Claims:We Claim:

1. An auto actuated position locking system for a circuit breaker (26), the circuit breaker (26) being a draw-out type air circuit breaker capable of racking movement within a cradle assembly to move between a connected, test, disconnected and a maintenance position with respect to switchgear, characterized in that the auto actuated position locking system comprising:
a locking link (20) configured on a rail assembly () for locking thereof, the locking link (20) having a first end and a second end, the second end having a torsion spring (21) configured thereon, the locking link creating auto-actuated locking and unlocking of rails at maintenance position without any human intervention and using less actuation force;
a side plate stopper (19) configured on the cradle side plates (11) and adapted to receive the first end of the locking link (20) for locking the rails at the maintenance position thereby allowing easy removal of the circuit breaker (26) therefrom during maintenance, such that upon remounting of the circuit breaker (26) on the rails the torsion spring (21) gets actuated thereby releasing the locking link (20) from the side plate stopper (19) for unlocking the rails at the maintenance position;
a slider link (25) along with a two-slider pin (22) configured on the rails and capable of sliding movement thereon in response to outward movement of a handle (23) configured on the cradle assembly for racking movement of the circuit breaker thereon; and
a return spring (24) configured on the rails and positioned below the locking link (20), the return spring (24) adapted for retreating the slider link (25) back to initial position upon contact therewith;
wherein the sliding movement of the slider link (25) causes collision of the two-slider pin (22) with the torsion spring (21) thereby rotating and releasing the locking link (20) from the side plate stopper (19) for unlocking the rails at the maintenance position in absence of the circuit breaker (26) mounted thereon.

Dated this 27th day of March 2017

Prafulla Wange
(Agent for Applicant)
IN-PA/2058 , Description:AUTO ACTUATED POSITION LOCKING SYSTEM FOR CIRCUIT BREAKER

Field of the invention
The present invention relates to draw-out type circuit breakers, and more particularly provides an auto-actuated position locking system for the draw-out type circuit breakers.
Background of the invention
Electrical transmission and distribution employs a device known as a circuit breaker, one of which is known as an “Air Circuit breaker” that is customarily used in Low Voltage Power distribution systems. The circuit breaker is used to carry, make & break current in low-voltage, high current applications. Two types of circuit breakers are available in the market- a fixed typed circuit breaker and a draw- out type circuit breaker. The draw-out type Air Circuit breaker comprises of a cradle assembly which is used to carry the circuit breaker and can move and hold the circuit breaker in four critical positions of any circuit breaker- “connected”, “test”, “disconnected” and “maintenance”. Typical advantage of the draw-out circuit breaker is that it helps in frequent maintenance of the circuit breaker and one can provide interlocked earthling and testing of the circuit breaker and also helps in easy replacement of the circuit breaker.
Maintenance personnel often use a Draw-out type circuit breaker to interrupt the flow of electrical energy through a circuit when the circuit, or electrical components connected thereto, require maintenance. It is thus desirable to lock out the circuit breaker to prevent an individual from inadvertently energizing the circuit while maintenance is being performed.
In existing draw-out circuit breakers and other electrical control devices, locking of the circuit breaker in the “connected” state requires that the handle of the device be pushed in and turned in a specified position, whereas the “Disconnected” state requires that the racking handle be pulled out and turned to a different position. Overhauling of the circuit breaker requires disengagement of the circuit breaker from the rail at maintenance condition. Thus, when the pullout handle on rail is pulled out to remove the circuit breaker from the disconnected position to maintenance, its de-latching with side plates of the cradle creates unlocking of the rails of rail assembly. Further remounting of the circuit breaker back on the rail requires, ensuring that the rails are in maintenance condition which does not allow unfavorable movement of the rails while remounting the circuit breaker thereon post maintenance. Hence a mechanism is required to hold the rails in maintenance condition while remounting of the circuit breaker is performed.
Presently, movement of the rails is achieved by rack-in mechanism connected by cam and follower type of joint between drop- plate rivet and cam profile of the rack-in mechanism. In the existing circuit breakers, locking of the rails in connected condition is achieved through service latch assembly and in test condition through constant engagement of the rivet with the cam profile. In case of disconnected condition locking of the rails is achieved by attaching a rear part of the handle with a protrusion of the side plate thereby restricting motion of the circuit breaker in an outward direction, whereas the inward direction motion is again restricted through drop-plate rivet and cam profile. Further, for locking the rails at the maintenance condition, a screw and nut assembly is connected with a protrusion from the side plate that works as a locking in the outward direction. However, the existing system provides no provision to prevent sudden unexpected inward movement of the rails while mounting the circuit breaker thereon. The current systems provide no locking mechanism to lock the rails in maintenance position so as to prevent sudden inward movement thereof while mounting the circuit breaker thereon. Such unexpected movement of the rails may lay to offset insertion of the circuit breaker into the cradle during remounting, while in some other cases that may even cause damage to the circuit breaker. Further, this may create safety issue for operator working with it.
Therefore, there is a need for an auto locking system to lock the rails at maintenance position in order to prevent any accidental hazards occurring while remounting the circuit breaker on the rails post maintenance. Accordingly, there exists a need to provide an auto-locking system for rails which overcomes the above mentioned drawbacks of the existing systems.
Objects of the invention
The primary object of present invention is to ensure locking of rails in maintenance position while remounting of the circuit breaker on the rails.
Another object of the present invention is to prevent movement of rails during insertion of the circuit breaker on the rails in maintenance position.
Summary of the invention
The present invention provides an auto actuated position locking system for a circuit breaker. The system helps in automatic locking and unlocking of rail assembly of the draw-out type circuit breaker at maintenance position to allow safe removal and safe remounting of the circuit breaker during maintenance. The draw-out type circuit breaker is capable of racking movement within a cradle assembly to move between a connected, test, disconnected and a maintenance position with respect to switchgear. The draw-out type circuit breaker is adapted for rack-in and rack-out movement within the cradle assembly that comprises of a cradle base plate having a racking assembly configured thereon, cradle side plates for guiding the circuit breaker and a rail assembly consisting of rails adapted to receive the circuit breaker for mounting thereon. The cradle base plate is connected to the rail assembly through a drop plate rivet. The racking assembly facilitates sliding movement of the rails within the cradle side plates thereby moving the circuit breaker within the cradle assembly. The racking assembly comprises of a rack, a racking screw, and a racking shaft. The racking shaft has a cradle cam assembled thereon for connecting the rack with the rail assembly such that rotation of the racking screw causes movement of the rack and the cradle cam thereby facilitating to and fro movement of the rail assembly within the cradle side plates. The movement of the rail assembly causes the movement of the circuit breaker mounted thereon. Hence, the racking assembly assists in rack-in and rack-out movement of the draw-out type circuit breaker thereby changing positions between the connected, test, disconnected and the maintenance positions with respect to the switchgear.
The auto actuated position locking system of the present invention is configured on the rails of the rail assembly within the cradle assembly, and comprises of a locking link, a side plate stopper, a slider link, and a return spring.
The locking link is configured on the rails for locking thereof at the maintenance position of the circuit breaker. The locking link includes a first end located opposite to a second end having a torsion spring configured thereon.
The side plate stopper is configured on the cradle side plates and adapted to receive the first end of the locking link for locking the rails at the maintenance position thereby allowing easy removal of the circuit breaker therefrom during maintenance. Upon remounting of the circuit breaker on the rails, the torsion spring gets actuated to release the locking link from the side plate stopper for unlocking the rails at the maintenance position.
The slider link along with a two slider pin is configured on the rails and is capable of sliding movement thereon in response to outward movement of a handle configured on the cradle assembly.
The return spring is configured on the rails and is positioned below the locking link for retreating the slider link back to initial position upon contact with the return spring.
Accordingly, locking of the rails at maintenance position includes moving the circuit breaker using the racking assembly from the disconnected position to the maintenance position to cause the first end of the locking link to engage and lock within the side plate stopper thereby locking movement of the rails and allowing the circuit breaker to be easily removed therefrom for performing maintenance thereof. Remounting of the circuit breaker on the rails after maintenance causes actuation of the torsion spring to release the locking link from the side plate stopper and unlocking the rails. Further, the rails can be unlocked even in absence of circuit breaker mounted thereon using the slider link. In this case, the handle is pulled out to push the slider link to cause collision of the two slider pin with the torsion spring thereby rotating the locking link and releasing the locked position of the rails in maintenance position. The return spring helps in retreating the slider link back to initial position upon contact with the return spring.
Brief description of the drawings
Figure 1 shows a schematic layout of the cradle assembly of the prior art used for racking movement of a draw-out type circuit breaker;
Figure 2 shows rails in locked condition at maintenance position of the rail assembly, in accordance with the present invention;
Figure 3 shows rails in unlocked condition at maintenance position of the rail assembly, in response to remounting of the circuit breaker thereon, in accordance with the present invention; and
Figure 4 shows rails in unlocked condition at maintenance position of the rail assembly, without remounting of the circuit breaker thereon, in accordance with the present invention.
Detailed description of the invention
The foregoing objects of the 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 an auto actuated position locking system for a circuit breaker. The auto actuated position locking system is capable of automatically locking and unlocking rail assembly of the draw-out type circuit breaker at maintenance position to allow safe removal and safe remounting of the circuit breaker during maintenance.
This 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.
Accordingly, the present invention provides an auto actuated position locking system, (hereinafter referred to as “the system”) for a circuit breaker (26).The circuit breaker (26) is a draw-out type circuit breaker capable of racking movement within a cradle assembly to move between a connected, test, disconnected and a maintenance position with respect to switchgear. When the circuit breaker (26) is completely racked in i.e. in 'Connected' position, the circuit breaker (26) terminals are in contact with cradle terminals through cradle jaws in the 'Connected' position. In this condition, both Power (main) circuit & control circuit are connected and the circuit breaker (26) can be switched ON. When the circuit breaker (26) is completely racked out i.e. in 'Disconnected' position, both the main circuit and the control circuit are disconnected. In the 'Test’ position, the power (main) circuit is not connected but the control circuit is connected. The circuit breaker (26) can also be drawn out to ‘Maintenance’ position where it can be lifted off the cradle for servicing and maintenance activities.
The cradle assembly, as shown in figure 1, comprises of a cradle base plate (14), cradle side plates (11), and a rail assembly (12). The cradle base plate (14) is connected with the rail assembly (12) using a drop plate rivet (18). The cradle base plate (14) includes a racking assembly mounted thereon for providing rank-in and rack-out movement to the rail assembly (12) for facilitating movement of the circuit breaker (26) mounted thereon. The cradle side plates (11) are provided for guiding the circuit breaker (26) while moving within the cradle assembly. The rail assembly (12) includes rails capable of receiving the circuit breaker (26) for mounting thereon such that movement of the rails facilitates movement of the circuit breaker (26).
The racking assembly includes a rack (17), a racking screw (16), and a racking shaft (15). The rack (17) is mounted on the cradle base plate (14) and poises rail in isolated condition by rotating the racking screw (16) connected to the rack (17). The racking shaft (15) extends from the rack (17) towards the rail assembly (12), and includes a cradle cam (13) assembled thereon at an end facing the rail assembly (12) such that the cradle cam (13) connects the rack (17) with the rail assembly (12). Rotation of the racking screw (16) causes reciprocation/movement of the rack (17) thereby causing rotation of the cradle cam (13). Further, the rotational movement of the cradle cam (13), particularly a cradle cam profile, imparts motion to the drop plate rivet (18) riveted on the rail assembly (12) thereby facilitating to and fro motion of the rails in flanges of the cradle side plates (11) to create draw-out feature of the circuit breaker(26). Particularly, the racking assembly facilitates sliding movement of the rails within the cradle side plates (11) thereby moving the circuit breaker (26) within the cradle assembly. Projections provided on housing of the circuit breaker (26) rest on the rail assembly (12) to facilitate free sliding movement thereon between connected, test, disconnected, and maintenance positions.
Referring now to figures 2 to 4, the system is configured within the cradle assembly, particularly on the rails of the rail assembly (12), for providing automatic locking and unlocking of the rails at maintenance position. The system comprises of a locking link (20), a side plate stopper (19), a slider link (25), and a return spring (24).
The locking link (20) is configured on the rails for locking thereof at the maintenance position of the circuit breaker (26). The locking link (20) includes a first end, and a second end situated opposite to the first end. The second end is further provided with torsion spring (21) configured thereon. In an embodiment, the locking link (20) is a sheet metal locking link having optimum weight and thickness and is riveted on the rails with the torsion spring (21) attached thereto.
The side plate stopper (19) is configured on the cradle side plates (11) and is adapted to receive the first end of the locking link (20) for locking the rails at the maintenance position thereby allowing easy removal of the circuit breaker (26) therefrom during maintenance. Locking of the rails at maintenance position avoids unexpected inward movement of the rails during removal of the circuit breaker (26) therefrom to perform maintenance thereof.
The slider link (25) is configured on the rails and includes a two-slider pin (22) mounted thereon. The slider link (25) is operably connected to a handle (23) configured on the cradle assembly. The slider link (25) is capable of sliding movement on the rails in response to outward movement of the handle (23) that is configured on the cradle assembly. Particularly, the handle (23) when pulled out causes sliding movement of the slider link (25) along with the two-slider pin (22) onto the rails. In an embodiment, the slider link (25) and the locking link (20) have identical profiles thereby reducing the tooling cost.
The return spring (24) is configured on the rails at a certain distance from the slider link (25) such that the return spring (24) lies diagonally below preceding the torsion spring (21) of the locking link (20). In an embodiment, the return spring (24) is located below the locking link (20) such that the two-slider pin (22) of the slider link (25) upon sliding hits the torsion spring (21) and thereafter further sliding of the slider link (25) causes collision thereof with the return spring (24) resulting into retreating of the slider link (25) to initial position upon contact with the return spring (24).

Working of the invention
The system is used for automatic locking and unlocking of the rails at maintenance condition for allowing secure removal and remounting of the circuit breaker (26) thereon. The system helps in automatic locking of the rails upon movement of the rail assembly (12) from the disconnected position further to the maintenance position. During movement of the rail assembly (12) from the disconnected position further to the maintenance position, the locking link (20) travels over the side plate stopper (19) against force of the torsion spring (21) such that the first end of the locking link (20) locks within the side plate stopper (19) thereby preventing inward movement of the rails at the maintenance position. Thus, the rails automatically gets locked at the maintenance position, as shown in figure 2, thereby allowing easy and secure removal of the circuit breaker (26) therefrom for performing maintenance thereof.
Subsequent to the maintenance of the circuit breaker (26), remounting of the circuit breaker (26) onto the rails causes actuation of the torsion spring (21) thereby actuating the locking link (20) and releasing the lock. Thus, the rails automatically get unlocked at the maintenance position, as shown in figure 3, in response to remounting of the circuit breaker (26) on the rails following maintenance. Upon unlocking of the rails, the rail assembly (12) can freely move from the maintenance position to the disconnected position.
In an alternate embodiment, the rails can be unlocked when at the maintenance position without remounting of the circuit breaker (26) thereon. Unlocking of the rails without mounting of the circuit breaker (26) thereon, involves the user/operator pulling the handle (23) outwards to cause the sliding movement of the slider link (25). In an embodiment, the handle (23) and the slider link (25) have synchronized movements. Upon sliding of the slider link (25), the two-slider pin (22) collides with the torsion spring (21) to cause rotation of the torsion spring (21) and in turn the locking link (20) thereby releasing the lock. Particularly, linear movement of the slider link (25) gets converted into rotational movement of the locking link (20) thereby unlocking the rails. The return spring (24) provides return movement to the slider link (25) to initial position. Thus, the rails can be unlocked at the maintenance position, as shown in figure 4, without mounting the circuit breaker (26) thereon.
Advantages of the present invention
1. The system helps in auto- actuated locking and unlocking of the rails at the maintenance position without any human intervention and using less actuation force.
2. The present invention ensures safety locking position of the rails in the maintenance position thereby maintaining rails in proper maintenance position while remounting the circuit breaker (26) after overhauling.
3. The system maintains both the rails in disconnected position simultaneously thereby ensuring safe and secure operation of remounting of the circuit breaker (26) by avoiding any damage.
4. The system provides synchronized mechanism and can be retrofitted into existing rail design.
5. The present invention provides a simple, cost effective, and reliable automatic locking and unlocking of the rails at the maintenance position.

The foregoing objects of the invention are 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.