DE4042050A1 - DEVICE FOR DETACHING A RECORDING CARRIER FROM AN IMAGE GENERATING SURFACE - Google Patents

Description

The invention relates to a device according to the preamble of claim 1. It is used in a printer with endless tape recording medium on which according to the so-called called electrophotographic process is printed. A such printer includes a retraction mechanism for one Image transmission loading device, which consists of an operating position is to be moved out if no printing is to be carried out lead is. The endless tape recording medium, to a photoconductive drum through the image transfer supply loader was pressed, with the withdrawal the charger from the photoconductive drum be solved.

In the electrophotographic process, e.g. B. in one Printer becomes a latent electrostatic image by Be thinning a photoconductive drum generated, the thereby is rotated. The latent electrostatic image is through Developed toner powder and this in its pictorial Transfer distribution to a record carrier that moved towards the drum in synchronism with the rotation of the drum becomes. The transferred toner image is on the recording Carrier fixed in a fuser. This procedure will  e.g. B. applied in an electrophotographic printer, in which information is stored on an endless tape recording medium printed, folded like a fan, and is provided with transport perforations, similar to one normal line printer u. Ä.

The fan-fold folded record carrier is on Transition between the pages with a perforier line, and it will be on these lines alternately folded in opposite directions and stacked in this form pelt supplied to the image forming device.

The printer must print on this endless belt Start drawing media in one place on each page, which is at a distance from the perforated tear line. The Printing process is thus at a distance from the front edge Direction of progressive pressure. The elec trophotographic process is carried out with an exposure processing unit, a development unit and an image Carrying unit carried out on the circumference of the photoconductor are arranged and successively during the Drum rotation are put into operation. Thus a Transfer the image from the drum to the recording medium, when the exposed drum portion is transferred to an image delivery point. Therefore the starting point for the Printing process on the endless tape recording medium a relative movement of the photoconductive drum relative be set to the record carrier. Before the print process begins, it is necessary to change the positional relationship between the start of imaging on the photoconductive Adjust the drum and the recording medium so that the Position of the photoconductive drum at which the exposure should start with the print start position on the respective Continuous sheet recording medium side collapses.

If the recording medium with the photoconductive Trom  mel is kept in contact, d. H. in the image transfer stood, and the position setting described above takes place, there is the problem that the photoconductive Material on the drum surface is worn and the Life of the photoconductive drum is shortened. Also the recording medium can be soiled with toner, that remained on the surface of the photoconductive drum ben is. To solve this problem, there are already Devices with which the image transfer loading device processing from the operating position of the image transmission is moved in which the endless tape recording medium touches the photoconductive drum. With such devices can the image transfer loading device with the end of a Transport process of the endless tape recording medium withdrawn.

Nevertheless, there is a problem with this too Withdraw the loading device from the operating position Completion of the printing of the endless tape recording medium ger, which is in sync with the rotation of the photoconductive trom mel was moved at a predetermined speed, not can be stopped immediately. He will then through his Mass inertia moved a little further, so that be with the part to be brought into contact with the photoconductive drum is loosened because it transpor with a conveyor mechanism tiert, which is behind the photo in the direction of transport conductive drum. Therefore, even with one Withdrawal of the image transfer loading device of the on Drawing medium with the photoconductive drum still in Stay in touch, causing it to print with toner again can be contaminated. This problem occurs more often if the fold on the respective tear line to the photoconductor capable drum surface is directed.

It is an object of the invention to provide an improved device for detaching a recording medium from a picture  area to be specified, which is effective when the image transfer loading device from its operating position is moved out.

The invention solves this problem by the features of Claim 1. Advantageous further developments are counter stood the subclaims.

With a device according to the invention, the direction, in which an endless tape recording medium is loosened, be regulated by the elasticity of the brush wires, so that the record carrier is safe from the photoconductive Imaging area is peeled off when no printing takes place.

The invention will now be described with reference to the drawing explained. In it show:

Fig. 1 is a side view of a printer with a detachment apparatus as an embodiment using an endless belt-voltage Aufzeich carrier,

Fig. 2A is a plan view of an integrated Bildübertragungsein of the printer of Fig. 1,

Fig. 2B is a partially enlarged diagram of an image transfer unit of gezeig th in Fig. 1 with the printer operating position of an image transfer charger means, and

Fig. 3 shows the partially enlarged view in FIG. 2B, image transfer unit with the retracted position of the image transfer charging device.

Fig. 1 shows a laser beam printer with an endless tape recording medium, which is folded like a fan. The printer brings out character information according to a computer printout. Ä. on the recording medium 20 by the electrophotographic method.

A toner cleaning unit 2 , a discharge unit 3 , a charging unit 4 , an optical scanning system 5 for directing a laser beam onto a photoconductive drum 1 in the direction of arrow A, a developing unit 6 and an image transfer unit 7 are on the periphery of the photoconductive drum in the order given in Ordered direction of rotation, which is indicated by an arrow B. Furthermore, a fixing unit 8 is arranged after the photoconductive drum 1 , and a tractor 9 is used to transport the recording medium 20 to the fixing unit 8 in the arrangement shown in FIG. 1. The tractor 9 is provided so that a tractor belt 91 with projections, not shown, engages in the transport perforations of the record carrier 20 , which are provided on its two edges.

While the photoconductive drum 1 is rotated in the direction of arrow B, the laser beam of the optical scanning system 5 scans its surface. It is modulated with pictorial information that creates an electrostatic latent image on the drum surface. The developing unit 6 applies toner to the latent electrostatic image and thereby creates a visible image. The toner image thus developed is transferred to the endless tape recording medium 20 at the image transfer unit 7 and fixed to the fixing unit 8 .

Fig. 2 shows a plan view of the image transfer unit 7 of the printer shown in Fig. 1. FIG. 2B shows a partial section along the line II in FIG. 2A. . As shown in Figures 2A and 2B, the image transfer unit 7 is disposed so that a corona charging unit at its both ends with arms 72, 72 71 - is kept 1, the axis on a pivot 73 with two brackets 11, 11 - 1 are pivotable. Both stand on a frame 10 of the laser printer, so that the loading unit 71 is arranged parallel to the axis of rotation of the photoconductive drum 1 and can be withdrawn from the operating position.

1 with two springs 75, 75 - - in the operating position, the arms 72, 72 are pushed upwards 1, the edges between the lower of the arms and the frame are arranged 10th As a result, the charging unit 71 is held in a predetermined position in which an image transmission can be brought about with it. Furthermore, a pressure element 76 with a semicircular cross section is arranged next to the loading unit 71 . When the loading unit 71 is in the operating position, the pressure element 76 presses the recording medium 20 upwards against the photoconductive drum 1 , so that the image transfer operation can be carried out on the recording medium 20 .

On the pivot axis 73 for the arms holding the loading unit 71 , a pressure roller 74 is supported with a downwardly projecting lever 74 a. It is through a further pair of springs 750, 750 - 1 pressed upwards against two stops 11 A, 11 A-1, each of the brackets 11, 11 - are provided. 1 A slide plate 12 is disposed on the frame 10 of the laser printer so that it along guide plates 12 - 1 can be moved, each of the frame 10 with a screw 12 - are mounted. 2 A transport roller 74 B forms the printing roller and transports the endless tape recording medium 20th

A plurality of oval openings 120 are provided on the sliding plate 12 . The sliding plate 12 can be moved in these openings 120 according to their length. One end of a spring 12 - 3 with one of the guide plates 12 - 1 is connected, the other end is Stigt BEFE on the sliding plate 12, as shown in Figure 2A.. Furthermore, one of the side walls 12 B of the sliding plate 12 is coupled to a driver 12 - 4 , which is in contact with a cam 12 - 5 , which has a part of small diameter and a part of large diameter according to the operating position and the withdrawal position of the loading unit 71st . When the loading unit 71 is in the operating position, the small diameter part of the cam 12 - 5 is in contact with the driver. When the load unit is to be retracted from the operating position 71, the cam 12-5 rotated by a drive, not shown, and the driver 12-4 is moved in the transport direction of the recording medium, while the cam 12-5 rotates. The sliding plate 12 is thereby displaced.

When the sliding plate 12 is moved in the transport direction, its upstanding end 12 A acts on a pin 77 which projects horizontally from a lever portion 74 A of the pressure roller 74 . Characterized it clockwise (Fig. 2B) is pivoted so as shown in FIG 3, the arms 72, 72 -. 1 against the force of the springs 75, 75-1 pushes down and thus the load unit 71 from the operating position retracted down becomes.

Upper and lower guides 13 U and 13 D for the recording carrier 20 face each other at predetermined intervals on the upstream side of the image transfer unit 7 . The record carrier 20 is the image transmission unit 7 via a transport path 13 which is formed between the upper and lower guides 13 U and 13 D out.

Each guide 13 U and 13 D is formed under a predetermined angle at an entry point downward and then at an intermediate point in the direction of the image transmission unit 7 extending upward. Furthermore, a brush 14 with a predetermined width over the entire width of the record carrier 20 is running on the upper guide 13 U on the edge facing the image transmission unit 7 BEFE Stigt.

The brush 14 is provided with wires that are close together and each have a specific diameter and length. The wires can be bent very easily, and their free ends protrude into the transport path 13 of the record carrier 20th

With this arrangement, if the printing is carried out with the loading unit 71 in the operating position, the endless tape recording medium 20 , which is fed to the image transmission unit 7 via the transport path 13 between the upper and lower guides 13 U and 13 D, goes up with the Pressure element 46 presses ge against the photoconductive drum 1 . Thus, its top surface comes into contact with the pho toleitfähigen drum 1 and the brush 14 at the outlet of the upper guide 13 U. Each wire of the brush 14 is thereby bent by the record carrier 20 upward and forward in the transport direction of the recording medium 20th

At the end of the printing process, ie when the printing operations are not to be carried out, the transport of the recording carrier 20 is interrupted and the sliding plate 12 is pushed ver. The arms 72, 72 are - pivoted 1, so that the loading unit is retracted from the operating position 71st At the same time, the record carrier 20 between the photoconductive drum 1 and the loading unit 71 is loosened by the inertia when it is stopped.

When the recording medium is loosened in the direction of drum 1 photoleitfä ELIGIBLE 20, it will remain independent of the return movement of the loading unit 71 in contact with the drum surface. Thus, there is a possibility that the recording medium 20 becomes soiled by the toner on the photoleitfä ELIGIBLE drum 1 when the printing operation is restarted. In this way, for example, a black stripe can be produced on the recording medium 20 .

However, since the wires of the brush 14 come into contact with the recording medium 20 , their frictional resistance largely prevents the recording medium 20 from moving due to its inertia when it is stopped. Since the wires are then released again by the recording medium 20, they return by elasticity to their normal to stand back, and thus the recording is support 20 is regulated so that, as Fig. 3 shows, tung in Rich to the charging unit 71 is loosened. In other words: since the wires of the brush 14 are easily bent only when the recording medium 20 is bent with the pressure element 76 upwards, they can also easily return to their normal state if the recording medium 20 is not pressed up . Since the brush 14 consists of a large number of wires, each of which has a very weak elastic restoring force, the brush 14 presses the recording medium 20 evenly and thus ensures a pressure effect downwards.

Thin wires made of acrylic resin, for example, can be used be detected, each having a predetermined elasticity. It is also possible to have a friction coefficient of the wires with a film, with its density, with its length, etc. so that the operations described above can be reached safely.

Claims (4)

1. Apparatus for detaching a recording medium from a recording surface in an electrophotographic printer in which an image transfer charging device between an operating position in which the recording medium is pressed against the recording surface and a rest position is movable to the recording medium from the recording surface detach, characterized by an elastic element ( 14 ), which is deformable by the recording medium ( 20 ) when pressed against the recording surface ( 1 ) and returns to its normal position by moving the image transfer loading device ( 71 ) into the rest position and the recording medium ( 20 ) detaches from the recording surface ( 1 ). 2. Device according to claim 1, characterized in that the elastic element ( 14 ) is a brush with a plurality of wires. 3. Device according to claim 2, characterized in that that the wires are made of acrylic resin. 4. Device according to one of the preceding claims, characterized in that the recording surface ( 1 ) is a photoconductive drum to which the recording medium carrier ( 20 ) is moved tangentially.