Abstract:
Shuttle blow molding apparatus having an extruder or a blow head for substantially continuously emitting a thermoplastic material in tubular or parison form at a moldable temperature downwardly along a vertical axis. A finite length of the thermoplastic material is grasped by a first mold set, which then moves downwardly with respect to the extruder or blow head to provide clearance for a second mold set to move to a position to grasp a second finite length of the emitted thermoplastic. The first mold set is then moved horizontally away to permit the emitted thermoplastic length therein to be blown into a hollow article, and thereafter removed from the first mold set that is permitted to return and engage an other finite length of the thermoplastic material. The second mold set follows the first mold set in a path of travel traced by the first mold set. A single in-mold labelling device can be provided to sequentially apply labels to the interior of the mold sets, while the mold sets are open, for application to the articles being blown in the mold sets.

Description:
FIELD OF THE INVENTION 
     This invention relates to a method of, and apparatus for, blow molding hollow articles of a thermoplastic material. More particularly, this invention relates to a method of, and apparatus for, blow molding hollow containers of a thermoplastic material. 
     BACKGROUND OF THE INVENTION 
     The production of thermoplastic containers by shuttle blow molding is described, for example, in U.S. Pat. No. 3,614,807 (Lagoutte). In shuttle blow molding, two or more sets of blow molds, each of which is made up of a pair of mold halves that open and close relative to each other, are moved, in sequence, to engage an extruded tube of thermoplastic material at a moldable temperature, or a spaced apart plurality of such tubes in equipment used to simultaneously manufacture a plurality of containers in each mold set. Each mold set is then moved laterally away to a station where the portion of the tube in the mold set is blown into its desired configuration, as determined by the configuration of a cavity that is defined by the halves of the mold set, the lateral movement of each mold set often involving a first motion coaxial with the extruded tube to stretch the tube to properly size it and/or to axially orient material therein. The halves of the mold set are then opened to permit removal of the blown article, and the mold set is then returned to grasp another section of the extruded tube or tubes for a repeat of the process. The mold sets of a given shuttle blow molding machine move in predetermined paths relative to one another so that sequential portions of the-extruded tube are usually grasped by one or another of the mold sets, without the need to employ intermittent extrusion of the thermoplastic tube or tubes. 
     In the manufacture of containers by shuttle blow molding it has become popular to apply labels to the containers, by introducing a label or an opposed pair of labels into the open molds before the preforms or parisons are engaged thereby, by equipment that applies labels to the interiors of the open mold halves, and this equipment is generally described as in-mold labelling equipment. Known types of in-mold labelling equipment have the capacity to feed labels to the mold sets of a shuttle blow molding machine at a rate equal to the total of the production rates of all mold sets of the shuttle blow molding machine. Unfortunately, however, known types of shuttle blow molding machines position the various mold sets at different positions from one another while containers are being blown therein. This, then, requires an in-mold labelling machine for each mold set, notwithstanding that the total capacity of the multiple in-mold labelling machines for a given shuttle blow molding machine far exceeds the molding capacity of all the mold sets of the machines. The use of an in-mold labelling machine in connection with a shuttle blow molding machine is described, for example, in U.S. Pat. No. 4,769,205 (Oles et al.). 
     Another disadvantage of known types of shuttle blow molding machines that applies even when the machine is not being used to apply labels to the containers in the mold is that article removal equipment must be provided for each mold set, because the article removal positions of the various mold sets differ from one another. 
     SUMMARY OF THE INVENTION 
     Shuttle blow molding apparatus according to the present invention is made up of an extruder that continuously, vertically downwardly extrudes a tube, or a plurality of spaced apart tubes, or a blow head that continuously produces parisons of containers, along a vertically downwardly extending path. The extruded tube or parison is made up of thermoplastic material at a suitable temperature for blow molding into a useful article, or articles, such as a container, or containers, of the type used in a wide variety of packaging applications. The shuttle blow molding apparatus also includes pair of mold sets, or a superimposed plurality of pairs of mold sets, each set being made up of an opposed pair of mold halves that close and open with respect to each other, and the inside surfaces of the mold halves are configured so that the mold halves, when closed, define a cavity, or a plurality of cavities in the case of apparatus having a multi-tube extruder, in which an article is blown from a length of extruded tube to conform to the configuration of a cavity. 
     The shuttle blow molding apparatus of the present invention also includes apparatus for moving each mold set, in sequence, to an elevated position in which it grasps a length of extruded tube and then downwardly to permit another mold set to engage another length of extruded tube, with some stretching of the extruded tube, if desired, being done during the downward motion of a mold set. Preferably, the first mold set remains in engagement with the extruded tube until the second mold set engages the tube for controlled stretching of the tube for optimum material distribution and for more accurate positioning of the extruded tube until it is engaged by the second mold set. 
     In any case, after each mold set has reached a lower position, it is moved laterally, and preferably along a downward incline, to permit the section of the tube in the mold set, whose halves are now closed, to be blown into the intended article. At the conclusion of the blowing operation, the mold set, now no longer vertically aligned with the extruder, is moved upwardly to the elevation at which it will grasp another length of tube for a repeat of the cycle, but still out of vertical alignment with the extruder. At this position, the halves of the mold set are opened and the blown article(s) removed, whereupon the mold set is moved horizontally back to its start position to grasp another length of tube to begin a repeat of the cycle. In this manner, each mold set discharges molded articles at the same location, and only one set of take-off equipment is required for each multiple mold set shuttle blow molding apparatus. 
     When desired, a single in-mold labelling device may be used to apply labels to the interiors of the mold sets in which each of the parisons in a series are extruded before the parisons are blown into containers by the mold sets of a shuttle blow molding apparatus according to the present invention. In this case it is only necessary to begin the process with a slightly pre blown parison that is emitted by a die head into which compressed air, in addition to molten plastic, is introduced. Alternatively, the shuttle blow molding apparatus according to the present invention is adaptable to the manufacture of tandem containers in which each tandem is made up of a pair of containers, each of which is joined open end to open end, which is popular for the manufacture of relatively small containers, for example, six ounce containers. The shuttle blow molding apparatus according to the present invention is also adapted to the manufacture of large containers with integral handles, and it is adapted to the manufacture of containers with precisely calibrated, closure-receiving finishes. 
     Accordingly, it is an object of the present invention to provide an improved method of, and apparatus for, producing hollow articles of a thermoplastic material in multiple mold sets that move, in sequence, in closed paths relative to an extruder. More particularly, it is an object of the present invention to provide a method and apparatus of the foregoing character in which finished articles can be removed from each of the mold sets at only a single position. It is also an object of the present invention to provide a method and apparatus of the foregoing character in which labels can be applied to the interiors of open mold sets at a single location prior to the blowing of parisons into containers in the mold sets. 
     For a further understanding of the present invention and the objects thereof, attention is directed to the drawing and the following brief description thereof, to the detailed description of the invention and to the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     FIG. 1 is a front elevational view of apparatus according to the present invention for producing blown articles of a thermoplastic material; 
     FIG. 2 is a side elevational view of the apparatus of FIG. 1; 
     FIGS. 3-8 are schematic views illustrating a sequence of steps to be followed in producing tandem blow molded containers by apparatus generally corresponding to that of FIGS. 1 and 2; 
     FIGS. 9-12 are schematic views illustrating a sequence of steps to be followed in producing blow molded containers with calibrated finishes by apparatus generally corresponding to that of FIGS. 1 and 2; and 
     FIGS. 13-15 are schematic views illustrating a sequence of steps to be followed in producing large containers with handles and pre applied labels by apparatus generally corresponding to that of FIGS.  1  and  2 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Shuttle blow molding apparatus according to the present invention is indicated generally by reference numeral  20  in FIGS. 1 and 2. The apparatus  20  includes an extruder  22  that substantially continuously downwardly extrudes a spaced apart pair of tubes T 1 , T 2  of thermoplastic material at a temperature sufficiently high to permit finite lengths of such tube to be blown into containers or other useful hollow articles. The blowing of successive lengths of each of the tubes T 1 , T 2  is done sequentially by a pair of mold sets  24 ,  26 , which may be of conventional construction. Each mold set  24  is made up of a pair of mold halves  24   a ,  24   b , which open and close with respect to one another to define, when closed, mold cavities in which lengths of the tubes T 1 , T 2  are blown into the desired articles. Likewise, each mold set  26  is made up of a pair of mold halves  26   a ,  26   b , which open and close with respect to one another to define, when closed, mold cavities in which successive lengths of the tubes T 1 , T 2  are blown into the desired articles. While the simultaneous molding of articles from tubes T 1 , T 2  is described, it is to be understood that it is contemplated that the apparatus  20  can be used to produce only one article at a time from a single extruded tube, or multiple articles from each tube and to produce one or more articles at a time from each of three or more extruded tubes. 
     The mold set  24  is mounted on a frame  28  for reciprocating motion in a horizontal plane, and the frame  28  is mounted on one or more vertical cylinders  30  for reciprocating motion in a vertical plane. Similarly, the mold set  26  is mounted on a frame  32  for reciprocating motion in a horizontal plane, and the frame  32  is mounted on one or more vertical cylinders  34  for reciprocating motion in a vertical plane. The cylinders  30  and the cylinders  34  are mounted on carriages  36 ,  38 , respectively, and the carriages  36 ,  38  are mounted for reciprocating horizontal motion on slides  40 ,  42 , respectively. 
     FIGS. 1 and 2 illustrate a step in the operation of the apparatus  20  in which the mold set  24  is open and is positioned sufficiently high to engage freshly extruded finite lengths of the tubes T 1 , T 2 , but out of horizontal alignment with the tubes T 1 , T 2 , and the mold set  26  is positioned immediately below the mold set  24  and is open, after removal of blown articles therefrom. Then, the mold set  24  is moved horizontally, to the left from the portion shown in FIG. 2, to the position shown in FIG. 1 to engage the finite lengths of the tubes T 1 , T 2 , and the mold set  26  is moved upwardly to the position previously occupied by the mold set  24 . 
     After the mold set  24  engages and clamps the lengths of the tubes T 1 , T 2 , it moves downwardly to stretch the lengths of the tubes T 1 , T 2  engaged therein, and to blow such lengths into containers or other articles by the introduction of blowing air into the molds of the mold set  24  by means, not shown. At this time, the mold set  26  is also moved horizontally to engage subsequent finite lengths of the tubes T 1 , T 2 , preferably while the tubes T 1 , T 2  are still engaged by the mold set  24 , and the mold set  24  is then moved horizontally to a take-off position at its lowermost elevation permitted by the cylinders  30  to permit blown containers to be removed therefrom, and is then returned to its uppermost position out of alignment with the tubes T 1 , T 2  to be ready to again move to grasp finite lengths of the tubes T 1 , T 2  after the mold set  26  has been lowered to make way for the mold set  24  to move into alignment with the extruder  22 . Preferably, the motions of the mold sets  24 ,  26  from lowermost positions in alignment with the extruder  22  to positions out of alignment with the extruder  22  will be at a somewhat downwardly inclined angle to assist in severing of the finite tube lengths in the lowermost mold set from those in the uppermost mold set. 
     It is to be noted that the take-away location for the blown articles in the mold set  26  is exactly the same as that for the blown articles in the mold set  24 , namely, the position occupied by the mold set  26  in FIG.  2 . Thus, the apparatus  20  does not require multiple sets of article removal equipment, notwithstanding that it employs multiple mold sets in the manufacture of plastic articles. Further, it is to be understood that the apparatus  20  may be used to manufacture plastic articles with three or more mold sets, notwithstanding that only two such mold sets are shown in FIGS. 1 and 2. 
     In the embodiment of FIGS. 3-8, elements that correspond to the elements of the embodiment of FIGS. 1 and 2 are identified by a 100 series numeral, the last two digits of which correspond to the two digits of the corresponding element of the embodiment of FIGS. 1 and 2. 
     Shuttle blow molding apparatus according to the embodiment of the invention illustrated in FIGS. 3-8 is indicated generally by reference numeral  120 , and the apparatus  120  includes an extruder  122  that substantially continuously downwardly extrudes a spaced apart pair of tubes T 1 , T 2  of thermoplastic material at a temperature sufficiently high to permit finite lengths of such tubes to be blown into containers or other useful articles. The blowing of successive lengths of each of the tubes T 1 , T 2  is done sequentially by a pair of mold sets  124 ,  126 , which may be of conventional construction. The mold sets  124 ,  126 , differ from the mold sets  24 ,  26  of the embodiment of FIGS. 1 and 2, respectively, in that each of the mold sets  124 ,  126  is suited for the manufacture of blown containers in tandem, that is, a pair of blown containers being simultaneously molded in each mold cavity and joined to each other open end to open end. In any case, the mold set  124  is also provided with bottom molds  124   c ,  124   d , and the mold set  126  is also provided with bottom molds  126   c ,  126   d . The motion of the mold sets  124 ,  126  through the various portions of the closed cycles that they move through, as will be hereinafter explained more fully, may be actuated by equipment, not shown, corresponding to the equipment used to move the mold sets  24 ,  26  of the embodiment of FIGS. 1 and 2 through the various steps of their motion cycles. 
     The motion cycle practiced by the apparatus  120  of FIGS. 3-8 may be considered to begin with the step that is illustrated in FIG. 3, wherein the mold set  124  is positioned at the higher of its two operating positions and out of alignment with the tubes T 1  and T 2 , and the mold set  126  is positioned at the lower of its two operating positions and also out of alignment with the tubes T 1  and T 2 . The next step in the cycle is the horizontal motion of the mold set  124  from the broken line position illustrated in FIG. 4 to a position in alignment with the tubes T 1  and T 2  to close on the tubes T 1  and T 2 , and this is preferably done with the extruded tubes T 1 , T 2  still engaged by the mold set  124  until the tubes T 1 , T 2  are engaged by the mold set  126 . Thereafter, as shown in FIG. 5, the mold set  124  is moved downwardly, to stretch the portions of the tubes T 1 , T 2  thereabove, and the mold set  126  is moved from its broken line position to its solid line position immediately thereabove. Then, the mold set  126  is moved into a position in alignment with the tubes T 1 , T 2 , from its broken line position as illustrated in FIG. 6, to its solid line position in FIG. 6, and, the mold set  124  moves further downwardly to provide clearance for the mold set  126  to move into its position to engage the tubes T 1 , T 2 . Thereafter, as shown in FIGS. 7, the mold set  124  is moved from its position in alignment with the tubes T 1 , T 2 , as shown by the broken line position of the mold set  124  in FIG. 7, to a position out of alignment with the tubes T 1 , T 2 , and preferably slightly downwardly, as shown by the solid line position of the mold set  124  in FIG.  7 . The downward motion of the mold set  124  in moving from its broken line position in FIG. 7 to its solid line position in FIG. 7 helps to sever the lengths of the tubes T 1 , T 2  in the mold set  124  from the lengths of the tubes T 1 , T 2  in the mold set  126 . The next step in the cycle practiced by the apparatus  120  of FIGS. 3-8 is illustrated in FIG. 8, wherein the mold set  126  is moved downwardly, while still in alignment with the extruded tubes T 1 , T 2 , to stretch the portions of the tubes T 1 , T 2  thereabove and to provide for clearance for the mold set  124  to be moved in to a position in alignment with the tubes T 1 , T 2  for a repeat of the process. Simultaneously, the mold set  124  is moved from its lowermost position, as shown in broken line in FIG. 8, to its uppermost position, as shown in solid line in FIG. 8, and take-away equipment, which is indicated generally by reference numeral  144 , is provided to remove blown articles from the mold set  124 , before the mold set  124  is moved from its solid line position in FIG. 8 to its solid line position in FIG.  4 . 
     In the embodiment of FIGS. 9-12, elements that correspond to the elements of the embodiment of FIGS. 1 and 2, or the embodiment of FIGS. 3-8, are identified by a 200 series numeral, the last two digits of which are the digits of the corresponding element of the embodiment of FIGS. 1 and 2, or the embodiment of FIGS. 3-8, as the case may be. 
     Shuttle blow molding apparatus according to the embodiment illustrated in FIGS. 9-12 is generally indicated by reference numeral  220 . The apparatus  220  includes an extruder  222  that substantially continuously downwardly extrudes a spaced apart pair of tubes T 1 , T 2  of thermoplastic material at a temperature sufficiently high to permit finite lengths of such tubes to be blown into containers or other useful hollow articles. The blowing of successive lengths of each of the tubes T 1 , T 2  is done sequentially by a pair of mold sets  224 ,  226 , which may be of conventional construction. The mold sets  224 ,  226 , are mounted for vertical motion and horizontal motion independently of each other by means, not shown, which may be similar to that illustrated in FIGS. 1 and 2. 
     FIG. 9 illustrates a step in the process practiced by the apparatus of FIGS. 9-12 in which the mold set  224  has just moved horizontally from a position out of alignment with the tubes T 1 , T 2 , as shown in broken line, to a position in alignment with the tubes T 1 , T 2 , as shown in solid line. At this time, the mold set  226  has moved downwardly from the position now occupied by the mold set  224 , causing a stretching of the tubes T 1 , T 2 , and movement of the articles in the mold  15  set into engagement with blow pins  246 , which are carried by a blow air manifold  248 . The blow pins  246  extend into the open ends of the articles in the mold set  226 , and the open ends of such articles, which are conventionally called finishes, are molded against the exterior of the blow pins  246 , to form very precisely calibrated finishes. 
     At the conclusion of the step illustrated in FIG. 9, the mold set  226  is moved, with the blow pins  246  and the blow air manifold  248 , from the position illustrated in broken line in FIG. 10 outwardly and downwardly to the position illustrated in solid line in FIG.  10 . The mold set  226  is then moved upwardly, still in engagement with the blow pins  246  to the position illustrated in FIG. 12, where the mold set  226  is now in position to be moved horizontally to engage finite lengths of tubes T 1  and T 2 , the mold set  224  having been moved downwardly to stretch the extruded tubes T 1  and T 2  and to bring the open ends of the containers in the mold set  224 , into engagement with another set of blow pins  246  that are carried by another blow air manifold  248 . 
     In the embodiment of the invention as illustrated in FIGS. 13-15, elements corresponding to the elements of the embodiment of FIGS. 1 and 2, or to the embodiment of FIGS. 3-8, or to the embodiment of FIGS. 9-11, are identified by a 300 series numeral, the last two digits of which are the two digits of the corresponding element of the invention of FIGS. 1 and 2, or the invention of FIGS. 3-8, or the invention of FIGS. 9-12, as the case may be. 
     Shuttle blow molding apparatus according to the embodiment of the invention that is illustrated in FIGS. 13-15 is indicated generally by reference numeral  320  in FIGS. 13-15. The apparatus  320  includes a blow head  322  that substantially continuously extrudes a series of parisons P from an extruded tube, the blow head  322  being an extruder with a source of compressed air leading thereinto to partially preblow the extruded tube into the parisons P 1 , and FIG. 13 illustrates a step in the cycle of operation of the embodiment of FIGS. 13-15 where a retractable in-mold labelling device  350  is being retracted after having applied a label L to an open mold set  324  or  326  that is positioned to engage a parison P that has just been emitted from the blow head  322 . The mold set  324 , which is out of vertical alignment with the blow head  322 , is then moved horizontally to engage the parison P to move it downwardly from the blow head  322  and form a blow molded article, such as a handle container, therein. While the mold set  324  is being moved downwardly with respect to the blow head  322 , another mold set  326  is moved upwardly from the position illustrated in FIG. 13, where it is positioned below the mold set  324 , into the position previously occupied by the mold set  324 , so that it is now in a position to move into alignment with the blow head  322  and engage another parison P, after the application of a label L to the interior of successor mold set by the in-mold labelling device  350 . This condition of the apparatus  320  is illustrated in FIG.  14 . 
     FIG. 15 illustrates a subsequent step in the operation of the apparatus  320  in which the mold set  326  has been moved into a position in alignment with the blow head  322 , as shown by the solid line position of the mold set  326 , from the position of the mold set  326  immediately prior thereto, which is illustrated in broken line. 
     Thus, in the embodiment of FIGS. 13-15, a plurality of labelled useful articles can be produced by apparatus having a plurality of mold sets with only a single set of in-mold labelling equipment, notwithstanding that there are a plurality of mold sets in which the articles are formed. 
     Although the best mode contemplated by the inventors for carrying out the present invention as of the filing date hereof has been shown and described herein, it will be apparent to those skilled in the art that suitable modifications, variations and equivalents may be made without departing from the scope of the invention, such scope being limited solely by the terms of the following claims and the legal equivalents thereof.