WO2024184723A1

WO2024184723A1 - Heater for a hand held appliance

Info

Publication number: WO2024184723A1
Application number: PCT/IB2024/051860
Authority: WO
Inventors: Giovanni LACAGNINA; Benjamin HOGAN; Robert Streeter
Original assignee: Dyson Technology Limited
Priority date: 2023-03-03
Filing date: 2024-02-27
Publication date: 2024-09-12
Also published as: GB202303147D0; GB2627816A

Abstract

Disclosed is heater for a hand held appliance. The heater comprises a support, a heating element supported by the support and a sensor assembly secured to the support. The sensor assembly is configured to measure a temperature of the support.

Description

Heater for a Hand Held Appliance

BACKGROUND

Hand held appliances such as hair care appliances and hot air blowers are known. Such appliances are provided with a heater to heat either fluid flowing through the appliance or a surface at which the appliance is directed. Such devices may have a pistol grip arrangement, with a handle including switches and a body which houses components such as a fan unit and a heater. Another form is for a tubular housing such as found with hot styling devices. Thus, generally the option is to have fluid and/or heat blowing out of an end of a tubular housing and either to hold onto that housing or be provided with a handle generally orthogonal to the tubular housing.

Traditional heaters are often made from a scaffold of an electrically insulating material, for example mica, around which a resistive wire such as nichrome wire is wound. Such heaters are prone to generating local temperature hot-spots and require safety features that can turn off the product in case of a faulty operation such as abnormally high temperature in the heater. These safety features traditionally comprise thermal fuses which are bulky and create obstructions in the airflow path. These thermal fuses generally need to be positioned carefully, in order to sense the abnormal temperatures quickly while avoiding false triggers which may be created by small fluctuations in the operating conditions of the appliance.

SUMMARY

According to an aspect of the present invention, there is provided a heater for a hand held appliance, the heater comprising a support, a heating element supported by the support, a sensor assembly secured to the support and configured to measure a temperature of the support.

Configuring the sensor assembly to measure the temperature of the support enables the support to operate as an extension of the temperature sensor and reduces the need for a bulky safety feature to be placed in an airflow path of the appliance.

Omission of a bulky safety feature for temperature measurement also means that the risk associated with incorrect positioning of the safety feature (e.g., not detecting the abnormal temperatures quickly enough or causing false triggers during normal operation due to possible small fluctuation in operating conditions) within the heater is removed and the airflow path is not obstructed with a bulky component.

In traditional open-wire heaters, a typical heating element is usually a coil, ribbon or a strip of wire that gives off heat when an electric current flows through it. The electrical energy passing through the heating element is converted into heat and radiates out in all directions. Generally, heaters comprising such heating elements comprise concentric circular heating elements positioned in front or behind an air moving device (e.g., an electric fan or motor) so they can transport heat more quickly by convection. As such, the air heats up as it passes through the appliance and comes into contact with the heating element of the appliance along the airflow path.

A benefit of an arrangement according to the first aspect is that the support member of the heater operates as a member of the sensor assembly, removing the need to introduce a bulky component to the airflow path. Accordingly, a more compact heater arrangement with accurate, quick, and reliable temperature measurement can be achieved.

The sensor assembly may be embedded in the support. This may help reduce the need for or obviate placement of a further safety feature for temperature measurement at another location and may provide a more compact heater than, for example, a traditional open-wire heater comprising a thermal fuse as a safety feature.

The sensor may be configured to measure temperatures at a plurality of points along a length and/or a width of the support. This may help to obtain a more reliable temperature measurement at a plurality of locations along the airflow path of the appliance and reduce the likelihood of possible small fluctuation in operating conditions triggering a faulty condition.

The sensor of the present invention may comprise a conductive trace. For example, the sensor may comprise an integrated RTD (Resistance Temperature Detector). RTD sensors have many advantages over thermal fuses. These advantages include higher accuracy, higher repeatability, better consistency, more precise measurement in extreme operation states, better long-term stability. The sensor of the present invention may further comprise a plurality of discrete conductive traces embedded in the support. This may aid in obtaining more reliable and accurate temperature measurements along the length and width of the heater.

A Resistance Temperature Detector (RTD) is a sensor whose resistance changes as its temperature changes. An RTD is a passive device and does not produce an output on its own. External electronic devices are used to measure the resistance of the sensor, for example by passing a small electrical current through the sensor to generate a voltage. Alternatively, the resistance of the sensor may be measured by applying a known voltage across two terminals of the RTD. This voltage applied across two terminals of the RTD may be up to around 24 V. In a further embodiment, the known voltage applied to the terminals of the RTD may be up to around 12 V and more preferably in the range of 3 V to 12 V. In a further embodiment, the known voltage applied to the terminals of the RTD may be in the range of 3 V to 5 V. The resistance value of the RTD may be in the range of 5 Ohms to 35 Ohms when measured at 25°C. Additionally or alternatively, the resistance value of the RTD may be in the range of 40 Ohms to 420 Ohms when measured at 470°C. In one example the resistance of the RTD may be in the range of 15 Ohms to 25 Ohms when measured at 25°C and 380 Ohms to 420 Ohms when measured at 470°C. Depending on the power output requirements of the heater, a different range of the RTD resistance may be defined. For example, the resistance value of the RTD may be in the range of 5 Ohms to 15 Ohms when measured at 25°C and in the range of 90 Ohms to 110 Ohms when measured at 470°C. In a further example, the resistance value of the RTD may be in the range of 15 Ohms to 25 Ohms when measured at 25°C and in the range of 60 Ohms to 80 Ohms when measured at 470°C. In a further example, the resistance value of the RTD may be in the range of 25 Ohms to 35 Ohms when measured at 25°C and in the range of 40 Ohms to 60 Ohms when measured at 470°C.

The heating element of the present invention may comprise a wire element. Wire elements in heaters are simple to manufacture. The wire elements may be configured to produce power outputs of up to around 1200 to 1500W, which are suitable for hair care appliances.

This may aid in reducing the cost, complexity, and assembly time of the heating element.

By nature, an electric heating element gets hot often and ordinary alloys cannot endure such extent of heat for a long period. It is therefore preferred that the heating element comprises nickel-based or iron-based material. The heating element may comprise nichrome material. This may provide high electric resistivity and prolonged service life, as well as endurance potential as a heating material.

The support may comprise a spacer extending along a central longitudinal axis and the sensor may be secured to the spacer. This may provide a space-efficient arrangement for heating element and sensor assembly along the airflow path.

The spacer may comprise or be formed from an electrically insulating material. For example, the spacer may comprise or be formed from a mica or a ceramic material. This may provide effective electrical insulation between windings of the thermally active heating element.

The spacer may comprise or be formed from a thermally conductive ceramic layer. Thermal conductivity of the ceramic layer may be in the range of 150 W/mK to 300 W/mK when measured at 0°C. Thermal conductivity of the ceramic layer may be in the range of 20 W/mK to 80 W/mK when measured at 500°C. Suitable ceramic materials include aluminium nitride, aluminium oxide and silicon nitride. This may provide a support comprising a spacer with higher thermal conductivity while providing electrical insulation. Advantageously this provides more accurate temperature readings. This may also be advantageous in ensuring better dissipation of thermal energy across the surface of the support therefore reducing the likelihood of temperature hot spots forming along the airflow path.

The spacer may comprise a multi-layered plate, such as a thermally conductive ceramic multi-layered plate. The multi-layered plate may comprise a sensor assembly, located between layers of electrically insulating material, such as ceramic or mica. The conductive trace may be a metal. Examples of suitable metals include tungsten, tantalum, molybdenum or any combination thereof. Preferably, the ceramic multi-layered plate comprises a high temperature co fired ceramic (HTCC). The track may be printed to ceramic material in its green state, covered with another layer of the ceramic material and then the multi-layered plate is sintered as a single unit.

The multi-layered plate may comprise two ceramic layers and the sensor assembly may be sandwiched between said two ceramic layers. This may provide a more compact support and sensor arrangement. The multi-layered plate may comprise further ceramic layers and sensor assemblies. This may provide a more reliable arrangement especially under more challenging operating conditions.

The spacer may further comprise insertion recesses. This may provide a space efficient arrangement for supporting various components of the heater.

The insertion recesses may be substantially uniformly spaced along the length of the spacer. This may reduce the cost, complexity, and assembly of the heater. This may also provide a more effective and even distribution of components that are supported by the insertion recesses.

The heating element may be located in the insertion recesses. This may be advantageous in ensuring the windings of the heating element are evenly spaced along the length of the support member and therefore reducing the chance of hot spots and restrictions to air or fluid flow through the heater. This may also aid in keeping individual windings of the heating element separate from each other, therefore preventing any potential electrical short-circuit faults.

The heater may comprise a further support for supporting the heating element, such that the further support may not comprise a sensor assembly. It is envisioned that the heater may comprise more than one support feature. However, it may not be necessary to secure a sensor assembly to each of the said support features. This may reduce a part count of the heater, which may reduce the cost, complexity, and assembly time of the heater. The further support may comprise a further spacer extending along and orthogonally from (or transverse to) a central longitudinal axis. For example, each space may have a generally planar shape having a central axis that lies in the plane. Multiple spacers may be arranged so the planes of the spacers are non-parallel but share a central axis, i.e. the planes of the spacers may cross each other at the central axis. This may provide continuous and even structural support to the heating element along the central longitudinal axis.

The further spacer may comprise or be formed from an electrically insulating material. For example, the further spacer may comprise or be formed from a mica or a ceramic material. This may provide effective electrical insulation between windings of the thermally active heating element.

The heating element may be wound along the length of the support. This may provide a greater volume for increased heat transfer from the heating element to the surrounding area.

The heating element may comprise a helical coil wound around the support structure. This may provide an increased heat transfer because the coils increase the amount of surface area in contact with the substance to be heated.

The heating element may be shaped into zig zags or undulations . This may be advantageous as a relatively larger heating surface area may be fitted in a relatively shorter spacer length. This may help the heater meet predefined space and performance requirements. This may also reduce cost, complexity, and assembly time for the heater.

The heater may comprise a housing extending around and along the length of the support structure. This may be advantageous in ensuring integration of the heater, for example in a handle of a handheld appliance. More specifically, handheld appliances may comprise a handle including switches and a body which houses components such as a fan unit and a heater in various forms, for example in a pistol grip arrangement.

The housing may be in the form of a tube such as found with hot styling devices. This may be advantageous when generally the option is to have fluid and/or heat blowing out of an end of a tubular housing and either to hold onto that housing or be provided with a handle orthogonal to the tubular housing.

According to a further aspect of the present invention, there is provided a hair care appliance such as a hairdryer or a hot styling brush comprising a heater according to the invention.

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

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows an exploded view of a heater according to the invention;

Figure 2 shows a cross section through the heater of Figure 1;

Figure 3 shows another cross section through the heater of Figure 1;

Figure 4 shows an exploded view of the heater of Figure 1;

Figures 5a and 5b show an appliance in which the heater of Figures 1 to 4 is used;

Figures 6a and 6b show an appliance in which the heater of Figures 1 to 4 is used; and

Figures 7a and 7b show an appliance in which the heater of Figures 1 to 4 is used.

DETAILED DESCRIPTION

Referring to Figures 1 to 4, there is described a heater module 10. The heater module 10 has a support structure 116 comprising a number of spacers 102, 104, 106, which extend radially out from a central longitudinal axis 108. Each of the spacers 102, 104, 106 has a generally planar shape. The spacers 100, 102 and 104 include insertion recesses 110, in which a heating element 112 is located. The heating element 112 is a wire, which is shaped into zig zags or undulations and then wound around spacers 102, 104, 106. The wire of the heating element 112 may be made from a suitable material, such as Nichrome. The spacers 102, 104, 106 provide support for the heating element 112 as it is wound around the central longitudinal axis 108 of the support structure 116. The insertion recesses 110 keep individual coils 114 of the heating element 112 separate from each other. The insertion recesses 110 maintain the spacing between different coils 114 of the heating element, reducing the chance of hot spots and restrictions to air or fluid flow through the heater.

The spacers 102, 104, 106 are formed from an electrically insulating material, such as Mica or ceramic. Suitable ceramic materials include aluminium nitride, aluminium oxide and silicon nitride.

In this embodiment, the spacers 102, 104, 106 overlap at the longitudinal axis 108 of the support structure 116 and project radially from this central axis 108 such that the support structure 116 has a star-shaped cross-section. The angles between the planes of each of the spacers 102, 104, 106 are equal such that the spacers 102, 104, 106 project at equal intervals around the circumference of the support structure 116. However other shapes can be used such as a quad or cross shaped support, or a tri-support which is geometrically similar to a triangular prism.

The spacers 102, 104 and 106 are formed from rectangular pieces of an electrically insulating material, such as Mica and/or ceramic. Referring to Figure 4, the spacer 102 is provided with an opening 102b configured to receive the spacer 104. The spacer 104 is provided with a further opening 104b configured to receive spacer 106. Accordingly, as shown in Figure 4, the spacers 102, 104 and 106 can be inserted and connected to one another along the central longitudinal axis 108 such that one long edge 102a, 104a, 106a of each of the spacers 102, 104 and 106 form an apex of the star-shaped support. This star shaped support 116 forms the frame around which a wire heating element 112 is wound. The spacers 102, 104 and 106 are connected to one another by interference fit to hold the spacers in position. The interference fit is at least partly a tapered interference fit. The interference fit is preferably a longitudinal interference fit.

Each of the spacers 102, 104 and 106 have insertion recesses 110 extending along the length of the longitudinal edges of the spacers 102, 104, 106. The long edges of the spacers 102, 104, 106 are the edges at the apexes of the support structure 116. In other words, the long edges are the outermost edges of the support structure 116 when the spacers 102, 104, 106 are connected to one another along the central longitudinal axis 108. The recesses 110 for each of the spacers 102, 104 and 106 are disposed along the length of the long sides 102a, 104a, 106a of each of the spacers 102, 104, 106. The wire heating element 112 is wound around the spacers 102, 104, 106 and held within the insertion recesses 110a. Thus, the spacers 102, 104, 106 provides supports for the heating element 112 along and around the length of the heater module 10.

At least one of the spacers 102, 104 and 106 further comprises a temperature sensor 118. The temperature sensor 118 includes a conductive trace 118a that is embedded within the spacer and a terminal 118b that is exposed for electrical connection. In one example, the temperature sensor comprises a thermistor, thermocouple, or other suitable temperature measuring sensor. In a preferred embodiment the temperature sensor comprises a resistive temperature detector (RTD).

Around the outside of the support structure 116, an outer tube 100 is provided. This outer tube 100 is optional and provides an insulating layer for the heater module 10 and whatever houses the heater module 10.

Figures 5a and 5b show a hot styling appliance 200 which incorporates a heater module 210. The hot styling appliance 200 has a body 220 and a styling head 240. The body 220 has an inlet 260 at one end where fluid is drawn into the appliance through the action of a fan unit 280. The fluid is subsequently heated by a heater 210 before entering the head 240. The heater 210 shown in Figure 5b may take the form of the heater 10, described above in relation to Figures 1 to 4. In order to enable a variety of temperature and flow rates through the appliance, a PCB 250 is provided. The PCB is electrically coupled to both the heater 210 and the fan unit 280 and can vary the power supplied to both. As an example, a user can choose different power and heater settings. The PCB 250 controls the power to heating element 112 so, for different temperature settings, heating performance can be varied. In addition, the speed at which the fan unit 280 is operated can be varied to enable wet hair to be dried quickly initially and then the one or more of the heat and power can be reduced or increased to enable styling. During use, a user holds the body 220 of the appliance 200, so the body 220 forms a handle of the appliance 200 and thus the heater 220 is positioned within the handle of the appliance 200.

The heater 10, described above in relation to Figures 1 to 4, is suitable for use in other heated blowers such as conventional hairdryers and in particular travel appliances where space is limited.

Figures 6a and 6b show a hairdryer 300 which incorporates heater 310. The hairdryer 300 is an amplifying hairdryer where the airflow 312 that is drawn into the appliance by the action of a fan unit 380 is augmented or increased by an entrained flow passing through a duct 372.

The hairdryer 300 has a handle 320 and a body 330. An inlet 360 is provided in the handle 320 at the distal end from the body 330. Fluid is drawn into the inlet 360 by the action of a fan unit 380 and flows within a fluid flow path 312 along the handle 320 from the inlet 360 towards the body 330. The fluid flow path 312 within the handle 320 is generally circular but, within the body it becomes annular.

In operation, the fan unit 380 draws fluid in through the inlet 360 and along the fluid flow path 312 to the body 330, through the heater 310 and to the fluid outlet 370. The action of this fluid flowing through the hairdryer and out of the fluid outlet 370 causes fluid to be entrained or pulled into the duct 372 at a second inlet 374 and along an entrained fluid flow path 376. As can be seen, the heater 310 is located within the handle 320. The heater 2310 shown in Figure 6b may take the form of the heater 10, described above in relation to Figures 1 to 4.

In this example the processed flow exits from the hairdryer as an annular ring that extends around the entrained flow. Thus, the output from the hairdryer is a heated ring of fluid surrounded on both sides by cooler air. As an alternative, the fluid outlet 370 is located within the body 330 and the heated fluid mixes with the entrained flow before the fluid exits from the appliance.

Power is supplied to the hairdryer via a cable 382 which enters the hairdryer 300 at the inlet 360. Internal wiring (not shown) provides power to the heater 310 and the fan unit 380 to run a motor that drives the impeller of the fan unit 380.

In order to provide a variety of temperature and flow rates through the appliance, a PCB 350 is provided. The PCB 350 is electrically coupled to both the heater 310 and the fan unit 380 and enables a user to vary power to both. As an example, the user can choose different power and heat settings. The PCB 350 controls the power to heating element so for low temperature settings, the heater is powered with lower electrical current. In addition, the speed of the fan unit 380 can be varied to change the flow through the appliance.

Figures 7a and 7b show a further hairdryer 400 having a curved outer profile which incorporates a heater 410. There is a straight section 420, which includes a handle 422, and a curved section 430. The heater 410 can be housed in the straight section 420 and/or the curved section 430. The heater 410 shown in Figure 7b may take the form of the heater 10, described above in relation to Figures 1 to 4.

A fluid flow path 412 is provided through the appliance from a fluid inlet 460 which is provided at a first end 462 of the straight section 420 to a fluid outlet 470. The fluid outlet 470 is provided adjacent or downstream of the distal end 432 of the curved section 430 from the straight section 420. In this embodiment, there is a second straight section 440 provided downstream of the heater 410 or between the curved section 14 and the fluid outlet 470. In all of the embodiments shown, the heating element 112 is made of two separate wires 112a and 112b. However, in an alternative embodiment the heating element 112 can be made from a single continuous wire. The two separate wires 112a and 112b can be controlled independently. Alternatively, the heating element 112 may comprise more than two separate wires that can be controlled independently. Each separate wire can be designed to have the same power output or different power outputs. For example, one wire can have twice the power output of the other. The different power outputs can be achieved by various arrangements that will be apparent to the skilled person. The arrangement may include using separate wires of different gauge or different length. Alternatively, the arrangement may include using separate wires of the same gauge and different length. In a further alternative, the arrangement may include using separate wires of different gauge and the same length.

Referring now to Figures 2 and 3, the heater 10 will be described in more detail. The heater 10 comprises spacers 102, 104, 106, each spacer being formed from a flat plate. At least one of the spacers, for example spacer 102, is a thermally conductive ceramic plate such as aluminium nitride. The plate 102 has a conductive trace 118a, which is typically screen printed onto the flat ceramic plate when in its green state. The ceramic plate may be covered with a further layer of the ceramic material. The ceramic plate, conductive trace and, if applied, the further layer of ceramic material are sintered as a single unit. Heat is dissipated from the heating element 112 via the airflow passing through the heater module 10 to the spacer 102. The conductive trace 118a is embedded in the thermally conductive spacer 102. When the heater 10 is used as the heater 210, 310 or 410 in the embodiments of Figures 5a and 5b, 6a and 6b or 7a and 7a, respectively, it may be electrically coupled to the respective PCB 250, 350, 450 via the terminal 118b.

In this example, the temperature sensor 118 is a resistance temperature detector (RTD). The conductive trace 118a of the temperature sensor 118 is thermally exposed to the thermally conductive spacer 102. The temperature of the area surrounding the spacers 102, 104, 106 is determined based on the measured current through the temperature sensor 118. To measure temperature with an RTD, at the site whose temperature is of interest, the RTD is thermally exposed. A known voltage is applied to the terminals of the RTD. Measured current through the RTD then provides a value indicative of the temperature surrounding the area in which RTD is placed. Alternatively, a known current is passed through the RTD. Measured voltage across the RTD then provides a value indicative of temperature surrounding the area in which RTD is placed.

In this example, only one of the spacers 102, 104 and 106 comprises a temperature sensor 118. However, in further examples, all or a subset of the spacers 102, 104 and 106 may comprise a temperature sensor 118.

The invention has been described in detail with respect to a hairdryer, however, it is applicable to any appliance that draws in a fluid and directs the outflow of that fluid from the appliance.

The appliance has been described without discussion of any attachment such as a concentrating nozzle or a diffuser, however it would be feasible to use one of these known types of attachment in order to focus the exiting fluid or direct the fluid flow differently to the manner in which it exits the appliance without any such attachment.

The invention is not limited to the detailed description given above. Variations will be apparent to the person skilled in the art.

Claims

1. A heater for a hand held appliance, the heater comprising: a support; a heating element supported by the support; a sensor assembly secured to the support and configured to measure a temperature of the support.

2. A heater according to claim 1, wherein the sensor assembly is embedded in the support.

3. A heater according to any of claim 1 or claim 2, wherein the sensor is configured to measure temperatures at a plurality of points along a length and/or a width of the support.

4. A heater according to any preceding claim, wherein the sensor comprises an integrated resistance temperature detector (RTD).

5. A heater according to any preceding claim, wherein the heating element comprises a wire element.

6. A heater according to any preceding claim, wherein the support comprises a spacer extending along a central longitudinal axis and the sensor assembly is secured to the spacer.

7. A heater according to claim 6, wherein the spacer is formed from an electrically insulating material.

8. A heater according to any of claims 6 or 7, wherein the spacer comprises a thermally conductive ceramic layer.

9. A heater according to claim 8, wherein the thermally conductive ceramic layer comprises a multi-layered plate.

10. A heater according to claim 9, wherein the multi-layered plate comprises two ceramic layers and the sensor assembly is sandwiched between two ceramic layers.

11. A heater according to any preceding claim, wherein the support comprises insertion recesses.

12. A heater according to claim 11, wherein the insertion recesses are substantially uniformly spaced along the length of the support.

13. A heater according to claim 11 or 12, wherein the heating element is located in the insertion recesses.

14. A heater according to any preceding claim, wherein the heater comprises a further support for supporting the heating element, and wherein the further support does not comprise a sensor assembly.

15. A heater according to claim 14, wherein the further support comprises a further spacer extending along and orthogonally from a central longitudinal axis.

16. A heater according to claim 15, wherein the further spacer is formed from an electrically insulating material.

17. A heater according to claim 15 or 16, wherein the further spacer is formed from mica.

18. A heater according to any preceding claim, wherein the heating element is wound along the length of the support.

19. A heater according to any preceding claim, wherein the heating element comprises a helical coil wound around the support structure.

20. A heater according to any preceding claim, wherein the heating element is shaped into zig zags or undulations.

21. A heater according to any preceding claim, wherein the heater comprises a housing extending around and along the length of the support structure.

22. A heater according to claim 21, wherein the housing is a tube.

23. A haircare appliance comprising a heater according to any preceding claim.

24. A hairdryer comprising a heater according to any of claims 1 to 22.

25. A hot styling appliance comprising a heater according to any of claims 1 to 22.