PALLET AND METHOD FOR ITS FABRICATION

The object of the invention is a pallet, preferably a pallet made from corrugated cardboard or corrugated paperboard, polypropylene corrugated cardboard or a similar material, and a technological method for its fabrication. The pallet of the invention can be designed as a »rack« pallet that allows use on an open rack and prevents U-sag, and as its variant »bridge« pallet, where this variant provides for stability on the rack and in packing, where the pallets are stacked into stacks and do not get sagged in the middle in the shape of the letter U when the forces are exerted on the centre of the pallet. The invention belongs to class F 42B 07/06 of the International Patent Classification.

The technical problem that is successfully solved by the present invention is construction and embodiment of such a pallet that provides for maximum technical properties of a paperboard or similar pallet in conditions of extreme load during transport, on an open rack and at the same time allows for a mechanical process of automated production in large quantities and shaping of constituent parts of the pallet, and determining the technological method for its fabrication; mechanical fabrication of such a pallet that will meet both technical and constructional rigidity requirements. A paperboard pallet is usually fabricated from one to two pieces which are formed into a supporting pallet through mutual assembly, folding and sticking. Fabrication of known pallets of this type usually comprises manual assembling, folding and sticking, and this is not in favour of a rapid and price efficient production of pallets.

One pallet construction of this type is disclosed in patent document ES 1093080. The basis for the fabrication of a pallet is a rectangular template with three sectors, a central one and two lateral ones, that need to be folded manually by using a special method. This construction does not allow for an automated mechanical production.

Basically, the pallet of the invention is designed as a pallet composed of three basic parts, a bottom part, an upper part and an envelope, basically as a rack pallet and with a modification thereof as a bridge pallet. All three parts are pre-shaped and can be mechanically assembled in an automated process that will be described in the continuation.

The invention will be explained in more detail by way of an embodiment and through the use of the accompanying drawings in which:

Figure 1 shows constituent parts of a rack pallet of the invention;

Figure 2 shows a template of a bottom part of the rack pallet;

Figure 3 shows the bottom part of the rack pallet;

Figure 4 shows a template of an upper part of the rack pallet;

Figure 5 shows the upper part of the rack pallet;

Figure 6 shows a template of an envelope of the rack pallet; Figure 7 shows constituent parts of a bridge pallet of the invention;

Figure 8 shows a template of a bottom part of the bridge pallet;

Figure 9 shows the bottom part of the bridge pallet;

Figure 10 shows a template of an upper part of the bridge pallet;

Figure 11 shows the upper part of the bridge pallet;

Figure 12 shows a template of an envelope of the rack pallet;

Figure 13 shows a leg of the template;

Figure 14 shows a detail of notches;

Figure 15 shows a detail of leg folding;

Figure 16 shows a detail of a notch of the upper part of the rack pallet;

Figure 17 shows a detail of the notch of the bottom part of the rack pallet;

Figure 18 shows a detail of a notch of the upper part of a bridge pallet; Figure 19 shows a detail of the notch of a bottom part of the bridge pallet;

Figure 20 shows a production line for mechanical assembly of pallets of the invention;

Figure 21 shows a machine for folding templates and applying adhesive;

Figure 22 shows the template.

The material, from which a pallet of the invention is made, is corrugated cardboard, corrugated paperboard, a material made from cellulose fibres composed of several glued layers. The external layer is flat, whereas interlayers join the flat layers between them in the shape of corrugations. The pallet may be composed of a large odd number of layers and interlayers. Apart from corrugated cardboard polypropylene (PP) can be used as a material for the pallet of the invention. PP is a thermostatic polymere applicable in various industries in packing, textile etc. A polypropylene corrugated cardboard is a material made from a thermostatic polymere in the shape of a corrugated cardboard, wherein the external layers are flat and joined by interlayers of various shapes.

When vertical forces are exerted on the surface of the rack pallet of the invention, the rack pallet exhibits special structural rigidity. Due to its special distribution of supporting legs, notches and folds, the forces are distributed very equally over the material and a vertical force is to a large extent redirected to a horizontal force that acts on supporting legs at an angle that provides for a better load capacity of the pallet on an open rack. Orientation of corrugations in interlayers of the corrugated cardboard is of key importance in providing the described technical properties of the pallet.

The rack pallet is a pallet, in which U-sag is prevented due to its technical properties and it is therefore meant to be arranged onto an open rack.

The rack pallet consists of three parts: an upper part 2a, a bottom part 1a, and an envelope 3a. Initially, the bottom part 1a (shown in Figures 2 and 3) is shaped like a template - flat bottom area with cutouts 10a in the shape of two asymmetric ellipses and square openings 10b with rounded corners that will represent a special opening in the fabricated pallet for pallet jacks with arranged wheels or for similar tools provided with wheels for manipulating the pallet.

A notch 10a' is formed when the bottom part 1a is folded from the cutout 10a, and when a leg 10a" is formed from a special cutout 10a formed by a material cutout, said leg being designed for a mechanical joining of the bottom part 1a of the pallet with the upper part 2a.

As already mentioned, the orientation of currugations in the interlayers of a corrugated cardboard is important: the orientation of the corrugations of the bottom part 1a must be oriented with respect to cutouts 10a and 10b towards a shorter side of the final product and towards the longer side of the template.

After reshaping, the bottom part 1a exhibits four legs 10a", sixteen notches 10a' and four square openings 10b with rounded corners.

Each leg 10a" of the bottom part 1a has four notches 10a' and is obtained by a double fold of the template of the bottom part 1a.

Initially, the upper part 2a (shown in Figures 4 and 5) is shaped like a template - flat bottom area with cutouts 20a in the shape of two asymmetric ellipses. A notch 20a' is formed when the bottom part 2a is folded from the cutout 20a, and when a leg 20a" is formed from a special cutout 20a formed by a material cutout, said leg being designed for a mechanical joining of the bottom part 1a of the pallet with the upper part 2a.

As already mentioned, the orientation of currugations in the interlayers of a corrugated cardboard is important: the orientation of the corrugations of the upper part 2a must be oriented with respect to cutouts 20a towards a longer side of the template.

After reshaping, the upper part 2a exhibits four legs 20a", sixteen notches 20a ¹ and four legs 20a" with rectangular cutouts 20a".

Each leg 20a" of the upper part 2a has four notches 20a' and is obtained by a double fold of the template of the upper part 2a.

By double folding the template's bottom part 1a and upper part 2a legs 10a" and 20a" are obtained, on which notches 10a' and 20a' are formed after the reshaping from the cutouts 10a and 20a.

The shape and dimension of notches 10a' and 20a' are shown in Figure 14, whereas individual parts are shown in Figures 16, 7.

Details of the notch 10a' are shown in Figure 17, and details of the notch 20a' are shown in Figure 18.

Ratios between the notch 10a' of the bottom part 1a and the notch 20a' of the upper part 2a are dimentionally defined by the following formula:

V _kt = (Ο,βΒ ± 0,02) - ¾ (0,36 ± 0,02) · ¾

~ = 0,5 ± 0,05

Figure 13 shows folding of parts of the template to form a leg. A detail of folding the template for the leg is shown in Figure 15. Zone 5 has the shape of a triangle, the dimensions and angles of which form a basis for an optimal transfer of forces to an area of the upper part 1a to the bottom part 2a and vice versa, and are determined by the properties of the applied material.

The legs 0a" or 20a" are formed by bending the template material with two single bends 2 and one double bend 4. A ratio of a distance L and a depth of a bend r with respect to the thickness of the applied material D is determined by the following formulas:

L = (2 ± 0,≤) ' D When the pallet is assembled, adhesive is applied on the upper edge of the legs 10a" and 20a" in order to stabilize the position of the bottom part 1a with respect to the upper part 2a of the pallet.

Figure 6 shows the envelope 3a. Initially, the envelope 3a is shaped like a template - flat with cutouts 30a in the shape of rectangles which will represent special openings in the fabricated pallet for receiving forks of a pallet jack.

The envelope 3a is meant to provide additional rigidity to the pallet at load capacity, U-slag, upside-down U, at additional strengthening when forces are exerted in all directions - shaking, pushing, flat non-applying areas and holding of the remaining two parts of the pallet in a proper position when loaded.

An area 30b renders additional rigidity to the pallet at upside down U- slag, stability and an adequate surface for applying adhesive, an area 30c is a quadrangular area that provides a flat applying surface, an area 30e renders additional rigidity to the pallet at upside down U-slag, stability and provides an adequate surface for applying adhesive, areas 30d and 30f provide additional stability and load capacity of the pallet and a suitable space for imprinting.

Openings 30a are intended for manipulation of the pallet by a pallet jack or similar devices.

The bridge pallet of the invention that is a variant of the rack pallet allows manipulation by a pallet jack from four sides and its construction prevents especially an upside-down U-slag. Owing to a special bridge, it can be also used on an open rack, yet in a limited scope. Orientation of corrugations in interlayers of the corrugated cardboard is of key importance in providing the described technical properties of the pallet.

The bridge pallet is a pallet, in which an upside-down U-sag is prevented due to its technical properties.

The bridge pallet consists of three parts: an upper part 6a, a bottom part 5a and an envelope 7a (all shown in Figure 7).

Initially, the bottom part 5a (shown in Figures 8 and 9) is shaped like a template - flat bottom area with cutouts 50a in the shape of two asymmetric ellipses, with square cutouts 50c and square openings 50b with rounded corners that will represent a special opening in the fabricated pallet for pallet jacks with arranged wheels or for similar tools provided with wheels for manipulating the pallet.

A notch 50a' is formed when the bottom part 5a is folded from the cutout 50a, and when a leg 50a" is formed from a special cutout 50a formed by a material cutout, said leg being designed for a mechanical joining of the bottom part 5a of the pallet with the upper part 6a.

As already mentioned, the orientation of currugations in the interlayers of a corrugated cardboard is important: the orientation of the corrugations of the bottom part 5a must be oriented with respect to cutouts 50b towards a shorter side of the final product and towards the longer side of the template. After reshaping, the bottom part 5a exhibits four legs 50a", sixteen notches 50a' and four square openings 50b with rounded corners.

Each leg 50a" of the bottom part 5a has four notches 50a' and is obtained by a double fold of the template of the bottom part 5a. Each leg is provided with cutouts 50a'".

Initially, the upper part 6a (shown in Figures 10 and 11) is shaped like a template - flat bottom area with cutouts 60a in the shape of two asymmetric ellipses.

A notch 60a' is formed when the upper part 6a is folded from the cutout 60a, and when a leg 60a" is formed from a special cutout 60a formed by a material cutout, said leg being designed for a mechanical joining of the bottom part 5a of the pallet with the upper part 6a.

As already mentioned, the orientation of currugations in the interlayers of a corrugated cardboard is important: the orientation of the corrugations of the upper part 6a must be oriented with respect to cutouts 60a towards a longer side of the template.

After reshaping, the upper part 6a exhibits four legs 60a", sixteen notches 60a' and four legs 60a" with rectangular cutouts 60a'".

Each leg 60a" of the upper part 6a has four notches 60a' and is obtained by a double fold of the template of the upper part 6a.

By double folding the template's bottom part 5a and upper part 6a legs 50a" and 60a" are obtained, on which notches 50a' and 60a' are formed after the reshaping from the cutouts 50a and 60a. The shape and dimension of notches 10a' and 20a' are shown in Figure 14, whereas individual parts are shown in Figures 16, 17.

Figure 12 shows the envelope 7a. Initially, the envelope 7a is shaped like a template - flat with cutouts 70a in the shape of rectangles which will represent special openings in the fabricated pallet for receiving of forks of a pallet jack.

The envelope 7a is meant to provide additional rigidity to the pallet at load capacity, U-slag, upside-down U, at additional strengthening when forces are exerted in all directions - shaking, pushing, flat non-applying areas and holding of the remaining two parts of the pallet in a proper position when loaded.

An area 70b renders additional rigidity to the pallet at upside-down U- slag, stability and an adequate surface for applying adhesive, an area 70c is a quadrangular area that provides a flat applying surface, an area 70e renders additional rigidity to the pallet at upside down U-slag, stability and provides an adequate surface for applying adhesive, areas 70d and 70f provide additional stability and load capacity of the pallet and a suitable space for imprinting.

Openings 70a, 70g are intended for manipulation of the pallet by a pallet jack or similar devices.

The shape and dimensions of the notches 50a' and 60a' of individual parts 5a, 6a are shown in Figures 18, 19. The method for mechanical fabrication of the pellet comprises three key phases: a phase of fabrication of the upper and bottom parts of the pallet, a phase of stacking of both, and a phase of wrapping with the envelope.

All key phases of pallet fabrication are inter-connected and form a continuous, uninterrupted, rapid process for pallet fabrication. The entire assembly of the device for mechanical fabrication of pallets comprises: two conveyors s11 and s12 of templates, two machines s21 and s22 for the preparation of the template, two machines s31 and s32 that fold and glue the template, two joining units s41 and s42, a rotary machine s5, a joining unit s6, a machine s7 for joining the upper and bottom parts of the pallet, a conveyor unit s8 for envelopes, a unit s9 for joining the envelope with the assembled parts of the pallet, a joining unit s10, two machines s111 and s113 for placing the envelope, and a rotary table s12.

The conveyors s11 and s12 for templates are the machines that store templates, check the templates for regularities, and release them to production process in compliance with a pre-programmed method.

The machines s21 and s22 for a preparation of the template allow fabrication of bends of imprints into the template material. They are equipped with special tools which, while rotating, imprint a special bend on certain zones on the template and the template is thus prepared for a further process.

The machines s31 and s32 are designed for a guided folding of the template and for applying adhesive, and also for producing supporting legs on the template at double folding. The process runs at equal motion, wherein first the inner legs are folded and then the external legs are folded.

The machine s31 , s32 for folding the templates and applying adhesive is shown in Figure 21. Figures 21 ,22 shows a template, wherein the length of the machine s31 , s32 depends on the length of the template of the pallet and on the angle a which is defined by the formula:

q = d—c = L _j — k - 4 · 1 ₀

0,90 < k < 1

The joining units s41 and s42 are composed of special guides and a pull strap; with their continuous guiding of the upper part and the bottom part of the pallet in a proper position, they allow for temporal synchronisation of the process.

The rotary machine s5 allows for a rapid change in position of the template for a further application of adhesive onto supporting legs, for process synchronization, and simultaneously ensures the proper position for a subsequent step of joining the bottom and upper parts of the pallet.

The rotary machine 5s is composed of a platform that constantly provides for a proper positioning of the template, a rotary axle that rotates by 45 % and thus allows for changed positioning of the template in a position, in which the supporting legs face upwards; via the guiding system it pushes the pallet towards adhesive application and towards the process of joining both parts of the pallet.

The joining unit s6 is made of special guides and a pull unit that serves for process synchronisation and enables movement of the bottom/upper part of the pallet in a proper position towards the machine for joining both pallet parts.

The machine s7 for joining the bottom and upper parts of the pallet is a machine unit meant for a precise - by preserving the input position of the upper/bottom parts of the pallet - joining of both parts, wherein all 16 notches on the bottom part and 16 notches on the upper part of the pallet get joined.

The conveyor unit s8 for envelopes stores envelopes checks their regularity and releases them according to a pre-programmed method to the unit for joining the envelope with the remaining two parts of the pallet.

The machine unit s9 provides for proper positioning of the envelope for joining with the other two parts of the pallet: a special method is followed to apply adhesive onto the envelope, then all parts are pushed towards the machines s111 and s113 for wrapping the envelope, wherein the position of the envelope and of the remaining two parts of the pallet are constantly preserved.

The joining unit s10 consists of special guides and a pull unit that provides for a proper position in guiding of the three parts of the pallet and for synchronisation of the process. In the machines s111 and s113 which function by the principle of continuous movement special guides gradually close the envelope at sides around the joined parts of the upper and bottom parts of the pallet. Here, two sorts of adhesive are applied on the upper part of the joined part of the pallet.

The method of fabrication starts with the automatic conveyor of the upper and bottom parts of the pallet; first the template is checked for regularity, then it is conveyed to a proper position to the machine s21 , s22 for making an imprint/bend.

The rotary table s12 is a machine unit that changes the position of three parts of the pallet into a position that is adequate for a further process of wrapping the envelope of the pallet.

The upper and bottom parts of the pallet then continue along the machine s31 , s32, wherein the inner legs are first formed, then the extemal legs are formed at the bottom part and then the inner and extemal folds are formed at the upper part; in this process two sorts of adhesive are automatically applied which stabilise the position of the legs for a further automatic production process.

Downstream of the machine s31 , s32, the bottom part of the pallet then enters the guided process which guides such template to the machine s 1. When the upper part of the pallet leaves the machine s31 , s32, it is put into a position for joining with the bottom part of the pallet through a joining part and the continuously guided position of the template.

The machine s7 represents a technological solution to mechanical joining of both parts of the pallet and allows for a continuous maintenance of the proper position of the template of the upper and bottom parts of the pallet until joining.

After joining is over, the process continues - while the position is continuously guided and the key spots of the obtained product pressed - to the machine s6, where the automatic hopper s8 positions the envelope of the pallet on the spot, at which joining of both parts of the pallet with the third part, the envelope, will take place after the adhesive is applied.

After joining is over, the pallet, while continuously guided, is conveyed to the machine s9 which provides for gradual wrapping and applying the adhesive for the final joining of the envelope with the other two parts of the pallet.

The pull strap of the wrapping machines s111 and s133 arranged on the bottom side of the pallet pulls the pallet forwards, whereas special guides at the side gradually close the envelope around the joined parts of the upper and bottom parts of the pallet.

During the process of closing of the envelope two sorts of adhesive are applied on the upper part of the joined part of the pallet of the invention. Once the envelope is completely wrapped, the pallet continuously moves forward where it is pressed downwards by special spring rollers from the upper side to achieve proper adhesion of the adhesive.