DE2032371A1 - Leaf removal device - Google Patents

Description

Patent attorneys Dipl ..- Ing. F. Weickmann, 2032371

. DIPL-INCH-WEICKMANN ₉ DIPL-PHYS-Dr-K-FINCKE

Dipl.-Ing. F. A-Weickmann, Dipl.-Chem. B. Huber

8 MUNICH 86, DEN

. PO Box 860 820

^X - MÖHLSTRASSE 22, CALL NUMBER 48 3921/22

XEROX CORPORATION, Rochester, NoT. 14603, V. St A.

Sheet peeling device

The invention relates to a device for detaching a sheet from a moving sheet carrier _f, in particular for a copy sheet arranged on a recording drum in an electrophotographic copying machine _{or the like}

In the electrophotographic process, a photoconductive Evenly electrostatically charged on a zeiohnungsf lache and then with a light image of the to be reproduced Originals exposed · As a result, the charge in the exposed parts is selectively diverted »so that a latent electrostatic image is generated. This can develop through the attraction of oppositely charged toner particles that are brought close to the picture surface. That The developed image is then transferred to another image carrier Transferred form of a copy sheet and generated on this a permanent record of the copied original

Ale copy sheet is a non-conductive material, such as paper, used · It is placed on the image-bearing fotoleitfähig * Aufzeiohnungsfläohö and subjected on its back side an electrical discharge * Daduroh formed on the sheet a leäufcg Rua, dl "cluroh their

203237]

The strength and polarity cause an electrostatic attraction of the toner particles from the photoconductive recording surface to the copy sheet *. During this image transfer, however in the paper, a charge existing in the unexposed Fläehenteilen the recording surface charge opposite induced, thereby the copy sheet is electrostatically adhered to the recording surface _e The removal of the copy sheet and loosely to it adhering toner image is in the electrophotographic process, a problem _e

Mechanical detachment devices have already been used with varying degrees of success for removing copy sheets from a moving photoconductive recording surface in automatic electrophotographic reproduction machines at the bottom, for example on the lower part of an electrophotographic drum tmengje Luf necessary and Luftgesohwindigkeit work such Geblä- '· sevorrichtungen with noise and are therefore unwanted they also produce contamination because the airflow loose toner particles by the Reproduktionsmaschi ne moves »Often critical machine parts are heavily soiled by the associated accumulation« * length of the synthetic hara powder

The main disadvantage of the blower devices and other me * · However, unhealthy detachment means consists in that They only work properly »when they are down on one photoconductive Aufzelohttungefliehe elnwirkeju ÖTwoal these

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. ■ ..;. ■ _"::; ■ -" ORIGINAL INSPECTED

The most effective arrangement for the detachment of the leaf, Practical considerations speak against it, since this results in the location of the various electrophotographic process devices In a production machine working with a recording drum, the detachment device had to be restricted previously located at the lowest, relatively inaccessible Troramelbereioh instead of at the top of the drum be, which required long and winding paper transport routes and complicated transport facilities «, ,

With different "success, the electrostatic separation is applied" In this method, the copy sheet to the photoconductive recording surface holding electrostatic forces by the action of a second _s corona discharge of sufficient strength and polarity can be eliminated, so that the electrostatic bond is overcome between the copy sheet and the recording surface · In this process, the copy sheet with the toner image attached to the looker is moved past a peeling orotron. After this neutralization of the electrostatic charges holding the sheet on the recording surface, the copy sheet can fall off the photoconductive recording surface by gravity. It is then picked up by a conveying device and fed to a process station following «*.

The object of the invention is to provide a device for Replacement of the copy sheet a to create the above avoids the disadvantages mentioned and in particular enables detachment at the top of a recording drum

To solve this problem sioh draws a device from

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initially mentioned type according to the invention by a lifting finger touching the sheet carrier for. Lifting and diverting of the leading edge of the sheet, to which a stationary guide is assigned which guides the sheet on a predetermined path, and by a vacuum device arranged on the guide for lifting the sheet from the lifting finger and placing it against the guide surface.

An embodiment of the invention is based on the following of the figures described »They show:

Figo1 the schematic representation of an automatically operating electrophotographic reproduction machine,> equipped with a device according to the invention is,

Figo2 shows the side view of the device according to the invention when the leading edge of a copy sheet lifts off a rotating drum surface,

Figo3 shows the side view of the device according to the invention not when the copy sheet is advanced along the guide surface in one of the drum surface touching position of the lifting finger,

4 shows a perspective illustration of the actuating mechanism for the lifting finger and

Figure 5 shows the internal construction of the stationary guide shown in Figure 2.

The automatic electrophotographic shown in Figol Reproduction machine includes an electrophotographic recording surface 10 with a photoconductive surface on a conductive surface in the form of a drum and on the horizontal shaft 1.2 in the machine frame (not shown) is rotatably mounted »It is shown in the Arrow direction with their surface one after the other at a number of electrodhotographic process stations in front of «

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beibewegto

The various process stations are regarding their function is briefly described below

At a charging station A, a uniform electrostatic charge is applied to the photoconductive layer of the drum angry

At an exposure station B, a light or radiation pattern is created of an original to be reproduced is projected onto the drum surface, reducing the charge present on it in the irradiated areas and distorted a latent electrostatic image A development station C is an electrophotographer erases developer material, the toner particles with one of the Drum charge contains opposite charge, cascaded across the drum surface, causing the toner particles to adhere adhere to the electrostatic latent image and visibly maoheno this in the configuration corresponding to the original

At an image transfer point D, the electrophotographic Electrostatic powder image from the drum surface transferred to an image carrier and this erfläohe detached from the drum object and

at a Trommelreinigungs- and toner collecting station E the Trommeloberfläohe is first treated by a corona discharge and then wiped with a Abstreiohblatt 'to collect all restliohen toner particles to remove and re-use in the elektrofotografisohen method _e Further, the Trommeloberfläohe is uniformly illuminated to a to achieve practically complete dissipation of any residual electrostatic charges.

In the embodiment shown, the charging station is A. placed near the lowest point of the drum as a drawer

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• - 6 -

The device is a corona discharge device 13, which contains one or more discharge electrodes which run across the drum surface and are fed by a high voltage source (not shown) ₀ The discharge electrodes are arranged within a shield which limits the discharge to the drum

At the lighting station B, a continuous photo is taken of a stationary original is projected onto the moving drum surface «» The optical scanning and projection device includes a stationary and transparent platen 14 on which the original to be copied is placed o! There is also an illumination lamp LMP-1 provided, which illuminates the original evenly A scanning system consisting of an object mirror 16, an image mirror 18 and an optical system 17 projects one after the other Image surface elements of the original on the drum surface. The optics are arranged and moved under the platen are parallel to their plane, making the original temporally related to the movement of the photosensitive Drum surface is scanned. "

The development station 0 follows the exposure station, having a housing 28 and a lower reservoir portion is disposed on the developing means 20, in · which a supply amount of a two-component developer is provided "A with I ¹ O rd heritage brass-provided conveyor 27 'connected to A drive device is coupled »serves to move the Ent« wioklerstoffes from the Vorratsfoereicfa. to the top of the housing development where he "gets into AEEN! experienced 29 He moved SiOH then down to u ± e upward moving f otole-it '' capable Trommeloberfläolia uai is AiAF. iies © Weis © in Sen picture area parts corresponding to there vorhami ©! i®ja.- ladiaag deposited ι ao that a developed © le? xte © fotögrafiii © li © s image "is created" Ser not used Bntiffloklwag; «* Ea- * ewi @ fc »

-7 -: ■■■■; ■■ ·. ■■■ ■. ■ ', -. *

Material falls from the development zone back into the lower part of the development housing, where new electrophotographic Toner according to the toner consumption with a refill device 21 is entered.

The development station is followed by the image transfer station Do. Here, individual copy sheets are fed one after the other with an alignment and conveying device 22 either from an upper sheet compartment 34 or a lower sheet feeder 35. According to their alignment, they pass through the registration rollers 52 and 53 i * ¹ contact with the drum surface. The developed image is then electrostatically transferred from this pad to a copy sheet using the transfer corotron 24. As will be explained in more detail below, the copy sheet is then lifted from the drum surface and transported along a stationary guide 26 into the fuser 30 ".

The copy sheet provided with the image and detached from the drum surface is guided along the stationary guide 26 into the gap between the upper fixing roller 31 and the lower fixing roller 32. Both rollers are rotated in the direction shown and generate pressure and heat on the Copy sheet, which fuses the toner image onto it.

After exiting the fuser, the copy sheet becomes via a curved path on a movable guide and Drive roller assembly 36 brought this guide can be preset so that the sheet either in the upper Sheet compartment 35 or in an output compartment 37. The machine can be controlled in such a way that copies printed on one side are fed into the upper sheet compartment 35, from which they are again passed through the machine to at the image transfer station to take another picture on their other side »

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At the drum cleaning and toner collecting station B there is more Toner on the drum surface first from a corona discharge device 39, the electrostatic bond between the residual toner and the drum surface neutralized. The remaining toner is then directed into a toner cleaning and recycling housing 40 where he from "the drum surface with a doctor blade (not The removed toner is transported with a screw conveyor along the drum surface and collected in the collecting part of the housing 40, it then gets back into the developing housing via conveyor tubes 41 for which purpose an endless conveyor is provided

The above description concerns the general operation of an electrophotographic reproduction machine, which is equipped with a release device according to the invention. This enables the copy sheets to be removed from the top of the electrophotographic drum. Through this novel arrangement it is possible to produce double-sided copies in a reproduction machine working with drum, with a minimal amount of space and paper handling mechanisms. To drive the drum, the conveyor mechanisms, the developing device and other devices each with predetermined and mutually adapted Speed, a drive unit (not shown) is "provided"

In the device shown in Figures 2 to 5, a copy sheet 50 is made from one of the sheet feeders 34 and 35 (lPig.1) moved to a stop 51 of the alignment roller 52. The forward movement of the respective leading edge of the sheet becomes duroh interrupted the stop momentarily for a time that allowed proper alignment of the sheet with the stop Then the pinch rollers 53 are brought up to the sheet, and the sheet is driven by one of the gears 54 and 55

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acting control mechanism quickly on the drum speed accelerated When it reaches the drum speed, so it is pushed up to the drum surface with an auxiliary device (not shown) so that both move at the same speed to transfer station D

The transfer corotron 24 is located at the transfer station just after the point where the copy sheet comes into contact with the drum surface. It causes an electrostatic charge on the click side of the copy sheet, which is not in contact with the drum surface ο This takes place through a uniform emission of ions, the polarity of which is opposite to that of the toner particles This creates a charge on the back of the copy sheet generated, 'whose strength to attract the toner particles of the drum surface on the copy sheet is sufficient. The transmission corotron generated; however, also a .even charge in the unexposed parts of the drum surface. The emission acting on the paper in the non-exposed parts of the surface induces a charge in the paper, which is opposite to the charge of the electrophotographic drum o Duroh this charge distribution is in the non-irradiated surface areas an electrostatic Draws the copy sheet to the drum surface holds on »

The total charge between different copy sheets and electrophotographic image areas can vary according to the total non- irradiated area that a charge is charged. can take change. If the copy has relatively small image areas, the image background is large, which means that the total electrostatic attraction between the copy sheet and the drum is correspondingly greater the whole

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induced electrostatic attraction between the copy sheet and the drum is correspondingly small. From this it can be seen that an apparatus for releasing a copy sheet from a drum must cause it to be released even with the strongest possible binding force if it is to function properly. In an apparatus operating with air flow to a smearing of the image _0, this results in increased often Further, a large air pressure and the contamination due to large through the machine swirling toner quantity _o

When the drum continues to rotate in the direction of the arrow shown, the copy sheet with the image, which is held on the drum surface, moves out of the area of the transfer corotron 24 and can now be detached * This detachment is first achieved with a lifting finger 25. This consists of a relatively thin material that has no adhesive properties, so that the finger rests freely on the drum surface. It is mounted on an axis 60 and lies in a plane perpendicular to the drum surface. As can be seen from Pig ₀ 4, the finger is rotatably mounted at the free end of its axis between a stationary part 61 and a holding part 62.It is movable in the axis on a screw 65 which protrudes through an elongated opening 64 of the finger and into the stationary part 61 is screwed. The top of the elongate opening resting on the screw 63 so that the finger is freely supported in the position shown in Figure <"4, ₀

The other end of the axle 60 is rotatably mounted in the side walls of a bearing housing 60. This is in turn fastened to a holder 69 which is fastened to the machine frame with screws 67 (W ± g <> 2). The holder 69 is provided with a horizontal holding flange 70 which carries an electromagnet SOL-1. This works against a torsion spring 72, The spring 72 is with the A © tise 60 over a Kopp «. A lever arm 71 is connected to the end of the Aoh8e 60

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attached and with the armature 73 of the electromagnet SOI-1 tied together. When the electromagnet is switched off, the torsion spring 72 assume their position of equilibrium · The spring acting via the coupling 74 normally keeps the lifting finger in the position shown in FIG. position shown above the drum. When the electromagnet SGL-1 is switched on, the Lever arm 71 is pulled down and moves the lifting finger into its contact with the drum surface, shown in Jig.2 Position.

The solenoid SOL-1 is driven by the (not shown) Machine control switched on and moves the lifting finger 25 downwards onto the surface of the rotating drum, and shortly before the front edge of a copy sheet arrives. The freely supported finger can rotate freely on the axis 60 when it comes into contact with the drum surface, so that it rests on the drum surface only by its own weight. It is wedge-shaped and so in the machine arranged that the chisel tip is between the copy sheet and moving the rotating drum surface when the solenoid SOIr-1 is turned on. As can be seen from Fig. 2, the lift finger lifts the leading edge of the sheet from the drum surface. As the drum continues to rotate the front part of the sheet is moved upwards along the inclined wedge surface to the stationary transport guide 26,

The stationary transport guide 26 contains a smooth, flat plate 78 which runs in the horizontal direction over the entire width of the paper and is provided with an elongated vacuum opening 89 _P This is provided in the longitudinal direction over the entire width of the plate. The plate forms the bottom of a housing 79 in which a vacuum chamber 80 (Pigo5) is provided. This is in communication with the pressure opening 89. It is connected to a vacuum pump (not shown) via a pipe 82,

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which is connected to the outlet opening 81 o The upper one Part of the vacuum chamber is formed by an inclined plate 86 which reduces the cross section * of the chamber with increasing distance from the outlet opening 81. This reduction occurs proportionally to the negative pressure loss within the chamber, so that at the negative pressure opening 89 a substantially uniform negative pressure prevailed

When the copy sheet 50 is advanced further, its leading edge touches the plate 78 in front of the elongated vacuum opening 89. The greater part of the copy sheet arrives at this point behind the leading edge into the influence of the negative pressure at the negative pressure opening 89. In the negative pressure chamber there is such a negative pressure that the non-imaged side of the advanced sheet of the lift finger lifted off and attached to the plate 78 in that shown in FIG Way is held · How the lifting finger is the lower one The surface of the plate 78 is covered with a non-adhesive material, for example with tetrafluoroethylene · This enables the copy sheet to slide smoothly on the plate.

When the copy sheet is held against the flat plate 78, so the solenoid SOL-1 is switched off and * enables the torsion spring 72 to return to its equilibrium position, so that the lifting finger 25 is lifted from the drum surface. At this point, that slides Copy sheet against flat platen 78 so that as the drum surface continues to rotate along the platen, it moves to the next Process station is moved · Although the acting on the sheet Negative pressure its free movement along the guides plate, it is not enough to power the electro- » table to peel off sheet adhering to the drum surface «In practice it has been shown that sheets with different Weight and different sizes slightly lifted from the top of a rotating drum and along one

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non-adhesive plate can be transported, though the plate with an angle of oa. 30 ° from the horizontal is arranged near the drum surface and a Negative pressure of 3 »8 to 6.5 cm water column prevailed at the negative pressure opening

In the described embodiment of the invention, the copy sheet is between the upper fixing roller 31 and the lower Fixing roller 32 of the fixing device 30 out. the lower fixing roller 32 is made of an elastomeric and resilient material of a lower hardness than the coating of the upper one Fixing roller 31 is provided. Are the roles in the position shown in Figo2 in mutual pressure, so they touch each other with a circumferential angle of several Degree. A heat radiator 33 is near the lower fixing roller arranged and keeps its surface at a temperature that is sufficient to fuse the toner image into the copy sheet. that their peripheral speed with the speed of of the copy sheet pushed along the plate 78 o · If the leading edge of the sheet is between the fixing rollers, so the trailing edge of the sheet can be freely at the transfer station pass by · Since either the trailing edge or the leading edge of the sheet is positively driven at certain times during the image transfer and sheet detachment, with the device according to the invention a completely safe handling of the copy sheets can be made possible · The only one There is a limitation with regard to the smallest sheet size, the distance between the fixing rollers and the transfer station is equivalent to. This distance is relatively short

In FIG. 5, a switch 83 is arranged inside the guide housing 79 above the vacuum chamber BO. His operating arm 84 protrudes through the vacuum chamber and the guide plate 78 in the movement area of the copy sheet.

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It serves as a sensing device to determine the passage of a copy sheet on the guide device. If this passage does not take place at a predetermined time, then
with the switch of the machine control indicated that a misdirection has occurred and the machine must be controlled in the Ausohaltecycle.

In the embodiment shown, two mutually acting fixing rollers are provided for the fixing device, which also transport the copy sheets. Instead, another paper transport device can also be provided which moves the copy sheet leaving the guide 26. For example, pressure rollers can be provided which guide the copy sheet to a subsequent process station which is relatively far from the image transfer station
is arranged. The invention has been described above using an exemplary embodiment, but is based on this
not limited »All within the scope of the following claims
possible embodiments are encompassed by the basic idea of the invention

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Claims (1)

2Ü32371 Claims 1 ,) Device for detaching a sheet from a moving sheet carrier, in particular for a copy sheet arranged on a recording drum in an electrophotographic copying machine, characterized by a lifting finger (25) which touches the sheet carrier (10) for lifting and removing the leading edge of the sheet, which is provided with a stationary guide (26) is assigned, which guides the sheet (50) on a predetermined path, and by a vacuum device (80, 89) arranged on the guide (26) for lifting the sheet (50) from the lifting finger (25) and applying it to the Guide surface (78). Device according to claim 1, characterized in that the guide (26) includes a guide surface (78) with a smooth surface, along which the respective sheet (50) can be pushed into sliding contact, 3ο device according to claim 2, characterized in that the guide surface (78) with a non-adhesive material is covered * Device according to claim 3, characterized in that the guide surface (78) coated with tetrafluoroethylene is. Device according to claim 4, characterized in that the guide surface (78) with a vacuum opening extending transversely to the direction of movement of the sheet (50) (89) is provided, which is arranged following the separation point in the direction of movement of the sheet (50) and a The detached sheet (50) rests against the guide surface (78) causes 6, device according to claim 5, characterized in that 009884/1931 . ■. - To - 16 - further a sheet feeding device (31, 32-) for movement of the sheet (50) is provided along a predetermined path 7ο Device according to one of claims 1 to 6, characterized ge indicates "that the lifting finger '(25) is wedge-shaped 8 «Device according to one of claims 1 to 7», characterized in that that the lifting finger rests freely on the surface of the sheet carrier (10) » Device according to one of claims 1 to 8, characterized in that a device (72, 60) for Lifting of the lifting finger (25) from the sheet carrier (TO) when a detached 'sheet (50) is in contact with the Mbrungsflache (78) is provided 09884 / 193T INSPECTED