US2400508A - Gas cooker - Google Patents

Description

R. HERMANN May 2l, 1946.

GAS COOKER Filed May 22, 1943 v F Ill /O 3 Sheets-Sheet l Flc. 2

May Z1, 1946. R. HERMANN 2,400,508

i GAS COOKER Filed May 22, 1945 .3 Sheets-Sheet 2 May 21, 1946. R. HERMANN GAS COOKER Filed May 22, 194:5 s shees-sneet' opengas rings orv Patented May y21p,r 1946 This vinventionY relate to 'iinproventi?I fililgas cookers. .Y In the' ordinar'ygas cooker whichy isin general use the-top lr hot plate comprises a number of burners arrangedfb'elow skeletonfsupports for cooking utensi1s.f'Ihe-'uten`sils are heated" directly byf the names and "110.11 prod ucts of `c'ombustion'from the burners. Tests: show that 'the efficiency "of this' metho'drfof4 heating Tis between 40 'and'50' 'per cent. *..Part ofrthe loss is' due to the fact that the rate of heat 'transference from a-gaseous'metlium to a v"solid `mediumis'cornparativelyrv4 low Aand the products ofconibustion are in contact With'thesurface ofthe utensil only forrarelatively short period'of time as they flow overit. Y yCookers, are kalso known which theburnrs are arranged below imperforate plates or ringson rin'gs'f are made of cast-iron'. to resist'oorro'si'ony by the 'products of combustion and cast-iron is a* in a round plate the bottom surface has ihad the;

form` of; a shallowinvertedcone.l .Such vplates when heated by gdirect contactfwiththe flamesof an'aerated or luminous gas-burneralefliable ete undercool the impingingharness-leading t to lincomplete combustion of the gasi andthe. forma tion of carbon inonoxide, To overcome this the gas can be burned with an excess'of secondary airl so that the products of. combustion jcontain only'` 20%V insteadrof. `80%* of possible carbon!` dioxide. content but suchten excessive dilution of the products of combustion-lowers the meantemper-A ature of the` gasesfand decreases the temperature gradient betweenA the gases and the coldplate.

It also introducesvairesh problem, namely. the' son :for misi zi`sti1at^i`-f the aeration is 'coi-rect at' Y complete combustion. f-

Another wayof approaching' the problem' isfto arrange the burner inside-'a"bellspacediromthe' plateso Tthat the 'combustion is complete' before the hot gases reach the" plate-"A'I'h'ehotgases thenhave to ris'eiup'wardly luntil theyrreachfthe "l Vlower surface of the hot plate and areturned y horizontally`outwards` This diversion causes a sistance to the' sudden changecin the direction of low pyramidal 'or=conical:underside, this'corn- `back pressure in the stream offhotgases which will yaiect combustiontif ther draught 'within the' bell, which actsas a 4draught .inducing combustionchambe'rfi's not'great'er than the sum' of therethe f'xgaseslfandf the frictional -resistancel to fiow oven'th'e"undersideoithecooker topxsurrounding theiplate. In thecaseiof, a. platejhavin'g a; shallbinedresistanceiwould f"requ'irea belli-oi? such depth'that it could"notibefhousediinside a' normal domestic :cooker without'.` increasing 1 the total height-of.thecooker-beyondipractical 'dimensions'.

` solidzzhot-:plate 'islmadei oiga-such a: streamlined formvrthat'the-hot'gases are deectedina smooth 'According to my inventionthe underside oi'v ay curven'from a vertical to ahorzontal direction whileretaining enough inertia-'to overcome the resistanceiof the cooker top surroundingthe plate 4against; the rapidremoval of-thefproductsiof com-- bustion." 1 This-enables Va- Ahell of i reasonable dimensions' to'be usedI and also allows the burner to i iuliillaall thefregulationson 'combustion at' all One. object-of my invention is to-provide'a solid hot-platezor ring'in-which'theoverall efliciency is considerably increased and Which'is f-ree'from the removal of the vgrez'adily increasedfvclume lof0 hot;r v

gases from around thejplate without having recourse to artificial ventilation.' Another way'of dealing with this probl'emfwouldbe tok mixgas and air inthe ycorrect ratio for combustionbefre Adangerofwarping'ordistortion f ,2; v e

heated ring or According to my invention a plate to-receive a cooking utensil comprises a vplateor 'disc which is preferably'made-ofor incorporates .:a material-of high heat conductivity andiwhich has a substantially attop butvaries infdepth lfrom^amaximum atthe centre ,to1 a .minimum Vat'fthe-outerfedge so vthat there' Yis a vminimum temperature'gradient ove'r the'area of,

the plate andthe-distribution of:heat is substan-v tialiy; uniform 'sot-hat the fplate: 4is'. not liable to warpinnuser'f ..Preierably the `underside of the plate is formed with dependingradiating ribsgfns or pegs gto provide the necessary area for the reception of heat from a burner or burners located below the plate.

Any material such as copper having a high heat conductivity and having a melting point sufiiciently far above the working temperature can be used for or incorporated in the plate but as these materials are liable to corrode rapidly, the whole surface of the plate, or at least that part burners; risj r`oflieatl andk corrosion resisting metal or with a layer of one or more metals. This coating may conveniently be applied by spraying.

The plate is preferably combined as a Y a burner and support which'fconsidrably creases the eilciency, and thegsupporhmay vpro-g` vide a surface by which heat is reflected'- back on;

to the plate.

Some practical forms of hot plates or Figure lisa-section of one half ofamodiiedf form ofassemblv Y s 1 Fig. 4a is a partialside viewftaken on line .Az-B- of 4. Q tj. f f; 11

Figures 5, v6 and VA7 are vertical .sections-.ofmod.- ied forms-ofplate.l 4

nl Figures 8 -andw9` are vertical half-sections'of further modified forms of plate. f L Figure lll-isa verticalsection-of a further modiiication.;..` The plate al'll'shown-in Figure,y l; ifs'made `as a casting, forging or` hot :stamping in.. copper-or other metal ofhighheat,conductivity.' The plate is circular in planand; theaupper surface-is flat to receivej'a cooking utensilE while theunder'surl-A face-is of inverted curvednconical outline increas` i'ng progressively in depthf towardsthe centre, the thickness *of tthe plate rdiminishing gradually/to'- wards thee'dge, so'that when the plate: is heated by a burner or burnersv below it the' temperature over the area-.of .theuppersurfaceof the plate is substantially*uniform.l IOnthe Vunderside-.of the plateare depending nsrII otrsubstantial depthgzthe lower r'edges ofthe nnsfbei'ng substantially-'lparal'1el'to vthe underside of `the plate; These kns radiate fromthe.` centre o'fthe platev and-some 'of them` extend 'as shownl from the centre to` 4the "outer" edge while shorter'finsf'are interposed. The fins are shown as being-made as integral parts of the plate but in an 'alternative `method o'f construction'the 'nsmay be made of lextrudedi'or other copper'strips which are 1o-v cated in a mouldfwhile the plate is-caston to themw Ribs orpegs mayof course be usedV instead of` fins. lTheA surface ofthe plate or 'at'leastthe lower surface and the ns are coated by spraying or by any other convenient method with one or more thin' layers I2 of metal resistant to heat and to acids-and alkalis, thecoating being suiciently thick Vto protect Athe copper-*against corrosion without seriously; affecting the Atransference of heat. 'The coating layers fm'ay rbe -'of 'alloys'of iron or steel, chromium, aluminum' lor" lother rnetals.V N.' ..1 I... 7.x

The kplate is conveniently combined as, a unit with a burner and support designed for it as shown in Figure 3. This support comprises a metal shell I3 of inverted frusta-corneal or bell shape in the bottom of which is mounted a burner or ring of burners I4. Openings I5 for the admission of air are provided around the shell adjacent to its base, and the plate is supported on the shell by the engagement of a small number of spaced pOints on the ribs vorhiinrs II on the underside' 'thffplate with-fan upstanding lip or ilan'g' I6 onthe shell so'th'at there is 'a minimum transference of heat by conduction from the :plate to the shell. The tapered or curved underside of the plate in conjunction with the ribs or fins provides a Vlarge number of upwardly and outwardlyr curvedY semi-streamlined passages for the products` Qf-cOmbuStiOn, and the effective area of the -ns progressively increases towards the outer, edge of the plate in inverse ratio to the progressively decreasing temperature and velocity of the. products of combustion.l y g The shell I3 may be lined with a moulded lining Il ofl heat insulating material such as steatite or flreclay,. as shown onthe-leftof'Figure 3, which reduces Vto a niinimum'the heat taken by the shell, and the smoothsurface of -the lining reflects backy the heat vradiated from the; burner flamesfand from the underside'of the plateevTo increase this effect: the surface of the .lining may be coated with-a bright or polished metalllayer sprayed or otherwise deposited onit.; f 1 u The.l:urn`ers I4;may beof the :non-,aerated or luminousrflame typeas-shown in .Figure -3 or .they maybe of thelaeratedsunsenftype, and-the flame may or may notimpinge directly. on the ns and the underside of the plate.

. vThe form of the plate givesesubstantially even distribution of heat over its area with consequent even heating of the utensil placed'on it andfree; dom-from warping of the plate. Further there is a minimum:y of risk=of smothering of thezproductsI of combustion `before complete' combustion has takenplace.

f Figure l Vshows a modiiiedv arrangement in which an 4aerated burneri 2U lis-used and the plate 2I isvprovided on its lower fface with a series of radially extending curvedconcavechannels 22 of such form as to give the bottom of' the plate a stream-lined upwardly curved shape from the center t6 the outside thereoffthe plate being supportedori a vvshell similar to that shown in Figurejs..

- Figure 'showsa plate!! in which a'number of recesses 25 are formed' to control the uniformity of the heatdistribution. Y I A Figure 6 shows a similar ns are replaced by pegs 21.

Figure lfshws a composit'eplatein'which the flat upper surface 28 of the plate on'which a utensil is placed is vof cast-iron while the lower surface 29 of the plate and the fins 30 are of copper, coated with a surface layer 3| of heat and corrosion resisting material'. The two `parts 'are keyed'together by headedl projections 32 on the copper embedded inthe cast-iron, and the plate may be formed by vplacing the 'copper 'part in a mould and casting the'iron on to it.

Figure 8 shows a ,cast-,irronplate 33 having inserts `of copper orother material of high. heat conductivity. There is a .central cavity inthe plate into which is castan insert 34 and on the underside of the` plate are spaced integral pegs 35into which are screwed copper :or'other studs 36.,-the lower ends of the holesv being closed by plate 26 which the iron or other plugs 31 welded in position after the studs 36 have been inserted.

Figure 9 shows a modied arrangement in which copper or like studs 40 are screwed into openings drilled from the upper surface of a castiron plate into integral pegs 4I projecting from the lower surface of the plate. The upper ends of the inserts are rivetted over as shown at 42- into countersunk recesses at the upper ends of the openings. The plate itself is formed in two parts 43 and 44 for convenience in manufacture, and the studs 40 serve not only to transmit heat through the plate from the bottom to the top but also to secure the two parts of the plate together.

Figure shows a cast-iron plate 45 having integral pegs 46 connected by fins 41 projecting from its lower surface. Copper or like studs 48 extend right through the plate and the pegs. The studs may simply be screwed in and rivetted over as `shown on the left of Figure l0. Alternatively to ensure effective contact between the copper and the iron the studs may be slotted from the lower end and wedge strips 49 are forced into the slots to expand the studs as shown on the right of Figure 10 Annular grooves 50 may be formed around the studs to allow for unequal expansion. Shorter copper or like studs 5l may be imbedded in the plate at intermediate points. Where the studs extend through the plate their lower ends are protected by ferrous plugs 52.

- I claim:

1. A cooking utensil supporting device for a gas cooker, comprising a plate having asubstantially flat top and an inverted curved frustoconical bottom surface, radially extending heatreceiving ns projecting downwardly from the bottom surface, means for supporting the plate, and gas burner means for heating the plate from below.

2. A cooking utensil supporting device for a. gas cooker, comprising a plate having a substantially flat top and an inverted curved frustoconical bottomsurface, spaced pegs projectingI downwardly from the bottom surface of the plate, means for supporting the plate, and gas burner means for heating the plate from below.

3. A cooking utensil supporting device for a gas cooker, comprising a composite plate having an upper member of cast-iron with a flat top and a lowermember of metal of high heat conductivity with an inverted curved frusto-conical bottom 5 surface, heat receiving members projecting down- `wardly from said bottom surface, and a coating of heat and corrosion resisting material on said bottom surface and said heat receiving members, the upper and lower members being rigidly keyed together.

4. A cooking utensil supporting device for a gas cooker, comprising a built-up plate having `an upper member of cast-iron with a flat top and a lower member of cast-iron with an inverted curved frusto-conical bottom surface, heat receiving projections extending downwardly from said bottom surface, and inserts of a metal of high heat conductivity incorporated in the plate and extending into bothmembers to convey heat from the bottom to the top of the plate.

5. A cooking utensil supporting device for a ga's cooker, comprising a composite plate having an upper member with a flat top, a lower member with an inverted frusto-conical bottom surj 2B face, heat receiving projections extending downwardly from said Lbottom surface, and inserts of a metal of high heat conductivity incorporated in and extending 'between said members and into said projections. l

6. A device for supporting a cooking utensil, comprising a plate having a substantially flat upper surface and having a lower surface which is substantially vertical adjacent the center and progressively varies in inclination from tlie center to the outer edge at which it is substantially horizontal.

7. A device according to claim 6, comprising in addition radially extending fins depending from the lower surface and being shaped similarly thereto.

8. A device according to claim 6, in which the upper surface of the plate is formed of cast iror and the lower surface is formed of copper.

9. A device according to claim 6, comprising in addition a plurality of separated members attached to the lower surface and projecting downwardly therefrom. Y

RICHARD HERMANN.

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