Hair dryer

Abstract

The invention relates to hair dryers. Various techniques for improving air flow in hair dryers are described, including a hair dryer providing laminar flow air. In another variant a hair dryer has a two air flow channels: one a hot air channel the other a cool air channel, with the cool air channel circumscribing the hot air channel. The nozzle end of the hair dryer is arranged such that the cool air channel extends forward of the hot air channel outlet. This allows a hair dryer to be placed close to, or on, a person's hair/head without and risk of burning the person's head. A hair dryer with external power supply is also described which reduces the weight of the housing held by a user.

Claims

1. A hair dryer having a hand-held housing comprising: an air inlet and an air outlet; an air flow assembly between said air inlet and said air outlet to draw air in from said air inlet and drive air out from said air outlet, wherein said air flow assembly comprises a DC powered motor; a nozzle including a hot air channel and a cool air channel, wherein said hot air channel connects to said air inlet in said hair dryer housing and said cool air channel connects to said air inlet in said hand-held housing, and wherein a cool air channel outlet of said nozzle extends beyond a hot air channel outlet of said nozzle; a heating element located in an air flow between said air inlet and said air outlet, wherein said air outlet comprises a hot air outlet and a cool air outlet and said hand-held housing comprises a hot air channel through which air is drawn from said air inlet past said heating element to said hot air outlet and a cool air channel through which air is drawn from said air inlet to said cool air outlet, wherein the cool air outlet circumscribes and is generally parallel to the hot air outlet such that two separate streams of air exiting the cool air outlet and the hot air outlet are emitted in the same direction; a laminar element located in between the heating element and the air outlet, the laminar element being arranged to compensate for a disturbance introduced into the air flow by the heating element; a sensor that senses activation of the DC powered motor; and a control circuit configured to activate said heating element responsive to said sensor sensing activation of said DC powered motor.

2. The hair dryer according to claim 1, wherein the air flow assembly comprises an integrated fan and motor assembly.

3. The hair dryer according to claim 2, wherein the integrated fan and motor assembly comprises the DC powered motor which is concentrically mounted around a drive shaft and an axial impeller having a plurality of blades which extend radially around the motor and which are connected to the drive shaft to drive the blades.

4. The hair dryer according to claim 3, wherein said integrated fan and motor assembly is housed within a generally cylindrical housing.

5. The hair dryer according to claim 4, wherein a plurality of strakes extend from an inner surface of the cylindrical housing whereby circular air currents within the housing are reduced.

6. The hair dryer according to claim 2, wherein the integrated fan and motor assembly comprises a fan and the DC powered motor concentrically mounted about an axis of rotation of said fan, wherein said fan comprises an axial impeller having a plurality of blades which extend radially around the motor.

7. The hair dryer according to claim 1, wherein said laminar element comprises an array of elongate tubes.

8. The hair dryer according to claim 7, wherein the tubes in said array of elongated tubes is parallel to one another.

9. The hair dryer according to claim 7, wherein at least some of the elongated tubes in said array of elongated tubes have a hexagonal cross-section.

10. The hair dryer as claimed in claim 7, wherein said array of elongated tubes is formed from silicone rubber.

11. The hair dryer as claimed in claim 7, wherein each tube of the array of elongated tubes has a length between 0.5 and 2.0 cm.

12. The hair dryer according to claim 1, wherein the cool air channel is defined by an outer duct which circumscribes the hot air channel.

13. The hair dryer according to claim 1, wherein the cool air channel extends beyond the hot air channel.

14. The hair dryer according to claim 1, further comprising a nozzle having an inlet which matches the outlet of the hairdryer housing and an outlet having a generally rectangular cross-section.

15. The hair dryer according to claim 14, wherein the nozzle is shaped so that the cross-section of the nozzle changes gradually from the nozzle inlet to the nozzle outlet whereby disturbance to the air flow within the nozzle is minimised.

16. The hair dryer according to claim 1, wherein the outlet of the nozzle has a generally rectangular cross section.

17. The hair dryer according to claim 1, wherein said cool air channel of the nozzle and/or housing comprises a plurality of strakes.

18. The hair dryer as claimed in claim 1, further comprising a power supply unit comprising an AC to DC converter for driving at least said DC motor.

19. The hair dryer as claimed in claim 18, wherein said power supply unit is external to said hand-held housing and coupled to said hand-held housing by a power cord.

20. The hair dryer as claimed in claim 18, wherein said power supply unit is configured to deliver both an AC supply and a DC supply to said hand-held housing, and wherein said power supply unit is configured to deliver said AC supply and said DC supply by combining a signal rail of each of said AC and DC supply.

21. The hair dryer as claimed in claim 20, wherein a neutral signal rail of said AC supply is coupled to one of said DC signal rails.

22. The hair dryer as claimed in claim 20, wherein a neutral signal rail of said AC supply is coupled to a 0V rail of said DC signal rails.

23. The hair dryer as claimed in claim 18, wherein said power supply unit comprises said control circuit.

24. The hair dryer as claimed in claim 23, wherein said sensor comprises a current sensor to sense an electrical current input to the DC powered motor.

25. The hair dryer as claimed in claim 23, wherein said control circuit further comprises a relay coupled between a power source and said powered heating element, and wherein said control circuit is configured to activate said relay responsive to said sensing.

26. The hair dryer as claimed in claim 1, wherein said control circuit is configured to sense activation of said DC motor by sensing a DC current delivered to said DC motor.

27. The hair dryer as claimed in claim 1, wherein said control circuit further comprises transistor switch coupled to said relay, and a protection diode connected across said relay.

28. The hair dryer as claimed in claim 1, wherein said heating element is AC powered.

29. The hair dryer as claimed in claim 1, wherein said air flow assembly further comprises a nose cone mounted co-axially with and downstream from said air flow assembly.

30. A hair dryer comprising: a housing that defines an air inlet and an air outlet, the air inlet having a circular shape; an air flow assembly located within the housing, the airflow assembly defining a passage fluidly connecting the air inlet and the air outlet and including a DC powered motor, the DC powered motor located proximate the air inlet and concentric with the circular shape; a heating element located in the passage connecting the air inlet and the air outlet; wherein the air outlet further includes a hot air outlet and a cool air outlet and the hair dryer housing includes a hot air channel through which air is drawn from the inlet past the heating element to the hot air outlet and a cool air channel through which air is drawn from the air inlet to the cool air outlet; a nozzle including a hot air channel and a cool air channel, wherein the hot air channel connects to the hot air channel in the hair dryer housing and the cool air channel connects to the cool air channel in the hair dryer housing, and wherein a cool air channel outlet of the nozzle extends beyond a hot air channel outlet of the nozzle; a laminar element located between the heating element and the air outlet, the laminar element being arranged to compensate for any disturbance introduced into the axial air flow by the heating element; a sensor electrically coupled to the DC powered motor and configured to detect activation of the DC powered motor; and a control circuit configured to: receive a signal from the sensor, the signal indicating activation of the DC powered motor, and activate the heating element in response to receiving the signal from the sensor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) For a better understanding of the invention and to show how it may be carried into effect reference shall now be made, by way of example only, to the accompanying drawings in which:

(2) FIG. 1 shows a hair dryer with nozzle attachment;

(3) FIG. 2 shows the hair dryer of FIG. 1 without a nozzle attachment;

(4) FIG. 3a shows a cross section of the hair dryer of FIG. 1;

(5) FIG. 3b shows a schematic view of the components of the hair dryer of FIG. 1;

(6) FIG. 4 shows a perspective view of the integral heater and fan assembly of the hair dryer of FIG. 1;

(7) FIG. 5 shows a perspective view of the integral fan/motor assembly of FIG. 4;

(8) FIGS. 6a and 6b show details of the laminar element of the hair dryer of FIG. 1;

(9) FIGS. 7a and 7b show details of the nozzle attachment shown in FIG. 1;

(10) FIG. 8 shows a hair dryer with external power supply unit;

(11) FIG. 9 shows a block diagram of the external power supply unit of FIG. 8;

(12) FIG. 10 shows an example of an AC power switching circuit for the heater;

(13) FIG. 11 shows details of the external power supply incorporating an AC power switching circuit, switched mode power supply and circuit for providing a shared neutral/DC supply to the hair dryer;

(14) FIG. 12a shows a smoke diagram of laminar flow air output from the hairdryer of FIG. 1;

(15) FIG. 12b shows the laminar flow output being used to style hair; and

(16) FIGS. 13a to 13d shows further details of the integral fan/motor assembly of FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(17) FIGS. 1 to 7b show a hair dryer 10 with a nozzle 20 coupled thereto. As explained in more detail below, the various components of the hair dryer, including the nozzle attachment, cooperate to ensure that the output from the hair dryer is generally in the form of a laminar flow. A laminar flow (streamline flow) occurs when a fluid, in this case air, flows in parallel layers with no disruption between the layers. This substantially reduces any form of fluid swirling and lateral mixing leading to minimal turbulence. As shown in FIG. 12a, the arrangement of all the components means that the laminar flow is retained for up to 20 to 30 cm from the nozzle. As shown in FIG. 12b, the nozzle attachment 20 provides a focussed stream of air which allows the hairdryer to be used as an airbrush.

(18) The hair dryer comprises a casing (or housing) 12 having an inlet end 16 protected by a finger guard and an outlet end 15 to which the nozzle attachment 20 is releasably coupled. In line with standard hairdryers, a handle 14 extends from the casing 12 to allow a user to hold the hairdryer. As shown in FIGS. 3a and 3b, the casing houses an integrated fan/motor assembly 50 for creating air flow through the hairdryer from the inlet end and to the outlet end. Positioned on the front of the fan assembly is a nose cone 48 and in front of the fan assembly 50 is a heater 46 to heat air which comes into contact with the heater 46. A laminar element 70 is positioned at the outlet end and is described in more detail in relation to FIGS. 6a and 6b.

(19) There are two airflow channels within the casing. It will be appreciated that this is an optional feature and that is possible to provide a laminar flow for a single hot air stream would also work.

(20) Both channels draw air through the inlet with a first airflow channel outputting hot air through an inner outlet 34 and a second airflow channel outputting unheated air through an outer outlet 34. The first airflow channel passes through the heater 46 and is thus generally centrally located within the casing. The second airflow channel comprises an outer duct 43 which circumscribes the heater 46. The air flow along the second airflow channel does not contact the heater and thus maintained at approximately room temperature. Accordingly, the second airflow channel acts as an insulator and minimises the transfer of heat from the heater to the outer housing of the wall. As shown more clearly in FIG. 2, the cool air channel outlet 34 of the hair dryer extends forwards of the inner hot air channel outlet 32. A plurality of air strakes 35 are positioned in the cool air channel, at least around the cool air channel outlet 34. The strakes 35 are generally planar projections extending from, and at an angle to, the exterior surface of the inner air channel. The strakes 35 help to control the exit flow of cool air and also maintain the structural integrity of the cool air channel.

(21) The separation of hot and cold (unheated) air continues in the nozzle 20. A cool air channel 24 extends through the nozzle and aligns with the cool air duct/channel 43 in the hair dryer body. A hot air channel 22 extends through the nozzle and aligns with the first airflow channel passing through the heater 46. The nozzle attachment 20 thus has two channels of air flow. The first inner channel 22 provides a hot air outlet and surrounding the hot air channel 24 is a cool air channel which provides a cool air outlet.

(22) As can be seen in FIG. 7a, the cool air channel outlet extends forwards of the inner hot air channel outlet. Extending the cool air channel allows the hairdryer (with or without nozzle attachment) to be placed close to a user's head without burning their head. Furthermore, if the hair dryer is accidently left with the outlet in contact with a carpet or other object, the cool air channel prevents any burn damage. The cool air outlet may extend forward of the hot air outlet by a few millimetres (2 mm or more for example)both on the hair dryer and on the nozzle.

(23) It is noted that allow the cool air outlet in the nozzle extends beyond the hot air outlet in the nozzle, there is little or no mixing of the two air flows within the nozzle. As explained above, the laminar flow produced by the hairdryer extends for upto 20 cm and the extension of the cool air outlet is not sufficient to disrupt this flow.

(24) The nozzle 20 is detachable allowing a stylist to select from one of a range of different nozzles. It will be appreciated however that in some variants the nozzle may be secured to the hair dryer and non-removable.

(25) FIG. 4 shows the heater unit 46 and integrated fan and motor assembly 50. The two parts snap fit together to form a combined unit 60 via a series of retaining clips 61. The hot air channel is defined as the channel within this combined unit. The heater unit comprises a heater element (not shown) positioned inside the heater unit to heat air as it passes over the heater element. Such heater elements may have any standard design. As schematically drawn in FIG. 3b, the heater unit may comprise a plurality of planar supports which are approximately axially aligned and which support a heating element in the form of a wire.

(26) FIG. 5 shows the integrated fan/motor assembly 50. As schematically drawn in FIG. 3b, the assembly comprises a fan 45 and a motor 51 housed within a generally cylindrical housing 47 to form a ducted axial impeller fan. Air is drawn through the inlet and forced through the housing 47 in an axial direction. A conventional axial flow fan generally comprises a cylindrical central hub section, a plurality of blades extending radially from the central hub section and a housing encasing the blades. A driving motor is attached to the hub section via a motor shaft to drive the fan into rotation. Such a conventional arrangement may be used in the present application. However, the arrangement of FIG. 5 and FIGS. 13a-d is an integrated fan/motor assembly which removes the need for a separate motor connected by a drive shaft to a separate fan. As shown in FIGS. 13a-d, this is achieved by mounting the fan blades 45 so that they extend radially from around the motor components themselves and by concentrically mounting the components of the motor around an axis of rotation of the fan. One example of an integrated fan/motor assembly is described in U.S. Pat. No. 6,457,953 and related applications which are incorporated by reference.

(27) The motor 51 is preferably a brushless DC motor as depicted in FIG. 13a. In other words, the motor 51 preferably comprises a coil subassembly and rotating permanent magnets 53 (as shown in FIG. 13c) and a fixed armature (stator). The magnets 53 are bonded onto the yoke 54 which also forms the casing onto which the fan blades are directly mounted. This arrangement eliminates the need for coupling the motor to a separate fan via a drive shaft. An electronic controller 57 replaces the brush assembly of a brushed DC motor and the electronic controller ensures that the motor keeps turning. A brushless motor typically is compact and high powered delivering a high rotation speed compared to a conventional AC motor.

(28) A motor and motor controller 57 are positioned on the axis of the fan within the fan assembly to control the speed of rotation of the fan. This may include, for example, off, medium speed, full speed although it will be appreciated that may intermediate speed levels may also be provided.

(29) Referring now to FIG. 13d, the fan assembly also includes air vent holes 55 positioned between the blades of the fan. These vent holes allow cooling of the motor and controller and prevent overheating. The fan blades may be arranged such that they force a quantity of air through these holes to improve cooling.

(30) The presence of a fast rotating axial impeller within the duct provides a high volumetric flow rate. Moreover, the air flow is generally uniform and is generally an axial flow. As schematically illustrated in FIG. 3a, the cylindrical housing 47 further comprises a plurality of stators 49 which are generally planar projections extending from, and at an angle to, the interior surface of the housing. Any generated circular air currents are removed by the stators 49 resulting in a generally laminar air flow being emitted from the integrated fan and motor assembly.

(31) The central axial motor creates a dead spot in the resultant flow. As shown in FIG. 5, a nose cone 48 is centrally mounted on the front of the integrated motor/fan assembly which helps to guide air towards the fan axis and ensure a uniform air flow across the entire cross-section.

(32) The air flow is generally laminar as it exits the integrated motor/fan assembly. As shown in FIG. 3b, the air in the first air channel passes over the heater element in the heater unit 46. To counteract any turbulence introduced in the heated air from the heater element, a laminar element 70 is positioned in the hot air channel outlet 32. The laminar element comprises a plurality of tubes which are aligned with each other to produce a laminar flow output of hot air.

(33) FIGS. 6a and 6b show the details of the laminar element 70. The laminar element comprises an array of tubes 76 (or elongate channels) which are all axially aligned with each other. The axial alignment of the channel forces air entering the array into a laminar air flow. The axes are generally aligned perpendicular to the plane of the outlet whereby the laminar air flow is generally perpendicular to the axis of the hairdryer housing. The laminar air flow may be arranged at a different angle to the axis of the hairdryer if desired.

(34) In the example shown, the tubes have a hexagonal cross-section. Tubes having other cross-sectional shapes may be used and a mixture of shapes may be used. However, the array should have minimal dead space between the tubes because such dead space will block air flow. Rectangular or square cross-sectional shapes also have minimal dead space but these have sharp corners which increase turbulence. Circular cross-sectional shapes are the optimum for preventing turbulence but clearly result in dead space. The hexagonal arrangement provides a reasonable comprise between reducing sharp corners within the tubes and reducing the waste space between tubes.

(35) Other arrangements may provide the same benefit, including. a mixture of shapes to maximise tessellation and minimise corners. However, the hexagonal arrangement is likely to be easier to manufacture than such a composite arrangement, e.g. by processes such as injection moulding.

(36) The laminar element may be manufactured from metal, plastic or silicone rubber. Silicone rubber is particularly useful as it is tolerant to a wide range of temperatures and does not get as hot to the touch as a metal, meaning that it is safer to use. Furthermore, this also means the laminar element may not need a guard in front or need to be recessed into the hair dryer, i.e. it can be positioned close to the outlet. The laminar element may also be removably mounted within the casing.

(37) The air flow is generally laminar as it exits the laminar element and flows into the inner channel of the nozzle (if one is attached). The nozzle attachment 20 is shaped to retain this uniform air flow whilst also minimising turbulence. The simplest way to achieve this would be to match the nozzle outlet to the shape of the outlet of the casing. However, this would result in an air flow having a generally circular cross-section which is not very useful for styling. Accordingly, the nozzle has an outlet which is the form of a generally elongate rectangle with curved edges (or flattened ellipse) and thus resembles an air-brush. The elongate outlet forms a blade of air for styling.

(38) As shown in FIGS. 7a and 7b, the nozzle has a hot air channel inlet which is generally circular and which matches the hot air channel outlet from the hair dryer. The nozzle has a cool air channel inlet which is annular and which matches the hot air channel outlet from the hair dryer. The nozzle is shaped to change gradually from a substantially circular inlet to a generally rectangular outlet to minimise turbulence within the hot and cool air flow channels. This is achieved by using curved surfaces with no sharp angles or step changes.

(39) As shown in FIG. 7b, a series of air strakes 25 are positioned within the cool air channel 24 which may help to guide and control the cool air flow through and out of the nozzle. The strakes 25 may also help maintain the structural integrity of the cool air channel. In use, the cool air channel provides a cool air shroud around the stream of hot air output from the nozzle which further limits any dispersement of the hot air stream providing a controllable narrow stream of hot air providing in effect an air brush.

(40) As described above, the fan assembly, heater unit, laminar element and nozzle all cooperate to ensure that the air output, particularly the hot air output is a laminar flow. It will be appreciated that each of these elements may be used alone or in combination. Without all co-operating elements, it is possible that a laminar flow as shown in FIG. 12b may not be achieved but a reasonable compromise between cost, effectiveness and manufacturing issues may be achieved.

(41) FIGS. 8 to 11 show a hairdryer which has an external power supply unit to reduce the weight of the hair dryer. It will be appreciated that this embodiment may be combined with the previous embodiment for producing a laminar airflow. In FIGS. 8 to 11, the hair dryer 90 comprises a hair dryer hand-held housing 10 (or any other variant as previously described) connected via power cable 42 to a power supply unit 44. The power supply unit is connected to mains power via plug 46. The power supply delivers both AC and DC power to the hair dryer body via a three core cable 42. AC power is used to power the heating elements and DC power to drive the DC brushless motor in the integrated fan and motor assembly.

(42) FIG. 9 shows a block diagram of the external power supply unit 44 of FIG. 8. The power supply comprises an AC input and switched mode power supply (SMPS) 82. An AC relay circuit (control circuit) 86 is used to control AC power delivery to the heater element 85 only when the DC motor driven fan 84 is activated. This provides a safety measure to ensures the heater element is not activated without a flow of air, thus preventing overheating. The AC (neutral) and DC (V/0V) rail are combined at the output of the power supply unit. This eliminates the need for a four core cable, meaning a lighter, conventional three core cable can be used to deliver both AC and DC power to the hair dryer from the external power supply.

(43) FIG. 10 shows an example schematic of the control circuit 86 used to control power delivery to the heater element. The circuit 86 is configured to only deliver power to the heater when the DC fan is activated to avoid the risk of the hair dryer overheating. Resistor R1 acts as a current sense, to providing a current sense signal to Q1 on the closing of SW1 (which activates the DC motor). Transistor Q2 is driven into saturation so that majority of the 12V is DC supply is supplied across the motor relay. Diode D1 is connected in reverse across the relay as a snub to protect the transistor from any current spike generated as the relay switches off.

(44) FIG. 11 shows a schematic of the power supply unit 44 of FIG. 8. The circuit is divided into three elements: the switched mode power supply circuit 82, the AC relay circuit 86 and the output circuit 84 providing a common mode line filter LF3 and shared neutral connection.

(45) On the input side there are AC mains live and neutral connections (nominally 230Vac for UK). An earth connection is also provided to allow more effective EMI filtering.

(46) The switched mode power supply circuit includes common mode line filters LF1 and LF2 on the primary side of transformer T1 to prevent high frequency interferences. Also shown are rectification diodes BD1 and transformer T1 arranged in a quasi resonant flyback configuration to generate a DC power source. This may be any DC voltage suitable for driving a brushless DC motor, such as 12V DC for example.

(47) The AC relay circuit (roughly denoted by the dotted line region 86) operates in a similar manner to the control circuit described in FIG. 10 by detecting delivery of a DC voltage to the V+ rail. On detection of a DC voltage on the secondary side of transformer T1 the relay is activated to connect the live L AC input and L1. L1 is then connected to the hair dryer via three core cable 42.

(48) To reduce cord weight between the power supply unit and the actual hair dryer, the neutral connection is coupled with the DC 0V output to provide a common/shared neutral output line. This means that only three conductors are required (+12V, 0V/neutral combination and a switched live as shown in FIG. 11). Within the hair dryer assembly, the +12V line is used to power the fan motor, the switched live is used to power other mains voltage level components such as the heater coil and ioniser. The low voltage 12V DC connection and the mains AC voltage are accordingly connected to different parts of the hair dryer with the only overlap being the current return path for both is on the same conductor: the DC 0V/AC neutral.

(49) The output of the SMPS 82 in FIG. 11 comprises a common mode line filter LF3 to attenuate unwanted high frequencies on the +12V DC output which may radiate as electromagnetic interference (EMI). The circuit has two outputs: V+ and V, each coupled via a separate side of the line filter LF3 to the SMPS providing a DC output. The main AC neutral input N is also coupled to the V output (denoted by N1 in FIG. 11). A three core cable including both DC and AC power rails can then used to power the hair dryer.

(50) No doubt many other effective alternatives will occur to the skilled person. It will be understood that the invention is not limited to the described embodiments and encompasses modifications apparent to those skilled in the art lying within the spirit and scope of the claims appended hereto.

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

(52) Throughout the description and claims, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

(53) Features, integers, characteristics or groups described in conjunction with a particular aspect, embodiment or example, of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith.