Abstract:
A device for conveying printed products through a printing-related machine includes at least one endless conveyor belt running over deflecting rollers and having at least one printed product resting thereon during a conveying operation, and a rotating frictional element provided for driving the conveyor belt, the frictional element being in contact with the conveyor belt on a side thereof whereon the printed product is transported.

Description:
BACKGROUND OF THE INVENTION  
       FIELD OF THE INVENTION  
         [0001]    The invention relates to a device for conveying printed products through a printing-related machine.  
           [0002]    It has become known heretofore to use conveyor belts in order to convey sheets through electrographic printing machines. The published German Patent Document DE 40 152 10 A1 discloses a device for transporting sheet materials, wherein the sheets are retained on the surface of a conveyor belt by electrostatic retaining forces. The conveyor belt is positioned over deflecting or idler rollers. One of the deflecting rollers is driven and causes the belt to be advanced by frictional contact on the side thereof directed away from the sheet. Located along the conveying distance are printing devices which successively apply individual colors of a multicolored printed image to a sheet. The length and width of the conveyor belt are adapted to the dimensions of the printing device. In order to produce a five-color printing image, five printing units are arranged in tandem or behind one another in series along the conveyor belt. Printing machines with a great overall length are produced thereby. When printing with one or two colors takes place on such a printing machine, a series of printing units remains unused, while the sheets always run through the entire conveying distance for five-color printing. A conveyor belt which runs over five printing units undergoes considerable stretching, which impedes control and regulation of the sheet transportation.  
         SUMMARY OF THE INVENTION  
         [0003]    It is accordingly an object of the invention to provide a device for conveying printed products through a printing-related machine which allows high flexibility when processing print jobs.  
           [0004]    With the foregoing and other objects in view, there is provided, in accordance with the invention, a device for conveying printed products through a printing-related machine, comprising at least one endless conveyor belt running over deflecting rollers and having at least one printed product resting thereon during a conveying operation, and a rotating frictional element provided for driving the conveying belt, the frictional element being in contact with the conveyor belt on a side thereof whereon the printed product is transported.  
           [0005]    In accordance with another feature of the invention, the conveyor belt is looped about the frictional element at an angle smaller than 180°.  
           [0006]    In accordance with a further feature of the invention, the frictional element is disposed in a vertically running section of the conveyor belt.  
           [0007]    In accordance with an added feature of the invention, the conveying device includes another conveyor belt adjacent to the first-mentioned conveyor belt and, for driving both of the mutually adjacent conveyor belts simultaneously, the frictional element is engageable with both of the conveyor belts on the side thereof, respectively, whereon the printed product is transported.  
           [0008]    In accordance with an additional feature of the invention, the conveying device includes another conveyor belt, and wherein, for conveying printed products at least approximately horizontally, the conveyor belts are arranged behind one another, the frictional element being provided in a section thereof wherein the conveyor belts, respectively, in relation to a vertical plane of symmetry, are looped about a sub-section of the frictional element and run over deflecting rollers.  
           [0009]    In accordance with yet another feature of the invention, the frictional element is a cylindrical drive roller.  
           [0010]    In accordance with yet a further feature of the invention, the printing-related machine is a printing machine with a plurality of printing modules arranged in accordance with a unit construction principle, a respective conveyor belt and a respective frictional element being assigned to each of the printing modules, at least one of the frictional elements being driven.  
           [0011]    In accordance with a concomitant feature of the invention, the conveying device includes a convexly curved guide over which the conveyor belt runs in a conveying path for printed products.  
           [0012]    By providing a rotating frictional element on that side of a conveyor belt whereon the printed products are transported makes it possible, in particular, for printing machines to be assembled from individual modules, the outlay for driving the conveyor belts of the modules being low. The belt lengths in a module are determinable quite well by suitable control technology. When a plurality of modules are provided in series or tandem, a printed product is transferred from module to module. Appropriate transport of the printed product can he controlled and regulated separately for each module.  
           [0013]    Other features which are considered as characteristic for the invention are set forth in the appended claims.  
           [0014]    Although the invention is illustrated and described herein as embodied in a device for conveying printed products through a printing-related machine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
       
    
    
       [0015]    The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein:  
       BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    FIGS.  1  to  3  are diagrammatic side elevational views of different embodiments of two-color printing machines, each having two printing modules; and  
         [0017]    [0017]FIGS. 4 and 5 are diagrammatic side elevational views of different embodiments of four-color printing machines, each having four printing modules.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]    Referring now to the drawings and, first, particularly to FIG. 1 thereof, there is illustrated therein a two-color printing machine with two printing modules  1  and  2 , arranged in tandem or behind one another in series, for printing sheets. The printing modules  1  and  2  are of identical construction. Each printing module  1  and  2  has a height-adjustable framework  3 ,  4 , a belt conveying system  5 ,  6 , in each case two ink-jet printing heads  7 ,  8 ;  9 ,  10 , a heat fixing arrangement  11 ,  12 , sheet-guiding elements  13 ,  14  and sheet-transporting rollers  15 ,  16 . The belt conveying systems  5 ,  6 , respectively, include a conveyor belt  17 ,  18 , a series of deflecting rollers  19  to  30  and belt-guiding elements  31 ,  32 . The belt conveying systems  5 ,  6  allow sheets to be transported in a planar and horizontal manner. Sheets are fed from a sheet pile to the printing module  1  in the direction of the arrow  33  by friction rollers  34  and  35 . Printed sheets are transported from the printing module  2  to a sheet pile in the direction of the arrow  36  with the aid of friction rollers  37  and  38 . The belt-guiding elements  31 ,  32  cause the conveying belts  17 ,  18  to run in a slightly convexly curved manner in the sheet-transporting path. The sheets are retained on the surface of the conveyor belts  17 ,  18  by electrostatic forces or with the aid of blowing-air or suction-air arrangements. The sheets assume the curved shape of the conveyor belts  17 ,  18 , as a result of which the sheets rest in a planar manner on the conveyor belts  17 ,  18  during transportation. Turned-over corners or appended edges of the sheets do not occur in practice. In accordance with the curvature of the conveyor belts  17 ,  18 , the ink-jet printing heads  7  to  10  are arranged slightly inclined relative to the vertical. Nozzle systems  39 ,  40 ,  41 ,  42  in the ink-jet printing heads  7  to  10  spray ink droplets at least approximately vertically onto the surface of the sheets located on the conveyor belts  17 ,  18 . The ink-jet printing heads  7  to  10  are distributed over the format width and are arranged transversely to the running direction of the conveyor belts  17 ,  18 . A special feature of the belt and sheet guidance exists in the region of a heat fixing device  11 ,  12  for freshly applied ink droplets. Via the deflecting rollers  21 ,  22 ,  23  and  27 ,  28 ,  29 , the conveyor belts  17 ,  18  are guided past the heat fixing devices  11 ,  12  and beneath the latter and the sheet-guiding elements  13 ,  14 . The sheet-guiding elements  13 ,  14  serve not only for sheet guidance but also as a heat protection shield. The heat fixing devices  11 ,  12  consequently have no adverse effect on the conveyor belts  17 ,  18 . The deflecting rollers  21 ,  28  acting on the sheet-transporting side may be tilted transversely to the running direction  40 ,  41  for lateral control of the conveyor belts  17 ,  18 .  
         [0019]    The printing modules  1 ,  2  are positioned a slight distance away from one another and are fixed to the base  42 , so that sheets are transferred in-register from the printing module  1  to the printing module  2 . In order to drive the conveying belts  17 ,  18  simultaneously, a frictional roller  43 , which is coupled to a motor, is provided. The frictional roller  43  is arranged symmetrically between the deflecting rollers  23  to  26 . The lengths of the conveyor belts  17 ,  18  by which the conveyor belts  17 ,  18  are looped around the frictional roller  43  are exactly the same so that the conveyor belts  17 ,  18  run synchronously. The conveyor belts  17 ,  18  are provided with a frictional coating on the sheet-transporting side thereof, which results in the provision of a particularly high coefficient of friction with respect to the frictional roller  43 .  
         [0020]    In the exemplary embodiments according to FIGS.  2  to  5 , the elements of the printing modules  44  to  55  and the frictional rollers  34 ,  35 ,  37 ,  38  fulfill the same functions as have been described for the printing modules  1 ,  2  according to FIG. 1.  
         [0021]    [0021]FIG. 2 likewise shows a two-color printing machine with printing modules  44 ,  45 . In contrast with FIG. 1, each printing module  44 ,  45  has assigned thereto separate frictional rollers  56 ,  57 , each of which is coupled to a motor. The frictional rollers  56 ,  57 , which act upon the sheet-transporting side, are located between the deflecting rollers, and are arranged vertically above one another, respectively, on the sheet-input side and the sheet-discharge side. The angle at which the conveyor belts  17 ,  18  are looped or wrapped around the frictional rollers  56 ,  57  and the belt lengths correspond to those in the embodiment according to FIG. 1. The synchronicity of the transporting speeds of the conveyor belts is ensured by a common motor-control circuit or mechanically by a gear transmission or flexible drive mechanism. The distance a between the printing modules  44  and  45  may be selected to be greater than has been described with respect to FIG. 1.  
         [0022]    The identical printing modules  46  and  47  of a two-color printing machine, which are shown in FIG. 3, include, for the purpose of driving the conveyor belts simultaneously, as has been described with regard to FIG. 1, a common frictional roller  58 , which is driven by a motor. In addition, the printing modules  46  and  47  include respective deflecting rollers  59  and  60  on the sheet infeed side and the sheet discharge side, respectively, the rollers  59  and  60 , like the frictional rollers  56  and  57  in FIG. 2, running along therewith on the sheet-transporting side of the conveyor belts. Due to the running of the deflecting rollers  59  and  60  along therewith, the lengths of the conveyor belts of the printing modules  44  and  45  in FIG. 3 are configured to be somewhat greater than the lengths of the conveyor belts of the printing modules  1 ,  2 ,  44 ,  45  shown in FIGS. 1 and 2.  
         [0023]    [0023]FIG. 4 illustrates a four-color printing machine with four printing modules  48  to  51 . This four-color printing machine may be produced by assembling together two of the two-color printing machines according to FIG. 1. Synchronous running of the conveyor belts within the printing modules  48 ,  49  and  50 ,  51 , arranged in groups of two, is achieved by jointly driving with the frictional rollers  61  and  62 . Synchronous running of the driven frictional rollers  61  and  62  may be ensured by a common motor control or a mechanical gear transmission.  
         [0024]    In the four-color printing machine shown in FIG. 5, four printing modules  52  to  55  are arranged in series or tandem. With respect to the belt lengths and the distances between the printing modules  52  and  55 , that which has been stated hereinabove with regard to FIG. 3, applies as well to FIG. 5. A driven frictional roller  63  to  66 , respectively, is provided between respective pairs of the printing modules  52  to  55 . The deflecting roller  67  on the sheet-discharge side runs along merely with a friction lock on the sheet-transporting side of the conveyor belts of the printing module  55 . The motors for driving the frictional rollers  63  to  66 , respectively, feed a given amount of power into the system as a whole. The tensioning conditions in the individual belts can thus be influenced specifically and independently of one another, as a result of which the individual colors may be printed in register over one another.  
         [0025]    The invention of the instant application has been described by way of example with reference to ink-jet printing machines, but is not intended to be limited thereto. The arrangement for conveying printed products, such as sheets, folded copies and finished products, may likewise be provided in a machine which inspects the printed products.