FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
As amended by the Patents (Amendment) Act, 2005
& THE PATENTS RULES, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION
A rotor shaft having helical groove
2. APPLICANTS
a) Name : Crompton Greaves Limited
b) Address : CG House, Dr Annie Besant Road, Worli, Mumbai - 400 030,
Maharashtra, India
c) Nationality : an Indian Company
J. INVENTORS
(a) Name : Parmane Sachin Bbimarao., Jain Prateek Kumar, Joshi Kishor Uddhav, Dhavileswarapu Srinivas
(b) Nationality: Indian
(c) Address : Analytics Centre, Global R&D Centre, Crompton Greaves Limited, Kanjur (E), Mumbai 400042, Maharashtra, India, Indian National
4. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the
manner in which it is to be performed.

BACKGROUND OF THE INVENTION
Motors, generators or other rotating machines generally get heated when used for extensive periods. For this reason these machines are usually cooled sometimes internally with help of certain mechanisms or externally depending on the conditions they operate in.
They may be provided with air ducts for allowing heated air to exit from the machine and cooler air from surrounding area to enter the body. Other mechanisms include providing external cooling mechanisms such as separate fans.
The designing of the surfaces inside of these machines may also generally be done to provide better flow of the air through the body thereof. The fluid dynamics of the air when the machine is in motion significantly affects the thermal performance.
Presently a motor consists of rotor stamping placed on circumferential plates along the core length of the shaft. The shaft along with circumferential plates and rotor rotates at a constant speed. There is formed a path between two circumferential plates along the length of the shaft which allows the air to flow through radial ducts in rotor. However for providing improved heat dissipation the air entering such confines of the rotor need to be accelerated more during the operation of the motor. The dynamics of the air should be such to provide smooth movement of the air.
Accordingly there is a need of simple yet effective mechanism to allow flow of the air inside the body of machines such as motor (or generator), alternators or the like.

SUMMARY
A rotor shaft of a motor is provided to have better heat dissipation characteristics. In one embodiment the rotor shaft comprises of atleast one groove along the longitudinal surface of the rotor shaft forming a helix from one end of the rotor shaft to the other end for smooth flow of air along said groove.
In another embodiment two grooves are provided to run along the longitudinal surface of the rotor shaft. Each groove forms a helix from one end of the rotor shaft to the other end.
In one embodiment the groove is provided to be semi-elliptical. The resistance offered to the air entering the groove is minimal owing to the helical profile of the groove and the shape of the groove being semi-elliptical. The smooth transfer of air is thereby enabled. Also during running condition the minimal resistance along with the rotational movement provides for improved acceleration of the air along the groove. Moreover, the effect on structural strength of the shaft will be less.
BRIEF DESCRIPTION OF THE DRAWINGS
Reference will be made to embodiments of the invention, examples of which may be illustrated in the accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in the context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments

Figure 1 illustrates a rotor shaft having groove as per one embodiment of the present invention.
Figure 2 illustrates cross sectional view of the rotor as shown in figure 1.
Figure 3 illustrates a rotor shaft having two grooves as per one embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A rotor shaft is described which enhances heat dissipation of the motor it is used in. In one embodiment channelized depressions are provided on the longitudinal surface of the rotor shaft forming a helix from one face of the rotor shaft to the other face for smooth flow of air along said channelized depression for heat dissipation.
In another embodiment two such channelized depressions are provided diametrically opposite to each other. Multiple such channelized depressions may be provided depending on the conditions the motor operates in.
In the following description, for purpose of explanation, specific details are set forth in order to provide an understanding of the invention. It will be apparent, however, to one skilled in the art that the invention may be practiced without these details. One skilled in the art will recognize that embodiments of the present invention, some of which are described below, may be incorporated into various types of motors having rotor shafts and requirement of heat dissipation there from. It is understood that one

skilled in art may modify or change the data used in the examples described in the specification.
Reference in the specification to "one embodiment" or "an embodiment" means that a particular feature, characteristic, or function described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment.
As per one embodiment of the present invention a rotor shaft of a motor is shown with reference to figure 1. The rotor shaft comprises of atleast one groove 103 along the longitudinal surface 105 of the rotor shaft. The groove forms a helix from one end 105a of the rotor shaft to the other end 105b. The groove allows for smooth flow of air for heat dissipation.
As shown in figure 2 the groove may be provided to be of semi-elliptical shape thereby enabling entry of air in the groove 203 smoothly. In other embodiments the shape of the groove may be semi-circular or rectangular.
In the running condition the groove allows the air to enter along the groove and run from one end to the other end. The helical shape of the groove provides for local acceleration of air thereby improving the air circulation therein. In one embodiment two grooves may be provided on the longitudinal surface of the rotor shaft as shown in figure 3. One of the grooves 301 runs from the one end of the rotor shaft along the longitudinal surface of the rotor shaft. The other groove 303 may

be started from one end of the rotor shaft diametrically opposite to the location where the first groove is started. Accordingly the grooves may run diametrically opposite to each other through the longitudinal surface of the rotor shaft. The double grooves enhance the heat dissipation by providing local acceleration of the air entering the grooves.
It may be understood by the person skilled in the art that numerous such grooves may be provided along the surface of the shaft for providing added heat dissipation while being aware of the dynamics of the air while the rotor shaft is in motion.
The resistance offered to the air entering the groove is minimal owing to the helical profile of the groove and the shape of the groove being semi-elliptical. The smooth transfer of air is thereby enabled. Also during running condition the minimal resistance along with the rotational movement provides for improved acceleration of the air along the groove.
The foregoing description of the invention has been described for purposes of clarity and understanding. Although embodiments of the present invention have been described relative to a few standards, and associated attributes therein, one skilled in the art will recognize that the present invention is also very much applicable to other such methods and systems. It is not intended to limit the invention to the precise form disclosed. Various modifications may be possible within the scope and equivalence of the appended claims.

We Claim:
1. A rotor shaft of a motor comprising:
atleast one groove along the longitudinal surface of the rotor shaft forming a helix from one end of the rotor shaft to the other end for smooth flow of air along said groove for heat dissipation.
2. The rotor shaft as in claim 1, wherein the groove is semi-elliptical.
3. The rotor shaft as in claim 1, wherein the groove is semi-circular.
4. The rotor shaft as in claim 1, wherein the groove is rectangular.
5. The rotor shaft as in claim 1 comprising:
two grooves positioned diametrically opposite to each other along the longitudinal surface of the rotor shaft.