JPH0611162Y2 - Blow-molded plastic hollow double-walled structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is for molding housing panels for various electronic devices, housing panels for furniture, housing panels for construction, panel members for automobiles, cases, containers, etc. The present invention relates to a blow-molded product having a hollow double-walled plastic structure that constitutes the product.

[Prior Art] Conventionally, a storage case for a machine tool or the like, which is a blow-molded product formed by blow molding a thermoplastic material into a hollow double-wall structure, has already been described in Japanese Utility Model Publication No. 59-143076. In this storage case, a weld rib is formed on the inner wall side at the time of blow molding, and the inner wall and the outer wall are integrally connected to each other for reinforcement.

[Problems to be Solved by the Invention] In a blow-molded product having a hollow double-wall structure such as the conventional storage case having a hollow double-wall structure described above, in order to improve the bonding strength of the weld rib, the compressed state of the weld rib is required. However, on the other hand, welding marks due to weld ribs appear remarkably on the surface. Therefore, the present inventor, as shown in FIG. 9, recesses a part of the parison a on the inner wall side toward the outer wall side by a thin protrusion b in order to prevent the appearance of the weld rib from being deteriorated by the marks generated during welding. We made an experiment to form a thin weld rib c, and the tip of the weld rib c was blown into the parison d on the outer wall side during blow molding.
There is a problem that it is difficult to elongate with a uniform thickness until the joint is joined, and a molding defect such as a pin hole at the tip portion is likely to occur. Even if the molding is performed well, as shown in FIG. 10, the base end portion e of the weld rib c on the inner wall side becomes particularly thin, and the strength of the weld rib c itself becomes low. It has also been found that the reinforcement due to integration becomes incomplete, resulting in a decrease in rigidity and strength of the molded product.

The present invention is intended to solve the problem in the case where such a thin weld rib is formed at the time of blow molding, and at the time of blow molding, the inner diameter of the weld rib is gradually reduced to form a thin tip portion. The entire weld rib is formed to have a uniform thickness without the formation of pinholes and thinned parts, and by doing so, the integration of double walls by the weld rib is completely integrated to improve the strength of the molded product. It is an object of the present invention to provide a blow-molded product having a hollow double-walled plastic structure that can be manufactured.

[Means for Solving the Problem] In order to achieve the object, the present invention is configured as follows.

That is, the structure is a blow-molded product in which a thermoplastic material is blow-molded into a hollow double-wall structure, and during blow molding, a part of the plasticized and melted parison is compressed to form a double-wall space. Is formed by forming a weld rib, and the weld rib is a blow-molded product having a hollow double-wall structure made of plastic, characterized in that the inner diameter is gradually reduced to form a thin tip portion. is there.

[Operation] In the blow molding of a plastic hollow double-walled blow-molded product according to the present invention, a mold having protrusions corresponding to the shape of the weld rib which gradually reduces the inner diameter to form the tip end thinly is used. Since it is used, a part of the parison comes into contact with the tip of the protrusion of the mold cavity, and its peripheral portion is blown while being supported by the step of the protrusion.
Therefore, as the blow progresses, the parison around the protrusion expands evenly along the stepped surface of the cavity to form a weld rib reaching the opposing wall. The weld rib is formed so that the inner diameter is gradually reduced and the tip portion has a thin shape, so that the extension of the parison is uniform and the entire thickness thereof is uniform.

[Embodiment] An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows an example of a blow-molded product having a hollow double-walled plastic structure, in which 1 is the inner wall, 2 is the outer wall, and the inner wall 1 and the outer wall 2 are joined together at their peripheral surfaces. A panel 3 having a heavy wall structure is configured. In this panel 3, a large number of weld ribs 4 are formed on the inner wall 1,
And the outer wall 2 is integrally connected by the weld rib 4. The surface of the outer wall 2 is a minute uneven surface for decoration. As shown in FIG. 2, the weld rib 4 is formed by gradually reducing the inner diameter from a concave portion 5 having a larger inner diameter toward the outer wall 2 side and forming a thinner tip portion 6. 6 is welded to the outer wall 2. In the weld rib 4, the width H between the inner surface of the recess 5 and the outer surface of the outer wall 2 is H = (2.1 to 6.5) × t _1, preferably H = (2.2 to 4.0), where t ₁ is the average wall thickness of the inner wall 1. ) × t ₁ range is specified. Also, the average thickness of the outer wall 2 is t ₂ , the thickness of the most compressed welded portion 7 is t ₃ , and the tip portion 6 is
The inner width of the part that rises 0.5 times from the deepest wall of D
Then, D = (0.3 to 2.5) × t ₁ t ₃ = (0.45 to 0.98) × (t ₁ + t ₂ ) Preferably, D = (1.1 to 2.1) × t ₁ t ₃ = (0.58 to 0.94) Set to the specified range of × (t ₁ + t ₂ ). It is preferable that the average thickness t ₂ of the average thickness t ₁ and the outer wall 2 of the inner wall 1 in the range of 1.5~3.5mm both. In addition, the width H between the inner surface of the recess 5 and the outer surface of the outer wall 2 is specified within the above range because the width H is 2.1 t.
Prone to molding defects there that Parisun inner surface near the Uerudoribu 4 during the blow molding will be welded is less than _1, the strength is impaired corners of Uerudoribu 4 When the width exceeds 6.5 T ₁ becomes thinner This is because the molding is favorably performed within the above range.

Also, when the inner width D exceeds 2.5 times t ₁ , the plasticized plastic that contacts the weld rib portion during molding is cooled and does not expand, the compressive force of the welded portion increases, and the weld mark on the surface of the outer wall 2 increases. Of the average wall thickness t ₁ of the inner wall 1
If it is less than 0.3 times, molding defects such as pinholes will occur at the time of molding, and the wall thickness will be extremely uneven and the bond strength will decrease. On the other hand, if the wall thickness t ₃ of the welded portion 7 exceeds 0.98 times (t ₁ −t ₂ ), poor welding will be noticeable, and if it is less than 0.5 times (t ₁ + t ₂ ), welding marks will be noticeable. However, within the above range, the bonding strength and appearance are good.

The hollow double-walled panel 3 configured as described above is
For example, as shown in FIG. 3, it is used as a housing panel 9 of an electronic device (electronic copying machine) 8.

The hollow double-walled panel 3 is constructed by blow molding a thermoplastic material, as shown in FIG.

That is, 10 and 11 are a pair of split molds, 12 and 13 are the cavities thereof, and one of the cavities 13 has the weld rib 4
Is provided with a protrusion 14 for forming the. This protrusion 14
Is a stepwise shape having a step portion 15 and a tip portion 16 having a small outer diameter so as to correspond to the shape of the weld rib 4. Reference numeral 17 is an extrusion head, and 18 is a molten parison.

In the blow molding of the hollow double-walled panel 3 using the pair of split molds 10 and 11, the parison 18 extruded from the extrusion head 17 is arranged between the split molds 10 and 11 as shown in FIG. Then, when the split molds 10 and 11 are closed, a part of the parison 18 corresponding to the protrusion 14 comes into contact with the tip portion 16 of the protrusion 14 on one cavity 13 side as shown in FIG. When it blows, the inner side of the parison 18 is welded together and blow-molded, so that the protrusion 14 is stepped as shown in FIG. The parison 18 is further expanded while being supported by the edge of the portion 15, and the parison 18 is in contact with the protrusion 14 as shown in FIG.

In FIG. 6, the central portion p of the plasticized parison 18 in contact with the projection 14 is cooled and the elongation thereof is reduced to some extent, but the contact area is as narrow as the thickness of the parison 17, and The approaching portion p ₂ of the central portion p in contact with the protrusion 14 of the parison 17 is sequentially extended toward the base side of the protrusion 14 so as to be bent at a substantially right angle as it is blow-molded, and finally the hollow portion of the welded portion 7 is formed. It is possible to prevent the accumulation of meat inside and to suppress the generation of welding marks due to the compressive force.

The thermoplastic material forming the hollow double-walled panel 3 is styrene-modified polyphenylene oxide,
ABS resin, polycarbonate, polyamide, polybutylene terephthalate, polypropylene, polyethylene, etc. are used, but the surface appearance is important and the housing panel used by itself as a structural member,
It is preferable to use the former five materials having a tensile strength (ASTM-D638) of 500 kg / cm ² or more.

The fine uneven surface formed on the surface of the outer wall 2 has a depth of 30
In particular, in the case of forming an extremely fine uneven surface of 30 to 80 μ, the traces due to welding of the weld rib 4 are conspicuous, so that the tip of the weld rib 4 is thin as described above, and Setting the compression ratio within the range is useful for maintaining good appearance.

The shape of the tip portion 6 of the weld rib 4 may be a cross-sectional square shape or the like other than the shape shown in the figure. The weld rib 4 is not a dotted shape but a linear weld rib 4'as shown in FIG. Can also be

According to the hollow double-walled panel 3 configured as described above, the welded portion 7 of the tip 6 is formed thin so that the weld rib 4 gradually reduces the inner diameter during blow molding. The weld rib 4 can be formed to have a uniform thickness without forming pinholes or thin portions during molding. Therefore, the weld rib 4 can completely bond and integrate the double walls, and the rigidity and strength of the molded product can be improved without impairing the appearance of the molded product.

[Advantage of the Invention] The present invention is a blow-molded product in which a thermoplastic plastic material is blow-molded to have a hollow double-wall structure. Weld ribs that integrally connect the heavy walls are formed, and the weld ribs are formed by gradually reducing the inner diameter to form a thin tip. Therefore, during blow molding, the weld ribs are gradually reduced in inner diameter. By forming a thin tip portion, the entire weld rib is formed to have a uniform thickness without producing pinholes or thin portions, and thus, the integration between the double walls by the weld rib is completed, This has the effect of improving the strength of the molded product.

[Brief description of drawings]

1 shows an embodiment of the present invention, FIG. 1 is an overall perspective view of a panel having a hollow double wall structure, FIG. 2 is an enlarged vertical perspective view of a part thereof, and FIG. 3 is a panel having a hollow double wall structure. FIG. 4 is a perspective view of an electronic device showing a usage example of FIG. 4, FIG. 4 is a cross-sectional view showing a blow molding aspect of a panel having a hollow double wall structure, and FIGS. 5, 6, and 7 show a molding aspect of the parison. FIG. 8 is a partial sectional view, FIG. 8 is a perspective view showing another embodiment of the present invention, and FIG. 9 is a partial perspective view showing a blow molding mode of a hollow double wall structure panel for explaining the problems of the present invention. Sectional drawing, FIG. 10 is a sectional view of a molded part of the same panel. 1 ... inner wall, 2 ... outer wall, 3 ... hollow double-walled panel, 4
… Weld ribs, 5… recesses, 6… tips, 7…
Welded portion, 10, 11 ... Pair of split molds, 12, 13 ... Cavity,
14 ... Protrusion, 15 ... Step, 16 ... Tip, 18 ... Parison

Claims (1)

[Scope of utility model registration request] 1. A blow-molded article obtained by blow-molding a thermoplastic material into a hollow double-wall structure, wherein a part of the plasticized and melted parison is compressed at the time of blow-molding to form a space between the double-walls. A blow-molded product having a hollow double-wall structure made of plastic, characterized in that a weld rib is formed integrally with the weld rib, and the weld rib is gradually reduced in inner diameter to form a thin tip portion.