WO2009050272A1

WO2009050272A1 - Unit and method for final folding in in-line manufacturing of corrugated board boxes

Info

Publication number: WO2009050272A1
Application number: PCT/EP2008/064050
Authority: WO
Inventors: Lennart Wiklund
Original assignee: Berg Industries AB
Current assignee: Berg Industries AB
Priority date: 2007-10-18
Filing date: 2008-10-17
Publication date: 2009-04-23
Anticipated expiration: 2010-04-18
Also published as: SE0702323L; SE530899C2

Abstract

A folding unit for final folding of the outer panels (55, 56) of a corrugated board sheet (18) in in-line manufacturing of corrugated board boxes, comprising a pair of parallel and laterally displaceable folding beams (1, 2) with a respective endless conveyor belt (3, 4), which extend from the inlet (19) of the folding unit to a pair of press rolls (9, 10) at the outlet (20) of the folding unit. A pair of folding rules (5, 6) are arranged under the respective folding beams (1, 2) and extend from the inlet (19) of the folding unit and towards, but not all the way to, the outlet (20) of the folding unit. A pair of folding bars (33, 34) which are fixedly positioned outside the respective folding rules (5, 6) and at an angle to the respective folding rules are arranged in the front portion of the folding unit, as seen in the transport direction (15) of the corrugated board sheets (18). A pair of folding belts (7, 8) are arranged under a respective folding rule (5, 6) to cooperate therewith and extend from an associated deflecting roller (16) with a vertical axis at the terminal end of the folding bars (33, 34) in the transport direction (15), to an associated deflecting roller (17) with a horizontal axis substantially adjacent the pair of press rolls (9,10). A lifting device (38, 39, 43) is positioned in front of the pair of deflecting rollers (17) and is brought into contact with the folded panels (55, 56) when the front edge (61) of the corrugated board sheet (18) has passed the lifting device (38, 39, 43) and successively lifts them, so that when said front edge (61) is introduced in the nip between the press rolls (9, 10) at least the portion of the panels (55, 56) that is situated between the press rolls (9, 10) and the lifting device (38, 39, 43) has been folded 180°.

Description

UNIT AND METHOD FOR FINAL FOLDING IN IN-LINE MANUFACTURING OF CORRUGATED BOARD BOXES

The present invention relates to a unit for final folding of corrugated board sheets in in-line manufacturing of corrugated board boxes, comprising a pair of parallel and laterally displaceable folding beams with a respective endless conveyor belt, which extend from the inlet of the folding unit to the outlet of the folding unit, a pair of folding rules, which are arranged under the respective folding beams and which extend from the inlet of the folding unit and towards, but not all the way to, the outlet of the folding unit, a pair of folding bars, which are fixedly positioned outside the respective folding rules and at an angle to the respective folding rules and which are arranged in the front portion of the folding unit, as seen in the transport direction of the corrugated board sheets, a pair of folding belts, which are arranged under a respective folding rule to cooperate therewith and which extend from an associated deflecting roller with a vertical axis at the terminal end of the folding bars in the transport direction, to an associated deflecting roller with a horizontal axis substantially adjacent the outlet, a corrugated board sheet supplied to the inlet of the folding unit being gripped by said pair of conveyor belts and transported along the folding rules, and the two outer panels of the corrugated board sheet being folded successively from 0° to 90° by the respective folding bar in cooperation with the associated folding rule, after which each 90° folded panel is brought into engagement with the respective folding belt and the folding rule cooperating therewith for continued folding and is delivered, at the outlet, by the pair of deflecting rollers with a horizontal axis and via a guide bar, with the panels folded 180°, to a pair of press rolls for final folding. The invention also relates to a method for final folding of corrugated board sheets in in-line manufacturing of corrugated board boxes, comprising the steps of feeding at a cycle rate corrugated board sheets into a folding unit during sizing, successively folding, in the first portion of the folding unit, as seen in the transport direction of the corrugated board sheet, the two outer panels of the corrugated board sheet from 0° to 90° by means of a pair of folding rules and a pair of folding bars cooperating therewith, successively folding, in the second portion of the folding unit, as seen in the transport direction of the corrugated board sheet, the two outer panels of the corrugated board sheet from 90° to 180° by means of a pair of folding belts and said pair of folding rules, and guiding, by means of a guide bar, the folded corrugated board sheet into a pair of press rolls for adhering a glue flap of one of the folded panels to the other folded panel.

Modern manufacturing of corrugated board boxes takes place in so- called in-line machines. These machines are characterised in that all the op- erations are performed in line in one and the same machine. Corrugated board sheets or blanks, which are adjusted to the dimensions of the boxes to be made, are fed one by one at a cycle rate by a feeding unit into the in-line machine.

The sheets are then printed in one or more printing units located after the feeding unit. This is followed by creasing, slotting and cutting of a glue flap, which is performed in the slotting unit of the machine. The next operation is to optionally punch out air holes, carrier holes or other punching, depending on the design of the boxes. This is performed in the so-called punching unit. After the punching unit comes the folding unit. In this unit, glue is applied to the glue flap of the sheet, after which the outer panels of the sheet are folded 180°. The glue flap is adhered to the outer part of the panel on the opposite side of the sheet.

With reference to Fig. 1 of the drawings, a corrugated board sheet 18 is illustrated, which has passed through the feeding unit, the printing unit, the slotting unit and the punching unit of the in-line machine and is about to be fed into the folding unit in the direction indicated by the arrow 15. The corrugated board sheet 18 is here completely flat, i.e. unfolded, and has been provided with opposite slots 50 and intermediate creasing lines 53 along which the corrugated board sheet is to be folded in the folding unit. The corrugated board sheet 18 is already provided with punched-out carrier holes 51 and printed matter 52, if required. The creasing lines 53 between the pairs of slots 50 and grooving lines 54 transversely to the creasing lines are used later when the corrugated board box is to be erected (not shown). In the embodi- ment shown, the corrugated board sheet 18 consists of two outer panels 55, 56 and two inner panels 57, 58. In the folding unit, the outer panels 55, 56 are folded 180° along the associated creasing lines 53 so as to be brought into contact with the inner panels 57, 58, a glue flap 59 on one of the outer panels 55 being adhered to the other outer panel 56. In this condition, the folded corrugated board sheet 18 can be bundled together with a plurality of similar, folded corrugated board sheets for transport to a consignee.

The folding precision is important for the quality of corrugated board boxes. The geometry of the final product/box is directly related to the folding precision. Erecting and filling machines require a high degree of precision to operate without problems. Correct folding means that the panels are folded parallelly and that the gap formed between the panels 55 and 56 has the same width as the slots 50 and that the width of the slots 50 is uniform. Variations in the gap width between the boxes are not desirable and may cause problems when erecting, filling and sealing the boxes. The occurrence of differences in the gap width between the bottom and the lid of the boxes is called fishtailing and may cause interruption when erecting, filling and sealing the boxes. To achieve high-precision folding, it is also of vital importance that the gap width varies as little as possible from one box to the next and that no fishtailing occurs in the individual boxes of a run.

The precision in the folding of the corrugated board boxes is determined by a number of factors. Straight feeding and transport of the sheets through the whole machine is necessary to achieve high-precision folding. The fold indications or so-called creasing lines, which are formed in the slot- ting unit of the machine, must be made in an optimal manner with sufficiently pronounced marking and without cracking of the paper layers of the corrugated board. This condition has become all the more vital considering the current use of an increasingly large variety of corrugated board grades and, in particular, the addition of more and more recycled fibres in the paper grades, in combination with the demand for higher folding precision.

When the sheets reach the machine's folding unit they must be transported in a straight line, the fold indications must be optimal and positioned absolutely parallel in the right position on the sheet, and the sheet must be transported in an absolutely straight line over the entire folding distance. All of these criteria must be met to enable high-precision folding. In the folding unit, the folding motion of the outer panels of the sheet must occur in an optimal manner, which means that the folding motion is controlled to be as gentle as possible, thereby ensuring optimal use of the folding distance. The longer the folding distance, the better the chances of achieving a gentle folding motion. In practice, however, the length of the folding distance is limited by cost and space requirements. This is why it is important to use the length of the available folding distance in an optimal manner. Folding is performed, inter alia, by means of folding belts (cf. Fig. 4) and the contact surface of the turned folding belts is concentrated to the front edge of the outer panels of the corrugated board sheets during folding. In this connection, it is vital to avoid an undesirable turning stress on the outer panels of the boxes during the folding sequence. This is the main reason for trying to obtain a folding motion that is as gentle as possible, thereby using the length of the folding distance in an optimal manner.

The production in an in-line machine is characterised by increasingly short series of box blanks. This means that the changeover time of the machines becomes more important for the machines' production capacity. In- creasingly, therefore, modern in-line machines are equipped with systems for automatic setting of the machines.

The present invention contributes to this development while allowing an improvement of the quality of corrugated board boxes through higher folding precision. Previously, the setting of the folding motion was dependent on the experience and precision of the machine operator, since many settings were carried out manually. The automatic system enables the machine to adapt its automatic folding motion to the size and geometry of the boxes.

BACKGROUND ART The process up to the so-called final folding is disclosed in Swedish patent no 528999. However, the actual final folding is not discussed in said patent. The final folding too has a considerable and vital influence on the fold- ing precision. The technique according to the present patent application ensures a final folding that provides for high-precision folding.

Final folding here means the part of the folding process that is achieved by press rolls.

PROBLEMS IN RELATED ART

With reference to Figs 2 and 3, a possible occurrence in conjunction with the final folding of a corrugated board sheet is illustrated. The sheet 18 is positioned with its front edge 61 , as seen in the direction of operation 15 of the machine, directly in front of the press rolls 9 and 10 (see Fig. 2). In this position, the guide bar 11 supports the sheet's 18 outer panels 55, 56, which are about to be folded 180°. The guide bar is arranged to support and guide the sheet into the press rolls 9, 10. This guiding action prevents the folded panels 55, 56 from being pushed backwards by the shock that would other- wise occur at the contact with the lower press roll 10. In this position, however, the folded panels are guided at the front portion of the sheet only. The reason that only the front portion of the folded panels is guided and brought into contact with the intermediate panels 57, 58 is that the sheet is folded successively as it is being transported in the forward direction through the machine (see arrow 15). Although the front portion of the panel has been folded 180°, as illustrated by section Ill-Ill in Fig. 4, the other panels are still not completely folded. This is illustrated by section M-Il and section l-l, respectively, in Fig. 4. The reason is that the folding belts 7, 8 have not yet turned the panels upwards to a position parallel to the transport belts 3, 4 over the full length of the folded panels. Another reason is that the guide bar 11 has not yet engaged with the folded panels 55, 56 over the whole length of the sheet 18, as seen in the operating direction 15 of the machine.

The above conditions are based on the ability of the corrugated board to bend and turn within certain limits and to resume its original shape without being damaged.

A further reason for the folded panels 55, 56 of the sheet hanging down is the sheet's own weight. The size and grade of the corrugated board determine the amount of bending of the folded panels. This is indicated by the curve-shaped lines illustrating the folded panels of the sheet in section l-l and section M-Il in Fig. 4.

It is a well known phenomenon that the best conditions for a satisfactory folding are achieved by parallel and simultaneous folding along the whole length of the folding lines 53 of the sheet, see Figs 1 and 5. Because the folding is not parallel along the folding lines, since the folding belts 7, 8 (Fig. 2) fold the panels of the box successively, and due to the bending of these panels, the accuracy will be adversely affected. This adverse effect of the folding is due to the fact that the folded panels 55, 56 hang down at the rear portion of the sheet 18, as seen in the operating direction 15 of the machine. At the front portion of the sheet 18, on the other hand, the folded panels are supported by the guide bar 11. This means that the front edges of the two folded panels 55, 56 may end up in a position after the front edges of the unfolded panels 57, 58, as seen in the operating direction of the machine, see Fig. 3. When the sheets then pass between the press rolls 9 and 10, the pressure in the nip between the rolls will set the folding in an incorrect position in which the front edges of the folded and unfolded panels of the sheet are not aligned. Even a very small "drag" of the folded panels 55, 56 relative to the unfolded panels 57, 58 will have a considerable effect on the folding precision and markedly reduces the folding performance. This is true in particular for boxes with great box height 60, see Fig. 3.

Even if the other steps of the folding have been carried out in an optimal manner, the final folding will have an adverse effect on the final outcome of the folding as described above. The defective folding caused by the condi- tions described above is called fishtailing and is illustrated in Fig. 3.

PRIOR ART

To counteract the undesirable effect described above in connection with the final folding a guide bar 11 (see Fig. 2) is used. The bar must be de- signed such that it is able to catch the folded panels during the folding process. This occurs before the panels have been folded 180°. The guide bar guides the panels into the nip between the press rolls 9, 10 so that they do not bump into the lower press roll 10. The drawback of this technique has been described above and is due to the folded panels not being lifted in the same way at the rear portion of the sheet 18 as at its front portion.

Prior art also comprises so-called support rollers or conveyor rollers 12, 13, as shown in Fig. 6. The function of these rollers is to convey the sheets 18 between the deflecting rollers 17 of the folding belts 7, 8 and all the way to the press rolls 9, 10. Another function they have is to guide the folded panels 55, 56 of the sheet 18, so that they do not collide with the lower press roll 10. Because the support rollers 12, 13 engage already the front portion of the sheet 18, the defective geometry, which is a result of the folded panels hanging down at the lower portion of the sheet 18, has not been adjusted but may, in principle, be transferred to the nip of the press rolls. Thus, this technique has only a limited effect on the detrimental influence of the final folding on the folding precision. In addition, this solution implies an extension of the in-line machine. This is unfavourable since the total length of the in-line ma- chine is already today an obstacle or problem when installing the machine in the converter halls of corrugated board factories.

Prior art further comprises the step of subsequently squaring the folded panels of the sheets 18 or box blanks, as we may now call them. This may occur in a separate squaring unit 14 located downstream of the folding sec- tion of the machine, see Fig. 7. The separate squaring unit 14 basically consists of a feed conveyor in which the folded box blanks are fed by means of lugs 22. The lugs feed the box blanks 18 by pushing on the rear edge of the box blanks. At the same time an abutment is formed by a number of press rollers 23 and lateral straightening rollers 24. In this way, squaring of the box blanks is obtained. In addition, the press rollers 23 are arranged to compress the glue joint 59 (see Fig. 1 ) in the box blanks and ensure a satisfactory contact. A further function of the lateral straightening rollers 24 is to adjust and align the folding of the box blanks from the side.

A drawback of the separate squaring unit 14 is that it takes up a great deal of space and considerably increases the total length of the in-line machine. A further drawback is that the separate squaring unit 14 has only a limited effect. This effect is particularly limited, or indeed non-existent, in the case of boxes with great box height 60 (Fig. 3). This is because the force act- ing against squaring of this type of boxes of great box height is so strong that it is practically impossible to square an incorrectly folded box afterwards.

As a rule, the counting unit of the in-line machine also has an incorporated squaring unit. This unit too has a limited effect, for the same reasons as those stated above in the case of a separate unit.

One object of the present invention, therefore, is to provide a unit and a method for final folding in in-line manufacturing of (corrugated) board boxes, providing high-precision folding of the corrugated board sheets.

Another object of the invention is to provide a folding unit for corru- gated board sheets which are to be used as corrugated board boxes, allowing monitoring of settings and fine adjustment of the folding without the need to interrupt the operation of the folding unit.

Yet another object of the invention is to provide a folding unit for folding together (corrugated) board sheets in an in-line machine, in which the setting of the different components of the folding unit is performed from an operating and setting console, which also controls other units in the in-line machine, based on input data concerning the dimensions and properties of the corrugated board sheet.

These objects are achieved according to the invention by a folding unit according to that stated by way of introduction, which is characterised by a lifting device, which is positioned at a distance in front of the pair of deflective rollers, as seen in the transport direction of the corrugated board sheets, and which is brought into contact with and successively lifts the folded panels when the front edge of the corrugated board sheet, as seen in the transport direction, has passed the lifting device, so that when said front edge is introduced in the nip between the press rolls at least the portion of the panels situated between the press rolls and the lifting device is folded 180°.

A method for using the folding unit according to the invention is characterised by the step of supporting, during the final folding process, the panels at a distance from the front edge of the corrugated board sheets, as seen in the transport direction, and successively lifting the panels as the front edge approaches the press rolls and until the front edge has been introduced in the nip between the press rolls, so that one panel length in the transport direction is folded 180° when the front edge of the corrugated board sheet is introduced in the nip between the press rolls.

Further developments of the invention will be apparent from the features stated in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the invention will now be illustrated for the purpose of exemplification and with reference to the accompanying drawings, in which: Fig. 1 is a top plan view of a sheet of board or corrugated board that is to be folded into a double-folded container or box blank for subsequent erection;

Fig. 2 is a partial, longitudinal side view of the unit for final folding of a corrugated board sheet in in-line manufacturing of corrugated board sheets according to prior art;

Fig. 3 is an example of inaccurate final folding of a corrugated board sheet resulting in so-called fishtailing;

Fig. 4 illustrates, in three vertical sections I, Il and III, the folding of the outer panels of the corrugated board sheet according to prior art; Fig. 5 is a view of the outer panels when folded 180°;

Fig. 6 illustrates another unit for final folding of a corrugated board sheet according to prior art;

Fig. 7 illustrates yet another unit for final folding of a corrugated board sheet according to prior art; Fig. 8 is a schematic, longitudinal side view of the structure of a folding unit according to prior art;

Fig. 9 schematically illustrates from above and in the longitudinal direction of the folding unit the structure of the known folding unit;

Fig. 10 is a partial, longitudinal side view of the unit for final folding of a corrugated board sheet in in-line manufacturing of corrugated board sheets according to the invention; Fig. 11 is a view according to Fig. 10 of the unit according to the invention in operation as the front edge of the corrugated board sheet passes the cam discs of the unit.

Figs 12-15 schematically and along the indicated vertical sections I-IV illustrate the procedure of the final folding as the corrugated board sheet gradually approaches and, finally, is introduced in the nip of the press rolls.

Fig. 16 is a cross-sectional view transversely to the transport direction of the corrugated board sheets, i.e. section B-B in Fig. 11 , of a preferred design of the unit for final folding according to the invention; Figs 17A-17E illustrate different embodiments of cam discs that may advantageously be used in the unit according to the invention;

Fig. 18 schematically illustrates an alternative lifting device according to the invention comprising hydraulic/pneumatic cylinders; and

Fig. 19 is a diagram of an in-line machine for manufacturing corrugated board boxes and the units included in the same as well as their automation;

DESCRIPTION OF THE INVENTION

With reference first to Figs 8 and 9, which schematically illustrate the structure of the folding unit, the folding unit comprises a pair of parallel, right and left folding beams 1 , 2, which extend continuously from the inlet 19 of the folding unit, i.e. where the corrugated board sheets 18 are fed into the folding unit, to the outlet 20 of the folding unit, where the corrugated board sheets 18 are fed into a pair of press rolls 9, 10 interconnecting the outer panels 55, 56 of the corrugated board sheet or box blank, as will be discussed more fully below. The folding beams 1 , 2 are displaceably carried by supports (not shown) of the machine base and can be moved laterally, i.e. transversely to the transport direction 15 of the corrugated board sheets 18, by means of associated actuating means (not shown), as is illustrated schematically in Fig. 9 and indicated by arrows 30 in the same figure. The actuating means are, for instance, a pair of hydraulic cylinders attached to the associated support and folding beam, as can be easily understood by a person skilled in the art.

The folding beams 1 , 2 are preferably box-shaped and each connected to a suction device, such as a fan (not shown), to create a negative pressure in the folding beams. At the underside of the folding beams, there are through grooves or slots and adjacent the underside of the folding beams 1 , 2 a right and a left conveyor belt 3, 4 extend along the underside of the folding beams from the inlet 19 of the folding unit to its outlet 20. The conveyor belts 3, 4 are endless and run between a driven and an idle deflecting roller 45 and via a tensioning roller 46 (see Fig. 6), as is known by a person skilled in the art. The conveyor belts 3, 4 are provided with a plurality of through holes, the corrugated board sheets 18 being sucked onto the conveyor belts by the negative pressure in the folding beams 1 , 2 and safely transported through the folding unit in the transport direction 15, cf. Fig. 2.

Under each folding beam 1 , 2, a right (5) (hidden) and a left folding rule 6, respectively, are arranged, which extend along the respective folding beams and under the conveyor belts 3, 4 from the inlet 19 of the folding unit and towards, but not all the way to, the outlet 20 of the folding unit. The fold- ing rules 5, 6 are laterally displaceable together with the associated folding beam 1 , 2. The smallest possible box size, i.e. the smallest possible width of the corrugated board sheet 18 and, in particular, the panels 57 and 58, is directly determined by the width of the folding beams 1 , 2 and on how closely they can be moved transversely to the transport direction 15. In the front portion or half of the folding unit, as seen in the transport direction, a right and a left folding bar 33, 34 are fixedly arranged outside, and in cooperation with, the respective folding rules 5, 6. The folding bars 33, 34 extend from a point above and at the outside of the respective folding rules 5, 6 to a point substantially in the same vertical plane as and vertically under the associated folding rule 5, 6.

At the inlet 19 of the folding unit, outside and above one (6) of the folding rules and, as seen in the transport direction 15, in front of its associated folding bar (34), a glue nozzle with control means 35 is positioned, whose position is adjusted to the position of the glue flap 59 of the corrugated board sheet 18 which is being fed.

Corrugated board sheets 18 are fed one by one and at a cycle rate at the inlet of the folding unit, gripped by the pair of conveyor belts 3, 4 and transported along the folding rules 5, 6. In this connection, glue is first applied from the glue nozzle 35 to the glue flap 59 of the corrugated board sheet, after which the outer panels 55, 56 of the corrugated board sheet 18 are caught by the folding bars 33, 34, which in cooperation with the respective folding rules 5, 6 successively fold down the outer panels, along their creasing lines 53, from 180° (flat corrugated board sheet) to 90°.

After the above-mentioned end point or extremity of the folding bars 33, 34, as seen in the transport direction 15, a right and a left endless folding belt 7, 8 are arranged under a respective folding rule 5, 6 to cooperate therewith. Each folding belt 7, 8 extends from an associated deflecting roller 16 with a substantially vertical axis at said end point of the respective folding bars 33, 34 to an associated deflecting roller 17 with a horizontal axis substantially adjacent the pair of press rolls 9, 10, see Fig. 2. The folding belts 7, 8 are thus turned from a vertical orientation at the deflecting roller 16 to a horizontal orientation at the deflecting roller 17. The folding belts 7, 8 cooper- ate with the associated folding rules 5, 6, the outer surface of which follows the turning of the folding belts in the transport direction 15 from an angle of 90° to the inner panels 57, 58 of the corrugated board sheet 18, which decreases in the direction of the end point of the folding rules in the transport direction, which is located approximately halfway between the deflecting roll- ers 16 and 17.

Preferably, the folding unit also comprises a right and a left support bar 31 , 32, which are each attached by means of an arm to the respective folding beams 1 , 2 and which have substantially the same extension in the transport direction 15 as the folding belts 7, 8. These support bars 31 , 32 serve to sup- port the outer panels 55, 56 which are folded and assume, due to their flexibility, an angle or vertical position relative to the inner panels 57, 58 of the corrugated board sheet that is advantageous for the folding of the panels 55, 56 and adapted to the turning angle of the folding belts 7, 8 in the transport direction 15. As shown in Fig. 9, the support bars 31 , 31 are arranged inwardly of the pair of folding belts 7, 8.

At the end of the support bars 31 , 32 and the folding beams 1 , 2, and between them, a guide bar 11 is displaceably arranged transversely to the transport direction 15 and just in front of the pair of rolls 9, 10, see Fig. 2. The guide bar 11 is displaceable in parallel with the pair of rolls 9,10. The pair of rolls 9,10 are stationary fastened to the support of the folding unit at its outlet 20, see Figs 2 and 10, and the roll nip is adjusted depending on the thickness of the sheet and the desired roll pressure. A detailed description of an in-line machine that is well suited for the present invention is found in Swedish patent no. SE 528999.

After having described the structure of the folding unit, its function will now be described briefly.

After the folding described above of the outer panels 55, 56 from 0° to 90° in the front portion or half of the folding unit, as seen in the transport direction 15, the outer panels 55, 56 are brought into engagement with the respective folding belts 7, 8, between the latter and the folding rules 5, 6 cooperating therewith, for continued successive inwards folding towards the inner panels 57, 58. When the corrugated board sheet 18 leaves the folding rules 5, 6, which end approximately halfway between the deflecting rollers 16, 17, as mentioned above, the folding of the outer panels 55, 56 is controlled individually and according to need. Subsequently, as the corrugated board sheets 18 approach the rear deflecting rollers 17, the outer panels 55, 56 have been folded almost 180° towards the inner panels 57, 58. The bent guide bar 11 then catches the folded panels 55, 56 and guides them together with the panels 57, 58 into the nip of the pair of rolls 9, 10, where a glue flap 59 on the outer panel 55 is pressed against and adhered to the other outer panel 56. The setting of the guide bar, which occurs in the lateral direction based on the relationship between the outer panels 55, 56 of the box, is motorised and automatically set to the right position via the console 21.

As mentioned previously in this description, there is a risk of the folded, outer panels 55, 56 of the corrugated board sheet 18 colliding with the lower press roll 10, thereby causing fishtailing, cf. Fig. 3. This is why the unit for final folding has been added and positioned at the outlet 20 of the folding unit, i.e. in the transport direction 15 of the sheets just in front of the press rolls 9, 10. A currently preferred embodiment of a final folding unit according to the invention will be described below with reference to Figs 10-15. To eliminate the risk of the folded outer panels of the corrugated board sheet colliding with the lower press roll it is, thus, of vital importance that they should be folded 180°, i.e. that they abut the inner panels 57, 58 when the front edge 61 of the sheet 18 is introduced in the nip between the press rolls 9, 10, and the aim of the present invention is to provide a unit and a method for achieving this.

With reference first to Fig. 16, the unit according to the invention is dis- placeable in a direction perpendicular to the transport direction 15 of the corrugated board sheets 18 (see double arrow in Fig. 16) between the folding beams 1 , 2 and, in the transport direction, upstream of the pair of press rolls 9, 10. Preferably, the unit comprises a carriage 27, which runs on a horizontal rail or bar 28. This motion allows lateral setting of the unit in the right position for optimal lifting of the folded outer panels 55, 56 of the sheet. This setting is dependent on the dimensions of the sheet and the size proportions between the folded panels. The setting is motohsed and carried out automatically by presetting of the programmable operating and setting console 21 of the in-line machine.

As will be easily understood by a person skilled in the art, the unit is moved along the rail 28 by means of a motor (not shown) connected to the console 21. The operator may also carry out a motohsed manual adjustment. The adjustment may also be an entirely manual operation. Also attached to the carriage 27 is the guide bar 11. The unit further comprises a support 29, which is fixedly attached to the frame 31 of the carriage 27. The support 29 consists of two separate, substantially mutually parallel legs, in which a shaft 32 is rotatably carried. The shaft 32 is driven by a motor 36, for instance by means of a belt or chain drive 37. The motor 36 is attached to the carriage 27. A pair of lifting discs 38, 39 are arranged on the shaft 32 and rotated by the motor 36. The guide bar 11 is positioned between the lifting discs 38, 39. Advantageously, although not shown, both the lifting discs 38, 39 and the guide bar 11 are arranged to be individually moved with the aid of actuating means (not shown) between the legs of the support 29.

The lifting discs 38, 39 are substantially identical and, in the embodiment shown in Figs 10-15, eccentric, i.e. they have a spiral or conchoidal pe- riphery 42. The shortest distance between the periphery 42 of the lifting discs 38, 39 and the through hole 40 provided therein for the shaft 32 is such that the shortest portion of the lifting disc between the periphery and the hole is not higher than the upper edge of the guide bar 11 at the portion of the guide bar where the lifting discs are situated, see Figs 10 and 12, in other words the lifting discs 38, 39, in an angular position, do not extend over the guide bar 11.

The unit for final folding according to Figs 10-15 operates in the following way. The sheets 18 are transported at a cycle rate through the folding section of the in-line machine. This means that the distance between the front edges 61 of the sheets is always the same, corresponding to a machine cycle. The servo-operation of the eccentric discs 38, 39 is controlled via the operating and setting console 21 of the machine such that one turn of the ec- centric discs corresponds to two machine cycles. When the front edge 61 of the sheet 18 reaches the eccentric discs 38, 39 and is situated above them, the discs are in a position where their shortest portion is facing upwards, see Fig. 10. In this position, the eccentric is positioned such that it does not extend over the guide bar 11. The guide bar 11 guides the front edge 61 of the folded panels 55, 56 of the sheet 18. While the front edge 61 of the sheet 18 is being conveyed forward past the eccentric discs 38, 39, the eccentric discs rotate gradually. Preferably, the peripheral speed of the eccentric discs 38, 39 correspond to the transport speed of the sheets 18 so as to further prevent the occurrence of fishtailing. As the eccentric discs continue their rotating mo- tion their greater portion will rise above the guide bar (see Fig. 11 ). Owing to this design of the eccentric, the folded panels 55, 56 of the sheet 18 will be lifted successively and gently as the sheet continues its forward movement. This is illustrated in Figs 12, 13 14 and 15. The accompanying sectional views I-IV illustrate the successive upward folding of the panels 55, 56 that is achieved by the eccentric discs 38, 39. The successive lifting of the folded panels 55, 56 of the sheet in the longitudinal direction occurs while the front edge 61 of the sheet travels the distance L (Fig. 15). This distance corresponds to the centre distance between the shaft 32 of the eccentrics and the press rolls 6, 7 plus approximately 20 mm. The lifting of the panels is maintained until the front edge 61 of the sheet has entered the nip between the press rolls 9, 10. When the folding of the sheet has been set at the front edge of the nip, the job of the eccentrics is more or less done and they are then to return to their initial position as shown in Fig. 12 so as to be in cycle with the next sheet. After the front edge 61 of the panels 55-58 has been introduced into the nip of the rolls, the final folding procedure is controlled essentially by the press rolls 9, 10 only. Thus, the lifting of the folded panels 55, 56 occurs before they are gripped by the nip between the press rolls 9, 10. By the extension of the portions of the eccentrics that lift the folded panels 55, 56 of the box and hold them in the lifted position until they are inserted between the press rolls corresponding to the transport distance L, it is ensured that the nip of the press rolls "locks" and secures the folding at the front edge of the sheet. This occurs before the short portion of the eccentric discs reaches its upper position, where it no longer lifts the folded panels of the sheet. Accordingly, the position of the eccentric discs is such that they lift the folded panels of the sheet to a position a certain distance along the panel in the feeding direction instead of at the front edge only, which is the case for the guide bar 11. The sheet illustrated in Figs 12, 13, 14 and 15 corresponds to a sheet of maximum size as seen in the operating direction 15 of the machine. In this case, the eccentric discs 38, 39 will complete two turns per sheet. This means that the folded panels of the sheet will also be lifted once more at the rear portion of the sheet. This lifting is less important, however, since by then the folding has already been set in the nip between the press rolls 9, 10. The reason for the second turn of the eccentrics during the sheet cycle is to ensure synchronization between the eccentrics and the sheet feed. The total lifting distance corresponds to the distance L according to Fig. 15, in other words it must be adapted to the space available in the machine. Because not only the front edge but also the front portion of the folded panels have been lifted when the front edge 61 of the sheet reaches the press rolls 9, 10 and is set by the pressure between the press rolls, the folded panels 55, 56 are geometrically more favourably positioned for ensuring an optimal folding than if only the front edge had been lifted, instead of the conical folding movement obtained if the panels are lifted at the front edge of the sheet only.

In-line machines are characterised by a large size range, which means that you can produce a wide range of large and small boxes in one and the same machine. In the case of medium-sized and slightly smaller boxes, as seen in the operating direction of the machine, the eccentrics will be automatically repositioned relative to the sheet cycle by the control system controlling the servo-operation of the eccentric, so that the folded panels are al- ways lifted and supported in an optimal manner when passing the eccentrics.

Depending on the size of the sheets in the operating direction of the machine, the rear portion of the sheet's folded panels is lifted by the eccentric discs being turned during the machine cycle. This setting allows the lifting operation to be optimized so as to occur as far into the sheet 18 as possible. The setting occurs through functions in the servo mechanism and is connected to the other automatic machine settings depending on the sheet size, i.e. by means of the operating and setting console 21. The machine operator may also carry out the setting separately. The designing of the device with two eccentric discs 38, 39, one on each side of the guide bar 11 , is an adap- tation to ensure optimal running with an outer glue flap, Fig. 16, or alternatively an inner glue flap, Fig. 18.

Fig. 16 shows a box blank where the glue flap 59 is located on the outside of the boxes to be produced. The shortest folded panel is supported by the eccentric disc 38, which is situated to the left of the guide bar 11. To run only this type of box blanks for boxes with an outer glue flap, it would be sufficient to have only one eccentric disc 38 in the machine. The glue flap would then lift the long folded panel and the eccentric disc 39 would be redundant. On the other hand, when running box blanks with an inner glue flap, which is much more common, the opposite is true, i.e. the eccentric disc 39 is required but not the eccentric disc 38.

Above, the lifting discs have been described as being spiral-shaped or conchoidal and rotating continuously during the lifting movement at a peripheral speed that corresponds to the conveying speed of the corrugated board sheets 18. A lifting disc of this kind is illustrated in detail in Fig. 17A. However, it is possible to have the lifting disc rotate in other ways. Fig. 17B illustrates a lifting disc with rollers 41 that are rotatably mounted along the periphery of the disc 42 and projecting therefrom to reduce friction when using intermittent movement to keep the support in its raised position for large sheet sizes. A characterising feature of the lifting discs according to the invention is that the distance between various points along the periphery of the disc 42 and through holes 40 (for the shaft 32) is not constant in order to obtain the above lifting function. Thus, Fig. 17C illustrates a lifting disc for intermittent rotation with three stops for each turn and Fig. 17D illustrates the same disc provided in the corners with friction-reducing rollers 41. Another shape of a lifting disc for intermittent rotation with two stops for each turn is shown in Fig. 17E and the same disc provided with friction-reducing rollers is shown in Fig. 17F.

The lifting disc may be replaced by one or two hydraulic or pneumatic cylinders 43 acting as a lifting mechanism for the folded outer panels 55, 56, which are attached to said frame 31 , see Fig. 18. In this case, the cylinders 43 are controlled by the operating and setting console 21. To reduce the friction against the panels 55, 56, they are preferably provided with wheels 44 by means of which they abut the panels. As in the case of the lifting discs, the cylinder or cylinders may be arranged for individual movement on the frame 31 in the longitudinal direction of the rail 28.

The actuating means for setting the folding beams 1 , 2 transversely to the transport direction 15, the actuating means for the lifting devices 39, 43, the actuating means for the carriage 27, the actuating means for the guide bar 11 and the control means for the glue nozzle 35 are all connected to an operating and setting console 21. When the dimensions and properties of the (corrugated) board sheets that are to be conveyed through the in-line machine and processed therein are programmed into the operating and setting console, all the units of the machine are set automatically according to the operations that are to be performed and that have been programmed.

Fig. 19 schematically illustrates the structure of an in-line machine for manufacturing corrugated board boxes and the units included in the same as well as their automation according to the invention. The setting of the various machine units, i.e. the inlet 61 , the printing unit 62, the slotting unit 63, the punching unit 64, the folding unit 65 and the counting and bundling unit 66 are fully motorised and adapted to be pre-programmed, on the one hand, to reduce the changeover time of the machine and, on the other, to ensure as ex- act and precise settings as possible. These settings are carried out centrally from the operating and setting console 21 and via a connection line to each unit and are readable on a computer screen. Up till now, the setting of the folding unit has been only partly motorised and pre-programmable. It is the setting of the folding in the second step, i.e. from 90° to 180°, that has been largely manual.

The invention also concerns setting the machine to obtain optimal final folding of the last 180° folding and is characterised in that the folding motion settings of the machine are motorised and fully automatic. For each type of box, i.e. on the basis of the box dimensions, a number of motorised units are set to obtain the best possible folding result.

With the system according to the invention, the setting of the final folding motion for each box blank that is to be run through the machine is accommodated to a calculated, optimal setting value. On the basis of this setting, the operator can, if needed, make fine adjustments depending on the operating conditions, such as the machine speed and the corrugated board grade. Owing to the motorization of the settings, they can be performed during operation in a safe manner for the machine operator The optimal setting can then be stored in a database, together with all other settings of the machine, so that the machine can be automatically set up to previous optimal settings in the case of recurrent orders.

Furthermore, the sheet has continuously been referred to in this text as "corrugated board sheet". It goes without saying that the invention is also applicable to other types of board than corrugated board.

The invention is not limited to that described above and shown in the drawings and can be modified within the scope of the appended claims.

Claims

1. A unit for final folding of corrugated board sheets (18) in in-line manufacturing of corrugated board sheets, comprising a pair of parallel and laterally displaceable folding beams (1 , 2) with a respective endless conveyor belt (3, 4), which extend from the inlet (19) of the folding unit to the outlet (20) of the folding unit, a pair of folding rules (5, 6), which are arranged under the respective folding beams (1 , 2) and which extend from the inlet (19) of the folding unit and towards, but not all the way to, the outlet (20) of the folding unit, a pair of folding bars (33, 34), which are fixedly positioned outside the respective folding rules (5, 6) and at an angle to the respective folding rules and which are arranged in the front portion of the folding unit, as seen in the transport direction (15) of the corrugated board sheets (18), a pair of folding belts (7, 8), which are arranged under a respective folding rule (5, 6) to coop- erate therewith and which extend from an associated deflecting roller (16) with a vertical axis at the terminal end of the folding bars (33, 34) in the transport direction (15), to an associated deflecting roller (17) with a horizontal axis substantially adjacent the outlet (20), a corrugated board sheet (18) supplied to the inlet (19) of the folding unit being gripped by said pair of conveyor belts (3, 4) and transported along the folding rules (5, 6), and the two outer panels (55, 56) of the corrugated board sheet (18) being folded successively from 0° to 90° by the respective folding bars (33, 34) in cooperation with the associated folding rule (5, 6), after which each 90° folded panel (55, 56) is brought into engagement with the respective folding belts (7, 8) and the folding rule (5, 6) cooperating therewith for continued folding and is delivered, at the outlet (20), by the pair of deflecting rollers (17) with a horizontal axis and via a guide bar (11 ), with the panels (55, 56) folded 180°, to a pair of press rolls (9, 10) for final folding, c h a r a c t e r i s e d by a lifting device (38, 39, 43), which is positioned, as seen in the transport direction (15) of the corrugated board sheets (18), at a distance (L) in front of the pair of deflecting rollers (17) and which is brought into contact with the folded panels (55, 56) when the front edge (61 ) of the corrugated board sheet (18), as seen in the transport direction (15), has passed the lifting device (38, 39, 43) and successively lifts them, so that when said front edge (61 ) is introduced in the nip between the press rolls (9, 10) at least the portion of the panels (55, 56) that is situated between the press rolls (9, 10) and the lifting device (38, 39, 43) is folded 180°.

2. A unit as claimed in claim ^ c h a r a c t e r i s e d in that the lifting device (38, 39, 43) is mounted on a carriage (27), which is dis- placeably arranged on a rail (28) transversely to the transport direction (15) of the corrugated board sheets (18) between the folding beams (1, 2).

3. A unit as claimed in claim 2, c h a r a c t e r i s e d in that the movement of the lifting device (38, 39, 43) in the vertical direction and the movement of the carriage (27) in the lateral direction are controlled from an operating and setting console (21), in which the dimensions and properties of the corrugated board sheets (18) have been input and which allows fine adjustment during operation of the folding unit.

4. A unit as claimed in claim 1 or 2, c h a r a c t e r i s e d in that the lifting device (38, 39, 43) comprises at least one lifting member (38,

39, 43), which together with the guide bar (11 ) is mounted on the carriage (27).

5. A unit as claimed in claim 4, c h a r a c t e r i s e d in that the lifting member(s) (38, 39, 43) and the guide bar (11 ) are individually dis- placeable on the carriage (27) transversely to the transport direction (15) of the corrugated board sheets (18).

6. A unit according to any one of the preceding claims, c h a r - a c t e r i s e d in that the lifting device (38, 39, 43) comprises a pair of identically shaped discs (38, 39) each having a through hole (40), wherein the distance between the periphery (42) of the disc and the hole (40) is not constant, that the discs (38, 39) are mounted on a common shaft (32) extending through said hole (40) and that the shaft (32) is rotated by a motor (36) which is controlled from said operating and setting console (21).

7. A unit as claimed in claim 6, c h a r a c t e r i s e d in that the discs (38, 39) have a spiral periphery (42).

8. A unit according to any one of claims 6-7, c h a r a c t e r - i s e d in that one or more rolls (41) is/are rotatably mounted at the periphery (42) of each disc (38, 39) and projecting therefrom.

9. A unit according to any one of claims 1 -5, c h a r a c t e r - i s e d in that the lifting device (38, 39, 43) comprises at least one hydraulic or pneumatic cylinder (43), at the upper end of which a wheel (44) is rotatably fastened to lift the folded panels (55, 56) of the corrugated board sheets (18). 10. A method for final folding of corrugated board sheets (18) in inline manufacturing of corrugated board boxes, comprising the steps of feeding at a cycle rate corrugated board sheets (18) into a folding unit during sizing, successively folding, in the first portion of the folding unit, as seen in the transport direction (15) of the corrugated board sheet (18), the two outer pan- els (55, 56) of the corrugated board sheet (18) from 0° to 90° by means of a pair of folding rules (5, 6) and a pair of folding bars (33, 34) cooperating therewith, successively folding, in the second portion of the folding unit, as seen in the transport direction (15) of the corrugated board sheets, the two outer panels (55, 56) of the corrugated board sheet (18) from 90° to 180° by means of a pair of folding belts (7, 8) and said pair of folding rules (5, 6), and guiding, by means of a guide bar (11 ), the folded corrugated board sheet (18) into a pair of press rolls (9, 10) for adhering a glue flap (59) of one of the folded panels (55) to the other folded panel (56), c h a r a c t e r i s e d by the step of supporting, during the final folding process, the panels (55, 56) at a distance from the front edge (61 ) of the corrugated board sheet (18), as seen in the transport direction (15), and successively lifting the panels (55, 56) as the front edge (61 ) approaches the press rolls (9, 10) and until the front edge (61 ) has been introduced in the nip between the press rolls (9, 10), so that one panel length (L) in the transport direction (15) is folded 180° when the front edge (61 ) of the corrugated board sheet (18) is introduced in the nip between the press rolls (9,

10).

11. A method as claimed in claim 10, c h a r a c t e r i s e d by the step of eliminating the supporting and lifting function when the front edge (61 ) has been introduced in the nip between the press rolls (9, 10).