EP0133484A1 - Sheet guiding roll free of smears for rotary sheet printing machines - Google Patents

Abstract

Smear-free transfer cylinder for sheet-fed rotary printing machines having a cylindrical casing formed with blow holes distributed over the entire sheet-carrying peripheral surface of the cylinder, includes air distribution elements respectively disposed in the blow holes for influencing blowing air flow out of the blow holes for forming a uniform air cushion, the air distribution elements being formed of air-permeable, elastic and slightly compressible material having a low specific gravity.

Description

The invention relates to a lubrication-free transfer drum for sheet-fed rotary printing machines, in which mechanically manufactured blowholes are provided in the drum jacket over the entire sheet-bearing drum circumference.

For transferring freshly printed sheets from one to the next printing unit or from the last printing unit to the delivery of a printing press, devices are known in which the sheet is supported by blowing air escaping from the sheet guiding means during its transport, thereby preventing smearing or even blurring of the still wet printing ink, which impairs quality should.

A device of this type is described in DE-PS 1 561 043, according to which, in the case of a delivery drum for sheet-fed printing machines, the sheets are pushed away by air streams emerging from openings arranged on the circumference of the drum, the drum as a whole with a cover made of known material to distribute the emerging air more uniformly , porous and air-permeable Maigrial is provided. The control of the air outlet from the individual openings requires an air control device inside the delivery drum which is very complex both in terms of construction and in terms of cost, the partial or temporal air control in particular causing great problems precisely at the points of the freshly printed sheet which are prone to smearing. Apart from this, there is always a great need for blowing air, which requires an unnecessarily large design of the units for blowing air generation. Even the smallest damage and contamination of the porous drum cover require its costly and time-consuming replacement.

In order to avoid these disadvantages of the prior art, the present invention has for its object to provide a maintenance-friendly transfer drum in which evenly over the without time-consuming settings and without considerable control engineering effort entire drum circumference with low blown air requirement should be reliably prevented from smearing freshly printed sheets by building an air cushion that is as free of turbulence and impulses as possible.

The object set in this way is achieved according to the invention in that in the blow holes of the drum shell the exiting blowing air is arranged to build up a uniform air cushion which has a flow-influencing air distribution element, which as a radially resilient bearing that automatically drops when a defined tensile force of the pressure sheet or a defined pressure load is exceeded, spherical or spherical arch supports are formed which can be rotated on all sides regardless of the direction.

The structural distribution of a large number of individual air distribution elements over the entire drum circumference enables particularly safe, quiet and smear-free sheet transport. Because the choice of material and the shape of the individual arch supports make it very easy to empirically determine the flow conditions required to build up a closed, turbulence-free and pulse-jet-free air cushion, thereby also changing conditions in the printing process as quickly as possible, e.g. Processing of a different paper thickness, which can be taken into account, optimization of a particularly stable sheet transport is possible. Due to the easy interchangeability of individual, e.g. dirty air distribution elements also ensure the greatest possible degree of ease of maintenance and thus operational safety of the transfer drum.

Even if there is an undesired relative movement of the sheet relative to the transfer drum, e.g. caused by running on the rubber blanket, smearing is largely avoided by the fact that the sheet can roll on the sheet carrier in all directions. The advantage here is that only the sheet carrier are caused to rotate, at which there is a risk of smearing the sheet, so that even with one. unwanted color transfer from the freshly printed sheet to the sheet carrier, which is always supported by the rotational movements of color-free surface areas of the sheet carrier.

According to an advantageous embodiment of the invention, the receiving holes in connection with the arch supports are designed as self-regulating blowing air valves supplied by a blowing air unit as a function of the tensile force or pressure load acting on the arch supports.

Depending on the pressure load or tensile force of the arch, immediately at the start of a relative movement taking place, these arch supports in particular partially deflect radially inwards at image areas prone to smearing, against the pressure of the springs, and thereby open - as far as necessary to form a sufficient air cushion - as required to serve as air channels Receiving holes from which the blowing air can then escape independently. To the extent that the bow is lifted and carried by the air cushioning of the blown air flowing out, the compressive forces or tensile loads acting on the bow carriers are also reduced, as a result of which they are pushed radially outward again and the valve openings are reduced or completely closed. This automatically regulates the blown air regulation based on the air requirement and can be used with a minimum of blown air and the blown air unit can be dimensioned relatively small. The special effect of the blown air valves with the ball-like or spherical arch supports as actuators compared to the known conventional valves for this purpose is that the air outflow is uniformly diffuse to all sides without the targeted formation of impulse jets, which means that a continuous air cushion can build up.

In a further development of the inventive concept, blown air leaks emerging from the closed blown air valves are used to form a constant air cushion. In order to achieve blown air leakage, rough and / or different tolerances are advantageously provided for the production of the push-on sleeves and / or arch supports. Using the fine tolerance or manufacturing-related annular gaps of the closed blower air valves evenly distributed over the entire drum surface, a constant and turbulence-free air cushion can be maintained without undesired side effects with a minimum of blown air requirement, which benefits a particularly quiet sheet transport.

Further advantageous embodiments of the invention are set out in claims 2 and 3 and 7 to 10 and in the description below.

The invention is described below with reference to a basic embodiment shown in the figures.

• Fig. 1 vereinfacht dargestellt einen Querschnitt durch die Grundausführung der Umführtrommel nach der Erfindung,
• Fig. 2 einen detaillierten Auszug von Fig. 1 mit Darstellung eines Bogenträgers in unbelastetem Zustand,
• Fig. 3 dieselbe Ansicht wie in Figur 2, jedoch in belastetem Zustand,
• Fig. 4 auszugsweise einen schematischen Längsschnitt durch die Umführtrommel gemäß Fig. l,
• Fig. 5 skizzenhaft dargestellte Varianten der Oberflächengestaltung der Umführtrommel nach Fig. 1 und 4 und

It shows:

• 1 shows a simplified cross section through the basic design of the transfer drum according to the invention,
• FIG. 2 shows a detailed excerpt from FIG. 1, showing a sheet carrier in the unloaded state,
• 3 shows the same view as in FIG. 2, but in a loaded state,
• 4 shows a schematic longitudinal section of the extracting drum according to FIG. 1,
• Fig. 5 sketchy variants of the surface design of the transfer drum according to FIGS. 1 and 4 and

1, the drum surface of a transfer drum 1 designed as a blown air drum, with schematically indicated sheet detection devices 2 and 3, is provided with mechanically manufactured, for example drilled, blow holes 4 over the entire drum circumference. The blow holes 4 are preferably distributed in a uniform structure in the drum jacket 17. 2n the blowing holes 4 are inserted with the drum surface flush with the socket 5, the openings on both sides are smaller than the sleeve diameter. Inserted spring elements 6, which are designed as compression springs, are supported on the lower sleeve base, the choice of which spring force is preferably determined empirically. Air-distributing elements 7 are arranged on the compression springs 6 and are designed as spherical or spherical arch carriers, the diameter of which is slightly larger than that of the outer plug-in sleeve openings. As a result, the arch supports 7 are held in the receptacles 5 and, in the state that is still unloaded from the arch, project slightly beyond the drum surface by the radially outwardly acting spring pressure, depending on the ratio of the diameter of the arch support 7 to the receptacle opening (FIG. 2). Balls with color-repellent surface and low specificity are preferably used as sheet carriers 7 shear weights and / or from a material that is only statically chargeable.

4 shows the path of the blowing air flowing through the transfer drum 1 with arrows 10, the blowing holes 4 with the push-in sleeves 5 and the arch supports 7 forming a unit as mechanical blowing air valves 11.

In a bearing 12 of the side wall 13 opposite the drive side of the printing press, a roller core 14 is mounted, which is provided at the end with a core bore 15. Within the side wall 13, an end disk 16 is fastened on the roller core 14, to which a drum jacket 17, preferably manufactured as a casting, is flanged in a known manner. In contrast to the basic design, the receiving holes 4 in the drum jacket 17 must be designed as through holes in this embodiment. On the side facing the inside of the drum, the end disk 14 is provided with an annular groove 18, which is connected to the core bore 15 of the roller core 14 via a blind bore 19.

The core hole 15 is coupled to an air blowing unit 22 by means of an air coupling 20 via line means 21. The air coupling 20 is indicated schematically in FIG. 4 as a stationary coupling sleeve 23, in which a coupling sleeve 24 driven into the end of the core hole 15 rotates. The blown air generated by the blown air unit 22 can thus flow via the line means 21, the air coupling 20, the core hole 15, the blind hole 19 and the annular groove -18 into the interior of the transfer drum 1 or its individual drum chambers 9.

As indicated in FIG. 5, the drum surface of the basic version of the transfer drum 1 can be provided with one or partially with several foils 25. The films 25 can be designed as a tensioning or adhesive film and - as indicated in the left part of FIG. 5 - consist of an air-impermeable material with hydrophilic surface properties, or instead be made of air-permeable material according to the right part of FIG. 5. The thickness 26 of the tensioning or adhesive film 25 may correspond to a maximum of the defined dimension 8 by which the arch supports 7 protrude beyond the drum surface.

The operation of the transfer drum 1 according to the invention is described in more detail below, it being pointed out that the same can also be used without the use of blown air.

A freshly printed sheet 27 is taken over by the sheet detection devices 2 and 3 in this way - e.g. after turning the sheet in perfecting machines - that its still damp side is directed downwards against the drum surface. In this case, however, the sheet 27 does not lie over the entire surface of the drum surface, but instead is supported exclusively over its entire surface in a punctiform manner by the sheet carrier 7 projecting slightly from the drum surface. This ensures the least possible contact between the arch and the wing, despite the extremely even arch support. The color-repelling surface design of the arch support 7 also makes it difficult to transfer color from the arch 27 to the arch support 7.

Should, contrary to expectations, the freshly printed ink smear slightly, e.g. During the peeling process of the sheet 27, due to a different subject distribution on the rubber blanket, different pressure is also exerted on the individual sheet carriers 7. Even with the smallest relative movements of the sheet 27 with respect to the drum surface, the sheet supports 7 contacting the pressure-moist points in areas of the sheet 27 which are at risk of lubrication are exposed to an increased tensile force or pressure load. As soon as this exceeds the counteracting spring force of the compression springs 6, these arch supports 7 deflect slightly radially inwards and thereby perform a rotary movement (FIG. 3). This rotary movement has a self-cleaning effect of the sheet carrier 7 as a result, as a result, any paint that is taken over is automatically stripped from the surface of the sheet carrier 7. Because of this, the sheet 27 is always supported by color-free punctiform surface areas of the sheet carrier 7.

The selection of the spring force of the compression springs 6 for the purpose of adaptation to given conditions such as printed matter, printing ink and the resulting different tensile forces of the sheet 27 is preferably determined empirically.

The alternative for anti-smudge support is in areas susceptible to lubrication, the air-impermeable film 25 shown in FIG. 5 with hydrophilic surface properties, for example by applying tension or gluing. In the areas in which the drum surface is provided with the tensioning or adhesive film 25, the covered sheet carriers 7 are in the radially indented position.

The smear-preventing effect of the drum surface is significantly increased by the use of blown air. In this case, the interior of the transfer drum is supplied with blown air via path 10 described above. As soon as the arch supports 7 are exposed to an increased tensile force or pressure load that exceeds the opposing spring force of the compression springs 6, they are - just as when using air without blowing - striving to move radially inwards to the flexible side. The blow holes 4 of the blow air valves 11 are opened to a greater or lesser extent, depending on the tension or pressure load on the arch supports 7, as a result of which an air outlet which is oriented towards the requirements is caused to be diffuse in all directions. As a result, an air cushion adapted to local requirements is built up, particularly in areas of the sheet 27 that are prone to smearing, which effectively prevents the freshly printed sheet from smearing.

With increasing support of the sheet 27 by the blowing air flowing out, the contact between the punctiform surface of the sheet carrier 7 and the freshly printed sheet underside decreases, which in turn leads to a reduction in the tensile forces and compressive loads acting on the sheet carrier 7. As a result, they strive radially outwards again into their raised, unloaded rest position and thus reduce the valve openings or close them automatically as soon as there is no longer any need for blown air. Because of this, a minimum of blown air can be used, which means that the blown air unit 22 can be made correspondingly small.

To achieve a continuous, as uniform and turbulence-free air cushion as arch supports 7 are preferably not yet end treated balls, for example with surface unevenness and still existing roundness. Slightly elliptical arch supports 7 can also be used. Due to the surface unevenness or out-of-roundness - even when the arch support 7 is not loaded by the arch - the outer receptacle openings are not completely closed. The air leaks diffusely emerging from all sides due to the slight tolerance and production-related annular gaps of the closed blower air valves can thus build up a constant air cushion that guarantees smear-free and quiet sheet transport.

Instead, however, it is also possible, when using dimensionally stable, completely round arch supports 7 with an absolutely smooth surface, which tightly seal the blown air valves 11, to apply the air-permeable tensioning or adhesive film 25 to the entire drum surface or partially specifically in areas particularly prone to lubrication. The sheet carrier 7 covered by the film 25 of the blown air valves 11 are then also in a radially engaged state, which causes a constant air outlet from them, which is fine on the surface of the air-permeable film 25 in order to avoid impulse rays and to distribute it over a larger area atomized, emerges. The image area of the sheet 27 which is particularly prone to smearing is thus specifically supported by an air cushion. Since the film 25, due to its maximum thickness 26, is no higher than the adjacent, non-indented sheet carrier 7, the sheet 27 can lie flat on all sides over its entire area.

The invention is of course not limited to the embodiment shown in the figures and laid down in the description. It goes without saying that numerous constructive modifications, e.g. different shapes of blow holes 4 and air distribution elements 7, use of other pressure-generating spring elements 6, or choice of other materials for producing the air distribution elements 7 are within the scope of the invention.

PARTS LIST

• 1 transfer drum
• 2 sheet detection device
• 3 sheet detection device
• 4 blow hole
• 5 receptacle
• 6 compression spring
• 7 air distribution elements
• 8 defined dimension
• 9 drum chamber
• 10 Blown Air Way
• 11 Blow air valve
• 12 bearings
• 13 side wall
• 14 roll core
• 15 core hole
• 16 face plate
• 17 drum casing
• 18 ring groove
• 19 blind hole
• 20 air clutch
• 21 pipe means
• 22 Blowing air unit
• 23 coupling sleeve
• 24 coupling sleeve
• 25 stretch or adhesive film
• 26 Thickness of the tension or adhesive film
• 27 sheets

Claims (10)

1. Lubrication-free transfer drum for sheet-fed rotary printing presses, in which mechanically manufactured blow holes are provided in the drum jacket over the entire sheet-bearing drum circumference, characterized in that
that in the blow holes (4) of the drum shell, the exiting blowing air is arranged to build up a uniform air cushion which has a flow-influencing air distribution element (7), which as a radially resilient bearing that automatically drops when a defined tensile force of the pressure sheet (27) or a defined pressure load is exceeded, ball-like or spherical arch supports are formed which can be rotated on all sides regardless of the direction. 2. Lubrication-free transfer drum according to claim 1 and / or 2, characterized in that
that the sheet carrier (7) in the blow holes (4) are loaded in the radial direction to the drum surface and protrude a defined dimension (8) beyond this. 3. Lubrication-free transfer drum according to one or more of the preceding claims,
characterized,
that the holder of the arch support (4) in the blow holes (4) open on both sides plug sleeves (5) are introduced, the diameter of the openings directed radially towards the drum surface is slightly smaller than that of the arch support (7) and their sleeve base to support the Compression springs (6) is provided. 4. Lubrication-free transfer drum according to one or more of the preceding claims,
characterized,
that the blowing holes (4) in connection with the arch supports (7) are designed as self-regulating, depending on the tensile force or pressure load acting on the arch supports (7), supplied by a blowing air unit (22) blowing air valves (11). 5. Lubrication-free transfer drum according to one or more of the preceding claims,
characterized,
that blown air leaks emerging from the closed blown air valves (11) are used to form a constant air cushion. 6. Lubrication-free transfer drum according to one or more of the preceding claims,
characterized,
that rough and / or different tolerances are provided for the production of the plug-in sleeves (5) and / or arc carrier (4) to achieve blown air leakage. 7. Lubrication-free transfer drum according to one or more of the preceding claims,
characterized,
that a tensioning or adhesive film (25) of selectable size can be applied at least partially to the drum surface at areas prone to lubrication. 8. Lubrication-free transfer drum according to one or more of the preceding claims,
characterized,
that the thickness (26) of the tensioning or adhesive film (25) corresponds at most to the defined dimension (8) by which the arch supports (7) protrude beyond the drum surface. 9. Lubrication-free transfer drum according to one or more of the preceding claims,
characterized,
that the tensioning or adhesive film (25) is designed to be air-permeable, as a result of which a more uniform distribution of air on the drum surface is possible in the areas prone to lubrication. 10. Lubrication-free transfer drum according to one or more of the preceding claims,
characterized,
that the tensioning or adhesive film (25) is made of air-impermeable, ink-repellent material when operating the transfer drum without blowing air.

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