Device for applying and dosing liquid or pasty materials

A device for applying and dosing liquid or pasty materials onto moving surfaces, especially onto paper or cardboard webs, is provided. The invention is characterized by a roll, optionally with an outer shell, the diameter of which can be controlled by the application of energy and, under predetermined or desired controllable conditions provides local variations in diameter along the length of the roll or roll shell as a function of time and/or space.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention is concerned with a device for applying and dosing liquid or 
pasty substances onto moving surfaces, such as paper or cardboard webs, 
for example. Preferably, the inventive device takes the form of an 
application or dosage roll. 
2. Background Technology 
The amount of pasty substance applied to a moving web from an application 
or dosing roll can generally be controlled by the following measures: 
a) by changing the gap between two cooperating rolls; 
b) by having a difference between the velocities of two cooperating rolls; 
and/or 
c) with the aid of a blade pressed on the roll with variable force. 
Volumetric control of the amount of substance applied is not possible. This 
means that, by having an appropriate gap width, for example, between two 
cooperating rolls, the amount applied is controlled by the cross-section 
of the particular gap section. 
Other application methods involve rolls with small surface cups from which 
excess substance is scraped off to a predetermined height, as well as a 
pair of rolls, of which one has a desired surface profile. In this case, 
the gap between the rolls can be adjusted. However, in order to obtain 
variable volumetric control of the amount applied, it is necessary to 
change rolls which, of course, involves interruption of production. 
SUMMARY OF THE INVENTION 
It is an object of the invention to overcome one or more of the problems 
described above. 
According to the invention, control of a variable amount of a substance 
applied from an applicator roll onto a web guided under tension over a 
dosage roll is provided. The invention is directed to an application 
device in which an applicator roll cooperates with a counter roll, with 
the formation of an application gap, in order to make a desired amount of 
coating material available for another applicator roll or for direct 
application from the counter roll onto a paper or cardboard web guided 
over it. 
Further objects and advantages of the invention will be apparent to those 
skilled in the art from the following detailed description, taken in 
conjunction with the drawings and the appended claims.

DETAILED DESCRIPTION OF THE INVENTION 
The application and dosage device of the invention comprises a roll, 
optionally with an external shell, having a diameter which can be varied 
by the application of energy and which, under predetermined controllable 
conditions, has a variable thickness along the length of the roll (or 
external shell) as a function of space and/or time. 
Fundamentally, according to the invention, the amount of a substance 
available can be adapted to the requirements of the particular operation; 
this can depend on the type of material applied (i.e., the coating 
material), on the rate of application (i.e., the velocity of the paper or 
cardboard web), on the amount needed to be applied, on the absorbency of 
the substrate (paper or cardboard, for example), etc. 
FIG. 1a illustrates a rotatable and readily deformable roll shell 1, 
preferably formed of rubber or a similar highly elastic synthetic 
material, inside of which is disposed a substantially cylindrical support 
3, formed of steel, for example, and which preferably also rotates, either 
in the same direction as the roll shell 1 or in the opposite direction. 
The space between the support 3 and the roll shell 1 is subdivided into 
individual chambers 5 by a plurality of ring lands 2. An excess pressure 
or, preferably, reduced pressure can be applied to the chambers 5 with the 
aid of a working fluid (for example, a hydraulic fluid or preferably a 
gas, such as air). For this purpose, the ring lands 2 each have one or, 
preferably, several throughbores 12. The roll shell 1 is deformed in the 
region between the ring lands 2 upon the application of reduced or excess 
pressure, such that the roll shell 1 will assume a wavy surface, as 
indicated in FIG. 3 by the dotted line curve 30. Naturally, the roll shell 
1 must remain tightly fixed against the ring lands 2 during operation, so 
the roll shell 1 is preferably shrink-fitted onto the lands 2. 
The degree of waviness (i.e., the amplitude and wavelength) of the shell 1 
can be increased or decreased by the magnitude of reduced or excess 
pressure, with a wavelength preferably between 0.3 and 1 mm. Of course, 
the spacing between the ring lands 2 must be correspondingly small. 
A similar embodiment is shown in FIG. 1b, in which the introduction of the 
working fluid is done through a hollow cylindrical support 3' with radial 
throughbores 17. Spacer rings 16 are provided for individual ring lands 2' 
in order to form individual pressure chambers 5'. Working fluid is 
introduced through a central pressure chamber 18 with a hollow cylindrical 
support 3'. The individual ring lands 2' are tensioned against one another 
in practice with the aid of the spacers 16, and their spacing is thus 
accurately established. Naturally, the ring lands 2' must also have 
throughbores which must be at least partially contiguous with the 
throughbores 17 of the cylindrical support 3'. In this case, it is 
possible to produce axially varying local pressures in sections by 
pressure chambers assigned to the various axial sections of the support 
3', and thus locally variable waviness can be produced in the roll shell 
1. 
FIG. 3 shows a variation of a roll 1' in which individual annular pressure 
stamps 25 are provided in opposed axial spacing with relation to a hollow 
cylindrical support 23. The pressure stamps each comprise individual ring 
segments 25, 25', 25", etc., as shown in FIG. 4. Ring wheels 26, onto 
which a deformable roll shell 21 is pressed, are disposed between the 
pressure stamps 25. By introducing a working medium through radial bores 
22 in the support 23 to the inside of the stamps (rings) 25, at these 
points the diameter of the roll shell 21 will increase so that the 
wariness shown by the dotted line 30 will be achieved. 
In FIG. 2, individual surface elements 13 protrude from and are guided by 
the radial outside surface of a roll shell 9. The elements 13 comprise 
piezoelements, the lengths of which are variable whereby their radial 
outer, free end surfaces define a wrapper cylinder which has a variable 
diameter. The piezoelements 13 are disposed in individual cylinder 
segments 14 which have assorted electrical wires 36 loading to a source of 
electricity. 
Naturally, the radially outer (front) surfaces of the stamp lie on an 
(imaginary) wrapper cylinder which can also comprise a flexible shell of, 
for example, rubber. 
This variability of the surface of the roll 6 depends on the inverse 
piezoelectric effect, so that upon application of an electrical field 
parallel to the direction of polarization of the piezoelectric crystal of 
the elements 13, expansion of the element 13 in the same direction is 
obtained. The component with the piezoelectric (inverse) effect is also 
called a piezoelectric translator (or briefly, piezotranslator). 
Naturally, by the application of external magnetic electrical fields, the 
length of small stamps made of the appropriate materials can be 
influenced. 
Thus, a roll with an irregular surface is obtained, whereby depressions 
exist between the individual stamps and the coating material which is 
introduced into these depressions. 
The situation is similar to that of the wavy surface of the roll shell 1 or 
21 of FIGS. 1 and 3, respectively, in which the coating material is taken 
up in the valleys of the waves. This form of ductor or dosage element is 
known in the art as wire-wound cylindrical rods or rolls. Such dosage rods 
are also obtained by incorporation of grooves into a rod or cylinder. In 
the case of the devices known in the art, these grooves are very fine and 
have a cross-section between 0.001 and 0.40 mm.sup.2. Correspondingly 
structured heat fields or electromagnetic radiation can also produce a 
corresponding waviness on a mantle surface when the material is chosen 
appropriately. 
FIGS. 5 to 7 show individual coating devices, in which paper webs W are 
coated with pasty or liquid compositions. A transfer gap between a roll 1 
(alternatively 1' or 6) of the invention and a counter roll 31, 41 or 51, 
is always formed. In FIG. 5, the respective directions of rotation of the 
two rolls 1 (1', 6) and 31 can be the same or opposed. In FIG. 6 the 
directions of rotation of the rolls 1 (1', 6) and 41 can be opposed. In 
FIG. 7 the rotation directions of the rolls 1 (1', 6) and 51 are the same. 
The foregoing detailed description is given for clearness of understanding 
only, and no unnecessary limitations should be understood therefrom, as 
modifications within the scope of the invention will be apparent to those 
skilled in the art.