JP3793072B2 - Preform molding method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an injection molding method and apparatus for a preform having a bottomed cylindrical shape used for blow molding a plastic container.
[0002]
[Prior art]
6 to 10 are schematic explanatory views of a conventionally known preform molding apparatus.
In the figure, 1 is a fixed platen, 2 is a cavity mold attached to the fixed platen, 3 is a support frame that is inserted and guided through a tie bar 4, and a rotating mold 6 is a hydraulic motor or the like in the support frame 3. The rotating device 5 is rotatably supported.
[0003]
6, a plurality of core dies 7, 7,... Project from the left and right surfaces of the rotating die 6. As shown in FIG. Reference numeral 8 denotes a support shaft of the rotary mold, and 9 and 9 denote driving cylinders of the support frame 3 installed on the fixed platen 1.
[0004]
A movable platen 10 is driven by a known mold clamping device (not shown) such as a toggle mechanism. Reference numeral 11 denotes a pressing plate for clamping the bolts attached to the movable platen 10, and the pressing plate 11 has core molds 7, 7,. A recess 12 is drilled so as not to occur.
[0005]
In order to form a preform by the above apparatus, the hydraulic cylinders 9 and 9 are driven to draw the support frame 3 toward the cavity mold 2, and the core mold 7 of the rotary mold 6 attached to the support frame 3, 7... Are inserted into the cavity mold and the mold clamping device is operated to bring the movable platen 10 close to the rotary mold 6, and the pressing plate 12 attached to the movable platen 10 is pressed against the rotary mold 6. The mold opening state shown in FIGS. 6 and 7 is changed to the mold clamping state shown in FIGS.
[0006]
When the resin is cooled to a predetermined temperature, the movable platen 10 is retracted to the original position, and the cylinders 9 and 9 are driven to disengage the support frame 3 from the cavity mold 2 and move it to the mold opening position. . Since the molded preform is mounted on the core molds 7, 7,..., The hydraulic motor 5 is operated to rotate the rotary mold 6 180 degrees, and the molded preform is the core molds 7, 7・ Removed from the machine and transported outside the machine. Such operations are repeated to perform a preform molding operation.
[0007]
In addition, when forming a thread part in the neck part of the preform, as shown in FIG. 10, neck molds 7a and 7b made of split molds are attached to the base part of the core mold 7, and When the reformed product is removed, the neck mold is expanded by a cylinder mechanism or the like. When the thread portion is not formed on the neck portion, it is not necessary to attach a neck mold.
[0008]
In recent years, since high temperature contents have been filled in PET bottles, it has become necessary to crystallize the neck of the bottle to improve heat resistance and mechanical strength.
Therefore, a heater is arranged around the neck portion (non-crystalline state) of the preform formed as disclosed in Japanese Patent Publication No. Sho 62-25491 as a means for crystallizing the neck portion of the bottle. The neck portion is crystallized by heating the neck portion.
[0009]
However, in such a means, the neck portion is deformed due to distortion or shrinkage due to heat during heating. Since the neck portion is formed with a screw into which the bottle cap is screwed, if the dimensional accuracy of the portion is not good, the contents may leak, resulting in a defective product.
Currently, heat-resistant bottle manufacturers use dedicated and expensive equipment for crystallizing the neck of the preform.
[0010]
[Problems to be solved by the invention]
The present invention provides a preform injection molding method and apparatus for easily crystallizing a neck portion without requiring expensive equipment as a means for crystallizing the neck portion of the preform. Objective .
[0011]
[Means for Solving the Problems]
In the preform injection molding method according to the first aspect of the present invention, a molten resin is injected and filled into a rotary mold comprising a cavity mold, a core mold and a neck mold, and the rotary mold is placed at 270 from a filling position. In the preform injection molding method of taking out the preform by rotating it, the neck mold is heated by a heating device provided in the neck mold before injection filling, and the melting into the cavity mold and the rotary mold The resin is filled, and after completion of the filling of the molten resin, the heating of the neck portion of the preform is continued for a predetermined time from the filling position to the 180 ° rotation position .
[0012]
The preform injection molding method according to claim 2 is the preform injection molding method according to claim 1, wherein when the molten resin is rotated by 90 ° from the filling position after completion of filling of the molten resin, the core metal The preform attached to the mold is prevented from being overcooled by forming a minute gap from the core mold .
[0013]
Furthermore, a preform molding apparatus according to a third aspect of the present invention is a preform for molding a preform by injecting and filling molten resin into a preform molding die comprising a cavity die, a core die and a neck die. In the injection molding apparatus , the core mold and the neck mold are formed on a rotating mold that is rotatable on a support frame , the support frame is slidable to a mold closing position and a mold clamping position, and the neck The mold is provided with a heating device for heating the neck portion of the preform for a predetermined time from the filling position to the 180 ° rotation position after completion of the filling of the molten resin , and the injection molding apparatus includes: A preform takeout chute is provided at a position where the rotary mold is rotated 270 ° from the filling position .
[0014]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a preform injection molding method and apparatus according to the present invention will be described with reference to FIGS. FIG. 1 is a plan view of an injection molding machine for preforms, showing a mold opened state. 2 is a cross-sectional view taken along line AA in FIG. 1, FIG. 3 is a cross-sectional view taken along line BB in FIG. 1, FIG. 4 is an enlarged view of a portion D in FIG. In the figure, the same parts as those of the known apparatus are denoted by the same reference numerals, and redundant description is omitted.
[0015]
The feature of the present invention is that the neck portion is heated and crystallized at the time of forming the preform, and for this purpose, the heating device h is attached to the neck portion molds 7a and 7b made of split molds. Another measure is to prevent overcooling of the molded preform. The detailed structure will be described below.
[0016]
Each core mold 7, 7... Is bolted to the back plate 14, and a core ring 7 ′ is bolted to the base of the core mold 7. Neck molds 7a and 7b made of split molds, and holders 7a 'and 7b' for attaching them to the upper surface, respectively, projecting the core mold 7 and the core ring 7 'from both sides and projecting dents and dovetails on the plate 15 It is slidably attached by an engaging means d such as. Reference numeral 16 denotes a protruding rod driven by a hydraulic cylinder or the like.
[0017]
Rollers 18 and 18 project from both ends of the holders 7a 'and 7b', and the rollers 18 and 18 are cam grooves 19 'formed in guide plates 19 and 19 attached to the back plate 14, respectively. Each is engaged with 19 '. Therefore, the holders 7a ′ and 7b ′ are opened and closed in conjunction with the vertical movement of the protruding plate 15, and at the same time, the neck molds 7a and 7b are opened and closed.
Other structures are the same as those of a conventional preform molding apparatus.
[0018]
Hereinafter, a method for crystallizing a preform neck by the method of the present invention using the device of the present invention will be described.
1 and 2, the hydraulic cylinders 9 and 9 are driven to draw the support frame 3 in the direction of the cavity mold 2, and the core mold 7 of the rotating mold 6 attached to the support frame 3. , 7,... Are inserted into the cavity mold 2 (state of FIG. 3) and the mold clamping device is operated to bring the movable platen 10 close to the rotary mold 6 and the pressing plate 12 attached to the movable platen 10 is moved. The pressing mold is clamped to the rotary mold 6 and the injection device 13 is advanced to fill the cavity mold 2 with PET resin. (First step)
[0019]
PET resin has the property of becoming transparent when cooled rapidly. In the first step, a cooling medium is supplied to the cooling fluid pipe W provided in the core mold 7 to cool the resin. Although not shown, the cavity mold is similarly fed with a cooling medium, and the resin filled in the mold starts to solidify in an amorphous state. The water temperature when cooling water is used as the cooling medium is 5 ° C to 30 ° C.
[0020]
Since the neck molds 7a and 7b are heated to 120 ° C. or higher by the heating device h attached to these molds, crystallization of the resin proceeds from the surface in contact with the neck molds 7a and 7b.
[0021]
When the resin in the cavity mold 2 is solidified, the mold clamping device is operated to move the movable platen 10 backward, and the hydraulic cylinders 9 and 9 are driven to separate the support frame 3 from the cavity mold 2 and the core mold 7. , 7,..., Move to the mold opening position with the preform molded product held. Then, the rotating device 5 such as a hydraulic motor is driven at the position to rotate the rotary mold 6 by 90 degrees, and the neck portion is crystallized by continuing to heat the neck portion at the position. (Second step)
[0022]
In the second step, the protruding rod 16 is actuated to slightly raise the protruding plate 15, thereby forming a minute gap in the contact surface between the neck molds 7a, 7b and the core ring 7 ', as well as a preform molded product and a core mold. Since a minute gap is also formed between the portions 7, the portion of the preform that is in contact with the core mold 7 and the core ring 7 ′ is prevented from being overcooled.
[0023]
The rotary mold 6 is provided with a core mold 7, a core ring 7 ', neck molds 7a and 7b, holders 7a' and 7b ', a protruding plate 15, a guide plate 19 and the like on the four outer peripheral surfaces of the rectangular parallelepiped. Therefore, while the preform molded product is processed in the second step, the processing in the first step is performed by the core die 7, the neck dies 7a and 7b and the cavity die 2 which are adjacent to each other. .
When the rotating mold 6 is rotated 90 degrees again at the mold opening position, the crystallization of the neck portion in the second step is continued in the third step, and the crystallization of the neck portion is completed in the third step.
[0024]
When the crystallization of the neck portion is completed in the third step, the rotary mold 6 is further rotated 90 degrees at the mold opening position, and when it is rotated to the preform molded product take-out position, the protruding plate 15 is further pushed up to push the mold. The reformed product is released from the core mold 7 and the holders 7a 'and 7b' and the neck molds 7a and 7b are greatly expanded, so that they are conveyed from the take-out chute 20 to the outside of the machine. (4th process)
[0025]
The time required for crystallization of the neck portion of the preform is generally in the range of 90 to 160 seconds, although it depends on the heating temperature of the neck mold. Therefore, the molding cycle is selected by setting the time from the first step to the end of the third step to be the above time.
[0026]
As described above, according to the present invention, the PET resin heated and melted at 270 ° C. or higher in the first step is injected and filled into the mold, and the parts other than the neck portion of the preform are rapidly cooled to be molded into an amorphous state. Then, the mold clamping device and the hydraulic cylinder are driven to move the support frame 3 to the mold opening position, and the rotary mold 6 is rotated 90 degrees at the position to move the core mold 7 and the neck molds 7a and 7b to the second position. After rotating to the process position, the mold clamping device and the hydraulic cylinder are driven again to restore the support frame 3 to the mold clamping position.
[0027]
The preform molded product attached to the former core mold while the resin injection and filling in the first process is performed in the latter core mold and cavity mold is the neck portion at the second process position. Heat treatment for crystallizing and supercooling prevention means other than the neck portion are performed. As described above, the rotary mold 6 rotates every 90 degrees, and the processes of the first to fourth steps are performed during one rotation.
[0028]
【The invention's effect】
According to the present invention, it is possible to easily and easily crystallize the neck portion in the preform molding process without preparing expensive equipment for crystallizing the neck portion of the preform. Therefore, it is possible to provide a preform free from defective products, and at the same time, there are useful effects that can reduce the installation space and equipment cost of the equipment.
[Brief description of the drawings]
FIG. 1 is a plan view of a preform injection molding machine according to the present invention.
FIG. 2 is a cross-sectional view taken along the line AA in FIG.
3 is a cross-sectional view taken along the line BB in FIG.
FIG. 4 is a detailed view of a portion D in FIG. 2;
FIG. 6 is a partially sectional front view of a schematic explanatory view of a conventionally known preform injection molding machine.
FIG. 7 is a partial sectional plan view of the same.
FIG. 8 is a partial cross-sectional front view showing the same mold clamping state.
FIG. 9 is a partial cross-sectional plan view showing the mold clamping state.
FIG. 10 is a sectional explanatory view of a neck portion of a mold of a known preform injection molding machine.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fixed platen 12 Recessed part 2 Cavity mold 13 Injection apparatus 3 Support frame 14 Back plate 4 Tie bar 15 Projecting plate 5 Rotating apparatus 16 Projecting rod 6 Rotating mold 17 Guide pin 7, 7 ... Core mold 18 Roller 7 'Core ring 19 guide plate 7a, 7b neck mold 19 'cam groove 7a', 7b 'holder 20 take-out chute 8 support shaft d dovetail and dovetail groove 9 hydraulic cylinder h heating device 10 movable platen W cooling fluid conduit 11 pressure disc

Claims (3)

In a preform injection molding method, molten resin is injected and filled into a cavity mold, a rotary mold comprising a core mold and a neck mold, and the rotary mold is rotated by 270 ° from a filling position to take out the preform . ,
Heat the neck mold with a heating device provided in the neck mold before injection filling ,
Filling the cavity mold and the rotating mold with the molten resin ,
A preform injection molding method , wherein after completion of filling of the molten resin, heating of the neck portion of the preform is continued for a predetermined time from the filling position to the 180 ° rotation position . After the filling of the molten resin is completed, when the rotating mold is rotated 90 ° from the filling position, the preform attached to the core mold is spaced apart from the core mold to form the preform. The preform injection molding method according to claim 1, wherein overcooling of the preform is prevented. In a preform injection molding apparatus for molding a preform by injecting and filling a molten resin into a preform mold comprising a cavity mold, a core mold and a neck mold ,
The core mold and the neck mold are formed on a rotating mold that can rotate on a support frame , and the support frame is slidable to a mold closing position and a mold clamping position,
The neck mold is provided with a heating device for heating the neck portion of the preform for a predetermined time from the filling position to the 180 ° rotation position after completion of the filling of the molten resin,
The preform injection molding apparatus is characterized in that the injection molding apparatus is provided with a preform takeout chute at a position obtained by rotating the rotary mold 270 ° from the filling position .

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