Device for through-flow processing of web material

In a screen drum device with a fan mounted endwise for generating suction through the screen drum surface, in front of a screen drum jacket, a baffle cover is usually provided. This baffle cover generates in a baffle chamber in front of the baffle cover, the accumulated pressure which is required for uniform processing of a web of material. In order to be able to handle optimally webs of different widths on the screen drum, the baffle cover in the vicinity of the narrow width of the goods is made so that it can be either removed completely or is given an opening mechanism, or the baffle cover has an additional screen cover located parallel thereto and displaceable with respect to the baffle cover. The holes in the baffle cover and screen cover are so arranged with respect to one another that when displacement by about one hole division takes place, most of the holes in the baffle cover can be covered by the ribs or non-permeable portions adjacent to the holes of the screen cover in order to be able to dry the material in the remaining part.

BACKGROUND OF THE INVENTION 
This invention relates to a device for through-flow process of web-form 
fabric, fleece, paper, tissue or the like with a fluid but especially 
gaseous, processing medium circulated throughout the entire device by a 
fan, with a permeable, e.g. a screen drum, traversed from the exterior to 
the interior and placed in a vacuum and having non-perforated walls at the 
ends, said drum serving as a transport element for the web-form material, 
which, to form the processing medium baffle chamber in front of a 
processing chamber, has associated with its a baffle cover with 
perforations, axially parallel to the drum, said perforations being 
arranged crosswise over the working width of the drum, the processing 
medium permeability of said cover being less than that of the drum. 
A screen drum design of this type is known. The baffle cover is required to 
distribute the recirculated fluid upstream from the processing chamber, in 
which the screen drum is rotatably mounted, uniformly over the working 
width of the drum, so that it then flow perpendicularly to the surface of 
the screen drum, in equal air flow volumes to the screen drum. This 
produces a uniform temperature distribution over the working width of the 
screen drum. The jacket or cylindrical casing for the screen drum can be 
made from a piece of perforated sheet metal over which a braided screen 
can be wrapped to even out the air flow through the perforations. The air 
permeability of this sheet metal jacket, however, is limited to 
approximately 45% of the total surface of the drum because of the ribs 
between the holes or perforations required for stability of the jacket. 
Drums whose jackets are composed of sheet metal strips extending radially 
are better. These drums, which are up to 96% permeably, are used 
especially for drying paper and fleece. 
When such screen drum designs are used, material webs of different widths 
must be handled. In order to limit the air flow to the width of the 
material web, the marginal areas of the drum which are not covered by the 
web of material to be treated can be covered in known fashion by an 
air-impermeable cloth. This method is too cumbersome, however, especially 
when the working width of the material changes rapidly It is also known 
from DE-OS 19 00 496 to limit the inflow area to the working width by 
using walls which are located outside the screen drum and which form a 
seal with the baffle cover. A design according to DE-OS 16 35 263 is 
better, in which the adjustment of the working width of the screen drum is 
achieved by walls or cover panels on the inside of the screen drum. This 
adjustability, however, is limited to only a small portion of the entire 
working width, and in particular, only the marginal areas can be covered 
in order to be able to use the middle of the drum. It is not good if, for 
example, only one marginal strip at the outer edge of the screen drum is 
to remain open, but the remainder of the screen drum is to be covered. 
Such a case occurs, for example, when drying fleece, paper or tissue which, 
when production begins, approach the continuous system at the same very 
high speed of 600 m/sec. or more, for example. Production of these goods, 
however, cannot begin over the entire working width of 2 to 5 m because 
the web must first be threaded around the many rolls and through the 
various processing assemblies in the continuous system. At the high feed 
rate, this is only possible with a narrow strip which must run on the 
operating side of the continuous system. But this narrow strip must 
likewise emerge dry from the dryer, and hence solidified, because 
otherwise the goods cannot be handled, at least they cannot be threaded 
into the system. 
Covering the working width of the screen drum except for this narrow strip, 
however, is not possible with known devices so that, in the past, the 
industry has been starting with the entire working width and drying the 
web as required. Then, however, the web is cut lengthwise, leaving a 
narrow remainder, while the wide part of the web is sent into the basement 
as scrap, so that only the remaining narrow strip can be threaded into the 
system. This method of beginning production consequently involves 
considerable losses. It is not possible to produce and dry only the narrow 
strip because when the entire working width of the drum is open, the strip 
will not dry on the drum. The air leakage is too great for effective 
drying to be possible in the heat treatment chamber. Consequently, the 
narrow, non-presolidified strip could not be manipulated after passing 
through the heat treatment device. The strip does not have the necessary 
strength, and it tears. 
SUMMARY OF THE INVENTION 
Hence an object of the invention is to develop a drum device by which the 
above-mentioned disadvantages can be overcome. The goal is also to be able 
to dry completely and hence solidify only a narrow strip on the heat 
processing drum. Then the system can be easily threaded without involving 
the considerable material losses that formerly occurred. 
Taking its departure from the known drum device initially described, the 
invention provides, for achieving the stated object, that the degree of 
permeability of the baffle cover can be increased to a maximum 
temporarily, at least over a partial area of the working width Hence, to 
start the system, the screen drum does not have to have its working width 
limited by inner cover panels, for example, in its through-flow area, but 
the effective opening width of the baffle cover is opened further to 
concentrate the air flowing through to the necessary working width. 
This avoids a telescopically overlapping sheet being pulled over the 
non-used width of the baffle cover to prevent the influx of air; instead, 
a portion of the baffle cover is rendered ineffective as a baffle cover. 
This is possible by pushing a partial area of the baffle cover over an 
adjacent area, so that no baffle cover exists in the partial area or by 
providing the baffle cover in the partial area with a device to increase 
air permeability. This can, advantageously, consist of pivotable flaps 
which are adjustable to open the baffle cover in this partial area. 
Another solution is advantageous when the baffle cover has associated with 
it, at least partially, a parallel aligned screen cover directly against 
and axially parallel thereto, whose holes in the cross section in the 
sliding direction are larger or at most equal to those of the baffle 
cover. To concentrate the incoming air, a screen panel which is likewise 
perforated is slid only slightly over the baffle cover so that with a 
limited working width, only those holes that are not required will be 
covered by this additional screen cover. Then the screen panel is moved, 
for example, by less than a portion of a hole. 
In this initial embodiment, the idea is to leave the perforations in the 
baffle cover in the type known previously and only enlarge partially the 
holes in the screen cover matching the degree of displacement. It is 
important to note in this regard that after the narrow strip of web 
material is threaded into the entire system, the web of material does not 
run suddenly over the entire working width, but can reach this working 
width only slowly. Consequently, the baffle cover must not abruptly become 
air-permeable over its working width, but instead the active holes in the 
baffle cover should open only as the working width increases. 
An improved solution of the basic idea according to the invention in which 
the baffle cover itself has associated with it, a parallel aligned second 
screen cover immediately adjacent to it and displaceable axially parallel 
thereto, is provided wherein the perforations in the baffle cover, as well 
as those in the screen cover, should be larger in a cross section in the 
displacement direction by a multiple in a marginal area of the cover than 
would correspond to the required flow cross section of the holes to form a 
baffle cover. This has the advantage that in the area of the screen drum 
in which the narrow strip runs around the drum, a large free cross section 
is available in the baffle cover so that when the other perforations over 
the working width of the baffle cover are uncovered by this large free 
opening or space, approximately 100% of the incoming accumulated air can 
also reach the screen drum through this large free opening. 100% drying of 
only this narrow strip is the consequence of this measure. 
Now if the web of material is fed as a narrow strip into the entire system, 
the production of the strip can be slowly expanded to the provided width 
of the web. At the same time, only a slight displacement of the screen 
cover with respect to the baffle cover creates a situation in which the 
corresponding airflows in, corresponding to the increase in the working 
width of the screen drum as well. 
The arrangement and the size of the holes in both the screen cover and 
baffle cover are dimensioned so that as close to 100% as possible of the 
incoming air volume can flow through the open perforations to the drum. If 
only the narrow strip is to be dried, the holes provided in the vicinity 
of this strip are given a maximum cross section while the other holes are 
automatically covered. If the working width after final starting of the 
device is increased, depending on the increase in the number of holes, the 
perforation cross section of the holes in the baffle cover is reduced 
overall so that 100% of the incoming air can now flow onto the screen drum 
after being held back over the larger area. Finally, the previously 
conventional stagnant air can flow uniformly over the working width of the 
screen drum, so that all the holes over the working width of the baffle 
and screen covers can form a uniform opening cross section together. 
There is a space in the processing chamber between the baffle cover and the 
screen drum. Because the screen drum jacket is not covered, there is a 
major risk that the air flowing through the open area of the baffle cover 
will be drawn diagonally into the area of the screen drum which is not 
covered by material. To prevent this as much as possible, the invention 
also provides that between the baffle cover and the drum, one, or with 
spacing several, radially directed walls are disposed around the drum with 
slight spacing Walls of this kind prevent axially directed improper 
ventilation of the drum. 
It is also advantageous to provide in the apparatus, a device that measures 
the width of the web of the incoming material, said device being 
functionally connected with a displacement device for the screen cover 
with respect to the baffle cover, in order thereby to adjust exactly the 
width of the material coming onto the screen drum with the position of the 
screen cover relative to the baffle cover and hence exactly with respect 
to the open inflow openings.

The screen drum device according to FIGS. 1 and 4 consists of a rectangular 
housing 1 divided by a partition 2 into a processing chamber 3 and a fan 
chamber 4. In processing chamber 3, a screen drum 5 is rotatably mounted 
and concentrically to the drum, in the fan chamber 4, a fan 6 is also 
rotatably mounted. The fan chamber can also be located in a separate fan 
housing, not shown. In any case, the fan subjects the interior of the 
screen drum 5 to a vacuum through an open end of the drum. In addition, 
the drum design for a wet processing device, which can also serve only to 
draw liquid away or for wet needling of fleece, is a part of the 
invention. The entire design must then be adapted accordingly. 
According to FIGS. 1 and 4, heating assemblies 7 are located above and 
below the fan 6 in the fan chamber 4, the assemblies consisting of tubes 
traversed by heating medium. In general, the screen drums with the jacket 
structure of this invention, which is up to 96% air permeable, are built 
with a very large diameter. Screen drum 5, during heat treatment, is 
covered over almost the entire circumferential surface with a fabric or 
paper 10 to be processed (FIGS. 4 and 8). Where the material is applied 
and removed again, however, the drum is shielded internally from the 
suction prevailing inside. Therefore, in FIGS. 1 and 4 inner covering 8 is 
shown which, however, in this embodiment could be mounted fixed at the 
level of the drum axis. A fine-mesh screen 9 shown only in FIGS. 1 and 4 
is wrapped around the outside of screen drum jacket 5; this screen is 
fastened to the ends of the drum at the two sides 11 and 12. 
A baffle cover 13 is mounted around drum 5 between housing wall 1 and 
partition 2. With a series arrangement with several screen drums, the 
baffle cover extends horizontally; in a single drum device, the baffle 
cover can also extend at a constant distance around the drum. 
The screen drum device according to the subject of the invention offers the 
option of drying, within a short time, a web of material 10' with a lesser 
web width, without screen drum 5 having to be provided with an expensive 
design for limiting the air permeability to the width of the web. There 
are several possibilities for this, all of which concentrate only on the 
design of baffle cover 13. According to FIG. 1, the baffle cover 13, which 
here again extends over the entire working width of screen drum 5, in the 
area where narrow web 10' rests on the screen drum and is to be treated 
there, consists of circular segments 13' which, in the case of processing 
web 10', are pushed outwardly out of their normal functional position and 
then pushed parallel to the axis of the screen drum over fixed baffle 
cover 13. This produces in the vicinity of web 10' an area 13'' which is 
free of the baffle cover so that the processing air now accelerated by fan 
6 over heating device 7 flows mainly through this annular slot (13'') and 
the web of material 10' is processed more intensively, so that the rapid 
drying can be expected. Of course, baffle cover segments 13' can be 
replaced by a second circular baffle cover offset radially outward, which 
then slides in the manner of a ring over baffle cover 13. 
A device can also be provided in free annular slot 13'' by which the air 
permeability of baffle cover 13 can be increased when necessary. According 
to the embodiment shown in FIGS. 2 and 3, this consists of circularly 
arranged pivotable flaps 22 which are movable in this partial area to open 
the baffle cover. For this purpose, a section of the baffle cover 13, as 
shown in FIG. 2, is bent upward to form flange 30 in the area where the 
cover is subjacent to web 10'. The respective axis 24 of a flap 22 is 
mounted in the flanges, said flap being mounted, i.e. to rotate or swing 
about the axis 24. To swing or rotate about axis 24, a lever mechanism 25 
is used which can be connected with a corresponding drive for simultaneous 
actuation of all flaps 22 around drum 5 in simple fashion. In the event of 
an opening, in other words, drying of web 10', flaps 22 are rotated as 
shown in FIG. 2 so that the flaps are substantially perpendicular to the 
cover 13. If, on the other hand, a web 10, being dried as shown in FIG. 4, 
extends over the entire working width of drum 5, flaps 22 are rotated 
through 90 degrees and thus, as shown in FIG. 3, partially rest on one 
another. So that in this case, air can flow through this area of the 
baffle cover as well, flaps 22 are provided with holes 23 so that the air 
permeability corresponds to that of the other section of the baffle cover 
13. The flaps according to FIG. 3 are bent at their outer ends over the 
screen cover is slid to the right (arrow 15), the through openings 21 of 
the baffle cover 13 are opened successively until the displacement 
position shown in FIG. 5 is reached and all the openings are permeable. 
Accordingly, in FIG. 5, web 10 also extends over the entire working width 
of screen drum 5. 
As shown in FIGS. 5 and 6, the holes in baffle cover 13 are of a constant 
size, such a size that the desired baffle pressure results in the baffle 
chamber The holes in screen cover 14 increase in cross section in sections 
toward the left; namely only in displacement direction 16. Therefore, when 
screen cover 14 is displaced to the left (arrow 16), first the through 
holes located at the far right are closed. Then the next group, and so on, 
while the holes in baffle cover 13 that are located further to the left 
remain open because of the shape of the elongated holes 17. The openings 
of elongated holes 17 can also become continuously larger. 
The special arrangement according to FIGS. 7 and 8 is even more 
advantageous. Here the perforations or holes in both baffle cover 13 and 
in screen cover 14 have different through-put cross sections. The goal is 
for those holes in the covers which remain open simultaneously, 100% 
permeability for the processing air is always achieved, which would be 
necessary if screen drum 5 were completely covered with web 10 as shown in 
FIG. 5. Therefore, elongated holes 17 in FIG. 7 are very large in the 
vicinity of narrow web 10'. A great deal of air flows through the very 
narrow open screen cover and optimally surface in order to achieve a 
better contact of the flaps in the closed state. To open the flap 
mechanism, levers 25 are then pivoted in the direction of arrows 26. 
In addition to a normal baffle cover 13, in the device shown in FIGS. 4-8, 
a screen cover 14 is also provided parallel to and immediately adjacent to 
said device. According to FIG. 4, the screen cover leaves an area free on 
the operating side (drive side of drum 5); screen cover 14 can pass 
through, however, as indicated by the dashed line. The two covers 13 and 
14 are mounted to be displaceable with respect to one another. 
Displacement serves to change the through-flow area of baffle cover 13 
and/or to open and close the through-flow openings in the baffle cover. 
The goal is to allow the air accelerated by the fan to pass through the 
baffle cover only at points where the air can also strike material 10, 10' 
resting on drum 5. The rest of the openings in the screen cover and baffle 
cover are supposed to be closed. 
In the embodiment shown in FIG. 4, on the left side (drive side) an area of 
the baffle cover 13 without screen cover covering 14 is associated with 
the drum 5. 
Only this strip of material is to be dried while the remaining area of the 
drum remains unused. Therefore, according to FIG. 6, the remaining holes 
in baffle cover 13 are covered by the ribs of the holes of screen cover 
14. Of course, screen cover 14 can also extend in the left-hand area over 
the baffle cover. Then only the holes in the baffle cover need to be flush 
with those in the screen cover. When the processes material 10'; in other 
words so that the material is discharged dry after going around screen 
drum 5. The holes outside the area of the web 10' are closed again. 
Transverse ventilation, flowing in the axial direction of the air to the 
flow area of screen drum 5 which has remained open is prevented by 
partitions 18 which radially extend from baffle cover 14 approximately to 
the surface of the screen drum. Therefore, only radially directed air flow 
can result. 
If the web of material 10' which has solidified after drying is then 
threaded into the entire system, normal production can begin. The web is 
slowly widened to the working width of the screen drum. The width of 
material 10' is scanned at the input to the screen drum. Accordingly, 
screen cover 14 shifts in the direction of arrow 19. Then the adjacent 
elongated holes open in succession; they are smaller in cross section 
because, when the following holes 17 are fully open, all of the air must 
be distributed over a larger area of the screen drum. If the screen drum 
according to FIG. 8 is then covered completely by material 10, the air 
flows uniformly over the width onto the material with the throughput 
openings being of the same size everywhere in both the screen cover and 
baffle cover (see partial enlargements corresponding to circular segments 
in FIG. 8). 
It is evident that for opening the holes over the working width or for 
correspondingly closing them, only a small displacement of screen cover 14 
relative to baffle cover 13 is necessary. It depends on the hole 
configuration of the covers. The displacement range is, therefore, less 
than or slightly more than only one hole division.