METHOD AND DEVICE FOR THE PREPARATION OF FOLDING LINES

TECHNICAL FIELD

The present invention relates to a method for the preparation of folding lines in corrugated board and a device for carrying out the method ^.

BACKGROUND OF THE INVENTION

Corrugated board is used for many purposes in e g the packaging, furniture, and building industries _. Depending on various ends, the board is cut to desired shape and is folded ^. In order to obtain the folds at desired locations, folding lines are prepared in advance in the board. This is conventionally carried out by grooving or impressing, which means that the board is impressed to form straight grooves by means of impression tools in the form of straight rulers, impression rulers or profiled rollers, grooving wheels etc ^. The grooving ofthe material in the region ofthe folding line may lead to the result that the material is subjected to such deformation that cracks and weakening because of such cracks may occur in said regions. Particularly when the corrugated board is a paraffin waxed corrugated board intended to be used for concrete casting moulds, such folding lines cause problems, since the corners will be weakened to the extent that they may not withstand the pressure and the liquid from the poured concrete ^.

BRIEF DISCLOSURE OF THE INVENTION

In order to eliminate the above mentioned problems, a method for the preparation of folding lines is suggested, which according to an aspect ofthe invention includes penetration of one ofthe lining papers ofthe corrugated board along two parallel lines and impression ofthe space between the two lines.

According to another aspect ofthe invention, the space between the two lines is impressed to between and V, ofthe thickness ofthe corrugated board, preferably to about half the thickness ofthe board plate.

According to another aspect ofthe invention, a device is designed for the preparation of folding lines in corrugated board, wherein the device comprises means for the

CONFIRMATION COPY

penetration of one ofthe outer lining papers ofthe corrugated board along two parallel lines, and means for impressing the material in the space between the two lines

These and other aspects and characteristic features ofthe invention will be apparent from the detailed description ofthe invention and from the appending claims

BRIEF DESCRIPTION OF DRAWINGS

In the following description ofthe preferred embodiments, reference will be made to the accompanying drawings, in which

Fig 1 is a side elevation of an embodiment ofthe device ofthe invention, partially shown only schematically, Fig 2 is a pian view ofthe device according to Fig 1 along the lines II-II in Fig 1,

Fig 3 shows an impression roller at a larger scale, Figs 4a-4c illustrate a method according to the invention for the preparation of folding lines and the appearance of a folded corner, and Fig 5 shows another conceivable embodiment of a device according to the invention

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described with reference to a first conceivable embodiment of a device for the preparation of folding lines in wall board panels The device according to Fig 1 and Fig 2 comprises a machine framework 10 in which a level work table 12 is provided. On the table there is a longitudinal side support 14, which can be displaced in the cross directions shown by arrows 16 In the table there are mounted a first 9, a second 18, and a third feed roll 42 for a corrugated board panel S, particularly a paraffin waxed corrugated board panel, resting on the work table 12 The feed rolls 9, 18, 42 are mounted in the table flush with the upper surface of work table 12 and are rotatable with their axes of rotation, e g axes 20 of feed roll 18, at right angle to the longitudinal 'direction of side support 14 A motor or other driving means 22 for rotating the second feeding roll 18 is shown in Fig 2 The first and third feeding rolls 9 and 42 can be rotated

synchronously with and by driving roll 18 via a conventional transmission Above the first driving roll 9, there is a first pressure roll 8

A slitting assembly 30 is provided vertically above the second feeding roll 18 The slitting assembly 30 comprises a carrier beam 32 extending over the table 12 parallel with the roll 18 The carrier beam 32 carries a number of slitting units 33 on the underside ofthe beam Each slitting unit 33 comprises a slitter holder 34, each slitter holder comprising two slitters 36 or knifes defining a slitter pair having their edges 31 parallel with a vertical plane coinciding with the side support 14 The distance between the slitters 36 in each slitter unit 33 can be regulated and set at any distance between about 2 and 20 mm, and the slitter units also can be adjusted by displacing the slitter holders 34 along the beam 32 and locking them in desired positions Further, the whole carrier beam 32 can be adjusted and positioned in the vertical direction according to arrows 38

The adjustment and fixation ofthe distance between the slitters within each slitting unit 33 can be provided by a number of means known in the art, such as by adjustment screws, locking screws in combination with spacers providing the desired distance, wedges and the like It is also possible to use exchangeable slitter holders 34, in which the distance between the slitters are pre-set and fixed

The distance to be chosen between the slitters 36 in each slitting unit 33 depends on the thickness ofthe board panel and on the angle ofthe corner that is to be folded Normally, therefore only a very limited number of distances need to be conceived. Four different positions ofthe slitters 36 relative to each other in each unit 33 is normally sufficient According to a possible embodiment, which is not shown in the drawings, the carrier beam 32, or sections of it, is/are designed as a revolving beam/sections having slitting units 33 on each side thereof in desired positions along the beam The slitters in all the four slitting units in each position along the beam are at different distances from each other, and each slitting unit, or at least three of them, have slitters 36 at a fixed distance, ^" while, as the case may be, only the fourth slitting unit has slitters which are displaceable relative to each other By this arrangement, the distances between the slitters easily can

be changed by revolving the beam or any revolvable section of it 90° about a rotational centre

After the slitting assembly 30, as seen in the feeding direction, a pair 40 of rolls 42 and 44 is provided, including the said third feeding roll. Their axes of rotation are parallel with the rotational axes of feeding roll 18, and the upper roll 44 carries a number of impression devices 46 in the form of rings or rollers mounted on roll 44. The rings 46 can be displaced along the roll and be fixed in desired positions by means of locating screws 41. The upper roll 44 can be displaced and positioned in desired vertical positions according to arrows 48.

Fig 3 shows the design ofthe impression ring 46 more in detail. It has a thickness of about 5 mm and is fastened to a second ring 47, which in its turn is fastened to the carrier roll 44 by means of a locking screw 41. The periphery of ring 46 is wedge- shaped, the wedge angle being about 50-60°. The edge 45 is rounded, the radius being about 1 mm.

The device is intended to work in the following manner. A corrugated board panel S is placed on the working table 12 with one edge against the side support 14. It is most convenient to make the folding lines square to the corrugations Therefore the board panel conveniently is placed such that the corrugations and the channels in the board are square to the side support 14. The corrugated board panel is pressed against the side support 14 by means of spring biased rollers 7 on the opposite side ofthe table. The panel is moved by means ofthe first feeding roll 9, Fig. 1, not shown in Fig. 2, towards the slitting assembly 30 The slitting units 33 are positioned sidewise to positions where the folding lines are desired on the panel S and also controlled vertically, so that the slitters 36 cut only through the upper lining paper 50 of panel S or slightly deeper but not through next flat paper sheet, which is an intermediate paper sheet 51 When the two outer lining papers are of different strength, the panel S is placed such that the weakest ^' lining paper 50 is turned upwards to be slit by the slitters Further, the distance a, Fig 4a, between the slitters within each slitting unit 33 is set. The distance a depends on the thickness of panel S and also on the angle ofthe corner to be folded The sharper the

corner is, the greater is distance a If the corrugated board panel S e g has a thickness of 7 mm, and the corner to be folded has an angle of 135°, a distance a = 5 mm is convenient If, on the other hand, the corner is to be square, i e 90°, the distance a should be increased to about 10 mm

The slitters 36 of each slitting unit 33 penetrate the upper lining paper 50 along two parallel slitting lines 52 having sharp side edges, Fig 4a

The panel S is moved further on by means of feeding rolls 9 and 18 towards the impression assembly 40. The rings 46 on the upper roll 44 are adjusted such that they are positioned in planes coinciding with a vertical plane in the centre between the slitters 36 in each slitting unit 33 The upper roll 44 is also adjusted in the vertical direction so that the wedge-shaped peripheral parts ofthe impression rollers will impress the space 54 between the slitting lines 52 to a desired depth b, Fig 4b, normally to about half the thickness of panel S Instead of adjusting the height of roll 44, it is also possible to use exchangeable impression rollers 46 having different diameters, wherein such impression rollers 46 for each occasion are chosen which have a diameter fitted for the achievement of a desired penetration depth in a panel S having a given thickness

Fig 4b also shows that only the wedge-shaped peripheral portion ofthe impression rollers operate in the groove 55 which is being established between the slitting lines 52 This in its turn also means that the impression roller 46 will not touch the shaφ side edges 56 ofthe groove, which is important If they were touched by the impression tool, they would easily be damaged, which could impair the fold.

The corrugated board panel ST which leaves the impression assembly 4 has now obtained folding lines in the form of longitudinal, impressed grooves 55, which are bordered by sharp side edges 56. The corrugated board now easily can be folded along these grooves to form a corner, Fig. 4c The method has a number of advantages By slitting the lining " paper 50 and pressing it down to a certain depth, the strip or ribbon 49 formed ofthe lining material between the slitting lines 52 is not destroyed Instead it is embedded in the folded corner and participates in establishing a strong corner construction As the board

panel is folded along the groove 55, the side edges 56 will meet and a very sharp corner is established Particularly if the corrugated board is used as mould material in concrete casting, it is important that the side edges abut each other in the corners and seal such that the poured concrete is prevented from escaping in the corners and/or damaging the corner Nor is there, according to the method, any particular risk of formation of cracks in the opposite lining paper, i e the lining paper forming the outer surface in the region of the corner, as is usual according to conventional folding procedures The material in the corner behaves in a controlled manner due to the slitting and impression in combination In conventional folding line preparations, it frequently happens that the board material is compressed and stretched in a manner which is difficult to control, which can cause formation of cracks and corners which are not shaφ, which makes it difficult for the material to resist the concrete during concrete casting

It is important that the slitters in each slitting unit are adjusted depending on the folding angle, as is above mentioned, in order that the side edges will abut each other in the corners when the board is folded to form a corner It is also important that only the upper lining paper is slit through and that the space between the slitting lines are not impressed too much, which otherwise might impair the strength ofthe corner If the corrugated board contains an intermediate paper, parallel with the surface lining papers, it is convenient that the intermediate paper is not slit by the slitters. In the shown embodiment, the slitting assembly is provided with non-movable slitters It is also conceivable to design the slitters as slitting wheels which penetrate and slit the lining paper as they are rotated Likewise it is conceivable that the impression ofthe space between the slitting lines is carried out by means of a non-movable presser which slides against the corrugated board panel and impresses the region between the slitting lines to form the groove 55 in that region as the board panel is moved relative to the stationary presser

Another embodiment is shown in Fig. 5 For certain products which require shorter "folding lines and which for example are to be punched out from a corrugated board panel, the method ofthe invention can be employed in a different mode In this case the corrugated board panel S is kept resting on the working table A device 60 is a combined

slitting and impression device, comprising two longitudinal slitting rulers 62 displaceable in the vertical direction on a carrier 64, the lower edge 66 of which functions as an impression tool between the slitting rulers 62. The slitting rulers 62 initially are displaced such that their edges are positioned below the impression tool 66. Then the whole device 60 is lowered vertically towards the corrugated board panel S such that the edges ofthe slitting rulers 62 will penetrate the upper lining paper ofthe corrugated board panel. The carrier 64 is moved further downwards at the same time as the slitting rulers 62 are moved upwards by means of a suitable motion means (not shown), such that their edges will be positioned above the wedge-shaped part 66 forming the impression tool. During continuing downward movement, the wedge-shaped impression tool 66 will impress the region between the established slitting lines such that a groove is established in the panel between the slitting lines. Of course it is also conceivable that the slitting rollers are fixed and that the impression tool is vertically displaced. In this mode a folding line is established in one and the same operation. It is also possible to combine the device with punching tools which punch out the product in a single working cycle.

It should be understood that the invention is not limited to the embodiments described above and shown in the drawings but can be modified within the scope ofthe appending claims. In the drawings, a corrugated board having two corrugated layers is shown, but the device and the method of course can be employed also for corrugated board having any number of layers. Further, the folding lines can be provided in the corrugated boards in any direction and not only in a direction square to the corrugations, i e square to the channels in the board.