US1728791A - Electric iron - Google Patents

Description

Sept. 17, 1929. F. F. FQRSHEE ET AL ,7

ELECTRIC IRON Original Filed Dec. 29, 1925 2 Sheets-Sheet 1 INVENTORS.

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I ATTORNEY Sept. 17, 1929.

F. F. FORSHEE ET AL I 1,728,791

ELECTRIC IRON Original Filed Dec. 29, 1925 2 Sheets-Sheet 2 WITNESSES F gjgNTOZS. &

- ran on? 66 @141- A Y Fran/1 777007/0/7. & -.I. m/l/ 1' ATTORNEY Patented Sept 17, 1929 I NI ED STA Es PATENT OFFICE-- FRANK F. FORSHEE AND FRANK THORNTON, OF MANSFIELD, OHIO, ASSIGNORS TO .WESTINGHO'USE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA ELECTRIC IRON Application filed December 29, 1925, Serial No. 78,101. Renewed October 26, 1928.

Our invention relates to electric heating Fig. 1 is a view in vertical cross-section of devices and particularly to electrically heata -flat iron embodying our invention; ed flat irons. Fig. 2 is a side view of a supporting mem- An object ,of our invention is to-provide a her for terminal members and the thermallyflat iron that. shall have its heating element actuable switch employed in the device illus- 55 embedded in itstop plate. I U r v trated in Fig.1;

;,Another object of our invention isto'pro- Fig. 3 is a plan view of the supporting vide a flat iron that shall have associated member illustrated in Fig. 2; therewith, a heatin unit which iseasily Fig. 4. is a plan view of the top/casting, manufactured, readi y located in its operaembodying our invention; 1 60 tive osi tion within the flat iron, and which Fig. 5 is a view in. vertical section taken on will ave long life. H I the line VV of Fig.4; and

v Heretofore,.the usua heater employed in Fig. 6 is a view in vertical section taken electrically heated flat irons comprised a on the line VI-VI of Fig. 4.

strip of mica, around which "was wound a Referring more particularly to Fig. 1, an 65 conductor of high resistancematerial. ,The electric fiat iron 11 comprises a body porresistor was disposed in a metallic sheath tion 12, a supporting member 13 and a cover from which it was suitablyinsulated by member, 14. The cover member 1a is atstrips of mica. Heat transfer from the tached to the body member 12 by a bolt 15 heating elementto the sole plate of the flat and encloses the top portion of the body iron has been efiected by a pressure clamp or member 12 and the supporting member 13 weight member that was secured above the therein. I heating element. v 4 I g The body portion 12 comprises a sole plate With this type'of construction, the heat 16, and a top plate 17 secured thereto by ing. elements were. subjected to very high bolts 18 and 19, which extend through the temperatures because of the relativelylow top member 17 and into the sole plate 16,

. thermal conductivity of mica and the - reand nuts 18a and 20.

sultingf temperature drops between the ele- The sole plate 16 has a polished bottom I ment' and the mica and between the mica surface 21, a bevelled edge 22 and a ground 30 and the sole plate. v top surface 23. Holes 24 and 25 are drilled In accordance with our invention, we have and tapped in the sole plate 16 from the surprovided a heating unit which comprises an face 23 to receive bolts 18 and 19.

electric resistance conductor and an oxidiz- The top plate17 has an annular groove 28 able tube or sheath which encloses the conin the bottom surface thereof which makes 35 ductor'and is located in a cast iron member. substantially a complete turn around its Bysubjecting the tube enclosing the resistor outer periphery and an opening 20 in its rear to a gaseous atmosphere of suitable oxygen central portion wherein the member 13 is content, the oxidizable metal ischanged to located. A heating element 26 comprises an oxide thereof, and simultaneously exan electric resistor 29 which is encased in a 0 pands sufiici'ently to, cause a compact and tube or helix 30 of oxidizable metal such as efficient heat path to exist between the elecmagnesium. The encased resistor element 29 trical conductor andthe cast iron member. is located in the groove 28.

Since the resistor is in good 'thermal con- The top casting 17 with the magnesium tactwith the iron member, it will operate at metal tube 30, which encloses the resistor 4 a much'lower temperature than is the case 29 located in the groove 27 is exposed to when the elements are insulated by mica; steam at a high pressure accordlng to the therefore, the heating element will, under method described in United States Letters reasonable circumstances, have much longer Patent No. 1,451,755, lssued to O. B. Backer life than mica insulated elements. on April 17, 1923 whereby the magnesium 50 In the accompanying drawings, metal 30 is changed to magnesium oxide.

The magnesium metal, as it is oxidized, expands substantially to 200% ofits original volume. The heating element is compacted by the resulting oxide, to efiect a high thermally-conductive relation between the conductor 29 and the top plate 17. The

magnesium oxide is of a crystalline structure which extends radially from the resistor 29, and provides an excellent heat path therefrom to the base plate 24. By reason of the efiicient'thermally-conductive path between the conductor 29 and the base plate 17, the resistor element 29 may be operated at a much lower temperature because the temperature gradients between the conductor 28, oxide 29 and the base plate 16 are materially reduced.

ince the heating unit 26 is treated in its operative position within the top plate 17, the base plate 16 may be polished and finished for assembly without marring the polished surface as would obviously result if the heating element 26 were located in the base plate 16. Obviously, it would be very difficult to treat the magnesium oxide covered conductor 29 in place in the base plate 16 before said base plate has been nickel-plated or polished because of the damaging effect of the acid solutions employed in the electro-plating processes.

The ends of the resistor 29 are brought upwardly through openings 31 and 32 in the top casting 17 illustrated in Fig. 4. One end of the resistor 29, which passes through the opening 32, is connected to a terminal 33 of a thermostat 34 which is supported by the member 13. From a second terminal, not shown, of the thermostat 34 a connection is made to terminal 35. The other end of the resistor 29, which passes through the opening 31, is connected to a secondv terminal similar to terminal 35 but which is not shown in the drawings.

The supporting member 13 is of substantially L-shape, and serves as a support for the terminals 35, only one of which is shown, and also serves to support the thermostat 34 in its operative osition, as illustrated in Fig. 1.

Openings 3 and 38 are provided in a short leg 39 of the member 13, wherein the terminals 35 are supported andheld firmly in position by a circular integral lug 41 on the terminals 35 and nuts 40. The terminals are insulated from the member 13 by insulating washers a of mica. An opening 42 is provided in the member 13 to permit the bolt 19 to pass therethrough. The member 13 is held firmly in place by the bolt 19 and a nut 20. The thermostat 34 is supported from the member 13 by a bolt 43 located in an opening 44 thereof, and secured thereto by a washer 46 and a nut 47. A pair of openings 48 and 49 are provided in the member 13 whereby the terminals 33 of the thermostat 34 may be 10- cated inposition in order that the resistor 29 heating means,

may be connected thereto. A depending lug 50 of the L-shape member 13 prevents sai member from bending downwardly so that the thermostat 34 will not touch the sole plate 16.

A thermally responsive member 51 of the thermostat 34 is located nearest the sole plate 16 in order that it may be subjected to substantially the temperature existing at the surface 21 of said sole plate. The supporting member 13 is secured to the top plate 24 by the bolt 19.

The thermostat 34 which we propose to use is described in U. S. Letters Patent No. 1,448,240 issued to J. A. Spencer on March 13,1923.

The cover member 14, as illustrated in Fig. 1, has a handle portion 52 attached thereto by supporting straps 53 and 54. The straps 53 and 54 are secured to the handle by bolts, not shown, and to the cover 14 by rivets 55 and 56. An opening in the rear portion of the cover member 14 permits the terminals 35 to extend outwardly therefrom, whereby an electrical connection may be effected to an electric power supply.

y means of our invention, we have provided an electrically heated iron which comprises a sole plate, that ma be finished and polished independently of the heating unit, a means for heating the aforesaid sole plate, a thermally-actuable switch for controlling the temperature of the sole plate, and a cover member for enclosing the body portion, the and the thermally-actuable switch. The heating means comprises substantially a cast iron member having a groove in its lower surface wherein a heating element is located and insulated therefrom by an oxidizable material such as magnesium.

The heating means provided in the device embodying our invention may be treated in an autoclave as described in the United States Letters Patent No. 1,451,755 issued to G. B. Backer on April 17 1923. Since the heating member is treated independently of the sole plate and since the heating unit lends itself to quantit production, we have provided an iron whic may be easily repaired or easily assembled, as the case may be, because of the simplicity of the heating unit.

Obviously other modifications and changes in the device illustrated in the drawings embodying our invention may be made without departing from the spirit and scope thereof.

We therefore desire that only such limitations shall be placed thereon as shall be imposed by the prior art.

We claim as our invention:

In an electrically heated iron, the combination with a body portion comprising a. top castin having a groove therein, a sole plate, a heating element located in the groove in said top casting, terminal pins for the heating element, and a thermally actuable control switch insurer igggcribed our names this27th day of Nov.

' FRANK F. FORSHEE.

mum; THORNTON.

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