WO1998058297A1 - Transfer printing device for an electrophotographic single-sheet printer and method for pressing a record carrier in a transfer printing device of this type - Google Patents

Transfer printing device for an electrophotographic single-sheet printer and method for pressing a record carrier in a transfer printing device of this type Download PDF

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Publication number
WO1998058297A1
WO1998058297A1 PCT/EP1998/003638 EP9803638W WO9858297A1 WO 1998058297 A1 WO1998058297 A1 WO 1998058297A1 EP 9803638 W EP9803638 W EP 9803638W WO 9858297 A1 WO9858297 A1 WO 9858297A1
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WO
WIPO (PCT)
Prior art keywords
pressure
transfer printing
rail
photoconductor
sheet
Prior art date
Application number
PCT/EP1998/003638
Other languages
German (de)
French (fr)
Inventor
Helmut Naeser
Original Assignee
OCé PRINTING SYSTEMS GMBH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to DE19725860.3 priority Critical
Priority to DE19725860 priority
Application filed by OCé PRINTING SYSTEMS GMBH filed Critical OCé PRINTING SYSTEMS GMBH
Publication of WO1998058297A1 publication Critical patent/WO1998058297A1/en

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Classifications

    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03GELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00Apparatus for electrographic processes using a charge pattern
    • G03G15/14Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base
    • G03G15/16Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base of a toner pattern, e.g. a powder pattern, e.g. magnetic transfer
    • G03G15/163Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base of a toner pattern, e.g. a powder pattern, e.g. magnetic transfer using the force produced by an electrostatic transfer field formed between the second base and the electrographic recording member, e.g. transfer through an air gap
    • G03G15/1635Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base of a toner pattern, e.g. a powder pattern, e.g. magnetic transfer using the force produced by an electrostatic transfer field formed between the second base and the electrographic recording member, e.g. transfer through an air gap the field being produced by laying down an electrostatic charge behind the base or the recording member, e.g. by a corona device
    • G03G15/165Arrangements for supporting or transporting the second base in the transfer area, e.g. guides

Abstract

The invention relates to a transfer printing device for an electrophotographic single-sheet printer, containing a photoconductor in the form of a rotating drum (2) or a continuous belt, and a transport device for transporting the sheets through a transfer printing area (17) on said photoconductor. According to the invention, the sheets being printed (16) move essentially in the same direction and speed as the surface of the photoconductor. The inventive transfer printing device (8) contains at least one pressing element (22) for pressing the sheet (16) onto the photoconductor. The pressing element (s) (22) consists of an extended rigid rail and one or several elastic material strips attached thereto. The transfer printing device (8) contains an extended rigid support rail (20) to which the at least one pressing element (22) can be applied or from which it can be removed in its entirety.

Description

 description

Transfer printing device for electrophotographic single sheet printer and method for pressing a recording medium in such a transfer printing device

The invention relates to a transfer printing device for an electrophotographic single-sheet printer, which contains a photoconductor in the form of a rotating drum or an endless belt and a transport device for transporting sheets to be printed through a transfer printing area on the photoconductor, in which the sheets to be printed are essentially the same Direction of movement and speed as the surface of the photoconductor, wherein the transfer printing device contains at least one pressure element for pressing the sheet against the photoconductor.

In an electrophotographic printer, an electrostatic latent image is formed on a photoconductor, which is developed with toner that adheres to the photoconductor in accordance with the electrical charge pattern. The developed toner image is then transferred to paper, film or other media, which are fed to the photoconductor in the form of individual sheets in a single-sheet printer. The process of transferring the toner from the photoconductor to the sheets to be printed is called transfer or transfer printing.

In the transfer printing area, in which a sheet lies directly against the photoconductor covered with toner, the toner is transferred onto the sheet with the aid of electrical charge. The elec- 'trical charge is produced in general by a corotron, which acts with its electric field on the back of the resting on the photoconductor sheet part.

At the end of the transfer area, the sheet with the print image transferred onto it moves away from the photoconductor and becomes transported between fixing rollers, where the toner image is fixed on the sheet by pressure and temperature. A prerequisite for high transfer printing quality is that the sheet lies intimately on the photoconductor in the transfer printing area. This is particularly important when printing on the back of the sheet. When the front is fixed in advance, the arch loses most of its original moisture, whereby its surface can deform and unevenness can be formed. Even the smallest unevenness in the range of hundredths of a millimeter can have a negative impact on the transfer printing quality by creating pressure lightening, so-called voids.

A further improvement in the print image is achieved by avoiding the spraying of toner from the photoconductor to the recording medium before the recording medium lies intimately on the photoconductor. In this case one speaks of "fogginess".

There are single sheet printers in which the sheet is pressed against the photoconductor with springy elements such as metal brushes or foils. The disadvantage is the heavy soiling and wear of the pressure elements, which makes frequent replacement necessary. Not least because of the high demands on the positional accuracy of the pressure elements, this exchange is complicated and time-consuming and causes corresponding machine downtimes.

The object of the invention is to provide a transfer printing device for an electrophotographic single-sheet printer, the wear parts of which can be replaced very quickly and easily.

This object is achieved in a generic transfer printing device according to the invention in that the pressure element or each pressure element consists of an elongated rigid rail and one or more elastic material strips attached to it and that the transfer printing device is a Contains elongated rigid mounting rail, to which the at least one pressure element can be attached as a whole or can be removed therefrom.

The elastic strip of material forms the actual resilient element, which presses an arch directly onto the photoconductor, while the rigid rail of the pressure element in connection with the rigid mounting rail makes it easy to establish the correct mounting position, for example with the aid of adapters or a correlating design Pressure element and the mounting rail. Thus, the mounting rail holds and positions the pressure element including the material strip attached to it, without any adjustment work being necessary. The installation and removal of the pressure element can therefore be carried out very quickly and without having to work particularly carefully.

In a preferred embodiment, the at least one pressure element is pivotally mounted on the mounting rail in the installed state, the elastic material strip (s) depending on the pivoting position of the rigid rail of the pressure element pressing a sheet to be printed against the photoconductor or being at a distance from it. In addition, a drive device is provided for pivoting the at least one pressure element. This design allows the pressure element to be lifted from the photoconductor during the gap between two successive sheets, so that the photoconductor is not touched directly. This prevents damage or a reduction in the lifespan of the photoconductor.

The drive device, for example a lifting magnet with elements for transmitting force to the pressure element, can be attached to the mounting rail, like a corotron or any other device for electrically charging the back of a sheet lying against the photoconductor, so that the transfer printing device forms an interchangeable unit.

A special step to mechanically connect the pressure element during installation with the drive device is omitted if the drive device contains one or more rocker arms or plungers which are movably mounted on the mounting rail and which the at least one pressure element in the installed state is removed from the photoconductor - Touch the opposite side, the pressure element being held against the rocker arm or plunger by one or more springs.

A further development of the invention enables a pressure element, which is to be pivoted on the mounting rail in the manner described further above, to be mounted both quickly and precisely. In this embodiment, at least two bearing bolts protrude from the mounting rail, which are arranged at a distance from one another along the length of the mounting rail and each have a head with a spherical cross section. In addition, at least two bores are formed in the rigid rail of the pressure element or each pressure element, which are arranged at a distance from the bearing bolts along the length of the rigid rail of the pressure element and in each of which a head of a bearing bolt is fitted when the pressure element is on the mounting rail is attached. In this way, the pressure element can be pivoted onto the bearing pin at least in the small angular range required, and at the same time its position is precisely defined transversely to it.

In a preferred embodiment, the at least one pressure element is pivotally held between the mounting rail and a cover rail, which extends essentially over the entire length of the mounting rail. There are at least two adjustable stops on the support rail against which the cover rail can be pivoted, the cover rail being in a ner can be locked against the stops pivoted position and allows access to the pressure element in a position remote from the stops in order to be able to remove or install it.

The pressure force of the pressure element can be optimally dimensioned through the bending stiffness of the elastic material strip and through the adjustment of the magnetic rocker arm cap, so that the force is strong enough on the one hand that there are no bumps or voids and on the other hand is not so strong, that the coating of the photoconductor or an existing printed image on the sheet side facing the pressure element suffers damage. A suitably set pressure force ensures that the sheet fits snugly in the effective area of the corotron, and also ensures smooth running, since small speed differences between sheet feeding speed and surface speed of the photoconductor are compensated, which benefits the printing quality. The optimal position of the leading edge of the elastic material strip in the direction of sheet travel with respect to the transfer corotron prevents toner spraying or "fogginess".

Preferably, one or more springs are attached to the cover rail, which bias the pressure element in the installed state in a direction away from the photoconductor. To assemble or disassemble a pressure element, the machine operator releases the cover rail and swivels the cover rail upwards. The pressure element can then simply be removed or inserted.

'The side facing the photoconductor side of the cover preferably has a sheet guide profile which directs alone or in combination with a fixed to the cover rail Bogenfüh- the leading edge of a sheet approximately in the transfer printing sheet reliably. An easy-to-use locking device for the cover rail is formed by attaching an elongated latch, which is parallel to the axis of the cover rail and pointing outwards, at one end of the cover rail outside of the sheet track, and in that a pivotable, resiliently pretensioned element is attached to the end plate of the mounting rail or to the side wall of the printer housing Pawl is mounted, which holds the bolt and thus the cover rail in the position pivoted against the stops.

In the case of a printer which is set up for different sheet formats, it is expedient to provide a plurality of pressure elements arranged in a line, which together extend over the entire printing width and each have their own drive for the pivoting movement towards and away from the photoconductor. For example, a longer and a shorter pressure element can be used, the total length of which is e.g. corresponds to the maximum sheet format and which are driven synchronously in the case of the maximum sheet format. The length of the longer pressure element corresponds to the next smaller common sheet format, and if sheets are printed with the smaller format, the drive of the shorter pressure element is switched off. The shorter pressure element keeps a distance from the photoconductor so that it is not touched directly by the pressure element. Like the periodic lifting of the longer pressure element in the gaps between successive sheets, this ensures that the coating of the photoconductor is not damaged or worn by the pressure element.

Each pressure element preferably contains a coherent elastic material strip which extends essentially over the entire length of the pressure element and which is glued to an elongated flat surface of the pressure element. The elastic material strip preferably consists of a plastic film, with PET film (polyethylene terephthalate) or Mylar film being particularly has proven to be suitable, particularly with regard to the service life and the constancy of the pressing force.

In cases where a toner mark sensor is used to detect toner marks on the photoconductor, it can also be attached to the mounting rail. A further development of the pressure element allows the toner mark sensor to be arranged directly in front of the pressure point. For this purpose, the pressure element is provided with a hole through which the toner mark sensor extends. The front of the elastic material strip pointing towards the photoconductor is held in the area of the hole for the toner mark sensor by the parts of the material strip located on the side thereof, so that an arc is pressed evenly along its entire length despite the toner mark sensor arranged directly in front of the pressure point.

The mounting rail, the rigid rail of the pressure element or the cover rail are preferably made from an extruded aluminum material. In this way, any desired profile shape can be provided, and the rails can be made particularly rigid. In addition, a low weight is possible, which is particularly important for the pressure element that moves back and forth relatively quickly.

Existing printers can easily be converted for the pressure element described, since only very few parts need to be changed. The electrical charge conditions in the area of the corotron are not changed by the pressure element. With the swivel-driven pressure element, the pressure can begin immediately behind the leading edge of the sheet and end close to the trailing edge of the sheet, so that the highest print quality is guaranteed up to the leading and trailing edge of the sheet. The transfer printing device according to the invention is particularly economical both in the manufacture of parts and in operation. The device can be accommodated in the smallest space and is nevertheless easily accessible. The only component with significant wear is the pressure element, which can also be easily replaced by the operating personnel.

The invention also relates to a method for pressing a sheet-shaped recording medium onto the transfer printing device of an electrophotographic printing or copying device. In this case, two asymmetrically designed pressure elements are provided, so that the recording medium can be pressed depending on the format. If the front edge of the recording medium corresponds to the smaller of the two pressure elements, only this pressure element is activated, otherwise both pressure elements are activated. The activation is preferably accomplished with solenoids that are controlled by an electronic control. A sensor can detect the width of the respective recording medium and a sensor signal can be used to activate the solenoids. Finally, a sensor can be provided which detects the front edge of the sheet and activates the pressure elements in a time-controlled manner in such a way that they move to the photoconductor of the transfer printing device at exactly the moment at which the front edge of the recording medium arrives at the photoconductor.

By providing the two pressure elements of different sizes, it is easily possible to replace one of the two pressure elements in the event of wear. In addition, only one pressure element often has to be exchanged if predominantly small sheet formats are printed.

An exemplary embodiment of the invention is explained below with reference to the figures. In it show:

FIG. 1 shows a cross section through a transfer printing device,

Figures 2A, 2B and 2C detailed views of a pressure element,

FIGS. 3A and 3B show more detailed representations of the transfer printing device from FIG. 1 in the drive region of a pressure element,

FIG. 4 shows a partial cross section through a mounting rail and a cover rail of the transfer printing device in the region of a screw stop,

FIG. 5 shows a partial cross section through the transfer printing device in the area of a toner mark sensor,

Figures 6A and 6B two top views of a drive assembly, and

Figures 7A, and 7B detailed views of the cover rail.

1 shows part of a photoconductor drum 2 in a single sheet electrophotographic printer. Below the photoconductor drum 2, the following assemblies are arranged in the figure from right to left: two sheet feed rollers 4, 6, a transfer printing device 8 and a sheet transport device 10, consisting of a deflection roller 12 and a conveyor belt 14 rotating around it extends to a fixing station, not shown.

The photoconductor drum 2, the sheet feed rollers 4, 6, the deflecting roller 12 and the conveyor belt 14 rotate or move in the directions indicated by arrows, around sheets 16 from a sheet feeder, not shown, through a transfer area 17 outlined with a dash-dotted line to convey the photoconductor drum 2 and then onto the conveyor belt 14.

In addition to the assemblies shown in the figure, the following assemblies are arranged one after the other on the circumference of the photoconductor drum 2, which are not shown in the figure: a charging device for uniformly charging the surface of the photoconductor drum 2, an exposure device for exposing the surface of the photoconductor drum 2 in accordance with one printing typeface, whereby an electrostatic latent charge pattern is formed on the photoconductor drum 2, which corresponds to the desired typeface, and a developing device for developing the latent charge pattern with toner, whereby a toner distribution corresponding to the desired typeface is formed on the photoconductor drum 2.

The toner image on the photoconductor drum 2 is transferred or transferred to a sheet 16 at the transfer printing device 8 by bringing the sheet 16 into close contact with the photoconductor drum 2 over an angular range of the photoconductor drum 2 and at the same time applying charge to its rear side that of the toner particles is opposite. The charges are generated by a corona discharge in a corotron 18.

The corotron 18 is fastened to a mounting rail 20 made of an extruded aluminum profile, which extends over a little more than the width of the photoconductor drum 2 and is removably attached to the side walls of the printer housing.

In addition to various other elements, which will be explained further below, two pressure elements 22, a longer and a shorter one, are mounted on the mounting rail 20, which extend together over the entire width of the photoconductor drum 2, have the same cross section and are arranged in a line immediately one behind the other are. A cross section through the pressure elements 22 is shown in FIGS. 2A and 2B, FIG. 2B being approximately to scale and FIG. 2A representing an approximately ten-fold magnification. Each pressure element 22 consists of a rigid rail 24 made of an extruded aluminum profile which has a flat surface on which an elastic material strip 28 is glued by means of a layer of adhesive 26. The elastic material strip 28 is a flat piece of PET film (polyethylene terephthalate film) or Mylar film, which is as long as the rail 24 and much wider than the adhesive surface on the rail 24.

A top view of one of the pressure elements 22, namely the longer pressure element 22, is shown in FIG. 2C. In the middle of the entire surface of the pressure element 22, a rectangular cutout or hole 27 is formed, the function of which is explained below. At both ends of the pressure element 22 and close to the edge of the pressure element 22 facing away from the elastic material strip 28 there is a circular hole 30 in each case. In FIG. 2A, a dash-dotted line 32 indicates the position of the axes of the holes 30.

In Fig. 2C, a dash-dotted line 34 indicates a pivot axis of the pressure element 22, around which the pressure element 22 is pivoted in time with the supplied sheets 16 (Fig. 1) against the photoconductor drum 2, so that the free edge of the elastic material strip 28 Presses sheet 16 over its entire length against the photoconductor drum 2 with a defined pressing force, but not in the spaces between successive sheets 16.

3A is a more detailed sectional view through a part of the transfer printing device 8, in which the pressure element 22 is mounted. The mounting rail 20 contains an approximately horizontal profile section, on the upper side thereof an elongate bead 36 is formed on which the pressure element 22 can be supported along its pivot axis 34.

A bearing bolt 38 is screwed into the support rail 20 at two points along the bead 36 at a distance from the bores 30 in the pressure element 22, as shown in FIG. 3B. Each bearing pin 38 has a head 40 which is spherical in a central part and whose diameter is precisely adapted to the diameter of the bores 30 in the pressure element 22. The bores 30 of the pressure element 22 are plugged onto the heads 40 of the bearing bolts 38, whereby the pressure element 22 can be pivoted in a suitable angular range around its pivot axis 34 and is also fixed transversely to the axis of the bearing bolt 38, so that the pressure point of the leading edge of the elastic Material strip 28 on the photoconductor drum 2 when pivoting the pressure element 22 against the photoconductor drum 2 is precisely defined.

Above the pressure element 22, i.e. towards the photoconductor drum 2, there is an elongated rigid cover rail 41 made of an extruded aluminum profile, which covers the rigid rails 24 of the two pressure elements 22 along their entire length, the elastic material strip 28 protruding towards the front in the direction of the photoconductor drum 2. On the edge of the cover rail 41 remote from the photoconductor drum 2, an elongated bearing shell 42 is formed, which is mounted in bearing bolts 44 (FIGS. 4, 7A), which are located outside the sheet track on end plates of the carrier rail 20 or on side walls of the printer housing are attached.

On the inside of the cover rail 41 facing the pressure element 22, an elongated bead 46 is formed, which lies opposite the bead 36 on the support rail 20 when the cover rail 41 is pivoted in the direction of the pressure element 22, the rigid rail 24 of the pressure learning tes 22 is held on the pivot axis 34 between the beads 36 and 46.

The transfer area is an integral part of the fixing station unit and can be used to pull it out of the press on slide rails. The cover rail 41 is thus free and can be pivoted upwards around the bearing bolts 44, the pressure element 22 becoming accessible and being able to be removed upwards by simply being plugged onto the heads 40 of the bearing bolts 38.

The cover rail 41 has on its outside facing the photoconductor drum 2 an arc-guiding contour in the form of a smooth, convex surface, along which a supplied arc 16 can slide, the arc 16 being passed between the convex surface and an arc guide plate 48, which is on it longitudinal ends outside the sheet track is attached to the cover rail 41.

On the inside of the cover rail 41 facing the pressure element 22, at least one leaf spring 50 is fastened, which presses against a bead 52 (best seen in FIG. 2A) on the upper side of the rigid rail 24. The leaf spring 50 presses the rigid rail 24 of the longer pressure element 22 against lever arms of second rocker arms 54, which are rotatably mounted on the support rail 20 at a distance from one another. In the case of the shorter pressure element 22, only one rocker arm 56 (FIG. 6A) is provided. The formation of the rocker arms 54, 56 and their drive are explained in more detail below.

The rocker arms 54, 56 can be moved by means of their drive so that the pressure element 22 is pivoted upward, so that the front edge of the elastic material strip 28 of the pressure element 22 presses against the photoconductor drum 2. In the closed state of the cover rail 41, the leaf spring 50 acts as an opening spring for automatically lifting the elastic material strip 28 from the photoconductor drum 2 as soon as the rocker arms 54, 56 are retracted.

The support rail 20 and the cover rail 41 are each somewhat longer than the total printing width or the total length of the pressure elements 22, and FIG. 4 shows a cross section through part of the support rail 20 and the cover rail 41 in the region of their longitudinal ends. In this area, the bulge 36 on the support rail 20 and the bulge 46 on the cover rail 41, which lie opposite one another, can best be recognized. In addition, one of the bearing bolts 44 can be seen on a side wall of the printer housing or on an end plate of the mounting rail 20, on which the bearing shell 42 of the cover rail 41 is seated.

As can be seen in FIG. 4, screw stops 58 are also screwed into the approximately horizontal profile section of the mounting rail 20 on which the bead 36 is formed. Two screw stops 58 are provided, one at each longitudinal end of the mounting rail 20.

The screw stops 58 form adjustable stops for the cover rail 41 and define their rest position pivoted against the support rail 20, in which the cover rail 41 can be locked, as will be explained in more detail below. When the lock is released, the cover rail 41 pivots upward in the direction of the arrow shown in FIG. 4 by the action of springs, not shown, whereby the pressure elements 22 are accessible and can be easily replaced by simply using their bores 30 (FIG. 2C) are placed over the heads 40 of the bearing bolts 38 (FIG. 3B).

5 is a more detailed sectional view through the part of the transfer printing device 8 in the region of the longitudinal center of the longer of the two pressure elements 22, ie in the region of the rectangular hole 27 in the pressure element 22 (cf. 2C). 5, however, the pressure element 22 is not shown completely in order to simplify the illustration. Only the front of the elastic material strip 28 can be seen, which in FIG. 5 just presses an arc 16 against the photoconductor drum 2 and is therefore curved.

As shown in FIG. 5, a toner mark sensor 60 is attached to the mounting rail 20 and extends through the hole 27 in the pressure element 22. The toner mark sensor 60 has a protective plastic housing 62, which is fastened below the approximately horizontal profile section of the mounting rail 20, on which the pressure element 22 rests. The toner mark sensor 60 is covered with a glass body 64 toward the photoconductor drum 2 or toward the sheets 16. The toner mark sensor 60 is used to detect toner marks on the photoconductor drum 2 in order to regulate the contrast of the printed image.

A cable harness 66 for wiring the toner mark sensor 60 is laid parallel to the mounting rail 20, as can be seen in FIG. 3A, specifically below the approximately horizontal profile section of the mounting rail 20 on which the pressure element 22 rests. In this way, the cable harness 66 can be routed to the outside without any problems, without interfering with the actuating mechanism.

In FIG. 5, one of a plurality of screws 68 extends through the mounting rail 20 for fastening a magnetic carrier 70, which is an assembly which extends along the length of the mounting rail 20 and which has a drive device for moving the pressing elements 22 for pressing the sheets 16 against one another represents the photoconductor drum 2.

6A and 6B are two views of the magnet carrier 70 corresponding to a view from the left and from above in FIG. 5.

The magnet carrier 70 is an elongated rigid rail with a lifting magnet 72, 74 at the longitudinal ends thereof is attached. The armature of the lifting magnet 72 is connected to the rocker arm 56 for the shorter pressure element 22 via a tab 76, and the armature of the lifting magnet 74 is connected to the two rocker arms 54 for the longer pressure element 22 via a tab 78 and a pull rod 80.

In connection with FIG. 3A, in which a section through the magnet carrier 70 along the line IIIA-IIIA in FIG. 6A is shown, it has already been mentioned that the upward-pointing lever arms of the rocker arms 54, 56 are the rigid rails 24 of FIG Touch the pressure elements 22 and press them upwards when the lifting magnets 72, 74 attract, so that the elastic material strips 28 of the pressure elements 22 press a sheet 16 against the photoconductor drum 2 in the transfer area 17.

The rocker arms 54 and 56 are made of a suitable plastic in order to reduce the friction on the rigid rails 24 of the pressure elements 22. The magnet carrier 70 is fastened to the mounting rail 20 of the transfer printing device 8 with three screws 68.

The two solenoids 72, 74 have different tightening forces. The stronger lifting magnet 74 actuates the longer pressing element 22, on which two rocker arms 54 press symmetrically, and the weaker lifting magnet 72 actuates the shorter pressing element 22, on which the rocker arm 56 presses. The anchor stroke is approx. 2 mm each. The armatures of the lifting magnets 72, 74 are adjusted by means of adjusting screws 82 accessible from the side so that they reach their end positions, in which they develop the greatest force, after this 2 mm stroke.

In addition, the rocker arm height position relative to the magnet carrier 70 can be set relative to the armature stroke (see dimension b in FIG. 6A). The setting is made via an elongated hole 90 machined in the magnet carrier 70. The pivoting height and pivoting height can thus be precisely determined. The spring action of the pressure elements 22, which is generated by the leaf springs 50 on the cover rail 41, and return springs integrated in the lifting magnets 72, 74 ensure that the magnet armatures are reset after the pressing process has ended. Solenoids 72, 74 with maintenance-free armature bearings (DU bearings) have been selected for the longest possible service life.

The solenoids 72, 74 can work independently of one another. In the case of a smaller sheet format, the front edge of which corresponds to the length of the longer pressure element 22, only the lifting magnet 74 works in time with the supplied sheets 16 in order to press the pressure element 22 against a sheet 16 and thus against the photoconductor drum 2, in which it is Gap between two successive sheets 16 is lifted from the photoconductor drum 2. In the case of a larger sheet format, which corresponds to the maximum printing width, the lifting magnet 72 is switched on in order to drive the shorter pressing element 22 synchronously with the longer pressing element 22. If more than two standard sheet formats are desired, the transfer printing device 8 is simply provided with additional pressure elements 22.

7A and 7B show further details of the cover rail 41, wherein FIG. 7A is a sectional view through an end of the cover rail 41 lying outside the sheet path and FIG. 7B is a plan view of the cover rail 41. A line IIIA - IIIA in FIG. 7B shows the sectional view of the cover rail 41 in FIG. 3A.

On the side of the cover rail 41 facing away from the operator and on its longitudinal edge remote from the bearing shell 42, an elongated latch 84 is fastened by means of rivets 86. The latch 84 extends a little beyond an end plate 88 of the transfer printing device 8, which extends transversely to the length of the mounting rail 20. The protruding beyond the end plate 88 the upright end of the bolt 84 forms a handle for manually pivoting the cover rail 41 with respect to the mounting rail 20. In the closed position of the cover rail 41 pivoted against the mounting rail 20 or the pressing elements 22, the bolt 84 arrives with a spring (not shown) biased pawl, which is mounted on the end plate 88 and which holds the cover rail 41 in the position defined by the adjusting screws 58 (Fig. 4). The pawl can be released by hand in order to release the bolt 84 and to be able to pivot the cover rail 41 upwards.

7A and 7B, one of the bearing bolts 44 for the cover rail 40 is also visible, which is fastened to the end plate 88 and projects into the bearing shell 42 of the cover rail 40.

FIG. 7B also shows one of the leaf springs 50 which are fastened on the underside of the cover rail 41. The leaf springs 50 constantly press the rigid rails 24 of the pressure elements 22 against the rocker arms 54, 56 when the cover rail 41 is closed, cf. also Fig. 3A.

7B, the sheet guide plate 48 can be seen, which extends on the convex upper side of the cover rail 41 and is riveted to it in the region of its ends. In the area of the sheet track there is a space between the top of the cover rail 41 and the sheet guide plate 48, through which the sheets 16 pass during operation, as can be seen in FIGS. 3A and 5. Reference list

2 photoconductor drum

4, 6 sheet feed rollers 8 transfer printing device

10 sheet transport device

12 deflection roller

14 conveyor belt

16 sheets 17 transfer area

18 corotron

20 mounting rail

22 pressure elements

24 rigid rails 26 layers of adhesive

27 holes

28 elastic material strips 30 holes

32 axis of the bore 34 pivot axis of the pressure element

36 Bead on the mounting rail

38 bearing bolts

40 head of the bearing pin

41 Cover rail 42 Bearing shell

44 bearing bolts

46 Bead on the cover rail 8 sheet guide plate 0 leaf spring 2 bead on the pressure element 4, 56 rocker arm 8 screw stop

60 toner mark sensor 2 plastic housing 4 glass body 6 cable harness 8 screw Magnetic carrier, 74 lifting magnet, 78 tab

pull bar

Set screw

bars

rivet

End plate

Long hole

Rocker cap

Claims

Expectations
1. Transfer device for an electrophotographic single sheet printer, which contains a photoconductor in the form of a rotating drum or an endless belt and a transport device for transporting sheets to be printed through a transfer area on the photoconductor, in which the sheets to be printed are essentially the same Movement direction and speed as the surface of the photoconductor, wherein the transfer printing device contains at least one pressure element for pressing the sheets onto the photoconductor, characterized in that the pressure element or each pressure element (22) consists of an elongate rigid rail (24) and one or more thereon attached elastic material strips
(28) and that the transfer printing device (8) contains an elongated rigid support rail (20) to which the at least one pressure element can be attached as a whole or can be removed therefrom.
2. Transfer device according to claim 1, characterized in that the at least one pressure element (22) is pivotally mounted on the mounting rail (20) in the installed state, the elastic material strip (28) depending on the pivoting position of the rigid rail (24 ) of the pressure element press a sheet (16) to be printed against the photoconductor (2) or are at a distance from it, and that a drive device (54, 56, 70, 72, 74, 76, 78, 80) for pivoting the at least one a pressure element is provided.
3. Transfer printing device according to claim 2, characterized in that the drive device (54, 56, 70, 72, 74, 76, 78, 80) is attached to the mounting rail (20).
4. Transfer printing device according to claim 2 or 3, characterized in that the drive device contains one or more rocker arms (54, 56) or plunger which are mounted on the mounting rail (20) and which the at least one pressure element (22) in the installed state touch its side facing away from the photoconductor (2), the pressure element being held against the rocker arm or tappets by one or more springs (50).
5. Transfer printing device according to one of the preceding claims, characterized in that at least two bearing bolts (38) protrude from the support rail (20), which are arranged at a distance from one another along the length of the support rail and each have a head (40) with one have a spherical cross-section, and that in the rigid rail (24) of the pressure element or each pressure element (22) at least two bores (30) are formed, which are arranged at a distance from the bearing bolts (38) along the length of the rigid rail of the pressure element and in each of which a head of a bearing pin is received in a snug fit when the pressure element is attached to the mounting rail.
6. Transfer printing device according to one of the preceding claims, characterized by a pivotably mounted cover rail (41) which extends substantially over the entire length of the mounting rail (20), at least two adjustable stops (58) being provided on the mounting rail against which the cover rail (41) can be pivoted, the cover rail being lockable in a position pivoted against the stops, in which the at least one pressure element (22) is pivotally held between the mounting rail and the cover rail, and in a position remote from the stops Access to the at least one pressure element allowed.
7. transfer printing device according to claim 6, characterized in that on the cover rail (41) one or more springs (50) are attached, which bias the pressure element (22) in the installed state in a direction away from the photoconductor (2).
8. Transfer printing device according to claim 6 or 7, characterized in that the side of the cover rail (41) facing the photoconductor (2) has a sheet guiding profile.
9. transfer printing device according to claim 8, characterized in that on the side of the cover rail (41) facing the photoconductor (2) also a sheet guide plate (48) is fixed, wherein a sheet to be printed (16) runs between the sheet guide profile and the sheet guide plate.
10. Transfer printing device according to one of claims 6 to 9, characterized in that at one end of the cover rail
(41) an elongated bolt (84) is fastened outside the sheet track and parallel to the axis of the cover rail and that a pivotable, spring-loaded latch is mounted on end plates of the carrier rail (20) or on the side walls of the printer housing, which latch ( 84) and thus holds the cover rail (41) in the position pivoted against the stops (58).
11. Transfer printing device according to one of the preceding claims, characterized in that on the mounting rail (20) a device for electrically charging the back of an on the photoconductor (2) adjacent sheet (16) is attached.
12. Transfer printing device according to one of the preceding claims, characterized in that on the mounting rail (20) a toner mark sensor (60) for detecting the toner contrast is also attached, the pressure element or at least one of the pressure elements (22) having a hole
(27), through which the toner mark sensor (60) extends, the toner mark sensor pointing to one
Aim on the photoconductor that lies in the sheet transport direction in front of the pressure point of the sheet (16) on the photoconductor (2).
13. Transfer printing device according to one of the preceding claims, characterized in that at least two pressure elements (22) arranged in a line are provided, which together extend over the entire printing width and each have their own drive (54; 56) for the pivoting movement on the Have photoconductor (2) closed and away from it.
14. Transfer printing device according to one of the preceding claims, characterized in that each pressure element (22) has a coherent elastic material strip
(28), which extends substantially over the entire length of the pressure element and which is glued to an elongated flat surface of the pressure element.
15. Transfer printing device according to claim 14, characterized in that the elastic material strip (28) consists of plastic.
16. Transfer printing device according to claim 15, characterized in that the elastic material strip (28) consists of PET film or Mylar film.
17. Transfer printing device according to one of the preceding claims, characterized in that the support rail (20), the rigid rail (24) of the pressure element (22) and / or the cover rail (41) each consist of an aluminum strand material.
18. Transfer printing device according to one of the preceding claims, characterized in that when successive sheets pass by, the pressure element (22) is pivoted away during the occurrence of a gap between the sheets so as not to injure the photoconductor.
19. A method for pressing a sheet-shaped recording medium onto the transfer printing device of an electrophotographic printing or copying device, wherein a first, smaller pressure element (22) and a second, larger pressure element (22) are provided, which are activated in a format-dependent manner such that only the smaller of the two pressure elements (22) is moved towards a photoconductor drum (2) of the transfer printing device if the front edge of the recording medium corresponds to the smaller of the two pressure elements (22) and both pressure elements (22) are activated when that Format of the recording medium corresponds to a predetermined maximum print width.
20. The method according to claim 19, wherein two independently controllable to activate the pressure elements
Solenoids are used.
21. The method according to claim 19 or 20, wherein the two pressure elements are moved synchronously to one another if the format of the recording medium corresponds to the predetermined maximum printing width.
22. The method according to any one of claims 19 to 21, characterized in that the transfer printing device is designed according to one of claims 1 to 18.
PCT/EP1998/003638 1997-06-18 1998-06-17 Transfer printing device for an electrophotographic single-sheet printer and method for pressing a record carrier in a transfer printing device of this type WO1998058297A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
DE19725860.3 1997-06-18
DE19725860 1997-06-18

Publications (1)

Publication Number Publication Date
WO1998058297A1 true WO1998058297A1 (en) 1998-12-23

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ID=7832903

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP1998/003638 WO1998058297A1 (en) 1997-06-18 1998-06-17 Transfer printing device for an electrophotographic single-sheet printer and method for pressing a record carrier in a transfer printing device of this type

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Cited By (1)

* Cited by examiner, † Cited by third party
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US7466935B2 (en) 2002-10-10 2008-12-16 Oce Printing Systems Gmbh Transferring and fixing system and method using a guided conveyor section and a free conveyor section

Citations (7)

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Publication number Priority date Publication date Assignee Title
DE2702110A1 (en) * 1976-01-19 1977-07-28 Konishiroku Photo Ind Bilduebertragungs-accessory device for an electrophotographic kopiergeraet
GB2207424A (en) * 1987-07-21 1989-02-01 Mita Industrial Co Ltd Guiding paper
EP0388342A2 (en) * 1989-03-17 1990-09-19 International Business Machines Corporation Electrophotographic machine with efficient transfer
US5300994A (en) * 1993-04-29 1994-04-05 Xerox Corporation Transfer system including a cam actuated segmented flexible transfer assist blade
US5300993A (en) * 1993-04-29 1994-04-05 Xerox Corporation Transfer assist apparatus
US5400125A (en) * 1993-10-01 1995-03-21 Siemens Aktiengesellschaft Transfer station with pressure element for an electrographic printer or copier means
US5568238A (en) * 1995-11-20 1996-10-22 Xerox Corporation Transfer assist apparatus having a conductive blade member

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Publication number Priority date Publication date Assignee Title
DE2702110A1 (en) * 1976-01-19 1977-07-28 Konishiroku Photo Ind Bilduebertragungs-accessory device for an electrophotographic kopiergeraet
GB2207424A (en) * 1987-07-21 1989-02-01 Mita Industrial Co Ltd Guiding paper
EP0388342A2 (en) * 1989-03-17 1990-09-19 International Business Machines Corporation Electrophotographic machine with efficient transfer
US5300994A (en) * 1993-04-29 1994-04-05 Xerox Corporation Transfer system including a cam actuated segmented flexible transfer assist blade
US5300993A (en) * 1993-04-29 1994-04-05 Xerox Corporation Transfer assist apparatus
US5400125A (en) * 1993-10-01 1995-03-21 Siemens Aktiengesellschaft Transfer station with pressure element for an electrographic printer or copier means
US5568238A (en) * 1995-11-20 1996-10-22 Xerox Corporation Transfer assist apparatus having a conductive blade member

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"CONSTANT FORCE TRANSFER FLAP TO ELIMINATE VOIDS ON SIDE TWO OF ELECTROPHOTOGRAPHIC PRINTER/COPIER OUTPUT", IBM TECHNICAL DISCLOSURE BULLETIN, vol. 33, no. 8, 1 January 1991 (1991-01-01), pages 72 - 75, XP000106998 *

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Publication number Priority date Publication date Assignee Title
US7466935B2 (en) 2002-10-10 2008-12-16 Oce Printing Systems Gmbh Transferring and fixing system and method using a guided conveyor section and a free conveyor section

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