US3235973A

US3235973A - Heat treating apparatus for sheet or web like material

Info

Publication number: US3235973A
Application number: US231259A
Authority: US
Inventors: Jr Horace L Smith
Original assignee: Hupp Corp
Current assignee: Hupp Corp
Priority date: 1962-10-17
Filing date: 1962-10-17
Publication date: 1966-02-22
Anticipated expiration: 1983-02-22
Also published as: CH426705A; AT261386B; CH447098A; GB1029580A; CH1281063A4

Description

Feb. 22, 1966 H. L. SMITH, JR 3,235,973

HEAT TREATING APPARATUS FOR SHEET 0R WEB LIKE MATERIAL Filed Oct. 17, 1962 2 Sheets-Sheet 1 0: 2 5 I Ll-I N (O N 8 IO N 00 a Q 4 (D N a (.0 E Q N I N g E INVENTOR Horace L Smith, J1:

ATTORNEYS Feb. 22, 1966 l H. SMITH, JR

HEAT TREATING APPARATUS FOR SHEET OR WEB LIKE MATERIAL 2 Sheets-Sheet 2 Filed Oct.

R O T. m V W O M u 5 I 8 7 2 6 m 8 5 4 O 7).( mm 5 M mu 0 H 4 7 w 4 .1 9 4 4 4 2 O O O 2 2v 2V 0 l /4 V 51 h m 6 H R Q l l WE UT T Horace L. Smith ATTORNEYS 3,235,973 HEAT TREATING APPARATUS FOR SHEET R WEB LIKE MATERIAL Horace L. Smith, Jr., Richmond, Va., assignor to Hupp Corporation, Cleveland, Ohio., a corporation of Virginia Filed Oct. 17, 1962, Ser. No. 231,259 8 Claims. (Cl. 34-155) This application is a continuation-in-part of my copending application Serial No. 166,182, entitled Heating, Drying and Curing Apparatus and Method, filed January 15, 1962.

The present invention relate-s to improvements in apparatus for heat treating sheet, Web or the like material such as for example heating, drying, curing and the like. More particularly, the invention relates to novel apparatus for processing such materials treated with or including a substance desired to be removed from the sheet, or physically modified by, exposure to heat, and is therefore applicable for example in paper drying, curing of thermoset resins, coronizing glass fabric, impregnation of materials with plastics, rubber, fixation of resin bonded dyes and pigments on web materials, single or multiple pattern dyeing or otherwise treating and developing special design such as lace or open area effects, in resinous fabrics, tapes, webs, and the like. The term sheet will be hereinafter used to include sheet, web and the like materials.

Methods and apparatus in said copending application are disclosed for overcoming disadvantages of conductive and heated air heating systems through the novel use of heat transfer by radiation and simultaneous cross ventilation of the products being heated. The cross ventilation for removing vapors as evolved during heating improves the final products obtainable, and the efficiency of the system, by removing the volatilized material from the immediate vicinity of the heaters and sheet material to avoid possible combustion, product contamination, and impairment of evaporation or volatilization from the material under treatment by removing the volatiles and vapors substantially as evolved transversely of the sheet.

I have discovered that the combination of heated air or gas streams moving longitudinally at relatively high velocity over the surface of sheet while it is being heated by radiant heat produces an apparent synergistic heating, evaporating and drying effect, i.e., in paper drying for example, much more drying can be achieved by the combination of radiant heat and heated air than by the sum of the effects of the individual heating media. While substantially improved results are attained by heating the sheet from one side only in accordance with my improved combinations, in the preferred embodiment radiant heating of both sides is carried out in combination with heated gas streams confined between the sheet material and radiators to scour the opposite surfaces of the sheet at relatively high velocity with respect to the sheet surface movement,

nited States Patent 0 and remove the volatile substances immediately upon emergence in the continuously changing hot gas atmosphere, whereby heat is simultaneously developed in the sheet, by radiant energy and contact with heated rapidly moving air streams. The rapidly moving air streams scour the heated volatile substances emerging, or about to emerge, as vapor, from the heated sheet. The action of the scouring gas contacting the sheet surfaces and physically aiding in removal of the volatile substances, promotes more rapid volatilization by removing the volatilized materials before they can condense or otherwise promote a cooling or other vaporization retarding effect.

The most pertinent prior art of which I am aware is U.S. Patent 2,861,354 to Hultgreen which discloses a compact device adapted to supplement the drying capacity of Too larger apparatus. The Hultgreen apparatus is comprised of a radiator element positioned in a housing suspended over the sheet material being dried, and a nozzle adapted to impinge air on the sheet at an angle of between 5 and degrees with despect to the plane of the sheet, and in a direction having a component which is opposite to the direction of sheet travel. The object of the air impingement is to promote surface turbulence on the sheet surface in the area irradiated by the radiant heater element to improve drying efficiency. Briefly, the present invention differs from the Hultgreen apparatus in that it (a) utilizes extended area radiating units which serve as guides for the rapidly moving air stream longitudinally of the sheet movement between direction changes, and (b) involves a complete heat treating apparatus having regulatable temperature and atmosphere zones which enable multi-phase heat treatment in a single apparatus, with high efiiciency, and increased speeds. Gas streams are directed essen tially parallel to the plane of the sheet, between large panel, or banks of, radiators to effectively impart heat to the sheet, remove the volatilized material, and improve the over-all heating efiiciency. Inlet and outlets between the legs of each run of the sheet permit regulation of the heating atmosphere in each run as desired depending on the operating temperatunm and effect on the sheet which is contemplated for a particular run.

One particular application of my present invention is the coronizing of glass fabric. The current glass fabric desizing, coronizing and setting processes, temperature ranges, and equipment and their relative advantages and disadvantages are disclosed in U.S. Patents to Klug 2,633,528; Waggoner 2,845,364; May 2,970,934; Caroselli 3,008,846; and Lotz 3,012,845. In the Klug, Waggoner and May processes, burning of the evolved combustibles occurs on the fabric with flame temperatures considerably above the maximum desirable fabric setting temperatures with adverse discoloration, considerable weakening of the fabric strength and consequent product market value deterioration. These disadvantages are to some extent avoided in the Caroselli and Lotz processing. In my improved apparatus, the glass fabric bearing organic size is passed through a multiplicity of individually ventilated runs in which the gas being introduced, length and temperature of heaters, and speed of travel are correlated so that flammable lower volatile materials are removed in the initial run or runs in an inert, i.e., non-oxidizable, atmosphere such for example as nitrogen, combustion products, carbon dioxide, or the like. The less combustible volatiles are removed under controlled atmospheric conditions with flameless oxidation of the remaining volatile constituents and impurities in the fabric, thereby effecting size removal, and improving fabric strength and colors. By operating at relatively high radiator surface temperatures, for example at the minimum desirable glass fabric setting temperature, and preventing combustion of volatiles in an inert atmosphere in the low volatile removal zone, and controlled, flameless coronizing and setting in the processing in subsequent zones, I produce improved, color, and strength glass fabrics with increased production and at lower cost.

Another particularly good application of my present invention is in drying paper or other similar products. I have discovered that a horizontal run drying apparatus embodying the principles of this invention may economically achieve very fast drying rates, and a product that has been heated uniformly, or as controlled, and which has substantially no wrinkles, cockles, or the like physical defects present in paper dried by conventional prior drying methods. For such use, multiple, slightly chordally arched, substantially horizontal drying runs are prefer ably established, with radiant heaters located on both sides of the paper sheet, and plural inlet and exhaust nozzles spaced along the runs and adapted to pass streams of gas longitudinally of and between the papers and radiators. The multiple run apparatus may be located in a conventional drying chamber, or for additionally improved results, in a chamber under subatmospheric pressure in which moisture in the paper volatilizes at a lower temperature and is therefore more quickly removed, and has a reduced tendency to absorb heat radiation.

It is therefore a .primary object of this invention to provide novel radiant heating apparatus for drying, and/ or curing sheet materials impregnated or coated with volatile or heat transformable substances by utilization of radiant heaters in controlled atmospheres.

Another object is to provide novel apparatus in which sheet heat treating, particularly desizing and coronizing glass fabric, and drying paper and the like materials, may be carried out in one or more heating zones defined by radiant heater elements, and in which the heating effect of the radiators is supplemented by a gaseous stream or' streams passing in contact with the heated surfaces of the sheet material at relatively high velocities.

I Another object is to provide a novel apparatus including radiant heater elements defining a heating zone,

guide means for passing the sheet through the heating zone and ventilating means for passing a stream or streams of gas longitudinally over the surfaces of the sheet material at relatively high velocities with respect to the speed' of sheet movement.

A further object is to provide, if desired, one or more improved padders or other suitable devices, for treating the material at various intervals in the heat treating process.

Still another object is to provide novel apparatus for heat treating sheet material in a plurality of substantially horizontal or vertical runs each comprised of a pair of draw sections between spaced rollers, in which a stream of air or other gas is passed over at least one side of the sheet in the draw sections while being exposed to heat radiation from heater elements.

Still other objects of this invention are to provide a novel heating element with heat exchange fins thereon adapted to coact with gas streams being passed over the product to provide for improved control of gas flow over the sheet surfaces, and to provide improved apparatus for directing streams of gas along the surface of the material being treated, including gas supply and exhaust plenums with nozzles for directing the gas longitudinally of the material surfaces in runs between rollers in which the gas is deflected by rollers opposite the supply plenums and in which the exhaust receives the deflected streams of gas at the end of oppositely traveling sheet draw.

Other objects and advantages of the present invention will become apparent from the appended claims and following description 'of the best mode of carrying out the present invention and modifications thereof, and from the accompanying drawing wherein:

FIGURE 1 is a sectional side elevation taken along line 1-1 of FIGURE 3, of a multiple run diagrammatically illustrated apparatus embodying the principles of the present invention;

FIGURE 2 is an end elevation of the apparatus illustrated in FIGURE 1 with portions of the casing of the apparatus broken away to illustrate its internal structure;

FIGURE 3 is a plan view of the apparatus illustrated in FIGURE 1 and showing the section line 11 along which FIGURE 1 was taken;

FIGURE 4 illustrates a modified multiple run arrangement and gas plenums located adjacent each roller in the run in the apparatus; and

FIGURE 5 illustrates an improved radiating element for providing radiant energy to the sheet being heat treated.

Referring now to the drawings, in FIGURE 1 product 10 is shown passing into a multiple run heat treating app t s located in housing 14, and w ich is preferably utilized in desizing glass fabric. Sheet 10 may be guided into and through the apparatus in any suitable manner, as for example, by guide roller 18 and

rollers

20, 21, 22, 23, 24, 25, 26, 27, and 28. The number of rollers will depend on the number of runs in the apparatus. The rollers may be idler or driven. If driven, a common motor with belt hook-up for example may be used, or individual roller power units may be used if it is desired to operate the rollers individually at differing speeds, for example, to compensate for expansion and contraction under differing temperature conditions of the individual. Radiators 32, preferably double faced with separately regulatable surface temperatures, extend from the bottom of the apparatus up to a point near

rollers

21, 23, 25, and 27 and double face radiators 36 extend from the top downwardly to a point near rollers 22, 24, 26, and 28 Alternately supporting the radiators from opposite ends creates, in effect, a plurality of partitions between each radiator pair in which individual heating zones are established and operating temperatures may be controlled substantially as desired depending on location of the particular zone and the sheet treatment :phase. The over-all arrangement of the

radiators

32 and 36 is such that substantially continuous controlled heat treatment of the material is effected as it passes through the apparatus.

As shown in FIGURE 1, gas is circulated over the upper and lower surfaces of sheet 10 while it is being irradiated, by a divided ventilating system comprised of upper and lower ventilating units indicated generally a and 51 respectively. Gas circulated by upper ventilating unit 50 is indicated by dash and dot arrows and solid line arrows indicate gas being circulated by lower unit 51. Upper ventilating unit 50 is comprised of a manifold inlet duct 54 and connecting

gas inlet plenums

58, 62 and 66, a manifold outlet duct and connecting outlet plenums 74-, 76 and 78. A blower 82 (FIGURES 2 and 3) powered by motor 83, draws in gas from a suitable source, the atmosphere for example, or a source of inert gas such as nitrogen or products of combustion from high temperature gas fired radiators for example, employed in a high temperature heating zone. The gas is then circulated through an air damper 86, and heater is heated gas is desired and not already heated as in the case of the products of combustion for example, and into inlet duct 54 and through the restricted blower outlet nozzles of

plenums

58, 62 and 66. The gas travels downwardly over the surface of an upwardly directed leg around the bottom edge of heaters 36 and is exhausted from the heating zone through the

outlet plenums

74, 76, and 78 (FIG- URES 1 and 3). Gas collected in main outlet duct 70 is recirculated to blower 82 and if desired, passed again into the heating zone. If the gases are vapor laden with volatiles evolved during the heating process in the heating zone, they may be entirely or partially exhausted through an exhaust outlet provided with a damper 94 (FIGURE 3) if desired, or passed in heat exchange relationship around blower 82 or a portion of inlet duct 54 to utilize the heat carried thereby, but without contaminating new gas being forced into the heating zone. The arrangement for lower ventilating system 51 (FIGURES 1, 2, and 3) is essentially the same as that of upper system 50. A blower powered by motor? 102 is provided to supply gas. A manifold inlet duct 106 entering at the bottom of housing 14 is provided! With a control damper 110 and a heater 114 also pro-- vided with a suitable bypass duct (not shown) if heating; is not desired.

Gas forced through inlet duct 106 is introduced into the heating zone in contact with the under surface off sheet 10 through

inlet plenums

118, 122, 126, and 130,, passes upwardly along the upward leg of each sheet run, over the top edge of radiator elements 32 at which: point it is deflected down into

exhaust plenums

134, 136, 138, and where it is introduced into manifold outlet duct 144 for recirculation through blower 100, partial or complete exhaustion through exhaust damper 150, or to a portion of duct 106 in heat exchange relation therewith to heat incoming gas.

It is possible to arrange the ducts in either the upper or lower gas ventilating systems so that the gases in contact with both sheet or web surfaces will travel in the direction of travel of the sheet. However, it has been found preferable to circulate them countercurrently as illustrated by the arrows in the drawings.

In desizing glass fabric, at high speeds, in accordance with this invention, the first zone is preferably operated above the combustion temperature of the most flammable size constituents and no higher than the fabric setting temperature (between about l100 and 1250 F.) in an atmosphere incapable of supporting combustion and at a speed sufficient to expose the fabric to the high temperature for only enough time to heat and volatilize or sublimate the combustible size constituents. Final coronizing and setting may then, if desirable, be effected in a final flameless controlled oxidizing atmosphere. This permits exposure of the fabric to very high temperature and consequent fast removal of the more volatile, combustible constituents of the size material, yet prevents damage to the fabric as experienced in prior methods in which the size has been burned ofi? resulting in adverse discoloration and weakening of the fabric.

In the first run (a run as used herein, refers to two adjacent legs of fabric contacting three consecutive rollers as shown in the drawing) radiator temperatures of about 500 F. to 1500 F. are preferred to quickly vaporize the lower temperature volatiles and most readily combustible constituents that may be embodied in the material under treatment. It is preferable to circulate sufiicient non-oxidizing nitrogen, carbon dioxide or gas radiator combustion products through about both sides of the fabric constituting the first run, i.e., the first up and down legs to prevent combustion of the volatilized or sublimated constitutents. In addition to maintaining the atmosphere of the initial high temperature zone incapable of supporting combustion, the run is timed through the hot zone in a manner to prevent injury to the web. So long as liquid sublimable volatile constituents are being vaporized the temperature of the material cannot rise above the vaporizing, boiling or sublimation temperatures of constituents to be removed. After removal of the lower vaporizing point, more combustible volatiles, the speed of material may be reduced through successive radiant heating zones to speed the removal of higher boiling, higher ignition point, volatiles and sublimates without raising the temperature of the web, sheet or fabric under treatment sufficiently high to damage it, by control of the atmosphere of the heating zones depending upon the character of the material under treatment, the economics of the operation and the desirability\ of maintaining neutral, oxidizing or reducing atmospheres, or utilization or elimination of convection in the heating and curing processes. Where the higher temperatures are used, for example, in removing yarn size material from glass fabric, radiant burners heating only one side of the material may be used since the temperature drop across the material will be relatively slight, thus effecting large savings on fuel and equipment heretofore used in such operations. However, as shown in FIGURES 1 and 4, double face radiators are preferred for greatest speed.

The spacing of the control switch mechanisms below the driving rollers may be uniform or varied to provide equal or differing festoon lengths to provide equal or differing relative times of passage of the material through the successive radiation zones depending upon the material to be treated. In the subsequent runs it may be desirable to operate at very high temperatures since after the initial run or runs, only high temperature volatiles will remain on the fabric, and to keep pace with the rapid movement of the fabric through the first runs, filament temperatures 6 up to 4000 F. may be desired. In the preferred operation of this invention, after fabric temperatures of 400- 1300 F. have been achieved, subsequent radiator temperatures should be in the order of 12002200 F. until the size is removed and in this last heating fiameless oxidation of the remaining constituents is permitted to occur for most rapid results as discussed in my copending application Serial No. 166,182.

The types of radiators in each section may be selected in accordance with the zonal temperatures and other conditions desired as the treatment of the material proceeds. For certain types of operation, radiator temperatures up to about 800 F. are required. For these, my improved radiators, utilizing high temperature heat transfer high boiling point hydrocarbon liquid media may be used (suitable media of this type are identified in copending parent application No. 166,182). For higher zonal temperature operation well known types of gas burning radiators may be used such as flame heated imperforate metal panel type radiators. F or still higher zonal temperatures radiating surfaces operating up to 1500 F. or higher, gas burning perforated ceramic tile operating between about 1200-2200 F. (as for example the well known panel or muflie type radiators, or Perfection-Schwank type perforated ceramic tile gas burning radiators described in United States Patent No. 2,775,294 and the like) may be used. The Perfection-Schwank type burners function entirely on controlled gas and primary air with complete fuel combustion and evolution of fully oxidized combustion products which are discharged from the radiating surfaces and are incapable of supporting combustion of the evolved volatiles. These hot gases emit radiant energy and may also be used for added convection heating of products which are not sensitive to the evolved gases. For still higher temperature operation electrically heated radiators such as resistance bar and filament heated bulb and quartz tube radiators that operate up to 4000 F. and higher may be used.

In subsequent runs the less combustible, less volatile constituents and impurities on the glass fabric are removed at higher temperatures developed by longer run lengths, higher radiator temperatures, or a combination thereof. Controlled introduction of an atmosphere containing controlled amounts of oxygen in combination with the high temperature radiators effects a fiameless oxidation to the remaining volatile constituents and impurities as discussed in my copending application Serial No. 166,182.

Another duct arrangement for ventilating the heating zone is illustrated in FIGURE 4, wherein alternate plenums in both upper and lower systems are adapted to be inlet and exhaust. Thus, plenums and 174 in the upper system are exit plenums while 178 is an inlet plenum as indicated by the arrows in FIGURE 4, fluid flowing from plenum 173 into the heating zone, passing around the lower end of radiators 36, and upwardly into the

adjacent plenums

170 and 174 and to exhaust. Similarly, in the lower system, 180 and 184 are exhaust plenums while plenum 188 introduces gas into the heating zone.

The various plenums illustrated in FIGURE 4 are sub stantially identical, and each has a hollow, boxlike configuration and a circularly sectioned top 190 which is concentric with and juxtaposed to the associated web supporting roller 192. Ingress to and egress from the plenums is afforded by a slot 194 in each cover 190 which preferably extends the length of the associated roller to insure a uniform flow pattern across the width of the Web. Sealing members 196, fixed between adjacent plenums in the embodiment of FIGURE 4, prevent fluid from escaping from the heating apparatus between the plenums.

FIGURE 5 illustrates in more detail an improved radiating element which may be utilized in the present invention. The radiating panels themselves are preferably constructed in accordance with the preferred radiating elements described in detail in my copending application Serial No. 166,182 in that they are panels comprised of tubular channels 200 through which heating fluid is circulated and heats both sides of the tubes, the connecting webs 202 and fins 204 to radiating temperatures. Fins 204 located between each of the hot fluid circulating channels 200 to prevent the gases passing through the heating zone from contacting the surfaces of the channels 200 and possibly cooling them slightly and to aid heat transfer to the sheet, and also to insure that the gases passing through the heating zone will remain substantially in contact with the surfaces of sheet 14 Webs 202, provide emitting surfaces between tubes 200 so that the area of emitting surface of each panel is substantially equal to its total area.

Instead of vertical runs, the sheet may be passed horizontally between radiators with suitable modification of the ventilating apparatus to direct gas streams across the horizontal legs of the sheet. This is particularly helpful in paper driving since the vertical run arrangement will create high tensile stresses in the paper, requiring shorter runs to prevent breakage.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

1. Multiple run heating apparatus for webs of sheet material, comprising:

(a) web guiding rollers disposed in spaced apart rows and arranged to form a web of sheet material trained alternately over successive rollers in opposite ones of said rows into a plurality of generally parallel runs;

(b) a series of parallel, spaced apart radiant heaters between said rows of rollers for evolving at least one volatile substance from said web without imparting significant heat to the atmosphere between said heaters and said web, said heaters being panels comprised of tubular channels having therein a liquid heat transfer media with a boiling point in the range of from about 500 to about 800 F., said heaters being so located that the runs of said web pass therebetween;

(c) fluid circulating means for effecting a flow of fluid between the runs of the web and the rad1ant heaters and generally parallel to said web to remove from adjacent said web the substances evolved therefrom by said radiant heaters including supply and exhaust duct means;

(d) means establishing fluid communication between said supply and exhaust duct means, whereby said fluid may be recirculated through said heating apparatus;

(e) means for controlling the proportion of evolved substances in the recirculated fluid including means for discharging a selectively variable proportion of the fluid flowing in said exhaust duct means therefrom and means for admitting fluid which is relatively free from said substances at a selectively variable rate to said supply duct means; and

(f) means independent of the operation of said radiant heaters for controlling the temperature of said fluid including at least one heating unit for raising the temperature of the fluid as it flows through said duct means, said heating unit supplying the major portion of the heat added to said fluid.

2. Multiple run heat treating apparatus as defined m claim 1, wherein said fluid circulating means further includes supply and exhaust plenums between said rollers with each supply plenum opposite an exhaust plenum, associated supply and exhaust plenums being in opposite ones of said rows and said supply plenums communicating with said supply duct means and having nozzles spanning the length of said rollers for discharging streams of fluid between said radiant heaters and the runs of said web.

3. Heat treating apparatus as defined in claim 2, where in:

(a) each of said nozzles terminates in a discharge opening located between a plane including the centerlines of the rollers in the row in which said nozzle is located and a plane tangent to the aforesaid rollers and on the side of said row nearest the other row of rollers; and

(b) the exhaust plenums have inlets thereto, said exhaust plenums and inlets being similar in configuration to the supply plenums and nozzles thereof and disposed in mirror image relation thereto.

4. Multiple run heat treating apparatus as defined in claim 2, wherein said supply and exhaust plenums comprise:

(a) a hollow boxlike structure extending beyond the side of the associated roller remote from the opposite row of rollers and partially surrounding said roller;

(b) a cover for each said plenum concentric with and juxtaposed to the associated roller;

(0) a slit in each cover extending the length of the roller associated therewith; and

(d) sealing means extending between adjacent plenums to prevent fluid from escaping from the heat treating apparatus between said plenums.

5. Heat treating apparatus for webs of sheet material,

comprising:

(a) sheet guiding rollers in parallel, spaced, side-byside relationship in two parallel spaced apart rows with the rollers in one row opposite the spaces in the opposite row and the distance between rollers substantially equal to the diameter of the rollers, whereby a web of sheet material trained alternately over successive rollers in opposite rows will extend between said rows in a plurality of parallel spaced apart runs;

(b) a radiant heater parallel to and between each pair of adjacent runs and adapted to heat a web of sheet material moving through the heating apparatus in said runs, said heaters being rectangular flat panels and having a width at least equal to the length of the rollers and being comprised of tubular channels having therein a liquid heat transfer media with a boiling point in the range of from about 500 to about 800 F., one end of each heater being opposite and spaced from a roller in one of said roller rows and the opposite end of each said heater being between adjacent rollers in the other of said rows and beyond a plane tangent to the sides of said adjacent rollers, whereby each of said heaters, the web moving along runs between which it is disposed, and the roller opposite the heaters one end constitute a generally U-shaped passage having juxtaposed first and second ends between said adjacent rollers, adjacent heaters being opposite and spaced from rollers in opposite rows, whereby the openings of adjacent passage are between rollers in the opposite ones of said rows;

(c) means for scouring evolved vapors from adjacent the surfaces of the web facing each heater in the two runs associated therewith comprising means for forcing a stream of fluid through each of said U- shaped passages and generally parallel to the runs of said web including a supply plenum adjacent and in fluid communication with one end of each passage and an exhaust plenum adjacent and in fluid communication with the other end of each of said passages and supply and exhaust duct means communicating with said supply and exhaust plenums, respectively;

(f) means independent of said radiant heaters for controlling the temperature of said fluid including at least one heating unit for raising the temperature of the fluid as it flows through said duct means, said heating unit supplying the major portion of the heat added to said fluid.

6. Heat treating apparatus as defined in claim 5,

wherein:

(a) said supply plenums are at least as long as said rollers and include inlet nozzles in fluid communication with the interiors of said plenums and extending substantially the length thereof;

(b) said exhaust plenums are at least as long as said rollers and include exhaust inlets in fluid communication with the interiors of said exhaust plenums and extending substantially the length thereof; and

(c) the supply and exhaust plenums associated with each of said fluid passages are disposed in parallel spaced relationship with the discharge opening of the supply plenum nozzle midway between one side of the associated heater and the run thereadjacent and the inlet to the exhaust plenum midway between the other side of said heater and the run thereadjacent.

7. Multiple run heat treating apparatus as defined in claim 1, wherein:

(a) the tubular channels of said radiant heaters are arranged in parallel, side-by-side relationship to form planar arrays; and

(b) said heaters further include webs between adjacent tubular channels to provide emitting surfaces therebetween and fins extending substantially normal to said webs to reduce the transfer of heat from said webs to said fluid by minimizing the contact of said fluid with said webs and said tubular channels.

8. Heat treating apparatus for webs of sheet material,

comprising:

(a) sheet guiding rollers in parallel, spaced, side-byside relationship in two parallel spaced apart rows;

(b) a supply plenum and an exhaust plenum between each pair of adjacent rollers in each of said rows,

said supply and exhaust plenums being at least equal in length to said rollers;

(c) the supply plenums associated with each row all having inlets thereto at one side of the rollers in said row and the exhaust plenums associated with the same row all having outlets on the opposite side of the rollers in said row;

(d) there being associated with each of said rows an independent fluid circulation system for eifecting a flow of fluid adjacent and generally parallel to the runs of a web of sheet material trained alternately over successive rollers in the opposite ones of said rows to thereby scour from adjacent the web volatile substances evolved therefrom, each said system comprising a blower, supply duct means connected between said blower and the inlets to the supply plenums in the associated row, and exhaust duct means connected between said blower and the outlets from the exhaust plenums in said row;

(e) a plurality of radiant heaters in the space between said rows of rollers for heating a web of sheet material moving through said apparatus;

(f) means establishing fluid communication between said supply and exhaust duct means, whereby said fluid may be recirculated through said heating apparatus;

(g) means for controlling the proportion of evolved substances in the recirculated fluid including means for discharging a selectively variable proportion of the fluid flowing in said exhaust duct means therefrom and means for admitting fluid which is relatively free from said substances at a selectively variable rate to said supply duct means; and

(h) means independent of said radiant heaters for controlling the temperature of said fluid including at least one heating unit in each of said supply duct means for raising the temperature of the fluid as it flows through said duct means, said heating units supplying the major portion of the heat added to said fluid.

References Cited by the Examiner UNITED STATES PATENTS 2,101,301 12/1937 Wellmar 34-157 X 2,268,986 1/1942 Hess 34-46 X 2,269,236 1/1942 Wellmar 34-161 X 2,553,516 5/1951 French 34-36 X 2,807,097 9/1957 Kullgren et a1. 34-68 3,151,950 10/1964 Neuman et al. 34-41 X FOREIGN PATENTS 580,646 7/1933 Germany.

16,799 5/ 1898 Switzerland.

WILLIAM F. ODEA, Primary Examiner.

NORMAN YUDKOFF, Examiner.

Claims

1. MULTIPLE RUN HEATING APPARATUS FOR WEBS OF SHEET MATERIAL, COMPRISING: (A) WEB GUIDING ROLLERS DISPOSED IN SPACED APART ROWS AND ARRANGED TO FORM A WEB OF SHEET MATERIAL TRAINED ALTERNATELY OVER SUCCESSIVE ROLLERS IN OPPOSITE ONES OF SAID ROWS INTO A PLURALITY OF GENERALLY PARALLEL RUNS; (B) A SERIES OF PARALLEL, SPACED APART RADIANT HEATERS BETWEEN SAID ROWS OF ROLLERS FOR EVOLVING AT LEAST ONE VOLATILE SUBSTANCE FROM SAID WEB WITHOUT IMPARTING SIGNIFICANT HEAT TO THE ATMOSPHERE BETWEEN SAID HEATERS AND SAID WEB, SAID HEATERS BEING PANELS COMPRISED OF TUBULAR CHANNELS HAVING THEREIN A LIQUID HEAT TRANSFER MEDIA WITH A BOILING POINT IN THE RANGE OF FROM ABOUT 500 TO ABOUT 800*F., SAID HEATERS BEING SO LOCATED THAT THE RUNS OF SAID WEB PASS THEREBETWEEN; (C) FLUID CIRCULATING MEANS FOR EFFECTING A FLOW OF FLUID BETWEEN THE RUNS OF THE WEB AND THE RADIANT HEATERS AND GENERALLY PARALLEL TO SAID WEB TO REMOVE FROM ADJACENT SAID WEB THE SUBSTANCES EVOLVED THEREFROM BY SAID RADIANT HEATERS INCLUDING SUPPLY AND EXHAUST DUCT MEANS; (D) MEANS ESTABLISHING FLUID COMMUNICATION BETWEEN SAID SUPPLY AND EXHAUST DUCT MEANS, WHEREBY SAID FLUID MAY BE RECIRCULATED THROUGH SAID HEATING APPARATUS; (E) MEANS FOR CONTROLLING THE PROPORTION OF EVOLVED SUBSTANCES IN THE RECIRCULATED FLUID INCLUDING MEANS FOR DISCHARGING A SELECTIVELY VARIABLE PROPORTION OF THE FLUID FLOWING IN SAID EXHAUST DUCT MEANS THEREFROM AND MEANS FOR ADMITTING FLUID WHICH IS RELATIVELY FREE FROM SAID SUBSTANCES AT A SELECTIVELY VARIABLE RATE TO SAID SUPPLY DUCT MEANS; AND (F) MEANS INDEPENDENT OF THE OPERATION OF SAID RADIANT HEATERS FOR CONTROLLING THE TEMPERATURE OF SAID FLUID INCLUDING AT LEAST ONE HEATING UNIT FOR RAISING THE TEMPERATURE OF THE FLUID AS IT FLOWS THROUGH SAID DUCT MEANS, SAID HEATING UNIT SUPPLYING THE MAJOR PORTION OF THE HEAT ADDED TO SAID FLUID.