Patent Application
20080044598
The invention will now be described, purely by way of a non-limiting example, with reference to the annexed plate of drawings, in which:
In
The plant 10 is represented in the form of a set of processing stations that are here supposed as being located in a single site and designed to carry out a processing cycle comprising different operations of treatment performed in cascaded fashion one after the other. Persons skilled in the sector will moreover appreciate that the aforesaid operations can, however, be performed in different premises or contexts and at different times, after prior storage and/or transfer of the intermediate products of the various processing steps illustrated.
In particular, the reference number 12 designates an extruder for plastic materials which operates with a vertical axis. A plastic material in the molten state is fed into the extruder 12 through an inlet duct 14, to undergo extrusion in a threading die 16 constituted, for example, by a die with an annular profile.
In particular, in the exemplary of embodiment illustrated herein, which is provided merely by way of example, the annular threading die 16 is constituted by a certain number of arched portions 160, separated from one another by a distance, for example of 1-2 cm. Each portion of a threading die 160 is designed to produce a respective strip B and has the profile illustrated in
In practice, the single portion of a threading die 160 has a certain length (for example, 50-60 mm, typically 56.4 mm) measured along its arched path of extension and comprises a certain number of segments 162 (eight in number, in the example illustrated).
Each segment 162 has then a length (once again measured along the arched path of extension of the portion of a threading die 160 of which the segment forms part) in the region of 6.7 mm and is connected to the adjacent segments 162 (or to the adjacent segment, in the case of the two end segments 162 in the portion of a threading die 160) by a thin portion or stretch 164.
Each thin portion 164 has a length, for example, of 0.4 mm, and a width or thickness (dimension in the radial direction with respect to the path of extension of the portion of a threading die 160) of, for example, 0.15 mm.
An important characteristic of the segments 162 is that they have a U-shaped cross section, hence one with two wider end parts or branches 1620 (once again the dimension in the radial direction with respect to the arched path of extension of the portion of a threading die 160) with respect to the central part 1622.
For simplicity of illustration, in
It will on the other hand be appreciated that the U shape is not to be considered imperative, since the characteristic of the end parts 1620 that are wider than the central part 1622 can be achieved also with other shapes (for example, a “bone” shape).
Purely by way of example, the end parts 1620 can present a width or thickness (once again the dimension in the radial direction with respect to the arched path of extension of the portion of a threading die 160) of 0.67 mm as against a width or thickness of the central part 1622 of 0.46 mm.
It is on the other hand evident that all the dimensional values mentioned previously are given purely by way of example and are not to be interpreted in a way that might in any sense limit the scope of the invention described herein.
At output from the threading die 16, there are hence present a plurality of strips B, each of which has, if viewed in cross section, the profile represented in
The material used for forming the strips B is usually a polyolefin-based material, such as a material chosen from the group constituted by polyethylene, polypropylene and/or mixes and/or copolymers thereof, polyethylene representing the currently preferred choice.
The material in question is usually pigmented so as to present en masse a colouring such as typically a green colouring, it being evident that this characteristic is not to be understood as in any sense limiting the scope of the invention.
Usually, the strips B coming from the threading die 16 are subjected to cooling by being dipped in a cooling bath contained in a tank 18 so as to enable their consolidation.
As has already been mentioned, each of the strips B reproduces the profile of drawing conferred upon it by the respective portion of a threading die 160, and is thus in the form of a strip constituted by a plurality of (for example, eight) filiform elements B1 (with widened ends, hence thickened with respect to the central part), set alongside one another and connected together by more slender connection portions B2.
Usually, as it is lowered into the cooling bath 18, each strip B tends to stretch out so that the substantial identity of shape with the portion of a threading die 160 does not usually correspond to an identity of dimensions. For example, the strip B can present a width in the region of 20 mm, with the segments B1 and the slender portions B2 that have homologous dimensions of width, respectively of 2.4 mm and 0.12 mm.
The dimensions of thickness can instead be approximately 300 micron and approximately 30 micron, respectively, for the segments B1 (maximum thickness in an area corresponding to the thickened ends) and for the slender portions B2.
Once again it is recalled that all the dimensional values, as quoted throughout the present description are provided purely by way of example and are not to be interpreted as in any sense limiting the scope of the invention described herein.
In any case, the slender connection portions B2 preferably have a thickness sufficient to cause them not to be brittle in normal conditions of manipulation of the strip B, where by “normal conditions of manipulation” is meant the conditions corresponding to the fact that the strip B is gripped by a person with his hand and felt, for example, by winding it around his fingers.
The strip B or each strip B consolidated by cooling (the solution herein represented, which envisages the simultaneous formation of a number of strips B, constitutes only a preferred, but non-imperative, embodiment of the invention) is then to be fed into a drawing assembly, for example, with motor-driven rollers, designated as a whole by 20.
The strip or strips B can be taken up in the course of a process that is either continuous (and in this case there will usually be provided one drawing assembly 20 for each strip B) or else discontinuous, in this case envisaging a gradual emptying from the tank 18 of the web/strips B that gradually accumulate therein.
It will likewise be appreciated that recourse to a technique of cooling by dipping constitutes just one from among the many choices possible for achieving the desired result of cooling/consolidation of the strip or strips B. Other techniques for achieving cooling are represented, for example, by exposure to the environment or else by exposure to jets of air or aeriform for cooling upon exit from the threading die 16.
Starting from the drawing assembly 20, the strip or strips B (in what follows reference will be made to just one strip, for reasons of simplicity of treatment) is/are sent on to an assembly for longitudinal stretching 22.
In a way in itself known, this assembly is normally constituted by an oven for heating the material and two or more sets of motor-driven rollers, each comprising two counter-rotating rollers, between which the strip B is made to advance (from left to right as viewed in
In this way, the strip B is subjected, in one or more stages, to an overall action of longitudinal stretching. For example, it is possible to operate (in a way in itself known) so as to apply a ratio of stretching of between 4:1 and 5:1 understood as the ratio between the rate of advance after and before the heating/stretching oven. The overall effect of this stretching is represented in
The strip B′ subjected to stretching (in what follows also referred to, for reasons of brevity, as “yarn”) has a width and a thickness that are smaller than that of the starting strip B, having, however, preserved in a practically unaltered way (for well-known physical reasons) its cross-sectional profile during stretching.
Consequently, also the yarn B′ deriving from stretching is obtained, if viewed in cross section as represented in
For example, in the case of the yarn B′, the segments B1′ can have a width of 1.1-1.3 mm and a thickness (maximum, in an area corresponding to the thickened ends) of 130-150 micron. The slender connection portions B2′ can instead typically have a width of approximately 30 micron and a thickness of 10 micron in the thinnest area.
Once again it is recalled that the aforesaid dimensional values are provided purely by way of example and are not to be interpreted as in any sense limiting the scope of the invention described herein.
In any case, the slender portions B2′ are very brittle, so that the single yarn B′ can be easily fibrillated, i.e., split into individual threads, each corresponding to one of the segments B1′, by breaking the slender portions B2′ with a modest stress such as the one deriving from the operation of twisting normally performed for winding the yarn B′ onto reels R according to the modalities and for the purposes described in the introductory part of the present description. The strip B′ thus behaves as a true strip, with all the resulting advantages, until the operation of twisting, when the strip then divides up into the individual strands.
In
This is basically a synthetic-grass structure S that comprises a sheetlike substrate K, from which there extends a plurality of filiform formations (constituted by the yarn B′) that simulate the grassy sward of natural grass cover.
Specifically, the weaving station 24 operates by “implanting” in the sheetlike substrate K formations each comprising a sort of tuft of yarn B′ having a looped part L that passes underneath the substrate K and two lateral branches that extend vertically above the substrate K, simulating blades of grass.
The synthetic-grass structure S is suited to receiving (once again according to altogether known criteria) a filling with particulate material F dispersed between the filiform formations so as to keep the filiform formations themselves in a substantially upright condition. For example, the particulate filling material (infill) F in question may be constituted by a substantially homogeneous mass of a granular material chosen from the group constituted by materials with a base of polyolefin and by materials with a base of vinyl polymer.
In any case, the characteristics of operation of the weaving station 24 and the criteria of production of the synthetic-grass covering S do not constitute elements of specific importance for the purposes of an understanding and implementation of the present invention. The solution according to the invention is suited in fact to being used also in the context of synthetic-grass coverings made according to criteria different from the ones represented in
For example (and without evidently wishing to limit the scope of the invention in any way), the filiform formations that extend above the sheetlike substrate K, instead of having their distal ends free (according to the plush or velvety configuration, represented in
Unlike what happens in fibrillation treatments of a traditional type, the structure of the yarn B′ means that the yarn B′ itself gives rise to a plurality of filiform elements B1′, the characteristics of which are defined precisely, for example, so that (according to a currently preferred, but non-imperative, embodiment) the filiform elements B1′ are substantially the same as one another.
The expression “currently preferred, but non-imperative, embodiment” is intended to take into account the fact that, in some applications, the fact that the filiform segments B1′ (and hence the segments B1 of
Whatever the choice adopted, the solution described herein in any case prevents one of the traditional drawbacks of the operations of fibrillation, namely, the fragmentation of each blade of yarn in an irregular (in effect random) way, with the consequent formation of fibrils of different width, frequently so thin as to break up and crumble under minimum stress. At the same time, the solution described herein does not alter appreciably the criteria of production of the synthetic-grass covering S, in particular as regards the development of the operation of “weaving” of the synthetic-grass covering. In particular, the (somewhat burdensome) operation, inevitably required by single-thread techniques, namely of having to aggregate a certain number of single threads to form a tuft, is avoided.
Persons skilled in the sector will likewise appreciate that the operation of separation of the segments B1′ (i.e., breaking of the slender portions B2′) is not in any way indissolubly linked to the possible re-twisting of the yarn B′.
Purely by way of example, the operation of separation of the segments B1′ (breaking of the slender portions B2′) can be performed or completed after the yarn B′ has been woven with the substrate K, for example, with an operation of brushing of the synthetic-grass covering formed by the yarn B′, performed, for instance, with a rotary brush that subjects the yarn B′ to mechanical stress, bringing about fragmentation of the yarn itself in an area corresponding to the slender portions B2′.
Albeit without wishing to be tied down to any specific theory in this connection, the present applicant has reasons to believe that the precision with which the segments B1′ are separated from one another, for example, following upon mere twisting of the strip or strip B′ of which the segments themselves originally form part, as well as the fact that, after separation, the segments preserve precisely their own individuality, without undergoing further fragmentation, are indissolubly linked to the mechanism of formation of the aforesaid strip B′ (and of the strip B from which the same is obtained by stretching), i.e., to the fact that the segments B1′ (and B1) present end parts (between which there extend the slender portions B2′ and, respectively, B2) thickened with respect to the central part, a fact which in turn derives from the portions of a threading die 160, in which the segments 162 have end parts 1620 that are wider than the central part 1622.
Of course, without prejudice to the principle of the invention, the details of construction and the embodiments may vary, even extensively, with respect to what is described and illustrated herein purely by way of non-limiting example, without thereby departing from the scope of the invention as defined by the annexed claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 06425589.6 | Aug 2006 | EP | regional |
