Bridge of a corrugating machine

Abstract

A bridge of a corrugating machine controls corrugated fiberboard single-face webs fed from single-face corrugating machines. The bridge comprising a stored web supply formed by the bottom-most of the single-face webs, the stored web supply loosely-lying; a fixed guide element introducing a first reversal of direction of the web in the direction opposite a course of fabrication; a fixed redirecting element; a redirecting roller mounted in a frame swivelable about a vertical axis, the redirecting roller cooperating with the fixed redirecting element to cause a second reversal of direction of the web back in the direction of the course of fabrication, wherein the redirecting roller is disposed above the fixed redirecting element such that a web course section is created running parallel to the swivel axis; and a steering frame having a braking roller feeding the web to a preheating station, the braking roller creates a desired web tension load.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of European patent application number EP07023823, filed Dec. 10, 2007, which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The invention relates to a machine for corrugating fiberboard, in particular, a bridge of this type of equipment.

BACKGROUND OF THE INVENTION

At the beginning of a corrugating machine, what is called a single-facer corrugating machine, or single-facer, is located in which a flat web is joined with a web that has been given a wave-like shape between two heated corrugating rollers and glued together to form a single-face web. In order to fabricate duplex corrugated fiberboard, constructed from a flat surface liner, a flute, a flat intermediate liner, a second flute, and a back-side surface liner, two single-facers arranged in tandem are required, the single-face webs of which in a subsequent fabrication step are glued together and to a liner web. Here the single-face web slides from a single-facer at a distance from the gluing station over a table that is disposed above the path of the web coming out of the closer single-facer. To produce triplex corrugated fiberboard, the feed of three single-face webs is effected in three stacked tiers. Each single-face web passes through an associated preheating station in preparation for gluing.

The bridge of a corrugating machine is a station disposed between the single-facers and the preheaters and comprising tables stacked in tiers and supporting the running single-face webs on their path, wherein single-face webs coming from the more-distant single-facers slide along a long straight extended path, while the lowest-most single-face web is pushed together by the closest single-facer on its short bottom table to form flutes and loops, thereby creating a stored web supply.

In order to achieve high quality and reduce trimming waste, a control device is provided at the end of the bridge for each single-face web, the control device, first of all, adjusting the load forces acting within the single-face corrugated fiberboard webs to a preset value and keeping these constant, and, secondly, aligning the position of the single-face webs so as to be centered relative to the equipment and holding them in this position. These actions even out irregularities in the position of the single-face corrugated fiberboards that are caused by the storing process, and maintain a constant web tension for the subsequent preheating.

Various constructional designs are in practical use today to control the lateral position and to control the web tension for single-face corrugated fiberboard webs. In particular, combined apparatus that solve both problems are quite popular since they have a very small footprint.

A combined apparatus of this type is described in DE 39 10 548/Niemann 1990 that combines a displacement frame with a braking device to increase web tension. The principle of an early version of the underlying displacement frame to control the lateral position of moving material webs was described in U.S. Pat. No. 3,326,435, issued to Shelton on Jun. 20, 1967. In the following discussion, a device of this type including the braking device is called a displacement frame.

A brochure from the company FIFE/Fife-Tidland 2006/presents another combined apparatus that also combines a control roller (also called a camberoller) with a braking device to increase web tension. The underlying camberoller was already assumed to be known in DE 1093 315/Leimer & Mack 1960/and is described in a very early form in U.S. Pat. No. 2,797,091, issued to Fife on Jun. 25, 1957. In the following discussion, this device including the braking device is called steering frame for short.

Both solutions are encumbered by disadvantages. The solution of Niemann 1990 using the displacement frame permits the control to be effective only in the direction of the web outlet. In addition, the ability to effect web corrections for this type of device is often so limited by mechanical constraints that it is often not adequate for the application under consideration. Another disadvantage is the fact that in the solution using a displacement frame a greater angular adjustment of the rollers is required for a given correction of the web course than would be necessary when compared with an apparatus based on Fife-Tidland 2006. However, the angle of the last roller in the displacement frame determines the distribution of web tension in the outlet of the displacement frame and thus also in the following preheating unit. The larger the correction of the web course, the more the angle of the last roller in the displacement frame deviates from a right angle relative to the fabrication-course direction, and the more irregular is the distribution of web tension.

In order to provide compensation, constructional designs, such as described in EP 0 722 899/Niemann & Wulf 1996, are often used to again improve the web-tension distribution for the preheating unit. In addition, a pre-control means based on EP 0 519 261/Niemann & Wulf/ is also used to augment the displacement frame. This enables the web course to be acted upon even on the bridge itself, and the constraint on correctability by the displacement frame itself is removed.

The solution using the steering frame according to /Fife-Tidland 2006/has the advantage that the web correction acts not only in the outlet but also in the intake, and can thus be observed on the bridge itself. In addition, the angular adjustment of the roller is smaller, with the result that the distribution of web tension at the outlet is more uniform than in the solution according to Niemann 1990. This is even more true the smoother the implementation is of the table surfaces of the bridge, since it is under such conditions that the site of the strongest bending of the web is displaced the furthest from the steering frame. As a result, it is generally possible to dispense with any ancillary devices as specified by Niemann & Wulf 1992.

This solution always functions flawlessly for the top single-face corrugated fiberboard webs since the intake to the steering frame has a sufficiently long extent. Significant difficulties are often encountered with the lower single-face corrugated fiberboard web in designing the machine and with its operational startup. In order to achieve the required length for the web intake, typically web redirecting means are integrated, thereby producing a folded web course with double-opposing redirections. The fundamentally advantageous action of the Fife-Tidland 2006 solution of also affecting the position of the web in the intake results in interactions with the web at these web redirecting means which can generate additional positional errors that are of significant magnitude.

Based on the known embodiment according to Fife-Tidland 2006 for a bridge of a corrugating machine, the fundamental problem to be solved by the invention is to improve the course of the bottom single-face corrugated fiberboard web so as to achieve reliable installation planning and simple operational startup.

SUMMARY OF THE INVENTION

In the known embodiment, the bottom-most of the single-face webs forms a loosely stored web supply and is delivered from this supply via a double-opposing reversal of direction to a steering frame having a braking roller, wherein the first direction reversal occurs through a fixed guide element in the direction opposite the fabrication course. According to the invention, the second direction reversal proceeds back in the direction of the fabrication course in two stages, wherein a redirection occurs first about a fixed redirecting element in a vertically-upwards-directed motion, while a redirecting roller swivelable about a vertical axis is provided above this fixed redirecting element by which the web is subjected to the second redirecting stage towards its steering frame in which the web now wraps around the swivelable redirecting roller by only approximately 90 degrees.

In this embodiment, the swivelable redirecting roller can be adjusted either automatically or in a controlled fashion parallel to the rollers of the following steering frame, thereby creating between the fixed redirecting element and the controllable redirecting roller a web course segment running parallel to the swivel axis, which segment is only twisted during the swivel adjustments, and thus is not subjected to any unilateral loads in tension that are ultimately responsible for the undesired reactions at the web redirecting means.

The braking device used to control the web tension on the segment behind the steering frame to the preheater requires a minimum web tension at the intake so that friction can be effective and the braking action can engage. If this minimum level of web tension is not achieved, the web then slides over the stationary braking roller and control of the web tension is no longer possible. The proposed guiding of the web during the second redirection creates enough resistance so as to generate the required web tension. In addition, fluctuations of the web tension created during the unlooping process of the corrugated fiberboard during removal from the stored supply are dampened with this web guide. Due to its up-and-down motion, the segment of the single-face corrugated fiberboard hanging freely between the first and the second redirecting means provides a partial compensation for the web fluctuations caused by the unlooping process.

In the most simple embodiment variant of the invention, the swivelable redirecting roller is freely swivelable and is moved into and held in the correct position only by the corrugated fiberboard itself. Here, first of all, the swivel axis of the redirecting roller must be disposed at the center of the equipment, and secondly, the steering frame must be implemented or adjusted such that the center of the translational-rotational path of motion approximately coincides with the swivel axis of the swivelable redirecting roller.

In order to ensure reliable operation and also to facilitate the feed-in of the web, stops are advantageously provided that limit the swivel angle of the swivelable roller so that this angle cannot significantly greater than the swivel angle of the control rollers.

In a development of the invention, the swivelable redirecting roller is also freely swivelable and is moved into the correct position and held there by the corrugated fiberboard web; however, in addition measures are applied to increase the friction between the corrugated fiberboard web and the roller, for example, a plasma coating or plastic coating of the roller surface. Similarly, the roller can be wound with adhesive tapes specially produced for this purpose.

In another embodiment, the swivelable redirecting roller is once again freely swivelable and is moved into the correct position and held there by the corrugated fiberboard web itself; however, additionally in order to create a certain positive fit the roller surface is designed with a rotational-axis-parallel structure such that the web side of the single-face corrugated fiberboard web running over this surface obtains an especially effective grip. For example, a structure can be used that has a negative height profile relative to the corrugated fiberboard, thereby creating a denticulation.

In yet another development, the swivelable redirecting roller is connected by tension cable to the steering frame such that the regulating forces are no longer transmitted by the corrugated fiberboard web, but instead by this tension cable.

In another embodiment, the swivelable redirecting roller is adjusted by a motor drive, and this drive is controlled by electronic means such that the redirecting roller is oriented parallel to the rollers of the steering frame. For this purpose, the steering frame must be equipped with a measuring sensor for its momentary position (angular position). Wherever the following discussion speaks in a simplified way only about angle transmitters, what is referenced is a measuring sensor with the meaning mentioned here.

In one design of the embodiment having a motor drive for the swivelable redirecting roller, this drive is controlled by electronic and automatic-control means such that the steering frame always operates with the braking device as much as possible in the frame's center position. To solve this problem, additionally a second controller is used that starting from an equi-angularly adjusted swivelable redirecting roller corrects the roller's angle once again to a certain degree. Since in practice the reaction of the steering frame to a change in angle by the swivelable redirecting roller does not occur immediately, and the occurring delay in reaction is determined by the speed of the corrugated fiberboard web, the known solutions should be used for the second controller whereby the controlling response is affected by the speed of the web. A known method is described in DE 33 04 799/Dingerkus 1983, and in place of the measuring devices used there for the web position, it is possible to use the angle sensors found here. A signal limiter following the second controller should limit the additional angular adjustment to the level compatible with the corrugated fiberboard web.

Finally, in a development of the swivelable redirecting roller, a twin roller that increases its wrap angle can be disposed immediately downstream, thereby producing an increase in the frictional engagement.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following discussion, the invention is explained further by describing embodiments based on the attached drawings.

FIG. 1 shows a segment of the corrugating machine for fabricating duplex corrugated fiberboard between the single-facer stations and the outlet to the gluing station.

FIG. 2 shows the upper part of the bridge with the course of the two single-face corrugated fiberboard webs.

FIG. 3 is schematic top view of the lower tier of the bridge.

FIG. 4 shows an embodiment of the swivelable redirecting roller.

FIG. 5 shows a swivelable redirecting roller with a downstream twin roller.

FIG. 6 is a top view based on FIG. 3 with a mechanical coupling of swivelable redirecting roller and associated steering frame.

FIG. 7 shows an electrical-electronic angular-position coupling of swivelable redirecting roller and associated steering frame.

FIG. 8 shows an embodiment based on FIG. 7 with additional elements.

DETAILED DESCRIPTION OF THE INVENTION

The top single-face web 1 from the stored web supply of single-face corrugated fiberboard pushed together in a loop-like fashion from the further-distant single-facer slides in the upper tier over a table, not provided with a reference number, to the web's steering frame 3 and then into a preheating station 34 where it wraps around the topmost heated drum and is heated in preparation for subsequent gluing. The web then passes through the gluing unit 36 in which the ridges of its flute obtain an application of glue and from here to the joining station 38 of the gluing machine.

The single-face web 2 of the nearby single-facer from the intermediate liner web of the duplex corrugated fiberboard to be produced and its glued-on flute are pushed together to form the stored web supply 8, wherein a stop 9 is reached when the accumulator is full, as illustrated in FIG. 1. In a manner to be described below, this bottom single-face web 2 moves to its bottom steering frame 4, and from here in the same way through a preheating station 34 and gluing unit 36 to the joining station 38.

The unwinder 32 for the other outer liner web 30 is located under the bridge, which web in the preheating station also wraps around a heated drum and moves from here to joining station 38 where the final structure of the duplex corrugated fiberboard is produced.

FIG. 2 shows further details, where here the accumulator is not completely filled with web supply 8. Steering frame 4 is adjusted on a translational-rotational path of motion transverse to the fabrication direction as governed by the signals of a measuring device 4d having a lamp 4e and used to determine the web position, the frame being guided here on bearings 4f. The center of this path of motion is located at 5a.

Steering frame 4 contains two control rollers 4a and 4c, and offset between these a braking roller 4b that opposes their rotation with a braking torque by means of a brake, not shown. It is important that a minimum tension load be effective in it when the web enters the steering frame in order to create a frictional grip with braking roller 4b so that this roller can develop its braking action.

On its path from web supply 8 to steering frame 4, a first reversal of direction occurs from the progressive direction of fabrication to the opposite direction via a fixed guide element 7 that is wrapped around more or less as a function of the fill level of web supply accumulator 8, or also acts in a supporting manner. From here the web runs in loose waves, dancing up and down in operation, to a fixed redirecting element 6 by which the web is diverted into a vertically-upward directed web course segment.

Above fixed redirecting element 6, a redirecting roller 5 is disposed that is swivelable about a centrally vertical swivel axis 5a. This roller is mounted between the cheeks of a swivel frame 5b, while the rotational axis of swivelable redirecting roller 5 displaced relative to swivel axis 5a by a given amount toward steering frame 4. The frame's translational-rotational path of motion has the center approximately coinciding with swivel axis 5a and due to the displacement the swivel motion of swivelable redirecting roller 5 is not a pure rotation about a vertical axis but rather an oscillating, i.e., pendulousness motion of short pendular length.

Fixed guide element 7 is preferably a fixedly mounted roller, however, depending on conditions it can also be an immovable rod. Fixed redirecting element 6 is preferably an immovable rod; however, under certain circumstance it can more advantageously be a fixedly mounted rotatable redirecting roller.

In the simplest case, swivelable redirecting roller 5 is completely freely swivelable, such that it is drawn into a swivel position only by the running web strand for steering frame 4, in which position it is aligned parallel to the frame's rollers. If this effect does not occur with sufficient reliability, the frictional coefficient of the roller surface can be increased by suitable means, or the surface can be furrowed in the direction of the surface lines, roughly corresponding to the corrugation of the single-face web passing over it, thereby creating a positive fit, as is illustrated in FIG. 4. Another possible approach is to dispose a twin roller 5.2 immediately downstream from swivelable redirecting roller 5.1, the twin roller increasing the wrap angle of upstream roller 5.1.

It is also possible to force the swivel motions of the swivelable redirecting roller by mechanical or electrical/electronic means. FIG. 6 shows how, for example, swivelable redirecting roller 5 can be connected to steering frame 4 by tension elements 10.

FIG. 7 shows the actuating motor 4h of steering frame 4, which motor is also actuated as a function of the signals from the lateral-position measuring device 4e/4d, and the frame additionally has an angular-position measuring sensor 4g, the signals of which are fed to the first input of a summing node 20a. Its second input is supplied with the signals from an angle sensor 5c of swivelable redirecting roller 5, and the signal resulting from subtraction passes to a controller 20b that controls an actuating motor 5d acting through a motor driver 20c on swivel frame 5b such that swivelable redirecting roller 5 follows the swivel motions of steering frame 4 and its rollers. In FIG. 8, the above-examined arrangement has been augmented with a speed correction element: a signal formed from the web speed V_Bahn and angular position φ of the steering frame is also fed to summing node 20a and summing node 20a is supplied by a limiter 20e that limits the resulting additional angular adjustment to an level compatible with the use. The signal obtained in second controller 20d from the steering frame angular-position signal and the speed signal takes into account the delay in the reaction of the steering frame as determined by the web speed to an angular change in the swivelable redirecting roller, as was described above as an advantageous development.

With the use of the invention, the installation and operational setup of a corrugating machine is accomplished with significantly less cost in terms of work and time, and a more stable operation is achieved.

LIST OF REFERENCE NUMBERS

• • 1 top single-face corrugated fiberboard web
  • 2 bottom single-face corrugated fiberboard web
  • 3 top steering frame
  • 4 bottom steering frame
  • 4a control roller
  • 4b braking roller
  • 4c control roller
  • 4d measuring device
  • 4e lamp of the measuring device
  • 4f bearings
  • 4g angular-position measuring sensor
  • 4h actuating motor
  • 5 swivelable redirecting roller
  • 5a swivel axis of the swivelable redirecting roller 5; center of the translational-rotational path of motion of steering frame 4
  • 5b swivel frame
  • 5c angle sensor
  • 5d actuating motor
  • 6 fixed redirecting element
  • 7 fixed guide element
  • 8 stored web supply
  • 9 accumulator stop
  • 10 tension element
  • 20a summing node
  • 20b controller
  • 20c motor driver
  • 20d second controller
  • 20e limiter
  • 30 outer liner web
  • 32 unwinder of the outer liner web
  • 34 preheating station
  • 36 gluing unit
  • 38 joining station

Claims

1. A bridge of a corrugating machine for controlling one or more corrugated fiberboard single-face webs feeding in from one or more single-face corrugating machines, the bridge comprising:

a stored web supply formed by the bottom-most of the single-face webs, the stored web supply is loosely-lying;

a fixed guide element, wherein a first reversal of direction of the web occurs via the fixed guide element in the direction opposite a course of fabrication;

a fixed redirecting element;

a redirecting roller mounted in a frame swivelable about a vertical axis the redirecting roller cooperating with the fixed redirecting element to cause a second reversal of direction of the web back in the direction of the course of fabrication, wherein the redirecting roller is disposed above the fixed redirecting element such that a web course section is created running parallel to the swivel axis; and

a steering frame having a braking roller feeding the web to a preheating station, wherein the braking roller operates to create a desired web tension load.

2. The bridge according to claim 1, wherein the rotational axis of the redirecting roller is offset relative to its swivel axis in the direction of the course of fabrication.

3. The bridge according to claim 1, wherein at least one of the fixed guide element and the fixed redirecting element is a fixed redirection rod.

4. The bridge according to claim 1, wherein the fixed guide element and the fixed redirecting element is a fixedly mounted roller.

5. The bridge according to claim 1, wherein a friction-enhancing coating is applied to the redirecting roller.

6. The bridge according to claim 1, whereby a structured surface of the redirecting roller corresponds to a corrugation path of the single-face web running over the redirecting roller.

7. The bridge according to claim 1, wherein a mechanical swivel-motion link is disposed between the redirecting roller and the steering frame.

8. The bridge according to claim 7, wherein the mechanical swivel-motion link is formed by one or more tension elements.

9. The bridge according to claim 1, wherein the redirecting roller further comprises an actuating-motor swivel drive and the steering frame further comprises an angular-position measuring sensor producing an signal, wherein the actuating-motor swivel drive is controlled by the signal from the measuring sensor such that the swivel position of the redirecting roller follows that of the steering frame.

10. The bridge according to claim 9, wherein the redirecting roller further comprises an angular-position sensor producing a signal, the signal is processed with the signal from the angular-position measuring sensor of the associated steering frame in a summing node to obtain the control signal for the actuating-motor swivel drive.

11. The bridge according to claim 10, wherein a correction signal is fed to a third input of the summing node, the correction signal being obtained from the signal of the angular-position measuring sensor associated with the redirecting roller and a signal derived from the speed of the single-face corrugated fiberboard web.

12. The bridge according to claim 1, wherein a twin roller is disposed between the redirecting roller and the steering frame, the twin roller operating to increase the wrap angle.

13. A method of controlling one or more corrugated fiberboard webs feeding in from one or more single-face corrugating machines, using a bridge, comprising the steps of:

feeding the bottom-most of the single-face webs into a stored web supply, the stored web supply is loosely-lying;

passing the web from the stored web supply around a fixed guide element to introduce a first reversal of direction of web in the direction opposite a course of fabrication;

passing the web along a fixed redirecting element;

passing the web along a redirecting roller, the redirecting roller being mounted in a frame swivelable about a vertical axis, the fixed redirecting element cooperating with the redirecting roller to introduce a second reversal of direction of web back in the direction of the course of fabrication, wherein the redirecting roller is disposed above the fixed redirecting element such that a web course section is created running parallel to the swivel axis, the fixed redirecting element and redirecting roller further cooperating to generate a desired web tension load; and

passing the web through a steering frame having a braking wheel, the braking wheel operating to feed the web in a braked fashion to a preheating station.

14. The method of claim 13, further comprising the step of adjusting the steering frame wherein the center of the translational-rotational path of motion coincides with the swivel axis of the redirecting roller.