GB2032321A

GB2032321A - Automatic punching apparatus for the punching of printing plates, especially for offset-roller rotary machines

Info

Publication number: GB2032321A
Application number: GB7932541A
Authority: GB
Original assignee: METJE H
Current assignee: METJE H
Priority date: 1978-09-23
Filing date: 1979-09-19
Publication date: 1980-05-08
Also published as: DE2841460B2; GB2032321B; DE2841460A1; FR2436678B1; FR2436678A1; DE2841460C3

Abstract

Punching apparatus for punching fitting holes in printing plates for use in offset-roller rotary printing comprises a supporting table 3, at least two punches, one or more pairs of rectangular lateral stop pins 8 arranged at some distance apart from each other, whereby the line connecting the contact surfaces of the or each pair of stop pins extends at right-angles to the line connecting the transverse sides of the punches, and one or more depth stop pins (7) located behind the punches, the stop pins (7), 8 having, adjacent their contact surfaces 12, contact devices 9 which are arranged, when a printing plate engages the contact surfaces of the stop pins, to actuate switches 11 controlling operation of the punches, so that the punches are only actuated when the printing plate is correctly aligned with the stop pins. The stop pins are preferably retractable. <IMAGE>

Description

SPECIFICATION Automatic punching apparatus for the punching of printing plates, especially for offset-roller rotary machines This invention relates to punching apparatus for punching fitting holes in printing plates or associated mounting foils, especially for use in offset-roller rotary printing, and of the kind comprising a supporting table, at least two punches, two rectangular lateral stop pins arranged at some distance apart from each other, whereby the line connecting the contact surfaces of the stop pins extends at rightangles to the line connecting the transverse sides of the punches, and at least one depth stop pin located behind the punches.

From German Offenlegungsschrift No. 2,604,874 a punching apparatus is known which has on its lateral side two rectangular stop pins arranged some distance apart from each other, the distance between their centre lines corresponding to the circumference of a platen, reduced by the width of its clamping channel. These pins are arranged in such a way that their contact surfaces lie on a connecting line which extends at right-angles to a line connecting the aligned punches. Moreover, this apparatus has a depth stop behind the punches.With this punching apparatus, however, there is difficulty in determining whether the printing plate to be punched rests properly against the lateral and depth stop pins during the punching operation, which is necessary in order to guarantee on the one hand reproducible punching positions and on the other hand the correct alignment of the printing plate on the punching apparatus.

It is an object of the present invention to improve the kind of punching apparatus previously mentioned so that before and during punching perfect alignment of the printing plate is guaranteed so that fully automatic punching may be carried out. In addition the punching apparatus may be arranged to be suitable for all current types of printing plate.

This is achieved according to the invention in that the lateral and depth stop pins have, adjacent their contact surfaces, contact devices which are arranged, when a printing plate engages the contact surfaces of the stop pins, to actuate switch means controlling operation of the punches. It is advantageous if the lateral and depth stop pins are retractable in the supporting table, and also if several pairs of lateral pins and several depth stop pins are provided in a staggered formation. Since the contact devices for indicating the installation of the printing plate are mounted in the pins, the pins may be arranged in the supporting table so as to be retractable without the precision being impaired.

Apparatus according to the invention may be of compact and mchanically sturdy construction in addition to guaranteeing that contacting errors are avoided. Where several depth stop pins and also several pairs of lateral stop pins are provided in the supporting table in a staggered formation, the apparatus is suitable for punching all types of print plates. To this end it is of course necessary that the stop pins be arranged in relation to each other according to the printing format of the various types of plates.

In a further development of the invention, the contact device comprises a contact lever pivotally mounted on its associated pin, the lower end of the contact lever lying against a lever arm which is under spring pressure of an actuator of the switch means and can be pivoted at one end. By this means the contact lever does not act directly on the actuator of the switch means but acts through the lever arm, which is therefore advantageous since by this means only small pressure forces are necessary and, in addition, operating movement is increased, whereby there exists a better range of adjustment of the exact closing point of the switch means. It is appropriate to use, as the switch means, a mechanical microswitch, which is distinguished by its robustness.

Alternatively, of course, it is also possible to use contactless magnetic switches.

To guarantee that the punching operation is only begun when all the switch means of withe stop pins are closed, the switch means are preferably connected in series whereby initiation of the operation is prevented when a switch means is still open due to inaccurate installation of the printing plate against one of the pins.

In fully automatic punching, the printing plate is placed on the supporting table and positioned against two lateral stop pins and one depth stop pin, whereby the switch means associated with each stop pin are closed, and after the closing of all three switch means the printing plate is fixed in position and the punching effected. When this has been completed the plate is released and subsequently removed. It is advantageous for the pins to be raised and lowered pneumatically or hydraulically, the operation of the punches also being carried out pneumatically or hydraulically, so that altogether a complete pneumatic or hydraulic pressure system can be used for operating the apparatus.

The following is a more detailed description of an embodiment of the invention, reference being made to the accompanying drawings in which: Figure 1 is a perspective view of a punching apparatus according to the invention, Figures 2 to 4 are diagrammatic views of positions of the stop pins provided according to the invention before and during punching, Figures 5 and 6 are part-sectional views of the stop pins used according to the invention, together with the appropriate contacts and the housing and the printing unit, and Figure 7 is a diagram of an electric circuit for the automatic operation of the punching apparatus according to the invention.

In Figure 1 a punching apparatus according to the invention is shown. This consists of a supporting table 1 having an underframe 2 and a supporting plate 3. In the example shown, at the head end of the supporting plate 3 four punch housings 4 are arranged some distance apart from each other, in which housings are mounted rectangular punches operated by a shaft 6 to which is coupled a lever arm 5 which can be driven, for example, pneumatically or hydraulically. The transverse sides of the punches are aligned with one another and the punches are all of equal size. In the area behind the punch housings 4 of the supporting plate 3, to be more precise behind the punches mounted in the punch housings 4, depth stop pins 7 are arranged in the supporting plate 3.Several such pins 7 (two being shown in Figure 1) are arranged in a staggered formation a certain distance one behind another, so as to provide alternative depth stops. The front pins are arranged to be retractable in the supporting plate 3, so that they do not provide an obstruction when it is wished to use a rearward pin as the depth stop. The pins 7 are rectangular or square.

At one side of the supporting plate 3 there are provided pairs of rectangular lateral stop pins 8 arranged at some distance apart from each other, the two pins of each pair being aligned. The distance between the centre lines of the pins of each pair of pins corresponds to the circumference of a platen of an offset roller printing machine, reduced bythe width of a clamping channel of the platen. The line connecting the aligned punches in the punch housings 4 extends afright-angles to the line connecting the contact surfaces of each pair of lateral pins 8.

Several pairs of lateral pins 8 can appropriately be arranged in the supporting plate to provide alternative lateral stops, two such pairs being shown in Figure 1. Again, the inner pins are arranged to be retractable in the supporting plate so as not to obstruct use of an outer pair of lateral stop pins. The lowering and raising of the depth stop pins and lateral stop pins can appropriately be carried out pneumatically or hydraulically. Due to the presence of several depth stops and several lateral stops, which can be lowered or raised as desired, all current types of printing plate can be punched on the apparatus.

As can be seen in Figures 2 to 6, the depth stop pins and lateral stop pins, which are basically the same, contain contact levers 9. A micro-switch 11 is operated by each contact lever 9. The contact levers 9 are pivotally mounted in the pins 7,8 in such a way that in the open position of the micro-switch 11 the upper end of the contact lever protrudes outwardly in relation to the contact surface 12 of the pin 8 or the corresponding contact surface of the pin 7. Each contact lever9 has on its lower end a projection 13 which engages a lever arm 10 which is pivotally mounted at one end on the microswitch 11. The lever arm 10 acts on the spring-loaded operating button 14 of the micro-switch 1 To receive the contact lever 9 each pin 7, 8 has a recess 15 which is open at one side.As can be seen in Figures 5 and 6, each pin, in this case pin 8, is arranged in a double-T shaped housing 16. This housing 16 is closed by a housing plate 17. The housing 16 is fixed to the lower side of the supporting plate 3 by the upper horizontal crosspiece 18 of the housing, and the hydraulic or pneumatic cylinder 21 for lowering or raising the pin is located on the lower cross-piece 19.

The piston rod 22 of the cylinder 21 is screwed into the lower end of the pin 8. In the area of the contact lever9,the housing plate 17 has a slot 23 which is so positioned that even in the lowered position of the pin 8 free movement of the contact lever 9 is permitted. The micro-switch 11 is adjustably fixed to a support bracket 24 at the lower end of the slot 23.

Within a sidewall of the housing 16 there is a recess 25, shown dotted in Figure 6, into which extends an abutment 26 which is laterally fixed to the pin 8. This abutment 26, in conjunction with the recess 25, serves to limit the lifting movement of the pin 8.

As can be seen from Figures 2 to 4, the upper end of the contact lever 9 projects outwardly in relation to the contact surface 12 of the pin both in the lowered position of the pin 8 and in the raised position. Thus, if a printing plate 27 is pushed against the pin 8, the upper end of the contact lever 9 is pushed into the recess 15 in the pin, so that the printing plate 27 comes into contact with the contact surface 12. The contact lever 9 thereby swings about its pivot axis 28, whereby the lever arm 10 is moved in the direction of the micro-switch 11 and thereby pushes the button 14 of the micro-switch 11 to operate the latter.The micro-switch 11 is adjusted in such a way that it is operated, through the button 14, lever arm 10 and contact lever 9, when the upper end of the contact lever 9, which is in contact with the printing plate 26, is flush with the contact surface of the pin. By means of this adjustment it is guaranteed that the micro-switch is only operated when a perfect contact is achieved between the edge of the printing plate and the contact surface of the stop pin.

The above-described design of the punching apparatus according to the invention permits automatic operation of the apparatus, since it is guaranteed that punching is only carried out when the printing plate to be punched lies accurately against both the depth stop pin and the pair of lateral stop pins. The operating cycle of a punching operation will be explained in greater detail with referenceto Figure 7.It is a presuppositon for the start of the punching operation that, after the printing plate has been positioned, it lies perfectly in engagement with the depth stop pin 7 and the two lateral stop pins 8, which have been raised from the supporting table according to the type of printing plate chosen, so that the micro-switch associated with each pin is closed. in Figure 7 the pairs of contacts S1, S2, S3 rep resent the micro-switches associated with the three pins respectively. When these three contacts, which are connected in series, are closed, a relay K1 is operated and the corresponding relay contacts (also indicated by K1) are closed. The closure of relay K1 activates relay K2, which works as a timing relay.

Furthermore relay K3 is closed, which is a selflatching relay. The closure of relay K3 activates a vacuum pump which serves to produce an underpressure under the printing plate, by which means the printing plate is retained in its installation position against the pins. Moreoever, by the closing of relay K3 a first contact energises a solenoid valve for a compressed-air cylinder to operate the lever arm 5. As soon as the vacuum produced under the printing plate reaches a determined value which is adjustable in advance, for example 70%, a vacuum switch S5 closes, whereby the compressed-air cylinder for the punch is activated, so that the punch is lowered or the cylinder piston raised. Afterthe resultant punching, when the cylinder piston has reached its upper position, a contact S4 closes and the relay K5 is energised. By this means the cylinder piston is lowered, and relay K3 drops out, the relay being up to this point self-latching. Thereby the punching operation is completed. On the removal of the punched printing plate the switches S, to S3 open again.

The described punching apparatus according to the invention is therefore characterised in that fully automatic punching of printing plates of any usual type is possible, and the contacts which are present in the lateral and depth stop pins guarantee that the punching is only carried out when the printing plate lies against all three stops exactly and at the same time.

Claims

1. Punching apparatusfor punching fitting holes in printing plates or associated mounting foils for use in offset-roller rotary printing, comprising a supporting table, at least two punches, two rectangular lateral stop pins arranged at some distance apart from each other, whereby the line connecting the contact surfaces of the stop pins extends at right-angles to the line connecting the transverse sides of the punches, and at least one depth stop pin located behind the punches, the lateral and depth stop pins having, adjacent their contact surfaces, contact devices which are arranged, when a printing plate engages the contact surfaces of the stop pins, to actuate switch means controlling operation of the punches.

2. Punching apparatus according to claim 1, wherein the lateral and depth stop pins are retractable in the supporting table, and several pairs of lateral pins and several depth stop pins are provided in a staggered formation.

3. Punching apparatus according to claim 1 or claim 2, wherein each contact device comprises a contact lever pivotally mounted on its associated pin.

4. Punching apparatus according to claim 3, wherein each contact lever is formed and pivoted in such a way that when a printing plate is not in engagement with the contact surface of its associated pin the upper end of the lever protrudes from the contact surface of the pin.

5. Punching apparatus according to claim 3 or claim 4, wherein the lower end of the contact lever lies against a lever arm which is under spring pressure of an actuator of said switch means and can be pivoted about one end.

6. Punching apparatus according to any one of claims 1 to 5, wherein the lateral and depth stop pins can be raised and lowered pneumatically or hydraulically.

7. Punching apparatus according to any one of claims 1 to 6, wherein said switch means comprise a micro-switch.

8. Punching apparatus according to any one of claims 1 to 7, wherein the switch means associated with the depth stop pins and lateral stop pins are electrically connected in series.

9. Punching apparatus according to claim 2 and any claim appendant thereto, wherein the switch means of the several pairs of lateral pins and of the respective associated depth stop pins are electrically connected in parallel.

10. A method for punching printing plates or associated mounting foils for offset-roller rotary printing machines and offset arc printing machines, using punching apparatus according to any of claims 1 to 9, wherein the printing plate or mounting foil is placed on the supporting table and positioned against two lateral stop pins and one depth stop pin whereby the switch means associated with each stop pin are closed, and after the closing of all three switch means the printing plate or mounting foil is fixed in position and the punching effected, whereafterthe printing plate or mounting foil is released and subsequently removed.

11. A method according to claim 10, wherein the printing plate or mounting foil is fixed in position by under-pressure produced beneath it.

12. Amethod according to claim 11, wherein the punching operation is initiated only after a predetermined under-pressure is achieved.

13. Punching apparatus substantially as hereinbefore described with reference to the accompanying drawings.