U.S. patent application number 12/945558 was filed with the patent office on 2011-03-10 for fan.
This patent application is currently assigned to DYSON TECHNOLOGY LIMITED. Invention is credited to Peter David GAMMACK, Frederic Nicolas, Kevin John Simmonds.
Application Number | 20110058935 12/945558 |
Document ID | / |
Family ID | 39790738 |
Filed Date | 2011-03-10 |
United States Patent
Application |
20110058935 |
Kind Code |
A1 |
GAMMACK; Peter David ; et
al. |
March 10, 2011 |
FAN
Abstract
A fan assembly for creating an air current, the fan assembly
having a base including a system for creating an air flow and a
side wall that, at least partially encloses the system for creating
the air flow and has a plurality of air inlets, wherein the
plurality of air inlets allow air to enter the base, and a nozzle,
mounted on the base, having an interior passage for receiving the
air flow from the base, and a mouth through which the air flow is
emitted from the fan assembly.
Inventors: |
GAMMACK; Peter David;
(Malmesbury, GB) ; Nicolas; Frederic; (Malmesbury,
GB) ; Simmonds; Kevin John; (Malmesbury, GB) |
Assignee: |
DYSON TECHNOLOGY LIMITED
Malmesbury
GB
|
Family ID: |
39790738 |
Appl. No.: |
12/945558 |
Filed: |
November 12, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12230613 |
Sep 2, 2008 |
|
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12945558 |
|
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Current U.S.
Class: |
415/183 |
Current CPC
Class: |
F04D 25/06 20130101;
F04D 29/681 20130101; F04D 25/08 20130101; F04F 5/16 20130101; F04F
5/46 20130101 |
Class at
Publication: |
415/183 |
International
Class: |
F01D 1/02 20060101
F01D001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 4, 2007 |
GB |
0717148.1 |
Sep 4, 2007 |
GB |
0717151.5 |
Sep 4, 2007 |
GB |
0717154.9 |
Sep 4, 2007 |
GB |
0717155.6 |
Aug 14, 2008 |
GB |
0814866.0 |
Claims
1. A fan assembly for creating an air current, the fan assembly
comprising: a base, comprising, a system for creating an air flow,
and a side wall, at least partially enclosing the system for
creating the air flow and comprising a plurality of air inlets,
wherein the plurality of air inlets allow air to enter the base;
and a nozzle, mounted on the base, the nozzle comprising, an
interior passage for receiving the air flow from the base, and a
mouth through which the air flow is emitted from the fan
assembly.
2. The fan assembly of claim 1, wherein the nozzle extends about a
first axis, and the plurality of air inlets is arranged about a
second axis substantially orthogonal to the first axis.
3. The fan assembly of claim 1, comprising a flow path extending
from each air inlet to an inlet to the system for creating the air
flow, wherein the inlet to the system for creating the air flow is
substantially orthogonal to each air inlet.
4. The fan assembly of claim 1, wherein the nozzle extends about a
first axis, and wherein the base has a depth in the direction of
the axis which is in the range from 100 to 200 mm.
5. The fan assembly of claim 1, wherein the base is substantially
cylindrical.
6. The fan assembly of claim 1, wherein the system for creating the
air flow further comprises an impeller driven by a motor.
7. The fan assembly of claim 6, wherein the impeller is a mixed
flow impeller.
8. The fan assembly of claim 6, further comprising a diffuser
located downstream of the impeller.
9. The fan assembly of claim 8, wherein the diffuser comprises a
disc having spiral blades.
10. The fan assembly of claim 6, wherein the motor is located
within a motor housing.
11. The fan assembly of claim 10, wherein the motor housing extends
about the impeller.
12. The fan assembly of claim 10, wherein the plurality of air
inlets extends about the motor housing.
13. The fan assembly of claim 1, wherein the fan assembly further
comprises a stationary base portion, and wherein the fan assembly
is rotatable about the stationary base portion.
14. The fan assembly of claim 1, wherein the mouth is annular.
15. The fan assembly of claim 14, wherein a width of the base is
less than 75% of the diameter of the mouth.
16. A fan assembly, comprising: a base, having at least one side
portion, the side portion comprising a plurality of air inlets
through which air can enter the base; an impeller, located internal
to the base and configured to draw air into the base through the
plurality of air inlets and to create an airflow; and an annular
outlet, to receive the airflow created by the impeller, and to
discharge the airflow from the fan assembly.
17. The fan assembly of claim 16, wherein the side portion of the
base is substantially cylindrical, and the plurality of air inlets
are positioned substantially orthogonal to an axis of rotation of
the impeller.
18. The fan assembly of claim 17, wherein a diameter of the base is
less than 75% of a diameter of the annular outlet.
19. The fan assembly of claim 17, wherein the impeller is an
asymmetrical impeller.
20. The fan assembly of claim 17, wherein the base further
comprises a bottom portion and an oscillation motor to rotate the
fan assembly about the bottom portion.
Description
REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/230,613, filed Sep. 2, 2008, which claims
the priority of United Kingdom Application Nos. 0717155.6,
0717148.1, 0717151.5 and 0717154.9, all filed Sep. 4, 2007, and No.
0814866.0, filed Aug. 14, 2008, the contents of which prior
applications are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a fan appliance.
Particularly, but not exclusively, the present invention relates to
a domestic fan, such as a desk fan, for creating air circulation
and air current in a room, in an office or other domestic
environment.
BACKGROUND OF THE INVENTION
[0003] A number of types of domestic fan are known. It is common
for a conventional fan to include a single set of blades or vanes
mounted for rotation about an axis, and driving apparatus mounted
about the axis for rotating the set of blades. Domestic fans are
available in a variety of sizes and diameters, for example, a
ceiling fan can be at least 1 m in diameter and is usually mounted
in a suspended manner from the ceiling and positioned to provide a
downward flow of air and cooling throughout a room.
[0004] Desk fans, on the other hand, are often around 30 cm in
diameter and are usually free standing and portable. In standard
desk fan arrangements the single set of blades is positioned close
to the user and the rotation of the fan blades provides a forward
flow of air current in a room or into a part of a room, and towards
the user. Other types of fan can be attached to the floor or
mounted on a wall. The movement and circulation of the air creates
a so called `wind chill` or breeze and, as a result, the user
experiences a cooling effect as heat is dissipated through
convection and evaporation. Fans such as that disclosed in U.S.D
103,476 and U.S. Pat. No. 1,767,060 are suitable for standing on a
desk or a table. U.S. Pat. No. 1,767,060 describes a desk fan with
an oscillating function that aims to provide an air circulation
equivalent to two or more prior art fans.
[0005] A disadvantage of this type of arrangement is that the
forward flow of air current produced by the rotating blades of the
fan is not felt uniformly by the user. This is due to variations
across the blade surface or across the outward facing surface of
the fan. Uneven or `choppy` air flow can be felt as a series of
pulses or blasts of air and can be noisy. A further disadvantage is
that the cooling effect created by the fan diminishes with distance
from the user. This means that the fan must be placed in close
proximity to the user in order for the user to receive the benefit
of the fan.
[0006] In a domestic environment it is desirable for appliances to
be as small and compact as possible due to space restrictions. It
is undesirable for parts to project from the appliance, or for the
user to be able to touch any moving parts of the fan, such as the
blades. Some arrangements have safety features such as a cage or
shroud around the blades to protect a user from injuring himself on
the moving parts of the fan. U.S.D 103,476 shows a type of cage
around the blades however, caged blade parts can be difficult to
clean.
[0007] Other types of fan or circulator are described in U.S. Pat.
No. 2,488,467, U.S. Pat. No. 2,433,795 and JP 56-167897. The fan of
U.S. Pat. No. 2,433,795 has spiral slots in a rotating shroud
instead of fan blades. The circulator fan disclosed in U.S. Pat.
No. 2,488,467 emits air flow from a series of nozzles and has a
large base including a motor and a blower or fan for creating the
air flow.
[0008] Locating fans such as those described above close to a user
is not always possible as the bulky shape and structure mean that
the fan occupies a significant amount of the user's work space
area. In the particular case of a fan placed on, or close to, a
desk the fan body or base reduces the area available for paperwork,
a computer or other office equipment. Often multiple appliances
must be located in the same area, close to a power supply point,
and in close proximity to other appliances for ease of connection
and in order to reduce the operating costs.
[0009] The shape and structure of a fan at a desk not only reduces
the working area available to a user but can block natural light
(or light from artificial sources) from reaching the desk area. A
well lit desk area is desirable for close work and for reading. In
addition, a well lit area can reduce eye strain and the related
health problems that may result from prolonged periods working in
reduced light levels.
SUMMARY OF THE INVENTION
[0010] The present invention seeks to provide an improved fan
assembly which obviates disadvantages of the prior art. It is an
object of the present invention to provide a compact fan assembly
which, in use, generates air flow at an even rate over the emission
output area of the fan.
[0011] According to a first aspect of the invention, there is
provided a bladeless fan assembly for creating an air current, the
fan assembly comprising a nozzle mounted on a base housing means
for creating an air flow through the nozzle, the nozzle comprising
an interior passage for receiving the air flow from the base and a
mouth through which the air flow is emitted, the nozzle extending
substantially orthogonally about an axis to define an opening
through which air from outside the fan assembly is drawn by the air
flow emitted from the mouth, wherein the nozzle and the base each
have a depth in the direction of the axis, and wherein the depth of
the base is no more than twice the depth of the nozzle.
[0012] Preferably the depth of the base is in the range of 100 mm
to 200 mm, more preferably around 150 mm. In this arrangement it is
preferred that the fan assembly has a height extending from the end
of the base remote from the nozzle to the end of the nozzle remote
from the base, and a width perpendicular to the height, both the
height and the width being perpendicular to the said axis, and
wherein the width of the base is no more than 75% the width of the
nozzle.
[0013] According to a second aspect of the present invention, there
is also provided a bladeless fan assembly for creating an air
current, the fan assembly comprising a nozzle mounted on a base
housing means for creating an air flow through the nozzle, the
nozzle comprising an interior passage for receiving the air flow
from the base and a mouth through which the air flow is emitted,
the nozzle extending substantially orthogonally about an axis to
define an opening through which air from outside the fan assembly
is drawn by the air flow emitted from the mouth, the fan assembly
having a height extending from the end of the base remote from the
nozzle to the end of the nozzle remote from the base, and a width
perpendicular to the height, both the height and the width being
perpendicular to the axis, and wherein the width of the base is no
more than 75% the width of the nozzle.
[0014] Both aspects of the invention provide arrangements in which
an air current is generated and a cooling effect is created without
requiring a bladed fan. The bladeless arrangement leads to lower
noise emissions due to the absence of the sound of a fan blade
moving through the air, and a reduction in moving parts and
complexity. The dimensions of the base are small compared to those
of the nozzle and compared to the size of the overall fan assembly
structure. The depth of the base of the fan assembly is such that
the fan assembly is a slim product, occupying little of a user's
work space area.
[0015] Advantageously the invention provides a fan assembly
delivering a suitable cooling effect from a footprint smaller than
that of prior art fans. Advantageously, by this arrangement the
assembly can be produced and manufactured with a reduced number of
parts than those required in prior art fans. This reduces
manufacturing cost and complexity.
[0016] In the following description of fans and, in particular a
fan of the preferred embodiment, the term `bladeless` is used to
describe apparatus in which air flow is emitted or projected
forwards from the fan assembly without the use of blades. By this
definition a bladeless fan assembly can be considered to have an
output area or emission zone absent blades or vanes from which the
air flow is released or emitted in a direction appropriate for the
user. A bladeless fan assembly may be supplied with a primary
source of air from a variety of sources or generating means such as
pumps, generators, motors or other fluid transfer devices, which
include rotating devices such as a motor rotor and a bladed
impeller for generating air flow. The supply of air generated by
the motor causes a flow of air to pass from the room space or
environment outside the fan assembly through the interior passage
to the nozzle and then out through the mouth.
[0017] Hence, the description of a fan assembly as bladeless is not
intended to extend to the description of the power source and
components such as motors that are required for secondary fan
functions. Examples of secondary fan functions can include
lighting, adjustment and oscillation of the fan.
[0018] Preferably, the width of the base of the fan assembly is in
the range from 65% to 55% the width of the nozzle, more preferably
around 50% the width of the nozzle. In a preferred embodiment the
height of the fan assembly is in the range 300 mm to 400 mm, more
preferably around 350 mm. The preferred features and dimensions of
the fan assembly result in a compact arrangement while generating a
suitable amount of air flow from the fan assembly for cooling a
user.
[0019] It is preferred that the base is substantially cylindrical.
This arrangement creates a fan assembly with a compact base that
appears tidy and uniform. This type of uncluttered design is
desirable and often appeals to a user or customer. In addition,
when placed on a desk or work surface the area of the desk surface
occupied by the base of the fan assembly is less than the space
occupied by other known fan assemblies. The nozzle occupies space
above the desk surface, extending away from the base without
obscuring the desk surface or impeding the user's access to the
surface of the desk.
[0020] Preferably the base has at least one air inlet arranged
substantially orthogonal to the axis. Preferably the base has a
side wall comprising said at least one air inlet. Locating air
inlets around the base provides flexibility in the arrangement of
the base and the nozzle, and enables air to flow into the base from
a variety of points thereby to enable more air to flow into the
assembly as a whole. More preferably, said at least one air inlet
comprises a plurality of air inlets extending about a second axis
substantially orthogonal to said first-mentioned axis. In this
arrangement it is preferred that the assembly has a flow path
extending from each air inlet to an inlet to the means for creating
an air flow through the nozzle, wherein the inlet to the means for
creating an air flow is substantially orthogonal to the or each air
inlet. The arrangement provides an inlet air path that minimises
noise and frictional losses in the system.
[0021] In either of the aforementioned aspects, the nozzle may
comprise a Coanda surface located adjacent the mouth and over which
the mouth is arranged to direct the air flow.
[0022] A Coanda surface is a known type of surface over which fluid
flow exiting an output orifice close to the surface exhibits the
Coanda effect. The fluid tends to flow over the surface closely,
almost `clinging to` or `hugging` the surface. The Coanda effect is
already a proven, well documented method of entrainment whereby a
primary air flow is directed over the Coanda surface. A description
of the features of a Coanda surface, and the effect of fluid flow
over a Coanda surface, can be found in articles such as Reba,
Scientific American, Volume 214, June 1963 pages 84 to 92. Through
use of a Coanda surface, air from outside the fan assembly is drawn
through the opening by the air flow directed over the Coanda
surface.
[0023] In the present invention an air flow is created through the
nozzle of the fan assembly. In the following description this air
flow will be referred to as primary air flow. The primary air flow
exits the nozzle via the mouth and preferably passes over the
Coanda surface. The primary air flow entrains the air surrounding
the mouth of the nozzle, which 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 mouth of the nozzle and, by
displacement, from other regions around the fan assembly. The
primary air flow directed over the Coanda surface combined with the
secondary air flow entrained by the air amplifier gives a total air
flow emitted or projected forward to a user from the opening
defined by the nozzle. The total air flow is sufficient for the fan
assembly to create an air current suitable for cooling.
[0024] The air current delivered by the fan assembly to the user
has the benefit of being an air flow with low turbulence and with a
more linear air flow profile than that provided by other prior art
devices. Linear air flow with low turbulence travels efficiently
out from the point of emission and loses less energy and less
velocity to turbulence than the air flow generated by prior art
fans. An advantage for a user is that the cooling effect can be
felt even at a distance and the overall efficiency of the fan
increases. This means that the user can choose to site the fan some
distance from a work area or desk and still be able to feel the
cooling benefit of the fan.
[0025] Advantageously, the assembly results in the entrainment of
air surrounding the mouth of the nozzle such that the primary air
flow is amplified by at least 15%, whilst a smooth overall output
is maintained. The entrainment and amplification features of the
fan assembly result in a fan with a higher efficiency than prior
art devices. The air current emitted from the opening defined by
the nozzle has an approximately flat velocity profile across the
diameter of the nozzle. Overall the flow rate and profile can be
described as plug flow with some regions having a laminar or
partial laminar flow.
[0026] Preferably the nozzle comprises a loop. The shape of the
nozzle is not constrained by the requirement to include space for a
bladed fan. In a preferred embodiment the nozzle is annular. By
providing an annular nozzle the fan can potentially reach a broad
area. In a further preferred embodiment the nozzle is at least
partially circular. This arrangement can provide a variety of
design options for the fan, increasing the choice available to a
user or customer.
[0027] Preferably, the interior passage is continuous, more
preferably substantially annular. This allows smooth, unimpeded air
flow within the nozzle and reduces frictional losses and noise. In
this arrangement the nozzle can be manufactured as a single piece,
reducing the complexity of the fan assembly and thereby reducing
manufacturing costs.
[0028] In the preferred fan arrangement the means for creating an
air flow through the nozzle is arranged to create an air flow
through the nozzle having a pressure of at least 400 kPa. This
pressure is sufficient to overcome the pressure created by the
constriction caused by the mouth of the nozzle and provides
pressure for an output air flow suitable for cooling a user. More
preferably, in use, the mass flow rate of air projected from the
fan assembly is at least 450 l/s, most preferably in the range from
600 l/s to 700 l/s. Advantageously this mass flow rate can be
projected forward from the opening and the area surrounding the
mouth of the nozzle with a laminar flow and can be experienced by
the user as a superior cooling effect to that from a bladed
fan.
[0029] In the preferred fan arrangement the means for creating an
air flow through the nozzle comprises an impeller driven by a
motor. This arrangement provides a fan with efficient air flow
generation. More preferably the means for creating an air flow
comprises a DC brushless motor and a mixed flow impeller. This
arrangement reduces frictional losses from motor brushes and also
reduces carbon debris from the brushes in a traditional motor.
Reducing carbon debris and emissions is advantageous in a clean or
pollutant sensitive environment such as a hospital or around those
with allergies.
[0030] The nozzle may be rotatable or pivotable relative to a base
portion, or other portion, of the fan assembly. This enables the
nozzle to be directed towards or away from a user as required. The
fan assembly may be desk, floor, wall or ceiling mountable. This
can increase the portion of a room over which the user experiences
cooling.
[0031] The mouth may be substantially annular. By providing a
substantially annular mouth the total air flow can be emitted
towards a user over a broad area. Advantageously, an illumination
source in the room or at the desk fan location or natural light can
reach the user through the central opening. The mouth may be
concentric with the interior passage. This arrangement will be
visually appealing and the concentric location of the mouth with
the passage facilitates manufacture.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] An embodiment of the invention will now be described with
reference to the accompanying drawings, in which:
[0033] FIG. 1 is a front view of a fan assembly;
[0034] FIG. 2 is a perspective view of a portion of the fan
assembly of FIG. 1;
[0035] FIG. 3 is a side sectional view through a portion of the fan
assembly of FIG. 1 taken at line A-A;
[0036] FIG. 4 is an enlarged side sectional detail of a portion of
the fan assembly of FIG. 1; and
[0037] FIG. 5 is a sectional view of the fan assembly taken along
line B-B of FIG. 3 and viewed from direction F of FIG. 3.
DETAILED DESCRIPTION OF THE INVENTION
[0038] FIG. 1 shows an example of a fan assembly 100 viewed from
the front of the device. The fan assembly 100 comprises an annular
nozzle 1 defining a central opening 2. With reference also to FIGS.
2 and 3, nozzle 1 comprises an interior passage 10, a mouth 12 and
a Coanda surface 14 adjacent the mouth 12. The Coanda surface 14 is
arranged so that a primary air flow exiting the mouth 12 and
directed over the Coanda surface 14 is amplified by the Coanda
effect. The nozzle 1 is connected to, and supported by, a base 16
having an outer casing 18. The base 16 includes a plurality of
selection buttons 20 accessible through the outer casing 18 and
through which the fan assembly 100 can be operated. The fan
assembly has a height, H, width, W, and depth, D, shown on FIGS. 1
and 3. The nozzle 1 is arranged to extend substantially
orthogonally about the axis X. The height of the fan assembly, H,
is perpendicular to the axis X and extends from the end of the base
16 remote from the nozzle 1 to the end of the nozzle 1 remote from
the base 16. In this embodiment the fan assembly 100 has a height,
H, of around 530 mm, but the fan assembly 100 may have any desired
height, for example around 475 mm. The base 16 and the nozzle 1
have a width, W, perpendicular to the height H and perpendicular to
the axis X. The width of the base 16 is shown labelled W1 and the
width of the nozzle 1 is shown labelled as W2 on FIG. 1. The base
16 and the nozzle 1 have a depth in the direction of the axis X.
The depth of the base 16 is shown labelled D1 and the depth of the
nozzle 1 is shown labelled as D2 on FIG. 3.
[0039] FIGS. 3, 4 and 5 show further specific details of the fan
assembly 100. A motor 22 for creating an air flow through the
nozzle 1 is located inside the base 16. The base 16 is
substantially cylindrical and in this embodiment the base 16 has a
diameter (that is, a width W1 and a depth D1) of around 145 mm. The
base 16 further comprises air inlets 24a, 24b formed in the outer
casing 18. A motor housing 26 is located inside the base 16. The
motor 22 is supported by the motor housing 26 and held in a secure
position by a rubber mount or seal member 28.
[0040] In the illustrated embodiment, the motor 22 is a DC
brushless motor. An impeller 30 is connected to a rotary shaft
extending outwardly from the motor 22, and a diffuser 32 is
positioned downstream of the impeller 30. The diffuser 32 comprises
a fixed, stationary disc having spiral blades.
[0041] An inlet 34 to the impeller 30 communicates with the air
inlets 24a, 24b formed in the outer casing 18 of the base 16. The
outlet 36 of the diffuser 32 and the exhaust from the impeller 30
communicate with hollow passageway portions or ducts located inside
the base 16 in order to establish air flow from the impeller 30 to
the interior passage 10 of the nozzle 1. The motor 22 is connected
to an electrical connection and power supply and is controlled by a
controller (not shown). Communication between the controller and
the plurality of selection buttons 20 enable a user to operate the
fan assembly 100.
[0042] The features of the nozzle 1 will now be described with
reference to FIGS. 3 and 4. The shape of the nozzle 1 is annular.
In this embodiment the nozzle 1 has a diameter of around 350 mm,
but the nozzle may have any desired diameter, for example around
300 mm. The interior passage 10 is annular and is formed as a
continuous loop or duct within the nozzle 1. The nozzle 1 is formed
from at least one wall defining the interior passage 10 and the
mouth 12. In this embodiment the nozzle 1 comprises an inner wall
38 and an outer wall 40. In the illustrated embodiment the walls
38, 40 are arranged in a looped or folded shape such that the inner
wall 38 and outer wall 40 approach one another. The inner wall 38
and the outer wall 40 together define the mouth 12, and the mouth
12 extends about the axis X. The mouth 12 comprises a tapered
region 42 narrowing to an outlet 44. The outlet 44 comprises a gap
or spacing formed between the inner wall 38 of the nozzle 1 and the
outer wall 40 of the nozzle 1. The spacing between the opposing
surfaces of the walls 38, 40 at the outlet 44 of the mouth 12 is
chosen to be in the range from 1 mm to 5 mm. The choice of spacing
will depend on the desired performance characteristics of the fan.
In this embodiment the outlet 44 is around 1.3 mm wide, and the
mouth 12 and the outlet 44 are concentric with the interior passage
10.
[0043] The mouth 12 is adjacent the Coanda surface 14. The nozzle 1
of the illustrated embodiment further comprises a diffuser portion
located downstream of the Coanda surface. The diffuser portion
includes a diffuser surface 46 to further assist the flow of air
current delivered or output from the fan assembly 100. In the
example illustrated in FIG. 3 the mouth 12 and the overall
arrangement of the nozzle 1 is such that the angle subtended
between the Coanda surface 14 and the axis X is around 15.degree..
The angle is chosen for efficient air flow over the Coanda surface
14. The nozzle 1 extends by a distance of around 5 cm in the
direction of the axis. The diffuser surface 46 and the overall
profile of the nozzle 1 are based on an aerofoil shape, and in the
example shown the diffuser portion extends by a distance of around
two thirds the overall depth of the nozzle 1.
[0044] The fan assembly 100 described above operates in the
following manner. When a user makes a suitable selection from the
plurality of buttons 20 to operate or activate the fan assembly
100, a signal or other communication is sent to drive the motor 22.
The motor 22 is thus activated and air is drawn into the fan
assembly 100 via the air inlet 24. In the preferred embodiment air
is drawn in at a rate of approximately 20 to 30 litres per second,
preferably around 27 l/s (litres per second). The air passes
through the outer casing 18 and along the route illustrated by
arrow F of FIG. 3 to the inlet 34 of the impeller 30. The air flow
leaving the outlet 36 of the diffuser 32 and the exhaust of the
impeller 30 is divided into two air flows that proceed in opposite
directions through the interior passage 10. The air flow is
constricted as it enters the mouth 12 and is further constricted at
the outlet 44 of the mouth 12. The constriction creates pressure in
the system. The motor 22 creates an air flow through the nozzle 16
having a pressure of at least 400 kPa. The air flow created
overcomes the pressure created by the constriction and the air flow
exits through the outlet 44 as a primary air flow.
[0045] The output and emission of the primary air flow creates a
low pressure area at the air inlets 24a, 24b with the effect of
drawing additional air into the fan assembly 100. The operation of
the fan assembly 100 induces high air flow through the nozzle 1 and
out through the opening 2. The primary air flow is directed over
the Coanda surface 14 and the diffuser surface 46, and is amplified
by the Coanda effect. A secondary air flow is generated by
entrainment of air from the external environment, specifically from
the region around the outlet 44 and from around the outer edge of
the nozzle 1. A portion of the secondary air flow entrained by the
primary air flow may also be guided over the diffuser surface 46.
This secondary air flow passes through the opening 2, where it
combines with the primary air flow to produce a total air flow
projected forward from the nozzle 1.
[0046] The combination of entrainment and amplification results in
a total air flow from the opening 2 of the fan assembly 100 that is
greater than the air flow output from a fan assembly without such a
Coanda or amplification surface adjacent the emission area.
[0047] The amplification and laminar type of air flow produced
results in a sustained flow of air being directed towards a user
from the nozzle 1. In the preferred embodiment the mass flow rate
of air projected from the fan assembly 100 is at least 450 l/s,
preferably in the range from 600 l/s to 700 l/s. The flow rate at a
distance of up to 3 nozzle diameters (i.e. around 1000 to 1200 mm)
from a user is around 400 to 500 l/s. The total air flow has a
velocity of around 3 to 4 m/s (metres per second). Higher
velocities are achievable by reducing the angle subtended between
the Coanda surface 14 and the axis X. A smaller angle results in
the total air flow being emitted in a more focussed and directed
manner. This type of air flow tends to be emitted at a higher
velocity but with a reduced mass flow rate. Conversely, greater
mass flow can be achieved by increasing the angle between the
Coanda surface and the axis. In this case the velocity of the
emitted air flow is reduced but the mass flow generated increases.
Thus the performance of the fan assembly can be altered by altering
the angle subtended between the Coanda surface and the axis X.
[0048] The invention is not limited to the detailed description
given above. Variations will be apparent to the person skilled in
the art. For example, the fan could be of a different height or
diameter. The base and the nozzle of the fan could be of a
different depth, width and height. The fan need not be located on a
desk, but could be free standing, wall mounted or ceiling mounted.
The fan shape could be adapted to suit any kind of situation or
location where a cooling flow of air is desired. A portable fan
could have a smaller nozzle, say 5 cm in diameter. The means for
creating an air flow through the nozzle can be a motor or other air
emitting device, such as any air blower or vacuum source that can
be used so that the fan assembly can create an air current in a
room.
[0049] Examples include a motor such as an AC induction motor or
types of DC brushless motor, but may also comprise any suitable air
movement or air transport device such as a pump or other means of
providing directed fluid flow to generate and create an air flow.
Features of a motor may include a diffuser or a secondary diffuser
located downstream of the motor to recover some of the static
pressure lost in the motor housing and through the motor.
[0050] The outlet of the mouth may be modified. The outlet of the
mouth may be widened or narrowed to a variety of spacings to
maximise air flow. The air flow emitted by the mouth may pass over
a surface, such as Coanda surface, alternatively the airflow may be
emitted through the mouth and be projected forward from the fan
assembly without passing over an adjacent surface. The Coanda
effect may be made to occur over a number of different surfaces, or
a number of internal or external designs may be used in combination
to achieve the flow and entrainment required.
[0051] Other shapes of nozzle are envisaged. For example, a nozzle
comprising an oval, or `racetrack` shape, a single strip or line,
or block shape could be used. The fan assembly provides access to
the central part of the fan as there are no blades. This means that
additional features such as lighting or a clock or LCD display
could be provided in the opening defined by the nozzle.
[0052] Other features could include a pivotable or tiltable base
for ease of movement and adjustment of the position of the nozzle
for the user.
* * * * *