FIELD OF INVENTION
The present invention relates to a door assembly with improved locking mechanism and sealing arrangement for arc fault safe panel (11). More particularly, the present invention relates to a multipoint locking door mechanism for switchgear panel (11).
BACKGROUND OF THE INVENTION
In the event of an occurrence of an arc fault, the door assembly is one of the most vulnerable areas in a switchgear panel. Also, since it is the door assembly that faces towards an operator / personnel, any damage to the door assembly may potentially be dangerous to the safety of the personnel. Hence, a door assembly having the strength to withstand the stresses rising out an arc fault, the sealing to prevent any leakage of arc or exhaust gases to the outside of the chamber, alongwith a smooth locking yet sturdy mechanism.
Since a door assembly normally has four edges and four corners, it is very important to ensure optimized strength at each of the mentioned locations.
Many designs employing different mechanisms have been used to address this situation. Patent Number US8419141B2 2013-04-16 titled Switchgear door assembly

latching system by Michael L. Niedzwiecki describes one such arrangement of multi door assembly linkages to address the same issue. Two separate latches are being employed to execute the interaction between multiple point door assembly links and locking rod. The key advantage of this system is that the door assembly elements can be replaced without doing any changes in the door assembly frame. In comparison, the proposed system employs a single latch locking mechanism. Moreover, the door assembly face forms an overlapping cover over the proposed locking mechanism, thereby, rendering safety to the operator even in case of a material fallout.
Patent Number US3229056A 1966-01-11 titled Switch panel with multiple switch and door assembly interlocks describes a multipoint locking mechanism. It goes on to further link the locking assembly with the operation of switch assemblies. However, the locking of door assembly and panel is limited to three location. Under the impact of an Arc-Fault, the pressure is very high. To address such a high pressure impact, more linkages/locking pins are required.
Patent Number US4405844A 1983-09-20 titled Door assembly interlock for electrical apparatus describes a lock arrangement for electrical panels. This system employs a set of linkages and a cam follower to obtain the desired locking. However, the points of locking are limited to three which may be insufficient for better arc-Fault Safe chambers.

Patent Number US6746092B2 2004-06-08 titled Apparatus for securing a door assembly of an arc-Fault Safe switchgear cabinet describes an apparatus for securing a door assembly of an arc-Fault Safe switchgear which includes a plurality of securing apparatuses that are mounted on a vertical flange of the switchgear cabinet. The securing apparatuses are each being formed with a locking hole that is engageable by a pin of a locking mechanism on a door assembly member. In this arrangement, each securing apparatus includes an anchor plate connected with a first bracket and a second bracket, with the first and second brackets being mounted on the flange of the switchgear cabinet. The locking hole is formed in the anchor plate, and the anchor plate is substantially planar and free of bends. This system therefore uses multiple brackets to ensure the operation. Also, these multiple brackets are mounted on the panel frame. For proper operation of this mechanism, the hole in the door assembly frame should match precisely with the corresponding hole in the bracket mounted in the door assembly. This drawback is overcome by the proposed solution in which the hook gets linked with the corresponding hole in panel frame.
Patent Number US20130293076A1 2013-11-07 titled Switchgear Panel With Improved Door Assembly describes a locking arrangement which ensures locking on three edges of the door assembly. The important point is that all the three locking plate are operated through a single latch.

Hence, one of the most important features in any industrial setup is to ensure absolute safety to the personnel involved. In typical industrial setup housing switchgear, the incidence of arc fault, though rare, have, always endangered the safety of personnel. Due to the expanding gases and the subsequent pressure rise inside the chamber, an arc Fault Safe switchgear panel must withstand high internal pressure and temperature. It is, therefore, very important that no arc gases escape the switchgear panel.
In arc-Fault Safe panels, the door assembly is the most vulnerable item and may potentially allow hot gases, having high temperature, to escape. The hot gases may also damage personnel involved due to extreme damages to the panel or due to small metallic fragments torn as a result of high pressure. To prevent any such damage, it is imperative to design a door assembly capable of withstanding the stresses and preventing any outburst of arc/gases. A latched door assembly is also preferred since the panel houses a circuit breaker that needs to be removed from/put inside the panel. This invention is to cater the above mentioned issue.
OBJECTS OF THE INVENTION
Therefore, it is an object of the invention to propose a door assembly with improved locking mechanism and sealing arrangement for arc fault safe panel which is capable of preventing hot gases having high temperature to escape from the safe switchgear panel which otherwise may cause severe damage to the personnel.

Another object of the invention is to propose a door assembly with improved locking mechanism and sealing arrangement for arc fault safe panel which is capable of withstanding the stresses and preventing any outburst of arc/gases.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The figures below illustrate the spatial arrangement of the various components that form together the door assembly (1) for a panel (11). The figures also indicate the locking mechanism, comprising of a set of linkages, resulting in the linear displacement of the lock plat.
Fig. 1: Shows a view of the complete door assembly (1) according to the invention.
Fig. la: Shows top half view of door assembly (1) structure.
Fig. lb: Shows sectional view at x-x of door assembly (1) structure.
Fig. 2: Shows an isometric view of top half of door assembly (1) indicating the multipoint locking assembly according to the invention.
Fig. 3: Shows an isometric view of indicating the linkages employed to operate the lock plate in accordance with the invention.
Fig. 4: Shows a view of the cross-section of a structural members (2a, 2b) that add
strength and ensure sealing to the door assembly (1) frame as per the invention.

Fig. 5a and Fig. 5b: Shows the door assembly (1) and panel (11) in locked and open condition.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
The principles discussed in this application are applicable to switchgear panels. The principles discussed below can be applied to medium voltage switchgear.
The figure 1 refers to a door assembly (1) embodying multiple attachments aimed to serve different purpose. The door is aimed at providing a sealed face onto a panel (11) with the help of the multipoint locking mechanism (5), the multipoint locking pins (Figure 5a) aimed to ensure tightening under stress, stress that is generated because of the pressure generated as a result of the energy due to an arc fault inside the switchgear panel (11). The door assembly (1) is attached to the panel (11) with the help of pivot (12) having a unidirectional rotational axis and is movable between open and closed positions. Door assembly (1) has a door structure comprising a face, and having top (3a), left vertical (3c), bottom (3b), and right vertical (3d) edges. Door assembly (1) can be pivoted to the panel (11) multiple hinges as pivot (12), although any suitable attachment ensuring unidirectional rotational motion may be used. The door assembly (1) structure comprising of a flat face with bends along the top, bottom, left and right side that are extended inwards to form a square loop on the inside.

With reference to Figure 1 and 4, a locking mechanism (5,5a,7,10) comprising a set of linkages (7,10) to operate the lock plate (5) is employed. The locking mechanism (5,58,7,10) is to ensure rectilinear motion of the lock plate (5) only on the defined rotational motion of the locking linkages (7, 10) The top structural member (2a, 2b) showcases the member made of metallic sheet put in place to ensure the sealing of the door assembly (1) frame with the said panel member (4). Gaskets (6) are mounted to the structural members (2a, 2b) so as to form a rectangular loop on the interior side of the door assembly (1). This placement of the gasket (6) and its sizing is such that, when the door assembly (1) is closed and latched, the gasket (6) provides a seal sufficient to prevent gases from escaping during an arc fault.
Figure 2 illustrates the inside top view of the door assembly (1). As shown, top (3a), left vertical (3c), bottom, and right vertical edges of door assembly (1) are inwardly flanged, so to form top (3a), left vertical (3c), bottom (3b), and right vertical (3d) flanges. The figure 2 also illustrates sealing structural member (2a, 2b), lock plate (5). The lock plate (5) is metallic and embodies multiple locking pins (5a) which when inserted into the slots in the panel (11) form a lock. The number of multiple locking pins (5a) can be changed according to design and stress parameters. It may be noted that lock plate (5) is mechanically connected to the linkages (7, 10). In general, linkages (7, 10) are mechanical connectors that cause the defined linear displacement in the lock plate (5).

Figure 4 illustrates the cross-section of structural member (2a, 2b). This figure indicates the sealing mechanism employed in this application. It consists of a door assembly (1) embodying a structural member (2a, 2b) employing door gaskets (6). The structural member in discussion forms a sealed edge with panel member (4) of the panel (11).
In operation, when ait operator rotates the said linkages (7, 10) by a pre-determined degree, the linkages (7, 10) activate the lock plate (5). This predetermined displacement of the lock plate (5) forms a lock with the panel (11) body. At the same position that the locking has been ensured, it is also ensured that the structural members (2a, 2b) in door assembly (1) have formed a sealed edge with the panel member (4), thereby preventing any gas from moving out of the panel (11).
Fig. 5a and Fig. 5b shows the door assembly in open and closed position when 5b shows the lock plate (5) embodies a plurality of locking pins (5a) which when inserted into slots (13) in the panel (11) form a lock.

WE CLAIM
1. A door assembly (1) with improved locking mechanism (5, 5a, 7, 10) and sealing arrangement (2a, 2b, 6) for arc fault safe panel (11), the said door assembly (1) comprising a face and having top, left vertical, bottom and right vertical flanges and attached to an panel (11) by multiple hinges (12) and having flat face with bends along the top, bottom, left and right side extended inwards for forming a square loop on the inside;
a door assembly (1) embodying a structural member (2a, 2b) having door gaskets (6) on both the edges at the top and bottom forming a sealed edge with the body of the panel member (4);
a lock plate (5) comprising a plurality of locking pins (5a) and mechanically connected with linkages (7,10); characterized in that,
a locking mechanism (5, 5a, 7, 10) comprising the set of linkages (7, 10) and locking pins (5a) for operating the lock plate (5) is disposed when the said linkages (7,10) ensures a rectilinear motion of the lock plate (5) only on the defined rotational motion of the linkages (7,10), wherein the lock plate (5) embodies a plurality of locking pins (5a) which when inserted into slots (13) in the panel (11), form a lock.

2. A door assembly (1) with improved locking mechanism as claimed in claim 1, wherein the number of multiple locking pins (5a) is optimized according to the desired stress parameters during the design of the door assembly (1).
3. A door assembly (1) with improved locking mechanism as claimed in claim 1, wherein the door assembly (1) houses a distinct and separate structure of frames mounted along top, bottom, left and right for mounting the gasket (6), when another pair of frames along the top and bottom edges forming a sealed edge for ensuring the sealing between the door assembly (1) and panel (11).
4. A door assembly (1) with improved locking mechanism as claimed in claim 1,
wherein a plurality of gaskets (6) are disposed in series and in parallel arrangement for
providing a seal when the door assembly (1) is closed.