FORM 2
The Patents Act 1970
(39 of 1970)
&
The Patent Rules 2003
COMPLETE SPECIFICATION
(See Section 10 and rule 13)
TITLE OF THE INVENTION:


JAW CAGE ASSEMBLY FOR JAW CLUSTER FOR DRAW OUT
TYPE CIRCUIT BREAKERS
APPLICANT:
LARSEN & TOUBRO LIMITED
L&T House, Ballard Estate, P.O. Box No. 278,
Mumbai, 400 001, Maharashtra . INDIA.
PREAMBLE OF THE DESCRIPTION:
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

A) TECHNICAL FIELD
[0001] The present invention generally relates to circuit breakers and particularly to a jaw cage for jaw cluster assembly in draw out type circuit breakers.
B) BACKGROUND OF THE INVENTION
[0002] The circuit breakers are used to protect equipments in an installation in case of a over current arising out of abnormal circuit conditions. A circuit breaker typically comprises a spring loaded contact system to carry, make, and break the current under normal and abnormal conditions involving a very high over-current.
[0003] Air circuit breakers use air as a medium to extinguish arcs in the circuit breakers used in industrial applications. The air circuit breakers are used for main power distribution in large industrial plants. The air circuit breakers are expected to operate to interrupt the fault current rapidly so as to minimize damage to the installations (downstream equipments) resulting from thermal and mechanical stresses. Two types of the air circuit breakers as per construction are fixed type and draw-out type. The circuit breakers are provided with complimentary draw-out construction for easy installation and separation from the cradle assembly without disturbing main power connections. The circuit breakers can be tested and serviced by mechanically moving it away from the cradle terminals coupled to the main power circuit.
[0004] In draw-out type of air circuit breakers, there are a cradle part which is fixed in panel, and a breaker part which is withdraw-able for some maintenance purposes. The

breaker part can be connected or disconnected from the cradle part connected to the main power circuit by an axial withdrawal motion of the breaker part. A jaw cluster assembly is provided to act as a link between the cradle part and the breaker part after rack-in position. Generally, the jaw cluster assembly may consist of jaw fingers, jaw springs, and a jaw cage.
[0005] The currently available jaw cages have large number of components such as a spacer, frame, supporter, spacer, and so on. These jaw cages have more complex mechanical arrangements. So, the manufacturing cost of those kinds of jaw cages is high. Also, the currently available jaw cages carry a load and do not be free in the service position (rack-in position) of the air circuit breakers. Hence, there is a need to provide a jaw cage of jaw cluster which is free and does not carry any load in the service position of the air circuit breakers. Also there is a need is to provide a simple jaw cage design at reduced cost.
[0006] The abovementioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.
C) OBJECT OF THE INVENTION
[0007] The primary object of the present invention is to provide a jaw cage assembly for jaw cluster for jaw arrangement in draw-out type air circuit breakers.
[0008] Another object of the present invention is to provide a jaw cage assembly to hold jaw springs in place in the jaw cluster against electrical forces.

[0009] Yet another object of the present invention is to provide a jaw cage assembly to permit the required swivelling motion of the jaw cluster in the cradle terminal only.
[0010] Yet another object of the present invention is to provide a jaw cage assembly to lock the jaw cluster in the cradle terminal for its movement.
[0011] Yet another object of the present invention is to provide a jaw cage for ease of assembly of the jaw cluster and ease of manufacturing of jaw cage.
[0012] These and other objects and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.
D) SUMMARY OF THE INVENTION
[0013] The various embodiments of the present invention provide a jaw cage assembly for jaw cluster assembly with jaw arrangement in draw-out type air circuit breakers. According to one embodiment of the present invention, the jaw cage has a horizontal bar to hold the two sets of jaw clusters from the top. Two vertical walls are provided integrally at the two edges of the horizontal bar. The vertical walls are formed integrally with the horizontal bar by bending the two extreme edges of the horizontal bar

orthogonally, the vertical walls are received in a guide groove provided at the jaw finger to prevent the lateral displacement of jaw fingers.
[0014] A bent edge is formed at the end of the vertical wall. The bent edges are provided at the vertical wall integrally to hold the bottom portion of the jaw finger assembly.
[0015] Two protrusions are provided at the middle section of the horizontal bar to hold the springs provided between the jaw fingers. The two protrusions are provided at the opposite sides in the horizontal bar to protrude in mutually opposite directions.
E) BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in-1 which:
[0017] FIG. 1 illustrates a side perspective view of a rack-out position of air circuit breakers according to one embodiment of the present invention.
[0018] FIG. 2 illustrates a side perspective view of a rack-in position of air circuit breakers according to one embodiment of the present invention.

[0019] FIG. 3 illustrates a side perspective view of locating a jaw cluster in the cradle terminal according to one embodiment of the present invention.
[0020] FIG. 4 illustrates a top perspective view of middle position of a jaw cluster in the cradle terminal according to one embodiment of the present invention.
[0021] FIG. 5 illustrates a top perspective view of swivelled position of a jaw cluster in the cradle terminal according to one embodiment of the present invention.
[0022] FIG. 6 illustrates a top perspective view of service position of the breaker according to one embodiment of the present invention.
[0023] FIG. 7 illustrates a side perspective view of assembly of a jaw cluster according to one embodiment of the present invention.
[0024] FIG. 8 illustrates a top perspective view of assembly of a jaw cluster according to one embodiment of the present invention.
[0025] Although specific features of the present invention are shown in some drawings and not in others. This is done for convenience only as each feature may be combined with any or all of the other features in accordance with the present invention.

F) DETAILED DESCRIPTION OF THE INVENTION
[0026] In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which the specific embodiments that may be practiced is shown by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and it is to be understood that the logical, mechanical and other changes may be made without departing from the scope of the embodiments. The following detailed description is therefore not to be taken in a limiting sense.
[0027] The various embodiments of the present invention provide a jaw cage assembly for jaw cluster assembly with jaw arrangement in draw-out type air circuit breakers. According to one embodiment of the present invention, the jaw cage has a horizontal bar to hold the two sets of jaw clusters from the top. Two vertical walls are provided integrally at the two edges of the horizontal bar. The vertical walls are formed integrally with the horizontal bar by bending the two extreme edges of the horizontal bar orthogonally. The vertical walls are received in a guide groove provided at the jaw finger to prevent the lateral displacement of jaw fingers.
[0028] A bent edge is formed at the end of the vertical wall. The bent edges are provided at the vertical wall integrally to hold the bottom portion of the jaw finger assembly.

[0029] Two horizontal protrusions are provided at the middle section of the horizontal bar to hold the springs provided between the jaw fingers. The two protrusions are provided at the opposite sides in the horizontal bar to protrude in mutually opposite directions.
[0030] According to one embodiment of the present invention, a jaw cage is designed with flaps on upper and down sides of the jaw cage, bent portions, and vertical walls in both sides of the jaw cage.
[0031] The flaps are designed such that the flaps cover the jaw springs sidewise up to a sufficient extent. Even though the jaw springs are located in the jaw cluster by their own force, the flaps prevent any movement of the jaw springs in sidewise due to any electrical force occurred during carrying current and short circuit.
[0032] The vertical walls of the jaw cage are located in front of the walls of the cradle terminal in the jaw cluster assembly. This mechanism locks further swiveling of the jaw cluster. Basically, the circular profile of the jaw fingers is to be fully fitted in the circular profile of the cradle terminal against all degrees of freedom except calculated amount of swiveling in the cradle terminal. This calculated amount of swiveling is necessary so that the jaw cluster gets aligned by itself so as to accommodate the breaker terminal adapters in horizontal direction while rack-in operation. Hence, the vertical walls of the jaw cage are designed to limit the swiveling of the jaw cluster after certain level to prevent the jaw

cluster obstructing the profile of the breaker terminal adapters during the rack-in operation.
[0033] The bent portions of the jaw cage are designed such that, the bent portions fit in corresponding slots given on cradle terminal. Thus, the bent portions of the jaw cage stop the movement of jaw clusters which may be happened due to short circuit forces. Also, the bent portions avoid arcing initiated at that time.
[0034] The jaw cage is designed such that, while forming assembly of the jaw cluster, the jaw cage holds the jaw fingers against force of spring, but does not carry any load in service position. When the breaker terminal is in the rack-in position, the jaw fingers are held by the cradle terminal and the breaker terminal adapters. At this time, the jaw cage becomes free. Ideally the jaw cage does not carry any load in service position.
[0035] For making assembly of the jaw cluster, the jaw springs are inserted in the jaw cluster from both the ends and fitted in the slots of the jaw finger. Protrusion of the jaw cage fits in slot of the jaw finger. For making assembly of the jaw cluster in the cradle terminal, it is enough to simply push the jaw cluster in the cradle terminal such that the bent portions of the jaw cage fit in the slots provided in the cradle terminal. So that entry chamfer of the breaker terminal adapter comes in front of the jaw fingers. Hence, the design of the jaw cage makes the assembly of the jaw cluster to be simple without
T
requiring any tool.

[0036] FIG. 1 illustrates a side perspective view of a rack-out position of air circuit breakers according to one embodiment of the present invention. With respect to FIG. 1, the air circuit breaker includes a cradle terminal 1, a breaker terminal adapter 2, and a jaw cluster 3. During rack-out position, the cradle terminal 1 and the breaker terminal adapter 2 are disconnected and the jaw cluster 3 is latched with the cradle terminal 2. The circular profile of the jaw fingers of jaw cluster 3 is fully fitted in the circular profile of the cradle terminal 1.
[0037] FIG. 2 illustrates a side perspective view of a rack-in position of air circuit breakers according to one embodiment of the present invention. With respect to FIG. 2, during rack-in position the breaker terminal adapter 2 is connected to the cradle terminal 1 connected to the main power circuit by an axial withdrawal motion of the breaker terminal adapter 2. The jaw cluster 3 is provided to act as a link between the cradle terminal 1 and the breaker terminal adapter 2 during the rack-in position.
[0038] FIG. 3 illustrates a side perspective view of locating a jaw cluster in the cradle terminal according to one embodiment of the present invention. With respect to FIG. 3, a bent portion of jaw cage 7 is designed such that, the bent portion of jaw cage 7 fits in corresponding slots in the cradle terminal 9. Thus, the bent portion of jaw cage 7 stops the movement of jaw clusters which may be happened due to short circuit forces. Also, the bent portion of jaw cage 7 prevents arcing initiated at that time.

[0039] FIG. 4 illustrates a top perspective view of middle position of a jaw cluster in the cradle terminal according to one embodiment of the present invention. With respect to FIG. 4, a vertical wall of jaw 11 cage is located in front of a vertical wall of cradle terminal 12. This is called as middle position of the jaw cluster 3 and the circular profile of the jaw fingers is to be fully fitted in the circular profile of the cradle terminal 1 in this middle position. This construction leads the swiveling of the jaw cluster 3 with the cradle terminal 1.
[0040] FIG. 5 illustrates a top perspective view of swivelled position of a jaw cluster in the cradle terminal according to one embodiment of the present invention. With respect to FIG. 5, the mechanism of vertical wall of jaw cage 11 locks further swiveling of the jaw cluster 3. Basically, the circular profile of the jaw fingers is to be fully fitted in the circular profile of the cradle terminal 1 against all degrees of freedom except calculated amount of swiveling in the cradle terminal 1. This calculated amount of swiveling is necessary so that the jaw cluster 3 gets aligned by itself so as to accommodate the breaker terminal adapter 2 in horizontal direction while rack-in operation. Hence, the vertical wall of the jaw cage 11 is designed to limit the swiveling of the jaw cluster 3 after certain level to prevent the jaw cluster 3 obstructing the profile of the breaker terminal adapters during the rack-in operation.
[0041] FIG. 6 illustrates a top perspective view of service position of the breaker according to one embodiment of the present invention. With respect to FIG. 6. the jaw cage is designed such that, while forming assembly of the jaw cluster 3, the jaw cage

holds the jaw fingers against force of spring, but does not carry any load in the service position. When the breaker terminal adapter 2 is in the service position (or rack-in position), the jaw fingers are held by the cradle terminal 1 and the breaker terminal adapter 2. At this time, the jaw cage becomes free. Ideally the jaw cage does not carry any load in the service position.
[0042] FIG. 7 illustrates a side perspective view of assembly of a jaw cluster according to one embodiment of the present invention. With respect to FIG. 7, while assembling of jaw cluster, the jaw fingers 4 are inserted in the jaw cage 5 with the circular portion of jaw fingers on the bent portion of jaw cage 7. Protrusions of jaw cage fit in the slot for jaw cage in jaw finger. Then, compression jaw springs 8 are inserted in the jaw cluster from both the ends and fitted in the slots for jaw springs in jaw fingers. The design of jaw cage allows the flaps of jaw cage 6 to come in front of the jaw springs 8 and locking movements of jaw springs 8 in sidewise. For making assembly of the jaw cluster in the cradle terminal, it is enough to simply push the jaw cluster in the cradle terminal such that the bent portions of the jaw cage 7 fit in the slots provided in the cradle terminal. So that entry chamfer of the breaker terminal adapter 10 comes in front of the jaw fingers for a smooth rack-in operation.
[0043] FIG. 8 illustrates a top perspective view of assembly of a jaw cluster according to one embodiment of the present invention. With respect to FIG. 8, the protrusions in jaw cage 13 fit in the slots for jaw cage in jaw finger 14. Then, compression jaw springs 8 are

inserted in the jaw cluster from both the ends and fitted in the slot for jaw spring in jaw finger 15.
G) ADVANTAGES OF THE INVENTION
[0044] Thus the various embodiments of the present invention provide a jaw cage design of jaw cluster for jaw arrangement of draw-out air circuit breakers. The jaw cage is designed such that, the assembly of jaw cluster is highly simplified. It does not involve any secondary operation such as welding, riveting or bending during the assembly of jaw cluster. It is enough that simply hold the jaw fingers against the jaw cage and push the jaw springs from front and back sides for the assembly of jaw cluster. Even simple fixture for pushing the jaw springs would be enough.
[0045] As the jaw cage does not carry any load in the service position, there is no need of having strong material for manufacturing of the jaw cage. Any manufacturing friendly material such as brass can be used for manufacturing of the jaw cage, which reduces required capacity of punching tool as well as bending tool. Manufacturing of jaw cage involves simple punching and bending operations at low cost due to its innovative design. Layout is such that sufficient margin is provided and thin walls are excluded. This enhances life of punch. This drastically reduces manufacturing cost.
[0046] When entry chamfer of breaker terminal adapter comes in front of jaw fingers, the swiveling of jaw cluster allows the jaw cluster to easily accommodate the breaker

terminal adapter. This prevents the jaw cluster obstructing the profile of the breaker terminal adapters during the rack-in operation, which may be happened due to manufacturing and assembly tolerances.
[0047] Although the invention is described with various specific embodiments, it will be obvious for a person skilled in the art to practice the invention with modifications. However, all such modifications are deemed to be within the scope of the claims.

[0048] It is also to be understood that the following claims are intended to cover all of the generic and specific features of the present invention described herein and all the statements of the scope of the invention which as a matter of language might be said to fall there between.
Date: March 30, 2009. Place: Bangalore.

CLAIMS
What is claimed is:
1. A jaw cage assembly for jaw finger assembly in air circuit breaker comprising:
a horizontal bar;
two vertical walls provided at the two edges of the horizontal bar; a bent edge formed at the end of the vertical wall; and two horizontal protrusions provided at the horizontal bar.
2. The assembly according to claim 1, wherein the horizontal bar is arranged to hold the two sets of jaw clusters from the top.
3. The assembly according to claim 1, wherein, the two horizontal protrusions are provided at the middle section of the horizontal bar to hold the springs provided between the jaw fingers.
4. The assembly according to claim 1, wherein the two protrusions are provided at the opposite sides in the horizontal bar.
5. The assembly according to claim 1, wherein the two horizontal protrusions are protrude d at mutually opposite directions.

6. The assembly according to claim 1, wherein the vertical walls are formed integrally with the horizontal bar by bending the two extreme edges of the horizontal bar orthogonally.
7. The assembly according to claim 1, wherein the vertical walls are received in a guide groove provided at the jaw finger to prevent the lateral displacement of jaw fingers.
To,
The Controller of Patents,
The Patent office,
Mumbai
8. The assembly according to claim 1, wherein the bent edges are provided at the vertical wall integrally to hold the bottom portion of the jaw finger assembly.