JPH0834032A - Hollow molded product and production thereof - Google Patents

Abstract

PURPOSE:To simultaneously perform the molding of two split bodies of a hollow molded product and the welding of the molded split bodies by one injection and to enhance the mutual bonding strength of the split bodies to efficiently produce the good hollow molded product. CONSTITUTION:A molten resin is injected into two cavities formed by two sets of the male and female molds provided to first and second molds 2, 3 to mold a pair of two split bodies 21, 22 for a hollow molded product. A pair of the molded split bodies 21, 22 are taken out to be set to welding molds 8, 9 in opposed relationship. The molds are clamped to allow the split bodies 21, 22 to about each other and the outer edges of the abutting surfaces 21b, 22b of the split bodies are welded by the injection of a molten resin to be integrated. At this time, projections are provided to the abutting surfaces 21b, 22b to bring the abutting surfaces to a close contact state and bonding projections 21a, 22a are provided to the outer edges of the split bodies so as to form recessed parts to enhance bonding strength. The split bodies 21, 23 are molded in two sets of the male and female molds simultaneously with welding and the same process is repeated on and after to contribute to the enhancement of productivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow molded article produced by injection molding and a method for producing the same.

[0002]

2. Description of the Related Art Japanese Patent Publication No. 2-38377, Japanese Patent Publication No. 4-5509 discloses a method for producing a hollow molded article.
The production method described in Japanese Patent No. 1 or the like is known. Tokkyo 2-3
In the manufacturing method described in Japanese Patent No. 8377, a male mold and a female mold for molding a divided body obtained by dividing a hollow molded product into two are provided in one mold, and a female mold that faces the male mold and the female mold in the other mold, respectively. ，
A hollow mold was manufactured by providing a male mold. In particular,
A pair of molds are matched at a first mold matching position, and molten resin is injected into a pair of cavities formed between a male mold and a female mold facing each other to mold each divided body. Then, one mold is slid to the second mold matching position, and the divided bodies left in each female mold are opposed to each other,
The molds are matched and the two divided bodies are butted against each other. Then, a molten resin was injected to the peripheral edge of the abutting surface to weld each divided body to each other to obtain a hollow molded article (prior art 1).

Further, the manufacturing method described in Japanese Patent Publication No. 4-55091 uses two sets of molds described in Japanese Patent Publication No. 2-38377, and at the same time each divided body is molded by one set of molds. The divided body formed in the previous step was welded by the other set of molds to manufacture a hollow molded article. That is, two sets of dies alternately slide between a first mold matching position for molding the divided bodies and a second mold matching position for welding the divided bodies, thereby The molding and the welding thereof are alternately performed (prior art 2). As described above, the conventional method for manufacturing a hollow molded product requires two mold matching positions for molding the divided body and welding the divided body. Therefore, in order to manufacture a hollow molded product, the mold had to be slid.

[0004]

However, according to the above-mentioned manufacturing method, one mold has to be slid to accurately match the molds at two positions, which is very difficult. And, unlike a general-purpose molding machine, such a molding machine
It had to be equipped with a slide mechanism, which resulted in high cost. Further, according to the conventional technique 1, the molding of the divided body and the welding thereof have to be performed separately, and there is a defect that it takes a long time to manufacture one hollow molded product. Furthermore, it is necessary to change the injection amount of the molten resin at the time of molding the divided body and at the time of welding the divided body,
The injection amount control circuit had to be added. On the other hand, in the prior art 2, the molding of the divided bodies and the welding thereof are performed at the same time, and the injection amount of the molten resin can be made constant at each time, but two sets of molds must be prepared for the production. It had to be complicated in structure.

In addition, in each of the above-mentioned conventional techniques, the divided bodies 91 and 92 are molded and the mold 3 is moved, but since one side of the divided body is separated from the mold 2, the divided body is started from that moment. The contraction of 91 and 92 started, and the divided body was not a little deformed (Fig. 13). Due to such deformation, the joining property between the divided bodies deteriorates, and when the outer edge is weld-molded, the molten resin R
Flowed out into the hollow portion P. Further, in the production of the hollow molded product, it is not possible to provide an object that plays a role of holding the divided bodies 91 and 92 therein, and the divided surface 95 is also generated by the injection pressure of the molten resin R injected into the joint cavity. , 96 was easy to transform. Due to these deformations, a gap is formed in the abutting surfaces of the divided bodies 91, 92, and the molten resin R is more likely to flow into the hollow molded product.

The present invention solves the above-mentioned problems, and the molding of the divided body obtained by dividing the hollow molded product into two and the welding of the molded divided body are simultaneously performed by one injection without sliding the mold. Further, it is an object of the present invention to provide a hollow molded article having a small number of defective products by increasing the bonding force between the divided bodies and a manufacturing method thereof.

[0007]

[Means for Solving the Problems] In order to achieve such an object,
The hollow molded article according to the first aspect of the present invention is a hollow molded article manufactured by injection molding, in which a pair of split bodies divided into two each have an engaging portion on each butt surface, and the butt surfaces relating to the above split body. Are adhered to each other, and the outer edge of the abutting surface is welded with a molten resin to be united. Here, the "engagement portion" refers to a convex protrusion or a concave groove provided along the abutting surfaces of the pair of split bodies, and is easily crushed or deformed by the mold clamping pressure to join the abutting surfaces to each other. The shape is not particularly limited as long as it has a structure.

The hollow molded article according to the second aspect of the present invention is the hollow molded article according to the first aspect of the present invention, in which the splitting body is integrally formed with a jointing projection that projects like a collar around the outer circumference of the splitting body near the butt surface. The butt surfaces are brought into close contact with each other, and the thickness of the sealing material obtained by solidifying the molten resin surrounding the outer periphery of the joining projection is larger than the width of the recessed portion formed between the joining projections. In addition, the method for manufacturing a hollow molded product according to the third aspect of the present invention is a method of manufacturing a hollow molded product by injecting a molten resin into two cavities formed by two sets of male and female molds provided in the first mold and the second mold. A first step of molding a pair of divided bodies divided into two, and a second step of taking out the pair of divided bodies formed in this first step and setting both of the taken out divided bodies to face each other in a welding mold. The third step of making a hollow molded product by abutting a pair of divided bodies set in the welding mold in the second step with a closed die, and welding the outer edges of the abutting surfaces of both divided bodies by injection of molten resin to integrate them. And, comprising a fourth step of taking out the hollow molded article made in the third step from the welding mold, after performing the first step and the third step at the same time, the fourth step, then, The second step is performed.

[0009]

According to the hollow molded article of the first aspect of the present invention, since the engaging portion of the abutting surface is easily crushed or deformed by the mold clamping pressure to join, a gap is not formed in the abutting surface of the divided body. Further, when the thickness of the sealing material in which the molten resin surrounding the outer periphery of the joining projection is solidified is larger than the concave width generated between the joining projections as in the second invention, the outer edge of the abutting surface is welded at the time of injection molding. , The molten resin fills the outer periphery of the joining projection and then flows into the recess. Therefore, a force for tightening the divided bodies is exerted, and the molten resin is prevented from entering the hollow portion. According to the method for molding a hollow molded product of the third invention, a molten resin is injected between two sets of male and female molds to form a pair of divided bodies into which the hollow molded product is divided into two parts, and it is attached to a welding mold. The third step of welding the pair of divided bodies thus obtained to complete the hollow molded article is simultaneously performed. After that, a fourth step of taking out the hollow molded article completed by the third step from the welding mold is performed, and the pair of divided bodies formed by the first step are taken out, respectively, and both the taken out divided bodies are taken out. A second step is performed in which the welding molds are attached so as to butt against each other. By repeating the above steps, a hollow molded product can be produced at the same time as molding a pair of divided bodies by one mold closing operation without sliding the mold.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments. (1) Example 1 Method for Manufacturing Hollow Molded Product FIGS. 1 to 9 show an example of a method for manufacturing a hollow molded product (here, a resonator) according to the present invention. First, a molding die used for manufacturing a hollow molded article will be described. The molding die 1 is composed of a movable die 2 as a first die and a fixed die 3 as a second die (FIG. 1). In the fixed die 3, a male die 5 is formed on the upper stage, a female die 6 is formed on the middle stage, and a welding die 9 as a second welding die is formed on the lower stage. On the other hand, the movable mold 2 is fixed to the movable mold 3 by closing the mold.
The male mold 5, female mold 6, and welding mold 9 of the female mold 4,
A male die 7 and a welding die 8 which is a first welding die are formed. Movable type 2
With the fixed mold 3, two sets of male and female molds and one set of welding molds can be formed.

At the outer edges of the male dies 5 and 7, butt forming surfaces 5a and 7a for forming the butt surfaces 21b and 22b of the divided bodies are formed. The bottom surfaces of the stepped recesses Z recessed from the mold surface correspond to the butt forming surfaces 5a and 7a (FIGS. 2 and 4). Grooves 5a ₁ and 7a ₁ having a triangular cross section are formed in the center of the butt forming surfaces 5a and 7a along the butt forming surface. Female 4,
6 is a divided body 21, 22 obtained by dividing the hollow molded product 23 into two.
The outside is molded. On the outer edges of the female molds 4 and 6,
In order to form the joining projections 21a, 22a of the divided body that project in a brim shape, the joining recesses 4a, 6a having a hook-shaped cross section are formed.
The joining recesses 4a and 6a extend outward from the step recess Z (FIG. 5). Therefore, when the joint recesses 4a and 6a and the pair of divided bodies 21 and 22 formed by the stepped recess Z are butt-joined to each other, a recess Y is formed between the joint protrusions 21a and 22a (FIG. 8). . Such male type 5,7
The female dies 4 and 6 form two molding cavities C1 and C2 as the fixed die 3 and the movable die 2 are closed (FIG. 1). The cavity C1 has a substantially rectangular box shape, and the cavity C2 has a substantially quadrangular truncated pyramid box shape. The cylindrical portion 53 provided on the male die 5 and the cylindrical recess 43 of the female die 4 form a nozzle forming portion C5 at the bottom of the cavity C1 as the mold is closed (FIG. 1).

The welding dies 8 and 9 are shaped so that the divided bodies 21 and 22 formed by the male dies 5 and 7 and the female dies 4 and 6 can be set (FIG. 5). A cavity C3 for welding for attaching the divided bodies 21 and 22 is formed by mold matching. When the divided bodies 21, 22 are set in the welding cavity C3, the welding dies 8, 9 and the outer edges of the divided bodies 21, 22 are
The joint sinus Q surrounding the outer edge is formed (FIGS. 6 and 8). The welding molds 8 and 9 are provided with a recess U on the outer edge thereof so as to accommodate the joining protrusion 21a. Then, the divided bodies 21, 22 are set in the first welding mold 8 and the second welding mold 9, respectively,
With the closed mold, a space for the joint sinus Q that encloses the joint protrusions 21a and 22a is obtained.

Using the above molding die 1, a hollow molded product is manufactured as follows. Prior to manufacturing, the molding die is attached to the injection side of an injection molding machine (not shown), and is provided between the male die 5 and the female die 6 of the fixed die 3 and the female die 6.
The sprue 10a is provided between the injection molding machine and the welding mold 9.
The molten resin injected into the
A hot runner 10 is formed to guide the cavities C1 and C2 and the joint cavity Q (FIGS. 1 and 6). A heating device (not shown) is provided around the hot runner 10 so that the resin inside the hot runner 10 can be kept in a molten state. Reference numeral 13 indicates a valve, and near the end of the runner 12 extended to the joining sinus Q side, it is possible to switch whether or not to send the molten resin from the sprue 10a to the joining sinus Q. . The valve 13 can be manually operated from the outside of the fixed mold 3 or the movable mold 2, and can be switched to injection or non-injection of molten resin.

Thus, first, the valve 13 is provided so that the molten resin R from the sprue 10a does not flow over the gate 12a.
To the non-injection state. Next, the movable mold 2 and the fixed mold 3 are closed. Then, the molten resin R is injected from the injection molding machine (not shown) to the sprue 10a. The injected molten resin R flows from the hot runner 10 to the cavities C1 and C2 via the runner 11 and the gates 11a and 11b (FIG. 3). Along with this, a pair of split bodies 21 and 22 obtained by splitting the hollow molded product 23 into two are molded (first step).

After the molten resin R injected into the cavities C1 and C2 is cooled and hardened, the movable mold 2 is moved to open the mold (FIG. 4). Then, the divided bodies 21 and 22 formed by the molten resin R injected into the cavities C1 and C2 appear.
The resin 11c cured in the runner 11 is removed and removed from the movable mold 2 and the fixed mold 3. Since the molten resin R in the hot runner 10 is heated, it does not cure,
It remains in the hot runner 10 while maintaining the molten state. Then, the divided bodies 21, 22 are taken out and set in the welding dies 8, 9 respectively (second step). And switch the valve 13,
The molten resin R is also injected into the runner 12 (FIG. 5). At this time, the female dies 4, 6 and the runners 11, 1
The inside of 2 is empty, and the divided bodies 21 and 22 are set in the welding dies 8 and 9.

Next, the movable mold 2 is moved to close the mold. Then, the molten resin R is injected from the injection molding machine to the sprue 10a.
Inject. The molten resin R flows from the hot runner 10 through the runner 11 and the gates 11a and 11b into the cavities C1 and C2 (first step). Further, the molten resin R is also injected into the joining cavity Q via the runner 12 and the gate 12a (FIG. 6). The molten resin R has a butt surface 21.
The outer edges of b and 22b are welded to integrate the divided bodies 21 and 22 to form a hollow molded product 23 (third step).

By forming the grooves 5a ₁ and 7a ₁ along the abutting molding surfaces of the male dies 5 and 7, on the abutting surfaces 21b and 22b of the split bodies 21 and 22, triangular protrusions serving as engaging portions are formed. The Ts face each other (FIG. 9). Therefore, when the divided bodies 21 and 22 are set in the welding dies 8 and 9 and the movable die 2 and the fixed die 3 are closed, the abutting surface 2
Protrusions T of 1b and 22b are abutted with each other and both divided bodies 2
1, 22 are joined together without a gap. The sizes of the protrusions T are set so as to collide with each other so as to absorb the variation caused by the contraction of the divided bodies 21 and 22 caused by the mold opening (FIGS. 4 and 5). However, since the protrusion T has a structure that is easily crushed by the mold clamping pressure, the abutting surfaces 21b, 22b
Ensure the seal of.

Further, in the present embodiment, due to the closed mold, the joint sinus portion having the sectional width D above the joint protrusions 21a and 22a and the sectional width B laterally to the joint protrusions 21a and 22a. Q
Are formed (FIG. 8). The cross-section widths B and D are the protrusions 2
It is made larger than the concave width A generated between 1a and 22a. That is, the cross-sectional widths B and D are set so that A <B and A <D.
Determine. Therefore, the molten resin injected into the joining cavity Q for welding and joining the divided bodies 21, 22 has a joining cavity with a cross-sectional width B, D prior to the inside of the depression Y having the depression width A. It will flow into Q. This is because the molten resin has the property of flowing into a wide void area earlier than a narrow void area. The molten resin R fills the outside of the joining projections 21a and 22a and then flows inward, so that the two divided bodies 21, 2
A force is applied to 2 from the outside to the inside. Therefore, the divided bodies 21 and 22 are welded while receiving the joining force from the molten resin itself.

After the molten resin injected into the cavities C1 and C2 and the joining cavity Q is cooled and hardened, the movable mold 2 is moved to open the mold, and the divided resin 21 is injected by the molten resin injected into the cavities C1 and C2. , 22 and one commercialized hollow molded product 23 appear (FIG. 7). After the molten resin R is cooled and hardened, the outer edges of the abutting surfaces 21b and 22b and the joining projections 21 are formed.
A seal material S is formed around a and 22a. As described above, the cross-sectional width B of the molten resin R is larger than the cross-sectional width B
In order to first fill the void related to D, the thickness of the sealing material S thus formed is larger than the recess width A. After this, the hollow molded product 23
Is taken out from the welding mold 8 (fourth step). Further, the resins 11c and 12c cured in the runners 11 and 12 are removed from the movable mold 2 and the fixed mold 3. And the cavity C
The divided bodies 21 and 22 molded in C1 and C2 are inserted into female molds 4 and 6, respectively.
And attach to the welding dies 8 and 9 (second step). After that, by repeating the same operation, the hollow molded products 23 are manufactured one after another. Here, in the subsequent injection molding, the molding of the pair of divided bodies 21 and 22 and the welding of the divided bodies are performed every time, so that the valve 13 is placed in a state in which the molten resin is injected into the runner 12. In this way, the subsequent injection amount of the molten resin is always kept constant.

Hollow Molded Product FIG. 10 shows a hollow molded product 23 obtained by the above manufacturing method.
Shown in The hollow molded product 23 has a hollow cubic shape having one nozzle, and the pair of divided bodies 21 and 22 has a butting surface 21.
b and 22b, the projections T, T are squeezed together when the molds are closed to form a joined state.
The outer edges of b and 22b are fused with a molten resin R to be united. The protrusion T forms a ridge having a triangular cross section and is provided in the entire area along the abutting faces 21b and 22b. By setting the protrusions T and T to collide with each other when the mold is closed, the abutting faces 21b and 22b are formed. The seal is secured.

Further, by forming the joining recesses 4a and 6a, joining projections 21a and 22a are formed on the outer circumferences of the divided bodies 21 and 22 near the abutting surfaces 21b and 22b, respectively.
The stepped recess Z forms a recess Y. Then, in order to receive the force in the joining direction from the molten resin R by the two divided bodies 22, 23, in providing the joining sinus Q as described above,
The thickness of the sealing material S in which the molten resin R surrounding the outer circumferences of the joining projections 21a and 22a is solidified is made larger than the recess width A. The molten resin R also enters the recess Y, and the divided bodies 21, 2
Aim for complete integration of 2. Reference numeral N indicates a connecting nozzle for attaching to an air cleaner hose or the like. The connection nozzle N is
It is made in the nozzle forming portion C5 and communicates with the hollow portion P.

The constricted portion g is a thin-walled portion corresponding to the side surface base portion of the joining projections 21a and 22a, and is formed by forming the joining depressions 4a and 6a into a hook shape in cross section as shown in FIG. When the outer edges of the abutting surfaces 21b and 22b are welded with the molten resin R to be united, the constricted portion g is formed to form the welding molds 8 and 9
The sandwiching portions 8b and 9b according to (3) facilitate tightening the joining projections 21a and 22a (FIG. 9). Clamping portions 8b and 9b are provided near the outer surfaces of the welding molds 8 and 9 and near the mold surface (FIG. 4). The sandwiching portions 8b and 9b come into contact with the constricted portion g that is the side surface base portion of the joining projections 21a and 22a of the split bodies 21 and 22 set in the welding dies 8 and 9. Since the constricted portion g is sandwiched by the sandwiching portions 8b and 9b when the mold is closed,
A defect (FIG. 13) in which the abutting surfaces 21b and 22b are deformed inward by the injection pressure of the molten resin is prevented (FIG. 9). Thus, the hollow molded article 23 having the hollow portion P is
It is a resonator product that applies the Helmholtz resonance principle to eliminate intake and exhaust noises. In addition, the hollow molded product 23
Is not limited to FIG. 10 and can have various shapes. In addition, the protrusion T and the joining protrusions 21a and 22
The sealing material S and the sealing material S may be partially provided.

(2) Example 2 Next, another example of the hollow molded article and the method for producing the same according to the present invention will be described. 11 and 12 are views showing another embodiment. FIG. 11 is a vertical sectional view corresponding to FIG. 2 and FIG. 12 is a vertical sectional view corresponding to FIG. The same parts as those in the above-mentioned embodiment are designated by the same reference numerals, and the description thereof will be omitted.

In this embodiment, the groove portion 5a ₁ of the butt molding surface 5a of one male die 5 is deformed. Instead of the groove 5a ₁ having a triangular cross section, a protrusion 5a ₂ having a triangular cross section is used. Protrusion 5a ₂ is formed in the other of the groove portions 7a ₁ from slightly smaller to the groove portions 7a ₁ and the corresponding position in a shape to be fitted into the groove 7a ₁ formed on the molding surface 7a (Figure 2). Therefore, the abutting surface 25b of the split body 25 which is formed by the male mold 5 having a protrusion 5a _2, a groove V corresponding to the shape of the projecting portion 5a ₂ is molded. On the other hand, the abutting surface 2 of the divided body 22 formed by the male die 7 having the groove portion 7a ₁
A protrusion T having a shape corresponding to the groove 7a ₁ is formed on 2b. When the divided bodies 25 and 22 having such engaging portions (grooves V and protrusions T) are attached to the welding dies 8 and 9, as shown in FIG. 12, a triangular cross section formed on the respective abutting surfaces 25b and 22b. The groove V and the protrusion T having a triangular cross-section slightly larger than the groove V are arranged to face each other. The protrusion T also has a structure that is easily crushed by the mold clamping pressure. When the movable mold 2 and the fixed mold 3 are closed, the groove V and the protrusion T are engaged with each other to form the two divided bodies 2.
5, 22 are joined together without a gap. Although the protrusion T is crushed as the mold is clamped, it exerts a wedge effect and is divided into two divided bodies 25, 2
2 is reliably joined, the joining force between the divided bodies 21, 22 is increased, and a hollow molded product 23 having no room for the molten resin R to enter the hollow portion P is obtained.

(3) Effects of the Embodiments According to the hollow molded article and the method for manufacturing the hollow molded article having the above aspects, the movable die 2 is aligned at the same position as the fixed die 3 during molding of the divided body and during welding thereof. Therefore, compared with the prior art in which there are two positions to be matched with each other, the mold structure can be simplified and a highly accurate hollow molded product 23 can be manufactured. Since a mold moving mechanism for performing mold matching at different positions is not needed, a hollow molded product can be molded by a general-purpose injection molding machine and no new equipment is required. In addition, a pair of divided bodies 21, 2 divided into two by one injection of the molten resin R with a simple structure of one set of the movable mold 2 and the fixed mold 3.
Since not only the molding of No. 2 but also the welding of the divided bodies can be performed at the same time, the hollow molded product 23 can be manufactured each time the molten resin is injected. Therefore, a large amount of hollow molded products 23 can be manufactured in a short time, which contributes to improvement in productivity. Furthermore, since the injection amount of the molten resin can be made constant every time, the injection amount control circuit is not required.

In addition, according to Example 1, the hollow molded article 2
When making 3, the abutting surfaces 21b, 22 of the split bodies 21, 22
The protrusions T having a triangular cross section formed in b collide with each other,
Since the two divided bodies 21 and 22 are joined together without a gap, it is possible to prevent the molten resin from flowing into the hollow body from the abutting surfaces 21b and 22b of the two divided bodies. In addition, the joint projections 21a, 2
Sealing material S in which molten resin R surrounding the outer periphery of 2a is solidified
Since the thickness is made larger than the concave width A, both split bodies 2
The welding power of 1 and 22 is increased to surely integrate the two. The injected molten resin R first flows into the voids of the joining sinus Q having the large cross-sectional widths B and D, and then into the voids having the concave recess width A, so that the two divided bodies 21 and 22 are clamped to each other. It is welded while receiving a pressing force. In this way, since the two divided bodies are welded and united while the bonding force is enhanced, there is no fear that the abutting surfaces 21b and 22b are opened when the two divided bodies are welded. Therefore, it is possible to prevent the molten resin from flowing into the hollow body from the abutting surfaces of the two divided bodies, which is useful for improving the yield.
In the second embodiment, since the projection T and the groove V engage with each other with a wedge effect, the sealing property at the abutting surfaces 25b and 22b of the divided bodies is further excellent and the outflow into the hollow molded product is prevented.

As described above, according to this embodiment, the productivity of the hollow molded product 23 is increased while using a general-purpose molding machine, and
The hollow molded product 23 having no product defect is provided at low cost.

The present invention is not limited to those shown in the above embodiments, but can be variously modified within the scope of the present invention depending on the purpose and application. Movable mold 2, fixed mold 3, female mold 4, 6, male molds 5, 7, welding molds 8, 9, butt surfaces 21b, 22b, joint projection 21
The shapes and sizes of a, 22a, the protrusion T, the groove V, etc. can be variously selected according to the purpose. In the above embodiment, the movable die 2 and the fixed die 3
Each of the male molds 5 and 7 and the female molds 4 and 6 was formed in the and, but two female molds (or male molds) were formed in the movable mold 2 and two male molds in the fixed mold 3 ( Alternatively, a female mold) may be formed. Grooves 5a ₁ 7a ₁ formed on the butt-formed surfaces 5a, 7a,
The projecting portion 5a ₂ is formed by the butt forming surfaces 5a of the divided bodies 21 and 22,
As long as 7a is engaged, it can have a shape other than a triangular cross section. The mold structure may be a hot-runner mold or a 3-plate cold runner mold. Although the joining projections 21a and 22a and the sealing material S are provided on the entire outer circumference to integrate the pair of divided bodies 21 and 22, they may be partially provided on the outer edge where both divided bodies are joined. .

[0029]

As described above, the hollow molded article and the manufacturing method thereof according to the present invention can not only perform molding of a pair of divided bodies and welding of the divided bodies at the same time by one injection, but By increasing the tight bond strength between the bodies and surely integrating them with molten resin to make a good hollow molded product, it contributes to the improvement of productivity and yield, and further, the sliding movement of the mold is eliminated to improve the manufacturing equipment. It has excellent effects such as contributing to simplification.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a molding die according to a first embodiment.

FIG. 2 is a partially enlarged vertical sectional view of a butt-molded surface.

FIG. 3 is a vertical cross-sectional view showing a state where molten resin is injected into a cavity formed by two sets of a male mold and a female mold.

FIG. 4 is a vertical cross-sectional view showing a mold open state after molding the divided body.

FIG. 5 is a vertical cross-sectional view showing a state in which the molded divided body is set in a welding mold.

FIG. 6 is a vertical cross-sectional view showing a state in which a molten resin has flown into a cavity formed by two sets of a male mold and a female mold and a joint sinus portion.

FIG. 7 is a vertical cross-sectional view showing a mold open state after molding of the divided body and the hollow molded article.

FIG. 8 is a partially enlarged vertical cross-sectional view around the holding portion in a mold closed state after the divided body is set in the welding mold.

FIG. 9 is a partially enlarged vertical cross-sectional view around the sandwiching portion immediately after the divided body is set in the welding mold and immediately before the mold is closed.

FIG. 10 is a cross-sectional perspective view of a hollow molded product.

FIG. 11 is a partially enlarged vertical cross-sectional view around a butt-molding surface of the second embodiment.

FIG. 12 is a partially enlarged vertical cross-sectional view of the surroundings of the sandwiching unit immediately after the split body of Example 2 is set in the welding mold and immediately before the mold is closed.

FIG. 13 is an explanatory sectional view of a conventional technique.

[Explanation of symbols]

 2 First mold (movable type) 3 Second mold (fixed type) 4, 6 Female type 5, 7 Male type 8 First welding type (welding type) 9 Second welding type (welding type) 21, 22, 25 split bodies 21a, 22a joining projections 21b, 22b butt surface 23 hollow molded product 25b butt surface A concave recess width C1, C2 cavity R molten resin S sealing material T engaging part (protrusion) V groove (projection)

Claims (3)

[Claims] 1. A hollow molded article manufactured by injection molding, wherein a pair of split bodies divided into two have engaging portions on their respective butting surfaces, and the butting surfaces of the above-mentioned split bodies are brought into close contact with each other. Hollow molded product made by welding the outer edges of the abutting surfaces with a molten resin and combining them. 2. An outer periphery of the divided body near the abutting surface is provided with a joint projection protruding in a brim shape integrally with the divided body, and the abutting surfaces are brought into close contact with each other to form between the joint projections. The hollow molded article according to claim 1, wherein the thickness of the sealing material obtained by solidifying the molten resin surrounding the outer periphery of the joining projection is larger than the width of the recess. 3. A pair of divided bodies obtained by injecting a molten resin into two cavities formed by two sets of male and female dies provided in a first mold and a second mold to divide a hollow molded product into two halves. The first step, the second step of taking out the pair of divided bodies formed in the first step, and setting both of the taken out divided pieces so as to face each other, and the welding step in the second step The pair of divided bodies thus formed are abutted by a closed mold, and the outer edges of the abutting surfaces of the two divided bodies are welded and integrated by injection of a molten resin to form a hollow molded product. A fourth step of removing the hollow molded article from the welding mold, wherein the first step and the third step are simultaneously performed, the fourth step is performed, and then the second step is performed. And a method for producing a hollow molded article.