INFRARED HAIRDRYER

Abstract

An infrared hairdryer of the present disclosure includes a housing with an air inlet and an air outlet. The housing includes a motorized fan, an infrared radiation source for emitting IR radiant heat, and a back reflector positioned between the fan and the infrared emitter. A filter is positioned at the outlet of the hairdryer, allowing IR wavelengths comprised between 1.2 μm and 15 μm, preferably between 2 and 8 μm to leave the hairdryer and stopping the IR wavelengths out of this range. The infrared source has a thermal inertia allowing the infrared source to reach a temperature up to 1000° C. in less than 10 seconds, preferably in less than 5 seconds.

Claims

1. An infrared (IR) hairdryer (1) comprising: a housing (7) with an air inlet (8) and an air outlet (9), the housing (7) including a motorized fan (4); an infrared radiation source (2) for emitting IR radiant heat; a back reflector positioned between the fan (4) and the infrared emitter (2); a filter (6) positioned at the outlet (9) of the hairdryer and configured to allow IR wavelengths comprised between 1.2 μm and 15 μm to leave said hairdryer and stopping the IR wavelengths out of this range; wherein the infrared source (2) has a thermal inertia allowing the infrared source (2) to reach a temperature up to 1000° C. in less than 10 seconds.

2. The infrared hairdryer according to claim 1, wherein the infrared radiation source (2) is in the form of a mesh or an etched foil.

3. The infrared hairdryer according to claim 2, wherein the etched foil has a thickness comprised between 30 and 150 μm.

4. The infrared hairdryer according to claim 2, wherein the mesh or the etched foil is arranged in a disc-shaped surface having a surface area greater than 30 cm.sup.2.

5. The infrared hairdryer according to claim 2, wherein the etched foil is made of FeCrAl alloy.

6. The infrared hairdryer according to claim 2, wherein the etched foil is maintained in the hairdryer (1) by a holder (13) made of mica allowing an electrical insulation.

7. The infrared hairdryer according to claim 1, wherein the infrared radiation source has a power density comprised between 5 and 15 W/m.sup.3.

8. The infrared hairdryer according to claim 1, wherein the filter (6) is a silicon window filter.

9. The infrared hairdryer according to claim 1, wherein the back reflector (5) is an anodized parabolic reflector made of aluminum.

10. The infrared hairdryer according to claim 1, wherein a side reflector (14) is provided to reflect peripheral radiation emitted by the emitter, said side reflector (14) being in the shape of a ring.

11. The infrared hairdryer according to claim 1, further comprising a deflector (11) to deviate the air stream in a peripheral stream along walls of the housing (7).

12. The infrared hairdryer according to claim 11, further comprising an air stream separator (15) having a central channel (12) to separate the air stream into two substreams, a central substream and a peripheral substream.

13. The infrared hairdryer according to claim 1, further comprising an outlet grid (10) at the air outlet (9) configured to prevent a user to be in contact with the filter (6).

14. The infrared hairdryer according to claim 1, wherein the motorized fan (4) is radial.

15. The infrared hairdryer according to claim 1, wherein the filter positioned at the outlet of the hairdryer is configured to allow IR wavelengths of 2 to 8 μm.

16. The infrared hairdryer according to claim 1, wherein the thermal inertia of the infrared source allows the infrared source to reach a temperature of up to 1000° C. in less than 5 seconds.

17. The infrared hairdryer according to claim 3, wherein the thickness of the etched foil is 50 to 120 μm.

18. The infrared hairdryer according to claim 4, wherein the surface area of the disc-shaped surface is greater than 40 cm.sup.2.

19. The infrared hairdryer according to claim 7, wherein the power density of the infrared radiation source is 10 W/m.sup.3.

20. An infrared (IR) hairdryer, comprising: a housing having an air inlet and an air outlet; a fan disposed in the housing and configured to cause an airflow to pass from the air inlet to the air outlet; an infrared radiation source disposed in the housing and configured to emit IR radiant heat; a back reflector between the fan and the infrared radiation source; a filter disposed at the air outlet and configured to allow only IR wavelengths of 1.2 μm to 15 μm to leave the hairdryer; wherein the infrared radiation source has a thermal inertia allowing the infrared source to reach a temperature of 1000° C. in less than 10 seconds.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG. 1 is a perspective view of one embodiment of a hairdryer according to the present disclosure.

[0029] FIG. 2 represents a first detailed cross-sectional view of the hairdryer of the present disclosure, wherein the air stream provided by the fan is deviated by a deflector in a peripheral stream, licking the walls of the housing of the hairdryer.

[0030] FIG. 3 represents a second detailed cross-sectional view of the hairdryer of the present disclosure.

[0031] FIG. 4 represents a third detailed cross-sectional view of the hairdryer of the present disclosure.

[0032] FIG. 5 represents a fourth detailed cross-sectional view of the hairdryer of the present disclosure.

[0033] FIG. 6 represents a detailed view of an etched emitter of the hairdryer according to the present disclosure.

[0034] FIG. 7 represents another embodiment of the hairdryer according to the present disclosure, with a deflector separating the air stream into a central substream and a peripheral substream.

[0035] FIG. 8 is another view of the embodiment of FIG. 7.

REFERENCE SYMBOLS

[0036] 1 Hairdryer [0037] 2 IR emitter (IR source) [0038] 3 Fan motor [0039] 4 Fan [0040] 5 Back reflector [0041] 6 Filter (silicon window) [0042] 7 Housing [0043] 8 Air inlet [0044] 9 Air outlet [0045] 10 Outlet grid [0046] 11 Deflector [0047] 12 Central channel [0048] 13 Mica holder (IR emitter support) [0049] 14 Side reflector [0050] 15 Air stream separator

DETAILED DESCRIPTION

[0051] The present disclosure relates to an infrared hairdryer 1 as illustrated by FIGS. 1 to 5 and 7, 8.

[0052] The infrared hairdryer comprises a housing 7 with an air inlet 8 and an air outlet 9. The housing includes a motor 3, which operates a fan 4 that blows an air stream out of the dryer by the air outlet 9. An infrared source 2 is located between the fan 4 and the air outlet 9 for emitting IR radiant heat. To be operational, the infrared hairdryer comprises a back reflector 5 provided between the fan 4 and the infrared source 2 and a filter 6 located at the outlet 9 of the hairdryer, as explained in more details below, in order to obtain emitted IR wavelengths of about 1.2 to about 15 μm, preferably of about 2 to 8 μm. The air stream provided by the fan is deflected by a deflector 11 in order to avoid the cooling of the IR emitter and maintain it at operational temperatures while removing the excess of heat from the body of the hairdryer.

[0053] The infrared source 2 has a low thermal inertia which allows to reach a temperature of up to 1000° C. in less than 10 seconds, preferably less than 6 seconds, 5 seconds or 4 seconds and most preferably, less than 3 seconds. The “thermal inertia” of a material represents its resistance to temperature change when a disturbance of its thermal equilibrium occurs. If the disturbance brings the material to a new equilibrium temperature, the thermal inertia is the time needed for this new equilibrium point to be reached. The infrared emitter has a power density comprised between 5 and 15 W/m.sup.3, preferably between 8 and 12 W/m.sup.3, for example 10 W/m.sup.3. The low thermal inertia of the infrared emitter allows the IR dryer to be operable in a few seconds.

[0054] The Stefan-Boltzmann law describes the relation between the power radiated from a black body and its temperature, and states that the total energy radiated per unit surface area of a black body across all wavelengths per unit time j* (also known as the black-body radiant emittance) is directly proportional to the fourth power of the black body's thermodynamic temperature T:

J*=σ.Math.S.Math.T.sup.4

[0055] (σ is the constant of Stefan-Boltzmann=5.670373×10.sup.−8 W m.sup.2 K.sup.−4 and S=emissivity compared to the black body).

[0056] Therefore, the total energy depends on the surface area (first power), and on the temperature (fourth power) of the IR source. To obtain a maximal total power output, the area of the emitter has to be maximized.

[0057] The infrared emitter 2 can be a mesh or an etched foil arranged in a disc-shaped surface, as illustrated by FIG. 6. The aim is to maximize the emission area within the disc surface. The surface area of the disc is greater than 30 cm.sup.2, preferably greater than 50 cm.sup.2.

[0058] A mesh has the property to offer, for the same heating surface, a smaller mass than a wire. The heating of the mesh is therefore faster.

[0059] A preferred alternative to the mesh is the etched foil, as illustrated in FIG. 6. A pattern is etched out of a metal foil, preferably made of a FeCrAl alloy and having a thickness comprised between 30 and 150 μm, preferably between 40 and 150 μm, for example of 100 μm. The etching technology allows the creation of a specific geometry leading to focused positions where the heating occurs in the foil. Indeed, the resistance increases in thinner parts of the etched foil, leading to increase the heating of these parts of the foil. It is possible to decrease the thermal inertia of the foil by creating an optimal design while avoiding the overheating of brittle parts of the foil. As illustrated in FIG. 6, the elements located in edges or turns are fuller than other parts of the foil. There is no resistive pattern at corners or on the legs of the foil and therefore no heating in unwanted areas. The etched foil is maintained in the hairdryer by a holder 13 made of a high temperature resistant material, for instance mica allowing an electrical isolation.

[0060] A back reflector 5 is provided between the fan 4 and the infrared emitter 2 to maximize IR radiation of the desired wavelength in the front direction and minimize radiation of the visible spectrum. This reflector is preferably an anodized parabolic reflector made of aluminum, having on its reflecting surface a darkly pigmented, anodized coating. In use, the infrared emitter 2 heats up and emits IR radiation. The wavelength of the IR radiation from the emitter 2 which is reflected by the parabolic reflector 5 is essentially in the range of about 0.8 μm and above, essentially all the remaining visible and IR radiation is absorbed. A side reflector 14 is also provided to reflect the peripheral radiation emitted by the emitter. The side reflector can have the shape of a ring, and is preferably made of aluminum.

[0061] The hairdryer comprises also a filter 6 to further narrow the wavelength and remove less preferred radiations. The filter is preferably a silicon window filter, located at the air outlet 9. The filter preferably filters out most of the IR radiation coming from the dryer except IR wavelengths greater than about 1.2 μm. The filter can be chosen to only allow IR wavelengths of about 1.2 to about 15 μm or preferably IR wavelengths of about 2 to 8 μm to be emitted, depending on the particular filter used. In order to obtain these results, the silicon resistivity must be between 0.25 pΩcm and 25 pΩcm.

[0062] In a preferred embodiment of the present disclosure, the hairdryer comprises a deflector 11 located in the housing to direct the flow. As illustrated by FIGS. 2 to 5, the deflector 11 has an elliptical shape to deviate the air stream provided by the fan in a peripheral stream, licking the walls of the housing. The air stream is blown out the hairdryer by the periphery without crossing the emitter, to maintain it at operational temperatures. The aluminum parts of the hairdryer are cooled to avoid overheating as the air stream provided by the fan is deflected by the deflector 11 to lick the walls of the housing.

[0063] In a second embodiment, the hairdryer additionally comprises an air stream separator 15 having a central channel 12 to separate the air stream into two substreams, a central substream and a peripheral substream. As illustrated by FIGS. 7 and 8, the central substream crosses the air stream separator 15 by the central channel 12 while the peripheral substream licks the walls of the deflector and the housing.

[0064] An outlet grid 10 is provided at the air outlet 9 to prevent the user to be in contact with the filter 6 which is at around 400° C. As a result, the grid must be made of a thin material as transparent as possible to prevent the transmission of the energy of the hairdryer and stay as cold as possible.

[0065] The hairdryer of the present disclosure has the advantage to dry hair efficiently and relatively quickly at low temperature, thanks to the combination of the selected wavelengths of infrared radiation and the low thermal inertia of the emitter. The hair temperature reaches 30-60° C. instead of 60-105° C. for a conventional hairdryer during drying. Furthermore, the heating time of the emitter is short, avoiding the user to wait before using the hairdryer at its optimum temperature and allowing a more precise temperature regulation.