Claims:1. A position locking system for circuit breaker having at least one rail assembly 19 to allow motion of a rail, the position locking system comprising:
at least one sheet metal locking link 21 riveted on the rail in flanges of at least a cradle side plate 20 of the circuit breaker; and
at least one position maintaining extension spring 27 operatively coupled to the attached to sheet metal locking link maintaining a position to achieve a position locking of the rail assembly/rails 19. 19
2. The position locking system as claimed in claim 1, wherein the circuit breaker comprises a slider adapted to move in a horizontal direction, and operates the sheet metal locking link by converting linear motion into rotational motion of the sheet metal locking link.
3. The position locking system as claimed in claim 1, the motion of the rail is imparted by using at least one handle 23, whilst in motion, a bent provided in the sheet metal locking link 21 travels over an inclined protrusion 31 of the cradle side plate 20 thereby energizing a lock spring 27 suspended in between the sheet metal locking link 21 and a lock spring support 28.
4. A position locking system for circuit breaker while extracting the circuit breaker out from a disconnected condition to a maintenance condition, wherein at least one locking link passes over an inclined protrusion from at least one side plate, thereby energies at least one spring attached to the locking link to provide a self-locking condition and obstruct the inward motion of rails of the circuit breaker in maintenance position.
, Description:TECHNICAL FIELD

[001] The present subject matter described herein, in general, relates to electrical protection devices, and more particularly relates to Air Circuit Breaker but not limited to be used in an air circuit breaker.

BACKGROUND

[002] Electrical transmission and distribution employs a device known as Circuit breaker; a kind of which known as “Air Circuit breaker” is customarily used in Low Voltage Power distribution systems. It is used to carry, make & break current in low-voltage, high current applications. Two types of circuit breakers are there one is fixed and other is draw- out. Draw out type Air Circuit breakers comprises of cradle assembly which used to carry breaker and can move and hold the breaker in four critical positions of any circuit breaker that is “connected”, “test”, “disconnect” and “maintenance”. Typical advantage of the draw out breaker is that is helps in frequent maintenance of circuit breaker and one can provide interlocked earthling and testing of breaker; it also helps in easy replacement of circuit breaker.

[003] In existing system, Locking of breaker in ‘dis-connected’ position provides by pullout handle ideal position. When handle pull out to remove breaker from disconnected position to maintenance, its de latching with side plates creates unlocking of rails.

[004] However, in present condition, the rail moves by rack in mechanism connected by cam and follower type of joint between drop- plate rivet and cam profile of rack in mechanism, Locking of rail for connected condition is achieved through service latch assembly, for test condition, constant engagement of rivet and cam profile proves sufficient while for disconnected condition, rear part of handle attaches with protrusion of side plate which restricts motion of breaker in outward direction while inward direction motion is again restricted through drop-plate rivet and cam profile. For maintenance condition, screw and nut assembly connects with protrusion from side plate that works as locking in outward direction. There is no locking in maintenance condition.

[005] In view of the above, it may be understood from the above drawbacks that current system has no provision for unexpected inward motion of rail while mounting the breaker. Hence, unexpected movement of rail may lay to offset insertion of breaker into cradle while remounting and in some cases that may cause damage to breaker. This may create safety issue for operator working with it.

[006] The above-described deficiencies of today's locking mechanism of circuit breakers in maintenance condition are merely intended to provide an overview of some of the problems of conventional systems, and are not intended to be exhaustive. Other problems with conventional systems and corresponding benefits of the various non-limiting embodiments described herein may become further apparent upon review of the following description.

SUMMARY OF THE INVENTION

[007] The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.

[008] An object of the present invention is to increase safety of breaker by employing position locking mechanism to maintain rail in maintenance condition while remounting of breaker.

[009] Another object of the present invention is to provide a provision of mechanism retains rail in maintenance condition, by auto engagement of locking link with protrusion made from side plate which restricts inward motion.

[0010] Another object of the present invention is to provide a mechanism to be used to lock the rails in “dis-connected” position.

[0011] Yet another object of the present invention is to provide an initial condition for locking link is maintained through spring and actuation link to actuate locking link which creates unlocks system.

[0012] Still another object of the present invention is to maintain a position actuation link through spring.

[0013] 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 ‘Maintenance’ position where it can be lifted off the cradle for servicing and maintenance activities.

[0014] The present invention concerns to the switchgear application wherein, the objective of the present invention is to provide an efficient position locking system for rails in maintenance condition and is also used for locking in “dis-connected” without any other changes in the existing system.

[0015] In a Draw out type of circuit breaker, the breaker is supported on the rail assembly, which is an integral part of the Cradle assembly. The Cradle assembly consists of the base plate, Racking assembly, side plates for guiding breaker and rail assembly.

[0016] The position lock is achieved by extracting breaker out from disconnected condition to maintenance condition. While doing so breaker locking link passes over inclined protrusion from side plate, energies spring attached to locking link. Link regains its resting position after completion of travel. Thus creates self-locking condition which obstructs inward motion of rails.

[0017] For desired motion of rail towards inward direction, lock must be removed which is achieved by actuating slider that transmits required amount of force which causes rotation of locking link, creates unlocked condition. Initial position of slider is maintained by spring provision.

[0018] The same linkages will be used for locking in “dis-connected” position by having just opposite inclined protrusion on side plates.

[0019] Sheet metal handle part is produced considering ergonomic concept for better gripping and also for assistance while actuating mechanism.

[0020] The present invention solves the problem of maintaining position of rail in maintenance condition while remounting breaker after overhauling. Thus, maintaining both rails in “dis-connected” and “maintenance” condition simultaneously results in safe and secure operation of remounting of breaker avoid any damage to product.

[0021] Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:

[0022] Figure 1 shows schematic layout of cradle assembly.

[0023] Figure 2 shows rail in locked condition (maintenance), in accordance with an embodiment of the present invention.

[0024] Figure 3 shows linkages in unlocked condition (maintenance), in accordance with an embodiment of the present invention.

[0025] Figure 4 shows linkages in locked condition (Dis-connected), in accordance with an embodiment of the present invention.

[0026] Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure. Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0027] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary.

[0028] 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 of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

[0029] 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.

[0030] It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0031] 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.

[0032] Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.

[0033] It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0034] The present invention will now be discussed using various components having reference numerals as provided below:
11 – Cradle base plate
12 – Rack-in screw
13 – Rack
14 – Cradle Cam Shaft Pinion
15 – Cradle Fascia
16 – Cradle Cam Shaft
17 – Cradle Cam Profile
18_ Drop Plate Rivet
19 – Rail Assembly
20 – Cradle Side Plate
21 -Locking Link
22 -Slider
23 -Handle
24 -Handle Rivet
25 -Slider Support
26 -Slider Spring
27 - Lock Spring
28 -Lock Spring Support
29 -Vertical Protrusion
30 -Screw and Nut Assembly
31 -Inclined Protrusion (Maintenance position)
32 -Drop - Plate Assemblies
33- Inclined Protrusion (Dis-connected position)

[0035] The specific feature of the present invention that achieves the technical advancement are as provided below:
i. Sheet metal locking link is riveted on rail and position maintaining extension spring is attached to it. Creating assembly as self-locking.
ii. Slider moves in horizontal direction, operates locking link by converting linear motion into rotational motion of locking link.
iii. Complex handle part is replaced by simple and inexpensive sheet metal part.
iv. Other parts used for locking of rails in “dis-connected” position get eliminated, by achieving it with the same mechanism used for “maintenance” condition thereby making it a multipurpose locking system.

[0036] As shown in figure, rack 13 mounted on Cradle Base Plate 11 connected with Rail Assembly 19 through Drop Plate Rivet 18, poises rail in isolated condition by rotating Rack-In Screw 12. Reciprocation of Rack 13 causes rotation of Cradle Cam Shaft Pinion 14 assembled on Cradle Cam Shaft 16. Cradle Cam Profile 17 attached to Cradle Cam Shaft 16 imparts motion to Drop Plate Rivet 18 riveted on Rail Assembly 19 facilitates to and fro motion of rail in flanges of Cradle Side Plate 20 and creates draw-out feature. Projections provided on breaker housing rest on Rail Assembly 19.

[0037] Application of pulling force on handle 23 imparts motion to rail and makes rail to travel. Whilst in movement bent prepared in Locking Link 21 travels over Inclined Protrusion 31 of Cradle Side Plate 20 energies Lock Spring 27 suspended in between Locking Link 21 and Lock Spring Support 28. Completion of travel releases energy from Lock Spring 27 returns Locking Link 21 to initial position and locking condition is achieved as represented in figure 2. Extraction travel span of rail assembly 19 from disconnected condition to maintenance condition is constrained by Screw and Nut Assembly 30 by latching same with Vertical Protrusion 29 produced in Cradle Side Plate 20.

[0038] During remounting of breaker, position locking of Rail Assembly 19 ensures operational safety. For Unlocking, Locking Link 21 is rotated by applying force on Slider 22 form rear end. Linear motion of Slider 22 towards cradle side energies Slider Spring 26 attached to Slider 22 and Slider Support 25 giving upon same reestablishes original position. Thus creating unlocked condition as shown in figure 3 to allow getting back Rail Assembly 19 to disconnected condition by application of push force at Handle 23 riveted on Rail Assembly 19 by two identical rivets 24.

[0039] The same linkages work when breaker moves from “Test” to “dis-connected” position. Locking link 21 gets locked against Inclined Protrusion 33. When inputs given to slider 22 the same gets unlock and breaker can be move out to maintenance position as shown in figure 4.

[0040] Apart from what is disclosed above, the present invention also includes some additional technical advantages/benefits, some of them are mentioned below:
i. The features of the invention provide self –locking capability for maintenance condition.
ii. Unlocked position is achieved by minimum human intervention.
iii. Ergonomic design results handling compatibility.
iv. Mechanism works for both ‘Dis-connected’ and ‘maintenance’ condition.
v. Sheet metal part with optimized weight and with minimum thickness requires optimum production energy.
vi. Sheet metal parts facilitates qualitative high rate production
vii. The present invention provides auto position lock for maintenance condition.
viii. The same mechanism can be used to lock the rails in “dis-connected” position.
ix. Self-position achieving mechanism with less actuation force.
x. Sheet metal parts produced through minimum number of operations result in reduction of cost.
xi. Assembly process of mechanism is easy and effective.

[0041] It may be clearly understood by a person skilled in the art that for the purpose of convenient and brief description, for a detailed working process of the foregoing system, devices, and unit, reference may be made to a corresponding process in the foregoing device/apparatus embodiments, and details are not described herein again.

[0042] In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus, and device may be implemented in other manners. For example, a plurality of units or components or mechanisms may be combined or integrated into another system, or some features may be ignored or not performed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections may be implemented through some interfaces. The indirect couplings or communication connections between the apparatuses or units may be implemented in electronic, mechanical, or other forms.

[0043] The various mechanisms described as separate parts may or may not be physically separate, and the parts displayed as mechanisms may or may not be physical units, may be located in one position, or may be distributed at various location of the device. Some or all of the units may be selected to achieve the objective of the solution of the embodiment according to actual needs.

[0044] In addition, the mechanisms in the embodiments of the present invention may be integrated into one processing unit, or each of the mechanisms may exist alone physically, or two or more mechanisms may be integrated into one mechanism.

[0045] Although a position locking linkages/mechanism for draw-out type air circuit breaker is disclosed, it is to be understood that the embodiments disclosed in the above section are not necessarily limited to the specific features or methods or devices described. Rather, the specific features are disclosed as examples of implementations of the position locking linkages/mechanism for draw-out type air circuit breaker.