TEMPERATURE ADJUSTMENT MOLD AND APPARATUS AND METHOD FOR PRODUCING RESIN CONTAINER

A temperature adjustment mold capable of performing local temperature adjustment in an axial direction from the inside of a preform while restricting shrinkage and deformation of the preform, for adjusting a temperature of an injection-molded bottomed resin-made preform includes a rod portion inserted into the preform and extending in the axial direction of the preform. The rod portion includes an annular projection portion that protrudes in a radial direction of the rod portion and contacts an inner peripheral surface of the preform. The rod portion contacts a bottom portion of the preform to restrict shrinkage in the axial direction of the preform. The projection portion restricts shrinkage in a radial direction of the preform, conducts heat between the rod portion and the preform, and adjusts a temperature at a predetermined part in an axial direction of the preform.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a temperature adjustment mold, an apparatus and a method for producing a resin container.

Description of the Related Art

Conventionally, a hot parison type blow molding apparatus is known as one of apparatuses for producing a resin container. The hot parison type blow molding apparatus is configured to blow-mold a resin container using residual heat from injection molding of a preform, and is advantageous in that it is possible to produce resin containers which are diversified and excellent in aesthetic appearance as compared with the cold parison type.

In general, the preform immediately after injection molding does not have a temperature distribution suitable for shaping the container. Therefore, in the hot parison type blow molding cycle, the temperature adjustment step of the preform is performed between the injection molding step and the blow molding step in order to suppress uneven temperature of the preform or impart a desired temperature distribution suitable for shaping the container to the preform.

In this type of temperature adjustment step, a temperature adjustment rod mold following the internal shape of the preform may be inserted into the preform, and the temperature adjustment rod mold may be brought into close contact with the inner peripheral surface of the preform to adjust the temperature (for example, JP 3330677 A and JP 3255485 A).

Since the conventional temperature adjustment rod mold is in close contact with the inner peripheral surface of the preform, it is not suitable for temperature adjustment that imparts a temperature difference in the axial direction. Therefore, for example, it has been difficult to improve the thickness distribution of the container by locally cooling a part corresponding to the thin portion of the container from the inside of the preform while restricting shrinkage and deformation of the preform.

SUMMARY OF THE INVENTION

One aspect of the present invention is a temperature adjustment mold for adjusting the temperature of a preform that is injection-molded, has a bottomed shape, and is made of resin. The temperature adjustment mold includes a rod portion inserted into the preform and extending in an axial direction of the preform. The rod portion includes an annular projection portion that protrudes in a radial direction of the rod portion and comes into contact with an inner peripheral surface of the preform. The rod portion comes into contact with a bottom portion of the preform to restrict shrinkage in the axial direction of the preform. The projection portion restricts shrinkage in a radial direction of the preform, conducts heat between the rod portion and the preform, and adjusts a temperature at a predetermined part in an axial direction of the preform.

DESCRIPTION OF THE EMBODIMENTS

In the embodiment, for easy understanding, the description of structures and elements other than main portions of the present invention will be simplified or omitted. In addition, in the drawings, the same reference numerals are assigned to the same elements. Further, shapes, dimensions, and the like of the respective elements illustrated in the drawings are schematically set and may not represent actual shapes, dimensions, and the like.

FIG.1is a diagram schematically showing a configuration of a blow molding apparatus20of the present embodiment. The blow molding apparatus20of the present embodiment is a hot parison type (also referred to as a one-stage type) apparatus that blow-molds a container using residual heat (internal heat quantity) from injection molding without cooling the preform10to room temperature.

The blow molding apparatus20includes an injection molding unit21, a temperature adjustment unit22, a blow molding unit23, a taking-out unit24, and a conveyance mechanism26. The injection molding unit21, the temperature adjustment unit22, the blow molding unit23, and the taking-out unit24are disposed at respective positions rotated by a predetermined angle (for example, 90 degrees) around the conveyance mechanism26.

The conveyance mechanism26includes a transfer plate28(not illustrated inFIG.1) that moves to rotate around an axis in a direction perpendicular to the paper surface ofFIG.1. On the transfer plate28, one or more neck molds27(not illustrated inFIG.1) for holding the neck portion of the preform10or the resin container (hereinafter simply referred to as a container) are arranged at each of predetermined angles. The conveyance mechanism26moves the transfer plate28by 90 degrees to convey the preform10(or the container) of which the neck portion is held by the neck mold27to the injection molding unit21, the temperature adjustment unit22, the blow molding unit23, and the taking-out unit24in this order. Note that the conveyance mechanism26further includes a lifting and lowering mechanism (vertical mold opening/closing mechanism) and a mold opening mechanism of the neck mold27, and also performs an operation of lifting and lowering the transfer plate28and an operation related to mold closing and mold opening (mold release) in the injection molding unit21and the like.

The injection molding unit21includes an injection cavity mold and an injection core mold (not illustrated), and produces the preform10illustrated inFIG.2. An injection device25that supplies a resin material, which is a raw material of the preform10, is connected to the injection molding unit21.

In the injection molding unit21, the injection cavity mold, the injection core mold, and the neck mold27of the conveyance mechanism26are closed to form a preform-shaped mold space. Then, by pouring the resin material from the injection device25into the mold space having such a preform shape, the preform10is produced by the injection molding unit21.

For example, the entire shape of the preform10is a bottomed cylindrical shape of which one end side is open and the other end side is closed. A neck portion is formed at an end portion of the preform10on the opening side.

The material of the container and the preform10is a thermoplastic synthetic resin, and can be appropriately selected according to the use of the container. Examples of specific types of material include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycyclohexanedimethylene terephthalate (PCTA), Tritan (registered trademark: copolyester produced by Eastman Chemical Co., Ltd.), polypropylene (PP), polyethylene (PE), polycarbonate (PC), polyethersulfone (PES), polyphenylsulfone (PPSU), polystyrene (PS), a cyclic olefin polymer (COP/COC), polymethyl methacrylate: acrylic (PMMA), polylactic acid (PLA), and the like.

In addition, even when the mold of injection molding unit21is opened, the neck mold27of the conveyance mechanism26is not opened, and the preform10is held and conveyed as it is. The number of the preforms10simultaneously molded by the injection molding unit21(that is, the number of containers that can be simultaneously molded by the blow molding apparatus20) can be appropriately set.

The temperature adjustment unit22performs temperature equalization and removal of uneven temperature of the preform10produced by the injection molding unit21, and adjusts the temperature of the preform10to a temperature suitable for blow molding (for example, approximately 90° C. to 105° C.) and a temperature distribution suitable for a container shape to be shaped. In addition, the temperature adjustment unit22also has a function of cooling the preform10in a high temperature state after the injection molding.

FIG.2is a longitudinal sectional view showing a configuration example of the temperature adjustment unit22. The temperature adjustment unit22includes a cavity mold (temperature adjustment pot mold, heating pot mold)31capable of accommodating the preform10, and a temperature adjustment rod32that is a mold member inserted into the preform.

The cavity mold31has a space for temperature adjustment having substantially the same shape as the outer shape of the preform10produced by the injection molding unit21. The cavity mold31is divided into at least three in the axial direction of the preform10, and includes an upper mold31a, a middle mold31b, and a lower mold31c.

The upper mold31ais a mold facing the outer peripheral surface in the vicinity of the neck portion of the preform10. The middle mold31bis a mold facing the outer peripheral surface of the body portion of the preform10. The lower mold31cis a mold facing the outer peripheral surface of the bottom portion of the preform10. The bottom surface of the upper mold31aand the upper surface of the middle mold31b, and the bottom surface of the middle mold31band the upper surface of the lower mold31care engaged with each other in a spigot structure to sandwich a heat insulating member therebetween, for example.

A heating member (not illustrated) such as a band heater (ring-shaped heater) or a rod-shaped heater is attached to each of the upper mold31a, the middle mold31b, and the lower mold31cof the cavity mold31. The upper mold31a, the middle mold31b, and the lower mold31care each maintained at a predetermined temperature by a heating member. Then, the outer peripheral side of the preform10is heated by the heat from the cavity mold31, and accordingly, the temperature of the preform10is adjusted. The body portion of the heated preform10contracts and deforms toward the inner diameter side and the neck portion side. The temperature distribution in the axial direction of the preform10can also be changed by changing the temperatures of the heating members of the upper mold31a, the middle mold31b, and the lower mold31c.

The temperature adjustment rod32is an example of a rod portion (rod member), and is configured to be able to move forward and backward in the axial direction (vertical direction in the drawing) with respect to the neck mold27holding the preform10in the temperature adjustment unit22.FIG.2shows a state where the temperature adjustment rod32is moved (lowered) to the lower side in the drawing by a rod drive mechanism (not illustrated) and inserted into the neck mold27and the preform10.

The diameter of the temperature adjustment rod32is set to be smaller than the inner diameter of the preform10. The tip end of the temperature adjustment rod32inserted into the preform10comes into contact with the bottom portion of the preform10. The axial length of the temperature adjustment rod32is set to a length that assumes the amount of shrinkage of the preform10until the temperature adjustment rod32is inserted after being conveyed out from the injection molding unit21. As a result, the temperature adjustment rod32has a function of maintaining the axial length of the preform10at a predetermined dimension at the time of temperature adjustment and restricting excessive shrinkage of the preform10.

Inside the temperature adjustment rod32, a flow path (not illustrated) through which the temperature adjustment medium flows is formed along the axial direction. Therefore, the temperature adjustment rod32is maintained at a predetermined temperature by the temperature adjustment medium flowing inside. In the present embodiment, a case where the temperature adjustment rod32is set to a temperature lower than that of the preform10and the preform10is cooled by the temperature adjustment rod32will be described, but the preform10can also be heated by the temperature adjustment rod32.

The temperature adjustment rod32has an annular projection portion33protruding radially outward.FIG.3is a transverse sectional view of the vicinity of the projection portion of the temperature adjustment unit22. Also inFIG.3, the flow path in the temperature adjustment rod32is not illustrated.

The projection portions33shown inFIGS.2and3are attachable to and detachable from temperature adjustment rod32, and include a pair of half ring bodies34made of a material having good heat conductivity. The half ring body34has an annular large diameter portion (projection portion33) on the outer peripheral side, and the attachment position can be adjusted in the axial direction of the temperature adjustment rod32. The pair of half ring bodies34(projection portions33) is fixed to the temperature adjustment rod32by fixing means (not illustrated).

The projection portion33has a function of coming into contact with a predetermined part in the axial direction of the preform10from the inside to adjust the temperature of the predetermined part. At a part which is in contact with the projection portion33inside the preform10, heat is conducted to the temperature adjustment rod32via the projection portion33. On the other hand, since air is interposed between the temperature adjustment rod32and the preform10at a part which is not in contact with the projection portion33inside the preform10, heat of the temperature adjustment rod32is less likely to be transferred. Therefore, it is possible to adjust the temperature distribution in the axial direction of the preform10at the position of the projection portion33.

In addition, the projection portion33comes into contact with the inner periphery of the preform10as described above, and accordingly, the preform10is less likely to shrink toward the inner diameter side from the projection portion33. Therefore, the projection portion33also has a function of maintaining the dimension in the radial direction of the preform10at the time of temperature adjustment and restricting excessive shrinkage of the preform10.

The outer diameter of the projection portion33is appropriately set in consideration of the temperature adjustment time by the projection portion33according to the amount of shrinkage of the preform10. When the outer diameter of the projection portion33is increased, the shrinking preform10and the projection portion33come into contact with each other relatively quickly, and the temperature adjustment time by the contact with the projection portion33becomes long. On the other hand, when the outer diameter of the projection portion33is reduced, the contact between the shrinking preform10and the projection portion33is delayed as compared with the case where the outer diameter of the projection portion33is large, and the temperature adjustment time is shortened. Therefore, by adjusting the outer diameter of the projection portion33, the contact time between the predetermined part of the preform10and the projection portion33changes, and the temperature adjustment time for the predetermined part of the preform10can be adjusted. The above adjustment may be performed, for example, by preparing a plurality of types of half ring bodies34having different outer diameters of the projection portions33and appropriately replacing the half ring body34according to the container shape to be produced and the specifications of the material of the preform10and the like.

FIG.2shows an example in which the projection portion33is disposed at the axially intermediate portion of the temperature adjustment rod32to cool the corresponding part of the preform10forming the shoulder portion of the container. By locally cooling the part of the preform10corresponding to the shoulder portion of the container to reduce the residual heat, the thickness of the shoulder portion of the container can be increased during blow molding, and the thickness distribution of the container can be improved.

FIG.4is a modification example ofFIG.2, and shows an example in which the vicinity of the boundary portion between the neck mold27and the upper mold31a(corresponding part below the neck of the preform10) is cooled by the projection portion33. Also inFIG.4, similarly to the example ofFIG.2, the projection portion33is formed of a pair of half ring bodies34. According to the example ofFIG.4, by locally cooling the underside of the neck to lower the fluidity of the resin at the same site, it is possible to suppress generation of burrs in the gap between the neck mold27and the upper mold31aor between the neck mold27and the blow mold upper surface.

FIG.5is a modification example ofFIG.4, and shows an example in which the projection portion33is integrally formed on the temperature adjustment rod32at the position below the neck. Also in the example ofFIG.5, the same effect as that ofFIG.4can be obtained.

FIG.6is another modification example ofFIG.2, and shows a configuration example in which an annular contact ring35constituting the projection portion33and a cylindrical spacer36are put on the temperature adjustment rod32. Note that the configuration and function of the cavity mold31inFIG.6are similar to those inFIGS.2to5, and thus redundant description will be omitted.

Inner diameters of the annular contact ring35and the cylindrical spacer36are each set to a dimension into which the temperature adjustment rod32can be inserted. At least one or more contact rings35and at least one or more (more preferably, two or more) spacers36are inserted into the temperature adjustment rod32and disposed concentrically on the outer circumference of the rod main body32bof the temperature adjustment rod32.FIG.6shows an example in which two contact rings35and two spacers36each are attached to the temperature adjustment rod32.

The outer diameter of the contact ring35is set to be larger than the outer diameter of the spacer36. The contact ring35attached to the temperature adjustment rod32protrudes to the outer peripheral side of the spacer36to come into contact with the inner side of the preform10, and conducts the heat of the preform10to the temperature adjustment rod32. Therefore, the contact ring35has a function of the projection portion33that comes into contact with a predetermined part in the axial direction of the preform10from the inside to adjust (cool) the temperature of the predetermined part.

The spacer36is attached to the temperature adjustment rod32to axially position the contact ring35. In addition, the spacer36has a function of forming an air layer with the inner periphery of the preform10without coming into contact with the preform10, for example. As described above, the temperature distribution in the axial direction of the preform10can be adjusted at the position of the contact ring35.

The temperature adjustment rod32includes a tip end piece32a. The tip end piece32ahas a larger diameter than the rod main body32b, and is attachable to and detachable from the tip end of the rod main body32b. The contact ring35and the spacer36are inserted into the rod main body32bin a state where the tip end piece32ais removed. The tip end piece32ais attached to the tip end of the rod main body32bafter the contact ring35and the spacer36are inserted into the rod main body32b, and prevents the contact ring35and the spacer36from coming off. More specifically, after the stepped portion at the lower end (tip end) of the temperature adjustment rod32is accommodated in the recess portion at the upper end of the tip end piece32a, a stopper pin (not illustrated) is inserted into the through-hole formed in each of the temperature adjustment rod32and the tip end piece to prevent the contact ring35and the spacer36from coming off. The spacer36and the tip end piece32afunction as fixing means for fixing the contact ring35(projection portion33) to the temperature adjustment rod32.

Also in the example ofFIG.6, the same effect as that ofFIG.2can be obtained. In the example ofFIG.6, the outer diameter and the number of the contact rings35and the axial position of the contact ring36defined by the spacer36can be appropriately changed by replacing the contact ring35and the spacer36.

Returning toFIG.1, the blow molding unit23performs stretch blow molding on the preform10having a temperature adjusted by the temperature adjustment unit22to produce the container.

The blow molding unit23includes a blow cavity mold which is a pair of split molds corresponding to the shape of the container, a bottom mold, a stretching rod, and an air introduction member (blow core mold, none of these illustrated). The blow molding unit23performs blow molding on the preform10while stretching the preform10. Consequently, the preform10is shaped into a shape of the blow cavity mold, and the container can be produced.

The taking-out unit24is configured to open the neck portion of the container produced by the blow molding unit23from the neck mold27and unload the container to the outside of the blow molding apparatus20.

(Description of Blow Molding Method)

Next, a blow molding method by the blow molding apparatus20of the present embodiment will be described.

FIG.7is a flowchart showing steps of the blow molding method. In the present embodiment, a mold adjustment step (S100) is performed before each step (S101to S104) described later of the blow molding method is performed.

The mold adjustment step is a step of adjusting the position of the projection portion33of the temperature adjustment rod32according to the shape or the like of the container to be shaped. As an example, the following operation is performed in the mold adjustment step.

First, the blow molding apparatus20is subjected to a test operation to obtain information on the container shape before adjustment. Next, the axial position of the projection portion33of the temperature adjustment rod32is adjusted based on the information on the container shape. At this time, the temperature adjustment time by the temperature adjustment rod32may be changed by changing the outer diameter of the projection portion33by changing the part or the like.

For example, when there is a thin portion in the axial direction of the container, the operator adjusts the position of the projection portion33of the temperature adjustment rod32such that the part of the preform10corresponding to the thin portion of the container comes into contact with the projection portion33. As a result, the part of the preform10corresponding to the thin portion of the container comes into contact with the projection portion33and is locally cooled, and the thickness distribution of the container after adjustment is improved.

In addition, for example, when a burr is generated under the neck of the container, the operator performs adjustment such that the projection portion33of the temperature adjustment rod32is positioned in the vicinity of the boundary portion between the neck mold27and the upper mold31a(corresponding part under the neck of the preform10). As a result, the part under the neck of the preform10is locally cooled, and the generation of burrs under the neck of the container is suppressed.

When the mold adjustment step is completed, each step of the blow molding cycle described below is executed.

In step S101, in the injection molding unit21, the resin is injected from the injection device25into the preform-shaped mold space formed by the injection cavity mold, the injection core mold, and the neck mold27of the conveyance mechanism26to produce the preform10.

In step S101, when the injection molding of the preform10is completed, the mold of injection molding unit21is opened, and the preform10is released from the injection cavity mold and the injection core mold. Next, the transfer plate28of the conveyance mechanism26moves to rotate by a predetermined angle, and the preform10held by the neck mold27is conveyed to the temperature adjustment unit22.

Subsequently, the temperature adjustment unit22performs temperature adjustment for bringing the temperature of the preform10close to a temperature suitable for the final blow.

In the temperature adjustment step, the preform10held by the neck mold27is accommodated in the cavity mold31by lowering the transfer plate28. When the temperature adjustment rod32is lowered, the temperature adjustment rod32is inserted into the preform10.

In the temperature adjustment unit22, the preform10is heated from the outside in a non-contact state by the cavity mold31. As a result, the temperature of the preform10is adjusted not to be equal to or lower than a temperature suitable for blow molding, and the uneven temperature generated from injection molding is also reduced. In addition, the inner peripheral surface of the preform10comes into contact with the projection portion of the temperature adjustment rod32due to the shrinkage of the preform10, and accordingly, a predetermined part of the preform10is locally cooled.

After the temperature adjustment step, the transfer plate28of the conveyance mechanism26moves to rotate by a predetermined angle, and the temperature adjusted preform10held by the neck mold27is conveyed to the blow molding unit23.

Subsequently, in the blow molding unit23, blow molding of the container is performed.

First, the blow cavity mold is closed, the preform10is accommodated in the mold space, and the air introduction member (blow core) is lowered, and accordingly, the air introduction member abuts on the neck portion of the preform10. Then, the stretching rod (longitudinal stretching member is lowered to hold the bottom portion of the preform10from an inner surface thereof, and while longitudinal stretching is performed as necessary, blow air is supplied from the air introduction member, and accordingly, the preform10is longitudinally stretched. Consequently, the preform10is inflated and shaped to be in close contact with the mold space of the blow cavity mold and is blow-molded into the container. Note that the bottom mold stands by at a lower position which is not in contact with the bottom portion of the preform10before closing the blow cavity mold, and quickly rises to the molding position before closing the mold or after closing the mold.

When the blow molding is completed, the blow cavity mold and the bottom mold are opened. Consequently, the container is movable from the blow molding unit23.

Subsequently, the transfer plate28of the conveyance mechanism26moves to rotate by a predetermined angle, and the container is conveyed to the taking-out unit24. In the taking-out unit24, the neck portion of the container is opened from the neck mold27, and the container is unloaded to the outside of the blow molding apparatus20.

This completes the series of steps of the blow molding cycle. Thereafter, by moving the transfer plate28of the conveyance mechanism26to rotate by the predetermined angle, the respective steps of S101to S104described above are repeated. Further, during an operation of the blow molding apparatus20, four sets of the containers having a time difference between each step are produced in parallel.

Hereinafter, functions and effects of the present embodiment will be described.

The temperature adjustment rod32of the present embodiment has an annular projection portion33that protrudes in the radial direction and comes into contact with the inner peripheral surface of the preform10. The projection portion33conducts heat between the temperature adjustment rod32and the preform10. As a result, in the present embodiment, the predetermined part in the axial direction of the preform10can be cooled from the inside by the projection portion33to adjust the temperature, and the thickness distribution of the container to be blow-molded can be improved.

In addition, the tip end of the temperature adjustment rod32comes into contact with the bottom portion of the preform10to restrict the shrinkage in the axial direction of the preform10. Then, the projection portion33comes into contact with the inner peripheral surface of the preform10to restrict shrinkage in the radial direction of the preform10. As a result, variations in the shape of the preform10at the time of temperature adjustment are suppressed, and it is easy to apply an appropriate temperature distribution to the preform10in each blow molding cycle.

In addition, the projection portion33of the present embodiment is provided on the half ring body34or the contact ring35attachable to and detachable from the temperature adjustment rod32, and can adjust the position in the axial direction. As a result, it is possible to easily adjust the position where the temperature of the preform10is adjusted according to the specification of the container or the like.

The protruding amount in the radial direction of the projection portion33can be changed by replacing the half ring body34or the contact ring35. As a result, the temperature adjustment time by the projection portion33can be adjusted by changing the timing at which the shrinking preform10and the projection portion33come into contact with each other.

Here, when the material of the preform10is polyethylene (PE) or high-density polyethylene (HDPE), the thermal shrinkage is higher than that of PET or the like, and the preform10is easily shrunk and deformed at the time of temperature adjustment. Moreover, it is known that these materials have less strain hardening property than PET and the like, and it is difficult to adjust the thickness during blow molding. The strain hardening property refers to a property of increasing the strength by molecular orientation until the thickness becomes uniform in such a manner that the weakest portion (usually the hottest part) of the preform first reaches the yield point and the next weakest portion starts to stretch during the blowing process. Therefore, when a preform of PE or HDPE is blow-molded, it is extremely important to appropriately adjust the temperature before blowing while suppressing shrinkage deformation of the preform. According to the present embodiment, it is possible to easily adjust the temperature of the preform suitable for container molding of PE or HDPE.

The present invention is not limited to the above-described embodiments, and various improvements and design changes may be made without departing from the gist of the present invention.

For example, in the above embodiment, a plurality of projection portions33may be provided in the axial direction of the temperature adjustment rod32.

In addition, the embodiments disclosed herein are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is indicated not by the above description but by the claims, and it is intended that the scope thereof includes meanings equivalent to the claims and all modifications within the scope.