Container molding unit with bottom detachment system

Abstract

Title: Container molding unit with bottom release system The present invention relates to a molding unit (1) for manufacturing a container from a plastic preform (2), this molding unit (1) comprising at least: a mold (3) comprising a wall (4) formed by two articulated half-molds (3A, 3B) defining an internal cavity (5) distributed around a principal axis of the mold (3) and defining at least partially an impression (6) for a side wall or body and having, at a lower end, a lower opening (7), a mold bottom (8) which fits into the lower opening (7) and has a top surface defining at least a partial impression of the bottom of the container, the mold bottom (8) being pierced in its center by an opening (9),a cylinder (15) comprising a piston (16) and a rod (17) at the end of which is mounted an insert (10) capable of sliding through said opening (9) of the bottom of the mold (8), between a position said to be deployed in which a free end of the insert (10) protrudes from the bottom of the mold (8) and a position said to be retracted in which the free end of the insert (10) is in the vicinity of the bottom of the mold (10), and a saddle (14) on which the bottom of the mold (8) is mounted, said saddle (14) comprising at least a lower stage (14A) and an upper stage (14B) mounted on the upper stage (14A), said saddle (14) internally defining a housing (17) in which the piston (16) of the cylinder (15) is mounted; said molding unit is remarkable in that the mold base (8) and / or the insert (10) includes pneumatic means for detaching the wall from the base of the blown container,said pneumatic detachment means simultaneously providing cooling of said bottom of the blown container. Figure for the abbreviation: Figure 2,

Description

Title of the invention: Container molding unit with bottom detachment system technical field

[0001] The present invention relates to the manufacture of containers, such as bottles, which are produced by stretch blow molding from preforms of plastic material (mainly thermoplastic, for example PET or recycled PET called rPET). State of the art

[0002] In the field of packaging, it is well known that a container comprises a wall part (generally cylindrical in shape), a neck open at an upper end of the wall part, and a bottom closed at a lower end of the wall part.

[0003] The manufacture of a container by blow molding generally comprises inserting a preform, also commonly called a blank, into a molding unit having a mold side wall defining a counter-impression of the container wall and a mold bottom defining a counter-impression of the container bottom, said preform having been preheated to a temperature above the glass transition temperature of the material, and injecting a pressurized fluid (such as air) into the hot preform. The blow molding can be (and generally is) completed by stretching the preform by means of a sliding rod called a stretching rod, which is inserted into the preform.

[0004] Thus, blow molding while being stretched in the longitudinal direction by a coaxially provided stretching rod is well known.

[0005] Furthermore, as the amount of material required to manufacture each container decreases continuously over the years for economic and environmental reasons, it is necessary to improve the structural rigidity of the container.

[0006] The improvement of the structural rigidity of the portion of the wall is achieved in a known manner by means of a series of annular grooves forming stiffeners whose function is to minimize the risk of ovalization of the container (i.e. the deformation of the cross-section of the container from a circular shape to an oval shape).

[0007] Several techniques are also known to ensure the structural rigidity of the container bottom. One technique consists of equipping the container bottom with rigidity artifacts such as ribs, the function of which is to minimize the risk of the bottom collapsing under bending stresses due to the hydrostatic pressure of the contents and, possibly, the weight of stacked containers on the same pallet.

[0008] Another technique consists of providing additional stretching of the container base material to mechanically increase its crystallinity (and thus its mechanical rigidity). As described in published PCT application WO 99 / 52701, this is generally achieved by means of a movable mold base mounted to slide relative to the mold side wall, so that the container material is first blown beyond the final shape in a retracted position of the mold base, and then stamped into the final shape by moving the mold base to a raised position in which it, together with the mold side wall, completes the counter-impression of the container. The molding unit comprises a cylindrical shell, and at least a portion of the mold base has a cylindrical support received to slide within the cylindrical shell.

[0009] The mold bottom is generally moved by means of a linear actuator such as a hydraulic or pneumatic cylinder, comprising a cylindrical housing and a rod which is slidably mounted inside the housing and to which the liner of the cylinder of the mold bottom is attached.

[0010] However, the outer surface of the embossed bottom of the container thus blown into the mold adheres to the lower inner surface of the bottom of the mold so that it is difficult to remove the container without the bottom of the container turning over, rendering the container unusable. Disclosure of the invention

[0011] One of the aims of the invention is therefore to remedy these disadvantages by proposing a molding unit of simple and inexpensive design which allows removal of the molded container without the bottom of the container turning over while cooling said bottom of the container and also cooling a mechanical part without having to use internal fluidic circulation.

[0012] To this end and in accordance with the invention, a molding unit is proposed for manufacturing a container from a plastic preform, this molding unit comprising at least: a mold comprising a wall formed by two articulated half-molds defining an internal cavity distributed around a main axis of the mold and defining at least partially an impression for a side wall or body and having, at a lower end, a lower opening, a mold base which fits into the lower opening and has an upper surface defining at least a partial impression of the bottom of the container, the mold base being pierced in its center by an opening, a cylinder comprising a piston and a rod at the end of which is mounted an insert adapted to slide through said opening of the mold base,between a so-called deployed position in which a free end of the insert protrudes from the bottom of the mold and a so-called , retracted in which the free end of the insert is in the vicinity of the bottom of the mold, and a saddle on which the bottom of the mold is mounted, said saddle comprising at least a lower stage and an upper stage mounted on the upper stage, said saddle internally defining a housing in which the piston of the cylinder is mounted; said molding unit is notable in that the bottom of the mold and / or the insert comprises pneumatic means for detaching the wall of the bottom of the blown container, said pneumatic detachment means simultaneously providing cooling of said bottom of the blown container.

[0013] Advantageously, said insert comprises a central recess connected to a fluid source under a determined pressure and, at its upper end, at least one orifice opening into said central recess.

[0014] Preferably, said insert has on its side wall, near its upper end, a plurality of orifices opening into said central recess.

[0015] Moreover, the axis of said orifices preferably forms an angle between 30 and 80° with the longitudinal axis of the insert.

[0016] Advantageously, said mold bottom comprises a plurality of channels opening onto the upper face of said mold bottom by forming orifices, said channels being fluidly connected to a source of pressurized fluid.

[0017] Furthermore, said mold bottom has a plurality of channels opening, at a first end, onto the upper face of the mold bottom by forming orifices, and opening, at the opposite end, into the central channel of the opening of the mold bottom in which the insert slides.

[0018] Incidentally, the central channel of the bottom of the mold includes, at least above the channels opening into said central channel, a sealing gasket.

[0019] Furthermore, the axis of said mold bottom channels forms an angle between 20 and 80° with the longitudinal axis of the insert.

[0020] Preferably, the channels of the bottom of the mold opening into the central channel extend to the orifices of the insert when said insert is in its retracted position.

[0021] Furthermore, the orifices of the insert are angularly distributed around the lateral wall of said insert.

[0022] In addition, the channels of the bottom of the mold are also angularly distributed around the central axis of said bottom of the mold.

[0023] Advantageously, said molding unit includes means for activating the circulation of the pressurized fluid in the bottom of the mold and / or in the insert in the manufacturing cycle of the containers, capable of controlling the start of said activation and the activation time so as to promote the detachment of the wall from the bottom of the blown container and / or to cool the insert and / or the bottom of the mold. Brief description of the drawings

[0024] Other advantages and features will become clearer from the following description of several embodiments, given by way of non-limiting examples, of the molding unit according to the invention, with reference to the accompanying drawings in which:

[0025] [Fig-1] is a perspective view of the molding unit according to the invention,

[0026] [Fig.2] is a radial cross-sectional view of the molding unit according to the invention re presented in [Fig.1],

[0027] [Fig.3] is a radial and perspective cross-sectional view of the unit's saddle molding according to the invention

[0028] [Fig.4] is a radial cross-sectional view of the saddle of the following molding unit the invention,

[0029] [Fig.5] is a top perspective view of the mold base and the unit insert molding according to the invention,

[0030] [Fig.6] is a radial cross-sectional view of the saddle of the following molding unit the invention, with the insert in the retracted position,

[0031] [Fig.7] is a radial cross-sectional view of the saddle of the following molding unit the invention, with the insert in the deployed position. Method of embodiment of the invention

[0032] In the remainder of the description of the molding unit according to the invention, the same numerical references designate the same elements. The different views are not necessarily drawn to scale.

[0033] Figures 1 and 2 show a molding unit 1 for manufacturing a container by blow molding (or stretch blow molding) from a plastic blank 2. In the illustrated example, the blank 2 is a preform, but it could be an intermediate container obtained from a preform that has undergone one or more preliminary forming operations. According to a preferred embodiment, the material from which the blank is made is PET and / or rPET (recycled PET).

[0034] Said molding unit 1 comprises, firstly, a mold 3. This mold 3 comprises a wall 4 formed by two articulated half-molds 3A, 3B, defining an internal cavity 5 distributed around a principal axis of the mold 3 which, when the containers to be formed are symmetrical of revolution, forms an axis of symmetry of the mold 3.

[0035] The cavity 5 defines at least partially an imprint 6 for a side wall or body of the container. The wall 4 has an opening 7 defining a passage for a mold base 8 having a central opening 9 and comprising an insert 10 mounted movable relative to the mold base 8 between a retracted position in which the insert 10 is away from the opening 9 (and therefore extends backward relative to the cavity 5), and a deployed position in which the insert 10 protrudes at least partially from the bottom of the mold 8 into the cavity 5.

[0036] The mold base 8 has a molding surface 9 defining an impression for the relevant part of the container 2. In the deployed position, the insert 10 protrudes from the mold base 8, thus completing the impression of the container, against which the material is applied during blow molding. The "stroke" of the insert 10 is the distance between the retracted position and the deployed position. For clarity, the mold 3 is shown in a configuration where the stroke of the insert 10 is relatively large compared to the height of the container. This configuration is not limiting; on the contrary, the stroke of the insert 10 can be small compared to the height of the container without departing from the scope of the invention.

[0037] Furthermore, said mold bottom 8 can be mounted movable relative to the wall 4 between a retracted position in which the mold bottom 8 is moved away from the opening 7 (and therefore extends backward relative to the cavity 5), and a deployed position in which the mold bottom 8 protrudes at least partially into the cavity 5.

[0038] As illustrated in [Fig.2], the blank 2, and then the container formed from it, rest on an upper face of the mold 3 by means of a collar 11 of the blank 2 (respectively of the container), which delimits a neck 12 of the blank 2 (respectively of the container), held out of the mold 3. Under the collar 11, the blank 2 (and then the container) has a body 13, which extends globally along the axial direction, and a bottom, which is initially hemispherical, then, once formed against the bottom of the mold 8, extends globally along the radial direction from a lower end of the body 13.

[0039] To form the container, the blank 2 is introduced into the mold 3, and a fluid (preferably a gas, for example air) is injected under pressure. Conventionally, the forming process can comprise at least two phases, namely: a pre-blowing phase, during which a fluid is injected into the blank 2 at a pressure called the pre-blowing pressure (the pre-blowing pressure being usually less than or equal to 15 bar, and for example in the order of 7 to 12 bar), and a blowing phase during which a fluid is injected into the blank 2 at a pressure called the blowing pressure (the blowing pressure being greater than or equal to 15 bar, and for example in the order of 30 to 40 bar).

[0040] Furthermore, the molding unit 1 also includes a stretching rod, not shown in the figures, capable of extending inside the blank 2, coaxially with the longitudinal axis of said blank 2, and of being moved along said longitudinal axis, in order to stretch said blank 2 during the pre-blowing step in particular in a manner well known in itself.

[0041] The molding unit 1 includes, secondly, a boxing system called a saddle 14. The term "boxing" is used here to designate an operation of pushing the material out of the container during the forming process. This saddle 14 comprises, firstly, a cylinder 15 for controlling the position of the insert 10 of the mold bottom 8, which is fixed to the upper end of said saddle 14.

[0042] Said cylinder 15 comprises a piston 16 extending in a housing 17 made in the saddle 14 and a rod 18 carrying at its upper end said insert 10. The piston 16 and the rod 18 are fixedly movable relative to the cylinder body formed by the housing 17 made in the saddle between a retracted position, corresponding to the retracted position of the insert 10 of the bottom of the mold 8, and a deployed position, corresponding to the deployed position of said insert 10 of the bottom of the mold 8.

[0043] With reference to figures 2 to 5, the insert 10 extends through the mold bottom 8 in the opening 9 coaxially with the drawing rod, said insert 10 being able to be moved from a so-called retracted position in which the upper end of the insert 10 extends inside the opening 9 which forms in the saddle 14 a central vertical channel 19, to a so-called active position in which said insert 10 protrudes from said mold bottom 8.

[0044] According to an essential feature, with reference to Figures 3 and 4, said insert 10 comprises pneumatic means for detaching the wall from the bottom of the blown container. More specifically, said insert 10 has a central recess 20 connected to a fluid source (not shown in the figures) under a predetermined pressure and, at its upper end, at least one orifice 21 opening into said central recess 20. In this particular embodiment, said insert 10 has on its lateral wall, near its upper end, a plurality of orifices 21 opening into said central recess 20. The axis of said orifices 21 forms an angle of between 30° and 80° with the longitudinal axis of said insert 10, and preferably an angle of between 30° and 50°.

[0045] Furthermore, advantageously, said mold bottom 8 also comprises a plurality of channels 22 opening onto the upper face of the mold bottom 8 by forming orifices 23, said channels 22 being fluidly connected to a source of pressurized fluid. More specifically, said mold bottom 8 comprises a plurality of channels 22 opening, at one end, onto the upper face of the mold bottom 8 by forming orifices 23, and opening, at the opposite end, into the central channel 19 of said mold bottom 8, through which the insert 10 extends. The axis of said channels 22 forms an angle of between 20° and 80° with the longitudinal axis of the insert 10. Said channels 22 of the bottom of mold 8 open into the central recess 19 extend to the orifices 21 of the insert 10 when said insert 10 is in its retracted position.Thus, when the insert 10 is in its retracted position, the orifices 21 of the insert 10 extend to the channels 22 of the bottom of the mold 8 in order to . supply with pressurized fluid and detach the bottom of the container from the bottom of the mold 8.

[0046] In this particular embodiment, the central channel 19 of the bottom of the mold 8 does not have a sealing gasket so that air also escapes at the level of the opening 9 of the bottom of the mold 8, between the insert 10 and the edge of the opening 9 of said bottom of the mold 8.

[0047] According to one embodiment, the central channel 19 of the bottom of the mold 8 may include, at least above the channels 22 opening into said central channel 19, a sealing joint.

[0048] Furthermore, and preferably, the orifices of the insert 10 are angularly distributed around the lateral wall of said insert 10 and the channels 22 of the bottom of the mold 8 are angularly distributed around the central axis of said bottom of the mold 8.

[0049] It will be observed that, advantageously, depending on the activation time of the pressurized fluid circulation in the insert 10 and / or the bottom of the mold 8 in the cycle, and the activation time, said activation means being included in a control unit not shown in the figures, the invention makes it possible to promote the detachment of the wall of the bottom of the blown container and / or to cool the bottom of the mold 8 which, by its integration and its mobility, lacks any internal cooling source, such as a fluidic circulation.

[0050] According to an alternative embodiment, with reference to Figures 6 and 7, the insert 10 extends, in the same way as before, through the mold bottom 8 in the opening 9 coaxially with the drawing rod, said insert 10 being able to be moved from a so-called retracted position in which the upper end of the insert 10 extends inside the opening 9 which forms in the saddle 14 a vertical channel 19, to a so-called active position in which said insert 10 protrudes from said mold bottom 8.

[0051] Furthermore, in the same manner as before, said insert 10 includes pneumatic means for detaching the wall from the bottom of the blown container. More specifically, said insert 10 has a central recess 20 connected to a fluid source (not shown in the figures) under a predetermined pressure and, at its upper end, at least one orifice 21 opening into said central recess 20. In this particular embodiment, said insert 10 has on its lateral wall, near its upper end, a plurality of orifices 21 opening into said central recess 20. The axis of said orifices 21 forms an angle of between 30° and 80° with the longitudinal axis of said insert 10, and preferably an angle of between 30° and 50°.

[0052] Thus, this variant of the embodiment differs from that previously described in that the bottom of the mold 8 does not have channels 22 opening into the central channel 19.

[0053] Finally, it is quite clear that the examples just given are only particular illustrations and in no way limiting as to the fields of application of the invention.

Claims

Claims

1. Molding unit (1) for manufacturing a container from a preform (2) made of plastic material, this molding unit (1) comprising at least: a mold (3) comprising a wall (4) formed by two articulated half-molds (3A, 3B) defining an internal cavity (5) distributed around a main axis of the mold (3) and defining at least partially an imprint (6) for a side wall or body and having, at a lower end, a lower opening (7), a mold base (8) which fits into the lower opening (7) and has an upper surface defining at least a partial imprint of the bottom of the container, the mold base (8) being pierced in its center with an opening (9), a jack (15) comprising a piston (16) and a rod (17) at the end of which is mounted an insert (10) capable of sliding through said opening (9) of the mold base (8),between a so-called deployed position in which a free end of the insert (10) projects relative to the mold base (8) and a so-called retracted position in which the free end of the insert (10) is located in the vicinity of the mold base (10), and a saddle (14) on which the mold base (8) is mounted, said saddle (14) comprising at least one lower stage (14A) and an upper stage (14B) mounted on the upper stage (14A), said saddle (14) internally defining a housing (17) in which the piston (16) of the jack (15) is mounted, characterized in that the mold base (8) and / or the insert (10) comprises pneumatic means for detaching the wall from the bottom of the blown container, said pneumatic detachment means simultaneously providing cooling of said bottom of the blown container.,

2. Molding unit (1) according to claim 1 characterized in that said insert (10) comprises a central recess (20) connected to a source of fluid under a determined pressure and, at its upper end, at least one orifice (21) opening into said central recess (20).

3. Molding unit (1) according to claim 2 characterized in that said insert (10) comprises on its side wall, near its upper end, a plurality of orifices (21) opening into said central recess (20).

4. Molding unit (1) according to claim 3 characterized in that the axis of said orifices (21) forms with the longitudinal axis of the insert (10) an angle of between 30 and 80°.

5. Molding unit (1) according to any one of claims 1 to 4 characterized in that said mold base (8) comprises a plurality of channels (22) opening onto the upper face of said mold base (8) forming orifices (23), said channels (22) being fluidically connected to a source of pressurized fluid.

6. Molding unit (1) according to claim 5 and any one of claims 2 to 4 characterized in that said mold base (8) comprises a plurality of channels (22) opening, at a first end, on the upper face of the mold base (8) forming orifices (23), and opening, at the opposite end, into the central channel (19) of the opening (9) of the mold base (8) in which the insert (10) slides.

7. Molding unit (1) according to claim 6 characterized in that the central channel (19) of the mold base (8) comprises, at least above the channels (22) opening into said central channel (19), a seal.

8. Molding unit (1) according to any one of claims 5 or 6 characterized in that the axis of said channels (22) of the mold base (8) forms with the longitudinal axis of the insert (10) an angle of between 20 and 80°.

9. Molding unit (1) according to claims 3 and 6 characterized in that the channels (22) of the mold base (8) opening into the central channel (19) extend in line with the orifices (21) of the insert (10) when said insert (10) is in its retracted position.

10. Molding unit (1) according to any one of claims 3 to 9 characterized in that the orifices (21) of the insert (10) are angularly distributed around the side wall of said insert (10).

11. Molding unit (1) according to any one of claims 5 to 10 characterized in that the channels (22) of the mold base (8) are angularly distributed around the central axis of said mold base (8).

12. Molding unit (1) according to any one of claims 1 to 11 characterized in that it comprises means for activating the circulation of the pressurized fluid in the mold base (8) and / or in the insert (10) in the manufacturing cycle of the containers capable of controlling the start of said activation and the activation time so as to promote the detachment of the wall from the bottom of the blown container and / or cool the insert (10) and / or the mold base (8).

Images