Abstract:
For use in a blow molding machine for containers, especially plastic bottles, a production line is provided for thermally pretreating preforms transported by holders, where each holder is loaded with at least one exchangeably fixed fitting such as a shielding plate. To reduce the exchange period for the holders the fitting is secured by a quick-change element which remains on the holder during the exchange and is adjustable on the holder between a secured position and a release position by the application of an external force, and which can be adjusted manually and/or mechanically.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims the benefit of priority of German Patent Application No. 102007040620.9, filed Aug. 27, 2007. The entire text of the priority application is incorporated herein by reference in its entirety. 
       FIELD OF THE DISCLOSURE 
       [0002]    The disclosure relates to a blow molding machine, particularly to changing out holder fittings for blow molding machines. 
       BACKGROUND 
       [0003]    Further technical developments have permitted a considerable increase in the production rates of modern blow molding machines. As in practice the tendency goes toward producing a very large number of different containers in one and the same blow molding machine, which differ, for example, by differently formed orifices and which require the retooling of the blow molding machine, the possible high production rates are opposed by inexpediently long exchange periods and complicated exchange procedures. Developments are being made to shorten the exchange periods for fittings such as preform mandrels significantly and to simplify and/or automate the exchange periods therefor. However, in blow molding machines used in practice, other fittings, e.g. shielding plates, which have to be exchanged during a retooling as well, are still exchanged by hand and in complicated exchange procedures. In the blow molding machine used in practice, each shielding plate is secured by a U-shaped spring bracket, which must be manually withdrawn from the holder and, after the new shielding plate was inserted, must be reinserted manually. The removal of the spring bracket requires a high expenditure of energy and great skills, while the reinsertion of the spring bracket requires a high targeted precision and a relatively strong thrust force. Therefore, the exchange period for each shielding plate is long. The exchange procedure is cumbersome, considering that often more than 100 shielding plates have to be exchanged over the production line. 
       SUMMARY OF THE DISCLOSURE 
       [0004]    The disclosure is based on the object to provide a blow molding machine of the aforementioned type as well as a holder for the fittings, both permitting short exchange periods and a comfortable exchange procedure and even a semiautomatic or fully automatic exchange of the fittings. 
         [0005]    As the quick-change element remains in the holder of the blow molding machine as the fittings are exchanged, the cumbersome and exhausting insertion procedure after the exchange is omitted. Moreover, the quick-change element now merely has to experience an adjustment on the holder by the application of an external force so as to allow the exchange of the fitting, which can be carried out fast and with a relatively small expenditure of energy. The motion of adjustment is very uncomplicated and definite, so that no special care has to be exercised. Despite the usually limited space surrounding the holder the exchange period becomes extraordinarily short, and the exchange procedure is much more comfortable as in the past. The holder for the fittings including the quick-change element has been designed to allow a fast and comfortable exchange from the very beginning, namely by both an operator and semi- or fully automatically by an automatic changer, whereby the simple motion of the quick-change element and the small expenditure of energy constitute important advantages for this purpose. 
         [0006]    In a useful embodiment the quick-change element defines an externally accessible press-button, which is pressed only substantially linearly in a direction transverse to the plug receptacle for the plug-in foot of the shielding plate. In doing so, the quick-change element is guided in the direction of adjustment against the force of a spring element, which may serve, for example, to produce and maintain the secured position. In an alternative embodiment the quick-change element could define a draw-button, which is drawn out of the secured position and into the release position substantially linearly against the force of the spring element. In each case, the quick-change element remains on the holder during the exchange, the spring element maintains the secured position, and the quick-change element only has to be moved by means of a short stroke and with a relatively small expenditure of energy. 
         [0007]    In one preferred embodiment the fitting comprises two parallel plug-in feet, for which two plug receptacles are provided on the holder. The quick-change element is assigned to only one plug receptacle. It would be possible, however, to secure both plug-in feet by one quick-change element, respectively, and to adjust both elements together. 
         [0008]    In one preferred embodiment an external force has to be applied to the quick-change element only for removing the fitting, while for the insertion of the fitting an internal force is applied by the plug-in foot itself, which temporarily displaces the quick-change element against the force of the spring element out of the secured position in the direction of the release position to such a degree that the plug-in foot can be inserted and the quick-change element automatically returns into the secured position by the force of the spring element. 
         [0009]    In another embodiment, however, the quick-change element requires, for example, the same external force application for both removing and inserting the fitting. 
         [0010]    In one expedient embodiment a circumferential cavity, preferably a circumferential groove is provided in the respective plug-in foot for the secured engagement of the quick-change element. To this end, the quick-change element comprises an engagement portion insertable into the circumferential cavity. The spring element has the task to maintain the secured position of the quick-change element. In the secured position, the plug-in foot and thus the fitting is then even locked and secured in a form-closed manner. This secured position is not released unintentionally even in the event of operational vibrations and/or thermal influences because the quick-change element engages into the plug-in foot in a lock-type manner. 
         [0011]    In a structurally simple embodiment, a channel for the quick-change element is provided in the holder, which crosses the plug receptacle. The quick-change element projects out of the channel with a press-button head, which is arranged on a shaft and externally accessible. Expediently, the spring element is designed as a helical spring supported between the shaft and the channel, which prestresses the quick-change element towards the secured position. Interacting limit stops on the shaft and the holder prevent the quick-change element from escaping from the holder under the spring force. 
         [0012]    Expediently, the channel entirely passes through the holder and the shaft projects over a channel opening at the end opposite the press-button head. On this projecting end the shaft carries the limit stop, which is preferably detachable for assembling purposes and which interacts with the channel opening so as to prevent the quick-change element from falling out. 
         [0013]    A space-saving construction is achieved if the shaft and/or the press-button head is/are passed through by a passage in the transverse direction, preferably by a passage having the shape of an oblong hole, which may be, for example in the direction of adjustment of the quick-change element, oversized with respect to the outer diameter of the plug-in foot. On the one hand, this passages allows the plug-in foot to travel therethrough when the fitting is inserted or removed, respectively, provided that the quick-change element has been displaced sufficiently far from the secured position towards or into the release position, and it guarantees on the other hand the form-closed engagement into the circumferential cavity of the plug-in foot as soon as the spring element has shifted the quick-change element into the secured position. Both opening portions of the passage then interact with the circumferential cavity in a form-closed manner, or at least the opening portion of the passage which interacts with the rear edge of the circumferential cavity in the draw-out direction of the plug-in foot. 
         [0014]    Expediently, the release position of the quick-change element is defined by an interaction between the press-button head and the channel opening facing the press-button head. This means that at least for removing the fitting the press-button head is pressed by the application of an external force until it abuts against the channel opening, because this guarantees that the plug-in foot can be inserted without any problems, without requiring a positioning of the quick-change element by the application of the external force. 
         [0015]    By means of the quick-change element, which can be handled comfortably and with a small expenditure of energy and which remains on the holder during the exchange, the exchange period per fitting can be reduced considerably even if the exchange is carried out manually. Moreover, this concept is also very well suited for automatic exchange procedures because only a single, substantially linear force has to be exerted to a certain degree on a certain location to adjust the release position and remove or insert the fitting. This can be accomplished by means of at least one automatic quick-change machine, which is mounted at one point of the production line and which correspondingly adjusts the quick-exchange element on a holder or a group of holders and/or inserts the fitting(s) and/or removes the fitting(s). All these actions can be performed automatically or semiautomatically with manual assistance. Thus, the exchange period can be reduced even more and the comfort for the user can be increased significantly. 
         [0016]    The automatic quick-change machine should comprise at least one quick-exchange element actuator and at least one fitting gripper, and preferably also at least one fitting magazine. The automatic quick-change machine can be moved and, if necessary, even be docked to the production line at a suitable place. It can exchange the fittings individually or in groups. It is even possible, if necessary at a reduced conveying speed, to make the automatic quick-change machine travel along with the production line or have it rotated, or arrange it stationarily as the production line is moved in cycles. 
         [0017]    In another preferred embodiment the automatic quick-change machine is arranged stationarily relative to the production line and is operated in cycles in coordination with advance motion cycles of the production line, or the automatic quick-change machine is integrated in a driven star-shaped rotor which is arranged at the production line or is transferable to the production line and which rotates along with the advance motion cycles or even at a continuous conveying motion of the production line, thereby exchanging the fittings individually. If necessary, the automatic quick-change machine is combined with an automatic quick-change machine for other fittings in order to change at each exchange cycle some or all fittings to be exchanged for a changeover to another type of orifice of the preforms. Thus, for example, the shielding plates and the preform mandrels could be exchanged simultaneously. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    An embodiment of the subject matter of the disclosure is explained by means of the drawings. In the drawings: 
           [0019]      FIG. 1  is a schematic representation of a blow molding machine comprising holders provided with fittings in a production line, 
           [0020]      FIG. 2  is a partial section of a holder with an inserted fitting, 
           [0021]      FIG. 3  is a partial section of a holder with a fitting just removed or just about to be inserted, 
           [0022]      FIG. 4  is an enlarged sectional representation of  FIG. 2 , and 
           [0023]      FIG. 5  is a schematic representation of a fully or semiautomatic fitting exchange system. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]      FIG. 1  schematically illustrates a blow molding machine M for containers, e.g. a stretch blow molding machine for plastic bottles. A blow molding station B comprising a non-illustrated star-shaped rotor equipped with blow molds is connected to a production line F, which extends at least section-wise through a heater H for preforms P to be treated by exposing them to radiation or in any other way by externally heating them or treating them thermally. The conveying direction of the production line F is shown by an arrow  1 . The production line F comprises a plurality of mandrel devices D located closely adjacent to each other, each with a suspended holder  2  mounted thereon and at least one fitting G 1  in the form of a preform mandrel  3 , which is exchangeably mounted on the holder  2  and which is inserted into an orifice  4  ( FIG. 2 ) of a respective preform P. In operation, the preform mandrels  3  are, if necessary, rotated about their axes, while they are thermally pretreated. 
         [0025]    The orifice  4  of the preform P comprises, for example, an external supporting ring  5  ( FIG. 2 ) and an external thread  6 . Specifically this portion (supporting ring  5  and at least a portion of the external thread  6 ) must be shielded during the thermal pretreatment of the preform because it already has the later shape as in the finished blown container and could become damaged by the thermal pretreatment required by the other part of the preform P. To this end, a so-called shielding plate  7  having one or two plug-in feet  9  is mounted on the holder  2  as an additional exchangeable fitting G 2 , which shields this sensitive region of the orifice  4  of the preform P with an inner bore  8 . 
         [0026]    The plug-in foot  9  is inserted with a peg-shaped or tubular end portion  11  into a plug receptacle  10  of the holder  2 , which is formed as a blind hole, where it is secured by a quick-change element S. Thus, the fitting G 2  cannot be detached from the holder  2 . To be able to remove the fitting G 2  from the holder  2 , the application of an external force to the quick-change element S is necessary, for example in the direction of an arrow  12 . Then ( FIG. 3 ) the fitting G 2 , i.e. the shielding plate  7 , can be separated by means of the plug-in feet from the holder  2  (in the direction of an arrow  13 ) and can be replaced by another fitting G 2  which, upon another application of force to the quick-change element S in the direction of arrow  12 , is inserted into the plug receptacle  10  and automatically secured by the quick-change element S. The newly inserted fitting G 2  differs, for example, by another size and design from the shielding plate  7  and the inner bore  8  thereof, whereas its end portion  11  mates the plug receptacle  10 . 
         [0027]    The end portion  11  of the plug-in foot  9  additionally includes a circumferential cavity  16  for the form-closed engagement of the quick-change element S, expediently a circumferential groove  16 , which shall be explained in more detail by means of  FIG. 4 . 
         [0028]    An exchange can be accomplished manually, by exerting the force on the quick-change element S in the direction of arrow  12  with a finger or a tool and by manually removing or inserting the fitting G 2 , or mechanically by an automatic or semiautomatic quick-change machine, which performs all or at least some of the aforementioned steps. 
         [0029]    In the embodiment shown in  FIG. 2 to 4 , the quick-change element S must be displaced by the application of an external force to allow the insertion and the removal of the fitting. Alternatively, it would be possible to shape the tip of the end portion  11  designated with  15  in  FIG. 4  conically or radiused in such a way that alone by introducing the end portion  11  the quick-change element S is temporarily pushed aside until the end portion  11  is seated in the plug receptacle  10  and is secured. 
         [0030]    In the embodiment shown in  FIG. 4 , the quick-change element S comprises a press-button head  17 , which is positioned on the holder  2  to be accessible from outside. A stop face  18  on the lower side of the press-button head  17  is oriented towards a stop face  19  on the holder and towards the opening of a channel  22 , respectively, which channel  22  passes through the holder  2  in a direction transverse with respect to the plug receptacle  10 . A pin-like shaft  20  is adjacent to the press-button head  17 , the free end of which projects out of the channel  22  and carries a limit stop  26  interacting with a stop face  24  of the holder so as to prevent the quick-change element S from falling out. A collar  21  is formed on the shaft  20 , while a collar  23  is formed in the channel  22 . A spring element  25 , e.g. a helical spring, is seated between the collars  21  and  23 , which prestresses the quick-change element S in the direction towards the secured position shown in  FIG. 4  and, without the end portion  11  in the plug receptacle  10 , makes the limit stop  26  rest against the stop surface  24 . The limit stop  26  is detachable, for example, for disassembling the quick-change element S. 
         [0031]    The shaft  20  passes through a passage  27  which, in a direction perpendicular to the plane of projection in  FIG. 4 , at least has a width in correspondence with the outer diameter of the end portion  11  and which, in the direction of adjustment of the quick-change element S in channel  22 , has a dimension x which may be greater than the outer diameter of the end portion  11 . Expediently, the passage  27  is an oblong hole, as is shown in  FIG. 4  by the bent lines of intersection on the periphery of the shaft  20 . In the holder  2 , a clearance  28  is recessed in the crossing area between the channel  22  and the plug receptacle  10 , into which the collar  21  of the shaft  20  can be moved when the quick-change element S is displaced against the force of the spring element  25  to abut between faces  18 ,  19 . 
         [0032]    Expediently, the circumferential cavity  16  in the end portion  11  is a circumferential groove having a core diameter x 2  smaller than the outer diameter x 1  of the end portion  11 . The end portion  11  forms a collar  29  at plug-in foot  9 , which delimits the insertion depth into the plug receptacle  10 . The end portion  11  and/or the quick-change element S may be cylindrical or may have any other optional cross-sectional shape. 
         [0033]    In the secured position shown in  FIG. 4 , parts of the edges of the opening of passage  27  grip behind the boundaries of the circumferential cavity  16 . This position is secured by the spring element  25 . The plug-in foot  9  cannot be unplugged. If an external force is then applied to the quick-change element S, for example in the direction of arrow  12  shown in  FIGS. 3 and 4 , which overcomes the force of the spring element  25 , the quick-change element S is displaced into its release position in which, for example, faces  18 ,  19  contact each other. Thus, the engagement between the edges of the opening of passage  27  and the boundaries of the circumferential cavity  16  is released. The plug-in foot  9  can be drawn out of the plug receptacle  10  by means of the end portion  11 . Upon inserting the new fitting, again, the securing element S is moved into the release position against the force of the spring element  25  (if appropriate, by the wedge effect of the tip  15 ) until the end portion  11  is properly placed in the plug receptacle  10 . Upon releasing the press-button head  17  (without any manipulation of the quick-change element S) the spring element  25  then presses the quick-change element S into the secured position shown in  FIG. 4 . 
         [0034]      FIG. 5  schematically illustrates an automatically operable quick-change system for the fittings G 2  and shielding plates  7 , respectively, in the production line F of the blow molding machine M. A stationarily arranged automatic changer  30  is provided at the production line F, which could be moved to the production line F and, if necessary, docked to the same, for example, for a changing procedure. In another alternative, the automatic changer  30  could be integrated in a star-shaped rotor, which operates in cycles according to the change cycles of the production line and exchanges one fitting G 2  after the other or a group of fittings at once. The automatic changer  30 , which is movable to the production line, for example, in the direction of arrow  36 , comprises at least one driven actuator  32  oriented toward the respective securing element S and applying the force to allow the removal or insertion of the fitting G 2  in the direction of the double arrow  13 ,  14 . The removal and insertion, respectively, is accomplished by correspondingly controlled grippers  31 ,  32 ,  33 . Moreover, the automatic changer  30  is provided with at least one magazine  35 ,  34 , expediently a magazine  34  for removed fittings G 2  and a magazine  35  for fittings G 2  to be inserted. 
         [0035]    Although the automatic changer shown in  FIG. 5  is only explained and illustrated in connection with the exchange of the fittings G 2  in the form of shielding plates  7 , it could in an alternative embodiment simultaneously also perform the exchange of other fittings, e.g. of the preform mandrels  3 . The respective automatic changer  30  could act as a semiautomatic machine, which means that one or the other manipulation is carried out by the automatic changer and/or an operator.