FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION:
"Linkage Mechanism for Door of Switchboard Cabinet"
2. APPLICANT:
(a) NAME: Larsen & Toubro Limited
(b) NATIONALITY: Indian Company registered under the
provisions of the Companies Act-1956.
(c) ADDRESS: LARSEN & TOUBRO LIMITED,
L&T House, Ballard Estate, P. O. Box: 278, Mumbai 400 001, India
3. PREAMBLE TO THE DESCRIPTION:
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.

Linkage Mechanism for Door of Switchboard Cabinet
Field of the invention
The present invention relates to a safety technology for a door of a switchboard cabinet and more particularly, to a linkage mechanism for the door of the switchboard cabinet.
Background of the invention
Door locking assembly/systems for switchgear cabinets known from the prior art serves the purpose of operating safety and protecting the staff that operate and maintain electrical installations. In the art, to secure an access door in an open position by a worker some form of manually operated retaining mechanism is used. The manually operated retaining mechanism usually includes a rod mounted on a rim of a cabinet housing that is manually inserted into a receiving hole on the open access door. However, the effectiveness of this manually operated retaining mechanism is completely dependent on the worker connecting up the retaining mechanism after opening the access door.
Also, the prior art door locking assembly/systems have disadvantages like a locking mechanism provided does not lock a latching arrangement itself until an external force in a particular direction is applied. There are chances that this force could be applied inadvertently causing the door to close thereby creating unsafe working conditions for the staff.
When the door is right or left hinged, the door needs hinging-space/opening depending on width of a switchboard cabinet/enclosure. This causes inconvenience when the location of the door is at a height and also, blocks the gangways when the door is open. For such applications hinging at top solves the problem but retaining the door in open condition is a challenge.

Accordingly, there is need to provide a linkage mechanism for locking a door of a switchboard cabinet/enclosure that overcomes the drawbacks of the prior art.
Objects of the invention
An object of the present invention is to hold a door of a switchboard cabinet/enclosure in a vertically upward position against the gravity.
Another object of the present invention is to provide self locking of the door in an open position.
Yet another object of the present invention is to provide an additional safety feature using a sleeve restricting movement of levers unless displaced manually.
Summary of the invention
Accordingly, the present invention provides a linkage mechanism for a door of a switchboard cabinet. The linkage mechanism comprises a first bracket, a second bracket, a first lever, a second lever, a stopper and a pin.
The first bracket is assembled on a corner pillar of the switchboard cabinet using a pair of screws. The second bracket is assembled on the door. The first lever is pivoted to the first bracket at one end. The second lever is pivoted to the second bracket at one end and to the first lever at another end. The stopper is adaptably designed to assemble in between the first lever and the second lever. The pin restricts extent of sliding of the stopper below the pivoting point of the levers. The first bracket, the second bracket, the first lever and the second lever are secured in respective positions using a plurality of rivets.
When a user opens a busbar portion of the door of the switchboard cabinet, the levers reach a dead center position and the stopper slides down due to gravity

thereby positioning the stopper at the pivoting point of the levers and stopping further movement of the levers causing hinging of the door at a top end thereby allowing the door to open and close in a vertical direction and locking the door in a final open position.
Brief description of the drawings
Other features as well as the advantages of the invention will be clear from the following description.
In the appended drawings:
Figure 1 shows a side view of a linkage mechanism for a door of a switchboard cabinet, in accordance with the present invention;
Figure 2 shows a perspective view of the linkage mechanism of figure 1;
Figure 3 shows an exploded view of the linkage mechanism of figure 1; and
Figure 4 shows an isometric view of a folded conformation of the linkage mechanism in a closed door condition, in accordance with the present invention.
Detailed description of the invention
The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.
The present invention provides a linkage mechanism for a door of a switchboard cabinet/enclosure. The linkage mechanism locks the door of the switchboard

cabinet/enclosure in a final position of an opening. The linkage mechanism facilitates hinging of the door at a top end thereby allowing the door opening and closing in a vertical direction. The linkage mechanism reduces hinging-space/opening that depends on width of the cabinet/enclosure.
The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description.
Referring to figures 1-4, a linkage mechanism (100) for a door (150) of a switchboard cabinet/enclosure (hereinafter "the cabinet") in accordance with the present invention is shown. The linkage mechanism (100) comprises a first bracket (10), a second bracket (20), a first lever (30), a second lever (40), a sleeve/stopper (50) and a pin (60). The linkage mechanism (100) engages with the door (150) at one end (not numbered) and a corner pillar (180) of the cabinet at the other end (not numbered). In an embodiment, the linkage mechanism (100) is a self locking mechanism.
The first bracket (10) is assembled on the corner pillar (180) using a pair of screws (not shown). The second bracket (20) is assembled on the door (150). The first lever (30) at one end (A) is pivoted to the first bracket (10) and at another end (B) pivoted to the second lever (40) thereby giving a specified movement to the first lever (30).
The second lever (40) is pivoted to the second bracket (20) at one end (C) and to the first lever (30) at another end (B). The first lever (30) and the second lever (40) are in a folded stage during a close position of the door (150). In an embodiment, the first bracket (10), the second bracket (20), the first lever (30) and the second lever (40) are fixed/secured in respective positions using a plurality of rivets (not shown).

The sleeve/stopper (50) (hereinafter "the stopper (50)") is adaptably designed to assemble in between the first lever (30) and the second lever (40). The stopper (50) drops/slides down facilitating a proper folding of the levers (30, 40) thereby causing the proper closing of the door (150). The stopper (6) prevents an accidental unlocking of the linkage mechanism (100).
The pin (60) restricts the extent of sliding of the stopper (50) due to gravity below the pivoting point (B) of the levers (30, 40).
Again referring to figures 1-4, in an operation, when a user/worker opens a busbar portion (not shown) of the door (150) of the cabinet, the levers (30, 40) reach a dead center position also called as an unfold stage. The stopper (50) slides down at the pivoting point (B) of the levers (30, 40) due to gravity thereby stopping further movement of the levers (30, 40). This causes hinging of the door (150) at the top end thereby allowing the door (150) to open and close in the vertical direction and locking the door in the final open position.
Advantages of the invention
1. The linkage mechanism (100) provides self locking of the door (150) in the open position.
2. The linkage mechanism (100) provides the additional safety feature using the stopper (50) that restricts the movement of levers (30, 40) unless displaced manually.
3. The linkage mechanism (100) facilitates holding of the door (150) in the vertically upward position against the gravity.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not

intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, and to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present invention.

We Claim:
1. A linkage mechanism (100) for a door (150) of a switchboard cabinet, the linkage mechanism (100) comprising:
a first bracket (10) assembled on a corner pillar (180) of the switchboard cabinet using a pair of screws;
a second bracket (20) assembled on the door (150);
a first lever (30) being pivoted to the first bracket (10) at one end (A);
a second lever (40) being pivoted to the second bracket (20) at one end (C) and to the first lever (30) at another end (B);
a stopper (50) adaptably designed to assemble in between the first lever (30) and the second lever (40); and
a pin (60) being capable of restricting extent of sliding of the stopper (50) below the pivoting point (B) of the levers (30, 40),
wherein, when a user opens a busbar portion of the door (150) of the switchboard cabinet, the levers (30, 40) reach a dead center position and the stopper (50) slides down at the pivoting point (B) of the levers (30, 40) due to gravity thereby stopping further movement of the levers (30, 40) and causing hinging of the door (150) at a top end thereby allowing the door (150) to open and close in a vertical direction and locking the door (150) in a final open position.
2. The linkage mechanism (100) as claimed in claim I, wherein the first bracket (10), the second bracket (20), the first lever (30) and the second lever (40) are secured in respective positions using a plurality of rivets.
3. The linkage mechanism (100) as claimed in claim 1, wherein first lever (30) and the second lever (40) are in a folded stage during a close position of the door (150).