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(11) | EP 2 983 450 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | HEATING ELEMENT, IN PARTICULAR FOR HAIR DRYER APPLIANCES |
| (57) A heating element, in particular for hair dryer appliances, comprises at least one
heating wire (1) suitable to be crossed by an electric current. The heating wire is
shaped so as to form a coil spring (12) that follows the course of a line wound around
two cylinders with parallel main axes (X, X'), the direction of rotation around one
cylinder being opposite to the direction of rotation around the other cylinder.
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[0002] There are already known heating elements for hair dryer appliances and similar equipment, comprising at least one heating wire suitable to act as a conductor for the passage of an electric current and therefore acting as an electrical resistance to heat an air flow that hits such heating wire. The heating wire is wound on an insulating support, usually formed by at least two crossed plates.
[0003] Since the market requires appliances that are ever more compact, easy to handle, lightweight and at the same time more efficient in terms of heating power, heating elements have been proposed with particular conformations of the heating wire so as to increase the density of the wire and still allow a good heat dissipation in confined spaces.
[0004] For example, in a known embodiment, the heating wire is shaped so as to form a cylindrical coil spring, i.e., formed by substantially circular coils when the wire is viewed from one end. This configuration allows having a high heating wire density and a good mechanical strength, especially during the steps of winding around the support element. However, the heat dissipation is not homogeneous and sufficiently ample space is required in the appliance to allow heat dissipation. Furthermore, fabrication is mostly manual and is difficult in the case of small diameter wires. Finally, the winding shape generates inductive phenomena that can cause the formation of electric arcs in the contacts of the switches.
[0005] A variant embodiment that proposes to overcome some of these drawbacks includes a corrugated configuration of the heating wire instead of a spring. In this case, higher powers can be achieved in more constrained spaces, since the heat dissipation is better. Heating elements wrapped with corrugated wire can be fabricated with a more easily automated process. However, these wires are weaker during handling, especially in case of wires of small diameter.
[0006] The purpose of this invention is to propose an electrical resistance heating element, in particular for hair dryer appliances, that allows realizing highly efficient, compact and manageable appliances while, at the same time, overcoming the drawbacks described above with reference to known heating elements.
[0007] This purpose is achieved with a heating element according to claim 1. The dependent claims describe preferred embodiments of the invention.
[0008] The characteristics and advantages of the heating element according to the invention will, in any case, be evident from the following description of its preferred embodiments, provided by way of non-limiting example, with reference to the accompanying drawings, wherein:
- Figure 1 shows, in perspective view, the configuration of the heating wire of a heating element according to the invention;
- Figure 2 is an end view of the heating wire;
- Figure 3 is an axial section of the heating wire; and
- Figure 4 is a plan view of the heating element.
[0009] In said drawings, numeral 1 denotes a heating element according to the invention as a whole. For simplicity, electrical connections and some electrical devices, such as temperature limiters, usually present in a heating element covered by this invention and known per se, have not been shown.
[0010] The heating element 1 comprises at least one heating wire 10 wound around an insulating support 50.
[0011] The heating wire 10 is suitable to be crossed by an electric current so as to heat an air flow that hits the heating element 1.
[0012] As shown, in particular in Figures 1 and 2, the heating wire 10 is shaped so as to form a coil spring 12 that follows the course of a line wound around two cylinders with parallel main axes X,X', the direction of rotation around one cylinder being opposite to the direction of rotation around the other cylinder.
[0013] The result of this course of the heating wire 10 is that the coils 12' of said coil spring 12 are "eight" shaped. In other words, as shown in Figure 2, when seen from the front, each coil 12 'is not circular but is formed by two intertwined circular elements.
[0014] In the example shown, these circular elements are the same since the two virtual cylinders around which the heating wire 10 is wound have the same diameter. In a variant embodiment, these cylinders have different diameters.
[0015] Furthermore, in an embodiment, these virtual cylinders have an elliptical, rather than circular, cross-section.
[0016] Turning now to the insulating support 50, in a preferred embodiment, said support 50 has an axially symmetrical structure that extends along a main support axis Y. For example, the support 50 has a cylindrical or conical structure or has a cylindrical or conical envelope.
[0017] In a preferred embodiment, the support 50 comprises two or more support plates 52 cross with each other along said main support axis Y. Along the edges of each support plate 52 there are provided seats 54 for housing the heating wire 10.
[0018] In a preferred embodiment, the heating wire 10 is wound on the insulating support 50 in such a way that the coils 12' of the heating wire extend in a primarily perpendicular direction to the main support axis Y. In other words, the axes of the virtual cylinders around which the heating wire 10 is wound lie on a plane orthogonal to the main support axis Y.
[0019] In an embodiment (not shown in the drawings), the heating wire 10 forms at least two coplanar coils around the insulating support 50.
[0020] In a variant embodiment, the heating element 1 comprises at least two heating wires 10 wrapped around the same insulating support 50. Such heating wires 10 can be connected together in series or in parallel. Of course, the different heating wires 10 can have different diameters and/or different shapes or sizes of the "eight" shaped coils 12'.
[0021] For example, the heating wires 10 form respective coaxial windings and, in a particular embodiment, such windings have coplanar coils. In this way, with the same extension of the insulating support 50 along the main support axis Y, the density of the heating wire is substantially double with respect to a single winding.
[0022] The configuration of the heating element described above allows achieving the intended purposes.
[0023] The "eight" shape of the coils 12' of the heating wire allows greatly increasing the density of the wire in the space. In addition, the flattened shape of the coils themselves, in the direction substantially orthogonal to the air flow that hits the heating element, offers a better exposure to the air flow and thus a more effective heat dissipation.
[0024] Therefore, it is possible to increase the heating power of the appliance in the same space occupied by the heating element or, for the same power dissipated, significantly reduce the overall dimensions and therefore the weight of the appliance, increasing its manoeuvrability.
[0025] The coil-spring shaped heating wire has excellent mechanical strength, since the elasticity offered by the spring shape allows bring the coils back into position even after the manipulation of the wire or of the heating element or after accidental falls of the appliance.
[0027] The higher density of the heating wire allows reducing the dimensions of the insulating support, with consequent reduction of the raw material used for its fabrication.
[0028] Finally, the particular "eight" shape of the coils of the heating wire allows eliminating the inductive effect produced by the current that circulates in the wrapped heating wire, to the advantage of the life of the switches of the appliance, and reducing electromagnetic interference generated by ' appliance.
[0029] To the embodiments of the heating element according to the invention, a man skilled in the art, to satisfy contingent requirements, may make modifications, adaptations and replacements of elements with others functionally equivalent, without departing from the scope of the following claims. Each of the characteristics described as belonging to a possible embodiment can be achieved independently from the other embodiments described.
1. Heating element, in particular for hair dryer appliances, comprising at least one
heating wire (1) suitable to be flowed through by an electric current, wherein said
heating wire is shaped so as to form a coil spring (12) that follows the course of
a line wound around two cylinders with parallel main axes (X, X'), the direction of
rotation around one cylinder being opposite to the direction of rotation around the
other cylinder.
2. Heating element according to claim 1, wherein each coil (12') of said coil spring
is shaped as an "eight".
3. Heating element according to claim 1 or 2, wherein said cylinders have different diameters.
4. Heating element according to any one of the previous claims, wherein said cylinders
have an elliptical cross section.
5. Heating element according to any one of the previous claims, comprising an insulating
support (50) on which said at least one heating wire is wound.
6. Heating element according to the previous claim, wherein said support has an axially
symmetrical structure that extends along a main support axis (Y).
7. Heating element according to the previous claim, wherein each coil of the heating
wire extends mainly in a direction perpendicular to said main support axis.
8. Heating element according to claim 6 or 7, wherein said insulating support is formed
of two or more support plates (52) crossing each other on said main support axis (Y),
housing seats (54) of the heating wire (10) being made along the edges of each support
plate.
9. Heating element according to any of the claims 6-8, wherein said support has a cylindrical
or conical shape or envelope.
10. Heating element according to any of the claims 5-9, wherein the heating wire forms
at least two coplanar coils around the insulating support.
11. Heating element according to any of the claims 5-10, comprising at least two heating
wires wound around a single insulating support.
12. Heating element according to the previous claim, wherein said heating wires form respective
coaxial windings.
13. Heating element according to the previous claim, wherein said windings have coplanar
coils.
14. Hair dryer appliance comprising at least one heating element according to any of the
previous claims.