Incremental printing of symbolic information – Ink jet – Combined
Patent
1997-01-30
1999-03-16
Le, N.
Incremental printing of symbolic information
Ink jet
Combined
347104, 1014071, G01D 1518
Patent
active
058836438
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a device and a method for printing markings on flat items (also referred to as consignments) wherein the items are conveyed to a print head and during printing are exposed to a vacuum force.
Mechanical printers can be used to cancel stamps, wherein the stamp layout, however, is very limited. Alternatively, it is possible to use non-contacting printing systems, in particular ink jet printers, with which high printing qualities can be achieved and for which a free design of the stamp layout is possible. Of advantage with this system is the lower wear as compared to mechanical systems. Particularly attractive is the use of printing systems that permit a free design of the stamp layout if stamps are to be canceled on one side of a consignment and advertisement is to be printed onto the same side or on the other side. In such a case, the advertisement logos can change from consignment to consignment, so that different clients can be addressed, depending on the point of destination.
In order to achieve a high printing quality, it is necessary with ink jet printers that the consignments are transported past the print heads at a preset distance, e.g. 0.5 mm, and with as little disturbance as possible. It is important here that the consignments are transported at a predetermined speed that is synchronized with the control for the print heads. The problem of a speed difference between the conveying belts and the consignments exists, in particular if the consignments are transported via conveyor belts that are arranged in pairs one above the other, between which the consignments are pulled along frictionally engaged. Such a speed difference is particularly disadvantageous if a uniform marking must be applied to the consignment by different print heads, which are arranged one after another and which print with a time delay.
SUMMARY OF THE INVENTION
It is thus the object of the invention to provide an improved device and a method, with which a safe and quiet transport of the consignments at a preset distance from the print heads is achieved.
This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the apparatus for printing on flat items during conveyance thereof in an item advancing direction include a perforated transport belt having a width, an outer face and an inner face. The outer face is oriented toward a first side of the perforated transport belt and the inner face is oriented toward a second side of the perforated transport belt. A cover belt is superposed on the inner face of the perforated transport belt for holding by friction an item sandwiched between the perforated transport belt and the cover belt. A drive moves the perforated transport belt and the cover belt together in the item advancing direction. A vacuum device extends along the outer face of the perforated transport belt on the first side thereof for pressing the item, sandwiched between and advanced by the perforated transport belt and the cover belt, with a pressing force against the inner face of the cover belt in a direction substantially perpendicular to the item advancing direction. A print head is disposed laterally externally of the width of the perforated transport belt on the first side thereof for printing on the advancing item, and a slide member is in engagement with the outer face of the perforated transport belt and guides the item past the print head.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an example of a print placed with the correct time delay and a print not placed with the correct time delay by two print heads that print with a time delay;
FIG. 2 is a view from above of a device according to the invention;
FIG. 3 is a view from the side of a device according to the invention;
FIG. 4 is a detailed illustration of the opening time for a thick consignment;
FIG. 5 is an embodiment of a vacuum pressure adjustment device for maintaining a constant normal force on the consignment.
REFERENCES:
patent: 4207579 (1980-06-01), Gamblin et al.
patent: 4447817 (1984-05-01), Naramore
patent: 5094554 (1992-03-01), Hurd et al.
Martin Uwe
Mok Josef
Kelemen Gabor J.
Le N.
Licentia Patent-Verwaltungs-GmbH
Vo Anh T. N.
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