GB2633038A

GB2633038A - Heater assembly

Info

Publication number: GB2633038A
Application number: GB2313134.5A
Authority: GB
Inventors: Elizabeth Fryer Poppy; Harry Scott-Miller George
Original assignee: Dyson Technology Ltd
Current assignee: Dyson Technology Ltd
Priority date: 2023-08-30
Filing date: 2023-08-30
Publication date: 2025-03-05
Also published as: WO2025046374A1; GB202313134D0

Abstract

A heater assembly 700 for use in a haircare appliance comprises a first heater 710 having an upstream end 712 and a downstream end 714; a second heater 720 having an upstream end 722 and a downstream end 724, wherein the downstream end of the first heater is upstream of the upstream end of the second heater; a downstream temperature sensor 780 provided at a downstream end of the second heater; and an intermediate temperature sensor 790 provided between the first and second heaters, and wherein the first heater, the second heater, the downstream temperature sensor and the intermediate temperature sensor are in communication with a heater control circuit, and the heater control circuit is adapted to control the heaters in response to an intermediate air flow temperature measured by the intermediate temperature sensor and/or a downstream air flow temperature measured by the downstream temperature sensor.

Description

Heater Assembly

BACKGROUND

Haircare appliances often include a heater or a heater assembly for heating an air flow. The heated air may then be directed towards a user's hair for the purposes of drying or styling. Such heaters are typically relatively simple, operating only between ON/OFF states.

SUMMARY

According to aspects of the forgoing disclosure, there are described a number of heater assemblies for use in a haircare appliance. The features of each heater assembly may be incorporated into any of the other heater assemblies depending upon the application of the heater assembly and the haircare appliance.

According to a first aspect, there is provided a heater assembly for use in a haircare appliance, the heater assembly comprising a first heater having an upstream end and a downstream end; and a second heater having an upstream end and a downstream end wherein the downstream end of the first heater is upstream of the upstream end of the second heater.

Put another way, there is provided a heater assembly comprising two heaters arranged end to end such that fluid, such as air, flows from the downstream end of the first heater to the upstream end of the second heater.

In other words, the provided heater assembly comprises two heaters provided in series such that fluid flowing past the heater assembly will encounter the downstream end of the first heater before reaching the upstream end of the second heater.

The provision of separated first and second heaters provides a greater amount of control over the heat applied to fluid flowing through the heater assembly. Compared to conventional heater assemblies where the heater assemblies include a single heater, or multiple integrated heaters such as co-wound open wire heaters, the heater assembly of the invention provides a more granular control over the heating of fluid flow at different stages of the heater assembly.

Optional features of the invention set out are applicable singly or in any combination with any aspect of the invention.

The first heater and the second heater may be any type of heater. For example, the first and second heater may be an open wire heater, formed from an open resistance wire, or a foil heater. The first heater and the second heater may both be the same type of heater or each heater may be different. The first and second heater may be single heater units or composite heater units comprising a plurality of heater sub-units.

In an embodiment, the heater assembly further comprises a common electrical connection provided between the first heater and the second heater, wherein the common electrical connection is used to electrically connect the first heater and the second heater in parallel. The common electrical connection may be a live connection or a ground connection.

The provision of a common electrical connection between first and second heaters reduces the amount of wiring needed within the heater assembly in order to drive the heaters. This both improves the simplicity of manufacture as well as improving fluid flow through the heater assembly.

In the example where the first and second heaters are open wire heaters, the first heater may be a first heater coil and the second heater may he a second heater coil. A heater coil is a resistive wire wound several times about a central axis, or longitudinal axis, to form a helical shape. The first and second heater coils may or may not be the same as each other. The first and/or second heater coils may comprise a formed wire or a straight wire. A formed wire may be a wire having one or more undulations along its length. The undulations of a formed wire may be defined by a waveform profile. The first and/or second heater coils may be comprised of a chromium-aluminium alloy wire.

A heater coil may be defined by one or more parameters, including coil pitch and/or waveform profile.

The coil pitch of a heater coil may refer to the distance between adjacent coils of the heater coil. In particular, the coil pitch may refer to the minimum distance between two points on adjacent coils of the heater coil. Put another way, the coil pitch may refer to the length of a line drawn parallel to the central axis of the heater coil between two adjacent coils of the heater coil. The first heater coil may have a coil pitch of 1.25mm or more. The second heater coil may have a coil pitch of 1.25mm or more.

The waveform profile of the first heater coil may have a waveform height of 4.5mm or more and a waveform pitch of 2.5mm or more. The waveform profile of the second heater coil may have a waveform height of 4.5mm or more and a waveform pitch of 2.5mm or more. The waveform profile of the first heater coil may be the same as the waveform profile of the second heater coil, or it may be different.

The coil pitch angle may refer to the angle of the winding of the wire about the axis. In particular, the coil pitch angle may refer to an angle defined based on a point on the heater coil and the central axis of the heater coil. More specifically, an origin point on the central axis may be defined by a line drawn normal to the central axis of the heater coil and connected to a first point on the heater coil. Three orthogonal axes are then defined, the first axis being the central axis of the heater coil, the second axis being defined by the line connecting the first point on the heater coil and the central axis and the third axis being defined orthogonally in relation to the first and second axes. The heater coil will pass through a plane defined by the first and third axis, thereby defining a second point. The angle between the third axis and a line between the second point and the origin of the three orthogonal axes defines the coil pitch. The first heater coil may have a coil pitch angle of 1.3 degrees or more. The second heater coil may have a coil pitch angle of L5 degrees or more.

The first heater coil and the second heater coil may be arranged coaxially about the central axis of the heater assembly. Put another way, the first heater coil and the second heater coil may share a common axis that extends longitudinally through the first heater coil and the second heater coil. The central axis of the heater assembly may also be the longitudinal axis of a main body of the haircare appliance.

In an embodiment, the heater assembly further comprises a coil supporting structure arranged coaxially about the central axis of the heater assembly within the first heater coil and the second heater coil and adapted to support the first heater coil and the second heater coil. The first heater coil and the second heater coil may effectively be wound about the coil supporting structure.

The coil supporting structure may take any suitable form for holding the first and second heater coils in place. For example, the coil supporting structure may comprise a plurality of radially projecting fins each of which may project radially from the central axis of the heater assembly. The radially projecting fins may project to the extent where they contact the inner surface of the first and second heater coils. The coil supporting structure may be a single unitary structure or may be a composite structure formed from composite parts. The coil supporting structure may be a single structure adapted to support both the first and second heater coils or may be formed of two or more sub-structures adapted to support the first and second heater coils individually. The plurality of radially projecting fins may include six radially projecting fins, which may or may not be spaced evenly about the central axis. The coil supporting structure may be formed from mica.

According to a second aspect, there is provided a heater assembly for use in a haircare appliance, the heater assembly comprising: a heater coil; and an aerodynamic structure, wherein the heater coil is wound about a central cavity, and wherein the aerodynamic structure is provided within the central cavity.

Put another way, there is provided a heater assembly with an air-shaping structure provided within an open space of a heater coil. In other words, there is provided a heater assembly having an air directing means provided within a heater.

By providing an aerodynamic structure within the central cavity of the heater coil, air flowing through the heater assembly may he directed away from the central cavity and towards the heater coil, thereby increasing the proportion of the air flowing through the assembly that comes into close proximity to the heater coil. In this way, the efficiency of the heater assembly may be increased.

In this example, the heater coil may be any conventional heater coil, such as a single heater coil or a dual-wound heater coil. The heater coil may comprise a first heater having an upstream end and a downstream end and a second heater having an upstream end and a downstream end, wherein the downstream end of the first heater is upstream of the upstream end of the second heater, and wherein the first heater comprises a first heater coil and the second heater comprises a second heater coil. In other words, the heater coil according to this aspect may include any of the heater arrangements, and specifically any of the heater coil arrangements, described above.

The aerodynamic structure may be formed in any suitable shape. The aerodynamic structure may be shaped to direct air away from the central axis of the heater assembly and towards the heater coil. The aerodynamic structure may comprise an upstream portion and a downstream portion, wherein the upstream portion comprises an elongate conical structure and the downstream portion comprises a truncated conical structure. Put another way, the upstream and downstream portions of the aerodynamic structure may have tapered forms, wherein the taper of the upstream portion has a shallower gradient than the taper of the downstream portion. The elongate conical structure and the truncated conical structure may be cones having a sharp point or they may comprise a rounded tip. The taper of the elongate conical structure and the truncated conical structure may be uniform or it may vary along the length of the conical structure. For example, the taper of the elongate conical structure and/or the truncated conical structure may increase, in a linear or nonlinear fashion, from the base of the given conical structure to the tip.

As outlined above, the heater coil may comprise a first heater coil and a second heater coil, wherein an upstream end of the second heater coil is downstream of a downstream end of the first heater coil. As already discussed, in such an arrangement, the first heater coil and the second heater coil may be arranged coaxially about the central axis of the heater assembly. Further, the aerodynamic structure may be arranged coaxially with the first heater coil and the second heater coil about the central axis of the heater assembly.

One or both of the first heater coil and the second heater coil may be tapered towards a downstream end of the heater assembly, such that a diameter of the upstream end of the first heater coil is greater than a diameter of the downstream end of the second heater coil. In some embodiments, the diameter of the upstream end of the first heater coil is greater than the diameter of the downstream end of the first heater coil and the diameter of the upstream end of the second heater coil is greater than the diameter of the downstream end of the second heater coil. In addition, the diameter of the downstream end of the first heater coil may be greater than the diameter of the upstream end of the second heater coil. This tapering of coils, reducing diameter towards the downstream end of the second coil, in combination with the aerodynamic effect of the aerodynamic structure further increases the contact between the air flow and the heater coils along the length of the heater assembly. A taper angle of the first heater and/or the second heater may be 1.5° or more. The taper angle may be as the angle between the central axis of the heater assembly and a line drawn along the points of intersection of the heater coil(s) with a plane defined by the central axis of the heater assembly and a line normal to the central axis.

A diameter of each loop of the second heater coil may smaller than a diameter of each loop of the first heater coil. Put another way, the taper of the heater coils may continue across both heaters.

As described above, the heater assembly may further comprise a coil supporting structure arranged coaxially about the central axis of the heater assembly within the first heater coil and the second heater coil and adapted to support the first heater coil and the second heater coil. The coil supporting structure may comprise any of the elements outlined above.

In addition, the coil supporting structure may be tapered towards a downstream end of the coil supporting structure, such that a diameter of an upstream end of coil supporting structure is greater than a diameter of the downstream end of the coil supporting structure. In other words, the coil supporting structure may be tapered to match a taper of the heater coil(s).

As outlined above, the coil supporting structure may comprise a plurality of radially projecting fins. In this case, the aerodynamic structure may comprise a plurality of recesses adapted to receive the plurality of radially projecting fins of the coil supporting structure.

According to a third aspect, there is provided a heater assembly for use in a haircare appliance comprising a heater control circuit, the heater assembly comprising: a first heater having an upstream end and a downstream end; and a second heater having an upstream end and a downstream end, wherein the downstream end of the first heater is upstream of the upstream end of the second heater; a downstream temperature sensor provided at a downstream end of the second heater, wherein the downstream temperature sensor is adapted to measure a downstream air flow temperature; and an intermediate temperature sensor provided between the first heater and the second heater, wherein the intermediate temperature sensor is adapted to measure an intermediate air flow temperature, and wherein the first heater, the second heater, the downstream temperature sensor and the intermediate temperature sensor are in communication with the heater control circuit, and the heater control circuit is adapted to control the first heater and the second heater in response to the intermediate air flow temperature and/or the downstream air flow temperature.

Put another way, there is provided a heater assembly comprising two temperature sensors for controlling the operation of the heaters, wherein the two temperature sensors are provided at different stages of the heater assembly. In other words, there is provided a heater assembly with multiple temperature testing points along an air flow path with at least one heater provided between them.

The first and second heaters include any of the heating arrangements, such as the first and second heating coils, described above. The heater assembly may also include the aerodynamic structure described above.

The downstream and intermediate temperature sensors may be any type of temperature sensor suitable for sensing the temperature of a fluid flowing through the heater assembly. For example, the downstream temperature sensor and/or the intermediate temperature sensor may be a thennistor.

The temperature sensors may be provided at any point between the central axis of the heater assembly and an outer edge of the heater assembly. For example, the downstream temperature sensor and the intermediate temperature sensor may be radially offset from the central axis of the heater assembly. In this way, the temperature sensors may be provided in the heated fluid flow, thereby providing a more accurate reading of the temperatures being achieved by the heater assembly.

The downstream temperature sensor and the intermediate temperature sensor may be rotationally offset from each other about the central axis, for example by 180° or thereabouts. The temperature sensors may be offset from each other by any angle from 0° up to and including 180°. Thus, the temperature sensors may measure the temperature of different portions of the fluid flow.

The heater assembly may comprise a heater supporting structure arranged coaxially about the central axis of the heater assembly and adapted to support the first heater and the second heater. The heater supporting structure may be the coil supporting structure described above in the case where the first and second heaters are first and second heater coils. As described above, a heater supporting structure may comprise a plurality of radially projecting fins. Such a plurality of radially projecting fins may define a plurality of fluid flow channels through the heater assembly. For example, if the plurality of radially projecting fins includes six radially projecting fins, the six radially projecting fins would define six fluid flow channels. In such a case, the downstream temperature sensor and the upstream temperature sensor may be provided in different fluid flow channels. Thus, a blockage in one of the fluid flow channels would be less likely to prevent a temperature reading be captured.

According to a fourth aspect, there is provided a haircare appliance comprising: a heater housing having a fluid input and a fluid output, the heater housing having an inner wall defining a fluid flow path between the fluid input and the fluid output the heater housing; any of the heater assemblies described above disposed in the fluid flow path of the heater housing, wherein the heater assembly is arranged such that an upstream end of the heater assembly, which may comprise a first heater, is disposed proximate the fluid input and a downstream end of the heater assembly, which may comprise a second heater, is disposed proximate the fluid output; and an airflow generator for generating airflow through the heater housing.

The haircare appliance may be any appliance for use in a method of treating the hair of a user with a heated air flow. For example, the haircare appliance may be a hair drier or a hair styler.

In an embodiment, the haircare appliance further comprises a heater control circuit for controlling the heater assembly. The heater control circuit may be adapted to control the heater assembly according to any suitable control scheme.

In the case where the heater assembly includes a first heater and a second heater, such as a first heater coil and a second heater coil as described above, the heater control circuit may be adapted to drive the first heater and the second heater independently of each other. For example, the heater control circuit may be adapted to drive the first heater and the second heater alternately with a duty cycle of 50% each.

The haircare appliance may include an airflow generator control circuit for controlling the airflow generator. The airflow generator control circuit may operate independently of, or in combination with, the heater control circuit to cause the airflow generator to cause fluid to flow through the haircare appliance.

The haircare appliance may include a power delivery system electrically connected to the heater assembly and adapted to provide power to the heater assembly. The power delivery system may be adapted to deliver at least 1000W, for example 1500W, to the heater assembly.

In some cases, as described above, the heater(s) of the heater assembly may be tapered from a wider upstream end to a narrower downstream end of the heater assembly. In such cases, or in cases where the cross-section of the heater(s) is uniform, the inner wall of the heater housing may be tapered from the fluid input to the fluid output, such that a diameter of the fluid input is greater than a diameter of the fluid output. For example, the inner wall of the heater housing may be tapered at an angle of 1.5° or more. The taper angle of the heater housing inner wall may be defined as outlined above.

As described above, the heater assembly may comprise an aerodynamic structure provided within a central cavity of a heater coil. Such an aerodynamic structure may take any of the forms discussed above. The ratio of the diameter of the aerodynamic structure to the diameter of the inner wall of heater housing may be 0.38. For example, the diameter of the aerodynamic structure may be 11mm and the diameter of the inner wall of the heater housing may be 28.8mm. The aerodynamic structure may be 40mm in length.

The central axis of the heater assembly may be aligned parallel with the longitudinal axis of the haircare appliance. Alternatively, the central axis of the heater assembly may not he parallel with the longitudinal axis of the haircare appliance. For example, an angle between the central axis of the heater assembly and a longitudinal axis of the haircare appliance may be 1.35° or more.

As outlined above, the heater assembly may comprise a downstream temperature sensor provided at a downstream end of the second heater, adapted to measure a downstream air flow temperature and an intermediate temperature sensor provided between the first heater and the second heater, adapted to measure an intermediate air flow temperature. In this case, the heater control circuit in communication may be adapted to control the first heater and the second heater in response to the intermediate air flow temperature and/or the downstream air flow temperature. In addition, an airflow generator control circuit in communication with the heater control circuit may be adapted to control the airflow generator in response to the intermediate air flow temperature and/or the downstream air flow temperature.

According to a fifth aspect, there is provided a method for controlling a heater assembly of a haircare appliance comprising an first heater having an upstream end and a downstream end and a second heater, having an upstream end and a downstream end, wherein the downstream end of the first heater is upstream of the upstream end of the second heater, the heater assembly further comprising a downstream temperature sensor provided at a downstream end of the second heater and an intermediate temperature sensor provided between the first heater and the second heater, the method comprising the steps of: measuring an intermediate air flow temperature using an intermediate temperature sensor of the heater assembly; measuring a downstream air flow temperature using a downstream temperature sensor of the heater assembly; and if the intermediate air flow temperature and/or the downstream air flow temperature is below a target temperature and the first heater and the second heater are inactive, activating the first heater and/or the second heater; or if the intermediate air flow temperature and/or the downstream air flow temperature is above an upper threshold, deactivating the first heater and the second heater.

The upper threshold may be any temperature up to 250°C, for example 140°C.

The method may comprise the further steps of controlling an air flow generation unit to generate an air flow through the heater assembly; and if the intermediate air flow temperature and/or the downstream air flow temperature is above an upper threshold, controlling the air flow generation unit to stop generating the air flow through the heater assembly.

According to a sixth aspect, there is provided a computer program product comprising instructions which, when the program is executed by a computer, cause the computer to carry out the methods described above in relation to one or more of the aspects and/or embodiments described herein.

According to a seventh aspect, there is provided a computer-readable medium having stored thereon the computer program product described above in relation to one or more of the aspects and/or embodiments described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows an elevation view of a heater assembly comprising a first heater and a second heater; Fig. 2 shows a perspective view of a heater support structure; Fig. 3 shows an elevation view of the heater support structure of Fig. 2; Fig. 4 shows a cross section of a heater assembly comprising an aerodynamic structure; Fig. 5 shows a perspective view of an aerodynamic structure; Fig. 6 shows an elevation view of a heater assembly comprising a downstream temperature sensor and an intermediate temperature sensor; Fig. 7 shows another elevation view of the heater assembly of Fig. 6; Fig. 8 shows a cross section of a heater assembly; Fig. 9 shows an exploded view of the heater assembly of Fig. 8; and Figs. 10A and 10B show perspective views of a main body of a haircare appliance.

DETAILED DESCRIPTION

Aspects of the present disclosure are described below with reference to the Figures. Fig. 1 shows an elevation view of a heater assembly 700 comprising a first heater and a second heater.

In the particular example shown in Fig. 1, the first heater is a first heater coil 710, the second heater is a second heater coil 720 and both heaters are open wire heaters formed from a formed chromium-aluminium alloy wire. It will be appreciated that the first and second heaters may be any type of heater arranged along a flow path.

When fluid, such as air, flows through the heater assembly 700, the fluid initially flows past the first heater coil 710 before flowing past the second heater coil 720.

The first heater coil 710 has an upstream end 712 and a downstream end 714. The second heater coil 720 has an upstream end 722 and a downstream end 724. The downstream end 714 of the first heater coil is upstream of the upstream end 722 of the second heater coil 720. Put another way, the upstream end 722 of the second heater coil is downstream of the downstream end 714 of the first heater coil.

The first heater coil 710 and the second heater 730 are arranged as heater coils arranged coaxially along a central axis 730 of the heater assembly. As shown in Fig. 1, the central axis of the heater assembly extends longitudinally through, and along the length of, the heater assembly. The central axis of the heater assembly may the same axis as the longitudinal axis of the haircare appliance, as discussed in further detail below, or it may be offset from the longitudinal axis of the haircare appliance.

As outlined above, a heater coil may be defined by a number of parameters, such as coil pitch and coil pitch angle.

The coil pitch of a heater coil may refer to the distance 732 between adjacent coils of the heater coil. The first heater coil may have a coil pitch of 1.25mm. The second heater coil may have a coil pitch of 1.25mm.

The coil pitch angle may refer to the angle of the winding of the wire about the axis. In particular, the coil pitch angle may refer to an angle 734 defined based on a point on the heater coil and the central axis 730 of the heater coil. The angle 734 between a line 736 normal to the central axis and a line 738 between a point on the heater coil and the intersection of the line normal to the central axis and the central axis defines the coil pitch angle. The first heater coil may have a coil pitch angle of 1.3°. The second heater coil may have a coil pitch angle of 1.5°.

In the arrangement shown in Fig. 1, the heater assembly 700 comprises a common electrical connection 740 provided between the first heater coil 710 and the second heater coil 720. The common electrical connection allows the first heater and second heater to be connected in parallel. The common electrical connection may be a ground connection or a live connection.

In use, the first heater coil 710 and the second heater coil 720 may be driven independently of each other, meaning that when the first heater is activated, the second heater may be deactivated. Similarly, when the second heater is activated, the first heater may be deactivated. The heaters may be run in such a manner in order to drive each heater with a duty cycle of 50%. Alternatively, the heaters may be run on different duty cycles, such as the first heater being run on a duty cycle of 60% and the second heater being run on a duty cycle of 40%, or vice versa. Indeed, the first, or second, heater may be driven with a duty cycle between 50% -100% and the second, or first, heater may be drive with a duty cycle between 50% -0%, according to various modes of operation of the heater assembly. Further, the first heater and the second heater may be driven according to different duty cycles by introducing periods where both heaters are activated at the same time and/or both heaters are deactivated at the same time. For example, both the first heater and the second heater may be driven with a duty cycle of 60%, where for 10% of the duty cycle both the first and second heaters are active. Indeed, both heaters may be driven with a duty cycle of up to 100%.

Figs. 2 and 3 show a perspective view and an elevation view of a heater support structure 750, respectively.

In the specific examples shown in Figs. 2 and 3, the heater support structure is a coil supporting structure; however, it will be appreciated that the heater support structure may be adapted into any form suitable for holding, or supporting, any type of heater.

The heater supporting structure shown in Figs. 2 and 3 is arranged coaxially about the central axis 730 of the heater assembly such that it lies within the first heater coil (not shown) and the second heater coil (not shown) in order to support the heater coils from within. The heater supporting structure, or coil supporting structure, comprises six radially projecting fins 760. The radially projecting fins may be spaced evenly about the central axis of the heater assembly.

In the example where the heater supporting structure 750 is a coil supporting structure, the radially projecting fins 760 may include a plurality of indents 765, or recesses, adapted to receive a portion of the heater coil.

Figs. 2 and 3 show an aerodynamic structure 770 provided with the heater supporting structure. The aerodynamic structure is described in further detail below with reference to Fig. 5.

Fig. 4 shows heater assembly 700 for use in a haircare appliance. In particular, Fig. 4 shows the heater assembly of Fig. 1 arranged within a heater housing 810, which comprises a fluid input 820 and a fluid output 830. In addition, Fig. 4 shows the aerodynamic structure 770 held coaxially with the first and second heater coils along the central axis of the heater assembly and within a central cavity of the first and second heater coils. The first heater coil 710, the second heater coil 720 and the aerodynamic structure 770 is held in place by way of the heater supporting structure (which is not shown here for clarity).

In the example shown in Fig. 4, both the first heater coil 710 and the second heater coil 720 are tapered towards a downstream end of the heater assembly, such that a diameter of the upstream end 712 of the first heater coil is greater than a diameter of the downstream end 724 of the second heater coil. In other words, the heaters are tapered towards the centre of the heater assembly towards the downstream end.

As air flows through a tubular structure, such as heater housing 810, the flow concentrates towards the centre of the tube. By tapering the heaters inwards, i.e., towards the central axis of the heater assembly, the downstream portion of the heaters will be in closer proximity to the maximum air flow.

The taper angle of the heaters 768 may be defined relative to the central axis of the heater assembly or any axis parallel to the central axis. In the example shown in Fig. 4, the taper angle is shown between the heater housing 810, which is parallel to the central axis of the heater, and the outer edge of the heater coils. As shown in Fig. 4, the taper angle is continuous across both heaters and may be an angle of 1.5° or more.

As a result of the taper, each loop of the first heater coil 710 and the second heater coil 720 will decrease in diameter from the upstream end 712 of the first heater coil to the downstream end 724 of the second heater coil.

The heater assembly of Fig. 4 also comprises a coil supporting structure (not shown) similar to the heater supporting structure shown in Figs. 2 and 3 arranged coaxially about the central axis of the heater assembly. The coil supporting structure may also include a taper to match that of the first and second heater coils, such that a diameter of an upstream end of coil supporting structure is greater than a diameter of the downstream end of the coil supporting structure.

The inner wall of the heater housing 810 in Fig. 4 is shown as being parallel to the central axis of the heater assembly. However, the inner wall of the heater housing may be tapered from the air input 823 to the air output 830, such that a diameter of the air input is greater than a diameter of the air output. For example, the inner wall of the heater housing may be tapered at an angle of 1.5° or more. The taper of the inner wall does not need to match the taper of the heater coils.

Fig. 5 shows a perspective view of the aerodynamic structure 770 of the heater assembly.

As shown in Fig. 5, wherein the aerodynamic structure 770 comprises an upstream portion 772 and a downstream portion 774. The upstream portion 772 comprises an elongate conical structure and the downstream portion comprises a truncated conical structure. In the example shown in Fig. 5, the ends of the conical structures are rounded. Further, the aerodynamic structure comprises a plurality of recesses adapted to receive the plurality of radially projecting fins of the coil supporting structure.

As air flows through the heater assembly, it will pass from the upstream portion 712 of the first heater coil 710 towards the downstream portion 714 of the first heater coil.

As the air flow approaches the downstream end of the first heater coil, it encounters the upstream portion 772 of the aerodynamic structure 770. The elongate conical shape of the upstream portion of the aerodynamic structure encourages air from the centre of the heater assembly out towards the heater coils. The air flow will then continue from the upstream portion 722 of the second heater coil 720 towards the downstream portion 724 of the second whilst being pushed away from the centre of the heater assembly and concentrating the air flow towards the heater coils, which may be tapered as discussed above.

In other words, the air flowing through the heater assembly is formed into an anulus of flowing air by the aerodynamic structure, which is similar in size and shape to the heater coils, thereby maximising contact between the heater coils and the air flow.

Figs. 6 and 7 show the heater assembly of Fig. 1 with a downstream temperature sensor 780 provided at a downstream end of the second heater coil 720, which is adapted to measure a downstream air flow temperature and an intermediate temperature sensor 790 provided between the first heater coil 710 and the second heater coil, which is adapted to measure an intermediate air flow temperature. The downstream air flow temperature is the temperature of the air flowing out of the downstream end of the heater assembly. The intermediate air flow temperature is the temperature of the air after it has passed the first heater coil but before it has reached the second heater coil. The downstream air flow temperature and the intermediate air flow temperature may be mass average temperatures.

The first heater coil 710, the second heater coil 720, the downstream temperature sensor 780 and the intermediate temperature sensor 790 may be in communication with a heater control circuit (not shown). The heater control circuit may be adapted to control the first heater and the second heater in response to the intermediate air flow temperature and/or the downstream air flow temperature. The various functions of the heater control circuit are described in further detail below.

The downstream temperature sensor and the intermediate temperature sensor may be thermistors.

In the examples shown in Figs. 6 and 7, the downstream temperature sensor and the intermediate temperature sensor are radially offset from the central axis of the heater assembly. Further, in the examples shown clearly in Fig. 7, the downstream temperature sensor 780 and the intermediate temperature sensor 790 are rotationally offset from each other about the central axis. Put another way, the temperature sensors are displaced from the central axis of the heater in opposite directions.

The heater assembly 700 shown in Figs. 6 and 7 may further comprise a heater supporting structure 750, as shown in Figs. 2 and 4, arranged coaxially about the central axis of the heater assembly and adapted to support the first heater and the second heater.

The radially projecting fins 760 of the heater supporting structure would then define a plurality of fluid flow channels through the heater assembly. For example, if the heater supporting structure comprised six radially projecting fins, six fluid flow channels would be defined. Due to the rotational offset of the temperature sensors from each other, the downstream temperature sensor 780 and the upstream temperature sensor 790 would be provided in different fluid flow channels.

Fig. 8 shows a fully assembled heater assembly 700 comprising all of the various aspects described above housed within a heater housing 810. Fig. 9 shows an exploded view of the heater assembly of Fig. 8. As demonstrated in these Figures, all of the concepts discussed herein may be incorporated into a single heater assembly for use in a haircare appliance. However, it will also be appreciated that each concept may he employed individually within a given heater assembly.

Figs. 10A and 10B show perspective views of a main body 1000 of a haircare appliance which may be used in embodiments of the present invention. The main body 1000 comprises an outer wall 1005 which functions as a handle for the haircare appliance, and which has a fluid inlet 1015 at a first end 1010 and a fluid outlet 1025 at a second end 1020, with a fluid flow path through the main body 1000 from the fluid inlet 1015 to the fluid outlet 1025. The outer wall 1005 defines an elongate tubular structure for the main body 1000, wherein the cross-sectional shape of the main body 1005 perpendicular to the longitudinal axis is elliptical or oval such that the main body 1000 is ergonomically designed to be comfortable for a user to hold.

The main body may contain any of the heater assembly 700 arrangements outlined above within a heater housing 810 contained in the main body 1000. As shown in Fig. 8, the heater housing comprises a fluid input 820 and a fluid output 830 and an inner wall of the heater housing defines a fluid flow path between the fluid input and the fluid output the heater housing. The fluid flow path of the heater housing forms part of the fluid flow path of the main body.

The main body 1005 houses an airflow generator, such as a motor, which is configured to generate a flow of fluid (in particular, air) along the fluid flow path. The fluid is optionally heated by a heater assembly as described above before exiting the main body 1000 at the fluid outlet 1025.

The haircare appliance may comprise various circuitry arrangements for controlling the functions of the haircare appliance. For example, the haircare appliance may comprise a heater control circuit in communication with the heater assembly, which is adapted to control the provision of power to the first and second heater, and an airflow generator control circuit for controlling the airflow generator. The heater control circuit and the airflow generator control circuit may be integrated on the same circuit board or on different circuit boards.

The heater control circuit may be adapted to control the first heater and the second heater in response to the intermediate air flow temperature and/or the downstream air flow temperature when the heater assembly includes the downstream temperature sensor and the intermediate temperature sensor as described above with reference to Figs. 6 and 7.

Further, the airflow generator control circuit may he in communication with the heater control circuit and adapted to control the airflow generator in response to the intermediate air flow temperature and/or the downstream air flow temperature.

The heater control circuit may be adapted, either independently or in combination with other control circuitry of the haircare appliance, to implement the following method for controlling the heater assembly comprising a downstream temperature sensor and an intermediate temperature sensor.

When the haircare appliance is being operated and air is flowing through the air flow path under the power of the airflow generator an intermediate air flow temperature may be measured using the intermediate temperature sensor and a downstream air flow temperature may be measured using the downstream temperature sensor.

If the intermediate air flow temperature and/or the downstream air flow temperature is below a target temperature, for example a target temperature to be measured at the intermediate and/or downstream thermistor, and the first heater and the second heater are inactive, the first heater and/or the second heater may be activated, for example according to the heater duty cycles discussed above. This threshold may be based on a target thermistor temperature.

If the intermediate air flow temperature and/or the downstream air flow temperature is above an upper threshold, for example 250°C, and the first heater and/or the second heater is active, the active heater(s) is deactivated.

In addition, by way of the communication link between the heater control circuit and the airflow generator control circuit, if the intermediate air flow temperature and/or the downstream air flow temperature is above an upper threshold, the air flow generation unit may be controlled to stop generating the air flow through the heater assembly.

The main body 1000 is connectable to a power supply via a power cable 1030 which extends from the first end 1010 of the main body 1000. However, in some embodiments, the main body 1000 may further house one or more batteries such that the power cable 1030 may not be required. In either case, the haircare appliance comprises a power delivery system electrically connected to the heater assembly. The power delivery system may be adapted to deliver at least 1000W, such as 1500W, to the heater assembly.

The main body comprises a user interface which may include control settings for the haircare appliance. In this embodiment, the user interface is split, with a first portion of the user interface 1040a being positioned towards a first end 1010 of the main body 1000, and a second portion of the user interface 1040b being positioned towards a second end 1020 of the main body 1000. However, it will be understood that, in other embodiments, the user interface may be generally positioned at a single location on the main body 1000.

The main body 1000 is configured to allow an attachment to be removably connected thereto, by comprising at least a portion of an attachment mechanism at or about the second end 1020 of the main body 1000. The attachment mechanism enables a user to create different hair styles and gives the haircare appliance additional functionality, by allowing the attachment to be removed and replaced with an alternative attachment.

Claims

CLAIMS1. A heater assembly (700) for use in a haircare appliance comprising a heater control circuit, the heater assembly comprising: a first heater (710) having an upstream end (712) and a downstream end (714); and a second heater (720) having an upstream end (722) and a downstream end (724), wherein the downstream end of the first heater is upstream of the upstream end of the second heater; a downstream temperature sensor (780) provided at a downstream end of the second heater, wherein the downstream temperature sensor is adapted to measure a downstream air flow temperature; and an intermediate temperature sensor (790) provided between the first heater and the second heater, wherein the intermediate temperature sensor is adapted to measure an intermediate air flow temperature, and wherein the first heater, the second heater, the downstream temperature sensor and the intermediate temperature sensor are in communication with the heater control circuit, and the heater control circuit is adapted to control the first heater and the second heater in response to the intermediate air flow temperature and/or the downstream air flow temperature.
2. The heater assembly (700) claimed in claim 1, wherein the downstream temperature sensor (780) is a thermistor.
3. The heater assembly (700) claimed in any of claims 1 to 2, wherein the intermediate temperature (790) sensor is a thermistor.
4. The heater assembly (700) claimed in any of claimed 1 to 3, wherein the downstream temperature (780) sensor and the intermediate temperature sensor (790) are radially offset from the central axis of the heater assembly.
5. The heater assembly (700) claimed in claim 4, wherein the downstream temperature sensor (780) and the intermediate temperature sensor (790) are rotationally offset from each other about the central axis.
6. The heater assembly (700) claimed in claim 5, wherein the downstream temperature sensor (780) and the intermediate temperature sensor (790) are rotationally offset from other by 180°.
7. The heater assembly (700) claimed in any of claims 5 to 6, wherein the heater assembly further comprises a heater supporting structure (750) arranged coaxially about the central axis of the heater assembly and adapted to support the first heater and the second heater.
8. The heater assembly (700) claimed in claim 7, wherein the heater supporting structure (750) comprises a plurality of radially projecting fins (760), wherein the plurality of radially projecting fins defines a plurality of fluid flow channels through the heater assembly.
9. The heater assembly (700) claimed in claim 8, wherein the plurality of radially projecting fins (760) comprises six radially projecting fins, wherein the six radially projecting fins define six fluid flow channels.
10. The heater assembly (700) claimed in claims 8 to 9, wherein the downstream temperature sensor (780) and the upstream temperature sensor (790) are provided in different fluid flow channels.
11. The heater assembly (700) claimed in any of claims 1 to 10, wherein the first heater (710) comprises a first heater coil, and wherein the second heater (720) comprises a second heater coil.
12. The heater assembly (700) claimed in claim 11, wherein the first heater coil and the second heater coil are arranged coaxially about the central axis of the heater assembly.
13. A haircare appliance (800) comprising: a heater housing (810) having a fluid input and a fluid output, the heater housing having an inner wall defining a fluid flow path between the fluid input and the fluid output the heater housing; the heater assembly (700) claimed in any of claims 1 to 12 disposed in the fluid flow path of the heater housing, wherein the heater assembly is arranged such that the first heater is disposed proximate the air input and the second heater is disposed proximate the air output; an airflow generator for generating airflow though the heater housing; and a heater control circuit in communication with the heater assembly and adapted to control the first heater and the second heater in response to the intermediate air flow temperature and/or the downstream air flow temperature.
14. The haircare appliance (800) claimed in claim 13, wherein the haircare appliance further comprises an airflow generator control circuit adapted to control the airflow generator.
15. The haircare appliance (800) claimed in claim 14, wherein the airflow generator control circuit is in communication with the heater control circuit, and wherein the airflow generator control circuit is adapted to control the airflow generator in response to the intermediate air flow temperature and/or the downstream air flow temperature.
16. A method for controlling a heater assembly of a haircare appliance comprising an first heater having an upstream end and a downstream end and a second heater, having an upstream end and a downstream end, wherein the downstream end of the first heater is upstream of the upstream end of the second heater, the heater assembly further comprising a downstream temperature sensor provided at a downstream end of the second heater and an intermediate temperature sensor provided between the first heater and the second heater, the method comprising the steps of: measuring an intermediate air flow temperature using an intermediate temperature sensor of the heater assembly; measuring a downstream air flow temperature using a downstream temperature sensor of the heater assembly; and if the intermediate air flow temperature and/or the downstream air flow temperature is below a target temperature and the first heater and the second heater are inactive, activating the first heater and/or the second heater; or if the intermediate air flow temperature and/or the downstream air flow temperature is above an upper threshold, deactivating the first heater and the second heater.
17. The method claimed in claim 16, wherein the upper threshold is 250°C
18. The method claimed in any of claims 16 to 17, wherein the method further comprises: controlling an air flow generation unit to generate an air flow through the heater assembly; and if the intermediate air flow temperature and/or the downstream air flow temperature is above an upper threshold, controlling the air flow generation unit to stop generating the air flow through the heater assembly.
19. A computer program product comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method of claims 16 to 18.
20. A computer-readable medium having stored thereon the computer program product of claim 19.