FORM 2
THE PATENT ACT 1970
& The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION:
"Operating Mechanism For Circuit Breakers With Single Axis Assembly"
2. APPLICANT:
(a) NAME: Larsen & Toubro Limited
(b) NATIONALITY: Indian Company registered under the
provisions of the Companies Act-1956.
(c) ADDRESS: LARSEN & TOUBRO LIMITED,
L&T House, Ballard Estate, P. O. Box: 278, Mumbai 400 001, India
3. PREAMBLE TO THE DESCRIPTION:
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.

Operating Mechanism For Circuit Breakers With Single Axis Assembly
Field of the invention
The present invention relates to circuit breakers, and more particularly, to a operating mechanism for the circuit breakers with single axis assembly.
Background of the invention
The circuit breakers consist of pair of fixed contact & moving contact. Circuit breakers uses mechanism to operate i. e. to open & close contacts in normal condition & to open the contacts in case of fault condition. The mechanisms used in low voltage switchgear consist of pivoted manual operated link which can be automatically tripped by the releases depending on occurrence of the fault. At the time of tripping, one link of mechanism is collapsed to achieve the opening of the contacts. The current circuit breakers which are in use uses separate pin to mount small latch and also moving contact support is used to mount moving contact on main assembly of mechanism. The growing use of modular devices in electrical installation has made the market competitive. So to meet high competition on cost basis & Volume basis, Product should have minimum, reliable cost effective components
A US Patent US4740770 is aimed to provide simplicity in mechanism which have simple and reliable construction along with suitability for automation. Though the mechanism in '770 patent is said to have automation friendly feature, it is not claimed to have a drop in feature.
Another European Patent EP 1173868 relates to a circuit breaker having latching device. The latching device of which can be unlatched between a manual control device and movable contact arm 1 at a latching point between a catch 6 and a release lever 5 by a release unit, characterized in that the movable contact arm'1

is located in a surrounding bracket 2 on a first axle bearing 3 so that it can move and rotate with the bracket, with the catch 6 also located off-centre on this axle bearing 3 and that the bracket 2 has a further axle bearing 4 on both sides, on which the release lever 5 is located off-centre in a fixed position but capable of rotation and around which the bracket 2 moves, as does the movable contact arm 1, unless it is in contact with a fixed contact 7, with the first axle bearing 3 limiting the disconnection path of the contact arm 1.
The mechanism as shown in figure 1 is basically made up of basic subassembly of contact arm 1 welded to support 11, bracket 2, axle bearings 2 and 3, The axle bearing has to be press fitted as shown prior to final subassembly. The limitation of this mechanism is feature of drop down assembly is not possible. Additionally The movable contact arm 1 has to be welded to support prior to subassembly adding manufacturing cost to it.
Accordingly, there is a need to provide an operating mechanism for the circuit breakers which overcomes drawbacks of the prior art.
Objects of the invention
An object of the present invention to provide a simple and novel construction for the operating mechanism of a circuit breakers in which mechanism components are designed to have lower manufacturing cost.
Yet another object of the present invention is to achieve drop in assembly which in turn reduces assembly cycle time and effectively cost of the mechanism.
Summary of the invention
Accordingly, the present invention provides a operating mechanism for circuit breakers. The operating mechanism comprises a housing supporting a pivot pin

in inbuilt bearing, a mechanism pivot pin pinned in the bearing, a manual input link pivoted in housing having constrained and angular displacement, a support mounted on the mechanism pivot pin with a mechanism spring, a small latch mounted on the support, a trip latch forming a mechanical link along with the plastic support, and the small latch, the trip latch mounted on the mechanism pivot for breaking the mechanism link in case of fault condition, a connector link connecting the manual input link with a toggle joint and the small latch, a flexible link providing flexible connection between the support and the moving contact to form a flexible joint therebetween. Wherein during the normal ON and OFF operation, force and motion given at the manual input is transferred via the connector link to the mechanical link, and thereafter to the moving contact through the flexible link, and during occurrence of fault when the circuit breaker is in ON condition, the mechanical link is collapsed by making to rotate the trip latch in anti-clockwise direction which further causes the mechanism spring to rotate the support in anti-clockwise direction thereby carrying the moving contact there along to opens up a circuit.
Brief description of the drawings
Figure 1 shows a circuit breaker having latching device, in accordance with the prior art;
Figure 2 shows a front view of an operating mechanism for a circuit breaker in off condition, in accordance with the present invention;
Figure 3 shows an elevated perspective front view of the operating mechanism of figure 2 in OFF condition;
Figure 4 shows an elevated perspective front view of the operating mechanism of figure 2 in ON condition;

Figure 5 shows a sectional view of the operating mechanism of figure 2;
Figure 6 shows a semi-exploded view of a link mounted components of the operating mechanism of figure 2; and
Figure 7 shows an exploded view of the operating mechanism of figure 2
Detailed description of the invention
The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.
The present invention provides a operating mechanism for circuit breakers with single axis assembly. The operating mechanism is simple and has novel construction for the operating mechanism of a circuit breakers in which mechanism components are designed to have lower manufacturing cost.
Referring now to figure 2 to 6, there is shown an operating mechanism (100) (hereinafter referred as to 'the mechanism (100)') for circuit breakers with single axis assembly. The mechanism (100) comprises a manual input link (1), a manual input link spring (2), a connector link (3), a small latch (4), a trip latch (5), a trip latch spring (6), a support (7), a flexible link (8), a mechanism spring (9), a moving contact (10), a housing (11), and a mechanism pivot pin (12).
Specifically, the mechanism (100) is housed in housing (11) with a first pin joint (17) in the inbuilt bearing (21) provided in the housing (11). The manual input link (1) is connected by second pin joint (16) in a projection of the housing (11) with a biased manual input link spring (2) to have constrained angular displacement. The manual input link spring (2) of the manual input link (1) of

which one arm (not shown) is resting on the projection of the housing (11) and a second arm (not shown) resting on the manual input link (1) tends to keep the manual input link (1) in off position.
Further, the mechanism pivot pin (12) is pinned in the bearing (21). The support (7) is mounted on the mechanism pivot pin (12) with the help of the mechanism spring (9). In an embodiment, the support (7) is a plastic support. The mechanism spring (9) provides for opening contacts for example, a moving contact (10) and the fixed contact, quickly and irrespective of the.manual input link (1) in case of occurrence of fault. The moving contact (10) is mounted with the first pin joint (17) so that the moving contact (10) have a limited angular displacement with respect to the support (7).
Furthermore, the flexible link (8) includes a first end (not shown) which is press fitted in the support (7) and a second end (not shown) rested on the moving contact (10) to form a flexible joint between them. This flexible joint (8) is also designed to have a proper contact force in ON condition. The trip latch (5) is also mounted on the mechanism pivot (12) with limited angular displacement with respect to the support (7). The trip latch (5) also carries a trip latch spring (6) which ensures a positive latching between the small latch (4) and the trip latch (5).
Specifically, the small latch (4) is mounted on a projection of the support (7) with a third pin joint (18). The movement of the small latch (4) is constrained by a provision of a stopper (not shown) on the support (7) so as to avoid wrong latching.
The connector link (3) is connected to the manual input link (1) by the third pin joint (18) which also forms a toggle pair. Specifically, a second end (not shown) of the connector link (3) is connected by a fourth pin joint (19) with the small latch (4) to complete a mechanism linkage.

During the normal ON and OFF operation, the force and motion is given at the manual input Jink (1) which in turn is transferred tc the moving contact (10) through the connector link (3). The next link after the connector link (3) of mechanism is formed by combination of the support (7), the small latch (4) and a trip latch (5). During normal ON and OFF operation, the support (7), the small latch (4) and a trip latch (5) acts as a rigid link to transfer the motion and the force to the moving contact (10) through the flexible link (8).
In the case of occurrence of fault, when the circuit breaker is in ON condition, the trip latch (5) is made to rotate in anti-clockwise direction so as to collapse the mechanical link formed by the small latch (4), the trip latch (5) and the support (7). The collapse of the mechanical link causes mechanism spring (9) to rotate the support (7) in anti-clockwise direction which carries the moving contact (10) along with it to opens up the circuit. The mechanism is designed in such a way that at the time of tripping, the moving contact (10) opens up irrespective of position of the manual input link (1). Specifically, a pivot (20) is responsible for opening of the moving contact (10) irrespective of manual input link (1). At the pivot joint (20), the small latch (4) allowed to rotate in anticlockwise direction in case of tripping. The small latch (4) adjusts itself around the pivot (20) such that the position of manual input link (1) won't affect opening of the moving contact (10). In the case of overload, the trip latch (5) is made to rotate by means of bimetal trip pin ( not shown). The short circuit situation operates a magnetic release (14) so that a hammer (13) hits the trip latch (4) to rotate it in anti-clockwise direction and to open contacts respectively.
Advantages of the invention
1. The mechanism (100) provides a single axis assembly feature which allows shorter total assembly time.

2. The mechanism (100) provides a simplified components design which reduces manufacturing cost.
3. The mechanism (100) use lower number of components adding reliability to the circuit breaker.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the spirit or scope of the present invention.

We claim
1. An operating mechanism for circuit breakers, the operating
mechanism comprising:
housing supporting a pivot pin in inbuilt bearing;
a mechanism pivot pin pinned in the bearing;
a manual input link pivoted in housing having constrained angular displacement, the manual input link having a spring to keep the manual link in off position;
a support mounted on the mechanism pivot pin with a mechanism spring, the mechanism spring enabling fast opening of the moving contact and a fixed contact during fault condition
a small latch mounted on the support;
a trip latch forming a mechanical link along with the support, and the small latch, the trip latch mounted on the mechanism pivot for breaking the mechanism link in case of fault condition;
a connector link connecting the manual input link with a toggle joint and the small latch;
a flexible link providing flexible connection between the support and the moving contact to form a flexible joint therebetween: and
Wherein during the normal ON and OFF operation, force and motion given at the manual input is transferred via the connector link to the mechanical link, and thereafter to the moving contact through the flexible link, and during occurrence of fault when the circuit breaker is in ON condition, the mechanical link is collapsed by making to rotate the trip latch in anti-clockwise direction which further causes the mechanism spring to rotate the support in anti-clockwise direction thereby carrying the moving contact there along to opens up a circuit.

2. The operating mechanism as claimed in claim I, wherein the support is a plastic support.
3. The operating mechanism as claimed in claim 1, wherein the manual input link is connected by a pin joint in a housing projection with a biased spring to have constrained angular displacement.
4. The operating mechanism as claimed in claim 1, wherein the trip latch includes a spring ensuring positive latching to ensure smooth operation.