The present invention is directed to a hair dryer, more particularly to a hair dryer with a nozzle specifically designed to effectively spread out wetted hair strands for expediting hair drying.

Japanese Patent Publication No. 5-137613 A discloses a hair dryer with a nozzle which is configured to have slats for rectification of an air flow directed towards a user's hair. Basically, the nozzle is designed to improve hair drying efficiency, i.e., heat transfer amount per unit time (Q) which is determined by Q=H·A·ΔT, where H is a heat transfer coefficient, A is a hair contact surface area, and ΔT is a temperature difference between the hair temperature and heated air temperature. In order to increase the heat transfer amount per unit time (Q) for expediting the drying wetted hairs and achieving rapid drying, it is required to increase at least one of A and ΔT. However, the increase of ΔT is not suitable as it necessitates to rise the temperature of the heated air, and brings about excessive heat which the user feel uncomfortable and which may damage the hair. Consequently, it is a best choice to increase the hair contact surface area. For this purpose, the nozzle of the conventional hair dryer is designed to increase the flow rate of the air flow. Nevertheless, the simple increase of the flow rate is found not effective for spreading out the wetted hair strands and increasing the hair contact surface area, but rather brings about a pressure loss through the nozzle. Accordingly, there has been a demand for effectively spreading out the wetted hairs in order to increase the hair contact surface area for rapid hair drying.

From WO 2004/006713 A1 a hair dryer essentially in line with the introductory portion of claim 1 is known. Documents JP 2005-334130 A and US 6,199,295 B1 disclose additional hair dryers and nozzles disclosing various features of the introductory portion of claim 1 of the present invention.

In view of the above problem, the present invention has been accomplished to provide a hair dryer which is capable of effectively spreading out the wetted hairs for enhanced drying capability.

This object is solved by a hair dryer according to claim 1, claims 2 to 7 relate to specifically advantageous realizations of the inventive hair dryer according to claim 1.

The hair dryer in accordance with the present invention includes a tubular casing with a flow channel extending along an axis of the casing, a blower mounted within the casing to generate a forced air flow directed through the flow channel, and a tubular nozzle disposed at one axial end of the casing in communication with the flow channel. The nozzle has its center axis aligned with the axis of the casing to discharge the forced air flow out through a discharge end. The feature of the present invention resides in that the nozzle has its interior space divided into a plurality of individual ducts by a separation plane extending radially about the center axis. With this arrangement, a weak flow zone where no direct air flow is given from the nozzle is formed downstream of the separation plane and between strong flow zones respectively formed downstream of the individual ducts to flow the forced air flow directly therefrom. The presence of the weak flow zone between the strong flow zones can localize the individual strong flow zones to thereby promote spreading out the wetted hairs, thereby assuring rapid hair drying.

The nozzle is preferred to have a partition which extends in the separation plane to divide the interior space of the nozzle into the two ducts. Thus, the weak flow zone can be suitably sized by the dimension of the partition in relation to that of each duct for optimum effect of spreading out the wetted hair strands.

Preferably, each of the ducts is tapered to have its opening narrower towards the discharge end than at its opposite axial end for effectively providing the strong flow zone.

Further, each of the ducts has its inner side wall defined by the partition to give a flat face at a downstream portion of the inner side wall. The flat face is preferred to extend in parallel with the separation plane. The presence of the flat face is found effective to avoid interference between the air flows discharged respectively from the ducts.

In a preferred embodiment, each of the ducts is configured to have its opening elongated along a diameter of the nozzle such that the user can orient the nozzle in a direction of effectively blowing the air depending upon the user's hair style.

The nozzle is additionally provided with a vent which is disposed outwardly of the ducts so as to direct an additional air flow for expediting the hair drying.

The casing includes an inner barrel which defines therein the flow channel and also defines an outer flow channel between the inner barrel the said casing. In this connection, the ducts are configured to receive the forced air flow through the flow channel within the inner barrel, while the vent is configured to receive the forced air flow through the outer flow channel. A heater is provided within one of the flow channel and the outer flow channel, preferably within the flow channel surrounded by the inner barrel so as to generate a cold air flow in addition to the hot air flow simultaneously for minimizing the damage caused by the hot air flow, yet assuring the rapid hair drying.

Preferably, the vent is configured to have its opening narrower towards the discharge end of the nozzle along the center axis than at its opposite axial end. Thus, the nozzle can provide an additional air flow of increased flow rate around the individual air flows from the ducts for enhancing the effect of spreading out the wetted hair strands. In this connection, the vent may be configured to converge towards a point downstream of the discharge end of the nozzle so as to increase the flow rate of the air flowing out of the vent for effectively spreading out the wetted hair strands in cooperation with the air flows directed from the individual ducts through the localized strong air flow zones.

These and still other advantageous features of the present invention will become more apparent from the following detailed description of a preferred embodiment and its modifications when taken in conjunction with the attached drawings.

• FIG. 1 is a vertical section of a hair dryer in accordance with a preferred embodiment of the present invention;
• FIG. 2 is a horizontal section of the above hair dryer;
• FIG. 3 is a perspective view of a nozzle utilized in the above hair dryer;
• FIG. 4 is a horizontal section of the above nozzle;
• FIG. 5 is a side view of the above nozzle;
• FIGS. 6 and 7 are graphs respectively illustrating flow rates at various points of the nozzle;
• FIG. 8 is a side view illustrating a modification of the nozzle;
• FIG. 9 is a perspective view illustrating another modification of the nozzle; and
• FIG. 10 is a perspective view illustrating a further modification of the nozzle.

Referring now to FIGS. 1 to 4, there is shown a hair dryer in accordance with a preferred embodiment of the present invention. The hair dryer includes a casing 10 elongated along an axis and a grip 20 extending at an angle from the casing 10. The casing 10 accommodates therein a blower 30 in the form of an axial flow fan driven by a motor 32 to generate an axially forced air flow directed from an air inlet 12 at the rear end of the casing 10 towards a nozzle 60 provided at the front end of the casing 10. The motor 32 is disposed downstream of the blower 30 and supported by a rectifier 34 having baffles for rectification of the forced air flow. As best shown in FIG. 2, the casing 10 includes a coaxial inner barrel 40 which is disposed downstream of the blower and upstream of the nozzle 60 to define therein a flow channel 42 leading to the nozzle and an outer flow channel 14 between the barrel 40 and an outer shell of the casing 10. The outer flow channel 14 receives the forced air flow through a port 42 at the rear end of the barrel 40 to direct the forced air flow to the nozzle 60. A heater 46 is disposed within the barrel 40 to heat the air flow directed through the flow channel 44 for providing a hot air flow, while it is disposed upstream of the port 42 so as to direct a cold air flow through the outer flow channel 14. The grip 20 is provided with a switch 22 for actuating the blower 30 as well as the heater 46.

Also accommodated with in the casing 10 is a mist generator 50 which, as shown in FIG. 1, is disposed outwardly of the inner barrel 40 and adjacent to the front top end of the casing 10 for discharging a mist of charged minute water particles out through an outlet 15. The mist generator 50 has an emitter electrode 52 which is configured to condense water from within a surrounding atmosphere and to receive a high voltage from a high voltage generator 54 for electrostatically atomizing the water into charged minute water particles.

The nozzle 60 is disposed at one axial end of the casing 10 downstream of the flow channel 44 with its center axis aligned with the axis of the casing 10, and has a discharge end at its front end for discharging the hot air and the cold air. As best shown in FIGS. 3 and 4, the nozzle 60 is shaped into a double tube composed of a cylindrical outer tube 62 and an inner tube 63 coaxial with the outer tube 62 and coupled thereto by means of circumferentially spaced ribs 61. A vent 64 is defined between the outer tube 62 and the inner tube 63 to communicate with the outer flow channel 14 at its rear end for passing the cold air flow therefrom. The inner tube 63 is shaped to communicate with the flow channel 44 at its rear end for passing the hot air flow therefrom. The inner tube 63 has its interior space divided into two ducts 65 by a partition 66 which lies in a separation plane S extending radially about the center axis X of the nozzle. As shown in FIG. 4, the inner tube 63 is tapered towards the discharge end such that the ducts 65 have their openings narrower towards the discharge end than at its rear end. Also, the outer tube 62 is tapered towards the discharge end to converge the vent 64 towards a point downstream of the discharge end.

The partition 66 is elongated over the full diameter of the inner tube 63 and has a horizontal cross-section, i.e., cross section perpendicular to its length, which converges to a closed sharp edge 69 at its rear axis end. The inner tube 63 has a circular opening at its rear end concentric with the axis of the barrel 40 so that the hot air flow from the barrel 40 can be guided uniformly into the inner tube 63 and is diverged at the sharp edge 69 to flow into the individual ducts 65 without causing turbulence. The partition 66 has an increased width W at its front open end, and is formed on its opposite sides at its front end portion with flat faces 68 which defines respectively inner side faces of the ducts 65 adjacent to the discharge end. The front open end of the partition 66 is fitted with a cap 67 having a rounded projection. Since the ducts 65 are separated from each other at its discharge end by the width W of the partition 66, the hot air flows discharged from ducts respectively through local strong flow zones downstream of the discharge end, while leaving a weak air flow zone between the strong flow zones. That is, the individual ducts 65 form the local strong flow zones downstream of the discharge end for directing the hot air flow, while the partition 66 forms the weak flow zone separating the local strong flow zone. The strong flow zones thus formed locally around the weak flow zone to create a waved air flow of varying flow rate, which is responsible for spreading out the wetted hair strands to increase chance of exposing the hair to the hot air and therefore expedite the hair drying. The vent 64 surrounding the ducts 65 is held in communication with the outer flow channel 14 to discharge the cold air flow fed from within the casing 10 in such a manner to form a cold air flow envelop around the localized strong flow zones, promoting to spread out the wetted hair strands in addition to relieving heat damage from applying to the hair. In this connection, with the provision of the presence of the flat faces 68 on the inner side of each duct adjacent the discharge end, it is possible to avoid interference between the individual air flows immediately discharged from the ducts for realizing efficient air flow through the strong flow zone in combination with the tapered structure of the ducts 65. Each of the ducts 65 defined by the inner side wall and an arcuate outer side wall is elongated to have a length along the length of the partition and a reduced width perpendicular to the length of the partition. Thus, the nozzle 60 is given directional selectivity for providing an optimum hair drying effect such that the can orient the nozzle in relation to the user's hair style for effective hair drying.

Referring to FIGS. 5 to 7, there is shown an optimum relationship among several dimensions of the nozzle 60, i.e., (a), (b), (c) along a line P passing through the center axis X perpendicular to the separation plane S, (e) and (d) along a line Q extending in parallel with the separation plane S and passing through a maximum length of the duct 65, and (f) along a line R extending in parallel with the separation plane S and passing through a width center of the vent 64 on the line P. Dimension (a) is a distance from the center axis to the flat face 68 of the duct 65, dimension (b) is a distance from the flat face 68 to the outer side of the duct 65, i.e. a maximum width of the duct, and dimension (c) is a distance from the outer side of the duct to the outer side of the vent 64. Dimension (d) is a distance from line P to interior face of the duct 65 along line Q, dimension (e) is a distance from the outer side of the vent 64 to the interior face of the duct along line Q, and dimension (f) is a distance from line P to the interior face of the vent 64 along line R.

FIG. 6 illustrates a schematic graph of a flow rate distribution along line P in relation to dimensions (a), (b) and (c) along line P with the dimensions shown in abscissa. As is seen in the graph, an optimum relation is founded to be a:b:c=1:3:2. Dimension (a) is preferred to be 3 mm to 5 mm for accelerating the hair drying without causing heat and unpleasant feeling to a user, and most preferably to be 4 mm. Accordingly, the width (W) of the partition 66 (W=2a) is preferred to be 6 mm to 10 mm, and most preferably 8 mm for creating the strong flow zones sufficient to spread out the wetted hair strands.

FIG. 7 illustrates a schematic graph of flow rate distributions along lines P, Q, and R in relation to dimensions (d), (e), (f) with the dimensions shown in coordinates. An optimum relation for effectively providing the strong flow zones is derived from the graph to be d:e:f = 8:1:4. Dimension (d) is selected to be 15 to 17 mm with associated dimensions (e) and (f) satisfying the above relation.

Although not illustrated in the figures, the vent 64 may be configured to have its opening narrower towards the discharge end of the nozzle along the center axis than at its rear axial end, in order to increase the flow rate of the air flow from the vent 64 for enhanced effect of spreading out the wetted hair strands.

FIG. 8 illustrates an alternative nozzle in accordance with a modification of the above embodiment which is basically similar to the above embodiment except that a pair of vents 64 is formed laterally outwardly of the ducts 65 generally in parallel therewith. The other configurations and functions are identical to the above embodiment, and therefore no duplicate explanation is made herein. Like parts are designated by like reference numerals.

FIG. 9 illustrates another modification of the nozzle which is similar to the above embodiment but is dispensed with the vent. Like parts are designated with like reference numerals without reciting duplicate explanation. In this modification, the nozzle is shaped to be bifurcated into two separate tubes which are separated by a partition 66 but have its rear end merged into a circular opening for connection with the front end of the casing.

FIG. 10 illustrates a further modification of the nozzle which is similar to the above embodiment except that more than two ducts are formed symmetrically about the center axis X. Like parts are designated by like reference numerals. The nozzle 60 is divided into five ducts 65 which have their respective rear ends merged into a single circular opening for connection with the front end of the casing. The ducts are each configured to have a triangular shaped cross section smaller towards the discharge end than at the rear end, and are circumferentially spaced about the center axis X as being divided from each other by a distance of W by means of separation planes S1 to S5 each extending radially about the center axis X of the nozzle. In this instance, the inner side wall of each duct is cooperative with the opposed inner side wall of the adjacent duct to constitute a partition having the width of W. With this arrangement, more than two strong flow zones are formed downstream of the individual ducts as being circumferentially spaced apart by the weak flow zones so as to generate the air flow of varying rate effective for spreading out the wetted hair strands.