EP0404759B1 - Single-page printer for duplex and simplex operation - Google Patents

Abstract

Printing device for printing one or both sides of single sheets fed consecutively by the printing device, comprising a printing channel (DK) with associated printing station (DS) and paper-transporting elements (P). The printing channel (DK) is coupled, on the input and output sides, to paper-transporting elements (P) and a return channel (RF) with a turning arrangement (W1), which, if necessary, returns the one-side printed sheets to the printing station (DS) for printing of the reverse side. The printing channel (DK) is connected to a paper-transporting channel system having paper-transporting elements (P) with separate duplex (DUK) and simplex (SK) channels for transporting separately the one-side or two-side printed single sheets to a common output channel (AK) having a second turning station (W2) for the duplex sheets. The simplex channel (SK) has a magazine which stores a first, one-side printed sheet at least until another two-side printed sheet to be delivered from the output channel before said first sheet has passed along the duplex channel (DUK).

Description

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 on the front side 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 feeding the print channel again, the back of the single sheet is printed. The single sheet is then placed in an output tray 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 print image to the corresponding front and back sides of the single sheets. The correct sequence when dispensing or depositing ensures 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 that contain both simplex and duplex printing, it is disadvantageous that all, even the sheets that are only to be printed on one side (simplex), 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 performance, 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 are immediately deposited, the entire print job must be sorted after being deposited in the storage container. This can only be done manually with considerable effort. Sorting devices that are otherwise required 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 of the known page printers, the form stack to be printed must be stacked in mixed and in pure duplex operation with the front of the individual forms facing down (face-down) in the storage container, so that after a double pass through the printing channel, the stack faces up and down the stock side is stacked. In this case, correct in terms of page 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 printing station is arranged above the pressure channel in the pressure channel.

The operator must therefore be aware of the exact 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 small. 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 malfunctions caused by tears or damage to the paper can be quickly remedied.

Copiers for making duplex copies are known from documents JP-A-58105248 and JP-A-58105249, which have paper storage devices in the form of intermediate containers for receiving faulty duplex copies. After the copying process has ended, the faulty copies are output separately into an output channel. The copiers have turning devices with return channels, through which the single sheets of the copying device are fed again.

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 enables a high printing speed with fast continuous sheet deposition even in mixed operation.

Another object of the invention is to design the single-sheet page printer in such a way that, in particular in form operation, in which a stack of forms of predetermined order and page position is fed to the printer, correct storage in the order and page position of the single sheets is ensured.

The printer should also be designed to be user-friendly, so that, in particular, faults in the paper flow can be easily identified 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 dependent claims.

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 via a return channel and a turning station into the printing channel 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, in the sequence of the printing process, a single sheet to be printed on both sides is placed in front of the single sheet to be printed on one side only, the single sheet to be printed only on one side is stored in the simplex channel until the single sheet to be printed out or to be previously printed is printed on both sides and via a separate one Duplex channel has been fed to an output channel.

The storage device in the simplex channel can consist of an intermediate container which can be loaded with and then removed from individual sheets, or advantageously of 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.

This additional turning device in connection with the storage device of the simplex channel makes the processing of forms considerably easier. Form stacks can now always be placed face up in the storage container, regardless of their composition from 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 storage bin.

In a further advantageous embodiment of the invention, a paper aligning device is located in the input region of the pressure channel or in the feed channel to the pressure channel, which positions the individual sheets removed from the storage container in the correct position before they are fed to the pressure channel.

This enables a correct printing position on the single 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 as it passes through the printing device. If there is an interruption in 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 path. 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 a in the area of the paper transport elements arranged on the input side Swiveling guide device that, depending on the paper format, direct single sheets of large formats directly to a stop edge of the storage container. Small paper formats are guided by the guide device past an additional paper transport roller, which accelerates the paper sheets again and thus also deposits on the stop edge of the paper storage bin.

• FIG 1 eine schematische Schnittdarstellung der Einzelblattdruckeinrichtung
• FIG 2 eine schematische Schnittdarstellung des Papierlaufes mit den Sensoren und den Papiertransportelementen
• FIG 3 eine schematische Darstellung der Anzeige- und Eingabevorrichtung an der Druckeinrichtung
• FIG 4 eine schematische Schnittdarstellung eines Papiertransportwalzenpaares
• FIG 5 eine schematische Schnittdarstellung einer Papierausrichteinrichtung
• FIG 6 eine schematische Schnittdarstellung einer Wendeeinrichtung
• FIG 7 eine schematische Schnittdarstellung eines eine Wendeeinrichtung antreibenden Getriebes
• FIG 8 eine schematische Schnittdarstellung eines Ablagebehälters
• FIG 9 eine schematische Schnittdarstellung einer Speichereinrichtung für Einzelblätter
• FIG 10 eine schematische Schnittdarstellung einer Papierweiche
• FIG 11 ein Blockschaltbild der Steuerungsanordnung für den Einzelblattdrucker
• FIG 12 ein Blockschaltbild des Hauptprozessors der Steuerungsanordnung der FIG 11 und
• FIG 13a, 13b ein Schema der Belegung des Seitenspeichers in Abhängigkeit von den zugeführten Druckdaten über die Zeit.

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 view of the paper run 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 view 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 view 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.

1, which works on the principle of electrophotography, contains three paper reservoirs V1, V2 and V3 with different capacities for receiving single sheets. The paper storage containers V1, V2, V3 are usually constructed 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 P1, P2 and P3. The paper storage 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, the printing channel DK contains paper transport elements in the form of a belt-shaped rotating 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 thermally fix a toner image printed on a recording medium (single sheet) in a known manner.

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 return channel RF containing driven roller pairs. 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 a row 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 AB1 and AB2. A waste container AF (copy tray) that can be controlled via the switch PW4 is also provided.

To determine the position of the continuous 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 still paper alignment devices PA1 to PA3 arranged, which serve to align the single sheet in the correct position before printing in the printing channel DK.

All 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 M1 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 single sheets E removed from the storage containers V1 to V3 and to feed them in an aligned form to the printing station DS.

They have the structure shown in principle in FIG. 5 and consist of an actual pair of paper transport rollers P consisting of a foam roller SW1 and a driven aluminum roller SW2. The driven roller SW2 stands over a clutch K, which consists of an electric actuated spring band coupling can exist in connection with a toothed belt Z driven by the motors M1 or M2. Furthermore, the clutch K contains a brake which ensures that when the frictional connection between the motor and the drive roller SW2 is released, the drive roller SW2 is braked and thus its rotation is inhibited.

A photoelectric scanning device LS1, whose output signal is evaluated by the device control of the printer, is located in front of the paper rollers P in the paper transport direction. The scanner LS1 scans the leading 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 V1 is pulled off with the aid of the paper rollers P1 and transported on a slideway 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 LS1 now recognizes the leading edge of the transported single sheet E and at that 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. However, the transport of the single sheet E on the slideway GL is maintained by the upstream paper rollers P1 of the storage container. The front edge of the single sheet E thus abuts the stationary paper rolls P and bulges out as shown in FIG. 5. Continued transport aligns the paper along its leading edge over the paper rollers P. After a defined time, the paper rollers P1 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 pair of paper rollers P1, not shown here, making it possible to pull the single sheet out of the paper rollers P1.

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 rollers P11 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 arranged downstream of the pair of paper rollers P11.

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 P1 in FIG. 5.

E.g. 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 rollers P11 and transported further until the end of the single sheet leaves the pair of paper rollers 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 assumes a position parallel to the paper channel PK.

Now the direction of movement of the paper rollers P11 reverses and the paper rollers P11 push the cut sheet past the paper rollers P10 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 P11 are coupled to a gear which has a structure corresponding to FIG. 7. The transmission contains a first direction-dependent clutch K1 and a second direction-dependent clutch K2. The couplings are connected to the motor M2 via a toothed belt Z1 on the drive side. 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 P11. 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. With the motor M2 rotating and the clutch K2 actuated, the toothed belt Z2 is moved in the direction of the arrow shown (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 a rapid speed.

Storage container (Fig. 8)

The AB1 and AB2 storage bins are suitable for holding different paper sizes. At their entrance they have a pair of paper rollers P12 which transports the single sheets fed from the output channel AK into the storage container AB1. 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 deposited flush with the rear wall R of the storage bin AB. The filing is done so that the first sheet to be filed is placed face down in the storage bin.

In order to be able to accomplish the storage of 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 back 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). As a result, the single sheets are 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 according to FIG. 9. In principle, this consists of a storage container SB, to which single 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 different paper channels - be it duplex channels or simplex channels - or to select the storage containers AB1 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 with solid lines, it is from above the paper channel leaves paper unaffected so that it is not redirected. In the case of the switch PW2, the paper slides into the simplex channel SK. If the solenoid 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 controller for the page printer is basically divided into a controller part C and the actual device controller G. The controller C is principally 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. Communication between the individual control parts takes place via a hardware / software interface that is uniform for all parts (network-like coupling, serial bus). Each submodule SUB1 to SUB5 is equipped with its own processor and can operate the associated unit of the printing device independently and is itself testable. This self-test capability means that both when the device is switched on and when requested of the main processor HP independent test routines are carried out. All control boards 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 contents of the non-volatile memory can be printed out if necessary. 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 via 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). 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 SUB5 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 synchronization of the sequence control with the peripheral speed of the photoconductor drum 12 takes place via the output signals F of a rotary pulse generator DI. The output of this rotary pulse generator DI (FIG. 2) is connected to all submodules SUB1 to SUB4 and supplies a synchronization signal F at cyclical intervals.

12, the main processor has the following structure:

A central processing unit CPU 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.

In the non-volatile memory SP3, consumption metabolism, printed / fixed page, maintenance intervals, error statistics as well as deviations from guide values etc. entered by the operator are stored. The connection to controller C is established via a common interface INT2.

The main processor HP has the task of coordinating all messages, commands and measurement data from the outdoor stations SUB1 to SUB4, checking for plausibility and forwarding them. It also establishes the connection to controller C via the interface INT2 and the system bus BUS2. In doing so, 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 levels that drive the associated units via output O. The submodules can be tested themselves, 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 V1 to V3, the feed channels 11 and the pressure channel DK and in particular the pressure start signal of the sensor LSSYN. The submodule SUB1 controls all units in this area. It detects and reports paper run errors.

The submodule SUB2 detects all sensors LS in the paper output area, i.e. in the area of the output containers AB1, AB2 and the waste container AF and in the output channel AK. Paper run errors are detected and reported to the main processor HP.

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

The submodule SUB4 controls the display device AZ on the printer. The display field AZ contains a keyboard and a display device (FIG. 3), with the paper device in the printer or, in the event of a paper transport fault, the fault location being shown via the display device. The sub module 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 via 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 important 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 transport malfunction occurs, it becomes shown on the control panel paper flowchart. The fault location can thus be localized automatically. The operator can now rectify the transport problem without wasting time.

In order to ensure continuous printing operation, a new single sheet reflecting the content of the destroyed single sheet is printed immediately after the resumption of the printing operation after the fault has been rectified. All the individual sheets located between the fault location and the printing station in the printing device are also newly created, so that the individual sheets are correctly deposited in the storage container AB1 or AB2. The unnecessary single sheets between the fault location and the printing station are automatically transported to the waste bin 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 SUB4 submodule 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 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 buffered page by page in a page memory PM of the controller C.

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 operation, and three rear-side memories are required for duplex operation. In mixed operation, i.e. when duplex and single sheets are mixed, this requirement fluctuates depending on the print 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 print format are used in the V1 storage container, single sheets in A3 format in the V2 storage container. It is even possible to use different paper sizes within one stack. The size of the photoconductor drum 12 is designed so that A4 size paper can be printed on it 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 using the photoconductor drum 12 in the transfer printing station 5.

The printing process as such should first be described using A4 format simplex mode.

Each storage container V1 to V3 contains sensors LS2 in the area of its paper transport elements P1 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 P1 to P3, the stack is automatically conveyed via the lifting table 10. The single sheet detected by the sensors LS2 is then fed with the aid of the paper transport rollers P1 to P3 up 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 V1 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 pressure channel DK.

At time T0, the printing device is in standby mode, the page memories are empty. At this point the 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 front edge of the single sheet and a scanning element that determines the presence of the single sheet. The synchronization position is defined as the drum section of the photoconductor drum 12, from the character generator 13 to the transfer printing station 15, folded over 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. At the time T2, sheet 1 has reached the synchronizing 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 the page memory PM has been written on the drum and the 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 in the direction of the synchronization position.

The printed sheets are transported to the fixing station F via the suction table 5 and fixed there. Their position is continuously scanned by the light barriers LS in the pressure channel DK.

Since these are single sheets in simplex mode, the single sheets are fed via the switch PW1 to the pair of paper rollers 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 AB1 or AB2 or the waste bin AF. In order to be able to compensate for the length of the simplex channel or to be able to ensure that the individual sheets are deposited securely in the storage containers AB1 and AB2, the individual sheets in the turning device W2 are accelerated to increased speed via the paper roller pairs P11 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 path, has a freewheel.

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.

Sec.= 1,2 Sec. (Druckleistung: 50 Seiten pro Minute) für eine Blattgröße A4, wird der Druckvorgang dann ausgelöst, wenn das jeweilige Blatt den Synchronisierpunkt LS SYN erreicht hat. Wenn die Datenübertragungszeit größer als die Zykluszeit ist (1,2 Sec.), wird das Blatt kurz vor der Synchronisierposition angehalten und erst dann weiterbefördert, wenn der jeweilige Seitenspeicher voll beschrieben ist. Beim Erreichen des Synchronisierpunktes LS SYN wird dann der Druckvorgang ausgelöst.In order to achieve the full printing speed of the page printer, the distance between two printed A4 pages must not exceed a defined distance, in this case, for example, 54 mm. However, the printing process and thus the paper feed from the storage containers V1 to V3 can only begin when the respective memory area of the page memory PM has been fully written. This would mean that the distance from the paper input tray (V1 to V3) to the synchronization point LS SYN should also not exceed 54 mm. For design reasons, however, it is not possible to place three storage containers at this distance. The distance of 54 mm can, however, be avoided if the paper is already being moved 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 $\frac{\text{60}}{\text{50}}$

Sec. = 1.2 Sec. (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 transfer time is longer 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 is fully written. When the synchronization point LS SYN is reached, the printing process is triggered.

Damit verbleiben für den Transport des Papieres von Warteposition bis zur Synchronisierposition: T = 2,4 Sec. - 0,955 = 1,45 Sec. Dies ergibt einen Weg von 318 mm. Bei der obengenannten Rechnung sind zusätzliche Verzögerungszeiten wie z.B. Schaltzeiten von Kupplungen nicht berücksichtigt.The waiting position of the paper is calculated as follows: At time T3 = T0 + 2.4 sec. the first memory area of the memory PM must have been emptied. At a process speed of 220 mm per second and one Print length of A4 of 210 mm results in a print time of

This leaves for the transport of the paper from the waiting position to the synchronization position: T = 2.4 seconds. - 0.955 = 1.45 sec. 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 V1 to V3 to this position, 1 sheet from all three input compartments is "drawn" to this waiting position LS3.

Print larger paper sizes

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 seconds. Two A4 page memories are available for writing on the A3 paper format. 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 can only begin when both memory areas have been emptied. The data transfer time for 25 pages per minute A3 is as follows:
Cycle time T = 2.4 seconds.
Printing time for

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

Duplex operation

In duplex mode, both the front and the back of the single sheets are described.

The feeding of the single sheets from the storage containers V1 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. The order of the printing process is different, however, since the single sheets to be written on both sides after writing the front page via the return channel RF must be fed back to the printing station.

In duplex mode for writing on a paper format A4, the order 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 printing the front side of sheet 4, alternating printing from front side, back side, front side, back side etc. takes place for better utilization of the computer interface. Printing capacity of 50 pages per minute, ie to achieve 25 sheets printed on both sides, therefore five storage locations for pages must be provided in the PM 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 Backs of sheet 2, the backs of sheets 3 and the backs of sheets 4. This is followed by the backs of sheets 5, the backs of sheets 6, the backs of sheets 7 and the backs of sheets 8.

A schematic 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 print 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 DVS8 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 occupancy of the memory PM by the write data over the time t in seconds or the cycle time T.

The throughput of the single sheets in duplex mode through the printing device is in principle as follows: After printing on 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 in Process speed pulled in. 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. With this increased transport speed, the single sheet is introduced into the turning station W1. There it is stopped as described and the direction of transport reversed. With reduced process speed, it is fed again to the pressure channel DK via the paper alignment device PA after turning. From the diagram of Fig. 13a, b it can be seen that when printing the front of the sheet 4, the back of the sheet 1 has already passed through the turning station W1 and is present at the synchronization position LS SYN. After printing on the back of the sheet 1, the front of the sheet 5, which was fed from the supply areas, is in contact with the synchronization mark LS SYN etc. After printing on the back, for example the back of the sheet 1, the sheet 1 is again via the fixing station F. the switch PW1 fed. This now guides the sheet 1 into the duplex simplex channel system, whereby it is fed to the switch PW2 at process speed via the pair of paper transport rollers P21. 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 fed to the turning device W2 at an increased speed via the pairs of paper rollers P32, P33, P34. This turning device turns the sheet 1 described on both sides again. It is then deposited in the storage container AB1 or AB2 via the output channel AK and the switches and paper rollers arranged there.

As described at the outset, the arrangement of the second turning station W2 enables the sheets to be placed face up in the storage containers V1 to V3, regardless of whether they are in simplex or duplex mode. In any case, this ensures that the filing takes place in the correct order in the storage containers AB1 or AB2 with the front facing downwards.

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 enables continuous printing with a constant process speed in mixed mode are followed by three sheets with simplex printing, after printing 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 simplex channel SK. 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 rollers in the simplex channel can be controlled directly via a clutch. After the completed 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 at an increased speed via the output channel AK in the storage containers AB, followed by the individual sheets which have likewise been accelerated to increased transport speed in the switch W2 E1, E2 and E3.

This order is only an example, it can be varied as required. 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 printer, it is also possible in mixed duplex simplex operation to process large and small paper sizes separately or mixed. (A4, A3). In duplex mode 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.

Claims (14)

1. Printer for printing on one side and both sides of single sheets fed to the printer consecutively in a mixed sequence of single sheets to be printed both on one side and on both sides, having the following features:

   a) A printing channel (DK) with associated printing station (DS) and paper-transport elements (P) is provided;

   b) a return channel (RF) which has paper-transport elements (P) and a turning device and which is coupled on the input and output sides to the printing channel and which, as required, after printing a front side feeds the single sheets again to the printing station (DS) for printing the reverse side;

   c) a paper-transport channel system which has paper-transport elements (P) and with separate duplex (DUK) and simplex (SK) channel adjoins the printing channel (DK) for the purpose of separately transporting the single sheets printed on both sides or on one side into a common output channel (AK);

   d) the simplex channel (SK) has a paper-storage device;

   e) a single sheet which is printed on one side and follows a single sheet printed on both sides in the sequence of the printed single sheets is stored in the paper-storage device (SK) by means of a control device (SUB2) for controlling the output sequence of the single sheets to the output channel (AK), until the single sheet printed on both sides has passed through the duplex channel (DUK).
2. Printer according to Claim 1 having the following further features: the paper-storage device is constructed as a storage channel (SK) which receives the single sheets consecutively.
3. Printer according to Claim 1 having the following further features: the paper-storage device has a paper supply container (SB) with paper extraction and paper-feed elements.
4. Printer according to one of Claims 1 to 3, having the following further features: the duplex channel (DUK) and/or the output channel (AK) has a further turning device (W2).
5. Printer according to one of Claims 1 to 4, having the following further features: a feed channel (11) with a paper alignment device (PA1, PA3) is connected to the printing channel (DK), the single sheets extracted from the stock containers (V1 - V3) being positioned in the paper aligning device (PA1, PA3) and then being fed to the printing channel (DK).
6. Printer according to one of Claims 1 to 4, having the following further features: a paper aligning device (PA2) is arranged in the printing channel (DK) in front of the printing station (DS).
7. Printer according to one of Claims 5 or 6, having the following further features: the paper aligning device has a motor-driven paper roller pair (P) with paper-position sensor (LS1) mounted upstream in the paper-transport direction and a drive device is provided which when the paper roller pair (P) is stationary presses the single sheet for a predeterminable alignment time with its front edge against the paper roller pair (SW1, SW2) as a function of the output signal of the paper-position sensor (LS1) via paper-transport elements (P1) mounted upstream of the paper sensor in the paper-transport direction and then transports on from the paper roller pair (P) the single sheet which is aligned in this way.
8. Printer according to one of Claims 1 to 7, having the following further features: paper-transport elements (P11) with a variable transport speed and reversible transport direction are provided with a roller pair comprising a pressure roller (SW1) and transport roller (SW2), a first and second electrically actuable coupling (K1, K2), a drive motor (M2) being coupled via drive means (Z1) to the drive side of the couplings and the transport roller (SW2) being coupled via drive means (Z2) to the drive side of the couplings.
9. Printer according to one of Claims 1 to 8, having the following further features: paper-transport elements are provided comprising a driver roller made of metal (SW2) and a pressure roller (SW1) made of elastic plastic material.
10. Printer according to one of Claims 1 to 9, having the following further features: the return channel (RF) transports the single sheets at a speed which is substantially higher than the printing process speed.
11. Printer according to one of Claim 1 to 10, having the following further features: paper-position sensors (LS) which detect the position of the single sheets are arranged in the paper-transport channels (DUK, RF, DK, SK, 11).
12. Printer according to one of Claims 1 to 11, having the following further features: when the printing operation is disturbed by defective paper-transport the position of the fault is displayed via the paper-position sensors (RS) on a display device (AZ) which displays the transport path of the paper.
13. Printer according to one of Claims 1 to 12, having the following further features: a separately actuable waste/paper supply container (AF) is provided.
14. Printer according to one of Claims 1 to 13, having the following further features: a paper supply container is provided for different paper formats with paper-transport elements (P12) arranged on the input side and with a pivotable guide device (LT) which, as a function of the paper format, transports single sheets of large paper formats (A3) directly to a stop edge (AB) and single sheets of small formats (A4) to said stop edge via an additional paper-transport element (22).

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