Patent Publication Number: US-2022234259-A1

Title: Moulding apparatus for forming a fastening device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of and claims the benefit of priority to U.S. Nonprovisional patent application Ser. No. 16/096,838, filed on Oct. 26, 2018, which is the U.S. national phase entry under 35 U.S.C. § 371 of International Application No. PCT/FR2017/051016, filed on Apr. 28, 2017, which claims priority to French Patent Application No. 1653866, filed on Apr. 29, 2016, French Patent Application No. 1653870, filed on Apr. 29, 2016, French Patent Application No. 1653872, filed on Apr. 29, 2016, French Patent Application No. 1653873, filed on Apr. 29, 2016, French Patent Application No. 1653888, filed on Apr. 29, 2016, French Patent Application No. 1653894, filed on Apr. 29, 2016, and French Patent Application No. 1653897, filed on Apr. 29, 2016, the entireties of each of which are herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present disclosure relates to the field of retaining devices, and in particular to the field of apparatuses for fabricating retaining devices with hooks. 
     Conventional apparatuses for making closure systems comprising self-gripping elements such as hooks conventionally make use of means for dispensing a plastics material into cavities formed in a molding roller or in a molding strip. 
     Furthermore, the plastics material is distributed into the cavities in such a manner that, on the plastics material dispenser means side, the material forms a continuous tape forming a base for the hooks or the hook preforms that are molded in the cavities. 
     The plastics material may be dispensed into the cavities by pressing extruded plastics material into the cavities, e.g. by using a pressure roller, or by injecting plastics material directly into the cavities. 
     Apparatuses for fabricating retaining device with hooks are known that comprise a molding strip, which is a strip forming a closed loop and tensioned over rotary drive means, e.g. two rollers. The plastics material is injected or pressed into the cavities in the molding strip facing one of the drive rollers or facing a molding support. The drive roller or the molding support thus closes the cavities of the molding strip facing the location where the plastics material is injected or pressed so as to define a given volume of plastics material that is to form a preform for the hooks or the hooks themselves. 
     Nevertheless, in the light of economic necessities, the travel speeds of the molding strip are such that while the plastics material is being dispensed into the cavities, it is possible that each cavity (or only some of them) is/are not completely filled with plastics material and that pockets of air become trapped in the cavities. As a result, not all of the preforms or hooks are formed in optimum manner on the base, and the performance of the retaining device with hooks may be diminished. 
     OBJECT AND SUMMARY OF THE INVENTION 
     The present disclosure seeks to remedy those drawbacks, at least in part. 
     To this end, the present disclosure provides a molding apparatus for forming a retaining device, the molding apparatus comprising a molding strip and a molding support, the molding strip having an inside face, an outside face, and a plurality of through cavities extending from the outside face to the inside face, the molding strip extending in a longitudinal direction and presenting both a transverse direction perpendicular to the longitudinal direction, and also a height direction perpendicular to the longitudinal direction and to the transverse direction, the inside face being configured to press against a molding face of the molding support, wherein the inside face of the molding strip and/or the molding face of the molding support includes an array of passages, the array of passages forming vents and connecting together the cavities when the molding strip is pressed against the molding support. 
     By way of example, the molding strip is a molding strip that forms a closed loop tensioned over rotary drive means for the molding strip, e.g. two rotary drive rollers. One of the rotary drive rollers of the molding strip may act as a molding support. The molding support could equally well be distinct from the rotary drive means. 
     In the molding apparatus, the plastics material is injected into the cavities via the outside face of the molding strip, facing the molding support, i.e. while the inside face of the molding strip is pressed against the molding face of the molding support. 
     Because of the vent-forming array of passages connecting the cavities to one another when the molding strip is pressed against the molding support, i.e. when the inside face of the molding strip is pressed against the molding face of the molding support, the cavities are not completely closed during injection of the plastics material. The cavities are therefore not airtight. 
     Thus, while the plastics material is reinjected into the cavities, even when the molding strip is traveling at high speed, the plastics material injected into each cavity pushes out the air present therein to the array of passages, and the air escapes to the atmosphere via the vents formed by the array of passages between the molding strip and the molding support. Air can escape to the atmosphere via the cavities that are not full of plastics material and that are connected, via the array of passages, to cavities that are being filled. Air can also escape to the atmosphere via the sides of the strip of the molding strip. It is thus possible to fabricate retaining devices at high speeds and to reduce considerably the pressure that is needed for filling the molding cavities, and also the force that needs to be supplied for unmolding the preforms and/or hooks. 
     It can be understood that air is no longer trapped in the cavities by the plastics material, and therefore does not oppose filling of the cavities by the plastics material. Also, it is ensured that the cavities are optimally filled with the plastics material, subsequently making it possible, for example, to obtain a retaining device with hooks that presents good hooking performance with a counterpart having loops and/or a counterpart having hooks. The “suction-cup” effect during unmolding of the hooks and/or preforms is then reduced, or even eliminated. The stresses exerted on the tape during unmolding are considerably reduced. 
     The inside face of the molding strip and/or the molding face of the molding support may present a maximum roughness height Rz that is greater than or equal to 1.0 micrometer (μm), preferably greater than or equal to 3.0 μm, and less than or equal to 50.0 μm. 
     The array of passages is formed by the roughness of the inside face of the molding strip and/or by the roughness of the molding face of the molding support. This roughness serves to form vents that serve to discharge air from the cavities into which the plastics material is being injected. Nevertheless, this roughness serves to control the quantity of plastics material that can leave the cavity via the inside face of the molding strip. 
     This roughness may be obtained by sanding the inside face of the molding strip and/or the molding face of the molding support with glass paper, e.g. with glass paper having grain size lying in the range 16 to 400, and in particular 240. 
     This roughness can also be obtained by sandblasting the inside face of the molding strip and/or the molding face of the molding support. 
     This roughness may also be obtained by chemical or laser graining, by knurling, or indeed by plasma spraying. 
     The inside face may present a rim surrounding the open portion of each cavity and projecting from the inside face, the rims defining between them the array of passages, each rim possibly presenting various heights, such that when the molding strip is pressed against the molding support, at least a portion of each rim is not pressed against the molding support, such that each cavity is in connection with the atmosphere via the array of passages. 
     Since the open portion of each cavity is surrounded by a rim projecting from the inside face of the molding strip, a portion of the array of passages is formed by the inside face of the molding strip, between the rims. Furthermore, since each rim presents varying height, when the molding strip is pressed against the molding support, at least a portion of the rim is not pressed against the molding support, such that a portion of the array of passages is also formed by the rim. 
     It can be understood that the height of the rim is measured relative to the outside face of the molding strip and that this height is the maximum height of the rim, measured in a section on plane parallel to the height direction, i.e. parallel to the axis of the cavities, and passing via the cavity. 
     A maximum difference between two heights of a given rim of a cavity may be greater than or equal to 1.0 μm, preferably greater than or equal to 2.0 μm, more preferably greater than or equal to 4.0 μm, and less than or equal to 100.0 μm, preferably less than or equal to 50.0 μm. 
     Since the rim presents varying height, a plurality of maximum heights of a given rim are compared as measured in various different section planes parallel to the height direction, and a maximum difference is determined between all of those heights, this maximum difference being greater than or equal to 1.0 μm so as to form an air passage between the cavity and the remainder of the array of passages. 
     Preferably, the maximum difference is greater than or equal to 6.0 μm, more preferably greater than or equal to 8.0 μm. 
     Preferably, the maximum difference is less than or equal to 50 μm. 
     The array of passages may extend in the longitudinal direction. 
     It can be understood that when the molding strip is pressed against the molding support, the array of passages enables vents to be formed that allows air to be discharged in the longitudinal direction. It can be understood that the array of passages may be formed solely by passages that are strictly parallel to the longitudinal direction. 
     The array of passages may extend in the transverse direction. 
     It can be understood that when the molding strip is pressed against the molding support, the array of passages enables vents to be formed that allows air to be discharged in the transverse and/or the longitudinal direction. It can be understood that the array of passages may be formed solely by passages that are strictly parallel to the transverse direction. 
     The array of passages may also be formed by passages extending parallel to the longitudinal direction and passages extending parallel to the transverse direction. 
     Each cavity may define a stem extending from the outside face towards the inside face and may have a head-forming end extending away from the stem towards the inside face of the molding strip. Each cavity may also define a stem, extending between the outside face and the inside space across the entire thickness of the molding strip. 
     It is thus possible to form a retaining element presenting a stem and a head, the head being connected to the base of the tape by the stem. 
     Each cavity of the molding strip may be configured to form a preform of a retaining element. 
     Thereafter, the preform may be deformed by known means in order to form a retaining element, or as described in detail in patent application number FR 1653894, incorporated by reference. 
     The molding support may be a molding roller. 
     Thus, one of the drive rollers of the molding strip is used as a molding support. 
     The molding strip may comprise 10 cavities per square centimeter (cavities/cm 2 ) to 500 cavities/cm 2 , in particular 250 cavities/cm 2 ±75 cavities/cm 2 . 
     Each cavity may have a height in the height direction greater than or equal to 5.0 μm, preferably greater than or equal to 20.0 μm, still more preferably greater than or equal to 100.0 μm, and less than or equal to 5000.0 μm, preferably less than or equal to 800.0 μm, still more preferably less than or equal to 500.0 μm. 
     When the cavities are not surrounded by respective rims, the height of the cavity is measured between the inside and outside faces of the molding strip, e.g. relative to two midplane surfaces defining each face. 
     When the cavities are surrounded by respective rims, the height of the cavity is measured from the outside face of the molding strip and relative to the highest point of the rim measured in a section plane parallel to the height direction, i.e. parallel to the axis of the cavity, and contained in the cavity. 
     The molding strip may comprise a material based on nickel. 
     Nickel makes it possible in particular to form the continuous endless or “looped” molding strip as a single piece made entirely of nickel. The molding strip therefore does not present any material discontinuity and thus any junction that might give rise to weakness in the molding strip. Specifically, if the molding strip is welded to form a loop, the weld zone is a zone of weakness in the molding strip. 
     The term “material based on nickel” is used to cover materials in which the mass content of nickel is in the majority. It can be understood that nickel is thus the element having the highest mass content in the material. By way of example, the nickel-based material is a metal alloy based on nickel having a mass content of at least 40% nickel, preferably at least 60% nickel, still more preferably at least 80% nickel. 
     The molding strip may also be made of nickel-plated steel, i.e. the molding strip is made from a strip of steel having the cavities perforated therein, and subsequently the strip of steel is covered in a plurality of layers of nickel, e.g. by electroplating. 
     This molding strip made out of nickel-plated steel comprises 5% to 20% by mass of nickel. 
     The molding strip may be obtained by an additive manufacturing method, e.g. by chemical or electrochemical deposition, by sintering a powder by laser, by lithography, by galvanoplasty, by electroforming, . . . . 
     In the longitudinal direction, the molding strip may present a length lying in the range 0.5 meters (m) to 5 m. 
     In the transverse direction, the molding strip may present width lying in the range 5 millimeters (mm) to 3000 mm. 
     Each cavity may present symmetry of rotation about an axis parallel to the height direction. 
     A retaining element or preform is thus formed that presents symmetry of rotation about an axis perpendicular to the base of the tape. It can be understood that during unmolding of the tape, the retaining elements or the preforms may be deformed plastically so that they no longer present symmetry of rotation after unmolding. 
     A portion of the array of passages surrounding at least one of the cavities may present a shape that is substantially hexagonal 
     This hexagonal shape makes it possible to arrange the cavities relative to one another in a “honeycomb” or staggered configuration. This arrangement of cavities makes it possible to achieve a dense arrangement of retaining elements. 
     A different maximum between the height of at least one of the rims and the height of a passage adjacent to said rim may be less than or equal to 100.0 μm. 
     Preferably, a different maximum between the height of at least one of the rims and the height of a passage adjacent to said rim may be less than or equal to 75.0 μm, still more preferably less than or equal to 50.0 μm. 
     The height of a passage is measured from the outside face of the molding strip, at the point presenting the minimum passage height when the passage height is measured in various different section planes parallel to the height direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other characteristics and advantages of the invention appear from the following description of embodiments of the invention given as non-limiting examples and with reference to the accompanying figures, in which: 
         FIG. 1  is a diagrammatic cross-section view of a molding apparatus for forming a retaining device; 
         FIG. 2  is a diagrammatic cross-section view of another molding apparatus for forming a retaining device: 
         FIG. 3  is a diagrammatic view of the inside face of a molding strip in a first embodiment of the molding strip; 
         FIG. 4A  is a cross-section view of the molding strip centered on the cavity in section plane IV-IV of  FIG. 3 ; 
         FIG. 4B  is a sectional view of the molding strip centered on the cavity in section plane IV-IV of  FIG. 3 , with the molding strip pressed against the molding support; 
         FIG. 5  is a diagrammatic view from above of the inside face of a molding strip in a second embodiment of the molding strip; 
         FIG. 6A  is a partial cross-section view in perspective showing the molding strip in section plane VI-VI of  FIG. 5 ; 
         FIG. 6B  is a sectional view of the molding strip centered on the cavity in section plane VI-VI of  FIG. 5 , with the molding strip pressed against the molding support; 
         FIG. 7A  is a partial cross-section view in perspective of the molding strip in section plane VII-VII of  FIG. 5 ; 
         FIG. 7B  is a sectional view of the molding strip centered on the cavity in section plane VII-VII of  FIG. 5 , with the molding strip pressed against the molding support; 
         FIG. 8  is a partial cross-section view of a cavity in another embodiment of the molding strip, with the molding strip pressed against the molding support; and 
         FIG. 9  is a sectional view of another embodiment of the molding support with the molding strip pressed against the molding support. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a diagrammatic cross-section view of a molding apparatus  10  for forming a retaining device. Said molding apparatus  10  comprises a molding strip  12  forming a closed loop and having an inside face  14 , an outside face  16 , and a plurality of through cavities  18  extending from the outside face  16  to the inside face  14 . 
     The molding strip  12  is tensioned over means for imparting rotary drive to the molding strip  12 , e.g. two rotary drive rollers  20  and  22 . One of the rotary drive rollers  20  for the molding strip  12  may act as a molding support  24 . In particular, only one of the two rollers needs to be driven in rotation by motor-drive means, e.g. the roller  20 , while the other roller  22  is idle (without motor-drive means) and is driven in rotation by the molding strip, itself being driven by the roller  20 . 
     The molding support  24  has a molding face  26  that is to press against the inside face  14  of the molding strip  12 . The inside face  14  of the molding strip  12  presses against the rotary drive rollers  20  for driving the molding strip  12 . 
     The molding apparatus  10  also has a dispenser device  28  for dispensing the plastics material  30  into the cavities  18  of the molding strip  12 . In  FIG. 1 , the dispenser device  28  for dispensing a material, e.g. a plastics material  30 , is arranged on the outside face  16  side of the molding strip  12 , facing the molding support  24 , i.e. the plastics material  30  is dispensed into the cavities  18  of the molding strip while the inside face  14  of the molding strip  12  is pressed against the molding face  26  of the molding support  24 . 
     For example, the dispenser device  28  may be a plastics material injector head. The plastics material injector head (or extruder head) has an opening of width in the transverse direction that is less than or equal to the width in the transverse direction of the molding strip  12 . 
     In  FIG. 1 , the dispenser device  28  is arranged at a certain distance from the outside face  16  of the molding strip  12  so as to form a gap  32  between the molding strip  12  and the dispenser device  28 . 
     While dispensing plastics material  30  into the cavities  18  of the molding strip  12 , a base  34  is also formed on the outside face  16  of the molding strip  12  so that, after unmolding, a tape  36  is formed comprising a base  34  having a plurality of retaining elements  38  or a plurality of retaining element preforms thereon. 
     The molding apparatus  10  also has an unmolding roller  40 . By way of example, the unmolding roller  40  may be configured to separate the base  34  of the tape  36  from the molding strip  12  under the effect of the tension of the tape  36  and of its change in direction. The unmolding roller  40  may be a suction roller and may have a rubber coating in order to make unmolding easier. 
     It should be observed that the molding apparatus  10  may also have a device for removing excess plastics material, such as a scraper  42  arranged in the example of  FIG. 1  on the inside face  14  side of the molding strip  12  and after the molding support  24  in the travel direction of the molding strip  12 . It can thus be understood that the scraper  42  is arranged after the dispenser device  28 . 
       FIG. 2  is a diagrammatic cross-section view of another molding apparatus  10  for forming a retaining device. 
     Below, elements that are common to the various embodiments are identified by the same reference numbers. 
     The molding apparatus  10  of  FIG. 2  differs from the molding apparatus  10  of  FIG. 1  in that, in  FIG. 2 , the molding support  24  is distinct from the rotary drive rollers  20  of the molding strip  12 . 
     The longitudinal direction X is defined in the travel direction of the molding strip  12 , the transverse direction Y is perpendicular to the longitudinal direction X, and the height direction Z is perpendicular to both the longitudinal direction X and the transverse direction Y. The XY plane defines a plane of the molding strip  12  between the two rotary drive rollers  20 ,  22  of the molding strip. 
     In the longitudinal direction, the molding strip  12  may present a length (or perimeter) lying in the range 0.5 m to 5 m when the molding strip  12  is cut and laid out flat. 
     In the transverse direction, the molding strip  12  may present a width lying in the range 5 mm to 3000 mm. The width of the molding strip  12  may be equal to 50 mm, 100 mm, or 200 mm, for example. 
     The molding strip  12  may also have 10 cavities/cm 2  to 500 cavities/cm 2 . By way of example, the molding strip  12  may have 250 cavities/cm 2 ±75 cavities/cm 2 . 
       FIG. 3  is a view of the inside face  14  of a molding strip  12 . This molding strip  12  has cavities  18  and it presents a maximum roughness height Rz of 3.23 μm measured in compliance with the ISO 4287 and ISO 4288 standards. This roughness has been measured along the profile  44 . Furthermore, along a given profile  44 , the arithmetical mean deviation Ra of the roughness profile is 532.21 nanometers (nm), likewise measured in compliance with the ISO 4287 and ISO 4288 standards. This roughness is obtained by sanding the inside face  14  of the molding strip  12  with glass paper, e.g.  240  grain glass paper. The sanding of the inside face  14  creates polishing scratches forming an array of passages  46  in the inside face  14  of the molding strip  12 . 
     In  FIG. 3 , each cavity  18  presents symmetry of rotation about an axis C parallel to the height direction Z. 
     In  FIG. 3 , it can be seen that the cavities  18  are in alignment along the longitudinal direction X and form a plurality of rows in the longitudinal direction X. In the embodiment of  FIG. 3 , the cavities  18  of a row are spaced apart from one another by a pitch P 1 , the pitch P 1  being measured between the axes C of two immediately adjacent cavities  18  in the same row. Two immediately adjacent rows are spaced apart from each other by a pitch P 2 , the pitch P 2  being measured in the transverse direction, and the cavities of two rows being offset from one another in the longitudinal direction by one-half of the pitch P 1 , i.e. by the pitch P 1  divided by 2, also written P 1 / 2 . This offset value is not limiting in any way. In the example of  FIG. 3 , the pitch P 1  is strictly greater than the pitch P 2 . 
       FIG. 4A  is a partial cross-section view of the molding strip  12  centered on the cavity  18 , shown in section on section plane IV-IV of  FIG. 3 . This section plane IV-IV is parallel to the ZY plane and contains the axis C of the cavity  18 . The molding strip  12  presents an outside face  16  and an inside face  14 . The inside face  14  presents roughness as defined above. The height H 1  of the cavity  18  as measured in the height direction Z is measured relative to two midplane surfaces each defining one of the faces, and in the present example between the outside face  16  of the membrane and an imaginary surface  48  represented in  FIG. 4A  by a midplane of the inside face  14 . 
     In the height direction Z, each cavity  18  has a height H 1  that is greater than or equal to 5.0 μm, preferably greater than or equal to 20.0 μm, still more preferably greater than or equal to 100 μm, and less than or equal to 5000.0 μm, preferably less than or equal to 800.0 μm, still more preferably less than or equal to 500.0 μm. 
     The cavity  18  has a first portion  18 A defining a stem of the retaining element  38  and a second portion  18 B forming one end of the cavity  18  that extends from the stem towards the inside face  14  of the molding strip  12  for forming a head (or a preform) of the retaining element  38 . The first portion  18 A defining the stem may be of cylindrical or frustoconical shape. For example, the first portion  18 A may present a diameter that decreases on going away from the outside face  16  and towards the inside face  14 . The second diameter  18 B forming the head typically extends radially or transversely relative to an axis parallel to the axis of the stem, i.e. parallel to the height direction. In particular, the diameter of the head becomes larger on going away from the portion  18 A towards the inside face  14  of the molding strip  12 . More particularly, the head is substantially frustoconical in shape. In a variant, it is possible to envisage forming a head that presents the shape of a hexahedron. In a variant, it is also possible to envisage that the cavity presents at least a portion of a rotary hyperboloid or hyperboloid of revolution. 
     The roughness of the inside face  14  of the molding strip  12  forms the array of passages  46 , the array of passages  46  forming vents  50  and connecting together the cavities  18  when the molding strip  12  is pressed against the molding support  24 , i.e. when the inside face  14  of the molding strip  12  is pressed against the molding face  26  of the molding support  24 , as shown in  FIG. 4B . 
       FIG. 5  is a view of the inside face  14  of a molding strip  12  in another embodiment of the molding strip  12 . This molding strip  12  has cavities  18 . As in the embodiment of  FIG. 3 , cavities  18  can be seen in  FIG. 5  that are aligned in the longitudinal direction X so as to form a plurality of rows in the longitudinal direction X. In the embodiment of  FIG. 5 , the cavities  18  of a row are spaced apart from one another at a pitch P 1 , the pitch P 1  being measured between the axes C of two adjacent cavities  18  in the same row. Two immediately adjacent rows are spaced apart from each other by a pitch P 2 , the pitch P 2  being measured in the transverse direction, and the cavities of two rows are offset from one another in the longitudinal direction by one-half of the pitch P 1 , i.e. by a pitch P 1  divided by 2, also written P 1 / 2 . Although identified by the same numerical references, it can be understood that the pitches P 1  and P 2  may differ between the embodiment of  FIG. 3  and the embodiment of  FIG. 5 . Thus, in the example of  FIG. 5 , the pitch P 1  is strictly greater than the pitch P 2 . 
     It should be observed that the array of passages  46  formed between the rims  52  includes a portion  64  of the array of passages  46  that surrounds a cavity  18  and that is substantially hexagonal in shape. More particularly, it is the bottom of the array of passages  46  surrounding a cavity  18  that presents this substantially hexagonal shape. 
     In  FIG. 5 , the inside face  14  of the molding strip  12  presents a rim  52  surrounding an open portion of each cavity  18  and projecting from the inside face  14  of the molding strip  12 . 
     In  FIG. 5 , each cavity  18  presents symmetry of rotation about an axis C parallel to the height direction Z. Nevertheless, the rim  52  need not present symmetry of rotation. 
     Thus, like the rim  52  projecting from the inside face  14  of the molding strip  12 , a portion of the array of passages  46  is formed by the inside face  14  of the molding strip  12  between the rims  52 . Furthermore, since each rim  52  presents varying heights HR 1 , HR 2 , HR 3 , and HR 4 , when the molding strip  12  is pressed against the molding support  24 , at least a portion of the rim  52  does not press against the molding support  24 , such that a portion of the array of passages  46  is also formed by a portion of the rim  52 . The area of the molding strip pressed against the face of the molding support is strictly less than 100% (not taking account of the area of the cavities), and more particularly less than 98%. The pressed area is greater than 5%. In certain embodiments, the area of the molding strip pressed against the face of the molding support lies in the range 15% to 45%. In certain embodiments, the area of the molding strip pressed against the face of the molding support lies in the range 55% to 90%. 
     As shown in  FIGS. 6A, 6B, 7A, and 7B , each rim  52  presents varying heights HR 1 , HR 2 , HR 3 , and HR 4 . These heights are measured relative to the outside face  16  of the molding strip  12 . Furthermore, these heights HR 1 , HR 2 , HR 3 , and HR 4  are the maximum heights of the rims  52  measured in a section plane parallel to the height direction Z, i.e. parallel to the axis C of the cavities  18  and passing via the cavities  18 . Preferably, the section plane contains the axis C. Specifically, in the section plane, in a section view, the rim  52  presents a maximum height. 
     In the height direction Z, each cavity  18  has at least one height HR 1 , HR 2 , HR 3 , or HR 4  that is greater than or equal to 5.0 μm, preferably greater than or equal to 20.0 μm, still more preferably greater than or equal to 100.0 μm, and less than or equal to 5000.0 μm, preferably less than or equal to 800.0 μm, still more preferably less or equal to 500.0 μm. 
     In the embodiment of  FIG. 5 , the rim  52  presents two maxima  54 ,  56  and two minima  58 ,  60 , the two maxima  54 ,  56  being separated by a minimum and the two minima  58 ,  60  being separated by a maximum. Thus, when going around the rim  52 , along the line of maximum heights  62 , i.e. the succession of maximum heights of the profile as measured in a section plane of the cavity  18 , a first maximum  54  is crossed and then a first minimum  58  prior to crossing a second maximum  56  and then a second minimum  60  in order to return to the first maximum  54 . 
     In the example of  FIGS. 5, 6A, 6B, 7A, and 7B , the maxima  54  and  56  correspond respectively to the heights HR 1  and HR 2 , and the minima  58  and  60  correspond respectively to the heights HR 3  and HR 4 . 
     In the examples of  FIGS. 5, 6A, 6B, 7A, and 7B , the height HR 1  of the first maximum  54  is different from the height HR 2  of the second maximum  56 . Likewise, the height HR 3  of the first minimum  58  is different from the height HR 4  of the second minimum  60 . 
     For example, a maximum difference between two heights of a given rim  52  of a cavity  18  may be greater than or equal to 1.0 μm, preferably greater than or equal to 2.0 μm, still more preferably greater than or equal to 4.0 μm and less than or equal to 100.0 μm, preferably less than or equal to 50.0 μm. For example, if it is considered that HR 1  is greater than HR 2  and that HR 3  is greater than HR 4 , the maximum difference is measured between HR 1  and HR 4  and may for example be equal to 14.0 μm. 
     Thus, since the rim  52  presents varying height, comparisons are made between a plurality of maximum heights of a given rim  52 , i.e. the maximum heights of the rim  52  measured in various different section planes parallel to the height direction, in other words, the height of the rim  52  taken along the line  62  of maximum heights. A maximum difference between all of these heights is determined, which maximum difference is greater than or equal to 1.0 μm, for example, so as to form an air passage between the cavity  18  and the remainder of the array of passages  46 . 
     It should also be observed that a maximum difference between the height of at least one of the rims  52  and a height HP of a passage  46  adjacent to said rim  52  is less than or equal to 100.0 μm, e.g. equal to 35.0 μm. 
     It can be seen that the rim  52  has a plateau  66  at the maximum  54 . In  FIG. 5 , the plateau  66  is substantially oblong in shape and presents a direction in the longitudinal direction of about 150.0 μm and a dimension in the transverse direction of about 45.0 μm. 
     While the molding strip  12  is in use, the dimensions of these plateaus  66  tend to increase as a result of friction wear between the molding strip  12  and the molding support  24 . Thus, on a new molding strip  12 , these plateaus  66  need not be present or may be present only on one of the maxima of the rim  52 . Thereafter, as a result of repeated contacts between the molding strip  12  and the molding support  24  and/or the rotary drive rollers  20 ,  22  for driving the molding strip  12 , the plateaus  66  may become present at all of the maxima of the rim  52  and their dimensions may vary from one rim to another and over time. 
       FIG. 8  is a fragmentary view in section and in perspective of a cavity  18  in another embodiment of the molding strip  12 , the molding strip  12  being pressed against the molding support  24 . 
     In the example of  FIG. 8 , the rim  52  that surrounds the cavity  18  and that projects from the inside face  14  of the molding strip  12  presents a line  62  of maximum heights comprising a succession of maxima and minima, such that when the molding strip  12  is pressed against the molding support  24 , the cavity  18  is in connection with the atmosphere and with the other cavities via the array of passages  46  forming vents  50 . 
       FIG. 8  may also represent a molding strip  12  in which the rim  52  that surrounds the cavity  18  and that projects from the inside face  14  of the molding strip  12  presents a line  62  of maximum heights that is substantially constant, i.e. the height HR measured from the outside face  16  are substantially equal, presenting a maximum roughness height Rz greater than or equal to 1.0 μm, and preferably greater than or equal to 3.0 μm and less than or equal to 50.0 μm. 
       FIG. 9  shows an embodiment of the molding apparatus  10  in which the molding support  24  presents a maximum roughness height Rz greater than or equal to 1.0 μm, preferably greater than or equal to 3.0 μm, and less than or equal to 50.0 μm. 
     In the embodiment of  FIG. 9 , the molding strip  12  does not have a rim. Nevertheless, it is possible to envisage combining the molding support  24  of  FIG. 9  with any one of the embodiments of the molding strip described above. 
     Thus, the inside face  14  of the molding strip  12  could equally well present a maximum roughness height Rz greater than or equal to 1.0 μm, preferably greater than or equal to 3.0 μm, and less than or equal to 50.0 μm, and/or the molding strip  12  could present rims  52  surrounding each of the cavities  18 . 
     Although the present disclosure is described with reference to a specific embodiment, it is clear that various modifications and changes may be made to these embodiments without going beyond the general ambit of the invention as defined by the claims. Also, individual characteristics of the various embodiments mentioned can be combined in additional embodiments. Consequently, the description and the drawings should be considered in a sense that is illustrative rather than restrictive. For example, the molding apparatus  10  of  FIGS. 1 and 2  has two rotary drive rollers  20  for the molding strip  12 , but it could have three. It can be understood that the number of rollers and the way they are arranged is not limiting. The number of rollers and the way they are arranged may be varied in order to adapt to the length of the molding strip  12  and/or to various configurations of stations of the molding apparatus  10 . For example, the rotor  22  could also be provided with motor-drive means, like the roller  20 . Furthermore, the pitch P 1  could be equal to the pitch P 2 , the pitch P 1  could be strictly less than the pitch P 2  when a rim surrounds each cavity, and conversely, when the inside face  14  of the molding strip  12  does not present any rims surrounding the cavities  18 , the pitch P 1  could be strictly greater than the pitch P 2 . It is also possible to envisage that two rows, taken in the longitudinal direction and that are immediately adjacent to each other, could be offset from each other in the longitudinal direction by a pitch that is different from one-half of the pitch P 1 . In the examples of  FIGS. 5, 6A, 6B, 7A, and 7B , the rim  52  presents two maxima and two minima. These examples are not limiting. 
     It should also be observed that the figures are not reproduced to scale. Thus, for better understanding, certain details have voluntarily been enlarged so that they can be shown. 
     In one embodiment, the molding strip is made of nickel and has a nickel content greater than 90%. It is equally possible to envisage using strips made of copper, brass, or metal alloys. Furthermore, it is equally possible to envisage using molding strips made of steel only and that are perforated, e.g. molding strips made of stainless steel. It is also possible to envisage making the molding strip out of an optionally reinforced organic material, e.g. a molding strip based on rubber or a molding strip made of epoxy carbon or a woven or knitted textile belt or indeed a woven or knitted metal textile belt. 
     In this example, the retaining device with hooks is made out of a plastics material. The term “plastics material” is used to mean a thermoplastic material, more particularly a polyolefin material based on a homopolymer or a copolymer. 
     By way of example, the following list of plastics materials: linear low density polyethylene (LLDPE), low density polyethylene (LDPE), metallocene polyethylene (m-PE), high-density polyethylene (HDPE), ethylene vinyl acetate (EVA), et polypropylene (PP), having a molecular weight distribution that is monomodal or multimodal (e.g. bimodal), in particular a composition comprising LLDPE and a plastomer, in particular a plastomer based on polyethylene. It would also be possible to use polyimide (PA), polylactic acid (PLA), polyhydroxyalkanoates (PHA), polyvinyl alcohols (PVOH), polybutadiene styrene (PBS). 
     Various systems and methods compatible with the present disclosure are described in patent applications FR 16/53866, FR 16/53870, FR 16/53872, FR 16/53873, FR 16/53888, FR 16/53894 and FR 16/53897, which are incorporated in full by reference in this description.