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)
TITLE OF INVENTION
An improved commutator with tapered insulation segments
APPLICANTS :
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR (S):
Pandya Ankit, Tiwari Laukush and Upadhyay Amarendra; all of Crompton Greaves Limited, Machines (M7) Division, D-5, Industrial Area, MPAKVN, Mandideep - 462046, Madhya Pradesh, India; all Indian Nationals
PREAMBLE TO THE DESCRIPTION:
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

Field of the Invention:
This invention relates to the field of motor assemblies.
Particularly, this invention relates to commutators of motors.
More particularly, this invention relates to an improved commutator with tapered insulation segments.
Background of the Invention:
A commutator is a rotary electrical switch in certain types of electric motors or electrical generators that periodically reverses the current direction between the rotor and the external circuit. A commutator is a common feature of a DC motor. This commutator consists of a number of segments of copper or of other suitable electrical conducting substance place together in the form of a ring with a sheet of electrical insulating substance between every two adjacent segments. The segments or bars of a commutator are held in position by an undercut clamping ring of an insulating material such as mica.
A commutator typically consists of a set of copper segments, fixed around part of the circumference of the rotating part of the machine (the rotor), and a set of spring-loaded brushes fixed to the stationary frame of the machine. The external source of current (for a motor) or electrical load (for a generator) is connected to the brushes.

Normally, the commutator bars and the insulation segments are placed side by side in an alternate manner and a cut is taken on the mica segment so that the surface of the mica segment is at a lower level as compared to the surface of the commutator.
The brushed are preferably carbon brushes which are used to contact the surface of the commutator. This action of making contact results in disposition of carbon dust particles on the commutator surface. The deposition of carbon dust particles on the surface may result in friction. It may alsc> increase chances of inter-bar sorting or flashover and a reduced life of commutator.
There is a need to provide a convenient and easy technique for disposing off carbon dust particles from over the commutator bars.
Prior Art:
JP5284694A discloses manufacture of commutator.
GB191001292 discloses Improvements in Commutators of Dynamo Electric Machines.
There is still a need for a better and efficient removal of carbon dust particles in a commutator to increase the life of the motor and reduce inter-bar sorting of commutator bars and chances of flashover.

Objects of the Invention:
An object of the invention is to provide a convenient and easy technique for disposing off carbon dust particles from over the commutator bars.
Another object of the invention is to increase the life of commutators, and motors, thereby.
Yet another object of the invention is to reduce friction and chances of flashover in a commutator.
Summary of the Invention:
According to this invention, there is provided an improved commutator with tapered insulation segments comprising plurality of commutator bars and insulation segments interspersed alternatively in an annular manner, characterised in that, the operative top surface of said insulation segments is coated with a glossy material and wherein said operative top surface of each of said insulation segment is a tapered operative top surface, said taper extending from the lateral side of the insulation segment to its medial side.
Preferably, said glossy material is a Silicon varnish SI 620.
Brief Description of the Accompanying Drawings:
Figure 1 illustrates a front view of an entire commutator assembly;

Figure 2 illustrates a schematic of a commutator bar and insulation segment along with carbon brush;
Figure 3 illustrates a schematic of the commutator bar along with a rough surface of undercut insulation segment.
Figure 5 illustrates a schematic of a straight insulation segment.
The invention will now be described in relation to the accompanying drawings, in
which:
Figure 4 illustrates a schematic of a insulation bar along with a polished surface of
undercut insulation (mica) segment; and
Figure 6, 7, and 8 illustrate a schematic of various views of the insulation bar along with a tapered polished surface of insulation (mica) segment.
Detailed Description of the Accompanying Drawings:
Figure 1 illustrates a front view of an entire commutator assembly (200).
Figure 2 illustrates a schematic of a commutator bar and insulation segment along with carbon brush.
Figure 3 illustrates a schematic of the commutator bar along with a rough surface of undercut insulation (mica) segment.

Figure 5 illustrates a schematic of a straight insulation segment.
The motor comprises a plurality of commutator bars (10) and insulation segments (12) placed alternatively to form a ring. The insulation segments are mica segments. The mica segments have a rough surface (14). This rough surface leads to the deposition of carbon dust particles from the carbon brush (16), which increases tracking in turn leading to flash over of commutator.
A dust groove (18) is provided at the medial side of the commutator segment to provide a channel wherein the dust may collect and is then cleared out.
According to this invention, there is provided an improved commutator with tapered insulation segments.
Figure 4 illustrates a schematic of a commutator bar along with a polished surface of undercut insulation (mica) segment; and Figures 6, 7, and 8 a schematic of various views of the commuter bar along with a tapered polished surface of insulation (mica) segment.
The tapered polished surface of commutator is represented by reference numeral 50, in the accompanying drawings.
In accordance with an embodiment of this invention, there is provided a glossy varnish applied to the mica segment thereby providing a gloss finished surface

(20). This glossy coat results in non-adherence of the dust particles to the commutator segment surface. These particles can be easily brushed off. The coat eliminates rough surface of mica segment and provides an easy egress path to carbon dust over to the dust groove (18).
The glossy coat may, preferably, be a Silicon varnish SI 620.
In accordance with another embodiment of this invention, there is provided a tapered operative top surface (22) of each of said commutator segments, said taper extending from the lateral side of the commutator segment to its medial side. This design of the commtator mica segment utilizes the effect of gravity in the easy removal of the carbon dust particles that keep on accumulating over a period of time due to the wear of carbon brushes over the surface of the commutator.
While this detailed description has disclosed certain specific embodiments of the present invention for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim,
1. An improved commutator with tapered insulation segments comprising: plurality of commutator bars and insulation segments interspersed alternatively in an annular manner, characterised in that, the operative top surface of said insulation segments is coated with a glossy material and wherein said operative top surface of each of said insulation segment is a tapered operative top surface, said taper extending from the lateral side of the insulation segment to its medial side.
2. An improved commutator with tapered insulation segments as claimed in claim 1 wherein, said glossy material is a Silicon varnish SI 620.