DE102005061334B4 - Stretch blow molding and stretch blow molding method - Google Patents

Abstract

Stretch blow molding apparatus for stretch blow molding of plastic containers from preforms, comprising a plurality of infrared radiation sources forming a heating section, which emit infrared radiation having a substantial active component in the near infrared region, in particular in the wavelength range between 0.8 μm and 1.5 μm, and one with respect to the continuous preforms arranged opposite the infrared radiation sources counter-reflector, wherein the plurality of infrared radiation sources comprises a light emitting diode array, characterized in that the light emitting diode array comprises light emitting diodes or laser diodes (5) having an emission wavelength in the range between 0.85 microns and 1.0 microns and the counter reflector (23) has a reflectivity at the emission wavelength of more than 99.9%, in particular more than 99.99%, wherein the light-emitting diodes are arranged as matrix (3) with rows and columns and wherein the rows are individually controllable and the light-emitting diode arrangement and the Counter-reflector (23), together with the preform receptacles associated foot and head reflectors (19, 21) and optionally a head or foot reflector arranged opposite this form a substantially closed radiation space (15).

Description

The invention relates to a stretch blow molding machine according to the preamble of claim 1 and to a method for stretch blow molding plastic containers according to the preamble of claim 9.

Stretch-blown PET (polyethylene terephthalate) beverage bottles are a large and expanding sub-market of the beverage packaging market. They have achieved this market position substantially thanks to their very good performance properties - in particular the extremely low empty weight in relation to the filling volume - and the easy and cost-effective manufacturability. There are a large number of large suppliers who are in fierce competition and are therefore exposed to heavy cost pressure. This forces the ever-increasing rationalization of the manufacturing process. The focus here is on shortened machine cycle times and energy savings.

The production of PET bottles takes place in a two-stage process. First of all, preforms, known as preforms, are produced by injection molding from a PET mass. In a second operation, these preforms are heated in a relatively short period of time to a drawing temperature of about 110 ° C, and finally they are fed in the heated state of a stretch blow mold, in the finally under supply of compressed air into the interior of the preform of the container (the bottle) is formed.

It is known and customary today to use for the heating of the preforms heating sections, which are equipped with infrared radiators and are passed through by the preforms. Furthermore, the use of elongated halogen lamps with a radiation characteristic is known, which has a significant active component in the near infrared range. These methods and arrangements are superior to the use of medium and long-wave infrared radiation in that the focus of the near infrared radiation spectrum is advantageously adapted to the transmission characteristics of plastics in general and PET.

A special device and method solution of this kind is in the date of the applicant DE 100 58 950 A1 described.

The WO 03/002922 A1 discloses a method for volume heating of a body with electromagnetic radiation having a narrowband or discrete spectrum or a band spectrum whose substantial active component is in the wavelength range of the near infrared.

The DE 101 06 607 A1 discloses an automated process for applying a location and time dependent temperature distribution on thermoplastic raw material for forming in a mold by a laser beam controlled over the surface of the raw material.

The WO 2006/056673 A1 discloses a method for producing a container from a thermoplastic blank comprising a treatment step in which the blank is heated using a beam of coherent electromagnetic radiation.

The WO 2006/060690 A2 discloses a system for direct introduction of selected thermal infrared radiation into articles for a wide variety of machining applications.

The DE 10 2005 060 429 A1 discloses a method and apparatus for blow molding containers. A preform made of a thermoplastic material is first subjected to thermal conditioning along a transport path in the region of a heating path. Subsequently, the preform is formed within a blow mold by blowing pressure into the container. In the area of the heating section, at least one radiant heater emits a heating radiation with a maximum radiation intensity at wavelengths between 0.4 micrometer and 1.0 micrometer.

Based on this prior art, the invention has the object to improve the known system and the known method to the effect that the energy used for the heating of the preforms, reduces the plant and extends the maintenance cycles and thereby further reduces the cost of manufacturing the plastic container become.

This object is achieved by a stretch blow molding with the features of claim 1 and a method having the features of claim 9. Advantageous developments of the inventive concept are the subject of the dependent claims.

The invention includes the essential idea to use for generating the advantageous effective radiation in the range of near infrared radiation sources with an inherently high efficiency. It further includes the idea of using particularly long-lived radiation sources, which allow a considerable extension of the maintenance cycles of the stretch blow molding. These considerations lead to the idea of providing a high-power light-emitting diode arrangement for generating the effective radiation.

Luminous or laser diodes are characterized by a high radiation yield in a desired wavelength range, based on the supplied electrical power, and are extremely durable. Their use in an application of the type in question so far was contrary to the consideration that thus sufficient radiation densities on the preforms are not feasible, but this prejudice could be refuted by the considerations and investigations of the inventors. The provision of a highly efficient counter-reflector tuned to the emission wavelength of the LEDs also contributes to this.

The proposed light-emitting diode solution advantageously makes it possible to shorten the length of the heating section to such an extent that it can fit on a blowing wheel of conventional dimensions of a stretch blow molding machine. A separate, upstream heating section with the corresponding space requirement can be dispensed with, resulting in a significant reduction in the space requirement of the entire system and associated cost savings. In a preferred embodiment, it is provided that the heating section has substantially only 1 m in length or less.

The idea of the invention is characterized in that the light-emitting diode arrangement comprises light-emitting diodes or laser diodes having an emission wavelength in the range between 0.85 μm and 1.0 μm and the counter-reflector a reflectivity at the emission wavelength of more than 99.9%, in particular more than 99 , 99%, has. This idea can be further developed by providing highly reflective sections of a carrier or a cover on the LED arrangement as well (in the interspaces between the LED emission surfaces) so that as complete utilization of the emitted radiation takes place using multiple reflections.

The advantageous very high reflectivity of the counter-reflector (and optionally of the additional reflector sections adjacent to the LEDs) can be expediently achieved by a wavelength-selective reflective dichroic coating of a suitable carrier (for example of aluminum with a very high surface quality).

A further increase in the overall efficiency of the heating section is achieved according to the invention in that the light-emitting diode arrangement and the counter-reflector form a substantially closed radiation space together with foot reflectors associated with the preform receivers and a head reflector arranged opposite thereto. In such an arrangement, even in the foot region of the preforms and over this hardly any radiation and no radiant heat is lost. The surfaces of the foot reflectors and the head reflector can be carried out highly reflective in an advantageous manner in coordination with the emission wavelength of the LEDs. A functionally analogous embodiment of a stretch blow molding with suspended preforms provides that their recordings act as head reflectors of the radiation space, while preferably (ie optionally) a foot reflector is additionally provided in order to complete the radiation space even better.

To increase the service life of the heating section, it is furthermore advantageous that a mechanical carrier of the light-emitting diode arrangement has means for liquid and / or gas stream cooling. The other components of the arrangement which are exposed to radiation can also be actively cooled, but this requirement must be met in a differentiated manner in accordance with the specific reflection properties and temperature profiles of the individual components.

A geometrical embodiment of the proposed arrangement according to the invention provides that the light-emitting diode arrangement has a planar matrix-like arrangement of light-emitting diodes whose height substantially corresponds at least to the height of the preforms. It is also advantageous if at least selected rows of the matrix-like light-emitting diode arrangement can be controlled individually in order to adapt the height of the generated radiation field to different preform heights. Thus, for example, a subarray of the LEDs whose height corresponds to the minimum height of preforms processed with the stretch blow molding unit can be controlled in total, while further LED rows lying above this subarray can be individually controlled to adapt the radiation field to the processing of higher preforms can.

In view of the fact that the through-heating and predetermined softening of the preforms in the foot region is of particular importance for the actual molding process of the plastic containers, the LED arrangement in a region corresponding to the foot region of the preforms is expediently designed to provide higher radiation densities. You can have an additional LED array or a line with increased density of light emitting diodes. The light exit surfaces of an additional LED line can be inclined relative to the arranged in a common plane light exit surfaces of the LED array array, whereby the line below the Fußpunktebene the preforms can be additionally arranged and yet radiates into the foot area.

Preferred embodiments of the proposed method largely correspond to the above-mentioned general or device aspects and will not be explained again in this respect. It should be noted, however, that the proposed solution for heating the preforms makes it possible in the subsequent forming step to supply the compressed air with a reduced pressure (compared with conventional IR preheating methods) by 5 bar or more. From the point of view of energy and cost savings, it is important that an overall energy efficiency of the heating step, determined by a standard method, of over 20% is realized.

Incidentally, advantages and expediencies of the invention result from the dependent claims and the exemplary embodiment described below with reference to the single FIGURE. The figure shows a heating section 1 a (not shown here) stretch blow molding for blowing PET bottles in a schematic representation. This representation is synoptic in a sense synonymous, since not all components shown here must be present in any meaningful execution.

The heart of the heating section is an LED matrix 3 with a multiplicity of laser diodes emitting in the wavelength range between 0.85 μm and 1.0 μm, arranged regularly in rows and columns 5 , The LED matrix arrangement 3 includes a lower subarray 3a , whose laser diodes are always driven together, and three arranged above LED lines 3b to 3d , which can be controlled individually, in a combination of two or together. Below the LED matrix arrangement 3 is still an additional LED line 7 provided, in the LEDs with a smaller distance and with respect to the LEDs of the matrix arrangement 3 inclined light exit openings are arranged.

A (for better heat dissipation preferred solid metallic) carrier body 9 the LED matrix arrangement 3 is ribbed on the back. He is a Strömungsleitwand 11 opposite, with the support body of the LED matrix assembly 3 as well as the back of the additional LED line 7 forms a flow channel. At one end of the carrier body 9 is a powerful tangential fan 13 arranged such that the blower air generated by it in the flow channel between the carrier body 9 and flow deflector 11 flows parallel to the course of the ribs on the carrier body and the carrier body and also the back of the additional LED row 7 can cool effectively.

The LED matrix arrangement 3 forms a boundary wall of a substantially closed radiation space 15 , in the one end face (in the figure from the left) injection molding preforms 17 on foot reflectors 19 run in and leave them over the other end face (in the figure to the right) to perform the actual stretch blowing step, after they were heated by the radiation of the LEDs. The foot reflectors 19 successively supplied preforms form, so to speak, the bottom of the radiation space, while covering a Kopfreflektor 21 and as the LED matrix assembly 3 opposite wall a counter reflector 23 is provided.

The pictorial representation is simplified insofar as a rectilinear passage of the preforms through the radiation space 15 is shown, while in practice an embodiment is preferred in which the radiation space is provided at a portion of the blowing wheel. The real trajectory of the preforms in the radiation space is then a section of a circular path. In adaptation to this can also the wall of the LED matrix arrangement 3 and optionally the counter reflector 23 be curved, or they may be constructed of mutually obtuse flat portions that form approximately a circle portion.

Especially with the counter reflector 23 It depends on a very high reflectance of the LED-facing surface by a wavelength-selective dichroic coating 23a this area is reached. A comparable coating can also be applied to the inside of the radiation space 15 facing surfaces of the foot reflectors 19 and the head reflector 21 be provided. It ensures a very high reflectance at the emission wavelength, which is preferably more than 99.99%.

Also useful is a comparable design of the spaces between the LEDs 5 on the front of the matrix arrangement 3 , On the one hand, this ensures a high radiation yield via the multiple reflections and thus reduces the thermal load on the LED matrix due to absorbed own radiation.

The embodiment of the invention is not limited to this example, but also in a variety of modifications, in particular in any combination of the features of the dependent claims possible.

Claims (14)

Stretch blow molding apparatus for stretch blow molding of plastic containers from preforms, comprising a plurality of infrared radiation sources forming a heating section, which emit infrared radiation having a significant active component in the near infrared region, in particular in the wavelength range between 0.8 μm and 1.5 μm, and one with respect to the continuous preforms arranged opposite the infrared radiation sources Gegenreflektor, wherein the plurality of infrared radiation sources comprises a light emitting diode array, characterized in that the light emitting diode array light emitting diodes or laser diodes ( 5 ) having an emission wavelength in the range between 0.85 μm and 1.0 μm, and the counter reflector ( 23 ) has a reflectivity at the emission wavelength of more than 99.9%, in particular more than 99.99%, whereby the light-emitting diodes are used as a matrix ( 3 ) are arranged with rows and columns and wherein the rows are individually controllable and the light emitting diode array and the counter reflector ( 23 ), together with the preform recordings associated foot and head reflectors ( 19 . 21 ) and optionally an oppositely arranged head or foot reflector a substantially closed radiation space ( 15 ) form. Stretch blow molding machine according to claim 1, characterized in that the heating section is provided in a section of the blowing wheel. Stretch blow molding machine according to claim 1 or 2, characterized in that the counter reflector ( 23 ) has a wavelength selective reflective dichroic coating. Stretch blow molding apparatus according to one of the preceding claims, characterized in that a mechanical support of the light-emitting diode arrangement has means for liquid and / or gas stream cooling. Stretch blow molding machine according to one of the preceding claims, characterized in that the light-emitting diode arrangement has a planar matrix-like arrangement of light-emitting diodes whose height is at least substantially equal to the height of the preforms ( 17 ) corresponds. Stretch blow molding machine according to claim 5, characterized in that at least selected rows of the matrix-like light-emitting diode arrangement can be controlled individually in order to adapt the height of the generated radiation field to different preform heights. Stretch blow molding machine according to claim 5 and 6, characterized in that the light-emitting diode array in an area corresponding to the foot region of the preforms at least one additional LED array or line with increased density of the LEDs has such that the radiation field generated in this area has a higher power density. The stretch blow molding apparatus according to any one of the preceding claims, characterized in that the heating portion has a length or arc length of 1 m or less. A method for stretch blow molding of plastic containers from preforms, wherein the preforms emit in a heating distance with a plurality of infrared radiation sources, which emit infrared radiation with a significant active content in the near infrared region, in particular in the wavelength range between 0.8 .mu.m and 1.5 .mu.m heated to a stretching temperature and then formed in a stretch blow mold by means of compressed air in container form, and in which the infrared radiation is generated in the near infrared region by a plurality of light-emitting diodes, characterized in that the of the preforms ( 17 ) absorbed energy in a first radiation passage practically completely into the preforms ( 17 ) and that the light-emitting diodes emit radiation in the range from 0.8 μm to 1.0 μm and from a counter-reflector ( 23 ) Radiation of the emission wavelength is reflected at least to the extent of 99.9%, in particular of more than 99.99%, and the individual lines of the light-emitting diode array and the counter-reflector are individually controllable (in the form of a matrix with rows and columns). 23 ) together with foot or head reflectors ( 19 . 21 ) associated with the preform recordings are a substantially closed radiation space ( 15 ) is formed. Method according to claim 9, characterized in that the heating of the preforms ( 17 ) is performed in a portion of the blowing wheel. A method according to claim 9 and 10, characterized in that as radiation in the range of the near infrared monochromatic radiation in the wavelength range between 0.85 microns and 1.0 microns is used. Method according to one of claims 9 to 11, characterized in that in the subsequent forming step, the compressed air is supplied to a method which operates with medium / long-wave IR radiation by 5 bar or more reduced pressure. Method according to one of claims 9 to 12, characterized in that an overall energy efficiency of the heating step is determined by a standard method of over 20%. Method according to one of claims 9 to 13, characterized in that on the preforms ( 17 ) acting radiation density is set larger in the footer than in the remaining height range.

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