Abstract:
A modular printing apparatus has a printing device with an inkjet print head and a box-shaped module that urges items toward the print head, for printing thereon. In an operating mode, the box-shaped module is inserted into the printing apparatus via a mechanical connection and can be removed from the printing apparatus in a service mode. A triggering mechanism acts on a locking mechanism with first and second force components that couple the locking mechanism and the mechanical connection element to one another in the operating mode to lock the box-shaped module in a bay of the printing apparatus at the printing apparatus. The second force component acts in an opposite direction in the service mode, to disengage the locking mechanism and the mechanical connection element to unlock and remove the box-shaped module.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention concerns a printing apparatus of modular design with a removable, box-shaped module. As used herein, a printing apparatus is an apparatus that is equipped to print on flat items during the passage of the flat items through the apparatus. In the case of a jam of the flat items to be printed in the transport path and disruptions of the passage of the flat items, the invention allows a removal of the box-shaped unit from the printing apparatus for the purpose of cleaning the sensors and the transport elements and to empty the ink capture reservoir, as well as for maintenance of the transport unit of the printing apparatus. The invention is suitable for use in franking machines, mail franking systems and other printing apparatuses or mail processing systems. 
     2. Description of the Prior Art 
     A transport device for flat items to be printed is known from European Patent Application EP 2072272 A2. That transport device has a driven transport belt driven on rollers, with the transport belt supported on a support plate. The flat items to be printed are pressed from below, counter to the force of gravity, onto the transport belt in the support region by means of support bars. During printing, the flat items are transported in the transport direction past at least one print head of a printing module and are pushed from above through a print window by means of the print head. The print window is arranged in a housing part of the printing apparatus at the edge of the transport belt. 
     A device to press flat items onto a transport module is known from European Patent Application EP 2072268 A2, wherein a support receptacle for pressure elements is arranged below a feed table and at least one of the pressure elements with a number of individually resiliently supported components is installed on the support receptacle, or wherein a number of pressure elements are arranged below the transport belt on the support receptacle, in the transport direction. 
     A device to spray an inkjet print head clear of accumulated ink is known from European Patent Application EP 2072263 A2 that has a feed table with a shaft support that can be deflected counter to an elastic force, the shaft support being equipped with at least one clearance shaft. 
     A device to spray an inkjet print head clear of accumulated ink that is used in Centormail® franking machine is known from German Published Application 102005052151 B3. The excess or ejected ink is absorbed by a mat of the ink capture reservoir, so the mat becomes full of ink, which is why the content of the ink capture reservoir is also called an ink sump. The ink sump is arranged below a cleaning and sealing station and is designed as a plug-in unit. Access to the ink sump takes place via a separate tray. 
     A device to press flat items onto a transport module is known from European Patent Application EP 2072271 A2, in which the pressure device is installed in a lower housing shell and is equipped with lowerable pressure elements that act on the flat item to be printed with an elastic force through an opening in a feed table for flat items. An actuation element that activates a lowering device to which the pressure elements are attached is arranged on the lower housing shell. The lowering still does not allow any access to the sensors, transport elements and pressure elements, but allows access to the inkjet print heads. Contact with the print heads could lead to an interfering electrical charge. 
     Known solutions for a franking machine implement a downward lowering or folding of the lower transport unit in order to correct an occurring paper jam. There is a risk of injury for an operator who may insert his or her fingers into the franking machine in order to clear the jam. Access to the sensors, transport elements and pressure elements, however, continues to be difficult or impossible. 
     Access to the ink sump likewise takes place via a separate bay. If the operator has forgotten to reinsert the sump shell after changing the mat, however, this can lead to contamination of the environment of the machine and of the machine itself. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide an arrangement that enables maintenance of a printing apparatus without the disadvantages that occur in the prior art. An operator of the printing apparatus should have the capability to exchange the mat in the ink sump, to exchange the elements of the pressure unit, and to clean the transport path. Access to the sensors should also be enabled and debris removal should be facilitated. Contact with (and thus an electrical charging) of the inkjet print heads should be avoided and the risk of injury to the operator should be reduced. Moreover, dryout of the inkjet print heads during the maintenance should be prevented. 
     A printing apparatus of modular design in accordance with the invention allows removal of a box-shaped module and has the following features: 
     A printing device has a movable print carriage in which at least one inkjet print head is installed. A control unit of the printing apparatus is programmed to switch from an operating mode into a service mode and to activate a motor to displace the print carriage in the y-direction transversely to the transport direction x of flat items to be printed. This activation is continued (maintained) after the switching until a sealed position has been reached by the at least one inkjet print head. In this sealed position a dryout of the inkjet print head is prevented by a cleaning and sealing station. The printing apparatus has a locking mechanism and a mechanical connection element integrally molded on a housing wall of the box-shaped module. The box-shaped module is inserted into the printing apparatus in the operating mode and can be removed from the printing apparatus in the service mode. A triggering mechanism acts on the locking mechanism with first and second force components. The locking mechanism and the mechanical connection element engage one another via the first force component that is active in the z-direction in the operating mode in order to lock the box-shaped module, inserted into the printing apparatus at said printing apparatus. The locking mechanism and the mechanical connection element are disengaged from one another via the second force component that is active counter to the z-direction in the service mode, in order to unlock the box-shaped module inserted into the printing apparatus before the box-shaped module can be removed from the printing apparatus. 
     The printing apparatus has an upper housing shell below which are arranged a lower housing shell and a box-shaped module that adjoin one another. The latter is removable depending on predetermined conditions. In the operating mode, the box-shaped module is locked by a locking means and cannot be removed. The box-shaped module that is to be inserted into the printing apparatus is a compact unit that can be removed by the operator, and includes a feed table for flat items, with an opening for a number of pressure elements of a pressure unit, with openings for guides and with one clearance shaft per inkjet print head, with an integrally molded ink sump reservoir and with a lowering device to lower the pressure unit. The box-shaped module is directed like a drawer by guidance means upon insertion and, in the service mode, enables an easy access to the ink sump and to the pressure unit. 
     In the operating mode, thus when the box-shaped module is not removed, the access to some assemblies is at least hindered and no access exists to either an inkjet print head or the transport belt, or to sensors in the transport path of the printing apparatus. The control unit that is provided to switch from the operating mode to the service mode waits for a user input via a user interface. For example, a switch to the service mode takes place after operation of an actuator. The locking mechanism is unlocked in the service mode by the triggering mechanism in order to release the box-shaped module. In the service mode the transport unit of the printing apparatus is deactivated. Due to removal of the box-shaped module, both the transport belt and the transport path of the printing apparatus (and the assemblies of the box-shaped module) are accessible. 
     The box-shaped module is supported on two guidance means that protrude forwardly through first and second openings on the front side of the lower housing shell. The upper housing shell encloses the transport unit, i.e. the drive unit with a transport belt opposite which a lowerable pressure device of the box-shaped module is situated in the event of operation. 
     During maintenance, the box-shaped module is designed so that it can be moved or shifted away from the lower housing case and thereby runs on the two guidance means that protrude at the lower housing shell. Depending on the occurrence of predetermined conditions, the module can be removed from the printing apparatus (a franking machine, for example) by the operator, which affords an accessibility to the sensors in the transport path and their maintenance or first enables a cleaning of the transport path. The box-shaped module has an ink sump reservoir. this is a large ink reservoir for the capture of ink that accumulates as waste material in the region of the cleaning and sealing station during the clearance cycles and in the printing region during the passage of goods. The ink reservoir is designed as a container that protrudes at the back of the box-shaped module, with an internally inlaid ink mat which, during operation, protrudes into a third opening on the front of the lower housing shell. 
     The first opening is arranged upstream (in terms of the mail flow) near the left side wall of the apparatus. The second opening is arranged downstream (in terms of the mail flow) near the right side wall of the apparatus, and the third opening is arranged to the left next to the second opening. 
     The guidance means that protrude from the lower housing shell are supported by a first frame wall that is likewise arranged in the lower housing shell at a distance from the rear frame wall. The first frame wall has a corresponding opening in order to support the first guidance means. 
     A second frame wall is arranged orthogonally to the rear frame wall and proceeds near the center of the lower housing shell in order to connect the first frame wall with the rear frame wall. The second frame wall is designed as elbow that is attached vertically with one of the two legs in the lower housing shell and protrudes with the respective other leg into the upper housing shell up to its forward region. The leg attached vertically in the lower housing shell has a maximum width that corresponds to the aforementioned distance and a height that exceeds the height of the lower housing shell. 
     A fourth opening is arranged to the left, next to the third opening on the front side of the lower housing shell. The first frame wall has two corresponding openings that are situated on the back of the front side of the lower housing shell opposite the respective third and fourth opening. The box-shaped module has a mechanical connection element protruding at the back side, which mechanical connection element protrudes into the fourth opening in the event of operation. The module remains locked by the mechanical connection element and the locking mechanism during the printing process. The module can be removed by the operator only when, after the control unit switches from the operating mode into the service mode, the motor is activated and the print carriage is driven into a sealed position by driven arrangement coupled with the motor. A cleaning and sealing station prevents the inkjet print heads from drying out in the sealed position. This is particularly advantageous in a rest phase and when the module is removed for a longer duration. It is advantageous that, after removing the box-shaped module, an operator cannot emit an electrical discharge to the print head electronics at the print head moved into the sealed position, which discharge could destroy the print head electronics. 
     The locking mechanism is unlocked when the print carriage arrives in the sealed position. The movement of the print carriage that is controlled by a control unit acts on a locking means by a triggering means. A first sensor is operationally connected with a microcomputer via an input/output unit of the control unit in order to determine whether the print carriage is located in the sealed position. If the print carriage arrives in proximity to this, a first switching point is crossed in order to cancel the locking of the module via the locking means while the microcomputer additionally activates the motor until the sealed position is reached. 
     In all other cases the module remains locked if the print carriage is not in proximity to the sealed position and the first switching point has thereby not been crossed. 
     After removal of the module, the operator now also has access to the sensors in the transport path for the purpose of cleaning them and to correct a jam of the flat items, for example of mail pieces (letter jam). 
     Given a removed module, an exchange of the ink mat by the operator and an exchange of the lower transport unit (brush) by the operator are possible. 
     A first sensor (photoelectric barrier or microswitch) can be arranged at a first position in order to emit a signal to the control unit depending on the position of the triggering mechanism or of the print carriage. 
     An additional switch is arranged at a suitable point within the apparatus in order to detect a presence of the ink sump reservoir with properly closed cover and to interrupt the current flow if this is not present. A software error thus could not lead to an unintentional shifting of the print carriage when the module is not inserted into the apparatus. The risk of injury to the operator is thus reduced when the module is removed. 
     Moreover, the unused apparatus transitions into a standby mode after a predetermined period of time. A circuit closer is connected to the power supply unit in order to trigger a reactivation of the power supply of the apparatus before switching into the operating mode. 
     The ink sump reservoir is oblong in shape and thereby extends in the y-direction, and should be provided with a cover that allows only specific regions to be open and prevents the mat from falling out. 
     The preferred embodiment allows a reactivation of the power supply of the apparatus and a switching into the operating mode only when the cover has been placed to cover the ink sump. 
     Embodiments of the ink sump reservoir are possible in which the ink sump shell is permanently arranged in the box-shaped module and filled with a mat, or in which a separate mat shell is used. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1   a  is a perspective schematic illustration of a printing apparatus with an inserted box-shaped module. 
         FIG. 1   b  is a perspective illustration of a printing apparatus with a removed box-shaped module. 
         FIG. 2   a  is a plan view of the printing apparatus in section parallel to the x/y-plane with an inserted, box-shaped module and removed upper housing shell. 
         FIG. 2   b  is a plan view of the printing apparatus presented in section parallel to the x/y-plane with a removed, box-shaped module and removed upper housing shell. 
         FIG. 3   a  is a side view from the left of printing apparatus shown in section parallel to the y/z-plane given an inserted box-shaped module, in operating mode; section through the printing apparatus at the line AA′ of  FIG. 2   b.    
         FIG. 3   b  is a side view from the left of printing apparatus shown in section parallel to the y/z-plane with an inserted box-shaped module, in service mode. 
         FIG. 4  is plan view of the apparatus sectioned parallel to the x/y-plane through the upper housing shell, without box-shaped module. 
         FIG. 5   a  is a circuit arrangement of an apparatus switched into a service mode. 
         FIG. 5   b  shows detail of an apparatus that is switched into an operating mode. 
         FIG. 6  is a perspective view of a detail of the apparatus from the rear right in operating mode, with the triggering mechanism and with the locking mechanism. 
         FIG. 7  is a perspective view of a detail of the apparatus from the rear left in service mode, with the print carriage in the sealed position and with a transmitted light sensor that is activated by the print carriage. 
         FIG. 8  is a perspective view of a detail of the apparatus without the print carriage. 
         FIG. 9   a  is a plan view of a detail of the apparatus with an inserted box-shaped module. 
         FIG. 9   b  is a plan view of the plastic support of the apparatus with the microswitch in the state during an inserted box-shaped module. 
         FIG. 9   c  is a plan view of the plastic support of the apparatus with the microswitch in the state during the insertion of the box-shaped module. 
         FIG. 10  is a perspective view of the cover. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A printing apparatus  1  given an inserted, box-shaped module  3  in a basic perspective view is shown from the upper front left in  FIG. 1   a . The printing apparatus has an upper housing shell  12 , below which a lower housing shell  4  is shown abutting the box-shaped module  3  in the y-direction. The upper housing shell  12  is mounted on the lower housing shell  4  such that it cannot be detached non-destructively in the z-direction. The lower housing shell  4  forms a rear lower part of the printing apparatus and forms a seal with the upper housing shell at the rear and to the sides. The box-shaped module  3  that can be removed only in service mode in the manner of a drawer is accommodated in the forward lower part of the printing apparatus and has a plurality of pressure elements B. In the front part, below the upper housing shell  12 , a transport belt  2  of a transport unit is visible which serves to transport mail pieces in the x-direction (transport direction) in the printing mode, wherein the x-, y- and z-directions form a Cartesian coordinate system. The pressure elements B press a flat piece P to be printed onto the transport belt  2  from below (thus in the z-direction) as soon as the piece P is supplied to the printing apparatus  1 . The printing mode is a special operating mode of the printing apparatus in which the at least one inkjet print head is positioned in the forward part of the upper housing shell  12 . 
     In  FIG. 1   b  a printing apparatus  1  is shown with a pulled-out, box-shaped module  3 , in a perspective view from above and to the left. In contrast to the printing mode, in the service mode the at least one inkjet print head is positioned in the rear part of the upper housing shell  12  after it was moved there (transversal to the transport direction, thus in the y-direction). The box-shaped module  3  is shown removed from the lower housing shell  4 , which is why two guidance means  41  and  42  are visible. The latter are designed as rails on which the box-shaped module is supported in the operating mode. They protrude forwardly through a first opening  4 . 1  and second opening  4 . 2  on the front side of the lower housing shell. 
     A third opening  4 . 3  and fourth opening  4 . 4  are situated between the first opening  4 . 1  and second opening  4 . 2 . The first opening is arranged upstream (in terms of the mail flow) near the left side wall of the apparatus, the second opening is arranged downstream (in terms of the mail flow) near the right side wall of the apparatus, and the third opening is arranged to the left next to the second opening. The pressure elements B are a component of a lowerable pressure device  30  of the box-shaped module  3  that moreover has an ink reservoir whose arrangement is explained in the following using  FIG. 2   a.    
     A plan view of the printing apparatus (shown in section parallel to the x/y-plane) with an inserted box-shaped module  3  (thus in the operating case) is shown in  FIG. 2   a . The removed upper housing shell  12  is drawn in dashed lines in order to clarify its position. The box-shaped module  3  has at its rear side a mechanical connection element  3 . 4  and an ink reservoir  3 . 03 , wherein the mechanical connection element  3 . 4  is designed as a hook that protrudes into the fourth opening on the front side of the lower housing shell  4 . The box-shaped module  3  is equipped with a feed table that has an opening at the top side for the pressure elements of the pressure device  30 . The latter is known from European Patent Application EP 2072268 A2, in which the “Device for pressing flat goods onto a transport module” is described in more detail. 
     The print carriage  24  has a first and second cavity  24 . 1  and  24 . 2  for insertion of a respective ink cartridge. The upper housing shell  12  has a transport unit (drive unit with a transport belt) that is attached to a chassis, as described in part in European Patent Application EP 2072272 A2 with the title: “Transportvorrichtung für zu bedruckende flache Güter” (“Transport device for flat goods to be printed”). 
     A print carriage  24  (drawn in the printing position) can be moved in the y-direction via a spindle drive (comprising a part of the print carriage, not shown in detail, and a spindle  72 ) by a motor  71  attached to a rear wall of a chassis. The rear frame wall  46  serves for attachment of the rails on which the print carriage  24  runs, as is known from the European Patent Application EP 2072272 A2. For better clarity, in  FIG. 2   a  only the guidance means for guidance of the box-shaped module are shown, and the aforementioned rails on which the print carriage  24  runs are omitted. 
     The rear frame wall  46  serves at least to support and possibly also for the attachment of both the first rail  41  and the second rail  42 . A first frame wall  45  has a corresponding opening in order to support the first rail  41 . A second frame wall  44  is arranged orthogonal to the rear frame wall  46  and runs near to the center of the lower housing shell  4  in order to connect the first frame wall with the rear frame wall. The second frame wall  44  is designed as an elbow that is attached vertically with its one leg in the lower housing shell, and protrudes with its other leg in the upper housing shell up to its front region. The leg attached vertically in the lower housing shell has a width that corresponds to the aforementioned distance and a height that projects beyond the height of the lower housing shell. A perspective presentation of the second frame wall  44  is shown in more detail in European Patent Application EP 2072272 A2. 
     The ink reservoir  3 . 03  is designed as a container with an inlaid ink mat that projects at the back side at the drawer  3 . This container extends into the third opening on the front side of the lower housing shell  4  in the inserted state. 
     A plan view of the printing apparatus  1  (shown in section, parallel to the x/y-plane) is shown in plan view in  FIG. 2   b  given a removed, box-shaped module  3 —i.e. in service mode—and given a removed upper housing shell. The position of the removed upper housing shell  12  is indicated again in dashed lines. The print carriage  24  (that is not shown with dashed lines) is located in the sealed position. A hook as a mechanical connection element  3 . 4  and an ink reservoir  3 . 03  are integrally molded on the rear side of the box-shaped module  3 . An opening for the pressure elements of the pressure device  30  is formed on the top side of the box-shaped module  3  in the feed table. In the operating mode the ink reservoir  3 . 03  is situated between the second rail  42  and the second frame wall  44  which are mounted on the rear frame wall  46  which stands in the lower housing shell. The ink reservoir  3 . 03  extends to below the pressure device  30  (which was indicated with dashed lines). Located below each of the inkjet print heads in the printing region is a clearance shaft on a shaft support  4  that can be deflected counter to a resilient force. Details in this regard are described in European Patent Application EP 2072263 A2 with the title: “Vorrichtung zum Freispritzen eines Tintendruckkopfes” (“Device for clearing an inkjet print head”). Provided on the left side of the second frame wall  44  is a locking mechanism  43  that is mounted so that it can rotate around a rotation axis  431  on the end thereof facing toward the rear frame wall  46  and has a hook  434  at the other end (facing toward the first frame wall  45 ). The function of the hook  434  is explained in the following using  FIG. 3   a , which shows a section through the printing apparatus on the line AA′ of  FIG. 2   b.    
       FIG. 3   a  shows a side view from the left of the printing apparatus (shown in section parallel to the y/z-plane) in the operating mode given an inserted box-shaped module. Below the upper housing shell  12  the transport belt  2  runs around a roller  5  that is arranged near the printing region and near the mail flow outlet. The roller is rotatable around a rotation axis which is situated parallel to the y-direction. An additional roller for the transport belt that is arranged near the printing region and near the mail flow inlet is not shown (since it is cut away). The drawn slice plane which lies parallel to the y/z-plane is arranged in the region counter to the x-direction, thus before the printing region. A slider  82  that serves as a triggering mechanism for a locking mechanism  43  is shown in the slice plane in the region situated after the transport belt in the y-direction. The slider  82  is designed as a flat elbow and is held in the indicated (second) position by a return spring  87 . The return spring  87  is designed as a tension spring. 
     The slider  82  is mounted at the second frame wall (not drawn in  FIG. 3   a ) such that it can be displaced in the arrow direction counter to the tension spring force. The return spring  87  is attached with its one end at a first attachment segment  827  of the slider  82  and is attached with its other end at the attachment segment  442  of the chassis. The slider  82  has one leg  821  with an oblong hole  820  which extends parallel to the y-direction. Two guide pins  441  and  442  are attached at the second frame wall and protrude though the oblong hole  820 . 
     The end of the oblong hole that faces toward the rear wall of the upper housing shell  12  lies near the first attachment segment  827  of the slider  82 . The first attachment segment  827  is integrally molded in the z-direction on the one side of the leg  821  and has an opening for attachment of the tension spring. A base is integrally molded approximately at a right angle on the opposite side of the leg, counter to the z-direction. The end of the base that is remote from the leg  821  supports an additional attachment segment  825  for the attachment of the one end of an additional tension spring  437 . Its other end is attached at an attachment segment  435  of the locking mechanism  43 . The locking mechanism  43  is designed as an angle lever and arranged in the region of the lower housing shell  4 . The pivot of the angle lever lies in an opening  430  at the remote end of the first leg  431 . A hook  434  whose tip extends in the z-direction is integrally molded at the end of the second leg  432  of the angle lever. The slider  82  of the apparatus reaches a second position as is presented in principle in  FIG. 3   a . The tension spring  437  attached at the additional attachment segment  825  of the slider  82  then exerts a tension force with a component in the z-direction on the locking mechanism  43  and with an additional component that is directed counter to the z-direction. In the operating mode the hook  434  therefore engages in the mechanical connection element  3 . 4  which is integrally molded on the outside of the back side of the box-shaped module  3 . The mechanical connection element  3 . 4  is designated as a hook, but this does not preclude other, alternative mechanical connection elements (such as eye hooks, tongues or box-shaped hooks reinforced by side walls or others). In the shown position the angle lever can be rotated clockwise—i.e. in the direction of the black arrow—around its pivot when the triggering mechanism is operated. 
     As used herein, a flat it can be, for example, a piece of mail. A mail piece P which has been supplied to the apparatus is clamped between the transport belt  2  and the pressure elements B of the lowerable pressure device  30  of the drawer  4  and transported in the transport direction (x-direction) by the further movement of the transport belt during the printing. The pressure elements B are attached on a support  32  which is mounted elastically on a floor plate  38  which is reinforced in the downward direction on the housing of the drawer. For example, a guidance element  34   i  and an associated compression spring  37   i  are provided at the corners of a base  34  in order to also be able to process larger thicknesses of the mail pieces P. The attachment segment  435  is integrally molded near the middle of the angle lever  43  and counter to the transport direction (x-direction). The shaft support  14  that can be deflected counter to an elastic force (the manner is not shown) is deflected corresponding to the thickness of the mail piece P. 
       FIG. 3   b  shows a side view from the left of the apparatus (shown in section parallel to the y/z-plane) with inserted drawer in the service mode. In the service mode the slider  82  of the apparatus reaches a first position in which the return spring  87  attached at the attachment segment  827  is tensioned, as is presented in principle in  FIG. 3   b . The tension spring  437  attached at the attachment segment  825  of the slider  82  is also tensioned and now exerts a pulling force with a component counter to the z-direction on the locking mechanism  43 . The pulling force acts with an additional component that is directed in the y-direction. The locking mechanism  43  therefore causes the hook  434  to be unlocked from the mechanical connection element  3 . 4  of the drawer  3 . The transport belt  2  is diverted around the roller  5  of the upper housing shell  12 , said roller  5  being is arranged at the side of the mail flow outlet. In this position the angle lever is rotatable counterclockwise around its pivot, i.e. in the direction of the white arrow, when the triggering mechanism is operated. 
     In the absence of a mail piece, the deflectable shaft support  14  is deflected just as much as the pressure elements B of the lowerable pressure device  30  of the drawer  3 . 
       FIG. 4  shows a plan view of the apparatus (in section through the upper housing shell parallel to the x/y-plane) without the drawer. The position of the guidance means  41  and  42  arranged below the upper housing shell is only indicated. Therefore they are only indicated with dashed lines. The transport belt and the rollers that are arranged in the upper housing shell  12  were likewise omitted for better clarity. Rather, what is shown is the position of the rails  48  and  49  on which the print carriage  24  runs when it is moved in the sealing position, for example. Integrally molded on the print carrier  24  is a carrier  24 . 4  which acts on the projection  824  integrally molded on the slider  82  to shift the slider into the sealed position (position I) upon travel of the print carriage. A slit through which the projection  824  extends in the x-direction is worked into the second frame wall  44  of the chassis. The slider  82  is directed by guide pins  441  and  442 . Given movement of the print carriage into the sealed position, the carrier  24 . 4  entrains the projection  824  extending through the slit, whereby the return spring  87  is tensioned. However, the tension spring  437  is attached at the attachment segment  825  of the slider  82 , which tension spring  87  now exerts a draw force in the y-direction on the locking mechanism as long as the print carriage  24  remains in the sealed position. 
       FIG. 5   a  shows a circuit arrangement of the control unit of an apparatus switched into a service mode. The electronic control unit  50  comprises a microcomputer  51  which activates at least one driver  596  that is connected with a first motor  61  via a microswitch  67 . 
     The control unit is programmed to switch into the service mode due to a corresponding user input via a user interface. A separate operating unit  9 . 1 ,  9 . 2  or a keyboard or a touchscreen can be used for this purpose. A circuit closer  57  is likewise connected to the control unit  50  in order to enable a return of the control unit  50  to the operating mode. A power supply unit can be arranged as an integrated component of the control unit  50  or can also be arranged separate (not shown) from the control unit  50  in the printing apparatus  1 . 
     The control unit  50  is connected with input means, for example with sensors  21 ,  22 ,  23  and with at least one operating unit  9 . 1  for manual selection and one operating unit  9 . 2  to confirm an input. A display unit (display)  54 , the motors  61 ,  71 ,  81  or, respectively, an actuator  91  are connected to the electronic control unit  50 . The control unit  50  is programmed to switch into the service mode upon a user input via a user interface. 
     After switching from the operating into the service mode, the microcomputer  51  and, via a first driver  596 , a first motor  61  are activated to shift the print carriage  24  transversal to the transport path of a flat good to be printed, wherein a first sensor  21  signals when a sealed position is reached by the at least one inkjet print head when the print carriage reaches a first position due to its movement in the y-direction. Upon removing the box-shaped module, the current flow of the first motor  61  is interrupted by the microswitch  67  so that no accidents due to a transversal shift of the print carriage can occur in the service mode. 
     A second sensor  22  and third sensor  23  are connected to the control unit  50  as well as a second motor  71 . After the control unit  50  of the printing apparatus is switched into the operating mode, the second motor  71  is activated in a print mode to drive a transport belt of the printing device to print a flat good when the second sensor  22  signals the presence of a flat good and the third sensor  23  signals that a trigger position for a printing has been reached by the feed of the flat good. 
     The triggering mechanism is a slider  82  that is shown schematically and in plan view on the leg  821  ( FIG. 5   a ). The top side of the leg is situated essentially parallel to the x/y-view. The slider  82  is directed via guide pins  441  and  442  that are attached so as to project on the left side of the second frame wall of the chassis (see also  FIG. 4 ). 
     When the print carriage as reached the sealed position in the service mode, the end of the leg  821  is offset by a distance a in the y-direction and is situated near the attachment segment  443  of the return spring  87 . The following integrally molded details are visible on the opposite end of the slider  82  in the y-direction: a projection  824  on the slider serves to shift the slider upon movement of the print carriage into the sealed position and is situated at a position I; an attachment segment  825  of the slider  82  to attach the tension spring  437 ; and an attachment segment  827  of the slider  82  to attach the return spring  87 . The stressed tension spring  437  has a tensile force component that points in the y-direction and produces the unlocking. 
     For example, the first sensor  21  is realized as a transmitted light sensor, and a vane  243  integrally molded on the print carriage serves to interrupt a beam of light of the transmitted light sensor that is emitted from the light source  21 . 1 . The light source  21 . 1  is connected via a conductor  19  to the input/output unit  59  for power supply. The light beam or, respectively, the remaining residual light is focused by the lens  21 . 2  onto a light detector  21 . 3 . The latter emits an analog signal corresponding to the received light intensity, which analog signal is converted via a nonlinear electronic element into a digital signal. Upon exceeding an adjustable threshold of the analog signal, a digital signal (H-level) is output to the control unit  50 . Given a ZERO level (no signal), the sealed position has been reached. 
       FIG. 5   b  shows a detail of the apparatus that is switched into an operating mode, wherein the slider  82  is used as a triggering mechanism and the sensor  21  is used in the form of a transmitted light sensor. The vane  243  integrally molded on the print carriage cannot contribute to the deactivation of the first sensor  21  in this case. Due to the effect of the return spring  87 , the slider  82  has been shifted so far counter to the y-direction that the projection  824  of the slider is situated in the position II. The light source  21 . 1  emits a light beam of maximum intensity that is focused by the lens  21 . 2  onto a light detector  21 . 3 . The latter emits a maximum signal corresponding to the received light intensity. The projection  824  is active given the displacement of the slider upon movement of the print carriage from the indicated position II into the position I. The attachment segment  825  serves to attach the tension spring  437 , and the attachment segment  827  serves to attach the return spring  87 . The position I is situated at a distance a from the position II in the y-direction. The stressed tension spring  437  has a draw force component that points opposite the y-direction, which produces the locking. 
     Alternatively, the first sensor  21  can be realized as a microswitch, and the projection  243  serves to operate the microswitch. 
       FIG. 6  shows a perspective representation of a detail of the apparatus from behind in the operating mode, with the triggering mechanism and with the locking mechanism. A slider  82 * that acts on the locking mechanism  43 * is used as a triggering mechanism. The slider  82 * has two attachment segments  825 * and  827 * to attach the two tension springs  437 * and  87 * and a projection  824 *. The projection  824 * serves to displace the slider from the indicated position II into the position I during the movement of the print carriage (not drawn) into the sealed position. A slit  440 * running in the y-direction is worked into the second frame wall  44 * of the chassis, through which slit  440 * the projection  824 * protrudes in the x-direction and can be shifted in the y-direction together with the slider  82 *. An elbow lever that, with its lever arm, locks the box-shaped module in the operating mode is used as a locking mechanism. 
     The pressure elements B* of the box-shaped module  3 * lie near the deflectable shaft bearing  14 * in the y-direction. The box-shaped module  3 * bears on the rear side a box-shaped hook  3 . 4 * in which the hook  434 * on the lever arm of the locking mechanism  43 * engages. Near the downstream (in terms of the mail flow) side of the box-shaped module  3 *, an ink sump shell  3 . 3 * extends in the y-direction on its back side. The latter has an ink reservoir  3 . 03 * and a cover (not shown). A transmitted light sensor is used as a first sensor  21 * that is directly activated by the print carriage (not drawn) as soon as the sealed position is reached. 
       FIG. 7  shows a perspective view of a detail of the apparatus from the left and to the rear in the service mode, with the print carriage  24 * in the sealed position and with the transmitted light sensor  21 * that is operated by the print carriage  24 *. A vane  243 * is integrally molded on the print carriage, which vane  243 * interrupts the light beam of the transmitted light sensor  21 * when the sealed position is reached. The print carriage  24 * moved into the sealed position is shown in  FIG. 7 . The print carriage  24 * is arranged so that it can be displaced in the y-direction and counter to this on two rails  48 * and  49 *. A spindle  72 * serves to drive the print carriage and is arranged below the rail  48 *, thus counter to the z-direction. A slide bearing (not visible) and a slide bearing  245 * as well as a spindle nut  244 * are integrally molded on the right (as seen from the rear) side wall of the print carriage  24 *, thus on that side that is nearest the second frame wall  44 * given an inserted box-shaped module. An additional slide bearing  246 * is integrally molded on the left side wall of the print carriage  24 * that is situated opposite the right side wall. The displaceable print carriage  24 * is thus borne at three points. The slide bearing  246 * slides on the rail  49 *, and the two other slide bearings slide on the rail  48 *. The slide bearings are adapted to the profile of the rails. The rails are designed as slide rods and have a round (advantageously a circular) profile. 
       FIG. 8  shows a perspective presentation of a detail of the apparatus from the left and to the rear with inserted box-shaped module  3 *. Upon insertion the latter is attached (the manner is not shown) onto the guidance means  41 * and  42 *. The latter are advantageously realized as slide rods, but other designs are possible. A microswitch  67 * is used as a sensor for the box-shaped module. The apparatus is switched from the service mode to the operating mode by the microcomputer as soon as the box-shaped module is inserted and the microswitch is operated by a vane  3 . 32 * which is integrally molded on a cover  3 . 31 *, wherein the cover is positively connected with the shell  3 . 3 * and at least partially covers the ink reservoir  3 . 03 * in spite of an opening  3 . 310 *. The vane is integrally molded on the end of the cover  3 . 31 * of the ink sump reservoir  3 . 3 * (on the left side as viewed from the rear) that is situated in the y-direction, on that side that is furthest removed from the second frame wall  44 * given an inserted box-shaped module. The latter has a window-like slit  440 * through which the projection of the slider protrudes in the manner shown in  FIG. 6 . 
       FIG. 9   a  shows a plan view of a detail of the apparatus with inserted box-shaped module. The detail concerns a plastic support  47 * for a microswitch  67 * that is used as a sensor to detect the proper insertion of the box-shaped module  3 *. The plastic substrate  47 * has an installation surface for the microswitch that is situated in the x/y-plane. Since—as shown—the cover  3 . 31 * is mounted so as to be locked on the ink sump reservoir, the microswitch is activated and a circuit is closed with the cable  611 * between the first driver  569 * and the first motor  61 *. An insertion of the box-shaped module  3 * is, for example, incorrect if the cover  3 . 31 * has not been placed and fastened on the ink sump reservoir  3 . 3 * before the insertion. The aforementioned circuit is then open. 
       FIG. 9   b  shows a plan view of the plastic support of the apparatus with the microswitch in the state of an inserted and correct box-shaped module. The microswitch  67 * used as a sensor has an elastic actuation arm  671 * that is operated by a slanted side edge  3 . 321 * of the vane  3 . 32 *. The microswitch  67 * emits a signal in order to produce a reactivation of the circuit. 
       FIG. 9   c  shows a plan view of the plastic support of the apparatus with the microswitch in the state during the insertion of the box-shaped module. The elastic actuation arm  671 * of the microswitch remains unactivated until the box-shaped module with the properly mounted ink sump cover has been inserted. 
       FIG. 10  shows a perspective presentation of the cover  3 . 31 * which is used to cover the ink sump housing. The cover  3 . 31 * has for each inkjet print head a centrally arranged window  3 . 311 * and  3 , 312 * in order to capture ink vapor or, respectively, the ink residues when the print carriage is moved near to a sealed position. The cover  3 . 31 * has attachment means. For example, a right lateral edge with two cams  3 . 321 * and  3 . 322 * is provided on the side of the vane  3 . 32 *, and two brackets  3 . 313 * and  3 . 314 * are provided on the left lateral edge situated opposite the right lateral edge. The ink sump housing (not shown) has suitable attachment means for positive connection with the aforementioned attachment means of the cover. 
     The box-shaped module can have an alternative design. For example, one or more mechanical connection elements can be used. The later can also be integrally molded or, respectively, mounted at points on the housing of the box-shaped module other than at the preferred point on the rear wall of said box-shaped module. The locking mechanism of the printing apparatus of modular design is of matching design, corresponding to this. 
     Although mechanical connection element is designated as a hook in the preferred exemplary embodiment, other alternative mechanical connection elements —such as eye hooks, clips or reinforced hooks designed like boxes and reinforced by side walls, or other connection elements—are not precluded. 
     A transmitted light sensor is preferred as a first sensor. As an alternative, a microswitch can be used, wherein the microswitch is directly operated by the print carriage as soon as the sealed position is reached. 
     Although at least one operating means  9 . 1 ,  9 . 2  is connected to the control unit  50  for user input in the preceding exemplary embodiment to switch into the service mode, other user interface alternatives should not be precluded. The display  54  can be a touchscreen that is designed for switching into the service mode by means of the control unit  50 . 
     Additional input and output means can be connected to the electronic control unit. 
     Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventors 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.