The present invention refers to a process for the manufacturing of pallets from different and profiled metal strip members given a certain shape, a tool for carrying out the forming of the profiled metal strip members to be assembled to pallets and forming one part of the necessary tool-equipment.

To use load carriers or pallets to carry goods is an well establi shed technique. In many cases the pallets are made of just wood, but pallets made of steel or of a combination of wood and steel exists. An ordinary pallet must comply with certain strength requirements and must also be liftable by fork-lifting means. One problem involved in using pallets made only or partially of wood is its disposition to absorb water. This means that the weight of the pallet may be increased up to twice the dry weight of the pallet. Another problem is the disposition of wood to lodge microorganisms and/or vermin. This often involve an expensive sanitation of pallets being carried between different parts of the world.

The main object of the present invention is to obtain a technique for a rational manufacturing of light-weight, high quality steel pallets and which pallets can withstand a certain deforming and correcting influ¬ ence, i.e. the life time of the pallets will be essentially longer than what is the case for e.g. ordinary pallets made of just wood.

Another object of the present invention is to obtain a rational assembling of the bent metal strip members to a pallet.

Yet another object of the present invention is to obtain a technique allowing a very easy adjustment of an assembling line, all the way from profiling, cutting, forming and welding of the strip members wherein pallets of different dimensions rapidly can be manufactured.

These objects stated above are according to the present invention obtained by giving the process, the tool and the pallet the character¬ izing clauses stated in the claims.

By having several first profiled strip members with certain lengths carried by conveyors from a store to a set of forming stations arranged side by side where a forming of the strip members is carried out by

locking them against dolly means, several identical members can be handled och formed at the same time. Thus the members are locked against dolly means and are formed by hydraulic activated bending tools to a desired shape, whereupon the tools are removed from the front of the formed strip members to expose these enabeling a robot to carry the strip members from the forming stations and to an exact position on an assembly line. Then second supplementary shaped metal strip members, preferably being roll-bent simultanously in a second similar but supplementary way compared to the first strip members, are transferred and placed partly overlapping and in different planes onto the strip members being first placed on the assembly line for a mutual assembling by welding. The assembled units in turn are assembled crosswise and are welded for making the finished pallet or pallet support. Thereafter a mounting of the load carrying surface can take place. As an alternative the load carrying surface can be formed by a type of end-bent strip members being placed closely onto the pallet support formed by the other strip members .

The expression forming used can in one way mean a conventional roll-bending, as in the examples mentioned below, and can in another way mean a forming with a stamping punching tool working together with an anvil of a resielient material arranged in a box. This k n o w n technique involve a very high and equally distributed pressure acting onto the whole component during forming. This in turn means that the spring back action after forming is at a minimum.

The invention will now be described in connection to embodiments shown in the drawings, where three different, roll-bent formed strip members are assembled in forming the pallet or pallet support.

Fig. 1 is a diagrammatic process line for pallets according to the invention and different examples showing how the profiled strip members can be differently formed by bending prior to assembling;

Fig. 2a - c show the differently bent profiled strip members and their cross sections in relation to the bendings;

Fig. 3a - b show how the profiled and bent members can be welded together;

Fig. 4a - b show diagrammatically a side view of the stationary half of a first set of roll-bending tools (4a) and also the movable suplementary half with further roll-bending means (4b);

Fig. 5a - c show, in a similar way as fig. 4, a diagrammatic side view of a second set of roll-bending tools during three different bending sequenses;

Fig. 6 shows a diagrammatic perspective view of a step-feeding device for handling and feeding the profiled strip members towards a vertical conveyor;

Fig. 7a shows a perspective view of a vertical magnetic conveyor being fed from the step-by-step feeding device according to fig. 6;

Fig. 7b shows a plan view of the initial transfer of a strip member to the pivotable part of the magnetic belt conveyor, and where

Fig. 8a - d diagrammatically show how robot technique is used to collect six simultanously and equally bent profiled strip members from a first bendning device and for laying them three-by-three onto two parallell manufacturing lines, while another or maybe the same robot at the same time picks up a second set of bent strip members to be placed three-by-three onto the two manufacturing lines.

In fig. 1 the manufacturing line 1 for steel pallets using the technique according to the invention is shown. A coil a with a flat steel strip B with a certain width is brought into a profiling device b and is cut at c . The cut profiled strip members d are moved to a store 2, or directely to a step-feeding device - see fig. 6. As an alternative the cut lengths of the profiled strip members can be brought from any other device. This is shown by the lorry in fig. 1.

Prior to handling of the profiled and cut strip members are described in connection to fig. 6 and 7, different pre-bent members

and their manufacturing will be described. Thus in fig. 1 to the right, and in fig. 2a - c, three different kinds of bent members 3a, 3b and 3c are shown. To the left in fig. 2 the cross sections of the profiles are shown. The three different bent members will form parts in a pallet where three pieces of the detail 3b are crosswise laid onto three of the details 3a, while three pieces of details 3c are put parallell onto the first details 3a and thus forming the pallet or the pallet s u pp ort . Possibly a load carrying surface (not shown) can be attached onto a pallet support. In the overlapping joints between the details 3a, 3b the cross sectional profile will be that shown in fig. 3b, while the cross section profile shown in fig. 3a is obtained with the overlapping joints between the detail 3c and 3b, or 3a, respectively. Thus the arrange¬ ment of the profile members shown in fig. 3b is preferred at such portions of the pallet being laid onto the ground or onto the floor not to cause damage to the ground.

In fig. 4a a first central set of bending means is shown together with a profiled strip member 3 carried by a magnetic belt conveyor. Again it can be said that six pieces of strip members are positioned in one plane above another and the bending actions to be described are performed simultanously at all sets of bending means. Two first hydraulic means 12a and 12b each including a roll-bending head 13a and 13b, respectively, are arranged at both sides of a stationary part 14 of the bending tool and having a locking and expanding portion 16 which - by hydraulic means (not shown) - is insertable to a locking and expanding position together with the tool-halves 17 - see fig. 4b -, whereby the hydraulic means exerts a force onto a plunger passing through the hole 15 and through corresponding holes in the stationary part 14. The two tool halves are connected to the hydraulic means 12c or to it's locking element. The hydraulic means and the p l u n g er preferably passes through all six sets of bendning tools as th e bendning actions preferably take place simultanously at all six sets. The locking and expanding part 16 at the stationary part 14 is caught with the hook-shaped locking means (not shown) into recesses (not shown) being arranged in the two halves of the tool 17. To have these pressed outwardly against the action of a spring force to a position where the halves form a correctely shaped and rigid bending tool, inner and oblique contact surfaces (not shown) are arranged on the

two halves of the tool and against which surfaces correspondingly formed surfaces (not shown) at the locking and expansion portion 16 are intended to press by a hydraulic action from plunger means. In fig. 4b it can be seen that the two outer profiles of the two halves of the tool are diverging down to allow a small over-bending (about 1,5 °) of the strip member as the elasticity of the metal otherwise would cause a spring back action of the strip member during bendning which would not result in perpendicular bending angles.

In fig. 4b it is shown how the hydraulic means 12a and 12b of the bending tools have carried out the initial bendning of a strip member. After that the hydraulic means 12c with its two roll-bending means 13c arranged on pivotable arms is in a position to initiate its bendning action downwards of two shankportions of the strip member to a horisontal plane above the initial horisontal supplying plane. When the initial bendning is finished at the central part of the strip member the hydraulic means 12a, 12b and 12c move back to their intial positions and the two parts of the tool 17 are resiliently brought back to their initial positions close to eachother. This makes it possible to remove the bending tool and the hydraulic means 12c to expose the front surfaces of the bent members, and to allow a later removal with a robot (see fig. 8 with accompanying text).

In fig. 5a the initial position at the one end of the profiled strip member is shown. It is emphasized that there also is a set of reversed bendning means compared to the one shown i fig. 5 and which is arranged at the other end of the strip member. The upper components 18 - 21 forming part of the tool set are in a ready position, separated from the bending planes, to allow a bending rearwards of the shank portions according to what has been indicated in fig. 4b. First when the shank portions have come down to a horisontal position against the dolly member 22, the tool components 18 - 21 are moved forward towards the position shown in fig. 5a. Thus, there is a clamping device 21 holding the strip member prior to bending, whereupon the hydraulic means 18a moves the roll-bendning means 19a with accompanying rollbendning tool to the postition shown in fig. 5b. Thereafter the hydraulic means 18b with accompanying roll-bendning means 19b is activated and the bendning is carried out in the original

supplying plane, the hydraulic means 18c with rollbendning means 19c performs the final bendning. These bending tools can also b e shaped in such a way that an "overbending" can occure.

Fig. 6 shows the discharging from e.g. a rolling device where profiled and cut strip members can be fed to a collecting table 6 having four conveyor belts 7. These belts carry the cut strip members one-by-one to a distributor 8 bringing them further to the vertical conveyor 9 shown in fig. 7a. This vertical conveyor has four conveying belts arranged vertically and which one-by-one moves the strip members to the magnetic belt conveyor 10a - lOf. Thus, when all conveyors each have been fed with one strip member they are all simultanously fed further to another vertical magnetic belt conveyor 11 having six magnetic conveying means.

Fig. 7b shows how the members are carried from the conveyor 10 to the conveyor 11. Fig. 7b also shows how the conveyor 1 1 is pivot- able to the conveyor 10. At 11' the conveyor 11 is shown in an inner pivoted or turned position, and at 11 the conveyor is in a position exposing the strip members to a bendning and a later removal with aid of robot means - se also fig. 8. From the conveyor 10 all six strip members are fed simultanously into six different sets of bending tools where three different bendning processes take place in each plane and where the bending in one plane has been described in connection to fig. 4 and 5.

Fig. 8 shows diagrammatically how a robot R pics up bent members being already bent in a bending station A with bending equipment for a simultanous bendning in six different planes. Fig. 8b shows how robot means R has been moved to a position above a first p allet assembly line for pallets to leave three of the bent strip members. Fig. 8c shows how the other six bent strip members are left on a second assembly line. Finally, fig. 8d shows the same robot means R and another robot means R' collecting another kind of alredy bent members from another bending station B. Fig. 8b shows how the robot means R holding the already bent strip members is movable in a x - direction to allow an adjustment to different manufacturing lines for assembling of different kinds of pallets, or pallet supports. The robot

technique described above is previously known and is not described in detail.

Finally it will also be mentioned that instead of welding the differently profiled and bent metal strip members put together, it can for certain applications also be possible and preferred to joint these components by riveting.