US2508552A

US2508552A - Electric heater

Info

Publication number: US2508552A
Application number: US611474A
Authority: US
Inventors: William R Tuttle
Original assignee: Tuttle & Kift Inc
Current assignee: Tuttle & Kift Inc
Priority date: 1945-08-20
Filing date: 1945-08-20
Publication date: 1950-05-23
Anticipated expiration: 1967-05-23
Also published as: DE966817C

Description

May 23, 1950 R TUTTLE 2,508,552

ELECTRIC HEATER Filed Aug. 20, 1945 2 Sheets-Sheet 1 MIL I l INVENTOR.

May 23, 1950 w, TUTTLE 2,508,552

ELECTRIC HEATER Filed Aug. 20, 1945 2 Sheeu- Sheet 2 IN V EN TOR.

Patented May 23, 1950 ELECTRIC HEATER William R. Tuttlc, Riverside, 111., assignor to Tuttle & Kift, Inc., Chicago, 111., a corporation of Illinois Application August 20, 1945, Serial No. 611,474

8 Claims. (Cl. 219-37) ,,Patent No. 2,456,343) and 566,856, both filed on December 6, 1944. Heating units of the type above referred to are usually located in a mounting that has a pan-like bottom under the unit, and as it is important that the pan and underside of the unit be accessible for cleaning, it is customary ,to arrange the heating unit so that it may be lifted in some manner for this purpose.

Preferably the heating unit is hinged to the mounting so as to tip up at one side of the pan- -like bottom, and the electrical conductors which supply current to the unit are connected therewith at or near the hinge so that they remain connected and merely bend in the tipping up of the .unit for cleaning purposes.

In such heating units it is important for effective transmission of heat to a utensil thereon, .that the top of the heating unit be flat so as to contact throughout its area with the bottom of the utensil, and in order to maintain the coils of the unit securely against displacement and at ,a uniform level in the manipulation of the unit yto and from the cleaning position, it has been customary to secure the coils of the heating unit to a frame or spider on the underside, which "swings with the unit and usually engages the mounting or the pan portion thereof to support the heating unit in the normal downturned position.

Such coil holding frames or spiders, however, not only obstruct the underside of the unit and interfere with ease of cleaning, but in the temperature changes to which the heating unit is subjected in the use thereof they prevent ex- ..pansive and contractive movement of the coils ,or convolutions of the heating unit at certain places with the result that distorting strains are imposed on the coils or convolutions at other places and also on the coil holder itself whereby parts of the coils or convolutions of the unit are so deflected or displaced from the normal level that the utensil on the heating unit contacts .therewith only a few places and an appreciable slowing down of heat transmission occurs.

This objectionable deflection or displacement of 56 the coils or convolutions due to restricted expansion and contraction thereof by the customary coil holder and the resultant slowing down of heat transmission is all the more pronounced in the newer type heating units that are now being used wherein the coils or convolutions of the unit are flattened on the top. This flattening decreases the vertical thickness of the coils or convolutions and increases the horizontal width so that the coils or convolutions bend more readily in up and down directions, and accordingly, the restriction of expansion and contraction by the coil holder finds relief rincipally in up and down deflection of the yielding portions of the coils or convolutions together with some tipping also of the flattened top faces thereof, all of which results in a greatly lessened area of contact with the utensil on the heating unit and a considerable slowing down of heat transmission to the utensil.

With my present invention no coil holder is employed, such as the coil holding frames or spiders hereinbefore referred to, to which it has been customary heretofore to attach the heating unit winding, but instead my heating unit is a loose winding which is pivoted at one side of the mounting, and merely rests loosely on the pan bottom or ribs thereof in the downturned position so that the coils of the heating unit are free to expand and contract without distorting strains, and in the upturned position the underside of the unit is free of any obstruction and completely accessible for easy and thorough cleaning. Moreover, the heating unit is formed so that it has some flexibility, especially when operating at high temperature, and can adapt itself to some extent to the bottom of a utensil thereon, thereby assuring greater contact therewith and better heat transmission than with previous units with rigid coils.

The principal objects of my invention are to provide an improved pivotally mounted electric heating unityto assure more perfect contact of the heating unit with a utensil placed thereon and better heat transmission from the heating unit to theutensil; to permit free and unrestricted expansion and contraction of the unit in the changing of the temperature thereof; to afford unobstructed access to the entire under side of the heating unit when upraised; to provide an improved mounting for the heating unit, and in general to simplify the heating unit and heating unit assembly, increase the efliciency, improve the appearance and convenience, and minimize the cost thereof, these and other objects being accomplished as pointed out more fully hereinafter and as shown on the accompanying drawing, in which:

Fig. 1 is a top view of a heating unit assembly constructed in accordance with my invention;

Fig. 2 is a side view of the assembly of Fig. l and showing a fragmentary portion of a range top in which the assembly is mounted;

Fig. 3 is a bottom View of the assembly of Fig. 1, a portion thereof being broken away;

Figs. 4 and 5 are enlarged sectional views on the lines 4-4 and 5-5 respectively of Fig. 1 oi portions of the pan-like support for the heating unit and fragmentary portionsof the heating unit thereon;

Fig. 6 is an outer end view of the hinge attachment of the heating unit to the pan-like support;

Figs. '7 and 8 are cross-sectional views of the hinge attachment taken on the lines 1--'! and 8--8 respectivelyof Fig. 2;.

Fig. 9 is a longitudinal. sectional View of the outer end of the heating unit taken on the line 9---9 of'Fig. 6;

Fig. 10 is a sectional View taken on the line Fig. 11 is a fragmentary sectional view of the inner end of the heating unit taken substantially on the line H--H of Fig. 1

Fig. 1-2' is a transverse sectional view of said inner end taken substantially on the line l'2 -l2 of Fig. 11;

Fig. 13 is a side view of the bracket or hanger for supporting the heating unit conductors at the underside of the pan-like-suppor't; and

Fig. 14 is a fragmentary portion of the heating unit coil showing'a differentmanner of supporting same.

Surface type heating units, to'whi'ch my invention is particularly applicable, are commonly used in the" top of electric ranges to support and heat cooking utensils and their contents, it being a common practice in such cases to provide the range top with openings in each of which is located a heating unit assembly consisting of a combination mounting ring, drain and reflector pan and a heating unit, the latter being located within the mounting ring directly over the drain and reflector pan and usually arranged to be lifted in some manner so' as to afford access to theinterior of the drain and reflector pan and to the underside of the heating unit for cleaning purposes.

A space is provided under the range top to accommodate the heating unit assembly which is inserted in the range top opening and extends for the most part intothis space, and this space, which is commonly located over the range oven and fairly shallow so as not to sacrifice oven space, also contains the electrical conductors through which current is supplied to the various heating units.

Inthe accompanying drawing in which my invention is illustrated in its application to a range top unit, the reference numeral 15 indicates a fragmentary portion of the ran e top and IB'the opening which may be provided with an upturned marginal flange H, as shown herein, for reinforcing, or it may have a downwardly offset seat'therearound as shown in my aforesaid application Serial No. 566,856.

Mounted in the opening I6 is a heating unit assembly comprising the heating unit is which inturn is mounted on a support 19 of pan-like 'form which has a large central recess or depression 20, in which the heating unit I8 is located, said pan-like support l9 being formed with a raised outwardly extending flange or rim 2| surrounding the depression or recess 20 and projecting out over the margin of the range top opening 16 for supporting the heating unit assembly, said flange 2! being preferably formed with a downturned edge 22 which rests directly on the range top [5.

This pan-like support 19 i preferably a casting, molded with a boss or plateau 23 rising from the center of the bottom wall 24 of the recess 20 to approximately the elevation of the rim 2| and around this boss 23 are three equally spaced radial ribs 25 which extend upwardly from the bottom wall 24' only part way to the top of the recess 20, as shown in Figs. 4 and 5, and are superposed over three corresponding stiffening ribs 26 on the underside of the bottom wall 24.

The ribs 25, which serve as supports for the heating' unit l8, preferably do not extend entirely from the boss 23 to the outer wall 21 of the recess 20 but are separated respectively therefrom at the opposite ends as indicated at 28 in Fig. 5 whereas the reinforcing ribs 26 extend from the outer periphery of the bottom wall 24 to the hollow 29 in the underside of the boss 23 as shown in Fig. 3, thereby substantially reinforcing and stiffening the bottom 24 of the pan-like holder I9 and insuring rigidity to the ribs 25 thereabove which support the heating unit 18 and the weight of any utensil and contents placed on the heating unit.

The heating unit I8 is of a type similar to that disclosed in my above mentioned application Serial No. 566,856 and hinged in a similar manner, the heating unit hereof comprising a metal tube 30 filled with a heat conductive electricall insulating material 3| within which is embedded the resistance or resistances which constitute the electric heating element, two

resistances

32 and 33 and a return conductor 34 being shown herein for purposes of illustration.

Any suitable insulation 31 may be employed, as for example, finely divided fused magnesium oxide which is compacted in the tube 30 to a hard dense mass so as to have high heat conductivity and hold the

resistances

32, 33 and return conductor 34 securely in place in proper insulated relation to one another and to the metal tube or sheath 30.

This metal tube or sheath 30 with the resistances and insulation therein is bent in flat spiral form with; the inner coil or convolution thereof of a size to loosely encircle the boss or plateau 23 at the center of the recess 20 of the pan-like support l9 and the outer convolution of a size to fit loosely within the surrounding wall 21 of the recess 20, substantially as shown in Fig. 1, and this outer convolution terminates in a tangential outer end portion 35 which is bent downwardly at an angle, substantially as shown in Fig. 2, to extend through an opening 36 in the bottom wall 24 of the pan-like support IQ for hinge connection therewith at the under side. It will be understood, of course, that a greater or even a less number of convolutions may be employed if desired.

The inner end of the sheath 3!) is hermetically sealed at 37 and within this sealed end the inner end of the return conductor 34 is joined to the inner ends of the

resistances

32 and 33 in any convenient manner, a form of connection that may be employed being disclosed in my aforesaid application Serial No. 566,855.

I prefer, however, instead of using a single return conductor 34 which is connected at the closed end 3! to both

resistances

32 and 33, to

provide each

resistance

32 and 33 with an extra lengthof wire at the inner end which is stretched out straight or nearly straight and bent back as shown in Figs. 11 and 12 so that each resistance has its own return conductor which is merely a continuation of the wire of the respective resistance, the return conductor for the resistance 32 being shown at 32a in Figs. 11 and 12 and bent back as indicated at 32b whereas the return conductor for the resistance 33 is shown at 33a in Fig. 12 and is similarly bent back from the outer end of the resistance 33 as indicated at 33b in said figure. These

return conductors

32a and 33a are 'preferably connected to a single terminal at the outer end of the heating unit and do not need to be insulated from one another throughout their length, and accordingly, may be twisted together if desired from the respective bends 32b and 33b to the outer terminal ends thereof if desired.

In the making of the heating unit the tube or sheath 30 is initially a tube of circular cross- "section and likewise the

resistances

32 and 33 are cylindrical helices which together with their

return conductors

32a and 33a are located in proper position in insulation 31' which is surficiently compacted in the tube 30 and around the

turn conductors

32a and 33a being maintained at the other side which is to be the bottom of the completed unit, after which the fiat spiral is compressed between suitably formed dies to compress the tube 30 and contents and form a relatively wide flat face 38 at the side of the tube where the

resistances

32 and 33 are located, and at the same time the other side of the tube is preferably shaped as shown in Figs. 5 and 12, with reverse bends 39 at the opposite sides of the rounded bottom 43 within which the return conductors 32a and 32b are located, it being understood, however, that this flattening 33 and reverse bending 39 is not continued to the outer end of the heating unit but terminates just beyond the downturn bend of said end so that the somewhat as shown in Figs. 5 and 12 While the reverse bends 33 on the underside of the unit impart greater rigidity to the unit and also serve to push up the under sides of the

resistances

32 and 33 closer to the top of the unit where the heat therefrom is intended to be utilized.

No coil holding frame or spider is used with this heating unit to hold the coils in separated relation and the tops of the coils at a uniform level as has been the practice previously with heating units of this character, but instead the flat spiral unit I8 is arranged on the pan-like support I 9 so that the coils or convolutions thereof merely rest directly on the tops of the ribs 25, the bent down outer end 35 of the unit, or an extension thereof, being pivotally secured in a bearing on the underside of the pan-like support IS in such a manner that the unit 18 rests firmly on the tops of the ribs 25 but may be lifted therefrom to an upright position, indicated by dotted lines at [8a in Figs. 1 and 2, to afford access to the underside of the heating unit and to the interior of the pan-like support IQ for cleaning purposes, it being understood, of course, that the up and down thickness of the unit 18 and the height of the ribs 25 is such that when the unit 18 is resting on the tops of the ribs 25 the top face 38 of the heating unit is sufficiently above the level of the marginal flange 2| of the panlike support [9 so that a pan or utensil placed on the unit 18 will be supported solely by the heating unit which in turn is supported by the ribs 25.

For pivotally attaching the heating unit l8 to the underside of the pan-like holder 1 3, the latter has a sheet metal pivot housing 4| on the underside, similar to that disclosed in my aforesaid application Serial No. 566,856, and comprising a sheet metal blank bent at 42 and 43 to form a top wall 44 with two similar depending

sides

45 and 46 spaced apart sufficiently to accommodate therebetween the end 35 or extension thereof of the heating unit, the inner ends of the

side walls

45 and 46 being provided with laterally extending ears 4'! and 48 respectively secured by cap screws 49 to lugs 53 and 5i respectively which de' pend from the bottom of the pan-like support I9, the arrangement being such that when the pivot housing 4| is attached to the lugs 50 and 5|, the top wall 44 of the housing is sufficiently below the flange Z! of the pan-like support E9 to admit the down turned edge H of the range top 15 freely therebetween and said top wall 44 is at a suitable inclination so that when the end 35 of the heating unit [8 or end extension thereof is interposed between the

housing side walls

45 and 46 against the top wall 44 the coils of the heating unit It will rest uniformlyon the supporting ribs 25 in the bottom of the pan-like support 19.

Preferably, the end 35 of the heating unit is not continued out through the pivot housing- 4| but instead is provided with a cylindrical extension 52, the inner end of which is telescoped a suitable distance onto the round tubular end 35 of the heating unit 18 and secured thereto by silver solder as at 53 or in other manner to insure an inseparable connection that is unaffected by the heat of operation of the heating unit [8, and this extension 52, which serves to enclose the facilities by which electrical conductors are connected with the outer extremities of the

resistances

32 and 33 and with the return conductor 34 or

return conductors

32a and 33a, extends outwardly through the housing 4! and is pivoted therein.

For pivotally holding this extension 52 in the housing 4!, the

side walls

45 and 46 thereof, which are preferably stiffened by flanges 5 along their lower edges, have matching perforations suitably located to receive the

legs

55 and 56 of a wide staple-like member 5'! at a proper location to hold the extension 52 up against the top wall 44 of the housing 4!, said staple-like member being retained in place by bending the projecting ends of the legs55 and 55 as indicated at'58. The openings through which the staple leg 56 passes are preferably slightly closer to the housing top wall 44 than the openings for the staple leg 55 and the extension 52 is provided with a circumferential groove 59 where the staple leg 56 engages therewith, this arrangement of the groove 59 and staple leg 56 engagement therewith serving to hold the extension 52 against endwise movement in the housing 4| when held therein by the staple member 51. Obviously with this construction the heating unit may be easily removed and replaced by merely removing the staple member 51.

Thus the downwardly inclined tangential outer end of the heating unit I 8 is pivotally held in the housing 4| in a position so that in the normal downturned location of the heating unit |8, the coils thereof are uniformly supported by the ribs 25 in the bottom of the pan-like support IS, the ieating unit, however, being tiltable to an upright position at one diametrical side of the panlike holder as indicated by the dotted lines at [8a in Figs. 1. and 2 so that the bottom of the heating unit It and the interior of the pan-like support 19 are readily accessible for cleaning, the heating unit extension 52 beingretained against axial movement at all times by the engagement of the staple leg 56 with the circumferential groove 59 thereof so that the heating unit returnsto the same position on the supporting ribs 25 each time it is tilted upwardly therefrom.

Preferably facilities are provided to hold the heating unit H3 in the upraised position and in the normal downturned position as well, and to this end, the side Wall 46 of the housing 4| is apertured to receive a ball 60 which is spring pressed to engage depressions 5| and 62 at suitable quarter turn locations around the extension 52 so that the ball 60 engages the depression 5| when the heating unit I8 is laid down flat against the supporting ribs 25 and releasably holds the heating unit in that position and engages the depression 62 when the heating unit is lifted to the up right position !8a and thereby releasably holds the heating unit in the upright position.

A plate spring 53 has the opposite ends secured to the side wall 45 of the housing 4| so as to bear at its middle against the ball 60 to spring press the ball into engagement with the depressions 6| and 62, the said side wall 45 having outturned

ears

64 and 65 with seats 66 in which the respective opposite ends of the spring 63 are engaged, and this spring may have a slight depression 61 at the center in which the outermost portion of the ball 60 seats. Preferablythe ball opening in the wall 56 is reduced to a size at the inner side of the Wall 46 less than the maximum diameter of the ball 50 so that the ball, although it projects through the opening sufliciently to freely engage the depressions 6| and 62 of the pivoted extension 52, will not pass completely through said opening and thus remains in said opening in the event that the extension 52 of the heating unit is removed from the housing 4|.

The

resistances

32 and 33 and the return conductor 3 or the pair of

return conductors

32a and 33a have terminals attached thereto Within the compacted insulation 3| of the bent down outer end 35 of the heating unit, the terminal for the resistance 32 being indicated at 68 in Figs. 9 and 10 and having the outer end of the resistance 32 tightly Wound on the inner end thereof as indicated at 69 in a manner to insure a good electrical connection, and similar terminals 10 and H are attached in a similar manner respectively to the outer ends of the resistance 33 and the single return conductor 34 of Fig. 5 or the pair of

return conductors

32a, 33a of Fig. 12, it being understood that the pair of return conductors, 32a, 33a serve the same purpose as the single conductor 34 and are both attached to the same terminal H.

These terminals 68, Hi and H project beyond the outer end of the heating unit into the extension 52 where they are connected respectively to flexible conductors l2, l3 and 74 through which current is supplied from a suitable source for energizing the

resistances

32 and 33, a switch, such, for example, as shown in Tuttle Patent 2,317,967 being customarily employed to selectively control the supply of current to the

resistances

32 and 33 in a manner to energize the resistances individually or conjointly at will and thereby optionally cause the heating unit to supply a number of different intensities of heat.

For connecting the conductors T2, T3 and 14 to the

respective terminals

68, 10 and H, each terminal is provided on its outer end with a metal ferrule 15 which is secured thereon in any convenient manner that will. afford a good electrical connection, for example, by squeezing or compressing the ferrule l5 against and into the opposite side of the projecting end of the terminal as indicated at it; in Figs. 9 and 10, and the respective conductor it or 14 has the insulation removed from the inner end and is electrically secured in the respective ferrule 15, likewise in any convenient manner, as for example, by squeezing the opposite sides of the ferrule against the conductor as indicated at 11.

A short bushin iii of electrical insulating material having three openings 19 therethrough of suitable size and location to accommodate the ferrules i5 is inserted the extension 52 against the outer end of the heating unit, with the ferrules 15 completely contained in the openings 19 thereof, after which. another bushing 80, likewise of electrically insulating material and with a central opening 5! just large enough to accommodate the three insulated conductors 12, I3 and 14 is inserted and locked in the outer end of the extension 52 which is preferably of such length or cut off to terminate at the outer end of the bushing 80.

This locking of the bushing in the extension 52 may be accomplished by providing the bushing with a peripheral groove 82 and pressing the metal of the extension 52 circumferentially therein as indicated in Fig. 9 to provide the circumferential groove 59 for engagement by the staple leg 56 to hold the extension 52 against endwise movement in the pivot housing 4|.

In view of the fact that the portions of the conductors 12, i3 and M where they enter the openings 19 of the inner bushing 18 are spread apart radially and circumferentially from the centralized location thereof in the opening 8| of the outer bushing, a slight bend 8-3 occurs in each conductor '12, I3 and i4 between the bushings l8 and 89, which, when the bushing 88 is jammed firmly in place and retained by the interlocking connection 59, 82 against these bent portions, provides a. locking of the conductors in the extension 52 whereby they are secured against Withdrawal from the extension 52 and any separating strain on the connections of the conductors with the terminals 68, 1E] and H is entirely eliminated.

Moreover, by reason of the conductor bends 83 which are clamped between the bushings l8 and 80, the inner end of the bushin 88 is spaced from the outer end of the bushing 18 and provides a convenient place where the depressions Gl and 62 in the extension 52 may be provided without interfering with the bushings.

:With this construction, the

conductors

12, 13 and 14 extend axially out from the end of the heating. unit l8 or end extension 52 thereof exactly at the axis of pivotal movement of the heating unit in the housing 4| so that in the lifting of the heating unit from the normal position in the pan-like support l9 to the upright cleaning position I811, no bending of the

conductors

12, 13, and 14 occurs but instead, merely a quarter turn twist thereof which these flexible conductors will safely withstand throughout the life-of the heating unit without any danger of breaking which has been frequently experienced with the connections of electrical supply conductors heretofore required with other heating units.

To avoid any imposition of pulling strains on the conductors 12, I3 and 14 or abrupt bending thereof at the outer end of the heating unit which might occur in carelessly installing these heating units if these conductors were left entirely free, a bracket 84 is preferably provided on the underside of the pan-like support l9 and secured thereto by set screws 85 threaded into enlargements 86 of a pair of the ribs to support the conductors l2, l3 and 14 which are looped back loosely in a wide bend from the outer end of the heating unit as shown in Figs. 1 and 2 and secured in this bracket, therebyproviding a predetermined arrangement of the conductors in the heating unit assembly which will permit the quarter turn twisting of the conductors in the pivotal movement of the heating unit without imposing any breaking down strains thereon.

With this heating unit assembly the coils of the unit lay down upon and are supported solely by the ribs 25 in the normal position. This not only permits-a more compact and neater arrangement of heating unit and mounting ring and refiector pan than heretofore with heating units wherein the coils were secured to a coil holder, but also leaves the underside of the heating unit entirely free and unobstructed so that it can be readily and thoroughly cleaned.

Moreover, the coils of the heating unit, since they are devoid of any coil holder or spider connection with one another and merely rest on the ribs 25, are not only free to expand and contract without restrictive strain or distortion in the heatin and cooling of the unit but because of the inner end being free the unit has greater flexibility and is capable of adapting itself to some extent to the weight of a utensil thereon, especially when operating at high temperature, so that the flattened top faces 38 of the coils contact more uniformly with the bottom of a utensil thereon than the previous frame or spider mounted heating coils, and better heat conductivity is accordingly assured.

Heating units other than that particularly illustrated herein may be employed. For example, the heating unit may have a single resistance as shown in my application Serial No. 566,856

for single heat use or for infinite variation of heat with a switch such as disclosed in Potter Patent No. 2,294,573 or the heating unit may have more than two resistors as shown in my application Serial No. 566,855.

Moreover while the cast pan-like mounting is preferable, it may be made otherwise as, for example, it may be stamped from sheet metal and the ribs 25 are not necessarily integral therewith. The ribs 25 may be omitted and the bot tom wall 24 provided with a plain top surface and a loose spider provided which rests on the bottom wall 24 and is provided with radial arms corresponding to the ribs 25 for supporting the heating unit in the same loose manner a in the illustrated construction, or the heating unit may i be provided on the underside at suitable intervals along the coil with lugs 81 such as shown in Fig. 14 welded thereto as at 88 for supporting the heating unit at suitable places on the bottom 24 of the pan-like mounting. The boss 23 at the center of the recess 20 of the pan-like support may be utilized for attachment of a name plate 89 if desired.

From the foregoing, it will be understood that while I have shown and described my invention in a preferred form, I am aware that various changes and modifications may be made therein without departing from the principles of my invention, the scope of which is to be determined by the appended claims.

What is claimed is:

1. In an electric heater of the class described the combination of a mounting with a heating unit supported thereon comprising a flat loose winding of metal tubing containing an electric heating element, one end of the tubing being free and closed and the other end being substantially tangential to the heating unit and at an angle to the plane thereof and having electrical conductors leading therethrough from the heating element said mounting having a bearing in which said substantially tangential end is journaled.

2. In an electric heater of the class described the combination of a mounting having a recess with an annular rim, a heating unit in the recess comprising a flat winding of metal tubing containing an electric heating element, said recess having a bottom above and below which are matching ribs which are integral with the bottom and extend outwardly from the center thereof, said winding being loosely supported on the said ribs at an elevation above the bottom and pivoted at one side of the recess under the annular rim to tilt upwardly from said ribs.

3. In an electric heater of the class described, the combination of a mounting and a flat spiral supported horizontally on the mounting and comprising a metal tube containing an electric heating element, said tube having a loose closed end constituting the inner end of the spiral and having at the outer end of the spiral a straight attaching portion extending substantially tangentially therefrom and at an angle to the plane of the spiral and containing electrical conductors which lead therethrough from the electric heat ing element, said tube having independent bearing engagement at separated places therealong with underlying correspondingly separated portions of the mounting whereby the spiral is supported horizontally on the mounting and free to lift upwardly therefrom, and a bearing on the mounting in which the aforesaid straight attaching portion of the tube is journaled.

4. In an electric heater of the class described, the combination of a, fiat spiral and a mounting having an annular rim within which the flat spiral is supported horizontally in a manner to tip upwardly therefrom, said flat spiral comprising a metal tube having a loose closed end constituting the inner end of the spiral and a straight attaching portion extending substantially tangentially from the outer end of the spiral and at an angle to the plane of the spiral, said tube having independent bearing engagement at separated places therealong with underlying correspondingly separated portions of the mounting within the annular rim, and a bearing on the underside of said annular rim in which said straight attaching portion of the tube is journaled.

5. In an electric heater of the class described, the combination of a mounting having a pan portion with an annular rim therearound and a flat spiral supported horizontally on said pan portion in a manner to tip upwardly therefrom, said fiat spiral comprising a metal tube having a loose closed end constituting the inner end of the spiral and a straight attaching portion extending substantially tangentially from the outer end of the spiral and at an angle to the plane of the spiral, and a bearing on the underside of said annular rim in which said straight attaching portion of the tube is journaled, said pan portion having upstanding ribs on the bottom. thereof which engage directly against said tube to support the latter at an elevation above the bottom of the pan.

6. An electric heater unit comprising a mounting which includes a pan, an electric heater overlying the pan and comprising a tube in the form of a flat spiral containing an electric heating resistance, one end of the tubebeing hinged to the mounting for tilting the heater into a substantially upright position, the other end of the tube being free and the entire tube being free to expand and contract, and the under side of the coiled tube and the upper side of the pan being unobstructed and accessible when the heater is tilted into an upright position upon its hinge.

7 An electric heater unit comprising a mounting which includes a pan, an electric heater overlying the pan and comprising a tube in the form of a flat spiral containing an electric heating resistance, one end of the tube being hinged to the mounting for tilting the coiled tube into a substantially upright position, the other end of the tube being free and the entire tube being free to expand and=contract, means onth'eupper side of the mounting for. supporting the coiled; tube in the operative positionthereof, the tube being unconnectedwiththegupporting means and free-- ly liftable therefrom and freely expansible contractible thereon, the under side of thexcoiledv.

tube and the upper side of the mounting being unobstructed'and accessible when the coiledtube is tilted into an upright position upon its hinge;

8. An electric heater unit comprising a pan,

an electric heater overlying the pan and compris'-- ing a tube in the form of a flat spiralcontaining,

an electric heating resistance; one end of the coiled tube being hinged at'the marginof' the pan for-tilting the coiled tube into a substantiallyupright position, the'other end of the coiledtube upper side of the pan being unobstructed andaocessible when the coiled tube is tilted into an upright position upon its hinge.

WILLIAM R. TUTTLE.

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

UNITED STATES PATENTS Number Name Date 1,973,629 Hofer Sept. 11, 1934: 1,998,330 Nivholson-et al Apr. 16, 1935 2,274,348, Sharp Feb. 24, 1942 2,368,051 Tuttle Jan. 23, 1945 2,392,076 Weigand Jan. 1, 1946'