Method for manufacturing annular rubber product

Abstract

To provide a method for molding an annular rubber product having an undercut portion using a mold without using a core.SOLUTION: A cross-sectional shape of a cavity 20 formed by an upper mold 12 and a lower mold 13 is rotated by 90° to have a non-undercut shape X, and is subjected to primary vulcanization. Thereafter, the semi-finished product removed after the primary vulcanization is held in a fixed jig and subjected to secondary vulcanization.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an annular rubber product.

Background Art

[0002] In FIG. 17, a method for manufacturing an O-ring 31 and a mold are shown. Raw rubber (preformed) is set between an upper mold 32 and a lower mold 33, and then the upper mold 32 and the lower mold 33 are closed using a press machine. Temperature and pressure are applied, and pressing is performed for a predetermined time. Thereafter, the upper mold 32 is raised as indicated by an arrow U (using the mold) to take out the O-ring 31 as a product. Further, FIG. 18 shows a method for manufacturing an X-ring 36 and a mold having undercuts 34, 35 with a sufficiently large radius R. By shifting the cross-sectional surfaces 37 of the upper mold 32 and the lower mold 33 up and down, even if the undercuts 34, 35 exist in the X-ring 36, the X-ring (product) 36 can be forcibly taken out (also called the "forced extraction method").

[0003] However, as shown in FIG. 19, in the case of a sealing material (annular rubber product) 40 having deep undercuts 38, 39, it is difficult to take out by the forced extraction method shown in FIG. 18 (described above). Therefore, conventionally, a mold and a method have been proposed in which a core that moves up and down integrally with the upper mold is provided, and a rubber molded product (having a deep undercut) is taken out together with the core (see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the mold structure described in Patent Document 1 needs to perform delicate and complex operations, is prone to failure, and has practical problems in terms of durability and the like. Therefore, as illustrated in FIG. 20, it is necessary to attach an inner core 41 and an outer core 42. Further, when the undercut 39 is deeper, as shown in FIG. 21, (the outer core 42 in FIG. 20) must be divided into two, and the semi-circular arc-shaped core halves 42A, 42A must be combined. Arrow R 42 ,R 42 indicates the direction of removing the semi-circular arc-shaped core halves 42A, 42A from the undercut 39 on the outer peripheral side of the sealing material 40.

[0006] In FIGS. 20 and 21, when the annular rubber product 40 such as a sealing material has deep undercuts 38, 39, the following problems exist. That is, (i) The problem that an inner core 41 and an outer core 42 are required and the molding die has a complicated structure. (ii) The problem that the setting of the inner core 41 and the outer core 42 (into the upper die 32 and the lower die 33) is troublesome. (iii) The problem that the removal of the molded annular rubber product 40 from the die is troublesome and time-consuming. Problems (i), (ii), and (iii) as described above have conventionally existed. Furthermore, in rubber products with an inner diameter of 400 mm or more that require the use of a large press machine, the structure is such that cores cannot be used due to equipment limitations. Therefore, large-diameter rubber products having deep undercuts 38, 39 as described above have conventionally been extremely difficult or impossible to manufacture.

Means for Solving the Problems

[0007] Therefore, in the method for manufacturing an annular rubber product having deep undercut portions in the radial outer direction and the radial inner direction, the cross-sectional shape of the cavity formed by the upper mold and the lower mold is made into a non-undercut shape rotated by a predetermined angle, and primary vulcanization is performed. Then, the taken-out semi-finished product that has been primarily vulcanized is made into an undercut shape rotated in the reverse direction by the predetermined angle, and secondary vulcanization is performed while being held by a fixing jig.

[0008] Also, in the method for manufacturing an annular rubber product having an undercut portion only in either the radial outer direction or the radial inner direction, the cross-sectional shape of the cavity formed by the upper mold and the lower mold is made into a non-undercut shape rotated by a predetermined angle, and primary vulcanization is performed. Then, the taken-out semi-finished product that has been primarily vulcanized is made into an undercut shape rotated in the reverse direction by the predetermined angle, and secondary vulcanization is performed while being held by a fixing jig.

[0009] Also, in the method for manufacturing an annular rubber product in which at least one of the radial inner peripheral surface and the radial outer peripheral surface is provided with bottomed small holes or small protrusions in the circumferential direction at a predetermined pitch, the cross-sectional shape of the cavity formed by the upper mold and the lower mold is made into a horizontally lying shape rotated by about 90°, and primary vulcanization is performed. Then, the taken-out semi-finished product that has been primarily vulcanized is held by a fixing jig in a posture rotated in the reverse direction by about 90°, and secondary vulcanization is performed.

Advantages of the Invention

[0010] According to the manufacturing method of the present invention, an annular rubber product having deep undercut portions in the radial direction can be easily and efficiently manufactured by a mold and a fixing jig having a simple structure.

Brief Description of the Drawings

[0011]

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Mode for Carrying Out the Invention

[0012] Hereinafter, the present invention will be described in detail based on the illustrated embodiments. In FIGS. 1, 2, 3, and 4, various annular rubber products 1 that can be manufactured by the manufacturing method according to the present invention are illustrated.

[0013] In FIGS. 1(A) and 1(B), an annular rubber product 1 having undercut portions 8, 8 in the radial outer direction R0 and the radial inner direction Ri is illustrated. In the cross-sectional shape shown in FIG. 1(A), it has an upper bulging portion 9 and a lower bulging portion 10 in a horizontally laid substantially rugby ball shape. Further, FIG. 1(B) has a cross-sectional X shape and has shallow arc-shaped recesses 11, 11 at the top and bottom respectively.

[0014] Also, in the cross-sectional shapes shown in FIGS. 2(A) and 2(B), an annular rubber product having an undercut portion 8 only in either the radial outer direction R0 or the radial inner direction Ri is illustrated. Also, in the annular rubber product 1 shown in FIG. 3, the cross-sectional shape is an oval (long in the vertical direction), and bottomed small holes 4... are arranged in the circumferential direction C at a predetermined pitch on the radial inner peripheral surface 2 and the radial outer peripheral surface 3. Also, in the annular rubber product 1 shown in FIG. 4, the cross-sectional shape is an oval, and small protrusions 5... are arranged in the circumferential direction C at a predetermined pitch on the radial inner peripheral surface 2 and the radial outer peripheral surface 3.

[0015] Regarding the method of manufacturing the variously shaped annular rubber products 1 illustrated in FIGS. 1, 2, 3, and 4, it will be sequentially described in detail below. First, as shown in FIG. 7 (and FIG. 1(A)), a method for manufacturing an annular rubber product 1 having deep undercut portions 8, 8 in the radial outer direction R0 and the radial inner direction Ri will be described.

[0016] As shown in FIG. 5, the cross-sectional shape of the cavity 20 formed by the upper mold 12 and the lower mold 13 is set to an undercut-free shape X that is rotated from the final annular rubber product 1 shown in FIG. 7 by a predetermined angle. In other words, the cavity 20 shown in FIG. 5 formed by the upper mold 12 and the lower mold 13 has an undercut-free shape X by rotating its cross-sectional shape from FIG. 7 by a predetermined angle - that is, 90°.

[0017] The raw rubber material in the cavity 20 having the undercut-free shape X shown in FIG. 5 is vulcanized for the first time at a predetermined temperature, and then taken out while maintaining the cross-sectional shape (posture) as shown in FIG. 5. The taken-out semi-finished product 21 that has been vulcanized for the first time is rotated reversely by the above-mentioned predetermined angle - that is, 90° - to form an undercut shape Y, and is held in a fixing jig 25 as shown in FIG. 6 while being vulcanized for the second time. That is, if it is taken out from this fixing jig 25, the final annular rubber product 1 having undercut portions 8, 8 as shown in FIG. 7 can be obtained. Note that the temperature for the first vulcanization is preferably, for example, 150°C to 200°C. Also, the temperature for the second vulcanization is preferably, for example, 250°C to 300°C.

[0018] Also, in the illustration of FIG. 6, the case where the cross-sectional shape of the fixing jig 25 for the second vulcanization is L-shaped is shown. It is also preferable to set it to a U-shaped as exemplified in FIG. 9, place the semi-finished product 21 that has been vulcanized for the first time in the storage groove 25A, and perform the second vulcanization. Also, as shown in FIG. 6, it may be desirable to make the cylindrical wall portion 25B in contact with the inner circumference of the semi-finished product 21 after the first vulcanization inclined at a small angle β of 20° or less. That is, after the second vulcanization is completed, it is possible to prevent the taken-out annular rubber product 1 from being deformed into a slightly inclined cross-sectional posture (from the regular cross-sectional posture), and it becomes easier to obtain a regular cross-sectional shape.

[0019] Next, FIGS. 8 to 10 show still another embodiment. As shown in FIG. 10 (and FIG. 1(B)), a method for manufacturing an annular rubber product 1 having deep undercut portions 8, 8 in the radial outer direction R0 and the radial inner direction Ri will be described.

[0020] As shown in FIG. 8, based on the final annular rubber product 1 shown in FIG. 10, the cross-sectional shape of the cavity 20 formed by the upper mold 12 and the lower mold 13 is held in an undercut with a sufficiently large radius R (radius) rotated by a predetermined angle - 90°. The raw rubber material in the cavity 20 having an undercut with a sufficiently large radius R (radius) shown in FIG. 8 is subjected to the first vulcanization at a predetermined temperature. Thereafter, it is taken out from the upper mold 12 and the lower mold 13 (by a so-called "forced ejection" method). That is, it is taken out with the cross-section and posture shown in FIG. 8.

[0021] The semi-finished product 21 after the first vulcanization taken out in this way is reversely rotated by the above-mentioned predetermined angle - that is, 90° - and held in a fixing jig 25 as shown in FIG. 9 in an undercut shape Y. In that posture, the second vulcanization is performed (for a predetermined time). The fixing jig 25 has a shape having a storage groove 25A, and the semi-finished product 21 after the first vulcanization having an undercut shape is subjected to the second vulcanization with the correct cross-sectional shape and posture. Note that the fixing jig 25 having an L-shaped cross-section shown in FIG. 6 may be used (instead of FIG. 9). Then, if it is taken out from the fixing jig 25 in FIG. 9, the final annular rubber product 1 having the undercut portions 8, 8 shown in FIG. 10 can be obtained.

[0022] Next, FIGS. 11 to 13 show still another embodiment. As shown in FIGS. 3 and 13, FIGS. 11 to 13 show a method for manufacturing an annular rubber product 1 in which bottomed small holes 4 are arranged at a predetermined pitch in the circumferential direction C on both the radial inner peripheral surface 2 and the radial outer peripheral surface 3.

[0023] As shown in FIG. 11, the cross-sectional shape of the cavity 20 formed by the upper mold 12 and the lower mold 13 is a lying-down shape X rotated by approximately 90° (from the cross-sectional shape of FIG. 13). 90 Then, primary vulcanization is performed. That is, the cavity 20 has a cross-section rotated by approximately 90° in the cross-sectional shape of the annular rubber product 1 as the finished product shown in FIG. 13. In FIG. 11, primary vulcanization is performed by the cavity 20 of the lying-down shape X formed by the upper mold 12 and the lower mold 13. 90 After that, while holding the taken-out semi-finished product 21 that has been primarily vulcanized in a posture rotated counterclockwise by approximately 90° with the fixing jig 25 (see FIG. 12), secondary vulcanization is performed.

[0024] The fixing jig 25 shown in FIG. 12 has an L-shaped cross-section, but the cylindrical wall portion 25B is inclined radially outward by a small angle β. Depending on the shape and dimensions of the cross-section of the annular rubber product 1, the overall diameter dimension, the difference in rubber material, vulcanization conditions such as vulcanization temperature, etc., after the secondary vulcanization in FIG. 12, the radial inner peripheral surface 2 and the outer peripheral surface 3 of the taken-out annular rubber product 1 may be useful for accurately being parallel to the axis L1 as shown in FIG. 13.

[0025] Note that the manufacturing method of the annular rubber product 1 in which small protrusions 5 as shown in FIG. 4 are arranged at a predetermined pitch in the circumferential direction C is also manufactured by the same method as FIGS. 11, 12, and 13. However, it is desirable to prevent deformation due to compression of the small protrusions 5 by forming relief through-holes 16... (for the small protrusions 5) as shown by the dotted line in FIG. 12 in the fixing jig 25.

[0026] In the annular rubber product 1 shown in FIGS. 3 and 4, the case where both the radial inner peripheral surface 2 and the radial outer peripheral surface 3 have the bottomed small holes 4 or the small protrusions 5 is illustrated. However, even when it has them only on either the radial inner peripheral surface 2 or the radial outer peripheral surface 3, it can be manufactured in the same manner by the method described in FIGS. 11 to 13 (not shown).

[0027] Next, FIGS. 14, 15, and 16 show still another embodiment of the present invention. That is, the annular rubber product 1 shown in FIG. 16 has an undercut shape Y having four undercut portions 8, 8, 8, 8. That is, it has undercut portions 8, 8, 8, 8 in four directions: the radial outer direction R0, the radial inner direction Ri, and the axial directions A1, A2.

[0028] Regarding the manufacturing method of the annular rubber product 1 having the undercut shape Y shown in FIG. 16, as shown in FIG. 14, the cross-sectional shape of the cavity 20 formed by the upper mold 12 and the lower mold 13 is an undercut-free shape X rotated by a predetermined angle - about 45° - based on the cross-sectional shape of the final annular rubber product 1 shown in FIG. 16. That is, the X-shaped annular rubber product 1 shown in FIG. 16 has four undercut portions 8, 8, 8, 8, but by simply rotating it by about 45°, it is converted into the undercut-free shape X as shown in FIG. 14. Note that as for the X shape shown in FIG. 16, there are various depths and shapes of the undercut portions 8, and there are also various shapes and lengths of the four protruding portions 7 in the X shape. Therefore, the rotation angle (about 45°) for converting to the undercut-free shape X in FIG. 14 can be selected as an optimal angle in the range of 35° to 55°.

[0029] By the way, the raw rubber material in the cavity 20 having the undercut-free shape X shown in FIG. 14 is subjected to primary vulcanization at a predetermined temperature. After that, when the upper mold 12 and the lower mold 13 are opened, the semi-finished product 21 that has been primary vulcanized with the cross-section and posture shown in FIG. 14 is taken out. The once-vulcanized semi-finished product 21 taken out in this way is rotated counterclockwise by the above-mentioned predetermined angle - that is, the optimal angle selected within the range of 35° to 55° - and held in the fixing jig 25 as shown in FIG. 15 in the undercut shape Y as shown in FIG. 15. In this posture, secondary vulcanization is carried out (over a predetermined time).

[0030] The fixing jig 25 has a shape with a storage groove 25A, and the once-vulcanized semi-finished product 21 with the undercut shape Y is subjected to secondary vulcanization with the correct cross-sectional shape and posture. Note that the fixing jig 25 with an L-shaped cross-section shown in FIG. 6 may be used (instead of FIG. 15). Then, if it is taken out from the fixing jig 25, the final annular rubber product 1 having the undercut portions 8, 8, 8, 8 shown in FIG. 16 can be obtained.

[0031] Next, as shown in FIGS. 2(A) and (B), a method for manufacturing the annular rubber product 1 having the undercut portion 8 only in the radial outer direction R0 or the radial inner direction Ri will be described. Basically, it can be manufactured in the same manner as the manufacturing method already described in FIGS. 1(A) and (B) and FIGS. 3 and 4.

[0032] That is, in the method for manufacturing an annular rubber product having an undercut portion 8 only in either the radial outer direction R0 or the radial inner direction Ri, the cross-sectional shape of the cavity 20 formed by the upper mold 12 and the lower mold 13 is set as the non-undercut shape X rotated by a predetermined angle, and primary vulcanization is performed. Then, the taken-out once-vulcanized semi-finished product 21 is held in the fixing jig 25 as the undercut shape Y rotated counterclockwise by the above-mentioned predetermined angle, and secondary vulcanization is performed. Specifically, in each of the embodiments shown in FIGS. 2(A) and (B), the above-mentioned predetermined angle is 90°, and the non-undercut shape X is a state in which the undercut portion (concave groove) 8 in each of FIGS. 2(A) and (B) is directed "upward" or "downward".

[0033] In addition, as the overall perimeter dimension of the annular rubber product 1 according to the present invention, for example, 900 mm or more is preferable. That is, it becomes certain and easy to hold the undercut shape Y in the fixing jig 25.

[0034] As described in detail above, the present invention relates to a method for manufacturing an annular rubber product having deep undercut portions 8 in the radial outer direction R0 and the radial inner direction Ri. The cross-sectional shape of the cavity 20 formed by the upper mold 12 and the lower mold 13 is set as the non-undercut shape X rotated by a predetermined angle, and primary vulcanization is performed. Then, the taken-out semi-finished product 21 after the primary vulcanization is held in the fixing jig 25 as the undercut shape Y rotated in the reverse direction by the predetermined angle, and secondary vulcanization is performed. Therefore, a conventional molding die (apparatus) provided with complicated inner cores 41 and outer cores 42 (shown in FIGS. 20 and 21) is not required, and a simple molding die is sufficient. Moreover, the troublesome work of setting the inner core and the outer core into the upper mold and the lower mold can be omitted. In addition, the work of taking out the annular rubber material from the mold and the fixing jig can be easily and quickly performed, and the work efficiency is also good.

[0035] Further, the present invention relates to a method for manufacturing an annular rubber product having an undercut portion 8 only in either the radial outer direction R0 or the radial inner direction Ri. The cross-sectional shape of the cavity 20 formed by the upper mold 12 and the lower mold 13 is set as the non-undercut shape X rotated by a predetermined angle, and primary vulcanization is performed. Then, the taken-out semi-finished product 21 after the primary vulcanization is held in the fixing jig 25 as the undercut shape Y rotated in the reverse direction by the predetermined angle, and secondary vulcanization is performed. Therefore, a conventional complicated molding die (apparatus) provided with an inner core or an outer core can be omitted, and a simple molding die is sufficient. Furthermore, the troublesome work of setting the inner core or the outer core into the upper mold and the lower mold can be omitted. Moreover, the work of taking out the annular rubber material from the mold and the core can be easily and quickly performed, and the work efficiency is also improved.

[0036] Further, the present invention relates to a method for manufacturing an annular rubber product in which at least one of a radial inner peripheral surface 2 and a radial outer peripheral surface 3 is provided with bottomed small holes 4 or small protrusions 5 at a predetermined pitch in the circumferential direction C; the cross-sectional shape of a cavity 20 formed by an upper mold 12 and a lower mold 13 is rotated about 90° to a lying-down shape X 90 As such, primary vulcanization is performed; thereafter, the taken-out semi-finished product 21 after primary vulcanization is held by a fixing jig 25 in a posture rotated counterclockwise by about 90°, and secondary vulcanization is performed. Therefore, it becomes possible to mold with a simple molding die that omits the core. That is, a simple molding die (see FIG. 11) that omits the inner core and the outer core (which were necessary in the past) is sufficient. Further, the troublesome work of setting the inner core and the outer core into the upper mold and the lower mold can be omitted. In this way, the apparatus can be simplified and the working efficiency can be remarkably improved.

Explanation of Signs

[0037] 1 Annular rubber product 2 Radial inner peripheral surface 3 Radial outer peripheral surface 4 Bottomed small hole 5 Small protrusion 8 Undercut portion 12 Upper mold 13 Lower mold 20 Cavity 21 Semi-finished product after primary vulcanization 25 Fixing jig C Circumferential direction R0 Radial outer direction Ri Radial inner direction X Non-undercut shape X 90 Lying-down shape Y Undercut shape

Claims

1. Radial outward direction (R 0 ) and a method for manufacturing an annular rubber product having a deep undercut portion (8) in the radial inward direction (Ri), The cross-sectional shape of the cavity (20) formed by the upper mold (12) and the lower mold (13) is set as an undercut-free shape (X) rotated by a predetermined angle, and primary vulcanization is performed. Thereafter, the taken-out semi-finished product (21) that has been primary-vulcanized is set as an undercut shape (Y) rotated reversely by the predetermined angle, and secondary vulcanization is performed while being held by a fixing jig (25). A method for manufacturing an annular rubber product, characterized by the above.

2. Radial outward direction (R 0 ) or only in either one of the radial inward direction (Ri), in the manufacturing method of an annular rubber product having an undercut portion (8), The cross-sectional shape of the cavity (20) formed by the upper mold (12) and the lower mold (13) is set as an undercut-free shape (X) rotated by a predetermined angle, and primary vulcanization is performed. Thereafter, the taken-out semi-finished product (21) that has been primary-vulcanized is set as an undercut shape (Y) rotated reversely by the predetermined angle, and secondary vulcanization is performed while being held by a fixing jig (25). A method for manufacturing an annular rubber product, characterized by the above.

3. In a method for manufacturing an annular rubber product in which at least one of the radial inner peripheral surface (2) and the radial outer peripheral surface (3) is provided with bottomed small holes (4) or small protrusions (5) in the circumferential direction (C) at a predetermined pitch. The cross-sectional shape of the cavity (20) formed by the upper mold (12) and the lower mold (13) is rotated by approximately 90° to form a lying-down shape (X 90 ), and primary vulcanization is performed. Thereafter, the taken-out semi-finished product (21) that has been primary-vulcanized is held by a fixing jig (25) in a posture rotated reversely by about 90°, and secondary vulcanization is performed. A method for manufacturing an annular rubber product, characterized by the above.

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