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:
SECONDARY ISOLATING CONTACT ASSEMBLY FOR CIRCUIT BREAKER
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 electrical switching devices and particularly to withdrawable type circuit breakers. The present invention more particularly relates to 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. It consists of power contacts and control contacts. The purpose of control contacts is to connect / disconnect the accessories / equipments connected in the control circuit.
[0003] A circuit breaker has been classified into two categories such as fixed type circuit breaker and Withdrawable type circuit breaker. The withdrawable type circuit breaker has withdraw-able unit also known as cradle unit and the breaker part.
[0004] Generally, circuit breakers are employed with secondary isolating contacts with a single point type of contact system. In case of a deformation of the contact terminal due to mishandling or nature of construction, the single point type of contact will result in loss of continuity, momentarily or permanently. This leads to low reliability of single point type of contact system.
[0005] Therefore, there exists a need to enhance the reliability of the contact system by using a wedge type of secondary isolating contacts.

[0006] The above mentioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.
C) OBJECTS OF THE INVENTION
[0007] The primary object of the present invention is to develop an improved circuit breaker with wedge type secondary isolating contacts to enhance the reliability of the contact system.
[0008] Another object of the present invention is to develop a circuit breaker with an improved female type of contact on the breaker part.
[0009] Yet another object of the present invention is to develop a circuit breaker with an improved male type of contact on the cradle unit.
[0010] Yet another object of the present invention is to develop a circuit breaker with a block type of secondary isolating contact to ensure proper aligning of the contact system in the circuit breaker.
[0011] 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
[0012] The above mentioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.

[0013] The various embodiments of the present invention provide a wedge type of secondary isolating contacts in circuit breakers. The secondary isolating contacts are also called as auxiliary type of contacts. The secondary isolating contact assembly generally comprises a secondary isolating contact provided at a circuit breaker part and another secondary isolating contact provided at a cradle/withdraw able unit. The secondary isolating contacts further include a female type of contact on the breaker part and a male type of contact on the cradle/ withdraw-able unit.
[0014] According to one embodiment of the present invention, a wedge type secondary isolating contact assembly for circuit breaker comprises a breaker side secondary isolating contact assembly. A female type contact is provided in the breaker side secondary isolating contact assembly. A cradle side secondary isolating contact assembly is connected to the breaker side contact assembly. A male type contact is provided in the cradle side secondary isolating contact assembly. The male type contact provided at the cradle side secondary isolating contact assembly is inserted into the female type contact provided at the breaker side secondary isolating contact assembly to form a wedge type contact system.
[0015] The contact system in the present invention is a wedge type contact system. The wedge type contact system includes a blade shaped male type contact. The wedge type contact system includes a jaw shaped female type contact to receive the blade shaped male type contact. The female type contact provided at the breaker side secondary isolating contact assembly is a jaw shaped female type contact. The male type contact provided in the cradle side secondary isolating contact assembly is a blade shaped male type contact. The jaw shaped female type contacts have resiliency property to hold the blade shaped male type contact upon insertion. The secondary isolating contact assembly further comprises a spring cage assembly provided both in the cradle

side secondary isolating contact assembly and in the breaker side secondary isolating contact assembly.
[0016] The embodiments herein provide a dual type of contact system to enhance the reliability of the contact system. The contact system is a wedge type of contact system which comprise of a male contact and a female contact of appropriate shapes
[0017] The wedge type of contact system is used for switching relatively light currents. The male contact of the wedge type of contact system includes a contact blade that is inserted into and withdrawn from the contact jaws of the female contact. The required contact pressing force is provided by the resilience of the contact jaw material. The contact jaw material is made of metals such as hard- drawn copper, bronze alloy or the like.
[0018] The Secondary Isolating Contacts (SIC) of a circuit breaker comprises two elements including a breaker side secondary isolating contacts and cradle (withdraw able unit) side secondary isolating contacts. The breaker side SIC contacts are mounted on the breaker unit includes a housing, a female contact, a spring cage clamp and a cover. The breaker side SIC contact is mounted in the housing by doing thermal riveting and then a cover is placed on it. There is no interdependency between breaker side SICs i.e. each SIC is an independent unit.
[0019] Each individual breaker side SIC is then placed into a mounting block which is having a "T" shaped slot. A "T" shaped protrusion provided on the breaker side SIC housing gets aligned into the "T" shaped slot in the mounting block. Further, a plurality of such breaker side SICs are mounted on the mounting block. Then the blocks of breaker side SICs are inserted on the

breaker side SIC bridge while keeping the feature of the individual contact for the breaker part.
[0020] Similarly cradle side SIC contacts are mounted on the cradle (withdraw able) unit comprising the housing, the male contact, the spring cage clamp and the cover. The cradle side SIC contact is mounted in the housing and then a cover is placed on it.
[0021] Finally male contacts of the cradle side SICs are inserted in to the female contacts of the breaker side SICs such that the male contacts fits tightly into the wedge shaped female contacts.
E) BRIEF DESCRIPTION OF THE DRAWINGS
[0022] 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:
[0023] FIG.l illustrates the front perspective view of a breaker side secondary isolating contact unit with the cover in open condition, according to one embodiment of the present invention.
[0024] FIG.2 illustrates a front perspective view of the breaker side
secondary isolating contact unit with the cover in closed condition, according
to one embodiment of the present invention.
[0025] FIG.3 illustrates the back perspective view of the breaker side
secondary isolating contact, according to one embodiment of the present
invention.

[0026] F1G.4 illustrates the side perspective view of the breaker side secondary isolating contact and the mounting block, according to one embodiment of the present invention.
[0027] FIG.5 illustrates the arrangement of the breaker side secondary isolating contacts on the mounting block, according to one embodiment of the present invention.
[0028] FIG.6 illustrates a perspective view of the secondary isolating contact bridge installed with a mounting block holding breaker side secondary isolating contacts, according to one embodiment of the present invention.
[0029] FIG.7 illustrates a top view of a breaker side secondary isolating contact bridge mounted with plurality of mounting blocks in assembled condition, according to one embodiment of the present invention.
[0030] FIG.8 illustrates a perspective view of a cradle side secondary isolating contact assembly with the cover in open condition, according to one embodiment of the present invention.
[0031] FIG.9 illustrates a perspective view of a cradle side secondary isolating contact assembly with the cover in closed condition, according to one embodiment of the present invention.
[0032] FIG. 10 illustrates a perspective view of a secondary isolating contact assembly, according to one embodiment of the present invention. [0033] FIG. 11 illustrates a front view of a secondary isolating contact assembly, according to one embodiment of the present invention.

[0034] FIG.12 illustrates a schematic representation of a wedge type of contact system used in a secondary isolating contact assembly, according to one embodiment of the present invention.
[0035] 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
[0036] 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.
[0037] The various embodiments of the present invention provide secondary isolating contacts in circuit breakers. The secondary isolating contacts are also called as auxiliary type of contacts. The secondary isolating contact assembly generally comprises a secondary isolating contact provided at a circuit breaker part and another secondary isolating contact provided at a cradle/withdraw able unit. The secondary isolating contacts further include a female type of contact on the breaker part and a male type of contact on the cradle/ withdraw-able unit.

[0038] According to one embodiment of the present invention, a secondary isolating contact assembly for circuit breaker comprises a breaker side secondary isolating contact assembly. A female type contact is provided in the breaker side secondary isolating contact assembly. A cradle side secondary isolating contact assembly is connected to the breaker side secondary isolating contact assembly. A male type contact is provided in the cradle side secondary isolating contact assembly. The male type contact provided at the cradle side secondary isolating contact assembly is inserted into the female type contact provided at the breaker side secondary isolating contact assembly to form a wedge type contact system.
[0039] The contact system is a wedge type contact system. The wedge type contact system includes a blade shaped male type contact. The wedge type contact system includes a jaw shaped female type contact to receive the blade shaped male type contact. The female type contact provided at the breaker side secondary isolating contact assembly is a jaw shaped female type contact. The male type contact provided at the cradle side secondary isolating contact assembly is a blade shaped male type contacts system. The jaw shaped female type contacts have resiliency property to hold the blade shaped male type contact upon insertion. The secondary isolating contact assembly further comprises a spring cage assembly provided both in the cradle side secondary isolating contact assembly and in the breaker side secondary isolating contact assembly.
[0040] The various embodiments of the present invention provide a secondary isolating contact assembly in a circuit breaker. The secondary isolating contact of the present invention is of a wedge type, which comprises a female type contact on the breaker part and. a male type contact on a cradle/withdraw-able unit. Generally a withdraw-able type circuit breaker is operated in three positions, such as a connected position, a test position and a

disconnected position. In the connected position, the power contacts and the control contacts of the circuit breaker are engaged. In the test position, only control contacts are engaged while in the disconnected position, both the power contacts and the control contacts are disengaged.
[0041] FIG. 1 illustrates the breaker Secondary Isolating Contact (SIC) assembly with a cover in open condition. The Breaker side SICs are mounted on the breaker unit, which comprises a housing 1, a female contact 2, a spring cage clamp 3 and a cover 4.
[0042] FIG. 2 illustrates the breaker secondary isolating contact with the cover closed condition. The secondary isolating contacts are placed inside the housing by thermal riveting and then the cover is placed on it The SIC is of wedge type. The wedge type of contact system is used for switching relatively light currents. The wedge type of contact system consists of a contact blade, which can be inserted into and withdrawn from contact jaws of comparative shape. The required contact pressing force is provided by the resilience of the contact jaw material. The contact jaw material can be hard- drawn copper, bronze alloy or the like. The wedge contacts described herein is widely used in single and double throw knife switches, ferrule and knife blade cartridge fuses and other cut-in devices. The female type SIC provided at the breaker has two jaws which are resiliency arranged to receive and hold a male type SIC provided in the cradle unit.
[0043] FIG. 3 illustrates the back view of the breaker side secondary isolating contact showing the wedge type of female contact 2, the housing 1, the spring cage clamp 3 and the cover 4. The housing 1 includes a protrusion 5 on at least one side. The protrusion 5 of the embodiment herein is preferably a "T" shaped protrusion to ensure firm abutting of the female contacts on to the mounting block (as shown in FIG. 4). The protrusion 5 is provided on the back

side of the breaker SIC housing l to mount the breaker SIC on the mounting block.
[0044] FIG.4 illustrates the breaker side secondary isolating contact mounted on the mounting block 6. The protrusion 5 on the back side of the breaker side SIC housing is aligned and inserted to the slot 7 on the mounting block 6. The slot 7 of the embodiment herein is preferably a "T" shaped slot to ensure firm abutting of the female contacts.
[0045] FIG. 5 illustrates the plurality of breaker side SICs mounted on the mounting block 6. For instance, 10 numbers of breaker side SICs are mounted on the mounting block. The slots 7 are provided on the mounting block 6 to mount plurality of breaker side SICs.
[0046] FIG.6 illustrates the insertion of blocks of the breaker side SICs on the secondary isolating contact bridge 8. Each block of breaker side SICs is provided with a protrusion on the back side to align and insert the breaker side SIC blocks into the slot on the breaker side SIC bridge 8. The protrusion of the embodiment herein is preferably a "T" shaped protrusion and the slot of the embodiment herein is preferably a "T" shaped slot.
[0047] With respect to FIG.7, plurality of breaker side SIC blocks (as shown in FIG. 5) comprising a housing 1 enclosing the breaker side SIC contacts 2 are inserted into the breaker side SIC bridge 8 through the slots 7. For instance, 6 numbers of breaker side SIC blocks are inserted into the breaker SIC bridge 8. Thus the blocks of breaker side SICs (as shown in FIG. 5) are fully assembled in the breaker side SIC bridge 8.
[0048] FIG.8 illustrates the cradle side secondary isolating contacts fully assembled in the cradle secondary isolating contact housing. The cradle side

SIC is mounted on the cradle (withdraw-able) unit of the circuit breaker. The cradle side SIC includes a housing 9, a male contact 10, a spring cage clamp 11 and a cover 12 to enclose the housing 9. The male contact 10 of the cradle SIC is mounted in the housing 9.
[0049] With respect to FIG.9, pluralities of the male contacts 10 are arranged in the housing 9 and the cover 12 is placed over the housing 9 to achieve a cradle side SIC assembly block.
[0050] With respect to FIG.10, a single block assembly of cradle side secondary isolating contact including a housing 9 and a cover 12 is inserted into the breaker side secondary isolating contact assembly provided with a housing 1 and a cover 4. The plurality of wedge shaped male contacts 10 in the cradle side SIC assembly are inserted inside the plurality of jaw shaped female breaker contacts 2in the breaker side SIC assembly. Wedge type of contact system is used for switching relatively low currents.
[0051] FIG. 1 i illustrates the cross sectional view of the cradle side secondary isolating contact assembly including a housing 9 and a cover 12 and a breaker side secondary isolating contact assembly including a breaker side SIC contact 10 enclosed in a housing l in inserted condition. With respect to FIG. 11, the male contacts 10 provided in the cradle side SIC assembly is inserted into the jaws 2 of the female type SIC contacts provided in the breaker side secondary isolating contact assembly.
[0052] With respect to FIG. 12, the wedge shaped male contact 10 in the cradle side SIC assembly is inserted into the blades in a respective jaw type female contact 2 provided in a breaker side SIC assembly. G) ADVANTAGES OF THE INVENTION

[0053] Thus the various embodiments of the present invention provide a wedge type of secondary isolating contacts which is wedge shaped. The use of wedge type secondary isolating contact increases the range of conductor sizes. The wedge type secondary isolating contact provides firm abutting of the male contact into the female contact, thereby improving the reliability of the contact system.
[0054] Secondary isolating contacts of the present invention use block type construction to ensure proper aligning and guiding of the contact system onto the mounting structures. This in turn prevents the dislocation of the secondary isolating contacts during the switching operation.
[0055] 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.
[0056] 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 wedge type secondary isolating contact assembly for circuit breaker comprising: a breaker side secondary isolating contact assembly; a female type contact provided in the breaker side secondary isolating contact assembly;
a cradle side secondary isolating contact assembly connected to the breaker side secondary isolating contact assembly;
a male type contact provided in the cradle side secondary isolating contact assembly;
wherein the male type contact provided at the cradie side secondary isolating contact assembly is inserted into female type contacts provided at the breaker side secondary isolating contact assembly to form a wedge type contact system.
2. The secondary isolating contact assembly in accordance with claim 1, wherein the wedge type contact system includ.es a blade shaped male type contact.
3. The secondary isolating contact assembly in accordance with claim 1, wherein the wedge type contact system includes a jaw shaped female type contact to receive the blade shaped male type contact.
4. The secondary isolating contact assembly in accordance with claim 1, wherein the female type contact provided at the breaker side secondary isolating contact assembly is a jaw shaped female type contact.

5. The secondary isolating contact assembly in accordance with claim 1, wherein the male type contact provided at the cradle side secondary isolating contact assembly is a blade shaped male type contact.
6. The secondary isolating contact assembly in accordance with claim 1, wherein the jaw shaped female type contacts have resiliency property to hold the blade shaped male type contacts upon insertion.
7. The secondary isolating contact assembly in accordance with claim 1, further comprising spring cage assembly provided both in the cradle side secondary isolating contact assembly and in the breaker side secondary isolating contact assembly.