GB2617736A

GB2617736A - Apparatus and method for drying and styling hair

Info

Publication number: GB2617736A
Application number: GB2310260.1A
Authority: GB
Inventors: Alexander Weatherly Robert; Gold Richard; Moore Timothy
Original assignee: Jemella Ltd
Current assignee: Jemella Ltd
Priority date: 2019-07-30
Filing date: 2019-07-30
Publication date: 2023-10-18
Anticipated expiration: 2039-07-30
Also published as: GB2617736B; GB202310260D0

Abstract

Apparatus 10 for drying and styling hair comprises first and second opposing arms 14, 16 adapted for movement between an open and a closed configuration. When the arms are closed they form an inter-arm chamber 13 across which the hair passes. An airflow conduit 15 is provided within and along at least one arm for delivering a flow of air along the conduit and into the inter-arm chamber. One or both of the arms comprises an airflow guide structure 24 which directs the air from a first direction substantially parallel to the length of the arm to a second direction which is towards the opposite arm. One or both of the arms further comprises a plurality of air vents 26 that are coupled to the inter-arm chamber and allow air to vent from the arm in a direction perpendicular to the first direction. The airflow guide structure 24 and the plurality of vents 26 may comprise a unitary structure. Air exiting from the vents may provide lift to roots. Also provided is a method of drying hair using such apparatus.

Description

APPARATUS AND METHOD FOR DRYING AND STYLING HAIR

Field of the Invention

The present invention relates to an apparatus for drying and styling the hair of a person (or conceivably an animal), for example after washing the hair or as part of a styling process. That is to say, the hair is wet (or "towel-dry") prior to use of the invention, and may then be dried and styled using the invention. Such drying and styling of the hair may be performed by a user in respect of their own hair, for example, or by a hair stylist. It should also be noted that the term "wet" as used herein should be interpreted broadly, to encompass not only hair wetted by water, but also hair wetted by liquids other than water. For example, hair may be wetted by a solvent-based colourant, which the invention may be used to dry.

Background to the Invention

Conventional handheld hairdryers, that incorporate an electrically-powered motorised fan to blow a current of cool or hot air in order to dry a person's hair, are well known. The fan draws ambient air into the body of the hairdryer and blows the current of air towards the hair to be dried. When hot air is to be blown, typically an electric heating element, incorporated within the body of the hairdryer, is used to heat the current of air before it leaves the hairdryer. Optionally, the hairdryer may be equipped with a concentrator nozzle attachment to intensify and direct the current of air, or a diffuser attachment to deliver the air more gently.

However, conventional hairdryers can often be noisy, heavy and bulky. Moreover, they can be awkward to use, and it can be difficult for a user (in particular a domestic user attending to their own hair) to achieve desired results, particularly in respect of styling the hair whilst drying it. For instance, a hairdryer will often be used simultaneously with a hairbrush or comb, or another piece of styling equipment, to style the hair during drying. The styling process may be, for example, to straighten the hair, or to provide "body and volume" to the hair (if necessary, preceded or succeeded by the application of styling products such as mousse, gel, wax, hairspray, etc.). Simultaneously manoeuvring a hairdryer and a brush (or a comb, etc.) around the head can be awkward for the user, and often requires a degree of skill to achieve the desired results.

Thus, whilst using a conventional hairdryer is the fastest method to dry hair, it can be very difficult and/or time-consuming to create a desired end result in respect of styling. To do this the user has to use a brush and/or additional hair styling tools.

As an alternative to conventional hairdryers, some people may use products such as hot air brushes or hot air paddle bushes when styling their hair. However, such products, whilst being easy to use, are slow in drying the hair.

A further category of products, that are both quick and easy to use, are so-called "wet to straight" hair straighteners. These are used to both dry and straighten hair, by drawing wet hair between a pair of heated plates mounted on opposing arms of the device. These devices tend to use conductive heating at high temperatures on wet hair (typically 185-230°C) but can be damaging to hair, and/or may be perceived to be damaging to hair, due to sounds of cavitation (sizzle) or the use of elevated temperatures around the denaturation temperature of wet hair.

Summary of the Invention

The present invention aims to provide alternative apparatus and methods to those of conventional handheld hairdryers in order to dry hair, by combining the functionality and benefits of a conventional hairdryer with those of a hair straightener, within one grip-sized device. Thus, advantageously, embodiments of the present invention provide, as a single handheld device, means for both drying and styling the hair, which is simple to use, and less awkward than manoeuvring a conventional hairdryer around the head simultaneously with a brush, comb or other piece of styling equipment.

According to a first aspect of the present invention there is provided apparatus for drying and styling hair, comprising: first and second mutually-opposing arms adapted for movement between an open configuration for receiving a length of wet hair therebetween and a closed configuration adjacent the hair, such that, in use, when the arms are in the closed configuration they form an inter-arm chamber across which the hair passes, and wherein an airflow conduit is provided within and along at least one of the first and second arms; and means for delivering a flow of air along the conduit in the at least one of the first and second arms, and subsequently into the inter-arm chamber.

The term "chamber" as used herein should be interpreted broadly, to encompass chambers that are partially open on at least one side, as well as those that are 10 enclosed.

By virtue of the configuration of the present apparatus, including the at least one airflow conduit and the inter-arm chamber formed by the arms when in the closed configuration, this enhances the delivery of air to the hair, enabling the hair to be dried/styled in a quick and easy manner, and also enabling improved energy efficiency to be achieved.

Preferably one or both of the arms further comprises an airflow guide structure arranged to receive the flow of air from the respective conduit and to direct the flow of air from a first direction that is substantially parallel to the length of the respective arm, to a second direction that is from the respective arm towards the opposing arm, into the inter-arm chamber. The provision of such an airflow guide structure further enhances the delivery of air to the hair, further facilitating the drying/styling process, and enabling a further improvement in energy efficiency to be achieved.

In a presently-preferred embodiment each of the first and second arms comprises a respective conduit and a respective airflow guide structure, and the means for delivering the flow of air is arranged to deliver the air along the conduit in each of the first and second arms and thence through the respective airflow guide structure and into the inter-arm chamber. This advantageously enables air to be delivered to the hair in the device simultaneously from above and below, enhancing the drying/styling process.

Preferably each airflow guide structure is offset from an imaginary centreline midway between the first and second arms when in the closed configuration. Such an offset advantageously creates an airflow restriction between the air and hair in use, to increase the speed of the airflow around the hair, to increase drying.

In the presently-preferred embodiment the offset of each airflow guide structure from the imaginary centreline is about 2 mm (i.e. the airflow guide structures are separated from one another by a distance of about 4 mm).

The conduit in the or each arm may advantageously act as a plenum chamber through which the air flows into the respective airflow guide structure and thence into the inter-arm chamber. This promotes uniformity of airflow from the or each arm through the respective airflow guide structure and into the inter-arm chamber.

Preferably the airflow guide structure in the or each arm comprises a cellular structure configured to direct the flow of air from the first direction to the second direction, the cellular structure comprising a plurality of cell walls which extend along the second direction into the respective plenum chamber.

Particularly preferably the depth of the cells into the respective plenum chamber progressively increases with distance along the respective arm. Such a configuration advantageously causes the incoming airflow in the first direction to turn and exit from the plenum chamber in the second direction and enter the inter-arm chamber with uniform airspeed.

In the presently-preferred embodiment the cellular structure has a hexagonal (honeycomb) structure. The inventors have found this to be beneficial in maximising the open area through the guide structure whilst minimising the area occupied by the cell walls, and thereby minimising airflow resistance due to the cell walls.

The or each airflow guide structure may further comprise a plurality of airflow redirecting channels configured to convey the flow of air from the second direction to third and fourth directions that are outward from the apparatus, substantially perpendicular to the length of the arms, the fourth direction being opposite to the third direction. By expelling air in these third and fourth directions, this enables air to be easily directed towards the roots of the hair, to dry the roots and enable root lift to be created.

In the presently-preferred embodiment the airflow redirecting channels extend between longitudinal edges and corresponding longitudinal sides of the airflow guide structure.

The device may further comprise mutually-opposing plates disposed on the first and second arms, the mutually-opposing plates being arranged to come together when the first and second arms are in the closed configuration. More particularly, first and second plates may be disposed on the first arm, and respective opposing first and second plates may disposed on the second arm. At least one of said plates may comprise means for applying heat to said length of hair in use, when the first and second arms are in the closed configuration, thereby aiding the drying/styling process.

Airflow conduits may be provided that extend behind the first and second plates of the respective arm, to receive air from said airflow redirecting channels and to direct airflow behind the first plate and outward through vents along the edge of the apparatus in substantially the third direction, and to direct airflow behind the second plate and outward through vents along the edge of the apparatus in substantially the fourth direction.

In certain embodiments the airflow guide structure including the cellular structure and the airflow redirecting channels, and the outward vents in the third and fourth directions, may be formed as a unitary structure (e.g. by 3D printing).

Preferably the device further comprises an airflow splitter arranged to divide airflow into the conduits in the first and second arms in the first direction. Optionally the airflow splitter may comprise a flexible member.

The means for delivering the flow of air may comprise a fan. The fan may advantageously incorporate a brushless motor designed to operate at high speeds (e.g. over 30,000 revolutions per minute) and low power (e.g. 15 W maximum, 3 W during normal operation), and may driven by a DC power supply. Such high-speed low-power parameters of the fan have been found to provide excellent drying performance, drying hair as quickly as a 2000 W conventional hairdryer, but using significantly less power.

The presently-preferred embodiment further comprises means for heating said airflow, such as one or more heating elements or coils, for example. To promote a generally uniform air temperature profile across the air stream, the apparatus may further comprise means for causing turbulence in the heated airflow (such as one or more baffles within the airflow) prior to the airflow reaching the inter-arm chamber. Alternatively, the means for heating said airflow may comprise the airflow guide structure, the airflow guide structure being formed of a material that generates heat on application of an electric current thereto.

Optionally the apparatus may further comprise one or more sets of flexible bristles on the first and/or second arms, outside or within the inter-arm chamber, arranged to promote the application of uniform tension to the hair passing across the inter-arm chamber in use.

According to a second aspect of the present invention there is provided a method of drying hair using the apparatus of the first aspect.

The method may further comprise using the apparatus to style the hair substantially simultaneously with drying the hair.

Brief Description of the Drawings

Embodiments of the invention will now be described, by way of example only, and with reference to the drawings in which: Figure 1 is a perspective overview of a combined hair dryer/styler device comprising means for blowing and heating air, an airflow splitter, and mutually-opposing drying/styling arms in an open configuration, with each arm incorporating a pair of heater plates and an airflow guide structure; Figure 2 shows the device of Figure 1 with the arms in a closed configuration; Figure 3 illustrates the device of Figure 1 in use; Figure 4 is a perspective longitudinal cross-sectional view of the device of Figure 1, showing some exemplary internal components; Figure 5 is a plan longitudinal cross-sectional view of the device of Figure 1; Figure 6 is a close-up perspective view of the arms of the device of Figure 1 in the open configuration; Figure 7 is a side cross-sectional view of the arms of the device of Figure 1 in the open configuration, through the airflow guide structure, showing the airflow guide structure of each arm as having a cellular structure in which the depth of the cells progressively increases with distance along the respective arm; Figure 8 is a longitudinal cross-sectional view as in Figure 7 but with the arms in the closed configuration, and also illustrating directions of airflow along and between the arms; Figure 9 is a perspective view of the arms of the device of Figure 1 closed around a representation of multiple strands of wet hair; Figure 10 is a transverse cross-sectional view through the arms of the device of Figure 1 in the closed configuration, and also illustrating directions of airflow; Figure 11 is a transverse cross-sectional view corresponding to that of Figure 10, through the arms of the device in the closed configuration (around hair) and showing more detail; Figure 12 is a perspective longitudinal cross-sectional view along the arms of the device of Figure 1 in the closed configuration around hair, illustrating airflow directional changes due to the airflow guide structure in each arm; Figure 13 is a perspective transverse cross-sectional view through the arms of the device of Figure 1 in the closed configuration around hair, again illustrating airflow directional changes; Figure 14 is a perspective view of an arm component of the device of Figure 1, without plates, again illustrating airflow directional changes; Figure 15 is a perspective longitudinal cross-sectional view of the arm component shown in Figure 14, again showing the airflow guide structure as having a cellular structure (with hexagonal cells) in which the depth of the cells progressively increases with distance along the structure; Figure 16 is a perspective longitudinal cross-sectional view of an alternative embodiment of a cellular airflow guide structure, in this case having rectangular cells in one linear dimension (again with the depth of the cells progressively increasing with distance along the structure); Figure 17 is a perspective longitudinal cross-sectional view of another alternative embodiment of a cellular airflow guide structure, in this case having rectangular cells in two linear dimensions (again with the depth of the cells progressively increasing with distance along the structure); Figure 18 is a perspective longitudinal cross-sectional view of the airflow splitter of the device of Figures 1-15 in close-up, and also showing a plurality of baffles and a diffuser grille; Figure 19 is another view of part of the device of Figure 1, showing inter alia the plurality of baffles between the fan and the arms; and Figure 20 is a graph of hair sample temperature against drying time, useful for

understanding background principles.

In the figures, like elements are indicated by like reference numerals throughout.

Detailed Description of Preferred Embodiments

The present embodiments represent the best ways known to the applicants of putting the invention into practice. However, they are not the only ways in which this can be achieved.

Overview of combined hair dryer/styler device Figure 1 is a perspective overview of a combined hair dryer/styler device 10 according to a presently-preferred embodiment, with arms 14, 16 in an open configuration, and Figure 2 shows the same device with the arms 14, 16 closed (as in use, e.g. as shown in Figure 3). Figures 4-15 show further views of parts of the device 10, with Figures 8-14 showing parts of the device in use.

Referring initially to Figures 1 and 2, the device 10 is an all-in-one handheld device that can be used to dry hair in a quick and easy manner, whilst also enabling styling of the hair (e.g. to straighten the hair, or to add "body and volume" to it).

The device 10 comprises a body part 12, and first and second mutually-opposing arms 14, 16 arranged in a broadly similar manner to the arms of a handheld hair styler. The first and second arms 14, 16 are adapted for movement between an open configuration (as shown in Figure 1) for receiving a length of wet hair therebetween, and a closed configuration (as shown in Figure 2) adjacent the hair, to create tension in the hair, such that, in use, when the arms 14, 16 are in the closed configuration they form an inter-arm plenum chamber (13, Figure 10) across which the hair passes.

Turning briefly to Figure 7, a first airflow conduit 15 is provided within and along the first arm 14, and a second airflow conduit 17 is provided within and along the second arm 16. In alternative embodiments only one of the arms may incorporate such an airflow conduit.

Referring to Figures 4 and 5, the device further comprises a fan assembly 38 within the body part 12, for delivering a flow of air along the first and second conduits 15, 17 in the first and second arms 14, 16. The fan assembly 38 has an impeller and is typically also provided with a filter.

As shown for example in Figures 1, 4, 5, 7 and 8, each of the first and second arms 14, 16 further comprises a respective airflow guide structure 24 arranged to receive the flow of air from the respective first or second conduit 15, 17 and to direct (i.e. steer) the flow of air from a first direction (D1, Figure 8) that is substantially parallel to the length of the respective arm (i.e. incoming air, lengthways along the device), to a second direction (D2, Figure 8) that is from the respective arm towards the opposing arm, i.e. inwards into the inter-arm plenum chamber 13 formed by the arms 14, 16 in the closed position. In alternative embodiments, only one of the arms 14, 16 may be provided with such an airflow guide structure 24, if only one of the arms incorporates an airflow conduit. The configuration and function of the airflow guide structure 24 are described in greater detail below. In yet other variants, the airflow guide structure(s) 24 may be omitted altogether.

As illustrated for example in Figure 1, the first arm 14 is a continuation of the body part 12, and the second arm 16 is coupled to the body part 12 by means of a hinge 18, by virtue of which the first and second arms 14, 16 are movable relative to one other (in the illustrated embodiment, by moving the second arm 16 towards the first arm 14). Thus, the first and second arms 14, 16 can be brought together, into the closed configuration (as shown in Figure 2), or moved apart, into the open configuration (as shown in Figure 1), by a user in use. In the illustrated embodiment, each of the arms 14, 16 widens relative to the body part 12 to form a "head" of the device 10, distal from the body part 12, although other embodiments are possible in which the head does not widen in the illustrated manner.

The hinge 18 can incorporate any suitable means for allowing the first and second arms 14, 16 to be moved relative to one other.

Preferably the hinge 18 also incorporates spring means configured to bias the first and second arms 14, 16 into the open configuration, such that the user is required to apply pressure to the arms to close them together (overcoming the effect of the spring means), and such that the arms 14, 16 automatically open, under the effect of the spring means, once the pressure is removed. For example, the hinge 18 may incorporate a leaf spring or a coiled spring.

The hinge 18 and the spring means can be one and the same. For example, the spring means itself can be used to couple the second arm 16 to the body part 12, thereby avoiding the need to provide a separate mechanical hinge and simplifying the overall construction of the device.

As shown in Figure 1, and in close-up in Figure 6, in the presently-preferred embodiment the inner surface of the first arm 14 incorporates first and second elongate heater plates 20a, 20b, parallel to each other and to the length of the arm 14. The second arm 16 also incorporates first and second elongate heater plates 22a, 22b (not visible in Figures 1 and 6, but shown for example in Figures 10 and 11) in corresponding positions to heater plates 20a and 20b. Each of the heater plates is provided with a respective electrical heating element, operable to cause the respective heater plates to heat up. In the presently-preferred embodiment the operating temperature of the heater plates is typically around 120-130°C.

The first and second arms 14, 16 and the first and second heater plates on each arm are arranged such that, when the device 10 is in the closed configuration, the first and second heater plates 20a, 20b of the first arm 14 come into contact with the first and second heater plates 22a, 22b of the second arm 16. Preferably the heater plates 20a, 20b, 20c, 20d are made of a material having relatively high thermal conductivity, and are preferably provided with one or more temperature sensors (e.g. a temperature sensor for each plate, or one or more temperature sensors that each serves a plurality of heater plates).

Optionally, flexible bristles may be provided alongside the heater plates 20a, 20b, 20c, 20d. More particularly, flexible bristles may be positioned on either or both sides of the first arm 14, and/or on either or both sides of the second arm 16, adjacent to the inlet/outlet of the hair to/from the heater plates 20a, 20b, 20c, 20d. Alternatively, or in addition, flexible bristles may be provided within or around the airflow guide structure 24, between the heater plates. Such bristles enable more uniform tension to be applied to the hair fibres within a section of hair passing through the chamber 13 formed by the arms 14, 16 in the closed position.

As shown in Figure 1, a control button or switch 23 may be provided on the device 10, to enable it to be turned on or off, together with an indicator light to show whether the power is on. A sound can also be played by a sound generator (not illustrated) when the device 10 is switched on and ready to use.

As shown in the cross-sectional views in Figures 4 and 5, a fan assembly 38 is mounted towards an end of the body part 12, distal from the first arm 14. The fan 38, driven by an electric motor, is operable to draw in air from the surrounding environment and to deliver a flow of air along the inside of the body pad 12; and then into and along the conduits 15, 17 in the arms 14, 16; and then into and through the inter-arm plenum chamber 13 formed by the arms 14, 16 in the closed position, around and through the hair to be dried.

Advantageously the fan 38 may incorporate a brushless motor designed to operate at high speeds (e.g. over 30,000 revolutions per minute) and low power (e.g. 15 W maximum, 3 W during normal operation), and may driven by a DC power supply. Such high-speed low-power parameters of the fan have been found to provide excellent drying performance, drying hair as quickly as a 2000 W conventional hairdryer, but using significantly less power.

An electrically-powered heating coil (or other electrical heating elements), operable to heat the air drawn in by the fan 38, is provided in part 30, towards the end of the body part 12 proximal to the first arm 14.

The heater plates 20a, 20b, 22a, 22b serve a number of purposes during use of the device 10. Firstly, with the user having sandwiched a length of wet hair between opposing plates 20a and 22a, and between opposing plates 20b and 22b (i.e. transversely across the plenum chamber 13 formed by the first and second arms 14, 16 in the closed configuration), and by drawing the device along the length of wet hair, the heater plates 20a, 20b, 22a, 22b subject the wet hair to a squeegeeing effect, removing excess unbound water, and also heat the hair 40 to promote subsequent evaporation of the water. Secondly, the heating provided by the heater plates 20a, 20b, 22a, 22b causes the walls of the plenum chamber 13 to be heated (via thermal conduction), and also helps maintain the temperature of the airflow delivered through the plenum chamber 13 by the fan 38. Thirdly, the heater plates 20a, 20b, 22a, 22b can be used to style the hair, as an integral part of the drying process.

The heater plates 20a, 20b, 22a, 22b are preferably configured as ceramic float plates with springs having a low spring rate or stiffness, thereby giving good control of hair tension.

Allowing for the airflow heating coil (or other heater elements) and the heater plates 20a, 20b, 22a, 22b, as well as the fan 38, the overall power consumption of the device 10 is around 600-800 W, which is significantly less than a 2000 W conventional hairdryer.

As shown in Figures 4 and 5, the electrical and electronic circuitry of the device 10 is housed within the body part 12 and the first and second arms 14, 16 (although predominately within the body part 12 and the first arm 14). In the example illustrated, a printed circuit board assembly 36 is provided within the body part 12. Electrical power is provided to the device 10 by means of a power supply located at the end of the body part 12 distal from the first arm 14. In the presently-preferred embodiment the power supply is an AC mains power supply. However, in an alternative embodiment the power supply may comprise one or more DC batteries or cells (which may be rechargeable, e.g. from the mains or a DC supply via a charging lead), thereby enabling the device 10 to be a cordless product.

Amongst other things, the circuit board assembly 36 includes four TRIACs 37, each for powering a respective one of the heater plates 20a, 20b, 22a, 22b.

Airflow guidance The device 10 incorporates a number of features that guide the airflow from the fan 38 to the user's hair 11 so as to enable the hair to be both dried and styled. These features will now be described in detail with particular reference to Figures 7-15.

As mentioned above, and as shown for example in Figure 7, in the presently-preferred embodiment each of the first and second arms 14, 16 (at the head of the device 10 distal from the body part 12) comprises a cellular airflow guide structure 24 in airflow communication with a respective first or second conduit 15, 17. The first and second conduits 15, 17 act as plenum chambers to supply air through the guide structure 24 of each of the first and second arms 14, 16.

Air is supplied to the first and second conduits 15, 17 by the action of the fan 38, via cylindrical part 30. Part 30 includes a heating element to heat the air, and, as shown in close-up in Figure 18, a set of elongate baffles 32 (at a plurality of angles, essentially star-shaped in cross-section), an airflow splitter 34, and a diffuser grille 31.

The elongate baffles 32 are arranged to mix the air, to reduce hotspots from the heater in the region between the inlet of the air heater and the outlet from the cellular airflow guide structure 24. This is of importance to achieve uniform air temperatures at the outlet of the cellular airflow guide structure 24, thereby achieving uniform drying across the hair section within the chamber 13. It also prevents the formation of hot spots in the air, which could damage the hair.

Accordingly, without such baffles it may be necessary to reduce the hair heating power and therefore reduce the drying speed of the device.

The airflow splitter 34, which is aligned across the diameter of the cylindrical part 30, is arranged to split the incoming airflow into separate upper and lower airflows, which feed directly into the first and second conduits 15, 17. Advantageously, the shape of the airflow splitter 34 is such as to guide the air into the first and second conduits 15, 17 without causing whistling from the air, thereby providing acoustic benefits.

More particularly, part 30 has a circular cross-section, the lower half of which (beneath the airflow splitter 34) corresponds with the cross-sectional geometry of the first conduit 15. The upper half of part 30 (above the airflow splitter 34) corresponds with the cross-sectional geometry of the second conduit 17. As shown in cross-section in Figure 8, as the second arm 16 is brought into the closed position the second conduit 17 fits snugly around the upper half of part 30, so that airflow can pass through the part 30, below and above the airflow splitter 34, into the first and second conduits 15, 17, without leaking.

Thus, as shown in Figure 8, the air enters the first and second conduits 15, 17 in a first direction D1 that is substantially parallel to the length of each of the first and second arms 14, 16.

As also shown in Figure 8, and in perspective longitudinal cross-section in Figure 15, the airflow guide structure 24 in each of the first and second arms 14, 16 includes a cellular structure comprising a plurality of cell walls. In the illustrated embodiment the cellular structure has a hexagonal (honeycomb) structure, although such a geometry is not essential and other geometries (for example as illustrated in Figures 16 and 17) may be used instead. However, a hexagonal (honeycomb) structure has been found to be beneficial in maximising the open area through the guide structure 24 whilst minimising the area occupied by the cell walls, and thereby minimising airflow resistance due to the cell walls. In the presently-preferred embodiment the cell width is about one tenth the cell length.

It should be noted that the depth of the cells of the airflow guide structure 24 into the respective conduit/plenum chamber 15, 17 progressively increases with distance along the respective arm 14, 16, in the direction away from the hinge 18.

By virtue of this arrangement, incoming air in the first direction D1 is steered from the first direction D1 to a second direction D2 that is substantially perpendicular to the first direction D1, inwardly towards the inter-arm chamber 13 that is formed by the arms 14, 16 in the closed position.

More particularly, the gradual change in the depth of the cells of the airflow guide structure 24 into the respective plenum chamber 15, 17 advantageously causes the incoming airflow in direction D1 to turn and exit from the plenum chamber in direction D2 and enter the inter-arm chamber 13 with uniform airspeed.

As Figure 8 also shows that, when the arms 14, 16 are in the closed position, the inner face of each airflow guide structure 24 is offset from an imaginary centreline midway between the first and second arms 14, 16 by a distance of 0.5 mm -4 mm (preferably about 2 mm). The position of the imaginary centreline is where hair 11 under tension will span the inter-arm chamber 13 in use (e.g. as shown in Figure 9). This offset of each airflow guide structure 24 from this imaginary centreline creates an airflow restriction between the air and hair in use, to increase the speed of the airflow around the hair, to increase drying.

The airflow guide structure 24 also includes a plurality of airflow redirecting channels 28, which extend between longitudinal edges and corresponding longitudinal sides of the airflow guide structure 24, as shown most clearly in Figure 14. These channels 28 are configured to convey the flow of air from the second direction D2 to third and fourth directions D3, D4 that are outward from the apparatus, substantially perpendicular to the length of the arms 14, 16, the fourth direction D4 being opposite to the third direction D3. Figure 13 also illustrates airflow directions D3 and D4. Incidentally, as shown in Figure 14, the airflow guide structure 24 including the cellular (e.g. honeycomb) structure and the airflow redirecting channels 28, along with the outward vents 26 in the third and fourth directions D3, D4, may be integrally formed are a unitary structure, e.g. by 3D printing.

Turning now to Figure 10, this illustrates further directions of airflow though the arms 14, 16 of the device 10 when viewed in transverse cross-section, facing towards the body part 12 of the device.

Starting in the centre of Figure 10, the air flowing in direction D2 can be seen entering the inter-arm chamber 13 from the plenum chambers 15, 17 via the cells of the airflow guide structures 24.

The air is then spread sideways and enters the airflow redirecting channels 28, from which the air then passes along airflow conduits 19a, 19b, 21a and 21b to leave the device via vents 26 in opposing directions D3 (via conduits 19a and 21a) and D4 (via conduits 19b and 21b). As shown in Figure 10, airflow conduits 19a, 19b, 21a and 21b respectively extend behind the heater plates 20a, 20b, 22a and 22b that are mounted on the first and second arms 14, 16.

For completeness, it should be noted that, although the directions of the airflow D3 and D4 upon leaving vents 26 may be said to be "substantially perpendicular" to the length of the arms 14, 16, the overall path followed by the air as it passes through the airflow redirecting channels 28 and along airflow conduits 19a, 19b, 21a and 21b, and then through the vents 26, is not linear.

Advantageously, the vents 26 direct the outgoing air towards the roots of the hair, to dry the roots and create root lift.

Figure 11 is a transverse cross-sectional view corresponding to that of Figure 10, through the arms 14, 16 of the device 10 in the closed configuration (around hair 11) and facing towards the body part 12 of the device. Looking along channels 15 and 17 in the direction of the body part 12, features of the cylindrical part 30 can be seen, including the diffuser grille 31 and the elongate baffles 32 end-on. Other features of Figure 11 correspond to those identified in Figure 10 and described above.

Figures 12 and 13 illustrate (in perspective longitudinal and transverse cross-sectional views respectively) airflow directional changes due to the airflow guide structure 24 and other features in each of the arms 14, 16 of the device 10.

As noted above, the first airflow direction D1 is substantially parallel to the length of each of the first and second arms 14, 16, as the air passes the baffles 32 and enters the first and second conduits (plenum chambers) 15, 17 in the respective first and second arms 14, 16. Then the cellular airflow guide structure 24 directs (i.e. steers) the flow of air from the first direction D1 to the second direction D2 inwards into the inter-arm chamber 13 that is formed by the arms 14, 16 in the closed position, through which the hair 11 passes in use.

The air is then spread sideways and enters the airflow redirecting channels 28, from which the air then passes along airflow conduits 19a, 19b, 21a and 21b behind the heater plates to leave the device via vents 26 in opposing directions D3 and D4.

Technical principles The expressions "to dry hair", "drying hair" and the like, as used herein, should be taken to refer primarily to the removal of "unbound" water that exists on the outside of hair when wet. Such "unbound" water should be contrasted with "bound" water, which exists inside individual hairs, and which can be interacted with when heat styling hair. There is no requirement to remove this "bound" water when drying hair in the context of the present invention, although removal of some bound water may occur during the drying process. Further removal of bound water usually occurs during the styling process.

Figure 20 is a graph of hair sample temperature against drying time, useful for understanding the technical principles associated with the present work. As the temperature of the hair is increased, the hair goes through a warming-up period and then first and second drying periods, as set out below. The first drying period relates primarily to the removal of unbound water, and the second drying period relates primarily to the removal of bound water.

* The "warming-up period": In this phase the ceramic heater plates are used to raise the temperature of the hair to that of the drying period where phase change of the liquid occurs (points A-B). The plates' surface cannot operate over 100-135°C (nominally 120°C) before water cavitation (sizzle) occurs on the plate.

* The "drying period 1": This phase is supported by heated airflow to dry unbound water on the hair (points B-C). Without a freshly heated airflow supporting the evaporation the hair will quickly cool and the drying rate will slow.

* The "drying period": This phase (points C-E) occurs when bound water on the hair evaporates and bound water is driven off from within the hair fibre.

* Styling/straightening can be achieved when forces are applied to the fibres and the bound and unbound water is driven off.

Problems and solutions provided by the present work In the present work the inventors have considered the following problems (amongst others) and have provided the following solutions thereto: Problem.1 -reducing volume of fan airflow and air heating power to fit within the grip of the user's hand The inventors have determined that, in general, drying hair with heated air is an inefficient use of energy, although traditional hair dryer technology is efficient at converting electrical energy to a high temperature airflow. Moreover, using heated air alone to dry hair is very inefficient, with most of the energy being lost in hot air to the atmosphere. To dry hair faster, traditional hair dryers have used higher air pressures and large volume flow rates by employing increasingly high speed motor and fan technologies with air heating to increase drying rates. However, this leads to reduced energy inefficiency, increased unit costs and increased noise levels.

On the other hand, using conductive heating plates is a very efficient way of heating water and hair to dry, helping to increase a quick-drying, compact and quiet product. However over temperatures of -100-143°C (nominally) liquid water in contact with the metal plates causes an audible sound of cavitation (sizzle), which causes a perception of damage. Hair temperatures over 143°C can lead to the denaturation of hair.

A possible solution to this would be to combine heated air blowing though conductive heater plates, but this would present an additional challenge by creating very high airflow resistance. This would require inefficient high-speed motor technologies to achieve the airflow pressures needed to pass hair through the hair and plates).

The solution provided by the present work is to enclose hair within a heated air plenum chamber 13 between conductive heater plates 20a, 20b, 22a, 22b. This enables the hair to be efficiently heated to evaporate more quickly toward the phase change temperatures of water with plate temperatures of -100-143°C (nominally 120°C) to avoid cavitation and damage. Moreover, heated plenum temperatures of 125-175°C (nominally 150°C) enables us to efficiently support and maintain phase change and evaporation without cavitation.

Problem 2 -minimising the range of air temperatures and air heating power, due 10 to large variations in airflow resistance of hair The inventors have determined that hair, and wet hair in particular, has a large variation in airflow resistance, depending on the size and water content of the section. A solution is therefore needed to avoid excessive temperature rise (hair damage) and large variations in air heater power and fan pressure requirements.

The solution provided by the present work is that the plenum chamber 13 enclosed around the hair enables heated air to pass around the hair (not just through the hair section), reducing the range of airflow resistance of the system. This helps to reduce the heater power and range in power requirements to regulate the air temperature, thereby increasing energy efficiency and reducing product size and cost.

By reducing the range of resistance in the airflow requirements of the system this also in turn enables lower speed motors/fans to be used, helping to increase the energy efficiency of the fan, and to reduce sound and cost.

Moreover, by designing system resistance to accurately meet the airflow and temperature requirements to dry hair when closed, this enables the product's air temperature when open to be cooler, thereby helping to improve the drying experience to the user and reducing losses of energy, and reducing the physical size of the air heater which would otherwise make the product bigger and less easy to use.

Problem 3 -achieving uniform air speed and changing air direction at the hair to air interface The inventors have determined that achieving uniform air temperature and speed across the hair-to-air interface is beneficial to maintain drying efficiency. However to achieve this within the context of the present product form requires a method to turn the air, with uniform air speed and pressure at the hair-to-air interface.

The solution provided by the present work is the provision of an airflow path that incorporates various features for guiding or steering the airflow, as follows: * The airflow splitter 34, which separates the airflow to the first and second arms 14, 16. It also prevents an excessive or uneven temperature rise on the edge of the section. It should be noted that the airflow splitter 34 can also be made larger and of a flexible material to vent air to the second arm 16 when the device is in the open condition.

This prevents air blowing hair off the heater plates 20a, 20b, 22a, 22b when the device is in the open condition and prevents hair restricting the air outlet in the open condition that could lead to increased airflow restriction and resistance in the system, that could otherwise cause overheating and hair damage.

* A plenum chamber 15, 17 within each of the arms 14, 16 that is shaped to allow airflow to fill each of the arms 14, 16, enabling more uniform airflow out of the cells of the cellular airflow guide structure 24.

* The cellular airflow guide structure 24 being of reduced cross-sectional width relative to the width of the arm 14, 16 in which it is located.

* The airflow guide structure 24 of each arm 14, 16 having a cellular (e.g. honeycomb or louvered) structure that extends into the plenum chamber 15, 17 within the respective arm, with the depth of the cells increasing in depth from the end of the arm proximal to the hinge 18, to the end of the arm distal from the hinge 18. This gradual change in the depth of the cells causes the airflow to turn and exit from the plenum chambers 15, 17 with uniform airspeed.

* An open off set distance from the nozzle outlet of the airflow guide structure 24 to the hair (when the first and second arms are in the closed configuration) of 0.5 mm -4 mm (nominally 2 mm) to create an airflow restriction between the air and hair, to increase the speed of the airflow around the hair, to increase drying. The open cross section between these features allows the air to pass around the hair to the plenum chamber outlet, without having to passing through the hair (which can otherwise restrict the airflow).

Problem 4 -achieving uniform air temperatures in the air stream The inventors have determined that achieving uniform air temperature across the air stream can be difficult if air heater windings are placed on the outer perimeter of an air duct (as is conventional practice). This causes the air temperature to be higher on the outer perimeter of the air stream relative to the centre of the air stream, giving a non-uniform distribution of heat across the air stream.

The solution provided by the present work is to place features in the air stream on the outside of the ring of the heater outlet, or inside the airflow, such as the baffles 32, to cause turbulence in the heated airflow and promote better mixing of air in the air stream before passing the airflow splitter 34. As a result, a more uniform air temperature profile across the air stream can be achieved.

Problem 5-drying the hair roots and creating root lift The inventors have determined that it is desirable to dry hair at the roots, e.g. with a view to creating root lift.

The solution provided by the present work is to provide air outlet vents 26 at the side and/or rear of the conductive heater plates 20a, 20b, 22a, 22b. These vents 26 direct the outgoing air towards the roots of the hair, to dry the roots and create root lift.

Problem 6 -limitation of plate cavitation (sizzle) with very wet hair over around 100-125°C The inventors have determined that plate cavitation (sizzle) with very wet hair over around 100-125°C is a limitation to drying speed.

The solution provided by the present work is based on the realisation that as the 10 unbound water on the hair evaporates, the plate temperature can be elevated to higher temperatures, to heat and dry hair faster and more efficiently.

Accordingly, a method is provided to measure the level of unbound water on the hair (moisture sensing), to enable the plate and/or air temperatures to be increased to accelerate the drying rate further. This may be done by providing temperature sensors in the device 10, for example in the following locations: * location "A" -upstream of the air to hair interface * location "B" -downstream of the air to hair interface * location "C" -to sense the temperature of the conductive heater plates, and/or power sensing A very large temperature difference between these sensors will indicate the arms 14, 16 are open, as the air will not be channelled past location B. The state of the arms 14, 16 being open can also be sensed by measuring the electrical power needed to elevate the air temperature, as the airflow system resistance will also change between the states of being open, closed, and closed with hair in.

The thermal loading of the plates in location C will indicate that hair is in the product (from power and/or temperature sensing).

A high temperature difference between the sensors will indicate water is evaporating (drying hair) and thus the hair is wet. On the other hand, a low temperature difference between the plates will indicate minimal phase change is occurring, so the hair is "dry".

Problem 7 -increasing the cooling rate of the heater plates As noted above, the inventors have determined that increasing the heater plate temperature in response to the presence of unbound water in hair enables faster drying. However if the user moves the device to a wetter section of hair the product's plates will ideally need to cool very quickly to prevent cavitation (sizzle) and or hair damage.

The present work provides a solution to this problem based on actively cooling the heater plates with air (from the fan) that passes over the plates. This enables accelerated cooling of the plates back down to 100-125°C. The air temperature can be controlled for example using an NTC (negative temperature coefficient) device and TRIAC control of the air heater.

A PTC (positive temperature coefficient) heater may also be beneficial to enabling a simple and compact conductive heater with an air heat sink.

Problem 8 -regulating the air temperature contacting the hair in open position The inventors have determined that it can be advantageous to regulate the maximum temperature rise to hair when the air outlet is restricted with hair during loading, to prevent hair damage, and/or to minimise energy losses to the atmosphere, to deliver cooler feeling air to the user. It is also desirable to regulate the air temperature to achieve fast drying and minimal hair damage.

The present work provides a solution to this problem by placing a NTC (negative temperature coefficient) device at the air heater outlet, between the air heater and hair contact surface, with a preferred location closest to the hair interface at the outlet nozzle. This enables the NTC to respond to changes in airflow resistance caused by hair restriction or increased temperature differences caused by increased airflow resistance when the arms are open. TRIAC control can be used to regulate the power to the air heater if an upper temperature limit is reached.

Problem 9 -to refresh hair on days when the hair is not washed The inventors have determined that users may wish to get a freshly washed and blow dry feeling to their hair on days when they do not have the time, ability or inclination to wash and dry their hair.

The present work provides a solution to this problem by enabling a fragrance to be emitted into the air stream generated by the device 10, to give the hair a fresh smell. To achieve this, a user-replaceable piezo-atomiser and/or a simpler fragrance reservoir and wick may be used to enable phase exchange (liquid to gas) into the air stream and thence onto the user's hair.

Problem 10 -to create a compact air heater to make a compact overall product form The inventors have determined that mains powered electrical air heaters are typically heated wire resistors formed to maximise the heated surface area in the air stream. This also adds complexity, size and cost, due to the requirement for a thermal fuse.

The present work provides a solution to this problem by recognising that a PTC (positive temperature coefficient) heater can enable a new form of air heater that merges the cellular (e.g. honeycomb) airflow guide structure 24 with an air heater, as a single product part. Thus, this merges the functionally of the two parts, making the overall product smaller and more compact. Moreover, because of the PTC effect, this can also negate the need for an additional thermal fuse (and the associated cost).

Problem 11-portability The inventors have determined that consumers desire products that are suitable 30 for "on the go" use, e.g. away from home, or in any event away from plug sockets (e.g. in the bathroom).

By virtue of the above-described energy savings, the present work enables a low voltage (LV) device 10 to be used for safe operation in the bathroom, and/or enables the device 10 to be used cordlessly (e.g. with a rechargeable battery) and/or a compact isolated power supply.

Modifications and alternatives Detailed embodiments and some possible alternatives have been described above. As those skilled in the art will appreciate, a number of modifications and further alternatives can be made to the above embodiments whilst still benefiting from the inventions embodied therein. It will therefore be understood that the invention is not limited to the described embodiments and encompasses modifications apparent to those skilled in the art lying within the scope of the claims appended hereto.

In the embodiments described above, each of the first and second arms 14, 16 contains a respective airflow conduit 15, 17 and is provided with a respective airflow guide structure 24. However, in alternative embodiments, only one of the arms 14, 16 may be provided with an airflow conduit and airflow guide structure 24. In yet other variants, the airflow guide structure(s) 24 may be omitted altogether.

In the embodiments described above, heater plates are provided symmetrically on either side of each arm 14, 16. However, as those skilled in the art will appreciate, it is not necessary that both these plates be heated, and in alternative embodiments only one plate may be heated, or neither of the plates may be heated. The squeegeeing effect of the plates may be sufficient in some circumstances to dry the hair in combination with the airflow, without either or both the plates being heated. Furthermore, unheated plates may be used to apply tension to the hair to provide a degree of styling. However, having at least one heater plate is preferred as it helps with the drying/styling process. Moreover, using a pair of heater plates, as in the presently-preferred embodiments, advantageously allows for bidirectional/ambidextrous use of the device.

In the embodiments described above, the airflow guide structure 24 in each of the first and second arms 14, 16 comprises a cellular structure having hexagonal (honeycomb) cells, configured to direct the flow of air from the first direction D1 to the second direction D2. However, in alternative embodiments, the cells of the airflow guide structure may be different shapes. For example, Figure 16 shows an perspective longitudinal cross-sectional view of an alternative cellular airflow guide structure 24a, in this case having rectangular cells in one linear dimension (with the depth of the cells progressively increasing with distance along the structure, in the same manner as the hexagonal cells described above). As another example, Figure 17 shows a perspective longitudinal cross-sectional view of another alternative cellular airflow guide structure 24b, in this case having rectangular cells in two linear dimensions (again with the depth of the cells progressively increasing with distance along the structure).

In the embodiments described above, the airflow is heated, e.g. by a heater element in the body 12 of the device, downstream of the fan 38. However, in alternative embodiments the means for heating the airflow may comprise the airflow guide structure 24 itself, the airflow guide structure being formed of a material that generates heat on application of an electric current thereto. In other alternative embodiments the device may not heat the air, relying instead on delivering air at a sufficiently high flow rate to dry the hair.

Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of the words, for example "comprising" and "containing", means "including but not limited to", and is not intended to (and does not) exclude other components, integers or steps.

The application also comprises the following numbered clauses: 1. Apparatus for drying and styling hair, comprising: first and second mutually-opposing arms adapted for movement between an open configuration for receiving a length of wet hair therebetween and a closed configuration adjacent the hair, such that, in use, when the arms are in the closed configuration they form an inter-arm chamber across which the hair passes, and wherein an airflow conduit is provided within and along at least one of the first and second arms; and means for delivering a flow of air along the conduit in the at least one of the first and second arms, and subsequently into the inter-arm chamber.

2. Apparatus according to clause 1, wherein one or both of the arms further comprises an airflow guide structure arranged to receive the flow of air from the respective conduit and to direct the flow of air from a first direction that is substantially parallel to the length of the respective arm, to a second direction that is from the respective arm towards the opposing arm, into the inter-arm chamber.

3. Apparatus according to clause 2, wherein each of the first and second arms comprises a respective conduit and a respective airflow guide structure, and the means for delivering the flow of air is arranged to deliver the air along the conduit in each of the first and second arms and thence through the respective airflow guide structure and into the inter-arm chamber.

4. Apparatus according to clause 3, wherein each airflow guide structure is offset from an imaginary centreline midway between the first and second arms when in the closed configuration.

5. Apparatus according to any of clauses 2 to 4, wherein the conduit in the or each arm acts as a plenum chamber through which the air flows into the respective airflow guide structure and thence into the inter-arm chamber.

6. Apparatus according to clause 5, wherein the airflow guide structure in the or each arm comprises a cellular structure configured to direct the flow of air from the first direction to the second direction, the cellular structure comprising a plurality of cell walls which extend along the second direction into the respective plenum chamber.

7. Apparatus according to clause 6, wherein the depth of the cells into the respective plenum chamber progressively increases with distance along the respective arm.

8. Apparatus according to clause 6 or clause 7, wherein the cellular structure has a honeycomb structure.

9. Apparatus according to any of clauses 6 to 8, wherein the or each airflow guide structure further comprises a plurality of airflow redirecting channels configured to convey the flow of air from the second direction to third and fourth directions that are outward from the apparatus, substantially perpendicular to the length of the arms, the fourth direction being opposite to the third direction.

10. Apparatus according to clause 9, wherein the airflow redirecting channels extend between longitudinal edges and corresponding longitudinal sides of the airflow guide structure.

11. Apparatus according to any preceding clause, further comprising mutually-opposing plates disposed on the first and second arms, the mutually-opposing plates being arranged to come together when the first and second arms are in the closed configuration.

12. Apparatus according to clause 11, wherein first and second plates are disposed on the first arm, and respective opposing first and second plates are disposed on the second arm.

13. Apparatus according to clause 11 or clause 12, wherein at least one of said plates comprises means for applying heat to said length of hair in use, when the first and second arms are in the closed configuration.

14. Apparatus according to clause 12 or clause 13 when dependent on clause 9 or clause 10, further comprising airflow conduits that extend behind the first and second plates of the respective arm, arranged to receive air from said airflow redirecting channels and to direct airflow behind the first plate and outward through vents along the edge of the apparatus in substantially the third direction, and to direct airflow behind the second plate and outward through vents along the edge of the apparatus in substantially the fourth direction.

15. Apparatus according to clause 14, wherein the airflow guide structure including the cellular structure and the airflow redirecting channels, and the outward vents in the third and fourth directions, are a unitary structure.

16. Apparatus according to any of clauses 3 to 15, further comprising an airflow splitter arranged to divide airflow into the conduits in the first and second arms in the first direction.

17. Apparatus according to clause 16, wherein the airflow splitter comprises a flexible member.

18. Apparatus according to any preceding clause, wherein the means for delivering the flow of air comprises a fan.

19. Apparatus according to clause 18, wherein the fan incorporates a brushless motor.

20. Apparatus according to clause 19, wherein the brushless motor is operable at speeds over 30,000 revolutions per minute.

21. Apparatus according to clause 19 or clause 20, wherein the brushless motor has a power consumption of no greater than 15 W. 22. Apparatus according to clause 21, wherein the brushless motor has a power consumption of about 3 W during normal operation.

23. Apparatus according to any preceding clause, further comprising means for heating said airflow.

24. Apparatus according to clause 23, further comprising means for causing turbulence in the heated airflow prior to the airflow reaching the inter-arm chamber.

25. Apparatus according to clause 24, wherein the means for causing turbulence comprises one or more baffles within the airflow.

26. Apparatus according to clause 23 when dependent on clause 2, wherein the means for heating said airflow comprises the airflow guide structure, the airflow guide structure being formed of a material that generates heat on application of an electric current thereto.

27. Apparatus according to any preceding clause, further comprising one or more sets of flexible bristles on the first and/or second arms, outside or within the inter-arm chamber, arranged to promote the application of uniform tension to the hair passing across the inter-arm chamber in use.

28. A method of drying hair using apparatus according to any preceding clause.

29. The method of clause 28, further comprising using the apparatus to style the hair substantially simultaneously with drying the hair.

Claims

CLAIMS1. Apparatus for drying and styling hair, comprising: first and second mutually-opposing arms adapted for movement between an open configuration for receiving a length of wet hair therebetween and a closed configuration adjacent the hair, such that, in use, when the arms are in the closed configuration they form an inter-arm chamber across which the hair passes, and wherein an airflow conduit is provided within and along at least one of the first and second arms; means for delivering a flow of air along the airflow conduit in the at least one of the first and second arms, and subsequently into the inter-arm chamber; wherein one or both of the arms further comprises an airflow guide structure arranged to receive the flow of air from the respective airflow conduit and to direct the flow of air from a first direction that is substantially parallel to the length of the respective arm, to a second direction that is from the respective arm towards the opposing arm, into the inter-arm chamber; wherein one or both of the arms further comprises a plurality of air vents that are coupled to the inter-arm chamber and that allow air to vent from the inter-arm chamber when the first and second arms are in the closed position; and wherein the air vents are arranged to vent air away from the respective arm in a direction that is substantially perpendicular to the first direction.
2. Apparatus according to claim 1, comprising a plurality of airflow redirecting channels configured to convey air from the inter-arm chamber towards the air 25 vents.
3 Apparatus according to claim 2, wherein the airflow guide structure and the airflow redirecting channels, and the plurality of vents form a unitary structure.
4. Apparatus according to claim 2 or 3, wherein the airflow redirecting channels are configured to convey air from the inter-arm chamber to vents that direct the air in third and fourth directions that are outward from the apparatus, substantially perpendicular to the length of the arms.
5. Apparatus according to any preceding claim, wherein each of the first and second arms comprises a respective conduit and a respective airflow guide structure, and the means for delivering the flow of air is arranged to deliver the air along the conduit in each of the first and second arms and thence through the respective airflow guide structure and into the inter-arm chamber.
6. Apparatus according to claim 5, further comprising an airflow splitter arranged to divide airflow into the conduits in the first and second arms in the first direction.
7. Apparatus according to claim 5 or 6, wherein each airflow guide structure is offset from an imaginary centreline midway between the first and second arms when in the closed configuration.
8. Apparatus according to any preceding claim, wherein the conduit in the or each arm acts as a plenum chamber through which the air flows into the respective airflow guide structure and thence into the inter-arm chamber.
9. Apparatus according to any preceding claim, wherein the airflow guide structure in the or each arm comprises a cellular structure configured to direct the flow of air from the first direction to the second direction, the cellular structure comprising a plurality of cell walls which extend along the second direction into the respective plenum chamber.
10. Apparatus according to claim 9, wherein the depth of the cells into the respective plenum chamber progressively increases with distance along the respective arm.
11. Apparatus according to claim 9 or claim 10, wherein the cellular structure has a honeycomb structure.
12. Apparatus according to any preceding claim, further comprising mutually-opposing plates disposed on the first and second arms, the mutually-opposing plates being arranged to come together when the first and second arms are in the closed configuration.
13. Apparatus according to claim 12, wherein first and second plates are disposed on the first arm, and respective opposing first and second plates are disposed on the second arm.
14. Apparatus according to claim 12 or claim 13, wherein at least one of said plates comprises means for applying heat to said length of hair in use, when the first and second arms are in the closed configuration.
15. Apparatus according to claim 13 when dependent on claim 4, further comprising airflow conduits that extend behind the first and second plates of the respective arm, arranged to receive air from said airflow redirecting channels and to direct airflow behind the first plate and outward through vents along the edge of the apparatus in substantially the third direction, and to direct airflow behind the second plate and outward through vents along the edge of the apparatus in substantially the fourth direction.
16. Apparatus according to any preceding claim, wherein the means for delivering the flow of air comprises a fan.
17. Apparatus according to any preceding claim, further comprising means for heating said airflow.
18. Apparatus according to claim 17, further comprising means for causing turbulence in the heated airflow prior to the airflow reaching the inter-arm chamber.
19. Apparatus according to claim 18, wherein the means for causing turbulence comprises one or more baffles within the airflow.
20. Apparatus according to claim 17 when dependent on claim 2, wherein the means for heating said airflow comprises the airflow guide structure, the airflow guide structure being formed of a material that generates heat on application of an electric current thereto.
21. Apparatus according to any preceding claim, further comprising one or more sets of bristles on the first and/or second arms, outside or within the inter-arm chamber.
22. Apparatus according to any preceding claim, wherein heated air is arranged to blow past or through the plates, to exchange heat between the air and the plates.
23. Apparatus according to claim 9 or any claim dependent thereon, wherein a cell wall at a distal end of the cellular structure is angled backwards relative to the other cell walls of the cellular structure.
24. Apparatus according to claim 13 or any claim dependent thereon, wherein the first and second plates on each arm extend along the respective arm and are angled inwards such that a separation between the first and second plates at a distal end of the arm is less than a separation between the first and second plates at a proximal end of the arm.
25. Apparatus according to any preceding claim, wherein the plurality of air vents are formed in a longitudinal edge of the respective arm to facilitate drying of hair roots during use.
26. A method of drying hair comprising using apparatus according to any preceding claim.
27. The method of claim 26, further comprising using the apparatus to style the hair substantially simultaneously with drying the hair.
28. The method of claim 26 or 27 comprising directing the vents towards roots of the hair to facilitate drying of the hair roots.