HEATER ASSEMBLY

Abstract

A heater assembly for a haircare appliance includes an air duct defining an air flow path extending from an upstream end to a downstream end; a first heater element positioned in the flow path, the first heater element having a first electrical path defined between cut-outs in a first sheet, the air flow path extending through said cut-outs; and a second heater element positioned in the flow path downstream of the first heater element, the second heater element having a second electrical path defined between cut-outs in a second sheet, the air flow path extending through said cut-outs. The heater assembly includes electrical circuitry for connection to a power source. The first and second electrical paths are provided in respective first and second circuit branches which are connected in electrical parallel within said circuitry.

Claims

1. A heater assembly for a haircare appliance, the heater assembly comprising: an air duct defining an air flow path extending from an upstream end to a downstream end; a first heater element positioned in the flow path, the first heater element having a first electrical path defined between cut-outs in a first sheet, the air flow path extending through said cut-outs; and a second heater element positioned in the flow path downstream of the first heater element, the second heater element having a second electrical path defined between cut-outs in a second sheet, the air flow path extending through said cut-outs, wherein: the heater assembly comprises electrical circuitry for connection to a power source; the first and second electrical paths are provided in respective first and second circuit branches; and the first and second circuit branches are connected in electrical parallel within said circuitry.

2. The heater assembly according to claim 1 further comprising a third heater element positioned in the flow path downstream of the second heater element, the third heater element having a third electrical path defined between cut-outs in a third sheet, the air flow path extending through said cut-outs.

3. The heater assembly according to claim 2 wherein the third electrical path is provided in a third circuit branch which is connected in parallel with the first and second circuit branches.

4. The heater assembly according to claim 1 wherein one of said heater elements is connected in series with a further heater element, within the corresponding circuit branch.

5. The heater assembly according to claim 1 wherein each of said heater elements is connected in series with a respective further heater element, within the corresponding circuit branch.

6. The heater assembly according to claim 1 wherein the circuitry includes power control components arranged to supply the different circuit branches with different voltages and/or currents.

7. The heater assembly according to claim 1 wherein the cut-outs of each of said electrical paths are formed by etching.

8. The heater assembly according to claim 1 wherein each of said electrical paths has a generally domed shape.

9. The heater assembly according to claim 1 wherein each of said electrical paths is generally planar.

10. The heater assembly according to claim 1 wherein the air duct is formed by a stack of annular elements each of which defines an axial portion of the air duct. This can make the heater assembly more customisable, allowing different lengths of flow path to be formed for different applications by utilising different numbers of annular elements.

11. The heater assembly according to claim 10 wherein each heater element is embedded within a respective one of said annular elements.

12. The heater assembly according to claim 10 wherein one of said annular elements forms a spacer between adjacent heater elements.

13. The heater assembly according to claim 1 wherein the electrical path of each heater element is positioned substantially entirely within the air flow path.

14. The heater assembly according to claim 1 wherein at least two neighbouring electrical path are spaced apart by no more than 5 mm.

15. A haircare appliance comprising the heater assembly according to claim 1.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0068] The invention will now be described with reference to the accompanying drawings in which:

[0069] FIG. 1 is a perspective view of a part of a heater assembly according to a first embodiment of the invention;

[0070] FIG. 2 is a perspective view of an annular element and heater element of the part of a heater assembly shown in FIG. 1;

[0071] FIG. 3 is a cross-sectional view of the annular element and heater element of FIG. 2;

[0072] FIG. 4 is a perspective view of a spacer of the part of a heater assembly shown in FIG. 1;

[0073] FIG. 5 is an electrical schematic of a heater assembly including the part shown in FIG. 1;

[0074] FIG. 6 is a perspective view of a part of a heater assembly according to a second embodiment of the invention;

[0075] FIG. 7 is an electrical schematic of a heater assembly including the part shown in FIG. 6; and

[0076] FIG. 8 is a perspective view of a hairdryer which may include the heater assembly of FIGS. 1 to 5 or FIGS. 6 and 7.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0077] Throughout the description and drawings, corresponding reference numerals denote corresponding features.

[0078] FIG. 1 shows a part 2 of a heater assembly according to a first embodiment of the invention. The heater assembly has an air duct 4 which defines an air flow path 6 through it, extending from an upstream end 8 to a downstream end 10. The air duct 4 is made up of a stack of annular element 12a, 12b, 12c, each of which defines a (relatively short) axial portion of the air duct 4.

[0079] In this specific embodiment the air duct 4 is generally circular in cross section, with a pair of flat sides 14 which give it a slight racetrack-shape. Each of the annular elements 12a-12c has a corresponding cross sectional shape. In this embodiment each of the annular elements 12a-12c, and thus the air duct 4 as a whole, is made from liquid crystal polymer.

[0080] Each of the annular elements 12a supports a heater element 20, any one of which may be a ‘first heater element’ within the meaning of the present invention. In this embodiment each of the annular elements 12a has a heater element 20 embedded in it due to the annular element 12a having been overmolded on top of its heater element 20. FIGS. 2 and 3 show one of the annular elements 6a with its heater element 20, each of the other heater elements 20 of the other annular elements 12a having the same shape.

[0081] In this embodiment, each heater element 20 is formed in its entirety from a bare metal sheet 22 in which a set of cut-outs 24 have been made by etching. Each heater element comprises a pair of contact tabs 26, for connection to a power supply via a controller as discussed later. An electrical path 30 is defined between the cut-outs 24 such that it runs in a zig-zag between the two contact tabs 26.

[0082] Extending from each apex of the zig-zagging electrical path 30 is a support structure 32 which has a thin bridge 34 that terminates in an hourglass-shaped support tab 36. The contact tabs 26 and support tabs 36 encircle the electrical path 30, and are embedded within the annular element 12a. This allows the electrical path 30 to be positioned entirely within the air flow path 6. The contact tabs 26 also project outwards beyond the annular element 12a so that they can be connected to electrical circuitry as described later.

[0083] For the avoidance of doubt, the thin bridges 34 may experience some slight electrical current flow through them during use. However, it is to be understood that such current flow would be minimal and would have negligible effect on the heater element 20 as a whole. They are not, therefore, considered to be part of the electrical path 30.

[0084] As noted above, in this embodiment the sheets 22 from which the electrical paths 30 (and indeed the entire heater elements 20) are formed are planar. The electrical paths 30, and indeed the heater elements 20 as a whole, are therefore also planar. In this case the heater elements 20 (and thus the electrical paths 30) are positioned normal to the air flow path 6.

[0085] The heater elements 20 embedded in the annular elements 12c, any one of which may constitute a ‘second heater element’ within the meaning of the present invention, have substantially the same shape and configuration of those of annular elements 12a. However, the heater element 20 of each of the annular elements 12a is formed from a sheet which is 0.1 mm thick, and the electrical path 30 of each of those heater elements is 0.3 mm wide. In contrast, the heater element 20 of each of the annular elements 12c is formed from a sheet which is 0.3 mm thick, and the electrical path 30 of each of those heater elements is 0.4 mm wide. Accordingly, the electrical paths 30 of the heater elements 20 of the annular elements 12c have a larger cross sectional area, in the direction of electrical flow, than those of the heater elements 20 of annular elements 12a. Those heater elements 20 further downstream in the air flow path 6 therefore experience less electrical heating.

[0086] In this embodiment the thickness (in the axial direction) of the annular elements 12a is selected such that within the group of heater elements 20 supported by those annular elements, the electrical path 30 of each heater element 20 is spaced apart from its neighbouring electrical path(s) 30 by 2 mm. Similarly, the thickness of the annular elements 12c is selected such that within the group of heater elements 20 supported by those annular elements, the electrical path 30 of each heater element 20 is spaced apart from its neighbouring electrical path(s) 30 by 2 mm. In some circumstances this spacing may be an optimum compromise, packing the electrical paths 30 relatively close together for the sake of compactness, but spacing them apart by far enough to prevent them touching after bowing due to thermal expansion. The electrical paths 30 (and indeed the the heater elements 20 as a whole) of this embodiment are made of metal, as discussed above, and are exposed directly to air flow in the air flow path 6. Accordingly, is it particularly important that the electrical paths 30 do not touch because the lack of insulative coating means that contact between them would cause a short circuit.

[0087] Although the electrical paths 30 of the group of heater elements 20 supported by annular elements 12a are spaced apart by 2 mm, and the same is true of the electrical paths 30 of the group of heater elements 20 supported by annular elements 12c, the electrical path 30 of the most downstream heater element 20 supported by an annular element 12a is spaced apart from the electrical path 30 of the most upstream heater element 20 supported by an annular element 12c by 6 mm. This is due to annular element 12b, which forms a spacer between those two heater elements 20 (and, in this embodiment, their respective annular elements 12a, 12c). In this embodiment, the spacer 12b supports a temperature sensor in the form of a thermocouple 38 within the air flow path 6, the purpose of which will be discussed later.

[0088] The part 2 of the heater assembly shown in FIG. 1 is connected to electrical circuitry which, in turn, is connectable to a power source such as a battery or mains electricity. An electrical schematic of the heater assembly 50, showing the electrical circuitry 52, is shown in FIG. 5. The electrical circuitry 52 has a controller 54 which has terminals 56 for connection to a power source (not shown), and first and second circuit branches 58a, 58c, provided in electrical parallel, via which electrical power from the power source can be supplied to the heater elements 20.

[0089] The first circuit branch 58a includes each of the heater elements 20 supported by an annular element 12a, those heater elements 20 being connected in series with one another. Accordingly, one or more of those heater elements 20 may constitute a ‘further heater element’ within the meaning of the present invention. The second circuit branch 58c includes each of the heater elements 20 supported by an annular element 12c, those heater elements 20 being connected in series with one another. One or more of those heater elements 20 may constitute a ‘further heater element’ within the meaning of the present invention, instead or as well.

[0090] As noted above, the two circuit branches 58a, 58c are connected in parallel with one another. Each circuit branch 58a, 58c has a corresponding set of power control components 60a, 60c via which electrical power can be supplied to that branch. In this case the power control components 60a are configured to provide the first circuit branch 58a with a higher voltage than is supplied to the second circuit branch 58c by power control components 60b.

[0091] The controller 54 is also connected to the thermocouple 38, and to a switch 62 positioned in the second circuit branch 58c. In use, the controller monitors the temperature of the air after it has passed through the heater elements 20 supported by annular elements 12a, and if the temperature exceeds a threshold the controller 54 opens the switch 62 so as to disconnect the heater elements 20 supported by annular elements 12c and prevent any further heating from taking place.

[0092] FIGS. 6 and 7 show a heater assembly 50 according to a second embodiment of the invention. The second embodiment is similar to the first embodiment, therefore only the differences will be described.

[0093] Whilst the first embodiment utilised two different sized heater elements 20, those supported by annular elements 12a and those supported by annular elements 12c, the second embodiment utilises four different sized heater elements 20, those supported by annular elements 12a, those supported by annular elements 12c, those supported by annular elements 12e and those supported by annular elements 12f. In this embodiment the heater elements 20 supported by annular elements 12a, 12c, 12e and 12f have electrical paths 30 formed from sheets which are 0.05 mm, 0.1 mm, 0.2 mm and 0.3 mm respectively and the widths of those electrical paths are 0.25 mm, 0.35 mm, 0.4 mm and 0.45 mm respectively.

[0094] Following the convention set out above, in which any one of the heater elements 20 supported by an annular element 12a could constitute a ‘first heater element’ and any one of the heater elements 20 supported by an annular element 12c could constitute a ‘second heater element’, it follows that any one of the heater elements 20 supported by an annular element 12e could constitute a ‘third heater element’ according to the present invention. However, for the avoidance of doubt any one of the heater elements 20 supported by an annular element 12f could constitute a ‘third heater element’. Furthermore, it is equally possible for one of the heater elements 20 supported by an annular element 12c to constitute a ‘first heater element’, one of the heater elements 20 supported by an annular element 12e to constitute a ‘second heater element’ and one of the heater elements 20 supported by an annular element 12f to constitute a ‘third heater element’.

[0095] The second embodiment also differs from the first embodiment in that there are two spacers 12b which support thermocouples 38, and a further spacer 12d which spaces apart the heater elements 20 (and their respective annular elements 12c, 12d) either side of it for the sake of flow smoothing but does not support any components in the air flow path 6.

[0096] The electrical circuitry 52 of the second embodiment has four circuit branches 58a, 58c, 58e and 58f, with corresponding power control components 60a, 60c, 60e and 60f, within which the heater elements 20 supported by annular elements 12am 12cm 12e and 12f respectively are connected in series. In this case power control components 60c, 60e and 60f are configured to be actively managed by the controller to adjust the voltages supplied to their respective circuit branches 58c, 58e, 58f based on feedback from the two thermocouples 38 so as to provide the smoothest possible heating along the length of the air flow path 6.

[0097] FIG. 8 shows a haircare appliance in the form of a hairdryer 70, which may comprise a heater assembly 50 according to one of the above embodiments of the invention. The hairdryer 12 has a cylindrical handle 72 with an air inlet 74 at its base, above which is a motor-driven fan (not visible) for drawing air through the hairdryer. An upper portion 76 of the handle 72 may comprise the heater assembly 50, hot air being ducted from the handle 72 and into a head 78 of the hairdryer before exiting through an annular outlet 80 at the front of the head. A flex (not shown) runs up into the bottom of the handle 72 so as to supply the hairdryer with mains electricity for driving the motor-driven fan (not visible) and powering the heater assembly 50.

[0098] It will be appreciated that numerous modifications to the above described embodiments may be made without departing from the scope of invention as defined in the appended claims. For instance, rather than being purely planar, the electrical paths of one or more heater elements may be domed, due to being formed between cut-outs in a domed sheet. The domed electrical paths may for example protrude slightly in the upstream direction along the flow path. As another example, the air duct (and the heater elements) may be square, hexagonal or octagonal rather than being generally round in cross section.