JPH0753433B2 - Injection molding shoe manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in a method for manufacturing an injection-molded shoe in which a shoe body is molded by injection molding after the shoe sole is molded, and the two are joined and integrated. Is.

(Prior Art) A method of manufacturing an injection-molded shoe in which the shoe body is injection-molded and then the shoe sole is injection-molded to combine and integrate the two has been known, but recently, as a method adapted to diversification of design, In the first method, a shoe sole is injection-molded as a first step, and then a shoe body is injection-molded as a second step to combine and integrate the shoe sole and the shoe body. When this method is used, the shoe body and the sole are colored in different colors, and they are connected to the shoe body on the lower surface of the shoe sole (hence the same color as the shoe body).
It can be said that this method is suitable for manufacturing injection-molded shoes with a wide variety of designs, because it has the advantage that it is possible to easily give a colorful color pattern to the bottom surface of the shoe sole by exposing the block-shaped pattern piece.

As an example of this method, first, a mold as shown in FIG. 4 is used as the first step (for convenience of explanation, description and illustration relating to providing the block-shaped pattern piece on the bottom surface of the shoe sole will be omitted). Omitted).

The mold shown in FIG. 5 is a mold for molding a shoe sole, which is composed of a bottom mold 1 and a dummy mold 2. By injecting an injection resin into a molding chamber 4 through an injection passage 3, a shoe sole 5 is formed.
(FIG. 6) is molded.

After molding the shoe sole, the dummy mold 2 is separated, and the side molds 6 and 7 and the last mold 8 which are molds for molding the shoe main body are set on the bottom mold 1 as shown in FIG. Next, resin is injected into the molding chamber 10 through the injection passage 9 to mold the shoe body 11 (Fig. 9), and an injection-molded shoe in which the shoe body 11 and the shoe sole 5 are integrally joined is obtained.

(Problems to be Solved by the Invention) However, in the above method, after the shoe sole material is injected, it is cooled for a certain period of time, but there is a problem that the compact (sole) shrinks during this cooling. For example, if the injection resin is vinyl chloride resin, it is usually 3% (volume shrinkage)
There is some contraction.

Therefore, as shown in Fig. 7, the parting line of the shoe sole
12 floats from the position shown by the solid line to the position shown by the chain double-dashed line,
As a result, when the shoe body is injection-molded, there is a drawback that parting with the shoe sole cannot be performed as designed.

Further, during cooling, the molded body (sole) shrinks not only in the longitudinal direction but also in the width direction (direction perpendicular to the longitudinal direction), so that the peripheral collar portion 13 (usually referred to as edge) of the shoe sole is Bend from the position shown by the solid line in the figure to the position shown by the chain double-dashed line. As a result, a slight gap 14 is formed between the side molds 6 and 7 during the molding of the shoe body, and the injection resin leaks out, and the resin forming the shoe body slightly overhangs on the peripheral flange 13 as shown in FIG. However, there is a drawback that a so-called edge biting phenomenon occurs in the drawing (15 indicates an overhanging portion) and the appearance is impaired.

The present invention has been made in view of the above points, and an object thereof is to provide a method for manufacturing an injection-molded shoe having an excellent appearance.

(Means for Solving Problems) A method for manufacturing an injection-molded shoe according to the present invention is a method for manufacturing an injection-molded shoe in which a shoe sole is injection-molded and then a shoe main body is injection-molded to integrate and integrate the two. Form a protrusion on the inner surface of the shoe sole,
At the time of molding the shoe main body, the last mold is brought into contact with the above-mentioned projection and the shoe sole is pressed downward through the projection, whereby the entire shoe sole is adapted to the mold inner surface shape of the bottom mold and kept in that state. It is characterized in that the main body is injection-molded.

(Example) Hereinafter, the Example of this invention is described based on drawing.

As the first step of the present invention, the shoe sole is injection-molded. For this molding, a shoe sole molding die as shown in FIG. 1A is used. The mold comprises a bottom mold 20 and a dummy mold 21, and the bottom mold 20 has a mold inner surface 22 having a shape corresponding to the shape of the shoe sole.
21 is provided with a recess 23 having a desired shape and size.
Further, an air vent hole 36 may be provided in the recess 23. By providing the air vent hole 36, it becomes easy to remove the dummy mold 21 and the shoe sole 26 from the mold. As shown in FIG. 1B, a sintered metal material 37 such as stainless steel or brass may be embedded in the air vent hole 36 to prevent the injection resin from entering the air vent hole 36.

An injection resin as a shoe sole material is injected into the molding chamber 24 of the mold through an injection passage 25, and the shoe sole 26 (see FIGS. 3 and 4).
Molding). A vinyl chloride resin is usually used as the shoe sole material, but a thermoplastic resin such as polyethylene or a thermoplastic rubber may also be used.

As mentioned above, since the dummy mold 21 is provided with the recessed portion 23, the inner surface of the obtained shoe sole 26 is provided with the protrusion 27 corresponding to the recessed portion 23 as shown in FIGS. 3 and 4. It is formed.
Although the protrusion 27 shown in FIGS. 3 and 4 has a cylindrical shape, it may have a polygonal prism shape such as a triangular prism or a quadrangular prism, or a conical shape or a truncated cone shape, and the shape thereof is not particularly limited. Further, the number of the protrusions 27 is also arbitrary, and an appropriate number is provided. Instead of providing a plurality of small protrusions, it is also possible to provide a long protrusion that continuously integrates them.

The height of the protrusion 27 is appropriately set within the range of x to x + 0.5 mm, preferably x + 0.2 mm, where x is the bottom thickness of the shoe body 26 (FIG. 2). When the protrusion is formed as a small columnar protrusion, the diameter of the protrusion is preferably 3 to 6 mmφ.

As shown in FIG. 4, the protrusions 27 are preferably provided in the vicinity of both side edges between the toe portion and the stepless portion, but they may be provided in other positions.

After molding the shoe sole, the dummy mold 21 is removed,
On the bottom mold 20 having 26, side molds 29, 30 and last mold 31 are set as shown in FIG. Reference numeral 32 denotes a lining cloth suspended in the last mold 31, and as the lining cloth 32, a knitted cloth such as nylon, rayon, and cotton is used.

When the mold is clamped at the time of molding the shoe main body, the bottom surface of the last mold 31 comes into contact with the protrusion 27 of the shoe sole, and presses the shoe sole 26 downward through the protrusion 27. As a result, the molded body (sole) contracts during the cooling process after injection of the shoe sole molding material, and even if the parting ruffin on the shoe sole floats as shown in FIG. As a result of being pushed downwards, the parting line returns to the original, original position, and the floating state is eliminated. Further, due to the above contraction, the peripheral collar portion 33 of the shoe sole is moved from the position shown by the solid line in FIG.
Even if it is bent to the position shown by the dotted line, it is spread in the width direction by the pressing force exerted on the protrusion 27, whereby the curved state of the peripheral flange portion 33 is forced and returns to the original, original position. .

In this way, the bottom of the last mold 31 pushes the protrusions 27 on the shoe sole, so that the entire shoe sole is covered by the inner surface 22 of the bottom mold 20.
Adapted to shape. Thus, the shoe sole is held in conformity with the shape of the inner surface of the mold to inject the injection resin as the material of the shoe main body into the molding chamber 34 of the mold, and the injection molding of the main body of the shoe as the second step. Do. As the material for the shoe body, a thermoplastic resin such as vinyl chloride resin or polyethylene, or a thermoplastic rubber is used, and the same material as the shoe sole material or a different material may be used. Further, by appropriately selecting the pigment to be mixed in the material, it is possible to manufacture an injection two-color shoe in which the shoe body and the sole have different colors.

As described above, since the shoe body is injection-molded while holding the shoe sole in conformity with the inner surface shape of the bottom mold, the parting between the shoe body and the shoe sole can be formed as designed. Further, since the curved state of the peripheral collar portion 33 of the shoe sole is corrected and returns to the position as it is, there is no gap between the side molds 29, 30 and the peripheral collar portion 33 as in the conventional case, and as a result, There is no leakage of the injection resin, and as shown in FIG. 2, the boundary between the shoe main body 28 and the sole 26 is clearly shown, and the so-called resin in which the shoe main body forming resin partially protrudes on the peripheral flange 33 as in the conventional case. The phenomenon of biting of the edge does not occur.

After the injection molding of the shoe main body is completed, the molds are opened, the molds are separated from each other, and the molded products are taken out to obtain an injection-molded shoe 35 in which the shoe main body 28 and the sole 26 are combined and integrated as shown in FIG. can get.

The present invention can be applied to the case of manufacturing boots by injection molding, for example, but is not limited to the manufacture of boots, and can also be applied to the manufacture of shoes or sandals.

(Effects of the Invention) According to the present invention, since the projection is formed on the inner surface of the shoe sole and the last mold is brought into contact with the projection during the molding of the shoe main body to press the shoe sole downward through the projection, It is possible to eliminate the floating of the parting line due to cooling shrinkage of the (shoe sole) and return it to the original predetermined position, and eliminate the inward bending of the collar rim of the shoe sole due to the above cooling shrinkage. According to the present invention, it is possible to restore the original shape to the original shape even if the shoe sole is deformed due to cooling shrinkage, and the original shape is maintained. In, injection molding of the shoe body can be performed.

Thus, according to the present invention, a clear parting between the shoe body and the sole can be performed as designed, and the resin for forming the shoe body is projected onto the peripheral collar portion of the sole (the phenomenon of biting by the edge). ) Can be prevented, so that an injection-molded shoe with a beautiful appearance can be produced.

[Brief description of drawings]

1A is a longitudinal sectional view of a shoe sole molding die used in the present invention, FIG. 1B is an enlarged view of a portion in FIG. 1A, and FIG. 2 is an injection-molded shoe obtained by the method of the present invention. Of FIG. 3 is a longitudinal cross-sectional view of the main part near the shoe sole, FIG. 3 is a vertical cross-sectional view of the main part showing the state during injection molding of the shoe main body according to the present invention, and FIG. The plan view, FIG. 5, and FIG. 6 are vertical cross-sectional views showing a shoe sole molding die and a shoe body molding die used in the production of conventional general injection-molded shoes, respectively. FIG. 8 is an explanatory view showing a floating state of a parting line in the conventional method, FIG. 8 is an explanatory view showing a curved state of a collar portion around the sole of the shoe in the conventional method, and FIG. 9 is a main part showing a so-called edge biting phenomenon. FIG. 20 …… Bottom mold, 26 …… Shoe sole 27 …… Protrusion, 28 …… Shoe body 31 …… Last mold

Claims (1)

[Claims] 1. A method of manufacturing an injection-molded shoe in which a shoe body is injection-molded and then the shoe body is injection-molded to combine and integrate the two, and a projection is formed on the inner surface of the shoe sole, and a last mold is formed at the time of molding the shoe body. Injecting the shoe body by abutting against the protrusion and pressing the shoe sole downward through the protrusion so that the entire shoe sole conforms to the shape of the inner surface of the bottom mold and is kept in that state. A method for manufacturing an injection-molded shoe, comprising: