JPH02220601A - Injection molding of multilayer sole - Google Patents

Abstract

PURPOSE:To prevent inferior goods from being produced as a result of a first- order main sole being floated or slid by an injection pressure for a second-order injection molding, by using a bottom mold providing through-holes in the surface thereof. CONSTITUTION:A first-order sole molding cavity is formed, which is composed of a bottom mold 1 providing through-holes 11 in the projections on the surface thereof, side molds 2 and a dummy last 3. A first-order injection molding material is poured in the molding cavity and finally filled to the through-holes 11, and thus a first-order main sole 6 providing float-preventing pieces 61 is molded. After that, after a dummy last 3 is removed, a last 5 hanging an upper 4 is set and a second-order main sole molding cavity is formed, which is composed of the first-order main sole 6, the side molds 2 and the bottom mold 1. Finally, after a second-order main sole 7 is molded by a second-order injection molding material being poured, the side molds 2 and bottom mold 1 are removed and the second-order main sole 7 is removed from the last 5. The first-order main sole is thus temporally fixed to the bottom mold 1 by the flat-preventing pieces 61. For that reason, it is perfectly prevented that the first-order main sole 6 is floated or slid, and inferior goods are not produced thoroughly.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) This invention relates to a manufacturing method for injection molding a multilayer shoe sole using a dummy last.

(Prior Art) Conventionally, injection molded shoes with multilayer soles using dummy lasts have been manufactured by the following method. First, a primary injection molding gap consisting of a dummy last, a side mold, and a bottom mold is formed, and the primary injection molding material is injected into it to form the primary outsole.The dummy last is removed, and then the bottom mold is formed. The last with the cover suspended is set to form a secondary outsole molding cavity consisting of the primary outsole and side molds.

Next, a secondary injection molding material is injected and a secondary outsole is molded, and then the side mold and bottom mold are opened and the shoe is taken off from the last to obtain an injection molded shoe with a multilayer sole.

(Problem to be Solved by the Invention) However, in this manufacturing method, when the dummy mold is taken out after the first injection molding and the primary outsole has been molded, the -next outsole is exposed to the upper surface of the bottom mold. It often popped up. If the second injection molding is performed in this state, the secondary injection molding material will get under the primary outsole, and if the first and second injection molding materials are different colors, the color separation will be unclear. There were some defective products. In order to eliminate this drawback, Special Publication No. 59-43162 and Special Publication No. 60-3
No. 4362 has been proposed, and the former has a recessed part on the side mold, and the latter has a cut-in part such as an overhang design on the bottom mold to prevent lifting. In either case, if the -next outsole is thick, the biting part can be removed sufficiently, which has the effect of preventing it from lifting up, but if the -next outsole is thin, the indented part cannot be removed enough, so the -next outsole becomes the second outsole. The injection pressure during the subsequent injection molding caused the parts to lift up or shift, resulting in defective products. Furthermore, these recessed portions and overhang designs require complicated processing, which increases the manufacturing cost of the mold and becomes a factor in increasing the cost of the product. The present invention provides a method for manufacturing injection molded shoes that eliminates these conventional drawbacks.

(Means for Solving the Problems) That is, the present invention provides a method for injection molding a multilayer shoe sole using a dummy last, which is characterized by using a bottom mold having through holes in the molding surface. This article focuses on the injection molding method for shoe soles. The holes used in the present invention do not need to have any particular shape as long as they are penetrating, but they should have a shape that is easy to drill.9 For example, as shown in Figure 3 (a) and (b), the molding surface of the bottom mold is flat, then V
A hole may be provided in the shape of a letter, or if there is a protrusion on the molding surface, a hole may be provided in the protrusion in an oblique opening, a figure 7 shape, or horizontally.

The size of the through hole may be 0.3 mm to 3.0 m in diameter.

The anti-lifting piece is molded to have the same size as the through hole at the same time as the final outsole. The anti-lifting piece has a diameter of 0.
If the diameter is less than 3 mm, it will be thin, so it will not be effective in preventing the outsole from lifting up. If the diameter is 3.0 mm or more, it will be thicker, which will increase the effect of preventing lifting, but it will be inconvenient to pick it up after the shoe is formed. It is.

The through-holes can be made in advance in places where lifting is expected, but since the through-holes can be easily made with a drill, etc., test production is carried out after the mold is made, and the next step is to check the lifting situation of the outsole. You may place it in an appropriate position after looking at it. The present invention can be implemented not only in the unit tooling method, but also in the direct tooling method.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings. As shown in Figure 1, the primary bottom molding cavity is made up of a bottom mold 1 with a through hole 11 (diameter 0.4 nu) provided in the protrusion of the molding surface of the bottom mold, a side mold 2, and a dummy last 3. The primary injection material is injected into the molding gap of the primary outsole and anchored to the through hole 11, thereby molding the primary outsole 6 provided with the anti-lifting piece 61. The bottom outsole 6 is temporarily fixed to the bottom mold 2 by a lifting prevention piece 61. Next, the dummy last 3 is removed, and the last 5 with the cover 4 suspended therein is set as shown in FIG. Next, form the bottom molding void. Next, a secondary injection molding material is injected into the secondary outsole molding gap to mold the secondary outsole 7. After forming the secondary outsole 7, the side mold 2. bottom mold 3
When the shoes were opened and the shoes were taken off from the last 5, injection molded shoes with clear color coding were obtained. When the shoe is taken off, the anti-lifting piece 61 is partially cut off and attached to the injection molded shoe and taken out.

The anti-lifting piece 61 did not necessarily have to be pinched, but could be easily pinched by one hand. As the injection molding material, polyvinyl chloride resin compositions and urethane resin compositions are usually used, but any resin used for injection molding materials may be used.

(Operations and Effects of the Invention) Since the present invention is configured as described above, a primary outsole provided with a prevention piece is molded. Therefore, −
Next, the outsole is temporarily fixed to the bottom mold by a lifting prevention piece. Therefore, when the dummy last is removed, the bottom outsole is completely prevented from lifting or shifting, and no defective products are produced. In particular, the present invention provides -
Even if the outsole is thin, it is effective because the lifting-preventing piece formed by the through hole can reliably prevent lifting. Furthermore, one through hole can be easily drilled even after the bottom mold is manufactured.

Therefore, there is no need to change the design of the outsole, and the cost is reduced.

[Brief explanation of the drawing]

The drawings show one embodiment, and the first and second figures are explanatory diagrams showing the manufacturing process of injection molded shoes of the present invention, and the third figures (a) and (b) are illustrations of the manufacturing process of injection molded shoes of the present invention. FIG. 3 is a cross-sectional view of a through hole. Explanation of symbols 1...Bottom mold, 11...Through hole, 2...
Side mold, 3...Dummy mold, 4...Flip cover, 5...Last, 6...-Next bottom, 61... Lifting prevention piece. 7...Secondary bottom

Claims (1)

[Claims] A method for injection molding a multilayer shoe sole using a dummy last, the method comprising using a bottom mold having through holes in the molding surface.