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
PROVISIONAL SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
A device for assembling a BLDC Motor external rotor
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTORS
Saple Chandrashekhar Rajaram and Kamble Deepak Gajanan, both of CG Global R&D Centre, Kanjur (E), Mumbai - 400042, Maharashtra, India, and all Indian National
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention :

FIELD OF INVENTION
This invention relates to a device for assembling a BLDC motor external rotor.
BACKGROUND OF INVENTION
Conventionally, sector magnets are stuck to the rotor housing manually and one after the other. This process leads to non-uniform air gap between sector magnets as well chances are there that wrongly stuck for which repositioning is either costlier or not possible due to the gluing to the rotor housing and as already damage is done to the magnet.
OBJECTS OF INVENTION
An object of the invention is to provide more uniform gap sector magnets in the rotor housing of a BLDC motor.
Another object of the invention is to eliminate the rejection rate of sector magnets which are placed incorrectly.
Another object of the invention is to introduce an arrangement having a platform to hold having a guide to hold rotor housing and an external concentric cylinder connected with each other by means of a central shaft which holds both the cylinders together concentrically.
Another object of the invention is the stepped shaft holding both cylinders of the assembly with two springs; one each between the inner cylinder and the guide bush and the other spring between sliding bush and the locking washer, such that the spring pressure is applied uniformly in the operation. The inner cylinder upon compressed


with the help of an external spring force, carries the positioned sector magnets into the rotor housing and can be retrieved back to its original position by the other spring.
Another object of the invention is that the external cylinder is made of magnetic material preferably from mild steel and the inner cylinder is made up of non-magnetic materials like aluminium, plastic which eventually acts as a guide for holding the sector magnets during the operation.
Another object of the invention is the clamping arrangement between the platform which holds the rotor housing and the concentric cylinder assembly for the purpose.
Another object of the invention is that the inner diameters of the rotor assembly and the external magnetic cylinder of the assembly remains same to facilitate the smooth transfer of sector magnets from the external un-glued cylinder into the glued inner diametrical surface of the rotor assembly, to complete the cycle.
DETAILED DESCRIPTION OF THE INVENTION
In the manufacturing of BLDC external rotor motor, sector magnets have to be glued by adhesive on the inner surface of the rotor. These sector magnets have to be stuck on the glued, inners surface of the rotor. This arrangement facilitates the same by introducing a pair of concentric cylinders each made of magnetic and non-magnetic cylinders. The gaps between these cylinders are such hat it can accommodate the desired sector magnets conveniently. While the outer cylinder is magnetic where the sector magnets are placed circumferentially without having glued, the inner cylinder which is made of a non-magnetic act as a guide. After setting all the sector magnets placed circumferentially having a circumferential uniform gap, the arrangement then


made to position over the rotor. The rotor is placed in a platform of the fixture. The entire set-up is then locked with bolts and nuts or any other locking means. The purpose of locking is to slide the set of sector magnets from the external cylindrical body into the glued inner diametric surface of the rotor housing, where the rotor housing inner diameter matched with the inner diameter of the external cylinder. With this process, the maintenance of uniform gap between the sector magnets is ensured while there are no chances of sector magnet being wrongly placed.
In accordance to the present invention, a uniform gap between the sector magnets of a rotor housing of a BLDC motor is provided.
In accordance to the present invention, is to provide an arrangement to eliminate the rejection rate of sector magnets that are placed incorrectly in the process.
In accordance to the present invention, is to introduce an arrangement having a platform to hold having a guide to hold rotor housing and an external concentric cylinder connected with each other by means of a central shaft which holds both the cylinders together concentrically.
In accordance to the present invention, a stepped shaft is provided to hold both cylinders of the assembly with two springs; one each between the inner cylinder and the guide bush and the other spring between sliding bush and the locking washer, such that the spring pressure is applied uniformly in the operation; the inner cylinder upon compressed with the help of an external spring force, carries the positioned sector magnets into the rotor housing and can be retrieved back to its original position by the other spring.


In accordance to the present invention, an external cylinder is made of magnetic material preferably from mild steel and the inner cylinder is made up of non-magnetic materials like aluminium, plastic which eventually acts as a guide for holding the sector magnets during the operation.
In accordance to the present invention, a clamping arrangement is provided between the platform which holds the rotor housing and the concentric cylinder assembly for the purpose.
In accordance to the present invention, the inner diameters of the rotor assembly and the external magnetic cylinder of the assembly is maintained same, so as to facilitate the smooth transfer of sector magnets from the external un-glued cylinder into the glued inner diametrical surface of the rotor assembly, to complete the cycle.