The present invention relates to a hair styling appliance and to a heating unit for a hair styling appliance. Heated hair styling appliances are designed to use the action of heat to form hair into a desired shape or style, including curls, waves and straightened sections of hair. In particular, but not exclusively, the present invention relates to a heating unit for a hair straightener appliance, also known as a hair styling iron, and to the hair straightener appliance itself.

Hair straighteners conventionally include two articulated arms which are hingedly attached to each other at one end and to which one or more heating plates are attached at the other end. Where both arms have a heating plate they are generally positioned on inner opposed surfaces of the arms. The heating plates generally have hair contacting surfaces which are designed to come into contact with hair to be styled during use of the hair straighteners. Such a straightener can be seen in WO2014/056957.

Heating plates for hair straighteners are conventionally made from a solid metal, ceramic or a combination of the two. They are also often resiliently mounted to the arm of the hair straightener such that they can move up and down or rock slightly as hair is pressed between the two arms. These resilient mounts are intended to ensure that hair pressed between the heating plates isn’t subjected to too much pressure. Also, the manufacturing tolerances of the product are less critical by using resilient mounts. However, pressure spots can still occur which can cause damage to the hair and affect the final styling.

In order to reduce the damage to hair caused by over compression, hair straighteners have been designed where the heating plate, or an opposed surface which contacts the heating plate, is segmented to help it conform to the hair which is pressed between the arms of the straightener. A problem does exist with such schemes however in that strands of hair can get trapped between the segments during use of the hair straightener. The use of segmented heating plates is therefore not a wholly satisfactory solution and there remains a need to provide a hair styling appliance in which the hair is uniformly heated across the selected sample of hair, avoiding overpressure in any selected area and avoiding heat being in a way in which the hair is damaged.

The present invention provides an improved heating plate and hair styling device in which these problems are considered

SUMMARY OF THE INVENTION.

According to one aspect of the invention, there is provided a heating unit for a hair styling appliance, the heating unit comprising a heating element which carries a contact member which defines a hair-contacting surface of the heating unit which makes direct contact with hair when applied to the hair styling appliance, and wherein the contact member includes a formed or a machined edge which serves to guide hair over the contact member and the heating element, in use.

The edge of the contact member may be a rolled edge or a machined edge.

The benefit of providing the rolled or machined edge on the contact member is that hair is drawn over the heating unit smoothly, to avoid snagging or damage being caused to the hair.

The heating unit may comprise a rigid mounting and a flexible support member, mounted within the rigid mounting, wherein the flexible support member supports the heating element so that the heating element is able to flex with the support member relative to the rigid mounting.

The contact member may be able to flex with the heating element relative to the rigid mounting.

In one embodiment, the rigid mounting defines a recess within which the flexible support member is received. It is another benefit of the invention that the heating element of the heating unit is able to flex, in use, by virtue of being mounted on the flexible support member. It has been found that the flexing of the heating element, which makes contact with the hair being styled, leads to a beneficial styling effect, and less damage being caused to the hair making direct contact with a heating plate of the heating unit. The flexing occurs in such a way that, regardless of where the hair applied pressure to the surface of the heating element by the hair, the same degree of deformation/flexing of the heating plate occurs.

In one embodiment, the heating element defines a heating surface on a hair-facing side of the heating element, wherein at least a part of the heating surface (or a surface of a member carried by the heating surface) stands proud of the rigid mounting so that a hair-contacting surface of the heating unit makes direct contact with hair when applied to the hair styling appliance.

Because the heating surface stands proud of the recess, and the hair makes direct contact with the contact member on the heating element, there is a beneficial styling effect for the hair. Hair styling is also achieved efficiently, maximising heat transfer to the hair without suffering heat losses through other components of the heating unit.

In embodiments, the flexible support member includes a support layer which defines a flexible support surface for the support surface of the heating element, a base layer, and a support structure arranged between the support layer and the base layer which is configured to provide substantially uniform deflection of the flexible support member for a downward force being applied at any point on the flexible support surface.

By way of example, the flexible support member includes a support portion, which defines a flexible support surface for the support surface of the heating element, and a support structure. The flexible support member may further include a base portion, wherein the support structure is arranged between the support portion and the base portion and is configured to provide substantially uniform deflection of the flexible support member for a downward force being applied at any point on the flexible support surface. This uniform deflection of the flexible support member, and the heating element which it carries, ensures that hair is heated uniformly across the whole surface of the heating element. This prevents heat pressure spots being applied to the hair and ultimately improves the final styling effect.

The support structure may, for example, include a pillar structure, for example a hollow pillar structure, which defines a plurality of openings which extend from one side of the flexible support member to the other.

The pillar structure may comprise a plurality of pillar pairs with adjacent pillars of a pair defining, at least in part, one of the plurality of openings have a substantially triangular cross section.

Typically, the plurality of pillar pairs, the base portion and the support portion are integrally formed.

In embodiments, the flexible support surface for the heating element may stand proud of the rigid mounting.

The flexible support member may be formed from silicone or any other suitably flexible material.

By way of example, the rigid mounting may form an integral part of a housing or casing for the hair styling appliance. For example, the rigid mounting may itself form a part of an arm of the hair styling appliance.

In other embodiments, the rigid mounting may be a separate unit mounted within a housing for the hair styling appliance.

By way of example, the rigid mounting may take the form of a frame and may have a curved base which mates, in use, with a recess of complementary form defined in the housing for the hair styling appliance. According to another aspect of the invention, there is provided a hair styling appliance including at least one heating unit as set out in the preceding paragraphs.

In embodiments, the housing for the hair styling appliance may form an arm or limb for the hair styling appliance, wherein the arm or limb may comprise a handle section which the user holds.

Typically, the hair styling appliance may comprise a pair of heating units and a pair of arms, each of the heating units being arranged in a respective arm so that the heating surface of the heating element of each heating unit faces a heating surface of the heating element of the other heating unit of the pair.

The hair styling appliance is particularly suitable for use in straightening hair.

The hair styling appliance may include means for providing power to the or each heating unit. For example, the hair styling appliance may include a battery unit for providing DC power to the or each heating unit. The battery unit may be a removable and/or rechargeable unit.

Because the contact member makes direct contact with the hair, there is a need to limit the power output of the heating element so as not to scald or scorch the sampled hair. This means that the appliance is most suited to being powered by a lower power DC battery arrangement, as opposed to AC mains power.

It will be appreciated that preferred and/or optional features of each aspect of the invention may be incorporated alone, or in appropriate combination, in the other aspects of the invention also.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the present invention may be more readily understood, an embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an isometric view of a hair styling appliance in the form of a hair straightener, in accordance with a first embodiment of the invention, with arms of the hair straightener closed together;

Figure 2 is side view of the hair straightener in Figure 1, also with the arms of the hair straightener closed together;

Figure 3 is a side view of the hair straightener in Figures 1 and 2, with arms of the hair straightener open fully;

Figure 4 is a top view of the hair straightener in Figures 1 to 3;

Figure 5 is an isometric view of the hair straightener in Figures 1 to 4 with the arms of the hair straightener open fully and with a heating unit of the hair straightener removed and shown separately;

Figure 6 is an exploded view of the heating unit shown in Figure 5;

Figure 7 is a side view of the heating unit shown in Figure 6;

Figure 8 is a section view of the heating unit shown in Figure 7 taken along line A-A in Figure 7;

Figures 9 to 15 show section views of various configurations for the flexible support member forming a part of the heating unit in Figure 8;

Figures 16, 17, and 18 illustrate three possible heater configurations for the heater plate of the heating unit in Figures 6 to 8,

Figure 19 is an isometric view of the hair straightener in Figures 1 to 5 with a hair sample present between the arms of the hair straightener; Figure 20 is a view similar to Figure 19 but with the hair sample removed to illustrate flexing of a heating plate of the heating unit when in use; and

Figure 21 is an exploded view of the heating unit with hair present to illustrate to illustrate how various elements of the heating unit flex, in use.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The hair styling appliance of the invention is typically of the type which has a rechargeable battery unit supplying DC power to the heating unit of the appliance and the invention has features which make it particularly suitable for use in an appliance which is powered in this way. Such appliances are particularly convenient as they are portable, can be used anywhere and are especially useful when travelling. However, the invention is equally applicable to a hair styling appliance which is powered through a power lead from an AC mains supply. The benefits of the invention will become apparent from the following description.

Referring to Figures 1 to 4, the hair straightener appliance, referred to general as 10, includes a first arm, referred to generally as 12, and a second arm, referred to generally as 14, which are joined together at one end by a hinge 16. The arms 12, 14 are movable about the hinge and can be closed together, against one another, as in the illustrations shown in Figures 1 and 2, or can be opened away from one another, as in the illustration in Figure 3. In this way the arms 12, 14 act like a pair of jaws, either shutting together against one another to close the jaws or moving away from one another to open the jaws.

As identified in Figure 2, each of the arms 12, 14 comprises a handle section 18, including the hinged end 16, and a heating section 20 at the end of each arm remote from the hinge 16. In use, the user grasps the handle section 20, applying pressure to the handle section in order to squeeze the arms 12, 14 together.

Generally, each arm 12, 14 of the hair straightener appliance includes a housing or casing. The casing includes an upper casing 22 and a lower casing 24, one being associated with each of the arms 12, 14. Each of the upper and lower casings 22, 24 takes the form of an integrally moulded part and is substantially identical to the other in external form. Both casings 22, 24 are typically formed from a plastic material and may be coated with a thin heat-resistant coating (typically a few microns in thickness) to provide an aesthetically pleasing finish to the appliance and to limit heat transfer to a user holding or touching the appliance.

As can be seen most clearly in Figure 1, the upper casing 22 includes an upper curved shell which closes against, and mates with, a lower curved shell of the lower casing 24, in a jaw-like fashion. The upper and lower casing 22, 24 in the heating section 20 of each arm defines a curved trough (not visible in Figures 2 to 4, and only the lower one 30 is visible in Figure 1) which receives a heating unit of the hair straightener appliance. A top of each heating unit 40, 42 is just visible in Figure 3 where the arms 12, 14 are shown separated from one another. Each heating unit 40, 42 is provided in the heating section 20 of each arm 12, 14, so that one is in the upper casing 22 and one is in the lower casing 24 and, for the most part, the heating units 40, 42 reside within the casings 22, 24.

The wall of each trough 30 in the handle section 20 is tapered at the end remote from the handle section so as to define a beaked end to each casing. As shown in Figure 2, the beaked end of the upper casing 22 is defined by reference numeral 32 and the beaked end of the lower casing 24 is defined by reference numeral 34. The casing 22, 24 for each arm is provided with a respective groove 36, 38 part way along its length which defines a boundary between the handle section 18 and the heating section 20 of each arm, and provides a visual aid to the user of the appliance regarding where the heating effect from the appliance occurs.

Referring especially to Figure 4, the hair straightener 10 has an associated battery unit 44 which resides within a recess provided in the handle section 18 of the upper casing 22. Typically, the battery unit 44 is a removable and/or rechargeable battery unit and a connection point is provided on the hair straightener (not shown) to connect the battery unit with recharging apparatus when, required. The battery unit 44 connects via internal wiring with an internal printed circuit board (also not shown in Figure 4) which controls the hair straightener 10 in a manner which would be known to a person familiar with the art. In other embodiments the battery unit 44 may be removable from the hair straightener 10 and charged remotely.

The heating units 40, 42 will now be described in further detail with reference to Figures 5 to 8. The heating unit 40, 42 is a multiple-component unit and includes several components arranged in a stack. Figure 5 shows the heating unit 42 which is to be housed within the lower casing 24 of the lower arm 14. Starting from the bottom of the stack, each heating unit 40, 42 includes a printed circuit board 50 (PCB - as mentioned above) which receives power from the battery unit 44 and which is programmed to control the hair straightener in response to various signals relating to, for example, on/off demands, heat settings and temperature control. The PCB 50 sits beneath and is affixed to the underside of a rigid mounting in the form of a frame 52 which also forms a part of the heating unit 42, as can be seen most clearly in Figures 7 and 8.

The frame 52 is typically formed from plastic and includes a base 56, two relatively long sidewalls 58, 60 and two relatively short end walls 62, 64 to connect the sidewalls together at each end. Together the sidewalls 58, 60, the end walls 62, 64 and the base 56 define a recess 54 (as best illustrated in Figure 8) for receiving other components of the heating unit 42. The internal cross section of the recess 54 defines a rectangular shape. The frame end wall 64 closest to the handle section 18 of the casing (when the heating unit is received within the casing 22, 24) is generally square shaped, whereas the frame end wall 62 remote from the handle section 18 is shaped to define a beaked end to the frame which has a corresponding form to that of the beaked end 32, 34 of the casing. This means that, when the heating unit 42 is received within the casing, the beaked ends of the frame and the casing 22, 24 cooperate together to fit together in a complementary fashion. A flexible support member 66 is received within the recess 54 in the frame 52 so that it lies against the base 56 of the frame 52. The flexible support member includes a lower frame-facing surface (visible in Figure 6), which faces the frame 52, and an opposed hair-facing surface 75 which is directed towards the hair, in use. The flexible support member 66 includes a front-facing side 72 and an opposed, rear-facing side 74, as viewed from the orientation shown in Figure 6. A heating element 68 is applied to the hair-facing surface 75 of the flexible support member 66, which is discussed in further detail below.

The heating element 68 defines a heating surface 77 on a hair-facing side of the heating element 68 and a support surface (not visible in Figure 6) on a support-facing side of the heating element 68 which mates with the hair-facing surface 75 of the flexible support member 66. On top of the heating element 68, a contact member 70, in the form of a shim or other suitable hair-contacting member, is mounted to the heating surface 77 of the heating element 68 to define a hair-contacting surface 79 of the heating unit 42. The contact member 70 may be comprised of a metal or alloy, including steel, copper, aluminium, brass and Nitinol.

Figures 9 to 15 show various configurations for the flexible support member 66 which forms a part of the heater unit 42. The flexing properties of the flexible support member 66 provide an important functionality for the heating unit 42, as discussed below.

The flexible support member 66 is an integrally formed member which is typically formed from silicone or another suitable flexible material. Referring to Figure 9, in a first embodiment of the invention the flexible support member 66 comprises a base portion 76, a top portion 78 and an intermediate portion 80 which forms a support structure between the base and top portions 76, 78. The area of the upper surface of the top portion 78 is broadly rectangular having two relatively long sides and two relatively shorter ends, as best seen in Figure 6. The area of the lower surface of the bottom portion 76 is the same as that of the top portion 78. The intermediate portion 80 includes a plurality of openings in the front-side 72 of the flexible support member 66 which extend fully through the flexible support member 66 and open at the rear-side 74. The openings define channels 82 which extend through the flexible support member 66 between the front and rear sides 72, 74. The thickness of the flexible support member is substantially uniform across its entire area.

The top portion 78 of the flexible support member 66 defines a flexible support surface 75 for the heating element 68 to rest on. The base portion 76 is received within the recess 54 of the frame 52 and lies against the floor of the recess 54. The flexible support member 66 is able to flex, vertically, when a downward force is applied to the upper surface of the top portion 78 when a hair sample is applied between the arms of the hair straightener.

Various other pillar structures are envisaged, as shown in Figures 10 to 15, as an alternative to that shown in Figure 9. In the embodiment of Figure 10, the intermediate portion 180 of the flexible support member 66 has a pillar structure comprising a plurality of pillars 186 which extend, at an angle to the vertical, between the top 178 and base portions 176. Each pillar 186 is angled to the vertical, with adjacent ones of the pillars 186 being angled away from each other. The effect of this pillar structure is that a plurality of triangular-shaped channels 182 extend through the flexible support member, from one side to the other 72, 74.

Not only does the support member in Figure 10 have flexibility, but the nature of the intermediate portion 180 and the channels 182 ensures that, when pressure is applied to the upper surface of the top portion 178, the degree of flexing of the support member 166 that occurs is substantially uniform, regardless of where on the surface of the top portion 78 a downward force is applied.

In the embodiment of Figure 11, the intermediate portion 280 is similar to that in Figure 9, but with the openings being of rounded rectangle form to define rounded rectangle channels 282 through the flexible support member 266.

In Figure 12, a pillar structure of the intermediate portion 380 includes a plurality of angled pillars 386, with the pillars on one side of a central V-shaped channel 388 being angled at one direction to the vertical and the pillars on the other side of the central V- shaped channel 388 being angled in the other direction to the vertical. The result of this pillar structure is that the channels 382 through the flexible support member 366 are shaped like a parallelogram in cross section.

Figure 13 is a further alternative configuration for the flexible support member 466 in which the base portion is removed altogether, and the flexible support member 46 includes only a top portion 478 and a plurality of vertical pillars 486 extending downwards from the top portion 478.

Figure 14 is similar to Figure 13, but with a base portion 576 as well as a top portion 578, with the pillars 586 extending between the base and top portions 576, 578.

In the configuration shown in Figure 15, the flexible support member 666 is similar to that shown in Figure 9, but with oval shaped openings to define oval shaped channels 682 through the flexible support member 666, from one side to the other.

In any of the configurations for the flexible support member, the material from which the flexible support member is made may have thermally insulating properties which ensure that heat from the heating element 68, which is supported by the flexible support member, is not readily transferred to the frame 52, as discussed in further detail below.

Referring to Figures 16 to 18, the heating element 68 typically comprises conductive heating tracks laid on or formed in the underside of a thick film base 94 which is applied to the flexible support member 66.

Figure 16 shows a first configuration for the conductive tracks 92 which are provided as three separate heater elements, with each of the heater elements having independent positive and negative electrical terminals 96 to which a current is supplied. The thick film base 94 may be formed from any suitable material which can transfer heat from the base to the hair to be straightened. Examples of suitable materials are metals and alloys of metals such as Aluminium, Copper, Steel, Titanium and Beryllium Copper. The thick film base 94 is shaped so as to correspond to the shape of the recess 54 in the frame 52.

Figure 17 shows an alternative configuration for the conductive tracks which are laid as six separate heater elements 98 on the thick film base 94, each of which has a positive and negative terminal 100 (only one of which is identified) to which current is supplied. Figure 18 shows a further alternative configuration for the conductive tracks 102 in which the terminals are arranged in a paired positive manner in which the positive terminals (e.g. 104) are paired to the same localised area on the base 94, and the negative terminals (e.g. 106) are paired to the same localised area on the base 94.

The conductive tracks 92, 98, 102 may be applied to the thick film base by screen printing conductive ink onto the thick film base 94. Alternatively, the conductive tracks may be formed by a chemical etching process whereby regions of the thick film base are removed by an etching process to create the conductive tracks.

It is a beneficial feature of the hair styling appliance 10 of the invention that at least the hair-contacting surface of the heating unit 68 stands proud of the recess 54 in the frame 52, as can be seen in Figure 8, so that it makes contact with the hair. Moreover, because the shim 70 is provided with a curved or ‘soft’ edge 90 (as shown in Figure 8), as hair is applied to the heating element and is passed over the shim 70, in use, it eases over the soft edge 90, rather than snagging.

The power of the heating element 68 is typically around 200W-250W when powered by a battery unit 44 (the power may be higher if powered by a mains supply). Because the heating element 68 of the appliance is so close to the hair, in use, with the very thin shim 70 on the heating plate providing the hair-contacting surface, it is necessary to limit the power of the appliance to prevent scorching of the hair. The appliance therefore lends itself to being powered by a relatively low power supply, such as portable battery unit 44, rather than by mains AC. The appliance can equally be powered by a DC source, but with the necessary adjustment to the heater configuration to maintain the power delivered at a suitable, relatively low level.

It will be appreciated that each of the arms 12, 14 of the straightener appliance is provided with an identical heating unit 42, with the hair-contacting surfaces of each heating unit 42 facing one another. When the arms 12, 14 are closed together about the hinge 16, a hair sample between them is clamped between the arms and, as the straightener is dragged over the hair sample, the heat from the facing heating units serves to apply a straightening effect to the hair sample. The appliance when in use can be seen in Figures 19, 20 and 21. In Figure 19 it can be seen how the hair sample 104 is received between the arms 12, 14 of the straightener and clamped between the two facing hair-contacting surfaces defined by the facing shims 70. The action of the hair sample 104 applying a downward force to the hair contacting surfaces of the shims 70 as the arms 12, 14 are closed together causes a flexing of the heating element 68, relative to the frame 52, which is facilitated by the flexible support member 66. This flexing effect is best illustrated in Figure 20, which shows the hair straightener of Figure 19 but with the hair sample removed from the illustration. Here it is evident how the hair-contacting surface has flexed in the region of the hair sample, by virtue of the flexing properties of the flexible support member 66 beneath it, whilst the rigid frame 52 retains its shape and structure.

The flexing effect can also be seen in Figure 21 which shows an exploded view of the stacked components of the heating unit with the hair sample 104 received between the facing arms 12, 14 of the straightener. Here it can be seen that the shim 70, the heating element 68 and the flexible support member 66 all flex together in the region in which the hair is received between the heating units 42. This flexing of the hair contacting surface has been shown to have a beneficial styling result. Furthermore, by virtue of the rolled, machined or otherwise formed soft edge of the shim 70, as hair is passed over the hair-contacting surface of the shim it cannot snag.

It will be appreciated that various other modifications to the invention may be made within departing from the scope of the invention as set out in the accompanying claims.