Document qaV5bygJkx5YQO0xZR0o8O4Mx

FILE NAME: McGraw-Edison (ME) DATE: 1950 Feb 23 DOC#: ME023 DOCUMENT DESCRIPTION: Patent - Enclosed heating element [Approved -1954 June 1] June 1, 1954 F ile d Feb. 23, 1950 J. R. G O M ER SA LL ENCLOSED HEATING ELEMENT 2,680,183 3 Sheets-Sheet 1 June 1, 1954 F ile d Feb. 23, 1950 J. R. G O M ER SA LL ENCLOSED HEATING ELEMENT 2,680,183 3 Sheets-Sheet 2 UOHN INVENTOR. R. G O M E R S& L L i*s>. -*7y , ~ r -- attorney. June 1, 1954 F ile d Feb. 23, 1950 J. R. G O M E R S A L L ENCLOSED HEATING ELEMENT 2,680,183 3 Sheets-Sheet 3 BY. <17 on* Patented June 1, 1954 2,680,183 UNITED STATES PATENT 2,680,183 en clo sed h ea tin g elem en t OFFICE " s S s .'S '-r poration of Delaware ' ' IIL' a eor- Application February 23,1950, Serial No. 145,752 4 Claims. (Cl. 219--19) iJ e m e 2 * 1TM t t a * > - - viriP ifr,an 0bject 0f th e presenfc invention to pro- menJ f electric-resistance heating Ele m ent suitable for electric toasters, broilers cook .X s v s : i ns o,e"s' s ce S i construction^ 8 & h e a to g element oi a modified element of Fig. 6 toaster of K g 8? 6" " * '0 irCUit di" t o the t e i r - th" - S " A further object is the provision of an m proved constructton , . r J e l e o ^ S S i - s s r s t r .; 10 - 2 f K S T S Y o o S T * " " * . According to my invention, I enclose a re^isf s o " " 11 ' * " IM M OOP S ' 13 | aJ ieJ 0f, a fu rth er m diflcation; 1 the vention I employ a round tube of a m atertaf , w ^ tran sp aren t to a substantial p ^ t h eat th a t will em anate from th e heating conduc- into a S j s h a p f a n ' d t o 00^ ^ 0*01' CTimp 3t 20 element of Fig. r 3T Sa n d tlVe f the heating onff tfnXe ih!e5atIisnagneleeimlIaerngteodf sFeicgt.io4n. of the termmimnaall The specific toaster of Fig ' 1 innindoc Q 0, oven fram e members (2 and fd n ?asing moval dauuccttoorr iiss llooosoe fthl efr"e-in1^. I6 then form th B 25 1" ~Circuit wires 22 f o r I h e electric' ' Z raCk f S ^ t S & ' i S Z ' Z l 'SSS S e e ta tS S h 1ltt 18 t Uilable fr the particular ments of the toaster, a switch for c o n S o lw r a ck TM 1 w itch d a haDdle 20 f01' controlling the tSohbTe ,s'pi macteede e0ansi`lfy01a' lo1n1g ptheTMe leltnegth oft toheEtrbr either at uniform intervals or in any desired pat tern of non-uniformity and insures that 30 heating elements8^ ," e tc io f^ v h to h L fs^beit S g Ts S i d T ^ a 8laSS * * > U t a S not be damaged in the fabrication process The th e tube a t only a few spots 35 ls only slight conduction of h eat thereto This construction permits a high con ductor tem perature for efficient radiatfon ac imum durability Iaonwd tusabfeetyte.m perature for max-" 40 These and other objects and advantages of g E K 1* aPParen t from the follow- 2 S i S S.IZi S i L i S i i S a w S n .n2 ,2 5 ,bS t<5ST bS PUt in t practice- In th e 40 1 ?s a sectional elevation of an electric toaster containing heating elements constructed * p Ccordance wnh the present invention; o n ^ e f t o e l l a t f H r i ' ' " 2 a aMl" " " cShaaSnn,eelf .4.W"an5d rlies foarrmousnd,0 the glass fnhp ac Fig. 3 is a detail on an enlarged scale consti tuting Flff laisceecti-o-n---ta-k-Je-i-ni-,-.o-.nv,the ..line 3 -3 of Fig i Ai` Tbu t o e ! , ,S toM H e , ube 2, 680,183 ing space as a t 56, 51 and 58, shown exaggerated in Figs. 2 an d 3, to allow for any difference m expansion between the glass tube and its sup face in contact with the air, operates at a tem perature fa r below th a t of th e nooon. P Flg 5 shows an alternative configuration 101 porting structure when heated. , P The m etal sheet 8 is preferably bright so th a t 5 E atu te consists of two similar p attern s of it serves as a reflector for radiant h ea. and short horizontal runs connected by single thereby both confines m ost of th e h e at to the the two p atterns connected to g .th e, by a sing oven space and increases th e intensity of rad ia long horizontal ru n across tn e ^top. T im ai tion applied to the bread. As is shown m B b. rangem ent perm its both 01 the ^ th e oven-fram e members 12 an d 14 . ^ e ben t- 10 located a t th e bottom edge oi the p a a e in . n. out ears 13 which constitute guides w ithin which supporting plate for the heating element of Fig^ th e channel pieces 48 lie for supporting tHe h e a t 5 is shown in Fig. 8. T here a plate has im m ed ing elem ent in th e toaster. T he upper lead `Q side channels 72 sim ilar co t h e I f n e l of conductor 34 is brought out to a screw te r Fio- 1 and in addition h a 3 a epaiaU ^han^ m inal 44 (Fig. 1) on th e outer face of m e oven io niece 14 running down its center for noiding t . fram e 12. The lower lead is riveted under a m etal grommet supported by insulating washei on plate 45, to w hich grommet, circuit-w ne 5 U-bends near th e center of the The leads are riveted under metal which are insulated from die plate 70 oy m is connected by a bolt 48. As is shown diagram m aacally m Fig- < m e 20 ^ T h ^ rib lm n C o n d u c to r bends most easily about separate heeating elem ents 38 of th e toaster are the longer axis of its cross section, and since n connected in parallel with each other andj-he resulting group is connected in series circuit, v. ith i loose a eiare t o o to M m >* e gss the crimped ribbon in the cui^ed parts a terminal tim er which includes a heating element S Z i S tube springs into foe ori.ntution sbou 60 and its sh u n t contacts 62, which are not 25 i r Figs 1 4 and 5 so th a t th e piane 01 dm 11b-on otherwise shown in the drawings, and a 0 - oem endieular to the plane of the curve of the series w ith th e m ain switch 24. Power is applied lube in t t e toaster of Fig. 1, for example the to th e two leads 83 and 64. As is shown more clearly m Figs. 8 and 9 tne ribbon is merely crimped and not twisted amally r-oouii 10 o fsr*^ pd^e-on toward the resistance conductor 34 preferably is m the foil 30 Figs. 10 end 11 of a th in ribbon which is deformed and lies loos,, in the tube. Preferably I first crimp the nboon to give it a generally zig-zag shape so th a t n com s s s vassset r r r TM nrises a series of longitudinal waves. A single short length of ribbon such as th is usually has 35 excellent uniformity, but various samples oi ab bon, even from th e same spool, may have m a axiafiy will have been selected to come ab t terially different thicknesses._ In m any heaters, junctions 88 between the curved ^ sirm gh 553?oi such as those used for electric toasters, n, is sirable th a t th e heating units be provided w ith 40 equal electric resistances so tn a t th e several ele m ents of any one to aster will perform alike. Ac cordingly, in form ing th e crimps, I make them, sharp so th a t th e crim ped ribbon will be short. I cut th e form ed ribbon to th e desired resistance 45 S ? s v S e longitudinal axis of t h . c-- value, stretch it out to the required length, attach or form the lead-ins, and insert it m a straight ribbon taken at spaced points 01 said axis different orientations about th a t ax . glass tube. I then form the tube to the desired shape by heating it. Finally, I soften the ends o I n Fig. 12 th e construction ox i 1 b ent into a surface th a t is pare 01 an erect cyi th e tube and pinch them against the wire. As 50 inder so th a t the straight portions sO of l 1m ay be seen in Figs. 8 and 9, this crimped ribbon have become curved in a horizontal plane, but conductor 34 touches th e glass t u b e o f gitudinal intervals a t th e crests 66 and 68 0 with a less sham curvature, and thereiore longei radius ofScurvature, th an the U-bends. Here th e waves (Fig. 9) an d th e n only a t tn e edges thp 90 angle of axial tw ist a t pom i 86 m the of th e ribbon (Fig. 8). Furtherm ore t j e wire 55 S b o n corresponds to th e difference in duection lies loose in th e glass tube and so will actually touch the tube only at a few of these corner like points. T h a t is to say, th e edges of t h e 11L- ribbon in each p a rt of th e tube lies approximately bon a t th e crests 65 and 68 of only some of the longitudinal waves contact the tube wmle the crests of other of th e waves will be spaced from the tube, as shown in Fig. 8. The overall thick ness or height of th e ribbon determ ined oy the wave form ation is such th a t the zone 01 leetangular cross section defined by the waves (Fig. nprnendicular to the radius of curvature of th p a rt The straight runs in th e tubes, as m_Figs. ,, j 11 ohould be regarded as portions of zero curvature and therefore as having a J ^ e n t pm-vature th a n do th e U-bends. The m eum 01 gg curvature of such straig h t portions m ust of course be regarded as having infinite value <md 8) in its greatest dimensions will be less th an the ^ i y 'n m f a t d im prered heating element is useful diam eter of th e tube. Accordingly, while the also in various other cooking and heating devices heat-generating ribbon is entirely supported by o r example the reflecting rad ian t heater of th e glass tube, it touches it only a t widely spaceo. 70 K - 13 W e a glass tube 00 having a crimped points and is able to conduct only a sm all am ount ribbon conductor 82 extending there tro u g h m s of h e a t thereto. Since glass is tran sp aren t, mo&u formed in the shape of a bifilar tap eied helix. of th e h e a t th a t radiates from th e ribbon passes The specific shape of this helix is best seen m out through th e glass w ithout heating it, and Fig. 14. A m etal rod 84 extending through the consequently th e glass, since it h as a large sur- 75 ,6 8 0 ,1 8 3 f f t i A e VlS f r SUPIl0 rt a t thS outerm ost P art of heating p1BP I J1 exposed constructions, the sectional area the ribbon would be less stiff nerim ^ ele2nen* of my present invention is su eexxeerrttssqffaarr ssmmaallilelrrr ffbobrcens iSagmainrset ctohme ptluibanet aanndd it heating conductors because an? p w -1 s danger t0 Persons from burns 5 sligbttvT s tietndency t set UP noise when it moves elem enM n f SnCk` ^ th e same reasons my SmoSSi" " re ^ For use in toasters and th e like, I now prefer Sr* S u c s r s S s f s s r i The fa it f L l t n PandS Under rising temperature, limffl ti l th * ^ crimPed ribbon lies loose fu rth er th l iL n mechanical forces it can exert against tteennrdielnnncy tto tgheeneturabtfe annodises.o fu rth er reduces any at^nnm Uf h elass ^ an excellent electric insulator itnhei ScSonIdauicttmor 5 w ?hi'?ch; 1 ?is" ot p0e1rlahteedraaat" redn ht eoar cI iIeIntly con1?duPce+triantUg 1a'et lhtigish litkeemlype4r0atbuerceosmfeorsueffxi- F % Wwh?rhntt S the tem Peratures of 800-1000 aTM ' WbSf glass reaches red heat,'to con- ? *, Wh\ch m ay be subjected. For greater l n dut eui rents th a t m ight be dangerous to a person handling the toaster or other appliance i n TM For uses'i n v o l v i n g a high-silica S^ss. am r.il 1 ? 1 g lower temPeratures, as for ey- e heating element was employed. The ability s S e heatel? T VenS' drying ovens and m ateriaii I f m ay ei? ploy resinous insulating m lthli 1 h as Polytrifluorochloroethylene methyl silicones, polystyrene, methyl m th- mito mTMy gnhaeSaSitetrUbceont0struPcetriaotne aret daucIoews ttehme phearzaaturdras rom such possible leakage currents. The asbestos paper spacers 52 th a t hold the acrylate or nylon. Such substances do nflTe-- glass tube out of direct contact with the metal brittll6 anddSffnr th a t dreaeSsognlaSwSil'l bbuet pthreefyerarreed lfeossr low enough Wp6n t]?e tem peratures involved are Pareto I S ' i Porcelaln' th pSh far less trans- Tsitaabbllee a t higherSrteeamSplleyraftourrmesedt-h aisn misecghlaasnsicaalnldy so may be preferred when th e higher fa'ansparency and pliability are not required. Poly- supporting channels 48 not only provide T s o ft and y ^ ^ mounting for the ^ ratohng th a t m ight result from the loose m ount5 mg, but also add materially to the electric insula tion. In particular they provide a low-leakage enough h i S f ^ ^ bes When they become hot At 'cnaucf objectionabie electric cur rents. Although asbestos may be somewhat hy- teti afluoi oethylene is resistant to higher tem 30 groscopic and by itself m ight contain enough peratures th a n are th e other resins but is limited moistui e a t room tem peratures to perm it danger- to uses m which pliability is not required h r a t i u i f t t i r m 611^ ' neverfcheIess. as the toaster conductor It m5i beat-generating m etal leave the' Ur6 18 thoroughly s p e lle d to rh , u ls out of direct contact with 35 time S ^ non-conductmg by the the atmosphere and only a limited supply of oxy time the t,lass reaches a tem perature a t which gen is available for its chemical erosion Ac the g ass, by itself, m ight conduct current. The cordingly i can operate a glass enclosed element asbestos and glass consequently provide a eom- ^ yn Z eSent T m tin a t a higber temperature^ posite m sulatm g construction which assures free- and obtain a longer life th a n is possible with 40 current0^ dangel'ous' or even annoying, leakage h S h ^ 1' ? 16 PMn 'i Vire heating elements. The current at room tem perature, a t high operating higher permissible temperature not only provides a more intern, rM tant heat but also p e . S S toThe6 ofher68 ^ dUring th tran sitiP from one S hlrfer L UerJ 3leP en t- Particularly w ith a shortei total length of conductor and glass tube I t will be apparent to those skilled in the a r t th a t my invention is capable of numerous modi- Z Z Z aZ l T tions with a consequent saving in cost. ' within the scope of the used T r f t L letailng.eIements, as for example those i d in toast!:rs' 1<; 13 desirable th a t th e h e a t- I claim: m tl? l0W 80 th a t i4 can cause very + u' A.n, electric heating element comprising a little dela,y m the heating and cooling of the sn t h eat`resistant electric-insulating m aterial 50 and of curved cross-section and a crimped m etal Such delay adds to th e diffi- tt`? f th ^ ln f CO]flrollin8' the toaster to make toast of S 2 S , ; esl5t,n" " S S S which +LCOir f gardless of th e tem perature to flrfin^Sh th 4 having lon'itudinal waves del ^ .h th e toaster m ay have been heated by i is i s s ssasssas previous operations. The low temperature of the eara"i n r **-- iissUssttoorreeddPmin tthhihsmldandneWrn, thine aamddoituinotn, mhyepartetshenatt construction provides adequate support for the tube and puts little or no strain u??n it c J S res2isttm el w elemen1t comprising a tube of h eatresisiant electric insulating material and of cir th e ? r? lly th tube can have a th in wall to fu r- calar cross section having a series of portions 0 extending m spaced parallel relation and U- ity6of I h ^ h e a t t ^ e l e m e n t ?16 * * * ^ ^ shaped bends in the tube connecting each adja- I have found th at under certain conditions a conductor m a tube will produce a high-pitched Smaetfaell eelcetcrtrficc hnePaatirnagilerIePsisrttainncse. rainbdboancrhiamvpinegd squeal-like noise as it heats up. This noise ap longituomal waves defining a zone of rectangular pears to be produced by the movement of the cross section extending continuously through all mf conductor acrss th e surface Oj. said parallel tube portions and said tube bends said ribbon making contact only at longitudinal' thhee ituubbee. }I find th a t thismnothisee ccuarnvebde paatrtlseaosft wffhrlu IS and 01Jly a t its edges a t crests of waves reduced, and usually elim inated by using a X vn w,,l t h .fh lf a11 of the tube and the opposite ends t tnhPCn f w and by haying ^ fit loose to of said ribbon having sealed connections with and th e tube As oetween a ribbon and a round wire the^ube118 Utwardly beyond the opposite ends of , aymg tb5 same heat dissipating surface per unit length, the ribbon has the smaller cross 3. An electric heating element as in claim 9 sectional area, and even with the same cross- wherein the greatest dimensions of the zone of 7 rectangular cross section defined by the waves of 0, 680,183 the ribbon are shorter than the diameter of the tube and the edges of the ribbon a t reeurrent wave crests are spaced from the wall of th e tube. 4. A heating element according to claim 2 wherein the faces of the waves of the ribbon m each U-bend of the tube lie substantially per pendicularly to the bend plane and the faces of the waves of the ribbon in the parallel tube por tions lie substantially perpendicularly to the wave faces in said U-bends of the tube. 10 1,104,054 1,334,850 1,395,963 2.061,516 2,150,285 2,244,960 2,332,392 2,344,908 2,464,147 R eferences C ited in the file of this patent UNITED STATES PATENTS Number 425,043 Number 1,032,267 Name D ate ,, 15 B a s tia n ____________ July 9,1912 Oo L in d e r------George et al. K p p e rs---- F r e s e -------M arek et al. N elson------M in ie r -----W hitman -- M y e rs ------- July 21, 1914 M ar. 23, 1920 _ Nov. 1,1921 Nov. 17, 1936 Mar. 14,1939 June 10,1941 Oct. 19, 1943 Mar. 21, 1944 _ M ar. 8, 1949 FOREIGN PATENTS Country Date G reat B rita in ---------- M ar. 4,1935