EP1737739A1

EP1737739A1 - Method for manufacturing load-carrying elements

Info

Publication number: EP1737739A1
Application number: EP05730931A
Authority: EP
Inventors: Kari Rantanen
Original assignee: SUOMEN KUITULAVA Oy
Current assignee: SUOMEN KUITULAVA Oy
Priority date: 2004-04-06
Filing date: 2005-04-06
Publication date: 2007-01-03
Anticipated expiration: 2025-04-06
Also published as: CN100528698C; EP1737739B1; FI20040503A; ATE441592T1; FI20040503A0; CN1984818A; DE602005016386D1; WO2005097607A1; FI117595B

Abstract

The invention relates to a method for manufacturing load-carrying beam-like elements (4) and to the manufacture of a loading base, such as a pallet, by using the elements thus obtained. The elements (4) consist of tubular paperboard cores (1) and covering paperboard (2) surrounding them, and for forming the elements, cores are aligned on a paperboard sheet or web, which is provided with weakening lines (9) transverse to the direction of the row of cores, the weakening lines allowing, in accordance with the invention, a beam (3) assembled from paperboard and cores to be divided into shorter parts, i.e. to be provided as beam-like elements, by cutting the beam (3) along each weakening line. The weakening lines (9) consist e.g. of perforations (9) made in the paperboard (2), and then the elements (4) are separated from the beam (3) by an impact directed to the elements. The elements (4) can be assembled e.g. with a connecting covering plate to form a pallet, where the load is exerted on the elements in the axial direction of the cores (1).

Description

Method for manufacturing load-carrying elements

The invention relates to a method for manufacturing load-carrying elements, in which tubular paperboard cores are disposed in a row and are assembled by means of a covering paperboard to form a beam aligned with the row of cores. The invention also relates to the manufacture of a loading base such as a pallet comprising the supporting elements thus obtained.

Paperboard cores manufactured by gluing helically wound board layers on top of each other to form a tube with a multi-layered mantle have been conventionally used as cores in paper rolls, on which the load is exerted laterally. Pallets utilising the high axial compression strength of the cores form a second object of application of paperboard cores. The cores and the covering paperboard are assembled into beams, which are aligned and joined by means of a covering plate to form a pallet, in which the core axes included in the beams are perpendicular to the plane of the pallet. The pallet may also comprise beams crosswise in two layers, and then no covering plate will be necessary in order to assemble the pallet. Such prior art disposable pallets made of recyclable material have been disclosed by FI patent specifications 93933 and 107600 B, among other publications.

In FI patent specification 93933, the beams for the pallet are manufactured by aligning the cores on a sheet of corrugated board, which is wrapped around the cores and bound to these by means of hotmelt glue. The sheet and the core row have equal lengths so that the beam thus formed will have open ends. FI patent specification 107600 B comprises a sheet of corrugated board shaped and dimensioned so as to surround the row of cores and also close the ends of the beam thus obtained.

It is also previously known in the manufacture of pallets to produce beams consisting of cores and covering paperboard in serial production, by disposing the cores on a continuous moving board web, which is wrapped around the cores and glued to them, forming a continuous beam which is eventually divided into sections of the desired lengths by means of a cutter of by sawing.

However, the cutting of a prior art beam that is previously assembled and glued involves a number of drawbacks. If adjacent cores bear on each other in the beam, a cutter performing a reciprocating linear movement has problems in hitting exactly between the cores with a precision such that the beam can be cut. The same applies to rectilinear sawing of the beam, which should be carried out without damaging cores in the vicinity of the cutting point. In the practice, cutting of the beam requires a gap to be left between the cores located on both sides of the cutting point. On the other hand, cutting the beam by means of a tool sawing or slitting the covering board and rotating around the beam at the cutting location is a more laborious operation. The cutting mark produced by the saw is often rough, and it is difficult to combine the two cutting manners, i.e. a linearly proceeding movement and a movement rotating around the beam, in a manufacturing process based on a continuous movement of the beam.

The purpose of the invention is thus to improve the process for manufacturing beams formed of paperboard cores and covering paperboard, comprising the cutting of a previously assembled beam into sections of specific lengths. The invention has the specific purpose of providing a solution by means of which a beam can be cut with less effort than before while producing a neat cutting mark. The method of the invention is characterised by the fact that, before the beam is assembled, the covering board is equipped with one or more weakening lines transverse to the direction of the row of cores and in that each element formed of paperboard and cores is separated by cutting the beam along the weakening line.

In accordance with the invention, the covering paperboard may have been weakened in advance to an extent such that no cutting tool is needed for detaching the element to be separated, i.e. the beam of a specific length forming the end product of the method, the beam being removed by a simple impact. The invention does not require the cutting location to be between the cores with the same absolute precision as does cutting of the beam by means of a linear cutter movement or by sawing, and hence the cores may be located closer to each other at the cutting location and even in contact with each other without preventing cutting of the beam.

The weakening lines required by the invention are preferably perforations of the covering paperboard. The weakening line may consist of dot-like or preferably linear perforations penetrating through the paperboard and covering the weakening line so that the portions on the two sides of the line are weakly joined only by narrow bridges between the perforations. The bridges are required to have only a strength such that the paperboard can be wrapped around the cores without breaking prematurely. Previously made long linear perforations and a minimum number of bridges also achieve the most even cutting mark. Light slitting of the board surface at the bridge locations also contributes to this.

A weakening line can be produced in a paperboard sheet or web e.g. by means of a reciprocating tool of saw blade type, which produces linear perforations in the paperboard that separate the bridges from each other. Assuming that a light impact is enough for final cutting of the beam, cutting the beam by means of said tool in accordance with the invention is a substantially easier and more secure operation than dividing an intact beam as in the prior art operation. Perforations or any similar weakening lines can be produced in the paperboard sheet or web while it is in a single plane, i.e. before starting to bend the web around the cores. It is also preferable to produce the weakening lines in the sheet or web before placing the cores on this. This allows the cores to be disposed in mutual contact also at the location of the weakening line.

The invention is particularly suitable for continuous manufacture of elements, i.e. beams of a specific length, which is performed by forming transverse weakening lines in a continuous paperboard web at intervals equalling the lengths of the elements, aligning cores on the web, wrapping the web around the row of cores to form a beam and dividing the beam along the weakening lines to form separate elements. The invention can optionally be implemented by producing a beam of a specific length comprising one or more transverse weakening lines, the beam being divided into parts by supporting the beam between the weakening lines and directing a blow or an impact simultaneously to both ends of the beam for detaching the part to be separated.

The method of the invention for producing a loading base, such as a pallet, comprises the manufacture as described above of elements consisting of paperboard cores and covering paperboard, i.e. beams of specific lengths, which are disposed next to each other and bound to each other to form a base, with the base receiving the load exerted on it in the axial direction of the cores. The beams can be connected to form a pallet by means of a covering plate, on which the load carried by the pallet is placed. Beams are preferably aligned on the pallet in succession and separated from each other, allowing a lifting fork to grip the rectangular pallet from all four sides of the pallet by penetrating between the beams. The invention will be explained in further detail below by means of examples and with reference to the accompanying drawings, in which

figure 1 is a schematic view of a continuous line for producing a continuous beam and for dividing it to beam-like elements of specific lengths, figure 2 shows a part of the production line with a conveyor conveying the continuous beam thus produced, figures 3 and 4 show the division into parts of a beam of a specific length and provided with weakening lines, figure 5 shows parts of a production line, on which cores are disposed on a continuous covering paperboard web to be provided with weakening lines in one embodiment of the invention, figure 6 shows an individual beam-like element to be produced on the production line of figure 5, figure 7 shows a pallet assembled from beam-like elements and a covering plate produced as in figure 1 , figure 8 shows a second pallet comprising beam-like elements produced In accordance with the invention, figure 9 is a section IX- IX of figure 8, and figure 10 is a section X-X of figure 8.

The production line of figure 1 produces in a continuously operating process a beam 3 consisting of tubular paperboard cores 1 and surrounding covering paperboard 2, the beam being divided at the end of the process into parts of specific lengths, i.e. beam-like elements 4 of specific lengths, which, owing to their strength, are suitable for carrying load in loading bases, such as pallets, for instance. Disposable pallets made entirely of paperboard have the advantage of their material being recyclable.

In a closer study of the process of figure 1, the beam 3 is formed of a continuous paperboard web 2 provided with longitudinal crease lines 5 and board core pieces 1 aligned on this. The crease lines 5 divide the web 2 into a central strip 6, inner border strips 7 on both sides of this and outer border strips 8 at the edges of the web. Before the cores 1 are brought onto the web 2, weakening lines 9 are produced at given intervals, extending from one edge of the other in the web. The weakening lines 9 may consist of perforations and narrow bridges between these, which retain the web assembled at the lines. At the moment of perforation, the web 2 is spread in one single plane, the perforations being made by means of a reciprocating tool 10 of saw-blade type perpendicularly to the plane of the web.

In the embodiment of the invention illustrated in figure 1 , the distance between the weakening lines 9 has been dimensioned so as to equal the summed diameters of two adjacent cores 1 in one row of cores. The cores 1 are disposed in the central strip 6 of the web 2, with the weakening lines 9 intersecting the row of cores at the location 11 between every second core. In the ideal case, the weakening line 9 passes through the point at which adjacent cores 1 touch each other, even though the invention does not necessarily require such exact positioning of the cores 1 relative to the weakening line 9. The contact between the cores 1 is not indispensable, but instead, it is possible to leave gaps between the individual cores or the pairs of cores between the weakening lines 9.

The cores are disposed on the web 2 by means of the vertically reciprocating tool 13 gripping the cores with its fork 12 as illustrated in figure 1. However, the cores 1 can be brought onto the web 2 in many different ways, as e.g. by pushing the cores from the side of the web or by continuously leading the cores along groove-like guides from the side or the top of the web. Such embodiments are known per se or obvious to those skilled in the art.

After the cores 1 have been disposed on the web, the web 2 is bent around the row of cores by means of guides (not illustrated). This results in a beam 3 with a rectangular cross-section, in which the crease lines 5 of the web form the edges of the beam, the central strip 6 of the web forms the bottom of the beam, the inner border strips 7 form the vertical sides of the beam and the outer border strips 8 form together the upper side of the beam. The aligned border strips 8 form a longitudinal seam line 14 on the upper side of the beam. To bind the beam 3, glue is applied to the web 2 and/or the cores 1 before the web is bent.

The continuous beam 3 provided with transverse weakening lines 9 obtained in the last process step is divided into parts by cutting the beam along each weakening line. This results in beam-like elements 4 of specific lengths, each of which has two adjacent paperboard cores 1 surrounded by the covering paperboard 2. The cutting tool consists of a hydraulically reciprocating hammer 15, which separates an element 4 by a light impact on this. Figure 2 shows belt conveyors 16 moving a finished beam 3 and having the additional function of supporting the beam so that the element 4 to be separated from its end each time is separated without efforts.

The production of the beam 3 can differ from the procedure described above by forming the weakening lines 9 before the web 2 is provided with longitudinally scored crease lines 5. The paperboard web 5 is preferably formed of a plurality of material webs on top of each other, and then the weakening lines 9 can be formed separately in each of these before the webs are joined together, so that their weakening lines coincide. The material webs are bound together by means of glue, and the crease lines 5 are preferably scored to the layered structure of the web 2 before the glue dries, i.e. while the web is moistened or softened by fresh glue.

A covering paperboard 2 glued in multiple layers imparts the beam 3 rigidity, which facilitates the division of the beam into elements 4 and produces stronger elements for various loading applications.

In figure 3, unlike the description above, the object of cutting is a beam 3 produced with specific dimensions and provided with weakening lines 9 enabling division. The weakening lines 9 divide the beam 3 into three parts, each of which comprises two adjacent core pieces 1 surrounded by the covering paperboard 2. With a view to cutting, the beam 3 has been disposed on a base 17, and cutting is performed by means of drive belts 19 rotating around the outermost parts of the beam and driven by hydraulic cylinders 18. By a pull at the belts 19, the beam 3 is divided as shown in figure 4 along weakening lines 9 into three elements 4 corresponding to figures 1 and 2.

Figure 5 illustrates a variation of the invention, in which the perforation tool cuts weakening lines 9 in the paperboard web 2, the lines matching the core pieces 1 defined by the lines and being spaced by areas 20, which are split off as the obtained continuous beam is divided into individual elements 4 as shown in figure 6. In this embodiment, each element 4 comprises three adjacent cores 1, and the ends of the elements have been rounded so as to match the circular profile of the cores by the shape of the weakening lines 9.

Figure 7 shows a paperboard pallet 21, which has been formed by disposing a total of nine beam-like elements 4 obtained as in figure 1 next to each other in three longitudinal and transverse rows and by binding them together with a covering plate 22, the axes of the cores 1 included in the elements being perpendicular to the plane of the plate. The covering plate 22 receives the load placed on the pallet, and the gaps 23 between the aligned elements 4 allow the loaded pallet to be shifted by means of the lifting fork of a forklift truck.

The application of the pallet 21 shown in figures 8-10 differs from the one of figure 7 in that, below the longitudinal rows of beam-like elements 4, base strips 24 have been disposed extending from one end to another of the rows, the base strips consisting of elongated paperboard strips having roughly the same width as that of the elements 4. The longitudinal edges 25 of the strips 24 have been bent upwardly so that the strip forms a shallow groove, into which each element 4 is fitted. The groove has been filled with filling paperboard 26 between the elements 4, cf. figure 10. The strips 24 and the pieces of paperboard filling 26 may consist of glued multi- layered paperboard as described above, corresponding to the one used for coating 2 the beam-like elements 4. The longitudinal base strips 24 have the double purpose of strengthening the pallet and above all of allowing it to be shifted on a roller conveyor in the longitudinal direction of the strips. The pallet can be lifted and shifted by means of a forklift truck owing to the gaps 23 between the rows of elements and the openings 27 between the elements 4 provided between the covering plate 22 of the pallet and the base strips 24.

It is obvious to those skilled in the art that the applications of the invention are not restricted to the example given above, but may vary within the scope of the accompanying claims. Thus, for instance, instead of one single continuous web or sheet, the covering paperboard of the beams may consist of two separate webs or sheets, one of which surrounds the cores 1 on their bottom side and the other one surrounds them on their top side, so that the webs or sheets form together the longitudinal sides of the elements. The cores are not necessarily surrounded by covering paperboard on all the longitudinal sides, but the beam and accordingly the elements separated from this can be left partly open, provided that the gluing is adequate for assembling the elements.

Claims

1. A method for manufacturing load-carrying elements (4), in which tubular paperboard cores (1) are aligned and assembled by means of a covering paperboard (2) to form a beam (3) aligned with the row of cores, characterised in that before the beam (3) is assembled, the paperboard (2) is provided with one or more weakening lines (9) transverse to the direction of the row of cores and in that each element (4) formed of paperboard and cores is separated by dividing the beam along the weakening line.

2. A method as defined in claim 1, characterised in that the weakening lines comprise perforations (9) made in the paperboard (2).

3. A method as defined in claim 1 or 2, characterised in that a weakening line (9) extends from one edge to another of a paperboard sheet or web (2) used for the beam (3).

4. A method as defined in any of the preceding claims, characterised in that a weakening line (9) intersects a row of cores between adjacent cores (1).

5. A method as defined in any of the preceding claims, characterised in that the cores (1) in a row are in mutual contact.

6. A method as defined in any of the preceding claims, characterised in that the weakening lines (9) are made in the paperboard sheet or web (2) while it is in one single plane.

7. A method as defined in any of the preceding claims, characterised in that the weakening lines (9) are made in the paperboard sheet or web (2) before this and the cores (1) are joined.

8. A method as defined in any of the preceding claims, characterised in that the row of cores is disposed on the paperboard sheet or web (2), which is wrapped around the cores (1) so as to form the longitudinal sides of the beam (3).

9. A method as defined in any of the preceding claims, characterised in that the beam (3) is divided by means of a sudden impact or blow at the element (4) to be separated from the beam.

10. A method as defined in any of the preceding claims, characterised in that elements (4) are manufactured continuously by forming transverse weakening lines (9) in a paperboard web (2) at intervals equalling the lengths of the elements, by disposing cores (1) on the web, by wrapping the web around the row of cores in order to form a beam (3) and by dividing the beam along the weakening lines into separate elements.

11. A method as defined in any of claims 1-9, characterised in that a beam (3) is manufactured, which has a specific length and comprises two or more transverse weakening lines (9), the beam being divided into elements (4) by supporting the beam between the weakening lines and by directing an impact or blow simultaneously to both ends of the beam for separating the element.

12. A method for manufacturing a loading base, characterised in that elements (4) are manufactured from paperboard cores (1) and covering paperboard (2) with the method defined in any of the preceding claims, the elements being disposed next to each other and bound together to form a base (21), with the base receiving load exerted on this in the axial direction of the cores.

13. A method as defined in claim 12, characterised in that elements (4) are aligned in succession on the base (21) so as to allow a lifting fork shifting the base to be pushed into the gaps (23) between the elements.

14. A method as defined in claim 12or 13, characterised in that a pallet (21) is formed of adjacent supporting elements (4) and a covering plate (22) connecting these.