DESCRIPTION
CEILING FAN
TECHNICAL FIELD
The present invention relates to ceiling fans connected to a hollow
shaft protruding upward from a motor that rotates blades, and a pipe
suspending from the ceiling.
BACKGROUND ART
One known technology to prevent drop accidents due to loosened or
detached screws in this type of conventional ceiling fans is to sound an
alarm when an attached screw becomes loose. For example, this is
disclosed in Patent Document 1.
This ceiling fan is described below with reference to Fig. 17. As
shown in the drawing, pipe 101 passing through the center of ceiling fan
is suspended from bracket 103 via semi-spherical flange 102. Bracket
103 is attached to mounting plate 105 by attaching screw 106. This
mounting plate 105 is attached to a ceiling face by wood screw 104.
Microswitch 107 is provided on bracket 103, and actuator 108 of
microswitch 107 makes contact with the ceiling face.

To increase the safety, an alarming device is activated via
microswitch 107 when wood screw 104 fixing mounting plate 105 or
attaching screw 106 fixing bracket 103 is loosened in the conventional
ceiling fan. However, if the shaft provided on the motor and the pipe
suspending from the ceiling are connected by a connecting bolt via a
through hole in this structure of ceiling fan, the through hole for the
connecting bolt may wear by a secular change and the hole may broaden.
Patent Document 2 discloses the next technology for a structure of
externally-rotating motor. A tubular portion is formed in the center of
an upper case where an external rotor of the externally-rotating motor is
embedded, and an upper ball bearing is press-fitted into this tubular
portion. A vertical central shaft of an internal stator is inserted through
this upper ball bearing, and a lower ball bearing, already press-fitted to
the vertical central shaft, is inserted into the tubular portion in the center.
A collar is provided between inner rings or outer rings of the upper and
lower ball bearings, and a coil spring is provided between the other rings.
The upper ball bearing is fixed to the tubular portion with an interference
fit, and the lower ball bearing is fixed to the vertical central shaft with a
clearance fit after the lower ball bearing is loosely fitted in the collar.
In this conventional motor, the outer ring of the upper ball bearing
is fixed inside the tubular portion, which is a bearing housing, with the
interference fit; and its inner ring is connected to the vertical central
shaft with the clearance fit. The outer ring of the lower ball bearing is
connected to the tubular portion with the clearance fit, and its inner ring
and the vertical central shaft are connected with the interference fit.

Accordingly, the weight of the rotor is applied in a direction that presses
the outer ring of the upper ball bearing downward from a top end of the
tubular portion. As deformation or deterioration of the coil spring
advance in line with operations, a certain level of appropriate preload
cannot be given to the upper and lower ball bearings, although an elastic
member such as a coil spring is inserted between the upper and lower ball
bearings. This causes distortion in a sliding face inside the upper and
lower ball bearings at an early stage, resulting in generating a sliding
noise. Reduction of this sliding noise has thus been demanded.
Patent Document 1: Japanese Patent No. 3032325
Patent Document 2:: Japanese Utility Model Unexamined
Publication No. S56-41115
SUMMARY OF THE INVENTION
A ceiling fan of the present invention has the following structure.
The ceiling fan has a motor that rotates multiple blades attached in the
horizontal direction. This motor includes a hollow shaft disposed upright
on the center of a disc-like stator, and a rotor around an outer periphery
of the stator. The blades are attached to the rotor and the rotor rotates
integrally with the blades. This motor further includes a cylindrical
bearing housing provided over the stator, a rotor support integrally
connecting this bearing housing and the rotor, and a pair of upper ball
bearing and lower ball bearing housed in this bearing housing and
rotatably supporting the rotor. This bearing housing has a base in its

center. The upper ball bearing is disposed over this base via an elastic
member, and the lower ball bearing is disposed below this base. The
upper ball bearing and the lower ball bearing are fixed to the hollow shaft.
With this structure, shaking and vibration of the motor associated
with the rotation of the bearing housing can be significantly reduced, and
thus the present invention can offer the ceiling fan with low noise and low
vibration. In addition, a press process in multiple operations become
unnecessary. This can reduce a damage to the ball bearing in an
assembly process as well as reduction of manhour.
BRIEF DESCRIPTION OF DRAWINGS
Fig. 1 illustrates a basic structure of a ceiling fan in accordance
with a first exemplary embodiment of the present invention.
Fig. 2 is a sectional view of a motor of the ceiling fan in accordance
with the first exemplary embodiment of the present invention.
Fig. 3 is a top view of the motor in accordance with the first
exemplary embodiment of the present invention..
Fig. 4 is an exploded sectional view of the motor in accordance with
the first exemplary embodiment of the present invention..
Fig. 5 is a schematic sectional view of a ball bearing in the motor
in accordance with the first exemplary embodiment of the present
invention..
Fig. 6 is a sectional view of another motor in accordance with the
first exemplary embodiment of the present invention..

Fig. 7 is a fragmentary sectional view of still another motor in
accordance with the first exemplary embodiment of the present invention.
Fig. 8 is a sectional view of still another motor to which a
horizontal detector is added in accordance with the first exemplary
embodiment of the present invention..
Fig. 9 is a sectional view of still another motor to which a light
bracket is added in accordance with the first exemplary embodiment of
the present invention..
Fig. 10 is a sectional view of still another motor to which a hook
rosette is attached in accordance with the first exemplary embodiment of
the present invention..
Fig. 11 is a sectional view of a suspension mechanism of a ceiling
fan in accordance with a second exemplary embodiment of the present
invention.
Fig. 12 is a sectional view of the suspension mechanism in
accordance with the second exemplary embodiment of the present
invention.
Fig. 13 is a magnified view of a key part of the suspension
mechanism in accordance with the second exemplary embodiment of the
present invention.
Fig. 14 is a top view illustrating the relationship between an
opening and a safety switch in accordance with the second exemplary
embodiment of the present invention.

Fig. 15 is a sectional view illustrating the relationship between a
connecting bolt and a pipe in accordance with the second exemplary
embodiment of the present invention.
Fig. 16 is a front view illustrating a connecting bolt and a pipe in
accordance with the second exemplary embodiment of the present
invention.
Fig. 17 illustrates a ceiling-suspended state of a conventional
ceiling fan.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Exemplary embodiments of the present invention are described
below with reference to drawings.
(FIRST EXEMPLARY EMBODIMENT)
Fig. 1 illustrates a basic structure of a ceiling fan in the first
exemplary embodiment of the present invention. The ceiling fan in the
first exemplary embodiment includes motor 1 that rotates multiple blades
2 provided in the horizontal direction. This motor 1 is suspended from
ceiling 4 using suspension mechanism 3.
Fig. 2 is a sectional view of motor 1 of the ceiling fan in the first
exemplary embodiment of the present invention. Fig. 3 is its top view,
and Fig. 4 is its exploded sectional view. Fig. 5 is a schematic sectional
view of a ball bearing in motor 1.

Motor 1 includes disc-like stator 6 to which hollow shaft 5 is
disposed upright on its center, and rotor 7 rotatably provided around the
outer periphery of this stator 6. Blade 2 is attached to rotor 7. Motor 1
further includes cylindrical bearing housing 71, rotor support 72 that
integrally connects this bearing housing 71 and rotor 7, and a pair of
upper ball bearing 41 and lower ball bearing 42 housed in bearing
housing 71 and rotatably supporting rotor 7. Bearing housing 71
includes base 73 in its center, upper ball bearing 41 disposed over this
base 73 via upper elastic member 81, and lower ball bearing 42 disposed
under base 73. An inner ring of upper ball bearing 41 and an inner ring
of lower ball bearing 42 are both fixed to hollow shaft 5.
Bearing housing 71 has upper opening 76 at an upper part and
lower opening 77 at a lower part relative to base 73 in the center. Upper
ball bearing 41 is housed in upper opening 76, and lower ball bearing 42
is housed in lower opening 77 with a clearance fit, respectively. The
inner ring of upper ball bearing 41 and the inner ring of lower ball
bearing are fixed onto hollow shaft 5 with an interference fit.
In cylindrical bearing housing 71, base 73 in substantially the
center and rotor support 72 are provided inside and outside of cylindrical
bearing housing 71 so as to improve rigidity of bearing housing 71, and
increase the holding power of upper ball bearing 41 and lower ball
bearing 42.
In addition, provision of base 73 between both bearings in bearing
housing 71 reduces a load applied to upper ball bearing 41 when the
weight of rotor 7 is applied as a downward load to upper ball bearing 41

and lower ball bearing 42 via bearing housing 71, although the downward
load is applied to the outer ring of lower ball bearing 42 from base 73.
Since an upward pressing force acts on upper ball bearing 41 by the
presence of upper elastic member 81, the upward load is applied. The
total of the load on lower ball bearing 42 and upper ball bearing 41, and
the upward pressing force acting on upper ball bearing 41 can greatly
reduce the load applied to upper ball bearing 41 and lower ball bearing 42.
A wave washer is preferable as this upper elastic member 81.
More specifically, as shown in Fig. 5, upper elastic member 81,
such as a spring, can apply an upward pressing force to upper ball
bearing 41, and the self-weight of lower ball bearing 42 and upper elastic
member 81 can apply a downward pressing force to lower ball bearing 42.
Balls in upper ball bearing 41 and lower ball bearing 42 are held by
contact angles 41A and 42A in contradicting directions. With respect to
preload directions 41B and 42B, an upward preload is applied to upper
ball bearing 41 and downward preload is applied to lower ball bearing 42.
This ensures application of substantially a fixed level of appropriate
preload.
As described above, the load applied to upper ball bearing 41 and
lower ball bearing 42 housed in bearing housing 71 can be reduced, and
upper ball bearing 41 and lower ball bearing 42 can be firmly retained by
improving the rigidity of bearing housing 71. Accordingly, shaking and
vibration associated with the rotation of bearing housing 71 can be
significantly reduced so as to stably rotate motor 1 with less shaking and

vibration. The present invention can thus offer the ceiling fan with low
noise and low vibration.
Upper ball bearing is fitted in from upper opening 76 of bearing
housing 71, and lower ball bearing 42 is fitted in from lower opening 77.
This enables assembly with increased dimensional accuracy, compared to
an assembly method of fitting upper and lower ball bearings from the
same direction. In addition, since upper ball bearing 41 and lower ball
bearing 42 are fixed to hollow shaft 5 with the interference fit, a
component (collar) needed for retaining a certain vertical distance at the
inner ring side can be eliminated.
Hollow shaft 5 includes upper guiding part 51 and lower fitting
part 52. The outside shape of guiding part 52 is smaller than that of
fitting part 52.
An external diameter of this guiding part 51 is set such that it
forms a clearance fit with an internal diameter of upper ball bearing 41
and lower ball bearing 42. Lower ball bearing 42, bearing housing 71
integrally provided with rotor 7, upper elastic member 81, and upper ball
bearing 41 can be pressed and assembled onto hollow shaft 5, which is
press-fitted to stator 6, by a single process. This eliminates multiple
press processes. Accordingly, the manpower can be reduced, and also a
damage to ball bearings during assembly can be reduced.
An upper end of cylindrical bearing housing 71, in which upper
ball bearing 41 is housed, and an upper end of upper ball bearing 41 are
made same height. This enables visual confirmation of accurate housing
of upper ball bearing with upper elastic member 81 in bearing housing 71.

In addition, the press operation can be executed using the upper end of
bearing housing 71 as a reference face. This facilitates the assembly
operation and improves the assembly quality.
The bearing housing has a fulcrum on its outer periphery at the
same height as the base. Fulcrum 74 of rotor supports 72 provided
radially from bearing housing 71 is provided opposite to the side of base
73 of bearing housing 71. Therefore, rotor 7 can form a rotating body
that rotates around the substantial center of upper ball bearing 41 and
lower ball bearing 42 by matching fulcrum 74 extending from bearing
housing 71 to the rear face of base 73. In other words, this rotating body
rotates around a point that generates the least vibration on hollow shaft 5
sandwiched by upper ball bearing 41 and lower ball bearing 42. This
results in less influence of shaking and vibration when motor 1 is
operated, and achieves the structure that can retain uniform distance
between stator 6 and rotor 7. Accordingly, electrical noise can be reduced.
Still more, since rotor supports 72 extend horizontally from
bearing housing 71, a rotating body in which rotor supports 72 extend
horizontally from on bearing housing 71 in the center, can be achieved.
Rotor supports 72 and base 73 thus become aligned in a cross-sectional
shape. This facilitates retention of accuracy at manufacturing die-
casting dies. This also allows to form die-cast parts in shapes that are
easy to inspect dimensions.
Fig. 6 is a sectional view of another motor of the ceiling fan in this
exemplary embodiment. Lower elastic member 82 is inserted between

base 73 and lower ball bearing 42. Other components are the same as
the structure shown in Fig. 2.
This structure prevents direct traveling of an impact to lower ball
bearing 42 via base 73 and traveling of faint vibration of blades 2 to
hollow shaft 5. In addition, lower ball bearing 42 can be protected from
damage. A wave washer is preferable as this lower elastic member 82.
With this structure, clearances among base 73, upper ball bearing 41, and
lower ball bearing 42 can be set small, contributing to downsizing and
slimming of motor 1.
Fig. 7 is a fragmentary sectional view of still another motor of the
ceiling fan in this exemplary embodiment. Overtemperature protective
device 63 for detecting a temperature of stator coil 61 is disposed on a
bottom face of stator coil 61 of stator 6.
This structure enables connection of stator coil 61 and internal
wiring 64 from overtemperature protective device 63 directly to a main
body circuit without passing through hollow shaft 5. Accordingly, there
is no need to draw wiring around, and thus measurement accuracy of
detected temperature can be retained by preventing error in detection
data. Still more, manpower can be reduced by improving assembly
operations. Furthermore, internal wiring 64 will not be damaged by
touching typically an edge when hollow shaft 5 is passed through. This
ensures reliable connection.
Fig. 8 is a sectional view of still another motor of the ceiling fan in
this exemplary embodiment. As shown in the drawing, circuit board 65
controlling motor 1 is disposed on board holder 66, and board holder 66 is

directly attached to the bottom face of stator 6. Circuit board 65 or board
holder 66 is disposed horizontally, and horizontal detector 67 that is set
horizontal is provided on circuit board 65 or board holder 66.
With this structure, the present invention can offer the ceiling fan
in which horizontal detector 67 detects an abnormal operation of motor 1
for any reason or any vibration due to earthquake, and safely stops the
operation of motor 1. Further safety can be ensured by adding vibration
sensor and revolution sensor to this horizontal detector 67.
Fig. 9 is a sectional view of still another motor of the ceiling fan in
this exemplary embodiment. In Fig. 9, light bracket 68 is provided on
the bottom face of stator 6 so that a lighting fixture can be attached
immediately under and close to rotor 7. This structure ensures the
suspension strength when a heavy lighting fixture is installed. In
addition, the horizontal level can be retained in installation. Accordingly,
the lighting fixture can be mounted immediately under and close to rotor
7. This enables the installation of a general thin lighting fixture with
large diameter.
Fig. 10 is a sectional view of further another motor of the ceiling
fan in this exemplary embodiment. In Fig. 10, hook rosette 69 to which
the lighting fixture can be attached on the bottom face of stator 6 is
provided. With this structure, a lighting fixture that is directly
mountable to commercial hook rosette 69 can be installed. Accordingly,
construction work for attaching the lighting fixture become easier, and
greater variation in lighting fixtures become available.

(SECOND EXEMPLARY EMBODIMENT)
Figs 11 and 12 are fragmentary sectional views of a suspension
mechanism of a ceiling fan in the second exemplary embodiment of the
present invention. Fig. 13 is a magnified view of its key part.
Suspension mechanism 3 includes pipe 31 connected to hollow shaft 5 of
motor 1 by connecting bolt 20, operation lever 35 for operating safety
switch 15, and suspender 34 for suspending pipe 31 from ceiling 4.
Hollow shaft 5 and pipe 31 have through hole 17, respectively, and they
are connected by connecting bolt 20. Details are described later.
Motor cover 11 is provided on a top part of motor 1, and opening 12
is created on its top face. Safety switch 15 is fixed inside motor cover 11
to the side of hollow shaft 5. Operation lever 35 for operating this safety
switch 15 includes fixing part 36 and arm 37 extending obliquely
downward from this fixing part 36. Fixing part 36 is fixed to pipe 31,
and arm 37 operates safety switch 15 through opening 12.
Safety switch 15 has operation button 15A, and this operation
button 15A is disposed at a lower part of opening 12. As described above,
arm 37 of operation lever 35 operates this operation button 15A. Safety
switch 15 has a normally open contact, and safety switch 15 is installed in
a state that this contact is closed by making arm 37 push operation
button 15A. A circuit is configured such that electricity is provided to
motor 1 through this contact. Accordingly, in normal use, the ceiling fan
is connected to the mains supply in a state that the contact of the safety
switch is closed by operation lever 35, and thus motor 1 can be operated.

One end of safety wire 39 for preventing dropping is fixed onto
ceiling 4, and a wire fixing part provided on the other end of safety wire
39 is fixed onto an outer peripheral face of hollow shaft 5 at the inner side
of operation lever 35. Safety switch 15 provided on the side of hollow
shaft 5, operation lever 35, and a joint portion of hollow shaft 5 and pipe
31 are entirely covered with canopy 32.
Fig. 14 is a top view illustrating the relationship between opening
12 in motor cover 11 and safety switch 15 of the ceiling fan in the second
exemplary embodiment. As shown in Fig. 14, an area of opening 12 is
extended along the circumferential movement of arm 37 of operation lever
35 around hollow shaft 5.
Fig. 15 is a sectional view illustrating the relationship between
connecting bolt 20 and pipe 31 of the ceiling fan in the second exemplary
embodiment. Fig. 16 is its front view. Connecting bolt 20 has head 21
and thread 22. A cross-section of this head 21 to the side of thread 22 is
a circular arc conforming to the outer face of pipe 31. A shape of head 21
seen from the side opposite to thread 22, relative to pipe 31, is an oval.
Connecting bolt 20 is screwed to nut 25 via flat washer 26 and
spring washer 27, and a pin (not illustrated) is inserted into pin-insert-
hole 28 created in thread 22 so as to prevent nut 25 from coming off.
In this structure, an end of hollow shaft 5 is inserted into an end of
pipe 31; and connecting bolt 20 is passed through each of through holes 17,
and tightened by screwing nut 25 in a manner such that a circular-arc
portion of head 21 of connecting bolt 20 conforms to an outer peripheral
face of pipe 31. This eliminates the need for supporting head 21 of

connecting bolt 20, and thus a tightening tool, such as a spanner, is used
only for nut 25. Installation work at a high place near the ceiling can
thus be facilitated. In addition, since the circular-arc portion of head 21
of connecting bolt 20 is fixed tightly onto the outer peripheral face of pipe
31, rotation or loosening of connecting bolt 20 can be reliably prevented,
increasing the safety.
Next, the safety operation at occurrence of some sort of
abnormality is described. If tightening force of connecting bolt 22 that
connects hollow shaft 5 and pipe 31 is insufficient, looseness occurs at the
joint by secular change after repeated operation and stop of the ceiling fan.
Then, through holes 17 in hollow shaft 5 and pipe 31 wear and their hole
diameters broaden. In this case, arm 37 of operation lever 35 deviates
corresponding to a relative increase in a turn area of hollow shaft 5 and
pipe 31, and the contact of safety switch 15 is opened. This stops current
supplied to motor 1, and thus the unsafe state is immediately and
automatically avoided. Furthermore, since the power will not turn on
even the power is turned on again, the user will be alerted of an abnormal
state of the suspended main body.
An opening area of opening 12 in the top face of motor cover 1 is
created along the circumferential direction that operation lever 35 moves
centered on hollow shaft 5 of motor 1. The turn area of hollow shaft 5
relative to pipe 31 increases as the hole diameters of through holes 17
wear and broaden by secular change, and operation lever 35 moves into
opening 12. Since operation lever 35 turns in the circumferential
direction around pipe 31, the shape of opening 12 is also extended in the

circumferential direction, so as to conform to the movement area of
operation lever 35. Accordingly, safety switch 15 reliably works to stop
power supply to motor 1 when there is an imminent danger.
In addition, the top end of operation button 15A of safety switch 15
is provided at a position lower than the top face of opening 12 of motor
cover 11. Therefore, it is difficult to forcibly push operation button 15A,
typically with a finger, when operation lever 35 deviates and safety switch
15 is in the open state. Accordingly, restarting of the ceiling fan by
intentionally operating operation button 15A after motor 1 is stopped,
while the joint of hollow shaft 5 and pipe 31 remains unstable, is
preventable.
Furthermore, the wire fixing part of safety wire 39 is fixed to the
outer peripheral face of hollow shaft 5 at an inner side of operation lever
35. This wire fixing part thus cannot be removed unless operation lever
35 is removed. Fixing of this wire fixing part at the inner side of arm 37
of operation lever 35 before shipment from a factory prevents easy
removal of safety wire 39 during installation of the main body. This
encourages contractors to use safety wire 39 in their installation work.
INDUSTIRAL APPLICABILITY
The ceiling fan of the present invention achieves a low-noise and
low-vibration motor, prevents danger of dropping of the ceiling fan and
abnormal vibrations, and facilitates installation. Accordingly, this
ceiling fan is suitable for installation in plants, offices, hotels, and houses.

CLAIMS
1. A ceiling fan comprising'-
a motor that rotates a plurality of blades horizontally
disposed, the motor including1
a hollow shaft disposed upright on a center of a disc-
like stator;
a rotor around an outer periphery of the stator, the
rotor being integrally rotated with the blades attached to the rotor!
a cylindrical bearing housing provided over the
stator;
a rotor support integrally connecting the bearing
housing and the rotor; and
a pair of upper ball bearing and lower ball bearing
housed in the bearing housing and rotatably supporting the rotor,
wherein the bearing housing includes a base in its center,
the upper ball bearing is disposed over the base via an elastic member,
the lower ball bearing is disposed under the base, and the upper ball
bearing and the lower ball bearing are fixed onto the hollow shaft.
2. The ceiling fan of claim 1,
wherein the bearing housing includes an upper opening in
its upper part and a lower opening in its lower part relative to the base as
a center, the upper ball bearing being housed in the upper opening with a
clearance fit, the lower ball bearing being housed in the lower opening

with a clearance fit, and the upper ball bearing and the lower ball bearing
being fixed onto the hollow shaft with an interference fit.
3. The ceiling fan of claim 1,
wherein the bearing housing has a fulcrum on its outer
periphery at a height same as the base.
4. The ceiling fan of claim 1,
wherein the rotor support is horizontally extended from the
bearing housing.
5. The ceiling fan of claim 1,
wherein the hollow shaft is formed of an upper guiding part
and a lower fitting part, an outside shape of the guiding part being
smaller than an outside shape of the fitting part.
6. The ceiling fan of claim 1,
wherein an upper end of the bearing housing and an upper
end of the upper ball bearing are made same height.
7. The ceiling fan of claim 1 further comprising:
an elastic member between the base and the lower ball
bearing.
8. The ceiling fan of one of claims 1 and 7,

wherein the elastic member is a wave washer.
9. The ceiling fan of claim 1 further comprising:
a suspension mechanism for suspending the motor from a
ceiling, the motor including:
the stator fixed to the hollow shaft protruding
upward from the motor: and
a safety switch that opens and closes a supply of
electricity to the stator,
wherein the suspension mechanism includes:
a pipe connected to the hollow shaft for
suspending the motor from the ceiling;
a connecting bolt for connecting the hollow shaft
and the pipe! and
an operation lever for opening and closing the
safety switch, the operation lever being moved in response to a relative
turn of the hollow shaft and the pipe so as to open a contact of the safety
switch.
10. The ceiling fan of claim 9,
wherein the hollow shaft and the pipe have a through hole,
respectively, through which the connecting bolt passes, and a contact of
the safety switch is opened when a hole diameter of the through hole
broadens.

11. The ceiling fan of claim 9,
wherein the motor includes a motor cover having an opening,
the safety switch is disposed inside the motor cover, and the safety switch
is operated by the operation lever through the opening.
12. The ceiling fan of claim 11,
wherein the opening is provided in a top face of the motor
cover in a circular arc shape around the hollow shaft.
13. The ceiling fan of claim 11,
wherein the safety switch includes an operation button, the
operation button being disposed at a lower part of the opening.
14. The ceiling fan of claim 11,
wherein the operation lever includes a fixing part and an
arm, the fixing part being fixed to the pipe, and the safety switch being
operated by the arm through the opening.
15. The ceiling fan of claim 9,
wherein the suspension mechanism includes a safety wire
for preventing dropping, one end of the safety wire being fixed onto the
ceiling, and an other end being fixed onto the hollow shaft at an inner side
of the operation lever.
16. The ceiling fan of claim 9,

wherein the connecting bolt includes a head and a thread, a
cross'section of the head to a side of the thread being a circular arc
conforming to an outer periphery of the pipe.
17. The ceiling fan of claim 16,
wherein a shape of the head seen from a side opposite to the
thread is an oval.
18. The ceiling fan of claim 16,
wherein the thread includes a pin-insert-hole for inserting a
pin so as to prevent a nut from coming off.
19. The ceiling fan of claim 1,
wherein the stator includes a stator coil, and an
overtemperature protective device for detecting a temperature of the
stator coil is disposed on a bottom face of the stator coil.
20. The ceiling fan of claim 1,
wherein the motor includes a circuit board and a board
holder for fixing the circuit board, the board holder being disposed on a
bottom face of the stator.
21. The ceiling fan of claim 20,

wherein the circuit board and the board holder are disposed
horizontally, and a horizontal detector is provided to detect a horizontal
direction.
22. The ceiling fan of claim 1 further comprising:
a light bracket on a bottom face of the stator, attachment of a
lighting fixture being feasible on the light bracket.
23. The ceiling fan of claim 1 further comprising:
a hook rosette on a bottom face of the stator, attachment of a
lighting fixture being feasible on the hook rosette.

A ceiling fan includes a motor for rotating multiple blades. This motor includes a hollow shaft that is disposed upright on the center of a
disc-like stator, and a rotor around an outer periphery of the stator. The rotor integrally rotates with the blades. This motor further includes a cylindrical bearing housing, and a pair of upper ball bearing and a lower ball bearing housed in this bearing housing. This bearing housing has a base in its center. The upper ball bearing is disposed over the base, and
the lower ball bearing is disposed under the base in this bearing housing. Both bearings are fixed onto the hollow shaft.