FR3114108A1 - Process for manufacturing an elastic binding thread - Google Patents

Abstract

Method of manufacturing an elastic binding thread. The invention relates to a method for manufacturing a stretchable binding thread in the form of a flat elastic tubular knitted cord or of square section for binding food, vegetable or industrial products, from at least one elastic thread characterized in that it comprises at least the following steps: - at least one elastic thread is chosen; - From at least one such yarn, a chain or a tubular sheath is knitted by means of a knitting cylinder (100) comprising N needles distributed regularly around said knitting cylinder (100), N being a number even between 4 and 24, by stopping at least two diametrically opposed needles of the knitting cylinder (100), said at least two needles being inactive and not making any stitches during knitting; - Said yarn is worked successively by the active needles of the knitting cylinder (100) and this cycle is repeated indefinitely to obtain said flat elastic tubular knitted cord. Figure for abstract: Fig.1

Description

Process for manufacturing an elastic binding thread

The present invention relates to a method of manufacturing an elastic binding thread, in the form of a flat or square cord, mainly intended to be used for binding various food products, for example meat or vegetables, vegetables , such as cut flowers, or even industrial products.

Traditionally, on knitting type jersey machines, or on warp stitch machines, cords of round section are made through a round knitting cylinder.

In the two cases mentioned above, the yarn is therefore knitted from round needle cylinders, consisting of a metal piece fluted around its circumference, equipped with needles which slide radially in the grooves of the piece.

The knitting cylinders conventionally used in the manufacture of binding cords generally have a number of needles between 2 and 24.

These needles each consist of a shaft, an upper end and a lower end. Said upper end is provided with a rounded hook, or beak, and with a latch, or valve, the latter being pivotally mounted under the hook in order to allow the opening and closing of the hook. The lower end of the needle has a heel allowing a cam to raise the needle in its groove.

For example, on classic knitting type machines, only one yarn is knitted at a time. When the knitting cylinder has twelve needles, the single yarn knitted works with the first needle which makes a stitch, then with the second which makes a stitch, and so on, until the twelfth needle, then a cycle begins again with the first needle.

As far as warp stitch machines are concerned, these work as many yarns as they have needles. After each stitch, the yarn donor cylinder pivots so that each yarn changes needle for the next stitch.

We thus already know, from French patent FR 2 4941 969, a process for manufacturing a stretchable binding thread, for holding food preparations, such as roast meat or fish, binding yarn obtained having a wide range of extensibility and an elastic return that is sufficiently soft to avoid projections, while being suitable for contact with food products.

The yarn manufacturing process includes the following steps:

– at least one yarn designed to be able to retain its mechanical properties during the cooking of a food preparation which it is intended to maintain, for example a food-grade polyester yarn, is chosen;

– is knitted, from at least one such yarn, a chain or a tubular sheath constituting said binding yarn;

– subjecting, after knitting, said chain or said tubular sheath to a heat treatment capable of giving it an elasticity at least greater than 20%, said treatment comprising a rise in temperature, by a treatment with steam, hot air or in hot water, up to at least 85° C., the temperature at which said chain or said sheath is maintained for a time greater than or equal to 3 minutes, before cooling the latter.

The purpose of the heat treatment here is to provide the knitted product with the elasticity characteristics required for the application (greater than or equal to 20%).

Here, a knitting machine comprising 1 or 2 or 3 or 4 or 5 or 6 needles, or even more than 6 needles, is used to obtain a knitted product of larger diameter. It is also envisaged the knitting of a binding thread by transformation of a single thread, by a single needle, which works it to produce a chain, or else of the same thread transformed by several needles, according to the principle of knitting , that is, a braid knitted on one or more needles.

However, the processes for manufacturing binding yarns known from the state of the art, using round cylinders, make it possible to obtain knitted products having a round section, which are liable to damage the products that said round cords are meant to bind.

On the contrary, the method in accordance with the present invention makes it possible to obtain, by the implementation of a round knitting cylinder, a knitted product consisting of a flat cord or of square section.

Such a structure, in the form of a flat or square cord, allows a better distribution of the pressure exerted by said cord on the product (food, vegetable or other) that it is intended to bind, in comparison with a cord elastic with a round section, which exerts pressure on a weaker surface of the product.

Also, by implementing the present process, a stretchable binding yarn is advantageously obtained consisting of a flat cord or of square section which allows a reduction in the damage to the products intended to be bound by said yarn.

• On choisit au moins un fil élastique ;
• On tricote, à partir d’au moins un tel fil, une chaînette ou une gaine tubulaire, au moyen d’un cylindre de tricotage comportant N aiguilles réparties régulièrement autour dudit cylindre de tricotage, N étant un nombre pair compris entre 4 et 24, en mettant à l’arrêt au moins deux aiguilles du cylindre de tricotage diamétralement opposées, lesdites au moins deux aiguilles étant inactives et n’effectuant aucune maille pendant le tricotage ;
• On travaille ledit fil successivement par les aiguilles actives du cylindre de tricotage et ce cycle est répété indéfiniment pour l’obtention dudit cordon tricoté tubulaire élastique plat.

To this end, the present invention relates to a process for the manufacture of a stretchable binding thread in the form of a flat elastic tubular knitted cord or of square section for the binding of food, vegetable or industrial products, from at least one elastic thread characterized in that it comprises at least the following steps:

• At least one elastic thread is chosen;
• From at least one such yarn, a chain or a tubular sheath is knitted by means of a knitting cylinder comprising N needles regularly distributed around said knitting cylinder, N being an even number between 4 and 24, by stopping at least two needles of the diametrically opposed knitting cylinder, said at least two needles being inactive and performing no stitches during knitting;
• Said yarn is worked successively by the active needles of the knitting cylinder and this cycle is repeated indefinitely to obtain said flat elastic tubular knitted cord.

Thus, in the method of the present invention, compared to the method conventionally implemented, at the time of knitting the yarn(s), at least two needles of the knitting cylinder are neutralized or inactivated, the two needles neutralized being diametrically opposed, the latter making no stitches during the knitting process.

The needles can be stopped regardless of the machine used for the knitting, namely a knitting type machine, with several needles on a fixed cylinder working a single thread, or a warp stitch machine, where as many threads are worked that there are needles, and where the yarn donor cylinder pivots after each stitch.

It has been demonstrated by the inventor that such inactivation of two diametrically opposed needles, or of more than two needles as will be explained below, has the effect of forming a longer flange between two stitches, in so that the tubular cord being knitted is flattened at the level of the two long flanges thus created, or that the geometry of said tube is modified, while increasing, in a particularly interesting manner, the elasticity of the cord. Indeed, the presence of long flanges confers greater elasticity on the cord finally obtained, compared to a round tubular cord obtained by the conventional implementation of the knitting process.

Thus, finally, the method according to the present invention makes it possible to obtain a flat tubular cord or of square section having improved adhesion with the product to be bound, in comparison with a conventional cord whose section is round, and without risk of damage said product to be bound.

In a first exemplary embodiment of the method of manufacturing a flat elastic tubular knitted cord or of square section, four needles of a knitting cylinder which comprises between 6 and 24 needles, namely a first pair of two successive needles, are inactivated and a second pair of successive hands, said second pair being diametrically opposed to the first pair.

In a second embodiment of this method, six needles of a knitting cylinder which comprises between 8 and 24 needles are inactivated, namely a first trio of three successive needles and a second trio of successive needles, said second trio being diametrically opposed to the first trio.

In a third embodiment of the method, eight needles of a knitting cylinder which comprises between 10 and 24 needles are inactivated, a first quartet of four successive needles and a second quartet of four successive needles, said second quartet being diametrically opposed to the first quartet.

The present invention also relates to a stretchable binder yarn capable of being obtained by implementing the knitting method of the invention, said yarn consisting of a flat elastic tubular knitted cord or of square section, unlike the yarns obtained traditionally in an industrial way, which have a round section.

Other aims and advantages of the present invention will appear during the description which will follow relating to embodiments which are given only by way of indicative and non-limiting examples.

The understanding of this description will be facilitated by referring to the single figure in the appendix representing, schematically, a top view of a particular and non-limiting embodiment of a knitting cylinder for implementing the method of the invention, said cylinder being provided with twelve needles, the needles opposite numbers 4 and 10 being inactivated for the manufacture of a flat elastic tubular knitted cord or of square section according to the present invention.

The present invention relates to a method of manufacturing a stretchable binding thread, the latter being in the form of an elastic tubular knitted cord, having the particularity of being flat or of having a square section.

The elastic tubular knitted cord according to the present invention will find an application in the maintenance of food products and preparations, such as meat roasts, paupiettes, or the like, vegetable products, such as for example, but not limited to, cut flowers or asparagus fresh.

In another interesting application, the cord according to the present invention can also be used for making sanitary masks.

The process for the manufacture of a stretch binding thread in the form of a flat elastic tubular knitted cord or of square section, from at least one elastic thread, implements a knitting cylinder 100 illustrated in FIG. 1, the latter being provided with a plurality of needles.

More particularly, said cylinder 100 used in the method of the invention comprises N needles, N being an even number between 4 and 24. Said needles are distributed in a regular manner on the perimeter of said cylinder 100, and are able to slide radially in grooves which are provided at the level of the periphery of the knitting cylinder 100.

By way of example, the knitting cylinder 100 which is illustrated in figure 1 is equipped with twelve needles, which are numbered from 1 to 12.

Each of these needles 1 to 12 may consist of a rod and a rounded hook, or beak, at the upper end of said rod, as well as a lock or valve, pivotally mounted under the hook to open and close said hook. At the lower end of the rod there is a heel allowing a cam to raise the needle in the groove in which it slides.

• On choisit au moins un fil élastique ; celui-ci peut être monomatériau et être constitué d’une matière élastique choisie parmi les élastomères, les gommes naturelles ou artificielles, ou être multimatériaux et comporter, en plus d’une matière élastique telle qu’indiquée précédemment, une matière non élastique choisie parmi le nylon, le polypropylène, le coton, la laine, le lin, le chanvre ou le jute. A noter encore que les fils utilisés peuvent être écrus ou teints, et peuvent être produits par guipage air, guipage simple, guipage double, torsion, retordage, ou autre.
• On tricote, à partir d’au moins ce fil, une chaînette ou une gaine tubulaire, au moyen du cylindre de tricotage 100 qui a été décrit ci-dessus, tout en inactivant, pendant la formation de la gaine tubulaire, au moins deux des aiguilles du cylindre de tricotage ;
• On travaille ledit fil successivement par les aiguilles actives du cylindre de tricotage 100, et ce cycle est répété indéfiniment jusqu’à obtenir un cordon de la longueur souhaitée, celle-ci pouvant bien évidemment être variable.

To return to the process for manufacturing a flat elastic tubular knitted cord or cord of square section of the invention, the latter comprises, in a particularly advantageous manner, at least the following steps:

• At least one elastic thread is chosen; this can be a single material and consist of an elastic material chosen from elastomers, natural or artificial rubbers, or be multi-material and comprise, in addition to an elastic material as indicated above, a non-elastic material chosen from nylon, polypropylene, cotton, wool, linen, hemp or jute. It should also be noted that the yarns used can be unbleached or dyed, and can be produced by air covering, simple covering, double covering, twisting, twisting, or other.
• From at least this yarn, a chain or a tubular sheath is knitted, by means of the knitting cylinder 100 which has been described above, while inactivating, during the formation of the tubular sheath, at least two of the knitting cylinder needles;
• Said yarn is worked successively by the active needles of the knitting cylinder 100, and this cycle is repeated indefinitely until a bead of the desired length is obtained, which can of course be variable.

Note here that the needles which are stopped during the step of forming the tubular sheath by the knitting cylinder 100, whether there are two or more than two, must be diametrically opposed.

Thus, with reference to FIG. 1 which is attached, on a knitting cylinder 100 comprising twelve needles 1 to 12, the opposite needles numbered 4 and 10 can be neutralized. These are then shown in dotted lines in the figure, while the active hands 1 to 3, 5 to 9, 11 and 12 are in solid lines.

Thus, the thread will pass needle 4 and needle 10 without making a stitch, and forming a flange between the needles bearing the numbers 3 and 5 and between the needles 9 and 11.

In this particular example, the length of the flanges between the needles 3 and 5 and that between the needles 9 and 11 makes it possible to confer a flat structure on the tubular knitted cord finally obtained.

The knitted tube indeed flattens with the knitting and winding tension.

In addition, the elasticity of the cord is increased here, in comparison with a cord obtained in a known and conventional manner, that is to say without stopping certain needles of the knitting cylinder.

Interestingly, it is possible, according to a variant of the method of the invention, to further increase the desired effect by stopping four, six or eight needles, namely two, three or four successive needles and the two, three or four successive needles which are opposed to them.

Thus, more particularly, during the knitting step of the method of the invention, it is possible to inactivate four needles of a knitting cylinder which comprises between 6 and 24 needles, a first pair of two successive needles and a second pair of successive hands, said second pair being diametrically opposed to the first pair.

With reference to Figure 1, it is therefore possible to inactivate, during the formation of the tubular sheath, the needles numbered 4 and 5, as well as the needles diametrically opposite them, namely the needles 10 and 11 Thus, the thread will pass from needle 3 to needle 6, then from needle 9 to needle 12, without making a stitch and forming a flange.

In a second embodiment of the method of the invention, six needles of a knitting cylinder which comprises between 8 and 24 needles can be stopped, a first trio of three successive needles and a second trio of needles successive, said second trio being diametrically opposed to the first trio.

Taking the illustration in figure 1, the trio of needles numbered 4, 5 and 6 would be inactivated, and the trio of needles 10, 11, 12 opposite it, and the thread would pass from needle 3 to needle 7, and from needle 9 to needle 13, without stitching.

In a third exemplary embodiment, it is possible to inactivate eight needles of a knitting cylinder which comprises between 10 and 24 needles, a first quartet of four successive needles and a second quartet of four successive needles, said second quartet being diametrically opposed to the first quartet.

Still with reference to figure 1, it is thus possible to stop the successive hands numbered 3, 4, 5, 6, as well as the hands 9, 10, 11 and 12.

These examples are particularly interesting, but they should not be considered as limiting the invention, and it is possible, depending on the size of the knitting cylinder 100 and the number of needles with which it is provided, that more than eight needles successive ones are inactivated during the knitting step.

It is also possible to stop four, six or eight needles which are not successive, but which are distributed over the perimeter of the knitting cylinder 100, and which are diametrically opposed two by two.

Thus, on a knitting cylinder 100 illustrated in Figure 1 it is possible to inactivate the needles numbered 1 and 4, and the needles which are diametrically opposed to them, respectively numbered 7 and 10.

Inactivating certain needles during the knitting step can be done in different ways.

For example, it is possible to simply remove, from the knitting cylinder 100 implementing the method of the invention, the needles which should be inactivated during the knitting step.

In another exemplary embodiment, the beak of the needles to be inactivated can be eliminated, or else shorter needles can be mounted in the grooves of the knitting cylinder 100, for the needles at rest.

It is also possible to use a knitting cylinder 100 without grooves at the locations of the needles to be inactivated, and therefore without needles at the desired locations.

The needles to be inactivated can be replaced by simple rods, with round or rectangular tips, therefore devoid of beak and valve, unlike the active needles, forming meshes, which necessarily comprise such elements.

Thus, it emerges from the foregoing that when, in the definition of the method of the invention, the inactivation or stopping of certain needles during the knitting step is indicated, this may correspond to an elimination of these needles which would normally be present on a knitting cylinder traditionally used for the manufacture of tubular cords having a round section.

The process of the present invention can be implemented with a single thread, transformed by several successive needles, according to the knitting principle, or on a warp-stitch type machine, with as many threads as needles, where the process of the invention applies to machines having a pivoting of the yarn donor cylinder.

In the latter case, the only change concerns the very structure of the cord which is elasticized by using an elastic core, made of elastomer, latex, rubber or any other thread or elastic fiber, placed in the center of the cord.

The present invention also relates to a stretchable binder yarn capable of being obtained by implementing the method of the invention and described above, said yarn consisting more specifically of a flat elastic tubular knitted cord or of square section.
Such a cord having a flattened structure or a square section is particularly advantageous for binding together particularly fragile products, and in particular products of vegetable origin which are particularly sensitive to significant pressures which may be applied locally at their external surface. , the structure of the cord of the invention making it possible to distribute this pressure when the cord is tied over a larger surface than a cord of round section.

Claims (6)

Process for the manufacture of a stretchable binding thread in the form of a flat elastic tubular knitted cord or of square section for the binding of food, plant or industrial products, from at least one elastic thread, characterized in that it includes at least the following steps:

• At least one elastic thread is chosen;
• From at least one such yarn, a chain or a tubular sheath is knitted by means of a knitting cylinder (100) comprising N needles distributed regularly around said knitting cylinder (100), N being an even number between 4 and 24, by stopping at least two diametrically opposed needles of the knitting cylinder (100), said at least two needles being inactive and not making any stitches during knitting;
• Said yarn is worked successively by the active needles of the knitting cylinder (100) and this cycle is repeated indefinitely to obtain said flat elastic tubular knitted cord.

Process according to Claim 1, characterized in that four needles of a knitting cylinder (100) which comprises between 6 and 24 needles, a first pair of two successive needles and a second pair of successive needles, the said second pair being diametrically opposed to the first couple. Process according to Claim 1, characterized in that six needles of a knitting cylinder (100) which comprises between 8 and 24 needles, a first trio of three successive needles and a second trio of successive needles, the said second trio being diametrically opposed to the first trio. Process according to Claim 1, characterized in that eight needles of a knitting cylinder (100) which comprises between 10 and 24 needles are inactivated or inactivated, a first quartet of four successive needles and a second quartet of four successive needles, the said second quartet being diametrically opposed to the first quartet. Process according to any one of Claims 1 to 4, characterized in that the elastic thread is composed of an elastic material chosen from elastomers, natural or artificial gums and of a non-elastic material chosen from nylon, polypropylene, cotton, wool, linen, hemp or jute. Stretchable binding thread obtainable by implementing the method according to any one of the preceding claims, characterized in that it consists of a flat elastic tubular knitted cord or of square section.