BLOW MOLD, BASE MOLD AND BLOW MACHINE

Description

[0001] The invention relates to a blow mold for producing containers in a blow or stretch blow molding process, comprising a bottom mold and two mold halves that together define a shape contour for the container, wherein the bottom mold comprises a mold surface for defining a section of the shape contour and a piping system for a cooling fluid for cooling the mold surface, wherein the piping system has a central channel for supplying the cooling fluid, several primary cooling channels branching off from the central channel and extending radially outwards from the central channel near the mold surface, and a collecting channel in flow communication with the primary cooling channels for collecting and discharging the cooling fluid.

[0002] The invention further relates to a base mold for a blow mold and a blow molding machine with a blow mold.

[0003] A generic blow mold of this type from the prior art is shown, for example, in DE 199 25 756 A1. Cooling fluid is supplied via a central channel, then distributed along the mold surface to be cooled via star-shaped primary cooling channels, directed away from the mold surface to be cooled at the end of the primary cooling channels by means of discharge channels, and collected in an annular channel. US 5,411,699 A, WO 2020 / 099755 A1, and US 2016 / 0325483 A1 also disclose actively cooled blow molds with bottom molds.

[0004] Known blow molds of the generic type are used particularly in high-performance blow molding machines or high-performance stretch blow molding machines designed according to the rotary principle. Such machines generally have a rotating blow wheel on which the blow molds are arranged. Also known are indexing machines in which the blow mold is stationary, with rotary machines generally allowing higher production rates, i.e., for example, more containers per blow mold in the same amount of time, than indexing machines.

[0005] Modern machines for container manufacturing, especially for beverage containers, often use a two-stage process in which pre-made container blanks are fed in as semi-finished products, which are then appropriately tempered, placed in a blow mold and formed into the desired containers.

[0006] Single-stage processes, in which raw plastic material is melted, formed into a blank and then directly shaped into the desired containers without intermediate cooling and storage, are also known, but do not achieve the production rates of the two-stage process.

[0007] Downstream processes such as filling and / or labeling often put the finished containers under pressure. For this to work, it is essential that the containers are sufficiently stable, which in particular requires adequate cooling of the hot material after demolding. Previously, this was not a problem because container production and downstream processing took place on different machines, between which the containers were exchanged via long conveyor belts, allowing sufficient time for complete cooling.

[0008] It has now become common practice to carry out container production and subsequent processing such as filling and / or labeling in the same machine, thereby eliminating intermediate conveying lines and drastically reducing the cooling time of the containers. At the same time, production rates have increased to such an extent that the dwell time of the containers in the blow mold is no longer sufficient to dissipate enough residual heat from the containers, even with active cooling of the molds.

[0009] In certain applications, particularly those involving carbonated beverages, it is therefore necessary to provide special cooling systems to adequately stabilize the bottoms of the containers. However, these cooling systems are structurally complex, often inefficient, and affect subsequent container treatment, sometimes requiring further costly measures such as drying after cooling with liquids.

[0010] The invention is based on the objective of increasing the production rate of containers compared to known solutions and / or reducing the need for post-cooling of manufactured containers before further processing.

[0011] The object is solved according to the invention by a blow mold of the aforementioned generic type, which is further developed in that the piping system also has several secondary cooling channels which are arranged in the flow direction of the cooling fluid between the primary cooling channels and the collecting channel and run radially inwards near the mold surface.

[0012] Within the scope of the invention, the term "radial" is to be understood as meaning that "radial in" means closer to the geometric center than "radial out". According to the invention, the cooling channels extending radially inward or radially outward need not be precisely aligned with the geometric center, but may be offset from it.

[0013] The secondary cooling channels according to the invention are characterized in particular by the fact that, after passing through the primary cooling channels, the cooling fluid is guided past the mold surface to be cooled a second time before being collected in the manifold and discharged from the mold. The return of the cooling fluid from the secondary cooling channels to the manifold can be achieved, as in the prior art, via suitable return or discharge channels that guide the cooling fluid away from the mold surface to be cooled and towards the manifold.

[0014] The secondary cooling channels according to the invention increase the surface area of ​​the cooling system, thereby achieving better heat transfer between the mold material and the cooling fluid. This allows a greater amount of heat to be dissipated from the mold via the cooling fluid in the same amount of time.

[0015] Another positive effect of the invention is that the particularly critical central area of ​​the base shape, in which a particularly large amount of waste heat has to be dissipated due to the generally greater material thickness of the container, is passed through twice by the cooling fluid, namely once when flowing through the primary cooling channels and once when flowing through the secondary cooling channels.

[0016] In one embodiment of the invention, the base shape has an annular connecting channel into which the primary cooling channels open and from which the secondary cooling channels branch off.

[0017] In an alternative embodiment of the invention, the base shape has several connecting channels, each connecting channel linking a primary cooling channel to a secondary cooling channel.

[0018] Advantageously, the connecting channel(s) are each formed by a recess in a base body of the base mold, the recess(s) being covered by a sleeve that is slid over the base body and sealed against it. The recesses can be easily produced, for example, by turning or milling.

[0019] It is particularly advantageous if the sleeve material includes a plastic component. This reduces the thermal conductivity of the sleeve compared to a metal version, resulting in less condensation on the outer surface of the sleeve facing away from the connecting channel.

[0020] It is also advantageous if the inlets of the primary cooling channels into the connecting channel(s) are offset vertically and / or circumferentially from the branches of the secondary cooling channels from the connecting channel(s). This allows the base to be uniformly permeated with cooling channels. This results in advantageously short diffusion lengths within the base, so that overall more waste heat comes into contact with the cooling fluid more quickly and can be dissipated.

[0021] Another advantage is that the arrangement of the cooling channels can be adapted to the geometry of the mold surface, so that even with a complex contour of the mold surface a uniform distance between the mold surface and the cooling channels is possible.

[0022] The mold surface is designed, for example, for a commonly used petaloid base of a beverage bottle and thus has a contour with five tension bands, which are arranged essentially on a hemisphere and between which support feet project beyond the idealized hemisphere. For this purpose, a base mold according to the invention has, for example, five primary cooling channels, which run approximately horizontally in the region of the contour for one of the support feet, as well as five secondary cooling channels, which are arranged obliquely in the region of the contour for one of the tension bands.

[0023] The problem underlying the invention is also solved by a blow mold of the aforementioned generic type, which is further developed by arranging a swirl body with a flow-modifying surface at the end of the central channel facing the mold surface. This embodiment of the invention with a swirl body has independent inventive character and can be used in isolation within the scope of the invention, but can also be combined with the discussed aspects of the invention to further improve bottom mold cooling.

[0024] The flow-altering surface of the swirl body leads to the fundamental inventive idea of ​​increasing the surface area of ​​the cooling system and thus improving, and in particular accelerating, the heat exchange between the material of the base form and the cooling fluid.

[0025] At the same time, the swirl body, through a suitable choice of surface contour, allows for targeted control of the cooling fluid flow within the cooling system channels, thus, for example, increasing the shear velocity of the flow. This results in the heat energy absorbed by the base shape being distributed more quickly within the cooling fluid, thereby further improving the overall heat exchange between the base shape and the cooling fluid.

[0026] A particularly suitable flow-altering surface contour is spiral-shaped or labyrinthine.

[0027] Preferably, the base form comprises a base body into which the swirl body is incorporated or inserted. Since the swirl body is generally larger than the diameter of the central bore, it is advantageous from a manufacturing perspective if, in addition, the central channel is formed in an insert that is at least partially form-complementary to the base body, wherein one end face of the insert is at least as large as the swirl body.

[0028] The problem underlying the invention is also solved by a base mold for a blow mold according to the invention.

[0029] The problem underlying the invention is further solved by a blow molding machine, in particular a stretch blow molding machine, with at least one blow mold according to the invention. The full potential of the invention is achieved when the blow molding machine is designed as a rotary machine and has a rotating blow wheel on which the at least one blow mold is arranged.

[0030] The invention is explained in more detail below with reference to an embodiment of the invention, which is illustrated in the drawing. The drawing shows... Figure 1 schematically shows a blow molding machine according to the invention; Figure 2a schematically shows a blow mold according to the invention in an open configuration; Figure 2b schematically shows the blow mold according to the invention made of Fig. 2a in a closed configuration; Figure 3 schematically shows a first embodiment of a base shape according to the invention; Figure 4a schematically shows a second embodiment of a base shape according to the invention; and Figure 4b schematically shows a sectional view of the base shape according to the invention. Fig. 4a .

[0031] A blow molding machine 1 according to the invention, which can in particular be designed as a stretch blow molding machine, is in Fig. 1 The exemplary blow molding machine 1 is designed according to the rotary principle and is based on a two-stage manufacturing process for plastic containers, in which, in a first stage, raw plastic materials are melted and processed into container blanks or preforms, for example by injection molding. The blow molding machine 1 according to the invention only implements the second stage of the manufacturing process, in which the preforms are formed into containers.

[0032] For this purpose, the pre-fabricated preforms are sorted, aligned, arranged in a continuous line, and finally singulated at an input station 2. In a heating device 3, the preforms are thermally prepared for forming and transferred to a blow molding station on a blow molding wheel 5 by means of a transfer device 4. During one revolution of the blow molding station on the blow molding wheel 5, the thermally conditioned preform is formed into a container, which is then removed from the blow molding station by means of another transfer device 6. The containers produced in this way leave the blow molding machine 1 as a continuous stream, which can then be fed into further processing, such as filling and / or labeling.

[0033] Each blowing station on the blowing wheel 5 has a blowing mold 10, which is schematically opened into Fig. 2a and in Fig. 2b The blow mold 10 comprises two blow mold halves 12, 12' and a base mold 14. To insert a preform and to remove a container, the blow mold is opened by unfolding the blow mold halves 12, 12' like a book and lowering the base mold 14. This configuration is shown in Fig. 2a shown. During the blow molding or stretch blow molding process, however, the mold 10 is closed and thus forms a hollow shape that defines the contour of the container to be produced. This configuration is shown as a sectional view along the parting line between the mold halves 12, 12' in Fig. 2b shown.

[0034] The base mold 14 is mounted on a base mold support 16 and is secured in the closed position by means of a locking ring 24, which engages in suitable shape-complementary contours of blow mold supports (not shown) for the blow mold halves 12, 12'.

[0035] A first embodiment for a base shape 14 according to the invention is in Fig. 3 The base shape 14 comprises a basic body 20 with a molded surface 22 that defines the bottom contour of the container. The basic body 20 can consist of several interconnected components or, as shown in Fig. 3 shown, consisting of a single component.

[0036] The bottom form 14 according to the invention has a cooling system with interconnected pipes or channels for a cooling fluid, in particular a liquid cooling fluid such as water with or without additives.

[0037] The cooling fluid is supplied via a connection (not shown) and guided towards the mold surface 22 by means of a central channel 30. The central channel 30 ends just below the mold surface 22, so that the remaining material thickness of the base body 20 is still sufficient to stabilize the mold surface 22 against the expected blowing pressure during the blowing process.

[0038] Several primary cooling channels 32 branch off from the central channel 30, of which the sectional view of the Fig. 3 Only one is visible. The primary cooling channels 32 extend radially outwards from the central channel 30 in a star shape close to the mold surface 22 in order to absorb the process heat transferred via the mold surface 22 to the bottom mold 14 by means of the cooling fluid.

[0039] The primary cooling channels 32 open into an annular connecting channel 34, which is formed on the outer circumference of the base body 20 of the bottom shape 14. The connecting channel 34 is designed as a recess in the base body 20, which can be produced very easily, for example, by turning or milling. The recess is closed by means of a sleeve 40 that fits over it, with circumferential seals 42 provided on both sides of the recess between the base body 20 and the sleeve 40, which seal the connecting channel 34 against the environment.

[0040] The sleeve 40 is preferably made of a material with poor thermal conductivity, in particular a plastic, in order to prevent, in particular, unwanted condensation of moisture on the outside of the sleeve 40.

[0041] Several secondary cooling channels 36 branch off from the connecting channel 34, directing the cooling fluid radially inwards again near the mold surface 22, thus providing further cooling of the bottom mold 14, particularly at the mold surface 22. The secondary cooling channels 36 are also shown in the illustration of Fig. 3 only one is visible, which is located, for example, opposite the primary cooling channel 32 shown.

[0042] While the primary cooling channels 32 run essentially horizontally, the secondary cooling channels 36 are arranged at an angle. This ensures not only a more uniform distribution of cooling channels 32, 36 across the base body 20, but also that sufficient material thickness remains between the cooling channels 32, 36 to guarantee the stability of the base body 20, especially in the central area.

[0043] The secondary cooling channels 36 each open into return channels 37, which connect the secondary cooling channels 36 to an annular collecting channel 38 in which the cooling fluid is collected and discharged from the bottom mold. For the functioning of the invention, it is irrelevant that the secondary cooling channels 36 no longer extend radially inwards after transitioning into the return channels 37, since this section is already located relatively far from the mold surface 22 and, accordingly, the cooling effect on the mold surface is hardly affected.

[0044] Instead of the exemplary single connecting channel 34, which extends over the entire circumference of the base body 20, the invention also allows for the provision of several connecting channels 34, each connecting one of the primary cooling channels 32 to one of the secondary cooling channels 36. These multiple cooling channels can also be formed, for example, as recesses in the base body 20, which are jointly covered by the sleeve 40. The sealing of the multiple connecting channels can be carried out individually or jointly.

[0045] For a uniform cooling effect, the cooling channels 32, 36 are preferably arranged circumferentially at uniform intervals. For example, with five primary cooling channels 32 and five secondary cooling channels 36, this results in an angle of 72° between two adjacent primary cooling channels 32 in the horizontal projection. The same applies to the secondary cooling channels 36. Furthermore, primary cooling channels 32 and secondary cooling channels 36 are arranged alternately in the circumferential direction, so that an angle of 36° results between adjacent cooling channels 32, 36 in the horizontal projection.

[0046] An alternative embodiment of a base shape 14 according to the invention is in Fig. 4a and in Fig. 4b depicted. This shows Fig. 4b a sectional view of the base shape 14 according to the invention along the in Fig. 4a designated line AA. In this embodiment of the invention, the central channel 30 is formed in an insert 52, which is inserted into the base form 14 from below in a form complementary to a bore of corresponding diameter and is suitably sealed. A swirl body 50 is provided above the insert 52, which in this example has a spiral surface and thereby influences or modifies the flow of the cooling fluid accordingly. This not only increases the heat transfer from the base form 14 or base body 20 to the cooling fluid, but also increases the shear rate within the cooling fluid and thus further accelerates or improves the heat absorption by the cooling fluid.

[0047] In the Fig. 4a and in Fig. 4b In the example shown, the primary cooling channels 32 are designed as an overlapping double bore. This increases the surface area of ​​the primary cooling channels 32 compared to a single bore with the same cross-section.

[0048] The return of the cooling fluid from the primary cooling channels 32 to the collecting channel 38 is shown in the example of the Fig. 4 through vertical return channels 37. However, within the scope of the invention it is also conceivable to additionally provide one or more connecting channels 34 as well as secondary cooling channels 36 in order to further improve the cooling effect. REFERENCE MARK

[0049] 1 Blow molding machine 2 Preform feeder 3 Heater 4 Transfer unit 5 Blow wheel 6 Transfer unit 10 Blow mold 12, 12' Blow mold halves 14 Bottom mold 16 Bottom mold support 20 Base body 22 Molding surface 24 Interlocking ring 30 Central channel 32 Primary cooling channel 34 Connecting channel 36 Secondary cooling channel 37 Return channel 38 Collecting channel 40 Sleeve 42 Seal 50 Swirl body 52 Insert

Claims

1. A blow mould (10) for producing containers in a blow mould or stretching process with a mould base (14) and two mould halves (12, 12'), which together specify a mould contour for the container, wherein the mould base (14) comprises a mould surface (22) for specifying a section of the mould contour and a conduit system for a cooling fluid for cooling the mould surface (22), wherein the conduit system comprises a central channel (30) for feeding the cooling fluid, a plurality of primary cooling channels (32) branching off from the central channel, which run radially outwards from the central channel (30) near the moulding surface (22), and a collecting channel (38) for collecting and discharging the cooling fluid, which is connected in a flowing manner to the primary cooling channels (32), characterized in that the conduit system also comprises a plurality of secondary cooling channels (36) which are connected in the flow direction of the cooling fluid between the primary cooling channels (32) and the collecting channel (38) and run radially inwards in the vicinity of the mould surface (22), wherein these secondary cooling channels (36) are characterized in that the cooling fluid is fed another time at the mould surface (22) to be cooled after passing through the primary cooling channels (32) before it is brought together in the collecting channel (38) and led out of the mould (10).

2. The blow mould (10) according to Claim 1, characterized in that the mould base (14) comprises a ring-shaped connecting channel (34) into which the primary cooling channels (32) open and from which the secondary cooling channels (36) branch off.

3. The blow mould (10) according to Claim 1, characterized in that the mould base (14) comprises a plurality of connecting channels (34), wherein one connecting channel (34) respectively connects a primary cooling channel (32) with a secondary cooling channel (36).

4. The blow mould (10) according to any one of the Claims 1 to 3, characterized in that the connecting channel (34) or the connecting channels (34) are each formed by a recess in a main body (20) of the mould base (14), wherein the recess or recesses are covered by means of a sleeve (40) pushed over the main body (20) and sealed against the main body (20), wherein one material of the sleeve (40) comprises, in particular, a plastic.

5. The blow mould (10) according to any one of the Claims 1 to 4, characterized in that the junctions of the primary cooling channels (32) into the connecting channel (34) or the connecting channels (34) are offset in height and / or circumferential direction in relation to the branches of the secondary cooling channels (36) from the connecting channel (34) or the connecting channels (34).

6. The blow mould (10) according to any one of the preceding claims, characterized in that a swirl body (50) with a flow-changing surface is arranged at the end of the central channel (30) facing the mould surface (22).

7. The blow mould (10) according to Claim 6, characterized in that the flow-changing surface is spiral in shape or labyrinth-like.

8. The blow mould (10) according to Claim 6 or 7, characterized in that the mould base (14) comprises a main body (20) into which the swirl body (50) is incorporated or inserted, wherein the central channel (30) is formed in an insert (52) fitted into the main body (20) at least in sections in a form-complementary manner, wherein one face of the insert (52) is at least as large as the swirl body (50).

9. A mould base (14) for a blow mould (10), wherein the mould base (14) is formed according to any one of the Claims 1 to 8.

10. A blow moulding machine (1), in particular, a stretch blow moulding machine, comprising at least one blow mould (10) according to any one of the Claims 1 to 8, wherein the blow moulding machine (1) is designed, in particular, as a rotary machine and has a circumferential blowing wheel (5) on which at least one blow mould (10) is arranged.