Patent Publication Number: US-2007098838-A1

Title: Injection molding machine for producing shaped plastic parts, preferably plastic cups

Description:
BACKGROUND OF THE INVENTION  
      The invention relates to an injection molding machine for producing shaped plastic parts, preferably plastic cups, according to the preamble of claim  1 .  
      In connection with manufacturing plastic cups, it is known that, after opening the injection mold, the plastic cups are removed by a removal unit and then blown off so that the plastic cups drop from the removal unit downwardly into stacking units. This can cause the plastic cups to become damaged, in particular when they have thin walls. Since the plastic cups are very lightweight, handling causes significant problems so that a safe production is not ensured.  
     SUMMARY OF THE INVENTION  
      The invention has the object to configure an injection molding machine of the aforementioned kind such that the shaped plastic parts produced in the injection mold can be reliably manipulated by means of the removal unit.  
      This object is solved for an injection molding machine of the aforementioned kind in accordance with the present invention by the characterizing features of claim  1 .  
      In the injection molding machine according to the invention, the shaped plastic parts produced in the injection mold are removed by the removal unit and put down in a controlled way. This putting down step is realized when the injection mold is closed again and the next shaped plastic part is injection molded. On the one hand, the shaped plastic parts are safely put down and, on the other hand, the time for removal of the shaped plastic parts is not impaired by this putting down step. The putting down step is significantly shorter than the time for injection molding the next shaped plastic part. In this way, it is ensured that when opening the injection mold the removal unit is already in the required position for removal of the shaped plastic part.  
      Further features of the invention can be taken from the additional claims, the description, and the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention will be explained in the following with the aid of two embodiments illustrated in the drawings. It is shown in:  
       FIG. 1  partially in plan view and partially in section an injection molding machine according to the invention for producing plastic cups;  
       FIG. 2 a  plan view onto a transfer unit for labels of the injection molding machine according to the invention;  
       FIG. 3 a  stacked injection mold of a second embodiment of an injection molding machine according to the invention in the closed position;  
       FIG. 4 a  side view of the injection mold according to  FIG. 3 ;  
       FIG. 5  in an illustration in accordance with  FIG. 3  the injection mold in the open position;  
       FIG. 6 a  plan view onto a part of the second embodiment of the injection molding machine according to the invention;  
       FIG. 7  in a schematic illustration the movement course of a removal unit and an insertion unit of the injection molding machine according to the invention according to  FIGS. 1 and 2 ;  
       FIG. 8  in a schematic illustration the removal of an injection molded plastic cup from the open injection mold as well as insertion of a label for the next injection molding step;  
       FIG. 9  in an enlarged and schematic illustration the insertion unit and the removal unit of the injection molding machine according to the invention;  
       FIG. 10 a  second embodiment of a removal unit and an input unit of the injection molding machine according to the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      The injection molding machine is used for injection molding plastic cups that are provided with at least one label that is fixedly connected to the plastic material. The labels are provided in at least one magazine  1  of the injection molding machine in which they are arranged behind one another and/or atop one another. They are removed by means of at least one transfer unit  2  from the magazine  1  and transferred to an insertion unit  3  with which the labels are placed into the injection mold  4 . In order to achieve a high output of the injection molding machine, several magazines  1  and accordingly several transfer units  2 , insertion units  3 , and one injection mold  4  with several cavities are provided. With such an injection molding machine, not only plastic cups but also other shaped plastic parts, for example, lids, tubes, and the like can be produced. The labels are preferably printed and can be comprised of plastic film, metal foil, multi-layer films and the like.  
      The magazines  1  are preferably inclined so that the labels contained therein will safely slide down and can be picked up by the transfer unit  2 . Such label magazines  1  are known and are therefore not explained in detail.  
      The transfer units  2  are provided on the vertical stand  5  ( FIG. 2 ) that is rotatably supported about vertical axis  6  in the injection molding machine. The transfer units  2  are arranged on the stand  5  so as to be pivotable to a limited extent about a horizontal axis.  FIG. 2  shows two transfer units  2  in an inclined position and two additional transfer units  2  in a horizontal position. Both positions are determined by stops  7 ,  8  provided on the stand  5  and formed in the embodiment by adjusting screws. The transfer units  2  are positioned in their respective end position against the screw heads. By means of the adjusting screws, the position of the transfer units  2  can be adjusted simply and precisely. The transfer units  2  are identical and have each a receiving part  9  in the form of a suction holder with which the label  12  is removed from the magazine  1 . The receiving parts  9  are provided at the end face with vacuum openings  10  by means of which vacuum can be generated for removing each label from the magazine  1 . Each label sticks to the end face of the receiving part  9  and can be transferred in a way to be described in the following to the insertion unit  3 . The receiving parts  9  are movable in the axial direction of the transfer unit  2 .  
      On opposite sides of the stand  5 , two transfer units  2  are positioned that are spaced from one another. In  FIG. 2  the receiving part  9  of the upper transfer unit  2 , respectively, is in the extended position while the receiving part  9  of the lower transfer units  9  are retracted. Since the magazine  1  is inclined, the transfer units  2  are moved into the slanted position shown in  FIG. 2  in which at least the axis of the receiving parts  9  is positioned on an extension of the axis of the magazine  1 . For receiving the labels  12 , the receiving parts  9  are extended so that they can pick up the leading label, respectively, from the magazines  1  by generating vacuum. Subsequently, the stand  5  is rotated about vertical axis  6  such that the receiving parts  9  with labels  12  are located opposite the insertion units  3 . During rotation of the stand  5 , the two transfer units  2  are pivoted about the horizontal axis so far that they assume the horizontal position, defined by the stops  7 , and then transfer the labels  12  safely to the insertion units  3 . The transfer units  2  located on the other side of the stand  5  are pivoted during the rotational movement of the stand  5  out of their horizontal position into the slanted position that is determined by the stops  8 . While the first transfer units  2  transfer their labels  12  to the insertion units  3 , the two second transfer units  2  pick up the next labels from the magazines  1 . Depending on the position of the magazines  1  and of the insertion units  3  in the injection molding machine, it can be required to extend and retract the receiving parts  9  during the rotational movement of the stand  5 . In  FIG. 1 , the labels  12  that are held by the receiving parts  9  of the transfer units  2  by vacuum are illustrated in an exemplary way. The labels  12  are plane and are supported reliably on the receiving parts  9 . As shown in  FIG. 2 , the receiving parts  9  have laterally adjacent to the vacuum openings  10  plane contact surfaces  13  for the labels  12 . Depending on the configuration of the labels  12 , it is possible to provide on the transfer units  2  correspondingly designed receiving parts  9  that, for this purpose, are arranged on the transfer units  2  advantageously so as to be easily exchangeable. The receiving parts  9  are positioned advantageously on rods  14  that are guided in the transfer units  2  and are preferably pneumatically loaded in order to be moved.  
      The insertion units  3  are positioned on a vertical shaft  15  ( FIG. 1 ) which is supported rotatably in the injection molding machine and on which the insertion units  3  are positioned atop one another at a spacing. In the embodiment, on the pivot shaft  15  two insertion units  3  are positioned above one another at a spacing. The insertion units  3  are advantageously identical and have an arm  16  projecting transversely away from the shaft  15 ; the arm has at its free end a receiving head  17  for the label  12 . In the illustrated embodiment, the receiving head  17  is of parallelepipedal shape and has slots (not illustrated) through which a vacuum force is applied onto the label  12 . It is then automatically wound onto the receiving head  17  in a cup shape. The receiving head  17  has an end face  18  as well as sidewalls  19  on which the label  12  rests areally as a result of the vacuum force.  
      For receiving the labels  12  from the transfer units  2 , the insertion unit  3  is in the transfer position illustrated in  FIG. 1 . The receiving parts  9  that secure the labels  12  by vacuum are extended after rotation of the stand  5  into the transfer position according to  FIG. 1  to such an extent that the labels  12  first come to rest against the end face  18  of the receiving heads  17  or are spaced minimally therefrom. Subsequently, the label is blown off by the receiving part  9  of the transfer units  2  and shortly beforehand vacuum is applied to the receiving heads  17  of the insertion units  3 . In this way, a safe transfer of the label  12  from the transfer units  2  to the insertion units  3  is ensured. Directly after the transfer of the labels  12  has taken place, the receiving parts  9  of the transfer units  2  are retracted. At the same time, the other transfer units  2  that have removed the label  12  from the respective magazine  1  are also retracted. When rotating the stand  5  about the vertical axis  6 , all of the receiving parts  9  are thus in the retracted position. As soon as the receiving parts  9  are again positioned opposite the magazines  1  or the insertion units  3 , they are extended. While on one side the labels  12  are transferred to the insertion unit  3 , on the opposite side the labels  12  are removed from the magazine  1 .  
      In the embodiment the magazines  1  and the insertion units  3  are positioned opposite one another so that the stand  5  is rotated by 180 degrees, respectively. Depending on the configuration of the injection molding machine, the magazines  1  and the insertion units  3  can have other positions relative to one another so that the stand  5  accordingly rotates about different angles. The shaft  15  of the insertion units  3  is fixedly connected to the movable mold part  20  of the injection mold  4  so that the shaft  15  upon opening and closing of the injection mold  4  is entrained by the mold part  20 . The mold part  20  is movable horizontally within the injection molding machine and provided with a female mold  21  into which, in a way to be described in the following, the label  12  is inserted by the receiving head  17 . The mold part  20  has positioned opposite thereto the mold part  22  with male mold  23 . The female mold  21  and the male mold  23  together form the mold for producing the plastic cup. The mold part  22  is fixedly connected to the machine while the mold part  20  is moveable for opening and closing the mold  4 .  
       FIG. 3  shows an injection mold  4  of a second embodiment of an injection molding machine. The injection mold  4  is of a stacked mold configuration in which several mold parts  20 , 22  are provided. In the embodiment, four mold parts  20 , 22  each are provided so that in the injection molding machine four plastic cups are simultaneously injection molded. The four injection molds according to  FIG. 3  are arranged adjacent and atop one another. In accordance with the number of injection molds there is also a corresponding number of insertion units  3  and transfer units  2  provided on the injection molding machine. As shown in  FIGS. 3 and 5 , the adjacently positioned mold parts  20  and  22  are monolithic so that upon opening of the injection molds ( FIG. 5 ) two injection-molded plastic cups can be removed simultaneously. As shown in  FIG. 5 , on the oppositely positioned sides of the mold part  20  a shaft  15  is provided on which two insertion units  3  above one another are fixedly supported, respectively. With them, the labels  12  can be inserted into the female molds  21  of the mold parts  20  when the injection mold is open. The receiving heads  17  are matched to the shape of the female molds  21 . In an exemplary way,  FIG. 5  shows the transfer position outside of the injection mold for the insertion units  3  and the insertion position in which the insertion units  3  insert the label  12  by means of the receiving heads  17  into the female molds  21 . In the female molds  21  the respective label  12  is secured in a way known in the art until the injection mold  4  is closed again. As soon as the receiving head  17  of the insertion unit  3  is immersed into the female mold  21 , the vacuum source is switched off or the wound label  12  is blown off so that it reaches the female mold  21 . Subsequently, the injection mold  4  can be closed and the plastic material can be injection molded about the label. When the injection mold  4  is open again, the injection-molded plastic cup  24  is seated on the respective male mold  23 . From this position, it can be removed by a removal unit  25  in a way to be described in the following.  
      In the embodiments according to  FIGS. 1, 2 ,  7 , and  8 , the removal unit  25  is rotatable about a vertical axle  26  that is fixed to the machine. Depending on the number of injection molds  4  or of the number of plastic cups  24  produced therein, several removal units  25  are arranged above one another on the axle  26 . At the upper and lower ends of the axle  26 , a radially projecting arm  27  is provided, respectively, that supports an axle  28  at its free which axle is positioned parallel to the axle  26 . Suction holders  29  are seated thereon with which the injection-molded plastic cups  24  seated on the male molds  23  can be removed. On the arms  27 , a rotary drive (not illustrated) for the axle  28  positioned parallel to the axle  26  is arranged. With it, the axle  28  upon rotation of the axle  26  is rotated relative to this axle such that the plastic cup  24  and thus the vacuum holder  29  are moved translatorily; see  FIG. 8 .  
      The insertion units  3  and the removal units  25  are positioned on opposite sides of the injection mold  4  wherein the removal units  25  are fixed to the machine while the insertion units  3  together with the movable mold part  20  are entrained upon opening and closing the injection mold.  
      As is shown in  FIG. 8 , by means of the removal units  25  the plastic cups  24  seated on the male molds  23  are removed while at the same time the labels  12  are inserted for the next injection molding step into the female molds  21  by means of the insertion units  3 . The insertion units  3  are rotated in the described way for the insertion process about shaft  15  that extends parallel to the axle  26  of the removal units  25 . The rotary movement of the axles  15 ,  26  is coordinated such that the insertion units  3  and the removal units  25 , when the injection mold is open, do not collide with one another. Advantageously, the rotational movements of the axles  15 ,  26  are coupled by a sequence control such that first the removal units  25  are pivoted into the open injection mold and, by means of the vacuum holders  29 , the plastic cups  24  are removed from the male mold  23 . With time delay the insertion units  3  are pivoted from the transfer position according to  FIG. 1  into the open injection mold in order to insert the labels  12  seated on the receiving head  17  into the female mold  21 . Subsequently, the insertion units  3  pivot back into the transfer position according to  FIG. 1  in order to receive the next labels  12  from the transfer units  2 .  
      Removal of the plastic cups  24  and insertion of the labels  12  into the female molds  21  for the next injection molding process is realized essentially simultaneously. In this way, in a unit of time a very large number of plastic cups can be injection molded. Since the insertion units  3  and the removal units  25  are pivoted at the same time into the open injection mold  4  and are immediately thereafter moved out again, the time between sequentially performed injection molding processes can be kept very short.  
       FIG. 7  shows the movement course of the insertion unit  3  from the time of opening the injection mold until insertion of the label  12  seated on the receiving head  17  into the female mold  21 .  FIG. 8  shows how the plastic cup  24  is moved translatorily by means of the removal unit  25  in that the axle  28  during the pivoting action is rotatably driven relative to the axle  26 . The end position of the removal units  25  is shown in  FIG. 7  in which the arm  27  is completely outside of the injection mold  4 .  
      In the embodiment according to  FIG. 3  to  FIG. 6 , the insertion units  3  pivot about a substantially larger angle than in the embodiment according to  FIGS. 1, 3 , and  7 . In the latter embodiment, the pivot angle between transfer position and insertion position is smaller than 180 degrees. In the embodiment according to FIGS.  3  to  6  this pivot angle is 270 degrees. In the transfer position the arms  16  of the insertion units  3  are positioned on one side of the mold parts  20 . Since in the illustrated embodiment according to FIGS.  3  to  6 , each mold part  20  has two female molds  21 , on the sides facing away from one another each mold part  20  is provided with an insertion unit  3 , respectively.  
      The removal units  25  correlated with the male molds  23  are rotatable from the initial position by 270 degrees into the removal position about the axle  26 . In contrast to the preceding embodiment, on the free end of a transversely projecting arms  27  of the removal units  25  no further axle is provided. Instead, on the free end of the arm  27  the vacuum holder  29  that removes the injection-molded plastic cup from the respective male mold  23 , respectively, is fixedly attached. In  FIG. 5 , the pivot travel of the insertion units  3  and the removal units  25  is indicated. Since the movement travel of these units overlap one another partially, the pivot movement of the units  3 ,  25  is controlled such that they do not collide with one another. In this embodiment, the injection-molded plastic cups  24  are also removed from the open injection mold and substantially simultaneously the labels for the next injection molding process are inserted. As soon as the units  3 ,  25  are again in their initial position, the injection mold  4  is closed and the next injection molding process is initiated.  
      The plastic cups  24  removed from the injection molds by the removal units  25  are transferred onto putting-down units  30  with which the plastic cups  24  are positioned into a receptacle  31  in a controlled way. The putting-down unit  30  has two arms  32 ,  33  positioned at a right angle relative to one another and provided at their free ends with suction holders  34 ,  35 . In the embodiment, the arms  32 ,  33  are positioned in a horizontal plane. The putting-down unit  30  can be rotated about an axle  36  by 180 degrees; the axle extends at 45 degrees between the arms  32 ,  33  and is positioned in the plane of the arms  32 ,  33 . This has the result that after pivoting about 180 degrees the arms  32 ,  33  have changed places.  
      The putting-down unit  30  in its initial position is arranged such that the suction holder  35  of the arm  33  is positioned opposite the suction holder  29  of the removal unit  25  ( FIG. 1 ). When the removal unit  25  pivots into the position illustrated in  FIG. 1 , the suction holder  35  engages the removed cup  24 . It is blown off the suction holder  29  of the removal unit  25  and secured on the suction holder  34  of the putting-down unit  30  by applying vacuum. Subsequently, the putting-down unit  30  is pivoted about axle  36  by means of drive  37  so that the plastic cup  24  is opposite the receptacle  31 . Subsequently, the suction holder  35  with the plastic cup  24  arranged thereat is extended and in this way the plastic cup  24  is inserted into the plastic cup  24  which is already within the receptacle  31 . In this way, in the receptacle  31  a stack of plastic cups  24  inserted into one another is formed. The suction holders  34 ,  35  are positioned on the rods (not illustrated) that can be extended from the respective arms  32 ,  33 .  
      While the plastic cups  24  are inserted into the receptacle  31 , the next plastic cup is removed at the same time by the removal unit  25  by means of the suction holder of the other arm. In this way, by switching back and forth the putting-down unit  30  the plastic cup removed from the injection mold  4  can be inserted into the receptacle  31 . It is horizontal. As soon as the receptacle  31  has formed the required stack length of plastic cups  24 , the stack is pushed out of the receptacle  31  and placed onto a conveyor belt or the like with which the plastic cup stack is transported farther to be packaged.  
      Depending on the number of injection molds and removal units  25  a corresponding number of putting-down units  30  and receptacles  31  is provided. With the injection molding machine several plastic cup stacks can thus be formed in a unit of time. In the embodiment according to  FIG. 3  to  6 , between the removal unit  25  and the putting-down unit  30  a linear unit  38 ,  39  is interposed. They have suction holders  40 ,  41  with which the plastic cups  24  can be picked up from the removal units  25  and the labels  12  can be inserted into the insertion units  3 . For this purpose, the plastic cups  24  are blown off the suction holders  29  of the removal units  25  and are attracted by the suction holders  40 . Subsequently, the linear units  38 ,  39  are moved in the direction of the movement arrows indicated in  FIG. 3  until the suction holders  40  are located in the transfer area of the putting-down unit  30 . Here, the plastic cups  24  are received in the described way by the putting-down units  30  and inserted into receptacles  31 .  
      In this embodiment, the magazines  1  for the labels are arranged on both sides of the linear units  38 ,  39 . Between them and the magazines  1  the transfer units  2  are arranged ( FIG. 6 ) with which the labels are removed from the magazine  1 , respectively, and transferred to the corresponding suction holders  41  of the linear units  38 ,  39 . As shown in  FIG. 3 , while the injection mold  4  is closed, by means of the suction holders  40 ,  41  the labels  12  are transferred to the insertion units  3  and, at the same time, the plastic cups  24  are removed from the removal units  25 . The labels  12  are wound in a cup shape, as in the injection molding machine according to  FIGS. 1 and 2 , about the suction holder  41  by suction air.  
      As shown in  FIG. 6 , in the movement direction on both sides of the linear units  38 ,  39  suction holders  40 ,  41  are provided. The linear units  38 ,  39  are moved into the transfer position illustrated in  FIG. 6  in which the plastic cups  24  secured by vacuum on the suction holders are transferred to the putting-down units  30 . The suction holders  34 ,  35  of the putting-down units  30  are configured such that simultaneously two plastic cups  24  can be received from the linear units. The plastic cups  24  that are seated on the suction holders of the linear units  38 ,  39  are blown off for transfer to the putting-down units  30  and by means of vacuum secured on the suction holders  34  or  35 . Subsequently, the putting-down units  30  are rotated about axle  28  by 180 degrees so that the plastic cups  24  on the suction holders  34 ,  35  are positioned opposite the receptacles  31 . The suction holders  34 ,  35  are extended in order to move the plastic cups  24  into the receptacles  31 . At the same time, by means of the suction holders of the other arm of the putting-down units  30 , the next plastic cups are removed from the removal units  25  in the described way. By pivoting the putting-down units  30  about the inclined axles  28 , the plastic cups  24  are stacked within a very short period of time in the receptacles  31 .  
      As shown in  FIG. 10 , the insertion unit  3  and the removal unit  25  in the initial position can also be arranged at an angle of approximately 90 degrees relative to one another. The insertion units  3  have the receiving head  17  provided at the free end of the arm  16  which receiving head receives the label to be inserted into the injection mold  4  in the way described above. It is transferred by means of the receiving part  9  of the transfer unit  2 . In accordance with the embodiment of FIGS.  3  to  5  and  9 , the removal units  25  have the arm  27  that projects transversely from the axle  26  and is provided at its free end with the suction holder  29  for removing the finished plastic cup  24 . It is transferred to the putting-down unit  30  in the described way that is illustrated only partially in  FIG. 10 .  
      The injection molding machine has a high output because by means of the stand  5  and the transfer units  2  provided on both sides the removal of the labels  12  from the magazine  1  and the transfer to the insertion units  3  is performed simultaneously. The transfer units  2  or their receiving parts  9  must perform only a very short stroke in order to transfer the labels  12  to the receiving heads  17  of the insertion units  3 . The label transfer is therefore performed very quickly. The receiving heads  17  of the insertion units  3  are provided about their circumference with slots (not illustrated) by means of which the suction air can act on the labels  12 . By applying vacuum, the labels  12  are automatically wound in a cup shape onto the receiving heads  17 .  
      When the receiving units  25  are embodied in accordance with  FIGS. 1, 2 ,  7 , and  8 , there is a very simple and quick transfer of the injection-molded plastic cups  24  to the putting-down units  30 . When the injection molding machine has several injection molds, for example  4  or  6 , then a corresponding number of magazines  1 , transfer units  2 , insertion units  3 , removal units  25 , and putting-down units  30  as well as receptacles  31  are provided. The molded parts  20 ,  22  are exchangeable so that a format change of the plastic cups can be done simply and quickly. By means of the putting-down units  30  the plastic cups  24  are reliably inserted into the receptacles  31  so that they can be stacked trouble-free in the receptacles  31 . When several plastic cups  24  are transferred simultaneously and inserted into the receptacles  31 , within a unit of time a very large number of plastic cups can be produced. The injection molding machine in this connection is very compact so that it can be installed even when tight space conditions are present. The described movements of the individual units of the injection molding machine are possible without plane-motion direct-contact mechanism only by means of servo motors or path control. The described winding technology, i.e., winding of the labels  12  onto the receiving heads  17  by applying vacuum, is suitable also for deep-drawing plastic cups. Insertion of the plastic cups  24  into the receptacles  31  is realized parallel to the injection molding process of the next plastic cups  24  so that a targeted stacking of the plastic cups  24  and injection molding of new the plastic cups can be performed simultaneously. In a configuration of the injection molding machine in accordance with  FIGS. 1, 2  and  7  through  9 , very short cycle times result. For insertion of the labels and the essentially simultaneous removal of the plastic cups  24 , the injection mold must be opened only for a very short period of time. The opening time of the injection mold is within a magnitude of approximately 0.2 to 0.4 seconds. This opening time of the mold is thus significantly reduced in comparison to injection molding machines with a linear system in which the insertion units  3  or the removal units  25  are not moved by a pivot movement but a linear movement into the open injection mold  4 .  
      The injection molds  4  can be arranged horizontally, vertically but also inclined within the injection molding machine. Accordingly, other units of the machine then have appropriately adjusted positions.