Double tapered part manufacturing method

Abstract

To form a double tapered part from an outer pipe and an inner pipe which have a small diameter end part and a large diameter end part at both ends of a tapered part respectively without requiring complex control for locus and / or attitude of the outer pipe and / or the inner pipe.SOLUTION: An assembly of an outer pipe and an inner pipe of which large diameter end parts are coaxially maintained and sandwich an elastic member, whereby a positional relationship between which is determined, is set to first holding means (first process), then, the assembly is set to second holding means separate from the first holding means in the state that a small diameter end part of the outer pipe and a small diameter end part of the inner pipe are coaxial with each other (second process), and further, by diameter reduction of the small diameter end part of the outer pipe and / or diameter expansion of the small diameter end part of the inner pipe, both are put together and fixed (third process). At least a part of a tapered part and the small diameter end part of the outer pipe are larger compared to a conventional one, and / or at least a part of a tapered part and the small diameter end part of the inner pipe is smaller compared to the conventional one at a point of time before the third process so that the outer pipe and the inner pipe do not interfere with each other in the processes.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a double tapered section. [Background technology]

[0002] Containers for passing or storing fluids inside generally have a cylindrical body and small-diameter ends (connection portions) at both ends for connecting to pipes, etc. It is also common to have a tapered portion with a gradually changing diameter (hereinafter sometimes referred to as a "tapered portion") interposed between the small-diameter end and the body. In particular, when attempting to pass and / or store a fluid inside the body while maintaining the temperature of the fluid, the tapered portions on the inlet and / or outlet sides of the body and the body have a double structure, and a gap is provided between the outer tube and the inner tube to ensure heat retention.

[0003] For example, Patent Document 1 (JP 2003-531994 A) discloses an exhaust gas device for exhaust gas equipment that includes a housing in which the inlet and outlet tapered sections have a double structure (with a gap between them). In manufacturing such a tapered section with a double structure (hereinafter, sometimes referred to as a "double tapered section"), an inner pipe (with a small diameter end, a tapered section, and a large diameter end) that is smaller than the outer pipe but has a similar shape is inserted inside the outer pipe (with a small diameter end, a tapered section, and a large diameter end).

[0004] In the double tapered portion disclosed in Patent Document 1, the small diameter end and the large diameter end are formed coaxially in both the outer tube and the inner tube, so that the inner tube can be inserted into the outer tube without interfering with each other. Even if the small diameter end and the large diameter end are not formed coaxially, depending on the configuration of the outer tube and the inner tube, it may be possible to insert the inner tube into the outer tube without interfering with each other.

[0005] For example, as illustrated in FIG. 8 , if the axis Ax12 of the small diameter end 12 of the outer pipe 10 and the axis Ax13 of the large diameter end 13 are parallel, and the axis Ax22 of the small diameter end 22 of the inner pipe 20 and the axis Ax23 of the large diameter end 23 are parallel, and further, when the outer pipe 10 and the inner pipe 20 form an assembly 40 having a double taper portion Pa as illustrated in FIG. 8( d ), the small diameter end 12 of the outer pipe 10 and the small diameter end 22 of the inner pipe 20 are coaxially arranged, and the large diameter end 13 of the outer pipe 10 and the large diameter end 23 of the inner pipe 20 are coaxially arranged, then the inner pipe 20 can be inserted into the outer pipe 10 in a direction parallel to the above-mentioned axes without interfering with each other, as illustrated in FIG. 8( c ). FIG. 8(e) is an enlarged view of a portion Pb surrounded by a thick broken line in FIG. 8(d).

[0006] As shown in Figure 8(e), the small diameter end 22 of the inner pipe 20 is inserted inside the small diameter end 12 of the outer pipe 10, with the small diameter end 22 of the inner pipe 20 slightly protruding from the small diameter end 12 of the outer pipe 10. This arrangement is suitable for joining the outer pipe 10 and the inner pipe 20 at their small diameter ends by means of welding or the like. As shown in Figure 8(b), an elastic member 30 is depicted on the outer peripheral surface of the large diameter end 23 of the inner pipe 20, sandwiched between the large diameter end 13 of the outer pipe 10 and the large diameter end 23 of the inner pipe 20 to maintain a predetermined positional relationship between the outer pipe 10 and the inner pipe 20.

[0007] On the other hand, when the axis of the small diameter end and the axis of the large diameter end of the outer tube and / or inner tube intersect at a predetermined angle or are in a geometrically twisted relationship (i.e., when the axis of the small diameter end and the axis of the large diameter end are neither coaxial nor parallel), there may be a location where the small diameter end of the outer tube interferes with the insertion trajectory of the small diameter end of the inner tube (hereinafter, this may be referred to as a "negative angle portion").

[0008] For example, in the outer pipe 10 and inner pipe 20 illustrated in Figures 9(a) and 9(b), respectively, the axis of the small diameter end is slightly tilted clockwise and toward the front of the drawing relative to the axis of the large diameter end (which is why the opening of the small diameter end is depicted in Figure 9). In other words, in the examples illustrated in Figures 9(a) and 9(b), the axis of the small diameter end and the axis of the large diameter end are in a geometrically twisted relationship in both the outer pipe 10 and the inner pipe 20.

[0009] For the outer tube 10 and inner tube 20 configured as described above, when an attempt is made to insert the inner tube 20 into the outer tube 10 while maintaining a coaxial positional relationship between the large-diameter end of the outer tube 10 and the large-diameter end of the inner tube 20 (i.e., in a direction parallel to the axes of the large-diameter ends of the outer tube 10 and the inner tube 20), interference (hereinafter sometimes referred to as "negative angle interference") tends to occur in the negative angle portion (the portion Pc surrounded by the thick dashed line in Figure 9(c)). Figure 9(d) is an enlarged view of the negative angle portion Pc, showing a state in which the small-diameter end 22 of the inner tube 20 comes into contact with the base-end portion of the small-diameter end 12 of the outer tube 10 (the portion Pd surrounded by the thick dashed line), preventing the inner tube 10 from being inserted to the desired position inside the outer tube 10.

[0010] When the axis of the small diameter end and the axis of the large diameter end of the outer tube and / or the inner tube are neither coaxial nor parallel, it is difficult to avoid negative angular interference when inserting the inner tube into the outer tube, making this a difficult task in the manufacturing process. Such a difficult task requires, for example, complex control of the trajectory and / or posture of the outer tube and / or the inner tube during the process of inserting the inner tube into the outer tube, but such control can lead to problems such as an increase in the complexity and size of manufacturing equipment and a decrease in production efficiency.

[0011] Furthermore, when the degree of negative angle interference is large (hereinafter, sometimes referred to as "large negative angle"), it may not be possible to insert the inner pipe into the outer pipe even with the complex control described above (i.e., it may not be possible to manufacture a double tapered portion). Furthermore, even if it is possible to insert the inner pipe into the outer pipe while avoiding negative angle interference, it is difficult to forcefully press the small diameter end of the inner pipe into the small diameter end of the outer pipe from the body side. Thus, when the axis of the small diameter end and the axis of the large diameter end of the outer pipe and / or inner pipe are neither coaxial nor parallel, it is difficult to press the small diameter end of the inner pipe into the small diameter end of the outer pipe.

[0012] On the other hand, from the standpoint of simplifying manufacturing equipment and improving production efficiency, for example, it is preferable to insert the inner tube into the outer tube by simple control of the trajectory and posture of the outer tube and / or inner tube, such as by moving the inner tube linearly only in the axial direction of the large diameter end, without requiring complex control of the trajectory and / or posture of the outer tube and / or inner tube during the process of inserting the inner tube into the outer tube.

[0013] Therefore, Patent Document 2 (JP 2001-280128 A) discloses a method in which the diameter difference between the small diameter end of the outer tube and the end of the inner tube is made relatively large, and after the end of the inner tube is inserted into the small diameter end of the outer tube, the small diameter end of the outer tube is reduced in diameter or the end of the inner tube is expanded in diameter to bring the two into tight contact. However, there is a natural limit to the amount of expansion and reduction of the small diameter end of the inner tube after insertion. Therefore, there is also a limit to how large the diameter difference between the small diameter end of the outer tube and the end of the inner tube can be. As a result, for example, when the negative angle is large, it is difficult to avoid negative angle interference simply by providing a diameter difference between the small diameter end of the outer tube and the end of the inner tube under simple control of the trajectory and posture of the outer tube and / or inner tube.

[0014] Furthermore, the gap between the outer tube and the inner tube is provided for the purpose of ensuring heat retention, and the gap between the outer tube, which includes the small diameter end, the tapered portion, and the large diameter end, and the inner tube is small throughout. Therefore, it is even more difficult to insert the small diameter end of the inner tube in a predetermined position inside the small diameter end of the outer tube in a predetermined orientation while avoiding negative angular interference, for example, by simply linearly moving the large diameter ends of the outer tube and the inner tube in the axial direction. This is all the more difficult when, for example, it is necessary to make the double tapered portion as compact as possible due to installation space constraints, etc. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] Special Publication No. 2003-531994 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-280128 Summary of the Invention [Problem to be solved by the invention]

[0016] As described above, there is a need in the art for a technology that enables the formation of a double tapered portion without requiring complex control of the trajectory and / or posture of the outer tube and / or inner tube during the process of inserting an inner tube having a small diameter end and a large diameter end at both ends of a tapered portion into an outer tube having a small diameter end and a large diameter end at both ends of a tapered portion. [Means for solving the problem]

[0017] Therefore, as a result of extensive research, the inventors have found that the above problem can be solved by first setting an assembly in a first holding means, in which the large diameter ends of the outer tube and inner tube are maintained coaxially and the positional relationship between the outer tube and inner tube is determined by sandwiching an elastic member (first step), then setting the assembly in a second holding means separate from the first holding means with the small diameter end of the outer tube and the small diameter end of the inner tube coaxial with each other (second step), and further fixing the two in close contact by reducing the diameter of the small diameter end of the outer tube and / or expanding the diameter of the small diameter end of the inner tube (third step).

[0018] Specifically, the method for manufacturing a double tapered portion according to the present invention (hereinafter sometimes referred to as the "method of the present invention") involves introducing an inner tube having a small diameter end and a large diameter end at both ends of a tapered portion into an outer tube having a small diameter end and a large diameter end at both ends of a tapered portion, tightly fixing the small diameter end of the outer tube to the small diameter end of the inner tube, and providing a gap between the outer tube and the inner tube at the tapered portion and the large diameter end.

[0019] The method of the present invention comprises the following first, second and third steps.

[0020] The first step is a step of achieving a first state in which a first assembly, which is an assembly of an outer pipe and an inner pipe, is set in a first holding means that holds at least the large-diameter end of the inner pipe. The first assembly is formed by introducing the inner pipe from its large-diameter end into the interior of the outer pipe, with the small-diameter end of the inner pipe at the leading edge, while maintaining the large-diameter ends of the outer pipe and the inner pipe coaxially. In the first assembly, at least a portion of the small-diameter end of the inner pipe reaches the inside of the small-diameter end of the outer pipe, and the positional relationship between the outer pipe and the inner pipe is determined by sandwiching an elastic member, which is an elastically deformable member, between the inner circumferential surface of the large-diameter end of the outer pipe and the outer circumferential surface of the large-diameter end of the inner pipe.

[0021] The second step is a step of achieving a second state in which the small diameter end of the outer tube and the small diameter end of the inner tube that constitute the first assembly are coaxial with each other, and the small diameter end side of the first assembly is set in a second holding means that is separate from the first holding means.

[0022] The third step is a step of achieving a third state in which the small diameter end of the outer tube and the small diameter end of the inner tube are tightly fixed together by reducing the diameter of the small diameter end of the outer tube and / or expanding the diameter of the small diameter end of the inner tube, thereby forming a second assembly.

[0023] Furthermore, in the method of the present invention, the outer pipe and the inner pipe are configured so that they do not interfere with each other in steps 1 and 2. Specifically, the diameter of at least a portion of the tapered portion and the small diameter end of the outer pipe in the first state is larger than the diameter of at least a portion of the tapered portion and the small diameter end of the outer pipe in the third state, to the extent that the outer pipe and the inner pipe do not interfere with each other in steps 1 and 2. Alternatively, or in addition to the above, the diameter of at least a portion of the tapered portion and the small diameter end of the inner pipe in the first state is smaller than the diameter of at least a portion of the tapered portion and the small diameter end of the inner pipe in the third state.

[0024] The method of the present invention having the above-mentioned configuration is particularly effective when it is difficult to avoid interference at a negative angle (negative angle interference) when introducing the inner pipe into the outer pipe because the axis of the small diameter end and the axis of the large diameter end are neither coaxial nor parallel, as described above. Therefore, in one preferred embodiment of the method of the present invention, the axis of the small diameter end and the axis of the large diameter end of the outer pipe and / or the inner pipe intersect at a predetermined angle or are in a geometrically twisted relationship.

[0025] Incidentally, when joining the outer pipe and the inner pipe at their small diameter ends by welding or other means after the third step, it is advantageous for the small diameter end of the inner pipe to protrude from the small diameter end of the outer pipe. In this way, it may be necessary to adjust the axial distance (tip distance) between the tip end surface of the small diameter end of the outer pipe and the tip end surface of the small diameter end of the inner pipe depending on the secondary processing performed after the third step. Therefore, in another preferred embodiment of the method of the present invention, in the second step, the inner pipe is pressed from the large diameter end side toward the small diameter end side of the small diameter end of the inner pipe by the first holding means while maintaining the second state described above. This causes the tip end surface of the small diameter end of the inner pipe to protrude from the tip end surface of the small diameter end of the outer pipe by a predetermined first distance in the axial direction of the small diameter end of the inner pipe.

[0026] Additionally, in order to manufacture a double tapered portion having high dimensional accuracy using the method of the present invention, it is preferable that the holding postures of the outer tube and inner tube subjected to the method of the present invention be uniquely determined. Therefore, in another preferred embodiment of the method of the present invention, a first mechanism configured to uniquely determine a first index, which is the posture of the outer tube in the rotation direction about the axis of the large diameter end of the outer tube, is configured in a pair of the first holding means and the outer tube. Furthermore, a second mechanism configured to uniquely determine a second index, which is the posture of the inner tube in the rotation direction about the axis of the large diameter end of the inner tube, is configured in a pair of the first holding means and the inner tube. In addition, the first index and second index of the first assembly are achieved by the first mechanism and the second mechanism, respectively. [Effects of the Invention]

[0027] As described above, in the method of the present invention, the large diameter end of a first assembly, which is composed of an outer tube, an inner tube, and an elastic member with a fixed positional relationship, is set in a first holding means (a first state is achieved by the first step), then the small diameter end of the first assembly is set in a second holding means separate from the first holding means with the small diameter end of the outer tube and the small diameter end of the inner tube coaxial with each other (a second state is achieved by the second step), and then the small diameter end of the outer tube is reduced in diameter and / or the small diameter end of the inner tube is expanded in diameter to tightly contact and fix the two together (a third state is achieved by the third step).

[0028] Additionally, in the method of the present invention, the outer pipe and the inner pipe are configured so that they do not interfere with each other in steps 1 and 2. Specifically, the diameter of at least a portion of the tapered portion and the small diameter end of the outer pipe in the first state is larger than the diameter of at least a portion of the tapered portion and the small diameter end of the outer pipe in the third state, to the extent that the outer pipe and the inner pipe do not interfere with each other in steps 1 and 2. Alternatively, or in addition to the above, the diameter of at least a portion of the tapered portion and the small diameter end of the inner pipe in the first state is smaller than the diameter of at least a portion of the tapered portion and the small diameter end of the inner pipe in the third state.

[0029] Therefore, according to the method of the present invention, a double tapered section can be formed without requiring complex control of the trajectory and / or posture of the outer and / or inner tube during the process of introducing an inner tube having a small-diameter end and a large-diameter end at both ends of the tapered section into an outer tube having a small-diameter end and a large-diameter end at both ends of the tapered section. As a result, problems such as increased complexity and size of the manufacturing equipment and reduced production efficiency can be avoided. This method of the present invention is particularly effective when, as described above, it is difficult to avoid negative angular interference during the process of introducing the inner tube into the outer tube because the axes of the small and large-diameter ends are neither coaxial nor parallel.

[0030] Furthermore, in a preferred embodiment of the method of the present invention, in the second step, while maintaining the second state described above, the first holding means presses the inner pipe from the large diameter end toward the small diameter end in the axial direction of the small diameter end of the inner pipe. This allows the tip surface of the small diameter end of the inner pipe to protrude from the tip surface of the small diameter end of the outer pipe by a predetermined first distance in the axial direction of the small diameter end of the inner pipe. This configuration is suitable, for example, when the outer pipe and the inner pipe are joined at their small diameter ends by means of welding or the like after the third step.

[0031] In addition, in a preferred embodiment of the method of the present invention, a first mechanism and a second mechanism are provided that are configured to uniquely determine the first and second indexing of the outer tube and the inner tube by the first holding means, and therefore, according to this embodiment, the positional relationship between the outer tube and the inner tube can be accurately controlled.

[0032] Other objects, other features and attendant advantages of the present invention will be readily apparent from the following description of the embodiments of the present invention which will be given with reference to the drawings. [Brief explanation of the drawings]

[0033] [Figure 1] 1 is a flowchart illustrating the flow of each step included in a method (first method) for manufacturing a double tapered portion according to a first embodiment of the present invention. [Figure 2] 10A and 10B are schematic diagrams illustrating a configuration in which the small diameter end portion of the outer tube and at least a part of the adjacent tapered portion are formed to have a diameter larger than the original shape. [Figure 3] 3 is a schematic diagram illustrating the change in shape of the outer tube and inner tube constituting the first assembly and the movement of the first holding means and second holding means as the processing progresses from the first step to the third step included in the first method using the outer tube and inner tube illustrated in FIG. [Figure 4] 10 is a schematic diagram illustrating a configuration in which the small diameter end portion of the inner tube and at least a part of the adjacent tapered portion are formed to have a diameter smaller than the original shape. FIG. [Figure 5]5 is a schematic diagram illustrating the change in shape of the outer tube and inner tube constituting the first assembly and the movement of the first holding means and second holding means as the processing progresses from the first step to the third step included in the first method using the outer tube and inner tube illustrated in FIG. [Figure 6] 10 is a flowchart illustrating the flow of each step included in a method (third method) for manufacturing a double tapered portion according to a third embodiment of the present invention. [Figure 7] 10A and 10B are schematic diagrams illustrating changes in the positional relationship between the outer tube and the inner tube as the first to third steps are performed in the third method. [Figure 8] FIG. 1 is a schematic diagram illustrating a state in which an inner tube is inserted into an outer tube when the outer and inner tubes are configured such that the axis of the small diameter end of the outer tube is parallel to the axis of the large diameter end, and the axis of the small diameter end of the inner tube is parallel to the axis of the large diameter end, and when a double taper section is formed, the small diameter end of the outer tube and the small diameter end of the inner tube are arranged coaxially, and the large diameter end of the outer tube and the large diameter end of the inner tube are arranged coaxially. [Figure 9] FIG. 10 is a schematic diagram illustrating a state in which negative angular interference occurs when inserting an inner tube into an outer tube when the axes of the small diameter ends and the large diameter ends of the outer and inner tubes are in a geometrically twisted relationship, making it impossible to insert the inner tube to the intended position inside the outer tube. DETAILED DESCRIPTION OF THE INVENTION

[0034] First Embodiment A method for manufacturing a double tapered portion according to a first embodiment of the present invention (hereinafter, sometimes referred to as a "first method") will be described below with reference to the drawings.

[0035] <composition> The first method is a method for manufacturing a double tapered portion, in which an inner tube having a small diameter end and a large diameter end at both ends of a tapered portion is introduced inside an outer tube having a small diameter end and a large diameter end at both ends of a tapered portion, and the small diameter end of the outer tube and the small diameter end of the inner tube are tightly attached and fixed, while a gap is provided between the outer tube and the inner tube in the tapered portion and the large diameter end.

[0036] The outer and inner tubes having the above-described configurations can be obtained by, for example, plastic processing such as press processing or spinning processing from a metal plate such as a steel plate or a metal pipe such as a steel pipe, but the molding method for the outer and inner tubes is not limited to these.

[0037] Fig. 1 is a flowchart illustrating the flow of each step included in Method 1. As illustrated in Fig. 1, Method 1 includes Step 1, Step 2, and Step 3 listed below.

[0038] The first step performed in step S10 is a step of achieving a first state in which the small-diameter end of a first assembly, which is an assembly of an outer tube and an inner tube, is set in a first holding means that holds at least the large-diameter end of the inner tube. The first assembly is formed by introducing the inner tube into the interior of the outer tube from its large-diameter end, with the small-diameter end of the inner tube positioned at the leading edge, while maintaining the large-diameter ends of the outer and inner tubes coaxially. In the first assembly, at least a portion of the small-diameter end of the inner tube reaches the inside of the small-diameter end of the outer tube, and the positional relationship between the outer tube and the inner tube is determined by sandwiching an elastic member, which is an elastically deformable member, between the inner circumferential surface of the large-diameter end of the outer tube and the outer circumferential surface of the large-diameter end of the inner tube. In other words, in the first assembly, the inner tube is merely housed inside the outer tube in a predetermined position and orientation by sandwiching the elastic member between the outer tube and the inner tube; the outer tube and the inner tube are not yet fixed to each other.

[0039] The method for assembling the first assembly from the outer tube and the inner tube in the first step is not particularly limited. For example, the first assembly may be assembled by manually introducing the inner tube into the outer tube, or by mechanically assembling the first assembly by introducing the inner tube into the outer tube using a mechanism such as a moving clamp or equipment such as a robot arm. Furthermore, the method for holding the first assembly with the first holding means is not particularly limited as long as it is capable of holding at least the large-diameter end of the inner tube. For example, as described in detail below, the large-diameter end of the inner tube can be fitted into a pressing block, which is a member having an inner core fitted into the large-diameter end of the inner tube and an abutting surface abutting the distal end surface of the large-diameter end of the inner tube. Additionally, the first holding means may include a member for holding the large-diameter end of the outer tube, and the large-diameter end of the outer tube may be held by this member.

[0040] Furthermore, the above-described process of assembling the first assembly and the process of setting the first assembly in the first holding means may be performed separately or simultaneously. Specifically, for example, the first assembly may be pre-assembled manually or mechanically as described above, and the assembled first assembly may then be set in the first holding means. Alternatively, the large-diameter end of the inner pipe may first be held by the first holding means, and the outer pipe may then be placed over the inner pipe held by the first holding means, thereby simultaneously assembling the first assembly and setting it in the first holding means.

[0041] The material and configuration of the elastic member are not particularly limited as long as it can be sandwiched and compressed between the inner circumferential surface of the large-diameter end of the outer tube and the outer circumferential surface of the large-diameter end of the inner tube, thereby maintaining the outer tube and the inner tube in a predetermined positional relationship by repulsive force, and can withstand the use environment of a container, etc., including a double tapered portion manufactured by method 1. A specific example of the elastic member is a tangle of metal fibers, such as a wire mesh or a wire net.

[0042] Furthermore, in the first assembly, as described above, the elastic member is sandwiched and compressed between the inner peripheral surface of the large diameter end of the outer pipe and the outer peripheral surface of the large diameter end of the inner pipe, and the repulsive force maintains the outer pipe and the inner pipe in a predetermined positional relationship. Therefore, the thickness of the elastic member before the first assembly is assembled needs to be larger than the radial size of the gap between the inner peripheral surface of the large diameter end of the outer pipe and the outer peripheral surface of the large diameter end of the inner pipe in the first assembly.

[0043] Furthermore, the means for disposing the elastic member between the inner peripheral surface of the large diameter end of the outer pipe and the outer peripheral surface of the large diameter end of the inner pipe is not particularly limited, as long as it can be clamped between the inner peripheral surface of the large diameter end of the outer pipe and the outer peripheral surface of the large diameter end of the inner pipe during the process of introducing the inner pipe into the outer pipe and assembling the first assembly in the first step. For example, before introducing the inner pipe into the outer pipe in the first step, the elastic member may be attached in advance to either or both of the inner peripheral surface of the large diameter end of the outer pipe and the outer peripheral surface of the large diameter end of the inner pipe by means such as welding.

[0044] In addition, the elastic member does not necessarily have to be disposed continuously around the entire circumference between the inner circumferential surface of the large diameter end of the outer pipe and the outer circumferential surface of the large diameter end of the inner pipe, as long as it is possible to maintain the outer pipe and the inner pipe in a predetermined positional relationship. For example, a plurality of elastic members may be disposed intermittently along the circumferential direction of the gap between the inner circumferential surface of the large diameter end of the outer pipe and the outer circumferential surface of the large diameter end of the inner pipe.

[0045] The second process executed in step S20 is a process of achieving a second state in which the small diameter end of the outer tube and the small diameter end of the inner tube constituting the first assembly are coaxial with each other, and the first assembly is also set in a second holding means separate from the first holding means.

[0046] As described above, in the second state, the large diameter end of the first assembly is set in the first holding means and the small diameter end is set in the second holding means. In the next step S30, a third step is performed to reduce the diameter of the small diameter end of the outer tube and / or expand the diameter of the small diameter end of the inner tube that constitutes the first assembly in the second state. Therefore, the second holding means is equipped with a mechanism that can reduce the diameter of the small diameter end of the outer tube and / or expand the diameter of the small diameter end of the inner tube. The specific configuration of such a mechanism will be described later with reference to the drawings.

[0047] The third process executed in step S30 is a process for achieving a third state in which the small diameter end of the outer tube and the small diameter end of the inner tube are tightly fixed together by reducing the diameter of the small diameter end of the outer tube and / or expanding the diameter of the small diameter end of the inner tube, thereby forming a second assembly.

[0048] As described above, in the third step, the small diameter end of the outer pipe and the small diameter end of the inner pipe constituting the first assembly in the second state are reduced in diameter and / or expanded in diameter, so that the small diameter end of the outer pipe and the small diameter end of the inner pipe are tightly fixed to each other to form a second assembly. That is, the second assembly is the double tapered portion to be manufactured by the first method.

[0049] In the third step, the second assembly may be formed by bringing the small diameter end of the outer pipe and the small diameter end of the inner pipe into close contact with each other only by reducing the diameter of the small diameter end of the outer pipe, or by bringing the small diameter end of the outer pipe and the small diameter end of the inner pipe into close contact with each other only by expanding the diameter of the small diameter end of the inner pipe. Alternatively, for example, when the difference in diameter between the small diameter end of the outer pipe and the small diameter end of the inner pipe is large, the second assembly may be formed by bringing the small diameter end of the outer pipe and the small diameter end of the inner pipe into close contact with each other by both reducing the diameter of the small diameter end of the outer pipe and expanding the diameter of the small diameter end of the inner pipe.

[0050] Furthermore, in the first method, the outer tube and the inner tube are configured so that they do not interfere with each other in steps 1 and 2. Specifically, the inner diameter of at least a portion of the tapered portion and the small diameter end of the outer tube in the first state is larger than the inner diameter of at least a portion of the tapered portion and the small diameter end of the outer tube in the third state, to the extent that the outer tube and the inner tube do not interfere with each other in steps 1 and 2. Alternatively, or in addition to the above, the outer diameter of at least a portion of the tapered portion and the small diameter end of the inner tube in the first state is smaller than the outer diameter of at least a portion of the tapered portion and the small diameter end of the inner tube in the third state.

[0051] As described above, before the third step is performed, the inner diameter of at least a portion of the tapered portion and the small diameter end of the outer pipe is larger than the inner diameter (original inner diameter) of at least a portion of the tapered portion and the small diameter end of the outer pipe that constitute the double tapered portion to be manufactured. And / or, before the third step is performed, the outer diameter of at least a portion of the tapered portion and the small diameter end of the inner pipe is smaller than the outer diameter (original outer diameter) of at least a portion of the tapered portion and the small diameter end of the inner pipe that constitute the double tapered portion to be manufactured. Therefore, it is possible to avoid the negative angle interference described above in the first step of introducing the inner pipe into the outer pipe and the second step of aligning the small diameter ends of the outer pipe and the inner pipe coaxially.

[0052] The manufacturing process of the double tapered portion by the first method will be described in detail below with reference to the drawings. As described above, in the first method, the outer tube and the inner tube are configured so that they do not interfere with each other in the first and second steps. Specific examples of such outer and / or inner tube configurations include a configuration in which the small-diameter end of the outer tube and at least a portion of the adjacent tapered portion are formed to have a larger diameter than the original shape of the double tapered portion to be finally manufactured, and / or a configuration in which the small-diameter end of the inner tube and at least a portion of the adjacent tapered portion are formed to have a smaller diameter than the original shape of the double tapered portion to be finally manufactured.

[0053] Figure 2 is a schematic diagram illustrating a configuration in which the small-diameter end of an outer pipe and at least a portion of the adjacent tapered portion are formed to have a diameter larger than the original shape. The outer pipe 10 and inner pipe 20 illustrated in Figure 2 have the same configuration as the outer pipe 10 and inner pipe 20 illustrated in Figure 9, which were referenced in the description of the prior art above. In both the outer pipe 10 and inner pipe 20, the axis of the small-diameter end and the axis of the large-diameter end are in a geometrically twisted relationship. However, in the outer pipe 10 illustrated in Figure 2(a), the small-diameter end 12 and the adjacent tapered portion 11 are formed to have a diameter larger than the original shape indicated by the dashed-dotted line (e.g., the shape illustrated in Figure 9(a)). On the other hand, the inner pipe 20 illustrated in Figure 2(b) has the original shape of the double tapered portion that will ultimately be manufactured.

[0054] 2(b), while the large diameter end 13 of the outer pipe 10 and the large diameter end 23 of the inner pipe 20 are maintained coaxially, the inner pipe 20 is introduced into the interior of the outer pipe 10 from the large diameter end 13 side of the outer pipe 10, with the small diameter end 22 side of the inner pipe 20 at the leading end (see the open arrow in FIG. 2(a)), thereby assembling a first assembly 40. In the first assembly 40, at least a portion of the small diameter end 22 of the inner pipe 20 reaches the inside of the small diameter end 12 of the outer pipe 10, and the positional relationship between the outer pipe 10 and the inner pipe 20 is determined by sandwiching an elastic member 30, which is an elastically deformable member, between the inner circumferential surface of the large diameter end 13 of the outer pipe 10 and the outer circumferential surface of the large diameter end 23 of the inner pipe 20.

[0055] The introduction of the inner pipe 20 into the outer pipe 10 may be achieved by inserting the inner pipe 20 into the fixed outer pipe 10, by fitting the outer pipe 10 onto the fixed inner pipe 20, or by bringing both the outer pipe 10 and the inner pipe 20 close to each other. As mentioned above, the first assembly 40 may be assembled manually or mechanically by a mechanism such as a moving clamp or equipment such as a robot arm.

[0056] In the conventional method for manufacturing a double tapered portion described with reference to FIG. 9 , negative angular interference occurs during the above process, causing the small diameter end 22 of the inner tube 20 to contact the proximal portion of the small diameter end 12 of the outer tube 10, making it impossible to introduce the inner tube 20 to a desired position inside the outer tube 10. However, in the outer tube 10 illustrated in FIG. 2( a), as described above, the small diameter end 12 and the adjacent tapered portion 11 are formed to have diameters larger than the original shape indicated by the dashed dotted line, thereby avoiding the occurrence of negative angular interference. As a result, as illustrated in FIG. 2( b), the inner tube 20 can be introduced to a desired position inside the outer tube 10, and at least a portion of the small diameter end 22 of the inner tube 20 can reach the inside of the small diameter end 12 of the outer tube 10.

[0057] The process of manufacturing the desired double tapered portion (second assembly) from the first assembly 40 having the above-described configuration through the first step (step S10) to the third step (step S30) will be described below with reference to FIGS. 2 and 3. FIG. 3 is a schematic diagram illustrating the change in shape of the outer and inner tubes constituting the first assembly and the movement of the first and second holding means as the process progresses from step 1 to step 3 included in the first method using the outer and inner tubes 10 and 20 illustrated in FIG. 2. In FIG. 3, enlarged views of portions P1 to P5 enclosed by thick dashed lines are depicted above the first holding means 110 and below the second holding means 120, respectively, and the finally obtained second assembly (double tapered portion) 50 is depicted in the upper right corner of the drawing.

[0058] FIG. 3(a) is a schematic diagram illustrating a state (first state) in which the first assembly 40 illustrated in FIG. 2 is set in the first holding means 110 by performing the first step described above. The first holding means 110 illustrated in FIG. 3 is a pressing block including an inner core 111 fitted into the large-diameter end 23 of the inner pipe 20 and an abutment surface 112 that abuts against the tip end surface of the large-diameter end 23. As shown in the enlarged view of portion P1, the inner core 111 is fitted into the large-diameter end 23 of the inner pipe 20, thereby determining the position of the large-diameter end 23 of the inner pipe 20 in a direction perpendicular to the axis and the orientation of the large-diameter end 23 relative to the axis (not tilted relative to the axis). Furthermore, the tip end surface of the large-diameter end 23 abuts against the abutment surface 112, thereby determining the position of the large-diameter end 23 of the inner pipe 20 in the axial direction. In this manner, the first state is achieved.

[0059] In the example shown in the enlarged view of portion P1, the tip surface of the large diameter end 13 of the outer pipe 10 does not abut against the first holding means 110, and a small gap G exists between them. However, the position of the large diameter end 13 of the outer pipe 10 in the axial direction may be precisely determined by abutting the tip surface of the large diameter end 13 of the outer pipe 10 against the first holding means 110. In some cases, the tip surface of the large diameter end 13 of the outer pipe 10 does not abut against the first holding means 110, and a small gap G is provided between them, in order to have the tip surface of the small diameter end 22 of the inner pipe 20 protrude from the tip surface of the small diameter end 12 of the outer pipe 10. Such cases will be described in detail later in the description of other embodiments of the present invention.

[0060] As described above, in the first assembly 40, the positional relationship between the outer pipe 10 and the inner pipe 20 is determined by the elastic member 30 sandwiched between the inner peripheral surface of the large diameter end 13 of the outer pipe 10 and the outer peripheral surface of the large diameter end 23 of the inner pipe 20. Therefore, the outer pipe 10 is also held by the inner pipe 20, which is held by the first holding means 110, via the elastic member 30. As a result, the first assembly 40 is held by the first holding means 110.

[0061] 2, the small diameter end 12 of the outer pipe 10 and at least a portion of the adjacent tapered portion 11 are formed to have a diameter larger than the original shape. Therefore, at the time when the first step is completed, as shown in the enlarged view of portion P2, the small diameter end 12 of the outer pipe 10 and the small diameter end 22 of the inner pipe 20 are separated from each other, and a gap exists between them. In the example shown in the enlarged view of portion P2, the tip surface of the small diameter end 12 of the outer pipe 10 and the tip surface of the small diameter end 22 of the inner pipe 20 are flush with each other, but they do not necessarily have to be flush with each other.

[0062] Next, the processing of the first method proceeds to the second step. Fig. 3(b) is a schematic diagram illustrating a state (second state) in which the first assembly 40 set in the first holding means 110 is also set in the second holding means 120 through the execution of the second step. The second holding means 120 illustrated in Fig. 3 includes an inner mandrel 121 fitted into the small diameter end 22 of the inner pipe 20 and an abutment surface 122 abutting against the tip end face of the large diameter end 23. In the second step illustrated in Fig. 3(b), as indicated by the solid arrow, the first holding means 110 is lowered by a driving mechanism (not shown), thereby bringing the first assembly 40 set in the first holding means 110 closer to the second holding means 120. As a result, the small diameter end 22 of the inner pipe 20 is fitted onto the inner mandrel 121 provided in the second holding means 120, and the tip end face of the large diameter end 23 is abutted against the abutment surface 122. As a result, a state (second state) is achieved in which the small diameter end 12 of the outer tube 10 and the small diameter end 22 of the inner tube 20 constituting the first assembly 40 are coaxial with each other, and the first assembly 40 is also set in a second holding means 120 separate from the first holding means 110.

[0063] 3(b), the first assembly 40 set in the first holding means 110 is set in the second holding means 120 by lowering the first holding means 110 as described above. However, in the second step, the first assembly 40 set in the first holding means 110 may be set in the second holding means 120 by raising the second holding means 120, or the first assembly 40 set in the first holding means 110 may be set in the second holding means 120 by bringing the first holding means 110 and the second holding means 120 closer to each other.

[0064] In the example shown in the enlarged view of portion P4, the tip surface of the small diameter end 22 of the inner pipe 20 protrudes slightly from the tip surface of the small diameter end 12 of the outer pipe 10 in the axial direction of the small diameter end. As mentioned above, this arrangement is suitable when the outer pipe 10 and the inner pipe 20 are joined at their small diameter ends by means of, for example, welding. This arrangement will be described in detail later in the description of other embodiments of the present invention.

[0065] Next, the processing in the first method proceeds to the third step. Fig. 3(c) is a schematic diagram illustrating a state (third state) in which the small diameter end 12 of the outer pipe 10 and the small diameter end 22 of the inner pipe 20 are tightly fixed together by reducing the diameter of the small diameter end 12 of the outer pipe 10 through the execution of the third step, thereby forming a second assembly 50. Therefore, as described above, the second holding means 120 has a mechanism capable of reducing the diameter of the small diameter end 13 of the outer pipe 10. Specifically, as illustrated in Fig. 3, the second holding means 120 has a split mold 131 configured to press the small diameter end 13 of the outer pipe 10 radially inward (centripetal direction) to reduce the diameter of the small diameter end 13, and a ram 132 that drives the split mold 131.

[0066] In the third step, as shown by the solid arrow in Fig. 3(c), the ram 132 is lowered to drive the split mold 131 in the centripetal direction as shown by the open arrow. As a result, as shown in the enlarged view of portion P5, the small diameter end 12 of the outer tube 10, which was formed to have an inner diameter larger than the original inner diameter, is reduced in diameter and tightly fixed to the small diameter end 22 of the inner tube 20, thereby achieving a state (third state) in which the second assembly 50 is formed.

[0067] In other words, according to the first method, a double tapered portion can be formed without requiring complex control of the trajectory and / or posture of the outer tube and / or inner tube during the process of inserting an inner tube having a small diameter end and a large diameter end at both ends of the tapered portion into the inside of an outer tube having a small diameter end and a large diameter end at both ends of the tapered portion.

[0068] 2 and 3, the above effect is achieved by configuring the outer pipe so that the small diameter end portion of the outer pipe and at least a part of the adjacent tapered portion have a diameter larger than that of the original shape. However, as mentioned above, the above effect can also be achieved by configuring the inner pipe so that the small diameter end portion of the inner pipe and at least a part of the adjacent tapered portion have a diameter smaller than that of the original shape.

[0069] Figure 4 is a schematic diagram illustrating a configuration in which the small-diameter end of an inner pipe and at least a portion of the adjacent tapered portion are formed to have a diameter smaller than the original shape. The outer pipe 10 and inner pipe 20 illustrated in Figure 4 have the same configuration as the outer pipe 10 and inner pipe 20 illustrated in Figures 9 and 2 referred to in the description of the prior art above, and in both the outer pipe 10 and inner pipe 20, the axis of the small-diameter end and the axis of the large-diameter end are in a geometrically twisted relationship. However, in the inner pipe 20 illustrated in Figure 4(a), the small-diameter end 22 and the adjacent tapered portion 21 are formed to have a diameter smaller than the original shape indicated by the dashed-dotted line (e.g., the shape illustrated in Figure 9(b)). On the other hand, the outer pipe 10 illustrated in Figure 4(b) has the original shape of the double tapered portion that will be finally manufactured.

[0070] 2(b), as illustrated in FIG. 4(b), while the large diameter end 13 of the outer pipe 10 and the large diameter end 23 of the inner pipe 20 are maintained coaxially, the inner pipe 20 is introduced into the interior of the outer pipe 10 from the large diameter end 13 side of the outer pipe 10, with the small diameter end 22 side of the inner pipe 20 at the leading end (see the open arrow in FIG. 4(a)), thereby forming a first assembly 40. In the first assembly 40, at least a portion of the small diameter end 22 of the inner pipe 20 reaches the inside of the small diameter end 12 of the outer pipe 10, and the positional relationship between the outer pipe 10 and the inner pipe 20 is determined by sandwiching an elastic member 30, which is an elastically deformable member, between the inner circumferential surface of the large diameter end 13 of the outer pipe 10 and the outer circumferential surface of the large diameter end 23 of the inner pipe 20.

[0071] As mentioned above, the introduction of the inner pipe 20 into the outer pipe 10 may be achieved by inserting the inner pipe 20 into the fixed outer pipe 10, by fitting the outer pipe 10 onto the fixed inner pipe 20, or by bringing both the outer pipe 10 and the inner pipe 20 close to each other. Also, as mentioned above, the first assembly 40 may be assembled manually or mechanically by a mechanism such as a moving clamp or equipment such as a robot arm.

[0072] In the conventional method for manufacturing a double tapered portion described with reference to FIG. 9 , negative angular interference occurs during the above process, causing the small diameter end 22 of the inner tube 20 to contact the proximal portion of the small diameter end 12 of the outer tube 10, making it impossible to introduce the inner tube 20 to a desired position inside the outer tube 10. However, in the inner tube 10 illustrated in FIG. 4( a), as described above, the small diameter end 22 and the adjacent tapered portion 21 are formed to have a diameter smaller than the original shape indicated by the dashed dotted line, thereby avoiding the occurrence of negative angular interference. As a result, as illustrated in FIG. 4( b), the inner tube 20 can be introduced to a desired position inside the outer tube 10, and at least a portion of the small diameter end 22 of the inner tube 20 can reach the inside of the small diameter end 12 of the outer tube 10.

[0073] The process of manufacturing the desired double tapered portion (second assembly) from the first assembly 40 having the above-described configuration through the first step (step S10) to the third step (step S30) will be described below with reference to FIGS. 4 and 5. FIG. 5 is a schematic diagram illustrating the change in shape of the outer and inner tubes constituting the first assembly and the movement of the first and second holding means as the process progresses from the first step to the third step included in the first method using the outer and inner tubes 10 and 20 illustrated in FIG. 4. In FIG. 5, as in FIG. 3, enlarged views of portions P1 to P5 surrounded by thick dashed lines are depicted above the first holding means 110 and below the second holding means 120, respectively, and the finally obtained second assembly (double tapered portion) 50 is depicted in the upper right corner of the drawing.

[0074] FIG. 5(a) is a schematic diagram illustrating a state (first state) in which the first assembly 40 illustrated in FIG. 4 is set in the first holding means 110 by performing the first step described above. The first holding means 110 illustrated in FIG. 5, like the first holding means 110 illustrated in FIG. 3, is a pressing block including an inner core 111 fitted into the large-diameter end 23 of the inner pipe 20 and an abutment surface 112 that abuts against the tip end surface of the large-diameter end 23. As shown in the enlarged view of portion P1, the inner core 111 is fitted into the large-diameter end 23 of the inner pipe 20, thereby determining the position of the large-diameter end 23 of the inner pipe 20 in a direction perpendicular to the axis and the orientation of the large-diameter end 23 relative to the axis (not tilted relative to the axis). Furthermore, the tip end surface of the large-diameter end 23 abuts against the abutment surface 112, thereby determining the position of the large-diameter end 23 of the inner pipe 20 in the axial direction. In this manner, the first state is achieved.

[0075] 5, as in FIG. 3, the tip surface of the large diameter end 13 of the outer pipe 10 does not abut against the first holding means 110, and a small gap G exists between them. However, the position of the large diameter end 13 of the outer pipe 10 in the axial direction may be precisely determined by abutting the tip surface of the large diameter end 13 of the outer pipe 10 against the first holding means 110. In some cases, the tip surface of the large diameter end 13 of the outer pipe 10 does not abut against the first holding means 110, and a small gap G is provided between them, in order to have the tip surface of the small diameter end 22 of the inner pipe 20 protrude from the tip surface of the small diameter end 12 of the outer pipe 10. Such cases will be described in detail later in the description of other embodiments of the present invention.

[0076] As described above, in the first assembly 40, the positional relationship between the outer pipe 10 and the inner pipe 20 is determined by the elastic member 30 sandwiched between the inner peripheral surface of the large diameter end 13 of the outer pipe 10 and the outer peripheral surface of the large diameter end 23 of the inner pipe 20. Therefore, the outer pipe 10 is also held by the inner pipe 20, which is held by the first holding means 110, via the elastic member 30. As a result, the first assembly 40 is held by the first holding means 110.

[0077] 4, the small diameter end 22 of the inner pipe 20 and at least a portion of the adjacent tapered portion 21 are formed to have a diameter smaller than the original shape. Therefore, at the time when the first step is completed, as shown in the enlarged view of portion P2, the small diameter end 12 of the outer pipe 10 and the small diameter end 22 of the inner pipe 20 are separated from each other, and a gap exists between them. In the example shown in the enlarged view of portion P2, the tip surface of the small diameter end 12 of the outer pipe 10 and the tip surface of the small diameter end 22 of the inner pipe 20 are flush with each other, but they do not necessarily have to be flush with each other.

[0078] Next, the processing of the first method proceeds to the second step. Fig. 5(b) is a schematic diagram illustrating a state (second state) in which the first assembly 40 set in the first holding means 110 is also set in the second holding means 120 as a result of the execution of the second step. The second holding means 120 illustrated in Fig. 5 includes an inner core 121 fitted into the small diameter end 22 of the inner tube 20 and an abutment surface 122 abutting on the tip end surface of the large diameter end 23. As described above, the second holding means 120 also includes a mechanism capable of expanding the diameter of the small diameter end 23 of the inner tube 20. Specifically, as illustrated in Figure 5, in the second holding means 120, the inner core wire 121 is configured as a split type that is configured to press the small diameter end portion 13 of the inner tube 20 outward (radially) in the radial direction to reduce the diameter of the small diameter end portion 23, and the second holding means 120 is equipped with a mandrel 133 that drives the split type inner core wire 121.

[0079] In the second step illustrated in FIG. 5(b), as indicated by the solid arrow, the first holding means 110 is lowered by a driving mechanism (not shown) to bring the first assembly 40 set in the first holding means 110 closer to the second holding means 120. This causes the small diameter end 22 of the inner tube 20 to fit onto the inner mandrel 121 of the second holding means 120, and the tip end face of the large diameter end 23 to abut against the abutment surface 122. At this time, the ram 132 may be lowered as indicated by the hatched arrow in FIG. 5(b), thereby driving the split mold 131 in the centripetal direction as indicated by the hollow arrow. This prevents the inner mandrel 121 as a split mold from opening outward in the radial direction (radial direction) as the small diameter end 22 of the inner tube 20 is fitted onto the inner mandrel 121. As a result of the above, a state (second state) is achieved in which the small diameter end 12 of the outer tube 10 and the small diameter end 22 of the inner tube 20 constituting the first assembly 40 are coaxial with each other, and the first assembly 40 is also set in the second holding means 120 separate from the first holding means 110.

[0080] 5(b), similarly to the second step illustrated in FIG. 3(b), the first assembly 40 set in the first holding means 110 is set in the second holding means 120 by lowering the first holding means 110 as described above. However, as described above, in the second step, the first assembly 40 set in the first holding means 110 may be set in the second holding means 120 by raising the second holding means 120, or the first assembly 40 set in the first holding means 110 may be set in the second holding means 120 by bringing the first holding means 110 and the second holding means 120 closer to each other.

[0081] In the example shown in the enlarged view of portion P4, the tip surface of the small diameter end 22 of the inner pipe 20 protrudes slightly from the tip surface of the small diameter end 12 of the outer pipe 10 in the axial direction of the small diameter end. As mentioned above, this arrangement is suitable when the outer pipe 10 and the inner pipe 20 are joined at their small diameter ends by means of, for example, welding. This arrangement will be described in detail later in the description of other embodiments of the present invention.

[0082] Next, the treatment in the first method proceeds to step 3. Fig. 5(c) is a schematic diagram illustrating a state (third state) in which the small diameter end 12 of the outer pipe 10 and the small diameter end 22 of the inner pipe 20 are tightly fixed together by the expansion of the small diameter end 22 of the inner pipe 20 through the execution of step 3, thereby forming a second assembly 50.

[0083] In the third step, as shown by the filled arrow in Fig. 5(c), the mandrel 133 is raised by a driving device (not shown), thereby driving the inner core metal 121 as a split mold in the radial direction as shown by the open arrow. As a result, as shown in the enlarged view of portion P5, the small diameter end portion 22 of the inner tube 20, which was formed to have an outer diameter smaller than the original inner diameter, is expanded in diameter and fixed in close contact with the small diameter end portion 12 of the outer tube 10, thereby achieving a state (third state) in which the second assembly 50 is formed.

[0084] As the inner core metal 121 serving as the split mold is driven in the radial direction as described above, the split mold 131 moves in the radial direction, and the drive ram 132 rises as indicated by the arrow hatched with diagonal lines.

[0085] As described above, the first method according to this aspect also makes it possible to form a double tapered section without requiring complex control of the trajectory and / or posture of the outer tube and / or inner tube during the process of inserting an inner tube having a small diameter end and a large diameter end at both ends of the tapered section into the inside of an outer tube having a small diameter end and a large diameter end at both ends of the tapered section.

[0086] In the above, the following modes have been described: one in which the small diameter end of the outer pipe and at least a portion of the adjacent tapered portion are formed larger than their original shapes, and the small diameter end of the outer pipe is reduced in diameter in the third step to tightly bond the outer pipe and the inner pipe together, thereby producing a second assembly as a double tapered portion; and another in which the small diameter end of the inner pipe and at least a portion of the adjacent tapered portion are formed smaller than their original shapes, and the small diameter end of the inner pipe is expanded in diameter in the third step to tightly bond the outer pipe and the inner pipe together, thereby producing a second assembly as a double tapered portion. However, although not shown, the second assembly may also be formed by forming the small diameter end of the outer pipe and at least a portion of the adjacent tapered portion larger than their original shapes and by forming the small diameter end of the inner pipe and at least a portion of the adjacent tapered portion smaller than their original shapes, and by reducing the small diameter end of the outer pipe and expanding the small diameter end of the inner pipe in the third step to tightly bond the outer pipe and the inner pipe together.

[0087] <effect> As described above, in the first method, the large diameter end of a first assembly, which is composed of an outer tube, an inner tube, and an elastic member with a fixed positional relationship, is set in a first holding means (a first state is achieved by the first step), then the small diameter end of the first assembly is set in a second holding means separate from the first holding means with the small diameter end of the outer tube and the small diameter end of the inner tube coaxial with each other (a second state is achieved by the second step), and then the small diameter end of the outer tube is reduced in diameter and / or the small diameter end of the inner tube is expanded in diameter to tightly contact and fix the two together (a third state is achieved by the third step).

[0088] Additionally, in the first method, the outer tube and the inner tube are configured so that they do not interfere with each other in steps 1 and 2. Specifically, the diameter of at least a portion of the tapered portion and the small diameter end of the outer tube in the first state is larger than the diameter of at least a portion of the tapered portion and the small diameter end of the outer tube in the third state, to the extent that the outer tube and the inner tube do not interfere with each other in steps 1 and 2. Alternatively, or in addition to the above, the diameter of at least a portion of the tapered portion and the small diameter end of the inner tube in the first state is smaller than the diameter of at least a portion of the tapered portion and the small diameter end of the inner tube in the third state.

[0089] Therefore, according to the first method, a double tapered portion can be formed without requiring complex control of the trajectory and / or posture of the outer tube and / or inner tube during the process of introducing an inner tube having a small-diameter end and a large-diameter end at both ends of a tapered portion into an outer tube having a small-diameter end and a large-diameter end at both ends of a tapered portion, thereby avoiding problems such as an increase in the complexity and size of manufacturing equipment and a decrease in production efficiency.

[0090] Second Embodiment A method for manufacturing a double tapered portion according to a second embodiment of the present invention (hereinafter, sometimes referred to as the "second method") will be described below.

[0091] As described above, in the first method, the outer tube and the inner tube are configured so that they do not interfere with each other in the first and second steps; in the first step, the large diameter end of the outer tube and the large diameter end of the inner tube are maintained coaxially while the inner tube is introduced into the inside of the outer tube, and the large diameter end side of the assembled first assembly is set in the first holding means; in the second step, the small diameter end side of the first assembly is set in the second holding means while the small diameter end of the outer tube and the small diameter end of the inner tube are coaxial with each other; and in the third step, the small diameter end of the outer tube and the small diameter end of the inner tube are tightly fixed in contact with each other by reducing the diameter of the small diameter end of the outer tube and / or expanding the diameter of the small diameter end of the inner tube, thereby producing the second assembly (i.e., the double taper portion).

[0092] The first method as described above can be applied even when the axis of the small diameter end and the axis of the large diameter end of the outer tube and / or inner tube are coaxial or parallel, but as mentioned above, it is particularly effective when it is difficult to avoid negative angular interference in the process of introducing the inner tube into the outer tube because the axis of the small diameter end and the axis of the large diameter end are not coaxial or parallel (i.e., in the outer tube and / or inner tube, the axis of the small diameter end and the axis of the large diameter end intersect at a predetermined angle or are in a geometrically twisted relationship).

[0093] <composition> Therefore, the second method is the above-mentioned first method, which is a method for manufacturing a double taper portion, characterized in that the axis of the small diameter end and the axis of the large diameter end of the outer tube and / or inner tube intersect at a predetermined angle or are in a geometrically twisted relationship.

[0094] 2 to 5, which were referred to in the description of the first method, the axes of the small diameter end and the large diameter end of each of the outer pipe 10 and inner pipe 20 are in a geometrically twisted relationship. Therefore, the first method exemplified with reference to these drawings already has the characteristics of the second method.

[0095] <effect> As mentioned above, when the axis of the small diameter end and the axis of the large diameter end are neither coaxial nor parallel (i.e., when the axis of the small diameter end and the axis of the large diameter end of the outer tube and / or inner tube intersect at a predetermined angle or are in a geometrically twisted relationship), it is difficult or impossible to avoid negative angular interference during the process of introducing the inner tube into the outer tube using the conventional method for manufacturing a double taper portion.

[0096] However, as described above, in the first method, the large diameter end of the first assembly, which is composed of an outer tube, an inner tube, and an elastic member with a fixed positional relationship, is set in a first holding means (a first state is achieved by the first step), then the small diameter end of the first assembly is set in a second holding means separate from the first holding means with the small diameter end of the outer tube and the small diameter end of the inner tube coaxial with each other (a second state is achieved by the second step), and then the small diameter end of the outer tube is reduced in diameter and / or the small diameter end of the inner tube is expanded in diameter to tightly contact and fix the two together (a third state is achieved by the third step).

[0097] Therefore, according to the second method, even if the axis of the small diameter end and the axis of the large diameter end of the outer tube and / or inner tube intersect at a predetermined angle or are in a geometrically twisted relationship, negative angle interference can be avoided and a double taper section can be smoothly formed without requiring complex control of the trajectory and / or posture of the outer tube and / or inner tube during the process of introducing the inner tube into the outer tube.

[0098] Third Embodiment Hereinafter, a method for manufacturing a double tapered portion according to a third embodiment of the present invention (hereinafter, sometimes referred to as a "third method") will be described with reference to the drawings.

[0099] As described above, it is advantageous for the small diameter end of the inner pipe to protrude from the small diameter end of the outer pipe, for example, in cases where the outer pipe and the inner pipe are joined at their small diameter ends by welding or other means after assembling the second assembly in step 3. In this way, it may be necessary to adjust the axial distance (tip distance) between the tip end surface of the small diameter end of the outer pipe and the tip end surface of the small diameter end of the inner pipe depending on the secondary processing performed after step 3.

[0100] <composition> Therefore, the third method is a method for manufacturing a double taper portion, which is the above-mentioned first method or second method, characterized in that in the second step, while maintaining the above-mentioned second state, the inner tube is pressed from the large diameter end side toward the small diameter end side in the axial direction of the small diameter end of the inner tube by a first holding means, thereby causing the tip surface of the small diameter end of the inner tube to protrude from the tip surface of the small diameter end of the outer tube by a first distance, which is a predetermined distance in the axial direction of the small diameter end of the inner tube.

[0101] FIG. 6 is a flowchart illustrating the flow of each step included in the third method. As illustrated in FIG. 6, in step S20, the second step included in the third method is performed, similar to the first and second methods described above. In this second state, the small diameter end of the outer pipe and the small diameter end of the inner pipe, which constitute the first assembly, are coaxial with each other, and the first assembly is also set in a second holding means separate from the first holding means. However, in step S20, the second step included in the third method is performed. While maintaining the second state, the first holding means presses the inner pipe from the large diameter end toward the small diameter end in the axial direction of the small diameter end of the inner pipe. This causes the tip end surface of the small diameter end of the inner pipe to protrude from the tip end surface of the small diameter end of the outer pipe by a first distance, which is a predetermined distance in the axial direction of the small diameter end of the inner pipe.

[0102] Except for the above points, this is the same as the flowchart illustrated in Fig. 1 referred to in the description of Method 1. Therefore, since Steps 1 and 3 have already been described in the description of Method 1, Step 2 will be mainly described below with reference to Fig. 7 in addition to Figs. 3 and 5 referred to in the description of Method 1.

[0103] Fig. 7 is a schematic diagram illustrating the change in the positional relationship between the outer tube and the inner tube as the first to third steps of the third method are performed. Fig. 7(a) is a schematic diagram illustrating a state (first state) in which the inner tube 20 is introduced into the outer tube 10 by performing the first step (see the black arrow) and a first assembly 40, which is an assembly of the outer tube 10 and the inner tube 20, is set in a first holding means (not shown). This diagram corresponds to Figs. 3(a) and 5(a) referred to in the explanation of the first method. Fig. 7(b) is an enlarged view of a portion P6 surrounded by a thick dashed line in Fig. 7(a), and corresponds to the enlarged view of portion P2 in Figs. 3 and 5. In addition, in the enlarged view of portion P6 illustrated in (b) of Figure 7, as in the enlarged views of portion P2 in Figures 3 and 5, the tip surface of the small diameter end 12 of the outer pipe 10 and the tip surface of the small diameter end 22 of the inner pipe 20 are flush with each other, but they do not necessarily have to be flush with each other.

[0104] Next, as illustrated in Fig. 7(c), by performing the second step, a state (second state) is achieved in which the small diameter end of the outer pipe 10 and the small diameter end of the inner pipe 20 constituting the first assembly 40 are coaxial with each other, and the first assembly 40 is also set in a second holding means (not shown), as in the first and second methods described above. In addition, in the second step included in the third method, while maintaining the second state, the inner pipe 20 is pressed in the axial direction of the small diameter end of the inner pipe 20 from the large diameter end side (upper side in Fig. 7(c)) to the small diameter end side (lower side in Fig. 7(c)) by the first holding means (not shown) (see the black arrow). This causes the tip end surface of the small diameter end of the inner pipe 20 to protrude from the tip end surface of the small diameter end of the outer pipe 10 by a predetermined first distance (hereinafter referred to as "D1") in the axial direction of the small diameter end of the inner pipe 20.

[0105] The process of causing the tip surface of the small diameter end of the inner pipe 20 to protrude from the tip surface of the small diameter end of the outer pipe 10 as described above will be described in detail below with reference to Figures 3 and 5. In the example shown in the enlarged views of portion P1 in Figures 3 and 5 referred to in the description of the first method, as described above, the tip surface of the large diameter end 13 of the outer pipe 10 does not abut against the first holding means 110, and a small gap G exists between them. On the other hand, the tip surface of the large diameter end 23 of the inner pipe 20 abuts against the abutment surface 112 of the pressing block serving as the first holding means 110. Therefore, in the second step included in the third method, as described above, when the first holding means 110 begins to press the inner pipe 20 from the large diameter end side 23 toward the small diameter end side 22 in the axial direction of the small diameter end 22 of the inner pipe 20 while maintaining the second state, the inner pipe 20 immediately begins to descend.

[0106] Thereafter, as the first holding means 110 continues to descend, it eventually abuts against the tip surface of the large diameter end 13 of the outer pipe 10, and the gap G disappears. Meanwhile, as described above, the tip surface of the small diameter end 12 of the outer pipe 10 is already abutting against the abutment surface 122 of the second holding means 120 when the second state is achieved. Therefore, the descent of the first holding means 110 is stopped when the first holding means 110 abuts against the tip surface of the large diameter end 13 of the outer pipe 10 and the gap G disappears. As a result, the descent distance of the inner pipe 20 as a result of the pressing by the first holding means 110 coincides with the gap G.

[0107] Therefore, as illustrated in the enlarged views of portion P2 in Figures 3 and 5 and the enlarged view of portion P6 in Figure 7(b), when the tip surface of the small diameter end 12 of the outer pipe 10 and the tip surface of the small diameter end 22 of the inner pipe 20 are flush with each other at the time when the second state is achieved, the amount of protrusion of the tip surface of the small diameter end of the inner pipe 20 from the tip surface of the small diameter end of the outer pipe 10 (i.e., the first distance D1) at the time when the execution of the second step included in the third method is completed coincides with the above-mentioned gap G (D1 = G).

[0108] On the other hand, when the tip surface of the small diameter end 12 of the outer pipe 10 and the tip surface of the small diameter end 22 of the inner pipe 20 are not flush with each other when the second state is achieved, the amount of protrusion of the tip surface of the small diameter end of the inner pipe 20 from the tip surface of the small diameter end of the outer pipe 10 when the second step included in the third method is completed (i.e., the first distance D1) is equal to the sum (E+G) of the amount of protrusion E of the tip surface of the small diameter end 22 of the inner pipe 20 from the tip surface of the small diameter end 12 of the outer pipe 10 when the second state is achieved and the gap G. Note that when the tip surface of the small diameter end 22 of the inner pipe 20 is recessed rather than protruding from the tip surface of the small diameter end 12 of the outer pipe 10 when the second state is achieved, the amount of protrusion E is treated as a negative value.

[0109] The enlarged views of portion P4 in Figures 3 and 5 show the positional relationship between the small diameter end of the outer pipe 10 and the small diameter end of the inner pipe 20 at the time when the execution of the second step included in the third method is completed as described above, and show the amount of protrusion of the tip surface of the small diameter end of the inner pipe 20 from the tip surface of the small diameter end of the outer pipe 10 (i.e., the first distance D1).

[0110] In the above description of the second step included in the third method, an example was given in which the steps of achieving the second state in which the small diameter end of the outer pipe and the small diameter end of the inner pipe constituting the first assembly are coaxial with each other and the first assembly is also set in a second holding means separate from the first holding means, and pressing the inner pipe with the first holding means from the large diameter end side toward the small diameter end side in the axial direction of the small diameter end of the inner pipe while maintaining the second state, thereby causing the tip surface of the small diameter end of the inner pipe to protrude from the tip surface of the small diameter end of the outer pipe by a first distance, which is a predetermined distance in the axial direction of the small diameter end of the inner pipe. However, the former step and the latter step may be performed separately as described above, or may be performed simultaneously in parallel.

[0111] <effect> As described above, in the second step included in the third method, not only is the second state achieved, but the first holding means presses the inner pipe from the large diameter end toward the small diameter end in the axial direction of the small diameter end of the inner pipe while maintaining the second state. This allows the tip surface of the small diameter end of the inner pipe to protrude from the tip surface of the small diameter end of the outer pipe by a predetermined first distance in the axial direction of the small diameter end of the inner pipe. This configuration is suitable, for example, when the outer pipe and the inner pipe are joined at their small diameter ends by means such as welding after the third step.

[0112] Fourth Embodiment A method for manufacturing a double tapered portion according to a fourth embodiment of the present invention (hereinafter, sometimes referred to as a "fourth method") will be described below with reference to the drawings.

[0113] In order to manufacture a double taper portion having high dimensional accuracy using the method for manufacturing a double taper portion according to the present invention (the method of the present invention), it is preferable that the holding posture of the outer tube and inner tube subjected to the method of the present invention be uniquely determined.

[0114] <composition> Therefore, the fourth method is a method for manufacturing a double taper portion which is any of the above-mentioned first to third methods, characterized in that a first mechanism, which is a mechanism configured to uniquely determine a first index, which is the posture of the outer tube in the rotational direction about the axis of the large diameter end of the outer tube, is configured in a pair with the first holding means and the outer tube, and a second mechanism, which is a mechanism configured to uniquely determine a second index, which is the posture of the inner tube in the rotational direction about the axis of the large diameter end of the inner tube, is configured in a pair with the first holding means and the inner tube, and the first index and second index of the first assembly are achieved by the first mechanism and the second mechanism, respectively.

[0115] The configuration of the first mechanism is not particularly limited as long as it can uniquely determine the first index, which is the attitude of the outer tube in the rotation direction around the axis of the large-diameter end of the outer tube. Specific examples of the configuration of the first mechanism include a configuration in which the first holding means and the outer tube are each provided with a mechanism including projections and depressions that engage or lock to prevent rotation of the outer tube around the axis of the large-diameter end of the outer tube, and when the first assembly is set on the first holding means to achieve the first state in the first step, the first holding means and the outer tube are engaged or locked together by the above mechanism. The same applies to the second mechanism.

[0116] 2 to 5 and 7, which were referred to in the description of the first to third methods, illustrate a specific example of the first and second mechanisms. The outer tube 10 illustrated in these figures has a protrusion 14 that protrudes in the axial direction from the tip surface of the large-diameter end 13. As illustrated in the enlarged views of portion P1 in FIGS. 3 and 5, the first holding means 110 has a recess 113 that is recessed in the axial direction at a position facing the protrusion 14 when the first assembly 40 is set in the first holding means 110 (first state). As a result, in the first state, the protrusion 14 of the outer tube 10 and the recess 113 of the first holding means 110 are fitted together, making it possible to uniquely determine a first index, which is the attitude of the outer tube 10 in the rotational direction about the axis of the large-diameter end 13 of the outer tube 10. That is, the convex portion 14 of the outer tube 10 and the concave portion 113 of the first holding means 110 constitute a first mechanism, and the first indexing of the first assembly 40 is achieved by the first mechanism.

[0117] 2 to 5 and 7 includes a recess 24 formed as a notch recessed in the axial direction from the tip surface of the large-diameter end 23. As illustrated in the enlarged views of portion P1 in FIGS. 3 and 5, the first holding means 110 includes a protrusion 114 that protrudes in the axial direction from a position facing the recess 24 on the abutment surface 112 when the first assembly 40 is set in the first holding means 110 (first state). As a result, in the first state, the recess 24 of the inner tube 20 and the protrusion 114 of the first holding means 110 fit together, making it possible to uniquely determine a first index, which is the orientation of the inner tube 20 in the rotation direction around the axis of the large-diameter end 23 of the inner tube 20. In other words, the recess 24 of the inner tube 20 and the protrusion 114 of the first holding means 110 constitute a second mechanism, and the second index of the first assembly 40 is achieved by the second mechanism.

[0118] <effect> As described above, the first state achieved by the execution of the first step becomes the second state by the execution of the second step, and the third state by the execution of the third step. However, as illustrated in Figures 3 and 5, from the first state to the third state, the convex portion 14 of the outer tube 10 is engaged with the concave portion 113 of the first holding means 110, and the concave portion 24 of the inner tube 20 is engaged with the convex portion 114 of the first holding means 110. That is, in the fourth method, the first indexing and the second indexing of the first assembly 40 are achieved by the first mechanism and the second mechanism, respectively, from the first step to the third step. As a result, the holding postures of the outer tube 10 and the inner tube 20 subjected to the fourth method are consistently and uniquely determined, and therefore, the fourth method can reliably manufacture double taper portions with higher dimensional accuracy.

[0119] For the purpose of explaining the present invention, several embodiments having specific configurations have been described above, sometimes with reference to the accompanying drawings. However, the scope of the present invention should not be construed as being limited to these exemplary embodiments, and it goes without saying that appropriate modifications can be made within the scope of the claims and the matters described in the specification. [Explanation of symbols]

[0120] 10…Outer tube 11...Tapered section 12…Small diameter end 13...Large diameter end 14...Convex part 20…Inner tube 21...Tapered section 22…Small diameter end 23...Large diameter end 24...recess 30...Elastic member 40…First assembly 50…Second assembly 110...Second holding means 111…Inner core metal 112…Abutting surface 113...recess 114...Convex part

Claims

1. A method for manufacturing a double tapered portion, comprising: introducing an inner tube having a small diameter end and a large diameter end at both ends of a tapered portion into an outer tube having a small diameter end and a large diameter end at both ends of a tapered portion; fixing the small diameter end of the outer tube and the small diameter end of the inner tube in close contact with each other; and providing a gap between the outer tube and the inner tube in the tapered portion and the large diameter end, a first step of introducing the inner pipe from the large diameter end side of the outer pipe into the interior of the outer pipe, with the small diameter end side of the inner pipe at the leading end, while maintaining the large diameter end of the outer pipe and the large diameter end of the inner pipe coaxially, until at least a portion of the small diameter end of the inner pipe reaches the inside of the small diameter end of the outer pipe, and achieving a first state in which a first assembly, which is an assembly of the outer pipe and the inner pipe whose relative positions are determined by sandwiching an elastic member, which is an elastically deformable member, between the inner peripheral surface of the large diameter end of the outer pipe and the outer peripheral surface of the large diameter end of the inner pipe, is set in a first holding means that holds at least the large diameter end of the inner pipe; a second step of achieving a second state in which the first assembly is also set in a second holding means separate from the first holding means, with the small diameter end of the outer pipe and the small diameter end of the inner pipe constituting the first assembly being coaxial with each other; a third step of achieving a third state in which the small diameter end of the outer pipe and the small diameter end of the inner pipe are tightly fixed to each other by reducing the diameter of the small diameter end of the outer pipe and / or expanding the diameter of the small diameter end of the inner pipe, thereby forming a second assembly; Including, the inner diameter of at least a portion of the tapered portion and the small diameter end portion of the outer pipe in the first state is larger than the inner diameter of at least a portion of the tapered portion and the small diameter end portion of the outer pipe in the third state, and / or the outer diameter of at least a portion of the tapered portion and the small diameter end portion of the inner pipe in the first state is smaller than the outer diameter of at least a portion of the tapered portion and the small diameter end portion of the inner pipe in the third state, to an extent that the outer pipe and the inner pipe do not interfere with each other in the first step and the second step. A method for manufacturing a double tapered portion.

2. 2. A method for manufacturing a double tapered portion according to claim 1, comprising: In the outer tube and / or the inner tube, the axis of the small diameter end and the axis of the large diameter end intersect at a predetermined angle or are in a geometrically twisted relationship. A method for manufacturing a double tapered portion.

3. 3. A method for manufacturing a double tapered portion according to claim 1 or 2, comprising: in the second step, while maintaining the second state, the first holding means presses the inner pipe from the large diameter end side toward the small diameter end side in the axial direction of the small diameter end of the inner pipe, thereby causing a tip surface of the small diameter end of the inner pipe to protrude from a tip surface of the small diameter end of the outer pipe by a first distance, which is a predetermined distance in the axial direction of the small diameter end of the inner pipe. A method for manufacturing a double tapered portion.

4. 3. A method for manufacturing a double tapered portion according to claim 1 or 2, comprising: a first mechanism configured to uniquely determine a first index, which is the attitude of the outer tube in a rotation direction around the axis of the large diameter end of the outer tube, is configured in a pair of the first holding means and the outer tube; a second mechanism configured to uniquely determine a second index, which is an attitude of the inner tube in a rotation direction around the axis of the large diameter end of the inner tube, is configured in a pair of the first holding means and the inner tube, the first indexing and the second indexing of the first assembly are accomplished by the first mechanism and the second mechanism, respectively; A method for manufacturing a double tapered portion.

5. 4. A method for manufacturing a double tapered portion according to claim 3, comprising: a first mechanism configured to uniquely determine a first index, which is the attitude of the outer tube in a rotation direction around the axis of the large diameter end of the outer tube, is configured in a pair of the first holding means and the outer tube; a second mechanism configured to uniquely determine a second index, which is an attitude of the inner tube in a rotation direction around the axis of the large diameter end of the inner tube, is configured in a pair of the first holding means and the inner tube, the first indexing and the second indexing of the first assembly are accomplished by the first mechanism and the second mechanism, respectively; A method for manufacturing a double tapered portion.

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