Heater for hand-held appliance

Abstract

The invention discloses a heater for a handheld appliance. The heater includes 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

Background Art

[0001] Handheld appliances such as hair care appliances and hot air blowers are known. These appliances are equipped with a heater to heat the fluid flowing through the appliance or the surface it is directed at. These devices may have a pistol-grip design with a handle containing a switch and a main body housing components such as the fan unit and heater. Another form of device is a tubular housing, such as that used in heat styling devices. Therefore, it is common practice to direct the fluid and / or heat out of one end of the tubular housing, with the housing being held or otherwise provided with a handle generally perpendicular to the tubular housing.

[0002] Conventional heaters are typically constructed from a support of electrically insulating material (such as mica) around which a resistive wire, such as nichrome, is wound. Such heaters are prone to developing localized temperature hotspots and require safety features that can shut down the product in the event of malfunctioning operation (such as abnormally high temperatures in the heater). These safety features traditionally include thermal cutoffs, which are bulky and create obstructions in the airflow path. These thermal cutoffs often need to be carefully positioned to quickly sense abnormal temperatures while avoiding false triggering that could occur due to minor fluctuations in the appliance's operating conditions. Summary of the Invention

[0003] According to one aspect of the present invention, a heater for a handheld device is provided, the heater including a support, a heating element supported by the support, and a sensor assembly secured to the support and configured to measure a temperature of the support.

[0004] 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 bulky safety features placed in the airflow path of the appliance.

[0005] Omitting bulky safety features for temperature measurement also means that the risks associated with incorrect positioning of safety features within the heater (e.g. not detecting abnormal temperatures quickly enough due to possible small fluctuations in operating conditions or causing false triggering during normal operation) are eliminated, and the airflow path is not blocked by bulky components.

[0006] In traditional open-wire heaters, the heating element is typically a coil, ribbon, or wire that releases heat when current flows through it. The electrical energy passing through the element is converted into heat and radiated in all directions. Typically, heaters incorporating this type of heating element consist of concentric circles of heating elements positioned in front of or behind an air moving device (e.g., a fan or motor) to transfer heat more quickly through convection. This heats the air as it passes through the appliance and comes into contact with the heating element along the airflow path.

[0007] A benefit of the arrangement according to the first aspect is that the support member of the heater operates as a member of the sensor assembly, thereby eliminating the need to introduce bulky components into the airflow path. Accordingly, a more compact heater arrangement with accurate, fast and reliable temperature measurement can be achieved.

[0008] The sensor assembly may be embedded in the support. This may avoid or help reduce the need for another safety feature for temperature measurement at another location and may provide a more compact heater than, for example, a conventional open wire heater that includes a thermal fuse as a safety feature.

[0009] The sensor can be configured to measure the temperature at multiple points along the length and / or width of the support. This can help to obtain more reliable temperature measurements at multiple locations along the airflow path of the appliance and reduce the likelihood of possible small fluctuations in operating conditions triggering a fault condition.

[0010] The sensor of the present invention may include conductive traces. For example, the sensor may include an integrated RTD (resistance temperature detector). RTD sensors offer many advantages over thermal fuses, including higher accuracy, greater repeatability, improved consistency, more precise measurements under extreme operating conditions, and improved long-term stability. The sensor of the present invention may also include multiple discrete conductive traces embedded in the support. This can facilitate more reliable and accurate temperature measurements across the length and width of the heater.

[0011] A resistance temperature detector (RTD) is a sensor whose resistance changes as its temperature changes. An RTD is a passive device and does not generate its own output. External electronics are used to measure the sensor's resistance, for example by passing a small current through the sensor to generate a voltage. Alternatively, the sensor's resistance can be measured by applying a known voltage across the RTD's terminals. This voltage applied across the RTD's terminals can be up to approximately 24 V. In another embodiment, the known voltage applied to the RTD's terminals can be up to approximately 12 V, and more preferably, in the range of 3 V to 12 V. In another embodiment, the known voltage applied to the RTD's terminals can be in the range of 3 V to 5 V. When measured at 25°C, the resistance value of the RTD can be in the range of 5 ohms to 35 ohms. Additionally or alternatively, when measured at 470°C, the resistance value of the RTD can be in the range of 40 ohms to 420 ohms. In one example, the resistance of the RTD can be in the range of 15 ohms to 25 ohms when measured at 25°C, and in the range of 380 ohms to 420 ohms when measured at 470°C. Depending on the power output requirements of the heater, different ranges of RTD resistance can be defined. For example, the resistance value of the RTD can 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 another example, the resistance value of the RTD can 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 another example, the resistance value of the RTD can 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.

[0012] The heating element of the present invention may include a wire element. The wire element in the heater is easy to manufacture. The wire element can be configured to produce a power output of up to about 1200 to 1500 W, which is suitable for hair care appliances. This can help reduce the cost, complexity, and assembly time of the heating element.

[0013] By nature, electrical heating elements often get hot, and common alloys cannot withstand this level of heat for long periods of time. Therefore, it is preferred that the heating element comprise a nickel- or iron-based material. The heating element may comprise a nickel-chromium alloy material. This can provide high resistivity and an extended service life, as well as the potential for durability as a heating material.

[0014] The support may comprise a spacer extending along the central longitudinal axis, and the sensor may be secured to the spacer.This may provide a space-saving arrangement for the heating element and sensor assembly along the airflow path.

[0015] The spacer may comprise or be formed of an electrically insulating material. For example, the spacer may comprise or be formed of mica or a ceramic material. This may provide effective electrical insulation between the windings of the thermally active heating element.

[0016] The spacer may comprise or be formed from a thermally conductive ceramic layer. The thermal conductivity of the ceramic layer may be in the range of 150 W / mK to 300 W / mK when measured at 0°C. The 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 aluminum nitride, aluminum oxide, and silicon nitride. This can provide a support member comprising a spacer with higher thermal conductivity while providing electrical insulation. Advantageously, this provides a more accurate temperature reading. This can also help ensure that heat energy is better dissipated on the surface of the support member, thereby reducing the possibility of temperature hot spots forming along the airflow path.

[0017] The spacer may comprise a multilayer board, such as a thermally conductive ceramic multilayer board. The multilayer board may include the sensor assembly between layers of electrically insulating material, such as ceramic or mica. The conductive traces may be metal. Examples of suitable metals include tungsten, tantalum, molybdenum, or any combination thereof. Preferably, the ceramic multilayer board comprises a high-temperature co-fired ceramic (HTCC). The traces may be printed onto the ceramic material in a green state, covered with another layer of ceramic material, and then the multilayer board may be sintered into a single unit.

[0018] The multilayer board can include two ceramic layers, and the sensor assembly can be sandwiched between the two ceramic layers. This can provide a more compact support and sensor arrangement. The multilayer board can also include additional ceramic layers and sensor assemblies. This can provide a more reliable arrangement, especially under more challenging operating conditions.

[0019] The spacer may also include an insertion recess. This may provide a space efficient arrangement for supporting the various components of the heater.

[0020] The insert recesses can be substantially evenly spaced along the length of the spacer. This can reduce the cost, complexity, and assembly of the heater. This can also provide a more efficient and even distribution of components supported by the insert recesses.

[0021] The heating element can be positioned within the insertion recess. This can help ensure that the heating element's windings are evenly spaced along the length of the support member, thereby reducing the chance of hot spots and restrictions on air or fluid flow through the heater. This can also help keep the individual windings of the heating element separated from one another, thereby preventing any potential electrical short circuit failures.

[0022] The heater may include additional supports for supporting the heating element, such that the additional supports do not include the sensor assembly. It is contemplated that the heater may include more than one support feature. However, it may not be necessary to secure the sensor assembly to each of the support features. This may reduce the number of parts in the heater, which may reduce the cost, complexity, and assembly time of the heater.

[0023] Additional support members may include additional spacers extending along the central longitudinal axis and orthogonally (or transversely) thereto. For example, each space may have a generally planar shape with a central axis lying in a plane. Multiple spacers may be arranged such that their planes are non-parallel but share a common central axis, i.e., their planes may intersect at the central axis. This provides continuous and uniform structural support for the heating element along the central longitudinal axis.

[0024] The additional spacers may comprise or be formed from an electrically insulating material. For example, the additional spacers may comprise or be formed from mica or a ceramic material. This may provide effective electrical insulation between the windings of the thermally active heating element.

[0025] The heating element may be wound along the length of the support. This may provide greater volume to increase heat transfer from the heating element to the surrounding area.

[0026] The heating element may comprise a helical coil wrapped around a support structure. This may provide increased heat transfer as the coil increases the amount of surface area in contact with the substance to be heated.

[0027] The heating element can be shaped like a zigzag or corrugated shape. This can be advantageous because a relatively large heating surface area can be fitted into a relatively short spacer length. This can help the heater meet predefined space and performance requirements. It can also reduce the cost, complexity, and assembly time of the heater.

[0028] The heater may include a housing surrounding the support structure and extending along the length of the support structure. This may facilitate integration of the heater, such as within a handle of a handheld device. More specifically, the handheld device may include a handle including a switch and a body housing components such as the fan unit and heater in various configurations, such as a pistol grip arrangement.

[0029] The housing may be of tubular form, such as used in heat styling equipment. This may be advantageous as the usual option is to blow fluid and / or heat out one end of the tubular housing and hold the housing or provide a handle orthogonal to the tubular housing.

[0030] According to another 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 present invention.

[0031] Features described above in conjunction with the first aspect of the present invention are also applicable to other aspects of the present invention, and vice versa. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 shows an exploded view of a heater according to the present invention;

[0033] Figure 2 Shown through Figure 1 Cross section of the heater;

[0034] Figure 3 Shown through Figure 1 Another cross section of the heater;

[0035] Figure 4 Shown Figure 1 Exploded view of the heater;

[0036] Figure 5a and 5b Shown where to use Figures 1 to 4 heater appliances;

[0037] Figure 6a and Figure 6b Shown where to use Figures 1 to 4 appliances with heaters; and

[0038] Figure 7a and Figure 7b Shown where to use Figures 1 to 4 The heater appliance. DETAILED DESCRIPTION

[0039] refer to Figures 1 to 4 , depicts a heater module 10. The heater module 10 has a support structure 116 that includes a plurality of spacers 102, 104, 106 extending radially outward 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 an insert recess 110 in which a heating element 112 is located.

[0040] The heating element 112 is a wire that is formed into a zigzag or corrugated shape and then wrapped around the spacers 102, 104, 106. The wire of the heating element 112 can be made of a suitable material, such as a nickel-chromium alloy. The spacers 102, 104, 106 provide support for the heating element 112 as it is wrapped around the central longitudinal axis 108 of the support structure 116. The insert recess 110 keeps the individual coils 114 of the heating element 112 separated from each other. The insert recess 110 maintains the spacing between the different coils 114 of the heating element, thereby reducing the chance of hot spots and the restriction of air or fluid flow through the heater.

[0041] The spacers 102, 104, 106 are formed of an electrically insulating material, such as mica or ceramic. Suitable ceramic materials include aluminum nitride, aluminum oxide, and silicon nitride.

[0042] In this embodiment, the spacers 102, 104, 106 overlap at the longitudinal axis 108 of the support structure 116 and project radially from the central axis 108, giving the support structure 116 a star-shaped cross-section. The angles between the planar faces of each of the spacers 102, 104, 106 are equal, so that the spacers 102, 104, 106 project at equal intervals around the circumference of the support structure 116. However, other shapes may be used, such as quadrilateral or cross-shaped supports, or three supports geometrically similar to a triangular prism.

[0043] The spacers 102, 104, and 106 are formed from rectangular pieces of electrically insulating material such as mica and / or ceramic. Figure 4 , the spacer 102 is provided with an opening 102b, and the opening 102b is configured to receive the spacer 104. The spacer 104 is provided with another opening 104b configured to receive the spacer 106. Accordingly, Figure 4 As shown, the spacers 102, 104, and 106 can be inserted and connected to each other along the central longitudinal axis 108 so that one long edge 102a, 104a, 106a of each of the spacers 102, 104, and 106 forms the apex of a star-shaped support 116. The star-shaped support 116 forms a frame around which the wire heating element 112 is wound.

[0044] The spacers 102, 104 and 106 are connected to each other by an interference fit to hold the spacers in place. The interference fit is at least partially a tapered interference fit. The interference fit is preferably a longitudinal interference fit.

[0045] Each of the spacers 102, 104, and 106 has an insertion recess 110 extending along the length of a longitudinal edge of the spacer 102, 104, 106. The long edge of the spacer 102, 104, 106 is the edge at the vertex of the support structure 116. In other words, when the spacers 102, 104, 106 are connected to each other along the central longitudinal axis 108, the long edge is the outermost edge of the support structure 116. The recess 110 for each of the spacers 102, 104, and 106 is provided along the length of the long side 102a, 104a, 106a of each of the spacers 102, 104, 106. The wire heating element 112 is wrapped around the spacer 102, 104, 106 and retained within the insertion recess 110a. Thus, the spacers 102, 104, 106 provide support for the heating element 112 along and around the length of the heater module 10.

[0046] At least one of the spacers 102, 104, and 106 further includes a temperature sensor 118. The temperature sensor 118 includes conductive traces 118a embedded within the spacer and terminals 118b exposed for electrical connection. In one example, the temperature sensor includes a thermistor, a thermocouple, or other suitable temperature measurement sensor. In a preferred embodiment, the temperature sensor includes a resistance temperature detector (RTD).

[0047] Around the outside of the support structure 116, there is provided an outer tube 100. The outer tube 100 is optional and provides an insulating layer for the heater module 10 and any parts that house the heater module 10.

[0048] Figure 5a and 5b A heat styling appliance 200 is shown incorporating a heater module 210. The heat 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 by the action of a fan unit 280. The fluid is then heated by the heater 210 before entering the head 240. Figure 5b The heater 210 shown in FIG. 1 may be of the type described above. Figures 1 to 4 The form of heater 10 is described.

[0049] To achieve a variety of temperatures and flow rates through the appliance, a PCB 250 is provided. The PCB is electrically connected to both the heater 210 and the fan unit 280 and can vary the power supplied to both. For example, a user can select different power and heater settings. The PCB 250 controls the power supplied to the heating element 112, thereby varying the heating performance for different temperature settings. Furthermore, the speed of the fan unit 280 can be varied to quickly dry wet hair initially, and then one or more of the heat and power can be reduced or increased to facilitate styling. During use, the user grasps the body 220 of the appliance 200, which forms the handle of the appliance 200, and the heater 220 is therefore positioned within the handle of the appliance 200.

[0050] As above about Figures 1 to 4 The heater 10 is suitable for use with other heated blowers, such as conventional hair dryers, particularly in travel appliances where space is limited.

[0051] Figure 6a and 6b Shown is a hair dryer 300 comprising a heater 310. The hair dryer 300 is an amplified hair dryer in which the air flow 312 drawn into the appliance by the action of the fan unit 380 is enhanced or increased by entrained flow through the duct 372.

[0052] The hair dryer 300 has a handle 320 and a main body 330. An inlet 360 is provided in the handle 320 at the distal end of the main body 330. Fluid is drawn into the inlet 360 by the action of the fan unit 380 and flows from the inlet 360 toward the main body 330 along the handle 320 within the fluid flow path 312. The fluid flow path 312 within the handle 320 is generally circular, but becomes annular within the main body.

[0053] In operation, the fan unit 380 draws fluid into the body 330 through the inlet 360 and along the fluid flow path 312, through the heater 310, and to the fluid outlet 370. The action of this fluid flowing through the blower and out of the fluid outlet 370 causes the fluid to be entrained or pulled into the conduit 372 at the second inlet 374 and along the entrainment fluid flow path 376. As can be seen, the heater 310 is located within the handle 320. Figure 6b The heater 2310 shown in FIG. 2 may be of the type described above. Figures 1 to 4 The form of heater 10 is described.

[0054] In this example, the treated fluid exits the blower as an annular ring extending around the entrained flow. Thus, the blower's output is a ring of heated fluid surrounded on both sides by cooler air. Alternatively, the fluid outlet 370 is located within the body 330, and the heated fluid mixes with the entrained flow before the fluid exits the appliance.

[0055] Power is supplied to the blower via a cable 382 which enters the blower 300 at an inlet 360. Internal wiring (not shown) provides power to the heater 310 and the fan unit 380 to operate the motor which drives the impeller of the fan unit 380.

[0056] To provide a variety of temperatures and flow rates through the appliance, a PCB 350 is provided. PCB 350 is electrically connected to both the heater 310 and the fan unit 380, allowing the user to change the power to both. For example, the user can select different power and heat settings. PCB 350 controls the power to the heating element, so that for a low temperature setting, the heater is powered with a lower current. Additionally, the speed of the fan unit 380 can be varied to change the flow rate through the appliance.

[0057] Figure 7a and Figure 7b Another hair dryer 400 is shown having a curved outer profile that contains a heater 410. There is a straight portion 420 including a handle 422, and a curved portion 430. The heater 410 may be housed in the straight portion 420 and / or the curved portion 430. Figure 7b The heater 410 shown in FIG. 4 may be of the type described above. Figures 1 to 4 The form of heater 10 is described.

[0058] The fluid flow path 412 is provided through the appliance from a fluid inlet 460 disposed at a first end 462 of the straight portion 420 to a fluid outlet 470. The fluid outlet 470 is disposed near or downstream of a distal end 432 of the curved portion 430 away from the straight portion 420. In this embodiment, there is a second straight portion 440 disposed downstream of the heater 410 or between the curved portion 430 and the fluid outlet 470.

[0059] In all of the illustrated embodiments, the heating element 112 is made of two separate wires 112a and 112b. However, in alternative embodiments, the heating element 112 can be made of a single continuous wire. The two separate wires 112a and 112b can be independently controlled. Alternatively, the heating element 112 can include more than two separate wires that can be independently controlled. 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 another wire. Different power outputs can be achieved through various arrangements that will be apparent to those skilled in the art. The arrangement can include using separate wires of different gauges or different lengths. Alternatively, the arrangement can include using separate wires of the same gauge and different lengths. In another alternative, the arrangement can include using separate wires of different gauges and the same length.

[0060] Now refer to Figure 2 and Figure 3 , the heater 10 will be described in more detail. The heater 10 includes spacers 102, 104, 106, each spacer being formed of a flat plate. At least one of the spacers, for example spacer 102, is a thermally conductive ceramic plate, such as aluminum nitride. Plate 102 has conductive traces 118a which are typically screen printed onto the flat ceramic plate when in its green state. The ceramic plate may be covered with another layer of ceramic material. The ceramic plate, conductive traces, and (if applied) the further layer of ceramic material are sintered into a single unit. Heat is dissipated from the heating element 112 to the spacer 102 via an air flow through the heater module 10. The conductive traces 118a are embedded in the thermally conductive spacer 102. When the heater 10 is used as Figure 5a and 5b , 6a and 6b or 7a and 7a, the heater 210, 310 or 410 may be electrically coupled to the corresponding PCB 250, 350, 450 via the terminal 118b.

[0061] 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, and 106 is determined based on the measured current passing through the temperature sensor 118. In order to measure the temperature with an RTD, the RTD is thermally exposed at the location of the temperature of interest. A known voltage is applied to the terminals of the RTD. The measured current passing through the RTD then provides a value indicating the temperature around the area where the RTD is placed. Alternatively, a known current is passed through the RTD. The measured voltage across the RTD then provides a value indicating the temperature around the area where the RTD is placed.

[0062] In this example, only one of the spacers 102 , 104 , and 106 includes the temperature sensor 118 . However, in other examples, all or a subset of the spacers 102 , 104 , and 106 may include the temperature sensor 118 .

[0063] The present invention has been described in detail with respect to a hair dryer, however, the present invention is applicable to any appliance that draws in a fluid and directs the fluid out of the appliance.

[0064] The appliance has been described without discussing any accessories such as concentrating nozzles or diffusers, however, it is feasible to use one of these known types of accessories to concentrate the exiting fluid or to direct the fluid flow in a manner different from that in which it would exit the appliance in the absence of any such accessories.

[0065] The present invention is not limited to the detailed description given above. Variations will be apparent to those skilled in the art.

Claims

1. A heater for a handheld device, comprising: Support members; a heating element supported by a support; A sensor assembly is secured to the support and configured to measure a temperature of the support.

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

3. The heater according to any one of claims 1 or 2, wherein: The sensors are configured to measure the temperature at a plurality of points along the length and / or width of the support.

4. A heater according to any one of the preceding claims, wherein The sensor includes an integrated resistance temperature detector (RTD).

5. A heater according to any one of the preceding claims, wherein The heating element comprises a wire element.

6. A heater according to any one of the preceding claims, wherein The support includes a spacer extending along a central longitudinal axis, and the sensor assembly is secured to the spacer.

7. The heater according to claim 6, wherein The spacer is formed of an electrically insulating material.

8. The heater according to any one of claims 6 or 7, wherein The spacer includes a thermally conductive ceramic layer.

9. The heater according to claim 8, wherein The thermally conductive ceramic layer includes a multilayer plate.

10. The heater according to claim 9, wherein The multilayer board includes two ceramic layers, and the sensor assembly is sandwiched between the two ceramic layers.

11. A heater according to any one of the preceding claims, wherein The support member includes an insertion recess.

12. The heater according to claim 11, wherein The insertion recesses are generally evenly spaced along the length of the support member.

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

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. The heater according to claim 14, wherein The further supports comprise further spacers extending along and orthogonal to the central longitudinal axis.

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

17. The heater according to claim 15 or 16, wherein The further spacers are formed from mica.

18. A heater according to any one of the preceding claims, 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 wrapped around the support structure.

20. A heater according to any preceding claim, wherein The heating element is shaped into a sawtooth or corrugated shape.

21. A heater according to any one of the preceding claims, wherein The heater includes a housing surrounding the support structure and extending along a length of the support structure.

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

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

24. A hair dryer comprising the heater according to any one of claims 1 to 22.

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

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