FR2792868A1 - Manufacturing shoelaces, comprises deforming strip or braid of material before injection molding plastic over it - Google Patents

Abstract

A strip or braid of material is deformed prior to injection molding plastic over it. Independent claims are also included for: (a) a device for performing as above includes an injection mould, a guide for the strip or braid, an ejection device and devices deforming the strip or braid to reduce its section; (b) a plastic tip produced on an end of a braid or strip produced as above using a device as above; (c) using part of (b) as a shoelace. Preferred Features: The strip or braid is of natural material with a flattened, hexagonal or circular cross section. The strip is stretched lengthwise upstream of the injection mould.

Description

Plastic overmolding process, associated overmolding device, end piece

  The overmold thus obtained, and braid segment provided with such a tip. The present invention relates to the technical field of overmolding by injection of plastic material, more particularly to a process for overmolding braids. It also relates to a device for implementing the overmolding process. It also relates to the molded end piece on the braid obtained by the process, and the braid provided with said molded end piece, as well as a use of the latter in the

footwear.

  The overmolding process according to the invention applies to braids, in particular of a textile nature, such as for example woven or knitted or braided braids, produced on weaving looms or knitting looms.

  or braiding looms, all these braids being more or less elastic.

  A person skilled in the art already knows in the prior art methods of overmolding by injection of plastic material, which consist in molding around the end of a cord or strap a plastic end piece having a particular function, like for example a loop or a ring, or a hook, ... The parts produced are used in particular as car accessories or as

  accessories for household appliances.

  The conventional overmolding process is done on long lengths of cords or straps by local molding and cutting on the molding area, so as to obtain two end pieces. It includes: - a molding phase during which plastic material is injected, in a defined area, inside an injection mold around the braid, the shape of the molded areas being defined by the imprints of the mold, - a drawing phase taking place after the molding phase, during which the molded zones are moved and placed in a conformator, - a cutting phase during which two blades cut and separate the molded zones and the connecting carrot which

  connects several molded areas together.

  The problem encountered and not yet resolved so far that the invention proposes to solve is that of the production by molding on a braid of a cylindrical end piece of any section, preferably circular or hexagonal, the largest

  dimension of this section being less than the significant dimension -

  diameter or width of the braid at rest.

  The braid is said to be at rest when it is not subjected to any

  stress and shows no deformation.

  The most common materials from which braids are made are textile in nature, such as polyester, cotton, acrylic,

  viscose, rayon, polypropylene, nylon, fibranne, polyamide.

  The braids can have a substantially circular or flattened section, we then speak of "round braids" or "flat braids". They can also have a substantially hollow tube shape,

  then speaks of "tubular braids".

  To simplify, we will speak of "diameter" of the braid to designate the largest dimension of its section, even when the latter is not circular.

  To clarify the description, usual dimensions are presented

  below: the round braids have a diameter ranging appreciably from 0.5 to millimeters, the flat braids have a diameter ranging appreciably from 2 to 30 millimeters, the tubular braids have a diameter ranging appreciably from 4 to 15 millimeters. The braids are more or less elastic, the elasticity being due to the natural elasticity of the strands constituting the braid, or to the presence of an eraser in the braid, or to the assembly more or less

flexible strands.

  When a gum is present, it is essentially a natural gum of circular section and whose diameter varies appreciably from

  0.2 to 2 millimeters, depending on the desired uses.

  Those skilled in the art are used to designating by "elastic braid" a braid whose strands are elastic or include a rubber or a braid in which the weaving, knitting or braiding is very flexible. It designates by "rigid braid" a braid whose strands are not elastic, do not include gum, and whose weaving,

  knitting or braiding is very tight.

  In practice, all the braids, whether called "elastic" or "rigid", have a certain elasticity, even low, which results in particular in elongation when they are subjected to a

longitudinal traction.

  The plastic materials used to make the molded end piece of the end of the braids described above are for example polypropylene, polyamide, polyacetal, etc. Each of these materials is available in a range of hardness and / or more color or

less extensive.

  The process for overmolding a braid, in particular of a textile nature, by injection of plastic material, said braid being able to be of substantially circular section or of flattened section, said braid being able to be rigid or elastic, is characterized in that it comprises a deformation phase of the braid before the plastic injection phase. The deformation can be an elongation of the braid obtained by longitudinal tensioning of the latter. The braid being elastic, even slightly, its section decreases and its length increases when it is subjected to longitudinal traction. This deformation is preferred,

  but not exclusively, for so-called round braids.

  The deformation can also be a folding of the braid which takes place substantially around a longitudinal axis thereof. This distortion

  is preferred, but not exclusively, for so-called flat braids.

  The deformation can also be a twisting of the braid which takes place substantially around a longitudinal axis thereof. This deformation is preferred, but not exclusively, for so-called tubular braids. The deformation can finally be a combination of elongation and / or folding and / or twisting deformations, or any other deformation

  which aims to reduce at least locally the section of the braid.

  When the braid is deformed before locally injecting plastic material, the part of the braid which has received the plastic material remains frozen in its deformed state once the plastic material has cooled. On the contrary, the parts of the braid which are respectively upstream and downstream of said part having received the injected plastic material regain the dimensions of the braid at rest, due to the elasticity properties.

braid.

  According to the invention, the device for molding braids by injection of plastic material, comprising in particular: - a device for guiding the braids upstream, - an injection press, - an injection mold, equipped with a set of impressions, - an automatic drafting system after injection, a cutting device, equipped with a set of two blades, - a discharge device, is characterized in that it comprises means for deformation of the

  braids to reduce at least locally the sections of braids.

  The means for deforming the braids comprises means for positioning and / or means for guiding the braids inside.

mold footprints.

  The means of deformation of the braids comprises means of

  tensioning of the braids upstream of the injection.

  The means of deformation of the braids comprises means of

  folding of the braids, arranged inside the injection mold.

  The means of deformation of the braids comprises means of

  twisting of the braids, arranged upstream of the injection mold.

  The invention also relates to the plastic end piece disposed at at least one of the ends of the braid, obtained by injection of plastic material according to the method previously presented and / or by means of the device previously presented, as well as the braid provided

  of such a plastic tip at at least one of its ends.

  An advantage of the end piece and / or of the braid provided with said end piece according to the invention is that it has a high resistance to tearing off and

  great resistance to crushing.

  In accordance with the invention, a preferred use of the braid consists in making lengths of braid provided with a tip according to the invention at each end, and in using them as shoe laces. An advantage of the braid according to the invention for such use is that its penetration into the eyelet of the shoe is facilitated by the

presence of the nozzle.

  Another advantage is that the tip does not dissociate from the braid, unlike the usual tips of laces, which are simple

  cellulose tubes laid and / or glued around the end of the laces.

  The tip according to the invention remains integral with the braid for an indefinite period.

  The invention will be better understood on reading the detailed description

  below, with reference to the appended figures, in which: - Figures 1 and 2 illustrate a cord provided with a loop-shaped endpiece, obtained by the method of the prior art, respectively in top view and in longitudinal section; - Figures 3 and 4 illustrate a braid provided with a tip, obtained by the method according to the invention, respectively in top view and in longitudinal section; - Figure 5 illustrates a block diagram of the braid overmolding device according to the invention, seen from above; - Figure 6 is a more detailed representation of the device according to the invention, seen from above; - Figure 7 shows a clamp of the device of Figure 6; - Figures 8 and 9 show two modes of folding the braid; - Figure 10 shows a typical assembly consisting of molded parts and the carrot, seen from above; - Figure 11 shows a molded tip according to a first embodiment, in longitudinal section; - Figures 12 and 13 show the sumoulage tip according to the first variant, in cross section respectively along the plane XII-XII and along the plane XIII-XIII of Figure 11; - Figure 14 shows a molded tip according to a second embodiment, in longitudinal section; - Figures 15 and 16 show the overmolding tip according to the second variant, in cross section respectively on the plane XV-XV and the plane XVI-XVI of Figure 14; Figure 17 shows in cross section a device for

folding and a folded braid.

  As illustrated in FIGS. 1 and 2, the cords or straps 100 overmolded according to the methods of the prior art retain their section dimensions at rest over their entire length, whether in the non-

  overmolded 300 or over overmolded areas 500.

  The overmolded braid 1 by the method according to the invention, illustrated in FIGS. 3 and 4, has an overmolded zone 5, the cross section of which is

  significantly lower than that of the non-overmolded zone 3.

  The overmolding process according to the invention is implemented by means of an overmolding device 7, a schematic diagram of which is shown in FIG. 5. The braids 1 to be overmold are in the form of long lengths of braids from continuous coils around which they are wound, or cartons in

which they are found.

  The method has three main phases which take place respectively in three successive parts of the overmolding device 7: an upstream part 9, a middle part 11, a downstream part 13, the direction of advance of the braids in the overmolding device 7

being indicated by the arrow 15.

  During the first phase, the braids 1 are given, that is to say that the reels or the cartons 17 are unwound automatically, o the braids 1 being arranged parallel to each other on guide devices 19 without particular tension, then are tensioned by means of upstream tensioning devices 21, to be ready to

  receive the injection of plastic material.

  During the second phase, the actual injection of plastic material takes place around each braid 1, into an injection mold 23 by means of an injection press 25, supplied with granules of

  plastic material by a press feeder 27.

  During the third phase, an automatic pulling device 37 pulls the ends of the braids downstream and a cut of a calibrated length of each braid is made, the cut having the result of separating the molding core from the overmolded ends , and to release downstream braid segments provided with a nozzle, said segments being

then evacuated.

  The overmolding device is shown in more detail in the

figure 6.

  The braids 1, preferably 12 in number, are arranged parallel to each other, at the entrance to the upstream part 9 of the overmolding device 7. They are guided in the direction indicated by the arrow 15 by means of a upstream guide device 19, then are tensioned between upstream tensioning devices 21 and a clamping device 29 integrated in the injection mold 23. The stretching direction

is indicated by arrow 70.

  These tensioning devices are preferably clamps 21, arranged side by side, each clamp 21 holding a braid 1, as shown in FIG. 7, the clamp 21 being seen perpendicular to the direction of advance of braid 15, and braid 1

being seen in cross section.

  The braids 1 therefore appear in the injection mold in a stretched state, item 30, the deformation of the braids 1 by induced elongation.

  a decrease in their diameter, due to the elasticity of these.

  The overmolding by injection of plastic material on the braids 1 in their stretched state takes place in the middle part 11 of the overmolding device 7. The course of the injection, conventional and known from

  the skilled person is not recalled here.

  This results in a molded assembly 31, which is illustrated in an enlarged view in FIG. 10. This molded assembly comprises a molding core 33 connecting together twelve pairs of end fittings 35 overmolded on the twisted braids 1. Once the overmolding is carried out, setting devices

  tension 21 and the clamping devices 29 are deactivated.

  The third phase of the process, which takes place in the downstream part 13 of the

  device 7, comprises three successive operations.

  During a first automatic drawing operation the braids 1 are pulled, in the direction indicated by the arrow 15, by means of a downstream drawing device 37 by a distance such that the molded assembly 31 is brought to a conformator in the cutting device 39. It is possible to adjust the position of the cutting device 39 so that

  define the length of the segments 80 of the resulting braids.

  During a second cutting operation, two blades of the cutting device, placed side by side and perpendicular to direction 15, lower to separate the molding core 33 from the twelve molded end pieces 35 upstream and the twelve molded end pieces downstream that it connects, as indicated by the section lines 41 illustrated in FIG. 10. The position of the blades is adjustable, so as to adapt as desired to a variable length of the molded end pieces 35. Twelve segments 80 are obtained downstream braids 1, the upstream ends of which have molded ends 35 (FIGS. 3, 4) which have just been produced, and the downstream ends of which have molded ends

  which were made in the previous cycle of the overmolding process.

  During a third operation, the segments 80 of braids provided at their ends with overmolded ends 35 are evacuated, for example by means of an evacuation device from below (47) or by an ultimate

  pulling device (not shown).

  The cycle of the overmolding device 7 is programmed such that the cutting of the braid segments 80 of a step N is carried out at the same time as the removal of the braid segments 80 of step N-1 and in

  same time as the injection of stage N + 1.

  FIGS. 11 to 16 illustrate the molded ends 35 obtained by the method and the device 7. The ends are cylindrical and their section is defined by the impressions of the injection mold. It can for example be circular or hexagonal, as illustrated respectively in

Figures 12 and 15.

  The method according to the invention requires that there is a specific mold for each shape of end piece 35 and for each size of end piece desired. Optionally, the impressions of the injection mold 23 are provided with clamping points, the presence of which causes clamping notches 43 on the molded end pieces 35. Said notches preferably have a conical shape of circular section and are preferably in number of four, distributed in two pairs of notches facing each other. An example of preferred dimensions of the molded ends 35 obtained by the method and the device according to the invention is indicated for a round braid of diameter 5.5 mm: For the ends of circular section: diameter: D = 4.5 mm - length : L = 16 mm - angle of the chamfer at the end of the end piece: A = 135 - position of the first pair of notches from the free end of the end piece: P1 = 5 mm - position of the second pair of notches from the free end of the endpiece: P2 = 11 mm - outlet diameter of the conical notch: DS = 1.5 mm inside diameter of the conical notch: Dl = 1.25 mm - angle of the cone: AC = 5 For the end caps of hexagonal section, the dimensions are those of a hexagon inscribed in a circle of diameter D = 4.5 mm and the notches open out preferably on two opposite edges of the

hexagonal cylinder.

  A first variant of the overmolding process is implemented when the braids 1 are so-called flat or tubular braids. In this case, an alternative or additional deformation of the

  braids 1, making them undergo a folding and / or twisting.

  The deformation by folding is carried out by means of a set of twelve folding devices 45, present in the injection mold, which can have the form of forks 45, as illustrated in FIG. 17. Preferably, a folding device 45 is present on either side of the zone of the braid 1 to be overmolded. Two other examples of local folding deformation are shown

in Figures 8 and 9.

  The twisting deformation is carried out by means of a twisting device, placed just upstream of the mold. This device consists for example of a device for rotating each of the twelve clamps 21 holding the twelve braids 1. This deformation is

  indicated by arrow 60 in Figure 6.

  According to a variant (not shown), the deformation by twisting

  could take place inside the injection mold.

  The invention is not limited to the embodiments which have just been described. One could envisage an overmolding device 7 which would simultaneously treat a different number of twelve braids, for example eight or ten braids, or twenty braids. In this case, the overmolding device 7 would include a mold, guide devices, clamping devices, deformation devices and a downstream pulling device which

  would be adapted to the number of braids to be treated simultaneously.

  Braids of a non-textile nature can also be overmolded by the method and the device according to the invention, such as for example

extruded braids.

Claims (15)

  1. Method for overmolding a braid (1), in particular of a textile nature, by injection of plastic material, said braid (1) being able to be of substantially circular section or flattened section, said braid (1) being able to be rigid or elastic , characterized in that it comprises a phase of deformation of the braid (1) before the injection phase of plastic material.   2. Overmolding method according to claim 1, characterized in that the deformation is a folding which takes place substantially around a longitudinal axis of the braid (1), in a determined area inside the injection mold (23).   3. Overmolding method according to claim 1 or 2, characterized in that the deformation is a twisting of the braid (1) in a zone   determined upstream of the injection mold (23).   4. Overmolding method according to any one of claims 1   to 3, characterized in that the deformation is an elongation of the braid (1). 5. Device for overmolding of braid by injection of plastic material, comprising in particular: - an injection mold (23), - a device for guiding the braids (19), - a set of imprints inside the mold ( 23), - a set of blades, - a discharge device (), characterized in that it comprises means of deformation (21, 29,) of the braids (1) to reduce at least locally the sections of the braids (1).   6. Overmolding device (7) according to claim 5, characterized in that it comprises means for tensioning (21) the braids (1) upstream of the injection mold (23).   7. Overmolding device (7) according to claim 5 or 6, characterized in that said deformation means (21, 29, 45) comprise means for folding (45) the braids (1) inside the imprints of the mold (23).   8. Overmolding device (7) according to claim 5 or 6, characterized in that said deformation means (21, 29, 45) comprise means for twisting the braids (1) upstream of the injection mold (23) . 9. Overmolding device (7) according to any one of   Claims 5 to 8, characterized in that it comprises points of   clamping inside the cavities of the injection mold (23), which   cause notches (43) on the molded ends (35).   10. end cap of plastic material (35), intended to be disposed at the end of a braid (1), said braid (1) being able to be of substantially circular section or of flattened section, said braid (1) being able to be rigid or elastic, characterized in that it is obtained by the process   overmolding according to claims 1 to 4 and by means of the device   overmolding (7) according to claims 5 to 9.   11. overmolding end piece (35) according to claim 10, characterized in   what it has a cylindrical shape of circular section.   12. overmolding end piece (35) according to claim 10, characterized in   what it has a cylindrical shape of hexagonal section.   13. overmolding end piece (35) according to any one of   Claims 10 to 12, characterized in that it comprises two pairs   notches (43) distributed along the longitudinal direction of the nozzle (35), the two notches (43) of the same pair being diametrically opposite. 14. Braid segment (80), said braid (1) can be of substantially circular section or flattened section, said braid (1) can be rigid or elastic, characterized in that it is provided with at least one of its ends of a plastic tip (35) obtained   by the overmolding process according to claims 1 to 4 and in   means of the overmolding device (7) according to claims 5 to 9.   15. Use of a braid segment (80) provided with a piece of material   plastic according to claims 10 to 14, as a lace shoe.