JPH04331115A - Joint structure of synthetic resin hollow body - Google Patents

Abstract

PURPOSE:To prevent molten resin for joining from leaking through the gap between the mating faces of a pair of half bodies by continuously forming a liplike projection having slightly larger height than the cooling shrinkage dimension of both half bodies in the longitudinal direction to at least one side of the mating faces. CONSTITUTION:The hollow half bodies 3, 4 respectively molded in a top force 1 and a bottom force 2 have flange parts 31, 32, 41, 42 projected to the outsides form the circumferential edges in the mating faces 30, 40 for these main body parts. Voids 34, 44 lengthened in the longitudinal direction are formed by clipping the outside faces of the respective flange parts. Therein liplike projection 43(33) having a triangular cross-section is formed on the mating face 40 of the flange parts 41, 42 of the half body 4 (or the mating face 30 of the half body 3). When both half bodies 3, 4 are mated, molten resin is introduced and hardened in a state wherein this projection 43 is collapsed. Thereby even when the mating faces 30, 40 are not mated by shrinkage of the product, molten resin is prevented from being leaked through the gap between the mating faces.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joining structure for producing a hollow body by abutting and joining injection molded half bodies.

0002

[Prior Art] Blow molding is a common method for manufacturing hollow containers, but due to the structural strength or shape of the hollow body, primary injection molding is performed on the divided halves. A two-stage molding method has been proposed in which the butted parts are joined by secondary injection molding of resin (Patent Publication No. 2).
-20410). However, in this type of two-stage molding, product shrinkage occurs when the half-split body of the primary injection molding hardens.
There is a problem in that when molten resin is injected into the abutting surface void in secondary molding, the abutting end surfaces are not sufficiently butted, and the molten resin leaks from the gap.

0003

[Problem to be Solved by the Invention] By the way, if it is possible to mold half bodies by predicting the degree of sinkage on the abutting surfaces due to product shrinkage, the above problem can be solved, but the degree of sinkage is uniform. However, it is virtually impossible to predict this and design a mold. Therefore, an object of the present invention is to provide a joint structure in which the molten resin for joining does not leak from the injection cavity during secondary molding even if product shrinkage occurs by devising the product shape of the half body in the primary molding. shall be.

0004

[Means for Solving the Problems] Although it is impossible to design a mold by predicting product shrinkage, the present invention provides a solution to shrinkage of half bodies in primary injection molding when the halves collide during secondary molding. This method was developed based on the fact that the above problem could be solved by forming a weir for preventing resin leakage with a protrusion larger than the amount of the resin leakage. In a structure in which a molten resin material for joining is secondarily injected into the abutting portion of the halves, at least one of the abutting surfaces of both halves has a shrinkage dimension slightly larger than the cooling shrinkage dimension of both halves. The gist of the synthesis is that lip-shaped protrusions of different heights are formed in advance in a continuous manner in the longitudinal direction, and when the two halves collide, the protrusions are crushed and molten resin is injected and hardened. Joint structure of resin hollow body.

[0005]

[Function] According to the present invention, the protrusions formed on the abutting surfaces of the half bodies during the primary molding are larger than the shrinkage of the half bodies after the primary molding, so that the protrusions are formed during the secondary molding. When the abutting surfaces of the two halves are butted against each other, the excess portion minus the amount of shrinkage due to the abutting against the opposing abutting surfaces is crushed, and the portion that is not crushed is the molten resin that forms the void in the opposing abutting surfaces. By damming the area around the injection cavity, it is possible to prevent the injected resin from leaking from the cavity (see FIG. 6).

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below based on specific examples shown in the accompanying drawings. FIG. 1 is a cross-sectional view showing the molded state of the joining structure of the present invention, showing the state before mold clamping for secondary molding after primary molding of each half of the hollow body. FIG. 2 is an enlarged perspective view of the main parts thereof, FIG. 3 is a sectional view showing a state in which molten resin is injected into the joint structure of the present invention after mold clamping for secondary molding, and FIG. 4 is an enlarged perspective view of the main parts. It is.

In the drawings, 1 is an upper mold, 2 is a lower mold, and hollow halves 3 and 4 are molded in each mold. The half body 3 has flange parts 31 and 32 protruding outward from the peripheral edge on the abutment surface 30 of the main body part, and the flange part 31
, 32 is cut out from the outer lower surface thereof and extends in the longitudinal direction.
4 is formed. On the other hand, the half body 4 also has flange parts 41 and 42 projecting outward from the peripheral edge of the main body part 40, and a lip-like projection 43 having a triangular cross section is formed on the abutting surface 40 to extend in the longitudinal direction. In addition, the flange portion 41,
A hollow space 44 extending in the longitudinal direction by cutting out the outer lower surface of 42
has been formed. The cavities 34, 44 may have various cross-sectional and longitudinal shapes. Further, the lip-shaped protrusion 33 may also be provided on the abutment surface 30 of the half body 3.

[0008] A lip-shaped protrusion 43 formed on the abutting surface.
When the halves 3 and 4 are brought into contact with each other, as shown in FIG. 3, the tips thereof come into contact with the opposing abutment surfaces 30 and are crushed, and the remaining portions form a dam. Therefore, the cavities 34, 44 of the flange parts 31 (32) and 41 (42) facing each other form an injection cavity R1 which is dammed inwardly by the projection 43, and the abutting surface Even if they do not completely abut, if the molten resin B is injected through the spool, it will not leak out from the space R1.

When the half bodies to which the present invention is applied have thick end faces, such as half bodies 5 and 6 which are hollow bodies with circular cross sections, as shown in FIG. 6, as shown in FIG. The projections 51 and cavities 52, 62 can be formed directly on the abutment surfaces 50, 60. In addition, as shown in FIG.
In addition to the abutment surface 50 on the side, a protrusion 61 protruding in the opposite direction to the protrusion 51 may be formed on the abutment surface 60 on the half body 6 side, and as shown in FIG. 5 abutment surface 5
A plurality of protrusions may be formed in parallel from zero. In short, the shape of the protrusion does not matter as long as it is shaped so that when the halves collide, the tips are crushed and the remaining portion forms the dam of the injection cavity.

0010

As is clear from the above description, according to the present invention, injection molded half bodies are abutted against each other in their end faces in a mold, and molten resin for joining is applied to the abutting portions. In a structure in which material is bonded by secondary injection of material, at least one of the abutting surfaces of the halves is formed with a protrusion that protrudes in the mold removal direction along the longitudinal direction of the abutting surface, so that the protrusion is higher than the product shrinkage dimension. When the mold is clamped during secondary molding of the half-split bodies, the tips always come into contact with the abutting surfaces of the opposing halves and are crushed;
The remaining part forms a weir for the injection cavity of the molten resin for bonding, and even if the abutting surfaces do not contact each other due to product shrinkage, the molten resin for bonding will flow through the gap between the abutting surfaces. Hollow body products that can be prevented from leaking and have a good appearance can be manufactured.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the molded state of the joint structure of the present invention;

[Figure 2] An enlarged perspective view of the main parts of Figure 1,

[Fig. 3] A cross-sectional view showing a state in which molten resin is injected into the joint structure of the present invention,

[Figure 4] An enlarged perspective view of the main parts of Figure 3,

[Fig. 5] A cross-sectional view when the first modification of the joining structure of the present invention is applied to another hollow body,

[Figure 6] Enlarged side view of the main part of Figure 5,

[Fig. 7] A cross-sectional view of a second modification of the joining structure of the present invention,

FIG. 8 is a sectional view of a third modification of the joining structure of the present invention.

[Explanation of symbols]

1 is an upper mold, 2 is a lower mold, 3 and 4 are hollow halves, 3
0 and 40 are abutment surfaces, 31 and 32 are flange parts, 41
, 42 is a flange portion, and 43, 51, 61 are lip-like projections R1 are injection cavities.

Claims (1)

[Claims] Claim 1: In a structure in which injection molded halves are brought into contact with each other in a mold with their end faces mutually abutted, and a molten resin material for joining is secondarily injected into the abutting portions, the two halves are joined. On at least one of the abutting surfaces of the body, a lip-shaped protrusion with a height slightly larger than the cooling shrinkage dimension of both halves is formed in advance in a continuous manner in the longitudinal direction. 1. A joint structure for synthetic resin hollow bodies, characterized in that a molten resin is injected and hardened while the protrusions are crushed.