EP1857283B1 - Method for clearing the jet of an ink printhead - Google Patents

Abstract

The method involves guiding a print carrier in a stationarily arranged ink print head. A print image, which serves for the free injection is applied to another print image in the print carrier in a mode irrelevant for a print image analysis, while maintaining a print position for the ink print head. A number of irrelevant prints is generated, stored and combined as the print image with an actual relevant print format at a resulting print image. Size and/or number of image points of an additional print image is smaller than an evaluated image point.

Description

The invention relates to a method for the free spraying of the nozzles of an ink jet print head, in particular in a franking and / or addressing machine.
It has been proven to take advantage of ink printing also in the field of machine franking and / or addressing. The printing takes place without contact by means of ink print head, see for example DE 44 24 771 C1 and EP 0 696 509 B1 , However, the ink printing technique has the disadvantage that often more ink is consumed for cleaning the ink print head than for printing. This is particularly serious in individual printing.

A postage meter machine with an ink jet printhead is known, see EP 0 696 509 B1 and US 5,806,994 in which the letters are transported horizontally and the nozzle surface is arranged parallel thereto. With this machine, the nozzles that are little or unused during printing are sprayed free as long as there is no letter in front of the print head. For this purpose, the letter transport device is provided with corresponding recesses and arranged below the same a collecting container for the sprayed ink. The ink consumption is reduced in this way compared to the priming, but the horizontal letter transport and appropriate design measures are a prerequisite.
By "free spraying" is meant the single or multiple actuation of one or more nozzles. In contrast, "priming" means a multiple consecutive free-spraying of all nozzles. Free spraying is therefore the ink-saving form of keeping the nozzles of an ink jet print head clean.

In addition, an ink printer with a variable cleaning algorithm is known, see EP 0 934 828 A2 , in which past franking imprints are recorded and evaluated - historical log - and from this a cleaning regime is derived. The "historical log" records information on maximum downtime, weekly mail flow and the number and type of processing per week. This does not take into account the nature of the impressions and thus the actual actuation of the individual nozzles.

On the other hand, an apparatus for cleaning an ink jet print head has been found in a franking and / or addressing machine, see DE 10 2005 052 150.9-27 in which the inkjet print head is stationarily but pivotally mounted behind a guide plate in a print window. The print carrier are guided by means of a transport device to the over the vertical inclined inclined guide plate and standing on an edge along. The cleaning and sealing device Like the inkjet print head behind the guide plate, it is adjustably arranged on and away from the same. The ink jet print head can be swiveled by means of associated adjustment means selectively into a print position or into different cleaning areas as well as into a sealing position.
In the printing position, the nozzle surface of the ink jet print head is arranged parallel to the guide plate and thus also to the print carrier.
In a first cleaning area, the inkjet print head is pivoted away from the print position so far that at least twice the distance to the print carrier exists, but all the ink drops still reach the print carrier. In this case, the effect is exploited that from twice the provided printing distance, the ink droplets drop into correspondingly smaller satellite drops whose range is so large that no recognizable print pattern is given more.
At higher transport speeds for the print carrier, this method is only limited applicable due to the inertia of the inkjet print head to be pivoted. The speed of rotation is also limited to avoid unwanted ejection of ink.

US 2006/0055715 A1 discloses a method according to the preamble of claim 1.

The purpose of the invention is an improvement in the print quality and an extension of the life of the printing device and the largest possible letter throughput.

The invention has for its object to provide a method for free spraying of the nozzles of an ink jet print head in a franking and / or addressing machine, in which the transport speed of the print carrier is unlimited and which is suitable for horizontally positioned as well as standing on an edge print carrier transport ,

According to the invention this object is achieved according to the main claim. Further advantageous features of the invention are the dependent claims.

The invention is based on the fact that it is now common in countries with large letters to provide postal items - in particular letters - with machine-readable coded relevant printed images (indicia imprint including clichés) to avoid lost postage and for security reasons.
This happens in the form of one-dimensional bar codes or more modern in the form of two-dimensional bar codes, see for example DE 20 2005 000 255 U1 ,
The individual evaluable pixels (pixels) of a printed image consist of a plurality of printing dots.
A pressure point is created by a single operation of a nozzle. With a pixel size of 0.5 mm edge length, a print density of 200 dpi (dots per inch) would result in around 600 print dots per pixel.
Accordingly, a method for the free spraying of the nozzles according to claim 1 is proposed according to the invention. This means that, with the nozzles involved, a considerably smaller number of pressure points than required for a relevant pixel or pixel are to be applied to the print carrier. The pressure points can be inserted into the so-called white pixels as well as superimposed on the dark pixels or elsewhere, without distorting the information content.
For the generation of the additional printed image at least the little or hardly used nozzles are actuated once. In this case, the printed image can be extended over one or more print carriers.
In the case of relevant print images, in which the nozzles in the upper and lower edge regions are actuated little or not at all, the spray-free pattern is adapted accordingly. Equivalently, the print density is set differently within the additional print image such that it is greater towards the upper and lower edge and in the overlap region than in the remaining region. This also serves to save ink and is the preferred free-spray variant. In order to be able to make a corresponding selection, a certain number of additional print patterns are generated and stored.
Maintaining the print position saves time and optimizes the letter run.

The invention will be explained in more detail below the embodiment.

• Fig. 1 einen beispielhaften Freistempelabdruck mit Details,
  1. a) einen vollständigen Freistempelabdruck mit zweidimensionalem Barcode, Werbeklischee und anderen Zusatzleistungen, wie eindimensionalem Adreß-Balkencode,
  2. b) ein Detail des zweidimensionalen Barcodes von 1a,
  3. c) ein Detail von 1b,
• Fig. 2 eine Übersicht möglicher irrelevanter Freispritzdruckbilder,
  1. a) Verteilung der Dots über den Druckträger bei Beteiligung aller Düsen,
  2. b) Verteilung der Dots über den Druckträger bei vorzugsweiser Beteiligung der Düsen im oberen und unteren Randbereich,
  3. c) Verteilung der Dots auf einer zeitlich nachgeordneten senkrechten Linie bei Beteiligung aller Düsen,
  4. d) Verteilung der Dots auf zwei zeitlich nachgeordnete senkrechte, miteinander fluchtende Linien bei Beteiligung der Düsen im oberen und unteren Randbereich,
  5. e) Verteilung der Dots auf einer zeitlich vorgeordneten senkrechten Linie bei Beteiligung aller Düsen,
  6. f) Verteilung der Dots auf zwei zeitlich vorgeordnete senkrechte, miteinander fluchtende Linien bei Beteiligung der Düsen im oberen und unteren Randbereich,
• Fig. 3 ein Blockschaltbild der Druckeransteuerung,
• Fig. 4 ein Flussdiagramm zum Blockschaltbild nach Fig. 3.

Show it:

• Fig. 1 an exemplary indicia imprint with details,
  1. a) a complete indicia impression with two-dimensional bar code, advertising cliche and other additional services, such as one-dimensional address bar code,
  2. b) a detail of the two-dimensional barcode of Fig. 1a,
  3. c) a detail of 1b,
• Fig. 2 an overview of possible irrelevant free-blown print images,
  1. a) distribution of the dots across the print carrier with the participation of all nozzles,
  2. b) distribution of the dots over the print carrier with preferential participation of the nozzles in the upper and lower edge area,
  3. c) distribution of the dots on a temporally subordinate vertical line with participation of all nozzles,
  4. d) distribution of the dots on two temporally subordinate vertical, aligned lines with participation of the nozzles in the upper and lower edge region,
  5. e) distribution of the dots on a temporally upstream vertical line with the participation of all nozzles,
  6. f) distribution of the dots on two temporally upstream perpendicular, aligned lines with participation of the nozzles in the upper and lower edge region,
• Fig. 3 a block diagram of the printer driver,
• Fig. 4 a flowchart for block diagram after Fig. 3 ,

For simplicity and ease of understanding, the illustration is partially schematic.

A complete indicia impression for testing according to 1a consists of the traditional franking imprint, the franking imprint in the two-dimensional barcode, an advertising cliché and other additional services, such as a one-dimensional address bar code arranged underneath.

In 1b shows a partial area of the franking imprint is represented in the two-dimensional barcode. Here it is easy to see how the pixels p are composed of a large number of dots d.

In Fig. 1c is the area after Fig. 1b so far enlarged shown that on the one hand the dimensions of a pixel in the x and y coordinate direction are clearly visible and on the other hand individual dots d of the free-spray image can be seen, which are within the white pixels of the relevant printed image Dr. It becomes clear that these dots are inevitably disregarded in an evaluation system oriented to the pixel size.

In Fig. 2a In the case illustrated, the free-spray image Db-dots, which differs from the reality, is distributed over the relevant print image Dr and the remaining print carrier B.

In Fig. 2b is a free spray image Db shown, which takes into account especially the upper and lower edge region of the maximum pressure range. These are the regions where the nozzles are otherwise rarely or not operated. This variant is particularly ink-saving and therefore preferred.

In Fig. 2c is a free spray image Db shown, in which all the nozzles are actuated simultaneously in time after the two-dimensional barcode, so that there is a vertical printing line. In this variant, the actual intensity of the actuation of the individual nozzles for generating the relevant printed image Dr is disregarded. However, it is at least ensured that each nozzle per print carrier B is actuated at least once.

In Fig. 2d is a free spray image Db shown, in which all the nozzles in the upper and lower edge region simultaneously after the two-dimensional time Barcode be actuated, so that there are two vertically aligned printing lines. It is assumed that all nozzles are operated for the barcode area. This variant has the same effect as the one after Fig. 2b and therefore equally advantageous.

In Fig. 2e is a free spray image Db shown in which all nozzles are operated simultaneously in front of the two-dimensional barcode. This pattern is the pendent to that Fig. 2c ,

In Fig. 2f is a free spray image Db shown, in which all nozzles in the upper and lower edge area are simultaneously actuated in time before the two-dimensional barcode. This pattern is the counterpart to that according to Fig. 2d ,

In Fig. 3 a block diagram of the printer driver is shown. It contains a memory 1 for the relevant printed image. The relevant printed image Dr contains information relating to postage, date of posting, postage meter, advertising cliché and supplementary letter services, such as express mail or Infopost. The information for this is determined via upstream facilities, such as the letter scale and dimensional scanner as well as sender requests. In addition to the memory 1, a memory 2 is provided, in which an empirically determined number of irrelevant printed patterns or free-spray patterns Di1 to Din is entered. Depending on the current and expected relevant print images Dr, the appropriate complementary free-spray pattern Di is selected manually or automatically. Both memories 1 and 2 are bidirectionally connected to a microprocessor 5. To the microprocessor 5 also the franking data input 3 is connected unidirectionally coming. The data supplied from the franking data input 3 are further processed in the microprocessor 5 to the current print image Dr and buffered in the memory 1. Furthermore, a memory 4 is bidirectionally connected to the microprocessor 5, in which the resulting printed image D is temporarily stored from relevant and irrelevant printed image Dr, Db. The microprocessor 5 is unidirectionally connected to a printing device 6, which receives the current resulting printed image D from the former.

In Fig. 4 is the associated flow chart for the block diagram after Fig. 3 shown. With the entry of a print carrier B in the franking machine its leading edge passes a sensor and thus triggers the start S for the print job Da. By means of the postage-relevant information from the franking data input 3, the franking pressure calculation Drb takes place and then the franking pressure preparation Drv. The relevant printed image Dr thus obtained is temporarily stored. When Frankierdruckaufbereitung Drv at the same time fall to the information on which nozzles are activated to what extent. This information is used to select A of a suitable irrelevant print pattern Di from a number n of permanently stored print patterns Di1 to Din. This print pattern Di is processed into an irrelevant print image Db and the same is temporarily stored. The relevant print image Dr and the supplementary irrelevant print image Db is combined to form a resulting print image D and this is passed to the pressure control. With execution of all print commands per print carrier B the printing process is finished.

Used reference signs

1

Memory for relevant print image Dr

2

Memory for irrelevant print patterns Di1, Di2 to Din

3

Frankierdateneingabe

4

Memory for total print image

5

microprocessor

6

print Setup

A

Print sample selection for free spraying

ace

Control data for printing device 6

B

Print carrier, letter

d

dot

D

resulting print image

There

Print job control

db

irrelevant print image

Di1 ... Din

irrelevant print patterns

Dr

relevant print image (franking imprint)

drb

Frankierdruckberechnung

Drv

Frankierdruckaufbereitung

fd

franking

j

Alternative decision yes

n

Alternative decision no

p

pixel

S

begin

Claims (4)

1. A method for spraying free the nozzles of an ink print head, especially in a franking and/or addressing machine in which the print media are carried along a stationarily arranged ink print head and in which, maintaining the print position of the print head, in addition to the respective print image, a print image exclusively serving the spraying-free is applied in a mode that is irrelevant to the analysis of the printed image, characterized in
   that the print image serving the spraying-free (Db) adapted to the respective relevant print image (Dr) is selected from a number (n) of generated and stored irrelevant print images (Di1 to Din) and that both print images (Db, Dr) are merged to generate a resulting print image (D) made in such a way that each nozzle is operated at least once.
2. A method according to Claim 1, characterized in
   that size and number of the printed points (dots), respectively, per image point (pixel) of the additional print image (Db) are substantially smaller than an analyzable pixel.
3. A method according to Claim 1, characterized in
   that, for generating the additional print image (Db), each nozzle is operated at least once, wherein the print image (Db) may extend over several print media and a superimposition of the relevant printed image is intended.
4. A method according to Claim 1, characterized in
   that the print density within the additional print image (Db) is differently fixed in such a manner that it is higher towards the upper and lower edge and in the area of superimposition than in the remaining area.

Images