Diaphragm valve and method for manufacturing same

Abstract

[Problem] To provide a diaphragm valve in which welding unevenness hardly occurs in a welded portion and sufficient welding strength is secured. [Solution] A diaphragm 10 has a cylindrical part 11 formed in an annular shape and extending along a central axis direction on an inner peripheral edge portion thereof. A valve body 20 has an insertion surface portion 22a inserted into an insertion hole 12 defined by the cylindrical part 11 of the diaphragm 10. The valve body 20 and a tip part 11a of the cylindrical part 11 of the diaphragm 10 are welded over the whole circumference. In the valve body 20, a recessed part 22c into which flows some metal melted by welding is formed in a welding region W with the tip part 11a of the cylindrical part 11 of the diaphragm 10.

Description

Diaphragm valve and manufacturing method thereof

[0001] The present invention relates to a diaphragm valve in which a valve element is connected to a diaphragm that seals a valve chamber, and a method for manufacturing the same.

[0002] A known example of a diaphragm valve in which a valve element is connected to a diaphragm that seals a valve chamber is the diaphragm valve disclosed in Patent Document 1. In this type of diaphragm valve, the diaphragm is connected to the valve element by welding. The outer circumferential surface of the valve element is fitted and inserted into a cylindrical portion formed on the inner circumferential edge of the annular diaphragm, and the tip of the cylindrical portion is joined to the valve element by welding.

[0003] Japanese Patent Application Publication No. 8-219303

[0004] However, when welding the diaphragm and the valve body, when welding the tip of the cylindrical part of the diaphragm to the outer surface of the valve body around the entire circumference, uneven welding is likely to occur, and there is a possibility that sufficient welding strength cannot be ensured.

[0005] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide a diaphragm valve in which welding unevenness is less likely to occur at the welded portion and sufficient welding strength is ensured, and a method for manufacturing the same.

[0006] The diaphragm valve of the present invention is a diaphragm valve including a valve body and a diaphragm connected to the valve body, wherein the diaphragm is formed in an annular shape and has a cylindrical portion at its inner peripheral edge extending along the central axis direction, the valve body has an insertion surface portion that is inserted into an insertion hole defined by the cylindrical portion of the diaphragm, the valve body and the tip end of the cylindrical portion of the diaphragm are welded together around the entire circumference, and the valve body has a recess formed in the welded area with the tip end of the cylindrical portion of the diaphragm into which some of the metal melted by welding flows.

[0007] Preferably, the insertion surface of the valve body is fitted into and inserted into the insertion hole of the diaphragm, and they are in surface contact with each other.

[0008] The method for manufacturing a diaphragm valve of the present invention is a method for manufacturing a diaphragm valve including a valve body and a diaphragm connected to the valve body, wherein the diaphragm is formed in an annular shape and has a cylindrical portion at its inner peripheral edge portion extending along the central axis direction, the valve body has an insertion surface portion, a convex portion formed around the entire circumference so as to protrude from the insertion surface portion, and a concave portion formed adjacent to the convex portion, the insertion surface portion of the valve body is inserted into an insertion hole defined by the cylindrical portion of the diaphragm, a tip end of the cylindrical portion of the diaphragm is abutted against the convex portion, and the valve body and the tip end of the cylindrical portion of the diaphragm are welded together around the entire circumference while guiding a portion of the valve body and the diaphragm that has been melted by welding into the concave portion.

[0009] Preferably, during the welding, the protrusion of the valve body is melted and removed from the insertion surface portion.

[0010] More preferably, the tip of the cylindrical portion of the diaphragm, the convex portion of the valve body, and the concave portion of the valve body are welded by irradiating them with a laser beam.

[0011] Preferably, the insertion surface of the valve body is fitted into the insertion hole of the diaphragm so that they come into surface contact with each other.

[0012] According to the present invention, the above-described configuration makes it possible to obtain a diaphragm valve in which welding unevenness is unlikely to occur at the welded portion and sufficient welding strength is ensured.

[0013] 2A is a cross-sectional view of a diaphragm valve according to one embodiment of the present invention. FIG. 2B is a cross-sectional view of a diaphragm according to one embodiment of the present invention. FIG. 2C is a cross-sectional view of a valve body according to one embodiment of the present invention. FIG. 2D is an enlarged cross-sectional view of the stem of the valve body of FIG. 2A. FIG. 2E is a partially enlarged cross-sectional view showing a state in which the valve body has been inserted into an insertion hole in the diaphragm. FIG. 2F is an enlarged cross-sectional view schematically showing a state in which the tip of the cylindrical part of the diaphragm and the valve body are laser welded. FIG. 2G is a partially enlarged cross-sectional view schematically showing a state after welding the diaphragm and the valve body.

[0014] Figure 1 shows a diaphragm valve according to this embodiment. The diaphragm valve includes a body 1, a bonnet 3, a stem 4, a handle 5, a diaphragm 10, and a valve element 20, with the diaphragm 10 sealing a valve chamber 1c. In Figure 1, reference numeral 7 denotes a bonnet insert provided between the diaphragm 10 and the bonnet 3, 25 denotes a seat attached to the valve element 20, 9 denotes an O-ring that seals between the bonnet 3 and the stem 4, 30 denotes an open / close indicator plate, 31 denotes a nameplate, and 32 denotes a set screw.

[0015] The body 1 is formed in a block shape from a metal such as a stainless steel alloy, with an inlet flow path 1a and an outlet flow path 1b formed on both sides, and a valve chamber 1c formed in the upper part that is open at the top and communicates with the inlet flow path 1a and the outlet flow path 1b. The bottom of the valve chamber 1c is tapered, and the portion near the opening of the inlet flow path 1a forms a valve seat 1d.

[0016] The diaphragm 10 is formed by press-molding a thin metal plate such as a stainless alloy, and as will be described later, its inner peripheral edge is welded to the outer periphery of the valve body 20. The diaphragm 10 is also hermetically sandwiched between the end face of the body 1 and the bonnet insert 7 by tightening the bonnet 3, whose outer peripheral surface is threadedly fitted to the body 1, against the body 1.

[0017] The bonnet 3 is made of a metal such as a stainless alloy and has a generally cylindrical shape. The outer circumferential surface of the bonnet 3 is threadedly engaged with the body 1, and the stem 4 is threadedly engaged with the inner circumferential surface of the bonnet 3.

[0018] The stem 4 is made of a metal such as a stainless steel alloy, and its outer periphery is threadedly engaged with the bonnet 3, allowing it to rotate and move up and down relative to the bonnet 3. A handle 5 is attached to the upper end of the stem 4 via a setscrew 32. The connecting portion 23 of the valve body 20 is rotatably engaged with the lower end of the stem 4.

[0019] The valve element 20 is made of metal such as stainless steel alloy and has a large-diameter disk-shaped seat portion 21 with an annular seat 25 attached to its underside that abuts against and separates from the valve seat 1d, a shaft portion 22 that extends upward from the seat portion 21 and is connected to the diaphragm 10, and a disk-shaped connecting portion 23 that is provided at the upper end of the shaft portion 22 and engages with the stem 4 so as to be rotatable but immovable in the axial direction. The seat 25 is made of resin such as fluororesin and is formed in an annular shape, and is attached to the seat portion 21 by caulking.

[0020] In the above-mentioned diaphragm valve, when the stem 4 is raised and lowered by rotating the handle 5, the valve body 20 rises and falls, and the diaphragm 2 also elastically deforms in the vertical direction, causing the seat 25 to abut against and separate from the valve seat 1d, thereby opening and closing the inlet flow path 1a and the outlet flow path 1b.

[0021] Next, the structures of the diaphragm 10 and valve body 20 before welding will be described with reference to Figures 2, 3A, and 3B. As shown in Figure 2, the diaphragm 10 is press-molded and has a cylindrical portion 11 extending along the central axis at its inner peripheral edge, with the cylindrical portion 11 defining an insertion hole 12 into which an insertion surface portion 22a of the valve body 20, described below, is fitted and inserted. A flat clamping portion 13 is formed at the outer peripheral edge of the diaphragm 10 and is clamped between the end face of the body 1 and the bonnet insert 7.

[0022] As shown in Fig. 3A, the valve element 20 has a seat portion 21, a shaft portion 22, and a connecting portion 23. As shown in Fig. 3B, the outer peripheral surface of the shaft portion 22 has an insertion surface portion 22a that is inserted into the insertion hole 12 of the diaphragm 10. The valve element 20 further has a convex portion 22b formed around the entire circumference and protruding from the insertion surface portion 22a, and a concave portion 22c formed around the entire circumference adjacent to the convex portion 22b. The convex portion 22b is chamfered on the side of the concave portion 22c. The outer diameter of the smallest diameter portion at the bottom of the concave portion 22c is smaller than the outer diameter of the insertion surface portion 22a.

[0023] Next, a method for assembling the diaphragm 10 and the valve body 20 will be described. First, as shown in Figure 4A, the insertion surface portion 22a of the valve body 20 is inserted into the insertion hole 12 of the diaphragm 10. The end face of the tip portion 11a of the cylindrical portion 11 of the diaphragm 10 abuts against the convex portion 22b of the valve body 20, thereby completing the positioning of the diaphragm 10 relative to the valve body 20. At this time, the insertion surface portion 22a of the valve body 20 is fitted and inserted into the insertion hole 12 of the diaphragm 10, and the dimensions are set so that the insertion hole 12 and the insertion surface portion 22a are in surface contact.

[0024] Next, as shown in Figure 4B, laser light LB is irradiated onto the tip 11a of the cylindrical portion 11 of the diaphragm 10, the convex portion 22b of the valve body 20, and the concave portion 22c of the valve body 20, to weld the cylindrical portion 11 of the diaphragm 10 and the valve body 20 over the entire circumference. Welding is performed by focusing light transmitted from a laser oscillator (not shown) using a lens built into a laser processing head (not shown) to a state suitable for processing, and outputting it as laser light LB. The incident angle of the laser light LB is inclined by approximately 3 degrees from the vertical direction.

[0025] This welding melts the tip end 11a of the cylindrical portion 11 of the diaphragm 10 and a portion of the valve element 20, including the protrusion 22b of the valve element 20, along the entire circumference, and some of the molten metal is guided to the bottom of the recess 22c of the valve element 20, as shown in FIG. 4C . Note that the dotted line in FIG. 4C indicates the shape before welding. Because the recess 22c is adjacent to the protrusion 22b, the molten metal naturally flows to the bottom of the recess 22c. Furthermore, the protrusion 22b of the valve element 20 melts and disappears from the insertion surface 22a. In this way, a welded region W is formed where the tip end 11a of the cylindrical portion 11 of the diaphragm 10 and the valve element 20 are welded together. After the tip end 11a of the cylindrical portion 11 of the diaphragm 10 and the valve element 20 are joined along the entire circumference by laser welding, the surface of the welded region is finished by electrolytic polishing.

[0026] According to this embodiment, by guiding a portion of the molten metal during welding to the recess 22c of the valve body 20, uneven welding in the circumferential direction is suppressed and the weld strength is improved. If the recess 22c were not present, excess molten metal would have no escape route and would be prone to uneven welding. However, by forming the recess 22c adjacent to the protrusion 22b, the excess molten metal naturally flows into the recess 22c, suppressing uneven welding. Furthermore, by forming the protrusion 22b on the valve body 20, the contact area between the tip end 11a of the cylindrical portion 11 of the diaphragm 10 and the valve body 20 is increased, thereby increasing the weld strength.

[0027] It should be noted that the present invention is not limited to the above-described embodiments. Those skilled in the art can make various additions and modifications within the scope of the present invention. In the above-described embodiments, an example was given in which the present invention was applied to a manual diaphragm valve, but the present invention can be applied to any valve that includes a valve body connected to a diaphragm that seals a valve chamber.

[0028] REFERENCE SIGNS LIST 1: Body 1a: Inlet flow passage 1b: Outlet flow passage 1c: Valve chamber 1d: Valve seat 3: Bonnet 4: Stem 5: Handle 7: Bonnet insert 9: O-ring 10: Diaphragm 11: Cylindrical portion 11a: Tip portion 12: Insertion hole 13: Clamping portion 20: Valve body 21: Seat portion 22: Shaft portion 22a: Insertion surface portion 22b: Convex portion 22c: Concave portion 23: Connecting portion 30: Open / close indicator plate 31: Nameplate 32: Set screw LB: Laser light W: Welding area

Claims

1. A diaphragm valve including a valve body and a diaphragm connected to the valve body, wherein the diaphragm is formed in an annular shape and has a cylindrical portion extending along a central axis direction at its inner peripheral edge, the valve body has an insertion surface portion to be inserted into an insertion hole defined by the cylindrical portion of the diaphragm, the valve body and a tip end of the cylindrical portion of the diaphragm are welded together around the entire circumference, and the valve body has a recess formed in the welded area with the tip end of the cylindrical portion of the diaphragm into which some of the metal melted by welding flows.

2. A diaphragm valve as set forth in claim 1, wherein the insertion surface of said valve body is fitted and inserted into the insertion hole of said diaphragm, so that they are in surface contact with each other.

3. A method for manufacturing a diaphragm valve including a valve body and a diaphragm connected to the valve body, wherein the diaphragm is formed in an annular shape and has a cylindrical portion extending along the central axis direction at its inner peripheral edge, and the valve body has an insertion surface portion, a convex portion formed around the entire circumference so as to protrude from the insertion surface portion, and a concave portion formed adjacent to the convex portion, the method comprising the steps of: inserting the insertion surface portion of the valve body into an insertion hole defined by the cylindrical portion of the diaphragm; bringing a tip end of the cylindrical portion of the diaphragm into contact with the convex portion; and welding the valve body and the tip end of the cylindrical portion of the diaphragm together around the entire circumference while guiding a portion of the valve body and the diaphragm that have been melted by welding into the concave portion.

4. The method for manufacturing a diaphragm valve according to claim 3, wherein the protruding portion of the valve body is melted and removed from the insertion surface portion during the welding.

5. A method for manufacturing a diaphragm valve as set forth in claim 3 or 4, wherein the tip of the cylindrical portion of the diaphragm, the convex portion of the valve body, and the concave portion of the valve body are welded by irradiating them with laser light.

6. A method for manufacturing a diaphragm valve as set forth in claim 3, wherein the insertion surface portion of the valve body is fitted into the insertion hole of the diaphragm so as to bring them into surface contact with each other.

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