JP5019416B2 - Compression molding method and apparatus - Google Patents

Description

  The present invention relates to a compression molding method for compression molding of pellets, and more particularly to a compression molding method having a centering function for pellets supplied into a cavity and an apparatus therefor.

  A conventional compression molding apparatus 40 of, for example, a synthetic resin cap has a configuration schematically shown in FIG. 4, and a male mold 43 serving as a core is fitted to a female mold 42 forming a cavity 41. The pellet 45 supplied to the cavity is compressed into a predetermined shape by the cooperation of the male mold 43 and the female mold 42. In the compression molding, as shown in FIG. 4A, molten resin that is continuously extruded from the extrusion die 46 of the molten resin extrusion device with the female mold 42 and the male mold 43 open is provided at the tip of the die 46. A rotary cutter (not shown) cuts to a predetermined length to form a pellet 45 and drops it into the cavity. Then, the male die 43 is lowered integrally with the stripper 44, and the stripper 44 is attached to the upper surface of the female die. In a state where the mold is closed by contact, the male mold 43 descends to compress the pellet 45 into a predetermined shape. At that time, as shown in FIGS. 4A to 4C, if the pellet is not supplied to the center of the cavity, the resin is biased during molding, and in an extreme case, as shown in FIG. In this way, molding defects such as the occurrence of the protruding portion 47 where the molten resin protrudes from the land on one side occur. In particular, when the pellet is formed of a composite resin, as shown in FIG. 5A, for example, a gas barrier resin or the like is included in the main body resin, and an encapsulated resin layer 51 such as a gas barrier layer is provided at a specific position inside the molded product. If the compression molding is not performed in a state where the pellet is located at the center of the cavity, the encapsulating resin layer 51 is biased as shown in FIG. 5B, for example. Defects occur.

  Pellets extruded from the extrusion die into a predetermined shape are cut by a cutter and dropped into the cavity.However, the pellet dropping trajectory always fluctuates depending on the cutter, resin state, resin amount, machine speed, etc. It is very difficult to drop it. Conventionally, the phase of the cutter and the position of the die head are adjusted on site to drop the pellet into the center of the cavity, but when the drop point at the tip of the pellet is aligned with the center of the cavity, the rear end of the pellet enters the cavity. Uniform adjustment is difficult, such as interference. In particular, in the case of a compression molding device such as a cap made of synthetic resin, a rotary type in which a large number of mold devices are arranged on a turret has been adopted in order to enable mass production (see Patent Document 1), and in recent years, a high speed Therefore, it is difficult to stably feed the pellets into the center of the cavity with respect to the rotating mold.

Conventionally, in the manufacture of synthetic resin lids, when a molten resin lump, which is a liner material, is supplied to the top wall inner surface of the lid and the liner is molded by compression molding, a projection is formed at the center of the top wall inner surface to form the top wall inner surface. The molten resin lump supplied to the center is prevented from moving (Patent Document 2), or the liner material supplied by forming an annular ridge at the center of the inner surface of the top wall is relatively to the inner surface of the top wall. Although it has been proposed not to move (Patent Document 3), these are devised to prevent the molten resin mass from moving on the premise that the molten resin mass is supplied to the center of the top wall. Yes, it does not have a centering function for positioning the resin mass supplied by being shifted from the central portion at the central portion. In addition, these are cases where a liner is formed on the inner surface of a cap that has already been formed. In a compression molding apparatus that directly supplies pellets to the mold cavity and compresses them, the pellets supplied out of the center of the cavity are supplied. A compression molding apparatus having a centering function so as to be positioned at the center is not yet known.
JP 11-129269 A Japanese Patent Publication No. 2-44699 Japanese Patent Publication No. 5-34132

  Therefore, the present invention has a centering function of the pellet so that the pellet is positioned at the center during molding even if the pellet is supplied to a position shifted from the center of the cavity, thereby suppressing the occurrence of molding defects due to the unevenness of the pellet. An object of the present invention is to provide a compression molding method and apparatus capable of improving the productivity of compression molding.

The compression molding method of the present invention that achieves the above object is a compression molding method for compressing and molding pellets supplied into a cavity of a female mold , wherein the central part of the bottom mold surface forming the cavity of the female mold is replaced with another bottom part. Centering of the pellet by the movable bottom mold surface is formed as a movable bottom mold surface that is separate from the mold surface, and is positioned below the cavity formation position at the center of the bottom mold surface of the cavity before clamping in a state that forms a stepped portion having the function, pellets supplying step for displacing the pellet in the cavity center portion by the pellets supplied by said state roll down to the stepped portion relative to the movable bottom mold surface The cavity forming process in which the movable bottom mold surface is flush with other bottom mold surfaces to form a cavity, and the pellets in the cavity are compressed from this state. And it is characterized in that comprising a compression molding process to start shape.

The compression molding apparatus according to claim 2 of the present invention for carrying out the compression molding method is a compression apparatus in which a male mold and a female mold having a cavity are relatively displaced to perform compression molding. The center of the bottom mold surface to be formed is formed as a movable bottom mold surface separate from the other bottom mold surfaces, and the stepped portion having a pellet centering function with respect to the cavity forming position is formed on the movable bottom mold surface. to be and have a displacement means for displacing into a cavity forming position for forming the step-forming position and the cavity, wherein the displacement means, the female support the movable bottom mold for supporting the female mold having a movable bottom mold surface Holding the female die relative to the female die support in the axial direction, and the displacement means is provided between the female die and the female die support, The movable bottom mold surface And positioning means for positioning a serial step portion formed positioned in the cavity forming position, and characterized in that said female mold is movable bottom mold surface comprising a biasing means for biasing so as to be located in the stepped portion forming position To do.

The invention according to claim 3 is the compression molding apparatus according to claim 2, wherein the male mold has a stripper on the outer periphery of the male mold so as to be movable relative to the male mold. The movable bottom mold surface is relatively displaced to the cavity forming position by pushing down the mold against the biasing means. The invention according to claim 4 is characterized in that the compression molding apparatus according to claim 2 or 3 is a compression molding apparatus for molding a cup-shaped synthetic resin molded product.

  According to the compression molding method and apparatus of the first and second aspects of the present invention, since the step portion is formed at the center of the bottom mold surface of the cavity before clamping, it is dropped and supplied to the cavity. Even if the pellets are supplied to a position shifted from the central part of the cavity, they are centered so that they are located in the central part at the time of molding, thereby suppressing the occurrence of molding defects due to the unevenness of the pellets and improving the productivity of compression molding. it can. In particular, in the case of molding of a multilayer composite resin molded product, the occurrence rate of molding defects is high because the arrangement of the inner layer resin changes due to the bias of the pellets. It is effective by molding a complex resin. Further, according to the compression molding apparatus of the third aspect, the center part of the bottom mold surface of the cavity is easily displaced between the step forming position and the cavity forming position by displacing the female mold in the axial direction on the female support. The structure is simple. According to a fourth aspect of the present invention, the movable bottom mold surface displacing means includes a positioning means for positioning the movable bottom mold surface between the step portion forming position and the cavity forming position. Since the movable bottom mold surface can be reliably positioned with a simple configuration and the movable bottom mold surface is always positioned at the step forming position by the urging means, the step portion is formed. Therefore, no special driving means is required, and the configuration can be simplified. Furthermore, according to the invention of claim 5, the stepped portion can be surely eliminated automatically in conjunction with the mold clamping at the time of mold clamping without providing a special driving means for driving the movable bottom mold surface. Can do. By applying the present invention to a cup-shaped molded product, particularly a container cap compression molding method and apparatus, the occurrence of molding defects due to uneven supply of pellets to the cavity is reduced even in recent high-speed production lines. Production efficiency can be increased.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a main part of a mold apparatus part of a compression molding apparatus according to an embodiment of the present invention. In this embodiment, a mold apparatus in the case of compression molding a synthetic resin cap is shown. ) Shows a state where the mold is open, and (b) shows a state where the mold is clamped.
The mold apparatus 1 of the compression molding apparatus according to this embodiment includes a female mold (lower mold) assembly 2 and a male mold (upper mold) assembly 3, and the female mold assembly 2 forms a cavity 4. A female die 5 and a female die support 6 are provided, and the female die 5 is integrally supported so as to be axially displaceable with a spring 13 interposed above the female die support 6. The basic structure of the present embodiment is that the central portion of the bottom mold surface forming the female cavity is formed separately from the other bottom mold surface 7 to be a movable bottom mold surface 15, and the movable bottom portion Displacement means for displacing the mold surface 15 to a step forming position for forming a step with the other bottom mold surface 7 and a cavity forming position for forming a cavity in alignment with the other bottom mold surface is provided. It is characterized by. In the present embodiment, the bottom mold surface is a flat surface, but, for example, a molded product having a convex portion or a concave portion at the center of the molding surface molded by the bottom mold surface, Since the cavity at the center position of the bottom mold surface has a shape having a recess or protrusion at the center, the cavity forming position of the movable bottom mold surface is higher than the protrusions of the molded product or the other bottom mold surface. It is in a position that is depressed or protruded by an amount corresponding to the recess.

  The female mold 5 of the female mold assembly 2 has a through hole formed in the center of the bottom mold surface 7 of the cavity 4, and a guide lot of a female mold support is fitted into the through hole as will be described later. The upper part of the through hole is a guide hole 8 for moving the movable bottom mold 16 having the movable bottom mold surface 15 of the female mold 5 up and down. As the cross-sectional shape and size of the guide hole 8, an optimum shape and size can be arbitrarily selected according to the size and shape of the cavity such as a circle, an ellipse, and a rectangle. Then, an upper end positioning surface 10 and a lower end positioning for forming a fixed section in the middle part of the through hole with a large diameter so that the female mold 5 is fitted to and supported by the female mold support 6 in the axial direction (up and down). A positioning space 9 having a surface 11 is formed. The lower end portion of the female die 5 has a spring receiving surface that receives a spring 13 that is an urging means inserted between the female die support 6 and a positioning engagement portion of the female die support described later. An annular engaging ridge 12 is engaged with the bottom surface of 17.

  On the other hand, as shown in FIG. 1, the female support 6 is a movable bottom mold 16 having a movable bottom mold surface 15 whose upper part is fitted into the female guide hole 8, and the lower part is outward. A positioning engagement portion 17 that protrudes and fits into the positioning space 9 and a spring fitting portion 18 formed with a small diameter from the lower portion thereof are formed. The height of the positioning engagement portion 17 is lower than the height of the female positioning space 9 by a height h, and the height of the female movable bottom die 16 that fits into the female guide hole 8 is as follows. It is formed at the same height as the guide hole 8.

  Accordingly, as shown in FIG. 1 (a), in a state where the female mold 5 is fitted and supported on the female support body 6, the female mold 5 is biased by the spring 13, and the engaging protrusion 12 is supported by the female mold. It contacts the lower end positioning surface 11 of the positioning engagement portion 17 of the body 6 and is in the uppermost position. In this state, a stepped portion 20 having a height h is formed between the female bottom mold surface 7 and the movable bottom mold surface 15 which is the top surface of the movable bottom mold 16 held on the female support. . In the state where the female die 5 is pushed down to the lowest position against the spring 13, the upper end positioning surface 10 of the female positioning space 9 is positioned and engaged with the female support member as shown in FIG. Positioned against the upper surface of the portion 17. In that state, the bottom mold surface 7 and the movable bottom mold surface 15 of the cavity 4 are just flush with each other, and a cavity having no step surface is formed. Therefore, in this embodiment, the positioning engagement portion 17 of the female support and the positioning space 9 formed in the female die serve as positioning means for positioning the movable bottom mold surface 15 at the stepped portion forming position and the cavity forming position. Yes.

  The male mold assembly 3 can adopt the same configuration as the conventional one, and the male mold 26 is fitted to the stripper 25 so as to be displaceable. In the case of a rotary molding apparatus, the stripper 25 and the male mold 26 of the male mold assembly 3 are driven by a stripper driving cam and a male driving cam, respectively, and driven up and down in the axial direction to supply pellets, mold clamping, and molding. The steps of mold opening and taking out the molded product are sequentially performed.

Next, a cap compression molding method using the compression molding apparatus of this embodiment having the pellet centering function configured as described above will be described with reference to a molding process diagram shown in FIG.
As shown in FIG. 2 (a), when the compression molding apparatus reaches the pellet supply position where the pellet extruder is located, the female mold 2 is urged by a spring 13 and the uppermost position of the female mold support 6 is reached. And a step 20 having a depth h is formed at the center of the cavity. In this state, the molten resin is extruded from the die head 27 and cut into a predetermined size with a cutter (not shown), so that it falls and is supplied as pellets 30 into the cavity. At that time, even if the pellet 30 is supplied to a position deviated from the center of the cavity, the stepped portion 20 is formed on the cavity bottom mold surface, so that the pellet 30 is natural as shown in FIGS. By rolling down to the step part, it moves to the center part of the cavity and is centered. In the meantime, the stripper 25 and the male mold 26 of the male mold assembly 3 are lowered substantially integrally, the lower end of the stripper 25 is brought into contact with the top surface of the female mold 5 and the mold closing is performed, and the stripper 25 is further lowered. By pushing down the female die 5 against the spring, the movable bottom die 16 is relatively raised, the upper end surface of the positioning engagement portion 17 of the female support 6 hits the upper end positioning surface 10, and the movable bottom portion beyond that. The rise of the mold 16 is prevented. In this state, the movable bottom mold surface 15 is exactly flush with the cavity bottom mold surface, and a cavity is formed (e). From this state, only the male mold 26 is lowered to start compression molding of the pellet, and the male mold is further lowered by a predetermined amount, whereby a cap 35, which is a cup-shaped resin molded product, is molded as shown ( f). Thereafter, the male mold assembly 3 is raised, the mold is opened, and a molded resin molded product is obtained. FIG. 3 is a cam diagram of a cam for driving the male mold (core) 26 and the stripper 25 of the male mold unit in the steps (a) to (f) of FIG. Diagrams and b are cam diagrams of the stripper drive cam. Each position of (a) to (f) in the figure corresponds to (a) to (f) of FIG.

  Since the obtained resin molded product is molded in a state where the pellet is located in the central portion of the cavity, a good molded product without resin bias can be obtained. In particular, when the molded product is not a single resin and includes an intermediate resin layer 51 such as a gas barrier resin layer, as shown in FIG. In the embodiment, a good molded article arranged on the top wall portion of the cap can be obtained. According to the present invention, not only in the molded product in which the part to be formed on the bottom mold surface is a flat surface, but also in the case of molding of a molded product having a convex part or a concave part, Positioning is possible. For example, when the mold surface has a protrusion at the center of the bottom mold surface (i.e., in the case of molding a molded product having a recess in the center), it is particularly difficult to supply pellets to the center, In the case of the present invention, since the step surface is positively formed at the center of the bottom mold surface when pellets are supplied, positioning becomes easy.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment. For example, in the above-described embodiment, the female mold 2 and the female mold support 6 are illustrated as being formed as an integral member, but in actuality, to assemble as illustrated, the female mold 2 and the female mold support 6 are formed. The body 6 must be divided into a plurality of members and assembled together. For example, the movable bottom mold 16 may be constituted by a member separate from the female support and fixed to the female support body by an appropriate means. The compression molding apparatus of the present invention is not necessarily limited to the compression molding of pellets of molten resin mass extruded from the die head, and can also be applied to the case where the preformed and cooled pellets are compressed while being heated.

  According to the present invention, since the pellets dropped and supplied into the cavity are automatically centered, a good compression molded product can be obtained without compression of the pellets, particularly a cup-shaped molded product such as a cap. However, the present invention is not necessarily limited to cup-shaped molded products, and can also be used for compression molding of various articles.

It is a principal part schematic sectional drawing of the metal mold | die part of the compression molding apparatus which concerns on embodiment of this invention, (a) has shown the state which the metal mold | die was open, (b) has shown the state clamped. It is process drawing which shows the compression molding process of the cap by the compression molding apparatus of this embodiment. It is a cam diagram of a male type drive cam and a stripper drive cam. It is process drawing which shows the compression molding process of the cap by the conventional compression molding apparatus. It is a cross-sectional schematic diagram of a cap molded product when an intermediate resin layer is included therein, and (a) is formed in a state where the intermediate resin layer is well arranged, and (b) is formed with an uneven intermediate layer. The cases of molding defects are shown respectively.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mold apparatus 2 Female mold assembly 3 Male mold assembly 4 Cavity 5 Female mold 6 Female support body 7 Bottom mold surface 8 Guide hole 9 Positioning space 10 Upper end positioning surface 11 Lower end positioning surface 12 Engaging protrusion 13 Spring 15 Movable bottom mold surface 16 Movable bottom mold 17 Positioning engagement part 20 Step part 25 Stripper 26 Male mold 27 Die head 30 Pellet 35 Cap

Claims (4)

In a compression molding method for compression molding pellets supplied into a female mold cavity,
The central part of the bottom mold surface that forms the female cavity is formed as a movable bottom mold surface that is separate from the other bottom mold surfaces. in a state in which the movable bottom mold surface so as to be positioned downward to form a stepped portion having a centering function of the pellet Te, the cavity center by pellets supplied by said state roll down to the step portion Pellet feeding step for displacing the pellet in the part,
A cavity forming step in which the movable bottom mold surface is relatively raised and the movable bottom mold surface is flush with other bottom mold surfaces to form a cavity;
A compression molding method comprising: a compression molding step of starting compression molding of pellets in the cavity from this state . In a compression apparatus that performs compression molding by relative displacement between a male mold and a female mold having a cavity, the central portion of the bottom mold surface forming the female mold cavity is used as a separate movable bottom mold surface from the other bottom mold surface. formed, and will by the movable Dosoko part mold surface have a displacement means for displacing into a cavity forming position for forming the step-forming position and the cavity to form a stepped portion having a centering function of the pellets with respect to the cavity forming position ,
The displacement means holds the movable bottom mold having the movable bottom mold surface on a female mold support that supports the female mold, and displaces the female mold relative to the female mold support in the axial direction. Is,
The displacing means is provided between the female mold and the female mold support, positioning means for positioning the movable bottom mold surface at the stepped portion forming position and the cavity forming position, and the female mold as described above. A compression molding apparatus comprising: a biasing means that biases the movable bottom mold surface so as to be positioned at the stepped portion forming position . A stripper is provided on the outer periphery of the male mold so as to be movable relative to the male mold, and when the mold is clamped, the stripper pushes down the female mold against the biasing means, thereby relatively moving the movable bottom mold surface. The compression molding apparatus according to claim 2 , wherein the apparatus is displaced to the cavity forming position. The compression molding apparatus according to claim 2 or 3 , wherein the compression molding apparatus is a compression molding apparatus for molding a cup-shaped synthetic resin molded product.

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