BLOW MOLD, BLOW MOLDING MACHINE AND METHOD FOR CONVERTING PLASTIC PREFORMS INTO PLASTIC CONTAINERS WITH AIR DISCHARGE

Description

[0001] The present invention relates to a blow mold, a blow molding machine, and a method for forming plastic preforms into plastic containers. Such methods and devices have long been known in the prior art. Typically, heated plastic preforms are introduced into a blow mold, which forms a cavity that serves to expand the plastic preforms into the plastic containers. Within this cavity, the plastic preforms are typically subjected to blowing air against an inner wall of these blow molded parts. This inner wall has the contour of the plastic container to be produced.

[0002] In such blow molding processes, and in particular stretch blow molding processes, the energy requirement of the application is determined, among other things, by the so-called final blow molding pressure. This is the pressure with which the plastic preform is completely formed into the desired container. It is therefore desirable to use the lowest possible final blow molding pressure. The limiting factor here is generally the shape of the last corners, particularly in the feet of a base cup. In order to ensure that the displaced air flows out of the blow mold, particularly during inflation of the containers, blow molds are already partly provided with venting openings according to the applicant's internal prior art. According to this prior art, holes are generally drilled in each corner of the foot of a base and, in some cases, another hole is drilled in a flank adjacent to a main diameter. These openings orHowever, holes limit the outflowing volume flow in such a way that the lowest possible blowing pressure is prevented.

[0003] The document US 4 865 206 A discloses a blow mold for producing plastic containers with at least two blow mold parts which form a cavity within which plastic preforms can be formed into the plastic containers by being subjected to a flowable medium, wherein an inner wall of the blow mold parts which delimits the cavity has a contour which produces a predetermined shape of the containers to be produced, wherein at least one section of a blow mold part produces a base of the plastic container, wherein in a section of a blow mold part at least one opening region is provided which enables a gaseous medium to be discharged during an expansion process of the container, wherein this opening region extends at least in sections along a first line and a second line, wherein these lines run at least in sections at an angle to one another which is different from 0°.

[0004] On the other hand, however, the choice of openings in the blow mold is also limited. If such an opening is chosen too large, part of the container's plastic could be pushed into it, which would then be visible or at least slightly noticeable on the resulting container.

[0005] The present invention is therefore based on the object of ensuring sufficient venting during the blow molding process without, however, compromising the visual appearance of the produced containers. This object is achieved according to the invention by the subject matter of the independent claims. Advantageous embodiments and further developments are the subject matter of the subclaims.

[0006] A blow mold according to the invention for producing plastic containers according to claim 1 has at least two blow mold parts, which form a cavity within which plastic preforms can be formed into the plastic containers by exposure to a flowable medium. An inner wall of the blow mold parts, which bounds this cavity, has a contour that creates a predetermined shape for the containers to be produced. Furthermore, at least one section of a blow mold part creates a base of the plastic container, with at least one opening region being provided in a section of the blow mold part, which allows for the discharge of a gaseous medium during an expansion process of the container.

[0007] According to the invention, this opening region extends at least in sections along a first line and along a second line, wherein these lines extend at least in sections at an angle to one another that is different from 0°.

[0008] In contrast to the prior art, in which only individual holes or a few holes are provided, it is proposed here to design the opening in such a way that it allows a larger flow cross-section, but on the other hand not so large that parts of the plastic container can be pressed into these opening areas.

[0009] This goal can be achieved by designing the opening areas in at least two lines that extend in different directions. On the one hand, the flow cross-section is sufficiently increased, as has been determined in experiments, and on the other hand, the opening areas or the individual openings can be kept small enough that the plastic containers are not pressed into them. The arrangement in at least two lines that are not parallel to one another offers the possibility of beneficially influencing the development of the feet in particular through ventilation. It would also be conceivable to arrange a large number of openings, for example in predetermined surface sections. Advantageously, at least one line has a length that is greater than 0.5 cm, preferably greater than 1 cm. Preferably, each of the lines has a length of more than 0.5 cm.For example, if the opening area is designed as a slot, the line path results directly from the path of this slot. If the opening area has multiple openings, the line is a geometric connecting line that connects these openings.

[0010] Advantageously, said lines are formed in the bottom contour of the blow mold. These geometric lines may intersect, but multiple lines may also be provided that do not intersect or touch. Two or more parallel lines are also conceivable. The applicant reserves the right to claim protection for this as well.

[0011] It is advantageous to provide a fork point where one line splits into two, for example. This allows the second line to branch off from the first line.

[0012] A venting volume is assumed here to be the volume of the entire area of ​​a foot of the container to be manufactured that is to be vented.

[0013] It is not according to the invention that the opening be designed as a continuous and / or interrupted gap; however, the line can also be defined by a plurality of adjacent openings. This is explained in more detail below with reference to the figures.

[0014] According to the invention, the opening area is arranged in a region of a base part of the blow mold that serves to create a base for the container. Petaloid bases known from the prior art typically have a plurality, for example, five or six, of such feet, which, as mentioned above, are particularly difficult to manufacture because the resulting compressed air partially prevents complete expansion. The aforementioned opening areas are arranged in these areas of the blow mold, which serve to form these feet.

[0015] According to the invention, a plurality of holes are arranged in the opening area, said holes being arranged along at least one of the two lines.

[0016] Advantageously, several opening areas along the lines are connected to each other via channels.

[0017] In a further advantageous embodiment, at least one bore has a diameter or width between 0.5 mm and 4 mm, preferably between 0.5 mm and 2 mm, and particularly preferably approximately 1 mm. It has been determined that such diameters allow for a sufficient flow cross-section on the one hand, but effectively prevent the penetration of plastic material during the expansion process on the other.

[0018] In addition, it would also be conceivable to use porous materials in certain areas of the base part, which provide a large number of small openings through which the gaseous medium can escape.

[0019] Using the procedures described here, the overall final blow-molding pressure of the containers can be reduced by up to 5 bar, thus lowering the energy costs of the machines as well as the required compressor size and thus also the costs. In some cases, it is also possible to simplify the machine technology, for example, eliminating air recycling. Furthermore, the load on the individual components of the corresponding blow-molding stations is reduced.

[0020] In a further advantageous embodiment, the distance between two holes arranged adjacently along the lines is less than 4 mm, preferably less than 3 mm, and preferably less than 2 mm. Advantageously, at least three, preferably at least four, and preferably at least five openings are arranged along each line. Thus, the lines are also determined by the position of these openings.

[0021] In a further advantageous embodiment, these opening areas are connected to channels within a wall of the blow molded parts, which serve to discharge the gaseous medium. It would be possible to combine the flow paths consisting of several, for example, circular holes into several channels.

[0022] Advantageously, these channels extend at least partially through the wall of the base part. The channels preferably establish a flow connection between an outer wall of the base part and an inner wall of the base part, and thus also between an interior space of the blow mold and an exterior space of the blow mold.

[0023] In a further advantageous embodiment, the channels extend at least in sections along a surface normal formed to the contour (the inner wall of the blow molded part that delimits the cavity). In this way, it is possible to remove the air very efficiently and quickly during the blow molding process. In this case, it would be possible to provide venting holes with a large pilot hole and a comparatively short throttle length (preferably less than 4 mm, preferably less than 3 mm, preferably less than 2 mm). The throttle can be an area between the blow mold or its inner wall and a pilot hole extending from outside or from an outer wall of the blow mold.

[0024] Advantageously, the opening areas are located in curved sections of the respective blow molded part.

[0025] In a further advantageous embodiment, the opening or venting areas (which may be configured, for example, as a bore) are located outside an actual contact surface of a filled container with a geometrically flat surface perpendicular to the container's longitudinal axis. Thus, in this embodiment, these opening or venting areas are located outside, for example, a base surface of such a container or the sections of the blow-molded part forming the base surface.

[0026] In a further advantageous embodiment, the blow mold part has a formation section for forming a base for the container, and the opening region is at least partially arranged in this formation section. These formation sections are usually the deepest regions of the respective blow mold when viewed with an upright container. Venting in this region is therefore very useful because this can promote the expansion of materials into these regions. An arrangement of the opening region in this formation section is also understood to mean that the opening regions approach this region forming the base within a range of ± 10 mm, preferably ± 8 mm, preferably ± 5 mm, and particularly preferably ± 2 mm.

[0027] In a further advantageous embodiment, the openings are also suitable for supplying a cleaning and / or sterilizing agent to the blow mold or the cavity of the blow mold, for example in a cleaning or sterilization operation.

[0028] The present invention is further directed to a device for forming plastic preforms into plastic containers according to claim 7, which has at least one forming device, which in turn has a pressurizing device for pressurizing the plastic preforms with a gaseous medium, and a blow mold for producing plastic containers with at least two blow mold parts, which form a cavity, within which plastic preforms can be formed into the plastic containers by being pressurized with a flowable medium. An inner wall of the blow mold parts, which delimits the cavity, has a contour which produces a predetermined shape of the containers to be produced, wherein at least one

[0029] Section of a blow-molded part produces a bottom of the plastic container, wherein in this section of the blow-molded part at least one opening area is provided which enables a gaseous medium to be discharged during an expansion process of the container.

[0030] According to the invention, the device comprises a vacuum generating device which, at least temporarily during the expansion process, sucks a gaseous medium out of the cavity through the opening region.

[0031] In this case, it is therefore proposed that the formation of the plastic containers be further promoted by releasing the gaseous medium through the opening area during the expansion process and preferentially sucking it away. This allows the container to be formed even at lower blowing pressures.

[0032] The device preferably has a plurality of such forming stations. In a further advantageous embodiment, the blow mold is designed as described above.

[0033] Preferably, the suction of the medium is at least temporarily coupled to another movement occurring during the forming process. Here, it is proposed that another movement used to form the containers be coupled to the suction. Such a coupling can be mechanical in nature and / or implemented via control technology.

[0034] This movement is preferably selected from a group of movements, including a stretch rod movement, a rotation of a blow molding wheel on which the forming device is arranged, a movement of the base part, and the like. For example, it can be specified that a specific movement of the stretch rod also simultaneously initiates suction of the gaseous medium. This suction can also begin at a specific predetermined position or rotational setting of the respective forming device. Thus, processes that already occur during blow molding can also be used as triggers for the suction.

[0035] The device therefore preferably comprises a control device that controls said extraction of the gaseous medium as a function of another process characteristic of the blow molding process. For example, extraction can be initiated at a specific time during the expansion process and preferably also terminated at a predetermined time. This allows for energy savings, since extraction does not have to occur continuously, but only at predetermined intervals.

[0036] It would also be possible for an extraction volume to be changed during the expansion process.

[0037] In a further advantageous embodiment, the device comprises a movable and in particular a rotatable support on which a plurality of said forming stations are arranged.

[0038] In a further advantageous embodiment, the device or the individual forming stations each comprise rod-like bodies that can be inserted into the plastic containers in order to stretch them in their longitudinal direction. These rod-like bodies are preferably so-called stretching rods.

[0039] The application device is advantageously a blowing nozzle which can be attached to a mouth area of ​​the plastic preforms in order to apply the gaseous medium and in particular blowing air to them in order to expand them.

[0040] The present invention is further directed to a base part for a blow mold for producing plastic containers. This base part has an inner wall with a contour that creates a predetermined base shape for the containers (10) to be produced. A plurality of spaced-apart opening regions are provided in the base part, allowing the discharge of a gaseous medium during an expansion process of the container.

[0041] According to the invention, these opening regions are arranged at least in sections in a section of the base part which creates a bottom side of the container, and these opening regions extend at least in sections along a first line and a second line, wherein these lines extend at least in sections at an angle to one another which is different from 0°.

[0042] As mentioned above, these opening areas can be formed by openings arranged along the lines. Preferably, the opening areas are arranged in a curved area of ​​the base part and in an area of ​​the base part intended to form a base for the container to be formed.

[0043] The present invention is further directed to a method for forming plastic preforms according to claim 9, wherein the plastic preforms are expanded by exposure to a gaseous medium within a cavity formed by a blow mold.

[0044] According to the invention, a gaseous medium is at least temporarily sucked out from a region of the blow mold cavity located outside the plastic preform. Advantageously, the gaseous medium is sucked out at least temporarily during the expansion process of the plastic preform. This space is a space that lies within the cavity formed by the blow mold, but outside the plastic preform. Advantageously, the gaseous medium is sucked out from a base region of the blow mold. Advantageously, this suction of the gaseous medium takes place in particular to form standing areas of the plastic container.

[0045] In an advantageous method, the suction of the medium is at least temporarily coupled to another movement occurring during the forming process. Further advantages and embodiments are apparent from the accompanying drawings.

[0046] Showing: Fig. 1A roughly schematic representation of a device for forming plastic preforms into plastic containers; Fig. 2A representation of a blow molding station with a blow mold for forming plastic preforms into plastic containers; Fig. 3A representation of a bottom part of a blow mold according to the invention; Fig. 4A representation of the Fig. 3 shown bottom part from the inside; Fig. 5 a representation of a further embodiment of a non-inventive bottom part of a blow mold; Fig. 6 a representation of the non-inventive bottom part from Fig. 5 in a further view; Fig. 7 a further representation of a base part; Fig. 8 a view of the Fig. 7shown base part; Fig. 9, 10 two further views of a non-inventive Fig. 11 a further embodiment of a base part according to the invention; Fig. 12, 13 two representations of a further base part according to the invention; Fig. 14 - 16 three non-inventive base parts; Fig. 17 a view of a non-inventive base part from below and Fig. 18 a further view of an embodiment of a base part in a view from below.

[0047] Fig. 1shows a roughly schematic representation of an apparatus according to the invention for forming plastic preforms 10 into plastic containers 20. The plastic preforms 10 are fed via a feed device 55, such as a feed star, and the finished containers are removed from the apparatus 50 via a discharge device, such as a discharge star 57. The forming device 50 has a rotatable carrier 54 on which a plurality of forming stations 52 are arranged. Each of these forming stations 52 has a blow mold 1.

[0048] Fig. 2shows a schematic view of a blow mold according to the invention. This blow mold has two side parts 2, 4 and a base part 6. Together, these two side parts and the base part 6 form a cavity 18 within which the plastic preforms are expanded to form the plastic containers. The vent openings described above are located in particular in the base part, but they can also be provided in the side parts, for example, in order to better form complex curvatures of the plastic container. The reference numerals 12, 14 refer to carrier shells which carry the blow mold parts 2, 4, and the reference numerals 22, 24 refer to blow mold supports to which the blow mold parts are fastened (via the carrier shells 12, 14).

[0049] Reference numeral 60 refers to a vacuum generating device, shown only schematically. This device can be controlled to extract air from the interior of the blow mold during a predetermined period of time during the expansion of the plastic preforms.

[0050] The following Figures 3 to 18 show different designs of floor parts. For clarity, not all reference symbols are repeated in the individual figures.

[0051] Fig. 3shows a representation of a base part from below. The opening areas 62 can be seen, which here each have a channel facing the containers and extending along lines L1 and L2, as well as connecting channels 64 which lead to openings 72 arranged on the outer surface 6b of the base part. It can be seen that two opening areas 62 are assigned to each supporting leg to be formed. Furthermore, it can be seen that the opening areas extend along two lines L1 and L2, whereby these two lines are not parallel to one another and also intersect here at an intersection point. This arrangement allows for the removal or suction of gaseous medium to be achieved in a particularly advantageous manner.

[0052] Fig. 4 shows another view of the Fig. 3shown base part. It can be seen here that the individual opening areas 62 are each arranged in the areas of the base part that serve to form the feet of the container to be produced. It can also be seen that the individual connecting channels, which extend through the wall 65 of the base part, each run in the direction of a surface normal N, which is perpendicular to the inner wall of the base part 6. In this way, angular formations in the discharge of blown air or air can be eliminated.

[0053] If, due to the position of the opening 72 (cf. Fig. 3 ) If the direction of the surface normal N is not possible (for the tool angle of attack), the direction of the surface normal can be replaced by an axis in the direction of the angle of attack between 0° and 90°. The angle 0° corresponds to the vertical axis from the center Z.

[0054] Reference numeral 6a refers to the section of the base region 6 in which the said openings or opening regions are arranged. This section preferably serves to form the feet of the container to be manufactured.

[0055] Fig. 5 shows a further embodiment of a base part 6. Here, too, channels 66 are provided on the surface facing the plastic preform, but here they are designed as continuous slots 67 that extend through the wall 65 of the base part. Air can be discharged through these slots. However, the channels formed on the inner wall or these slots also extend in two different directions L1 and L2.

[0056] Fig. 6 shows a further representation of the Fig. 5 shown bottom part. Here again, the channels 66 and the slots 67 are visible.

[0057] In the specific embodiments shown here, a total of ten opening areas 62 are provided, with two opening areas 62 each being assigned to a base to be formed of the container to be produced.

[0058] The Figs. 7 and 8 show a further embodiment of a base part. Here, too, channels 66 are provided on the inner wall of the blow mold, as well as connecting channels 64, which extend through the wall 65 of the base part. In this embodiment, the opening regions 62 are each crow's foot-shaped and therefore also have two non-parallel lines L1 and L2. In addition, however, further lines, such as L3, can also be provided, which also do not run parallel to the other two lines. Fig. 7The illustration shown or a corresponding base part is also particularly suitable for removing or extracting air from those areas which will later create the feet.

[0059] Fig. 8 shows a further illustration from which it is again clear that the opening areas 62 are arranged in those sections 63 of the base part which serve to produce the feet.

[0060] The Figs. 9 and 10 show a further embodiment of a base part 6. Here, too, the channels on the inner wall of the base part are formed in a crow's foot pattern. However, here again, they are not connected by individual channels, but rather by opening slots that protrude through the wall 65 of the base part. On the inside of the base part, the slots or openings preferably adapt to the contour of the container to be formed.

[0061] Fig. 116 again shows a representation with channels 66 and adjoining connecting lines 64. However, it should be noted that the structure could also be reversed, namely a plurality of openings arranged on the inner wall of the base part, each having channels leading to the outer wall of the base part. In this case, however, as mentioned above, said openings would also be arranged along the respective lines L1 and L2.

[0062] The Fig. 12 and 13 show a further embodiment. It can be seen that a first line L1 is provided here, which extends in a wave-like manner around the base part 6. The second line L2 is a closed line, which is arranged directly on the base and which runs towards a central region Z of the base part 6. Here, too, a plurality of connecting channels 64 are provided, which run through the wall 65 of the base part 6.

[0063] Fig. 13 shows a further representation of the Fig. 12 shown floor section. Here, too, the two lines L1 and L2 are visible, as well as the connecting channels 64.

[0064] Fig. 14 shows a further embodiment of a base part not according to the invention. Here, too, the two lines L1 and L2 are visible, but here again, connecting channels 64 are not provided; instead, the connection to the outside is again formed as a slot 67 in the wall 65 of the base part.

[0065] Fig. 15 shows a further representation of the Fig. 14 shown base part. Here again one can see the two lines L1 and L2 as well as the slots 67, which run through the wall 65 of the base part.

[0066] Fig. 16 shows a further representation of the Fig. 15 and 14shown part of the floor, whereby here again the areas forming the respective lines L1 and L2 can be seen.

[0067] Fig. 17 shows a view of a base part from below, again showing the opening areas. In this case, slots are arranged in the wall 65 of the base part.

[0068] At the Fig. 18 In the embodiment shown, no slots are provided in the wall 65, but rather the channels 64 shown in some of the previous figures, which each lead to the openings 72.

[0069] The applicant reserves the right to claim all features disclosed in the application documents as essential to the invention, provided that they are new, individually or in combination, compared to the prior art. List of reference symbols

[0070] 1Blow mold 2, 4Side parts 5Wall 6Bottom part 6aSection 6bOuter surface 10Plastic preforms 12, 14Carrier shells 18Cavity 20Plastic containers 22, 24Blow mold carrier 50Forming device 52Forming stations 54Rotatable carrier 55Feeding device 57Discharge star 62Opening areas 64Connecting channels 65Wall 66Channels 67Slots 72Openings L1, L2 lines L3 further line NFace normal Zcentral area

Claims

1. Blow mould (1) for producing plastic containers (20) with at least two blow mould parts (2, 4, 6) which form a hollow space (18) inside which plastic parisons (10) can be transformed by the application of a flowable medium to the plastic containers (20), wherein an inner wall of the blow mould parts (2, 4, 6) delimiting the hollow space (18) has a contour which produces a predetermined configuration of the plastic containers (20) to be produced, wherein at least one portion of a blow mould part (6) produces a bottom of the plastic container, wherein in a portion of a blow mould part (2, 4, 6) at least one opening region (62) is provided which enables discharge of a gaseous medium during an expansion process of the plastic containers, wherein this opening region (62) extends at least in sections along a first line (L1) as well as a second line (L2), wherein these lines run at least in some sections at an angle different from 0° relative to one another, characterized in that wherein in the opening region (62) a plurality of holes is arranged, wherein these holes are arranged along at lest one of the two lines (L1, L2) and along each line at least three holes are arranged and wherein the opening region is arranged in a region of a bottom part of the blow mould (1) which serves to produce a supporting foot of the container (20) and at least one hole has a diameter which is betwenn 0,5 mm and 4 mm, preferably between 0,5 mm and 2 mm.

2. Blow mould (1) according to claim 1, characterized in that a distance between two holes arranged next to each other along one of the lines (L1, L2) is smaller than 2 mm.

3. Blow mould (1) according to at least one of the preceding claims, characterized in that channels (64) which serve to discharge the gaseous medium adjoin the opening regions (62) within a wall of the blow mould parts.

4. Blow mould (1) according to claim 3, characterized in that the channels (64) extend at least in some sections along a surface normal to the contour.

5. Blow mould according to at least one of the preceding claims, characterized in that the blow mould part (6) has a forming portion (66) for forming a standing surface of the containers (20) and the opening region is arragned at least partly in the forming portion (66).

6. Apparatus (50) for forming plastic preforms (10) into plastic containers (20) with at least one forming device which has an application device in order to apply a gaseous medium to the plastic preforms, as well as a blow mould (1) according to at lest one of the preceding claims for producing plastic containers (20) with at least two blow mould parts (2, 4, 6) which form a hollow space (12) inside which plastic preforms (10) can be formed by the application of a flowable medium to the plastic containers (20), wherein an inner wall of the blow mould parts (2, 4, 6) delimiting the hollow space (18) has a contour which produces a predetermined configuration of the plastic containers (20) to be produced, wherein at least one portion of a blow mould part (6) produces a bottom of the plastic container (20), wherein in a portion (6a) of a blow mould part (2, 4, 6) at least one opening region (62) is provided which enables discharge of a gaseous medium during an expansion process of the container, wherein the apparatus (50) has a vacuum generating device (60) which at least intermittently during the expansion process extracts a gaseous medium from the hollow space (12) through the opening region.

7. Apparatus (50) according to claim 6, characterized in that the extraction of the medium is coupled at least intermittently to a further movement which takes place during the forming process.

8. Bottom part (6) for a blow mould (1) for producing plastic containers (20), wherein the bottom part has an inner wall with a contour which produces a predetermined bottom configuration of the plastic containers (10) to be produced, wherein in the bottom part (6) a plurality of opening regions (62) are provided which are spaced at least partially apart from one another and enable discharge of a gaseous medium during an expansion process of the plastic container, wherein these opening regions (62) are arranged at least in some portions in a portion of the bottom part (6) which forms an underside of the plastic container (10) and this opening regions (62) extend at least in some sections along a first line (L1) as well as along a second line (L2), wherein these lines (L1, L2) run at least in some sections at an angle different from 0° relative to one another, characterized in that in the opening region (62) a plurality of holes is arranged, wherein these holes are arranged along at lest one of the two lines (L1, L2) and along each line at least three holes are arranged and at least one hole has a diameter which is between 0,5 mm and 4 mm, preferably between 0,5 mm and 2 mm.

9. Method for forming plastic prefroms, wherein the plastic preforms (10) are expanded by application of a gaseous medium within a hollow space formed inside a blow mould according to at least one of the preceding claims 1 to 5, wherein a gaseous medium is extracted at least intermittently from a region of the hollow space outside the plastic preform.

10. Method according to claim 9, characterized in that the extraction of the medium is coupled at least intermittently to a further movement which takes place during the forming process.