Patent Publication Number: US-2012036693-A1

Title: Method for changeover of a blow molding machine

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a continuation patent application under 35 USC 120 of U.S. patent application Ser. No. 12/321,018, filed Jan. 15, 2009, entitled, “METHOD FOR CHANGEOVER OF A BLOW MOLDING MACHINE and claiming priority of German Patent Application No. 10 2008 004 773.2, filed on Jan. 16, 2008, both of which applications are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a method for changeover of a blow molding machine. In particular, the invention relates to a method for changeover of a blow molding machine which includes a plurality of blow mold holders. Each blow mold holder carries a multi-part blow mold. At least one blow mold is connected with a media supply. 
     BACKGROUND OF THE INVENTION 
     A blow molding machine is being particularly used for stretch blow molding of preforms. The blow molding machine itself comprises at least one blow mold. For the stretch blow molding of preforms for plastic bottles blow molds are being used, in which a preform is being blown into shape, which means being outlined, in the inside of the blow mold with excess pressure. The blow mold can comprise for example two half-molds, which are pivotable about a common axis. By pivoting about this axis, said half-molds can be closed so that a cavity is formed inside the blow mold, which is limited by the two half-molds, and a preform can be formed therein. European patent EP 1 276 598 B1 discloses, for example, the embodiment of such a blow mold holder. 
     European patent EP 0 572 107 B1 discloses a work head changer for a rotary vessel processing system. The rotary vessel processing system comprises a pivotable body for transporting containers within a defined interval. Likewise, a plurality of work heads is provided which are situated at the circumference of the pivotable body in the same separation distance, in order to treat each container, which is transported by means of the pivotable body, in a treatment process. The treatment process can comprise, for example, a process for attaching caps or a filling process. A connection between the pivotable body and each work head is being provided in order to mount each work head in a removable way on the pivotable body. The work head changer comprises a control system for controlling the rotation of the pivotable body so that each work head is being stopped consecutively and in turn at a predetermined work head exchanging device. Likewise, a work head feeding mechanism is provided which carries out the exchanging step at the corresponding work head changer for removing a work head. After the work head had been removed, a new work head can be placed into the provided empty position. 
     German patent application DE 10 2005 035 233 A1 discloses a holding device for blow mold segments. The blow mold segments are arranged in a support element. Thereby, the blow mold segments are detachably fixed in the support element with at least one locking element. For each blow mold segment, the locking element is provided with both a positively locking retention and a non-positively locking retention. For exchanging the blow mold segments, the support element must be opened in such a way so that the corresponding processes for the exchange of the blow mold segments must be carried out in one position only. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to provide a method which enables a changeover of a blow mold machine in such a way that the changeover time for the changeover of the blow mold machine is reduced to a minimum. 
     The above-mentioned object is solved by a method for changeover of a blow molding machine in which the blow molding machine has a plurality of blow mold holders, each of which carries a multi-part blow mold. At least one part of the blow mold is connected with a media supply, including the steps of:
         assigning at least two working areas at the blow molding machine. Different processes are carried out at each working area;   opening the blow mold holder and releasing the media supply prior to the arrival or at a first working area;   removing the parts of the blow mold from the blow mold holder at a second working area and replacing the parts of the blow mold with a blow mold of another type; and   closing the blow mold holders and connecting the media supply.
 
It is advantageous if at least two working areas are provided for the changeover of a blow molding machine and different processes are carried out at each working area for the changeover of the blow molding machine. For the changeover of the blow molding machine, the blow mold holder is opened and/or the intended media supplies with the blow mold holder and blow mold elements respectively are released at least at the first working area. At a second working area the multi-part blow molds are removed from the blow mold holder and replaced with a blow mold of another type. Finally the blow mold holder is closed and/or the media supply is reconnected. It is also possible that the blow mold holder is opened at a respective working area before the blow mold holder arrives. Likewise, the blow mold can be closed after leaving the working area. A cam element can be used for this, for example.
       

     An expenditure of time for carrying out the processes at the plurality of working areas is assessed in such a way that the expenditure of time is equal at each working area. The advantage is that there are no holding times when the blow mold holders are exchanged at least from the first working area to the second working area. Holding times are necessary only if the processes at all working areas are finished except for one working area. The exchanging process has to wait for the ‘slowest’ working area. 
     The expenditure of time at the at least first working area for opening the blow mold holders and for releasing the media supplies is substantially equal with the expenditure of time for removing the blow mold, replacing the blow mold and closing the blow mold holder, and connecting the media supply. 
     It is particularly advantageous if at least three working areas are provided. The blow mold holder is opened and the media supply is released at a first working area. At a second working area, the multi-part blow mold is removed from the blow mold holder and replaced with a blow mold of another type. At a third working area, the blow mold holders are closed and the media supply is reconnected. 
     It is also possible to release the fastening of the blow mold parts at the first working area. At the third working area, the fastening elements of the blow mold parts can be tightened again. It is also possible to release and tighten the fastenings of the blow mold parts at that working area at which the blow mold parts are replaced with blow mold parts of another type. 
     If two working areas are provided for the replacement of the blow molds and for the changeover of the blow molding machine respectively, in one embodiment, the expenditure of time at the first working area is equal with the expenditure of time at the first and second working area respectively. As a matter of course, the expenditure of time at the first working area is reduced if the blow mold holders are opened before they arrive at the first working area. Likewise, the expenditure of time is reduced for a working area if the blow mold holder is not closed in the working area provided for closing the blow mold holder. 
     It is of advantage if the intended processes are carried out automatically at each working area. It is also possible for the intended processes to be carried out automatically at each working area except for the one working area at which the blow mold is removed and the blow mold is replaced. The removing of the blow mold and the replacement of the blow mold are carried out manually. 
     At least one robot is provided at a corresponding working area for carrying out the processes automatically. At least some portions of the processes, which are necessary for the changeover of the blow molding machine, are carried out automatically by the robot. 
     Experience has shown that the expenditure of time for carrying out the processes at each working area should range between 20 and 60 seconds. 
     It is of advantage when the processes for the changeover of a blow molding machine are carried out simultaneously at different working areas in order to obtain a corresponding saving of time for the changeover of a blow molding machine and consequently reduce the dead time of a blow molding machine during the changeover. The changeover of the blow mold holders from the first working area to the second working area is adjusted in such a way that a cycle time goes according to the longest expenditure of time needed at a working area. 
     The blow mold holders are arranged at a transport device and the transport device moves the blow mold holders between the working areas according to the cycle time. 
     The transport device can be designed in a linear way. It is also possible that the transport device is designed in the shape of a wheel and the wheel carries the plurality of blow mold holders. 
     If only the blow mold of another type is to be inserted and the height of the bottle to be blown remains the same, only a first blow mold half, a second blow mold half and a base part of the blow mold are exchanged at the working area at which the blow mold of another type is to be inserted. Furthermore, in some cases only the first blow mold half and the second blow mold half need to be exchanged, since the base part remains the same, too. This is frequently used when standard bases are used for relatively simple bottles. 
     If not only the type of the blow mold is being changed but also the height of the bottle to be blown, then a first blow mold half, a second blow mold half, a base part of the blow mold and a stop for the stretching rod are exchanged at the working area at which the blow mold of another type is inserted. 
     In one embodiment the blow mold parts are exchanged only in case the lockings for the corresponding blow mold parts had been released on the blow mold holders. Accordingly, the locking is to be closed again after the parts had been inserted into the blow mold holder. The process can be carried out automatically or manually. Another embodiment is that the blow mold parts at the blow mold holder are first of all fastened without being locked and that the locking takes place by means of closing the blow mold holder. Likewise, the locking is being opened when the blow mold holder is being opened. It is obvious for a skilled person how to fasten and/or release the separate blow mold parts in the blow mold holder. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will now be explained in greater detail on the basis of the accompanying figures, in which 
         FIG. 1  shows a schematic view of a blow molding machine connected with a heating system, which supplies the blow molding machine with preforms having a defined temperature. 
         FIG. 2  shows a schematic view of the three working areas at which the processes for exchanging the blow molds are carried out. 
         FIG. 3  shows a schematic view of a first working area at which the changeover of the blow molding machine had already begun. 
         FIG. 4  shows the situation of the changeover of the blow molding machine, in which the blow mold holder, which had already been opened at the first working area, has been transported to the second working area. 
         FIG. 5  shows the situation in which the newly arrived blow mold holder is opened at the first working area, and the blow molds and the blow mold part respectively is exchanged at the second working area at the same time. 
         FIG. 6  shows the situation in which the blow mold holder, which is provided with new blow mold parts, has been transported to the third working area. 
         FIG. 7  shows the situation in which the blow mold holder has been closed again at the third working area. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     It is to be understood that the described three working areas in the following description of the method for changeover of a blow molding machine should not be regarded as limiting the invention. It is self-evident for a skilled person to provide a blow molding machine with less than three working areas and with more than three working areas at which the changeover of a blow molding machine can be carried out. It is also to be understood that the number of parts of the blow mold or the stop for the stretching rod (not shown), which are to be exchanged, are not to be regarded as limiting the invention. The following description relates to blow mold parts which are connected with a media supply. This is, however, only one of many embodiments. Depending on the requirements of the plastic bottle to be produced, all blow mold parts are provided with a media supply or at least a particular part of the blow mold is provided with a media supply. Furthermore, it is pointed out that same reference numbers refer to the same elements throughout the various figures. 
       FIG. 1  shows a schematic view of a device with which plastic bottles can be basically produced by means of a stretch blow molding process. The device  1  basically includes a heating system  2  in which preforms for the plastic bottles to be produced are heated to a certain temperature so that plastic bottles can be produced from this preforms in the blow molding process or stretch blow molding process. The blow molding machine  3  is attached to the heating system  2 . Inside the heating system  2 , a transport device  4  is provided which transports a plurality of preforms past a heating device  5 . The transport device  4  is shielded with heat reflective tiles  6  to the inside of the heating system  2 . The preforms are being transported into the heating system  2  at a transfer point  7 . The heated preforms are being handed over at an output position  8  to an input position  9  for the blow molding machine  3 . The finished plastic bottles are being handed over to further processing or filling (not shown) at an output position  10  of the blow molding machine. 
     The blow molding machine shown in  FIG. 1  comprises a transport device  11  onto which the plurality of blow mold holders  12  is arranged. The transport device  11  is designed in the shape of a wheel in this schematic view of the blow molding machine  3 . It is also possible that the transport device  11  is basically designed in a linear way. The blow molding machine  3  is surrounded by several walls  14 . A first working area  15 , a second working area  16  and a third working area  17  are provided on at least one wall  14  of the blow molding machine  3  as shown in this embodiment. At these working areas  15 ,  16 ,  17 , the changeover of the blow molding machine  3  can be carried out. As already mentioned, the changeover of the blow molding machine  3  can be carried out automatically at each working area  15 ,  16 ,  17 . For this automatic process of the changeover of the blow molding machine  3 , particular robots or conventional handling devices (not shown) are intended for. It is also possible that the changeover of the blow molding machine  3  can be carried out manually at one or at the other working area. In one embodiment, a manual changeover of the blow molding machine  3  at a working area is recommended only in case the efforts for an automatic changeover of the blow molding machine  3  would be too huge at this working area. Whether the changeover of the blow molding machine  3  is carried out automatically and/or manually at each working area  15 ,  16 ,  17  should not be regarded as limiting the invention. Cam element  30  is used to open and close blow mold holders as described below. 
       FIG. 2  shows a schematic view, where the blow mold holders  12 , which are arranged inside the blow molding machine  3 , are assigned to the corresponding working areas  15 ,  16 ,  17 , so that a changeover of the blow molding machine  3  can be carried out. For a better clarification of the method, the blow mold holder  12  is shown both from above and from a lateral view in the views of  FIGS. 2 to 7 . The blow mold holder  12  is designed in a multi-part way and thus carries the multi-part blow mold  22 , which consists of a first part of the blow mold  22   1 , a second part of the blow mold  22   2 , and a third part of the blow mold  22   3  in the embodiment shown. The third part of the blow mold  22   3  is the base part which finally is the base part of the plastic bottle to be produced. The first part of the blow mold  22   1  is connected with a corresponding media supply  20   1 . Likewise, the second part of the blow mold  22   2  is connected with a corresponding media supply  20   2 . The third part of the blow mold  22   3 , too, is connected with a corresponding media supply  20   3 . Since the blow mold holder  12  is formed proportionally, a closure element  24  is provided for locking the blow mold holder  12 . After the closure element  24  has been released, the blow mold holder  12  can be separated. For the separation of the blow mold holder  12 , blow mold holder  12  can be swung apart about an axis  26 . With reference to the procedural step shown in  FIG. 2  the transport device  4  of the blow molding machine had been controlled in such a way that in each case a blow mold holder faces each working area  15 ,  16 ,  17 . The blow mold holders  12  shown in  FIG. 2  are all still closed. 
     In the following, the individual procedural steps concerning the changeover of a blow molding machine  3  are described without naming the individual elements of the blow mold holder in order to preserve clarity of the following figures. 
       FIG. 3  shows a situation of the method according to the invention for changeover of a blow molding machine  3  in which the blow mold holder  12  has been swung apart about an axis  26  at the first working area  15 . Furthermore, the corresponding media supplies  20   1 ,  20   2  and  20   3  have been released from the corresponding parts of the blow mold  22   1 ,  22   2 , and  22   3  at this first working area  15 . It can also be seen from  FIG. 3  that each of the working areas  15 ,  16 ,  17  is provided with a corresponding shield  28 . This shield  28  is provided because of working safety. 
       FIG. 4  shows such a situation of the method according to the invention for changeover of a blow molding machine  3  in which the transport device  4  of the blow molding machine  3  has transported the blow mold holders  12  to the next working area. In  FIG. 4 , the opened blow mold holder, which has been opened in the first working area  15 , is now situated at the second working area  16 . In order to exchange the parts of the blow mold  22   1 ,  22   2 , and  22   3  at the second working area  16 , the shield  28  of the second working area  16  is being removed and pushed aside respectively. The blow mold holder  12 , which is situated in the second working area  16 , is thus ready for a manual or automatic handling of the process for changeover of a blow molding machine  3 . 
       FIG. 5  shows such a situation of the method according to the invention for changeover of a blow molding machine  3  in which processes are carried out at the blow mold holder  12  for changeover of a blow molding machine  3  at the first working area  15  and at the second working area  16  each. While the individual parts of the blow mold  22   1 ,  22   2 , and  22   3  are being replaced at the second working area  16 , the blow mold holder  12  is being opened at the first working area  15  and the media supplies  20   1 ,  20   2  and  20   3  are being released. The shield  28  prior to the second working area  16  is removed in order to enable the exchange of the parts of the blow mold  22   1 ,  22   2 , and  22   3 . It is of particular advantage when the expenditure of time for carrying out the processes in the first working area  15  is approximately equal with the expenditure of time for carrying out the processes in the second working area. 
       FIG. 6  shows a situation of the method according to the invention for changeover of a blow molding machine  3  in which the blow mold holder  12 , which had faced the second working area  16  in  FIG. 5 , has now been transported to the third working area  17 . Further transport of the blow mold holders  12  from one working area to the next working area is carried out only if the processes are finished at each working area  15 ,  16  and  17 . Consequently it is evident that the cycle time of the transport device  4  has to act in accordance with that working area which needs the longest expenditure of time for carrying out the processes. The optimal situation would be if the expenditure of time was of the same length at each working area for carrying out the required processes. This would result in an optimal usage of the dead time of the blow molding machine  3 . In the situation shown in  FIG. 6  of the method according to the invention for changeover of a blow molding machine  3 , a new and still closed blow mold holder  12  has been inserted at the first working area  15  by the transport device  11 . The opened blow mold holder  12  has arrived at the second working area  16 , and from said blow mold holder  12  now the parts of the blow mold  22   1 ,  22   2 , and  22   3 .must be exchanged The opened blow mold holder  12  arrived at the third working area carrying now another type of the blow mold  22  or parts of the blow mold  22   1 ,  22   2 , and  22   3 . Furthermore, the media supplies  20   1 ,  20   2  and  20   3  are still not connected with the parts of the blow mold  22   1 ,  22   2 , and  22   3  at the third working area  17 . 
       FIG. 7  shows such a situation of the method according to the invention for changeover of a blow molding machine  3  in which at all working areas  15 ,  16 ,  17  processes are being carried out. A blow mold holder  12  is being opened at the first working area  15  by the interaction of cam element  30  with cam follower  32 . For this purpose, a closure element  24  is released and the blow mold holder is swung about the axis  26  and consequently separated by the action of the cam element on the cam follower. Likewise, the media supplies  20   1 ,  20   2  and  20   3  are released from the corresponding parts of the blow mold  22   1 ,  22   2 , and  22   3 . Simultaneously the shield  28  is opened at the second working area  16  and the parts of the blow mold  22   1 ,  22   2 , and  22   3  are exchanged with other blow mold parts of another type. At the third working area  17  processes for changeover of a blow molding machine  3  are also carried out at the same time with the processes being carried out at the first working area  15  and at the second working area  16  simultaneously. 
     At the third working area  17 , the blow mold holder  12  is flapped about the axis  26  by the interaction of cam element  30  with cam follower  32  and closed with the closure element  24 . Likewise, the media supplies  20   1 ,  20   2  and  20   3  are reconnected with the corresponding blow mold parts. The transport device  4  of the blow molding machine  3  transports blow mold holders  12  till such time to the corresponding working areas  15 ,  16 ,  17  as long as all blow mold holders  12 , which are available in the blow molding machine  3 , have a new blow mold type. By means of the method according to the invention, the resulting dead time owing to the changeover of the blow molding machine  3  is reduced to a minimum (20 to 60 minutes for example). 
     A method, according to the invention, for changeover of blow molding machine  3  is as follows. The following should be viewed in light of  FIGS. 1 through 7 . The blow molding machine has a plurality of blow mold holders  12 , and each blow mold holder includes a respective blow mold  22 , with a respective plurality of parts. The method includes the following steps: automatically opening a blow mold holder from the plurality of blow mold holders; removing the respective blow mold from the blow mold holder; replacing the respective blow mold with a another blow mold different from the respective blow mold; and automatically closing the blow mold holder. 
     In one embodiment, the blow mold holder includes cam follower  32 . Automatically opening the blow mold holder includes using cam element  30 , in cooperation with the cam follower; or automatically closing the blow mold holder includes using the cam element in cooperation with the cam follower. 
     In one embodiment: the respective plurality of parts includes locking device, or closure element  24 , and the other blow mold includes another plurality of parts with a locking device. Also, removing the respective blow mold includes releasing the locking device and removing the respective plurality of parts from the blow mold holder, and replacing the respective blow mold includes inserting the other plurality of parts and closing the other locking device. 
     In one embodiment, the plurality of blow mold holders is arranged at transport device  4 , which moves the plurality of blow mold holders. The transport device has a shape of a wheel and the plurality of blow mold holders is arranged at a periphery of the wheel. In one embodiment the changeover is carried out in working area  16 , which is situated in the periphery of the blow molding machine and at a position which does not overlap with output position  8  and transfer point  7 . 
     A method, according to the invention, for changeover of blow molding machine  3  is as follows. The following should be viewed in light of  FIGS. 1 through 7 . The blow molding machine has a plurality of blow mold holders  12 , and each blow mold holder includes a respective blow mold  22 , with a respective plurality of parts. The method includes the following steps: automatically opening a blow mold holder from the plurality of blow mold holders before the blow mold holder arrives at working area  16 , a working area at which the respective blow molds are exchanged; removing the respective blow mold from the blow mold holder; replacing the respective blow mold with another blow mold different from the respective blow mold; and automatically closing the blow mold holder. 
     In one embodiment, the blow mold holder includes cam follower  32 , and automatically opening and closing the blow mold holder includes using cam element  30 , in cooperation with the cam follower. In one embodiment, the respective plurality of parts includes a locking device, or closure element  24 , and the other blow mold includes another plurality of parts with another locking device. Then, removing the respective blow mold includes releasing the locking device and removing the respective plurality of parts from the blow mold holder, and replacing the respective blow mold includes inserting the other plurality of parts and closing the other locking device. 
     In one embodiment, the plurality of blow mold holders is arranged at transport device  4 , which moves the blow mold holders. The transport device has a shape of a wheel and the plurality of blow mold holders is arranged at a periphery of the wheel. In one embodiment, the changeover is carried out in working area  16 , which is situated in the periphery of the blow molding machine and at a position which does not overlap with output position  8  and a transfer point  7 . 
     A method, according to the invention, for changeover of blow molding machine  3  is as follows. The following should be viewed in light of  FIGS. 1 through 7 . The blow molding machine has a plurality of blow mold holders  12 . Each blow mold holder includes a respective cam follower  32 , and a respective blow mold  22 , including a respective plurality of parts. The method includes the following steps: automatically opening a blow mold holder from the plurality of blow mold holders using cam element  30 , in cooperation with the respective cam follower for the blow mold holder; removing the respective blow mold from the blow mold holder; replacing the respective blow mold with another blow mold different from the respective blow mold; and automatically closing the blow mold holder using the cam element in cooperation with the respective cam follower of the blow mold holder. 
     A method, according to the invention, for changeover of blow molding machine  3  is as follows. The following should be viewed in light of  FIGS. 1 through 7 . The blow molding machine has a plurality of blow mold holders  12 , and a blow mold holder from the plurality of blow mold holders includes a blow mold  22 , including a plurality of parts. The method includes the following steps: automatically opening the blow mold holder using cam element  30 ; removing the blow mold from the blow mold holder; replacing the blow mold with another blow mold different from the blow mold; and automatically closing the blow mold holder using the cam element. 
     The present invention has been described with respect to preferred embodiments. It is possible for a skilled person to carry out amendments or changes of the present invention without departing from the scope of the claims below.