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
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTORS
Savant Sidharth Ratnakar and Agnihotri Shyam, both of Fans & Appliances Division, Crompton Greaves Limited, Plot No 1, Bethora Industrial Estate, Bethora, Ponda, Goa 403401, India, both Indian Nationals
PREAMBLE JO 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.
This invention also relates to a ceiling fan comprising the motor gear.
BACKGROUND ART
Ceiling fans are generally driven by single phase external rotor AC induction motor comprising a housing formed by a top end shield and bottom end shield fitted together. The housing is rotatably held around a stationary fan shaft extending into the housing. The motor also comprises a stator disposed in the housing and fitted onto the fan shaft and a rotor disposed around the stator in spaced apart relationship and fixed to the bottom end shield or top end shield of the housing. The fan blades are rigidly fitted on the housing in a radially spaced apart relationship. The housing rotates with the rotor of the motor and in turn rotates the blades. Normally a ceiling fan rotates at speeds in the range of 150-350 rpm. In order to enable the fan to rotate at these speeds and at the required sweep, the stator should have around 12-18 poles. Due to the large number of poles, the size of the motor increases and renders it bulky and heavy. As the rotor rotates around the stator and as the rotor and stator are large in size, end shields of the housing have to be necessarily circular in shape. If a different shape is to be given to the bottom end shield of the housing, say for aesthetic purpose, then add on components of the required shapes are to be fitted to the bottom end shield. This adds to the cost of the ceiling fan. The stator and rotor occupy the entire area of the housing because of which the capacitor of the fan has to be located outside the housing along with the terminal block and long lead wires connecting the motor to the capacitor. The capacitor and the motor connections are hidden by a lower canopy which has to be large enough to
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cover the capacitor and connections. The lower canopy and leadwires also add to the cost of the fan. For smooth running of the motor with minimal noise, it is essential to maintain an uniform air gap between the rotor and stator. As the motor is large in size, it is difficult to maintain an uniform air gap between the rotor and stator around the entire circumference of the motor. Non-uniformity in the air gap between the rotor and the stator results in humming noise during rotation of the fan and also hampers the speed of the rotation of the fan. As the fan speed depends on the number of poles of the stator, different pole configurations are required for different fan speeds. This calls for large number of inventories to be maintained. External rotor AC induction motors are also generally expensive. Single phase internal rotor AC induction motors are also used to drive ceiling fans. Internal rotor AC induction motors are compact and cost effective besides being able to give high speeds. In internal rotor motor driven ceiling fans, the blades are fitted to the fan shafts with spiders. Balancing of the spiders on the ceiling fan shafts is, however, difficult as the diameter of the fan shafts is small. If the blades are not properly balanced, they to tend to flap during rotation of the fans. In order to overcome this problem it is known to mount the blades on the rotor with shanks. For proper balancing of the blades on the rotor, the size of the rotor is increased to provide a larger surface area for mounting. Additionally, mounting of the fan blades on the rotor requires special shanks which are expensive and the mounting procedure is also complicated and time consuming.
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OBJECTS OF INVENTION
An object of the invention is to provide a ceiling fan motor, which is compact and economical.
Another object of the invention is to provide a ceiling fan motor, which can operate over a wide range of speeds.
Another object of the invention is to provide a ceiling fan motor, which operates with negligible humming noise.
Another object of the invention is to provide a ceiling fan motor, which can have different shapes or geometries without add on components.
Another object of the invention is to provide a ceiling fan motor, which does not require large number of inventories for different speeds.
Another object of the invention is to provide a ceiling fan motor, wherein the fan capacitor and associated connectors can be located in the housing thereby eliminating the lower canopy and long leadwires and associates cost.
Another object of the invention is to provide a ceiling fan motor, which provides sufficient surface area for mounting and balancing the fan blades without using complicated mounting arrangements.
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Another object of the invention is to provide a ceiling fan comprising the above motor.
DETAILED DESCRIPTION OF INVENTION
According to the invention there is provided a ceiling fan motor comprising an internal rotor motor located eccentrically in a housing comprising a top end shield and bottom end shield fitted together, the housing being rotatably held around the fan shaft extending into the housing, the motor shaft being connected to the housing through an epicyclic speed reduction gear train.
According to the invention there is also provided a ceiling fan comprising the above ceiling fan motor with the blades of the fan mounted on the housing in radially spaced apart relationship.
The following is a detailed description of the invention with reference to the accompanying drawings, in which:
Fig 1 is a cross sectional view of a ceiling fan motor according to an embodiment of the invention; and
Fig 2 is a schematic view of the epicyclic speed reduction gear train connected to the bottom end shield and internal rotor motor of Fig 1.
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As shown in Fig 1 of the accompanying drawings, the ceiling fan motor 1 comprises an internal rotor motor 2 (which is a single phase internal rotor AC induction motor) located in a housing 3 comprising top end shield 3a and bottom end shield 3b fitted together. The motor shaft 5 protrudes out from one end of the casing 3c of the motor. The rotor and stator of the motor are marked 6 and 7, respectively. The housing 3 is rotatably held around a stationary fan shaft 11 extending into the housing using bearings (not shown). The motor is located in the housing with its shaft 5 eccentric with the fan shaft 11. 12 is a driver gear mounted at the end of the motor shaft protruding out from the motor casing. 13 is a driven gear disposed around the driver gear in mesh with the driver gear and fitted to the bottom end shield of the housing. The motor is mounted on a bracket 14 extending radially from the fan shaft and fitted to the fan shaft. The blades (not shown) of the fan are mounted on the housing in a radially spaced apart relationship using shanks (not shown). During operation of the fan, the driver gear rotates with the motor shaft and in turn drives the driven gear, housing and fan blades. The gear ratio of the driver and driven gears is selected depending upon the speed reduction required.
According to the invention the ceiling fan motor comprises an internal rotor motor which is small in size and compact and economical. With a high speed internal rotor motor, the fan can be rotated at different speeds and sweeps of the fan blades by using the driven gear and driver of different gear teeth ratio. Therefore, large inventories for different fan speeds need not be maintained. As the internal rotor motor is small in size it is easy to maintain an uniform air gap between the rotor and stator. Because of uniform air gap, humming noise is reduced. As the internal rotor motor is small it does not occupy the entire area of the housing and the bottom shield of the housing need not be
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circular and can be of any other geometry thereby eliminating the cost of add on components required for different shapes or geometries of the bottom end shield. As the internal rotor motor is small in size it does not occupy the entire area of the housing and the capacitor along with the terminal block and lead wires connecting the motor to the capacitor can be accommodated in the housing. The length of the lead wires also can be reduced. Therefore, the lower canopy can be eliminated and cost of lower canopy and long leadwires can be avoided. As the blades are mounted on the housing, sufficient surface area is available for mounting and balancing the fan blades on the housing and the blades can be mounted using simple shanks. Also the blades do not flap during operation of the motor thereby enabling the fan to rotate at the required speeds and sweeps.
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We Claim:
1. A ceiling fan motor comprising an internal rotor motor located eccentrically in a housing comprising a top end shield and bottom end shield fitted together, the housing being rotatably held around the fan shaft extending into the housing, the motor shaft being connected to the housing through an epicyclic speed reduction gear train.
2. A ceiling fan motor as claimed in claim 1, wherein the speed reduction gear train comprises a driver gear mounted at one end of the motor shaft and a driven gear disposed around the driver gear in mesh with the driver gear and fitted to the housing, being supported on a bracket which in turn is supported on the fan shaft.
3. A ceiling fan motor as claimed in claim 1 or 2, wherein the motor is a high speed motor.
4. A ceiling fan motor as claimed in anyone of claims 1 to 3, wherein the motor is single phase AC induction motor or any other suitable motor.
5. A ceiling fan comprising a motor as claimed in any one of claims 1 to 3, wherein
the blades of the fan are mounted on the housing in radially spaced apart relationship.
Dated this 17th day of April 2007.

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Abstract
A ceiling fan motor (1) comprises an internal rotor motor (2) located eccentrically in a housing (3) comprising a top end shield (3a) and bottom end shield (3b) fitted together. The housing is rotatably held around the fan shaft (11) extending into the housing. The motor shaft (5) is connected to the housing through an epicyclic speed reduction gear train (12 and 13) (Fig 1).