-Pole shaft
13-Trip input link
14-Coupler link
15-Trip slider link
16-Slider support pin
17-Slider reset spring
18- Main trip actuator link
19-Trip actuator support pin
20-Trip actuator reset spring
21-Guide roller
22-Locking link
23-Locking link Support pin
24-Locking link reset spring
25- Mounting plate
26-Actuator
27-Actuator pin
28-Actuator reset spring
29-Panel slider input link
30-Panel locking link