FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION (See section 10 and rule 13]
1. TITLE OF THE INVENTION:
Mechanism Cam Assembly for Motor Control Centre (MCC) Module of Circuit
Breaker
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. 0. 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.


Mechanism Cam Assembly for Motor Control Centre (MCC) Module of
Switchboard
Field of the invention
The present invention relates to low voltage switchgear applications, and more specifically,to a mechanism cam for motor control centre (MCC) module of draw out type in switchboard.
Background of the invention
Mechanism cam is a part of racking mechanism of a motor control centre (MCC) module of a switchboard which converts the rotary motion of an actuating handle to a linear movement of power contacts connected to the module. Current racking mechanism uses a rack and screw mechanism, in which linear motion is achieved through multiple turns of the screw. Accordingly, the required positions of module mechanism, for example, isolated, test and connected are achieved through specific number of rotations of the screw.
However, the distinctness between the isolated, test and connected positions of the circuit breaker are not clear as the above-mentioned positions are determined only by specific number of rotations of the screw and may require additional mechanism to indicate distinctiveness between the isolated, test and connected positions of the circuit breaker.
Accordingly, there exists a need to provide a mechanism which overcomes abovementioned drawbacks.
Objects of the invention
An object of the present invention is to provide distinctness in isolated, test and connected position of the module.
Another object of the present invention is to provide a racking mechanism movement within single rotation of an actuating shaft.

Summary of the invention
Accordingly, the present invention provides a mechanism cam assembly for motor control centre (MCC) module of a switchboard. The assembly comprises a cam secured over a shaft of the MCC module. The cam is being capable of moving through and fro along the length of the shaft. The cam includes a helical slot configured along surface thereof, wherein the cam includes power contacts coupled thereto.
The assembly further comprises a guide member configured on an end of the shaft for accommodating an actuating shaft thereto for rotating the shaft anda bush member mounted over the shaft. The bush member is capable of sliding through the helical slot of the cam upon rotation of the shaft.
Upon rotating the shaft in 90° from its initial isolated position, a secondary contact mechanism of the module operates to engage auxiliary contacts thereof thereby achieving a test position. Further, when the shaft is rotated in 75 °, the bush member slides through the helical slot and gets displaced thereby moving the cam forward to connect the power contacts with mains supply to have connected position. Furthermore, when the shaft is rotated in 15°'the shaft gets locked in connected position.
Brief description of the drawings
Figure 1 shows a perspective view of a mechanism cam assembly in isolated position;
Figure 2 shows a perspective view of the mechanism cam assembly in test
position;

Figure 3 shows a perspectiveview of the mechanism cam assembly in service position;
Figure 4 shows a perspective view of the mechanism cam assembly in locked service position; and
Figure 5 shows cross sectional view of the mechanism cam assembly in the locked service position.
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.
Accordingly, the present invention provides a mechanism cam assembly for motor control centre (MCC) module of a switchboard. The mechanism cam assembly provides distinctness in isolated, test and connected position of the circuit breaker.
Referring to figures 1-3, there is shown a mechanism cam assembly (100) (hereinafter the assembly (100]') for motor control centre (MCC) module of a switchboard in various positions. The assembly (100) comprises a cam (10), a guide member (20) and the bush member (30).
The cam (10) is secured over a shaft (40) of the MCC module (not shown). The cam (10) moves through and fro along the length of the shaft (12). The cam (10) includes a helical slot (12) configured along surface thereof. The cam (10) includes power contacts (50) coupled thereto. The helical slot (12) of the cam (10)has a linear profile during initial 90° degree and final 15° degrees with helical profile in middle 75 °

In an embodiment, the cam (10) along with the helical slot (12) is made of casted aluminium alloy having strength.
Further, the guide member (20) is configured on an end of the shaft (40) for accommodating an actuating shaft (22) thereto for rotating the shaft (40). In an embodiment, the guide member (20) includes a female portion capable of accommodating a male portion of the actuating shaft (22).
Furthermore, the bush member (30) is mounted/secured over the shaft (40). The bush member (30) is capable of sliding through the helical slot (12) of the cam (10) upon rotation of the shaft.
The initial position of assembly (100) is called isolated position in which the power contacts (50) remain isolated from the main supply. Upon rotating the shaft (40) in 90° from its initial isolated positionfrefer figure 1), by means of insertion of the actuating shaft (22) in the guide member of the shaft (40), a secondary contact mechanism of the circuit breaker operates to engage auxiliary contacts thereof thereby achieving a test position, as shown in figure 2. Further, when the shaft (40) is rotated in 75 °, the bush member (30) slides through the helical slot (12) and gets displaced thereby moving the cam (10) forward to connect the power contacts (50) with mains supply to have connected position as shown in figure 3. Furthermore, when the shaft (40) is rotated in 15°'the shaft gets locked in connected (service) position, as shown in figures 4 and 5.
The cam (10) is a part of racking mechanism of MCC module which converts the rotary motion of actuating shaft to the linear movement of power contacts (50). Further, the slope of helical slot (12) in the cam (10) is such that the required displacement of the power contacts (50) is achieved in 75°rotation of the shaft (40). Further, the helical slot (12) is made linear after 75° till 90 degree, in order to get a stable final locked connected position.
Advantages of the invention

1. The assembly (100) achieves mechanism movement within single rotation of
handle.
2. The assembly (100) provides clear distinction between the three positions.
3. The assembly (100) achieve operator independence for mechanism
displacement.
4. The assembly (100) avoids back lashing of the power contacts.
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 mechanism cam assembly for motor control centre (MCC) module
of a switchboard, the mechanism cam assembly comprising:
a cam secured over a shaft of the MCC module, the cam being capable of moving through and fro along the length of the shaft, the cam having a helical slot configured along surface thereof, wherein the cam includes power contacts coupled thereto;
a guide member configured on an end of the shaft for accommodating an actuating shaft thereto for rotating the shaft; and
a bush member mounted over the shaft, the bush member capable of sliding through the helical slot of the cam upon rotation of the shaft;
wherein upon rotating shaft in 90°from its initial isolated position, a secondary contact mechanism of the circuit breaker operates to engage auxiliary contacts thereof thereby achieving a test position, and thereafter when the shaft is rotated in 75 °, the bush member slides through the helical slot and gets displaced thereby moving the cam forward to connect the power contacts with mains supply to have connected position, and further moving of the shaft in 15°locks the shaft in connected position.
2. The mechanism cam assembly as claimed in claim 1, wherein the
helical slot of the cam has a linear profile during initial 90° degree and final 15°
degrees with helical profile in middle 75 °