PALLET AND ITS METHOD OF MANUFACTURE

Abstract: The invention relates to a pallet (1) made of recyclable cardboard and its method of manufacture. Beams (2) are formed of tube-like paper-board core pieces (3) arranged in line and of the cardboard (4) surrounding them, the beams being attached to each other crosswise in two layers so that the axes of the core pieces included in the beams are placed perpendicularly to the level of the pallet. In addition to the beams (2), the pallet (1) may include a covering plate (14) of cardboard and an intermediate plate (15) of cardboard between the layers of the beams. The invention is characterized in that, when assembling the beams (2), the paper-board core pieces (3) of essentially a round cross section are compressed in order to flatten them in the cross direction of the resulting beam. The diameter of the core pieces (3) is decreased by 1-20 %, suitably about 10 % in said direction during flattening. The flattening increases the contact surfaces between the core pieces (3) and the surrounding cardboard (4) on which the core pieces and the cardboard are glued to each other.

Description: PALLET AND ITS METHOD OF MANUFACTURE The object of this invention is a method for manufacturing a pallet in which beams are formed of tube-like paper-board core pieces arranged in a row and of the cardboard surrounding the core pieces, the beams being attached to each other cross-wise in at least two layers so that the axes of parallel paper-board core pieces included in the beams are placed perpendicularly with respect to the level of the pallet. In addition, the invention is directed to a pallet provided in accordance with the invention. Pallets are traditionally made of wood which gives them a high load-carrying capacity. A wooden pallet can generally be used several times but in practice the pallets end up in waste dumps very quickly. It is also well-known to manufacture the pallet from cardboard which can be recycled back to the manufacturing of recycled pulp after use. This avoids the waste problem caused by the pallets. However, a drawback with cardboard pallets compared with wooden pallets has been their lower strength and load-carrying capacity. Patent application FI-923261 describes a cardboard pallet intended mainly for disposable use comprising beams formed of parallel, tube-like paper-board core pieces and the cardboard surrounding them, the beams being attached to each other in a cross-wise manner in two layers so that the axes of the core pieces included in the beams are perpendicular with respect to the level of the pallet. Cores, which are generally used as core pieces of paper rolls, are manufactured by glueing layers of paper-board, which are twisted spirally, on top of each other into a tube having a thick jacket formed of numerous paper-board layers. The solution utilizes the high compression strength in the axial direction of the cores to improve the load-carrying capacity of the recyclable cardboard pallet. The purpose of the present invention is to improve the manufacturing method of the cardboard pallet according to patent application FI-923261 in such a manner that the strength of the pallet is further improved. The manufacturing method of the pallet according to the invention is characterized in that when assembling the beams, the paper-board core pieces having an essentially round diameter, are compressed in order to flatten them in the cross direction of the beam thus formed. The flattening of the paper-board core pieces according to the invention results in that the contact surfaces between the core sides and the cardboard layers, which form the sides of the resulting beam and come against the core sides, are increased, the contact surfaces serving as areas of adhesion between the parts in question. The core pieces and the cardboard layers surrounding them may thus be glued to each other on a larger area than before, making the beam stiffer. If the core pieces in the line are in contact with each other, the flattening also increases the contact surfaces between the core pieces, whereby also these surfaces may be glued or otherwise attached to each other in a stronger manner. Because of the invention, the bending strength of the beam increases and the susceptibility to buckling is decreased, and the capability of the pallet, assembled of beams, to carry spotlike loading, in particular, is increased. This increased strength of the pallet is due to not only the denser mutual contact of the core pieces and the surrounding cardboard layers and stronger attachment, but also to the bias applied to the beams during the flattening which, for its part, increases the load-carrying capacity of the pallet. When flattening, according to the invention, the core pieces whose cross-section is initially round, their diameter may be decreased by 1-20%, preferably 5-15%, and optimally about 10% in the cross direction of the resulting beam. The diameter of the core pieces in the axial direction of the beam may be retained essentially unchanged. In practice, the assembly of the beams of the pallet can be carried out so that the paper-board core pieces are placed against each other in a line on a cardboard sheet provided with folds corresponding to the edges of the beam. The strip limited by adjacent folding lines of the sheet, on which the core pieces are placed, is slightly narrower than the diameter of the core pieces. After this, the sheet is folded around the core pieces by pressing the sides of the core pieces simultaneously so that they are flattened to a diameter corresponding to the width of the strip of the sheet below. The core pieces and the cardboard sheet, folded around them by pressing in the above-mentioned way, are preferably seamed to each other using glue applied on the contact surfaces in advance, whereby the core pieces in the resulting beam stay flattened and biased inside the cardboard layer surrounding them on each side. The assembly of the beams as well as attaching the beams to each other into a pallet may be carried out using only glue as the fixing device, which is separated from the mass in the recycling process after the pallet has been used. Suitable glues include, for instance, hot melt glues and quickly drying cold glues. On the other hand, it is also possible to use rivets to secure the glue joints of the pallet. In case the goods to be loaded are self-supporting, for instance rigid boxes or other similar packages corresponding to the size of the pallet, the pallet may be formed only using beams attached to each other crosswise. However, it is preferable to provide the pallet with a covering plate of stiff cardboard fixed on top of the beams, whereby the pallet may also be used for loading of smaller sized or loose goods such as sacks. Likewise, it is preferable to provide the pallet with a spacing plate of suitable stiff cardboard between the superimposed layers of beams, which further increases the bending strength of the pallet. The pallet according to the invention and manufactured according to the above-described manner, comprising beams formed of tube¬ like paper-board core pieces arranged in a rows and the cardboard surrounding them, the beams being connected to each other crosswise in at least two layers so that the axes of the paper-board core pieces included in the beams are perpendicular with respect to the level of the pallet, is characterized in that the paper-board core pieces are flattened in the cross direction of the beam in such a way that their diameter in said direction is smaller than that in the axial direction of the beam. The diameter of the paper-board core pieces in the cross direction of the beam may thus be 80-99%, preferably 85-95%, and ideally about 90% of the diameter of the core pieces in the axial direction of the beam. The invention is described in the following in more detail with the aid of an example with reference to the appended drawings in which: Fig. 1 shows the paper-board core pieces arranged in line on the corrugated cardboard sheet which is to be wrapped around them, as viewed from above, Fig. 2 shows the paper-board core pieces and the slightly folded corrugated cardboard sheet as viewed forward at an angle, Fig. 3 shows the beam formed from the paper-board core pieces and the corrugated cardboard sheet according to Figs. 1 and 2 , Figs. 3a-3c show the end of the beam according to three alternative embodiments of the invention, Fig. 4 shows a part of the beam according to Fig. 3 as viewed from the top and partly cut open, Fig. 5 shows the process in which the corrugated cardboard sheet is wrapped around the paper-board core pieces to provide the beam according to Fig. 3, Fig. 6 shows the pallet formed from the beams, the covering plate and the spacing plate between the layers of the beams according the Fig. 3, and Fig. 7 shows a corner of the pallet according to Fig. 6 on a larger scale. Cardboard pallet 1 according to the invention, which is finished in Fig. 6, comprises beams 2 according to Fig. 3 which are attached to each other crosswise in two superimposed layers, the beams being assembled of tube-like paper-board core pieces 3 arranged in line and cardboard sheet 4 which is to be wrapped around them. According to Figs. 1 and 2, sheet 4 is provided with folds 6 corresponding to edges 5 of the resulting beam 2, the folds dividing the sheet into strips 8-10 which form sides 7 of the beam. The width of middle strip 8 of the sheet, on which paper- board core pieces 3 are arranged in line against each other, corresponds to the cross-directional width of resulting beam 2. The width of intermediary strips 9 of the sheet corresponds to the height of the resulting beam 2 which is essentially the same as the length of core pieces 3 in the axial direction thereof. The width of the two edge strips 10 of the sheet which, according to Figs. 3 and 4, form one of the sides of beam 2, is half of the width of middle strip 8. Fig. 1, representing sheet 4 and paper-board core pieces 3 arranged in line on the sheet before folding the same around the core pieces, shows that the diameter of paper-board core pieces 3 of round cross-section is slightly larger than the width of middle strip 8 of the sheet. However, in connection with the formation of beam 2, paper-board core pieces 3 are flattened in the cross-direction of the beam in such a manner that the cross- directional diameter of the core pieces in the finished beam is according to Fig. 4, excluding the the material thickness of sides 7 of the beam, the same as the cross-directional width of the beam. The diameter of core pieces 3 may be decreased 1-20%, preferably 5-15%, and most preferably c. 10% in the cross- direction of beam 2 during the flattening, while core pieces 3 retain their initial diameter in the axial direction of the beam, provided that they have been in contact with each other at the starting time of the flattening. Paper-board core pieces 3 are deformed during flattening so that the width of the contact surfaces between them and sides 7 of the beam formed of sheet 4 is increased considerably as well as the mutual contact surfaces of the core pieces which, in principle, would be linear without the flattening. These contact surfaces serve as adhesion areas ■ on which sheet 4 and paper-board core pieces 3 are glued to each other in beam 2. Fig. 3a shows beam 2 which has reinforcement plate 16 glued below the layer of corrugated cardboard 4 on the bottom of the beam, plate 16 being made of glued and compressed paper-board. Reinforcement plate 16 is as wide as beam 2 and extends from one end to the other of the beam. Thus reinforcement plate 16 is of recyclable material just as the other parts of the pallet and intended especially to increase the capability of the beam to carry spotlike loads applied on the pallet. Fig. 3b shows beam 2 which differs from the one in Fig. 3a only in that reinforcement plate 16 is placed inside the bottom of the beam made of corrugated cardboard 4 immediately below paper- board core pieces 3. Fig. 3c further shows an alternative application in which plate-like, internal reinforcement element 17 of the layer of corrugated cardboard 4 extends to the other vertical side of the beam in addition to the bottom of beam 2. Reinforcement 16, 17 of recyclable material is bound in place with glue and intended to divide the spotlike loads applied to the pallet to the entire length of the beam and thus to decrease the risk of buckling. Fig. 5 shows schematically a process in which the sheet of corrugated cardboard 4 is folded around paper-board core pieces 3 and the core pieces are simultaneously pressed in order to flatten them in the cross-direction of the resulting beam. The process employs pressing means 13 mounted on conveying belt 11 rotatably with respect to articulation spots 12, sheet 4 and core pieces 3 being forced between the pressing means, while the pressing means are in an opened position because of the curving of the belt. When belt 11 is straightened, pressing means 13 are twisted towards each other into a position where the distance between them is the same as the cross-directional width of the resulting beam. Core pieces 3 are thus subjected to compression between pressing means 13 which flattens them to the desired diameter in accordance with the dimensions of the beam. After the flattening, edge strips 10 of sheet 4 are finally turned on top of core pieces 3 and the compression is maintained until the glue, which bounds the parts of the beam to each other, is hardened. Pallet 1 according to Fig. 6 comprises covering plate 14 of stiff cardboard, a layer of beams under it made up of three mutually parallel beams 2, intermediary plate 15 of stiff cardboard under the beams, and a lower layer of beams made up of three mutually parallel beams 2 at the very bottom. Beams 2 are situated in said layers perpendicularly against each other. When parallel beams 2 in both layers are situated in a distance from each other, it is possible to transfer the pallet by a lifting fork pushed to the gaps between the beams. Fig. 7, representing a corner of pallet 1 according to Fig. 6, shows that both covering plate 14 and intermediary plate 15 are formed of double corrugated cardboard where the direction of the corrugations is perpendicular with respect to the direction of beams 2 immediately under the plate. Thus placed, plates 14, 15 increase the stiffness of the pallet, in addition to which the intermediary plate 15 serves in the pallet as a fixing element attaching the superimposed layers of beams to each other and contributing to the cohesion of the pallet. It is clear to those skilled in the art that different embodiments of the invention are not limited to the above- described example but can vary within the appended Claims.

Claims: CLAIMS 1. A method for manufacturing a pallet (1) , in which beams (2) are formed of tube-like paper-board core pieces (3) arranged in line and of cardboard (4) surrounding them, the beams being attached to each other crosswise in at least two layers in such a manner that the axes of the parallel paper-board core pieces included in the beams are placed perpendicularly with respect to the level of the pallet, c h a r a c t e r i z e d in that when assembling the beams (2) , the paper-board core pieces (3) of essentially a round cross section are compressed in order to flatten them in the cross-direction of the resulting beam. 2. A method according to Claim 1, c h a r a c t e r i z e d in that the diameter of the paper-board core pieces (3) is decreased in the cross-direction of the beam (2) by 1-20% during flattening. 3. A method according to Claim 2, c h a r a c t e r i z e d in that the diameter of the paper-board core pieces (3) is decreased in the cross-direction of the beam (2) by 5-15%, preferably about 10% during flattening. 4. A method according to any of the preceding Claims, c h a r a c t e r i z e d in that the flattening of the paper- board core pieces (3) is carried out so that the diameter of the pieces in the axial direction of the beam (2) remains essentially unchanged. 5. A method according to any of the preceding Claims, c h a r a c t e r i z e d in that the paper-board core pieces (3) are arranged in line on a cardboard sheet (4) which is folded around the pieces, and that the flattening of the pieces is carried out in connection with the folding of the sheet. 6. A method according to any of the Claims, c h a r a c t e r i z e d in that the paper-board core pieces (3) and the cardboard (4) surrounding them are bound into a beam (2) by glue. 7. A method according to any of the preceding Claims, c h a r a c t e r i z e d in that the pallet (1) is further provided with a covering plate (14) of stiff cardboard and at least one intermediary plate (15) between the layers of the beams. 8. A pallet (1) manufactured by the method according to any of the preceding Claims, comprising beams (2) made up of tube-like paper-board core pieces (3) arranged in line and of the cardboard (4) surrounding them, the beams being attached to each other crosswise in at least two layers so that the axes of the paper-board core pieces included in the beams are perpendicular to the level of the pallet, c h a r a c t e r i z e d in that the paper-board core pieces (3) are flattened in the cross- direction of the beam (2) so that their diameter in said direction is smaller than that in the axial direction of the beam. 9. A pallet according to Claim 8, c h a r a c t e r i z e d in that the diameter of the paper-board core pieces (3) in the cross-direction of the beam (2) is 80-99%, preferably 85-95%, and most preferably about 90% of the diameter of the pieces (3) in the axial direction of the beam. 10. A pallet according to Claims 8 or 9, c h a r a c t e r i z e d in that the pallet (1) comprises, in addition to the beams (2) , a covering plate (14) of stiff cardboard and at least one intermediary plate (15) between the layers of the beams. 11. A pallet according to any of Claims 8 to 10, c h a r a c t e r i z e d in that the layer of cardboard (4) surrounding the paper-board core pieces (3) in each beam (2) is of corrugated cardboard and that a reinforecement plate (16, 17) of cardboard, extending from one end of the beam to the other, is further placed below the paper-board core pieces.

Inventors: BJOERNMAN TOMMI, RANTANEN KARI, BJOERNMAN, TOMMI, RANTANEN, KARI
Applicants: BJOERNMAN TOMMI, RANTANEN KARI, WISAPAK OY AB, BJOERNMAN, TOMMI, RANTANEN, KARI
Application year: 1995
Main classification: B65D19
IPC codes: B65D19