Fluid reaction surfaces (i.e. – impellers) – Support mounting – carrier or fairing structure
Reexamination Certificate
1999-06-15
2001-05-22
Look, Edward K. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
Support mounting, carrier or fairing structure
C416S005000
Reexamination Certificate
active
06234757
ABSTRACT:
BACKGROUND
1.0 Field of the Invention
The present invention relates generally to ceiling fans and, more particularly, to a system for suspending a ceiling fan.
2.0 Related Art
Ceiling fans have become an increasingly popular supplementary means of conditioning air within both commercial and residential buildings. Notwithstanding the widespread use of ceiling fans, one continuing problem which faces ceiling fan designers is the tendency of ceiling fans to “wobble”, or pivot about the point of suspension. Ceiling fan wobble may exist regardless of the type of conventional system used to mount the ceiling fan, due to fan blade imbalance, which may result from a variety of discrepancies associated with the ceiling fan blades including variations in blade pitch angle, dihedral angle, uneven circumferential spacing between adjacent blade pairs, blade warpage and uneven radial spacing of the blades from the vertical axis of rotation. However, ceiling fan wobble is more prevalent in ceiling fans suspended from a ceiling by a canopy and downrod arrangement, as subsequently discussed in greater detail. Ceiling fan wobble and the associated vibration creates undesirable noise, is visually distracting and may adversely affect the service life of the ceiling fan.
The fan blades of ceiling fans must be positioned at a certain optimum distance from the floor to achieve proper air circulation within the room in which they are installed. This may be accomplished in rooms having relatively high or vaulted ceilings by suspending the fan from the ceiling with a system which includes a canopy and downrod/ball assembly. While conventional systems of this type have enjoyed widespread use, they have a tendency to exacerbate the fan wobble problem as subsequently discussed in conjunction with
FIGS. 1-7
.
FIG. 1
is a fragmentary elevation view, partially in cross-section, illustrating a portion of a ceiling fan
10
and a conventional system
12
for suspending fan
10
from a ceiling (not shown). Ceiling fan
10
includes a motor (not shown) and a plurality of fan blades (not shown) connected to a rotatable portion of the motor, typically by blade irons (not shown). Ceiling fan
10
further includes a motor housing
14
, which may have a unique configuration or decorative outer surface. The ceiling fan
10
typically includes a switch housing suspended below the motor housing
14
and may optionally include a light fixture. A stationary portion of the motor, such as the stator shaft (not shown) may be connected to the motor housing via an adapter
16
, with the upper portion of adapter
16
being shown in FIG.
1
. Adapter
16
is connected to the suspension system
12
, for supporting the ceiling fan
10
.
The suspension system
12
includes a hollow canopy
18
having an upper end portion
20
which is effective for mounting the ceiling fan directly to the ceiling or to an electrical junction box disposed above the ceiling. With regard to canopy
18
, the upper end portion comprises an annular flange which may be attached to the ceiling or junction box via brackets (not shown). The suspension system
12
further includes a downrod
22
having a lower end which is attached to the adapter
16
, typically by threading the lower end of the downrod
22
into adapter
16
. The suspension system
12
further includes a ball
24
disposed in surrounding relationship with an upper end of the downrod
22
and connected thereto by a fastener, such as a set screw (not shown) extending radially through an annular wall of ball
24
into engagement with the downrod
22
.
Canopy
18
defines an interior space
28
and includes a seat
30
extending upwardly from a lower end
32
of canopy
18
and defining an aperture
34
formed in the lower end
32
. Seat
30
is discontinuous in a circumferential direction as subsequently explained further. The ball
24
is disposed partially within the interior space
28
defined by canopy
18
, with a spherical outer surface
26
of ball
24
engaging an arcuate inner surface of the seat
30
. As shown in
FIG. 1
, a portion of ball
24
extends through the aperture
34
and protrudes below the lower end
32
of canopy
18
. The suspension system
12
further includes a pin
36
which extends through apertures
37
formed in the upper end of the downrod
22
and includes opposing ends
38
,
40
which are disposed in longitudinally extending slots
42
formed in the ball
24
. This permits the vertical suspension loads of the ceiling fan
10
to be reacted through the downrod
22
, pin
36
and ball
24
to the canopy
18
.
The spherical outer surface
26
of the ball
24
and the arcuate inner surface of the seat
30
of canopy
18
permits the ball
24
to pivot within seat
30
of canopy
18
. Accordingly, the ceiling fan may pivot about the center of rotation of ball
24
, corresponding to the center (indicated at G in
FIGS. 3
,
4
,
5
and
7
) of the spherical radius defining the outer surface of the ball
24
. The foregoing pivoting of ball
24
and resultant pivoting of the ceiling fan
10
, is necessary for the following reasons. In the first instance, ball
24
must be free to pivot when ceiling fan
10
is mounted to a vaulted, or sloped ceiling. In this instance, the design intent is that a longitudinal centerline axis
54
of the ceiling fan
10
remains substantially vertically disposed. Another reason for requiring the ball
24
to pivot within seat
30
of canopy
32
, is to accommodate wobble of ceiling fan
10
due to an imbalance of the fan blades or rotating portion of the motor. Rigidly mounting the ceiling fan
10
to the ceiling (i.e., eliminating the pivoting motion of ball
24
within seat
30
) would result in damage to the ceiling as a result of the ceiling fan wobble which typically occurs.
The canopy
18
further includes a radially extending tab
50
which engages a longitudinally extending slot
52
formed in the outer surface
26
of the ball
24
. The tab
50
is located circumferentially at a position where the seat
30
of canopy
18
is discontinuous. Furthermore, as shown in
FIG. 2
, the tab
50
extends radially outward from the bottom end
32
of canopy
18
. It is important to note that when the ceiling fan is at rest, with the ball
24
engaged in seat
30
of canopy
18
as shown in
FIG. 1
, the tab
50
of canopy
18
engages the slot
52
of ball
24
at a position which is below the center G of the spherical radius defining the outer surface of the ball
24
. This causes the ball
24
to pivot about an axis which does not pass through the center G as subsequently discussed.
The engagement of the tab
50
in slot
52
of ball
24
reacts the rotational torque created by the motor of the ceiling fan
10
and prevents the ball
24
from rotating within seat
30
about a longitudinal centerline axis
54
of the fan
10
. Accordingly, the ceiling fan
10
is prevented from rotating about the longitudinal centerline axis
54
of the ceiling fan
10
. This prevents the electrical wires (not shown) which pass upward through the hollow interior of the downrod
22
to the junction box, from becoming entangled. However, the local pinning of the ball
24
, via tab
50
in slot
52
, causes the ball
24
to pivot within seat
30
, in reaction to the motor torque, so that the centerline axis
54
is canted relative to vertical, during operation of the ceiling fan
10
. Furthermore, the inventor has determined that as the ball
24
pivots within seat
30
of canopy
18
an undesirable rotation (less than one revolution) of the ball
24
and downrod
22
occurs in reaction to the motor torque. This motion is superimposed on the generally circular motion created by imbalances in the fan blades or other rotating components, which normally occurs. The partial rotation of the ball
24
and downrod
22
, in reaction to the motor torque, exacerbates the ceiling fan wobble problem as further discussed in conjunction with
FIGS. 3-7
. Furthermore, it is believed that the partial rotation of the ball
24
and downrod
22
in reaction to the motor tor
Baker, Donelson Bearman & Caldwell
Hunter Fan Company
Look Edward K.
McAleenan James M.
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