EP1839097B1 - Device for electrographic printing or copying using liquid colouring agents - Google Patents

Abstract

In an apparatus for the electrographic printing or copying using liquid coloring agents consisting of a carrier liquid and toner particles, including a latent image carrier and at least one supply element in the form of a slot-like supply nozzle via which the liquid toner is applied to the latent image carrier and a suction element by which excess liquid coloring agent is removed from the latent image carrier, a de-coupling channel is arranged between the suction element and the supply element.

Description

The invention relates to a device according to the preamble of claim 1, for electrographic printing or copying using liquid colorants, with a latent image carrier and at least one feed element designed as a slot-shaped feed nozzle, by means of which the liquid colorant can be applied to the latent image carrier, as well as a suction device Take-off element, by means of which excess parts of the liquid colorant are removable from the latent image carrier.

Such a device is for example from the GB 2 243 227 A known. In the known device, liquid toner is applied to a latent image carrier formed as an image roller. For this purpose, the device has a slot-shaped outlet through which liquid toner is applied to the image roller by means of a pump. In the direction of movement of the image roller behind the slit-shaped outlet, a slot-shaped inlet is arranged, which is acted upon by a negative pressure. As a result, toner, which does not adhere to the image roller, sucked from the image roller. Between the outlet and the inlet, an electrode is arranged, which has a small distance from the surface of the image roller.

Since the inlet is located behind the electrode in the direction of movement of the image roller, toner which is jammed by the electrode can not be picked up by it. Although an overflow passage is arranged in the direction of movement of the image roller in front of the outlet, however, only toner, which is located on the side of the outlet facing away from the electrode, enters the latter. Toner adhered to the image roller can not be picked up by the passage.

From the DE 32 30 862 A1 An apparatus is known in which, for developing a charge image, which is applied to an electrically coated image carrier, the image carrier is wetted with a liquid developer or colorant from a dispersant or a carrier liquid and toner particles. Through the charge image, part of the toner on the surface of the image carrier is bound imagewise. The remaining toner is removed so that no background tint is created. Furthermore, so much dispersant is removed from the image carrier that remains on the image carrier only so much dispersant that the further treatment of the developed charge image is done properly and quickly. For this purpose, a separating member is provided, which is moved relative to the image carrier and whose surface is just immersed in the liquid developer applied to the image carrier, so that a portion of the dispersant contained in the liquid developer is removed, for example by adhesion. In addition, an electric field is applied between the separator and the image carrier, the field direction of which depends on the charge of the toner contained in the liquid developer. By this electric field of non-imagewise bound toner is attracted to the separator.

In the known device, the liquid developer is applied to the image carrier by means of a separate element spatially separated from the collecting organ. Since the element must also be arranged at an exact distance from the image carrier, it is thus necessary to set the distance of the element from the image carrier as well as the distance of the separating member from the image carrier separated from each other, wherein in particular the distance of the Abscheideorgans of the Image carrier must be set very accurately. Because of this distance it depends on whether unneeded toner or excess dispersant is removed with the required thoroughness from the image carrier.

Furthermore, from the DE 100 27 173 A1 an apparatus and method for electrographic printing or copying using liquid Colorants, which regularly consist of a carrier liquid and toner particles, known, in which an applicator element is present, which carries a layer of a colorant. There is an air gap between the liquid layer and the surface of the latent image carrier facing it. To color the latent image on the latent image carrier, droplets are transferred from the liquid layer to the surface of the latent image carrier, overcoming the air gap. As a result, the latent image is colored to a colorant image. This colorant image can be transferred directly to an existing example of paper Endbildträger.

The device also has a cleaning station, which serves to clean the latent image carrier after the Umdrucken the colorant image of the remaining colorants and restore a defined initial state. The cleaning station may include a suction device which sucks the liquid dye residue from the surface of the image carrier. The extracted exhaust air can be filtered and the liquid colorant are deposited, which is preferably used again in the further printing process.

In addition, from the US 6,385,421 B1 a printing device is known, which has a designed as an image roller latent image carrier. On the image drum four developer units are arranged, by means of which each liquid toner is applied in different colors on the image drum. The toner is applied by means of transfer rollers, which on the one hand dip into a reservoir in which liquid toner is located, and on the other hand rest on the surface of the latent image carrier.

In the direction of movement of the image roller behind the transfer rollers each have a vacuum nozzle is arranged, by means of which excess liquid toner is removed from the latent image carrier. By using rollers to transfer the liquid toner to the latent image carrier, high print speeds can not be achieved.

Furthermore, from the EP 0 223 693 A2 a plotter toner station for an electrostatic printer, which has a write head and a developer unit attachable to the write head. By means of the write head, a charge is applied to a typically made of paper final image carrier, which passes the write head. Following the write head, the final image carrier passes through the developer unit. The developer unit has a roller, by means of which toner is applied to the final image carrier. For this purpose, the roller is previously sprayed by means of a spray unit with liquid toner.

After toner has been applied to the final image carrier, the final image carrier passes through a vacuum chamber, by means of which excess toner is removed from the final image carrier. For this purpose, the vacuum chamber has openings through which toner, which is located at not provided with charge points of Endbildträgers is sucked from the final image carrier.

By transferring the toner by means of a roller on the image carrier, a high printing speed is not possible.

It is an object of the invention to form a device mentioned in such a way that it has a low height when reaching a high printing speed.

The solution of this problem arises from the features of the characterizing part of claim 1. Advantageous developments of the invention will become apparent from the dependent claims.

According to the invention, an apparatus for electrographic printing or copying using liquid colorants, which regularly consist of a carrier liquid and toner particles, with a latent image carrier and at least one feed element designed as a slot-shaped feed nozzle, by means of which the liquid colorant can be applied to the latent image carrier, and a designed as a suction pickup element, by means of the excess Parts of the liquid colorant can be removed from the latent image carrier, characterized in that a decoupling channel is arranged between the acceptance element and the feed element.

Characterized in that the feed element is designed as a slot-shaped feed nozzle, and that below the feed element, a return channel is arranged, it is possible to apply the liquid colorant by means of a surge on the latent image carrier.

Because the removal element is designed as a suction device, excess parts, in particular of the dispersant, can be removed in a simple manner and very reliably from the latent image carrier. Since the removal of the liquid colorant from the latent image carrier depends on the negative pressure of the suction device, it can be achieved by controlling the negative pressure in a very simple manner that almost all excess parts of the liquid colorant are removed from the latent image carrier without the parts forming the colorant image be removed from the latent image carrier. This has a very beneficial effect on the quality of the prints or copies produced by the device.

It is very advantageous that a decoupling channel is arranged between the acceptance element and the feed element. This ensures that the suction device has no effect on the feed. The sucked by the suction device optionally from the direction of the feed element air is completely provided by the decoupling channel, so that no suction is exerted on the feed element.

In a particular embodiment of the invention, a scraper is arranged in the direction of movement of the latent image carrier behind the feed nozzle, which is arranged at a first predetermined distance from the latent image carrier. As a result, the amount of adhering to the latent image carrier surplus parts of the liquid colorant can be limited. However, the scraper is not to completely remove the excess portions of the colorant from the latent image carrier, it may be located at a relatively large distance of about one to two tenths of a millimeter from the latent image carrier. This avoids that stuck in the liquid colorant impurities such as granular particles stuck in the gap between the scraper and the latent image carrier, whereby the latent image carrier could be damaged. Furthermore, out of roundness or a non-circular running of the image roller because of the relatively large distance of the surface of the image roller from the scraper does not affect. It can therefore on safety measures, which avoids that the scraper does not come into contact with the surface of the image roller even in a non-circular image roller or in a non-circular running of the image roller, can be dispensed with.

An embodiment of the invention in which a return flow channel is arranged in front of the wiper in the direction of movement of the latent image carrier is also very advantageous, such that liquid colorant retained by the wiper passes into the return flow channel. Thus, the portion of the surge that does not adhere to the latent image carrier may enter the return passage, which is advantageously connected to the liquid colorant reservoir.

The reflux channel can be formed or arranged so that the developer unit can be arranged laterally by a latent image carrier designed as an image roller. This has a very advantageous effect on the height of the device, which is very noticeable especially in color printers or color copiers.

Also very advantageous is an embodiment of the invention in which the suction device has a nozzle opening which is designed such that at least twice, in particular at least eight times, preferably at least ten times as much air can be sucked in from the direction away from the feed element than by means of the latter Feed element facing direction. This ensures that the particles leaving the suction of the Dispersants are sucked back into the suction device. By the suction, the particles can atomize, whereby the colorant image adhering to the latent image carrier is slightly dried. By controlling the negative pressure can thus be set the degree of drying of adhering to the latent image carrier colorant image. This is very advantageous because in some applications it is required that the colorant image adhering to the latent image carrier is not completely dry.

Particularly advantageous is an embodiment of the invention, in which a limiting element is present, by means of which the colorant supply amount of the feed element is adjustable. In this way it can be achieved that the latent image carrier is applied exactly with such a colorant amount, which is required to produce a saturated colorant image. This is very advantageous in terms of the removal of excess portions of the liquid colorant from the latent image carrier, since the amount of excess portions of the liquid colorant is thereby minimized.

In a further particular embodiment of the invention it is provided that the supply element and the decrease element are arranged at a second predetermined distance from the latent image carrier in a developer unit detachably connected to the device. This considerably simplifies the arrangement of the feed element and of the take-off element on the latent image carrier. Since the feed element and the decrease element are fixed in the developer unit, in this embodiment of the device according to the invention, it is only necessary to arrange the developer unit exactly on the latent image carrier. This can be done in an advantageous manner by means of a stop, by means of which the position of the developer unit can be specified exactly and reproducibly.

Due to the fixed, usually unchangeable arrangement of the feed and the take-off element in the developer unit, the distance of the pickup element is also fixed by the feed. This requires the The distance of the pickup element from the feed element, in particular after a removal of the developer unit from the latent image carrier, can not be readjusted, as a result of which the products produced by means of the device are of consistent quality.

The advantages of this embodiment of the device according to the invention are particularly evident during maintenance work. Instead of respectively removing the feed element and the pickup element separately from the device or arranging them again on the device, in the device according to the invention only the entire developer unit needs to be removed or reattached. Costly adjustments are almost completely eliminated.

In a further particular embodiment of the invention it is provided that existing elements are arranged between the feed element and the pickup element of a conductive material, which are arranged at a fourth predetermined distance from the latent image carrier. By means of the elements consisting of a conductive material, it can be achieved in an advantageous manner that there is an electric field existing between the developer unit and the latent image carrier over a relatively long distance. As a result, there is a very good development of the colorant image on the latent image carrier. If a second feed element is present, the respective elements can be formed from a conductive material. Conveniently, the developer unit is made entirely of a conductive material.

Very advantageous in the device according to the invention is that it can be designed so that it can be arranged laterally on a designed as an image roller latent image carrier. As a result, a plurality of developer units can be arranged one above the other at a low overall height, which is very advantageous especially in the case of color printers or color copiers. Furthermore, it is very advantageous in particular for the device according to the invention that flooding of the image roller, development of the latent image and removal of the excess Parts of the liquid colorant from the latent image carrier no moving parts are present. By the suction of the excess parts of the liquid colorant from the latent image carrier can be dispensed with, to use a rotating with the image roller deposition roller. This is very advantageous because the Abscheidewalze must be arranged very expensive regularly on the image roller so that it does not come into contact with the surface of the image roller even in a non-circular image roller or in a non-circular run of the image roller.

Further advantages of the present invention will become apparent from the following description of a particular embodiment with reference to the drawings.

The single figure shows a schematic arrangement of a device according to the invention from the side in section.

As can be seen from the figure, a developer unit 2 is arranged on a latent image carrier 1 designed as image roller 1. The image roller 1 rotates in the direction of the arrow 1 '. The developer unit 2 is made of metal such as aluminum and is connected to a voltage source, not shown in the figure, so that it has a potential of several hundred volts (about four hundred to seven hundred volts) with respect to the image roller 1.

At its end facing the image roller 1, the developer unit 2 has a feed element 3a designed as a slot-shaped feed nozzle. The feed nozzle 3a is formed by an upper wall 8 of the developer unit 2 and a displaceable in the direction of the image roller 1 plate 5a. Through the plate 5a, the amount of the colorant passed through the supply nozzle 3a onto the surface of the image roller 1 which consists of a carrier liquid and toner particles can be adjusted. Depending on the distance of the plate 5a from the image roller 1, the amount of colorant is larger or smaller. The distance of the plate 5 a from the image roller. 1 is adjusted so that the present on the image drum 1 latent image is colored to a saturated colorant image.

Below the plate 5a, a reflux channel 6a is arranged, which does not catch on the image roller 1 adhering colorant. The reflux channel 6 is connected to the reservoir of the colorant, so that the collected from the return channel 6 colorant can be reused and re-image roller 1 can be supplied.

The image roller 1 facing wall 7a of the return channel 6a is formed so that it runs in the direction of rotation 1 'of the image roller 1 over a range of a few centimeters at a distance of about 0.2 millimeters from the surface of the image drum 1. In this way, it forms a scraper 7a, which limits the thickness of the adhering to the image roller 1 colorant to about 0.2 millimeters. The excess portion of the colorant is retained by the scraper 7a and enters the return channel 6a.

Below the reflux channel 6a, a second feed nozzle 3b is arranged, which is formed by the wall of the return channel 6a and a second plate 5b. The second plate 5b is also displaceable in the direction of the image roller 1. Furthermore, below the second feed nozzle 3b, a second return channel 6b is arranged, whose wall facing the image roller 1 forms a second scraper 7b, which likewise limits the thickness of the colorant adhering to the image roller 1 to approximately 0.2 millimeters.

The arrangement of a second feed nozzle 3b and a second return channel 6b can achieve that a saturated colorant image can be applied to the latent image carrier in each case. If this is already achieved by means of the first feed nozzle 3a, it goes without saying that the second feed nozzle 3b and the second return flow channel 6b are dispensed with.

Disposed on the lower side of the developer unit 2 is a channel 4 which can be subjected to a negative pressure and which has an outlet opening 4a, by means of which excess colorant can be sucked out of the image roller 1. The negative pressure is adjustable, so that such a negative pressure can be adjusted that almost all excess parts of the liquid colorant are removed from the image drum 1, but stick the parts forming the colorant image on the image roller 1. The outlet opening 4a of the channel 4 is formed so that the sucked from the channel 4 air for the vast majority of the feed nozzle 3a side facing away from the channel 4 passes. That is, the air sucked into the passage 4 passes through a gap formed by the lower wall of the developer unit 2 and the surface of the image drum 1. As a result, an atomization of still adhering to the image roller 1 carrier liquid takes place.

In order to prevent air drawn in from the channel 4 from being sucked in from the direction of the feed nozzles 3a, 3b, a decoupling channel 9 is arranged below the second return channel 6b. Both ends of the decoupling channel 9 are open, so that ambient air can freely penetrate into the decoupling channel 9.

The developer unit 2 is arranged in a guide, not shown in the figure, so that it can be removed in a simple manner from the image roller 1 or arranged on the image drum 1. For this purpose, the developer unit 2 is moved in the direction of the arrow 2 '.

To adjust the distance of the developer unit 2, and thus in particular the distances of the plate 5a and the second plate 5b and the scraper 7a and the second scraper 7b, a stopper 2a is provided, against which a protruding element 2b of the developer unit 2 abuts. Through the guide and the stopper 2a, the developer unit 2 can be easily arranged with the highest accuracy on the image drum 1.

By adapted to the curvature of the image drum 1 end face of the developer unit 2, the developer unit 2 can be arranged laterally on the image drum 1. As a result, a small overall height of the device is achieved, whereby a plurality of devices can be arranged one above the other at a low overall height, as may be the case for example with color printers or color copiers.

Claims (8)

1. Device for electrographic printing or copying using liquid colouring agents, comprising a latent image carrier (1) and at least one feed element (3a, 3b) which is in the form of a slot-like feed nozzle and by means of which the liquid colouring agent can be applied to the latent image carrier (1), and a take-off element (4) which is in the form of a suction element and by means of which the excess parts of the liquid colouring agent can be removed from the latent image carrier (1), characterized in that a decoupling channel (9) is arranged between the take-off element (4) and the feed element (3a, 3b), which decoupling channel (9) is formed in such a way that the air sucked in by the suction device, optionally from the direction of the feed element, is made available completely through the decoupling channel.
2. Device according to Claim 1, characterized in that a scraper (7a, 7b), which is arranged at a first predetermined distance from the latent image carrier (1), is arranged behind the feed nozzle (3a, 3b) in the direction (1') of movement of the latent image carrier (1).
3. Device according to Claim 2, characterized in that a return-flow channel (6a, 6b) is arranged before the scraper (7a, 7b) in the direction (1') of movement of the latent image carrier (1), in such a way that liquid colouring agent retained by the scraper (7a, 7b) enters the return-flow channel (6a, 6b).
4. Device according to any of Claims 1 to 3,
   characterized in that a limiting element (5a, 5b) by means of which the colouring agent feed quantity of the feed element (3) can be adjusted is present.
5. Device according to any of Claims 1 to 4,
   characterized in that the feed element (3a, 3b) and the take-off element (4) are arranged, at a second predetermined distance from one another, in a developer unit (2) detachably connected to the device.
6. Device according to Claim 5, characterized in that a stop (2a) which limits the distance of the developer unit (2) from the latent image carrier (1) to a third predetermined distance is present.
7. Device according to any of Claims 1 to 6,
   characterized in that the take-off element (4) has a nozzle opening (4a) which is formed in such a way that by means of it at least twice, in particular at least eight times, preferably at least ten times, as much air can be sucked in from the direction facing away from the feed element (3a, 3b) as from the direction facing the feed element (3a, 3b).
8. Device according to any of Claims 1 to 7, characterized in that elements (5a, 7a, 5b, 7b) which consist of a conductive material and are arranged at a fourth predetermined distance from the latent image carrier (1) are arranged between the feed element (3a) and the take-off element (4).

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