US2442659A - Surface heater for electric ranges - Google Patents

Description

June 1, 1948. F. H. M CORMICK SURFACE HEATER FOR ELECTRIC RANGES Originl Filed July 5, 1940 '4 Sheets-Sheet l June 1, 1948.

F. H. M CORMICK SURFACE HEATER FOR ELECTRIC RANGES 4 Sheets-Sheet 2 Original Filed July 5, 1940 88 86 ea 92 /05 K22 June 1, 1948. MCCORMICK 2,442,659

SURFACE HEATER FOR ELECTRIC RANGES Original Filed July 5, 1940 4 Sheets-Sheet 3 HHHLHH HHHH INVENTOR.

qhAglk e-w June 1, 1948. F. H. M CORMICK SURFACE HEATER FOR ELECTRIC RANGES 4 Sheets-Sheet 4 Original Filed July 5, 1940 F iy 9.

Patented June 1, 1948 UNITED STATES PATENT OFFICE SURFACE HEATER FOR ELECTRIC RANGES Francis H. McCormick, Oakwood, Ohio, assignor to General Motors Corporation, Dayton, Ohio, a corporation of Delaware Original application July 5, 1940, Serial No. 344,018, now Patent No. 2,320,041, dated May 7 25, 1943. Divided and this application March 19, 1943, Serial No. 479,689

Claims. 7 V 1 This invention relates to a domestic appliance and more particularly to surface heaters for electric ranges.

This application is a division of my copending application Serial No. 344,018, filed July 5, 1940, forDomestic appliance (Patent 2,320,041, granted May 25,1943) 7 It is an object of -m invention to provide a surface heater of the tubular sheath type in which the upper surface of the sheath is held rigidly in a single plane.

It is another objectof my invention to provide an arrangement for a surface heater of the tubular sheath typewhereby the heater can be readily cleaned without disturbing the electrical connections.

It is another object of my invention to provide an arrangement of a surface heater of the tubular sheath type in which the terminal connections are adequately shielded from spillage.

It is another object of my invention'to provide aterminal member for a surface heater in which theterminal connections are so located as to be protected from spillage.

It is still another object of my invention to provide a surface heater of the tubular sheath type in which the sheath is very small in diameter so that it may bemore readily formed into the desiredrconfiguration in order to obtain the desired heat distribution.

It is another object of my invention to provide a two-element surface heater of the tubular sheath type having an improved configuration to provide improved heat distribution.

Furtherobjects and advantages of the present invention will be apparent from the following description, reference being had to the accompanylng drawings, wherein a preferred form of the present invention is clearly shown.

In the drawings:

Fig. 1 is atop view of one of the surface heaters of anelectric range including its terminal block;

Fig. 2 is a sectional view taken along the line 2-2 of Fig. 1; r

Fig. 3 is a sectional view taken along the line 3-4 of Fig. 1;

Fig. 4 is a sectional view taken along the line ll of Fig. 3;

"Fig. 5 is a sectional view showing the method of lifting up one of the surface heaters for cleaning purposes;

Fig. .6 is an exposed view of the terminal block and connections;

Fig. '7 is a sectional view-of the terminal block taken along-the line l-1 ofFig. 2;

Fig. 8 is a sectional view taken along the line 8-8 of Fig. 2; I

Fig; 9 is a top view of a larger heating unit; and Y.

Fig. 10 illustrates the method of welding used to construct the unit.

As shown in Fig. 5, my improved heating units are provided with extensions connecting with the terminal block so shaped that the surface heating units may be readily tilted up for cleaning purposes without disturbing the electrical connections. The terminal blocks are so formed that the connectionsfrom the surface heating units and from the switch mechanism enter upon the bottom sides of the block so that the entrances are protected from spillage from above as shown in Fig. 2.

I have shown an electric range in which the surface heaters are of the tubular sheath type. The surface'heaters' are of the two-element type for general operation with a three-Wire Edison circuit with the inner element operating at maximum wattage when connected to a volt circuit and the outer element operating at maximum Wattage when connected to a 230 volt circuit. The two'elements of each unit are welded to a framework and surrounded by a ring in order to insure rigidity. The ends of each of the connections extend downwardly and thence are curved outwardly to terminate in their respective terminal blocks which are located beneath thetop surface of the electric range where they are shielded from spillage.

Referring now to the drawings and more particularly to Fig. 1 there is shown a surface heating unit 26 supported in the flanged aperture of the supporting top 22 of an electric range. This heating unit includes an inner element 6i? and an outer element 62.

The inner element 60 begins with a looped end 64 and extends in a clockwise direction around a central disk 66 to the extent of nearly 360 after which it extends radially outwardly as indicated by the reference character 68, thence downwardly to form a portion indicated by the reference character 10 followedby a lower portion 12 which is curved outwardly and upwardly so that its two ends enter the termina1 block 14 upon its 'face 16. This face 16 is turned slightly downwardly so thatliquid cannot drain into the interior of the'termin'al block through the apertures provided for the sheathed elements. The outer element 62 begins with the looped end l8 which is adjacent the radially extending portion 68 and extends in a counter-clockwise direction around the inner element 60 until it again reaches the radially extendingportion 68, after which it extends directly downwardly as designated by the reference character 80,,fol1owed by an outer upwardly extending curve 82 so that it also enters the terminal block 14 through the face 75. The downwardly and outwardly extending portions of both elements are all parallel.

Eachof theelements contains. a-helical electrical conductor such as the conductorst and 86. These conductors are each surrounded'by amagnesium oxide designated by the reference character 88, and the insulating material is enr closed Within a tubular metal sheath, preferably of high chrome-nickel steel. The sheath of the inner element is designated by the reference character 90 and the sheath of the outer element by 92. The elements may be madeby any suitable process, for example, one similar to that shown in the Lightfoot Patent 1,3593% may be used for its manufacture. After the elements are bent to the shape shown in Fig. 1 they are slightly flattened upon their upper surface as shown in Figs. 1 and 2, thus providing a greater contact area with the kitchen utensils used.

These elements are rigidly supported upon a frame-work formed by the crossed stainless steel channel members 94 and 96 which are each provided with a narrow bead 95 for contact welding the members to the bottoms-of the elements as hereafter explained. These channels are notched at their centers to provide an overlapping joint beneath the ornamental disk 66 whichis fastened to another disk 98 which in turn is spot-welded to the channel members 94 and 95 in order to reinforce their overlapping joint to firmly hold the channel members together.

The elements 60 and 62 are preferably fastened to the crossed channels 94 and 96 by contact or projection welding. This step is illustrated in Fig. 10 whichshows a portion of the inner element 60 together with" a portion of one of the channels 95. As shown, the crossed channel members are supported upon a lower supporting member I52 which is shaped so that it supports the channel members directly beneath the narrow'bead 95 which is provided for welding purposes. The two elements are then placed upon the crossed channel members in proper position after which a pivoted weighted member 154 is brought to bear upon the upper surface of the elements 60 and 62 in order to hold them 'firmly upon the various portions of the bead 95. The lower supporting member I52 is-connected by a suitable conductor I56 to the secondary coil I58 of a transformer. The primary coil I60 of the transformer is connected to apower source'under the control of a manual switch I62. Theother end of the secondary coil I58 is connected by'a conductor I 64 to a pivoted supporting arm I65 for the weighted member I54. When the switch I 62 is closed current passes'through the secondary circuit and sufficient current to Weld passes between the elements and the channels at the crossing points between the beads and the various portions of the elements. This provides a simple method for simultaneously welding the elements to the channels at the crossing points and insures'a substantially flat top surface for all portions of the elements forming the main portion of the heating unit. I ;call this projection welding.

The opposite endsof the channel members are provided with notches similar to the notch IIlI in Fig. 3. Each of these notches Illl receives the adjacent struck-in portion I03 of the rim I05 whichsurrounds-the outer element 62. The ends of the channels are each provided with adownwardly projecting lip IIlI which together with a lower projection [09 firmly locks the ends 'ofthe channels to the projecting portions of the rim I05. The lower projections :III9 are bent .outwardly as shown in dotted lines in Fig. 9 in order to allow'the projection I513 tobe placed in the notch IfiI. After this'the projections H39 are bent straight again so that the projections I03 are firmly locked in place within notches IIII.

' The rim Iiifiis made from a straight strip of metal and is curled into circular form with its joint adjacent the terminal I4. This joint is made rigid by the connecting piece III which is welded to the two ends of the strip forming the rim so as to make a firm joint which is practically invisible. This connecting piece III also serves to locate the surface heaters radially,

since it is provided with a tongue adapted to register'with the notch I I3 provided in the flange H5 surrounding the aperture provided in the supporting surface 22 of the range. The rim IIl5 is provided with a flange II! which rests upon the flange II5 of the supporting top 22. .By'this construction the upper surfaces of each element are'maintained rigidly in a single plane.

Beneath each heating unit is a metal reflector I9 which may be formed of aluminum coated steel, chrome plated metal or stainless steel in order to reflect the radiant energy from the heating elements for insulating purposes. This reflector II9 reflects any heat rays from the heating element upwardly onto the bottomsurface of the container being used upon thesurface heater. The reflector H9 is provided with the flange IZI which rests upon the flange 5 beneath the rim I95. The reflector H9 is .provided with the drain aperture I23 beneath the central disk 66 so as to catch and drain any spillage which may fall between the convolutions of the heating elements from the containers used on top of the range. The'spillage will-pass through the flanged aperture I23 onto a drain pan normally provided beneath the reflector. The reflector H9 is provided with a cut-outor cut-away portion I25 through whichthe downwardly extending portions I0 and 8B of the inner and outer heating elements pass. 7

It should be notedthat the terminal block"'I-"-,is not beneaththe heating unit but is beneath the supporting top 22 of the range sothat any liquid which spills upon the heating .unit willnot fall upon the terminal block and, possibly enter to cause'a short circuit. 'Also by curving theater minal outwardly in the manner describedthe entire assembled heating element may be lifted upwardly as shown in Fig. 5 without disturbing the electrical connections to the switch mechanism. This exposes the reflector I I9 which may also be lifted and entirely removed for more convenient cleaning if desired, without further disturbance. p

Within the sheathing of each element, the helical electrical resistors are connectedat their ends to a solid electrical conductor terminal such as the conductor terminal -I3I. This conductor I3l protrudes from the end of the sheathing which is cut off to expose the end-of the solid conductor terminal I3I. The end ofsthershea'thin is fitted into a metal cap I 33 whic'h'is fastened to the terminal block Mby the screws which are threaded into the bushing I21. "The terminal block I4 is molded of some suitable electrical insulating plastic as shown in fFig. 6

with the threaded bushing I21 lodged directly The threaded aper ture ME in each of the terminal lugs l 31 then registers with the center of one of the round passages I43 extending to the face I45 of the terminal block 14. A cup washer l4! fits into each of the recesses I43 and one of the binding screws I43 receives the eyeletted end of one of the flexible conductors I50 extending from the switch mechanism. Each of these binding screws extend through the aperture in one of the cup washers M1 and is threaded into one of the terminal lugs IS! in order to provide the necessary electrical connection between the particular flexible conductor extending from the switch mechanism and the conductor terminal l3! which connects to the helical conductor within the sheathing. When in operating position, the face 16 as well as the face I45 of the terminal block 74 are each turned partially downwardly so that liquid falling upon the terminal block in its normal position will not enter the passages provided for the different conductors but these passages will be protected by the impervious upper faces of the block.

This two-part heating unit is connected to a three-wire Edison circuit through a multi-heat switch mechanism to secure various other lower wattage inputs with resulting changes in heat distribution for various cooking purposes. Several of the circuits which apply are disclosed in my copending application S. N. 236,471, filed October 22, 1938 (Patent 2,259,258, granted October 14, 1941).

In Fig. 9 I have shown a heating unit which is larger in size than the unit shown in Figs. 1 to 5, but which is identical in other respects excepting that the outer element 222 is provided with a loop 220 within the inner element 224. Like the smaller unit 26 the larger unit is supported within the flanged aperture of the range top 226 which covers the terminal block 228. The unit is provided with a rim 236 which rests upon the flange of the aperture in the range top 226. This rim is provided with struck-in portions 232 which support the ends of the crossed stainless steel channel members 234 which are each provided with a narrow welding bead 236 upon which rests the bottoms of the two elements at the points at which they cross the channel members 234. The channel members 234 are provided with a central disk 238 as in the smaller unit. The elements 222 and 224 are fastened to the crossed channel members by projection welding as in the smaller unit. The end portions of the elements extend downwardly and are curved outwardly so that they extend into one of the downwardly turned faces of the terminal block 228 exactly in the manner as shown best in Figs. 2 and 5 in connection with the smaller unit.

The provision of the additional inner loop 220 of the outer element 222 greatly improves the heat distribution of the larger unit by providing heat in the center as well as the edge portions by the outer element and in particular makes it possible to make the outer element much longer than the inner element. This lends itself admirably to my preferred arrangement of operating the inner element at a. maximum wattage upon 115 volts and the outer element at maximum wattage upon 230 volts in standard three-wire Edison circuit.

As mentioned in connection with the smaller unit, the elements of the larger unit are connected by flexible electric conductors to a multiheat switch mechanism which in turn is connected to a three-wire Edison circuit source in order to secure various lower wattage inputs with resulting changes. Several of the circuits which apply are disclosed in my copending application S. N. 236,471, filed October 22, 1938.

While the form of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, as may come within the scope of the claims which follow.

What is claimed is as follows:

1. An electric surface heater including a tubular sheath type heating element, an inverted channel supporting member transverse to the heating element having a bead formation in the longitudinal central portion of said supporting member extending transversely to and in contact with the adjacent tubular portions of the heating element, said heating element being welded to said formation at said points of contact.

2. An electric heater including a circular rim, intersecting inverted channel members extending transversely across the rim and fastened at their ends to the rim and secured together at their intersection, and a heating element supported upon and welded to the longitudinal central portions of said members to form a unitary structure.

3. An electric surface heater including a sheathed heating element having a sinuous form, a plurality of cross supporting inverted channel members intersecting said element at a plurality of points along the longitudinal center lines of said members, said element and members being welded together at said plurality of points.

4. An electric surface heater including a sheathed heating element having a sinuous form, a cross supporting inverted channel member intersecting said element at a plurality of points along th longitudinal center line of said member, said element and member being welded together at said plurality of points.

5. An electric heater including a circular rim, intersecting inverted channel supporting members extending transversely across said rim and fastened at their ends to the rim and fastened together at their intersection, a tubular sheath heater element having a sinuous form intersecting said supporting members at a plurality of points along the longitudinal center of said members, said element and members being welded at said plurality of points.

FRANCIS H. MCCORMICK.

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

UNITED STATES PATENTS Number Name Date 1,085,089 Lachman Jan. 20, 1914 1,998,330 Nicholson et al Apr. 16, 1935 2,094,480 Vogel Sept. 28, 1937 2,214,583 Hepler Sept. 10, 1940 2,302,808 Smith Nov. 24, 1942' FOREIGN PATENTS Number Country Date 636,652 Germany Oct. 12, 1936

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