Mold, method for manufacturing gasket, and gasket

Abstract

To manufacture gaskets with reduced warping caused by a curvature of a mold.SOLUTION: A mold for forming an endless gasket includes a first forming section and a second forming section. The first forming section includes: a first spiral section in which a first forming groove and a second forming groove are formed in a spiral pattern; and a first inverting section inside the first spiral section. The first inverting section includes: a first arc section which follows the first spiral section; a first curved section which in curved in an arc shape from an end of the first arc section; a second curved section which is curved in the opposite direction of the first curved section from an inner end of the second forming groove; and a first straight section which connects the first curved section and the second curved section. The second forming section includes: a second spiral section in which the third forming groove and the fourth forming groove are formed in a spiral shape; and a second inverting section inside the second spiral section. The second inverting section includes: a second arc section which follows the second spiral section; a third curved section which is curved in an arc shape from an end of the second arc section; a fourth curved section which is curved in the opposite direction of the third curved section from an inner end of the fourth forming groove; and a straight second straight section which connects the third curved section and the fourth curved section.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the manufacture of gaskets. [Background technology]

[0002] To mold a gasket with a sufficiently long circumferential length into the planar shape of the product (e.g., annular) using a molding die, a very large molding die is required. Therefore, for example, Patent Document 1 discloses a technique for manufacturing a gasket using a molding die in which two spiral molding portions are formed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-301874 Summary of the Invention [Problem to be solved by the invention]

[0004] In the configuration of Patent Document 1, the inverted portions located inside each spiral-shaped molded portion are S-shaped, with arc-shaped portions curved in opposite directions. Therefore, there is a problem that strong distortions remain in the gasket after molding in the mold at the locations corresponding to the inverted portions. In consideration of the above circumstances, one aspect of the present disclosure aims to manufacture a gasket with reduced distortions caused by the curved portions of the mold. [Means for solving the problem]

[0005] In order to solve the above problems, a molding die according to one aspect of the present disclosure is a molding die for molding an endless gasket, and has a molding space including a first molding portion and a second molding portion, the first molding portion including a first spiral portion in which a first molding groove and a second molding groove adjacent to each other are spirally formed, and a first inverted portion connecting an inner end of the first molding groove to an inner end of the second molding groove inside the first spiral portion, the first inverted portion including a first arc portion extending from the inner end of the first molding groove along an inner circumference of the first spiral portion, a first curved portion curved from the end of the first arc portion in an arc shape with a smaller diameter than the first arc portion, and a second curved portion curved from the inner end of the second molding groove in an arc shape with a smaller diameter than the first arc portion to the opposite side from the first curved portion. a first straight portion connecting the first curved portion and the second curved portion, the second spiral portion including a third spiral portion in which adjacent third and fourth molding grooves are spirally formed, and a second inverted portion connecting inner ends of the third and fourth molding grooves inside the second spiral portion, the second inverted portion including a second arc portion extending from the inner end of the third molding groove along the inner circumference of the second spiral portion, a third curved portion curving from the end of the second arc portion in an arc shape with a smaller diameter than the second arc portion, a fourth curved portion curving from the inner end of the fourth molding groove in an arc shape with a smaller diameter than the second arc portion toward the opposite side from the third curved portion, and a second straight portion connecting the third and fourth curved portions. A gasket manufacturing method according to one aspect of the present disclosure produces an endless gasket using the molding die according to any one of the above aspects.

[0006] A gasket according to one embodiment of the present disclosure is an endless gasket that includes a first portion and a second portion located at each point that divides the circumference of the gasket into two equal parts, wherein the first portion includes a first curved portion that curves convexly toward the outside of the gasket, a second curved portion that curves convexly toward the inside of the gasket, and a first straight portion that connects the first curved portion and the second curved portion, and the second portion includes a third curved portion that curves convexly toward the outside of the gasket, a fourth curved portion that curves convexly toward the inside of the gasket, and a second straight portion that connects the third curved portion and the fourth curved portion. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is a plan view of a molding die according to the first embodiment. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] FIG. 2 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 10 is a plan view of a molding die in a comparative example. [Figure 5] FIG. [Figure 6] FIG. 10 is a plan view of a molding die according to a second embodiment. [Figure 7] FIG. 10 is a plan view of a molding die according to a third embodiment. [Figure 8] FIG. 10 is a plan view of a forming die according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0008] The embodiments for carrying out the present disclosure will be described with reference to the drawings. Note that the dimensions and scale of each element in each drawing may differ from those of the actual product. Furthermore, the embodiment described below is an exemplary embodiment that may be envisioned when carrying out the present disclosure. Therefore, the scope of the present disclosure is not limited to the embodiment exemplified below.

[0009] A: First embodiment A-1: Molding mold 100 1 is a plan view of a molding die 100 according to a first embodiment of the present disclosure. The molding die 100 is a mold for forming an endless gasket 50 (see FIG. 5) by injection molding. The molding die 100 of the first embodiment is used to manufacture a large annular gasket 50 having a diameter of, for example, 500 mm or more (or even 1000 mm or more).

[0010] FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1. As illustrated in FIGS. 2 and 3, molding die 100 is composed of a first split die 41 and a second split die 42. A first groove 411 is formed on the surface of first split die 41 that faces second split die 42. First groove 411 is a groove with a semicircular cross-section. Furthermore, a second groove 421 is formed on the surface of second split die 42 that faces first split die 41. Second groove 421 is a groove with a semicircular cross-section.

[0011] The first groove portion 411 and the second groove portion 421 are formed to have the same shape in a plan view and overlap each other. The inner wall surfaces of the first groove portion 411 and the second groove portion 421 define a space for molding the gasket 50 (hereinafter referred to as the "molding space S"). The molding space S is a space into which the liquid elastic material that will be used to form the gasket 50 is poured. In other words, the molding space S is an endless, continuous, curved internal space inside the molding die 100. The cross-sectional shape of the molding space S is circular. Note that, for convenience, the illustration of a flow path for supplying the elastic material to the molding space S is omitted in FIG. 1.

[0012] As illustrated in FIG. 1, the molding space S of the molding die 100 includes a first molding portion 10, a second molding portion 20, and a connecting portion 30. The first molding portion 10 and the second molding portion 20 are portions whose planar shapes are roughly circular. The first molding portion 10 and the second molding portion 20 are formed to be spaced apart from each other. FIG. 1 shows the center C1 of the first molding portion 10 and the center C2 of the second molding portion 20. The connecting portion 30 is a linear portion that connects the first molding portion 10 and the second molding portion 20 to each other. That is, one end of the connecting portion 30 is connected to the first molding portion 10, and the other end of the connecting portion 30 is connected to the second molding portion 20.

[0013] The first forming section 10 includes a first spiral section 11 and a first inverted section 12. The first spiral section 11 is a section in which a first forming groove 111 and a second forming groove 112 adjacent to each other are formed in a spiral shape. Specifically, the first spiral section 11 is a spiral section that rotates while approaching the center C1 of the first forming section 10. While FIG. 1 illustrates an example in which the first spiral section 11 is formed by approximately one spiral turn, the number of turns of the first spiral section 11 is arbitrary. For example, the first spiral section 11 may be formed by two or more spiral turns.

[0014] The first molding groove 111 and the second molding groove 112 are spaces formed in a spiral (arc) shape. The second molding groove 112 is located inside the first molding groove 111. The first molding groove 111 includes an outer end X1 and an inner end Y1. The outer end X1 is the end of the first molding groove 111 located on the outside of the spiral. The inner end Y1 is the end of the first molding groove 111 located on the inside of the spiral. Similarly, the second molding groove 112 includes an outer end X2 and an inner end Y2. The outer end X2 is the end of the second molding groove 112 located on the outside of the spiral. The inner end Y2 is the end of the second molding groove 112 located on the inside of the spiral.

[0015] The first inverted portion 12 is a portion that connects the inner end Y1 of the first forming groove 111 and the inner end Y2 of the second forming groove 112 inside the first spiral portion 11. In other words, the first inverted portion 12 is surrounded by the first spiral portion 11. As illustrated in FIG. 1 , the first inverted portion 12 includes a first arc portion 120, a first curved portion 121, a second curved portion 122, and a first straight portion 123. The first arc portion 120, the first curved portion 121, the second curved portion 122, and the first straight portion 123 are connected to each other to form the curved first inverted portion 12.

[0016] The first arc portion 120 is an arc-shaped portion that extends from the inner end Y1 of the first molding groove 111 along the inner circumference of the first spiral portion 11. That is, the first arc portion 120 extends in an arc shape along the second molding groove 112 inside the second molding groove 112. Specifically, the first arc portion 120 is formed in a semicircular shape centered on the center C1 of the first molding portion 10. The end Za in FIG. 1 is the end of the first arc portion 120 on the opposite side to the inner end Y1 of the first molding groove 111.

[0017] The first curved portion 121 is a portion that curves in an arc shape from the end Za of the first arc portion 120. Specifically, the first curved portion 121 is formed in a semicircular shape with a smaller diameter than the first arc portion 120. For example, the diameter of the first curved portion 121 is approximately half the diameter of the first arc portion 120.

[0018] The second curved portion 122 is a portion that curves in an arc shape from the inner end Y2 of the second molding groove 112. Specifically, the second curved portion 122 is formed in a semicircular shape with a smaller diameter than the first arc portion 120. For example, the diameter of the second curved portion 122 is approximately half the diameter of the first arc portion 120.

[0019] The first curved portion 121 and the second curved portion 122 are curved in opposite directions. Specifically, the first curved portion 121 is an arc-shaped portion that is convex toward the right in Fig. 1, and the second curved portion 122 is an arc-shaped portion that is convex toward the left in Fig. 1. The radius of curvature of the first curved portion 121 and the radius of curvature of the second curved portion 122 are equal to each other.

[0020] The first straight portion 123 is a straight portion that connects the first curved portion 121 and the second curved portion 122. Specifically, the first straight portion 123 connects an end of the first curved portion 121 that is close to the center C1 and an end of the second curved portion 122 that is close to the center C1. That is, the first curved portion 121 and the second curved portion 122 are located on opposite sides of the first straight portion 123. The planar shape of the approximately S-shaped portion of the first inverted portion 12 that is formed by the first curved portion 121, the second curved portion 122, and the first straight portion 123 is point-symmetric with respect to the center C1 of the first shaped portion 10.

[0021] The length of first straight portion 123 is, for example, 1 / 5 or more of the radius of curvature (or the radius) of first curved portion 121 or second curved portion 122. Specifically, the radius of first curved portion 121 and second curved portion 122 is 50 mm or less, and the length of first straight portion 123 is 10 mm or more. However, the length of first straight portion 123 is not limited to the above example.

[0022] The second forming section 20 includes a second spiral section 21 and a second inverted section 22. The second spiral section 21 is a section in which the mutually adjacent third forming groove 211 and fourth forming groove 212 are formed in a spiral shape. Specifically, the second spiral section 21 is a spiral section that turns while approaching the center C2 of the second forming section 20. While FIG. 1 illustrates an example in which the second spiral section 21 is formed by approximately one spiral turn, the number of turns of the second spiral section 21 is arbitrary. For example, the second spiral section 21 may be formed by two or more spiral turns.

[0023] The third molding groove 211 and the fourth molding groove 212 are spaces formed in a spiral (arc) shape. The fourth molding groove 212 is located inside the third molding groove 211. The third molding groove 211 includes an outer end X3 and an inner end Y3. The outer end X3 is the end of the third molding groove 211 located on the outside of the spiral. The inner end Y3 is the end of the third molding groove 211 located on the inside of the spiral. Similarly, the fourth molding groove 212 includes an outer end X4 and an inner end Y4. The outer end X4 is the end of the fourth molding groove 212 located on the outside of the spiral. The inner end Y4 is the end of the fourth molding groove 212 located on the inside of the spiral.

[0024] The second inverted portion 22 is a portion that connects the inner end Y3 of the third forming groove 211 and the inner end Y4 of the fourth forming groove 212 inside the second spiral portion 21. In other words, the second inverted portion 22 is surrounded by the second spiral portion 21. As illustrated in FIG. 1 , the second inverted portion 22 includes a second arc portion 220, a third curved portion 221, a fourth curved portion 222, and a second straight portion 223. The second arc portion 220, the third curved portion 221, the fourth curved portion 222, and the second straight portion 223 are connected to each other to form the curved second inverted portion 22.

[0025] The second arc portion 220 is an arc-shaped portion that extends from the inner end Y3 of the third molding groove 211 along the inner circumference of the second spiral portion 21. That is, the second arc portion 220 extends in an arc shape along the fourth molding groove 212 inside the fourth molding groove 212. Specifically, the second arc portion 220 is formed in a semicircular shape centered on the center C2 of the second molding portion 20. The end Zb in FIG. 1 is the end of the second arc portion 220 on the opposite side to the inner end Y3 of the third molding groove 211.

[0026] The third curved portion 221 is a portion that curves in an arc shape from the end Zb of the second arc portion 220. Specifically, the third curved portion 221 is formed in a semicircular shape with a smaller diameter than the second arc portion 220. For example, the diameter of the third curved portion 221 is approximately half the diameter of the second arc portion 220.

[0027] The fourth curved portion 222 is a portion that curves in an arc shape from the inner end Y4 of the fourth molding groove 212. Specifically, the fourth curved portion 222 is formed in a semicircular shape with a smaller diameter than the second arc portion 220. For example, the diameter of the fourth curved portion 222 is approximately half the diameter of the second arc portion 220.

[0028] The third curved portion 221 and the fourth curved portion 222 are curved in opposite directions. Specifically, the third curved portion 221 is an arc-shaped portion that is convex toward the left in Fig. 1, and the fourth curved portion 222 is an arc-shaped portion that is convex toward the right in Fig. 1. The radius of curvature of the third curved portion 221 and the radius of curvature of the fourth curved portion 222 are equal to each other.

[0029] The second straight portion 223 is a straight portion that connects the third curved portion 221 and the fourth curved portion 222. Specifically, the end of the third curved portion 221 that is close to the center C2 and the end of the fourth curved portion 222 that is close to the center C2 are connected to each other by the second straight portion 223. In other words, the third curved portion 221 and the fourth curved portion 222 are located on opposite sides of the second straight portion 223. The approximately S-shaped portion of the second inverted portion 22 that is formed by the third curved portion 221, the fourth curved portion 222, and the second straight portion 223 has a shape that is point-symmetric with respect to the center C2 of the second shaped portion 20.

[0030] The length of the second straight portion 223 is, for example, 1 / 5 or more of the radius of curvature (or the radius) of the third curved portion 221 or the fourth curved portion 222. Specifically, the radius of the third curved portion 221 and the fourth curved portion 222 is 50 mm or less, and the length of the second straight portion 223 is 10 mm or more. However, the length of the second straight portion 223 is not limited to the above example.

[0031] The shapes of the first curved portion 121, the second curved portion 122, and the first straight portion 123 in the first shaping portion 10 are substantially the same as the shapes of the third curved portion 221, the fourth curved portion 222, and the second straight portion 223 in the second shaping portion 20. Therefore, the length of the first straight portion 123 and the length of the second straight portion 223 are equal to each other.

[0032] As described above, the connecting portion 30 is a linear portion that interconnects the first molding portion 10 and the second molding portion 20. The connecting portion 30 is composed of the fifth molding groove 31 and the sixth molding groove 32. The fifth molding groove 31 is a linear portion that interconnects the outer end portion X2 of the second molding groove 112 in the first molding portion 10 and the outer end portion X3 of the third molding groove 211 in the second molding portion 20. The sixth molding groove 32 is a linear portion that interconnects the outer end portion X1 of the first molding groove 111 in the first molding portion 10 and the outer end portion X4 of the fourth molding groove 212 in the second molding portion 20. The connecting portion 30 in the first embodiment extends in a direction parallel to the first linear portion 123 and the second linear portion 223.

[0033] The length of the connecting portion 30 is greater than the radius of the first molded portion 10 and the second molded portion 20. However, a configuration in which the length of the connecting portion 30 is less than the radius of the first molded portion 10 or the second molded portion 20, or a configuration in which the length of the connecting portion 30 and the radius of the first molded portion 10 or the second molded portion 20 are equal to each other is also conceivable.

[0034] 1 shows a straight line L that passes through the center C1 of the first molding section 10 and the center C2 of the second molding section 20. The connecting section 30 in the first embodiment intersects with the straight line L in a plan view. Specifically, the straight line L intersects with a central point Z0 of the connecting section 30 in the longitudinal direction (hereinafter referred to as the "central section"). As can be understood from the above explanation, the planar shape of the molding space S formed by the first molding section 10, the second molding section 20, and the connecting section 30 is a point-symmetric shape with the central section Z0 of the connecting section 30 as the center.

[0035] Fig. 4 is a plan view of a molding die 100 according to a comparative example. As illustrated in Fig. 4, the first straight portion 123 and the second straight portion 223 of the first embodiment are omitted in the comparative example. That is, the first curved portion 121 and the second curved portion 122 are directly connected, and the third curved portion 221 and the fourth curved portion 222 are directly connected. Furthermore, in the comparative example, the connecting portion 30 is omitted. That is, the first molding portion 10 and the second molding portion 20 are directly connected.

[0036] In the comparative example, a crease caused by a portion of the molding space S where the first curved portion 121 and the second curved portion 122 are connected (a portion near the center C1) or a portion of the molding space S where the third curved portion 221 and the fourth curved portion 222 are connected (a portion near the center C2) may remain in the gasket 50. In contrast to the comparative example, in the first embodiment, the first straight portion 123 is located between the first curved portion 121 and the second curved portion 122, and the second straight portion 223 is located between the third curved portion 221 and the fourth curved portion 222. Therefore, according to the first embodiment, it is possible to manufacture a gasket 50 in which a crease caused by a portion of the molding space S between the first curved portion 121 and the second curved portion 122 or a portion between the third curved portion 221 and the fourth curved portion 222 is reduced compared to the comparative example.

[0037] In the first embodiment, in particular, the length of the first straight portion 123 is ⅕ or more of the radius of curvature of the first curved portion 121 or the second curved portion 122, and the length of the second straight portion 223 is ⅕ or more of the radius of curvature of the third curved portion 221 or the fourth curved portion 222. That is, the lengths of the first straight portion 123 and the second straight portion 223 are sufficiently ensured. For example, the lengths of the first straight portion 123 and the second straight portion 223 are 10 mm or more. Therefore, the aforementioned effect of being able to manufacture a gasket 50 with reduced distortion due to the curved portions (121, 122, 221, 222) of the forming mold 100 is particularly effective.

[0038] A-2: Manufacturing method of gasket 50 The endless gasket 50 is manufactured by injection molding using the above-described molding die 100. The manufacturing procedure for the gasket 50 using the molding die 100 is as follows. (1) The elastic material is heated and melted, and injected into the molding space S of the mold 100. (2) The elastic material in the molding space S is hardened (vulcanized). (3) The hardened elastic material is released from the mold 100 as the gasket 50 . (4) After being released from the mold, the gasket 50 is unfolded into an annular shape.

[0039] According to the above manufacturing method, the gasket 50 molded using the molding die 100 is developed into the planar shape (e.g., annular) of the product state after being released from the molding die 100. Therefore, compared to a form in which the gasket 50 is molded in the planar shape of the product state, it is possible to make the molding die 100 required to mold a large gasket 50 smaller.

[0040] Examples of materials for the gasket 50 include various elastic materials such as ethylene propylene diene rubber (EPDM), vinyl methyl silicone rubber (VMQ), acrylic rubber (ACM), butyl rubber (IIR), nitrile rubber (NBR), fluororubber (FKM), chloroprene rubber (CR), silicone rubber (SR), urethane rubber (U), polyurethane rubber (PUR), and hydrogenated nitrile rubber (HNBR).

[0041] A-3: Gasket 50 5 is a plan view of a gasket 50 according to the first embodiment. The gasket 50 is an endless molded product formed in a ring shape. The gasket 50 is used as a sealing device for sealing gaps between multiple components. The cross-sectional shape of the gasket 50 according to the first embodiment is a circle that corresponds to the cross-sectional shape of the molding space S.

[0042] Fig. 5 shows the gasket 50 immediately after it has been released from the molding die 100. Therefore, the gasket 50 in Fig. 5 still retains a crease corresponding to the shape of the molding space S. Therefore, by correcting the crease in the gasket 50 after it has been released from the mold, the gasket 50 is formed into an annular shape.

[0043] 5, the gasket 50 after demolding includes a first portion 51 and a second portion 52. The first portion 51 and the second portion 52 are located at positions that divide the circumference of the gasket 50 into two equal parts. In other words, when the gasket 50 is divided into the first portion 51 and the second portion 52, the total lengths of the two sections are equal.

[0044] The first portion 51 includes a first curved portion 511, a second curved portion 512, and a first straight portion 513. The first curved portion 511 and the second curved portion 512 are portions curved in an arc shape. The first curved portion 511 is a portion corresponding to the first curved portion 121 of the forming die 100. The second curved portion 512 is a portion corresponding to the second curved portion 122 of the forming die 100. Therefore, the first curved portion 511 and the second curved portion 512 are curved in opposite directions. Specifically, the first curved portion 511 is curved convexly toward the outside of the gasket 50. On the other hand, the second curved portion 512 is curved convexly toward the inside of the gasket 50.

[0045] First straight portion 513 corresponds to first straight portion 123 of forming die 100. Specifically, first straight portion 513 is a linear portion that interconnects first curved portion 511 and second curved portion 512. In other words, one end of first straight portion 513 is connected to first curved portion 511, and the other end of first straight portion 513 is connected to second curved portion 512.

[0046] As described above, the length of the first straight portion 123 in the forming die 100 is ⅕ or more of the radius of curvature of the first curved portion 121 or the second curved portion 122. Therefore, the length of the first straight portion 513 in the gasket 50 is ⅕ or more of the radius of curvature of the first curved portion 511 or the second curved portion 512. Specifically, the radii of the first curved portion 511 and the second curved portion 512 are 50 mm or less, and the length of the first straight portion 513 is 10 mm or more. However, the length of the first straight portion 513 is not limited to the above example.

[0047] The second portion 52 includes a third curved portion 521, a fourth curved portion 522, and a second straight portion 523. The third curved portion 521 and the fourth curved portion 522 are portions curved in an arc shape. The third curved portion 521 is a portion corresponding to the third curved portion 221 of the forming die 100. The fourth curved portion 522 is a portion corresponding to the fourth curved portion 222 of the forming die 100. Therefore, the third curved portion 521 and the fourth curved portion 522 are curved in opposite directions. Specifically, the third curved portion 521 is curved convexly toward the inside of the gasket 50. On the other hand, the fourth curved portion 522 is curved convexly toward the outside of the gasket 50.

[0048] The second straight portion 523 corresponds to the second straight portion 223 of the forming die 100. Specifically, the second straight portion 523 is a linear portion that interconnects the third curved portion 521 and the fourth curved portion 522. That is, one end of the second straight portion 523 is connected to the third curved portion 521, and the other end of the second straight portion 523 is connected to the fourth curved portion 522.

[0049] As described above, the length of the second straight portion 223 in the forming die 100 is 1 / 5 or more of the radius of curvature of the third curved portion 221 or the fourth curved portion 222. Therefore, the length of the second straight portion 523 in the gasket 50 is 1 / 5 or more of the radius of curvature of the third curved portion 521 or the fourth curved portion 522. Specifically, the radii of the third curved portion 521 and the fourth curved portion 522 are 50 mm or less, and the length of the second straight portion 523 is 10 mm or more. However, the length of the second straight portion 523 is not limited to the above example.

[0050] As described above, in gasket 50 of the first embodiment, first curved portion 511 and second curved portion 512 are connected by first straight portion 513, and third curved portion 521 and fourth curved portion 522 are connected by second straight portion 523. Therefore, compared to a gasket in which first curved portion 511 and second curved portion 512 are directly connected and third curved portion 521 and fourth curved portion 522 are directly connected (for example, a gasket manufactured according to the comparative example of FIG. 4), it is possible to reduce any remaining distortion in gasket 50 after molding due to the curved portions (121, 122, 221, 222) of molding die 100.

[0051] In the first embodiment in particular, the length of first straight portion 513 is ⅕ or more of the radius of curvature of first curved portion 511 or second curved portion 512, and the length of second straight portion 523 is ⅕ or more of the radius of curvature of third curved portion 521 or fourth curved portion 522. That is, the lengths of first straight portion 513 and second straight portion 523 are sufficiently ensured. For example, the lengths of first straight portion 513 and second straight portion 523 are 10 mm or more. Therefore, the aforementioned effect of being able to reduce any kinks caused by the curved portions (121, 122, 221, 222) of forming mold 100 is particularly effective.

[0052] B: Second embodiment A second embodiment will be described. In the following embodiments, elements that have the same functions as those in the first embodiment will be denoted by the same reference numerals as those in the first embodiment, and detailed descriptions thereof will be omitted as appropriate.

[0053] 6 is a plan view of a molding die 100 in the second embodiment. As in the first embodiment, a molding space S including a first molding portion 10, a second molding portion 20, and a connecting portion 30 is formed in the molding die 100 of the second embodiment. The configurations of the first molding portion 10 and the second molding portion 20 are the same as in the first embodiment. A gasket 50 similar to that shown in FIG. 5 is manufactured by injection molding using the molding die 100 of the second embodiment.

[0054] In the first embodiment, a configuration was exemplified in which the connecting portion 30 intersects with the straight line L passing through the center C1 of the first molding portion 10 and the center C2 of the second molding portion 20. In the second embodiment, as exemplified in Fig. 6, the connecting portion 30 extends in a direction parallel to the straight line L passing through the center C1 of the first molding portion 10 and the center C2 of the second molding portion 20. That is, the molding space S in the first embodiment has a point-symmetric planar shape with respect to the central portion Z0 of the connecting portion 30 as the center, whereas the molding space S in the second embodiment has an axisymmetric planar shape with respect to a line perpendicular to the straight line L.

[0055] Specifically, the fifth molding groove 31 of the connecting portion 30 interconnects the outer end X2 of the second molding groove 112 in the first molding portion 10 and the outer end X4 of the fourth molding groove 212 in the second molding portion 20. In addition, the sixth molding groove 32 of the connecting portion 30 interconnects the outer end X1 of the first molding groove 111 in the first molding portion 10 and the outer end X3 of the third molding groove 211 in the second molding portion 20.

[0056] The second embodiment also achieves the same effects as the first embodiment. In the first embodiment, the connecting portion 30 intersects the straight line L, so it is easier to ensure the overall length of the molding space S compared to the second embodiment in which the connecting portion 30 is parallel to the straight line L. Therefore, the first embodiment has the advantage of making it easier to manufacture a gasket 50 with a long circumferential length.

[0057] C: Third embodiment 7 is a plan view of a molding die 100 in the third embodiment. A molding space S including a first molding portion 10 and a second molding portion 20 is formed in the molding die 100 of the third embodiment. The configurations of the first molding portion 10 and the second molding portion 20 are the same as those in the first embodiment. A gasket 50 similar to that shown in FIG. 5 is manufactured by injection molding using the molding die 100 of the second embodiment.

[0058] 7, the third embodiment is a form in which the connecting portion 30 illustrated in the first embodiment is omitted. That is, in the third embodiment, the first molding portion 10 and the second molding portion 20 are directly connected. Specifically, the outer end portion X1 of the first molding groove 111 in the first molding portion 10 and the outer end portion X4 of the fourth molding groove 212 in the second molding portion 20 are connected to each other, and the outer end portion X2 of the second molding groove 112 in the first molding portion 10 and the outer end portion X3 of the third molding groove 211 in the second molding portion 20 are connected to each other.

[0059] The third embodiment also achieves the same effects as the first embodiment. Note that in the first and second embodiments, the first molded portion 10 and the second molded portion 20 are connected to each other via a linear connecting portion 30. Therefore, the first and second embodiments have the advantage that, compared to a configuration in which the first molded portion 10 and the second molded portion 20 are directly connected (the third embodiment or the comparative example in FIG. 4), it is possible to manufacture a gasket 50 in which the kinks corresponding to the portion of the molding space S between the first molded portion 10 and the second molded portion 20 are reduced.

[0060] D: Modification Specific modified embodiments that can be added to the embodiments exemplified above are shown below. Two or more embodiments arbitrarily selected from the following examples may be combined as appropriate within the scope of not being mutually contradictory.

[0061] (1) In the above-described embodiments, the molding space S has been exemplified as having a circular cross-sectional shape, but the cross-sectional shape of the molding space S is arbitrary. For example, the above-described embodiments are similarly applied to a molding die 100 in which the cross-sectional shape of the molding space S is polygonal (e.g., rectangular). The cross-sectional shape of the gasket 50 is also arbitrary. For example, the above-described embodiments are similarly applied to a gasket 50 in which the cross-sectional shape is polygonal (e.g., rectangular).

[0062] (2) In the first and second embodiments, the molding space S includes the first straight portion 123 and the second straight portion 223. However, as illustrated in FIG. 8, in a configuration in which the first molding portion 10 and the second molding portion 20 are connected via a connecting portion 30, the first straight portion 123 or the second straight portion 223 may be omitted.

[0063] (3) The term "nth" (n is a natural number) in this application is used only as a formal and convenient label to distinguish each element in the description and does not have any substantive meaning. Therefore, there is no room for restrictive interpretation of the position of each element or the order of manufacture, etc., based on the term "nth."

[0064] E: Notes The following configurations can be understood from the above-described exemplary embodiments. Note that, in order to facilitate understanding of each embodiment, reference numerals in the drawings are written in parentheses for convenience, but this is not intended to limit the present disclosure to the illustrated embodiments.

[0065] A molding die (100) according to one aspect (aspect 1) of the present disclosure is a molding die (100) for molding an endless gasket (50), and has a molding space (S) including a first molding section (10) and a second molding section (20), and the first molding section (10) has a first spiral section (11) in which a first molding groove (111) and a second molding groove (112) adjacent to each other are spirally formed, and a groove (Y1) connecting an inner end (Y1) of the first molding groove (111) and an inner end (Y2) of the second molding groove (112) inside the first spiral section (11). The first inverted portion (12) includes a first arc portion (120) extending from an inner end (Y1) of the first forming groove (111) along the inner circumference of the first spiral portion (11), a first curved portion (121) curved from an end (Za) of the first arc portion (120) in an arc shape with a smaller diameter than the first arc portion (120), a second curved portion (122) curved from an inner end (Y2) of the second forming groove (112) in an arc shape with a smaller diameter than the first arc portion (120) to the opposite side of the first curved portion (121), and The second forming section (20) includes a first straight portion (123) that is linear and connects the first curved portion (121) and the second curved portion (122), and the second forming section (20) includes a second spiral portion (21) in which a third forming groove (211) and a fourth forming groove (212) adjacent to each other are spirally formed, and a second inverted portion (22) that connects an inner end (Y3) of the third forming groove (211) and an inner end (Y4) of the fourth forming groove (212) inside the second spiral portion (21). The second inverted portion (22) is connected to the inner end (Y3) of the third forming groove (211). The fourth molding groove (212) includes a second arc portion (220) extending from the inner end (Y4) of the fourth molding groove (212) along the inner circumference of the second spiral portion (21), a third curved portion (221) curved from the end (Zb) of the second arc portion (220) in an arc shape with a smaller diameter than the second arc portion (220), a fourth curved portion (222) curved from the inner end (Y4) of the fourth molding groove (212) in an arc shape with a smaller diameter than the second arc portion (220) to the opposite side from the third curved portion (221), and a straight second straight portion (223) connecting the third curved portion (221) and the fourth curved portion (222).

[0066] According to the above-described embodiment, the first straight portion (123) is located between the first curved portion (121) and the second curved portion (122) located inside the first spiral portion (11), and the second straight portion (223) is located between the third curved portion (221) and the fourth curved portion (222) located inside the second spiral portion (21). Therefore, compared to a case where a forming die (100) is used in which the first curved portion (121) and the second curved portion (122) are directly connected and the third curved portion (221) and the fourth curved portion (222) are directly connected, a gasket (50) can be manufactured in which distortions caused by the curved portions of the forming die (100) are reduced.

[0067] In a specific example (Aspect 2) of Aspect 1, the molding space (S) further includes a linear connecting portion (30) connecting the first molding portion (10) and the second molding portion (20). According to the above aspect, the first molding portion (10) and the second molding portion (20) are connected to each other via the linear connecting portion (30). Therefore, compared to using a molding die (100) in which the first molding portion (10) and the second molding portion (20) are directly connected, a gasket (50) can be manufactured in which the distortion corresponding to the portion between the first molding portion (10) and the second molding portion (20) is reduced.

[0068] In a specific example (Aspect 3) of Aspect 2, the connecting portion 30 intersects with a straight line L passing through the center C1 of the first molded portion 10 and the center C2 of the second molded portion 20. According to the above aspect, it is easier to manufacture a gasket 50 with a long circumferential length compared to an embodiment in which the connecting portion 30 is parallel to the straight line L passing through the center C1 of the first molded portion 10 and the center C2 of the second molded portion 20.

[0069] In a specific example (Aspect 4) of any of Aspects 1 to 3, the length of the first straight portion (123) is at least 1 / 5 of the radius of curvature of the first curved portion (121) or the second curved portion (122), and the length of the second straight portion (223) is at least 1 / 5 of the radius of curvature of the third curved portion (221) or the fourth curved portion (222). According to the above aspects, the lengths of the first straight portion (123) and the second straight portion (223) are sufficiently ensured, so that the aforementioned effect of being able to manufacture a gasket (50) with reduced distortion due to each curved portion is particularly effective.

[0070] In a specific example (Aspect 5) of Aspect 4, the length of the first straight portion (123) is 10 mm or more, and the length of the second straight portion (223) is 10 mm or more. According to the above aspect, the lengths of the first straight portion (123) and the second straight portion (223) are sufficiently ensured, so the aforementioned effect of being able to manufacture a gasket (50) with reduced distortion due to each curved portion is particularly effective.

[0071] In one embodiment (embodiment 6) of the present disclosure, a method for manufacturing a gasket (50) is a method for manufacturing an endless gasket (50) using a molding die (100), the molding die (100) having a molding space (S) including a first molding portion (10) and a second molding portion (20), the first molding portion (10) having a first spiral portion (11) in which a first molding groove (111) and a second molding groove (112) adjacent to each other are spirally formed, and an inner end (Y1) of the first molding groove (111) and an inner end (Y2) of the second molding groove (112) are spirally formed inside the first spiral portion (11). The first inverted portion (12) includes a first arc portion (120) extending from the inner end (Y1) of the first forming groove (111) along the inner circumference of the first spiral portion (11), a first curved portion (121) curved from the end of the first arc portion (120) in an arc shape with a smaller diameter than the first arc portion (120), and a second curved portion (121) curved from the inner end (Y2) of the second forming groove (112) in an arc shape with a smaller diameter than the first arc portion (120) to the opposite side from the first curved portion (121). The second forming section (20) includes a second spiral section (21) in which a third forming groove (211) and a fourth forming groove (212) adjacent to each other are spirally formed, and a second inverted section (22) that connects an inner end (Y3) of the third forming groove (211) and an inner end (Y4) of the fourth forming groove (212) inside the second spiral section (21). The second inverted section (22) is a second spiral section (21) in which a third forming groove (211) and a fourth forming groove (212) adjacent to each other are spirally formed, and The gasket (50) includes a second arc portion (220) extending from the inner end (Y3) along the inner circumference of the second spiral portion (21), a third curved portion (221) curved from the end of the second arc portion (220) in an arc shape with a smaller diameter than the second arc portion (220), a fourth curved portion (222) curved from the inner end (Y4) of the fourth molding groove (212) in an arc shape with a smaller diameter than the second arc portion (220) toward the opposite side from the third curved portion (221), and a straight second linear portion (223) connecting the third curved portion (221) and the fourth curved portion (222). According to the above aspect, it is possible to manufacture a gasket (50) in which distortions due to the curved portions of the forming mold (100) are reduced.

[0072] A gasket (50) according to one embodiment (embodiment 7) of the present disclosure is an endless gasket (50) including a first portion and a second portion located at each point that divides the circumference of the gasket (50) into two equal parts, wherein the first portion includes a first curved portion (511) that curves convexly toward the outside of the gasket (50), a second curved portion (512) that curves convexly toward the inside of the gasket (50), and a first straight portion (513) that connects the first curved portion (511) and the second curved portion (512). The second portion includes a third curved portion (521) that curves convexly toward the outside of the gasket (50), a fourth curved portion (522) that curves convexly toward the inside of the gasket (50), and a second straight portion (523) that connects the third curved portion (521) and the fourth curved portion (522). In the above embodiment, the first curved portion (511) and the second curved portion (512) are connected by the first straight portion (513), and the third curved portion (521) and the fourth curved portion (522) are connected by the second straight portion (523). Therefore, compared to a gasket (50) in which the first curved portion (511) and the second curved portion (512) are directly connected and the third curved portion (521) and the fourth curved portion (522) are directly connected, it is possible to reduce the distortion remaining after molding due to the curved portions of the forming mold (100).

[0073] In a specific example (Aspect 8) of Aspect 7, the length of the first straight portion (513) is at least 1 / 5 of the radius of curvature of the first curved portion (511) or the second curved portion (512), and the length of the second straight portion (523) is at least 1 / 5 of the radius of curvature of the third curved portion (521) or the fourth curved portion (522). According to the above aspect, the lengths of the first straight portion (513) and the second straight portion (523) are sufficiently ensured, so the aforementioned effect of being able to reduce distortions caused by each curved portion of the forming mold (100) is particularly effective.

[0074] In a specific example (Aspect 9) of Aspect 8, the length of the first straight portion (513) is 10 mm or more, and the length of the second straight portion (523) is 10 mm or more. According to the above aspect, the lengths of the first straight portion (513) and the second straight portion (523) are sufficiently ensured, so the aforementioned effect of being able to reduce the curl caused by each curved portion of the forming mold (100) is particularly effective. [Explanation of symbols]

[0075] 100...forming die, 10...first forming portion, 11...first spiral portion, 111...first forming groove, 112...second forming groove, 12...first inverted portion, 120...first arc portion, 121...first curved portion, 122...second curved portion, 123...first straight portion, 20...second forming portion, 21...second spiral portion, 211...third forming groove, 212...fourth forming groove, 22...second inverted portion, 220...second arc portion, 221...third curved portion, 22 2...fourth curved portion, 223...second straight portion, 30...connecting portion, 31...fifth molding groove, 32...sixth molding groove, 41...first split mold, 411...first groove portion, 42...second split mold, 421...second groove portion, 50...gasket, 51...first portion, 511...first curved portion, 512...second curved portion, 513...first straight portion, 52...second portion, 521...third curved portion, 522...fourth curved portion, 523...second straight portion.

Claims

1. A molding die for molding an endless gasket, a molding space including a first molding portion and a second molding portion; The first molding section a first spiral portion in which a first molding groove and a second molding groove adjacent to each other are formed in a spiral shape; a first inverted portion connecting an inner end of the first forming groove and an inner end of the second forming groove inside the first spiral portion, The first inversion portion is a first arc portion extending from an inner end of the first molding groove along an inner periphery of the first spiral portion; a first curved portion that curves from an end of the first arc portion into an arc shape having a smaller diameter than the first arc portion; a second curved portion curved from an inner end of the second molding groove toward an opposite side to the first curved portion in an arc shape having a smaller diameter than the first arcuate portion; a first linear portion that is linear and connects the first curved portion and the second curved portion, The second molding section a second spiral portion in which a third molding groove and a fourth molding groove adjacent to each other are formed in a spiral shape; a second inverted portion connecting an inner end of the third molding groove and an inner end of the fourth molding groove inside the second spiral portion, The second inversion portion is a second arc portion extending from an inner end of the third molding groove along an inner periphery of the second spiral portion; a third curved portion curved from an end of the second arc portion into an arc shape having a smaller diameter than the second arc portion; a fourth curved portion curved from an inner end of the fourth molding groove in an arc shape having a smaller diameter than the second arc portion toward the opposite side to the third curved portion; a second linear portion that is linear and connects the third curved portion and the fourth curved portion Molding mold.

2. The molding space is The molded article further includes a linear connecting portion that connects the first molded portion and the second molded portion. The mold of claim 1.

3. The connecting portion intersects with a straight line passing through the center of the first molded portion and the center of the second molded portion. The mold of claim 2.

4. a length of the first straight portion is equal to or greater than 1 / 5 of a radius of curvature of the first curved portion or the second curved portion; The length of the second straight portion is equal to or greater than 1 / 5 of the radius of curvature of the third curved portion or the fourth curved portion. The mold according to any one of claims 1 to 3.

5. The length of the first linear portion is 10 mm or more, The length of the second straight portion is 10 mm or more. The mold of claim 4.

6. Manufacture endless gaskets using a molding die A method for manufacturing a gasket, comprising: the mold has a molding space including a first molding portion and a second molding portion, The first molding section a first spiral portion in which a first molding groove and a second molding groove adjacent to each other are formed in a spiral shape; a first inverted portion connecting an inner end of the first forming groove and an inner end of the second forming groove inside the first spiral portion, The first inversion portion is a first arc portion extending from an inner end of the first molding groove along an inner periphery of the first spiral portion; a first curved portion that curves from an end of the first arc portion into an arc shape having a smaller diameter than the first arc portion; a second curved portion curved from an inner end of the second molding groove toward an opposite side to the first curved portion in an arc shape having a smaller diameter than the first arcuate portion; a first linear portion that is linear and connects the first curved portion and the second curved portion, The second molding section a second spiral portion in which a third molding groove and a fourth molding groove adjacent to each other are formed in a spiral shape; a second inverted portion connecting an inner end of the third molding groove and an inner end of the fourth molding groove inside the second spiral portion, The second inversion portion is a second arc portion extending from an inner end of the third molding groove along an inner periphery of the second spiral portion; a third curved portion curved from an end of the second arc portion into an arc shape having a smaller diameter than the second arc portion; a fourth curved portion curved from an inner end of the fourth molding groove in an arc shape having a smaller diameter than the second arc portion toward the opposite side to the third curved portion; a second linear portion that is linear and connects the third curved portion and the fourth curved portion A method for manufacturing gaskets.

7. An endless gasket, a first portion and a second portion located at two equal positions along a circumference of the gasket; The first portion is a first curved portion that is curved convexly toward an outside of the gasket; a second curved portion that is curved convexly toward the inside of the gasket; a first linear portion that is linear and connects the first curved portion and the second curved portion, The second portion is a third curved portion that is curved convexly toward the outside of the gasket; a fourth curved portion that is curved convexly toward the inside of the gasket; a second linear portion that is linear and connects the third curved portion and the fourth curved portion gasket.

8. a length of the first straight portion is equal to or greater than 1 / 5 of a radius of curvature of the first curved portion or the second curved portion; The length of the second straight portion is equal to or greater than 1 / 5 of the radius of curvature of the third curved portion or the fourth curved portion. The gasket of claim 7.

9. The length of the first linear portion is 10 mm or more, The length of the second straight portion is 10 mm or more. The gasket of claim 8.

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