EP0575786B1 - Device for automatically catching a broken paper web - Google Patents

Description

The present invention relates to a device for automatically catching a paper web torn during a run, which is provided with means for introducing the torn paper web into means for withdrawing the web.

The invention finds a particularly advantageous application in the field of printing and, when a paper web is torn when it is passed through an offset printing machine, prevents clogging by winding the paper web onto a blanket cylinder of the last printing unit.

Offset printing units usually consist of four parallel cylinders, which are in surface contact with one another via one of their surface lines. The printed paper web runs between the two central cylinders, the so-called "blanket cylinders", which are surrounded by a linen blanket which is covered with an elastomeric material. Since the printing ink used to print the paper web is generally very viscous, the printed web tends to stick to the damp blanket cylinders. When the printing press is in operation, the paper web is tensioned using rollers. These roles are e.g. the feed rollers arranged in front of the printing units and the cooling rollers arranged behind the printing units and the dryer. The tensioned paper web is thus released from the damp blanket cylinders, this detachment being interrupted abruptly in the event of the web tearing.

Furthermore, if hot-drying offset printing ink is used in the printing press, a hot air dryer with a total length of, for example, between 8 and 12 meters is provided serves to evaporate the solvents of the ink applied to the paper web and to polymerize their resin. This dryer is arranged after the printing units and is traversed by the running printed paper web without it being supported by rollers. Since the dried paper web is less elastic than the moist paper web, the paper web can tear in the dryer. If the paper web tears in the dryer, it usually wraps around a blanket cylinder of the last printing unit due to the adherence of the ink applied to the paper web, which in some cases can develop considerable adhesive forces. After a certain number of revolutions, during which the torn paper web winds itself up on the blanket cylinder, the number of paper layers reaches a value which is large enough to destroy the blanket or even the cylinders. Before the printing press comes to a complete standstill, the risk of malfunction is all the greater as two layers of paper are wound onto the blanket cylinder with each revolution, one of the layers of paper coming from the printing unit and the other from the dryer.

In order to remedy the disadvantages described above, a device for securing against rotation for a torn paper web is known from European patent EP 0 092 659.

This device is arranged between the last printing unit and the dryer. The main component of this device consists of a pair of pinch rollers, which comprises a stationary roller arranged laterally below the paper web in progress and a pressure roller arranged above the paper web, both rollers being set in rotation in accordance with the throughput speed of the paper. In normal continuous operation, the two rolls are pushed apart so that the printed, moist paper web can pass through without touching it and without smearing occurring. If the paper web breaks, the tear of Optical detectors, which are attached to the output of the last printing unit, are clearly detected, and a trigger signal is sent without delay to a mechanism that holds the pinch roller that has moved away. The pinch roller is then released and brought into a position to act on the torn paper web. As long as the printing machine is not stopped, the paper web coming from the last printing unit continues to run and is wound around one of the two pinch rollers of the device under consideration, instead of being wrapped around a blanket cylinder of the printing unit. The diameter of the roll around which the paper wraps increases as the other roll moves away to allow the paper to be picked up.

It should be noted, however, that as the diameter increases, the roll on which the paper web winds tends to wind up longer and longer sections of the paper web with each revolution. This roll thus exerts an ever increasing tensile force on the paper web, so that the paper web is able to tear again. To prevent this, it would be necessary to equip the device with a friction clutch system which allows the two pinch rollers to be driven and this drive to be regulated so that the rollers spin in the pinch position as soon as the tension in the pressure unit coming and has reached its normal value on a torn paper web winding on the reels and the diameter of the reel continues to increase. The adaptation of such a friction clutch system is complex and without guarantee for the result.

On the other hand, the torn paper web wrapping around the pinch rollers is covered with damp printing ink, so that it is difficult to remove the paper stuck to the roller when the printing machine is stopped.

In addition, there is always the danger that the two pinch rollers rotating close to each other on both sides of the continuous paper web come into close contact with one another, which is a danger to the operating personnel.

Another safety device for reacting to web breaks is known from DE-A-3 735 330.

In order to eliminate the various difficulties of the prior art described, a new automatic device for catching a paper web torn in the passage is proposed according to the invention, with means for introducing the torn paper web into means for removing the web, the device allowing this torn paper web to be automatically pulled into a storage container without being wrapped around any roll.

According to the invention, the means for drawing off comprise two parallel rollers which are arranged on one side of the horizontally traveling paper web in such a way that the axes of the rollers lie horizontally and are oriented perpendicular to the direction of movement of the paper web, the device having drive means for rotationally driving the two Rolls in the opposite direction, which are in slight surface contact with one another along one of their surface lines, so that the rolls have a surface speed which approximately corresponds to the speed of movement of the paper web.

If the continuous paper web breaks, the device according to the invention advantageously allows the torn web to continue to be captured. Until the printing machine has come to a complete stop, the torn paper web is inserted between the rotating rollers and pulled by them at the speed of the web in order to be drawn off into a storage container without the paper web being wrapped around one of the rollers of the device.

According to one embodiment of the device according to the invention, the insertion means consist of a deflection device which is arranged on a side of the paper web opposite the rollers and which is provided with blower means arranged opposite a receiving area formed by the rotating rollers. The deflection device is supplied with compressed air as soon as a monitoring system has verified that the paper web has been torn off.

As soon as the monitoring system of the device according to the invention indicates that the paper web in the passage, in particular through the dryer of the printing press, has been torn off, the deflection device of the device is supplied with compressed air and the blower means exert a blower pressure on the torn paper web, causing it to move between the two parallel, rotating rollers is introduced.

In addition, according to the invention, the two rolls each have a detaching device which helps prevent the paper web from being wound around the two rolls.

Fig. 1

zeigt einen Ausschnitt einer Vorderansicht einer Offset-Druckmaschine mit Heißtrockner und mit einer erfindungsgemäßen automatischen Einfangvorrichtung,

Fig. 2

eine Vorderansicht der erfindungsgemäßen Vorrichtung,

Fig. 3

einen Schnitt durch die Vorrichtung der Fig. 2 gemäß der Schnittlinie A-A, und die

Fig. 4

zeigt in einer Teilansicht die Unterseite der erfindungsgemäßen Vorrichtung der Fig. 2.

The following description with reference to the drawings attached as a non-exhaustive example clarifies what the invention consists of and how it can be carried out.

Fig. 1

shows a detail of a front view of an offset printing machine with a hot dryer and with an automatic capture device according to the invention,

Fig. 2

2 shows a front view of the device according to the invention,

Fig. 3

a section through the device of FIG. 2 along the section line AA, and

Fig. 4

2 shows a partial view of the underside of the device according to the invention from FIG. 2.

1, an offset printing machine with a hot dryer is shown, which comprises two printing units (10, 20), each with two blanket cylinders (11, 11 ', 21, 21'), which have a horizontally continuous paper web (32 ) are arranged. This device also comprises a dryer (4) arranged after the last printing unit (10). As can be seen in FIG. 1, the paper web (32) is stretched between two feed rollers (2, 2 ') and two outlet rollers (3, 3'). In addition, in the exemplary embodiment shown, a monitoring system (5, 5 ') arranged directly behind the last printing unit (10) allows a break in the paper web (32) to be detected and a trigger signal to be sent to the automatic catching device according to the invention, which is shown in FIG. 1 arranged directly in front of the entrance of the dryer (4) and provided with the reference symbol (8).

Of course, in other embodiments of the invention, the monitoring system (5, 5 ') can be arranged anywhere between the last printing unit (10) and the two outlet rollers (3, 3').

2, 3 and 4, the automatic device according to the invention is shown. This device has means for pulling off the torn paper web, in this case two rollers (30, 31) of the same diameter which run parallel to one another and are arranged on the same side of the horizontally moving paper web (32), the diameter being approximately 120 mm. The two rollers (30, 31) are arranged below the paper web (32) in such a way that their axes are horizontal and perpendicular to the direction of movement of the paper web. The rollers (30, 31) consist of metal, such as steel, the roller (30) being bare Surface has, while the roller (31) has a surface covering made of rubber.

3 and 4, the rollers (30, 31) also both have a plurality of circular grooves (54) which are arranged lengthwise at regular intervals on the surface of each roller. The surface of both rollers accordingly has projections (54 ') and depressions (54). The projections (54 ') and the depressions (54) of the two rollers (30, 31) lie opposite each other. The rollers (30, 31) are set in rotation in opposite directions by drive means, which are explained in more detail below. According to the embodiment shown in FIGS. 2, 3 and 4, the roller (30) rotates in the sense of the direction of movement of the paper web (32) and the roller (31) in the opposite sense. The two rollers set in rotation produce a receiving area (12) directly below the paper web (32). The roller (31) is attached to a swiveling device described below in such a way that the two rollers are in slight surface contact with one another at the level of their projections (54 ') and in particular at the level of one of their surface lines.

3 and 4, the roller (30) is rotatably held in two bearings (33 and 34) which are provided in two parallel bearing housings (35, 36). The roller (30) comprises a drive pulley (61) fastened to one of its bearing journals by means of a wedge connection, which is connected via a belt (40) to a pulley (39) of a drive means, in this case an electric motor (37).

The motor (37) is a variable speed motor and is mounted on a bracket (38) connected to the bearing housing (36) such that the axis of the motor (37) is parallel to the axis of the roller (30). The role (30) is from the Motor (37) driven by the speed of the paper web (32).

As can also be seen in FIGS. 2, 3 and 4, the roller (31), which has two bearing pins at its two ends, is freely rotatably mounted in the swivel device. The pivoting device in this case consists of two levers (42, 43) which are rotatably supported on the bearing housings (35, 36) by means of two pivot bolts (44, 45). Two pneumatic cylinders (46, 47) which are rotatably attached to the bearing housings (35, 36) by means of pivot bolts (48, 49) can act on the levers (42, 43) by means of their rods (50, 51).

In addition, two screws (52, 53) are provided for regulating the surface contact of the roller (31) with the roller (30) by limiting the pivoting movement of the levers (42, 43). In normal operation, the pneumatic cylinders (46, 47) are activated so that the contact between the two rollers (30, 31) is "light" in order to avoid heating the rubber applied to the surface of the roller (31).

The electric motor (37), which runs at a speed proportional to the machine speed, functions as follows. The speed of rotation of the motor (37) is converted into an electrical voltage, which is transmitted in an electronic circuit (58) and compared with a voltage originating from the main drive of the printing press (not shown) and transmitted from the current conductor (59). In turn, the electronic circuit (58) generates a precision supply voltage (60) for the motor (37) so that its speed of rotation is proportional to the speed of the printing press.

In addition, the two rollers (30, 31) each have a detaching device which has a stripper (55, 56), for example in the form of a comb. The scraper (55) of the roller (30) is attached to the bearing housings (35, 36), the teeth of its comb shape engaging in the grooves (54) of the roller (30). The comb-shaped scraper (56) of the roller (31), which is identical to the scraper (55), is attached to the two levers (42, 43). It is arranged in front of the roller (31) in such a way that the teeth of the comb engage in the grooves (54) of the roller (31). These two wipers advantageously prevent the torn paper web (32) from being wound onto each of the two rollers (30, 31).

As can be seen better in FIGS. 2 and 3, the device according to the invention also has means for introducing the torn paper web into the means for drawing off, in this case it being a side of the paper web (32) opposite the rollers. arranged deflection device (70). In this embodiment, the deflection device (70) is arranged above the paper web (32). The deflection device (70) comprises blower means, in this case blowing nozzles (71), which are distributed along an axis parallel to the axes of the rollers, that is to say perpendicular to the direction of movement of the paper web.

In a typical example, the rollers (30, 31) are arranged at a distance of 20 mm below the paper web, while the deflection device is arranged at a distance of approximately 20 mm above the paper web. The blowing nozzles (71) are distributed over the entire width of the paper web at a mutual distance of, for example, 100 mm. The deflection device (70) is supplied in the middle with compressed air at a pressure of, for example, 7 x 10 ihrer Pa. This supply is triggered by the monitoring system (5, 5 ') as soon as it detects tearing of the paper web (32). The blowing nozzles blow the compressed air onto the torn paper web and ensure its introduction into the receiving area (12) formed by the two rotating rollers (30, 31). The two rollers (30, 31) in contact with one another thus allow the rollers (30, 31) introduced into the receiving area (12) pull torn paper web (32) even if it is crumpled or even crumpled.

In order to obtain a sufficient supply of compressed air without the pressure in the entire compressed air system decreasing, the device according to the invention has a reservoir (76) arranged in the vicinity of the deflection device (70). The reservoir (76) and the deflection device (70) are connected to a compressed air supply network (73) by means of an electrovalve (72) of a known type. In addition, this solenoid valve (72) is connected to the monitoring device (5, 5 ') and is actuated by an electrical signal coming from the monitoring system (5, 5') as soon as it detects a break in the paper web (32).

In its idle state, i.e. as long as the paper web (32) passes through in normal operation, the solenoid valve connects the reservoir (76) to the compressed air supply network (73), so that the reservoir (76) can be filled with compressed air. On the other hand, the deflection device (70) is not supplied with compressed air.

If the solenoid valve (72) receives the electrical signal from the monitoring system (5, 5 '), it interrupts the compressed air supply to the reservoir (76) and connects it directly to the deflection device (70).

The deflection device (70), which is supplied with compressed air, exerts dynamic pressure on the torn paper web (32) via blowing nozzles (71), which allows the torn web to be introduced into the receiving area (12) of the rolls (30, 31). The web introduced in this way is pulled by the rollers (30, 31) which are in contact with one another and drawn off into a receiving container (75) arranged below the wipers (55, 56). It must be noted that as soon as the web (32) is captured, the pneumatic cylinders (46, 47) under constant pressure act as elastic means and allow the rollers (30, 31) to move away from one another while maintaining a constant pressure on the paper web if the paper web wrinkles or crumples. After the machine has been completely switched off, the rollers (30, 31) can be pushed apart to facilitate the removal of the torn web. It is therefore sufficient to empty the receptacle (75) and thread the paper web (32) back into the printing press.

In an embodiment variant of the embodiment shown in FIGS. 2, 3 and 4, the rollers (30, 31) can both consist of bare metal or, in contrast, both can be covered with rubber. On the other hand, the rollers (30, 31) can be arranged above the paper web, while the deflection device (70) is arranged below the paper web (32). Finally, the roller (30) can also be freely rotatably supported, while the roller (31) is set in rotation by an electric motor and, in turn, sets the roller (30) in rotation.

On the other hand, in a further variant of the embodiment of the device according to the invention shown in FIGS. 2, 3 and 4, the drive means of the roller (30) with variable rotational speed can comprise a mechanical transmission system which is operated via belts or the like. is directly connected to the drive mechanism of the printing press.

Claims (10)

1. Apparatus for the automatic capture of a paper web (32) which has torn whilst running through, having means for introducing (70; 71) the torn paper web into means for drawing-off the web, characterized in that the means for drawing-off comprise two mutually parallel rollers (30, 31) which are arranged on one side of the horizontally advancing paper web (32) in such a way that the axes of the rollers (30, 31) lie horizontally and are aligned perpendicular to the direction of movement of the paper web (32), and in that the apparatus has drive means (37) for the rotary drive of the two rollers (30, 31) in opposite directions, said rollers being disposed in light surface contact with one another along one of their generating lines so that the rollers (30, 31) have a surface speed which corresponds approximately to the speed of movement of the paper web.
2. Apparatus according to Claim 1, characterized in that the introducing means are composed of a deflection device (70) which is arranged on a side of the paper web (32) opposite the rollers (30, 31) and is provided with blower means (71) arranged opposite a receiving region (12) formed by the rotating rollers (30, 31), the deflection device (70) being supplied with compressed air as soon as a monitoring system (5, 5') detects the tearing of the paper web (32).
3. Apparatus according to Claim 2, characterized in that the blower means are a multiplicity of blower nozzles (71) which are mounted distributed along an axis running parallel to the axes of the rollers (30, 31).
4. Apparatus according to one of Claims 1 to 3, characterized in that the drive means comprise a motor (37) of variable rotary speed, which motor sets at least one of the rollers (30, 31) in rotation.
5. Apparatus according to one of Claims 1 to 4, characterized by two levers (42, 43), which are acted upon, in particular, by two pneumatic cylinders (46, 47) and on which one of the rollers (30, 31) is arranged so as to be freely rotatable, the levers (42, 43) being provided for bringing the two rollers (30, 31) into light surface contact with one another by means of the two cylinders (46, 47) so that the roller set in rotation drives the roller which is mounted so as to be freely rotatable.
6. Apparatus according to one of Claims 1 to 5, characterized in that the two rollers (30, 31) each have a detachment device (55, 56) in order to avoid the paper web (32) winding up onto either of the two rollers (30, 31).
7. Apparatus according to Claim 6, characterized in that each detachment device is an, in particular, comb-like scraper (55, 56).
8. Apparatus according to one of Claims 1 to 7, characterized in that the two rollers (30, 31) consist of polished metal.
9. Apparatus according to one of Claims 1 to 8, characterized in that at least one roller (30, 31) is coated with rubber.
10. Apparatus according to one of Claims 1 to 9, characterized by a supply reservoir (76), arranged very near to the receiving region (12), for compressed air which serves to drive the torn paper web (32) into the receiving region (12), and by an electrovalve (72) which connects the reservoir (76) to a compressed-air supply network (73) of the deflection device (70) and is linked to the monitoring system (5, 5'), thus guaranteeing the simultaneous supply of the deflection device (70) with air containing [sic] in the reservoir (76).

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