Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-06-18
2001-02-06
Le, N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S030000, C347S031000
Reexamination Certificate
active
06183059
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a device for cleaning an ink jet print head, particularly in a postage meter and/or addressing machine.
Prior art postage meter and/or addressing machines on the market print primarily with ink rollers or thermal print heads.
Recently effort has been directed to exploiting the advantages of ink jet printing to the field of applying postage and/or addressing mail by machine. The printing operation is thereby contact-less by means of ink jet print heads. Reference is had, in this context, to German Patent DE 44 24 771 C1 and to German Utility Model DE 94 20 734 U1.
A postage meter has been proposed in German Patent DE 196 05 014 C1 in which the letters are conveyed upright, tilting slightly backward, with the aid of a conveyor belt.
The letters there rest on a guide plate with a printing window in which the ink jet print head is fixed. The letter is moved past the printing window or ink jet print head and during this time is imprinted on the side facing away from the observer. The problem of ink jet print head cleaning and sealing, however, is not addressed there.
A device for cleaning an ink jet print head has become known from international publication WO 96/15908, wherein the ink jet print head is secured so as to be pivotable out of a printing position into a cleaning position and/or sealing position and vice versa. A cleaning and sealing device is also disposed behind the guide plate but in such a way that it is linearly adjustable toward and away from the ink jet print head.
The cleaning and sealing device includes a sealing cap, adapted to the ink jet print head, with suction slits for each row of nozzles. The device also includes a transversely adjustable wiper lip and a downstream suction pump.
In the sealing cap, on one end, a vacuuming region is also provided, with a central suction opening for the wiper lip. The wiper lip can be adjusted with a spindle drive. In that process the wiper lip slides under pressure along the nozzle face of the ink jet print head and in so doing carries away residual ink located thereon. In the associated vacuuming region, the wiper lip is stopped and vacuumed off. Via the suction opening, however, only the residual ink located in the lower middle part of the wiper lip is vacuumed off, so that the next time the nozzle face is wiped off there is a danger that it will smear. A further consideration is that when the wiper lip is separated from the nozzle face, some of the residual ink remains behind on the print head edge because of adhesion; it can collect into a droplet and then drip into the space located below the ink jet print head. There is also the danger that when the cleaning and sealing device is disconnected from the ink jet print head, the wiper lip, which is curved under pressure, will suddenly snap back and throw off some of the residual ink still present on the wiper lip by centrifugal force. Not only can it thus cause undesired contamination but it can even cause damage in the device, especially if the ink is conductive.
A further ink jet printer is known from Japanese patent disclosure JP 08 048043, in which a compartment with a replaceable, absorbent filling for cleaning the wiper lip is provided in the housing of an ink jet print head.
It is a desirable goal to improve cleaning the ink jet print head and maintaining the ink jet print head clean.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a device for cleaning an ink jet print head, which overcomes the above-mentioned disadvantages of the prior art devices and methods of this general type and wherein an ink jet print head disposed stationary behind a guide plate can be adjusted out of the printing position into a cleaning position and/or into a sealing position and back again, and wherein a cleaning and sealing device adapted to the ink jet print head and provided with a wiper lip can be coupled for proper function with the ink jet print head. In particular, the function of the wiper lip is to be improved.
With the foregoing and other objects in view there is provided, in accordance with the invention, an ink jet print head assembly in a postage meter and/or addressing machine, comprising:
an ink jet print head disposed in a postage meter and/or addressing machine behind a guide plate for imprintable media, the ink jet print head having a housing and a front face, and being pivotally mounted between a printing position and a cleaning position;
a cleaning and sealing device disposed behind the guide plate and mounted to be linearly adjustable toward and away from the ink jet print head;
the cleaning and sealing device including a sealing cap adapted to a front face of the ink jet print head, a transversely adjustable wiper lip, and a vacuuming device;
the sealing cap having a suction region defined on one end thereof for cleaning the wiper lip; and
the housing of the ink jet print head having a compartment formed therein and a replaceable absorbent filling disposed in the compartment, the compartment and the filling being operatively associated with the suction region for the wiper lip and being adapted to a contour thereof.
In accordance with an added feature of the invention, the absorbent filling terminates even with a nozzle plane toward the front side of the ink jet print head, and the compartment is adapted to the dimensions of the wiper lip.
Because the ink jet print head and the cleaning and sealing device are disposed on the same side of the guide plate for the imprintable media, a closed, compact structure of the postage meter and a simple design of the imprintable media transport system are made possible.
Due to the fact that the ink jet print head is merely pivoted, a fast and precise return from the cleaning position to the printing position is assured. The adjusting mechanisms for the ink jet print head and for the cleaning and sealing device can be connected to one another and designed in such a way that coupling with accurate positions and reliable function is made possible.
Because the nozzle face to be cleaned and the absorbent filling are disposed in alignment with one another, both the article to be cleaned (i.e., the nozzle face) and the cleaning means (i.e., the wiper lip) can be cleaned in a single course of motion.
In accordance with an additional feature of the invention, the absorbent filling is secured in the compartment by a force-lock and/or by a form-lock. The absorbent filling is thus easily replaced. Constant cleaning quality can be achieved without problems. The absorbent filling absorbs not only ink residue but also dust particles. This is important, since as a consequence of the imprintable media being moved past the nozzle face, paper dust is created and deposited on the assembly to an increased extent.
Because of the improved cleaning of the wiper lip, in turn, better cleaning of the nozzle face of the ink jet print head is achieved and smearing of the nozzles is avoided.
In accordance with another feature of the invention, rubber-elastic flanges are inserted in the sealing cap associated with rows of nozzles on a nozzle face of print head and with the wiper lip, respectively, and a suction pump communicates with the rubber-elastic flanges through a hose connection, and wherein, when the sealing cap is docked with the ink jet print head, the flanges are force-locked on the nozzle face and the filling, respectively.
In accordance with again another feature of the invention, the ink jet print head is rigidly mounted on a rotatable shaft.
In accordance with yet another feature of the invention, the wiper lip comprises a wiper lip housing with a rubber-elastic, T-shaped doctor blade insert and a holding plate retaining the doctor blade insert in the wiper lip housing, and including guide shafts secured outside of and parallel to the sealing cap along which the wiper lip is linearly movable.
In accordance with a concomitant feature of the invention, the suction openings are formed centrally in the doctor blade insert and the hou
Muhl Wolfgang
Seikel Michael
Francotyp-Postalia AG & Co.
Greenberg Laurence A.
Hsieh Shih-Wen
Le N.
Lerner Herbert L.
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