Abstract:
A method of reforming the end portion and sealing surface of a blow molded plastic container includes directing energy from a non-contact heater onto the annular end portion of the container neck finish so as to heat the end surface to its softening temperature while leaving the remainder of the neck finish relatively unheated. The heated annular end portion of the neck finish is then engaged by an unheated forming tool so as to reform and cool the end sealing surface of the neck finish. Heating and reforming the neck finish end portion in separate steps allows the heating step to be controlled either by intensity of the heat source or dwell time of the container adjacent to the heater. Employing an unheated forming tool reduces the tendency of the container neck finish to stick to the tool.

Description:
[0001]     The present invention relates to blow molded plastic containers, particularly extrusion blow molded plastic containers, and more particularly to reforming the end surface of the container neck finish after molding and trimming.  
       BACKGROUND AND SUMMARY OF THE INVENTION  
       [0002]     Extrusion blow molding plastic containers involves extruding a tube of monolayer or multilayer plastic material, capturing the tube between opposed mold sections, blowing the tube to the contours of the mold cavity, opening the mold, removing the container, and trimming the end of the container neck finish. This trimming operation can involve removal of a dome or moil from the neck finish, which is a convenience element for the blow molding operation and can be recycled as process regrind. In another type of extrusion blow molding operation, the trimming operation can involve separation of two containers that are molded end-to-end. In either event, the trimming operation can leave an uneven end surface for later sealing engagement with a container closure. Furthermore, the end surface of the container neck finish may have mold parting line seams that can deleteriously affect sealing engagement with a container closure. It typically is necessary to induction weld a liner disk to the container end surface after filling the container to obtain a satisfactory container seal.  
         [0003]     It has been proposed to reform the end surface of the neck finish by contacting the neck finish end surface with a heated forming tool. This tool simultaneously heats the end portion of the neck finish to the softening temperature of the plastic material, and reforms the end surface in an effort to eliminate mold parting line seams, trim scars and other post-molding scars. However, the container neck finish tends to stick to the hot forming tool. It is also difficult to control the temperature of the forming tool so as to obtain a desired temperature at the forming surface of the tool. Furthermore, the combination of the tendency of the container to stick to the forming tool and the difficulty of controlling the forming surface temperature of the tool makes the tool/container contact time process window very narrow and difficult to control. The dwell time, during which the forming tool is in contact with the end portion of the neck finish, should be minimized to achieve desired production speeds. It is a general object of the present invention to provide a method and apparatus for reforming a container neck finish end surface after molding to prepare the end surface for enhanced sealing engagement with a closure, which overcome some or all of the problems and difficulties previously discussed. Another general object of the present invention is to provide a container having a neck finish end sealing surface reformed employing the method and/or the apparatus of the present invention.  
         [0004]     A method of reforming the end portion and sealing surface of a blow molded plastic container in accordance with one aspect of the present invention includes directing energy from a non-contact heater onto the annular end portion of the container neck finish so as to heat the end surface to its softening temperature while leaving the remainder of the neck finish relatively unheated. The heated annular end portion of the neck finish is then engaged by an unheated forming tool so as to reform and cool the end sealing surface of the neck finish. Heating and reforming the neck finish end portion in separate steps allows the heating step to be controlled by the intensity of the heat source and/or the dwell time of the container adjacent to the heater. Employing an unheated forming tool reduces the tendency of the container neck finish to stick to the tool. The container neck finish can be heated with additional or more powerful non-contact heaters while not affecting the dwell time in contact with the forming tool, thereby giving a greater level of process control.  
         [0005]     An apparatus for reforming an end portion and sealing surface of a blow molded plastic container in accordance with another aspect of the present invention includes a non-contact heater for focusing radiant heat energy onto a container neck finish end portion to heat at least an end surface of the end portion to the softening temperature of the plastic material while leaving the remainder of the neck finish relatively unheated. An unheated forming tool is provided to contact, reform and cool the end portion of the container finish after heating by the heater. The unheated forming tool preferably has a surface for engagement with the heated end portion of the container neck finish. In two preferred embodiments of the invention, the unheated forming tool has a portion for opposed abutment with a shoulder on the unheated portion of the container neck finish or with tooling that engages the container neck finish to limit engagement of the reforming tool with the neck finish.  
         [0006]     A plastic container in accordance with a further aspect of the present invention has a blow molded and trimmed neck finish with an axially facing end surface that is free of mold parting line seams, trim scars and other post-mold scars. In preferred embodiments in accordance with this aspect of the invention, the blow molded and trimmed neck finish has a radially inwardly extending end flange, with the end flange having an external surface forming the axially facing end surface of the neck finish. In accordance with yet another aspect of the invention, the neck finish has an end surface, preferably planar, and a flange, preferably circumferentially continuous, that extends radially inwardly and axially downwardly from the neck finish end surface.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     The invention, together with additional objects, features , advantages and aspects thereof, will be best understood from the following description, the appended claims and the accompanying drawings, in which:  
         [0008]      FIG. 1  is a schematic diagram that illustrates non-contact heating of the end portion of a container neck finish in accordance with one presently preferred aspect of the invention;  
         [0009]      FIG. 2  is a schematic diagram that illustrates contacting the heated container neck finish end portion with a forming tool in accordance with one embodiment of the present invention;  
         [0010]      FIG. 3  is an enlarged fragmentary view of the portion of  FIG. 2  within the area  3 ;  
         [0011]      FIG. 4  is a fragmentary schematic diagram that illustrates a container neck finish end portion and forming tool in accordance with a second embodiment of the invention;  
         [0012]      FIG. 5  is a fragmentary sectional view on an enlarged scale of the portion of  FIG. 4  within the area  5 ;  
         [0013]      FIGS. 6 and 7  are sequential schematic diagrams similar to that of  FIG. 5  but showing sequential steps in accordance with the method of the present invention;  
         [0014]      FIG. 8  is a schematic diagram of a further embodiment of the invention;  
         [0015]      FIG. 9  is a fragmentary view on an enlarged scale of the portion of  FIG. 8  within the area  9 ;  
         [0016]      FIG. 10  is a fragmentary sectional view of a container neck finish reformed in accordance with one aspect of the present invention; and  
         [0017]      FIGS. 11 and 12  are fragmentary sectional views showing a further embodiment of the forming head in accordance with the present invention.  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0018]      FIGS. 1-3  illustrate a method and apparatus for reforming the end sealing surface of a plastic container neck finish in accordance with one presently preferred embodiment of the invention. Referring to  FIG. 1 , a plastic container  10  has a neck finish  12  with an end portion  14  that includes a radially inwardly and axially upwardly extending flange  16 . (Directional words such as “upwardly” and “downwardly” are employed by way of description and not limitation with respect to the orientation of the apparatus and the containers illustrated in the drawings. Directional words such as “axial” and “radial” are employed by way of description and not limitation with respect to the axis of the container finish or the reforming tool as appropriate.) Flange  16  typically is formed by a trimming operation after extrusion blow molding, for example, in which container  10  is severed from a moil or the like. Flange  16  as initially formed has a radially outwardly and axially upwardly facing surface that typically forms the end sealing surface of the neck finish.  
         [0019]     Neck finish  12  of container  10  is positioned adjacent to a non-contact heater  18 . By “non-contact” is meant that the heating energy is transferred to neck finish  12  by radiation, and not by physical contact with the neck finish. Heater  18  may comprise an infrared heater, a quartz lamp, a focused light or the like. Heater  18  preferably is constructed to focus the heating energy onto the neck finish end portion  14  so as to heat at least the end surface of flange  16  to the softening temperature of the plastic material while leaving the remainder of neck finish  12  substantially unheated. That is, the end portion of the neck finish, comprising at least the end surface, is heated to its softening temperature, while the remainder of the neck finish (and indeed the remainder of the container) is substantially unheated by heater  18 .  
         [0020]     After heating neck finish end portion  14 , a forming tool head  20  is brought into contact with the end portion of the container neck finish, as shown  FIGS. 2 and 3 . Forming tool head  20 , which is unheated, preferably includes a shell  22  having a central plug  24  removably received therein. Adjacent end portions of shell  22  and plug  24  form an annular channel  26  for opposed facing engagement with finish end portion  14 . That is, after heating finish end portion  14  to its softening temperature, unheated forming tool head  22  is brought into contact with the container neck finish so that heated end portion  14  is engaged under pressure by the opposing surface of channel  26 . The neck finish end portion thereby is reformed, cooled and solidified by the opposing surface of channel  26  so as to form a smooth neck finish end surface for sealing engagement with a closure or the like. Plug  24  is threadably received within shell  22  in this embodiment so that the adjacent portions of channel  26  can be brought into alignment without having a shoulder or step in the channel surface between the plug and shell. This threaded engagement is illustrated at  28  in  FIG. 2 . Plug  24  and shell  22  preferably are such that a small radial gap  31  extends from channel  26  to pocket  30 . This gap  31  preferably is annular and of substantially uniform radial width, such as on the order of 0.001 inch. Gap  31  allows air to vent from the contact area of channel  26 . Gap  31  also functions as a thermal barrier between plug  24  and chuck  22 . Pocket  30  preferably is connected to the external atmosphere by one or more passages  32  to minimize heating of plug  26  and chuck  22  due to contact with the container neck finishes during reforming, and to vent the air from gap  31 .  
         [0021]      FIGS. 1 and 4 - 7  illustrate a reforming apparatus and process in accordance with a second embodiment of the invention. In  FIGS. 4-7 , the forming tool head  34  includes a shell  36  and a plug  38 . Shell  36  and plug  38  have opposed channel segments that together form a annular channel  40  for engaging and reforming the container neck finish end portion, as in the previous embodiment. Plug  38  again is positionable within shell  36  in this embodiment to bring the adjacent channel segments into smooth alignment, and air channels and passages  42 ,  44 ,  46 ,  48  are provided in plug  38  and shell  36  to minimize heating of the surfaces that form forming channel  40 . An air vent gap  31 , preferably annular, circumferentially continuous and of substantially uniform radial dimension, again is formed between the outer periphery of plug  38  and the opposing surface of shell  36 , both of which preferably are cylindrical.  
         [0022]     The container  50  illustrated in  FIGS. 4-7  has a neck finish  52  with an end portion  54  and a flange  56  in accordance with another aspect of the invention. That is, as best seen in  FIG. 5 , flange  56  has an external groove  58  that extends circumferentially around the flange, at about the mid portion of the flange, in a plane perpendicular to the axis of the neck finish. The purpose of groove  58  is to localize bending of flange  56  during the reforming operation to the end portion of the flange, as shown in  FIG. 7 . Neck finish end portion  54  also has an axially facing shoulder  60  in the embodiment of  FIGS. 4-7 . This axially facing external shoulder  60  cooperates with an opposed axially facing shoulder  62  on shell  36  to limit axial motion of toot  34  and container neck finish  52  with respect to each other, as shown in  FIG. 7 , and thereby to limit and control bending of flange  56  and to maintain dimensional tolerance stability during the reforming operation. Neck finish shoulder  60  preferably is spaced sufficiently from flange  56  so as not to be heated substantially by the focused energy from heater  18  ( FIG. 1 ), so that contact by tool shoulder  62  does not reform shoulder  60 .  
         [0023]      FIGS. 8 and 9  illustrate a reforming tool head  70  in accordance with another embodiment of the invention. Head  70  includes a shell  72  and a plug  74  that are mounted to a holder  76  by a screw  78 . An air vent gap  31  again is formed between the outer periphery of plug  74  and the opposing surface of shell  72 . A collar  80  is adjustably threadably received on holder  76 . Collar  80  preferably is adjusted on holder  76  to abut a pair of clamp arms  82 ,  84  that hold container  50  in position beneath head  70 . Thus, collar  80  cooperates with clamp arms  82 ,  84  to limit and control the bending of flange  56 , but without contacting a shoulder on container finish  52  as in the embodiment of  FIGS. 4-7 .  FIG. 8  also illustrates cooling of head  70  by means of a pump  86  that circulates a coolant, such as a water/glycol mixture, through a chiller  88 . Chiller  88  has an associated control  90  for setting a desired coolant temperature.  
         [0024]      FIGS. 11-12  illustrate a reforming tool head  100  in accordance with a further embodiment of the invention. A shell  102  has a pocket  104  within which a plug  106  in mounted by a screw  108 . Plug  106  has a conical surface  110  and a peripheral flat surface  112  that faces the neck finish of the container. When head  100  is brought into engagement with the container neck finish ( FIG. 12 ), the flange  56  is engaged by the conical surface  110  to reform the flange axially inwardly. The end surface  92  is engaged by the flat surface  112 .  
         [0025]     In the four illustrated embodiments of the invention ( FIGS. 1-3 ,  FIGS. 1 and 4 - 7 ,  FIGS. 1 and 8 - 9 , and  FIGS. 1 and 11 - 12 ), the neck finish end portion is first subjected to focused non-contact heating so as to heat at least the end surface of the neck finish end portion to its softening temperature while leaving the remainder of the neck finish substantially unheated. The neck finish end portion is then engaged by an unheated forming tool so as to reform the heated and softened end portion of the neck finish. As noted above, the heating operation can be accomplished using various techniques, including an infrared lamp, radiant heater, quartz lamp, focused light energy, etc. The unheated forming tool may be at room temperature (ignoring the heating effects due to contact with the heated neck finish end portion), or may be cooled by circulation of a coolant fluid such as air or another media. The pressure applied by the forming tool and the reforming tool contact time may be adjusted empirically to obtain the desired end surface reformation at the container neck finish end portion. The neck finish end portion takes the shape of the opposing surface(s) of the forming tool, which leaves the neck finish end surface free of features that can deleteriously affect the ability to seal against the neck finish end surface, such as mold parting line mismatch seams, nicks and other features created in the production and trimming process. The neck finish  52  in  FIG. 10  has an end surface that preferably is planar, and a flange  56  (or  16  in  FIGS. 1-3 ) that extend radially inwardly and axially downwardly from the end surface. Flange  56  preferably is circumferentially continuous.  
         [0026]     The container of the present invention can be of monolayer plastic construction, or can be of multilayer plastic construction in which intermediate layers may or may not extend into the neck finish end portion of the container. At least the end surface of the container neck finish end portion is heated to a temperature at which the plastic is soft and suitable for reforming. For polypropylene, it has been found that the reforming temperature can be in the range of about 220 to 320\F, more preferably about 275 to 315\F, and most preferably about 300\F. The forming surface of the unheated reforming tool is maintained at a temperature of not more than about 100\F. In an implementation of the embodiment of  FIGS. 8-9 , chiller  88  is controlled to maintain a temperature of about 60\F at reforming head  70 . The heated neck finish is engaged by the reforming tool preferably about three seconds or less after heating.  
         [0027]     There have thus been disclosed an apparatus and method for reforming a container neck finish end surface, and a container having a reformed neck finish end surface, that fully satisfy all of the objects and aims previously set forth. The invention has been disclosed in conjunction with three presently preferred embodiments thereof, and a number of modifications and variations have been discussed. Other modifications and variations will readily suggest themselves to persons of ordinary skill in the art. Although the invention has been disclosed in conjunction with reforming the trimmed end of an extrusion blow molded container neck finish, the invention in its broadest aspects can be applied to other types of container neck finishes. For example, the invention in its broadest aspects can be implemented in conjunction with injection or compression molded neck finishes on containers made in a reheat blow molding operation or an injection/extrusion/blow molding operation. The invention is intended to embrace these and all other modifications and variations that fall within the spirit and broad scope of the appended claims.