Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C33/00—Moulds or cores; Details thereof or accessories therefor
  • B29C33/38—Moulds or cores; Details thereof or accessories therefor characterised by the material or the manufacturing process
  • B29C33/3828—Moulds made of at least two different materials having different thermal conductivities
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C33/00—Moulds or cores; Details thereof or accessories therefor
  • B29C33/38—Moulds or cores; Details thereof or accessories therefor characterised by the material or the manufacturing process
  • B29C33/40—Plastics, e.g. foam or rubber
  • B29C33/405—Elastomers, e.g. rubber
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
  • B29C43/02—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of definite length, i.e. discrete articles
  • B29C43/10—Isostatic pressing, i.e. using non-rigid pressure-exerting members against rigid parts or dies
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
  • B29C43/32—Component parts, details or accessories; Auxiliary operations
  • B29C43/36—Moulds for making articles of definite length, i.e. discrete articles
  • B29C43/42—Moulds for making articles of definite length, i.e. discrete articles for undercut articles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2001/00—Articles provided with screw threads
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2023/00—Tubular articles
  • B29L2023/20—Flexible squeeze tubes, e.g. for cosmetics

Definitions

• the invention relates to a method of manufacturing by compression molding of plastic parts having a neck provided with a dispensing orifice. These parts are containers or parts of molded containers.
• the invention is more particularly intended for the conditions of production in high rates of molded objects which have an axisymmetric neck delimiting a substantially circular orifice, for example flexible plastic tube heads, comprising a neck provided with a orifice. distribution and a shoulder connecting said neck to a flexible cylindrical skirt.
• flexible tube heads comprising a neck provided with a orifice. distribution and a shoulder connecting said neck to a flexible cylindrical skirt.
• a flexible tube is produced by assembling two parts manufactured separately: a cylindrical flexible skirt of given length (typically 3 to 5 times the diameter) and a head comprising a neck provided with a dispensing orifice and a shoulder connecting said neck with cylindrical skirt.
• the head of plastic material (s) can be molded separately and then welded to one end of the skirt, but the latter is advantageously molded and welded autogenously to the skirt using either an injection molding technique (FR 1 069414) or a compression molding technique for an extruded blank (FR 1 324471.
• the skirt is fitted around a punch, one of its ends protruding slightly from the end of the punch, said punch end serving as a mold for producing the internal surface of the tube head (inside of shoulder and neck).
• a matrix is used which is pressed against the end of the punch, the imprint of this matrix defining the outer surface of the shoulder and the neck.
• the blank is brought to an appropriate temperature and placed in the space between two moving parts of the compression tooling then is compressed by mutual approximation of the moving parts of the tooling.
• the mass of the blank whose shape typically obtained by extrusion is far from the final shape, undergoes significant plastic deformation.
• the plastic material flows so as to fill the cavities of the impressions of the mobile parts until relative immobilization of said mobile parts.
• Said imprints when the movable parts of the tool are joined, delimit the volume of the plastic part provided with its neck, in this case the tube head.
• said imprints are drawn so that the neck, once molded, has a top wall which has a notch whose contour delimits the desired shape of the dispensing orifice.
• the moving parts of the compression molding tool are a punch - whose imprint at least partially defines the interior surface of the head of the tube - and a die - whose imprint defines at least partially the outer surface of the tube head.
• the notch made has a section through a diametral plane passing through the axis of the neck which, typically in V or U, is oriented in a direction substantially parallel to the axis of the neck, in that it is made a slight angle with said axis, typically between 0 and 45 °, preferably between 0 ° and 30 °.
• the top wall of the neck has a small residual thickness and constitutes a more fragile zone, which we will call hereinafter rupture zone or even breakable zone.
• the breakable zone is, by the very presence of the notch, thinner than the neighboring zones.
• the residual thickness under the notch is less than 30% of the overall thickness of the transverse wall outside the notch.
• it is between 0.1 and 0.6 mm. As it is thin, it cools faster than the other parts of the neck, which makes it possible to apply forces causing the rupture less brutal than shocks, that is to say with forces generating deformation rates of the order of 10 3 s -1 .
• the small thickness of the breakable zone causes a delicate problem because it is necessary to adjust in an extremely fine way the air gap existing at the end of the travel between the mobile parts of the tool, in particular in the vicinity of the cavity used to shape the breakable zone. .
• a compression tooling comprising a first movable part and a second movable part, said first movable part being, at least in the part of the imprint contributing to the shaping of said breakable zone, in a less rigid material than that of said second movable part.
• the combination of the two materials - one metallic, the other less rigid, typically a plastic material - allows contact between the two molding parts without risk of damage to one of them. It is thus possible to limit the fine adjustment of the air gap (reduction of the adjustment time) and reduce the risk of deterioration of the tools.
• an insert made of a less rigid material than that of the other mobile part may for example be a plastic insert placed in a cavity provided for this purpose in the imprint of a movable part of the molding tool. It is also possible to equip the impression of one of the movable parts of the compression tool with the plastic plug intended to close the dispensing orifice and use this plug as part of the molding tool, at least for as regards the shaping of the part of the neck which comprises the breakable zone.
• a cavity is formed in the matrix and this cavity is filled with a plug intended to close the dispensing orifice.
• the stopper is placed in such a way that its internal surface at least partially serves as a molding imprint for shaping said neck, at least at its breakable zone.
• the blank is thus compressed between a punch and a die, the latter being fitted with a plug and a direct overmolding is carried out by compression of this part of the neck on the plug.
• the fineness of adjustment of the air gap is limited to the level of the breakable zone and the risk of deterioration of the tools can be easily reduced (mechanical stop on the cap, stop of the tools on the shoulder in the event of a defect in the presence of the cap, etc.).
• a part having a neck provided directly with its cap with contacting surfaces which correspond perfectly, which ensures a hermetic closure of the container throughout the duration of its use.
• the cavity formed in the matrix can be designed so as to fully support the plug during compression, so that said plug does not deform under the effect of compression forces. Conversely, it is possible to design the cavity in such a way that the plug meets only local support and that it deforms elastically during the compression of the blank by imposing a given shape on the external surface of the neck. The latter, once stabilized, is, at least locally, prestressed by a part of the plug which tends to return to its initial shape when the compression forces are no longer applied. After removing the part + cap assembly from the mold, the cap shrouds and / or encloses the neck, which reduces the risk of unscrewing after shaping the head.
• the part of the stopper concerned by the lack of support can be for example the bottom of the stopper: the depression of the bottom causes a general deformation of the stopper which results mainly in a longitudinal extension of the side wall. The latter shrinks longitudinally when the stresses are relaxed and traps the reliefs (typically the screw thread (s), the snap-on bead (s), etc.) produced on the external wall of the neck .
• the reliefs typically the screw thread (s), the snap-on bead (s), etc.
• the part of the stopper affected by the lack of support can also be the side wall of the stopper: by drawing the stopper and the cavity appropriately (the side wall is not supported by the matrix on a large part of its surface but it must still ensure the centering of the plug), the compression forces result in a local expansion of the side wall. The compression force is maintained until the plastic material of the neck is stabilized. Then the compression force is released and the side wall of the cap retracts by "fretting" the neck.
• the cavity formed in the matrix can for example have a cylindrical part towards the bottom to ensure the centering of the stopper and a conical part widening towards the surface of the impression: the hooping which will result will be more intense at the base of the neck.
• the clamping force resulting from this local hooping substantially proportional to the value of elastic deformation of the part of the cap concerned, makes it possible to ensure the anti-unscrewing of the cap after shaping the head, which presents an alternative solution. or complementary to the installation of a grain of rice at the end of the fillet.
• the example presented below shows the shaping of a tube head provided with a neck by overmolding on a plug according to a process which is adapted from a process described in example 4 of the international application.
• PCT / FR02 / 00686 filed by the applicant.
• the breakable zone is shaped using a molding part which has the shape of a toric edge and this toric edge belongs either to the male tool (punch), or to the plug.
• the rupture is made on the external surface but the risk of appearance of burr is low since the steel toric edge makes it possible to impose sharp angles, therefore a high coefficient of multiplication of the stresses prevailing in the area breakable during rupture.
• the top wall is not necessarily a wall of constant thickness. It can have different parts, some of which can be massive, but it has at least one part that acts as a wall blocking the dispensing orifice.
• the molded part according to the invention has a neck which is not immediately provided with an orifice: the latter is produced in a subsequent step after the first unscrewing of the plug. In this way, the compression can be carried out from a blank which is not necessarily toroidal, with a massive shape which is easier to handle and which also has the following advantages: on the one hand, it is easier to obtain in a reproductive manner by weight (improvement in compression molding conditions) and on the other hand it is subject to less intense, less rapid and less heterogeneous cooling.
• the amount of material thus obtained depends on the displacement perpendicular to the direction of extrusion of a blade of shearing external to the die and not the displacement of a sliding valve in the axial direction inside the die and having to seal discontinuously an annular orifice.
• the neck is surmounted by a top wall which closes the orifice and part of which - the cover - is partially or entirely detached later.
• the top wall comprises at least four zones: a zone for applying mechanical force, a zone for transmitting mechanical force intended to be applied to cause tearing of the rupture zone, a zone breakable and a support area.
• the breakable zone is notched with a notch, the section of which by a diametral plane passing through the axis of the neck has a shape typically in U or in V oriented in a direction slightly inclined with respect to the axis of the neck.
• the bisector of the V is slightly inclined relative to the axis of the neck and describes a cylinder or a cone having an angle at the center less than 90 °, preferably less than 60 °.
• said bisector makes an angle between 0 and 45 °, preferably between 0 ° and 30 ° with the axis of said neck.
• the angle of the V is between 30 and 90 °, typically between 40 and 50 °.
• the V does not necessarily have its branches symmetrically around its bisector.
• the desired orifice is simply circular and the breakable zone is an annular notch whose section is a V whose internal branch (that is to say the branch closest to the axis) is slightly inclined by relative to the axis and whose outer branch is more strongly inclined.
• the internal branch of the V makes an angle with the axis less than 5 °
• the bisector makes an angle of 25 ° with the axis of the neck
• the external branch makes with said axis an angle less than 55 °.
• the shape of the cut locally promotes a concentration of the stresses generated by the application of a mechanical force, whether this is a force or a moment applied in a particular place of the cover.
• the transverse wall may be of small extent, for example limited to the breakable zone, but it must be present to orient the notch so that its axis is substantially parallel to that of the neck.
• the rupture of the cover can be carried out subsequently by the user.
• the molding impressions are drawn so that the cover - that is to say the part of the transverse top wall of the neck which is surrounded by the breakable zone - obtained comprises a protuberance in counter skin which is anchored in the cork.
• a slight relief such as a grain of rice, can be provided at the end of the screw thread.
• the undercut protrusion can also pass through the thickness of the stopper: in this way, the material is somehow extruded through the stopper and can be used to fill the top of the stopper. While using the same standard plug base, we therefore integrate a decor personalized on the top of the cap, for example the brand of the packaged product, the logo of the manufacturer of the said product, etc.
• FIGURES The figures represent diametrical sections of tube heads, parts of the compression molding tool or plugs.
• FIG. 1 illustrates the device before overmolding by compression of the tube head on the plug.
• FIG. 2 illustrates the device after overmolding by compression of the tube head on the stopper
• Figures 3, 5 and 7 illustrate the parts of the tooling provided with the toric edge which makes it possible to shape the breakable zone ( Figure 3: punch; Figures 5 and 7: plug)
• Figures 4, 6 and 8 detail the assembly of the tube head + plug obtained after overmolding.
• EXAMPLE Figures 1 to 8
• the molding of the neck on the cap is carried out by adapting the method described in Example 4 of international application PCT / FR02 / 00686 filed by the applicant. In this process, it is a matter of making a flexible tube.
• the tube head is molded and welded to a cylindrical skirt obtained by cutting from a sleeve. In this particular case, the head is welded to the skirt simultaneously with its shaping by compression molding.
• a plug 805 which is placed in a central cavity of the matrix 830.
• this plug may have itself been molded shortly before using the same matrix but it can also have been obtained independently on another molding device. Outside this cavity, the imprint has a shape which defines the outside surface of the shoulder 82 of the tube.
• the internal surface of the plug 805 defines the external surface of the neck 83 and of the base of the neck.
• the punch 835 is provided with a skirt 801, the end 802 of which protrudes slightly from the shoulder 846 of the punch.
• the stopper 805 has an average thickness of 1 mm.
• the internal surface of the plug possibly provided with one or more screw threads, defines the external surface of the neck to be shaped.
• the part of the imprint of the matrix 830 not covered by the stopper defines the outer surface of the shoulder.
• the matrix 830 acts as a support tool.
• a blank 820 made of low density polyethylene is taken from the extruder outlet and is deposited on the tooling. This deposit can be made either on the end of the punch or in the imprint of the die 820. It is advantageous to place this blank 820 on the end of the punch 835, for example above the protruding part of the punch 835 , this one being then presented "head up", opposite to what is illustrated in FIG. 1. In such a configuration, the part of the blank which comes into contact with the punch cools - by conduction - a little faster than the rest of the draft and will flow little. The surface imperfections related to the greater cooling of the plastic material at this location, the friction and the heterogeneous flow of the resulting material will remain on the seal which will then be detached. They will therefore not see each other.
• the blank 820 is compressed by bringing the punch and the matrix together until the target shape of the head is obtained. Under the effect of this translation, the blank 820 is deformed and the flow of the plastic is guided by the free surfaces of the residual air gap which gradually decreases in volume.
• the punch 835 and the die 830 are joined, they define a molding cavity where the end 802 of the skirt is trapped.
• the plastic material of the blank flows and fills the various parts of the volume delimited by the imprints of the punch and of the die, thus forming the shoulder 82 and the neck 83, provided with 'a transverse top wall 84.
• the toric edge 90 imposes the shape of the notch 85 which surmounts a breakable zone 86.
• the plastic material also comes into contact with the end 802 of the skirt.
• the plastics of the head and the skirt are welded together without further heat or material. They remain welded together after a slight pressure maintenance and after cooling.
• the breakable element can be secured to the plug, including a protuberance 89 or 89 ′ undercut therein. In this way, the tube will be effectively opened during the first unscrewing of the stopper and the breaking force, associated with the force of the first unscrewing, guarantees the inviolability of the tube before its first use.
• a slight relief such as a grain of rice, can be provided at the end of the screw thread.
• the undercut protrusion can pass through the thickness of the stopper (89 " Figures 7 and 8) and the material thus extruded through the stopper can be used to fill the top of the stopper and in particular incorporate a personalized decoration, for example the logo of the manufacturer of the packaged product or the brand of the packaged product.
• a personalized decoration for example the logo of the manufacturer of the packaged product or the brand of the packaged product.

Applications Claiming Priority (3)

Publications (1)

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• 2002
  • 2002-08-27 FR FR0210605A patent/FR2843909B1/fr not_active Expired - Fee Related
• 2003
  • 2003-08-26 AU AU2003278214A patent/AU2003278214A1/en not_active Abandoned
  • 2003-08-26 WO PCT/FR2003/002581 patent/WO2004020168A2/fr not_active Application Discontinuation
  • 2003-08-26 EP EP03769528A patent/EP1534489A2/de not_active Withdrawn

Non-Patent Citations (1)

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