DE102020131364A1 - Device and method for producing plastic preforms and mold therefor - Google Patents

Abstract

Device (1) for producing plastic containers (20) with a carrier (12), a plurality of molds (14) being arranged on the carrier (12), each of which has at least a first mold part (14a) and a second mold part (14b ) have, wherein the first mold part (14a) and the second mold part (14b) in a closed state form a cavity which corresponds to the negative mold of the plastic container (20) to be produced. According to the invention, at least one molded part (14a, 14b) has an electrically conductive coating at least in sections and/or is designed to be electrically conductive.

Description

The present invention relates to a device and a method for manufacturing plastic containers and a mold for manufacturing plastic containers. Such devices and methods have long been known from the prior art. In the production of plastic packaging and in particular plastic containers, a container is usually formed from a preform, which itself was previously produced in an injection molding process, using the stretch blow molding process. The preform is transferred to a mold and shaped by stretching and simultaneous pressure build-up using a pressure medium.

The molds usually consist of aluminum or steel workpieces, into which the (negative) contour of the container is introduced using machining processes. During the process, the mold surface is dry. The molds can be tempered or cooled directly or indirectly, for which purpose tempering medium channels or the like can be provided in the molds. When the container is blown, the outer wall of the container lies against the contours of the mold and thus obtains its shape.

It is known from the internal status of the applicant that the molds usually consist of at least two mold parts which, in the closed state, form a mold gap between them at a contact or contact area of the two mold parts. Under certain circumstances, this mold gap can be seen and felt as a so-called parting line on the formed plastic container. In order to compensate for these mold gaps, there is an additional pressure pad behind one of the two mold halves. In order for the container to achieve its dimensional stability, it needs time to transfer its heat to the mold and cool down accordingly. This represents a significant part of the process time. Depending on the mold temperature, process and container design, this part of the process time can also be longer.

The cooling time is one of the performance-limiting factors in the container stretch blow molding process, as it significantly reduces the output of the system. There is also the problem that the outermost plastic layer cools down suddenly as soon as it is in contact with the mold, while the inner layers are still warm. This creates the phenomenon of the falling parting seam in the area of the mold separation/mold gap, which makes the containers appear out of round or misshapen. This represents a limitation in the container quality.

The object of the present invention is therefore to provide a device and a method with which heat transfer from the container to be produced and the mold can be improved. Furthermore, the present invention is also based on the object of providing a mold suitable for this purpose. According to the invention, this object is achieved by the subject matter of the independent claims. Advantageous embodiments and developments are the subject of the dependent claims.

The invention is therefore directed towards a device for producing plastic containers with a carrier, with a large number of molds being arranged on the carrier, each of which has at least a first mold part and a second mold part, the first mold part and the second mold part being in a closed State form a cavity which corresponds to the negative mold of the plastic container to be produced.

According to the invention, at least one molded part has an electrically conductive coating at least in sections and/or is designed to be electrically conductive.

It is therefore proposed according to the invention to coat the molds or at least one molded part either completely or partially with an electrically conductive and wear-resistant coating and/or to produce the molded parts from a material which is electrically conductive. As will be described in more detail below, an electrical potential is applied at least to the electrically conductive areas and a liquid is applied to them, preferably in an area in which there is no container in the mold, so that due to the applied electrical potential and the charge of the added liquid deposits the liquid on the mold surface and thereby cools the mold and thus the container, so that heat transfer from the plastic to the mold is improved.

This electrically conductive coating or design of the molded parts and the introduction of the liquid onto at least the electrically conductive areas result in a shorter cooling time of the container until dimensional stability is achieved and thus a higher output. In addition, a more uniform cooling of the inner and outer surfaces of the container can be achieved, which means that there are no longer any dividing seams that fall in and a higher bottle quality is achieved. This means that the pressure pad mentioned above can also be dispensed with.

Overall, the plant potential is increased by the inventive design of the mold.

An entire inner wall of at least one molded part preferably has an electrically conductive coating and/or is designed to be electrically conductive. Particularly preferably, the entire inner wall of both molded parts has an electrically conductive coating and/or is designed to be electrically conductive.

The carrier mentioned above, on which a plurality of molds are arranged, can preferably be a movable and in particular rotatable carrier. A transport device is preferably also arranged on this, via which the molds are transported through the device for producing the plastic preforms. If the device for producing plastic containers is a linear machine, the carrier is preferably a stationary carrier.

In a preferred embodiment, the mold is a blow mold or an injection mold, with the blow mold preferably being used to produce plastic containers and the injection mold being used to produce plastic preforms, which are then formed into plastic containers in the blow mold.

The blow mold is preferably constructed in several parts and has at least two mold (side) parts, which can be moved relative to one another to open and close the blow mold, and a locking mechanism to lock the mold parts together. In addition, the blow mold preferably also has a base part. The base part preferably also has an electrically conductive coating at least in sections and/or is designed to be electrically conductive.

In a closed state, the two mold (side) parts and the bottom part preferably form a cavity which corresponds to the negative contour of the finished plastic container or the one to be produced. The plastic preforms are introduced into the open blow mold and, with the blow mold closed, expanded to form the plastic containers by the action of a liquid and/or gaseous medium, the plastic container being pressed against the inner contour of the molded parts by the action of the liquid and/or gaseous medium. Furthermore, the device preferably comprises an application device, which introduces the liquid and/or gaseous medium into the plastic preforms, and a blowing nozzle, which can be placed against a mouth of the plastic preforms in order to apply the blowing air or the liquid to the plastic preforms. In addition, a valve arrangement is preferably also provided, which controls the supply of the liquid and/or gaseous medium to the plastic preforms.

In a further advantageous embodiment, the blow molds each have stretching rods which stretch the plastic preforms in their longitudinal direction. The blow molding machine or the carrier and the blow molds are particularly preferably arranged within a clean room which separates the blow molding machine from a non-sterile environment. Drive devices for closing, locking and/or opening the blow molds are preferably located outside the clean room.

The blow molds are preferably transported within the clean room, with the clean room preferably being delimited by a plurality of walls. The clean room is preferably delimited by at least one stationary wall and a wall that moves relative to this stationary wall. In this case, for example, the carrier on which the forming stations or blow molds are arranged can already have or form one of these walls and in particular the moving wall. In particular, the clean room separates the blow molds from a non-sterile environment.

The injection mold is also preferably constructed in several parts and in particular in two parts from two mold (side) parts and preferably also has a locking mechanism for locking the mold parts. In a closed state, the molded parts preferably form a cavity which corresponds to the negative contour of the finished plastic preform or the one to be produced. To produce or shape the plastic preforms, liquid plastic material is injected under pressure into the mold and then cooled.

The shape mentioned preferably has a cross section deviating from a circular cross section and is therefore preferably used for producing plastic containers with an oval cross section or for producing oval plastic containers. For this purpose, the plastic preforms are heated unevenly before blow molding (so-called preferential heating) and then formed into plastic containers in the mold.

In the following, for the sake of simplicity, the term plastic container is used uniformly, including both the in the blow mold plastic containers produced from plastic preforms as well as the plastic preforms produced in the injection mold.

In a preferred embodiment, the first molded part and the second molded part are made or formed from different materials and preferably from electrically conductive materials and particularly preferably from electrically conductive metals. The materials are preferably selected from a group of materials that contains copper, aluminum, brass, iron, chromium, stainless steel, alloys thereof or the like. In addition, preferably electrically conductive plastic or ceramic materials are also conceivable. If the mold is made of an electrically conductive material, the coating mentioned can preferably be dispensed with.

In a further preferred embodiment, a first molded part and/or a second molded part has at least one electrical connection in order to electrically connect at least one section of the electrically conductive coating and/or at least one section to which the first molded part and/or the second molded part is connected is designed to be conductive to apply an electrical potential. In this case, the electrical potential is preferably applied to the coating or the electrically conductive design of the molded parts via an electrical structure known from the prior art.

Furthermore, in a preferred embodiment, the device has an application device, which introduces a liquid film into the mold, preferably in a defined and finely atomized form, and in particular applies it to the electrically conductive coating.

This application device is preferably a nozzle, via which the liquid medium, which is preferably under pressure, can be finely atomized.

Due to the electrical potential applied and the charge of the added liquid, the liquid is preferentially deposited on the mold surface, as a result of which the area of the mold that is provided with the electrically conductive coating is specifically wetted. The amount of liquid added ensures that no macroscopic droplets of the liquid form. The liquid on the mold surface advantageously improves heat transfer from the plastic preform to the mold, which reduces the temperature delta in the wall cross-section of the container or the temperature difference between the inner and outer walls of the container. In addition, the dimensional stability of the bottle is achieved more quickly as a result.

The liquid can preferably be water, for example, which can interact electromagnetically with other bodies due to its dipole properties.

The liquid or the liquid film is particularly preferably introduced into the mold or applied to the coating in an area in which the mold is empty, i. H. in which there is no container within the mould.

Preferably, it is also conceivable that the mold itself or the first and/or the second mold part have openings through which the liquid is introduced into the mold. Accordingly, the mold preferably has an internal liquid supply. For this purpose, for example, channels already present in the mold can advantageously be used for introducing the liquid into the mold.

Furthermore, it is also conceivable that the molds are preferably moved during rotation by the blow wheel or the carrier through an area of the carrier in which the finely atomized liquid is located or in which the liquid surrounds the preferably entire mold and itself as a spray mist so puts on the electrically conductive areas or sections of the mold. A region of the carrier can preferably be designed as a space which is preferably delimited and/or closed off from the environment, but is not necessarily sealed. The carrier preferably has, at least in sections, a region which is preferably delimited from the environment by a plurality of walls. These walls are preferably arranged in a stationary manner in said section of the carrier and preferably do not rotate with the carrier. However, it would also be conceivable for these walls to preferably move with the carrier.

In a preferred embodiment, the application device is arranged in a stationary manner on the device or arranged in a rotating manner on the carrier. A loading device is particularly preferably assigned to each forming station

As already mentioned above, in a particularly preferred embodiment the mold is designed without a pressure pad.

The present invention is also directed to a method for producing plastic containers with a carrier, with a plurality of molds being arranged on the carrier, each of which has at least a first molded part and a have a second molded part, the first molded part and the second molded part forming a cavity in a closed state, which corresponds to the negative mold of the plastic container to be produced.

According to the invention, at least one molded part is coated at least in sections with an electrically conductive coating and/or is designed to be electrically conductive.

It is therefore also proposed on the process side to coat at least one molded part at least in sections with an electrically conductive and wear-resistant coating and/or to produce the molded parts from a material that is electrically conductive, so that by applying an electrical potential to the electrically conductive areas and a Introducing a liquid onto the coating can improve heat transfer from the plastic to the mold.

In a particularly preferred method, an electrical potential is accordingly applied to at least one section of the electrically conductive coating and/or to at least one section on which the first molded part and/or the second molded part is designed to be electrically conductive.

In a further preferred method, at least the area of the mold is wetted with a liquid film which has the electrically conductive coating and/or which is designed to be electrically conductive.

By applying the potential and introducing the liquid to the electrically conductive areas of the molded parts, it is achieved that the cooling time of the container until dimensional stability is reached can be shortened and the output of the device is thereby increased. Furthermore, a higher bottle quality can be achieved as a result of a more uniform cooling of the inner and outer walls of the container.

The method is particularly preferably suitable and intended for operating the device described above for producing plastic containers.

The present invention is also directed to a mold for producing plastic containers, the mold being constructed in several parts and having at least a first mold part and a second mold part, which can be moved in relation to one another for opening and closing the mold, the first mold part and the second mold part form a cavity in a closed state, which corresponds to the negative mold of the plastic container to be produced.

According to the invention, at least one molded part has an electrically conductive coating at least in sections and/or is designed to be electrically conductive.

The mold is preferably arranged in the above-described device for producing plastic containers. A large number of such molds is particularly preferably arranged in the above-described device for producing plastic containers.

• 1 eine schematische Darstellung einer erfindungsgemäßen Vorrichtung zum Herstellen von Kunststoffbehältnissen;
• 2 eine schematische Darstellung einer ersten erfindungsgemäßen Form;
• 3 eine schematische Darstellung einer zweiten erfindungsgemäßen Form;
• 4 eine schematische Darstellung einer dritten erfindungsgemäßen Form; und
• 5 eine schematische Darstellung einer vierten erfindungsgemäßen Form.

Further advantages and embodiments result from the accompanying drawings. It shows:

• 1 a schematic representation of a device according to the invention for the production of plastic containers;
• 2 a schematic representation of a first form according to the invention;
• 3 a schematic representation of a second form according to the invention;
• 4 a schematic representation of a third form according to the invention; and
• 5 a schematic representation of a fourth form according to the invention.

1 shows a schematic representation of a device 1 for producing plastic containers 20. The molds 14 present here are blow molds, so that here plastic preforms 10 are fed to individual molding stations 8 and preferably, while they are being transported by a transport device 2, to plastic containers 20 to be expanded. After this expansion, the plastic containers 20 are removed from the device 1 again. At the in 1 The device 1 according to the invention for the production of plastic containers 20, which is shown as an example, is therefore a blow molding machine. As already mentioned above, the molds of the device according to the invention can also be injection molds in which the plastic preforms are produced, in which case the device 1 according to the invention for producing plastic containers is an injection molding machine.

A feed star (not shown) can be provided, which feeds the plastic preforms to the device 1, and a discharge device (also not shown), in particular also a transport star, which feeds the finished art material containers 20 removed from the device again.

The device 1 has a carrier 12 on which a multiplicity of forming stations 8 are arranged. This carrier can, for example, as in 1 shown, be a blowing wheel which is rotatable with respect to an axis of rotation D (which here runs perpendicularly to the plane of the figure and thus vertically). Each individual molding station 8 has a mold 14 which is preferably composed of two mold parts 14a, 14b and a base mold (not shown). The molds 14 are arranged on mold carriers 16 and can be removed from them or placed on them.

The reference numeral 6 denotes a base support on which the support 12 is rotatably mounted. The reference number 18 designates a housing which at least partially surrounds the carrier 12 . The housing 18 preferably separates its interior, which is designed as a sterile or clean room, from a normal atmosphere.

The reference number 5 refers to a mold parting seam, which is formed in a closed state of the mold 14 between the mold parts 14a and 14b.

2 shows a schematic representation of a first mold 14 according to the invention. The mold 14 has a first mold part 14a, a second mold part 14b and a bottom part 14c. The first mold part 14a is arranged on a first mold carrier shell 15a and the second mold part 14b on a second mold carrier shell 15b. The mold carrier shells 15a, 15b are in turn arranged on mold carriers (not shown here). Reference number 38 denotes an electrically conductive coating which is attached at least in sections to at least one molded part 14a, 14b. According to the embodiment of 2 the coating 38 is completely attached to the first and the second mold part. As mentioned above, it could also be preferred that instead of the coating provided on the molded parts, the molded parts 14a, 14b themselves are made of a material which is electrically conductive. The reference numerals 34 identify electrical connections via which an electrical potential can be applied to the molded parts 14a, 14b or the coating 38 of the molded parts 14a, 14b.

3 shows a schematic representation of a second mold 14 according to the invention. The mold parts 14a, 14b, the mold carrier shells 15a, 15b and the coating 38 applied to the mold parts can also be seen again. The mold 14 shown in this embodiment preferably has channels 32 for guiding a flowable and particularly preferably liquid medium. The above-mentioned liquid 35 is applied to the mold 14 or to the coating 38 via these channels 32 .

By applying an electrical potential to the in 3 Not shown electrical connections, the liquid 35 is deposited on the areas of the mold parts 14a and 14b which have the coating 38, so that heat transfer from the plastic of the plastic container (not shown here) to the mold is improved and the cooling time of the container is shortened .

4 shows a schematic representation of a third form 14 according to the invention. In contrast to FIG 3 In the embodiment shown, the liquid 35 is not applied to the coating 38 via channels arranged in the mold parts 14a, 14b, but preferably via an external application device (not shown).

Here, too, the liquid 35 is applied to the areas of the molded parts 14a, 14b which have the coating 38 by applying an electrical potential to the coating 38 .

5 shows a schematic representation of a fourth mold 14 according to the invention. In this embodiment, the liquid is applied in the form of a spray mist 36 to the mold parts 14a, 14b or their coating 38, with the mold 14 preferably being transported through the spray mist 36 for this purpose.

The spray mist 36 can preferably be applied to at least one section of the in 1 The carrier 12 shown can be produced, for which purpose at least one section of the carrier can be designed as a closed space or space that is delimited from the environment.

The applicant reserves the right to claim all features disclosed in the application documents as essential to the invention, provided they are new compared to the prior art, either individually or in combination. It is also pointed out that the individual figures also describe features which can be advantageous in and of themselves. The person skilled in the art recognizes immediately that a specific feature described in a figure can also be advantageous without adopting further features from this figure. Furthermore, the person skilled in the art recognizes that advantages can also result from a combination of several features shown in individual figures or in different figures.

reference list

1

contraption

2

transport device

5

form parting seam

6

base carrier

8th

forming station

10

plastic preform

12

carrier

14

shape

14a

first molding

14b

second molding

14c

bottom part

15a

first mold carrier shell

15b

second mold carrier shell

16

mold carrier

18

Housing

20

plastic container

30

application device

32

channels

34

electrical connection

35

liquid

36

spray mist

38

coating

D

axis of rotation

Claims (11)

Device (1) for producing plastic containers (20) with a carrier (12), a plurality of molds (14) being arranged on the carrier (12), each of which has at least a first mold part (14a) and a second mold part (14b ), wherein the first molded part (14a) and the second molded part (14b) form a cavity in a closed state, which corresponds to the negative mold of the plastic container (20) to be produced, characterized in that at least one molded part (14a, 14b) at least in sections has an electrically conductive coating and/or is designed to be electrically conductive. Device (1) after claim 1 , characterized in that the mold (14) is a blow mold or an injection mold. Device (1) after claim 1 , characterized in that the first molded part (14a) and the second molded part (14b) are made of different materials. Device (1) after claim 1 , characterized in that the first molded part (14a) and/or the second molded part (14b) has at least one electrical connection in order to connect to at least one section of the electrically conductive coating and/or to at least one section to which the first molded part (14a ) and / or the second molded part (14b) is designed to be electrically conductive to apply an electrical potential. Device (1) according to at least one of the preceding claims, characterized in that the device (1) has an application device (30) which preferably defines and finely atomizes a liquid film into the mold and applies it in particular to the electrically conductive coating. Device (1) after claim 5 , characterized in that the loading device (30) is arranged in a stationary manner on the device (1) or is arranged in a rotating manner on the movable carrier (12). Device (1) according to at least one of the preceding claims, characterized in that the mold (14) is designed without a pressure pad. A method for producing plastic containers (20) with a carrier (12), wherein a multiplicity of molds (14) are arranged on the carrier (12), each of which has at least a first mold part (14a) and a second mold part (14b), wherein the first mold part (14a) and the second mold part (14b) form a cavity in a closed state, which corresponds to the negative mold of the plastic container (20) to be produced, characterized in that at least one mold part (14a, 14b) is provided at least in sections with an electrically conductive coating is coated and / or is formed electrically conductive. procedure after claim 8 , characterized in that an electrical potential is applied to at least one section of the electrically conductive coating and/or to at least one section on which the first molded part (14a) and/or the second molded part (14b) is designed to be electrically conductive. procedure after claim 8 , characterized in that at least the area of Mold (14) is wetted with a liquid film which has the electrically conductive coating and/or which is designed to be electrically conductive. Mold (14) for producing plastic containers (20), the mold (14) being constructed in several parts and having at least a first mold part (14a) and a second mold part (14b) which are positioned relative to one another to open and close the mold (14) are movable, the first mold part (14a) and the second mold part (14b) forming a cavity in a closed state, which corresponds to the negative mold of the plastic container (20) to be produced, characterized in that at least one mold part (14a, 14b) at least in sections has an electrically conductive coating and/or is designed to be electrically conductive.

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