WO1990004679A1

WO1990004679A1 - Method for the manufacture of load-carrying elements including pallets

Info

Publication number: WO1990004679A1
Application number: PCT/DK1989/000251
Authority: WO
Inventors: Torben Rasmussen
Original assignee: Brødrene Hartmann A/S
Priority date: 1988-10-25
Filing date: 1989-10-25
Publication date: 1990-05-03
Also published as: SE467058B; GR1000659B; CN1045616A; EP0441847A1; AT398094B; CA2001299A1; GR890100679A; SE9101241L; CH677945A5; BR8905454A; NZ231148A; NL8921188A; ATA903189A; AU644778B2; DK592388D0; DK592388A; CN1025061C; JPH04502184A; AU4513389A; DK166736B1

Abstract

By means of a procedure for the manufacture of load carrying elements, including pallets, a fluidized fibre raw material is deposited on a moulding foundation through suction of a pulp of the fibre raw material on that foundation. For this purpose the foundation is applied with an easily drainable pulp created by the fluidized fibre raw material in such an amount and the suction is carried out controlled in such a way that on the foundation through suction a fibre raw material is deposited having such wall thickness that substantially provides the desired load capacity of the element.

Description

Method for the manufacture of load-carrying elements including pallets The present invention concerns a method for the manu¬ facture of load-carrying elements, including pallets by the depositing of a fluidized fibre raw material on a moulding foundation by suction of a pulp of the fibre raw material on this foundation.

A fluidized fibre raw material means a starting mate¬ rial, which may be in wet form, of a fibrous nature and suited for the manufacture of the desired objects. Such starting material may for instance be a fibre pulp material as used for instance for trays and cartons for packaging of fragile and sensitive objects such as fruit, flowers, eggs and objects of for instance glass. The pulp material usually consists of a suspended, fibrous cellulose.

It is well known for this purpose to use a production technique by which the starting material in the form of a pulp is by a depositing process placed against the outline- forming outside of a mould which is permeable to let a ga¬ seous working medium, through a suction effect, affect the material through the material of the mould and thus mould the contour of the material on the mould through suction.

The object of the invention is to indicate how this in itself suitable production technique may be used not only to manufacture relatively small and light objects but also to manufacture large, rather heavy objects characterized by extremely high load capacity which are substantially based on a corresponding thickness of the material layer deposited on the moulding foundation. In comparison with this the wall thickness of the said small and light objects is rather thin and the rigidity necessary in practice is usually obtained by deliberately forming the wall panels which for instance support the said objects as the walls produce a rather rigid total object by mutually supporting each other.

According to the invention the stated objective is a- chieved by applying to the foundation an easily drainable pulp made of the fluidized fibre raw material in such quan¬ tity and by controlling the suction in such a way that a fibre raw material layer of such thickness as to provide substantially the load capacity desired for the element.

This will by using the above production technique also enable the manufacture of elements with high load capacity such as pallets and building elements which may, contrary to the said packaging examples, display rather even and smooth outer surface and which in itself displays a high de¬ gree of form stability. The depositing of a fibre raw mate¬ rial layer of the defined thickness means that the negative pressure in the fibre raw material layer used for suction may procure a material density which is highest at the out¬ side of the material layer directed towards the mould sur¬ face and which will have a reinforcing effect as it is placed at a distance from the through-going centre plan of the deposited object. By using the layer thickness of the element thus manu¬ factured its load capacity may according to the invention also be increased by procuring in the fibre raw material layer and distributed over this one or more variations in the layer thickness by correspondingly locally varying the suction effect during a joint suction process for the fibre pulp volume necessary for the manufacture of the whole ele¬ ment. In this way it will be possible in one and the same working process, i.e. the depositing of the fibre raw mate¬ rial on the moulding foundation, to mould both the final outside desired for the element and, by using the thickness of the material layer, a load capacity increasing moulded structure in the actual material object forming the element. According to the invention such a structure will for in¬ stance be able to be shaped as a connected structural pat- tern with a thicker layer thickness compared with the parts of the element.

According to the invention a suitable way for the car¬ rying through of the method is characteristic in that, for suction of an easily drainable pulp of the fibre raw mate- rial in the desired thickness, a mould is used which at ne¬ gative pressure is permeable by a gaseous active working me¬ dium and which has a by the working medium permeable mould surface the permeability of which is adjusted to the thick¬ ness of the fibre raw material layer to be deposited by suc¬ tion of the pulp on this surface.

In this way it is possible to achieve such interaction between the draining ability of the pulp and the suction capability of the mould surface that also elements having thick fibre layer thickness owing to the desired load capa¬ city may be manufactured rationally.

In order to achieve local variations in the layer thickness of the fibre raw material layer of the element, a mould having a mould surface with a permeability varying in accordance with the layer thickness of the local varia¬ tion or variations respectively or the coherent structural pattern of the easily drainable fibre pulp layer deposited on the mould surface by suction may be used according to the invention.

This means that the depositing of fibre raw material on the mould surface will vary according to the permeability of this surface which results in local variations in the suction effect which, in areas with poor mould surface per¬ meability, causes reduced depositing of fibre raw material in the mould surface whereas the depositing will be high in areas with high mould surface permeability.

According to the invention, an embodiment of this me- thod may be characterized by the use for suction of an easily drainable pulp of the fibre raw material in the de¬ sired thickness of a mould which at negative pressure is permeable by a gaseous active working medium which at least as regards the outline-forming part consists of a partial composite material the particles of which are fixed together for the formation of a contour-stable mould surface at the same time as they together limit passages open to the work¬ ing medium, which passages extend through the composite ma¬ terial to the outside surface of the mould, and that the thickness of at least the composite material layer forming the mould surface is adjusted according to the thickness of the fibre raw material layer to be deposited by suction of the pulp to this surface. Such a mould may be manufactured on the basis of a cheap, inorganic raw material such as sand as well as by means of a production technique which is simple, of short duration and thus also cheap. The total production costs of the mould may thus be kept at a low level and this form of construction will consequently be suitable for the produc¬ tion of a small number of products.

In order to achieve local variations in the layer thickness of the element's fibre raw material layer a mould may, according to the latter procedure, be used in which the composite material formed by the mould surface has a thick¬ ness that varies in accordance with the layer thickness of the local variation or variations, respectively, or the de¬ sired coherent structural pattern of the easily drainable fibre pulp layer deposited on the mould surface by suction. According to the invention a mould may be used the per¬ meable mould surface of which is composed of particles with varying particle size, the particle size being small in the part forming the mould surface of the mould and larger in an underlying supporting layer for this part. In this way it is possible to procure good passage for air and at the same time procure for the element to be manufactured a rather smooth mould outside which will result in the element obtaining an even surface. The mould strength necessary for the carrying through of a production process may be achieved in a simple way by mixing the mould particles with suitable binding^•agents which may contain adhesion-improving agents and by hardening the mould manufactured by such mixture by for instance heat treatment. Also wedging between the particles may be used to give the mould strength.

Furthermore, according to the invention it is possible to use a mould having at the bottom a basic part in which the composite particles are linked together by a real fusion compound whereas the particles in the rest of the mould are linked together by a hardening conglutinating compound. Such a mould is characterized by good strength which will also enable it to resist considerable working pressure. It is also within the scope of the invention to use a mould the mould surface of which is shaped with such strength that the mould may be used for the finishing pres¬ sing of a moulded element. Finishing pressing may not only be used for quick removal of water from the pulp layer de¬ posited on the mould surface, but also to achieve an espe¬ cially good material density in the deposited, rather thick fibre material layer and thus an especially high degree of form stability in the final element. The desired porosity of the mould may be achieved by an appropriate choice of the size and distribution of the particles of which the permeable mould surface may be com¬ posed both to obtain favourable conditions for the fixing compound between the particles and for a suitable dimension- ing of the porosity in order to avoid an undesired pressure drop through a building material which is unnecessarily dense.

•The above procedure and mould may as mentioned in prac¬ tice be used for the production of elements of various fibre-containing suspensions, everything in the presence of the auxiliary materials which may be necessary to create connection in the material layer obtained by suction onto the mould.

The removal of an object formed by the depositing of a fluidized fibre raw material on the outline-forming out¬ side of the mould surface by means of a gaseous working me¬ dium may in practice take place by the object being affected by compressed air through the air passages of the mould and thus lifted free of the mould. In practice the object will, however, usually still be rather soft and it may therefore for the purpose of removing the object from the casting mould be appropriate to use a transfer mould which is adap¬ ted to interact with the side of the object pointing away from the mentioned outline-forming outside for the removal of the object from this outside and for the subsequent plac- ing of the object on for instance a conveyer belt taking the object to a drying chamber. It is within the scope of the invention also to manufacture such a transfer mould from a particle composite material as mentioned above by binding the material particles together for the creation of an open, stable structure with air passages going through to the out¬ side of the mould and by connecting the thus created mould to a source for a suction provoking vacuum.

The transfer mould is producible directly on the basis of an object produced on the casting mould as on this object a first auxiliary mould (negative) of for instance gypsum is produced corresponding to the side of the object pointing away from the casting mould and on this first auxiliary mould (negative) a second auxiliary mould (positive) is pro- duced for instance also from gypsum and the transfer mould (negative) is then formed directly on this second auxiliary mould.

The permeable mould surface may be kept clean by, prior to the start of the depositing process or the transfer pro- cess, exposing for cleaning purposes the mould surface to an air current passing through the mould passages for a ga¬ seous medium.

A mould used in accordance with the invention and con¬ structed by a particle composite material may be manufac- tured in such a way that it may after use or in case of wear be regenerated as the particle-shaped building material of the mould may be recycled.

For the manufacture of a pulp which is to be easily drained, according to the invention, as fibre raw material at least partly a starting material containing long fibres may be used which is processed to a pulp partly by means of a shake-out in a pulper, partly by a preceding, separate, controlled dry grinding by which the starting material is divided into dosage amounts and divided into-its fibres whereupon the object is manufactured from the pulp thus cre¬ ated.

The use of a pulper as an essential step in the proces¬ sing of the fibre raw materials for the creation of a pulp from which the desired objects are to be manufactured takes place among other things in cases where the fibre raw mate¬ rials are received in the form of dry substances in bales, for instance as paper waste. Heavy whirl formation is produced in the pulper by which the single parts of the material rub against each o- ther and is thereby divided and the raw materials separated into fibres.

Especially in case of heterogeneous material such as waste or recycled paper it has to be anticipated that this separation is carried out successively so that the fibres released first are exposed to a higher degree of additional substantial processing than the fibres released later. In other words the processing in the pulper will in its pro- ceedings thus be uncontrolled and thus heterogeneous. The said additional processing results in an increase in both the degree of grinding ( °SR-Schopper-Riegler) and thus the formation of mucus in the pulper, which negatively affects the subsequent draining of the object manufactured from the pulp and increases the shrinkage of the object during drain¬ ing and drying of its material.

The method according to the invention achieves that to the pulper is at least partly added a fibre raw material the fibres of which are already to a substantial degree se- parated into single fibres why they are more instant and at the same time susceptible to the self-grinding effect and mixing effect obtained in the pulper. As the pulper proces¬ ses a more uniform raw material also the grinding degree ob¬ tained in the pulper through self grinding may be adjusted to be more uniform and the above-mentioned binding of water in the pulp leaving the pulper will thus be more control¬ lable.

The same procedure will, however, also result in other advantages which are especially valuable in case of recyc- ling of paper waste.

Recycled paper waste exists in many different qualities and gradings. If this material prior to the shake-out in the pulper is exposed to a separate, controlled dry grinding, it is often possible to use a poorer and thus cheaper mate¬ rial quality, than if the division process was only carried out as a shake-out in the pulper. It lies within the scope of the invention to carry out the preceding separate dry grinding as mentioned above as a multiple-stage process whereby it is possible to separate the starting material in dosage amounts in a special effi¬ cient manner. In this particular way also e.g. waste paper material containing plastic, water resistant paper, plastic laminated cartons and paper, to the degree desired can be separated into fibres and other particles. Separated constituents not being paper can be screened off before entering the pulper, or it is possible to let these constituents since they exist in pulverized form enter into the following production pro¬ cess.

At a performance of the method a long fibre starting material having been subjected to a separate controlled dry grinding be added to an already in the pulper formed pulp and be subjected to a joint time-limited shake-out with this.

In this manner an object can be manufactured whose fibre material is partly mainly bound by hydrogen fibre bin- dings partly have been mixed with air suspended fibre mate¬ rial for whose binding glue is normally used. It has turned out that in this way it is possible to abandon a traditional complete hydrogen binding of the whole pulp, which means that the drain and thereby the production time for the ob- ject can be substantially reduced. Furthermore the method makes it possible to obtain a strict control of the desired object strength characteristics as it will be possible to have strict control of these by the addition of glue.

These advantages are of major importance for a rational and thus economic industrial manufacture also of large form stable objects by the application of the suction technique described. It will e.g. be possible to carry out a multiple-stage dry grinding by the application of a tearing machine also called a shredder followed by a treatment in a hammer mill which thus can receive the material from the shredder in do- sage amounts and which exposes the material to a further grinding process before it if required also in special do¬ sage amounts it added to the pulper for the actual shake-out processing.

The separate, controlled dry grinding suggested accord- ing to the invention of the fibre raw materials prior to their shake-out in the pulper also provides the possibility for the co-application of recycling waste paper in cases where the objects to be manufactured must be shrink proof and measure proof. A starting material with a high content of wooden fibre causes less shrinkage that if the fibre were cellulose fibre. It has turned out that by applying the me¬ thod according to the invention it is even possible to add to a wooden paper raw material a substantial amount of cheap recycling paper including carton waste which not necessarily is wooden since it is possible -to manufacture due to the preceding separate controlled dry grinding of the raw mate¬ rial a pulp which causes no undesired shrinkage of the ob¬ jects manufactured.

It is a well know principle for the manufacture of ob- jects of a fluidized fibre raw material to utilize auxiliary materials such as filling material and chemicals and binding agents. The auxiliary materials decide whether the objects manufactured shall be more or less strong, hard or transpa¬ rent, or weak, soft and absorbing. The present invention is also advantageous in connection with the application of such auxiliary materials.

The division of the manufacturing process in multiple- stages actually increases the possibility of adding the auxiliary materials at different stages of the total ma/iu- facturing process. The achieved open structure of the final pulp, obtained as a result of this particular invention, even facilitates a better access for auxiliary materials so that e.g. a binding material may be applied more or less in¬ tegrating on the surface of the objects in order to increase the weight. The addition of auxiliary material under the preceding separate, controlled dry grinding will in a espe- cially good manner be able to further a particular uniform distribution of the auxiliary materials in the manufactured fibre mass. It is of course also still possible to add the auxiliary materials to the pulper.

Furthermore, it lies within the scope of the invention that the shake-out in the pulper is carried out as a manu¬ facturing process dependent on the preceding separate, con¬ trolled grinding. In other words the obtained degree of self grinding in the pulper can be adjusted in accordance with the degree of the grinding which according to the circum- stances has been carried out at the preceding dry grinding stage(s) . As an example, a paper pulp which in the pulper ^" is separated into a normal, at self grinding obtained grin¬ ding degree of 60° SR (Schopper-Riegler) , be added dry grounded fibre material whereafter the mixture is processed in the pulper for 5 minutes more. Objects manufactured from such a mixture pulp may be provided with a special heavy thickness, porosity and permeability. This means that the products can have good drain qualities and therefore also can be manufactured with large wall thicknesses. An easily drainable pulp manufactured according to the invention facilitates unproblematically a uniform addition of the fibre suspension over the mould even in cases of ma¬ nufacturing objects with large wall thickness.

Waste paper, also called return paper, may be very com- posite, and contain fibre with a large variety of fibre lengths. However, it has actually turned out that the ave¬ rage fibre length is so large that the above mentioned ad¬ vantages especially as regards drainage and structure may be obtained when this paper material forms part-of the ma- nufacturing process.

The method according to the invention will also be a- vailable for the processing of so-called virgin material.

In the following the invention will be explained in de- tail with reference to^'the drawing in which

Fig. 1 diagrammatically shows a survey of process pro¬ ceedings summing up the proceeding phases which may take place during the proceeding of a process for the manufacture of for instance a pallet,

Fig. 2 examples of combinations of various phases of process proceedings.

Fig. 3 an inclined presentation of a first embodiment for a load-carrying element in the form of a pallet manufac¬ tured by means of the process according to the invention and showing one of the corner parts of the pallet from which the actual corner section is separated,

Fig. 4 schematic from the side another embodiment for a pallet.

Fig. 5 viewed from the side (Fig. 5b) and sectionally along the line V-V (Fig. 5a) a third embodiment for a pal¬ let.

Fig. 6 schematic cross section through a fourth embo- diment for a pallet,

Fig. 7 inclined presentation of a fifth embodiment for a pallet.

Fig. 8 schematic cross section through a sixth embo¬ diment for a pallet, Fig. 9 schematic pallet with a tension rope.

Fig. 10 schematic pallet with a wooden support rail.

Fog. 11 schematic pallet with a support rail of fibre raw material.

Fig. 12 schematic cross section through a pallet con- structed from elements of varying layer thickness.

Fig. 13 another embodiment for such pallet

Fig. 14 a third embodiment for a pallet containing a single element of varying layer thickness.

Fig. 15 a cross section through an embodiment for "the supporting legs of a pallet, and

Fig. 16 schematic a mould with deposited element of fibre raw material, both the mould surface and thus also the deposited element having varying layer thickness.

The diagram of proceedings shown in Figs. 1 and 2 com¬ prises a total of fourteen process phases. The production process will, according to the production process, be able 5 to be carried out by the use of all these phases, or only some of the phases, but it may also be a question of using some of the phases and then concurrently introducing the re¬ sulting product as a supplement to a coherent production process. 10

Example 1

All 14 process phases are used.

Example 2 15 Phase 1 up to and including phase 5 is carried out fol¬ lowed by phases 8 and 9 and finally phases 11 to 14 are car¬ ried out.

Example 3

2.0 One production line is used from phase 1 to phase 5 and another production line for phase 4 and possibly phases 5, 6 and 7. The wet fibre pulp created in the second production line is added to the product resulting from the first pro¬ duction line. The work is continued with usually several of

25; the subsequent phases.

In- this way a product is produced in which the fibre material manufactured in the second production line is main¬ ly bound by hydrogen fibre bindings whereas the first pro¬ duction line produces a fibre material suspended in air and

3.0^" to the binding of which glue is normally used. In this way it is possible to achieve a total degree of grinding, which is optimum, and simultaneously an optimum addition of glue. This means that this embodiment for the process allows com¬ prehensive consideration of the quality of the available raw

35 material.

In the following some embodiments for pallets will be described. The pallets are manufactured by means of the pro¬ cess according to the invention. As shown in proceeding diagram in Figs. 1 and 2 the pallets are manufactured from a suspension of a fluidized fibre raw material as the suspension is in an aqueous phase deposited by suction on a contour-shaping foundation. As de- 5 scribed above an easily drainable pulp is created from the fluidized fibre raw material. This pulp is deposited on the contour-shaping foundation in such quantity, and the nega¬ tive suction pressure used for depositing of the pulp on the foundation is controlled in such a way that a fibre raw ma-

10 terial layer is deposited on the foundation in such thick¬ ness that this in all essentials achieves the load capabi¬ lity desired for the element, i.e. in the present case the pallets.

The water content of the applied pulp may be up to 75

15 p.c. and this water content may then be removed by pressing and/or drying. As the load capacity of the end product, the pallets, is substantially to depend on the thickness of the fibre raw material layer deposited on the contour-shaping foundation, it is an essential prerequisite of a economical

20 production that the employed pulp is easily drainable. The invention comprises a procedure for the production of a pulp with this property.

The end product may then be used as it is or it may to¬ gether with similar products form part of another end pro-

25 duct, for instance in the form of a laminate construction. Experience has shown that it is possible in this way to manufacture pallets with a low net weight of 5 to 8 kg for a pallet size of 800 x 1200 mm and with a carrying ca¬ pacity of approx. 500 kg. The carrying capacity will depend

)30 on the quality of the employed fibre suspension and of the actual pallet's structural design of which some examples will be given in the following.

Fig. 3 shows schematically part of a pallet 10 designed with integrated legs and with strengthening ribs.

35 Example a) : measurements 800 x 1200 x 120, shaped three dimensionally in a single working process with "wet" weight 18 kg and weight after drying 6 kg. Example b) : measurements 800 x 1200 x 120, shaped three dimensionally with "wet" weight 18 kg, weight after heat pressing 12 kg and weight after drying 6 kg.

Fig. 4 shows schematically a pallet in the form of a laminate as the pallet has a bottom part 16, which substan¬ tially corresponds to part 10 in Fig. 3, and an upper, even cover plate 18, which is also designed in accordance with the procedure according to the invention.

Example c) : measurements 800 x 1200 x 123, part 16 of the pallet is shaped three dimensionally with "wet" weight 12 kg and weight after drying 4 kg. The cover plate 18 is manufactured on an even moulding surface: "wet" weight 6 kg, weight after heat pressing 4 kg, weight after drying 2 kg. The cover plate 18 is glued to the top side of bottom part 16.

The cover plate 18 may have holes for the reception of the legs from a pallet lying in a pile above.

Fig. 5 shows a pallet of the same type as shown in Fig. 4, however, with the difference that the upper part 20 of the pallet is shaped three dimensionally with strengthening ribs 22 which correspond with the shaped rib parts 24 in the bottom part 16. Measurements 600 x 800 x 140.

Example d) ; the under side 16 of the pallet is designed with "wet" weight 7.5 kg and weight after drying 2.5 kg, and the upper part of the pallet is designed with "wet" weight 4.5 kg and weight after drying 1.5 kg.

Fig. 6 shows a pallet, measurements 800 x 1200 x 150. Example e) : The pallet has a three dimensional centre, part 26 with "wet" weight 6 kg and weight after drying 2 kg as well as two cover plates 28 each shaped on an even mould¬ ing surface and with "wet" weight 6 kg, weight after heat pressing 4 kg and weight after drying 2 kg. Furthermore, the plate has nine three dimensional legs 30 with "wet" weight of each 0.3 kg and weight after drying 0.1 kg. Glue for, as- sembling of cover plates and legs 0.05 kg. Finished product weight: 6.95 kg.

Fig. 7 shows a pallet, measurements 800 x 1200 x 150. Example f) : The pallet is composed of two uniform, three dimensional plate elements 32 each having hollow pro¬ jections 34 projecting transversely to the plate part. The plate elements are mounted with their projections 34 point- ing towards and lying against each other.

- Each plate element 32's "wet" weight is 9 kg, weight after drying is 3 kg, each has nine 100 mm tall legs, "wet" weight of each 0.3 kg and weight after drying 0.1 kg. Glue for assembling 0.05 kg. Weight of the finished product: 6.95 kg.

Fig. 8 shows a pallet containing to trapeze profiled centre plates 36, whose ribs 38 cross, and two outside, even cover plates 40. Legs, which are not shown, are glued to one side of these plates. Both the trapeze shaped and the even plates 36 and 40, respectively, may be manufactured either by the piece by discontinuous moulding or continuously on continuous belt followed by respectively even or trapeze profiled male and female stamping rollers. This results in a high degree of flexibility for the production of the pallet as it is pos¬ sible to choose a larger og smaller number of plate layers which furthermore, owing to the pressing process, only re¬ sults in low drying costs.

Example g) : Two trapeze profiled fillers 36 with "wet" weight after moulding 4.5 kg, "wet" weight after pressing 3.0 kg and weight after drying 1.5 kg. Two even cover plates 40 with "wet" weight after moulding 4.5 kg, "wet" weight af¬ ter pressing 3.0 kg and weight after drying 1.5 kg. Nine legs (not shown) each with "wet" weight after moulding 0.3 kg and weight after drying 0.1 kg. Glue for assembling 0.05 kg.

In the stated embodiments the plate parts and legs of the pallets may be shaped together in a joint suction opera¬ tion or they may be shaped in separate suction operations. The legs may also, where desired, be manufactured from an¬ other material than fibre raw material but experience has shown that by using the procedure according to the invention it is possible to manufacture legs with sufficient load capacity and robustness and at the same time low weight, as stated in the examples.

Furthermore, the process according to the invention makes it possible without problems to add to the fibre pulp special reinforcement fibres where an especially high degree of strength is desired.

In the design of the elements it is also possible to consider the placing of additional, outside straining a- gents. Figs. 9 to 11 show some examples of load-carrying e- lements in the form of pallets as a common support rail 44 of for example wood is placed, as for instance shown in Fig. 10, under the legs of the pallet, or as shown in Fig. 11 the use of a special pallet frame 50 composed by legs 46 and a common support rail 48 and manufactured from the same mate¬ rial as the pallet's plate part 52.

As already mentioned the invention's characteristic de¬ positing of a fibre raw material layer of such thickness that this essentially produces the load capability desired for the element renders the opportunity of exploiting the layer thickness for an additional increase in the load ca¬ pability in the way that in the fibre raw material layer va¬ riations are made in the layer thickness, for instance as a coherent structural pattern. This means that by means of variations in the layer thickness, for instance rib-like formations are created in which the layer thickness of the elements is thicker than in the other areas of the element. If the forming and arrangement of such or similar formations are suitable, an increased rigidity may be achieved in the element whereby its load capacity is increased.

Figs. 12 to 15 show examples of such variations. As also mentioned above such variations are achieved by using a mould which at negative pressure is permeable by a gaseous active working medium which mould has a mould surface, «per- meable by the working medium, with a permeability varying in accordance with the desired variations in the layer thickness of the layer. Fig. 12 shows a cross section of a pallet constructed from two rib profiled interior elements 54 which on the out¬ side are covered by to even cover plates 56. Each interior element 54 has been manufactured in one single working pro- cess from a fibre raw material which is deposited on the mould surface of the suction mould with a wall thickness va¬ rying from rib top to rib bottom the largest wall thickness being at the rib top 54a and the smallest at the rib bottom 54b. The cross section profile of the rib formation is an- gular and the interior elements 54 are lying against each other at the top 54a.

Fig. 13 shows a cross section of the same type of pal¬ let with the difference, however, that the interior elements 54 are lying together at the bottom 54b so that the rib tops 54a carry the cover plates 56.

Fig. 14 shows a cross section of a pallet with only one single interior element 58, which with its tops 58a and bot¬ toms 58b lie against exterior, even cover plates 60. As men¬ tioned, also this interior element 58 is manufactured in one single working process with such variation in the layer thickness that this is largest at the rib top 58a and smal¬ lest at the rib bottom 58b.

Fig. 15 shows an example of a supporting leg 62 of a pallet. The leg 62 is pot shaped and manufactured in one single active working process through suction of a fibre raw material as described. Also this element has varying layer thickness and it is thicker at the bottom 62b.

Fig. 16 illustrates how such variations in the layer thickness may be achieved according to the invention. As schematically illustrated a mould 64 which at negative pres¬ sure is permeable by a gaseous active working medium is used for suction onto the mould surface of the mould of an easily drained pulp created from fluidized fibre raw material, which mould has a by the working medium permeable mould sur- face 66. In accordance with the creation of a rib profiled pallet element 68 in which the material layer is thick in the rib top 68a and thin in the rib bottom 68b a mould with a rib profiled mould surface 66 with varying permeability is used, the mould surface 66 being thick at the mould surface tops 64b and thin at the mould surface bottoms 64a. This results in the suction effect being weaker at the part of the mould surface created by the mould surface tops 64b than at the part created by the mould surface bottoms 64a. This will in its turn result in less depositing during suc¬ tion of the added fibre pulp of fibre material at the mould surface tops 64b which form the rib tops 68a whereby the layer thickness of these and consequently the rib formation created by them achieves a rather high degree of thickness and strength. This production technique may in principle be used in connection with many different variations in the layer thickness and the above-mentioned is only meant as a typical example of this.

The useability of the invention has been illustrated above by examples of pallets. It may with equal advantage be used also for the production of many other kinds of load carrying elements including wall elements for various pur- poses, building elements and insulating elements. Further¬ more, the above shows that the process according to the in¬ vention has opened up for suitable employment of many kinds of starting materials and additives. The invention also o- pens up the possibility of unproblematic incorporation of foils or reticular objects in the outside of the created ob¬ ject.

Claims

PATENT CLAIM

1. Method for the manufacture of load carrying ele¬ ments, including pallets, by depositing of a fluidized fibre raw material on a form giving foundation by means of suction of a pulp of fibre raw material on this foundation characte¬ rized by the application to the foundation of an easily drainable pulp made of the fluidized fibre raw material in such amounts, and that the suction is carried out and con- trolled in such a way that on the foundation by suction is deposited a fibre raw material layer with such wall thick¬ ness that this in all essentials procures the desired load capacity of the object.

2. Method in accordance with claim 1 characterized by, distributed over the fibre raw material layer, one or more variations in the wall thickness are procured in the said layer through the suction effect being correspondingly va¬ ried locally in a common suction process for the fibre pulp quantity necessary for the manufacture of the whole ele- ent.

3. Procedure in accordance with claim 2 characterized in that the depositing of the fibre raw material with a thickness corresponding to the desired load capacity is pro¬ cured as a coherent structured pattern with a larger wall thickness in comparison with the other areas.

4. Method in accordance with any of the claims 1-3, characterized by the fact that for suction of an easily drainable pulp of the fibre raw material in the desired wall thickness, a mould is used which at negative pressure is permeable by a gaseous active working medium, and which has a by a working medium permeable mould surface the permeabi¬ lity of which is adjusted to the thickness of the fibre raw material layer to be deposited by suction of the pulp on this surface.

5. Method in accordance with claim 4, for the carrying out of procedure in accordance with claims 2 or 3, characte¬ rized by the fact that a mould is used whose mould surface has a permeability which varies in accordance with the wall thickness of the local variation(s) , respectively, or the desired coherent structured pattern of the by the suction on the form surface deposited easily drained fibre pulp layer.

6. Method in accordance with claim 4, characterized by the fact that for suction of an easily drainable pulp of the fibre raw material in the desired wall thickness, a mould is used which at negative pressure is permeable by a gaseous active working medium, and which at least for the contour giving part of the mould is manufactured by a particle com¬ posite material whose particles are fixed together for the creation of a contour stable mould surface and at the same time restricting open passages for the working medium ex- tending through the composite material to the mould outside surface and that the thickness in at least of the composite material layer forming the mould surface is adjusted to the thickness of the fibre raw material layer which is to be de¬ posited through suction of the pulp on this surface.

7. Method in accordance with claim 5, characterized by the fact that a mould is used by means of which the layer of composite material forming the mould surface is manufac¬ tured with a thickness varying in accordance with the wall thickness of the local variation(s) , respectively, or the desired coherent structured pattern of the through suction on the mould surface deposited, easily drainable fibre pulp layer.

8. Method in accordance with any of the claims 4 to 7, characterized by the fact that a mould is used whose per- meable mould surface is composed of particles of different particle size, the particle size being small in the mould forming surface part and bigger in a lower supporting layer for this part.

9. Method in accordance with claim 8, characterized by the fact that a mould is used whose particles are clad with a layer formed by a binding agent.

10. Method in accordance with claim 9, characterized by the fact that a mould is used whose binding agent is thermo-setting.

11. Method in accordance with claim 9 characterized by the fact that a mould is used whose binding agent -consists of adhesion-improving agent.

12. Method in accordance with claim 8 characterized by the fact that a mould is used by which the particles have a rounded form.

13. Method in accordance with claim 8 characterized by the fact that a mould is used by which the particles are in a wedging compound with each other.

14. Method in accordance with claims 5 or 6 charac¬ terized by the fact that a mould is used having below a ba- sis part in which the composite particles are connected with each other through a real fusion compound while the par¬ ticles of the rest of the mould are linked to each other through a hardening conglutination compound.

Ϊ5. Method in accordance with any of the claims 4-14 characterized by the fact that a mould is used whose mould surface is designed with such a strength that the mould is applicable for finishing pressing of an object.

16. Method in accordance with any of the previous claims characterized by the fact that as fibre raw material at least partly a long fibre starting material is used which is processed into a pulp partly by the application of a shake-out in a pulper, partly by a preceding, separate, con¬ trolled dry grinding, whereby the starting material is se¬ parated into dosage amounts and divided into fibre whereaf- ter the object is manufactured from the pulp thus created.

17. Method in accordance with claim 16 characterized by the fact that the preceding separate dry grinding con¬ trolled manufacturing process is carried out as a multiple- stage process.

18. Method in accordance with claim 16 or 17 characte¬ rized by the fact that the shake-out is carried out as con¬ trolled manufacturing process dependent on the separate dry grinding.

19. Method in accordance with any of the claims 16-18 characterized by the fact that a long fibre starting mate¬ rial having been subjected to a separate, controlled dry grinding is added in dosage amounts to a pulp already cre¬ ated in the pulper and subjected to a common time-limited shake-out with this.

20. Method in accordance with any of the claims 16-19 characterized by the fact that an addition of auxiliary material is undertaken in connection with the preceding se¬ parate dry grinding.

21. Method in accordance with any of the claims 16-20 characterized by the fact that an addition of auxiliary material during further application of the created pulp.

22. Method in accordance with any of the claims 16-21 characterized by the fact that a pulp is manufactured as stated in claim 16, and that this pulp in dosage amounts is added another already manufactured pulp whereafter the ob¬ ject is manufactured from the mixture thus created.

23. Load carrying element consisting of a fluidized fibre raw material characterized by the fact that the ele¬ ment is manufactured by means of the method in accordance with one or more of the claims 1 to 22.

24. Pallet consisting of a plate part and connected supporting legs characterized by the fact that the pallet is manufactured by means of the method according to one or more of the claims 1 to 22.