Title:
Ultrasonic Hairstyling Device
Kind Code:
A1
Abstract:
A device for styling hair includes a wand defining a handle grip surface and a first styling surface spaced from the handle grip surface and a plate defining a second styling surface, the plate being pivotally coupled to the wand to clamp the hair between the first styling surface and the second styling surface. The device further includes a heating element in thermal communication with the first styling surface or the second styling surface to transfer heat to the hair via the first styling surface or the second styling surface, respectively, and an ultrasonic transducer configured to generate ultrasonic vibrations. The ultrasonic transducer includes a horn in contact with the wand or the plate to transmit the ultrasonic vibrations to the hair via the first styling surface or the second styling surface, respectively.


Inventors:
Yahnker, Christopher Ryan (Raleigh, NC, US)
Costello Jr., Leo F. (Raleigh, NC, US)
Wang, Nathan (Raleigh, NC, US)
Attride, Roy (Raleigh, NC, US)
Application Number:
12/899355
Publication Date:
05/12/2011
Filing Date:
10/06/2010
Assignee:
Goody Products, Inc. (Atlanta, GA, US)
Primary Class:
International Classes:
A45D1/04; A45D1/14
View Patent Images:
Primary Examiner:
STEITZ, RACHEL RUNNING
Attorney, Agent or Firm:
Lempia Summerfield Katz LLC (B&S) (One North LaSalle Street Suite 2900 Chicago IL 60602)
Claims:
What is claimed is:

1. A device for styling hair comprising: a wand defining a handle grip surface and a first styling surface spaced from the handle grip surface; a plate defining a second styling surface, the plate being pivotally coupled to the wand to clamp the hair between the first styling surface and the second styling surface; a heating element in thermal communication with the first styling surface or the second styling surface to transfer heat to the hair via the first styling surface or the second styling surface, respectively; and an ultrasonic transducer configured to generate ultrasonic vibrations, wherein the ultrasonic transducer includes a horn in contact with the wand or the plate to transmit the ultrasonic vibrations to the hair via the first styling surface or the second styling surface, respectively.

2. The device of claim 1, wherein the wand is oriented along a longitudinal axis, and wherein the ultrasonic transducer is oriented along the longitudinal axis such that the ultrasonic vibrations are generated in a direction parallel to the longitudinal axis.

3. The device of claim 1, wherein the ultrasonic transducer is disposed within the wand.

4. The device of claim 3, wherein the ultrasonic transducer includes a horn with a rim in contact with an interior surface of the wand that defines an annular interface through which the ultrasonic vibrations travel.

5. The device of claim 1, wherein the wand includes a barrel that terminates at an end cap, wherein the plate is curved to match a curvature of the barrel, and wherein the ultrasonic transducer includes a horn in contact with the end cap.

6. The device of claim 5, wherein the barrel has a length equal to a wavelength of the ultrasonic vibrations or a multiple of the wavelength.

7. The device of claim 1, further comprising an arm pivotally coupled to the wand, wherein the plate is mounted on the arm, and wherein the first and second styling surfaces are flat.

8. The device of claim 1, further comprising a flat plate mounted on the wand, the flat plate having a first side that defines the first styling surface and a second side in contact with the ultrasonic transducer.

9. The device of claim 8, wherein the ultrasonic transducer is oriented in alignment with the wand, and wherein the ultrasonic transducer includes a horn adapter to direct the ultrasonic vibrations laterally toward the flat plate.

10. The device of claim 8, wherein the flat plate has a length equal to a wavelength of the ultrasonic vibrations or a multiple of the wavelength.

11. The device of claim 1, wherein the wand includes a handle that defines the handle grip surface and further includes a barrel extending from the handle and defining the first styling surface.

12. The device of claim 11, wherein the ultrasonic transducer is disposed in contact with, and external to, the barrel.

13. A device for styling hair comprising: a first arm defining a first handle grip surface; a second arm pivotally coupled to the first arm and defining a second handle grip surface; a first flat plate mounted on the first arm and defining a first styling surface spaced from the first handle grip surface; a second flat plate mounted on the second arm and defining a second styling surface spaced from the second handle grip surface, the first and second flat plates being positioned to clamp the hair between the first and second styling surfaces; a heating element in thermal communication with the first flat plate or the second flat plate to transfer heat to the hair via the first styling surface or the second styling surface; and an ultrasonic transducer secured to the first arm and configured to generate ultrasonic vibrations, wherein the ultrasonic transducer includes a horn in contact with the first flat plate to transmit the ultrasonic vibrations to the hair via the first styling surface.

14. The device of claim 13, wherein the first arm is oriented along a longitudinal axis, and wherein the ultrasonic transducer is oriented along the longitudinal axis such that the ultrasonic vibrations are generated in a direction parallel to the longitudinal axis.

15. The device of claim 13, wherein the ultrasonic transducer is disposed within the first arm.

16. The device of claim 13, wherein the ultrasonic transducer is oriented in alignment with the first arm, and wherein the ultrasonic transducer includes a horn adapter to direct the ultrasonic vibrations laterally toward the first flat plate.

17. The device of claim 13, wherein the first flat plate has a length equal to a wavelength of the ultrasonic vibrations or a multiple of the wavelength.

Description:

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. provisional application entitled “Ultrasonic Curling Iron,” filed Oct. 6, 2009, and assigned Ser. No. 61/249,074, and U.S. provisional application entitled “Ultrasonic Flat Iron,” filed Oct. 28, 2009, and assigned Ser. No. 61/255,657, the entire disclosures of which are hereby expressly incorporated by reference.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

The present disclosure is generally directed to hairstyling devices, and more particularly to curling irons and flat irons.

2. Description of Related Art

Traditional techniques for styling hair involve the application of heat. Attempts to style hair faster or create more robust holds have been based on increasing the amount of heat applied to the hair. The heat acts upon water molecules contained in the center of the hair. Restructuring the hydrogen bonds between the water molecules allows the hair to retain the desired styling.

Unfortunately, elevated amounts of applied heat tend to dry and damage hair, rendering the hair difficult to style, reducing shine, and ultimately resulting in unhealthy hair. Excessive heat can damage the outer layers of the hair, i.e., the cuticle, resulting in split ends. The hair becomes more limp and unable to hold desired styling, once the cuticle and inner shaft of the hair lose the water content that would otherwise provide strength.

SUMMARY OF THE DISCLOSURE

In accordance with one aspect of the disclosure, a device for styling hair includes a wand defining a handle grip surface and a first styling surface spaced from the handle grip surface, a plate defining a second styling surface, the plate being pivotally coupled to the wand to clamp the hair between the first styling surface and the second styling surface, a heating element in thermal communication with the first styling surface or the second styling surface to transfer heat to the hair via the first styling surface or the second styling surface, respectively, and an ultrasonic transducer configured to generate ultrasonic vibrations. The ultrasonic transducer includes a horn in contact with the wand or the plate to transmit the ultrasonic vibrations to the hair via the first styling surface or the second styling surface, respectively.

In some cases, the wand is oriented along a longitudinal axis, and the ultrasonic transducer is oriented along the longitudinal axis such that the ultrasonic vibrations are generated in a direction parallel to the longitudinal axis. Alternatively or additionally, the ultrasonic transducer is disposed within the wand. The ultrasonic transducer may then include a horn with a rim in contact with an interior surface of the wand that defines an annular interface through which the ultrasonic vibrations travel.

The wand may include a barrel that terminates at an end cap. The plate may be curved to match a curvature of the barrel. The ultrasonic transducer may include a horn in contact with the end cap. Alternatively or additionally, the barrel may then have a length equal to a wavelength of the ultrasonic vibrations or a multiple of the wavelength.

In some cases, the device further includes an arm pivotally coupled to the wand. The plate may be mounted on the arm. Alternatively or additionally, the first and second styling surfaces may be flat.

The device may include a flat plate mounted on the wand. The flat plate may have a first side that defines the first styling surface and a second side in contact with the ultrasonic transducer. The ultrasonic transducer may then be oriented in alignment with the wand, and the ultrasonic transducer may include a horn adapter to direct the ultrasonic vibrations laterally toward the flat plate. The flat plate may have a length equal to a wavelength of the ultrasonic vibrations or a multiple of the wavelength.

In some cases, the wand may include a handle that defines the handle grip surface and also include a barrel extending from the handle and defining the first styling surface. The ultrasonic transducer may then be disposed in contact with, and external to, the barrel.

In accordance with another aspect of the disclosure, a device for styling hair includes a first arm defining a first handle grip surface, a second arm pivotally coupled to the first arm and defining a second handle grip surface, a first flat plate mounted on the first arm and defining a first styling surface spaced from the first handle grip surface, and a second flat plate mounted on the second arm and defining a second styling surface spaced from the second handle grip surface. The first and second flat plates are positioned to clamp the hair between the first and second styling surfaces. The device further includes a heating element in thermal communication with the first flat plate or the second flat plate to transfer heat to the hair via the first styling surface or the second styling surface, and an ultrasonic transducer secured to the first arm and configured to generate ultrasonic vibrations. The ultrasonic transducer includes a horn in contact with the first flat plate to transmit the ultrasonic vibrations to the hair via the first styling surface.

The first arm may be oriented along a longitudinal axis, and the ultrasonic transducer may be oriented along the longitudinal axis such that the ultrasonic vibrations are generated in a direction parallel to the longitudinal axis.

In some cases, the ultrasonic transducer is disposed within the first arm. Alternatively or additionally, the ultrasonic transducer is oriented in alignment with the first arm, and the ultrasonic transducer includes a horn adapter to direct the ultrasonic vibrations laterally toward the first flat plate.

BRIEF DESCRIPTION OF THE DRAWINGS

Objects, features, and advantages of the present invention will become apparent upon reading the following description in conjunction with the drawing figures, in which like reference numerals identify like elements in the figures.

FIG. 1 is a perspective, cutaway view of an exemplary curling iron constructed in accordance with one or more aspects of the disclosure.

FIG. 2 is a perspective, end view of the curling iron of FIG. 1 to depict an exemplary ultrasonic transducer in greater detail.

FIG. 3 is a perspective view of the ultrasonic transducer of FIG. 2 to depict one or more aspects of the disclosure relating to embodiments having a Langevin transducer configuration.

FIG. 4 is a cross-sectional view of a housing of the curling iron shown in FIGS. 1 and 2 taken along the lines 4-4 of FIG. 2 to depict the mounting of the ultrasonic transducer of FIGS. 1-3 within the housing in an axial orientation and barrel position in accordance with several aspects of the disclosure.

FIG. 5 is a schematic diagram of an exemplary drive circuit for controlling the operation of the ultrasonic transducer of FIGS. 2-4.

FIG. 6 is a perspective, cutaway view of an exemplary flat iron constructed in accordance with one or more aspects of the disclosure.

FIG. 7 is a perspective, partial view of an arm of an exemplary flat iron constructed in accordance with another embodiment.

FIG. 8 is a perspective view of an exemplary ultrasonic transducer of the flat irons of FIGS. 6 and 7.

FIG. 9 is a cross-sectional view of an arm of a flat iron similar to the view shown in FIG. 4 to depict an exemplary mounting of the ultrasonic transducer of FIG. 8 within the arm.

FIG. 10 is a schematic diagram of another exemplary drive circuit for controlling the operation of the ultrasonic transducers of the disclosed hairstyling devices.

FIGS. 11A and 11B are graphical diagrams of data collected during energy transmission testing of the disclosed hairstyling devices.

FIG. 12 is a perspective, end view of another exemplary curling iron constructed in accordance with an alternative embodiment in which an ultrasonic transducer is secured to an exterior barrel surface.

FIG. 13 is a perspective view of an alternative transducer mounting configuration in which a modified Langevin transducer transfers vibration energy radially through a flattened horn surface.

DETAILED DESCRIPTION OF THE DISCLOSURE

The disclosure is generally directed to an ultrasonic hair styling device that transmits ultrasonic vibrations to the hair to reduce the amount of heat applied for styling. The disclosed devices generally improve hairstyling by decreasing the time and temperature level of the applied heat, thereby improving the overall health of the hair, increasing shine, and improving styling hold. In this way, users of the disclosed devices can style hair faster and create longer-lasting holds without having to resort to the application of more heat. Instead of conventional styling heat levels of 400-450° F., use of the disclosed devices has effectively styled hair at temperature levels around about 250° F. to about 350° F.

The ultrasonic vibrations generally apply energy to the hair via the styling elements or surfaces in contact with the hair. The energy from the ultrasonic vibrations then adds to the energy applied by the heat such that the total energy reaches a level appropriate for styling. The energy from the ultrasonic vibrations also results in improved heat distribution in the styling elements or surfaces, which may also help reduce the time needed to achieve and set the desired styling. In hairstyling devices involving wet-to-dry operation, the ultrasonic vibrations lead to faster drying and, thus, lower amounts of applied heat. For these reasons, the likelihood or risk of damage to the hair decreases.

Although described below in connection with curling irons and flat irons, the ultrasonic vibrations may be useful in connection with a variety of hair styling tools or techniques. Thus, the disclosed hair styling devices are not limited to curling irons or flat irons. Nonetheless, in some cases, the ultrasonic vibrations may be transferred while the hair is clamped or otherwise fixed between styling tools or elements. In this way, contact between the vibrating elements of the disclosed devices in the hair is ensured.

Turning to the drawing figures, FIG. 1 depicts a curling iron 20 having an elongate housing 22. A base portion of the housing 22 forms a handle 24 from which a barrel 26 of the housing 22 extends. The handle 24 provides a handle grip surface 28 for an operator of the curling iron 20 to grasp during use. The barrel 26 provides a styling surface 30 spaced from the handle grip surface 28 to avoid or minimize unwanted user contact with the styling surface 30. The styling surface 30 is generally configured for winding hair to be styled around the barrel 26 to form curls or other styling effects. To that end, the elongate housing 22 and each portion thereof may be generally cylindrically shaped, although the handle 24 and the barrel 26 may be shaped otherwise and, moreover, need not be similarly shaped. The handle 24 and the barrel 26 are configured such that the housing 22 is shaped as a wand or an arm.

The handle 24 and the barrel 26 may be integrally formed to any desired extent. The handle 24, for instance, may include a rubberized, plastic, or other grip (not shown) mounted upon an extension of the barrel 26. In other cases, one or both of the portions of the elongate housing 22 may be formed via interlocking or interconnected half- or other shells. For example, the handle 24 may include a molded, two-piece construction consisting of two matching, half-cylinder plastic covers secured to one another via one or more screw or other fasteners. These and other parts of the handle 24 may be constructed of a variety of materials other than plastics, including stainless steel. The barrel 26 may include one or more components constructed of stainless steel, iron, aluminum, or other thermally conductive materials. In some cases, the handle 24 and the barrel 26 are discrete structures connected to one another via one or more fasteners, one or more snap-fit connectors, or some other coupling mechanism. Alternatively, the handle 24 may be configured as a sleeve that fits over a tube or other housing that runs the length of the device to also form the barrel 26.

The handle 24 includes a number of user interface or control elements. To this end, the handle 24 may have a non-circular cross-sectional shape. The example shown, for instance, has a longitudinal ridge 31 that runs the entire length of the handle 24. The ridge 31 presents a panel or other section of the grip surface 28 for the user interface or control elements. The ridge 31 and other projections may also improve the grip surface 28. In other cases, the handle 24 may have an oval or other non-circular cross-sectional shape to configure the grip surface 28 in a desired manner. Similarly, the barrel 26 need not have a circular cross-sectional shape as shown in the event that, for instance, a different curl or other styling effect is desired.

Both the handle 24 and the barrel 26 are configured as hollow tubes to accommodate a number of functional elements, such as electrical components and circuitry. These components generally support the operation of the curling iron 20, which includes ultrasonic vibration as described below. In this example, the handle 24 houses a circuit board 32 shaped as an elongate strip oriented lengthwise and mounted within the handle 24 via one or more screw or other fasteners. The barrel 26, in turn, houses one or more heating elements 34 and an ultrasonic transducer 36. The heating elements 34 are generally disposed within the barrel 26 in thermal communication with the styling surface 30 to transfer heat to the hair wound around the barrel 26. In this example, each heating element 34 includes a thermally conductive strip 38 disposed and extending along an interior wall of the barrel 26. Each strip 38 may have any desired shape, including, for instance, a flat or curved plate. Both the heating elements 34 and the ultrasonic transducer 36 are generally oriented lengthwise within the barrel 26.

Each heating element 34 may be conventionally constructed and configured. Suitable heating element materials include ceramics and metals. In this example, each heating element 34 includes an elongate, flat, ceramic plate disposed upon a flat or other mount inside the barrel 26. Each mount may be constructed of a heat conductive material to encourage the transfer of heat from the heating element 34 to the styling surface 30 of the barrel 26. The barrel 26 in this case has a pair of opposing heating elements positioned lengthwise within the barrel 26. Each heating element 34 may run the length of the barrel 26 or any desired segment thereof. In this example, each heating element 34 extends from an inner end of the barrel 26 to the electronic transducer 36, stopping short of the outer end of the barrel 26 as shown. Any number of heating elements 34 may be disposed within the barrel 26 at a variety of locations, including those that reach the outer end of the barrel 26 as with, for instance, the embodiment described below. One potential advantage of the disclosed hair styling devices, however, is that the number, size, or intensity of the heating elements 34 may be reduced as a result of the application of ultrasonic vibrations, as described below. Nonetheless, the disclosed hair styling devices may still include a conventional amount of heating capacity to provide the operator with various operational options, including a non-ultrasonic option. In these and other ways, the curling iron 20, for instance, may be configured to present a range of possible heating levels to the operator to accommodate different hairstyling requirements arising from, for instance, differing hair thickness.

The curling iron 20 also includes a clip assembly 40 pivotally secured to the elongate housing 22. The clip assembly 40 may include one or more springs or other elastic elements to bias the clip assembly 40 toward the barrel 26 to thereby clamp and hold the hair in position between the styling surface 30 of the barrel 26 and a plate 42 of the clip assembly 40. The plate 42 extends lengthwise along the barrel 26 and has a styling surface 44 on an inward facing side. The plate 42 is generally capable of moving the styling surface 44 into a position facing or opposite from the styling surface 30 of the barrel 26. The barrel 26 and the plate 42 may be configured so that the shapes of the styling surfaces 30 and 44 are matching or complementary. For instance, the plate 42 may be curved to an extent to match the curvature of the barrel 26.

In this example, the plate 42 is pivotally coupled to the elongate housing 22 via a pivot link 46 of the clip assembly 40. The pivot link 46 has one or more ends that terminate at a respective pivot joint or hinge 48 at which the clip assembly 40 is secured to the elongate housing 22. In this example, the clip assembly 40 has two diametrically opposed pivot joints 48 at an inner or proximate end 50 of the barrel 26. Each pivot joint 48 includes a pin, bolt, or other pivot element 52 that passes through the pivot link 46 and the barrel 26. The pivot link 46 generally extends laterally outward from the barrel 26 to form a lever 54, which may, in turn, include a grip surface 56 to facilitate operator engagement during operation. The manner in which the clip assembly 40 is pivotally coupled may vary considerably. For instance, in some cases, the clip assembly 40 is secured to the handle 24.

The shape, construction, and other characteristics of the handle 24, the barrel 26, and the clip assembly 40 may vary considerably from the example shown. A variety of different configurations and constructions are well suited for use with the ultrasonic features of the disclosed hairstyling devices.

The circuit board 32 includes a number of circuit elements 58 to control each heating element 34 and the ultrasonic transducer 36. The circuitry responsible for controlling the heating and ultrasonic vibrating functions may be integrated to any desired extent. In some cases, a separate circuit board may be disposed within the elongate housing 22 to handle one of the two functions alone. In any event, the circuit elements 58 may be disposed in a location within the elongate housing 22 (e.g., near a base end of the handle 24) to avoid the heat generated by the heating elements 34. Because one or more of the circuit elements 58 may also constitute sources of heat, the circuit elements 58 may be nonetheless configured for operation in an elevated temperature environment. Temperature levels within the housing 22 may exceed normal operating temperatures even though the circuit elements 58 are spaced from the heating elements 34. To help dissipate heat, one or more of the circuit elements 58 may include a heat sink 60. For example, one or more copper elements may be disposed upon a circuit board 32 or a respective one of the circuit elements 58. In some cases, the curling iron 20 may include a barrier, divider, wall, or other element within the housing 22 to block the transmission of heat from the barrel 26 to the components within the handle 24.

The circuit board 32 is coupled to a power source via a power cord 62. In other examples, the circuit board 32 is coupled to a battery or other portable power source, which may be rechargeable via, for instance, the power cord 62. The circuit board 32 is also coupled to one or more control or input elements 64. One or more of the control elements 64 may be directed to activating and deactivating the curling iron 20 or one or more operational features thereof, including ultrasonic vibration. Other control elements 64 may be directed to selecting or determining operational parameters, such as heat level and ultrasonic vibration. For instance, an operator may be given an opportunity to adjust the heat level to a lower temperature when the ultrasonic vibration feature is activated. In other cases, the heat level is automatically reduced upon activation of the ultrasonic vibration feature. More generally, an operator may adjust the temperature level to customize the curling iron 20 for personal use requirements or preferences.

The positioning, structural configuration, and other physical characteristics of the electrical and circuit-related components of the curling iron 20 may also vary considerably from the example shown. For example, circuit elements may be disposed on more than one circuit board or otherwise spaced apart to improve heat dissipation. Details regarding the electrical characteristics of the circuit-related components are provided below.

As described below, the ultrasonic transducer 36 is generally configured to generate ultrasonic vibrations to improve and facilitate hairstyling through lower levels of applied heat. In this example, the ultrasonic transducer 36 includes an assembly of components disposed within the barrel 26. In that way, the vibrations generated by the transducer 36 are transmitted through the barrel 26 to the styling surface 30, at which point the vibrations are, in turn, transmitted to the hair in contact therewith. To that end, the ultrasonic transducer 36 is generally disposed in a position that allows the vibrations to be transmitted to the styling surface 30 and, ultimately, to the hair being styled. In this example, the transducer 36 is mounted or oriented lengthwise along a longitudinal axis of the barrel 26. The longitudinal axes of the barrel 26 and the transducer 36 are aligned such that the ultrasonic vibrations are generated in a direction parallel to the longitudinal axis. This transducer orientation allows the size and length of the transducer 36 to be maximized in the limited space available within the barrel 26. However, as shown with the examples described below, the location and orientation of the transducer 36 may vary, including, for instance, non-axial orientation involving a radial mount.

With reference now to a FIG. 2, a partial view of the curling iron 20 is shown to depict one possible location of the ultrasonic transducer in greater detail. In this example, the ultrasonic transducer 36 is disposed adjacent an end cap or plug 66 of the barrel 26. The transducer 36 is shown in phantom to depict how a front face 68 of the ultrasonic transducer 36 is in contact with the end cap 66. To this end, the transducer 36 is positioned at an outer or distal end 69 of the barrel 26 such that the front face 68 abuts the end cap 66. As described further below, the transducer 36 is also positioned, shaped and sized for further contact with the barrel 26. Generally speaking, the width of the transducer 36 may result in contact with the longitudinal wall(s) of the barrel 26. In this case, the transducer 36 is configured such that an inner longitudinal wall of the barrel 26 is contacted by a rim 70 of the transducer 36 to form an annular interface at the front face 68. In this way, the vibrations generated by the transducer 36 may be transmitted to the styling surface 30 via both the end cap 66 and the annular interface with the barrel 26. As also shown in FIG. 3, the rim 70 extends along the longitudinal axis of the transducer 36 to form a cylindrical surface or band for the annular interface with the barrel 26.

The ultrasonic transducer 36 may be disposed at other locations within the elongate housing 22. For example, the transducer 36 may be disposed at the inner end 50 of the barrel 26. In that case, the front face 68 of the transducer 36 may again be adjacent another end cap or other face (not shown) to maximize the surface area of the interface between the transducer 36 and the barrel 26. In such cases, the transducer 36 may not extend the entire width of the barrel 26 so as to allow electrical connections and other elements to pass by the transducer 36 to reach the heating elements 34 (FIG. 1). To that end, the rim 70 may include a gap or spacing to act as a pass-through for wiring, etc. In other cases, the annual interface may be the sole transmission conduit for the ultrasonic vibrations. If the transducer 36 is disposed not at either end of the barrel 26, but rather at a point therebetween, the contact between the rim 70 and the inner surface of the barrel 26 may form the only transmission conduit between the barrel 26 and the transducer 36 for the ultrasonic vibrations. Still other cases may position the transducer 36 within the handle 24, at a wall or other element separating the handle 24 and the barrel 26, or at any other location within the housing 22.

The ultrasonic transducer 36 may be secured within the elongate housing 22 via an adhesive layer or film 72 between the rim 70 and the inner surface of the barrel 26 (also shown in FIG. 4). A variety of adhesive materials are well suited for the mounting, including, for instance, those products commercially available from 3M Corporation, which may be applied to the inner surface(s) of the barrel 26. The 3M adhesive products may be configured as a pressure-sensitive film. The adhesive material is generally insensitive to the elevated heat levels within the barrel 26. The material from 3M Corporation is rated for use at up to 550 F. degrees. The adhesive layer 72 generally addresses the challenge of securing the transducer 36 without dampening or otherwise interfering with the transmission of the ultrasonic vibrations. To that end, the adhesive layer 72 may be configured and applied as a thin film. In some cases, the ultrasonic transducer 36 is alternatively or additionally inserted into the barrel 26 or, more generally, the elongate housing 22 in a pressure-fit arrangement. In that way, the ultrasonic vibrations do not experience a significant barrier to transmission through the annular or other interface between the transducer 36 and the styling surface 30. Furthermore, an adhesive layer need not be applied between the transducer 36 and the end cap 66, thereby allowing the vibrations to pass through that interface without adhesive-related dissipation.

FIG. 3 shows the ultrasonic transducer 36 in greater detail. The transducer 36 generally includes a horn 80, a piezoelectric section 82, and a reflector 84. In this example, these stages of the transducer 36 are arranged in the Langevin configuration. The horn 80 is generally configured as a front-end stage to transmit the ultrasonic vibrations generated in the piezoelectric section 82. To that end, the horn 80 is shaped and otherwise configured for efficient transfer and transmission of the vibrations. In this example, the horn 80 is shaped as a truncated cone (or frustum) such that a tapered section of increasing diameter extends forward from the piezoelectric section 82. The horn 80 terminates in a front face 86, which may be flat to maximize contact with the end cap 66, the barrel 26 (FIG. 1) or other component of the housing 22. The reflector 84 is positioned behind the piezoelectric section 82 as a back-end stage of the transducer 36 generally designed to reflect or direct the ultrasonic vibrations in the desired transmission direction through the front end stage (e.g., through the front face 86 of the horn 80 toward the barrel 26 or the housing 22). The reflector 84 is sized and weighted to that end. For example, a solid cylinder of stainless steel or other dense material may be used as the reflector 84. The reflector 84 is set at a distance that is a direct multiple of the wavelength of the vibrations so that wave reflections will be in phase with the waves emanating from the piezoelectric section 82.

The piezoelectric section 82 is disposed between the front- and back-end stages of the transducer 36. The piezoelectric section 82 includes a set of piezoelectric discs 88 arranged in a stack. Each disc 88 may be made of Lead zirconate titanate (PZT) or other piezoelectric ceramic(s) or other material(s) with the piezoelectric property of changing shape upon the application of an electric field. PZT and other ceramic materials are useful in the curling iron context due to heat compatibility, as the heating elements 34 are conventionally raised to temperature levels of approximately 400-450° F. for hairstyling (or 250-350° F. with the benefit of ultrasonic vibration as described herein). The piezoelectric discs 88 as well as the transducer 36 are commercially available from Sunnytec Electronics Co. Ltd. (Taiwan). The disc stack is generally configured so that the vibrations generated by the discs 88 are in phase for constructive amplification. In this case, the stack includes four discs 88 oriented axially, or longitudinally, within the housing 22 (FIG. 1). Other disc arrangements are possible, but an even number of discs is useful for maintaining a constructive interference scenario for the vibrations. Electrodes 90 are positioned on each side of the discs 88 to apply an excitation or drive signal to each disc 88. The excitation signal may include an AC component with, for instance, a 160 Volt peak-to-peak amplitude. The amplitude may be increased to amplify the strength of the resulting vibrations. Amplitudes as high as 320 V peak-to-peak have been found to be suitable. The number of piezoelectric discs 88 may be increased to accommodate the higher amplitudes. Other characteristics of the excitation signal, including frequency, may be established through pulse density modulation. The frequency (or effective frequency) of the excitation signal generally determines the frequency of the vibrations generated by the transducer 36. As a result, the excitation signal frequency is generally selected in accordance with the desired vibration frequency of the transducer 36.

Positive and negative pairs of the electrodes 90 are reached via U-shaped contacts 92, which generally run along the stack lengthwise before bending radially inward toward the electrodes 90. Each contact 92, in turn, is connected to wiring (not shown) that leads to the circuit board 32 (FIG. 1). The contacts 92 may be integrally formed with the electrodes 90. More generally, each contact 92 may be configured as a plate having a flat section. In some cases, the flat section of the plate may provide a stable surface for mounting the transducer 36 within the housing 22 (FIG. 1).

The three stages of the transducer 36 are secured to one another by a bolt or other fastener 94 that extends axially forward from the reflector 84 through the discs 88 of the piezoelectric stage 82 to reach the horn 80. To that end, each disc 88 and each electrode 90 may have a hole (not shown) formed in the center thereof to allow the bolt 94 to pass through. The bolt 94 may have a threaded end 96 configured to engage a matching threaded opening (not shown) in the horn 80. The bolt 94 may be welded or otherwise fixed to the reflector 84 at its other end. In some cases, the bolt 94 may be integrally formed with the reflector 84. During assembly of the transducer 36, the reflector 84 is rotated relative to the horn 80 for compression of the stages of the transducer 36. The horn 80 and the reflector 84 include opposed pairs of flattened sections 98, 100, respectively, to allow a wrench or other tool to help tighten the assembly to reach a suitable level of compression.

FIG. 4 shows the exemplary axial mounting of the transducer 36 within the outer end 69 of the barrel 26 in greater detail. The front face 68 of the horn 80 is disposed along, and in contact with, the end cap 66 of the barrel 26. The rim 70 is sized so that the annular interface and contact between the transducer 36 and the barrel 26 spans the entire circumference of an inner surface 102 of the barrel 26. In this case, the adhesive layer 72 is, in fact, limited to the annular interface such that the vibrations passing through the front face/end cap interface avoid any dampening or suppression that would otherwise arise from the presence of an intermediate adhesive layer. The adhesive layer 72 may also be used to secure the end cap 66 in place at the outer end 69 of the barrel 26. Additional mounting hardware (not shown) may be disposed within the barrel 26 to hold the transducer 36 in place.

The heating elements 34 in this example are disposed along the inner surface 102 of the barrel 26. However, the heating elements 34 need not be curved to match the curvature of the barrel 26 and, thus, need not be disposed in contact with the inner surface 102 across their entire width or length. Instead, the heating elements 34 are more generally disposed along the barrel 26 at a radial position outward of the transducer 36 and either directly or indirectly coupled to the inner surface 102. An indirect coupling may include heat-conductive mounting hardware (not shown) that establishes the transmission of heat from the elements 34 to the inner surface 102 and, from there, through the barrel 26 to the styling surface 30 opposite the inner surface 102.

The transducer 36 has an overall axial length LT and a horn length LH, as defined in FIG. 4. Generally speaking, these length dimensions are selected to maximize the generation and transmission of ultrasonic vibrations through resonance of the transducer 36. To that end, the dimensions LT and LH may be about λ/2 and λ/4, respectively, where λ is the wavelength of the ultrasonic vibrations generated by the transducer 36. When these length conditions are met (or approximately met), the transducer 36 may be driven to an oscillation mode having a node (where vibration amplitudes are at or near a minimum) at a rear face 104 of the reflector 84 and an anti-node (where vibration amplitudes are at or near a maximum) at the front face 68 of the horn 80. Under these conditions, the vibrations generated by the transducer 36 form standing waves within the transducer 36, effectively reflecting from the back-stage reflector 84 and combining in phase with those traveling forward to the horn 80 to reach the front face 68 at peak strength. In one example, the overall axial length LT is 56 mm and the horn length LH is 17 mm.

Notwithstanding the foregoing, the diameter of the barrel 26 may present challenges for the design and mounting of the transducer 36 and thereby cause a deviation from the ideal λ/4 configuration. In some cases, the diameter of the rim 70 of the horn 80 may be limited by the diameter of the barrel 26. As a result, the length of the horn 80 may be shorter than the optimal length in order to achieve resonant operation with the other stages of the transducer 36. In one example with a 1.5″ diameter barrel, the horn 80 is shorter than the optimal length to ensure that the horn 80 resonates at the same frequency as the piezoelectric stage. The shorter horn length also helps to maintain a proper mass differential between the reflector and horn stages in the interest of ensuring that the vibrations are directed toward the horn.

With the horn-shaped (or frustoconical) transducer configuration shown in FIGS. 1-4, the lengths may be selected for operation at a number of natural resonant frequencies between about 20 kHz and about 1 MHz. In some cases, the piezoelectric discs 88 may be configured such that the operating (i.e., vibration) frequency exceeds about 50 kHz. The vibration frequency for one exemplary embodiment involving the horn-shaped transducer configuration was above about 60 kHz and, in some cases, about 87.5 kHz. The vibration frequency may be selected in accordance with other operational parameters, including power consumption, temperature level, weight, and size. Differences in barrel geometry and size may result in different resonant frequencies. Thus, the foregoing operational frequencies are exemplary in nature due to the exemplary nature of the transducer assembly 36, which has a front face diameter of 29.5 mm, a disc/reflector diameter 15.04 mm, and a reflector length of 25.44 mm.

During operation, the vibrations generated by the piezoelectric discs 88 travel axially forward to the horn 80. Once at the horn 80, the vibrations travel further forward to transmit energy to the end cap 66 via the front face 68. The vibrations of the horn 80 also spread radially to transfer energy to the barrel 26 via the annular interface between the rim 70 and the inner surface 102 of the barrel. Through these transmission paths, the ultrasonic energy eventually reaches the hair clamped between the styling surface 30 and the styling surface 44 (FIG. 1). There, the ultrasonic energy is applied to the moisture entrapped in the medulla of the hair.

The transmission of ultrasonic energy improves the styling of the hair by facilitating heat transfer within the barrel 26 and by accelerating the restructuring of hydrogen bonds with the hair. On the one hand, the ultrasonic vibrations result in more efficient transfer of heat from the heating elements 34 to the hair through excitation of the molecules within the barrel 26. The excitation of the barrel molecules lowers the heat transfer resistance of the barrel 26. More effective transmission of heat through the barrel 26 lowers the possibility of undesirable hot spots along the barrel, which could otherwise damage hair. More effective heat transmission also lowers the overall heating required to raise the temperature of areas along the barrel 26 other than the hot spots. The general result is more uniform distribution of heat along the barrel 26. Turning to the effects on the hair itself, the vibrations apply energy to the hydrogen bonds between the water molecules in the medulla of the hair. To style hair, these weak electrochemical bonds are broken so that the molecular bonds can be reformed with the molecules in different positions. The ultrasonic energy supplies part of the total amount of energy required to break the bonds. As a consequence, less energy is required from the heat, which ultimately helps to prevent damage to the hair follicle resulting from the heat. For all of these reasons, the hair can be styled faster, which, in turn, lowers the total amount of heat applied to the hair, thereby reducing the possibility for damage.

With reference now to FIG. 5, an exemplary drive circuit 110 for the ultrasonic transducer 36 (FIGS. 1-4) includes several components for controlling and generating the drive signal. The circuit 110 as shown does not include any components for controlling or powering the heating elements 34 (FIGS. 1 and 4). However, the drive and heating control circuitry may be integrated to any desired extent. For example, the input control parameters for activation/deactivation, heating levels (e.g., low, medium and high), and ultrasonic operation may be delivered to both the drive and heating control circuitry for integrated operation. The circuit 110 includes an EMI line filter 112, which is optional depending on whether interference on the AC power line provided to the curling iron 20 is considered a problem. In some cases, such interference or other noise may affect the operation of the circuit 110 to an extent that the drive signal includes harmonic or other undesired frequency components. The operation of the curling iron 20 may, as a result, become less efficient (e.g., through diversion of power away from the effective frequencies). Alternatively or additionally, the presence of undesired components in the drive signal may lead to vibration at undesired frequencies, such as audible frequencies. In this example, the filtered AC line power is provided to a high voltage AC-to-DC converter 114 and a low voltage AC-to-DC converter 116. The high voltage converter 114 includes a bridge rectifier 118 and capacitor C3 configured to generate a high DC voltage input V_hv suitable for use in generating the drive signal. The low voltage converter 116 includes a bridge rectifier 120 and a voltage regulating network 122 to generate an output suitable for use as a power supply Vcc for the logic devices of the circuit 110. In this case, the network 122 includes a Zener diode D3 to lower the output of the bridge rectifier 120 and a regulator 124 to generate a stable power supply voltage Vcc of 12 Volts. The regulator 124 may include one of the linear regulators commercially available from National Semiconductor Corporation associated with product number LM78L12.

The exemplary drive circuit 110 is configured as a full H-bridge driver circuit. Other control circuits may instead include other self-oscillating, switched power supplies, such as a half bridge driver circuit. Still other alternatives may be based on a driven circuit configuration in which, for instance, a crystal is used to set an operating frequency. In this case, the power supply voltage Vcc is provided to a timer 126 configured and set in a stable mode for use as an oscillator. To that end, the timer 126 is coupled to a resistor R12 to set the frequency and duty cycle parameters. A commercially available timer suitable for use as the timer 126 may be obtained from National Semiconductor Corporation associated with product number LM555. The oscillating output of the timer 126 may be provided to a divider 128 configured to, for instance, reduce the duty cycle by 50%. A full-bridge driver 130 receives the oscillating signal to develop switch control signals for two full-bridge switch circuit pairs 132. In operation, the switch circuit pairs 132 are selectively activated in accordance with the switch control signals to generate an AC output drive signal based on the high DC voltage input V_hv and apply the signal to the ultrasonic transducer (FIGS. 1-4) to drive the transducer 36 for generation of the ultrasonic vibrations.

One or more of the above-identified integrated circuit chips or circuit components may be coupled to a heat sink. The heat sink(s) help maintain the operating temperatures of the chips and components to levels within a desired operating temperature range. The heat generated by the heating elements 34 (FIG. 1) as well as the heat generated by the operation of the drive circuit 110 itself may lead to temperatures within the housing 22 (FIG. 1) that would otherwise be elevated to undesirable levels. That said, the operation of the oscillator and other AC-related components of the circuit 110 has been found to remain functional despite the heat levels reached during operation. For instance, the operating temperatures may result in a slight shift in the frequency of the drive signal. In some cases, the frequency shift may be inconsequential, while in other cases other parameters can be adjusted to compensate for the shift.

In some cases, one or more circuit elements may be incorporated into the drive circuit 110 to address spurious vibration modes or other undesired vibrations. For example, a potentiometer may be added to prevent undesirable harmonic frequencies of the drive signal frequency from reaching the transducer. Otherwise, the harmonic frequencies may be audible to the operator of the curling iron or the operator's pets. The potentiometer may be configured to modify the duty cycle of the oscillator output.

The drive signal generated by the circuit 110 may have a peak-to-peak amplitude of about 160 Volts. With the full H-bridge driver is used, the amplitude may be increased to as high as 320 Volts, in which case the number of piezoelectric discs may be increased accordingly to accommodate the higher amplitude. Thus, the amplitude may fall within the range of about 160 Volts to about 320 Volts for some embodiments. With these amplitudes, the drive signal may, for instance, provide 10-100 Watts of power to the ultrasonic transducer. The amplitudes may exceed that range in some cases (e.g., transformer-based circuits) to deliver more energy to the hair and the barrel, although at the cost of increased component size and weight.

The drive circuit 110 does not include a transformer to generate the high AC drive voltage, despite the prevalence of transformers in ultrasonic drive circuits. A transformer would add significant and undesirable amounts of size and weight to the hairstyling device. While the non-transformer drive circuit described above may be limited to lower drive voltage amplitudes, that factor can be offset by the selection of the drive frequency and optimal tuning of the transducer horn. For example, the transducer geometry may be adjusted and analyzed to operate at a natural resonant frequency of the transducer. An FEA package was used to analyze and determine the natural resonant frequencies. Geometric adjustments then led to an operational frequency close to the natural resonant frequency of the transducer and the drive frequency of the piezoelectric discs. The mounting of the transducer may also lead to improved transfer of the axial horn vibrations to the barrel. Notwithstanding the foregoing, all component values shown in FIG. 5 are exemplary in nature in multiple respects, including, for instance, that the component values are directed to generating a drive signal with a frequency of 40 kHz.

Turning to FIG. 6, the benefits of ultrasonic vibration are now described in connection with another exemplary hairstyling device. Like the curling iron 20 described above, a flat iron 140 is configured to transmit ultrasonic energy to the hair being styled via one or more styling surfaces. In this case, the styling surface(s) are flat for hair straightening rather than curved for hair curling. Differences relating to ultrasonic vibration between the hairstyling devices are driven by the device geometries. For example, some of the differences relate to the direction in which the vibrations propagate. With flat and other non-circular device geometries, the vibrations may travel laterally, longitudinally, or any combination thereof. These and other differences and similarities are described further below.

The flat iron 140 includes an elongate housing 142 that has several components in common with the housing 22 described above. The housing 142 similarly defines a handle grip surface 144 and a styling surface 146 spaced from the handle grip surface 144. A plate 148 is also pivotally coupled to the housing 142 to clamp the hair between a styling surface 149 of the plate 148 and the styling surface 146. In this case, however, the plate 148 is carried by another elongate housing 150 (rather than a clip), and the styling surface 146 is an exterior face of another plate 152 carried by the housing 142. The housing 150 is configured as a pivoting arm (or wand) with a proximal, linked end 154 upon which a pivot joint 156 is mounted for coupling with a proximal, linked end 158 of the pivoting arm (or wand) of the housing 142. The two wands or arms extend outward from the linked ends to define a longitudinal axis of each housing 142, 150. The plates 148 and 152 are disposed at distal, free ends 160 and 162 of the housing arms, respectively, at locations disposing the styling surfaces 146, 149 opposite one another. The housing 150 also has a handle grip surface 164 so that an operator can grasp the two wand-shaped housings 142, 150 to bring the styling surfaces 146, 149 toward one another. In this manner, the plates 148, 152 can act as pressure plates to apply pressure to the hair to be styled therebetween. The pivot joint 156 is spring-loaded to bias the flat iron 140 open when no inward force is applied to the handle grip surfaces 144, 164.

Each plate 148, 152 may be fixedly or otherwise mounted within a recess, notch, or other hole in its respective housing. The plates may be made from stainless steel, aluminum, copper, or any other suitably thermal conductive material. Each housing 142, 150 may be made from stainless steel, aluminum, plastic, or any other desired material.

The flat iron 140 also includes a power cord 166 for delivery of power to one or more control circuits (not shown) disposed within one or both of the housings 142, 150. In this case, a control circuit may be disposed within the housing 142 in proximity to a control panel 168 that includes user interface elements 170, 172 for operator control of the flat iron 140. The control panel 168 may be used to activate and deactivate an ultrasonic vibration feature of the flat iron 140 provided by an ultrasonic transducer 174. The control panel 168 may also be used to select a temperature level or other operational parameters. Heat is applied to the hair clamped between the styling surfaces 146, 149 via one or more heating elements 176 in thermal communication with a respective one of the surfaces 146, 149. Each heating element 176 may be configured as a flat plate secured to an interior side of one of the plates 148, 152. In this case, the housing 142 is shown with one of the heating elements 176, although, in other cases, the other housing 150 may contain the sole (or an additional) heating element secured to the plate 148.

The ultrasonic transducer 174 is again configured as an assembly of sections or stages disposed within a hollow interior space of a wand or arm of the hairstyling device. The transducer 174 is generally configured to generate ultrasonic vibrations to facilitate energy transmission with one or both of the pressure plates 148, 152 and to transfer vibration energy to the hair clamped therebetween. However, in this case, the interior space provided by each housing 142, 150 of the flat iron 140 may not be sufficiently large or appropriately shaped to mount the Langevin transducer described above in a manner that disposes the front face of the horn in contact with a matching surface within the housing. However, it may remain beneficial to orient the transducer 174 axially within the housing, with the longitudinal axes of the transducer 174 and the housing aligned. Consequently, the transducer 174 in the depicted example is configured with a horn 178 having an adapter that translates the longitudinal, axial vibration into vibration in a lateral direction toward one of the plate 152. To that end, the horn 178 includes an L- or elbow-shaped head 180 that projects forward from a cylindrical section of the horn 178 adjacent a piezoelectric stage 182. After extending forward, the L-shaped head 180 projects laterally downward to place an outer end 183 in contact with an interior surface 184 of the plate 152. The remainder of the transducer 174 may rest upon, and be secured to the heating element 176 or other surface or component within the housing 142. A similarly mounted transducer may be housed within the housing 150 for transmission of ultrasonic vibrations through the plate 148. In operation, the vibration mode causes the head 180 to move laterally (as opposed to axially) toward and away from the plate 152. The transducer 174 thus vibrates along a hammer-like motion path.

Despite the directional translation of the vibration propagation achieved by the head 180, the profile of the flat iron wands or arms may, in some cases, be too thin to mount the transducer 174 within the housing. The thickness of the heating element 176 may also be a factor. Part of the problem may also arise from a transducer selected or configured for a desired resonant frequency, power capacity, or other operational parameter that ends up being too large for the housing.

FIG. 7 depicts one optional solution in which a flat iron wand or arm 190 has a main housing 192 and a transducer cover 194. The main housing 192 may be configured in a similar manner to those described above, with the exception of a hole on an outward facing side 196 from which the transducer cover 194 flares or extends laterally outward. In this way, the transducer cover 194 defines a secondary housing or enclosure that provides additional space for an interior transducer mount. The transducer (not shown) may have a configuration like any of the transducers described herein, including the Langevin configuration shown in FIG. 3. Thus, the transducer may be mounted in longitudinal alignment as described above, with or without the adapter translation that allows the transducer to meet the interior surface of a plate 198. However, with sufficient additional space under the cover 194, the transducer may be mounted laterally with the front face of an adapter-free Langevin horn in contact with the interior surface of the plate 198, such that the longitudinal axis of the transducer is orthogonal to the longitudinal axis of the main housing 192. Thus, the main housing 192 and the transducer cover 194 may be shaped as desired and, furthermore, be integrally formed to any desired extent, including, for instance, as a unitary molded component.

With reference now to FIGS. 8 and 9, a Langevin transducer 200 with a vibration-translating horn adapter 202 is shown in greater detail. Starting from a back end, the transducer 200 has a reflector stage 204 in compression fit with a piezoelectric stage 206 and a horn stage 208. The reflector and piezoelectric stages 204, 206 may be configured in a manner similar to the example described above. The horn stage 208 may have a cylindrical section 210 having an inner end 212 adjacent the piezoelectric stage 206 and an outer end 214 adjacent the horn adapter 202. The outer end 214 may have a flat face from which an axially oriented arm 216 of the horn adapter 202 extends forward. The arm 216 may be integrally formed with the cylindrical section 210 to any desired extent or, alternatively, be attached to the cylindrical section 210 via a variety of different attachment techniques (e.g., welding, adhesive, etc.). The arm 216 projects outward until reaching a corner or shoulder 218 of the adapter 202, at which point another arm 220 projects laterally downward. The arms 216, 220 need not be rectilinear as shown, and may be solid, hollow, or any combination thereof.

As shown in FIG. 9, a bottom or downward facing surface 222 of the arm 220 is disposed in contact with an inner face 224 of a styling plate 226. The face 224 is exposed for such contact between a heating element 227 and an inward face 228 of a housing 230. The horn adapter 202 may be secured to the inner face 224 via an adhesive layer or film. Alternatively or additionally, the adapter 202 may be fixed to the plate 226 via welding or other attachment techniques. In some cases, the horn adapter 202 is fixed in place by mounting hardware that engages the housing 230 or the heating element 227. For example, the mounting hardware may engage electrode plates 232 of the piezoelectric stage 206. The adapter 202 may be optionally attached to an inner surface of the heating element 227 or other component or surface within the housing 228.

The overall length LT and horn length LH dimensions of the transducer 200 may be selected in accordance with the above-described considerations. The horn length includes the combined length of the cylindrical section 210 and the adapter 202. The length of the reflector stage 204 is noted as LR and may be a direct multiple of the wavelength in the interest of constructive interference (as is the case with the above-described example).

As described above, the transducer 200 may be configured with dimensions offset from the desired lengths in order to ensure that the horn resonates at substantially the same frequency as the ceramic discs of the piezoelectric stage. As a result, the piezoelectric discs are driven with a frequency corresponding with the resonant frequency of the transducer. Thus, the horn length is shorter than λ/4. One exemplary transducer has a main body length of 56 mm, a horn length of 28 mm, a disc diameter of 15.04 mm, a cylindrical horn section diameter of 16.25 mm, an adapter (hammer) width of 12 mm, and an adapter (hammer) lateral extension width (or height) of 15 mm.

Operation of the transducer configuration shown in FIGS. 8 and 9 has been shown to provide a number of optional resonance points between about 20 kHz and about 1 MHz that may be selected as the operating frequency. The transducer has effectively transmitted ultrasonic energy at about 67.5 kHz, about 75 kHz, and about 77.5 kHz.

With reference now to FIG. 10, a drive circuit 240 is configured for controlling the transducer of FIGS. 8 and 9. The drive circuit 240 has several features in common with the drive circuit described above and may, in fact, be used to control the other transducers described herein. The drive circuit 240 is also generally configured as a full H-bridge driver, albeit with different circuit elements. For instance, the circuit 240 includes a bridge rectifier 242 to develop the high DC voltage from which the drive signal is generated. An output of the bridge rectifier is also delivered to an AC-to-DC converter 244 for generation of a 15 Volt power supply, which, in turn, is fed to a regulator 246 that develops a 5 Volt power supply used by an oscillator 248 and an inverter 250. The oscillator 248 establishes the frequency of the drive signal by passing its oscillating output to a pair of full-bridge drivers 252, either directly or indirectly through the inverter 250. Each driver 252 then sends switch control signals in accordance with the oscillator frequency to a pair of switch circuits 254, the terminals of which are connected across the transducer discs in the full H-bridge configuration.

FIGS. 11A and 11B graphically depict the results of experiments that show the increases in energy transmission arising from the application of ultrasonic vibrations. With a curling iron configured as described above in connection with FIG. 1, the power transmission increased about 14% when the ultrasonic vibrations were applied. With the flat iron of FIG. 6, the power transmission increased at least about 10%. The increases were measured via a determination of the amount of energy transferred to a wet cloth. Specifically, the barrel (or flat plate) was heated to its maximum temperature setting with the ultrasonic transducer both turned on and turned off. In each case, a wet cloth with a known weight was applied to the barrel (or plate), and the iron was allowed to heat the cloth for five minutes. The cloth was then weighed to determine how much water has been removed. From that determination, the amount of energy transferred to the cloth was calculated. The same curling (or flat) iron was used in each case so that thermal masses, maximum temperatures, and other iron variables remained constant.

FIG. 12 shows an ultrasonic curling iron 260 constructed in accordance with another exemplary embodiment. The curling iron 260 may be similar to the curling iron described above with the exception of the transducer and heating element locations. In this case, an ultrasonic transducer 262 is disposed outside of a barrel 264. Even though the transducer 262 is not housed within the barrel 264, the transducer 262 is again disposed and oriented along the longitudinal axis of the barrel 264. The transducer 262 is secured to an exterior side 266 of an end cap 268 of the barrel 264 in any desired manner. As described above, the transducer 262 may have a horn with a flat front face to maximize the surface area in contact with the exterior side 266 of the end cap 268. The transducer 262 may be housed within an enclosure 270 coupled to the barrel 264 via one or more fasteners, an adhesive layer, or any other attachment mechanism. This alternative location for the transducer 262 may provide design flexibility if, in fact, space within the barrel 264 is too limited for a desired transducer configuration, size, geometry, etc. The transducer 262 is shown schematically in FIG. 12, and need not have the Langevin transducer configuration shown. Despite the alternative transducer location, the vibration transmission path still passes through a styling surface 272 of the barrel 264.

One advantage of this exterior mounting of the embodiment of FIG. 12 is that the heating element(s) may run the entire length of the barrel 264. With the transducer 262 not disposed within the barrel 264, the transducer 262 does not block the extension of the heating elements. As a result, the heating elements (or one end thereof) may be disposed at or near a distal end 274 of the barrel.

FIG. 13 depicts another alternative Langevin-based transducer configuration that does not rely on a lateral translation of the vibrations via a horn adapter. In this example, a transducer 280 includes a substantially frustoconical horn stage 282 extending forward from piezoelectric and reflector stages 284, 286. The horn stage 282 is generally shaped so that a contact interface with a plate 288 disposed along the horn stage 282 is formed. To that end, the horn stage 282 includes a pair of diametrically opposed flat surfaces 290, each of which may have a parabolic outline. The surfaces 290 may lie in parallel planes such that, when the transducer 280 is oriented axially along the plate 288, one of the surfaces 290 lies flat against a top side of the plate 288 to increase the contact surface area. To that end, an opening 292 in a heating element 294 may provide access to the top side of the plate 288. In other cases, the opening 292 may be cut out to match the shape of the transducer surface.

Generally speaking, the material(s) from which the transducer horns described above are made are selected to ensure effective transmission of the ultrasonic vibrations through the interface between the horn and the barrel, plate, or other component. Effective transmission generally avoids reflection at the interface, which may occur in situations where the impedance of the materials on either side of the interface do not sufficiently match. Suitable materials for the transmission of ultrasonic vibrations in the context of hairstyling devices include aluminum and duraluminum because the acoustic impedance of these materials is approximately halfway between (i.e., an average of) the acoustic impedances of the ceramic (PZT) discs (45 MRay) and the water in the hair being styled (1.5 MRay), i.e., the final medium. Aluminum and duraluminum, for instance, have acoustic impedances of 17.3 MRay and 17.6 MRay, respectively. Duraluminum may be preferable over aluminum because it is harder. Other materials may be used, including those that have crystalline or polycrystalline material structures.

Notwithstanding the advantages of the foregoing examples, the transducer may be mounted in a variety of locations on the hairstyling devices. For instance, the transducer may be mounted on the clip or clamp of a curling iron. The transducers also need not be oriented axially, i.e., along the longitudinal axis of barrel. Even when the transducer is oriented axially, the horn may be configured to transmit vibrations in a direction transverse to the longitudinal axis of the barrel. Thus, the vibrations may be transmitted through the barrel, plate, or other housing structure radially, longitudinally, laterally, or any combination thereof. A variety of other translation sections other than the elbow-shaped adapter described above may be used to change the direction of the vibrations. Each housing or styling surface may contain or have more than one transducer associated therewith.

The transducers may be mounted on a flat surface extruded onto the inner surface of the above-described barrels or wands. The flat surface may be similar to those formed for supporting heating elements. The transducers may alternatively or additionally mounted to an end of the plates described above for transmission of the vibration longitudinally.

The plate with which the transducer is contact in some of the above-described embodiments may be floating relative to the wand or arm housing via one or more springs. The plate is indirectly coupled to the wand housing via the spring(s), in contrast to the plates described above which are rigidly fixed to the wand housing. The separation or indirect coupling of the plate and the wand housing may reduce the amount of vibration energy absorbed by, or dissipated via, the housing.

The above-described barrels, plates and other objects with which the transducers are in contact may be sized to maximize wave transmission within the plate or object. For instance, the plate or barrel may have a length or other dimension equal to the wavelength or a direct multiple thereof.

Other ultrasonic generators may be used. As described above, the device responsible for generating the ultrasonic vibrations may be located at various positions, including those within the barrel, handle, arm, wand, or other hollow structure or housing, as well as those exterior to, but in contact with, such structures, as well as those in contact with some other element in contact with the hair, such as a clip or clamp. Thus, in some cases, the ultrasonic generator is not in direct contact with the barrel or other iron structure.

The construction and configuration of the wands, arms, and elongate housings of the devices described above may vary widely from the examples shown. They need not be of uniform construction, circumference, diameter, or two-piece construction

The disclosed hairstyling devices are not limited to curling irons with clips or spring-loaded clamps. The ultrasonic vibrations may be applied to the hair via clipless wands in which the hair is wrapped around a rod or styled using an iron with a Marcel handle.

A variety of horn shapes may be used with the disclosed hairstyling devices. The transducer horns are not limited to cylindrical or frustoconical shapes. In this way, the disclosed hairstyling devices may accommodate a wide range of barrel diameters and shapes. The disclosed hairstyling devices are also not limited to Langevin transducers or bolt-clamped transducer stacks. A variety of different piezoelectric arrangements may be used, such that the configuration and construction of the sections, stages, or components may vary from the examples shown above.

Although certain curling irons and flat irons have been described herein in accordance with the teachings of the present disclosure, the scope of coverage of this disclosure is not limited thereto. On the contrary, all embodiments of the teachings of the disclosure that fairly fall within the scope of permissible equivalents are disclosed by implication herein.