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
Ceiling fan motor and method of making the same
INVENTOR
Name : Bilur Rajanish Nayak
Address : Crompton Greaves Limited, Fans & Appliances Division, 1 GIDC,
Bethora Industrial Estate, Bethora, Ponda, Goa
Nationality : Indian National
APPLICANTS
Name : CROMPTON GREAVES LIMITED
Nationality: Indian Company
Address : CG House, Dr Annie Besant Road, Worli, Mumbai 400025, Maharashtra, India
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 INVENTION
This invention relates to a ceiling fan motor and method of making the same.
BACKGROUND OF INVENTION
A ceiling fan motor comprises a casing formed of a top end shield and a bottom end shield fitted together. A plurality of fan blades are fitted on the top end shield in a radially spaced apart relationship. A disc shaped stator comprising a plurality of magnetic material laminations stacked one above another and riveted or stitched together is fitted at the lower end of the fan shaft extending into the casing. A rotor ring comprising a plurality of magnetic material laminations stacked one above another and riveted or stitched together is disposed around the stator and fixed to the top or bottom end shield. The rotor ring and top or bottom end shield combination rotates around the fan shaft as a single unit. One method of construction of a rotor ring and top end shield combination comprises integrating the rotor ring into the top end shield during pressure die casing of the top end shield with aluminium alloy such as LM6 grade. Aluminium alloy is not a good conductor of electricity. Therefore, during operation of the fan motor, the rotor offers high electrical resistance and reduces the rpm and efficiency of the motor and the fan. During pressure die casting it is, however, possible to maintain concentricity between the rotor ring and the stator so as to reduce the air gap between the rotor ring and the
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stator and ensure smooth rotation of the rotor ring and the fan. Another method of construction of a top end shield and rotor combination comprises integrating the
rotor ring die casted onto aluminium such as LMO grade into the pressure die casted top end shield with aluminium alloy such as LM24 grade. The die casted rotor ring is provided with lugs whereby it is screw fitted onto the corresponding lugs in the top end shield manually. In such a configuration it is extremely difficult to maintain concentricity on the rotor inner diameter during machining. Therefore, larger air gap is required to be provided between the rotor ring and the stator in order to ensure smooth rotation of the rotor ring and the top end shield and the fan. Larger air gap between the rotor ring and the stator reduces the rpm and efficiency of the motor and increases power consumption of the motor. Aluminium being a good conductor of electricity the fan speed is, however, increased.
OBJECTS OF INVENTION
An object of the invention is to provide a ceiling fan motor which has increased rpm
and efficiency.
Another object of the invention is to provide a ceiling fan motor which has reduced power consumption.
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Another object of the invention is to provide a method of making the above ceiling fan motor.
DETAILED DESCRIPTION OF INVENTION
According to the invention there is provided a ceiling fan motor comprising a rotor ring made with magnetic material laminations stacked one above another and riveted or stitched together, the rotor ring being die casted onto aluminium and integrated into the top end shield during pressure die casting of the top end shield with aluminium alloy.
According to the invention there is also provided a method of making a ceiling fan motor, the method comprising
i) making a rotor ring with magnetic material laminations by stacking them one
above another and riveting or stitching them together;
ii) integrating the rotor ring onto aluminium by die casting with aluminium; and
iii) further integrating the rotor ring into the top end shield of the fan motor during pressure die casting of the top end shield with aluminium alloy.
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Fig 1 of the accompanying drawings is a schematic crosssectional view of the rotor ring and top end shield combination of the invention in which the rotor ring 1 is integrated onto aluminium marked 2 by die casting with aluminium. The rotoring is further integrated into the top end shield 3 during pressure die casting of the top end
shield with aluminium alloy. Screw holes in the top end shield for fitting it to the bottom end shield (not shown) are marked 4. Fan shaft hole and aperture for the top bearing (not shown) are marked 5 and 6, respectively. The aluminium used for die casting is preferably aluminium grade LMO. The top end shield is pressure die cast preferably with aluminium alloy grade LM24 or LM6. The bottom end shield is also pressure die cast preferably with the same aluminium alloy namely LM24 or LM6 grade. According to the invention manual fixing of the rotor ring to the top end shield is eliminated. Instead the rotor ring is die casted onto aluminium and integrated into the top end shield by pressure die casting with aluminium alloy. Therefore, it is possible to maintain concentricity between the rotor ring and stator, reduce the air gap between the rotor ring and the stator and ensure smooth rotation of the rotor ring around the stator. Aluminium being a good conductor of electricity, rpm of the fan and air delivery are increased and power consumption is reduced even at low voltages of operation of the fan.
Comparative studies were carried out with ceiling fan motors comprising rotor ring integrated into the top end shield during pressure die casting of the top end shield with aluminium alloy grade LM6 (conventional ceiling fan motor 1) and die casted rotor ring and screw fitted onto the top end shield made by pressure die casting with aluminium alloy grade LM24 (conventional ceiling fan motor 2) and ceiling fan motor
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of the invention. Aluminium used for die casting the rotor ring of conventional fan motor 2 and fan motor of the invention was LMO grade. The motor rating was 230V
and the blade dimensions were 1200mm sweep. The performance details of the fan motors at 230Volts and 180 Volts were as shown in the following Tables 1 and 2,
respectively.
Table 1

Fan motor Average rpm Average air delivery Cuft / min Average powerconsumptionwatts
Conventional fan motor 1 350 203 75
Conventional fan motor 2 370 225 76
Fan motor of invention 403 253 70
Table 1 shows that there is an increase in speed and air delivery and saving in power consumption in the case of the fan motor of the invention at 230 volts as compared to the conventional fan motors 1 and 2.
Table 2

Fan motor Average rpm Average air delivery Cu feet / min Average powerconsumptionwatts
Conventional fan motor 1 290 195 46
Conventional fan motor 2 280 175 44
Fan motor of invention 350 230 43
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Table 2 shows that even at low voltages of 180 volts the increase in speed and air delivery and reduction in power consumption are achieved in the case of the fan motor of the invention as compared to the conventional fan motors 1 and 2.
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We Claim:
1. A ceiling fan motor comprising a rotor ring made with magnetic material laminations stacked one above another and riveted or stitched together, the rotor ring being die casted onto aluminium and integrated into the top end shield during pressure die casting of the top end shield with aluminium alloy.
2. A ceiling fan motor as claimed in claim 1, wherein the rotor ring is die casted onto aluminium grade LMO and the top end shield is pressure die casted with aluminium alloy grade LM 24 or LM6
3. A method of making ceiling fan motor, the method comprising :
i) making a rotor ring with magnetic material laminations by stacking them one
above another and riveting or stitching them together;
ii) integrating the rotor ring onto aluminium by die casting with aluminium; and
iii) further integrating the rotor ring into the top end shield of the fan motor during pressure die casting of the top end shield with aluminium alloy.
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4. A method as claimed in claim 3, wherein the rotor ring is integrated onto aluminium by die casting with aluminum grade LMO and the rotor ring is further
integrated into the top end shield of the fan motor during pressure die casting of the top end shield with aluminium alloy grade LM24 or LM6.
Dated this 7th day of March 2007.
(Jose M A)
of Khaitan & Co
Agent for the Applicants
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Abstract
A ceiling fan motor and a method of making the same. A rotor ring (1) is made with magnetic material laminations by stacking the laminations one above another and riveting or stitching them together. The rotor ring is die casted onto aluminium (2) and integrated into the top end shield (3) during pressure die casting of the top end shield with aluminium alloy (Fig 1).