DE102005061334A1 - Stretch blow molding machine for making plastic containers from preforms comprises a heating section with an array infrared-emitting light-emitting diodes - Google Patents

Abstract

Stretch blow molding machine for making plastic containers from preforms comprises a heating section comprising an array (3) of LEDs and a back reflector on either side of the preform travel path. The LEDs emit in the near infrared.

Description

The The invention relates to a stretch blow molding according to the preamble of Claim 1 and a method for stretch blow molding of plastic containers after the preamble of claim 11.

beverage bottles of stretch blown PET (polyethylene terephthalate) form one big and expanding submarket of the beverage packaging market. This market position They have a lot of thanks to their very good performance characteristics - in particular the extremely low curb weight in relation to the filling volume - and the light and cost-effective Manufacturability achieved. There are a lot of big providers, which are in fierce competition and therefore a strong one Cost pressure are exposed. This forces to ever-advancing Rationalization of the manufacturing process. In the foreground stand here shortened Machine cycle times and energy savings.

The Production of PET bottles takes place in a two-stage process. First be by injection molding from a PET mass preforms, the so-called preforms. In a second operation, these preforms are in a relatively short Heated time to a drawing temperature of about 110 ° C, and after all they are warmed up State fed to a stretch blow mold, in the finally under feed compressed air inside the preform of the container (the bottle) formed becomes.

It is known and common today, for heating the preform heating sections equipped with infrared heaters and preforms to go through. Furthermore, the use of elongated Halogen lamps with a radiation characteristic known, the one has a significant active component in the near infrared range. These Procedures and arrangements are medium and long wavelength use Far superior to infrared radiation, as being focused in the near Infrared radiation spectrum in an advantageous manner the transmission characteristics of plastics in general and PET specially adapted.

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

From Based on this prior art, the invention has the object underlying, the known system and the known method to the effect improve the energy input for heating the preforms, the plant is downsized and the maintenance cycles extended and this further the manufacturing cost of plastic containers on be reduced.

These Task is by a stretch blow molding with the features of the claim 1 and a method having the features of claim 11 solved. Appropriate training of the inventive concept are the subject of the dependent claims.

The Invention includes the essential idea, for generating the advantageous effective radiation in the field of near infrared radiation sources with an inherently high Use efficiency. It further includes the idea to use particularly long-lived radiation sources, which is a considerable renewal allow the maintenance cycles of the stretch blow molding. These considerations flow in the idea of generating the active radiation, a light-emitting diode arrangement provide high power.

light- or laser diodes are characterized by a high radiation yield in a desired Wavelength range, based on the supplied electric power, and are extremely durable. your Use in an application of the type in question stood so far the consideration contrary, that thus sufficient radiation densities on the preforms could not be realized, but this prejudice could by the considerations and investigations of the inventors are refuted. Contributes to this too the provision of a highly efficient tuned to the emission wavelength of the LEDs Counter reflectors at.

The proposed light-emitting diode solution makes it possible in an advantageous way, the length the heating section to shorten so far that this on a blowing wheel more usual Dimensions of a stretch blower takes place. A separate, upstream heating section With the appropriate space requirements can be eliminated, which is a considerable Reduction of the space requirement of the entire system and related Cost savings. In a preferred embodiment provided that the heating section essentially only 1 m in length or less.

An advantageous development of the inventive concept is characterized in that the light emitting diode array comprises light-emitting diodes or laser diodes having an emission wavelength in the range between 0.85 .mu.m and 1.0 .mu.m and the counter-reflector a reflectivity at the emission wavelength of over 99.9%, in particular of more than 99.99%, has. This idea can be further developed by the fact that also on the LED arrangement (in spaces between the LED emitting surfaces) highly reflective sections of a Carrier or a cover are provided so that using as many reflections as complete as possible utilization of the emitted radiation takes place.

The advantageous very high reflectivities of the counter-reflector (and optionally the additional reflector sections adjacent to the LEDs) let yourself expediently through a wavelength selective reflective dichroic coating of a suitable support (e.g. made of aluminum with very high surface quality).

A further increase the overall efficiency of the heating section let yourself achieve that the light emitting diode array and the counter reflector Foot reflectors associated with the preform recordings and one opposite arranged head reflector a substantially closed radiation space form. In such an arrangement is also in the footer the preforms and over this little radiation and no radiant heat lost. Also the surfaces of the Fußreflektoren and the head reflector can advantageously in accordance with the emission wavelength of LEDs designed to be highly reflective be. A functionally analogous execution a stretch blow molding machine with hanging Preforms provides that their recordings as head reflectors of the Radiation space act while preferably (ie optional) a foot reflector additionally provided is to complete the radiation room even better.

to increase the service life of the heating section is further advantageous that a mechanical support of the Light emitting diode arrangement comprises means for liquid and / or gas stream cooling. Also the others with Radiation applied components of the device can be actively cooled, but this requirement is in accordance with the specific reflective properties and temperature profiles of the individual components differentiated fulfill.

A functional geometric execution the proposed arrangement provides that the light emitting diode array a plane having a matrix-like arrangement of light emitting diodes whose height substantially at least the height corresponds to the preforms. Next advantage is if at least selected Lines of the matrix-like LED array individually controllable are to the height of the generated radiation field to adapt to different preform heights. For example, a sub-array of LEDs whose height is the minimum height of the stretch blown processed preform corresponds to a total of be controllable while above this Sub-array lying more LED lines to adjust the radiation field to the processing higher Preforms can be controlled individually.

in the Considering that for the actual molding process of the plastic container and the heating predetermined softening of the preforms in the foot area is of particular importance, For example, the LED array is one corresponding to the foot area of the preforms Range expediently to provide higher Radiation densities formed. You can do this with an additional LED array or a line with elevated Have density of light-emitting diodes. The light exit surfaces of a additional LED line can opposite arranged in a common plane light exit surfaces of the LED matrix arrays inclined be arranged, whereby the line below the Fußpunktebene of the preforms in addition can be and still in the foot area shine.

preferred Embodiments of the proposed method largely correspond to the above-mentioned general or device aspects and will not be explained again here. It should be noted, however, that the proposed solution for warming the preforms allow in the following Forming step the compressed air with a (compared to conventional IR preheating method) 5 bar or more reduced pressure is supplied. From the perspective Of energy and cost savings it is important, an energetic Overall efficiency of the heating step, determined by a standard method, realized by over 20%.

Advantages and expediencies of the invention will become apparent from the dependent claims and the 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 ge may be curved, or they may be constructed of mutually obtuse flat portions that form approximately a circle section.

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 execution The invention is not limited to this example, but also in a variety of modifications, especially in any Combinations of the features of the dependent claims, possible.

Claims (16)

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, characterized in that the plurality of infrared radiation sources comprises a light emitting diode array. Stretch blow molding machine according to claim 1, characterized that the heating section is provided in a portion of the blowing wheel. Stretch blow molding machine according to claim 1 or 2, 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 microns and 1.0 microns includes and the counter-reflector has a reflectivity at the emission wavelength of over 99.9%, especially of more than 99.99%. Stretch blow molding machine according to claim 3, characterized that the counter-reflector is a wavelength-selective reflective Has dichroic coating. Stretch blow molding machine according to one of the preceding claims, characterized in that the light-emitting diode arrangement and the counter-reflector together associated with the preform record foot or head reflectors and optional one opposite this arranged head or foot reflector form a substantially closed radiation space. Stretch blow molding machine according to one of the preceding claims, characterized in that a mechanical support of the light-emitting diode arrangement Having 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 substantially at least the height corresponds to the preforms. Stretch blow molding machine according to claim 7, characterized that at least selected Lines of the matrix-like LED array individually controllable are to the height of the generated radiation field to adapt to different preform heights. Stretch blow molding machine according to claim 7 or 8, characterized in that the light-emitting diode arrangement is in a foot region at least one additional row of LEDs corresponding to the preforms or line with elevated Density of the LEDs has such that the generated radiation field a higher one in this area Power density has. Stretch blow molding machine according to one of the preceding claims, characterized characterized in that the heating section a length or arc length of 1 m or less. Process for stretch blow molding of plastic containers Preforms, in which the preforms in a heating section with a plurality of infrared radiation sources, which infrared radiation with a significant proportion of active in the range of the near infrared, in particular in the wavelength range between 0.8 μm and 1.5 μm, emit, heated to a stretching temperature and then in a stretch blow mold are formed by means of compressed air in container form, characterized in that the infrared radiation in the region of near infrared generated by a plurality of light emitting diodes and which was not absorbed by the preforms in a first radiation pass Energy almost complete reflected back into the preforms becomes. Method according to claim 11, characterized in that that warming the preforms is carried out in a section of the blowing wheel. Method according to claim 11 or 12, characterized that as near infrared radiation is monochromatic Radiation in the wavelength range between 0.85 μm and 1.0 microns used becomes. Method according to one of claims 11 to 13, characterized that in the subsequent Forming step the compressed air with a versus method, with medium / long-wave IR radiation work is supplied to 5 bar or more reduced pressure. Method according to one of claims 11 to 14, characterized that an overall energy efficiency of the heating step, determined by a standard method, realized by over 20%. Method according to one of claims 11 to 15, characterized that the radiation density acting on the preforms in their footer set larger is considered the rest Height range.