Haircare attachment

Abstract

A haircare attachment comprises a first outlet 112 for discharging a first airflow, a second outlet 122 for discharging a second airflow, a first guide surface 111 extending downstream from the first outlet for guiding the first airflow, and a second guide surface 121 extending downstream from the second outlet for guiding the second airflow. The surfaces attract the airflow using the Coanda effect. The first and second guide surfaces form external surfaces of the attachment and are convergent so as to cause the first and second airflows to converge. The guide surfaces are preferably symmetrically arranged. The surfaces preferably converge to a common downstream edge and the angle between the surfaces may be in the range of 30-50°.The height of the first or second outlets may vary along their widths. The attachment may have a neck portion 180 and a head of the attachment may be rotatably attached to the neck. The neck may bend the flow through 90°. The attachment may comprise a bore 195 extending laterally therethrough.

Description

B ACKGROUND Some haircare appliances, such as hair dryers, discharge heated air to dry and style hair. In some examples, the haircare appliance may include a concentrator nozzle through which air is concentrated into a narrow jet or blade of air. As a result, more targeted drying and styling of the hair can be achieved. SUMMARY According to a first aspect there is provided a haircare attachment comprising a first outlet for discharging a first airflow; a second outlet for discharging a second airflow; a first guide surface extending downstream from the first outlet for guiding the first airflow; and a second guide surface extending downstream from the second outlet for guiding the second airflow. The first and second guide surfaces form external surfaces of the haircare attachment and are convergent so as to cause the first and second airflows to converge. With this arrangement, the first and second airflows converge to provide a single, combined jet of air. By generating the jet of air in this way (i.e., through the convergence of two distinct airflows), turbulence may be reduced, which may aid in styling. Additionally and / or alternatively, the haircare attachment may better assist the user in targeting the jet at a section of hair that is intended to be styled. By providing the attachment with a plurality of outlets (which discharge airflows that converge) a more concentrated jet of air may be achieved in comparison to, for example, a concentrator nozzle with a single outlet. However, the resultant combined jet of air can still exhibit turbulence. That is, combining two airflows can induce turbulence into the resultant jet of air and lead to a more diffuse jet. By providing guide surfaces downstream of the outlets, the airflow from each outlet attaches to the respective guide surface via the Coanda effect. As a result, the amount of turbulence that is induced when the two airflows converge can be reduced. Thus, a singular, more concentrated, and less turbulent jet of air may be generated by the attachment. Each of the guide surfaces forms an external surface of the haircare attachment. As a result, the airflow that attaches to each guide surface is unconstrained on a side of the airflow opposite to the guide surface (because there is no opposing surface that covers the guide surface). This can help to reduce the turbulence arising at the convergence of the airflows. Further, by providing first and second guide surfaces that form part of the external surfaces of the attachment, the user can see the guide surfaces during use. Being able to see the guide surfaces can assist the user in orientating the attachment, and thus the combined jet, at the desired angle and position relative to the hair. Accordingly, the haircare attachment may allow a user to better target a desired section of hair. The first outlet and second outlet may be portions of a common outlet. As an example, where the common outlet has the shape of a rectangular ring, the portion of the common outlet along one of the long sides may be the first outlet and the portion of the common outlet along the opposite long side may be the second outlet. The guide surfaces may face away from each other. In this way, it is the constrained sides (as opposed to the unconstrained sides) of the two airflows that ultimately join to form the resultant jet, such that less turbulence may be induced in the resultant combined jet. The first outlet and the first guide surface may be mirror-symmetrically arranged with the second outlet and second guide surface. In this way, the resulting combined jet of airflow may flow along a plane of symmetry between the guide surfaces. This geometry makes orienting the haircare attachment in the desired orientation easier for the user, because the user can see the symmetrically arranged guide surfaces and thus more easily determine the direction of the resulting combined jet of air. Each outlet may comprise a slot. By providing slots, the airflows discharged from the outlets may have a more laminar form, which may improve attachment of the airflows to the guide surfaces. By improving the attachment of the airflows, a less turbulent, less diffuse jet of air may be generated by the convergence of the two airflows. Additionally, by providing the outlets as slots, a blade-like jet of air may be generated by the converging airflows, which can aid styling. Each guide surface may comprise an upstream edge extending along a width of the respective outlet. Each outlet may have a width of between 70 mm and 90 mm. Each outlet may have a height of between 2 mm and 5 mm. Each outlet may have an aspect ratio (width : height) of between 35:1 and 18:1. Each outlet may have an open area of between 140 mm2 and 450 mm2. These dimensions and / or open area may be particularly effective in generating a blade-like jet of air from the converging airflows, which, as noted above, can aid styling. Additionally, these dimensions and / or open area may result in airflows that better attach to the guide surfaces at flow rates typical of many haircare appliances (e.g., in the region of 6 L / s to 16 L / s). The width of each outlet may be defined as a direction that is substantially parallel to the upstream edge or downstream edge of the respective guide surface extending from the outlet. As already noted, by improving the attachment of the airflows to the guide surfaces, a less turbulent, less diffuse jet of air may be generated by the converging airflows. A height of each outlet may vary along a width of the outlet. By varying the height of the outlet, the velocity of the airflow discharged from the outlet may be more uniform across the width of the outlet. This is because friction acting on the airflows may vary along the width of the outlets, resulting in airflow velocities that vary along the width of the outlets. Varying the height of the outlets can help counteract variances in friction such that a more uniform airflow velocity is achieved across the width of each outlet. The height at a centre of each outlet may be greater than that at the sides of the outlet. In some examples, the height may increase gradually from the side of the outlet to the centre of the outlet. Friction from the walls may be higher at the sides of each outlet and therefore, if the outlet were of uniform height, the airflow velocity at the centre of the outlet may be higher than that at the sides. By increasing the height of the outlet at the centre of the outlet, a more uniform airflow velocity may be achieved across the width of the outlet. In some examples, the variation in the height of each outlet may be such that the outlet has a bowed, cambered, convex crown, or tapered shape. The ratio of the height of the outlet at the centre relative to the height of the outlet at a side may be greater than or equal to 1.25 and less than or equal to 1.75, and may be, for example, around 1.5. The first guide surface may comprise a first downstream edge. The downstream edge may extend parallel to a lateral axis of the first outlet (i.e., parallel to the width of the first outlet). The second guide surface may comprise a second downstream edge. The second downstream edge may extend parallel to a lateral axis of the second outlet (i.e., parallel to the width of the second outlet). In some examples, the first downstream edge may be spaced from the second downstream edge. The spacing between the two downstream edges may be no greater than 10 mm, and optionally may be no greater than 5 mm. By employing a spacing that is no greater than 10 mm, and optionally no greater than 5 mm, a more concentrated jet of air may be achieved when compared with larger spacings. The first downstream edge and second downstream end may be connected by an end wall. The first and second guide surfaces may converge to a common downstream edge of the guide surfaces (i.e., the guide surfaces may be joined at the common downstream edge). This may allow the two airflows to be brought as close together as possible before detaching from the guide surfaces. In this way, a more concentrated and / or less turbulent jet of air may be generated by the converging airflows. A common downstream edge may be regarded as one having a height of no greater than 2.5 mm. The height of the downstream edge may be the distance between the first guide surface and second guide surface at the downstream edge. The common downstream edge may be rounded. That is, the common downstream edge may comprise a convex profile extending between the first guide surface and second guide surface. The common downstream edge may extend parallel to a lateral axis of the first outlet (i.e., the width of the first outlet) and / or a lateral axis of the second outlet (i.e., the width of the second outlet). A first imaginary plane containing the upstream and downstream edges of the first guide surface and a second imaginary plane containing the upstream and downstream edges of the second guide surface may have a dihedral angle of no less than 30 degrees and / or no greater than 50 degrees. By having a dihedral angle that is no less than 30 degrees, improved convergence of the two airflows may be achieved, resulting in a more concentrated jet of air. By contrast, if the dihedral angle were shallower than this, less convergence may arise resulting in a less concentrated jet of air. By having a dihedral angle that is no greater than 50 degrees, the two airflows may converge in a relatively gentle manner, resulting in single, combined jet of air with a higher forward velocity and lower turbulence. By contrast, if the dihedral angle were much steeper than this, the two airflows may converge in a more violent manner, resulting in a lower forward velocity and higher turbulence. The angle between the first guide surface and second guide surface at a region adjacent to (or proximate to) the downstream edges may be no greater than 10 degrees, and may be no more than 5 degrees. Tn other words, regions at the downstream edges of the guide surfaces (i.e., across which air flows immediately before separating from the guide surfaces) may be close to parallel (i.e., having an angle therebetween of no more than 10 degrees, or no more than 5 degrees) so that the two airflows leaving the guide surfaces are also close to parallel. In this way, turbulence arising when the airflows converge may be reduced. This is because the smaller the angle, the smaller the velocity components of the airflows are in opposing directions at the point where they converge. The first guide surface and / or second guide surface may be concave. More particularly, the first and second guide surfaces may be concave in a direction parallel to the airflows along the guide surfaces (i.e., from an upstream edge to a downstream edge of each guide surface). In this way, the airflow exiting the respective outlet may be turned by the concave guide surface. As a result, the airflow may converge with the other airflow at a shallower angle than the angle between the airflows at the outlets, resulting in single, combined jet of air with a higher forward velocity and lower turbulence. The first outlet and / or second outlet may be arranged such that the airflow discharged from the outlet impinges on the respective guide surface (i.e., the angle between the airflow direction at the outlet and the guide surface may be greater than zero degrees). This can improve the attachment of the airflow to the guide surface. This impingement of the airflow onto the respective guide surface may be achieved by shaping the internal airflow passages immediately upstream of each outlet so that each airflow, discharged from the respective outlet, is directed towards the respective guide surface. The length of the first guide surface and / or second guide surface between respective upstream and downstream edges may be greater than or equal to 10 mm and / or less than or equal to 40 mm, and in some examples may be about 25 mm. Guide surfaces of this length may allow the user to be able to see the shape of the guide surfaces and the downstream edges thereof, which can assist the user in positioning the resulting combined airflow in the desired orientation relative to the hair. A width of the first guide surface and / or second guide surface may increase in a downstream direction (i.e., in a direction from the upstream edge to the downstream edge of the guide surface). Where the airflow is laminar, widening the guide surface can widen and thin the airflow over the guide surface. The width of a guide surface may increase linearly or non-linearly. For example, the width of the guide surface may increase at an increasing rate in the downstream direction. The haircare attachment may further comprise sidewalls provided along at least aa part of the lateral edges of the first and / or second guide surface. The lateral edges of the first and / or second guide surface extend between the upstream edge and downstream edge of the guide surfaces. The sidewalls may help to constrain the airflows along the guide surfaces and / or reduce the entrainment of ambient air into the airflows. A dihedral angle between a sidewall and a respective guide surface may be obtuse. Moreover, the dihedral angle may be greater than 90 degrees and less than or equal to 130 degrees. In some examples, the dihedral angle may be about 110 degrees. Having an obtuse angle can reduce deceleration of the airflow over the guide surface in the regions adjacent the lateral edges of the guide surface, thereby increasing the uniformity of the resulting combined airflow. At least one guide surface may be contactable with a user’s hair. That is, by being external surfaces of the attachment, the guide surfaces may be exposed such that they can be brought into contact with the user’s hair. The attachment may comprise one or more internal walls. The internal walls may define a first airflow passage and a second airflow passage. The attachment may further comprise one or more external walls spaced from the one or more internal walls to insulate the external walls from the airflow moving through the airflow passages. By spacing the external walls from the internal walls, an thermal insulation gap (e.g., an air gap) may be provided between the walls. The attachment may therefore be used with a heated airflow over a prolonged period and the external walls may nevertheless be sufficiently cool for the user to comfortably touch them. The internal walls and external walls may be integrally formed with each other. This may simplify assembly of the haircare attachment during manufacture. The haircare attachment may comprise an air inlet for receiving airflow from the haircare appliance. The attachment may comprise a first airflow passage fluidly connecting the air inlet to the first outlet, and a second airflow passage fluidly connecting the air inlet to the second outlet. The first airflow passage and the second airflow passage may each comprise an arcuate section. Moreover, the arcuate sections of the airflow passages may arc about a common axis. The first airflow path may turn a first portion of the airflow received at the air inlet through an angle of at least 90 degrees. The second airflow path may turn a second portion of the airflow received at the air inlet through an angle of at least 90 degrees. At least part of the arcuate section of the airflow passages may subtend an angle of at least 90 degrees. The first and / or second airflow passages may be arranged to form a convergent nozzle at the respective first and / or second outlets. That is, the cross-sectional area of the airflow passage (taken in a plane perpendicular to the airflow) may decrease towards the respective outlet. This can accelerate and thin the airflow before it is discharged from the outlet, thereby assisting in providing a concentrated, high-velocity combined jet of air from the haircare attachment. The haircare attachment may comprise an airflow splitting surface that splits the airflow received at the inlet into a first airflow and a second airflow. The first airflow passage may carry the first airflow to the first outlet, and the second airflow passage may carry the second airflow to the second outlet. The first guide surface, the second guide surface and the airflow splitting surface may collectively form an aerofoil. By arranging the guide surfaces and the airflow splitting surfaces as an aerofoil, pressure losses due to the air flowing around the airflow splitting surface and over the guide surfaces may be reduced and thus a higher velocity jet of combined air may be generated by the attachment. Moreover, the turbulence induced when splitting the airflow from the air inlet into the first airflow and second airflow may be reduced by forming the airflow splitting surface and the guide surfaces as an aerofoil. The airflow splitting surface may define a part (e.g., the innermost surface) of each of the first airflow passage and the second airflow passage. The first guide surface, the second guide surface and the airflow splitting surface may enclose a bore. For example, where the first guide surface, second guide surface and airflow splitting surface collectively form an aerofoil, the aerofoil may have a bore extending therethrough, such that it is hollow. The bore may extend through the attachment. Moreover, the bore may extend laterally through the attachment, i.e., the bore may extend through the width of the attachment such that a longitudinal axis of the bore is parallel to the downstream edges of the guide surfaces. In this way, the thermal mass of the attachment may be reduced and consequently the reduction in temperature of the airflow as a result of contact with the airflow splitting surface and the guide surfaces may be smaller. Moreover, the physical mass of the haircare attachment can be reduced, thereby reducing material usage and making it easier for the user to hold and manoeuvre the haircare appliance. The aerofoil may be a symmetric aerofoil, i.e., symmetric about a centreline of the aerofoil. In this way, the first and second airflows over the first and second guide surfaces, respectively, may have the same flowrate, leading to more uniform convergence of the first and second airflows at the downstream edge(s) of the guide surfaces. The trailing edge of the aerofoil may be provided by the downstream edge(s) of the guide surfaces. The leading edge of the aerofoil may be provided by the airflow splitting surface. The haircare attachment may comprise a head comprising the first outlet, the second outlet, the first guide surface and the second guide surface. The haircare attachment may further comprise a neck, and the head may be rotatably attached to the neck, e.g., by a joint between the head and the neck. The neck may be attachable to a main unit of the haircare appliance and the neck may comprise a passage for carrying airflow from the main unit to the head. The head may be rotatable relative to the neck to change an orientation of the combined airflow generated by the convergence of the first airflow and the second airflow. The head may be rotatable relative to the neck about an axis parallel to the direction in which the combined airflow is discharged from the attachment. Consequently, as the head rotates relative to the neck, the combined airflow also rotates. Where the combined airflow generated by the attachment is a narrow or blade-like jet of air, the head may be rotatable relative to the neck about an axis parallel to a plane of the combined airflow. As a result, rotation of the head causes the plane of the combined airflow to rotate. The head may be rotatable about 360 degrees relative to the neck. Rotating the head relative to the neck, and thus relative to the haircare appliance, facilitates a user changing the orientation of the combined jet, which in turn can aid styling. The neck may comprise a bend through approximately 90 degrees. In this way, a main unit of the haircare appliance may be held vertically by a user (i.e., such that the airflow discharged from an outlet of the main unit is vertical), which may be more ergonomic, and the attachment may generate a combined jet in a generally horizontal direction towards the user’s hair. The neck may comprise an inner wall and an outer wall, the passage of the neck being defined by the inner wall. The outer wall may be spaced apart from the inner wall to thermally insulate the outer wall from the airflow moving through the passage of the neck. By spacing the outer wall from the inner wall, an insulation gap (e.g., an air gap) may be created between the walls. The attachment may therefore be used with a heated airflow over a prolonged period and the outer wall of the neck may nevertheless be sufficiently cool for the user to comfortably touch it. The neck may be rotatable with respect to a main unit of the haircare appliance to which it is attached, and accordingly, the outer wall remaining cool may allow the user to comfortably reorientate the neck with respect to the main unit during use of the haircare attachment. The head may comprise an outer shell. The outer shell may comprise the one or more internal walls and one or more external walls of the head. The airflow splitting surface may be disposed within the outer shell adjacent an aperture in the outer shell and the first guide surface and second guide surface may extend from the airflow splitting surface at said aperture in the outer shell. In this way, the first airflow passage and second airflow passage may be at least partly defined between the airflow splitting surface and the outer shell. The first outlet and second outlet may be provided between the upstream edges of the respective guide surfaces and the outer shell. Where the airflow splitting surface and the guide surfaces collectively form an aerofoil, it can be understood that an upstream portion of the aerofoil comprised by the airflow splitting surface may reside inside the outer shell, and a downstream portion of the aerofoil comprised by the first and second guide surfaces may be positioned outside of the outer shell such that the first and second guide surfaces form external surfaces of the haircare attachment. The guide surfaces and / or the airflow splitting surface may be connected to (e.g., attached to or integrally formed with) the outer shell at lateral edges of the guide surfaces and / or the airflow splitting surface, respectively. The guide surfaces and / or the airflow splitting surface may be integrally formed with at least a portion of the outer shell. According to a second aspect there is provided a haircare appliance comprising a main unit comprising an airflow generator for generating an airflow; and the haircare attachment to the first aspect; wherein the haircare attachment is attached to the main unit. Any of the optional features set out with respect to the first aspect may be employed in the second aspect. Optional features of the second aspect will now be set out. These are applicable singly or in any combination with any aspect. The haircare attachment may be releasably attached to the main unit. The airflow generator may be configured to generate an airflow having a flowrate of between 6 L / s and 16 L / s and / or the flowrate of each of the airflows discharged from the outlets may be between 3 L / s and 8 L / s. BRIEF DESCRIPTION OF THE DRAWINGS Figure lisa perspective view of a haircare appliance; Figure 2 is a perspective view of a haircare attachment of the haircare appliance; Figure 3 is a plan view of the haircare attachment; Figure 4A is a cross-sectional slice of the haircare attachment in the plane A—A of Figure 3; Figure 4B is a cross-sectional slice of the haircare attachment in the plane B—B of Figure 3; Figure 4C is a cross-sectional slice of the haircare attachment in the plane C—C of Figure 3; and Figure 5 is a perspective view of the haircare attachment in which a section has been taken through the haircare attachment. DETAILED DESCRIPTION Figure lisa perspective schematic of a haircare appliance 1 comprising a main unit 200 to which a haircare attachment 100 is attached. The main unit 200 comprises an airflow generator configured to generate an airflow for receipt by the haircare attachment 100 and a heater (not shown) configured to optionally heat the airflow. The haircare attachment 100 is releasably attached to the main unit 200. In some examples, the haircare attachment 100 may be rotatably attached to the main unit 200 such that a user can orient the haircare attachment 100 relative to the main unit 200. The haircare attachment 100 will now be discussed in further detail with reference to Figures 2 to 5. Figure 2 is a perspective schematic of the haircare attachment 100. The haircare attachment 100 is configured to converge two jets of air into a single, combined, low turbulence jet of air. The single, combined jet of air can be directed by a user towards their hair in order to dry and style the hair. The haircare attachment 100 comprises a head 101 attached to a neck 180. The neck 180 is attachable to the main unit 200 and comprises an air inlet 150 for receipt of an airflow into the haircare attachment 100 from the main unit 200. The head 101 comprises an outer shell 160, which receives the airflow from the neck 180, and first and second guide surfaces 111, 121 extending from first and second outlets 110, 120 in the outer shell 160. The head 101 comprises the first outlet 110 for discharging a first airflow and the second outlet 120 for discharging a second airflow. Extending downstream of the first outlet 110 is the first guide surface 111 for guiding the first airflow; similarly, the second guide surface 121 extends downstream of the second outlet 120 for guiding the second airflow. The first and second guide surfaces 111, 121 each form an external surface of the hair attachment 110 and are convergent so as to cause the first and second airflows to converge as they flow down the guide surfaces 111, 121 from the outlets 110, 120. The airflow from each outlet 110, 120 attaches to the respective guide surface 111, 121 through the Coanda effect. The attachment of the airflows to the respective guide surfaces 111, 121 reduces the entrainment of ambient air into the airflows, thereby substantially maintaining the flow profiles of the airflows from the outlets 110, 120, and reducing the amount of turbulence that is induced when the two airflows combine with each other. Since each of the guide surfaces 111, 121 forms an external surface of the haircare attachment 100, the airflow that attaches to each guide surface 111, 121 is unconstrained on a side opposite to the respective guide surface 111, 121 (i.e., the haircare attachment 100 does not include an opposing surface that covers that guide surface 111,112). This helps to reduce turbulence arising at the convergence of the airflows because there is not an expansion of the flow area adjacent the point of convergence that would otherwise result from an enclosed channel into a more open space. Moreover, the guide surfaces 111, 121 being external surfaces allow the user to see the guide surfaces 111, 121 during use of the haircare attachment 100, which can assist the user in orientating the haircare attachment 100, and thus the combined airflow, at the desired angle to the hair. In the case of the haircare attachment 100 illustrated in the Figures, the first and second guide surfaces 111, 121 converge to a common downstream edge 131 of the guide surfaces 111, 121 such that the two airflows are brought as close together as possible before detaching from the guide surfaces 111, 121. This again assists in providing a more concentrated and / or less turbulent jet of air. The shape of the first and second airflows along the respective guide surfaces 111, 121 is primarily a function of the shape of the respective outlets 110, 120 from which they are discharged. As can be seen in Figure 2, each outlet 110, 120 is a slot having a width parallel to the common downstream edge 130 of the guide surfaces 111, 121. Each guide surface 111, 121 also comprises an upstream edge 112, 122 that extends along the width of the slot (i.e., also parallel to the common downstream edge 130). Each slot is bounded on one side by the upstream edge 112, 122 of the respective guide surface 111, 121 and on the opposite side by a wall of the outer shell 160. Both the upstream edge 112, 122 and the wall of the outer shell 160 extend along the width of the slot. The height of each slot is the dimension of the slot in a direction perpendicular to the guide surfaces 111, 121. The height of the slot determines the height of the airflows discharged from the outlets 110,120. The height is defined by the position of the upstream edges of the guide surfaces 111, 121 relative to the walls of the outer shell 160 that are adjacent the upstream edges 111, 121. By providing the outlets 110,120 as slots, the airflows discharged from the outlets have a high width-to-height aspect ratio (e.g., between 35:1 and 18:1). Consequently, the airflows over the guide surfaces 111, 121 are more laminar than if the width-to-height aspect ratios was lower. Accordingly, the attachment of the airflows to the guide surfaces 111, 121 is improved, and a less turbulent, less diffuse jet of air may be generated when the airflows converge into a single, combined jet. In order to further constrain the first and second airflows to provides a less turbulent, less diffuse combined jet of air, the head 101 further comprises sidewalls 116, 126 provided along both lateral edges 114, 124 of the first and second guide surfaces 111, 121. These sidewalls 116, 126 extend away from the guide surfaces 111, 121 such that a substantially u-shaped, wide-bottomed, channel is provided by each of the guide surfaces 111, 121 and the respective sidewalls 116, 126 located on either side thereof. The sidewalls 116, 126 also assist in reducing entrainment of ambient air into the first and second airflows. Features of the haircare attachment 100 will now be discussed in more detail with reference to Figures 3 and 4A - 4C. Figure 3 illustrates a plan view of the haircare attachment 100, and Figures 4A - 4C illustrate cross-sectional slices of the attachment along the planes A— A (Figure 4A), B—B (Figure 4B), and C—C (Figure 4C) in Figure 3. Figure 3 more clearly illustrates how the width of the first guide surface 111 increases in a downstream direction from the upstream edge 112 to the common downstream edge 130. The rate of increase in width of the first guide surface Illis constant. Although not visible in Figure 3, the second guide surface 121 similarly increases in width from the upstream edge 122 to the common downstream edge 130. The sidewalls 116, 126 on the lateral edges 114, 124 of the guide surfaces 111, 121 are integrally formed with at least a portion of the outer shell 160 of the head (i.e., they extend from the outer shell 160 of the head along both lateral sides of both guide surfaces 111,121). Although not discernible from Figure 3, the guide surfaces 111, 121 are also integrally formed with at least a portion of the sidewalls 116, 126 and / or at least a portion of the outer shell 160. Figures 4A and 4B show how the first outlet 110 and first guide surface 111 are mirror-symmetrically arranged with the second outlet 120 and the second guide surface 121 about an imaginary plane 2 that extends parallel to, and through, the common downstream edge 130 and is equidistant between the upstream edges 112, 122. In this way, the resulting combined jet of air leaving the downstream edge 130 extends along the aforementioned imaginary plane 2. Figure 4A also illustrates how the airflow that is received by the air inlet 150 into the neck 180 reaches the air outlets 110, 120. The neck 180 comprises an airflow passage 185 through which the airflow 184 passes to reach the head 101. The neck 180 comprises a bend through 90 degrees, such that when the air inlet 150 is positioned to receive a vertical flow of air (as in Figure 4A), the haircare attachment 100 generates a combined jet of air travelling in a generally horizontal direction. Having entered the head 101, the airflow 184 is split within the head 101 and flows along a first airflow passage 113 fluidly connecting the air inlet 150 to the first outlet 110 and a second airflow passage 123 fluidly connecting the air inlet 150 to the second outlet 120. The first and second airflow passages 113, 123 are defined in part by one or more internal walls 161 of the outer shell 160 and by an airflow splitting surface 170 disposed inside the outer shell 160. The airflow splitting surface 170 splits the airflow 184 at the air inlet 150 into the first and second airflows 184a, 184b along the first and second airflow passages 113, 123, respectively The airflow splitting surface 170 and the internal wall 161 comprise arcuate sections that result in the first airflow passage 113 and second airflow passage 123 also having arcuate sections that turn the respective airflows through an angle prior to reaching the respective outlets 110, 120. As is perhaps best appreciated from Figure 4B, the arcuate sections of the first and second airflow passages 113, 123 arc about a common axis 133 and subtend an angle of more than 90 degrees. As can be appreciated from Figure 4A, the airflow flowing into the head 101 from the neck 180 is substantially horizontal in the orientation of the haircare attachment 100 shown in Figure 4A (i.e., parallel to the plane of symmetry 2 between the two guide surfaces 111, 121). Subsequently the airflow 184 splits into first and second airflows 184a, 184b that flow along the respective first and second airflow passages 113, 123. The first and second airflow passages 113, 123 define convergent nozzles at the first and second outlets 110, 120. That is to say that the cross-sectional areas of the airflow passages 113, 123 decrease at the outlets 110, 120 such that the airflows 184a, 184b are accelerated and thinned before being discharged from the outlets 110, 120. The first guide surface 111, the second guide surface 121 and the airflow splitting surface 170 collectively form an aerofoil. The airflow splitting surface 170 provides the leading edge of the aerofoil and the common downstream edge 130 provides the trailing edge of the aerofoil. Because of the symmetry of the first and second guide surfaces 111, 121 and because the airflow splitting surface 170 is also symmetric about the same plane 2, the aerofoil is a symmetric aerofoil. The position of the aerofoil relative to the outer shell 160 is such that an upstream portion of the aerofoil comprised by the airflow splitting surface 170 resides inside the outer shell 160, and the downstream portion of the aerofoil comprised by the first and second guide surfaces 111, 121 is positioned outside of the outer shell 160 such that the first and second guide surfaces 111, 121 are external surfaces of the haircare attachment 100. Figures 4A and 4B also illustrate the construction of the head 101 and the neck 180 in more detail. Considering first the head 101, the outer shell 160 of the head 101 comprises a double wall structure, wherein an internal wall 161 is spaced apart from an external wall 162 by an air gap 163. In this way, the external wall 162 of the outer shell 160 is thermally insulated from the internal wall 161 by the air gap 163. The neck 180 likewise comprises a double wall structure, wherein an inner wall 181 is spaced apart from an outer wall 182 by an air gap 183. Should a heated airflow pass through the haircare attachment 100 over a prolonged period of time, the external walls 162, 182 of the head 101 and the neck 160 may remain at a sufficiently cool temperature that the user can comfortably touch the walls, for example, to reorientate the head 101 with respect to the neck 180. The neck 180 is connected to the head 101 by a rotatable joint 190 that permits rotation of the head 101 relative to the neck 160. More particularly, the head 101 rotates relative to the neck 160 about an axis parallel to the direction in which the combined airflow is discharged from the haircare attachment 100. In the present example, the rotatable joint 190 comprises a c-clip seated within annular grooves formed in the head 101 and the neck 180. By having a rotatable joint 190 between the head 101 and the neck 180, the orientation of the combined airflow leaving the common downstream edge 130 can be changed. The combined airflow may be regarded as a narrow or blade-like jet of air that moves along a plane. Rotation of the head 101 then causes the plane of the combined airflow to rotate. In addition to the head 101 being rotatably attached to the neck 180, the neck 180 may be rotatably attached to the main unit 200. In particular, the neck 180 may be rotatable relative to the main unit 200 about a first axis (e.g., a vertical axis in Figures 4A and 4B), and the head 101 may be rotatably relative to the neck 180 about a second axis (e.g., a horizontal axis in Figures 4A and 4B) that is orthogonal to the first axis. This provides the user with more options to orientate the combined airflow. As can be seen in Figures 4A and 4B, the first and second guide surfaces 111, 121 are each concave in a direction from the respective upstream edge 112, 122 of each guide surface 111, 121 to the common downstream edge 130. The airflows at the upstream edges 112, 122 of the guide surfaces 111, 121 therefore converge at a given angle. However, since the guide surfaces 111, 121 are concave, the airflows are turned and converge at a shallower angle at the common downstream edge 130 of the guide surfaces 111, 121. By converging the airflows at a shallower angle, the resulting single, combined jet of air may have a higher forward velocity and / or lower turbulence. The first outlet 110 and second outlet 120 are each angled towards the guide surfaces 111, 121 such that the airflows discharged from the outlets 110,120 impinge on the respective guide surface 111, 121. That is to say that the direction of the airflow discharged from each of the outlets 110,120 is not parallel to the respective guide surface 111,121 (at the upstream edge 112, 122) but is instead angled slightly towards the guide surface 111, 121. This can then improve attachment of the airflows to the guide surfaces 111, 121. Figure 4C illustrates the configuration of the sidewalls 116, 126 with respect to the guide surfaces 111, 121. The sidewalls 116, 126 do not extend perpendicularly from the respective guide surfaces 111, 121. Rather, the sidewalls 116, 126 extends obliquely from the guide surfaces 111, 121. The dihedral angle between each sidewall 116, 126 and the respective guide surface 111, 121 (along the lateral edge 114, 124) is therefore greater than 90 degrees. In the present example, the angle is approximately 110 degrees. Having an oblique or obtuse angle reduces the deceleration of the airflow that occurs in the corners where the sidewalls 116, 126 meet the guide surfaces 111, 121. This in turn increases the uniformity of the velocity profile of the airflows over the guide surfaces 111, 121 and thus the uniformity of the velocity profile of the resulting combined airflow. Turning now to Figure 5, the height of each of the outlets 110, 120 is not constant but instead varies along the width of the outlet 110, 120. In particular, the height of each outlet 110, 120 is greater at the centre of the outlet 110, 120 than at the sides of the outlet 110,120. The same is true of the airflow passages 113, 123 immediately upstream of the outlets 110,120, i.e., the height of the airflow passages 113, 123 in the vicinity immediately upstream of the outlets 110,120 varies in the same way. By varying the height of the outlets 110, 120 and the airflow passages 113, 123, the airflow discharged from each of the outlets 110, 120 may have a more uniform velocity profile across the width of the outlet 110, 120. Friction from the walls 161, 170 of the attachment 100 act on the airflows as they flow through the first and second airflow passages 113, 123. The airflows experience a greater contact area with the walls 161,170 at the sides of each airflow passage 113,123. Friction is therefore greatest at the sides of each airflow passage 113,123 and, if unmitigated, may mean that the velocity of the airflow discharged from each outlet 110, 120 is lower at the sides and higher at the centre of the outlet 110, 120. By varying the height of the outlets 110, 120, variances in friction can be counteracted such that a more uniform airflow velocity is achieved across the width of each of the outlets 110,120. As is evident from the Figures (notably Figures 2 and 5), the haircare attachment 100 comprises a bore 195 that extends laterally through the head 101 of the attachment 100. The bore 195 is defined or enclosed by the first guide surface 111, the second guide surface 112, and the airflow splitting surface 170. As noted above, the first guide surface 111, the second guide surface 112 and the airflow splitting surface 170 collectively form an aerofoil. The bore 195 then extends laterally through the aerofoil such that the aerofoil is hollow. The first airflow passage 113 extends around a first side of the bore 195 (e.g., an upper side in the Figures), and the second airflow passage 123 extends around a second opposite side of the bore 195 (e.g., a lower side in the Figures). By providing a bore 195 through the haircare attachment 100, the thermal mass of the attachment 100 is reduced and therefore potential drops in the temperature of the airflows 184a, 184b moving through the attachment 100 (e.g., due to contact with the airflow splitting surface 170 and the guide surfaces 111, 112) may be reduced. Additionally, the physical mass of the haircare attachment 100 can be reduced, thereby reducing material usage and making it easier for the user to hold and manoeuvre the haircare appliance 1.

Claims

1. A haircare attachment comprising:a first outlet for discharging a first airflow;a second outlet for discharging a second airflow;a first guide surface extending downstream from the first outlet for guiding the first airflow; anda second guide surface extending downstream from the second outlet for guiding the second airflow,wherein the first and second guide surfaces form external surfaces of the attachment and are convergent so as to cause the first and second airflows to converge.

2. The haircare attachment according to claim 1, wherein the first outlet and the first guide surface, and the second outlet and the second guide surface are mirror-symmetrically arranged.

3. The haircare attachment according to claim 1 or 2, wherein each outlet comprises a slot, and each guide surface comprises an upstream edge extending along a width of the respective slot.

4. The haircare attachment according to any preceding claim, wherein each outlet has at least one of: a width of between 70 mm and 90 mm, a height of between 2 mm and 5 mm, an aspect ratio of between 35:1 and 18:1, and an open area of between 140 mm2 and 4502 mm.

5. The haircare attachment according to any preceding claim, wherein the first and second guide surfaces converge to a common downstream edge of the guide surfaces.

6. The haircare attachment according to any preceding claim, wherein a first imaginary plane containing upstream and downstream edges of the first guide surface, and a second imaginary plane containing upstream and downstream edges of the second guide surface have a dihedral angle of no less than 30 degrees and / or no greater than 50 degrees.

7. The haircare attachment according to any preceding claim, wherein the first guide surface and / or the second guide surface is concave, and wherein optionally the guide surface is concave in a direction from an upstream edge to a downstream edge of the guide surface.

8. The haircare attachment according to any preceding claim, wherein a width of the first guide surface and / or the second guide surface increases in a downstream direction.

9. The haircare attachment according to any preceding claim, wherein a height of the first outlet and / or the second outlet varies along a width of the outlet, and wherein optionally the height of the outlet at a centre of the outlet is greater than that at a side of the outlet.

10. The haircare attachment according to any preceding claim, further comprising sidewalls provided along at least a part of lateral edges of the first and / or second guide surface, and wherein optionally the sidewalls extend obliquely from the guide surface.

11. The haircare attachment according to any preceding claim, wherein, in use, each guide surface is contactable with a user’s hair.

12. The haircare attachment according to any preceding claim, wherein the haircare attachment comprises:an air inlet for receiving airflow from a haircare appliance;a first airflow passage fluidly connecting the air inlet to the first outlet; anda second airflow passage fluidly connecting the air inlet to the second outlet,wherein the first airflow passage and the second airflow passage each comprise an arcuate section, and wherein optionally the arcuate sections of the first airflow passage and the second airflow passage arc about a common axis.

13. The haircare attachment according to claim 12, wherein the first airflow path turns a first portion of the airflow received at the air inlet through an angle of at least 90 degrees, and the second airflow path turns a second portion of the airflow received at the air inlet through an angle of at least 90 degrees.

14. The haircare attachment according to claim 12 or 13, wherein the arcuate section of each of the airflow passages subtends an angle of at least 90 degrees.

15. The haircare attachment according to any one of claims 12 to 14, wherein:the haircare attachment comprises an airflow splitting surface that splits the airflow received at the inlet into the first airflow and the second airflow; andthe first guide surface, the second guide surface, and the airflow splitting surface collectively form an aerofoil.

16. The haircare attachment according to any preceding claim, wherein: the haircare attachment comprises a head rotatably attached to a neck; the head comprises the first outlet, the second outlet, the first guide surface, and the second guide surface;the neck is attachable to a haircare appliance and comprises a passage for carrying airflow from the haircare appliance to the head; andthe head is rotatable relative to the neck to change an orientation of a combined airflow generated by the convergence of the first airflow and the second airflow.

17. The haircare attachment according to claim 16, wherein the neck comprises a bend through 90 degrees.

18. The haircare attachment according to claim 16 or 17, wherein the neck comprises an inner wall and an outer wall, the passage is defined by the inner wall, and the outer wall is spaced from the inner wall to insulate the outer wall from the airflow moving through the passage of the neck.

19. The haircare attachment accordingto any one of claims 12to 18, wherein the haircare attachment comprises a bore extending laterally through the haircare attachment, the first airflow passage extends around a first side of the bore, and the second airflow passage extends around a second opposite side of the bore.

20. A haircare appliance comprising:a main unit comprising an airflow generator for generating an airflow; and the haircare attachment according to any one of the preceding claims, wherein the haircare attachment is attached to the main unit, and wherein optionally5 the haircare attachment is releasably attached to the main unit.

Images