JPS5817603B2 - How to make injection molded shoes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing injection molded shoes having a shoe-like or sock-like lining fabric with a midsole, in which residual gases such as air and excess foaming gas are removed from a closed mold during molding. The purpose of the present invention is to provide a method for manufacturing injection molded shoes with high commercial value by eliminating the adverse effects of the residual gas on the molded product by discharging the residual gas.

Conventionally, when injection molding material containing a foaming agent is injected in a heated molten state into the molding cavity of a shoe injection mold to perform foam molding, cooling of the molded product is slow due to the heat insulation effect of the countless air bubbles generated inside the molded product. If the mold is demolded without sufficient cooling, foaming ability remains even after demolding, resulting in deformation of the molded product due to secondary foaming.

Parts such as the heel of the sole of a shoe, which are thicker than other parts, may not be sufficiently cooled even though other parts have cooled, resulting in deformation due to secondary foaming. This was particularly noticeable in the thick parts.

Therefore, one way to avoid this deformation is to design shoes that do not create local thickness differences.
In this case, the outer shape of the shoe becomes extremely monotonous, making it unsuitable for producing products with high added value.

In addition, to avoid this deformation, there was a method of demolding the molded product after sufficiently cooling it, but this had the disadvantage of lengthening the production cycle, lowering manufacturing efficiency, and increasing product cost. .

In addition, even if we try to dissipate excess gas from the breathable insole when foaming by using a breathable material for the sock-like lining fabric or the inner sole of the jacket, foaming generally does not occur. Since gas tends to concentrate in the center of the compact, sufficient dissipation of excess gas cannot be expected.

In addition, thermoplastic elastomers such as styrene-butadiene, polyurethane, and ethylene-vinyl acetate copolymers have been used as injection molding materials for shoes, but these materials have good rebound properties. When molded as the sole of a shoe, there is less slippage when walking, less loss of flexibility even at low temperatures, and although it exhibits physical properties similar to rubber, it does not require vulcanization, etc. It has the following advantages.

However, when this material is used for injection molding as a foamable material, its tensile strength at high temperatures is relatively low due to its physical properties, so the size of the foamed cells may be reduced inside the molded product, especially in the center of the thick part. However, the molten wall could not resist the foaming pressure and broke, causing the bubbles to burst one after another and coalesce, resulting in the formation of a large cavity in that area.

The present invention provides a method for manufacturing injection molded shoes that eliminates the conventional drawbacks as described above. 3 is covered with a jacket 5 or a sock-like lining 5' having an inner sole 4, and the needle-like protrusion 2 is passed through the inner sole 4 so as to make a hole 6, and an outer mold 7 is attached to the last 3. are combined to form a molding cavity 9 including the outsole molding cavity 8, and the needle-shaped protrusion 2 is made to protrude from the bottom surface of the last to at least an intermediate position of the thickness of the outsole molding cavity 8, and foaming injection is carried out into the molding cavity 9. The present invention relates to a method for manufacturing injection molded shoes, which is characterized in that a molding material 10 is injected and press-fitted.

The expandable injection molding material 10 applied in the present invention is
Thermoplastic polymer materials such as thermoplastic resins such as polyvinyl chloride and polyethylene, thermoplastic elastomers such as styrene-butadiene systems, polyurethane systems, and ethylene-vinyl acetate copolymers, and thermoplastic polymers containing these as main components. With molecular formulations.

A formulation can be used in which a foaming agent is contained in the molding material, and the foaming agent is decomposed during injection molding to cause foaming within the molding cavity 9.

As the blowing agent, commonly known blowing agents can be used.

This foamable injection molding material 10 is injected and press-fitted.

The shaping mold is composed of a last 3 and an outer mold 7, and the last 3 and the outer mold 7 are made of a metal material.

The injection molded shoes to be manufactured in the present invention are called short shoes or boots, and short shoes will be manufactured.

In this case, as shown in FIG. 1, the last 3 is generally coated with a cover 5, and the last 3 is combined with a side mold 7' as an outer mold 7 and a bottom mold 7'' to form the main sole. Gap 8 and, if necessary, peripheral tape forming gap 8'
What constitutes a series of.

On the other hand, when manufacturing boots, as shown in FIG. and the bottom mold T'i to form the body molding cavity 8.
'' and outsole molding voids 8 are formed in series, and when these laces 5 and sock-like lining fabrics 5' are attached to the last 3, the inner sole 4 provided integrally with the last 3 is formed in a series. A needle-like protrusion 2 protruding from the bottom surface 1 passes through it, and a hole 6 is made in the middle bottom 4.

The above-mentioned side mold 7' is generally of a type called a split mold, which is divided into two or more parts, whether in the shoe manufacturing site 3 or in the case of boot manufacturing.

If necessary, a split mold can also be used for the bottom mold 7''.

The number of needle-like protrusions 2 that are made to protrude from the bottom surface 1 of the last 3 may be one or more.

The length of the needle-like projection 2 is such that the tip 11 of the needle-like projection 2 is at least in the middle of the thickness of the outsole forming gap 8 at the position on the bottom surface 1 of the last 3 where the needle-like projection 2 is installed. It is preferable to set it as approximately.

It is preferable that the tip 11 of the needle-like protrusion 2 is sharp so that it can easily penetrate the inner sole 4.

The needle-like protrusion 2 has a conical shape, an elliptical conical shape, or a polygonal shape such as a circular, elliptical, triangular, quadrangular, or star-shaped cross section as shown by a to e in FIG. 4, respectively. It may have a polygonal pyramid shape such as a quadrangular pyramid shape, and may have a groove 12 extending in the length direction of the needle-like projection 2 on the side surface of the pyramid shape.

The shape of the groove 12 can be appropriately adopted such as a 7-shape, a U-shape, a U-shape, a trapezoid, etc. in cross section.

By forming grooves 12 in the shape of a 7-shape or the like on each of a plurality of side surfaces of the needle-like protrusion 2 having a polygonal pyramidal shape, it can be made into a polygonal pyramidal shape, such as a star-shaped cross section as shown in FIG. 4e.

As shown in FIG. 2, these needle-like protrusions 2 may be made of the same metal as the last 3 and may be formed so as to protrude seamlessly from the bottom surface 1 when the last 3 is molded.

Alternatively, as shown in Fig. 1, a hole is drilled in the bottom surface 1 of the last 3, and a needle-shaped protrusion 2 formed separately from the same or different metal as the last 3 is inserted into this hole with its base inserted. By doing so, it may be bonded to the bottom surface 1.

According to the present invention, since the needle-like protrusion 2 protrudes from the bottom surface 1 of the last 3 into the outsole molding cavity 8, the foamable injection molding material 10 press-fitted therein is heated to a high temperature and in a fluid state to form the outsole molding cavity 8. When filling the space 8, the foamed gas collides with the protruding needle-like protrusion 2, and the foamed gas, which tends to concentrate particularly in the middle position of the thickness of the gap 8, passes through the collided needle-like protrusion 2 and reaches the bottom surface 1 of the last 3. direction, through the hole 6 of the inner sole 4 through which the needle-like protrusion 2 penetrated; and from the gap between the surface of the last 3 and the lace cover 5 or sock-like lining 5', or from the gap between the lace cover 5 and the sock-like lining 5'; Through the fine gaps in the fibers of the fabric that makes up the sock-like lining fabric 5,
It is thought that it will dissipate into the outside air.

Therefore, in this case, if the needle-like projection 2 is provided with one or more grooves 12 in the length direction toward the tip 11,
The foaming gas is transmitted using the groove 12 as a guide, and is easily moved to the last 3 side of the inner sole part 4, and the excess foaming gas is efficiently dissipated to the outside air.

In the foamable injection molding material 10, there is a tendency for foaming gas to concentrate or coarse foaming to occur in the molded body at the middle position of the molding cavity 9 of the mold. Although it is difficult to dissipate the gas, the protruding needle-like protrusion 2 allows the excess bubble gas at the intermediate position to be easily moved to the last 3 side of the inner sole 4 and dissipated.

For this reason, the foamable injection molding material 10 can be used regardless of whether the material of the midsole 4 is breathable or non-breathable, as long as the sleeve 5 or sock-like lining 5' has a midsole 4. The present invention can be carried out without any modification.

In addition, the needle-like protrusion 2 made of metal or the like and having a large specific heat is positioned on the bottom surface 1 of the last 3 so as to protrude from a part that is particularly thick compared to other parts, such as the heel part. By doing so, the needle-like protrusions 2 speed up the cooling of the thick portion where they are located, so that deformation due to secondary foaming after demolding the molded article can be avoided.

By increasing the number of needle-like protrusions 2 or increasing their thickness, the cooling of the molded product in the area where the needle-like protrusions 2 are located is accelerated, and at the same time, the amount of molding material is reduced. The sole of the shoe is made lighter to make the shoe easier to wear, and more materials are saved to lower the product cost.

When the grooves 12 are formed in the needle-like protrusions 2, the surface area of the side surfaces is set as a dog, so that the foamable injection molding material 10 that comes into contact with the grooves 12 is heated more quickly, and the molded product is cooled more quickly. It becomes convenient.

The installation parts of the last 3 of the needle-like protrusions 2 on the bottom surface 1 may be scattered over the entire bottom surface 1 as shown in FIG. It is also possible to concentrate on the parts that make up the .

The holes 6 in the midsole 4 formed by the needle-like protrusions 2 can be easily hidden by attaching or placing an insole on the surface of the midsole 40, so that they do not look unsightly. Can be configured.

In the present invention, since the needle-shaped protrusion 2 penetrates from the bottom surface 1 of the last 3 to the midsole 4 and protrudes into the sole molding cavity 8, excess foaming gas inside the molded body is removed from the foamable injection molding material 10. When the foaming gas flows, it can be transmitted to the surface and ejected to the last 3 side of the middle bottom part 4, so that there is no secondary foaming after demolding due to this excess foaming gas, which eliminates deformation of the molded product. , because demolding can be accelerated, the molding cycle can be accelerated and mass production can be carried out.
Product cost can be lowered.

Even if the necessary parts of the shoe are thickened, there is no permanent secondary foaming, so the design of the shoe is free, and many designs are possible, giving the shoe a wide variety of appearance and high product value. can do.

Since a non-breathable material can be used as the material for the insole 4, an adhesive can be applied to the surface of the insole 4 that is bonded to the outsole, so that the adhesion between the insole 4 and the outsole can be made stronger. Also,
Since a laminated sheet made by bonding two or more pieces of fabric or sheet material together with an adhesive can be used as the material for the midsole 4, the midsole 4 can be made stronger.
The durability of shoes can be increased.

Even when a material with low tensile strength at high temperatures, such as a foamable thermoplastic nidistomer, is used as the injection molding material 10, it is possible to avoid the concentration of excess foaming gas inside the molded product, so that bubbles due to the foaming pressure of the gas can be avoided. Since the walls of the molded body are not destroyed, a large cavity is not formed inside the molded body.

Therefore, the injection molding material 10 is not subject to any limitations and can be applied to a wide variety of applications.

Furthermore, the needle-like protrusion 2 penetrates the inner sole portion 4 to form the outsole molding cavity 8.
By protruding inward, the amount of foamable injection molding material 10 required for molding is reduced by the volume of the needle-like protrusion 2, and the product cost is reduced by saving material, and the needle-like protrusion 2 remains after molding. This part becomes a void, which reduces the weight of the shoe and makes it easier to wear, and the void created by the needle-like projections also provides cushioning properties as the sole of the shoe.

Since the needle-like protrusion 2 makes a hole 6 in the middle bottom part 4 and is exposed to the bottom molding cavity 8, the foamable injection molding material 10 that comes into contact with it is easily cooled, thereby preventing demolding of the molded product. This makes it possible to speed up the production cycle, enable mass production, and reduce product costs.

[Brief explanation of drawings]

1 and 2 are explanatory views showing examples of embodiments of the present invention, FIG. 3 is a partial perspective view of one example of the last heel portion, and FIG.
Figures a, b, c, d, e each show a cross-sectional view of the needle. 1...Bottom surface, 2...Acicular projection, 3...
...Last, 4...Middle bottom, 5...
・Socket cover, 5′...Sock-like lining fabric, 6...
Hole, 7... Outer mold, 8... Bottom molding void, 9... Molding void, 10... Foamable injection molding material.

Claims (1)

[Scope of Claims] 1. A last having one or more needle-like protrusions protruding from the bottom thereof is covered with a jacket or sock-like lining having an inner sole, and the needle-like protrusions are passed through the inner sole, The last is combined with an outer needle lead to form a molding cavity including a bottom molding cavity, and
A method for manufacturing injection molded shoes, characterized in that the needle-like protrusions are made to protrude from the bottom surface of the last to at least an intermediate position in the thickness of the outsole molding cavity, and a foamable injection molding material is injected and press-fitted into the molding cavity. 2. Claim 1, characterized in that a groove extending in the length direction of the needle-like projection is formed on the side surface of the needle-like projection.
The method of manufacturing shoes described in Section. 3. The method for manufacturing shoes according to claim 1 or 2, wherein the midsole is made of a non-breathable material.