JP3877885B2 - Method for manufacturing a valve body for a butterfly valve - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a resin valve body in a butterfly valve that is excellent in chemical resistance, corrosion resistance, heat resistance and the like and is widely used in the food industry, the pharmaceutical industry and the like.
[0002]
[Prior art]
Conventionally, this type of resin valve element is generally known, and specifically disclosed in JP-A-9-12625.
The valve body according to the publication has a circular arc cross section, a core body is formed by joining a pair of core plates having a hollow portion inside, and a bearing body that supports the valve shaft in the diameter direction of the core body is attached, Furthermore, a valve body is provided so that a hole communicating with the cavity is formed on the surface of the core body and the resin of the resin layer to be coated is filled in the cavity.
[0003]
[Problems to be solved by the invention]
However, according to the above-described conventional example, during resin molding, the resin is filled in the cavity while the resin is flowing on the outer periphery of the core body, so that the resin flow changes each time. In addition, it is difficult to predict the position of the weld portion where the molten resin filled in the mold finally branches and flows. In particular, in order to change the weld position as necessary, it is necessary to repeat the trial and error to actually mold and check whether it is the optimal weld position, thereby finding the resin molding conditions, which increases the development man-hours and the amount of work. Is real.
[0004]
And since the weld part produced by resin molding is located on the surface of the core body, the crack of the weld part appears on the surface of the product and the resin is easily cracked and peeled off. Although measures such as attaching a degassing pin to a portion where burn cracking is likely to occur are taken into account, these countermeasures have been demanded because they cannot be sufficiently improved.
[0005]
In order to solve the conventional problems, the present invention has been developed as a result of intensive studies, and in the manufacture of a resin valve body for a butterfly valve, the welded part crack caused by resin molding is a resin valve body. The purpose of this is to stabilize the quality of the valve body so that it does not appear on the surface.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is a valve body of a butterfly valve in which a core metal is surrounded by a synthetic resin, and the core metal is inserted into a mold having a resin injection gate. the metal core to form a communication hole for connecting the front and back of the through holes and the core metal outer periphery of the center hole inside and penetrations of the core to the surface located on the opposite side of the resin injection gate in the resin, the resin The flow of the resin injected from the injection gate is branched into two or more places passing through the communication hole and the outer periphery of the cored bar, and turns around the outer peripheral surface of the cored bar opposite to the injection gate. A butterfly valve that is formed and a weld portion formed near the center portion of the cored bar is buried in the center hole of the cored bar from the through hole so that the joined weld part does not remain on the surface of the valve body This is a method for manufacturing a valve body.
The invention according to claim 2 is a method for manufacturing a valve body for a butterfly valve in which a taper pin inserted from the upper and lower sides of a mold is inserted into a central hole of a core metal and is filled with molten resin in this state.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a method for producing a resin valve body for a butterfly valve in the present invention will be specifically described with reference to the drawings.
Although the butterfly valve in this example is not shown in the drawings, a seat ring formed of an elastic member such as rubber or synthetic resin is mounted inside a short cylindrical valve body, and an arc-shaped valve body is installed inside the seat ring. open or close the flow path of the seat ring by rotating the upper and lower stem, which adjusts the flow passage.
[0008]
5 to 7, a hollow is formed in the center hole 2 of the circular cored bar 1, and upper and lower stem bearing portions 3 and 4 are provided on the upper and lower portions of the center hole 2. An engagement flat surface 3a for engaging the stem is formed, and further, a through-hole communicating with the inside of the center hole 2 on the outer surface of the center hole 2 of the cored bar 1 on the surface opposite to the resin injection gate 9 described later 6 is formed by casting or processing means, and a plurality of communication holes 7 for connecting the resin 5 on the front side 1b and the back side 1c are provided in the wing part 1a of the core 1.
The metal core is formed by casting, pressing or forging. However, it is advantageous that the metal core can be formed in one step.
[0009]
As shown in FIG. 8, the core metal 1 is inserted into the molds 8a and 8b of the molding machine, and the molten resin 12 is filled from the gate 9 for injection molding with the taper pins 10 and 11 inserted from above and below.
For this resin, materials such as PA (nylon), POM (polyacetal), PC (polycarbonate), PPS (polyphenylene sulfide) are appropriately selected and used.
[0010]
In FIG. 8, the molten resin 12 filled from the gate 9 branches into two or more places where the flow passes through the communication hole 7 and the outer periphery of the core metal 1, and passes through different paths , respectively, on the opposite side of the gate 9. Since it goes around the back side 1c of the outer periphery of the cored bar 1 and gathers again in the vicinity of the through hole 6 and rejoins, the molten resin 12 is led from the through hole 6 to the cavity of the center hole 2 and buried, so The welded portion does not remain on the surface of the valve body.
That is, in FIG. 8 or FIG. 4, the molten resin 12 is injected from the gate 9 into the gap between the core metal 1 and the mold 8 b, and the molten resin 12 is filled into the gap between the core metal 1 and the mold 8. In the vicinity, there is a flow in which the molten resin 12 passes through the communication hole 7 and exits to the back side 1c of the outer peripheral surface of the core metal 1 and flows around the outer periphery of the core metal 1 and exits to the back side 1c of the outer periphery of the core metal 1. On the back side 1c of the outer periphery of the core metal 1, the resin that has come out in the vicinity of the communication hole 7 and the molten resin that has turned around the outer periphery of the core metal 1 are filled while being joined, and the resin is near the center of the back side 1c of the outer periphery of the core metal 1. After the joining of the two ends, the molten resin 12 is introduced into the cavity of the center hole 2 from the through hole 6 and buried therein, so that the welded portion that has joined does not remain on the surface of the valve body.
[0011]
Next, after cooling and solidifying, when the upper and lower taper pins 10 and 11 are removed and the molds 8a and 8b are released, the core body 1 is surrounded by the synthetic resin 5 as shown in FIG. Can be obtained.
[0012]
In this example, the gate 9 and the through-hole 6 are each arranged at the center of the valve body. However, the present invention is not limited to this, and the object of the present invention can be achieved if each is arranged on the opposite surface.
Further, although the bearing portions 3 and 4 are integrated with the core metal 1, the bearing portions 3 and 4 may be formed separately and the bearing portions may be joined to the core metal 1.
The cored bar can also be applied to a cored body as in the conventional example described above.
[0013]
【The invention's effect】
Therefore, according to the manufacturing method of a butterfly valve for resin valve body definitive to the present invention, since the molten resin around the back side of the core periphery by the flow from the flow and the core outer circumference through the communication hole, the weld portion produced by resin molding Because the resin is guided and buried inside the cavity through the through-hole on the back side of the outer periphery of the core metal, burn-off cracks due to the weld part do not remain on the surface of the valve body product, and the valve body has a stable quality Can be obtained.
[0014]
Further, since the valve body of the butterfly valve in the present invention has few cutting parts and can be stably formed by a simple process, an inexpensive butterfly valve body can be mass-produced.
[Brief description of the drawings]
FIG. 1 is a partially cutaway front view showing a valve body of a butterfly valve according to the present invention.
FIG. 2 is a plan view of FIG.
FIG. 3 is a cross-sectional view taken along line AA in FIG.
4 is a cross-sectional view taken along line BB in FIG. 1. FIG.
FIG. 5 is a partially cutaway front view of the cored bar in FIG. 1;
6 is a cross-sectional view taken along line CC in FIG.
7 is a cross-sectional view taken along the line DD of FIG.
FIG. 8 is an explanatory cross-sectional view showing a state in which a resin valve body according to the present invention is molded.
[Explanation of symbols]
1 cored bar
1b Front side
1c Back side 2 Center hole 5 Synthetic resin 6 Through hole
7 Communication hole 9 Resin injection gate

Claims (2)

A valve body of a butterfly valve in which a metal core is surrounded by a synthetic resin, and the metal core is inserted into a mold having a resin injection gate, and the core metal has a surface located on the side opposite to the resin injection gate. to penetrations and the center hole inside of the core to the front and back of the through holes and the metal core periphery to form a communication hole for connecting with resin, the resin flow injected from the resin injection gate, the communication hole and the core A weld that is branched to two or more locations that pass through the outer periphery and travels to the outer peripheral surface of the metal core on the side opposite to the injection gate to form a weld portion that is a confluence of the resin and is formed near the central portion of the metal core It said through by embeddability inside the center hole of the metal core from the hole, the manufacturing method of the butterfly valve valve element, characterized in that the weld portion joined was not allowed to remain on the surface of the valve body.   The method for manufacturing a valve body for a butterfly valve according to claim 1, wherein a taper pin inserted from above and below the mold is inserted into the center hole of the core metal and filled with molten resin in this state.

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