Field of the Invention

The present invention relates to a hair styling appliance and to a method of operation of a hair styling appliance. Heated hair styling appliances are designed to use the action of heat and mechanical pressure and/or airflow to form hair into a desired shape or style.

Background

A hair straightener appliance utilises heated plates attached to pivoted arms which can be held, by a user, in a closed position with a tress of hair clamped between the heated plates. The tress of hair can be styled into a changed shape once the hair is heated above a transition temperature.

The temperature of the heated plates during use of the appliance is typically at least 160°C and may be higher, such as at least 180°C or at least 200°C or even about 210°C, depending in part on the type of hair being styled. The appliance may be corded or cordless (battery powered) and in either case before use the heated plates are typically at ambient temperature. Accordingly, there is usually a delay between switching the appliance on and the appliance being at the required operating temperature. Furthermore, after use, the heated plates remain hot for some time even after the power is switched off.

A known hair styling appliance is disclosed for example in WO 2020/141295 A1.

Summary of the Invention

When a hair styling appliance of the type disclosed in WO 2020/141295 A1 is switched off, since the heated plates remain hot for some time, the user cannot easily tell whether the appliance is safe to store, for example in a handbag or pocket. If the appliance remains too hot, there is a risk of injury or a risk of damage to surrounding items.

The present invention has been devised in light of the above considerations.

The present inventor has realised that it would be of particular interest to employ a means that does not require electrical power in order to provide an indication that the appliance is at a temperature that is safe to store.

In a first aspect, the present invention provides a hair styling appliance comprising: a first arm and a second arm each having a free end and a hinge end, and being coupled together at their respective hinge ends, to allow the first arm and the second arm to be moveable between a closed position and an open position; biasing means configured to bias the first and second arms towards the open position; hair contact faces provided at the free ends of the first and second arms, the hair contact faces facing each other, at least one of the hair contact faces being provided with a heater; and a temperature sensitive magnetic latch arrangement configured to hold the first and second arms in the closed position when the temperature of at least part of the magnetic latch is below a first threshold temperature and to release the first and second arms from the closed position to allow the biasing means to cause the first and second arms to move to the open position when said at least part of the magnetic latch is above the first threshold temperature.

In a second aspect, the present invention provides a method of operating a hair styling appliance, the hair styling appliance comprising: a first arm and a second arm each having a free end and a hinge end, and being coupled together at their respective hinge ends, to allow the first arm and the second arm to be moveable between a closed position and an open position; biasing means configured to bias the first and second arms towards the open position; hair contact faces provided at the free ends of the first and second arms, the hair contact faces facing each other, at least one of the hair contact faces being provided with a heater; and a temperature sensitive magnetic latch arrangement, wherein the method comprising the steps: switching on the power to heat the heater, with the magnetic latch arrangement holding the first and second arms in the closed position while the temperature of at least part of the magnetic latch is below a first threshold temperature; and when said at least part of the magnetic latch is above the first threshold temperature, the magnetic latch releasing the first and second arms from the closed position and the biasing means moving the first and second arms to the open position, thereby indicating that the appliance is heating to be ready for use.

In a third aspect, the present invention provides a method of operating a hair styling appliance, the hair styling appliance comprising: a first arm and a second arm each having a free end and a hinge end, and being coupled together at their respective hinge ends, to allow the first arm and the second arm to be moveable between a closed position and an open position; biasing means configured to bias the first and second arms towards the open position; hair contact faces provided at the free ends of the first and second arms, the hair contact faces facing each other, at least one of the hair contact faces being provided with a heater; and a temperature sensitive magnetic latch arrangement, wherein the method comprising the steps: a user using the heated plates to style hair; with the temperature of at least part of the magnetic latch being above a first threshold temperature, the magnetic latch not being capable of holding the first and second arms in the closed position against the urging of the biasing means, switching off the power to the heater, thereby allowing the heated plates to cool so that said at least part of the magnetic latch cools to below the first threshold temperature; and the user closing the first and second arms to the closed position against the urging of the biasing means and the magnetic latch retaining the first and second arms in the closed position, thereby indicating that the appliance is ready for storage. Accordingly, in the first to third aspects of the invention, the temperature sensitive magnetic latch arrangement can provide both a means for holding the first and second arms in the closed position when the appliance is suitably cool and a means for allowing the first and second arms to move to the open position to indicate that the appliance is above a threshold temperature. Advantageously, the temperature sensitive magnetic latch arrangement need not require electrical power.

The heater may be in the form of an electrical heater such as an electrical resistance heater. The heater may be provided as part of the hair contact face of at least one of the arms or may be provided in thermal contact with the hair contact face. In some embodiments, the hair contact face is a face of a plate. The plate may be a flexible or non-flexible hair contacting plate. The temperature sensitive magnetic latch arrangement may be disposed in thermal contact with the heater, for example via the plate. In this way, the temperature of the magnetic latch can be ensured to be close to the temperature of the hair contact face of the appliance.

The temperature sensitive magnetic latch arrangement may comprise a temperature sensitive magnetic element having a Curie temperature such that:

(i) when the temperature of the temperature sensitive magnetic element is below the first threshold temperature, the temperature sensitive magnetic element is ferromagnetic, and

(ii) when the temperature of the temperature sensitive magnetic element is above the first threshold temperature, the temperature sensitive magnetic element is non-ferromagnetic.

When the temperature of the temperature sensitive magnetic element is above the first threshold temperature, the temperature sensitive magnetic element may be paramagnetic.

The Curie temperature of the temperature sensitive magnetic element may be in the range 50-150°C. The lower limit of this range is optionally 60°C, 70°C, 80°C or 90°C. The upper limit of this range is optionally 140°C, 130°C, 120°C or 110°C. Different suitable ranges for the Curie temperature use different endpoints independently selected from the disclosed lower and upper limits. A particularly suitable Curie temperature of the temperature sensitive magnetic element is about 100°C in view of the ready availability of suitable materials having this Curie temperature. Such materials may for example be used in homeware appliances such as cooking appliances, the Curie temperature corresponding to the boiling point of water and this temperature being reasonably indicative for a suitable threshold temperature for the present hair styling appliance.

Suitable materials for the temperature sensitive magnetic element include nickel-copper based alloys such as Monel™. For example, the temperature sensitive magnetic element may be formed from an alloy consisting of 52-67 wt% Ni, 27-34 wt% Cu and the remainder optionally Fe, Mn, Si, Al, Ti, and/or C and incidental impurities.

The temperature sensitive magnetic latch arrangement may comprise a first magnetic element on the first arm and a second magnetic element on the second arm. The first magnetic element may comprise a permanent ferromagnet and the second magnetic element may comprise a soft ferromagnetic material. In some embodiments, the first magnetic element may comprise a permanent ferromagnet and the temperature sensitive magnetic element in combination. In this case, the temperature sensitive magnetic element may be disposed over the permanent ferromagnet in the first arm. The temperature sensitive magnetic element may be interposed between the hair contact face and the permanent ferromagnet. In plan view from the hair contact face, the diameter of the temperature sensitive magnetic element may be greater than or equal to the diameter of the permanent ferromagnet. Accordingly, in the closed configuration, the temperature sensitive magnetic element may be interposed between the permanent ferromagnet and the second magnetic element. This allows the temperature sensitive magnetic element to control the degree of attraction between the permanent ferromagnet and the second magnetic element. When the temperature of the temperature sensitive magnetic element is below the Curie temperature, the temperature sensitive magnetic element is ferromagnetic and so there is a relatively high degree of attraction between the first and second magnetic elements. When the temperature of the temperature sensitive magnetic element is above the Curie temperature, the temperature sensitive magnetic element is paramagnetic and so there is a relatively low degree of attraction between the first and second magnetic elements.

In an alternative embodiment, the second magnetic element may comprise the temperature sensitive magnetic element. Accordingly, when the appliance is in the closed configuration, the permanent ferromagnet (first magnetic element) and the soft ferromagnetic material (second magnetic element) are magnetically attracted to each other provided that the second magnetic element is at a temperature below its Curie temperature. At the time of writing, it is considered that this alternative embodiment is not so preferred as the arrangement identified further above in which the first magnetic element comprises a permanent ferromagnet and the temperature sensitive magnetic element in combination. With the permanent ferromagnet covered by the temperature sensitive magnetic element, for example, when the temperature of the temperature sensitive magnetic element is above the Curie temperature, then there is only a small magnetic field emitted by the arrangement and so it is less likely that unwanted items such as hairpins or clips would be attracted to the arrangement.

The temperature sensitive magnetic latch arrangement may be disposed closer to the free ends of the first and second arms than the biasing means. This means that the temperature sensitive magnetic latch arrangement may benefit from a mechanical leverage effect, in order to counteract, in the closed configuration, the urging of the biasing means on the arms towards the open configuration.

The appliance may have a central pack disposed between the first arm and the second arm. The biasing means may be adapted to support the central pack symmetrically between the first arm and the second arm. The central pack may house a power source such as a rechargeable battery. It is possible in some embodiments for the pack to form part of one of the arms. In this case the appliance may not be symmetrical, in the sense that at one side there is a first arm this is pivotable with respect to a combination of a second arm and associated body (or pack) containing, for example, a power source and/or control electronics. The invention includes the combination of the aspects and optional features described except where such a combination is clearly impermissible or expressly avoided.

Summary of the Figures

Embodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which:

Fig. 1 is a side view of a hair styling appliance according to the prior art, with the arms in a closed position.

Fig. 2 is a side view of the hair styling appliance shown in Fig. 1 with the arms in an open position.

Fig. 3 shows a first configuration of a spring mechanism between the arms, suitable for use with the appliance of Fig. 1 .

Fig. 4 shows an alternative configuration of the spring mechanism between the arms, suitable for use with the appliance of Fig. 1 .

Fig. 5 shows a side view of a hair styling appliance according to an embodiment of the invention, with the arms in a closed position.

Fig. 6 shows a side view of the hair styling appliance of Fig. 5 but with the arms in an open position.

Detailed Description of the Invention

Aspects and embodiments of the present invention are discussed further below with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art. All documents mentioned in this text are incorporated herein by reference.

Embodiments of the invention are described with reference to the disclosure of WO 2020/141295 A1 , which proposes a hair styling appliance and in some respects the embodiments of the present invention can be considered to be modifications of the disclosure of WO 2020/141295 A1 .

A hair styling apparatus 10 according to the prior art, as shown in Figs. 1 and 2, comprises a first arm 12, a second arm 14 and a central pack 16, which are pivotally joined together at one end by a hinge 18. The hair styling apparatus 10 comprises a handle section 20 towards the hinge end of the arms and a hair contacting section 22 towards the distal end of the arms. The hair contacting section 22 comprises a plate 24, 26 arranged on at least one of the facing surfaces of the arms. The plate 24, 26 can be a flexible or non-flexible hair contacting plate, which has an increased temperature when the hair straightening apparatus 10 is in use. When the hair straightening apparatus 10 is not in use, the plate will generally be at the ambient temperature. A longitudinal axis, x, is indicated in Figs. 1 and 2, which extends lengthways through the centre of the hair styling apparatus 10.

The hair styling apparatus 10 is typically a battery operated hair straightener, wherein the hair contacting section 22 comprises a heated metal plate. In such an embodiment, an electrical connector 28 is located at the hinge end of the hair styling apparatus 10, and the central pack 16 is a battery pack assembly.

The hair styling apparatus of WO 2020/141295 A1 incorporates a biasing means (not shown in Figs. 1 and 2) in the form of one or more springs adapted to support the central pack 16 between the first and second arms. This symmetrical, balanced arranged improves the ergonomics of the hair styling apparatus. Suitable biasing means are described below with reference to Figs. 3 and 4.

Figs. 3 and 4 schematically illustrate options for elastically securing the arms and central pack to one another, enabling the arms to be biased into the open position and also smoothly closeable by the user.

Fig. 3 illustrates a first coil spring 162 attached between an internal surface of the first arm 12 and an adjacent surface of the central pack 16 and a second coil spring 164 attached between an internal surface of the second arm 14 and the central pack 16. This symmetrical arrangement is mechanically simple and reliable whilst maintaining a balanced weight distribution within the styling apparatus. Alternatively or additionally, a third and fourth coil spring 166, 168 can be positioned in closer proximity to the hinge end 18 of the styling apparatus 10. Such an alternative arrangement of the coil springs is also shown in Fig. 3.

Fig. 4 schematically illustrates a first leaf spring 170 positioned between an internal surface of the first arm 12 and an adjacent surface of the central pack 16 and a second leaf spring 172 positioned between an internal surface of the second arm 14 and the central pack 16. The first and second leaf springs 170, 172 are formed out of metal and may be flat or cylindrical in cross-section and each of the first and second leaf springs may be composed of one or more leaf springs. Again, this symmetrical arrangement is mechanically simple and reliable whilst maintaining a balanced weight distribution within the styling apparatus. In one arrangement, the first and second arms comprise a metal arm structure 174, 176 and the leaf springs 170, 172 are integrally formed with the metal arm structure. Such a metal arm structure is beneficial with respect to the rigidity of the apparatus and an outermost surface of the metal arm structure is covered by a plastics layer.

Turning now to a discussion of the embodiments of the invention, Fig. 5 shows a side view of a hair styling appliance 200 according to an embodiment of the invention, with the arms in a closed position. Fig. 6 shows a side view of the hair styling appliance of Fig. 5 but with the arms in an open position.

As shown in Figs. 5 and 6, the hair styling appliance 200 comprises a first arm 212 and a second arm 214. Each arm has a free end 212a, 214a and a hinge end 212b, 214b, and the arms are coupled together by hinge 218 at their respective hinge ends, to allow the first arm 212 and the second arm 214 to be moveable between a closed position (Fig. 5) and an open position (Fig. 6). The hair styling appliance 200 further comprises biasing means configured to bias the first and second arms towards the open position. In Figs. 5 and 6, the biasing means is shown schematically as spring 213 but it is to be understood that the biasing means could have the format shown in Figs. 3 or 4.

A central pack 216, best seen in Fig. 6, is disposed symmetrically between the first arm 212 and the second arm 214.

The first arm 212 is provided with a flexible hair contact plate 224 located over and in thermal contact with first heater 225. Similarly, the second arm 214 is provided with a flexible hair contact plate 226 located over and in thermal contact with second heater 227. The flexible hair contact plates provide hair contact faces that opposingly face each other near the free ends of the first and second arms.

The hair styling appliance 200 further comprises a temperature sensitive magnetic latch arrangement 250. This is configured to hold the first and second arms in the closed position when the temperature of at least part of the magnetic latch is below a first threshold temperature. This is further configured to release the first and second arms from the closed position to allow the biasing means to cause the first and second arms to move to the open position when said at least part of the magnetic latch is above the first threshold temperature.

The temperature sensitive magnetic latch arrangement 250 comprises a first magnetic element 252, 254 on the first arm 212 and a second magnetic element 256 on the second arm. The first magnetic element comprises a permanent ferromagnet 252 (e.g. Nd-based permanent magnet) and the second magnetic element may comprise a soft ferromagnetic material (e.g. mild steel).

The first magnetic element further comprises a temperature sensitive magnetic element 254. The temperature sensitive magnetic element 254 is disposed over the permanent ferromagnet 252 in the first arm 212, under the flexible hair contact plate 224 and in thermal contact with it. As shown in Fig. 6, the temperature sensitive magnetic element 254 is interposed between the flexible hair contact plate 224 and the permanent ferromagnet 252.

In plan view from the hair contact face, the diameter of the temperature sensitive magnetic element 254 is greater than the diameter of the permanent ferromagnet 252. As shown in Fig. 5, in the closed configuration, the temperature sensitive magnetic element 254 is interposed between the permanent ferromagnet 252 and the second magnetic element 256. This allows the temperature sensitive magnetic element 254 to control the degree of attraction between the permanent ferromagnet 252 and the second magnetic element 256.

When the temperature of the temperature sensitive magnetic element 254 is below the Curie temperature (e.g. 100°C), the temperature sensitive magnetic element 254 is ferromagnetic and so there is a relatively high degree of attraction between the first and second magnetic elements. When the temperature of the temperature sensitive magnetic element is above the Curie temperature, the temperature sensitive magnetic element 254 is paramagnetic and so there is a relatively low degree of attraction between the first and second magnetic elements.

The temperature sensitive magnetic latch arrangement may be disposed closer to the free ends of the first and second arms than the biasing means. This means that the temperature sensitive magnetic latch arrangement may benefit from a mechanic leverage effect, in order to counteract, in the closed configuration, the urging of the biasing means on the arms towards the open configuration.

The biasing means 213 may present a spring force of about 3N, meaning that a force of about 3N is sufficient to compress the spring. Therefore, accounting for the effect of mechanical leverage provided by the arms 212, 214, this indicates the attractive force required between the first and second magnetic elements to retain the appliance in the closed configuration below the threshold temperature.

In use, the user switches on the power to heat the heaters from ambient temperature towards an operating temperature. The magnetic latch arrangement holds the first and second arms in the closed position while the temperature of the temperature sensitive magnetic element 254 is below the threshold temperature. When the temperature of the temperature sensitive magnetic element 254 is above the threshold temperature, the temperature sensitive magnetic element 254 changes from ferromagnetic to paramagnetic. This has the effect of reducing the attraction between the first and second magnetic elements so that the biasing means is able to overcome the attractive force between the first and second magnetic elements and the biasing means moves the first and second arms to the open position. This indicates to the user that the appliance is heating to be ready for use. An added benefit of the arrangement described is that the appliance will warm up faster when in the closed configuration.

After using the appliance to style hair, the user will switch off the appliance but for at least some time the temperature of the temperature sensitive magnetic element 254 will remain above the threshold temperature. In this case, even if the user closes the arms, the magnetic latch is not capable of holding the first and second arms in the closed position. As the appliance cools towards ambient temperature, the temperature of the temperature sensitive magnetic element will approach and fall below the Curie temperature. When the user closes the arms, the magnetic latch will retain the first and second arms in the closed position, thereby indicating that the appliance is ready for storage.

A further advantage of using the magnetic latch arrangement described herein is that it is resistant to damage in the event that the arms are forced open. With a mechanical latch arrangement, forcing the arms open would be expected to damage, weaken or loosen the mechanical latch, which may not be readily capable of repair. However, in the case of the magnetic latch arrangement, the arms will be held closed unless the arms are opened with a force sufficient to overcome the attractive force between the first and second magnetic elements. In that case, the first and second magnetic elements are not typically damaged or weakened and are available to retain the arms in the closed position again when the arms are brought back together.

*** The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

Throughout this specification, including the claims which follow, unless the context requires otherwise, the word “comprise” and “include”, and variations such as “comprises”, “comprising”, and “including” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment. The term “about” in relation to a numerical value is optional and means for example +/- 10%.