JPH056506B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a gasket for a joint used in containers and piping for the food industry.
In particular, the present invention relates to a method of manufacturing a gasket whose liquid contact surface is covered with a fluororesin outer skin.

[Prior Art] Conventionally, gaskets of this type have generally been made of rubber, but since the wetted surface of this rubber gasket is also rubber, it is suitable for use with cola, juice, coffee, etc. However, when containers, piping, etc. are used for storing or producing different types of products, there is an inconvenient problem in that the odors of the food products are transferred. For this reason, gaskets must be cleaned and replaced every time different types of products are stored or produced, which takes time and effort.

Furthermore, gaskets have been known that have a structure in which a ring-shaped outer skin of tetrafluoroethylene resin having a U or V-shaped cross section and a cushion material attached to the outer skin are integrally bonded together (see Japanese Utility Model Publication No. 1590/1983). reference).

The tetrafluoroethylene resin used for the outer skin of the above gasket has extremely excellent physical properties such as chemical resistance, non-adhesiveness, permeation resistance, and washability. Because of this, food odors do not stick to the product.

[Problems to be solved by the invention] However, the gasket described in the above publication has the following problems:
The U or V-shaped cross section creates a small but unacceptable gap between the wetted surface and, for example, a coupling member. In other words, during the storage and production of different products as described above, not only the odor or taste of the different product remaining in the voids is transferred to other products, but in some cases, the residual liquid that remains in the voids may also be transferred. This is undesirable from a food hygiene perspective as it causes microbial contamination.

As a solution to the above-mentioned drawbacks, for example, the first
An annular gasket having the configuration shown in FIGS. 3 through 3 is preferred.

That is, the elastic annular body A made of rubber or the like constituting this annular gasket has a trapezoidal cross section in the tightening direction, and has a seal portion 1 in which the bottom of the trapezoid is the wetted surface. The entire liquid-contacting surface (a) of the part and at least the portions of the side surfaces (c) and (d) which are subjected to tightening that are continuous with the liquid-contacting surface are covered with a thin outer skin B of fluororesin.

FIG. 4 shows a state in which the annular gasket is fitted into the threaded joint of the pipe and tightened. In the figure, 2 is a mail part, 3 is a liner, 4 is a support ring, and 5 is a cap nut.

If the seal part 1 of the elastic ring body is formed to have a trapezoidal cross-section like the annular gasket described above, even if there is a fluororesin outer skin that is harder than the elastic ring body, the trapezoidal side surface will prevent the gasket from forming. A high tightening pressure can be obtained in proportion to the created taper angle θ, and side surfaces A and C are in close contact with the joint member without leaving any gaps. In addition, the liquid-contact surface A and side surfaces B and C of the seal part 1 are covered with a thin fluororesin outer skin A, which prevents food from staining the elastic ring without impairing its elasticity. can.

However, the fluororesin used for the outer skin for covering the seal portion of the elastic ring is difficult to mold compared to other synthetic resins, and in particular, tetrafluoroethylene resin cannot be molded by general injection molding or extrusion molding. For this reason, a powder metallurgy method is applied in which powdered resin is compressed and preformed at room temperature and then sintered above its melting point (360°C to 380°C). , it is not possible to reduce the thickness and form a product with a bent part with a small radius of curvature. Further, even if a thin sheet-like product is produced by this method, distortion occurs in the bent portions and cracks occur, so that the desired product cannot be obtained.

The present invention has been made in view of the above points, and its main purpose is to provide a method for manufacturing an annular gasket having a novel configuration.

Another object of the present invention is to provide both the elasticity required for the sealing part of the gasket and the function of preventing odor from being stained by the fluororesin, and to provide a gasket that can prevent problems from being stained between the liquid contact surface and, for example, a joint member. It is an object of the present invention to provide a method for easily manufacturing an annular gasket having a structure that does not form such voids and exhibits excellent sealing performance.

Still another object of the present invention is to provide a method for easily producing an annular gasket in which the seal portion of the gasket, which has a trapezoidal cross-section, is covered with a thin outer skin of tetrafluoroethylene resin that is curved with an extremely small radius of curvature. It is about providing.

[Means for Solving the Problems] The present invention has been made to achieve the above object, and the seal portion of an elastic ring body having a seal portion having a trapezoidal cross section in the tightening direction is made of fluororesin. In the method for manufacturing an annular gasket covered with an outer skin, a fluororesin annular body having a thickness equal to the sealing portion of the elastic annular body is molded by a conventional method, and the inner part of the fluororesin annular body is cut by cutting. The circumferential surface is formed into a hollow trapezoidal cross section with the bottom side of the trapezoid and the outer circumferential surface with the open top side, and the annular body having the hollow trapezoidal cross section is fitted into the trapezoidal seal portion of the elastic annular body, and the abutment between the two is formed. The above-mentioned problems are solved by a method of bonding and fixing with an adhesive applied to the contact surface.

[Function] In the method for manufacturing an annular gasket of the present invention, the outer skin having a hollow cross section for covering the trapezoidal cross-sectional seal portion of the elastic annular body is formed by cutting the annular body to a required thickness. Therefore, no distortion or cracks occur at the bent portion with a small radius of curvature.

[Example] FIGS. 5 to 9 show an example of manufacturing the annular gasket shown in FIGS. 1 to 3.

In FIGS. 5 and 6, A is an elastic ring body made of a rubber material, 1 is the seal portion having a trapezoidal cross section as described above, and this rubber elastic ring body A is formed by the conventional vulcanization molding method. obtained by.

To obtain the outer skin B of tetrafluoroethylene resin for covering the trapezoidal cross-sectional seal portion of the elastic ring A, first, as shown in FIGS. An annular body b of fluororesin having a thickness of 1 is manufactured by a conventional method (for example, powder metallurgy), and then, as shown in FIG. 9, it is formed into a hollow trapezoid shape by cutting.

Next, the inner surface of the hollow trapezoidal outer skin B is subjected to a surface treatment to impart adhesiveness using a conventional method, and then an adhesive is applied, and the adhesive is applied to the inner surface of the outer skin B, which is in the shape of a hollow trapezoid. , fix with adhesive and complete.

As described above, according to the manufacturing method in which a fluororesin annular body b having the required thickness is first manufactured and then cut into a hollow trapezoidal outer skin, it is extremely thin and has a small radius of curvature. It is possible to easily form a skin having a part.

The above example uses tetrafluoroethylene resin for the outer skin, but PFA, EPF, FTFE, PUDE
Even if a fluororesin such as the above is used, the same outer skin as described above can be obtained.

[Effects of the Invention] According to the method of the present invention, an annular gasket having a structure that has both the elasticity required for the sealing part of the gasket and the odor stain prevention function due to the fluororesin, and exhibits excellent sealing performance. You can definitely get it easily.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway plan view of an annular gasket that is a target of the method of the present invention, Fig. 2 is a vertical side view, Fig. 3 is an enlarged sectional view of the sealing part, and Fig. 4 is a view of the annular gasket in use. 5 is a plan view of the elastic annular body, FIG. 6 is a longitudinal side view, FIG. 7 is a plan view of the fluororesin annular body to be used as the outer skin, FIG. 8 is a longitudinal side view, and FIG. 9 is a cutting diagram. FIG. 3 is a vertical cross-sectional view of the outer skin completed by processing. A...Elastic ring body, 1...Trapezoidal seal portion, 2...
...Mail part, 3...Liner, 4...Support ring, 5...Bag nut, B...Outer skin.

Claims (1)

[Claims] 1. In a method for manufacturing an annular gasket in which the seal portion of an elastic ring body having a seal portion having a trapezoidal cross-section in the tightening direction is covered with a fluororesin outer skin, a fluorocarbon resin having a thickness of the seal portion of the elastic ring body is coated with a fluororesin outer skin. The annular body is formed into a hollow trapezoidal cross section by cutting, with the inner circumferential surface serving as the base of the trapezoid and the outer circumferential surface serving as the open upper side. 1. A method for manufacturing an annular gasket characterized by fitting the annular gasket into the gasket and fixing it with an adhesive applied to the abutting surfaces of the two.