Abstract:
A multiple layer paper web is provided with an electrostatic charge for the purpose of adhering the multiple webs to each other. A pair of oppositely charged rollers contact the surface of the multiple layer printing aper web and impart the charge to the web. The pair of oppositely charged rollers are positioned directly before a cylinder folding group of a web-fed rotary printing press.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a device for electrostatically charging a multilayer ribbon or paper web train. 
     DESCRIPTION OF THE PRIOR ART 
     It is generally known and described in EP 0 230 305 A2 that in rotogravure printing the incoming material webs or respectively paper web train or ribbons, are made to adhere to each other electrostatically, which adheres is called ribbon adherence. The stability of the material webs or paper web trains is increased by means of this electrostatic interlocking, so that the danger of a formation of corners of the printed products in the folding apparatus is reduced. Electrodes, which are arranged at both sides of the material webs and at a distance from the material webs are provided for applying the electrostatic charge. 
     In connection with this electrostatic charge, its low effectiveness on the paper web train or ribbon is disadvantageous, so that it became necessary to arrange additional devices, for example electrostatically charged guide devices, as disclosed in EP 0 230 305 A2 in order to reduce the effects of the so-called whip action, which leads to the formation of corners. 
     DE 31 17 419 C2 describes a method for the electrostatic charging of a multilayer paper web train ribbon. Here, the ribbon is charged by means of contactless acting electrodes after the webs have been brought together to form a ribbon downstream of a pair of compression rollers. 
     DE 27 54 179 C2 discloses a method for the electrostatic charging of a multilayer ribbon, wherein the edge areas of each layer are individually charged by means of rollers. 
     EP 0378350 A2 discloses a transport device for paper sheets in a plotter. This transport device has transport rollers for electrostatically charging a paper sheet and a plastic sheet. 
     U.S. Pat. No. 4,462,528 A describes a device for holding a web. This device has brushes, by means of which the web is held electrostatically. 
     SUMMARY OF THE INVENTION 
     The present object of the invention is based on providing a device for the electrostatic charging of a multilayer ribbon. 
     In accordance with the invention, this object is attained by the use of two rollers which press the ribbon or paper web train together and which also act as charging electrodes. Alternatively, the paper web train or ribbon can be electrostatically charged by oppositely polarized charge electrodes in the form of electrically conductive brushes which touch the paper web train or ribbon. 
     The advantages which can be achieved by means of the invention lie, in particular, in that charging of the paper web train ribbon takes place in a manner which is so lasting, that further devices for preventing, or reducing the formation of corners can be omitted. For example, an already provided pair of drawing rollers, which is required for the operation of the folding apparatus and has been modified in its design for the purpose of transmitting a voltage, is used as the device for charging the ribbon. 
     The strength of the voltage required for charging the ribbon is reduced in comparison with the voltage required by the prior art. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of present the invention are represented in the drawings and will be described in greater detail in what follows. 
     Shown are in: 
     FIG. 1, a schematic representation of a longitudinal folding device, as well as the ribbon entry into a cylinder folding group; 
     FIG. 2, a longitudinal section through one roller of a pair of rollers of the present invention in accordance with FIG. 1; 
     FIG. 3, a representation analogous to FIG. 2, but with a second preferred embodiment; and in 
     FIG. 4, a representation analogous to FIG. 2, but with a third preferred embodiment. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A longitudinal folding device  3  with a pair of funnel folding rollers  4 , as well as two pairs of rollers, for example, drawing roller pairs  6 ,  7 , are arranged ahead of the entry for a multilayer ribbon  1 , formed of for example, a plurality of paper webs, into a cylinder folding group  2 , for example, of a folding apparatus of a rotary printing press. This structure is depicted most clearly FIG.  1 . 
     The cylinder folding group  2  has a cutter cylinder  8  and a collection cylinder  9 , which operates against the cutter cylinder  8  and, in turn, works together with a folding jaw cylinder  11 . The printed products, which have been transversely folded in the cylinder folding group  2 , are supplied to a further processing station by means of a conveying device, for example a belt conveyor device which is not specifically shown in the drawings. 
     The second pair of drawing rollers  7 , arranged directly in front of the entry into the cylinder folding group  2 , consists of a first roller  13 , seated fixed in a lateral frame, and a second roller  16 , which is seated on a pivot arm or bearing element  14  as seen in FIG.  2 . This second roller  16  can be placed against the first roller  13  seated fixed in the lateral frame, with both rollers  13  and  16  of the second pair of drawing rollers  7  constituting the charging electrodes. The running paper web trainer ribbon  1  is conducted between the two rollers  13 ,  16 . 
     In accordance with a first preferred embodiment as seen in FIG. 2 both rollers  13 ,  16  consist of a cylinder- or hollow cylinder-shaped roller body, a metal body  17 , which has a shell  18  of a resilient covering of reduced conductivity, for example rubber of a hardness of approximately 85° Shore. The metal body  17  is connected, fixed against relative rotation, at both ends by means of hubs  19 —only one end being represented in FIG.  2 —with the shaft journal  21 . 
     The hubs  19  are fastened, electrically insulated, by means of ball bearings  22  in the bearing element  14 . An insulation which consists, for example, of respective bushings  23  of insulating material, for example a resin-bonded fabric, arranged between the pivot arm, or respectively the bearing element  14 , and the ball bearing  22 , which has a radial bore  24  for receiving a cable feed  26 . The cable feed  26  receives a feed line, for example a cable  27  which, for the purpose of transferring energy via an intermediate ring  25 , is pressed by means of a spring-loaded contact element  28  against the ball bearing  22 . 
     At its end remote from the roller  16  the shaft journal  21  is connected, fixed against relative rotation, with an annular flange  29 , which, in turn, is in connection, fixed against relative rotation, via a piece  31  of insulating material with a driveshaft  32 . 
     Each one of the rollers  13 ,  16  of the second drawing roller pair  13  can be separately driven. Moreover, the first roller  13  of the second pair  7  of drawing rollers is connected with a negative pole of a d.c. source, not represented, of approximately 5 kilovolts, for example a high tension d.c. generator, and the second roller  16  of the second pair  7  of drawing rollers is connected with a positive pole of the d.c. source. The polarity can also be reversed. 
     The paper web train or ribbon  1  preferably consists of paper webs, which are weakly mineralized and highly resistive. 
     It is also possible to drive only one roller  13  or  16  of the pair of rollers  13 ,  16 , or neither of the rollers of the pair of rollers  13 ,  16 . 
     In accordance with a second preferred embodiment as seen in FIG. 3, both charge electrodes, which are designed as rollers  33 ,  34 , also consist of a cylinder- or hollow cylinder-shaped metal body  36 , which has a multi-layer shell  37  comprised of with a lower, electrically insulating layer  38 , a center layer  39  which conducts electricity well, and an outer layer  40 , which is of only limited electrical conductivity. 
     At an end of each of the respective rollers  33 ,  34  a metallic contact ring  42  is arranged on a roller end face. An interior diameter of contacting  42  is in connection with the shaft journal  43 , and a peripheral surface of contact ring  42  is in an electrically conducting connection with the electrically conducting center layer  39  of the roller shell  37 . This can be achieved, for example, in that the contact ring  42  has a shell-like contact surface  44  on its periphery, which extends concentrically in respect to the metal body  36  and which in turn supports contact tips  46 , which are arranged on the end face of contacting  42  in a ring shape, are spaced apart from each other and are connected with the material of the center layer  39  of shell  37  which center layer  39  conducts electricity well. 
     The shaft journals  43 —only one of which is represented—are seated in the bearing element  14  in bearings  47 , which are also surrounded by an insulating material  48 . 
     A wiper element  49 , which is fixed on the bearing element  14  and which is insulated against it, is connected with the contact surface  44  of the contacting  42 , and is pressed by means of a spring force against the contact surface  44 . As in the first preferred embodiment, the wiper element  49  is connected with a cable feed  26   4  and a cable  27 . 
     In accordance with a third preferred embodiment, as seen in FIG. 4, the rollers  51 ,  52  which act as charge electrodes, respectively each consist of a stationary shaft journal  53 , fixed on the frame  14  in an insulating material  48  and having a roller body or metal body  36 . The metal body  36  is provided with an electrical high conductivity layer  39 , for example a steel shell, above which an outer layer  40  of limited electrical conductivity is arranged. One bearing  47  is arranged on both sides or ends of each of the rollers  51 ,  52  between the shaft journal  53  and the steel shell  39 . 
     The supply of electrical energy to the rollers  51 ,  52  takes By place via a cable  27 , which is in electrically conducting contact with the shaft journal  53 , for example with an exterior surface  54  of the shaft journal  53 . 
     It would, of course, also be possible to arrange the shell  39 ,  40  fixedly on the metal body  36  and to seat the journals  53 , electrically insulated and rotatably in the bearing element  14  fixed in place in the lateral frame. In this case the cable  27  would have to be connected by means of a collector ring with the exterior  54  of the shaft journal  53 . 
     In accordance with a fourth preferred embodiment which is, not specifically represented, the transfer of electrical energy to the ribbon  1  can also take place by means of conducting brushes, for example carbon brushes, arranged on both sides of the material webs of the ribbon  1 . 
     It is furthermore possible to design the first and second rollers  13 ,  16 ,  33 ,  34 ,  51 ,  52  of the second drawing roller pair  7  also in the form of so-called sandwich rollers. 
     Such sandwich rollers consist, for example, of a rotatably seated shaft, which receives a number of disks, which are arranged, fixed against relative rotation, on the shaft in the radial direction. Here, a disk made of metal, for example steel, alternates with an adjoining disk, which consists of a metal body having an electrically well conducting layer  39 , and above it an outer layer  40  of limited electrical conductivity such as shown in FIGS. 3 and 4. Electrical energy is introduced via the shaft journal. 
     Such a sandwich roller can be placed against a ribbon  1  as an individual roller, or also in opposing pairs, for example as a pair of drawing rollers. 
     When used in pairs, both sandwich rollers should be arranged in such a way that a metal disk of the first roller is placed opposite a layered disk of the second roller, and vice versa. Each roller of the pair of rollers has a different polarity. 
     While preferred embodiments of a method and a for electrostatically charging a multilayer train or paper web ribbon in accordance with the present invention have been set forth fully and completely hereinabove, it will be apparent to one of skill in the art that a number of changes in, for example, the source of drive power for the rollers, the specific type of printing press and folding group used and the like could be made without departing from the true spirit and scope of the present invention which is accordingly to be limited only by the following claims.