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:
GUIDING MECHANISM FOR SECONDARY ISOLATING CONTACTS IN 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 relates to a guiding mechanism for circuit breakers. The present invention more particularly relates to a guiding mechanism for secondary isolating contacts in circuit breakers.
B) BACKGROUND OF THE INVENTION
[0002] A circuit breaker is used in an electrical system to carry, make
and break the circuit. The circuit breaker consists of power contacts and control contacts. The control contact connects/disconnects the accessories/equipments connected in the control circuit. A circuit breaker has been categorized into two versions namely a fixed and a withdraw-able type. The withdraw-able type of version consists of withdraw-able unit also known as cradle and the breaker part.
[0003] Generally, circuit breakers are employed with secondary
isolating contacts with a one level of alignment for transition from maintenance position to connected position. However, with this one level of arrangement there are issues like misalignment of cradle secondary isolating contacts (SICs) and breaker secondary isolating contacts (SICs) and also deformation of contacts. The deformation of the contact terminals results in loss of continuity either momentarily or permanently which in turn leads to low reliability of secondary isolating contact system. The withdraw-able type of circuit breaker has three positions, namely a connected, a test and a disconnected position. In connected position, the power contacts and control contacts are engaged. Further in test position, only control contacts are engaged and in the disconnected position, both the control and power contacts are disengaged.

[0004] In the existing technique, there are two levels of alignment
provided for secondary isolating contacts (SIC). In the first level, an alignment is done between a breaker SIC bridge (moving) and a cradle SIC bridge (fixed). This alignment is achieved by providing scope for horizontal movement to the breaker SIC bridge to get adjusted within the cradle SIC bridge. In the second level, an alignment is done between a breaker secondary isolating contact and a cradle secondary isolating contact where either of the two contacts includes a profile for ease of alignment of the corresponding contacts. After first level of alignment, there is a clearance provided between the breaker SIC bridge and the cradle SIC bridge for movement of the bridge. This clearance creates a misalignment between the axes of the breaker SIC contacts and the corresponding cradle SIC contact. This misalignment is to be adjusted to make proper contact between the respective contacts of the cradle SIC and the breaker SIC. In current design, the misalignment of the of the whole breaker SIC bridge so that each of the breaker SIC contacts gets aligned with the cradle SIC contacts. This constitutes second level of alignment. In this case, the load of the whole bridge comes on a single contact which is getting aligned initially and due to this arrangement the metai contact gets deformed due to the load.
[0005] Further the current designs have an interdependence of one
breaker SIC on the adjacent SICs for their location. This imposes difficulty in the assembly of individual SICs. Further due to dependent positioning of SICs, the removal of a single SIC from the breaker SIC bridge is difficult.
[0006] Hence, there exists a need to provide a guiding mechanism for
circuit breakers for aligning the secondary isolating contacts to enhance the reliability of the contact system. There also exists a guiding mechanism which does not necessitate any interdependency between secondary isolating contacts for effective alignment.

[0007] The above mentioned shortcomings, disadvantages and
problems are addressed herein and which will be understood by reading and studying the following specification.
C) OBJECT OF THE INVENTION
[0008] The primary object of the present invention is to provide a
guiding mechanism for aligning secondary isolating contacts in circuit
breakers.
[0009] Another object of the present invention is to provide a guiding
mechanism to enhance the reliability of the contact system in circuit breakers.
[0010] Yet another object of the present invention is to provide a
guiding mechanism which does not cause any deformation of SIC contacts during alignment.
[0011] Yet another object of the present invention is to provide a
guiding mechanism which ensures a reliable alignment between the secondary isolating contacts.
[0012] Yet another object of the present invention is to provide a
guiding mechanism where one SIC in breaker SIC block does not depend on the adjacent SICs.
[0013] Yet another object of the present invention is to provide a
guiding mechanism which enables to remove a single SIC from the breaker SIC block.

[0014] Yet another object of the present invention to provide a guiding
mechanism which is relatively less expensive.
[0015) 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.
C) SUMMARY OF THE INVENTION
[00161 The above mentioned shortcomings, disadvantages and
problems are addressed herein and which will be understood by reading and studying the following specification.
[0017] The various embodiments of the present invention provide a
guiding mechanism for secondary isolating contacts in circuit breakers. The mechanism includes a breaker secondary isolating contact, a cradle secondary isolating contact, a breaker secondary isolating contact block, a cradle secondary isolating contact block, a mounting block mounted over the breaker secondary isolating contact bridge, a cradle secondary isolating contact bridge and a breaker secondary isolating contact bridge. The breaker secondary isolating contact bridge is aligned with the cradle secondary isolating contact bridge in the first level of alignment. The breaker secondary isolating contact block is aligned with the cradle secondary isolating contact block in the second level of alignment. The cradle secondary isolating contact is aligned with the breaker secondary isolating contact in the third level of alignment. The secondary isolating contacts are designed to ensure proper aligning of the contact system in the circuit breakers.
[0018] According to one embodiment of the present invention, the
breaker secondary isolating contact includes a T-shaped protrusion to provide for alignment.

[0019] According to one embodiment of the present invention, the
mounting block includes a T-shaped slot to align with the T-shaped protrusion on the secondary isolating contacts.
[0020] According to one embodiment of the present invention, the
breaker secondary isolating contact block includes a T-shaped slot to provide for alignment.
[0021] According to one embodiment of the present invention, the
breaker secondary isolating contact is mounted on breaker secondary isolating contact housing.
[0022] According to one embodiment of the present invention, the
cradle secondary isolating contact is mounted in cradle secondary isolating contact housing.
|0023] According to one embodiment of the present invention, a
movement of the breaker secondary isolating contact bridge aligns the breaker secondary isolating contact with the cradle secondary isolating contact.
[0024] According to one embodiment of the present invention, the
breaker secondary isolating contact bridge moves in horizontal direction to align the breaker secondary isolating contact with the cradle secondary isolating contact.
[0025] According to one embodiment of the present invention, the
cradle secondary isolating contacts comprise an entry chamfer to provide alignment of the contacts.

[0026] According to one embodiment of the present invention, the
mounting block provides an option to independently mount each of the secondary isolating contacts.
[0027] According to one embodiment of the present invention, the
breaker secondary isolating contact comprises ten individual secondary isolating contacts.
E) BRIEF DESCRIPTION OF THE DRAWINGS
[0028] 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 which:
[0029] FIG.l illustrates a breaker secondary isolating contact
assembly, according to an embodiment of the present invention.
[0030] FJG. 2 shows a top view of the mounting block, according to an
embodiment of the present invention.
[0031] FIG. 3 shows a rear view of the cradle secondary isolating
contact block, according to an embodiment of the present invention.
[0032] FIG. 4 shows an isometric view of a cradle secondary isolating
contact block, according to an embodiment of the present invention.
[0033] FIG.5 shows an isometric view of a cradle secondary isolating
contact block, according to another embodiment of the present invention.

[0034] FIG. 6 shows a perspective view of the circuit breaker assembly
illustrating the second level of contact alignment, according to an embodiment of the present invention.
[0035] FIG. 7 shows a top view of third level of alignment between a
cradle secondary isolating contact and the breaker secondary isolating contact, according to an embodiment of the present invention.
[0036] FIG. 8 shows a top view of the T shaped slot and the T shaped
protrusion in the guiding mechanism for circuit breakers, according to an embodiment of the present invention.
[0037] FIG.9 shows a front view of the overall guiding mechanism
provided for secondary isolating contacts in circuit breakers, according to an embodiment of the present invention.
[0038] FIG. 10 shows a front view of the overall guiding mechanism in
circuit breakers, according to an embodiment of the present invention.
[0039] 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
[0040] 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.
[0041] The various embodiments of the present invention provide a
guiding mechanism for secondary isolating contacts in circuit breakers. The mechanism includes a breaker secondary isolating contact, a cradle secondary isolating contact, a breaker secondary isolating contact block, a cradle secondary isolating contact block, a mounting block mounted over the breaker secondary isolating bridge, a cradle secondary isolating contact bridge and a breaker secondary isolating contact bridge. The breaker secondary isolating contact bridge is aligned with the cradle secondary isolating contact bridge in the first level of alignment. The breaker secondary isolating contact block is aligned with the cradle secondary isolating contact block in the second level of alignment. The cradle secondary isolating contact is aligned with the breaker secondary isolating contact in the third level of alignment. The secondary isolating contacts are designed to ensure proper aligning of the contact system in the circuit breakers.
[0042] According to one embodiment of the present invention, the
breaker secondary isolating contact includes a T-shaped protrusion to provide for alignment.
[0043] According to one embodiment of the present invention, the
mounting block includes a T-shaped slot to align with the T-shaped protrusion on the breaker secondary isolating contacts.
[0044] According to one embodiment of the present invention, the
breaker secondary isolating contact block includes a T-shaped slot to provide
for alignment.

[0045] According to one embodiment of the present invention, the
breaker secondary isolating contact is housed in breaker secondary isolating contact housing.
[0046] According to one embodiment of the present invention, the
cradle secondary isolating contact is mounted in cradle secondary isolating contact housing.
[0047] According to one embodiment of the present invention, a
movement of the breaker secondary isolating contact bridge aligns the breaker secondary isolating contact with the cradle secondary isolating contact.
[0048] According to one embodiment of the present invention, the
breaker secondary isolating contact bridge moves a horizontal direction to align the breaker secondary isolating contact with the cradle secondary isolating contact.
[0049] According to one embodiment of the present invention, the
cradle secondary isolating contacts comprise an entry chamfer to provide alignment of the contacts.
[0050] According to one embodiment of the present invention, the
mounting block provides an option to independently mount each of the secondary isolating contacts.
|0051] According to one embodiment of the present invention, the
breaker secondary isolating contact block comprises ten individual secondary isolating contacts.

[0052] FIG.l illustrates a breaker secondary isolating contact assembly
where ten breaker secondary isolating contacts are mounted in a mounting block and FIG. 2 shows a top view of the mounting block, according to an embodiment of the present invention. The guiding mechanism includes a breaker secondary isolating contact I, a breaker secondary isolating contact housing 2, a mounting block 3and an entry chamfer for a breaker secondary isolating contact block 4. The breaker secondary isolating contact block 3 includes ten individual breaker secondary isolating contacts. Further a cradle secondary isolating contact block includes ten individual cradle secondary isolating contacts. The secondary isolating contacts are designed with a T-shaped protrusion to ensure proper aligning or guiding of contact system in the circuit breakers. The mounting block 3 is provided with a T-shaped slot to accommodate the T-shaped protrusion of the secondary isolating contacts. The breaker secondary isolating contact 1 is housed in the breaker secondary isolating contact housing 2.
|0053| FIG. 3 shows a rear view of cradle secondary isolating contacts block. according to an embodiment of the present invention, while FIG. 4 shows an isometric view of cradle secondary isolating contact block, according to an embodiment of the present invention. The guiding mechanism includes a cradle secondary isolating contact 5, a cradle secondary isolating contact housing 6. a cradle secondary isolating contact cover 7, and an entry chamfer 4 for aligning the breaker secondary isolating contact block 3 with a cradle secondary isolating contact block 9. The cradle secondary isolating contact block 9 consists of the cradle secondary isolating contacts 5, the cradle secondary isolating contact housing 6 and the cradle secondary isolating contact cover 7.
[0054] FIG.5 shows an isometric view of cradle secondary isolating
contact block, according to another embodiment of the present invention. The isometric view of the cradle secondary isolating contact block 9 shows a

support 10 for the cradle secondary isolating contact block 9. an entry chamfer 1 I, and a cradle secondary isolating contact bridge 12. The cradle secondary isolating contact bridge 12 consists of the cradle secondary isolating contact block 9 and the breaker secondary isolating contact block 3. The bi-directional play of +/-2mm is provided in a breaker secondary isolating contact bridge to enable the movement of the breaker secondary isolating bridge in a horizontal direction. The breaker secondary isolating contact bridge is mounted on the breaker part of the circuit breaker. Further during insertion of the contacts from a maintenance position to a disconnected position, the mounting bridge 13 of the breaker secondary isolating contact I gets self-aligned with a cradle secondary isolating contact cross bar 10. The entry chamfer 11 is provided on the breaker secondary isolating contact bridge and on the cradle secondary isolating contact bridge 11.
[0055] FIG. 6 shows a top view of second level of alignment in the
circuit breakers, according to an embodiment of the present invention. The second level of alignment in the circuit breakers includes the breaker secondary isolating contact block 3 and a breaker secondary isolating contact bridge 13. The second level of alignment is done between the breaker secondary isolating contact block 3 and the cradle secondary isolating contact block 9. The breaker secondary isolating contact block 3 includes ten individual breaker secondary isolating contacts. The cradle secondary isolating contact block 9 includes ten individual cradle secondary isolating contacts. Further arrows 15 shows the direction of movement of the breaker secondary isolating contact block 3. with T-shaped protrusion, in the the breaker secondary isolating contact bridge, with T-shaped slot, for self alignment.
[0056J FIG. 7 shows a top view of third leve] of alignment between a
cradle secondary isolating contact and the breaker secondary isolating contact, according to an embodiment of the present invention. The top view

of the breaker secondary isolating contact block 9 shows a support 10 for the cradle secondary isolating contact block 9. an entry chamfer 11. and a cradle secondary isolating contact bridge 12. The cradle secondary isolating contact bridge 12 consists of the cradle secondary isolating contact block 9 and the breaker secondary isolating contact block 3. The third level of alignment is between the breaker secondary isolating contact I and the cradle secondary isolating contact 5. The cradle secondary isolating contact 5 includes an entry chamfer and the breaker secondary isolating contact 5 includes a profile to provide an ease of alignment of the corresponding contacts. The guiding assembly includes the cradle secondary isolating contact 5 with the cradle secondary isolating contact housing 6 and the cradle secondary isolating contact cover 7.
[0057] FIG. 8 shows a top view of the T shaped slot and the T shaped
protrusion to provide for the guiding mechanism for circuit breakers, according to an embodiment of the present invention. The guiding assembly includes the breaker secondary isolating contact 1 housed in the breaker secondary isolating contact housing 2. Further the guiding assembly includes the mounting block 3 and an entry chamfer for the breaker secondary isolating contact block 4. The secondary isolating contacts are designed to ensure proper aligning or guiding of contact system in the circuit breakers. The mounting block 3 is designed with a T shape slot 21 and the breaker secondary isolating contact housing 2 is provided with a T shape protrusion 20 to align into the T shape slot 21 in the mounting block 3. The T shape protrusion 20 provided on the breaker secondary isolating contact housing 2 gets aligned into the T shape slot 21 in the mounting block 3. Further this alignment makes the assembly easier and there is no dependence of one secondary isolating contact on the other for its location. The mounting block 3 provides independent mounting for each secondary isolating contact.

[0058] FIG.9 shows a front view of the overall guiding arrangement
provided for secondary isolating contacts in circuit breakers, according to an embodiment of the present invention. The front view of the overall guiding arrangement for the circuit breakers includes the cradle secondary isolating contact bridge 12 aligned with a breaker secondary isolating contact bridge 14. The guiding assembly also includes the entry chamfer 11 for self aligning the breaker secondary isolating contact bridge 14. The breaker secondary isolating contact bridge 14 has a direction of motion in direction shown by arrow 17, The breaker secondary isolating contact bridge 14 can adjust itself in the direction shown by arrow 16 when it reaches the chamfer 11 on cradle secondary isolating contact support.
[0059] FIG. ]0 shows a front view of the overall guiding assembly in circuit breakers, according to an embodiment of the present invention. The guiding mechanism includes the cradle secondary isolating contact bridge 12 aligned with the breaker secondary isolating contact bridge 14. The guiding mechanism further includes a cradle assembly 18 and a breaker assembly 19. The breaker secondary isolating contact bridge 14 movement aligns the breaker secondary isolating contact 1 with the cradle secondary isolating contact 5.
G) ADVANTAGES OF THE INVENTION
[0060] The embodiments of the present invention provide does not
cause any deformation of secondary isolating contacts thereby providing an effective and reliable alignment.
[0061] The assembly of one SIC in breaker SIC block is not dependent
on adjacent SICs which make the mounting and removal of the SICs from the breaker SIC block easier.

[0062] The independent positioning of the SICs enables to assemble
only the required number of breaker SICs thereby making the arrangement economic.
[0063] 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.
[0064] 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.

CLAIMS
What is claimed is:
1. A guiding mechanism for secondary isolating contacts in circuit breakers, the mechanism comprising : a breaker secondary isolating contact; a cradle secondary isolating contact; a breaker secondary isolating contact block; a cradle secondary isolating contact block:
a mounting block mounted over the breaker secondary isolating contact bridge;
a cradle secondary isolating contact bridge; and a breaker secondary isolating contact bridge.
Wherein the breaker secondary1 isolating contact bridge is aligned with the cradle secondary isolating contact bridge, the breaker secondary isolating contact block is aligned with the cradle secondary isolating contact block, the breaker secondary isolating contact is aligned with the cradle secondary isolating contact where the breaker secondary isolating contacts are provided with a predefined profile to provide for alignment of contact system in the circuit breakers.
2. The guiding mechanism according to claim 1, wherein predefined profile
of the breaker secondary isolating contacts include a T-shaped protrusion.
3. The guiding mechanism according to claim 1, wherein the mounting block includes a T-shaped slot to align with the T-shaped protrusion of the breaker secondary isolating contacts.
4. The guiding mechanism of claim 1. wherein the breaker secondary isolating contact and the cradle secondary isolating contact are aligned by a T-shaped protrusion on breaker secondary isolating contact block and a T-shaped slot on breaker secondary isolating contact bridge.
5. The guiding mechanism of claim 1. wherein the breaker secondary isolating contact is mounted in breaker secondary isolating contact housing.
6. The guiding mechanism of claim ], wherein the cradle secondary isolating contact is mounted in cradle secondary isolating contact housing.

7. The guiding mechanism of claim I, wherein the breaker secondary isolating contact block is moved in the T-shaped slot to align the breaker secondary isolating contact with the cradle secondary isolating contact.
8. The guiding mechanism of claim 1, wherein the breaker secondary isolating contact bridge is moved in at least one of horizontal direction to align the breaker secondary isolating contact with the cradle secondary isolating contact.
9. The guiding mechanism of claim 1, wherein the cradle secondary isolating contact comprises an entry chamfer to provide alignment of the contacts.
10. The guiding mechanism of claim 1. wherein secondary isolating contact block comprises of a plurality of breaker secondary isolating contacts aligned with the cradle secondary isolating contacts.