Abstract:
An electrographic printing device has at least one printing unit with a toner image carrier. A printing device for producing a toner image prints at least one mark on a photoconductor belt. The toner contained on the photoconductor belt is transferred to a transfer belt at a first transfer point and transferred from said transfer belt to a strip-shaped support material at a second transfer point. A sensor situated on the transfer belt detects the passage of the mark and a control unit determines the time that has elapsed between the time of printing and the time at which the mark is detected and controls the transportation of the strip-shaped support material accordingly.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is directed to an electrographic printer device with at least one printing unit having a toner image carrier on whose circumferential surface toner can be applied according to an image-like distribution. 
     2. Description of the Related Art 
     Such a printer device is utilized in a printer or copier, whereby a latent image is applied on the toner image carrier with the assistance of an electrographic method. This can ensue, for example, by illuminating a photoconductor or by magnetizing a magnetically sensitive layer. Toner agglomerates to the latent image according to the image-like distribution of the electrical charges or of the magnetic poles. This toner is transferred onto a carrier material, generally paper, at a transfer printing location and is fixed thereon later. 
     An apparatus with such a printer device should work fast and be flexibly employable. Often, toner images must be printed onto a form that has form windows into which individual characters are to be printed. The characters must thereby be positioned exactly within the form windows. Given multi-color printing, the individual chromatic sub-images must be congruently printed in order to generate a multi-color image. All of this makes high demands of the mechanism. 
     European Patent Document EP 0523870 discloses a printer device wherein a plurality of sub-images of different colors are generated successively and spaced from one another on a photoconductor band. The sub-images are individually transferred onto a sheet-shaped recording medium at a transfer printing location, whereby the recording medium is repeatedly conducted past the transfer printing location such that the sub-images are transfer-printed as congruently as possible. The spacing of two successive sub-images is equal to the circumference of the rollers on which the photoconductor runs or to a multiple thereof, whereby the individual rollers respectively have the same circumference. A non-uniform rotational motion, for example due to an eccentricity of the roller axes, then has the same effect in all sub-images, so that the congruently transfer-printed sub-images yield a full-color image without color errors. 
     Given the known printer device, a slippage can occur between the drive rollers and the photoconductor band. For example, the unrolled circumference of the drive roller in a revolution is longer than the distance by which the photoconductor band moves forward. Moreover, the mechanics at the transfer printing locations can change. When printing on a form, for example, it is important that the toner image is printed in predetermined sections of the form. The slippage between the photoconductor band and the drive rollers is not constant but can change due to external influences such as, for example, temperature or atmospheric humidity or as a result of aging. The changes in the mechanism at the transfer printing locations are also dependent on external influences. These changes are difficult to determine. When the toner images can no longer be precisely printed onto the form due to a slippage or a modifications of the mechanics, this is often only noticed later and leads to rejects. 
     German Patent Document DE 198 21 218 shows a printer device wherein the differently colored sub-images are to be congruently transfer-printed onto a transfer band. For this purpose, a number of marks which are detected when they pass by a sensor are arranged at the transfer band. The detection signal of the marks is kept in a fixed phase relation with a line synchronization signal by controlling the circumferential speed of the transfer band. This requires a substantial circuit outlay. 
     Another printer device wherein differently colored sub-images are congruently transfer-printed is disclosed by the German Patent Document DE 198 06 551. Given this printer device, one mark for each sub-image is printed onto a paper web as the recording medium. The reflectivity of the marks congruently printed on top of one another is measured for checking the alignment of the individual sub-images relative to one another. The drive of the individual printing units is regulated on the basis of this check result. This printer device, too, requires considerable circuit outlay. A positionally exact printing in a form window cannot be achieved given this known printed device. 
     Given a printer device disclosed by the German Patent Document DE 38 08 620, the leading edge of a sheet-shaped recording medium is detected with a sensor and the feed of the recording medium is controlled dependent on this detection. 
     Although a positionally exact printing in a form window can thereby be achieved given a sheet-shaped recording medium, this does not lead to the desired outcome given a band-shaped recording medium. 
     European Patent Document EP 0 281 055 recites a printer device wherein a position sensor for a drum is provided. This printer device, too, can only be employed for sheet-shaped recording media. 
     Patent Abstracts of Japan JP-A-06027829 discloses components of a printer device wherein a mark is applied on a transfer band, the mark being moved past a sensor together with the transfer band. The passing of the mark is acquired with the assistance of a controller and the rotational speed of the transfer band is identified. Dependent on the result of the determination of the rotational speed, a drive motor is influenced with the assistance of a further controller in order to correct this rotational speed of the transfer band to a predetermined value. It is assured in this way that the transfer band maintains a predetermined rotational speed. 
     SUMMARY OF THE INVENTION 
     An object of the PRESENT invention is to provide a printer device that recognizes a transfer of toner images that is not in proper order. 
     This object is achieved by an electrographic printer device with at least one printing unit having a toner image carrier on whose circumferential surface toner can be applied according to an image-like distribution, whereby the toner image carrier has a photoconductor, whose outer circumferential surface can be charged with a latent charge image, and a transfer band onto which the toner present on the photoconductor can be transferred at a first transfer printing location, a carrier material is conducted past the transfer band such that the toner arranged thereon can be transferred onto the carrier material at a second transfer printing location, a printing mechanism for generating the toner image and that prints at least one mark onto the photoconductor is arranged along a circumferential section of the photoconductor, at least one sensor that acquires the passing of the mark is arranged at the transfer band, a controller determines the transit time of the mark from the printing time of the printing mechanism up to the acquisition time at the sensor, and whereby the transport of the band-shaped carrier material is influenced in controlling fashion dependent on the transit time. 
     In the invention, the mark moves with a constant speed from the acquisition time until the transfer printing time in the steady state. The time that the toner image requires until the transfer printing onto the carrier material can therefore be calculated from the transit time. When the printing quality deteriorates as a consequence of a change in the slippage, for example due to a modified ambient temperature, this change in slippage also causes a change in the transit time that is monitored by the controller. A change in the slippage is thus indirectly recognized and the printing event can be correspondingly controlled. For example, the transport of the carrier material can be influenced in a controlling fashion dependent on the transit time, for example by halting the printing operation or by readjusting the transport velocity. 
     In a development of the invention, the transit time is compared to a predetermined rated value, a signal being generated when the latter is upwardly or downwardly transgressed. Given a deviation from the predetermined rated value, the slip has changed or modifications have occurred in the mechanisms. The transport of the band-shaped carrier material can be influenced in a controlling fashion dependent on the generated signal. In one exemplary embodiment of the invention, the operation of the printer device can be interrupted dependent on the signal. The printing of rejects is thus avoided. 
     According to another example of the invention, the base time that the toner image applied by the printing mechanism requires in order to be transfer-printed at the second transfer printing location is determined in a calibration event. The rated time is then defined on the basis of the base time. For example, the rated time can amount to 98% of the base time. When the transit time of the mark coincides with the rated time in this case, then it is assured that the toner image is transfer-printed onto the carrier material at exactly the desired location. 
     In a development of the invention, the base time is redetermined given occurrence of the signal. As mentioned, the signal is generated given a deviation of the transit time from the rated time. This means that the base time has changed and the toner images are no longer printed onto the carrier material at the desired location. The base time must thus be redetermined and the transport of the band-shaped carrier material must be controlled in conformity with the modified slippage. For example, the time between the generation of the latent image and the start of the transport of the carrier material can be adapted to the modified base time. 
     The sensor is preferably arranged close to the second transfer printing location. The deviation of the transit time from the base time is especially small then. As a result thereof, the toner image can be very precisely placed on the carrier material. 
     One development is characterized in that the printer device has at least one image generating unit for generating a latent charge image on the photoconductor and at least one developer station that inks the charge image with toner. A uniform print image with a high resolution can be achieved as a result thereof. The printer device can also have a plurality of developer stations, as a result whereof a multi-color printing is possible. 
     In one version of the invention, a second printing unit for generating a toner image is provided at that side of the carrier material facing away from the first printing unit. A duplex printing is possible in this way, whereby both sides of the carrier material are then simultaneously printed. 
     According to a further aspect of the invention, the electrographic printer device has at least one printing unit with a toner image carrier on whose circumferential surface the toner can be applied according to an image-like distribution, whereby the toner image carrier has a photoconductor, whose outside circumferential surface can be charged with a latent charge image, and a transfer band onto which the toner present on the photoconductor can be transferred at a first transfer printing location, a carrier material is conducted past the transfer band such that the toner arranged thereon can be transferred onto the carrier material at a second transfer printing location, a printing mechanism for generating the toner image is arranged along a circumferential section of the photoconductor, at least one mark is arranged on the transfer band, at least one sensor that acquires the passing of the mark is arranged at the transfer band, a controller determines the revolution time of the mark on the transfer band, and whereby the printer device is influenced in a controlling fashion dependent on the revolution time. 
     Given a such a printer device of the invention, successive toner images can be congruently transfer-printed onto the transfer band. The revolution time of the mark is determined by the controller on the basis of the acquisition of the passing of the mark at the sensor, whereby the revolution time likewise changes given a change in the slip or, respectively, given a change in the length of the transfer band. As a result thereof, a change in slip or, respectively, a change in the length of the band is recognized, and the printing event can be controlled dependent on the revolution time. Although the slippage itself or, respectively, the change in length of the transfer band is not identified, the toner images can be precisely arranged thereon in this way. 
     Preferably, the time between the application of two successive toner images on the photoconductor is determined on the basis of the revolution time. The photoconductor and the transfer band thereby run with the same, constant speed. The toner images can thus be placed exactly on the transfer band in an especially simple way. 
     In one development, the revolution time is determined in a calibration event. As a result thereof, a revolution time is available for the following printing events on whose basis the time between the application of two successive toner images on the photoconductor band can be determined. Preferably, a calibration event is implemented in parallel to every printing event. The printer device can thus be especially quickly and exactly controlled. 
     In a collecting mode, the transfer band is repeatedly conducted past the first transfer printing location, and a toner image is transferred onto the transfer band onto the previous toner image at every renewed passage. In this way, toner images can be especially simply superimposed. A cleaning mechanism of the transfer band should thereby be pivoted away from it. 
     At every repeated passage, the transfer band is pivoted away from the carrier material so that a contamination of the carrier material and a smearing of the toner images on the transfer band are avoided. 
     One development is characterized in that, based on the revolution time, the time between the application of two successive toner images onto the photoconductor is set such that they are congruently transfer-printed when the transfer band passes by the first transfer printing location. The transfer band runs with a constant speed, and a change in the revolution time then means that the length of the transfer band has changed. The time between the application of two successive toner images onto the transfer band must thus be modified. 
     The mark can be permanently arranged on the transfer band. For example, a reflective lamina can be glued or riveted onto the transfer band or the mark can be a slot in the transfer band. A long service life and a high precision in the determination of the revolution time are thus assured. 
     In one development, a reflex sensor that detects the passing of the toner mark is employed. A simple structure derives as a result thereof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is explained in greater detail below on the basis of the drawing. 
     FIG. 1 is a schematic illustration of an exemplary embodiment of a printer device with a sensor for the acquisition of a mark. 
     FIG. 2 is a graph of the executive sequence of a printing event of the printer device. 
     FIG. 3 is a schematic illustration of another exemplary embodiment for multi-color printing. 
     FIG. 4 is a graph of an executive sequence of a collecting mode of the exemplary embodiment according to FIG.  3 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows an exemplary embodiment of a printer device with a first printing unit  10  and with a second printing unit  12  that are arranged at surfaces of a paper web  14  that face away from one another. The paper web  14  is moved forward in the direction indicated by the arrow A by a drive roller  16 . It can also be pulled back by the drive roller  16  in order, for example, to realize a defined restart. A fixing station  18  and a cooling device  20  arranged along the paper web  14  in this sequence in forward direction following the printing units  10  and  12 . The printer device and its function are described in detail in published PCT Application WO 98/39691, which is a constituent part of this disclosure of this application. 
     The first printing unit  10  has a first photoconductor band  22  that runs over rollers, which shall not be discussed in further detail here, and that moves in the direction indicated by the arrow B. A first character generator  24  and a first developer station  26  are arranged at the first photoconductor band  22 . At a first transfer printing station  28 , the first photoconductor band  22  is in contact with a first transfer band  30  (likewise conducted over rollers that are not explained in detail here) that moves in the direction of the arrow C. 
     At a second transfer printing location  32 , the first transfer band  30  is in contact with what is the upper surface of the paper web  14  in FIG.  1 . Close to the second transfer printing location  32 , a first reflected light barrier  34  is arranged at the first transfer band  30  in its moving direction preceding the second transfer printing location  32 . 
     The second printing unit  12  is constructed similar to the first printing unit  10 . It has a second photoconductor band  36 , a second character generator  38  and a second developer station  40 , whereby the second photoconductor band  36  moves in the direction of the arrow D and is in contact with a second transfer band  44  at a third transfer printing location  42 . This moves in the direction of the arrow E and is in contact at a fourth transfer printing location  46  with what is the bottom surface of the paper web  14  in FIG. 1. A second reflected light barrier  48  is arranged at the second transfer band  44  close to the fourth transfer printing location  46 . 
     The printer device has a device controller GS for controlling the printing operation. The device controller GS is connected to a control panel CP with which print commands can be input to it. The controller ST, the device controller GS and the control panel CP as well as their function are described in greater detail in published PCT application WO 98/39691. The controller ST is connected to the character generators  24  and  38 , to the reflected light barriers  34  and  48  and to the drive roller  16  via signal lines or, respectively, control lines, which are shown schematically in FIG.  1 . 
     The functioning of the first printing unit  10  is explained below. The same applies to the second printing unit  12 . The first character generator  24  applied a latent charge image onto the first photoconductor band  22 . The character generator  24  can be an LED character generator, as disclosed, for example, by the published PCT application WO 98/39691, or it can generate the latent image with laser diodes. This charge image is inked with toner by the first developer station  26 . 
     The toner image is transfer-printed onto the first transfer band  30  at the first transfer printing station  28 . At the second transfer printing location  32 , the toner image is transfer-printed onto the paper web  14  and fixed in the fixing station  18 . The paper web  14  heated by the fixing is subsequently cooled in the cooling device  20 . 
     Additionally, the first character generator  24  respectively applies a mark onto the first photoconductor band  22  as a latent image outside the actual printing region at the beginning of each and every image. These marks are likewise inked with toner at the first developer station  26  and transfer-printed onto the first transfer band  30  at the first transfer printing location  28 . These toner marks are acquired by the first reflected light barrier  34 . Dependent on its acquisition conditions, this generates a signal that is transmitted to the controller ST. 
     In a calibration event, the base time that a print image requires from the printing time at the first character generator  24  until the transfer printing time onto the paper web  14  at the second transfer printing location is identified. The photoconductor band  22 , the transfer band  30  and the paper web move with the same constant speed. The transport of the paper web  14  is started with such a time delay dependent on this base time that the toner images are transfer-printed exactly into the desired form windows at the second transfer printing location  32 . 
     So that the deviation of the transit time of the toner mark from the printing time at the first character generator  24  up to the acquisition time at the first reflected light barrier  34  from the base time is as small as possible, the first reflected light barrier  34  is arranged as close as possible to the second transfer printing location  32 . The majority part of the distance, for example 98%, that the toner image covers until the transfer printing onto the paper web  14  is thus monitored. The rated time is then defined as 98% of the base time. The print image is printed into the form on the paper web with the desired precision when the measured transit time corresponds to the rated time. When there is enough space, the reflected light barrier  34  can also be arranged directly at the second transfer printing location  32 . 
     The printing operation is interrupted when the measured transit time upwardly or downwardly transgresses a predetermined limit value. The paper web  14  is pulled back to such an extent that, given a restart of the printing event, the printing can be continued at the most recent printing position without leaving a gap free. A new calibration event is subsequently implemented. To this end, the above-described procedure can be implemented anew or the new base time can be determined from the most recently measured transit time or, respectively, from the average of the most recently measured transit times. A restart of the printing event is then implemented on the basis of this new base time. 
     FIG. 2 shows the time sequence of the event that has just been described. The time t is entered as the abscissa and the speed P of the paper web  14  is entered as the ordinate. The paper web  14  is at rest at a time T 0  and the first character generator  24  begins to write the four printed pages So 1  through So 4  onto the first photoconductor band  22 . The second character generator  38  begins to write four pages Su 1  through Su 4  onto the second photoconductor band  36  at a later point in time T 1  since the base time for the second printing unit  12  is shorter than for the first printing unit  10 . The paper web  14  is then at rest in a region B 1  up to a point in time T 2 . It is then accelerated up to its final speed in a region B 2  up to a point in time T 3 . 
     In a region B 3 , the pages So 1  through So 4  are transfer-printed at the second transfer printing location  32  and the pages Su 1  through Su 4  are transfer-printed onto the paper web  14  at the fourth transfer printing location  46 . When the controller thereby finds a deviation of the measured transit time from the rated time, the print operation is interrupted at a point in time T 4 . The paper web  14  is stopped in a region B 4  up to a point in time T 5  and pulled back to such an extent that a new printed page can be printed into the area provided therefor in the next, unprinted form given a restart. 
     During the event that has just been described, the controller has determined the new base time and lets the first character generator  24  begin—at a time T 6 —to write four further pages So 5  through So 8  onto the first photoconductor band. At a later point in time T 7 , the second character generator  38  also begins to write four further pages Su 5  through Su 8  onto the second photoconductor band  36 . 
     Dependent on the new base time, the paper web remains at rest in a region B 5  up to a new point in time T 8  and is again accelerated to its final speed in a region B 6 . From the point in time T 9 , the pages So 5  through So 8  are then transfer-printed onto the paper web  14  at the second transfer printing location  32  and the pages Su 5  through Su 8  are transfer-printed onto the paper web  14  at the fourth transfer printing location  46  in a region B 7 . 
     FIG. 3 shows a second exemplary embodiment of an electrographic printer device with a first printing unit  50  and with a second printing unit  52  similar to the first printing unit  10  and the second printing unit  12  of the first exemplary embodiment in FIG.  1 . Identical elements have the same reference characters as therein. Instead of the first developer station  26 , five developer stations  26   a  through  26   e  are arranged here at the first photoconductor band  22 ; and, instead of the second developer station  40 , likewise five developer stations  40   a  through  40   e  are arranged at the second photoconductor band  36  here. 
     A mirror lamina (not shown) is respectively firmly attached to the first and to the second transfer band  30  and  44  as a mark. For detecting the passage of the mark, a first reflected light barrier  54  and a second reflected light barrier  56  are respectively arranged at the first transfer band  30  and at the second transfer band  44 . 
     The printing event of the second exemplary embodiment corresponds to that of the first exemplary embodiment. Over and above this, however, a multi-color print image can be generated on the paper web  14  in the operating mode of “collecting mode” given the second exemplary embodiment. This collecting mode is disclosed in detail in the published PCT application WO 98/39691. The executive sequence of such a collecting mode is explained below only for the first printing unit  50 . The same applies to the second printing unit  52 . 
     The transport of the paper web  14  is stopped and this is pulled back to such an extent that transfer printing can be carried out onto the following, unprinted form on the paper web  14  at the second transfer printing location  32  give a restart of the paper transport. Given a first revolution of the first photoconductor band  22 , the first character generator  24  generates four latent images corresponding to four printed pages on the band  22 . These four latent images are inked with toner in a first color by the developer station  26   a.  These four toner images having the first color are transferred onto the first transfer band  30  at the first transfer printing location. 
     At the beginning of the collecting mode, the first transfer band  30  is pivoted away from the paper web  14  at the second transfer printing location, so that the toner images do not smear when running past the paper web  14  or do not smear the latter. The first reflected light barrier  54  acquires the mark on the first transfer band  30  and forwards a signal to a controller according to its acquisition condition. The controller is similar to the first exemplary embodiment but is not entered in FIG.  3 . It determines the revolution time of the mark from the signals and forms an average therefrom. The first photoconductor band  22  and the first transfer band  30  circulate with the same, constant speed, and, using the revolution time of the mark, the point in time is determined at which the first character generator  24  must begin to generate four further latent images corresponding to four further printed pages on the first photoconductor band  22 , so that these are congruently transfer-printed onto the first transfer band  30  onto the four toner images. 
     At the indicated point in time, the first character generator  24  begins to generate another four latent images corresponding to four more printed pages on the first photoconductor band  22  in a second revolution of the first photoconductor band  22 . The developer station  26   b  inks these four latent images with toner in a second color, and these four latent images are congruently transfer-printed onto the first transfer band  30  onto the four toner images with the first color at the first transfer printing location  28 . 
     In a similar way, respectively four further latent images can be successively generated on the photoconductor band  22  by the first character generator  24  in a third, a fourth and in a fifth revolution of the first photoconductor band  22 , can be inked with toner of a third, a fourth and a fifth color by the developer stations  26   c ,  26   d  and  26   e,  and can be congruently transfer-printed on the first transfer band  30  onto the four toner images having the first and the second color at the first transfer printing location  28 . 
     In this method, toner images with a number of colors can be congruently transfer-printed on the first transfer band  30  in the collecting mode. Subsequently, the first transfer band  30  is pivoted back against the paper web  14  at the second transfer printing location  32 , and the paper transport is restarted such that the four pages which are congruently transfer-printed multi-color on the first transfer band  30  can be transfer-printed onto the desired position on the paper web  14 . The collecting mode has thus been ended, and a new collecting mode can be subsequently started or further printing can continuously ensue in one color. 
     The second printing unit  52  can implement a similar collecting mode parallel to the collecting mode of the first printing unit  10 . A different number of developer stations per photoconductor band can also be employed. 
     FIG. 4 shows an executive sequence in the collecting mode given the exemplary embodiment of FIG.  3 . The time t is entered as the abscissa and the speed P of the paper web  14  is entered as the ordinate. Similar to FIG. 2, the first character generator  24  begins to generate five printed pages as latent images on the first photoconductor band  22  at a time T 0 . Subsequently, the collecting mode is started, whereby four latent images corresponding to four printed pages are generated on the first photoconductor band  22  by the first character generator  24  during the time T TF1  that the first transfer band  30  requires for one revolution, and these are inked with red toner by one of the developer stations, for example the developer station  26   b.    
     In a second pass, one latent image is generated on the photoconductor band  22  and, for example, is inked with green toner by the developer station  26   c  because only the fourth page is supposed to contain green; and, in a third pass, four latent images corresponding to four printed pages are again generated, and these are inked with black toner by the developer station  26   c.    
     At a time T 1  following the time T 0 , the second character generator  38  also begins to generate five latent images on the second photoconductor band  36 . Subsequently, the second printing unit  12  likewise begins a collecting mode, whereby two latent images that the developer station  40   b  inks with green toner are generated during the time T TF2  in a first pass of the second transfer band  44 . Two latent images are generated in a second pass and four latent images are generated in a third pass, respectively during the time T TF2 , these being inked with red or, respectively, with black toner by the developer station  40   a  or, respectively,  40   c.    
     Similar to FIG. 2, the paper web is accelerated to its final speed from time T 2  through time T 3 . In the region B 8 , the first five toner images are then respectively transfer-printed onto the paper web  14  at the second or, respectively, fourth transfer printing location  32  and  46 . In the region B 9 , the first and the second transfer band  30  and  44  are pivoted away from the paper web  14  and no transfer-printing of toner images onto the paper web  14  ensues at the second or, respectively, at the fourth transfer printing location  32 ,  46 . The paper web  14  is pulled back between the times T 4  and T 5  and then remains at rest until the time T 8 . By time T 9 , the paper web  14  is again accelerated to its final speed, and the transfer bands  30  and  44  are in turn pivoted against the paper web  14 . 
     In the region B 10 , the toner images which are transfer-printed onto the transfer bands  30  and  44  during the collecting mode are transfer-printed onto the paper web  14  at the transfer printing locations  32  and  46 . Following thereupon, single-color printing can continue without interruption. In FIG. 4, five further printed pages are transfer-printed with black toner by time T 10 . Subsequently, the paper web is again stopped and pulled back. 
     So that brief-duration synchronization fluctuations of the photoconductor bands  22  and  36  and of the transfer bands  30  and  44  are as slight as possible and have only a slight influence on the printing quality, the length of the individual bands respectively amounts to a multiple of the circumference of the rollers on which the bands respectively run. 
     The two exemplary embodiments that have been presented above can also be combined. In this case, a printer device is available with which precision printing can be carried out on a form at high speed. As needed, this printing can also ensue multi-colored. 
     Given the illustrated exemplary embodiments, a carrier band in the form of a continuous paper web  14  is employed as the carrier material. The invention, however, can also be utilized in printer devices wherein single sheets are employed as the carrier material. The employment of a photoconductor drum is also possible instead of the photoconductor bands  22  and  36 . 
     The above-described printer device is closely related to German patent application 198 56 146.6 which corresponds to PCT application PCT/EP99/09436 (WO 00/34832), whose content is herewith incorporated into the disclosure by reference. 
     Although other modifications and changes may be suggested by those skilled in the art, it is the intention of the inventor to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of their contribution to the art.