EP0149737B1 - Corrugated cardboard stacking device - Google Patents

Abstract

1. Corrugated cardboard stacking device for a format depositing means (12) for corrugated cardboard sections behind a transverse cutting means (21), comprising several series-connected belt type conveyors (13, 14, 15, 16) adapted to be separately driven by individual driving means and receiving the corrugated cardboard sections in an overlapping scale flow formation, with a separating means (23, 24) behind a first belt type conveyor (13) for the formation of a predetermined gap in the scale flow, with at least one format depositing means (12) arranged behind the last belt type conveyor (16) and working to the lifting principle and provided with a vertically adjustable stacking platform (19), with a control device (25) for the individual driving means (FM1, FM2, FM3, FM4) of the belt type conveyors (13 to 16) and for the stroke of the stacking platform (19), with the belt type conveyors (13 to 16) behind the separating means (23, 24) being adapted to be run simultaneously upward during the operation of stacking off from a stationary speed of operation for the purpose of extending the gap in accordance with the speed and to be subsequently run down again in a cascade-like manner, characterized in that the separating means (23, 24) in case of response will lift the corrugated cardboard section respectively disposed thereabove and will be activated for the purpose of accumulating the following corrugated cardboard sections until the series-connected belt type conveyor is free of formats, and in that the belt type conveyors (14, 15, 16) disposed behind the separating means (23, 24) during the cascade-like running down movement are adapted to be adjusted to a speed deviating from the operating speed and which is selected dependant on the respective length of format in such a manner that the forward edge of the foremost corrugated cardboard section reaches the format depositing means (12) at the arrival thereof in the starting position.

Description

The invention relates to a conveyor device according to the preamble of claim 1.

In corrugated cardboard plants, the longitudinally cut and grooved corrugated cardboard web goes into a so-called cross cutter, which cuts the corrugated cardboard web into individual formats. The cross cutter can be moved so that you can switch from one format length to the other - even during production. The individual formats are usually stacked in a so-called format tray. The stacking is usually carried out from above on a height-adjustable platform. The formats coming from the cross cutter must therefore be raised to the stacking level. For this purpose, a mostly relatively long transfer conveyor section is arranged between the cross cutter and the format stacker. The speed at which the formats come out of the cross cutter as the last processing machine is considerably higher than the transport speed of the conveyor device between the cross cutter and the format stacker. As a rule, the ratio of the speeds is 10: 1. A flow of overlapping corrugated cardboard sections therefore results on the conveying device, the extent of the overlap depending on the one hand on the speed ratio and on the other hand on the format length. The conveyor device is normally set to a certain operating speed, which can be matched to a certain format length. It is also not changed when the format length is changed.

However, the continuous operation described must be interrupted when the stack in the format depositor has reached its desired height or when the desired number of formats has been stacked. In a known conveyor device according to US-A-4 040 618, a relatively long conveyor belt is arranged behind the cross cutter, and a relatively short conveyor belt is located between the long conveyor belt and the format stacker. Shortly before a stack change, a braking device between the conveyor belts is actuated and the short conveyor belt is driven at a higher speed when the longer conveyor belt is reduced to half the normal speed. The braking device remains activated only until the stacking platform is in the ready position again. During the entire preparation time, however, there is a scaling on the long conveyor belt in front of the braking device. As is known, the preparation time is the size according to which all processes during the stack change on the conveyor device must be based. It is composed of the clearing time of the conveyor behind the braking device, the lowering time of the lifting platform into the delivery position, the removal time of the stack from the lifting platform and the start-up time of the lifting platform in the starting position. Except for the clearing time of the conveyor section, all other times are fixed and cannot be shortened. For this reason, the short transfer conveyor belt in the known device is too short. There is also a build-up on the longer conveyor belt during the entire preparation time, since the braking device is activated for a longer time. Although the scaling of the formats can be increased to a certain extent, if the braking time is too long, irregular congestion can occur with the risk of malfunctions. The conveyor between the cross cutter and format stacker is susceptible to malfunctions anyway. The higher the system speed, the greater this vulnerability. With the known conveyor device, the system speed can therefore only have a limited height.

It is known from DE-A-28 52 603 described in the preamble of claim 1 to provide a series arrangement of individual belt conveyors and in this connection to provide a combined arrangement of two endless belt conveyors, one of which consists of a conventional endless conveyor belt and the other of one Endless conveyor is formed, one half of which contains cross bars. If the formats reach the cross bars, they are conveyed at the speed of the bars. The other endless conveyor belt, however, can be driven at a higher speed. In this way, it is possible to fill a gap in a scale stream without accumulation. Such a gap is necessary if a batch change is to take place with continuous feeding to the format depositor. When a gap is drawn, the speed of the second conveyor with the strips is equal to the belt speed of the belt conveyor proceeding in the conveying direction. The size of the gap therefore depends on the time that the strips are in transport engagement with the formats and on the greater speed of the belt conveyors following in the conveying direction. The acceleration of the belt conveyors, which are driven to pull a gap at a higher speed, and their maximum speed are, however, limited, since otherwise the formats can no longer be transported properly. In addition, with the known stacking device, it is difficult to determine the exact location of a gap. This is particularly important when changing the format in the so-called permanent run of a corrugated cardboard machine in order to prevent incorrect formats from being stacked.

It is well known that formats of different lengths are not put on the same stack filed. A change in format length is therefore always associated with a batch change. Regardless of the braking or scaling of the formats in a separating device according to the last known device, the time in which the new format arrives at the format depositor depends on its length. Accordingly, a long format arrives earlier than a shorter format. The speeds are therefore to be set in the known device so that the longest formats do not arrive too early at the format depositor. However, this means that time is wasted for smaller formats.

The invention is therefore based on the object of providing a conveying device for a format stacker for corrugated cardboard sections behind a cross cutter, which ensures a cleanly aligned shingled stream arriving at the format stacker at the correct time even when driving different section lengths when changing stacks.

This object is achieved by the features of the characterizing part of the new claim 1.

In the conveyor device according to the invention, although a braking device similar to the device described at the outset is used, it is only activated briefly in the invention, and only as long as it takes that the belt conveyor downstream of the braking device conveys the formats available on it at a higher speed . There is therefore a greater overlap before the braking device. However, this can be accepted, since it is naturally much shorter than the long braking in the known conveyor device. After the braking device has been deactivated, the individual belt conveyors in the invention are specifically driven after the braking device in such a way that the front edge of the front corrugated cardboard section reaches the format depositor when it is in its starting position. This is irrespective of whether a very long or a very short format arrives. The device according to the invention therefore enables optimal use of the preparation time.

According to one embodiment of the invention, the control device contains a computer, and a section counter is assigned to the separating device, which sends the counting pulses to the computer, the computer generating a signal for actuating the separating device when the counting pulses reach a predetermined desired value. A plurality of separately activatable initiators that are offset in height and assigned to the stroke of the stacking platform are connected to the computer, and the computer generates a signal for the separating device before the setpoint is reached when the stacking platform triggers an activated initiator. The calculator can be set to the desired number of formats, which is desired for a stack. Usually the formats are flat, flat plates. However, various influences can easily cause individual plates to bulge more or less. With a predetermined number of formats in the stack, this results in a different stack height. In many cases, the stack height must not exceed a predetermined upper limit. In the embodiment according to the invention, the separation device can be triggered even though the number of pieces set in the computer has not yet been reached.

The total number of pieces of the computer can also be divided into even stacks.

• Fig. 1 zeigt in Seitenansicht eine Fördervorrichtung und einen nachgeschalteten Formatableger nach der Erfindung.
• Fig. 2 zeigt schematisch eine Förderstrecke der Vorrichtung nach Fig. 1 sowie im Blockschaltbild eine Steuerung dafür.

An embodiment of the invention is explained in more detail below with reference to drawings.

• Fig. 1 shows a side view of a conveyor and a downstream format depositor according to the invention.
• Fig. 2 shows schematically a conveyor line of the device according to Fig. 1 and in the block diagram a control therefor.

1 shows two tracks 10 and 11 of a transfer conveyor device between a cross cutter, not shown, and a stacking station with a first format stacker 12, which is assigned to the conveyor track 11. The other format depositor assigned to the conveyor track 10 is not shown.

Each conveyor track 10, 11 is assigned a plurality of conveyors, specifically a belt conveyor 13, 13 ', 14, 14', 15, 15 'and 16, 16'. Brake conveyors 17, 18 and 17 ', 18' are assigned to belt conveyors 13 and 13 ', respectively. One is used to stop formats coming from the cross cutter and to drop them onto the conveyor belt underneath, which is driven at a lower speed than the line speed. The belt conveyors 13 to 16 are driven by separate drive motors FM1, FM2, FM3 and FM4. The conveyors 13 'to 16' have corresponding drives, not shown.

The format stacker 12 has a height-adjustable stacking platform 19. In the upper area, a photocell arrangement 20 is provided, with the aid of which the upper level (shown in dash-dotted lines) of the platform or of the format lying on top is set. When storing, the platform 19 is therefore lowered more or less continuously until the desired stack height is reached.

The operation of the device shown in FIG. 1 will be explained with reference to FIG. 2. In Fig. 2 only the conveyors 13 to 16 of the lower track are considered. A corrugated cardboard web 20 is fed to a cross cutter 21 and separated into formats here. Depending on the setting of the cross cutter 21, the length of the formats is variable. The formats arrive at the first belt conveyor 13 from the cross cutter 21, being stopped beforehand by the brake car 17 and 18 (not shown in FIG. 2). Since the conveying speed v1 of the conveyor 13 is only one tenth of the line speed, the formats are shingled one above the other, as indicated at 22. An adjusting cylinder 23 is arranged between the transfer conveyors 13 and 14, which cooperates with a brake tappet 24, which can optionally be moved into a plane below the conveying plane or above the conveying plane, as indicated in dashed lines.

The conveyor drives FM1 to FM4 are controlled by a computer 25. The adjusting cylinder 23 is also controlled by the computer 25. There is also an active connection to the computer 25 for a DC motor 26 for driving the stacking platform 19 in the format stacker 12. The photocell arrangement 20 is connected to the computer 25, as are five initiators 28 along the travel path of the platform 19 or sensors on the cross cutter 21 for the system speed, the format number and format length. The format thickness, a number of stacks and a total number of pieces are also entered into the computer 25. The statement "total number of pieces" means the number of pieces of a given format, i.e. given length.

The operation of the device shown is as follows.

The formats coming from the cross cutter 21 are deposited in scaled form on the belt conveyor 13 and transported at the speed v1. The speed v1 is one tenth of the system speed, and consequently also the speed in the cross cutter 21. The speeds v2 to v4 of the other conveyors 14 to 16 are also equal to v1. The scaled formats are stacked in the format stacker 12 on the stacking platform. In the starting position, the platform 19 is at the level 29 shown in broken lines. As the stacking progresses, the platform 19 is continuously lowered by the direct current motor 16. The photocell arrangement ensures that the level 29 is approximately maintained. If the sensor 27 determines that formats are no longer being transferred, the DC motor 26 moves to the delivery position and the stack on the platform 19 can be removed. A trigger (not shown) causes the computer 25 to move the platform 19 back up to the starting position for the new stack formation. However, the adjustment to the delivery position does not only take place on the basis of the signal from the sensor 27, but a corresponding presetting in the computer 25 is required.

With an approximately predetermined stack height, only a certain number of formats can be stacked per stack. Therefore, both the format thickness and the number of batches to be calculated are entered into the computer. By means of counting pulses from the cross cutter 21, the computer 25 can determine how many formats have been placed on the conveyors. With the aid of the computer 25, it is also possible to determine the number of formats conveyed not only at the exit of the cross cutter 21, but in the region of the ram 24. If the computer 25 determines that the desired number of pieces has passed the plunger 24, the adjusting cylinder 23 is activated by the computer 25. Its plunger 24 slightly lifts the scaled formats and prevents them from being transported further via the plunger. At this time, the drives FM2 to FM4 are controlled to a higher speed so that the remaining formats reach the format stacker 12 as quickly as possible. Since the speeds v2 to v4 are known to the computer 25, it can also be determined when the last format has left the conveyor 14. After this time, the speed of the FM2 drive is reduced again. The same happens with the FM3 and FM4 drives. As soon as they have submitted the last format, they will be driven at a reduced speed. The speeds v2 to v4 of the conveyor drives FM2 to FM4 are the same. The size of the speed, however, depends on the length of the formats that follow when the plunger 24 releases the feed again. This release takes place at the time when the conveyor 14 immediately following the separating device is emptied and driven at a lower speed. As can be seen, the overhang of the front format, which has been stopped by the ram 24, depends on the format length. As a result, the longer format reaches the end of the conveyor section earlier than a shorter one at the same speed. Therefore, the computer 25 calculates the speed of the drives FM2 to FM4 from the format length such that, after the ram 24 becomes inactive, the front edge of the first format is just before being stored in the format depositor 12 when the platform 19 has reached its starting position. The availability time of platform 19 is another variable that the computer has to take into account. However, it is already known. However, it can be arbitrarily adjusted using the computer if circumstances arise that accelerate or delay the batch change.

It can be seen that the plunger 24 of the separating device is only in engagement for a very short time, a maximum of 2 seconds, so that only a relatively slight jam forms in front of the separating device, which is harmless for the correct placement.

For a given format thickness, the travel path of the platform 19 can be divided according to how many formats have been stored when the platform 19 is at a predetermined location. The Separator 24 is actuated when a desired number has passed to accommodate a predetermined number of formats in the stack. However, it can now happen that the stack height has already reached the target height by discarding individual formats with a smaller number of formats. The initiators 28 are therefore provided, which are set to different format lengths and format thicknesses. If the platform 19 reaches an activated initiator 28 at a point in time when the number of pieces on the platform 19 together with the number of pieces on the conveying path behind point 24 the total number of pieces of the stack has not yet been reached, the adjusting cylinder 23 is nevertheless actuated. A smaller number than the target number of pieces is therefore stacked. This prevents stack heights that are too large from being driven.

Claims (2)

1. Corrugated cardboard stacking device for a format depositing means (12) for corrugated cardboard sections behind a transverse cutting means (21), comprising several series-connected belt type conveyors (13,14,15,16) adapted to be separately driven by individual driving means and receiving the corrugated cardboard sections in an overlapping scale flow formation, with a separating means (23, 24) behind a first belt type conveyor (13) for the formation of a predetermined gap in the scale flow, with at least one format depositing means (12) arranged behind the last belt type conveyor (16) and working to the lifting principle and provided with a vertically adjustable stacking platform (19), with a control device (25) for the individual driving means (FM1, FM2, FM3, FM4) of the belt type conveyors (13 to 16) and for the stroke of the stacking platform (19), with the belt type conveyors (13 to 16) behind the separating means (23, 24) being adapted to be run simultaneously upward during the operation of stacking off from a stationary speed of operation for the purpose of extending the gap in accordance with the speed and to be subsequently run down again in a cascade-like manner, characterized in that the separating means (23, 24) in case of response will lift the corrugated cardboard section respectively disposed thereabove and will be activated for the purpose of accumulating the following corrugated cardboard sections until the series-connected belt type conveyor is free of formats, and in that the belt type conveyors (14, 15, 16) disposed behind the separating means (23, 24) during the cascade-like running down movement are adapted to be adjusted to a speed deviating from the operating speed and which is selected dependant on the respective length of format in such a manner that the forward edge of the foremost corrugated cardboard section reaches the format depositing means (12) at the arrival thereof in the starting position.

2. Cardboard stacking device according to claim 1, characterized in that the control means comprises a computer (25) the separating means (23, 24) having associated thereto a section counter transmitting counting pulses onto the computer, the computer (25) generates a signal for actuating the separating means (23, 24) when the counting pulses reach a predetermined set value, the computer having connected thereto several initiators (28) associated with the lifting distance of the stacking platform (19) which are offset in height and adapted to be separately actuated, and the computer (25) actuating the signal for the separating means (23, 24) already before the preset value is reached, when the stacking platform releases an activated initiator.

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