Heating Unit for Rollers Employing Magnetic Inductance

This application claims the benefit of U.S. Provisional Patent Application No. 63/634,713 filed on Apr. 16, 2024, the disclosure of which is incorporated herein by reference in its entirety for all purposes.

The invention relates generally to the field of hair styling, and more particularly to a heating unit for rollers.

Human hair, when exposed to sufficient heat (about 400 degrees F.) for sufficient time (roughly 3 minutes or less depending on hair type) undergoes a chemical change that creates waves and/or curls that, once cooled, can last for days. This has made modern hair styling quick and easy. In former times the only method to facilitate this chemical reaction was to set wet hair in rollers or rags and wait, usually overnight, until the hair had dried around the roller. Today one can still spend an expensive two hours at a salon to sit with wet-rolled hair under a hot dryer. More recently, chemical perms were introduced, but they lost popularity because they result in permanent hair damage.

All hot roller devices currently on the market operate by bringing the rollers into direct contact with a heated post. Accordingly, they provide only small diameter rollers, no more than 1.75″ diameter, because larger diameter rollers are impractical. In particular, they can take upwards of 20 minutes to heat up due to a relatively low heat transfer efficiency of about 400 W, and they consume significant power, typically around 0.13 KWh. Conventional rollers are also heavy, requiring clips to stay in place. Other hot curling tools such as irons, wands, and brushes suffer from the same limitations, they heat slowly, consume a lot of energy to do so, and their barrel sizes are too small to offer the ability to reliably deliver root lift. The commercially available small rollers and other products create curl, but not lift. One prior art system that offered a 2 inch diameter roller, “The Caruso,” employed steam, but the mechanism to deliver steam to the roller made the roller unwieldy and too heavy to sit high on the scalp, dragging the hair flat across the scalp, thus providing only curl and no lift.

Despite this, hot rollers remain popular because they provide one thing other hot tools cannot, freedom. While hot irons, wands, and brushes keep the user tethered to a wall outlet for as much as thirty minutes or more while painstakingly heat styling their hair piece by piece, rollers provide freedom of movement by allowing users to arrange the rollers around their head in minutes and then attend to other tasks while their hair first heats then cools.

Presently, the lift & wave style has been available only through application of a large round brush and a blow dryer working in tandem. This is almost impossible to do on one's own head and requires a stylist to properly create. Drybar, for example, founded in 2010 by Alli Webb, is a California-based chain of salons that is dedicated to providing only blowouts. They have also introduced a line of hair styling tools dedicated to optimizing their styling options, however, none of the styling tools provide lift.

What is needed, therefore, is a way to mimic a salon blowout at home, while providing the hands-free freedom of movement that hot rollers offer.

The embodiments of the present disclosure provide a heating unit that allows larger rollers to be quickly heated, and larger rollers that pair with these heating units, and combinations of the two. Heating units disclosed herein employ magnetic inductance to be able to rapidly heat rollers that are 2 inches in diameter and larger without the need for direct contact to a heat source. The heating units of the present disclosure are able to heat rollers that are 2 inches in diameter or larger to at least 400 degrees. The rollers are also light weight, and the combination of light weight and high temperature provide lift to the hair root, and not curl to the hair shaft. According to embodiments disclosed herein, rollers can be heated in as little as 5 seconds or less due to a heat transfer efficiency of about 1400 W, at a cost of about 0.002 kWh.

An exemplary heating unit comprises, consists of, or consists essentially of, a housing including a lid and a lower portion, with a first magnetic core disposed within the lower portion and a second magnetic core disposed within the lid, wherein the first magnetic core includes two parallel legs, and a plurality of conductive windings is wound around one of the two legs. When the lid is engaged with the lower portion the first and second magnetic cores together form a square closed core. When energized, the conductive windings generate a magnetic field within the square closed core that induces an electric current to circulate in a roller disposed around the second of the two legs. An exemplary roller for use with the heating unit comprises a cylinder of an electrically conductive material, such as aluminum, having an inside diameter of at least two inches and including a plurality of bristles protruding perpendicular to the exterior surface.

Reference will now be made in detail to some specific examples including the best modes contemplated by the inventors. Examples of these specific embodiments are illustrated in the accompanying drawings. While the present disclosure is described in conjunction with these specific embodiments, it will be understood that it is not intended to limit the invention to the described embodiments. On the contrary, it is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. In addition, although many of the components and processes are described below in the singular for convenience, it will be appreciated by one of skill in the art that multiple components and repeated processes can also be used to practice the techniques of the present disclosure.

shows a cross-sectional view of an exemplary heating unitincluding a housing, a magnetic core, and windings. The housingcan be opened to provide access to the inside of the heating unit, as shown in, to insert and remove rollers, also known as hair curlers.shows a side view of the heating unitwith a lidpartially open and two rollersinserted into the heating unit. Whileis a simple cross-sectional view,presents a cross-sectional view overlaid with side views of two rollers.

The housingis a protective and cosmetic shell designed to provide structure to the internal components, protect users from electrical contact, help position rollersvia bosses or other features, and provide a cosmetic cover. The housingcan be fabricated from a variety of materials including injection molded plastic such as polycarbonate or ABS plastic. In the case of a metallic or otherwise electrically conductive housing, electromagnetic shielding may be employed between the magnetic coreand the housingto prevent unwanted heating of the housing.

The housingcomprises two pieces, a lower portionand an upper portion forming the lid. In the embodiment shown inthe lidis hinged to the lower portion, but in other embodiments the lidlifts straight off the lower portionto completely detach therefrom. In still further embodiments, the lidis configured to slide longitudinally relative to the lower portion, such as through the use of tracks.

The magnetic corecomprises, in some embodiments, a square closed core comprising a U-shaped or C-shaped core disposed within the lower portion, and a straight core disposed in the lidand arranged such that when the lid is closed, the straight core is brought together with the C- or U-shaped core to complete the square closed core. In the embodiments illustrated bythe magnetic corecomprises a combination of an E-shaped coreand a straight coreto create two magnetic loops,that both pass through the windings, as shown in. It will be appreciated that more complex magnetic cores can be made to accommodate additional rollers.

Each of the parallel arms of the C- or U-shaped core or E-shaped corewill be referred to herein as legs. In embodiments in which a C- or U-shaped core is employed, the windingsare disposed around one leg, while a rollerfits over the other leg. In embodiments in which an E-shaped coreis employed, the windingsare disposed around the center leg of the three legs, and rollerscan be positioned over the outer two legs. Various embodiments include more than two legs, to accommodate more than two rollers, symmetrically arranged around a central hub leg around which the windingsare disposed.

In various embodiments, the magnetic corecomprises laminated silicon steel with a high relative magnetic permeability (a unitless value) of at least 5000. Individual layers of silicon steel for lamination can be produced, for instance, by plasma cutting, laser cutting, manual shearing, or stamping from sheets of the silicon steel. In various embodiments the steel comprises grain-oriented silicon steel. An exemplary commercially available material known by the industry designation EI150 is suitable for making magnetic cores. Individual lamination layers can be between 0.01″ to 0.035″ thick, with a thickness in one embodiment of 0.02″. Individual laminations are coated so that the layers of silicon steel are electrically insulated from one another.

In other embodiments, the magnetic corecomprises a ferrite core such as for higher frequency applications above 500 Hz. Here, the frequency refers to that of the alternating current from an AC power supply. Below 500 Hz silicon steel is preferred. In some embodiments, an oscillating tank circuit can be employed to produce a frequency of 3-10 kHz, or 200-400 kHz, for example. These frequency ranges are within the induction heating band and within the allowable FCC EM spectrum. Hysteresis losses for silicon steel increase due to eddy currents with increasing frequency.

The windingscan be fabricated from enameled copper wire, for example, but can also be made from any conductive material that is electrically isolated from the magnetic coreand that allows adjacent windings to be insulated from each other. In one embodiment, the windingscomprise 350 turns of 12GA enameled copper wire. Other embodiments may contain any number of turns, wire gauges, and supply currents. Wall heating unitsof the disclosure draw power from the public power grid at 120V and 60 Hz, the voltage and frequency can be varied from this to be delivered to the windingsto meet design requirements such as to limit current draw as well as to avoid core saturation.

Rollerssuitable for use with embodiments of the heating unitcomprise cylinders of an electrically conductive material with a diameter of 2 inches or more and including bristles protruding from the exterior surface. Rollersare sized to fit over the legs of the magnetic core, to allow the magnetic field to pass though with few losses either through air or another material. In one embodiment, the rolleris made from 6061 aluminum. Low density materials such as aluminum are heated more quickly through magnetic induction. In other embodiments the rollerscan utilize any number of other electrically conductive materials with or without specialty coatings, including 304 stainless steel and titanium. An example of such a specialty coating is titanium nitride. As illustrated, embodiments of rollersare bristled, and therefore they require no additional clips to secure them to the hair, thus avoiding dragging hair downward across the scalp which has the effect of flattening roots. In some embodiments the bristles are made of silicone to protect the hair and prevent tangling.

When the windingsare energized with an alternating current, they produce an oscillating magnetic field around the windings. The windingscan be produced by winding a conductive wire around a bobbin to produce a solenoid which can then be placed over a leg of the magnetic core. Since the relative permeability of the magnetic coreis significantly less than that of the surrounding air, the magnetic field produced by the windingsis channeled through the transformer corethereby completing a magnetic loop through the windingsas shown in. The use of an E-shaped coretogether with a straight coreto produce a square closed core (sometimes called an EI core) provides a balanced return path for the magnetic field. Since the rollersare electrically conductive and form continuous loops, the magnetic field passing through their centers induces an opposing magnetic field that in turn causes an internal electrical current to circulate within the rollers. The rollersserve as an electrical load, essentially becoming shorted single-turn secondary windings. The circulating current within each rolleris characterized by a high current at a low voltage. Because of the internal electrical resistance of the rollers, the electrical current causes the rollersto heat.

provides a top view of an exemplary four-station heating unit, with the lidremoved. In the embodiment of, the heating unitincludes two magnetic cores, each comprising an E-shaped core, each magnetic coreconfigured to heat two rollers.

is a circuit diagramfor an exemplary four-station heating unit such as the four-station heating unit. Each of the magnetic coresis represented as a transformer. In operation, a microcontrollerreceives input from a user interfacefor example to heat two rollersin positions 1 and 2. The microcontrollersignals a solid state relayto close in order to allow alternating current supplied by an AC power supplyto flow through windingsto cause the rollersto heat. A thermal sensordisposed proximate to a roller, or disposed in contact with the roller, creates a changing analog signal in response to the changing temperature of the roller. An analog to digital converterchanges the analog signal into a digital one, which is received by the microcontroller. The microcontrollercontrols the solid state relayto open once the digital signal reaches a threshold indicating that the rolleris sufficiently hot. The microcontrollercan additionally provide a signal to the user through the user interface, such as a sound, an indicator light, or by providing text (e.g. “Ready”) on a display, or any combination of these.

The microcontrolleris powered by direct current supplied by a DC-DC converterthat in turn receives direct current from a full wave bridge rectifierin electrical communication with the AC power supply. More specifically, the alternating current produced by the power supplyis split into three paths, where one path goes to one relayand one transformer, a second path goes to the second relayand second transformer, while the third goes to the bridge rectifier. The direct current voltage from the bridge rectifiercan be adjusted as appropriate for the microcontroller, thermal sensors, and for triggering the relays.

The thermal sensorcan be, for instance, a K-type thermocouple, while in other embodiments the thermal sensorcomprises an infrared sensor. The thermal sensorcan be located in the housingnear or touching each roller. In those embodiments that employ an infrared sensor, the thermal sensordoes not contact the roller.

While the present disclosure has been particularly shown and described with reference to specific embodiments thereof, it will be understood by those skilled in the art that changes in the form and details of the disclosed embodiments may be made without departing from the spirit or scope of the invention. Specifically, there are many alternative ways of implementing the processes, systems, and apparatuses described. It is therefore intended that the invention be interpreted to include all variations and equivalents that fall within the true spirit and scope of the present invention. Moreover, although particular features have been described as part of each example, any combination of these features or additions of other features are intended to be included within the scope of this disclosure. Accordingly, the embodiments described herein are to be considered as illustrative and not restrictive.