US2506554A - Hinged heating unit - Google Patents

Description

May 2, 1950 w. R; TUT TLE I v HINGED HEATING UNIT Filed Dec. 6, 1944 2 Shuts-Sheet 1 M y 2, 0 w. R. 111m 2,50

HINGE!) HEATING UNIT Filed Dec. 6, 1944 2 Sheets-Stunt 2 NTOR.

Patented May 2, 1950 HINGE!) HEATING UNIT William R. Tuttle, Riverside, 111., assignor to Tuttle & Kift, Inc., Chicago, Ill., a corporation of Illinois Application December 6, 1944, Serial No. 566,856

8 Claims. 1

My invention relates to electric heating units of the sheathed resistor type and has reference more particularly to a construction thereof that is particularly adaptable to pivotal mounting.

This application is a continuation in part of my co-pending application Serial No. 566,855 (Patent No. 2,456,343) which discloses a coiled tubular sheath closed at one end and containing a resistor which has all of its terminals projecting from the other end of the sheath, and is also a continuation in part of my co-pending appli-- cation Serial No. 430,684 (Patent No. 2,368,051) which discloses the opposite ends of the tubular sheath of a coiled electric heater aligned and journaled in aligned bearings.

For many years it has been the prevailing practice, particularly in surface type heaters for electric ranges and similar purposes, to utilize a helical resistance which is enclosed in a tubular metal sheath and insulated therefrom by an insulating powder, such as magnesium oxide, which fills the tube and is compacted in and around the resistance so as to hold it centrally in the tube. Such sheathed resistors may be bent in the various shapes that may be required for the particular heating purpose and may also be flattened if desired to increase surface contact thereof with a utensil or other article to which heat is to be communicated from the heater.

When such heaters are used as surface units for electric ranges and other similar purposes, it has been customary to bend them in serpentine, spiral, or other appropriate form to provide the required heating area with suitable concentration and distribution of heat in that area, and moreover such units are usually located over a pan like member which not only serves as a refiector to direct the radiated heat from the unit to the pan or utensil that is placed thereon but also serves to collect any drippings or overflow from the pan or utensil.

In such cases it is frequently necessary to clean the unit on the underside and also to clean the reflector pan thereunder and accordingly it is the practice, when these heating units are employed for range surface units and similar purposes, to arrange the heating unit for removal or suflicient lifting from the pan like reflector to afford access to the reflector pan and to the underside of the unit for cleaning.

Hinging of the unit at one side of the reflector pan so that it can be tipped up therefrom for cleaning is the most desirable arrangement to permit separation of the unit from the pan for cleaning the underside of the unit and the reflector pan, but such hinging has heretofore been difiicult and uneconomical because of the peculiar nature of these heaters and the electrical connections which must be capable of shifting as the unit is tipped up and at the same time maintained intact at all times.

In the prevailing types of surface heating units, it has been the practice to enclose each resistor in a sheath with the terminals of the resistor projecting from the opposite ends of the sheath and with such sheathed resistances, when bent in this conventional serpentine or spiral form it is necessary to extend both ends thereof to the place of hinging so that electrical connections may be made with the end terminals of the resistance at a place where such connections are least disturbed in the tipping up operations for cleaning. At least one end of the resistance usually terminates centrally of the heating area where it is not only difilcult to extend same satisfactorily to the place of hinging but it involves awkward and undesirable bending of the sheathed heater to locate both terminals at the place of hinging.

Moreover, it is desirable in these surface heaters of electric ranges to provide a number of different intensities of heat and for this purpose it is customary to employ several separate resistances, each independently sheathed, and connected through suitable switch as indicated in Tuttle Patent 2,317,967 to be selectively energized separately and conjointly to afford a number of different heating stages, in which cases it is even more awkward and difficult to locate the terminals of the several sheathed resistances at the place of hinging.

Furthermore even with a single sheathed heater having a terminal at each end as they are commonly made, it is quite difficult to provide a satisfactory hinge connection thereof for lifting from the reflector pan and the difficulties thereof are greatly increased when several such sheathed resistances are employed because of the additional terminals that must be extended to the hinging location and each provided at that location with an electrical connection therewith that permits and is unaffected by repeated tipping up of the unit that is necessary for cleaning.

Various forms of hinging connections have been employed for this purpose, usually with some cumbersome form of fitting or housing into which all of the terminal ends of the sheathed resistors are secured and oftentimes with some awkward. form of hinging which does not lend itself to easy manipulation of the heating unit to the tipped up cleaning position and return thereof to the normal position of use.

The principal objects of my invention are to provide an improved form of sheathed resistor which may be hinged in a simple and satisfactory manner so that it may be readily swung to and from its normal position; to permit several resistors to be employed, if desired, in the heater with the same simplicity and convenience of ance; to' permit a better distribution and more eflicient utilization of the heat output of electrical heaters; to eifect economies that will materially reduce the cost of electrical heaters; to arrange the terminals so that electrical connections with a hinged heater are conveniently made and in such manner that they are not impaired by repeated swinging of the, heater to and from its normal position; to provide an improved composite assembly of heater, reflector pan and mounting ring; and in general to simplify, facilitate manufacture, minimize cost, increase the eiflciency and utility of sheathed resistor heaters and assemblies thereof and permit hinging of the heater in a more satisfactory and convenient manner than heretofore, these and other objects being accomplished as pointed out hereinafter andas'shown in the accompanying drawings in which Fig. l is a top view of a heatin unit made in accordance with this invention, assembled for mounting'in a range top, parts of the heating unit'and mountin ring being broken away to disclose details of construction;

Fig. 2 is aside view of the hinge mounting of the unit of Fig. 'l-and shows a fragmentary portion of the range top in which'the assembled unit is mounted;

"Fig. 3 is an end view of the hinge mounting of the unit ofFig. 1; a

is a sectional view 'Of the inner end of the sheathed heater taken on the line 43- 3 of Fig. I;

Fig. 5 is a sectional View of the'unit'assembly taken on theline 5- 5 of Fig.1. and showing adjoining portions of the range top in which the unit assembly is mounted, one of the arms of the wire "spider whichsupports the heating unit having the outer end portion thereof broken away to disclose the other spider arm therebehind;'and

Fig. 5 is a view similar to Fig.5 but showing the heating unit in the tipped up position.

Insaid drawings, which illustratean embodiment of the inventionsuitable for use as a sur- 1 face unit of an electric range orthe like, the reference numeral H indicates a range top in which the unit is mounted and which has the usual opening l'2 'therethrough within which the heating unit assemblyis located.

A ring 53,.simi1ar tothe'rings usually provided for mounting electrical heating units in range tops, fits in'the opening [2 and 'supports'the unit, said ringconstitutin apart of the unit assembly and having an 'outturned annular flange [4 around the top'which rests on the margin of the range top opening, saidmargin being preferably depressed as'indicatefd at ['5 to provide an annularseat for-the flange In so that the top'oi the ring is is flush or substantially flush with the range top ll.

This-ring 13" has a depending skirt portion '16 formed therearound at its lower end with an inwardly extendin flange li', preferably folded' as shown, upon which a reflector and drain pan is is removably "supported, said'drain pan i8, which may have a central drain opening labeing provided with an outturne'd marginal flange 2% which extends over the supporting flange Ii.

pace for'air circulation is provided around the pan i8 andto this end the diameter of the 7 pan is su rhcientlyless than the internal diameter of the skirt Site-leave asubstantial ventilation 7 space between the'skirt I'E'and thepan margin 253, and the folded flange I i is also bumped up at intervals therearound to provide spaced elevations upon which the marginal flange 20 of the pan tests so that between the elevations the skirt flange I? to aiford substantial ventilation space therebetween.

The flange I! and bumps 2i preferably slope downwardly from the skirt as shown and the pan margin 20 is correspondingly sloped, which correspondingly sloped arrangement not only serves to facilitate centralized positioning of the pan is within the skirt IE but also provides upward direction of air flow between the overlappin pan margin and skirt flange jlhe central drain opening itjwh'ich also contributes to ventilationfis p'referably sufiiciently large-so that the finger may be engaged-therein for convenience "in removing th'e drain {pa-n which merely rests upon thebu'mps orele'vatio'ns 2i and'i's liftable readily therefrom. a

The heating unit 22 is of'conventional metal tubular sheathed type wherein a lielicalresistance wire is embedded "in compacted insulation'with-e in a length ofseam'less or butt welded tubing but diiiersfrom 'such' conventional metal tubular sheathed heating units in the respect that all of the terminals for thecontained-resistance are atone'end of the metal tube'and the other end thereof is closed as for'example by contracting and. welding together that end of themetal tube or by welding a closure'cap thereon as explained in my aforesaid application Serial No. 566,855.

"In :my aforesaid application Serial 'No.'566, 855 of even :date herewith metal tubular sheathed heating units are disclosed havingmore than one helical resistance embedded in compacted insulation within a single tubular -metal sheath which is closed at one end and has all of the terminals at the other-end and any of such plural resistance heating units with all of the terminals at one end may be "employed in connection with the present invention although for illustrative purposes herein I have merely shown'a single helical resistance with a return wire leading therefrom at the inner closed end-of the tubular sheath to the other end of .the tubular sheath where two terminals project for connection with the source of current by .Which the resistor is energized.

In the illustrated heating unit 2.2, which 'is bent in the'form of .a flat spiral to .providea suitable heating surface for cooking and similar purposes as required in suriace type units of electric ranges, the helical resistance is, indicated at 2'3 and extends from end toend ofitheimetal tubular sheath 24 which is closed atthe inner end as indicated "at' 25 and 'at'the outer end of said sheath said'res'istance '23 is provided with alter, minal 23a of lowjresistance'which is electrically connected fwith the resistance 23 within the sheath near theouterend thereo'f and projects therefrom for 'connectioniwith a suitable source of electric current.

A return wire 2? leadsfrom the inner end of the helical resistance23 back through the tubular sheath 2a to the outer end thereofwhere it ,is also provided withfa terminal 21a of low resistance whichis likewiseelectrically connected within the sheath near the outer end thereof with the return'wire 27 and projects from the outer'end' of the tubular'shefath 214.

H Thisjreturn wire maybe a separate conductor joined to "the helical ,resistance '23 at the inner'cl'os'e'd'end'of'thetubular sheath 24 but I prefer to employ as the return wire an additional integral portion of the wire of which the resist-' ance 23 is formed, and running back within the tube 24 under the resistance 23 to the outer end of the sheath, it being understood, of course, that the resistance 23 and return wire 2! are embedded in compacted insulation 28 in separated relation from one another and from the sheath 2% so that they are electrically insulated from one another and from the sheath 24 throughout their length.

In practice, I have found that a particular satisfactory return wire may be provided by forming a helix of the resistance Wire of a greater length than required for the resistance 23 and then stretchin out number of surplus coils of the helix at one end almost straight and bending this almost straight length back as shown in Fig. i in parallel spaced relation to the helix 23 to serve as the return wire but leaving enough twist therein for lengthwise extensibility to insure some extra length for expansion and contraction and any longitudinal strains that may be exposed on the return wire in the manufacture or use of the unit.

The helix 23 is of ordinary cylindrical form when assembled in the tube 25 and the connected ends of the helix and of the return length 22 are held in the proper location at one end of the tube 24 while the insulation 28 is supplied and compacted in the tube as will be understood by reference to my aforesaid application Serial No. 566,855 of even date herewith, the insulation being sufliciently compacted so that the assembled structure may thereafter be bent into the spiral form disclosed herein and also flattened without disturbing the relative location of the resistance 23 and return wire 22 in the tube. Ordinarily, in units such as disclosed herein, the flattening occurs after the bending into the spiral form, in which operation the helix 23 is deformed transversely into a shape that conforms substantially to the flattened shape of the sheath or tube 24 as shown herein.

For holding this spiral sheathed unit rigidly in fiat spiral form a spider 29 is employed formed of a stiff heavy wire which is bent into the requisite form with three radial arms 36 the upper lengths 33, 3B and 3'! of which are welded to the spiral unit as indicated at 3| This spider 29 is preferably formed of a single length of wire with a down turned end 32 at the center of the spider and the wire leading from the top of said down turned end 32 radially outward at then downwardly and back to the center as at 34, then radially outward as at 35, then upward and back to the center as at 36, then radially outward as at 3?, and then downwardly and back to the center as at 38 where it terminates in an upturned end 39, said downturned end 32 and upturned end 39 being rigidly secured to one another by Welding or in other convenient manner to form a composite hub from which the three wire arms radiate, and the intersections of the top wires 33, 35, 3? and bottom wires 34, 35 and 38 being secured together and to the upper and lower ends of the composite hub 32, 39 by welding so as to afford ample rigidity.

A dish or shell 26 is usually provided at the center of these units which may serve as a name plate and this is attached to the arms of the spider in any convenient manner.

This spider 29 is particularly advantageous as it not only is easily produced but it affords an especially strong reinforcement and support for the spiral unit and moreover it provides a ventilated support all parts of which are rounded d and has no sharp edges that might scratch or injure the hands in cleaning the unit.

The outer ends of the spider arms 30 rest loosely on the flange 20 of the pan I8, preferably at the places where the flange 20 rests on thebumps 2| and thus the heating unit 22 and itsspider are supported by the mounting ring l3 and preferably at a suitable elevation so that the flat top of the heating unit is only slightly above the top of the ring flange M which as previously indicated is substantially at the same level as the For this purpose the outer end portion 42 of.

the unit 22 is arranged to extend tangentially from the outer convolution of the unit as shown in Fig. 1 and is inclined downwardly from the plane of the unit as shown in Fig. 2, this downward inclination being sufficient so that this end portion 42, at the place where it extends outward- 1y from the ring- I3 is well below the flange Hi to afford ample space therebetween to accommodate the mar-gin of the top H as will be understood from Fig. 2, and this tangential downwardly in-.

clined end portion 42 is engaged in a correspondingly inclined housing 43 on the ring !3 in which said portion 42 is free to turn and thus provide a hinge connection of the unit with the ring !3 which allows the unit to rest normally on the pan rim 2!! as shown in Fig. 5 and to swing upwardly to the position shown in Fig. 6. In this latterposition the underside of the unit is freely accessible for cleaning as is also the pan l8, and it will also be understood that in this position of the unit the pan I3 is freely removable so that it may be cleaned more readily and also to give access to the space under the range top.

The housing 43 is preferably of sheet metal shaped in elongated open bottom box form as shown in Fig. 3 and of an interior size so that the unit end portion 42, which is round, is closely confined but free to turn therein. Preferably bearing engagement with the housing 43 is limited to a selected length at the outer end of the tangential portion 42 and to this end, in the swaging operation of making the unit, a substantial portion at the end, as for example up to the point Mi in Fig. 1, is left of a larger diameter than the remainder of the unit and with a gradual taper t5 therefrom down to the size to which the remainder of the unit is swaged. For example with a unit that is swaged to a diameter of threeeighths of an inch, the portion at the terminal end up to the point 4 3 may be left one-half inch in diameter with a gradual taper ,5 therefrom down to the point 46 beyond which the sheathed unit is reduced to the three-eighths inch diameter, it being understood that it is the threeeighths inch diameter portion that is coiled in the serpentine form to produce the utensil supporting surface and that this serpentine coiled portion is subsequently flattened, but that the flattening extends only to the point where the tangential portion 42 is deflected downwardly as is clearly shown in Fig. l, the tangential portion 42 remaining round.

pier holding the end portion 42 in the open bottom housing 43, a wire fastener t! of wide staple-like form has the legs 58 thereof inserted through the side walls of the housing near the bottom thereof so that the legs engage the end portion 42 at the bottom and'hold said end portion 42 against the top wall'of the housing, said end portion 42 being formed with a circumferential groove 49 in which one of the legs '48 of the, wire fastener engages to hold the end portion against axial movement in the housing. The wire fastener is held in place by bending the outer extremities of legs 58' as indicated at'iifi.

For holding the heating unit in the tipped up position of S a leaf spring'si is'secured at its opposite ends to the outerwall of the housing 33 and at its middle beers with substantial tension against a ball 52 which projects through an opening 53 in the side wall of the housing to engage the enlarged end portion of the unit 22. This enlarged portion of the unit has two depressions lid'and E5 lrcumferentially spaced approxmately 90 degrees apart, which are engageable by the spring pressed ball 52 and suitably arranged so'that when the unit is in the tipped up position of 6 the ball is spring pressed into the depression as so that it holds the unit in the tipped up position whereas when the unit is in the normal position-of Fig. l the ball 52 is spring pressed in the depression 55 to hold the unit positively in that position.

The pivot housing ll; may be attached to the ring 13 in any convenient manner that will insure ample rigidity, the housing in the present case having the outer wall provided with an extension 56 thereof shaped to, conform to the contour of the skirt iii of the ring and secured thereto by welding or in any other convenient manner, said outer wall and extension being also preferably provided with a continuous outturned flange El along-the bottom thereof for reinforcing.

At the opposite side of the housing the housing Wall is terminated at the skirt l6 and a brace 58' is attached at one end to said housing wall and at the other end to theskirt it as shown to hold the housing in rigid relation to the ring 53.

. The wall of the housing 43 at the sidethereof where the spring 5! is located is preferably formed with outturned ears Etand {iii to receive and hold the ends of the spring 5!, the ear spring 55 is insertibie endwise whereas the other ear 38 has a slot 62 which is at the top so that the corresponding end vof the spring is in sertiblc iaterally into the slot-52.

' The ball opening 53 in the housing wall is of suitable shape and size so that the ball 52 may notbeipressed entirely 'the-retlirough'by the spring 5!, and by reason thereof the ball is retained in said opening when the heating unit end is removed from the housin 53. 7

It is to be understood of course that the skirt iii of the ring iii has an opening therethrough at the inner end of the housing 43 to loosely accommoda-te the tangentialend 42 of the unit, said opening being indicated at as in Fig. l, and it will also be undcrstood'that when mounted in arange, conductors are-connected to the exposed terminals 23a and El a of the unit at the outer extremity of the tangential'end'which projects slightly beyond the outer end of the housing 43 as, shown in Figs. 1 and2.

Heating units, like that 'shown'herein, but havingtwo or more helical resistances therein and .all the terminals at one end of the enclosing preferably having a closed slot into which the end of the sheath maybe employedif desired instead of'theillustrated heating unit with its single resistance 23 and single return wire 21, as for-example two resistances of different wattage capacities may be employed, both connected to a single return wire or each having its own return wire and each resistance and each return wire having a terminal,

all of which are located at the same end of thesheath and usable with switch-es'such as disclosed in the aforesaid Tuttle Patent 2,317,967 to provide a number of different stages of heat, or as a fur ther example, three resistances each of a different wattage capacity may be employed, without any return wires, and all connected together at r the closed end of the enclosing sheath and pro-j vided with exposed terminals at the other end of the sheath, it being understood that the heating unit 22 hereof, which is usable with an ordinaryswitch for single heat purposes or with a switch such as shown in Potter Patent No. 2,294,523 for infinite variation of heat intensity, is merely illustrative-of the convenience and economy of metal tubular sheathed heating units with all 'the'terminals at one end of the sheath and the simple mounting for which such units are adaptable.

Flexible conductors are connected with the terminals of the unit to supply current thereto, as for example to the terminals 23a. and 27a, of the illustrated embodiment, and as the terminals are close to the pivotal axis of the unit there is no appreciable bending of the conductors which is likely to break the insulation or wires in repeated tipping up 'of the unit but merely a slight twisting' thereof which has no appreciable breakdown effect on the conductors such as is commonly experienced with other hinge arrangements 'of heating units.

From the foregoing, it will be understood that I have provided a heating unit and mounting thereof which is simple, substantial and with important advantages over heating units and assemblies heretofore available. The heating unit is of neat, compact and substantial appearance because of the single coil. construction without the one or more ends leading back underneath to the place of hinging which were required in previous surface heating units and because of the wire spider which lends attractiveness and obvious stability to the unit, and there are no abrupt or unnecessary bends which are usually difiicult to make and are usually the places where the unit ismostlikely to break down.

Moreover the hihging of the unit is simple and substantial and more readily accomplished than in previous surface heating units, and also permits conductors to be connected with the unit at a place and in a manner that assures so little bending thereof that they are immune to the wear and 'tear therein occasioned with previous hinging arrangements.

'Furt e'rmore with this heating unit there is substantial economy in manufacture due not only to the employment of a single sheath for all resistances instead of separate sheaths therefor when several resistances are employed, but there is also a saving in tubing, insulation and conductors that has been required heretofore to extend'both ends of the sheathed resistances to the place of hing'ing for connection of the current supply conductors therewith.

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 the invention, the scope of which is to be determined by the appended claims.

electrically energizable helical resistance and a return conductor both of which extend lengthwise of the tube and are electrically insulated throughout their length from one another and from the tube and are electrically connected to one another at the inner closed end of the tube and a each having a terminal at the outer end of the said substantially tangential outer end portion of the tube.

2. In a heater of the class described the combination of a mounting ring having a substantially tangential bearing, a heater coil in the ring comprising a metal tube coiled the form of a fiat spiral and having an outer end portion extending substantially tangentially from the outer coil of the spiral and iournaled in said bearing, said tube having therein an electrically energizable resistance which extends lengthwise of the tube and is electrically insulated therefrom, and a pair of terminals at the outer end of the sub stantially tangential outer end portion of the tube and electrically connected respectively with the opposite ends of said resistance.

3. An electrical heater comprising a length of metal tubing which is open at one end and closed at the other end and coiled in fiat spiral form with a straight portion at the open end thereof extending tangentially from the outer coil of the flat spiral, and a supporting frame for said flat spiral having a bearing in which said tangential portion of the tubing is engaged for hinging the flat spiral to the supporting frame, said tubing having a plurality of electrical conductors, at least one of wh ch is a helical resistance, extending lengthwise thereof in side by side relation and insulated from one another and from the tubing and said conductors having terminals projecting from the outer end of the aforesaid tangential portion and said conductors being connected together at the other closed end of the tubing.

4. In an electrical heater of the class described the combination or a mounting ring having a bearing extending substantially tangentially therefrom, a coiled heater supported in the opening of said ring and having an end portion projecting outwardly through said bearing and provided with separate electrical terminals projecting from the outer end thereof, said coiled heater comprising a metal tube with at least two conductors, one of which is a helical resistance, extending through said tube from the aforesaid terminals to the other end of the tube, the latter end of the tube being permanently closed and the conductors being connected together therein at said closed end of the tube.

5. A pivotally mounted electric heater comprising a bearing and a fiat winding of metal tubing one end of said tubing being open and engaged in the bearing and the other end of said tubing being closed and free, said tubing having therein an electrically energizable resist- 10 ance which extends lengthwise of the tubing and is electrically insulated therefrom and provided with leads through which the energizing current is supplied thereto from the exterior of the tubing, all of which said leads project outwardly through said open end of the tubing.

6. A pivotally mounted electric heater comprising a bearing and a flat winding of metal tubing, one end of said tubing being open and the ether end of said tubing being closed, the end portion of the tubing at the open end thereof being located at the margin of the flat winding and engaged in the bearing to provide the-pivotal mounting of the heater and the tubing at the closed end thereof being free, said tubing having th rein an electrically energizable resistance which extends lengthwise of the tubing and is electrically insulated therefrom and provided with leads through which the energizing current is supplied thereto from the exterior of the tubing, all of which said leads project outwardly through said open end of the tubing.

7. A pivotally mounted electric heater comprising a bearing and a fiat winding of metal tubing, one end of said tubing being open and the other end of said tubing being closed, the end portion of the tubing at the open end thereof being extended substantially tangentially from the margin of the fiat winding and engaged in the bearing to provide the pivotal mounting of the heater and the tubing at the closed end thereof being free, said tubing having therein an electrically energiz-able resistance which extends lengthwise oi the tubing and is electrically insulated therefrom and provided with leads through which the energizing current is supplied thereto from the exterior of the tubing, all of which said leads project outwardly through said open end of the tubing.

8. A pivotally mounted electric heater comprising a bearing and a flat winding of metal tubing, one end of said tubing being open and the other end of said tubing being closed, the end portion of the tubing at the open end thereof being extended through the bearing as the journal member thereof to provide the pivotal mounting of the heater and the tubing at the closed end being free, said tubing having therein an electrically energizable resistance which extends lengthwise of the tubing and is electrically insulated therefrom and provided with leads through which the energizing current is supplied thereto from the exterior of the tubing, all of which said leads extend from the open end of the tubing through that portion of the tubing which is engaged in the bearing.

WILLIAM R. TUTTLE.

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

UNITED STATES PATENTS Number Name Date 1,268,990 Moeller June 11, 1918 1,359,400 Lightfoot Nov. 16, 1920 1,823,925 Woodson Sept. 22, 1931 1,998,330 Nicholson et al. Apr. 16, 1935 2,271,978 Hjelmgren Feb. 3, 1942 2,368,051 Tuttle Jan. 23, 1945

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