EP0579017B1 - Device for tensioning a printing plate on a plate cylinder - Google Patents

Description

The invention relates to a clamping device for clamping a printing plate on a plate cylinder, with fitting elements for receiving the printing plate with its register punchings, with a front clamping unit for receiving and for clamping the printing plate at its front end on the side of the register punchings, with a rear clamping unit for receiving and clamping the printing plate at its rear end opposite the register punchings, the fitting elements being associated with sensor elements coupled to indicators to indicate a precise fit of the printing plate with its register punchings on the fitting elements, and with a tensioning unit for tensioning the printing plate in the circumferential direction of the printing cylinder.

Such a tensioning device is known from EP-A-0 195 848.

Even with modern printing machines, which are largely automated, it is necessary to set up the machine at the start of the printing process to ensure that the print image appears in the correct position on the printing paper and that, in particular in the case of multicolor printing, the different printing inks appear in the correct position on top of one another, so that the printed image is correct and the desired color effect is achieved.

In offset printing, relatively thin metal foils are used as printing plates, in which the front edge seen in the printing direction is used as the reference edge.

In order to ensure the correct position of the printed image on the paper, so-called register punchings are made on the front edge of the printing plate, with which the printing plate is placed on dowel pins. If an offset printing plate is to be clamped onto a plate cylinder, the printing plate is first inserted with its front edge into a front clamping unit of the plate cylinder in such a way that the register punchings lie against the peg elements provided therein. Then the pressure plate is clamped in the front clamping unit and the plate cylinder is slowly rotated until the pressure plate has wrapped around the outer surface of the plate cylinder and can be clamped with its rear end opposite the register punchings in a rear clamping unit, which in addition to the front clamping unit Plate cylinder is arranged.

If the pressure plate is fixed at both ends in the clamping units, the clamping units are moved towards one another, as a result of which the pressure plate is tensioned in the circumferential direction of the plate cylinder. In this process, which is carried out in a conventional manner with the aid of clamping screws, the pressure plate is subjected to high tensile forces.

The press can then be set up, for which the front and side registers and, if necessary, the inclined register can be adjusted.

If the printing plate is not correctly positioned on the dowel pins with its register punchings when clamping onto the plate cylinder, and the printing plate is fully clamped before this error is discovered, then a subsequent correction is hardly possible, since local deformations, markings and Like. Can arise.

Thus, the printing plate can become unusable due to an assembly error and must be replaced by a new printing plate, which causes considerable costs, in particular due to the downtime of the machine.

From DE-A-3 000 576 a tensioning device for tensioning a printing plate on a plate cylinder is also known, in which the pressure plate is tensioned by means of tensioning rails arranged in a pit of the plate cylinder, onto each of which a plate end can be clamped by means of clamping rails and which by the clamping rail can be screwed in and is supported on a wall of the pit clamping screws can be moved approximately in the circumferential direction of the cylinder. Positioning devices are also provided, by means of which the pressure plate end on the tensioning rail and the tensioning rail on the plate cylinder can be brought into a precisely defined position. The distance between a reference surface of the cylinder pit and the tensioning rail is measured by a measuring device and a zero position of the tensioning rail is indicated by a measured value from a signal transmitter.

The object of the invention is to provide a tensioning device for tensioning and adjusting a printing plate on a plate cylinder, with which assembly errors are largely excluded, and which enables the printing plate to be set up easily and quickly.

According to the invention, this object is achieved in a tensioning device according to the type mentioned at the outset in that the sensor elements are arranged on the front clamping unit and in that adjusting devices for adjusting the printing plate with respect to the printing cylinder are provided, which are adjustable for setting up in an initial position and with which cooperates at least one further sensor element to indicate whether the actuating devices are in the starting position.

According to the invention, sensor elements are thus provided, via which the complete installation of the register punchings on the fitting elements is checked. In this way, it is determined whether the register punchings lie completely against the fitting elements in the desired manner, so that the machine operator can only clamp the pressure plate at its front end after checking this condition, and incorrect assembly is thus avoided.

Since the actuating devices must first be reset to their starting position at the beginning of the pressing process, an additional check is made possible in this way with the aid of the at least one additional sensor element as to whether the respective actuating device is in its starting position. The subsequent setup process is thus considerably simplified since the previous check ensures that the print registers are adjusted starting from their starting position.

In a preferred development it is provided that the fitting elements are pin-like elements which are designed as sensor elements.

This measure enables a particularly simple construction, since no additional sensor elements are required, but rather the sensor elements are integrated with the fitting elements.

In an advantageous further development of the invention, the sensor elements are designed as electrical contact elements, via which an electrical circuit is closed via the pressure plate when the register punchings are completely in contact.

Although in principle the sensor elements can also be constructed differently, that is to say, for example, they can be designed as inductive or capacitive sensor elements, in this embodiment the Sensor elements enables a particularly simple and reliable check of the desired mounting position of the pressure plate, since on the one hand electrical contact elements have a relatively simple structure and on the other hand a complete contact of the register punchings on the sensor elements is always ensured when the circuit via the pressure plate is closed.

In a further embodiment of the invention it is provided that at least one sensor element is coupled to an indicator for the optical and / or acoustic display of the state of the sensor element.

This measure has the advantage that a simple optical or acoustic check of the compliance with the necessary conditions during the clamping or tensioning process is made possible. So it can Installers are signaled in a simple manner whether the pressure plate with its register punchings lies correctly on the fitting elements and whether the actuating devices are in the starting position.

In a preferred development of this embodiment, the indicators are designed as LEDs, which are integrated in the sensor elements. If indicators are provided which signal the correct placement of the register punchings on the fitting elements, and indicators are provided which signal that the actuating devices are in their starting position, LEDs of different colors can be integrated into the fitting elements for this purpose, for example.

In a further embodiment of the invention it is provided that the front clamping unit has a hydraulic, pneumatic or motorized actuating device which can only be activated when the pressure plate with its register punchings lies completely against the fitting elements and the actuating devices for adjusting the pressure plate in their initial positions are located.

In this embodiment, it is thus ensured that the front clamping unit can only be actuated if both preconditions for correct tensioning of the pressure plate are met, namely if on the one hand the pressure plate with its register punchings lies completely against the fitting elements and on the other hand the adjusting devices for adjusting the Pressure plate are in their starting positions. In this way, assembly errors are completely excluded, and the assembly process is considerably simplified and shortened. Before the pressure plate is clamped, it is first checked whether the actuating devices are in their initial position.

Compliance with this condition can easily be checked using the relevant indicators. The printing plate with its register punchings is then placed on the fitting elements, the correct position being indicated by indicators. The actuating device can then be activated, for which purpose a single button, lever or the like is preferably provided. The clamping process on the front clamping unit now runs automatically.

In an additional development of the invention, the clamping process on the front clamping unit is interrupted if the pressure plate should move, so that a complete contact of the pressure plate with its register punchings on the fitting elements is no longer guaranteed.

A preferred embodiment of the invention is explained below with reference to the drawing.

Fig. 1

eine Teil-Seitenansicht eines Plattenzylinders mit der erfindungsgemäßen Vorrichtung in schematischer Darstellung und

Fig. 2

eine Aufsicht auf die vordere Klemmeinheit mit einer an die Paßelemente mit ihren Registerstanzungen angelegten Druckplatte in schematischer Darstellung.

Show it:

Fig. 1

a partial side view of a plate cylinder with the device according to the invention in a schematic representation and

Fig. 2

a plan view of the front clamping unit with a pressure plate applied to the fitting elements with their register punchings in a schematic representation.

In Fig. 1, the numeral 12 indicates a section of a plate cylinder of an offset sheet-fed printing press, which has on its surface an approximately rectangular recess 11 running in the axial direction, within which a tensioning device according to the invention, which is designated by the numeral 10, is arranged is.

A front clamping unit, which is provided for clamping a pressure plate 14 at its front end 65, which is provided with register punchings, is designated overall by the number 30.

A correspondingly constructed rear clamping unit 32 is arranged below the front clamping unit 30. Both clamping units 30, 32 can be displaced in relation to the edge of the recess 11 in the tangential direction of the plate cylinder 12 via hydraulic actuating devices 46 and 47, as indicated by the arrows 40, 41.

The clamping units 30, 32 are each connected via a guide 19 or 21 to an intermediate plate 34 or 36. Each intermediate plate 34 or 36 is in turn adjustable via an adjusting device 42 or 44 in the axial direction of the plate cylinder 12.

The actuators are not described in detail here and are only indicated schematically in the drawing, since they are known per se. In addition, further adjusting devices can be provided.

The front clamping unit 30 and the rear clamping unit 32 each have a rectangular inner clamping rail 18 or 26, which runs in the axial direction of the plate cylinder 12. An outer clamping rail 20 or 28 is provided parallel to the inner clamping rail 18 or 26, which is slightly beveled towards the outside in order to achieve a better adaptation of the shape to the circumference of the plate cylinder 12, since the tensioning device 10 may not project beyond the circumferential line of the plate cylinder 12 at any point.

The outer tensioning rails 20 and 28 are each connected to the inner tensioning rails 18 and 26 via a hydraulic cylinder, which is indicated schematically by the number 22 and 24, respectively. The outer clamping rails 20 and 28 can be moved via the hydraulic cylinders 22 and 24 in the direction of the inner clamping rails 18 and 26, so that an intermediate pressure plate 14 can be securely clamped between the clamping rails.

According to FIG. 2, two fitting elements 16, 17 are arranged on the inner clamping rail 18 of the front clamping unit 30, against which the pressure plate 14 with its register punchings 50, 52 can be placed.

Since the register punchings 50, 52 are attached to the front edge 64 of the pressure plate 14 in a semicircular shape, a first fitting element 16 has a circular shape, the radius being a few hundredths of a millimeter smaller than the radius of the register punchings 52, and a second fitting element 17 has approximately one oval shape, the rounding having a noticeably smaller radius than the radius of the register punch 50. This shape of the fitting elements 16, 17 enables the printing plate 14 with its register punchings 50, 52 to fit perfectly against the fitting elements 17, 16. The fitting elements 16, 17 are simultaneously designed as electrical contact elements and thus as sensor elements to make electrical contact with produce the electrically conductive pressure plate 14. Within each fitting element 16, 17 two LED elements 56, 60 and 54, 58 are arranged side by side, which are recognizable from the outside.

A control unit, which is indicated only schematically in FIG. 2 and which is designated by the number 62, is connected to the LEDs via suitable control lines. For each fitting element 16, 17, an LED 56 or 54 is connected in series with the applied voltage, so that when the circuit is closed via a pressure plate 14 between the fitting elements 16, 17, both LEDs light up. The two remaining LEDs 58 and 60 are controlled via the control unit 62 in such a way that they only light up when four additional sensor elements 48, 49 and 68, 69 connected to the control unit 62 signal that the actuating devices 42, 44, 46 , 47 are in their starting position.

If a printing plate is to be clamped on the plate cylinder, both clamping units 30, 32 are first released and the actuating devices 42, 44, 46, 47 are moved into their starting position. If the starting position is reached, this is indicated by the associated LEDs 58, 60 lighting up. Now the printing plate with its two register punchings is placed on the fitting elements until the reaching of the desired end position is signaled by the lighting up of the other two LEDs 54, 56, which expediently have a different color than the two LEDs mentioned above. The front clamping unit 30 can now be activated when the control unit 62 emits an enable signal. The hydraulic cylinder 22 is thus actuated and the pressure plate is clamped at its front end. If the pressure plate moves during the clamping process, this process is automatically interrupted.

If the pressure plate is clamped at its front end in the intended manner in the front clamping unit, the plate cylinder is set in a slow rotation until the pressure plate has laid out on the cylinder from the outside and is inserted with its rear end into the rear clamping unit 32 can. Now the pressure plate is also clamped at its rear end by actuating the hydraulic cylinder 24. The pressure plate is then clamped onto the plate cylinder, for which purpose the preferably hydraulic actuating devices 46 and 47 are actuated, as a result of which the front clamping unit 30 and the rear clamping unit 32 are moved towards one another in the tangential direction of the plate cylinder 12 in the direction of the arrows 37, 38, so that the printing plate is clamped onto the plate cylinder with high force.

Claims (7)

1. Tensioning device for tensioning a printing plate on a plate cylinder, with mating elements (16, 17) for receiving the printing plate (14) with its register punchings (50, 52); with a front clamping unit (30) for receiving and clamping the printing plate (14) at its front end (65) on the same side as the register punchings (50, 52); with a rear clamping unit (32) for receiving and clamping the printing plate (14) at its rear end (66), which is the opposite end from the register punchings (50, 52), sensor elements coupled to indicators (54, 56; 58, 60) being associated with the mating elements (16, 17) in order to indicate accurately fitting abutment of the printing plate (14), with its register punchings (50, 52), against the said mating elements (16, 17); and with a tensioning unit (34) for tensioning the printing plate (14) in the peripheral direction of the printing cylinder (12), characterised in that the sensor elements are disposed on the front clamping unit (30) and that setting arrangements (42, 44, 46, 47) for adjusting the printing plate (14) with respect to the printing cylinder (12) are provided which are adjustable for the purpose of setting-up into a starting position and with which at least one further sensor element (48, 49, 68, 69) interacts in order to indicate whether the setting arrangements are located in the starting position.
2. Tensioning device according to claim 1, wherein the mating elements (16, 17) are pin-like elements which are constructed as sensor elements (16, 17).
3. Tensioning device according to claim 1 or 2, wherein the sensor elements (16, 17) are constructed as electrical contact elements via which an electrical current circuit is closed, via the printing plate (14), when the register punchings (50, 52) are fully in abutment.
4. Tensioning device according to one or more of the preceding claims, wherein at least one sensor element (16, 17; 48, 49, 68, 69) is coupled to an indicator (54, 56; 58, 60) for optically or acoustically indicating the condition of the sensor element.
5. Tensioning device according to claim 4, wherein the indicator (54, 56; 58, 60) is constructed as an LED.
6. Tensioning device according to one or more of the preceding claims, wherein the front clamping unit (30) has a hydraulic, pneumatic or motor-driven actuating arrangement (22) which is activatable only when the printing plate (14) is fully in abutment, with its register punchings (50, 52), against the mating elements (16, 17) and the setting arrangements (42, 44, 46, 47) for adjusting the printing plate (14) are in their starting position.
7. Tensioning device according to claim 6, wherein the clamping operation is interrupted as soon as the printing plate (14) is no longer fully in abutment, with its register punchings (50, 52), against the mating elements (16, 17).

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