US1101821A - Electric heating device. - Google Patents

Description

T. VAN ALLER.

ELECTRIC HEATING DEVICE.

APPLICATION FILED JUNE 7, 1912.

Figl.

TYEHU 172m! LLEH Patented June 30, 1914.

JNVENTUR I .565 ATTUHNEY.

UNITED STATES PATENT OFFICE.

TYCHO VAN ALLER, OF SCHENECTADY, NEW YORK, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC HEATING DEVICE.

Specification of Letters Patent.

PatentedJune 30, 1914.

Application filed June 7, 1912. Serial No. 702,158.

To all whom it may concern:

Be it known that I, TYCHOVAN ALL-ER, a citizen of the United States, residing at Schenectady, in the .county of Schenectady, State of New York, have invented certain new and useful Improvements in Electric Heating Devices, of which the following is a specification.

This invention relates to electric heating devices, one of the objects of my invention being to provide means whereby a device of this character may be automaticall controlled in a reliable, simple and e cient manner,

In the use of such electric heating devices as fiat-irons and the like, it is desirable that the heat generated should be varied to a considerable extent. In the case of a fiatiron, for instance, the amount of heat required will depend upon the nature of the work done. heavy, damp material, a relatively large amount of heat must be generated, otherwise j the iron will become too cool to operate effectively. On the other hand, if the iron is being used on thin material which is relatively dry, a small amount of heat should? be furnished, in order that the iron shall not become overheated. In other words, it. is desirable that the supply of heat be automatically regulated to the demand.

One of the objects of my invention is to J provide an electrically heated device of the character in which the demand for heatis variable, with a heating unit which of itself f will regulate the amount of current supplied at any particular time to the demand at that I ance wire may be operated at a high tem- Another object ofmy invention is to pro- 5 vide improved means whereby, in case the heat supplied is not being used, the current will be cut off so as to save current and in time.

some cases to prevent serious scorching or perhaps fire, as for instance where the iron is accidentally left in contact with the work for a considerable time.

material having a positive temperature coefficient, 11.6., one in which the specific resistance will increase with the temperature and rely upon the heating element for the reeistance variation. It has been heretofore proposed .to use a resistance element of this character, but since the range of variation If the iron is being used on of resistance with the arrangement sug-- gestcd was small, a resistance material having a positive temperature coeflicient was merely employed as ,an auxiliary or separate resistance for reducing the current, the change in the specific resistance being taken advantage of to cause a relay to operate and vary the amount of extra resistance in circuit. I have found that certain metals, such, for instance, as iron, having a positive temperature coefficient, may be employed in such a way that the resistance clement itself will furnish sufficient variation of resistance upon change of temperature to regulate the supply of current to the demand within the limits of practical requirements. Iihave found, for instance, that by using iron as the resistance element and causing it to operate efficiently throughout a wide range of temperature that practically perfect regulation can be obtained. To this end, I preferably, though not always necessarily, provide some means for preventing oxidation of the 11011 or other resistance metal, and

therefore make it possible to operate the perature, at which it would otherwise quickly oxidize, without any noticeable oxidation, so that a wide range of temperature and therefore a wide range of current values may be employed.

In carrying out the second object of my invention, I provide means whereby, in case the specific resistance of the resistance .element is increased to a predetermined extent by the increase in temperature, the decrease of current flow incident thereto will cause the circuit to be opened' and the fiat-iron or similar device permanently cut out of circuit. Assuming the case of a fiat-iron accidentally left by the operator in contact with .a piece of cotton material, the heat not being carried away by contact with damp or which would cause the material to be scorched, I cause the circuit to be opened and cut out the fiat-iron entirely. This is I preferably accomplished by the opening of an under-load cutout switch which can only be closed by hand after the temperature has dropped to a safe value.

Other objects and purposes of my invention will appear in the course of the following specification, in which I have shown my invention embodied in concrete form for purposes of illustration.

In the accompanying drawings illustrating my invention embodied in concrete form,

Figure 1 is a plan view of a flat-iron with the upper plate removed to show the heating unit; and Fig. 2 is a similar view showing the flat-iron provided with an automatic cutout.

Referring to the drawing, 1 represents the base of a flat-iron having a resistance element 2 mounted in heat conductive relation therewith. For purposes of illustration, I have shown the unit as consisting of a metal ribbon 2 wound upon a flat V-shaped support of insulating material 3, such as mica or the like, although any suitable arrangement or construction of the unit may be employed without departing from the spirit of my invention. The material of the ribbon 2 is preferably of iron or other metal having a high positive temperature coefiicient of resistance. The unit is placed in good thermal relation with the iron base so that any change in temperature of the base will be quickly communicated to the heating unit and the heat from the unit will be quickly communicated to the iron. This good thermal relationship between the unit and the iron is exceedingly important. The metal of the resistance ribbon having a positive temperature coefficient will cause the current supplied to the iron base and hence the heat supplied thereto to automatically regulate itself to the demand. If, for instance the iron base is placed in contact with heavy damp material, the iron base will, of course, be quickly cooled. Owing to the good thermal relationship between the iron and the unit, this decrease of temperature will cause heat to be quickly extracted from the heating unit and the temperature of the heating unit to drop. This decrease of temperature causes the specific resistance of the resistance metal to be decreased and consequentl a proportional increase in current flow. ince more current will now flow through the resistance material, the temperature of the unit will be increased and this increase in temperature will be immediately communicated to the iron base. The net result is, that while the iron base will be cooled for an instant, an additional supply of heat will immediately become available and the iron will promptly rise to the proper temperature. In this way, the temperature of the flat-iron may be kept substantially uniform and the amount of current used varied with the requirements. In other words, when work is being donewhich requires only a small amount of heat, then only a small amount of heat is generated and a small amount of current consumed,

whereas when the work requires more heat order to accomplish this, it is necessary thatv the metal shall in some cases attain a comparatively high temperature. If, for instance, iron is used, this high, temperature will cause deterioration of the iron due to oxidation. In order to overcome this difficulty, I treat the metal in such a way as to render it non-oxidizing even at a high temperature. This may be done very effectively, especially in the case of iron resistance material, by treating the iron by the process described in my application above referred to. One method of carrying out this process, which has been found to be very successful in practice, is as follows: Powdered aluminum is thoroughly mixed with a certain percentage of powdered'zinc and sal ammoniac and the metal to be treated is placed in an oven surrounded by the powdered mixture. The oven is then completely closed and slowly rotated. A temperature of about 700 C. is maintained in the oven for about two hours. One mixture which has been found to give excellent results contained 60 pen cent. aluminum; 10 per cent. sal ammoniac; and 30 per cent. graphite. Iron wire treated by this process has been ke t at red heat for over two hundred hours wit out any apparent oxidation. It is obvious that by using iron wire treated in this way a high temperature can be maintained for a long time without deterioration of the unit, and thus the current supplied may be varied throughout a wide range.

In Fig. 2, I have shown my device in connection with an automatic switch which will cut off the flat-iron when the current decreases to a predetermined value. Any well known form of underload cutout which is suitably calibrated and adjusted will serve my purpose. As shown in the drawing, the cutoutsimply consists of a coil 4 which is adapted to be connected in series with the heating wire :2 and with the supply lines 5 and 6. A core 7 operating within the solenoid is weighted at its lower end and connects through a rod 8 extending through a stationary insulating support 9 with an insulating member 10 having a flange at each end. The switch member 11, in the form of a loop, is pivoted at 12 so that its free end engages the spring contact 13 which is provided with a shoulder 14 which latches the switch member in closed position. The flanges on the member 10 engage the switch member to open and close the same. \Vhen the current is above a predetermined value, the core will be held in raised position and the switch closed after it has once been closed by means of the knob 15. In this raised position the circuit will be closed through the winding 4, switch arm 11, and the resistance wire 2 of the flat-iron. hen the current in the winding 4 falls below a predetermined value, which value may be regulated by regulating the weights 16 upon the core, or in any other well known manner, the switch contacts will be opened by the dropping of the core and the supply of current cut oif from the wire 2. This automatic cutout acts as a safety device to cut off the current in case the iron is left in circuit, either accidentally or otherwise, for so long a period and under such conditions as might. cause fire. If. for instance, the flatiron should he accidentally left in contact with inflammable material, the temperature of the unit will rise and the resistance of the unit correspondingly increase. No means being supplied for carrying away the heat. the temperature will continue to rise and the current to decrease until a balance is reached in which the radiation losses will equal the energy input. The underload sw tch is therefore set so as to open the circuit when the current is reduced to a predetermined value corresponding to a rise in temperature of the flat-iron beyond which it would not be considered safe. If the fiatiron were left upon a stand, the radiating surface would be increased to such an extent that the temperature might not rise to a point at which the cutout will operate, al though it can be set to operate at substantially any value. It will be seen that I have provided an electrically heated device in which the current supplied 18 automatically regulated to the demand solely by means of the heating unit itself and likewise provide automatic means for cutting off the heater if it becomes hot enough to be dangerous, and while I have described my invent-ion as embodied in concrete form and as operatin in a specific mannerfor purposes of illustration, it should be understood that I do not limit myself thereto, since various modifications thereof will suggest themselves to those skilled in the art without departing from the spirit of my invention, the scope of which is set. forth in the annexed claims.

What I claim as new, and desire to secure by Letters Patent ofthe United States, is I 1. An electric heating device comprising a. body to be heated and aresistance conductor composed of iron with a non-onidizable surface and in good thermal relation w th said body so as to regulate the heat supplied to said body by the changes of resistance of the iron conductor due to changes of temperature.

2. An electric heating device comprising a body to be heated, a resistance conductor for heating the same having a high positive temperature coeflicient and arranged to regulate the heat delivered to the said body by changes of resistance of said conductor due to changes of temperature, and an electroresponsive device for cutting the device out of circuit when the current in said conductor decreases to a predetermined value.

3. An electric heating device com rising a body to be heated, a non-oxidizab e resistance conductor for heating the same having a high positive temperature coefiicient and 'arranged to regulate the heat delivered to the said body by changes of resistance of said conductor due to changes of temperature, and an electromagnetic switch having its winding in series with said conductor for cutting the conductor out of circuit when the current therein decreases to a predetermined value.

In witness whereof, I have hereunto set my hand this 6th day of June, 1912.

TYCHO VAN ALLER. \Vitnesses BENJAMIN B. HULL, HELEN ORFORD.

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