DE102024116094A1 - Stretch blow molding machine and method for operating the stretch blow molding machine - Google Patents

Abstract

The invention relates to a stretch blow molding machine, in particular for forming beverage bottles from preforms, with a plurality of blowing stations (2), each of which has a blow mold (5) and a linearly motor-driven stretching rod assembly (7) held on a support structure (1), wherein a rod section (11) facing away from the respective blow mold (5) and linearly movable relative to the support structure (1) is arranged in an enclosure (12). According to the invention, the enclosure (12) provides access to the rod section (11) by having at least a first side wall section (13) and a second side wall section (14), which are movable relative to each other.

Description

The invention relates to a stretch blow molding machine, in particular for forming beverage bottles from preforms, with a plurality of blowing stations, each comprising a blow mold and a linearly motor-driven stretching rod assembly held on a support structure, wherein a rod section facing away from the respective blow mold and movable linearly relative to the support structure is arranged in an enclosure. The invention further relates to a method for operating the stretch blow molding machine.

Stretch blow molding processes produce high-quality bottles, particularly from polyethylene terephthalate (PET), with excellent mechanical and optical properties. Furthermore, good barrier properties are achieved even with low weight and thus minimal material usage. Additionally, these containers, especially PET beverage bottles, can be fully or almost fully recycled, minimizing the use of virgin PET. Finally, bio-based PET variants are also available, made from renewable rather than fossil raw materials.

A two-stage process is typically used, in which a preform is first manufactured, particularly by injection molding. The preforms are then heated upon being fed into the stretch blow molding machine and subsequently formed into the containers described above. The forming of the preforms into containers, for example in the form of bottles, preferably occurs axially by mechanical stretching with the stretching bar and radially by pressure forming in the corresponding blow mold. For known methods and devices, reference is also made to the textbook “ Blow molding of plastic bodies", 2nd, updated edition 2022, Carl Hanser Verlag Munich, ISBN 978-3-446-45552-8 Reference is made to the following. Stretch blow molding is explained in detail in Chapter 3 (pages 149-214).

In the stretch blow molding process, the preform undergoes several stages or steps during its transformation into the container. Circulating stretch blow molding machines are widely used in practice, where the multiple blowing stations are arranged around a rotating blow wheel. Depending on the position of the blow mold along its circular path, for example, depending on an angular position, the movement of the stretching bar is then determined, which mechanically stretches the preform through direct contact.

In practice, various drive mechanisms for the horizontal bar are known. For example, the movement of the horizontal bar can be mechanically controlled by a cam. Pneumatic or hydraulic drives are also known.

The present invention relates specifically to a linear motor-driven stretching rod arrangement, wherein the drive is provided by an electric linear motor. Generic embodiments of stretch blow molding systems according to the preamble of claim 1 are derived from EP 1 484 160 A1 , EP 2 735 429 A1 and EP 3 513 944 B1 known.

According to this prior art, the pull-rod arrangement comprises, on the one hand, the pull-rod that moves directly into the preform and, on the opposite side, a linearly movable rod section connected to it, which forms the rotor of the electric linear motor. The rotor interacts with a stator arranged on the support structure. In particular, the stator can have several coils, which then interact with a plurality of permanent magnets on the rod section.

It is known to arrange the linearly movable rod section in an enclosure that protects the rod section, which acts as the rotor of the electric linear motor, from contamination and damage. It must also be taken into account that, due to the arrangement of permanent magnets along the rod section, magnetizable or magnetic particles, screws or other parts, tools, or the like can be magnetically attracted to the rod section.

In practice, tubular enclosures around the linearly movable rod section are commonly known. These enclosures are typically attached to the supporting structure, such as a stator housing, by means of screws. For maintenance purposes, the enclosure can be removed by loosening the screws, thus providing access to the rod section, which usually moves freely within it. This allows, in particular, cleaning, inspection, lubrication, or other treatment of the rod section.

In a design known from practice, it is further provided that grounding between the rod section and the housing is achieved by means of sliding contacts.

The present invention is based on the objective of simplifying the handling and, in particular, the maintenance of a stretch blow molding machine.

The invention relates to a stretch blow molding machine according to claim 1 and a method for operating the stretch blow molding machine according to claim 13.

Based on a generic stretch blow molding machine, the invention provides that, for access to the rod section, the enclosure has at least a first side wall part and a second side wall part, which are movable relative to each other.

The mobility of at least two side wall sections relative to each other allows the enclosure to be put into different configurations, in particular an open position and a closed position.

According to a preferred embodiment of the invention, the pull-bar arrangement comprises a linear motor with a stator arranged on the support structure and with the rod section as a runner.

The stator can, for example, be formed by at least one coil, preferably several coils arranged in series. The rod section, acting as the rotor, then advantageously features a multitude of permanent magnets, so that an alternating field is generated along the length of the rod section or rotor, and the rotor can be moved along its longitudinal direction by appropriately controlling the stator coils. Such a linear motor is characterized by a simple design, a comparatively low dynamic mass, low wear, and high accuracy.

The stretching rod that enters the die during the stretch blow molding process is preferably formed separately, with the stretching rod and the rod section being coupled to each other in a suitable manner as a runner. The connection can be provided, for example, by a screw connection or another suitable type of coupling. Advantageously, the stretching rod and the rod section are arranged coaxially to avoid lateral tilting moments and to obtain an overall linear movement that is easy to control.

Accordingly, the pull-up bar and the runner also exhibit a uniform linear extension and retraction movement with a uniform stroke. The stroke required also depends on the container size that is manufactured or can be manufactured with the stretch blow molding machine. Considering typical container heights, the stroke can, for example, range between 200 mm and 400 mm.

It should be noted that the present invention is not limited to beverage bottles, although this is a particularly preferred application. Furthermore, it is also possible, in principle, to provide beverage bottles with a greater height. The specified range of a planned stroke is therefore not limiting.

Preferably, a free end of the rod section is completely enclosed within the housing. Furthermore, it is preferred that the rod section is freely movable within the housing without direct contact, so that a gap remains between the housing and the rod section. As will be explained in more detail below, this makes the rod section more easily accessible, for example, for cleaning.

According to the prior art, it is known to provide grounding between the bar section and a one-piece housing by means of sliding contacts. Such grounding is not excluded within the scope of the invention, but is disadvantageous in many cases due to the design of the housing with at least two mutually movable side wall parts. If necessary, grounding can then also be achieved by means of electrically conductive seals or, more generally, electrically conductive bushings through which the bar section and/or the attached pull-up bar are guided.

Especially when the rod section is designed as a runner with permanent magnets, the housing is also intended to keep out dirt, particles, screws, tools, or the like that attracted by magnetic forces. Against this background, it is also advisable, taking into account the usual decrease in field strength with increasing distance, that the housing has a suitable oversize relative to the rod section.

The material of the housing is not limited within the scope of the invention, with plastic and metal being particularly suitable. Among the metallic materials, aluminum and stainless steel are especially appropriate because they do not interact, or only minimally interact, with the magnetic forces of the runner when the latter is equipped with several permanent magnets.

In principle, the first side wall section and the second side wall section can also be made of different materials.

If the enclosure is made entirely or partially of plastic, this is particularly important. a transparent plastic is also being considered, so that a visual inspection through the enclosure is possible.

According to a preferred embodiment of the invention, the first side wall part is attached to the supporting structure, wherein the second side wall part is then movably attached to the first side wall part.

In such a design, the first side wall section usually remains attached to the supporting structure even in the open position of the enclosure, while the second side wall section is open in an open position, for example swung open or removed.

In principle, it is possible to remove the second side panel in such a design so that it can be stored separately and is not in the way during maintenance or inspection of the pole section. However, there is a risk that the second side panel could unintentionally fall off and potentially be damaged or lost altogether.

According to a particularly preferred embodiment of the invention, the second side wall section is not completely loose in the open position, but is held either on the supporting structure or, preferably, on the first side wall section. It is conceivable, for example, that the first side wall section and the second side wall section are hingedly connected, with the second side wall section then forming an opening door or flap of the enclosure.

Such a door or flap can extend, for example, over 10% to 50%, in particular 20% to 40% of the enclosure's surface area.

A hinged connection can be achieved by at least one hinge. It is also conceivable that such a hinged connection could be released, for example, by lifting the second side panel in an open position. An operator can then decide whether the second side panel remains attached to the first in the open position or is removed, depending on maintenance requirements or available space.

The measures described allow for particularly easy maintenance of the rod section. For example, the rod section can be cleaned, greased, and/or otherwise treated very easily.

Typically, the entire enclosure can be removed from the supporting structure. For example, in the previously described design, the first side panel may be attached to the supporting structure with screws, a bayonet fitting, or similar fasteners. During routine maintenance, however, removing the first side panel is unnecessary, although further disassembly is generally possible for specific assembly and maintenance purposes, as is standard practice.

According to a preferred embodiment of the invention, for the purpose of particularly easy handling, the side wall parts are held together in a closed position by a tool-free, releasable holding device. If, for example, the second side wall part is to be completely removable from the first side wall part, a connection can be provided by means of snap hooks, pins, or the like, whereby connecting and disconnecting can then be effected, for example, by a vertical movement when hooking or unhooking.

In the case of a particularly pivotable connection of the at least two side wall parts, the tool-free detachable holding device can, for example, have a locking bolt, a magnetic closure, a captive screw, a snap lock or the like, whereby in principle a combination of the different options is also possible.

In a typical design, the two side wall sections do not need to be completely airtight when closed, and in particular, not completely airtight. However, the arrangement of a seal between the two side wall sections is also a possibility. For example, if the first side wall section has an opening and the second side wall section forms a closing door or flap at the opening, a seal around the opening between the two side wall sections can also be advantageous. Such an optional design can also help to retain dirt in the form of small particles.

In the case of a potentially tight or substantially tight design of the enclosure, a vent opening may also be provided at a protected location or one exposed to only minor contamination in order to allow pressure equalization during the movement of the rod section in the enclosure and the resulting volume changes.

A seal ensures that even when closing a door or flap, the noise is soft and gentle. The stop is reached, while also achieving a certain degree of damping against vibrations or other shocks. These advantages can also be achieved additionally or alternatively through elastic and/or wear-resistant stops and/or contact surfaces.

Additionally or alternatively, it is also conceivable that during normal operation of the stretch blow molding machine, the housing is moved into the closed position by the movement provided for. For example, according to a preferred embodiment, the stretch blow molding machine comprises a blow wheel on which the blowing stations are arranged. During operation of the stretch blow molding machine, the blow wheel rotates and centrifugal forces act upon it, whereby, particularly in an embodiment as a door or flap, the second side wall section can also be moved into the closed position by the centrifugal forces with a suitable arrangement.

The height of the enclosure, determined along a longitudinal direction of the rod section, can be, for example, between 300 mm and 600 mm, in particular between 150 mm and 500 mm.

The invention also relates to a method for operating the previously described stretch blow molding machine, wherein in a blow molding operation containers, in particular beverage bottles, are formed from preforms, while the housing with the at least side wall parts is in a closed position and wherein in a maintenance operation the housing is opened for access to the rod section.

• 1 eine schematische Ansicht einer Streckblasanlage mit einer Vielzahl von Blasstationen,
• 2 eine schematische Ansicht einer Blasstation mit einer Reckstangenanordnung,
• 3A und 3B Detailansichten der Reckstangenanordnung in unterschiedlichen Konfigurationen.

The invention is explained below with reference to figures.

• 1 a schematic view of a stretch blow molding machine with a large number of blowing stations,
• 2 a schematic view of a blow station with a horizontal bar arrangement,
• 3A and 3B Detailed views of the horizontal bar arrangement in different configurations.

The 1 shows a stretch blow molding machine for forming beverage bottles from preforms.

In a typical configuration, the stretch blow molding machine has a support structure 1 in the form of a blow wheel, on which a plurality of blowing stations 2 are arranged. Preforms are transferred at an input section 3 to the blowing stations 2 that are open there. After the blowing stations 2 close, the preforms are then formed into containers, in particular beverage bottles, before the formed containers are removed from the blowing stations 2 at an output section 4.

The 2 Figure 2 shows a schematic view of one of the blowing stations 2. The transformation of the preforms into the containers takes place in a blow mold 5, whereby during the stretch blowing process the preform is first stretched with a stretching bar 6 of a stretching bar arrangement 7 and then formed into the container by applying an internal pressure.

Within the scope of the invention, the pull-up bar arrangement has a linear motor drive. Specifically, a linear motor 8 with a stator 9 formed by coils is provided, wherein the stator 9 is attached to the support structure 1 by a motor housing.

The linear motor 8 further comprises a rotor equipped with permanent magnets 10, which, connected to the stretching rod 6, forms a linearly movable rod section 11 opposite the blow mold 5. The rod section 11 and the stretching rod 6 are coaxially connected, with the linear motor 8 enabling precise movement of the stretching rod 6 during the stretch blow molding process.

The rod section 11 forming the runner is surrounded and protected by an enclosure 12.

According to the invention, the enclosure 12 comprises a first side wall part 13 and a second side wall part 14, which are movable relative to each other.

According to a comparative analysis of 3A and 3B The first side wall section 13 has the form of a housing with an opening 15. The first side wall section 13 is attached to the motor housing and thus also to the support structure 1, for example, by screws, while the second side wall section 14 is pivotally held against the first side wall section 13 as a door.

The 3A indicates a closed position and the 3B an open position.

In the blowing operation, the enclosure 12 is as in 3A shown closed, whereby for maintenance operation with a stationary system the second side wall part 14 can be swung open as a door.

In the 3A and 3B The illustration shows, by way of example, that the second side wall part 14 is attached to the first side wall part as a door via hinges 16. 13 is supported. Various design options arise in the design of the hinge 16 or other connection.

For example, it may be provided that the side wall parts 13, 14 can be separated from each other without tools at the hinge 16 or another connection, in order to optionally remove the second side wall part 14 completely.

In principle, the entire housing 12 can also be removed by loosening the fastening screws of the first side wall section 13 as shown. However, for normal maintenance, it is sufficient to remove the second side wall section 14, which forms a door, as shown in 3B The illustration shows how to open the rod section 11, thereby exposing it. The rod section 11 can then be cleaned, greased, or otherwise treated, for example.

Depending on the arrangement of the second side wall section 14, it can also be provided, for example, that the movement of the supporting structure 1, in particular in the form of a blower wheel, automatically moves the second side wall section 14 into the closed position, for example by centrifugal forces, according to the 3A is being pressured.

Additionally or alternatively, the hinge 16 can also be bistable or have a detent position in the open position. The second side panel 14 is then held in the open position with a certain force, which can further facilitate operation.

In the 3A and 3B Furthermore, a tool-free releasable holding device 17 is shown schematically. The holding device 17 holds the second side wall part 14 in the closed position against the first side wall part 13. The holding device 17 can, for example, have a locking bolt, a mechanical lock, a captive screw, a snap lock, or a latch.

The 3B Figure 16 shows an exemplary embodiment of the hinges 16, which also allows for the simple and complete removal of the second side wall section 14 from the first side wall section 13. For this purpose, the second side wall section 14 can be lifted in the open position and thus released from the hinges 16. However, such removal is neither intended nor necessary during normal maintenance, in which case the second side wall section 14 remains held in the open position by the hinges 16 on the first side wall section 13.

Reference symbol list

1

supporting structure

2

Blow stations

3

Input section

4

Output section

5

blow mold

6

horizontal bar

7

Horizontal bar arrangement

8

Linear motor

9

stator

10

Permanent magnet

11

Rod section

12

Enclosure

13

first side wall section

14

second side wall section

15

opening

16

hinge

17

Holding device

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• EP 1 484 160 A1 [0006]
• EP 2 735 429 A1 [0006]
• EP 3 513 944 B1 [0006]

Cited non-patent literature

• Blow molding of plastic bodies", 2nd, updated edition 2022, Carl Hanser Verlag Munich, ISBN 978-3-446-45552-8 [0003]

Claims (13)

Stretch blow molding machine, in particular for forming beverage bottles from preforms, with a plurality of blowing stations (2), each of which has a blow mold (5) and a linear motor-driven stretching rod assembly (7) held on a support structure (1), wherein a rod section (11) facing away from the respective blow mold (5) and linearly movable relative to the support structure (1) is arranged in an enclosure (12), characterized in that for access to the rod section (11) the enclosure (12) has at least a first side wall part (13) and a second side wall part (14) which are movable relative to each other. Stretch blow molding machine according to Claim 1 , characterized in that the pull-bar arrangement (7) has a linear motor (8) with a stator (9) arranged on the support structure (1) and with the rod section (11) as a rotor. Stretch blow molding machine according to Claim 2 , characterized in that the runner has a plurality of permanent magnets (10). Stretch blow molding machine according to one of the preceding claims, characterized in that a free end of the rod section (11) is completely enclosed in the housing (12). Stretch blow molding machine according to one of the preceding claims, characterized in that the first side wall part (13) is attached to the supporting structure (1) and that the second side wall part (14) is movably attached to the first side wall part (13). Stretch blow molding machine according to Claim 5 , characterized in that the second side wall part (14) forms an opening door or flap of the enclosure (12). Stretch blow molding machine according to one of the preceding claims, characterized in that the first side wall part (13) and the second side wall part (14) are pivotably connected to each other. Stretch blow molding machine according to one of the preceding claims, characterized in that the side wall parts (13, 14) are held together in a closed position by a tool-free releasable holding device (17). Stretch blow molding machine according to one of the preceding claims, characterized in that the stretch rod arrangement (7) has an electrically conductive seal. Stretch blow molding machine according to one of the preceding claims, characterized in that the housing (12) is tubular and surrounds the linearly movable rod section (11) without contact. Stretch blow molding machine according to one of the preceding claims, characterized in that the first side wall part (13) and/or the second side wall part (14), preferably only the second side wall part (14), is formed from a transparent material, in particular a transparent plastic. Stretch blow molding machine according to one of the preceding claims characterized in that the housing (12) has a height between 300 mm and 600 mm along a longitudinal direction of the rod section (11). Method for operating a stretch blow molding machine according to one of the Claims 1 until 12 , wherein in a blow molding operation containers, in particular beverage bottles, are formed from preforms, while the housing (12) with the at least two side wall parts (13, 14) is in a closed position and wherein in a maintenance operation the housing (12) is opened for access to the rod section (11).