EP0195848B1 - Device for attaching and registering printing plates to printing cylinders of lithographic machines for offset printing - Google Patents

Description

The present invention relates to an attachment device for attaching the printing plates to the printing cylinders of offset planographic printing presses, the printing cylinder having two opposing tensioning rails in a cylinder pit and mechanical stop probes connected to a light-emitting diode and connected to a voltage source being provided interact in the recesses provided in the pressure plate.

As is known per se, in the case of offset flat printing, the quality of the colored prints depends, among other things, on the flawless placement of the printing plates for the individual colors on the associated cylinder.

In practice, an inaccurate attachment of even a single one of the printing plates provided can, in practice, be all processing phases carried out before the printing phase, e.g. the photographic selection of the images, the assembly of the texts and the selected positives on the astralon, the assembly pair on the printing plate etc. impair with subsequent serious economic effects and loss of time.

From DE-A-3 000 576 a device for register-accurate clamping of flexible printing plates on the plate cylinder of a printing press by means of clamping rails arranged in a pit of the plate cylinder is known. One end of the plate can be clamped onto the clamping rails by clamping rails. In order to achieve the exact position of the pressure plate in relation to the tensioning rail, a register pin in the tensioning rail engages in a recess 9 obtained in the register in the pressure plate. The register-precise clamping of the printing plate is then carried out by determining the position of the tensioning rail relative to the plate cylinder. For this purpose, the tensioning rails can be moved approximately in the circumferential direction of the cylinder by means of tensioning screws which can be screwed into them and are supported on a wall of the plate cylinder pit. In order to compensate for disadvantageous wear effects on the tensioning screws, DE-A-3 000 576 enables the positioning rail to be adjusted from the zero position and to be readjusted with the proposed positioning device. The positioning device - consists of a measuring device measuring the distance between a reference surface of the cylinder pit and the tensioning rail, a display device indicating the zero position of the tensioning rail and an adjusting device adjusting the zero position with a stylus.

The disadvantage of this device is that the register pin for the pressure plate is attached directly to the movable clamping rail. The printing plate is then clamped by moving the clamping rail carrying the register pin, so that the register pin itself is moved. This can severely affect the alignment of the printing plates, so that compliance with the printing plate orientation differs depending on the clamping. Due to the fact that the printing plate is positioned in register on the movable clamping rail, an exact lateral and extensive positioning of the clamping rail itself with respect to the plate cylinder is additionally required. The alignment process is lengthy and in itself not perfect. The device according to DE-A-3 000 576 also requires a large number of mechanical and electrical individual parts and is also complex.

DE-A-3 325 583 shows a stop system for printing plates, in particular for printing plate punches, the problem to be solved is to improve the stop system in such a way that a special design of the contact pins for receiving mechanical contactors can be omitted. For this purpose, the contact pins themselves are designed as electrical contactors. DE-A-3 325 583 does not contain any suggestion to include a signaling element in the stop pin itself. FIG. 2 of this document also shows that the proposed stop pin device requires several individual parts and a complex switching control.

The present invention has for its object to provide an attachment device for attaching the printing plates to the printing cylinder of offset planographic printing presses, which is able to carry out the attachment process of the printing plates in a simple, fast and extremely reliable manner, whereby the operator is provided with perfect, clear evidence of the accuracy of the attachment process carried out.

The above-mentioned object is achieved according to the invention by the features of the characterizing part of claim 1.

According to the invention, three mutually independent stop probes are provided. Each stop probe has its own light emitting diode. Each individual light-emitting diode only lights up when a correct relative position of the printing plate has been reached at each individual point. The stop probes thus work independently of one another. This ensures that the printing plate is always properly positioned, even if the recesses in the printing plate are deformed or enlarged.

Further features can be found in the subclaims.

With an attachment device according to the invention. A number of important advantages are achieved by specifying the exact positioning of the printing plate on the printing cylinder.

A first advantage is a significant reduction in the time required to start up the offset printing presses. This is important because of the color printing The process on these printing machines is usually carried out with four colors and therefore four printing cylinders or printing plates are required. It should be emphasized that such a time reduction can be achieved for every cylinder.

Another important advantage can be seen in the significant reduction in the printing plate deformations achieved, since the printing plates can be attached to the printing cylinders practically without any risk of twisting. Another important advantage of the attachment device according to the invention is that any possibility of deformation is avoided or eliminated which can be traced back to subsequent rough readjustments of the pressure plate which are carried out by actuating the clamping screws of the pressure plate clamping jaws. Of course, during a reprinting process, the best possible preparation process is achieved in a shorter time.

Another advantage is also a dramatic reduction in the amount of ejection material or paper that arises when the printing press is started up. Because the exact color overlay when commissioning the printing. machine can be reached in a shorter time, it is no longer necessary to work with tests as in the known attachment systems.

Due to the confirmation of the precise printing plate positioning achieved by the light signaling, the attachment devices according to the invention can also be handled with extreme simplicity and effectiveness. The effectiveness is based on safe contact between the rectilinear stop sides, i.e. the visual collimation principle is used.

The design of the stop and signal units according to the invention makes it possible to equip existing pressure cylinders with the same.

Further advantages and details of the attachment device according to the invention for attaching the printing plates to the printing cylinders of offset planographic printing machines can be found in the following description with reference to the accompanying drawings, which represent a preferred embodiment given as an example.

• Fig. 1 eine perspektivische Ansicht eines mit der erfindungsgemaessen Ansetzvorrichtung zum Ansetzen der Druckplatte versehenen Druckzylinders;
• Fig. 2 eine Teildraufsicht in groesserem Massstab des Druckzylinders von Fig. 1 im Bereich der Druckplattenspannbacken;
• Fig. 3 eine Schaltungsanordnung der erfindungsgemaessen Anschlag- und Signaleinheiten, und
• Fig. 4 ein Detail in groesserem Massstab einer erfindungsgemaessen Anschlag- und Signaleinheit.

Show it:

• 1 is a perspective view of a printing cylinder provided with the attachment device according to the invention for attaching the printing plate;
• FIG. 2 is a partial plan view on a larger scale of the printing cylinder from FIG. 1 in the area of the printing plate clamping jaws;
• 3 shows a circuit arrangement of the stop and signal units according to the invention, and
• 4 shows a detail on a larger scale of a stop and signal unit according to the invention.

In the different figures, the same parts have the same reference numerals. 1 designates a printing cylinder for an offset planographic printing machine, not shown, in which each printing cylinder 1 carries its own printing plate, designated 2. The printing cylinder 1 has, in a manner known per se, a flattening 3 in which the two printing plate clamping jaws 4, 5, which serve to tension or block the printing plate 2 in the region of their two end margins, are received or held. Such pressure plate clamping jaws, designed as opposing strip sections, are known per se and are therefore not described in detail.

The attachment device according to the invention in each case consists of a mechanical stop probe 6 which is designed as a block and has a square cross section in the present example. In the block of the stop probe 6, which acts as a touch probe, a receptacle opening is provided which serves to receive a light-emitting diode or LED 8, the diode connection ends 8a, 8b of which are switched on in a circuit described in more detail below. The stop probe 6 is firmly connected to the support plate 9 provided with openings 10, the latter serving to fasten the stop probe 6 in the body of the pressure cylinder 1.

The mechanical stop probe 6 and the associated LED 8 each form a stop and signal unit 11. In the example shown, three stop and signal units 11 are used, which are arranged along an axis-parallel line of the printing cylinder 1, namely in the vicinity of the pressure plate clamping jaw 4. With 12 in the pressure plate 2 worked recesses are designated, the fit between the latter and the mechanical. Stop probes 6 can be seen in particular from FIG. 2. The two lateral signal units 11 are used to control a circumferential contact to fire the respectively assigned LED 8, whereas the middle signal unit 11 provides for their LED 8 to be fired when touching the side. In the case of the mechanical stop probes 6 and also the fitting recesses 12, mutually interacting sides are provided which have a straight course. These pages are labeled 6a and 12a. The central signal unit 11 provided with the side cooperating sides 6b and 12b therefore has the task of ensuring the lateral alignment, the fitting recess having a greater axial length than the block and a greater width than the width of the latter. The circuit arrangement or circuit provided for the signal units 11 contains a voltage source 13, a resistor 14 for limiting the operating current and a switch 15. In the example shown, the electrical components mentioned are connected in series with one another, the circuit being closed via the body of the printing cylinder 1 is. In the case of a voltage source in the form of a battery with 6 or 9 V, the resistance value of the resistor 14 can be approximately 1 k 0. The stop probes 6 are made of ground steel according to ISO / h5 standards and have a cross section that is smaller than the cross section of the fitting recess 12 provided in the pressure plate 2, one side of the stop probe 6 as a reference plane for the edge of the pressure plate fitting recess, as above mentions, serves. The stop probe 6 is of course mounted in an electrically insulated manner in the pressure cylinder 1.

With the attachment device according to the invention or with the signal units 11 according to the invention, the precise attachment is achieved by forming an engagement contact between the longitudinal and transverse sides 12a / 12b of the fitting recesses 12 and the adjacent sides 6a / 6b of the stop probes 6 by the ignition of the assigned LED diodes 8 signaled immediately. Because of this diode ignition, which signals the exact positioning of the pressure plate 2 and is maintained during the subsequent clamping phase of the pressure plate 2 by means of the tensioning rail 4, the operator can proceed not only in a simpler manner, but above all in a faster and more secure manner. In order to keep the consumption of electrical energy as low as possible, the LEDs 8 are switched off by the switch 15 after the attachment process has taken place. The switch 15 is then closed only for the subsequent preparation phase for a new printing plate.

In practice, all individual parts can be replaced by other technically and / or functionally equivalent parts.

The LEDs could e.g. through further electrical signaling components, e.g. Indicator lights, magnetic or acoustic indicators, etc. are replaced. The dimensions, the geometrical designs of the block-like stop probes as well as the openings in the pressure plates, the number of signal units and furthermore the circuit components can be freely selected.

Claims (3)

1. Device for attaching printing plates to printing cylinders of lithographic machines for offset printing, the printing cylinder having in a cylinder gap two tension bars lying opposite one another and mechanical stop probes connected to a light emitting diode and to a voltage source being provided, said stop probes cooperating with fitting recesses provided in the printing plate, characterized by the combination of the following features:

a) there are provided three mechanical stop probes (6) which are mounted directly on the printing cylinder (1) along an edge (parallel to the axis) of the cylinder gap (3), and designed as parallelepiped blocks which are electrically insulated with respect to the printing cylinder (1),

(b) each stop probe (6) has a receiving locating opening (7) for receiving a light emitting diode (8) and forms a signal unit (11) with the latter, it being possible to close an electrical circuit via the voltage source (13), the blocks and the printing plate (2), the three signal units (11) being connected in parallel in said circuit.

2. Attachment device according to Claim 1, characterized in that each stop probe (6) is permanently connected to a carrier plate (9) which is provided with two elongated hole-like through- openings (10) which are open towards an outer side of the mentioned carrier plate (9).

3. Attachment device according to Claim 1, characterized in that the three stop probes (6) are permanently connected to the one end face of the cylinder gap (3), receiving the tension bars (4, 5), of the printing cylinder (1).

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