Tampon printing process

A tampon printing process which uses a printing plate having at least one printing form at its surface, wherein the printing form is filled with printing medium at time intervals and the printing medium is subsequently transferred from the printing form onto a support by means of a tampon.

The present invention relates to a tampon printing process which uses a 
printing plate having at least one printing form at its surface. The 
printing form is filled with printing medium at time intervals, and the 
printing medium is transferred from the printing form to a support by 
means of a tampon. 
BACKGROUND OF THE INVENTION 
Tampon printing processes as a special kind of rotogravure process have 
been known for some time. The image to be printed is sunk, etched or 
engraved as negative in the printing form of a printing plate. The 
negative in the printing plate may also be created by means of 
electroerosion. A transfer body, the so-called tampon, usually based on 
silicone rubber, takes up the printing medium left in the grooves or holes 
of the printing form after wiping off and transfers the print image onto 
the support or object to be inscribed or decorated. Such a tampon printing 
device is described, for example, in DE-OS 19 39 437. 
However, the known technique of tampon printing has some drawbacks which 
mainly relate to the precise metering of printing medium into the printing 
form, e.g., by means of a metering pot located at the top. Lately however, 
this exactness has gained in importance since, according to DE-OS 37 27 
232, the tampon printing process is used for dosing medicinal agents. 
The following deficiencies were discovered: 
subsequent dripping from the metering pot, which is used to apply the 
metering medium, during its motion relative to the printing form, 
undesired temperature changes of the printing medium during the relative 
motion between metering pot and metering form or printing plate, 
respectively, 
undesired inclusion of air on contact of the empty printing form with the 
metering pot, and 
delays caused by the relative motion of the metering pot to the printing 
plate. 
DESCRIPTION OF THE INVENTION 
It is the object of the present invention to overcome the above 
disadvantages, technical limits and difficulties by improving the previous 
tampon printing processes and to provide a tampon printing process which 
allows high accuracy, in particular when medicinal agents are metered, and 
an increased production rate at high precision. 
To solve this problem the present invention proposes in a tampon printing 
process of the present kind, to fill the printing form with a printing 
medium from the bottom by means of feed channels connecting the printing 
form with a printing medium storage unit and passing the printing plate 
from below. 
As a result the printing medium advantageously flows through the feed 
channels, which pass the printing plate from below, and directly flows 
into the bottom of the printing form. To this end, the channels are 
distributed over the bottom area of the printing form at an adequate 
number of places the channels and are shaped in a geometrically suitable 
manner, whereby round, square, slot or sieve-like openings ensure an even 
distribution of printing medium on the bottom of the printing form. The 
filling is controlled by an intermittent pressure acting on the printing 
medium, whereby the dosage of the amount of printing medium to be supplied 
into the printing form is controlled by the duration of the feed pressure 
and/or the intensity of the feed pressure. 
Another possibility is to transport the printing medium into the printing 
form by means of a volumetric metering device, such as a piston pump or 
hose pump. The advantage of this alternative is the fact that filling the 
printing form is independent of the viscosity of the printing medium to a 
large extent. 
Prior to entering the feeding channels the printing medium is 
advantageously passed through a collecting chamber to even out the 
pressure and is then supplied from this chamber into the individual feed 
channels. In this connection it may be useful to form the individual 
channels with different flow areas and/or extensions in order to create 
different flow resistances on passage of the printing medium through the 
individual channels. In addition, the new tampon printing process allows 
the printing form to be filled with printing medium at temperatures other 
than room temperature, preferably at elevated temperatures. The 
temperature level desired for the filling process may be adjusted by means 
of heating elements located in the printing form and/or in the preceding 
chamber. This may, for example, be caused by the necessity to influence 
the viscosity of the printing medium. 
A very advantageous tampon printing process, wherein the printing form is 
filled with printing medium at repeated time intervals within a sequence 
of working cycles, results according to the present invention by the fact 
that the support is led over the printing form in the form of a tape 
intermittently under tension and at a small distance. During each filling 
phase of the printing form, the tape is conveyed by one grid distance and 
stopped for one printing being pressed against the printing form by means 
of a tampon; then the tampon is lifted and the tape lifted off the 
printing form and conveyed by one grid distance. During this procedure the 
printing form is filled with printing medium from below for the subsequent 
operating cycle. In this manner the tampon is kept free from printing 
medium and clean so that smudged print images are completely avoided. In 
this tampon printing process the whole motion travel relates to the 
transport of the supporting web and to a straight upstroke and downstroke 
of the tampon, as well as to the supply of printing medium from the 
bottom, which may be effected, for example, by a displacer similar to that 
of a fuel injection pump. An air jet may, for example, be used to lift off 
the tape from the print image, simultaneously to the lifting of the tampon 
.

FIG. 1 shows a printing form 1 which is incorporated in a printing plate 2; 
the feed channels 9 ending in the bottom of the printing form 1 are 
connected with a collecting chamber 7. The collecting chamber 7 serves to 
even out the feed pressure for the printing medium which is transported 
under pressure from a printing medium storage tank (not shown) through the 
feeding conduct 15. It can be seen that the printing form 1 is filled with 
printing medium from the bottom with great advantage by supplying the 
printing medium from below from the pipe 15 via the collecting chamber 7 
and through the variety of channels 9. The channels 9 pass through the 
printing plate 2. 
FIG. 2 illustrates another embodiment of the feeding channels 9 having 
branches 10, a collecting chamber 7 and opening regions 14 in the bottom 
of the printing form 1. The channels 9 may, for example, be tubes of a 
small diameter suitably ending as a screen plate 4, whereby the printing 
medium is evenly distributed over the area of the printing form through 
the multitude of pores 4; this is shown in FIG. 4 in plan view. 
The plan view on a part of the printing plate 2 with a printing form 1 
(FIG. 3) shows a variety of openings 5 of individual channels 9 which are 
geometrically distributed over the area of printing form 1 in the bottom 
or in the end region of channels 9 in the bottom of the printing form 1. 
FIG. 5 shows a cross section through a part of a printing plate 2 with a 
bottom of printing form 1 provided with passages. The printing form 1 can 
be filled with printing medium from below via a collecting chamber 7. The 
attachment 16 forming the collecting chamber 7 is connected to the 
printing plate 2 by means of a seal 11 and threaded joints 17. The 
printing plate 2 is provided with heating elements 12 and 13 by means of 
which the printing plate may be heat-regulated. 
Wiping-off which is necessary when the printing form is filled from the top 
and the disadvantages relating thereto are advantageously avoided by the 
process according to the present invention. 
Metering the printing medium--in particular if an active 
substance-containing medium is concerned--can be effected with the highest 
possible precision; in addition, due to significantly shorter cycle times, 
a considerable increase of productivity resulting in a reduction of 
production costs can be achieved. Until today it has not been possible to 
achieve short cycle times--as are feasible now by the present 
invention--because of the required mechanical operating motion of the 
parts of the device. 
The process can be used with advantage in transfer operations by which 
flowable media are to be transferred to a substrate used as support by 
means of a phased and defined dosage from a storage vessel. 
A very convenient printing process possible by means of the present 
invention is represented in FIG. 6 as purely schematic flowsheet. A 
support 20 is printed with a medium which is supplied into the printing 
form 1 of the printing plate 2 from a storage vessel (not shown) by means 
of a geometrical pressure feeding device (not shown) through the supply 
pipe 15 via the collecting chamber 7 in the manner shown in FIGS. 1 to 5. 
The support 20 in the form of a tape is unwound from a supply reel 21 
under tension, intermittently passed over the printing form 1 at a small 
distance and transported by one grid distance during each filling phase of 
the printing form 1. Below the tampon 22, which is lifted during 
conveyance, the tape 20 is stopped for one printing operation and pressed 
against the printing form by the tampon 22. In this manner the print image 
is transferred or printed from the printing form 1 to the support 20. 
Immediately after that, the tampon 22 is lifted and the web taken off the 
printing form 1 and conveyed by one grid distance. In the course of this 
procedure the printing form 1 is filled with printing medium from below 
for the next printing operation. Lifting-off the printed tape 20 from the 
printing form 1 may, for example, be effected by means of nozzles 23. 
Now, the underside of the stretched tape is provided with printed images 24 
which have to be dried. For this purpose, a drying station 25 may be 
located at a distance from the printing station. Here the new print image 
is dried by known means, e.g. in a hot-air-tunnel. Subsequently, the 
printed support can be wound onto a take-up reel 26. Instead of the 
take-up unit, finishing devices may be provided. 
It is understood that the present invention shall not be limited to the 
embodiments demonstrated in the examples. For example, the devices may be 
formed for the use in multiple printing, printing forms may be formed by 
etching, engraving, electroerosion, and the feeding channels in the bottom 
of a printing form 1 may be arranged in any desired distribution. The new 
printing process according to the present invention offers new and 
economical ways for an accurate dosage, in particular of medicinal agents, 
using extremely economical means and operating methods. In this respect 
the present invention represents an optimum solution of the object given 
in the beginning of this description.