Containers with improved petal bases and mold bases for producing such containers

Abstract

The present invention relates to a container obtained by blow molding or stretch-blow molding from a blank made of a plastic material. The container comprises a body consisting of a substantially cylindrical wall, a shoulder at the upper end of the body extension, a neck at the shoulder extension, and a petal-shaped base at the lower end of the body. The base typically includes a wall having an outwardly convex shape, from which at least three legs extend. The legs are formed by protruding portions that protrude toward the outside of the container, extending from a central region of the base in the form of pellets, with the material remaining substantially amorphous toward the periphery of the base, which connects to the body. The most protruding portions or tips of the legs are coplanar, forming a seat by allowing the container to remain planar. The seat is circular and has a diameter referred to as the seat diameter φa. Each leg has an end face that extends at a gentle slope from the central region of the base to the base of the leg. The container is notable in that each leg has two substantially flat sides, each laterally adjacent to a valley, and the sides of the legs are connected to the valley by concave cavities, the radius of curvature of which is not constant from the central region of each valley to the connecting region.

Description

[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 materials such as polyethylene terephthalate (PET) and / or recycled polyethylene terephthalate (rPET). More particularly, the present invention relates to containers with a petal bottom and to a mold bottom for producing such containers, which allows for better distribution of material during blow molding of the bottom and, ultimately, for better mechanical integrity of the bottom of said container. [Background technology]

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

[0003] Containers intended for carbonated beverages, where the pressure of gases dissolved in the liquid results in high mechanical stresses, are mostly provided with a petal-shaped base, with protruding legs in the form of petals separated by convex walls, called recesses or valleys, extending radially from the central region of the base. The legs are intended to support the container when it is placed on a surface, and the valleys are intended to absorb the (thermal and mechanical) loads exerted by the contents.

[0004] The performance of the petal bases in terms of their mechanical integrity, i.e., their ability to deform in a limited or controlled manner, is measured not only during filling but also during storage in the containers, which may be prolonged and may take place under extreme temperature and humidity conditions rarely encountered in temperate countries, but usually in countries with continental, tropical or desert climates.

[0005] A frequent deformation that one seeks to avoid is the collapse of the central region of the base, since this would result in susceptibility to "stresses", changes in the configuration of the legs and ultimately a lack of stability of the container. It is also noted that container manufacturers would like to be able to meet the demands of their suppliers, thereby without slowing down the production rate of said containers or, even in contrast, leading to a higher production rate if possible.

[0006] In this regard, improved technical solutions have already been proposed to improve the stability over time of the base of pressure-filled storage containers in a hot and humid atmosphere without affecting the production speed, as is the case in particular in patent application FR 2 897 292.

[0007] French Patent Application Publication No. 2 897 292 describes a mold bottom for a mold for producing containers, in particular bottles, made of a thermoplastic material such as PET by blow molding or stretch blow molding, the container having a base of the so-called petal type with a body and a number of equidistant, angularly distributed legs separated from one another by radial valleys with convexly flared bottoms, extending approximately parallel to the axis of the container, and the mold bottom has a molding cavity with a number of cavities for molding the container bottom, the cavities being equidistant, angularly distributed, separated from one another by radial ridges with concavely flared tops, extending approximately parallel to the axis of the mold bottom, the bottoms of the cavities being distributed over a substantially circular contour. The mold bottom is characterized in that, considered radially on both sides of its deepest point, each cavity is defined in radial cross section outwardly by a curved surface portion that is substantially in the form of a circular arc and inwardly by at least two angled, bent planar portions that intersect the curved surface portion along straight edges of a substantially circumferential extent, the planes that include the straight edges and are tangent to the curved surface portion being substantially perpendicular to the axis of the mold cavity, and the planar portions adjacent to the curved surface portion have an inclination of 12° to 8° relative to the tangent plane.

[0008] With this arrangement, the curved surface portion and the folded planar portion are connected together by edges that provide a reinforced bearing line for each leg of the container bottom in a generally circumferential extent where each leg rests on the planar support, and this edge maintains the bearing contact of the legs on the flat surface despite the deformation and / or tilting that the legs undergo under the influence of the collapse of the central portion of the container bottom.

[0009] This type of mold bottom improves the stability of the stored container over time, but does not fully satisfy the constraints of mechanical performance (ideally high), weight (ideally low), and blow moldability (ideally easy).

[0010] To remedy these problems, French Patent Application Publication No. 2967975 describes a container made of plastic material comprising a body and petal bodies extending from the body, the bottom comprising a bottom wall with an outwardly convex overall shape from which extend legs formed by protrusions, the legs being separated in pairs by portions of the bottom wall forming concave valleys extending radially from a central region of the bottom to the periphery of the bottom, said container having a recess extending from the central region to the periphery and located near the periphery.

[0011] Such containers have the advantage of exhibiting improved resistance to deformation, particularly in maintaining the central area of ​​the base under hydrostatic pressure, possibly combined with the pressure of dissolved gases in the case of carbonated beverages. These performance aspects are observed not only during filling but also during long-term storage under hash humidity and pressure conditions.

[0012] However, none of these prior art mold bottoms and / or containers allows for sufficient mechanical integrity of the container when rPET is used to manufacture the latter. This is because the use of rPET makes it more complicated to distribute the material during stretch-blow molding and / or blow molding of the container. Specifically, in this case, it is more difficult to blow up the amorphous material located in the center of the bottle bottom, which creates the risk of increased stress between the amorphous and bi-oriented regions. "Stress" is understood to mean stress markings in the material, such as cracks or fissures, that weaken the container bottom. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] French Patent Application Publication No. 2897292 [Patent Document 2] French Patent Application Publication No. 2967975 Summary of the Invention [Problem to be solved by the invention]

[0014] One of the objects of the present invention is therefore to remedy these problems by proposing a container and a mould bottom for producing such containers of simple and inexpensive design, which allows for high production speeds while providing good mechanical integrity of the container bottom. [Means for solving the problem]

[0015] To this end, the invention provides a container obtained by blow molding or stretch blow molding from a blank made of plastic material, the container comprising a body constituted by a substantially cylindrical wall, a shoulder at the upper end of the body in the extension of said body, a neck in the extension of the shoulder, and a petal-type bottom at the lower end of said body, said bottom having a wall with an outwardly convex overall shape, from which at least three legs extend towards the periphery of the bottom, the at least three legs being formed by protrusions that protrude outward from the container and extend from a central region of the bottom in the form of pellets, The container is notable in that in the central region of the legs the material remains substantially amorphous, the latter being connected to the body, the furthest protruding portions or tips of the legs being coplanar and together forming a seat within which the container can remain planar, the seat being circular and having a so-called seat diameter φa, each leg having an end face extending at a gentle gradient from the central region of the bottom towards the base of said leg, the container having two substantially flat side faces, each laterally adjacent to a valley, the side faces of the legs being connected to the valley by concave fillets, the radius of curvature of which is not constant from the central region of each valley to the connecting region.

[0016] Such a leg structure, and more particularly such a particular structure of the concave fillet connecting the sides of two adjacent legs to the valley 6, advantageously allows the material to move more easily towards the seat and thus makes it possible to obtain a more gradual transition from the center of the material towards the seat region in the valley region during the stretch blow molding manufacturing step.

[0017] Preferably, said radius of curvature of the concave fillet is variable along the length L1 of the valley from the central region and is substantially constant from said length L1 to the connection region.

[0018] Said length L1 is between 0.2 and 0.8 times the seat diameter φa, and is preferably equal to 0.5 times said seat diameter φa.

[0019] Further, along a portion L2 of the length L1, the concave fillets are separated by a space E of 2 mm or less, with the beginning of the length L2 being the central region. The space E may be zero.

[0020] Said length L2 from the central region is between 0.1 and 0.4 times the seat diameter φa, and preferably equals 0.3 times said seat diameter φa.

[0021] Further, along the remaining length L3 of length L1, called the transition length, the radius of curvature of the concave fillet gradually decreases until it reaches a substantially constant value of the radius of curvature of the concave fillet defined for the region extending between the end of length L1 and the connection region.

[0022] A further subject of the invention relates to a mould bottom for a mould for producing containers, in particular bottles, made of a thermoplastic material such as PET, by blow moulding or stretch blow moulding, said container having a body constituted by a substantially cylindrical wall, a shoulder at the upper end of the body in the extension of said body, a neck in the extension of the shoulder, and a petal-type bottom at the lower end of said body, said bottom having a wall with an outwardly convex overall shape from which extend at least three legs formed by protrusions angularly distributed equidistantly, extending approximately parallel to the axis of the container and separated from one another by radial valleys with a convex curved radially widening bottom, said mould bottom comprising: The mold has at least three cavities, which are angularly distributed equidistantly to form the bottom of the container and are separated from one another by radiating ridges having concave, radially expanding apexes that extend substantially parallel to the axis of the mold bottom, the bottoms of the cavities being distributed over a substantially circular contour corresponding to the so-called seat diameter φa of the container, each cavity having a bottom surface that extends at a gradual gradient from a central region of the bottom to the bottom of the cavity, and the mold bottom is notable in that it has convex fillets on both sides of the apex connecting the ridges extending on both sides of the apex, the radius of curvature of the convex fillets not being constant from the central region to the edge of the central imprint.

[0023] Preferably, said radius of curvature of the convex fillet is variable along a length L1 from the central region to the apex and is substantially constant from said length L1 to the edge of the central impression.

[0024] Said length L1 is between 0.2 and 0.8 times the seat diameter φa, and is preferably equal to 0.5 times said seat diameter φa.

[0025] Further, along a portion L2 of the length L1, the portion L2 corresponding to the length starting at the central region, the convex fillets are separated by a space E of 2 mm or less. The space E may be 0.

[0026] Said length L2 from the central region is between 0.1 and 0.4 times the seat diameter φa, and preferably equals 0.3 times said seat diameter φa.

[0027] Further, along the remaining length L3 of length L1, called the transition length, the radius of curvature of the convex fillet gradually decreases until it reaches a constant radius of curvature value of the convex fillet defined for the region extending between the end of length L1 and the edge of the central stamp.

[0028] A final subject of the invention relates to a molding device for producing containers, in particular bottles, from preforms made of a thermoplastic material such as PET, by blow molding or stretch blow molding, said containers having a body constituted by a substantially cylindrical wall, a shoulder at its upper end in the extension of said body, a neck in the extension of the shoulder, and a petal-type bottom at the lower end of said body, said bottom having a wall with an outwardly convex overall shape from which extend at least three legs formed by protrusions, which are angularly distributed equidistantly and separated from one another by radial valleys with convex curved radially widening bottoms that extend substantially parallel to the axis of the container, said molding device comprising at least one mould bottom that can be movably attached to a side wall that defines a cavity with the imprint of a portion of the container, said side wall comprising two mould halves, The two half moulds each define a half imprint of the body of the container and are mounted rotatably relative to each other between a so-called open position and a so-called closed position, in which the half moulds are angularly spaced apart from each other to allow the introduction of the preform and the removal of the moulded container, and the mould bottom is lowered relative to the half moulds, and in the closed position the half moulds are pressed together, sandwiching the mould bottoms together to form cavities and define the full imprint of the container to be formed, the mould bottom having at least three cavities which are angularly distributed equidistantly and separated from each other by radiating ridges having convex radially expanding tops which extend substantially parallel to the axis of the mould bottom, the bottoms of the cavities being distributed over a substantially circular contour, the device being notable in that the mould bottom is designed in accordance with the above-mentioned invention.

[0029] Further advantages and features will become more clearly apparent from the following description of a single embodiment variant, given as a non-limiting example, according to the invention, with reference to the attached drawings, in which: [Brief explanation of the drawings]

[0030] [Figure 1]1 is a partial perspective bottom view of the bottom of a container having a petal base according to the present invention; FIG. [Figure 2] 2 is a side view of the lower part of the base of the container having a petal base according to the present invention shown in FIG. 1. FIG. [Figure 3] FIG. 3 is a bottom view of the bottom of the container according to the present invention shown in FIGS. 1 and 2. [Figure 4] 3 is a schematic cross-sectional view of two adjacent legs of the bottom of the embodiment variant of the container according to the invention shown in FIGS. 1 and 2; FIG. [Figure 5] FIG. 2 is a perspective view of the bottom of a mold according to the present invention. [Figure 6] FIG. 6 is a top view of the mold bottom according to the present invention shown in FIG. 5. [Figure 7] 7 is a cross-sectional view of the mold bottom of FIG. 6 taken along the section VII-VII′. DETAILED DESCRIPTION OF THE INVENTION

[0031] In the remainder of the description of the container according to the invention, like reference numerals refer to like elements. The different figures are not necessarily drawn to scale.

[0032] 1 to 4, the container 1 according to the invention is, for example, a bottle intended to contain soft drinks or carbonated drinks. It is made from PET and / or rPET by stretch blow molding or injection blow molding. In particular, it is to this type of container that the present invention preferably relates. However, it is clear that said container 1 can be made from any other thermoplastic material known per se, or from a mixture of various materials, without departing from the scope of the present invention.

[0033] In the usual way, the container 1 has a body 2 forming a cylindrical wall and extending from a petal-type base 3, at the top of which there is a shoulder which leads to a neck which terminates in a mouth designed by threading or in any other way to receive a cap, the shoulder, neck, mouth and cap not being shown in FIG. 1.

[0034] The petal base 3 comprises legs 4 formed by protrusions extending from a substantially hemispherical wall 5 with outward convexities and forming valleys 6 between two adjacent legs 4, the hemispherical wall 5 forming the bottom of the valleys 6. The upper end of each leg 4 opens into the body 2.

[0035] In this particular embodiment, the petal base 3 has five lobes forming a leg 4, which are angularly distributed equidistantly and separated from one another by radiating valleys 6, which extend substantially parallel to the longitudinal axis of the container 1 and have a convex, curved, radially expanding base. All valleys 6 converge towards a so-called central region 7 of the bottom 3, which consists of a slightly outwardly protruding circular plate or pellet, in which the material remains substantially amorphous. The bottom 3 of the container 1 is connected to the main body 2 of the container 1 by a so-called connection region 8, which is substantially in the form of a cylinder of revolution.

[0036] Thus, the legs 4 are separated in pairs by portions of the bottom wall 5, called valleys 6, which extend radially in a star shape from a central region formed by the central region 7 to a periphery formed by the connecting region 8. In cross section, the valleys 6 are outwardly concave, i.e., lie on a plane perpendicular to the radial direction. The radius of curvature of the valleys 6 may be variable. More specifically, it is preferably smaller closer to the central region 7 and relatively larger closer to the connecting region 8.

[0037] Furthermore, the valley 6 has, in the vicinity of the central region 7, an inner portion 9 that is convex outward in radial cross section, and, in the vicinity of the connection region 8, an outer cross section 10 that is concave outward in radial cross section.

[0038] In the example shown in the drawings, the base 3 comprises five legs 4 and five valleys 6, distributed in a regularly alternating star shape. This number represents a good compromise, however, it can be less (but not less than three) or more (but preferably not more than seven). Furthermore, the most protruding parts or tips 16 of the legs 4 are coplanar and jointly form a seat on which the container 1 can rest on a flat surface, said seat being circular and having a so-called seat diameter, denoted in the remainder of this specification by φa, and each leg 4 has an end face 13 that extends at a gentle slope from the central region 7 of the base 3 to the base of said leg 4.

[0039] Each leg 4 has two substantially flat side surfaces 12, each laterally adjacent to the valley 6. The side surfaces 12 are not vertical (because blowing the mold on the bottom 3 would be difficult, if not impossible), but are inclined and open outward from the valley 6. The side surfaces 12 are connected to the end surface 13 by fillets 14. Each leg 4 is further bounded radially by an outer surface 15 that extends to the vicinity of the tip 16 of the leg 4 at the continuation of the body 2 and is connected to the outer surface 15 by fillets 17. The outer surface 15 is not cylindrical, but is substantially in the form of a cone of revolution centered on the longitudinal axis of the container 1. Furthermore, in radial cross section, this surface 15 is not straight, but is convex with a large radius of curvature. At the periphery of the bottom 3, the surface 15 is connected to the body 2 by a connecting region 8, which is in the form of a fillet.

[0040] Advantageously, the bottom 3 is further provided with a radial groove 18 which extends in a concave manner in the bottom 3 along the valley 6 towards the interior of the container 1 .

[0041] More specifically, each radial groove 18 extends along the midline of the valley 6 from the vicinity of the central region 7 to the vicinity of the connecting region 8. In top view, each groove 18 has a substantially elongated shape, with its edges parallel along most of its length and both of its ends tapering. In radial cross section, each groove 18 has a profile in the form of a flared U. Said grooves 18 have the function of reinforcing the base 3. Under the influence of mechanical stresses exerted on the container 1 (in particular under the influence of the pressure prevailing in a container filled with carbonated liquid), the grooves 18 tend to creep by expanding and flattening, widening the valley 6 and consequently making the legs 4 more vertical, which counteracts the overall collapse of the base 3.

[0042] Furthermore, each valley 6 widens from the central region 7 to the connecting region 8. This widening is preferably continuous, meaning that the edges of the valleys 6 form an angle between each other that is not zero at any point. In the example shown, the valleys 6 have a tulip- (or bell-) shaped profile in plan view, but this shape is not limiting and the edges of the valleys 6 could be straight, so that said valleys 6 have a V-shaped profile.

[0043] Furthermore, advantageously, said side surfaces 12 of the legs 4 are connected to the valleys 6 by concave fillets 19, the radii of curvature of which, indicated in FIG. 4 by R1a and R1b, are not constant from the central region 7 to the connecting region 8 of each valley 6.

[0044] More specifically, the radius of curvature of the concave fillet 19 is variable along a length L1 from the central region 7 to the valley 6 and is substantially constant from the length L1 to the connection region 8. The length L1 is between 0.2 and 0.8 times the seat diameter φa, and is preferably equal to 0.5 times the seat diameter φa.

[0045] Furthermore, the length L1 can be decomposed into two lengths L2 and L3, i.e., L1 = L2 + L3. The length L2 corresponds to the length whose starting point is the central region 7, and the space E between the concave fillets 19 of two adjacent legs 4 separated by a valley 6 is minimal. Preferably, along this length L2, the space E between the concave fillets 19 of two adjacent legs 4 separated by a valley 6 is equal to or less than 2 mm. It should be noted that the space E may also be 0, i.e., equal to 0. In this case, the concave fillets 19 of two adjacent legs 4 then intersect at a distance L2 from the central region 7. The length L2 from the central region 7 is between 0.1 and 0.4 times the seat diameter φa, and preferably equal to 0.3 times the seat diameter.

[0046] Along said length L3, called the transition length, the radius of curvature of the concave fillet 19 gradually decreases until it reaches a substantially constant value of the radius of curvature of the concave fillet 19 defined for the region extending between the end of the length L1 and the connection region 8.

[0047] It should be noted that such a leg structure, and more particularly such a particular structure of the concave fillet 19 connecting the sides 12 of two adjacent legs to the valley 6, advantageously allows the material to move more easily towards the seat and thus makes it possible to obtain a more gradual transition of material in the valley 6 region from the center to the seat region during the stretch blow molding manufacturing step.

[0048] Reference is now made to Figures 5 to 7, which show a mould bottom 100 intended to equip a mould for producing, by blow moulding or stretch blow moulding, containers 1, in particular bottles, according to the invention, made of thermoplastic material, more particularly rPET and / or PET, as described above with reference to Figures 1 to 4.

[0049] The mold bottom 100 is provided with a molding cavity 101 for molding the bottom 3 of the container 1, having a number of cavities 102 equal to the number of legs 4 of the bottom 3 of the container 1, generally 3 to 7, in practice 4 to 6 (5 in the example shown in Figures 1 to 5), the cavities being angularly distributed equidistantly (in this example at an angular interval of 72° from one another), extending substantially parallel to the axis of the mold bottom 100 (which is also the axis of the molding cavities C) and separated from one another by radial ridges 103 (i.e., substantially radially extending protrusions of the molding cavities C which result in the formation of the above-mentioned valleys 6 in the bottom 3 of the molded container 1). Each ridge 103 has a peak 104 which widens in a concave radial curve in the form of a circular arc starting from the edge of a central impression 105. The bottom 106 of the cavity 101 is distributed over a substantially circular contour 107 with a given base diameter φa, which corresponds to the seat diameter φa of the bottom 3 of the container 1. The center of the molding cavity 101 has a protruding central area 108 in which a circular cavity 109 of shallow depth is recessed for forming the pellets in the aforementioned central area 7 of the bottom 3 of the container 1. According to the invention, each cavity 102 has a bottom surface 110 that extends with a gentle gradient from the central area 108 of the mold bottom 100 to the bottom of the cavity 102. Considered radially on both sides of its deepest point, each cavity 102 is delimited in a radial cross section outward by a curved surface portion 111 that is substantially in the form of a circular arc, and inward by a surface portion 112 with a so-called connecting curve.

[0050] Furthermore, the mold bottom has convex fillets 119 on both sides of the top 104 connecting the ridges 103 extending on both sides of the top, and the radius of curvature of the convex fillets is not constant from the central region 108 to the edge of the central imprint 105.

[0051] More specifically, the radius of curvature of the convex fillet 119 is variable along a length L1 from the central region 108 to the apex 104 and is substantially constant from the length L1 to the edge of the central impression 105. The length L1 is between 0.2 and 0.8 times the seat diameter φa, and preferably equal to 0.5 times the seat diameter φa.

[0052] Furthermore, the length L1 can be decomposed into two lengths L2 and L3, i.e., L1 = L2 + L3. The length L2 corresponds to the length whose starting point is the central region 108, and the space E between the convex fillets 119 of a single apex 104 is minimum. Preferably, along this length L2, the space E between the convex fillets 119 of a single apex 104 is equal to or less than 2 mm. Note that the space E may also be 0, i.e., equal to 0. In this case, the convex fillets 119 then intersect at a distance L2 from the central region 108. The length L2 from the central region 108 is between 0.1 and 0.4 times the seat diameter φa, and preferably equal to 0.3 times the seat diameter φa.

[0053] Along said length L3, referred to as the transition length, the radius of curvature of the convex fillet 119 gradually decreases until it reaches a constant radius of curvature value of the convex fillet 119 defined for the area extending between the end of length L1 and the edge of the central imprint 105.

[0054] A final subject of the invention, not shown in the figures, relates to a molding apparatus for producing containers by blow molding or stretch blow molding, as mentioned above.

[0055] In a conventional manner, the molding apparatus comprises at least one mold bottom movably mounted on a side wall defining a cavity having a partial impression of the container body, the side walls of which are arranged to rotate relative to one another between an open position, in which the mold halves are angularly spaced apart from one another to allow the introduction of a preform and the removal of the formed container, and a closed position, in which the mold halves are pressed together to sandwich the mold bottoms together and form a cavity defining the entire impression of the formed container. The mold bottom has at least three cavities, angularly distributed equidistantly and separated from one another by radiating ridges with concave, radially expanding apexes extending substantially parallel to the axis of the mold bottom, the bottoms of the cavities being distributed over a substantially circular contour. The molding apparatus is distinguished by the fact that the mold bottom is designed as described above with reference to Figures 1 to 4.

[0056] Finally, it is clear that the examples just given are only specific illustrations that are in no way limiting with regard to the field of application of the invention.

Claims

1. Container obtained by blow molding or stretch blow molding from a blank made of plastic material, a body comprising a substantially cylindrical wall; a shoulder portion at the upper end of the body, the shoulder portion being an extension of the body; The neck is an extension of the shoulders, a petal-type bottom at the lower end of the body; the bottom has a wall with an outwardly convex overall shape, from which at least three legs extend towards the periphery of the bottom, the at least three legs being formed by protrusions which protrude outwards from the container and extend from a central region of the bottom in the form of pellets, in which the material remains substantially amorphous, the latter being connected to the body, the most protruding parts or tips of the legs being coplanar and together forming a seat within which the container can remain planar, the seat being circular and having a so-called seat diameter φa, and each leg having an end face which extends at a gentle gradient from the central region of the bottom towards the base of said leg, 1. A container characterized in that each leg has two substantially flat sides laterally adjacent to a valley, the sides of the legs being connected to the valley by a concave fillet, the radius of curvature of which is not constant from the central region of each valley to the connecting region.

2. The radius of curvature of the concave fillet is the length L of the valley from the central region. １ and the length L １ 2. The container of claim 1, wherein the thickness is substantially constant from the first region to the connecting region.

3. The length L １ Container according to claim 2, characterized in that is between 0.2 and 0.8 times the seat diameter φa, and is preferably equal to 0.5 times said seat diameter φa.

4. Length L １ Part L ２ along which the concave fillets are separated by spaces E of 2 mm or less and have a length L ２ Container according to claim 2 or 3, characterized in that the starting point of is in the central region.

5. 5. The container according to claim 4, wherein the space E is 0.

6. The length L from the central region 7 ２ 6. A container according to claim 4, wherein is between 0.1 and 0.4 times the seat diameter φa, and is preferably equal to 0.3 times said seat diameter φa.

7. The length L, called the transition length １ The remaining length L ３ The radius of curvature of the concave fillet along the length L １ 7. A container according to claim 4, wherein the radius of curvature of the concave fillet defined for the region extending between the end of the container and the connection region gradually decreases until it reaches a substantially constant value.

8. A mould bottom for a mould for producing containers, in particular bottles, made of a thermoplastic material such as PET by blow moulding or stretch blow moulding, The container comprises: a body having a substantially cylindrical wall; a shoulder portion at the upper end of the body, the shoulder portion being an extension of the body; The neck is an extension of the shoulders, a petal-type base at the lower end of the body; The bottom has a wall with an outwardly convex overall shape, from which at least three legs extend, the at least three legs being formed by equidistant angularly distributed protrusions separated from one another by radial valleys extending generally parallel to the axis of the container and having a convexly curved, radially expanding base; the mold bottom has at least three cavities, the at least three cavities being equidistantly angularly distributed and separated from one another by radiating ridges having concave radially extending apexes extending substantially parallel to the axis of the mold bottom to form the bottom of the container; the bottom of said cavity is distributed over a substantially circular contour corresponding to the so-called seat diameter φa of the container, Each cavity comprises a mold bottom having a bottom surface that extends at a gentle slope from a central region of the bottom to the bottom of the cavity; A mold bottom having convex fillets on both sides of the top connecting the ridges extending on both sides of the top, the radius of curvature of the convex fillets not being constant from the central region to the edge of the central stamp.

9. The radius of curvature of the convex fillet is the length L from the central region to the apex. １ and the length L １ 9. The mold bottom according to claim 8, characterized in that it is substantially constant from the edge of the central stamp to the edge of the central stamp.

10. The length L １ 10. Mold bottom according to claim 9, characterized in that is between 0.2 and 0.8 times the seat diameter φa, preferably equal to 0.5 times said seat diameter φa.

11. The length L １ Part L ２ The L corresponding to the length whose starting point is the central region ２ 11. A mold base according to claim 9 or 10, characterized in that along the length of the mold base, the convex fillets are separated by a space E of 2 mm or less.

12. The mold base according to claim 11, characterized in that the space E is 0.

13. The length L from the central region ２ 13. A mould bottom according to claim 11 or 12, characterized in that is between 0.1 and 0.4 times the seat diameter φa, and is preferably equal to 0.3 times said seat diameter φa.

14. The length L, called the transition length １ The remaining length L ３ The radius of curvature of the convex fillet along the length L １ 14. A mold bottom according to claim 11, characterized in that the radius of curvature of the convex fillet defined for the area extending between the end of the mold bottom and the edge of the central stamp gradually decreases until it reaches a substantially constant value.

15. 1. A molding apparatus for producing containers, in particular bottles, from preforms made of a thermoplastic material such as PET by blow molding or stretch blow molding, comprising: The container comprises: a body comprising a substantially cylindrical wall; a shoulder at the upper end of the body, the shoulder being an extension of the body; The neck is an extension of the shoulders, a petal-type base at the lower end of the body; the bottom has a wall with an outwardly convex overall shape, from which extend at least three legs formed by protrusions, the protrusions being equidistantly angularly distributed and separated from one another by radial valleys extending generally parallel to the axis of the container and having convexly curved radially expanding bottoms, and the molding device comprises at least one mold bottom that can be movably attached to a side wall defining a cavity with an imprint of a portion of the container; the side wall comprises two half moulds, each of which defines a half imprint of the body of the container, and which are rotatably mounted relative to one another between a so-called open position, in which the half moulds are angularly spaced apart from one another and the mould bottoms are lowered relative to the half moulds to allow the introduction of the preform and the removal of the moulded container, and in which the half moulds are pressed together, sandwiching the mould bottoms together to form a cavity and define a full imprint of the container to be formed; 15. An apparatus in which the mold bottom has at least three cavities, which are angularly distributed equidistantly and separated from one another by radiating ridges extending substantially parallel to the axis of the mold bottom and having convex radially expanding ridges, the bottoms of the cavities being distributed over a substantially circular contour, characterized in that the mold bottom is designed as claimed in any one of claims 8 to 14.

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