EP2399481B1 - Hairdressing appliance with jaws - Google Patents

Description

The present invention relates to the technical field of hairdressing appliances such as curling irons or straighteners.

Such devices generally comprise two jaws at least one of which is heated and which are hinged together so as to be able to pinch a lock of hair to be shaped. One of the jaws or both jaws are then heated directly or indirectly by an electric heating member whose temperature is regulated by a thermostatic system to reach a temperature determined according to a temperature value possibly selected by a user of the apparatus, as for example described in the document WO2007 / 141276 .

Such a type of hairdressing apparatus makes it possible with some practice to obtain a good smoothing result. This good smoothing result is obtained by applying a significant pressure force to keep the jaws closed and apply sufficient pressure on the lock of hair to be treated. Possibly, the user can use both hands to increase this effort for a better result. In all cases, the maintenance of this significant pressure effort during the entire treatment cycle of the hair is painful and restrictive for the user. Laboratory tests have shown that the combination of the tension of the hair and the heat applied by the iron with a reasonable clamping pressure makes it possible to obtain a result equivalent or even better than that obtained with iron alone by applying a pressure more important.

In order to remedy the aforementioned drawback of hardness and possible monopolization of both hands, it appeared the need for a new type of straightener that allows to recreate these conditions of tensioning and heating the hair, without the two hands are mobilized, so as to facilitate the task of the user.

• deux mâchoires, première et deuxième, allongées et articulées entre elles pour être mobiles entre une position ouverte et une position fermée dans laquelle elles définissent par des surfaces de travail en regard une zone de traitement de cheveux,
• une première plaque de lissage qui forme la surface de travail de la première mâchoire et qui est articulée sur la première mâchoire,
• des moyens de contrainte qui sont interposés entre la plaque de lissage et la première mâchoire et qui tendent à éloigner la plaque de lissage de la première mâchoire et à la placer dans une position de repos,
• des moyens électriques de chauffage associés à l'une au moins des surfaces de travail.

In order to achieve this objective, the invention relates to a hairdressing apparatus comprising at least:

• two jaws, first and second, elongated and articulated together to be movable between an open position and a closed position in which they define by working surfaces facing a hair treatment area,
• a first smoothing plate which forms the working surface of the first jaw and which is articulated on the first jaw,
• stressing means which are interposed between the smoothing plate and the first jaw and which tend to move the smoothing plate away from the first jaw and into a rest position,
• electric heating means associated with at least one of the working surfaces.

According to the invention, the hairdressing apparatus comprises means of articulation of the first smoothing plate on the first jaw defining an axis of rotation Δ of the first smoothing plate with respect to the first jaw, this axis of rotation Δ being substantially parallel to the working surface of said smoothing plate and to a longitudinal median plane M of the working surface.

Thus, when closing the hair styling device on a lock of hair to be treated, the smoothing plate of the first jaw will tend to pivot towards the jaw so that its portion located near the axis of rotation Δ will be closer to the second jaw than the part of the smoothing plate opposite to the axis of rotation. This movement of the smoothing plate will give the hair treatment area a wedge shape which contributes to creating in the narrowing zone of the wedge, located near the axis of rotation, a zone of different friction, or even greater friction. When moving the hair styling device, the traction exerted on the lock of hair will therefore be greater in the narrowing zone than in the opposite region of the treatment zone. The smoothing plate is understood as a flat plate or a curved plate.

According to the invention, the axis of rotation Δ of the first plate is located between the median plane M and a first lateral plane L which is parallel to the median plane and passes through a longitudinal edge of the first jaw. When the axis rotation is not in the median plane, this gives an asymmetry of the treatment area. The asymmetry of the treatment zone at the origin of this difference in traction or friction therefore allows a user, who will have made sure to preferentially arrange the hairstyling apparatus so that the axis of rotation is the opposite scalp, stretching the part of the hair located between the scalp and the narrowing area and therefore particularly the part of the hair located in the rest of the treatment area. However, the heating of the hair in traction in the treatment zone provides an optimal smoothing and much higher than that which would result from a simple heating of the hair by pinching.

Thus, it has been found possible to obtain, with a hairdressing appliance according to the invention, the temperature of the electric heating means of which is set at around 170 ° C., the same results, with equivalent hair quality, as those obtained with a hairdressing appliance according to the prior art simple pinch whose temperature of the electric heating means is set at about 230 ° C. This reduction of the treatment temperature for the same quality of result makes it possible to preserve the treated hair while reducing the electrical consumption.

According to an alternative embodiment of the invention, the hairdressing apparatus comprises a second smoothing plate which forms the working surface of the second jaw and which is articulated on the second jaw via hinge means defining a axis of rotation Δ 'of the second smoothing plate relative to the second jaw, this axis of rotation Δ' being substantially parallel to the working surface of the second smoothing plate and to a median plane M 'of the working surface .

According to one characteristic of the invention, the axis of rotation Δ 'of the second plate may be located between the median plane M' and a first lateral plane L 'which is parallel to the median plane and passes through a longitudinal edge of the second jaw.

In order to accentuate the wedge effect, the axes of rotation of the first and second smoothing plates will preferably be located substantially opposite one of the other. However, such an arrangement is not strictly necessary for producing a hairdressing appliance according to the invention.

According to a characteristic of the invention, the axis of rotation Δ of the articulation means is located between the median plane M and a second lateral plane L "which is parallel to the median plane and passes through a longitudinal edge of the smoothing plate Thus, the region plumb with the axis of rotation Δ allows to get a good pinch of the lock of hair to ensure good traction of the latter.

According to the invention, the axis of rotation Δ of the articulation means may be located substantially in the plane of the working face or on the contrary be located between the corresponding jaw and a plane passing through and parallel to the working surface.

According to one characteristic of the invention, the axis of rotation Δ of the articulation means is located at a distance from the median plane which is greater than half the distance separating the median plane M from the second lateral plane L ". allows to accentuate the friction difference between the area of the smoothing plate located near the axis of rotation and the area of the smoothing plate located opposite the axis of rotation.

According to an alternative embodiment intended to accentuate, during the implementation of the apparatus, the friction differential between the zone of the smoothing plate located near the axis of rotation and the zone of the smoothing plate located opposite the axis of rotation, the first smoothing plate comprises, directly above the corresponding hinge pin, a frictional relief which is adapted to cooperate with a facing element so as to define, in the closed position of the jaws on a lock of hair, a pressure region generating during movement of the device on the lock of hair a traction force additional to the traction force generated by the treatment zone.

In the context of this variant embodiment, the facing element may be formed of a frictional relief carried by the second smoothing plate.

Still in order to optimize the traction effect, according to one embodiment of a hairdressing appliance according to the invention, the first jaw at least comprises at least one friction bar which is located on the same side of the median plane M as the hinge axis Δ and which is adapted to cooperate with a facing element so as to define, in the closed position, jaws on a a lock of hair, a traction zone generating during the movement of the device on the lock of hair a traction force additional to the traction force generated by the treatment zone.

In the context of this embodiment, the friction bar may be located between a longitudinal edge of the first jaw and a longitudinal edge of the first smoothing plate.

In the context of this embodiment, the element cooperating with the friction bar can be carried by the second jaw.

According to the invention and still in the context of this embodiment, the friction bar can be stationary relative to the first jaw or movable relative to the latter.

Thus, according to a feature of the invention, the friction bar is movable relative to the first jaw and the hairdressing apparatus comprises spacer means which are interposed between the friction bar and the first jaw, and which tend to move the friction bar away from the first jaw.

In the context of this feature, the constraint means associated with the smoothing plate can be adapted to exert on the smoothing plate a constraint lower than the stress exerted on the friction bar by the spacing means associated with the bar. friction.

In the context of the embodiment of the friction bar hairdressing apparatus and according to a variant of the invention, in the open position of the jaws, each working surface of a jaw is set back relative to each bar of friction carried by the said jaw.

In the context of this variant embodiment, the hairdressing apparatus may comprise means for adjusting the value of this withdrawal.

For this purpose, the friction bar may, for example, be movable relative to the jaw that carries it and the adjustment means are adapted to allow a change in the distance between the jaw and a friction surface, the friction bar, facing the other jaw.

It can also be envisaged that the adjustment means are adapted to allow a modification of the distance between the axis of rotation of the smoothing plate and the corresponding jaw.

In the context of the embodiment of the friction bar hairdressing apparatus and according to a variant of the invention, the second jaw may also comprise at least one counter-friction bar located opposite the friction bar of the first jaw.

According to the invention, the friction bar can be heated by complementary electric heating means. The friction bar may also be heated by the electrical heating means of the adjacent work surface.

According to the invention, the friction bar can be made in any suitable manner. Thus, the friction bar or the surface of the friction bar intended to be in contact with the lock of hair may be composed or at least partially coated with a tensor material and resistant to a high temperature, such as in particular a silicone. In the case of a silicone coating, the silicone layer may have a thickness of between 0.1 and 10 mm, it may have a hardness between 5 and 90 shores, preferably in a range between 40 and 50 shores, preferably equal to 46 shore A. The silicone is resistant to high temperature at least above 100 ° C, or even 150 ° C and up to about 270 ° C, or even 300 ° C.

This silicone can be overmoulded, crimped or engaged in a friction bar slide. This silicone aims to stretch, brake, evenly apply the lock of hair to be treated on the counter-support next to the friction bar. Any material alternative to silicone and making it possible to achieve at least one of the three results mentioned can also be envisaged.

According to the invention, the hairdressing appliance may comprise a second smoothing plate which forms the working surface (S ₂ ) of the second jaw and which is articulated on the second jaw via a ball joint arranged substantially in the middle of the second smoothing plate.

Of course, the various features, variants and embodiments of the invention may be associated with each other in various combinations to the extent that they are not incompatible or exclusive of each other.

• La figure 1 est une vue de côté d'un appareil de coiffure selon l'invention dont les mâchoires sont en position ouvertes.
• La figure 2 est une section droite transversale selon la ligne II-II des mâchoires de l'appareil de coiffure illustré à la figure 1 les mâchoires étant en position ouverte
• La figure 3 est une section droite transversale analogue à la figure 2 montrant les mâchoires en position fermées en train de pincer une mèche de cheveux.
• La figure 4 est une section droite transversale analogue à la figure 2, montrant une variante de réalisation de l'appareil de coiffure selon l'invention mettant en oeuvre une plaque de lissage pivotante sur chaque mâchoire.
• La figure 5 est une section droite transversale analogue à la figure 2 montrant une autre forme de réalisation, des mâchoires de l'appareil de coiffure, selon laquelle l'une des mâchoires comprend une plaque de lissage pivotante associée à une barre de friction.
• Les figures 6 à 10 sont des sections des mâchoires analogues à la figure 2 montrant des variantes de la forme de réalisation de l'appareil de coiffure illustré à la figure 5.

Moreover, various other features and advantages of the invention emerge from the description below made with reference to the accompanying drawings which illustrate non-limiting embodiments of a hairdressing appliance according to the invention.

• The figure 1 is a side view of a hairdressing apparatus according to the invention whose jaws are in the open position.
• The figure 2 is a transverse cross-section along line II-II of the jaws of the hairdressing apparatus illustrated in figure 1 the jaws being in the open position
• The figure 3 is a transverse cross-section similar to the figure 2 showing the jaws in the closed position pinching a lock of hair.
• The figure 4 is a transverse cross-section similar to the figure 2 , showing an alternative embodiment of the hairdressing apparatus according to the invention implementing a pivoting smoothing plate on each jaw.
• The figure 5 is a transverse cross-section similar to the figure 2 showing another embodiment of the jaws of the hairdressing apparatus, wherein one of the jaws comprises a pivoting smoothing plate associated with a friction bar.
• The Figures 6 to 10 are jaw sections analogous to the figure 2 showing variants of the embodiment of the hairdressing apparatus illustrated in figure 5 .

In these figures, the common references designate elements common to the various forms and / or variants of embodiment.

A hairdressing apparatus according to the invention, as illustrated in FIG. figure 1 and designated as a whole by the reference A, comprises two elongated jaws 1 and 2 of generally parallelepipedal shape and each extending along a longitudinal axis λ, λ '. The jaws 1 and 2 are connected near one of their ends by a hinge or pivot link 4 axis Ω Thus, the jaws 1 and 2 are hinged together and movable between an open position O as illustrated in FIGS. Figures 1 and 2 , and a closed position F represented at figure 3 . Each jaw 1 and 2 comprises, near an end opposite the link 4, a working surface respectively S ₁ , S ₂ . These working surfaces S ₁ , S ₂ are located opposite one another and extend over only a portion of the length of the jaws 1 and 2, so as to define in the closed position F a treatment zone T hair. Each working surface S ₁ and S ₂ has, according to the example shown, a generally rectangular shape and is made of a thermally conductive material having a surface state adapted to be placed in contact with hair without the risk of damaging them. Thus, each working surface S ₁ , S ₂ could for example be smooth by being polished or possibly covered with an enamel, a ceramic material, a polymer material with a low coefficient of friction or a low enamel coefficient of friction or a layer of glass.

According to a first embodiment and as shown more particularly by figures 2 and 3 the working surface S ₁ is formed by a first movable smoothing plate 5 while the working surface S ₂ of the second jaw 2 is formed by a second fixed smoothing plate 5 '. The second smoothing plate 5 'extends over the entire width of the second jaw 2 being fixed rigidly thereon. The second smoothing plate 5 'is then associated with electric heating means 6 in contact with the rear surface of the plate 5', located opposite the working surface S ₂ . The electric heating means 6 can be made in any appropriate manner such as for example in the form of a resistive heating element CTP or infrared emission. The electric heating means 6 are therefore located inside the second jaw 2. The heating means 6 are for example designed to maintain a target temperature predetermined automatically. The heating means 6 could also be connected to unrepresented control means allowing selection by a user of a set temperature. The heating means and / or their control unit are supplied with electrical energy by a connecting cord which extends from one end of the second jaw 2 opposite to the working surface S ₂ . Of course, the power supply of the hairdressing apparatus A could also be provided by batteries or batteries arranged inside one and / or the other of the jaws 1 and 2. The embodiments of FIG. heating means and the possible control unit are well known to those skilled in the art and therefore do not require further description in the context of the present invention.

According to the illustrated example, the first smoothing plate 5 is fixed on the first jaw 1 by means of articulation means 8 which define a pivot connection between the smoothing plate 5 and the first jaw 1. The articulation means 8 here comprise, on the one hand, a cylinder of revolution 9 integral with the first jaw 1 and, on the other hand, a complementary housing 10 arranged in the smoothing plate 5 to fit the cylinder 9. , the first smoothing plate 5 is rotatable relative to the first jaw 1 according to an axis of rotation Δ substantially parallel to the longitudinal axis λ of the first jaw 1. The axis of rotation Δ is, in addition, substantially parallel to the working surface S ₁ of the smoothing plate 5 and to a median plane M of the smoothing plate 5. The median plane M is perpendicular to the working surface S ₁ and divides the latter into two equal parts . The axis of rotation Δ is offset laterally with respect to the smoothing plate 5 so as to be located between the median plane M and a first lateral plane L which is parallel to the median plane M and passes through a longitudinal edge of the first jaw 1.

Hairdressing apparatus A also comprises means of constraint 11 which are interposed between the first smoothing plate 5 and the first jaw 1. The constraining means 11 tend to move the smoothing plate 5 away from the first jaw 1 so as to remember it in a rest position, as illustrated in figure 2 . According to the illustrated example the means of constraint 11 comprise two permanent magnets 12, 13 mounted in opposition so as to repel each other. Of course, the constraining means 11 could be made in any suitable manner such as, for example, in the form of a spring blade or helical springs or one or more hollow blocks or solid elastically deformable material.

The hairdressing apparatus A thus constituted is implemented in the following manner. When a user wishes to smooth a strand of hair 15, he comes to close the apparatus A on said wick, as shown in FIG. figure 3 . The user will then be careful to place the axis of rotation Δ opposite the scalp C with respect to the first smoothing plate 5. In this closed position, the first smoothing plate 5 will tend to rotate around the Δ axis in the direction of the arrow F ₁ . Thus, the first 5 and second 5 'smoothing plates define a treatment zone T which has a wedge or trapezoidal shape in cross section. The region 16 of the treatment zone T located near and / or vertically above the axis of rotation Δ is then narrower than the region situated at the free end of the first smoothing plate 5. The pressure exerted on the lock of hair 15 is therefore greater in the region 16 than that exerted in the rest of the treatment zone T so that the friction at the region 16 is greater than that in the rest of the treatment zone. T.

The difference in friction between the region 16 and the rest of the treatment zone T combined with a displacement of the smoothing device A, opposite the scalp C, in the direction of the arrow F ₂ , induces a in tension of the portion of the lock of hair 15 located between the scalp C and the region 16 and in particular in the rest of the treatment zone T. It should be noted that during the movement of the apparatus, the region of traction 16 exerts on the hair a traction T ₁₆ higher than that T _T exerted by the treatment zone T. This traction T ₁₆ contributes to promote the smoothing effect of the heat applied by the smoothing plate 5 'of the second jaw 2 Thus, this tensioning makes it possible to obtain a better smoothing result than that which would be obtained with the same apparatus in the absence of pivoting of the first smoothing plate 5.

According to the invention, the second smoothing plate 5 'can also be pivoted as shown in FIG. figure 4 . According to this example, the second smoothing plate 5 'is articulated on the second jaw 2 by means of articulation means 18 substantially similar to the articulation means 8 and comprise a revolution cylinder 19 secured to the second jaw 2 on which is engaged a complementary housing 20 arranged in the second smoothing plate 5 '. Thus the articulation means 18 define an axis of rotation Δ 'substantially parallel to the longitudinal axis λ' of the second jaw 2. The axis of rotation Δ 'is, in addition, substantially parallel to the working surface S ₂ of the second smoothing plate 5 'and a median plane M' of the second smoothing plate 5 '. The median plane M 'is perpendicular to the working surface S ₂ and divides the latter into two equal parts. The axis of rotation Δ 'is offset laterally with respect to the smoothing plate 5' so as to be situated between the median plane M 'and a first lateral plane L' which is parallel to the median plane M 'and passes through a longitudinal edge of the second jaw 2. The hairdressing apparatus A further comprises biasing means 21 interposed between the second jaw 2 and the second smoothing plate 5 '. According to this example, the stressing means 11 of the first smoothing plate 5 and the stressing means 21 of the second smoothing plate 5 'comprise helical springs which are compressed during the pivoting of the corresponding smoothing plates.

According to the example of the figure 4 the first smoothing plate 5 is also associated with heating means 26 made in the same manner as the heating means 6 of the second smoothing plate 5 '.

Moreover, in order to accentuate the friction at the nip situated vertically above the axes Δ and Δ ', facing each other, the first smoothing plate 5 comprises, in a vertical manner the axis of rotation Δ, a friction relief 27 intended to cooperate with a complementary element 28 facing. According to the illustrated example, the complementary element 28 is formed by a friction relief carried by the second smoothing plate 5 'in line with the corresponding axis of rotation Δ'. The friction reliefs 27 and 28 may be made in any appropriate manner and for example in the form of an overmolded silicone relief on the corresponding smoothing plate. Thus, during the implementation of the hairdressing apparatus A, the friction reliefs 27 and 28 cooperate to define in the closed position of the jaws on the lock of hair a pulling zone generating during movement of the apparatus a force traction greater than that of the rest of the treatment zone T as explained above.

According to another embodiment of the invention more particularly illustrated in the figure 5 in order to accentuate the pulling effect by dissociating it possibly from the treatment provided by the smoothing plates, a friction bar 30 is used at the level of the first jaw 1 distinct from the first smoothing plate 5. the example illustrated, only the first smoothing plate 5 is pivotable while the second smoothing plate 5 'is fixed as has been described in connection with the figure 2 . The friction bar 30 is rigidly attached to the first jaw 1 and extends along the left edge of the first smoothing plate 5. The friction bar 30 is located on the same side of the median plane M as the rotation axis Δ. The fiction bar 30 thus extends between the edge of the smoothing plate 5 located near the axis Δ and the corresponding edge of the jaw 1. According to the illustrated example, the friction bar 30 is formed by a rod of Silicone attached to the first jaw 1. The friction bar 30 is furthermore made to define a friction surface 31 which protrudes from the working surface S ₁ of the first plate 5. The surface Work S ₁ is thus set back with respect to the friction surface 31. The value of the measured shrinkage R, between the plane of the working surface S ₁ and a parallel plane passing through the friction surface 31, is, for example, between 0.1 mm and 5 mm.

The friction bar 30 is then adapted to cooperate with a facing element, in this case the second smoothing plate 5 ', so as to define, in the closed position of the jaws on the lock of hair 15, a traction zone 32 which will have the same function as the traction region 16 described above. The implementation of the hairdressing apparatus with such a drawbar will be carried out as explained above in connection with the Figures 1 to 3 .

It may, moreover, be noted that according to the example of figure 5 the axis of rotation Δ of the first smoothing plate 5 is situated between the median plane M and a second lateral plane L "which is parallel to the median plane M and which passes through a longitudinal edge 33 of the adjacent smoothing plate 5 in the friction bar 30. In the present case, the axis of rotation Δ is located at a distance d from the median plane M greater than half the distance separating the median plane M from the second lateral plane L ". The distance d is therefore greater than a quarter of the width of the smoothing plate 5. In addition, the axis of rotation Δ is placed between the jaw 1 and a plane passing through the working surface S ₁ of the first plate of smoothing 5.

The figure 6 illustrates a variant embodiment of the hairdressing apparatus according to which the friction bar 30 is fitted on the first jaw 1 so as to be able to move in translation parallel to the median plane M. The hairdressing appliance then comprises spacer means 35, formed in the form of one or more helical spring, which are interposed between the friction bar 30 and the first jaw 1. The spacing means 35 tend to move the friction bar 30 away from the first jaw 1. The spacing means 35 are preferably adapted to exert on the friction bar 30 a stress greater than that exerted by the stressing means 11 on the first smoothing plate 5.

The figure 7 illustrates another variant embodiment of the hairdressing apparatus A very close to that described in connection with the figure 6 but which differs from the latter in that it is implemented adjustment means 36 of the value of the shrinkage R between the friction surface 31 and the working surface S ₁ . According to this example, the adjustment means 36 are in the form of a screw system making it possible to adjust the value of the shrinkage R while preventing the movements of the friction bar 30 during the use of the apparatus A on a wick, except to act on the adjustment means 36.

The figure 8 shows yet another embodiment of the hairdressing apparatus A according to which the friction bar 30 is rigidly mounted on the first jaw 1 so as to be stationary relative thereto. According to the example of the figure 8 , the shrinkage adjustment means 36 are adapted to modify the distance between the axis of rotation Δ and the first jaw 1. For this purpose, the adjustment means 36 comprise a carriage 37 adapted to the jaw 1 so as to be movable in translation parallel to the median plane M. The position of the carriage 37 relative to the jaw 1 is then adjusted by means of a screw system 38. The carriage 37 comprises, at its end opposite the first jaw 1, a housing 39 for receiving a hinge cylinder 40 integral with the first smoothing plate 5.

The figure 9 illustrates yet another embodiment of the invention that the two jaws 1 and 2 each have a structure similar to that of the first jaw described in connection with the figure 6 . Thus, the second jaw 2 comprises a counter-friction bar 45 located opposite the friction bar 30. The friction against bar 45 is movable in translation parallel to the plane M 'with interposition between the friction against-bar 45 and the second jaw 2 of spacing means 46. The constraining means 21 associated with the second smoothing plate 5 'are then adapted to exert on the latter a constraint lower than the stress exerted by the spacer means 46 on the against friction bar 45.

The figure 10 illustrates another embodiment different from the embodiment of the figure 5 in that the first plate 5 is pivotally mounted on the spring 11 about the axis of rotation Δ. The spring may be one or more coil springs for example or two spring blades riveted on the frame 2 and arranged under the second plate 5 '. This first plate 5 is arranged next to the friction bar 30. The second smoothing plate 5 'which forms the working surface (S ₂ ) of the second jaw 2 is articulated on the second jaw 2 via a ball joint 100 arranged substantially in the middle of the second smoothing plate 5 '. The ball allows a rocking movement of the second plate.

Of course, various other modifications can be made to the hairdressing apparatus according to the invention within the scope of the appended claims.

Claims (15)

1. A hairdressing device comprising at least:

   - two jaws, the first (1) and the second (2), elongated and articulated to each other to be mobile between an open position (O) and a closed position (F) in which they define a hair treatment zone (T) by opposite working surfaces (S₁, S₂)

   - a first straightening plate (5) which forms the working surface (S₁) of the first jaw and which is articulated on the first jaw

   - stressing means (11) which are interposed between the straightening plate and the first jaw and which tend to space the straightening plate away from the first jaw (1) and place it in a rest position

   - electrical heating means (6) associated with at least one of the working surfaces (S₁)

   characterised in that it comprises means (8) to articulate the first straightening plate (5) on the first jaw (1) defining an axis of rotation (Δ) of the first straightening plate (5) with respect to the first jaw (1), this axis of rotation (Δ) being substantially parallel to the working surface (S₁) of said straightening plate (5) and to a longitudinal median plane (M) of the working surface (S₁), and being located between the median plane (M) and a first lateral plane (L) which is parallel to the median plane and passes through a longitudinal edge of the first jaw (1).
2. A hairdressing device according to claim 1, characterised in that it comprises a second straightening plate (5') which forms the working surface (S₂) of the second jaw (2) and which is articulated on the second jaw (2) by articulation means (18) defining an axis of rotation (Δ') of the second straightening plate (5') in relation to the second jaw (2), this axis of rotation (Δ') being substantially parallel to the working surface (S₂) of the second straightening plate (5') and to a median plane (M') of the working surface (S₂).
3. A hairdressing device according to claim 2, characterised in that the axis of rotation (Δ') of the second plate is located between the median plane (M') and a first lateral plane (L') which is parallel to the median plane (M') and passes through a longitudinal edge of the second jaw (2).
4. A hairdressing device according to one of claims 1 to 3, characterised in that the axis of rotation (Δ, Δ') of the articulation means (8, 18) is located between the median plane (M, M') and a second lateral plane (L") which is parallel to the median plane (M, M') and passes through a longitudinal edge of the straightening plate (5, 5').
5. A hairdressing device according to one of claims 1 to 4, characterised in that the axis of rotation (Δ) of the articulation means (8) is located at a distance (d) from the median plane (M) which is greater than half of the distance separating the median plane (M) from the second lateral plane (L").
6. A hairdressing device according to one of the preceding claims, characterised in that the first straightening plate (5) comprises, directly above the articulation axis (Δ), a raised friction element (27) which is designed to cooperate with a facing element (28) so as to define, when the jaws (1, 2) are in closed position on a lock of hair (15), a pressure region (16) generating, during the displacement of the device on the lock of hair, a traction force in addition to the traction force generated by the treatment zone (T).
7. A hairdressing device according to one of claims 1 to 5, characterised in that at least the first jaw (1) comprises at least one friction bar (30) which is located on the same side of the median plane (M) as the articulation axis (Δ) and which is designed to cooperate with a facing element (5', 45) so as to define, when the jaws (1, 2) are in closed position on a lock of hair, a traction zone generating, during the displacement of the device on the lock of hair, a traction force in addition to the traction force generated by the treatment zone (T).
8. A hairdressing device according to the preceding claim, characterised in that the friction bar (30) is located between a longitudinal edge of the first jaw (1) and a longitudinal edge of the first straightening plate (5).
9. A hairdressing device according to one of the two preceding claims, characterised in that the friction bar (30) is immobile with respect to the first jaw (1).
10. A hairdressing device according to one of the three preceding claims, characterised in that the friction bar (30) is mobile with respect to the first jaw (1) and that the device comprises spacing means (35) interposed between the friction bar (30) and the first jaw (1), and which tend to space the friction bar (30) away from the first jaw (1).
11. A hairdressing device according to one of the three preceding claims, characterised in that when the jaws are in open position, each working surface (S₁, S₂) of a jaw (1, 2) is recessed (R) with respect to each friction bar (30) carried by said jaw.
12. A hairdressing device according to one of claims 7 to 11, characterised in that the second jaw (2) comprises at least one friction counter-bar (45) located opposite the friction bar (10) of the first jaw.
13. A hairdressing device according to one of claims 7 to 12, characterised in that the friction bar (30) is composed of or coated at least partially with a tensor material resistant to high temperatures.
14. A hairdressing device according to the preceding claim, characterised in that the material is a silicone.
15. A hairdressing device according to claim 1 or 2, characterised in that it comprises a second straightening plate (5') which forms the working surface (S₂) of the second jaw (2) and which is articulated on the second jaw (2) by means of a ball joint (100) arranged substantially in the middle of the second straightening plate (5').

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