A FAN ASSEMBLY
FIELD OF THE INVENTION
The present invention relates to a nozzle for a fan assembly, and a fan assembly
comprising such a nozzle.
BACKGROUND OF THE INVENTION
A conventional domestic fan typically includes a set of blades or vanes mounted for
rotation about an axis, and drive apparatus for rotating the set of blades to generate an
10 air flow. The movement and circulation of the air flow creates a 'wind chill' or breeze
and, as a result, the user experiences a cooling effect as heat is dissipated through
convection and evaporation. The blades are generally located within a cage which
allows an air flow to pass through the housing while preventing users fiom coming into
contact with the rotating blades during use of the fan.
15
US 2,488,467 describes a fan which does not use caged blades to project air from the
fan assembly. Instead, the fan assembly comprises a base which houses'a motor-driven
impeller for drawing an air flow into the base, and a series of concentric, annular
nozzles connected to the base and each comprising an annular outlet located at the fiont
20 of the nozzle for emitting the air flow from the fan. Each nozzle extends about a bore
axis to define a bore about which the nozzle extends.
Each nozzle is in the shape of an airfoil. An airfoil may be considered to have a leading
edge located at the rear of the nozzle, a trailing edge located at the front of the nozzle,
25 and a chord line extending between the leading and trailing edges. In US 2,488,467 the
chord linc of cach nozzlc is parallcl to thc bore axis of the nozzlcs. Thc air outlct is
located on the chord line, and is arranged to emit the air flow in a direction extending
away from the nozzle and along the chord line.
30 Another fan assembly which does not use caged blades to project air from the fan
assembly is described in WO 2010/10045 1. This fan assembly comprises a cylindrical
base which also houses a motor-driven impeller for drawing a primary air flow into the
base, and a single annular nozzle connected to the base and comprising an annular
mouth through which the primary air flow is emitted Erom the fan. The nozzle defines
an opening through which air in the local environment of the fan assembly is drawn by
5 the primary air flow emitted from the mouth, amplifying the primary air flow. The
nozzle includes a Coanda surface over which the mouth is arranged to direct the primary
air flow. The Coanda surface extends symmetrically about the central axis of the
opening so that the air flow generated by the fan assembly is in the form of an annular
jet having a cylindrical or hto-conical profile.
10
SUMMARY OF THE INVENTION
In a first aspect, the present invention provides a nozzle for a fan assembly, the nozzle
comprising:
an air inlet;
at least one air outlet;
an annular inner wall at least partially defining a bore through which air from
outside the nozzle is drawn by air emitted from said at least one air outlet;
an outer wall extending about a longitudinal axis and about the inner wall; and
an interior passage located between the inner wall and the outer wall for
20 conveying air from the air inlet to said at least one air outlet;
wherein the interior passage has a first section and a second section each for
receiving a respective portion of an air flow entering the interior passage through the air
inlet, and for conveying the portions of the air flow in opposite angular directions about
the bore;
25 and wherein each section of the interior passage has a cross-sectional area
formcd from thc intcrscction with thc interior passage by a planc which cxtcnds through
and contains the longitudinal axis of the outer wall, and wherein the cross-sectional area
of each section of the interior passage decreases in size about the bore.
30 The air emitted from the nozzle, hereafter referred to as a primary air flow, entrains air
surrounding the nozzle, which thus acts as an air amplifier to supply both the primary
air flow and the entrained air to the user. The entrained air will be referred to here as a
secondary air flow. The secondary air flow is drawn from the room space, region or
external environment surrounding the nozzle. The primary air flow combines with the
entrained secondary air flow to form a combined, or total, air flow projected forward
5 fkom the front of the nozzle.
We have found that controlling the cross-sectional area of each section of the nozzle in
this manner can reduce turbulence in the combined air flow which is experienced by a
user located in fkont of the nozzle. The reduction in turbulence is a result of minimising
10 the variation in the angle at which the primary air flow is emitted fkom around the bore
of the nozzle. Without this variation in the cross-sectional area, there is a tendency for
the primary air flow to be emitted upwardly at a relatively steep angle, relative to the
longitudinal axis of the nozzle, fiom the portion of the interior passage located adjacent
to the air inlet, whereas the portion of the air flow emitted from the portion of the
15 interior passage located opposite to the air inlet is emitted at a relatively shallow angle.
When the air inlet is located towards the base of the nozzle, this can result in the
primary air flow being focussed towards 'a position located generally in front of an
upper end of the nozzle. This convergence of the primary air flow can generate
turbulence in the combined air flow generated by the nozzle.
The relative increase in the cross-sectional area of the interior passage adjacent to the air
inlet can reduce the velocity at which the primary air flow is emitted from the base of
the nozzle. This velocity reduction has been found to reduce the angle at which the air
flow is emitted from this portion of the interior passage. Through controlling the shape
25 of the interior passage so that there is a reduction in its cross-sectional area about the
borc, any variation in thc anglc at which the primary air flow is cmittcd from thc nozzle
can be significantly reduced.
Thc variation in the cross-scctional arca of each scction of thc intcrior passagc is sccn
30 from the intersection with the interior passage by a series of planes which each extend
through and contain the longitudinal axis of the outer wall, upon which the outer wall is
centred. The variation in the cross-sectional area of each section of the interior passage
may also be referred to as a variation in the cross-sectional area of an air flow path
which extends from a first end to a second end of the section of the interior passage, and
so this aspect of the present invention also provides a nozzle for a fan assembly, the
5 nozzle comprising an air inlet; at least one air outlet; an annular inner wall at least
partially defining a bore through which air from outside the nozzle is drawn by air
emitted fiom said at least one air outlet; an outer wall extending about a longitudinal
axis and about the inner wall; and an interior passage located between the inner wall and
the outer wall for conveying air from the air inlet to said at least one air outlet; wherein
10 the interior passage has a fist section and a second section each for receiving a
respective portion of an air flow entering the interior passage through the air inlet, and
for conveying the portions of the air flow in opposite angular directions about the bore;
along a flow path extending fiom a first end to a second end of the section; and wherein
the cross-sectional area of the flow path decreases in size about the bore.
15
The cross-sectional area of each section of the interior passage may decrease step-wise
about the bore. Alternatively, the cross-sectional area of each section of the interior
passage may decrease gradually, or taper, about the bore.
20 The nozzle is preferably substantially symmetrical about a plane passing through the air
inlet and the centre of the nozzle, and so each section of the interior passage preferably
has the same variation in cross-sectional area. For example, the nozzle may have a
generally circular, elliptical or "race-track" shape, in which each section of the interior
passage comprises a relatively straight section located on a respective side of the bore.
25
Thc variation in thc cross-scctional arca of cach scction of thc intcrior passage is
preferably such that the cross-sectional area decreases in size about the bore from a first
end for receiving air from the air inlet to a second end. The cross-sectional area of each
scction preferably has a minimum value locatcd diametrically oppositc thc air inlct.
30
The variation in the cross-sectional area of each section of the interior passage is
preferably such that the cross-sectional area has a first value adjacent the air inlet and a
second value opposite to the air inlet, and where the first value is at least 1.5 times the
second value, and more preferably so that the first value is at least 1.8 times the second
5 value.
The variation in the cross-sectional area of each section of the interior passage may be
effected by varying about the bore the radial thickness of each section of the nozzle. Tn
this case, the depth of the nozzle, as measured in a direction extending along the axis of
10 the bore, may be substantially constant about the bore. Alternatively, the depth of the
nozzle may also vary about the bore. For example, the depth of each section of the
nozzle may decrease from a first value adjacent the air inlet to a second value opposite
to the air inlet.
15 The air inlet may comprise a plurality of sections or apertures through which air enters
the interior passage of the nozzle. These sections or apertures may be located adjacent
one another; or spaced about the nozzle. The at least one air outlet may be located at or
towards the front end of the nozzle. Alternatively, the at least one air outlet may be
located towards the rear end of the nozzle. The nozzle may comprise a single air outlet
20 or a plurality of air outlets. In one example, the nozzle comprises a single, annular air
outlet surrounding the axis of the bore, and this air outlet may be circular in shape, or
otherwise have a shape which matches the shape of the front end of the nozzle.
Alternatively, each section of the interior passage may comprise a respective air outlet.
For example, where the nozzle has a race track shape each straight section of the nozzle
25 may comprise a respective air outlet. The, or each, air outlet is preferably in the form of
a slot. Thc slot prcfcrably has a width in the rangc from 0.5 to 5 mrn.
The inner wall preferably defines at least a front part of the bore. Each wall may be
formcd from a singlc componcnt, but altcrnativcly onc or both of thc walls may bc
30 formed from a plurality of components. The inner wall is preferably eccentric with
respect to the outer wall. In other words, the inner wall and the outer wall are
preferably not concentric. In one example, the centre, or longitudinal axis, of the inner
wall is located above the centre, or longitudinal axis, of the outer wall so that the crosssectional
area of the internal passage decreases from the lower end of the nozzle
towards the upper end of the nozzle. This can be a relatively straightfbnvard way of
5 effecting the variation of the cross-section of the nozzle, and so in a second aspect the
present invention provides a nozzle for a fan assembly, the nozzle comprising an air
inlet, at least one air outlet, an interior passage for conveying air fiom the air inlet to
said at least one air outlet, an annular inner wall, and an outer wall extending about the
inner wall, the interior passage being located between the inner wall and the outer wall,
10 the inner wall at least partially defining a bore through which air from outside the
nozzle is drawn by air emitted fiom said at least one air outlet, wherein the inner wall is
eccentric with respect to the outer wall.
As discussed above, the cross-sectional area of each section of the nozzle is preferably
15 measured in a series of intersecting planes which each pass through the centre of the
outer wall of the nozzle and each contain a longitudinal axis passing through the centre
of the outer wall. However, due to the eccentricity of the inner and outer walls the
cross-scctional area of cach scction of the nozzle may be measurcd in a series of
intersecting planes which each pass through the centre of the inner wall of the nozzle
20 and each contain a longitudinal axis passing through the centre of the inner wall. This
axis is co-linear with the axis of the bore.
The at least one air outlet is preferably located between the inner wall and the outer
wall. For example, the at least one air outlet may be located between overlapping
25 portions of the inner wall and the outer wall. These overlapping portions of the walls
may comprisc part of an intcrnal surfacc of thc inncr wall, and part of an cxtcrnal
surface of the outer wall. Alternatively, these overlapping portions of the walls may
comprise part of an internal surface of the outer wall, and part of an external surface of
thc inncr wall. A scrics of spaccrs may be angularly spaccd about one of thcsc parts of
30 the walls for engaging the other wall to control the width of the at least one air outlet.
The overlapping portions of the walls are preferably substantially parallel, and so serve
to guide the air flow emitted from the nozzle in a selected direction. In one example,
the overlapping portions are frusto-conical in shape so that they are inclined relative to
the axis of the bore. Depending on the desired profile of the air flow emitted from the
nozzle, the overlapping portions may be inclined towards or away from the axis of the
5 bore.
Without wishing to be bound by any theory, we consider that the rate of entrainment of
the secondary air flow by the primary air flow may be related to the magnitude of the
surface area of the outer profile of the primary air flow emitted from the nozzle. When
10 the primary air flow is outwardly tapering, or flared, the surface area of the outer profile
is relatively high, promoting mixing of the primary air flow and the air surrounding the
nozzle and thus increasing the flow rate of the combined air flow, whereas when the
primary air flow is inwardly tapering, the surface area of the outer profile is relatively
low, decreasing the entrainment of the secondary air flow by the primary air flow and so
15 decreasing the flow rate of the combined air flow.
Increasing the flow rate of the combined air flow generated by the nozzle has the effect
of dccreasing the maximum velocity of the combined air flow. This can make the
nozzle suitable for use with a fan assembly for generating a flow of air through a room
or an ofice. On the other hand, decreasing the flow rate of the combined air flow
generated by the nozzle has the effect of increasing the maximum velocity of the
combined air flow. This can make the nozzle suitable for use with a desk fan or other
table-top fan for generating a flow of air for cooling rapidly a user located in front of the
fan.
Thc nozzlc may have an annular front wall cxtcnding betwccn thc inncr wall and thc
outer wall. To reduce the number of components of the nozzle, the front wall is
preferably integral with the outer wall. The at least one air outlet may be located
adjaccnt thc front wall, for cxamplc bctwccn thc borc and thc front wall.
3 0
Alternatively, the at least one air outlet may be configured to direct air over the external
surface of the inner wall. At least part of the external surface located adjacent to the at
least one air outlet may be convex in shape, and provide a Coanda surface over which
air emitted from the nozzle is directed.
5
The air inlet is preferably defined by the outer wall of the nozzle, and is preferably
located at the lower end of the nozzle.
The present invention also provides a fan assembly comprising an impeller, a motor for
10 rotating the impeller to generate an air flow, and a nozzle as aforementioned for
receiving the air flow. The nozzle is preferably mounted on a base housing the impeller
and the motor.
Features described above in connection with the first aspect of the invention are equally
15 applicable to the second aspect of the invention, and vice versa.
BRIEF DESCRIPTION OF THE INVENTION
An embodiment of the present invention will now be described, by way of example
only, with reference to the accompanying drawings, in which:
Figure 1 is a front perspective view, fiom above, of a first embodiment of a fan
assembly;
Figure 2 is a front view of the fan assembly;
Figure 3(a) is a Icfi sidc cross-scction vicw, taken along line E- E in Figurc 2;
Figure 3(b) is a cross-sectional view through one section of the nozzle of the fan
assembly, takcn along linc A-A in Figurc 2;
3 0
Figure 3(c) is a cross-sectional view through one section of the nozzle of the fan
assembly, taken along line B-B in Figure 2;
Figure 3(d) is a cross-sectional view through one section of the nozzle of the fan
5 assembly, taken along line C-C in Figure 2.
Figure 4 is a front perspective view, from above, of a second embodiment of a fan
assembly;
10 Figure 5 is a front view of the fan assembly of Figure 4;
Figure 6(a) is a left side cross-section view, taken along line E- E in Figure 5;
Figure 6(b) is a cross-sectional view through one section of the nozzle of the fan
15 assembly, taken along line A-A in Figure 5;
Figure 6(c) is a cross-sectional view through one section of the nozzle of the fan
assembly, taken along line B-B in Figure 5; and
20 Figure 6(d) is a cross-sectional view through one section of the nozzle of the fan
assembly, taken along line C-C in Figure 5.
DETAILED DESCRIPTION OF THE INVENTION
Figures 1 and 2 are external views of a frst embodiment of a fan assembly 10. The fan
25 assembly 10 comprises a body 12 comprising an air inlet 14 through which a primary
air flow cntcrs the fan asscmbly 10, and an annular nozzlc 16 mountcd on the body 12.
The nozzle 16 comprises an air outlet 18 for emitting the primary air flow from the fan
assembly 10.
30 The body 12 comprises a substantially cylindrical main body section 20 mounted on a
substantially cylindrical lower body section 22. The main body section 20 and the
lower body section 22 preferably have substantially the same external diameter so that
the external surface of the upper body section 20 is substantially flush with the external
surface of the lower body section 22. In this embodiment the body 12 has a height in
the range from 100 to 300 rnm, and a diameter in the range from 100 to 200 mm.
The main body section 20 comprises the air inlet 14 through which the primary air flow
enters the fan assembly 10. In this embodiment the air inlet 14 comprises an array of
apertures formed in the main body section 20. Alternatively, the air inlet 14 may
comprise one or more grilles or meshes mounted within windows formed in the main
10 body section 20. The main body section 20 is open at the upper end (as illustrated)
thereof to provide an air outlet 23 (shown in Figure 3(a)) through which the primary air
flow is exhausted from the body 12.
The main body section 20 may be tilted relative to the lower body section 22 to adjust
15 the direction in which the primary air flow is emitted from the fan assembly 10. For
example, the upper surface of the lower body section 22 and the lower surface of the
main body section 20 may be provided with interconnecting features which allow the
main body section 20 to move relative to the lower body section 22 while prcventing the
main body section 20 from being lifted from the lower body section 22. For example,
20 the lower body section 22 and the main body section 20 may comprise interlocking Lshaped
members.
The lower body section 22 comprises a user interface of the fan assembly 10. The user
interface comprises a plurality of user-operable buttons 24, 26, a dial 28 for enabling a
25 user to control various functions of the fan assembly 10, and a user interface control
circuit 30 conncctcd to thc buttons 24,26 and thc dial 28. The lower body scction 22 is
mounted on a base 32 for engaging a surface on which the fan assembly 10 is located.
Figurc 3(a) illustrates a sectional vicw through thc fan asscmbly 10. Thc lowcr body
30 section 22 houses a main control circuit, indicated generally at 34, connected to the user
interface control circuit 30. In response to operation of the buttons 24, 26 and the dial
28, the user interface control circuit 30 is arranged to transmit appropriate signals to the
main control circuit 34 to control various operations of the fan assembly 10.
The lower body section 22 also houses a mechanism, indicated generally at 36, for
5 oscillating the lower body section 22 relative to the base 32. The operation of the
oscillating mechanism 36 is controlled by the main control circuit 34 in response to the
user operation of the button 26. The range of each oscillation cycle of the lower body
section 22 relative to the base 32 is preferably between 60" and 120°, and in this
embodiment is around 80". In this embodiment, the oscillating mechanism 36 is
10 arranged to perform around 3 to 5 oscillation cycles per minute. A mains power cable
(not shown) for supplying electrical power to the fan assembly 10 extends through an
aperture 38 formed in the base 32. The cable is connected to a plug for connection to a
mains power supply.
15 The main body section 20 houses an impeller 40 for drawing the primary air flow
through the air inlet 14 and into the body 12. Preferably, the impeller 40 is in the form
of a mixed flow impeller. The impeller 40 is connected to a rotary shaft 42 extending
outwardly from a motor 44. In this embodiment, the motor 44 is a DC brushless motor
having a speed which is variable by the main control circuit 34 in response to user
20 manipulation of the dial 28. The maximum speed of the motor 44 is preferably in the
range from 5,000 to 10,000 rprn The motor 44 is housed within a motor bucket
comprising an upper portion 46 connected to a lower portion 48. The upper portion 46
of the motor bucket comprises a diffuser 50 in the form of an annular disc having
curved blades.
2 5
Thc motor buckct is located within, and mountcd on, a generally frusto-conical impeller
housing 52. The impeller housing 52 is, in turn, mounted on a plurality of angularly
spaced supports 54, in this example three supports, located within and connected to the
main body scction 20 of the base 12. The impcllcr 40 and thc impcllcr housing 52 are
30 shaped so that the impeller 40 is in close proximity to, but does not contact, the inner
surface of the impeller housing 52. A substantially annular inlet member 56 is
connected to the bottom of the impeller housing 52 for guiding the primary air flow into
the impeller housing 52. An electrical cable 58 passes from the main control circuit 34
to the motor 44 through apertures formed in the main body section 20 and the lower
body section 22 of the body 12, and in the impeller housing 52 and the motor bucket.
5
Preferably, the body 12 includes silencing foam for reducing noise emissions from the
body 12. In this embodiment, the main body section 20 of the body 12 comprises a first
foam member 60 located beneath the air inlet 14, and a second annular foam member 62
located within the motor bucket.
A flexible sealing member 64 is mounted on the impeller housing 52. The flexible
sealing member prevents air fiom passing around the outer surface of the impeller
housing 52 to the inlet member 56. The sealing member 64 preferably comprises an
annular lip seal, preferably formed from rubber. The sealing member 64 further
15 comprises a guide portion in the form of a grommet for guiding the electrical cable 58
to the motor 44.
Returning to Figurcs 1 and 2, the nozzle 16 has an annular shape. The nozzle 16
comprises an outer wall 70 extending about an annular inner wall 72. In this example,
20 each of the walls 70, 72 is formed from a separate component. The nozzle 16 also has a
front wall 74 and a rear wall 76, which in this example are integral with the outer wall
70. A rear end of the inner wall 72 is connected to the rear wall 76, for example using
an adhesive.
25 The inner wall 72 extends about a bore axis, or longitudinal axis, X to define a bore 78
of the nozzlc 16. Thc borc 78 has a gcncrally circular cross-scction which varies in
diameter along the bore axis X from the rear wall 76 of the nozzle 16 to the front wall
74 of the nozzle 16. In this example, the inner wall 72 has an annular rear section 80
and an annular front scction 82 which cach cxtcnd about thc borc 78. Thc rcar scction
30 80 has a frusto-conical shape, and tapers outwardly fiom the rear wall 76 away from the
bore axis X. The front section 82 also has a frusto-conical shape, but tapers inwardly
towards the bore axis X. The angle of inclination of the front section 82 relative to the
bore axis X is preferably in the range from -20 to 20°, and in this example is around 8".
As mentioned above, the front wall 74 and the rear wall 76 of the nozzle 16 may be
5 integral with the outer wall 70. The end section 84 of the outer wall 70 which is located
adjacent to the inner wall 72 is shaped to extend about, or overlap, the front section 82
ofthe inner wall 72 to define the air outlet 18 of the nozzle 16 between the outer surface
of the outer wall 70 and the inner surface of the inner wall 72. The end section 84 of the
outer wall 70 is substantially parallel to the front section 82 of the inner wall 72, and go
10 also tapers inwardly towards the bore axis X at an angle of around 8". The air outlet 18
of the nozzle 16 is thus located between the walls 70, 72 of the nozzle 16, and is located
towards the front end of the nozzle 16. The air outlet 18 is in the form of a generally
circular slot centred on, and extending about, the bore axis X. The width of the slot is
preferably substantially constant about the bore axis X, and is in the range from 0.5 to
15 5 rnrn. A series of angularly spaced spacers 86 may be provided on one of the facing
surfaces of the sections 82, 84 to engage the other facing surface to maintain a regular
spacing between these facing surfaces. For example, the inner wall 72 may be
connected to thc outer wall 70 so that, in the absence of the spacers 86, the facing
surfaces would make contact, and so the spacers 86 also serve to urge the facing
20 surfaces apart.
The outer wall 70 comprises a base 88 which is connected to the open upper end 23 of
the main body section 20 of the body 12, and which has an open lower end which
provides an air inlet for receiving the primary air flow from the body 12. The remainder
25 of the outer wall 70 is generally cylindrical shape, and extends about a central axis, or
longitudinal axis, Y which is parallel to, but spaced from, the bore axis X. In othcr
words, the outer wall 70 and the inner wall 72 are eccentric. In this example, the bore
axis X is located above the central axis Y, with each of the axes X, Y being located in a
planc E-E, illustratcd in Figurc 2, which cxtcnds vertically through thc ccntre of thc fan
30 assembly 10.
The outer wall 70 and the inner wall 72 defme an interior passage 90 for conveying air
fiom the air inlet 88 to the air outlet 18. The interior passage 90 extends about the bore
78 of the nozzle 16. In view of the eccentricity of the walls 70,72 of the nozzle 16, the
cross-sectional area of the interior passage 90 varies about the bore 78. The interior
5 passage 90 may be considered to comprise first and second curved sections, indicated
generally at 92 and 94 in Figures 1 and 2, which each extend in opposite angular
directions about the bore 78. With reference also to Figures 3(a) to 3(d), each section
92,94 of the interior passage 90 has a cross-sectional area which decreases in size about
the bore 78. The cross-sectional area of each section 92,94 decreases from a first value
10 A1 located adjacent the air inlet of the nozzle 16 to a second value A2 located
diametrically opposite the air inlet, and where the two sections 92, 94 are joined. The
relative positions of the axes X, Y are such that each section 92, 94 of the interior
passage 90 has the same variation in cross-sectional area about the bore 78, with the
cross-sectional area of each section 92, 94 decreasing gradually fiom the first value A1
15 to the second value A2. The variation in the cross-sectional area of the interior passage
90 is preferably such that A1 L 1.5A2, and more preferably such that A1 2 1 .8Az. As
shown in Figures 3(b) to 3(d), the variation in the cross-sectional area of each section
92, 94 is effected by a variation in the radial thickness of cach section 92, 94 about the
bore 78; the depth of the nozzle 16, as measured in a direction extending along the axes
20 X, Y is relatively constant about the bore 78. In one example, A1 - 2500 mrn2 and A2 -
1300 mm2. In another example, A1 - 1800 mm2 and A2 =; 800 rnrn2.
To operate the fan assembly 10 the user presses button 24 of the user interface. The
user interface control circuit 30 communicates this action to the main control circuit 34,
25 in response to which the main control circuit 34 activates the motor 44 to rotate the
irnpcller 40. The rotation of the impellcr 40 causcs a primary air flow to be drawn into
the body 12 through the air inlet 14. The user may control the speed of the motor 44,
and therefore the rate at which air is drawn into the body 12 through the air inlet 14, by
manipulating the dial 28 of thc user interface. Depending on the spccd of thc motor 44,
30 the primary air flow generated by the impeller 40 may be between 10 and 30 litres per
second. The primary air flow passes sequentially through the impeller housing 52 and
the air outlet 23 at the open upper end of the main body portion 20 to enter the interior
passage 90 of the nozzle 16 via the air inlet located in the base 88 of the nozzle 16.
Within the interior passage 90, the primary air flow is divided into two air streams
5 which pass in opposite angular directions around the bore 78 of the nozzle 16, each
within a respective section 92, 94 of the interior passage 90. As the air streams pass
through the interior passage 90, air is emitted through the air outlet 18. The emission of
the primary air flow from the air outlet 18 causes a secondary air flow to be generated
by the entrainment of air fiom the external environment, specifically from the region
10 around the nozzle 16. This secondary air flow combines with the primary air flow to
produce a combined, or total, air flow, or air current, projected forward from the nozzle
16.
The increase in the cross-sectional area of the interior passage 90 adjacent to the air
15 inlet can reduce the velocity at which the primary air flow is emitted fiom the lower end
of the nozzle 16, which in turn can reduce the angle, relative to the bore axis X, at
which the air flow is emitted from this portion of the interior passage 90. The gradual
rcduction about the bore 78 in the cross-sectional area of each section 92, 94 of the
interior passage 90 can have the effect of minimising any variation in the angle at which
20 the primary air flow is emitted from the nozzle 16. The variation in the cross-sectional
area of the interior passage 90 about the bore 78 thus reduces turbulence in the
combined air flow experienced by the user.
Figures 4 and 5 are external views of a second embodiment of a fan assembly 100. The
25 fan assembly 100 comprises a body 12 comprising an air inlet 14 through which a
primary air flow cntcrs the fan assembly 10, and an annular nozzle 102 mounted on thc
body 12. The nozzle 102 comprises an air outlet 104 for emitting the primary air flow
from the fan assembly 100. The body 12 is the same as the body 12 of the fan assembly
10, and so will not be dcscribcd again in detail hcrc.
30
The nozzle 102 has an annular shape. The nozzle 102 comprises an outer wall 106
extending about an annular inner wall 108. In this example, each of the walls 106, 108
is formed h m a separate component. Each of the walls 106, 108 has a fiont end and a
rear end. The rear end of the outer wall 106 curves inwardly towards the rear end of the
5 inner wall 108 to define a rear end of the nozzle 102. The fiont end of the inner wall
108 is folded outwardly towards the fiont end of the outer wall 106 to define a fiont end
of the nozzle 102. The front end of the outer wall 106 is inserted into a slot located at
the front end of the inner wall 108, and is connected to the inner wall 108 using an
adhesive introduced to the slot.
The inner wall 108 extends about a bore axis, or longitudinal axis, X to define a bore
110 of the nozzle 102. The bore 110 has a generally circular cross-section which varies
in diameter along the bore axis X from the rear end of the nozzle 102 to the front end of
the nozzle 102.
15
The inner wall 108 is shaped so that the external surface of the inner wall 108, that is,
the surface that defmes the bore 110, has a number of sections. The external surface of
thc inner wall 108 has a convex rcar section 112, an outwardly flared frusto-conical
front section 114 and a cylindrical section 116 located between the rear section 1 12 and
20 the front section 114.
The outer wall 106 comprises a base 11 8 which is connected to the open upper end 23
of the main body section 20 of the body 12, and which has an open lower end which
provides an air inlet for receiving the primary air flow from the body 12. The majority
25 of the outer wall 106 is generally cylindrical shape. The outer wall 106 extends about a
ccntral axis, or longitudinal axis, Y which is parallcl to, but spaccd from, thc borc axis
X. In other words, the outer wall 106 and the inner wall 108 are eccentric. In this
example, the bore axis X is located above the central axis Y, with each of the axes X, Y
bcing locatcd in a plane E-E, illustratcd in Figurc 5, which cxtcnds vertically through
30 the centre of the fan assembly 100.
The rear end of the outer wall 106 is shaped to overlap the rear end of the inner wall 108
to define the air outlet 104 of the nozzle 102 between the inner surface of the outer wall
106 and the outer surface of the inner wall 108. The air outlet 104 is in the form of a
generally circular slot centred on, and extending about, the bore axis X. The width of
5 the slot is preferably substantially constant about the bore axis X, and is in the range
from 0.5 to 5 mm. The overlapping portions 120, 122 of the outer wall 106 and the
inner wall 108 are substantially parallel, and are arranged to direct air over the convex
rear section 112 of the inner wall 108, which provides a Coanda surface of the nozzle
102. A series of angularly spaced spacers 124 may be provided on one of the facing
10 surfaces of the overlapping portions 120, 122 of the outer wall 106 and the inner wall
108 to engage the other facing surface to maintain a regular spacing between these
facing surfaces.
The outer wall 106 and the inner wall 108 defme an interior passage 126 for conveying
15 air from the air inlet 88 to the air outlet 104. The interior passage 126 extends about the
bore 1 10 of the nozzle 102. In view of the eccentricity of the walls 106, 108 of the
nozzle 102, the cross-sectional area of the interior passage 126 varies about the bore
110. The interior passage 126 may be considered to comprisc first and second curved
sections, indicated generally at 128 and 130 in Figures 4 and 5, which each extend in
20 opposite angular directions about the bore 110. With reference also to Figures 6(a) to
6(d), similar to the first embodiment each section 128, 130 of the interior passage 126
has a cross-sectional area which decreases in size about the bore 110. The crosssectional
area of each section 128, 130 decreases from a first value A1 located adjacent
the air inlet of the nozzle 102 to a second value Az located diametrically opposite the air
25 inlet, and where ends of the two sections 128, 130 are joined. The relative positions of
thc axes X, Y arc such that cach scction 128, 130 of the intcrior passage 126 has thc
same variation in cross-sectional area about the bore 11 0, with the cross-sectional area
of each section 128, 130 decreasing gradually from the first value A, to the second
value A2. Thc variation in the cross-scctional arca of the intcrior passagc 126 is
30 preferably such that A, 2 1 .5A2, and more preferably such that A, 2 1.8Az. As shown
in Figures 6(b) to 6(d), the variation in the cross-sectional area of each section 128, 130
is effected by a variation in the radial thickness of each section 128, 130 about the bore
110; the depth of the nozzle 102, as measured in a direction extending along the axes X,
Y is relatively constant about the bore 110. In one example, A1 - 2200 mm2 and A2 =:
1200 mm2.
The operation of the fan assembly 100 is the same as that of the fan assembly 10. A
primary air flow is drawn through the air inlet 14 of the base 12 through rotation of the
impeller 40 by the motor 44. The primary air flow passes sequentially through the
impeller housing 52 and the air outlet 23 at the open upper end of the main body portion
10 20 to enter the interior passage 126 of the nozzle 102 via the air inlet located in the base
1 18 of the nozzle 102.
Within the interior passage 126, the primary air flow is divided into two air streams
which pass in opposite angular directions around the bore 110 of the nozzle 102, each
15 within a respective section 128, 130 of the interior passage 126. As the air streams pass
through the interior passage 126, air is emitted through the air outlet 104. The emission
of the primary air flow from the air outlet 104 causes a secondary air flow to be
gencrated by the cntrainmcnt of air from the external environment, specifically from thc
region around the nozzle 102. This secondary air flow combines with the primary air
20 flow to produce a combined, or total, air flow, or air current, projected forward from the
nozzle 102. In this embodiment, the variation in the cross-sectional area of the interior
passage 126 about the bore 110 can minirnise the variation in the static pressure about
the interior passage 126.
25 In summary, a nozzle for a fan assembly has an air inlet, an air outlet, and an interior
passage for conveying air fbm thc air inlct to thc air outlct. Thc intcrior passagc is
located between an annular inner wall, and an outer wall extending about the inner wall.
The inner wall at least partially defines a bore through which air from outside the nozzle
is drawn by air cmittcd fbm the air outlct. Thc cross-sectional arca of thc intcrior
30 passage varies about the bore. The variation in the cross-sectional area of the interior
passage can control the direction in which air is emitted from around the air outlet to
reduce turbulence in the air flow generated by the fan assembly. The variation in the
cross-sectional area of the interior passage may be achieved by arranging the inner wall
so that it is eccentric with respect to the outer wall.
We claim:
A nozzle for a fan assembly, the nozzle comprising:
an air inlet;
at least one air outlet;
an annular inner wall at least partially defming a bore through which air from
outside the nozzle is drawn by air emitted fiom said at least one air outlet;
an outer wall extending about a longitudinal axis and about the inner wall; and
an interior passage located between the inner wall and the outer wall for
conveying air fiom the air inlet to said at least one air outlet;
wherein the interior passage has a frst section and a second section each for
receiving a respective portion of an air flow entering the interior passage through the air
inlet, and for conveying the portions of the air flow in opposite angular directions about
15 the bore;
and wherein each section of the interior passage has a cross-sectional area
formed fiom the intersection with the interior passage of a plane which extends through
and contains the longitudinal axis of thc outer wall, and wherein the cross-sectional arca
of each section of the interior passage decreases in size about the bore.
2. A nozzle as claimed in claim 1, wherein the cross-sectional area of each section
of the interior passage tapers about the bore.
3. A nozzle as claimed in claim 1 or claim 2, wherein each section of the interior
25 passage has the same variation in cross-sectional area.
4. A nozzle as claimed in any preceding claim, wherein the cross-sectional area of
each section of the interior passage decreases in size about the bore from a first end for
rccciving air from thc air inlct to a sccond cnd.
5. A nozzle as claimed in any preceding claim, wherein the cross-sectional area of
each section has a minimum value located diametrically opposite the air inlet.
6. A nozzle as claimed in any preceding claim, wherein the cross-sectional area of
5 each section has a first value located adjacent the air inlet and a second value located
diametrically opposite the air inlet, and wherein the first value is at least 1.5 times the
second value.
7. A nozzle as claimed in claim 6, wherein the first value is at least 1.8 times the
10 second value.
8. A nozzle as claimed in any preceding claim, wherein each section of the nozzle
has a radial thickness which varies in size about the bore.
15 9. A nozzle as claimed in any preceding claim, wherein each section of the nozzle
has a substantially constant depth about the bore.
10. A nozzle as claimed in any preceding claim, wherein the inner wall is eccentric
with respect to the outer wall.
1 1. A nozzle for a fan assembly, the nozzle comprising:
an air inlet;
at least one air outlet;
an interior passage for conveying air from the air inlet to said at least one air
25 outlet;
an annular inncr wall; and
an outer wall extending about the inner wall, the interior passage being located
between the inner wall and the outer wall, the inner wall at least partially defining a
borc through which air from outsidc the nozzle is drawn by air emittcd fiom said at lcast
30 one air outlet;
wherein the inner wall is eccentric with respect to the outer wall.
12. A nozzle as claimed in any preceding claim, wherein each of the inner wall and
the outer wall extends about a respective longitudinal axis, and wherein the longitudinal
axis of the outer wall is located between the air inlet and the longitudinal axis of the
5 innerwall.
13. A nozzle as claimed in claim 12, wherein the longitudinal axis of the inner wall
is located vertically above the longitudinal axis of the outer wall.
10 14. A nozzle as claimed in any preceding claim, wherein said at least one air outlet
comprises a single air outlet.
15. A nozzle as claimed in claim 14, wherein the air outlet is annular.
15 16. A nozzle as claimed in claim 14 or claim 15, wherein said at least one air outlet
is located between the inner wall and the outer wall.
17. A nozzle as claimed in any prcccding claim, wherein said at lcast one air outlet
is located at the front of the nozzle.
18. A nozzle as claimed in any of claims 14 to 17, wherein said at least one air
outlet is located between overlapping portions of an internal surface of the inner wall
and an external surface of the outer wall.
25 19. A nozzle as claimed in claim 18, wherein said overlapping portions are
substantially parallel.
20. A nozzle as claimed in claim 18 or claim 19, wherein said overlapping portions
are hsto-conical.
21. A nozzle as claimed in any of claims 18 to 20, wherein the overlapping portions
inclined towards an axis of the bore.
22. A nozzle as claimed in any of cIaims 1 to 16, wherein said at least one air outlet
5 is located towards the rear of the nozzle.
23. A nozzle as claimed in any of claims 1 to 16 and 22, wherein said at least one air
outlet is located between overlapping portions of an external surface of the inner wall
and an internal surface of the outer wall.
10
24. A nozzle as claimed in claim 23, wherein said at least one air outlet is
configured to direct air over an external surface of the inner wall.
25. A nozzle as claimed in claim 24, wherein the external surface of the inner wall
1 5 comprises a Comda surface,
26. A fan assembly comprising an impeller, a motor for rotating the impeller to
generate an air flow, and a nozzle as claimed in any preceding cIaim for receiving the
air flow.
20
27. A fan assembly as claimed in claim 26, wherein the nozzle is mounted on a base
housing the impeller and the motor.
28. A nozzle for a fan assembly or a fan assembly substantially as herein described
25 with reference to the accompanying drawings.