US1486265A - Annealing leer or furnace - Google Patents

Description

R. D. PIKE ANNEALING LEER OR FURNACE March 11 19.24. 1,486,265

Filed-Oct. 25. 1922 4 Sheets-Sheet 1 INVENTOR.

ANNEALING LEER OR FURNAGB Filed Oct. 25 1922 4 Sheets-Sheet 2 I N VEN TOR.

TTO NE March `11 1924. 1,486,265

K R. D. PIKE ANNEALING LEER 0R FURNAE Filed Oct. 25 1922 4 Sheets-Sheet 3 HVVENTOR.

R. D. PIKE ANNEALING LEER on FURNACE March 11 1924.

Filed Oct. 25 1922 4 Sheets-Sheet 4 Maz' l 71TH 12W fo mf'ple By vqfforneffs Patented Mar. 1,1, 1924.

UNITED STATES PATENT on-Ica ROBERT,` D. PIKE, 0F SAN FRANCISCO,` CALIFORNIA.

ANNEALING LEER OR FURNACE.

Application med october 25, 1922. serial NQ. 596,732.

-of the continuously operated type in which the glassbottles orother articles are passed more or less continuously through a -hori- Zonta] muflle or tunnel composed of refractory material; and during such passage are subjected to a more or less predetermined sequence of temperature to accomplish z the process known as annealing. It is most usual in modernpractice to impart the necessary temperature to the glass articles by causing to circulate in suitably Vde si,g;ned dues around the outside of the mule,'hot gases of combustion. These are usually hottest near the front end of the leer where the articles enter, they lsame being raised as quickly as possible to the desired maximum annealing temperature and then being allowed to slowly lcool during the remainder of the passage through the muiile. This method of annealing is economical because the fuel employed is relatively cheap, but only produces` indifferent results in respect of uniformly removing the internal stress of the glass. This is because, in order to entirely remove these internal stresses, i. e. to perfectly anneal the glass, it is necessary 'to subject the glass article to a predetermined rate of heating andvcooling, depending upon the nature of the article and the temperature at any given time of the annealing process or degree of passage through the mule. These temperatures may only be allowed to vary within very narrow permissible limits, say of i5 deg. C. It will be obvious to anyone acquainted with thefiring of gaseous or liquid fuels employed in modern leer prac` tice that no such regulatio'nis possible, and such being the case, perfectI annealing is not possible.

"It has been thought for some time that electric heating would be amenable to the' desired degree of temperature control to giveperfect annealing and a horizontal mufile leer has been built in which all of the heating has been accomplished by means of batteries of electrical resistances, most of which are placed. inside the Inutile next to the vertical walls. In principle, this leer is the same as the fuel fired leer just described, except that the necessary heat, instead of being supplied by the combustion of fuel -outside of the mule, is supplied by passingv an electric current through batteries or sets of metallic resistors, most of which are located -inside the Inutile. But unlike the fuel fired leer, the amount and position of the energy supplied in the electrically heated leer is subject to fine automatic control. This is accomplished by inserting a thermocouple through the center of the roof of the muffle in the locality heated by the battery of resistors which it is desired to regulate. This thermocouple comes within a few inches of the top of the glass articles. The electro, motive force of thethermocouple is used to actuate a chain of electric control apparatus of any suitable design, which controls the current passing through the battery of resistors in question so as to maintain a constant temperature of the thermocouple. In this way it has been possible to maintain the temperature of thermocouples placed about 4 feet apart within i5 deg. C. of a predetermined temperature.

But the current consumption of such a leer has been'found to be excessive, and the annealing not yet as perfectly under control as was to be expectedvfrom the close control of the temperature of` the thermocouples.

I have attached thermocouples to a botv tle passing through such a leer, and have found that the actual temperature of the glass is quite different from the temperatures recorded by the thermocouples inserted through the roof to Within a -fewinches of the glass articles. The discrepancy was most noteworthy in the receiving end of the leer where the bottles heated up more slowly the relative transparency of glass to wave lengths of the visible spectrum concernedin transmitting heat energy b v radiation from the electric resistors, which are at a glowing red heat. It is desired that this heat should be eiciently transferred to the glass for heating it up to annealing temperature, but instead of such being the case, this radiant energy passes completely through the almostV transparent glass and is transposed into sensible heat on the internal walls of the muffle back of the resistors and on the surface of the thermocouples. These latter, therefore, register temperatures considerably higher than the true temperatures of the glass in the heating region of the leer; and the excessive temperature of the inside face of the muiiie results in high losses by radiation.

The most e'ective means inside the leer for transferring the heat energy from the resistors to the glass articles is the stray convection currents caused by the risin of heated air in contact with the heate resistors and inside walls of the mulie and the corresponding fall of cooler air through the glass articles, thus setting up a circulation of air which transfers heat from the resistors to the glass articles by means of convection. It is obvious that this same condition will exist whether the mulile be heated internally by electric resistors or eX- ternally by fuel. But these convection currents are stray and accidental and are not employed systematically to help accom'- plish the heat transfer work of the leer. In the portion of the electrically heated leer devoted to cooling, the thermocouples do not record the true temperature of the glass which tends to cool slowly for 'the same reason that it heated slowly, and the result of this is that more electric current is admitted to the resistors in the cooling region than is really necessary to maintain the desired time cooling curve of the glass articles, and this current is sheer waste.

The object of my invention is to provide strong systematically effected vertical convection currents within the leer which will cause an efficient transfer yof heat from the walls or resistors in the heating region to the glass articles, and from the latter to the walls in the cooling region; and these same convection currents sweeping strongly over the glass articles and thermocouples in turn, will cause the latter to register the true tempera-ture of the glass and to control the electric input accordingly. In this way I am able to closely control the true temperature of the glass, thus causing perfeet annealing and at the same time to greatly decrease the electric input to the resistors by reducing the temperature of the inside of the mufile in the heating portion and by reducing the electrical input in the cooling portion.

My invention also provides a means for combining the `use of fuel, and electricity whereby advantage is taken of the cheapness of the former and the ease of regulation of the latter.

Referring to the drawings:

Fig. 1 is a longitudinal section through the center line of leer.

Fig. 2 is a side elevation.

I`Fig. 3 is a section on the line A-A of Fig. 4 is a section on the line B-B of Fig. l.

Fig. 5 is a plan view.

Fig. 6 is a section on the line C-C of Figs. 3 and 4.

Fig. 7 shows a section of a portion of an electrically heated leer embodying my invention.

Fig. 8 shows a modified form of electrically heated leer provided with a fan or fans for circulating the convection currents.

In the drawings, l is a horizontally disposed tunnel or muiie, and 1 is a noneated extension thereof which permits the glass articles to cool to atmospheric temperature before being discharged. The muiile 1 is composed of a top wall or arched roof 2 made of so called cupped tile 2 of fire clay or other suitable material, and formed with a plurality of openings 3; a side wall 4, the upper part of which is composed of cupped tile 4 and base of fire brick 4; and a bottom wall 5 composed of cupped tile 5. Ordinary flat shapes could be substituted for the cupped tile, but the latter are chosen because it is desired to make the walls-of the mulile highly conductive to heat.

6 is a pan-likelconveyor of any suitable design which moves slowly through the leer conveying the glass articles which are placed upon it from the receiving to the discharge end. Said conveyor is perforated with small holes to allow convectioh currents to pass vertically through it and it runs on guides .8 whichare supported on I-beams 9, which, in turn, rest in the brick work. The conveyor )asses over wheels 10 to which rotation is imparted by any suitable means. A door 11 closes the receiving end when bottles are not being put in. A bafiie 12 is provided for retarding the formation of currents of air in or out.

Electric heating elements or resistors 13 are placed along the interior side walls of the Inutile 'and are supported on bracket bricks 14 and 14". These resistors are arranged in sets or batteries, and forv each battery or set there is provided athermocouple 15. These latter are connected with automatic electric control apparatus of any suitable design which so regulates the current to the several batteries or sets of resistors that the temperature reading of the thermocouple is kept practically constant at the desired points for the proper annealing of the glass articles which are being conveyed through the muHle at a constant rate of travel b the pan conveyor 6.

The mu e 1 is backed on both sides and top by partition tiles 16 made of a refractory or semi-refractory material. These partition tiles are composed of partitions 16 and vertical passages 16". The vertical passages 16I connect through horizontal ducts 17 with the interior of the muHle 1 at the bottom of the same and through the vertical ducts 3 with the interior ofthe muHle at the top center of the roof. The vertical passages 16" give a continuous connection between the ducts 3 and the ducts 17. The continuity of the tiles, themselves, is broken for purely structural reasons at the edge of the roof, and the thrust of the roof arch is taken up by skew backs 18, 19, and I- beams 20 and 21 and tie rods 22.

The partition tiles, in turn, are backed up bv the wall 23 composed of cup tile 23',

which, as above, are used to make the wall highly conducting to heat, and the said tile are composed of some suitable refractory material.

Walls 23 and 5 on the bottom of the muHle are backed by a system of Hues 24. These Hues on the bottom are backed on the lower side by another wall 25 composed of cup tile supported on I-beams 26. The Hues 24 are backed on the side and top by the tire brick wall 27 and insulating brick wall The system of Hues 24 entirely surrounds the Inutile from end to end, the individual Hues in said system being differentiated by the exponents a to j, inclusive.

At the receiving end this Hue system is connected with the fire box 29, which is heated by an oil or gas burner 30 through the vertical Hue 24, This latter conducts the heated gases to the top of the muHle and thence along the top through the opening 24b against a baille 31, which defliects gases downwardly through the Hue 24, thence across the bottom against a baffle 32, thence around through the Hue 24' across the bottom o the muHle outwardly, thence upwardly through the Hue 24 along the top of the mutlie against a baHle 31', thence down through the Hue 248 across the bottom toward the center through the Hue 24h outwardly through the Hue 24i and upwardly through the Hue 241, etc. until the gases of combustion finally pass out through the Hues 33 and 33 into the stack flues 34 and thence up the stack 35.

A fan 36 is connected through a pipe 37 controlled by a damper 38 to the Hue 24j just above the point where the latter enters into the stack Hue 34. Dampers 39, 40 are arranged in the Hues 33, 33 and a damper 41 is arranged in Hue 241. If it is desired to have all of the gases of combustion enter damper 38, and this will circulate around through the Hue system 24 and out through a pipe 42. Thus, the discharge portion of the muHle can be either heated by the gases of combustion or cooled by air at will, or, by adjusting the necessary dampers, any desired combination of these two effects may be had.

In operation of the leer, the fuel burner in the tire box 29 and the placing of the dampers 39, 40, 41, 38 are so adjusted that 'the' temperature readings on the thermocouples 15 are slightly below the temperatures desired for perfect annealin The fuel fired and the adjustment of ampers are then kept constant. The small additional amount of temperature necessary is then supplied by electric current admitted to the resistors 13 by the automatic electric control referred to above, but not shown, which also takes care of all the normal variations in operation and automatically maintains a constant reading on the thermocouples 15 with the use of a very small amount of electric current. This quantity of electric current is necessarily very small because the principal heat energy required by the leer is supplied by the fuel burned in fire box 29, and only a small amount of it b the electric current, but the quantity of t e latter is sufficient to effect the automatic control of the temperature necessary for perfect annealing.

^ The combined use of the fuel and electricity, with the manifest advantage of the economy of the former and the delicatead-v justability of the latter, is made possible by the construction of the walls of the muHle. Heat from the resistors 13 and from the gases in Hues 24 passes through the highly conductive walls 2 and 4 and 23. respectively, into the partition tile 16, whence, by reason of the large surface exposed by the partitions, it is `converted into sensible heat in the air in the Hues 16". On the other hand, as has been shown above, the

having a higher temperature than the air surrounding the glass bottles, and this promotes an active circulation of air up through the flues 16 down through 3, thence down through the glass articles, through the holes 7 in the pan conveyor 6 and around its edges, thence over wall 5, where air begins to be heated, through flue 17 and up through the iues 16 again.

This active and systematic circulation of convection currents insures that the thermocouples l5 will register' the true temperature of the glass, or nearly so, because the glass, due to these currents, will tend quickly to become of the same temperature as its surroundings.

Another great advantage is that, as the heat flow is in opposite directions toward the center of the partition tile inwardly from the gases and outwardly from the resistors, no heat from the latter can possibly escape through the outside walls of the leer and be dissipated to the atmosphere, thusv eliminating a great source of loss of heat energy in electric leers as at present constructed.

In the cooling portion of the leer where heat is being extracted from the glass articles, the circulation of convection currents is opposite to that just described, i. e., upward through the articles and downward through the flues 16".

The principle of heating as above described consists in imparting heat from both sides to an enclosed air current surrounding a muiiie, which heat is transferred to the articles in the interior of the muie by convection currents induced by the temperature difference between theV articles being heated (or cooled) and the surrounding air current and the flu'es which enclose it; and such a principle of heating makes possible the simultaneous use of heating by resistors within the muie and by hot gases of combustion from without.

It is obvious that many variations of the above construction may be employed without departing from the spirit of my invention. For example, the heating by gases of combustion can be omitted entirely and all the heating done by the electricity, or the latter can be omitted and all heating done by the former. However, an important advantage in the way of economy resides in the cornbination of the two methods of heating.

A type of electrically heated/leer is shown in Fig. 7. In this form of the device the walls are preferably constructed of fire brick A backed by hollow partition tile B, the latter having vertically extending passageways. These passageways at the bottom connect with the inside of the mule through ports C. The roof of the `leer is made of standard arched brick D backed by partition tile E. The passagewa s in the partition tile E communicate wit the interior of the muie through ports F.

when the latter is being heated, ecause the y glass is an inefficient absorber of radiant energy, and this difference of temperature will cause an active circulation in the direction ofthe solid arrows, which in turn will promote transfer of heat to the bottles and reduce transfer to the outside through the walls. i

When heat is to be abstracted from the glass the direction of the currents is reversed, as shown by the dotted arrows.

Another form of electrically heated leer embodying my invention is illustrated in Fig. 8. In this form the roof is made straight and the inner course of cupped tile has been omitted therefrom. The side walls of the muie include a course of cupped tile G backed by a hollow tile H. The vertical passageways in the hollow tile communicate with the bottom of the muiie through ports I, and at their upper ends these passageways communicate with passageways in a course of hollow tile J, which latter are laid upon T-bars K. At intervals the hollow tile J are provided with ports L opening into the interior of the muile at the top thereof. The circulation of convection currents will be similar to that indicated in Fig. 7.

In this form I also show near the front end of the Inutile one or more propeller fans M suspended from drive shafts N extending through the roof of the mule on the middle line of the same. to aid the circulation of convection currents in certain cases. As the temperature gradient between the glass articles in the leer and the walls of the muiie4 decreases the natural circulation of the currents will decrease accordingly. In such cases the circulation may be aided by the use of these fans.

The term muflie, as used herein, is intended to apply to a tunnel heated interiorly, as in the case of an electrically heated leer, as well as to a tunnel heated ex teriorly, as in the case of a gas heated leer.

While the present leer or furnace is primarily intended for annealing glass articles, it is capable of use for heating or annealing various other articles, as, for example, heat treating steel. Y

Having thus described my invention, what I claim and desire to secure by Letters Patent is 1, The method of transferring heat to, or abstracting heat from, glass articles in an annealing leer which consists in causing a circulation of convection currents in the These fans are used Vrior of the mu e.

2. The method of transferring heat to, or abstracting heat from, glass articles in an annealing leer which consists of forming enclosed passageways within'the walls of the mule and connecting said passageways with the interior of the muille at the top and bottom of the latter and subjecting the Walls to tem rature control, whereby to cause convectlon currents to be circulated in the r uired direction over the glass articles within the mulle.

3. The method of transferring heat to, or abstracting heat from, glass articles in an annealing leer which consists in forming a lining for the side walls of the muffle with material of good thermal coductivity, arranging hollow tiles between the lining and shell of said walls, placing the passageways of the hollow tiles in communicationwith the interior of the mule at the bottom and top of the latter and subjecting the lining of the side walls to temperature control whereby to cause convection currents to` be circulated inthe required direction over the glass articles within the muflle.

4. The method of transferring heat to, or abstracting heat from, glass articles in an annealin leer which consists in forming the mu e of the leer with -side walls having vertically extending enclosed passagewa s, putting the .passageways within the wa s into communication with the interior of the mule at the bottom of the latter, forming in the roof of the mullle enclosed passageways communicating with the passageways in the side walls and putting the passageways in the roof into cornmunication with lthe interior of the muflle at the top of the latter, and subjecting said walls to temperature control to cause convection currents to be circulated in the reuired direction throu h the interior of t e mule and throng the passageways within the walls and roof.

5. The method of annealin lass articles in an annealing leer wlici consists in forming the side walls of the mume with vertically extendin passageways in communication at their` ower endswith the bottom of the mume and openin into the to of the muflle through the roo thereof, an

appl ing heat to -o posits sides of the walls of t e mullle so t at air` within the passageways will be raised to a higher tem` perature than the air surroundin the glass articles within the where y convection currents will be- )circulated over the glass articles and through said passageways.

6. A method of annealing glass articles in an annealing leer which consists in forming the walls of the muile with vertically extending passageways opening into the interior of the mufle lat the bottom thereof and communicating passa eways in the Iroof opening into the top 0% the muflle, arrangin gas heated lues on the exterior of the wa ls and electrically heated .means on the interior walls of the muiile whereby air within the passageways will be heated from both sides, thereby raising the temperature to a point higher than the air surrounding the glass articles within the mufle for the purpose of causing convection currents to be circulated over the glass articles and .through the passageways.

7. A method of annealing glass in an annealing leer which consists in forming enclosed vertical passageways within the side walls of the mulle, connecting said passageways at the bottom with the bottom of the mule, connecting said passageways at the top with the interior of the muflle through the roof` thereof, whereby the air within the passageways will be ali'ected by changes in the temperature of the surrounding walls, thus setting up a circulation of convection currents over the glass articles.

8. A glass annealing leer comprising a mulle, enclosed passageways formed in the walls of the muilie and communicating with the interior thereof, said passageways being so arranged as to receive heat transmitted from the 'walls of the muie so as to cause convection currents to be circulated over the Y articles .within the muille.

9. A glass annealing leer comprising a mulle .having its side walls formed with a lining of tile capable of readily conducting heat, hollow tile back of the lining having lvertically extending passageways, said passageways communicating with the interior of the mule at the bottom and with the top of the muflie through the roof thereof whereby the lining will transmit heat to the air within the passageways of the hollow tile and cause circulation of convection currents through the muflie and hollow tile.A

10. A glass annealing leercomprising a mule having its side walls formed of hollow tile with vertically extending passageways, a course of heat-conducting tile forming a lining for the walls and ay course of heat-conducting tile forming a shell for the walls, the passageways in the hollow tile being in communication with the bottom and top of the muille whereby heat will be transmltted to the air in the passageways of the partition tile, thereby causing a circulation of convection currents through the mule and passageways. l s

11. A glass annealing leer comprising a muiiie having its side walls formed of hollow tile with vertically extending passageways, a course of heat-conducting tile forming a lining for the walls and a course of heat-conducting tile forming a shell for the walls, the passageways in the hollow tile being in communication with the bottom and top of the muiiie, electrically controlled means for heating the lining of the muiiie and fuel fired means for heating the shell of the mufie whereby heat will be imparted from both sides to air within the passageways, thus causing a circulation of convection currents through the interior of the muie and passageways.

12. A yglass annealing leer comprising a Inutile havingits side walls formed of hollow tile with vertically extending passageways, a lining and shell for said mulile formed of material capable of readily transmitting heat, the passageways in the hollow tile being in communication with the bottom and top of the Inuiile and means Jfor heating the walls of the muiiie on opposite sides of the passageways whereby to set up a circulation of convection currents through said passageways and through the interior of the mu e.

13. A glass annealing leer comprising a muHe having its side walls formed of hollow tile with vertically extending passageways, a lining and shell encasing said hollow tile, a fire box for heating the mutie, a system of iues connected with the tire box and extending in series from end to end of the muile, said iues extending*` vertically on the exterior of the side walls across the top of the roof and beneath the floor of the muie, and said passageways being in cornmunication with the interior of the mule at the bottom and top of the latter.

14. A glass annealing leer comprising a muiiie having its side Walls formed of hollow tile with vertically extending passageways, a lining and shell encasing said hollow tile, a fire box for heating the mufiie, a system of lues connected with the re box and extending in series from end to end of the mulile, said lues extending vertically on the exterior of the side walls across the top of the roof and beneath the floor of the muie, said vpassageways being in communication with the interior of the muie at the bottom and top of the latter, and means for varying the point of outlet for the heated gases passing through said flue system.

15. A method of transmitting heat to, or

abstracting heat from, articles in an annealing leer which consists in causing a circulation of down or up currents over the articles in the mule by the formation of passa ways for the air in the interior of the si e walls of the muie, placing such passageways in communication with the mule at the top and botom, heating the interior of the muiiie and subjecting the air within the mulile to the action of a fan whereby ,to aid the natural circulation of the currents.

16. The method of annealing glass articles in an annealing leer which consists in forming the side walls of the muiiie with enclosed vertically extending passageways, placing such passageways at one end in communication with the bottom ofthe muie and at the opposite end with the top of the muffle and heating the interior of the muiile electrically, so as to set up a circulation of convection currents through said passageways and across the articles in the muiiie.

17. A method of annealing glass articles in an annealing leer which consists in forming the side walls of the muiie with enclosed vertically extending passageways, placing such passageways at one end in communication with the bottom of the muiiie and at the opposite end with the top of the muiile and arranging electric heating elements within the muiie upon the side walls thereof, whereby convection currents will be circulated through said passageways and across the articles in the muiiie.

18. A glass annealing leer comprising a muiiie having its side walls formed with enclosed vertically extending passageways connected at one end with the bottom of the muiiie and at the other end with the top of the muiiie, electric heating elements arranged within the muiiie on the side walls thereof and thermo-couples disposed within the muiile adjacent the glass articles undergoing annealing, whereby the tem erature gradient between the articles un ergoing l treatment and the walls of the mufiie will be reduced by the circulation of convection currents.

19. A furnace for heat treating purposes comprising a muiile having its side walls formed with enclosed passageways opening into the muitle at the top and bottom and means for causing currents to be circulated through said passageways and over the articles undergoing treatment.

20. A furnace for heat treating urposes comprising a muiiie having its side walls formed with enclosed passa ways opening into the mule at the top an bottom, and a fan within the muiile for circulatin currents through said passageways an over the articles undergoing treatment.

21. A furnace for heat treating purposes comprising a mule, electric heating means within the muie, the walls of said mule being provided with vertically extending assageways opening at one end into the ttom of the muie and at the opposite end `into the top of the mume, said passageways 22. A furnace for heat treating purposes comprising a lnule having vertically eX- tending passageways in its side Walls Opening at one end into the bottom of the mule and at the opposite end into the top of the mufle, electric heating means Within the Inule adjacent the Walls which contain the passageways, thermo-couples within the mule adjacent the articles undergoing treatment and means for circulating currents through said passageways and over the articles undergoing treatment.

HUBERT D.

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