JPH11156925A - Hollow double-wall structure and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hollow double-wall structure not generating the deformation strain due to cooling shrinkage after molding though enhanced in strength and rigidity by the insertion of a pipe. SOLUTION: A hollow double-wall structure 1 is constituted of a surface wall 2, the rear wall 3 opposed to the surface wall 2 so as to leave an interval and the peripheral wall 4 forming a hollow part between the surface and rear walls 2, 3. The straight pipe 6 is arranged in the hollow part. The pipe attaching structure 7 of the pipe 6 consists of the surrounding part 8 integrally connected to the rear wall 3 to surround the entire peripheral surface of the pipe 6 and the support part 9 provided to the rear wall 3 in a recessed state to support a part of the peripheral surface of the pipe 6. Recessed parts 11, 11 holding the play interval to the end surface of the pipe 6 are provided to the region corresponding to the end part of the pipe 6 of the rear wall 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow double-walled structure obtained by blow molding a thermoplastic, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, an inner wall formed in a hollow portion of a plastic hollow double-walled structure constituting an interior wall, a partition, a door of a building, a floor trunk lid or a rear parcel elf of an automobile or the like. A technique for improving strength and rigidity by inserting a flat and curved rod into a rib is described in Japanese Patent Application Laid-Open No. 9-155957.

[0003]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. 9-15 / 1997
The technology described in Japanese Patent No. 5957 was developed by the present applicant, but as a result of subsequent studies, it has been found that the following problems mainly exist in blow molding.

[0004] That is, in the technique described in Japanese Patent Application Laid-Open No. 9-155957, the rod inserted into the hollow double-walled structure to be blow-molded is flat and curved. The cooling shrinkage that occurs during the process of cooling the hollow double-walled structure after blow molding exhibits a phenomenon that is partially hindered by the inserted rod-shaped body, and the difference in shrinkage due to this phenomenon causes deformation distortion. is there.

[0005] In the case where a metal body is inserted into a plastic molded body, the shrinkage rate upon cooling is
Since plastic is much larger than metal, it has been found that strains due to shrinkage accumulate in portions surrounding the metal body, and this accumulated strain causes cracks in the molded body.

Accordingly, the present invention has been made to solve the above-described problems, and it is an object of the present invention to arrange a straight pipe in a hollow portion and to form a pipe on a back wall which is integral with a pipe mounting structure. By providing a concave portion for maintaining a play interval with respect to the end face of the pipe at a portion corresponding to the end portion, a lightweight and rigid hollow double-walled structure can be obtained, and the hollow double-walled structure after blow molding. In the process of cooling and shrinking, the sliding property against the surface of the pipe due to the shrinkage of the part in contact with the pipe is good, and moreover, the part of the length of the pipe which is relatively increased can be released in the recess on the back wall. In addition, by providing a support portion that is recessed in the back wall and supports a part of the peripheral surface of the pipe in the pipe mounting structure to which the pipe is mounted, cooling around the pipe is accompanied by cooling. To reduce the accumulation of strain due to shrinkage,
Accordingly, it is an object of the present invention to obtain a hollow double-walled structure that does not generate deformation distortion due to cooling shrinkage after molding even if strength and rigidity are improved by inserting a pipe.

[0007]

In order to achieve the above object, a hollow double-walled structure according to the present invention comprises a front wall, a back wall opposed to the front wall at an interval, a front wall and a back wall. And a peripheral wall forming a hollow portion between the hollow wall portion and a hollow pipe, wherein a straight pipe is disposed in the hollow portion, and the pipe is connected at least integrally with the back wall. A pipe mounting structure including a surrounding portion surrounding the entire peripheral surface of the pipe and a supporting portion recessed in the back wall and supporting a part of the circumferential surface of the pipe, and a portion corresponding to an end of the pipe on the back wall. Is characterized by forming a concave portion for maintaining a play interval with respect to the end face of the pipe.

In the method for manufacturing a hollow double-walled structure according to the present invention, a hollow portion is formed between a front wall, a back wall opposed to the front wall at an interval, and the front wall and the back wall. Blow molding a hollow double-walled structure composed of a peripheral wall to be formed, and a pipe formed integrally with the back wall in a cavity of a mold forming a back wall of a pair of split molds. A sliding mold that forms a surrounding portion surrounding the entire peripheral surface of the pipe, and a protrusion that is recessed in the back wall and forms a supporting portion that supports a part of the peripheral surface of the pipe, and is provided. It is characterized in that a pipe is inserted therebetween and blow molding is performed.

In the present invention, a straight pipe does not necessarily mean straightness in a strict sense, but may have any straightness that does not hinder the slipperiness of the resin with respect to the surface of the pipe. .

[0010]

1 to 4 show a hollow double-wall structure according to an embodiment of the present invention. FIG. 1 is a perspective view seen from the back side, and FIG. FIG. 3 is an enlarged sectional view taken along line BB of FIG. 1, and FIG. 4 is a plan view seen from the back surface.

FIG. 5, FIG. 6 and FIG. 7 show blow molding of a hollow double-walled structure according to an embodiment of the present invention.
FIG. 5 is a partial cross-sectional view showing a state in which the sliding die is advanced and the mold is closed, and FIG. 6 is a partial cross-sectional view showing a state in which the sliding die after closing the mold is retracted to complete the blow molding. FIG. 7 is a partial cross-sectional view showing another portion in a state where the blow molding has been completed.

In FIG. 1, reference numeral 1 denotes a hollow double-walled structure. The hollow double-walled structure 1 has a panel shape,
Reference numeral 2 denotes a front wall, 3 denotes a back wall, and 4 denotes a peripheral wall. As shown in FIGS. 2 and 3, the back wall 3 faces the front wall 2 at an interval, and By the front wall 2 and the back wall 3
And a hollow portion 5 is formed between them.

A straight pipe 6 is provided in the hollow portion 5 of the hollow double-walled structure 1, and the pipe 6 is mounted by a pipe mounting structure 7 integrally connected to the back wall 3. . The pipe mounting structure 7 is integrally formed with the back wall 3 and surrounds the entire peripheral surface of the pipe 6. The surrounding portion 8 is recessed in the back wall 3 and supports a part of the peripheral surface of the pipe 6. It consists of part 9. The surrounding portion 8 and the supporting portion 9 are formed at a plurality of locations alternately in the length direction of the pipe 6. The surrounding portion 8 of the pipe mounting structure 7 is also welded and integrated with the front wall 2. Reference numeral 10 denotes the welded portion.

As shown in FIG. 1, recesses 11 and 11 for maintaining a play interval with respect to the end face of the pipe 6 are formed in portions of the back wall 3 corresponding to both ends of the pipe 6.

In the illustrated embodiment, a cylindrical pipe is used as the pipe 6. However, the pipe 6 is not limited to this, and may be, for example, a triangular cylinder, a square cylinder, a polygonal cylinder, or an elliptical cylinder. Shape. In any case, the pipe 6 may have a straight shape.

The hollow double-walled structure 1 according to the present invention comprises AB
S resin, modified polyphenylene oxide resin, polycarbonate resin, polyamide resin, polypropylene resin,
It is made of a blowable thermoplastic resin such as a polyethylene resin. In addition, the pipe 6 is subjected to a surface treatment such as plating to improve the slipperiness of the surface as necessary.

The hollow double-wall structure 1 according to the present invention is shown in FIG.
Or blow molding as shown in FIG. The pipe 6 and the parison 15 are arranged between one split mold 12 for forming the front wall 2 and the other split mold 13 for forming the back wall 3.

Next, after the mold closing process or the mold closing is completed, the sliding mold 16 is advanced from the cavity 14 and the parison 1 is closed.
5 are welded to each other (FIG. 5), the sliding mold 16 is retracted to the surface of the cavity 14, and the pressurized fluid is blown into the parison 15 to complete blow molding. (Fig. 6).

When the blow molding is completed, as shown in FIG. 6, the surrounding portion 8 of the pipe mounting structure 7 is formed integrally with the back wall 3 and integrally welded to the front wall 2. . Further, as shown in FIG. 7, the support portion 9 of the pipe mounting structure 7 is
It is formed so as to be recessed in the back wall 3. The support portion 9 is also welded to the front wall 2 and integrated.

After blow molding, the front and rear walls 2 and 3 constituting the hollow double-walled structure 1 are cooled by cooling the split molds 12 and 13.
Then, the surface of the peripheral wall 4 is cooled and solidified by cooling to such an extent that the shape is maintained, and the mold is opened.

In the hollow double-walled structure 1 according to the present invention, a straight pipe 6 is provided in the hollow portion 5, and the pipe 6 of the back wall 3 which is integral with the mounting structure 7 of the pipe 6 is provided. By providing concave portions 11 and 11 for maintaining a play interval with respect to the end surface of the pipe 6 at a portion corresponding to the end portion, a lightweight and rigid hollow double-walled structure 1 can be obtained, and the hollow double-walled structure 1 can be hollowed after blow molding. In the process of cooling and shrinking the double-walled structure 1, the sliding property with respect to the surface of the pipe 6 due to the shrinkage of the portion in contact with the pipe 6 is good, and the length of the pipe 6 is relatively increased. The recesses 11 in the wall 3 can escape. Besides,
The back wall 3 is attached to the pipe mounting structure 7 to which the pipe 6 is mounted.
By providing the supporting portion 9 which is recessed in the pipe 6 and supports a part of the peripheral surface of the pipe, it is possible to reduce accumulation of distortion due to contraction around the pipe 6. For this reason, even if the hollow double-walled structure 1 has improved strength and rigidity by inserting the pipe 6, it does not generate deformation distortion due to cooling shrinkage after molding and does not generate cracks. It will be.

In addition, the hollow double-walled structure 1 according to the present invention has a support portion 9 recessed in the back wall 3 in a part of the pipe mounting structure 7, and the support portion 9 has a pipe portion. Since the hollow double-walled structure 6 is exposed, it is possible to easily recognize that the pipe 6 is inserted into the hollow double-walled structure 1 when the hollow double-walled structure 1 is discarded, and the separation thereof can be performed reliably and easily. At this time, the hollow double-walled structure 1 can be easily split by biting the splitting tool into the recessed support portion 9, so that the sorting operation is easier.

The ratio between the surrounding portion 8 and the supporting portion 9 in the pipe mounting structure 7 is determined by the required physical properties. Increasing the ratio of the surrounding portion 8 improves the strength and rigidity of the hollow double-walled structure, and increasing the number of the supporting portions 9 facilitates the work at the time of sorting and collecting.

[0024]

According to the present invention, a straight pipe is provided in the hollow portion, and a play corresponding to the end of the pipe is provided at a portion corresponding to the end of the pipe on the back wall integrated with the pipe mounting structure. By providing a recess that keeps the space,
A lightweight and rigid hollow double-walled structure can be obtained, and in the process of cooling and shrinking of the hollow double-walled structure after blow molding, slipperiness with respect to the pipe surface due to shrinkage of a portion in contact with the pipe is reduced. In addition to being able to escape the relatively increased length of the pipe in the recess in the back wall, the pipe mounting structure for mounting the pipe has By providing a support part that supports a part of the surface, the accumulation of distortion due to shrinkage due to cooling around the pipe is reduced,
Thus, even if the strength and rigidity are improved by inserting a pipe, a hollow double-walled structure that does not generate deformation distortion due to cooling shrinkage after molding can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view of a hollow double-walled structure according to the present invention as viewed from the back side.

FIG. 2 is an enlarged sectional view taken along line AA of FIG.

FIG. 3 is an enlarged sectional view taken along line BB of FIG. 1;

FIG. 4 is a plan view of the hollow double-walled structure according to the present invention as viewed from the back surface side.

FIG. 5 is a partial cross-sectional view showing a state in which a sliding die is advanced and the die is closed.

FIG. 6 is a partial cross-sectional view showing a state where the sliding mold after closing the mold is retracted to complete blow molding.

FIG. 7 is a partial cross-sectional view showing another portion in a state where blow molding has been completed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hollow double wall structure 2 Front wall 3 Back wall 4 Peripheral wall 5 Hollow part 6 Pipe 7 Pipe mounting structure 8 Surrounding part 9 Support part 10 Welding part 11, 11 Depression 12 One split mold 13 The other split mold 14 Cavity 15 Parison 16 Sliding die 17 Projection

Claims (2)

[Claims] 1. A hollow double-walled structure comprising a front wall, a back wall facing the front wall at an interval, and a peripheral wall forming a hollow portion between the front wall and the back wall. A straight pipe is disposed in the hollow portion, and at least a portion surrounding the entire peripheral surface of the pipe is connected to at least the back wall and is recessed in the back wall, so that a peripheral surface of the pipe is formed. A hollow portion having a pipe mounting structure including a support portion for supporting a part thereof, and a concave portion for maintaining a play interval with respect to the end surface of the pipe is formed in a portion of the back wall corresponding to the end of the pipe. Double wall structure. 2. A hollow double-walled structure comprising a front wall, a back wall opposed to the front wall at an interval, and a peripheral wall forming a hollow portion between the front wall and the back wall. A method of blow molding, wherein a sliding die is formed integrally with a back wall of a mold cavity forming a back wall of a pair of split molds to form a surrounding portion surrounding the entire peripheral surface of a pipe. A mold and a projection formed in the back wall and forming a support portion for supporting a part of the peripheral surface of the pipe are provided, and the pipe is inserted between the molds and blow molded. A method for producing a hollow double-walled structure.