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 THE INVENTION
A sheath assembly for connecting multiple lead wires of a flameproof induction motor
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai - 400 030, Maharashtra, India, an Indian Company
INVENTORS
Desale Rajgopal and Dhokane Prakash, Technology Department, LT Motors, (M3) Crompton Greaves Ltd A6/2 MIDC Area, Ahmednagar, Maharashtra, India, both 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 a sheath assembly for connecting lead wires of a flameproof induction motor.
BACKGROUND OF THE INVENTION
Electrical equipments like induction motors used in hazardous environments such as coal mines face the danger of explosions owing to the presence of inflammable gases. Arc and sparks produced by the normal operation of equipment, like motor starters, contactors, and switches, can ignite a hazardous location atmosphere. The gases present in such locations may seep through the equipment body in gaps and joints, and when this happens while the equipment in operation and may result in an explosion causing severe man and material damage. Damage caused by such explosion in electrical equipments can be reduced by containing the explosion within the equipment. Design practices offer solutions to contain explosions within the equipment and are referred to as flame proof standards for e.g. IS/IEC 2148 confirms to flame proof standards for an electrical motor. Adhering to such standards includes designing the joints and gaps of an induction motor with recommended dimensions to offer a minimum volume which is enough to 'quench' the flame and thereby and stopping it from reaching the volatile surrounding environment.
A flame proof induction motor comprises a rotor mounted on a shaft and rotatably disposed in a stator which is located within a motor housing. The rotor shaft is rotatably mounted in a pair of endshields fitted at the ends of the motor housing. The motor also comprises a terminal box mounted on the motor housing. The terminal box

communicates with the motor housing through an opening in the motor housing. Lead wires from the stator windings are connected to a set of terminal studs in the terminal box. The conventional manner in which the terminal wires from the stator windings motor are currently brought to the terminal box involves the use of terminal studs which are molded in plastic wherein one end of the terminal stud is secured to the stator windings and the other end is exposed in the terminal box to receive rated power supply. Terminal studs are manufactured adhering to flame proof standards as described above. Every lead wire that needs to be connected to the stator windings requires a terminal stud to be provided. However, terminal studs as a means in flameproof induction motors may not be feasible when the number of wires which need to be connected to the stator windings are as many as 10 to 12, as it may be difficult to accommodate such many terminal studs on the stator case of an induction motor.
There is a need to facilitate connection of a plurality of wires to electrical equipments in a combustible/inflammable environment.
OBJECTS OF THE INVENTION
An object of the invention is to provide a sheath assembly for connecting multiple lead wires of a flameproof induction motor.
Several aspects of the invention are described below with reference to examples for illustration. It should be understood that numerous specific details, relationships, and methods are set forth to provide a full understanding of the invention. One skilled in the relevant art, however, will readily recognize that the invention can be practiced

without one or more of the specific details, or with other methods, etc. In other instances, well known structures or operations are not shown in detail to avoid obscuring the features of the invention.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention a sheath assembly is provided for an isolated contact for a plurality of lead wires arriving out of a flameproof induction motor housing. The assembly comprises of a cylindrical bush with its one end fixed to a flange having holes to draw the plurality of lead wires from the stator winding of the induction motor. The other end of the bush is mounted on a circular hub provided within an end cover. The bush is secured firmly with the hub provided on the end cover by means of a hex head lock washer. The cylindrical bush is filled up with epoxy after the pluralities of wires are drawn through it.
The following is a detailed description of the invention with reference to the accompanying drawing, in which:
Figure 1 is a side perspective view of a flameproof induction motor, the sheath assembly and the end cover according to the present invention.
Figure 2 section view of the sheath assembly as mounted between in the end cover on the stator case of the flameproof induction motor according to the present invention.
In the drawings, like reference numbers generally indicate identical, functionally

similar, and/or structurally similar elements.
Figure 1 is a side perspective view of a flameproof induction motor, the sheath assembly and the end cover according to the present invention. In figure 1 the stator case 6 of the flame proof induction motor is shown containing a rectangular opening. The lead wires 5 of the stator winding are shown arriving out of the stator case. Encapsulating bush 1 is shown having a circular flange at one of its ends. The circular flange contains holes to draw each of the lead wires through the cylindrical bush 1. Cylindrical bush 1 is placed in a hub 3 provided within end cover 2. End cover 2 is mounted on to the stator case 6 by means of lock nuts. Hex headed lock washer 4 firmly secures the cylindrical bush 1 against the hub 3 provided in the end cover 2.
Figure 2 shows the section view of the sheath assembly as mounted between in the end cover on the stator case of the flameproof induction motor according to the present invention. The end cover 2 is mounted on the stator case 6 by means of lock nuts 9. The cylindrical bush 1 is shown filled with epoxy 8. Epoxy is a fire resistant materia] and a good insulator. The dimensions of the hex headed lock washer 4 and the thickness of the threading provided on the cylindrical hub 1 is designed so as to meet flameproof standards. The lead wires as arriving out of the cylindrical bush 1 from the end cover 2 can be connected to power supply terminals externally by a user.
The cylindrical bush 1 eliminates the need of connecting a plurality wires by means of terminal studs as known in the prior art.

We claim:
1. A sheath assembly providing an isolated contact for a plurality of lead wires arriving out of a flameproof induction motor housing, the assembly comprising of: a cylindrical bush with its one end fixed to a flange having holes to draw the plurality of lead wires, the other end of the bush being threaded and mounted in a circular hub provided within an end cover and firmly secured thereon by means of a hex head lock washer, wherein the cylindrical bush is filled up with epoxy after the plurality of wires are drawn through it and wherein the end cover is secured fixedly to the motor housing by means of lock nuts.