Installation for processing a paper web or corrugated cardboard web

An installation for the detection of projecting material defects in a paper web or corrugated cardboard web moved in a feed direction. The device comprises a sensor device comprising a first sensor unit with a first emitter for emitting first sensor beams and a second emitter for emitting second sensor beams and with a second receiver, wherein the first sensor beams run parallel to the material surface to be monitored of the paper web or corrugated cardboard web and travel along a first signal path S1 in-between. The sensor device further has a second sensor unit comprising a second emitter for emitting second sensor beams and a second receiver, wherein the second sensor beams run parallel to the material surface and travel along a second signal path S2 in-between. The first and second sensor units are oriented in such a way that the distance between the first and second sensor beams relative to the feed direction changes along their signal paths S1, S2.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a United States National Phase application of International Application PCT/EP2014/053108 filed Feb. 18, 2014 and claims the benefit of priority under 35 U.S.C. §119 of German Patent Application DE 10 2013 202 871.7 filed Feb. 21, 2013, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The invention is directed to an installation for processing a paper web or corrugated cardboard web comprising a material defect detection device. Furthermore, the invention relates to a method for the detection of projecting material defects in a paper web or corrugated cardboard web, which is moved in a feed direction, by means of a material defect detection device.

In this disclosure, projecting material defects are defined as, among others, material defects which project outwards from the actual material surface, such as excessive glue, folds/creases, torn edges or web holes with projecting areas or edges, the essential criterion being that the material defect projects from the material surface.

BACKGROUND OF THE INVENTION

A large number of the most various devices for the detection of projecting material defects in moving material webs are known from prior art. In many cases, profile sensor devices are used for this purpose which are arranged above or below the material web to be monitored so as to monitor said material web from above or below. Profile sensor devices of this type need to be arranged in a horizontal cascade which makes them extremely complex and expensive. The same applies to visual monitoring systems.

Furthermore, simple light barriers are used in particular in the processing of narrow webs. These systems are however unable to detect the position of the defect. Moreover, the system often needs to be mechanically adjusted to different material web thicknesses.

Another problem of these known solutions is that false alarms occur frequently. Material defects of this type may result in severe damages during subsequent processing of the material web. The damages may occur on processing devices, on the material web itself or on the surroundings. In many cases, the material defects cause damages in particular in digital printing devices such as inkjet digital printing devices since these devices usually comprise sensitive fine ceramic components.

SUMMARY OF THE INVENTION

Therefore, it is the object of the invention to provide an installation comprising a material defect detection device that is extremely cost-effective and simple. Another object is to prevent false alarms. In particular, damages to the printing device caused by material defects shall be preventable in a simple and fail-safe manner. Yet another object of the invention is to provide a corresponding method for the detection of projecting material webs on a moved material web by means of a material defect detection device of this type.

These objects are achieved according to the invention by an installation for processing a paper web or corrugated cardboard web, the installation comprising a first supply device for supplying the paper web or corrugated cardboard web to be processed; a printing device arranged downstream of the supply device for applying a print to the paper web or corrugated cardboard web, a device for the detection of material defects in a paper web or a corrugated cardboard web moved in a feed direction, the device comprising a sensor device with a first sensor unit comprising a first emitter for emitting first sensor beams, and a first receiver assigned to the first emitter for receiving the first sensor beams, wherein in order to detect the material defects, the first sensor beams run parallel to the material surface to be monitored of the material web and travel along a first signal path S1between the first emitter and the first receiver; and at least one second sensor unit comprising a second emitter for emitting second sensor beams, and a second receiver assigned to the second emitter for receiving the second sensor beams, wherein in order to detect the material defects, the second sensor beams run parallel to the material surface to be monitored of the material web and travel along a second signal path S2between the second emitter and the second receiver, wherein the first sensor unit and the second sensor unit are oriented in such a way that the distance between the first sensor beams and the second sensor beams relative to the feed direction changes along their signal paths S1, S2, and a signal evaluation unit, which is in signal communication with the first receiver and the second receiver for evaluation of the detected material defects, wherein the device for the detection of material defects in the paper web or corrugated cardboard web is arranged near the paper web or corrugated cardboard web between the first supply device and the printing device for the detection of material defects in the material web that are problematic for printing, and by a method for the detection of projecting material defects in a paper web or corrugated cardboard web moved in a feed direction, the method comprising the steps of providing a first supply device for supplying the paper web or corrugated cardboard web to be processed, providing a printing device arranged downstream of the first supply device for applying a print to the paper web or corrugated cardboard web, and providing a device for the detection of material defects in a paper web or a corrugated cardboard web moved in a feed direction, the device comprising a sensor device with a first sensor unit comprising a first emitter for emitting first sensor beams, and a first receiver assigned to the first emitter for receiving the first sensor beams, wherein in order to detect the material defects, the first sensor beams run parallel to the material surface to be monitored of the paper web or corrugated cardboard web and travel along a first signal path S1between the first emitter and the first receiver; and at least one second sensor unit comprising a second emitter for emitting second sensor beams; and a second receiver assigned to the second emitter for receiving the second sensor beams, wherein in order to detect the material defects, the second sensor beams run parallel to the material surface to be monitored of the paper web or corrugated cardboard web and travel along a second signal path S2between the second emitter and the second receiver, wherein the first sensor unit and the second sensor unit are oriented in such a way that the distance between the first sensor beams and the second sensor beams relative to the feed direction changes along their signal paths S1, S2, and a signal evaluation unit, which is in signal communication with the first receiver and the second receiver for evaluation of the detected material defects, wherein the device for the detection of material defects in the paper web or corrugated cardboard web is arranged near the paper web or corrugated cardboard web between the first supply device and the printing device for the detection of material defects in the material web, which are problematic in the printing process. The gist of the invention is that at least two sensor units generate sensor beams which, in order to detect a material defect, run across the material surface(s) to be monitored of the material web and have a distance from each other that varies along their signal paths in the feed direction. In other words, the first and second sensor beams are not parallel to each other. The material web is monitored from the sides. The material web is formed by the paper web or corrugated cardboard web.

Depending on the position of the material defect relative to the longitudinal edges of the material web, the material defect requires different amounts of time to pass through the first and second sensor beams. If, for example, the material defect is located at a position in the material web where the distance between the first and second sensor beams relative to the feed direction is smaller than at another position, it requires less time. The feed rate of the material web is naturally constant across its width in the feed direction. Therefore, the position of the material defect is easily determinable or calculable by means of the time required to pass through the first and second sensor beams, the feed rate and the geometric arrangement of the sensor beams relative to each other.

The converse is equally true. So if, for example, the material defect is located at a position in the material web where the distance between the first and second sensor beams relative to the feed direction is greater than at another position, it requires more time.

It is advantageous if the emitters emit pulsed sensor beams.

In a favorable embodiment, the sensor units do not change their position during operation. In other words, the orientation of the first and second sensor beams relative to each other advantageously remains the same during operation.

It is advantageous if the emitters and/or the assigned receivers are distance-adjustable relative to each other. As a result, they are easily adjustable to different widths of the material webs. A stationary arrangement of the sensor units taking into account the maximum width of the material webs is however preferred.

In a favorable embodiment, the emitters and/or the assigned receivers are adjustable in the region of the respective sensor unit in a direction perpendicular to the upper side or lower side of the material web. This allows the sensor units to be adjusted to the thickness of the material web, for example. Corresponding mounting devices are preferably provided on frame parts.

The sensor units may for example be optical sensor units, ultrasound sensor units, sound wave sensor units or the like.

It is advantageous if the sensor units are secured to a common frame.

It is expedient if the signal evaluation unit comprises at least one control device.

In an advantageous embodiment, an optical and/or acoustic signal is emitted when a material defect is detected. In addition or as an alternative thereto, the region of the material web in which the material defect is located is preferably cut out automatically. In addition or as an alternative thereto, subsequent processing installations are readjusted accordingly to prevent collision with the projecting material defect. A tracking function for material web deviations allows the compensation mechanisms described above to be synchronized with the point of time the material web defect passes through. The amount of paper waste is therefore reduced to a minimum.

The signal connection between the sensor unit and the signal evaluation unit may be wired or wireless. The signal connection allows signals to be transmitted between the sensor unit and the signal evaluation unit that correspond to the material defects.

Preferably, the material web is an endless material web.

Monitoring takes place on a material surface, which is either an upper or a lower side. Alternatively, monitoring may take place on both material surfaces.

It is expedient if the signal evaluation unit is capable of adjusting the position of the paper web or corrugated cardboard web at least in the region of the printing device and/or of the printing device in such a way as to prevent collision between the detected material defect and the printing device. To this end, the printing head or printing heads of the printing device is/are lifted off or moved further away from the material web, for example. As an alternative or in addition thereto, the course of the material web is changed in such a way that the distance between the printing head or printing heads and the material web is increased. As an alternative or in addition thereto, the printing heads are protected from the material defect by a protection device such as a seal. To this end, the protection device is preferably actuated correspondingly. The risk of causing damages to sensitive parts or components is thus preventable.

In particular, the position of the at least one printing head is adjusted when the printing head is disposed in the web region of the material defect and said printing head has a critical distance from the material web in relation to the height of the material defect. This information, which is obtainable preferably by means of a sensor but also by manual operation, is available in the signal evaluation unit. In order to coordinate this, it is advantageous if the response time of the actuating device and/or the speed of the installation is taken into account.

The first supply device is preferably a supply roll device. Other alternative embodiments are conceivable as well.

In an advantageous embodiment, the printing device is a digital printing device. Other alternative printing devices are conceivable as well.

The signal evaluation unit which detects the orientation angle of the material defect, the width of the material defect and/or in particular the position of the material defect relative to the paper web or corrugated cardboard web by means of a feed rate of the paper web or corrugated cardboard web in the feed direction and a period of time which passes between the detection of the material defect by the first sensor unit and the detection thereof by the at least second sensor unit is able to determine as well if the material defect has a problematic position or extension. Material defects located for example in a lateral edge area of the material web are usually irrelevant because the edge area will in most cases be cut off. If this is the case, it is advantageous if the signal evaluation unit does not emit an error message. Therefore, the tolerances are preferably defined such as to meet the requirements of a particular order specification.

In one embodiment, the first and/or second sensor beams run obliquely to the feed direction across the width of the paper web or corrugated cardboard web. If only the first or second sensor beams run obliquely to the feed direction, then the remaining sensor beams will be perpendicular to the feed direction.

The arrangement of the sensor units such that the first emitter and the second emitter have an emitter distance SA between each other relative to the feed direction, wherein the first receiver and the second receiver have a receiver distance EA between each other relative to the feed direction, wherein the emitter distance SA and the receiver distance EA differ from one another by at least 10%, more preferably by at least 50%, and most preferably by at least 100%, allows material defects to be localized with a high level of precision. The relationship of the emitter distances and receiver distances relative to each other is preferably selected as a function of the width of the material web.

It is advantageous if the first emitter and the first receiver and/or the second emitter and the second receiver are arranged laterally adjacent to the material web. This embodiment is extremely advantageous for practical reasons as it allows the material web to be monitored across its entire width.

The embodiment in which the first and second sensor beams form an angle W1, W2with a vertical extending perpendicular to the paper web or corrugated cardboard web relative to the feed direction, wherein the angles W1, W2, have different absolute values, again allows defects to be localized with a high level of precision. The angles are in each case preferably between 5° and 55°, more preferably between 15° and 50°, more preferably between 20° and 45°. The angles may be identical to or different from each other. Alternatively, the first and second sensor beams form angles relative to a transverse direction perpendicular to the feed direction the absolute values of which are identical.

The sensor beam curtain generated by the first emitter and/or the second emitter generate a sensor beam curtain with first or second sensor beams, respectively, which are parallel to each other, wherein the first or second sensor beams, respectively, have different vertical distances from the material surface to be monitored of the paper web or corrugated cardboard web in order to determine the height of the detected material defects, is preferably perpendicular to the monitored material surface(s) of the material web. The first and/or second receivers are correspondingly configured to detect sensor beams having different vertical distances from the monitored material surface. If, for example, only the sensor beam closest to the material web is interrupted by a projecting material defect, this allows one to easily determine the height of the material defect. It is smaller than the vertical distance of the next sensor beam of the sensor beam curtain relative to the material web. The same applies to the other sensor beams in the sensor beam curtain. In an advantageous embodiment, “multiple light barriers” are used which are able to separately detect, for example by means of a CCD (charged coupled device), a number of sensor beams arranged one above the other. This allows one to easily change the tolerance settings for the material web projection and to set reference values for various thicknesses of the material web.

The embodiment in which the sensor beam curtain covers one or both of the material surfaces of the paper web or corrugated cardboard web ensures a simple and cost-effective monitoring of both sides of the material web.

In the embodiment in which the sensor beam curtain is configured and arranged in such a way as to run across the thickness of said paper web or corrugated cardboard web, the material web is also exposed to sensor beams coming from the side, thus allowing the thickness of the material web to be determined.

Preferably, the first and/or second sensor unit is/are configured as an optical sensor unit, with the first and/or second sensor beams being light sensor beams. This embodiment results in a particularly fail-safe sensor device. Electrical pulses are advantageously converted, by the respective emitter of the optical sensor unit, into light pulses which are converted back into electrical signals by the assigned receiver of the optical sensor unit. The electrical signals are easily evaluable by the signal evaluation unit.

The embodiment in which the signal evaluation unit converts the detected period of time that passes between the detection of the material defect by the first sensor unit and the detection of the material defect by the at least second sensor unit into path length differences for determining the position of the material defect while the feed rate of the paper web or corrugated cardboard web is being increased or reduced allows the position of the material defect to be determined even if the feed rate of the material web is increased or reduced. This conversion by integrating the distance traveled by the material defect over the time difference between the two sensor beam input times allows the length of the defect in the feed direction to be decoupled from the feed rate of the material web. When a desired minimum defect length is specified in the feed direction, the number of false alarms is reduced even more.

The embodiment in which subsequent processing devices are adjusted accordingly when a material defect is detected to prevent collision with the projecting material defect, the embodiment in which the printing device and/or the paper web or corrugated cardboard web is/are adjusted, if necessary, at least in the region of the printing device to prevent collision between the printing device and the detected projecting material defect, and the embodiment in which the printing device is protected from material webs dangerous to the printing device by means of at least one protection device result in an installation that is extremely fail-safe. In particular, it is possible to prevent damages thereto caused by critical or dangerous material defects. “Critical” or “dangerous” material defects are in particular those material defects, which are likely to cause damages to the printing device or the at least one printing head thereof due to their position, size and/or height. If necessary, the position of the paper web or corrugated cardboard or of the printing device is adjusted accordingly.

In the joining device that joins the printed material web to the corrugated second material web, the material webs are advantageously glued or welded to each other. The corrugating device is preferably a corrugating roller. Other supply devices are conceivable as well.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring toFIGS. 1, 2, the following is a description of a simplified material defect detection device1. The material defect detection device1comprises a sensor device2and a signal evaluation unit3which is in signal communication with the sensor device2. The sensor device2in turn comprises a first sensor unit4and a second sensor unit5which is preferably identical to the first sensor unit4. Seen in the feed direction6of a material web7to be monitored, the second sensor unit5is arranged downstream of the first sensor unit4. The sensor units4,5are arranged next to the material web7. More precisely, they are in each case arranged on the sides next to the material web7.

The first sensor unit4has a first emitter8and a first receiver9assigned to said first emitter8. The second sensor unit5on the other hand has a second emitter10and a second receiver11assigned to said second emitter10. The first emitter8emits first light sensor beams12which are received by the first receiver9if the connection between them is not interrupted. The second emitter10emits second light sensor beams13which are received by the second receiver11if the connection between them is not interrupted.

The material web7has a first longitudinal edge14and a second longitudinal edge15which is parallel to the first longitudinal edge14. The two longitudinal edges14,15extend in the feed direction6of the material web7. The material web7further has a transverse direction16perpendicular to the feed direction6or the longitudinal edges14,15, respectively. In other words, the transverse direction16extends across the width of the material web7. The material web7further has an upper side17and a lower side18opposite to the upper side17. In this disclosure, the material web7is a paper web or a corrugated cardboard web. It is substantially arranged in a plane in the region of the entire sensor device2. The material web7is continuously moved, by means of a feed device (not shown inFIGS. 1, 2), in the feed direction6at a feed rate which is usually not constant but may also be constant.

In this embodiment, the emitters8,10are arranged on the side of the material web7next to the first longitudinal edge14while the receivers9,11are arranged on the side of the material web7next to the second longitudinal edge15. Near the first sensor unit4, the material web7is located in a first plane. Near the second sensor unit5on the other hand, the material web7is located in a second plane. The first plane and the second plane may be located in a common plane; they may however also be oblique or offset to each other. InFIG. 1, the first and second planes are located in a common plane.

The first emitter8is arranged upstream of the second emitter10. Between the emitters8,10, there is an emitter distance SA relative to the feed direction6. The first receiver9is arranged upstream of the second receiver11. Between the receivers9,11, there is a receiver distance EA relative to the feed direction6. In this embodiment, the emitter distance SA relative to the feed direction6is greater than the receiver distance EA, preferably at least 1.1 times the receiver distance EA.

For narrow webs (width smaller than 1000 mm), the emitter distance SA relative to the feed direction6is considerably greater, preferably at least twice, more preferably at least three times the receiver distance EA. For wider webs (width larger than 1000 mm), the emitter distance SA relative to the feed direction6is between 1.1 and 1.9 times, preferably between 1.2 and 1.8 times the receiver distance EA.

According to an alternative embodiment, the receiver distance EA in the feed direction6is greater than, preferably at least 1.1 times the emitter distance SA. The above description concerning the distances applies conversely.

The relationship between emitter distance SA and receiver distance EA is preferably selected by taking into account the available installation space, the maximum feed rate of the material web and/or the desired resolution, in other words the precision of defect localization.

The light sensor beams12,13run in each case obliquely to the feed direction6or the transverse direction16. The first light sensor beams12form a first angle W1with a vertical19to the longitudinal edges14,15while the second light sensor beams13form an angle W2with the vertical19. Preferably, the angles W1, W2are in each case between 5° and 55°, more preferably between 15° and 50°, more preferably between 20° and 45°. The angles W1, W2may be identical to or different from each other.

The first light sensor beams12travel along a first signal path S1between the first emitter8and the first receiver9while the second light sensor beams13travel along a second signal path S2between the second emitter10and the second receiver11.

Each of the emitters8,10generates a light sensor beam curtain comprising the first or the second light sensor beams12,13, respectively. The first light sensor beams12in the first light sensor beam curtain are in each case parallel to each other and to the material web7. They run at different vertical distances from each other. The second light sensor beams13in the second light sensor beam curtain are in each case parallel to each other. They run at different vertical distances from each other. The lowermost first light sensor beams12in the first light sensor beam curtain run vertically below and adjacent to the lower side18of the material web7in the region of the first sensor unit4. The lowermost second light sensor beams13in the second light sensor beam curtain run vertically below and adjacent to the lower side18in the region of the second sensor unit5. The uppermost first light sensor beams12in the first light sensor beam curtain run vertically above and adjacent to the upper side17of the material web7in the region of the first sensor unit4. The uppermost second light sensor beams13in the second light sensor beam curtain run vertically above and adjacent to the upper side17in the region of the second sensor unit5. Additional light sensor beams12,13are provided between the uppermost and the lowermost first and second light sensor beams12,13. Since the light sensor beams12,13also run across the thickness of the material web7, the thickness thereof is determinable by means of the sensor device2as well.

The following is a description of the functioning of the material defect detection device1while in operation. The upper side17of the material web7is monitored. By means of the feed device, the material web7is moved at a feed rate in the feed direction. The emitters8,10emit light sensor beams12or13, respectively. Having traveled along the signal paths S1or S2, respectively, the first light sensor beams12are received by the first receiver9and the second light sensor beams13are received by the second receiver11when no material defect is detected that projects from the upper side17of the material web7. The signal evaluation unit3does not emit an error message.

It may occur that only the first receiver9or only the second receivers11does not receive all or any of the first and second light sensor beams12,13at a particular point in time. In this case, there are two procedures to choose from depending on the type of material web monitoring. The results of the detection are correspondingly transmitted to the signal evaluation unit3which will however not emit an error message. It is then assumed that a defect has occurred. Since it cannot be localized, the defect might also be interpreted as a critical material defect.

If both the first and the second receivers9,11do not receive all or any of the first light sensor beams12or second light sensor beams13, respectively, at a particular point in time, the signal evaluation unit3will emit an error message indicating that there is a projecting material defect20on the upper side17of the material web7.

The height of the material defect20perpendicular to the upper side17is determined by means of the light sensor beams12and13which are interrupted in the respective light sensor beam curtain. The more light sensor beams12or13are interrupted, the greater the height of the material defect20.

The length of the material defect20in the feed direction6is determined by means of the period of time during which the first and/or second light sensor beams12,13are interrupted. The feed rate of the material web7and the change of the feed rate over time are known.

The distance of the material web20from the longitudinal edges14,15in the transverse direction16is determined by means of the period of time that passes between the interruption of the first light sensor beams12and that of the second light sensor beams13. The shorter said period of time, the shorter the distance of the material defect20from the receivers9,11which—as already described—are arranged at a smaller distance from each other in the feed direction6than the emitters8,10. The feed rate in the feed direction6and the change of the feed rate over time are known.

This also allows one to determine the angle of the material defect20relative to the longitudinal edges14,15by taking into account the different maskings of the sensor beams.

Referring toFIG. 3, a sensor device2is arranged between a supply roll21and a processing device22. The basic design of the sensor device2corresponds to that of the sensor device2according to the above description to which reference is made. It is arranged downstream of the supply roll21the material web7is wound on. Via the sensor device2, the material web7is moved in the feed direction6towards the processing device22. The processing device22may be a printing device, more preferably a digital printing device, a corrugating device, a gluing device, a laminating device, a heating device, a longitudinal cutting device, a cross-cutting device, a separating device, a stacking device or the like.

The sensor device2is preferably arranged on a frame23. In the sensor device2, the material web7is guided around a number of rotatable deflection rollers24to28. The first deflection roller24deflects the material web7downwards by approximately 90°. The second and third deflection rollers25and26are arranged downstream of the first deflection roller24. The first sensor unit4for monitoring the material web7is arranged between these deflection rollers25,26.

The fourth deflection roller27is arranged downstream of the third deflection roller26. The material web7is again deflected by the third deflection roller26. The second sensor unit5for monitoring the material web7is arranged between the third and fourth deflection rollers26and27. The measurement performed by means of the emitters8,10and the receivers9,11preferably takes place above the respective points of entry into the rollers24to28to prevent the measurements from being affected by oscillations of the material web7. In contrast to the sensor device2according toFIGS. 1, 2, the material web7of the sensor units4,5is disposed in different planes which are oblique to each other. Downstream of the fourth deflection roller27, the fifth deflection roller28is arranged where the material web7is again deflected by approximately 90°, allowing the material web7to return to its original feed direction6upstream of the sensor device2. By means of the deflection rollers24to28, a controlled or higher web tension is achieved.

The lowermost first light sensor beams12and the lowermost second light sensor beams13impinge on the rolls25,26or27, respectively while the remaining first and second light sensor beams12,13are arranged above the lowermost light sensor beams12,13or perpendicular thereto. As a result, the first and second sensor units4,5not only allow material defects20to be detected but also the thickness of the material web7to be determined.

The following is a more detailed description, with reference toFIG. 4, of a material defect detection device1the basic design of which corresponds to that according toFIG. 3. Identical components are designated by the same reference numerals as in the preceding embodiment to which reference is made. Structurally different components having the same functionality are designated by the same reference numerals followed by an “a”. The frame23ahas two frame parts29which are substantially identical and parallel to each other. Each of the deflection rollers24to28has an axis30to34which are mounted for rotation in the frame parts29and are parallel to each other.

The material web point of entry is located at the first deflection roller24. The material web point of exit is located at the fifth deflection roller28. Downstream of the deflection roller28, the material web7has a different direction than upstream of the deflection roller24. The emitters8,10are secured to one of the frame parts29while the receivers9,11are arranged on the other frame part29. The first sensor unit4is arranged between the second and third deflection rollers25and26while the second sensor unit5is arranged between the fourth and fifth deflection rollers27and28.

In the region of the first sensor unit4, the material web7is substantially perpendicular to the material web7in the region of the second sensor unit5. Another orientation is alternatively conceivable as well.

The emitters8,10are again arranged in such a way as to monitor the upper side17of the material web7. The receivers9,11are arranged in such a way as to receive the light sensor beams12and13which are again parallel to the material web7in the region of the respective sensor unit4,5.

The lowermost first and second light sensor beams12,13are directed towards the deflection rollers25,26or27, respectively.

The following is a description, with reference toFIGS. 5 to 7, of a corrugated cardboard installation which is provided with at least one material defect detection device1according toFIGS. 1 to 4.

The material web7is supplied to the machine35by the supply roll21. The material web7is an endless paper web. The material web7is a base web for the corrugated cardboard produced in the machine35.FIG. 6shows an enlarged side view of the material web7. The material web7comprises a material base layer36with a coating37, a so-called primer, which increases the print quality. The thickness relationship between the material base layer36and the coating37according toFIG. 6is not true to the actual thickness relationship. It is not necessary for the coating37to be applied to the material web7before it is wound up; it may still be applied to the material web7later when it has been wound off the supply roll21.

Between the supply roll21and the machine35, the material web7passes through a first digital printing press38comprising a printing head39by means of which a print is applied to the upper side17of the material7according to the requirements specified in a printing order. The digital printing press38is connected to an order control device41via a signal line40.

In the machine35, the printed material web7is connected to another or second material web42which is wound off a second supply roll43. Having been wound off, the material web42is guided through adjacent corrugating rollers44arranged in the machine35in order to produce a corrugation. Having been guided through the corrugating rollers44, the second material web42is in the form of a corrugated web.

Afterwards, an adhesive is applied to the tips of the corrugated material web42in a gluing device45; the corrugated material web42is then joined to the material web7in the machine35by pressing them together in a gap between a pressing roller46and one of the corrugating rollers44. As a result, a single face corrugated cardboard web47is obtained which is moved upwardly out of the machine35and deflected by a deflection roller48in a working direction49. The corrugated cardboard web47is then moved to a preheating device50.

A third supply roll51for a third material web52serving as an additional cover layer for the corrugated cardboard web47is arranged downstream of the machine35when seen in the working direction49. The third material web52is sometimes also referred to as laminating web; in this case, the first material web7is referred to as cover layer.

Downstream of the second supply roll51, the third material web52is at first deflected by a deflection roller53in such a way as to be transported in the working direction49. Afterwards, the third material web52is rotated by 180° by two further deflection rollers54,55in such a way that its side facing downwards between the deflection rollers53,54now faces upwards, wherein downstream of the deflection roller55, the third material web52is moved in a direction opposite to the working direction49.

Downstream of the deflection roller55, the third material web52passes through a second digital printing press56which forms a digital printing device together with the first digital printing press38. In the second digital printing press56, a print is applied—by means of a printing head57—to the side of the third material web52facing upwards after being discharged from the deflection roller55according to the requirements specified in a printing order. The third material web52has a double-layer structure as well, comprising a base material layer and a coating in such a way that the print is applied, by means of the printing head57of the second digital printing press56, to the coating of the third material web52. The coating may also be applied to the third material web52after winding off and before entering the second digital printing press56.

For controlling the printing order, the second digital printing press56is connected to the order control device41via a signal line58. Having passed through the digital printing press56, the third material web52is again deflected by substantially 180° by means of additional deflection rollers59,60, with the result that the third material web52is substantially transported in the working direction49again.

Downstream of the deflection roller60, the third material web52is transported to the preheating device50. The preheating device50comprises two heatable heating rollers61arranged one above the other. The corrugated cardboard web47and the third material web52move one above the other in such a way as to partly surround the respective heating rollers61.

Downstream of the preheating device50, a gluing device62is arranged which comprises a gluing roller63part of which is immersed in a glue bath64. The corrugated material web42of the corrugated cardboard web47is in contact with the gluing roller63.

Downstream of the gluing device62, a heating and pressing device65is arranged which comprises a horizontal table66comprising heating plates, the table66extending in the working direction49. An endlessly driven pressure belt68is provided above the table66which pressure belt68is deflected via three rollers67.

Between the pressure belt68and the table66, a pressure gap69is formed through which the corrugated cardboard web47and the third material web52are guided so as to be pressed together. The heating and pressing device65is used to produce a three-layer corrugated cardboard web70.

FIG. 7shows a second part of the corrugated cardboard installation after the corrugated cardboard web70has been discharged from the heating and pressing device65. A longitudinal cutting and corrugating device71is arranged in the working direction49downstream of the heating and pressing device65which longitudinal cutting and corrugating device71is made of two corrugating stations72arranged one behind the other and two longitudinal cutting stations73arranged one behind the other. The corrugating stations72comprise corrugating tools74which are in each case arranged one above the other so as to form a pair through which the corrugated cardboard web70is guided. Each of the longitudinal cutting stations73comprises knives75which are drivable for rotation and are engageable with the corrugated cardboard web70to cut the corrugated cardboard web in a longitudinal direction.

Seen in the working direction49, a separating device76is arranged downstream of the longitudinal cutting and corrugating device71to separate longitudinally cut web portions77,78of the corrugated cardboard web70from each other. The web portions77,78are then transported to a cross-cutting device79. The cross-cutting device79comprises an upper pair of cross-cutting rollers80for the upper web portion77and a lower pair of cross-cutting rollers81for the lower web portion78. The rollers of the pairs of rollers80,81are in each case provided with a cutting bar82which extends radially outwards and perpendicular to the working direction49. The cutting bars82of a pair of cross-cutting rollers80,81interact to separate the web portions77,78in a transverse direction. An upper conveyor belt83is arranged downstream of the upper pair of cross-cutting rollers80which conveyor belt83is deflected by rotatable rollers84.

A deposit station85having a vertical stop device86is arranged downstream of the upper conveyor belt83, allowing corrugated cardboard sheets87, which have been cut from the web portion77by means of the cross-cutting device79, to be deposited thereon in such a way as to form a stack88. As indicated inFIG. 7by a directional arrow89, the deposit station85is height-adjustable. For further transport of the stack88, the deposit station85may in particular be lowered down to a machine bottom90on which the corrugated cardboard installation is arranged.

Another lower conveyor belt91is arranged downstream of the lower pair of cross-cutting rollers81, the conveyor belt91being used to stack corrugated cardboard sheets92cut from the web portion78by means of the cross-cutting device79on another deposit station93. As shown by a directional arrow95, the lower conveyor belt91may be lifted so as to be adapted to the height of the stack94.

As already mentioned, the material defect detection device1is arranged in the corrugated cardboard installation.

The material defect detection device1is for example arranged between the supply roll21and the machine35.

It is advantageously arranged between the supply roll21and the digital printing press38.

In addition or as an alternative thereto, the material defect detection device1is preferably arranged between the supply roll51and the digital printing press56.

In addition and/or as an alternative thereto, the material defect detection device1is arranged between the supply roll51and the digital printing press56.

If the primer is applied inline, it makes sense to arrange the material web monitoring system downstream of this process step since the moisture involved in this process may result in an uneven corrugated cardboard.

According to an alternative embodiment, no third material web52is used. According to an alternative embodiment, further material webs are used.