Heater assembly

Abstract

A heater assembly and haircare appliance including the same. The heater assembly comprises: a power input terminal, through which electrical power can be provided; a ceramic heater; a radiator, connected to the ceramic heater and configured to heat air flowing past the radiator; and a thermal fuse (e.g. bimetallic switch), configured to electrically isolate the ceramic heater from the power input terminal if the temperature of the thermal fuse exceeds a trip temperature. The heater assembly may comprise a clamp, wherein the thermal fuse may be thermally coupled by conduction to the ceramic heater via the clamp.

Description

[0001] HEATER ASSEMBLY

[0002] BACKGROUND

[0003] Haircare appliances often include a heater assembly for heating an air flow. The heated air may then be directed towards a user for the purposes of drying or styling.

[0004] SUMMARY

[0005] In a first aspect, embodiments of the invention provide a heater assembly for a haircare appliance, the heater assembly comprising: a power input terminal, through which electrical power can be provided; a ceramic heater; a radiator, connected to the ceramic heater and configured to heat air flowing past the radiator; and a thermal fuse, configured to electrically isolate the ceramic heater from the power input terminal if the temperature of the thermal fuse exceeds a trip temperature.

[0006] The thermal fuse allows for a heater assembly of reduced complexity, requiring no active components for the purposes of thermal cutoff in the event of an unsafe failure in the heater assembly (for example runaway heating, a software control failure, or a motor failure). When integrated into a product, the resulting heater assembly also takes less space than if it required active components.

[0007] The thermal fuse may be a single operation thermal fuse. In this way, the isolation of the ceramic heater from the power input terminal may be permanent.

[0008] The ceramic heater may be configured to provide a first temperature zone and a second temperature zone, the first temperature zone being heated, in operation, to a temperature greater than a temperature of the second temperature zone, and wherein the thermal fuse is located in the second temperature zone. The first and second temperature zones may be located on the ceramic heater, for example on a surface thereof. This allows for a broader range of thermal fuses to be used. For example, including thermal fuses which are not rated to the temperature attained by the first temperature zone (which may be required for normal device operation).

[0009] The ceramic heater may include a plurality of resistive elements, and there may be a greater number of resistive heating elements in the first temperature zone than the second temperature zone. The second temperature zone may contain no heating elements. In some examples, there may be a single resistive element which has a total path length through ceramic heater, wherein a greater proportion of the total path length is within the first temperature zone than the second temperature zone.

[0010] The heater assembly may include a cooling heatsink located on or adjacent to the second temperature zone. There may be a gap between the cooling heatsink and the radiator, and the thermal fuse may be nearer to the cooling heatsink than to the radiator. The ceramic heater may include a first surface and a second surface opposite to the first surface, and the radiator and thermal fuse may be located on the first surface and the cooling heatsink is located on the second surface. The cooling heatsink may be mounted to face the thermal fuse across the ceramic heater.

[0011] The ceramic heater may include a recess. At least a portion of the thermal fuse may be located within the recess. Such an arrangement can enhance the thermal coupling between the thermal fuse and the recess. The thermal fuse may include a mount and a fuse element, and the fuse element may be located within the recess. This can aid a pocket of air being trapped around the fuse element, and so enhance thermal coupling between the fuse element and the recess. The mount may form a portion of the electrical connection between the ceramic heater and the power input terminal, such that mechanical disconnection of the thermal fuse from the heater assembly causes the electrical isolation of the ceramic heater.

[0012] The heater assembly may comprise a clamp. The clamp may provide additional surface contact between the ceramic heater and the thermal fuse. For example, the clamp may have one or more additional clamping surfaces that provide additional heat conduction pathways between the ceramic heater and the thermal fuse.

[0013] The thermal fuse may be positioned to one side of the radiator. The thermal fuse may be mounted on a side of the ceramic heater. The thermal fuse may be mounted on a short side of the ceramic heater. The side (e.g. the short side) may be one end of the ceramic heater, for example an upstream or downstream end, upstream or downstream with respect to the airflow direction through the ceramic heater. The side may be parallel to the airflow direction through the ceramic heater. Thus, the thermal fuse may be generally aligned with an airflow direction through the radiator. Mounting the thermal fuse on the side that is parallel to the airflow direction through the ceramic heater may allow for a more compact ceramic heater in the airflow direction of the ceramic heater (e.g. the ceramic heater may have a shorter length compared to when the thermal fuse is mounted on an upstream or downstream (airflow) end). The thermal fuse may be mounted out of the airflow path which may avoid the effects of heat connection on the thermal fuse and focus the impact of heat conduction on the thermal fuse. Thus, the thermal fuse may be mounted out of the airflow path and generally aligned with the airflow direction through the radiator. The recess, when present, may be located on the short side of the ceramic heater, and the thermal fuse may include a mount and fuse element, the fuse element being located within the recess.

[0014] The thermal fuse may be mounted in a portion of the radiator. The thermal fuse may be mounted in a portion of the radiator spaced from the ceramic heater.

[0015] The radiator may comprise a plurality of fins projecting from a surface of the ceramic heater. Each fin may extend along a longitudinal direction of the ceramic heater.

[0016] The thermal fuse may be or may comprise a bimetallic switch. The bimetallic switch may also be referred to as a bimetallic thermostat, or a bimetallic thermal fuse. The bimetallic switch may include a bimetallic element, such as a bimetallic disc or a bimetallic snapaction blade. The bimetallic element is an example of a fuse element. Other examples of thermal fuses include a fusible resistor (e.g. a temperature-sensitive resistor (e.g. a temperature-sensitive resistor (PTC) thermistor), and other fusible links (e.g. a temperature-sensitive alloy that melts when exposed to excessive heat).

[0017] The heater assembly may comprise a clamp, sometimes referred to as a clip or holder. The clamp may be for thermally conductively coupling the ceramic heater and the thermal fuse. For example, the thermal fuse may be thermally coupled by conduction to the ceramic heater via the clamp.

[0018] The clamp may comprise a first portion. The first portion of the clamp may be engaged with a first side of the ceramic heater. The clamp may comprise a second portion. The second portion may be engaged with a second side of the ceramic heater. The first side of the ceramic heater may be opposite the second side of the ceramic heater. Providing two portions of the clamp in contact with the ceramic heater and thermal fuse may improve responsiveness and reliability. For example, the trip time of heater may decrease as a result, leading to a safer heater.

[0019] The clamp may be made of a metal, such as aluminium or copper. The thermal fuse may be held to the ceramic heater by a clamping force exerted on the ceramic heater by the clamp. The clamp may be biased to counteract size variations (e.g. thickness variations) of the ceramic heater. The clamp may be configured to expand (e.g. against the bias) when engaged with the ceramic heater.

[0020] The thermal fuse may wrap around the ceramic heater and / or the thermal fuse.

[0021] In a further aspect, embodiments of the invention provide a haircare appliance including the heater assembly of the first aspect. The heater may include any one, or any combination insofar as they are not incompatible, of the optional features set out with reference to the first aspect.

[0022] The haircare appliance may further comprise a fan configured in use to push air through the radiator. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 shows a perspective illustration of a heater assembly;

[0024] Figure 2 shows a perspective illustration of a variant heater assembly;

[0025] Figure 3 shows a perspective illustration of a further variant heater assembly;

[0026] Figure 4 shows a perspective illustration of a further variant heater assembly;

[0027] Figure 5A shows a perspective illustration of a further variant heater assembly;

[0028] Figure 5B shows a partial perspective illustration of a further variant heater assembly; Figure 5C shows a perspective illustration of a variation of the heater assembly in Figure 5 A;

[0029] Figure 6 shows a perspective illustration of a further variant heater assembly;

[0030] Figure 7 shows a haircare appliance;

[0031] Figure 8 shows a perspective illustration of a further variant heater assembly with a case;

[0032] Figure 9A shows a perspective illustration of a clamp applied to the further variant heater assembly shown in Figure 6;

[0033] Figure 9B shows a cross-section illustration (through A-A of Figure 9A) of the clamp applied to the further variant heater assembly shown in Figure 9A;

[0034] Figure 10A shows a perspective illustration of a further clamp applied to a further variant heater assembly; and

[0035] Figure 10B shows a cross-section illustration (through B-B of Figure 10A) of the further clamp applied to the further variant heater assembly shown in Figure 10A.

[0036] DETAILED DESCRIPTION

[0037] Figure 1 shows a perspective illustration of a heater assembly 10, suitable to installed within a haircare appliance such as a hair dryer or hair styler. The heater assembly includes a power input terminal 12, in this example a wire connection, through which electrical power can be provided.

[0038] The heater assembly also includes a ceramic heater 14, in this example provided as a generally rectangular ceramic heater. In some examples, the ceramic heater is made from a material having a positive temperature coefficient such that heat is produced when a voltage is applied across the ceramic heater. In other examples, the ceramic heater includes one or more resistive heating elements (e.g., wires) which may be embedded within the ceramic.

[0039] The heater assembly also includes a radiator 16, connected to the ceramic heater and configured to heat air flowing past the radiator. In this example, the radiator has two components. A first component of the radiator, 16a, is located on one side of the ceramic heater and a second component of the radiator, 16b, is located on another side of the ceramic heater (here, the opposite side). The first component and the second component may be substantially identical (albeit mirrored), or one may be larger than the other. The radiator in this example is formed of a plurality of fins which project from the ceramic heater. The fins may be made, for example, from copper and arranged to define a plurality of parallel airflow paths through the radiator. The fins may connect to one another to form an undulating profile when viewed along the airflow direction, and may be formed as a single piece of metal. A maximum height of the radiator from the ceramic heater may vary across the width of the ceramic heater, for example initially increasing before plateauing and subsequently decreasing.

[0040] The ceramic heater 14 is connected to the power input terminal 12 through a bimetallic switch 18, which is configured to isolate the ceramic heater from the power input terminal if the temperature of the bimetallic switch exceeds a trip temperature. For example, the ceramic heater may be configured to heat to, or around, 300°C and the bimetallic switch may be configured to trip at, or around, 260°C. The bimetallic switch is, in this example, configured such that once tripped, it does not reset until a temperature lower than the trip temperature. That is, a reset temperature of the bimetallic switch may be lower than the trip temperature (for example, around -35°C). In this example, the bimetallic switch includes a bimetallic disc which bridges two contacts. When the temperature of this bimetallic disc exceeds the trip temperature, it deforms causing the connection between the two contacts to be broken. A first of the contacts is in series connection with the ceramic heater, and a second of the contacts is in series connection with the power terminal. Hence, the connection between the ceramic heater and the power terminal is broken when the bimetallic disc deforms. The bimetallic switch is attached to the ceramic heater via a mount. The heater assembly in Figure 1 also includes a cooling heatsink 19 which is positioned adjacent to radiator 16 and the bimetallic switch 18 so as to sit between them on a surface of the ceramic heater 14. The cooling heatsink 19 is spaced from radiator, for example by a gap of around 2 mm. The result is that, in operation, the portion of the ceramic heater on which the bimetallic switch is located is maintained at a lower temperature than the portion of the ceramic heater on which the radiator 16 is located. In this example, like the radiator 16, the cooling heatsink comprises a first component 19a and a second component 19b, located on opposing sides of the ceramic heater 14. These components of the cooling heatsink may be substantially identical (albeit mirrored), or one may be larger than the other.

[0041] Figure 2 shows a perspective illustration of a variant heater assembly 20, where it shares features with the heater assembly 10 discussed above, like features are indicated by like reference numerals. The heater assembly 20 differs from that shown in Figure 1 in that the bimetallic switch 18 is positioned closer to the radiator 16, in the location which in Figure 1 held the first component 19a of the cooling radiator. The bimetallic switch is positioned to face the second component 19b of the cooling radiator across the ceramic heater 14.

[0042] Figure 3 shows a perspective illustration of a further variant heater assembly 30, where it shares features with the heater assemblies discussed above, like features are indicated by like reference numerals. The heater assembly 30 differs from those shown previously in that the bimetallic switch 18 is mounted in a portion of the radiator 16. The radiator in this example has the same second component 16b as previously discussed, although this may be omitted. The radiator also includes a modified version 32 on the first component, in that it includes a cutaway section providing a mounting point for the bimetallic switch 18. This results in the bimetallic switch being spaced from the ceramic heater 14. The bimetallic switch, in this example, is generally aligned with an airflow direction through the radiator 16. In this example, the primary heat transfer mechanism from the ceramic heater to the bimetallic switch is via convection (through hot air transferred to the bimetallic switch) rather than (in the previous examples) conduction. Figure 4 shows a perspective illustration of a further variant heater assembly 40, where it shares features with the heater assembles discussed above, like features are indicated by like reference numerals. The heater assembly 40 differs from those shown previously in that the ceramic heater 42 is configured to provide a first temperature zone and a second temperature zone, the first temperature zone being heated, in operation, to a temperature greater than a temperature of the second temperature zone. The bimetallic switch 18 is located in the second temperature zone, and so is heated in use to a temperature lower than the radiator 16. In examples where the ceramic heater includes a plurality of resistive heating elements embedded in the ceramic, there may be a greater number of heating elements in the first temperature zone than the second temperature zone. In other examples, the ceramic heater element includes only one resistive heating element which has a total path length through the ceramic heater. A greater proportion of the total path length being within the first temperature zone relative to the second temperature zone. In further examples, where the ceramic heater is formed of a positive temperature coefficient material, it may be engineered to have a higher density in the first temperature zone than the second temperature zone. The result of these is that a higher wattage of heating power is provided in the first temperature zone, and so to the radiator, than to the second temperature zone, and so the bimetallic switch.

[0043] Figure 5A shows a perspective illustration of a further variant heater assembly 50, where it shares features with the heater assembles discussed above, like features are indicated by like reference numerals. The heater assembly 50 differs from those shown previously in that the ceramic heater 52 includes a recess 54 relative to an upper surface of the ceramic heater. This recess is shown more clearly in Figure 5B, where the bimetallic switch 18 is removed. The recess is rectangular in shape, and extends only partially into the ceramic heater so as to provide a recess bed and recess sidewalls. In the example in Figure 5 A, the bimetallic switch is mounted as before with the bimetallic disc being spaced from the ceramic heater and attached to the ceramic heater via it’s mount. Figure 5C shows a complete perspective illustration a variation of the heater assembly 50 where the bimetallic switch 18 is flipped by 180°, so that the bimetallic disc is located within the recess 54. The ceramic heater 52 may be configured in the same way as the ceramic heater 42 discussed above, so as to provide differing temperature zones. Figure 6 shows a perspective illustration of a further variant heater assembly 60, where it shares features with the heater assembles discussed above, like features are indicated by like reference numerals. The heater assembly 60 differs from those shown previously in that the ceramic heater 62 is shorter in length, and the bimetallic switch 64 is mounted on a short side of the ceramic heater. The ceramic heater 62 has a recess located on the same short side, and the bimetallic switch 64 extends into this recess as shown in Figure 6.

[0044] In an alternative embodiment (not shown), the bimetallic switch 64 may be arranged on a side (e.g. short side) of the ceramic heater in the airflow direction. In the example provided in Figure 6, the bimetallic switch 64 is not aligned with the airflow direction and is instead provided transverse to the airflow direction. In the alternative embodiment, the bimetallic switch 64 may be mounted on a side adjacent to the side to which the bimetallic switch 64 is mounted in Figure 6.

[0045] Figure 7 shows a haircare appliance 70. The appliance has an outer housing 72, and an airflow inlet 74 and airflow outlet 76 formed in that housing. A fan 78 (driven by a motor) is provided within the housing, and configured to draw air in through the airflow inlet 72 and push it past a heater assembly 80. The air, heated by the heater assembly, is then expelled from the appliance through the airflow outlet 76. The heater assembly 80 may be provided as any of the heater assemblies discussed above. The airflow through the device is indicated by the arrow, and defines an airflow direction. The heater assembly 80 is positioned so that the fins of the radiator 16 are aligned with the airflow direction, and so the air flows between the fins before exiting through the airflow outlet 76.

[0046] Figure 8 shows a perspective illustration of a further variant heater assembly 80 with a case 81. The heater assembly 80 comprises the case 81, a ceramic heater 84, a radiator 86, a thermal fuse 87 (for example, a bimetallic switch). The case 81 encloses the ceramic heater 84 and the radiator 86 such that the thermal fuse 87 is positioned outside of an airflow path 85. The thermal fuse 87 is thermally conductively coupled with a longitudinal side edge of the ceramic heater 84, as illustrated by dashed lines representing a portion of the longitudinal side edge. Positioning the thermal fuse 87 at the side and away from the airflow path 85 may help to reduce the impact of the thermal fuse 87 on the airflow, and / or may restrict the influence of thermal convection on the thermal fuse 87 so that heat transfer is predominately by heat conduction. Heat transfer is predominately by heat conduction may allow for a more responsive thermal fuse 87 compared to a thermal fuse 87 that is also influence by heat convection.

[0047] Figure 9A shows a perspective illustration of a clamp 95 applied to the variant heater assembly 90 shown in Figure 6. The heater assembly 90 comprises a ceramic heater 94 and a thermal fuse provided in the form of a bimetallic switch 98. The bimetallic switch 98 and clamp 95 are together applied to a transverse end of the ceramic heater 94 at a downstream end of the airflow.

[0048] Figure 9B shows a side illustration (through A-A of Figure 9A) of the clamp applied to the further variant heater assembly 90 shown in Figure 9A. The clamp 95 is biased inwards and holds the bimetallic switch 98 to the ceramic heater 94 under a clamping force. The clamp 95 has two portions: a first portion 97 arranged to physically contact a first face of the ceramic heater 94 and a second portion 99 arranged to physically contact a second face of the ceramic heater 94, opposing the first face. In cross-section, the clamp 95 is substantially H-shaped. The clamp 95 wraps around the bimetallic switch 98 and the ceramic heater 94, such that the clamp 95 is in contact with three adjacent surfaces of each of the bimetallic switch 98 and the ceramic heater 94. This wrapped-around configuration may increase surface contact between the bimetallic switch 98 and the ceramic heater 94, which may result in increased heat conduction and increased responsiveness of the bimetallic switch 98.

[0049] Even though a bimetallic switch has been disclosed as the example thermal fuse, a different type of thermal fuse may be used in other embodiments. Such an example is shown in Figures lOA and 10B.

[0050] Figure 10A shows a perspective illustration of a further clamp 105 applied to a further variant heater assembly 100 and Figure 10B shows a cross-section illustration (through B-B of Figure 10 A) of the further clamp 105 applied to the further variant heater assembly 100 shown in Figure 10A. The heater assembly 100 comprises a ceramic heater 104 and a thermal fuse provided in the form of a fusible resistor 108. The fusible resistor 108 and clamp 105 are together applied to a transverse end of the ceramic heater 104 at a downstream end of the airflow. The clamp 105 is biased inwards and holds the fusible resistor 108 to the ceramic heater 104 under a clamping force. The clamp 105 has two portions: a first portion 107 arranged to physically contact a first face of the ceramic heater 104 and a second portion 109 arranged to physically contact a second face of the ceramic heater 104, opposing the first face. In cross-section, the clamp 105 is H-shaped. The clamp 105 wraps around the fusible resistor 108 and the ceramic heater 104, such that the clamp 105 is in contact with three adjacent surfaces of each of the fusible resistor 108 and the ceramic heater 104. This wrapped-around configuration may increase surface contact between the fusible resistor 108 and the ceramic heater 104, which may result in increased heat conduction and increased responsiveness of the fusible resistor 108.

Claims

CLAIMS1. A heater assembly for a haircare appliance, the heater assembly comprising: a power input terminal, through which electrical power can be provided; a ceramic heater; a radiator, connected to the ceramic heater and configured to heat air flowing past the radiator; and a thermal fuse, configured to electrically isolate the ceramic heater from the power input terminal if the temperature of the thermal fuse exceeds a trip temperature.

2. The heater assembly of claim 1, wherein the ceramic heater is configured to provide a first temperature zone and a second temperature zone, the first temperature zone being heated, in operation, to a temperature greater than a temperature of the second temperature zone, and wherein the thermal fuse is located in the second temperature zone.

3. The heater assembly of claim 2, wherein the ceramic heater includes a plurality of resistive heating elements, and wherein there is a greater number of resistive heating elements in the first temperature zone than the second temperature zone.

4. The heater assembly of any preceding claim, wherein the heater assembly includes a cooling heatsink located on or adjacent to the second temperature zone.

5. The heater assembly of claim 4, wherein there is a gap between the cooling heatsink and the radiator, and the thermal fuse is nearer to the cooling heatsink than to the radiator.

6. The heater assembly of claim 4, wherein the ceramic heater includes a first surface and second surface which is opposite to the first surface, and wherein the radiator and thermal fuse are located on the first surface and the cooling heatsink is located on the second surface.

7. The heater assembly of claim 6, wherein the cooling heatsink is mounted to face the thermal fuse across the ceramic heater.

8. The heater assembly of any of claims 1 - 7, wherein the ceramic heater includes a recess, and at least a portion of the thermal fuse is located within the recess.

9. The heater assembly of claim 8, wherein the thermal fuse includes a mount and a fuse element, wherein the fuse element is located within the recess.

10. The heater assembly of any of claims 1 - 3 or 8, wherein the thermal fuse is mounted on a short side of the ceramic heater.

11. The heater assembly of claim 10 as dependent on claim 8, wherein the recess is located on the short side of the ceramic heater, and the thermal fuse including a mount and a fuse element, the fuse element being located within the recess.

12. The heater assembly of any of claims 1 - 3, wherein the thermal fuse is mounted in a portion of the radiator.

13. The heater assembly of claim 12, wherein the thermal fuse is mounted in a portion of the radiator spaced from the ceramic heater.

14. The heater assembly of any preceding claim, wherein the radiator comprises a plurality of fins projecting from a surface of the ceramic heater.

15. The heater assembly of claim 14, wherein each fin extends along a longitudinal direction of the ceramic heater.

16. The heater assembly of any one of claims 1 - 15, wherein the thermal fuse is or comprises a bimetallic switch.

17. The heater assembly of any of claims 1 - 3, wherein the thermal fuse is positioned to one side of the radiator.

18. The heater assembly of claim 17, wherein the thermal fuse is out of an airflow path of the air flowing through the radiator.

19. The heater assembly of any one of claims 1 - 18, comprising a clamp, wherein the thermal fuse is thermally coupled by conduction to the ceramic heater via the clamp.

20. The heater assembly of claim 19, wherein the clamp comprises a first portion engaged with a first side of the ceramic heater, and a second portion engaged with a second side of the ceramic heater.

21. The heater assembly of claim 20, wherein the first side of the ceramic heater is opposite the second side of the ceramic heater.

22. The heater assembly of any one of claims 19 - 21, wherein the thermal fuse is held to the ceramic heater by a clamping force exerted on the ceramic heater by the clamp.

23. The heater assembly of any one of claims 19 - 22, wherein the thermal fuse wraps around the ceramic heater and / or the thermal fuse.

24. A haircare appliance including the heater assembly of any preceding claim.

25. The haircare appliance of claim 24, further comprising a fan configured in use to push air through the radiator.

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