JPS6251425A - Forming of hollow double walled container - Google Patents

Abstract

PURPOSE:To eliminate fold fins due to shifting of a resin, which is in contact with a cavity, by a method wherein shifting of a parison, which is in contact with the cavity surface near a pinch-off portion, is stopped over a period ranging from the state of the parison just before being pinched off to that has been pinched off during the closing of the cavity. CONSTITUTION:Firstly, a pre-blown parison 4 is hangingly arranged between both forces 1 and 2, which are set apart. Secondly, both the forces 1 and 2 are started to be closed. Just before the parison 4 is pinched off by the forces 1 and 2, negative pressure is applied to pores 3. Thus, the parison 4 in the neighborhood of a pinch-off portion is fixed by suction to the inner surface of a cavity by means of the sucking force through the pores 3. After that, both the forces 1 and 2 are completely closed and the pinch-off portion of the parison 4 is pinchingly pressed so as to blow-mold by blowing pressurized fluid in the parison 4. Because the parison 4 in the neighborhood of the pinch-of portion is fixed over the period ranging from the midway of the closing of the forces 1 and 2 to the end of their closing, the shifting of the parison 4 in said portion along the cavity surface is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention involves suspending a parison between a mold having a concave cavity and a mold having a convex cavity, and then closing both molds. The present invention relates to a method for forming a hollow double-walled container with both cavities.

BACKGROUND ART As a molding method of this type, the method disclosed in Japanese Patent Publication No. 49-44112 is widely known.

The method for forming a hollow double-walled container according to the above-mentioned conventional example is as shown in Figs. WJ3 to Fig. 6. Let parison C hang down (Fig. 3), and then press both molds.

d (Fig. 4) and both cavities α.

At C, a hollow double-walled container f is formed.

The hollow double-walled container f has a main body f1 and a lid f! are connected at a hinge part f1, and an integral latch f4 is provided on the edge of the lid body, and a locking protrusion f on which the integral latch 8 is locked is provided on the edge of the main body f1. It is formed.

The hollow double-walled container f has the shape shown in FIGS. 5 and 6, and the lid f! is connected to the main body f via a hinge portion so as to be openable and closable, and the lid body is held in a closed state by the engagement of the integral latch 8 and the locking protrusion fe. It has become.

Problems to be Solved by the Invention In the hollow double-walled container f molded by the above-mentioned conventional hollow double-walled container molding method, as shown in FIG. Thin streak-like s due to folded flesh near the surface? The reason why the above-mentioned streak-like lines occur is as follows:
This is thought to be due to the fact that during pinch-off, the optical parison is sandwiched between the pinch-off parts of both molds and moves into the cavity, where it rubs against the inner surface of the cavity. Moreover, the above-mentioned line 1 appears particularly frequently at a location where the nine parisons are compressed and move significantly, such as near the protruding part of the integral latch f4.

Means and Effects for Solving the Problems The present invention has been made in view of the above-mentioned problems, and provides a method for molding a hollow double-walled container with a clean appearance without generating slit-like lines near the pinch-off portion. The object is to prevent the parison in contact with the cavity surface near the pinch-off portion from moving relative to the cavity surface from just before the pinch-off when the cavity is closed until the pinch-off state is reached.

Example An embodiment of the present invention will be described based on FIGS. 1 and 2.

In the figure, 1 is a mold having a concave cavity 1a, and 2 is a mold having a convex cavity 2cL.
, 2, a plurality of pores 3 are opened in the cavity 1a near the pinch-off part of the mold 1 on the concave side for molding the outer wall of the molded product.

Each of the pores 3 is connected to an air suction device (not shown) provided outside the mold 1.

The molding method of the present invention will be explained below using the apparatus having the above configuration.

Harrison 4 gripped between both types 1 and 2 separated
Then, both molds 1.2 are closed, and just before parison 4 is pinched off with mold 1.2 (Fig. 1)
A negative pressure is applied to the pore 3. As a result, the parison 4 near the pinch-off portion is suctioned and fixed to the inner surface of the cavity by the suction force of the pores 3.

Then, both molds 1.2 are completely closed, the pinch-off portion of the parison 4 is pinched, and pressurized fluid is blown into the parison 4 to perform blow molding.

The parison 4 in the vicinity of the pinch-off portion is fixed to the cavity from the middle of closing to the completion of closing of the molds 1 and 2, thereby preventing this portion of the parison 4 from moving along the cavity surface.

In the above embodiment, the suction pore 3 is formed into a concave cavity 1.
Although an example is shown in which it is provided on the a side, it may be provided on the convex cavity 2a side or on both sides as necessary.

Further, as the other side of the above embodiment, instead of the pores 3, this portion may be locally cooled to cool the parison in this portion faster than other portions to prevent its fluidity.

Effects of the Invention According to the present invention, the part of the parison in contact with the cavity near the pinch-off part is fixed, and creases due to resin movement in this part are eliminated, and the appearance of streaks is prevented, resulting in a clean appearance. be able to.

[Brief explanation of the drawing]

Figures 1 and 2 show the main parts of an embodiment of the present invention.
Fig. 1 is a cross-sectional view showing the state immediately before pinch-off, Fig. 2 is a sectional view showing the pinch-off state, Figs. 3 to 6 show conventional examples, Figs. The figure is an external view, and FIG. 6 is a sectional view. 1.2 is the mold, 1a12a is the cavity, 3 is the pore, 4
is parison.

Claims (3)

[Claims] (1) In a molding method in which a hollow double-walled container is formed by compressing the parison 4 between a concave cavity 1a and a convex cavity 2a, the pinch-off begins immediately before the pinch-off when both cavities 1a and 2a are closed. A method for molding a hollow double-walled container, characterized in that the parison in contact with the cavity surface in the vicinity of the pinch-off portion is prevented from moving relative to the cavity surface while the container is in the pinch-off state. (2) The parison in contact with the cavity surface near the pinch-off part is sucked through the pore 3 opened in the cavity from just before the pinch-off until the pinch-off state is reached, and the parison in this area is fixed to the cavity surface. A method for forming a hollow double-walled container according to claim 1. (3) The parison in contact with the cavity surface near the pinch-off portion is locally cooled from just before the pinch-off until the pinch-off state is reached, thereby fixing the parison in this area to the cavity surface. A method for forming a hollow double-walled container according to claim 1.