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
  • B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
  • B29C49/08—Biaxial stretching during blow-moulding
  • B29C49/10—Biaxial stretching during blow-moulding using mechanical means for prestretching
  • B29C49/12—Stretching rods
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
  • B29B11/00—Making preforms
  • B29B11/14—Making preforms characterised by structure or composition
• • 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
  • B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
  • B29C49/071—Preforms or parisons characterised by their configuration, e.g. geometry, dimensions or physical properties
• • 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
  • B29C2949/00—Indexing scheme relating to blow-moulding
  • B29C2949/07—Preforms or parisons characterised by their configuration
  • B29C2949/0715—Preforms or parisons characterised by their configuration the preform having one end closed
• • 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
  • B29C2949/00—Indexing scheme relating to blow-moulding
  • B29C2949/07—Preforms or parisons characterised by their configuration
  • B29C2949/074—Preforms or parisons characterised by their configuration having ribs or protrusions
  • B29C2949/0747—Preforms or parisons characterised by their configuration having ribs or protrusions at bottom portion
• • 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
  • B29C2949/00—Indexing scheme relating to blow-moulding
  • B29C2949/07—Preforms or parisons characterised by their configuration
  • B29C2949/076—Preforms or parisons characterised by their configuration characterised by the shape
  • B29C2949/0768—Preforms or parisons characterised by their configuration characterised by the shape characterised by the shape of specific parts of preform
  • B29C2949/078—Preforms or parisons characterised by their configuration characterised by the shape characterised by the shape of specific parts of preform characterised by the bottom
• • 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
  • B29C2949/00—Indexing scheme relating to blow-moulding
  • B29C2949/07—Preforms or parisons characterised by their configuration
  • B29C2949/081—Specified dimensions, e.g. values or ranges
  • B29C2949/0849—Curvature, e.g. radius
  • B29C2949/0856—Curvature, e.g. radius of the bottom
• • 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
  • B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
  • B29C49/02—Combined blow-moulding and manufacture of the preform or the parison
  • B29C49/06—Injection blow-moulding

Definitions

• the field of the invention is that of the design and manufacture of plastic containers.
• the invention relates to a plastic container preform.
• a plastic container is obtained by blow molding or stretch blow molding of a preform within a mold in the cavity of the container.
• the preform Prior to its blow molding or its stretch blow molding, the preform is heated until its constituent material reaches or exceeds its glass transition temperature.
• the glass transition temperature is between 75 ° C and 80 ° C.
• a preform usually includes:
• a neck which extends in the extension of the body from a first end thereof, the neck being separated from the body by a collar;
• the vast majority of preforms have a convex bottom, hemispherical in shape or more generally convex outward.
• the bottom material must, from a convex profile, turn around to adopt a concave profile.
• microcracks are liable to propagate when the container is pressurized, but also when the container is in contact with chemicals such as lubricants which may be found on the conveyor lines existing between two container processing stations.
• the decrease in the individual manufacturing cycle time results in a reduction in the contact time of the container with the mold, and therefore less cooling of the container in the mold.
• certain plastics (this is notably the case of PET, which is widely used in the manufacture of containers) have a "shape memory": in fact, during blowing or stretch-blow molding, these materials undergo changes. internal stresses which tend to relax if the temperature is still too high while the internal pressure has fallen in the container. The relaxation causes a form of axial and radial narrowing of the vessels, which in some way kind, tend to return to their initial shape, namely that of the preform. In fact, the shrinkage ceases quickly after exiting the mold, due to cooling, and a container cannot regain the shape of a preform after stress relieving.
• this memory effect induces on the one hand unwanted deformations on the bottoms of the containers, which then become unstable on the laying planes, and on the other hand a reduction in their mechanical strength.
• the reduction in mechanical strength is for example due to the sagging of the bottom of the container which can cause micro cracks which may subsequently weaken the containers under the effect of mechanical (pressure) or chemical (lubricants) stresses.
• An example of unwanted deformation is a sagging of the bottom of the container.
• the concave bottom of the deformed container has an arch of a lower height than expected. Indeed, due to insufficient cooling of the container, and more specifically of the lower part of the container, the concave bottom of the container collapses when it comes out of the mold.
• the aim of the invention is in particular to overcome the drawbacks of the prior art.
• the object of the invention is to provide a preform which makes it possible to obtain containers in which the deformation of the bottom at the exit of the mold is eliminated or, at the very least, limited.
• the invention also aims to provide such a preform which makes it possible to obtain containers whose bottoms have sufficient structural mechanical characteristics to withstand the various pressures and / or stresses to which it is subjected.
• the invention further aims to provide such a preform which makes it possible to increase the production rates of containers which comply with the desired aesthetic and mechanical criteria.
• a plastic container preform comprising: - a symmetrical body of revolution around a central axis;
• the bottom having an annular bead forming a laying plane of the preform, the bottom having an outer skin oriented towards the outside of the preform and an inner skin oriented towards the inside of the preform, characterized in that at least one of the internal skin and of the external skin has, radially from the central axis to the annular bead, a profile having a break in curvature.
• the break in curvature of the preform is preserved during the blowing or stretch-blow molding of the container, on the bottom of the formed container.
• the break in curvature thus forms a stop to the unwinding of the arch towards the outside of the container. This is further explained by the memory effect offered by PET on the one hand and by the shape geometry of the curvature break on the other hand.
• the container formed from the preform therefore retains all of its aesthetic and mechanical qualities for use.
• Another major advantage is to allow better centering of the preforms during a step of stretching and blowing the preform.
• a drawing rod can easily come to take position in the bottom of the preform (if necessary via a specific design to cooperate with the bead) and / or the preform can be suitably positioned on a mold base.
• the profile comprises, from the central axis to the annular bead:
• the second radius is less than 9 mm.
• Such a value of the second radius makes it possible to achieve the breaking of curvature in a straightforward manner.
• a value greater than 9 mm presents a major risk of forming a continuity with the first portion or the third portion, which would promote sagging of the bottom formed.
• the first portion of the profile has a flat, concave or convex shape.
• the preform can be adapted depending on the structure and design of the container bottom to be manufactured.
• the preform has a parting plane at an intersection between the bottom and the body, the parting plane having a thickness EP.
• This parting line defines a border between the bottom of the preform and its body.
• the profile has a maximum height, measured on the central axis, greater than or equal to 5% and less than or equal to 40% of the thickness (EP) of the parting line.
• Such a height prevents sagging of the bottom of the containers and limits the increase in injection cycle times.
• the profile of the internal skin has a maximum height different from the maximum height of the profile of the external skin.
• the bottom has a thickness EF greater than or equal to 60% and less than or equal to 100% of the thickness EP of the parting line.
• the thickness EF of the bottom is greater than or equal to 70% and less than or equal to 90% of the thickness EP of the parting line.
• Such a thickness of the bottom makes it possible to facilitate the flow of the material during the manufacture of the container while allowing the bottom of the container to present the desired guarantees in terms of mechanical strength.
• the first portion of the profile has a diameter greater than or equal to 3mm.
• Such a diameter facilitates cooperation between the preform and an extension rod in the manufacture of a container by stretch-blow molding.
• the first portion of the profile has a diameter less than or equal to 40% of a diameter of the preform at the parting plane.
• This limit on the diameter of the first portion makes it possible to guarantee good flow of the material during the blowing or stretch-blow molding of the preform.
• the profile of the internal skin is parallel to the profile of the external skin.
• FIG. 1 is a perspective view of a preform according to the invention, showing an inset of details on an enlarged scale;
• FIG. 2 is a schematic view of a profile of an internal or external skin of a preform according to the invention;
• FIG. 3 is a schematic sectional representation of a preform according to the invention, according to a first embodiment
• FIG. 4 is a schematic sectional representation of a preform according to the invention, according to a second embodiment
• FIG. 5 is a schematic sectional representation of a preform, according to a third embodiment
• FIG. 6 is a schematic sectional view of a preform in a mold during a stretch blow molding phase.
• Figure 1 illustrates a plastic preform 1 according to the invention. This preform 1 is used for making plastic containers.
• Preform 1 includes:
• the body 3 has, at a first end, the neck 2 from which it is separated by a collar 5 and, at a second opposite end, the bottom 4 which closes the preform 1.
• the neck 2 comprises a thread 6 allowing the fixing of a stopper when the preform is transformed into a container and the latter is closed and filled, and a bead 7 forming means of retained by a tamper-evident ring integral with a stopper (not shown).
• the preform 1 is substantially cylindrical of revolution about a central axis X.
• the body 3 and the bottom 4 are advantageously cylindrical of revolution around the central axis X.
• the neck 2 meanwhile, is partially symmetrical in revolution around the central axis X, only the thread 6 is not symmetrical.
• the preform 1 has an internal skin Pi and an external skin Pe.
• the preform is made of PET, the glass transition temperature of which is around 75 degrees.
• the base 4 has an annular bead 8 forming a laying plane of the preform 1.
• this annular bead 8 forms a continuous line describing a circle, or exceptionally an ovoid shape depending on the general shape of the preform.
• FIG. 2 which illustrates a skin P of the preform 1, regardless of whether it is an internal skin Pi or an external skin Pe, the skin P presents, radially, from the central axis X up to the annular bead 8, a profile having a break in curvature.
• curvature break it is designated a break in the profile of the P skin.
• the profile is not made of a line having a single radius of curvature, but includes several lines each having its own radius of curvature.
• the inner skin Pi or the outer skin Pe defines a generally single curve.
• the profile comprises, from the central axis X to the annular bead 8:
• the break in the curve is then formed by the second radius of curvature presented by the second portion 10.
• the second radius of curvature is less than or equal to 9 mm. Such a value makes it possible to create the break in the curve in order to make a real and clear distinction between the first portion 9 and the third portion 11.
• the second portion 10 by its second radius, makes it possible to prevent a continuity of radius between the first portion 9 and the third portion 11.
• the first portion 9 and the third portion 11 it is possible to observe an intersection between their extension.
• This intersection is unique and not achieved by a collinearity such as would have been the case in the absence of the second portion 10 or by a second portion 10 having a radius of curvature equal to the first radius of curvature and / or to the third radius of curvature, and having a center of radius of curvature identical to the first radius of curvature and / or to the third radius of curvature.
• the break in curvature can also be defined by a center of radius of curvature of the second portion 10 distinct from the center of radius of curvature of the first portion 9 and / or of the third portion 11.
• the first portion 9 of the profile has a flat concave or convex shape.
• the preform has a parting plane 12 at an intersection between the bottom 4 and the body 3, the parting plane 12 having a thickness EP.
• the profile has a maximum height H measured on the central axis, which height H is greater than or equal to 5% of the thickness EP of the parting line 12 and less than or equal to 40% of said thickness EP of the parting line 12.
• the profile of the internal skin Pi has a maximum height Hi equal to the maximum height He of the profile of the external skin Pe (in order not to overload the figures, the references He and Hi are only visible in figure 4).
• the profile of the internal skin Pi has a maximum height Hi different from the maximum height He of the profile of the external skin Pe.
• the first portion 9 of the profile has a diameter d greater than or equal to 3 mm.
• the diameter d of the first portion 9 of the profile is less than or equal to 40% of a diameter D of the preform 1 at the level of the parting line 12, as illustrated in FIG. figure 5.
• the radius measured between the central axis X and the second portion 10 is preferably greater than or equal to 1.5mm and less than or equal to 20% of the diameter D.
• the profile of the internal skin Pi is parallel to the profile of the external skin Pe.
• the internal skin Pi and the external skin Pe have a degree 1 homothety.
• the internal skin Pi and the external skin Pe are at least partially parallel to each other, the bottom 4 of the preform 1 and more particularly the internal skin Pi and the outer skin Pe then exhibit a degree of homothety greater than degree 1.
• the first portion 9 of the internal skin Pi and the first portion 9 of the external skin Pe both have a concave shape oriented towards the inside of the preform 1.
• the first portion 9 of the internal skin Pi and the first portion 9 of the external skin Pe both have a convex shape oriented towards the inside of the preform 1.
• the first portion 9 of the internal skin Pi and the first portion 9 of the external skin Pe are both flat.
• the internal skin Pi can have a convex shape on its first portion 9 and the first portion 9 of the outer skin Pe may have a concave shape.
• first portion 9 of the outer skin Pe may have a convex shape and the first portion 9 of the inner skin Pi may have a concave shape.
• one of the first portion 9 of the outer skin Pe and of the first portion 9 of the inner skin Pi has a flat, concave or convex shape, the other of the first portion 9. of the outer skin Pe and the inner skin Pi have a different shape.
• the bottom 4 has a thickness EF measured along the central axis X between the internal skin Pi and the external skin Pe, greater than or equal to 60% of the thickness EP of the joint plane 12 and less or equal to 100% of said thickness EP of the parting line 12.
• the thickness EF of the bottom 4 is greater than or equal to 70% of the thickness EP of the parting line 12 and less than 90% of the thickness EP of the parting line 12.
• the bottom 4 of the preform thickens from the annular bead 8 to the parting line 12.
• the bottom 4 of the preform according to the invention allows, thanks to its break in curve in particular:
• a first variant makes it possible to press the plastic material of the preform 1 against the mold M.
• a second variant also makes it possible to reinforce the centering of the preform 1 by surrounding the first portion 9, the second portion 10 and at least partially the third portion 11 of the bottom 4.
• the rupture of curvature forms a reinforcement making it possible to limit the sagging of the bottom of the container, and in particular of the bottom of the vault of the container, which is formed by the first portion 9 of the preform 1.
• the rupture of curvature forms a stop in the sagging of the bottom of the container and makes it possible to maintain an arch to the container. This sag limitation is increased with the physical memory of the PET.
• Such sagging occurs in particular when the bottom of the container is not sufficiently cooled at the outlet of the mold, such a lack of cooling generally coinciding with too short a contact time between the plastic material and the mold during the manufacture of the container, and more precisely during the blow-molding or stretch-blow molding step.
• the release formed by the first portion 9, the second portion 10 and the third portion 11 of the profile of the outer skin Pe with the annular bead 8 of the preform 1, makes it possible to ensure a centering of the preform 1 on the mold base M during the stretch-blow molding phases.
• the mold M may in particular have a projection at the imprint of the annular bead 8 of the preform 1 or, of the profile of the outer skin Pe of the preform 1, to allow a form cooperation between the preform 1 and the base. of mold M.
• the blowing rates can be increased by virtue of the preform 1 according to the invention since, even in the absence of prolonged contact between the material and the mold during the blowing or the stretch-blow molding, the deformation of the bottom of the container at the outlet of the mold is controlled and / or limited, which allows the container to be used despite a risk of deformation, since the avoidance of sagging of the bottom allows the container to maintain stability on a plane deposit.
• the deformation of the bottom may be barely perceptible by the user depending on the value of the radii of curvature of each of the first portion 9, of the second portion 10 and of the third portion 11 of the preform 1.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Physics & Mathematics (AREA)
• Geometry (AREA)
• Blow-Moulding Or Thermoforming Of Plastics Or The Like (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=70295450

Family Applications (1)

Country Status (4)

Family Cites Families (3)

• 2020
  • 2020-02-25 FR FR2001833A patent/FR3107468B1/fr active Active
• 2021
  • 2021-02-22 WO PCT/EP2021/054315 patent/WO2021170533A1/fr unknown
  • 2021-02-22 EP EP21705573.0A patent/EP4110571A1/de active Pending
  • 2021-02-22 US US17/801,384 patent/US20230101346A1/en active Pending

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