Container having an improved petaloid bottom, and mould bottom for producing such a container

Abstract

The present invention relates to a container which is obtained by blow moulding or stretch blow moulding from a blank made of plastics material. The container 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 bottom at the lower end of said body. The bottom includes a wall which has a generally outwardly convex shape and from which at least three feet extend. The feet are formed by protrusions projecting towards the outside of the container and extend from a central region of the pellet-shaped bottom where the material has remained substantially amorphous towards a periphery of the bottom where the bottom connects to the body. The most protruding parts or tops of the feet are coplanar and jointly form a seat by means of which the container can rest on a planar surface. The seat is circular and has a diameter referred to as seat diameter φa, and each foot has an end face which extends in a gentle slope from the central region of the bottom towards the base of said foot. The container is noteworthy in that each foot has two substantially planar flanks which each laterally border a valley, the flanks of the feet being connected to the valley by concave hollows, of which the radius of curvature is not constant from the central region to the connection region of each valley.

Description

[0001] Description

[0002] TITLE: Improved petaloid-bottomed container and mold base for making such a container

[0003] Technical field

[0004] 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 base and a mold base for the manufacture of such a container allowing better distribution of the material during the blowing of the base and, ultimately, better mechanical strength of the base of said container.

[0005] State of the art

[0006] In the field of PET container manufacturing, 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 base, 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.

[0007] Containers intended for carbonated beverages, in which the pressure of the gas dissolved in the liquid induces significant mechanical stresses, are mostly provided with petal-shaped bases: the base comprises protruding, 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.

[0008] 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 continental, tropical or desert climates.

[0009] A common deformation that one wishes to avoid is the sagging of the central area of ​​the base, because it 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 in the production rate of said containers, or even if possible on the contrary with higher production rates.

[0010] In this regard, an improved technical solution has already been proposed to improve 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.

[0011] 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.

[0012] 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.

[0013] Although this type of mold base improves the stability over time of the bases of the preserved containers, it does not provide total satisfaction of the constraints of mechanical performance, ideally high, of weight, ideally low, and of blowability, ideally easy.

[0014] In order to overcome these drawbacks, document FR2967975 describes a plastic container comprising a body and a petaloid bottom extending the body, the bottom comprising a bottom wall of generally convex shape towards the outside, from which protrude feet formed by protrusions, the feet being separated two by two by portions of the bottom wall forming hollow valleys which extend radially from a central zone of the bottom to a periphery of the bottom, container in which each valley widens from the central zone towards the periphery, and has a concave portion located close to the periphery.

[0015] Such a container has the advantage of having increased resistance to deformation. In particular, we note a good maintenance of the central zone of the bottom under hydrostatic pressure, 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 in severe conditions of humidity and pressure.

[0016] 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.

[0017] Disclosure of the invention

[0018] One of the aims of the invention is therefore to overcome 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.

[0019] 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 bottom in the form of a pellet, 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 rest on a flat surface,said base being circular and having a so-called base 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 each foot has two substantially flat sides which each laterally border a valley, said sides of the feet being connected to the valley by concave fillets whose radius of curvature is not constant from the central area towards the connection area of ​​each valley.,

[0020] Such a construction of the foot, and more particularly such a specific construction of the concave fillets connecting the flanks of two adjacent feet to a valley 6, advantageously allows the material to move more easily towards the seat and therefore to obtain a more gradual transition of the material at the valley from the center to the seat zone during the stretch-blow molding manufacturing step. 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.

[0021] Said length Li is between 0.2 and 0.8 times the seat diameter (fa and, preferably, equal to 0.5 times said seat diameter cfa.

[0022] Furthermore, on a part L2 of the length Li, said concave fillets 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. Said space E can be zero.

[0023] Said length L2 from the central zone is between 0.1 and 0.4 times the seat diameter cfa and is preferably equal to 0.3 times said seat diameter cfa.

[0024] Furthermore, over a length L3 remaining from the length Li, 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.

[0025] 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 bottoms of said cavities being distributed on a substantially circular contour corresponding to the so-called seat diameter 4>a of the container, and each cavity having a bottom face which extends in a gentle slope from the central zone of the bottom towards the bottom of the cavity; said mold base is remarkable in that it 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.,

[0026] 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.

[0027] Said length Li is between 0.2 and 0.8 times the seat diameter (fa and, preferably, equal to 0.5 times said seat diameter cfa.

[0028] Furthermore, on a part L2 of said length Li, 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 can be zero.

[0029] Said length L2 from the central zone is between 0.1 and 0.4 times the seat diameter cfa and is preferably equal to 0.3 times said seat diameter cfa.

[0030] Furthermore, over a length L3 remaining from the length Li, called the transition length, the radius of curvature of the convex fillets gradually decreases until it reaches the value of the constant radius of curvature of the convex fillets defined for the area extending between the end of the length Li to the edge of the central imprint.

[0031] 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 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 device is remarkable in that the mold base is arranged according to the invention described above.,

[0032] Brief description of the drawings

[0033] Other advantages and characteristics will emerge more clearly from the following description of a single variant embodiment, given as a non-limiting example, in accordance with the invention, with reference to the appended drawings in which:

[0034] [Fig. 1] is a partial perspective view from below of the bottom of a petaloid-bottomed container according to the invention,

[0035] [Fig. 2] is a side view of the lower part of the bottom of the petaloid-bottomed container according to the invention shown in Fig. 1,

[0036] [Fig. 3] is a bottom view of the bottom of the container according to the invention shown in Figures 1 and 2,

[0037] [Fig. 4] is a schematic sectional representation of two adjacent feet of the bottom of the variant embodiment of the container according to the invention shown in Figures 1 and 2,

[0038] [Fig. 5] is a perspective view of a mold base according to the invention,

[0039] [Fig. 6] is a top view of the mold base according to the invention shown in Figure 5,

[0040] [Fig. 7] is a sectional view of the mold base of Figure 6, along section plane VII-VII'. Embodiment of the invention

[0041] In the following 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.

[0042] With reference to Figures 1 to 4, 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.

[0043] 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 figure 1.

[0044] Said petaloid base 3 comprises feet 4 formed by outgrowths 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.

[0045] 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 outward 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. Thus, the feet 4 are separated two by two by portions of the base 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 may be variable. More precisely, it is preferably small near the central zone 7, and relatively larger near the connection zone 8.

[0046] 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.

[0047] 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 4>a, and each foot 4 has an end face 13 which extends in a gentle slope from the central zone 7 of the base 3 towards the base of said foot 4.

[0048] 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.

[0049] Advantageously, the bottom 3 is also provided with radial grooves 18 which extend hollowly towards the inside of the container 1, at the bottom 3 and along the valleys 6. 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. Said grooves 18 have the function of stiffening the bottom 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 bottom 3.

[0050] 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.

[0051] Furthermore, advantageously, said sides 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. 4, is not constant from the central zone 7 to the connection zone 8 of each valley 6.

[0052] 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 (fa and, preferably, equal to 0.5 times said seat diameter cfa.

[0053] Furthermore, said length Li can be broken down into two lengths L2 and L3, i.e. 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 2 mm. 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 4>a and is preferably equal to 0.3 times said seat diameter.

[0054] 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 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.

[0055] 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 sides 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.

[0056] Referring now to Figures 5 to 7, there is shown a mold base 100 intended to equip a manufacturing mold, by blow molding or stretch blow molding, 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 4.

[0057] 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 ridge 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 (fa which corresponds to the seat diameter cfa of the bottom 3 of the containers 1. The center of the molding cavity 101 comprises a central zone 108 projecting in the center of which is hollowed out a circular cavity 109 of shallow depth, for the formation of the pellet of the aforementioned central zone 7 of the bottom 3 of the container 1. According to the invention, each cavity 102 has a bottom face 110 which extends in a gentle slope from the central zone 108 of the mold bottom 100 towards the bottom of the cavity 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.

[0058] Furthermore, said mold base 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 imprint 105.

[0059] 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 cfa and, preferably, equal to 0.5 times said seat diameter cfa.

[0060] Furthermore, said length Li can be decomposed into two lengths L2 and L3, i.e. LI=LZ+L3. Said length L2 corresponds to the length, the starting point of which is the central zone 108, in which the space E between the convex fillets 119 of the same ridge 104 is minimal. Preferably, over this length L2, the space E between said convex fillets 119 of the same ridge 104 is less than or equal to 2 mm. It will be noted that said space E can be zero, i.e. equal to 0. In this case, the convex fillets 119 then meet at a distance L2 from the central zone 108. Said length L2 from the central zone 108 is between 0.1 and 0.4 times the seat diameter cfa and is preferably equal to 0.3 times said seat diameter cfa.

[0061] Over said length L3, called the transition length, the radius of curvature of the convex fillets 119 gradually decreases until it reaches the value of the constant radius of curvature of the convex fillets 119 defined for the zone extending between the end of the length Li to the edge of the central imprint 105.

[0062] 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.

[0063] 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 1 to 4.,

[0064] Finally, it is clear that the examples just given are only specific illustrations and are in no way limiting as to the fields of application of the invention.

Claims

Claims

1. 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 base in the form of a pellet, where the material has remained substantially amorphous, towards a periphery of the base 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 rest on a flat surface, said base being circular and having a diameter called the base 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, characterized in that each foot has two substantially flat sides which each laterally border a valley, said sides of the feet being connected to the valley by concave fillets whose radius of curvature is not constant from the central area towards the connection area of ​​each valley.

2. Container according to claim 1 characterized in that 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.

3. Container according to claim 2 characterized in that said length Li is between 0.2 and 0.8 times the seat diameter 4>a and, preferably, equal to 0.5 times said seat diameter 4>a.

4. Container according to any one of claims 2 or 3 characterized in that over a part L2 of the length Li, said concave fillets 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.

5. Container according to claim 4 characterized in that said space E is zero.

6. Container according to any one of claims 4 or 5 characterized in that said length L2 from the central zone 7 is between 0.1 and 0.4 times the seat diameter 4>a and is preferably equal to 0.3 times said seat diameter 4>a.

7. Container according to any one of claims 4 to 6 characterized in that, over a length L3 remaining from the length Li, called the transition length, the radius of curvature of the concave fillets decreases progressively 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.

8. 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 crest, the bottoms of said cavities being distributed over a substantially circular contour corresponding to the so-called seat diameter 4>a of the container, and each cavity having a bottom face which extends in a gentle slope from the central zone of the bottom towards the bottom of the cavity, characterized in that it 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.,

9. Mold base according to claim 8 characterized in that 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.

10. Mold base according to claim 9 characterized in that said length Li is between 0.2 and 0.8 times the seat diameter (fa and, preferably, equal to 0.5 times said seat diameter cfa.

11. Mold base according to any one of claims 9 or 10 characterized in that over a part L2 of said length Li, 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 2mm.

12. Mold base according to claim 11 characterized in that said space E is zero.

13. Mold base according to any one of claims 11 or 12 characterized in that said length L2 from the central zone is between 0.1 and 0.4 times the seat diameter cfa and is preferably equal to 0.3 times said seat diameter cfa.

14. Mold base according to any one of claims 11 to 13 characterized in that, over a length L3 remaining from the length Li, called the transition length, the radius of curvature of the convex fillets decreases progressively 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 impression.

15. 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 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 imprint 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 extension, 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 8 to 14.,

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