Forming mold for gasket and method of manufacturing the gasket

Abstract

The object of the present invention is to provide a gasket forming mold with a structure in which curling of the reversing section of the gasket molding does not occur easily. To achieve said object, the forming mold for integrally forming an endless shaped gasket has forming grooves as cavities in the parting surfaces of the forming mold and the forming grooves have a reversing section in a part thereof. The reversing section has two linear portions and the ends of the two linear portions are connected by an arc-shaped curved section. The two linear portions are arranged at literally-symmetrical positions and are arranged so that a distance therebetween is enlarged little by little from one end toward the other. The ends where said distance is enlarged are connected by the circular arc-shaped curved section.

Claims

1. A forming mold for integrally forming an endless-shaped gasket, the forming mold comprising: a forming groove that is configured as a cavity space provided in a parting surface of the forming mold, wherein the forming groove has a reversing section in a part thereof, wherein the reversing section has two straight sections, and end portions of the two straight sections are connected by a circular arc-shaped curved section, and wherein the two straight sections are arranged at linearly symmetrical positions and are arranged so that a distance between the straight sections is enlarged little by little from one end toward the other end, and the end portions having the enlarged distance are connected by the circular arc-shaped curved section.

2. A method of manufacturing an endless-shaped gasket, comprising: providing a forming mold that includes: a forming groove that is configured as a cavity space provided in a parting surface of the forming mold, wherein the forming groove has a reversing section in a part thereof, wherein the reversing section has two straight sections, and end portions of the two straight sections are connected by a circular arc-shaped curved section, and wherein the two straight sections are arranged at linearly symmetrical positions and are arranged so that a distance between the straight sections is enlarged little by little from one end toward the other end, and the end portions having the enlarged distance are connected by the circular arc-shaped curved section; and forming the endless-shaped gasket by depositing a rubber material into the forming mold.

Description

BRIEF EXPLANATION OF THE DRAWINGS

(1) FIG. 1 is a plan view of a parting surface in a forming mold according to an embodiment of the present invention;

(2) FIG. 2 is an enlarged cross sectional view of a substantial part of the forming mold; and

(3) FIG. 3 is a plan view of a parting surface in a forming mold according to the prior art.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

(4) Next, a description will be given of an embodiment according to the present invention with reference to an accompanying drawings.

(5) FIG. 1 shows a plane of a parting surface 2 in a state in which a forming mold 1 according to an embodiment of the present invention is opened.

(6) The forming mold 1 according to the embodiment is structured such as to integrally mold a large-diameter O-ring which is formed into a planar circular ring shape as an endless-shaped gasket, is provided on a plane of a parting surface 2 thereof with one endless-shaped forming grove 3 as a product cavity space, and is provided in a part of the forming groove 3 with a reversing section 4. The reversing section 4 has two linear sections 5 and 6, and end portions b and c of these two linear sections 5 and 6 are smoothly connected to each other by a circular arc-shaped curved section 7.

(7) Further, two linear sections 5 and 6 are arranged at linearly symmetrical positions around a line (a center line) A, and are arranged in a V-shaped manner so that a distance therebetween is enlarged little by little from one end (a lower end in the drawing) toward the other end (an upper end in the drawing), and the end portions b and c having the enlarged distance are connected smoothly to each other by the circular arc-shaped curved section 7.

(8) Further, the endless-shaped forming groove 3 is constructed by a combination of sections listed up below, as a whole, and each of the sections is smoothly connected.

(9) Linear section 5 between a and b in a left side on the drawing

(10) Circular arc-shaped curved section 7 between b and c around a point B

(11) Linear section 6 between c and d in a right side on the drawing

(12) Circular arc-shaped curved section 8 between d and e around a point C

(13) Circular arc-shaped curved section 9 between e and f around a point D

(14) Circular arc-shaped curved section 10 between f and g around a point E

(15) Circular arc-shaped curved section 11 between g and h around a point F

(16) Circular arc-shaped curved section 12 between h and i around a point G

(17) Circular arc-shaped curved section 13 between i and j around a point H

(18) Circular arc-shaped curved section 14 between j and a around a point I

(19) The points B and F are arranged on the line A. The points C and I, the points D and H and the points E and G are respectively arranged at linearly symmetrical positions around the line A. The curved sections 8 and 14, the curved sections 9 and 13 and the curved sections 10 and 12 are respectively set so that radius of curvature are equal. Therefore, the endless-shaped forming groove 3 is formed into a linearly symmetrical shape around the line A as a whole thereof.

(20) Further, as shown by a cross section in FIG. 2, a burr groove 15 and a biting groove 16 are provided in each of an outer peripheral side and an inner peripheral side of the forming groove 3. Further, since the forming mold 1 is constructed by a combination of a pair of divided molds 1A and 1B, the forming groove 3, the burr groove 15 and the biting groove 16 are provided in each of the parting surfaces 2 of the divided molds 1A and 1B.

(21) In the forming mold 1 having the structure mentioned above, two linear sections 5 and 6 are provided in the reversing section 4 and the end portions b and c of these two linear sections 5 and 6 are connected to each other by the circular arc-shaped curved section 7 as mentioned above. Therefore, a curling shape (a curling shape due to forming) is hard to be generated in the reverse section of the formed product which is formed by the combination of these linear sections 5 and 6 and the curved section 7 in comparison with the conventional S-shaped structure.

(22) Further, two linear sections 5 and 6 are arranged at the linearly symmetrical positions around the line A, and are arranged in the V-shaped manner so that the distance therebetween is enlarged little by little from one end toward the other end, and the end portions b and c having the enlarged distance are connected to each other by the circular arc-shaped curved section 7. As a result, the radius of curvature of the curved section 7 is prescribed by the distance between b and c (the distance between the other ends of the linear sections 5 and 6) in place of the distance between a and d (the distance between one ends of the linear sections 5 and 6. Therefore, the radius of curvature of the curved section 7 is set larger than the case that the radius of curvature is prescribed by the distance between a and d. Accordingly, since the radius of curvature of the curved section 7 is greater as mentioned above, the curling shape is hard to be generated in the reversing section of the formed product.

(23) In order to sufficiently obtain the effects mentioned above, it is preferable to set lengths L1 and L2 of the linear sections 5 and 6 to be at least equal to or more than 30 mm, and further preferably equal to or more than 60 mm, and set the radius of curvature of the curved section 7 and the radius of curvature of the other curved sections 8 to 14 to be equal to or more than R70.

(24) A manufacturing method according to the present invention integrally mold a large-diameter O-ring which is formed into a planar circular ring shape by using the forming mold 1. The O-ring is generally formed by a rubber material. The O-ring is used, for example, in a semiconductor manufacturing device. On the basis of the combination of the linear sections 5 and 6 and the curved section 7 in the embodiment mentioned above, the reversing section 4 may be arranged in a center portion of the spiral forming groove as shown in FIG. 3.