U.S. patent application number 13/052830 was filed with the patent office on 2011-09-29 for fan.
This patent application is currently assigned to Dyson Technology Limited. Invention is credited to Nicholas Gerald FITTON, Kevin John Simmonds.
Application Number | 20110236228 13/052830 |
Document ID | / |
Family ID | 42228162 |
Filed Date | 2011-09-29 |
United States Patent
Application |
20110236228 |
Kind Code |
A1 |
FITTON; Nicholas Gerald ; et
al. |
September 29, 2011 |
FAN
Abstract
A portable fan includes a casing having an air inlet, and an air
outlet having an interior passage for receiving an air flow, and a
mouth for emitting the air flow, the interior passage extending
about an opening through which air is drawn by the air flow emitted
from the mouth. The fan includes an impeller and a motor for
rotating the impeller to generate an air flow between the air inlet
and an air outlet which has a static pressure of at least 150 Pa
downstream from the impeller. A filter unit is detachably connected
to the casing. A filter of the filter unit is located upstream of
the air inlet to remove airborne particulates from the air flow
before it enters the casing.
Inventors: |
FITTON; Nicholas Gerald;
(Malmesbury, GB) ; Simmonds; Kevin John;
(Malmesbury, GB) |
Assignee: |
Dyson Technology Limited
Malmesbury
GB
|
Family ID: |
42228162 |
Appl. No.: |
13/052830 |
Filed: |
March 21, 2011 |
Current U.S.
Class: |
417/234 |
Current CPC
Class: |
F04F 5/16 20130101; F04D
29/703 20130101; F04F 5/44 20130101; F04D 29/626 20130101; F04D
25/084 20130101; F04D 25/08 20130101 |
Class at
Publication: |
417/234 |
International
Class: |
F04B 53/20 20060101
F04B053/20 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 23, 2010 |
GB |
GB1004813.0 |
Claims
1. A portable fan comprising: a casing having an air inlet; an air
outlet comprising an interior passage for receiving an air flow,
and a mouth for emitting the air flow, the interior passage
extending about an opening through which air is drawn by the air
flow emitted from the mouth; an impeller and a motor for rotating
the impeller to generate an air flow between the air inlet and an
air outlet which has a static pressure of at least 150 Pa
downstream from the impeller; and a filter unit detachably
connected to the casing, the filter unit comprising a filter
located upstream of the air inlet.
2. The fan of claim 1, wherein the motor and the impeller are
arranged to generate an air flow having a static pressure in the
range from 250 to 1.5 kPa.
3. The fan of claim 1, wherein the filter unit comprises at least
one seal for engaging an outer surface of the casing.
4. The fan of claim 1, wherein the filter unit is in the form of a
sleeve locatable about the casing.
5. The fan of claim 1, wherein the filter is substantially annular
in shape.
6. The fan of claim 5, wherein the filter unit comprises two
annular discs between which the filter is located.
7. The fan of claim 6, wherein each disc comprises a raised rim
extending towards the other disc for retaining the filter between
the discs.
8. The fan of claim 6, wherein the filter is adhered to the
discs.
9. The fan of claim 1, wherein the filter unit comprises a filter
housing, and the filter is adhered to the filter housing.
10. The fan of claim 1, wherein the filter unit comprises an outer
cover comprising a plurality of apertures.
11. The fan of claim 1, wherein the casing comprises a base surface
and a side wall, and wherein the air inlet is located in the side
wall of the casing.
12. The fan of claim 1, wherein the air inlet extends at least
partially about the casing.
13. The fan of claim 1, wherein the air inlet comprises an array of
apertures.
14. The fan of claim 1, wherein the casing is substantially
cylindrical in shape.
15. The fan of claim 1, wherein the air outlet is detachably
connected to the filter unit.
16. The fan of claim 1, wherein the filter unit comprises a first
seal for engaging the casing, and a second seal for engaging the
air outlet.
Description
REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the priority of United Kingdom
Application No. 1004813.0 filed Mar. 23, 2010, the entire contents
of which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a portable fan.
Particularly, but not exclusively, the present invention relates to
a floor or table-top fan, such as a desk, tower or pedestal
fan.
BACKGROUND OF THE INVENTION
[0003] 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 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 from coming into
contact with the rotating blades during use of the fan.
[0004] The use of fans in hospitals to keep patients cool is
widespread, both in general wards and in isolation wards. For
example, depending on the medical condition of the patient it may
be preferable to reduce the body temperature of the patient using a
fan rather than by using pharmaceuticals. When a fan is assigned to
a patient, generally that fan is treated as an item of medical
equipment and so, like other medical equipment, will require
frequent cleaning by a nurse or other hospital employee. The
cleaning of bladed fans can be time consuming for the employee, as
the cage housing the blades of the fan needs to be disassembled
before the blades of the fan can be cleaned. This disassembly
usually requires the use of a screw driver, which cannot be carried
by a nurse on a hospital ward. Often, it can be more convenient for
the hospital to engage a specialist cleaning company to clean the
fan off site, although this can be very expensive.
[0005] WO 2009/030879 describes a fan assembly 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 a primary air flow into the base, and an annular nozzle
connected to the base and comprising an annular slot through which
the primary air flow is emitted from the fan. The nozzle defines a
central opening through which air in the local environment of the
fan assembly is drawn by the primary air flow emitted from the
mouth, amplifying the primary air flow.
[0006] The time required to clean off the external surfaces of this
type of "bladeless" fan is much shorter than that required to clean
a fan having caged blades, as there is no requirement to dismantle
any parts of the fan to access any exposed parts of the fan. For
example, the external surfaces of the fan may be wiped clean using
a cloth. While this level of cleaning may be sufficient for
bladeless fans which are assigned to patients on general wards,
when the bladeless fan is assigned to a patient in an isolation
ward or infection containment ward there remains a need to keep the
internal components of the base clean to avoid cross-contamination
when the fan is assigned to another patient.
SUMMARY OF THE INVENTION
[0007] The present invention provides a portable fan comprising a
casing having an air inlet; an air outlet comprising an interior
passage for receiving an air flow, and a mouth for emitting the air
flow, the interior passage extending about an opening through which
air is drawn by the air flow emitted from the mouth; an impeller
and a motor for rotating the impeller to generate an air flow
between the air inlet and an air outlet which has a static pressure
of at least 150 Pa downstream from the impeller; and a filter unit
detachably connected to the casing, the filter unit comprising a
filter located upstream of the air inlet.
[0008] The filter unit is preferably in the form of a disposable
filter unit which can be replaced when, for example, the fan is
assigned to a different patient, when the fan is moved with the
patient from an isolation ward to a general ward, or when the
filter has reached the end of a prescribed usage period. This can
significantly reduce the costs associated with the use of the fan,
as the frequency with which the fan may need to be taken off site
for cleaning can be significantly reduced. The fan is arranged to
generate an air flow with a static pressure of at least 150 Pa,
preferably in the range from 250 to 1.5 kPa, so that the air flow
is not choked when the filter unit is attached to the casing.
[0009] The filter unit may be locatable over or around the casing
so that the filter is located upstream from the air inlet of the
casing to remove airborne particulates from the air flow generated
by the impeller before the air flow enters the casing. The filter
unit is preferably manually connectable to the casing to allow a
user to attach the filter unit to the fan, and subsequently detach
the filter unit from the fan, without the need for a tool.
[0010] The filter preferably comprises a high energy particle
arrester (HEPA) filter. The filter may also comprise one or more of
a foam, carbon, paper, or fabric filter. The filter preferably has
a surface area in the range from 0.5 to 1.5 m.sup.2 which is
exposed to the air flow generated by the fan. To minimize the
volume of the filter, the filter is preferably pleated to form a
filter which is substantially annular in shape for surrounding the
air inlet of the casing. In this case, the filter unit may comprise
two annular discs between which the filter is located. These discs
can be easily wiped clean during use of the filter unit. Each disc
may comprise a raised rim extending towards the other disc for
retaining the filter between the discs. The filter may be readily
adhered to the discs during the construction of the filter unit.
The discs may together be considered to form at least part of a
filter unit to which the filter is adhered during construction of
the filter unit.
[0011] The filter unit preferably comprises at least one seal for
engaging an outer surface of the fan. This can enable the filter
unit to form one or more air-tight seals with the fan to ensure
that the air flow generated by the fan passes through the filter
and not around the filter. Preferably, the filter unit is
attachable to the casing so that the filter is located over the air
inlet of the fan. In a preferred embodiment the filter unit is in
the form of a sleeve which is locatable about an outer surface of a
casing. Forming the filter unit in the form of a sleeve can enable
the filter unit to be easily pushed or pulled over the casing of
the fan as required. The filter unit may comprise a first seal for
engaging the casing of the fan, and a second seal for engaging the
air outlet of the fan so that an air flow is drawn through the
filter unit between the seals and through the filter. The casing
may be in the form of a base, which may be free-standing on a
floor, desk, table or other surface.
[0012] The filter unit may comprise an outer cover comprising a
plurality of apertures through which air enters the filter unit.
This outer cover can provide a first, relatively coarse filter of
the filter unit to prevent airborne objects such as insects or
large particles of dust from coming into contact with the filter,
and can prevent the filter from being contacted by a user,
particularly during the attachment of the filter unit to the fan,
and so prevent damage to the filter. The outer cover is preferably
transparent to allow a user to see the amount of dust or debris
which has been captured by the filter.
[0013] The casing may comprise a base surface and a side wall, with
the air inlet being located in the side wall of the casing. The air
inlet may extend at least partially about the casing, and may
comprise an array of apertures. The casing may be substantially
cylindrical in shape. The motor and the impeller are preferably
located within the casing. A diffuser is preferably located
downstream from the impeller.
[0014] The air outlet may be detachably connected to the filter
unit. Part of the filter unit may be surrounded by part of the air
outlet when the filter unit is attached to the fan. For example,
the air outlet may comprise a base which is located over part of
the filter unit when the air outlet is connected to the filter
unit.
[0015] The casing may have a first connector, and the air outlet
may have a second connector. The filter unit may include a third
connector, which is substantially the same as the second connector,
for co-operating with the first connector to removably connect the
filter unit to the casing, and a fourth connector, which is
substantially the same as the first connector, for co-operating
with the second connector to removably connect the air outlet to
the filter unit. This can allow the air outlet to be connected
either directly to the casing, or for the filter unit to be
connected between the casing and the air outlet. The type of
connection made between the filter unit and the casing, and between
the air outlet and the filter unit, is the same as the type of
connection which is made between the air outlet and the casing in
the absence of the filter unit. This facilitates the connection of
the filter unit to the casing and the air outlet, as the technique
for connecting the air outlet to the casing is the same as that for
connecting the filter unit to the base, and for connecting the air
outlet to the filter unit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Preferred features of the invention will now be described,
by way of example only, with reference to the accompanying
drawings, in which:
[0017] FIG. 1 is a front view of a fan;
[0018] FIG. 2 is a perspective view of the base of the fan of FIG.
1;
[0019] FIG. 3 is a perspective view of the air outlet of the fan of
FIG. 1;
[0020] FIG. 4 is a lower perspective view of a portion of the air
outlet of the fan of FIG. 1;
[0021] FIG. 5 is a sectional view of the fan of FIG. 1;
[0022] FIG. 6 is an enlarged view of part of FIG. 5;
[0023] FIG. 7 is a side view of an accessory for attachment to the
fan of FIG. 1;
[0024] FIG. 8 is a perspective view, from above, of the accessory
of FIG. 7;
[0025] FIG. 9 is a sectional view of the accessory of FIG. 7;
[0026] FIG. 10 is a perspective view of the fan of FIG. 1 with the
accessory of FIG. 7 attached thereto; and
[0027] FIG. 11 is a sectional view of the fan of FIG. 10.
DETAILED DESCRIPTION OF THE INVENTION
[0028] FIG. 1 is a front view of a fan 10. The fan 10 is preferably
in the form of a bladeless fan 10 comprising a base 12 and an air
outlet 14 connected to the base 12. With reference also to FIG. 2,
the base 12 comprises a substantially cylindrical outer casing 16
having a plurality of air inlets 18 in the form of apertures formed
in the outer casing 16 and through which a primary air flow is
drawn into the base 12 from the external environment. The base 12
further comprises a plurality of user-operable buttons 20 and a
user-operable dial 22 for controlling the operation of the fan 10.
In this example the base 12 has a height in the range from 200 to
300 mm, and the outer casing 16 has an external diameter in the
range from 100 to 200 mm.
[0029] As shown in FIG. 3, the air outlet 14 has an annular shape
and defines an opening 24. The air outlet 14 has a height in the
range from 200 to 400 mm. The air outlet 14 comprises a mouth 26
located towards the rear of the fan 10 for emitting air from the
fan 10 and through the opening 24. The mouth 26 extends at least
partially about the opening 24, and preferably surrounds the
opening 24. The inner periphery of the air outlet 14 comprises a
Coanda surface 28 located adjacent the mouth 26 and over which the
mouth 26 directs the air emitted from the fan 10, a diffuser
surface 30 located downstream of the Coanda surface 28 and a guide
surface 32 located downstream of the diffuser surface 30. The
diffuser surface 30 is arranged to taper away from the central axis
X of the opening 24 in such a way so as to assist the flow of air
emitted from the fan 10. The angle subtended between the diffuser
surface 30 and the central axis X of the opening 24 is in the range
from 5 to 25.degree., and in this example is around 15.degree.. The
guide surface 32 is arranged at an angle to the diffuser surface 30
to further assist the efficient delivery of a cooling air flow from
the fan 10. The guide surface 32 is preferably arranged
substantially parallel to the central axis X of the opening 24 to
present a substantially flat and substantially smooth face to the
air flow emitted from the mouth 26. A visually appealing tapered
surface 34 is located downstream from the guide surface 32,
terminating at a tip surface 36 lying substantially perpendicular
to the central axis X of the opening 24. The angle subtended
between the tapered surface 34 and the central axis X of the
opening 24 is preferably around 45.degree.. The overall depth of
the air outlet 14 in a direction extending along the central axis X
of the opening 24 is in the range from 100 to 150 mm, and in this
example is around 110 mm.
[0030] FIG. 5 illustrates a sectional view through the fan 10. The
base 12 comprises a lower base member 38, an intermediary base
member 40 mounted on the lower base member 38, and an upper base
member 42 mounted on the intermediary base member 40. The lower
base member 38 has a substantially flat bottom surface 43. The
intermediary base member 40 houses a controller 44 for controlling
the operation of the fan 10 in response to depression of the user
operable buttons 20 shown in FIGS. 1 and 2, and/or manipulation of
the user operable dial 22. The intermediary base member 40 may also
house an oscillating mechanism 46 for oscillating the intermediary
base member 40 and the upper base member 42 relative to the lower
base member 38. The range of each oscillation cycle of the upper
base member 42 is preferably between 60.degree. and 120.degree.,
and in this example is around 90.degree.. In this example, the
oscillating mechanism 46 is arranged to perform around 3 to 5
oscillation cycles per minute. A mains power cable 48 extends
through an aperture formed in the lower base member 38 for
supplying electrical power to the fan 10.
[0031] The upper base member 42 may be tilted relative to the
intermediary base member 40 to adjust the direction in which the
primary air flow is emitted from the fan 10. For example, the upper
surface of the intermediary base member 40 and the lower surface of
the upper base member 42 may be provided with interconnecting
features which allow the upper base member 42 to move relative to
the intermediary base member 40 while preventing the upper base
member 42 from being lifted from the intermediary base member 40.
For example, the intermediary base member 40 and the upper base
member 42 may comprise interlocking L-shaped members.
[0032] The upper base member 42 has an open upper end, and
comprises an array of apertures 50 which extend at least partially
about the upper base member 42. The apertures 50 provide the air
inlet 18 of the base 12. The upper base member 42 houses an
impeller 52 for drawing the primary air flow through the apertures
50 and into the base 12. Preferably, the impeller 52 is in the form
of a mixed flow impeller. The impeller 52 is connected to a rotary
shaft 54 extending outwardly from a motor 56. In this example, the
motor 56 is a DC brushless motor having a speed which is variable
by the controller 44 in response to user manipulation of the dial
22. The maximum speed of the motor 56 is preferably in the range
from 5,000 to 10,000 rpm. The motor 56 is housed within a motor
bucket comprising an upper portion 58 connected to a lower portion
60. The motor bucket is retained within the upper base member 42 by
a motor bucket retainer 62. The upper end of the upper base member
42 comprises a cylindrical outer surface 64. The motor bucket
retainer 62 is connected to the open upper end of the upper base
member 42, for example by a snap-fit connection. The motor 56 and
its motor bucket are not rigidly connected to the motor bucket
retainer 62, allowing some movement of the motor 56 within the
upper base member 42.
[0033] Returning to FIG. 2, the upper end of the upper base member
42 comprises two pairs of open grooves 66 formed by removing part
of the outer surface 64 to leave a shaped `cutaway` portion. The
upper end of each of the grooves 66 is in open communication with
the open upper end of the upper base member 42. The open groove 66
is arranged to extend downwardly from the open upper end of the
upper base member 42. A lower part of the groove 66 comprises a
circumferentially extending track 68 having upper and lower
portions bounded by the outer surface 64 of the upper base member
42. Each pair of open grooves 66 is located symmetrically about the
upper end of the upper base member 42, the pairs being spaced
circumferentially from each other. An annular sealing member 69
extends about the outer surface of the upper base member 42, and is
located beneath the tracks 68 of the grooves 66.
[0034] The cylindrical outer surface 64 of the upper end of the
upper base member 42 further comprises a pair of wedge members 70
having a tapered part 72 and a side wall 74. The wedge members 70
are located on opposite sides of the upper base member 42, with
each wedge member 70 being located within a respective cutaway
portion of the outer surface 64.
[0035] The motor bucket retainer 62 comprises curved vane portions
76, 78 extending inwardly from the upper end of the motor bucket
retainer 62. Each curved vane 76, 78 overlaps a part of the upper
portion 58 of the motor bucket. Thus the motor bucket retainer 62
and the curved vanes 76, 78 act to secure and hold the motor bucket
in place during movement and handling. In particular, the motor
bucket retainer 62 prevents the motor bucket from becoming
dislodged and falling towards the air outlet 14 if the fan 10
becomes inverted.
[0036] With reference again to FIG. 5, one of the upper portion 58
and the lower portion 60 of the motor bucket comprises a diffuser
80 in the form of a stationary disc having spiral fins 82, and
which is located downstream from the impeller 52. One of the spiral
fins 82 has a substantially inverted U-shaped cross-section when
sectioned along a line passing vertically through the upper base
member 42. This spiral fin 82 is shaped to enable a power
connection cable to pass through the spiral fin 82 to the motor
56.
[0037] The motor bucket is located within, and mounted on, an
impeller housing 84. The impeller housing 84 is, in turn, mounted
on a plurality of angularly spaced supports 86, in this example
three supports, located within the upper base member 42 of the base
12. A generally frusto-conical shroud 88 is located within the
impeller housing 84. The shroud 88 is preferably connected to the
outer edges of the impeller 52, and is shaped so that the outer
surface of the shroud 88 is in close proximity to, but does not
contact, the inner surface of the impeller housing 84. A
substantially annular inlet member 90 is connected to the bottom of
the impeller housing 84 for guiding the primary air flow into the
impeller housing 84. The top of the impeller housing 84 comprises a
substantially annular air outlet 92 for guiding air flow emitted
from the impeller housing 84 towards the air outlet 14.
[0038] Preferably, the base 12 further comprises silencing members
for reducing noise emissions from the base 12. In this example, the
upper base member 42 of the base 12 comprises a disc-shaped foam
member 94 located towards the base of the upper base member 42, and
a substantially annular foam member 96 located within the impeller
housing 84.
[0039] A flexible sealing member is mounted on the impeller housing
84. The flexible sealing member inhibits the return of air to the
air inlet member 90 along a path extending between the outer casing
16 and the impeller housing 84 by separating the primary air flow
drawn in from the external environment from the air flow emitted
from the air outlet 92 of the impeller 52 and the diffuser 80. The
sealing member preferably comprises a lip seal 98. The sealing
member is annular in shape and surrounds the impeller housing 84,
extending outwardly from the impeller housing 84 towards the outer
casing 16. In the illustrated embodiment the diameter of the
sealing member is greater than the radial distance from the
impeller housing 84 to the outer casing 16. Thus the outer portion
100 of the sealing member is biased against the outer casing 16 and
caused to extend along the inner face of the outer casing 16,
forming a seal. The lip seal 98 of the preferred embodiment tapers
and narrows to a tip 102 as it extends away from the impeller
housing 84 and towards the outer casing 16. The lip seal 98 is
preferably formed from rubber.
[0040] The sealing member further comprises a guide portion 104 for
guiding a power connection cable 106 to the motor 56. The guide
portion 104 of the illustrated embodiment is formed in the shape of
a collar and may be a grommet. The electrical cable 106 is in the
form of a ribbon cable attached to the motor at joint 108. The
electrical cable 106 extending from the motor 56 passes out of the
lower portion 60 of the motor bucket through spiral fin 82. The
passage of the electrical cable 106 follows the shaping of the
impeller housing 84 and the guide portion 104 is shaped to enable
the electrical cable 106 to pass through the flexible sealing
member. The guide portion 104 of the sealing member enables the
electrical cable 106 to be clamped and held within the upper base
member 42. A cuff 110 accommodates the electrical cable 106 within
the lower portion of the upper base member 42.
[0041] FIG. 6 illustrates a sectional view through the air outlet
14. The air outlet 14 comprises an annular outer casing section 120
connected to and extending about an annular inner casing section
122. Each of these sections may be formed from a plurality of
connected parts, but in this embodiment each of the outer casing
section 120 and the inner casing section 122 is formed from a
respective, single molded part. The inner casing section 122
defines the central opening 24 of the air outlet 14, and has an
external peripheral surface 124 which is shaped to define the
Coanda surface 28, diffuser surface 30, guide surface 32 and
tapered surface 34.
[0042] The outer casing section 120 and the inner casing section
122 together define an annular interior passage 126 of the air
outlet 14. Thus, the interior passage 126 extends about the opening
24. The interior passage 126 is bounded by the internal peripheral
surface 128 of the outer casing section 120 and the internal
peripheral surface 130 of the inner casing section 122. As shown in
FIG. 4, the outer casing section 120 comprises a base 132 having an
inner surface 134. Formed on the inner surface 134 of the base 132
are two pairs of lugs 136 and a pair of ramps 138 for connection to
the upper end of the upper base member 42. Each lug 136 and each
ramp 138 upstands from the inner surface 134. Thus the base 132 is
connected to, and over, the open upper end of the motor bucket
retainer 62 and the upper base member 42 of the base 12. The pairs
of lugs 136 are located around the outer casing section 120 and
spaced from each other so that the pairs of lugs 136 correspond to
the spaced arrangement of the pairs of open grooves 66 of the upper
end of the upper base member 42 and so that the location of the
pair of ramps 138 corresponds to the location of the pair of wedge
members 70 of the upper end of the upper base member 42.
[0043] The base 132 of the outer casing section 120 comprises an
aperture through which the primary air flow enters the interior
passage 126 of the air outlet 14 from the upper end of the upper
base member 42 and the open upper end of the motor bucket retainer
62.
[0044] The mouth 26 of the air outlet 14 is located towards the
rear of the fan 10. The mouth 26 is defined by overlapping, or
facing, portions 140, 142 of the internal peripheral surface 128 of
the outer casing section 120 and the external peripheral surface
124 of the inner casing section 122, respectively. In this example,
the mouth 26 is substantially annular and, as illustrated in FIG.
4, has a substantially U-shaped cross-section when sectioned along
a line passing diametrically through the air outlet 14. In this
example, the overlapping portions 140, 142 of the internal
peripheral surface 128 of the outer casing section 120 and the
external peripheral surface 124 of the inner casing section 122 are
shaped so that the mouth 26 tapers towards an outlet 144 arranged
to direct the primary flow over the Coanda surface 28. The outlet
144 is in the form of an annular slot, preferably having a
relatively constant width in the range from 0.5 to 5 mm. In this
example the outlet 144 has a width of around 1 mm. Spacers may be
spaced about the mouth 26 for urging apart the overlapping portions
140, 142 of the internal peripheral surface 128 of the outer casing
section 120 and the external peripheral surface 124 of the inner
casing section 122 to maintain the width of the outlet 144 at the
desired level. These spacers may be integral with either the
internal peripheral surface 128 of the outer casing section 120 or
the external peripheral surface 124 of the inner casing section
122.
[0045] Referring to FIGS. 3 and 4, to attach the air outlet 14 to
the base 12, the air outlet 14 is inverted from the orientation
illustrated in FIG. 4 and the base 132 of the air outlet 14 is
located over the open upper end of the upper base member 42. The
air outlet 14 is aligned relative to the base 12 so that the lugs
136 of the base 132 of the air outlet 14 are located directly in
line with the open upper ends of the open grooves 66 of the upper
base member 42. In this position the pair of ramps 138 of the base
132 is directly in line with the pair of wedge members 70 of the
upper base member 42. The air outlet 14 is then pushed on to the
base 12 so that the lugs 136 are located at the base of the open
grooves 66. The sealing member 69 of the base 12 engages the inner
surface 134 of the base 132 of the air outlet 14 to form an
air-tight seal between the base 12 and the air outlet 14.
[0046] To secure the air outlet 14 to the base 12, the air outlet
14 is rotated in a clockwise direction relative to the base 12 so
that the lugs 136 move along the circumferentially extending tracks
68 of the open grooves 66. The rotation of the air outlet 14
relative to the base 12 also forces the ramps 138 to run up and
slide over the tapers 72 of the wedge member 70 through localized
elastic deformation of the open upper end of the upper base member
42. With continued rotation of the air outlet 14 relative to the
base 12, the ramps 138 are forced over the side walls 74 of the
wedge members 70. The open upper end of the upper base member 42
relaxes so that the ramps 138 are generally radially aligned with
the wedge members 70. Consequently, the side walls 74 of the wedge
members 70 prevent accidental rotation of the air outlet 14
relative to the base 12, whereas the location the lugs 136 within
the tracks 68 prevents lifting of the air outlet 14 away from the
base 12. The rotation of the air outlet 14 relative to the base 12
does not require excessive rotational force and so the assembly of
the fan 10 may be carried out by a user.
[0047] To operate the fan 10 the user depresses an appropriate one
of the buttons 20 on the base 12, in response to which the
controller 44 activates the motor 56 to rotate the impeller 52. The
rotation of the impeller 52 causes a primary air flow to be drawn
into the base 12 through the air inlet 18. Depending on the speed
of the motor 56, the primary air flow generated by the impeller 52
may be between 20 and 30 litres per second. The pressure of the
primary air flow at the outlet 92 of the base 12 may be at least
150 Pa, and is preferably in the range from 250 to 1.5 kPa. The
primary air flow passes sequentially through the impeller housing
84, the upper end of the upper base member 42 and open upper end of
the motor bucket retainer 62 to enter the interior passage 126 of
the air outlet 14. The primary air flow emitted from the air outlet
92 of the base 12 is generally in an upward and forward
direction.
[0048] Within the air outlet 14, the primary air flow is divided
into two air streams which pass in opposite directions around the
central opening 24 of the air outlet 14. Part of the primary air
flow entering the air outlet 14 in a sideways direction (generally
orthogonal to the axis X) passes into the interior passage 126 in a
sideways direction without significant guidance, whereas another
part of the primary air flow entering the air outlet 14 in a
direction parallel to the axis X is guided by the curved vanes 76,
78 of the motor bucket retainer 62 to enable the air flow to pass
into the interior passage 126 in a sideways direction. As the air
streams pass through the interior passage 126, air enters the mouth
26 of the air outlet 14. The air flow into the mouth 26 is
preferably substantially even about the opening 24 of the air
outlet 14. Within each section of the mouth 26, the flow direction
of the portion of the air stream is substantially reversed. The
portion of the air stream is constricted by the tapering section of
the mouth 26 and emitted through the outlet 98.
[0049] The primary air flow emitted from the mouth 26 is directed
over the Coanda surface 28 of the air outlet 14, causing a
secondary air flow to be generated by the entrainment of air from
the external environment, specifically from the region around the
outlet 98 of the mouth 26 and from around the rear of the air
outlet 14. This secondary air flow passes through the central
opening 24 of the air outlet 14, where it combines with the primary
air flow to produce a total air flow, or air current, projected
forward from the air outlet 14. Depending on the speed of the motor
56, the mass flow rate of the air current projected forward from
the fan 10 may be in the range from 300 to 400 litres per second,
and the maximum speed of the air current may be in the range from
2.5 to 4 m/s.
[0050] The even distribution of the primary air flow along the
mouth 26 of the air outlet 14 ensures that the air flow passes
evenly over the diffuser surface 30. The diffuser surface 30 causes
the mean speed of the air flow to be reduced by moving the air flow
through a region of controlled expansion. The relatively shallow
angle of the diffuser surface 30 to the axis X of the opening 24
allows the expansion of the air flow to occur gradually. A harsh or
rapid divergence would otherwise cause the air flow to become
disrupted, generating vortices in the expansion region. Such
vortices can lead to an increase in turbulence and associated noise
in the air flow which can be undesirable, particularly in a
domestic product such as a fan. The air flow projected forwards
beyond the diffuser surface 30 can tend to continue to diverge. The
guide surface 32 extending inwardly towards the axis X converges
the air flow towards the axis X. As a result, the air flow can
travel efficiently out from the air outlet 14, enabling rapid air
flow to be experienced at a distance of several meters from the fan
10.
[0051] FIGS. 7 to 9 illustrate an external accessory for the fan
10. The accessory is in the form of a filter unit 200 which is
detachably attachable to the fan 10 to allow the filter unit 200 to
be removed for cleaning or replacement.
[0052] The filter unit 200 is in the form of a generally
cylindrical sleeve which is locatable around the upper base member
42 of the base 12 so that the filter unit 200 is located over the
air inlet 18 of the fan 10, as illustrated in FIGS. 10 and 11. This
allows the filter unit 200 to remove airborne particles from the
primary air flow generated by the fan 10 before the primary air
flow enters the base 12 of the fan 10.
[0053] The filter unit 200 comprises a generally annular filter 202
for removing airborne particles from the primary air flow. The
filter 202 is preferably in the form of a radially pleated high
energy particle arrester (HEPA) filter. The filter 202 has a
surface area that is exposed to the incoming primary air flow
generated by the fan which is in the range from 0.5 to 1.5 m.sup.2,
and in this example is around 1.1 m.sup.2. The filter 202 is
surrounded by a cylindrical outer cover 204, which is preferably
formed from plastics material, to protect the filter 202 and thus
allows a user to handle the filter unit 200 without contacting the
filter 202. The cover 204 is preferably transparent to allow a user
to examine visually the state of the filter 202 during use or after
a period of use. The cover 204 comprises a plurality of apertures
(not shown) through which the primary air flow enters the filter
unit 200, and thus provides a relatively coarse first stage of
filtration of the filter unit 200 to prevent relatively large
airborne objects or insects from entering the filter unit 200. The
filter unit 200 may further comprise additional filter media
between the filter 202 and the cover 204, or downstream from the
filter 202. For example, this additional filter media may comprise
one or more of foam, carbon, paper, or fabric.
[0054] The filter 202 and the cover 204 are sandwiched between two
annular plates 206, 208 of the filter unit 200. Each plate 206, 208
includes a circular inner rim 210 and a circular outer rim 212
which both extend partially towards the other plate 206, 208. The
filter 202 and the cover 204 are located between the rims 210, 212
of the plates 206, 208, and are preferably secured to the plates
206, 208 using an adhesive.
[0055] The upper plate 206 comprises a lower collar 214 which is
located radially inwardly from the inner rim 210 of the upper plate
206. The lower collar 214 extends axially downwards from the upper
plate 206. The inner diameter of the lower collar 214 is
substantially the same as the inner diameter of the base 132 of the
air outlet 14 of the fan 10. Similar to the base 132 of the air
outlet 14, the inner surface of the lower collar 214 comprises two
pairs of lugs 216 and a pair of ramps (not shown) for connection to
the upper end of the upper base member 42 of the base 12 of the fan
10. The shape of the lugs 216 and the ramps of the lower collar
214, and the angular spacing between the lugs 216 and the ramps of
the lower collar 214, are substantially identical to those of the
lugs 136 and ramps 138 of the base 132 of the air outlet 14.
[0056] The upper plate 206 further comprises an upper collar 218
which is located radially inwardly from the lower collar 214. The
upper collar 218 extends axially upwards from the inner
circumferential periphery of the upper plate 208. The outer
diameter of the upper collar 218 is substantially the same as the
outer diameter of the outer surface 64 of the open upper end of the
upper base member 42. Similar to the upper base member 42, the
upper collar 218 comprises two pairs of open grooves 220 and a pair
of wedge members 222. The open grooves 220 are substantially
identical to the open grooves 66 of the outer surface 64 of the
upper base member 42, and the spacing between the open grooves 220
is substantially the same as that between the open grooves 66. The
wedge members 222 are substantially identical to the wedge members
70 of the outer surface 64 of the upper base member 42, and the
spacing between the wedge members 222 is substantially the same as
that between the wedge members 70. A first annular sealing member
224 of the filter unit 200 extends about the outer surface of the
upper collar 218, and is located beneath the circumferentially
extending tracks 226 of the grooves 220.
[0057] The collars 214, 218 are preferably integral with the upper
plate 206, which is preferably formed from plastics material.
[0058] The lower plate 208 includes a relatively small collar 228
which extends axially downwardly from the inner rim 210 of the
lower plate 208. The collar 228 comprises a circumferentially
extending groove located on its inner surface. A second annular
sealing member 230 of the filter unit 200 is located within this
groove. The collar 228 is preferably integral with the lower plate
208, which is also preferably formed from a plastics material.
[0059] To attach the filter unit 200 to the fan 10, first the air
outlet 14 is detached from the base 12. To detach the air outlet 14
from the base 12, the air outlet 14 is twisted relative to the base
12 in the opposite direction (anti-clockwise) to that for attaching
the air outlet 14 to the base 12. With a suitable torque applied
manually by the user, the upper end of the upper base member 42 is
again caused to flex locally radially inwardly. This localized
deformation of the upper base member 42 allows the ramp 138 to be
rotated over the wedge members 70, while the lugs 136 are moved
simultaneously along the tracks 68 of the grooves 66. Once the lugs
136 reach the ends of the tracks 68, the air outlet 14 may be
lifted from the base 12.
[0060] Although the detachment of the air outlet 14 from the base
12 requires a greater force to be applied to the air outlet 14 than
the force required for attachment, the resilience of the upper base
member 42 is selected so that the detachment of the air outlet 14
may be performed manually
[0061] The user then attaches the filter unit 200 to the base 12.
The technique for attaching the filter unit 200 to the base 12 is
essentially the same as that for attaching the air outlet 14 to the
base 12. The user locates the open lower end of the collar 228 of
the lower plate 208 over the open upper end of the upper base
member 42, and lowers the filter unit 200 around the base 12. When
the bottom end of the lower collar 214 of the upper plate 206 is
located immediately above the open upper end of the upper base
member 42, the user rotates the filter unit 200 until the lugs 216
of the filter unit 200 are located directly in line with the open
upper end of the open grooves 66 of the upper base member 42. In
this position the pair of ramps of the filter unit is directly in
line with the pair of wedge members 70 of the upper base member 42.
The filter unit 200 is then pushed further on to the base 12 so
that the lugs 216 of the filter unit 200 are located at the base of
the open grooves 66 of the base 12. To secure the filter unit 200
to the base 12, the filter unit 200 is rotated in a clockwise
direction relative to the base 12 so that the lugs 216 move along
the circumferentially extending tracks 68 of the open grooves 66.
The rotation of the filter unit 200 relative to the base 12 also
forces the ramps to run up and slide over the tapers 72 of the
wedge members 70 through localized elastic deformation of the upper
base member 42. With continued rotation of the filter unit 200
relative to the base 12, the ramps are forced over the side walls
74 of the wedge members 70. The upper base member 42 relaxes so
that the ramps are generally radially aligned with the wedge
members 70. Consequently, the side walls 74 of the wedge members 70
prevent accidental rotation of the filter unit 200 relative to the
base 12, whereas the location the lugs 216 within the tracks 68
prevents lifting of the filter unit 200 away from the base 12.
[0062] As shown in FIG. 11, when the filter unit 200 is attached to
the base 12 the second sealing member 230 of the filter unit 200 is
located beneath the air inlet 18 of the base 12, and engages the
outer surface of the base 12 to form an air-tight seal between the
base 12 and the filter unit 200. As also shown in FIG. 10, the
buttons 22 and user operable dial 22 of the base 12 remain
accessible by the user when the filter unit 200 is attached to the
base 12.
[0063] The air outlet 14 is then attached to the filter unit 200.
The attachment of the air outlet 14 to the filter unit 200 is
essentially the same as the attachment of the air outlet 14 to the
base 12. The base 132 of the air outlet 14 is located over the
upper collar 218 of the filter unit 200, and the air outlet 14 is
aligned relative to the base 12 so that the lugs 136 of the base
132 of the air outlet 14 are located directly in line with the open
upper end of the open grooves 220 of the filter unit 200. The air
outlet 14 is then pushed on to the filter unit 200 so that the lugs
136 are located at the base of the open grooves 220. The first
sealing member 224 of the filter unit 200 engages the inner surface
134 of the base 132 of the air outlet 14 to form an air-tight seal
between the filter unit 200 and the air outlet 14. Again, to secure
the air outlet 14 to the filter unit 200 the air outlet 14 is
rotated in a clockwise direction relative to the filter unit 200 so
that the lugs 136 move along the circumferentially extending tracks
226 of the open grooves 220 of the filter unit 200. The rotation of
the air outlet 14 relative to the filter unit 200 also forces the
ramps 138 to run up and slide over the tapers of the wedge members
222 of the filter unit 200 through localized elastic deformation of
the upper collar 218. With continued rotation of the air outlet 14
relative to the filter unit 200, the ramps 138 are forced over the
side walls of the wedge members 220. The upper collar 218 relaxes
so that the ramps 138 are generally radially aligned with the wedge
members 220. Consequently, the side walls of the wedge members 200
prevent accidental rotation of the air outlet 14 relative to the
filter unit 200, whereas the location the lugs 136 within the
tracks 226 of the grooves 200 prevents lifting of the air outlet 14
away from the filter unit 200.
[0064] The assembled combination of the fan 10 and the filter unit
200 is shown in FIGS. 10 and 11. The air-tight seals that the
filter unit 200 makes with the base 12 and the air outlet 14 force
the primary air flow to pass through the filter 202 of the filter
unit 200 to remove airborne particulates from the primary air flow
before it enters the base 12. In addition to purifying the air in
the local environment of the fan 10, the removal of airborne
particulates from the primary air flow before it enters the base 12
can significantly reduce the rate at which dust and debris can
build-up on the internal components of the fan 10, thereby reducing
the frequency at which the fan 10 needs to be cleaned. The filter
unit 200 may be easily replaced for cleaning or replacement by
detaching the air outlet 14 from the filter unit 200, which is
performed in the same manner as the removal of the air outlet 14
from the base 12, and subsequently detaching the filter unit 200
from the base 12. This can be performed quickly and easily without
the use of any tools. When the use of the filter unit 200 is no
longer required, the filter unit 200 can be rapidly removed from
the fan 10 by detaching the filter unit 200 from the base 12, and
re-attaching the air outlet 14 directly to the base 12.
* * * * *