Air heating device for a hair dryer, ventilation device for a hair dryer and method for assembling a heating device for hair dryer

Abstract

An air heating device for a hair dryer, comprises a support structure (2) extending along a central axis (A) and provided with a plurality of longitudinal walls (4) extending radially, a resistive winding (3) extending around the support structure (2), a temperature sensor (7) placed in electrical connection with the resistive winding (3) and constrained to a longitudinal wall of the plurality of longitudinal walls (4). A pre-heating element (9) is constrained to a longitudinal wall of the plurality of longitudinal walls (4) and placed near and operatively upstream of the temperature sensor (7) as well as within an axial encumbrance area of the resistive winding (3).

Description

[0001] The present invention relates to an air heating device for a hair dryer, a ventilation device for a hair dryer and a method for assembling an air heating device for a hair dryer.

[0002] Thus, the main application of the present invention is in the field of small electrical appliances, and more specifically in the production and manufacture of heating components to be inserted into the ventilation duct of a hair dryer.

[0003] The hair dryer sector, which for several years was the subject of little innovation at the end-product level, has in recent times undergone a considerable innovation push in terms of both technology and design. One of the recent trends is to replace the conventional axial / centrifugal hybrid fans with purely axial fans, in order to make available systems with further reduced sizes and capable of generating a less turbulent and, for ventilation purposes, more efficient flow.

[0004] This, while introducing some undoubted advantages, has brought with it some issues related to the reliability of the safety devices.

[0005] As is known, in fact, in order to ensure maximum safety of the hair dryer (as well as other electric heating devices, such as heaters or similar), such devices are equipped with temperature sensors (e.g. thermostats) and possibly additional safety elements, such as fuses, which are activated when the temperature in the detection zone exceeds a pre-set threshold value.

[0006] It follows that, in order to guarantee efficiency and reliability, especially in the professional field, it is absolutely necessary that the sensor can correctly detect the temperature of the resistive winding, in order to prevent it from rising beyond dangerous values, capable of triggering meltdowns or fires, or to fuse triggering values for the appliances that are equipped with them.

[0007] Disadvantageously, however, in known devices the temperature sensor is generally placed in the radially internal zone of the device, i.e. a zone that, due to the poorly turbulent motion generated by the axial fan, is traversed by an air flow that has only marginally come into contact with the resistive winding.

[0008] This results in a considerable delay in the temperature detection by the sensor, with consequent risks for the safety of the user.

[0009] The object of the present invention is therefore to make available an air heating device for a hair dryer, a ventilation device for a hair dryer and a method for assembling an air heating device for a hair dryer that are capable of overcoming the disadvantages of the above-mentioned known technique.

[0010] In particular, it is an object of the present invention to make available an air heating device for an efficient and reliable hair dryer.

[0011] Said objects are achieved by an air heating device for a hair dryer, as well as by a ventilation device for a hair dryer and by a method for assembling an air heating device for a hair dryer having the features of one or more of the following claims.

[0012] In particular, the objects of the present invention are achieved by an air heating device for a hair dryer, comprising a support structure and a resistive winding.

[0013] The support structure preferably extends along a central axis, in use aligned to a direction of an air flow of the hair dryer.

[0014] Preferably, the support structure is provided with a plurality of longitudinal walls extending radially, angularly spaced from each other, with respect to said central axis.

[0015] The resistive winding preferably extends around said support structure. Preferably, the resistive winding defines a plurality of turns arranged in succession along the central axis (more preferably according to a substantially helical pattern).

[0016] More preferably, it is noted that the resistive winding extends axially between a first end portion and a second end portion.

[0017] Preferably, the device also comprises a temperature sensor placed in electrical connection with said resistive winding and constrained to a longitudinal wall of the plurality of longitudinal walls, in a radially internal position with respect to the resistive winding.

[0018] According to one aspect of the invention, the heating device comprises a pre-heating element constrained to a longitudinal wall of the plurality of longitudinal walls.

[0019] Preferably, the pre-heating element is placed near the temperature sensor. Preferably, moreover, the pre-heating element is placed operatively upstream of the temperature sensor, with reference to said direction of the air flow of the hair dryer.

[0020] Preferably, the pre-heating element is located within an axial encumbrance area of the resistive winding.

[0021] Advantageously, in this way it is possible to heat the air flowing in the radially internal zone of the heating device, aligning its temperature to that hitting the winding and making the measurement by the temperature sensor more reliable.

[0022] This allows to obtain a more reliable and efficient device, optimal for both domestic and professional use.

[0023] Preferably, moreover, the temperature sensor and the pre-heating element are fixed in axial succession on the same longitudinal wall.

[0024] Preferably, moreover, the temperature sensor and the pre-heating element are placed, in succession, in an axial position interposed between the first end portion and the second end portion of the resistive winding.

[0025] In other words, both the temperature sensor and the pre-heating element are placed in a zone radially internal to the resistive winding and within the axial encumbrance of said resistive winding.

[0026] The heating device is preferably inserted into a ventilation device for a hair dryer equipped with an axial fan operatively placed upstream of the heating device itself and configured to generate an air flow directed towards the heating device.

[0027] Advantageously, the presence of the pre-heating element increases the heating efficiency and measurement accuracy of the sensor, increasing the reliability of the system.

[0028] The structure subject-matter of the invention, moreover, is particularly suitable for automating its assembly through a specific assembly method, which is also the subject-matter (independent) of the present invention. The method envisages for providing at least one first flat plate extending mainly along its own central axis, at least one second flat plate extending mainly along its own central axis and provided with a notch defining a housing, at least one temperature sensor, at least one pre-heating element and at least one resistive wire.

[0029] The temperature sensor and the pre-heating element are fixed to the first flat plate, arranging them in succession with one another along said central axis.

[0030] Preferably, the fixing takes place by means of automatic machines, more preferably by coupling the temperature sensor and the pre-heating element together beforehand and then by fixing both elements in one piece to the first flat plate, more preferably by means of rivets.

[0031] Then, the first flat plate is coupled to the second flat plate, so as to define a support structure provided with a plurality of longitudinal walls extending radially, angularly spaced from each other, with respect to said central axis;

[0032] Preferably, the temperature sensor and the pre-heating element are placed in the housing.

[0033] Finally, with the support structure provided and equipped with a temperature sensor and the pre-heating element, the resistive wire is wound around the longitudinal walls to define a resistive winding.

[0034] These and other characteristics, together with the relative advantages, will become clearer from the following exemplary, therefore not limiting, description of a preferred, therefore not exclusive, embodiment of an air heating device and a ventilation device for a hair dryer as illustrated in the attached figures, in which: figure 1 shows a schematic overall view of a ventilation device for a hair dryer according to the present invention; figure 2 shows a detail of the heating device of figure 1; figures 3 to 10 show partial perspective views, with some parts removed to highlight others, of an air heating device for a hair dryer in different embodiments.

[0035] With reference to the attached figures, an air heating device for a hair dryer 100 according to the present invention is indicated with the number 1.

[0036] The heating device 1 is preferably inserted within a ventilation device 20 for a hair dryer 100, wherein a fan 21, preferably of the axial type, is operatively placed upstream of the heating device 1 and configured to generate an air flow directed towards the heating device 1; the direction "B" of the air flow is therefore starting from the fan 21 towards the heating device 1.

[0037] Said ventilation device 20 is preferably placed inside a ventilation duct 101 of the hair dryer 100 and controlled by a control unit or electronic board placed in the body 102 of the hair dryer 100.

[0038] The heating device 1 is of the type commonly referred to as "resistor" as it comprises, in addition to a support structure 2 (better described below), a resistive winding 3 which, if traversed by electric current, overheats so as to raise the temperature of an air flow incident to it.

[0039] In general, therefore, the air heating device 1 comprises a support structure 2 around which at least one resistive winding 3 is wound, which in use is hit by an air flow generated by the fan 21, placed operatively upstream, in order to raise its temperature.

[0040] Preferably, the support structure 2 extends along a central axis "A", in use aligned to the direction "B" of the air flow of the hair dryer.

[0041] The support structure 2 is provided with a plurality of longitudinal walls 4, extending radially with respect to the central axis "A".

[0042] Preferably, the longitudinal walls are angularly spaced from each other with respect to said central axis "A".

[0043] Preferably, the longitudinal walls 4 each extend radially starting from the central axis "A" up to a radially external edge 4a.

[0044] Preferably, the radially external edge 4a of each longitudinal wall 4 has a toothed shaping in order to define a succession of housing seats for the resistive winding 3.

[0045] In other words, between two successive teeth there is a hollow that accommodates therein a section of the resistive winding resting on the radial wall 4, preventing axial sliding thereof.

[0046] The resistive winding 3 therefore extends around the support structure 2, preferably defining a plurality of turns 8 arranged in succession along the central axis "A".

[0047] Preferably, the resistive winding 3 extends axially between a first end portion 3a and a second end portion 3b; more preferably, therefore, the succession of turns 8 extends between the first 3a and the second end portion 3b.

[0048] The resistive winding 3 extends resting on the longitudinal walls, in particular on the radially external edges 4a, defining the plurality of turns 8 arranged in succession along the central axis "A".

[0049] In the preferred embodiment, the resistive winding 3 comprises a crimped resistive wire extending helically around the support structure 2.

[0050] Note that, in order to maximize heat transfer, the resistive wire forming the resistive winding 3 is shaped according to at least one predetermined waveform which may comprise sinusoidal and / or zig-zag and / or square and / or spiral wave undulations and, more generally, of any shape.

[0051] In the illustrated embodiment, each turn 8 of the winding extends circumferentially around the support structure 2 according to a crimped pattern defining a succession of apexes and grooves.

[0052] Preferably, the turns 8 are sized so that at each radial wall 4 an anchoring wave is placed, defined by at least one apex of the crimped wire surmounting the radially external edge 4a.

[0053] Advantageously, this structure gives stability to the winding, maximising its efficiency and, above all, guaranteeing its robustness to impacts. Alternatively, however, the resistive winding 3 could have a different shape, defined by helical, rectilinear or other wires.

[0054] In order to guarantee the controllability and / or safety of the winding 6, both from a thermal and electrical point of view, the heating device 1 preferably comprises a temperature sensor 7 placed in electrical connection with the resistive winding 3 in order to allow a control of the power supply useful to reduce the risk of tripping by the safety device.

[0055] Said temperature sensor 7, preferably a thermostat, is preferably calibrated (with temperatures from 60 °C to 170 °C) to open the contact, reversibly, upon exceeding a temperature limit value.

[0056] In certain embodiments, moreover, a safety device (not illustrated) placed in electrical connection with said resistive winding 3 is also provided.

[0057] The safety device is preferably a thermal fuse, more preferably calibrated (with temperatures from 70°C to 260 °C) to prevent overtemperatures under abnormal operating conditions.

[0058] Preferably, the temperature sensor 7 is constrained to a longitudinal wall of the plurality of longitudinal walls 4, in a radially internal position with respect to the resistive winding 3.

[0059] In this regard, preferably, between the longitudinal walls 4 there are at least a first longitudinal wall 5 and a second longitudinal wall 6 adjacent to each other.

[0060] Note that, in the preferred embodiment, the support structure 2 comprises a first flat plate 50 and a second flat plate 60 both extending mainly along the central axis "A" and coupled to each other by axial sliding fitting.

[0061] In greater detail, the first flat plate 50 and the second flat plate 60 have respective through slots aligned with the central axis "A" and along which the two plates are coupled maintaining an angular offset, preferably by about 90°.

[0062] The two flat plates 50, 60 define, once coupled, the longitudinal walls 4.

[0063] In this regard, preferably the first flat plate 50 defines two first longitudinal walls 5 and the second flat plate defines two second longitudinal walls 6. The first 50 and the second flat plate 60, as well as the longitudinal walls 4 resulting from their coupling, are preferably made of mica or other material with similar properties.

[0064] Preferably, at least one second longitudinal wall 6, near the central axis "A", has a notch 6a defining a housing, i.e. a space capable of receiving at least in part components preferably anchored to the first longitudinal wall 5.

[0065] Preferably, the temperature sensor 7 is fixed to the first longitudinal wall 4 and placed at least in part in the housing defined by the notch 6a of the second longitudinal wall 6.

[0066] Preferably, in fact, the first 5 and the second longitudinal wall 6 are angularly close to each other and the temperature sensor 7 is preferably placed near the central axis "A" in order to interfere only marginally with the air flow.

[0067] To reduce the pressure drops associated with the presence of the temperature sensor 7, maximizing its approach to the central axis "A", the notch 6a of the second longitudinal wall 6 is made at a fixing zone of the temperature sensor 7 and to define a housing that accommodates it at least in part, that is, for the part interfering with a plane defined by the second longitudinal wall 6.

[0068] Preferably, the temperature sensor 7 is fixed to the first longitudinal wall 5 by means of rivets or other quick fixing system.

[0069] In the preferred embodiment, the temperature sensor 7 extends, with reference to the direction "B" of the air flow passing through the hair dryer 100, between a first terminal 7a and a second terminal 7b.

[0070] Preferably, the fixing members (e.g. rivets) for fixing the temperature sensor 7 to the first longitudinal wall 6 are associated with said first 7a and second terminal 7b.

[0071] According to one aspect of the invention, the heating device 1 comprises a pre-heating element 9 constrained to a longitudinal wall 4 of the plurality of longitudinal walls.

[0072] The pre-heating element is in turn preferably defined by a resistor (metallic or ceramic) which, when crossed by an electric current, overheats proportionally to it.

[0073] Preferably, with reference to the direction "B" of the air flow of the hair dryer 100, the pre-heating element 9 is placed near and operatively upstream of the temperature sensor 7.

[0074] In this way, the air flowing in the zone radially internal to the resistive winding 3, which is only marginally heated by the wire, undergoes overheating before coming into contact with the temperature sensor 7, making the measurement more reliable.

[0075] According to one aspect of the invention, the pre-heating element 9 is placed within an axial encumbrance area of the resistive winding 3.

[0076] In other words, the pre-heating element 9 is placed in an axial position interposed between the first end portion 3a and the second end portion 3b of the resistive winding 3.

[0077] Advantageously, this allows the axial position of the temperature sensor 7 to be advanced, bringing it to a zone where the air has a maximum temperature and thus making the measurement more useful.

[0078] Thus, both the temperature sensor 7 and the pre-heating element 9 are placed at an axial position interposed between the first end portion 3a and the second end portion 3b of the resistive winding 3.

[0079] Preferably, the temperature sensor 7 and the pre-heating element 9 are fixed in axial succession on the same longitudinal wall 4.

[0080] Preferably, therefore, both the temperature sensor 7 and the pre-heating element 9 are constrained to the first longitudinal wall 5.

[0081] Note that the pre-heating element 9 also extends, with reference to the direction "B" of the air flow passing through the hair dryer 100, between a first terminal 9a and a second terminal 9b and comprises a heating portion 9c interposed between them.

[0082] The pre-heating element 9 therefore has a main axial development (i.e. aligned to the central axis "A"), with the heating portion 9c at least partly axially interposed between the first 9a and the second terminal 9c.

[0083] Said first 9a and second terminal 9b are fixed to the respective longitudinal wall 4, i.e. preferably to the first longitudinal wall 5.

[0084] Preferably, the first 9a and the second terminal 9b are riveted to the first longitudinal wall 5.

[0085] In the preferred embodiment, the second terminal 9b of the pre-heating element 9 is superimposed or coincident with the first terminal 7a of the temperature sensor 7.

[0086] Preferably, both the temperature sensor 7 and the pre-heating element 9 are placed in the housing obtained in the second longitudinal wall 6 of the support structure 2.

[0087] With reference to what is illustrated in the attached figures, the pre-heating element 9 extends axially from a first eyelet 10a, corresponding to the first terminal 9a, to a second eyelet 10b, corresponding to the second terminal 9b.

[0088] This first 10a and second 10b eyelet are riveted to the first longitudinal wall 5.

[0089] In the preferred embodiment, also the temperature sensor 7 extends between two eyelets and the second eyelet 10b of the pre-heating element 9 is riveted to the first longitudinal wall 5 together with the eyelet of the temperature sensor 7 corresponding to the first terminal 7a.

[0090] The second terminal 9b of the pre-heating element 9 and the first terminal 7a of the temperature sensor 7 are therefore defined by two substantially concentric eyelets.

[0091] Preferably, the heating portion 9c of the pre-heating element 9 is defined by a crimped or curved resistive wire shaped to increase the heat exchange area between the first 9a and the second terminal 9b.

[0092] In the preferred embodiment, illustrated in detail in figure 2, the pre-heating element 9 comprises a helical resistive wire 11 extending between the first terminal 9a and the second terminal 9b, with said first 9a and second terminal 9b defined by respective circular end turns 11a folded with respect to the heating portion 9c of the pre-heating element 9c. Alternatively, with reference for example to figures 4, 6, 8 and 10, the pre-heating element 9 could comprise a heating portion 9c connected to the two terminals 9a, 9b in a reversible manner, for example by means of pliers or clamps 12.

[0093] The object of the present invention is also a method for assembling a heating device for hair dryers, preferably but not exclusively of the type described so far.

[0094] We will therefore proceed hereinafter to describe the method in greater detail, emphasising from the outset that all of the features mentioned and described in connection with the device or the hair dryer, where not expressly indicated or in the event of incompatibilities, are to be considered applicable mutatis mutandis to the description of the method subject-matter of the present invention.

[0095] The method envisages providing at least the first flat plate 50 and the flat plate 60, both extending mainly along the central axis "A".

[0096] In this regard, it should be noted that the central axis "A" extends along an axial centreline of the first 50 and second flat plate 60.

[0097] The second flat plate 60 has, near the central axis "A", an oblong notch 60a defining a housing or an accommodating area.

[0098] In addition, at least the temperature sensor 7 and the pre-heating element 9, as well as a resistive wire 30, are provided.

[0099] According to the invention, the temperature sensor 7 and the pre-heating element 9 are fixed to the first flat plate 50, arranging them in succession with one another along said central axis "A".

[0100] Preferably, the temperature sensor 7 and the pre-heating element 9 are aligned along a direction parallel to the central axis "A".

[0101] In the preferred embodiment, the temperature sensor 7 and the pre-heating element 9 are fixed to the first flat plate 50 near the central axis, more preferably along said central axis "A".

[0102] Preferably, the temperature sensor 7 and the pre-heating element 9 are fixed to the first flat plate 50 by quick fixing, more preferably by riveting in accordance with what is described above.

[0103] The first flat plate 50 is then coupled to the second flat plate 60, so as to define a support structure 2 provided with at least four longitudinal walls 4 extending radially, angularly spaced from each other, with respect to said central axis "A".

[0104] The coupling is performed in such a way that the temperature sensor 7 and the pre-heating element 9 are placed in the housing defined by the notch 6a of the second flat plate 60.

[0105] At this point, the two flat plates are fixed together, the resistive wire 30 is wound around the longitudinal walls 4 to define the resistive winding 3. The invention achieves its intended purpose and achieves important advantages.

[0106] In fact, the provision of a structure in which the temperature sensor is associated with a pre-heating element operatively arranged upstream, but placed in the encumbrance of the resistive winding, allows to maximize the accuracy of the measurement, allowing the position of the sensor to be advanced and reducing the weight of the pre-heating element.

Claims

1. Air heating device for a hair dryer, comprising: - a support structure (2) extending along a central axis (A), in use aligned with a direction (B) of an air flow of the hair dryer, and provided with a plurality of longitudinal walls (4) extending radially and angularly spaced from each other, with respect to said central axis (A); - a resistive winding (3) extending around said support structure (2); - a temperature sensor (7) placed in electrical connection with said resistive winding (3) and constrained to a longitudinal wall of the plurality of longitudinal walls (4), in a radially internal position with respect to the resistive winding (3); characterised in that it comprises a pre-heating element (9) constrained to a longitudinal wall of the plurality of longitudinal walls (4) and placed: - near the temperature sensor (7); - operatively upstream of the temperature sensor (7), with reference to said direction (B) of the air flow of the hair dryer; - within an axial encumbrance area of the resistive winding (3), wherein: - the resistive winding (3) extends axially between a first end portion (3a) and a second end portion (3b); - the temperature sensor (7) and the pre-heating element (9) are placed, in succession, in an axial position interposed between the first end portion (3a) and the second end portion (3b) of the resistive winding (3).

2. Device according to claim 1, wherein the temperature sensor (7) and the pre-heating element (9) are fixed in axial succession on the same longitudinal wall.

3. Device according to any one of the preceding claims, wherein the temperature sensor (7) and the pre-heating element (9) each extend between a first terminal (7a, 9a) and a second terminal (7b, 9b), both fixed, preferably riveted, to the respective longitudinal wall.

4. Device according to claim 3, wherein the second terminal (9b) of the pre-heating element (9) is superimposed or coincident with the first terminal (7a) of the temperature sensor (7).

5. Device according to claim 3 or 4, wherein the pre-heating element (9) extends axially from a first eyelet (10a), corresponding to the first terminal (9a), to a second eyelet (10b), corresponding to the second terminal (9b); said first (10a) and second eyelet (10b) being riveted to the longitudinal wall.

6. Device according to any one of the preceding claims, wherein the pre-heating element (9) comprises a heating portion (9c) defined by a crimped or curved resistive wire shaped to increase the heat exchange area between the first (9a) and the second terminal (9b).

7. Device according to any one of the preceding claims, wherein the pre-heating element (9) comprises a helical resistive wire (11) extending between the first terminal (9a) and the second terminal (9b), with said first (9a) and second terminal (9b) defined by respective turns of circular ends (11a) folded with respect to the heating portion (9c) of the pre-heating element (9c).

8. Device according to any one of the preceding claims, wherein the temperature sensor (7) and the pre-heating element (9) are: - fixed to a first longitudinal wall (5) of the plurality of longitudinal walls (4) of the support structure (2); - placed in a housing obtained in a second longitudinal wall (6) of the plurality of longitudinal walls (4) of the support structure (2) coupled to the first longitudinal wall (5).

9. Ventilation device for a hair dryer, comprising: - a heating device (1) according to any one of the preceding claims; - an axial fan (21) operatively placed upstream of the heating device (1) and configured to generate an air flow directed towards the heating device (1).

10. Method for assembling a heating device (1) for hair dryer, comprising: - providing at least one first flat plate (50) extending mainly along its own central axis (A); - providing at least one second flat plate (60) extending mainly along its own central axis (A) and provided with a notch (60a) defining a housing; - providing at least one temperature sensor (7); - providing at least one pre-heating element (9); - providing a resistive wire (30); - fixing the temperature sensor (7) and the pre-heating element (9) to the first flat plate (50), arranging them in succession with one another along said central axis (A); - coupling the first flat plate (50) to the second flat plate (60), so as to define a support structure (2) provided with at least four longitudinal walls (4) extending radially, angularly spaced from each other, with respect to said central axis (A) and wherein the temperature sensor (7) and the pre-heating element (9) are placed in the housing; - winding the resistive wire around the longitudinal walls (4) to define a resistive winding (3), so that the temperature sensor (7) and the pre-heating element (9) are placed, in succession, in an axial position interposed between a first end portion (3a) and a second end portion (3b) of the resistive winding (3).

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