DE102010006898A1 - Method and apparatus for blow molding containers - Google Patents

Abstract

The method and the device are used for blow molding containers. After thermal conditioning within a blow mold of a blow molding machine, a preform is formed into the container by the action of blowing pressure. The blow mold is designed as part of a blow molding station and is heated at least in regions. At least one electric heating element is used to heat the blow mold. The electrical heating element is positioned in at least one cavity of the blowing station in such a way that the heating element is surrounded by a fluid-type heat exchanger that at least partially fills the cavity.

Description

The invention relates to a method for blow-molding of containers, in which a preform is converted after thermal conditioning within a blow mold of a blow molding machine by blowing pressure into the container and in which the arranged as part of a blowing station blow mold is heated at least partially.

The invention further relates to a device for blow-molding of containers, which has at least one blowing station with a blow mold, and in which the blow mold is at least partially coupled with at least one tempering.

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 sufficient 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.

Depending on the properties of the container to be produced, it may be necessary to temper the blow molds in whole or in part, in particular to heat. According to the prior art, such heating of the blow molds is usually used within the blow molds and / or arranged within carriers of the blowing stations Temperiermittelkanäle. Through these channels, heated oil or heated water is passed. In blow molding machines with rotating blowing wheels, it is necessary in such a procedure to transport the temperature control medium into the area of the blowing wheel via rotary couplings and piping and tubing and to drain it off again.

It is also already known to equip the blowing stations with electrical heating elements. For this purpose, the electrical heating elements are inserted into recesses provided and either cast in, surrounded with heat-conducting pastes or mechanically wedged to ensure sufficient heat transfer. Although such measures can be achieved a good heat transfer, disassembly of the heating elements, however, proves to be extremely laborious or sometimes even not feasible.

Object of the present invention is therefore to improve a method of the aforementioned type such that a temperature of the Blow mold with low material and labor is supported.

This object is achieved in that for heating the blow mold at least one electric heating element is used, which is positioned in at least one cavity of the blowing station such that the heating element is surrounded by a cavity at least partially filling fluid-like heat transfer.

Another object of the present invention is to construct a device of the aforementioned type such that a temperature of the blow mold with low material and labor is supported.

This object is achieved in that the tempering is formed as an electric heating element and disposed in at least one cavity of the blowing station and that the cavity is at least partially filled with a fluid-like heat exchanger.

By inserting the electric heating element in a cavity of the blowing station and filling this cavity with the fluid-like heat exchanger, it is possible to avoid lines and rotary joints for transport of a liquid heat exchanger and on the other hand to ensure easy interchangeability of the electric heating element.

According to one embodiment, it is envisaged that oil is used as the heat exchanger.

It is also possible that water is used as a heat exchanger.

Another embodiment is provided by using a gel-like substance as the heat exchanger.

A stable and at the same time lightweight construction is achieved in that walls bounding the cavity are stabilized relative to one another by at least one spacer element relative to one another.

A modular construction is thereby supported and soiling is avoided by closing the cavity relative to an environment.

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 vertical section through a blowing station with cavities for receiving electrical heating elements,

6 a horizontal section through the arrangement according to 5 and

7 a schematic representation for illustrating the structural realization and arrangement of the heating elements.

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 ) becomes. 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 illustrated embodiment, 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 ) such a cam-controlled use that of 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 ( 40 ).

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 ). Alternatively to the 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 a vertical section through a blow station partially shown similar to 2 , but with a rotated by 180 ° arrangement. It can be seen that in the area of the blowing station ( 3 ) a cavity ( 41 ) is arranged, in which a heating element ( 42 ) is used. The heating element ( 42 ) is formed as an electric heating element and may preferably tubular within the cavity ( 41 ).

In the illustrated embodiment, the cavity ( 41 ) in the region of an intermediate element ( 43 ) arranged between the mold halves ( 5 . 6 ) and the carriers ( 19 . 20 ) is arranged. Typically, such an intermediate element ( 43 ) is constructed as a so-called shell mold. Such a mold shell typically has a design similar to half a cylinder shell.

Alternatively, it is also thought, the cavity ( 41 ) or a plurality of cavities ( 41 ) in the region of at least one of the mold halves ( 5 . 6 ) or at least one of the supports ( 19 . 20 ). It is also possible, an arrangement in the region of the bottom part ( 7 ).

6 shows a horizontal section through the arrangement according to 5 , Notwithstanding the embodiment in 1 is in this embodiment the carrier ( 19 ) relative to the blowing wheel ( 25 ) immovably arranged. For positioning the carrier ( 20 ) an adjusting device ( 44 ). The adjusting device ( 44 ) is in this embodiment of two levers ( 45 . 46 ) formed by a pivot joint ( 47 ) are interconnected. The lever ( 45 ) is via a pivot joint ( 48 ) with the carrier ( 29 ) connected. The lever ( 46 ) points in the region of its pivot ( 47 ) facing away from a pivot bearing ( 48 ) on. The adjusting device ( 44 ) is thus constructed similar to a knee lever in the illustrated embodiment.

From the cross section in 6 it can be seen that the cavity ( 41 ) of a relatively thin wall ( 49 ) is surrounded. To stabilize the cavity ( 41 ) it is possible to enter the cavity ( 41 ) Distance elements ( 50 ). In particular, it is thought to use as spacers balls that are loose in the cavity ( 41 ) and have a diameter which is approximately the inner diameter of the cavity ( 41 ) in a radial direction of the blowing station ( 3 ) corresponds.

Inside the cavity ( 41 ) is on the one hand the heating element ( 42 ) or a plurality of heating elements ( 42 ) arranged. In addition, in the cavity ( 41 ) filled a fluid-like substance for heat transfer. This substance may be, for example, oil, water or another liquid. It is also thought of the use of gel-like substances.

6 illustrates a construction of the blowing station ( 3 ), in which the walls ( 49 ) of the cavity ( 41 ) one of the intermediate element ( 43 ) separate tempering element ( 51 ) train. As a result, a very modular shell-like structure is provided in which in a radial direction of the blowing station ( 3 ) outside the carrier ( 19 . 20 ), then towards the blow mold ( 4 ) first the intermediate element ( 43 ) and then the tempering element ( 51 ) are arranged. Both the intermediate element ( 43 ) as well as the tempering element ( 51 ) have in the illustrated embodiment, a shell-like basic contour similar to an approximately half cylinder shell segment.

In an arrangement of several heating elements ( 42 ) in the area of the blowing station ( 43 ), it is also possible to have a plurality of mutually sealed cavities ( 41 ) and to temper the respective areas differently. This can be done in a simple manner by different activations of the electrical heating elements ( 42 ) respectively. A mixing of the fluid-like heat exchanger within the cavity ( 41 ) is supported by flow processes caused by the heating process.

7 shows for further illustration the assignment of a heating element ( 42 ) to a tempering element ( 51 ) and another heating element ( 42 ), which only works together with a support bar ( 52 ) is shown. The heating elements ( 42 ) extend in this embodiment as a pipe coils. For electrical supply connections ( 53 . 54 ).

As material for the walls of the tempering element ( 51 ) metal is advantageously used. With regard to the material for the intermediate element ( 43 ) is intended on the one hand also on the use of metal, but beyond that also on the use of plastic.

According to the invention, in particular, every blow station ( 3 ) with regard to the tempering of the blow molds ( 4 ) as a separate unit. There are thus no hoses or piping for connection, but the blowing stations are connected only via corresponding electrical lines to an associated control.

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 (10)

A method of blow-molding containers in which a preform is thermoformed into the container after thermal conditioning within a blow mold of a blow molding machine and wherein the blow mold arranged as part of a blow station is heated at least in regions, characterized in that for heating the blow mold ( 4 ) at least one electrical heating element ( 42 ) used in at least one cavity ( 41 ) of the blowing station ( 3 ) is positioned such that the heating element ( 42 ) of a cavity ( 41 ) is surrounded at least partially filling fluid-like heat exchanger. A method according to claim 1, characterized in that oil is used as a heat transfer medium. A method according to claim 1, characterized in that water is used as a heat exchanger. A method according to claim 1, characterized in that a gel-like substance is used as the heat exchanger. Method according to one of claims 1 to 4, characterized in that the cavity ( 41 ) bounding walls ( 49 ) relative to each other by at least one spacer element ( 50 ) are stabilized relative to each other. Method according to one of claims 1 to 5, characterized in that the cavity ( 41 ) is sealed relative to an environment. Apparatus for blow-molding containers, which has at least one blowing station with a blow mold, and in which the blow mold is at least partially coupled to at least one tempering element, characterized in that the tempering element as an electric heating element ( 42 ) and in at least one cavity ( 41 ) of the blowing station ( 3 ) is arranged and that the cavity ( 41 ) is at least partially filled with a fluid-like heat exchanger. Apparatus according to claim 7, characterized in that two of the cavity ( 41 ) bounding walls ( 49 ) relative to each other by at least one spacer element ( 50 ) are stabilized. Apparatus according to claim 7 or 8, characterized in that the cavity ( 41 ) is closed to an environment. Device according to one of claims 7 to 9, characterized in that the cavity ( 41 ) in the region of an intermediate element ( 43 ) arranged between a support ( 19 . 20 ) of the blowing station ( 3 ) and the blow mold ( 4 ) is positioned.

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