JP3503675B2 - Lip seal manufacturing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a lip seal, which is a kind of a sealing device. 2. Description of the Related Art For example, when a lip seal 51 shown in FIG. 3 is manufactured, it is conventionally manufactured using a mold 71 shown in FIG. The lip seal 51 shown in FIG. 3 is specifically a plug tube seal (also called a plug tube gasket) for sealing between the head cover of the cylinder and the plug tube, and the mounting portion 5 in which a reinforcing ring 53 is embedded.
2. A seal lip 55 having a connecting portion 54 and a garter spring 56 is integrally formed in a staggered or substantially s-shaped cross section using rubber as a molding material. On the other hand, a mold 71 in FIG. 4 is a combination of a plurality of split dies, and includes a sprue 72, a runner 73, an injection gate 74, and a cavity 75, and is incorporated in the cavity 75 in advance before molding. The injection gate 74 is formed on the inner wall of the cavity 75 by a portion 75a forming a seal lip base end 55a and a seal lip tip so that the garter spring 56 does not deviate from the home position even when pressed by the injection pressure of the molding material 76. It is open between the portion 55b forming the portion 55b. That is, while the garter spring 56 is originally set at the outer peripheral edge of the seal lip tip portion 55b, the injection gate 74 is not at the position shown in FIG. If the opening is formed around the portion 75c forming the portion 55c, there is a possibility that the garter spring 56 may be lifted up by the pressure of the molding material 76 injected into the cavity 75 from the opening and deviate from a fixed position. When the opening 74 is located at the above-mentioned position, the garter spring 56 is pressed against the lower surface of the cavity 75 by the pressure of the molding material 76 injected into the cavity 75 from the opening 74, so that the garter spring 56 deviates from the fixed position. Can be prevented. Therefore, when forming the lip seal 51 shown in FIG. 3, the lip seal 51 is first formed by using the mold 71 shown in FIG. The lip seal 51 is removed from the injection gate portion 5 to remove burrs.
7 is a scalpel cut (see line C in FIG. 4). However, in the prior art, as described above, the injection gate 74 is formed on the inner wall of the cavity 75 by the portion 75a forming the seal lip base end 55a.
Because of the opening between the seal lip tip 55b and the portion 75b that forms the seal lip tip 55b, the portion that forms the seal lip sliding end 55c due to the flow of the molding material 76 injected into the cavity 75 from here. The flow end 76a of the molding material 76 is located between the injection end 74c and the sliding end 55c of the lip seal 51 of FIG.
A weld line (not shown) is generated on the inner diameter surface 55d between the gate and the injection gate portion 57. Therefore, conventionally, in order to eliminate the weld line, the inner surface 55d is particularly subjected to a matte finish as a finishing process, so that the manufacture of the lip seal 51 requires extra work such as a matte finish. In addition, in the above prior art, FIG.
Since the injection gate portion 57 remains as a relatively large annular projection (stepped) even after the scalpel cutting as shown in FIG. 7, the annular projection is caught when the plug tube 58 is inserted, and the seal lip 55 is turned up. Sometimes. SUMMARY OF THE INVENTION In view of the above, the present invention has been made in view of the above-mentioned problems, and is intended to manufacture a lip seal capable of removing a weld line from a seal lip without applying a satin finish as in the prior art. The aim is to provide a method. It is another object of the present invention to provide a method of manufacturing a lip seal in which an injection gate portion does not remain as a large protrusion after a scalpel cut, thereby improving tube insertability. In order to achieve the above object, a method for manufacturing a lip seal according to the present invention comprises a base end (5) of a seal lip connected to a mounting portion (2) of a lip seal (1).
The injection gate (24) is opened between the part (25a) forming the a) and the part (25b) forming the seal lip tip (5b), and a part closer to the tip of the seal lip than the injection gate (24). Part (2) for radially enlarging the product shape to generate a weld line
7) A mold (2) having a cavity (25) shaped as
Step 1) of forming the lip seal (1) according to (1), and the lip seal (1) formed by
And cutting off the enlarged molded portion formed by the enlarged portion (27) . In the manufacturing method of the present invention having the above-described steps, a weld line is generated in the enlarged molded portion to be cut in the second step, and the weld line is cut from the product as a part of the enlarged molded portion. Things. Therefore, a clean cut surface without a weld line is formed on the seal lip, so that the satin finish is not required. In addition, by cutting off the injection gate portion (trace) from the product also as a part of the enlarged molded portion, it is possible to prevent the injection gate portion from remaining as a relatively large convex portion as in the related art. . Next, an embodiment of the present invention will be described with reference to the drawings. Using the mold 21 shown in FIG. 1, the lip seal 1 shown in FIG. 2 is formed. First, the lip seal 1 shown in FIG.
A plug tube seal (also referred to as a plug tube gasket) for sealing between a head cover of a cylinder and a plug tube, and is a cylindrical mounting portion 2 in which a metal reinforcing ring 3 having a substantially L-shaped cross section is embedded. An annular seal lip 5 provided with a garter spring 6 on the outer peripheral edge of the connecting portion 4 and the distal end portion 5b is integrally formed in a staggered or substantially s-shaped cross section using rubber as a molding material. The seal lip 5 has a base end 5a connected to the mounting portion 2 via the connecting portion 4, and also has the above-mentioned distal end 5b. The difference between the lip seal 1 of FIG. 2 and the seal lip 51 of FIG. 3 is that the tapered cut surface 7 is provided on the inner end surface of the seal lip 5 on the base end 5a side of the sliding end 5c. And the point that there is no annular convex portion of the injection gate portion 57 in the seal lip 51 of FIG. On the other hand, the mold 21 of FIG. 1 is a combination of a plurality of split dies, and includes a sprue 22, a runner 23, an injection gate 24, and a cavity 25, and is incorporated in the cavity 25 in advance before molding. The injection gate 24 is formed on the inner wall of the cavity 25 by a portion 25a forming the seal lip base end portion 5a and a seal lip tip so that the garter spring 6 does not deviate from the home position even when pressed by the injection pressure of the molding material 26. It is open between the portion 25b forming the portion 5b. The mold 21 in FIG. 1 differs from the mold 71 in FIG. 4 in that the portion of the cavity 25 on the tip side of the seal lip from the injection gate 24 expands radially inward from the product shape. The injection gate 24 is opened at the upper end of the enlarged portion 27, and the wall surface 27a of the enlarged portion 27 is formed in a tapered shape diverging downward so as not to form an undercut portion in the product. ing. In molding the lip seal 1 shown in FIG. 2, first, the lip seal 1 is formed using the mold 21 shown in FIG.
Then, the mold is opened and released, the lip seal 1 is taken out of the mold 21, and then a scalpel cut is performed to remove burrs. At this time, as shown by a line C in FIG.
The enlarged molded portion formed integrally with the seal lip 5 by the enlarged portion 27 of the cavity 25 is cut off together with the injection gate portion, the runner portion and the sprue portion (all not shown), and the above-mentioned portion is formed on the inner surface of the seal lip 5. A tapered cut surface 7 is formed. In the mold 21 shown in FIG. 1, the injection gate 24 is opened on the inner wall of the cavity 25 between the portion 25a forming the seal lip base 5a and the portion 25b forming the seal lip tip 5b. Molding material 26 injected into the cavity 25 from here
The flow end of the molding material 26 is located at the enlarged portion 27 in relation to the flow of the flow, and a weld line is correspondingly generated on the inner diameter surface of the enlarged molded portion of the lip seal 1 in FIG. Therefore, by cutting off the enlarged molded part in the above cutting step, the weld line or its generation part can be removed from the product, thereby eliminating the need for the satin finish conventionally performed to erase the weld line. Further, since a clean cut surface 7 having no weld line is formed on the product instead of the matte-finished surface, the quality of the product can be stabilized and the sealing property can be improved.
In addition, since the injection gate portion is cut off from the product as a part of the enlarged molded portion, it is possible to prevent the injection gate portion from remaining as a relatively large convex portion as in the related art. 8 can be improved. Also, as described above, the wall surface 2 of the enlarged portion 27
7a is formed in a tapered shape diverging downward so as not to form an undercut portion in the product,
The release of the product can be facilitated, and the occurrence of cracks in the seal lip 5 at the time of release can be prevented. In the above-described embodiment, the sliding end 5c of the seal lip 5 is also indexed by a female cut. It is also possible. The present invention has the following effects. That is, in the manufacturing method of the present invention having the above-described steps, a weld line is generated in the enlarged molded portion to be cut in the second step, and this weld line is cut from the product as a part of the enlarged molded portion. This eliminates the need for the satin finish which has conventionally been performed to erase the weld line. In addition, since a clean cut surface without a weld line is formed on the product instead of the matte-finished surface, the quality of the product can be stabilized and the sealing property can be improved. In addition, since the injection gate portion is cut off from the product as a part of the enlarged molded portion, it is possible to prevent the injection gate portion from remaining as a relatively large convex portion as in the related art. Can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view showing a method of manufacturing a lip seal according to an embodiment of the present invention, and is a cross-sectional view of a main part of a mold used in the manufacturing method. FIG. 3 is a cross-sectional view of a main part of a lip seal manufactured by a manufacturing method. FIG. 3 is a cross-sectional view of a main part of a lip seal manufactured by a manufacturing method of a lip seal according to a conventional example. And a cross-sectional view of a main part of a mold used in the manufacturing method. [Description of Signs] 1 Lip seal 2 Mounting part 3 Reinforcement ring 4 Connecting part 5 Seal lip 5a Base end 5b Tip 5c Sliding end 6 Garter Spring 7 Cut surface 8 Plug tube 21 Die 22 Sprue 23 Runner 24 Injection gate 25 Cavity 25a Seal lip base end forming part 25b Seal lip tip forming part 26 Molding material 27 Enlarged part 2 7a wall

Claims (1)

(57) [Claim 1] A portion (25) forming a seal lip base end (5a) connected to a mounting portion (2) of a lip seal (1).
a) and the portion (2) forming the seal lip tip (5b).
5b), an injection gate (24) is opened, and a part closer to the tip of the seal lip than the injection gate (24) is radially enlarged from the product shape to generate a weld line
Forming a lip seal (1) with a mold (21) having a cavity (25) having an enlarged portion (27) for forming the lip seal (1); 2
Removing the enlarged molded portion formed in the enlarged portion (27) by taking out from the enlarged portion ( 1).