A hair styling appliance

Abstract

A hair styling appliance comprises an airflow unit (40, fig.2), a heating unit (50, fig. 2) and a control unit (60, fig.3) for controlling the airflow unit and the heating unit. The control unit causes the appliance to perform a predefined sequence of at least two consecutive stages to style the hair of a user, where each stage has a different flow rate and / or heat setting. The control unit is configured to cause the hair styling appliance to transition between the two consecutive stages and to cause the hair styling appliance to create a pulse in the airflow to indicate the transition to the user. The control unit may alternatively perform a predefined sequence comprising at least two pairs of consecutive stages where a first alert is provided between the first pair of stages and a second alert is provided between the second pair of stages. The first alert and second alert are of different types.

Description

B ACKGROUND Some hair styling appliances can be used in a predefined sequence when styling hair. Different stages of the predefined sequence may involve changes in the settings of the hair styling appliance. SUMMARY A first aspect of the present invention provides a hair styling appliance comprising: an airflow unit for generating an airflow; a heating unit for heating the airflow; and a control unit for controlling the airflow unit and the heating unit, wherein: the control unit is configured to control the airflow unit and the heating unit to perform a predefined sequence comprising at least two consecutive stages to style the hair of a user, the airflow unit having a different flow rate and / or the heating unit having a different heat setting in each of the two consecutive stages, and the control unit is configured to cause the hair styling appliance to transition between the two consecutive stages and to cause the hair styling appliance to create a pulse in the airflow to indicate the transition to the user. In some instances, the two consecutive stages may not be audibly and / or haptically discernible from one another by the user. The pulse in the airflow may provide an audible and / or haptic alert to the user of the hair styling appliance to confirm that the hair styling appliance has transitioned from performing a first stage of the two consecutive stages to performing a second stage of the two consecutive stages. The user is therefore assured that the predefined sequence is progressing. In addition, by generating a pulse in the airflow, an alert can be provided without the need for an additional feedback component, such as a sound generator and / or a vibration motor. An audible and / or haptic alert may be preferable to a visual alert because the hair styling appliance may be used at positions and orientations for which the hair styling appliance is not readily visible to the user. The control unit may be configured to cause the hair styling appliance to automatically transition between the two consecutive stages without user input to change a setting of the airflow unit or the heating unit. This may provide improved styling results. Additionally, potential damage to the hair may be avoided, and / or improved efficiency may be achieved. Furthermore, styling may be more convenient for the user, since the user is not required to do anything in order to transition between the two consecutive stages. Airflow during the pulse may be different to airflow during each of the two consecutive stages. Changing the airflow during the pulse may generate an audible and / or haptic alert without causing a visible change to an outside of the hair styling appliance. Changing the airflow during the pulse may cause a change in a characteristic of noise generated by the device, by an amount that is audibly discernible to a user. The characteristic may comprise one or more of: an overall intensity of the noise, a balance of frequency content of the noise and a pitch of one or more dominant sounds within the noise. The hair styling appliance may comprise a restrictor and / or baffle to selectively interact with the airflow, and the control unit may be configured to cause the pulse by causing the restrictor and / or baffle to interact with the airflow differently during the pulse compared to during the two consecutive stages. The restrictor and / or baffle may be configured to redirect at least a portion of the airflow during the pulse, for example along a different path or through a selectively openable outlet. To cause the hair styling appliance to create the pulse, the control unit may be configured to cause a change in flow rate of the airflow generated by the airflow unit. The airflow unit may thus be used to generate the airflow to both perform the predefined sequence and provide the alert to the user. This may negate a need for an additional component to cause the pulse in the airflow. The airflow unit may comprise an electric motor. To cause the change in flow rate, the control unit may be configured to cause a change in a speed of rotation of the motor. The airflow unit may also comprise an impeller rotatable by the electric motor to generate the airflow. To cause the change in flow rate, the control unit may be configured to cause a change in a speed of rotation of the impeller. The change in the speed of rotation of the motor and / or the impeller may be audibly and / or haptically discernible to a user, for example due to a resulting change in pure tones and / or frequencies within noise emitted by the airflow unit. A speed of rotation of the electric motor may be greater than zero during the pulse. This may prolong a working life of the motor and / or enable a pulse of shorter duration to be generated. A speed of rotation of the impeller may be greater than zero during the pulse. The control unit may be configured to cause the airflow unit to generate a first flow rate during a first stage of the two consecutive stages, a second flow rate during a second stage of the two consecutive stages, and a third flow rate during the pulse, wherein the third flow rate is different to each of the first flow rate and the second flow rate. A user may therefore be able to audibly and / or haptically discern the alert from the two consecutive stages. The first flow rate and the second flow rate may be the same as one another or different to one another. The third flow rate may be less than each of the first flow rate and the second flow rate. Reducing the flow rate during the pulse may reduce a risk of disrupting hair being styled by the hair styling appliance during the predefined sequence. In some examples, the third flow rate may be zero or substantially zero. The third flow rate may be different from each of the first flow rate and the second flow rate by at least 5% of each of the first flow rate and the second flow rate. This may enable a user to more easily audibly and / or haptically discern the third flow rate from the first and second flow rates, compared to a lower percentage. The hair styling appliance may be configured to generate a first sound level during a first stage of the two consecutive stages, a second sound level during a second stage of the two consecutive stages, and a third sound level during the pulse, the third sound level being at least IdB different to each of the first sound level and the second sound level, or at least 2dB different to each of the first sound level and the second sound level, or at least 3dB different to each of the first sound level and the second sound level. This may enable a user to more easily audibly and / or haptically discern the third sound level from the first and second sound levels, compared to a smaller difference. The pulse may have a duration of at least 0.2 seconds. This may enable a user to more easily identify the pulse compared to a lesser duration. The pulse may have a duration of no more than 1 second, or no more than 0.8 seconds, or no more than 0.5 seconds. Accordingly, the pulse may not unnecessarily prolong the predetermined sequence. The control unit may be configured to cause the hair styling appliance to create the pulse between the two consecutive stages. This may minimise a number of changes in operation of the hair styling appliance compared to causing the pulse during one of the two consecutive stages, for example after the second stage has commenced. The control unit may be configured to cause the hair styling appliance to create a plurality of pulses in the airflow to indicate the transition between the two consecutive stages. This may be more easily identifiable by a user compared to a single pulse. A second aspect of the present invention provides a hair styling appliance comprising: an airflow unit for generating an airflow; a heating unit for heating the airflow; and a control unit for controlling the airflow unit and the heating unit, wherein the control unit is configured to: control the airflow unit and the heating unit to perform a predefined sequence comprising a plurality of stages to style the hair of a user, the airflow unit having a different flow rate and / or the heating unit having a different heat setting in consecutive stages of the plurality of stages; cause the hair styling appliance to transition between stages of the plurality of stages; and cause a first alert to be issued to the user at a first transition between a first pair of consecutive stages of the plurality of stages, and a second alert, of a different type to the first alert, to be issued to the user at a second transition between a second pair of consecutive stages of the plurality of stages. In some instances, some stages of the plurality of stages may not be audibly and / or haptically discernible from one another by the user such that the user may not know how far through the predefined sequence the hair styling appliance has progressed. The hair styling appliance allows the user to discern the first transition from the second transition. The first alert and the second alert are visually, audibly and / or haptically different in type from one another, such that the user knows whether the first alert or the second alert has been issued, and thus whether the first transition or the second transition has occurred. The control unit may be configured to cause the hair styling appliance to automatically transition through the plurality of stages without user input to change a setting of the airflow unit or the heating unit. This may provide improved styling results. Additionally, potential damage to the hair may be avoided, and / or improved efficiency may be achieved. Furthermore, styling may be more convenient for the user, since the user is not required to do anything in order to transition through the plurality of stages. The second pair of consecutive stages may be a final pair of stages in the predefined sequence. The user may therefore be informed that the predefined sequence is nearing completion. The control unit may be configured to turn the airflow unit and / or the heating unit off for a second stage of the second pair of consecutive stages. The second alert may therefore be indicative that hair styling appliance may be removed from the hair that has been styled during the predefined sequence. To cause the first alert and / or the second alert to be issued, the control unit may be configured to cause the hair styling appliance to create one or more pulses in the airflow. The one or more pulses in the airflow may provide an audible and / or haptic alert to the user. An alert may therefore be provided without the need for an additional feedback component, such as a sound generator and / or vibration motor. An audible and / or haptic alert may be preferable to a visual alert because the hair styling appliance may be used at positions and orientations for which the hair styling appliance is not readily visible to the user. Airflow during the pulse may be different to airflow during each of the two consecutive stages. Changing the airflow during the pulse may generate an audible and / or haptic alert without causing a visible change to an outside of the hair styling appliance. Changing the airflow during the pulse may cause a change in a characteristic of noise generated by the device, by an amount that is audibly discernible to a user. The characteristic may comprise one or more of: an overall intensity of the noise, a balance of frequency content of the noise and a pitch of one or more dominant sounds within the noise. The hair styling appliance may comprise a restrictor and / or baffle to selectively interact with the airflow, and the control unit may be configured to cause the pulse by causing the restrictor and / or baffle to interact with the airflow differently during the pulse compared to during the two consecutive stages. The restrictor and / or baffle may be configured to redirect at least a portion of the airflow during the pulse, for example along a different path or through a selectively openable outlet. The first alert may comprise a first number of pulses, and the second alert may comprise a second number of pulses, different to the first number. It may then be easier for the user to discern the first alert from the second alert. The first alert may have a first duration, and the second alert may have a second duration, different to the first duration. For example, the first alert may comprise one or more pulses that are generated for the first duration, and the second alert may comprise one or more pulses that are generated for the second duration. By having alerts of different durations, the user may more easily discern the first alert from the second alert. The second duration may differ from the first duration by at least 0.5 seconds and / or a factor of at least two. It may then be easier for the user to discern the first alert from the second alert compared to a smaller time period and / or factor. To cause the hair styling appliance to create the first alert and / or the second alert, the control unit may be configured to cause a change in flow rate of the airflow generated by the airflow unit. The airflow unit may thus be used to generate the airflow to both perform the predefined sequence and provide the alert to the user. This may negate a need for an additional component to generate the alerts. The airflow unit may comprise an electric motor. The airflow unit may also comprise an impeller rotatable by the electric motor to generate the airflow. To cause the change in flow rate, the control unit may be configured to cause a change in a speed of rotation of the motor and / or be configured to cause a change in a speed of rotation of the impeller. The change in the speed of rotation of the motor and / or the impeller may be audibly and / or haptically discernible to a user, for example due to a resulting change in pure tones and / or frequencies within noise emitted by the airflow unit. A speed of rotation of the electric motor may be greater than zero during the first alert and / or the second alert. The alerts may therefore be generated without unduly impacting the performance of the hair styling appliance. A speed of rotation of the impeller may be greater than zero during the first alert and / or the second alert. The control unit may be configured to cause the airflow unit to generate a first flow rate during a first stage of the first pair of consecutive stages or the second pair of consecutive stages, a second flow rate during a second stage of the first pair of consecutive stages or the second pair of consecutive stages, and a third flow rate during the first alert or the second alert, wherein the third flow rate is different to each of the first flow rate and the second flow rate. A user may therefore be able to audibly and / or haptically discern the alert from the first stage and the second stage of the pair of consecutive stages. The first flow rate and the second flow rate may be the same as one another or different to one another. The third flow rate may be less than each of the first flow rate and the second flow rate. Reducing the flow rate during the alert may reduce a risk of disrupting hair being styled by the hair styling appliance during the predefined sequence. In some examples the third flow rate may be zero or substantially zero. The third flow rate may be different from each of the first flow rate and the second flow rate by at least 5% of each of the first flow rate and the second flow rate. This may enable a user to more easily audibly and / or haptically discern the third flow rate from the first and second flow rates, compared to a lower percentage. The hair styling appliance may be configured to generate a first sound level during a first stage of the first pair of consecutive stages or the second pair of consecutive stages, a second sound level during a second stage of the first pair of consecutive stages or the second pair of consecutive stages, and a third sound level during the first alert or the second alert, the third sound level being at least IdB different to each of the first sound level and the second sound level, or at least 2dB different to each of the first sound level and the second sound level, or at least 3dB different to each of the first sound level and the second sound level. This may enable a user to more easily audibly and / or haptically discern the third sound level from the first and second sound levels, compared to a smaller difference. The first alert and / or the second alert may have a duration of at least 0.2 seconds. This may enable a user to more easily identify the alert compared to a lesser duration. The first alter and / or the second alert may have a duration of no more than 1 second, or no more than 0.8 seconds, or no more than 0.5 seconds. Accordingly, the alert may not unnecessarily prolong the predetermined sequence. The control unit may be configured to cause the hair styling appliance to create the alert between the first and second stages of the pair of consecutive stages. This may minimise a number of changes in operation of the hair styling appliance compared to creating the alert during one of the first and second stages, for example after the second stage has commenced. Optional features of aspects of the present invention may be equally applied to other aspects of the present invention, where appropriate. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a hair styling appliance according to an example; Figure 2 is a schematic section through a handle unit of the hair styling appliance of Figure 1; Figure 3 is a block diagram of electrical components of the handle unit of Figure 2; Figure 4 is a flow diagram of a predefined sequence performed by the hair styling appliance of Figure 1; Figure 5 is a graph showing a temperature and a flow rate output of the hair styling appliance during the predefined sequence of Figure 4; and Figure 6 is a graph showing motor speed during an alert issued by the hair styling appliance. DETAILED DESCRIPTION The hair styling appliance 10 of Figures 1 to 3 comprises a handle unit 20 and an attachment 100 removably attachable to the handle unit 20. The handle unit 20 comprises a main power supply connection 22, a housing 30, an airflow unit 40, a heating unit 50 and a control unit 60 communicatively connected to the airflow unit 40 and the heating unit 50. The housing 30 is tubular in shape and comprises an inlet 31 through which an airflow is drawn into the housing 30 by the airflow unit 40, and an outlet 32 through which the airflow is discharged from the housing 30. The airflow unit 40 is housed 30 within the housing 30 and comprises an impeller 41 driven by an electric motor 42. The heating unit 50 is also housed within the housing 30 and comprises one or more heating elements 51 to heat the airflow. The control unit 60 receives power via the main power supply connection 22, and controls the airflow unit 40 and the heating unit 50. More specifically, the control unit 60 controls the flow rate of the airflow unit 40 and the heat setting of the heating unit 50 by controlling an amount of power supplied to the airflow unit 40 and the heating unit 50, respectively. The control unit 60 comprises user controls 61 and a control module 62. The user controls 61 are provided on an external surface of the housing 30 and are used to power on and off the hair styling appliance 10. The user controls 61 may also be used to select a flow rate (e.g., high, medium, low) of the airflow unit 40, and to select a heat setting (e.g., high, medium, low, off) of the heating unit 50. In this example, each of the user controls 61 comprises a slidable switch. However, other forms of user control may be used such as buttons, dials or a touchscreen. The control module 62 comprises a printed circuit board (PCB) carrying electronic components such as a processor and a memory storing instructions that, when executed by the processor, cause the control module 62 to control the airflow unit 40 and the heating unit 50. The control module 62 may control the airflow unit 40 and the heating unit 50 in response to inputs from the user controls 61. For example, in response to inputs from the user controls 61, the control module 62 may power on and off the airflow unit 40 and the heating unit 50, adjust the flow rate the airflow unit 40, and / or adjust the heat setting of the heating unit 50. As described below in more detail, the control module 62 may control the airflow unit 40 and the heating unit 50 to perform a predefined sequence comprising a plurality of stages in order to style hair of a user. The attachment 100 is intended for use in curling hair. The particular attachment illustrated in Figure 1 corresponds to the barrel attachment of the Dyson Airwrap® hair styler. The attachment 100 will not therefore be described here in any great detail. However, in short, the attachment 100 comprises a barrel 101 having an inlet 102 at one longitudinal end. A plurality of outlets 103 in the form of slots are formed around a circumferential periphery of the barrel 101. During use, when the attachment 100 is attached to the handle unit 20, the airflow generated by the airflow unit 40 enters the interior of the barrel 101 via the outlet 32 and the inlet 102. From there, the airflow is discharged through the outlets 103 in a clockwise or counterclockwise direction around the barrel 101. This then encourages hair to wrap and curl around the barrel 101. Referring now to Figure 4, the control module 62 controls the airflow unit 40 and the heating unit 50 in a predefined sequence 300 to style the hair of a user when the attachment 100 is attached to the handle unit 20. The predefined sequence 300 may be initiated upon powering on the appliance 10. Alternatively, the predefined sequence 300 may be initiated upon actuation of a dedicated switch of the user controls 61. The predefined sequence 300 comprises four stages 301, 302, 303, 304. The first stage 301 is used to wrap and tension the hair. The second stage 302 is used to help shape the hair by breaking hydrogen bonds in the hair. The third stage 303 is used to help lock in the shape of the hair by cooling the hair and / or reforming the hydrogen bonds, and the fourth stage 304 is used to release the styled hair from the appliance 10. In other examples, the predefined sequence 300 may comprise two, three or more than four stages. In other examples, the stages could be for different purposes to those mentioned above. At each stage, the airflow unit 40 has a different flow rate and / or the heating unit 50 has a different heat setting to an adjacent, i.e. immediately preceding or immediately following, stage. Controlling the airflow unit 40 and the heating unit 50 in this way may provide better styling results compared to a user manually selecting a heat and / or flow setting of the appliance 10 for each stage. Additionally, it may improve the efficiency of the appliance 10 and / or reduce potential damage to the hair. The control unit 60 determines when to cause a transition from one of the stages to a next, or following, stage. The control unit 60 may determine when to cause a transition based on a time spent in a particular stage of the predefined sequence 300. This then provides a relatively simple method for determining when to cause a transition between stages. The control unit 60 may, additionally or alternatively, determine when to cause a transition between the stages based on other parameters, for example the presence of hair around the barrel 101, a characteristic, such as temperature or moisture content, of hair around the barrel 101, which may each be detected in any suitable manner such as by a temperature sensor of the appliance 10. This may improve styling results without damaging the hair, and / or improve the efficiency of the appliance 10, for example by reducing a risk of overheating or over-drying the hair. For example, a larger amount of hair may require a longer dwell time on the barrel 101 in one or more of the stages in order to achieve the desired style. In addition to determining when to transition, the control module 62 may also define the flow rate of the airflow unit 40 and / or the heat setting of the heater 50 within one or more of the stages based on a characteristic of the hair. For example, cooler hair and / or hair with a higher moisture content may require a higher flow rate and / or a higher heat setting in order to achieve the desired style. The control unit 60 may also define the number of stages and / or the order of the stages in response to the presence of hair on the barrel 101 and / or characteristic of the hair. For example, the control unit 60 may determine that an additional stage may be required between the first stage and the second stage if the hair has a moisture level above a threshold. In this example, the control module 62 automatically causes a transition between consecutive stages in the predefined sequence 300 in response to determining when to cause the transition between the consecutive stages. By way of example, the control unit 60 may receive a signal from a sensor, the signal indicative of a characteristic (e.g., temperature or moisture content) of the hair and then cause the appliance 10 to automatically transition from one stage to the next when the characteristic reaches a threshold. By automatically transitioning between stages, improved styling results may be achieved because the transition is performed when determined rather than waiting for an action by a user. Additionally, potential damage to the hair may be avoided, and / or improved efficiency may be achieved, for example by reducing a risk of over-heating or over-drying the hair. Furthermore, styling may be more convenient for the user, since the user is not required to do anything in order for the appliance 10 to transition between stages. It will be appreciated that, in other examples, the control module 62 may alternatively cause the appliance 10 to generate a user alert in response to determining when to transition. The control module 62 then causes the appliance to transition between consecutive stages in response to a user input (e.g. such as a button on the user controls 61). The user is therefore provided with an alert of when to transition, but the user nevertheless has the ability to cause the appliance 10 to remain longer within a particular stage, if desired. The user therefore has greater control over the styling process. For example, the user may wish for the appliance 10 to remain longer in a particular stage if the temperature or moisture content of the hair is, in the view of the user, unsatisfactory. Figure 5 graphically depicts flow rate generated by the airflow unit 40 (as a solid line) and a temperature of the heating elements 51 (as a dashed line) during the predefined sequence 300. The predefined sequence 300 commences at a start time To. The first stage 301 occurs between the start time To and a first time Ti. The second stage 302 occurs between the first time Ti and a second time T2 after the first time Ti. The third stage 303 occurs between the second time T2 and a third time T3 after the second time T2. The fourth stage 304 occurs after the third time T3. In the first stage 301, the control module 62 causes the airflow unit 40 to generate a high flow rate HF and places the heating unit 50 on a medium heat setting MH, which helps to wrap and tension the hair. The medium heat setting MH lowers the density and increases the pressure of the airflow within the attachment 100 compared to a low heat setting LH. This, together with the high flow rate HF, results in a higher air velocity at the outlets 103 of the attachment 100, which in turn better encourages the hair to wrap around the barrel 101. Additionally, the medium heat setting MH reduces the stiffness of the hair compared to the low heat setting LH by breaking hydrogen bonds in the hair to soften the structure of the hair, which improves wrapping of the hair around the barrel 101. The attachment 100 comprises a capacitive sensor, which generates a signal indicative of the presence and amount of hair wrapped around the barrel 101 and transmits the signal to the control module 62. On the basis of the signal, the control module 62 determines the presence of hair. Upon determining that the hair has wrapped around the barrel 101, the control module 62 causes a transition to the second stage 302. In the second stage 302, the control module 62 causes the airflow unit 40 to generate a high flow rate HF and places the heating unit 50 on a high heat setting HH. In the high heat setting HH, the heating elements 51 have a higher heat output than in the medium heat setting MH, such that the airflow has a higher temperature in the second stage 302 than in the first stage 301. The high flow rate HF retains the hair on the barrel 101, whilst the high heat setting HH heats the hair to a higher temperature than in the first stage 301, and so breaks hydrogen bonds within the hair. The control module 62 keeps the appliance 10 in the second stage 302 for a set period of time, at the end of which the control module 62 causes a transition to the third stage 303. The set period of time may depend on the amount of hair that is present on the attachment 100, as determined by the control module 62 based on the signal from the capacitive sensor. For example, the control module 62 may continue the second stage 302 for a longer period of time in response to a larger amount of hair on the barrel 101. Conceivably, the attachment 100 may comprise one or more sensors for sensing the temperature and / or the moisture content of the hair. Based on signals from the one or more sensors, the control module 62 then determines the temperature and / or moisture content of the hair to determine when to cause a transition to the third stage 303. In this way, improved styling results may be achieved without potentially over-drying the hair. In the third stage 303, the control module 62 causes the airflow unit 40 to generate a low flow rate LF, less than the high flow rate HR, and places the heating unit 50 on a low heat setting LH. In the low heat setting LH, the heating elements 51 have a lower heat output than in the medium and high heat settings MH, HH, such that the airflow has a lower temperature in the third stage 303 than in the first and second stages 301, 302. As a result, the hair on the barrel 101 is cooled to lock in the shape that was created in the second stage 302. By having a low flow rate LF, the shape of the hair may be locked without disturbing or otherwise spoiling the shape of the hair. The control module 62 keeps the appliance 10 in the third stage 303 for a set period of time, at the end of which the control unit 60 causes a transition to the fourth stage 304. Again, the period of time spent in the third stage 303 may depend on the amount of hair that is present on the attachment 100, as determined from the signal from the capacitive sensor. Moreover, should the attachment 100 comprise a sensor(s) for sensing the temperature and / or the moisture content of the hair, the control unit 60 may receive a signal(s), for example from the sensor(s) for sensing the temperature and / or the moisture content of the hair, indicative of the temperature and / or moisture content and determine, on the basis of the signal(s), when to cause a transition to the fourth stage 304. For example, the control module 62 may cause the transition to the fourth stage 304 when a temperature of the hair drops below a threshold, thus ensuring that the shape of the hair is locked. Alternatively, the control module 62 may cause the transition to the fourth stage 304 when the moisture content of the hair drops below a threshold, thereby avoiding over-drying of the hair. In the fourth stage 304, the control module 62 powers off the airflow unit 40 and the heating unit 50. The hair may then be released from the attachment 100 by the user without spoiling the shape or style of the hair. The high flow rate HF is around 14 L / s and the low flow rate LF is around 9 L / s. To generate the high flow rate HF, the motor 42 rotates at a speed of around 110,000 rpm. To generate the low flow rate LF, the motor 42 rotates at a speed of around 80,000 rpm. In the high heat setting HH, the heating elements 51 have a temperature of around 150 degrees Celsius, in the medium heat setting MH the heating elements 51 have a temperature of around 120 degrees Celsius, and in the low heat setting LH the heating elements 51 have a temperature of around 30 degrees Celsius. It will be appreciated that other flow rates and temperatures may be used in other examples. During performance of the predefined sequence 300 by a comparative appliance it may be difficult for the user of the appliance to discern, visually, audibly and / or haptically, whether a transition between stages of the predefined sequence 300 has occurred, for example, due to the airflow being similar in consecutive stages, or due to ambient conditions making changes in operation of the appliance difficult to detect. This may be true whether the transition was instigated automatically by the control unit 60 or in response to a user input at the user controls 61. The user may therefore not be fully confident as to how far through the predefined sequence 300 the appliance has progressed. To mitigate this, the control unit 60 of the appliance 10 described herein with reference to the Figures is programmed to generate an alert to indicate to the user that a transition between stages has occurred. At a first transition, from the first stage 301 to the second stage 302, and at a second transition, from the second stage 302 to the third stage 303, the control unit 60 generates a first type of alert Al. At a third transition, from the third stage 303 to the fourth stage 304, the control unit 60 causes the appliance 10 to generate a second type of alert A2, which is able to be differentiated from the first type of alert Al by the user. In this example, to generate the first and second types of alert Al, A2, the control module 62 causes a pulse in a speed of the electric motor 42 between consecutive stages of the predefined sequence 300. Each pulse is haptically and audibly discernible to the user of the appliance 10 compared to operation of the appliance 10 during the stage preceding the pulse and the stage following the pulse. In this example, a noise level and a pitch of dominant sounds within noise generated by the appliance 10 changes during the pulse, by an amount that is audibly discernible to the user of the appliance 10 compared to operation of the appliance 10 during the stage preceding the pulse and the stage following the pulse. In other examples, a balance of frequency content of the noise additionally or alternatively changes during the pulse, by an amount that is audibly discernible to the user of the appliance 10 compared to operation of the appliance 10 during the stage preceding the pulse and the stage following the pulse. In this example, the appliance 10 generates around 78 dB of noise when performing the first stage 301 and the second stage 302, around 73 dB of noise when performing the third stage 303 and substantially zero dB of noise when performing the fourth stage 304. In contrast, the appliance 10 generates around 68 dB of noise during the pulse. In the example of Figure 5, the first type of alert Al occurs at the first time Ti, after the first stage 301 has been completed and before the second stage 302 has commenced, and at the second time T2, after the second stage 302 has been completed and before the third stage 303 has commenced. The second type of alert A2 occurs at the third time T.% after the third stage 303 has been completed and before the fourth stage 304 has commenced. To generate the first type of alert Al, the control module 62 causes a pulse in a speed of the electric motor 42 by causing the speed of the motor 42 to drop so that an idle flow IF is generated for around 0.4 seconds, before increasing the speed of the electric motor 42 to a speed required to generate the flow rate required for the following stage of the predefined sequence 300. To generate the second type of alert A2, the control module 62 causes two pulses in the speed of the electric motor 42 by twice causing the speed of the motor 42 to drop to generate the idle flow IF for around 0.4 seconds and then to increase to the speed required to generate the low flow LF of the third stage 303. The two pulses in the speed of the motor 42 are separated by a period of around 0.4 seconds, during which the electric motor 42 is at a speed required to generate the low flow LF of the third stage 303. The control module 62 then causes the appliance 10 to enter the fourth stage 304 by causing the airflow unit 40 and the heating unit 50 to turn off. In the present example, the idle flow IF is around 4 L / s and the speed of the motor 42 drops to around 40,000 rpm during the pulse. This then has the benefit that a pulse may be generated without unduly disrupting the style of the hair. However, it will be appreciated that other flow rates and motor speeds may be used to generate a pulse. By way of example, a pulse may be generated by dropping the flow rate and the motor speed to around 6 L / s and 53,000 rpm respectively. Figure 6 shows the first type of alert Al, at the first transition, in more detail. At the first time Ti, the control module 62 causes the motor 42 to decelerate from a first motor speed Ml required to generate the high flow HF, to a second motor speed M2 required to generate the idle flow IF. The deceleration takes around 0.2s. The control module 62 then maintains the motor 42 at the second motor speed M2 for around 0.4s, before causing the motor 42 to accelerate back to the first motor speed Ml. The acceleration takes around 0.2s. Accordingly, the first type of alert Al may have a perceived duration that is greater than 0.4s. It will be appreciated that a similar speed profile of the motor 42 may be observed at the second transition, and for each pulse of the second type of alert A2 at the third transition. Due to the different number of pulses in the first and second types of alert Al, A2, the user is able to differentiate between the first type of alert Al and the second type of alert A2. The second type of alert A2 indicates to the user that the user can release styled hair from the appliance 10. In other examples, the second type of alert A2 may differ from the first type of alert Al in a different manner. For example, the first and second types of alert Al, A2 may differ in duration by such an amount that the user can differentiate between the first and second types of alert Al, A2. It will be appreciated that a third type of alert, different in type to the first type of alert Al and the second type of alert A2, may instead be generated by the control unit 60 at the first or second transition. Accordingly, the user may be able to differentiate the first transition from the second transition. The attachment 100 of Figure 1 is provided by way of example only; the appliance 10 may comprise additional or alternative attachments. By way of example, the appliance 10 may include the round volumizing brush of the Dyson Airwrap® hair styler. Alternatively, the appliance 10 may comprise a single, fixed attachment that is non-removeable. Whilst particular embodiments have been described, it will be understood that various modifications may be made without departing from the scope of the invention as defined by the claims.

Claims

1. A hair styling appliance comprising:an airflow unit for generating an airflow;a heating unit for heating the airflow; anda control unit for controlling the airflow unit and the heating unit, wherein the control unit is configured to:control the airflow unit and the heating unit to perform a predefined sequence comprising at least two consecutive stages to style the hair of a user, the airflow unit having a different flow rate and / or the heating unit having a different heat setting in each of the two consecutive stages, andcause the hair styling appliance to transition between the two consecutive stages and to cause the hair styling appliance to create a pulse in the airflow to indicate the transition to the user.

2. The hair styling appliance of claim 1, wherein, to cause the hair styling appliance to create the pulse, the control unit is configured to cause a change in flow rate of the airflow generated by the airflow unit.

3. The hair styling appliance of claim 2, wherein: the airflow unit comprises an electric motor; and to cause the change in flow rate, the control unit is configured to cause a change in a speed of rotation of the motor.

4. The hair styling appliance of claim 2 or claim 3, wherein the control unit is configured to cause the airflow unit to generate a first flow rate during a first stage of the two consecutive stages, a second flow rate during a second stage of the two consecutive stages, and a third flow rate during the pulse, wherein the third flow rate is different to each of the first flow rate and the second flow rate.

5. The hair styling appliance of claim 4, wherein the third flow rate is different from each of the first flow rate and the second flow rate by at least 5% of each of the first flowrate and the second flow rate and / or the third flow rate is less than each of the first flow rate and the second flow rate.

6. The hair styling appliance of any one of the preceding claims, wherein the hair styling appliance is configured to generate a first sound level during a first stage of the two consecutive stages, a second sound level during a second stage of the two consecutive stages, and a third sound level during the pulse, the third sound level being at least IdB different to each of the first sound level and the second sound level.

7. The hair styling appliance of any one of the preceding claims, wherein the pulse has a duration of no less than 0.2 seconds and / or no more than 1 second.

8. The hair styling appliance of any one of the preceding claims, wherein the control unit is configured to cause the hair styling appliance to create a plurality of pulses in the airflow to indicate the transition between the two consecutive stages.

9. A hair styling appliance comprising:an airflow unit for generating an airflow;a heating unit for heating the airflow; anda control unit for controlling the airflow unit and the heating unit, wherein the control unit is configured to:control the airflow unit and the heating unit to perform a predefined sequence comprising a plurality of stages to style the hair of a user, the airflow unit having a different flow rate and / or the heating unit having a different heat setting in consecutive stages of the plurality of stages;cause the hair styling appliance to transition between stages of the plurality of stages; andcause a first alert to be issued to the user at a first transition between a first pair of consecutive stages of the plurality of stages, and a second alert, of a different type to the first alert, to be issued to the user at a second transition between a second pair of consecutive stages of the plurality of stages.

10. The hair styling appliance of claim 9, wherein the second pair of consecutive stages is a final pair of consecutive stages in the predefined sequence.

11. The hair styling appliance of claim 9 or claim 10, wherein the control unit is configured to turn the airflow unit and / or the heating unit off for a second stage of the second pair of consecutive stages.

12. The hair styling appliance of any one of claims 9 to 11, wherein, to cause the first alert and / or the second alert to be issued, the control unit is configured to cause the hair styling appliance to create one or more pulses in the airflow.

13. The hair styling appliance of any one of claims 9 to 12, wherein the first alert comprises a first number of pulses, and the second alert comprises a second number of pulses, different to the first number.

14. The hair styling appliance of any one of claims 9 to 13, wherein the first alert has a first duration, and the second alert has a second duration, different to the first duration.

15. The hair styling appliance of any one of claims 9 to 14, wherein, to cause the first alert and / or the second alert to be issued, the control unit is configured to cause a change in flow rate of the airflow generated by the airflow unit.

16. The hair styling appliance of claim 15, wherein: the airflow unit comprises an electric motor; and to cause the change in flow rate, the control unit is configured to cause a change in a speed of rotation of the motor.

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