US2018886A

US2018886A - Glass furnace

Info

Publication number: US2018886A
Application number: US734914A
Authority: US
Inventors: Ferguson John
Original assignee: Individual
Current assignee: Individual
Priority date: 1934-07-13
Filing date: 1934-07-13
Publication date: 1935-10-29
Anticipated expiration: 1952-10-29

Description

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UNITED STATES j Musee "Johnlergmlndlanapohld myn, ismael-inne. man' scam. (cols-si' A'nuinvenuourelatesto-meieeizxiefum-Tee which is particularlyadapted for the manufac tureofglnss,butwhichisusefulaswellforotherV purpos. The principal object-of the invention .lstoimprovcuponthesimpiicity of'theoonstruc- 'tion,reliabilitsandeaseofoperationofanelec tric furnace andthe mechanism for Onefeatureoftheinventlonresidesintheuse ofafurnacehaving a-`central'dischargeopening andhavin'goneofitselectrodesintheformofa vertically movable plunger positioned above the' dischargeopeningandservingbothasanelectrcde and asameans for controllingthedischargeof glassfrom said opening.

Another feature of tbe invention resides in the proportioning and arrangement of the electrodes sothatgraphitemaybeusedasanelectrodema-- terialk without mbstantial .discoloration of the glass. Heretofore, it has been impossible to use graphite in the manufacture ofhigh grade glass due to the discoloring .eect thereof.

, Another feature of the invention resides in the construction of the electrode by means of which itisprotecteiagainstchemlcalactioninthe sones of greatest chemical activity.

. Other objects and features of the invention will be lmderstood from thef accompanying drawing and the following description and claims:

llg. 1 is a central vertical section through'a lglassfurnace constructed inacc'orciance withthe invention. ngzisasectionalviewthroughthe same taken onthe line 2 2 of Fig. 1.V Y

Inthedrawlng,thereis shown,'by way of illustration, an electric furnace having a substantiallyat hearth Il with a central collecting well `Il formed in the-floor thereof. A discharge opening I! is placed inthe floor ofthe collecting well Il; 'lhefurnaceiscoveredhny ahood |I,theapex ofwhich communicates withahopper il by means of a passage Il. Supported upon brackets Il withinthehood Il there is a distributing cone,

l1 which serves to distribute the batch material I8 abouttheperipheryofthehearth.-

An outer-electrode Il consists of aplurality of arcuate blocks Il preferably of graphite, said blocksbeingclampedbyatwo-piecemetallichoop Il toform ab structure adjacent the outer elbcofthehcartln Armsllextendfromtbe hoopllandaresuitablyinsulatedfromthehood meemraleleemaeeenmueraplunseru preferablyl formed of graphite and supported uponthe-lowerendofarodllextendingupward thfmlghatubell. Withinthetubethmil 'tothelever 2l.

' bevariedas w PATENT oFElcEt a manine n of man; mam-m preventing electrical contactv between the rodi and the said tube.' The upper part of the graphite plungerml is surro unded b y a shell 21 of refractory ma The upper end of the rod 24 is pivotally connected to a lever 2l which is' fulcrumed upon a. bracket 2| carried by the hopper Il. The opposite end of the lever 2l is connected to thepiston rod Il of a pneumatic cylinder 3L* By means l0 nected by conductors I! the arms 22' and the by aconductor It 20 A opposite terminal conn" Communicating with them-interior ofthe furthere isl a` pipe I1 through which the gaseous products of chemical action may escape, A

valve 3l insaid pipe serves to control the escape 25 `of said products in such manner as to preserve a super-atmospheric pressure within the furna. In the operation of -the furnace, the batch material for manufactm'e of glass is placed in the hopper Il and passes downwardly through'the 30 passage IS over the distributing coney I1 into the outer sone of the The batch -is melted by electric currents passing between the electrodes and the melted glass moves continuously from the sone of the outer electrodes toward that of 'the 35 inner electro'de. The glass which has received the longest heat treatment in thefurnace is collected -in theweil Il and is discharged therefrom through the opening Il. Alternate upward and downward movements of the electrode Il provide 40 the well known gob f eed by means of which successive masses of glass of thevproper weight for molding various typos of glass articles are discharged through the opening l2. If continuous 'new feeding from meenemen. n xs desired, the 4s same is controlled by placing the electrode 2l :'.n a stationary-nommen at the proper height to permitthedesired rateofflow. This rate maythen by suitable movement of the electrode.

With the concentration of current usually found adjacent the electrodes of an electric furnace', it has heretofore been impossible to use graphite electrodes without a disintegration of the electrede, which produces a marked discoloration of Il rent concentration at the electrode surface is maintained at less than ten amperes per square inch of active electrode surface that there is no appreciable disintegration of the graphite and hence no discoloration of the glass. By virtue of 'the design of electrodes and furnace hereinxillustrated wherein the entire volume of material within'the outer electrode carries current, a large amount of energy can be released for melting the batch without exceeding the current concentration which would cause disintegration.

Heretofore a further disadvantage in theuse of graphite as an electrode in the manufacture of glass has been the oxidation of the graphite at the highl temperatures commonly employed. In the present invention this dimculty is avoided by the use of ,a closed furnace from which the discharge of the products of combustion is regu'-` lated to maintain a super-atmospheric pressure. In the manufacture or mass, this product of combustion is principally carbon dioxide which has no affinity for graphite. The super-atmospheric pressure maintained need be only sumcient to prevent entrance of atmospheric oxygen.

Another difficulty heretofore experienced in the use of graphite is the chemical attack thereon at the metal line or line of contact' between -the molten glass and the unmeltedbatch mav terial. rThis is the zone of greatest chemical activity. 'I'he outer electrode in the present invention is completely submerged in the molten glass and, therefore, does not reach the zone of greatest chemical activity. 'I'he inner electrode is positioned at a point where normally no unmelted batch material is found and, for that reason, is substantially immune from attack. However, if the furnace is overloaded with unmelted batch or if for any reason the distributing corne` I1 is not used, batch material would reach the inner electrode, which would then be in contact with the metal line. For this purpose the refractory shell 21 is supplied to protect the graphite against the extreme chemical activity at the metal line.

The foregoing description illustrates a preferred form of the invention but the details thereof may be varied by those skilled in the art withvout departing from 'the scope .of the invention as defined by the appended claims.-

The invention claimed is:

2,018,883 the glass. I have found, however. that if the cur-- l. In an electric furnace, the combination of a hearth having a collecting well with a discharge opening in the floor thereof, a pair of electrodes. one of said electrodes extending into said well, electric circuits arranged to pass a current between said electrodes, and means for vertically reciprocating the last mentioned electrode to control flow of material from said discharge- 2. In an electric glass'furnace, the combina-10 tion of a hearth having a central discharge'opening, a circular outer electrode adjacent the periphery thereof, a central electrode positioned above said discharge opening, said central electrode being formed of graphite, and electric cirl5 cuits arranged to pass a current between said electrodes, the proportion of said central elec'- trode and the magnitude of said current being such that the current density at said central electrode is not greater than ten amperes per 20 Square inch of active electrode surface.

3. In an electric glass furnace, the comblna. tion of a hearth, a pair of of electrodes, and electric circuits arranged to pass a current be- 'tween said electrodes,.the proportions of said 25 electrodes and the magnitude of said current.- being such that the current density at either of said electrodes is not greater than ten amperesy per square inch of active electrode surface,

i whereby graphite may be used for the electrode 3 0 ing, a circular outer electrode adjacent the periphery thereof, a -central electrode positioned 45 above said discharge opening, electric circuits to pass a currentl between said elec-` trodes, and a -shell of refractory material surrounding said'central electrode at and above the metal line. f

' JOHN FERGUSON.