JPH06328512A - Mold for forming cylindrical molding - Google Patents

Abstract

PURPOSE:To prevent generation of a weld line even when the opening of an injection passage is provided in the position eccentric from the center of the bottom of a cylindrical molding by providing the recessed part of a cold slug well which incorporates the periphery of the position opposite to the opening of the injection passage and is extended according to the eccentric quantity at the side opposite to the opening through the center. CONSTITUTION:A first core mold 44 is provided in a male mold 4 and arranged movably in the vertical direction for a stripper plate 42 placed on a female mold 2 and regulates the internal surface of the wall of the top panel of a vessel cover. The recessed part 444 of a cold slug well is provided on the bottom 442 regulating the internal surface of the wall of the top panel of the vessel cover in the first core mold 44 of the male mold 4. The recessed part 444 of the cold slug well is made elliptical so as to incorporate the periphery of the position opposite to the opening 242 of an injection passage 24 formed in the female mold 2 and extend according to the eccentric quantity S at the side opposite to the opening 242 through the center. Thereby the recessed part of cold slug well is firstly filled with synthetic resin material injected to the space of the mold and thereafter fluidized toward the end part of the space of the mold.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding die for a cylindrical molded product having an end wall, and more specifically, for molding a cylindrical molded product such as a container lid by injection molding a synthetic resin. Regarding molds.

[0002]

2. Description of the Related Art A mold for injection-molding a tubular molded product such as a container lid is an end wall (top wall) of the tubular molded product (container lid).
Molding for molding a cylindrical molded product (container lid) between a female die having a concave portion defining an outer surface and an outer peripheral surface of a cylindrical side wall (skirt wall) and the peripheral surface of the concave portion in cooperation with the female die. A male mold that forms a space and defines the inner surface of the end wall (top wall) and the inner wall of the cylindrical side wall (skirt wall) of the cylindrical molded product (container lid), and the female mold is formed into the molding space. An injection passage is provided that opens to the. The opening of the injection passage is generally a cylindrical molded product (container lid) in the recess so that the synthetic resin injected from the opening into the molding space reaches the end of the molding space at the same time as much as possible. Is provided at the center of the bottom surface that defines the outer surface of the end wall (top wall).

However, when irregularities such as characters and figures are formed on the outer surface of the end face wall (top wall) of the cylindrical molded product (container lid), the opening of the injection passage should be opened from the appearance. )
In some cases, the opening cannot be provided at the center of the bottom surface that defines the outer surface of the end wall (top wall), and the opening must be provided at an eccentric position. When the opening of the injection passage is provided eccentrically from the center of the bottom surface that defines the outer surface of the end surface wall (top wall) of the cylindrical molded product (container lid), the synthetic resin injected from the opening is
There is a slight time delay in reaching the end of the molding space on the side close to the opening, and reaching the end of the molding space on the side far from the opening. Therefore, during this time delay, on the side far from the opening, the synthetic resin that reached the end of the molding space first flows in from both sides, so the cylindrical molded product (container lid) cylindrical side wall (skirt wall) far from the opening. ), A so-called weld line is generated, which becomes a factor of impairing the appearance. When knurls are formed on the outer peripheral surface of the tubular side wall (skirt wall) of the tubular molded product (container lid), the outer appearance of the knurl does not deteriorate so much, but the tubular side wall (skirt wall) is formed by a flat surface. If so, the weld line is unacceptable in appearance. The occurrence of such a weld line becomes more remarkable as the thickness of the molded product becomes thinner.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above facts, and its main technical problem is that the opening of the injection passage is deviated from the center of the bottom surface defining the end face wall of the cylindrical molded product. Another object of the present invention is to provide a molding die for a tubular molded product, which can effectively prevent the occurrence of weld lines even if it is provided at the centered position.

[0005]

In order to achieve the above technical object, according to the present invention, an outer peripheral surface of a cylindrical side wall of a cylindrical molded product and an outer surface of an end face wall that closes one end of the cylindrical side wall are defined. Forming a molding space for molding a cylindrical molded product between the female mold having the concave portion and the peripheral surface of the concave portion in cooperation with the female mold, and forming the end wall inner surface and the cylindrical side wall of the cylindrical molded product. A molding die for a tubular molded product, comprising: a male die defining an inner peripheral surface, wherein the female die is provided with an injection passage opening at a position eccentric from a center of a bottom surface defining the outer surface of the end wall in the recess. In the mold, hot water extending corresponding to the amount of eccentricity through the center of the bottom surface defining the inner surface of the end surface of the male mold, including the periphery of the position facing the opening of the injection passage, and the center opposite to the opening. With a recess
A mold for molding a tubular molded article is provided.

[0006]

A molding space is formed from an opening of an injection passage provided at a position eccentric from a center of a bottom surface which is formed in a female mold forming a molding die for a cylindrical molded product and defines an outer surface of an end face wall of the cylindrical molded product. The synthetic resin injected therein first fills the molten metal pool concave portion formed in the male mold, and flows from the molten metal pool concave portion toward each end of the molding space in each direction. The basin recess is provided on the bottom surface that defines the inner surface of the male end face wall, and is formed on the side opposite to the opening through the center including the periphery of the position facing the opening and corresponding to the eccentric amount. Therefore, the synthetic resin flowing from the basin recess toward the end portions of the molding space in each direction reaches the end portions of the molding space in each direction at substantially the same time.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment applied to a container lid molding die as a molding die for a tubular molded article constructed according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a vertical cross-sectional view showing an embodiment of a container lid molding die constructed according to the present invention, and FIG. 2 is an injection molding of a synthetic resin for molding a container lid into the container lid molding die of FIG. FIG. 3 is a vertical cross-sectional view showing a state in which the female mold and the male mold are opened from a state in which the synthetic resin is injected into the container lid molding die shown in FIG. The container lid molding die in this embodiment is composed of a female die 2 and a male die 4. The female mold 2 is provided with a recess 22 that defines the outer surface of the top wall of the container lid and the outer peripheral surface of the skirt wall. The female mold 2 has a distance S from the center O of the bottom surface 222 that defines the outer surface of the top wall of the container lid.
An injection passage 24 having an opening 242 is provided at a position that is eccentric. The male die 4 is arranged so as to be movable on the stripper plate 42 placed on the female die 2 in the vertical direction with respect to the stripper plate 42, and defines the inner surface of the top wall of the container lid. Core mold 44, a second core mold 46 integrally formed with the first core mold 44 and defining the inner peripheral surface of the skirt wall of the container lid, the second core mold 46 and the stripper plate 42. And a third core mold 48 that is movably arranged in the vertical direction in the figure and defines the end surface of the skirt wall of the container lid, and in the state of FIG. A molding space 6 for molding the container lid is formed in cooperation with the concave portion 22 of the female mold 2. On the bottom surface 442 that defines the inner surface of the top surface wall of the container lid of the first core mold 44 of the male mold 4, a hot water pool recess 444 is provided. The basin recess 444 passes through the center including the periphery of a position facing the opening 242 of the injection passage 24 formed in the female mold 2 and passes through the center to the eccentricity S on the side opposite to the opening 242.
Is formed in an elliptical shape extending corresponding to. That is, the basin pit 444 is formed from the left and right ends in the figure to the bottom surface 442.
The distance from the radial outer peripheral edge to each other is substantially the same, or the length from the center O to the right end in the figure where the opening 242 is located is slightly smaller than the length from the center O to the left end in the figure opposite to the opening 242. Make it longer and in the figure from the left end to the bottom surface 4
It is formed so that the distance to the facing outer peripheral edge of 42 is slightly shorter than the distance from the right end to the facing outer peripheral edge of the bottom surface 442 in the drawing in which the opening 242 is located.

The container lid molding die according to the present embodiment is constructed as described above, and the molding of the container lid using the die will be described below. The female mold 2 and the male mold 4 are assembled as shown in FIG. 1 when molding the container lid.
When the female die 2 and the male die 4 are combined, a synthetic resin material 8 such as polypropylene and polyethylene which is heated and melted by an injection molding machine (not shown) is injected, and the synthetic resin material is applied to the female die 2 as shown in FIG. It is made to flow into the molding space 6 from the opening 242 through the formed injection passage 24. At this time, the synthetic resin material that has flowed into the molding space 6 through the opening 242 first fills the molten metal pool recess 444, and then flows to the ends of the molding space 6 in each direction. By the way, the opening 242 of the injection passage 24 is provided at a position eccentric from the center O of the mold by a distance S. And the distance from the left and right ends to the respective radial outer peripheral edges of the bottom surface 442 in the drawing is substantially the same, or the center from the length from the center O to the right end in the drawing where the opening 242 is located. The length from O to the left end on the side opposite to the opening 242 is slightly longer, and the distance from the left end to the facing outer peripheral edge of the bottom surface 442 in the drawing is the right end to the bottom surface 442 facing in the drawing in which the opening 242 is located. Since it is formed so as to be slightly shorter than the distance to the outer peripheral edge, the synthetic resin material filled in the molten metal pool recess 444 reaches the end portions of the molding space 6 in each direction at substantially the same time. When the molding space 6 is filled with the synthetic resin material 8 in this way, after the required cooling time elapses, the male die 4 is moved upward with respect to the female die 2 as shown in FIG. The first core die 44, the second core die 46, and the third core die 48 in the die 4 are moved upward in the drawing with respect to the stripper plate 42 and die-cutting, whereby the circular top wall 12 and the The container lid 10 having the cylindrical skirt wall 14 hanging down from the peripheral edge of the top wall 12 is obtained.

The container lid shown in FIGS. 4 to 6 was injection-molded by the container lid molding die as described above. That is, the outer diameter (D) of the container lid (top wall): 82.5 mm, the height (H) of the container lid (skirt): 21.5 mm, the thickness of the top wall (t
1): 1.3 mm, eccentric distance (S) from the center of the container lid (top wall) to the opening 242 of the injection passage 24: 3 mm, elliptical convex formed on the back surface of the top wall by the basin recess 444 Distance (a1) from the center of the container lid (top wall) of the portion 122 to the end opposite to the opening: 13 mm, from the center of the container lid (top wall) of the elliptical convex portion 122 to the opening side end Distance (a2): 8 mm, the elliptical convex portion 122
(B) is 10 mm, and the thickness (t2) of the ceiling wall on which the elliptical convex portion 122 is formed (t2) is 1.5 mm. A mold for forming the container lid 10 is manufactured, and JIS K- 67
58 Flowability by test method (MRF): 22 g / min
Injection pressure: 951k
Injection molding was performed at g / cm ² and an injection temperature of 230 ° C. As a result, no weld line was generated on all the molded container lids.

In the above embodiment, the oval shape is used as the basin recess 444 formed on the bottom surface 442 of the first core mold 44 which defines the inner surface of the top wall of the male mold 4 in the container lid molding mold. However, the shape of the basin recess is not limited to this. For example, as shown in FIG.
The puddle recess 446 formed on the bottom surface 442 of the first core mold 44 may be fan-shaped, or may be a circular puddle recess 448 as shown in FIG. In short, the molten metal pool recess formed in the bottom surface that defines the inner surface of the top wall of the male die in the container lid molding die corresponds to the opening of the injection passage formed at a position eccentric from the center of the female die. It may be a concave portion that extends through the center including the periphery of the position facing the opening and on the side opposite to the opening corresponding to the eccentricity. Further, in each of the above-mentioned embodiments, the mold for molding the container lid has been described, but the present invention is not limited to only the mold for molding the container lid, and various tubular molded products having an end face wall It goes without saying that it can be applied to a molding die.

[0012]

The mold for molding a cylindrical molded product according to the present invention is configured as described above, and in the mold in which the injection passage is opened at a position eccentric from the center in the female mold, the bottom surface of the male mold is used. At the time of injection molding, a basin recess is provided on the side opposite to the opening including the periphery of the position facing the opening of the injection passage formed in the female mold and passing through the center and corresponding to the eccentricity. The synthetic resin material injected into the molding space from the opening of the injection passage formed in the female mold first fills the recess of the molten metal pool, and then flows toward the end of the molding space. It is possible to make the timings of reaching the end portions in each direction substantially the same. Therefore, it is possible to prevent the occurrence of a weld line on the side far from the opening of the injection passage due to the difference in the arrival time of the synthetic resin material. Therefore, it is possible to mold a thin cylindrical molded product.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an embodiment in which the present invention is applied to a container lid molding die.

FIG. 2 is a vertical cross-sectional view showing a state in which a synthetic resin for molding a container lid is injected into the container lid molding die shown in FIG.

FIG. 3 is a vertical cross-sectional view showing a state where a female mold and a male mold are opened from a state where a synthetic resin is injected into the container lid molding die shown in FIG.

4 is a plan view of a container lid molded by the container lid molding die shown in FIG. 1. FIG.

5 is a bottom view of the container lid shown in FIG.

6 is a vertical cross-sectional view of the container lid shown in FIG.

FIG. 7 is a bottom view of a main part of a male mold forming a container lid molding die according to another embodiment of the present invention.

FIG. 8 is a bottom view of a main part of a male mold forming a container lid molding mold according to still another embodiment of the present invention.

[Explanation of symbols]

 2: Male type 4: Female type 6: Molding space 10: Container lid 12: Top wall 14: Skirt wall 22: Recessed portion 24: Injection passage 42: Stripper plate 44: First core type 46: Second core type 48 : Third core mold 242: Opening 444: Hot water pool recess

Claims (1)

[Claims] 1. A female mold having a concave portion defining an outer peripheral surface of a cylindrical side wall of a cylindrical molded product and an outer surface of an end face wall that closes one end of the cylindrical side wall, and a peripheral portion of the concave portion in cooperation with the female mold. A male mold for forming a molding space for molding a cylindrical molded product between the surface and a surface and defining an inner surface of an end face wall and an inner peripheral surface of a cylindrical side wall of the cylindrical molded product. In a molding die for a cylindrical molded product, which is provided with an injection passage opening at a position eccentric from the center of the bottom surface defining the outer surface of the end wall, the injection passage is formed on the bottom surface defining the inner surface of the end wall of the male die. A mold for molding a tubular molded product, characterized in that a basin recess is provided on the side opposite to the opening including the periphery of the position facing the opening and on the side opposite to the opening, corresponding to the amount of eccentricity. .