US2478507A - Electrically heated sadiron - Google Patents

Description

8- 9, 1949. F. w. SCHARF ELECTRICALLY HEATED SADIRON 2 Sheets-Sheet 1 Original Filed NOV. 1, 1941 INVENTOR. gfiA/v/ WSGHARF JY/m ' ATTORNEY Aug. 9, 1949. F. w. SCHARF 2,478,507

ELECTRICALLY HEATED SADIRON Original Filed Nov. 1, 1941 I 2 Sheets-Sheet 2 INVENTOR.

FHA/v WSCHAR/ ATTORNEY Patented Aug. 9 1949 UNITED STATES PATENT OFFICE ELECTRICALLY HEATED SADIRON Frank W. Scharf, Glendale, Mo., assignor to Me- Graw Electric Company, Elgin, Ill., a corporation of Delaware 1 Claim. 1

This invention relates to electrically heated sadirons, and is particularly directed to an iron having improved electric heating means as disclosed and described in my copendin application, Serial No. 417,437, filed November 1, 194 issued October 8, 1946, as Patent No. 2,408,886, of which the present application is a division.

One object of the invention is to provide a sadiron with electric heating means embedded in the sole plate and in highly eificient heat transfer relationship therewith.

Another object of the invention is to provide for the efficient heating of the sadiron sole plate while minimizing heat losses from the heating means through radiation and conduction to the upper portion of the sadiron structure.

Still another object of the invention is to improve the heating efliciency of sadirons of the type employing relatively thin sole plates.

A further object of the invention is to provide an electrically heated sadiron employing a multiplicity of electrically heated closed cells.

An additional object of the invention is to provide a sadiron with efiicient electric heating means which does not require replacement in its entirety in the event of breakage, with the result that heater replacement costs are reduced.

Other objects and advantages of the invention will become apparent from the embodiment thereof illustrated in the accompanying drawings and the following description thereof.

In the drawings:

Fig. 1 is a vertical longitudinal sectional view through an electrically heated sadiron embodying my invention;

Fig. 2 is a top plan view of the sole plate of the iron shown in Fig. 1, the iron housing and certain other parts being omitted;

Fig. 3 is a fragmentary vertical section taken on line 33 of Fig. 2 to show one of the heating cells;

Fig. 4 is a plan view of one of the heating elements;

Fig. 5 is a side view of the heating element shown in Fig. 4; and,

Fig. 6 is a fragmentary vertical section taken on line 6-6 of Fig. 2.

In conventional electrically heated irons and particularly in those embodying a relatively thin soleplate, the electric heating unit is usually of relatively large area and either disposed against the upper surface of the soleplate or located in a large recess defined by a peripheral flange at the outer edge of the soleplate. The first ofsuch arrangements is objectionable from the standpoint of heating efficiency in that an appreciable portion of the heat from the heating unit is transmitted upwardly through radiation or conduction into the upper portion of the iron where it is not desired. The latter arrangement is generally more efficient, but reduces the mass of metal in, and the heat retaining efficiency of, the the soleplate, with the result that the thickness of the soleplate may be required to be greater for the purposes of heating efficiency than where the heating element is located above the soleplate.

The present invention provides an improvement over prior constructions just referred to through the provision of a multiplicity of closed heating cells interiorly of the soleplate. In such cells are housed individual electric heating units surrounded by and faced on the bottom by metal of the soleplate proper and faced on the top side by removable metal cover means which comprise an essential part of the soleplate for heat exchange purposes. The individual heating cells and special heating elements therein are relatively thin, thereby minimizing the thickness of the soleplate required for their employment.

Further, the heating cells and heating elements are of relatively small area so that a multiplicity thereof will be employed in a suitable arrangement to insure uniform heating throughout the entire area of the soleplate.

Referring now to the drawings, I have shown therein an electric sadiron generally designated I I. Such iron includes a soleplate [2 which preferably, although not necessarily, is relatively thin. While the same may be made of iron or steel, I prefer to make it of high heat conducting material such as brass or copper, but my invention is not limited to making the soleplate of any particular material.

The soleplate I2 is substantially triangular in shape to provide a form now usually used for sadirons. A series of wells or recesses l3 are formed in the upper surface of the soleplate, the same being preferably made circular so that it is relatively easy to form them by drilling or machining the same to the desired depth. As best shown in Fig. 2 the wells are of relatively small diameter and arranged throughout the area of the soleplate, preferably one being located adjacent the front end of the soleplate and the others being arranged in two rows extending along opposite sides of the center line to accommodate therebetween a thermostatic control, or in some cases parts supporting the iron upper structure. In any event it will be apparent that due to the small size of the wells they may be efficiently arranged to properly heat the soleplate without interfering with connections between the soleplate and other parts of the iron.

Wells [3 are closed on their upper side to form a) heating cells located entirely interiorly of the soleplate, and preferably located substantially midway of the thickness thereof. In order that the cells be relatively thin, and to insure good heat conduction throughout the entire upper area of the soleplate above the cells, it is preferred to close the wells by a series of individual metal discs or plugs it. which fit into the wells and make close fitting engagement with the surrounding metal of the soleplate. In order that plugs or discs M may be retained in proper operative position and to insure proper heat conduction at their meeting line with the soleplate metal, I may crimp or swage the well wall at a plurality of circumferential points 15 over against the outer peripherial edge of the discs, as best shown in Fig. 3. Located in each of the heating cells defined by the closed wells I3 is a small thin electric heating element is comprising an intermediate substantially circular piece of thin electric insulating'material ll, such as mica, having a series of aligned recesses over a part of its opposing outer peripheral portions, as will be understood from Figs. 4 and 5, to permit winding thereon of a resistor strip is of a suitable material to be traversed by the heating current. The heating elements are made of a size only slightly smaller than the Wells, and the only reason spacing is employed at all is to insure against accidental contact between resistor strip I8 and the surrounding metal of the well wall.

I provide two dielectric sheets or discs l9 and 26 to insulate the electric heating elements from the metal bottom wall of the well and from the metal removable closure discs 54. For heat exchange purposes it is preferable that the electric heating elements with their protective sheets is and 2t be fitted tightly between the bottom Wall of the well and the cover disc.

The terminal leads 2! from each of the heating elements may be made of increased current carrying capacity as by doubling over the end portions of the resistor strand I8, and I prefer to provide a bushing 22 for each terminal lead. I make this bushing of any suitable retractable material which has the characteristics of electric insulation as well as high temperature resistance, since a heating'element of this kind will cause a temperature of the order of 500 F. to 700 F., or even higher. Each bushing 22 is provided with a lower or inner end portion of increased diameter such as possessed by the usual wood screw adapted to seat on one side of supporting element ll. As shown in Figs l and the two terminal leads 2| of each heating element may be located at diametrically opposite points beyond the winding of the resistor element. As will be understood from Fig. 3, apertures are provided in the well cover discs M through which the terminal insulating bushings 22 extend to a pointsomewhat above the upper surface level of the soleplate.

The various heating elements are connected in series, as will be seen in Fig. 2 with the adjacent terminals 2! of adjacent heating elements detachably interconnected to a suitable coupling 23. An insulating strip 24 with suitable apertures ma be slipped over the bushings of adjacent heating elements to lie between the interconnected terminals and the metal top surface of" the soleplate, thereby providing additional 28 which project rearwardly from the back end of the soleplate. The control circuit for the heating elements will ordinarily include an automatic switch, such as 29, which is here controlled by a thermostat 30 housed in a recess 3| in the soleplate between the opposite lines of heating cells and provided with a cover 32.

As will be best understood from Fig. 6 the various heating cells are separated from each other by upstanding portions 33 of the soleplate. Such soleplate portions with the well cover el ments i l form an uninterrupted metal heat conducting surface above all the heating cells, and the entire arrangement is Well adapted to effect efficient and uniform heating of the entire soleplate.

As will be apparent from Fig. l the upper portion of the iron includes a housing 34, and a ventilated handle 35 to which air is conducted from the ventilated rear extension 36 of the housing surrounding housing supporting beams 27 and 28. Housing 34 is supported entirely from such rear support with its lower edge in spaced relation to the front end and side edges of the soleplate. The interior of the housing is thus ventilated to minimize heating thereof. To further decrease heating of the housing 34 by radiation from the soleplate a heat insulating cell comprising a band or strip 31 of a metalor alloy having a relatively high thermal reluctance may be provided, the same generally conforming to the shape of the soleplate and being mounted at its rear end on beams 27 and '2-8.

It will be understood that the form and arrangement of the housing, handle, thermostat, heating cell and the mounting means therefor form the subject-matter of my application, Serial No. 417,437, issued October 8, 1946 as Patent No. 2,408,886, and are here to be considered merely illustrative of the desirable form of sadiron embodying the heating elements of the present invention.

It will be further understood that the form and arrangement of the heating cells and heating elements are merely illustrative of a preferred construction of the invention, and that the scope of the invention is to be determined from the appended claim.

Iclaim:

An electrically heated sadiron including a metal soleplate formed with a series of small laterally and longitudinally spaced wells extending downwardly from the upper side thereof, individual electric heating discs housed in the respective wells, metal cover means closing the upper ends of the wells, insulating bushings extending through the cover means and having enlarged inner ends held by said cover means, and electric connections extending above the soleplate between adjacent heating elements and down through said bushings to connect with the heating elements.

FRANK W. SCHARF.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 872,208 Wiegand a Nov. 26, 1907 930,638 W'hitmore a Aug. 10, 1909 979,291 Happe Dec. 20, 1910 2,024,856 Graham Dec. 17, 1935 2,277,439 'J'eps'o'n r Mar. 24, 192

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