Injection molding apparatus

Abstract

To reliably avoid a synthetic resin material from flowing out onto an outer peripheral surface of an open end of a pouch by improving an injection molding device that inserts the open end of a pouch and injection molds a mouth and neck end.SOLUTION: There is provided an injection molding device that comprises a mold and synthetic resin injection means, and is configured in that: at least a radially inner region of an upper surface of a bottom wall is defined not by an inner mold member 12 but by a cylindrical additional inner mold member 14 formed separately; the additional inner mold member 14 is arranged in a freely movable manner between a molded cavity defining position where a tip surface thereof defines at least a radially inner region of the top surface of the bottom wall and a molding cavity blocking position where a tip surface is located at a portion corresponding to or below a lower surface of the bottom wall to block a molding cavity defining a hanging wall from the molding cavity defining the bottom wall; and the additional inner mold member 14 is provided with selective positioning means 20 for selectively positioning it in the mold cavity defining position and the mold cavity blocking position.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to an injection molding apparatus for injecting and molding a synthetic resin mouth neck member by inserting an opening end portion of a synthetic resin film pouch. More specifically, the present invention relates to an injection molding apparatus for injecting and molding a mouth neck member having an annular bottom wall that abuts or is close to the opening end of the pouch and a cylindrical hanging wall that hangs down from this bottom wall and is joined to the inner peripheral surface of the opening end portion of the pouch, to produce a composite container composed of the pouch and the mouth neck member.

Background Art

[0002] Patent Document 1 below discloses a composite container (bag cup) composed of a synthetic resin film pouch having a circular opening end and a mouth neck member (mouth ring) heat-welded to the inner peripheral surface of the opening end portion of the pouch. The mouth neck member includes an annular bottom wall (flange portion) and a cylindrical hanging wall (body portion) that hangs downward from this bottom wall, and the outer peripheral surface of the hanging wall is heat-welded to the inner peripheral surface of the opening end portion of the pouch.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As described above, the composite container disclosed in Patent Document 1 is formed by positioning the hanging wall of the mouth and neck member within the opening end of the pouch as required and heat-welding the opening end of the pouch to the hanging wall. This results in a relatively complicated formation process, and also has the problem that the joint strength between the opening end of the pouch and the hanging wall of the mouth and neck member is not always sufficient. To solve this problem, the present inventors attempted to insert the opening end of the pouch and injection-molde the mouth and neck end. As an injection molding apparatus for such injection molding, they prototyped an injection molding apparatus comprising a mold composed of an inner mold means and an outer mold means, and a synthetic resin injection means for supplying molten synthetic resin material. The inner mold means includes an inner mold member that defines at least the radially inner region of the upper surface of the bottom wall, along with the inner circumferential surface of the hanging wall of the mouth and neck member and the inner circumferential surface of the bottom wall. The inner mold member has at least one resin channel formed in it that opens to a surface defining the inner circumferential surface of the hanging wall, and the synthetic resin injection means supplies molten synthetic resin material to the molded cavity through the resin channel.

[0005] However, it has been found that injection molding using the injection molding apparatus described above tends to have a problem (which will be discussed further later) in which the synthetic resin material supplied through the resin channel flows into the molding cavity that defines the bottom wall before it is sufficiently filled into the molding cavity that defines the hanging wall, and therefore before the radial inward tilting of the pouch's opening end is sufficiently prevented, and this synthetic resin material flows out onto the outer surface of the pouch's opening end that has tilted radially inward.

[0006] This invention was made in view of the above facts, and its main technical objective is to improve the injection molding apparatus as described above to reliably prevent synthetic resin material from flowing out onto the outer surface of the opening end of the pouch. [Means for solving the problem]

[0007] As a result of diligent study and experimentation, the inventors have found that the above-mentioned main technical problems can be solved by defining at least the radially inner region of the upper surface of the bottom wall with a separately formed cylindrical additional inner mold member instead of an inner mold member, and by arranging this additional inner mold member so as to be movable between a molded cavity defining position in which its tip surface defines at least the radially inner region of the upper surface of the bottom wall, and a molded cavity blocking position in which its tip surface is located at or below the part corresponding to the lower surface of the bottom wall and blocks the molded cavity defining the hanging wall from the molded cavity defining the bottom wall, and by attaching a selective positioning means to the additional inner mold member to selectively position it between the molded cavity defining position and the molded cavity blocking position.

[0008] In other words, according to the present invention, as an injection molding apparatus that achieves the above-mentioned main technical problem, An injection molding apparatus for inserting the open end of a pouch made of synthetic resin film and injection molding a neck member having a ring-shaped bottom wall that abuts against or is close to the open end of the pouch and a tubular hanging wall that hangs down from the bottom wall and is joined to the inner circumferential surface of the open end of the pouch, The system comprises a mold consisting of an inner mold means and an outer mold means, and a synthetic resin injection means for supplying a molten synthetic resin material. The internal molding means includes an internal mold member that defines the inner circumferential surface of the hanging wall and the inner circumferential surface of the bottom wall of the neck member, as well as a cylindrical additional internal mold member that defines at least the radially inner region of the upper surface of the bottom wall. The inner mold member has at least one resin channel formed in it that opens to the surface defining the inner circumferential surface of the hanging wall, and the synthetic resin injection means supplies molten synthetic resin material to the molded cavity through the resin channel. The additional inner mold member is movable between a molded cavity defining position in which its tip surface defines at least a radially inward region of the upper surface of the bottom wall, and a molded cavity blocking position in which its tip surface is located at or below the portion corresponding to the lower surface of the bottom wall, and blocking the molded cavity defining the hanging wall from the molded cavity defining the bottom wall. The additional inner mold member is equipped with selective positioning means for selectively positioning the additional inner mold member at the molded cavity designated position and the molded cavity blocking position. An injection molding apparatus characterized by the above is provided.

[0009] Preferably, the selective positioning means positions the additional inner mold member at the mold cavity blocking position until at least 90% or more of the synthetic resin material flowing through the resin channel has flowed into the mold cavity defining the hanging wall, and thereafter positions the additional inner mold member at the mold cavity defining position. The outer mold means includes a pair of openable and closable outer mold members, each of which preferably has an inner surface and two circumferential end surfaces that cooperate to define the outer and lower surfaces of the bottom wall and abut against the outer surface of the opening end of the pouch. The neck member includes a cylindrical mounting wall extending upward from the bottom wall, preferably having male threads formed on the outer surface of the mounting wall. The hanging wall is preferably thinner than the bottom wall. The opening formed in the inner mold member is preferably located on the surface defining the lower half of the inner surface of the hanging wall. [Effects of the Invention]

[0010] In the injection molding apparatus of the present invention, a sufficient amount of synthetic resin material is filled into the molding cavity defining the hanging wall, and the additional inner mold member is positioned at the molding cavity blocking position until the radial inward tilting of the opening end of the pouch is prevented. After that, the additional inner mold member is moved to the molding cavity defining position, and the flow of synthetic resin material into the molding cavity defining the bottom wall can begin, thus reliably preventing the synthetic resin material from flowing out onto the outer surface of the opening end of the pouch. [Brief explanation of the drawing]

[0011] [Figure 1] A front view showing an example of a composite container having a mouth and neck member injection-molded by an injection molding apparatus configured according to the present invention. [Figure 2] A plan view of the composite container shown in Figure 1. [Figure 3]Cross-sectional view taken along line III-III of FIG. 2. [Figure 4] Cross-sectional view taken along line IV-IV of FIG. 2. [Figure 5] Front view showing the pouch of the composite container shown in FIG. 1. [Figure 6] Plan view of the pouch shown in FIG. 5. [Figure 7] Cross-sectional view showing a preferred embodiment of an injection molding apparatus configured according to the present invention together with a composite container. [Figure 8] Front view showing the inner mold member in the injection molding apparatus shown in FIG. 7. [Figure 9] Plan view of the inner mold member shown in FIG. 8. [Figure 10] Cross-sectional view taken along line X-X of FIG. 9. [Figure 11] Perspective view of a pair of outer mold members in the injection molding apparatus shown in FIG. 7. [Figure 12] Enlarged view of part A of the process of injection molding a neck member using the injection molding apparatus shown in FIG. 7.

Mode for Carrying Out the Invention

[0012] [[ID=�5]]Hereinafter, a preferred embodiment of an injection molding apparatus configured according to the present invention will be described in more detail with reference to the accompanying drawings.

[0013] For the sake of convenience, prior to the injection molding apparatus configured according to the present invention, a composite container provided with a neck member injection molded thereby will be described. An example of such a composite container is shown in FIGS. 1 to 3. <°

[0014] Referring to FIGS. 1 to <3, the composite container 100 is composed of a pouch <02 made of a synthetic resin film and a neck member <04 made of a synthetic resin obtained by inserting the pouch <02 and injection molding as will be described in detail later. <°

[0015] Referring to Figures 5 and 6, the pouch 102 has an opening end 106 at its upper end, which is preferably circular. The pouch 102 can be formed from a single synthetic resin film (in which case there is one side seal), but in the illustrated embodiment it is formed from two synthetic resin films, and two side seals 108a and 108b are arranged at a 180-degree interval in the circumferential direction. Furthermore, in the illustrated embodiment, bifurcated seals 110a-1 and 110a-2 and 110b-1 and 110b-2 are provided, extending downward from the lower ends of each of the two side seal portions 108a and 108b toward both sides in the circumferential direction and radially inward, respectively. In addition, a bottom seal 112-1 is provided connecting one lower end of the bifurcated seals 110a-1 and 110a-2 to one lower end of the bifurcated seals 110b-1 and 110b-2, and a bottom seal 112-2 is provided connecting the other lower end of the bifurcated seals 110a-1 and 110a-2 to the other lower end of the bifurcated seals 110b-1 and 110b-2. Thus, a cup-shaped pouch 102 is formed, closed except for the open end 106. The synthetic resin film forming the pouch 102 may preferably be a single-layer film or a laminated film made by laminating multiple layers. A preferred example is a three-layer synthetic resin film having an inner layer made of low-density polyethylene with excellent adhesion to the neck member 104, which is conveniently made of high-density polyethylene as will be mentioned later; an intermediate layer made of nylon with excellent gas barrier properties; and an outer layer made of polyethylene terephthalate with excellent mechanical properties. The illustrated pouch 102 can be formed by heat welding two synthetic resin films at the side seal portions 108a and 108b, the bifurcated seals 110a-1 and 110a-2 and 110b-1 and 110b-2, and the bottom seals 112-1 and 112-2. The pouch 102 itself may be in a form well known to those skilled in the art, and therefore a detailed description of the pouch 102 itself will be omitted in this specification.

[0016] Continuing the explanation with reference to Figures 1 to 4, the neck member 104 in the illustrated embodiment comprises an annular bottom wall 114 and a cylindrical hanging wall 116 that hangs downward from the inner periphery of the bottom wall 114, with the hanging wall 116 being thinner than the bottom wall 114. It is convenient that the lower surface of the bottom wall 114 abuts against or is close to the upper end, i.e., the opening end 106, of the pouch 102. The lower end of the inner circumferential surface of the hanging wall 116 is inclined radially outward toward downward, and the thickness of the lower end of the hanging wall 116 gradually decreases toward downward. As will be described in more detail later, the neck member 104 is formed by inserting the opening end of the pouch 102 and injection molding, and the outer circumferential surface of the hanging wall 116 of the neck member 104 is joined to the inner circumferential surface of the opening end of the pouch 102. The illustrated neck member 104 further includes a cylindrical mounting wall 118 extending upward from the center in the width direction on the upper surface of the bottom wall 114. An annular groove 120 is provided near the upper end of the outer circumferential surface of the mounting wall 118, and an annular groove 122 is provided near the lower end. In addition, a male thread 124 is provided on the main outer circumferential surface of the mounting wall 118. Such a neck member 104 can be molded from a suitable synthetic resin such as polyethylene, polypropylene, nylon, and polyethylene terephthalate. If the pouch 102 is formed from a three-layer synthetic resin film having an inner layer made of low-density polyethylene, an intermediate layer made of nylon, and an outer layer made of polyethylene terephthalate as described above, it is advantageous for the neck member 104 to be made of high-density polyethylene in terms of adhesion to the polyethylene inner layer, etc.

[0017] In the composite container 100 as described above, the required contents are contained within the composite container 100, and a lid (not shown) is attached to the neck member 104 to close the opening defined on the top surface of the neck member 104. The lid, which can be formed from a suitable synthetic resin such as polyethylene, polypropylene, nylon, and polyethylene terephthalate, similar to the neck member 104, may be of a well-known form, for example, having a circular top wall and a cylindrical skirt wall hanging down from the periphery of this top wall, with a female thread formed on the inner surface of the skirt wall, and is attached to the neck member 104 by fitting it onto the neck member 104 and screwing the female thread formed on the skirt wall into the male thread formed on the mounting wall 118 of the neck member 104.

[0018] Next, with reference to Figures 7 to 12, a preferred embodiment of an injection molding apparatus configured according to the present invention for inserting the opening end of the pouch 102 and injection molding the neck member 104 will be described. The injection molding apparatus, shown as number 2 overall, comprises a mold and a synthetic resin injection means 6. The mold consists of an inner mold means 8 and an outer mold means 10. The inner mold means 8 includes an additional inner mold member 14 together with the inner mold member 12. As clearly shown in Figures 8 and 10, the inner mold member 12 has a cylindrical main part 16a, a short cylindrical protruding part 16b, and an inverted frustoconical lower part 16c whose outer diameter gradually decreases downward. The lower end of the main part 16a has an outer diameter that gradually increases downward and is smoothly connected to the upper end of the outer circumferential surface of the protruding part 16b. The additional inner mold member 14 is thin-walled cylindrical in shape, and its inner diameter corresponds to the outer diameter of the main part 16a of the inner mold member 12. When forming the neck member 104, the additional inner mold member 14 is fitted onto the main portion 16a of the inner mold member 12, and the additional inner mold member 14 is equipped with a selective positioning means, which will be described later. Thus, the inner circumferential surfaces of the bottom wall 114 and the hanging wall 116 of the neck member 104 are defined by the outer circumferential surfaces of the main portion 16a and the protruding portion 16b of the inner mold member 12, the inner circumferential surface of the mounting wall 118 of the neck member 104 is defined by the outer circumferential surface of the additional inner mold member 14, and the radially inward region on the upper surface of the bottom wall 114, i.e., the radially inward region from the mounting wall 118, is defined by the lower end surface of the additional inner mold member 14. See also Figure 12(e).

[0019] The inner mold member 12 has multiple resin channels 18a and 18b formed at positions spaced circumferentially, or in the illustration, at two positions spaced 180 degrees apart. Each of the resin channels 18a and 18b has a main portion 18a-1 and 18b-1 extending vertically downward from the upper end surface of the inner mold member 12, and a downstream portion 18a-2 and 18b-2 extending radially outward downward from the lower ends of the main portions 18a-1 and 18b-1, opening to the lower end of the main portion 16a of the inner mold member 12, i.e., the surface defining the lower half of the inner circumferential surface of the hanging wall 116 of the neck member 104. The synthetic resin injection means 6 supplies molten synthetic resin material to the molded cavity from the upper surface of the inner mold member 12 via the resin channels 18a and 18b.

[0020] Referring to Figure 12 along with Figure 7, the additional inner mold member 14 is equipped with a selective positioning means 20, which allows the additional inner mold member 14 to move between a molded cavity defining position (shown in Figures 12(b) to (e)) where its tip surface defines at least a radially inward region of the upper surface of the bottom wall 114, and a molded cavity blocking position (shown in Figure 12(a)) where its tip surface is located in a portion corresponding to the lower surface of the bottom wall 114, blocking the molded cavity defining the hanging wall 116 from the molded cavity defining the bottom wall 114. The selective positioning means 20 may be driven by an appropriate source such as compressed air, hydraulics, or an electric motor. In the illustrated embodiment, the tip surface of the additional inner mold member 14 abuts against the upper edge of the pouch 102 at the molded cavity blocking position, and as a result, the molded cavity blocking position corresponds to the lower surface of the bottom wall 114. However, if the outer peripheral surface of the additional inner mold member 14 aligns with the inner peripheral surface of the pouch 102, the molded cavity blocking position may be located below the lower surface of the bottom wall 114.

[0021] Referring to Figure 11 along with Figure 7, the outer molding means 10 includes a pair of outer mold members 22a and 22b. The pair of outer mold members 22a and 22b are symmetrical in shape with respect to each other and are movable between a closed position in which their circumferential end faces, described later, abut each other, and an open position which is radially outwardly displaced from the closed position. As can be clearly understood by referring to Figure 11, each of the pair of outer mold members 22a and 22b has a substantially semicircular inner circumferential surface 24a and 24b and circumferential end faces 26a-1 and 26a-2 and 26b-1 and 26b-2 (Figure 11 shows the inner circumferential surface 24a and circumferential end faces 26a-1 and 26a-2 of the outer mold member 22a, but only a part of the inner circumferential surface 24b of the outer mold member 22b is shown, and the reference numeral for the unshown part of the outer mold member 22b is shown in parentheses after the reference numeral for the corresponding part of the outer mold member 22a). As can be understood by referring to Figure 7 together with Figure 11, the inner circumferential surfaces 24a and 24b work together to define the outer circumferential and lower surfaces of the bottom wall 114 of the mouth neck member 104 and the outer circumferential surface of the mounting wall 118. The inner circumferential surfaces 24a and 24b also define the outer circumferential surface of the hanging wall 116 via the pouch 102. The circumferential end surfaces 26a-1 and 26b-1 abut each other, and the circumferential end surfaces 26a-2 and 26b-2 also abut each other. Shallow recesses 28a-1 and 28a-2 and 28b-1 and 28b-2 are provided on each of the circumferential end surfaces 26a-1 and 26a-2 and 26b-1 and 26b-2, respectively, to receive the side seal portions 108a and 108b of the pouch 102. In the illustrated embodiment, the outer molding means 10 also includes a pair of additional outer mold members 30a and 30b that are laminated on the upper surfaces of a pair of outer mold members 22a and 22b, and the upper end surface of the mounting wall 118 is defined by the lower edges of this pair of additional outer mold members 30a and 30b.

[0022] When molding the mouth and neck member 104 using the injection molding apparatus 2 as described above, the opening end of the pouch 102 is inserted into the mold, as shown in Figure 7. More specifically, the opening end of the pouch 102 is fitted onto the lower end of the main part 16a and the protruding part 16b of the inner mold member 12, and the upper ends of the side seal parts 108a and 108b of the pouch 102 are positioned within the recesses 28a-1 and 28a-2 and 28b-1 and 28b-2 in the circumferential end faces 28a-1 and 28a-2 and 28b-1 and 28b-2 of the pair of outer mold members 22a and 22b, and are tightly gripped. The lower parts of the inner circumferential surfaces 24a and 24b of the pair of outer mold members 22a and 22b are in close contact with the outer circumferential surface of the opening end of the pouch 102. Then, the molten synthetic resin material is injected from the synthetic resin injection means 6 through the resin channels 18a and 18b into the molding cavity defined in the mold, thereby forming the mouth and neck member 104.

[0023] When forming the neck member 104 by injecting molten synthetic resin material into the molded cavity, the selective positioning means 20 positions the additional inner mold member 14 as required. Referring to Figure 12 along with Figure 7, in the illustrated embodiment, the selective positioning means 20 positions the additional inner mold member 14 at the molded cavity blocking position until the synthetic resin material flowing in through the resin channels 18a and 18b has flowed into at least 90% of the molded cavity defining the hanging wall 116, and thereafter positions the additional inner mold member 14 at the molded cavity defining position. Since the shape of the molded cavity and the cross-sectional areas of the resin channels 18a and 18b are predetermined in the design, the amount of synthetic resin material flowing into the molded cavity can be estimated from the inflow pressure and time of the synthetic resin material. If desired, the amount of synthetic resin material flowing in may be measured by placing the required sensors in the resin channels 18a and 18b or in the molded cavity. From the above, in the state before the inflow of the synthetic resin material begins, the additional inner mold member 14 is located in the molded cavity blocking position as shown in Figure 12(a). After the inflow of the synthetic resin material begins and the required amount flows into the molded cavity defining the hanging wall 116, the additional inner mold member is moved to the molded cavity defining position as shown in Figure 12(b). As a result, as shown in Figures 12(c) to (e), the synthetic resin material is sequentially filled into the molded cavity defining the hanging wall 116, the molded cavity defining the bottom wall 114, and the molded cavity defining the mounting wall 118.

[0024] Here, if the additional inner mold member 14 is not positioned as described above, according to the inventor's experience, depending on the shape of the neck member 104 to be molded and the inflow pressure of the synthetic resin material, the synthetic resin material may flow into the molded cavity defining the bottom wall 114 before it is sufficiently filled into the molded cavity defining the hanging wall 116, resulting in the following problems. That is, if the synthetic resin material flows into the molded cavity defining the bottom wall 114 before it is sufficiently filled into the molded cavity defining the hanging wall 116, the synthetic resin material that has flowed into the molded cavity defining the bottom wall 114 will tilt the opening end of the pouch 102 radially inward, overflow it, and flow out onto the outer circumferential surface of the opening end of the pouch 102, resulting in the hanging wall 116 not being properly molded. In other words, the opening end of the pouch 102 is prevented from tilting radially inward due to the presence of the hanging wall 116. However, if the synthetic resin material flows into the molded cavity defining the bottom wall 114 before it is sufficiently filled into the molded cavity defining the hanging wall 116, the synthetic resin material will tilt the opening end of the pouch 102 radially inward in the areas where the hanging wall 116 does not exist. If the hanging wall 116 is not properly molded, the joint between the mouth / neck member 104 and the pouch 102 will be insufficient and will also be undesirable in appearance.

[0025] Thus, in the injection molding apparatus of the present invention, the additional inner mold member 14 is positioned at the molding cavity blocking position until a sufficient amount of synthetic resin material is filled into the molding cavity defining the hanging wall 116, thereby preventing the radial inward tilting of the opening end of the pouch 102. After that, the additional inner mold member 14 is moved to the molding cavity defining position, and the inflow of synthetic resin material into the molding cavity defining the bottom wall 114 can be started, thereby reliably preventing the synthetic resin material from flowing out onto the outer circumferential surface of the opening end of the pouch 102. Furthermore, in the illustrated embodiment, the hanging wall 116 of the neck member 104 is thinner than the bottom wall 114, and the hanging wall 116 is easily elastically deformable. Therefore, even if the hanging wall 116 gets caught on the inner mold member 12 when removing the neck member 104 from the inner mold member 12 after the molding is complete, the sticking is resolved by the elastic deformation of the hanging wall 116, and the neck member 104 can be removed from the inner mold member 12. On the other hand, if the bottom wall 114 is thin and easily elastically deformable, the strength of the neck member 104 will be insufficient, which is undesirable. When the inner diameter of the hanging wall 116 is 90 mm, it is preferable that the wall thickness of the hanging wall 116 be 0.5 to 2.0 mm and the wall thickness of the bottom wall 114 be 1 to 10 mm.

[0026] Although preferred embodiments of the injection molding apparatus of the present invention have been described in detail above with reference to the attached drawings, the present invention is not limited to the above embodiments, and further modifications are possible within the scope of the present invention. For example, in the illustrated embodiment, the mouth and neck member 104 injected by the injection molding apparatus of the present invention included a mounting wall 118, but this may be omitted. In the case of a mouth and neck member in which the mounting wall 118 is omitted, the mouth and neck member is sealed by attaching paper to the upper surface of the bottom wall, etc. Also, in the illustrated embodiment, the pouch 102 had two side seal portions 108a and 108b, but such side seal portions may not exist. If side seal portions do not exist, the recesses 28a-1 and 28a-2 and 28b-1 and 28b-2 in the circumferential end faces 28a-1 and 28a-2 and 28b-1 and 28b-2 of the pair of outer mold members 22a and 22b are omitted. [Explanation of symbols]

[0027] 2: Injection molding equipment 4: Molding mold 6: Synthetic resin injection molding means 8: Inner mold means 10: Outer mold means 12: Inner mold member 14: Additional inner mold member 18: Resin channel 20: Selective positioning means 100: Composite container 102: Pouch 104: Oral and cervical member 114: Bottom wall 116: Hanging wall

Claims

1. An injection molding apparatus for inserting the open end of a pouch made of synthetic resin film and injection molding a neck member having a ring-shaped bottom wall that abuts against or is close to the open end of the pouch and a tubular hanging wall that hangs down from the bottom wall and is joined to the inner circumferential surface of the open end of the pouch, The system comprises a mold consisting of an inner mold means and an outer mold means, and a synthetic resin injection means for supplying a molten synthetic resin material. The internal molding means includes an internal mold member that defines the inner circumferential surface of the hanging wall and the inner circumferential surface of the bottom wall of the neck member, as well as a cylindrical additional internal mold member that defines at least the radially inner region of the upper surface of the bottom wall. The inner mold member has at least one resin channel formed in it that opens to the surface defining the inner circumferential surface of the hanging wall, and the synthetic resin injection means supplies molten synthetic resin material to the molded cavity through the resin channel. The additional inner mold member is movable between a molded cavity defining position in which its tip surface defines at least a radially inward region of the upper surface of the bottom wall, and a molded cavity blocking position in which its tip surface is located at or below the portion corresponding to the lower surface of the bottom wall, and blocking the molded cavity defining the hanging wall from the molded cavity defining the bottom wall. The additional inner mold member is equipped with selective positioning means for selectively positioning the additional inner mold member at the molded cavity designated position and the molded cavity blocking position. An injection molding apparatus characterized by the following.

2. The injection molding apparatus according to claim 1, wherein the selective positioning means positions the additional inner mold member at the mold cavity blocking position until the synthetic resin material flowing through the resin channel has flowed into at least 90% of the mold cavity defining the hanging wall, and thereafter positions the additional inner mold member at the mold cavity defining position.

3. The injection molding apparatus according to claim 1 or 2, wherein the outer molding means includes a pair of openable and closable outer mold members, each of which cooperates to define the outer peripheral surface and bottom surface of the bottom wall and has an inner peripheral surface that abuts against the outer peripheral surface of the opening end of the pouch and two circumferential end surfaces.

4. The injection molding apparatus according to claim 1, wherein the neck member includes a cylindrical mounting wall extending upward from the bottom wall, and male threads are formed on the outer circumferential surface of the mounting wall.

5. The injection molding apparatus according to claim 1, wherein the hanging wall is thinner than the bottom wall.

6. The injection molding apparatus according to claim 1, wherein the opening formed in the inner mold member is located on a surface that defines the lower half of the inner circumferential surface of the hanging wall.

Images