Patent Publication Number: US-10786984-B2

Title: Segment wheel for a device for printing on hollow bodies

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. National Phase, under 35 U.S.C. § 371, of PCT/EP2018/052510, filed Feb. 1, 2018; published as WO 2018/188830 A1 on Oct. 18, 2018, and claiming priority to DE 10 2017 206 392.0, filed Apr. 13, 2017, the disclosures of which are expressly incorporated herein by reference in their entireties. 
     FILED OF THE INVENTION 
     The present invention relates to a segmented wheel of a device for printing on hollow bodies. The segmented wheel has a plurality of segments formed on its periphery. A printing blanket for printing on the hollow bodies is, or at least can be arranged on at least one segment of the segmented wheel. 
     BACKGROUND OF THE INVENTION 
     As is known from WO 2012/148576 A1, for example, in a device used in the packaging industry for decorating hollow bodies, each of which has a cylindrical lateral surface, in most cases a plurality of printing units are used. In such cases, each of these printing units transfers a printing ink onto a printing blanket, which is used jointly by these printing units. The lateral surface of the hollow body in question is then decorated with a print motif, e.g. a multicolored print motif, by a relative movement between the lateral surface of the hollow body in question and the printing blanket, in particular by rolling the lateral surface of the hollow body in question along said printing blanket, which has been inked-up in advance, in particular with multiple colors. 
     A device of this type for printing on or for decorating hollow bodies, each of which has in particular a preferably cylindrical lateral surface, is used, for example, in conjunction with a system for producing such hollow bodies which typically has a plurality of work stations, wherein the hollow bodies are printed on or decorated by means of a printing process, and therefore these hollow bodies may also be referred to generally as printed products. In such a system, the hollow bodies to be printed on are produced in a large-scale production process in which, for example, several hundred or even several thousand pieces are produced per minute, for example between 1500 and 3000 pieces per minute. Hollow bodies of this type are made of metal, in particular steel or aluminum, for example, or are made of plastic. Metal hollow bodies of this type are used, for example, as beverage cans or as aerosol cans. Plastic hollow bodies of this type are produced, e.g. in the form of thermoplastic molded articles and are used, e.g. as cartons for packaging liquid or paste-like food products, for example, especially dairy products or beverages. However, the hollow body may also be a round tubular body made of either a plastic or aluminum, with a tube being defined as an elongated, sturdy but malleable container, which is intended for filling particularly with a paste-like substance. Tubes made of aluminum are produced, e.g. in a backward extrusion process. Tubes made of plastic are produced as seamless tubes, e.g. by means of extrusion. Another possible type of hollow body that can be printed on in a device as described above is containers or vessels, such as bottles or flasks, preferably cylindrical and made of glass. 
     Beverage cans are preferably made of aluminum and are typically what are known as two-part cans, in which a circular base together with a preferably straight cylinder shell are produced from of a single work piece, i.e. from a slug or from a blank, i.e. a circular disk, in a forming process, for example in a cold extrusion process or in a tensile-pressure forming process, preferably by deep drawing, in particular by deep drawing and ironing, to form a hollow body which is open at one end, known as a can blank, and in which, in a final manufacturing step, a circular lid is placed on the cylinder and is attached to the cylinder by flanging, forming an air-tight seal. 
     Tinplate cans are another type of can. Tinplate is tin-plated sheet steel. The thickness of the sheet steel used to produce tinplate cans is 0.15 mm to 0.49 mm, for example, and the thickness of the tin plating is 0.2 μm to 0.8 μm, for example; the tin plating provides protection against corrosion. Tinplate cans are what are known as three-part cans. To produce the shell for a tinplate can, a rectangular strip of sheet steel is bent into a preferably straight cylinder, and the ends of this strip that has been bent into a cylinder are welded together at a butt joint. A circular base and a circular lid are then placed onto the cylinder and the edges are flanged. To make the tinplate can in question more resistant to dents, each of the three parts, i.e., the cylinder shell, the base and the lid, preferably has a corrugated profile, for example. 
     An aerosol can, also called a spray can, is a metal can used for spraying liquids. The liquid filled into an aerosol can is pressurized, and propane, butane, dimethyl ether or mixtures thereof, or compressed air or nitrogen, for example, is used as the propellant for dispensing the liquid from the can. 
     The aforementioned WO 2012/148576 A1 describes a device for decorating cans, in which an assembly of multiple printing units is provided, each having an inking unit for the multicolored decoration of a plurality of cans, wherein each of the inking units belonging to one of the printing units has an ink fountain for supplying ink, wherein in each ink fountain, an ink fountain roller for picking the printing ink up from the associated ink fountain is provided, wherein in each inking unit, a duct roller is provided, each duct roller receiving printing ink from the ink fountain roller in question, wherein in a roller train situated downstream of the respective duct roller in the inking unit in question, a plurality of oscillating ink distribution rollers and a plurality of ink transfer rollers are provided, each interacting with at least one of the ink distribution rollers, wherein for each inking unit, a plate cylinder having at least one printing plate is provided, and only a single ink forme roller cooperates with each plate cylinder to apply the printing ink. 
     Known from U.S. Pat. No. 5,233,922 A is a segmented wheel for a device for printing on hollow bodies, in which a plurality of segments is formed on the periphery of said segmented wheel, with a printing blanket for printing on the hollow bodies being arranged on at least one segment, the segmented wheel having a main body, and each segment being arranged pivotably relative to the main body. 
     DE 1 225 201 B also relates to a segmented wheel for a device for printing on hollow bodies, with a plurality of segments being formed on the periphery of said segmented wheel, a printing blanket for printing on the hollow bodies being arranged on at least one segment, the segmented wheel having a main body, and each segment being arranged pivotably relative to the main body. The segments may be embodied as individual integral parts or as multi-part elements. In the case of a two-part embodiment, the two parts of the relevant segment are connected to one another by means of screws. The segments are connected to the main body via a pivot bearing. 
     From the subsequently published DE 10 2016 201137 A1, a device for printing on hollow bodies is known, which comprises a segmented wheel having a plurality of segments on its periphery, with a printing blanket for printing on the hollow bodies being arranged on at least one segment of the segmented wheel. 
     WO 2004/109581 A2 discloses an apparatus for carrying out a contactless digital printing method, e.g. an inkjet printing method, for printing on round objects, in particular two-part cans, individually if necessary, without the use of a printing blanket, in which a plurality of print heads are preferably provided, each of which prints in a single printing ink. 
     From DE 10 2006 004568 A1, a short inking unit for a printing machine is known, comprising a printing forme cylinder, an ink forme roller cooperating with the printing forme cylinder, and an anilox roller that contacts the ink forme roller and is associated with a device for supplying ink, wherein at least one leveling roller is disposed between the point where ink is supplied and the contact nip between the anilox roller and the ink forme roller with respect to the direction of rotation of the anilox roller, and the device for supplying ink is embodied as a chamber doctor blade. 
     Known from DE 101 60734 A1 is a printing machine that comprises at least one printing forme, a dampening unit for dampening the printing forme with a dampening medium, an inking unit for inking the printing forme with a printing ink and a dehumidifying device with a heating roller (temperature control roller) for reducing the amount of dampening medium that is conveyed together with the printing ink, wherein the inking unit is embodied as a leverless short inking unit, in which one inking unit roller of the inking unit includes a first rolling contact point at which the inking unit roller is in rolling contact with the heating roller, and the inking unit roller also has a second rolling contact point, and wherein the shortest path along which printing ink is conveyed from the inking unit roller to the printing forme is determined by at most one intermediate roller. 
     Known from DE 32 32780 A1 is an inking unit for offset printing machines for printing onto sheets or webs, having a plate cylinder that receives the necessary ink from at most two ink forme rollers which have an elastic surface and which cooperate with an inking cylinder to which the ink is fed via an ink feeding system that generates a continuous ink film, wherein an ink forme roller having nearly the same diameter as the plate cylinder is disposed downstream of the inking cylinder, wherein the inking cylinder is associated with a dampening unit having at least one roller for transferring the dampening medium, and wherein the dampening medium is transferred to the inking cylinder in the direction of rotation thereof downstream of the ink application and upstream of the contact point thereof with the ink forme roller. 
     Known from DE 10 2006 048286 A1 is a method for driving a printing unit which has a short inking unit in a processing machine having an anilox roller and an associated doctor blade device, along with an ink forme roller located downstream of the anilox roller, and a plate/forme cylinder downstream of the ink forme roller in the direction of ink flow, wherein the plate/forme cylinder is operatively connected to a rubber blanket cylinder and the rubber blanket cylinder is operatively connected to a printing cylinder which guides the printing substrate, wherein the anilox roller is driven by an independent drive, wherein during printing/varnishing operation, the main drive supplies an input drive to a drive wheel of the printing cylinder and to a drive wheel of the rubber blanket cylinder and to a second and a first drive wheel of the plate/forme cylinder and to a drive wheel of the ink forme roller and to a drive wheel of the anilox roller, while the independent drive of the anilox roller is inactive, and wherein during set-up operation, the drive connection to the main drive between first drive wheel and second drive wheel of the plate/forme cylinder is disconnected, the independent drive of the anilox roller is activated, and the independent drive applies drive torque to the drive wheel of the anilox roller and to the drive wheel of the ink forme roller and to the first drive wheel of the plate/forme cylinder. 
     Known from DE 196 24440 A1 is a device for filling depressions in a cylinder of a printing machine with a fluid, wherein at least two doctor blade devices for filling depressions in the cylinder with the fluid are arranged on the cylinder, wherein an applicator for the fluid, connected to a fluid conveyance system, and a working blade disposed downstream of said applicator in the direction of rotation of the cylinder are provided, wherein the doctor blades are mounted on a bar, and the wiped off fluid is discharged to a collecting basin. 
     Known from DE 89 12194 U1 is an inking unit for use in a printing machine, having a working doctor blade that can be set against an anilox roller, along with an ink trough with ink conveying means, wherein the working doctor blade, the ink trough and the means for conveying the ink to the anilox roller are combined to form a single modular unit and the modular unit is removably attachable to a carrier structure mounted on the printing machine. 
     Known from DE 10 2007 052761 A1 is an anilox printing unit, which includes an ink forme roller and an anilox roller as inking unit rollers, the anilox roller being mounted on rocking levers, wherein the anilox roller and the ink forme roller each have bearer rings, and a device for pressing the bearer rings of one inking unit roller against the bearer rings of the other inking unit roller includes springs to compensate for diameter differences resulting from manufacturing tolerances. 
     DE 43 00683 A1 discloses an inking unit of a rotary printing press, having an ink forme roller with annular grooves formed in its lateral surface. 
     A distribution roller having a plurality of pliable rings arranged side by side in the axial direction is known from U.S. 516,620. 
     Known from DE 28 51426 A1 is a device for printing on the lateral surface of hollow bodies, wherein a transport device is provided for transporting the hollow bodies to be printed about a rotational axis, wherein a plurality of printing units are provided, wherein each hollow body to be printed on can be transported by means of the transport device into the printing zone of at least one of the printing units, and wherein at least one of the printing units has a printing forme cylinder and an inking unit having a single ink forme roller. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to devise a segmented wheel for a device for printing on hollow bodies, with which a production adjustment to a different format of hollow body can be carried out economically. Even smaller lot sizes, which lead to a frequent resetting of the production system due to the need to change the decorative pattern after short production periods, should be able to be produced economically and efficiently. 
     The object of the present invention is attained, according to the present invention, by a segmented wheel having a main body, wherein the main body is made of a metallic material. Each of the segments which is formed along the periphery of the main body is arranged at a joint. The segments are each detachably connected to the main body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       One exemplary embodiment of the invention is illustrated in the set of drawings and will be described in greater detail below. Advantages to be achieved with the invention will be mentioned in connection with the exemplary embodiment. 
       In the figures: 
         FIG. 1  shows a device for printing on or for decorating hollow bodies, each of which has a lateral surface; 
         FIG. 2  shows an inking unit, in particular for the device shown in  FIG. 1 , in a first operating position; 
         FIG. 3  shows the inking unit in particular for the device shown in  FIG. 1  in a second operating position; 
         FIG. 4  shows a chamber doctor blade system, in particular for the inking unit shown in  FIGS. 2 and 3 ; 
         FIG. 5  shows a plate changer in a first operating position; 
         FIG. 6  shows the plate changer of  FIG. 5  in a second operating position; 
         FIG. 7  shows a magazine for printing blankets; 
         FIG. 8  shows a device for vertical transport of the magazine shown in  FIG. 7 ; 
         FIG. 9  shows a device for the horizontal transport of one of the printing blankets at a time, between the magazine shown in  FIG. 7  and a mounting position on a segmented wheel in the device shown in  FIG. 1 ; 
         FIG. 10  shows the magazine of  FIG. 7  in its operating state disposed on the device provided for its vertical transport; 
         FIG. 11  shows a cross-sectional view of the device for horizontal transport of one of the printing blankets at a time, as shown in  FIG. 9 , with a deployed spatula for removing a used printing blanket from the segmented wheel; 
         FIG. 12  shows a perspective view of the device for horizontal transport of one of the printing blankets at a time, as shown in  FIG. 9 , with the deployed spatula; 
         FIG. 13  shows the device of  FIG. 1  for printing on or decorating hollow bodies, each of which has a lateral surface, with a schematic representation of the segments of the segmented wheel; 
         FIG. 14  shows a perspective, detailed representation of the segmented wheel along with its shaft; 
         FIG. 15  shows a perspective, detailed representation of the drive for driving the rotation of the segmented wheel; 
         FIG. 16  shows a sectional view of the segmented wheel with its drive, in the condition as arranged in the device for printing on hollow bodies; 
         FIG. 17  shows a production sequence for producing a color gradient on a hollow body; 
         FIG. 18  shows a hybrid device for printing on hollow bodies; 
         FIG. 19  shows the segmented wheel with replaceable segments; 
         FIG. 19 a    shows an enlarged portion of the segmented wheel; and 
         FIG. 20  shows a single changeable segment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In a preferred embodiment, the printing, in particular, of the lateral surface of a hollow body with, e.g. a multicolor print motif, i.e. at least one printed image, is carried out in a letterpress process. Alternative printing methods include, e.g., a screen printing process or an offset printing process or a digital printing process without printing formes. In the following, the invention will be described by way of example in connection with a letterpress process. To execute the letterpress process, a printing plate is arranged as a printing forme on the lateral surface of a plate cylinder. The printing plate ready for use in the printing process is a printing forme with a print relief, said print relief reproducing the print image intended for use in the printing process in a mirror image, wherein in an error-free printing operation, only the print relief is involved in the transfer of ink that has been supplied by the inking unit to the plate cylinder onto the printing blanket. The printing forme or the printing plate has a plate-shaped, preferably flexible substrate of finite length, e.g. made from a steel sheet, wherein a printing element, in particular flexible, is arranged on said substrate. At least the opposing ends of the substrate in the circumferential direction of the plate cylinder may be either pre-curved, e.g. corresponding to the curvature of the lateral surface of the plate cylinder, or bent, to enable easier mounting of the printing forme, i.e. here in particular the printing plate, on the plate cylinder. The substrate of the printing forme or the printing plate has a thickness ranging from 0.2 mm to 0.3 mm, for example. The total thickness of the printing plate, including its substrate, ranges from 0.7 mm to 1.0 mm, for example, and is preferably approximately 0.8 mm. The printing element is made of a plastic, for example. To produce the printing plate which is ready for use in the printing process, the printing element is exposed, e.g. with a negative film that mirrors the print image, and unexposed areas are then removed from the printing element, e.g. by washing or by means of a laser. 
     A device for printing on or decorating hollow bodies, each of which has in particular a preferably cylindrical lateral surface, preferably has a plurality of printing units, e.g. eight or ten or even more—also called printing stations—, wherein at least one of these printing units, and in the preferred embodiment each of these printing units, has a rotatable printing forme cylinder, in particular a printing forme cylinder configured as a plate cylinder. The printing units or printing stations and optionally also the printing forme cylinders in this device are each mounted in a frame and can be used in the same printing process to produce a print motif in multiple colors on the same hollow body, the number of colors corresponding to the number of printing units or printing forme cylinders involved. Each printing forme cylinder or plate cylinder is preferably mounted as a cantilevered component, with the printing forme cylinder or plate cylinder in question being mounted at one of its end faces, e.g. on a preferably conical journal. Typically, only a single printing plate is arranged on the lateral surface of each plate cylinder, with the substrate of the printing plate fully or at least largely spanning the circumference of the plate cylinder in question, in particular more than 80% thereof. The length of the printing element of the printing plate in the circumferential direction of the plate cylinder in question is preferably shorter than the circumference of the plate cylinder in question. The printing forme or the printing plate is or at least can be arranged by means of its substrate, in particular magnetically, on the lateral surface of any of the plate cylinders, i.e. the printing forme or the printing plate is preferably held there magnetically, i.e. by means of a magnetic holding force. In an alternative or additional variant of the device for printing on or decorating hollow bodies, each of which has a preferably cylindrical lateral surface, at least one of the printing units, or each of a plurality of these printing units, is configured as a printing unit that prints in a digital printing process without the use of printing formes, with such a printing unit having, in particular, at least one inkjet print head or one laser. 
     The especially simultaneous transfer of a plurality of printing inks in particular to the lateral surface of the hollow body in question requires proper register to be maintained during ink transfer in order to achieve good print quality in the printing process. For a true-to-register arrangement of the printing forme or the printing plate on the lateral surface of the printing forme cylinder or plate cylinder in question, in the preferred embodiment a plurality of register pins, e.g. the position of each being adjustable, are preferably provided on the lateral surface of the printing forme cylinder or plate cylinder in question, which pins engage in corresponding recesses formed on the printing forme or on the printing plate, thereby giving the printing forme or printing plate a defined position in its arrangement on the lateral surface of the printing forme cylinder or plate cylinder in question. In a preferred embodiment, each printing forme cylinder or plate cylinder has a diameter of between 100 mm and 150 mm, in particular between 120 mm and 130 mm, and the axial length of each printing forme cylinder or plate cylinder is between 200 mm and 250 mm, for example, in particular between 200 mm and 220 mm. The printing plate to be arranged on the lateral surface of the plate cylinder in question has a width in the axial direction of the plate cylinder in question that ranges from 150 mm to 200 mm, and is preferably about 175 mm. 
     Each printing forme cylinder, e.g. configured as a plate cylinder, used in the printing process uses its printing forme or its printing plate to transfer a specific printing ink onto a printing blanket. The printing inks used are typically premixed, in particular specially customized inks, which are specifically adapted in terms of their respective printability to the material of the hollow body to be printed on, depending upon whether the surface to be printed on is made e.g. of aluminum, tinplate, or plastic. In a preferred embodiment of a device for printing on or decorating hollow bodies, each of which has, e.g. a cylindrical lateral surface, a device for transferring printing ink from the printing forme or the printing plate to the lateral surface of the hollow body in question is provided. This device for transferring ink is preferably embodied, e.g. as a segmented wheel that rotates about a horizontal axis, in particular, wherein a plurality of printing blankets, e.g. eight, ten, twelve or even more, preferably are or at least can be arranged one behind the other on the periphery of this segmented wheel, i.e. along its circumference. As an alternative to the segmented wheel, and depending on the printing method that is used, the device for transferring printing ink may also be embodied as a decorating drum or as a printing blanket cylinder or as a transfer cylinder, each of which is rotatable about an axis of rotation, at least during printing. The printing blankets have hitherto been arranged on the periphery of the segmented wheel by attaching each of the printing blankets to the periphery of the segmented wheel, e.g. by an adhesive connection, preferably by gluing. Each of the preferably multiple printing forme cylinders or plate cylinders is or at least can be thrown radially onto the printing blankets that are arranged on the periphery of the segmented wheel in question. In a particularly preferred embodiment of a device for printing on or decorating hollow bodies, each of which has, e.g. a cylindrical lateral surface, a greater number of printing blankets are provided one behind the other along the periphery of the segmented wheel than the number of printing forme cylinders or plate cylinders which are or at least can be thrown radially onto the segmented wheel. The device for transferring printing ink, preferably in the form of a carousel, in particular the segmented wheel, has a diameter of, e.g. 1,400 mm to 1,600 mm, preferably of about 1,520 mm to 1,525 mm, and when e.g. eight printing forme cylinders or plate cylinders are assigned to said device, it has e.g. twelve printing blankets arranged one behind the other around its periphery. The surface of each printing plate is preferably configured as harder than the respective surface of the printing blankets. The surface of the printing blankets is preferably flat, i.e. without profiling. In an operating mode in which the printing forme cylinders or plate cylinders involved in the printing process are each thrown radially onto the printing blankets of the rotationally driven segmented wheel, the respective printing formes of these printing forme cylinders or the respective printing plates of these plate cylinders roll along the printing blankets that are moved by the segmented wheel, with each of the printing plates pressing at least its print relief, e.g. 0.2 mm to 0.25 mm deep into the respective printing blanket, thereby producing a flattened area in the printing blanket in question, i.e. a roller strip, extending in the axial direction of the segmented wheel. The intensity of this flattening is or can be adjusted, e.g. prior to or at the start of a printing process, e.g. by means of remote actuation, by adjusting the contact pressure exerted by the printing forme cylinder or plate cylinder in question on the printing blanket in question of the segmented wheel. 
     Each of the hollow bodies to be printed on here by way of example, e.g. each of the two-part cans to be printed on, is moved, e.g. by means of a transport device that preferably transports the hollow bodies to be printed on along at least a portion of a circular path, that is, a circular arc, around a rotational axis, preferably by means of a feed wheel, in particular by means of a mandrel wheel, in a continuous movement or in a set cycle, up to at least one of the printing units belonging to the device for printing on hollow bodies, each of which has a lateral surface, and is thereby transported into the printing zone of at least one of these printing units. For example, each of the hollow bodies to be printed on is moved by means of the transport device, e.g. embodied as a feed wheel, up to at least one of the printing blankets arranged, e.g. on the segmented wheel, or each of the hollow bodies to be printed on is transported directly and immediately, i.e. without assistance from a device for transferring printing ink, e.g. embodied as a segmented wheel, into the respective printing zone of at last one of these printing units, which is the case when the printing unit in question prints in a direct printing process, for example in an inkjet printing process. 
     The feed wheel or mandrel wheel which, like e.g. the segmented wheel, rotates about a preferably horizontal axis, has a plurality of holders, e.g.  24  or  36 , concentrically to its circumferential line in preferably equidistant distribution, e.g. each in the form of a clamping mandrel or a spindle that projects cantilevered from an end face of the mandrel wheel, wherein each holder holds or at least is capable of holding one of the hollow bodies to be printed on. A transport device embodied as a mandrel wheel is also characterized herein as a turntable with spindles. A mandrel wheel is described, e.g. in EP 1165318 A1. A description of suitable holders, spindles and/or clamping mandrels may be found in WO 2011/156052 A1, for example. In the following, each clamping mandrel will be referred to simply as a mandrel. The longitudinal axis of each mandrel is oriented parallel to the axis of the mandrel wheel. In the case involving printing on hollow bodies, each of which is embodied, e.g. as a two-part can, each of these hollow bodies is moved, e.g. by means of a conveyor device, e.g. a belt conveyor, up to the transport device, embodied e.g. as a mandrel wheel, where it is inverted at a transfer station onto one of the mandrels of the mandrel wheel by suction, e.g. by means of a vacuum, and is then held by the mandrel in question, while the transport device embodied as a mandrel wheel transports the respective hollow body to be printed on, e.g. to the segmented wheel which is loaded with at least one printing blanket and thus in the direction of at least one of the printing units, or in an alternative embodiment that has no segmented wheel, for example, directly to at least one of the printing units. Typically, a large number of hollow bodies to be printed on are fed to the mandrel wheel in rapid succession by the conveyor device. A conveyor device of this type is described, e.g. in EP 1132207 A1. 
     A gap measuring less than 1 mm in width, e.g. measuring 0.2 mm in width, is preferably formed between the inner wall of a respective hollow body to be printed on and the surface of the relevant mandrel of the mandrel wheel, so that the hollow body to be printed on is not held on the mandrel in question by means of a press fit. Each mandrel can be rotated about its respective longitudinal axis, e.g. by means of a motor, and in particular is adjustable to a specific circumferential speed, so that in addition to being rotated by the mandrel wheel, each hollow body to be printed on that is held by a mandrel can be rotated by a rotation that is or at least can be executed independently by the mandrel. The hollow body to be printed on is preferably inverted onto one of the mandrels of the mandrel wheel during a phase when the mandrel in question is stationary; during said stationary phase, the mandrel in question executes no rotational movement about its own longitudinal axis. The loading of each mandrel with a hollow body to be printed on is preferably verified, e.g. in a contactless manner by means of a sensor. If a mandrel is not loaded with a hollow body to be printed, the mandrel wheel will moved, e.g. in such a way that contact of the unoccupied mandrel with a printing blanket of the segmented wheel is reliably prevented. 
     Before being fed, e.g. to the mandrel wheel, two-part cans to be printed on are produced, e.g. deep-drawn from a circular blank, in a processing station disposed upstream of the mandrel wheel. In an additional processing station, the rim of each two-part can is trimmed at its open end face. In additional processing stations, each two-part can is washed, for example, in particular its inside is washed out, and optionally, the inner wall and the base of the two-part can in question is also coated. At least the exterior lateral surface of each two-part can is primed, for example, in particular with a white primer. Once the printing on its lateral surface is complete, each two-part can is removed from its respective holder, e.g. on the mandrel wheel, e.g. by means of compressed air or by means of a preferably reversible magnet, and is fed to at least one processing station located downstream of the mandrel wheel, e.g. to a coating station for coating the exterior lateral surface of each printed two-part can and/or to a rim processing station. The printed two-part cans pass in particular through a dryer, e.g. a hot air dryer, to cure the at least one printing ink applied to their respective lateral surfaces. 
     The printing process for printing in particular on the lateral surfaces of hollow bodies, in particular two-part cans, held, e.g. on the mandrel wheel, begins with each of the printing inks that are required for the print image to be printed onto the lateral surface of each hollow body being applied, e.g. by the respective printing plate of the plate cylinder that is thrown, e.g. onto the segmented wheel, to the same one of the printing blankets arranged on the periphery of the segmented wheel. The printing blanket in question, inked up in this manner with all the necessary printing inks, then transfers these printing inks simultaneously onto the lateral surface of the hollow body to be printed on by means of direct surface contact between the printing blanket and the lateral surface of the hollow body to be printed on during a single revolution of said hollow body to be printed on about its longitudinal axis, said hollow body being held on one of the mandrels of the mandrel wheel. During the transfer of the printing inks from the printing blanket onto the lateral surface of the hollow body, the hollow body to be printed on, held, e.g. by one of the mandrels of the mandrel wheel, rotates at the same circumferential speed as the printing blanket in question, arranged, e.g. on the periphery of the segmented wheel. The respective circumferential speeds of hollow body and printing blanket or segmented wheel are thus synchronized with one another, with the hollow body to be printed on, which is held, e.g. on one of the mandrels of the mandrel wheel, being accelerated appropriately, e.g. starting from a stationary position, beginning from its first point of contact with the relevant printing blanket and continuing as its lateral surface rolls along a path of the first, e.g. 50 mm of the circumferential length of the printing blanket, in particular until it reaches the circumferential speed, e.g. of the segmented wheel. The segmented wheel that carries the printing blanket in question therefore determines the circumferential speed to be set, e.g. at the respective mandrel of the mandrel wheel. The circumferential speed of the printing forme cylinder that carries the printing forme or of the plate cylinder that carries the printing plate also preferably is or will be adjusted based upon the circumferential speed, e.g. of the segmented wheel. The mandrel wheel and the segmented wheel can be driven, e.g. by the same central machine drive and are optionally coupled to one another mechanically, e.g. via a gear set. In the embodiment according to the invention, however, the mandrel wheel and the segmented wheel are each driven individually by a separate drive, and the respective rotational behavior of each is controlled or regulated by a control unit. 
     In the following, various details relating, in particular, to the above-described device for printing on or decorating hollow bodies each of which has, e.g. a cylindrical lateral surface will be described by way of example.  FIG. 1  shows a simplified schematic representation of an example of a generic device for printing on or decorating hollow bodies  01 , e.g. two-part cans  01 , each having a preferably cylindrical lateral surface, in particular, wherein said hollow bodies  01  are fed, e.g. sequentially, by a conveyor device to the transport device configured, e.g. as a rotating or at least rotatable feed wheel, in particular as a mandrel wheel  02 , and are held on said transport device, each on a single holder. In the following, based upon the selected exemplary embodiment of the printing machine or the device for printing on hollow bodies, it will be assumed that this transport device is configured preferably as a mandrel wheel  02 . A device for transferring printing ink, e.g. a rotating or at least rotatable segmented wheel  03 , around the periphery of which a plurality of printing blankets are arranged one behind the other, preferably cooperates with mandrel wheel  02 . Assigned to segmented wheel  03 , mentioned by way of example, and arranged along its circumferential line, a plurality of printing forme cylinders, in particular plate cylinders  04 , that are or at least can be thrown radially onto this segmented wheel  03  are provided, with a printing forme, in particular a printing plate, being arranged on the lateral surface of each of these printing forme cylinders or plate cylinders  04 , said printing plate being suitable in particular for carrying out a letterpress printing process. A specific printing ink is fed by means of an inking unit  06  to each of the printing forme cylinders or plate cylinders  04  for the purpose of inking up the printing forme or printing plate thereof. In the following, it will be assumed by way of example that each of the printing forme cylinders is configured as a plate cylinder  04  that carries at least one printing plate. 
       FIGS. 2 and 3  show a simplified schematic representation of a number of details of inking unit  06 , one of which cooperates with each plate cylinder  04 , and which is provided, e.g. for use in the device shown in  FIG. 1  for printing on or decorating in particular hollow bodies  01 , each having a preferably cylindrical lateral surface. The inking unit  06  proposed here advantageously has a very short roller train, i.e. consisting of only a few rollers, preferably a maximum of five, in particular a two-roller train, for transporting ink from an ink reservoir to the relevant plate cylinder  04 . In the case of a two-roller train, said roller train consists of only a single ink forme roller  07  and one anilox roller  08 . An inking unit  06  with a roller train consisting of no more than five rollers is classified as a short inking unit.  FIG. 2  shows an example of a (short) inking unit  06  having a two-roller train in a first operating position, in which ink forme roller  07  and anilox roller  08  are thrown onto one another, ink forme roller  07  is thrown onto plate cylinder  04 , and plate cylinder  04  is thrown radially onto the device, in particular the segmented wheel  03 , for transferring printing ink from plate cylinder  04  onto the lateral surface of the hollow body  01  in question. In contrast,  FIG. 3  shows a second operating position for the inking unit  06  shown in  FIG. 2 , in which ink forme roller  07  and anilox roller  08  are thrown off of one another, ink forme roller  07  is thrown off of plate cylinder  04 , and plate cylinder  04  is thrown off of the device for transferring printing ink, in particular the segmented wheel  03 . The throw-on and throw-off mechanism will be described further below. 
     Plate cylinder  04  and anilox roller  08  are each rotated, e.g. separately, each by a motor  11 ;  12 , in particular in the preferred inking unit  06  as shown in  FIGS. 2 and 3 , in which the motor  11 ;  12  in question is in particular controlled or at least controllable, e.g. in terms of its respective speed, by e.g. an electronic control unit. The device for transferring printing ink, configured, e.g. as a segmented wheel  03 , is rotationally driven by a dedicated drive in the preferred embodiment or by a central machine drive in an embodiment not according to the invention. Ink forme roller  07  is or is to be rotationally driven by anilox roller  08  by means of friction or likewise separately by a motor. In the preferred embodiment, the outer diameter d 07  of ink forme roller  07  is equal to the outer diameter d 04  of plate cylinder  04 , which carries at least one printing forme, in particular at least one printing plate. At least one printing plate is or at least can be arranged on the lateral surface of plate cylinder  04 , so that in the embodiment in which the outer diameters d 04 ; d 07  are equal, the circumferential lengths of plate cylinder  04 , which carries the printing plate, and ink forme roller  07  are also equal. In the preferred embodiment, when the inking unit  06  that cooperates with the plate cylinder  04  is in the first operating position, in which ink forme roller  07  and anilox roller  08  are thrown onto one another, ink forme roller  07  is thrown onto plate cylinder  04 , and plate cylinder  04  is thrown onto segmented wheel  03 , at least the centers of plate cylinder  04 , ink forme roller  07  and anilox roller  08  are arranged along the same straight line G. To detect the rotation of ink forme roller  07 , a detection device, e.g. in the form of a rotary encoder is provided, said rotary encoder being rigidly connected, in particular, to the shaft of ink forme roller  07 . The signal generated by the rotary encoder with a rotation of ink forme roller  07  is used by the control unit to adjust or if necessary to track the rotational speed of ink forme roller  07  by means of the rotation of anilox roller  08  such that synchronization between plate cylinder  04  and ink forme roller  07  is or is to be established, and therefore such that the circumferential speed of ink forme roller  07  coincides with the circumferential speed of plate cylinder  04  within predefined permissible tolerance limits. To achieve this goal, it may be provided that the control unit adjusts the circumferential speed of anilox roller  08 , preferably during the adjustment phase carried out by the control unit, in such a way that the anilox roller has a lead or lag time relative to the circumferential speed of plate cylinder  04 , in particular briefly, and thus not permanently. By configuring plate cylinder  04  and ink forme roller  07  as having equal circumferential lengths, and by establishing synchronization between plate cylinder  04  and ink forme roller  07 , the adverse effect on print quality of ghosting is largely avoided. The drive concept described herein involving a friction-driven ink forme roller  07  also has the advantage that a separate drive for ink forme roller  07  is not required, which saves on cost and also facilitates replacement of ink forme roller  07 , e.g. during maintenance and repair operations, due to the simpler mechanical construction. In its preferred embodiment, ink forme roller  07  has a closed, preferably rubberized lateral surface. The lateral surface of anilox roller  08  is coated, e.g. with a ceramic, with a hachure, e.g. of 80 lines per centimeter of axial length of anilox roller  08  or a saucer structure being formed in the ceramic layer. To enable the largest possible volume of printing ink to be fed into the roller train of inking unit  06  with each revolution of anilox roller  08 , the outer diameter d 08  of anilox roller  08  is preferably configured as larger than the outer diameter d 07  of ink forme roller  07 . This is meant to give anilox roller  08  the greatest possible delivery volume. In  FIG. 2 , the directions of rotation of segmented wheel  03 , plate cylinder  04 , ink forme roller  07 , and anilox roller  08  are each indicated by a rotational arrow. 
     In the preferred embodiment, at least anilox roller  08  has a temperature control device for controlling the temperature of the lateral surface of anilox roller  08 . The temperature control device of anilox roller  08  operates e.g. using a temperature control fluid that is introduced into the interior of anilox roller  08 , the temperature control fluid being, e.g. water or some other liquid coolant. The temperature control device of anilox roller  08  can be used to influence the delivery volume of anilox roller  08 , as said device influences the viscosity of the printing ink to be transported by inking unit  06 . The delivery volume of anilox roller  08  and the viscosity of the printing ink to be transported by inking unit  06  in turn ultimately impact the ink density of the printing ink to be applied to the cylindrical lateral surface of the hollow body  01  to be printed on. The thickness of the ink film formed by the printing ink to be applied to the cylindrical lateral surface of hollow body  01  to be printed on is, e.g. less than 10 μm, in particular approximately 3 μm. 
     The ink reservoir of inking unit  06  is embodied, e.g. as a chamber doctor blade system  09  that operates in conjunction with anilox roller  08 . Advantageously, in this chamber doctor blade system  09 , at least one ink trough, a doctor blade bar which is or at least can be set axially parallel against anilox roller  08 , and preferably also a pump for delivering the printing ink form a single structural unit. This chamber doctor blade system  09  is held or mounted in inking unit  06 , i.e. on a frame of inking unit  06 , preferably on only one side, e.g. by means of a suspension, so that once this modular unit has been released from the frame of inking unit  06  it can be removed from inking unit  06  in a simple manner laterally, i.e. by a movement directed axially parallel to anilox roller  08 , e.g. by pulling on a handle disposed on said structural unit, and can thereby be replaced. This modular unit of chamber doctor blade system  09  preferably forms a cantilever arm on a side frame of inking unit  06 .  FIG. 4  shows a perspective view of chamber doctor blade system  09 , configured as a separate modular unit, in cooperation with anilox roller  08  of inking unit  06 . 
     Once anilox roller  08  has received printing ink from the ink reservoir, i.e. in particular from chamber doctor blade system  09 , anilox roller  08  transports this printing ink immediately and directly or via additional rollers of the roller train which is part of inking unit  06  to the preferably only one ink forme roller  07 . In a region downstream of the chamber doctor blade system  09 , which is set against anilox roller  08 , between chamber doctor blade system  09  and ink forme roller  07  in the direction of rotation of anilox roller  08 , a rider roller  13  preferably is or at least can be thrown onto anilox roller  08  for the purpose of improving the transport of ink by anilox roller  08 . Rider roller  13  is arranged axially parallel to anilox roller  08 . Rider roller  13  is not considered to be part of the roller train of inking unit  06  because it does not transfer printing ink from anilox roller  08  to another roller. Rider roller  13 , which is rotationally driven by anilox roller  08 , e.g. by means of friction, has a rubberized lateral surface, for example. As rider roller  13 , which is thrown onto anilox roller  08 , rolls along the lateral surface of anilox roller  08 , it draws a portion of the printing ink that has been received by anilox roller  08  from chamber doctor blade system  09  out of the hachure or the saucers of anilox roller  08  and deposits at least some of this printing ink onto lands that are formed on the lateral surface of anilox roller  08 . Rider roller  13  rolling along anilox roller  08  thus causes anilox roller  08  to deliver a greater volume of printing ink to ink forme roller  07 . As a further consequence, an anilox roller  08  that includes, e.g. a temperature control device also improves the efficacy of controlling the ink density in that the rider roller  13  rolling along anilox roller  08  contributes to supplying a greater volume of printing ink. Regardless of the specific configuration of anilox roller  08 , i.e. with or without a temperature control device, rider roller  13  rolling along anilox roller  08  thus reduces both differences in density that can arise due to manufacturing tolerances of the anilox roller  08  and the risk of the hachure or saucers of anilox roller  08  being visible on the printing substrate, i.e. in this case on the lateral surface of the hollow body  01  to be printed on, due to an insufficient application of ink, at least in some areas. 
     In a highly advantageous embodiment of the device for printing on hollow bodies, a plate changer  14  is provided, e.g. for each printing forme cylinder, in particular plate cylinder  04 , preferably in a fixed assignment thereto, with which plate changer the printing forme intended for the printing forme cylinder in question or the printing plate intended for the plate cylinder  04  in question can be replaced, preferably automatically, within e.g. the relevant device for printing on or decorating hollow bodies  01 , each having in particular a cylindrical lateral surface.  FIGS. 5 and 6  show a perspective view of a preferred embodiment of a plate changer  14  of highly advantageous configuration, in two different operating positions for performing a plate change or printing forme change that can be completed within a very short setup time, preferably automatically, reliably and preferably also while maintaining register.  FIG. 5  shows a first operating position, in which, e.g. a printing plate may be brought forward on the printing forme cylinder or plate changer  14  or removed from plate changer  14 , axially to the side of the printing unit.  FIG. 6  shows a second operating position, in which, immediately upstream of the printing forme cylinder or plate cylinder  04  and lengthwise thereto, e.g. a printing plate may be placed from plate changer  14  directly onto the assigned plate cylinder  04 , or a printing plate may be removed from plate cylinder  04  and transported away with plate changer  14  to its first operating position. Plate changer  14  has in particular a planar, e.g. table-shaped bearing surface  16 , on which e.g. a printing plate that is or will be arranged on plate cylinder  04  can be supported, preferably fully. Bearing surface  16  is preferably arranged such that it is movable bidirectionally, i.e. movable back and forth, along a linear transport path, in particular longitudinally to the rotational axis of the associated printing forme cylinder or plate cylinder  04 , between at least two defined positions. In a first position of bearing surface  16 , located to the side of the printing unit, plate changer  14  assumes its first operating position, and in a second position of bearing surface  16 , located immediately upstream of the printing forme cylinder or plate cylinder  04  and longitudinally thereto, the plate changer assumes its second position. In the first operating position, bearing surface  16  of plate changer  14  is located at least partially upstream of an end face of the printing forme cylinder or plate cylinder  04  in question. In the second operating position, bearing surface  16  of plate changer  14  is preferably at least partially beneath the lateral surface of the printing forme cylinder or plate cylinder  04 . Bearing surface  16  of plate changer  14  moves, e.g. along a cross-member  17  arranged longitudinally with respect to the printing forme cylinder or plate cylinder  04 . Bearing surface  16  of plate changer  14  thus has an axial travel path with respect to the printing form cylinder or plate cylinder  04  in question. At the positions that define the first and second operating positions of plate changer  14 , the movement of bearing surface  16  is limited in each case, e.g. by a stop. At least the substrate of the printing plate in question is formed, e.g. by a trimming process, which is carried out in particular using register marks, such that the printing plate in question can be arranged true to register on bearing surface  16  of plate changer  14 . For this purpose, at least two edges of the substrate of the printing plate in question, disposed perpendicular to one another, are brought into direct contact with stops, in particular formed by register pins, located on bearing surface  16  of plate changer  14 , with a first edge of the substrate of the printing plate in question abutting against a first register pin and a second edge of the substrate of the printing plate in question, orthogonal to the first edge, abutting against a second register pin, and with the position of one of these two register pins being variable and preferably adjustable. By adjusting the variable-position register pin, e.g. the relevant printing plate can be aligned true to register. The variable-position register pin may be adjusted manually or automatically. Since the printing plate is supplied to the relevant plate cylinder  04  true to register, e.g. no centering pin or any other register device is provided is on plate cylinder  04 . 
     In its preferred embodiment, in addition to bearing surface  16  for receiving a printing plate to be supplied, in particular true to register, e.g. to plate cylinder  04 , plate changer  14  has, e.g. a compartment in which, e.g. a printing plate that has been removed from plate cylinder  04  may be placed. A printing plate held, e.g. by means of its substrate, in particular magnetically, on the lateral surface of the plate cylinder  04  in question is or at least can be lifted off of the lateral surface of the plate cylinder  04  in question, e.g. by means of a tool guided tangentially to the printing forme, e.g. by means of a spatula guided between the substrate of the printing plate and the lateral surface of the plate cylinder  04  in question. The end of a printing plate that has been lifted off of the lateral surface of the plate cylinder  04  in question is introduced by a rotation of the plate cylinder  04  in question into the appropriate compartment of plate cylinder  04 . The further rotation of said plate cylinder  04  then pushes the entire printing plate detached from the lateral surface of the relevant plate cylinder  04  into the appropriate compartment of plate changer  14 . 
     A printing plate to be supplied, preferably true to register, to the plate cylinder  04  in question is held, in particular after being aligned true to register, on bearing surface  16  of plate changer  14  by a magnetic holding force. At least one plunger, and preferably two plungers arranged spaced apart longitudinally along the plate cylinder  04  in question, is/are provided, each having a direction of action directed opposite the magnetic holding force and toward bearing surface  16  of plate changer  14 , e.g. substantially orthogonal thereto; with said at least one plunger, at least one end of the printing plate held on bearing surface  16  of plate changer  14 , said end facing the plate cylinder  04  in question, can be detached from said bearing surface  16  and can be transferred to the plate cylinder  04  in question by way of a stroke movement of the at least one plunger. The at least one plunger is or at least can be actuated pneumatically, for example. The printing forme or the printing plate is held on bearing surface  16  of plate changer  14  or on the lateral surface of plate cylinder  04  by means of magnets, with each of these magnets preferably being embodied as a permanent magnet. The above-described configuration of plate cylinder  04  has the advantage that no conveyor device is required for transferring the printing plate to the relevant plate cylinder  04  or for removing the printing plate from the relevant plate cylinder  04 , and therefore, plate changer  14  can be realized very inexpensively. In particular, a plate change can be carried out automatically using the plate changer  14  described above. 
     The throwing on and/or throwing off of printing forme cylinder or plate cylinder  04 , ink forme roller  07  and/or anilox roller  08  and/or the adjustment of the contact pressure exerted by each of these is carried out by means of a throw-on/throw-off mechanism, illustrated by way of example in  FIGS. 2 and 3 , which will now be described in detail. In the preferred embodiment, the printing forme cylinder or plate cylinder  04  is mounted, in particular at both ends, on a load arm of a first, preferably one-sided lever assembly  18 , consisting of a force arm and the load arm, wherein the force arm and the load arm, which is arranged at a fixed angle relative to the force arm, of this first lever assembly  18  can be pivoted jointly about a first rotational axis  19 , directed axially parallel to plate cylinder  04 . A first drive  21 , e.g. in the form of a hydraulic or pneumatic working cylinder and preferably controllable by a control unit, is operatively connected to the force arm of the first lever assembly  18  for the purpose of applying torque about the first rotational axis  19 , wherein upon actuation of this first drive  21 , the printing forme cylinder or plate cylinder  04  arranged on the load arm of this first lever assembly  18  is either thrown off of a printing blanket, e.g. of the segmented wheel  03  or thrown onto the same, depending upon the direction of action of said drive. To limit the contact pressure exerted by the printing forme cylinder or plate cylinder  04  against the printing blanket in question, e.g. of segmented wheel  03 , a first stop  22  which limits the path traveled by the pivoting movement of the printing forme cylinder or plate cylinder  04  toward segmented wheel  03  is provided, for example for the force arm of the first lever assembly  18 . The contact pressure exerted by the printing forme cylinder or plate cylinder  04  against segmented wheel  03  can be adjusted using the first drive  21 . 
     In the preferred embodiment, ink forme roller  07  is also mounted, in particular at both ends, on a load arm of a preferably one-sided second lever assembly  23 , consisting of a force arm and the load arm, wherein the force arm and the load arm of this second lever assembly  23  are pivotable jointly about the first rotational axis  19 , which is aligned axially parallel to plate cylinder  04 . Likewise in the preferred embodiment, anilox roller  08  is also mounted, in particular at both ends, on a load arm of a preferably one-sided third lever assembly  24 , consisting of a force arm and the load arm, wherein the force arm and the load arm of this third lever assembly  24  are pivotable jointly about a second rotational axis  26 , which is aligned axially parallel to anilox roller  08 , wherein the second rotational axis  26  of the third lever assembly  24  is located on the second lever assembly  23 , and wherein the second rotational axis  26  is embodied as fixed on the second lever assembly  23 . On the load arm of the first lever assembly  18 , a preferably controllable second drive  27  is arranged, which when actuated acts on the force arm of the second lever assembly  23 , and which can be used to throw ink forme roller  07  onto or off of plate cylinder  04 , depending upon the direction of action of second drive  27 . On the load arm of the second lever assembly  23 , a preferably controllable third drive  28  is arranged, which when actuated acts on the force arm of the third lever assembly  24 , and which can be used to throw anilox roller  08 , preferably together with chamber doctor blade system  09 , onto or off of ink forme roller  07 , depending upon the direction of action of third drive  28 . The second drive  27  and/or the third drive  28  is/are each also embodied, e.g. in the form of a hydraulic or pneumatic working cylinder. It may be provided that second drive  27  and third drive  28  are or at least can be actuated, e.g. jointly and preferably also simultaneously. The pivoting movement of the load arm of the second lever assembly  23  is limited, e.g. by a first stop system  29  which is preferably adjustable, in particular by means of an eccentric, whereby the contact pressure exerted by ink forme roller  07  against the printing forme cylinder or plate cylinder  04  is or at least can be limited. The pivoting movement of the load arm of the third lever assembly  24  is limited, e.g. by a second stop system  31  which is preferably adjustable, in particular by means of an eccentric, whereby the contact pressure exerted by anilox roller  08  against ink forme roller  07  also is or at least can be limited.  FIG. 2  shows a first operating state, by way of example, in which the first drive  21  and the second drive  27  and the third drive  28  are not activated, or each is in its idle state, in which anilox roller  08  is thrown onto ink forme roller  07 , and ink forme roller  07  is thrown onto the printing forme cylinder or plate cylinder  04 , and the printing forme cylinder or plate cylinder  04  is thrown onto segmented wheel  03 .  FIG. 3  shows a second operating state, by way of example, in which the first drive  21  and the second drive  27  and the third drive  28  are activated, or each is in its working state, in which anilox roller  08  is thrown off of ink forme roller  07 , and ink forme roller  07  is thrown off of the printing forme cylinder or plate cylinder  04 , and the printing forme cylinder or plate cylinder  04  is thrown off of segmented wheel  03 . The force arm and/or load arm of each of the three aforementioned lever assemblies  18 ;  23 ;  24  is or are each embodied, e.g. as a pair of opposing lever rods or side frame walls, between which either the printing forme cylinder or plate cylinder  04  or the ink forme roller  07  or the anilox roller  08  is arranged, each in its respective assignment as described above. Each of the three aforementioned lever assemblies  18 ;  23 ;  24  is arranged in a different vertical plane, spaced apart from the others, so that none of the lever assemblies can impede the pivoting of the others. 
     As described above and as shown in  FIG. 13 , typically a plurality of printing blankets  33 , e.g. eight to twelve, are arranged one behind the other on the periphery of segmented wheel  03 , and during the printing process, as this segmented wheel  03  rotates about a rotational axis  34 , printing formes of the printing forme cylinder or printing plates of plate cylinder  04  roll along the printing blankets  33  that are moved by said segmented wheel  03 . During rolling, each of the printing plates presses at least its print relief, e.g. 0.2 mm to 0.25 mm deep into the respective printing blanket  33 , thereby subjecting the printing blankets to wear and tear, as a result of which, depending upon their condition and, in particular, their mechanical stress, the printing blankets may need to be replaced after a certain number of prints, e.g. after 50,000 hollow bodies  01  have been printed. When a device for printing on or decorating hollow bodies  01 , i.e. known as a decorator, having this type of segmented wheel  03  is used in a large-scale production operation to produce, e.g. several hundred or even a few thousand such hollow bodies  01  per minute, e.g. between 1,500 and 3,000 pieces per minute, the printing blankets  33  arranged on the periphery of the segmented wheel  03  need to be replaced quite frequently, in some cases every half hour or about every forty-five minutes. To keep the productivity of such a device for printing on or decorating hollow bodies  01  high, a solution for performing the necessary replacement of the printing blankets  33  arranged on the periphery of segmented wheel  03  with the shortest possible setup time is sought. 
     It is therefore proposed to provide a device, assigned to segmented wheel  03 , for automatically changing the printing blankets  33 . In the preferred embodiment, each of these printing blankets  33  to be arranged on segmented wheel  03  is applied adhesively, in particular by gluing, to a preferably flat, tabular metal substrate having a material thickness of, e.g. 0.2 mm. Each preferably magnetizable metal substrate is then arranged, together with the printing blanket  33  disposed thereon, in particular in the proper position, on one of the segments  32  on the periphery of segmented wheel  03 , e.g. by means of at least one of the holding magnets  81  provided there on the periphery for each blanket  33  or the substrate thereof. To support the arrangement of each metal substrate in the proper position on the appropriate segment  32  on the periphery of segmented wheel  03 , an acutely angled mounting arm  38  is provided, e.g. at the leading edge  37  of the respective metal substrate in the direction of rotation of segmented wheel  03 , and when the respective metal substrate is arranged on one of the segments  32  on the periphery of segmented wheel  03 , this mounting arm  38  engages into a recess  36  formed on the periphery of this segmented wheel  03 , aligned parallel to the rotational axis  34  thereof and embodied, e.g. as a groove, and comes to rest, in particular in a form-fitting connection, on a leading edge  39  of the recess  36  in question in the direction of rotation of segmented wheel  03 . Each of the printing blankets  33  is preferably embodied as a rubber blanket. The direction of rotation of segmented wheel  03  during the printing process is indicated in  FIG. 13  by a rotational arrow. During the printing process, hollow bodies  01 , each of which is moved on a clamping mandrel by the mandrel wheel  02 , which rotates about rotational axis  41 , up to segmented wheel  03 , are pressed by a predominantly radial movement of the clamping mandrel concerned individually and briefly in succession, i.e. typically for a single revolution of hollow body  01  to be printed, against the printing blanket  33  currently printing. 
     The device for automatically changing the printing blankets  33  is preferably modular in construction and includes as modules—as shown by way of example in  FIGS. 7 to 12 —e.g. a magazine  42  for a plurality of printing blankets  33 , e.g. up to twelve ( FIG. 7 ), along with a device  43  for vertical transport of the aforesaid magazine  42  ( FIG. 8 ) and a device  44  for transporting one of printing blankets  33  horizontally between magazine  42  and a mounting position on segmented wheel  03  ( FIG. 9 ).  FIG. 10  shows the magazine  42  in its operating state located on the device  43  provided for its vertical transport. Magazine  42  includes, in a preferably cuboid housing, a plurality of compartments stacked vertically, in each of which a single printing blanket  33  is or at least can be stored on its back, i.e. lying on its substrate, preferably in a horizontal alignment, wherein in the housing, e.g. at least as many compartments are provided as the number of segments  32  for printing blankets  33  located on the periphery of the assigned segmented wheel  03 . Each of the compartments is open, e.g. on at least one of its longitudinal sides, to enable a respective printing blanket  33  to be inserted into or removed from the open side of the respective compartment. This magazine  42  preferably is or at least can be mounted, as a module that can be easily replaced, e.g. without the use of tools, on or at a support of the device  43  for vertical transport of said magazine  42 . The device  43  for the vertical transport of magazine  42  is configured to carry out, e.g. a lifting movement, with the vertical travel path measuring, e.g. about 200 mm. The lifting movement of the device  43  for vertical transport of magazine  42  is carried out, e.g. by means of a trapezoidal threaded spindle, preferably driven by an electric motor. To transport the individual printing blankets  33  between magazine  42  and a mounting position on a segment  32  of segmented wheel  03 , a device  44  for transporting these printing blankets  33  horizontally is provided. This device  44  for transporting printing blankets  33  horizontally has, e.g. a carriage  46  that is movable bidirectionally, in particular linearly, between two end points, with carriage  46  transporting or at least being capable of transporting a single printing blanket  33  at a time. A printing blanket  33  removed automatically from magazine  42  is transported on carriage  46 , preferably lying on its back, to a mounting position, e.g. located beneath segmented wheel  03 , where it is received by a segment  32  of segmented wheel  03 . A printing blanket  33  to be removed from a segment  32  of segmented wheel  03  is preferably peeled off of the segment  32  in question by means of a spatula  47  which is or at least can be set against the segment  32  in question, and is transported, e.g. lying on carriage  46 , from its removal position on the periphery of segmented wheel  03  to magazine  42 , wherein in the preferred embodiment, the spatula  47 , which is set at an acute angle or tangentially against the segment  32  in question of segmented wheel  03 , combined with a rotational movement of segmented wheel  03  directed toward the spatula  47 , lifts the metal substrate of the printing blanket  33  in question, held in particular magnetically on the periphery of segmented wheel  03 , off of the segment  32  in question, and thus off of the periphery of said segmented wheel  03 . In  FIG. 11 , spatula  47  is shown in both an operating position in which it is set against the relevant segment  32  of segmented wheel  03 , and in a parked operating position, these operating positions being occupied alternately. 
     The replacement or changing of at least one of the printing blankets  33  arranged on the periphery of segmented wheel  03  is then preferably carried out as follows: 
     Segmented wheel  03  conveys, by means of its rotation, a printing blanket  33  which is arranged on the periphery of said wheel and is to be removed, into a position at which a removal of said printing blanket  33  can be carried out by means of the device for automatically changing the printing blankets  33 . Carriage  46  of the device  44  for transporting printing blankets  33  horizontally travels along its travel path up to the end point which is closest to the removal point of the printing blanket  33  to be removed. This position of carriage  46  is preferably monitored by sensory elements and/or by a first switching element  48 , e.g. by means of an inductive or capacitive proximity switch. Spatula  47  is then preferably set against the trailing edge  37 , in the direction of rotation of segmented wheel  03 , of the metal substrate of the relevant printing blanket  33  to be removed. By rotating segmented wheel  03  at least briefly in the direction opposite its direction of rotation used during the printing process, the printing blanket  33  to be removed, which is preferably held magnetically on the periphery of segmented wheel  03 , is peeled off of the periphery of said segmented wheel  03 , i.e. the metal substrate of printing blanket  33  is lifted away from its position resting on segmented wheel  03 . Spatula  47  is then moved away from the periphery of segmented wheel  03 . The printing blanket  33  that has been detached from the relevant segment  32  of segmented wheel  03  then either drops by virtue of gravity directly into a magazine for worn printing blankets  33  or is transported to said magazine for worn printing blankets by means of carriage  46  of the device  44  for transporting printing blankets  33  horizontally. 
     A new printing blanket  33  glued to a metal substrate is loaded in at least one compartment, preferably in each of the compartments of the magazine  42  provided for a plurality of new printing blankets  33 , and said magazine  42  is preferably located in a raised upper position by means of the device  43  for vertical transport thereof. The carriage  46  of the device  44  for horizontally transporting one printing blanket  33  at a time between magazine  42  and the mounting position on segmented wheel  03  is situated beneath the compartment that contains the new printing blanket  33 . The device  43  for vertical transport lowers this magazine  42 , thereby placing the new printing blanket  33  onto carriage  46  of the device  44  for horizontal transport. The process is monitored, preferably by sensory means and/or by a second switching element  49 , e.g. by means of an inductive or capacitive proximity switch, to determine whether the new printing blanket  33  has actually been placed on carriage  46  of the device  44  for horizontal transport. If not, an error message is issued. Otherwise, i.e. if no error is detected, carriage  46  of the device  44  for transporting printing blankets  33  horizontally moves along its travel path up to the end point closest to the mounting position for the new printing blanket  33 , with this position of carriage  46  in turn being monitored, preferably by sensory means and/or by a third switching element  51 , e.g. by means of an inductive or capacitive proximity switch. Segmented wheel  03  is also already located in a rotational angle position suitable for receiving the new printing blanket  33 , with this rotational angle position being located, e.g. at or near the bottom of segmented wheel  03 . In the preferred embodiment, the position of the new printing blanket  33  is aligned at least true to register by said printing blanket abutting against at least stop  52 , before being mounted on the periphery of segmented wheel  03 . For moving carriage  46  of the device  44  for transporting printing blankets  33  horizontally, a drive is provided, said drive being embodied, e.g. as a compressed air cylinder. To mount the new printing blanket  33  on the periphery of segmented wheel  03 , said segmented wheel  03  rotates in the direction of rotation used during the printing process, thereby drawing the new printing blanket  33  up onto its periphery. Carriage  46  of the device  44  for transporting printing blankets  33  horizontally is then moved back to the magazine  42  for the plurality of new printing blankets  33 , to retrieve another new printing blanket  33 , if necessary. 
     To reduce setup times, it is advantageous to configure a device for printing on hollow bodies  01  such that said device includes a segmented wheel  03  which is rotatable about a rotational axis  34 , wherein segmented wheel  03  has a plurality of segments  32  in a row along its periphery, each for receiving one printing blanket  33 , wherein at least one of the printing blankets  33  located on one of the segments  32  is arranged to roll or at least to be capable of rolling along the hollow body  01  to be printed on, wherein a plurality of printing units are provided, wherein at least one of the printing units is or at least can be thrown onto at least one of the printing blankets  33  arranged on the periphery of segmented wheel  03 , wherein at least one of the printing units includes a printing forme cylinder  04 , wherein in association with the relevant printing forme cylinder  04 , a plate changer  14  for automatically changing a printing forme is located on said printing forme cylinder  04 , and wherein in association with segmented wheel  03 , a device for automatically changing at least one of the printing blankets  33  arranged on the periphery of said segmented wheel  03  is provided. Said plate changer  14  preferably has a bearing surface  16 , onto which the printing forme that is or will be arranged on printing forme cylinder  04  can be placed, said bearing surface  16  being movable bidirectionally along a transport path between at least two defined positions. The printing forme to be supplied to the printing forme cylinder  04  in question is held, e.g. by a magnetic holding force on the bearing surface  16  of plate changer  14 . The device for automatically changing the printing blankets  33  is modular, in particular, and includes as modules a magazine  42  for a plurality of printing blankets  33 , along with a device  43  for vertically transporting said magazine  42 , and a device  44  for horizontally transporting one of the printing blankets  33  at a time between magazine  42  and one of the segments  32  of segmented wheel  03 . Magazine  42  has a plurality of vertically stacked compartments, in each of which a single printing blanket  33  is or at least can be stored, within a housing. Each of the printing blankets  33  is preferably stored lying on its back and/or in a horizontal alignment in magazine  42 . Device  43  for vertically transporting magazine  42  is configured to execute, e.g. a lifting movement, and/or device  44  for transporting printing blankets  33  horizontally has a carriage  46  which is movable bidirectionally between two endpoints, wherein a single printing blanket  33  is or at least can be transported at a time by carriage  46 . Plate changer  14  and the device for automatically changing the printing blankets  33  are each controlled, e.g. by a control unit, wherein plate changer  14  and the device for automatically changing printing blankets  33  are active in particular at the same time, and each carries out its changing of a printing plate or a printing blanket  33 , e.g. during the same interruption in the production process being run on this device for printing on hollow bodies  01 . The printing forme to be arranged on printing forme cylinder  04  is preferably arranged on bearing surface  16  of plate changer  14  true to register with respect to its mounting position on printing forme cylinder  04 , and/or the printing blanket  33  to be arranged on the periphery of segmented wheel  03  is arranged on the carriage  46  of the device  44  for transporting printing blankets  33  horizontally in the correct position with respect to its mounting position on a segment  32  of segmented wheel  03 . An inking unit  06  for transporting printing ink to printing forme cylinder  04  is preferably embodied as a short inking unit that includes an anilox roller  08 . 
     With respect to a device for printing on hollow bodies  01 , which includes a segmented wheel  03  that is rotatable about a rotational axis  34 , wherein the segmented wheel  03  has a plurality of segments  32  in a row along its periphery, each for receiving a printing blanket  33 , wherein at least one of the printing blankets  33  arranged on one of the segments  32  is arranged rolling or at least capable of rolling along the hollow body  01  to be printed, wherein every two adjacent segments  32  are separated from one another by a recess  36  aligned parallel to the rotational axis  34  of segmented wheel  03 , it is also advantageous for each of the printing blankets  33  to be disposed on a plate-shaped metallic substrate, wherein the substrate along with the printing blanket  33  disposed thereon is or at least can be arranged as such, and replaceable in its entirety, on one of the segments  32  of segmented wheel  03 , wherein the substrate arranged on one of the segments  32  of segmented wheel  03  is held on this segment  32  in a form-fitting and/or in a force-fitting connection. Each substrate of a printing blanket  33  is bent, preferably at an acute angle, at its leading edge  37  in the direction of rotation of segmented wheel  03 , wherein when said substrate is located in the operating position on a segment  32  of segmented wheel  03 , this bent edge  38  is placed at a leading edge  39 , in the direction of rotation of segmented wheel  03 , of the appropriate recess  36  formed on the periphery of segmented wheel  03 , wherein the bent edge  38  of the substrate is or at least can be arranged in a form-fitting connection on this edge  39  of recess  36 . The plate-shaped metallic substrate is embodied in particular as flexible, and together with the printing blanket  33  arranged on it forms, e.g. a metal printing blanket. The substrate arranged on one of the segments  32  of segmented wheel  03  is held on this segment  32  by a magnetic force. Eight to twelve segments  32 , for example, each for receiving one printing blanket  33 , are arranged in a row with preferably equidistant spacing along the periphery of segmented wheel  03 . Assigned to segmented wheel  03 , e.g. a device for automatically changing printing blankets  33  is provided, wherein the device for automatically changing printing blankets  33  is preferably modular in construction, and includes as modules a magazine  42  for a plurality of printing blankets  33  along with a device  43  for vertical transport of the aforementioned magazine  42  and a device  44  for horizontal transport of one of the printing blankets  33  at a time between magazine  42  and one of the segments  32  of segmented wheel  03 . Magazine  42  has in particular a plurality of compartments stacked vertically within a housing, in each of which a single printing blanket  33  is or at least can be stored. The housing of magazine  42  contains e.g. at least as many compartments as the number of segments  32  for printing blankets  33  on the periphery of the associated segmented wheel  03 . In the preferred embodiment, the device  43  for vertically transporting magazine  42  is configured to execute a lifting movement, and/or device  44  for transporting printing blankets  33  horizontally has a carriage  46  which is movable bidirectionally between two endpoints, wherein a single printing blanket  33  is or at least can be transported at a time by carriage  46 . 
     This also results in a method for operating a device for printing on hollow bodies  01  which has a segmented wheel  03 , wherein a printing blanket  33  is arranged on at least one segment  32  of the segmented wheel  03 , which has a plurality of segments  32  one behind the other on its periphery, wherein when the segmented wheel  03  rotates, at least one printing blanket  33  arranged on one of the segments  32  rolls along the hollow body  01  to be printed on, wherein a device for automatically changing printing blankets  33 , assigned to segmented wheel  03 , in response to a command issued to its control unit, automatically removes the printing blanket  33  to be arranged on the relevant segment  32  of the segmented wheel  03  from a magazine  42 , and transports it to the segment  32  in question of segmented wheel  03 . The device for automatically changing printing blankets  33  has a device  44  for horizontally transporting printing blankets  33 , with a movable carriage  46 , wherein each of the printing blankets  33  to be transported is transported lying on carriage  46 . A printing blanket  33  lying on carriage  46  is preferably arranged in the proper position with respect to a mounting position on one of the segments  32  of segmented wheel  03 . A plurality of printing blankets  33  in particular are stored in magazine  42 , and these printing blankets  33  are placed individually, one after the other, on carriage  46  of the device  44  for transporting printing blankets  33  horizontally, and are transported in succession to one of the segments  32  of segmented wheel  03 . A printing blanket  33  to be arranged on one of the segments  32  of segmented wheel  03  is arranged on the segment  32  in question, in particular by means of a form-fitting connection produced between the relevant segment  32  and the printing blanket  33  by a rotation of this segmented wheel  03 . A printing blanket  33  arranged on one of the segments  32  of segmented wheel  03  is preferably held on the segment  32  in question, e.g. by a magnetic force connection. A printing blanket  33  that has been removed from one of the segments  32  of segmented wheel  03  is likewise preferably transported away from the segmented wheel  03  in question by the device  44  for transporting printing blankets  33  horizontally. It is preferably provided that the device  44  for transporting printing blankets  33  horizontally alternatingly transports a printing blanket  33  that has been removed from one of the segments  32  of segmented wheel  03  away, and transports a new, i.e. unused printing blanket  33  from magazine  42  to an unoccupied segment  32  of segmented wheel  03 , i.e. to a segment  32  on which no printing blanket  33  is currently arranged. A switching element  49  monitors the process, e.g. to determine whether a printing blanket  33  removed or to be removed from magazine  42  has actually been placed on carriage  46  of the device  44  for horizontal transport, and/or whether it has been placed in the proper position. 
       FIG. 14  again shows a perspective view of segmented wheel  03  of the device for printing on hollow bodies  01 , in which a plurality of segments  32 , e.g. twelve segments, each for accommodating one printing blanket  33 , are arranged in a row along the periphery of said segmented wheel  03 . This segmented wheel  03  is preferably made of a casting material, e.g., cast iron, and weighs more than 500 kg, in particular approximately 1,000 kg or more. Segmented wheel  03  has an outer diameter ranging from 1,400 mm to 1,600 mm, for example. Segmented wheel  03  is mounted on its shaft  53  in a frame  66  of this device for printing on hollow bodies  01 , preferably at both ends of said shaft, e.g. each end being mounted in particular in double-row roller bearings  63 , and the rotation of the segmented wheel is driven by a drive. Said drive for driving the rotation of segmented wheel  03  is configured as an electric motor  58  having a stator  61  and a rotor  62  with a hollow shaft  54 , wherein the hollow shaft  54  is or at least can be arranged coaxially with shaft  53  of segmented wheel  03 . In the condition in which it is disposed in the device for printing on hollow bodies  01 —as shown in the sectional view of  FIG. 16 —shaft  53  of segmented wheel  03  projects into the installation space of motor  58 , and shaft  53  of segmented wheel  03  and rotor  62  of motor  58  are connected rigidly to one another. Segmented wheel  03  is preferably connected rigidly to its shaft  53  at both ends, e.g. by means of clamping elements  67 , and is thereby secured to shaft  53 . The motor  58  provided for driving the rotation of segmented wheel  03  is preferably configured as a high-pole electrical direct drive having a number of poles e.g. greater than twenty and/or is configured as a permanently energized brushless DC motor and is illustrated perspectively by way of example in  FIG. 15 . Said motor  58  has, e.g., a cooling device or is at least connected to such a device, said cooling device being configured as a liquid cooling system.  FIG. 15  shows two ports for this liquid cooling system, formed on housing  59  of motor  58 , specifically one port for coolant inflow  56  and another port for coolant outflow  57 . In an advantageous embodiment, this motor  58  is configured as a torque motor. A preferably digital control unit for controlling or regulating said motor  58  is provided, wherein the control unit adjusts or at least is capable of adjusting a position on the periphery of this segmented wheel  03  relative to a position on the lateral surface of a hollow body  01  to be printed, preferably with a positioning accuracy of less than 0.1 mm, by positioning shaft  53  of segmented wheel  03  in the stator of motor  58 . Likewise provided, e.g. on the end of shaft  53  opposite motor  58 , is a rotary encoder  64 , wherein said rotary encoder  64  has a high angular resolution, e.g. of 27 bits, and detects an angular position of shaft  53  of segmented wheel  03  and provides a measured value that corresponds to the angular position of shaft  53  of segmented wheel  03  to the control unit that controls or regulates motor  58 . Motor  58  and/or the rotary encoder are preferably each connected via a control bus to the control unit that controls or regulates motor  58 . 
     The aforementioned embodiment of the rotary drive of segmented wheel  03  has the advantage that said drive is configured as decentralized as well as gearless and clutchless. This drive of segmented wheel  03  is therefore backlash-free and compact. In conjunction with the control unit of said drive, a position on the periphery of said segmented wheel  03  relative to a position on the lateral surface of a hollow body  01  to be printed can be adjusted easily with a positioning accuracy of less than 0.1 mm, which has a very beneficial effect on the achievable print quality. In conjunction with the double-row bearing of segmented wheel  03 , a highly precise concentricity of said segmented wheel  03  likewise results, thereby ensuring a uniform transfer of ink from the respective inking units  06  to the relevant printing blankets  33  arranged on the periphery of segmented wheel  03 . With the solution described here, a high acceleration and thus short run-up times of 10 seconds or less can also be realized for segmented wheel  03 . Furthermore, the proposed drive for segmented wheel  03  has the advantage of being low-noise and low-maintenance. Overall, this results in a highly efficient drive for segmented wheel  03 . 
       FIG. 19  again shows the segmented wheel  03  already described in conjunction with  FIGS. 14 and 16 , but here in a particularly advantageous embodiment. Segmented wheel  03 , which during the printing process is mounted in frame  66  of the device for printing on hollow bodies, has a main body  76  preferably produced from a metallic material, e.g., from a welded structure or from cast iron, with a plurality of segments  32 , e.g. twelve, being arranged or at least arrangeable, in particular spaced from one another, along the periphery of main body  76 , each at a joint  77 . Segmented wheel  03  therefore is not configured as a single integral part on which segments  32  are already molded, rather each of these segments  32  represents a separate machine element that can be separated from main body  76  and is arranged changeably on main body  76 . Each of these segments  32  is suitable—as previously in the same manner—for receiving a printing blanket  33  in the manner described above. 
     One advantage of changeable segments  32  on segmented wheel  03  is that, e.g. when converting the machine assembly to produce hollow bodies  01  of a different format from the current production run, e.g., to cans having a shorter or longer can height and/or a different can diameter, an adjustment in the format of the printing blankets  33  required for printing can be carried out faster and more easily. In a machine assembly having a segmented wheel  03  onto which segments  32  are already molded, in order to convert the production process to hollow bodies  01  of a different format, the entire segmented wheel  03  must be replaced; considering the typical size of segmented wheel  03  with an outer diameter in the range of 1,400 mm to 1,600 mm, for example, and/or the typical weight of more than 500 kg, in particular more than 1,000 kg, for example, this requires considerable effort and unreasonably long setup times. 
     To produce a printed image of high print quality on hollow bodies  01  in the printing process, a segmented wheel  03  must meet very strict requirements in terms of concentricity, meaning that such a segmented wheel  03  must be machined very accurately, i.e., with low permissible manufacturing tolerances. With a segmented wheel  03  onto which segments  32  are already molded, this is expensive and requires great effort due to the relatively large outer diameter of 1,400 mm to 1,600 mm, for example. What can be accomplished during an initial production process by means of relatively rare and costly large-scale machining equipment is possible in the event of damage to the segments  32  or other parts of segmented wheel  03  only by means of highly costly repair measures that are extremely difficult to perform in the machine assembly, such as leveling, cutting, welding and grinding the damaged area, or by replacing the entire segmented wheel  03 . For the operator of such a machine assembly, in addition to high repair costs this means long production downtimes, since the entire machine assembly is shut down for the duration of the repairs. Finally, with integral segmented wheels  03 , no variation in the materials used, e.g. to decrease the inertia of the segmented wheel  03  in question, is possible. 
     A segmented wheel  03  having a plurality of segments  32  arranged along the periphery of its main body  76 , in particular spaced from one another, each at a joint  77  as seen in  FIG. 19 , and thus changeable, simplifies manufacturing of the segmented wheel  03  in question, and its modular construction facilitates its adaptation to different formats dependent on the respective production process, and if necessary, facilitates the repair of damaged areas on said segmented wheel  03 , in particular on the segments  32  thereof, to be performed in the machine assembly. 
     In the embodiment of segmented wheel  03  shown in  FIG. 19 , the individual, changeable segments  32  are preferably configured as finished ( FIG. 20 ). This means that the finished segments  32  need to correspond with high precision to the desired outer diameter of the relevant segmented wheel  03  only in terms of their respective surface curvature. The remaining geometries play a subordinate role in terms of tolerances. In the main body  76  of segmented wheel  03 , the manufacturing tolerances of the outer geometry are likewise subordinate in importance. The individual segment  32  shown by way of example in  FIG. 20  has, e.g., at least one holding magnet  81  for holding a printing blanket  33  having a magnetizable metal substrate on the periphery of the segmented wheel  03 , in particular in the proper position, after said segment  32  has been mounted on the main body  76  of said segmented wheel  03 . 
     The required high accuracy in terms of the concentricity and radius of the respective running surfaces of the relevant printing blankets  33  is achieved by a process of aligning the segments  32 , performed, e.g. with the aid of a rider gauge  79  that is movable in particular along the periphery of the segmented wheel  03  ( FIG. 14 ), while main body  76  of segmented wheel  03  is disposed in the machine assembly, and is fixed, e.g. by casting a compensation gap  82 , as seen in  FIG. 19 a   . At each relevant joint  77  between a respective segment  32  and the main body  76 , a compensation gap is formed, with a joint face coating  83  arranged in the relevant compensation gap  82 , said joint face coating  83  preferably being formed as, e.g., a low-viscosity casting material or as a filler compound. Each respective segment  32  is thus cast in particular to fit precisely at its joint  77  with main body  76  of segmented wheel  03 . At the joint  77  in question, the compensation gap  82  has a gap width d 82  of, e.g., at least 1 mm up to, e.g., 5 mm. In addition, each of the segments  32  is fixed to main body  76  and/or is detachably connected to main base body  76 , e.g. by means of at least one connecting element  78 . The at least one connecting element  78  that connects each respective segment  32  to the main body  76  of segmented wheel  03  is configured in each case, e.g., as a cylindrical screw or as a tapered pin. 
     A joint face coating  83  is used to adapt and fit machine parts with the most stringent requirements in terms of precision. It allows adaptations within the μm range without costly mechanical preliminary treatment or post-treatment. It has a high static compression resistance of, e.g., 100 N/mm 2  and/or a contact area ratio of, e.g., 100%. A joint face coating  83  has very high adhesive force and cures without technically relevant shrinkage. A joint face coating of this type is available, e.g., from SKC Gleittechnik GmbH in D-96469 Roedental. 
     Advantageously, with the above-described device for printing on hollow bodies  01 , a so-called “flying production change” can be carried out, i.e. a change is made from a first printing process to a second printing process without an interruption of production. As long as a printing blanket change is not required, production is switched over while segmented wheel  03  continues, i.e., rotates without interruption, and proceeds with printing on hollow bodies  01 . In a machine assembly in which several thousand of these hollow bodies  01  are produced per minute, e.g., between 1,500 and 3,000 pieces per minute, an uninterrupted change in production means an enormous increase in efficiency. And even if a change of at least one of the printing blankets is required with the production change, the makeready times for the decorator can be shortened considerably by the following method. 
     Thus, a method for operating a device for printing on hollow bodies  01  is proposed, said device having a segmented wheel  03  that rotates about its axis  34  and has a plurality of printing blankets  33  arranged in a row along its periphery, and having a plurality of plate cylinders  04 , preferably in a star-shaped assignment to said segmented wheel  03 , i.e., on the periphery thereof, and each bearing a printing forme or a printing plate  68 , wherein a specific printing ink is supplied to each of these plate cylinders  04  for inking up its printing forme or its printing plate  68 , in each case by means of an inking unit  06  preferably configured as a short inking unit and having a roller train, in particular comprising two rollers. Depending on the printing process to be executed for printing on the hollow bodies  01 , a selected set of plate cylinders  04  are thrown, e.g. radially, onto segmented wheel  03  or are thrown off of said segmented wheel  03 . In a first printing process, each of a first subset of plate cylinders  04 , each bearing an inked-up printing forme or an inked-up printing plate  68  and thrown onto the rotating segmented wheel  03 , transfers printing ink onto a plurality of the printing blankets  33  arranged on said segmented wheel  03 . Upon completion of the first printing process, at least some of the plate cylinders  04  thrown onto segmented wheel  03  in the first printing process are thrown off of said rotating segmented wheel  03 . To execute a second printing process that is different from the first printing process, while segmented wheel  03  continues to rotate without interruption, a second subset of plate cylinders  04 , each bearing an inked-up printing forme or an inked-up printing plate  68 , is then thrown, in particular radially, onto said segmented wheel  03 , so that each of these plate cylinders  04  transfers printing ink onto a plurality of the printing blankets  33  arranged on said segmented wheel  03 . The printing blankets  33  in turn transfer the respective printing ink onto hollow bodies  01  to be printed, which are advanced to the rotating segmented wheel  03 , e.g. by means of a mandrel wheel  02 . 
     In a preferred embodiment, when the first printing process is completed, those inking units  06  that supplied printing ink to the first subset of plate cylinders  04  in the first printing process are each thrown off of this first subset of plate cylinders  04 . In addition, at the start of the second printing process, those inking units  06  that will supply printing ink to the second subset of plate cylinders  04  in the second printing process are each thrown onto this second subset of plate cylinders  04 . 
     The rotation of segmented wheel  03  is preferably driven separately, as described above, i.e., at least independently of the plate cylinders  04  and/or the inking units  06 , by a motor  58  configured, e.g., as a direct drive. Each of the plate cylinders  04  that is or at least can be thrown onto segmented wheel  03  is also rotationally driven separately, i.e. at least independently of segmented wheel  03 , by a motor  11 . Each of the inking units  06  has exactly one ink forme roller  07  that is or can be thrown onto the relevant plate cylinder  04 , or is or can be thrown off of said plate cylinder  04 , and, e.g., one anilox roller  08  that conveys printing ink to the ink forme roller  07  in question, wherein the respective ink forme roller  07  and optionally the relevant anilox roller  08  are each rotationally driven independently, i.e., separately, by a motor  12 . Alternatively, each respective ink forme roller  07  may be rotationally driven by friction, e.g. by the respective anilox roller  08  located in the same inking unit  06 . The aforementioned separate drives  11 ;  12 ;  58 , i.e., the motor  58  that separately drives the rotation of segmented wheel  03  and/or the respective motor  11  that separately drives the rotation of the respective plate cylinder  04  and/or the motor  12  that separately drives the rotation of the respective ink forme roller  07  and/or the anilox roller  08  is or are preferably each controlled or regulated, independently and preferably individually, by a control unit. The respective throwing on and/or throwing off of the relevant plate cylinders  04  and/or the relevant inking units  06  is preferably also controlled by the control unit, each independently of the others and each dependent upon the printing process to be carried out. 
     To shorten makeready times, the respective printing forme or the respective printing plate  68  on at least one plate cylinder  04  that is not involved in the printing process currently running, i.e. that is not currently thrown onto the rotating segmented wheel  03 , is preferably changed automatically during said running printing process, in each case using a plate changer  14 , e.g. as described above. To change at least one of the printing blankets  33  arranged on segmented wheel  03 , segmented wheel  03  is brought to a standstill, and at least one printing blanket  33  arranged on this segmented wheel  03  is preferably changed automatically using a device for automatically changing the printing blankets  33 . 
     Furthermore, the above-described device for printing on hollow bodies  01  can be used to carry out a method for printing on hollow bodies  01 , in which printing ink is transferred onto each of the hollow bodies  01 , in each case by one of the printing blankets  33  arranged in a row along the periphery of a segmented wheel  03  rotating about its axis  34 , in which at least two plate cylinders  04 , arranged in succession in the direction of rotation of segmented wheel  03  and each bearing a printing plate  68 , are used, in which a first printing ink applied by a first inking unit  06 , which is engaged against a first plate cylinder  04 , onto the printing plate  68  of said cylinder is transferred onto a first printing blanket  33  of the printing blankets  33  arranged on the periphery of segmented wheel  03 , and from there is back-split, i.e. transferred by back-splitting, onto the printing plate  68  of a second plate cylinder  04  situated downstream of the first plate cylinder  04  in the direction of rotation of segmented wheel  03 . With a second inking unit  06  engaged on the second plate cylinder  04 , a second printing ink different from the first printing ink is applied to the printing plate  68  of said second plate cylinder. The first printing ink applied by back-splitting and the second printing ink applied by the second inking unit  06 , each to the printing plate  68  of the second plate cylinder  04 , are then transferred together onto a second printing blanket  33  of the printing blankets  33  arranged on the periphery of segmented wheel  03 . The different printing inks applied to the printing plate  68  of the second plate cylinder  04  are applied to said printing plate  68  in various adjoining regions, with the printing inks applied to the printing plate  68  of the second plate cylinder  04  blending in their respective border region  71 . The printing inks  69  applied to printing plate  68  of the second plate cylinder  04  are then transferred onto the second printing blanket  33 , reproducing the blending of said inks that occurs in their respective border region  71 . 
     For inking up the printing plates  68 , e.g. a short inking unit, i.e. an inking unit  06  having a roller train consisting of a maximum of five rollers, or in the preferred embodiment an inking unit  06  having a roller train consisting of two rollers  07 ;  08 , said inking unit being thrown onto the respective plate cylinder  04 , is used in each case, wherein only a single ink forme roller  07  is assigned to the respective plate cylinder  04  in each case. In each of the respective inking units  06 , an ink forme roller  07  the circumferential length of which corresponds to the circumferential length of the respective plate cylinder  04  is used, in particular. Accordingly, in the preferred embodiment, the outer diameter d 04  of the plate cylinder  04  bearing the printing plate  68  in question and the outer diameter d 07  of the ink forme roller  07  thrown onto said plate cylinder  04  are equal. 
     For inking up the first plate cylinder  04 , e.g. a fully sheathed ink forme roller  07  is used. For inking up the second plate cylinder  04 , e.g. a fully sheathed ink forme roller  07  or preferably a coated ink forme roller  07  with depressions introduced on its lateral surface is used, these depressions being formed based, in particular, upon the printing image to be printed and/or, e.g. in the axial direction and/or in the circumferential direction. For printing on the hollow bodies  01 , e.g. printing blankets  33  in which depressions are introduced may be used. The depressions in the lateral surface of the ink forme roller  07  used for inking up the second plate cylinder  04  and/or in the printing blankets  33  used for printing the hollow bodies  01  are introduced in each case, e.g. by mechanical engraving or by milling or by lasers. 
     In the preferred embodiment, the first inking unit  06  inks up at least one planar first printing image area formed on printing plate  68  of the first plate cylinder  04 , and the second inking unit  06  inks up at least one planar second printing image area formed on printing plate  68  of the second plate cylinder  04 . Due to its position and size, the second printing image area formed on printing plate  68  of the second plate cylinder  04  encompasses the region in which printing ink is transferred or back-split from the respective surface of the at least one first printing image area formed on printing plate  68  of the first plate cylinder  04 . And the ink forme roller  07  of the second inking unit  06 , which is used for inking up printing plate  68  of the second plate cylinder  04 , has in its lateral surface a depression as described above in the respective surface that corresponds to the at least one first printing image area of printing plate  68  arranged on the first plate cylinder  04 . 
     The respective circumferential speeds of the first plate cylinder  04  and of the ink forme roller  07  that inks up the printing plate  68  arranged on this first plate cylinder  04 , and the respective circumferential speeds of the second plate cylinder  04  and of the ink forme roller  07  that inks up the printing plate  68  arranged on this second plate cylinder  04  are synchronized with one another, e.g. by a control unit, in particular with respect to a common reference point. Therefore, each plate cylinder  04  and its associated ink forme roller  07  are synchronized. To produce the intended ink gradients, this synchronization must exist for all printing units  73  and inking units  06  that are involved in production, at any given time during the relevant production process, i.e., including immediately following a machine stop. In addition, the respective circumferential speeds of the hollow bodies  01  to be printed and of segmented wheel  03  are synchronized with one another. 
     With this method, in the execution of a letterpress printing process, color gradients known as rainbow printing effects are produced, with which the design depth achievable in printing can be increased and/or security features can be produced. The selective use of color gradients allows totally novel decorative patterns to be produced on hollow bodies  01 , in the axial direction and/or the circumferential direction thereof. This is possible with the described method even using short inking units, including such inking units that have a roller train with, e.g. only two rollers. 
       FIG. 17  shows three phases of a production sequence for producing a color gradient on a hollow body  01 , with at least two inking units  06  being used in this device for printing on hollow bodies  01 , each inking unit having an ink forme roller  07 , the respective circumferential length of which is equal to the flat length of the printing plate  68  used in the same inking unit  06 . In a first production phase ( FIG. 17 a   ), in a first inking unit  06  having a first, e.g. fully sheathed, ink forme roller  07 , a first printing ink  69  is applied to a first printing plate  68  arranged on a first plate cylinder  04 . The first printing plate  68  then rolls off onto a first printing blanket  33  that is cooperating with the first plate cylinder  04  and is arranged on the segmented wheel  03 , which is rotating about its axis  34 , thereby producing the ink application shown in  FIG. 17 a    in both a sectional view and a plan view on said first printing blanket  33 . In a second production phase ( FIG. 17 b   ), in a second inking unit  06  that has a second ink forme roller  07  having, e.g. a depression in the circumferential direction, a second printing ink  69  is applied to a second printing plate  68  arranged on a second plate cylinder  04 . The second printing plate  68  then rolls off onto a second printing blanket  33  that is cooperating with the second plate cylinder  04  and is likewise arranged on the rotating segmented wheel  03 , thereby producing the ink application shown in  FIG. 17 b    in both a sectional view and a plan view on said second printing blanket  33 .  FIG. 17 c    shows, by way of example, a third production phase in which both the first printing ink  69  and the second printing ink  69  are applied to mutually adjoining regions of the printing plate  68  arranged on the second plate cylinder  04 , the first printing ink  69  having been applied to the second printing plate  68  by back-splitting. By transferring the two printing inks  69  together onto the second printing blanket  33  cooperating with the second plate cylinder  04 , the ink application shown in  FIG. 17 c    in both a sectional view and a plan view is produced, in which in each respective boundary region  71  between the two printing inks  69  applied to the second printing blanket  33 , a mixing of inks caused by back-splitting is produced, forming a color gradient or a rainbow printing effect. This color gradient can then be transferred onto the hollow body  01  to be printed. 
     Another highly advantageous method for printing on hollow bodies includes the method steps in which printing ink  69  is transferred onto each of the hollow bodies  01  by a different one of the printing blankets  33  arranged in a row along the periphery of a segmented wheel  03  rotating about its axis  34 , in which case printing ink  69  is applied to the relevant printing blanket  33  by a plurality of printing units  72 ;  73  arranged along the periphery of segmented wheel  03 . In that case, in the direction of rotation of segmented wheel  03 , a first subset of printing units  73  applies printing ink  69  in a contact process, preferably in a letterpress process but possibly also in a screen printing process or an offset printing process, to the relevant printing blanket  33 , and each of a second subset of printing units  72  applies printing ink  69  in a plateless digital printing process to the relevant printing blanket  33 , wherein all of the printing inks  69  that will ultimately be transferred from the respective printing units  72 ;  73  onto the hollow body  01  in question are first collected on the relevant printing blanket  33  and are then transferred together from the relevant printing blanket  33  onto the hollow body  01  in question. In that case, the printing unit  72  applying at least one printing ink  69  in a plateless digital printing process onto the relevant printing blanket  33  is preferably located within an angular range φ of ±45° with respect to the zenith of segmented wheel  03 , and thus in an upper region of said segmented wheel  03 . At least one inkjet print head  74  or one laser is advantageously used for the printing unit  72  applying at least one printing ink  69  in a plateless digital printing process onto the relevant printing blanket  33 . It is particularly advantageous for each printing unit  72  applying at least one printing ink  69  in a plateless digital printing process onto the relevant printing blanket  33  to be in the form of a double array, i.e. a printing unit  72  in which two printing devices, e.g. two inkjet print heads  74 , each preferably applying the same printing ink to the relevant printing blanket  33 , are arranged in a row in the circumferential direction of segmented wheel  03 . As an alternative to the double array, a single array or some other multiple array may be used. Thus, the printing unit  72  applying at least one printing ink  69  in a plateless digital printing process to the relevant printing blanket  33  applies at least one of the printing inks cyan and/or magenta and/or yellow and/or black. Each of the printing units  73  applying the printing ink  69  in a letterpress printing process or in a screen printing process or in an offset printing process onto the relevant printing blanket  33  preferably applies a particular premixed, e.g. customized or product specific special ink. For the precise angular position control of segmented wheel  03 , it is advantageous for the rotation of segmented wheel  03  to be driven by a direct drive configured as a motor  58 . As described above, in the preferred embodiment the hollow bodies  01  to be printed on are advanced to the rotating segmented wheel  03  by a mandrel wheel  02  rotating counter to segmented wheel  03  about an axis  41 , and the relevant printing blanket  33  with the printing inks  69  collected thereon rolls off against the relevant hollow body  01 , transferring said printing inks  69  onto said hollow body. In addition, to shorten makeready times, at least one printing blanket  33  arranged on segmented wheel  03  can be changed automatically using a device for automatically changing printing blankets  33 . Each printing unit in the first subset of printing units  73  that print, e.g. in a letterpress printing process uses an inking unit  06  that is thrown onto the respective plate cylinder  04  and that has a roller train consisting of a maximum of five rollers, i.e., preferably a short inking unit. Alternatively or additionally, each printing unit in the first subset of printing units  73  that print, e.g. in a letterpress printing process uses an inking unit  06  that is thrown onto the respective plate cylinder  04  and that has only a single ink forme roller  07 . 
       FIG. 18  shows a schematic diagram of the device for printing on hollow bodies  01 , having one printing unit  72  that prints in a multi-color, e.g. four-color, plateless digital printing process and having a plurality of printing units  73 , e.g. six, each of which prints in a letterpress printing process or in a screen printing process or in an offset printing process. The result is a hybrid device for printing on hollow bodies  01 , with which even smaller print runs or batch sizes of hollow bodies  01  that entail more frequent changes to the decorative pattern in the device for printing on hollow bodies  01  can very advantageously be efficiently produced. 
     While a preferred embodiment of a segmented wheel of a device for printing on hollow bodies, in accordance with the present invention, has been set forth fully and completely herein above, it will be apparent to one of skill in the art that various changes could be made thereto, without departing from the true spirit and scope of the subject invention, which is accordingly to be limited only by the appended claims.