Claims:
Field of the invention

The present invention generally relates to a motor control centre, and more particularly to a safety shutter arrangement for power contacts of withdrawable feeders in a switchboard.

Background of the invention

Safety of the operating personnel is paramount in any electrical application. It is therefore necessary that the construction of a switchboard takes in to account of electrical hazard due to touch or ingress.

A motor control centre houses switchgear and other equipments that are required for protection and control of the motors/loads. The switchgear assemblies are usually housed in a compartment known as feeders. The feeders are then stacked vertically to form the motor control centre.

Typically, these feeders are withdrawable, i.e., the feeder can be removed from the switchboard for maintenance or due to breakdown. The electrical supply to such withdrawable system is achieved through fixed and moving power contacts. The fixed contacts are present in the structure (switchboard) and the movable contacts are present in the withdrawable feeders.

In the absence of a withdrawable feeder in a switchboard, the fixed live power contacts are exposed and hence prone to accidental touch by the operating personnel during maintenance. In order to prevent this, the contacts have to be shielded/insulated in the absence of a feeder.

Various patents of the prior art discloses shielding the contacts in absence of the feeder. Specifically, US Patent 6414839 discloses a shutter mechanism for vertical bus of motor control center. The patent discloses a shutter mechanism for personnel safety. It’s a spring operated mechanism with lever to open and close shutter.

Another US Patent 4565908 discloses a draw out switchgear apparatus with retractable shutter mechanism for terminal stabs. The patent discloses a levering mechanism-with shaft, a lever, extension rods, springs and moving components that are actuated by the movement of switchgear apparatus position.

However, the mechanisms of the prior art that offer protection against accidental contact are complex, bulky and use many components. The prior art mechanisms are either spring or gravity operated, both of which are not fail-safe options. During the working of the mechanism either the spring may malfunction due to wear and tear or the gravity force fails to operate the mechanism. The prior art mechanism are manufactured with tight tolerance for effective working, hence become costly.

Accordingly, there exists a need to provide a safety shutter mechanism for power contacts of withdrawable feeders in switchboard, which overcomes abovementioned drawbacks.

Objects of the invention

An object of the present invention is to provide non-gravity and non-spring operated safety shutter mechanism.

Another object of the present invention is to provide retrofit safety shutter mechanism which can be used on an existing switchboard.

Yet another object of the present invention is to provide a pad- lockable safety shutter mechanism which can be locked in shutter closed state.

Summary of the invention

Accordingly, the present invention a safety shutter mechanism for power contacts of withdrawable feeders in switchboard. The safety shutter mechanism comprises a tray having withdrawable feeders placed thereon The mechanism further comprises a plurality of fixed power contacts mounted on a switchboard structure, wherein the plurality fixed contact are live. The mechanism further comprises a plurality of moving power contacts mounted on the withdrawable feeder. The plurality of moving contacts are energized when the plurality of moving contacts engage with the plurality of fixed contacts.

The mechanism furthermore comprises a fixed shutter mounted on the switchboard structure and a moving shutter mounted on the switchboard. Specifically, the moving shutter is capable of sliding over the fixed shutter. The mechanism also comprises at least one actuator mounted on the withdrawable feeders. Wherein upon inserting the withdrawable feeders in the switchboard structure, the actuator of the withdrawable feeder operate to push the moving shutters up thereby allowing engaging the moving power contacts with the fixed contacts. Further, when the withdrawable feeders are taken out from the switchboard, the actuators operate to retract the moving shutter to its original position, thereby restricting the access to the fixed power contacts.

Brief description of the drawings

Figure 1 shows a safety shutter mechanism in a switchboard, in accordance with the present invention;

Figure 2a and 2b shows fixed shutter and retractable/movable shutter of the switchboard, in accordance with the present invention;

Figure 3 shows retractable/movable shutter guiding mechanism for the switchboard, in accordance with the present invention;

Figure 4 shows withdrawable feeder with actuators and moving power contacts, in accordance with the present invention;

Figure 5a and 5b shows a cross-sectional view of the safety shutter mechanism, in accordance with the present invention; and

Figure 6 shows a padlock for the safety shutter mechanism, 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 embodiment.

The present invention provides a safety shutter mechanism for power contacts of withdrawable feeders in a switchboard. The safety shutter mechanism provides operator safety from live power contacts in the absence of a feeder in the switchboard. This is achieved by a safety shutter arrangement. The shutter mechanism is such that the shutter open and close with respect to state of the withdrawable feeder. If the feeders are placed in the switchboard (Draw-in), the shutter has to open to provide access to the fixed power contacts of the switchboard. Similarly, when the feeder is taken out (draw-out) from the switchboard the shutter has to close and restrict the access. Both the opening and closing of the shutter happens automatically without the intervention of the operator.

The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures.

Referring now to figure 1- 6 there is shown a safety shutter mechanism (200) (hereinafter ‘the mechanism (200)’) for power contacts of withdrawable feeders (50) in a switchboard (100), in accordance with the present invention. The switchboard (100) is a fixed structure with many compartments as shown is figure 1. Specifically, the switchboard (100) comprises a tray (90) having withdrawable feeders (50) placed thereon.

The safety shutter mechanism (200) comprises a plurality of fixed power (12) contacts mounted on a switchboard structure (100). The pluralities of fixed contact (12) are live having electrical hazard.

The safety shutter mechanism (200) further comprises a plurality of moving power contacts (14) mounted on the withdrawable feeder (50). The plurality moving contacts (14) are energized when the plurality of moving contacts (14) engage with the plurality of fixed contacts (12). Specifically, the supply to the withdrawable feeders (50) is through the power contacts (12, 14).

The present invention is characterized in that the safety shutter mechanism (100) comprises a fixed shutter (16) mounted on the switchboard structure (100). Further, the safety shutter mechanism (200) comprises a moving shutter (18) (also known as retractable shutter) mounted on the switchboard (100) as shown in figure 1. The moving shutter (18) is capable of sliding over the fixed shutter (16) as shown in figure 2 (a).

The moving shutter (18) is guided along its plane as shown in Figure 3. These guides (A) ensure that the travel required for the moving shutter (18) for opening and closing is achieved as required for proper engagement of the fixed contact (12) and the moving contact (14).

The safety shutter mechanism (200) furthermore comprises at least one actuator (20) mounted on the withdrawable feeders (50) as shown in figure 4. In an embodiment, the actuator (20) is a plate with gradually increasing slope such that when the actuator (20) engages the moving shutter (18), lifts the moving shutter (18) and when disengages the moving shutter (18), falls down the moving shutter (18).

As depicted in figure 5a and 5b, when the withdrawable feeders (50) are inserted (draw-in) in switchboard (100), the actuators (20) in the feeder (50) operate to push the retractable or movable shutter (18) up (open) as shown in figure 5b. As the moving shutter (18) open , the moving power contacts (14) can move and engage with the fixed contacts (12) and thus energizing the feeder (50).

Similarly, when the feeder (50) is taken out (draw-out) from the switchboard (100), the actuators (20) operate to retract (close) the moving shutter (18) to its original position. Thus, restricting the access to the fixed power contacts (12) which are behind the fixed shutter (16).

In an embodiment, of the present invention, the safety shutter mechanism (100) can be locked using a padlock (30) as shown in figure 6 so as it restrict unauthorized access to the power terminals.

Advantages of the invention

1. The safety shutter mechanism (100) is a retrofit mechanism which can be used on an existing switchboard.
2. The safety shutter mechanism (100) provides a failsafe mechanism in which probability of shutter not closing is almost nil.
3. The safety shutter mechanism (100) provides padlocking feature

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.
, Description:1. A safety shutter mechanism for power contacts of withdrawable feeders in switchboard, the safety shutter mechanism comprising:
a tray having withdrawable feeders placed thereon;
a plurality of fixed power contacts mounted on a switchboard structure, wherein the plurality fixed contact are live;
a plurality of moving power contacts mounted on the withdrawable feeder, the plurality moving contacts are energized when the plurality of moving contacts engage with the plurality of fixed contacts;
a fixed shutter mounted on the switchboard structure;
a moving shutter mounted on the switchboard, the moving shutter capable of sliding over the fixed shutter; and
at least one actuator mounted on the withdrawable feeders;
wherein upon inserting the withdrawable feeders in the switchboard structure, the actuator of the withdrawable feeder operate to push the moving shutters up thereby allowing to engage the moving power contacts with the fixed contacts and when the withdrawable feeders are taken out from the switchboard, the actuators operate to retract the moving shutter to its original position, thereby restricting the access to the fixed power contacts.

2. The safety shutter mechanism as claimed in claim 1, wherein the moving shutter is guided over guides on the fixed shutter.

3. The safety shutter mechanism as claimed in claim 1, wherein the guides ensure that the travel required for the moving shutter for opening and closing is achieved as required for proper engagement of the fixed contacts and moving contacts.

4. The safety shutter mechanism as claimed in claim 1, wherein a padlock is provided to lock the shutter mechanism to restrict unauthorized access to the power terminals.