FIELD OF THE INVENTION

The present invention relates to hair dryers and to an attachment for a hair dryer.

There are myriad different approaches to providing hair dryers for consumer use. The primary consideration for such hair dryers is that they provide a flow of heated air in a sufficient quantity to evaporate water from the user's hair.

That goal is typically realized using a blower or ventilator that directs air over a heating device, such as a resistance coil, and then to an outlet. Both axial- flow and centrifugal blowers have been used in known hair dryers. Hair dryers, in particular hand-held hair dryers, have been in general use for many years, and have found wide acceptance in the consumer market. As the market has matured, commercial success has demanded an increased ability to perform the hair dryer's main task, that is, drying hair, while providing a device that is quiet, safe and comfortable to use. To increase drying ability, one approach that will obviously work is simply to increase the heat of the air expelled from the unit. This approach has the drawback of increasing the possibility of burns to the user.

A solution is proposed by US 5,841,943, wherein a pulsating attachment for use with an electric hair dryer is disclosed. The pulsating attachment can be attached to a tubular end of the hair dryer. The attachment comprises an asymmetric and unbalanced rotatable impeller for rotating as a single fan blade which blocks part of the exit area. The expelled air rotates the impeller or fan blade creating a pulsating spiral flow in which an area of heated air travels in a spiraling manner around a central axis of the hair dryer. In fact, when looking at a cross-section of the stream of air that is expelled from the hair dryer one would see a hot area of air performing a circular motion around a central axis. This means that the stream of air will also be received by the user's hair in such a circular movement, which means that the user's hair will receive interrupted streams of hot air instead of a constant stream. Although this would allow increased temperatures to be used for the stream of air, there is still the risk of burning when the user will inadvertently move the hair dryer in a response to an oscillation due to the rotating unbalanced fan blade. Furthermore, by interrupting the stream of hot air by the rotating fan blade the effectiveness of the increased air temperature of the known hair dryer is at least partly reduced. Additionally, legislation in many countries prohibits the use of ever higher temperatures for user safety considerations.

OBJECT OF THE INVENTION

The present invention aims to provide a hair dryer, an attachment for a hair dryer and a hair dryer provided with such an attachment that provides an improved drying performance while maintaining the temperature of the expelled air within safety limits and that is safe and comfortable to use.

SUMMARY OF THE INVENTION

According to a first aspect of the invention an attachment for a hair dryer is provided, the attachment comprising a coupling means being adapted to be coupled to an outlet of said hair dryer for expelling a stream of air, and a flow guide means having a fixed flow guide surface for guiding the stream of air, said flow guide surface being, at least partly, angled with respect to a central axis of the attachment. The angled flow guide surface will provide the air with a substantially tangentially directed velocity component in addition to a velocity component which is in the same direction as the central axis of the attachment, i.e. the principal direction of flow of the stream of air. Due to this tangential component turbulence of the stream of air leaving the hair dryer through the attachment will increase and the stream of air will undergo a mixing effect. This mixing effect in turn has the effect that the temperature of the stream of air being expelled by the hair dryer will be equalized and only a relatively minor temperature gradient will be present over a cross-section of the stream of air, where the lowest temperature can be found at an interface of the air from the hair dryer and the ambient air.

As the stream of air is not interrupted a body of substantially uniform temperature distribution and over a cross-section a nearly constant temperature distribution is provided which allows good control of the maximum temperature of the stream of air and ensures that no so-called hotspots are present which are often found in conventional hair dryers.

Another advantage of the equalized temperature distribution in the stream of air is that due to the absence of hotspots the same amount of heat can be transferred to a reduced flow of air. This will not only reduce the power consumption of the hair dryer, but will also in particular reduce the amount of noise produced by the hair dryer. Alternatively, a more powerful hair dryer can be provided in which more heat is transferred to the flow of air, i.e. the flow of air is maintained the same but the heater transfers more heat.

In an embodiment of the invention the flow guide means comprise a number of flow guide vanes which extend radially inward within an inner circumference of the attachment. The use of vanes allows the stream of air to be expelled from the hair dryer in the most unrestricted way possible, by only deflecting the stream of air.

In a practical embodiment of the invention the flow guide means comprise a number of flow guide vanes which extend radially inward within an inner circumference of the coupling means. The use of vanes allows the stream of air to be expelled from the hair dryer in the most unrestricted way possible, by only deflecting the stream of air. Having the flow guide vanes extending within an inner circumference of the coupling means reduces the overall size of the attachment which is more comfortable to use and easier to store.

In an embodiment of the invention the flow guide vanes are twisted, in particular helically twisted, around their respective longitudinal axis. In this manner the amount of deflection or amount of tangential velocity component is given to the stream of air being expelled from the hair dryer can more easily be controlled.

In an embodiment of the invention the flow guide vanes are twisted along their respective longitudinal axis such, that part of the flow guide surface is substantially parallel to the central axis of the attachment and part of the flow guide surface is substantially perpendicular to the central axis of the attachment. This will ensure that part of the stream of air still has a predominant velocity component that is in the same direction as the central axis of the attachment, and consequently in the direction that the hair dryer is aimed at, which in turn ensures that the stream of air maintains a good overall speed. By providing part of the flow guide surface such that it is substantially perpendicular to the central axis of the attachment, part of the air stream is given a strong tangential component yielding the advantageous mixing effect.

In an embodiment of the invention the flow guide surface is substantially perpendicular to the central axis of the attachment near a distal end of the flow guide vanes. Alternatively, the flow guide surface is substantially parallel to the central axis of the attachment near the central axis. Both alternatives are believed to provide good mixing results. In an embodiment of the invention the flow guide means are provided in a sunburst, so that the tangential velocity component imparted to the stream is independent on the location where the stream of air is expelled.

According to a second aspect of the invention a hair dryer is provided that comprises a housing with an inlet and an outlet for a stream of air to flow through, said housing enclosing a ventilator drivable by a drive motor for flowing the stream of air through the housing, and a heater for heating said stream of air, and coupled to the outlet, an attachment according to any of the previous claims.

According to a third aspect of the invention a hair dryer comprises a housing having a central axis, said housing comprising an outlet for a stream of air to flow through, and a flow guide means. The flow guide means comprises a static flow guide surface for guiding the stream of air, said flow guide surface being, at least partly, angled with respect to the central axis of the housing. The flow guide means belonging to the third aspect of the invention can be seen to embody the same inventive concept as the flow guide means in all the embodiments of the attachment as described above and consequently exhibits the same advantages. These are not repeated here to avoid unnecessary repetition.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantageous embodiments of the attachment according to the invention and a hair dryer comprising such an attachment are described in the claims and in the following description with reference to the drawing, in which:

Fig. 1 shows a hair dryer with schematically depicted temperature profiles of a conventional hair dryer and a hair dryer with an attachment according to the invention;

Fig. 2 shows schematically an outlet of a hair dryer with an attachment according to the invention;

Fig. 3 A shows in a front elevation an attachment according to the invention;

Fig. 3B shows in a perspective view the attachment of Figure 3 A, and

Fig. 4 shows a temperature distribution over a cross-section A-A in Figure 1.

DETAILED DESCRIPTION OF EXAMPLES

Figure 1 shows in a side elevation a hair dryer 1 which comprises a housing 2 having an inlet 3 for air to enter the housing 2. The hair dryer further comprises an outlet 4 through which air can be expelled from the hair dryer 1. The housing 2 further comprises a handle 5 on which several switches 6 are provided. The switches 6 are used for controlling the hair dryer 1 , and may comprise an ON-OFF switch, a speed switch and a temperature control switch for example. Inside the housing 2 there is provided a drive motor that drives a ventilator or blower that accelerates the air that entered the housing 2 through inlet 3 towards the outlet 4 and across a heater (not shown) that heats the air if so required. In the example of Figure 1 , the drive motor is an electrical motor that is powered using the mains, but a battery powered hair dryer is also conceivable.

Figure 1 further schematically shows as indicated by arrows 10 how a hot stream of air is expelled from the outlet 4 of the hair dryer 1. The stream of air has a substantially conical cross-section indicated by the dashed boundary lines 11. The cross- section of the stream of air increases along the longitudinal direction or central axis X of the housing 2, indicated by a dashed line, due to interaction with ambient air, slowing the stream of air down and entraining ambient air in the stream of air. At a certain distance away from the outlet 4 of the hair dryer 1 a cross-section A-A through the stream of air is indicated. In Figure 1 to the left of the cross-section A-A two temperature profiles, respectively temperature profile I and temperature profile II, are depicted and show the temperature distribution in the cross-section A-A in two different situations. Temperature profile II will be discussed later in more detail together with a discussion of Figures 2 - 4.

Temperature profile I is a typical temperature profile as found in a conventional hair dryer. Such a hair dryer comprises an outlet which may be fully opened toward the surroundings, but often is provided with a grating to prohibit easy access the in the internal workings of the hair dryer from the outside. Along the central axis X the temperature T (without scale, refer to Figure 4 for an example showing temperatures) of the stream of air in cross-section A-A is given. Looking just at temperature profile I it can be seen, that profile I has a very distinct profile which shows a global maximum value Maxl, a local minimum value Min2 located on the central axis X and a minimum value Mini which can be found on the conical boundary line 11. In practice this means that a user using the conventional hair dryer will experience so-called hotspots in the stream of air that is expelled from the hair dryer.

During use the user will feel the temperature of the stream of air and in particular these hotspots as these are the hottest areas in the stream of air. Due to aspects of user comfort, retail requirements and safety considerations, the maximum temperature of the stream of air is limited, for example to a maximum of 100 °C. Hence, in case of temperature profile I this maximum is the value of Maxl. This means that the amount of heat supplied by the heater to the stream of air is limited by the value of Max 1 and consequently, also due to the hotspots, a far from optimal drying action is achieved.

Another problem associated with the conventional hair dryer is that the amount of heat that can be transferred to stream of air is limited by the occurrence of the hotspots. Apart from the earlier mentioned problem with the closest prior art of record, the further problem of the occurrence of hotspots in more conventional hair dryers is also solved by the present invention, as the inventors realized that by mixing the stream of air when it is being expelled from the hair dryer, the mixing that will occur will equalize the temperature distribution and consequently reduce or even remove the occurrence of hotspots. This is depicted by temperature profile II where it can be seen that a more flattened temperature profile is obtained. This will be explained in more detail referring to Figures 2 through 4.

Figure 2 shows in cross-section the outlet 4 of the hair dryer 1 of Figure 1. As indicated with arrows 12, a stream of air is flowing through the housing 2. Coupled with the outlet 4 is an attachment 20 which comprises a coupling means 21, hereinafter referred to as a coupling frame 21, provided with a flange 22 and a recess 23 which abuts an inner surface 24 of the outlet 4. The recess 23 may be provided with an annular groove 25. The attachment further comprises a flow guide means generally denoted by reference numeral 30. The flow guide means 30 comprises a number of flow guide vanes 31 which extend radially inward within an inner circumference of the coupling frame 21. In particular, the flow guide vanes 31 can be considered to extend radially inward from an inner surface of the housing 2. In the example of Figure 2 the coupling frame 21 has a circular cross-section. However, other cross- sections are also conceivable depending on the specific design of the outlet 4 of the hair dryer 1. The flow guide vanes 31 are fixedly mounted in the coupling frame 21, which is in turn fixedly coupled to the outlet 4, and have a static flow guide surface 32 for guiding the stream of air. The flow guide surface 32 is, at least partly, angled with respect to a central axis B of the coupling frame 21. As can be seen in Figure 2 the stream of air indicated by arrows 12 passes the attachment 20 under the influence of a non-shown blower and is given a tangential velocity component in addition to the longitudinal or principal velocity, as is indicated by arrows 13 and 13', where arrows 13 in solid lines indicate the direction of flow at the upper half of the attachment and arrows 13' in hatched lines indicate the direction of flow at the lower half of the attachment. It will be clear that consequently a rotational movement is provided to the stream of air that is expelled from the hair dryer 1. A front elevation view of the attachment 20 in isolation is shown in Figure 3 A, also indicating with arrow 14 how stream of air being expelled from the hair dryer is rotating.

As depicted in Figure 3B, the flow guide vanes 31 are preferably helically twisted along their respective longitudinal axis h, which is only indicated in Figure 3B for one flow guide vane 31a, such that a part 33 of the flow guide surface 32 is substantially parallel to the central axis B of the coupling frame 21 and a part 34 of the flow guide 32 surface is substantially perpendicular to the central axis B of the coupling frame 21. In particular, the flow guide surface 32 is substantially perpendicular to the central axis B of the coupling frame 21 near the coupling frame 21, or in other words near a distal end of the flow guide vanes 31. This is more clearly shown in Figure 3B. The effect thereof will be that the area where the hotspots, i.e. the maximum temperature Maxl, were found will be subjected to a larger mixing effect.

The equalizing effect of the attachment 20 and the tangential velocity component that is added to the stream of heated air being expelled from the hair dryer can be learned in more detail from Figure 4.

Figure 4 shows a temperature distribution over a cross-section A-A in Figure 1 , wherein the upper diagram shows the temperature distribution that corresponds to temperature profile I, and wherein the lower diagram shows the temperature distribution that corresponds to temperature profile II, i.e. the hair dryer provided with the attachment according to the present invention. As can be clearly seen, in the situation with the attachment of the invention installed, the temperature of the stream of air varies between 50 and 70 °C, whereas the hair dryer without the attachment has a temperature profile with a temperatures ranging between 30 and 100 °C, while in both cases the amount of heat transferred by the heater of the hair dryer has been kept the same. In the above examples the flow guide vanes 31 are shown to be evenly distributed and are all of the same or at least a similar design. The present invention is however not limited thereto. In particular it is conceivable that the way in that the flow guide vanes 31 are distributed in an irregular pattern, which may contribute to increasing the amount of turbulence in the flow of air that is expelled through the outlet 4 of the hair dryer 1. Furthermore, it is also conceivable that the design of the flow guide vanes 31 is different for different for the individual flow guide vanes. This may also contribute increasing the amount of turbulence in the flow of air that is expelled through the outlet 4 of the hair dryer 1. In the above the present invention has been described by means of an attachment for a hair dryer, in which the attachment comprises flow guide means which embodies the different aspects of the present invention.

The present invention is however not limited to the example of the attachment, but is equally applicable to a hair dryer comprising a housing, wherein the housing comprises a flow guide means that embodies the same inventive concept as the flow guide means in all its embodiments that is part of the attachment as described above and consequently exhibits the same advantages. This embodiment of the present invention is not further depicted in the drawing to avoid unnecessary repetition, but it will be clear to a person skilled in the art how to provide the housing with the flow guide means according to the invention, for example by injection moulding in case the housing is made of a plastics material.

It is further noted that the attachment does not necessarily need to be provided with a coupling frame. It is also conceivable that the flow guide vanes may in some way couple with an inner surface of the housing, for example by means of a circumferential groove that houses (part of) a distal end of the flow guide vanes.

While preferred embodiments of the invention have been depicted and described, it will be understood that various modifications and changes can be made other than those specifically mentioned above without departing from the scope of the invention.