JPS61228942A - Manufacture of diaphragm - Google Patents

Abstract

PURPOSE:To reduce the cost of manufacturing a diaphragm with bellows by a method in which a cap-shaped molding having a thin horizontal stage portion in its tiered portions is formed, and the molding is folded at the horizontal stage portions to form the bellows. CONSTITUTION:Molding is made by using a cap-shaped mold having tiered portions 21 formed by stretching bellows 11 and thin horizontal stage portions 21a to be folded in the tiered portions 21. When the thickness of an uprising wall 21b is 0.6mmt, that of the horizontal stage portion 21a is 0.4-0.3mmt. The tiered portions 21 are folded at the horizontal stage portions 21a to obtain a diaphragm 10 with the bellows 11. Since the portions 21a are of a small thickness, top and bottom portions 11a and 11b can be exactly and easily formed at given positions. The upper and lower molds 26 and 27 may have staged projections 26a and staged recessions 27a for each, which are easily formed by cutting the molds.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for manufacturing, by molding, a diaphragm having a bellows portion in which a plurality of peaks, φ, and valleys are arranged concentrically on a plane.

As this type of diaphragm lO, there is one used for sealing the brake reservoir tank 2, as shown in FIG. In addition, 3 is a mask cylinder, 5 is a piston, 6 is a piston cup, and 7 is a coil spring.

Here, molding refers to compression molding, which has conventionally been generally used to manufacture diaphragms, as well as transfer molding and molding.
Also includes injection molding.

<Prior art> The above diaphragm 10 is shown in FIG. 8 or 9 on a plane.
As shown in the figure, round or rectangular peaks and valleys 11a-11b
The bellows portion 11 is provided with a plurality of bellows portions 11 arranged concentrically. The diaphragm 10 is usually formed using an upper mold 16 as shown in FIGS. This was done by compression molding using a lower mold 17.

<Problems to be Solved by the Invention> However, since the pitch of the ridges 11a or troughs 11b of the bellows portion 11 of the diaphragm 10 is generally short, the upper die 16 or the lower die for shaping the ridges or troughs is short. The annular protrusion 16a or 17a formed on the mold 17 is thin (usually 2 mm before vk
), therefore, it is difficult to process the mold by cutting, etc., and it is necessary to give strength to the annular protruding strip 16a (or 17a), so it is necessary to use a mold material with special strength (induction hardened, etc.). ) was required. Therefore, the cost of the mold increases, and the annular protrusion of the mold is also easily damaged, resulting in an increase in the manufacturing cost of the diaphragm having the bellows portion.

Means for Solving the Problems> The method for manufacturing a diaphragm of the present invention includes a stepped portion formed by stretching a bellows portion, and the horizontal stepped portion, which is the portion to be bent, of the stepped portion is formed on a vertical wall. The above-mentioned problem is solved by molding a hat-shaped molded product having a thinner wall than the main part, and then bending the stepped part at the horizontal step part to form a bellows part. .

<Example> The method for manufacturing the diaphragm of this invention will be described below.

This will be explained based on an example.

Diaphragm materials include NBR, EPOM, and CR.
, Co, ECO and other rubber materials, and polyolefin-based thermoplastic elastomers.

When manufacturing the diaphragm 10 as shown in FIGS. 7 and 8, first, as shown in FIG. A hat-shaped molded product having a thin horizontal stepped portion 21a is molded. At this time, the thin horizontal stepped portion 21a is formed as shown in FIG. , upper and lower vertical wall portions 21b, 21b of the horizontal step portion 21a
A step may be provided at the lower end and the upper end of the wall to create a thin part with approximately uniform wall thickness, or as shown in FIG.
It is conceivable that the upper and lower ends of 1b' are alternately tapered or stepped (from the viewpoint of accurate positioning of the bending part and shape retention), and that the horizontal step part 21a is made into a thin wall part. Also, care should be taken to ensure that the upper die 26 does not become undercut. Note that when the thickness of the general portion (vertical wall portion) 21b is 0.6 at, the thickness of the horizontal portion 21a is 0.4 w 0.3 mat. Note that 27 is a lower mold.

Next, a stepped portion 2 is formed by stretching the bellows portion.
By folding a cap-shaped molded product having a bellows part 11 by bending the stepped part 21 at the horizontal step part 21a, a diaphragm 10 having a bellows part 11 as shown in FIGS. 7 and 8 can be obtained. can. At this time, since the horizontal step portion 21a is thin, the peaks and valleys 11a and flb are reliably and easily formed at predetermined positions.

<Actions and Effects of the Invention> As described above, the method for manufacturing a diaphragm of this invention is as follows:
After molding with a molded product shape that has a stepped part formed by stretching the bellows part and a horizontal step part where the stepped part is to be bent, the horizontal step part is thin. Since it is a method of forming bellows parts by folding and folding, there is no need to form thin annular protrusions on the molds (upper and lower molds). It is only necessary to form the stepped convex portion 26a1 and the four stepped portions 27a, respectively, and processing by cutting the mold is easy, and the mold material does not need to be particularly strong.Therefore, the mold cost can be reduced. As a result, the manufacturing cost of diaphragms with bellows parts can be significantly reduced.

[Brief explanation of the drawing]

1 to 4 show an example of a molding die used in the diaphragm manufacturing method of the present invention, FIG. 1 is a schematic half-sectional view of the mold when the mold is closed, and FIG. Fig. 3 is an enlarged sectional view of the main part showing another example, Fig. 4 is a schematic half-sectional view of the mold when the mold is opened, and Fig. 5 is the conventional one. Fig. 6 is a half-sectional view when the mold is closed, showing an example of the molding die used in the manufacturing method of the diaphragm, Fig. 6 is a half-sectional view when the mold is open, and Fig. 7 is a half-sectional view of the mold when it is attached to the brake reservoir tank. 8 is a cross-sectional view of the diaphragm, FIG. 8 is a plan view of the diaphragm shown in FIG. 7, and FIG. 9 is a plan view showing another example of the diaphragm shown in FIG. 7. 10... diaphragm, 11... bellows part. 11a...Mountain part, ttb...Trough part, 21...Step-like part 21a...Horizontal step part, 21b...Vertical wall part, 26...Upper mold. 27...lower. Patent applicant

Claims (1)

[Claims] In a method of manufacturing a diaphragm having a bellows portion having a plurality of peaks and valleys arranged concentrically on a plane by molding, the stepped portion is formed by stretching the bellows portion. and after molding into a hat-shaped molded product shape in which the horizontal step portion, which is the planned bending portion of the step-like portion, is thinner than the vertical wall portion, the step-like portion is bent at the horizontal step portion. A method for manufacturing a diaphragm, characterized in that it is folded to form a bellows part.