Injection mold

An injection mold includes a sliding member having a partial cavity surface which forms part of a cavity surface, and an adjacent member having a partial cavity surface which forms part of the cavity surface. A sliding surface of the sliding member is guided by a sliding surface of the adjacent member and is linearly movable by a relative sliding distance. A portion from the partial cavity surface to the sliding surface of at least one of the sliding member and adjacent member is continuously coated with a heat insulating coat, and a range over which the sliding surface is coated with the heat insulating coat is so set as to exceed an end of the relative sliding distance, where an edge of the partial cavity surface of the adjacent member contacts with the sliding surface of the sliding member.

FIELD OF THE INVENTION

The present invention relates to an injection mold in which at least a portion of the cavity surface is coated with a heat insulating coat, and which is used in plastic injection molding.

BACKGROUND OF THE INVENTION

As an injection mold having improved cavity surface transfer properties, an injection mold having a heat insulating structure (Japanese Patent Laid-Open No. 53-86754) is conventionally known. The surface transfer properties of this injection mold are improved by interposing a heat insulating material layer between a thin metal layer forming the cavity surface and a backing material, thereby decreasing the cooling rate of an injection-molded product during injection molding.

Unfortunately, the above prior art has the following unsolved problem.

An injection mold uses sliding members, such as an ejector pin, slide core, and inclined core, having partial cavity surfaces which form portions of the cavity surface. Each of these sliding members is slidably guided by the sliding surface of an adjacent member which is adjacent to this sliding member, and protruded into the cavity or retracted into the adjacent member, i.e., linearly moved. This linear motion is repeated for each molding cycle. Consequently, a load such as the frictional force is repetitively exerted on the edge of a heat insulating coat with which the sliding member or adjacent member is coated. This causes easy peeling of the heat insulating coat.

The edge of the heat insulating coat with which the sliding member or adjacent member is coated is formed by masking or machining. Therefore, the adhesion of the edge is lowered by a load generated when the masking material is peeled or when machining is performed. This presumably further promotes .peeling.

SUMMARY OF THE INVENTION

The present invention has been made in consideration of the unsolved problem of the above-mentioned prior art, and has as its object to provide an injection mold having high durability because a heat insulating coat with which at least one of a sliding member and adjacent member is coated has a high peeling resistance.

To achieve the above object, according to a first aspect of the present invention, there is provided an injection mold comprising a sliding member having a partial cavity surface which forms part of a cavity surface, and an adjacent member having a partial cavity surface which forms part of the cavity surface, a sliding surface of the sliding member being guided by a sliding surface of the adjacent member and linearly movable by a relative sliding distance, wherein a portion from the partial cavity surface to the sliding surface of at least one of the sliding member and adjacent member is continuously coated with a heat insulating coat, and a range over which the sliding surface is coated with the heat insulating coat is so set as to exceed the relative sliding distance.

According to a second aspect of the present invention, there is provided an injection mold comprising a sliding member having a partial cavity surface which forms part of a cavity surface, and an adjacent member having a partial cavity surface which forms part of the cavity surface, a sliding surface of the sliding member being guided by a sliding surface of the adjacent member and linearly movable by a relative sliding distance, wherein a portion from the partial cavity surface to the sliding surface of at least one of the sliding member and adjacent member is continuously coated with a heat insulating coat, a range over which the sliding surface is coated with the heat insulating coat is so set as to exceed the relative sliding distance, and an entire region from the heat insulating coat to the sliding surface is continuously coated with a protective coat.

According to a third aspect of the present invention, there is provided an injection mold comprising a sliding member having a partial cavity surface which forms part of a cavity surface, and an adjacent member having a partial cavity surface which forms part of the cavity surface, a sliding surface of the sliding member being guided by a sliding surface of the adjacent member and linearly movable by a relative sliding distance, wherein a portion from the partial cavity surface to the sliding surface of at least one of the sliding member and adjacent member is continuously coated with a heat insulating coat, and an entire region from the heat insulating coat to the sliding surface is continuously coated with a protective coat.

According to a fourth aspect of the present invention, there is provided an injection mold comprising a sliding member having a partial cavity surface which forms part of a cavity surface, and an adjacent member having a partial cavity surface which forms part of the cavity surface, a sliding surface of the sliding member being guided by a sliding surface of the adjacent member and linearly movable by a relative sliding distance, wherein at least a portion of the partial cavity surface of at least one of the sliding member and adjacent member is continuously coated with a heat insulating coat, and an entire region from the heat insulating coat to the sliding surface is continuously coated with a protective coat.

In the present invention having the above arrangements, even when the sliding member is repetitively linearly moved as it is guided by the adjacent member, a load such as the frictional force is not applied on the edge of the heat insulating coat with which at least one of the sliding member and adjacent member is coated. Since this increases the peeling resistance of the heat insulating coat, the durability of the injection mold improves.

Further objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments of the present invention with reference to the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1A and 1Billustrate an injection mold according to the first embodiment, in whichFIG. 1Ais a schematic partial sectional view showing the state in which a sliding member and adjacent member form a cavity surface, andFIG. 1Bis a schematic partial sectional view showing the state in which the sliding member protrudes into the cavity by a relative sliding distance.

As shown inFIGS. 1A and 1B, the injection mold according to this embodiment has an adjacent member1and sliding member2adjacent to each other. A sliding surface2bof the sliding member2is slidably guided by a sliding surface1bof the adjacent member1such that a partial cavity surface2aof the sliding member2protrudes into the cavity by a relative sliding distance e from the state in which the partial cavity surface2ais leveled with that partial cavity surface1aof the adjacent member1, which forms a portion of the cavity surface.

A portion from the partial cavity surface2ato the sliding surface2bof the sliding member2is continuously coated with a heat insulating coat3. The range over which the sliding surface2bis coated with the heat insulating coat3is so set as to exceed the relative sliding distance e.

In this embodiment, in the state in which the sliding member2protrudes into the cavity by the relative sliding distance e, a corner1cbetween the partial cavity surface1aand sliding surface1bof the adjacent member1does not contact an edge3aof the heat insulating coat3on the sliding surface2bof the sliding member2, so no overload is exerted on the edge3a. This improves the peeling resistance of the heat insulating coat3.

FIGS. 2A and 2Billustrate a modification of the injection mold according to the first embodiment, in whichFIG. 2Ais a schematic partial sectional view showing the state in which a sliding member and adjacent member form a cavity surface, andFIG. 2Bis a schematic partial sectional view showing the state in which the sliding member is retracted into the mold body by a relative sliding distance.

As shown inFIGS. 2A and 2B, the injection mold according to this modification has an adjacent member11and sliding member12adjacent to each other. A sliding surface12bof the sliding member12is slidably guided by a sliding surface11bof the adjacent member11such that a partial cavity surface12aof the sliding member12is retracted into the adjacent member by a relative sliding distance e from the state in which the partial cavity surface12ais leveled with that partial cavity surface11aof the adjacent member11, which forms a portion of the cavity surface.

A portion from the partial cavity surface11ato the sliding surface11bof the adjacent member11is continuously coated with a heat insulating coat13. The range over which the sliding surface11bis coated with the heat insulating coat13is so set as to exceed the relative sliding distance e.

In this modification, in the state in which the sliding member12is retracted into the adjacent member by the relative sliding distance e, a corner12cbetween the partial cavity surface12aand sliding surface12bof the sliding member12does not contact an edge13aof the heat insulating coat13of the adjacent member11, so no overload is exerted on the edge13a. This improves the peeling resistance of the heat insulating coat13.

FIGS. 3A and 3Billustrate another modification of the injection mold according to the first embodiment, in whichFIG. 3Ais a schematic partial sectional view showing the state in which a sliding member and adjacent member form a cavity surface, andFIG. 3Bis a schematic partial sectional view showing the state in which the sliding member protrudes into the cavity by a relative sliding distance.

As shown inFIGS. 3A and 3B, the injection mold according to this embodiment has an adjacent member21and sliding member22adjacent to each other. A sliding surface22bof the sliding member22is slidably guided by a sliding surface21bof the adjacent member21such that a partial cavity surface22aof the sliding member22protrudes into the cavity by a relative sliding distance e from the state in which the partial cavity surface22ais leveled with that partial cavity surface21aof the adjacent member21, which forms a portion of the cavity surface.

A portion from the partial cavity surface22ato the sliding surface22bof the sliding member22is continuously coated with a heat insulating coat23. The range over which the sliding surface22bis coated with the heat insulating coat23is so set as to exceed the relative sliding distance e. Also, a portion from the partial cavity surface21ato the sliding surface21bof the adjacent member21is continuously coated with a heat insulating coat24. The range over which the sliding surface21bis coated with the heat insulating coat24is so set as to exceed the relative sliding distance e.

In this modification, in the state in which the sliding member22protrudes into the cavity by the relative sliding distance e, a corner21cbetween the partial cavity surface21aand sliding surface21bof the adjacent member21does not contact an edge23aof the heat insulating coat23on the sliding surface22bof the sliding member22, so no overload is exerted on the edge23a. This improves the peeling resistance of the heat insulating coat23.

Note that the injection mold of this modification can also be so constructed that the sliding member22is retracted into the adjacent member as shown inFIGS. 2A and 2B. Even in this injection mold, in the state in which the sliding member22is retracted into the adjacent member by the relative sliding distance e, a corner22cbetween the partial cavity surface22aand sliding surface22bof the sliding member22does not contact an edge24aof the heat insulating coat24of the adjacent member21, so no overload is exerted on the edge24a.

Injection molds of other embodiments will be explained below by taking a sliding member as an example.

FIG. 4is a schematic partial sectional view of a sliding member of an injection mold according to the second embodiment. In the injection mold according to this embodiment, a portion from a partial cavity surface32ato a sliding surface32bof a sliding member32is continuously coated with a heat insulating coat33. The range over which the sliding surface32bis coated with the heat insulating coat33is so set as to exceed a relative sliding distance e. In addition, an entire region from the partial cavity surface32ato the sliding surface32bis continuously coated with a protective coat34.

In this embodiment, a load such as the frictional force is not directly applied on the heat insulating coat33. This makes the peeling resistance and durability higher than those of the injection mold according to the first embodiment.

FIG. 5is a schematic partial sectional view of a sliding member of an injection mold according to the third embodiment. In the injection mold according to this embodiment, a portion from a partial cavity surface42ato a sliding surface42bof a sliding member42is continuously coated with a heat insulating coat43. In addition, an entire region from the partial cavity surface42ato the sliding surface42bis continuously coated with a protective coat44.

FIG. 6is a schematic partial sectional view of a sliding member of an injection mold according to the fourth embodiment. In the injection mold according to this embodiment, a partial cavity surface52aof a sliding member52is continuously coated with a heat insulating coat53. In addition, an entire region from the partial cavity surface52ato a sliding surface52bis continuously coated with a protective coat54.

FIG. 7is a schematic partial sectional view of a sliding member of an injection mold according to the fifth embodiment. In the injection mold according to this embodiment, a partial cavity surface62aexcept for a portion h near a sliding surface62bof a sliding member62is continuously coated with a heat insulating coat63. In addition, an entire region from the partial cavity surface62ato the sliding surface62bis continuously coated with a protective coat64.

FIG. 8is a schematic partial sectional view of a sliding member of an injection mold according to the sixth embodiment. In the injection mold according to this embodiment, a portion from a partial cavity surface72ato a sliding surface72bof a sliding member72is continuously coated with a heat insulating coat73. The range over which the sliding surface72bis coated with the heat insulating coat73is so set as to exceed a relative sliding distance e (FIG. 1B). In addition, a jagged portion75is formed on that surface of the heat insulating coat, which opposes the sliding surface72b. The sliding member72is strongly connected via the jagged portion75.

FIG. 9is a schematic partial sectional view of a sliding member of an injection mold according to the seventh embodiment. In the injection mold according to this embodiment, a sliding member82is continuously coated with a heat insulating coat83similar to that shown inFIG. 8. In addition, an entire region from a partial cavity surface82ato a sliding surface82bis continuously coated with a protective coat84.

FIG. 10is a schematic partial sectional view of a sliding member of an injection mold according to the eighth embodiment. In the injection mold according to this embodiment, a portion from a partial cavity surface92ato a sliding surface92bof a sliding member92is continuously coated with a heat insulating coat93. A jagged portion95is formed on that surface of the heat insulating coat93, which opposes the sliding surface92b. The heat insulating coat93is strongly connected to the sliding member92via the jagged portion95. In addition, an entire region from the partial cavity surface92ato the sliding surface92bis continuously coated with a protective coat94.

FIG. 11is a schematic partial sectional view of a sliding member of an injection mold according to the ninth embodiment. In the injection mold according to this embodiment, a partial cavity surface102aexcept for a portion h near a sliding surface102bof a sliding member102is continuously coated with a heat insulating coat103. A jagged portion103ais formed on that surface of the heat insulating coat103, which opposes the sliding surface102b. In addition, an entire region from the partial cavity surface102ato the sliding surface102bis continuously coated with a protective coat104.

The above second to ninth embodiments are explained by taking the sliding member as an example. The adjacent member or the sliding member and adjacent member are similar to those shown inFIGS. 2A and 2BandFIGS. 3A and 3Bas modifications of the first embodiment, so a detailed description thereof will be omitted.

In the present invention, a heat-resistant polymer material is preferably used as the heat insulating coat.

Also, the protective coat is preferably a single-layered coat or multilayered coat made of, e.g., a metal such as Ni, Ti, Cr, Zr, or Si, ceramics such as an oxide, carbide, or nitride of any of these metals, or diamond.

Experiments were conducted to confirm the effects of the injection molds according to the present invention. The results of these experiments will be explained below.

EXPERIMENTAL EXAMPLE 1

An injection mold having an ejector pin as a sliding member was used in injection molding an injection molding product by changing the combination of the arrangement of the ejector pin and the arrangement of an adjacent member, and the number of times of injection molding before a heat insulating coat peeled was checked. The results are shown inFIGS. 14 and 15.

Note that as the arrangement of the sliding member and the arrangement of the adjacent member in Examples 1 to 35 shown inFIG. 14, the arrangements of the sliding members shown inFIGS. 1,4,5,6,7, and10were used.

Note also that in each of Examples 1 to 35, a 0.1 mm thick polyimide vacuum deposited polymerized coat (manufactured by VACUUM METALLURGICAL CO., LTD.) was used as the heat insulating coat, and a 0.001 mm thick CrN coat was used as the protective coat.

FIG. 12is a schematic partial sectional view of an injection mold used in Comparative Example 1. The injection mold of this comparative example has an adjacent member201and sliding member202adjacent to each other. A sliding surface202bof the sliding member202is slidably guided by a sliding surface201bof the adjacent member201such that a cavity surface202aof the sliding member202protrudes into the cavity by a relative sliding distance from the state in which the cavity surface202ais leveled with a cavity surface201aof the adjacent member201.

A portion from the cavity surface202ato the sliding surface202bof the sliding member202is continuously coated with a heat insulating coat203. The range over which the sliding surface202bis coated with the heat insulating coat203is so set as not to exceed the relative sliding distance. In addition, the heat insulating coat203extending from the cavity surface202ato the sliding surface202bis coated with a protective coat204.

FIG. 13is a schematic partial sectional view of an injection mold used in Comparative Example 2. The injection mold of this comparative example has an adjacent member301and sliding member302adjacent to each other. A sliding surface302bof the sliding member302is slidably guided by a sliding surface301bof the adjacent member301such that a cavity surface302aof the sliding member302protrudes into the cavity by a relative sliding distance from the state in which the cavity surface302ais leveled with a cavity surface301aof the adjacent member301.

The cavity surface302aof the sliding member302is coated with a heat insulating member303. The heat insulating member303is also coated with a protective coat304.

In each of Comparative Examples 1 and 2, the number of times of injection molding before the heat insulating coat peeled was checked following the same procedure as in Examples 1 to 35. The results are shown inFIG. 15.

As shown inFIGS. 14 and 15, in each of Examples 1 to 35, 10,000 times or more of injection molding were necessary before the heat insulating coat peeled, indicating high durability. In contrast, the heat insulating coats peeled when the numbers of times of injection molding were13and122in Comparative Examples 1 and 2, respectively.

EXPERIMENTAL EXAMPLE 2

The combination of the sliding member (FIG. 8) and the adjacent member (FIG. 1) in Example 11 described above was used to check the number of times of injection molding before the heat insulating coat peeled by changing the material of the protective coat. The results are shown inFIG. 16. Note that electroless plating, physical vapor deposition, and chemical vapor deposition were used as coat formation methods, and thickness of the protective coat was set to 1 μm. As shown inFIG. 16, in each of Examples 37 to 44, 10,000 times or more of injection molding were necessary before the heat insulating coat peeled, indicating high durability.

In each of the above embodiments as described above, the peeling resistance of the heat insulating coat is high, and this improves the durability. Therefore, high-quality injection molded products having excellent outer appearance can be stably molded.