Method and apparatus for continuous application of foam to a planar textile structure

Method of continuously applying a foamed treatment medium to a planar textile structure which includes applying the foam directly to a planar follower guidable synchronously into areal contact with the planar textile structure, and transfering the foam from the planar follower into the planar textile structure by applying vacuum, and apparatus for carrying out the method.

The invention relates to a method for the continuous application of foamed 
treatment medium to planar textile structures. Depending upon the type of 
treatment medium, the application and the subsequent destruction of the 
foam can be followed by a fixation of the treatment medium on the textile 
material. The invention relates further to apparatus for performing the 
method. Finishing media of all kinds such as dyes, natural and synthetic 
resins and the like insofar as foaming, especially in aqueous solution, is 
at all possible, are applicable as treatment media. 
In a heretofore known German Published Non-Prosecuted Application DE-OS No. 
27 15 862, textile finishing media which are basically liquid can be wiped 
onto the respective textile web of material in foam form by means of a 
knife or a wiper, and very uniform foam applications can be obtained. In 
the course of rationalization, there is a striving or endeavor to employ 
foams having a concentration of the respective treatment medium which is 
as high as possible. This means, accordingly, thin, so-called heavy foam 
layers. 
In wiping foam onto webs of material to be treated therewith, difficulties 
are encountered if open material or material structured in some manner are 
to be coated with the foam. In the case of relief material or mesh 
material, the raised parts of the surface of the web of material obviously 
receive a foam layer of lesser thickness than do the depressed areas when 
the foam is wiped on. The consequently different treatment may already 
become intolerable when thin, heavy foam layers are applied. In the case 
of open articles such as curtains, wiping-on also for thick foam layers 
hardly makes any sense. If the web of material is standing still, 
non-uniformities of the treated web of material further result. If very 
thin and/or accordingly highly concentrated foams are to be wiped on, a 
special device for lifting the wiper when it passes seams must further be 
provided. 
It is an object of the invention to provide an improved method as well as 
corresponding apparatus for applying a foamed treatment medium to a planar 
structure, which permits uniform application of the foam even when the 
articles are structured in some manner or are open, and does not cause 
non-uniform treatment in the event of a temporary standstill of a web of 
material to be foamed, or when a seam in the web of material is passed. 
With the foregoing and other objects in view, there is provided, in 
accordance with the invention, a method of continuously applying a foamed 
treatment medium to a planar textile structure, which comprises applying 
the foam directly to a planar follower guidable synchronously into areal 
contact with the planar textile structure, and transferring the foam from 
the planar follower into the planar textile structure by applying vacuum 
or negative pressure thereto. According to the invention, the foamed 
treatment medium is applied to the planar follower or backing cloth at 
normal pressure and is transferred from the planar follower to the planar 
textile structure by vacuum or negative pressure. 
With the method according to the invention, the foam is applicable to the 
backing cloth follower by a wiper or any other means for applying a foam 
which permits the formation of a uniformly thick foam layer. Due to the 
fact that, in accordance with the invention, the foam is not applied 
directly to the web of material to be foam-coated, but is instead 
initially applied to a backing cloth follower which can subsequently be 
brought into contact with a web of material synchronously and areally, a 
completely uniform foam application can be achieved regardless of any 
structuring of the goods and even with open articles. 
The effect desired according to the invention becomes particularly 
advantageous if the foam, after being applied to the backing cloth 
follower which is especially air-tight or air-impermeable, is to be 
transferred through vacuum from the backing cloth follower, after the 
latter has joined or run together with the web of material, onto and into 
the planar structure of the web of material in an evacuated space or 
chamber. If a pressure (for example, about 0.01 to 0.1 bar absolute) is 
selected so that it is low compared to the internal pressure (for example 
about 1 bar) of the bubbles of foam, the bubbles burst completely and 
almost instantaneously when they enter the vacuum space or chamber. Before 
they burst, however, the foam bubbles which originally had a diameter of 
about 0.001 to 0.1 millimeters cannot become larger in direction toward 
the (impermeable) backing cloth follower and, therefore, wet the interior 
of the planar structure to be treated. Depending upon the layer thickness 
of the applied foam and the quality of the web of material treated, the 
latter or the fiber content thereof can be provided fully or partially 
with the treatment medium. 
In order to ensure that the foam uniformly applied to the backing cloth 
follower remains distributed without any disturbance of this uniformity, 
especially without any backing-up or damming when the backing cloth 
follower areally joins or runs together with the web of material to be 
treated and when it enters the vacuum space or chamber, it is advantageous 
for a relatively small suction force to be exerted on the foam lying on 
the backing cloth follower from the planar structure beforehand just 
before the latter merges or runs together with the backing cloth follower. 
The suction force or pull should be only strong enough so that it prevents 
backing-up or damming of the foam; a sucking of the foam into the web of 
material, on the other hand, is unnecessary or undesirable. Through the 
aforedescribed inlet area, what is accomplished is that the foam is drawn 
by the suction pull acting thereon into the inlet gap of the vacuum space, 
which is formed at the location where the web of material and the backing 
cloth follower run together, and can therefore not back up or dam ahead of 
the inlet gap. 
In accordance with another mode, the method invention comprises guiding the 
planar follower, which is air-impermeable, over a drum having, at the 
surface thereof, a support layer subjected to vacuum, guiding the planar 
textile structure between the shell of the drum and the planar follower 
and running the planar textile structure, even considerably before the 
planar follower, onto the drum shell, and exerting suction pressure on the 
foam disposed on the planar follower from a peripheral section of the drum 
disposed ahead of a line at which the planar follower runs up on the drum 
shell. In principle, a device can be used for carrying out this method 
such as has been described, for example, in German Published Prosecuted 
Application DE-AS No. 25 02 149, wherein, however, a cover layer of fine 
capillaries is disposed on the supporting wire screen surrounding the 
drum. 
In accordance with another aspect of the invention, there is provided, an 
apparatus for performing the method of continuously applying a foamed 
treatment medium to a planar textile structure comprising a drum having, 
at the shell surface thereof, an evacuatable support layer, an 
air-impermeable planar follower spanning part of the drum periphery for 
guiding the planar structure on the drum shell surface, the planar 
follower having an inlet section supported by at least one roller, and a 
wiper disposed opposite the one roller for uniformly distributing foamed 
treatment applied to the planar follower region preceding the wiper. 
In accordance with a further feature of the invention, the drum has a 
peripheral section forward of a run-up line at which the planar follower 
runs up on the drum, the peripheral section being uncovered by the planar 
follower yet subjectible to suction pull. 
In accordance with a concomitant feature of the invention, the 
air-impermeable planar follower is formed of smoothly ground rubber. 
Other features which are considered as characteristic for the invention are 
set forth in the appended claims. 
Although the invention is illustrated and described herein as embodied in 
method for continuous application of foam to a planar textile structure 
and apparatus for carrying out the method, it is nevertheless not intended 
to be limited to the details shown, since various modification and 
structural changes may be made therein without departing from the spirit 
of the invention and within the scope and range of equivalents of the 
claims.

Referring now to the drawing, there is shown in FIGS. 1 and 2, an 
embodiment of the apparatus for implementing the method according to the 
invention which includes a cylinder shell or casing 1 with a multiplicity 
of holes 5 which can be connected on the inside of the cylinder 2 to a 
vacuum or negative pressure space or chamber or a non-illustrated vacuum 
pump, by means of lines 4 which extend, for example, parallel to the 
cylinder axis 3, for generating a vacuum or negative pressure; a support 
layer 7 which evenly or uniformly distributes or equalizes the vacuum on 
the drum surface 6; and an endless follower or backing cloth 8 which is 
air-impermeable and is pressed by the vacuum against the cylinder surface 
6 or the support layer 7, respectively, with an inlet section, the planar 
textile structure 9 which is to be treated being guided at the drum 
surface 6 between the backing cloth follower 8 and the support layer 7. 
The backing cloth follower 8 runs over rollers 10 and 11 on the one side 
and the surface 6 of the cylinder shell 1 on the other side. It is 
advantageous to connect to the non-illustrated vacuum pump only those 
lines 4 for feeding the vacuum to the surface 6 of the cylinder shell 1 
which are provided for supplying the region of the drum surface 6 covered 
by the backing cloth follower 8 at times i.e. when the cylinder revolves. 
According to FIG. 1, the sector of the periphery of the cylinder shell 1 
encompassed within the angles .alpha.+.sym. should, according to this 
rule, not be subjected to the vacuum i.e. the lines 4 belonging to this 
sector of the cylinder periphery would have to be decoupled from the 
connection to the vacuum chamber or space or the vacuum pump by means of a 
revolving control head. 
According to the illustrated embodiment, the planar textile structure 9 to 
be treated is introduced by means of a roller 12 between the support layer 
7 on the cylinder surface 6 and the backing cloth follower 8 and is drawn 
over one of the rollers 11 and the roller 13 out of the apparatus, for 
example, to a plaiting-down device. 
According to the invention, the foam provided for treating the planar 
structure 9, which may be a dyeing agent as well as some other treatment 
medium or agent is not applied directly to the planar structure 9, but 
first to the backing cloth follower 8 in the inlet region, preferably in 
vicinity of a roller 10. The foam can be applied to the backing cloth 
follower 8, for example, by means of a slit nozzle 15 extending parallel 
to the axis of the roller 10. A wiper or doctor 16 is then suitable for 
evenly or uniformly distributing or equalizing the foam. 
From the point of application at the wiper 16, the foam 17 travels together 
with the backing cloth follower 8 through the inlet region to the region 
where the backing cloth follower 8 meets or runs together with the planar 
structure 9 at the surface 6 of the cylinder shell 1 and is transferred to 
the planar structure 9 respectively during or after the running together 
of the backing cloth follower 8 and the planar structure 9. Depending upon 
the choice of the thickness of the applied foam layer 17, a uniform 
treatment, which is either complete or encompasses part of the layer 
thickness of the planar structure 9 can be attained in the manner 
described hereinbefore. 
In the region in which the backing cloth follower 8 meets or runs together 
with the planar structure 9, the danger exists that the foam may back up 
or become dammed, so that it becomes difficult to control the application 
of the foam accurately. It may therefore be advantageous to apply the 
vacuum which acts from the interior of the cylinder to a sector of the 
periphery of the cylinder shell 1 which is encompassed in FIG. 1 of the 
drawing by the angle .beta. and not covered by the backing cloth follower 
8, before the backing cloth follower 8 and the planar structure 9 run 
together, so that the foam which is to be applied or brought to the planar 
structure 9 or already lies on it, is attracted or drawn to the textile 
material already in this region. 
The cover layer or support layer 7, which is to be arranged advantageously 
directly on the surface 6 of the cylinder shell 1, has the purpose of 
achieving uniform distribution of the vacuum directed through the holes 5 
to the surface 6 of the cylinder shell 1. This support layer 7 may, for 
example, be a wire screen fabric which is connected to the surface 6 by 
means of strips 18. The strips 18 should extend substantially parallel to 
the axis 3 of the cylinder shell 1 in order to prevent the development of 
a suction pull in peripheral direction of the cylinder.