The present invention relates to a fan assembly for generating an air flow within a room. In its preferred embodiment, the present invention relates to a ceiling fan.

A number of ceiling fans are known. A standard ceiling fan comprises a set of blades mounted about a first axis and a drive also mounted about the first axis for rotating the set of blades. In a first aspect, the present invention provides a fan assembly for generating an air flow within a room, the fan assembly comprising a casing having a plurality of inlet sections and a plurality of outlet sections each for receiving air from a respective inlet section, each inlet section comprising an air inlet, an impeller and a motor for driving the impeller to draw an air flow through the air inlet section and into a respective air outlet section, each outlet section having an interior passage for receiving air from its respective inlet section and an air outlet, the casing defining a bore about which the outlet sections extend and through which air from outside the fan assembly is drawn by the air emitted from the outlet sections. The air emitted from the casing, referred to subsequently as a primary air flow, entrains air surrounding the casing, and so the fan assembly 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 subsequently as a secondary air flow. The secondary air flow is drawn from the room space, region or external environment surrounding the casing. The primary air flow combines with the entrained secondary air flow to form a combined, or total, air flow projected from the casing.

The primary air flow is generated by motor-driven impellers located within the inlet sections of the casing. With the rotation of each impeller, a respective air stream is drawn into the casing through a respective air inlet of the casing. In one example, the casing comprises two inlet sections, with each inlet section comprising an air inlet, an impeller and a motor for rotating the impeller to draw an air stream into the casing through the air inlet. The primary air flow is thus formed from the two air streams drawn into the casing through the air inlets. We have found that the noise generated during the use of a fan assembly operating two motors and two impellers simultaneously to draw a primary air flow of a desired flow rate into the casing can be lower than the noise generated when using a single motor and a single impeller to draw the same primary air flow into the casing. The noise generated within the casing due to the passage of air through the casing tends to increase with increasing air stream velocity. For a desired air flow rate through the casing, we have found that generating that desired air flow with two separate air streams, rather than from one air stream, can allow the velocity of each air stream to be relatively low, thereby reducing noise within the casing. Another advantage is that the physical sizes of the motors and impellers used to draw the air streams into the casing can be relatively small, which can enable each air inlet section, and so the casing as a whole, to have a relatively compact shape and size.

Each inlet section is preferably arcuate in shape. Each inlet section may also extend about the bore defined by the casing. In one example, each inlet section extends about the bore by an angle in the range from 90 to 180°. The inlet sections are preferably arranged to convey air into the outlet sections in the same angular direction. Each inlet section is preferably arranged to convey air into an outlet section in a direction which is tangential to the bore of the casing.

Each outlet section is preferably arcuate in shape. In one example, the casing comprises two outlet sections, with each outlet section being semi-circular in shape. The outlet sections are connected together so that the casing has an annular shape. The inlet sections and the outlet sections may be concentric. The inlet sections may extend partially about the outlet sections to maintain the annular shape of the casing; depending on the lengths of the inlet sections, the casing may have a coiled shape extending about the bore of the casing. Alternatively, the inlet sections may have the same curvature as the outlet sections. For example, the inlet sections may be located above the outlet sections to minimise the outer diameter of the casing.

In one example, the plurality of inlet sections comprises a first inlet section and a second inlet section, and the plurality of outlet sections comprises a first outlet section for receiving air from the first inlet section and a second outlet section for receiving air from the second inlet section. These sections may be arranged so that at least part of the first outlet section is located beneath the second inlet section, and at least part of the second outlet section is located beneath the first inlet section. To provide a relatively smooth flow of air between the inlet sections and the outlet sections, each inlet section preferably has a curved, preferably generally serpentine, outlet conduit for conveying air into its associated outlet section. The outlet conduit is preferably located downstream from an arcuate inlet conduit of generally uniform cross-section, and which houses the impeller and the motor of the inlet section. The shapes adopted by the inlet conduit and the outlet conduit can eliminate abrupt changes in the direction of the air path between the air inlet and the outlet section which receives the air stream generated by rotation of the impeller, thereby reducing the loss of energy in the air stream as it passes into the outlet section. To minimise the size of the inlet section, the impeller is preferably an axial flow impeller, but the impeller may be a mixed flow impeller. The inlet section preferably comprises a diffuser located downstream from the impeller for guiding the air flow towards the outlet section.

The air inlet of the first inlet section may be substantially co-planar with the air inlet of the second inlet section. Each air inlet is preferably substantially orthogonal to the air outlets of the casing. Each air inlet is preferably located at the end of the inlet conduit of its respective inlet section. This air inlet is preferably a tangential air inlet for admitting the air stream into the fan assembly in a direction which is substantially tangential to the bore of the casing. This allows the air stream to enter the casing without any sharp changes in the direction of the air stream immediately downstream from the air inlet. The interior passage of each outlet section preferably has a cross-section which varies about the bore. As the air stream passes through the outlet section, the flow rate of the air stream remaining within the outlet section decreases about the bore as air is emitted from the casing. In order to maintain a substantially constant air stream velocity within the outlet section, the cross-sectional area of the outlet section preferably decreases in a direction extending from the inlet section. In one example, the interior passage of each outlet section has a first end for receiving an air stream from its respective inlet section, and a second end located diametrically opposite to the first end, and wherein the cross- sectional area of the interior passage decreases from the first end to the second end. By maintaining a substantially constant air stream velocity within the outlet section, the velocity at which the air stream is emitted from the outlet section may be substantially constant about the bore, with the result that the velocity of the combined air flow generated by the fan assembly can be substantially even about the bore axis. Each outlet section preferably comprises a first arcuate side wall partially defining the bore, a second side wall, an upper wall extending between the side walls and a lower wall located opposite to the upper wall. The air outlet may be located between the lower wall and the first side wall, or in the lower wall. The outlet section may have a generally rectangular cross-section. The variation in the cross-section area of the outlet section may be effected in one of a number of different ways. For example, the distance between the upper wall and the lower wall may vary about the bore. The distance between the first side wall and the second side wall may be relatively constant about the bore. Alternatively, the distance between the first side wall and the second side wall may also vary about at least part of the bore.

Each air outlet is preferably in the form of a slot. Each slot may be semi-circular in shape. The air outlets are preferably configured to emit the primary air flow away from the axis of the bore, preferably in the shape of an outwardly tapering cone. We have found that the emission of the primary air flow from the casing in a direction which extends away from the bore axis can increase the degree of the entrainment of the secondary air flow by the primary air flow, and thus increase the flow rate of the combined air flow generated by the fan assembly. References herein to absolute or relative values of the flow rate, or the maximum velocity, of the combined air flow are made in respect of those values as recorded at a distance of 1.5m in front of the air outlet of the casing.

Without wishing to be bound by any theory, we consider that the rate of entrainment of the secondary air flow by the primary air flow may be related to the magnitude of the surface area of the outer profile of the primary air flow emitted from the casing. When the primary air flow is outwardly tapering, or flared, the surface area of the outer profile is relatively high, promoting mixing of the primary air flow and the air surrounding the casing and thus increasing the flow rate of the combined air flow. Increasing the flow rate of the combined air flow generated by the casing has the effect of decreasing the maximum velocity of the combined air flow. This can make the fan assembly suitable for use as a ceiling fan for generating a flow of air through a room or an office.

The first side wall preferably comprises a section adjacent the lower wall which extends towards the lower wall in a direction which tapers away from the bore axis. An angle of inclination of the section of the side wall to the bore axis may be between 0 and 45°. This section of the side wall preferably has a shape which is substantially frusto-conical. The air outlet may be arranged to emit the primary air flow in a direction which is substantially parallel to this section of the side wall. This section of the side wall may define with the lower end wall the air outlet of the outlet section. This section of the side wall may be integral with part of the lower wall.

The air outlets preferably extend about the bore axis. The casing may comprise a plurality of air outlets angularly spaced about the bore axis.

The outlet sections of the casing may be isolated from each other. Alternatively, the outlet sections may be in fluid communication so that air may pass from one outlet section to another outlet section. This can further assist in maintaining a constant primary air flow velocity about the bore. For example, the air outlets of the casing may be connected to form a single circular air outlet, with the bore axis passing through the centre of the air outlet. Alternatively, or additionally, the interior passages of the outlet sections may be in fluid communication, so that each outlet section is arranged to receive air from, and emit air into, another one of the outlet sections. For example, each outlet section may comprise a first inlet port for receiving the air stream from the inlet section, a second inlet port for receiving air from one of the other outlet sections, and an outlet port for emitting air into one of the other outlet sections. Where the casing comprises a first semi-circular outlet section and a second semi-circular outlet section, the second inlet port of the first outlet section is arranged to receive air from the second outlet section, and the outlet port of the first outlet section is arranged to return air to the second outlet section. Similarly, the second inlet port of the second outlet section is arranged to receive air from the outlet port of the first outlet section and the outlet port of the second outlet section is arranged to return air to the first outlet section.

The second inlet port and the outlet port of each outlet section preferably have the same cross-sectional area. The first inlet port preferably has a larger cross-sectional area than the second inlet port. The first inlet port is preferably located adjacent to the second inlet port. The first inlet port is preferably co-planar with the second inlet port so that the direction in which air from the inlet section enters the outlet section is substantially the same as the direction in which air from the other outlet section enters the outlet section. This can minimise turbulence within the outlet section. The second inlet port is preferably located diametrically opposite to the outlet port. This communication between the outlet sections of the casing may be considered to provide the casing with a single, continuous interior passage for receiving air from each of the inlet sections, and at least one air outlet. Therefore, in a second aspect the present invention provides a fan assembly for generating an air flow within a room, the fan assembly comprising a casing having a plurality of inlet sections, each inlet section comprising an air inlet, an impeller and a motor for driving the impeller to draw an air flow through the air inlet section, an interior passage for receiving air from the inlet sections and at least one air outlet, the casing defining a bore about which the interior passage extends and through which air from outside the fan assembly is drawn by the air emitted from said at least one air outlet. The fan assembly preferably includes a support assembly for supporting the casing on a ceiling of a room. The support assembly preferably comprises a mounting plate which is attachable to the ceiling of the room.

Features described above in connection with the first aspect of the invention are equally applicable to the second aspect of the invention, and vice versa.

Preferred features of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a front perspective view, from above, of a fan assembly;

Figure 2 is a top view of the fan assembly;

Figure 3 is a left side view of the fan assembly;

Figure 4 is a front view of the fan assembly; Figure 5 is a sectional view taken along line C-C in Figure 3; Figure 6 is a sectional view taken along line D-D in Figure 4; and

Figure 7(a) is a sectional view taken along line E-E in Figure 3, and Figure 7(b) is an enlarged part of Figure 7(a). Figures 1 to 4 are external views of an example of a fan assembly 10 for generating an air flow within a room. In this example, the fan assembly 10 forms part of a ceiling fan which is connectable to a ceiling of a room. A support assembly (not shown) is provided for supporting the fan assembly 10 on the ceiling of the room. The support assembly may comprise any form of known support or supports, such as a frame, arms, chains, or the like, for supporting the fan assembly 10 on the ceiling.

The fan assembly 10 comprises an annular casing. The casing has a first inlet section 12 and a second inlet section 14 for drawing a primary air flow into the fan assembly 10. The casing also has a first outlet section 16 for receiving air from the first inlet section 12, and a second outlet section 18 for receiving air from the second inlet section 14. The outlet sections 16, 18 are semi-circular in shape, and are connected together so as to extend about a central bore axis X to define a bore 20 of the casing. The bore 20 has a generally circular cross-section. The inlet sections 12, 14 are arranged to convey air into the outlet sections 16, 18 in the same angular direction; as viewed in Figure 2, each air inlet 12, 14 is arranged to convey air to its respective outlet section 16, 18 so that air enters each outlet section 16, 18, and subsequently passes through the outlet sections 16, 18, in an anticlockwise direction. With reference also to Figures 5 to 7, each outlet section 16, 18 has a semi-circular interior passage 22, 24 which extends partially about the bore 20 for receiving air from a respective inlet section 12, 14, and at least one air outlet 26, 28 for emitting air from the casing. In this example, each outlet section 16, 18 comprises a single air outlet 26, 28 in the form of a semi-circular slot. The interior passages 22, 24 of the casing may be isolated from each other, but in this example, and as described in more detail below, the interior passages 22, 24 are connected together to allow air to pass from one outlet section to the other. In this case, the casing may be considered to comprise a continuous interior passage, formed from two half sections 22, 24, which extends about the bore 20 of the casing to convey air to the air outlets 26, 28, which together define a generally circular slot from which the air flow is emitted from the casing. Each outlet section 16, 18 has a generally rectangular cross-section, as defined by various walls of the casing. In more detail, the casing has an annular inner side wall 30 extending about the bore 20 of the casing, and an annular outer side wall 32 extending about the inner side wall 30. In this example, the radial distance between the inner side wall 30 and the outer side wall 32 is substantially constant about the bore axis X. An annular lower wall 34 extends between the side walls 30, 32. The walls 30, 32, 34, define in part the interior passages 22, 24 and the air outlets 26, 28. The air outlets 26, 28 are located between the inner side wall 30 and the lower wall 34. The air outlets 26, 28 are located in a plane which is perpendicular to the bore axis X, and preferably have a relatively constant width in the range from 0.5 to 5 mm. The air outlets 26, 28 are located between the lower wall 34 and a lower part 36 of the inner side wall 30. The internal surface of the lower part 36 of the inner side wall 30 is shaped to guide air through the air outlets 26, 28 in a direction which is inclined to, and extends away from, the bore axis X. In this example, air is emitted through the air outlets 26, 28 in a direction which is inclined at an angle of around 15° to the bore axis X. The lower part 36 of the inner side wall 30 and the lower wall 34 are connected together by a plurality of webs 38 (one of which is indicated in Figure 5) which extend across the air outlets 26, 28 and serve to control the width of the air outlets 26, 28. These webs 38 are angularly spaced about the bore axis X, for example at 20° or 30° intervals.

Each interior passage 22, 24 is also defined in part by a respective upper wall 40, 42 of its respective outlet section 16, 18. Each upper wall 40, 42 extends between the side walls 30, 32. Each upper wall 40, 42 extends about the bore 20 of the casing with the same curvature as the lower wall 34. Each upper wall 40, 42 is shaped so that the separation between each upper wall 40, 42 and the lower wall 34 varies continuously about the bore axis X. This has the effect of varying the cross-sectional areas of the interior passages 22, 24 about the bore axis X. In this example, each upper wall 40, 42 is arranged at an angle to the lower wall 34 so that the separation between the upper wall 40, 42 and the lower wall 34 decreases gradually from one end of the interior passage 22, 24 to the other end of the interior passage 22, 24. The angle of inclination between the upper walls 40, 42 and the lower wall 34 is preferably in the range from 0 to 10°. In this example, each upper wall 40, 42 is inclined at an angle of around 3° to the lower wall 34. In addition to varying the distance between the upper wall 40, 42 and the lower wall 34, the radial distance between the inner side wall 30 and the outer side wall 32 may vary about at least part of the bore axis X to effect the desired variation in the cross-sectional area of the interior passage 22, 24.

As a result, the interior passage 22, 24 of each outlet section 16, 18 is in the form of part of a scroll having a cross-sectional area that varies continuously about the bore axis X. In this example, the upper walls 40, 42 are arranged so as not to contact the lower wall 34 so that each outlet section 16, 18 has a relatively large scroll inlet section and a relatively small scroll outlet section, with the cross-sectional area of the interior passage 22, 24 of the outlet section 16, 18 decreasing continuously between these scroll sections. With reference to Figures 7(a) and 7(b), each outlet section 16, 18 has a first inlet port 44 for receiving air from a respective inlet section 12, 14, a second inlet port 46 and an outlet port 48. The first and second inlet ports 44, 46 are located at one end of the interior passage 22, 24, and the outlet port 48 is located at the other end of the interior passage 22, 24. The first inlet port 44 is located adjacent to the second inlet port 46, and in this example the inlet ports 44, 46 are substantially co-planar. Each of the air inlet ports 44, 46 is arranged to convey air into the interior passage 22, 24 in a direction which is substantially tangential to the bore 20 of the casing, and so the air inlet ports 44, 46 are preferably located in a radial plane passing through, and containing, the bore axis X. This can minimise the generation of turbulence immediately downstream from the inlet ports 44, 46. In this example where the casing comprises two outlet sections 16, 18, the second inlet port 46 of the first outlet section 16 is arranged to receive air from the outlet port 48 of the second outlet section 18, and the second inlet port 46 of the second outlet section 18 is arranged to receive air from the outlet port 48 of the first outlet section 16. As the outlet sections 16, 18 are semi-circular, the outlet port 48 is located diametrically opposite to the inlet ports 44, 46. Each inlet section 12, 14 is arcuate in shape, and has a curvature which is substantially the same as the curvature of the outlet sections 16, 18. Each inlet section 12, 14 preferably extends about the bore axis X by an angle between 90 and 180°; in this example, each inlet section 12, 14 extends about the bore axis X by an angle of around 130°. The inlet sections 12, 14 are arranged so that the first inlet section 12 extends around the bore axis X, above the second outlet section 18, to convey air into the first outlet section 16, and the second outlet section 14 extends around the bore axis X, above the first outlet section 16, to convey air into the second outlet section 18. To provide a relatively smooth flow of air between the inlet sections 12, 14 and the outlet sections 16, 18, each inlet section 12, 14 has a curved, generally serpentine, outlet conduit 50 for conveying air to the first inlet port 44 of its respective outlet section 16, 18. The outlet conduit 50 is located to one end of an arcuate inlet conduit 52 of generally uniform cross-section. An air inlet 54 of the inlet section 12, 14 is located at the other end of the inlet conduit 52. The air inlet 54 is a tangential air inlet, in that the air inlet admits air into the fan assembly 10 in a direction which is substantially tangential to the bore 20 of the casing. This allows air flow to enter the casing without any sharp changes in the direction of the air flow immediately downstream from the air inlet, and so can reduce noise generated by turbulence within the inlet section 12, 14. Each inlet conduit 52 houses an impeller 56 and a motor 58 for driving the impeller 56 to draw air into the inlet section 12, 14 of the casing. To minimise the size of the inlet section, the impeller 56 is preferably an axial flow impeller, but the impeller may be a mixed flow impeller. The inlet section 12, 14 also houses a diffuser 60 located downstream from the impeller 56, and comprising a plurality of diffuser vanes. A main control circuit for receiving control signals from a remote control, and for controlling the motors 58 in response to the received control signals, may be located within one of the inlet conduits 52. Alternatively, or additionally, a user interface may be located on the inlet conduit 52. This user interface may comprise one or more buttons or dials for allowing the user to activate and de-activate the motors 58, and to control the speed of the motors 58. The main control circuit is preferably arranged to control each motor 58 so that, during use of the fan assembly 10, each impeller 56 is rotated at the same speed. As a result, the flow rate of air entering the first inlet section 12 is substantially the same as the flow rate of air entering the second inlet section 14. Power cables for supplying electrical power to the motors 58 may each extend through an aperture located in a respective inlet conduit 52.

The inlet sections 12, 14 may comprise one or more silencing arrangements. In this example, each inlet conduit 52 includes tubular silencing foam 62 extending around the internal surface of the inlet conduit 52 located between the air inlet 54 and the impeller 56, and tubular silencing foam 64 extending around the internal surface of the inlet conduit 52 located between the impeller 56 and the outlet conduit 52.

To operate the fan assembly 10 the user depresses an appropriate button of the user interface or the remote control. A control circuit of the user interface communicates this action to the main control circuit, in response to which the main control circuit activates the motors 58 to rotate the impellers 56. The rotation of the impellers 56 causes air streams to be drawn into the inlet sections 12, 14. The user may control the speed of the motors 58, and therefore the rate at which air is drawn into the casing, using the user interface or the remote control. Each air stream passes through a respective inlet section 12, 14 to enter a respective outlet section 16, 18 through its first inlet port 44. As the air streams passes through the casing, a relatively small amount of air is conveyed between the outlet sections 16, 18 through the second outlet ports 46. However, the majority of the air is emitted through the air outlet 26, 28. As viewed in a plane passing through and containing the bore axis X, air is emitted through the air outlets 26, 28 in a direction extending away from the bore axis X. The emission of air from the air outlets 26, 28 causes a secondary air flow to be generated by the entrainment of air from the external environment, specifically from the region around the fan assembly 10. This secondary air flow combines with the emitted air to produce a combined, or total, air flow, or air current, projected from the fan assembly 10.