US2606989A - Electric toaster - Google Patents

Description

2 SHEETS SHEET 1 J. R. GOMERSALL ELECTRIC TOASTER Aug. 12, 1952 Filed Feb. 25, 1950 INVENTOR. JOHN It GOMERSIILL mid "7M Aug 1952 J. R. GOMEl QSALL 2,606,989

ELECTRIC TOASTER Filed Feb. 25, 1950 2 SHEETS-SHEET 2 IN VEN TOR. JOHN R. GOMERSRLL Patented Aug. 12, 1952 ELECTRIC TOASTER John R. Gomersall, Elgin, 111., assignor to McGra'w Electric Company, Elgin, 111., a corporation of Delaware Application February 23, 1950, Serial No. 145,753

12 Claims. 1

The present invention relates to electric heaters and particularly to heating elements having resistance conductors enclosed in glass tubes or the like.

For use in toasters and the like glass-enclosed heaters have certain advantages, including the protection of the resistance conductor against,

oxidation and mechanical injury, and the provision of good support for the conductor while permitting free radiation of heat therefrom. But glass becomes less and less insulating as its temperature increases, and although with proper construction the temperature of the glass tube can be kept well below that of the heating conductor itself, it is desirable in certain devices to provide further insulation in the supports for the tube. Furthermore, because of the brittleness of glass it is important that the glass tube be so supported that it will not be subjected to severe strains or shocks.

Objects of the invention include the provision of an improved, glass-enclosed electric heating element for a toaster, the provision of a new and improved support for such a heating element, and the provision of an improved electric toaster construction. To this end I have provided an improved construction wherein the heating element is mounted at its two electric terminals and given support at additional points only by an improved low-leakage mounting, and wherein the tube is self-supporting and so convoluted that its own resilience provides protection against mechanical shocks. These and other objects and advantages will be apparent from the following description of one specific embodiment which illustrates the manner in which the invention may be carried out. In the drawings:

Figure l is a pictorial view of a toaster partly broken away to show a heating element construction therein which constitutes the preferred form of the present invention;

Fig. 2 is an enlarged pictorial view of the lower mounting of the heating element;

Fig- 3 is a bottom plan view, also enlarged, of the lower mounting;

Fig. 4 is an elevational view, partly in section, of the same lower mounting;

' Figs. 5-8 are detail views showing the terminal construction employed in the heating element of Fig. 1;

Figs. 9-11 show a modification of the lower mounting shown in Figs. 2-4;

Figs. 12 and 13 show another construction therefor; and

Figs. 14-16 show still another construction.

.Except for the heating elements, the toaster shown in Fig. 1 is substantially like that shown in U. S. Patent 2,012,788. It includes a plurality of individual oven chambers Hi, each enclosed by a metal box having end walls [2 and side walls 14. The two heating elements l5, of which only one is shown, are disposed on opposite sides of this well-like oven space for toasting the two sides of a single piece of bread which may be supported on a carrier 18 and held away from contact with the heating elements by vertical guard wires 26. The bread-supporting rack 18 is moved up and down by mechanism not shown. It is moved down manually and it pops up under control of a suitable timer here shown as a clock 22, in a manner now well known. The toaster includes electric terminals 26, 27, 28 and 29, and also others (not shown) to which the heating elements may be connected.

The heating element [5 includes a glass tub I6 convoluted to substantially fill a square plane and to have ends extending from the two upper corners. A convolute electric conductor 2! extends through this tube and has metal terminal members 32 sealed in the ends of the tube for attachment to the terminals 26 and 28 carried by the toaster frame. The pattern in which the tube I6 is bent comprises two half patterns, each composed of horizontal runs ll connected together at their ends by U-bends, with a single long run ii? at the bottom for connecting the two half patterns, as is shown in Fig. 1.

The convolute conductor 2| is in the form of a crimped ribbon, and the glass tube It is round so that the ribbon touches the tube only in a few spots. Thus as is indicated in the sectional view of Fig. 4, contact between the ribbon and glass can occur at most only at two points, such as 34, at the crest of each bend of the ribbon. Furthermore, the conductor lies loose in the tube so that actual contact occurs at only a few of these points. This slight physical contact be tween the wire and the glass provides poor heat conduction to the glass and the transparency of the glass insures poor absorption of radiation. Consequently the cooling effect of the outside air keeps the glass much cooler than the metal resistor. Preferably the element 15 is constructed as follows: A length of crimped ribbon is cut to the required value of electric resistance, then stretched out to the required length, provided with a seal-in lead (to be described presently), and inserted in a straight glass tube of the required length. The glass tube is then formed and the terminals 32 attached.

It is desirable that the convolute tube I6 be given support in addition to that at the terminals 32, but since glass reduces its electric resistance at high temperatures it is desirable also to provide a special insulating construction for such a support and thereby eliminate such electricshock hazard as might result from letting the metal frame of the toaster touch an excessively hot portion of the glass tube.

A third support for the heating element includes a glass stub 36 that is fused to the bottom horizontal run 19 of the tube l6 and extends down therefrom. In the specific form here shown this stub consists of a piece of glass tube that sets over a pin 38 on a bracket 10 which is fastened to the wall [4 of the oven structure. The support tube 36 is simple, cheap, rugged and effective. Glass is a poor heat conductor compared to metals and therefore the metalbracket 40 cools at least that part of tube 36 that touches it. The air draft moves up through the oven space and so carries heat away from the stub 36 and bracket 46 rather than toward them. Accordingly the stub tube 36 is far cooler than the resistor-containing tube l6 and so provides good electric insulationand presents no shock hazard to persons using the toaster. Just above the bottom horizontal run l'9of the tube [6 is a bumper spring 42. As is shown best in Fig. 4, this spring is spaced slightly above'the glass tube so that during the normal operation of the toaster it will not touch the glass. However, should the 'stub '36 be raised from its seat on bracket 40. as when-the toaster is jolted or 'dropped,the tube stopsagainst the bumper-42. The resilience of the glass tube l6 permits such movement of the bottom portion, and the bumper, by absorbing the shock, reduces the strain on other portions of the tube, particularly on the portions near the terminals 32: The bumper 42'is pivoted on a bracket 44 and has a slot 46 that may be engaged bya screw driver or the like for turning it into and out of thetuberetaining position in which it is shown in Figs. 1, 2 and 4. It is yieldingly held in that position bya spring washer 48 cooperating with cam surfaces 56 formed in the bumper 42 and bracket 44.

Figs. -8 show the construction of the terminals32l The end of the heating-conductor'ribbon' 2| is doubled back on itself and spot-welded as at 5ll'to form a portion of double thickness as at 52 which will constitute a seal' in-lead. This lead may be conveniently formed before the ribbon'is inserted in the glass tube l6; Then, the tube It having been formed, a short glass bushing 54 is slipped onto its end. A metal connector 56 is slipped into the otherend'of the bushing 54 and the end'of the doubled lead 52 is threaded throughthe hole 58in the connector and folded back. The terminal is-comple'ted by riveting a grommet 60 into hole "58" to clamp the lead 52, and by heatin and pressing the two pieces of glass at B2 to fuse the bushing 54 and tube l6 togethe r and to seal in the lead 52.

Figs. 9-11 show a modified construction of the lower mounting. Therein the spring bumper for the lower run 16 of the tub econsists of a single spring strip 66 riveted to the bracket 40, and extending up alongside thestub 36 and over thetube I9 but spaced therefrom. Fig. 9 shows theposition of the-parts during normal use of the toaster. Fig. shows'how thespring 66 catches the tube with its hooked end'68 when a jolt unseats the stub 36. When a heating ele ment is to be installed orremoved, the spring maybe bent to-one side as in Fig. 11.

Figs. 12 and 13 show another construction for the low-leakage support at the bottom of the heating element. There a depending glass stub 72 has a ring-like enlargement or flare 14 formed thereon. A bracket 16 mounted similarly to bracket 46 carries a spring clip 18 into which flare 14 may be pressed. The clip resiliently grips the tube 72 and resists displacement in any direction.

Figs. 14-16 show still another construction for the bottom support. There the bottom run IQ of tube [6 is provided with a ring-like enlargement or flare 82 which snaps into a spring clip 84- on a bracket 86 that is mounted similarly to bracket 46'. Although the flare 82 will not provide as cool a glass-to-metal contact as will the other constructions it is cooler than the adjacent,

unenlarged parts of the tube I9.

Of the several constructions for the lower support, that of Figs. 1-4 is the one I now prefer. The glass is cool at its point of contact with the metal of bracket 40 to prevent objectionable leakage currents, and the sprin bumper l 2 positively prevents more than a, slight lifting of the lass structure off bracket 40.

The structure or" Figs. 9-11 similarly insures that the glass will be cool at the point of normal contact with the metal of the support. Although the bumper 66 permits somewhat more move ment, it is cheaper and under certain conditions can be moved aside more easily for the removal or insertion of the heating unit.

' The structure of Figs. 12 and 13 provides a firm grip on the coolest part of the glass, and under certain conditions permits the removal and insertion of the heating unit to be eifected more easily than do the constructions of Figs. 2- and 9. The structure of Figs. 14-16 similarly'pro vides a firm grip on the glass, and is'cheaper than that of Figs. 12 and 13, but under similar operating conditions will not provide as cool a contact with the metal support.

I have found the heater construction'ofthe present invention to be sufficiently resistant to mechanical shocks that it survives accidents that are likely to damage the case or other parts of the toaster. Further, I find that it has a low electric leakage through the glass to theframe, and is cheaper than prior constructions.

It will be apparent to those skilled in the art that the invention is capable of numerous modi fications and variations and accordingly their vention should be limited only by the scope of the appended claims.

I claim:

1. An improved electric'heater for a toaster or the like consisting substantially of aglass'tube convoluted in two zig-zag patterns each constituting substantially half of a plane, rectangular configuration, and each comprising 'aplurality of approximately parallel transverse runs connected only by U-bends near the longiaudinal center line and an outer edge of the config ura tion', said patterns joining each other bya' long transverse run along one edge of the configuration, means for supporting said convolute' tu-be at only a few separated points, the tube being self supporting therebetween, and a heat=gencrating electric conductor extending through said tube.

2. An electric heater for a toaster or thelike consisting substantially of a glass tube having two ends convoluted in two zig-zag patterns each constituting substantially half of a vertical, plane, rectangular configuration and'comprising a plurality of approximately horizontal runs connected by U-bends near the vertical center line and an outer edge of the configuration, each said pattern beginning at the upper outer corner and joining the other at the bottom center, an electric conductor extending through said tube, and means near the ends of said tube and near said upper corners for supporting said tube.

3. The combination of claim 2 wherein said supporting means comprises terminals at the ends of said tube and at the said upper corners of said configuration adapted to support said tube and facilitate its connection in an electric circuit.

4. The combination of claim 3 wherein there is included means for also supporting said tube near the bottom of said configuration.

5. The combination of claim 3 wherein there is included a spring supporting clip for engaging said tube near the bottom of said configuration.

6. The combination of claim 2 wherein there is included a low-leakage support for the bottom run of said tube near the center thereof.

7. In an electric toaster or the like, in combination, a frame structure, a vertical, flexible, electric heating element consisting substantially of a glass tube convoluted in a planar pattern, a conductor in said tube, spaced terminals for said conductor at the upper edge of the pattern, and a glass projection extending down from a bottom run of said conductor-containing tube for providing a low-temperature support-engaging part, insulated terminal supports on said frame con nected to said element terminals for supporting said element and connecting it in an electric circuit, a bottom support on said frame engaging said projection and bearing up thereagainst for giving support to the lower part of said flexible heating element, and a bumper above said bottom run but spaced thereabove for preventing displacement of said element from said bottom support, but normally lying free of contact therewith.

8. The combination of claim 7 wherein said bumper comprising a horizontal spring strip and means for supporting it for swinging movement about a vertical axis to swing out of said position.

9. Th combination of claim 7 wherein said bumper comprises a defiectable hook-shaped spring.

10. In an electric toaster or the like, in combination, an electric heater consisting substantially of a glass tube having two ends convoluted in two zig-zag patterns each constituting substantially half of a vertical, plane, rectangular configuration and each including a plurality of approximately horizontal runs connected by U-bends near the vertical center line and an outer side edge of the configuration, each said pattern beginning at an upper corner of the configuration and joining the other by a long transverse run along the bottom edge of the configuration, an electric conductor extending through said tube, means near the ends of said tube and near said upper corners for supporting said tube, a short glass stub-tube fused to said transverse run at the bottom edge and extending down therefrom, and a support engaging the bottom end of said stub-tube.

11. The combination of claim 10 wherein there is included a resilient bumper above said transverse run of said tube and spaced therefrom, whereby to stop upward movement thereof but normally to remain out of direct contact there with.

12. In an electric toaster or the like having therein an exposed conducting surface and an electric heating element having a high operating temperature, said heating element including a horizontally extending glass tube containing a heat-generating metallic element, the improvement which includes low-leakage means for supporting said tube intermediate its ends, said means consisting of an entirely metal-free supporting structure engaging the tube, said tube-engaging supporting structure consisting of a vertical hollow glass stub having its upper end fused to the side of the tube at an intermediate point, and further supporting means entirely spaced from the tube, said further supporting means consisting of a rigid metal member engaging the lower end of said glass stub and supporting the load of said glass stub and said horizontal tube.

JOHN R. GOMERSALL.

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

UNITED STATES PATENTS Number Name Date 540,073 Reed May 28, 1895 1,032,267 Bastian July 9, 1912 1,158,487 Hadaway Nov. 2, 1915 1,334,850 George et al Mar. 23, 1920 1,548,305 Dalton Aug. 4, 1925 1,637,846 Kolster Aug. 2, 1927 1,680,768 Dalton Aug. 14, 1928 1,681,736 Kull Aug. 21, 1928 1,820,202 Smalley Aug. 25, 1931 1,886,558 Kuhn et a1 Nov. 8, 1932 1,942,496 Siegel Jan. 9, 1934 2,012,788 Ireland Aug. 27, 1935 2,180,600 Mills Nov. 21, 1939 2,215,587 Kerschbaum Sept. 24, 1940 2,391,382 Bilan Dec. 25, 1945

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