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:
An interlocking system for locking the down rod onto the motor shaft of
the ceiling fan; and a ceiling fan thereof
APPLICANT:
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTORS:
Nayak Gajanan of Crompton Greaves Ltd, Fans Division, Plot No. 1, IDC Industrial Estate, Bethora, Ponda, Goa - 403409, India; an Indian National.
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:
The present invention relates to the field of mechanical assemblies
Particularly, this invention relates to the down-rod and the motor shaft of the ceiling fan.
BACKGROUND OF THE INVENTION:
A ceiling fan is a fan, usually electrically powered, suspended from the ceiling of a room that uses hub-mounted rotating paddles to circulate air. While a ceiling fan does not necessarily lower the temperature, it does make the room feel cooler by providing a circulatory breeze.
It is important to consider the size of the room when selecting a ceiling fan. The larger the room size, the more powerful a fan motor should be and relatively larger length of the blades are needed to be able to generate enough air movement resulting in a circulatory breeze. Similarly, the height of ceiling of the room determines the suspension height of the ceiling fan. For the suspension of the ceiling fan at a particular height, a downrod is used
A downrod is a metal pipe used to suspend the fan from the ceiling. Downrods come in many lengths.
Torque is induced by the motor in order to provide angular displacement of the blades connected to the motor. Torque, also known as the moment of force, is a measure of energy requires to start the running ability of a body that rotates about a

fixed axis in which the forces acts. When the motor starts, it has a relatively high torque, usually 1.5 to 2.5 times of the full load torque depending upon which type of machine is being driven because of frequency of start, Figure 1 illustrates a front perspective view of the downrod of the prior art.
In the downrod (100) of the prior art, a hollow shaft (12) is used. The hollow downrod includes at least two slits at its diametrically opposite lateral sides. This slit (14) is substantially linear from the operative bottom of the downrod to a point located substantially above on the downrod, culminating into a first circular hole (16). A first pair of circular holes (16) can be seen at the operative top of the two slits (14), respectively.
Further, the downrod (100) includes a second pair of circular holes (18), at its diametrically opposite lateral sides, at the relative bottom of the hollow shaft (12) but spaced apart from the slits (14)
The downrod (100) can be guided and fitted over the motor shaft of the ceiling fan. A tightening element, preferably a bolt is passed through the second pair of circular holes (18). Increasing the tension of the tightening element shall facilitate in the fastening of the downrod (100) on the motor shaft of the ceiling fan.
The starting torque of the ceiling fan results in the partial angular displacement of the downrod (100) of the fan. I.e. the downrod starts to angularly displace due to the motor shaft which is gripped in the downrod (100) and which motor shaft angularly displaces to effect angular displacement of the blades, and fan, in general. This results in the bolt holding the downrod and the motor shaft to receive a yank. Over time, the repeated yanks lead to the deterioration of the bolt.

Thus a need remains to eliminate the problem of angular displacement of the downrod of the ceiling fan to further prevent the deterioration of the bolt holding the downrod and the motor shaft.
OBJECTS OF THE INVENTION:
An object of the invention is to prevent the angular displacement of the downrod of the ceiling fan due to starting torque.
Another object of the invention is to eliminate the risk of deterioration of the locking bolt holding the downrod and motor shaft of the ceiling fan.
Yet another object of the invention is to increase the life of the locking bolt holding the downrod and motor shaft of the ceiling fan.
SUMMARY OF THE INVENTION:
According to the invention, there is provided an interlocking system for preventing angular displacement of a downrod in a fan due to torque exerted from a co-axially, and partially concentrically, placed shaft; said system comprises:
a. stepped element, in said downrod, being defined by at least a linear
indentation adjoining the lengthwise edge of a linear slit in said downrod, said
linear indentation being located at the external circumference of the downrod
and further being defined by a stepped projection adapted to extend beyond
the general inner circumference of said downrod; and
b. notch, on said shaft, corresponding to said stepped element on said downrod,
said notch adapted to receive said stepped element, thereby locking said down
rod onto said shaft.

According to the invention, there is also provided an improved fan, with a downrod and a torque exerting, co-axially, and partially concentrically, placed shaft, having an interlocking system for preventing angular displacement of said downrod; said system comprises: I. stepped element, in said downrod, being defined by at least a linear indentation adjoining the lengthwise edge of a linear slit in said downrod, said linear indentation being located at the external circumference of the downrod and further being defined by a stepped projection adapted to extend beyond the general inner circumference of said downrod; and II. notch, on said shaft, corresponding to said stepped element on said downrod, said notch adapted to receive said stepped element, thereby locking said down rod onto said shaft.
Typically, said stepped element comprises said stepped projection adapted to extend beyond the general inner circumference of said downrod and forming a stepped element with respect to the adjacent inner circumferential surface.
Typically, said stepped element comprises said linear indentation and said corresponding stepped projection adapted to start at a point located at a predefined distance, from the bottom of said downrod and having their end points at the operative bottom of said downrod.
Typically, said linear indentation on said downrod starts at an operative point located at a distance of 1.00 cm from the operative bottom of said downrod.
Typically, said notch is a notch of pre-defined width, said width being in conformity with the width of the stepped element of said downrod such that the stepped element fits, widthwise, into said notch on said shaft.

Typically, said notch is a notch of pre-defined depth, said depth being at least equal to one fifth the height of said stepped element of the downrod such that said stepped element resists angular displacement motion from said shaft, if any.
According to this invention, there is further provide an improved downrod, for preventing angular displacement of said downrod, wherein, said downrod comprises a stepped element, in said downrod, being defined by at least a linear indentation adjoining the lengthwise edge of a linear slit in said downrod, said linear indentation being located at the external circumference of the downrod and further being defined by a stepped projection adapted to extend beyond the general inner circumference of said downrod
According to this invention, there is still further provide an improved shaft, for preventing angular displacement of said downrod, wherein, said downrod comprises a notch, on said shaft, corresponding to said stepped element on said downrod, said notch adapted to receive said stepped element, thereby locking said down rod onto said shaft.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 illustrates a front isometric view of the downrod of the prior art.
The invention will now be described in relation to the accompanying drawings, in which:
Figure 2 illustrates a bottom isometric view of the downrod;
Figure 3 illustrates a side isometric view of the downrod;

Figure 4 illustrates a front isometric view of the shaft of the ceiling fan; and
Figure 5 illustrates an isometric view of the interlocked downrod and shaft of the ceiling fan.
DETAILED DESCRIPTION OF THE INVENTION:
According to the invention, there is provided an interlocking system for preventing rotation of the downrod in a ceiling fan due to torque. According to this invention, there is provided an improved downrod and an improved shaft (on ceiling fan) with the interlocking system for preventing rotation of the downrod.
Figure 2 illustrates a bottom isometric view of the downrod.
Figure 3 illustrates a side isometric view of the downrod.
In accordance with an embodiment of this invention, there is provided a downrod (200) for suspending the ceiling fan such that the downrod has at least a linear indentation (20) adjoining the lengthwise edge of a linear slit (16), the linear indentation being located at the external circumference of the downrod. Further, the corresponding internal circumferential surface equivalent to the linear indentation is a stepped projection (21) such that it extends beyond the general inner circumference of the downrod and forms a stepped projection with respect to the adjacent circumferential surface. The linear indentation (22) and the corresponding stepped projection (21) start at a point located at a predefined distance, from the bottom of the downrod (200) and have their end points at the operative bottom of the down-rod (200).

Preferably, the linear indentation (20) on the down-rod (200) starts at an operative point located at a distance of 1.00 cm from the operative bottom of the down-rod.
According to another embodiment of the invention, there is provided a notch (22) on the motor shaft (300) of the ceiling fan corresponding to the linear indentation (20) on the downrod (200). The notch comes into contact with the stepped projection (21) on the inner circumference of the downrod (200).
Figure 4 illustrates a front isometric view of the shaft of the ceiling fan; and
The width of the notch (22) is in conformity with the width of the stepped element (20, 21) of the downrod (200) such that the stepped element (20, 21) fits, widthwise, into the notch (22) on the shaft (300).
The depth of the notch (22) is at least equal to one fifth the height of the stepped element (20, 21) of the downrod (200) such that the stepped element (20, 21) resists angular displacement motion from the shaft (300), if any.
Figure 5 illustrates an isometric view of the interlocked downrod and shaft of the ceiling fan.
The downrod (200) can be guided and fitted over the motor shaft (300) of the ceiling fan such that the stepped element (20, 21) in the downrod (200) slides into the notch (22) on the motor shaft (300), thereby locking the downrod (200) onto the motor shaft of the ceiling fan.
This interlocking system prevents the angular displacement of the downrod of the ceiling fan. It further eliminates the risk of deterioration of the locking bolt holding

the downrod and motor shaft of the ceiling fan, thus increasing the life of the said bolt.
While this detailed description has disclosed certain specific embodiments of the present invention for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim;
1. An interlocking system for preventing angular displacement of a downrod in
a fan due to torque exerted from a co-axially, and partially concentrically,
placed shaft; said system comprising:
a. stepped element, in said downrod, being defined by at least a linear
indentation adjoining the lengthwise edge of a linear slit in said downrod,
said linear indentation being located at the external circumference of the
downrod and further being defined by a stepped projection adapted to
extend beyond the general inner circumference of said downrod; and
b. notch, on said shaft, corresponding to said stepped element on said
downrod, said notch adapted to receive said stepped element, thereby
locking said down rod onto said shaft.
2. An interlocking system as claimed in claim 1, wherein said stepped element comprising said stepped projection adapted to extend beyond the general inner circumference of said downrod and forming a stepped element with respect to the adjacent inner circumferential surface.
3. An interlocking system as claimed in claim 1, wherein said stepped element comprising said linear indentation and said corresponding stepped projection adapted to start at a point located at a predefined distance, from the bottom of said downrod and having their end points at the operative bottom of said downrod.

4. An interlocking system as claimed in claim 1, wherein said linear indentation on said downrod starts at an operative point located at a distance of 1.00 cm from the operative bottom of said downrod.
5. An interlocking system as claimed in claim 1, wherein said notch is a notch of pre-defined width, said width being in conformity with the width of the stepped element of said downrod such that the stepped element fits, widthwise, into said notch on said shaft.
6. An interlocking system as claimed in claim 1, wherein said notch is a notch of pre-defined depth, said depth being at least equal to one fifth the height of said stepped element of the downrod such that said stepped element resists angular displacement motion from said shaft, if any.
7. An improved downrod with said interlocking system of claim 1, for preventing angular displacement of said downrod, wherein, said downrod comprising a stepped element, in said downrod, being defined by at least a linear indentation adjoining the lengthwise edge of a linear slit in said downrod, said linear indentation being located at the external circumference of the downrod and further being defined by a stepped projection adapted to extend beyond the general inner circumference of said downrod
8. An improved shaft for a fan, with said interlocking system of claim 1, for preventing angular displacement of said downrod, wherein, said downrod comprising a notch, on said shaft, corresponding to said stepped element on said downrod, said notch adapted to receive said stepped element, thereby locking said down rod onto said shaft.

9. An improved fan, with a downrod and a torque exerting, co-axially, and partially concentrically, placed shaft, having an interlocking system for preventing angular displacement of said downrod; said system comprising:
I. stepped element, in said downrod, being defined by at least a linear
indentation adjoining the lengthwise edge of a linear slit in said
downrod, said linear indentation being located at the external
circumference of the downrod and further being defined by a stepped
projection adapted to extend beyond the general inner circumference of
said downrod; and
II. notch, on said shaft, corresponding to said stepped element on said
downrod, said notch adapted to receive said stepped element, thereby
locking said down rod onto said shaft.
10. An improved fan as claimed in claim 9, wherein said stepped element comprising said stepped projection adapted to extend beyond the general . inner circumference of said downrod and forming a stepped element with respect to the adjacent inner circumferential surface.
11. An improved fan as claimed in claim 9, wherein said stepped element comprising said linear indentation and said corresponding stepped projection adapted to start at a point located at a predefined distance, from the bottom of said downrod and having their end points at the operative bottom of said downrod.
12. An improved fan as claimed in claim 9, wherein said linear indentation on said downrod starts at an operative point located at a distance of 1.00 cm from the operative bottom of said downrod.

13. An improved fan as claimed in claim 9, wherein said notch is a notch of predefined width, said width being in conformity with the width of the stepped element of said downrod such that the stepped element fits, widthwise, into said notch on said shaft.
14. An improved fan as claimed in claim 9, wherein said notch is a notch of predefined depth, said depth being at least equal to one fifth the height of said stepped element of the downrod such that said stepped element resists angular displacement motion from said shaft, if any.
15. An improved downrod with said improved fan of claim 9, for preventing angular displacement of said downrod, wherein, said downrod comprising a stepped element, in said downrod, being defined by at least a linear indentation adjoining the lengthwise edge of a linear slit in said downrod, said linear indentation being located at the external circumference of the downrod and further being defined by a stepped projection adapted to extend beyond the general inner circumference of said downrod
16. An improved shaft with said improved fan of claim 9, for preventing angular displacement of said downrod, wherein, said downrod comprising a notch, on said shaft, corresponding to said stepped element on said downrod, said notch adapted to receive said stepped element, thereby locking said down rod onto said shaft.