EP0006820B1 - Method of moulding bodies from wood particles, apparatus therefor and the moulded bodies - Google Patents

Description

The present invention relates to a method of manufacturing pieces of agglomerated wood particles, comprising a bottom and at least one wall or wing extending at a certain angle relative to said bottom, as well as to a device for implementing it. of this process and the parts made by this process.

The invention is particularly applicable to the manufacture of parts having a bottom and at least one wall extending relative to this bottom at a relatively large angle, for example close to 90 °. Thus, the invention allows for example the manufacture of crates, boxes, crates, or many other parts made of agglomerated wood particles.

Known wood particle materials are currently produced by various techniques; some of these techniques use wood chips or sawdust and require a large amount of resin for polymerization, without leading to satisfactory performance.

Other methods, on the contrary, use elongated particles or elongated wood fibers such as those produced and treated for example in French patent FR-A-1,573,928, addition 95,386, and French patent application FR-A- 2,332,858, fibers which are characterized by a great length with respect to the section and also of uneven sections, either on the same fiber, or from one fiber to another.

These particles can be agglomerated with a minimum quantity of resin and lead to objects of fairly complicated shape and having exceptional mechanical qualities.

In general, the compression of these particles is carried out in a mold and provision has already been made, when it is desired to produce a hollow part, for example in the form of a box or crate, to have in the mold a sheet of abundant particles or having possibly undergone a first precompression, as a result of which different pistons come, in different directions, to compress the sheet of fibers to give it its final shape, as a result of which, the sheet of particles or fibers found polymerized.

If such a method is satisfactory, as for the qualities of the article obtained, it however requires a relatively heavy and complex installation, which translates into the cost price of the parts obtained.

Also known, for example from French patents FR-A-1 090 834 and 1 457 930, are processes in which a sheet of binder-coated particle is precompressed flat and then is definitively compressed in its final form in a mold in two parts by bringing together the two parts of the mold in a direction substantially perpendicular to said bottom.

However, these methods do not make it possible to obtain parts in which the walls or wings extend relative to the bottom with an angle close to the perpendicular.

The invention therefore proposes to provide a method for manufacturing pieces of agglomerated particles or wood fibers having a bottom and at least one wing or wall extending at a significant angle relative to said bottom, and this in a simple manner, practical and by using equipment, and in particular press means, which are not very important, while making it possible to obtain particularly rapid industrial production rates.

To this end, the invention provides a method of manufacturing pieces of agglomerated wood particles comprising a bottom and at least one wall or wing extending at a certain angle relative to said bottom and in particular with an angle close to the perpendicular, process in which a sheet of particles coated with binder is precompressed flat and then is definitively compressed in its final shape in a two-part mold by bringing the two parts of the mold together in a direction substantially perpendicular to said bottom, characterized in that the precompression is applied at least to the part or parts of the ply to form said wall or wing with a higher degree of compression on this or these parts than that possibly exerted on the part to form the bottom, so as to obtain a pre-compressed ply whose ratio of the initial thickness to the thickness of the pre-compressed web in the parts to form the wings is greater than that parts to form the bottom.

By relatively large angle between the bottom and the wall or the wing means an angle which can go up to 86 °, this angle being preferably close to 80 to 83 ° but can also be much less.

Preferably, when the compression ratio between the initial expanding ply and the finished part is 25 to 40, the pre-compression ratio between the thickness of the initial expanding ply and the thickness of the precompressed wall or wing is between 10 and 18.

Thus, in a particular embodiment of the invention, intended for manufacturing parts having substantially a U-section with a bottom of two wings forming an angle fairly close to the perpendicular with the bottom, a first precompression of the parts of the ply having to form the two wings, bringing for example the thickness of these parts to a value 2 to 3 times greater than that of the wings in the finished state, and preferably also a precompression of the part forming the bottom to a thickness between 10 and 15 of the final thickness of the bottom. The tablecloth having the precompression is then loaded into a mold having a female part which is substantially U-shaped and a corresponding male part capable of penetrating the female part.

During penetration of the male mold part, the parts to form the wings fold correspondingly and are then compressed between the side walls of the mold parts while the bottom is compressed between the corresponding surfaces of the mold parts. .

Surprisingly, it has been found that when the wings form an angle fairly close to 80 °, for example 83 °, the press which actuates the mold should only develop significant molding power during the very last phase, as a 'example a pressure of 100 to 120 kg / cm ² on the bottom, and once the mold parts are brought closer to the necessary distance corresponding to this high pressure, the pressure can be released to a much lower value, for example of the order of 70 to 80 kg / cm ² , while the part remains compressed in the initial state corresponding to the strong compression, this probably due to the effects of wedges acting between the compressed part and the mold parts and the weak reaction of the overcompressed material.

Preferably, the polymerization takes place in the mold and extremely short durations, for example of the order of 10 to 20 seconds have been reached.

After the polymerization, the mold parts are moved aside, the part is ejected.

Ejection, in the case of parts in the form of a profile, for example in a U shape, can be carried out at the same time as the introduction of a new precompressed sheet.

In addition, the invention has the advantage of requiring only a very short stroke under high pressure, if care has been taken to sufficiently compress the bottom during the step of precompressing the wings or the side walls.

In the case where it is sought to produce a product not having a general U shape, but a box shape with four or more walls, it is advantageous to provide a sheet with cutouts at the different corners of the bottom between two parts d 'adjacent wings.

When the ply, after precompression, is inserted into the compression mold, the wings come to fold down and the corresponding edges of two adjacent wings come to be arranged one near the other. The continuation of the descent of the movable part of the mold causes, by displacement of material, the connection between the two wings, a connection which remains definitively maintained after polymerization.

It is thus possible to manufacture, for example, boxes having a bottom and several sides, for example four, the sides extending almost perpendicularly to the bottom and this in a single molding operation with a simple two-part mold.

The invention also makes it possible to mold in said walls or wings, and also if desired in the bottom, ribs or grooves or other deformations.

The invention also relates to a device for the implementation of this method comprising means for producing a sheet of wood particles coated with binder, a precompression station for this sheet and means for definitive compression of this sheet in a mold, characterized in that said precompression station includes means for applying precompression at least to the part or parts of the ply which must form said wall or wing with a greater degree on this or these parts than that possibly exerted on the part to form the bottom.

According to a preferred embodiment of the invention, the female part of the mold has, facing the wing to be compressed, a wall extending, relative to the bottom, at said relatively large angle, this part being surmounted by a second part preferably vertical or very close to vertical, and having a rough surface, for example by means of striations.

At the start of the compression phase, this rough part tends to prevent the downward sliding of the material forming the wing, under the effect of the penetration of the male mold part favoring the compression of the wing, which at the as the male part descends, decreases in thickness and also in height until it leaves this rough part and is finally compressed against the female mold wall part extending with said relatively large angle.

Preferably, the device comprises means for automatic transfer of the sheet to the precompression station and from the precompression station to the mold, as well as means for automatic evacuation from the mold.

In a particular embodiment, the device can advantageously comprise, before the precompression station, a station capable of slightly compressing the plentiful sheet of particles coated with binder in order to give a certain cohesion to this sheet and allow subsequent easier transport. This can be achieved for example by scrolling the teeming web between two endless slightly converging bands. At the exit from the ply, it is advantageous to be able to provide cutting or cutting means making it possible to form sections of ply which are then sent to the precompression station.

Advantageously, the precompression station includes a table on which the web section is arranged and a plate of suitable shape allowing compression of one or more lateral parts in front of the side walls or wings while the central part is little or not compressed.

In a preferred embodiment, the precompression station supplies a battery of compression stations by means of corresponding transfer means. Thus by way of example or may provide two batteries of three compression stations each comprising a mold in two parts, transfer means being capable of alternately bringing the sections to the different molds.

Advantageously, the transfer means may include parts capable of being folded laterally so as to incline precompressed parts of the section relative to the bottom of the section for easier introduction into the mold. In the case where parts with a U-shaped section are produced which have no variations in length, it is easy to provide molds having two open ends and allow the section to penetrate, with its wings folded by one of the ends, in the mold while the section which has been compressed in the mold is simultaneously evacuated by the other side.

The invention also relates to the parts obtained by the method according to the invention.

• -la figure 1 représente une vue de dessus générale d'un dispositif selon l'invention,
• -la figure 2 représente une vue de côté de ce dispositif,
• - la figure 3 représente une vue en boute d'un ensemble de presses de ce dispositif,
• - la figure 4 représente une vue en élévation d'un dispositif de précompression selon l'invention,
• -la figure 5 représente une vue en coupe d'un dispositif d'introduction dans le moule,
• -la figure 6 représente schématiquement, vues en coupe transversale, différentes étapes du procédé selon l'invention,
• - la figure 7 représente schématiquement une pièce en U terminée.

Other advantages and characteristics of the invention will appear on reading the following description, given by way of nonlimiting example, and referring to the appended drawing in which:

• FIG. 1 represents a general top view of a device according to the invention,
• FIG. 2 represents a side view of this device,
• FIG. 3 represents a bottle view of a set of presses of this device,
• FIG. 4 represents an elevation view of a precompression device according to the invention,
• FIG. 5 represents a sectional view of a device for introducing into the mold,
• FIG. 6 schematically represents, seen in cross section, different stages of the method according to the invention,
• - Figure 7 schematically shows a finished U-shaped part.

The device according to the invention shown comprises means for manufacturing, transferring and impregnating particles constituted by wood fibers defibrated in the direction of the fibers, according to document FR-A-2 336 858.

The wood fibers which constitute the particles described in the present example, are fibers corresponding to the aforementioned French patent and having lengths of the order of 70 mm on average with larger or smaller individual lengths and sections of the order of 0.6 mm ^2. These fibers are obtained by defibering wooden logs lengthwise.

The fibers after having been impregnated with a small percentage of binder, for example 8% of binder, in accordance with the aforementioned French patent, first arrive in the form of a continuous abundant ply 1 carried by a conveyor belt 2 at a station calendering comprising an upper endless belt 3 gradually approaching the inner carpet to gradually cause slight compression of the fiber web.

The sheet of fibers comes out in state 4 and there is taken care of by a cutting device. The latter first of all carries a retractable stop 5 capable of temporarily immobilizing the sheet of fibers while the conveyors are slipping, and a vertically movable knife 6 working with a counter knife not shown, and capable of cutting the sheet into sections of ply 7. These sections are then taken care of in an accelerated manner so as to be brought to a precompression device 8.

As a variant, it is advantageously possible to cut the ply of fibers which leaves in state 4 a saw, for example a circular saw carried by a carriage moving with the ply and at the same speed as the latter, during the operation sawing, then returning to the initial position after the sawing operation.

The precompression device 8 has a lower table 9 on which rests an individual section 7 and a plate 10 capable of being brought closer to the table 9 by two jacks 11 which can provide a compression force of 120 to 200 kg / cm ² on the section of ply 7.

The thickness of the section of ply 7 is for example of the order of 30 to 50 mm while the initial thickness of the ply, before passing between the strips 3 is of the order of 100 to 120 mm. After precompression, the precompressed wings have, after elastic return, a thickness of the order of 6 to 7 mm for a desired thickness of final product of the order of 3 mm.

When the section has been precompressed at this precompression station, it is transferred by a suitable transfer means 12 to an assembly composed of two parallel groups of three presses. This group of presses is supplied by suitable transfer means 13 moving laterally capable of presenting the sections 14 which have been pre-compressed in front of the different individual presses.

The means 13 can be strips moving laterally relative to the outlet of the precompression station and taking charge of the sections 14 delivered by the means 12.

We see in Figure 1 the different sections 14 in this position. Above the transfer means 13, can move support means 15, capable of individually pushing a section 14 in a direction perpendicular to the direction of movement of the conveyor belts 13.

These means 15 thus make it possible to push back the sections towards supply means 16 for the various individual presses where compression and polymerization take place. Due to the existence of six compression and polymerization stations 17, the total duration of feeding, compression and polymerization can be approximately six times greater than the duration of precompression at station 8.

The various compression stations 17 are supplied automatically by the means 16 which, as can be seen in FIG. 6, comprise a plate 18 with two edges 19 which can be folded down by jacks 20. These plates 18, of small thickness , roll on rollers and can introduce the section 14, the wings of which are folded back ₃ , into the female mold 21, in the manner of tart shovels to withdraw back when the section is in the mold. The movement can be transmitted by a mobile retractable arm 22.

When a precompressed section 14, with folded wings, has been introduced into the female mold part 21 and the plate 18 has come out of the mold, the upper male mold part 23 is brought closer to the female part and, towards the end of the race we develop a compression power of 100 to 120 kg / cm ² . When the end of travel is reached, the pressure is lowered to approximately 70 to 80 kg / cm ² and this pressure is maintained while the polymerization is carried out simultaneously by heating the mold. The total duration can be less than 20 seconds.

At the end of the compression and polymerization operation, the male mold part 23 is again moved upwards and the part formed by the mold end opposite the end by which the folded section is ejected entered. The shaped part designated by 24 is thus taken care of first by longitudinal distance means such as strips 25 and then by lateral transfer means 26 to be brought to a central evacuation strip 27.

The different individual operating operations at the material level will now be described in more detail with particular reference to FIG. 6.

In step A in Figure 6 we see the section of ply 7 cut and having undergone a very slight precompression to give it strength. The section 7 is then brought to the table 9 where it is compressed by bringing the plate 10 closer together. It can be seen that the impression made in the plate 10 has a hollow part of greater depth, the bottom 25 of which corresponds to the part which is to form the bottom in the section of tablecloth. After a setback, the side plate parts 26 are less deep and therefore make it possible to give the wings of the section 14 a significantly greater degree of compression than that of the central part of this section.

After the wings of the section 14 have been folded back, it is introduced, as seen in C, into the female mold part 21. This female mold part has a generally U-shaped section with a flat base and two edges the faces 27 of which are preferably inclined by 83 ° relative to the horizontal.

The height of the faces 27 corresponds substantially to the height of the finished product. Beyond the upper end of the wall part 27, extends a female wall part 28 vertical or very close to the vertical so as to facilitate the passage of the male mold element 23.

This part 28 preferably has a height greater than the height of the part 27.

Advantageously, this part 28 has, as shown in FIG. 6C ', a rough surface 28', for example by means of a scribing, a knurling or in any other way.

Before the descent of the male mold part 23, the folded wings 26 extend as far as the upper part of the female mold 28, and when the male mold part 23 is lowered, the roughness of the surface 28 slows the descent towards the bottom of the upper part of the wing 26, so that, as the mold part 23 descends downward, it progressively compresses the wings 26, decreasing both their thickness and their length.

The male mold part 23 has a lower surface 29 intended to mold the bottom and lateral parts 30 having substantially the same inclination as the parts 27. A sudden detachment leads to a flat projection 31 whose role is to push down l 'protruding end of the wings and seal the mold. We see in position D the form finally taken.

When the mold is in its completely closed position shown in D, experience shows that it is possible to maintain only a relatively low pressure in order to maintain the state of pressure which was reached under high pressure during the downward movement, this is probably due to wedge effects between the mold walls and the material.

Referring to Figure 7, we see a U-shaped part molded according to the invention and having, in its wings and at the bottom, ribs. The ribs at the level of the wings are preferably produced in vertical planes, those of the bottom possibly being in any direction.

When producing ribs such as those shown in FIG. 7 on the side walls of the molded part, it is understood that it suffices to give the male and female parts of the mold an appropriate shape to obtain these ribs by simply bringing the male and female mold parts together.

If on the contrary, it is desired to make reliefs or ribs in the wings extending parallel to the bottom 24, it is then necessary to provide in the male and female mold parts, corresponding slides. Thus, by way of example, it is possible to provide, in the male part, normally erased slides capable of moving horizontally. At the start, the ends of these slides are flush with the side wall of the male element, the continuity of which they provide locally. As the male mold part 23 descends, these slides, by any mechanism, are pushed outward at the time of the end of travel of the male element, and will push the material already seriously compressed that 'they meet towards the corresponding face of the female mold part.

This corresponding face also has complementary slides maintained for example flush with the surface 27 by springs and pushed horizontally away from the walls 27 by the slides of the male mold part.

To extract the molded object, it is then necessary, prior to the ascent of the male mold part 23, to bring the sliders of this male part back to its interior.

Thus, the invention makes it possible, surprisingly, to economically manufacture, using compression in one direction only, parts made of particles of great length, having in themselves excellent mechanical qualities but which are difficult to handle.

Claims (15)

1. A method of producing bodies made of agglomerated wood particles and comprising a base and at least one wall or wing extending at a certain angle relative to the said base, and in particular at an angle close to the perpendicular, wherein a sheet (7) of particles coated with a binding agent is precompressed flat, and is then compressed into its final shape in a mould made in two parts (21, 23) by bringing together the two parts of the mould in a direction substantially perpendicular to the said base, characterised by the fact that the precompression is applied at least to the part or parts of the sheet which is or are to form the said wall or wing, with a greater degree of compression on this part or these parts than that which may be exerted on the part which is to form the base, so as to obtain a precompressed sheet where the ratio of the initial thickness to the thickness of the precompressed sheet is higher in the parts which are to form the wings than in the parts which are to form the base.

2. A method according to Claim 1, characterised by the fact that after having brought the two parts of the mould together with a certain amount of compression force, this compression force is partially relieved.

3. A method according to either of Claims 1 and 2, characterised by the fact that the polymerisation is effected in the mould in the compression position.

4. A method according to any of Claims 1 to 3, characterised by the fact that the internal angle between the base and the said wall lies between 94° and 100°.

5. A method according to any one of Claims 1 to 5, characterised by the fact that for a thickness ratio between the initial sheet and the final body of 25 to 40°, the precompression of the parts which are to form the wings is carried out to give a thickness ratio between the initial sheet and these parts of between 10 and 18.

6. A method according to any of Claims 1 to 5, characterised by the fact that the sheet is fed continuously, that the sheet is subjected to a first compression to give it strength, that the sheet is cut up into sections of sheet, that the said sections of sheet are supplied to a plurality of moulds, that before causing them to penetrate into the moulds the parts which are to form the rims or the walls are folded, and that moulding and polymerisation are then carried out.

7. A method according to any of Claims 1 to 6, characterised by the fact that the part or parts of the sheet which are to form the said wall or wing is or are wider than the height of the finished body.

8. Apparatus for carrying out the method according to any of Claims 1 to 7, comprising means for producing a sheet from particles of wood coated with a binding agent, a precompression station (8) for this sheet, and means (17) for the final compression of this sheet in a mould, characterised by the fact that the said precompression station comprises means (9, 10) for applying the precompression at least to the part or parts of the sheet which are to form the said wall or wing at a higher level on this part or these parts than that which may be exerted on the part which is to form the base.

9. Apparatus according to Claim 8, characterised by the fact that it comprises means (12, 13) for transferring the sheet automatically to the precompression station and from the precompression station to the mould, as well as means (27) for automatic evacuation from the mould.

10. Apparatus according to either of Claims 8 and 9, characterised by the fact that it comprises means which are able to effect a first compression of the sheet before the precompression, the said means comprising two endless belts (2, 3) which converge progressively towards each other.

11. Apparatus according to Claim 10, characterised by the fact that downstream of the said two belts it comprises a sectioning device (6) enabling sections of sheet to be obtained.

12. Apparatus according to any of Claims 8 to 11, characterised by the fact that at the exit from the precompression station it comprises laterally extending transfer means (13) for aligning the sections with a plurality of presses (17).

13. Apparatus according to any of Claims 8 to 12, characterised by the fact that, to form reliefs extending substantially parallel with the base of the final body, the mould has complementary internal sliding devices mounted one on one part of the mould and the other on the other part of the mould, one of the sliding devices being able to emerge out of its part from an initial position flush with the surface of the part, and the other sliding device being able to be pushed back inside its part under the effect of the thrust of the first sliding device.

14. Apparatus according to any of Claims 8 to 13, characterised by the fact that the mould comprises a female part (21) whereof the walls (27, 28) which correspond to the wings of the precompressed sheet are higher than the final wings.

15. Apparatus according to Claim 14, characterised by the fact that the upper portion of the said wall of the female part has a roughened surface (28').

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