Patent Application
20220378165
The present disclosure is related to an infrared hairdryer.
Hairdryers using infrared (IR) radiation have been used in the past but they were not quite successful in the market for various reasons. This type of hairdryers was equipped with large bulky infrared lamps, making the handling of those devices difficult. In addition, infrared hairdryers of the prior art produce often excessive temperatures, i.e. up to 230 degrees, damaging the hair structure.
Document FR2428991 tried in 1976 to avoid the drawbacks of those IR lamp hairdryers by proposing a less bulky IR hairdryer emitting specific wavelengths in lower temperature ranges. This document discloses a hairdryer that includes a fan to blow an air stream at low velocity out of the dryer, an IR energy source to emit infrared radiation, an anodized parabolic reflector which modifies the radiated energy by only reflecting selected wavelengths, and a transparent IR filter to further narrow the emitted IR radiation to the desired wavelength range. The hairdryer of this document uses a selected range of wavelengths of infrared radiation in order to produce low temperatures, around 90° C., when the hairdryer is placed at a distance of 25 cm. The preferred wavelength ranges disclosed in this document are about 2 to 3 and 6 to 8 μm, because water absorbs the main energy at this wavelength. The maximum IR absorption spectrum of wet hair and the most efficient drying occur when these wavelengths are emitted from the dryer. An advantage of this disclosure is that as the hair is being dried, the dry hair protects the scalp since it does not absorb the selected IR wavelengths.
Nevertheless, the disadvantage of this device is that the heating time of the emitter is high, up to 80 seconds, and the user has to wait before using the hairdryer at its optimum temperature.
The present disclosure aims to provide an infrared hairdryer using a narrow range of wavelengths of infrared (IR) radiation, with an infrared emitter having low thermal inertia, to be able to reach its working temperature in a few seconds leading to a precise temperature regulation for an optimal drying.
Another aim of the present disclosure is to provide an infrared hairdryer with an improved air stream adapted to the particular configuration of an infrared hairdryer.
The present disclosure is related to an infrared hairdryer, using in particular a selected range of wavelengths of infrared (IR) radiation, and having an improved IR emitter with low inertia.
The present disclosure teaches an infrared hairdryer comprising:
a filter 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 said hairdryer and stopping the IR wavelengths out of this range;
wherein 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.
According to preferred embodiments, the infrared hairdryer is further limited by one of the following features or by a suitable combination thereof:
The present disclosure relates to an infrared hairdryer 1 as illustrated by
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.
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/m3, preferably between 8 and 12 W/m3, for example 10 W/m3. The low thermal inertia of the infrared emitter allows the IR dryer to be operable in a few seconds.
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·S·T
4
(σ is the constant of Stefan-Boltzmann=5.670373×10−8 W m2 K−4 and S=emissivity compared to the black body).
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.
The infrared emitter 2 can be a mesh or an etched foil arranged in a disc-shaped surface, as illustrated by
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.
A preferred alternative to the mesh is the etched foil, as illustrated in
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.
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.
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
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
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.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 19219027.0 | Dec 2019 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/070419 | 7/20/2020 | WO |
