GB2468328A

GB2468328A - Fan assembly with humidifier

Info

Publication number: GB2468328A
Application number: GB0903690A
Authority: GB
Inventors: Nicholas Gerald Fitton; John Scott Sutton; Peter David Gammack; James Dyson
Original assignee: Dyson Technology Ltd
Current assignee: Dyson Technology Ltd
Priority date: 2009-03-04
Filing date: 2009-03-04
Publication date: 2010-09-08
Also published as: GB0903690D0

Abstract

Apparatus for generating a current of moist air, the apparatus comprising a humidifier 100 and a fan assembly 10, the fan assembly 10 having a nozzle 14 comprising an interior passage for receiving an airflow and a mouth 26 for emitting the airflow, the nozzle 14 defining an opening 24 through which air from outside the nozzle 14 is drawn by the airflow emitted from the mouth 26, the humidifier 100 being located behind the nozzle 14 such that the moist air emitted there from is also drawn through the opening 24. The interior passage and mouth 26 may be annular and extend around the opening 24. A Coanda surface 28 may be located adjacent to the mouth 26, with a diffuser 30 located downstream of the Coanda surface. The humidifier 100 may comprise a mist outlet 106 located directly behind the lowest part of the Coanda surface 28.

Description

Humidifying Apparatus The present invention relates to humidifying apparatus. In a preferred embodiment, the present invention relates to humidifying apparatus for generating a current of moist air in a room, office or other domestic environment.

Domestic humidifying apparatus is generally in the form of a portable appliance having a casing comprising a reservoir for storing a volume of water, and a fan for creating a flow of air through an air duct of the casing. The stored water is conveyed, usually under gravity, to an atomizing device for producing water droplets from the received water. This device may be in the form of high frequency vibrating device, such as a transducer. The water droplets enter the flow of air passing through the air duct, resulting in the emission of a mist into the environment. The appliance may include a sensor for detecting the humidity of the air in the environment, and for controlling the 1 5 transducer to adjust the rate at which the water is atomized so as to maintain the humidity of the air in the environment at a desirable level.

The flow rate of the air emitted from such a humidifier tends to be relatively low, for example in the range from I to 2 litres per second. Consequently, the rate at which the humid air is dispersed into a room can be very low. As a result, it may take a long period of time for a user located several metres from the humidifier to experience a rise in the humidity of the air in its local environment. Furthermore, as the humidity of the air in the environment local to the humidifier will rise relatively rapidly, the humidity detected by the sensor may not be indicative of the humidity of the air local to the user, and so the rate at which the water is atomized by the transducer may be reduced before the user has experienced an increase in the humidity of its local environment.

The present invention provides apparatus for generating a current of moist air, the apparatus comprising a humidifier for emitting moist air into the atmosphere and a fan assembly comprising means for creating an air flow and a nozzle comprising an interior passage for receiving the air flow and a mouth for emitting the air flow, the humidifier being located behind nozzle, the nozzle extending about and defining an opening through which both air from outside the nozzle and the moist air emitted from the humidifier are drawn by the air flow emitted from the mouth.

An advantage for a user is that through the entrainment of the mist emitted from the humidifier within an air current generated by the fan assembly, the moisture within the air current can be rapidly conveyed away from the humidifier to a distance of up to several metres. For example, the air current generated by the fan assembly may have a flow rate in the range from 50 to 600 litres per second.

The fan assembly is preferably in the form of a bladeless fan assembly. Through use of a bladeless fan assembly an air current can be generated without the use of a bladed fan.

In comparison to a bladed fan assembly, the bladeless fan assembly leads to a reduction in both moving parts and complexity. Furthermore, without the use of a bladed fan to project the air current from the fan assembly, a relatively uniform air current can be generated and guided into a room or towards a user. The air current can travel efficiently out from the nozzle, losing little energy and velocity to turbulence.

The term bladeless' is used to describe a fan assembly in which air flow is emitted or projected forward from the fan assembly without the use of moving blades.

Consequently, a bladeless fan assembly can be considered to have an output area, or emission zone, absent moving blades from which the air flow is directed towards a user or into a room. The output area of the bladeless fan assembly may be supplied with a primary air flow generated by one of a variety of different sources, such as pumps, generators, motors or other fluid transfer devices, and which may include a rotating device such as a motor rotor and/or a bladed impeller for generating the air flow. The generated primary air flow can pass from the room space or other environment outside the fan assembly through the interior passage to the nozzle, and then back out to the room space through the mouth of the nozzle.

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 assembly.

The shape of the nozzle of a bladeless fan assembly is thus not constrained by the requirement to include space for a bladed fan. Preferably, the nozzle surrounds the opening. The nozzle may be an annular nozzle which preferably has a height in the range from 200 to 400 mm. The interior passage is preferably annular, and is preferably shaped to divide the air flow into two air streams which flow in opposite directions around the opening.

Preferably, the mouth of the nozzle extends about the opening, and is preferably annular. The nozzle preferably comprises an inner casing section and an outer casing section which define the interior passage and the mouth of the nozzle. Each section is preferably formed from a respective annular member, but each section may be provided by a plurality of members connected together or otherwise assembled to form that section. The outer casing section is preferably shaped so as to partially overlap the inner casing section to define an outlet of the mouth between overlapping portions of the external surface of the inner casing section and the internal surface of the outer casing section of the nozzle. The outlet is preferably in the form of a slot, preferably having a width in the range from 0.5 to 5 mm. The nozzle may comprise a plurality of spacers for urging apart the overlapping portions of the inner casing section and the outer casing section of the nozzle. This can assist in maintaining a substantially uniform outlet width about the opening. The spacers are preferably evenly spaced along the outlet.

The nozzle may be inclined so that the air current is emitted upwardly from the fan assembly. For example, the nozzle may be inclined so that the air current is emitted at an angle in the range from 5 to 25° to the horizontal. This can enable the current of moist air emitted from the apparatus to be angled away from a floor or other surface upon which the apparatus is located. This can reduce the risk of the moisture within the air flow collecting on the surface, rather than evaporating into the atmosphere. The fan assembly preferably comprises means for oscillating the nozzle relative to the humidifier so that the humid air current is swept over an arc, preferably in the range from 60 to 1200. For example, a base of the fan assembly may comprise means for oscillating an upper part of the base, to which the nozzle is connected, relative to a lower part of the base.

The maximum air flow of the air current generated by the fan assembly is preferably in the range from 300 to 800 litres per second, more preferably in the range from 400 to 700 litres per second.

The nozzle may comprise a surface located adjacent the mouth and over which the mouth is arranged to direct the air flow emitted therefrom. This surface is preferably a Coanda surface. Preferably, the external surface of the inner casing section of the nozzle is shaped to define the Coanda surface. The Coanda surface preferably extends about the opening. 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 in which a primary air flow is directed over a 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, an increased amount of air from outside the fan assembly is drawn through the opening by the air emitted from the mouth.

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 is emitted from the mouth of the nozzle and preferably passes over a Coanda surface. The primary air flow entrains 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, and passes predominantly through the opening defined by the nozzle.

The primary air flow directed over the Coanda surface combined with the entrained secondary air flow equates to a total air flow emitted or projected forward from the opening defined by the nozzle. Preferably, the entrainment of air surrounding the mouth of the nozzle is such that the primary air flow is amplified by at least five times, more preferably by at least ten times, while a smooth overall output is maintained.

Preferably, the humidifier comprises a mist outlet located directly behind part, preferably the lowest part, of the Coanda surface of the nozzle. The speed at which the air flows through the opening of the nozzle tends to reach a maximum value adjacent the Coanda surface, and so through positioning the mist outlet directly behind part of the Coanda surface the mist can become entrained within the part of the air flow drawn into the opening with the greatest speed. This can maximise the speed with which the water droplets within the air current are emitted from the humidifying apparatus.

Preferably, the nozzle comprises a diffuser surface located downstream of the Coanda surface. The external surface of the inner casing section of the nozzle is preferably shaped to define the diffuser surface.

Preferably the means for creating an air flow through the nozzle comprises an impeller driven by a motor. This can provide a fan assembly with efficient air flow generation.

The means for creating an air flow preferably comprises a DC brushless motor and a mixed flow impeller. This can avoid frictional losses and carbon debris from the brushes used in a traditional brushed motor. Reducing carbon debris and emissions is advantageous in a clean or pollutant sensitive environment such as a hospital or around those with allergies. While induction motors, which are generally used in bladed fans, also have no brushes, a DC brushless motor can provide a much wider range of operating speeds than an induction motor.

Part of the humidifier may be connected to or integral with part of the fan assembly.

For example, the humidifier may comprise a base and a water tank removably locatable on the base, with the base of the humidifier being connected to the base of the fan S assembly. Alternatively, the apparatus may comprise a stand having a first support surface for receiving the fan assembly, and a second support surface for receiving the humidifier. This can ensure that the humidifier is located at an optimum distance from the fan assembly. The stand may have a lower surface shaped to define a channel beneath the second support surface for receiving a mains cable of the fan assembly.

Allowing part of a mains cable of the fan assembly to be arranged beneath the second support surface of the base reduces the amount of that cable which is exposed, for example on a work counter.

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 perspective view of a humidifying apparatus; Figure 2 is a front view of the apparatus of Figure 1; Figure 3 is a sectional view taken along line A-A in Figure 2 of the base and part of the nozzle of the fan assembly of the apparatus of Figure 1; Figure 4 is an enlarged sectional view taken along line A-A in Figure 2 of part of the nozzle of the fan assembly of the apparatus of Figure 1; and Figure 5 is a sectional view taken along line A-A in Figure 2 of the stand and the humidifier of the apparatus of Figure 1.

With reference first to Figures 1 and 2, an example of a humidifying apparatus comprises a fan assembly 10 and a humidifier 100 located behind the fan assembly 10.

The fan assembly 10 is preferably in the form of a bladeless fan assembly comprising a base 12 and a nozzle 14 mounted on and supported by the base 12. The base 12 comprises a substantially cylindrical outer casing 16 having a plurality of air inlets 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 assembly 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.

The nozzle 14 has an armular shape and defines a central opening 24. The nozzle 14 has a height in the range from 200 to 400 mm. The nozzle 14 comprises a mouth 26 located towards the rear of the fan assembly 10 for emitting air from the fan assembly 10 and through the opening 24. The mouth 26 extends at least partially about the opening 24.

1 5 The inner periphery of the nozzle 14 comprises a Coanda surface 28 located adjacent the mouth 26 and over which the mouth 26 directs the air emitted from the fan assembly 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 assembly 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°, and in this example is around 15°. 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 assembly 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°. The overall depth of the nozzle 24 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.

Figure 3 illustrates a sectional view through the base 12 of the fan assembly 10. The outer casing 16 of the base 12 comprises a lower casing section 40 and a main casing section 42 mounted on the lower casing section 40. The lower casing section 40 houses a controller (not shown) for controlling the operation of the fan assembly 10 in response to depression of the user operable buttons 21 shown in Figures 1 and 2, and/or manipulation of the user operable dial 22. The lower casing section 40 may also house a mechanism for oscillating the main casing section 42 relative to the lower casing section 40. The range of each oscillation cycle of the main casing section 42 relative to the lower casing section 40 is preferably between 60° and 120°, and in this example is around 90°. In this example, the oscillating mechanism 48 is arranged to perform around 3 to 5 oscillation cycles per minute. A mains power cable (not shown) extends through an aperture 44 formed in the lower casing section 40 for supplying electrical power to the fan assembly 10.

The main casing section 42 of the base 12 has an open upper end to which the nozzle 14 is connected, for example by a snap-fit connection. The main casing section 42 comprises a cylindrical grille 50 in which an array of apertures is formed to provide the air inlets 20 of the outer casing 16 of the base 12. The main casing section 42 houses an impeller 52 for drawing the primary air flow through the apertures of the grille 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 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. One of the upper portion 58 and the lower portion 60 of the motor bucket comprises a diffuser 62 in the form of a stationary disc having spiral blades, and which is located downstream from the impeller 56.

The motor bucket is located within, and mounted on, an impeller housing 64. The impeller housing 64 is, in turn, mounted on a plurality of angularly spaced supports 66, in this example three supports, located within the main casing section 42 of the base 12.

A generally frustro-conical shroud 68 is located within the impeller housing 64. The shroud 68 is shaped so that the outer edges of the impeller 52 are in close proximity to, but does not contact, the inner surface of the shroud 68. A substantially annular inlet member 70 is connected to the bottom of the impeller housing 64 for guiding the primary air flow into the impeller housing 64. Preferably, the base 12 further comprises silencing foam for reducing noise emissions from the base 12. In this example, the main casing section 42 of the base 12 comprises a disc-shaped foam member 72 located on the lower surface 74 of the main casing section 42, and a substantially annular foam member 76 located within the motor bucket.

Figure 4 illustrates a sectional view through the nozzle 14. The nozzle 14 comprises an annular outer casing section 80 connected to and extending about an annular inner casing section 82. Each of these sections may be formed from a plurality of connected parts, but in this embodiment each of the outer casing section 80 and the inner casing section 82 is formed from a respective, single moulded part. The inner casing section 82 defines the central opening 24 of the nozzle 14, and has an external peripheral surface 84 which is shaped to define the Coanda surface 28, diffuser surface 30, guide surface 32 and tapered surface 34.

The outer casing section 80 and the inner casing section 82 together define an annular interior passage 86 of the nozzle 14. Thus, the interior passage 86 extends about the opening 24. The interior passage 86 is bounded by the internal peripheral surface 88 of the outer casing section 80 and the internal peripheral surface 90 of the inner casing section 82. The outer casing section 80 comprises a base 92 which is connected to, and over, the upper casing section 80 of the base 12, for example by a snap-fit connection.

The base 92 of the outer casing section 80 comprises an aperture through which the primary air flow enters the interior passage 86 of the nozzle 14 from the open upper end of the main body section 42 of the base 12.

The mouth 26 of the nozzle 14 is located towards the rear of the fan assembly 10. The mouth 26 is defined by overlapping, or facing, portions 94, 96 of the internal peripheral surface 88 of the outer casing section 80 and the external peripheral surface 84 of the inner casing section 82, respectively. In this example, the mouth 26 is substantially annular and, as illustrated in Figure 4, has a substantially U-shaped cross-section when sectioned along a line passing diametrically through the nozzle 14. In this example, the overlapping portions 94, 96 of the internal peripheral surface 88 of the outer casing section 80 and the external peripheral surface 84 of the inner casing section 82 are shaped so that the mouth 26 tapers towards an outlet 98 arranged to direct the primary flow over the Coanda surface 28. The outlet 98 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 98 has a width of around 1.1 mm. Spacers may be spaced about the mouth 26 for urging apart the overlapping portions 94, 96 of the internal peripheral surface 88 of the outer casing section 80 and the external peripheral surface 84 of the inner casing section 82 to maintain the width of the outlet 98 at the desired level. These spacers may be integral with either the internal peripheral surface 88 of the outer casing section 80 or the external peripheral surface 84 of the inner casing section 82, Returning to Figures 1 and 2, in this example the fan assembly 10 is removably located on a stand 200. The stand 200 has a front section 202 and a rear section 204 located behind the front section 202. The front section 202 of the stand 200 comprises a support surface 206 for receiving and supporting the lower surface of the base 12 of the fan assembly 10. The support surface 206 preferably has a diameter which is substantially the same size as the external diameter of the base 12. The stand 200 may comprise an annular rim 208 extending at least partially about the support surface 206 for affording some stability to the fan assembly 10 when it is located on the support surface 206. An aperture 210 may be formed in the front section 202 of the stand 200 for receiving the power cable of the fan assembly 10 and for leading the power cable to a channel 212 formed in the lower surface of the rear section 204 of the stand 200. The channel 212 is shaped to guide the power cable beneath the rear section 204 of the stand to an opening 214 from which the power cable may extend from the stand 200 to a socket.

The rear section 204 of the stand 200 comprises a support surface 216 for receiving and supporting the lower surface of the humidifier 100. The humidifier 100 comprises a base 102 and a water tank 104 removably mountable on the base 102. The water tank 104 comprises a mist outlet 106 located in the upper surface 108 of the water tank 104 for emitting mist from the humidifier 100. Mist is conveyed to the mist outlet 106 from a duct 110 passing upwardly through the water tank 104, resulting in the emission of mist from the humidifier 100 in a generally vertical direction. The water tank 104 further comprises a water reservoir 112 extending about the duct 110. The water reservoir 112 preferably has a capacity in the range from 2 to 4 litres. A spout 116 is removably connected to the lower surface 114 of the water tank 104, for example through co-operating threaded connections. Thus, in this example the water tank 104 is filled by removing the water tank 104 from the base 102, turning it through 180° so that the spout 116 is projecting upwardly, unscrewing the spout 116 from the water tank 104 and introducing water into the water reservoir 112 through an aperture 117 exposed by removing the spout 116 from the water tank 104. The spout 116 comprises a spout aperture 118 which is normally closed by spring-loaded valve 119 to prevent leakage of water from the water reservoir 112. Once the water reservoir 112 has been filled, the user reconnects the spout 116 to the water tank 1 02, turns the water tank back through 180° and replaces the water tank 104 on the upper surface 120 of the base 102.

The upper surface 120 of the base 102 comprises recessed portions l22a, 122b which define a channel 124 for receiving water from the water tank 104. The channel 124 extends centrally across the base 102, and has a width in the range from one third to one half of the diameter of the base 102. A pin 126 extending upwardly from the recessed portion 1 22a of the upper surface 120 protrudes into the spout 116 when the water tank 104 is located on the base 102. The pin 126 pushes the valve 119 upwardly to open the spout aperture 11 8, thereby allowing water to pass under gravity from the water tank 104 and into the base 102. This results in the channel 124 becoming filled with water to a level Li substantially co-planar with the upper surface of the pin 126. The level of water within the water reservoir 112 is indicated by way of example at L2 in Figure 5.

The recessed portion 122b of the upper surface 120 comprises an aperture 128 for exposing the surface of a piezoelectric diaphragm 130 located beneath the upper surface of the base 102. An 0-ring sealing member 132 forms a water-tight seal between the upper surface 120 of the base 102 and the piezoelectric diaphragm 130. A drive circuit 134 is located beneath the upper surface 120 of the base 102 for actuating ultrasonic vibration of the piezoelectric diaphragm 130 to atomise water located within the channel 124.

The base 102 further comprises a fan (not shown) for generating an air flow through the humidifier, and a motor (not shown) for rotating the fan. The drive circuit 134 preferably controls the actuation and the speed of the motor. The fan is located within a duct formed in the base 102 of the humidifier 100. The duct comprises an inlet in the form of a plurality of apertures formed in the side wall 136 of the base 102, and an outlet 138 which is located in a non-recessed portion of the upper surface 120 of the base 102, and therefore above the level of water within the channel 124. The outlet 138 of the duct is spaced from the lower surface 114 of the water tank 102 so that air emitted from the fan passes over the surface of the water located in the channel 124 before entering the duct 110 of the water tank 102.

The base 102 of the humidifier 100 further comprises a plurality of user-operable buttons and/or at least one user-operable dial for controlling the operation of the humidifier 100. This can enable the user to vary at least one of the speed of the fan and the frequency of the vibration of the piezoelectric diaphragm 130 to adjust the rate at which water is emitted from the humidifier 100. A sensor in the form of a humidistat may also be provided for sensing the humidity of air in the external environment, and for supplying a signal indicative of the detected humidity to the drive circuit 134. The drive circuit 134 may be arranged to vary automatically one of the speed of the fan and the frequency of the vibration of the piezoelectric diaphragm 1 30 to maintain the detected humidity at or around a pre-selected value. This value may be pre-set in the drive circuit 134, or selected by the user through manipulation of, for example, a user-operable dial located on the base 102 of the humidifier 100. In this example, water may be emitted from the humidifier 100 at a rate in the range from 0.3 to 0.7 litres per hour, while the flow rate of air from the humidifier 100 may be in the range from Ito 2 litres per second. A level sensor may be provided in the water tank 104 for detecting the level L2 of water in the water reservoir 112. In response to a signal from this level sensor which is indicative of the level L2 has fallen below a pre-set minimum level, the drive circuit 134 may be arranged to stop the fan and the vibration of the piezoelectric diaphragm 130, and to output a visual alert to the user, for example using an LED.

With reference to Figure 1, the base 102 and the water tank 104 may each comprise a concave front section 140 having a radius which is approximately size as the radius of the outer casing 16 of the base 12 of the fan assembly 10. This allows the mist outlet 106 to be located in close proximity to the nozzle 14 of the fan assembly, and also ensures that the humidifier 100 is mounted on the stand 200 in the correct orientation.

In this example, the mist outlet 106 is spaced from the rear surface of the nozzle 14 of the fan assembly 10 by a distance in the range from 5 to 30 cm. The mist outlet 106 is located directly behind, and approximately level with, the lowest portion of the Coanda surface 28 of the nozzle 14 of the fan 10.

To operate the fan assembly 10, the user depresses an appropriate one of the buttons 20 on the base 12 of the fan assembly 10, in response to which the controller 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 of the fan assembly 10 through the air inlets.

Depending on the speed of the motor 56, the primary air flow may be between 20 and litres per second. The primary air flow passes sequentially through the impeller housing 64 and the aperture formed in the base 92 of the outer casing section 80 of the nozzle 14 to enter the interior passage 86 of the nozzle 14. Within the nozzle 14, the primary air flow is divided into two air streams which pass in opposite directions around the central opening 24 of the nozzle 14. As the air streams pass through the interior passage 86, air enters the mouth 26 of the nozzle 14. The air flow into the mouth 26 is preferably substantially even about the opening 24 of the nozzle 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.

The primary air flow emitted from the mouth 26 is directed over the Coanda surface 28 of the nozzle 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 nozzle 14. This secondary air flow passes through the central opening 24 of the nozzle 14, where it combines with the primary air flow to produce a total air flow, or air current, projected forward from the nozzle 14.

Depending on the speed of the motor 56, the mass flow rate of the air current projected forward from the fan assembly 10 may be up to 400 litres per second, preferably up to 600 litres per second, and the maximum speed of the air current may be in the range from 2.5 to 4 mIs.

The even distribution of the primary air flow along the mouth 26 of the nozzle 14 ensures that the air flow passes evenly over the diffuser surface 30. The diffuser surface 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 central 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 presence of the guide surface 32 extending substantially parallel to the central axis X of the opening 30 further converges the air flow. As a result, the air flow can travel efficiently out from the nozzle 14, enabling the air flow can be experienced rapidly at a distance of several metres from the fan assembly 1 0.

When the fan assembly 10 is operating, the user may switch on the humidifier 100 by pressing the appropriate button on the outer surface 136 of the base 102 of the humidifier 100. In response to the depression of the button, the drive circuit 134 of the humidifier 100 activates the motor to rotate the fan to generate a flow of air through the humidifier 100. Simultaneous with the actuation of the motor of the fan, the drive circuit 134 actuates the vibration of the piezoelectric diaphragm 130 to atomise water present within the channel 124, which creates airborne water droplets above the water located within the channel. As water within the channel 124 is atomised, the channel 124 is constantly replenished with water from the water reservoir 112, so that the level LI of water within the channel 124 remains substantially constant while the level L2 of water within the water reservoir 112 gradually falls.

With rotation of the fan, air is drawn into the humidifier 100 through the apertures located in the side wall of the base 102, passes through the duct within the base 102 and is emitted from the outlet 138 of this duct. The air flow passes over the water located in the channel 124, causing the airborne water droplets to become entrained within the air flow generated by the fan. The air flow passes upwardly through the spout 116 and is emitted from the mist outlet 106 in the form of a mist or fog. This mist is drawn through the central opening 24 of the nozzle 14 as part of the secondary air flow generated by the emission of the primary air flow from the mouth 26 of the nozzle 14.

Consequently, the mist is conveyed away from the humidifier 100 within the air current generated by the fan assembly 10, thereby enabling a humid air current to be experienced rapidly at a distance of several metres from the humidifier 100. Through oscillation of the main casing portion 42 of the base 12, and thus oscillation of the nozzle 14, relative to the humidifier 100, this humid air current can be swept over an arc in the range from 60 to 120°, preferably around 90°, to increase rapidly the dispersion of the humid air into a room.

Claims

CLAIMS1. Apparatus for generating a current of moist air, the apparatus comprising a humidifier for emitting moist air into the atmosphere and a fan assembly comprising means for creating an air flow and a nozzle comprising an interior passage for receiving the air flow and a mouth for emitting the air flow, the humidifier being located behind nozzle, the nozzle extending about and defining an opening through which both air from outside the nozzle and the moist air emitted from the humidifier are drawn by the air flow emitted from the mouth.
2. Apparatus as claimed in claim 1, wherein the fan assembly is a bladeless fan assembly.
3. Apparatus as claimed in claim 1 or claim 2, wherein the interior passage is shaped to divide the received air flow into two air streams each flowing along a respective side of the opening.
4. Apparatus as claimed in any one of the preceding claims, wherein the interior passage is substantially annular.
5. Apparatus as claimed in any one of the preceding claims, wherein the mouth extends about the opening.
6. Apparatus as claimed in any one of the preceding claims, wherein the nozzle comprises an inner casing section and an outer casing section which together define the interior passage and the mouth.
7. Apparatus as claimed in claim 6, wherein the mouth comprises an outlet located between an external surface of the inner casing section of the nozzle arid an internal surface of the outer casing section of the nozzle.
8. Apparatus as claimed in claim 7, wherein the outlet is in the form of a slot extending at least partially about the opening.
9. Apparatus as claimed in claim 7 or claim 8, wherein the outlet has a width in the range from 0.5 to 5 mm.
10. Apparatus as claimed in any one of the preceding claims, wherein the nozzle comprises a surface located adjacent the mouth and over which the mouth is arranged to direct the air flow.
11. Apparatus as claimed in claim 10, wherein the surface is a Coanda surface.
12. Apparatus as claimed in claim 11, wherein the Coanda surface extends about the opening.
13. Apparatus as claimed in claim 11 or claim 12, wherein the humidifier comprises a mist outlet located directly behind part of the Coanda surface of the nozzle.
14. Apparatus as claimed in claim 13, wherein the mist outlet is located directly behind the lowest part of the Coanda surface.
15. Apparatus as claimed in any one of claims 11 to 14, wherein the nozzle comprises a diffuser located downstream of the Coanda surface.
16. Apparatus as claimed in any one of the preceding claims, comprising a stand having a first support surface for receiving the fan assembly, and a second support surface for receiving the humidifier.
1 7. Apparatus as claimed in claim 16, wherein the stand has a lower surface shaped to define a channel beneath the second support surface for receiving a mains cable of the fan assembly.
1 8. Apparatus for generating a current of moist air substantially as hereinbefore described with reference to the accompanying drawings.