Abstract
The present invention relates to synthetic fibers and artificial lawn comprising such a fibre. More particularly, the invention relates to grass-like monofilament type fibers having a curved cross section and an artificial grass lawn, especially an artificial grass sports field, comprising such a fibre. According to an aspect of the invention, a synthetic fibre is provided of the monofilament type for use in an artificial lawn, in particular an artificial sports lawn, which synthetic fibre has a curved cross section, wherein the synthetic fibre has a centre line arc length to maximum thickness of less than 8, preferably between 4.5 and 3.8, and even more preferably between 4.4 and 4.0. In an other aspect of the invention, a synthetic fibre is provided of the monofilament type for use in an artificial lawn, in particular an artificial sports lawn, which synthetic fibre has a curved cross section, wherein the circumferential surface of the fibre is provided with a wave shaped pattern.
Claims
1. A synthetic monofilament fibre for use in an artificial lawn which synthetic fibre has a curved cross section, wherein the synthetic fibre has a centre line arc length to maximum thickness ratio of between 4.5 and 3.8 and a circumferential surface of the synthetic fibre is provided with a sine wave shaped pattern.
2. The synthetic fibre according to claim 1, wherein the synthetic fibre has a centre line arc length to maximum thickness ratio between 4.4 and 4.0.
3. The synthetic fibre according to claim 1, wherein the synthetic fibre has a linear mass density between 1000 tex and 2500 tex.
4. The synthetic fibre according to claim 1, wherein the sine wave shaped pattern extends in the longitudinal direction of the fibre.
5. An artificial lawn comprising a substrate having artificial fibres according to claim 1.
6. A synthetic monofilament fibre for use in an artificial lawn which synthetic fibre has a cross section that falls within a curved outer envelope, wherein a circumferential surface of the synthetic fibre is provided with a wave shaped pattern falling within the curved outer envelope and wherein the synthetic fibre has a centre line arc length to maximum thickness ratio of between 4.5 and 3.8.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) FIG. 1a-1b show preferred embodiments of a synthetic fibre having a centre line arc length to maximum thickness ratio according to an aspect of the invention.
(2) FIG. 1c-1d show preferred embodiments of a synthetic fibre having a centre line arc length to maximum thickness ratio according to an aspect of the invention and a circumference provided with a wave shaped pattern.
(3) FIG. 2-11 show a synthetic fibre according to other aspects of the invention wherein the fibre has different cross sectional shapes and the fibre is provided with different shapes around the circumferential surface;
(4) FIGS. 12 and 13 schematically show a few embodiments of an artificial lawn comprising a synthetic fibre according to the invention.
DETAILED DESCRIPTION OF THE DRAWINGS
(5) For a better understanding of the invention, like elements will be indicated by the same reference numbers in the description of the figures below.
(6) FIG. 1a shows in a cross sectional view an embodiment of the invention wherein with reference number 10a a synthetic/artificial fibre, for example a synthetic grass sports fibre is illustrated, which is preferably of a monofilament type obtained by an extrusion process.
(7) The bending radius 10a6 or amount of curvature of the fibre 10a shown in FIG. 1a has an effect on the characteristics of the artificial lawn in which it is provided. Increasing the curvature will increase the flexural stiffness of the fibre, which as a result thereto will not unnecessarily assume a flat orientation in the artificial lawn of which the fibre 10a forms part. Increasing the stiffness, however, can decrease the playing characteristics of the artificial lawn because when played on, it can lead to an increased risk of injuries and in particular when sliding tackles are made thereon.
(8) Decreasing the stiffness however, will tend the fibre to assume a more flat orientation during play on the artificial lawn. As a result the fibre's functionality as regards to the playing characteristics of the artificial lawn will be lost. Bare patches on the field will appear and the risk of injury is increased there.
(9) An optimal stiffness is therefore required to on the one hand prevent a flat orientation and on the other hand still provide a relative soft player friendly artificial lawn with low risk of injuries. An artificial fibre having such characteristics is in an embodiment of the invention disclosed in FIGS. 1a-1d.
(10) FIG. 1a shows that the fibre 10a has a curved shape, which curve radius 10a6 shown in FIG. 1a is only indicative. The invention is not restricted to the curvature shown in FIG. 1a, also a more curved fibre or a less curved fibre are considered incorporated in an embodiment of the invention. The ratio between the concave surface radius 10a7 (R2) and the convex surface radius 10a8 (R1) is in this embodiment less than 0.9, and preferably between 0.6 and 0, and even more preferably between 0.35 and 0. The fibre shown in FIG. 1b has a flat surface at its concave side R2.
(11) Besides the stiffness other characteristics of a fibre influence the playability of an artificial grass sports field. In order to provide a natural like artificial grass sports field the fibres used therein, should also have an optimal flexibility and resilience. Flexibility can prevent the fibre from splitting or fracture when undergoing high material stress when being played on. Resilience is needed for the fibre to re-assume an erect orientation after impact of forces applied thereon during play.
(12) The fibre 10a shown in FIG. 1a is tapered near the edges 10a1a, 10a1b and reaches its maximum thickness at the centre portion 10a1c. The fibre 10a shown here has relative thin edges 10a1a, 10a1b. Increasing this thickness will increase the stiffness of the fibre. The edges 10a1a and 10a1b are preferably round. The fibre 10 according to the invention does therefore not only have non-sharp edges, which have a positive effect on the playing characteristics, it also decreases the risk of injuries when for example making a sliding or tackle.
(13) The centre line arc length 10a6 of the fibre 10a disclosed in FIG. 1a is clearly larger than the thickness T 10a3, measured at the middle, central part 10a1c of the fibre. The centre line arc length 10a6 is determined by, and defined as, the length of dotted line Rc 10a6 from one end of the fibre 10a1a to the other 10a1b. According to the invention the ratio (L/T) between the centre line arc length 10a6 and the maximum thickness 10a3 is less than 8, preferably between 4.5 and 3.8, and even more preferably between 4.4 and 4.0.
(14) The linear mass density of a fibre according to an aspect of the invention and according to the preferred embodiment disclosed by FIG. 1, is in the range between 1000 tex and 2500 tex. As the centre arc line length to thickness ratio is dependent upon the fibre's tex, the centre arc line length or thickness of a fibre according to an aspect of the invention can be calculated when the tex and one of the centre arc line length and thickness is given.
(15) The above stated characteristics can be changed, and an optimum combination of stiffness, flexibility and resilience can be achieved according to an aspect of the invention wherein the fibre is a fibre 10a having a L/T ratio as it is described above, the fibre 10a exhibits improved characteristics. Study shows that especially the stiffness of a fibre 10a according to this aspects has substantially increased with respect to prior art fibres. The fibre 10a characteristics are such that not only a sufficient resilience and flexibility is achieved, but also that it exhibits a flexural stiffness such that it will not unnecessarily assume a flat orientation in the artificial lawn, or the artificial grass sports field in case of a synthetic grass sports fibre of which the fibre 10a forms part of.
(16) Such a fibre according to an aspect of the invention and according to FIGS. 1a-1d, are preferably made of polypropylene, polyethylene, polyamide, a co-polymer, or a blend of one or more of the these polymers. In possible embodiments of the synthetic fibre, the fibre may therefore be made of rubber, which is permanently elastic synthetic polymer, or of a synthetic (co)polymer which will remain within the elastic range upon being subjected to a load.
(17) The previously mentioned characteristics can be changed, and an optimum combination thereof can be achieved according to an aspect of the invention wherein the fibre is a fibre 10c as shown in FIG. 1c, being provided with a wave shaped pattern around the circumferential surface. The wave shaped pattern is provided with nodes 10c9b and antinodes 10c9a. The fibre 10c shown in FIG. 1c has an unequal amount of nodes 10c9b and antinodes 10c9a on both sides. The concave side of the fibre 10c, which side is above the centre portion 10c1c of the fibre 10c, is in this preferred embodiment provided with seven nodes 10c9b and six antinodes 10c9a. The convex side of the fibre 10c, which side is below the centre portion 10c1c of the fibre 10c, is in this preferred embodiment provided with eleven nodes 10c9b and ten antinodes 10c9a. The nodes 10c9b of the fibre function as stiffness-enhancing means and the size, amount and position can be changed to influence the stiffness needed for a particular artificial lawn.
(18) The way the fibre 10c is provided with a wave shaped surface increases it's natural look. Light rays striking the surface of the fibre 10c are directed in a different direction than the direction they originated from. Parallel rays of light striking a fibre 10c according to the invention having a wave shaped surface will be directed to different directions. The amount of waves/antinodes and nodes and the size/dimension of the waves influence this light scattering effect. Study showed that a fibre 10c according to the invention which is provided with a wave shaped pattern as indicated in FIG. 1c has an increased light scattering effect and therefore such a natural look that it closely reassembles real grass.
(19) In FIG. 2 a different, further embodiment of the invention is shown wherein a fibre 20 is provided with a wave shaped pattern, which is a sine wave shape pattern. Such a pattern has even smoother transitions in-between the positive 21a and negative antinodes 21b. The nodes 21c disclosed in FIG. 2 lack shape edges. The smooth transition between the antinodes (positive 21a, and negative 21b) prevent the fibre from splitting or fracture, and an increased lifetime is herewith achieved.
(20) The fibre 20 shown in FIG. 2 has relative small and sharp edges 20a and 20b and an optimal L/T ratio of 3.8. This ratio however is at its maximum 5, preferably it lies between 3 and 4.5 and more preferably between 3.5 and 4 and is as indicated above, optimal at a ratio of 3.8. The concave side of the fibre 20 is provided with eight nodes 21c and seven antinodes 21a, 21b. The other side which in this figure lies below the central portion 20c of the fibre 20, being the convex side of the fibre 20, is provided with ten nodes 21c and 9 antinodes 21a, 21b.
(21) In FIG. 3 a different embodiment of the invention is disclosed wherein a fibre 30 has a curved cross section with a wave shaped pattern around the circumferential. The wave shaped pattern consists of nodes 31c and positive antinodes 31a. The negative side of a sine shape, being the negative antinode, is absent in this pattern. The advantage of such a pattern is that it has a larger amount of stiffness enhancing means provided around its circumferential, as each positive antinode 31a functions as such a stiffness enhancing mean. In this embodiment the fibre 30 has round edges 30a, 30b which are relatively thin. The L/T ratio of the fibre 30 shown in FIG. 3 is at its optimum at 3.8.
(22) The concave side of an embodiment of the fibre 30 shown in FIG. 3 is provided with seven (positive) antinodes 31a and eight nodes 31c, and on its convex side the fibre 30 is provided with nine (positive) antinodes 31a and ten nodes 31c.
(23) In FIG. 4 yet a different embodiment of the invention is disclosed wherein a fibre 40 has a curved cross section with a wave shaped pattern around the circumferential. The wave shaped pattern consists of nodes 41c and negative antinodes 41b. Such a wave shaped pattern is likely, because of its shape, to concentrate light rays in the negative antinode 41b waves. As a result thereof a shadow casting effect is achieved increasing the natural likeness of the fibre 40 by making the fibre 40 more dull looking. The L/T ratio of the fibre 40 shown in FIG. 4 is at its optimum at 5.1. The concave side of an embodiment of the fibre 40 shown in FIG. 4 is provided with seven (negative) antinodes 41b and eight nodes 41c. On its convex side, the fibre 40 is provided with nine (negative) antinodes 41b and ten nodes 41c.
(24) In FIG. 5 yet another embodiment of the invention is disclosed wherein a fibre 50 has a curved cross section with a wave shaped pattern around the circumference. The wave shaped pattern consists of nodes 51c and both negative antinodes 51b as well as positive antinodes 51a. Such a wave shaped pattern will have a shadow casting effect which is different on the concave side of the fibre 50 with respect to the convex side of the fibre 50. The fibres 50 can be provided in bundles in an artificial lawn or artificial grass sports field, and they tend to assume a different orientation with respect to each other. When looking at an artificial lawn or sports field provided with such fibres 50 they seem to have different colors which increases its natural look.
(25) The L/T ratio of the fibre 50 shown in FIG. 5 is at its optimum at 4.3. The concave side of an embodiment of the fibre 50 shown in FIG. 5 is provided with seven (negative) antinodes 51b and eight nodes 51c and on its convex side the fibre 50 is provided with nine (positive) antinodes 51a and ten nodes 51c.
(26) FIG. 6 shows an embodiment of the invention wherein a fibre 60 has a curved cross section with a wave shaped pattern around the circumference. The wave shaped pattern consists of nodes 61c and both negative antinodes 61b on the convex side as well as positive antinodes 61a on its concave side. Such a wave shaped pattern will have a shadow casting effect which is different on the concave side of the fibre 60 as to the convex side of the fibre 60. The fibres 60 tend to assume a different orientation with respect to each other and will therefore seem to have different colors which increases its natural look.
(27) The L/T ratio of the fibre 60 shown in FIG. 6 is at its optimum at 4.3. The concave side of an embodiment of the fibre 60 shown in FIG. 6 is provided with seven (positive) antinodes 61a and eight nodes 61c and on its convex side, the fibre 60 is provided with nine (negative) antinodes 61b and ten nodes 61c.
(28) In FIG. 7 a different embodiment of the invention is disclosed wherein a fibre 70 has a curved cross section with a wave shaped pattern around the circumferential, however the fibre is, seen in cross sectional view, flat at one side. The wave shaped pattern, which in this embodiment is a sine shaped pattern, consists of nodes 71c and both negative antinodes 71b as well as positive antinodes 71a. Such a sine shaped pattern will decrease the risk of splitting or fracture due to the smooth transitions at the nodes. The L/T ratio of the fibre 70 shown in FIG. 7 is at its optimum at 2.7. The flat side of an embodiment of the fibre 70 shown in FIG. 7 is provided with seven (both positive and negative) antinodes 71a, 71b and eight nodes 71c and on its convex side, the fibre 70 is provided with nine (both positive and negative) antinodes 71a, 71b and ten nodes 51c.
(29) In FIG. 8 an embodiment of the invention is disclosed wherein a fibre 80 has a curved cross section with a wave shaped pattern around the circumferential, however the fibre is, seen in cross sectional view, flat at one side. The wave shaped pattern consists of nodes 81c and positive antinodes 81a. The L/T ratio of the fibre 80 shown in FIG. 8 is at its optimum at 2.7. The flat side of this embodiment of the fibre 80 is provided with seven (positive) antinodes 81a and eight nodes 81c and on its convex side, the fibre 80 is provided with nine (positive) antinodes 81a and ten nodes 81c.
(30) In FIG. 9 another embodiment of the invention is disclosed wherein a fibre 90 has a curved cross section with a wave shaped pattern around the circumference, wherein the fibre is, seen in cross sectional view, flat at one side. The wave shaped pattern consists of nodes 91c and negative antinodes 91b. The L/T ratio of the fibre 90 shown in FIG. 9 is at its optimum at 2.9. The flat side of this embodiment of the fibre 90 is provided with seven (negative) antinodes 91b and eight nodes 91c and on its convex side the fibre 90 is provided with nine (negative) antinodes 91b and ten nodes 91c.
(31) In FIG. 10 yet another embodiment of the invention is disclosed wherein a fibre 100 has a curved cross section with a wave shaped pattern around the circumferential, wherein the fibre is, seen in cross sectional view, flat at one side. The wave shaped pattern consists of nodes 101c and both positive and negative antinodes 101a, 101b. The L/T ratio of the fibre 100 shown in FIG. 10 is at its optimum at 2.9. The flat side of this embodiment of the fibre 100 is provided with seven (negative) antinodes 101b and eight nodes 101c and on its convex side the fibre 100 is provided with nine (positive) antinodes 101a and ten nodes 101c.
(32) In FIG. 11 yet another embodiment of the invention is disclosed wherein a fibre 110 has a curved cross section with a wave shaped pattern around the circumferential, wherein the fibre is, seen in cross sectional view, flat at one side. The wave shaped pattern consists of nodes 111c and both positive and negative antinodes 111a, 111b. The L/T ratio of the fibre 110 shown in FIG. 11 is at its optimum at 2.9. The flat side of this embodiment of the fibre 110 is provided with seven (positive) antinodes 111a and eight nodes 111c and on its convex side the fibre 110 is provided with nine (negative) antinodes 111b and ten nodes 111c.
(33) FIGS. 12 and 13 show a few embodiments of an artificial lawn such as an artificial grass sports field in which a synthetic fibre according to the invention can be used. In both figures the artificial lawn comprises a backing 1, to which the several synthetic fibres 2 (corresponding to the fibres 10a-d, 20, 30, 40, 50, 60, 70, 80, 90, 100 and 110 shown in FIGS. 1 to 11) are attached at the locations indicated by reference numeral 3, for example by tufting or weaving. The extruded synthetic fibre 2 may be individually attached to the backing 1 or in a bundle of, for example twined, fibres 2a-2c. The backing member in FIG. 13 has an open structure and is composed of a grid of supporting yarns 1a-1b, to which the synthetic fibres 2 are attached.
