GB2285253A

GB2285253A - Adjusting distribution of overlapped sheets along a feed path

Info

Publication number: GB2285253A
Application number: GB9425076A
Authority: GB
Inventors: Nokihisa Adachi; Minoru Naito
Original assignee: Isowa KK
Current assignee: Isowa KK
Priority date: 1993-12-28
Filing date: 1994-12-13
Publication date: 1995-07-05
Also published as: JP3276761B2; ITMI942612A1; ITMI942612A0; JPH07196221A; IT1271792B; DE4446114A1; GB9425076D0

Description

1 2285253 METHOD OF CONTROLLING SINGLING OF CORRUGATED BOARD SHEETS

BACKGROUND OF THE INVENTION

This invention relates to a method of controlling singling of corrugated board sheets. More particularly, this invention relates to a method of controlling singling of corrugated board sheets in the process that a continuous corrugated board sheet web is cut by a cutter into sheet blanks having a predetermined length, and the thus cut sheet blanks fed one after another from the cutter are to be transported toward a stacker locating downstream, while the cut-sheet blanks partly overlap one after another such that the rear end portion of a preceding cut-sheet blank may overlap with the front end portion of the following blank, in which the singling operation can smoothly be achieved without impairing the alignment of the thus singled cut-sheet blanks coping with an increase of production speed in the corrugator line upstream than the cutter and in accordance with severe specifications such as increased range of the length of cut-sheet blanks from very short ones to very long ones.

In the corrugator line where corrugated board sheets are produced continuously, a long corrugated board sheet web produced through a double facer is cut successively by a rotary cutter into cut-sheet blanks having a predetermined length in the final step or thereabout and then forwarded to subsequent steps where slotting, creasing, etc. are to be carried out. In the above-described process, the sheet blanks cut into a predetermined length are stacked one after another in a stacker disposed downstream side of the corrugator line. For such purpose, a multiplicity of sheet blanks cut by the rotary cutter are separated into sheet bunches by the length, and the bunches thus formed are transported intermittently on a known conveyor. For example, as disclosed in Fig. 1 of Japanese Unexamined Patent Publication (Kokai) No. 129161/1977t a preceding cut-sheet blank having a predetermined length is allowed to overlap partly with the following cut- sheet blank having the same length (this state is termed as "singling") on a belt conveyor, and the cut-sheet blanks are transported by the bunch in such singled state.

Meanwhile, when a continuous corrugated board sheet web is to be cut into cut-sheet blanks having a predetermined length, it often happens that the cut-sheet length-is required to be changed frequently in compliance with the requests of customers. Such change in the cut-sheet length (so-called "order change") is managed by changing the rotational speed of the rotary cutter disposed in the corrugator line. If such order change is implemented, another bunch of cut-sheet blanks whose length is changed is forwarded following the bunch of cut-sheet blanks before size change. Thus, two bunches of cut-sheet blanks of different lengths must securely be separated from each other in the event of any order change, such that the rear end portion of the last blank of the bunch before size change may not interfere on a singling conveyor system with the front end portion of the first blank after size change. For such purpose, various methods of separating the bunch before order change from the bunch after order change on the conveyor system have been proposed.

As described above, a so-called singling conveyor system is disposed on the route of the corrugator line between the outlet of the rotary cutter and the loading section of the stacker. The singling conveyor system is adapted to have (1) a function of receiving, at a reduced speed, sheet blanks cut out by the cutter and fed at a high speed so as to achieve singling thereof to an appropriate density; (2) and a function of separating the preceding bunch of cut- sheet blanks from the following bunch in accordance with a predetermined order change and with the amount of the stacked blanks. Under such circumstances, since various requirements including increase in the production speed of corrugator line (e.g. 300 m/min at the maximum), increased range of cut-sheet length (e.g. ranging from the shortest size of 400 mm to the longest size of 6,000 mm), diversification of flute type of corrugated board sheet, diversification of sheet materials, frequent order changes and increase of small lot orders are recently imposed on the corrugator line, the singling conveyor system is also required to meet these severe requirements. The present applicant already filed a patent application corresponding to Japanese Unexamined Patent Publication (Kokai) No. 165266/1988 as a proposal of singling control method which can meet such requirements. According to this official gazette, the singling conveyor system Is driven at a speed inversely proportional to the cut-sheet length corresponding to the production speed Vs of the double facer in the corrugator line, and a length where the blanks do not overlap with one another (finite difference) can substantially constantly be secured.

The invention according to the above patent application can extremely suitably be put into practical uses, provided that the cut-sheet length of the sheet blanks is within the range of frequent use. However, it was found that there occur inconveniences in the action of singling very short or very long cut-sheet blanks, if the range of the length of cut- sheet blanks to be cut out from a corrugated board sheet web is widened, as described above. For example, it is presumed that sheet blanks cut into a very small length of 500 mm by the cutter are to be received by the singling conveyor system according to the abovedescribed singling control method which can provide a constant finite difference. Provided that the length where the preceding cut-sheet blank does not overlap with the following blank (finite difference) is 206 mm, the overlapping portion becomes 300 mm, and thus the singling density is extremely lowered to such a degree as substantially no frictional force to be caused by the own weights of the sheet blanks can be expected. Accordingly, the singling state of the cut- sheet blanks tends to be disturbed coupled with the reduction in the frictional force to make the arrangement of the cut-sheet blanks on the conveyor out of order, disadvantageously. It can also be pointed out that the sheet transporting speed is inevitably increased as the result that the conveyor system is driven at a speed inversely proportional to the cut-sheet length to readily cause disorder in the state of stacking in the stacker, disadvantageously.

Further, for example, cut-sheet blanks having a very long size of 4,000 mm are to be received by the singling conveyor system in the same overlapping manner as described above. Provided that the length where the preceding cutsheet blank and the following cutsheet blank do not overlap with each other (finite difference) is 200 mm, the blank overlapping length amounts to as long as 3,800 mm. In this case, since the singling density becomes too great such that 20 sheet blanks overlap one after another per cut-sheet length of 4,000 mm (4,000 -4- 200 = 20), the load of the motors for driving the conveyor system is increased, so that the capacity of the motors must be increased, disadvantageously. Further, since the number of the cutsheet blanks staying on the conveyor system is great when the bunch is to be separated from the following bunch in accordance with an order change, the number of blanks to be loaded on the stacker becomes too much. Accordingly, the loading speed in the stacker is increased to make follow-up control difficult, disadvantageously.

This invention was proposed in view of the problems inherent in the prior art and in order to solve them suitably, and it is an objective of the invention to provide a systemwhich can carry out the singling action smoothly in accordance with frequent order changes, smalllot orders, etc. without making the state of singling out of order and which can separate the preceding bunch of cut sheet blanks from the following bunch suitably.

SUMMARY OF THE INVENTION

In order to overcome the above problems and attain the intended object suitably, this invention provides a method of controlling singling of corrugated board sheet blanks, which comprises cutting a long corrugated board sheet web produced in a double facer successively into cut-sheet blanks having a predetermined length; feeding the thus obtained cut-sheet blanks to a series of conveyors belonging to a first group including at least one suction conveyor and to another series of conveyors, belonging to a second group, disposed in series with respect to the first group conveyors so as to transport the cut-sheet blanks in such a way that a rear end portion of a preceding blank may overlap with a front end portion of a following blank; and driving the conveyor at an increased speed, in the event of any order change, after detection of arrival of the last blank before order change at the suction conveyor belonging to the first group, so that a bunch of cutsheet blanks before order change may be separated from a bunch of cutsheet blanks after order change; wherein the conveyors belonging to the first group are driven at a speed inversely proportional to the cut-sheet length corresponding to a production speed in the double facer so as to carry out an ordinary singling operation; whereas the conveyors belonging to the second group are driven at a speed proportional to the production speed of the double facer, such that the singling density of the blanks transported on the second group conveyors may be different from that of blanks transported on the first group conveyors.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of this invention that are believed to be novel are set forth with particularity in the appended claims. The invention, together with the objects and advantages thereof, may best be understood by reference to the following description of the preferred embodiments taken in conjunction with the accompanying drawings in which:

Fig. 1 is a schematic diagram of a singling conveyor system disposed on the downstream side of a corrugator line, in which the singling control method of the invention is implemented; Fig. 2 is an explanatory chart showing that a suitable singling density can be obtained when the singling control method according to a preferred embodiment is to be implemented on the singling conveyor system shown in Fig. 1, in any of the case where the length of the cut-sheet blanks is within the common range (2), the case where the cut-sheet length is extremely small (1) and the case where the cut-sheet length is extremely great (3); and Fig. 3 shows schematically in side view cut-sheet blanks which are overlapped one after another to present the socalled singled state.

PREFERRED EMBODIMENT OF THE INVENTION The method of controlling singling of corrugated board - 7 sheets according to this invention will now be described by way of a preferred embodiment with reference to the attached drawings. Fig. 1 schematically shows a singling conveyor system disposed on the downstream side of a corrugator line for producing corrugated board sheets, in which the singling control method according to this invention is to be implemented. In Fig. 1, a rotary cutter 10, which is disposed on the downstream side of a double facer 11, cuts a corrugated board sheet web 12 produced continuously through the double facer 11 into cut-sheet blanks 14 having a predetermined length. A multiplicity of conveyors are arranged in series on the downstream side of the rotary cutter 10 so that the cut-sheet blanks 14 cut by the cutter 10 are adapted to be fed finally in a predetermined state of singling into a stacker 16 provided at the downstream extremity of the corrugator line. The multiplicity of conveyors are roughly divided into two groups: (1) a transfer conveyor system 18 which receives one after another the cut-sheet blanks 14 cut by the rotary cutter 10 and transports them at predetermined intervals; and (2) a singling conveyor system 20 which carries out singling of the cut- sheet blanks and also separates one bunch of cut-sheet blanks from another bunch in compliance with an order change and the like, as described above.

For example, the transfer conveyor system 18 shown in Fig. 1 consists of a cutter outlet conveyor 22 and a deflector conveyor 24 for rejecting defective sheet blanks. Incidentally, the cutter outlet conveyor 22 is provided with a suction chamber 26 for sucking on the transportation surface thereof under a negative pressure a cut-sheet blank 14 fed at a high speed. Meanwhile, the singling conveyor system 20 consists of a first suction conveyor 30 provided with a suction chamber 28, a second suction conveyor 34 provided with a suction chamber 32, a first separating conveyor 36, a second separating conveyor 38, a first slanted conveyor 40 and a second slanted conveyor 42, which are arranged in series. A leaf spring stand 44 for urging the cut-sheet blanks 14 downward is disposed above the first and second suction conveyors 30,34. However, the leaf spring stand 44 may be replaced by other mechanisms so long as they can exhibit such urging function, and a constitution in which a multiplicity of brushes or belts are suspended or a high-pressure air is blown against the cut-sheet blanks 14 may be employed instead. Incidentally, the stacker 16 is designed to stock a multiplicity of singled cut-sheet blanks fed thereto as stacked therein, and a sinking type stacker in which a seat loading table 46 descends gradually is employed in the illustrated embodiment.

The control block for the series of conveyors shown in Fig. 1 essentially consists of motors Mi to M8 for driving the respective conveyors, drive units DU1 to DU8 disposed with respect to the motors M1 to M8 correspondingly and a sequencer S for giving control commands to the driving units DU1 to DU8. A rotar y pulse generator PGO for detecting the speed of producing corrugated board sheets 12 is disposed to the rotational system of the double facer 11, and the pulse train to be output from the rotary pulse generator PGO is counted by a high-speed counter module 48. Further, the respective conveyors in the transfer conveyor system 18 and the singling conveyor system 20 are provided with rotary pulse generators PG1 to PGn correspondingly, and pulse trains to be output therefrom are linked through a specialized multi-counter 50 to a central processing unit (CPU) 52 in the sequencer as pieces of information of tracking the travel of cut-sheet blanks 14 on the respective conveyors. The rotary cutter 10 is provided with an optical sensor 54 which detects cutting of the corrugated board sheet web.12 by the cutter 10 so as to input the cutting signal to the CPU 52. Incidentally, transmission and receiving of data relating to the schedule of producing a corrugated board sheet web 12 and of signals on order changes are carried out via a link of an optical communication network and the like linking the sequencer to a host production controlling unit 56.

By the way, the singling conveyor system 20 shown in Fig. 1 consists of a first suction conveyor 30 and a second suction conveyor 34, each provided with a function of sucking a cut-sheet blank-thereon under a negative pressure; a first separate conveyor 36 and a second separate conveyor 38, which are disposed next to the first and second suction conveyors 30,34 and which have no sucking function; and a first slanted conveyor 40 and a second slanted conveyor 42. In addition, the leaf spring stand 44 for urging the cut-sheet blanks 14 downward is disposed above these two suction conveyors 30,34 having sucking functions, as described above. Thus, for convenience's sake, (1) the first and second suction conveyors 30,34 both having sucking functions are defined as a first group, and (2) a series of conveyors 36,38,40,42 having no sucking function are defined as a second group in the following description. Based on such definitions, in the singling control method according to this embodiment, at least the first suction-conveyor 30 belonging to the first group is driven at a speed inversely proportional to the cut-sheet length corresponding to the production speed in the upstream double facer 11 disposed upstream, while the conveyors 36,38,40 42 belonging to the second group are driven proportional to the production speed of the double facer 11. However, the speed of driving the second suction conveyor 34 in the first group is adapted to be selected, depending on the overall operation state in the singling conveyor system 20, from the speed inversely proportional to the cut-sheet length corresponding to the production speed in the singling conveyor system 20, the speed proportional to the production speed of the double facer 11 and an intermediate of these two speeds.

For example, as shown in Fig. 3, provided that the cutsheet length of the blank 14 is If, and the length where two cut-sheet blanks 14(1),.14(2) do not overlap each other (so-called finite difference) is 1 and that the production speed of the double facer 11 is Vs, at least the first suction conveyor 30 in the first group is driven at a speed of V30 VS (production speed) x 1 (finite difference)/If (cut-sheet length). Namely, the speed at which the first suction conveyor 30 is driven is inversely proportional to the cut-sheet length corresponding to the production speed Vs, and thus the cut-sheet blanks 14 carried to the conveyor 30 are subjected to singling with a substantially constant finite difference 1. Incidentally, the second suction conveyor 34 may be designed to be selectively driven at the speed inversely proportional to the cut-sheet length corresponding to the production speed Vs depending on the vacuum suction force and the spring urging force in the first suction conveyor 30. The series of conveyors belonging to the second group are to be driven at a speed proportional to the production speed Vs of the double facer 11 (provided that 7 sheet blanks are to be subjected to singling, the second group conveyors are driven at a speed of Vs (production speed) x 1/7. It should be noted here that the second suction conveyor 34 is also driven selectively at the speed proportional to the production speed Vs depending on the vacuum suction force and the spring urging force in the second suction conveyor 34 belonging to the first group.

Since the first group conveyors are driven at a speed inversely proportional to the cut-sheet length corresponding to the production speed, as described above, cut-sheet blanks 14 are successively subjected to singling with a substantially constant finite difference 1 onto the first suction conveyor 30 (and on the second suction conveyor 34), even if the length of the cut-sheet blanks 14 to be cut by the cutter 10 should be changed. Accordingly, an appropriate vacuum suction force is applied to the blanks 14 to achieve deceleration without causing disorder in the state of singling. The singling density of the bunch of cut-sheet blanks 14 thus subjected to singling at a substantially constant finite difference 1 can be changed to an appropriate level at a constant rate (e.g. 7 sheets, if a 7-sheet bunch is to be formed), irrespective of the length of the cut- sheet blanks 14, by driving the series of conveyors belonging to the second group at a speed proportional to the production speed Vs. In other words, the singling density of the bunch of blanks belonging to the first group is changed gradually to the singling density of the blanks to be assumed on the second group conveyors as the blanks are transported, and thus the singling density of the blanks on the latter series of conveyors is already changed to an appropriate level, i.e. a predetermined number of singled blanks over a predetermined length.

In this singling control method, if the cut-sheet length If of the blanks 14 is within the common range widely adapted by uses, as shown in Fig. 2(2), singling of the bunch of blanks 14 can be achieved with an appropriate finite difference 1 on both the first group conveyors and the second group conveyors. Namely, the cut-sheet blanks 14 transferred to the first group conveyors are allowed to overlap one after another with an ideal finite difference 1, so that a vacuum suction force can effectively be exerted on each blank carried on the suction conveyors, and that an appropriate frictional force is also generated between the blanks. Accordingly, the bunch of blanks can be transferred to the second group conveyors with no - 12 disorder in the state of singling. While the second group.conveyors are driven at a speed proportional to the production speed Vs, no substantial difference from the driving speed at which the first group conveyors are driven is generated, so long as the cut-sheet length If of the blanks 14 is within the common range. Thus, the bunch of blanks can also be transported on the second group conveyors with no disorder in the state of singling where the appropriate finite difference 1 is substantially maintained.

Next, it is presumed that cut-sheet blanks 14 having a very small length (e.g. 500 mm) are to be transported, for example, based on a 7-layering mode. If the blanks have such small length, and provided that the production speed is 200 m/min, the first suction conveyor driving speed will be considerably as high as: 80 m/min = 200 m/min x 200 mm/500 mm, because the speed at which the first suction conveyor 30 belonging to the first group is driven is inversely proportional to the cut-sheet length corresponding to the production speed. However, the finite difference between the blanks is as small as about 200 mm. Accordingly, the number of singled blanks present per cutsheet blank length If is about 2.5, leading to very low singling density. The state of singling tends to be out of order due to the reduced frictional force between the blanks or between the blanks and conveyor belts in the prior art method, but the bunch of blanks which are initially singled to a low density can be resingled to an appropriate density over the second group conveyors which are driven at a low speed of 1/7 (in this case 28 m/min) proportional to the production speed Vs, as shown in Fig. 2-(1). Since a g:eat difference is generated between (1) the driving speed of the first suction conveyor 30 in the first group (inversely proportional to the cut-sheet length corresponding to the production speed Vs) and (2) the driving speed of the conveyors belonging to the second group (production speed Vs x 1/K) in the case where the cut-sheet length is extremely small as described above, the second suction conveyor 34 belonging to the first group is driven at an intermediate speed of (1) and (2).{54 m/min = 28 m/min + (80 m/min - 28 m/min) -i.. 2) so as to smoothly change the singling density.

On the contrary, it is presumed that cut-sheet blanks 14 having an extremely great length (e.g. 6,000 mm) are to be transported, for example, based on a 7-layering mode. if the blanks have such great length, the singling density of 30 cut-sheet blanks (6,000/200 = 30) will be extremely high, because the speed at which the first suction conveyor 30 belonging to the first.group is driven is inversely proportional to the cut-sheet length corresponding to the production speed and is considerably low (for example, when the production speed is 200 m/min, 6. 6 m/min 1- 200 m/min x 200 mm/6,000 mm) to provide a very small finite difference between the blanks of as small as about 200 mm. Accordingly, the frictional force to be generated between the blanks is increased to apply great load onto the motors for driving the conveyors, disadvantageously, in the prior art method. However, according to the control method of the invention, the series of conveyors belonging to the second group may selectively be driven at a high speed of 1/7 (in this case at 28 m/min) proportional to the production speed Vs, as shown in Fig. 2-(3), so that the densely singled bunch of blanks are resingled appropriately to a sparser density. In the case where the cut-sheet length is extremely great as described above, the second suction conveyor 34 belonging to the first group is adapted to be driven substantially at an intermediate speed of (1) the driving speed of the first suction conveyor 30 belonging to the first group (inversely proportional to the cut-sheet length corresponding to the production speed Vs)

14 and (2) the driving speed of the conveyors belonging to the 'second group (production speed Vs x 1/K) (in this case 17.3 m/min 1-, 6. 6 m/min - 6. 6 m/min) -;- 2).

Claims

What is Claimed is:

1. A method of controlling singling of corrugated board sheet blanks, which comprises: cutting a long corrugated board sheet web (12) produced in a double facer (11) successively into cut-sheet blanks (14) having a predetermined length; feeding the thus obtained cut-sheet blanks (14) to a series of conveyors belonging to a first group including at least one suction conveyor (30) and to another series of conveyors, belonging to a second group, disposed in series with respect to said first group conveyors so as to transport said cut-sheet blanks (14) in such a way that a rear end portion of a preceding blank (14) may overlap with a front end portion of a following blank (14); and driving said conveyor (30) at an increased speed, in the event of any order change, after detectior of arrival of the last blank (14) before order change at said suction conveyor (30) belonging to said first group, so that a bunch of cut-sheet blanks (14) before order change may be separated from a bunch of cut-sheet blanks (14) after order change; wherein said conveyors belonging to the first group are driven at a speed (Vs-x k/1f) inversely proportional to the cut-sheet length (If) corresponding to a production speed (Vs) in said double facer (11) so as to carry out an ordinary singling operation; whereas said conveyors belonging to the second group are driven at a speed (Vs x 1/K) proportional to the production speed (Vs) of said double facer (11), such that the singling density of said blanks (14) transported on said second group conveyors may be different from that of blanks (14) transported on said first group conveyors.

2. The method of controlling singling of corrugated board sheet blanks according to Claim 1, wherein a second suction - 16 conveyor (34) is provided in the first group, and said second suction conveyor (34) is selectively driven depending on the condition either at the speed (Vs x k/1f) inversely proportional to the cut-sheet length (If) corresponding to the production speed (Vs) in said double facer (11) or at the speed (Vs x 1/K) proportional to the production speed (Vs) of said double facer (11).

3. The method of controlling singling of corrugated board sheet blanks according to Claim 1, wherein said conveyors belonging to the second group are adapted to be driven at a speed lower than the speed at which said conveyors belonging to the first group are driven, when said cutsheet blanks (14) are too.short to obtain sufficient singling density.

4. The method of controlling singling of corrugated board sheet blanks according to Claim 1, wherein said conveyors belonging to the second group are adapted to be driven at a speed higher than the speed at which said conveyors belonging to the first group are driven, when said cutsheet blanks (14) are very long to provide an excessively high singling density.

5. The method of controlling singling of corrugated board sheet blanks according to Claim 3 or 4, wherein said second suction conveyor (34) provided in said first conveyor group is driven at an intermediate level of the speed at which said first conveyor group are driven and the speed at which the conveyors belonging to said second group are driven.

6. The method of controlling singling of corrugated board sheet blanks according to any of Claims 1 to 5, wherein said first conveyor group consists of a first suction conveyor (30) and a second suction conveyor (34) which are arranged in series.

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7. The method of controlling singling of corrugated board sheet blanks according to any of Claims 1 to 5, wherein said second conveyor group. consists of a first separating conveyor, a second separating conveyor (38), a first slanted conveyor (40) and a second slanted conveyor (42), which are disposed in series.

8. A method of controlling singling of corrugated board sheet blanks, substantially as hereinbefore described with reference to the accompanying drawings.

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