Mechanism for Locking Safety Shutters in Draw-Out Circuit Breakers
Field of the invention
The present invention relates to circuit breakers, and more particularly, to a mechanism for locking safety shutters in draw-out circuit breakers.
Background of the invention
Generally, draw-out type circuit breakers are mounted on a cradle assembly inside a panel. The cradle assembly has provision for conducting terminals which are electrically live when main power supply is on. On backside of the cradle assembly, shutters are mounted so as to provide isolation between cradle terminals/contacts and circuit breaker terminals/contacts when the circuit breaker remains out of operation. The shutters are intended to open when the circuit breaker pole terminals touch or form electrical contact with the cradle terminals when circuit breaker is racked to electrically 'connected' position.
To provide isolation between the cradle terminals and the circuit breaker terminals, when the circuit breaker is not operable, the shutters remain close. When the circuit breaker is unloaded from the cradle assembly, the cradle terminals remain electrically live, which may pose danger to operator.
Accordingly, there exists a need of an arrangement which restricts access of the operator from front side to the cradle terminals, and also prevents opening of the shutters.

Object of the invention
An object of the present invention is to ensure locking of safety shutters, when circuit breaker is out of operation.
Another object of the present invention is to provide an enhanced electrical safety to operator when the circuit breaker is in unloaded condition from cradle for activities like maintenance work.
Summary of the invention
Accordingly, the present invention provides a mechanism for locking safety shutters in draw-out circuit breakers. The safety shutters are mounted on rear side of a cradle thereby concealing terminals of the cradle from front side. The mechanism comprises a plurality of protrusions configured on middle portion of the safety shutters
Further, the mechanism comprises a top plate mounted on front side of upper half of the safety shutters. The top plate includes curved ribs configured on upper portion thereof for inserting the top plate in a gap between rear plane of the safety shutters and rear upper portion of the cradle. The top plate further includes one or more windows configured on a lower portion thereof. The one or more windows are capable of securing to one or more protrusion of the plurality of the protrusions of the safety shutters.
Furthermore, the mechanism comprises a bottom plate mounted on front side of lower half of the safety shutters. The bottom plate includes a fixing means configured on lower portion thereof for fixing the bottom plate to the bottom rear plane of the cradle and a second window configured on upper portion

thereof. The second window is being capable of inserting into the protrusion of the plurality of protrusions of the safety shutters.
wherein upon assembling the top plate in front of the upper half of the safety shutters and inserting the one or more windows in the protrusions of the safety shutters, and assembling the bottom plate in front of the lower half of the safety shutters and inserting the second window in the protrusion of the safety shutters, a lock is capable of being secured between the first window and the second window thereby restricting access to the plurality of shutters from front.
Brief description of the drawings
Figure 1 shows a mechanism for locking safety shutters, in accordance with the present invention.
Figure 2 shows a perspective view of the mechanism of figure 1;
Figure 3 shows a mechanism for locking safety shutters with a top plate mounted on upper half of the safety shutters, in accordance with the present invention;
Figure 4 shows a mechanism for locking safety shutters with a bottom plate mounted on lower half of the safety shutters, in accordance with the present invention;
Figure 5 shows the top plate of the mechanism of figure 1; and
Figure 6 shows the bottom plate of the mechanism of figure 1.

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.
Accordingly, the present invention provides a mechanism for locking safety shutters in draw-out circuit breakers. The mechanism provides isolation when a circuit breaker is not operable and the shutters remain closed. In order to prevent opening of the safety shutters, the mechanism provides locking system for shutters in circuit breakers.
Referring to figure 1 to 6, there is shown a mechanism (100] for locking safety shutters (150) of a locking safety shutters in draw-out circuit breakers (200).The safety shutters (150) are mounted on rear side (164) of a cradle (160) thereby concealing terminals of the cradle (160) from front side (162). The safety shutters (150) are to be installed on rear side (164) of the cradle (160) in order to provide isolation and to prevent access to cradle live contacts to ensure electrical safety of the operator.
The mechanism (100) comprises a plurality of protrusions (10) configured on middle portion of the safety shutters (150).
Further, the mechanism (100) comprises a top plate (20) mounted on front side of upper half (152) of the safety shutters (150).

The top plate (20)includes curved ribs (22) configured on upper portion (24) thereof for inserting the top plate (20) in a gap between rear plane of the safety shutters (150) and rear upper portion of the cradle (160).
The top plate (20) further includes a one or more windows (26) configured on a lower portion (28) thereof. The one or more windows (26) are being capable ofsecuring to one or more protrusions(lOa) of the plurality of the protrusions (10) of the safety shutters (150).
The top plate (20) is mounted in such a way that the top plate (20) obstructs access to the upper half (152) of the safety shutters (150) i.e. in turn access to top cradle terminals.
Furthermore, the mechanism (100) comprises a bottom plate (30) mounted on front side of lower half (154) of the safety shutters (150). The bottom plate (30) includes a fixing means (32) configured on lower portion (34) thereof for fixing the bottom plate (30) to the bottom rear plane of the cradle (150).The bottom plate (30) further includes a second window (36) configured on upper portion (38) thereof. The second window (36) is being capable of inserting into the protrusion (10b) of the plurality of protrusions (10) of the safety shutters (150). In an embodiment, the fixing means of the bottom plate (30) includes screw or any other fixing method that uses hardware.
The bottom plate (30) is installed in such a way so as to arrest access to the lower half (154) of the safety shutter (150) and in turn to the lower cradle terminals.

The mechanism (100) also includes a lock [not shown) which is capable of being secured to the any one of the plurality of protrusions (10) to which the first window (26) and the second window (36) gets secured thereby restricting access to the plurality of shutters (150) from front. The lock when mounted in one of the plurality of protrusions (lO)ensures that the other end of the locking plates (20, 30) does not get dislodged from its place even after intentional effort.
During assembly of the mechanism (100), the top plate (20) is secured to the front of the upper half (152) of the safety shutters (150). Specifically, the curved ribs (22) of the upper portion (24) of the top plate (20) are inserted in a gap (156) between backplane [158] of the safety shutters (150) and the rear portion (164) of the cradle (160). Further, the top plate (20) is angular rotated towards down side, thereby inserting the one or more windows (26) present on lower portion (28) of the top plate (20) through the protrusions (10a) of the safety shutter (150). The protrusions (10a) are designed to accommodate the lock thereon.
Further, the bottom plate (20) is secured to the front of the lower half (34) of the safety shutters (150) by fixing means (32). Specifically, the fixing means (32) configured on lower portion (34) of the bottom plate (30) are fixed to bottom rear plane (164) of the cradle (160). The bottom plate (30) is then angularly rotated towards upper side of the safety shutter (150) such that the second window (36) present on the upper half (38) of bottom plate (30) gets inserted through protrusion (10b) configured on the safety shutters (150)on which the lock is to be housed.
Overlapping area between assembled top plate (20) and the bottom plate (30) ensures entrapment of plates against each other.

In an embodiment, either upper half (152) or lower half (154] of the safety shutters (150) i.e. the top cradle terminals or bottom cradle terminals are locked as shown as shown in figure 3 and 4 respectively.
Advantages of the invention
1. The mechanism (100) provides provision of safety shutter locking to prevent access from front side.
2. The mechanism (100) provides a single lock which locks both lower and upper half of safety shutters.
3. The mechanism (100) has multiple provisions for mounting lock
4. The mechanism (100) provides that even after mounting the lock at extreme end, other end of the top plate and the bottom plate does not get dislodged.
5. The mechanism (100) provides provision for locking either of the upper or of lower half of shutters alone with same locking arrangement.
6. The mechanism (100) provides complete enclosure to safety shutters and to the cradle terminals in turn from front side of the switchboard panel.
7. The mechanism (100) provides operator's enhanced safety.
8. The mechanism (100) provides modular design and ease of assembly.
The foregoing object the invention is accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiment. Detailed descriptions of the preferred embodiment are provided herein; however, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure, or matter.

The embodiments of the invention as described above and the methods disclosed herein will suggest further modification and alterations to those skilled in the art. Such further modifications and alterations may be made without departing from the spirit and scope of the invention.

We Claim:
1. A mechanism for locking safety shutters in draw-out circuit breakers, the safety shutters being mounted on rear side of a cradle thereby concealing terminals of the cradle from front side, the mechanism comprising:
a plurality of protrusions configured on middle portion of the safety shutters;
a top plate mounted on front side of upper half of the safety shutters, the top plate having curved ribs configured on upper portion thereof for inserting the top plate in a gap between rear plane of the safety shutters and rear upper portion of the cradle, and one or more windows configured on a lower portion thereof, the one or more windows being capable of securing to one or more protrusions of the plurality of protrusions on the middle portion of the safety shutters;
a bottom plate mounted on front side of lower half of the safety shutters, the bottom plate having a fixing means configured on lower portion thereof for fixing the bottom plate to the bottom rear plane of the cradle and a second window configured on upper portion thereof, the second window being capable of getting inserted into the protrusion of the plurality of protrusions of the safety shutters,
wherein upon assembling the top plate in front of the upper half of the safety shutters and inserting the one or more windows in the protrusions on the middle portion of the safety shutters, and assembling the bottom plate in front of the lower half of the safety shutters and inserting the second window in the protrusion of the safety shutters, a lock is capable of being secured to the any one protrusion of the plurality of protrusions, thereby restricting access to the plurality of shutters from front.

2. The mechanism as claimed in claim 1, wherein the fixing means of the bottom plate includes screw.