US2668897A - Smoothing iron - Google Patents

Description

Feb. 9, 1954 J. H. BEACH ET Al.

SMOOTHING IRON Filed Jan. 6, 1949 f muhlllsli. Q

I VENT Bea Va A TORNEY Patented Feb. 9, 1954 SMOOTHING IRON Justice H. Beach and John E. Vance, Canton, Ohio, assignors to The Hoover Company, North Canton, Ohio, a corporation of Ohio Application January 6, 1949, Serial No. 69,496

7 Claims. (Cl. B19-25) The present invention relates to the art of smoothing irons and more particularly to an improvement in the control mechanism for electric heaters for such devices.

Automatic controls for electrically heated smoothing irons have been developed to a high degree, but their control range is wide because of the heat conduction problem throughout the area of the ironing sole plate and to the thermostat. This problem is particularly aggravated in irons of the type in which the sole plate is heated by a cast-in rod type heating element. In irons of this type the thermostat is necessarily rather remote from the heating element, infact it generally is in contact with one of the least well heated portions in the ironing sole plate. As a result of these conditions the iron .sole plate temperature tends to overshoot the control point to an extraordinary degree on the first heating cycle of the iron during any period of use and to a large degree during subsequent heating periods.

It is an object of the present invention to provide a control mechanism for an electrically heated smoothing iron provided with an auxiliary heat conducting element which aids in conducting heat from the heating element to certain presently not too well heated portions of the sole plate and to the thermostat in order to provide better heat distribution in the sole plate and more accurate and reliable control of the sole plate temperature by the thermostatic mechanism.

It is a further object of the present invention to provide an iron of the type embodying a sole plate vwith a cast-in rod type heating element which has additionally a cast-in element of high heat conductivity arranged to conduct heat directly from the heating element to certain selected portions of the sole plate and to the control thermostat mount.

Other objects and advantages of the invention will become apparent as the description proceeds when taken in connection with the accompanying drawing in which:

Figure l is a side elevational view partly in section of a smoothing iron embodying our invention;

Figure 2 is a sectional elevational view of the sole plate and heat conducting element shown in Figure 1; and

Figure 3 is a fragmentary plan view of a portion of the heat conducting element.

Referring now to the drawing in detail and rst to Figure 1 thereof, there is illustrated a l.

smoothing iron which embodies a cast aluminum alloy sole plate I having on its upper surface a generally V-shaped ridge 2 in which is cast a rod type electric heating element 3. The sole plate is conventional in shape, that is, pointed in front rounding to a wide rear end. The heating element is generally U-shaped roughly paralleling the perimeter of the sole plate except at the rear where it terminates in conventional electrical connecting terminals. As shown most clearly in Figure 1 the iron also embodies a cover shell 4 overlying the sole plate and secured thereto by a known means, not shown, which forms no part of the present invention. A manipulating handle structure 5 is secured to the cover shell and sole plate assembly. A temperature control dial 6 is positioned between the handle legs.

As shown most clearly in Figures 2 and 3 a thermostatic switch mechanism 1 is mounted upon the sole plate by a securing bolt 8 and is arranged to be adjusted by a shaft mechanism 9 which carries and is operated by the manipulatable control dial 6. y

The switch mechanism 'I comprises electrical contact blades I0 and II of a spring material normally biased into engagement with each other. Underlying the lower blade II there is a bimetallic thermostat I2 which carries an operating button I3 on its end to contact the lower face of the upper blade IU for opening and closing the electrical circuit controlling the heating element 3 as the thermostat I2 exes upwardly and downwardly, respectively. The thermostat structure 'I and 8 per se forms no part of the present invention but it is of a known type in which the blades I0 and II are electrically insulated from each other and from the other parts of the apparatus.

As shown most clearly in Figures l and 2 the thermostat structure is positioned in the central rear portion of the sole plate between the side runs of the rod type heating element 3 so that it is comparatively remote in a thermal sense from all portions of the heating element. A heat conducting element I4 is cast into the sole plate I and extends transversely thereof. The end portions I5 of the heat conductor are wrapped substantially around the side runs of the heating element 3 and are preferably brazed or otherwise secured thereto to insure an excellent thermal bond between the heat conductor and the heating element. The heat conductor includes a central portion I6 which lies above and in contact with the upper surface of the sole In the operation of the foregoing device rota-A tion of the dial 6 raises and lowers the shaft 9 in a known manner which in turn raises and low-A ers the spring contact element "Hv relative to the sole plate and hence raises andv lowers the point at which the electrical circuit -can -becom-- pleted by the contact elementsy I@ and Il. In

this manner the points at which the switch is opened and closed by operation of the thermostat l2 are varied and the soleplate temperature is varied accordingly.

The objectionable features of priorl constructions in which the thermostattends dangerously to overshoot the control point during an initial heating cycle and to control thereafter in a wide temperature range have been found Vto be very materially improved by the present` construction. The heat conductor Hl is preferably made of copper and is brazedto-the heating element 3 hence there is provided a direct path from the heating element to the thermostat heating assembly having a very high conductivity.l Considerable heat is dissipated from the copper strip finto the body of'the sole plate-between the thermostat andthe heating element. l This however is an advantageous anddesirable feature because this portion of the sole plateis vthe most difficult tov'heat andtends lnaturally yto llag somewhat behind portions which are closer to theheating element. The improved heat conducting path between the heating elementrand the thermostat has been found by experiment to decreasethe initial overshoot Very materially landto maintain the thermostat in closer accordance with the sole plate resulting avnarrower cycling variation in -sole plate temperatures vfor any particular control dial setting. The heat conducting element herein disclosed performs the -dual function-of aiding'the heating of a diicult to heat part of the sole plate and also in conducting heat into the thermostatic element at a rate suilicient to insure that the same accurately reflects sole plate temperature under all operating conditions.

The copper heat conducting element may have an insulating coating on selected parts thereof in order to inhibit the heat `flow into areas of the sole plate which are adequately heated directly. Such a coating can be applied, for example, by dipping the copper strips in sulphuric acid prior to assembly to form a sulphide coating thereon. The coating may then be ground oif areaswhere it is undesirable. The need for such a coating depends upon the weight of the particular heat conductor and also upon the detail design of the particular sole plate.

The invention has been illustrated and described herein as applied to a sole plate embody'- ing a concentrated type heating element embedded in the sole plate and ocooperating with a heat conductor having direct heat exchange relation with the heater and thermal control. As used herein, the term, concentrated heating element, means one in which the area of theheat'- ing structure per se is appreciably less than the area of the sole plate, and the heating element directly contacts only a portion of the sole plate area. The expression, direct heat transfer, as used herein, means that the elements in direct heat transfer relation are either in contact or in such relative proximity to each other through an intermediate. heat conducting device that there is no substantialheat flow resistance between them.

The invention herein is applicable to types of concentrated heating elements other than the rod type illustrated in the drawing. It is within the scope of the-invention to embed the heating "element -in the sole'plate in other ways than that illustrated or to utilize a heating element which is merely pressed into contact with one surface of the sole plate. The heat conductor may be completely embedded in the sole plate and pass under the thermal control base close to the surface of the sole -plate if desired; for'some ,iron constructions this arrangement -provides sutilcient heat conductionl to the thermal control and is desirable from a construction standpoint.

While we Vhave illustrated and described the invention in considerable detail, it isto be under,- stoodl that various changes may be made linthe arrangement, proportion andi constructionv of parts without departing from the spiritof. the invention or the scope ofthe appended-claimen We claim: l

1. A smoothingiron including-,a solexplatef-a rod typeelectrical heating element `cast intosaid sole plate, a control. structure v for governing' 'the energization Vof said heating` element-including@ heat responsive device 4positioned yremotely from said heating element, vanda Aheat. conductormof materialwhaving a lhigher.heatfcomiuctivity than the vmaterial of/said'soleplate having-one. portion thereofv in direct7 thermal .-contact s with said heating ,element and another portionin i*direct heat conducting relation with said-heat responsive device.

2. A smoothing ironiincluding a `sole plate, a rod type electrical heating-l element cast into lsaid sole plate, a -heatY conductorv of material l.having a higher heat conductivityv than the material of said sole plate having a portion -cast in saidsole plate in direct thermal-contact with `said :heating element and another portion removed from said heating element in contact with saidisole `plate and having an exposed surface, va control structure for governing the energization of said heating velementincluding.a -heat responsive operative device, and means'lforsecuring lsaid ycontrol structure to saidsole platein engagementwith the exposed surface of saidheat-conductorf 3. A smoothingA iron including ea sole"plate, a concentrated heating element embedded infsaid sole plate, a control structure including a thermal element for governing said heating elementpositioned vremotelyfrom the portionA of-said `sole plate in which saidheating element is embedded, and a copper heat conductor .having one 4part thereof in direct thermal Contact withIsaid em;- bedded heating element-and another part-thereof in direct thermal con-tact withlsaid. control structure.

4. A smoothing'iron including'asole plate, a

-concentrated'heating element embeddedin said sole plate, a control structure including-a thermal element forl governing-said vheating element positioned remotely from-the .portion of saidsole plate in which said heating element isy embedded.

.fand-'a copper heatvconductor `havingone part thereof in direct thermal contact with said embedded heating element and another part thereof in direct thermal contact with said control structure, and a heat iow resistant coating on those portions of said conductor not in Contact with said heating element and said control structure.

5. An iron including a sole plate, an elongated rod type heating element embedded in said sole plate, said heating element having spaced apart portions substantially paralleling the side edges of said sole plate, a control structure including a thermally responsive element for governing the operation of said heating element positioned between said spaced apart portions of said heating element, a heat conducting element having a higher heat conductivity than said sole plate having parts thereof embedded in said sole plate and in direct thermal contact with said spaced portions of said heating element at its ends, the central portion of said heat conducting element lying on the surface of said sole plate in direct thermal contact With said control structure.

6. A sole plate for smoothing irons comprising a metal body portion, an elongated rod type heating element embedded in the metal of said sole plate, and a heat conducting member having a higher heat conductivity than the metal of said body portion, said heat conducting member having a part embedded in said body portion embracing and in direct thermal contact with said heating element and a part removed from said heating element having a surface exposed above said body portion.

7. An iron including a sole plate, an elongated rod type heating element embedded in said sole plate, said heating element having spaced apart portions substantially paralleling the side edges of said sole plate, a control structure including a thermally responsive element for governing the operation of said heating element positioned between said spaced apart portions of said heating element, a heat conductor constructed of material having a higher heat conductivity than the material of said sole plate, said heat conductor having end portions embedded in said sole plate and partially embracing the spaced apart portions of said heating element and a central portion contacting said sole plate and having a surface exposed above said sole plate, and means for securing said control structure to said heat conductor in contact with the exposed surface thereof.

JUSTICE H. BEACH.

JOHN E. VANCE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,764,301 Harpster June 17, 1930 2,148,407 Pierson Feb. 21, 1939 2,257,451 Barnes Sept. 30, 1941 2,320,013 Scharf May 25, 1943 2,328,152 Kuhn et al Aug. 31, 1943 2,333,521 Clark et al. Nov. 2, 1943 2,362,591 Smith Nov. 14, 1944 2,372,270 Happe Mar. 27, 1945 2,396,238 Beck Mar. 12, 1946 2,427,379 Ashbaugh Sept. 16, 1947 2,475,572 Schreyer July 5, 1949 2,485,664 Scott Oct. 25, 1949 2,506,941 Scott May 9, 1950

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