Abstract:
A method for pre-treating preforms ( 12 ) made of thermoplastic plastic, before they are shaped into containers ( 13 ) by means of a stretch blow molding process and filled with liquid. The preforms ( 12 ) are tempered and sterilized for the subsequent stretch blow molding process. Tempering of the preforms ( 12 ) is carried out by means of microwave radiation and by sterilization of the preforms ( 12 ) during the pre-treatment.

Description:
[0001]    This is a continuation of prior International Application PCT/EP2009/062532, filed Sep. 28, 2009, which claims priority to German Patent Application DE 10 2008 056 346.3, filed Nov. 7, 2008, the entire disclosures of which are hereby incorporated by reference herein. 
     
    
       [0002]    The present invention relates to a method for pre-treating preforms. The invention furthermore relates to a blow molding apparatus for pre-treating and blow molding preforms into containers. 
       BACKGROUND 
       [0003]    When producing beverage containers in a blow molding process, the so called preforms are first heated to an adequate temperature. The preforms are then fixed in blow molds and transformed into the desired container shape by controlled injection of air. Only when they have the desired container shape, they have the necessary volume to be filled with liquid. The containers usually have to be sterilized before filling to guarantee a long shelf life of the bottled liquid. With sufficient sterilization the addition of preservatives in beverages can be reduced. 
         [0004]    Methods have been developed whereby the preforms are sterilized after tempering and before blow molding. These methods have been developed due to increasingly higher demands on the cleanness of the containers and due to the desired minimization of preservatives in beverages. Thereby a largely sterile process up to filling can be achieved and maintained. 
         [0005]    EP 1 056 481 B1 describes a method for sterilizing hollow bodies, whereby a vaporized sterilizing medium is applied on the surfaces to be sterilized. The evaporation of the sterilizing agent is done outside the hollow body close to its opening. The sterilizing agent is introduced to and aspired from the inside of the hollow body, thereby generating a gas stream that distributes the agent to all surface areas. The hollow body can either be already in the shape of a beverage container or it can be a preform which is then blow molded into a beverage container. 
         [0006]    JP 04 04 49 02 A describes a method for the sterilization of preforms before they are tempered and blow molded into the desired shape of a beverage container. 
         [0007]    It has been customary to heat the preforms to the required temperature for blow molding by means of hot air and/or by infrared radiation. From WO 2007/131701 A2 a heating device for plastic preforms is known that uses microwave radiation. 
       SUMMARY OF THE INVENTION 
       [0008]    It is an object of the present invention to provide a fast and simple heating of the preforms, as well as a related sterilization of these in order to achieve a largely closed process for the subsequent transformation of the preforms into containers and their filling with liquid. 
         [0009]    The present invention provides a method for pre-treating preforms of thermoplastic synthetic material, before they are formed into containers by means of a stretch blow molding process and filled with liquid. In this method the preforms are tempered and sterilized for the subsequent blow molding process. The tempering or heating of the preforms is done by microwave radiation. The sterilization of the preforms is preferably performed during radiation by the introduction of liquid and/or gaseous sterilizing medium into the preforms. 
         [0010]    According to a preferred embodiment of the invention the container is produced by a stretch blow molding process in a stretch blow molding apparatus. The difference between a stretch blow molding apparatus and a blow molding apparatus is that the stretch blow molding apparatus comprises an additional so called stretching rod, which stretches the container in the axial direction simultaneously to the blowing process. This gives the final container a biaxial orientation which leads to an improved stability of the container. This is especially advantageous for containers to be filled with carbonated beverages. 
         [0011]    It is particularly advantageous when the sterilization of the preforms is done during and/or immediately after the microwave radiation. This allows a continuous and automatic process in which the tempering and sterilization of the containers may take place simultaneously or overlapping in time. It is already known that the preforms can be heated by microwave radiation to the suitable temperature required for the stretch blowing process. In connection with the present invention it has now be recognized that the introduction of a suitable fluid, gas, liquid or gas-liquid-mixture can be advantageous in terms of interaction of microwave radiation with the thermoplastic material of the preforms. This effect can be used advantageously to sterilize the preforms already during tempering. A suitable liquid sterilizing medium can be used with certain characteristics as subsequently described. The fluid must be able to activate the microwave radiation and enhance the sterilizing effect. The fluid is introduced into the preforms where it can interact with the microwaves advantageously, enhancing the effect of the radiation. This can furthermore lead to an improved heating effect, especially and/or the preforms can be heated to the required temperature with a lesser radiation intensity. 
         [0012]    Liquid and/or gaseous hydrogen peroxide (H 2 O 2 ), peracetic acid or the like can be used as sterilizing medium. The sterilizing medium can be introduced into the preform as liquid and/or in a gaseous form. A mixture of hot air and hydrogen peroxide, peracetic acid or the like can be used as sterilizing medium. Basically, other sterilization media which show the same effect can also be used. It is advantageous if the sterilizing medium shows the desired interaction with the microwave radiation. Thereby the radiation can be more efficiently used and/or the heating of the preforms is improved. 
         [0013]    According to a preferred embodiment of the inventive method the sterilizing medium is introduced into each preform by at least one nozzle. This can be done quickly and the sterilizing medium gets distributed homogeneously in the preform, especially on the inner surface of the preform. The nozzle is preferentially arranged in the holder or retaining thorn for the preforms. Furthermore an additional aspiration unit can be provided so that after the introduction of the sterilizing medium into the preforms and the heating by radiation, the sterilizing medium can be aspirated out of the preforms quickly and completely. 
         [0014]    It is of further advantage if the sterilizing medium is vaporized by the microwave radiation and develops its sterilizing effect on the inner surface of the preforms. After sterilization and during or after tempering the preforms can be rinsed with a suitable washing medium to remove any traces of the sterilizing medium. 
         [0015]    The tempering and sterilization of the preforms is preferably done in a continuous process, especially on a rotary machine. 
         [0016]    The present invention furthermore comprises a stretch blow molding apparatus for the pre-treatment and stretch blow molding of preforms made of thermoplastic plastic into containers. The apparatus comprises handling means for handling and continually treating and transporting preforms, a tempering unit for heating the preforms and a sterilization unit, whereby the tempering unit comprises a microwave radiation unit. The sterilization unit is at least partially integrated in the handling means, so that the sterilization of the containers can be done in the context and/or in an advantageous combination with the microwave radiation leading to a warming of the preforms. 
         [0017]    An advantageous embodiment of the stretch blow molding apparatus according to the invention has handling means that each comprise retaining thorns for holding the preforms in their neck region. The retaining thorns have nozzles for the introduction of the sterilizing medium into the preforms. The nozzles of the retaining thorns can each comprise inlet and/or outlet pipes for the sterilizing medium that can be aspired after the treatment via the nozzles or other suitable aspiration devices. 
         [0018]    The apparatus according to the invention can especially be a rotary apparatus, whereby the preforms are continuously transformed into sterilized containers. 
         [0019]    The term preform used in the present context generally means a pre-product of containers, especially beverage containers. Preforms are sometimes also called blanks. Blanks are unilaterally closed tubes having an open end with a neck region, with which they are placed in a form to be formed into containers by stretch blow molding. The preforms are made of a suitable thermoplastic plastic, for instance PET (Polyethylene). 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    In the following passages, the attached figures further illustrate exemplary embodiments of the invention and their advantages. The size ratios of the individual elements in the figures do not necessarily reflect the real size ratios. It is to be understood that in some instances various aspects of the invention may be shown exaggerated or enlarged to facilitate an understanding of the invention. 
           [0021]      FIG. 1  shows a schematic representation of a tempering and sterilization unit. 
           [0022]      FIG. 2  shows a cross section of a handling unit for a preform. 
           [0023]      FIG. 3  shows an enlarged part of the handling unit for a preform according to  FIG. 3 . 
           [0024]      FIG. 4  shows a top view of an apparatus for the production of containers. 
           [0025]      FIG. 5  shows a schematic representation of an apparatus for the production of containers. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    The schematic representation of  FIG. 1  shows a handling apparatus  10  for the treatment of preforms  12 . The handling apparatus  10  comprises a tempering unit  51  and a sterilization unit  52  that are integrated in single treatment stations  20 . In this method the preforms  12  are treated in a continuous process, whereby the preforms can be moved on a circular path through the tempering unit  51  during heating and simultaneously be sterilized by the sterilization unit  52 . The treatment stations  20  are mounted together on a carrier  22 . On the carrier  22  further components can be attached; e.g. eight microwave radiation units  24  are attached in this embodiment. The functions of such a unit are described in WO 2007/131701 A2. The tempering units  51  are connected to the microwave radiation units  24  and together they run around the axis A of the apparatus and the sterilization unit  52  during the treatment of the preforms  12 . 
         [0027]    As has already been described, the preform  12  is heated to the required temperature by means of the tempering unit  51  and the microwave radiation unit  24 . To get a uniform heating of the preforms  12 , the preforms  12  are pushed through a resonator  28 , which is connected with the tempering unit  51 . The sterilization of the preforms  12  is done with a sterilization unit  52  that is at least partially integrated in the handling apparatus  10  in relation and/or in an advantageous combination with the microwave radiation unit  24  leading to a warming of the preforms  12 . 
         [0028]    The handing over of the preforms  12  to the handling apparatus  10  can be done by means of a device located upstream, for example a star, especially a saw tooth star or clamping star. 
         [0029]      FIG. 2  shows a cross section of a handling unit  30  for a preform  12 . The handling unit  30  comprises a preform retaining unit  32  and a driving unit  34 . In the shown embodiment the preform retaining unit  32  is designed as a retaining thorn, which reaches into the opening of the neck region  33  of the preform  12  thereby retaining it. The driving unit  34  is preferentially a drive that fulfills all motion requirements. First of all a lowering motion is necessary, which introduces the preform  12  along its longitudinal axis B into the resonator  28  (shown in  FIG. 1 ) from above. On the other hand a controlled lifting is necessary to lift out the preform  12  along its longitudinal axis  13  from the resonator  28  (shown in  FIG. 1 ). The preform retaining unit  32  furthermore comprises a nozzle  36  that serves for the introduction of liquid and/or gaseous sterilizing medium into the preform  12 . The sterilizing medium is introduced into the preform  12  during radiation with microwaves and evaporates when the preform  12  is heated. The sterilizing medium thus develops its sterilizing effect on the surface  40  of the preform  12 . In the shown embodiment the sterilization unit  52  is connected to the handling unit  30  and to the tempering unit  51  at the same time. Optionally the sterilization can also be performed after the heating of the preform  12 . 
         [0030]      FIG. 3  shows an enlarged section of a sterilization unit  52  for a preform  12  according to  FIG. 2 .  FIG. 3  again clearly shows the handling unit  30  for the preform  12 . During the pre-treatment the preform  12  is held by the preform retaining unit  32 , which enters the opening in the neck region  33  of the preform  12 . The nozzle  36  comprises inlet and/or outlet pipes, through which the sterilizing medium is fed into and aspired from the preforms  12 , whereby the sterilizing medium develops its sterilizing effect on the surface of the preforms  12  through additional heating. 
         [0031]      FIG. 4  shows another embodiment of the arrangement of the treatment stations and of the apparatus for the production of containers. The preforms  12  are handed over to the handling apparatus  10  by means of a feeder  50 . The preforms  12  are handed over to individual tempering units  51  connected to a microwave radiation unit  24 . The preforms  12  are heated to the required temperature by microwave radiation and immediately handed over to a sterilization unit  52  located downstream. In the sterilization unit  52  the preforms  12  are sterilized and rinsed if necessary. Subsequently the pre-treated preforms  12  are transferred to a stretch blow molding machine  54  by an arrangement of transport stars. In the stretch blow molding machine  54  the preforms  12  are shaped into finished containers. After the production of the containers they can be transferred to a filling apparatus  56  and subsequently to a capping unit and/or a labeling machine. 
         [0032]      FIG. 5  shows a schematic representation of an apparatus for the production of containers  13 . The preforms  12  are tempered and sterilized in a handling apparatus  12 . Then they are handed over to a stretch blow molding device  54 . There the pre-treated preforms  12  are formed into containers  13  of the desired shape. 
         [0033]    The invention has been described with reference to a preferred embodiment. Those skilled in the art will appreciate that numerous changes and modifications can be made to the preferred embodiments of the invention and that such changes and modifications can be made without departing from the spirit of the invention. It is, therefore, intended that the appended claims cover all such equivalent variations as fall within the true spirit and scope of the invention.