FIELD

The present invention relates to a hair-styling appliance in the form of a hair straightener.

BACKGROUND

Hair straighteners use heat, pressure and/or airflow to straighten or style hair. A pair of opposed plates capture a tress of hair between them, usually near the scalp. The hair straightener is then drawn along the tress to straighten or style the hair.

SUMMARY

In accordance with a first aspect, there is provided a hair straightener comprising: a first arm comprising a first hair contact surface; and a second arm comprising a second hair contact surface, the second arm being coupled for movement towards the first arm; wherein: the first and second hair contact surfaces are configured to capture a tress of hair between them when the first and second arms are moved towards each other in use; the first hair contact surface defines a series of tress-corralling recesses disposed along its length; and the second hair contact surface does not define a tress-corralling recess.

In use, the tress-corralling recesses corral the tress of hair as it is drawn between the first and second hair contact surfaces, while the use of a second hair contact surface that does not define a tress-corralling recess may reduce pinching or grabbing of the hair.

The second hair contact surface may be flat. This may improve smoothing and/or polishing of the hair tress where it is in contact with the second hair contact surface.

The second hair contact surface may be, in longitudinal section, convex in the direction of the first hair contact surface. This may improve smoothing and/or polishing of the hair tress where it is in contact with the second hair contact surface, while encouraging corralling of the hair tress towards a central region of the first and second hair contact surfaces.

In accordance with a second aspect, there is provided a hair straightener comprising: a first arm comprising a first hair contact surface; and a second arm comprising a second hair contact surface, the second arm being coupled for movement towards the first arm; wherein: the first and second hair contact surfaces are configured to capture a tress of hair between them when the first and second arms are moved towards each other in use; the first hair contact surface defines a series of tress-corralling recesses disposed along its length; and the second hair contact surface defines tress-corralling recesses that are shallower than the first tress-corralling recesses.

In use, the tress-corralling recesses corral the tress of hair as it is drawn between the first and second hair contact surfaces, while the use of a second hair contact surface that defines tress-corralling recesses that are shallower than the first tress-corralling recesses may reduce pinching or grabbing of the hair.

The second hair contact surface may comprise the same number of tress-corralling recesses as the first hair contact surface.

Alternatively, the second hair contact surface may comprise fewer tress-corralling recesses than the first hair contact surface.

In all aspects, the first hair contact surface may be scalloped in longitudinal section, and each scallop may define one of the tress-corralling recesses. The use of multiple scallops may improve the corralling of the hair tress. In all aspects, the first hair contact surface may be sinuate in longitudinal section, and each trough of the sinuate section may define one of the tress-corralling recesses. The use of a sinuate longitudinal section may improve the corralling of the hair tress.

In all aspects, the first hair contact surface may comprise a plurality of teeth in longitudinal section, and a region between each adjacent pair of the teeth may define one of the tress-corralling recesses. The use of such teeth may improve the corralling of the hair tress.

In accordance with a third aspect, there is provided a hair straightener comprising: a first arm comprising a first hair contact surface; and a second arm comprising a second hair contact surface, the second arm being coupled for movement towards the first arm, wherein the first and second hair contact surfaces are configured to capture a tress of hair between them when the first and second arms are moved towards each other in use; the hair straightener being operable in at least two of the following modes: a first mode, in which the first hair contact surface is heated more than the second hair contact surface; a second mode, in which the second hair contact surface is heated more than the first hair contact surface; and a third mode, in which both the first hair contact surface and the second hair contact surface are heated.

By being capable of operating in at least two of the three modes, the hair straightener may use less power and/or provide improved or at least alternative options for the styling of hair.

In the first mode, only the first hair contact surface may be heated, and in the second mode, only the second hair contact surface may be heated. The hair straightener may comprise at least one sensor for sensing a position and/or orientation of the hair straightener, the hair straightener being configured to operate in one of the modes responsive to the hair straightener being in a first position and/or orientation as sensed by the at least one sensor. This may reduce power consumption and/or provide improved or at least alternative options for the styling of hair.

The hair straightener may be configured to operate in another of the modes responsive to the hair straightener being in a second position and/or orientation as sensed by the at least one sensor, the second position and/or orientation being different to the first position and/or orientation. This may reduce power consumption and/or provide improved or at least alternative options for the styling of hair.

The first and/or the second position and/or orientation may comprise a range of positions and/or orientations. Being responsive to a range or positions and/or orientations may improve usability.

The at least one may sensor comprise at least one light sensor, and the hair straightener may be configured to operate in the first or the second mode, such that whichever of the first hair contact surface and the second hair contact surface is closer to a user’s head is heated, and the other of the first hair contact surface and the second hair contact surface is unheated. This may reduce power consumption and/or provide improved or at least alternative options for the styling of hair.

The at least one light sensor may comprise at least: a first light sensor disposed to sense light levels on a side of the hair straightener corresponding to the first arm; and a second light sensor disposed to sense light levels on a side of the hair straightener corresponding to the second arm; the first and second light sensors allowing determination of which of the first hair contact surface and the second hair contact surface is closer to a user’s head. The first light sensor may be disposed on the first arm and the second light sensor may be disposed on the second arm.

The at least one sensor may comprise an inertial measurement unit.

The at least one sensor may comprise an accelerometer.

The hair straightener may be operable in only two of the first, second, and third modes.

In accordance with a fourth aspect, there is provided a method of operating a hair straightener, the hair straightener comprising: a first arm comprising a first hair contact surface; a first heater configured for heating the first hair contact surface; a second arm comprising a second hair contact surface, the second arm being coupled for movement towards the first arm, wherein the first and second hair contact surfaces are configured to capture a tress of hair between them when the first and second arms are moved towards each other in use; a second heater configured for heating the second hair contact surface; and at least one position and/or orientation sensor; the method comprising: sensing, using the at least one position and/or orientation sensor, a position and/or orientation of the hair straightener; responsive to the sensed position and/or orientation, operating the hair straightener in a first mode in which the first heater heats the first hair contact surface more than the second heater heats the second hair contact surface; sensing, using the at least one position and/or orientation sensor, a change in the position and/or orientation of the hair straightener; and responsive to the sensed position and/or orientation, operating the hair straightener in a second mode in which the second heater heats the second hair contact surface more than the first heater heats the first hair contact surface. Operating the hair straightener in the first mode may comprise heating only the first hair contact surface.

Operating the hair straightener in the second mode may comprise heating only the second hair contact surface.

BRIEF DESCRIPTION OF DRAWINGS

In order that the present invention may be more readily understood, embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure l is a perspective view of a hair straightener in an open;

Figure 2 is a perspective view of the hair straightener of Figure 1, in a closed position;

Figure 3 is a schematic longitudinal section through first and second arms of the hair straightener;

Figure 4 is a schematic longitudinal section through first and second arms of a further hair straightener;

Figure 5 is a schematic longitudinal section through first and second arms of a further hair straightener;

Figure 6 is a schematic longitudinal section through first and second arms of a further hair straightener;

Figure 7 is a schematic longitudinal section through first and second arms of a further hair straightener;

Figure 8 is a schematic longitudinal section through first and second arms of a further hair straightener;

Figure 9 is a perspective view of the first plate of the hair straightener of Figures 1 to 3;

Figure 10 is a plan view of the first plate of Figure 9;

Figure 11 is a side elevation of the first plate of Figures 9 and 10;

Figure 12 is a transverse section through lines XII-XII of the first plate of Figures

9 to 11; Figure 13 is a schematic longitudinal section through first and second arms of a further hair straightener;

Figure 14 is an end view of the hair straightener of Figure 13;

Figure 15 is a schematic longitudinal section through first and second arms of a further hair straightener;

Figure 16 is a front elevation of the hair straightener of Figure 15 being used to straighten the left-hand side of the user’s hair;

Figure 17 is a front elevation of the hair straightener of Figure 15 being used to straighten the right-hand side of the user’s hair; and

Figure 18 is a flowchart showing a method of operating a hair straightener.

DETAILED DESCRIPTION

Referring to the drawings, there is shown a hair straightener 100. Hair straightener 100 comprises a first arm 102 and a second arm 104 coupled for movement relative to first arm 102. In the illustrated example, first arm 102 is connected to second arm 104 by way of a hinge (not shown) mounted to a body 106, although the skilled person will appreciate that other forms of coupling allowing relative movement between first arm 102 and second arm 104 may be employed.

First arm 102 comprises a first hair contact surface comprising an outer surface of a first plate 108. Second arm 104 comprises a second hair contact surface comprising an outer surface of a second plate 110. First plate 108 and second plate 110 are disposed on inner surfaces of first and second arms 102 and 104.

First plate 108 and second plate 110 are heated by respective electric resistance heaters (not shown). The heating can be continuous, or triggered by a user or by the closing (or partial closing) of the first and second arms 102 and 104.

When hair straightener 100 is in the open position, a tress of hair 112 may be positioned between first plate 108 and second plate 110. First arm 102 and second arm 104 are then pressed together, to capture the tress of hair 112 between them as shown in Figure 2. Hair straightener 100 may then be drawn away from the user’s scalp, with the heat and pressure from first plate 108 and second plate 110 straightening the tress of hair 112 as it passes between them.

First plate 108 defines a series of tress-corralling recesses 114 disposed along its length. Tress-corralling recesses 114 take the form of parallel channels extending transversely across first plate 108.

The number of tress-corralling recesses 114 can be selected to suit the particular application and desired results. For example, the number of tress-corralling recesses 114 may be between 10 and 20. It has been found that around 15 recesses with a spacing of 6mm peak to peak and a depth of 3mm provide a good compromise of comfort and functionality.

In the implementation of Figure 3, first plate 108 is scalloped in longitudinal section, such that each tress-corralling recess 114 is defined by one of the scallops. The outer surface of second plate 110 is substantially flat in longitudinal section. The scalloped tresscorralling recesses 114 on first plate 108 may provide corralling of the tress of hair 112, while flat second plate 110 may provide straightening and polishing of the tress of hair 112 in contact with it, all while providing acceptable pinching/pulling of the tress of hair 112.

In the implementation of Figure 4, first plate 108 is sinuate in longitudinal section, such that each trough of the sinuate section defines one of tress-corralling recesses 114. The outer surface of second plate 110 is substantially flat in longitudinal section. The tresscorralling recesses 114 defined by sinuate first plate 108 may provide corralling of the tress of hair 112, while flat second plate 110 may provide straightening and polishing of the tress of hair 112 in contact with it, all while providing acceptable pinching/pulling of the tress of hair 112. In general, it is desirable that the peaks defining the recesses terminate in a relatively sharp point in cross section. This is to ensure that hair is encouraged away from the peaks and into the adjacent recesses when the hair straightener is in use. The less pointed the peaks, the greater the chance of pinching and pulling of the hair as it is trapped between the peak and the opposite plate. Such pinching and pulling may optionally be reduced by preventing the plates from coming into contact with each other, which can be achieved, for example, by way of a stop mechanism (not shown) that stops the arms before the plates come into contact with each other.

In the implementation of Figure 5, first plate 108 defines a plurality of teeth 116 in longitudinal section. A region between each adjacent pair of teeth 116 defines one of the tress-corralling recesses 114. The outer surface of second plate 110 is substantially flat in longitudinal section. The tress-corralling recesses 114 defined by teeth 116 may provide corralling of the tress of hair 112, while flat second plate 110 may provide straightening and polishing of the tress of hair in contact with it, all while providing acceptable pinching/pulling of the tress of hair 112.

The implementation of Figure 6 has a first plate 108 similar to that shown in Figure 3. However, the outer surface of second plate 110 is convex in longitudinal section. This arrangement may allow for a greater bulk of the tress of hair 112 to be contained more centrally between first plate 108 and second plate 110, which may reduce pinching/pulling of the tress of hair 112.

The implementation of Figure 7 has a first plate 108 similar to that shown in Figures 3 and 6. However, the outer surface of second plate 110 defines a series of further tresscorralling recesses 118. There are, however, fewer further tress-corralling recesses 118 on second plate 110 than there are tress-corralling recesses 114 on the first plate 108.

A second plate having an outer surface that is convex in longitudinal section, or which has further tress-corralling recesses 118 such as those described in relation to Figure 7, may be used with a first plate 108 having a different configurations, such as the first plate configurations of Figures 4 and 5, as well as to implementations having differently shaped tress-corralling recesses.

Figure 8 shows a further hair straightener 600, in which features generally corresponding with those of other described implementations are indicated with the same reference signs. Hair straightener 600 comprises a second hair contact surface in the form of second plate 110, which defines further tress-corralling recesses 120. Further tress-corralling recesses 120 are shallower than first tress-corralling recesses 114.

Tress-corralling recesses 114 define a first depth 122 and further tress-corralling recesses 120 define a second depth 124. First depth 122 and second depth 124 may be measured from the deepest point in each recess to the top of the adjacent peaks. Alternatively, first depth 122 and second depth 124 may be calculated as an average depth of the recesses.

Alternatively, the first and/or second hair contact surfaces may be scalloped in longitudinal section, each scallop defining one of the tress-corralling and/or further tresscorralling recesses (as shown for first plate 108 in Figure 3).

Alternatively, the first and/or second hair contact surfaces may be sinuate in longitudinal section, each trough of the sinuate section defining one of the tress-corralling and/or further tress-corralling recesses (as shown for first plate 108 in Figure 4).

Alternatively, the first and/or second hair contact surface may comprise a plurality of teeth in longitudinal section, a region between each adjacent pair of the teeth defining one of the tress-corralling recesses (as shown for first plate 108 in Figure 5).

The general shape and arrangement of first plate 108 and second plate 110 may differ. For example, first plate 108 may employ scalloped tress-corralling recesses while second plate 110 may employ a sinuate longitudinal section. Any other combination of longitudinal section shape and arrangement for the first and second plates may be employed. Optionally, either or both of first plate 108 and second plate 110 may be resiliently biased away from first arm 102 and second arm 104 respectively, for example by way of one or more springs (not shown). This allows a user to clamp the tress of hair 112 between first plate 108 and second plate 110 with less pinching or pulling.

Second hair contact surface may comprise the same number of tress-corralling recesses as the first hair contact surface. Alternatively, second hair contact surface comprises fewer tress-corralling recesses than the first hair contact surface, as shown in Figure 7, for example.

Optionally, an inlet to each hair-corralling recess may converge to help with corralling the tress of hair 12. For example, Figure 9 shows a perspective view of first plate 108, Figure 10 shows a plan view of first plate 108, Figure 11 shows a side elevation of first plate 108, and Figure 12 shows transverse section XII-XII through first plate 108 in Figure 9. Each tress-corralling recess 114 has a converging portion 126 in plan, as well as a converging portion 128 in section.

Converging portion 126 gradually corrals the tress of hair 112 into the corresponding recess, while reducing pulling that might be caused by the hair encountering a sharp- edged entrance to tress-corralling recess 114.

Converging portion 128 gradually corrals the tress of hair 112 deeper into tress-corralling recess 114, again while reducing pulling that might be caused by the hair encountering a sharp-edged entrance to tress-corralling recess 114.

Figure 13 shows a further hair straightener 700, in which features generally corresponding with those of other described implementations are indicated with the same reference signs. In contrast with earlier-described implementations, the surfaces of first plate 108 and second plate 110 of hair straightener 700 are both substantially flat in longitudinal section. Hair straightener 700 comprises a first heating element 130 extending adjacent first plate 108, and a second heating element 132 extending adjacent second plate 110. First heating element 130 is connected to be driven by a first drive circuit 134, and second heating element 132 is connected to be driven by a second drive circuit 136.

First drive circuit 134 and second drive circuit 136 are controlled by a controller 138. Controller 138 may, for example, comprise a microprocessor (not shown) programmed to implement the functionality described herein.

Hair straightener 700 is operable in at least two modes.

For example, in a first mode, controller 138 controls first drive circuit 134 and second drive circuit 136 such that first plate 108 is heated more than second plate 110. For example, in the first mode, controller 138 may control first drive circuit 134 to drive first plate 108 while controlling second drive circuit 136 to not drive second plate 110.

In a second mode, controller 138 controls first drive circuit 134 and second drive circuit 136 such that second plate 110 is heated more than first plate 108. For example, in the second mode, controller 138 may control second drive circuit 136 to drive second plate 110 while controlling first drive circuit 134 to not drive first plate 108.

Optionally, hair straightener 700 may be operable in a third mode, in which controller 138 controls first drive circuit 134 and second drive circuit 136 such that first plate 108 and second plate 110 are heated similarly.

Depending upon the implementation, hair straightener 700 may be operable in any two (and only two) of the first, second and third modes described above, or may be operable in all three of the first, second and third modes described above. The particular mode in which hair straightener 700 operates may be selected in any suitable way. For example, hair straightener 700 may include a user interface 142 with which a user can select the operating mode of hair straightener 700, from the available operating modes. User interface 142 may comprise, for example, one or more switches, dials, buttons, touchscreens, or other user interface elements allowing a user to select various options including operating modes such as those described herein.

Depending upon the implementation, the first mode and/or the second mode will always be available. That is, there will always be a mode available in which one of first plate 108 and second plate 110 is heated more than the other plate (which includes the possibility of the other plate not being heated). Heating only one of first plate 108 or second plate 110 offers the ability to focus the straightening and styling effect of hair straightener 700 on one side of a tress of hair being straightened. This is because the first plate 108 or second plate 110 that is heated more than the other plate will have a greater straightening and styling effect than the other, less-heated plate.

An unexpected side-effect of one of first plate 108 and second plate 110 being heated more than the other plate is that the less-heated plate causes less straightening and therefore flattening of the hair with which it is in contact. Reduced straightening and flattening of this sort may result in increased volume as compared with the increased straightening and flattening caused by the more-heated plate, which provides the user with additional options for hair styling.

As one example, by orientating hair straightener 700 such that the less-heated of first plate 108 and second plate 110 is on the side of a hair tress to be styled that is closer to the user’s head or neck, the less-heated plate causes less straightening and flattening than the more-heated plate. The result is that the volume of hair in contact with the less-heated plate is reduced less than that of hair in contact with the more-heated plate, while the more-heated plate provides greater straightening and polishing of the hair with which it is in contact. Overall, the result (compared to heating both plates) may be improved overall volume while still attaining a straightened and polished outer hair surface. While manual mode selection is described above, in other implementations, mode selection may be performed automatically, or semi-automatically, based on a position and/or orientation of hair straightener 700.

For example, hair straightener 700 may comprise a sensor in the form of an inertial measurement unit (MCU) 140. MCU 140 comprises accelerometers that sense translation and rotation, and is configured to output to controller 138 signals representative of the sensed translation and rotation.

Based on the received signals, controller 138 selects the operating mode of hair straightener 700.

Hair straightener 700 can be configured to operate in one of the modes responsive to the hair straightener being in a first position and/or orientation as sensed by the at least one sensor.

For example, MCU 140 may sense the rotational orientation of hair straightener 700. As shown in Figure 14, hair straightener 700 is in a rotational position such that first plate 108 is above second plate 110, with the right hand edge of first plate 108 being above the left hand edge of first plate 108 at an angle of about 30°. Based on the determination that first plate 108 is higher than second plate 110, it can be determined that second plate 110 is closer to the user’s head, and therefore may be heated less (or not at all) in at least one mode. This initial determination may be further confirmed if it is determined that hair straightener 700 is rotated such that first plate 108 rotates lower relative to second plate 110, after closing of the arms and before or during a stroke along tress of hair 112.

If, on the contrary, hair straightener 700 is in a rotational position such that first plate 108 is below second plate, it can be determined that first plate 108 is closer to the user’s head, and therefore may be heated less (or not at all) in at least one mode. This determination may be further confirmed if it is determined that hair straightener 700 is rotated such that second plate 110 rotates lower relative to first plate 108, after closing of the arms and before or during a stroke along tress of hair 112.

Optionally, the operating mode selection may be made at least partly on the basis of an overall operation mode selected by the user. For example, the user may place hair straightener 700 into a manual mode, in which the first, second or third mode is manually selectable before or while hair straightener 700 is being used to straighten hair. The user is therefore completely in control of whether first plate 108 or second plate 110 is heated more than the other plate, and/or both plates are heated similarly, depending upon which modes are available.

Alternatively, the user may place hair straightener 700 into an automatic mode, in which first plate 108 or second plate 110 is heated more than the other plate based upon signals from the orientation/position sensor.

Optionally, the user interface may allow the user to cycle through the first, second, and/or third mode, as well as selecting an overall operating mode, if available.

Figure 15 shows a further hair straightener 800, in which features generally corresponding with those of other described implementations are indicated with the same reference signs.

Instead of the MCU 140 of hair straightener 700, hair straightener 800 uses sensors in the form of a first light sensor 144 disposed on an outer surface of first arm 102, and a second light sensor 146 disposed on an outer surface of second arm 104, to infer a position and/or orientation of hair straightener. Both first light sensor 144 and second light sensor 146 are positioned about halfway along the length of first plate 108 and second plate 110, respectively, although other positions may be used depending upon the implementation and desired functionality. First light sensor 144 and second light sensor 146 are configured to sense light levels, and to output to controller 138 a signal indicative of those sensed light levels. Based on the light level sensed by each of first light sensor 144 and second light sensor 146, controller 138 determines a position of first plate 108 and second plate 110 relative to a tress of hair to be straightened or styled.

For example, whichever of first arm 102 and second arm 104 is placed closer to the user’s head or neck will tend to be at least partly shaded from ambient light by the tress of hair, and the user’s head or neck. In addition, ambient light tends, in general, to move in a downward direction, whether from light fixtures fixed to a ceiling, or from sunlight, whether direct or dispersed by clouds. As such, whichever light sensor is positioned lower than the other will typically sense less light.

Accordingly, controller 138 will determine that whichever of first light sensor 144 and second light sensor 146 light sensor senses less light is positioned closer to the user’s neck or head. Accordingly, controller 138 will control first and second drivers such that the plate that is closer to the user’s neck or head is driven less, or not at all, such that its temperature is lower than that of the other plate. The result is that the volume of hair closer to the user’s head or neck and in contact with the less-heated plate is reduced less than that of hair in contact with the more-heated plate, while the more-heated plate provides greater straightening and polishing of the hair with which it is in contact. Overall, the result (compared to heating both plates) may be improved overall volume while still attaining a straightened and polished outer hair surface.

The use of hair straightener 800 to straighten hair is shown in Figures 16 and 17. In Figure 16, a user 802 is using hair straightener 800 to straighten a tress of hair 112. User 802 can hold hair straightener 800 such that body 106 is pointing to the front or rear, depending upon which is more comfortable.

Tress of hair 112 is held between first plate 108 and second plate 110. First light sensor 144 is pointing more towards the ceiling than second light sensor 146, and is not shaded by the rest of hair straightener 800, tress of hair 112, or user 802. Accordingly, first light sensor 144 indicates to controller 138 a higher light level than that indicated by second light sensor 146. From this, controller 138 determines that second arm 110 is closer to user 802 than first arm 108, and therefore heats second plate 110 less than first plate 108.

User 802 draws hair straightener 800 along tress of hair 112 such that it is straightened and styled. As described above, the use of less heat on the inner surface of the tress of hair (relative to the user’s head and neck) may result in more volume, while the greater heat on the outer surface of the tress of hair provides greater polishing and smoothing. The process may be repeated for other tresses of hair on the same side of the user’s head.

Turning to Figure 17, user 802 has moved hair straightener 800 to straighten a further tress of hair 113 on the other side of their head. Because of the way user 802 has moved and rotated hair straightener 800, second arm 104 is now positioned higher than first arm 102. As such, second light sensor 146 is pointing more towards the ceiling than first light sensor 144, and is not shaded by the rest of hair straightener 800, tress of hair 113, or user 802. Accordingly, second light sensor 146 indicates to controller 138 a higher light level than that indicated by first light sensor 144. From this, controller 138 determines that first arm 108 is closer to user 802 than second arm 110, and therefore heats first plate 108 less than second plate 110.

User 802 draws hair straightener 800 along further tress of hair 113 such that it is straightened and styled. As described above, the use of less heat on the inner surface of the tress of hair (relative to the user’s head and neck) may result in more volume, while the greater heat on the outer surface of the tress of hair provides greater polishing and smoothing. The process may be repeated for other tresses of hair on the same side of the user’s head.

Although the use of two light sensors is described, the skilled person will appreciate that a greater number of light sensors may be used to improve position and/or orientation sensing. For example, multiple light sensors can be spaced along a length of one or both of the hair straightener’s arms. This may improve the ability of controller 138 to determine an orientation and/or position of the hair straightener more accurately in different lighting conditions and/or in different orientations or use cases.

Similarly, a single light sensor may be used to determine an orientation or position. This may be done by determining a change in the sensed light, and inferring from that a change in, for example, orientation. For example, decreasing light levels while in use may suggest that the hair straightener is being rolled in the direction of the user’s head or neck, based upon which controller 138 may determine which of the plates is in contact with the hair closer to the user’s head or neck.

The skilled person will appreciate that one or more light sensors can be combined with one or more MCUs (or other position and/or orientation sensors). This may allow more accurate orientation/position sensing.

Other sensors, including different types of sensors, may be used. For example, one or more cameras may be positioned to capture imagery while (and/or immediately before) the hair straightener is used. By analysing the images, changes in position and/or or orientation may be determined, and then used to control plate heating as described above. Other examples of different sensor types that can be used include accelerometers, force measurements sensors, and inertial measurement units.

The hair straightener may also comprise one or more sensors for allowing controller 138 to determine when the arms have been moved into, or close to, the closed position, and/or out of the fully open position. This information may be used as an input for determining when and how to drive first plate 108 and second plate 110 relative to each other, as described above. For example, in an implementation, neither plate is heated when the hair straightener is in an open position. The plate closest to the user’s head or neck may then be heated when it is sensed that the arms have moved from the open position. Alternatively, both plates may be heated, but only one of them (the one on the side of the user’s hair away from the head/neck side) continues to be heated after it is sensed that the arms have moved from the fully open position.

Whatever form of position and/or orientation sensor(s) are employed, the position or orientation may be sensed in an absolute sense and/or in relative sense. For example, the position and/or orientation sensor may be capable of determining which direction is “up”, and can measure position and/or orientation relative to that direction. Alternatively, the position and/or orientation sensor may be capable only of measuring position and/or orientation based on relative rotation and/or translation of the hair straightener, without being capable of identifying an absolute position or orientation. Any combination of such sensors may be used to suit particular implementation requirements.

The way in which heat is delivered to either or both of the plates may also be controlled in various ways to achieve different functional and performance outcome. For example, where it is desirable to reduce energy consumption (e.g., when battery power is in use), one of the modes may have only the outer plate being heated.

Optionally, the temperature and/or power output of first plate 108 and/or second plate can vary as the hair straightener is used. For example, at the start of a stroke, both first plate 108 and second plate 110 can be heated. Then, as the sensor(s) determine which side of the hair is closer to the head and/or neck, power to the plate on that side can be turned off or reduced relative to that suppled the other plate. The heat can be turned off at the start of, or during, the stroke, and/or modulated down over some portion of the stroke.

Optionally, one or both of first plate 108 and second plate 110 can have zoned heating, such that more power can optionally be delivered along the middle portion of the plate or plates in use. This focuses heat where there will typically be more hair in ordinary use. The temperature at different points along the length of the or each plate can optionally be controlled as the hair straightener is moved along a tress of hair that it is styling. Optionally, one or more temperature sensors (not shown) may be used to sense a temperature of first plate 108 and/or second plate 110. A temperature of first plate 108 and/or second plate 110 can be controlled, for example by controller 138, based on the temperature sensed by the one or more temperature sensors.

Although the use of a controller comprising a microcontroller has been described, any other suitable form of controller or control system may be used, using any suitable combination of analogue and/or digital hardware, and/or software.

Turning to Figure 18, there is shown a method 160 of operating a hair straightener. The hair straightener can be similar to any of the previously described implementations, but for convenience will be described with reference to hair straightener 700 shown in Figure 13.

Method 160 comprises sensing 162, using the MCU 140, a position and/or orientation of hair straightener 700.

Responsive to the sensed position and/or orientation, hair straightener 700 is operated 164 in a first mode in which first heater 130 heats first plate 108 more than second heater 132 heats second plate 110.

Using MCU 140, a change in the position and/or orientation of hair straightener 700 is sensed 166.

Responsive to the change in sensed position and/or orientation, hair straightener 700 is operated 168 in a second mode in which second heater 132 heats the second plate 110 more than first heater 130 heats the first plate 110.

The first mode can comprise heating only first plate 108 and the second mode can comprise heating only second plate 110. Optionally, either or both of first plate 108 and second plate 110 can include haircorralling recesses, such as those described in relation to Figs 1 to 12. It may be desirable in at least some implementations to heat the plate with hair-corralling recesses less than the plate without them (or to heat the plate with the deeper hair-corralling recesses less than the other plate, if both plates have such recesses).

Optionally, either or both of first plate 108 and second plate 110 may be flexible along some or all of their lengths. Optionally, either or both of first plate 108 and second plate 110 may be profiled in transverse section. For example, either or both of first plate 108 and second plate 110 may be convex or concave in transverse section.

Although the invention has been described with reference to various implementations, the skilled person will appreciate that the invention may be embodied in many other forms, limited only by the scope of the claims.