Patent Publication Number: US-2022234252-A1

Title: Injection molding machines and related methods for producing preforms

Description:
This application is a continuation of International Application Serial No. PCT/CA2020/051384, filed Oct. 16, 2020, which claims the benefit of Provisional Application Ser. No. 62/915,965, filed Oct. 16, 2019, the entire contents of which are hereby incorporated by reference. 
    
    
     FIELD 
     The specification relates generally to injection molding, and more specifically to injection molded preforms, and injection molding machines and related methods for producing preforms. 
     BACKGROUND 
     U.S. Pat. No. 5,759,654 (Cahill) discloses an injection molding process for making a multiple layer, plastic structure. A plastic sleeve is placed and then enclosed in a mold cavity. A flowing heated plastic is conducted into the mold cavity, radially inside the sleeve, and forced radially outward against the sleeve. The flowing plastic forces the sleeve outward and forms, with the sleeve, an integrally bonded laminated structure. The mold is opened and the plastic structure is removed, and this structure may then be reformed to form a container particularly suitable for containing beverages, foods, cosmetics, pharmaceuticals and chemicals. 
     U.S. Pat. No. 4,797,244 (Sauer) discloses a multiwalled plastic container having a barrier liner and an outer wall providing structural support for the liner. 
     U.S. Pat. No. 5,851,471 (Schloss et al.) discloses a method of injection molding a multi-layer preform from a combination of virgin and recycled plastic such as PET so that the resultant blow-molded bottle has a reduced tendency for bottom failure in spite of the use of recycled plastic. A first plastic preform for providing the inner layer of the multi-layer preform is provided with spaced channels on the exterior surface of a closed end thereof extending from a central region of that end to the sidewalls. An injection mold cavity is provided with a like plurality of channels formed therein in a closed end thereof communicating with the injection gate of an injection molding apparatus. The first plastic preform is inserted into the injection mold cavity with the respective channels of the preform and the injection mold cavity substantially aligned. A second layer of plastic material is overmolded onto the first layer by injection molding in the cavity. A third layer of plastic material may be overmolded on the second layer to form a three-layer preform. Preferably the first and third layers are formed from virgin plastic and the second layer is formed from recycled plastic. 
     SUMMARY 
     The following summary is intended to introduce the reader to various aspects of the applicant&#39;s teaching, but not to define any invention. In general, disclosed herein are one or more methods or apparatuses related to injection molding. 
     According to some aspects, a method for injection molding a preform includes: (a) loading a barrier membrane into a first mold cavity; (b) injecting melt into the first mold cavity to undermold the barrier membrane and form a preform inner layer on an inside of the barrier membrane; (c) moving the preform inner layer and the barrier membrane from the first mold cavity into a second mold cavity; and (d) injecting melt into the second mold cavity to overmold the barrier membrane and form a preform outer layer on an outside of the barrier membrane. 
     In some examples, the barrier membrane is sealed between the preform inner layer and the preform outer layer. In some examples, the preform inner layer defines at least a portion of a preform interior surface of the preform, and the preform outer layer defines at least a portion of a preform exterior surface of the preform. 
     In some examples, the barrier membrane is formed of a generally thin, film-like article, shaped to line the first mold cavity, and impermeable to at least one of gas and light. 
     In some examples, step (a) includes positioning a sidewall of the barrier membrane and a base of the barrier membrane extending radially inwardly from the sidewall against a cavity inner surface of the first mold cavity, and step (b) includes injecting melt through a gate opening in the base of the barrier membrane. 
     In some examples, step (a) includes moving an end-of-arm tooling holding the barrier membrane from a retracted position, in which the end-of-arm tooling is clear of the first mold cavity, to an advanced position in which a loader of the end-of-arm tooling is in alignment with the first mold cavity for transferring the barrier membrane to the first mold cavity. 
     In some examples, during step (b), melt is injected into a first mold space between a membrane inner surface of the barrier membrane and a core outer surface of a mold core received in the first mold cavity. 
     In some examples, during steps (c) and (d), the preform inner layer is held on the mold core. 
     In some examples, step (c) includes rotating a center mold section holding the mold core from a first position in which the mold core is in alignment with the first mold cavity, to a second position in which the mold core is in alignment with the second mold cavity. 
     In some examples, during step (d), melt is injected into a second mold space between a membrane outer surface of the barrier membrane and a cavity inner surface of the second mold cavity. 
     According to some aspects, a method for injection molding a preform includes (a) loading a barrier membrane into a first mold cavity; (b) injecting melt into the first mold cavity to cover a first side of the barrier membrane with a first preform layer; (c) moving the first preform layer and the barrier membrane from the first mold cavity into a second mold cavity; and (d) injecting melt into the second mold cavity to cover a second side of the barrier membrane opposite the first side with a second preform layer. 
     In some examples, the barrier membrane is sealed between the first and second preform layers. In some examples, the first side of the barrier membrane corresponds to a membrane inner surface of the barrier membrane directed toward an interior of the preform, and the second side of the barrier membrane corresponds to a membrane outer surface of the barrier membrane opposite the membrane inner surface. 
     According to some aspects, an injection molded preform is formed according to one of the methods of the present disclosure. 
     According to some aspects, a preform extends along an axis between an open end and a closed end. The preform includes an preform inner layer; an preform outer layer; and an intermediate barrier membrane between the preform inner layer and the preform outer layer. The barrier membrane has a generally cylindrical membrane sidewall extending along the axis, a membrane base extending radially inwardly from the membrane sidewall at the closed end of the preform, and a gate opening in the membrane base. The gate opening is filled with material forming one of the inner preform layer and the outer preform layer. In some examples, the gate opening is coaxial with the axis. In some examples, the barrier membrane is sealed between the inner preform layer and the outer preform layer. 
     According to some aspects, an injection molding machine for producing preforms includes: (a) a base extending lengthwise along a horizontal machine axis; (b) a first platen supported by the base and holding a first mold section, the first mold section having a plurality of first mold cavities; (c) a second platen supported by the base and translatable relative to the first platen along the machine axis between mold-open and mold-closed positions, the second platen holding a second mold section, the second mold section having a plurality of second mold cavities; and (d) a rotary apparatus slidably supported by the base axially intermediate the first and second platens and translatable therebetween along the machine axis. The rotary apparatus holds at least one center mold section having a plurality of mold cores. When the platens are in the mold-open position, the rotary apparatus is operable to rotate the center mold section about a vertical axis among at least a first position and a second position. When the center mold section is in the first position, the mold cores are in alignment with the first mold cavities for forming a plurality of first molds when the platens are in the mold-closed position. The first molds are shaped for receiving a barrier membrane and undermolding the barrier membrane to form a preform inner layer on an inside of the barrier membrane. When the center mold section is in the second position, the mold cores are in alignment with the second mold cavities for forming a plurality of second molds when the platens are in the mold-closed position. The second molds are shaped for receiving the barrier membrane and the inner preform layer and overmolding the barrier membrane to form a preform outer layer on an outside of the barrier membrane. The machine further includes (e) a barrier membrane loading apparatus adjacent the first platen. The loading apparatus includes an end-of-arm tooling having a plurality of loaders for loading the barrier membranes into the first mold cavities. The end-of-arm tooling is moveable between a retracted position clear of the first mold cavities, and an advanced position in which the loaders are between the first and center mold sections and in alignment with the first mold cavities for transferring the barrier membranes to the first mold cavities. 
     In some examples, the machine further includes a first injection apparatus supported by the base for injecting melt into the first mold cavities, a second injection apparatus supported by the base for injecting melt into the second mold cavities, and a control system configured to: (i) operate the barrier membrane loading apparatus to move the end-of-arm tooling to the advanced position and load the barrier membranes into respective first mold cavities; (ii) operate the first injection apparatus to inject melt into each first mold to undermold each barrier membrane and form the preform inner layer on the inside of each barrier membrane; (c) operate the rotary apparatus to move the mold cores from the first position to the second position while the barrier membranes and corresponding preform inner layers are held on respective mold cores; and (d) operate the second injection apparatus to inject melt into each second mold to overmold each barrier membrane and form the preform outer layer on the outside of each barrier membrane. 
     In some examples, the rotary apparatus supports horizontally opposed first and second center mold sections and horizontally opposed third and fourth center mold sections perpendicular to the first and second center mold sections. Each center mold section is movable among at least the first and second positions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings included herewith are for illustrating various examples of articles, methods, and apparatuses of the present specification and are not intended to limit the scope of what is taught in any way. In the drawings: 
         FIG. 1  is a schematic elevation view taken from the operator side of an example injection molding machine shown in a mold-open condition; 
         FIG. 2  is a schematic elevation view like that of  FIG. 1 , but with the machine shown in a mold-closed condition; 
         FIG. 3  is a schematic side view of an example molded preform formed by the machine of  FIG. 1 ; 
         FIG. 3A  is a cross-sectional view taken along line  3 A- 3 A of the preform of  FIG. 3 ; 
         FIG. 3B  is a cross-sectional view taken along line  3 B- 3 B of the preform of  FIG. 3 ; 
         FIG. 4  is a schematic top view of a clamp portion of the machine of  FIG. 1 ; 
         FIG. 5A  is a schematic showing a loader of the machine of  FIG. 1  holding a barrier membrane of the preform of  FIG. 3  in alignment with and spaced apart from a first mold cavity of the machine of  FIG. 1 ; 
         FIG. 5B  is a schematic showing the loader and barrier membrane in the first mold cavity; 
         FIG. 5C  is a schematic showing melt being injected into the first mold cavity between the barrier membrane and a mold core of the machine of  FIG. 1  to form a preform inner layer; 
         FIG. 5D  is a schematic showing the barrier membrane and the preform inner layer held on the mold core; 
         FIG. 5E  is a schematic showing the barrier membrane and preform inner layer in a second mold cavity of the machine of  FIG. 1 , and melt being injected between the barrier layer and the second mold cavity to form a preform outer layer; and 
         FIG. 5F  is a schematic showing the barrier membrane between the preform inner and outer layers. 
     
    
    
     DETAILED DESCRIPTION 
     Various apparatuses or processes will be described below to provide an example of an embodiment of each claimed invention. No embodiment described below limits any claimed invention and any claimed invention may cover processes or apparatuses that differ from those described below. The claimed inventions are not limited to apparatuses or processes having all of the features of any one apparatus or process described below or to features common to multiple or all of the apparatuses described below. It is possible that an apparatus or process described below is not an embodiment of any claimed invention. Any invention disclosed in an apparatus or process described below that is not claimed in this document may be the subject matter of another protective instrument, for example, a continuing patent application, and the applicants, inventors or owners do not intend to abandon, disclaim or dedicate to the public any such invention by its disclosure in this document. 
     Referring to  FIGS. 1 and 2 , an example of an injection molding machine  100  is shown set up for producing preforms that can be used as input material for subsequent processing, for example, a blow molding operation to produce beverage (or other types of) containers. 
     Referring to  FIGS. 3-3B , schematic illustrations of an example preform  10  producible by the machine  100  are shown. In the example illustrated, the preform  10  has a generally elongate tubular body  12  extending along a preform axis  14  between an open end  16  and an opposed closed end  18 . A threaded portion  22  for receiving a closure is provided adjacent the open end  16 . A radially outwardly extending annular flange  24  is adjacent the threaded portion  22 , with the threaded portion  22  axially intermediate the open end  16  and the flange  24 . Referring to  FIG. 3A , the preform  10  has an inner surface  26 . In the example illustrated, the inner surface  26  includes a generally cylindrical inner side portion  28  extending along the axis  14  (between the open and closed ends  16 ,  18 ), and a generally concave inner end portion  30  extending radially inwardly from the inner side portion at the closed end  18 . The preform  10  has an outer surface  32  spaced apart from the inner surface  26 . The outer surface  32  includes a generally cylindrical outer side portion  34  extending along the axis  14  and a convex outer end portion  36  extending radially inwardly from the outer side portion  34  at the closed end  18 . The spacing between the inner and outer surfaces  26 ,  32  generally defines a preform wall thickness  38 . 
     In the example illustrated, the preform  10  is formed of an inner preform layer  40  (also referred to as a first preform layer  40 ), an outer preform layer  42  (also referred to as a second preform layer  42 ), and an intermediate barrier membrane  44  between the inner preform layer  40  and the outer preform layer  42 . In the example illustrated, the inner preform layer  40  defines at least a portion of the inner surface  26  and the outer preform layer  42  defines at least a portion of the outer surface  32 . In the example illustrated, the inner preform layer  40  defines the inner end portion  30  and the inner side portion  28  of the inner surface  26 , and the outer preform layer  42  defines the outer end portion  36  and at least a portion of the outer side portion  34  of the outer surface  32  (up to an underside of the flange  24 , in the example illustrated). 
     In the example illustrated, the barrier membrane  44  is formed of a generally thin, film-like article, and is impermeable to one or more of gas and light, which can help to, for example, extend shelf life of product stored in containers produced using the preform  10 . As described in more detail below, the barrier membrane  44  is premanufactured, and subsequently under- and overmolded with the inner and outer preform layers  40 ,  42 , respectively, to form the preform  10 . The barrier membrane  44  can be premanufactured using, for example, a thermo-forming or injection molding process, prior to formation of the preform  10 . 
     In the example illustrated, the barrier membrane  44  is sealed between the inner and outer preform layers  40 ,  42 . The barrier membrane  44  has a membrane sidewall  50  extending along the axis  14  (and positioned between the inner and outer side portions  28 ,  34 ) and a membrane base  52  extending radially inwardly from the membrane sidewall  50  at the closed end  18  of the preform  10  (and positioned between the inner and outer end portions  30 ,  36 ). The membrane sidewall  50  is generally tubular in the example illustrated. In the example illustrated, the barrier membrane  44  has a gate opening  54  in the membrane base  52 . As described in more detail below, the gate opening  54  can accommodate injection of melt from a mold gate through the barrier membrane  44  to form the inner preform layer  40  (or in some examples, the outer preform layer  42 ). When the preform  10  is formed, the gate opening  54  can be filled with material forming one of the inner preform layer  40  and the outer preform layer  42 . In the example illustrated, the material forming the inner preform layer  40  fills the gate opening  54 . In the example illustrated, the gate opening  54  is coaxial with the axis  14 . 
     Referring to  FIGS. 1 and 2 , in the example illustrated, the machine  100  for molding the preform  10  includes a base  102  extending lengthwise along a horizontal machine axis  104 . A first platen  106  is supported by the base  102  and holds a first mold section  106   a  having a plurality of first mold cavities  108 . A second platen  110  is supported by the base  102  and holds a second mold section  110   a  having a plurality of second mold cavities  112 . The second platen  110  is translatable relative to the first platen  106  along the machine axis  104  between a mold-open position (shown in  FIG. 1 ) and mold-closed position (shown in  FIG. 2 ). In the example illustrated, the second platen  110  is slidably supported by the base  102  for translating towards and away from the first platen  106 , which is stationary in the example illustrated. 
     In the example illustrated, a rotary apparatus  114  is slidably supported by the base  102  axially intermediate the first and second platens  106 ,  110 , and is translatable between the first and second platens  106 ,  110  along the machine axis  104 . In the example illustrated, the rotary apparatus  114  holds at least one center mold section  116  having a plurality of mold cores  118 . Referring to  FIG. 4 , in the example illustrated, the rotary apparatus  114  supports horizontally opposed first and second center mold sections  116   a ,  116   b  and horizontally opposed third and fourth center mold sections  116   c ,  116   d  perpendicular to the first and second center mold sections  116   a ,  116   b.    
     When the platens  106 ,  110  are in the mold-open position, the rotary apparatus  114  is operable to move the center mold section  116  about a vertical axis among at least a first position and a second position. Referring to  FIG. 2 , when the center mold section  116  is in the first position, the mold cores  118  are in alignment with the first mold cavities  108  for forming a plurality of first molds when the platens  106 ,  110  are in the mold-closed position. The first molds are shaped for receiving the barrier membrane  44 , and undermolding the barrier membrane  44  to form the inner preform layer  40  on an inside (also referred to as a first side) of the barrier membrane  44 . In the example illustrated, the first center mold section  116   a  is shown in the first position. 
     When the center mold section  116  is in the second position, the mold cores  118  are in alignment with the second mold cavities  112  for forming a plurality of second molds when the platens  106 ,  110  are in the mold-closed position. The second molds are shaped for receiving the barrier membrane  44  and the inner preform layer  40  formed on the inside of the barrier membrane  44 , and overmolding the barrier membrane  44  to form the outer preform layer  42  on an outside (also referred to as a second side) of the barrier membrane  44 . In the example illustrated, the second center mold section  116   b  is shown in the second position. 
     Referring to  FIGS. 1 and 2 , in the example illustrated, the machine  100  further includes a barrier membrane loading apparatus  130  adjacent the first platen  106 . Referring to  FIG. 2 , the loading apparatus  130  includes an end-of-arm tooling  132  having a plurality of loaders  134  for loading the barrier membranes  44  into the first mold cavities  108 . The end-of-arm tooling  132  is moveable between a retracted position (shown in  FIG. 2 ) clear of the first mold section  106   a  (and the first mold cavities  108 ), and an advanced position (shown in  FIG. 1 ) in which the loaders  134  are between the first and center mold sections  106   a ,  116  and in alignment with the first mold cavities  108  for transferring the barrier membranes  44  to the first mold cavities  108 . In the example illustrated, the end-of-arm tooling  130  is movable vertically between the retracted and advanced positions. 
     Referring to  FIG. 2 , a plurality of tie bars  124  extend parallel to the machine axis  104  between the first and second platens  106 ,  110 . The second platen  110  can be releasably locked to the tie bars  124  for exerting a clamp load across the mold sections  106   a ,  110   a ,  116  when the first and second platens  106   108  are in the mold-closed position. 
     Referring to  FIG. 1 , in the example illustrated, the machine  100  further includes a first injection apparatus  140  supported by the base  102  for injecting melt into the first mold cavities  108 , and a second injection apparatus  142  supported by the base  102  for injecting melt into the second mold cavities  112 . In the example illustrated, the first injection apparatus  140  is supported by the base  102  behind (i.e. axially outboard of) the first platen  106  for injecting melt into the first mold cavities  108  through the first platen  106 , and the second injection apparatus  142  is supported by base  102  behind (i.e. axially outboard of) the second platen  110  for injecting melt into the second mold cavities  112  through the second platen  110 . The second injection apparatus  142  is translatable along the machine axis  104  to accommodate translation of the second platen  110  during movement between the mold-open and mold-closed positions. 
     In the example illustrated, the machine  100  further includes a control system  150  ( FIG. 1 ) including one or more controllers configured to operate the machine components according to the processes disclosed herein to produce the preforms  10 . 
     Referring to  FIGS. 5A and 5B , in use, when the platens  106 ,  110  are in the mold-open position, the barrier membrane  44  is loaded into the first mold cavity  108 . Referring to  FIG. 5A , to load the barrier membrane  44 , the end-of-arm tooling  132  holding the barrier membrane  44  is moved from the retracted position to the advanced position and inserted into the first mold cavity  108  for transferring the barrier membrane  44  to the first mold cavity  108 . Referring to  FIG. 5B , the barrier membrane  44  is shaped to line the first mold cavity  108 , and when loaded, the sidewall  50  and base  52  of the barrier membrane  44  are positioned against an inner surface of the first mold cavity  108 , with the gate opening  54  of the barrier membrane in alignment (and coaxial) with a gate  146  of the first mold cavity  108 . 
     After the barrier membrane  44  is released from the loader  134  and transferred into the first mold cavity  108 , the end-of-arm tooling  132  is withdrawn from the first mold cavity  108  and moved to the retracted position (clear of the mold area), and the platens  106 ,  110  are moved to the mold-closed position to form the first mold. 
     Referring to  FIGS. 5C and 5D , when sufficient clamp load has been applied across the first mold, melt is injected into the first mold cavity  108  (via operation of the first injection apparatus  140 ) to undermold the barrier membrane  44  and form the inner preform layer  40  on the inside of the barrier membrane  44 . In the example illustrated, melt is injected into the first mold cavity  108  through the gate  146  of the first mold cavity  108  and the gate opening  54  of the barrier membrane  44 . In the example illustrated, melt is injected into a first mold space  152  of the first mold between the barrier membrane  44  and an outer surface of the mold core  118 , which shapes at least a portion of the inner surface  26  of the preform  10 . 
     Referring to  FIGS. 5D and 5E , once injection into the first mold is complete, the clamp force is relieved, the platens  106 ,  110  are moved to the mold-open position, and the barrier membrane  44  and the inner preform layer  40  formed on the barrier membrane  44  are moved from the first mold cavity  108  to the second mold cavity  112 . In the example illustrated, the barrier membrane  44  and inner preform layer  40  are held on the mold core  118  during movement from the first mold cavity  108  to the second mold cavity  112 . In the example illustrated, moving the barrier membrane  44  and inner preform layer  40  to the second mold cavity  112  includes moving the center mold section  116  from the first position to the second position, and then moving the platens  106 ,  110  to the mold-closed position. 
     Referring to  FIGS. 5E and 5F , when sufficient clamp load has been applied across the second mold, melt is injected into the second mold cavity  112  (via operation of the second injection apparatus  142 ) to overmold the barrier membrane  44  and form the outer preform layer  42  on the outside of the barrier membrane  44 . In the example illustrated, melt is injected into a second mold space  154  between the barrier membrane  44  and an inner surface of the second mold cavity  112 , which shapes at least a portion of the outer surface  32  of the preform  10 . Once injection into the second mold is complete, the clamp force is relieved, the platens  106 ,  110  are moved to the mold-open position, and the preform  10  can be allowed to cool and/or ejected for subsequent handling and/or post-mold cooling.