JP3114125B2 - Molding method of synthetic resin cap - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic resin cap to be fitted to a container such as a bottle, and more particularly to a mold for molding at the time of molding having a screw or the like formed on a skirt wall engaging with the neck of the container. The present invention relates to a method for forming a synthetic resin cap, which is likely to be forcibly pulled out.

[0002]

2. Description of the Related Art Conventionally, as a cap for a beverage bottle or the like, a screw 42 is formed on the inner peripheral surface of a skirt wall 41, as shown in FIG. In many cases, a synthetic resin cap 40 having a bilder bluef band (hereinafter simply referred to as a PP band) 43 in which the bridging portions 44 are detachably connected as slits 45 is frequently used. This kind of synthetic resin cap is integrally molded by injection molding or compression molding. However, as shown in FIG. 9, if there is a screw portion or a PP band portion, an undercut portion is formed in a molding die,
Forcible removal occurs at the time of die removal, and the portion is easily damaged.
In particular, in the case of a cap having a PP band portion, since a slit is provided, if the portion is forcibly removed, a large stress acts on the bridging portion and the PP band is cut off, resulting in many defective products. There is a problem. Therefore, conventionally, for example, as described in Japanese Patent Application Laid-Open No. 1-235615 and Japanese Patent Publication No. 2-61893, the molding die at that portion is divided to prevent the forcible removal at the time of die removal. In addition, various ideas are required for the mold, which causes the complexity of the mold and the accompanying loss of molding time.

[0003] On the other hand, the die removal of the screw portion is usually carried out simply by pushing out with an eject pin in a conventional mold without any special measures. Therefore, there are inevitably problems such as forced removal and deformation of the screw thread. In order to solve this problem and to finish the screw portion neatly, for example, a structure may be employed in which the core portion of the mold is rotated so that the die portion can be turned. However, such a structure complicates the mold, causing a problem that the price of the mold increases and the productivity decreases. Also,
In the case of a cap having a locking stopper or a positioning projection, it is impossible to turn the cap, and the cap must be forcibly removed.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned conventional problems in molding a synthetic resin cap. In order to eliminate the complexity of the mold and the decrease in productivity when forming the cap, the mold can be simplified and the undercut parts such as the screw part can be finished finely, which leads to cost reduction and production. It is an object of the present invention to provide a novel method for molding a synthetic resin cap capable of improving the performance.

[0005]

As a result of various studies to achieve the above object, the present inventor has found that a part of a cap is formed into an expanded shape so that the undercut portion of the cap is reduced to zero or only a small part. The inventors have found that the molding is stopped to achieve simplification and speed-up of the molding die, and have reached the present invention. That is, the molding method of the synthetic resin cap of the present invention,
A method for molding a synthetic resin cap having a top wall and a skirt wall, wherein the hinge has a joining edge so as to cross at least a portion that causes an undercut, such as a threaded portion of the cap, a slit or a liner stopper projection. And a step of forming a deployment cap in a state where the deployment cap is expanded into two parts by being connected with each other, and a step of closing the deployment cap from a hinge portion and bonding a joining edge.

The hinge and the joining edge may be formed, for example, by forming the hinge along the axial direction of the skirt wall, and forming the joining edge along the axial direction of the skirt wall from the lower end of the skirt wall opposite to the hinge. And the top of one skirt wall is formed along the lower surface of the top wall to reach the upper end of the hinge, the hinge is formed along the axial direction of the skirt wall, and the joining edge is Various forms can be adopted, such as a form in which the hinge reaches the upper end of the hinge via the wall, a form in which the hinge is formed in the top wall, and a joint edge is formed in the skirt wall from both ends of the hinge to the lower end of the skirt wall. . When a screw having a thread cut is formed on the skirt wall for gas release or the like, it is preferable to form a joining edge along the cut.

[0007]

Since a synthetic resin cap having a screw portion and a slit is first formed in an unfolded state, the inner surface of the skirt wall is unfolded, and the screw portion and the PP band connecting portion are formed in an unfolded state. The undercut part is not formed and the thread and slit are not caught by the die when the die is removed, so-called forced removal is eliminated, the die is easily removed, and the thread and the bridging part are not damaged. Can be molded. In this method, since there is no undercut portion as compared with the conventional method, the production speed is remarkably improved, and the die is simplified, so that a low-cost die can be used. After the deployment cap formed in the unfolded state is released from the mold, it is closed from the hinge portion in the next joining step and the joining edges are joined together, so that a complete cap is obtained. In the cap thus obtained, the thread and the PP band portion are not damaged in the molding process, so that a product with a clear thread and an extremely high yield can be obtained.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings. 1 and 2 show a deployment cap in an intermediate step of the cap molding method according to the present invention. The present invention eliminates the undercut portion which occurs when molding in a conventional process by forming the projection such as a screw portion in such a deployed state so that the projection direction of the projection substantially coincides with the die-cutting direction. Thus, the mold is simplified. The deployment cap 1 of this embodiment is a form of an intermediate process for manufacturing a cap 10 having a cylindrical skirt wall 2 shown in FIG. 3, in which a hinge 4 is formed along the axial direction of the skirt wall 2 and a joining edge is formed. 5 is formed from the lower end of the skirt wall 3 opposite to the hinge to the top of the skirt wall along the axial direction of the skirt wall, and the top of one skirt wall is formed so as to reach the upper end of the hinge along the lower surface of the top wall 3. Then, the skirt wall 2 is bisected from the middle via a hinge, and is developed and formed with the top wall 3 attached to the top of one skirt wall. The cap is skirt wall 2
On the inner surface, a screw 6 to be screwed to the neck of the bottle mouth is formed,
A PP band portion 7 is formed at a lower portion via a bridging portion 8. Reference numeral 9 denotes a slit between the bridging portions.

FIGS. 4 (a) and 4 (b) show the main parts of the apparatus for forming the expansion cap. In the deployment cap, the skirt wall is divided into two parts from the center, and the semicircular tube is just separated by a hinge part.
Since it is in a continuous state, if the skirt wall 2 which is developed in two rows with the core part end face and the female mold center part end face is formed, the undercut part can be eliminated and the mold can be formed. Can be very simplified. That is, the molding die is a mold in which the first die 15 of the core portion forming the male die forms the inner surface of the deployment cap, and has a screw molding surface on the end surface 16 thereof. Further, the second mold 17 which is a central member of the female mold assembly is provided.
Is a molding surface of the outer peripheral surface of the skirt wall and the outer peripheral surface of the PP band in a state where the semicircular pipe is just connected via the hinge. The second mold 17 has an intermittent ridge 19 for forming the slit 9 formed between the lower end of the skirt wall and the PP band portion. In addition, 20, 21,
Reference numerals 22 and 23 are constituent members of the female assembly.

[0010] With the above-described molding apparatus, the deployment cap is molded in a state where the screw portion and the PP band connection portion are deployed. Therefore, since there is no undercut portion and there is no forced removal portion at the time of removing the mold, the removal of the mold is smooth and easy, and the molding can be performed favorably without damaging the thread and the bridging portion. After the expansion cap 1 molded in the expanded state is die-cut, it is sent to the next joining step. In the joining step, the deployment cap 1 is closed via the hinge 4 and the joining edge 5 is closed.
Is heated by high-frequency heating or the like, and a complete cap can be obtained by heat-sealing the joining edges as shown in FIG. The cap 10 thus obtained
Since the thread and the PP band are not damaged in the molding process, a product with a clean thread and an extremely good yield can be obtained.

FIGS. 5 and 6 show the cap 1 of the above embodiment.
13 shows another embodiment of the deployment cap state of the intermediate step of No. 0. In the deployment cap 30 of this embodiment, the cap is divided into two parts, the top wall 3 as well as the skirt wall 2, the hinge 31 is formed along the axial direction of the skirt wall 2, and the joining edge 32 is formed from the lower end of the skirt wall to the top wall. , Is formed to reach the upper end of the hinge, and is completely expanded into two parts. FIG. 7 shows still another embodiment of the deployment cap of the cap 10 of the above embodiment. In the deployment cap 35 of this embodiment, the hinge 36 is formed on the top wall, and the joining edge 37 is formed.
Are formed on the skirt wall 2 so as to reach the lower end of the skirt wall from both ends of the hinge. As described above, the form of the deployment cap can employ various forms, and it is essential that the form has no undercut. Further, in each of the above-described embodiments, the joining edge is formed in a straight line. However, as shown in FIG. it can.

In addition, a cap having a screw portion formed with a vertical thread for gas release for releasing gas at the time of opening, such as a cap for a sparkling beverage bottle such as a carbon dioxide beverage, As shown in FIG. 2 or FIG. 6, in the case where a joint edge is provided on the skirt wall to form a deployment cap, the joint edge is provided along the cut line of the screw, so that even if joint unevenness occurs in the joint portion, the screw may be screwed. Does not affect the thread engagement. Further, the joining of the joining edges can be performed by an appropriate method such as fusion joining or adhesion. Furthermore, by changing the color of the resin in the two divided portions as needed, a two-color cap can also be obtained, and a high value-added cap can be obtained.

[0013]

The present invention has the following special effects. Since the synthetic resin cap is molded in the unfolded state, the inner surface of the cap is unfolded to form an undercut portion, so-called unremovable portion does not occur, and it is easy to remove the mold, and the screw thread and the bridging portion are damaged. It can be molded well without any need. Therefore, the cap obtained by joining the formed deployment caps does not break the screw thread or the PP band portion in the forming process, so that a product with an extremely high yield can be obtained. In this method, since there is no undercut portion, the production speed is remarkably improved as compared with the conventional method, and the mold is simplified, so that a low-cost mold can be used.

[Brief description of the drawings]

FIG. 1 is a plan view of a deployment cap in an intermediate step of the present invention.

FIG. 2 is a front view thereof.

FIG. 3 is a front view of the cap obtained after the final step.

4A is a cross-sectional view of a main part schematically showing a molding die during molding of a deployment cap, and FIG. 4B is a cross-sectional view taken along line AA of FIG.

FIG. 5 is a plan view of another embodiment of the deployment cap in the intermediate step of the present invention.

FIG. 6 is a front view thereof.

FIG. 7 is a front view of still another embodiment of the deployment cap in the intermediate step of the present invention.

FIG. 8 is a front view of another embodiment of the cap obtained after the final step in which the shape of the joining edge is changed.

FIG. 9 is a front view showing a partial cross section of a conventional synthetic resin cap with a PP band.

[Explanation of symbols]

 1, 30, 35 Deployment cap 2 Skirt wall 3 Top wall 4, 31, 36 Hinge 5, 32, 37, 38 Joining edge 6 Screw 7 PP band section 8 Bridge section 9 Slit 10 Cap 15 First type (core member) 17 Type 2

Claims (5)

(57) [Claims] 1. A method for molding a synthetic resin cap having a top wall and a skirt wall, comprising a joining edge so as to cross at least a portion causing an undercut, and being connected by a hinge portion. A method of molding a synthetic resin cap, comprising: a step of molding a deployment cap in a state of being developed into two parts; and a step of closing the deployment cap from a hinge portion and bonding a joining edge. 2. The deployment cap, wherein a hinge is formed along an axial direction of the skirt wall, and a joining edge is formed from a lower end of the skirt wall opposite the hinge to a top of the skirt wall along an axial direction of the skirt wall; 2. The method of molding a synthetic resin cap according to claim 1, wherein the top of the skirt wall on one side is formed so as to reach the upper end of the hinge along the lower surface of the top wall. 3. The composite according to claim 1, wherein the deployment cap has a hinge formed along the axial direction of the skirt wall, and a joining edge formed from the lower end of the skirt wall to the upper end of the hinge via the top wall. Method for molding resin caps. 4. The method of molding a synthetic resin cap according to claim 1, wherein the unfolding cap has a hinge formed on a top wall and a joining edge formed on the skirt wall so as to reach a lower end of the skirt wall from both ends of the hinge. . 5. The method of molding a synthetic resin cap according to claim 1, wherein the skirt wall is formed with a thread having a thread cut along the joint edge of the skirt wall.