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 fixture for testing the stator of an external rotor motor
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTORS
More Sachin Vasant and Patil Vinod Padmakar, both of Crompton Greaves Ltd, M7 Division, Crompton Greaves Ltd, CG Global R&D Centre, Kanjur (E), Mumbai 400042, 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 fixture for testing the stator of an external rotor motor. BACKGROUND OF THE INVENTION
An external rotor motor is mounted within the wheel hub of an automotive vehicle for driving thereof. The external rotor motor comprises of a stator and a rotor. The stator is mounted on a stationary shaft. The rotor is mounted over the stator describing a clearance therewith and supported on one side by a rotating threaded side end shield mounted on the shaft through a bearing. On the other side, a break side end shield mounted on the shaft through a bearing supports the rotor. The outer races of the bearings to which the respective end shields are mounted are rotating and the inner races mounted on the shaft are rigid. Magents are mounted on the inner surface of the rotor facing the stator in the clearance between the stator and rotor. Usually, lead wires from the stator emerge from the shaft at the break side end shield. Upon energizing the stator through the lead wires, magnets are energized and the rotor is rotated along with the end-shields. Usually, the external testing of the motor for various operational parameters such as back emf, no load speed, torque, power etc is done after installing the motor in the wheel hub of the automotive vehicle at the manufacturing premises itself. During such a testing, upon energizing the stator, if the wheel does not rotate or rotates in a reverse direction, it is concluded that the stator windings are faulty. To fix this fault, the entire assembly is disassembled to remove the stator. Such is cumbersome, time consuming and counter productive. There is a need to facilitate the testing of the stator even before the motor is assembled completely.

OBJECTS OF THE INVENTION
An object of the invention is to provide a fixture for testing the stator of an external rotor motor.
Another object of the invention is to provide a fixture for testing the stator of an external rotor motor during the assembly of the motor-
DETAILED DESCRIPTION OF THE INVENTION
According to the invention, there is provided a fixture for testing the stator of an external rotor motor, the fixture comprising a platform having a hole and a locking bush mounted to the bottom surface of the platform corresponding to the hole; one end of the motor shaft being supported within the locking bush through the hole, a bearing housing mounted on the top surface of the platform coaxially to the hole and a bearing mounted within the bearing housing such that the outer race of the bearing being rigidly mounted to the inner surface of the bearing housing and the rotatable inner race of the bearing being rigidly mounted to the rotating end shield of the motor.
Preferably, the rotating end shield of the motor is mounted to the inner race of the bearing through an annular disc in thread engagement with the end-shield of the motor and the motor shaft is in thread engagement with the locking bush.
These and other aspects, features and advantages of the invention will be better understood with reference to the following detailed description, accompanying drawings and appended claims, in which,
Fig 1 is a schematic view of a fixture for testing the stator of an external rotor motor with a partially assembled external rotor motor inserted therein.

Fig 2 is a cross-sectional view of the fixture for testing the stator of an externa] rotor motor with a partially assembled external rotor motor inserted therein.
Fig 3 is an exploded view of the fixture for testing the stator of an external rotor motor.
Referring to figures 1-3, a partially assembled external rotor motor 1 is inserted into a fixture 2 for testing the stator 3 of the motor 1. To test the stator 3, only the threaded side end shield 4 is mounted to the rotor 5 leaving away the break side end shield (not shown). In the external rotor motor 1, the stator 3 is mounted rigidly on the center of the motor shaft 6. The rotor 5 is mounted over the stator 3 describing a clearance therewith and supported by a rotating threaded side end shield 4 mounted on the shaft 6 through a motor bearing 8. The outer race of the motor bearing 8 to which the threaded end shield 4 is mounted is rotating and the inner race mounted on the shaft 6 is rigid. Magnets 9 are mounted on the inner surface of the rotor 5 facing the stator 3 in the clearance between the stator 3 and rotor 5. The lead wires 10 from the stator 3 emerge from the shaft 6 at the break side end shield. The fixture 2 comprises of a table 11 having a flat surface, locking bush 12, bearing housing 13 and a bearing 14. Optionally, an annular disc 15 is also provided. A hole 16 is provided at the center of the table of a size big enough to pass the motor shaft 6 there through. Coaxially below the hole 16, a locking bush 12 having threads at the inner surface thereof is mounted to the bottom surface of the table 11. The locking bush 12 is essentially a bowl like structure adapted to thread engagingly hold the motor shaft end 18 therein. On the top surface of the table 11, the bearing housing 13, which is essentially a ring shaped structure, is mounted coaxially to the hole 16 of the table 11. To provide better rigidity, the bearing housing 13 is mounted on the table 11 through a shoulder plate 19 such that the hole in the plate 19 and that of the bearing housing

13 remain coaxial to the hole 16 of the table. The bearing 14 is inserted into the bearing housing 13 such that the rigid outer race thereof remains fixed to the inner surface of the bearing housing 13. The hole of the bearing 14 remains coaxial to the hole of the bearing housing 13. Optionally, an annular disc 15 is provided coaxially within the bearing 14 such that the outer surface of the disc 15 is fixed to the rotatable inner race of the bearing 14. The inner surface of the annular disc 15 is provided with threads for thread engagement with the end shield 4 of the motor 1. Else, the end shield 4 of the motor 1 is directly fixed to the inner surface of the bearing 14.
The motor shaft end 18 at the threaded side end shield 4 of the motor provided with threads is inserted into the locking bush 12 through the annular disc 15, bearing 14, bearing housing 13, table 11 and thread engaged therewith. Thus, the motor 1 is supported on the fixture 2 upstandingly such that the break end side remains atop. Simultaneously, the thread end side end shield 4 of the motor also gets thread engaged with the inner surface of the annular disc 15. Upon energizing the stator 3 through the lead wires 10, the rotor 5 and consequently the end shield 4 rotates. Consequently, the annular disc 15 in thread engagement with the end shield 4 is also rotated by virtue of it being in contact with the movable inner race of the bearing 14.
According to the invention, the fixture enables an unhindered rotation of the end shield in spite of the brake end shield not assembled onto the motor. Therefore, upon energizing the stator, if the rotor/end shield does not rotate or rotates in a reverse direction, a lot of time is saved in replacing the stator which otherwise would have been wasted in removing the motor from the wheel hub and dismantling the entire motor. The productivity is thus improved.

Although the invention has been described with reference to a specific embodiment, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiment, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can be made without departing from the scope of the invention as defined in the appended claims.

We claim:
1. A fixture for testing the stator of an external rotor motor, the fixture
comprising
a. a platform having a hole and a locking bush mounted to the bottom
surface of the platform corresponding to the hole; one end of the motor
shaft being supported within the locking bush through the hole;
b. a bearing housing mounted on the top surface of the platform coaxially
to the hole; and
c. a bearing mounted within the bearing housing such that the outer race
of the bearing being rigidly mounted to the inner surface of the bearing
housing and the rotatable inner race of the bearing being rigidly
mounted to the rotating end shield of the motor.
2. The fixture for testing the stator of an external rotor motor as claimed in claim 1, wherein the rotating end shield of the motor is mounted to the inner race of the bearing through an annular disc in thread engagement with the end-shield of the motor.
3. The fixture for testing the stator of an external rotor motor as claimed in claim 1, wherein the one end of the motor shaft is in thread engagement with the locking bush.