US3403454A - Heat treating apparatus for web and sheet material - Google Patents

Description

Oct. 1, 1968 H- L. SMITH, JR

HEAT TREATING APPARATUS FOR WEB AND SHEET MATERIAL '7 Sheets-Sheet 1 Original Filed March 24, 1966 INVENT OR Home: 1.6mm, Jn

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ATTORNEYS Oct. 1, 1968 H. L. SMITH, JR 3,403,454

HEAT TREATING APPARATUS FOR WEB AND SHEET MATERIAL Original Filed March 24, 1966 v Sheets-Sheet 2 FIZZ:

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4- "j :V N Q N INVENTOR Hora L. Smith, Jz

ATTORNEYS Oct. 1, 1968 H. 1.. SMITH, JR

HEAT TREATING APPARATUS FOR WEB AND SHEET'MATERIAL 7 Sheets-Sheet 5 Original Filed March 24, 1966 $1 53 .53 22 213mm 5&3 -m 3 8 58 212mm 58 5&8 2

mm n d 58 5&3 5B 25 ....wm 8 g mm NW 1/ 1 .53 53 mm 5&5 zmium 1 Ban 5&8 53 555E V N H x ...-W\:W mmbm l l/llfim l wl I HM?! l H/\ 1 f f ATTORNEYS Oct. 1, 1968 H. L. SMITH, JR

HEAT TREATING APPARATUS FOR WEB AND SHEET MATERIAL 7 Sheets-Sheet 4 Original Filed March 24, 1966 ATTORNEYS mzw Oct. 1, 1968 H. 1.. SMITH, JR 3,403,454

HEAT TREATING APPARATUS FOR WEB AND SHEET MATERIAL 7 Sheets-Sheet 5 Original Filed March 24, 1966 INVENTOR Horace L. Smith, Jr.

ATTORNEYS '7 Sheets-Sheet 6 H. L. SMITH, JR

HEAT TREATING APPARATUS FOR WEB AND SHEET MATERIAL K W ATTORNEYS Oct. 1, 1968 3,403,454

HEAT TREATING APPARATUS FOR was AND SHEET MATERIAL H. 1.. SMITH, JR

'7 Sheets-Sheet 7 Original Filed March 24, 1966 INVENTOR Horace LSm/M, Jr:

ATTORNEYS United States Patent 3,403,454 HEAT TREATING APPARATUS FOR WEB AND SHEET MATERIAL Horace L. Smith, Jr., Richmond, Va., assignor to White Consolidated Industries, Inc., a corporation of Delaware Continuation of application Ser. No. 537,132, Mar. 24,

1966. This application Apr. 5, 1967, Ser. No. 628,783

29 Claims. (CI. 34-68) ABSTRACT OF THE DISCLOSURE Fluid supply and radiant heating systems for drying and similar apparatus including main supply and return ducts, branch ducts extending transversely across the main ducts, and an arrangement for directing fluid from the branch supply ducts into contact with the material being treated and for exhausting the fluid and evolved volatiles into the branch exhaust ducts. For applications requiring the application of heat to the product, radiant heaters may be incorporated in the foregoing structure and a single system may be used to heat the treating fluid and the radiant heaters. Apparatus employing flu-id supply and radiant heating systems in accord with the foregoing.

Relation to other applications This application is a continuation of application No. 537,132 filed Mar. 24, 1966, and now abandoned.

In one aspect this invention relates to novel improved fluid supply and radiant heating systems for various types of drying and similar apparatus and, more specifically, to novel improved drying and other apparatus having fluid supply systems as disclosed herein and to the combination of radiant heaters with such systems.

The use of air and other fluids to evolve and/or scour away evolved volatiles in drying and similar apparatus is a well-known technique as discussed in U.S. Patent No. 3,199,213 issued Aug. 10, 1965, to F. H. Milligan et al., for Method of Changing the Moisture Content of Wood, for example. Previously known systems have, however, had a number of significant disadvantages. Among these is an inability to supply the fluid in a manner effective to control the moisture content across the web or sheet of material being dried, which results in a lack of uniformity in the processed product.

A further drawback of many previously known dryers is that fluid is delivered so that it flows parallel to the material being treated at a relative low temperature and velocity. As discussed in the Milligan patent just mentioned, such dryers are inefficient and uneconomical in addition to being incapable of providing good control over the treatment of the material.

Another disadvantage of many heretofore known dryers and similar devices is that there is a lack of uniformity in the velocity with which the spent fluid and its burden of evolved volatiles is exhausted from the vicinity of the sheet or web being treated and/or the lack of a capability for exhausting the fluid in the immediate area in which it impinges on the sheet or web. This also results in a nonuniform final product.

A further disadvantage of numerous prior systems is that they are not, as a practical matter, susceptible of being employed in conjunction with radiant heaters. This is a serious deficit since, as pointed out in my copending application No. 254,674 filed Jan. 29, 1963, for Heat Treating Method and Apparatus (which is now abandoned), for example, the combined use of radiant heating and a scouring gas materially increases the efliciency with which many products may be dried or similarly processed.

Another drawback of many previously known systems is that they are only usable in one type of dryer such as a festoon dryer or a tunnel dryer, for example. This makes the design and manufacture of fluid supply and return systems relatively expensive as they must be produced on virtually a custom-made basis.

Yet another disadvantage of heretofore known dryers and similar devices is in the amount of ductwork required. A related drawback is that such devices often require an excessive amount of space to accommodate the ductwork and other components of the fluid supply and return system.

One important and primary object of the present invention resides in the provision of novel improved dryers and similar devices which are free of the above-discussed drawbacks of similarly known devices of this type.

A related important and primary object of this invention is the provision of novel improved fluid supply and return system for dryers and like devices which eliminate the foregoing disadvantages of such devices.

The novel fluid and supply return systems of the present invention, by which the foregoing and other important objects of this invention are attained, include main supply and return ducts arranged in side-by-side fashion. A number of branch supply and return ducts extend transversely across the two main ducts, supply ducts being alternated with return ducts.

Nozzles or other flow directing members are located at spaced intervals along the branch supply ducts to direct the treating fluid from the ducts at high velocity (and preferably at high temperature) into contact with the material being treated. The high velocity fluid evaporates volatiles in the material and scours the evolved volatiles away from the surface of the material to prevent the formation of a stagnant boundary layer which would materially reduce the evolution of the volatiles. Moreover, the rapid evaporation of the volatiles produces an evaporative cooling effect, which cools and prevents heat damage to the surfaces of the material being treated.

Inlets located in the branch exhaust ducts in a similarly spaced arrangement facilitate the removal of the treating fluid and its burden of evolved volatiles from the dryer or other device. The exhaust arrangement also ensures that the volatiles and treating fluid are exhausted from the vicinity of the web at uniform velocity, contributing further to the uniformity of treatment.

In processes involving the application of heat to the product, tubular type radiant heaters are incorporated in the fluid supply and return systems. The legs of the radiant heaters form part of the branch duct walls, and the fluid supply nozzles and exhaust inlets are fixed to or formed in branch duct wall members fixed between the heater legs. This arrangement is highly efficient and compact and yet is relatively inexpensive to produce.

Multiple pass apparatus branch ducts (and radiant heaters) may be located on both sides of the main supply and return ducts. Thus arranged, a single unit is capable of heating products in both of the passes between which it is located and/or of scouring evolved volatiles therefrom, which materially reduces the cost of many forms of drying apparatus.

The present invention also includes a system for heating both the treating fluid and the radiant heaters by use of a single liquid heating unit connected to the radiant heaters and a heat exchanger over which the treated fluid is adapted to pass. Provision is made for independently regulating the flow of the heat transfer liquid through the radiant heaters and the heat exchanger so that the radiant heaters and the treating fluid can be maintained at different temperatures. An arrangement is also preferably provided for recirculating treating fluid from the dryer or other treating apparatus to the heat exchanger to minimize the loss of the sensible heat in the treating fluid. Vent and make-up ducts may also be provided to vary the proportion of recirculated fluid and thereby control its content of evolved volatiles.

One important advantage of the novel fluid supply and return system just described is that it may be incorporated in a variety of diflerent types of dryers and similar devices without modification. Among these are various single pass dryers, tunnel dryers, 'festoon dryers and other types of multiple pass dryers, and various forms of coating apparatus.

A further important advantage of this system is that it requires much less space than is commonly required by previously known supply and return systems. In part this is due to the partial or total elimination of external ducts along the dryer or other treating device for supplying the treating fluid and to the compactness of the system. Also, as discussed above, a single unit can be employed to supply treating fluid to two passes on opposite sides of the unit, resulting in a significant reduction in ductwork and the space required for it.

A significant reduction in size can also be eflected in dryers and similar devices by constructing them in accord with the principles of this invention because the supply and return units can be arranged to provide a substantially continuous array of branch supply and return ducts over a given area. This provides substantially more capacity per given area than the conventional dryer which employs transversely extending supply and exhaust plenums located at opposite sides of a radiant heater to supply and carry away the treating fluid.

Another important advantage of dryers and similar devices constructed in accord with the present invention is that they are capable of producing a more uniform and higher quality product. This is because the fluid supplied can be uniformly distributed across the product being treated; or the distribution can be selectively regulated to eliminate the wet streaks which occur in paper drying and similar processes. Uniformity is also enhanced in the present invention by the continuous removal of the spent drying fluid and its burden of evolved volatiles at a uniform velocity and closely adjacent its point of impingement on the web. Still further uniformity may be provided by tapering the branch ducts to provide uniform distribution of the treating fluid to the supply nozzles and a uniform flow of the spent fluid into the branch return ducts.

Yet another important advantage of this invention is that it provides a highly eflicient combination of radiant heating and high velocity scouring fluid. This results in significant increases in processing rates in many applications of the present invention such as paper drying, the drying and curing of coatings, and others.

From the foregoing, it will be apparent that other important objects of the present invention reside in the provision of novel, improved fluid supply and return units for drying apparatus and the like, which:

(1) Can be incorporated in a wide variety of dryers and similar devices.

(2) Require significantly less space than fluid supply and return systems heretofore known.

(3) Provide a highly eflicient combination of radiant heating and high velocity scouring fluid which may also be at a high temperature, thereby materially increasing the rate at which volatile constituents can be evolved from the product being treated.

(4) Are capable of producing an evaporative cooling efiect which prevents overheating of the material being treated.

(5) Are capable of providing a uniform or other controlled distribution of treating fluid across the span of the material being treated and uniform exhausting of the spent treating fluid and its burden of evolved volatiles from adjacent the vicinity of the web,

(6) Incorporate radiant heaters as integral components.

(7) Are capable of simultaneously supplying radiant heat and treating fluid to products on opposite sides of the unit.

Still other important objects of the present invention include the provision of novel, improved dryers and the like which include fluid supply and return systems and fluid supply-return and radiant heating systems constructed in accord with the present invention and which:

(1) Require substantially less space than previously known devices of like capacity.

(2) In conjunction with the preceding object, require significantly less ductwork than the previously known devices.

(3) In conjunction with the two preceding objects, have alternating branch supply and return ducts which virtually continuously span the pass or passes for the material being treated.

(4) Are more eflicient and therefore capable of operating at higher rates than heretofore known units of like capacity.

(5) Are capable of producing a more uniform product of higher quality than previously known units.

(6) Include radiant heaters and a fluid heater and a single liquid :heating unit for supplying a heated transfer medium to both the radiant heaters and the fluid heater.

(7) Include an arrangement for recirculating spent treating fluid to retain its sensible heat and vent and make-up systems for controlling the proportion of recirculated fluid and, therefore, its volatiles content.

Other objects, additional advantages, and further important features of the present invention will become more fully apparent from the appended claims and as the ensuing detailed description and discussion proceeds in conjunction with the accompanying drawing, wherein:

FIGURE 1 is a diagrammatic section through a novel, improved dryer constructed in accord with the principles of the present invention;

FIGURE 2 is a section through a novel, improved fluid supply-return and radiant heating unit constructed in accord with the principles of the present invention;

FIGURE 3 is a section through the dryer of FIGURE 1, taken substantially along line 33 of the latter figure;

FIGURE 4 is a section through the unit of FIGURE 2, taken substantially along line 4-4 of the latter figure;

FIGURE 5 is a section through the unit of FIGURE 2, taken substantially along line 5-5 of the latter figure and showing the ports providing communication between main supply and return ducts and brach supply and return ducts incorporated in the latter;

FIGURE 6 is a diagrammatic illustration of the main system duct work which may be employed in delivering the fluid to and exhausting spent fluid from the main supply and return ducts of the fluid supply-return and radiant heating units;

FIGURE 7 is a diagrammatic view of a system for heating the treating fluid and the radiant heaters and for circulating the treating fluid through the supply-return and radiant heating units;

FIGURE 8 is a partly diagrammatic section through a multiple pass dryer, illustrating the arrangement and type of fluid supply-return and radiant heating units employed in apparatus of this type;

FIGURE 9 is diagrammatic view, partly sectioned, of coating apparatus equipped with fluid supply-return and radiant heating units constructed in accord with the principles of the present invention; and

FIGURE 10 is a diagrammatic sectional view through a novel, improved tunnel dryer equipped with fluid supplyreturn and radiant heating units constructed in accord with the principles of the present invention.

Referring now to the drawing, FIGURE 1 depicts a novel, improved single pass dryer 20 which features fluid supply-return and radiant heating units 22 constructed in accord with the principles of the present invention for dryig the product to be treated. Dryer 20 also includes a series of parallel, spaced apart, rotatably mounted rolls 24 establishing a path 26 for the product or material being dried, which is in the form of a web 28. As shown in FIGURE 1, units 22 are located on both sides of path 26 to dry web28 by simulataneously applying radiant heat to both sides of the web to evolve volatiles from it. Units 22 also direct air or other treating fluid at high velocity into contact with the sides of the web to assist in evolving the volatiles and to scour away evolved volatiles from adjacent its surfaces. The high velocity fluid prevents retardation of the drying process by eliminating the formation of a stagnant layer adjacent the web and, in addition, causes evaporative cooling adjacent the surfaces of the material being treated and thereby prevents it from being overheated. It is preferred that the treating fluid also be heated, preferably to a temperature typically on the order of 300 to 650 F. since, as explained in the Milligan patent mentioned above, hot, high velocity air is a highly effective drying agent; and the same is true for other treating fluids.

Referring now to FIGURES 24, each of the novel fluid supply-return and radiant heating units 22 incorporated in dryer 20 includes a main duct pair consisting of elongated main supply and return ducts 30 and 32 separated by a common dividing wall 34. The main ducts 30 and 32 extend lengthwise of dryer 20 with two main duct pairs above and two below the path 26 of the product being dried. The two main duct pairs above path 26 are arranged in end-to-end relationship as are the main duct pairs below path 26. Thus, dryer 20 employs four fluid supply-return and radiant heating units, two of these being arranged in end-to-end relationship above path 26 and two similarly arranged below the path.

Referring now specifically to FIGURE 2 and 4, each of the units 22 includes a number of branch supply and return ducts 36 and 38 extending transversely across the associated main supply and return ducts 30 and 32. As shown in FIGURE 4, the main and branch ducts are integral, the common top wall 48 of the main ducts forming the bottom walls for the branch ducts and the side walls of the main ducts forming the end walls for the branch ducts. Branch supply ducts are alternated with branch return ducts (see FIGURES 4 and 5); and the branch return ducts are arranged with their side walls 42 in abutting relationship (see FIGURE 2).

Branch supply ducts 36 communicate with main supply ducts 30 through apertures 44 (see FIGURE 5) in the common wall 40 between the main and branch ducts adjacent the wall 34 separating the main supply and return ducts. Branch return ducts 38 similarly communicate with main return duct 32 through apertures 46 in common wall 40 on the side of common partition 34 opposite apertures 44.

Air or other treating fluid is accelerated and directed normally at high velocity (typically on the order of 2,000- 15,000 feet per minute) against web 28 by nozzles 48 fixed to the top wall 50 of each branch supply duct 36. The nozzle inlets communicate with the interior of the duct through apertures 52 in its top wall 50. As shown in FIGURE 3, nozzles 48 are disposed in spaced apart relationship the length of each of the branch supply ducts 36. The treating fluid exiting from nozzles 48 contacts the surfaces of web 28 at high velocity, scouring away from the surfaces volatiles evolved from the web. The spent fluid, together with its burden of evolved volatiles, flows into branch return ducts 38 through inlet apertures 54 (see FIGURE 4) formed in the top walls 56 of the branch return ducts.

It will be apparent, from the foregoing, that a uniform distribution of the treating fluid across the span of web 28 can be provided by uniformly spacing nozzles 48 the length of branch supply ducts 36. Similarly, where desired, controlled nonuniform distribution of the treating fluid can be provided by appropriate spacing of the nozzles. For further control over the distribution of the treating fluid against web 28, dampers or other flow control members (not shown) may be located at the inlet ends of nozzles 48.

Another important feature of the arrangement just described is that the inlets 54 to branch return duct 38 are distributed uniformly the length of the branch duct and are adjacent supply nozzles 48. This insures that the spent treating fluid, together with its burden of evolved volatiles, flows with uniform velocity into the return ducts over the entire length thereof and that the spent fluid flows into these ducts at points closely adjacent those at which it impinges upon the web being treated. This provides uniform exit velocities for the spent fluid, which further insures uniform treatment of the web being dried. For other than uniform distributions of the treating fluid, the exhaust openings can of course be spaced at varied intervals like nozzles 48.

As discussed above, it is important that the treating fluid be directed at high velocity against the material being treated as low velocity fluid is not effective to scour away evolved volatiles or to cause evaporative cooling of the material. Typically, the impingement velocity will be on the order of 2,000-15,000 feet per minute as mentioned above. Even higher velocities may be beneficially employed, however, to increase the scouring and evaporative cooling effect. The only significant limitations on this velocity are the ability of the material being treated to withstand the impact of the fluid and the expense of providing equipment capable of delivering fluid at extremely high velocities.

As discussed above, volatiles may be evolved from the web 28 being treated merely by supplying air or other treating fluid at high velocity and high temperatures through nozzles 48. However, in the preferred embodiment of the present invention, volatiles are evolved much more rapidly, thereby materially increasing the efliciency of units 22, by incorporating in them one or more tubular type radiant heaters 58. Each heater consists of a plurality of parallel, spaced apart, straight legs 60 (see FIGURES 3 and 5) having coplanar centerlines and extending in the same direction as branch ducts 36 and 38. The legs 60 are connected by end bends 62 alternately located at opposite ends of the heater.

As is best shown in FIGURE 2, legs 60 of the radiant heater partially define the top walls 50. and 56 of branch supply and return ducts 36 and 38, respectively; and alternate legs 60 also partially define the side walls of the branch ducts, being welded to branch duct wall members 42 of the latter. The configurations of the branch duct top walls 50 and 56 are completed by wall members 64 and 66, respectively, which are welded or otherwise fixed between adjacent radiator legs 60. As shown in FIGURE 2, fluid supply nozzles 48 are fixed to branch duct wall members 64; and the inlet apertures to branch return ducts 38 are formed in wall members 66 so that, as shown in FIG- URE 3, the rows of nozzles 48 and exhaust apertures 54 are disposed between adjacent legs 60 of the radiant heater.

In the particular embodiment of the invention illustrated in FIGURES 2-4, there are two rows of supply nozzles 48 associated with each branch supply duct 36 and two rows of inlet apertures to branch return duct 38 associated with each of the branch return ducts. The number of rows may of course be varied as desired; but it is preferred that a single or double row of apertures be used since this insures a row of inlet apertures adjacent each row of nozzles. As discussed above, this adjacent relationship is important in obtaining uniform exit velocities for the treating fluid by removing it from adjacent the surface of the material being treated as near as possible to the area at which the fluid impinges upon the web being treated.

Referring next to FIGURES 6 and 7, the treating fluid is supplied to the main supply duct 30 in each unit 22 by a blower 68 connected through a duct 70 to a fluid heater 7 72. As it flows through the fluid heater, the treating fluid is heated as it flows over a heat exchanger 74. From fluid heater 72, the heated treating fluid flows through a main system supply duct 76 and branch system supply ducts 78 into the main suply ducts 30 of units 22 (see also FIG- URE 6), the branch system ducts being connected to the main unit ducts at about the midpoint of the latter. Similarly, the spent treating fluid and its burden of evolved volatiles flows from branch return ducts 38 of the various units 22 through ports 46 into the associated main unit return ducts 32. From these ducts, the spent fluid and its burden flows through branch system return ducts 80 into main system return ducts 82.

As discussed previously, in the present invention, main system return ducts 82 are preferably connected to the inlet of circulating blower 68 so that the spent treating fluid may be recirculated through the system, thereby eliminating the loss of sensible heat which would result if the spent fluid were discharged from the system.

In many applications of the present invention, such as in the drying of paper, for example, the percentage of moisture or other volatiles in the treating fluid must be closely controlled to produce the desired characteristics in the treated product. To permit such control, main system return duct 82 is provided with a make-up duct 84; and a vent duct 86 is located in the duct 70 between blower 68 and fluid heater 72. Valves 88 and 90 control the flow through make-up and vent ducts 84 and 86, respectively. By properly adjusting valves 88 and 90, the proper proportion of spent recirculated fluid can be discharged from the system and replaced with treating fluid having a lower content of volatiles to maintain the volatile content at the desired level. Valves 88 and 90 may be adjusted manually or, if desired, may be automatically controlled by a control system of the type disclosed in my US. Patent No. 3,208,158 issued Sept. 28, 1965, for Dryers.

Referring now to FIGURE 7, the heat exchanger 74 in fluid heating unit 72 and radiant heaters 58 are of the type through which a heated fluid heat transfer medium is circulated to elevate them to the desired temperature. The preferred heat transfer mediums are high boiling point organic liquids and eutectic mixtures of inorganic salts, which can be circulated at extremely high temperature in liquid form. Suitable media of this type are discussed in detail in my copending application Ser. No. 323,848 flled Nov. 14, 1963 for Heat Exchangers, which is hereby incorporated by reference in this application.

The advantage of employing liquid heat transfer media is that the problems appurtenant to the high pressures associated with high temperature steam are eliminated and yet the radiant heaters and the treating fluid may be heated to temperatures of several hundred degrees Fahrenheit.

The system illustrated in FIGURE 7 for heating and circulating the liquid heat transfer medium includes a storage tank 92 from which the liquid can be pumped by a transfer pump 94 through a conduit 96 to a drain 98 or to the main circulation system, which includes main return and supply conduits 100 and 102 and is a closed loop through which the liquid is circulated by a main circulation pump 104.

From main return conduit 100 the heat transfer liquid flows into a liquid heating unit 106 where it is heated to the desired temperature. This unit may be of any desired construction and includes a temperature responsive controller 108 which so regulates the flow of fuel to the heating unit through conduit 110 as to maintain the temperature of the heated liquid flowing into main supply conduit 102 constant.

From main supply conduit 102, part of the heated liquid flows through branch supply conduit 112 to the heat exchanger 74 in fluid heater 72. The volume of flow through conduit 112 is controlled by temperature responsive controller 114, which is connected to a valve 116 in conduit 112 and has a sensor (not shown) in the main system fluid supply duct 76. Controller 114 regulates valve 116 so as 8 to maintain the temperature of the treating fluid flowing into main system supply duct 76 constant. From fluid heating unit 72, the heat transfer liquid flows through branch return conduits 118 and 120 back into main return conduit 100.

Referring now to FIGURES 3 and 7, part of the heated heat transfer liquid flowing through main supply conduit 102 is diverted through branch supply conduit 122 to the radiator or radiators 58 of the dryer in which they are incorporated. From supply conduit 122, the heated liquid is pumped through the radiator or radiators 58 in each zone of the dryer by an independent zone pump 124 (only one of which is shown) with its outlet connected to the radiator or radiators and its inlet connected to conduit 122 by a branch supply conduit 126.

As shown in FIGURE 3, each radiator 58 is connected, at its outlet end, to a branch return conduit to recirculate the liquid to the heating unit. Each branch circulation system also includes a branch bypass conduit 132 connected between its branch inlet conduit 126 and a branch return conduit 134 connected between radiator 58 and return conduit 130. Flow through bypass conduit 132 is regulated by a three-way valve 136 which, in turn, is adjusted by a temperature responsive controller 138 with its temperature responsive probe located on the side of radiator 58 facing the product to be treated.

As long as radiator 58 remains at the desired temperature, pump 124 circulates the heat transfer liquid through the closed branch loop consisting of conduit 126, radiator 58, and bypass conduit 132. When the temperature of the radiator starts to drop, controller 138 adjusts valve 136 to divert less liquid through bypass conduit 132 and more into return conduit 130. This permits fresh, hotter liquid to flow from conduit 122 into the branch system to bring radiator 58 back to the desired temperature.

One of the important features of the fluid circulation system just described is that the temperature of the heat exchanger 74 in fluid heating unit 72 and the temperatures of radiators 58 can be independently regulated. This permits the temperatures of these components to be so adjusted that the radiant energy supplied by the radiators will be at the most eflective wave length range and the treating fluid will be at the optimum temperature.

Where more than one radiator 58 is employed in each zone, each radiator can be connected in parallel between supply and return conduits 122 and 130 in the manner just described as shown in FIGURE 3. This is an important practical feature of the present invention inasmuch as it permits independent control of the radiator temperatures in succeeding zones of the dryer in which they are incorporated, adding to the flexibility of the dryer.

Inasmuch as the details of the fluid heating and circulating system just described such as the bypass system 140 provided to maintain constant flow through heating unit 106 are not by themselves part of the present invention, it is not considered necessary to describe them further herein. Systems of the type just described are discussed in more detail in my US. Patent No. 3,236,292 issued Feb. 22, 1966, for Dryers, which is hereby incorporated by reference herein.

The novel fluid supply-return and radiant heating units discussed above may be employed in various types of multiple pass driers as Well as the single pass type described above. One type of multiple pass dryer in which such units may be incorporated is the festoon or multiple run vertical dryer 142 of FIGURE 8.

Dryer 142 includes a plurality of rotatably supported rolls 144 arranged in upper and lower rows 146 and 148. The rolls in upper row 146 are directly above the spaces between the rolls in lower row 148 to direct the web 150 of product to be treated through the dryer in a plurality of parallel, spaced apart passes 152 extending between the two rows of rolls. As the web of product 150 moves through dryer 142, it is dried and evolved volatiles are carried away from it by fluid supply'return and radiant heating units 154 and 156 oriented adjacent and parallel to passes 152 so that the centerlines of the radiant heater legs lie in planes parallel to the passes and the fluid supply nozzles are at equal distances from the passes. Units 154, which are located outside the outermost pass 152, may be identical to the units 22 described above. These units are oriented with their nozzles and radiant heaters facing the pass 152 adjacent which they are located.

The fluid supply-return and radiant heating units 156 are each located between a pair of adjacent passes 152 and, like units 154, extend generally from one row of roll 144 to the other. Units 156 are identical to those described previously except that there are branch ducts and radiant heaters on both sides of the main duct pairs in these units, the arrangement of these components on both sides of the main duct pairs being identical. This modification adapts each unit 156 for simultaneously heating and scouring volatiles from portions of web 150 in two passes on opposite sides of the unit. Thus, the combination of units 154 and 156 insures that, in each of the passes 152, both sides of web 150 are simultaneously radiantly heated and contacted by high velocity fluid to assist in evolving volatiles and to scour away those volatiles which have evolved While preventing overheating of the web.

As shown in FIGURE 8, between or adjacent each of the passes 152, there are two fluid supply-return and radiant heating units 154 or 156 connected in end-to-end relationship. This arrangement divides dryer 142 into an upper zone 158 and a lower zone 160. If desired, temperatures and other parameters may be varied in each of these zones for a particular application of dryer 142. Control of the radiant heater temperature is readily accomplished by the control arrangement illustrated in FIG- URES 3 and 7. Similarly, the temperature, velocity, etc. of the treating fiuid can readily be controlled by installing flow control dampers, which may be temperature responsive, in the branch system supply ducts 162 through which the treating fluid is supplied to units 154 and 156.

As mentioned previously and as shown in FIGURE 8, dryer 142 is of the vertical run type. However, it will be readily apparent to those skilled in the arts to which this invention relates that the arrangement of fluid supplyreturn and radiant heating units illustrated in FIGURE 8 is equally adaptable to a multiple run drier of the horizontal type.

FIGURE 9 illustrates the application of the principles of the present invention to coating apparatus identified generally by reference character 164. This apparatus includes an unwind stand 166 from which the web 168 to be coated is fed through the coating apparatus. From stand 166, the web passes through a conventional coating station 170 where the desired coating material is applied to one side 172 of the web. From the coating station, the web passes over a series of rotatably supported rolls 174, which define a path 176 for the web and are preferably arranged to periodically change the direction of web and thereby prevent high speed flutter in the manner discussed in my US. Patent No. 3,228,114 issued Jan. 11, 1966, for Multiple Run Drier. As shown in FIGURE 9, only the uncoated side of the web contacts rolls 174.

As the coated web moves through pass 176, the coating is cured or dried by radiant energy and high velocity heated air or other fluid emanating from fluid supplyretnrn and radiant heating units 178, which may be identical to the corresponding units 22 and 154 described above. From the last path defining roll 174, the finished web 168 is led over a direction changing roll 180 to a rewind stand 182.

Coating apparatus 164 may be supplied with a heat transfer liquid for the radiant heaters in units 178 and a heating unit for the treating fluid in the same manner as the dryer 20 illustrated in FIGURE 1 and the festoon dryer 142 illustrated in FIGURE 8.

FIGURE illustrates the application of the principles of the present invention to a dryer 184 of the tunnel type. Tunnel dryers are commonly employed for drying wallboard, veneers, and similar relatively thick products.

As shown in FIGURE 10, a tunnel dryer typically includes a casing 186 with a product inlet 188 in one end wall 190 and an outlet 192 in the opposite end wall 194 for the product 196 being treated. As the web or sheet of product 196 moves through casing 186, it is supported by an endless belt 198 trained around rotatably supported rolls 200 and 202 at opposite ends of the casing.

During its passage through the casing, the product 1% is dried by radiant heat and high velocity air or other fluid from fluid supply-return and radiant heating units 204, which may be identical to those described previously. As shown in FIGURE 10, units 204 are located closely adjacent and both above and below the path 206 of the material through the dryer so that it is simultaneously heated from both sides. As is also shown in FIGURE 10, units 204 extend substantially the entire distance between the rolls and 202 at opposite ends of the casing 186; and two (or even more) units are arranged in end-to-end relationship to span this distance. As discussed in conjunction with the embodiment of the present invention illustrated in FIGURE 8, this divides the dryer into zones in which different temperature and other conditions may be maintained.

Because of their uncommon thickness, products of the type dried in tunnel dryers are subject to curling, cockling and other forms of warpage. To prevent this, the product 196 being dried may be maintained flat as it moves through casing 186 by a second, upper endless belt 208 trained around rolls 210 and 212 at opposite ends of the casing above rolls 200 and 202. For products which are not subject to such warpage the upper belt may, of course, be omitted.

As shown in FIGURE 10, belts 198 and 208 pass between units 204 and the product 196 being dried. These belts are therefore preferably of an open mesh construction so that the radiant energy and the treating fluid can penetrate to the product through the belt and so the fluid and its burden of evolved volatiles can pass back through the belt into the fluid return ducts of units 204.

The details of the tunnel dryer are not, by themselves, part of the present invention; and it is therefore not considered necessary to discuss them further herein. Tunnel dryers of the type illustrated in FIGURE 10 are disclosed in detail in my copending application No. 530,146 filed Feb. 25, 1966, for Apparatus, which is hereby incorporated by reference.

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 United States Letters Patent is:

1. Multiple run treating apparatus for continuous webs, comprising:

(a) a plurality of rotatably supported rolls in two parallel, spaced apart rows defining a plurality of parallel, spaced apart passes extending from one to the other of said rows for a web trained alternately over succeeding rolls in alternate ones of said rows; and

(b) a ventilating system for effecting a flow of fluid into contact with the surfaces of said web as it moves through each of said passes, said ventilating system including:

(0) a plurality of main duct pairs each including a main supply duct and a main return duct arranged in side-by-side relationship, there being duct pairs between adjacent passes and adjacent the outer sides of the outermost passes;

(d) branch supply and return ducts extending across and communicating with the main supply and return duct in each main duct pair;

(e) fluid supply means at spaced intervals along each said branch supply duct and communicating therewith for directing fluid from the associated branch supply duct toward the pass thereadjacent; and

(f) at least one fluid inlet to each branch return duct for fluid from the pass thereadjacent;

(g) there being branch supply and return ducts on both sides of the main duct pairs between passes and on the sides of the outer main duct pairs facing the outermost passes, whereby fluid is supplied to and removed from both sides of each pass.

2. The apparatus of claim 1, together with a tubular radiant heater on each side of the main duct pairs between passes and on the sides of the outer main duct pairs facing the outermost passes for heating the web moving through said passes from both sides thereof.

3. The apparatus of claim 1, wherein there are plural main duct pairs between adjacent passes and adjacent the other sides of the outermost passes and independent fluid supply and return means for each of said main duct pairs, thereby dividing the passes between said rows of rolls into a plurality of zones.

4. Coating apparatus for web material, comprising:

(a) means for applying a coating material to one side of the web to be coated; and

(b) means for curing said coating including:

(c) a plurality of parallel, spaced apart rolls establishing a pass for the coated material and adapted to support the uncoated side of said material, and

(d) a radiant heating and ventilating system on the opposite side of the pass from said rolls including:

(e) a tubular radiant heater closely adjacent and generally parallel to the pass for the coated material;

(f) branch supply and return ducts extending transversely of said pass on the opposite side of the radiant heater therefrom;

(g) fluid supply means at spaced intervals along said branch su ply ducts for directing fluid from said branch supply ducts into contact with the coated side of said material;

(h) at least one fluid inlet to each of the branch return ducts; and

(i) means including main supply and return ducts on the side of the branch ducts opposite the radiant heater for supplying fluid to and evacuating it from the branch supply and return ducts, respectively.

5. A radiant heating and fluid supply system, compris- (a) a tubular radiant heater having a plurality of elongated, spaced apart legs;

(b) a plurality of branch supply and return ducts dis posed in side-by-side relationship;

(c) means for supplying fluid to said branch supply ducts including a main supply duct, said branch supply and return ducts extending across the main supply duct at intervals therealong and communicating therewith;

(d) the side walls of the branch supply and return ducts being fixed to legs of said radiant heater and the walls of said ducts opposite the main supply duct comprising said heater legs and wall members fixed to and between said heater legs;

(e) fluid discharge means at spaced intervals along said branch supply ducts and communicating therewith for discharging fluid from each said branch supply duct to the area thereadjacent; and

(f) at least one inlet to each of said branch return ducts.

6. The radiant heating and fluid supply system of claim 5, wherein:

(a) at least one of the wall members forming the said opposite wall of each of the plural supply ducts has a row of spaced apart apertures therein; and

(b) said fluid discharge means comprise nozzles fixed to said supply ducts and communicating with the interiors thereof through the apertures in said wall members.

7. The radiant heating and fluid supply system of claim 6, wherein:

(a) the said opposite walls of said supply ducts include plural wall members; and

(b) there is a row of said nozzles fixed to each of said wall members.

8. The radiant heating and fluid supply system of claim 6, wherein the fluid inlets to the return ducts are apertures in the wall members forming the said opposite sides of said return ducts.

9. Apparatus for treating web and sheet material and the like, comprising:

(a) a fluid supply system which includes:

(b) at least three main duct pairs, each of which comprises a main supply duct and a cooperating main return duct, the ducts in each pair being arranged in side-by-side relation and the main duct pairs being disposed in parallel spaced apart relationship to provide at least two passes through the apparatus for the material to be treated;

(c) branch supply and return ducts extending transversely of and across said passes between said main ducts and the passes thereadjacent and communicating with the main supply and return ducts, there being a first series of branch supply and return ducts on one side of each inner main duct pair and a second series of branch supply and return ducts on the opposite side of each said inner main duct pair and a single series of branch supply and return ducts associated with each of the outer main duct pairs, said single series of branch ducts being on the side of the outer duct pair facing the adjacent inner duct pair, whereby the branch ducts define and are located on both sides of each of the passes through said apparatus;

(d) fluid discharge means at spaced intervals along the branch supply ducts for effecting flows of fluid from said branch supply ducts toward the passes for the material to be treated;

(e) inlets to said branch return ducts facing the passes for the material to be treated; and

(f) means for guiding the material to be treated through said apparatus by way of the passes between said branch ducts.

10. A radiant heating and fluid supply system, comprising:

(a) a tubular radiant heater having a plurality of spaced apart legs, the centerlines of the radiant heater legs being parallel and lying in the same plane and said legs being connected into a single fluid channel by end bends joining adjacent legs and alternately located at opposite ends of said legs;

(b) a plurality of branch supply and return ducts all lying substantially to one side of said heater, said branch supply and return ducts all being disposed in side-by-side relationship and branch return ducts being alternated with branch supply ducts;

(c) fluid discharge means at spaced intervals along said branch supply ducts and communicating there with for discharging fluid from said branch supply ducts to the areas thereadjacent;

(d) at least one fluid inlet to each of the branch return ducts; and

(e) main supply and return ducts extending transversely of said branch supply and return ducts on the side thereof opposite said heater.

11. Heat treating apparatus for web and sheet material and the like, comprising:

(a) means establishing a path for the material to be treated; and

(b) at least one radiant heating and fluid supply system located adjacent said path and comprising:

(c) a tubular radiant heater having a plurality of spaced apart fluid conducting legs;

(d) a plurality of branch supply and return ducts all lying substantially to one side of said radiant heater, said branch supply and return ducts being arranged in side-by-side relationship and said branch supply ducts being alternated with said branch return ducts;

(e) said supply and return ducts all having wall members opposed to the path of the material to be treated and the exposed surfaces of said wall members all lying in a common plane more remote from said path than the portions of said radiant heater fluid conducting legs, whereby said legs are exposed to thereby emit radiant energy directly to the material to be treated;

(f) fluid discharge means at spaced intervals along said supply ducts, each said fluid discharge means being oriented to effect a flow of fluid from the associated supply duct toward the path of the material to be treated;

(g) at least one inlet to each of said return ducts, each said inlet facing the path of material to be treated and said inlets being spaced away from said path; and

(h) means for supplying fluid to the supply ducts.

12. The apparatus of claim 11, wherein there are radiant heating and fluid supply units on both sides of the'path of the material being treated for simultaneously treating both sides of said material.

13. The apparatus of claim 11, wherein the centerlines of the radiant heater legs lie in at least one plane, each said plane being parallel to the path of the product through the treating apparatus, whereby there is a substantially uniform distribution of radiant energy from said heater to the product being treated.

14. The heat treating apparatus of claim 11, together with:

(a) main supply and return ducts extending along and adjacent the path of the material to be treated and on the opposite sides of the branch ducts therefrom; and

(b) means providing fluid communication between the main supply duct and the branch supply ducts and between the branch return ducts and the main return duct.

15. The heat treating apparatus of claim 11, wherein the branch ducts are arranged in abutting relationship.

16. The heat treating apparatus of claim 14, wherein each said fluid discharge means comprises an aperture extending through the sides of the branch supply ducts opposite said main ducts.

17. The heat treating apparatus of claim 14, wherein there are a plurality of independent fluid inlets to each of said branch return ducts, said inlets being in and spaced along the sides of said branch ducts opposite the main ducts.

18. The heat treating apparatus of claim 14:

(a) wherein the main supply and return ducts are arranged in side-by-side relationship; and

(b) there are plural pairs of main ducts, each including a main supply duct and a main return duct cooperating therewith.

19. The heat treating apparatus of claim 18, wherein the main duct pairs are disposed in parallel spaced apart relationship to provide at least one pass through the apparatus for the material to be treated.

20. The heat treating apparatus of claim 18, wherein the main duct pairs are arranged in end-to-end relationship.

21. The heat treating apparatus of claim 18, together with:

(a) means for supplying fluid to said main supply ducts including a main system supply duct and a branch system supply duct connected between the main system supply duct and each of the aforesaid main supply ducts; and

(b) a main system return duct and branch system return ducts connected from each of the aforesaid main return ducts to the main system returnvduct.

22. The heat treating apparatus of claim 18, together with:

(a) fluid circulating means having an inlet and an outlet;

(b) first duct means connecting said outlet to said main supply duct; and

(c) second duct means connecting said main return duct to the inlet of the fluid circulating means for returning fluid thereto.

23. The heat treating apparatus of claim 22, together with:

(a) a fluid vent duct connected to said second duct means;

(b) a fluid make-up duct connected to said first duct means; and

(c) selectively adjustable valves in said vent and makeup ducts for adjusting the amount of fluid respectively discharged and admitted through the vent and make-up ducts, respectively.

24. The heat treating apparatus of claim 22, together with a fluid heater interposed in said first duct means for heating the fluid flowing to said main supply duct.

25. Heat treating apparatus for web and sheet material and the like, comprising:

(a) means establishing a path for the material to be treated, said path establishing means providing at least two path segments extending in different directions; and

(b) at least one radiant heating and fluid supply system located adjacent said path and comprising:

(c) a tubular radiant heater having a plurality of spaced apart fluid conducting legs associated with each of said segments, the cen-terlines of the legs of each said radiant heater lying in at least one plane which is parallel to the path of the product through the segment with which the radiant heater is associated;

(d) a plurality of supply and return ducts all lying substantially to one side of each said radiant heater, said branch supply and return ducts being arranged in side-by-side relationship and branch supply ducts being alternated with branch return ducts;

(e) fluid discharge means at spaced intervals along said supply ducts, each said fluid discharge means being oriented to effect a flow of fluid from the associated supply duct toward the path of the material to be treated;

(f) at least one inlet to each of said return ducts, each said inlet facing the path of material to be treated and said inlets being spaced away from said path; and

(g) means for supplying fluid to the supply ducts.

26. Treating apparatus for web and sheet type material, comprising:

(a) an elongated casing having inlet and outlet openings at the opposite ends thereof for the material to be treated;

(b) means for supporting said material as it moves through said casing comprising rolls at the opposite ends of said casing adjacent said openings and an endless, flexible, open mesh belt trained around said rolls to provide material supporting and return legs; and

(c) a ventilating system for effecting a flow of fluid into contact with said material as it moves through said casing, including:

((1) co-operating main supply and return ducts extending lengthwise of said casing and located between the legs of said belt;

(e) branch supply and return ducts between said main ducts and the material supporting leg of said belt, said branch ducts extending transversely in the casing across the main ducts and communicating therewith, the sides of the branch ducts opposite the main ducts being adjacent and parallel to the path of the material through said casing;

(f) fluid supply means at spaced intervals along each of said branch supply ducts for directing fluid from the associated duct through the openings in said belt toward the material being treated; and

(g) at least one fluid inlet to each branch return duct.

27. Treating apparatus for web and sheet type material,

comprising (a) an elongated casing having inlet and outlet openings at the opposite ends thereof for the material to be treated;

(b) means including a first set of rolls and a first belt of open mesh construction trained therearound to provide a material bearing leg for supporting said material as it moves through said casing; and

(c) a ventilating system for effecting a flow of fluid into contact with said material as it moves through said casing, including:

(d) -co-operating main supply and return ducts extending lengthwise of said casing;

(e) branch supply and return ducts between said main ducts and the path of the material through the casing, said branch ducts extending transversely in the casing across the main ducts and communicating therewith, the sides of the branch ducts opposite the main ducts being adjacent and parallel to the path of the material through said casing;

(f) fluid supply means at spaced intervals along each of said branch supply ducts for directing fluid from the associated duct toward the material being treated;

(g) at least one fluid inlet to each branch return duct;

(h) means for preventing wrinkling, cockling, and other distortions of the material being treated as it moves through said casing including a second set of rolls adjacent the first set of rolls and a second endless belt of open mesh construction trained around the second set of rolls for pressing said material against the material bearing leg of the first belt; and

(i) a second ventilating system as aforesaid between the legs of the second belt for effecting a flow of fluid into contact with the side of the material opposite that facing the first ventilating system.

28. Treating apparatus for web and sheet type material,

comprising ing, said branch ducts extending transversely in the casing across the main ducts and communicating therewith, the sides of the branch ducts opposite the main ducts being adjacent and parallel to the path of the material through said casing;

(f) fluid supply means at spaced intervals along each of said branch supply ducts for directing fluid from the associated d-uct toward the material being treated;

(g) at least one fluid inlet to each branch return duct;

and

(h) radiant heater means between the main duct pairs and the material supporting leg of the endless belt for supplying radiant energy through openings in said belt to said material.

29. Heat treating appanatus for web and sheet material and the like, comprising:

(a) means establishing a path for the material to be treated;

(b) at least one radiant heating and fluid supply system located adjacent said path and comprising:

(c) a radiant heater means;

(d) fluid supply and return ducts extending across said path at intervals therealong;

(e) fluid supply means at spaced intervals along each said supply duct for directing fluid from the associated duct toward the path of the material to be treated;

(f) at least one inlet to each of said return ducts, each said inlet facing the path of material to be treated; and

(g) means including a fluid heating unit having a heater therein for supplying heated fluid to said supply ducts; and

(h) means including a single heating unit for eflecting a flow of a heated heat transfer medium through said radiant heater means and the heater of said fluid heating unit, said last-named means including first and second temperature responsive means for independently controlling the flow of the heat transfer medium through said radiant heater means and the heater of said fluid heating unit, respectively, and thereby independently regulating the temperature of said radiant heater means and the heater of the fluid heating unit.

References Cited UNITED STATES PATENTS 2,900,738 8/1959 Ofien 34-155 XR 3,084,448 4/1963 Dungler 34-155 2,229,285 1/ 1941 Gehnrich 34-160 XR 2,389,586 11/1945 Andrews 34-68 2,473,629 6/1949 Andrews 263-3 2,896,335 6/ 1959 Dungler 34-68 3,065,686 11/1962 Geocaris 98-40 3,208,158 9/1965 Smith 34-122 3,23 6,292 2/ 1966 Smith -11 3,254,422 6/ 1966 Deflel 34-18 FOREIGN PATENTS 639,183 11/ 1936 Germany.

FREDERICK L. MATTESON, 111., Primary Examiner.

H. B. 'RAMEY, Assistant Examiner.

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