US3068340A - Domestic appliance - Google Patents

Description

Dec. 11, 1962 R. D. BREMER ETAL 3,068,340

DQMESTIC APPLIANCE Filed Sept. 16, 1957 2 Sheets-Sheet l INVENTOR. Alfred J Sacks/eder BY Robert 0. Bremer The/r Attorney Dec. 11, 1962 R. D. BREMER ETAL DOMESTIC APPLIANCE Filed Sept. 16, 1957 2 Sheets-Sheet 2 "I INVENTOR.

I, Alfred J Sacks/eder sYfioberl 0. Bremer The/r Alla/nay United States Patent 9 3,068,340 DOMESTIC APPLIANCE Robert D. Brenner and Alfred J. Sacksteder, Dayton, Ohio, assignors to General Motors Corporation, De troit, Micln, a corporation of Delaware Filed Sept. 16, 1957, Ser. No. 684,159 3 Claims. Jl. 219-37) This invention relates to a domestic appliance and more particularly to electric surface heaters such as are used on ranges, hot-plates and similar appliances.

Recently, there has been developed an unusually thin form of sheathed tubular surface heaters having sufficient elasticity to conform to the bottom of the pans to be supported and heated thereon. There has been a problem in arranging the proper support for such heaters without diminishing their ability to conform to the bottom surface of the pan.

It is an object of this invention to provide an attachment between the support and the thin tubular sheathed surface heaters which does not diminish the ability of the heaters to conform to the bottom surface of the pan and yet ties the heaters to the support.

It is another object of this invention to provide a structure and method which will readily and simply resiliently fasten both coils of a two-coil thin tubular sheathed surface heater to its support.

It is another object of this invention to provide an easy method of welding and a simple welded structure for welding either a single or a two-coil tubular sheathed surface heater to its support without burning or damaging or causing leakage of the sheath.

These and other objects are attained in the form shown in the drawing in which a two-coil thin tubular sheathed surface heater is mounted upon a five-armed spider of stainless steel strip. The bottoms of several of the arms are notched at one or more places to receive loops of a resistance wire bracket. The opposite ends of these wire brackets are welded to either the same or adjacent turns of the two coils. The resistance wire has a high electrical resistance and melts at a lower temperature than the stainless iron sheath.

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

In the drawings:

FIGURE 1 is a top view of a surface heater embodying one form of my invention;

FIGURE 2 is a fragmentary vertical sectional view taken along the lines 22 of FIGURE 1;

FIGURE 3 is a fragmentary vertical sectional View taken along the lines 33 of FIGURE 2; and

FIGURE 4 is a top view of a modified form of the invention.

Referring now to the drawing, there is shown a flanged rim having an upper outwardly extending ornamental flange adapted to extend over and rest upon the portion of the range top 22 bordering the flanged opening 24. The rim 20 is provided with an inner supporting ledge 26 upon which rests the outwardly extending flange of the drip pan 28. Supported upon the top of the flange of the drip pan 28 is a five-armed support 30 of stainless steel strip which has round-nosed projections 32 at the ends of the arms extending beneath integral projections 34 on the rim. The projections 32 and 34 interengage to resiliently hold the rim 20, the support 30 and the drip pan 28 together.

Above the support 30 is a two-coil electric surface heater of the thin tubular sheath type including an outer coil 33 of two turns or loops having the end portions 35 and 36 extending to the right beneath the rim 20 and an inner coil 38 of four turns or loops having the terminals 40 and 42 extending outwardly to the right under the rim 20. These coils 33 and 38 are both of the thin tubular sheath type each containing a coiled resistance wire 44 and 46 embedded in solid electrical insulation 48 and 50, such as magnesium oxide. The magnesium oxide of each are enclosed in a thin tubular sheath 52 and 54 of a suitable nickel chromium iron such as Incoloy having a composition of about 3035% nickel, 20% chromium and the remainder iron, and melting at a temperature of about 2,515 F. This sheath has a diameter of .230" and a wall thickness of .022. Instead of this, an alloy of 25% chromium, 12% nickel and the remainder iron, melting at between 2550 and 2650 F. may also be used.

To provide a simple method of resiliently attaching the coils 33 and 38 to the support 30, at least one or two of the arms of the support 30 adjacent to and opposite the terminals 35, 36, 40 and 42 are each provided with a notch 56 on their lower edge between the adjacent turns of the coils 33 and 38. These notches or slots 56 each receive the resilient yoke of a resistance wire alloy bracket 58 of the configuration shown in FIGURE 3 with the wire extending from the notch along both sides of the arm in the form a U and having one end portion 60 extending initially radially and then at right angles transverse to and laterally beneath the coil 33 and the opposite end portion 62 extending initially radially and then at right angles transversely to and laterally beneath the adjacent turn of the coil 38. This configuration of successive right angle bends in different planes allows lateral and upward movement of the coils 33 and 38 relative to the support 30. This wire is suitable for welding and has a high electrical resistance. It has a composition of about 60% nickel, 16% chromium, with the remainder iron, and has a melting point of 2460 F. and a diameter of .057. The transverse opposite end portions 60 and 62 of these wire brackets 58 are resistance welded to the adjacent bottom portions of the adjacent turns of the heaters 33 and 38 so as to connect with one bracket both coils to two of the arms of the support 30.

This welding is preferably accomplished while the two coils 33 and 38, the support 30 and the brackets 58 and 66 are inverted upon an electrically conductive metal welding support. The two electrodes 64 and 65 of the welder engage and press the ends 62 and 60 of the transverse portions of each of the brackets 58 against the adjacent surface of the coils 33 and 38 as if FIGURE 3 were inverted. At a suitable potential, the AC. welding current is applied to the electrodes 64 and 65 and flows from the electrode 64 through both adjacent end 60 of the bracket 58 and the sheath of the heater 38 to and through the welding support and the adjacent and contacting portions of the sheath of the heater 33 and the opposite end 60 of the bracket 58 to the second electrode 65. To achieve the desired heat balance for welding the current flow through the sheaths is reduced by a parallel current flow directly through the continuous wire bracket 58 between the electrodes 64 and 65 for heating the bracket 58. In addition, the wire size of the brackets and their electrical resistance and length are so chosen that the contacting surfaces of the brackets reach welding temperatures slightly before or at the same time as the sheath. This welding method particularly prevents any burning, cracks or other damage to the sheaths adjacent the welds which might cause leakage and also because of the reduced current flow through the sheath minimizes marring of the top surface of the coils.

Because of the higher resistivity and the lower melting point coordinated with the wire size of this welding wire bracket, a better heat balance during welding is obtained 'ice and the weld of the wire to the tubular sheaths is made without any danger of overheating and creating tiny holes in the sheath which would permit leakage and without any burning or other damage to the sheath. The brackets are inexpensive, readily assembled and welded. The yoke of the brackets 58 need not extend to the closed end of the slots 56 so that the coils 33 and 38 have a limited amount of movement in the vertical direction relative to the support 30 so that the coils may readily accommodate themselves to irregularities and particularly lack of flatness of the bottom of pans and other utensils which may be used thereon. To prevent the bending of the outer turn or loop of the coil 33, one or more additional wire brackets 66 of the same material as the brackets 58 may be looped through the notches 68 in the bottoms of one or more of the arms of the support 30 opposite the terminals 35, 36, 40, and 42. The ends of the brackets 66 are welded to the outer turn or loop of the coil 33 by the same welding process used for the brackets 58. Each end of each bracket 66 is provided with two right angle bends in difierent planes to provide resiliency for absorbing the thermal expansion of the coils 33 and 38. The top surface of the sheaths may be flattened as shown particularly in FIGURE 2 so as to provide greater surface area contact and also to compact the solid electrical insulation surrounding the resistance wire conductors 44 and 46.

In the modified form of FIG. 4 the flanged rim 20, the range top 22 and the five-armed support 30 are identical to the corresponding members of FIGS. 1-3. The heater is difierent in that it is formed of two sheathed tubular port 30 by two wire brackets 143 and 145 which may be identical to the wire brackets 58 of FIGS. 1-3 and which may be welded to the sheath of the heaters 131 and 133 in a manner similar to that described for FIGS. 13. It is only necessary that one of the brackets 143 be provided upon the arm of the support 30 opposite the terminals and the second, 145, be provided on the nearest arm at the left of the terminals, as viewed in FIG. 4. In

addition, there is another bracket 147 also identical to the brackets 58 and welded in a similar manner to the inner rnost turns or loops of the sheaths of the heaters 131 and 133 over the intermediate arm of the support 30 on the left side thereof, as shown in FIG. 4. The support 30 is notched to receive the U-shaped portions of the brackets in the manner shown in FIGS. 2 and 3. This provides a simple, inexpensive means of resiliently connecting the 4 heaters 131 and 133 to the support 30 with the same advantages as obtained by the brackets 58 and 66 in FIGS. 1-3.

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. A surface heater including a supporting spider having a plurality of outwardly extending arms, a sheathed heating means supported upon said spider, and a welding wire looped around one of the arms of said spider and having end portions provided with two right angled bends in different planes with a portion transverse to the sheath welded to the sheath of said heating means.

A surface heater including a supporting spider having a plurality of outwardly extending arms, a sheathed heating means including an electrical resistance wire embedded in solid electrical insulation enclosed in a metal sheath supported on said spider, the bottom of said spider being provided with a notch, and welding wire extending through said notch having portions on opposite sides of said notch provided with a substantial bend extending in a plane substantially perpendicular to the axis of the sheath of the adjacent portion of the heating means and welded to said metal sheath.

3. A surface heater including a supporting spider having a plurality of outwardly extending arms, a sheathed heating means in the form of separate coils of electrical resistance wire embedded in solid electrical insulation and enclosed in a separate metal sheath, said coils of said heating means being supported upon said spider, and welding wire having an intermediate portion connected to said spider and having a portion on one side of said intermediate portion provided with a bend in one direction extending in a plane substantially perpendicular to the axis of the adjacent portion of the sheath of said heating means and welded to one separate sheath and a portion on the other side of said intermediate portion provided with a bend in the opposite direction extending in a plane substantially perpendicular to the axis of the adjacent portion of the sheath of said heating means and welded to another separate sheath.

References Cited in the file of this patent UNETED STATES PATENTS 2,654,825 Cunningham Oct. 6, 1953 2,662,153 Gunther Dec. 8, 1953 2,662,157 Vallorani Dec. 8, 1953 2,725,456 Weyrick Nov. 29, 1955 2,784,300 Zuk Mar. 5, 1957 2,816,206 Eckblad Dec. 10, 1957 2,943,178 Aldous June 28, 1960

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