MOLD, BLOW MOLDING DEVICE, AND INJECTION MOLDING DEVICE

A mold includes a first mold for receiving a neck mold that holds a neck part of a resin preform having a bottom, and for enclosing the preform inside, and a second mold inserted into the neck mold. At least one of a first sliding surface between the neck mold and the first mold and a second sliding surface between the neck mold and the second mold includes a solid lubricant embedded therein.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a mold, a blow molding apparatus, and an injection molding apparatus.

Description of the Related Art

Blow molding (“hot parison” process) apparatuses are one of commonly known apparatuses for producing resin containers. In a “hot parison” process blow molding apparatus, preforms are blow-molded into resin containers as the preforms are intermittently transferred sequentially from one to another of an injection molding unit, a temperature adjusting unit, and a blow molding unit, on a rotating transfer plate. The above blow molding apparatus forms resin containers by utilizing the residual heat contained in injection-molded preforms, which offers advantage over a “cold parison” process in producing a wide variety of resin containers with good appearance.

For the molds used for injection molding, there have been proposed a configuration, for example, in which solid lubricants are embedded in each of sliding surfaces of guide holes used for guiding a mold when the mold is opened and closed, and sliding surfaces of a sliding mold (e.g., JP 1-320121 A), and a configuration in which a lubricant-impregnated member is accommodated in a groove formed in a surface that makes contact with a moving mold used for removing the molded piece from a core (e.g., JP 60-134615 Y) .

The mold used in the blow molding apparatus described above is made up of a plurality of mold components, many of which are driven by actuators. These mold components must be positioned precisely relative to the preform when the mold is closed for favorable molding of the preforms or resin containers.

In the above blow molding apparatus, mold components that face each other have inclined surfaces, for example, which slide against one another, to ensure accuracy in positioning the mold components that hold and transfer the preforms and other mold components. In such a case, it is essential to apply a lubricant on the sliding surfaces so as to prevent abnormal wear (galling) of the mold components. Application of lubricant to numerous parts of a blow molding apparatus is a cumbersome task. Absence of lubricant by oversight can significantly increase risk of damage to the mold components.

SUMMARY OF THE INVENTION

The present invention in one aspect resides in a mold including a first mold for receiving a neck mold that holds a neck part of a resin preform having a bottom, and for enclosing the preform inside, and a second mold inserted into the neck mold, at least one of a first sliding surface between the neck mold and the first mold and a second sliding surface between the neck mold and the second mold including a solid lubricant embedded therein.

DESCRIPTION OF THE EMBODIMENTS

For ease of understanding of the embodiment, description of the structures and elements other than primary features of the present invention will be simplified or omitted. Same elements in the drawings are given the same reference numerals. It should be understood that the drawings are schematics of various elements and not illustrations of actual shapes and dimensions.

FIG.1is a schematic diagram illustrating the configuration of the blow molding apparatus in one embodiment. The blow molding apparatus in this embodiment is a “hot parison” process (herein also referred to as a one-stage process) apparatus in which preforms are not cooled down to room temperature and blow-molded into containers utilizing the residual heat (internal energy) from the injection molding step retained in the preforms.

The blow molding apparatus20preferably includes four molding stations, specifically, an injection molding unit21, a temperature adjusting unit22, a blow molding unit23, an ejection unit24, and a transfer mechanism26. The injection molding unit21, temperature adjusting unit22, blow molding unit23, and ejection unit24are disposed in positions rotated by a predetermined angle (of, for example, 90 degrees) around the transfer mechanism26.

The transfer mechanism26includes a rotating plate26a(not shown inFIG.1) that rotates around an axis perpendicular to the paper plane ofFIG.1. On the rotating plate26aare arranged neck molds27(not shown inFIG.1) that hold neck parts12of preforms11or resin containers (hereinafter simply “container”)15, one or more at every predetermined angle. The transfer mechanism26rotates the rotating plate26aand transports preforms11(or containers15), held by the neck molds27at their neck parts12, sequentially from one to another of the injection molding unit21, temperature adjusting unit22, blow molding unit23, and ejection unit24. The transfer mechanism26is also able to move the rotating plate26aup and down, and to perform operations relating to the closing and opening of the mold (demolding) of the preforms11in the injection molding unit21.

The injection molding unit21includes an injection mold cavity31and an injection mold core32as shown inFIGS.2A,2Band produces preforms11. As shown inFIG.1, to the injection molding unit21is connected an injection device25that melts and supplies resin material that is the raw material of the preforms11.

The preform11has an overall cylindrical shape with a bottom, one end open and the other end closed, as shown inFIG.2B. A neck part12is formed at the open end of the preform11.

The container and preform11are made of a thermoplastic synthetic resin. The material may be selected as suited in accordance with the specifications of the container. Concrete examples of the material include PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PCTA (polycyclohexylenedimethylene terephthalate), Tritan (registered trademark, copolyester made by Eastman Chemical Company), PP (polypropylene), PE (polyethylene), PC (polycarbonate), PES (polyethersulfone), PPSU (polyphenylsulfone), PS (polystylene), COP/COC (cyclic olefin polymer/copolymer), PMMA (polymethyl methacrylate or acrylic), PLA (polylactic acid), and so on. Additives such as colorant may be added to these resin materials as required.

FIG.2Ais a diagram illustrating a state before the mold is closed in the injection molding unit21, andFIG.2Bis a diagram illustrating a state after the mold has been closed in the injection molding unit21.

The injection mold cavity31is the mold that defines the outer contour of the preform11except the neck part12and receives the neck mold27(i.e., the injection mold cavity31abuts against or engages with the neck mold27). The inner circumference of the neck mold27serves as the mold that defines the shape of the neck part12of the preform11. The injection mold core32is the mold that defines the inner contour of the preform11. The injection mold core32is inserted into the neck mold27from above in the drawing, with the neck mold27being set on the injection mold cavity31and the molds are closed. The injection mold cavity31is one example of a first mold, and the injection mold core32is one example of a second mold.

In the injection molding unit21, the injection mold cavity31, injection mold core32, and the neck mold27of the transfer mechanism26are clamped together to form a mold cavity conforming to the shape of the preform. Preforms11are produced at the injection molding unit21by injecting resin material from the injection device25into this mold cavity in the shape of the preform as shown inFIG.2B.

Solid lubricants (solid lubricants)28are embedded in respective first sliding surfaces between the neck mold27and injection mold cavity31, and second sliding surfaces between the neck mold27and injection mold core32. These solid lubricants embedded in respective sliding surfaces can minimize galling of the mold components in the injection molding unit21.

For example, as shown inFIG.2A, a plurality of solid lubricants28are embedded at equal intervals in an annular form along the outer circumference of the injection mold core32in a tapered proximal end part32aof the injection mold core32that slides against the inner circumferential surface27bof the neck mold27. Similarly, a plurality of solid lubricants28are embedded at equal intervals in an annular form along the inner circumference of the injection mold cavity31in a tapered bearing surface31aof the injection mold cavity31that receives the neck mold27.

In each sliding surface, the solid lubricants28are arranged at intervals also in the axial direction along which the components slide against each other. The number of solid lubricants arranged in the axial direction is suitably set in accordance with the axial length of the sliding surface.

FIG.3Ais a diagram illustrating the outer appearance of the neck mold27.FIG.3Bis a longitudinal cross-sectional view ofFIG.3A.FIG.3Cis a lateral cross-sectional view of line IIIc-IIIc inFIG.3A, andFIG.3Dis a lateral cross-sectional view of line IIId-IIId inFIG.3C.

As shown inFIG.3A, a plurality of solid lubricants28are embedded in the outer circumferential surface27aof the neck mold27that faces the bearing surface31aof the injection mold cavity31. As shown inFIG.3C, the solid lubricants28embedded in the outer circumferential surface27aof the neck mold27are arranged at equal intervals in an annular form along the outer circumference of the neck mold27. Similarly, a plurality of solid lubricants28are embedded in the inner circumferential surface27bof the neck mold27that faces the proximal end part32aof the injection mold core32as shown inFIG.3B. As shown inFIG.3D, the solid lubricants28embedded in the inner circumferential surface27bof the neck mold27are arranged at equal intervals in an annular form along the inner circumference of the neck mold27.

The solid lubricant28described above is made of powder containing, for example, a main ingredient such as carbon material powder, graphite powder, molybdenum sulfide, polytetrafluoroethylene, paraffin, or the like and a binder, and produced by sintering the powder that has been packed and molded into a predetermined shape and demolded. The solid lubricants28may be anchored to the mold components by press-fitting them into the mold components, or may be fixed using an adhesive.

Solid lubricants28similar to those in the injection molding unit21are given the same reference numeral and repetitive descriptions of their configuration will be omitted in the following.

The neck mold27of the transfer mechanism26stays closed even after the molds are opened in the injection molding unit21, and keeps holding the neck part12and transfers the preform11. The number of preforms11that can be molded simultaneously in the injection molding unit21(i.e., the number of containers15that can be molded simultaneously in the blow molding apparatus20) may be suitably set.

The temperature adjusting unit22adjusts the temperature of the preform11produced at the injection molding unit21to temperature suited for final blowing (about 90° C. to 105° C., for example) by making the temperature of the preform11uniform or by removing temperature variations. The temperature adjusting unit22also serves to cool down hot preforms11after the injection molding.

As shown inFIGS.4A and4B, the temperature adjusting unit22includes a cavity41and a core42. The cavity41is one example of a first mold, and the core42is one example of a second mold.

The cavity41is a mold having a temperature adjusting space41aof substantially the same shape as that of the preform11produced at the injection molding unit21, i.e., is able to accommodate a preform11inside. Air outlet holes41care formed in a bottom part of the temperature adjusting space41aof the cavity41for letting out the air as the preform11is being inserted.

The core42is a mold to be inserted into the preform11, and disposed such as to be moved to and from the neck mold27holding the preform11at the temperature adjusting unit22. InFIG.4A, the core42is retracted and not shown.FIG.4Bon the other hand shows a state in which the core42has moved downward in the drawing and is inserted into the neck mold27.

The cavity41and the core42each have a flow passage (not shown) inside for a temperature adjusting medium (cooling medium) to flow through. Therefore the cavity41and the core42are maintained at a predetermined temperature by the temperature adjusting medium flowing inside. The preform11at the temperature adjusting unit22is adjusted to a predetermined temperature by heat exchange between the cavity41facing the preform on the outside and the core42facing the preform on the inside.

Solid lubricants28are embedded in respective first sliding surfaces between the neck mold27and the cavity41, and second sliding surfaces between the neck mold27and the core42. These solid lubricants28embedded in respective sliding surfaces can minimize galling of the mold components in the temperature adjusting unit22.

For example, as shown inFIG.4B, a plurality of solid lubricants28are embedded at equal intervals in an annular form along the outer circumference of the core42in a tapered proximal end part42aof the core42that slides against the inner circumferential surface27bof the neck mold27. Similarly, as shown inFIG.4A, a plurality of solid lubricants28are embedded at equal intervals in an annular form along the inner circumference of the cavity41in a tapered bearing surface41bof the cavity41that receives the neck mold27. As described in the foregoing, solid lubricants28are embedded in the outer circumferential surface27aand inner circumferential surface27bof the neck mold27that transfers the preform11.

Referring back toFIG.1, the blow molding unit23performs blow molding to the preform11that is temperature-adjusted at the temperature adjusting unit22, to produce containers.

The blow molding unit23includes a blow mold cavity51that is a pair of split mold halves corresponding to the shape of the container15, a bottom mold52, and an air injection member (not shown) that doubles as a stretch rod.FIG.5Aillustrates a state before the blow mold cavity51and bottom mold52are closed, andFIG.5Billustrates a state after the blow mold cavity51and bottom mold52have been closed.

The blow mold cavity51a mold part that defines the shape of the container15except for the bottom surface. The blow mold cavity51is split in a parting plane along the up-down direction inFIGS.5A and5Band configured to be opened and closed in the left-right direction inFIGS.5A and5B. The blow mold cavity51is one example of a first mold.

The bottom mold52is a mold that defines the shape of the bottom surface of the container15and is disposed below the blow mold cavity51. A mold cavity that defines the shape of the container15is formed by the bottom mold52and the blow mold cavity51being closed. The bottom mold52waits below the preform11where it does not touch the bottom of the preform11before the blow mold cavity51is closed, for example, and is driven to move up quickly to a molding position (FIG.5B) after the mold is closed.

The air injection member, which is a hollow tubular body for blowing air into the preform, is brought into contact with the neck part of the preform. The air injection member is movable up and down in the drawing and serves to stretch the preform11along the vertical axis by moving down. The air injection member is one example of a second mold.

Solid lubricants28are embedded in third sliding surfaces between the blow mold cavity51and the bottom mold52. These solid lubricants28embedded in the sliding surfaces can minimize galling of the mold components of the blow mold cavity51and bottom mold52. Although not shown inFIGS.5A and5B, solid lubricants28are embedded in respective first sliding surfaces between the blow mold cavity51and the outer circumferential surface27aof the neck mold27, and second sliding surfaces between the inner circumferential surface27bof the neck mold27and the air injection member.

For example, as shown inFIG.5A, a plurality of solid lubricants28are embedded at equal intervals in an annular form along the outer circumference of the bottom mold52in a cylindrical or tapered proximal end part (contact part)52aof bottom mold52that slides against the blow mold cavity51. On the other hand, a plurality of solid lubricants28are embedded at equal intervals in an annular form along the inner circumference of a cylindrical or tapered opening51ain the blow mold cavity51that receives the proximal end part52aof the bottom mold52(bearing surface that receives the proximal end part52aof the bottom mold52).

The bottom mold52further includes a forming part52cthat defines the bottom surface shape of the container15, a cylindrical or tapered middle part52bthat connects the forming part52cand the proximal end part52a, and a step52dthat connects the middle part52band the proximal end part52aand defines an uppermost position of the bottom mold52. The proximal end part52ahas a larger diameter than the middle part52b. The blow mold cavity51further includes a second opening51bthat is cylindrical or tapered in a portion that faces or opposes the middle part52bwhen the mold is closed. The opening51ahas a larger diameter than the second opening51b. No solid lubricants28are embedded in the outer circumferential surface of the middle part52band the inner circumferential surface of the second opening51band they are configured such that there is a predetermined gap between them, this gap serving as an air vent.

The ejection unit24is configured to release the neck part12of the container produced at the blow molding unit23from the neck mold27and allow the container to be taken out of the blow molding apparatus20.

Description of Blow Molding Method

Next, a blow molding method using the blow molding apparatus20of this embodiment is described.

FIG.6is a flowchart illustrating the steps of the blow molding method.

Step S101: First Injection Molding Step

First, resin material is injected from the injection device25into the mold cavity formed by the injection mold cavity31, injection mold core32, and the neck mold27of the transfer mechanism26at the injection molding unit21to produce a preform11.

After the molds are opened in the injection molding unit21, the rotating plate26aof the transfer mechanism26rotates a predetermined angle so that the preform11held by the neck mold27and containing the residual heat from the injection molding step is transferred to the temperature adjusting unit22.

Step S102: Temperature Adjusting Step

Next, at the temperature adjusting unit22, the temperature of the preform11is adjusted to be closer to a temperature suitable for final blow molding.

In the temperature adjusting step, first, the preform11is accommodated inside the temperature adjusting space41aof the cavity41. Next, the core42is inserted into the preform11held in the cavity41.

Since the cavity41and the core42are configured to conform to the shape of the preform11, the preform11remains in a desired shape even during the temperature adjusting step.

The preform11faces the cavity41and the core42during the temperature adjusting step so that the temperature of the preform11is adjusted such as not to fall below a temperature suitable for blow molding, and also any unevenness in temperature that occurred during the injection molding is reduced.

After that, the rotating plate26aof the transfer mechanism26rotates a predetermined angle so that the preform11, whose temperature has been adjusted, held by the neck mold27, is transferred to the blow molding unit23.

Step S103: Blow Molding Step

Next, blow molding of a container15is performed at the blow molding unit23.

First, the blow mold cavity51is closed to accommodate the preform11in the mold cavity. In the case where the preform11is longer than the container15, the bottom mold52waits below far enough not to touch the bottom part of the preform11before the blow mold cavity51is closed. After the blow mold cavity51is closed, the bottom mold52is then quickly lifted to a molding position.

The air injection member (blow mold core) is brought down approximately at the same time as the blow mold cavity51and bottom mold52are closed, and brought into contact with the neck part12of the preform11. The stretch rod is moved down to press the bottom part of the preform11from inside, and air is blown into the preform from the air injection member to stretch the preform11inside the mold cavity in the horizontal axis, while also stretching the preform in the vertical axis as required. The preform11is thus inflated to make tight contact with the mold cavity formed by the blow mold cavity51and the bottom mold52and formed into the desired shape, i.e., blow-molded into the container15.

Step S104: Container Ejection Step

After the blow molding has ended, the molds are opened in the blow molding unit23. This allows the container15to be moved away from the blow molding unit23.

Successively, the rotating plate26aof the transfer mechanism26rotates a predetermined angle so that the container15is transferred to the ejection unit24. At the ejection unit24, the neck part12of the container15is released from the neck mold27, and the container15is taken out of the blow molding apparatus20.

A series of blow molding process steps is thus complete. The rotating plate26aof the transfer mechanism26is then rotated a predetermined angle, whereupon the steps S101to S104described above are repeated.

The present invention is not limited to the embodiment described above. Various improvements and design changes may be made without departing from the subject matter of the present invention.

In the above embodiment, one example was described in which solid lubricants28are embedded in both of the two mold components sliding against each other. Instead, the solid lubricants28may be embedded in only one of the two mold components sliding against each other. Alternatively, the mold for the injection molding, for example, may have solid lubricants28embedded in one of the first sliding surface between the neck mold27and the injection mold cavity31and the second sliding surface between the neck mold27and the injection mold core32, and may not have solid lubricants in the other.

A blow molding apparatus20that uses the mold according to the present invention may be equipped with a plurality of injection molding units upstream of the temperature adjusting unit22to mold multilayer preforms11by performing injection molding twice or more, for example (which would be a “hot parison” process blow molding apparatus with 5 or 6 molding stations). Another alternative is an apparatus configuration without the temperature adjusting unit22(which would be a “hot parison” process blow molding apparatus with three molding stations, i.e., an injection molding unit21, a blow molding unit23, and an ejection unit24).

The mold according to the embodiment may also be applied to a blow molding apparatus without an injection molding unit.FIG.7Ais a diagram illustrating a schematic configuration of a two-stage (“cold parison”) process blow molding apparatus20a.

The blow molding apparatus20aincludes a preform supply unit60, a blow molding unit23, a heating unit62(temperature adjusting unit22ain a broader sense), a transfer mechanism26, and a container ejection unit61. The heating unit62includes a looped heated transfer path, and a heating device (not shown) such as an infrared heater that can heat up the body part of the preform to a temperature suitable for blowing. The transfer mechanism26includes a first holding member26a1disposed in the heating unit62for holding a preform received from the preform supply unit60and transports the same, a second holding member26b1that receives the preform from the heating unit62and transports the same to the blow molding unit23, and a third holding member26c1that transports the container from the blow molding unit23to the container ejection mechanism61. The mold used in the blow molding unit23of the blow molding apparatus20ahas the same configuration as that of the embodiment described in the foregoing.

The preform supply unit60receives preforms (made of PET, for example) that were produced and prepared beforehand in an injection molding apparatus elsewhere, and loads the same onto the first holding member26a1. The container ejection unit61includes a container holding part (not shown) disposed adjacent the blow molding unit23for receiving containers that were produced in the blow molding unit23and transported thereto by the third holding member26c1. The heating unit62heats the preform held on the first holding member26a1, as the preform is spun and transported inside the heating device.

In this blow molding apparatus20a, preforms fed by the preform supply unit60are heated in the heating unit62up to a temperature suited for blowing (100 to 110° C., for example), after which the preforms are transferred to the blow molding unit23. In the blow molding unit23, the preform is accommodated in a mold made up of a blow mold cavity51and a bottom mold52, and blow-molded into a container of a desired shape. After the blow molding, the containers are transferred to the container ejection unit61.

The mold according to the embodiment may also be applied to an injection molding apparatus without a blow molding unit.FIG.7Bis a schematic diagram illustrating the configuration of a two-stage injection molding apparatus70.

The injection molding apparatus70includes an injection molding unit21, an ejection unit71, a cooling unit72(temperature adjusting unit22ain a broader sense), and a transfer mechanism26. The cooling unit72includes a cooling pot (not shown) that accommodates the preform to cool the body part of the preform from outside, and a cooling rod (not shown) inserted into the hollow body part of the preform to cool the body part from inside. The transfer mechanism26includes a first holding member26a1that transports the preform from the injection molding unit21to the cooling unit72, and a second holding member26b1that transports the preform from the cooling unit72to the ejection unit71. To the injection molding unit21is connected an injection device25. The mold used in the injection molding unit21of the injection molding apparatus70has the same configuration as that of the embodiment described in the foregoing.

The injection molding apparatus70carries out injection molding of preforms, wherein a resin material (PET, for example) is injected from the injection device25into a mold cavity formed by a neck mold27, an injection mold cavity31, and an injection mold core32that are clamped together in the injection molding unit21. The preforms are then removed in a hot state (with the outer surface temperature in the body part being 100 to 130° C., for example), after which they are transferred to the cooling unit72. At the cooling unit72, the preforms are cooled to the extent that no shrinkage deformation such as sink marks will occur if left under normal temperature (with the outer surface temperature in the body part being 50 to 60° C., for example). Once the preforms are sufficiently cooled, they are transported to the ejection unit71next.

Further, the embodiments disclosed herein should be considered illustrative in all aspects and not limiting. The scope of the present invention is defined not by the description above but by the claims, which are intended to include all changes that come within the meaning and range of equivalency of the claims.