US1440515A

US1440515A - Melting furnace

Info

Publication number: US1440515A
Application number: US382062A
Authority: US
Inventors: Holley G Wellman; Charles D Gilpin
Original assignee: Individual
Current assignee: Individual
Priority date: 1920-05-17
Filing date: 1920-05-17
Publication date: 1923-01-02
Anticipated expiration: 1940-01-02

Description

Jan. 2, 1923. 1,440,515.

G. WELLMAN ET AL.

MELTING FURNACE.

FILsD MAY 11. 1920. a suus-SHEET 1` @wfmmm Jan. 2, 1923.

H. G. WELLMAN ET AL.

MELTING FURNACE.

FILED MAY 17, 1920.

3 SHEETS-SHEET 2.

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0MM. 6a p//v MLM.

Jan. 2, 1923. 1,440,515. H. G. WELLMAN ET AL.

MELTING FURNACE.

m50 MAY 17. :920. a sHrzErs-snzf 3.

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Patented dan. 2, 1923.

liiiTED STriTES PATENT OFFCE.

EOLLEY G. WELLMAN ND CHARLES D. GIL? 1N. OF CLEVELAND, 01H30.

MELTNG FURNCE.

pplication filed ey 17,

To u!! iff/mm. if may courent:

Bc it known thut we. lloLLi-: (iv Einnahme und Guinnes- D. (lumix. citizens of the Vnitcd ritutes. residentsofCleveland.county of Cuyahoga. and State of hio. have invented new and useful Improvements in Melting Furnaces. ot' which the Jfollowing is a specification. the principle of the invention being hei-cin explained und the liest mode in 1U which we have contemplated applying: that principle, so us to distinguish it from other inventions.

(lor invention relates to furnaces, and particularly to devices ot' this charactcr adopted to melt non-ferrous metals for nothing ln'onzc. brass und similar castings. 'lhe purpose of the invention is to provide a furnace in which las or oil run be utilized as the heating medium. combined with electrical heating. Thr object is to secure the economy ot' installation und operation possible iu `gas or oil heating. and also. et the necessary stage in the melting'. secure the neutral or reducing atmosphere in the furr, nare and the ease oi control in the heat, supplv. possible through electric heating. Spccilically. we hout the charge to o point where it approaches the oxidiaingr tcnipern turc by menus of thi` ,uns or oil heating'. and then finish the melting by means nt electric heating. Also. we utilize `the heating effect of the ras or oil not only to raise the temperature o'l the charge. hut also to bring un electric heating element to a'teinperature which will require :i much smaller variation in voltage than is usually required for the oiicrution ol :i furnace of the resistance type.

The annexed drawings and the following description set vforth in detail certain means n embodying our invention. the disclosed means. however. constituting.r but unc of thc various mechanical forms in which the principle of the invention um)` hc applied.

li said annexed drawings:

5 ldigznre 1 represents u vertical. longituflinul ser-tion of our improved furnace:

Figure 2 represents ii plan View of the saine:

Figure 3 represents u fragmentary transverse. vertical section tulcen in the plane in-v dicated hv the line lll-dill. Figure l:

Figure 4 represents n horizontal section ot another foi-1n of our improved furnace: one of the arc design. in which electrodes are 5 used for the electric heating; and in which i520. Serial lio. 352,062.

view the arrangement is shown during the heating by gas or oil;

Figure represents a view similar t0 that, of Figure L showing the conditions during! the electric heating;

Figure (l represents a vertical section of thc forni or' furnace shown in Fighrcs Land token in the plane indicated by the line ll--VL Figure Figure T is a diagrammatic view. showin-,fr the adapta tion of the invention. when utilized lFor several small units grouped ou one transformer. nuto-transformer or generator. for making different alloys at the saine time.

Referring to the annexed drawings: There is indicated hy the ordinal 1 u furnace body of heat-resistin r material rotatably mounted in bearings 72 y means of trunmons 2, the rotation or tiltingr `of the furnace being effected through a suitable gear 3, pinion 4 and hund wheel 5. The furnace 1 is formed with a chamber G within which is disposed a crucible 7 adapted to hold the charge B. When it is desiredto discharge the contents ofthe erucible 7, the' same is effected through the. spout il. We do not wish, howevere to limit ourselves to the use of a erueible.Y since, if desired. the metal can be melted upon u. hearth. Two

flexible conductors

10 and 11 are sho-wn connected respectively at the

points

12 and 13 with any lsuitable main circuit. removable top 14 is provided For the furnace 1. which is disposed adjacently the top of the crucible T. the electric circuitpassing through said top und also through the field ol a solenoid 15. The conductors l() and ll have suiiiclent slack to allow for the necessary movements of the furnace 1 and `the top 14. The specific path of th circuit through the. top 14 includes two carbon electrodes 16 und 1T. a heating element 1S and two terminals 19 connecting the electrodes. respectively. to the conductors. The heating element 18 is preferably a carbon compound'having;r a negative temperature resistance coefiicient so that its olnnic value is greater when cold than when it is hot. The top is removed to one side of the furnace when charging, by means of attaching the chains of a crane to hooks 45. it will be noted that "che heating element, 18 is disposed in the vicinity 0f the chamber G, so as to be heated b' the gas or oil` but is protected from oxi ization by any suit able means, the means herein shown being e.

small section 20 of the top 14, which top is huilt of refractory material.

The solenoid 15 has a plunger 21 formed on one side with teeth 22 adapted to mesh with a pinion 23, keyed to a shaft 24. To this shaft 24 are also keyed upon opposite sides of the furnace 1 two

bevel gears

25 and 26. The bevel gear 25 meshes with a bevel gear 27 keyed to a shaft 28. This shaft 28 is connected to a valve 29 controlling the air furnished to the mixer throu h air line 31. The gas or oil is controlled y the valve 30 having connections with the fuel line 32` Check valves 33 are provided in each of the

lines

31 and 32 to prevent air from backing up into the gas or oil pipes, or vice veisain the event that one of the valves 30 or 29 is closed. The mixer and burner diiecting the flame into the chamber 6 is indicated by the ordinal 34. The bevel gear 26 meshes with ai bevel gear 35 keyed to u shaft 36 which in turn is secured to the waste outlet valve 37.

It is a parent from the foregoing dev Scription t at the early heating of the charge 8 by the gas or oil from the burner 34 will gradually heat the element 18 decreasing the ohmic value of the same, so that an increasing amount of current can betransmitted through the electric circuit, tbesolenoid plunger 2l gradually being drawn into the coil 15, which action, through the teeth 22, gear 23, etc., is utilized graduali to turn oil' the s or oil at the valve 30 an to close the outet 36, so that the heating medium rudually changes over from oil or gas to e ectricity.

vWe have provided adjustments whereby the amount of increase of current necessary to effect n certaindrop in the gas or oil can be varied. Also, it will be noted that we have keyed a crank 89 to the end of the shaft 24, upon which crank is hung a weight 38, whose position can be adjusted. For

controlling the drop in the gas heating, we

have provided adjacently the bottom of the solenoid plunger 21 a series of various

sized weights

42, 48, 44, etc., which can be picked up at predetermined positions by the plun `ger 21, whereby the necessary electric force to pull the plunger 21 into the coil 15 can be set as required. Also, the conditions can thus be changed or adjusted so as to require varying amounts of current to lift the plun- Iiger 21 through different parts of its stroke. The differential in the pull of the solenoid is equalized by the differential in the pull of the weights. In order that, if the electric current is unexpectedly interru ted, the plunger 21 may not drop away rom the coil 15 and thus op? up the valves 29 and e a 30, we have provi paw] 41 adapted to co-operate with ratchet teeth 40 formed u lon the side of the plunger 21 o posite to trat upon which the teeth 22 are ormed` Referring particularly to Figures 4, 5

und 6, there is therein disclosed a-form of furnace preferably of the rocking type, de signed to melt the charge upon a hearth, and in which the electric heating is edected by means of striking and maintainin an are between two

electrodes

53 and 55. he fur nace wall is indicated by the ordinal 46 and a feed mouth for the same by the ordinal 47, the dschar @out being indicated by 48. Two sets o doors are provided, 52 and 54, within which are mounted the

electrodes

53 and 55 respectively, and 49 and 50, within one of which a gas or oil burner 5l is mountA ed, and within the other of which is formed a discharge outlet 50 for the waste gas products. As illustrated in these heures,

the necessary heating by gas or oil is effected by means of closin the doors 49 and 5U and then, when it is esired to change over to the electric heating, the

doors

49 and 50 ure opened und the

doors

52 and 54 containing the electrodes are closed. The electrodes *are then adjusted to strike the desired arc.

Referring to Figure 7. a diagram of an arrangement is shown whereby several smul] furnaces may be grouped on one transformer, auto-transformer or generator, to produce different alloys. Due to the diversity feature of the load, 1t will be possible to make the continuous capacity of the immediate source of ower much smaller than thc combined pea loads of the various furnaces. There is indicated by the ordinal 56 an alternating current circuit, 57 denoting a switch and 58 an auto transformer, which furnishes differential voltages to the conductors 59, (30 and 6l withrespect to the conductors G2. The electric heating elements or resistors are indicated by the

ordinals

63, 64 und G5, and the several switches hy the ordinnls 66, 6T and 68. Regulatingr switches are indicated by the ordinals 69, T() and Tl. so that any particular furnace can be supplied with roltage 59-62, 60-62, or (3l-62. This arrangement reudily lends itself to nu economical and exible installation for u group of furnaces.

Our improved furnace will be found of particular service in small plants, where, due yto the non-continuity of operations, the shutting down of the electric heating necessitates a re-heating of the furnace before it becomes effective, when next it is desired to utilize the same.

It is not'necessary to interconnect the ,uns and oil and electric heating!I in the manner which we have described, nor to utilize the electric current during the heating by gus and oil. The two forms of heating may be utilized absolutely separately, as. for instance, illustrated in Figures 4. 5 and 6. The se arate and independent heating also would e feasible with the apparatus shown in Figures 1, 2 and 3.

The methods of operation would be varied llO for melting various kinds of materials, but for making castings out of brass or bronze ingots, the operation would be about as follows:

The charge is placed in the crucible after first moving the top 14 to one side and the oil or gas burner then lighted. A constant potential will be connected to l2 and 13. The proper weights 42. 43, 44, ete., will be placed in the solenoid mechanism, these weights having been determined by past experience in melting the same metal. During the `early stages of the heating, the flame will be controlled by the operator by means of valves of the usual kind (not shown). At first, the current through the resistor 1S will be negligible, but as the furnace becomes heated, the ohmic value of the resistor will decrease. thus allowing a greater flow of current, which in turn will still further heat the nresistor, alllowing more current to flow. `If it is desired, the current need not be thrown through the resistor until the latter has been well heated and the charge has nearly reached the melting condition. The solenoid regulating weights. 42, 43 and 44, will be so chosen that as the charge approaches the tempera-ture where oxidation becomes a serious facto-r, the resistor 1S will have been sufficiently heated to allow the solenoid plunger .21 to be lifted by the resulting current, this lifting being done in one or several stages by the means of one or several of the

weights

42, 43, 44, as may prove desirable. This lifting of the plunger 21 will, of course` shut off the air and fuel valves 29 and 30 and close the waste gas valve 37 by one or several steps so that the source of heat will immediately or gradually become entirely electrical and the oxygen from the outside Will be cut ofi'. Heating will then proceed as in the case of an ordinary electric furnace of the resistance type.

Almost any combination of automatic control for this electric heating can be installed, ranging from a simple overload circuit breaker, which can be set to interrupt the current when the latter reaches a predetermined point, to a more or less elaborate arrangement of contactors controlled by a pyrometer, and arranged to increase or decrease the voltage by small steps in order to hold the final temperature constant. It should be noted, however, that any such arrangement need cover only a comparatively small range of voltage owing to the pre-heating of the resistor; whereas, in the straight electric furnace using this'type of resistor, a voltage range of as high as four to one may be necessary in order to obtain the desired results. This necessary range of voltage greatly increases the cost and complicates the auxiliary apparatus. Of course, it will be well known to those skilled in the art that compressed air and oil or gas are available in most foundries and are in any event readily and economically provided. The automatic control of the fuel supply, as well as of the electric current, may be dispensed with in cases where original cost is a serious item, and where the furnace may readily be kept under supervision. In the event that metals of various melting point-s are to he combined in the furnace, the original charge can consist of the metal having the highest melting point., and the automatic device may be set for such metal. Yhen it reaches the proper temperature. the cover 14 may he removed and the other metals added, the electric` heating heilig continued as long as may he desired. i

The operation of the arc type of combination furnace shown in Figures 4. 5 and 6 will be somewhat similar to that of the resistor type except that the automatic change from fuel to electric heating would require much more complicated apparatus and therefore is probably not desirable. This is due to the fact that the electrodes must necessarily he protected from the flame of the burners unless they be withdrawn by some such device as shown in said figures. The melting of the charge in this furnace, therefore, consists in pre-heating the charge to a desirable point by means of closing the

fuel doors

49 and 50, and then replacing said doors with the electrode doors and 54, striking an arc between said electrodes and maintaining the same for the desired period.

Either the type of furnace shown in Figures l to 3, or the type shown in Figures 4 to (i may be operated entirely with fuel or entirely with electricity. This is a very desirable condition, inasmuch as alloys which oxidize slightly may thus, if desired. be melted entirely with fuel, while those which oxidize particularly easily can be melted entirelyI by electricity. Furthermore, a failure either of the fuel or electric power would still leave the furnace in commission.

lnsofar as the desirable features of electric heating are concerned, it should be kept in mind that the electric type of furnace is gradually replacing the crucible and other processes, so that. although until recently used largely for the melting of silver and bearing metal alloys, it is now used for brass of all kinds, aluminum` various alloys and other materials. New non-ferrous combinations and new uses for the common nonferrous metals and alloys are constantly developed, for which the use of the electric heating feature of our furnace is very desirable, at the same time preserving for the early stages of the melting the low cost of operation possible in gas or oil melting.

le are aware of the fact that it is not new to heat preliminarily by gas and later by electricity in the same furnace or cham- El I) llt titl

her. and we do not malte claim to any such conihination ot' apparatus. (hir invention relates to fuel and electric heatin"` and means intcrconnecteil so that the operation of one is a tl'ected hy the other: or the use ot' an electric heating' element l1a\'in; r a negatiyc temperature resistance coetticient and disposed within the heating' area otl gas or oil: or the use oll jas and electric heating means so interconnected as to he recipro rahly replaceahie in thtI furnace chamber; or the use of a source ol' electric energy snpplyin; r Various voltages conihincd with means for selectively heating charges in various furnaces with the desired voltages from said source ot' electric energy. 1We are also adiiscd that glas and electric heating hare heen comhined in a two-furnace method. or in methods in which the hearth is positively removed from an area in which its cfnitcnts are suhjected to gas heatingy to an arca in which it it is suhjected to electric heating'. hm our claims relate to a onet'nr nace method in which the furnace is maintained in a tifo-d position.

7What we claim is:

t. ln a meltingr furnace, the comhination ot a chamhcred furnace hody forming a rereptacle hir the charge; means tot' heating the charge with `as or oil including' means tor controlling' said heating; and means for heatin; if the charge electrically includingr means for controllingr said heating` said two sets ot' controlling means heilig interconnccted.

2. in a meltiim` furnace. the comhination ot' a rhamhered Vfurnace hotly forming;r a receptacle for the charge; means tor heating' the charge with gras or oil; and means l'or heating the charge eh-ctrically. said two sets ot heatilr;T means being' interconnected so that an ette: tire increase in the electric heat intr means results in a decrease in the iras or oil herding' means.

it. ln a melting' furnace. the comhination ot' a chanihercd furnace hod)I fortuin;r a re ccptacle for the charge; means for heating `the charge with gas or oil; and means for heating' thc charge electrically in the same hcating r area` said two scts of heating means heine' interconnecttal so that an ctiectiye increase in the electric heating' means results ina decrease inthe glas or oil heating' meansl. `In a melting furnace. the comhination ol' a chanihered furnace hody torminrgr a reccptacle for the charge: means t'or heating the charge with gas or oil; lneans for heat ing' the charge electri 'ally. said two sets of heating' means heiner interconnected so that an effective increase in the electric heating1 means results in a decrease in the ,Q'as or oil heating means: and means for yaiyingr the ratios hetween said increase and decrease.

5. In a melting furnace. the combination of a chamhered furnace hody forming;f a receptacle for the charge: means for heatingr the charge with gas or oil; means for heat.- ing the charge electrically, said two sets of heating;r means being iutereonnectwl so that an etfectiye increase in the eleetric heatiner means results in a decrease in the gas or oil heating means; and means for varying the ratios hetween said increase and decrease in different portions ot' the heatingr range.

(i. In a meltingr furnace. the combination ot' a chamhered furnace hotly torinimgr a receptacle for the charge: means for heating' the charge with gas or oil; an electrical heating' element disposed within the heating' area of said gas or oil and haring' a negfzr tire temperature resistance coefficient; and means for heatimgf the charge electrically. said element heine' disposed in the circuit ot' said electrical heating means.

T. ln a melting furnace, the combination` ot' a chamhered furnace hotly forming a receptacle for the charge: means tor heating tht` charge with gas or oit: an electrical hcating element dispostai within the heating' area of said gas or oil and having a negative tem peratnrc resistance coetlieient; means for heating the charge eleetrieatly. said clement heine' disposed in the circuit of said eter:- trical heating means; and means influenced hy a gradual effective increase in the electric heating to ei'eet a corresponding decrease in the ras or oil heating.r means.

t4. lin a melting furnace, the conihination ot' a chamhered furnaee body: a erucihle disposed therein; a top ot' refractory material for said hotly disposed adjacently the top ot said .-rncihleg a heating element iinhcdded in said top adjacently said crucihle and harin;i a negative temperature resistance co ctiicicnt: an electric circuit within which said element is contained; means furnishingr heating gas or oil to said chamber: and means connected to said last-mentioned means and .said circuit and adapted to reduce the heating value ot' said gas or oil correspondingr to the increase in the electric circuit.

E). ln a melting' furnace, the comhination of a chamhered furnace hody: a crucihle dispt'ised therein: a top ot' refractory material for said hody disposed adjacently the top of said crueihle: a heating: element imhedded in said top adjacently said crucihle and havin? a negative temperature resistance co-eieient; an electric: circuit within which said element is contained: means t'urnishing heating gas or oil to said chamber; a solenoid forming part of said electric eircuit: valves in the gas or oil line and in the chaniher waste outlet; and means connected to said valves and the plunger of said solenoid.

lit)

10. In a` melting fuirizii'eE lli@ i'fiiiiliiiiiitiiiii of a Chaiiibered furnace body fni'iiiinggj i1 iuc-eptacle for the` charge; ii'ieiiiis foi' lizitiigiV the Charge with gas 0i' oil; means 'For limiting tlie irliaig electrically; iiiiziiis iiifiiiviicml liy :iii effective increase in iliv elimti'ii" lient iiig 5ml liiiiliiig tu ilci'iijiirw liv im iii nil heating; iiiiil iidiiistiililfi iiiiiiii` iuiitiuliiig lie fiiiictinriiiig 0f amil l:i:i-iiiif-iitioiivcl iiiiiiins.

il. In a inciting Ji'iiiiiiiciv= iliij iiiiiiiiiiizitiiiii uf ii cliuiiibeieii f'iiiiiucv liiiilji' 'i iiiiiiig' ii i'ur cvptzicl@ for the charge: iiifsiiiis fm' iieiitiii;iv iiliif charge with gas Oi* Oil :iii eliUti'iiiil limiting element disposed within iiiii liiiiiiig :ii'vii ril said gais, iii'- iiiil iiiid having :i iivggjiil iw tviiiA iiiii'aiili'v risisi-iiiice iiiellii-iiiiil: iiioziiw im liiiiiiii'i5gf lie, @liiiiim iflQi-*iiiiifiiij-g niiiil iiliiiiiiii living! iiiiiimriiiil iii iliix iiiviiii :iiiiil ifili iiimil iiilaiiiiigL iiioaiiii; iiiiiiiiis iiiiiiiiiiiiril by iiii iilfeClii'v increase isi vfliwiiv lii'fiitiiig iiiirl iiiiliiig; to defiiiimi ifiiel Sli wiiiig;

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