US2376866A - Oven - Google Patents

Description

May 29, 1945. w. F. BUTLER 2,376,866

" OVEN Filed sept. 25, I942 2 Sheets-Sheet 1 4 T To ENE Y5 May 29, 1945. yv. F. BUTLER 2,376,365

' OVEN 7 Filed Septp25, 1942 ZSheets-Sheet 2 :lTi

IN V EN TOR.

HTTOENEYS Patented May 29, 1945 American Can Compan poration of New Jersey y, New York, N. Y.,"a cor- Application September 25, 1042, Serial No. 459,727

' Y '7 Claims. (01. ass-s) The present invention relates to'conveyor Ovens for heat treating flexible metallic sheets having freshly applied lithographing or other coating material on a surface thereof, such coating being dried by heat while the sheet is in an oven follow-. ing which the dried sheet is-cooled in a second oven before discharge from the machine and has particular reference to maintaining the conveyors of the ovens at predetermined tempera'- tures to facilitate quick heating and 'quick cooling of the sheets. I

In high speed production of drying of freshly coated metallic sheets, such as tin-plate and the like material, it has been found that for quick results it is just as important to apply heat directly to the sheet'stock including its under or uncoated side as it is to apply the heat as by radiation to the freshly coated side.

An important factor of the instant invention in the drying of sheets appertains to raising the the temperature of the sheet to its limit in a minimum of time and upon its initial entrance into the oven following which'this high heat is maintained on the sheet for suflicient time to complete the drying action. Such invention con-1 templatesthe embodiment of these features inan apparatus which willpermit of efficient drying of sheets on a high speed production schedule.

An object therefore of the invention is the provision of a drying oven for freshly coated sheet material wherein the sheets are propelled along a predetermined path of travel and are held in firm contact with a belt conveyor which is maintained at a constant predetermined rem-t perature so that the heat of the belt will be transmitted by conduction to the body of the sheet by way of the surface of. the sheet opposite to that carrying the freshly applied coating material thus resulting in thoroughly drying the coat- I ing material on the sheet ina minimum of time.

' vention, with parts broken away;

Numerous other objects and advantages of the invention will be apparent as it is better under from the following description, which.

aken in connection with the accompanying drawin'gs, disclosesa preferred embodiment thereof.

Referring to the drawings: I

Figure l is a longitudinal sectional view taken through a" drying oven embodying the instant invention, with parts broken away;

Fig. 2 is a fragmentary sectional detail tak through a drying oven embodying the instant in- Fig. 3 is a side elevation of theframe housing for driving mechanismin the lower portion of the machine, with parts broken away; and

. Figs. 4, 5' and 6 are transverse sectionaldetails taken substantially along the respective lines 4-4,5-5,6--6inFig.1. I As a preferred embodiment of the invention the drawings illustrate a vertical drying oven in which freshly coated sheets A are propelled upwardly through adrying chamber B of a heat treating section C and thence downwardly through the chamber to a transfer mechanism. The transfer mechanism delivers the hot and dried sheets to a vertical cooling section D for cooling, when cooled the sheets are discharged to a suitable place of deposit for subsequent operationsor for storage.

The freshly coated sheets A are delivered into the heating section C of theoven in a horizontal position and with the freshly coated wet surface up, in any suitable manner, such as for example,

. byway of an endless chain entrance conveyor ll (Figs. 1 and 3)'having feed dogs I! secured thereto at spaced intervals along the chain. The oven end 'of the entrance conveyor operates'over a.

\ driving sprocket [amounted on a cross shaft ll Another object is the provision of such a dry-- ing oven whe'r'einthe temperature of the' moving sheets may be controlled at all points in the'oven so that a maximum heat may be applied to a sheet as soon as it enters the oven and a lower or equal heat may thereafter be maintained throughout the remainder. of the travel of the sheet in the drying oven to rapidly dry the coating material.

Another object is the provision of an apparatus of this character wherein cooling of the dried sheets is efiected in a manner similar to that of heating, that is, by heat conduction as well as heat radiation and wherein high speed, and uniform continuous 'production'may be" maintained in a minimum space.

journaled 'inbearings l5 formed in the base of a pair of spaced vertical side frames 16. These frames constitute the main frame of the oven.

Adjacent'the oven end of the entrance conveyor I l the feed dogs I 2 propel the entering sheets up- .wardly along a curved guide rail [8 which is secured by brackets l9 to the side frames IS. The inner or upper end of the curved guide rail terxninates adjacent the path of travel .of a vertically disposed andconsta ntly moving -endless belt conveyor 2|. This belt conveyor is made preferably of stainless steel although other nonmagnetic materials may be used with-equally ood results. I v

The belt conveyor 2| constitutes a dryingconveyor and operates over a lower driving pulley 22 and an upper drum-shaped and hollow idler pulley 28. The driving pulley 22 is mounted on a main drive shaft 25 (see also Fig; which is journaled in bearings 28 formed in the oven side frames It. This drive shaft is rotated in any 7 suitable manner, such as for example, by driving trance conveyor actuating gear 3 which is mounted on the conveyor'shaft ll sprocket l3. 1

adjacent the driving 'The upper pulley 23 of the conveyor. 2|

' rotates freely on a stationary shaft 38 (see also Fig. 4) Icarried iii-bearings 33 -formed1in the upper the shaft .38 is, keyed in its aring. to hold the shaft stationary. Y I V r Adjacent-the er face of the drying conveyor 2| there are a plurality of stationarymagnets-IZ v disposed at spaced intervals along both of the; a vertical-runs of the conveyor. Theresultl is a magnetic field throughout, the area. These mag nets-preferabl are permanentmagnetsbut electro-magnets may be utilized if desired. The magnets extend transversely of the belt conveyorbetweenthejtwo side frames 13 and have. their I ends in notches l3 formed in the frames, 3 'asbestshowninFlgs.'land2-. g I fl Idler rollers disposed at spaced intervals between themagnets 42 engage against the moving conveyor belt 2| and thus-maintainit in a pre- 1 determined spaced relation to the magnets so that '1 lien V sieves upwardly along the curved. guide l8 its lower or uncoatedisurfac'ecome's into engage-'1 1 ment with-themoving dryingbelt conveyor 2| at aplace adjacentonejof the magnets 42. The

next and onup to the topfoi' theoventinue to bemaintainedinfpla'ce on the conveyor i and over the top by a" plurality ofspaced and parallel auxiliary top I! which are iden-. tical' with; the magnets-.42. @1886 WP magnets are disposed inside the hollow upper pulley and the outer faces of the magnets are near the'inner suriaceof thepulley; Magnets "are secured-in with this "construction-the pulley 23 freely roends' of thevertical side frames l6. Oneendof Y the conveyor will not drag across the face ofthe magnets; These rollers, vhavej trunnions which; aw meta t s i the s d frames v sesame han" magnets draw the sheet into close contact with the conveyor and thus cause the'sheet to clin to and ridewith the: conveyor. Infthis manner 1 a sheet clinging to the conveyor is,'carried,up- 1 wardlyjpassing throughfthe magnetic field, alon one side of the oven-fromzone magnet ito the 7 At the top of the oven; where .the' V nveyor belt 2| passes over the upper pulleyf23; the sheets cona stationary'segmentai barrel shaped bracket,- which is'dispo ed inside'of the hollow pulley and 1 is'keyed in 'place'on the stationary shaft 38.-

, pulley composed of two half sections which allow for easy assembly outside of the bracket 46.

-sheets,, the freshlyapplied coating on the outer During this up, over and down travel of the sheet surface is thoroughly and quickly dried. This drying action is brought about by a plurality of heating elements 43 which are disposed adjacent to the outer surface of the conveyor along its verticaLruns and around the top of the upper pulley 23. These heating elements preferably are long tubular heaters which extend transversely of the conveyor and which are 3 formed for the internal combustion of a gas and air mixture which is within and which burns inside of-the tube. This causes the tube to become incandescent and to radiate heat across the f path of travel of the sheets carried on the con- -veyor.: j k I v One end of each tubular heater .48 projects through one ofthe side frames l6 (see Fig. 4)

1. and is secured into agas manifold 5| located adjacent and outside. of .the frame. This manifold leads from any suitable source of supply ofheatinggas. c. I 125 Thus as-the coated surfaces of the'sheets A 1' move past'the heaters 43 with the conveyor, the

heat created adjacent the conveyor helps dry the coating on the sheets. In order to concentrate this radiated heat onthe conveyor and the sheets thereon, the major upper portion of the conveyor is enclosed by surrounding sides, ends andctop of an insulated housing on casing 33. This'casing is secured to the side frames i8 and extendsyup- 1 wardly, close to the vertical runs or the conveyor and around the upper pulley 23. The casing en-.-,' tirely enclosesthe heating elements 48 and the magnets and sets oil between its inner walls the heating chamber B hereinbefore mentioned. .At the top of the casing a'vent stack having an adjustable damper 35 is provided topermit es- I icape ofjfumes from the drying coatingmaterial ofthesheets. .7

Hence with the greater portion of the moving conveyor 2| enclosed in the casing 33,.the1'conveyor belt is continually maintained in a heated condition at a predetermined temperature. The

- incandescenthe'ating elements 48 between the sheets radiate heatsdirectly to the belt and compensate for. any heat losses. In other words.

when a sheet enters the heating chamber by..- 7 way of the curved guide rail 1 8, its rearmost or l. uncoated'sur'iace immediately comes into'engagement with the hot surface'of the conveyor and thereby begins theimmediate transfer of, heat by conduction. to the sheet through the rear surface.

. a ,By this means a sheet'may be quickly and ther I oughly heated throughouig its entire thickness in a minimum 0f time andin fact befor'e actual drying of the coating material .begins to take place. With'such favorable drying'con ditions present, it willfbe a parent that the drying of- V thecoajting' material takes place from the inner surface as well as its outer surface. This not onlyfgreatly expedites the drying action but results in-fa more uniform bake than heretofore attained.

' tates aroundthe magnets and thus permits of the I continuous travel of the conveyorand its sheets over the pulley; Following 'over-the-top" movenient thev sheets passdownthe opposite side of the oven,- being still heldmagnetically on the. movingconvey'or byi'the row of magnets. .It will be understood thatthepulley 23 is a split Since direct conduction of heat to a cold sheet fromthe hot belt results in heat losses at the be ginning of the drying action, it is desirable .to maintainagreater temperature adjacent the entrance end of the chamber B than throughout the i V remainder of. the'chamber. This is accomplished very eflectively in the present oven for each heating. element is provided with a manually operw able control device. Thus each heater. may be regulated independently of the others, thereby providing complete control of the temperature at any heater throughout the chamber.

In the present disclosure such control devices are shown as hand valves 56 (Fig. 4) having valve stems 51 which are threaded into bosses 58 formed on the gas manifold 5|. The inner seat 59 formed in the manifold end of the particular heater 48 involved. Hence by rotating the valve stems, the entrance to the heaters may be opened up or restricted as desired and thus the volume of gas entering the heaters is under complete control. 1

Upon the completion of the travel of a sheet A end of each of the stems cooperates with a valve j through the drying chamber B the sheet is dried but is Still slightly tacky. In this condition it is in a rectangular pattern as shown in .Fig. 1.

These pulleys are mounted on cross-shafts 68 carried in bearings'and bearing brackets 69 which extend out from the inner faces of the side frames The magnetic drive pulley 66 is continuously rotated by a spur gear H! which is mounted on the pulley shaft 68. This gear meshes with a driving gear ll which is formed integrally with a gear I2 which is mounted on a short shaft 13 (Fig. 5) carried in a bearing 14 formed in the adjacent side frame It. The gear 12 meshes with and is driven by the main driving gear II.

In this construction of transfer unit the driving pulley 86 is located adjacent the heating conveyor 2| on the approach side of the sheet so that the transfer belt will be pulled tight along all runs excepting the top run. The belt is purposely made loose so that there is a predetermined amount of slack along the top run and thus gives this run a concave effect. I

As a dried sheet E on the drying conveyor 2| move into position adjacent the transfer device it passes almost entirely out of range of the magnets 42 in the drying chamber B and reaches a position where its lower portion hangs loosely on the conveyor while its upper portion is still held by the lowermost magnet 42. In this loosely hanging position the magnetic driving pulley it attracts the lower edge of the sheet and draws it away from the conveyor, carryin it over the pulley and into engagement with the slack run of the conveyor belt and with the tacky side of the sheet facing upwardly away from the belt. The belt carries the sheet to the cooling section D in this position and thus prevents smearing of the tacky coating on the sheet during the transfer of the latter.

The cooling sectionD includes a vertically disposed cooling belt conveyor 15 (Figs. 1 and 6) which is disposed adjacent the transfer belt 65 and operates over a lower driving pulley l6 and an upper hollow, drum shaped idler pulley 11. The 'driving pulley I6 is mounted on a drive shaft 18 which is journaled in bearings ll formed in the side frames l8. Pulley 16 is rotated by a spur v to cooling conveyor.

ear 82 which is mounted on the drive shaft and which meshes with and is rotated by the transfer drum gear 68. This pulley rotates in a bath of cold water, which is retained within a tank 08 mounted on a base 84 connecting the side frames It. The tank extends up above the pulley and is formed with bearing outlets 85 for the drive shaft 18. A wringer roller 88 is disposed within the tank 83 above the level of the water bath therein and frictionally rotates with the outer surface of the belt to wipe off the water c1ing-' ingthere X The water within the tank .3 is maintained at a low cooling temperature by brine or other cooling medium which is circulated through a pipe coil 89 located in the bottom of the tank and immersed in the water of the tank. One end of the pipe coil leads from a suitable source of the cooling medium while the opposite end leads to a return pipe or to a suitable place of disposal for the used coolant. The cold water in the tank maintains the belt conveyor I5 which operates over the driving pulley, in a constantly cooled condition. I

The upper or idler pulley 11 of the cooling conveyor 15 rotates, freely on a stationary'shaft 9|,

theends of which are fixed in bearings formed in a vertical extension 92 of the side frames l8.

This idler pulley is identical in construction and operation with the idler pulley 23 in the drying section 0 of the oven.

Between the lower and upper pulleys 10, ll of the cooling section D there are a plurality of spaced stationary magnets 95 which are disposedadjacent the inner surfacesof the vertical runs of the cooling conveyor 15. The ends of these magnets are secured to the'frame extensions 92. In like manner to the magnets within the heating section pulley 23 there are a plurality of transverse top magnets 96 disposed inside the idler I I pulley 11. These top magnets 96 are stationary and are secured to, a stationary segmental barrel shaped bracket 91 which is keyed to the stationarypulley shaft 9| inside the pulley. Main magnets 95 and auxiliary magnets 9 hold the sheets for cooling. Idler rollers 98 disposed between the magnets 96, as in the heating section B, prevent dragging of the cooling conveyor across the face of these magnets. Hence when a dried sheet E is carried by the transfer belt 65 into place adjacent the cooling conveyor 15, the sheet moves into the range of the magnets 95 along that side and is attracted The constantly moving cooled conveyor carries the sheet upwardly. over the top of the idler pulley 91, and thencedowne wardly toward the bottom of the conveyor.

During this travel of the sheet it gives up its heat to the cooled conveyor 15 by heat conduction. The heat of the sheet then is dissipated in the cooling tank 83 as the conveyor passes therethrough. A certain amount of the heat of the sheet is dissipated into the cooler atmosphere surrounding the conveyor as by radiation for the cooling conveyor is exposed to the airand is -not discharge drum rotates freely on a stationaary' shaft I 02 having its ends secured in bearings formed in the side frames IS. The drum is con-' tinuously rotated by a gear I03 (see also Fig; 3)

whlch'is secured to the drum and which is driv} en by the coolin conveyor drive gear 82. Within the drum there is a pluralityof transverse-magnets 105 which are arranged nearthe inner s'urfaceof the drum. These magnets are bolted to astationary segmental barrel shaped bracket I06 located' within the drumand keyed to the stationary shaft I02. r f x Hencewhen a sheet Ecomes into position between the cooling conveyor 15 and the discharge drum I01, it moves out of the range of themag- :nets adjacent the conveyor and comes into the range ofthe magnets in the drum. The sheet is attracted to the discharge drum "and moves with itas the drum rotates.

The discharge drum l! carries a sheet E clingiing to it, for approximately one-quarter revolution, *Here the sheet moves out of the ran e of the magnets I within the drum and accordingly falls away from the drum. The freed sheet is received on, an endlessbelt discharge conveyor ill which carries the sheet to any suitablelplace of deposit; The even end of this conveyor operatesover a pulley I I2 which is mounted on a cross shaft ll 3jjournaled in bearings H4 formed in the side frames l6 (see'also'Fig. 3).. This conveyor may be actuated inany suitable'manner in time with the moving parts of the oven.

Withsuch a construction of oven natureof the drying and the cooling conveyors saves; considerable floor space while providing for a simple, durable machine which may be operated at high speeds and which is capable of iini form continuous production of sheet treatment with'ease of machine'maintenance.

It is thought that the invention and many of its attendant advantages will be understood from the'foregoing description, and it will be apparent that -:various changes maybe made in the form, construction and arrangement of the parts without departing fromthe spirit and scope of the invention orsacrificing all of its material advantages, theiform hereinbefore described being merely a preferred embodiment thereof.

cated inside of said casing and adjacent said conveyor for maintaining theconveyor at a predetermined temperature to facilitate transfer of conveyor heat directly to the sheets by heat conduction when the sheets are received on said conveyor and for drying the sheet coating by radiating heat as the sheets move upwardlyand downwardly inside of said casing, and. means connecting with each-of said he'atingelements for regulating its heat output so that the temperature along the conveyor may be controlled at desired places within said casing. f V 3 l 2. In a machine for handling and heat treat ing flexible metallic sheets having freshly applied lithograph coating on one side thereof,

the combination of a vertically disposed end-'- less non-magnetic belt conveyor forpropelling the sheets along a predetermined path of travel extended along both runs and over one end of I said conveyor, upper and lower pulleys over the vertical which said conveyor operates, a'plurality of mag-.

nets arranged inside of and adjacent to both runs of said conveyor, a plurality of auxiliary magnets disposed inside of said upper pulley, said magnets creating a magnetic field for holding the sheetson the conveyor while passing along said conveyor runs and over said upper pulley, a casing for partially surrounding said conveyor, and heating elements located outside of both runs of said conveyor and outside of said .upper' pulley for heating the conveyor and for pair of endless non-magnetic belt conveyors for propelling the sheets along predetermined vertical paths of vtravel,a.plurality of magnets arranged adjacent both runs of each of said 'conveyors and creating a magnetic field for holding the sheets on the conveyors during passage therewith, transfer means disposed between 'said conveyors-for receiving the sheets from one and for delivering the'sheets to. the other of said conveyors, heating elements located adjacent one, 1 of said conveyors for heating the belt conveyor and for creating radiating heat to dry the fresh lithograph coating on the sheets as the sheets 1 move with said heat conveyor, and a tank containing a cooling liquid located adjacent the second conveyor and in a position so that said s c- 1 0nd belt conveyor passes into the cooling liquid and heat is thereby extracted whereby the sheets are cooled by transfer of heat by conduction from sheet to belt conveyor in addition to heat radiated from the sheet while carried by said second conveyor,

. .4. In a machine for handling and heat treat ring flexible metallic sheets havfiig freshly applied lithograph coating on one side thereof, the

combination of a pair of vertically disposed endless non-magnetic first and second belt conveyors for propelling the sheets along predetermined paths of travel and to which conveyors the said coated sheets are fed in series, means for actuating said conveyors in unison, a plurality of magnets arranged adjacent each run of each of said conveyors and creating a magnetic field for holding the sheets with their uncoated surface against said runs of the movingconveyors, a transfer mechanism disposedbetween said conveyors for receiving the sheets from the first and for delivering them to the second of said con-,

veyors, heating elements located adjacent the first of said conveyors for heating the same and for creating radiating heat to dry the fresh lithograph coating on the sheets as the sheets move withthe first conveyor, a casing surrounding the first of said conveyors for confining the heat emanating from said heating elements, a tank containing a cooling liquid located beneath the second conveyor and in, a position so that said second conveyor dips into the COOllZlt. liquid and its temperature is reduced, and means for maintaining the cooling liquid at a predetermined low temperature whereby the sheets are cooled by transfer of heat .by conduction from sheet to conveyor in addition'to heat radiated from the heat treating means located exteriorly oi the sheet while carried by said exposed second conveyor.

5. In a machine for handling and heat treating flexible metallic sheets having freshly applied lithograph coating, the combination of a vertically disposed endless non-magnetic belt conveyor for propelling the sheets up, over and down a predetermined vertical path of travel, a plurality of magnets arranged inside of both runs of said conveyor and around one end thereof, said magnets creating a magnetic field for holding the sheets on the conveyor throughout the entire path of the sheets with the conveyor, heat treating means located outside of the sides and top of said conveyor for heating the conveyor and for creating a, heating zone through which the coated sheets pass while on said conveyor' whereby the sheets are heated by heat conduc-- tion from said conveyor and the coated surface is subjected to a radiating heat in the heating zone to quickly dry the coating, and devices for feeding the freshly coated sheets to said conveyor at the bottom and for discharging the dried sheets also at the bottom of the conveyor.

6. In a machine for handling and heat treating flexible metallic sheets having freshly applied lithograph coating, the combination of a pair of endless non-magnetic belt conveyors for propelling the sheets along predetermined vertical paths of travel, a plurality of magnets arranged adjacent both runs of each of said conveyors and creating a magnetic field for holding the sheets on the conveyors during passage therefirst of said conveyors for maintaining the belt -lconveyors at the desired temperatures for heat treament of the sheets so that the first of said conveyors transfers heat to the sheets and the second conveyor extracts heat from the sheets, and cooling means located exteriorly of said second conveyor.

7. In a machine for handling and heat treating'flexible metallic sheets having freshly applied lithograph coating on one side thereof, the

combination of a pair of juxtaposed endless nonmagnetic belt drying and cooling conveyors for propelling the sheets along a predetermined vertical path of travel, a plurality of magnets arranged adjacent both runs of each of said conwith, transfer means disposed between said conveyors for receiving the sheets from one and for delivering them to the other of said conveyors,

radiation against the coated surface, a manually operable valve connecting with each of said gas burners for regulating its heat output so that the temperature in said heating chamber may be controlled, means for transferring the sheets from the first drying conveyor to the second cooling conveyor, and means for cooling said second conveyor.

WILLIAM F. BUTLER.

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