[0002] So-called folding rollers are used in folding apparatuses of web-fed rotary presses or in folding machines for sheet stock or for signatures. A folding roller pair, for example in a rotary knife folding unit, in co-action forms a folding nip, which impresses a fold on a printing substrate passing through the same. It is often the case that the dimensioning and the angular velocity of the folding rollers are selected in such a way that each individual sheet of a series of printing substrates in a sheet stock is substantially placed at the same azimuthal angular position of the folding rollers, and the fold is impressed using substantially the same azimuthal angular sections on the roller member of the folding rollers. This is particularly the case when the folding rollers are provided in certain sections with recesses or plane sectors.

These recesses or plane sectors, also referred to as non-contact surfaces, are provided in the folding surface regions of the folding rollers, for example, which could come into contact with the trailing ends or back corners of the sheets, to prevent dog's ears from forming or other damage from occurring. Folding rollers of this type having non-contact surfaces on the roller members are described, for example, in U. S. Patent 4,781, 667. In addition, folding rollers often have annular recesses encircling the folding roller axis and/or are provided or covered with sleeve-shaped sections or rings that are axially movable on the shaft member.

Folding rollers of this kind are discussed, for example, in the German Patent Application DE 37 43 642 Al.

[0003] It is immediately clear that the constant repetition of the folding action at a specific azimuthal angular position leads to wear at the aforementioned surface positions and surface sections on the peripheral body of the folding rollers. To minimize this wear, ceramic materials are commonly used for the roller member of the folding rollers. In spite of these improved surface properties, it turns out in practice that, after about one year, the wear is already so extensive that the folding rollers or at least the roller member need to be replaced.

However, replacing folding rollers in a folding apparatus of a web-fed rotary press, in particular in rotary knife folding units, is a time-consuming process that often takes several hours and, therefore, necessitates production downtime which, in turn, entails substantial costs.

[0004] The object of the present invention is, therefore, to devise a folding roller which will make it possible to change a worn surface section of its roller member for placing the fold, without having to completely or partially replace the folding roller.

[0005] This objective is achieved in accordance with the present invention by a folding roller having the features set forth in claim 1. Advantageous refinements of the present invention are delineated in the dependent claims.

[0006] In accordance with the present invention, a folding roller for folding a printing substrate in a folding device, in particular in a rotary knife folding unit, includes a shaft member and a roller member (peripheral body, peripheral tube) which is accommodated on the shaft member and which has or forms a folding surface, in particular a smooth or even folding surface. The roller member has at least two axial segments whose azimuthal phase angles are variable relative to one another, in that at least one of the two segments may be releasably connected to the shaft member in various azimuthal angular orientations. Together, the shaft member and the roller member form the folding roller. In other words, the roller member is releasably fastened to the shaft member so that, on the one hand, given an engaged connection, a kinematics is able to collectively drive the two members, and, on the other hand, given a released connection, a phase variation in the segments of the roller member is attainable. In particular, the roller member may have a ceramic or metallic surface, in particular a folding surface.

[0007] By varying the phase angles of the segments relative to one another, it is advantageously possible to orient various surface sections or surface zones for placing the fold at specific azimuthal angles, for individual time segments or specific production time periods. Bit by bit, a substantial portion of the entire surface of the segment or of the segments, preferably the entire surface of the fold placement zone, is able to be utilized in this way. By repeatedly varying the phase, the service life of the folding roller may be increased several times over: when the segment of the folding roller is regularly rotated by 360/n degrees (n being a natural number), the service life may be increased by n-times.

Practice has shown that, typically after one year, the width of a worn placement zone is about 15 degrees in the azimuthal angular direction.

[0008] In this way, it is possible to avoid having to completely replace the folding rollers for a longer period of time than is possible using conventional folding rollers.

[0009] In particular, in the folding roller according to the present invention, one segment of the at least two segments on the folding surface, may have one plane sector or one non- contact surface in an azimuthal angular section. In this context, the segment having the plane sector on roller member may be fixed in a defined azimuthal angular orientation. While the azimuthal angular orientation of the other one of the two segments is varied relatively thereto, the azimuthal angular position of the plane sector on the folding surface may remain in the same phase as the time period of the series of sheets to be folded. Alternatively thereto, the segment that does have a plane sector may be permanently fixed. When the azimuthal angular orientation of the other segment, thus of the segment having the plane sector, is varied, the same phase as the time period of the series of sheets to be folded may be reached again by a reverse phase change of the shaft member of the folding roller.

[0010] The folding surface of the folding roller according to the present invention preferably has a ceramic material which advantageously has a wear-reducing effect.

Moreover or alternatively thereto, the folding roller may include at least one segment of the roller member that has at least one annular recess. Annular recesses permit the passage of sections of a sheet to be folded, for example, that are provided with adhesive.

[0011] The segments of the roller member of the folding roller according to the present invention may be sleeve-shaped. In other words, the segments may surround the shaft member in a tubular or hollow cylindrical shape. This make it possible to ensure an effective contact and a uniform torque transmission between the shaft member and the roller member.

[0012] In one especially advantageous specific embodiment of the folding roller, the azimuthal angular orientation is continuously variable. In other words, the releasable connection may be engaged independently of specific, discrete azimuthal angular positions.

This is the case, for example, when the releasable connection is a clamped connection, a frictionally engaged connection, or an adhesive connection.

[0013] One or two of the folding rollers according to the present invention may be used in a folding roller pair: A folding roller pair according to the present invention, whose folding rollers, which are rotationally mounted about their substantially in parallel aligned shafts, in co-action form a folding nip for a printing substrate, has at least one folding roller according to the present invention, as described here.

[0014] With the folding roller according to the present invention, an especially beneficial rotary knife folding unit is also devised. A rotary knife folding unit includes a folding knife that is movable on a hypocycloidal path and a folding roller pair having substantially in parallel aligned shafts into whose nip the folding knife drives in the extremal position along its path. In particular, in a folding apparatus of a web-fed rotary press, a rotary knife folding unit of this kind is used to produce a longitudinal fold, more precisely a second longitudinal fold. A rotary knife folding unit in accordance with the present invention includes a folding roller pair according to the present invention, thereby advantageously prolonging the service life of the rotary knife folding unit.

[0015] The present invention may be employed in folding machines for sheet stock or in folding apparatuses of web-fed rotary presses. A folding apparatus may be of the type that works with pins or of the type that works without pins. The web-fed rotary press may be a commercial web press or a newspaper printing press. Typical printing substrates are paper, paperboard, cardboard, organic polymer films, or fabric. In other words, a folding apparatus according to the present invention of a web-fed rotary press has a folding roller pair according to the present invention and/or a rotary knife folding unit according to the present invention, along the lines of this specification.

[0016] Further advantages, advantageous embodiments and refinements of the present invention are described with reference to the following figures, as well as their descriptions.

Specifically, they show: [0017] Figure 1 one preferred embodiment of a folding roller according to the present invention; [0018] Figure 2 a view of a folding roller pair in a preferred embodiment in accordance with Figure 1, along the folding roller axes; [0019] Figure 3 a schematic representation of a folding roller pair according to the present invention in a rotary knife folding unit of a folding apparatus; and [0020] Figure 4 a schematic representation for illustrating the variation in the azimuthal angle of a segment of the embodiment in accordance with Figure 1.

[0021] Figure 1 shows one preferred embodiment of a folding roller 10 according to the present invention. A shaft member 12 supports a peripheral body or roller member 14, which has a first segment 16 and a second segment 18, both of these being sleeve-shaped. Roller member 14 forms a folding surface. First segment 16 is fixedly connected to shaft member 12. Second segment 18 is able to be or is releasably connected to the shaft member, in this embodiment in a clamped connection. A variation 20 in the azimuthal angle of second segment 18 may be undertaken: second segment 18 may be fastened or fixed to shaft member 12 in various azimuthal angular orientations. Second segment 18 may be released from a first azimuthal angular position and be rotated in the azimuthal angular direction around shaft member 12. Eventually, it may be reconnected to shaft member 12 at another azimuthal angular position. The azimuthal angular position may be continuously varied, thus not in quantized steps. First segment 16, in particular its portion of the folding surface, is disposed rotationally symmetrically about shaft member 12. Second segment 18 is fixed by fastening means 24, here by a number of screws, to shaft member 12. A sheet to be folded contacts the folding roller in the partial surface of the folding surface defined by permanent fold placement zone 36 situated on second segment 18 and active fold placement zone 38 situated on first segment 16. These zones 36,38 are graphically enhanced for the sole purpose of providing a clear representation in the figures, and they do not differ in geometry or material from the folding surface. The surface of permanent fold placement zone 36 is small in comparison to the surface of active fold placement zone 38. For this reason, the fold is substantially impressed on the sheet by active fold placement zone 38. Consequently, the wear occurs primarily in active fold placement zone 38, so that, by adjusting the azimuthal angle of first segment 16 relative to second segment 18, a surface section not affected by wear is used as a new, replacement fold placement zone, while retaining permanent fold placement zone 36 does not have any negative effect on a continued use of the folding surface.

[0022] Figure 2 is a view of a folding roller pair in a preferred embodiment in accordance with Figure 1, along the folding roller axes. Each shaft member 12 supports one roller member 14 each, a section through second segment 18 being shown here. Fastening means 24, in this case screws, clamp roller member 14 to shaft member 12 and fix its azimuthal angular orientation. In the nip formed by the folding rollers, a sheet or a signature is indicated, which is folded by the co-action of the contrarotating folding rollers.

[0023] For each of the folding rollers, in an azimuthal angular section, plane sectors 22 are discernible which lie in those angular regions which cooperate in the nip when the trailing edge, the back corners of the sheet or of the signature pass through the folding rollers. As already mentioned in the introductory part of this specification, in the embodiment according to the present invention, the geometry of the folding rollers and the kinematics are matched to the size and sequence of the sheets to be folded, so that there is a fixed phase relation between the rotation of the folding rollers and the period of the series of sheets.

[0024] Figure 3 relates schematically to a folding roller pair 26 according to the present invention in a rotary knife folding unit 28 of a folding apparatus 30. For the sake of simplicity, a view is shown of folding roller pair 26 along the plane of action of the folding knife (not shown) of rotary knife folding unit 28. Shaft member 12 supports first segment 16 and second segment 28 (releasably fixable by fastening means 24). This group is connected to shaft 32 via a screw connection 34, so that the drive or kinematics of folding apparatus 30 of rotary knife folding unit 28, acts on the group, thereby being able to set the same into rotation.

[0025] Figure 4 schematically illustrates the effects of the variation in the azimuthal angle of a segment of the embodiment of folding roller 10 of the present invention in accordance with Figure 1. When a fold placement zone on first segment 16 of roller member 14 is worn, the connection of second segment 18 to shaft member 12 fixed by fastening means 24 may be released. A relative variation 20 in the azimuthal angle between first and second segments 16, 18 may be undertaken, for example by rotating shaft member 12, so that there is no need for any further phase coordination of the folding apparatus, since the azimuthal angular position of second segment 18 relative to the folding apparatus is retained. In this manner, another surface section of first segment 16 arrives at the azimuthal angle of permanent fold placement zone 36 and forms an active fold placement zone 38, while worn fold placement zone 40 exibits an azimuthal angular phase displacement relative to permanent fold placement zone 36. Second segment 18 is again clamped to shaft member 12 by the action of fastening means 24. The operation may be repeated several times in an analogous manner, in particular when active fold placement zone 38 exhibits excessive wear. For that reason, Figure 4 also shows another worn fold placement zone 42 from an earlier azimuthal angular adjustment that had been made analogously to the adjustment just described.

REFERENCE NUMERAL LIST [0026] 10 folding roller [0027] 12 shaft member [0028] 14 roller member [0029] 16 first segment [0030] 18 second segment [0031] 20 azimuthal angular adjustment [0032] 22 plane sector [0033] 24 fastening means [0034] 26 folding roller pair [0035] 28 rotary knife folding unit [0036] 30 folding apparatus [0037] 32 shaft [0038] 34 screw connection [0039] 36 permanent fold placement zone [0040] 38 active fold placement zone [0041] 40 worn fold placement zone [0042] 42 additional worn fold placement zone