Blow molding tooling for high cavitation applications

An injection station of an injection blow molding machine and a method for forming parisons and molded articles. The injection station includes a die plate with a keyway formed through a least a portion of a surface of the die plate. The keyway separates front and back portions of the surface of the die plate. The injection station further includes a resin injection tooling comprising a draw bar, with at least a portion of the draw bar operable to be positioned within the keyway of the die plate, a base plate secured to a back side of the draw bar and operable to be secured to the back portion of the surface of the die plate and, and a manifold secured to a top of the base plate, with the manifold being configured to discharge resin into cavities to form the parisons.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate to an injection apparatus, system, and method. In particular, embodiments of the present invention relate to an injection station and an injection tooling of an injection blow molding machine for use in high cavitation applications.

2. Description of the Related Art

Injection blow molding is a technique used for creating various containers such as plastic bottles. The injection blow molding process is performed with an injection blow molding machine that first injection molds a resin into a plurality of parisons of desired shapes and then blow molds the parisons into the final molded articles.

An injection station of the injection blow molding machine typically includes a split parison mold assembly that defines a plurality of cavities within which parisons are formed. Hot melt resin injection nozzles have nozzle gate inserts that are seated in gate openings of the cavities for injecting resin into the cavities so as to form the parisons. To remove a set of newly formed parisons from the mold, an upper mold half is raised off a bottom mold half, and cores that carry the new parisons are then lifted and rotated out of the mold. A new set of cores is placed in the cavities of the bottom mold half and the mold is closed, creating a diametrical sealing relationship between each tip of the nozzle gate insert and the wall of its gate opening and preparing the mold cavities to receive hot melt resin through the nozzles.

Each nozzle is coupled, at its base, with a resin manifold that is secured to a die plate via a base plate. Prior to performing the injection blow molding, the manifold is heated to a desired operating temperature. Hot melt resin is supplied to each nozzle at the nozzle's base from a resin source associated with the manifold. The resin then flows through the nozzles and to the parison mold. In certain tooling applications, such as tooling described in U.S. Pat. No. 7,771,189 (the '189 patent) filed on Mar. 3, 2008, and entitled “INJECTION MOLDING APPARATUS WITH REPLACEABLE GATE INSERT,” which is incorporated by reference herein in its entirety, a gap of between 0.000 and 0.010 inches (hereinafter, a “gap” or a “zero gap”) may exist between the inside of the nozzle gate insert and the front end of the nozzle to allow independent movement of the cavities and the manifold. Such movement may arise due to the difference in thermal expansion of the cavities and the manifold since the cavities and the manifold may be operated at different temperatures. As such, hot melt resin will fill the gap and be cooled down enough to form a seal during injection of the hot melt resin into the cavity. However, the holt melt resin that collects within the gap can cause significant hydraulic backpressure against the nozzle and the resin manifold. Especially in injection tooling applications that use a plurality of nozzles to form a plurality of parisons, such hydraulic backpressures may exert forces in excess of thirty tons on the resin manifold and/or on the base plate. Such a force can cause the resin manifold and/or the base plate to move backward, to bend upward, and/or to bow, thus causing the gap to increase and eventually causing resin to leak from the interface of the nozzle gate insert and the front end of the nozzle.

As mentioned, before the nozzles can inject the hot melt resin into the cavities, the hot melt resin is required to be heated to a beginning operating temperature (e.g., between 350 to 560° F.). Additionally, the resin must maintain at least an injection operating temperature while being transferred through and injected from the manifold. Such an injection operating temperature is maintained using heat supplied to the injection tooling components by external sources. However, any heat applied to the resin manifold and/or the base plate tends to cause the manifold and/or base plate to deform, such as by bending or bowing. Such deformations make it difficult to maintain the zero gaps, especially in a high cavitation mold.

Thus, it would be desirable to have an injection station of an injection blow molding machine that is configured to maintain a resin manifold securely in place during operation, even with the presence of hydraulic forces between every nozzle gate insert and corresponding front end of the nozzle.

SUMMARY OF THE INVENTION

Some embodiments of the invention disclose an injection station of an injection blow molding machine, with the injection station comprising a die plate with a keyway formed through a least a portion of a surface of the die plate, and with the keyway separating front and back portions of the surface of the die plate. The station further includes a draw bar, with at least a portion of the draw bar being positioned within the keyway of the die plate, a base plate secured to the back portion of the surface of the die plate and to a back side of the draw bar, and a manifold secured to a top of the base plate, with the manifold being configured to discharge resin into cavities to form the parisons.

Other embodiments of the invention disclose an injection tooling for attachment to a die plate of an injection station, with the tooling comprising: a base plate configured to be secured to a top surface of the die plate, with the base plate including a main section and a plurality of projections extending rearward from the main section, and a manifold secured to a top of the base plate, with the manifold being configured to discharge resin into the cavities to form the parisons.

Some embodiments of the invention disclose a method of operating an injection station of an injection blow molding machine. The method includes the initial step of securing an elongated draw bar within a keyway formed through a top surface of a die plate, with the draw bar including at least one tab extending from a back side of the draw bar. A next step includes engaging a base plate with the draw bar, with the base plate including at least one notch such that during the engaging step, the tab of the draw bar is engaged with the notch of the base plate. Next, the base plate is secured to the draw bar, a rear portion of the base plate is secured to the die plate, and a manifold is secured to a top portion of the base plate.

DETAILED DESCRIPTION

Embodiments of the present invention broadly include an injection station10, as illustrated inFIGS. 1-2, which is configured for use in an injection blow molding machine for injection molding a resin into a plurality of parisons. Upon injection molding the resin, the resulting parisons may be blow molded, via a separate station of the machine, into a plurality of molded articles. As illustrated inFIGS. 1-2, the injection station10may include a lower die plate12secured to a machine (not shown), an upper die plate14overlying lower die plate12and that is moveable (by means not illustrated) vertically toward and way from the lower die plate member12on upright guides16, a series of parison molds18, each including a lower mold half20secured to the lower die plate12and an upper mold half22secured to the upper die plate14, and a resin injection tooling24positioned between the lower and upper die plates12,14generally rearward of the parison molds18. With the lower and upper die plates12,14in a closed position (e.g.,FIGS. 1-2), the parison molds18are likewise closed, such that the lower and upper mold halves20,22cooperatively form a parison cavity25(see, e.g.,FIGS. 3-4) within which resin may be injected to form parisons. As used herein, the terms “forward” or “front” refers to a direction toward the parison molds18, while the terms “rearward” or “back” refers to a direction towards the upright guides16.

As best illustrated inFIGS. 3-7, the resin injection tooling24of embodiments of the present invention includes: a draw bar26operable to be positioned within a keyway28formed through a least a portion of a top surface of the lower die plate12, with the keyway28generally separating the top surface of the lower die plate12into a front portion30and a back portion32(seeFIG. 5), a base plate34secured to a back side of the draw bar26and operable to be secured to the back portion32of the surface of the lower die plate12, and a manifold36secured to a top of the base plate34. In operation, the manifold36is configured to receive hot resin from a resin source (not shown) and to discharge resin into the cavities25to form the parisons. The components of the resin injection tooling24may be formed from various types of material having high strength and durability. For example, such components may be formed from high-grade steel, such as a high-grade stainless steel.

Beginning with the manifold36, as best illustrated inFIGS. 4 and 7, the manifold36is generally elongated and includes a series of injection nozzles38positioned on its front side. The manifold36receives hot resin from via an inlet sprue40(seeFIGS. 4 and 6), with such resin being directed through internal passages in the manifold36to each of the injection nozzles38. As such, the manifold36is operable to inject hot resin under pressure into the cavities25to form the parisons. As previously mentioned, during use of injection tooling that includes a zero gap between the nozzle and the gate insert, e.g., the tooling described in the '189 patent, the pressure generated during the injection of the resin from the nozzles can be significant. Especially in embodiments in which the manifold includes a plurality of nozzles, such pressure can be, for instance, several thousand to tens of thousands of pounds per square inch. Also as previously mentioned, the resin must be maintained at a sufficiently high temperature during injection. Such temperatures may be maintained through various heating devices associated with the injection station10, such as may include hot water conduits, electrical heaters, or the like. For example, as illustrate inFIGS. 2-6, the manifold36may include a plurality of heating elements42, in the form of electrical heating cartridges that extend through a length of the manifold36.

Because of the high pressures and high temperatures involved during injection of the resin into the molds18, certain components of the resin injection tooling24will tend to deform or will otherwise be forced out of alignment, which can interfere with the injection of the resin and creation of the parisons. Specifically, manifold36that includes a plurality of injection nozzles38will tend to bow backwards, especially near either or both of the manifold's36ends. The bowing of the manifold36is generally due to a hydraulic backpressure that results from the pressure of the resin as it is injected through the nozzles38and into the parison cavities25. Such bowing not only affects the manifold36, but may also affect the base plate34, which supports the manifold36on the die plate12of the injection station10. In addition to bowing, the hydraulic backpressure may also force the manifold36and the base plate34upward, away from the die plate12. Furthermore, because of the high temperatures, various components of the resin injection tooling24may be prone to deform, with such deformation being due to thermal expansion/contraction caused by temperature differences experienced by the components. As a result of such misalignments and deformations, the injection of resin into the molds18to form parisons may be inhibited or prevented entirely.

To overcome such problems, the components of the injection station10and/or the resin injection tooling24include a plurality of features that help to ensure consistent alignment throughout operation. In particular, as illustrated inFIGS. 3-7, the die plate12of the injection station10will include the keyway28formed through its top surface, with the keyway28sized so as to receive the draw bar26of the resin injection tooling24. The draw bar26may be formed from an elongated generally rectangular piece of material. As best shown inFIGS. 5-6, the draw bar26may include a plurality of tabs50extending rearward from a top portion of the draw bar26.

With the draw bar26received within the keyway28, the draw bar26is restricted from translating forward or rearward about the top surface of the die plate12. The draw bar26may be secured in place within the keyway28via a plurality of vertically-positioned threaded fasteners, such as draw bar bolts52, which extend through a plurality of corresponding vertical apertures extending through the draw bar26and through aligned threaded apertures formed in the keyway28of the die plate12. As such, with the draw bar26secured within the keyway28via the draw bar bolts52(e.g., as illustrated inFIGS. 3-4 and 8), the draw bar26is restricted from translating forward or rearward about the surface of the die plate12and is further restricted from moving vertically away from the die plate12.

Returning toFIGS. 3-4, the base plate34is operable to be positioned on the top surface of the die plate12, and specifically on the die plate's12back portion32, just rearward of the draw bar26. The base plate34is elongated with a length that generally corresponds with the draw bar26. With reference toFIGS. 5-6, the base plate34includes a main section54and one or more projections56extending rearward from the main section54. As best illustrated byFIG. 5, a front side of the main section54includes one or more notches58formed within a top portion of the base plate34. As will be discussed in more detail below, the notches58of the base plate34will correspond with the tabs50of the draw bar26, such that the tabs50can be received within the notches58for engaging the base plate34with the draw bar26.

As best illustrated byFIG. 6, the main section54of the base plate34may include one or more legs60extending from a bottom portion of the base plate34, and the projections56may include one or more risers62extending from a bottom portion of the projections56, such that the base plate34is operable to contact the die plate12via said legs and risers60,62so as to present a gap (see, e.g.,FIGS. 3-4 and 9) between at least a portion of the die plate12and at least a portion of the base plate34. Additionally, as best illustrated byFIG. 5, a top portion of the base plate34includes a recess64formed along the length of the base plate34. As will be discussed in more detail below, the manifold36may be received within the recess64when the manifold36is secured to the base plate34. In some embodiments, such as illustrated inFIG. 5, the recess64of the base plate34will include one or more pedestals66within the recess64. When the manifold36is received within the recess64, the manifold36may rest on the pedestals66such that a gap (see, e.g.,FIGS. 3-4 and 8-9) is presented between at least a portion of the base plate34and a portion of the manifold36.

As mentioned, the base plate34includes a plurality of projections56extending rearward from the base plate's34main section54. As best illustrated byFIG. 3, the projections56may be spaced apart along a length of the base plate34, such that voids68are presented between each of the adjacent projections56. In some embodiments, such as illustrated inFIGS. 5-6, one or more of the projections56will include an elongated aperture70extending generally vertically from a top side of the projection56through to a bottom side of the projection56. As such, a threaded fastener, such as in the form of a shoulder bolt72, is operable to be inserted through the elongated aperture70and into an aligned threaded aperture formed in the die plate12so as to secure the base plate34to the back portion of the die plate12(see, e.g.,FIG. 9). In some embodiments, the shoulder bolt72may also be associated with one or more washers for facilitating the securement of the base plate34to the die plate12. As will be described in more detail below, although the shoulder bolt72is operable to secure the base plate34to the die plate12, a clearance may exist between a head of the shoulder bolt72and a top surface of the projection56. Such a clearance may provide for the projection56and/or the base plate34to expand or shift about the surface of the die plate12, with such expansion/shifting being due to thermal effects. In some embodiments, such clearance may be between 0.000 and 0.004 inches, between 0.001 and 0.003 inches, or 0.002 inches. In additional embodiments, one or more of the projections56will include a threaded aperture extending generally horizontally from a back side of the projection56to the projection's56elongated aperture70. As such and as illustrated inFIGS. 3, 5-6, and 9, a threaded fastener, such as in the form of a jack bolt74, is operable to extend through the horizontally-extending threaded aperture so as to contact the shoulder bolt72that extends through the elongated aperture70.

As illustrated inFIGS. 3-4, the base plate34is operable to be secured to the draw bar26. As previously described, with the draw bar26secured to the die plate12within the keyway28, the base plate34can be positioned with its front side adjacent to the back side of the draw bar26. As such, the tabs50of the draw bar26will be received within the notches58of the base plate34, thereby coupling the draw bar26and the base plate34together. As illustrated inFIGS. 3, 5-6, and 10, the base plate34can be further secured to the draw bar26via one or more threaded fasteners, in the form of drawbolts76, which extend generally horizontally through horizontal apertures formed through the main section54of the base plate34. The drawbolts76are operable to engage with generally horizontal threaded apertures formed through the back side of the draw bar26and through at least a portion of the draw bar's26thickness.

Finally, as mentioned above, embodiments provide for the manifold36to be secured to the top portion of the base plate34by having the manifold36be received within the recess64of the base plate34. In particular, a bottom portion of the manifold36may rest on the pedestals66within the recess64of the base plate34. In some embodiments, such as best illustrated inFIGS. 3-4 and 8, the bottom portion of the manifold36will have a smaller cross-section than a remaining portion of the manifold36, such that the bottom portion of the manifold fits within the recess64while other portions of the manifold36overhang the base plate34. Nevertheless, with the manifold36resting on the pedestals66, the bottom portion of the manifold36is bound by the recess64of the base plate34, such that the manifold36is incapable of translating forward or rearward beyond the recess64. In some embodiments, such as illustrated inFIGS. 5-6 and 8, the manifold36will be secured to the base plate34via one or more threaded fasteners, in the form of manifold bolts78, which extend generally vertically through vertical apertures formed through the main section54of the base plate34. The manifold bolts78are operable to engage with vertical threaded apertures formed through a bottom side of the manifold36and through at least a portion of the manifold's36height.

In operation, the components of the injection station10and/or the resin injection tooling24provide for parison to be formed in a precise manner without such components bowing, lifting, or otherwise becoming misaligned. In particular, the draw bar26can be secured to the die plate12by first positioning the draw bar26within the keyway28of the die plate12. Thereafter, the draw bar26can be secured to the die plate12via the draw bar bolts52. With the draw bar26positioned within the keyway28, the draw bar26is restricted from translating forward or rearward about the top surface of the die plate12. Additionally, the draw bar bolts52restrict the draw bar26from moving vertically away from the die plate.12.

Next, the base plate34is positioned on the die plate12, as previously described, with the front side of the base plate34contacting the back side of the draw bar26. As such, the tabs50of the draw bar26will be received within the notches58of the base plate34. The base plate34is further drawn to and secured to the draw bar26via the drawbolts76extending through the base plate34and the draw bar26. Further, the base plate34is secured to the die plate12via the shoulder bolts72extending through the elongated apertures70of the projections56and into the die plate12. Thus, the base plate34is restricted from translating forward or rearward by its engagement with the draw bar26, with such engagement enhanced via the drawbolts76. Additionally, the base plate34is restricted from translating vertically away from the die plate34on a front side via the tabs50engaged with the notches58and on a rear side via the shoulder bolts72.

Finally, the manifold36can be attached to the base plate34as previously described, by positioning at least a portion of the manifold36within the recess64at the top portion of the base plate34. Additionally, the manifold36is secured to the base plate34via the manifold bolts78extending through the base plate34and into the manifold36. As such, the recess64of the base plate34restricts the manifold from translating forward or rearward, while the manifold bolts78restrict the base plate34from translating vertically away from the base plate34.

Generally, the draw bar26, the base plate34, and the manifold36of the resin injection tooling24will be assembled, as described above, before the injection station10is operational. As previously noted, the operational temperatures of the components of the injection station10and/or the resin injection tooling24can be quite high (e.g., between 350 to 560° F.). However, before the injection station10becomes operational, the temperature of the components of the injection station10and/or the resin injection tooling24may not be as high. For example, a pre-operational temperature of the components of the injection station10and/or the resin injection tooling24may be a general room temperature (e.g., 60 to 90° F.). Given such potential temperature changes undergone by the components of the injection station10and/or the resin injection tooling24between pre-operational and operational stages, the materials of which certain components of the resin injection tooling24are formed, such as the manifold36and the base plate34, may expand or contract due to thermal effects. Such thermal effects may unwantedly enhance bowing of the components or otherwise may force the components out of alignment.

Nevertheless, embodiments of the present invention provide for the reduction or termination of any bowing of the components of the resin injection tooling24. Embodiments may, thus, provide for the components of the resin injection tooling24to maintain appropriate alignment throughout operation. For example, even if the base plate34expands during the transition of the injection station10from the pre-operational to the operational stages, the elongated apertures70allow the base plate34, including the projections56, to expand rearward about the shoulder bolts72. In more detail, and as previously mentioned, the head of the shoulder bolts72may include a clearance (e.g., 0.002 inches) with respect to the top surface of the projections56. As such, should the base plate34expand while the injection station10is becoming operational, or even during operation, the base plate34and its projections56are able to expand around the shoulder bolts72. It should be noted, that even though the clearance between the head of the shoulder bolts72and the projections56allows the base plate34to expand, the shoulder bolts76secure the base plate34to the die plate12, such that the base plate34is restricted from translating vertically away from the die plate12.

Furthermore, it is understood that the projections56of the base plate34are formed so as to minimize any potential amounts of thermal expansion of the base plate34. Specifically, because the projections56are spaced apart and separated by voids68, a total volume of material made up by the projections56is small compared to a volume of the main section54of the base plate34. As such, a temperature gradient of the base plate34is similarly small from a front side of the base plate34to the back side of the base plate34. Such a small temperature gradient provides for symmetrical heating and reduces any amount of thermal expansion experienced by the base plate34.

Once the injection station10and/or the resin injection tooling24reaches operational temperatures and the manifold36begins injecting resin into the molds18, the hydraulic backpressure caused by such injections tends to force the manifold36rearward. Such a hydraulic backpressure is especially significant at the ends of the manifold36, which can cause the manifold36to bow rearward. Such bowing can be further enhanced by the thermal expansion seen by various components of the injection station10and/or the resin injection tooling24, as previously described. Embodiments of the present invention alleviate and/or prevent such bowing via the draw bar26. In particular, as previously described and as may best be seen inFIG. 9, the draw bar26is restricted from translating forward or rearward by its placement within the keyway28. Similarly, the base plate34is restricted from translating forward or rearward because it is secured to the draw bar26via the drawbolts76(see, e.g.,FIG. 10). In particular, the drawbolts76positioned adjacent to ends of the base plate34prevent bowing by alleviating rearward movement of the base plate34at the base plate's34ends. As such, with the draw bar26and the base plate34restricted from forward or rearward translation, the manifold36is likewise restricted from such forward or rearward translation, including bowing at its ends. Furthermore, the heating elements42may prevent the manifold36from bowing by reducing a temperature gradient within the manifold. In particular, a front portion of the manifold36may generally have a high temperature during operation, with such higher temperature being due to the presence of the nozzles38that inject heated resin into the molds18. The heating elements42, and particularly the heating elements42positioned through a back portion of the manifold36, may provide additional heat to the back portion of the manifold36. As such, the heating elements42will function to create a consistent temperature throughout the manifold36, so as to reduce any temperature gradient experienced by the manifold36. By reducing the temperature gradient experienced by the manifold36, any manifold36bowing that may be caused by temperature effects can be correspondingly be reduced.

Thus, embodiments of the present invention provide for reduction and/or prevention of deformations and misalignments of the resin injection tooling24, with such deformation and misalignments being potentially due to hydraulic backpressure and/or heat deformations.

Finally, in addition to facilitating assembly of the components of the injection station10and/or the resin injection tooling24, embodiments of the present invention may facilitate the disassembly of certain components of the injection station10and/or the resin injection tooling24. In particular, once the base plate34is secured to the draw bar26, it can be difficult to remove the base plate34. Such removal may be required for maintenance of the injection station10. Embodiments of the present invention facilitate such disassembly via the jack bolts74, which are inserted through the back sides of one or more of the projections56. To begin disassembly, the drawbolts76can be removed from the draw bar26. As such, the base plate34is no longer secured to the draw bar26. Next, the shoulder bolts72can be loosened from the die plate12. It should be noted that the shoulder bolts72should only be loosened such that the base plate34can translate forward or rearward about the die plate12, but that the shoulder bolts72should still be engaged with the die plate12. As such, the jack bolts74can be actuated such that they are forced against the shoulder bolts72. Such an actuation is operable to force the base plate34rearward away from the draw bar26. Once the base plate34has been sufficiently displaced from the draw bar26, the shoulder bolts72may be completely removed, and the base plate34may be removed from the die plate12.

Although the invention has been described with reference to the preferred embodiment illustrated in the attached drawing figures, it is noted that equivalents may be employed and substitutions made herein without departing from the scope of the invention as recited in the claims.