Stencil squeegee device

A squeegee device destined to be used in a movable stencil, comprises a support structure for a squeegee element which, in operation, is held slightly curved under some pressure in contact with the stencil, a closure strip being mounted upstream of the squeegee element and also being in contact with the stencil, so forming an adjustable gap being sealed at both ends, means being provided for the supply of pressurized viscous substance to said gap.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a squeegee device for pressing a viscous 
substance through the perforations in a movable stencil on to an advancing 
substrate, the device being provided with a support structure for a 
squeegee element, a supply for the substrate, and a biasing member whereby 
the squeegee element is held in contact with the stencil. 
2. Discussion of the Prior Art 
A squeegee device of this kind has been used in the art and is known from 
European Patent Application Publication No. 0,011,314, see FIGS. 10 and 
11. The viscous substance to be used with this device may consist of a 
printing paste or thickened liquid (ink). In the known device, the 
squeegee element includes an acute angle with the stencil, such angle 
mostly being the main factor determining the ink application. In the known 
device, some attempt is made to render the adjustment of the angle between 
the squeegee element and the stencil independent of the force with which 
the squeegee element is held in contact with the stencil. This force 
particularly influences the so-called penetration, this being important 
particularly in the printing of fabrics. In the above-mentioned known 
device, a quantity of substance is present in the wedge angle between the 
squeegee element and the stencil. A dynamic pressure occurs in this 
substance or so-called ink roll and is the main cause for the substance 
being pressed through the stencil perforations. The substance is usually 
supplied via a metering pipe disposed in the support structure, the 
substance flowing from said pipe in an open system toward the wedge-shaped 
space with possible deviations in uniformity of the substance applied, 
particularly if the squeegee element is very long. 
SUMMARY OF THE INVENTION 
It is a primary object of the present invention to provide a squeegee 
device whereby the application of the substance to the substrate can be 
controlled as required within close limits without influencing the degree 
of penetration, another object being to obtain maximum uniformity of the 
substance applied to the substrate, both in the direction of the width and 
in the direction of the length of the substrate. 
In the squeegee device according to the invention, these objects are 
realized by the use of a closure strip borne by the support structure and 
having its front edge also held in contact with the stencil in a zone 
which, as considered in the direction of advance, is situated some 
distance upstream of the squeegee element so that a passage gap is formed 
between the strip and those edges of the squeegee element which are in 
contact with the stencil, means also being provided for the pressurised 
supply of the viscous substance and for laterally sealing off the ends of 
the gap. 
As a result of these features a specific static pressure of the substance 
is created in the space between the squeegee element and the closure 
strip. This pressure will urge the strip against the stencil with a force 
proportional to this pressure. As a result a good seal is obtained along 
the one side of the gap. The same static pressure and also some dynamic 
pressure is exerted on the squeegee element in a direction away from the 
stencil. This force can be accurately controlled by means of the biasing 
member. In this way great freedom is obtained in respect of controlling 
the application of the substance, particularly in the case of a foam 
material. 
In a favorable embodiment of the squeegee device according to the present 
invention, the closure strip is mounted displaceably in the support 
structure so that the width of the gap is adjustable. By increasing this 
width it is possible to obtain better utilization of the absorptive power 
of the substrate. The optimum relationship between the amount of substance 
and the "definition" (i.e. the sharpness (clearness) of the printed 
design) are also governed by the gap width. 
According to another embodiment of the present invention, the squeegee 
element consists of a prismatic plastic bar, preferably of polyethylene, 
which, on the one hand, is borne by an L-shaped gusset and which, on the 
other hand, is subject to the direct action of the biasing member. This 
bar, which offers little resistance to the stencil traveling therealong, 
takes over the task of the conventional doctor so that the squeegee device 
can be adapted to the substance being used by means of a predetermined 
cross-sectional shape. 
According to still another embodiment of the present invention, the closure 
strip consists of spring strip steel and said strip rests on a metal part 
of the supporting structure, which part extends close to the front edge of 
the strip. Alternatively, the strip may be made from a plastic, since the 
static pressure of the substrate in the gap is largely absorbed by the 
metal part of the support structure. It is also possible to use a plastic 
sheet of little rigidity without the risk of any bulging under the 
influence of the static pressure. 
The present invention also related to a method of applying a viscous 
substance to an advancing substrate by means of a stencil, using a 
squeegee device as described hereinbefore. In this method at least one 
pump is used to supply the substance ready for use, the output of the pump 
or pumps being kept in direct proportion to the speed of advance of the 
substrate while the requisite quantity of the substance applied is 
determined by controlling the force of the biasing member and by adjusting 
the width of the passage gap. Preferably, the drive for the viscous 
substance feed pump or pumps is coupled to the substrate advancing means. 
It is then possible to keep the supply of substance per unit area of the 
substrate constant irrespective of the printing speed and the properties 
of the substrate. 
According to an embodiment of this method, the viscous substance is 
supplied in a foamed condition from a mixer connected both to a substance 
supply pump and to a metered gas supply. This latter is particularly 
important when a foam material has to be applied, the quality of which 
rapidly declines after it has been prepared. Another advantage of this is 
that it is not necessary to make up stocks of the foam material and when 
the method is concluded there is very little unused material lost. 
The features of the present invention which are believed to be novel are 
set forth with particularity in the appended claims. 
Other claims and many of the attendant advantages will be more readily 
appreciated as the same becomes better understood by reference to the 
following detailed description and considered in connection with the 
accompanying drawings in which like reference symbols designate like parts 
throughout the figures.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIG. 1, the squeegee device consists of a supporting 
structure 1 in the form of a box-shaped housing provided with a pipe 2 in 
the middle for the supply of the substance, e.g. an ink paste or a foam 
substance. Near the bottom, the supporting structure 1 is provided with a 
squeegee element 3 secured in a mounting 5 of the support structure by 
means of an inflatable clamping hose 4. The squeegee element 3 consists of 
a metal sheet 6, e.g. of spring steel, the free edge of which is provided 
with a prismatic plastic bar 7. In this figure bar 7 is of square section 
and rests by a rib against the inside of a cylindrical stencil 8. A bag 9 
in the form of a hose is also clamped in the mounting 5 and is filled with 
a fluid, the pressure of which can be increased or reduced. Bag 9 forms a 
biasing member for the squeegee element 3 and rests against a part of the 
support structure 1 at the top and against the sheet 6 and bar 7 at the 
bottom. So far the device described is substantially the same as the 
aforementioned publication EU No. 0,011,314. 
The stencil 8 is in contact with a substrate 10 consisting mainly of a web 
of textile or plastic. The squeegee element 3 includes an angle .alpha. 
with the substrate. A closure strip 11 is formed by a band 12, e.g. of 
spring strip steel and a metal part 13 disposed at some distance from the 
squeegee element. Part 13 is secured on an additional extension 14 of the 
housing-shaped support structure 1. The front edge 15 of the closure atrip 
11, i.e. the metal band 12, is in contact with the stencil 8 in a zone 
which, as considered in the direction of advance , is situated at some 
distance upstream of the squeegee element 3. A passage gap 16 is thus 
formed between the strip and those edges of the squeegee element which are 
in contact with the stencil 8. 
Near its underside, the pipe 2 comprises a number of holes 17 for the 
passage of the viscous substance supplied inside the pipe 2. This supply 
is effected at some pressure so that the space 18 is filled with the 
substance. Space 18 is bounded by the pipe 2, the extension 14, the 
mounting 5, the squeegee element 3, the closure strip 11 and the stencil 
8. The width of the gap 16 is indicated by S. 
Referring now to FIG. 2 during the operation of the squeegee device, there 
is a certain pressure build-up in the viscous substance at the gap 16. 
This pressure build-up consists of a dynamic pressure component as a 
result of the wedge effect between the squeegee element 3 and the 
traveling stencil 8. This component of the pressure increases over the 
width S of the gap 16, see the top of the figure. As a result of the fact 
that the substance is supplied with some excess pressure via the pipe 2, 
there is a static pressure component denoted in the middle part of the 
figure. The total pressure is the sum thereof and is indicated in the 
bottom part of the figure. This pressure provides good sealing at the edge 
15 of the metal band 12, while the biasing member 9 ensures that the bar 7 
presses against the inside of the stencil 8 with the required force. The 
substance will now be pressed on to the substrate 10 through the 
perforations in the stencil 8. 
Referring now to FIGS. 3A-C three variants of the squeegee element 3, each 
consist of a sheet 6 and a prismatic bar 7. Variant A is substantially the 
same as the squeegee element shown in FIG. 1. Variant B allows a larger 
angle .alpha. despite the slight inclination of the sheet 6. Variant C 
prevents dynamic pressure from forming as a result of the side of the 
plastic prism situated perpendicularly to the stencil (no wedge angle). In 
this way application control is possible solely by the static pressure of 
the pump or a pressure vessel. 
Referring now to FIG. 4 an embodiment is shown in which the closure strip 
11 is mounted displaceably in the support structure 1. To this end, an 
actuating lever 19 having a pivot 20 is provided. at one or both ends of 
the support structure. The width S of the gap 16 can thus be adjusted. 
In the variant shown in the latter figure and in FIG. 5, the squeegee 
element 3 consists of a prismatic plasiic bar 7, which is preferably made 
from polyethylene. This bar is carried by an L-shaped gusset 21. In this 
way it is a simple matter to adjust the height of the bar 7 with respect 
to the support structure 1, and hence the position with respect to the 
closure strip 11. The biasing member 9 acts directly on the bar 7, said 
member bearing at the top against an angle section 22 provided for the 
purpose. FIG. 5 also shows an embodiment with a plastic band 12. 
Referring now to FIG. 6 in a variant the substrate 10 moves vertically 
upwards instead of horizontally. Otherwise there are no basic differences 
from the variant of FIG. 1, except for structural details. Substrate 10 is 
supported at the gap 16 by a conventional roller 23. 
Referring now to FIG. 7A a diagram shows the installation of the squeegee 
device in a stencil with the means for the pressurised supply of the 
viscous substance and for lateral sealing of the ends of the gap 16. The 
viscous substance is contained in a tank 24, said substance being fed to a 
vessel 26 by means of a pump 25. A (conventional) pressure control system 
27 is provided on this vessel, while a level sensor 28 is provided to 
switch the motor 29 of pump 25 on and off. A hose 30 connects the interior 
of vessel 26 to the pipe 2 of the squeegee device. Pipe 2 is sealed at the 
left-hand end in the figure. The two ends of the space 18 are closed to 
prevent a pressure loss in the viscous substance. The two ends of the gap 
16 are sealed off by means of plate-like elements 31 of cellular rubber, 
having a closed cellular structure. 
Referring now to FIG. 7B a top plan view is shown of the device just 
described. 
Referring now to FIG. 8 in an installation the motor 29 of the feed pump 25 
for the viscous substance ia coupled via a controller 32 to a tachometer 
33 of the substrate 10. 
Referring now to FIG. 9 in an extension of the installation of FIG. 8, the 
viscous substance to be supplied consists of a material which is prepared 
in situ. To this end, the hose 30 coupled to the pipe 2 is connected to an 
emulsifier 34 driven by a motor 35. Connected to the emulsifier 34, on the 
one hand, is a conduit 36 by means of which the substance is supplied from 
the tank 24 and, on the other hand, a metered gas supply via the conduit 
37. The latter also contains a flowmeter 38 and a control valve 39. 
A number of printing tests were carried out with the squeegee device 
according to the present invention, using the following substances: 
(a) normally used printing concentrations with pigment and reactive 
dispersed etc. dye systems in non-foamed form; 
(b) formulations identical to coating formulations aa per e; 
(c) mechanically foamed formulations with a binder system for pigments. 
______________________________________ 
Formulation: 
______________________________________ 
emulsifier w bayer 
10 gr 
acrafix uc 100 gr 
acramin 3187 n 200 gr 
acramin clw 100 gr 
acraconc c 15 gr (+10) 
nekanil ln basf 10 gr 
pigment 100 gr 
water 465 gr 
1000 gr 
______________________________________ 
A number of coating tests were also carried out with the following 
substances: 
(d) mechanically foamed ink formulations; 
______________________________________ 
example: ink formulations for reactive dye: 
______________________________________ 
cold water 18950 gr 
urea 7500 gr 
sodium bicarbonate 
1750 gr 
ludigol 750 gr 
cibacron violet f 2 ra 
750 gr 
nekalin ln 300 gr 
40000 gr 
______________________________________ 
(e) mechanically foamed acrylate dispersions and PVC plastisols; 
EXAMPLE 
Three methods can be used for the preparation of mechanically whipped PVC 
foam: 
a. A formulation in which a PVC type is used which already contains a foam 
stabiliser, e.g. vestolit b 7022 made by Huels. 
b. A formulation using a metal soap as a foam stabiliser. 
c. A formulation in which a silicon product is used as foam stabiliser. 
______________________________________ 
a. vestolit b 7022 100 gr 
dioctylphthalate 30 gr 
benzyl buryphthalate 40 gr 
filler (e.g. calcium carbonate) 
50 gr 
b. vestolit 7021 100 gr 
santiciser 160 (plasticiser) 
40 gr 
dioctylphthalate 25 gr 
(+) metal soap (k.l.o.p.) 5 gr 
filler (e.g. calcium carbonate) 
50 gr 
(+) barium calcium zinc complex. 
c. vestolit b 7021 100 gr 
dioctylphthalate 30 gr 
benzyl butylphthalate 40 gr 
filler (e.g. calcium carbonate) 
50 gr 
wacker foam stabiliser up 2242 
3 gr 
barium cadmium stabiliser 
2 gr 
foam density about 500 g/liter 
100 gr 
gelation temperature about 170.degree. C. 
Rohm and Haas acrylate foam formulation 
primax 200 (acrylate dispersion) 
primax 110 7.5 gr 
(foaming agent + stabiliser) 
titanium dioxide (50%) 10 gr 
foam density about 200 g/liter 
______________________________________ 
(+) alternatively usable 
(f) mechanically foamed formulations used for applying various finishing 
products to textiles; 
The following substances were used: 
1. Crease removal for, e.g., 100% cotton, PE cotton and other natural 
fibers or mixtures of synthetic and natural fibers. 
______________________________________ 
a. synthetic resin 
200-400 gr/l 
b. catalyst 50-150 gr/l 
c. plasticiser(s) 
60-120 gr/l 
d. foaming agent 
5-10 gr/l 
e. additives 0-10 l 
______________________________________ 
a. Synthetic resin p A distinction is made here between the 
self-reticulating types and the reactant types. The latter react with the 
hydroxyl groups of the fiber only under the influence of a catalyst e.g. 
1. Self-reticulating types: dimethylol urea 
2. Reactant types: dimethylol-dihydroxy-ethylene-urea (most frequently 
used). 
Some commercial names: 
a-1. kaurit's basf 
a-2. 
fixpret cpn basf 
sancowad k resin 7901 sandoz 
knittex gm conc ciba-geigy. 
b. Catalyst 
The catalysts most used are metal salts, e.g. zinc nitrate, zinc chloride 
and magnesium chloride. Ammonium salts are used particularly for 
cellulose-containing substrates e.g. 
ammonium nitrate 
ammonium chloride 
ammonium sulphate. 
Complex catalysts are used mainly in the sdc process (=shock drying 
condensation process) e.g. condensol sk basf. 
c. Plasticiser(s) 
The standard plasticisers used in finishing can also be used here. 
The only restriction is that the plasticiser must not give the resulting 
foam excessive stability. Silicon-based plasticisers (particularly in high 
concentrations) may act as anti-foaming agents. 
The following can be used for example: 
sancowad k 7906 sandoz 
sancowad k 7911 sandoz 
basosoft on basf 
avivan splciba geigy 
avivan ra ciba geigy 
d. Foaming agent 
Nonyl phenols containing 5-10 mol ethylene oxide or sulphonates of higher 
alcohols are used for example e.g. 
nekanil ln basf 
laviron waz (spec) henkel 
sancowad an sandoz 
sancowad n 1 sandoz 
irgapadol 4232 ciba geigy. 
e. Additives 
Some of the most important are the following for example: 
1. Chemicals for improving tearing strength e.g. 
perapret hvn basf 
siligene base 
2. Chemicals to allow making (working) up in the clothing industry. These 
are generally: Polyethylene dispersions e.g. 
perapret pe 40 basf 
sancowad k7903 sandoz 
3. Foam stabilisers or laminate stabilisers synthetic thickeners (e.g. 
hydroxyethyl cellulose) Used: 
natrosol 250 hhr 
tylose h 4000 
irgapadol 4187 
komperlan kd 
4. Optical brighteners e.g. 
blankopher bru bayer 
uvitex 2 bt-130% ciba-geigy 
uvitex ernp 250% ciba-geigy 
leukophor bcr sandoz 
leukophor ehb sandoz 
2. Waterproofing 
In principle it is possible to use formulation 1. The choice of synthetic 
resin catalyst and the like is adjusted according to the waterproofing 
agent. 
Synthetic resin: knittex fa conc. ciba geigy 
Waterproofing agent: 
phoboton ws conc ciba geigy 
phoboton bc ciba geigy 
During the test program using the above tests it was found that the new 
squeegee device can generate an optimum and uniform dynamic pressure at 
the gap 16. It was also found that with many substances most of the 
application control can be achieved by simply the static pressure in the 
substance. It is then possible to use a squeegee element according to 
FIGS. 3B, 4 and 5. The facility shown in FIG. 4 for controlling the width 
S of the gap 16 can also be used as a factor for the application control 
of the substance. 
The tests carried out with substances consisting of the normal printing 
pastes show the great flexibility in respect of application control. The 
supply of the printing paste to the squeegee is carried out as shown in 
FIGS. 7 and 8. The controller 32 used in FIG. 8 enables adjustment of the 
required volume of substance per linear metre of substrate. 
The tests using foamed substances also gave good results. For working up 
foam it is desirable to keep the time between the foam production and 
application as short as possible. This is all the more important the lower 
the stabilisation of the foam. The phenomena occurring in such conditions 
are a change of foam structure and moisture secretion. The result will 
then be uneven foam production. In the installation of FIG. 9, the 
emulsifier or foam mixer 34 is coupled on-line to pipe 2 and the foam 
residence time is restricted to a minimum. The contents of the squeegse 
system are also kept to a minimum. In this way it is possible successfully 
to use very unstable foam systems. 
As a result of the construction of the squeegee device, the foam does not 
come into contact with the shearing forces of the advancing stencil 8 
until it reaches the gap 16. This is very important to keep the foam 
quality as constant as possible. It has also been found that the stencil, 
which forms a perforate partition between the substance and the substrate, 
ensures that the application becomes virtually independent of the 
hydrophilic properties of the substrate. 
The use of special fine-mesh rotation stencils 8 having a large passage 
percentage gives virtually no loading on the foam. 
It should be noted that in a squeegee system as described, for example, in 
the publication EU No. 0,011,314 the use of foam entails a residence time 
under difficult shearing conditions, the residence time being so long and 
uncontrolled that it is impossible to achieve a good printing result 
unless extremely stable foam substances are used. However, these give rise 
to problems elsewhere in the process because such foam materials are 
difficult to destroy and therefore are not absorbed sufficiently quickly 
by the substrate. 
When viscous substances in the form of foam materials are used, it is 
desirable for the foam production to proceed continuously without any 
interruptions therefore. Under those conditions it is impossible to obtain 
an on/off control using level sensors. The installation of FIG. 7 is 
therefore suitable only for normal printing pastes. The variant shown in 
FIG. 8 illustrates an installation which ensures uninterrupted coupling to 
the advancing substrate. This control can be extended as shown in FIG. 9, 
in which the amount of gas supplied, i.e. the so-called blow ratio, is 
kept constant. For very accurate control, flow measurement should also be 
carried out on both the gas and the substance via the elements 38.