JPH04290718A - Injection molding method for long narrow cylindrical container - Google Patents

Abstract

PURPOSE:To obtain a molded product having a peripheral wall with thin and uniform thickness by a method wherein a male mold is allowed to advance toward a female mold in a state filled with a rather small amount of a molten resin from a gate to perform mold clamping and both molds are again filled with the molten resin under pressure to eliminate an unfilled part and, after cooling, the molds are opened to take out the molded product. CONSTITUTION:A female mold 4 and a male mold 7 are brought to a slightly opened state to be filled with a rather small amount of a molten resin 10 from a gate 3. The male mold 7 is allowed to advance toward the female mold 4 to perform mold clamping. Both molds are again filled with the molten resin 10 under pressure to eliminate an unfilled part. After cooling, the molds are opened to take out a molded product. As the molten resin 10, one with degree of crystallization of 30% or less is used.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for injection molding elongated cylindrical containers such as blood collection tubes.

0002

[Prior Art] Generally, in order to injection mold an elongated cylindrical container such as a blood collection tube, a deep tapered round hole with a concave spherical bottom wall and a gate opened at the center point of the concave spherical surface of the round hole are used. An injection mold is used, which includes a female mold having a cylindrical shape and a male mold having a long round bar with a convex spherical tip.

[0003] Then, molten resin is injected from the gate,
This molten resin was poured between the round hole of the female mold and the long round bar of the male mold to form an elongated cylindrical container.

[0004] During this molding, it was necessary to stabilize the core (long round bar) of the male mold.

[0005]

[Problems to be Solved by the Invention] However, when molding is performed using the conventional injection molding method described above, due to the depth and injection pressure, the molding material may enter unevenly, resulting in poor centering and poor wall thickness. There was a problem that it was not possible to stably supply uniform molded products.

An object of the present invention is to solve the above-mentioned conventional problems.

That is, an injection molding method for an elongated cylindrical container that can stabilize the core (long round bar) of the male mold and form a molded product having a thin and uniformly thick peripheral wall has been developed. It is to provide.

[0008]

[Means for Solving the Problems] In order to solve the above problems, the present invention includes a deep tapered round hole with a concave spherical bottom wall and a gate opened at the center point of the concave spherical surface of the round hole. The female mold and the male mold each have a long round bar with a convex spherical tip. Fill a small amount of resin through the gate, then move the male mold forward relative to the female mold to clamp the mold, and fill with molten resin again and apply holding pressure to compensate for the unfilled parts. Then, after cooling, the mold was opened and the molded product was taken out.

[0009]

[Operation] When moving the male mold forward relative to the female mold, the long round bar of the male mold pushes the molten resin, so no large force is applied to the long round bar of the male mold. Therefore, this round rod does not fall down, and the molten resin flows uniformly between the round hole of the female mold and the round rod of the male mold.

[0010] As a result, the round long bar of the male mold is maintained in a stable state, and a molded product having a thin peripheral wall of uniform thickness is formed.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the injection molding method for elongated cylindrical containers according to the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing a state in which resin is injected from the gate of an injection mold used in the injection molding method for an elongated cylindrical container according to the present invention, and FIG. It is a sectional view showing a state where the side mold is advanced.

The injection mold used in the injection molding method for an elongated cylindrical container according to the present invention has a deep taper round hole 2 whose bottom wall is a concave spherical surface 1 and a concave spherical surface 1 of the round hole 2.
A female mold 4 is provided with a gate 3 opened at the center of the mold, and a male mold 7 is provided with a long round bar 6 having a convex spherical surface 5 at the tip.

Next, a method for injection molding an elongated cylindrical container according to the present invention will be explained.

First, the female mold 4 and the male mold 7 are opened slightly, and a small amount of molten resin 10 is filled from the gate 3 (see FIG. 1).

After that, the male mold 7 is attached to the female mold 4.
The mold is clamped by advancing the mold (see Figure 2).

Then, the molten resin 10 is filled again and a holding pressure is applied to compensate for the unfilled portion.

Next, after cooling, the mold is opened and the molded product is taken out.

As the molten resin 10, one having a crystallinity of 30% or less is used.

When a small amount of molten resin 10 is filled from the gate 3, the molten resin 10 comes into contact with a part of the female mold 4 and a part of the male mold 7.

[0021] At this time, a thin solidified layer is formed on the wall surface of the female mold 4, so that even when the molten resin 10 is injected again, it remains in close contact with the wall without peeling off.

When filling the molten resin 10 again, it is necessary to do so while the previously filled molten resin 10 is sufficiently melted.

When the male mold 7 is advanced relative to the female mold 4, the long round bar 6 of the male mold 7 pushes the molten resin 10, causing the long round bar 6 of the male mold 7 to press against the molten resin 10. Since no large force is applied to the round bar 6, the round bar 6 will not fall down.
The molten resin 10 flows uniformly between the round hole 2 of the female mold 4 and the round rod 6 of the male mold 7.

[0024] As a result, the long round bar 6 of the male mold 7 is maintained in a stable state, and a molded product having a thin peripheral wall of uniform thickness is formed.

[0025]

[Effects of the Invention] As explained above, according to the present invention, the core (long round bar) of the male side mold can be stabilized, and a molded product having a peripheral wall with a thin and uniform thickness can be formed. It is possible to improve the quality effect.

Furthermore, since variations in wall thickness can be eliminated, the wall thickness of the molded product can be further reduced.

[0027] This makes it possible to reduce material costs.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a state in which resin is injected from a gate of an injection mold used in the injection molding method for an elongated cylindrical container according to the present invention.

FIG. 2 is a sectional view showing a state in which the male mold is advanced relative to the female mold.

[Explanation of symbols]

1 Concave spherical surface 2　Deep taper round hole 3 Gate 4 Female side mold 5 Convex spherical surface 6. Long round bar 7 Male side mold 10 Molten resin 1

Claims (1)

[Claims] [Claim 1] A female mold with a deep tapered round hole with a concave spherical bottom wall and a gate opened at the center of the concave spherical surface of the round hole, and a long round bar with a convex spherical tip. With the female and male molds slightly opened, a small amount of molten resin is filled from the gate, and then the female mold is The male mold is moved forward against the mold, the mold is clamped, the molten resin is filled again, and holding pressure is applied to compensate for the unfilled areas.Then, after cooling, the mold is opened and the molded product is taken out. An injection molding method for an elongated cylindrical container, characterized by: