Abstract:
An air processing cylinder useful in drying, curing, thermal bonding, cooling, and web transferring materials such as fabrics, papers, and the like. Air is exhausted out of the cylinder surface through a plurality of conduits equipped with distribution means for profiling the flow of air. The drying cylinder further includes a duct network on its outer shell for exhausting air out of one axial area only or, alternatively, the drying cylinder may contain multiple duct networks for exhausting air out of several axial areas, each having its own flow characteristics.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates to an air processing apparatus for drying, curing, thermal bonding, cooling, and web transferring permeable or semi-permeable webs such as fabrics, paper, or the like. 
   Typical of such an apparatus is the honeycomb system described in U.S. Pat. No. 4,542,596. In this system, a non-rotating structure within the roll provides multiple zones for web processing and a vacuum is applied to a plurality of honeycomb grilled conduits so that the web can be dried uniformly and without the ‘blind spots’ which characterize other devices. Unfortunately however, this patented system is flow limited due to the vacuum source and, also, it is limited because air flow through the conduits is not distributed evenly. Moreover, the incorporation of multiple vacuum means within the roll so as to create different zones of air flow on the drying cylinder is difficult to achieve because of the limited space within the cylinder. 
   The present invention is an improvement over this and other known devices because it allows multiple zones to be created within a cylinder without an internal non-rotating structure; moreover, it allows air to flow equally through the inlet and outlet holes of the conduits so that a web can be dried evenly. 
   As a result, the present invention makes it possible to isolate and direct air flow into a greater number of separate zones on a single cylinder so that the process air of one zone cannot mix with the process air of another zone. 
   This ability to selectively isolate and direct air flow into a multiplicity of zones is a feature not shared by the apparatus covered in U.S. Pat. No. 4,542,596 so that now, for the first time, it is possible to obtain economies in energy and other advantages such as isolating contaminants which, heretofore, were impossible to achieve. 
   These advantages are obtained by incorporating within each cylinder a stationary air distribution tube which distributes process air uniformly throughout the cylinder in an axial direction. 
   This distribution tube is fixed within the cylinder but it is distinguishable from the non-rotating structure of U.S. Pat. No. 4,542,596 because it revolves as the cylinder revolves and, therefore, is not stationary. 
   The air which is impelled by the distribution tube within the cylinder ultimately escapes through the outer porous shell through a multiplicity of air zones, a feature which distinguishes this invention from those devices which exhaust the process air from the drying roll in an axial manner. 
   SUMMARY OF THE INVENTION 
   It is an object of this invention to provide a novel roll for the through-air processing of permeable and semi-permeable webs. Typical applications include, for example, drying, cooling, and thermal bonding paper, fabrics, webs, and other sheet-like material. 
   Another object is to provide a novel cylinder which because of its high open area lends itself to the tensioning of impermeable products. 
   The roll of this invention provides for exhausting air out of one axial area only, or it may contain several axial areas, each having various air flow characteristics, and each of which may be exhausted simultaneously or preferentially, depending on the material which is to be treated. 
   Air is exhausted from the roll through the outer surface of the shell, a feature which makes it possible to enhance and control air flow by varying the shell length, something that is not possible with rolls that exhaust air through their axial ends only. 
   In the present invention, the object is to use the surface of the cylinder for both air supply and air exhaust. 
   By comparison, known devices, specifically those which exhaust air from a cylinder&#39;s axial ends in high flow applications, reach air velocities that are so high as to make energy consumption excessive. 
   The present invention overcomes this drawback in energy consumption and achieves significant economies by neither limiting nor directing the air exhaust exclusively to the cylinder&#39;s roll ends. Instead, the exhaust air is impelled and directed through the shell of the cylinder, and the exhaust area can be expanded for any roll size merely by extending the width of the roll so as to keep exhaust velocities low and minimize energy consumption. 
   Since air is forced out of the cylinder surface, the area available for exhausting air is virtually unlimited and it can be increased by merely increasing the length of the cylinder. This exhaustability has significant process advantages over devices which employ cylinders whose exhaust area is confined to the cylinders axial ends. 
   Accordingly, the structure of the present roll makes it useful in high-flow applications because the exhaust air flow area can be increased by simply extending the outside length of the shell to any desired degree. 
   Structurally, the roll of this invention consists of an outer shell and, beneath the shell exterior, one or more channels equipped with distribution means for profiling the flow of air. The ends of the roll are capped. 
   The shell may be comprised of any porous material. For example, when high-flow applications are needed, highly porous shells having a high open area in excess of 50% are desirable. 
   Typical shells include, for example, honeycomb type shells or square grids fabricated from thin material as, for example, material measuring 0.2 to 4 mm in thickness. When a high-open-area type shell construction is used, the shell is covered with a wire screen that bridges the grid and supports the product which is to be dried. 
   Within each roll, beneath the outer surface of the shell, axial dividers extend radially and intersect an inner cylinder to form channels. And within each channel there is contained a perforated plate that serves as a distribution means for profiling the flow of air. Although the normal object of this plate is to uniformly distribute air flow in the axial direction, it can also be used to vary the flow profiles. 
   These channels limit the air flow to the radial and axial directions only and, thus, make it possible to divide the roll into numerous circumferential zones which may be processed independently. 
   Thus, for example, the roll can be divided into a high flow zone for web transfer onto the roll followed by a zone where hot air is supplied for drying and, also, a zone where there is no air flow so that the product can be easily transferred off the roll. 
   This ability to divide the roll both circumferentially and axially makes it possible to achieve a checkerboard of processing zones so that several operations can be independently achieved on the same roll. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an elevational view with portions cut away to illustrate the elements of the drying cylinder. 
       FIG. 2  is an elevational view of the drying cylinder for use in the air processing of a paper web or the like made up of a plurality of axially extended grilled segments. 
       FIG. 3  is an enlarged fragmentary elevational view of that section of the drying cylinder which is contained within the phantom lines shown in  FIG. 2 . 
       FIG. 4  is a sectional view taken along line  4 — 4  of  FIG. 2  with portions cut-away. 
       FIG. 5  is a sectional view taken along line  5 — 5  of  FIG. 2 . 
       FIG. 6  is a perspective view of another embodiment of the drying cylinder which is shown within a housing equipped with an air intake duct and showing sections cut away to illustrate air flow. 
       FIG. 7  is a perspective view of an alternative design showing a drying cylinder equipped with a second air intake duct, also with portions cut away to illustrate air flow. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The use of this apparatus in drying permeable and semi-permeable webs is best illustrated by  FIG. 1  which shows a web  20  being fed onto the drying cylinder of this invention by conventional guideroll means (not shown). 
   The drying cylinder  12  ( FIGS. 1 and 2 ) consists essentially of a cylindrical hub  14  mounted on an axle  19  which is rotatably mounted in a pair of bearings  18 . The cylinder  12  includes a plurality of axially extending conduits  22  arranged together in cylindrical configuration. These conduits  22  are formed by a plurality of radial plates  24  ( FIG. 2 ) extending along the longitudinal axis of the drying cylinder  12 . Plates  24  extend outward radially from hub  14  to the periphery of cylinder  12 . Each of the conduits  22  has their radial plates  24  converging toward each other so as to form a generally inwardly tapered channel  15  where they intersect the cylindrical hub  14  ( FIG. 3 ). 
   The conduits  22  are covered by a cylindrical shell  41  ( FIG. 3 ) comprised of a screen  44  and a cylindrical underframe or support structure  46 . This support structure  46  may be in the form of a perforated plate equipped with a reticulated pattern of holes which are shown as inlet ports  48   a  and outlet ports  48   b  in  FIGS. 1 and 4  or it may take the form of a honeycomb-type shell or grid-type structure. In either case, the support structure  46  and radial plates  24  are fabricated from steel or other suitably rigid material and the screen  44  is steel wire mesh or an interwoven fabric. 
   The support structure  46  generally has an open surface area which is capable of accommodating a wide range of applications. Typical of these are operations in which the open areas are in excess of 50%, in which case the inlet ports  48   a  and outlet ports  48   b  cover a combined area of more than one-half the total surface; however, this process is not limited to rolls with large open areas only, and it is to be understood that smaller open areas as, for example, those of less than 50%, are also within the scope of this invention. If the support structure  46  is a perforated plate, its radial thickness may be in the range of from about 0.2 to 4 mm; however, if a honeycomb or grid-type structure is employed then their respective radial thicknesses will be appreciably greater and may be in the range of from about 25–200 mm. The support structure  46  is covered by a screen  44  that supports the web  20 . The axially extending conduits  22  are sealed at their ends by circular end portions  34  as shown in  FIGS. 4 and 5  or each respective end may be sealed individually. 
   A vertically disposed divider air dam  36 , which is parallel to the end portions  34 , extends partially through the drying cylinder  12  and divides each conduit  22  longitudinally into a front chamber  50  having inlet ports  48   a  and a rear chamber  52  having outlet ports  48   b . The air dam  36  extends circumferentially around the drying cylinder  12  as shown in  FIG. 5 . 
   An inner cylindrical axial air distributor  26 , constructed and arranged to be concentric with the longitudinal axis of the cylindrical hub  14 , divides each of the conduits radially into an outer chamber  28  and inner chamber  30  ( FIGS. 2 and 3 ). The inner cylindrical axial air distributor  26  is perforated with flow port means in the form of apertures  32   a  and  32   b  ( FIG. 4 ) which provide for air flow between said inner chamber  30  and outer chamber  28 . As seen in  FIGS. 1 and 4 , the apertures become progressively smaller as they near the air dam  36  and larger as they approach the end portions  34 . This has the effect of evenly distributing air flow; however, other means of evenly distributing air flow as, for example, by the use of a longitudinally extended graduated slot may also be employed. Moreover, it should be noted that the apertures in the air distributor may be sized to any desired dimension so as to achieve any desired air flow profile or, alternatively, the position of the radial plates  24  may be varied to obtain the desired flow profile. 
   The exterior of drying cylinder  12  is partially enclosed by a housing  38 . A pair of axial seals  40  extend along the longitudinal axis of the cylindrical hub  14  and seal the drying cylinder  12  against the housing  38  as shown in  FIG. 2 . The seals  40  extend axially across the width of the conduits  22  so as to eliminate any gap between the seal and the radial plate and thus avoid or minimize air leakage. Thus, the web  20  can be removed at the sector S where the web  20  is not enclosed by the housing  38  since there is no air flow in that zone. 
   The housing  38  includes a front intake duct  54  ( FIG. 6 ), arranged to supply air to the inlet ports  48   a , and a rear exhaust duct  56 . A circumferential air seal  53  ( FIGS. 1 and 5 ) is positioned between the intake and exhaust ducts to prevent air leakage therebetween. In embodiments where a plurality of intake and/or exhaust ducts are used (discussed below), it should be understood that seals would be disposed between these intake/exhaust ducts as well. A second circumferential air seal  55  ( FIG. 4 ) is secured to the outboard edge of the housing  38  to prevent leakage of air from housing  38 . Still another seal  55  is fitted onto the outboard edge of the exhaust duct  56  to avoid having outside air leak into the system. 
   The air flow illustrated by the arrows in  FIGS. 1 ,  2 ,  3 ,  6 , and  7  is produced by a vacuum source ( 42 ,  42   a , and  42   b ) located at the exhaust opening  61  ( FIGS. 1 and 6 ), which draws air into the inlet ports  48   a  and through the apertures  32   a  of the air distributor  26 . The air then flows longitudinally through the conduits  22  under the air dam  36  to the rear chamber  52  ( FIG. 4 ). The air is then drawn through the apertures  32   a  of the air distributor  26  and expelled through the outlet ports  48   b  to the exhaust duct  56 ; however, it should be noted that other means for channeling air through the conduit as, for example, by the use of blower means may also be employed. 
   According to another embodiment as shown in  FIG. 7 , the drying cylinder includes two areas or zones of desired air flow. In this embodiment, an upper intake and exhaust duct network  60  combines with vacuum source  42   a  to form a first zone  66  and a lower intake and exhaust duct network  62  combines with vacuum source  42   b  to form a second zone  68 . If desired, the lower intake duct can be removed as shown in  FIG. 6 , or multiple intake and exhaust duct networks for multiple zones can be employed. 
   Because air is exhausted out of the outer diameter of the shell, this system is not flow limited and, in fact, air flow can be enhanced and controlled by extending the width of the shell. This is a significant advantage over rolls that exhaust air out the axial ends only. 
   In summary, this drying cylinder is comprised of plates that penetrate radially into the cylinder and form conduits which intersect an inner cylindrical hub  14 . The conduits are further divided axially to create within the cylinder multiple zones which produce various air flow characteristics on the outer surface of the drying cylinder. Further, the inlet and outlet holes of the air distributor  26  are sized to permit the air to flow evenly or create a desired profile. Although a honeycomb type shell may be used, it is not essential and other types of shells may also be employed. 
   While the preferred embodiments have been fully described and depicted for the purposes of explaining the principles of the present invention, it will be appreciated by those skilled in the art that modifications and changes may be made thereto without departing from the spirit and scope of the invention set forth in the appended claims.