DE102008021692B4 - Process for the production of a surface for printing machines and a drum cap for transfer drums in printing machines - Google Patents

Abstract

Process for the production of a surface for printing presses from two surface elements with a joining device, whereby the joining of a preformed rigid surface element and a flexible surface element using an adhesive (2) as an intermediate layer compensating for deviations in shape, the flexible surface element during the joining and hardening of the adhesive (2) is fixed by means of negative pressure on a shaping die (6) which defines the desired shape of the surface.

Description

The invention relates to a method for producing a printing material-carrying surface for printing machines according to the features of claim 1 and a drum cap for transfer drums in printing machines according to the features of claim 4.

In rotary printing machines, web-shaped or curved printing materials are transported on the outer surfaces of rotating cylinders or drums and along straight or curved guide surfaces or guide rods, the mechanical guide being able to be supplemented with a pneumatic sheet guide. During the transport of printing material, there are, among other things, It is important to minimize relative movements between the substrate and the outer surface of cylinders or drums, to avoid undesired surface contact between guide surfaces and freshly printed substrate areas due to uneven guide surfaces, and to prevent damage to the substrate due to insufficient gaps between the surfaces carrying the substrate.

In sheet-fed printing machines, transfer drums are arranged between printing units, which take over freshly printed sheets of printing material from an upstream printing cylinder and transfer them to a downstream printing cylinder of the following printing unit. The outer surfaces on the transfer drums required for sheet guidance are formed by so-called drum caps. Drum caps are sections of a cylinder jacket which, in contrast to printing unit cylinders, have a lightweight design, since they are only used to transport sheets and are not exposed to any stress from printing equipment or processing units. Pneumatic sheet guiding devices are usually assigned to the transfer drums, which, by generating air cushions, place the sheets on the mostly coated surfaces of the drum caps and thus ensure that the sheet side printed in the previous printing unit remains free of smear when the sheets are less rigid ( DE 195 13 426 A1 ).

(RTK = Trommelkappenradius, RDZ = Druckzylinderradius, dBmax = maximale Bedruckstoffstärke, Smin = Mindestsicherheit, Tabs = absolute Fertigungstoleranz)
erfolgen, wobei das Spaltmaß X = RDZ - RTK zwischen Druckzylindermantel und Trommelkappe minimiert wird. Ist der Spalt X zu klein, kommt es zur Pressung zwischen Trommelkappe und Bedruckstoff.The drum caps have a smaller radius than the radius of the impression cylinder in order to form sufficiently dimensioned air gaps with the adjacent printing cylinders for the sheet to pass through. In order to avoid damage to the freshly applied print image when the sheet is transferred from the upstream printing cylinder to a downstream transfer drum, it is necessary, however, to minimize the relative movement between the sheet trailing edge conveyed at the circumferential speed of the printing cylinder and the drum cap surface, which rotates more slowly due to the smaller drum cap radius. This can be done by increasing the drum cap radius to the maximum permissible value $$\text{RTK}=\text{RDZ}-\text{dBmax}-\text{Smin}-\text{Tabs}$$

(RTK = drum cap radius, RDZ = impression cylinder radius, dBmax = maximum substrate thickness, Smin = minimum security, tabs = absolute manufacturing tolerance)
take place, whereby the gap dimension X = RDZ - RTK between the pressure cylinder jacket and the drum cap is minimized. If the gap X is too small, there is pressure between the drum cap and the printing material.

The above equation shows that while maintaining the minimum security, the air gap can only be reduced by minimizing the absolute manufacturing tolerance tabs. Here, however, it has been shown that the usual simple sheet metal constructions have no potential for a reduction in the tabs manufacturing tolerances, because the design-related shape and position tolerances do not allow a higher concentricity of the lateral surfaces.

On the other hand, the known machining processes, which achieve a higher concentricity, are too expensive to use and, if they are to be implemented, would result in an undesirable increase in weight due to the need for greater wall thicknesses for the drum caps.

However, undesired printing material contacts can also occur on curved or flat sheet guide plates along the printing material path due to inaccuracies in shape and positional deviations of the surfaces guiding the printing material.

The invention is therefore based on the object of creating a cost-effective structural solution for surfaces carrying printing material, with which a reduction in shape and position tolerances of the surfaces can be achieved.

According to the invention, the object is achieved by a method with the features of the first claim or a drum cap with the features of the fourth claim.

The proposed solution is based on the fact that the manufacturing tolerances in the production of surfaces leading to the printing material are reduced by joining a flexible guide plate fixed in a precisely shaped die with a compensating adhesive with a base frame stiffening the guide plate and a stiffening plate approximating the desired shape of the guide plate, whereby those occurring in the sheet metal construction of the base frame and the stiffening plate Deviations in shape can be compensated for with the leveling adhesive layer.

The proposed method for producing a dimensionally accurate, printing material-guiding surface for printing machines is characterized by the joining of a preformed, rigid surface element and a flexible surface element using an adhesive as an intermediate layer that compensates for deviations in shape, the flexible surface element being applied over the entire surface of a die during the joining and curing of the adhesive The desired shape of the surface-specifying form matrix is fixed over the whole or part of the area.

First, a base frame consisting of a one-piece or multi-part rigid stiffening plate and this supporting frame is produced using traditional joining technology with customary manufacturing tolerances, the stiffening plate being designed according to the shape of the surface leading to the printing material and having a perforation. After the supporting base frame has been joined, a guide plate, which is to be designed with a precise shape, is sucked by means of negative pressure onto a high-precision molding die, which specifies the desired target shape of the surface guiding the printing material. The flexible guide plate rests against the forming die without any gaps and is fixed with negative pressure. After applying an adhesive to the guide plate as an intermediate layer to compensate for the shape and position errors of the stiffening plate, the stiffening plate with the base frame is placed on the guide plate and pressed into the adhesive layer, with excess adhesive escaping through the holes of the perforation in the stiffening plate and an additional form-fitting bond the stiffening plate 3 creates. Finally, coupling elements are fixed on the base frame in a predetermined position relative to the guide plate, which corresponds exactly to the structural specifications for the intended fixing points at the installation site. After the adhesive layer has hardened, the guide plate, which is precisely connected to the base frame, can be removed from the joining device, reworked, completed and installed.

The solution according to the invention is characterized by the simplicity of manufacture. The base frame can be manufactured with the rough tolerances customary for sheet metal constructions; straightening processes are simplified. With the proposed method, short assembly times can be achieved because there is no need for complex adjustments to the coupling elements to compensate for the previously unavoidable form errors. In sheet-fed rotary printing presses, an improvement in the substrate feed (reduction of scratches) is brought about by reducing the circumferential speed differences between the impression cylinders and the transfer drums.

• 1: Darstellung eines Grundgestells für eine Trommelkappe
• 2: Darstellung des Fügeverfahrens einer Trommelkappe mit Formmatrize

In the following, the invention will be explained using the example of the production of a drum cap for a sheet-fed rotary printing press. The associated drawings show:

• 1 : Representation of a base frame for a drum cap
• 2 : Representation of the joining process of a drum cap with a molding die

Two drum caps are used in each case on transfer drums that are usually double-sized, the shell-shaped outer surfaces of which each extend over sectors of less than 180 ° of the drum circumference.

First one is made from a curved stiffening plate 3 and frames 4th Existing base frame for supporting and positioning the jacket sheet that carries the printing material 1 the drum cap is manufactured using traditional welding technology with the usual manufacturing tolerances. The base frame consists of a perforated, shell-shaped stiffening plate 3 , which is shaped to correspond to the radius of curvature of the drum cap surface and a perforation 5 has, and curved transverse and straight longitudinal ribs 4th , which are initially inserted into one another with a form fit and then welded to one another at defined points ( 1 ). On the front edge in the direction of rotation, the base frame has a hollow bar instead of a longitudinal bulkhead 8th to further improve the rigidity and to accommodate the connecting elements with the drum body in the area of the front edge (in the direction of rotation) a parallel hollow bar 8th within the drum cap profile or this at the front edge delimiting that of the ribs 4th connects and additionally at least with the stiffening plate 5 can be materially or positively connected. At its ends that go beyond the width of the stiffening plate, there are tabs on both sides 7th arranged for the attachment of the drum caps to the gripper bridges of the transfer drum.

Another hollow rod (not shown) in the rear cap area can be used to accommodate coupling means for a drum cap drive for pivoting the drum caps in and out. This hollow bar is through holes in the inner ribs 4th Passed through without contact and only with the outer ribs 4th firmly connected. The release of the hollow bar in the inner ribs 4th has the effect that the power flow of the actuators does not pass through the jacket plate while they are being swiveled in or out 1 directed, but only to the outer frames 4th be transmitted. This also contributes to the dimensional stability of the drum caps.

With the rib structure of the base frame, the lightest possible cap structure is created, which has a high degree of strength and elasticity.

After joining the frames 4th of the base frame is the perforated stiffening plate 3 placed on the rib structure, aligned and welded to the rib structure. Instead of the base frame with an open cross-section, a deformation-resistant double-shell surface structure can be used, the perforated stiffening plate being connected to a second surface element, which has a different curvature, on opposite sides, so that both surface elements form a closed profile in cross-section. In the open cross-section between the stiffening plate 3 and the planar element can form ribs to increase the rigidity of the planar structure 4th arranged and / or the open cross-section be filled with a curable or self-curing substance, for example a metal foam or an adhesive.

Then the base frame with the actual jacket sheet 1 the drum cap by means of compensating adhesive in a joining device with a molding die that is subjected to negative pressure 6th joined. The joining device is simple and inexpensive to manufacture. The stiffening plate 3 of the base frame ensures the dimensional stability of the outer surface after joining as an inner second shell. The outer jacket surface gives the drum cap the necessary dimensional accuracy.

For this purpose, a flexible jacket sheet corresponding to the length and width of the extended guide surface of the drum cap is used 1 into a high-precision molding die 6th a joining device inserted, which the desired radius of curvature of the jacket sheet 1 having ( 2a) . The molding die 6th has a plurality of air openings which are connected to a negative pressure generating air supply system. The gap-free molding of the cladding sheet is achieved by means of negative pressure 1 realized on the forming die surface, not the jacket sheet 1 with its entire surface, but the cladding sheet 1 initially only on one of its stretched edges by means of a vacuum build-up in the corresponding surface area to the target contour of the molding die 6th is pulled. On the jacket sheet 1 after it has been fixed to the molding die 6th a preferably non-shrinking adhesive of constant shape 2 applied and then the base frame - on the fixed edge of the jacket sheet 1 starting - with the stiffening plate 3 progressively slowly and using gravity or pressure means into the adhesive layer 2 inserted, leaving excess glue 2 through the perforation holes 5 in the stiffening plate 3 can escape and creates an additional form-fitting bond on the stiffening plate ( 2 B) .

The one from the perforation holes 5 Excess adhesive that escapes is particularly important in the area of the ribs 4th to increase strength. Hole diameter of the stiffening plate suitable for drum caps 3 are in the range from 5 to 10 mm and appropriate hole spacings between 10 mm and 50 mm.

The stiffening plate 3 preferably has a radius of curvature which corresponds to the lateral surface guiding the printing material - reduced by the sheet metal and adhesive layer thickness. The curvature of the stiffening plate 3 but can also be designed differently than that of the outer surface in order to be able to use the varying thickness of the adhesive layer 2 and thus to achieve an increase in the rigidity of the lateral surface in critical areas, which is reinforced in sections.

During the further pressing of the base frame onto the jacket sheet 1 this is progressively placed on the molding die 6th and is finally applied to the target contour of the forming die over the entire surface with negative pressure 6th drawn. The shape and position deviations of the stiffening plate 3 compared to that in the molding die 6th fixed jacket sheet 1 are about the different layer thicknesses of the adhesive layer in between 2 compensated ( 2c ).

In the last step before the adhesive layer hardens 2 the mounting of the receptacles for the connecting elements with the drum body takes place.

In order to compensate for the inaccuracies of the base frame in relation to the fastening points on the drum body, receptacles with adjustment options for the connecting elements to be fixed on the base frame are provided. For example, bushings can be glued into the bores provided for fastening the drum cap on the drum body, and these into the tabs 7th are introduced at the front edge of the base frame. Taking advantage of the play of the sockets in the holes in the brackets 7th the sockets are precisely aligned with the jacket sheet. The fixing means (clamping devices, receiving mandrels, etc.) of the joining device provided for fixing the sockets in the bores during hardening are for this purpose highly accurate to the jacket sheet 1 or to the molding die 6th adjustable.

Instead of the adjustable coupling elements, it is also possible to make highly precisely positioned bores in the transfer drum body, which make subsequent alignment of the drum caps relative to the drum axis superfluous.

After the adhesive layer has hardened 2 and the fixing of the connecting elements on the base frame, the drum cap of the joining device can be removed. The drum cap now has an exact coaxiality and concentricity of the jacket sheet 1 relative to the axis of rotation of the transfer drum.

Due to the proposed rigid drum cap profile, deformation of the drum caps, which is caused by the radial forces (centrifugal forces) occurring during printing, is prevented, so that the width of the air gap for the sheet passage no longer changes depending on the speed. This means that the addition of a gap reserve to compensate for positional and deformation play is no longer necessary, so that the air gaps between the transfer drum and adjacent cylinders and thus also the bow movements relative to the drum cap can be minimized.

In an analogous manner, printing substrate guide elements with curved guide surfaces for the pneumatic or sliding guidance of printing substrates are produced. Accordingly, joining devices with a flat molding die are used for flat guide surfaces 6th used. Likewise, dimensionally stable or warp-resistant guide surfaces can be formed in the display area, in particular in the area where the heat emissions from dryers are effective, by means of a curved stiffening plate 5 is connected to a flat or curved guide plate for the substrate guide. The air space between the two surface elements can simultaneously serve as an air box, the guide plate having air openings and the outer ribs 4th close the air space of the open cross-section airtight at the sides. For example, a concave curve guide section under the lower chain drum, a flat guide plate in the ascending branch of the chain circle or a convex curve guide section in the transition area between the ascending and horizontal chain circle section can be formed according to the invention.

When producing flat and curved surfaces, it can be useful for reasons of cost to use the stiffening plate 3 assemble from several sheet metal parts, for example to realize cutouts in the surface leading to the printing material or changing radii of curvature from several sections of the stiffening plate 3 to shape. The height differences that may occur when joining the sheet metal parts due to weld seams or gaps between the sheet metal parts are caused by the adhesive layer 2 also with balanced.

Instead of adhesives 2 You can also use foams that cure with constant volume as a connecting layer between the stiffening plate 3 and cladding sheet 1 or guide surface can be used. An advantage of thermally stable foams lies in the thermal insulation of the base frame and other machine parts located underneath, for example, compared to the effects of heat from dryers that are arranged along the path of the printing material. For this purpose there is a larger distance between the stiffening plate 3 and precisely shaped jacket or guide surface, which is advantageous by inserting spacers or by holding means, which spaced the base frame from the molding die 6th fix, can be produced.

The proposed method is also suitable for creating guide surfaces for pneumatic printing material guides. For example, the stiffening plate 3 and the jacket or guide surface guiding the printing material has corresponding openings, which are opened by means of appropriately positioned air openings in the forming die 6th and with the help of the negative pressure applied, the adhesive escaping from the air openings 2 vacuum and in this way keep the air openings free for the later application of air to the guide surface.

The method according to the invention is in principle also suitable for the production of surfaces guiding printing material with a non-metallic guiding surface, for example made of a plastic, whereby the adhesive 2 must be adapted to the material pairing stiffening plate / guide surface.

List of reference symbols

1

Cladding sheet

2

Glue, glue layer

3

Stiffening plate

4th

Ribs, transverse and longitudinal ribs

5

Perforation, perforation holes

6th

Form die

7th

Tab

8th

Hollow bar

Claims (7)

Method for producing a surface for printing presses that carries printing material from two surface elements with a joining device, with the joining of a preformed, rigid surface element and a flexible surface element below Use of an adhesive (2) as an intermediate layer compensating for deviations in shape, the flexible surface element being fixed by means of negative pressure to a shaping die (6) that defines the desired shape of the surface during the joining and curing of the adhesive (2). Procedure according to Claim 1 , with the following steps: - joining a base frame, which is formed from - a stiffening plate (3) and this supporting frame (4) or - a surface structure with a stiffening plate (3), the stiffening plate (3) having the shape of the surface leading to the printing material is designed accordingly and has a perforation (5), - application of a flexible guide plate corresponding in length and width to the dimensions of the surface leading to the printing material by means of negative pressure on a forming die (6) of the joining device, which specifies the desired shape of the surface leading to the printing material, - application an adhesive (2) on the guide plate as a form error of the stiffening plate (3) compensating intermediate layer, - placing the stiffening plate (3) with the base frame on the guide plate and pressing into the adhesive layer (2), with excess adhesive (2) between the guide plate and stiffening plate (3) escapes through the holes of the perforation (5) and enters e creates an additional form-fitting bond on the stiffening plate, - curing of the adhesive layer (2). Procedure according to Claim 1 for the production of surfaces leading to printing material with a radius of curvature with the following steps: - joining a base frame for the drum cap, which is formed from - a stiffening plate (3) and frames (4) or - a surface structure with a stiffening plate (3), the stiffening plate (3) is shaped according to the radius of curvature of the surface leading to the printing material and has a perforation (5), - suction of a flexible guide plate at a stretched edge on a forming die (6), which defines the curvature of the surface leading to the printing material, by means of negative pressure, - application an adhesive (2) on the guide plate as a form error of the stiffening plate (3) compensating intermediate layer, - placing the stiffening plate (3) with the base frame first on the edge area of the guide plate adjacent to the molding die (6) and pressing into the adhesive layer (2), the guide plate with the excess adhesive (2 ) progressively applied to the stiffening plate (3) and the forming die (6) and the guide plate on the entire forming die (6) is drawn to the target contour with negative pressure, - curing of the adhesive layer (2). Drum cap for transfer drums in printing machines, characterized by - a base frame with - a curved and perforated stiffening plate (3) or - a planar support structure, which has a curved and perforated stiffening plate (3), and - a sheet-metal sheet that is accurate in shape and curved with the drum radius (1), whereby - the stiffening plate (3) is shaped according to the radius of curvature of the casing plate (1) and the casing plate (1) is supported on the underside facing away from the printing material, - a shape deviation between the stiffening plate (3) and the casing plate (1) of the stiffening plate (3) compensating adhesive layer (2) is. Drum cap after Claim 4 , characterized in that the surface structure is designed as a deformation-resistant double-shell surface structure, wherein - the perforated stiffening plate (3) is connected to a second surface element on opposite sides so that both surface elements form a closed profile in cross-section, - in the open cross-section between the Stiffening plate (3) and the planar element to increase the rigidity of the planar structure frames (4) are arranged and / or the open cross-section is filled with a hardenable or self-hardening substance. Drum cap after Claim 4 , characterized by the arrangement of connecting elements to the drum body on the base frame of the drum cap in a predetermined position relative to the jacket plate (1). Drum cap after Claim 4 , characterized by the arrangement of connecting elements on the base frame of the drum cap in a predetermined position relative to the casing sheet (1), the connecting elements being aligned with fixing means of the joining device.

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