Method for joining metal fittings to flexible metal pipes

Abstract

To exactly and surely join a connecting metal fixture to a metal-made flexible tube at high work efficiency without causing the deterioration damage of the tube.SOLUTION: In a method for joining a nipple (connecting metal fixture) 10 to an axial end part of a metal-made flexible tube 1 having a tube 2 formed into a bellows shape, and a cylindrical blade 3 for covering an external peripheral side of the tube 2, a cylindrical ring 4 is fit into an external periphery of the axial end part of the metal-made flexible tube 1, an axial end part of the blade 3 is gripped between a one-end internal periphery of the ring 4 in the axial direction and a crest part 2a of an end part of the tube 2 in the axial direction by diameter-contracting an axial one end part 4a of the ring 4 by caulking or the like, and at a gripping part of the blade 3, the nipple (connecting metal fixture) 10 is joined to the axial end part of the metal-made flexible tube 1 by welding the ring 4, the tube 2, the blade 3 and an external periphery of an axial one end of the nipple (connecting metal fixture) 10 which is made to abut on the gripping part.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a method for joining a connector to a flexible metal pipe, and more particularly to a method for joining a connector to an axial end of a flexible metal pipe by welding. [Background technology]

[0002] For example, flexible metal tubes are used as flexible joints that connect various fluid pipes that transport fluids. These flexible metal tubes have a core made of a bellows-shaped tube formed by repeatedly forming peaks and valleys in the axial direction, and are covered with a cover material called a braid made by weaving thin steel wires (see, for example, Patent Document 1).

[0003] To both axial ends of such a flexible metal tube, connectors such as flanges and nipples are generally joined by welding to connect the flexible metal tube to other fluid pipes. The following methods have been used to join these connectors to the flexible metal tube.

[0004] That is, a braid covering the outer periphery of a tube of a predetermined length is roughly cut to a length slightly longer than the length of the tube, and then cylindrical rings are fitted onto the outer peripheries of both axial ends of the braid from the outside so that the two fit together, and the ends of the braid are trimmed to be even for welding. Then, after joining the axial ends (opening end ends) of the three components (tube, braid, and ring) by welding, a connecting fitting is butted against these three welded components, and this connecting fitting is further joined to the axial end of the metal flexible tube by welding. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-055901 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the conventional method of joining a connector to a flexible metal tube, the inner diameter of the ring is large relative to the outer diameter of the blade, making it difficult to maintain the blade concentric with the ring. This requires a welding worker to align the ring to the desired position when welding the ring to the blade and tube. Furthermore, the tube or blade may be misaligned on the side where welding begins, resulting in misalignment, and the radial gap between the ring and the blade may become uneven around the circumference on the opposite side. Ultimately, the welding between the ring, blade, and tube may also become uneven around the circumference, making it more likely to result in poor welding. In this case, it is difficult to visually inspect the weld from the outside after welding to confirm the state of penetration of the weld metal around the entire circumference of the blade.

[0007] Furthermore, when welding three parts with different shapes and configurations, i.e., a tube which is a thin corrugated tube, a braid which is a braided metal wire, and a ring which is a thick plate pipe, it is difficult to melt the weld metal into these three parts at the same time to join the three parts, and the welding quality largely depends on the experience and skill of the welding worker, which creates the problem of inconsistent welding quality.

[0008] In addition, in the next process, a separate connector is welded to the location where the three components (tube, blade, and ring) were welded together in the previous process. However, because the alignment of the tube and connector is done visually and by eye, there is a possibility that the two may become misaligned, resulting in the connector being joined at an angle relative to the tube. Furthermore, because the connector is welded to the location where the three components (tube, blade, and ring) are welded together, the same location must be welded twice, which increases the number of work steps, reduces work efficiency, and subjects the welded location to two heat cycles. This causes excessive thermal stress due to the welding heat at the welded location, which can lead to deterioration and damage, especially in thin-walled tubes.

[0009] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a method for joining a connector fitting to a metal flexible tube, which can quickly and reliably connect the connector fitting to the end of the metal flexible tube by welding while accurately aligning the centers of each part. [Means for solving the problem]

[0010] In order to achieve the above object, the method for connecting a connector to a metal flexible pipe according to claim 1 comprises: A method for connecting a connector to an axial end of a flexible metal tube, the method comprising: a tube formed into a bellows shape by alternately forming peaks and valleys in the axial direction; and a cylindrical braid covering the entire exterior of the tube, a tube end adjusting step of adjusting the end of the tube so that the peak portion is at the very end; a ring member assembling step of assembling a cylindrical ring member from the outside to the axial end of the metal flexible tube; Material By reducing the diameter of the axial tip end portion of the ring member in the assembled state, the ring member Beyond The inner circumferential side of the end portion is pushed into the end of the tube toward the most extreme valley portion, and the blade is sandwiched between the end of the ring member and the axially inner surface of the most extreme peak portion. Impossible and a welding process in which the end of the connecting fitting, which is the object of connection, is pressed from the outside against the ridge at the very end of the tube, and the end of the connecting fitting, the end of the tube, the end of the blade, and the tip of the ring member are welded around the entire circumference.

[0011] According to the above method, the diameter of the tip of the ring member is reduced by, for example, crimping, and the tip is stabilized by being inserted into the valley portion at the very end of the tube. At the same time, the blade is sandwiched between the inner peripheral edge of the ring member and the peak portion at the very end of the tube. Therefore, no radial gap occurs between the ring member and the blade, and stable contact is ensured along the entire circumference. Therefore, by welding in this state, the molten metal penetrates the weld uniformly along the entire circumference, allowing the joining fitting to be reliably and firmly joined to the axial end of the metal flexible tube.

[0012] In addition, it is easy for workers to align the three parts, and subsequent welding work can also be done accurately, ensuring high welding quality without requiring extensive experience or high skill on the part of the worker.Furthermore, the fitting is connected to the flexible metal tube by simultaneously welding four parts only once: the outer periphery of the connection end of the fitting, the braid that makes up the flexible metal tube, the ring member that sandwiches it, and the tube.This reduces the number of work steps, improves work efficiency, and effectively prevents deterioration and damage to thin-walled tubes due to excessive heat history. [Effects of the Invention]

[0013] According to the present invention, the four components of the metal flexible tube, namely the tube, blade, and ring member, which have different shapes and configurations, and the connecting fitting are precisely aligned and then joined simultaneously in a single welding operation, thereby achieving the effect of accurately and reliably joining the connecting fitting to the metal flexible tube with high work efficiency and without causing deterioration or damage to the tube. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a partial cross-sectional view cut in half showing a state before a ring member at a connection end of a metal flexible tube that is a connection target in a connection method according to an embodiment of the present invention is crimped; [Figure 2]10 is a partial cross-sectional view cut in half showing a state after a ring member at a connection end of a metal flexible tube, which is a connection target of a connection method according to an embodiment of the present invention, has been crimped. FIG. [Figure 3] 1 is a partial cross-sectional view cut in half showing a state in which a receiving portion is formed on a tube at a connection end of a metal flexible tube that is a connection target of a connection method according to an embodiment of the present invention. [Figure 4] 1 is a partial cross-sectional view cut in half showing a state before a connecting fitting at a connecting end of a flexible metal tube, which is a connection target of a connecting method according to an embodiment of the present invention, is fitted into a receiving portion of the tube. [Figure 5] 1 is a partial cross-sectional view cut in half showing a state in which a connecting fitting at a connecting end of a flexible metal tube, which is a connection target of a connecting method according to an embodiment of the present invention, is fitted into a receiving portion of the tube. [Figure 6] 1 is a partial cross-sectional view cut in half showing a state in which a connecting fitting at a connecting end of a metal flexible tube, which is a connection target of a connecting method according to an embodiment of the present invention, is fitted into a receiving portion of the tube and welded. [Figure 7] FIG. 5 is a partial cross-sectional view for explaining the receiving portion shown in FIGS. 3 and 4. [Figure 8] FIG. 10 is a partial cross-sectional view cut in half showing a bent state of a connection end portion of a tube in a connection method according to another embodiment of the present invention. [Figure 9] 9 is an enlarged explanatory view showing a bent state of the connection end portion of the tube shown in FIG. 8. FIG. [Figure 10] 9 is a partial cross-sectional view cut in half illustrating a welding step according to the embodiment shown in FIG. 8. FIG. [Figure 11] 9 is a partial cross-sectional view cut in half showing a state in which the entire welding step according to the embodiment shown in FIG. 8 has been welded. DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0016] First, the basic structure of a metal flexible tube used as a flexible joint for connecting various fluid pipes for conveying fluids will be described with reference to Fig. 1. Although Figs. 1 to 6 only show one axial end (right end) of the metal flexible tube, the other axial end (left end) of the metal flexible tube is configured in the same way. In the following, only the method of connecting a connector (a nipple in this embodiment (see Figs. 4 to 6)) to one axial end (right end) of the metal flexible tube will be illustrated and described, but because the method of joining the connector to the other axial end (left end) of the metal flexible tube is similar, illustrations and descriptions of this method will be omitted.

[0017] As shown in Fig. 1, a metal flexible tube 1 is configured with a tube 2 formed into a bellows shape by repeatedly forming peaks 2a and valleys 2b alternately in the axial direction, and a cylindrical braid 3 covering the outer periphery of the tube 2. Here, both the tube 2 and the braid 3 are made of stainless steel (SUS), and the braid 3 is configured by braiding multiple metal wires in a mesh pattern, and the braid 3 and the tube 2 can be freely flexed and deformed around their axis.

[0018] As can be seen from FIG. 1 , as a prerequisite step, the end of the tube 2 to be connected is cut and adjusted so that a ridge 2a is present at the very end (tube end adjustment step). Next, in order to connect the connector shown in FIGS. 4 to 6 (a nipple 10 is shown as an example in this embodiment) to the axial end of the metal flexible tube 1, as shown in FIG. 1 , a cylindrical ring member 4 with an inner diameter slightly larger than the outer diameter of the braid 3 is inserted into both axial ends of the braid 3 of the metal flexible tube 1 (only the right axial end is shown in FIG. 1 ) and assembled with the distal end of the metal flexible tube 1 (ring member assembly step). At this time, as described above, the ridge 2a is located at the very end of the axial end of the tube 2. The braid 3 has a length that covers the entire length of the tube 2, and in this embodiment, the axial end is cut to a length that slightly protrudes beyond the outer axial end of the tube 2. In this embodiment, the ring member 4 is made of stainless steel (SUS).

[0019] Next, as shown in Fig. 2, one axial end 4a of the ring member 4 (the right end on the open end side of the tube 2 in Fig. 2) is crimped by a predetermined length using roller processing or the like to reduce its diameter from the state shown in Fig. 1 (ring member crimping process). As a result, one axial end 4a of the ring member 4 is formed into a tapered cylinder whose diameter gradually reduces toward the outer end opening (toward the right in Fig. 2), and the inner peripheral edge of the open end presses against the outer peripheral surface of the outer end (the right end in Fig. 2) of the blade 3 all around, while being slightly pressed into the valley portion 2b located at the very end of the tube 2 (the first valley portion axially inside the peak portion 2a located at the very end).

[0020] At this time, the blade 3 is sandwiched between the tip of the inner peripheral edge of the open end of the ring member 4 and the inner slope of the outermost peak portion 2a.

[0021] Furthermore, the axial end side (outer end) of the blade 3 is deformed into a tapered cylindrical shape that opens toward the opening side (right side in Figure 2). In this state, no radial gaps are generated between the ring member 4 and the blade 3 or tube 2, and the three components of the ring member 4, blade 3, and tube 2 are reliably and accurately aligned.

[0022] As described above, the three components of the ring member 4, the blade 3, and the tube 2 are reliably and accurately aligned, eliminating the need for workers to align the ring member 4, which was previously required, and reducing the burden on the workers.

[0023] 3, one peak 2a located at the axial end of the tube 2 is press-formed and bent inward of the tube 2 (receiving portion forming step). In this embodiment, the peak 2a is bent at a substantially right angle to form a concave receiving portion 2A at the outer axial end (opening end) of the tube 2.

[0024] 3 and 4 to make it easier to understand the shape of the receiving portion 2A. As shown in the figure, a circular recess is formed at the tip of the tube 2, and as can be seen from Figure 4, the inner diameter φD of this receiving portion 2A is set slightly larger than the outer diameter φd of the cylindrical portion 10A formed at one axial end of the nipple 10, which is the connecting fitting (φD > φd).

[0025] Here, nipple 10 according to this embodiment is a cylindrical member integrally formed with tool engagement portion 10B at its axially intermediate portion, with cylindrical portion 10A having an outer diameter φd formed on one axial side of tool engagement portion 10B (left side in FIG. 4), and male thread portion 10C formed on the outer periphery of the other axial side of tool engagement portion 10B (right side in FIG. 4). Tool engagement portion 10B has an outer diameter shape like a regular hexagonal prism so that it can be engaged with a tool (not shown), such as a wrench, for rotating nipple 10 about its axis. Furthermore, stainless steel (SUS) is used as the material for nipple 10.

[0026] To join the nipple 10 to one axial end (the right end in the illustrated example) of the flexible metal tube 1, as shown in Fig. 5, the outer periphery of one axial end (the left end in Fig. 5) of a cylindrical portion 10A formed at one axial end of the nipple 10 is fitted axially into the inner periphery of a concave receptacle portion 2A formed at the open end of the tube 2 of the flexible metal tube 1. This allows the nipple 10 to be temporarily assembled to the flexible metal tube 1 in a state in which the nipple 10 is accurately aligned with the tube 2, blade 3, and ring member 4, which have already been aligned on the flexible metal tube 1 side. Note that, although the above-mentioned receptacle portion 2A is formed by press working as an example, it can also be formed by pressing the cylindrical portion of the connection side end of the nipple 10 from the outside against the ridge portion 2a at the axial end of the tube 2 to bend the ridge portion 2a inward.

[0027] 5, the outer periphery of the cylindrical portion 10A at one axial end of the nipple 10 is simultaneously welded to one axial end (the right end in FIG. 6) of each of the braid 3 constituting the flexible metal tube 1, the ring member 4 that holds it, and the tube 2, as shown in FIG. 6 (welding step). This allows the nipple 10 to be connected to the axial end (the right end in FIG. 6) of the flexible metal tube 1. As described above, a nipple (not shown) is also joined by welding in a similar manner to the other axial end (the left end) of the flexible metal tube 1.

[0028] As described above, in this embodiment, one axial end 4a of the ring member 4 is crimped to reduce its diameter, and the inner peripheral edge of the open end presses the outer end of the blade 2 around the entire circumference into the valley portion 2b at the axial end of the tube 2, and at the same time sandwiches the blade 3 and presses it against the crest portion 2a. This prevents radial gaps from occurring between the ring member 4, the blade 3, and the tube 2, and ensures that the three components of the ring member 4, the blade 3, and the tube 2 are aligned reliably and accurately, stabilizing the state of the temporary assembly before welding these three components together, eliminating the need for an operator to align the three components and making it possible to subdivide the work.

[0029] Furthermore, one of the ridges 2a at the axial end (open end) of the tube 2 is formed by press molding or the like to form a recessed receiving portion 2A, and the outer periphery of the axial end of the cylindrical portion 10A of the nipple 10, which is the connecting fitting, is fitted into this receiving portion 2A, thereby accurately and reliably aligning the nipple 10 with the tube 2. Therefore, the nipple 10 is not joined at an angle to the axis of the tube 2, and the two are joined while maintaining a concentric state.

[0030] Then, from the above state, the outer periphery of one axial end of the nipple 10 is simultaneously welded to the four components of the flexible metal tube 1: the braid 3, the ring member 4 that holds it, and the axial ends of the tube 2. This allows all of the components to be connected to be connected in a single welding operation. This effectively prevents deterioration and damage to the thin-walled tube 2, which is susceptible to heat, due to excessive thermal history, thereby improving the durability of the tube 2 and, ultimately, the flexible metal tube 1. Furthermore, as described above, the diameter of the one axial end 4a of the ring member 4 is reduced by crimping, eliminating radial gaps between the ring member 4 and the braid 3 or tube 2. This allows the molten metal 20 (see FIG. 6 ) to penetrate the weld uniformly around the entire circumference during welding. This allows the nipple 10 to be reliably and firmly joined to the axial end of the flexible metal tube 1, ensuring high welding quality without requiring extensive experience or high skill from the worker.

[0031] Next, another embodiment will be described with reference to Figures 8 to 11. Note that the same members as those in the above embodiment are given the same reference numerals.

[0032] A feature of the method according to this embodiment is that, before performing the welding process around the entire circumference, the endmost peaks 2a of the tube 2 are bent axially inward along the entire circumference to form a flat surface 2B (flat surface forming process). In other words, the portion that abuts the end face 10D of the connecting end of the nipple 10 becomes the flat surface 2B. This method differs from the above-described embodiment in that a flat surface is formed in a circular shape rather than forming a concave receiving portion 2A as in the above-described embodiment. Figure 9 shows an enlarged view of the end of the tube 2 on which this flat surface 2B is formed. As shown, the endmost peaks 2a are bent axially inward, and the outer surface is flat.

[0033] The entire assembly is then welded with the end face 10D of the nipple 10 in contact with the circular flat surface 2D. Therefore, although the nipple 10 cannot be immersed in the receiving portion 2A, it can be connected regardless of the shape of the connecting end of the connecting fitting. This means that special preparation work is not required for various connection targets. For example, there is no need to cut the connecting fitting to fit the shape of the receiving portion 2A.

[0034] Furthermore, the end surface 10D of the nipple 10 and the circular flat surface 2D of the tube 2 can be brought into stable contact with each other, ensuring stable welding.

[0035] Furthermore, the thickness of the thin tube 2 at the tip end is increased by the flat surface forming process, which improves stability during welding. That is, the occurrence of damage due to heat application can be avoided.

[0036] The flat surface forming step does not necessarily have to be performed after the ring member diameter reducing step, but can also be performed before the ring member diameter reducing step.

[0037] 10, it is also possible to weld the tips of the three components, the ring member 4, the blade 3, and the tube 2, once this flat surface forming process has been performed (the welded parts are shown in black in the figure). In this case, the welding process will not be completed in one welding operation, but there is an advantage in that the welding state of the three components, for example, the penetration state of the blade 3, can be visually checked while performing accurate welding.

[0038] FIG. 11 shows the state where welding of the entire circumference of the ends of the ring member 4, the blade 3, the tube 2 and the nipple 10 has been completed, but it is of course possible to weld these four parts simultaneously.

[0039] In each of the above embodiments, an example has been described in which a nipple 10 is joined as a connecting fitting to a metal flexible tube 1, but the method of the present invention can also be applied to a method of joining any other connecting fitting other than a nipple 10, such as a pipe or a flange lap joint, to a metal flexible tube 1.

[0040] In addition, in the above embodiment, the materials of the tube 2, braid 3, and ring member 4 that constitute the metal flexible tube 1, and the nipple 10 that is a connecting fitting connected to the metal flexible tube 1, are all made of stainless steel (SUS), but any material other than stainless steel (SUS) can be selected for these.

[0041] Furthermore, the present invention is not limited to the application of the above-described embodiments, and it goes without saying that various modifications are possible within the scope of the claims and the technical ideas described in the specification and drawings. [Explanation of symbols]

[0042] 1 Metal flexible tube 2 tubes 2A Tube Receptacle 2a The ridge at the very end of the tube 2b Valley at the end of the tube 3 blades 4 Ring member 4a One axial end of the ring member 10 Nipple (connecting fitting) 10A Nipple cylindrical part 10B Nipple tool engagement part 10C Male thread of nipple 20 Molten Metal φD Inner diameter of receiving part φd: Outer diameter of the cylindrical part of the nipple

Claims

1. A method for connecting a connector to an axial end of a flexible metal tube, the method comprising: a tube formed into a bellows shape by alternately forming peaks and valleys in the axial direction; and a cylindrical braid covering the entire exterior of the tube, a tube end adjusting step of adjusting the end of the tube so that the peak portion is at the very end; a ring member assembling step of assembling a cylindrical ring member from the outside to an axial end portion of the metal flexible tube; a ring member diameter reduction step in which a diameter of a tip end portion of the ring member in an assembled state is reduced in an axial direction, thereby pushing an inner peripheral side of the tip end portion of the ring member toward the most extreme valley portion of the end of the tube, and sandwiching the blade between the end of the ring member and an inner surface in the axial direction of the most extreme peak portion; a welding process in which the end of the connecting fitting, which is the object of connection, is pressed from the outside against the crest at the very end of the tube, and the end of the connecting fitting, the end of the tube, the end of the braid, and the tip of the ring member are welded together around the entire circumference; A method for joining a connector to a metal flexible pipe, comprising:

2. Before the welding step, a receiving portion forming step is performed in which the ridge portion at the very end of the tube is bent inward in the axial direction along the entire circumference to form a receiving portion into which the connection side end of the connecting fitting is fitted, 2. The method for joining a connector to a flexible metal pipe according to claim 1, wherein the welding step is performed with the end of the connector on the connection side housed in the receiving portion.

3. A method for joining a connecting fitting to a metal flexible tube as described in Claim 2, characterized in that the receiving portion forming process is performed by bending the endmost peak portion axially inward from the outside over the entire circumference by press molding.

4. A method for joining a connecting fitting to a metal flexible tube as described in Claim 2, characterized in that the receiving portion forming process is carried out by pressing the connecting side end of the connecting fitting against the outermost ridge portion in the axial direction.

5. Before the welding step, a flat surface forming step is performed in which the ridge portion at the very end of the tube is bent inward in the axial direction along the entire circumference to form a flat surface around the entire circumference against which the end face of the connection side end of the connection fitting abuts; 2. The method for joining a connector to a flexible metal pipe according to claim 1, wherein the welding step is performed with the end face of the connector on the connection side abutting against the flat surface.

Images