Hair setting roller

A hair setting roller includes a dielectric cylinder encircled by an electrical resistance magnetic heating element secured to it and adapted to be attracted by a permanent magnet mounted in apparatus having a pair of laterally spaced electric supply contacts. Electrically connected to the opposite ends of the heating element are electric contacts for engaging the supply contacts while the magnet overcomes a force tending to separate the roller and magnet, whereby to heat the heating element electrically. The heating element has a magnetic permeability that decreases as its temperature increases until the attraction of the magnet for the device becomes weaker than the separating force acting on the roller.

U.S. Pat. No. 3,559,658 shows hair setting apparatus provided with a pair 
of laterally spaced electric supply contacts connected to wires adapted to 
be plugged into an electrical outlet. Between the contacts there is a 
permanent magnet. The apparatus has surfaces inclined downwardly away from 
the contacts for supporting a hair setting roller. This roller includes a 
cylinder made from a ferrous alloy that has a predetermined curie point. 
Coiled around the cylinder but insulated from it is an electric heating 
coil, the ends of which are connected to contacts that will engage the 
supply contacts when the roller is held in heating position by the 
attraction of the magnet for the alloy. The heating coil is encircled, 
engaged and concealed by a plastic shell, around which a woman can wrap 
strands of her hair to curl it. As the heating coil raises the temperature 
of the shell and the alloy inside of the coil, the magnetic permeability 
of the alloy decreases until the attraction between the alloy and the 
magnet is no longer sufficient to hold the roller in heating position. The 
roller then rolls down away from the supply contacts and is ready for use. 
This separation of the roller from the supply contacts is designed to 
occur at a temperature that will result in the roller having the proper 
temperature for hair setting. 
Since in the patented construction the heating coil and the ferrous alloy 
magnetic element are separate parts of a hair roller, assembly problems 
occur. Also, problems of electrical insulation between the coil and alloy 
arise at the operating temperature. Because the heating coil and the 
magnetic element are separated, thermal coupling is a variable, which is 
undesirable. The direct engagement of the heating coil with the plastic 
shell limits the temperature to which the coil can be raised, because if 
the temperature is too high, the shell may be melted. 
It is among the objects of this invention to provide improved hair setting 
apparatus of the general type shown in the above patent, in which the 
roller is simpler in construction, easier to make, easier to assemble, 
less expensive, more quickly heated, more consistent in its temperature 
and safer to use.

Referring to FIGS. 1 to 3 of the drawings, a box-like stand 1, preferably 
molded from a plastic, has outer and inner side walls 2 and 3. The inner 
walls are provided with parallel dog leg slots 4 that slope downwardly 
from near the front end of the stand where its top is open. The slots 
slope toward the rear end of the stand a short distance and then are 
inclined upwardly at a lesser angle beneath the top of the stand. Molded 
in the inner side walls of the stand at the rear ends of the slots is a 
pair of laterally spaced electric supply contacts 5 that are connected by 
wires 6 to an electric plug (not shown) that can be plugged into a 
conventional electrical outlet in a house or beauty parlor. Between, and 
somewhat behind, the contacts a permanent magnet 7 is rigidly mounted, 
such as by molding its ends in the inner side walls of the stand, or by 
any other suitable means. 
A hair roller can roll along the inclined lower walls of the stand slots. 
This roller, like the one shown in the abovementioned patent, is designed 
to be electrically heated by making electrical contact with the supply 
contacts 5 while the roller is held in heating position at the rear or 
inner ends of the slots by means of the magnetic attraction of the 
permanent magnet for it. When the temperature of the roller reaches a 
certain point, which has been predetermined, the roller automatically 
rolls forward away from the supply contacts and is ready for use. It can 
be lifted out of the outer ends of the slots. 
In accordance with this invention, the hairsetting roller includes a 
cylindrical shell 9 of a suitable plastic that encircles a dielectric 
cylinder 10, preferably a glass tube. "Dielectric cylinder" as used herein 
also includes a nonmagnetic metal cylinder coated on its outside with an 
insulating material, or wrapped in insulation. The glass tube is longer 
than the plastic shell and projects from its opposite ends. Encircling the 
tube between it and the shell is an electrical resistance magnetic heating 
element 11 that is secured to the tube, with the shell spaced from the 
heating element. The magnetic heating element is attracted magnetically by 
permanent magnet 7 when the roller is at the inner end of the stand slots, 
whereby the roller is held in that position temporarily as shown in FIG. 
2. The opposite ends of the magnetic heating element are electrically 
connected to exposed cylindrical electric contact bands 12 which, when the 
roller is close to the magnet, will engage supply contacts 5 so that 
electric current will flow through the heating element and heat it to 
raise its temperature and thereby the temperature of the plastic shell. 
The roller need not touch the magnet. Each contact band 12 is located 
between a pair of end flanges 13 and 14 on the roller and is electrically 
connected with the heating member in the manner that will be described in 
connection with FIG. 5. 
It is a feature of this invention that the magnetic heating element is 
formed from a material that has a curie point at which it loses 
substantially all of its magnetic permeability. One such material is a 
soft ferrite, a layer or coating of which can be applied to the outside of 
the glass tube in any well-known manner, such as by spraying. Nickel-zinc 
ferrite, magnesium-zinc ferrite and copper-magnesium-zinc ferrite are 
examples of some of the soft ferrites that can be used. 
Another way of forming the magnetic heating element is shown in FIG. 5, 
where a coil 16 of ferrous alloy wire, such as 52 nickel magnetic ferrous 
wire, is wound around a glass tube 17. The coil, which has a curie point, 
can be held in place on the tube by electric contacts 18 formed by 
spraying a narrow band of metal around each end of the tube in overlapping 
engagement with the ends of the wire. Another way of anchoring the coil is 
to resistance heat the end portions of the wire electrically sufficiently 
to soften the adjoining areas of the glass so that the ends of the wire 
can be pressed into the glass. Then end contact bands are formed over the 
end convolutions of the coil. The end contacts 18 project from the 
opposite ends of an encircling shell 19 of plastic, which is provided with 
end flanges 20. Rigidly mounted on the ends of the glass tube are flange 
members 21 that are spaced from the shell flanges. These flange members 
have cylindrical portions 22 that fit snugly in the ends of the tube. 
Flange members 21 and flanges 20 correspond to flanges 14 and 13 in FIG. 
1. 
Each flange member 21 also has a ring portion 23 encircling the tube end 
and spaced from it. The ring portion spans the space between the flange 
member and the adjacent shell flange 20. Projecting laterally from each 
ring portion 23 are several circumferentially spaced spring prongs 24 that 
extend through slots 25 in the shell flange and the shell itself. The free 
ends of these prongs are shaped to engage the inner surface of the shell 
flange to attach the flange member to it and to hold the shell away from 
the heating element. The ring portion 23 is encircled by a metal contact 
band 26 provided with circumferentially spaced lugs 27 that extend 
radially inward between the spring prongs and have bent inner ends 
pressing against contact 18. These contact bands 26, which correspond to 
contact bands 12 in FIG. 1, roll on the lower walls of the stand slots and 
engage the supply contacts when the roller is in heating position. The 
four flanges of the roller serve as guides to hold the roller in place in 
the slots. 
Flanges 14 in FIG. 1 are held in place by spring prongs 28 in the same way 
as flange members 21 in FIG. 5. Also, contact bands 12 are electrically 
connected in the manner shown in FIG. 5 to sprayed-on contacts (not shown) 
engaging the ends of the ferrite coating in FIG. 1. 
A safety feature is illustrated in FIG. 5, in which the wire coil 16 is 
divided into two parts connected midway between the ends of the roller by 
a fusible link 30. If something went wrong with the apparatus and the 
roller started to overheat, the link would melt and break the circuit 
through the heating element. 
The roller, whether provided with a ferrite coating or a wire coil, is 
designed so that the curie point of the heating element is not reached in 
use. At some desirable temperature below the curie point, called herein 
the cross-over temperature, a combination of reduction in magnetic 
permeability due to an increase in temperature, and a force tending to 
separate the roller from the magnet, will result in the roller being 
released from the magnet and it will roll away from the supply contacts. 
Usually, the separating force will be simply gravity, the effect of which 
will depend upon the weight of the roller and the inclination of the lower 
walls of the stand slots 4. However, gravity can be aided, or replaced by 
a spring pressing the roller in a direction away from the supply contacts. 
Or, as shown in FIG. 4, the permanent magnet 31 can be mounted in the 
stand 32 on a pivoted arm 33 and be urged away from the hair setting 
roller 34 by a spring or by gravity. In any event, when the cross-over 
temperature is reached, the hair setting roller separates from the supply 
contacts and is then ready for use. An advantage in having the magnet fall 
away from the roller is that it can be made to open a microswitch 35 in 
the circuit feeding the supply contacts, so even if the roller does not 
move away from those contacts the circuit will be broken and overheating 
prevented. Of course, the magnet must remain close enough to a roller at 
the inner ends of the slots to permit the magnet to be swung back toward a 
cool roller by the magnetic attraction between them. 
It will be seen that by combining the heating element and the magnetic 
element of the roller into a single element, the construction of the 
roller is simplified and its cost reduced. There is no problem in 
insulating a heating element from a magnetic element because they are one 
and the same. For the same reason the problem of thermal coupling is 
eliminated. The spacing of the plastic shell from the heating element 
allows the latter to be raised to a higher temperature than would be the 
case if the shell engaged the heating element. 
According to the provisions of the patent statutes, I have explained the 
principle of my invention and have illustrated and described what I now 
consider to represent its best embodiment. However, I desire to have it 
understood that, within the scope of the appended claims, the invention 
may be practiced otherwise than as specifically illustrated and described.