DESC:TECHNICAL FIELD

The present subject matter described herein, in general relates to a circuit breakers, and more particularly, to an improved racking mechanism of draw out circuit breakers and their position based latching arrangement.

BACKGROUND

An electrical circuit breaker may be defined as a unit designed to carry, make and break current and protect the equipments connected in the electrical circuit from abnormal conditions like overload, under-voltage or short circuit etc. A circuit breaker is commonly used as an electrical switching device.

There are two popular versions of circuit breakers namely, Fixed and Draw-Out type. In the Draw out type, the breaker can be removed without dismantling the terminals, in order to facilitate maintenance and secure stability. Unlike fixed breakers, draw out breakers are housed inside the cradle or cassette. They can be racked-in and out from cradle.

In a Draw out type of circuit breaker, positions of breaker with respect to cradle are normally defined as 'Disconnected', 'Test' and 'Connected'. When breaker is completely racked in i.e. in 'Connected' position, breaker terminals are in contact with cradle terminals through cradle jaws in the 'Connected' position. In this condition, both Power (main) circuit and control circuit are connected and the breaker can be switched ON. When the breaker is completely racked out i.e. in 'Disconnected ' position, both main circuit and control circuit are disconnected. In the 'Test’ position, Power (main) circuit is not connected but control circuit is connected. The breaker can also be drawn out to extended position where it can be lifted off the cradle for servicing and maintenance activities.

The present racking mechanisms use a power screw to transmit rotational motion of racking handle to translational motion of a sliding rack. A pinion engages with rack, transforming rack motion to rotation of a pinion shaft, which in turn transfers motion via a cam arrangement responsible for racking of the circuit breaker.

Further, the present racking mechanisms have huge amount of transmission losses during conversion of translational to rotational motion. Also, most of the present racking mechanisms are inefficient as there are non consequential force components lost due to transforming of translational to rotational motion and then back to translation of breaker, as they use a rotary cam to transfer forces to the rails on which breaker sits.

Further, due to present complex racking mechanisms with a larger number of components efficiency losses involved are extensive. There is high expenditure incurred in manufacturing and also a high possibility of malfunction due to higher failure modes. It gives rise to a requirement of simple robust mechanism which can eliminate these issues.

Furthermore, the present racking mechanisms require a certain degree of cam rotation in order to latch the breaker in position. This cause’s backlash error as dead turns exists, wherein the breaker does not travel on racking handle rotation, causing discrepancy when breaker is racked in or out.

Thus due to above mentioned drawbacks, there exists a need for an efficient improved racking mechanism that has high transmission efficiency leading to less effort in racking the breaker. Further, the proposed solution should be simple, cost effective and must have a robust design. The proposed racking mechanism must have a negligible backlash error, with minimal discrepancy in rack in and rack out operations. The proposed racking mechanism must have a self latching arrangement, with minimal play, in all positions of circuit breaker and must have ergonomic manual disengagement integrated into the rail assembly.

SUMMARY

This summary is provided to introduce concepts related to an improved racking mechanism with auto-latch and de-latch arrangement in a circuit breaker. This summary is not intended to identify essential features of the subject matter nor is it intended for use in determining or limiting the scope of the subject matter.

In one implementation, the invention is intended to provide an improved racking mechanism with auto-latch and de-latch arrangement in a circuit breaker.

In one implementation, an efficient improved racking mechanism that has high transmission efficiency leading to less effort in racking the breaker is disclosed. The proposed solution is simple, cost effective and has a robust design. The proposed racking mechanism provides a negligible backlash error, with minimal discrepancy in rack in and rack out operations. The proposed racking mechanism have a self latching arrangement, with minimal play, in all positions of circuit breaker and have an ergonomic manual disengagement integrated into the rail assembly.

In one implementation, in a Draw out type of circuit breaker is disclosed. The breaker is supported on the rail assembly (12), which is an integral part of the Cradle assembly (11). The Cradle assembly consists of the base plate (13), Racking assembly (14), side plates (15) for guiding breaker and rail assembly. Racking operation is accomplished by the racking assembly mounted on the base plate (13).

Accordingly, in one implementation, a mechanism for racking a circuit breaker on draw-out rails along with a positive engagement latching arrangement is disclosed. The mechanism comprises of a cradle assembly (11). The cradle assembly (11) further comprises of a rail assembly (12), a base plate (13), a racking assembly (14) mounted on the base plate (13) to perform the racking operation; and at least one side plate (15) for guiding breaker and rail assembly.

BRIEF DESCRIPTION OF THE ACCOMPANYINGDRAWINGS

The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to refer like features and components.

Figure 1 illustrates a cradle assembly overview is shown, in accordance with an embodiment of the present subject matter.

Figure 2 illustrates details of racking arrangement while engaging in spring loaded camis shown, in accordance with an embodiment of the present subject matter.

Figure 3 illustratesdetails of engagement of spring loaded cam in racking arrangement is shown, in accordance with an embodiment of the present subject matter.

Figure 4 illustrates the de-latching linkage overview is shown, in accordance with an embodiment of the present subject matter

Figure 5 illustrates the actuation of de-latching linkage is shown, in accordance with an embodiment of the present subject matter

DETAILED DESCRIPTION

Preferred embodiments of the present disclosure will be described herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail.

The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

Accordingly, the disclosedinvention is related to an improved racking mechanism with auto-latch and de-latches arrangements in a circuit breaker.

Construction of the connector assembly of the present invention is explained with reference to the accompanying figures.

List of components used in the figure are:

1. Cradle assembly (11)
2. rail assembly (12)
3. base plate (13)
4. Racking assembly (14)
5. side plates (15)
6. Racking power screw (16)
7. Compound rack (17)
8. Cross member (18)
9. Spring loaded cam (19)
10. Additional Support Members (20)
11. De-latching linkages (21)

In one implementation, a draw out type of circuit breaker, the breaker is supported on the rail assembly (12), which is an integral part of the Cradle assembly (11). The Cradle assembly consists of the base plate (13), Racking assembly (14), side plates (15) for guiding breaker and rail assembly. Racking operation is accomplished by the racking assembly mounted on the base plate (13).

According to the embodiment of the present invention, the racking assembly (14) and latching arrangement of an air circuit breaker are described below:

Racking assembly as shown in figure 2, the assembly consists of the racking power screw (16) which is rotated by using a racking handle. The racking screw (16) is engaged with a compound rack (17) via an internal thread in the rack,in a manner that allows thecompound rack (17) to slide to and fro as the racking screw (16) is rotated. Theracking screw (16) has nuts welded onto it positioned apart so as to limit the travel of the compound rack (17). The compound rack (17) is rigidly coupled to a cross member (18)bearing the spring loaded cam (19), which latches & de-latches with thedrop plate assembly (22) of the rail assembly (12), on which the circuit breaker is mounted. The rotation of the racking handle causes the power screw (16) to rotate which, in turn moves the rack inside (towards “Connected” position) or outside (towards “Disconnected” position) depending upon whether it is a rack-in (Clockwise) or rack-out (Anti-Clockwise) operation. The cross member (18) sequentially transfers motion of the compound rack (17) , guided by additional support members (20) to the spring loaded cam (19) which is engaged, by means of its spring function with the drop plate assembly (22) when breaker is pushed into “Disconnected position”.

Latching arrangement as shown in figure 2 and figure 3, it consists of a spring loaded cam (19) which is actuated by means of cam action of drop plate assembly (22), when rail mounted breaker is pushed into cradle (11) to “Disconnected” position. There from, spring loaded cam (19) constantly maintains positive engagement with the rail via the drop plate assembly (22), unless actuated otherwise. The de-latching linkages (21) shown in fig. 4 and 5 are interacting with the pulling (23) handle on the rails, which when actuated and pulled outward, pushes down the spring loaded cam (19) thus disengaging the breaker from the racking mechanism and bringing it out from “Disconnected “ position to “Maintenance”.

The object of the present invention is to provide a racking assembly which integrates an efficient mechanism for racking the circuit breaker on draw-out rails along with a simple yet robust positive engagement latching arrangement which can be defeated when required by user.

Referring now to figure 1 illustrates a cradle assembly overview is shown, in accordance with an embodiment of the present subject matter. In one embodiment the detailed working of figure 1 is as given above.

Referring now to figure 2 illustrates details of racking arrangement while engaging in spring loaded cam is shown, in accordance with an embodiment of the present subject matter. In one embodiment the detailed working of figure 2 is as given above.

Referring now to figure 3 illustrates Details of engagement of spring loaded cam in racking arrangement is shown, in accordance with an embodiment of the present subject matter. In one embodiment the detailed working of figure 3 is as given above.

Referring now to figure 4 illustrates the de-latching linkage overview is shown, in accordance with an embodiment of the present subject matter. In one embodiment the detailed working of figure 4 is as given above.

Referring now to figure 5 illustrates the actuation of de-latching linkage is shown, in accordance with an embodiment of the present subject matter. In one embodiment the detailed working of figure 5 is as given above.

In one implementation, a mechanism for racking a circuit breaker on draw-out rails along with a positive engagement latching arrangement is disclosed. The mechanism comprises of a cradle assembly (11). The cradle assembly (11) further comprises of a rail assembly (12), a base plate (13), a racking assembly (14) mounted on the base plate (13) to perform the racking operation; and at least one side plate (15) for guiding breaker and rail assembly.

In one implementation, the racking assembly (14) comprises of a racking power screw (16); a compound rack (17); a cross member (18); a spring loaded cam (19); an additional support members (20); and a de-latching linkages (21); and a drop plate assembly (22).

In one implementation, the racking power screw (16) is rotated by using a racking handle; and a nut is welded to the racking screw (16) which is engaged with a compound rack (17) connected to the rail assembly (12), on which the circuit breaker is mounted, by means of a cross member (18).

In one implementation, the rotation of the racking handle causes the power screw (16) to rotate which, in turn moves a rack inside or outside; and the cross member (18) sequentially transfers a motion of the compound rack (17), to the spring loaded cam (19) which is engaged with the drop plate assembly (22) of the rails on which the breaker is mounted.

In one implementation, the rack moves inside or outside depending upon a rack-in or rack-out operation.

In one implementation, the transfer of the motion of the compound rack (17) is guided by additional support members (20).

In one implementation, the latching arrangement comprises of the spring loaded cam (19) actuated by means of cam action of, when rail mounted breaker is pushed into the cradle (11) to a “Disconnected” position, thereby the latching arrangement maintains positive engagement with the rail using the drop plate assembly (22).

In one implementation, the de-latching linkages (21) interacts with the pulling (23) handle on the rails.

In one implementation, the de-latching linkage (21) interacts with the pulling (23) handle on the rails which when actuated pushes down the spring loaded cam (19) disengages the breaker from the mechanism.

Exemplary embodiments discussed above may provide certain advantages. Though not required to practice aspects of the disclosure, these advantages may include those provided by the following features:

a racking power screw (16);
a compound rack (17);
a cross member (18);
a spring loaded cam (19);

One feature of the invention is that, it eliminates stage wise transmission losses completely by avoiding conversion of translational to rotational motion.Existing methods of racking are inefficient as there are non consequential force components lost due to transforming of translational to rotational motion and then back to translation of breaker. Disclosed invention relies purely on a racking power screw (16) to convert users’ rotational movement of the racking handle to linear translation of the compound rack (17) and henceto the cross member (18) bearing the spring loaded cam (19)which is responsible for racking operation of the breaker via the rail assembly (12). Most present racking mechanisms use a power screw to transmit rotational motion of racking handle to translational motion of a sliding rack. A pinion engages with rack, transforming rack motion to rotation of a pinion shaft, which in turn transfers motion via a rotary cam responsible for racking of the circuit breaker.

Another feature of the invention is that, the current racking mechanisms utilizing a rotary cam type component for interacting with the breaker rails require a certain degree of vacant cam rotation in order to latch the breaker in position. This causes backlash error as dead turns exists, wherein the breaker does not travel on racking handle rotation, causing discrepancy when breaker is racked in or out. The present invention employs a linear travel spring loaded cam (19) to achieve the latching function with the rail assembly (12). It eliminates the probability of backlash error occurrence altogether because of negligible play in the cam, possible only due to the linear travel nature of the cam design. Minimal discrepancy in rack in and rack out operations is achieved.

Another feature of the invention is that, the simple, cost effective yet robust racking mechanism design with high transmission efficiency, leads to less effort in racking the breaker.
On the other hand present complex racking mechanisms with a larger number of components involveextensiveefficiency losses. There is high expenditure incurred in manufacturing and also a high possibility of malfunction due to higher failure modes.

Yet another feature of the invention is that, the self latching arrangement, with minimal play, in all positions of circuit breaker is provided.

Still another feature of the invention is that, an ergonomic manual disengagement of the spring loaded cam (19)integrated into the rail assembly(12) is achieved.

To summarize, the features are as follows:
1. The disclosed invention embodies a simple, robust racking system to withstand enormous forces during short circuit conditions.
2. High efficiency in transmission with minimal exertion of input energy as a pre requisite, with direct transmission of linear force and almost zero conversion losses
3. Negligible backlash error, as rotary type latching arrangement is replaced by linear latching system
4. Self latching arrangement on pushing of draw out breaker rails into cradle
5. Positive engagement latching in any desired position of breaker due to minimal play in latching arrangement
6. Ergonomic manual disengagement integrated into the rail assembly for disengaging of breaker rails from racking assembly

Although implementations for the an improved racking mechanism with auto-latch and de-latch arrangement in a circuit breakerhave been described in language specific to structural features and/or the methods, it is to be understood that the appended claims are not necessarily limited to the specific features or methods described. Rather, the specific features are disclosed as examples of, an improved racking mechanism with auto-latch and de-latch arrangement in a circuit breaker.

It is intended that the disclosure and examples above be considered as exemplary only, with a scope of disclosed embodiments should be considered with indicated by the claims in the followingsection.
,CLAIMS:1. A mechanism for racking a circuit breaker on draw-out rails along with a positive engagement latching arrangement, the mechanism comprising:
a cradle assembly (11) comprising
a rail assembly (12);
a base plate (13);
a racking assembly (14) mounted on the base plate (13) to perform the racking operation; and
at least one side plate (15) for guiding breaker and rail assembly.

2. The mechanism as claimed in claim 1, wherein the racking assembly (14) comprises:
a racking power screw (16);
a compound rack (17);
a cross member (18);
a spring loaded cam (19);
an additional support members (20); and
a de-latching linkages (21); and
a drop plate assembly (22).

3. The mechanism as claimed in claim 1 and 2, wherein
the racking power screw (16) is rotated by using a racking handle; a nut is welded to the racking screw (16) which is engaged with a compound rack (17) connected to the rail assembly (12), on which the circuit breaker is mounted, by means of a cross member (18).

4. The mechanism as claimed in claim 1 to 3, wherein
the rotation of the racking handle causes the power screw (16) to rotate which, in turn moves a rack inside or outside;
the cross member (18) sequentially transfers a motion of the compound rack (17), to the spring loaded cam (19) which is engaged with the drop plate assembly (22) of the rails on which the breaker is mounted.

5. The mechanism as claimed in claim 1 to 4 , wherein the rack moves inside or outside depending upon a rack-in or rack-out operation.

6. The mechanism as claimed in claim 1 to 4, wherein the transfer of the motion of the compound rack (17) is guided by additional support members (20).

7. The mechanism as claimed in claim 1 and 2, wherein the latching arrangement comprises:
the spring loaded cam (19) actuated by means of cam action of, when rail mounted breaker is pushed into the cradle (11) to a “Disconnected” position, thereby
the latching arrangement maintains positive engagement with the rail using the drop plate assembly (22).

8. The mechanism as claimed in claim 1, 2, and 7, wherein the de-latching linkages (21) interacts with the pulling (23) handle on the rails.

9. The mechanism as claimed in claim 1, 2, 7, and 8, wherein the de-latching linkages (21) interacts with the pulling (23) handle on the rails which when actuated pushes down the spring loaded cam (19) disengages the breaker from the mechanism.