Improved petaloid-bottom container and mold base for manufacturing such a container

Abstract

Improved petaloid-based container and mold base for manufacturing such a container. The present invention relates to a container obtained by blow molding or stretch blow molding from a plastic blank, comprising a body consisting of a substantially cylindrical wall, a shoulder extending from said body at one upper end thereof, a neck extending from the shoulder, and a petaloid-type base at the lower end of said body, said base having a wall generally convex outwards, from which extend at least three feet formed by protrusions projecting outwards from the container, extending from a central, pellet-shaped area of ​​the base, where the material has remained substantially amorphous, towards a periphery of the base where the latter connects to the body.The most projecting parts or apexes of the feet are coplanar and together form a base on which the vessel can rest on a flat surface, said base being circular and having a diameter called the base diameter φa, and each foot having an end face that slopes gently from the central area of ​​the bottom towards the base of said foot; said vessel is remarkable in that said end face of each foot comprises at least two sections, a first section called the central section extending from the central area of ​​the bottom towards the apex of the foot and having a concavity oriented outwards, and a second section called the peripheral section extending from the central section to the base of the foot and having a convexity oriented outwards. Figure 1,

Description

Title of the invention: Improved petaloid-bottomed container and mold base for manufacturing such a container Technical field

[0001] The present invention relates to the manufacture of containers, in particular bottles, obtained by blow molding or stretch blow molding from blanks, also commonly called preforms or intermediate containers, made of plastic material such as Polyethylene Terephthalate (PET) and / or recycled Polyethylene Terephthalate (rPET). More particularly, the present invention relates to a container with a petaloid bottom and a mold bottom for the manufacture of such a container allowing better distribution of the material during the blowing of the bottom and, ultimately, better mechanical strength of the bottom of said container. State of the art

[0002] In the field of manufacturing PET containers, it is well recognized that a container generally comprises an open neck, through which the contents (usually a liquid) are introduced, a body, which gives the container its volume, and a bottom, which closes the body opposite the neck and forms a base intended to ensure the holding and support of the container when it rests on a surface.

[0003] Containers intended for carbonated drinks, in which the pressure of the gas dissolved in the liquid induces significant mechanical stresses, are mainly provided with petal-shaped bases: the base comprises projecting, petal-shaped feet, separated by convex wall portions, called hollows or valleys, which extend radially from a central area of ​​the base. The feet are intended to ensure the container is held in place on a surface; the valleys are intended to absorb the forces (thermal, mechanical) exerted by the contents.

[0004] The performance of a petaloid base is measured by its mechanical strength - that is, its ability to deform in a limited or controlled manner - not only during filling, but also during storage of the container. Storage can be prolonged, and carried out under severe temperature and humidity conditions that are exceptionally encountered in temperate countries but ordinarily in countries with a continental, tropical or desert climate.

[0005] A common deformation that one wishes to avoid is the sagging of the central area of ​​the bottom, because this results in sensitivity to "stress", a modification of the configuration of the feet and, ultimately, a lack of stability of the container. It should also be noted that container manufacturers wish to be able to satisfy the requests of traders without resulting in a reduction of the production rate of said containers, or even if possible on the contrary with higher production rates.

[0006] In this regard, an improved technical solution has already been proposed which improves the stability over time of the bottoms of containers stored, filled under pressure, in a hot and humid atmosphere, without affecting the production rate. This is the case, in particular, of document FR2897292.

[0007] Document FR2897292 describes a mold base for a mold for manufacturing, by blow molding or stretch blow molding, containers, in particular bottles, made of thermoplastic material such as PET, said containers having a body and having a bottom of the so-called petaloid type with several feet which are distributed angularly in an equidistant manner, which extend approximately parallel to the axis of the container and which are separated from each other by radiating valleys with a convex base, said mold base having a molding cavity comprising, for molding the above-mentioned bottom of the containers, several cavities which are distributed angularly in an equidistant manner, which extend approximately parallel to the axis of the mold base and which are separated from each other by radiating ridges with a concave crest, the bottoms of said cavities being distributed over a substantially circular contour.Said mold base is characterized by the fact that each cavity, considered radially on either side of its deepest point, is defined: towards the outside by a portion of curved surface which, in radial section, is substantially in an arc of a circle and towards the inside by a portion of surface in a broken plane with at least two slopes which intersects said portion of curved surface along a straight edge of substantially circumferential extent, the plane, containing said straight edge, which is tangent to said portion of curved surface being substantially perpendicular to the axis of the molding cavity and the portion of plane adjacent to the portion of curved surface having a slope of between approximately 12° and 8° relative to said tangent plane.

[0008] Thanks to this arrangement, the two portions of curved and broken plane surfaces are connected by an edge materializing, for each foot of the container bottom, a stiffened support line of approximately circumferential extent by which each foot rests on a flat support. This edge remains the support contact of the foot on a flat support regardless of the deformation and / or the inclination undergone by the foot under the effect of a collapse of the central part of the container bottom.

[0009] Although this type of mold base improves the stability over time of the bases of the preserved containers, it does not provide a solution that fully satisfies the constraints of mechanical performance, ideally high, of weight, ideally low, and of blowability, ideally easy.

[0010] In order to overcome these drawbacks, document FR2967975 describes a plastic container comprising a body and a petaloid bottom extending the body, the base comprising a base wall of generally convex shape towards the outside, from which protrude feet formed by outgrowths, the feet being separated two by two by portions of the base wall forming hollow valleys which extend radially from a central zone of the base to a periphery of the base, container in which each valley widens from the central zone towards the periphery, and has a concave portion located near the periphery.

[0011] Such a container has the advantage of having increased resistance to deformation. In particular, good maintenance of the central area of ​​the bottom under hydrostatic pressure is noted, possibly combined with the pressure of the dissolved gas in the case of a carbonated beverage. These performances are observed not only during filling but also during prolonged storage under severe conditions of humidity and pressure.

[0012] However, all these mold bases and / or containers of the prior art do not provide sufficient mechanical strength for the containers when rPET is used for their manufacture. Indeed, the use of rPET complicates the distribution of the material during the stretching and / or blowing of the container. Indeed, it is, in this case, more difficult to burst the amorphous material located in the center of the bottom of the bottle, which generates an increased risk of stress developing between the amorphous zone and the bi-oriented zone. "Stress" means signs of stress in the material, such as cracks or fissures for example, which weaken the bottom of the container. Disclosure of the invention

[0013] One of the aims of the invention is therefore to remedy these drawbacks by proposing a container and a mold base for the manufacture of such a container of simple and inexpensive design providing good mechanical strength of the base of the containers while allowing high manufacturing rates.

[0014] To this end, and in accordance with the invention, there is provided a container obtained by blow molding or stretch blow molding from a plastic blank, which comprises a body consisting of a substantially cylindrical wall, a shoulder in the extension of said body at an upper end thereof, a neck in the extension of the shoulder, and a petaloid-type bottom at the lower end of said body, said bottom comprising a wall of generally convex shape towards the outside, from which at least three feet originate, formed by protrusions projecting towards the outside of the container, and which extend from a central zone of the pellet-shaped bottom, where the material has remained substantially amorphous, towards a periphery of the bottom where the latter is connected to the body, the most projecting parts or tops of the feet are coplanar and together form a base by which the container can resting on a flat surface, said seat being circular and having a so-called seat diameter, and each foot having an end face which extends in a gentle slope from the central area of ​​the bottom towards the base of said foot; said container is remarkable in that said end face of each foot comprises at least two sections, a first so-called central section extending from the central area of ​​the bottom towards the top of the foot and having an outwardly oriented concavity and a second so-called peripheral section extending from the central section to the base of the foot and having an outwardly oriented convexity.

[0015] Such a construction of the foot, and more particularly such a specific construction in the form of a curve connecting the feet towards the center, advantageously allows the material to move more easily towards the seat and therefore to obtain a more progressive transition of the material from the center towards the seat area during the stretch-blow molding manufacturing step.

[0016] Preferably, the radius of curvature of the second peripheral section is between 0.5 and 3 times the seat diameter.

[0017] Furthermore, the radius of curvature of the central section is preferably between 0.3 and 0.6 times the seat diameter.

[0018] Furthermore, the radius of curvature of the peripheral section and / or the radius of curvature of the central section is not constant.

[0019] Incidentally, the bottom guard corresponding to the height between the central zone of the bottom and the tops of the feet, that is to say the seat plane, is between 0.05 and 0.15 times the seat diameter.

[0020] Advantageously, each foot has two substantially flat flanks which each laterally border a valley, said flanks of the feet being connected to the valley by concave fillets whose radius of curvature is not constant from the central zone towards the connection zone of each valley.

[0021] Such a construction of the foot, and more particularly such a specific construction of the concave fillets connecting the sides of two feet adjacent to a valley, advantageously allows the material to move more easily towards the seat and therefore to obtain a more progressive transition of the material at the level of the valley from the center towards the seat zone during the stretch-blow molding manufacturing step.

[0022] Preferably, said radius of curvature of the concave fillets is variable over a length Li of the valley from the central zone and is substantially constant from said length Li to the connection zone.

[0023] Said length Li is between 0.2 and 0.8 times the seat diameter. <pa et, de préférence, égale à 0,5 fois ledit diamètre d’assise <pa.

[0024] Furthermore, over a part L2 of the length LH, said concave fillets are separated by a space E which is less than or equal to 2 mm, the starting point of the length L2 being the central zone. Said space E may be zero.

[0025] Said length L2 from the central zone is between 0.1 and 0.4 times the seat diameter. <pa et est, de préférence égal à 0,3 fois ledit diamètre d’assise <pa.

[0026] Furthermore, over a length L3 remaining from the length LB called the transition length, the radius of curvature of the concave fillets gradually decreases until it reaches the value of the substantially constant radius of curvature of the concave fillets defined for the zone extending between the end of the length Li to the connection zone.

[0027] Another subject of the invention relates to a mold base for a mold for manufacturing by blow molding or stretch blow molding, containers, in particular bottles, made of thermoplastic material such as PET, said containers having a body consisting of a substantially cylindrical wall, a shoulder in the extension of said body at an upper end thereof, a neck in the extension of the shoulder, and a petaloid-type bottom at the lower end of said body, said bottom comprising a wall of generally convex shape towards the outside, from which at least three feet start formed by protrusions which are distributed angularly in an equidistant manner, which extend approximately parallel to the axis of the container and which are separated from each other by radiating valleys with a bottom of convex curvilinear radial extent, said mold base comprising, for molding said bottom of the containers,at least three cavities which are distributed angularly in an equidistant manner, which extend substantially parallel to the axis of the mold base and which are separated from each other by radiating ridges with a concave radial extent, the bases of said cavities being distributed on a substantially circular contour corresponding to the so-called seat diameter <pa du récipient, et chaque cavité présentant une face de fond qui s'étend en pente douce depuis la zone centrale du fond vers le fond de la cavité ; ledit fond de moule est remarquable en ce que ladite face de fond de chaque cavité comprend au moins deux sections,a first section called central extending from the central zone of the mold bottom towards the bottom of the cavity and having a convexity oriented towards the inside of the mold bottom and a second section called peripheral extending from the central section to the bottom of the cavity and having a concavity oriented towards the inside of the mold bottom.

[0028] Preferably, the radius of curvature of the second peripheral section is between 0.5 and 3 times the seat diameter. <pa.

[0029] Furthermore, the radius of curvature of the central section is preferably between 0.3 and 0.6 times the seat diameter. <pa.

[0030] Furthermore, the radius of curvature of the peripheral section and / or the radius of curvature of the central section is not constant.

[0031] Incidentally, the bottom guard corresponding to the height between the central zone of the mold bottom and the bottom of the cavities is between 0.05 and 0.15 times the seat diameter. <pa.

[0032] Advantageously, said mold base comprises, on either side of the crest, a convex fillet connecting the ridges extending on either side of the crest, the radius of curvature of said convex fillet not being constant from the central zone towards the edge of the central impression.

[0033] Preferably, said radius of curvature of the convex fillets is variable over a length Li of the crest from the central zone and is substantially constant from said length Li to the edge of the central imprint.

[0034] Said length Li is between 0.2 and 0.8 times the seat diameter. <pa et, de préférence, égale à 0,5 fois ledit diamètre d’assise <pa.

[0035] Furthermore, on a part L2 of said length Lb, said length L2 corresponding to a length whose starting point is the central zone, the convex fillets are separated by a space E less than or equal to 2 mm. Said space E may be zero.

[0036] Said length L2 from the central zone is between 0.1 and 0.4 times the seat diameter. <pa et est, de préférence égal à 0,3 fois ledit diamètre d’assise <pa.

[0037] Furthermore, over a length L3 remaining from the length LH called the transition length, the radius of curvature of the convex fillets gradually decreases until it reaches the value of the substantially constant radius of curvature of the convex fillets defined for the zone extending between the end of the length Li to the edge of the central imprint.

[0038] A final object of the invention relates to a molding device for the manufacture, by blow molding or stretch blow molding, of containers, in particular bottles, from preforms made of thermoplastic material such as PET, said containers having a body consisting of a substantially cylindrical wall, a shoulder in the extension of said body at an upper end thereof, a neck in the extension of the shoulder, and a petaloid-type bottom at the lower end of said body, said bottom comprising a wall of generally convex shape towards the outside, from which at least three feet originate formed by protrusions which are distributed angularly in an equidistant manner, which extend approximately parallel to the axis of the container and which are separated from each other by radiating valleys with a bottom of convex curvilinear radial extent,which molding device comprises at least one mold base capable of being movably mounted in a side wall which defines a cavity in the impression of a part of the container, said side wall comprising two, half-molds each defining a half-cavity of the body of the container and mounted to rotate relative to each other, between a so-called open position, in which the half-molds are angularly spaced apart from each other and the mold base is lowered relative to the half-molds to allow the introduction of the preform and the evacuation of the formed container, and a so-called closed position, in which the half-molds are applied against each other and trap the mold base between them to thus form the cavity and define the total cavity of the container to be formed, said mold base comprising at least three cavities which are distributed angularly in an equidistant manner, which extend substantially parallel to the axis of the mold base and which are separated from each other by radiating ridges with a concave radial crest, the bases of said cavities being distributed over a substantially circular contour;said device is remarkable in that the mold base is arranged according to the invention described previously.; Brief description of the drawings

[0039] Other advantages and characteristics will emerge more clearly from the following description of a single variant embodiment, given by way of non-limiting example, in accordance with the invention, with reference to the appended drawings in which:

[0040] [Fig-1] is a partial perspective view from below of a petaloid-bottomed container according to the invention,

[0041] [Fig.2] is a side view of the lower part of the following petaloid-bottomed container the invention shown in [Fig.l],

[0042] [Fig.3] is a bottom view of the bottom of the container according to the invention shown in Figures 1 and 2,

[0043] [Fig.4] is a sectional view of the bottom of [Fig.3], according to section plane IV-IV',

[0044] [Fig.5] is a view of the sectional section of the sectional view shown in the [Fig.4],

[0045] [Fig.6] is a partial perspective view from below of an alternative embodiment of the bottom of a container with a petaloid bottom according to the invention,

[0046] [Fig.7] is a side view of the lower part of the variant execution of the container with a petaloid bottom according to the invention shown in [Fig.6],

[0047] [Fig.8] is a bottom view of the bottom of the following embodiment of the container the invention shown in Figures 6 and 7,

[0048] [Fig.9] is a schematic cross-sectional representation of two adjacent feet of the bottom of the variant embodiment of the container according to the invention shown in Figures 6 and 7

[0049] [Fig. 10] is a perspective view of a mold base according to the invention,

[0050] [Fig. 11] is a top view of the mold base according to the invention shown in [Fig. 10],

[0051] [Fig. 12] is a sectional view of the mold base of [Fig. 11], according to section plane XII-XIF. Method of carrying out the invention

[0052] In the remainder of the description of the container according to the invention, the same numerical references designate the same elements. The different views are not necessarily drawn to scale.

[0053] With reference to Figures 1 to 3, the container 1 according to the invention is a bottle, intended for example to contain a fizzy or carbonated drink. It is made of PET and / or rPET by extrusion-blow molding or injection-blow molding of its constituent material. It is in fact to this type of container that the invention is preferentially applied. However, it is quite obvious that said container 1 may be made of any other thermoplastic material known per se or of a mixture of various materials without departing from the scope of the invention.

[0054] Said container 1 usually comprises a body 2 forming a cylindrical wall and extending from a base 3 of the petaloid type, surmounted by a shoulder, leading to a neck, terminated by a threaded neck or adapted in any other way to receive a stopper, the shoulder, the neck, the neck and the stopper not being shown in [Fig.l].

[0055] Said petaloid base 3 comprises feet 4 formed by protrusions starting from a substantially hemispherical wall 5 with convexity facing outwards and forming valleys 6 between two adjacent feet 4, the hemispherical wall 5 forming the bottom of said valleys 6. The upper end of each foot 4 ends at the body 2.

[0056] In this particular embodiment, said petaloid base 3 has five protrusions forming the feet 4, which are distributed angularly in an equidistant manner, which extend approximately parallel to the longitudinal axis of the container 1 and which are separated from each other by radiating valleys 6 with a base of convex curvilinear radial extent. All the valleys 6 converge towards a so-called central zone 7 of the base 3, said central zone 7 being constituted by a circular plate or pellet with a slight external projection, where the material has remained substantially amorphous. The base 3 of the container 1 is connected to the body 2 of the container 1 by a so-called connection zone 8 which is substantially cylindrical in revolution.

[0057] Thus, the feet 4 are separated two by two by portions of the bottom wall 5 called valleys 6, which extend radially in a star shape from the central zone formed by the central zone 7 to the periphery formed by the connection zone 8. The valleys 6 are concave outwards in cross-section, that is to say along a plane perpendicular to the radial direction. The radius of curvature of the valleys 6 can be variable. More precisely, it is preferably low near the central zone 7, and relatively higher near the connection zone 8

[0058] Furthermore, the valleys 6 have, in the vicinity of the central zone 7, an internal section 9 which is convex towards the outside in radial section and, in the vicinity of the connection zone 8, an external section 10 which is concave towards the outside in radial section.

[0059] In the example illustrated in the drawings, the base 3 comprises five feet 4 and five valleys 6, regularly alternating and distributed in a star shape. This number constitutes a good compromise; it could however be less (but greater than or equal to three), or greater (but preferably less than or equal to seven). Furthermore, the most projecting parts or summits 16 of the feet 4 are coplanar and jointly form a seat by which the container 1 can rest on a flat surface, said seat being circular and having a so-called seat diameter which will be noted in the remainder of the description <pa, et chaque pied 4 présente une face d'extrémité 13 qui s'étend en pente douce depuis la zone centrale 7 du fond 3 vers la base dudit pied 4.

[0060] Each foot 4 has two substantially flat sides 12 which each laterally border a valley 6. Said sides 12 are not vertical (because the bottom 3 would then be difficult, or even impossible, to blow), but inclined, opening from the valley 6 towards the outside. Said sides 12 are connected to the end face 13 by a fillet 14. Each foot 4 is also delimited radially by an external face 15 which extends in the extension of the body 2 to the vicinity of the top 16 of the foot 4, to which the external face 15 is connected by a fillet 17. The external face 15 is not cylindrical but substantially conical of revolution around the longitudinal axis of the container 1. Moreover, in radial section this face 15 is not straight but convex with a large radius of curvature. At the periphery of the bottom 3, the face 15 connects to the body 2 by the connection zone 8 which is in the form of a fillet.

[0061] Advantageously, the bottom 3 is, moreover, provided with radial grooves 18 which extend in a hollow towards the interior of the container 1 along the valleys 6.

[0062] More precisely, each radial groove 18 extends along a median line of a valley 6, from a vicinity of the central zone 7 to the vicinity of the connection zone 8. Each groove 18 has a substantially oblong shape in plan, the edges of which are parallel over most of the length, and the ends of which are both tapered. In radial section, each groove 18 has a flared U-shaped profile. The function of said grooves 18 is to stiffen the base 3. Under the effect of the mechanical stresses exerted on the container 1 (in particular under the effect of the pressure prevailing in the container filled with a carbonated liquid), the grooves 18 tend to creep by expanding and flattening, which causes a widening of the valleys 6 and, consequently, a verticalization of the feet 4 which opposes the overall collapse of the base 3.

[0063] Furthermore, each valley 6 widens from the central zone 7 towards the connection zone 8. This widening is preferably continuous, that is to say that the edges of the valleys 6 form between them an angle at all points that is not zero. In the example shown, the valleys 6 have a tulip-shaped (or bell-shaped) outline in plan, but this shape is not limiting, and the edges of the valleys 6 could be straight, said valleys 6 then having a V-shaped outline.

[0064] In a particularly advantageous manner, said end face 13 of each foot 4 comprises at least two sections 13a, 13b, a first so-called central section 13a extending from the central zone 7 of the bottom towards the top 16 of the foot 4 and having a concavity oriented towards the outside and a second so-called peripheral section 13b extending from the central section 13a to the base of the foot 4 and having a convexity oriented towards the outside.

[0065] Such a construction of the foot, and more particularly such a specific construction in the form of a curve connecting the feet towards the center, advantageously allows the material to move more easily towards the seat and therefore to obtain a more progressive transition of the material from the center towards the seat area during the stretch-blow molding manufacturing step.

[0066] Preferably, the radius of curvature of the second peripheral section 13b is between 0.5 and 3 times the seat diameter. <pa et le rayon de courbure de la première section centrale 13a est, de préférence, compris entre 0,3 et 0,6 fois ledit diamètre d’assise <pa. De cette manière, le déplacement de la matière est optimal lors de l’étape d’étirage-soufflage.

[0067] In this particular embodiment, the radius of curvature of the peripheral section 13b and the radius of curvature of the central section 13a are constant, and of different values; However, it is quite obvious that the radii of curvature of the peripheral section 13b and of the central section 13a could be equal without departing from the scope of the invention.

[0068] Furthermore, it is also quite obvious that the radius of curvature of the peripheral section 13b and / or the radius of curvature of the central section 13a may not be constant over the entire length of each section 13a, 13b without departing from the scope of the invention.

[0069] Incidentally, the bottom guard corresponding to the height between the central zone 7 of the bottom 3 and the tops 16 of the feet 4, that is to say the seat plane, is between 0.05 and 0.15 times the seat diameter. <pa.

[0070] According to an alternative embodiment of the bottom of the container according to the invention, with reference to figures 6 to 9, said petaloid bottom 3 comprises in the same way as previously feet 4 formed by protrusions starting from a substantially hemispherical wall 5 with convexity turned towards the outside and forming valleys 6 between two adjacent feet 4, the hemispherical wall 5 forming the bottom of said valleys 6. The upper end of each foot 4 ends at the body 2.

[0071] In the same way as previously, said petaloid bottom 3 has five protrusions forming the feet 4, which are distributed angularly in an equidistant manner, which extend approximately parallel to the longitudinal axis of the container 1 and which are separated from each other by radiating valleys 6 with a bottom of convex curvilinear radial extent. All the valleys 6 converge towards a so-called central zone 7 of the bottom 3, said central zone 7 being constituted by a circular plate or pellet with a slight external projection, where the material has remained substantially amorphous. The bottom 3 of the container 1 is connected to the body 2 of the container 1 by a so-called connection zone 8 which is substantially cylindrical in revolution.

[0072] Thus, the feet 4 are separated two by two by portions of the bottom wall 5 called valleys 6, which extend radially in a star shape from the central zone formed by the central zone 7 to the periphery formed by the connection zone 8. The valleys 6 are concave outwards in cross-section, that is to say along a plane perpendicular to the radial direction. The radius of curvature of the valleys 6 can be variable. More precisely, it is preferably small near the central zone 7, and relatively larger near the connection zone 8.

[0073] Furthermore, the valleys 6 have, in the vicinity of the central zone 7, an internal section 9 convex towards the outside in radial section and, in the vicinity of the connection zone 8, an external section 10 concave towards the outside in radial section,

[0074] In the example illustrated in the drawings, the base 3 comprises five feet 4 and five valleys 6, regularly alternating and distributed in a star shape. Furthermore, the most projecting parts or summits 16 of the feet 4 are coplanar and jointly form a seat by which the container 1 can rest on a flat surface, said seat being circular and having a so-called seat diameter which will be noted in the remainder of the description <pa, et chaque pied 4 présente une face d'extrémité 13 qui s'étend en pente douce depuis la zone centrale 7 du fond 3 vers la base dudit pied 4.

[0075] Each foot 4 has two substantially flat sides 12 which each laterally border a valley 6. Said sides 12 are not vertical (because the bottom 3 would then be difficult, or even impossible, to blow), but inclined, opening from the valley 6 towards the outside. Said sides 12 are connected to the end face 13 by a fillet 14. Each foot 4 is also delimited radially by an external face 15 which extends in the extension of the body 2 to the vicinity of the top 16 of the foot 4, to which the external face 15 is connected by a fillet 17. The external face 15 is not cylindrical but substantially conical of revolution around the longitudinal axis of the container 1. Moreover, in radial section this face 15 is not straight but convex with a large radius of curvature. At the periphery of the bottom 3, the face 15 connects to the body 2 by the connection zone 8 which is in the form of a fillet.

[0076] Advantageously, the bottom 3 is also provided with radial grooves 18 which extend hollowly towards the interior of the container 1, at the bottom 3 and along the valleys 6.

[0077] More precisely, each radial groove 18 extends along a median line of a valley 6, from a vicinity of the central zone 7 to the vicinity of the connection zone 8. Each groove 18 has a substantially oblong shape in plan, the edges of which are parallel over most of the length, and the ends of which are both tapered. In radial section, each groove 18 has a flared U-shaped profile. The function of said grooves 18 is to stiffen the base 3. Under the effect of the mechanical stresses exerted on the container 1 (in particular under the effect of the pressure prevailing in the container filled with a carbonated liquid), the grooves 18 tend to creep by expanding and flattening, which causes a widening of the valleys 6 and, consequently, a verticalization of the feet 4 which opposes the overall collapse of the base 3.

[0078] Furthermore, each valley 6 widens from the central zone 7 towards the connection zone 8. This widening is preferably continuous, that is to say that the edges of the valleys 6 form between them an angle at all points that is not zero. In the example shown, the valleys 6 have a tulip-shaped (or bell-shaped) outline in plan, but this shape is not limiting, and the edges of the valleys 6 could be straight, said valleys 6 then having a V-shaped outline.

[0079] In a particularly advantageous manner, said end face 13 of each foot 4 comprises at least two sections 13a, 13b, a first so-called central section 13a extending from the central zone 7 of the bottom towards the top 16 of the foot 4 and having a concavity oriented towards the outside and a second so-called peripheral section 13b extending from the central section 13a to the base of the foot 4 and having a convexity oriented towards the outside.

[0080] Preferably, the radius of curvature of the second peripheral section 13b is between 0.5 and 3 times the seat diameter. <pa et le rayon de courbure de la première section centrale 13a est, de préférence, compris entre 0,3 et 0,6 fois ledit diamètre d’assise <pa. De cette manière, le déplacement de la matière est optimal lors de l’étape d’étirage-soufflage.

[0081] In this particular embodiment, the radius of curvature of the peripheral section 13b and the radius of curvature of the central section 13a are substantially constant, and of different values; However, it is quite obvious that the radii of curvature of the peripheral section 13b and of the central section 13a could be equal without departing from the scope of the invention.

[0082] Furthermore, it is also quite obvious that the radius of curvature of the peripheral section 13b and / or the radius of curvature of the central section 13a may not be constant over the entire length of each section 13a, 13b without departing from the scope of the invention.

[0083] Incidentally, the bottom guard corresponding to the height between the central zone 7 of the bottom 3 and the tops 16 of the feet 4, that is to say the seat plane, is between 0.05 and 0.15 times the seat diameter. <pa.

[0084] This variant embodiment is distinguished from that previously described by the fact that said flanks 12 of the feet 4 are connected to the valley 6 by concave fillets 19 whose radius of curvature, denoted Rla and Rlb in [Fig. 9], is not constant from the central zone 7 to the connection zone 8 of each valley 6. More precisely, said radius of curvature of the concave fillets 19 is variable over a length Li of the valley 6 from the central zone 7 and is substantially constant from said length Li to the connection zone 8. Said length Li is between 0.2 and 0.8 times the seat diameter <pa et, de préférence, égale à 0,5 fois ledit diamètre d’assise <pa. Par ailleurs, ladite longueur Li peut être décomposée en deux longueurs L2 et L3, i.e.that Li=L2+L3, Said length L2 corresponds to the length, the starting point of which is the central zone 7, in which the space E between the concave fillets 19 of two adjacent feet 4 separated by a valley 6 is minimal. Preferably, over this length L2, the space E between said concave fillets 19 of two adjacent feet 4 separated by a valley 6 is less than or equal to 2mm. It will be noted that said space E can be zero, i.e. equal to 0. In this case, the concave fillets 19 of two adjacent feet 4 then meet at a distance L2 from the central zone 7. Said length L2 from the central zone 7 is between 0.1 and 0.4 times the seat diameter <pa et est, de préférence égal à 0,3 fois ledit diamètre d’assise <pa.Over said length L3, called the transition length, the radius of curvature of the concave fillets 19 gradually decreases until it reaches the value of the constant radius of curvature of the concave fillets 19 defined for the zone extending between the end of the length Li up to the connection zone 8.

[0085] It will be noted that such a construction of the foot, and more particularly such a specific construction of the concave fillets 19 connecting the flanks 12 of two feet adjacent to a valley 6, advantageously allows the material to move more easily towards the seat and therefore to obtain a more progressive transition of the material at the level of the valley 6 from the center towards the seat zone during the stretch-blow molding manufacturing step.

[0086] Referring now to Figures 10 to 12, there is shown a mold base 100 intended to equip a manufacturing mold, by blowing or stretching- blowing, of containers 1, in particular bottles, made of thermoplastic material, and more particularly of rPET and / or of PET, according to the invention as described previously with reference to figures 1 to 5.

[0087] Said mold base 100 is provided with a molding cavity 101 which comprises, for molding the above-mentioned base 3 of the containers 1, a plurality of cavities 102 in number equal to the number of feet 4 of the base 3 of the containers 1, generally between three and seven, in practice between four and six (five in the example illustrated in Figures 1 to 5), which are distributed angularly in an equidistant manner (mutual angular spacing of 72° in this example), which extend approximately parallel to the axis of the mold base 100 (which is also the axis of the molding cavity C) and which are separated from each other by radiating ridges 103 (i.e. projecting parts, elongated substantially radially, of the molding cavity C which lead, in the base 3 of the molded container 1, to the formation of the above-mentioned valleys 6).Each dorsal 103 has a crest 104 of concave radial curvilinear extent, which is in the shape of an arc of a circle originating on the edge of the central impression 105. The bottoms 106 of the cavities 101 are distributed on a substantially circular contour 107 having a given base diameter <pa qui correspond au diamètre d’assise <pa du fond 3 des récipients 1. Le centre de la cavité 101 de moulage comporte une zone centrale 108 en saillie au centre de laquelle est creusée une cavité 109 circulaire de faible profondeur, pour la formation de la pastille de la zone centrale 7 précitée du fond 3 de récipient 1. Conformément à l'invention, chaque cavité 102 présente une face de fond 110 qui s'étend en pente douce depuis la zone centrale 108 du fond de moule 100 vers le fond de la cavité 102.Each cavity 102, considered radially on either side of its deepest point, is defined towards the outside by a portion of curved surface 111 which, in radial section, is substantially in an arc of a circle and towards the inside by a portion of surface 112 with a so-called connecting curve.

[0088] In the preferred embodiment illustrated in Figures 10 to 12, said bottom face 110 of each cavity 102 comprises at least two sections 110a, 110b, a first so-called central section 110a extending from the central zone 108 of the mold bottom 100 towards the bottom of the cavity 102 and having a convexity oriented towards the inside of the mold bottom 100 and a second so-called peripheral section 110b extending from the central section 110a to the bottom of the cavity 102 and having a concavity oriented towards the inside of the mold bottom 100.

[0089] In the same way as for the container 1 previously described, the radius of curvature of the second peripheral section 110b is, preferably, between 0.5 and 3 times the seat diameter. <pa et le rayon de courbure de la première section centrale 110a est, de préférence, compris entre 0,3 et 0,6 fois ledit diamètre d’assise <pa. De cette manière, le déplacement de la matière est optimal lors de l’étape d’étirage-soufflage.

[0090] In this particular embodiment, the radius of curvature of the peripheral section 110b and the radius of curvature of the central section 110a are constant, and of different values; However, it is quite obvious that the radii of curvature of the peripheral section 110b and of the central section 110a could be equal without departing from the scope of the invention.

[0091] Furthermore, it is also quite obvious that the radius of curvature of the peripheral section 110b and / or the radius of curvature of the central section 110a may not be constant over the entire length of each section 110a, 110b without departing from the scope of the invention.

[0092] Incidentally, the bottom guard corresponding to the height between the central zone 108 of the mold bottom 100 and the bottom of the cavities 102 is between 0.05 and 0.15 times the seat diameter. <pa.

[0093] According to an alternative embodiment according to the invention, not shown in the figures, said mold base 100 comprises, on either side of the crest 104, a convex fillet 119 connecting the ridges 103 extending on either side of the crest, the radius of curvature of said convex fillet not being constant from the central zone 108 towards the edge of the central impression 105.

[0094] More precisely, said radius of curvature of the convex fillets 119 is variable over a length Li of the crest 104 from the central zone 108 and is substantially constant from said length Li to the edge of the central imprint 105. Said length Li is between 0.2 and 0.8 times the seat diameter. <pa et, de préférence, égale à 0,5 fois ledit diamètre d’assise <pa. Par ailleurs, ladite longueur Li peut être décomposée en deux longueurs L2 et L3, i.e. que Li=L2+L3, Ladite longueur L2 correspond à la longueur, dont le point de départ est la zone centrale 108, dans laquelle l’espace E entre les congés convexes 119 d’une même crête 104 est minimal. De préférence, sur cette longueur L2, l’espace E entre lesdits congés convexes 119 d’une même crête 104 est inférieur ou égal à 2mm. On notera que ledit espace E peut être nul, i.e. égal à 0. Dans ce cas, les congés convexes 119 se rejoignent alors à une distance L2 depuis la zone centrale 108.Said length L2 from the central zone 108 is between 0.1 and 0.4 times the seat diameter <pa et est, de préférence égal à 0,3 fois ledit diamètre d’assise <pa. Sur ladite longueur L3, dite longueur de transition, le rayon de courbure des congés convexes 119 diminuer progressivement jusqu’à ce qu’il atteigne la valeur du rayon de courbure constant des congés convexes 119 défini pour la zone s’étendant entre la fin de la longueur Li jusqu’au bord de l’empreinte centrale 105. .

[0095] A final object of the invention, not shown in the figures, concerns a molding device for the manufacture, by blow molding or stretch-blow molding, of containers, as described previously.

[0096] Said molding device comprises, in the usual manner, at least one mold base capable of being mounted movably in a side wall which defines a cavity in the impression of a part of the container, said side wall comprising two half-molds each defining a half-impression of the body of the container and mounted in rotation relative to each other, between a so-called open position, in which the half-molds are angularly spaced from each other and the mold base is lowered relative to the half-molds to allow the introduction of the preform and the evacuation of the formed container, and a so-called closed position, in which the half-molds are applied against each other and trap the mold base between them to thus form the cavity and define the total impression of the container to be formed, said mold base comprising at least three cavities which are distributed angularly in an equidistant manner,which extend substantially parallel to the axis of the mold base and which are separated from each other by radiating ridges with a concave radial extent, the bottoms of said cavities being distributed over a substantially circular contour. Said molding device is distinguished by the fact that said mold base is arranged as described previously with reference to figures 6 to 8.,

[0097] Finally, it is quite obvious that the examples which have just been given are only particular illustrations and in no way limitative as to the fields of application of the invention.

Claims

Claims

1. Container (1) obtained by blow molding or stretch blow molding from a plastic blank, which comprises a body (2) consisting of a substantially cylindrical wall, a shoulder in the extension of said body (2) at an upper end thereof, a neck in the extension of the shoulder, and a petaloid-type bottom (3) at the lower end of said body (2), said bottom (3) comprising a wall of generally convex shape towards the outside, from which at least three feet (4) originate, formed by protrusions projecting towards the outside of the container, and which extend from a central zone (7) of the bottom (3) in the form of a pellet, where the material has remained substantially amorphous, towards a periphery of the bottom (3) where the latter is connected to the body (2), the most projecting parts or summits (16) of the feet (4) are coplanar and jointly form a base by which the container can rest on a flat surface,said seat being circular and having a so-called seat diameter <pa, et chaque pied (4) présentant une face d'extrémité (13) qui s'étend en pente douce depuis la zone centrale (7) du fond (3) vers la base dudit pied (4), caractérisé en ce que ladite face d’extrémité (13) de chaque pied comprend au moins deux sections (13a, 13b), une première section dite centrale (13a) s’étendant depuis la zone centrale (7) du fond en direction du sommet (16) du pied (4) et présentant une concavité orientée vers l’extérieur, et dont le rayon de courbure est compris entre 0,3 et 0,6 fois le diamètre d’assise <pa, et une seconde section dite périphérique (13b) s’étendant depuis la section centrale (13a) jusqu’à la base du pied (4) et présentant une convexité orientée vers l’extérieur, et dont le rayon de courbure est compris entre 0,5 et 3 fois le diamètre d’assise <pa.,

2. Container according to claim 1 characterized in that the radius of curvature of the peripheral section (13b) is not constant.

3. Container according to any one of claims 1 or 2 characterized in that the radius of curvature of the central section (13a) is not constant.

4. Container according to any one of claims 1 to 3 characterized in that the bottom guard corresponding to the height between the central zone (7) of the bottom (3) and the tops (16) of the feet (4), i.e. the seat plane, is between 0.05 and 0.15 times the seat diameter <pa.

5. Container according to any one of claims 1 to 4, characterized in that each foot (4) has two substantially flat sides (12) which each laterally border a valley (6), said sides (12) of the feet (4) being connected to the valley (6) by concave fillets (19) whose radius of curvature is not constant from the central zone (7) towards the connection zone (8) of each valley (6).

6. Container according to claim 5 characterized in that said radius of curvature of the concave fillets (19) is variable over a length Li of the valley (6) from the central zone (7) and is substantially constant from said length Li to the connection zone (8).

7. Container according to claim 6 characterized in that said length Li is between 0.2 and 0.8 times the seat diameter <pa et, de préférence, égale à 0,5 fois ledit diamètre d’assise <pa.

8. Container according to any one of claims 6 or 7 characterized in that over a part L2 of the length Lh said concave fillets (19) are separated by a space E which is less than or equal to 2mm, the starting point of the length L2 being the central zone (7).

9. Container according to claim 8 characterized in that said space E is zero.

10. Container according to any one of claims 8 or 9 characterized in that said length L2 from the central zone (7) is between 0.1 and 0.4 times the seat diameter <pa et est, de préférence égal à 0,3 fois ledit diamètre d’assise <pa.

11. Container according to any one of claims 8 to 10, characterized in that, over a length L3 remaining from the length Lh called the transition length, the radius of curvature of the concave fillets (19) decreases progressively until it reaches the value of the substantially constant radius of curvature of the concave fillets (19) defined for the zone extending between the end of the length Li to the connection zone (8).

12. Mold base (100) for a mold for manufacturing containers (1), in particular bottles, by blow molding or stretch blow molding, in

13.

14. thermoplastic material such as PET, said containers having a body (2) consisting of a substantially cylindrical wall, a shoulder in the extension of said body (2) at an upper end thereof, a neck in the extension of the shoulder, and a petaloid-type bottom (3) at the lower end of said body (2), said bottom (3) comprising a wall of generally convex shape towards the outside, from which at least three feet (4) start, formed by protrusions which are distributed angularly in an equidistant manner, which extend approximately parallel to the axis of the container (1) and which are separated from each other by radiating valleys (6) with a bottom of convex curvilinear radial extent, said mold bottom (100) comprising, for molding said bottom (3) of the containers (1), at least three cavities (102) which are distributed angularly in an equidistant manner,which extend substantially parallel to the axis of the mold base (100) and which are separated from each other by radiating ridges (103) with a crest (104) of concave radial extent, the bottoms (106) of said cavities (102) being distributed over a substantially circular contour (107) corresponding to the so-called seat diameter <pa du récipient (1), et chaque cavité (102) présentant une face de fond (110) qui s'étend en pente douce depuis la zone centrale (108) du fond vers le fond (106) de la cavité (102), caractérisé en ce que ladite face de fond (110) de chaque cavité (102) comprend au moins deux sections (110a, 110b), une première section dite centrale (110a) s’étendant depuis la zone centrale (108) du fond de moule (100) en direction du fond (106) de la cavité (102) et présentant une convexité orientée vers l’intérieur du fond de moule (100), et dont le rayon de courbure est compris entre 0,3 et 0,6 fois le diamètre d’assise <pa,and a second so-called peripheral section (110b) extending from the central section (110a) to the bottom (106) of the cavity (102) and having a concavity oriented towards the inside of the mold bottom (100), and whose radius of curvature is between 0.5 and 3 times the seat diameter <pa., Mold base (100) according to claim 12 characterized in that the radius of curvature of the peripheral section (110b) is not constant. Mold base (100) according to any one of claims 12 or 13 characterized in that the radius of curvature of the central section (110a) is not constant.

15. Mold base (100) according to any one of claims 12 to 14 characterized in that the bottom guard corresponding to the height between the central zone (108) of the mold base (100) and the bottom (106) of the cavities (102) is between 0.05 and 0.15 times the seat diameter <pa.

16. Mold base (100) according to any one of claims 12 to 15 characterized in that it comprises, on either side of the crest (104), a convex fillet (119) connecting the ridges (103) extending on either side of the crest (104), the radius of curvature of said convex fillet (119) not being constant from the central zone (108) towards the edge of the central impression.

17. Mold base (100) according to claim 16 characterized in that said radius of curvature of the convex fillets (119) is variable over a length Li of the crest (104) from the central zone (108) and is substantially constant from said length Li to the edge of the central imprint (105).

18. Mold base (100) according to claim 17 characterized in that said length Li is between 0.2 and 0.8 times the seat diameter <pa et, de préférence, égale à 0,5 fois ledit diamètre d’assise <pa.

19. Mold base (100) according to any one of claims 17 or 18 characterized in that on a part L2 of said length Lb said length L2 corresponding to a length whose starting point is the central zone (108), the convex fillets (119) are separated by a space E less than or equal to 2mm.

20. Mold base (100) according to claim 19 characterized in that said space E is zero.

21. Mold base (100) according to any one of claims 19 or 20 characterized in that said length L2 from the central zone (108) is between 0.1 and 0.4 times the seat diameter <pa et est, de préférence égal à 0,3 fois ledit diamètre d’assise <pa.

22. Mold base (100) according to any one of claims 19 to 21 characterized in that, over a length L3 remaining of the length called the transition length, the radius of curvature of the convex fillets (119) decreases progressively until it reaches the value of the substantially constant radius of curvature of the

23. convex fillets (119) defined for the area extending between the end of the length Li to the edge of the central imprint (105). Molding device for the manufacture, by blow molding or stretch blow molding, of containers, in particular bottles, from preforms made of thermoplastic material such as PET, said containers having a body consisting of a substantially cylindrical wall, a shoulder in the extension of said body at an upper end thereof, a neck in the extension of the shoulder, and a petaloid-type bottom at the lower end of said body, said bottom comprising a wall of generally convex shape towards the outside, from which at least three feet originate, formed by protrusions which are distributed angularly in an equidistant manner, which extend approximately parallel to the axis of the container and which are separated from each other by radiating valleys with a bottom of convex curvilinear radial extent,which molding device comprises at least one mold base capable of being mounted movably in a side wall which defines a cavity in the impression of a part of the container, said side wall comprising two half-molds each defining a half-impression of the body of the container and mounted in rotation relative to each other, between a so-called open position, in which the half-molds are angularly spaced from each other and the mold base is lowered relative to the half-molds to allow the introduction of the preform and the evacuation of the formed container, and a so-called closed position, in which the half-molds are applied against each other and trap the mold base between them to thus form the cavity and define the total impression of the container to be formed, said mold base comprising at least three cavities which are distributed angularly in an equidistant manner,which extend substantially parallel to the axis of the mold base and which are separated from each other by radiating ridges with a concave radial extent, the bases of said cavities being distributed over a substantially circular contour, characterized in that the mold base is arranged according to any one of claims 12 to 22.,

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