US1767249A - Electric heater - Google Patents

Description

June 24, 19.30. H, v EK|E Er ELECTRQIC HEATER original Fuse Aug. 9. 1920 a sheen-sneu v1,-

smeg@ /fnV////f /z/lll/f/l/ /A c HG2 8 4 INVENTORS l? /6 52 Herbeftv Lnckie AND Wotsun H. Woodford ATTORN EY y 2 t l 8 W/Qs u June 24, 1930. H. v. I EcKu-z E1' AL 1,767,249

ELECTRI C HEATER Original Filed Aug. 9, 1920 FIG. 5

INVENTORS Herbert V. Leckie AND Watson H. Woodford M m f. WW E w mw sm 4 Mm [C wm mw mw uw f ma M w WW mm a M E m@ l mlm .P A Tm. f m .MKNVA June 24, 1930. H. v. LECKIEET AL 1,767,249

ELECTRIC HEATER Original Filed Aug. 9. 1920 3 Sheets-Sheet 3 21 INVENTORS Herbert V. LecKe AND Watson H. Woodford wlTN E55 BY Patented .lune 24 .1930 l UNITED STATES PATENT OFFICE HERBERT LECXIE 0F STBATFOBD, AND WATSON-BL WOODFOBD, OF BBIDGEPORT, CONNECTICUT, ASSIGNOES TO REMINGTON ARMS COMPANY, INC., A CORPORATION ELECTRIC HEATER` Application led August 9, 1920, Serial No. 402,276. Renewed December 18, 1928.

ture of the heater is lautomatically held approximately constant. l Another object is to accomplish this result by the use of a conductor having a high positive temperature coeiiicient in series with a conductor having a very low temperature coefficient, positive or negative. Y

A further object is to provide an electric heater device having a relatively low thermal drop between the heat generating conductor `and the heat consuming snrfacesywhereby the working temperature of the conductor is greatly reduced, making it possible to utilize the cheaper kinds of resistance wire. On this account it will not be necessary to useI such expensive conductors as those made of the Well-known nickel-chromium alloysV which have been specially developed to resist very high temperatures.

A further object is to prevent the heat loss as much as possible by providing those surfaces of such heaters which are notused for consuming heat with a coatinr which will reduce radiation of heat there rom.

These several objects are attained by the construction shown in the attached drawings, wherein the invention isshown embodied in an electric iron. It is to be noted, however, that the invention may find expression in mechanical form in other electric heater de- `vicesas for example, soldering irons, water andkroom heaters, utensils', etc.

In said drawings, l

Fig. 1 is a central vertical sectional'view of "an electric iron illustrating the present invention, the handle .supports and cord supporting spring beingl shown 1n. elevation.

' Fig. 2 is a sectional view on line 2 2 of Fig. 1.

Fig. 3 is a top plan view of the insulating core, the conductor being shown in place.

Fig. 4 is a bottom view of the core, the conductor being shown in place. f v

Fig. 5 shows graphs of resistance and current at different temperatures as shown by experiment.

Fig. 6 is a side elevation of an electric iron provided with a modified form of handle.

Fig. 7 is a front View of the iron of Fig. 6.

Fig. "8 is a sectional view on thev line 8-8 of Fig. 6.

In said drawings the numeral 9 designates a flat core of insulatin material formed with grooves 10 on its top ace for housing a portion of the heat generating conductor C and f having a spiral groove 1,1 on its bottom face for housing the remaining portion of the conductor. The contour of this core generally corresponds to the contour of the particular heater in which it is to'be used. For an electric iron it will have substantially the contour shown in Figs. 3 and 4. This core is preferably formed with a lower fiange 12 and an upper flange 13, extending around its outer rim fora fpur ose to be described later.' This core also pre erably is `formed with a central aperture 14 ofany convenient size and shape, also preferably surrounded by an upper fiange 15 and a lower fiange 16. In order to reta-in the conductor in the grooves 10 and 11Y and to keep them electrically insulated and to exclude air therefrom and thereby prevent oxidation, the spaces between the flanges 13 and 15 and 12 and 16'.

respectively, are filled in with a plastic composition 17 which is a relatively good con- .ductor of heat. This composition will be described later. Thecore and the plastic material 17 with the conductor C imbedded therein forms the heating unit. of the iron or other heater. This unit is surrounded by f the metallic body 1S of the iron, preferably of cast iron, brass, copper or aluminum, thev heating unit being preferably incased in the body 18 by having the body cast around it.y The iron body serves as a heat storing device and its bottom face or sole 18 serves as a heat applying or distributing surface.

The numeral 2O designates a block of in` sulating material carrying terminals 21 to which the covered wires 22 and the heat generating conductors are connected, Figs. 1 and 8J Any suitable means may be employed for covering the connections but it is preferred to utilize the combined connection box and iron stand shown in the drawings. rlhis preferably comprises the box 23 fastened to the top of the iron body by suitable means, the downwardly and rearwardly extending support 24 and the upwardly and rearwardly extending support 25. The top of the box is perforated as at 26 for the electric cord which may, as is usual, be sup-- ported by a coil spring 27 attached to the ox 23 possibly by integral ears 28. rlhe shape of the supports 24 and 25 is such that the support 25 may be formed from material cut from the central portion of the support 24. The supports 24; and 25 form an iron supporting stand on which the iron may be supported when not in use.

rlhe numeral 3Q represents thehandle, at#

tached to the iron body in any suitable way as by the handle strap 31 secured to the iron body by screws 32. vThe part 33 ofthe handle, about two thirds its length from the front end, is of relatively small diameter from which point the handle increases in diameter forwardly to a maximum at 34, near the forward end of the handle. This general shape has been found by experiment to be a great improvement over handles heretofore used. Most of the work of ironing is done by sliding the iron forwardly across the work under considerable pressure. In order that this may be done without undue tiring of the arm and linger muscles, the stronger fingers, first, second and third, should grip the handle at a point where it increases in diameter forwardly. The handle disclosed herein fulfills this requirement and has been found a great improvement. Bearwardly from the point 33 the handle increases in diameter to the point 35. This enables the fourth linger to grip the handle for drawing the iron rearwardly and also prevents the hand sliding against the rear handle strap.

it is desirable to reduce heat losses from electric irons and other heaters as much as possible both for the comfort of the operator and to reduce the cost of operation. To this end and to improve the appearance it has been found desirable to cover those surfaces of the iron or other heater which are not used for applying or distributing heat with a substance 40 which is a poor Conductor of heat and has a smooth preferably white heat refiective surface, which will reduce heat radiation to a minimum. It has been found that ordinary vitrilied enamel forms an excellent coating for this purpose. The finished heater body is coated with the siliceous'or other material generally used for this purpose and it is then baked in an oven Vat a high temperature. The resulting coV- ering is of a good appearance, can be easily kept clean, and, unlike nickel plating, will not be discolored by heat.

Any suitable plastic composition may be used for the core 9, such as Portland cement, asbestos, soapstone, talc or quartz, etc.` with the possible addition of sodium silicate. The selected ingredients are moistened to a proper consistency and pressed into a properly shaped mold and allowed to set.

rl'he imbedding composition 17 must (1) be easily molded and then set; (2) it must be heat conductive; (3) it need not be electrically conductive but slight conductivity is not harmful; (il) it must not give off gases at the casting in temperature, (about 2400 degrees Fahr.) (5) it must not crumble or crack at this high temperature; (6) its coeliicient of expansion should not be excessive so as to enable it to resist sudden changes of temperature.

After extensive research it was found that the following composition met all these diflicult requirements Part by volume Ground slate 1 Baked ground slate i 1 ,Crystolon (silicon carbide fused at a high temperature, made and sold under this name by the Norton Co.) 1

After mixing these ingredients the mixture is moistened by a solution of sodium silicate and, if desired, a small quantity ofy soapstone is added. The resulting mortar is plastered over the core, in the grooves of which the conductor C has been laced. Enough of the incitar' is used to ll the space surrounded by the flanges 12 and 13. These flanges conveniently serve to hold the mortar in position and also to measure the quantity applied thereby assuring units of equal thickness. The resulting units are allowed to dry for a few days and are then baked at a temperature of about 1600 degrees Fahr., the mortar forming a hard, brittle refractory cover for the conductors.

After application of the imbedding compound the heating unit is complete and ready to be cast in. The insulating block 2O is placed in position and the ends C and Cb of the conductor are connected with the terminals 21. These parts are then placed into a mold having the shape of the finished iron and molten metal is poured into the mold and completely surrounds the heating unit. The contraction of the metal in cooling places the incased heating unit under enormous pressure with the result that intimate mechanical and thermal relation is brought about and the possibility of breakage or disarrangement of the parts is entirely obviated. IVhen the casting is removed from the mold the heating element isr enclosed therein. After machining the sole and tapping holes for the screws 32 the iron is ready for its enamel coating and for assembling.

As far as certain of 'the features of the present invention are concerned, anysuitable conductor C may be employed. It is preferred, however, to make use of an improved heat generating conductor the resistance of' which will increase with temperature, i. e.. have a ositive resistance temperature coefficient. p t has been proposed heretofore to secure this result by employing a heating conductor of iron which has a very high positive co-efficient. These attempts were apparently unsuccessful for the reason that not enough space is available in .such electrically heated devices to permit of the use of a sufiicientalength of the proper sized wire; this for the reason that the resistance of' iron is quite low and its permissible working temperature is likewise 10W. Such high Vresistance alloys as nickel-steel, nickel-chromium, etc., have a negligible temperature coefficient' and therefore can not be utilized for regulation. After considerable experiment we have discovered that when iron is used in series with a high resistance conductor the resulting combined` conductor will have sufficient regulating effect while also giving sufficient resistance to enable it to be` placed in the small space available.

In the drawings that part of the conductor C whichlies above the core 9 and designated (l, is preferably composed of a substance having a high positive resistance temperature coefficient, as iron, and the part C2 below the core is preferably of high resistance material having a low temperature coefficient, positive or negative, as for example, nickelsteel, nickel-chromium, orvother suitable alloy. i

Very good regulating effects have been obtained with the two conductors so proportioned that the iron. furnishes 10% of the total resist-ance '(at low temperature) and the high resistance alloy 90 per cent. The iron wire therefore furnishes onlyfa small part of the heat generated. `At low tempel'- atures, Ithis may be only 10 per cent of the total but at high temperatures the total resistance is increased and the regulating wire may furnish as much as 18 per cent ofthe total resistance. These figures are merely illustrative. l i

lFig. 5 shows graphically the regulating effect of iron-wire in series with high resistance alloy wire. By reference to curve A it will be seen that from degrees Fahr. to 500 degrees the resistance was increased about 41 per cent. Curve B sho Ns a corresponding decrease in energy input.

In the construction illustrated the conductors C1 and C2 are in intimate'thermal relation with the body of the iron and the telnpel-ature of the conductors will vary closely with the temperature of the iron body. Therefore, when the iron orl other heater is cold, the resistance is low and a heavy current is drawn so that the heater will be quickly brought up to working temperature. As the temperature rises, resistance increases and if the heater remains idle a point will' soon be reached where the heat input ust equals heat lost by convection, conduction and radiation. As no heat is available for further raising the temperature of the iron the highest temperature has been reached and this temperature will be sustained indefinitely. If, however, heat consumption is increased, as by use of the device, the temperature will be reducedf This lowers the temperature of the iron conductor C, reducing its resistance. `More lieat is developed and the temperature is raised, with the general result that the temperature is held fairly constant in spite of `variations in heat energy consumed.

It has been proposed heretofore to use in series two conductors having respectively, positive and negative resistance temperature coefficients with the object of overcoming the effect of the negative coefficient or for securing a combination conductor having a zero coefficient so that the resistance will not be affected by temperature changes. But a conductor having a high positive temperature coefficient has not to our knowledge been heretofore used in series with a high resistance conductor having a negligible coefficient for the purpose of obtaining a high resistance combination conductor having a high positive resistance temperat-ure coefficient for purposes of regulation.

In order to improve the responsiveness of the regulating conductor C, it has been found Very beneficial to formthis conductor of two strands twisted together shown in Fig. 3. In this way the'surface of the conductor is greatly increased without increasing the total cross-sectional area. This decreases the thermal drop between the conductor and the iron body and therefore increases the responsiveness of the-regulating conductor.

As stated above the core 9 is preferably formed with a substantially central aperture 14. This improves the circulation of the molten metal in the mold`and therefore aids greatly in avoiding blow holes, etc. In the finished iron this provides a tie bar 50 between the top plate 51 and the bottom 52 of the iron which strengthens the iron and increases the heat conduction.

In Figs. 6, 7 and 8 is illustrated a modified form of electric iron. In this form the front handle support is omitted and the handle supported only from@ rear handle strap 60 in cantilever fashion. Tie handle 61 is isa supported on a tie rod G2 attached to the strap preferably by riveting. The handle is slid over the rod and fastened in place in any suitable way as by a holding screw 63. The shape of the .handle is preferably substantially the sar-.ie as the handle shown in Fig. l. This construction has been found a great improvement as it permits of entering almost the entire iron into sleeves and other openings of the clothing being ironed. 1n the case of the forms heretofore used this was prevented by the front handle strap. Another advantage is that the danger of burns due to the fingers coming into contact with the front handle strap is entirely' absent. A further advantage is that such a handle may be grasped so that its forward end lies against the palm with the fingers extending rearwardly. This position is of advantage in certain operations and greatly reduces fatigue due to the choice of different positions of the hands and fingers.

The strap 60 is widened out at its lower part and preferably bifurcated as shown in Figs. 7 and 8. The bottom ends are bent laterally to provide feet 64 bearing on the iron body and attached thereto by screws 65. These screws may also be utilized to Secure the connection box 23 in place by having ears 23 formed thereon and overlying the feet 6a and formed with holes to receive the screws 65.

The construction shown 1n the drawings and described herein illustrate the application ofthe present invention to electric irons. It is to be understood, however, that many of the features thereof are applicable to electric heaters in general and that others can now by applying current knowledge adapt this invention to other physical applications thereof without omitting certain features that, in view of the present condition of the art, fairly constitute essential characteristics of the generic or specific aspects of this invention7 and therefore such adaptations should and are intended to be comprehended within the vmeaning and range of equivalency of the following claims:

l. An electrically heated device comprising in combination a heat storing and applying body and a resistance for heating said body, comprising a high resistance conduc-4 tor having a very low positive resistancev temperature coeiiicient and a regulating conductor` in series therewith having a; high positive resistance -temperature, coeicient.

2.v An electrically heated device comprising in combination a heat storing and applying body and a resistance for heating said body,-a high resistance conductor having a very low resistance temperature coeicient and a regulating conductor in series therewith having a high positive resistance temperature -coeflicient, both conductors being adjacent to said heat storingand applying body, and connected therewith by short heat conducting paths of relatively great cross sectional area.

3. An electrically heated device comprising in combination a heat storing and applying body and a resistance .for heating said body, comprising a high resistance metallic conductor having a negligible resistance temperature coefficient and a regulating conductor in series therewith having ahigh positive resistance temperature coefiicient.

4. A resistance conductor comprising in combination a conductor of nickel-steel and a regulating conductor of iron in series therewith.

5. An electrically heated device comprising in combination a heat storing and applying body and a resistance for heating said body, comprising a nickel-steel conductor and a regulating conductor of iron in series therewith.v

6. An electrically heated device comprising in combination a heat storing and applying body and a resistance for heating said body7 comprising a high resistance metallicV tor in series therewith having a high posi-,

tive resistance temperature coefficient, said regulating conductor comprising a plurality of strands in parallel.

f 7 In -an electrically heated device, a relatively flat insulating core having a contour corresponding to the contour of the device, an aperture in said core, a series of grooves in each face of said core surrounding said aperture, a heating conductor in one of said series of grooves, and a regulating conductor in the second series of grooves.

8. `In an electrically heated device, an insulating core having a contour corresponding to the contour of the device, an aperture in said core, a groove in the upper side lof said core surrounding said apertu1e,\a continuous heating conductor in said groove, a`spiral groove in the lower face' of said core, a/continuous conductor in said spiral groove",` said conductor being connected in series with the' continuous conductor in the first groove.

9. An insulating core for heating units of an electrically heated device, comprising\a relatively fiat body of insulating material having a contour corresponding to the contour of such device, a series of grooves in the a series of grooves formed in the upper sur-A face of said core upwardly extending ribs ,separating the grooves of said series, a second series of grooves formed in the lower surface of said core, downwardly extending ribs separatin g the grooves of said second series, upwardly and downwardly extending flanges projecting beyond said ribs, and a` heat storing and applying body surrounding said core and filling the aperture therein.

11. In an electric heater, an insulating core comprising a relatively flat body of insulating'material having a contour corresponding to the contour of the heater, a central aperture in said core, upwardly and downwardly extending flanges surrounding said core and said aperture and a heat storing and applyvtourof the heater', grooves formed in said ing. body surrounding said core and filling said aperture. l

f 12. A heating unit for electric heaters comprising in combination an insulating core having a contour corresponding to the concore, outwardly projecting ribs separating said grooves, a flange surrounding said core integral therewith and projecting outwardly beyond said ribs, a heatgenerating conductor in Said grooves and a plastic heat conducting composition covering said conductor and said grooves and filling the space within said flange.

13. A heating unit for electric heaters compri sing in combination an insulating core having a contour corresponding to the contour of the heater, grooves formed in the top and bottom faces of said core, ribs separating said grooves, a heat generating conductor in said grooves, upwardly and downwardly extending flanges surrounding said core and extending beyond said ribs and a heat conducting composition covering said conductor and said. ribs and filling the space bounded by said flanges.

14. A heating unit for electric heaters comprising in combination an insulating core having a contour corresponding to the contour of the heater, a central aperture in said core, a groove formed in said core extending around said aperture, a heat generating conductor in said groove, a flange extending I around said core, a flange surrounding said aperture, said flanges forming a recess above sald groove and a heat conductlng vcomposition covering the conductor 1n sa1d groove and filling the recess' bounded by saidflanges..

15. A heating unit for electric heaters comprising in combination an insulating core having a contouricorresponding to the contour of the heater, a central aperture in said core, grooves formed in the top and bottom faces of said core around said aperture, a heat generating conductor in said grooves, upwardl and downwardly extending flanges surroun ing said core and aperture, said flanges forming recesses over Sald gIOQYeS,

and a heat conducting composition covering the conductor in said grooves and filling .the recesses bounded by said flanges.V

16. In an electric heater, a heating unit comprising in combination an insulating core having a contour corresponding to the contour of the heater, grooves formed in said core, ribs separating said grooves, a heat generating conductor in said grooves, a flange surrounding. said core 'and extending outwardly beyond said ribs, a heat conducting composition covering said conductor and said ribs and filling the space bounded by said flange, and a heater. body surrounding said unit, and in close contact therewith.

17 .In an electric heater, a heating unit comprising in combination an insulating core having a contour corresponding to the contour of the heater, grooves formed in the top and bottom faces of said core, ribs separating said grooves, a heat generating conductor in said grooves, upwardly and downwardly extending flanges surrounding said core and extending beyond said ribs, a heat conducting composition coveringfsaid conductor and said ribs and filling the space bounded by said flanges, and a heater body surrounding said unit and in close contact therewith.

18. In` an electric heater, a heat-ing unit comprising an insulating core having a contour corresponding to the' contour of the heater, a central aperture in said core, a groove formed in said core extending around said aperture, a heat generating conductor in said groove", a flange extending around said core and a flange surrounding' said aperture,`

a heating unit comprising an insulating core A :having a contour corresponding to fthe contour of the heater, a central aperture' in said core, spiral grooves formed inthe top and bottom faces of said core around said aperture, a heat generating conductor in said grooves, upwardly and downwardly extending flanges surrounding said core and aperture respectively and forming recesses over said grooves, a heat conducting composition covering said conductor and filling the recess bounded by said flanges, and a heater bod'y filling said aperture and surrounding said unit in close contact therewith.

20. An electric heater comprising a heat storing and applying body having cast therein a heating element comprising a core of insulating material having a contour corresponding to the contour of the heater, a central' iso .esv

core and said. aperture and forming conductor containing grooves.

21. An electric heater comprising a heat storing and applying body having cast therein a heating unit comprising an insulating core having a contour corresponding to the contour of the heater, grooves formed in said core, ribs separating said grooves, a heat generating conductor in said grooves, a flange surrounding said core and extending outward beyond sai ribs, and a heat conducting composition covering said conductor and said ribs and filling the spaces bounded by said flange. v

22. A n electric heater comprising a heat storing and applying body having cast therein a heating unit comprising an insulating core having a `contour corresponding to the contour of the heater, a central aperture in said core, grooves formed in the upper and lower faces of said core around said aperture, ribs separating lsaid grooves, a heat generating conductor in said grooves, upwardly and downwardly extending flanges surrounding said core and aperture and extending outwardly beyond said ribs to form recesses over said grooves,and a heat conducting composition covering the conductor in said grooves and filling the recesses bounded by said flanges.

. HERBERT V. LECKIE.

WATSON H. WOODFORD.

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