FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
AND
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2005
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
HYBRID DESIGN OF EXTERNAL ROTOR FAN
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTORS
Kamble Deepak Gajanan and Bharnuke Anirudha of Crompton Greaves Ltd, Engineering Department, Global R&D, Kanjur (E), Mumbai - 400 042, 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:

TECHNICAL FIELD OF THE INVENTION :
The present invention relates to an external rotor fan,
More particularly, the present invention relates to a hybrid external rotor fan which eliminates the cantilever action of the motor and reduces the noise and vibration of the external motor fan.
BACKGROUND OF THE INVENTION
Conventional external rotor motors have a stator, a rotor that rotates around the stator, a rotor shaft that rotates centrally in relation to the rotor and a rotor shaft bearing means. The rotor shaft bearing means function to eliminate at least some of the vibrations produced by the motor.
U. S. Patent No. 6,225,722 discloses a rotor shaft (26) that extends through the stator (2) and is supported by a rotor shaft bearing means (27). The rotor shaft bearing means is in the form of a relatively long slide bearing bushing. However, there are several disadvantages to such a construction. First, the bushing is usually made from a soft material such as brass, etc. and wears out at a relatively fast rate. Second, the bushing does not eliminate the cantilever effect of the external rotor motor. Third, the motor is relatively expensive to construct.
OBJECTS OF THE INVENTION :
An object of the present invention is to provide a hybrid external rotor fan that eliminates the cantilever action of the motor of the rotor fan.

Another object of the present invention is to provide a hybrid external rotor fan that reduces the noise and vibration produced by the external rotor fan while in operation, Yet another object of the present invention is to provide a hybrid external rotor fan that has a simple construction which that is easy to assemble and has a low cost of manufacture.
SUMMARY OF THE INVENTION:
The present invention relates to a hybrid design of external rotor fan having a housing having a front end and a back end. Further, a cover having an opening is disposed at the back end of the housing. A stator is disposed inside the housing and the stator has a central opening. A shaft disposed inside the housing, wherein the front end portion of the shaft extends through the central opening of the stator and the back end portion of the shaft extends through the opening of the cover at the back end of the housing. Further, a bush is disposed around the circumference of the shaft, wherein one end of the bush is connected to the stator and a is bearing encapsulated within the opening of the cover at the back end of the housing, wherein the bearing is connected to the end portion of the shaft extending through the opening of the cover. Further, a circlip is disposed within the opening of the cover at the back end of the housing to secure the bearing within the opening in the cover at the back end of the external rotor fan.
BRIEF DESCRIPTION OF DRAWINGS :
The hybrid external rotor fan according to the present invention is schematically depicted in the drawings and will be described in detail below.

FIG. 1 shows a sectional view of the hybrid design of an external rotor fan according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION :
As shown in FIG.l, the hybrid design of the external rotor fan of the present invention preferably has a housing (1) with a front end (2) and a back end (3). The hybrid external rotor fan further has a cover (4) which is attached at the back end (3) of the housing (1). Further, the cover (4) preferably has at least one opening (5).
A stator (6) is disposed preferably within the housing (1) and has an opening (7). The opening (7) is located preferably in the central portion of the stator (6). A shaft (8) having a front end portion (9) and a back end portion (10) is disposed inside the housing (1). The shaft (8) is disposed within the housing (1) in a manner such that preferably the front end portion (9) of the shaft (8) passes through the central opening (7) of the stator (6) and may be connected to the front end (2) of the housing (1). The back end portion of the shaft (10) is preferably connected to the cover (4) at the back end of the housing (3) and preferably passes through the opening (5) of the cover (4).
The hybrid external rotor fan further has a bush (11) disposed around the circumference of the shaft (8) to dampen the vibrations emitted by the shaft (8) during operation of the external rotor fan of the present invention. Preferably, the bush (11) may be embodied in the form of an elongate hollow tubular structure, wherein one end of the bush (11) is connected to the stator (6). The hybrid external rotor fan further comprises a bearing (12), preferably a ball bearing, which is encapsulated within the opening (5) of the cover

(4) at the back end (3) of the housing. The bearing (12) is rotatably connected to the back end portion of the shaft (10). The positioning of the bearing (12) at the back end (3) of the housing eliminates the cantilever effect of the motor. A circlip (13) is disposed within the opening (5) which secures the bearing (12) inside the opening (5) of the cover (4).
The hybrid external rotor fan according to the present invention also comprises other standard components such as sensor (14), PCB (15), blades (16), rotor ring (17), etc. which perform their known functions in the external rotor fan. Further, the various components maybe assembled and connected by conventional methods such as press fitting, etc. or connected with fasteners, such as screws, etc. which are well known in the art.
While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications maybe made without departing from the invention in its broader aspects, and therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.

We Claim,
1. A hybrid design of external rotor fan comprising:
a housing having a front end and a back end;
a cover having an opening, disposed at the back end of the housing;
a stator disposed inside the housing, wherein the stator has a central opening;
a shaft disposed inside the housing, wherein the front end portion of the shaft
extends through the central opening of the stator and the back end portion of the
shaft extends through the opening of the cover at the back end of the housing;
a bush disposed around the circumference of the shaft, wherein one end of the
bush is connected to the stator;
a bearing encapsulated within the opening of the cover at the back end of the housing, wherein the bearing is connected to the end portion of the shaft extending through the opening of the cover; and
a circlip disposed within the opening of the cover at the back end of the housing to secure the bearing within the opening in the cover at the back end of the external
rotor fan.