JPH0420594Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) This invention is particularly effective for blow molding synthetic resin bent products such as L-shaped and S-shaped. The present invention relates to a suction ventilation structure in a split mold used in a suction-type parison feeding method, which is a type in which a parison extrusion die of an extruder and a parison inlet of the split mold are in contact with each other.

(Prior art) In general, a pair of split molds is used which has an open mold cavity half having a parison inlet half opening to the outside at the upper end of the mold cavity half and a parison outlet opening half opening to the outside at the lower end. If the parison extrusion die of the extruder is brought into contact with the parison inlet of the closed split mold and the parison is supplied into the mold cavity by suction from the parison outlet, the parison inlet of the split mold should be placed outside. It is necessary to provide an open ventilation hole. Therefore, conventionally, a ventilation gap is provided between the lower end surface of the extrusion die and the open end of the parison inlet, or between the outer circumferential surface of the extrusion die and the inner circumferential surface of the parison inlet. .

However, in these conventional ventilation structures, in order to smoothly supply the parison into the mold cavity using sufficient suction, it is desirable to widen the opening area of the ventilation gap. At times, the parison bulged outward from the ventilation gap and there was a risk of bursting.

(Problems to be solved by the invention) This invention has a sufficient ventilation area to enable smooth supply of the parison into the mold cavity by suction, and also prevents the expansion of the parison to the outside during blow molding. The purpose of the present invention is to provide a split-type ventilation structure that can prevent leakage and rupture.

(Means for Solving the Problems) In order to achieve the above object, the present inventor conducted various studies and found that the reason why the parison bulges outward during blow molding is that the ventilation gap is We discovered that even when the width is narrow, it is long and continuous horizontally.Based on this, the ventilation structure of the present invention has one half of the parison inlet opening to the outside at the top end of half the mold cavity, and one half of the parison inlet opening to the outside at the bottom end. In a pair of split molds each having an open mold cavity half face with an open parison outlet half face, sufficient suction is applied to the part close to the above parison inlet half face to feed the parison into the mold cavity as a whole. The structure includes a large number of suction ventilation holes that penetrate from the inside of the mold cavity to the outside and have a diameter that is small enough to not allow the parison to bulge out. Embodiments of the present invention will be described below with reference to the drawings.

In Figures 1 and 2, the split mold 1 has a rectangular block-shaped split mold body 2, and bolts 4 on the upper side of the main body 2...
A mold cavity half surface 5 is formed on the closing surface of the split mold 1 and extends from the auxiliary body 3 to one side of the main body 2 and is bent in an approximately L-shape. At the upper end of the auxiliary body 3 of the mold cavity half surface 5, there is a parison inlet half surface 6 which opens to the outside on the upper side of the auxiliary body 3, and at the lower end of the mold cavity half surface 5, a parison inlet opening to the outside from one side of the main body 2. The outlet half surfaces 7 are provided respectively to form an open mold cavity half surface which opens to the outside at both ends, and the auxiliary body 3 of such a split mold 1 is formed.
A ventilation structure is provided.

The auxiliary body 3 has an inner circumferential surface formed into a conical half surface that expands from the inlet half surface 6 to the mold cavity half surface 5, and has a large number of suction devices penetrating inside and outside the mold cavity on the conical half surface. Ventilation holes 8... are provided, and the total opening area of the ventilation holes 8... is made such that the total opening area is the area necessary to utilize sufficient suction to feed the parison into the mold cavity. At the same time, the diameter of each small ventilation hole 8 is made small enough to prevent the parison from bulging out to the outside during blow molding.

In use, a pair of split molds 1, 1 having a symmetrical structure are closed with a parison extrusion die D of an extruder sandwiched between the parison inlet halves 6, 6 as shown in the first diagram. , a mold nest consisting of mold cavity halves 5, 5 is formed in both split molds 1, 1. Next, extrude the parison P from the extrusion die D into the mold cavity, and
When suction to the outside is started by an appropriate means from the outlet consisting of the outlet halves 7, 7, each small ventilation hole 8...
The air that has flowed from the outside into the upper end of the mold cavity passes through the outside of the extruded parison P and flows inside the mold cavity to the outlet, and this airflow guides the parison P into the mold cavity. In this case, sufficient air is introduced into the mold cavity through the small ventilation holes 8 to guide the parison smoothly and reliably.

When the tip of the parison P is introduced to a position where it slightly protrudes outside from the outlet, the suction is stopped, the tip of the parison P is sealed (closed) by an appropriate means, and the outlet is closed, and then the parison P is inserted into the parison P by an appropriate means. Blow molding is performed by blowing air. At this time, the inflated parison also comes into pressure contact with the ventilation holes 8, but does not bulge out from the ventilation holes.

(Effect of the invention) According to the ventilation structure of the split mold used in the suction-type parison supply of the present invention, sufficient suction is required to supply the parison into the mold cavity through the entire large number of ventilation holes. By forming a wide opening area, sufficient air can be introduced from the outside and flowed into the mold cavity, and each small ventilation hole does not allow the parison to bulge outside during blow molding. It enables proper blow molding and is extremely effective in practice.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a front view of a split mold, and FIG. 2 is an enlarged cross-sectional view taken along the - line in FIG. 1. 1...Split mold, 5...Half side of mold cavity, 6...Half side of parison inlet, 7...Half side of parison outlet, 8...
Ventilation hole for suction.

Claims (1)

[Scope of Claim for Utility Model Registration] A pair of split molds having open mold cavity halves, each having a parison inlet half opening to the outside at the top end of the mold cavity half face and a parison outlet opening opening to the outside opening at the bottom end of the mold cavity half face. In this case, a portion close to the half surface of the parison introduction port has an opening area necessary to utilize sufficient suction to feed the parison into the mold cavity as a whole, and a small diameter to the extent that the parison does not bulge outward. A split mold ventilation structure used for suction-type parison supply, with numerous suction ventilation holes that penetrate from the inside of the mold cavity to the outside.