EP0582903A1 - Device for checking the registered positioning of a printing plate on the plate cylinder of printing machines, in particular offset sheet printing machines - Google Patents

Abstract

A device for checking the in-register positioning of a printing plate on the plate cylinder (1) of printing machines has, in the tension rail (3, 4) for receiving this printing plate, measuring sensors, by means of which the in-register position can be detected in the form of electrically interrogatable signals. So that these signals can be interrogated directly by machine control, for example in conjunction with an automatic or manual printing-plate feed, contact faces are mounted in the region of the tension rail. These contact faces are assigned sensing heads (29, 30) which are mounted on the frame movably relative to the plate cylinder and which can be pressed against these very contact faces after a corresponding angular positioning of the plate cylinder. During the introduction of a new printing plate, therefore, an evaluation unit for receiving the signals is connected to the measuring sensors. <IMAGE>

Description

The invention relates to a device for monitoring the registration of a printing plate on the plate cylinder of printing machines in accordance with the preamble of claim 1.

In sheetfed offset printing machines, the printing plates for the differently colored partial images are each mounted on a plate cylinder. Each printing plate is fastened (clamped) with an edge assigned to the start of printing in a clamping rail and then placed around the outer circumference of the cylinder until its rear edge, which is assigned to the printing end, can in turn be fastened in a clamping rail. The pressure plate is then tensioned.

Since the prints should have a very high accuracy of fit right from the start in order to reduce waste, the individual printing plates must be very carefully, i.e. be inserted in register with their respective front edge in the corresponding pressure start clamping rail. For this purpose, the pressure plates often have recesses in the form of punched-outs on the edge assigned to the start of printing, which cooperate with corresponding dowel pins in the tensioning rails. However, there is only a perfect fit when the respective printing plate leading edge is applied exactly to such devices.

From EP 0 075 900 B1 a device for checking the register-accurate clamping of printing plates is known, in which feeler pins are arranged in the pressure start clamping rail which the register-correct position of the printing plate can be determined by touching the printing plate edge with the feeler pins. This previously known device provides in particular a display device arranged inside the cylinder pit, by means of which the pressure plate to be adjusted via an adjustable front tensioning rail can be specifically adjusted. From EP 0 195 848 B1 a device with a similar effect is known, in which blocks which are electrically insulated from the pressure cylinder are provided as stop probes and which cooperate with corresponding punchings in the pressure plate. The integrated light-emitting diodes, the power supply of which is produced when the pressure plate or the edge of the fitting perforation touches the electrically insulated probes, make it possible to determine whether the pressure plate has been aligned in register.

However, these previously known devices briefly outlined above are only suitable for manual printing plate mounting, since the operator has to read the corresponding optically given signals directly in the cylinder pit or on the sensors themselves while inserting the printing plate or aligning the printing plate.

DD 69 382 PS discloses dowel pins which are electrically insulated from the plate cylinder and which, when they come into contact with the pressure plate or an edge of the pressure plate, result in an electrically closed contact. This closed electrical contact in this way can be queried by the printing press control system via a measured value transmitter. Such a device could thus also be used for automated printing plate feed. The disadvantage here, however, is that a measured value transmitter, for example consisting of a slip ring and current collector, must be provided, which results in additional susceptibility to faults.

A device for automatically changing printing plates, in which the above-mentioned measuring arrangement could be used, is known from DE 39 40 796 C2. Here is a printing plate from a Storage chamber inserted into a clamping rail of a plate cylinder via transport rollers, for which purpose this was previously moved into a specific angular position. A position detector not specified in this document determines whether the pressure plate is correctly positioned within the tensioning rail assigned to the start of printing, whereupon, if this is the case, the devices for closing the tensioning rail (clamp) are actuated.

A device, which can be referred to as a printing plate insertion aid, for feeding printing plates into the printing start clamping rail, in which a type of system table is placed on the correspondingly positioned plate cylinder, is known from JP-A 62-22 1541. This system table has pivotable dowel pins, which interact with corresponding punched-out areas of the pressure plate. If these are swiveled away from the conveying path of the pressure plate, the pre-positioned pressure plate falls into the open pressure start clamping rail. According to this document, however, there is no provision for an electrical interrogation of the correct installation of the pressure plate within the rail.

The object of the present invention is therefore to expand a device for checking the registration-correct installation of a printing plate in accordance with the preamble of claim 1, so that a position signal is also available outside the plate cylinder without great expenditure on construction. The correct position of a printing plate should be ascertainable.

This object is achieved by the characterizing features of the first claim. Further developments of the invention result from the subclaims.

According to the invention it is provided that the signal pick-up of the sensor or sensors within the clamping rail takes place on the frame side movable against the plate cylinder probe heads, which during the insertion of the pressure plate in the clamping rail For example, contact surfaces located on the tensioning rail can be pressed. The electrical signal of the sensor or sensors therefore does not have to be looped out of the plate cylinder via a measured value transmitter, but is taken off (automatically or by hand) with the device according to the invention during the process of inserting the plate.

The probes are connected to an evaluation unit, by means of which the signal picked up via the contact surfaces can be evaluated with regard to the correct position of the pressure plate when it is inserted into the tensioning rail. If this is the case, the correct position of the printing plate can either be indicated optically and / or a signal can be given to a machine control, which, for example, causes an automatic clamping of the printing plate (motor acting on the plate cylinder on the frame side or integrated in the plate cylinder).

In the simplest case, the sensors inside the tensioning rail can be dowel pins which are partially or totally electrically insulated from the tensioning rail and interact with corresponding punched-out areas on the pressure plate front edge. If the dowel pins are completely or only partially insulated from the potential of the plate cylinder, touching the edge of the pressure plate in the area of the cut-out results in a conductive connection between the plate cylinder and dowel pin (short circuit), which after tapping via the probe and contact surface in an evaluation unit as the correct position of the pressure plate can be evaluated within the tensioning rail.

With such a design of the sensors as dowel pins, the contact surface can be attached directly to the front end of the dowel pin, which protrudes from the tensioning rail. However, it is also possible to glue special foils or the like, which are then the contact surfaces, to the self-electrically insulating tensioning rail. Of course, other devices for using the inventive devices also come as sensors Device in question. The sensors can also be integrated in the tensioning rail and can be designed, for example, as buttons or sensors.

In the case of a plurality of sensors, in particular dowel pins, which are spaced apart from one another in the clamping rail in the axial direction of the plate cylinder, a plurality of probes are preferably provided which, after corresponding plate cylinder positioning (insertion of pressure plate), can be pressed onto the contact surfaces assigned to the sensors. With such an arrangement, each individual sensor can thus be queried by an evaluation unit, so that the location of the incorrect system can be inferred. Of course, it is also possible to link the signals of the several sensors already in the tensioning rail or in the plate cylinder in terms of circuitry in the manner of a logical "and" and thus to arrange only one contact area on the tensioning rail. Accordingly, only one probe is required to tap this signal.

If the sensors are dowel pins that are electrically insulated from the plate cylinder and are queried by an evaluation unit to determine the correct position of the pressure plate, the sensors are purely passive elements. A power supply inside the plate cylinder is therefore not necessary. If the sensors are designed as active sensors or the like, a power supply for operating them in the plate cylinder would have to be provided accordingly. This could also be formed by appropriate probes and contact surfaces, but also by a battery or rechargeable battery to be provided in the plate cylinder, which is possible in particular in the case of sensors with low power consumption.

According to the invention, the probe heads are mounted on the frame side and are movable relative to the plate cylinder and can be adjusted to the corresponding contact surfaces in the area of the tensioning rail after the plate cylinder has been correspondingly positioned in an angular manner. The or the For example, probes can be suspended in a linearly movable manner. According to a preferred embodiment of the invention, however, the probes are pivotable about a pivot axis running parallel to the axis of the plate cylinder and in particular attached to a movably displaceable protection in front of the printing unit, and can be pressed against the contact surfaces by an actuating means that becomes effective when compressed air is applied.

If two dowel pins with electrical insulation from the tensioning rail and plate cylinder are provided, which are to be connected to the evaluation unit via two probes for signal evaluation, these probes can be attached at the same axial spacing on a rail which is suspended parallel to the axis of the plate cylinder on a swivel axis . To insert the pressure plate, this rail is placed with the probes on the clamping rail of the plate cylinder. The invention is very advantageous if the probes are attached to a specially designed rail which extends over the format width of the plate cylinder and is to be made in this way on the outer circumference of the plate cylinder in the area of the start of printing, so that this leads to an insertion surface located towards the plate cylinder The front edge of the pressure plate can be inserted into the open detection area of the tensioning rail. Such a rail thus results in a funnel-shaped enlargement of the open detection area of the tensioning rail, one surface being formed by the rail and the other surface being part of the outer circumference of the plate cylinder in the area of the start of printing. Due to the probes placed on the electrically insulated dowel pins, for example, it can now be determined directly during the insertion of the pressure plate into the detection area whether it is correctly seated on the dowel pins.

On the rail that can be adjusted on the plate cylinder or directly on the probe heads, in particular, adjustable stops can be provided, via which the probe heads or the rail on the clamping rail directly or on the plate cylinder (bearer ring) are supported so that the force of pressing the probes on the contact surfaces can be limited. In particular, the probes are designed as tips which can be pressed under spring force onto the contact surfaces, as are used, for example, in oscillographs. The probes can thus be designed only as a resilient contact or else with electronic components matched to impedance signal voltage tap.

The invention is very advantageous if the probe heads are attached to a device which can be adjusted to the plate cylinder and by means of which an automatic or manually supported feeding of a printing plate into the tensioning rail takes place. In particular, this can be the case on a printing plate cassette which is pivotably mounted with respect to the plate cylinder, as is known from the prior art.

Fig. 1

einen Schnitt durch ein Druckwerk mit einer bevorzugten Aufhängung der Tastköpfe,

Fig. 2

eine Ansicht der Aufhängung der Tastköpfe gemäß Fig. 1 über die Formatbreite,

Fig. 3

die Ansicht der Spannschiene von oben mit den erfindungsgemäßen Paßstiften und

Fig. 4

ein Paßstift gemäß Fig. 3 im Detail.

Furthermore, an embodiment of the invention is explained with reference to the drawings. It shows:

Fig. 1

a section through a printing unit with a preferred suspension of the probes,

Fig. 2

2 shows a view of the suspension of the probes according to FIG. 1 over the format width,

Fig. 3

the view of the tensioning rail from above with the dowel pins and

Fig. 4

a dowel pin according to FIG. 3 in detail.

Fig. 1 shows in section the part of a printing unit of a sheet-fed offset printing press in series. Between two side frame walls of this printing unit, a plate cylinder 1 is mounted, which in a cylinder pit 2 has a tensioning rail 3, 4 assigned to the beginning of printing DA and the end of printing DE.

In front of the printing unit with the plate cylinder 1 and the blanket cylinder 5 arranged underneath, a protection 6 is slidably arranged over a guide rail attached to a side frame wall of the printing unit, which is in a basic position according to FIG. 1 during printing operation. The arrow can be pushed up according to the arrow.

In an upper part of the protection 6, a pivot axis 7 is preferably attached as a swivel joint, on which a sheet metal profile 8 is suspended. The sheet profile 8 has a slight curvature and has the format width of the plate cylinder 1. At the pivotable end of the sheet profile 8, a rail 9 is attached or generated by appropriate profiling. This can be turned on or off from the outer circumference of the plate cylinder 1 (FIG. 1). On an upper cross member 10 of the protection 6, a guide plate 11 is also attached, which extends almost down to the upper edge of the sheet profile 8. Opposite the guide plate 11, a guide plate 12 is also attached to the guard 6, which has two bent legs. Brushes 13 are attached to the concave inside of the sheet profile for the gentle transport of a pressure plate to be fed, so that a new pressure plate to be fed in when the sheet profile 8 is pivoted and thus the rail 9 is set correspondingly to the angular positioning of the plate cylinder 1 (see FIG. 1) directly in the opened one Detection area 17 of the front clamping rail 3 can be introduced. The pressure plate is fed manually through the slot in the two guide plates 11 and 12 (FIG. 1). Brushes 14 can also be arranged on the guide plate 11. When the sheet profile 8 is turned on, the side of the rail 9 facing the plate cylinder 1 thus results in an insertion surface 15, thus a funnel-shaped enlarged area of the detection area 17. The brushes 13 in the sheet profile 8 are set deeper so that the guide path of the pressure plate directly over the brushes opens into the plane of the insertion surface 15.

This particularly advantageous type of suspension for the pivotable probes ensures that the protection 6 does not have to be pushed up to introduce a new pressure plate, that is to say it can remain in the position shown in FIG. 1. A pneumatic cylinder 19 acts on an angle lever 20 together with driving pins for pivoting the sheet-metal profile 8 and the rail 9 in and out (on one or both side frame walls of the printing unit). The sheet metal profile 8 together with the rail 9 is only pivoted for insertion of a new pressure plate into the detection area 17 of the clamping rail 3 and swiveled down again as soon as the new pressure plate is clamped in the clamping rail 3, that is to say attached. Then the mounting of the new printing plate on the plate cylinder 1 begins by slowly rotating the plate cylinder 1 in the direction of the arrow (FIG. 1).

Two dowel pins 21, 22 are arranged axially spaced from one another in the clamping rail 3 associated with the start of pressure DA in a manner known per se (FIG. 1). Fig. 3 shows this arrangement of the dowel pins 21, 22 in the clamping rail 3 from above. 1 and 3, the dowel pins 21, 22 are attached in a lower part of the clamping rail 3 and extend through corresponding recesses 23 through the upper part of the clamping rail 3, and are thus accessible from outside the plate cylinder 1. In this embodiment of a tensioning rail 3, chosen only as an example, the lower part is movable relative to the upper part, the detection area 17 is thus closed by moving the lower part relative to the upper part of the tensioning rail 3 (FIG. 1).

In Fig. 3 the front edge of a pressure plate D is shown, two punchings 24, 25 are made in this front edge according to the design of the dowel pins 21, 22 and their axial spacing, which with the corresponding dowel pins 21, 22 when the pressure plate D is in correct contact the tensioning rail 3 correspond.

4, a dowel pin 21, 22 is shown in detail. According to this embodiment, the dowel pin 21, 22 is in two parts executed, the one part consists of the dowel pin 21, 22 with a slot 26 inserted therein on the end face. In this slot 26, a filler 27 is inserted as a second part in an electrically insulated manner, which completes the outer contour missing through the slot 26 in the alignment pin 21, 22. An end face of this filler 27 thus forms the contact surface 28. According to the embodiment of FIG. 4, both dowel pins 21, 22 are formed in the tensioning rail 3 according to FIG. 3. It is provided that a dowel 21 has the slot 26 in the circumferential direction of the plate cylinder 1 and a dowel 22 has the slot 26, for example, inclined at 45 ° to the circumferential direction of the plate cylinder. Due to the electrically insulated connection of dowel pin 21, 22 and the corresponding filler pieces 27, the register-correct system can be checked by touching the edge of the punched-out portions 24, 25 of the pressure plate D. If the edges of the cutouts 24, 25 fit snugly against the outer contour of the dowel pin 21, 22, the filler pieces 27 are connected to one another in an electrically conductive manner with respect to the dowel pins 21, 22. Since a slot 26 and thus the corresponding filler 27 of a dowel pin 21 is inclined to the circumferential direction of the plate cylinder 1 (FIG. 3), a positional error of the printing plate D in the oblique or side register direction can thus be determined.

Corresponding to the axial spacing of the dowel pins 21, 22, two probes 29, 30 are attached to the rail 9 of the sheet metal profile 8, which press the contact surfaces 28 of the dowel pins 21, 22 directly in the pivoted-in state of the rail 9 (pneumatic cylinder 19 activated) (FIG. 1 and 2). It can thus be determined in an evaluation unit (not shown) whether the filler pieces 27 are connected to one another in an electrically conductive manner with respect to the dowel pins 21, 22 due to the correct seating of the pressure plate D. In a simple embodiment of the invention, it can thus be determined whether the potential of the filler pieces 27 has been pulled down to the electrical potential of the plate cylinder 1 by this short circuit. An electrical conductivity test can also be carried out by the probe heads 29, 30, for example by a current flow is detected. Both direct current and alternating current can be used in such a query. A corresponding threshold value setting in conjunction with adjustable sensitivities also allows changes in the conductivity of the filler pieces 27 with respect to the dowel pins 21, 22 due to the influence of dampening solution or the like to be taken into account. The probe heads 29, 30 and their contacts are of course electrically insulated from the plate cylinder 1.

Fig. 2 shows a view from the printing unit, the protection against the printing unit cylinders 6 with the sheet profile 8 and the rail 9 attached to it. Also shown is the guide plate 11 attached to the crossmember 10 and that on the guide plate 11 and the concave inside of the sheet profile 8 attached brushes 13, 14. The sheet profile 8 and the rail 9 are mounted about a pivot axis 7 which extends between two frame parts of the protection 6. At both ends of the rail 9, two stops 16 are attached, which in particular can be adjustable and, in the exemplary embodiment shown here, serve to engage the rail 9 in such a way on the plate cylinder 1 that there is a defined gap between the insertion surface 15 and the start of pressure DA on the plate cylinder 1 results and on the other hand to avoid excessive pressure forces of the probe heads 29, 30 against the contact surfaces 28. 2, the probes 29, 30 are attached below the insertion surface 15. As already indicated above, such a suspension of the probes 29, 30 on a rail 9 providing an insertion surface 15 provides a very advantageous way of querying the sensors formed by the dowel pins 21, 22 on the one hand and on the other hand a very convenient way of inserting a new one Printing plate.

According to this exemplary embodiment of the invention, the rail 9 and the sheet metal profile 8 remain in position until the pressure plate is inserted into the detection area 17 of the tensioning rail 3 and this detection area 17 is closed after the pressure plate has been correctly positioned. Closing the tensioning rail 3 or of the detection area 17 takes place only when correct positioning of the printing plate has been ascertained via the probe heads 29, 30 which interrogate the alignment pins 21, 22. If the pressure plate was clamped, the rail 9 pivots back into its position shown in dashed lines in FIG. 1 and the pressure plate can be pulled up completely.

Reference list

1

Plate cylinder

2nd

Cylinder pit

3rd

Tensioning rail (start of printing)

4th

Tensioning rail (printing end)

5

Blanket cylinder

6

protection

7

Swivel axis

8th

Sheet profile

9

rail

10th

traverse

11

Guide plate

12th

Guide plate

13

to brush

14

to brush

15

Insertion surface

16

attack

17th

Detection area

18th

19th

Pneumatic cylinder

20th

Angle lever

21

Dowel pin

22

Dowel pin

23

Recess

24th

Punching

25th

Punching

26

slot

27

Filling piece

28

Contact area

29

Probe

30th

Probe

THERE

Start of printing

DE

End of printing

D

printing plate

Claims (15)

Device for checking the correct registration of a printing plate on the plate cylinder of printing presses, in particular sheetfed offset printing presses, in which the plate cylinder in a cylinder pit has a clamping rail for receiving the printing plate edge assigned to the start of printing and in the clamping rails at least one electrically interrogable sensor is provided, from which a signal can be taken is when the pressure plate is oriented in register with respect to the tensioning rail,
characterized by
that in the area of the tensioning rail (3) for tapping the signals of the sensor or sensors (21, 22), at least one contact surface (28) providing the measuring signal is assigned to them, that according to the number of contact surfaces (28) provided, at least one frame-side, opposite the plate cylinder (1) has a movably mounted probe head (29, 30) so that each probe head (29, 30) can be set against a contact surface (28) when the plate cylinder (1) is inserted into a 3) the intended angular position has been moved. Device according to claim 1,
characterized by
that if there are several sensors (21, 22) spaced apart from one another in the axial direction of the plate cylinder (1), a contact surface (28) and a movably mounted probe head (29, 30) are provided in the tensioning rail (3). Device according to claim 1 or 2,
characterized by
that when the sensor or sensors are configured as dowel pins (21, 22) arranged in the tensioning rail (3), which are attached in whole or in part electrically insulated from the latter, the contact surfaces (28) on the ends of the tensioning rail (3) projecting from the end Dowel pins (21, 22) are arranged. Device according to claim 3,
characterized by
that the dowel pins (21, 22) in the tensioning rail (3) consist of two electrically insulated parts (21, 22, 27), the part (21, 22) connected to the tensioning rail being electrically at the potential of the plate cylinder (1 ) and the second part (27) forms a contact surface (28) at the front end of the dowel pin (21, 22). Device according to claim 4,
characterized by
that the part (21, 22) of the dowel pin (21, 22) connected to the tensioning rail (3) has a slot (26) introduced from its end face, into which a filler piece (27) is let in so as to be electrically insulated, so that a punched-out section is provided (24, 25) with correct position of the pressure plate results in an electrically conductive connection between filler (27) and dowel pin (21, 22). Device according to claim 5,
characterized by
that at least two dowel pins (21, 22) are arranged axially spaced apart from one another in the tensioning rail (3) and one dowel pin (21) the slot (26) in the circumferential direction of the plate cylinder (1) and a second dowel pin (22) the slot (26) in a direction inclined to the circumferential direction of the plate cylinder (1). Device according to one of claims 1 to 6,
characterized by
that the probe head or heads (29, 30) are pivotally suspended on a pivot axis (7) running parallel to the axis of the plate cylinder (1). Device according to claim 7,
characterized by
that the pivot axis (7) for the one or more probes (29, 30) is attached to a protection (6) arranged in front of the printing unit cylinders, which can be displaced in particular via a linear guide attached to a side frame wall of the printing unit. Device according to claim 7 or 8,
characterized by
that with at least two provided probes (29, 30), these are arranged on a rail (9) which can be adjusted to the plate cylinder (1) or the tensioning rail (3) and runs parallel to the pivot axis (7). Device according to claim 9,
characterized by
that the rail (9) has stops at both ends, with which it can be supported on the bearer rings of the plate cylinder (1). Device according to claim 9 or 10,
characterized by
that the probe heads (29, 30) are arranged on a rail (9) which extends over the format width of the plate cylinder (1) and can be adjusted in such a way on the outer circumference of the plate cylinder (1) in the region of the start of printing (DA) that an insertion surface (15) of the rail (9) facing the plate cylinder (1), the front edge of a pressure plate can be inserted into the open detection area (17) of the tensioning rail (3). Device according to one of the preceding claims,
characterized by
that the probe heads (29, 30) are attached to a device which can be set on the plate cylinder (1) and via which a pressure plate can be inserted into the open detection area (17) of the tensioning rail (1). Device according to one of the preceding claims,
characterized by
that the probes (29, 30) have spring-loaded tips on the contact surface (28). Device according to one of the preceding claims,
characterized by
that positioning means which become effective when the compressed air is acted upon are provided for positioning the probes (29, 30) on the contact surfaces (28). Device according to one of the preceding claims,
characterized by
that the probes (29, 30) acting on the plate cylinder (1) or the tensioning rail (3) and in particular adjustable stops (16) are assigned, by means of which the pressing force of the probes (29, 30) against the contact surface (28) can be limited .

Images