EP0404759A1 - Single-page printer for duplex and simplex operation. - Google Patents

Abstract

Installation for printing on one side or on both sides of separate sheets introduced sequentially into the installation, comprising a printing channel (DK) to which is associated a printing station (DS) and paper transport elements (P). The printing channel (DK) is coupled, on the input side and the output side, to a return channel (RF) comprising paper transport elements (P) and a reversing device (W1) and through which the sheets printed on their front side can be returned, if necessary, to the printing station (DS) for back side printing. The print channel (DK) is connected to a paper transport channel having paper transport elements (P) with a separate duplex channel (DUK) and a simplex channel (SK) for the separate transport of the printed sheets of the two sides or only one side up to a common output channel (AK) with a second reversing device (W2) for duplex sheets. The simplex channel (SK) has a tray that holds a first sheet, printed on one side, at a minimum until another sheet, printed on both sides, has to exit before this first sheet through the exit channel. , has traversed the duplex channel (DUK).

Description

Single sheet page printer for duplex and simplex operation.

The invention relates to a single sheet page printer for duplex and simplex operation.

In electrophotographic printers, the single sheet removed from a storage container in the printing channel of the printer device is first printed in duplex mode, then returned via a return channel to the input of the printing channel and turned in a turning device located there. After being fed back into the printing channel, the back of the single sheet is then printed. The single sheet is then deposited in an output container via an output channel.

In order to maintain a continuous printing operation at a constant printing process speed, one or more sheets are continuously fed to the printing channel and the return device. The control of the printer then assigns the corresponding printed image to the corresponding front and back sides of the single sheets. The correct sequence for the delivery or filing is ensured by the fact that all sheets to be printed are guided over the print channel and the return channel including the turning device.

In the case of mixed print jobs, ie print jobs which contain both simplex and duplex printing, it is disadvantageous that all, even the sheets (simplex) to be printed on only one side, are again guided past the printing station. In the worst case, the processing speed of such a page printer is reduced to almost half of its output, which would otherwise be possible with pure simplex operation. For example, if a print job contains a large number of single sheets that are only printed on one side and otherwise only a small number of single sheets to be printed on both sides, see above the entire print job must still be carried out in duplex mode.

If, in mixed operation, the unprinted backs are not returned via the return channel, but instead are placed directly, the entire print job must be sorted after being placed in the storage container. This can only be done manually with considerable effort. Otherwise required sorting devices have a complicated structure and require increased operating effort.

With electrophotographic printing devices it is also possible to print pre-printed forms. These can e.g. Advertising brochures with personal data, invoices, tax forms or the like.

In the form operation in the known page printers, the form stack to be printed must be stacked in the mixed and pure duplex operation with the front of the individual forms down (face-down) in the storage container, so that after a double pass through the printing channel, the Stack side and position direction is stacked on the supply side. In this case, correct in terms of sides and position means that the first sheet to be printed is placed with its front side down in the storage container.

If there is a stack of forms that is only to be printed on one side, it is therefore necessary to place the stack of forms in the storage container with the single side to be printed on, with only one pass through the printing channel for each individual sheet. It is assumed that the actual pressure station is arranged above the pressure channel in the pressure channel.

The operator must therefore know exactly about the structure of the stack when inserting a stack of forms and place it in the storage container in the correct position. This is cumbersome and can lead to errors.

Page printers with single sheet operation are relatively complicated in terms of paper transport, and the required tolerances in the paper channel are low. Such page printers with a printing speed of 50 pages per minute or more are operated around the clock in shift operation. It is therefore necessary to make such printing devices user-friendly, so that e.g. paper transport disruption occurring by tears or damage to the paper can be quickly remedied.

The aim of the invention is to provide a single-sheet page printer for duplex and simplex operation of high printing speed and high printing quality, which, even in mixed operation, enables a high printing speed with fast, continuous sheet storage.

A further object of the invention is to design the single-sheet side printer in such a way that, particularly in the form of operation in which a stack of forms is supplied to the printer in a predetermined order and page position, the order and page position of the single sheets are correctly is guaranteed.

The printer should also be designed to be easy to use, so that faults in the paper flow in particular can be easily recognized and remedied.

This object is achieved in a printing device of the type mentioned at the outset according to claim 1. Advantageous embodiments of the invention are characterized in the subclaims.

In the printing device according to the invention, only the pages to be printed are fed to the printing station. ie Even in mixed operation, sheets that are only to be printed on one side are no longer transported into the printing channel again via a return channel and a turning station after printing, but are fed to a Simplex channel after printing. This simplex channel is designed as a storage device and opens into the storage device via an output device. If a single sheet to be printed on both sides is placed in front of the single sheet to be printed on one side only in the sequence of the printing process, the single sheet only to be printed on one side is stored in the simplex channel until the single sheet to be previously printed or to be deposited is stored printed on both sides and fed to an output channel via a separate duplex channel.

The storage device in the simplex channel can consist of an intermediate container which can be loaded with single sheets and in turn removed therefrom, or advantageously an elongated storage channel in which the single sheets to be printed on one side can be stored one behind the other. Depending on the sequence of duplex sheets in the print job, the simplex sheets from the simplex channel are entered into the output channel.

In an advantageous embodiment of the invention, the duplex channel has a further turning device.

The processing of forms is made considerably easier by this additional turning device in connection with the storage device of the simplex channel. Form stacks can now, regardless of their composition, be placed in the storage container face-up in the storage container, regardless of their composition, consisting of single sheets that are only printed on one side and single sheets that are printed on both sides. The stack of forms is then printed and deposited in such a way that the first sheet to be printed is always face down in the discharge container. In a further advantageous embodiment of the invention there is a paper aligning device in the entrance area of the printing channel or in the feed channel to the printing channel, which positions the individual sheets removed from the storage container in the correct position before they are fed to the printing channel.

This enables a correct printing position on the individual sheets. Due to the exact position of the single sheets, it is also possible to reduce the distance from single sheet to single sheet in the printing channel and thus to increase the printing speed.

The paper alignment device consists in a simple manner of a pair of paper rollers with an upstream paper position scanner, the single sheet being pressed against the stationary pair of paper rollers. It bulges out and aligns itself along the rollers.

In order to be able to further increase the printing speed, in a further advantageous embodiment of the invention the single sheets to be printed on both sides are transported in the return channel at a speed which is substantially higher than the printing process speed.

Sensors distributed in the pressure channel detect the position of each individual sheet during the passage through the printing device. If there is an interruption of the printing operation as a result of a malfunction of the paper transport, the malfunction position is displayed on a display device representing the paper run. This enables the fault to be localized quickly and reliably.

In order to be able to process and store paper formats of different sizes, in a further embodiment of the invention the storage containers have in the area of the paper transport elements arranged on the input side Swiveling guide device that, depending on the paper format, guides single sheets of large formats directly up to a stop edge of the storage container. Small paper formats are guided by the guide device past an additional paper transport roller, which accelerate the paper sheets again and thus also deposits on the stop edge of the paper storage container.

Embodiments of the invention are shown in the drawings and are described in more detail below, for example. Show it

1 shows a schematic sectional view of the single sheet printing device

2 shows a schematic sectional illustration of the paper path with the sensors and the paper transport elements

3 shows a schematic representation of the display and input device on the printing device

4 shows a schematic sectional illustration of a pair of paper transport rollers

5 shows a schematic sectional illustration of a paper alignment device

6 shows a schematic sectional illustration of a turning device

7 shows a schematic sectional illustration of a transmission driving a turning device

8 shows a schematic sectional illustration of a storage container

9 shows a schematic sectional illustration of a storage device for single sheets

10 shows a schematic sectional illustration of a paper switch

11 shows a block diagram of the control arrangement for the single sheet printer 12 shows a block diagram of the main processor of the control arrangement of FIGS. 11 and

13a, 13b show a diagram of the occupancy of the page memory as a function of the pressure data supplied over time.

The single-sheet page printer shown in FIG. 1, which works on the principle of electrophotography, contains three paper storage containers VI, V2 and V3 with different capacities for holding single sheets. The paper storage containers VI, V2, V3 are constructed in the usual manner and have a motor-driven base plate 10 which can be moved in the direction of the arrow in accordance with the paper supply. As a result, a paper stack arranged in the paper storage container is raised in accordance with the consumption of the paper, so that the uppermost single sheet of the paper stack can always be pulled off the paper stack via paper transport elements PI, P2 and P3. The paper supply containers are connected via paper feed channels 11 to a pressure channel DK of the printing device. The

Printing channel DK contains the actual printing station DS with an electrophotographic printing device consisting of a photoconductor drum 12, an exposure station 13 with an LED comb (not shown here) which can be controlled depending on the character, a developer station 14, a transfer printing station 15 and a cleaning station 16. Furthermore, ent holds the pressure channel DK paper transport elements in the form of a belt-shaped circumferential suction table S and on the input side a paper alignment device PA2, the function of which will be described later, and a fixing station F made of electrically heated heating rollers which are driven by an electric motor and which are in a known manner on one Thermally fix the record carrier (elπzelblatt) overprinted toner image.

A paper transport element P5-P8 in the form of a motor is coupled to the pressure channel DK on the input and output sides driven roller pairs contain αer return channel RF. The return channel RF also has a turning device W1, the function of which will be explained later.

Controlled by a paper switch PW1, the pressure channel DK is followed by a paper transport channel system with a separate duplex channel DUK and a separate simplex channel SK, which end in a common output channel AK. The single sheets printed on both sides are transported in the duplex channel DUK and the single sheets printed on the one side in the simplex channel SK. The duplex or simplex channel is controlled via a switch PW2. The simplex channel SK is designed as an elongated paper channel with paper transport elements arranged therein. It can hold up to three single sheets in succession and serves as a storage channel. At the end of the duplex channel there is another turning device W2. This turning device W2 connects the duplex channel to the output channel Ak.

The output channel AK has switches PW3 and PW4 that guide the single sheets into two storage containers ABI and AB2. A waste container AF (copy tray) which can be controlled via the switch PW4 is also provided.

To determine the position of the passing single sheets and to control the paper transport elements P, all paper channels have paper scanning sensors LS (shown as black triangles) which consist of light barriers. The output signals of these sensors LS are evaluated by an evaluation circuit, which will be explained later, and thus a display device AZ is controlled. The display device AZ (FIG. 3) is located on the front of the printer and also has an input keyboard T.

In the feed channel 11 of the storage container and at the entrance of the pressure channel there are also paper alignment devices PA1 to PA3 are arranged, which serve to align the single sheet in the correct position before printing in the printing channel DK.

All the paper transport elements P, including the fixing station F and the photoconductor drum 12, are driven by two motors M1 and M2. The motor M1 drives the paper transport elements in the print channel and in the input area, the motor M2 the paper transport elements in the return channel RF, in the duplex channel DUK, in the simplex channel SK and in the output area AK. All paper transport elements (pairs of paper rolls P) have electrically controllable couplings, e.g. Spring band couplings and are connected to the two assigned motors Ml or M2 via toothed belts, which are not shown here for reasons of clarity. The paper transport elements consist of a pair of rollers (FIG. 4) with an upper foam roller SW1 and a lower driven roller SW2 made of aluminum, between which the single sheet E is transported by friction.

The structure of the individual elements of the printing device will now be described in more detail below.

Paper alignment device (Fig 5)

Paper alignment devices PA1 to PA3 are arranged in the paper feed channels 11 of the storage containers V1-V3 and at the entrance of the pressure channel DK. They serve to align the individual sheets E removed from the storage containers VI to V3 and to feed them to the printing station DS in aligned form.

You have the construction in Fig. Auf¬ shown in principle 5 and consist of an actual paper transport walzeπpaar P from a foam roller SW1 and a driven to _¬ aluminum roller SW2. The driven roller SW2 stands over a clutch K, which consists of an electrically Actuated spring band coupling can exist in connection with a toothed belt Z driven by the motors Ml or M2. Furthermore, the clutch K contains a brake which ensures that when the non-positive connection between the motor and the drive roller SW2 is released, the drive roller SW2 is braked and its rotation is thus inhibited.

A photoelectric scanning device LSI, whose output signal is evaluated by the device controller of the printer, is located in front of the paper roll P in the paper transport direction. The scanning device LSI scans the front edge of the single sheet.

This paper registration device works as follows:

After actuation of the clutch K, the uppermost sheet of the paper stack in the paper supply container VI is drawn off with the aid of the paper rollers PI and transported on a slide track GL in the feed channel 11. By pulling it off the stack, it can happen that the single sheet does not slide exactly straight to the slide GL, but that it is transported at an angle. This would result in an oblique print image. The scanning device LSI now recognizes the front edge of the transported single sheet E and at this moment switches off the drive of the paper rollers P via the control of the printer. The brake contained in the clutch K immediately stops the paper rollers P. The transport of the single sheet E on the slideway GL is, however, maintained by the upstream paper rollers PI of the storage container. The front edge of the single sheet E thus abuts the standing paper rolls P and bulges out as shown in FIG. 5. Through continued transport, the paper is aligned along its leading edge over the paper rollers P. After a defined time, the paper rollers PI of the storage container are deactivated and the paper rollers P are driven again. That is how it is aligned Single sheet E is transported over the paper rollers P, a free wheel arranged in the clutch K of the paper roller pair PI, not shown here, making it possible to pull the single sheet out of the paper rollers PI.

Turning device (Fig. 6)

In order to be able to turn the single sheet in duplex mode, the printing device contains two turning stations W1 and W2. A pair of paper rollers P10 is arranged at the entrance of the turning station. Another pair of paper rolls Pll in the middle of the turning station. The turning station also has a paper channel PK which consists of two metal profiles. The paper channel PK is widened in a funnel shape at the entrance area of the turning device. Another paper channel PK is downstream of the pair of paper rollers Pll.

The paper roller pair P10, like all paper roller pairs, is driven by a motor M via a toothed belt. It can be switched on and off via a corresponding coupling. In principle, its structure corresponds to the structure of the pair of paper rollers PI in FIG. 5.

E.g. If a single sheet E is fed to the turning device W2 via the duplex channel DUK, the pair of paper rollers P10 transports the single sheet into the paper channel PK, the rear wall of the paper channel PK deflecting the paper so that it slides into the paper channel PK. After passing through the paper channel PK, the single sheet E is grasped by the pair of paper rolls Pl1 and transported further until the end of the single sheet leaves the pair of paper rolls P10.

Due to the inherent elasticity of the paper sheet E, this straightens up at the end, so that it slides past the pair of paper rollers P10 and takes up a position parallel to the paper channel PK.

Now the direction of movement of the paper rollers Pll reverses and the papering rollers Pll push the single sheet past the paper rollers PIO into the output channel AK or at the turning device W1 into the pressure channel DK.

In order to generate the forward-backward movement of the single sheet, the paper rollers P1 are coupled to a gear which has a structure corresponding to FIG. 7. The transmission contains a first direction-dependent clutch K 1 and a second direction-dependent clutch K 2. The couplings are connected on the drive side to the M2 motor via a ZI toothed belt. On the output side, the clutch K1 has an output wheel larger in diameter than the clutch K2. Both driven wheels are connected via a toothed belt Z2 to the drive roller SW2 of the pair of paper rollers Pll. The clutches K1 and K2 are actuated alternatively, so that when the clutch K1 is actuated, the clutch K2 is disengaged and when the clutch K2 is actuated, the clutch K1. When the motor M2 is rotating and the clutch K2 is actuated, the toothed belt Z2 is shown in FIG The direction of the arrow moves (K2) and the single sheet E is drawn into the paper channel PK at a slower speed. After the clutch K2 has been deactivated and the clutch K1 has been actuated, the movement of the toothed belt Z2 reverses in the direction of the arrow K1 and, due to the size of the driven wheel K1, the single sheet E is pushed out into the output channel AK at high speed.

Storage container (Fig. 8)

The ABI and AB2 storage bins are suitable for holding different paper formats. At their entrance they have a pair of paper rollers P12 which transports the single sheets fed from the discharge channel AK into the storage bin ABI. ^" In order to be able to easily remove the single sheets from the storage bin AB in the case of different formats, the single sheets are stored flush with the rear wall R of the storage bin AB. The storage takes place in such a way that the first sheet to be deposited is placed face down in the storage bin. In order to be able to store different paper formats, the storage container AB has a guide device LT. This guide device consists of a guide plate 21 which can be pivoted by means of a lifting magnet 20 and an additional paper transport roller 22.

In the illustrated lowered state of the guide plate 21, paper sheets of smaller size are introduced so that they come into engagement with the paper transport roller 22. This paper transport roller 22 detects the single sheet, accelerates it again so that it hits the rear side R of the storage container AB in free flight.

For stacking papers of larger formats (A3), the guide plate 21 is pivoted upwards (shown in dashed lines). The individual sheets are thereby deflected and passed under the paper transport roller 22. Due to their size, they can be transported almost to the rear wall AB through the paper rollers P12.

Storage device (Fig. 9)

Instead of an elongated simplex channel SK for serial recording and storage of the single sheets printed on one side, it is also possible to arrange a storage arrangement corresponding to FIG. 9. In principle, this consists of a storage container SB, to which individual sheets E are fed on one side via paper transport elements (paper rollers P). These single sheets deposited in the storage container SB can then be removed again via paper transport elements P arranged on the output side at the bottom of the storage container SB.

Turnout (Fig. 10)

In order to be able to feed the individual sheets to the various paper channels - be it duplex channels or simplex channels - or to select the storage containers ABI or AB2, the printer channels PW1 to PW4 are in the paper channels Turnouts arranged. These switches have a structure corresponding to FIG. 10. In principle, they consist of a guide element 24 which can be actuated via a lifting magnet 23 and which is pivotably arranged in the paper channel PK in such a way that in a first state, shown by solid lines, it is from above leaves paper unaffected so that it is not redirected. In the case of the switch PW2, the paper slides into the Simplexkaπal SK. If the lifting magnet 23 is activated, the guide element 24 consisting of a guide plate swings into the paper channel PK and the single sheet is deflected, for example in the case of the switch PW2, into the duplex channel DUK. The lifting magnet is moved against a spring 25 which, after switching off the lifting magnet 23, returns the guide element 24 to its starting position.

Control (Fig. 11-13)

The control for the page printer is basically divided into a controller part C and the actual device control G. The controller C is basically constructed in accordance with US Pat. No. 4,593,407. It has the task of accepting the print data coming in from a computer H, preparing them page by page and controlling the character generator 13 of the printing station as a function of the characters to be displayed. The device control G in turn serves for the coordinated execution of all printer functions. It has a modular structure and consists of a main processor HP and various submodules SUB1 to SUB5, which ensure independent monitoring of the assigned printer units. The communication between the individual control parts is via a einheit¬ for all parts Liche hardware / software interface position ^"(net-shaped coupling, serial bus). Each submodule SUB1 to SUB5 is equipped with a dedicated processor and can independently operate the associated unit of the printing means and is self-testable This self-test capability means that both when the device is switched on and when requested Main processor HP independent test routines are performed. All control modules of the printer in the device control are registered with regard to their status in a non-volatile memory. The controller can access these values. In addition, the content of the non-volatile memory can, if necessary, be printed out. There are also interfaces for additional devices.

11 and 12 show the basic structure of the device control in the form of a block diagram. 12 shows a block diagram of the structure of the main processor HP.

All submodules SUB1 to SUB5 and the main processor HP are connected to one another with a serial interface INT1, which is controlled by line drivers. The serial interface INT1 is controlled under the control of the main processor HP via a BIT bus. The interface protocol corresponds to the usual HDLC / SDLC description (fast data transfer). In order to relieve the load on the interface and to simplify the cable routing to the individual units, the units are controlled by the associated submodules SUB1 to SUBS directly via power amplifiers (not shown here). The main processor HP periodically checks the function of the individual submodules SUB1 to SUB5. A monitoring circuit (hardware / watchdog) checks the process in the main processor. The sequence control is synchronized with the peripheral speed of the photoconductor drum 12 via the output signals F of a rotary pulse encoder DI. The output of this rotary pulse generator DI (FIG. 2) is connected to all submodules SUB1 to SUB4 and supplies a synchronizing signal F at cyclical intervals.

12, the main processor has the following structure: A central unit ZPU is connected to three memories SP1 to SP3 and an input / output unit EA. The memory SP1 is a read-write memory, the memory SP2 is an electrically programmable read-only memory and the memory SP3 is a non-volatile data memory. The input / output unit EA detects, among other things, the synchronization pulse F.

Consumption metabolism, printed / fixed page, maintenance intervals, error statistics and deviations from guide values etc. entered by the operator are stored in the non-volatile memory SP3. The connection to the controller C takes place via a conventional interface INT2.

The main processor HP has the task of coordinating, checking for plausibility and forwarding all messages, commands and measurement data from the external stations SUB1 to SUB4. It also establishes the connection to controller C via the interface INT2 and the system bus BUS2. In this case, bidirectional commands and messages are transferred. The correct program sequence in the device control is continuously monitored via the monitoring circuit U (watchdog circuit).

As already explained, five submodules SUB1 to SUB4 independently monitor and control the aggregates assigned to them. Communication between the individual modules SUB1 to SUB5 and the main processor HP takes place via a hardware / software interface INT1 which is uniform for all parts. Each submodule has its own processor with an input buffer that transmits the data supplied via input I to the processor and power stages that drive the associated units via output 0. The submodules are themselves testable, ie test routines are carried out independently when the device is switched on and when the main processor HP responds. The submodule SUB1 monitors all sensors LS of the storage containers VI to V3, the feed channels 11 and the pressure channel DK and in particular the pressure start signal of the sensor LS SYN. The submodule SUB1 controls all units in this area. It detects and reports paper running errors.

The submodule SUB2 detects all sensors LS in the paper output area, i.e. in the area of the output containers ABI, AB2 and the waste container AF as well as in the output channel AK. Paper running errors are recognized and communicated to the main processor HP.

The SUB2 submodule monitors the LS sensors in the simplex and duplex channels DK and SK as well as in the feedback channel RF. It controls the paper flow in these channels and detects paper running errors.

The SUB4 submodule controls the control panel AZ on the printer. The control panel AZ contains a keyboard and a display device (FIG. 3), the display showing the paper flow in the printer or, in the event of a paper transport fault, the fault location. The submodule SUB4 in connection with the control panels AZ represents the interface between the operator or maintenance technician and the printing device. All operator inputs and all information from the device are made on the control panel. This essentially consists of a display for displaying the information and a keyboard for entering various commands and parameters. In addition, it has some special controls and indicators.

An essential function of the display device of the paper run on the control panel is the display of paper transport malfunctions.

The paper flow is continuously monitored by the LS sensors. If a sports disorder occurs, it becomes shown on the control panel paper flowchart. The location of the fault is thus automatically localized. The operator can now fix the transport problem without wasting time.

In order to ensure continuous printing operation, a new single sheet representing the content of the destroyed single sheet is printed immediately after the resumption of printing operation after the fault has been remedied. All single sheets between the fault location and the printing station in the printing device are also newly created, so that correct storage of the single sheets in the storage container ABI or AB2 is guaranteed. The superfluous single sheets between the fault location and the printing station are automatically transported into the waste container AF.

The sensors of the printing station DS are recorded with the submodule SUB5. These are e.g. Temperature sensor and microswitch in the fuser. Transport monitoring sensors in the developer station etc. The submodule SUB5 controls the units, the fixation lamps, motors, fans, charging controls, etc. The errors that occur are reported to the main processor HP.

Instead of controlling the control panel AZ via the submodule SUB4, it is also possible to control the control panel directly via the main processor HP. Then the submodule SUB4 is omitted. Function description:

As stated at the beginning, the page printer is designed for simplex duplex and mixed operation. The print data for the individual pages are fed from the external computer H to the controller C of the page printing device in the sequence front-back. In order to ensure continuous printing operation at a constant process speed - in this case 50 pages per minute - depending on the length of the print channel DK, the return channel RF and the process speed, the entered print data must be stored page by page in a page memory PM of controller C are temporarily stored.

Given the required printing capacity and the dimensions of the return or printing channel, two front-side memories are required in the illustrated embodiment in simplex mode, and three rear-side memories are required for duplex mode. In mixed operation, i.e. when duplex and single sheets are mixed, this requirement fluctuates depending on the printing sequence. In order to have a certain redundancy available, the page memory PM is designed on seven pages.

Furthermore, the side printing device is designed for printing on different paper formats. For example, single sheets in A4 printing format can be used in storage container VI, single sheets in A3 format in storage container V2. It is even possible to use different paper sizes within a stack. The size of the photoconductor drum 12 is designed so that it can be printed on A4 size paper with a normal circulation. If a single sheet of size A3 is to be printed, then two photo images of size A4 are applied in succession to a single sheet of size A3 with the photoconductor drum 12 in the transfer printing station 5.

The printing process as such should first be described using the simplex mode in A4 format. Each storage container VI to V3 contains sensors LS2 in the area of its paper transport elements PI to P3. These sensors LS2 detect the level of the stack. If there is no single sheet in the access area of the paper transport rollers PI to P3, the stack is automatically fed in via the lifting table 10. The single sheet detected by the sensors LS2 is then advanced with the aid of the paper transport rollers PI to P3 to a light barrier LS3. This light barrier 3 defines the waiting position of the single sheets before entering the feed channel 11 or the pressure channel DK. Since the storage containers VI to V3 have different positions in the printer, but the individual sheets must travel the same way in the feed channel 11 for synchronization reasons, the light barriers LS3 defining the waiting position are at the same distance from the entrance of the printing channel DK.

At time TO, the printing device is in standby mode, the page memories are empty. At this point, computer H begins to send the data for page 1. The printer stores the data for page 1 in a first memory area of the page memory PM and transports sheet 1 from the waiting position towards a position defined by the position of the light barriers LS SYN. The scanner LS SYN consists of two scanning elements, namely a scanning element for the leading edge of the single sheet and a scanning element that determines the presence of the single sheet. The synchronizing position is defined as the drum section of the photoconductor drum 12 from the character generator 13 to the transfer printing station 15 folded into the printing channel.

At time T1, the computer begins to send data for page 2. The page printer stores the data for page 2 in a second memory area of the page memory PM and transports the sheet 2 from the waiting position in the direction of the synchronization position LS SYN. Currently Point T2, sheet 1 has reached the synchronization position. At the same time, the printer writes the print data from the first memory area of the page memory PM onto the photoconductor drum 12.

At time T3, the last date from the first memory area of page memory PM was written on the drum and computer H begins to send data for page 3. The page printer stores the data for page 3 in the now empty first memory area of the page memory PM and transports the sheet 3 from the waiting position towards the synchronization position.

The printed sheets are transported to the fixing station F via the suction table S and fixed there. Their position is continuously scanned by the light barriers LS in the pressure channel DK.

Since it is single sheets in simplex operation, the single sheets are fed via the switch PW1 to the pair of paper rolls P21, which transports the single sheets through the switch PW2 at process speed into the simplex channel SK. In the simplex channel SK, the single sheets are moved via the paper transport rollers P22, P23, P24, P25, P26 into the turning device W2 and from there without turning into the output channel AK with the paper rollers P28 and P29, the switches PW3 or PW4 and the storage container ¬ ter ABI or AB2 or the waste container AF. In order to be able to compensate for the length of the plex channel or to ensure that the individual sheets are deposited securely in the storage container ABI and AB2, the individual sheets in the turning device W2 are accelerated to increased speed by the paper roller pairs Pl1 arranged there. So that this acceleration can take place safely, the pair of paper rollers - in this case, the pair of paper rollers P26, which is arranged immediately in front of such an acceleration section, has a free-wheel. As a result, the single sheet can be pulled out of the paper roller pair P26, which is working at process speed. The paper rollers P27, P28 and P29 in the output channel work at increased speed. Each of the paper roller pairs P in the simplex channel SK can be individually controlled via couplings.

In order to achieve the full printing speed of the page printer, the distance between two printed A4 pages may be a defined distance, in this case e.g. Do not exceed 54 mm. However, the printing process and thus the paper pull from the storage containers VI to V3 can only begin when the respective memory area of the page memory PM is fully written. This would require that the distance from the paper input tray (VI to V3) to the

Synchronization point LS SYN should also not exceed 54 mm. For constructional reasons, however, it is not possible to bring three storage containers to this distance. However, the distance of 54 mm can be avoided if the paper is already being conveyed from a waiting position towards the synchronization point LS SYN when the first date is read. If the data transmission time of the connected computer is less than the cycle time of-^ sec. = 1.2 seconds. (Printing performance: 50 pages per minute) for a sheet size A4, the printing process is triggered when the respective sheet has reached the synchronization point LS SYN. If the data transmission time is greater than the cycle time (1.2 seconds), the sheet is stopped shortly before the synchronization position and is only conveyed on when the respective page memory has been written to in full. When the synchronization point LS SYN is reached, the printing process is triggered.

The waiting position of the paper is calculated as follows: At time T3 = T0 + 2.4 sea. the first memory area of the memory PM must have been emptied. At a process speed of 220 mm per second and one A4 printing length of 210 mm results in a printing time of - 2-10 ^ sea. = 0.955 lake. This leaves for the transport of the paper from the waiting position to the synchronizing position: T = 2.4 sea. - 0.955 = 1.45 lake. This gives a path of 318 mm. Additional delay times such as clutch switching times are not taken into account in the above calculation.

Since it is not possible for structural reasons to move the three input memories VI to V3 to this position, 1 sheet from all three input compartments is "drawn" to this waiting position L23.

Printing larger paper formats Since an A3 paper format has to be created by subsequent printing, the printing performance is 25 pages per minute. The cycle time is 2.4 sea. Two A4 page memories are available for writing on the paper format A3. This means that the first A3 half page is written into the first memory area of the page memory PM and the second A3 half page into the second memory area of the page memory PM. However, data cannot be written to the drum until the A3 page has been completely transferred. On the other hand, data transfer to the next page cannot begin until both memory areas have been emptied. The data transmission time for 25 pages per minute A3 is as follows: cycle time T = 2.4 sea. Print time for 420 mm = - ° _j lake. = 1.91 lake.

This leaves 2.4 lake for the transmission of the second half side. - 1.91 lake. = 0.49 lake. or seen on a full A3 page 2 x 0.49 lake. = 0.98 lake.

Duplex operation

In duplex mode, both the front and the

Backside described as single sheets. The feeding of the single sheets from the storage containers VI to V3 to the printing station corresponds to the simplex operation. However, it is necessary to provide a larger storage space for the page storage PM.

The computer H supplies the data for the printed pages in the order of front page sheet 1, back page sheet 1, front page sheet 2, back page sheet 2 etc. However, the order of the printing process is different since the single sheets to be written on both sides after writing the front page the return channel RF must be fed to the printing station again.

In duplex mode for writing on a paper format A4, the sequence of the page delivered by the computer is therefore as follows:

Front sheet 1, back sheet 1, front sheet 2, back sheet 2 etc.

Assuming eight single sheets are printed in duplex mode, the following sequence results: front sheet 1, front sheet 2, front sheet 3, front sheet 4, back sheet 1, front sheet 5, back sheet 2, front Sheet 6, back sheet 3, front sheet 7, back sheet 4, front sheet 8, back sheet 5, back sheet 6, back sheet 7, back sheet 8.

After the front of sheet 4 has been printed, an alternating printing of the front, back, front, back, etc. is carried out for better utilization of the computer interface. Pressure output of 50 pages per minute, ie 25 sheets printed on both sides to achieve, so _are:. to provide five memory locations for pages in the PM page memory. While a page memory location is regularly occupied with the front pages of the single sheets, four pages of the page memory PM are occupied with four back pages. Namely with the back of the sheet 1, the Back sides of the sheet 2, the back sides of the sheet 3 and the back sides of the sheet 4. This is followed by the back sides of the sheet 5, the back sides of the sheet 6, the back sides of the sheet 7 and the back sides of the sheet 8.

A diagram of the impression in duplex mode is shown in FIGS. 13a, b. The designations BPM1, BPM2, BPM3, PM1, PM2 mean the individual pages of the page memory PM. "Print" denotes the imprint at the transfer printing station and "Data" the computer data entered by the computer H. VS1 to VS8 the front of sheets 1 to 8, RS1 to RS8 the back of sheets 1 to 8. DVS1 to DVSδ the computer data front of sheets 1 to 8 and DRS1 to DRS8 the computer data of the back of sheets 1 to 8. The diagram gives the memory PM is occupied by the write data over the time t in seconds or the cycle time T.

The passage of the single sheets in duplex mode through the printing device is in principle as follows: After printing the front of the first sheet, this sheet is deflected after passing through the fixing station F from the switch PW1 into the return channel RF and into the return channel RF through the paper rollers P5 drawn in at process speed. After reaching the paper transport rollers P6, the paper is accelerated to a higher speed by these paper transport rollers. The paper transport rollers P5 contain a freewheel, so that the single sheet can easily be pulled out of these paper rollers P5. The single sheet is introduced into the turning station W1 at this increased transport speed. There it is stopped as described and the transport direction is reversed. With reduced process speed, it is fed again to the pressure channel DK via the paper alignment device PA after turning. 13a, b show that when the front of the sheet 4 is printed, the back of the sheet tes 1 has already passed through the turning station Wl and is present at the synchronization position LS SYN. After printing the back of sheet 1, the front of sheet 5, which has been fed from the supply areas, lies against the synchronization mark LS SYN etc. After printing the back, for example the back of sheet 1, sheet 1 is again over the Fixierstatioπ F the switch PW1 supplied. This now directs the sheet 1 into the duplex simplex channel system, whereby it with process speed

10 digkeit over the pair of paper rollers P21 the switch PW2 is supplied. The switch PW2 directs the sheet 1 described on both sides into the duplex channel DUK. There it is accelerated by the pair of paper rollers P31 and at an increased speed via the pairs of paper rollers P32, P33, P34

15 fed to the turning device W2. This turning device turns the sheet 1 described on both sides again. It is then deposited in the storage container ABI or AB2 via the output channel AK and the switches and paper rollers arranged there.

20th

As described above, the arrangement allows the second turning station W2, that the sheets in Formularbe¬ powered independently whether simplex or duplex mode in the Vorratsbehälterπ VI to V3 with the front side up ²⁵ can be stored. In any case, this ensures that the storage takes place in the correct order in the storage containers ABI or AB2 with the front downward.

- ⁵⁰ A reversal of the order in the storage container requires a reversal of the order in the storage container.

The arrangement of the duplex and simplex channels as separate channels in connection with a second turning device "now also enables continuous printing operation with constant process speed in the mixing operation. are printed, followed by three sheets with simplex printing, then after printing on the front of the first sheet, the sheet is returned via the return channel RF and turned in the turning station W1. However, the following simplex sheets are transported into the SK simplex channel. There they are stored, for example as shown in FIG. 2, in the order E1, E2, E3. This is possible because each of the paper rolls in the simplex channel can be controlled directly via a clutch. After the finished first duplex sheet has passed through the duplex channel DUK at an increased speed and the sheet has been turned in the turning station W2, the duplex sheet is deposited in the storage containers AB at an increased speed via the output channel AK, followed by those likewise in the switch W2 increased transport speed accelerated single sheets E1, E2 and E3.

This sequence is only an example and can be varied as desired. In any case, it is ensured that a continuous process speed can be maintained by the arrangement of the channels and the turning station even with mixed duplex and simplex operation, because only the pages to be printed are guided past the transfer station 15. With the printing device, it is also possible in mixed duplex simplex operation to process large and small paper formats separately or mixed. (A4, A3). In duplex operation for A4 paper formats, the A4 page is divided into two A3 pages and stored in page memories. Printing only begins when both memories are fully written. The procedure for printing the back of an A3 format is similar.

14 claims 14 figures Reference list

VI, V2, V3 paper storage container

10 base plate

PI, P2, P3 paper transport elements

11 paper feed channels

DK pressure channel

DS printing station

12 photoconductor drum

13 character generator, exposure device

14 developer station

15 transfer station

16 cleaning station

S suction table

PA1, PA2, PA3 paper alignment device

Fuser

P5, P6, P7, P8 paper transport elements, paper rollers

RF return channel

Wl turning device

PW1 switch

DUK duplex channel

SK simplex channel

AK output channel

PW2 switch

W2 turning device

PW3, PW4 switch

ABI storage container

AB2 storage container

AF waste bin

LS paper scanning sensors

AZ display device

T keyboard

Ml, M2 engines

SW1 foam roller

SW2 aluminum roller

K clutch

Z timing belt LSI scanner, light barrier

GL slideway

PIO pair of paper rollers

Pll pair of paper rollers

PK paper channel

ZI, Z2 timing belts

P12 pair of paper rollers

SB storage container

R rear wall

LT control device

20 solenoid

21 baffle

22 Paper transport roll

23 solenoid

24 guide element

25 spring

C controller

G Device control

H calculator (Houst computer)

HP main processor

INT1 interface interface

U monitoring circuit

DJ rotary pulse encoder

F output signals, rotary pulse encoder

CPU central processing unit

SPl, SP2, SP3 memory

EA input / output unit

Busl device control bus

Bus2 system bus

I entrance

0 output of the modules

LS2 sensors for VI, V2, V3

P21 to P26 paper roll pairs, simplex channel

P27 to P29 pairs of paper rollers, outlet channel

P31 to P33 pairs of paper rollers, duplex channel

BPM1 to BPM3 pages of the page memory

PM1, PM2 Priπt imprint at the transfer station

Data Computer data entered by computer H.

VS1 to VS8 front of sheets 1 to 8 RS1 to RS8 back of sheets 1 to 8 DVSl to DVS8 computer data of the front of sheets to 8 DRSl to DRS8 computer data of the back of sheets 1 to 8 t time in seconds

T cycle time

Claims

Claims

1. Printing device for single-sided and double-sided printing of single sheets fed serially from the printing device with the following features: a) A printing channel (DK) with an assigned printing station (DS) and paper transport elements (P) is provided; b) a paper transport element (P) and a reversing device (Wl) having a return channel (RF) is coupled to the print channel on the input and output side, which, after printing on a front side, the individual sheets for printing on the rear side of the print station ( DS) feeds again; c) a paper transport channel system with separate duplex (DUK) and simplex channel (SK) for separate transport of the single-sided or one-sided printed sheets into a common output channel (AK) is connected to the printing channel (DK). on; d) the simplex channel (SK) has a paper storage device which stores a first single sheet printed on one side at least until a single sheet printed on both sides before this single sheet has passed through the duplex channel (DUK).

2. Printing device according to claim 1, so that the paper storage device is designed as a storage channel (SK) which receives the individual sheets serially.

3. Printing device according to claim 1, which also means that the paper storage device has a storage container (SB) with paper removal and paper feed elements.

4. Printing device according to one of claims 1 to 3, characterized in that the duplex 1 channel (DUK) and / or the output channel (AK) has a further turning device (W2).

5. Druckeiπrichtung according to any one of claims 1 to 4,

⁵ characterized by a feed channel (11) connected to the pressure channel (DK) with a paper alignment device (PA1. PA3), the single sheets removed from the storage containers (V1-V3) being positioned in the paper alignment device (PA1, PA3) and ^{10 are} then fed to the pressure channel (DK).

6. Printing device according to one of claims 1 to 4, d a d u r c h g e k e n n z e i c h n e t that in the printing channel (DK) in front of the printing station (DS) a paper

I ⁵ straightening device (PA2) is arranged.

7. Printing device according to one of claims 5 or 6, characterized in that the Papierausrichteinrichtung having a motor-driven patent ⁰ pierwalzenpaar (P) with vorgela¬ in the paper transport direction gertem Papierpositionsabtaster (LSI), and that a drive arrangement is provided, which in dependence on the output signal the paper position scanner (LSI) with the paper roll pair (P) stationary in the paper transport

^{25 in the} direction of the paper transport elements (PI) upstream of the paper scanner, the single sheet presses a predeterminable alignment time with its front edge against the pair of paper rollers (SW1, SW2) and that the single sheet thus aligned is then transported further by the pair of paper rollers (P).

30

8. Printing device according to one of claims 1 to 7, characterized by Papiertransportelemeπte (Pll) with variable transport speed and reversible transport direction with a pair of rollers, from pressure roller 5 (SW1) and transport roller (SW2), a first and second electrically operable clutch (Kl, K2), a drive motor (M2) via drive means (ZI) with the Drive side of the clutches and the transport roller (SW2) is coupled to the output side of the clutches via drive means (Z2).

9. Printing device according to one of claims 1 to 8, g e k e n n z e i c h n e t by Papiertransportele¬ elements, with a drive roller made of metal (SW2) and a pressure roller (SW1) made of elastic plastic material.

10. Printing device according to one of claims 1 to 9, so that the return channel (RF) transports the single sheets at a speed which is substantially higher than the printing process speed.

11. Printing device according to one of claims 1 to 10, g e k e n n z e i c h n e t arranged in the Papiertransport¬ channels (DUK, RF, DK, SK, 11), the position of the individual sheets detecting paper position sensors (LS).

12. Printing device according to one of claims 1 to 11, so that in the event of a malfunction of the printing operation due to faulty paper transport via the paper position sensors (LS), the fault position is displayed on a display device (AZ) representing the paper path.

13. Printing device according to one of claims 1 to 12, g e k e n n z e i c h n e t by a separately controllable waste storage container (AF).

14. Printing device according to one of claims 1 to 13, characterized by a storage container for different paper formats with paper transport elements arranged on the input side (P12) and a pivotable guide device (LT) which, depending on the paper format, individual sheets of large paper formats (A3) directly and single sheets of small paper formats (A4) are transported via an additional paper transport element (22) to a stop edge (AB).