Hair Dryer

This invention relates to hair dryers, particularly electric hair dryers of the hand-held type.

Electric hair dryers of the hand-held type are generally known and often include a hollow cylindrical hair-winding attachment having air blowing holes disposed along its length. Hair may be wound around the exterior of the hair-winding attachment and dried by hot air blown out through the air blowing holes. However, when a large quantity of hair is wound around such a hair-winding attachment or when the temperature of the ambient atmosphere is high, the temperature of the hot air being blown out through the air blowing holes may become excessively high and damage the hair wound around the hair-winding attachment or deform the hair-winding attachment or dryer body, which may, for example, be of plastic materials.

An object of the claimed invention is to provide a hair dryer having a hair-winding attachment provided with means to ensure that excessively hot air is not blown out through the air blowing holes of the hair-winding attachment. This is accomplished by means to detect hot air in the hair-winding attachment which is approaching an excessive temperature and to vent that hot-air from the hair dryer through a hot air vent. The hot air vent is controlled by a valve which opens when the air in the hair-winding attachment of the dryer rises to a predetermined abnormal temperature which is less than that of any excessive temperature. The temperature-sensitive means to actuate the valve may sense temperature indirectly or directly. An indirect temperature-sensitive valve actuating means may comprise, for example, a means in which the valve is biased in its closed position (closing the hot air vent) by a spring. The valve is opened by air pressure sensitive means acting against the force of the spring when the air pressure within the hair dryer rises to a level associated with the predetermined abnormal temperature. In a direct system, the valve is actuated by a solenoid or other means which includes means for directly sensing the air temperature in the hair dryer.

FIG. 1 is a side elevational view of a first embodiment of the hair dryer of the claimed invention;

FIG. 2 is a side view, in cross-section, of the hair dryer illustrated in FIG. 1;

FIG. 3 is partial side view, in cross-section, of the hair dryer illustrated in FIG. 1, detailing certain portions of the hair-winding attachment thereof;

FIG. 4 is a view, in cross-section, of the hair-winding attachment illustrated in FIG. 3, taken along the line IV--IV;

FIG. 5 is a front elevational view of the hair dryer illustrated in FIG. 1 showing the tip of the hair-winding attachment;

FIG. 6 is a partial side view, in cross-section, of the tip portion of the hair-winding attachment of the hair dryer illustrated in FIG. 1;

FIG. 7 is an exploded perspective view of the tip portion of the hair-winding attachment of the hair dryer illustrated in FIG. 1;

FIG. 8 is a diagram showing the temperature distribution at the air blowing holes of the hair-winding attachment of the hair dryer illustrated in FIG. 1;

FIG. 9 is a partial side view, in cross-section, of the tip portion of the hair-winding attachment for a second embodiment of the hair dryer of the claimed invention;

FIG. 10 is a partial side view, in cross-section, of the tip portion of the hair-winding attachment for a third embodiment of the hair dryer of the claimed invention, showing the valve thereof in its closed position;

FIG. 11 is a partial side view, in cross-section, of the tip portion of the hair-winding attachment for the third embodiment of the hair dryer of the claimed invention, showing the valve thereof in its open position.

An embodiment of the invention is shown in FIGS. 1 through 8. In this embodiment, the hair dryer comprises a main body 3 consisting of a body portion 1 and a hair-winding attachment 2. Body portion 1 is shaped like a cylinder and provided with a revolving electrical connector 4 on the central part of the rear end thereof from which an electrical power cord 5 extends. Air suction holes 6 are provided at the periphery of the revolving connector 4. An airflow guide 7 for air drawn into the hair dryer through air suction holes 6 is located inward of air suction holes 6 in body portion 1. Motor support 8 to which an electric motor 9 is secured is provided inward of airflow guide 7 in body portion 1. Fan 10 is fitted on the shaft of electric motor 9 between motor 9 and airflow guide 7. A rectifier 11 is secured to the side of motor support 8 near the front end of body portion 1, i.e., inward of motor support 8 in body portion 1, and a heater 13 with thermo-switch 12 and a switch 14 are provided between rectifier 11 and the front end of body portion 1, these elements being connected in the usual manner. A mouthpiece 15 to which hair-winding attachment 2 is fixed is provided on the front end of said body portion 1. Hair-winding attachment 2 comprises a cylindrical metallic body 2a and a bristle foundation 2b. Cylindrical body 2a is provided along its length with air blowing holes 16 which decrease sequentially in size from the mouth piece 15 to the free or tip end of hair-winding attachment 2. Associated with each air blowing hole 16 is an air rectifier tab 17 which extends obliquely and inwardly from the end of its respective air blowing hole which is furthest from mouthpiece 15 toward the axis of cylindrical hair-winding attachment 2. It is possible to form these tabs 17 and their associated air blowing holes 16 by cutting one end and two sides of an air blowing hole 6 from cylindrical body 2a and bending the flap so formed inwardly, trimming as appropriate. The tab 17 also decrease in size sequentially from the mouth piece 15 to the free end or tip of the cylindrical hair-winding attachment 2. The tabs 17 serve as air rectifying pieces. They deflect hot air coming from the body portion of the dryer out through their respective air blowing holes 16. The bristle foundation 2b tightly envelops the cylindrical body 2a and is provided with a multiplicity of radially projecting bristles 18 as well as holes 19, each hole 19 communicating with and fitted to a corresponding air blowing hole 16. A hot air vent part 20 is provided at the tip of hair-winding attachment 2, the hot air vents thereof being controlled by valve 22. Four bimetallic sheets 21 extend inwardly of and around hot air vent part 20 to form valve 22. Each bimetallic sheet 21 has the shape of an isosceles trapezoid and is attached to hot air vent part 20 by its base about which it may flex. The bases of the four bimetallic sheets 21 meet to form a square and in normal operation of the hair dryer (i.e., at normal hot air temperatures for the hair dryer) their sides join to form a truncated pyramid which acts to close the hot air vents of hot air vent part 20. The low expansion rate metal sheet of each of the bimetallic sheets 21 faces the inner surface of cylindrical body 2a. Thus, on sufficient heating the bimetallic sheets 21 flex away from another and open the hot air vents of hot air vent part 20. The dimensions and materials of the bimetal sheets 21 of valve 22 are so chosen to effect opening when the air temperature in the hair drying attachment 2 rises to a predetermined abnormal level, which level is less than an excessive level. Further, because under normal operating conditions, the valve 22 is a truncated pyramid with its apex opposing the flow of hot air in the cylindrical hair-winding attachment 2, it acts as an air rectifying piece, deflecting the hot air coming from the body portion of the dryer out through those air blowing holes 16 at the tip of cylindrical hair-winding attachment 2, i.e., along that part of hair-winding attachment 2 approximately commensurate with the length of the truncated pyramid, as measured perpendicularly from its base to its apex. There is thus no need for air rectifying tabs 17 for those air blowing holes 16.

In operation, cord 5 is inserted into an electrical socket and upon turning on the switch 14, the dryer sucks ambient air through air suction holes 6 with the revolution of the fan 10 actuated by the motor 9 and, at the same time, the heater 13 generates heat. The sucked air, passing by the motor support 8, heater 13, and mouthpiece 15, is guided by tabs 17 of the hair-winding attachment 2 and blown out through air blowing holes 16. Accordingly, on winding hairs around hair-winding attachment 2 and actuating the dryer, hair curling is performed. The temperature distribution of the air blown through the air blowing holes 16 along the entire length of the hair-winding attachment 2 is shown in FIG. 8. In FIG. 8, the ordinate and the abscissa represent temperature and length along the axis of the hair-winding attachment 2. respectively, wherein a, b, and c indicate, respectively, the joint part of hair-winding attachment 2 (i.e., the part joining mouthpiece 15), an intermediate point between the joint part and the free end or tip, and the free end or tip itself. Straight line Q.sub.1 indicates the results of measurements conducted on a conventional dryer having air blowing holes which are equal in size to each other whereas Q.sub.2 and Q.sub.3 represent similar measurements on hair dryers embodying the claimed invention. Lines 1.sub.1 and 1.sub.2 represent temperature conditions for hair curling; the zone under line 1.sub.1 implies weak conditions for curling; that between 1.sub.1 and 1.sub.2, moderate ones; and that above 1.sub.2, strong ones in which the air is felt as quite hot. It can be seen from these results that when air blowing holes 16 and their respective air current rectifying tab pieces 17 decrease sequentially in size from the joint part of hair-winding attachment 2, the temperature difference between the ends of hair-winding attachment 2 is small and the temperatures are within a moderate range, thereby ensuring adequate hair curling along the entire length of hair-winding attachment 2 without any adverse affects.

When the quantity of hair wound around hair-winding attachment 2 is large, closure of the air blowing holes may occur and the air temperature will then rise in the hair-winding attachment 2. When the temperature of the air rises higher than a predetermined maximum, flexure of the bimetal sheets 21 occurs due to the difference in thermal expansion rates of the components of the bimetallic sheets. The bimetallic sheets are, as mentioned, ordinarily joined to form a truncated pyramid, closing the hot air vents of hot air vent part 20. On flexing, these bimetallic sheets separate, thus opening the hot air vents of hot air vent part 20. The hot air is thus vented from the hair dryer before any excessive rise in the air temperature can occur. As a result, the temperature of the air in the hair dryer falls to an appropriate degree in the hair-winding attachment 2, the bimetal sheets of valve 22 return to their initial state and the valve 22 thus closes.

The hair dryer of the claimed invention as described above thus has the following advantages:

(1) Hot air vents are provided in a hot air vent part 20 separately from blowing holes 16 for blowing hot air on hair wound on the hair-winding attachment 2. These hot air vents are controlled by a valve 22 which opens when the air temperature in hair-winding attachment 2 rises to a predetermined abnormal temperature, thus preventing excessive rises of the temperature of the air in hair-winding attachment 2.

(2) The use of bimetal sheets 21 in valve 22 of this embodiment ensures more exact sensing of temperature rise than in an indirect system, permitting simpler structure, as well as exact operation in opening and closing of the valve 22 because of the direct action of the bimetal sheets 21.

(3) Since hot air vent part 20 is provided at the tip of and coaxially with hair-winding attachment 2 around which hairs are wound, hot air blown out through the hot air vents thereof does not directly blow upon the user's skin, thereby ensuring safety.

(4) Since, under normal operating conditions, the bimetal sheets 21 which comprise valve 22 form the shape of a truncated pyramid projecting inwardly along the axis of the hair-winding attachment 2, hot air blown through air blowing holes 16 near the tip of hair-winding attachment 2 can be rectified by valve 22 itself and deflected out those air blowing holes 16, whereby the blowing air current is made uniform in intensity, and thus no air rectifier tabs are required for those air blowing holes 16.

(5) Since air blowing holes 16 as well as air current rectifying tabs 17 decrease in size sequentially as they approach the tip portion of the hair-winding attachment 2, the temperature of hot air blown through air blowing holes 16 is made uniform throughout the entire body of hair-winding attachment 2, that is, without excessive heat at the tip of hair-winding attachment 2, thereby enabling easy handling of the hair dryer.

A second embodiment of the claimed invention is shown in FIG. 9. In this dryer, a bimetal sheet 23 of the same kind as those used in the first embodiment for valve 22 is in this embodiment formed into a bowl-like body whose center is affixed to a projection 24 of the central axis of the hot air vent part 20'. The edge of this blow-like body extends around the hot air vents of hot air vent part 20' so as to close them. The low expansion rate bimetallic sheet component of bimetal sheet 23 faces the inside of hair-winding attachment 2, i.e., faces away from hot air vent part 20'. When the air temperature in hair-winding attachment 2 rises to predetermined abnormal degree, bimetal sheet 23 flexes about its point of attachment, reversing its shape, as shown by the imaginary line and accordingly the hot air vents of hot air vent part 20' open, venting the hot air and thus avoiding a further rise in air temperature into the excessive range.

A third embodiment of the claimed invention is shown in FIGS. 10 and 11. In this embodiment, valve 22 is composed of a memory alloy piece 25 in the shape of coil and a valve plate 36. Valve plate 26 is secured to the end of the memory alloy piece 25 closest to hot air vent part 20"; this end is free to move in the direction of the axis of hair-winding attachment 2. The other end of memory alloy piece 25 is fixed more inwardly in hair-winding attachment 2. The memory alloy piece 25 is biased so as to resiliently close the air blowing hole 20" by means of the valve plate 26 and its materials and dimensions so selected as to open the air vent of hot air vent part 20" by contraction of said coiled alloy piece 25, as shown in FIG. 11, at a deformation point which is previously selected to conform to a predetermined abnormal degree of temperature. In this case, the opening-closing stroke of the valve plate 26 can be made as wide as necessary to enable rapid fall of temperature in hair-winding attachment 2.