Method for treating hair and associated assembly

Abstract

Method for treating hair using one or more microwave applicators (200(1),... 200(N)) each arranged to receive a lock to be treated, the one or more applicators (200(1),... 200(N)) being connected to a microwave-generating system (100), the method comprising the steps of: • - a) determining for each applicator (200 (1),... 200 (N)) receiving a lock to be treated, by varying the microwave frequency transmitted to the applicator (200(13,...200(33) by the system (100) and comparing measurements representative of the variation in the power reflected by the applicator (200 (1),...200 (N)) when the frequency varies, a respective working frequency value optimized for the applicator, • - b) treating the hair received by each applicator (200(13,...200( N3), the system (100) feeding each applicator at its respective optimized working frequency.

Description

[0001] Description

[0002] Title: Method for treating hair and associated assembly

[0003] Technical field

[0004] The present invention relates to the field of cosmetic treatment of hair.

[0005] Prior art

[0006] Methods for styling hair using a microwave hair treatment are known, for example from patent application W02013183021, the hair potentially being under tension, flattened, rolled up or otherwise shaped, and being wetted by a liquid such as water or a shaping composition, for example comprising an oxidant or a base such as a hydroxide.

[0007] There is a need to facilitate treatment of hair by microwaves, and in particular to benefit from a treatment method and assembly allowing hair to be treated quickly and efficiently.

[0008] Summary of the invention

[0009] The invention aims to meet this need and, according to one of its aspects, relates to a method for treating hair using one or more microwave applicators each arranged to receive a lock to be treated, the one or more applicators being connected to a microwave-generating system, the method comprising the steps of:

[0010] a) determining for each applicator receiving a lock to be treated, by varying the microwave frequency transmitted to the applicator by the system and comparing measurements representative of the variation in the power reflected by the applicator when the frequency varies, a respective working frequency value optimized for the applicator,

[0011] - b) treating the hair received by each applicator, the system feeding each applicator at its respective optimized working frequency.

[0012] The invention makes it possible to treat the hair received in each applicator at an optimized frequency, that is to say the frequency among the tested frequencies that results in the best absorption of the applied microwaves, since the unabsorbed power is reflected.This improves the efficiency of the treatment. The optimized working frequency may depend on the amount (moisture content, for example) and / or on the nature of the liquid wetting the lock, or on the number, arrangement, nature or condition of the hair from which the lock is formed.

[0013] In addition, the invention makes it possible to work with several applicators simultaneously, under conditions that mean that these applicators do not all have the same responses to the microwave wavelength. By determining the best working frequency for each applicator, it is possible to limit treatment disparities between the various applicators, and thus obtain a uniform treatment.

[0014] It is possible to vary, during the frequency exploration aiming to find the best frequency for a given applicator, said frequency incrementally, with a constant or variable increment. For example, the microwave frequency is varied with an increment of less than 100 MHz in step a).

[0015] Various strategies for searching for the optimum frequency may be implemented; in one example, the optimum frequency is sought via a constant-increment frequency sweep, from a low frequency to a high frequency.

[0016] For example, the frequency varies in a range between 500 MHz and 300 GHz, for example between 500 MHz and 10 GHz, better still from 900 MHz to 5 GHz, and most preferably from 2 GHz to 3 GHz. It is also possible to implement a plurality of microwave sources each having a defined transmission frequency or frequency range that is at least partially complementary to an overall range, the sweep then consisting in separately switching on each source one after the other, in particular in an order of increasing frequency. The optimized frequency will then correspond to a microwave source that will be activated in treatment step b).

[0017] Preferably, the power of the microwaves before distribution to the various applicators ranges from 10 W to 300 W, or even from 10 W to 100 W.During the implementation of the method, each lock present in each applicator may be wetted by a liquid and / or subjected to mechanical tension, for example as a result of being wound on a support contained in the applicator.

[0018] Each applicator may be configured to apply a flexion, traction, torsion and / or compression to the hair. For example, each applicator comprises a hair curler or a clamp.

[0019] The wetting liquid may be water or any other composition. By way of example, it may be a question of a hair-shaping composition, for example an oxidizing composition used in hairdressing (conventionally called a fixer) or a composition comprising a base belonging to the hydroxide family.

[0020] Each applicator generally comprises an enclosure allowing the lock to be treated to be enclosed substantially hermetically in order to limit leakage of microwave radiation to the exterior.

[0021] Each applicator comprises an electrically conductive element allowing the microwaves to be radiated into the enclosure, for example a conductive strand devoid of shielding.

[0022] The microwaves may be transmitted to each applicator by any suitable means such as a coaxial cable, for example a coaxial cable of predefined impedance, 50 ohms for example.

[0023] According to one preferred embodiment, the method is implemented with several applicators, this allowing faster treatment of the hair. The number of applicators for example ranges from 2 to 12. Preferably, the applicators are identical.

[0024] As mentioned above, in step a), a frequency sweep may be performed within a predefined frequency range, the frequency sweep for example being performed in increments, for example from a low end of said range. As a variant, the frequency exploration may be carried out differently, by decreasing the frequency, or randomly.The sweep may be performed very quickly. Thus, according to one embodiment, step a) lasts less than 1 second, and for example less than 0.1 seconds.

[0025] The treatment in step b) depends on the desired result and on the power, and may last longer than step a), and for example last more than 10 seconds, for example more than 30 seconds, and for example more than one minute. In particular, each applicator is fed, in step b), for more than 10 seconds.

[0026] Preferably, the optimized working frequency corresponds to the frequency at which the power reflected by the applicator is minimal. Since the total power is equal to the absorbed power plus the reflected power, the power absorbed by the applicator is then maximum (maximum specific absorption rate or SAR), this indicating a maximum absorption of the microwaves by the hair and compounds present in the enclosure of the applicator, and thus a conversion of the microwaves into heat that in principle is optimal.

[0027] The method may comprise, in step a), measuring the power transmitted by the microwavegenerating system to each applicator as the microwave frequency is varied, the optimized working frequency corresponding to the frequency at which the ratio between the transmitted power and the reflected power is maximum.

[0028] Preferably, in step b), the applicators are simultaneously fed by the system at the respective optimized working frequencies (in other words: with all the optimized frequencies). Thus, the treatment is carried out on several locks in parallel at the optimized working frequency of each applicator. Such a feed regime does not exclude the presence, in the signal transmitted to each applicator, of components at additional frequencies other than the optimized working frequency, these additional frequencies corresponding to the optimized working frequencies of the other applicators.

[0029] In one embodiment, the system generates a single signal (i.e., a signal transmitted over a single channel, over the same coaxial cable for example) containing components at the various optimized working frequencies, and the single signal is then divided and transmitted to the various applicators via respective channels.The single signal may be divided and transmitted to the various applicators by a divider. A divider is a passive multi-port network that divides a radio-frequency signal input into the divider into a plurality of output signals. It is, for example, a Wilkinson divider or another type of divider, for example one based on a direct combiner, a multi-port branch-line directional coupler or multi-port rat-race coupler or a so-called 3 dB hybrid combiner.

[0030] According to one embodiment, the single signal is generated, before amplification, by a single source. The single source for example comprises a signal synthesizer allowing several fundamentals of the same amplitude to be generated simultaneously, at predefined frequencies.

[0031] As a variant, the signals at the various optimized working frequencies are generated by as many oscillators, the signals of which are combined to form the single signal.

[0032] Preferably, the micro wave-generating system comprises an amplifier that receives the single signal as input and amplifies it. This makes it possible to reduce costs by avoiding the need for multiple amplifiers; however, if the source is sufficiently powerful, or if the oscillators mentioned above are sufficiently powerful, it is possible not to provide an additional amplifier of the single signal.

[0033] In order to compensate for drift in the optimized working frequencies of the applicators, for example due to the fact that the moisture of the hair decreases within the enclosure, a quantity representative of the reflected power is measured in step b) for each applicator and the optimized working frequency is adjusted depending on the quantity representative of the measured reflected power. It is thus possible to adapt the optimized working frequency of each applicator as it varies in step b), for example as the liquid wetting the lock evaporates.

[0034] It is also possible to interrupt the treatment, and perform another frequency exploration by performing step a) again.

[0035] The method may thus comprise a succession of alternations of steps a) and b).According to another of its aspects, the invention also relates to an assembly for treating hair, and in particular for implementing the method defined above, comprising:

[0036] one or more microwave applicators, each arranged to receive a lock to be treated,

[0037] a microwave-generating system, comprising a control unit arranged to: a) determine for each applicator receiving a lock to be treated, by varying the microwave frequency transmitted to the applicator, by recording measurements representative of the variation in the power reflected by the applicator when the frequency varies, and by comparing the various recorded values, a respective working frequency value optimized for the applicator,

[0038] b) command each applicator to be fed at its respective optimized working frequency.

[0039] Said quantity representative of the variation in the reflected power may be measured using a radio-frequency directional coupler.

[0040] Preferably, the assembly comprises a plurality of applicators and a plurality of lines for feeding these applicators. Each line may comprise a radio-frequency directional coupler for measuring the power reflected by the applicator connected to that line.

[0041] Preferably, the generating system comprises a single power amplifier.

[0042] In one example of embodiment of the invention, the output power of the amplifier is adjustable by varying the attenuation coefficient of an attenuator placed upstream of the amplifier, the control unit for example being configured to control the attenuator based on a measurement of the output power of the amplifier and on a power setpoint.

[0043] According to one embodiment, the generating system comprises a single source controlled by the control unit to generate the signals at the various optimized working frequencies respectively corresponding to the various applicators.As a variant, the signals at the various optimized working frequencies are generated by several oscillators, and better still by as many oscillators as there are signals to be combined.

[0044] According to one embodiment, the generating system comprises a signal divider, and preferably a Wilkinson divider, the outputs of which are connected to the various lines for feeding the applicators.

[0045] Brief description of the drawings

[0046] The invention will possibly be better understood on reading the following detailed description of one non-limiting example of implementation thereof, and on examining the appended drawing, in which:

[0047] [Fig 1] shows one example of a treating assembly according to the invention, and

[0048] [Fig 2] is a block diagram illustrating various steps of one example of a method according to the invention,

[0049] Detailed description

[0050] Figure 1 shows an assembly for treating hair comprising up to N applicators 200(i),...200(N)each intended to contain at least one lock of hair (not shown), and a microwave-generating system 100 the components of which are connected to an electrical power supply 400, which is for example connected to a 110 or 240 V mains. N for example ranges from 1 to 15, and better still from 2 to 12.

[0051] The system 100 may comprise, as shown, the following constituent elements:

[0052] A frequency synthesizer 110. It may be a question of the synthesizer sold by Texas Instruments under the reference LMX2582EVM;

[0053] A programmable attenuator 120 that receives the signal from the synthesizer 110. It may be a question of the one sold under the reference PE70AXX by Pasternack; An amplifier 130 at the output of the attenuator 120. It may be a question of the amplifier sold under the reference SKU 1047 by Empower RF Systems;

[0054] A divider 140, for example a Wilkinson divider;Couplers 160 on each of the lines 201(i),... 201(N)connected to the applicators 200(i),... 200(N). It is for example a question of bidirectional couplers sold under the reference PE2CP1015 by Pasternack;

[0055] A circulator 150 upstream of the divider 140;

[0056] Couplers 180 and 190 that may take the form of a single bidirectional coupler, identical to coupler 160, placed between the amplifier 130 and the circulator 150; A control unit 199, for example one based on a microcontroller or an FPGA, which receives the signals from the various couplers, in such a way as to read the transmitted and / or reflected powers, and which controls the synthesizer 110 and the attenuator 120;

[0057] A circulator 150 protecting part of the system 100 from excessively high reflected power coming from the applicators 200(i),... 200(N).

[0058] The signal generated by the synthesizer 110 is attenuated by the attenuator 120, then amplified by the amplifier 130, for example with a factor of about 10, before being transmitted to the various applicators 200(i) ... 200(N), via the divider 140 and the lines 201(i)... 201(N).

[0059] According to the invention, the system 100 is arranged to determine the best working frequencies of each of the applicators 200(1)... 200(N).

[0060] This may be done based on a frequency sweep, as illustrated in Figure 2.

[0061] In step SOO, the control unit 199 reads an initial frequency from its memory, for example the low end of the interval to be explored, the initial value being equal to 1.5 GHz for example.

[0062] In the next step S10, the control unit 199 commands the synthesizer 110 to generate a sinusoidal signal at the initial frequency, for example with a power of 5 W (resulting in a power of about 50 W being output from the amplifier 130) for a predefined length of time and receives from the various couplers 160 information indicating the power reflected by each thereof.For example, the reflected power is, at the frequency of 1.5 GHz, 10 W for the first 200(i) of the applicators and 5 W for the last 200(N).

[0063] In step S20, the control unit 199 determines that the sweep has not ended, and in step S30’, the frequency is incremented, for example by 100 MHz.

[0064] In step S10, the control unit 199 controls the oscillator 110 to the current frequency.

[0065] For example, the power reflected by the applicator 200(i) at the frequency of 1.6 GHz is 5 W and the power reflected by the applicator 200(N)is 15 W.

[0066] In step S20, the control unit 199 again determines that the sweep has not ended, and the method continues to step S30’ in which the frequency is incremented.

[0067] In step S10, the control unit 199 controls the oscillator 110 to the current frequency.

[0068] The power reflected by the applicator 200(i) is then, for example, 10 W and the power reflected by the applicator 200(N)is 20 W, at the frequency of 1.7 GHz.

[0069] Once the sweep has ended, the control unit 199 can compare the various levels of power reflected by each applicator, at each of the tested frequencies, and find for each applicator the frequency that gave the minimum reflected power.

[0070] With the example of the above values, the control unit may thus determine that the optimized working frequency for the applicator 200(i) is 1.6 GHz and that the optimized working frequency for the applicator 200(N)is 1.5 GHz.

[0071] In step S40, the control unit 199 then commands the synthesizer 110 so that it simultaneously generates, for a predefined length of time, fundamentals (i.e. sinusoidal signals) at the various working frequencies.In the example of the above values, the control unit will thus command the synthesizer 110 to simultaneously generate at least:

[0072] - a fundamental at a frequency of 1.5 GHz and,

[0073] - a fundamental at a frequency of 1.6 GHz.

[0074] These fundamentals are simultaneously amplified by the amplifier 130 after possible attenuation by the attenuator 120, to obtain a signal of a desired power, of about 50 W for example, which is received by the various applicators, and at least by the applicator 200(i) and the applicator 200(N), which may thus treat the locks they contain with maximum efficiency.

[0075] To illustrate the control of the attenuator, assuming that the control unit receives, from the coupler 190, a transmitted power output by the amplifier 130 equal to 55.55 W, and that the power setpoint is 50 W, the control unit 199 controls the attenuator 120 so that it implements an attenuation of 11.1% in order to obtain, at the output of the amplifier 130, a power of 50 W.

[0076] The process of steps SOO to S40 may be repeated during the treatment, for example about ten times.

Claims

Claims1. Method for treating hair using one or more microwave applicators (200(i), ... 200(N)) each arranged to receive a lock to be treated, the one or more applicators (200(i), ...200(N)) being connected to a microwave-generating system (100), the method comprising the steps of:a) determining for each applicator (200(i), ...200(N)) receiving a lock to be treated, by varying the microwave frequency transmitted to the applicator (200(i),...200(N)) by the system (100) and comparing measurements representative of the variation in the power reflected by the applicator (200(i),...200(N)) when the frequency varies, a respective working frequency value optimized for the applicator,- b) treating the hair received by each applicator (200(1),...200(N)), the system (100) feeding each applicator at its respective optimized working frequency.

2. Method according to Claim 1, wherein, in step a), a frequency sweep is performed within a predefined frequency range.

3. Method according to Claim 2, the frequency sweep being performed in increments, in particular from a low end of said range.

4. Method according to any of the preceding claims, step a) lasting less than 0.1 seconds.

5. Method according to any of the preceding claims, each applicator being fed, in step b), for more than 10 seconds.

6. Method according to any of the preceding claims, wherein the optimized working frequency corresponds to the frequency at which the power reflected by the corresponding applicator is minimal.

7. Method according to any of Claims 1 to 6, wherein, in step b), the applicators (200(i), ...200(N)) are simultaneously fed by the system (100) at the respective optimized working frequencies.

8. Method according to Claim 7, wherein the system (100) generates a single signal containing components at the various optimized working frequencies, and the single amplified signal is divided and transmitted to the various applicators (200(1),...200(N)).

9. Method according to Claim 8, wherein the single signal containing the components at the various optimized working frequencies is generated, before amplification, by a single source (110).

10. Method according to any of the preceding claims, wherein a quantity representative of the reflected power is measured in step b) for each applicator (200(i),...200(N)) and wherein the optimized working frequency is adjusted depending on the quantity representative of the measured reflected power.

11. Assembly for treating hair, comprising:one or more microwave applicators (200(i),...200(N)), each arranged to receive a lock to be treated,a microwave-generating system (100), comprising a control unit (199) arranged to:a) determine for each applicator (200(i),...200(N)) receiving a lock to be treated, by varying the microwave frequency transmitted to the applicator (200(i),...200(N)), by recording measurements representative of the variation in the power reflected by the applicator (200(i),...200(N)) when the frequency varies, and by comparing the various recorded values, a respective working frequency value optimized for the applicator,b) command each applicator (200(i),...200(N)) to be fed at its respective optimized working frequency.

12. Assembly according to Claim 11, the generating system comprising a plurality of applicators (200(i),...200(N)) and a plurality of lines (201(i),...201(N)) for feeding these applicators (200(i),...200(N)).

13. Assembly according to Claim 12, comprising a single power amplifier (130).

14. Assembly according to Claim 13, comprising a single source (110) controlled by the control unit (199) to generate the signals at the various optimized working frequencies respectively corresponding to the various applicators (200(i),...200(N)).

15. Assembly according to any of Claims 12 to 14, the lines being connected to a signal divider (140), and preferably to a Wilkinson divider.

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