FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION (See section 10 and rule 13)
1. TITLE OF THE INVENTION:
"Moulded Case Circuit Breaker with Improved Mechanism"
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.

Moulded Case Circuit Breaker with Improved Mechanism
Field of the invention
The present invention relates to circuit breakers, and more particularly, to improved operating mechanism for the circuit breaker.
Background of the invention
The circuit switching devices and circuit interrupters such as circuit breakers, motor starters, motor controllers and other load controllers are used to protect electrical circuitry and equipment from damage due to abnormal conditions, such as an overload condition or a relatively high level short circuit or fault condition.
One such switching device is a moulded case circuit breaker (MCCB) which is generally used to provide over current and short circuit protection for various types of electrical equipment. The MCCB have three stable positions i.e. ON, OFF and TRIP conditions of contacts as described above.
The MCCB comprises of three systems i.e. contact system, mechanism system and release system. Out of all the operations mentioned above i.e. ON, OFF and TRIP are performed by the mechanism. The release system senses any abnormal condition (over current or short circuit) and executes tripping signal to the mechanism. After receiving the trip command from the release system, mechanism separates moving and fixed contacts. To perform all the above mentioned operations, the MCCB follows toggling mechanism i.e. a spring stores energy up to dead centre and releases the energy, once the spring crosses the dead centre and takes the contacts to their respective position. The basic working of the MCCB mechanism is explained by considering conventional method which is in use as shown in figure 6. The figure 6 shows the MCCB

(200) in OFF condition i.e. the moving contacts (6) and the fixed contact (9) are apart, The MCCB (200) mechanism consist of a main latch (II), an upper link (14), a lower link (12), a drive shaft (13), a fork (1), a knob (10), a toggle pin (4) and a mechanism springs (3). They together build a four bar link mechanism. It can be seen from the figures that the spring (3) with one end at fork (1) and the other end at floating pin (4) tries to pull the floating pin (4) in positive X direction and the complete assembly is in equilibrium with a stopper in the driveshaft (13). To switch ON the MCCB (200), the mechanism springs (3) axis has to cross the upper link (14) which is the toggling position of the mechanism. Once the spring (3) axis crosses the upper link (14), direction of force on the floating pin (4) changes from positive X direction to negative X direction and through the lower link (12), the drive shaft (13) rotates and make the contacts which is shown In fig. 7.
Figure 6 and 7 shows a generalized mechanism of the MCCB (200) of the prior art wherein the more number of components are required for operation thereof. Also it can be seen that all the pin joints have to be riveted.
The above and various other limitations and needs of the conventional mechanism arrangement necessitate an improved mechanism arrangement system. Accordingly, there exists a need to provide an arrangement which overcomes the above cited limitations and also provides additional flexibility.
Objects of the invention
An object of the present invention is to provide elimination of components from the mechanism of a moulded case circuit breaker keeping features same.
Another object of the present invention is to reduce the cost and assembly time and hence increase productivity of a moulded case circuit breaker.

Yet another object of the present invention is to lead to lesser friction and overall performance of the moulded case circuit breaker.
Summary of the invention
Accordingly, the present invention provides a moulded case circuit breaker with improved mechanism. The circuit breaker comprises a knob operating the circuit breaker, and a fork having a first end and a second end. The first end is positioned near the knob. The circuit breaker further comprises a toggle pin movably mounted between driveshaft and latch. The spring has one end attached to the toggle pin and other end coupled to the fork, wherein the force applied on the knob moves the fork thereby extending the spring. The circuit breaker furthermore comprises a driveshaft having one end coupled to the toggle pin and other end coupled to a moving contact, a latch supported on the toggle pin. The toggle pin roll over the latch and the driveshaft when the toggle pin receives force exerted by the spring when extended. When direction of the spring force changes from any one of positive x-direction to negative X-direction and negative X-direction to positive x-direction , the toggle pin roll over the latch and drive shaft profile which in turn rotates the drive shaft to attains any one of ON and OFF position.
Brief description of the drawings
Figure 1 shows a moulded case circuit breaker in accordance with the present invention, with a trip condition;
Figure 2 shows a moulded case circuit breaker in accordance with the present invention, with OFF condition;;
Figure 3 shows a moulded case circuit breaker in accordance with the present invention, with ON condition;

Figure 4 shows a driveshaft of the moulded case circuit breaker in accordance with the present invention;
Figure 5 shows a latch of the moulded case circuit breaker in accordance with the present invention;
Figure 6 shows a moulded case circuit breaker of the prior art, in OFF condition; and
Figure 7 shows a moulded case circuit breaker of the prior art in ON condition.
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 moulded case circuit breaker with improved mechanism which provides elimination of components from the mechanism of a moulded case circuit breaker keeping features same. The moulded case circuit breaker with improved mechanism reduces the cost and assembly time and hence increases productivity thereof. Further, the moulded case circuit breaker with improved mechanism leads to lesser friction and overall performance.
Referring now to figure 1-5, there is shown a moulded case circuit breaker (100) (hereinafter 'the MCCB (100)') with improved mechanism. The MCCB (100) includes a knob (10). a fork (20), a toggle pin (30), a spring (40), a driveshaft (50), and a latch (60),
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6 MAR 2013

The knob (10) operates the MCCB (100). The fork (20) is positioned near the knob (10). Specifically, the fork (20) includes a first end (22) and a second end (24). Specifically, the first end (22) of the fork (20) is positioned near the knob (10).
The toggle pin (30) is movably mounted on driveshaft (50). Further, the spring (40) includes one end attached to the toggle pin (30) and other end coupled to the fork (20). The force applied on the knob (10) moves the fork (20) and thereby extends the spring (40).
Furthermore, the driveshaft (50) includes one end coupled to the toggle pin (30) and other end coupled to a moving contact (52). The moving contact (52) is capable of being engaged with a fixed contact (54). The driveshaft (50) in accordance with the present invention has an improved profile as shown in figure 5.
The latch (60) is supported on the toggle pin (30). The toggle pin (30) rolls over the latch (60) and the driveshaft (50) when the toggle pin (30) receives force exerted by the spring (40) when extended. The latch (60) in accordance with the present invention has an improved profile as shown in figure 4.
When the direction of the spring (40) force changes from any one of positive x-direction to negative X-direction and negative X-direction to positive x-direction, the toggle pin (30) roll over the latch (60), and the drive shaft (50) profile which in turn rotates the drive shaft (50) to attain any one of ON and OFF position of the MCCB (100).
In the present invention, the latch (60) profile and the driveshaft (50) are made in such a manner that the toggle pin (30) roil over them and follows the same circular paths as it was following in the conventional method (In conventional MCCB (200), the toggle pin follows a circular path having radius equal to the

length of an upper link with centre at the latch upper link hinge point. In the same time, the toggle pin follows another circular path having radius equal to the length of the lower link with centre at driveshaft lower link hinge point). Figure 1 shows the MCCB (100)-in TRIP condition, figure 2 shows the MCCB in OFF condition and figure 3 shows the MCCB (100) in ON condition.
For example, when the MCCB (100) is in OFF condition as shown in figure 2, to switch ON the MCCB (100), the force is applied on the knob (10). As the fork (20) moves, the spring (40) extends and the force required to move the spring (40) further increases as the toggle pin (30) does not move. This is because of the direction of the spring (40) force. As the direction of the component of the spring (40) force changes from positive x-direction to negative X-direction, the toggle pin (30) starts to roll over the latch (60) and the driveshaft (50) profile which in turn rotates the driveshaft (50) and the MCCB (100) attains ON position as shown in the figure 3.. Though, in the absence of the upper link, the dead centre is not visible, but as motion of the toggle pin (30) is restricted to in a fixed circular path, the dead centre remain in the same fixed line. As the spring (40) axis crosses the dead centre, the force direction changes. Similar is the case when the MCCB (100) operates from ON to OFF condition.
Advantages of the invention
1. The MCCB (100) provide elimination of components thereby reducing cost and assembly time and hence increase productivity thereof.
2. The MCCB (100) lead to lesser friction and overall performance thereof.
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. A moulded case circuit breaker with improved mechanism comprising:
a knob operating the circuit breaker;
a fork having a first end and a second end, the first end positioned near the knob;
a toggle pin movably mounted on a driveshaft, the driveshaft having one end coupled to the to the toggle pin and other end coupled to a moving contact;
a spring having one end attached to the toggle pin and other end coupled to the fork, wherein the force applied on the knob moves the fork thereby extending the spring; and
a latch supported on the toggle pin, wherein the toggle pin roll over the latch and the driveshaft when the toggle pin receives force exerted by the spring when extended,
wherein, when direction of the spring force changes from any one of positive x-direction to negative X-direction and negative X-direction to positive x-direction , the toggle pin roll over the latch and drive shaft profile which in turn rotates the drive shaft to attains any one of ON and OFF position.
2. The moulded case circuit breaker as claimed in claim 1, wherein the
moving contact is capable of being engaged with a fixed contact.