[0001] This invention relates to flexible panels or matting consisting of a plurality of
entangled thermoplastic polymer filaments partly bonded together at their points of
contact.
[0002] This type of article has been known for some time and has found application in numerous
technical sectors, such as soil drainage, protection against erosion, concrete reinforcement,
the support and reinforcement of polymer or thermosetting foams, and the reinforcement
of resins, mixes and conglomerates.
[0003] Such matting can be produced by two different processes, namely a so- called wet
process and a so-called dry process, which give rise to products of different geometry
and different mechanical characteristics.
[0004] These known processes are described in Italian Patents 883371, 1061875, 1257665 and
US 42 1269, to which reference should be made for further information.
[0005] With the wet process, non-stretched monofilament matting is obtained of virtually
parallelepiped shape with flat sides, whereas with the so-called dry process the matting
can present at least one profiled surface, for example with protuberances.
[0006] The surface profiling is obtained by dropping the filaments onto a surface provided
with projections, for example a rotating cylindrical surface, or a translating web
presenting a plurality of geometrical projections.
[0007] It has been observed that by using the dry process, matting is obtained with mechanical
characteristics substantially better than those of matting obtained by the wet process,
and moreover the presence of said protuberances in the final product is useful in
all those applications in which the purpose of the matting is substantially to retain
a material, such as soil or polymer foam, which lies above it or is partially embedded
in it.
[0008] For these reasons, in the environmental field, matting obtained by the dry process
is currently used presenting at least one profiled surface, it being generally positioned
on inclined ground and then covered with soil.
[0009] To improve soil consolidation it is current practice to cover this with a grass layer,
so that the grass roots act as a further soil retention element.
[0010] Such matting has however shown various drawbacks in this application.
[0011] A first drawback lies in the fact that the known products have a poor capacity for
copenetration by cultivatable soil, because of the fact that said projections are
partially impermeable to soil passage.
[0012] Hence after installation, the product presents practically empty spaces below each
protuberance. In this manner air cells are created within said spaces which are deleterious
to the development of the root system of the grass layer, the roots of which become
dry and die on contact with the air.
[0013] In addition, depending on the inclination of the slope on which the matting is used,
it can happen that one side of said projections lies in a horizontal position, or
even inclined downwards, hence compromising the soil retention capacity of the product,
which is its basic requirement.
[0014] An object of the present patent is to overcome the said drawbacks within the framework
of a reliable low-cost solution.
[0015] This and further objects are attained according to the invention by a flexible matting
of low density and high voids index, the surface of which comprises a plurality of
close-apart protuberances, said protuberances being hollow and provided with at least
one open side in such a manner as to define a pocket or chamber to receive the material,
such as soil, with which the matting is covered when installed.
[0016] Said matting is obtained by a dry process of the aforesaid type, using as the filament
reception surface a translating surface provided with projections.
[0017] According to the invention, said projections present at least one portion inclined
to the direction of movement of the surface at the moment of impact by the filament.
[0018] Said inclined portion is preferably flat, its inclination to the direction of movement
being defined by the angle α subtended between the surface and the direction perpendicular
to the direction of movement.
[0019] In the case of a non-flat portion the angle α is that subtended between the tangential
plane at the point considered and said perpendicular direction.
[0020] The translating surface carrying the projections is preferably a rotating cylindrical
surface.
[0021] In this case an angle β is defined subtended in the anticlockwise direction between
the diametrical horizontal plane of the cylinder and the diametrical plane passing
through the point of impact of the filaments.
[0022] In the case of a horizontal flat translating surface the angle β is obviously zero.
[0023] The filament falling velocity is indicated by V
C and the translation velocity of the surface and relative projections is indicated
by V
P.
[0024] These velocities are always considered as vectors.
[0025] For the required result to be achieved, the vectorial difference between V
C and Vp must be represented by a resultant vector
which is directed in such a manner as not to intersect at least an inclined portion
of the translating surface.
[0026] In other words the vector V
R which expresses the relative velocity of the vertically falling filament to said
inclined portion must be directed against said inclined portion with a positive angle
of incidence close to zero or with a negative angle of incidence.
[0027] In this respect, if the angle of incidence is zero, the filaments slide parallel
to the inclined portion and lie without entanglement, this also happening for very
small angles of incidence, i.e. close to zero.
[0028] The constructional and operational characteristics of the invention will be apparent
from the ensuing description of a preferred embodiment thereof given by way of non-limiting
example and illustrated in the accompanying drawings.
[0029] The described embodiment relates to a cylindrical translating surface provided with
square-based pyramidal projections the walls of which constitute inclined portions
of the translating surface, but is also suitable for a flat translating surface for
which the angle β is considered equal to zero.
[0030] Figure 1 is a perspective view of a first embodiment of the product of the invention.
[0031] Figure 2 is a schematic perspective view of the production plant of the invention.
[0032] Figure 3 shows a first schematic configuration of the plant of the invention.
[0033] Figure 4 shows a second possible configuration of the production plant of the invention.
[0034] Figure 5 is an enlarged view of diagrams showing the velocities of the filaments
and of the translating surface of Figure 3 and Figure 4 for various values of the
angle β.
[0035] Figure 6 shows a further possible configuration of the plant of the invention.
[0036] Figures 1 to 4 show the matting 1, the surface of which consists of a plurality of
protuberances 2, aligned along several parallel rows and inclined at an angle of between
30° and 45° to the sides of the matting. Specifically, said protuberances 2 arc hollow
and present an open side defining a chamber 3 for receiving the material with which
the matting is generally covered when installed.
[0037] The matting 1 is produced by the plant 4 shown in Figure 2, comprising a die 5 provided
with a plurality of holes aligned along several parallel rows, through which the filaments
of thermoplastic material are extruded. The thermoplastic material is fed to the die
via a usual extruder, not shown, at a temperature of between 160°C and 270°C.
[0038] Said extruder is fed in its turn by a usual hopper, not shown as it is of known type.
[0039] The theoretical filament extrusion velocity is between 10 and 15 m/min, and preferably
about 12 m/min.
[0040] However the actual falling velocity V
C of the filament is from 1 to 1.5 times greater because of the stretching of the filament
and the consequent reduction in its cross-section.
[0041] Below the die 5 there is provided a rotating cylinder 8 having its axis parallel
to the rows of holes in the die, and presenting on its outer surface a plurality of
square-based right pyramids 9 of height preferably between 20 and 50 mm.
[0042] As can be seen from the figure, the pyramids are disposed in mutually aligned rows
in the manner of a helix of predetermined inclination, preferably of between 30° and
45° to the horizontal axis of the cylinder 8.
[0043] To obtain the matting 1 with at least one open side for passage of the material,
the vertical falling velocity V
C of the filaments must be regulated, relative to the translation velocity V
P of the inclined wall of the pyramids, such that the vectorial difference between
the two is a vector V
R having a direction and sense such as not to encounter the wall.
[0044] Figure 5 shows the velocity diagrams for the two cases of β = 90° and β = 120° in
a roller of diameter 200 mm provided with pyramidal cusps with a square base of side
15 mm and having a height of 25 mm, with an angle at their vertex of 40° and an angle
α of 20°.
[0045] The actual falling velocity V
C of the filament has been assumed to be 20 m/min, and the modulus of the velocity
V
P to be 4 m/min.
[0046] From the graphical calculation it can be seen that with β = 120°, the resultant V
R is substantially parallel to the front face of the pyramid in the direction of motion,
which means that said face does not encounter the falling filaments, and is hence
substantially open.
[0047] If the filament falling velocity V
C is decreased, or the modulus of the pyramid wall translation velocity V
P is increased, the resultant V
R becomes directed towards the wall, which is hence closed.
[0048] With P = 90°, the graphic calculation shows that V
R cuts both the front wall and the rear wall of the pyramid, which are hence closed.
[0049] In order for one of these walls, and in this case the rear wall, to be open, V
C must be decreased or V
P increased; the graph shows with dashed lines that vector V'
R starting from which the wall begins to remain open. For this, the value of Vp is
6 m/min.
[0050] Figure 4 shows the particular case in which β = 0°. In this case, as V
C is perpendicular to V
P, the relationship between the modules which has to be respected is the following:
i.e.
[0051] Figure 6 shows the limiting case in which β = 180°. In this case, as in the case
in which β = 0°, the front and rear walls in the direction of movement are always
empty.
[0052] Those inclined portions of the projections from which
is distanced are not struck by the filaments, which hence deposit in a non-interlaced
condition, and leave said portions substantially permeable to the passage of the material.
[0053] In contrast, on those portions of the projections opposite the preceding, a thickened
structure of interlaced filaments is created which is impermeable to passage of the
material. In this manner a chamber open on one side is defined, in the manner of a
pocket, for receiving the material with which the matting 1 is covered.
[0054] It should be noted that the matting 1 of the invention can also be obtained by replacing
the cylinder 8 with a translating surface on which there are disposed a plurality
of pyramids 9, or projections of any type provided they are suitable for the purpose.
[0055] The velocity diagram appropriate for this configuration is that of Figure 4 referred
to β = 0°.
[0056] In this latter case said translating surface is preferably inclined to the horizontal
plane by an angle of between 0° and α°, to facilitate the phenomenon.
1. Matting of interlaced and entangled filaments of low-density thermoplastic material,
the matting having a high voids index and comprising a plurality of hollow protuberances
arranged in several parallel rows, characterised in that at least a part of said protuberances presents at least one open portion, defined
by non- interlaced filaments, such as to create a chamber for receiving the material
with which the matting is intended to be covered.
2. Matting as claimed in claim 1, characterised in that said protuberances are without their lower base.
3. Matting as claimed in claim 1, characterised in that said hollow protuberances are positioned alongside each other in adjacent parallel
rows.
4. A device for manufacturing entangled monofilament matting provided with protuberances
having at least one portion not occupied by the filaments according to claim 1, comprising
a die of vertical axis for extruding parallel alignments of said filaments, a rotating
cylinder positioned below said die and having its axis horizontal and parallel to
said alignments, and a series of projections regularly distributed on said cylinder
having at least one portion inclined to the direction of movement of the surface at
the moment of impact by the filament, characterised in that the distance between the cylinder axis and the mean vertical plane in which the filaments
fall is chosen such that the vector VR, resulting from the difference between the vector VC, namely the velocity of the vertical fall of the filament, and the vector VP, namely the velocity of translation of the inclined portion, cuts the inclined portion
at an angle equal to zero or at a negative angle such that said inclined portion does
not encounter the falling filaments.
5. A device as claimed in claim 4, characterised in that said projections are arranged in rows mutually aligned in the manner of a helix.
6. A device as claimed in claim 5, characterised in that said helix along which the projections are arranged has an inclination of between
30° and 45° to the cylinder axis.
7. A device as claimed in any one of claims 4 to 6, characterised in that said projections are right pyramids.
8. A device as claimed in claim 7, characterised in that the base of said pyramids is square.
9. A device as claimed in claim 8, characterised in that the bases of said pyramids have at least one side in common with the adjacent pyramids.
10. A process for producing matting of interlaced and entangled filaments of low-density
thermoplastic material according to claim 1, comprising the steps of extruding a thermoplastic
material through the die and collecting the vertically falling extruded filaments
on a translating surface provided with a plurality of profiled projections having
at least one portion inclined to the direction of movement of the surface at the moment
of impact by the filament, characterised in that the vector VR which expresses the relative velocity of the vertically falling filament,
resulting from the difference between the vector VC, namely the velocity of the vertical fall of the filament, and the vector VP, namely the velocity of translation of the inclined portion, to said inclined portion
is directed against said inclined portion with an angle equal to zero or at a negative
angle such that said inclined portion does not encounter the falling filaments.
11. A process as claimed in claim 10, characterised in that said translating surface is a flat conveyor belt on which a plurality of right pyramidal
projections are disposed.
12. A process as claimed in claim 11,
characterised in that the translation velocity Vp of the belt is related to the vertical falling velocity
V
C of the filament by the following relationship:
where α is the half-angle at the vertex of the pyramids.
13. A process as claimed in claim 12, characterised in that said belt is preferably inclined to the horizontal plane by an angle between 0° and
α°.
1. Natte de filaments entrelacés et entremêlés d'une matière thermoplastique de faible
densité, la natte ayant un indice élevé de vides et comprenant plusieurs protubérances
creuses disposées en plusieurs lignes parallèles, caractérisée en ce qu'une partie au moins des protubérances présente au moins une partie ouverte délimitée
par des filaments non entrelacés, afin qu'une chambre de logement de la matière dont
la natte est destinée à être recouverte soit créée.
2. Natte selon la revendication 1, caractérisée en ce que les protubérances sont dépourvues de base inférieure.
3. Natte selon la revendication 1, caractérisée en ce que les protubérances creuses sont disposées les unes le long des autres dans des lignes
parallèles adjacentes.
4. Dispositif de fabrication d'une natte monofilament emmêlée ayant des protubérances
qui possèdent au moins une partie qui n'est pas occupée par les filaments selon la
revendication 1, comprenant une filière d'axe vertical destinée à extruder des alignements
parallèles des filaments, un cylindre rotatif disposé sous la filière et ayant son
axe horizontal et parallèle aux alignements, et une série de saillies réparties régulièrement
sur le cylindre et ayant au moins une partie inclinée vers la direction de déplacement
de la surface au moment de l'impact du filament, caractérisé en ce que la distance comprise entre l'axe du cylindre et le plan vertical médian dans lequel
tombent les filaments est choisi de manière que le vecteur VR, résultant de la différence entre le vecteur Vc, désignant la vitesse de chute verticale du filament, et le vecteur Vp, désignant la vitesse de translation de la partie inclinée, coupe la partie inclinée
avec un angle égal à zéro ou un angle négatif tel que la partie inclinée ne rencontre
pas les filaments qui tombent.
5. Dispositif selon la revendication 4, caractérisé en ce que les saillies sont disposées par lignes alignées mutuellement à la manière d'une hélice.
6. Dispositif selon la revendication 5, caractérisé en ce que l'hélice le long de laquelle sont disposées les saillies a une inclinaison comprise
entre 30 et 45° par rapport à l'axe du cylindre.
7. Dispositif selon l'une quelconque des revendications 4 à 6, caractérisé en ce que les saillies sont des pyramides droites.
8. Dispositif selon la revendication 7, caractérisé en ce que la base des pyramides est un carré.
9. Dispositif selon la revendication 8, caractérisé en ce que les bases des pyramides ont au moins un côté en commun avec les pyramides adjacentes.
10. Procédé de production d'une natte de filaments entrelacés et entremêlés d'une matière
thermoplastique de faible densité selon la revendication 1, comprenant des étapes
d'extrusion d'une matière thermoplastique par la filière et de collecte des filaments
extrudés qui tombent verticalement sur une surface mobile en translation ayant plusieurs
saillies profilées qui ont au moins une partie inclinée vers la direction de déplacement
de la surface au moment de l'impact du filament, caractérisé en ce que le vecteur VR qui représente la vitesse relative du filament tombant verticalement, résultant de
la différence entre le vecteur Vc, qui désigne la vitesse de chute verticale du filament, et le vecteur Vp, qui désigne la vitesse de translation de la partie inclinée, par rapport à la partie
inclinée est dirigé vers la partie inclinée avec un angle égal à zéro ou un angle
négatif tel que la partie inclinée ne rencontre pas les filaments qui tombent.
11. Procédé selon la revendication 10, caractérisé en ce que la surface du déplacement en translation est une courroie transporteuse plate sur
laquelle sont disposées plusieurs saillies en forme de pyramide droite.
12. Procédé selon la revendication 11,
caractérisé en ce que la vitesse de déplacement en translation V
p de la courroie est liée à la vitesse de chute verticale V
c du filament par la relation suivante :
α étant le demi-angle au sommet des pyramides.
13. Procédé selon la revendication 12, caractérisé en ce que la courroie est inclinée de préférence par rapport au plan vertical d'un angle compris
entre 0° et α°.
1. Fasermatte (1) aus verflochtenen und verwickelten Fäden aus thermoplastischem Werkstoff
mit niedriger Dichte, wobei die Fasermatte (1) einen hohen Hohlraumindex und eine
Vielzahl von in mehreren parallelen Reihen angeordneten, hohlen Höckern (2) aufweist,
dadurch gekennzeichnet, dass mindestens ein Teil der Höcker (2) mindestens einen offenen Abschnitt aufweist, der
durch nicht verflochtene Fäden festgelegt ist, um eine Kammer zur Aufnahme des Werkstoffes
zu schaffen, mit dem die Fasermatte (1) bedeckt werden soll.
2. Fasermatte (1) nach Anspruch 1,
dadurch gekennzeichnet, dass die Höcker (2) ohne ihre untere Basis ausgebildet sind.
3. Fasermatte (1) nach Anspruch 1,
dadurch gekennzeichnet, dass die hohlen Höcker (2) aneinander entlang in aneinander angrenzenden, parallelen Reihen
positioniert sind.
4. Vorrichtung zur Herstellung von verwickelter Monofilamentfasermatte (1), die mit Höckern
(2) versehen ist, die mindestens einen Abschnitt aufweisen, der nicht von den Fäden
belegt ist, nach Anspruch 1, die eine Matrize (5) mit Vertikalachse, um parallele
Anordnungen der Fäden zu extrudieren, einen sich drehenden Zylinder (8), unter der
Matrize (5) positionierten, dessen Achse horizontal und parallel zu den Anordnungen
verläuft, und eine Reihe von regelmäßig auf dem Zylinder (8) angeordneten Vorsprüngen
aufweist, die mindestens einen Abschnitt aufweisen, der zum Zeitpunkt des Auftreffens
des Fadens in die Bewegungsrichtung der Oberfläche geneigt ist, dadurch gekennzeichnet, dass der Abstand zwischen der Zylinderachse und der mittleren Vertikalebene, in welche
die Fäden fallen, so ausgewählt ist, dass der Vektor VR, der aus der Differenz zwischen dem Vektor VC, nämlich der Geschwindigkeit des vertikalen Falles des Fadens, und dem Vektor VP, nämlich der Translationsgeschwindigkeit des geneigten Abschnittes, resultiert, den
geneigten Abschnitt in einem Winkel gleich Null oder in einem negativen Winkel so
schneidet, dass der geneigte Abschnitt nicht auf die fallenden Fäden trifft.
5. Vorrichtung nach Anspruch 4,
dadurch gekennzeichnet, dass
die Vorsprünge in zueinander ausgerichteten Reihen in der Art einer Spirale angeordnet
sind.
6. Vorrichtung nach Anspruch 5,
dadurch gekennzeichnet, dass
die Spirale, entlang welcher die Vorsprünge angeordnet sind, eine Neigung zwischen
30° und 45° zu der Zylinderachse aufweist.
7. Vorrichtung nach einem der Ansprüche 4 bis 6,
dadurch gekennzeichnet, dass
die Vorsprünge reguläre bzw. gerade Pyramiden (9) sind.
8. Vorrichtung nach Anspruch 7,
dadurch gekennzeichnet, dass
die Basis der Pyramiden (9) quadratisch ist.
9. Vorrichtung nach Anspruch 8,
dadurch gekennzeichnet, dass
die Basen der Pyramiden (9) mindestens eine Seite gemeinsam mit den angrenzenden Pyramiden
(9) aufweisen.
10. Verfahren zur Herstellung einer Fasermatte (1) aus verflochtenen und verwickelten
Fäden aus thermoplastischem Werkstoff mit niedriger Dichte nach Anspruch 1, welches
die Schritte des Extrudierens eines thermoplastischen Werkstoffes durch die Matrize
(5) und das Sammeln der vertikal fallenden, extrudierten Fäden auf einer sich verschiebenden
Oberfläche umfasst, die mit einer Vielzahl von profilierten Vorsprüngen versehen ist,
die mindestens einen Abschnitt aufweisen, der zum Zeitpunkt des Auftreffens des Fadens
in die Bewegungsrichtung der Oberfläche geneigt ist, dadurch gekennzeichnet, dass der Vektor VR, der die relative Geschwindigkeit des vertikal fallenden Fadens ausdrückt,
die aus der Differenz zwischen dem Vektor VC, nämlich der Geschwindigkeit des vertikalen Falles des Fadens, und dem Vektor Vp, nämlich der Translationsgeschwindigkeit des geneigten Abschnittes, zu dem geneigten
Abschnitt resultiert, gegen den geneigten Abschnitt in einem Winkel gleich Null oder
in einem negativen Winkel so ausgerichtet wird, dass der geneigte Abschnitt nicht
auf die fallenden Fäden trifft.
11. Verfahren nach Anspruch 10,
dadurch gekennzeichnet, dass
die sich verschiebende Oberfläche ein flaches Förderband ist, auf dem eine Vielzahl
von regulären bzw. geraden pyramidalen Vorsprüngen angeordnet ist.
12. Verfahren nach Anspruch 11,
dadurch gekennzeichnet, dass
die Translationsgeschwindigkeit V
P des Bandes mit der vertikalen Fallgeschwindigkeit V
C des Fadens durch das folgende Verhältnis in Verbindung steht:
wobei α der Halbwinkel am Scheitelpunkt der Pyramiden ist.
13. Verfahren nach Anspruch 12,
dadurch gekennzeichnet, dass
das Band vorzugsweise in einem Winkel zwischen 0° und α° zu der Horizontalebene geneigt
ist.