Method of printing a raised pattern of liquid

The invention is directed to a method of printing a pattern on a substrate, the liquid retained within the printing screen is in a first position directly above the point of tangency between the screen and substrate so that a lesser quantity of liquid is deposited to provide raised beads of liquid comparable in size to the size of the apertures of the screen. The reservoir of liquid is shifted away from the point of tangency and therefore a larger quantity of liquid passes through the apertures because the apertures are now spaced from the substrate. The larger quantities of liquid flow together and therefore, a pattern is provided larger than the aperture size of the screen.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention is directed to a method of printing a raised pattern of 
liquid on a non-porous substrate. Depending upon the position of the 
reservoir of liquid within the printer, the pattern printed can be the 
same as the pattern of the printer screen or the resulting pattern may be 
an enlargement of the pattern of the printer screen. 
2. Description of the Prior Art 
U.S. Pat. No. 3,921,521 is directed to a printer with a printing screen and 
reservoir therein used for the purpose of printing a liquid. 
The printer of the patent is normally used to print on a porous substrate 
and the liquid which passes through one aperture of the screen tends to 
blend with material passing through an adjacent aperture. 
SUMMARY OF THE INVENTION 
The invention is directed to a method of printing a raised pattern on a 
substrate. Th substrate has non-porous surface and it receives a pseudo 
plastic thixotropic liquid that provides a raised bead of liquid which is 
in the shape of the aperture of the printer screen. The printer screen is 
placed tangent to the substrate and the reservoir of liquid within the 
screen is positioned at a first position directly above the point of 
tangency. There is printed a plurality of raised beads of liquid on the 
substrate which are substantially the same size as the apertures in the 
screen. 
By shifting the reservoir of liquid within the screen from the first 
position to a point in the direction of screen movement so that the 
reservoir of liquid is offset from the point of tangency, the pattern 
printed will not retain the definition of the apertures of the screen. 
Shifting the reservoir of liquid causes more liquid to pass through each 
aperture and the liquid will laterally flow so that a number of beads of 
liquid flow together to form an enlarged pattern of raised liquid.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
There is disclosed herein a method of printing a raised pattern 2 or 4 on a 
substrate 6. The substrate is provided with a non-porous surface to 
receive a pseudo plastic thixotropic liquid 10 that, at a first quantity 
of deposition, will not have noticeable lateral flow of the liquid and 
will yield a bead of raised liquid that will retain the geometric design 
of the apertures of the print screen. At a second larger quantity of 
deposition, the liquid will have a noticeable lateral flow so that a 
number of beads of raised liquid will flow together to form a different 
larger pattern of liquid 4 due to the shear weight of the extra deposited 
liquid which causes the lateral flow. 
There is first provided a substrate to be printed with the substrate having 
a non-porous surface 8 to receive the printed liquid 10. A printer 16 is 
provided with a circular screen 12 having apertures 14 therein. The 
apertures are of the desired geometric design and size to be printed in 
the pattern of FIG. 2. The screen is placed tangent to and above the 
substrate. Positioned wthin the screen is a source of liquid 20 which 
feeds liquid downward to form a reservoir 22 of liquid. The reservoir is 
retained within a wall structure 21 and 23 which has, at the lower ends 
thereof, blades 24 and 26. The blades are resilient and blade 24 is 
adjustable positioned on the wall 21 and blade 26 is pivoted to wall 23. 
The lower ends of the blades 24 and 26 rub against the inside of the 
screen 12 and there is retained the reservoir of liquid between the two 
blades. 
In FIG. 1, line 18 represents the point of tangency between the screen 12 
and the substrate 6 and it can be seen that the reservoir 22 of liquid 10 
is within the screen and at a first position directly above the point 
where the screen is tangent to the substrate. Movement of the screen 12 
and the substrate 6 will result in the depositing of a first quantity of 
liquid on the substrate and the amount of liquid deposited will yield a 
bead 28 of liquid on the substrate. The bead will retain a geometric 
design and size comparable to that of the aperture in the screen. Th 
rheology of the pseudo plastic thixotropic liquid 10 is controlled so that 
there is no more than 10% to 50% lateral flow of the liquid once it is 
deposited on the substrate. The moving of the substrate and the screen 
together in a continuous manner will deposit a plurality of beads of 
liquid on the substrate while the screen and substrate are in contact. 
Because of the wiping action of the blades 24 and 26, it can be seen that 
the amount of liquid deposited is basically the amount of liquid that can 
be held within an aperture with a thickness for the liquid equal to the 
thickness of the wall of the screen. 
It is possible to move the retained reservoir of liquid within the screen 
from its first position directly above the point where the screen is 
tangent to the substrate, to a second position with the reservoir of 
liquid offset in the direction of screen movement. This is shown by the 
partial views of blade 24' and blade 26' which define the second position 
of the retained liquid offset from the point of tangency which is shown by 
line 18. The moving of the substrate and screen together in a continuous 
manner will deposit a plurality of beads of liquid of a larger quantity of 
liquid than was deposited when the reservoir was in its first position. 
This occurs because the deposition of liquid is occurring partly at the 
time the screen and substrate are not in contact and therefore, the 
quantity of liquid being deposited is greater than the volume of 
apertures. The second larger quantity of liquid is deposited and the 
liquid will have a noticeable lateral flow so that a number of beads of 
liquid flow together to form the pattern of FIG. 3. It can be seen in FIG. 
3 that there is formed a pattern of raised liquid larger than and of a 
different shape from the apertures of the screen. The flow occurs because 
the larger quantity of liquid will have a shear weight which will cause 
lateral flow of the liquid.