DE102012001229A1 - Method and apparatus for blow molding containers - Google Patents

Abstract

The method and apparatus are used for blow molding containers. In the area of a heating section, preforms are heated from a thermoplastic material and then transferred to a blowing device. In the area of the blowing device, the preforms are transformed into the containers by the action of a blowing pressure within blow molds. In the area of the blowing device, a sealing element is arranged.

Description

The invention relates to a method for blow-molding of containers, are heated in the preforms of a thermoplastic material in the region of a heating section and then transferred to a blowing device in which the preforms are transformed by the action of a blowing pressure within blow molding to the containers.

The invention further relates to a device for blow-molding of containers, which has a heating section for heating preforms of a thermoplastic material and which is provided with a blowing device having at least one blowing station for forming the preforms into the container.

In a container molding by blowing pressure preforms of a thermoplastic material, such as preforms made of PET (polyethylene terephthalate), supplied to different processing stations within a blow molding machine. Typically, such a blow molding machine has a heating device and a blowing device, in the region of which the previously tempered preform is expanded by biaxial orientation to form a container. The expansion takes place with the aid of compressed air, which is introduced into the preform to be expanded. The procedural sequence in such an expansion of the preform is in the DE-OS 43 40 291 explained. The introductory mentioned introduction of the pressurized gas also includes the introduction of compressed gas into the developing container bubble and the introduction of compressed gas into the preform at the beginning of the blowing process.

The basic structure of a blowing station for container molding is in the DE-OS 42 12 583 described. Possibilities for tempering the preforms are in the DE-OS 23 52 926 explained.

Within the blow molding apparatus, the preforms as well as the blown containers can be transported by means of different handling devices. In particular, the use of transport mandrels, onto which the preforms are plugged, has proven to be useful. The preforms can also be handled with other support devices. The use of gripper tongs for handling preforms and the use of expansion mandrels which are insertable into a muzzle region of the preform for mounting are also among the available constructions.

Handling of containers using transfer wheels, for example, in the DE-OS 199 06 438 in an arrangement of the transfer wheel between a blowing wheel and an output path described. The already described handling of the preforms takes place firstly in the so-called two-stage process, in which the preforms are first produced in an injection molding process, then temporarily stored and later conditioned in terms of their temperature and inflated to a container. On the other hand, there is an application in the so-called one-step process, in which the preforms are suitably tempered and then inflated immediately after their injection molding production and adequate solidification.

With regard to the blow molding stations used, different embodiments are known. In blow stations, which are arranged on rotating transport wheels, a book-like unfoldability of the mold carrier is frequently encountered. But it is also possible to use relatively movable or differently guided mold carrier. In fixed blowing stations, which are particularly suitable for receiving a plurality of cavities for container molding, typically plates arranged parallel to one another are used as mold carriers.

In the blastchnischen deformation of the preforms in the container, the interior of the preforms is provided with a considerable internal pressure to perform the blowing process. In this case, it is undesirable that a thread area of the preform also deforms, since otherwise the accuracy of fitting of caps used to close the containers would be adversely affected.

In order to avoid such unwanted preforms, it is already known to mechanically support the threaded area on the outside, moreover, an external sealing of the preform is known so that a substantially equal pressure prevails on both sides of the threaded portion. For this purpose, the threaded portion of the preform is typically surrounded by a compensation space, which is sealed against a support ring of the preform.

In such a seal damage to the support ring of the preform must be avoided, in addition, a secure seal must be ensured even with an occurrence of manufacturing tolerances and taking into account the aging of the components used and temperature-induced material expansions. An all requirements simultaneously optimally fulfilling seal for such a compensation chamber has not yet become known.

Another problem is when preforms are processed that have no support ring. Here thus eliminates the support ring as a contact surface.

The object of the present invention is therefore to improve a method of the type mentioned in the introduction in such a way that a high operational reliability is achieved with a simple mechanical construction.

This object is achieved in that in the region of the blowing device, a sealing element is guided against a portion of the preform and that the sealing element is inserted into a mouth portion of the preform and sealingly clamped against an inside taper of the preform.

Another object of the present invention is to construct a device of the aforementioned type such that a high operational reliability is supported with a simple design effort.

This object is achieved according to the invention in that a sealing element for sealing the preform extends in the region of an interior of the preform and has at least one contact region sealingly adjacent to an inside taper of the preform.

The sealing element, for example a sleeve-shaped and annular element, is thus introduced into the mouth section of the preform until a mechanical contact between the end section of the sealing element introduced into the preform and the inward tapering of the preform is achieved. The taper can be achieved, for example, by a reduction in the wall thickness running in the direction of the opening of the preform, but it is also conceivable to incline a wall of the preform such that a shoulder-like or wedge-like structure is achieved. It is therefore essential that the sealing element can be guided against an inside region of the preform, in which the inner diameter of the preform is reduced. As a result, a sealing mechanical contact between the sealing element and the inside of the preform is possible.

Preferably, the taper of the preform is located so as to extend from the opening of the preform in the direction of the longitudinal axis to the outer threaded portion of the preform. As a result, with a pressure build-up within the preform, the threaded area is kept free of an acting internal pressure.

In the drawings, embodiments of the invention are shown schematically. Show it:

1 A perspective view of a blowing station for the production of containers from preforms,

2 a longitudinal section through a blow mold, in which a preform is stretched and expanded,

3 a sketch to illustrate a basic structure of a device for blow molding containers,

4 a modified heating section with increased heating capacity,

5 a longitudinal section through a mouth portion of a preform with inventive taper,

6 an enlarged view of detail VI in 5 after an introduction of the sealing element and

7 one opposite 6 modified embodiment.

The basic structure of a device for forming preforms ( 1 ) in containers ( 2 ) is in 1 and in 2 shown.

The device for forming the container ( 2 ) consists essentially of a blowing station ( 3 ), which are blown ( 4 ) into which a preform ( 1 ) can be used. The preform ( 1 ) may be an injection-molded part of polyethylene terephthalate. To enable insertion of the preform ( 1 ) in the blow mold ( 4 ) and to allow removal of the finished container ( 2 ) the blow mold ( 4 ) from mold halves ( 5 . 6 ) and a bottom part ( 7 ), which by a lifting device ( 8th ) is positionable. The preform ( 1 ) in the area of the blowing station ( 3 ) of a transport mandrel ( 9 ), which together with the preform ( 1 ) passes through a plurality of treatment stations within the device. But it is also possible to use the preform ( 1 ), for example via pliers or other handling means directly into the blow mold ( 4 ).

To enable a compressed air supply line is below the transport mandrel ( 9 ) a connecting piston ( 10 ) disposed of the preform ( 1 ) Supplies compressed air and at the same time a seal relative to the transport mandrel ( 9 ). In a modified construction, it is basically also conceivable to use solid compressed air supply lines.

A stretching of the preform ( 1 ) takes place in this embodiment by means of a stretch rod ( 11 ), by a cylinder ( 12 ) is positioned. According to another embodiment, a mechanical positioning of the stretch rod ( 11 ) carried out over curve segments which are acted upon by Abgriff. The use of curve segments is particularly useful when a plurality of blow molding stations ( 3 ) are arranged on a rotating blowing wheel

At the in 1 In the embodiment shown, the stretching system is designed such that a tandem arrangement of two cylinders ( 12 ). From a primary cylinder ( 13 ), the stretch rod ( 11 ) first before the beginning of the actual stretching process into the area of a soil ( 14 ) of the preform ( 1 ) hazards. During the actual stretching process, the primary cylinder ( 13 ) with extended stretch rod together with a primary cylinder ( 13 ) carrying carriages ( 15 ) from a secondary cylinder ( 16 ) or via a cam control. In particular, the secondary cylinder ( 16 ) in such a curve-controlled manner that a leadership role ( 17 ), which slides along a curved path during the execution of the stretching process, a current stretching position is specified. The leadership role ( 17 ) is from the secondary cylinder ( 16 ) pressed against the guideway. The sled ( 15 ) slides along two guide elements ( 18 ).

After closing in the range of girders ( 19 . 20 ) arranged mold halves ( 5 . 6 ) there is a locking of the carrier ( 19 . 20 ) relative to each other by means of a locking device ( 20 ).

For adaptation to different shapes of a mouth section ( 21 ) of the preform ( 1 ) is according to 2 the use of separate thread inserts ( 22 ) in the area of the blow mold ( 4 ) intended.

2 shows in addition to the blown container ( 2 ) also shown in dashed lines the preform ( 1 ) and schematically a developing container bubble ( 23 ).

3 shows the basic structure of a blow molding machine with a heating line ( 24 ) and a rotating blowing wheel ( 25 ) is provided. Starting from a preform input ( 26 ), the preforms ( 1 ) of transfer wheels ( 27 . 28 . 29 ) in the area of the heating section ( 24 ). Along the heating route ( 24 ) are radiant heaters ( 30 ) as well as blowers ( 31 ) arranged to the preforms ( 1 ) to temper. After a sufficient temperature of the preforms ( 1 ) these are to the blowing wheel ( 25 ), in whose area the blowing stations ( 3 ) are arranged. The finished blown containers ( 2 ) are provided by further transfer wheels of a delivery line ( 32 ).

To get a preform ( 1 ) into a container ( 2 ), that the container ( 2 ) Has material properties which have a long useful life from inside the container ( 2 ), in particular beverages, special process steps in the heating and orientation of the preforms ( 1 ) be respected. In addition, advantageous effects can be achieved by adhering to special dimensioning regulations.

As a thermoplastic material different plastics can be used. For example, PET, PEN or PP can be used.

The expansion of the preform ( 1 ) during the orientation process is carried out by compressed air supply. The compressed air supply is in a Vorblasphase in which gas, for example, compressed air, is supplied at a low pressure level and divided into a subsequent Hauptblasphase in which gas is supplied at a higher pressure level. During the pre-blowing phase, compressed air is typically used at a pressure in the interval of 10 bar to 25 bar and during the main blowing phase compressed air is supplied at a pressure in the interval of 25 bar to 40 bar.

Out 3 is also apparent that in the illustrated embodiment, the heating section ( 24 ) from a plurality of circulating transport elements ( 33 ) is formed, the chain-like strung together and along deflection wheels ( 34 ) are guided. In particular, it is envisaged to open a substantially rectangular basic contour by the chain-like arrangement. In the illustrated embodiment, in the region of the transfer wheel ( 29 ) and an input wheel ( 35 ) facing the extent of the heating section ( 24 ) a single relatively large-sized deflection ( 34 ) and in the region of adjacent deflections two comparatively smaller dimensioned deflection wheels ( 36 ) used. In principle, however, any other guides are conceivable.

To enable a dense arrangement of the transfer wheel ( 29 ) and the input wheel ( 35 ) relative to each other, the arrangement shown to be particularly useful, since in the region of the corresponding extent of the heating section ( 24 ) three deflection wheels ( 34 . 36 ), in each case the smaller deflection wheels ( 36 ) in the area of the transition to the linear curves of the heating section ( 24 ) and the larger deflection wheel ( 34 ) in the immediate transfer area to the transfer wheel ( 29 ) and to the input wheel ( 35 ). Alternative to Use of chain-like transport elements ( 33 For example, it is also possible to use a rotating heating wheel.

After a finished blowing of the container ( 2 ), these are picked up by a picking wheel ( 37 ) from the field of blowing stations ( 3 ) and via the transfer wheel ( 28 ) and an output wheel ( 38 ) to the output section ( 32 ).

In the in 4 illustrated modified heating section ( 24 ) can by the larger number of radiant heaters ( 30 ) a larger amount of preforms ( 1 ) are tempered per unit time. The blowers ( 31 ) direct cooling air into the area of cooling air ducts ( 39 ), which the associated radiant heaters ( 30 ) in each case opposite and deliver the cooling air via outflow openings. Due to the arrangement of the outflow directions, a flow direction for the cooling air is substantially transverse to a transport direction of the preforms ( 1 ) realized. The cooling air channels ( 39 ) in the area of the radiant heaters ( 30 ) opposite surfaces provide reflectors for the heating radiation, it is also possible on the discharged cooling air and a cooling of the radiant heater ( 30 ) to realize.

5 shows an inside taper of the preform, which is realized as a running towards an opening opening enlargement of the inner diameter of the preform. This will be according to 5 achieved by a sectionally inclined wall of the preform. Thereby, a heel-like or ramp-like structure is provided on the inside of the preform. This structure extends at least in sections inclined to the longitudinal axis of the preform.

6 shows the arrangement according to 5 after insertion of a sleeve-shaped sealing element. This lies with its end on the inside diameter increase of the preform and thereby achieved in acting in a longitudinal direction of the preform contact pressure a sealing effect.

According to the embodiment in FIG 7 the end region of the sealing element has a more rounded outer contour.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 4340291 A [0003]
• DE 4212583 A [0004]
• DE 2352926 A [0004]
• DE 19906438A [0006]

Claims (2)

A process for the blow molding of containers, in which preforms are heated from a thermoplastic material in the region of a heating section and then transferred to a blowing device, in which the preforms are formed by blowing a blow pressure within the blow molds to the containers, characterized in that in the Blower a sealing element ( 49 ) in a mouth section ( 21 ) of the preform ( 1 ) is inserted and sealed against an inward taper of the preform is braced. Apparatus for blow-molding containers which has a heating section for heating preforms of a thermoplastic material and which is provided with a blowing device which has at least one blowing station for shaping the preforms into the containers, characterized in that a sealing element ( 49 ) for sealing the preforms ( 1 ) in the region of an interior of a mouth section ( 21 ) of the preform ( 1 ) and one at an inside taper of the preform ( 1 ) has a sealing contact area.

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