Web guide roller

Abstract

The invention relates to a web guide roller (1) for guiding a web-shaped substrate, comprising a roller body (2) with a circumferential surface (3) and at least one recess formed therein in the form of a groove (4), wherein the part of the circumferential surface (3) outside the at least one groove (4) forms a running surface (5) for the web-shaped substrate, wherein the running surface (5) forms a specific contact surface Ts with respect to a defined length Ls, and wherein the roller body (2) has a roller body length Lk in its axial extension from a first roller edge (7-1) to a second roller edge (7-2), wherein a roller center (6) lies substantially centrally between the first roller edge (7-1) and the second roller edge (7-2). The invention further relates to a printing press comprising such a web guide roller (1).The invention is based on the object of creating a solution that ensures sufficient stretching of the substrate web across the width, even with web widths that are significantly below the design width, while still enabling simple and thus cost-effective production of the rollers. This object is achieved according to the invention in that the at least one groove (4) is designed such that the specific contact area Ts increases from the roller center (6) toward the first roller edge (7-1) and toward the second roller edge (7-2).

Description

[0001] The invention relates to a web guide roller for guiding a web-shaped substrate, comprising a roller body with a lateral surface and at least one recess designed as a groove therein, wherein the part of the lateral surface outside the at least one groove forms a running surface for the web-shaped substrate, wherein the running surface forms a specific support portion Ts with respect to a defined length Ls, and wherein the roller body has a roller body length Lk in the axial extension from a first roller edge to a second roller edge, wherein a roller center lies substantially centrally between the first roller edge and the second roller edge.

[0002] Furthermore, the invention relates to a printing machine comprising at least one printing unit for printing a substrate web and at least one device for guiding the substrate web, wherein the printing machine comprises at least one web guide roller according to the invention.

[0003] As is known from the prior art, web guide rollers can be constructed in different ways: Versions with a so-called spindle bearing are used, in which the web guide roller comprises a roller body with a roller body length Lk and a spindle, the length of the spindle being greater than the roller body length Lk and in which the roller body is rotatably mounted on the spindle by means of plain bearings or mostly roller bearings, while the continuous spindle is mounted in a rotationally fixed manner on a holder or between the side walls.

[0004] Furthermore, designs with a so-called roller bearing are known, in which the roller body comprises at least one spindle pin which is rotatably mounted in a holder or in a side wall.

[0005] What both designs have in common is that only the running surface, as part of the outer surface of the roller body, comes into contact with the substrate web, whereby the maximum roller body length is adapted to the maximum web width of the substrate web to be processed.

[0006] In machines that process substrate webs, such as web-fed printing machines, at least one substrate web is guided through the machine for processing, in order to be guided at least from an unwinder to at least one processing station, such as a printing unit, or in order to guide the at least one substrate web from a first processing station, such as a printing unit, to a second processing station, such as a folding structure or a folding unit.

[0007] For this purpose, driven or non-driven web guide rollers are used, which are at least partially wrapped around the substrate web to guide the web. Although such web guide rollers may appear relatively simple from a technical perspective, the technical requirements for such web guide rollers are demanding in order to ensure the required properties, such as minimal influence on the web tension, enabling precise web guidance in and perpendicular to the web travel direction, preventing the deposit of pretreated substrate webs, ensuring uniform web tension across the width of the substrate web, and preventing wrinkling.

[0008] Various web guide rollers are known from the prior art, which have different smooth or structured surfaces, or which have a concave or convex or a cylindrical cross-section in order to ensure a uniform web tension across the width of the substrate web and thus avoid the formation of wrinkles and corrugations.

[0009] For this reason in particular, web guide rollers with a concave cross-section are very often used in order to build up a higher web tension in the area of ​​the roller edges and thus in the area of ​​the web edges due to the larger diameter and thus to stretch the web outwards.

[0010] However, on the one hand, the production of concave web guide rollers is relatively complex, and on the other hand, their effectiveness is only guaranteed for the web widths for which the web guide rollers were designed. For web widths significantly narrower than the design width, concave web guide rollers offer little or no benefit.

[0011] Furthermore, web guide rollers are known from the prior art which have concentric or helical grooves distributed evenly over the outer surface in order to allow the air cushion between the outer surface or the running surface of the roller body and the substrate web to escape, since otherwise, due to the high web speeds, an air cushion would be created between the substrate web and the running surface as a result of the laminar boundary layer.

[0012] The recessed grooves on the outer surface of the roller body reduce the contact area, as the substrate web rests only on the running surface and not on the bottom of the grooves. The running surface of the substrate web is therefore the outer surface of the roller body minus the area left open by the grooves.

[0013] The contact ratio T of a web guide roll is the ratio of the running surface to the outer surface. The contact ratio is often expressed as a percentage, with the contact ratio being 100 percent if the outer surface had no groove(s) along the entire roll body length Lk, so that the running surface is equal to the outer surface.

[0014] However, if the contact area is to be variable over the length of the roller body, a specific contact area Ts is used, which represents the running surface actually in contact with the substrate web through the outer surface, relative to a defined specific length Ls, for example, 100 mm or 1000 mm. This specific contact area Ts can thus also be specified as a percentage, whereby the specific contact area Ts is 100 percent if the outer surface has no groove(s) relative to a defined specific length Ls, so that relative to a specific length Ls, the running surface is equal to the outer surface.

[0015] The invention is therefore based on the object of creating a solution which makes it possible to ensure sufficient stretching of the substrate web across the width even with web widths which are significantly below the design width and yet still enable simple and thus cost-effective production of the rollers.

[0016] The object is achieved according to the invention in that the at least one groove is designed such that the specific contact area Ts increases from the roll center to the first roll edge and to the second roll edge.

[0017] Such a web guide roller has the advantage that, due to the increased contact area between the substrate web and the outer surface of the web guide roller, greater friction is generated in the edge region of the substrate web. This increases the contact area toward the web edge, resulting in a web tension that increases toward the web edges, thus stretching the substrate web widthwise. Thus, concave web guide rollers are no longer required, or the concavity can be reduced accordingly.

[0018] According to one embodiment of the invention, the specific contact area Ts increases from the roll center to the two roll edges essentially linearly and / or step-like and / or non-uniformly.

[0019] Such a design has the advantage that the friction and thus the stretching of the substrate web increases relatively evenly towards the outside, so that this shape enables a uniform web tension build-up and this solution can be applied for a very wide range of different web widths.

[0020] According to a further embodiment of the invention, the specific contact area Ts increases progressively or degressively from the center of the roll toward the two roll edges. Such a configuration has the advantage that the friction, and thus the stretching of the substrate web, increases unevenly toward the outside, which may be necessary, for example, with very wide substrate webs to ensure uniform stretching of the web, especially if the substrate web is subjected to a processing process that is critical with regard to wrinkling before and / or after the web guide roll.

[0021] According to a further embodiment, the web guide roller comprises a plurality of concentric grooves at a distance a, wherein at least one groove in the region of the roller center has a first groove width b1 as a groove width b, wherein the groove width b decreases in each roller edge to a second groove width b2, wherein the second groove width b2 is smaller than the first groove width b1.

[0022] This design has the advantage that, with its concentric grooves, the outer bearing portion of the web guide roller can be manufactured very economically and yet very efficiently. By varying the groove width b along the length of the roller body, the desired increase in the bearing portion can be influenced and implemented very efficiently.

[0023] According to a further embodiment of the invention, the web guide roller comprises a plurality of concentric grooves at a distance a, wherein at least one groove in the region of the roller center has a first groove width b1 as a groove width b, wherein the distance a increases from a first distance a1 in the region of the roller center to a second distance a2 in the region of the two roller edges.

[0024] This design, with its consistently identical concentric grooves, offers the advantage of increasing the contact area of ​​the web guide roller toward the outside in a very economical yet efficient manner. By varying the spacing of the grooves along the length of the roller body, the desired increase in contact area can be very efficiently influenced and implemented.

[0025] According to a further embodiment of the invention, the web guide roller comprises at least one spiral or helical groove which has a first groove width b1 in the region of the roller center, wherein the at least one groove has a second groove width b2 in the region of the roller edges, wherein the second groove width b2 is smaller than the first groove width b1.

[0026] This design has the advantage that such a web guide roller combines the advantages of a uniform stretching of the substrate web across the web width and the reduction of wrinkling, particularly in the case of a plurality of substrate webs lying one above the other.

[0027] According to a further embodiment of the invention, the web guide roller comprises at least one spiral or helical groove which has a first groove width b1 in the region of the roller center and wherein the spiral or helical groove has a first pitch p1 in the region of the roller center, wherein the at least one spiral or helical groove has a second pitch p2 in the region of the roller edges, wherein the second pitch p2 is greater than the first pitch p1. Such a configuration has the advantage that it is possible to keep the groove width constant over the length of the roller body, which can simplify the production of such a roller body and that the specific contact area Ts can nevertheless be varied over the length of the roller body.

[0028] According to a further embodiment of the invention, the web guide roller comprises at least one spiral or helical groove which has a first number n1 of grooves, a first pitch p1 and a first groove width b1 in the region of the roller center, wherein the web guide roller has a second number n2 of grooves in the region of the roller edges, wherein the second number n2 is smaller than the first number n1.

[0029] Such a design has the advantage that the specific contact area Ts can also be varied over the length of the roller body by means of grooves while maintaining the same groove width and the same pitch of the at least one helical groove by adding at least one additional groove, which simplifies the production of such a web guide roller depending on the manufacturing possibilities.

[0030] Preferred developments of the invention will become apparent from the dependent claims and the following description. Various embodiments of the invention are explained in more detail, without being limited thereto, with reference to the drawings. Herein: Fig. 1 Possibilities for the course of the specific contact area Ts over the roll body length Lk Fig. 2 A web guide roll with grooves of different widths over the roll body length Lk Fig. 3 A web guide roll with grooves spaced at different distances from one another over the roll body length Lk Fig. 4 A web guide roll with a helical groove of different widths over the roll body length Lk Fig. 5 A web guide roll with, for example, a helical groove with a different pitch over the roll body length Lk Fig. 6 A web guide roll with at least one helical groove with a different number of grooves over the roll body length Lk

[0031] Fig. 1 shows various embodiments of the inventive distribution of the specific contact area Ts over the roll body length Lk. The roll body length Lk is plotted along the abscissa, with the roll center 6, i.e. the area of ​​the web guide roll 1 or the roll body 2, which in the axial extension of the roll body length Lk lies essentially centrally between the first roll edge 7-1 and the second roll edge 7-2, also being shown and being defined by half the roll body length Lk / 2, since such web guide rolls 1 are preferably constructed symmetrically to the roll center 6 in order to ensure a symmetrical effect on the web.

[0032] The specific contact area Ts is plotted on the ordinate, which, as already explained above, results from the ratio of the running surface 5 as the actual contact area of ​​the lateral surface 3 with the substrate web relative to a defined specific length Ls, such as 100 or 1000 mm. As in Fig. 1 executed, it is also possible to specify the specific contact ratio Ts in percent, whereby the specific contact ratio Ts is 100 percent if the lateral surface 3 has no groove 4 or no grooves 4 in relation to a defined specific length Ls, so that the running surface 5 is equal to the lateral surface 3. The selected specific contact ratio Ts depends on the substrate to be processed, for example whether it is paper, cardboard or a plastic film.

[0033] Fig. 1a shows a variant in which the specific contact ratio Ts increases linearly from a first specific contact ratio Ts1 to a second specific contact ratio Ts2 starting from the roll center 6 towards the roll edges 7.

[0034] Specifically, this means that in the area of ​​the roller edges 7, i.e. in the area of ​​the ends of the roller body 2, a larger portion of the outer surface 3 of the roller body 2 of a web guide roller 1 is in contact with a substrate web than in the area of ​​the roller center 6. Conversely, this means that in the area of ​​the roller center 6, a larger portion of the outer surface 3 of the roller body 2 is recessed by grooves 4 than at the roller edges 7.

[0035] Fig. 1b shows an exemplary profile of the specific contact area Ts, in which the specific contact area Ts increases step-wise from a first specific contact area Ts1 towards the roll edges 7 to a second specific contact area Ts2, starting from the roll center 6.

[0036] Specifically, this means that in the area of ​​the roller edges 7, i.e. in the area of ​​the ends of the roller body 2, a larger portion of the outer surface 3 of the roller body 2 of a web guide roller 1 is in contact with a substrate web than in the area of ​​the roller center 6. Conversely, this means that in the area of ​​the roller center 6, a larger portion of the outer surface 3 of the roller body 2 is recessed by grooves 4 than at the roller edges 7. The gradation of the groove width b and / or the number of grooves 4 per specific length can be carried out in steps at intervals over the roller body length Lk, which contributes to standardization.

[0037] Fig. 1c shows an exemplary course of the specific contact ratio Ts, in which the specific contact ratio Ts increases progressively or degressively and / or parabolically from a first specific contact ratio Ts1 towards the roll edges 7 to a second specific contact ratio Ts2, starting from the roll center 6.

[0038] Fig. 1d shows an example of a non-uniform increase in the specific contact area Ts starting from a first specific contact area Ts1 in the roll center 6 to a second specific contact area Ts2 in the area of ​​the roll edges 7, wherein the increase in the Fig. 1d In the example shown, the curve is predominantly linear, but this does not constitute a restriction for a non-uniform curve, since this can also occur with a stepped and / or progressive and / or degressive and / or parabolic curve. Rather, a non-uniform curve within the meaning of this invention is a curve in which the specific contact area Ts increases from the roll center 6 from a first specific contact area Ts1 to the roll edges 7, generally to a second specific contact area Ts2, but can also stagnate or even decline in sections.

[0039] Although not in the Fig. 1a bis 1d shown, it is also possible to combine these embodiments with each other, so that, for example, the specific contact area Ts in the area of ​​the roll center 6 runs linearly and / or step-like over any desired portion towards the roll edges 7 and only runs progressively or degressively or parabolically in the area of ​​the roll edges 7.

[0040] Fig. 2 shows an exemplary design of a web guide roller 1 with a variable specific contact area Ts. Fig. 2 The web guide roller 1 shown comprises a roller body 2 with a roller body length Lk and a spindle 8, wherein at least the roller body 2 is mounted so as to be rotatable about the longitudinal axis 9. The roller body 2 has a roller body length Lk which extends along the longitudinal axis 9 and extends from a first roller edge 7-1 to a second roller edge 7-2. The roller center 6 is arranged substantially centrally between the first roller edge 7-1 of the roller body 2 and the second roller edge 7-2 of the roller body 2; the distance between the roller center 6 and each roller edge 7 is thus half the roller length Lk.

[0041] In addition, the roller body 2 comprises grooves 4, which in the Fig. 2 shown example are designed as concentric grooves 4 around the longitudinal axis 9. In the Fig. 2 In the example shown, the grooves 4 are distributed at equal distances a from one another over the roller body 2. As can be seen from the details A and B shown, the grooves 4 are machined into the outer surface 3, so that the outer part of the outer surface 3 forms the running surface 5. The running surface 5 is thus the part of the outer surface 3 of the roller body 2, which is in contact with the Fig. 1 is in contact with a substrate web (not shown). The running surface 5 is thus the outer surface 3 of the roller body 2 minus the area recessed by the grooves 4.

[0042] In order to increase the specific contact area Ts from the roll center 6 to the roll edges 7, the grooves 4 do not have a uniform groove width b over the roll body length Lk. Rather, a groove 4 in the region of the roll center 6 has a first groove width b1, and the groove width b decreases to a second groove width b2 in the direction of the roll edges 7, so that the second groove width b2 is smaller than the first groove width b1.

[0043] In Fig. 2 The different groove widths b are represented by lines of different thicknesses, with a wide line symbolizing a large groove width b and a narrow line symbolizing a small groove width b. In detail A, the first grooves 4 away from the roll center 6 are shown enlarged. These grooves 4 arranged in the region of the roll center 6 have a first groove width b1 according to the enlarged detail A.

[0044] In detail B, the grooves 4 adjacent to the first roll edge 7-1 and the second roll edge 7-2 are shown enlarged. These grooves 4 arranged in the area of ​​the roll edges 7 have a second groove width b2 according to the enlarged detail B. As can be seen from the line width in the illustration of the web guide roll 1 and from the groove widths b1 and b2 shown in details A and B, the second groove width b2 in the area of ​​the roll edges 7 is smaller than the first groove width b1 in the area of ​​the roll center 6. Consequently, the proportion of the running surface 5 in the area of ​​the roll edges 7, based on a specific longitudinal length Ls, is larger in the area of ​​the roll center 6, so that the specific contact area Ts is also larger in the area of ​​the roll edges 7 than in the area of ​​the roll center 6.

[0045] The groove width b can be varied uniformly and thus linearly and / or step-like and / or progressively and / or degressively and / or parabolically and / or non-uniformly over the roller body length Lk from the roller center 6 to the roller edges 7, so that the specific contact area Ts can be varied as desired over the groove width b.

[0046] Although in Fig. 2 While only one groove 4 with a rectangular cross-section is shown, a groove 4 can have any shape. Thus, the grooves 4 can have the shape of a semicircle or half an ellipse. However, it is also possible to generally use a rectangular contour and round the corners toward the running surface 5 as well as within the groove 4.

[0047] Typically, the first groove width b1 is in a range of 3 to 25 millimeters, in particular in a range of 3 to 12 millimeters. The second groove width b2 is in a range of 2 to 20 millimeters, in particular in a range of 2 to 8 millimeters.

[0048] Fig. 3 shows a further exemplary embodiment of a web guide roller 1 with a variable specific contact area Ts. Fig. 3 The web guide roller 1 shown comprises a roller body 2 with an identical structure to that shown in Fig. 2 shown web guide roller 1. However, Fig. 3 Another alternative to changing the specific contact ratio Ts over the roll body length Lk. Fig. 3 In the variant shown, grooves 4 are arranged concentrically to the longitudinal axis 9, distributed over the length of the roller body Lk, which in the case of the Fig. 3 In the example shown, all have the same groove width b. The same groove width b shown in Fig. can also be seen in the details C and the enlarged view of a groove 4 in the detail C.

[0049] In order to vary the specific contact ratio Ts over the roll body length Lk, the Fig. 3 In the example shown, the distance a between the grooves 4 increases from a first distance a1 in the area of ​​the roller center 6 to a second distance a2 in the area of ​​the two roller edges (7-1, 7-2). Due to the increased distance a between the grooves 4 in the area of ​​the roller edges 7, a larger part of the lateral surface 3 comes into contact with the substrate web as a running surface 5 in this area, so that, as a result of this measure, the specific contact area Ts is higher in the area of ​​the roller edges 7 than in the area of ​​the roller center 6.

[0050] Although in Fig. 3 illustrated variant, the grooves 4, which are arranged on the roller body 2, have the same groove width b, so that the groove width b remains constant over the roller body length Lk of the roller body 2, it is also possible for the groove width b to change over the roller body length Lk. For example, in addition to the changed distance a between the grooves 4, the groove width b can decrease from a first groove width b1 in the region of the roller center 6 to a second groove width b2 in the region of the roller edges 7, so that the effect of the increased distances a between the grooves 4 in the region of the roller ends 7 is further enhanced.

[0051] However, it is also possible to increase the distances a between the grooves 4 in the area of ​​the roller edges 7 relative to the roller center 6 and yet increase the groove width b in the area of ​​the roller edges 7 relative to the roller center 6 in order to allow sufficient outflow of a possible air cushion between the substrate web and the running surface 5. By adjusting the distances a and the groove width b, a higher specific contact area Ts can still be achieved in the area of ​​the roller edges 7 than in the area of ​​the roller center 6.

[0052] Fig. 4 shows a further possible embodiment of a web guide roller 1 according to the invention, which is fundamentally identical in structure to the Figuren 2 and 3 shown rollers, which is why a repetition of the basic structure is omitted.

[0053] Fig. 4 shows a very schematic representation of a web guide roller 1, which has a spiral or helical groove 4. Although in Fig. 4 While a web guide roller 1 with only one helical groove 4 is shown schematically, a design with a plurality of helical grooves 4 offset from one another is also possible.

[0054] In Fig. 4 However, for the sake of simplicity and clarity, a web guide roller 1 with only one helical groove 4 was shown. Fig. 4 In the example shown, the groove 4 has a first groove width b1 in the region of the roll center 6. This first groove width b1 can also be seen on an enlarged scale in section AA, marked as a detail. This helical groove 4 is designed such that the groove 4 has a second groove width b2 in the region of the two roll edges 7-1, 7-2, wherein the second groove width b2 is smaller than the first groove width b1, which in turn can be seen on an enlarged scale in section BB, marked as a detail.

[0055] By narrowing the at least one helical groove 4 towards the roller edges 7 or by widening the groove 4 in the area of ​​the roller center 6 relative to the roller edges 7, the specific contact area Ts is greater in the area of ​​the roller edges 7 than in the area of ​​the roller center 6.

[0056] The change in the groove width b starting from the roll center 6 to the roll edges 7 can be changed uniformly and thus linearly and / or step-like and / or progressively and / or degressively and / or parabolically and / or non-uniformly, so that the specific contact area Ts can be changed as desired over the groove width b.

[0057] Although in Fig. 4 While only one groove 4 with a rectangular cross-section is shown, a groove 4 can have any shape. Thus, the grooves 4 can have the shape of a semicircle or half an ellipse. However, it is also possible to generally use a rectangular contour and round the corners toward the running surface 5 as well as within the groove 4.

[0058] Fig. 5 shows a further possible embodiment of a web guide roller 1 according to the invention, which is fundamentally identical in structure to the Figuren 2 , 3 und 4 shown rollers, which is why a repetition of the basic structure is omitted.

[0059] Fig. 5 shows a very schematic representation of a web guide roller 1, which has a spiral or helical groove 4. Although in Fig. 5 schematically shows a web guide roller 1 with only one helical groove 4, a design with a plurality of helical grooves 4 offset from one another is also possible. In Fig. 5 However, for the sake of simplicity and clarity, a web guide roller 1 with only one helical groove 4 was shown. Fig. 5 In the example shown, the helical groove 4 has a first groove width b1 in the region of the roll center 6. The spiral or helical groove 4 also has a first pitch p1 in the region of the roll center 6. The helical groove 4 is further configured such that it has a second pitch p2 in the region of the roll edges 7, wherein the second pitch p2 is greater than the first pitch p1. The pitch p is the distance along the longitudinal axis 9 that is covered by a point moving on the helical groove 4 after one complete rotation.

[0060] Because the second pitch p2 in the area of ​​the roll edges 7 is greater than the first pitch p1 in the area of ​​the roll center 6, the ratio of the running surface 5 to the shell surface 3 is greater in the area of ​​the roll edges 7 than in the area of ​​the roll center 6, which is why the specific contact area Ts is greater in the area of ​​the roll edges 7 than in the area of ​​the roll center 6.

[0061] The change in the pitch p starting from the roll center 6 to the roll edges 7 can be changed uniformly and thus linearly and / or step-like and / or progressively and / or degressively and / or parabolically and / or non-uniformly, so that the specific contact area Ts can be changed as desired via the pitch P.

[0062] Although in Fig. 5 While only one groove 4 with a rectangular cross-section is shown, a groove 4 can have any shape. Thus, the grooves 4 can have the shape of a semicircle or half an ellipse. However, it is also possible to generally use a rectangular contour and round the corners toward the running surface 5 as well as within the groove 4.

[0063] Although in Fig. 5 illustrated variant, the helical groove 4, which is arranged on the roller body 2, has the same groove width b over the roller body length Lk, so that the groove width b is constant over the roller body length Lk of the roller body 2, it is also possible that the groove width b changes over the roller body length Lk.

[0064] For example, in addition to the changing pitch p, the groove width b can decrease from a first groove width b1 in the area of ​​the roll center 6 to a second groove width b2 in the area of ​​the roll edges 7, so that the effect of the increased pitch p2 of the groove 4 in the area of ​​the roll ends 7 is further enhanced.

[0065] However, it is also possible to increase the groove width b between the grooves 4 in the area of ​​the roller edges 7 relative to the roller center 6, from the roller center 6 to the roller edges 7, in order to allow sufficient outflow of a possible air cushion between the substrate web and the running surface 5. By adjusting the pitches p and the groove width b, a higher specific contact area Ts can still be achieved in the area of ​​the roller edges 7 than in the area of ​​the roller center 6.

[0066] Fig. 6 shows a further possible embodiment of a web guide roller 1 according to the invention, which is fundamentally identical in structure to the Figuren 2 , 3 , 4 and 5 shown web guide rollers 1, which is why a repetition of the basic structure is omitted.

[0067] Fig. 6 shows a very schematic representation of a web guide roller 1, which has a continuous spiral or helical first groove 4-1. Although in Fig. 6 schematically shows a web guide roller 1 with only one helical first groove 4-1 extending over the entire roller body length Lk, a design with a plurality of helical first grooves 4-1 offset from one another and extending over the entire roller body length Lk is also possible. Fig. 6 However, for the sake of simplicity and clarity, a web guide roller 1 with only one helical first groove 4-1 running continuously over the entire roller body length Lk was shown.

[0068] In the Fig. 6 In the example shown, the helical first groove 4-1, which is continuous over the entire length of the roller body Lk, has a constant pitch p over the entire length of the roller body Lk. Fig. 6 In the example shown, the groove width b of the first groove 4-1 is constant over the entire roller body length Lk, as can be seen on an enlarged scale in section AA.

[0069] In the Fig. 6 In the example shown, in addition to the helical first groove 4-1 running over the entire length of the roller body Lk, a helical second groove 4-2 is integrated in the area of ​​the roller center 6, which in the case of the Fig. 6 example is offset by 180° in the circumferential direction to the first groove 4-1. In the Fig. 6 In the example shown, the second groove 4-2 has the same pitch p and the same groove width b as the first groove 4-1, as can be seen on an enlarged scale in the section BB. The roller body 2 thus has a first number of grooves n1 in the area of ​​the roller center 6, in which Fig. 6 In the example shown, the first number of grooves n1 is equal to two, and has a second number of grooves n2 in the area of ​​the roller edges 7-1 and 7-2, in which Fig. 6 In the example shown, the second number of grooves n2 is equal to one, so that the second number of grooves n2 is smaller than the first number of grooves n1.

[0070] Since fewer grooves 4 are machined into the outer surface 3 of the roller body 2 in the area of ​​the roller edges 7 than in the area of ​​the roller center 6, the running surface 5, which can be brought into contact with the substrate web, is larger in the area of ​​the roller edges 7 than in the area of ​​the roller center 6, so that the specific contact area Ts is larger in the area of ​​the roller edges 7 than in the area of ​​the roller center 6.

[0071] Although in Fig. 6an exemplary web guide roller 1 is shown, in which the pitch p of the first groove 4-1 and the second groove 4-2 as well as the groove width b of the first groove 4-1 and the second groove 4-2 are constant over the entire roller body length Lk, it is also possible that in the area of ​​the roller edges 7 the spiral or helical first groove 4-1 and the spiral or helical second groove 4-2 in the area of ​​the roller edges 7 have a second pitch p2, wherein the second pitch p2 is greater than the first pitch p1 and / or have a second groove width b2 in the area of ​​the roller edges (7-1, 7-2), wherein the second groove width b2 differs from the first groove width b1.

[0072] The second groove width b2 in the area of ​​the roll edges 7 is preferably smaller than the first groove width b1, so that the specific contact area Ts in the area of ​​the roll edges 7 can be increased again.

[0073] However, it is also possible for the second groove width b2 in the area of ​​the roller edges 7 to be larger than the first groove width b1 in order to ensure better dissipation of the air cushion between the substrate web and the outer surface 3 of the roller body 2, particularly if only a small number of grooves n is present in the area of ​​the roller edges 7. By adjusting the number of grooves n and the groove width b, a higher specific contact area Ts can nevertheless be achieved in the area of ​​the roller edges 7 than in the area of ​​the roller center 6. List of reference symbols

[0074] 1Web guide roll 2Roll body 3Shell surface 4Groove 5Running surface 6Roll center 7Roll edge 8Spindle 9Longitudinal axis aSpacing bGroove width nNumber of grooves LkRoller body length LsDefined length TsSpecific contact area

Claims

1. Web guide roller (1) for guiding a web-shaped substrate, comprising a roller body (2) with a lateral surface (3) and at least one recess formed therein in the form of a groove (4), wherein the part of the lateral surface (3) outside the at least one groove (4) forms a running surface (5) for the web-shaped substrate, wherein the running surface (5) forms a specific support portion Ts with respect to a defined length Ls, and wherein the roller body (2) has a roller body length Lk in its axial extension from a first roller edge (7-1) to a second roller edge (7-2), wherein a roller center (6) lies substantially centrally between the first roller edge (7-1) and the second roller edge (7-2), characterized in that the at least one groove (4) is designed such that the specific contact area Ts increases from the roll center (6) towards the first roll edge (7-1) and towards the second roll edge (7-2).

2. Web guide roller (1) according to claim 1, characterized in thatthe specific contact area Ts increases linearly and / or step-like and / or non-uniformly from the roll center (6) to the two roll edges (7-1, 7-2).

3. Web guide roller (1) according to one of claims 1 or 2, characterized in that the specific contact area Ts increases progressively or degressively from the roll center (6) to the two roll edges (7-1, 7-2).

4. Web guide roller (1) according to one of claims 1 to 3, wherein the web guide roller (1) comprises a plurality of concentric grooves (4) at a distance a, wherein at least one groove (4) in the region of the roller center (6) has a first groove width b1 as a groove width b, characterized in that the groove width b in each roller edge (7-1, 7-2) decreases to a second groove width b2, wherein the second groove width b2 is smaller than the first groove width b1.

5. Web guide roller (1) according to claim 4, characterized in thatthe first groove width b1 is in a range of 3 to 12 millimeters and that the second groove width b2 is in a range of 2 to 8 millimeters.

6. Web guide roller (1) according to one of claims 1 and 3, wherein the web guide roller (1) comprises a plurality of concentric grooves (4) at a distance a, wherein at least one groove (4) in the region of the roller center (6) has a first groove width b1 as a groove width b, characterized in that the distance a increases from a first distance a1 in the region of the roller center (6) to a second distance a2 in the region of the two roller edges (7-1, 7-2).

7. Web guide roller (1) according to claim 6, characterized in that the groove width b remains constant over the roller body length Lk of the roller body (2) or changes over the roller body length Lk of the roller body (2).

8. Web guide roller (1) according to one of claims 1 and 3, wherein the web guide roller (1) comprises at least one spiral or helical groove (4) which has a first groove width b1 in the region of the roller center (6), characterized in that the at least one groove (4) in the region of the roller edges (7-1, 7-2) has a second groove width b2, wherein the second groove width b2 is smaller than the first groove width b1.

9. Web guide roller (1) according to one of claims 1 to 3, wherein the web guide roller (1) comprises at least one spiral or helical groove (4) which has a first groove width b1 in the region of the roller center (6) and wherein the spiral or helical groove (4) has a first pitch p1 in the region of the roller center (6), characterized in that the at least one spiral or helical groove (4) in the region of the roller edges (7-1, 7-2) has a second pitch p2, wherein the second pitch p2 is greater than the first pitch p1.

10. Web guide roller (1) according to claim 9, characterized in that the groove width b1 either remains constant over the roll body length Lk or changes over the roll body length Lk.

11. Web guide roller (1) according to one of claims 1 and 3, wherein the web guide roller (1) comprises at least one spiral or helical groove (4) which has a first number of grooves n1, a first pitch p1 and a first groove width b1 in the region of the roller center (6), characterized in that the web guide roller (1) has a second number of grooves n2 in the region of the roller edges (7-1, 7-2), wherein the second number of grooves n2 is smaller than the first number of grooves n1.

12. Web guide roller (1) according to claim 11, characterized in thatin the region of the roller edges (7-1, 7-2) the spiral or helical grooves (4-1, 4-2) in the region of the roller edges (7-1, 7-2) have a second pitch p2, wherein the second pitch p2 is greater than the first pitch p1 and / or in the region of the roller edges (7-1, 7-2) have a second groove width b2, wherein the second groove width b2 differs from the first groove width b1.

13. Printing machine comprising at least one printing unit for printing a substrate web and at least one device for guiding the substrate web, characterized in that the printing machine comprises at least one web guide roller (1) according to one of claims 1 to 12.

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