Circuit for feeding ink to an ink-jet printing head

Recorders – Record receiver deforming

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Details

137 92, 346140R, G01D 1518, G01D 1800

Patent

active

046283293

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a circuit for feeding ink to an ink-jet printing head. It is also concerned with any printer which is equipped with said circuit.
A number of problems arise in the ink-jet printing technique and the chief problems are recalled below. In the first place, the orifice employed for the formation of the jet is of small size (of the order of 75 microns) and there is a possibility that it may be choked by a dust particle. It is important in this case to have a rapid means for clearing this orifice.
Furthermore, the printing qualities of a printer of this type are intimately related to the rate of discharge of ink through the orifice. The rate of discharge is liable to be modified as a result of variation in pressure of the ink upstream of the orifice and also as a result of a variation in viscosity of the ink. This latter may arise from evaporation loss of the ink solvent which is often highly volatile.
The precise aim of the present invention is to solve all these problems and relates to a circuit for feeding ink to a printer which is of simple constructional design, provides very flexible operation and makes it possible with a minimum number of components (two pumps and four electrovalves) to obtain in particular a control of pressure and viscosity of the ink.
The invention is more precisely concerned with a circuit for feeding ink to an ink-jet printing head, of the type comprising an ink reservoir, the bottom wall of which has a first outlet connected to a pipe for supplying ink to a pressurizing pump which feeds the body of the printing head via a feed pipe 20; an inlet connected to a delivery pipe which conveys the unused ink withdrawn at the level of a recovery trough and aspirated by means of a depressurizing pump; and a second outlet connected to a wetting pipe joined to the depressurizing pump; the feed circuit being characterized in that it additionally comprises a first auxiliary circuit mounted between the ink supply pipe and the feed pipe and capable of measuring the pressure existing within the feed pipe.
The invention is also concerned with an ink feed circuit which is also equipped with a second auxiliary circuit comprising a combination of electrovalves which are capable of carrying out the clearing of the inkdrop discharge orifice and producing a positive interruption of the ink jet.
It is also concerned with an ink feed circuit equipped with a third auxiliary circuit comprising means for measuring the viscosity of the ink.
It is finally concerned with a circuit of this type equipped with means for treatment of solvent vapors before discharging them into the ambient atmosphere.
A better understanding of the invention will be gained by means of the following explanations and accompanying figures, wherein:
FIG. 1 is a schematic illustration of one example of construction of an ink feed circuit for supplying ink to a printing head in accordance with the invention;
FIG. 2 is a schematic illustration of one example of construction of a device which is capable of measuring the viscosity of the ink and cooperates with the pressurization circuit of FIG. 1.
For the sake of enhanced clarity, the same elements are designated by the same references in all the figures.
FIG. 1 therefore illustrates schematically a circuit for feeding ink to an ink-jet printing head 10. A circuit of this type essentially comprises an ink pressurization circuit and a depressurization circuit for sucking unused ink drops 100 at the level of the recovery trough 11.
The ink is stored in a sealed reservoir 1 which, in accordance with the invention, comprises an internal partition 22 placed parallel to the side walls of the reservoir, therefore at right angles to the bottom wall (ab) of this latter.
The ink level 38 which is always lower than the height 37 of the internal partition 22 falls progressively from this level to the bottom of the reservoir. The bottom level 21 of the ink is detected by means of a sensor 42. This ink is conveyed by means of a feed pipe 18 which passes through the bottom wall (ab)

REFERENCES:
patent: 3835881 (1974-09-01), Dal
patent: 4067020 (1978-01-01), Arway
patent: 4130126 (1978-12-01), Chocholaty
patent: 4314264 (1982-02-01), Box
patent: 4337468 (1982-06-01), Mizuno
patent: 4346388 (1980-06-01), Wiley
patent: 4403227 (1983-09-01), Bertschy
patent: 4422085 (1983-12-01), Sumitomo

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