US2222192A

US2222192A - Flatiron

Info

Publication number: US2222192A
Application number: US234628A
Authority: US
Inventors: Edwin E Arnold; William J Russell
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1938-10-12
Filing date: 1938-10-12
Publication date: 1940-11-19
Anticipated expiration: 1957-11-19
Also published as: CH216669A; BE436638A; GB532844A; FR860344A; NL59864C

Description

Nov. 19, 1940. E. ARNOLD ETAL 2,222,192

FLATIRON Filed Oct. 12, 1938 Patented Nov. 19,

omen STATES PATENT OFFICE FLATIRON Application October 12, 1938, Serial No. 284,828

4 Claims.

Our invention relates to electrically heated devices, and particularly to fiatirons, or the like, having recesses therein for the reception of ceramically insulated heating elements.

While the mere inclusion of a helical heating element within an elongated heater recess or slot positioned within the sole plate of a flatiron and suitably insulated therefrom has previously been proposed, the present heating unit assembly is considered to embody valuable and important improvements thereover for the reasons set forth below.

First considering a helically wound resistor or heating element positioned within a heater slot, such heating element cannot produce a sufiicient wattage and ironing heat for the presentday requirements of the housewife, inasmuch as the size of the wire used in such element in order to provide the necessary total ohmic resistance, is necessarily relatively small. If it be desired. to increase the size of the wire used in such helical heating elements so as to produce an element providing the desired wattage, the diameter of such wire becomes relatively large and of insuflicient electrical resistance to permit direct connection across the ordinary domestic supply circuit. Upon making such a coil of increased diameter, in order to overcome this detect, it is evident that a relatively wide trough or slot would be required within the iron, a feature which cannot be employed in an iron of ,ordinary size because of the necessity of assembling other apparatus therein, such as a thermostat.

In addition, such a wide heater slot necessitates expensive cover plates of corresponding or greater width which have a tendency to warp in usejthus exposing the insulating medium and resulting in its deterioration. Furthermore, in such a wide slot structure substantially one-half of the heat is radiated or conducted upwardly, that, is, in a non-useful direction, requiring special heat insulation to prevent overheating the user's hand.

To overcome the disadvantages of a single helical resistance element, it has been proposed to use two helical elements, one above or alongside the other. Such methods, while permitting a certain limited increase in the wattage of such resistance unit as a whole, does not permit full radiation from such resistance element on account of the insulation space inherently present k the use of two side-by-side coils necessarily involves a relatively wide slot, the disadvantages of which have been set forth above.

Consequently it will be appreciated that the prior art was handicapped by serious disadvantages which materially limited the overall delivered heat in flatirons of normal size.

Various metallic covers or cover plates have been devised for mechanically protecting and increasing the thermal efliciency of an iron using heating elements as hereinabove described.

It has been proposed, among other things, to use cover plates initially wider than the groove or heater slot which, in some cases, may have tapered side walls. Such cover plates are in the form of hollow troughs or channels and, upon being pressed downwardly within the slot, their upwardly extending flange portions contact such side walls at acute angles. The friction of such anguiarly related flanges on the walls thus constitutes substantially the only means for retaining the cover plate within the heater-slot. Such construction permits the cover plate to loosen, thus exposing the insulation. 1 It has also been proposed to use inverted channel-shaped cover plates, which have down wardly extending flanges. In such a case, these smooth flanges have even less frictional contact with the side walls, and are forced to rely mainly on their bond with the insulating material to retain their desired location. p

A further disadvantage of such proposed cover plates is that in some instances they are necessarily placed in position before the cementitious insulating material has hardened. In other words, a bond between the cementitious insulating material and the cover plate is used to retain the plates in position. This method of retaining the cover plates is very ineflicient inasmuch as such bond is readily broken when the iron is 40 jarred or bumped.

In an attempt to overcome this disadvantage, it has been proposed to increase the initial pressure upon the plates. However, due to the insulating material being soft, there is the serious danger of shifting the heating coil or soft insulation, which causes short-circuits between adjacent portions of the element and the walls of the slot.

Consequently it will be appreciated that, in addition to the diflicuities, and disadvantages of the prior art heating elements, as set forth above, the art has been handicapped by serious disadvantages in the cover plate structure.

Inv order to overcome all of the dimculties set 2 1 i/ a,aaa,ioa

forth above, and provide a fully satisfactory natironofnormalsiseba'vingrelativelyhishdeintegral with the base. This construction affords ashort. high-capacity metallic path for effecting a maximum delivery of heat. The width of the element is governed by the permissible width of the slot which is usually considerably narrower than its height.

The heating element and insulating material 15 are mechanically protected and retained'within the slot by means of an upwardly arched clamping plate which is initially narrower than the slot. The plate upon being subjected to sufiicient pressure, flattens or straightens out and forms an intimate metal-to-metal bond or union with the side walls of the slot while further compacting the previously separately hardened insulating material and forcing it to make an intimate bond or union with the slot side walls and the cover plate.

One obiect of our invention, therefore. is to provide a flatiron having an exceptionally efflcient ellipticalor substantially rectangularsectioned high-wattage heating coil positioned ,0 within a relatively narrow elongated heater channel or slot and insulated from the walls thereof by means of a suitable refractory or cementitious material in intimate contact .with said walls.

A further object of our invention is to provide a cover plate for heating elements of the type set forth, which wilf form an intimate metal-tometalbondorunionwiththewallsoftheheater slot. a

A still further object of our invention is to provideanatironhavingaslottedsoleplatewithan ellipticaily coiled heating element insulatedly disposed therein and an initially arched cover plate therefor, initially narrower than the slot, horisontallyensll nithesidewallsofsuchslottc lowing description of a device embodying our invention,orwillbeapparentfromsuchdescrip- In the accompanying drawing: Figure 1 is a side elevational view of the completed iron embodyins my invention;

Fig. 2 is a perspective view of the sole plate and heating element associated therewith;

Fig.3is a sectional view takenalong theline m-m of Fla. 2:.

. l 'lgasandoareenlargedfragmentarysectionsl views similar to Fig. 8, showing the cover plate in its various positions;

Fig.6isanenlargedfragmentarysecti view similar to Fig. 3, showing the metal-to-metal '0 bond between the cover plate and the slot; and l'ig.'lisasectionalviewilhistratingapimchpress structure forforming the cover plate.

. Referring to the accompanying drawing, we

showaflatiron ilcomprisingasoleplate l2,a main cover It andahandle it. Thesoleplate n (i -id a) has a channel-likeslot ll extending aroundthesoleplatenearitsedgeasoastodeme a ushiy triangular central recessed area 2. whichisadaptedtoretainathermostatic switchlhsuchasthatdescribedandclaimdina I copending application of I. K. Clark, Serial No. 237,270, filed October 2'1. 1988, and assigned totheassignee ofour present application. A heating element 22 is surrounded and supported within the slot II by insulating material ll, 1. which is retained therein by a clamping cover iplate ll. as hereinafter described. J

The sole plate I! is preferably formed from a cast material which, due to the processor cuting, produces a rough exterior surface. This roughened surface is easily ground and polished to make a suitable working ironing surface. However, the narrow slot It. being formed integrally .with the sole plate. also has a roughened sandiikewallwhichaidsinretainingthecoverplate 28 within the slot II, as hereinafter described.

The slot It is formed primarilyby the metallic upwardly extending portions or walls It of the sole plate It. These portions being formed of a heat conducting metal integral with the sole plate, readily and witha maximum eiilciency. conduct the heat produced within the slot II to the working surface of the sole plate.

The heating element 2! in our structure is formed of a suitable electrical resistance wire into substantially an elliptical or rectangular coiled element, with the longer sides thereof substantially parallel, as shown in Pig. 8. mils structure permits the elongated substantially parallel sides of the heating element to be positioned relatively close to the side walls of the slot ll. with the heating element formed in such a manner. it is obvious that substantially all of the heat developed thereby will be readily and eiiiciently conducteddirectlytothesidewallsoftheslot and will have to penetrate a minimum average thickness of insulation. In other words, there willt not be an inenicient centrally located hot 890 Th heating element 22 is insulated from and supported within the slot II. w th its maior asis extendinginthedirectionoftheslotdeptmby meansofasuitablecementitiousorceramicreof E. K. Clark, serial No. 257,167, filed liebruary 18,l939,andassignedtotheassigneeofour present application. This method permits the insulating material 24 to be positioned about and withintheheatingelementsoastoformasolid homogeneous mass. This heating structure, formed in accordance with the above-identified application, is positioned within the narrow not It as a imit to form a suitable efficient heating element for the ilatiron. The cover plate II is then positioned over the heating element structureandincloserelationtheretoforrigidlyretainingsuchstructurewithintheslot il,ashereinafter described.

The metallic cover plate It is preferably formed fromasinglesheetofmetalsoastohavean initialcrosssectionnarrowerthantheslctil with substantially the same general configuration as the slot. The cover plate is given an initial arch or convex upward curvature (a downward curvature in the punch-press. see Fig. 7) before beinginitiallyseveredfromthestock. 1

to Fig. '7 of the drawing, it will be seen that the die 30 of the punch press, operating within the hold-down plate 22, is formed so as to stretch or shape the plate 26 into an arched position before shearing it from the initial stock plate 3|. The cover 26 then retains the initial arch formed therein and remains narrower than the slot l8. The cover plate 26, being narrower and of substantially the same general configuration, is then easily placed within such slot upon the ceramic heating element assembly.

The cover plate 26 is preferably formed as a single solid unitary member. However, if it be desired, the plate may have a series of staggered transverse notches therein to permit more ready expansion and contraction thereof.

In assembling the iron embodying our invention, the sole plate i2 is originally cast, leaving the roughened narrow slot i6 which is substantially narrower than its height. The elliptical heating element 22, being formed substantially the same width as the slot l8 and suitably insulated by a method as described by E. K. Clark in his aboveidentifled copendlng application, is then positioned within the slot IS with the parallel sides thereof being positioned close to and parallel with the side walls of the slot l8 so as to be in direct thermal communication with the sole plate l2.

The cover plate 26, initially formed narrower than the slot l8 and having an upwardly arched cross-section, is then positioned within the slot l8 upon the insulated heating element structure as shown in Fig. 4, after hardening of the insulation. A suitable pressure device, not shown, substantially the same general shape as the slot I8, is then positioned upon the cover plate 26 and pressure applied thereto. Inasmuch as the pressure-applying device is substantially the same shape as the slot l8, such pressure applying device will apply a uniform pressure to the cover plate 26 throughout its entire length. In addition, as the cover plate 26 is arched or convexed upwardly, the pressure applying device will then cause the cover plate to become broken-arched or to straighten out. During this action, the cover plate will first be retained within the slot by cooperating with the solid insulating material 24, and will then engage the side walls of the slot l6. As the outer edge of the cover plate 26 engages the roughened side walls of the slot l8, the friction therebetween will limit the downward movement of the cover plate.

In addition to the friction between the side walls of the slot I B and the edges of the cover plate 26, the lower corners of the cover plate edges will bite into the side walls, as the cover plate starts to straighten out. With the con-- tinued application of pressure the cover plate 26 will tend to completely straighten out (see Fig. 5), causing the edges of such plate to emboss themselves into the contour of the slot walls as clearly shown in Fig. 6. By embossing we mean that the edge surface of the cover plate will conform to and engage with the irregular surface of the side walls, such as shown in Fig. 6, thereby forming an intimate metal-to-metal bond or union.

In addition to the edges of the cover plate embossing themselves into the contour of the slot walls, such plate will fill the bite" originally formed in the walls as the plate started to straighten out. In other words, there'will be a small substantially triangular portion 35 (see Fig. 6) of the cover which will extend into the slot side walls. The vertex of this triangular portion will be at the top. Accordingly, with the cover plate extending and embossed into the slot side walls, it will be practically impossible for such cover plate to be removed from the slot, let alone being Jarred loose, due to normal usage.

After the cover plate 26 has been brokenarched or straightened, the edges thereof will thus have an intimate metal-to-metal bond therewith. This bond between the cover plate 26 and the slot side walls is of such a character that it hermetically seals such slot to afford full protection for the heating element 22 and insulating material 24.

This broken-arch or straightening out method of forming a metal-to-metal bond permits us to use a cover plate of substantial thickness which in itself will be a good heat conductor, ensuring a maximum thermal efllciency for the fiatiron, as hereinafter described.

When pressure is applied to cover plate l8 tending to straighten it out, such pressure is imparted to the insulating mass 24. This pressure thus causes the initially hardened insulating material to be further compacted. .During this periodfin which the insulating material is being compressed and before the cover plate bites into the slot side walls, such insulating material is forced to conform to the irregular surface of the slot walls. In other words, the insulating material will be compressed into a homogeneous mass with an intimate bond or union with the slot walls and bottom. This intimate union or bond thus ensures a maximum thermal conductivity between the insulating material and iron sole plate.

The elliptical or substantially rectangular heating element 22 embodied in our invention permits the application of pressure upon the insulating material without any danger of shifting resistors and the consequent danger of short circuits therebetween. In addition, the fact that the elliptical or substantially rectangular heating element 22 is initially set in its illustrated position, surrounded by hardened ceramic insulation, it follows that the element 22 will not shift toward either slot side wall or bottom during the homogenizing of the insulating material.

t, therefore, follows that the elliptical or substantlally rectangular shaped heating element 22 permits full direct radiation and conduction of heat to the heater slot side walls so as to effect a maximum delivery of heat to the operating surface of the fiatiron, through the cooperation of the metallic slot side walls. In addition, it is obvious that the clamping plate 26, which is initially narrower than the slot l8, upon being subjected to sufilcient pressure, expands or straightens out and forms an intimate embossed metal-tometal hermetically sealing bond or union with the side walls of the slot.

It is further obvious that due to the intimate metal-to-metal bond between the relatively heavy cover plate and the slot side walls, such cover plate will readily conduct the heat which would be radiated upwardly if it were not for the cover plate bond, to the slot side walls. This narrow cover plate structure in combination with the homogeneous insulating mass and substantially rectangular heating element thus ensures a maximum thermally efficient flatiron.

Various modifications may be made in the device embodying our invention without departing from the spirit and scope thereof, and we desire, therefore, that only such limitations shall be piacedthereonasareimposedbythepriorart and the appended claims.

We claim as our invention:

1. A iiatiron comprising, in combination, a sole plate having formed therein a slot, an electrical heating element disposed within and insulated from the inner walls of such slot, and a tieaily coiled electrical heating element disposed within the slot, insulating material surrounding and retaining the element therein, and a we! plate therefor, initially narrower than the slot. engaging the side walls in a plane substantially normal thereto.

4. A ilatiron comprising, in combination, a sole plate having iormed therein a slot oi greater depth than width. an elliptieally coiled electrical heating element disposed within the slot with the major axis thereof positioned substantially normaltothebaseandparalleltothesidewalls oi the slot. insulating material surrounding the element and supporting it within the slot. and a cover plate therefor, initially narrower than the slot. broken-arched into a metal-to-metal bond with the side walls of the slot.

EDWIN E. ARNOLD.

WILLIAM J. RUSSELL.