Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Patent
1992-06-05
1995-08-29
Smith, Matthew S.
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
347 84, B41J 2175
Patent
active
054464862
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a liquid-jet printer device for recording information on an information carrier in the form of characters or symbols and including a print head in which a plurality of liquid channels are arranged to discharge a series of liquid jets or liquid droplets according to a predetermined pattern during predetermined printing periods, whereby the liquid channels in the print head present outlet openings for discharge of the print liquid under pressure and within which valve parts are arranged, switchable for opening and closing respectively of the liquid channels, and inlet ends for connection of the liquid channels to a supply conduit for supply of print liquid by means of a pump arrangement under pressure from a liquid container.
BACKGROUND OF THE INVENTION
In liquid-jet printers, more particularly matrix printers for large printing with individually printed characters or symbols which, depending on a control unit, are continually changed, very high demands are made on the grouping of those valves which are located in each individual channel and which switch between open and closed positions in order to eject those liquid droplets under pressure which, according to a pattern determined by the control unit, are ejected onto an object which, for instance, moves past the print head. With unsatisfactory grouping of the valves, a risk of leakage arises such that the print liquid collects in the outlet openings of the print head also during periods between each print moment, for example, during changing from one object to another. Thus there is a risk that the print liquid thickens and dries due to its exposure to air, with the subsequent risk of blocking the outlet openings in the print head.
The above problem can be partially solved by manufacturing the valves with high quality seals, though in practice a certain amount of wear nevertheless occurs and thus periods of reduced sealing and risk of leakage arise. Even with high quality seals, a small quantity of print liquid remains in the outlet openings, with the risk of blockage if the intervals between the print moments are too long.
SUMMARY OF THE INVENTION
The object of the present invention is to eliminate the above-mentioned problems and to provide a liquid-jet printer device with which a high degree of operational reliability is achieved.
The said object is achieved according to the present invention by a device of the aforementioned type which comprises means for maintaining an operating pressure in the supply conduit only during said printing periods during which printing occurs, and for pressure relief to atmospheric pressure or sub-atmospheric pressure during idle periods between the print moments, and means to achieve a small return flow of print liquid during said idle periods so that the outlet openings are substantially emptied of said liquid.
Preferred embodiments of the present invention are detailed in the dependent claims.
The invention will be described in more detail in the following, by way of example only, with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a first embodiment of a liquid-jet printer device according to the invention;
FIG. 2 shows a second embodiment of a liquid-jet printer device according to the invention, and
FIG. 3 shows a third embodiment of a liquid-jet printer device according to the present invention.
DETAILED DESCRIPTION
A liquid-jet printer device according to the invention is shown in FIG. 1 and consists of an ink-jet printer with a print head 1, a liquid container 2 for ink and a supply conduit 3 for the delivery of ink from the liquid container 2 to the print head 1. The liquid delivery is ensured by a liquid pump 4 arranged in the supply conduit 3 since the liquid container 2 is positioned at a level below the level of the print head. Additionally, a bypass conduit 5 is arranged around the pump 4 with an adjustable throttle valve 6 which assures a reduced return flow of ink to the liquid container which shall be describ
REFERENCES:
patent: 4152710 (1979-05-01), Matsuba et al.
patent: 4207582 (1980-06-01), Yamamoto
patent: 4337469 (1982-06-01), Takano et al.
patent: 4555719 (1985-11-01), Arway et al.
patent: 5220345 (1993-06-01), Hirosawa
IBM Technical Disclosure Bulletin, vol. 22, No. 10, Mar. 1980, "Start/Stop Valve for Ink Jet Printer," by K. R. Primmer.
IBM Technical Disclosure Bulletin, vol. 18, No. 10, Mar. 1976, "Ink Jet Head," by R. E. Pelkie, N. C. Smith and R. E. Tomek.
PCT International Search Report, 90/02125, Apr. 2, 1991.
Markpoint System AB
Smith Matthew S.
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