JP6345021B2 - Side by side - Google Patents

Description

The present invention relates to a parallel joint rod with a tube-like rod body.

  In a side-by-side casket that joins a plurality of housings, a configuration in which the rear end portion of the heel-side housing is inserted inside the front end portion of the heel-side housing may be employed. The inner peripheral surface of the tubular casing is usually a forward tapered shape that gradually increases in diameter toward the rear side, which is the base side. On the other hand, the circumferential surface has a reverse taper shape in which the diameter gradually increases toward the front side, which is the tip side, so that a good seamed state can be obtained.

  Since such a tubular casing is manufactured by winding a prepreg around a mandrel as a core material and heating and firing, the shape of the outer peripheral surface of the mandrel matches the shape of the inner peripheral surface of the tubular casing. It is said. Therefore, in the configuration in which the inner peripheral surface of the front end portion of the housing has an inversely tapered shape, the outer peripheral surface of the mandrel also has an inversely tapered shape in which the diameter gradually increases toward the front side. When decentering toward the side, it is necessary to forcibly pull out the reverse tapered portion of the mandrel from the housing over a long section.

  That is, the inner diameter of the housing is minimized at the rear end of the joint portion having a reverse taper shape, and the diameter gradually increases from there to the rear side, so the reverse taper portion of the mandrel is Then, it moves to the rear side while being elastically deformed so as to spread the reverse tapered portion of the housing outward in the radial direction. And even if the reverse tapered portion of the mandrel passes through the location of the minimum inner diameter of the housing, it further proceeds to the rear by a predetermined length from there and the inner diameter of the housing becomes larger than the outer diameter of the front end portion of the mandrel. In the same way, the reverse tapered portion of the mandrel elastically deforms the casing radially outward. However, if the housing is elastically deformed radially outward over a section where the reverse tapered portion of the mandrel is long at the time of decentering, the shape of the housing, particularly the shape of the front side thereof, is difficult to stabilize, and the joining portion Is difficult to form with high accuracy.

  On the other hand, there is a method in which the inner peripheral surface of the front end portion of the housing is formed into a reverse taper shape by reaming after heating and firing, that is, after molding (see Patent Document 1 below). However, since post-processing is required, there are problems that the manufacturing process increases and the manufacturing cost increases, and it is difficult to center the reaming, and it is not easy to ensure the coaxiality of the inner peripheral surface. In addition, the inner surface of the reverse taper shape is not a molding surface but a machined surface that has been machined by reamer processing, so that the reinforcing fiber is cut and the inner surface is likely to be rough. There is also a problem that the inner peripheral surface of the shape is worn and the joint portion is likely to be loose.

  Therefore, in order to form the inner surface of the reverse tapered shape by molding using a mandrel, there is a method of dividing the mandrel back and forth as in Patent Documents 2 and 3 below. That is, a mandrel part on the front side for forming the inner peripheral surface of the reverse taper shape and a mandrel part on the rear side for forming the inner peripheral surface of the forward taper shape whose diameter increases toward the rear side. As a two-piece configuration consisting of the above, the above-mentioned problem at the time of decentering is to be solved by pulling out the front mandrel part to the front side at the time of decentering.

  However, this method has the advantage that the mandrel can be smoothly decentered, but on the other hand, there is a problem that it is difficult to ensure the coaxiality of the two front and rear mandrel parts with high accuracy, and it is not always easy to manufacture. I couldn't say that further improvements were required.

JP 2009-39011 A Japanese Patent Publication No.54-33997 JP 2014-64520 A

Therefore the present invention has been made in view of the above problems, an easy to manufacture, and to provide also ensure ease Inami splicing rod accuracy of splicing portion.

The present invention has been made to solve the above-mentioned problems, and in the parallel splicing rod according to the present invention, the rear end portion of the tip side housing is joined inside the front end portion of the tubular base side housing. a parallel joint rod that is, the outer peripheral surface of the rear end portion of the rod tip side rod body has been painted, the inner peripheral surface of Saomoto side rod body is a molded surface formed by molding, rod source side The housing is located at the front end, the outer peripheral surface of the rear end portion of the tip side housing is in contact with the inner peripheral surface of the reverse taper shape that expands toward the front side, and the joint located on the rear side of the inner circumferential surface, and a main inner peripheral surface of the forward tapered shape gradually increased in diameter toward the径略constant straight shape or rear, and the next focus for the peripheral surface Omonai peripheral surface between the front of which is stepped portion is formed inside diameter of the rear side is larger than the inner diameter, the maximum inner diameter at the front region than the step portions and d1, in the region side after the step part When the small inner diameter is d2, the relation of d1 ≦ d2 is established, and the base side casing expands toward the front side at a larger taper rate than the inner peripheral surface for joining at the opening end. It is characterized by having an end inner peripheral surface of a reverse taper shape . The heel side is the front side and the heel side is the rear side. The parallel splicing rod according to the present invention is a splicing spear in which the rear end portion of the tip side housing is joined to the inside of the front end portion of the tubular base side housing, The outer peripheral surface of the rear end portion is unpainted, the inner peripheral surface of the heel side housing is a molding surface formed by molding, the heel side housing is located at the front end, and the tip side heel The outer peripheral surface of the rear end of the body is in contact with the inner peripheral surface of the reverse taper shape that expands toward the front side, and the rear surface of the inner peripheral surface for connection, and the diameter is substantially constant. It has a straight inner shape or a forward tapered main inner peripheral surface that expands toward the rear, and the inner diameter on the rear side of the front inner diameter is between the inner peripheral surface for connection and the main inner peripheral surface. Is formed, and the relationship is d1 ≦ d2 where d1 is the maximum inner diameter in the region in front of the step and d2 is the minimum inner diameter in the region behind the step. The base side housing is provided with an end inner peripheral surface having a taper ratio different from the inner peripheral surface for joining at the opening end, and the end inner peripheral surface is smaller in taper ratio than the inner peripheral surface for joining. Thus, it is a reverse taper shape with a diameter increasing toward the front side, a straight shape with a substantially constant diameter, or a forward taper shape with a diameter decreasing toward the front side.

  In the case of the parallel joint rod having the above structure, since the step portion is formed between the inner peripheral surface for joining and the main inner peripheral surface, the mandrel formed with the reverse tapered portion is arranged on the rear side. When pulling out toward the side, the section where the casing is forcibly pulled out while being elastically deformed radially outward can be shortened. That is, the region in front of the stepped portion is elastically deformed radially outward by the inversely tapered portion of the mandrel, but the stepped portion has a sharply increased inner diameter. In the rear region, the section that is elastically deformed radially outward by the inversely tapered portion of the mandrel is shorter than the conventional configuration without the stepped portion. Therefore, the mandrel can be pulled out smoothly after the reverse tapered portion of the mandrel passes through the stepped portion. And since the inner peripheral surface of the joint with a reverse taper shape is not a processed surface formed by post-reaming reaming, but a molding surface formed by molding, it is easy to ensure coaxiality, and for a long period of time. Even if used, it is hard to be worn out, and it is difficult for rattling to occur at the seam, and a good seam is maintained for a long time.

  In particular, it is preferable that d1 ≦ d2 is satisfied, where d1 is a maximum inner diameter in a region in front of the stepped portion and d2 is a minimum inner diameter in a region in the rear of the stepped portion. With this configuration, after the reverse tapered portion of the mandrel passes through the stepped portion, the housing is not elastically deformed by the reverse tapered portion of the mandrel, and the section where the mandrel is forcibly pulled out is a step. Only the area in front of the part is sufficient.

  Moreover, it is preferable to equip the opening end part with the end inner peripheral surface of the reverse taper shape diameter-expanded toward the front side with a taper rate larger than the inner peripheral surface for joining. The rear end portion of the tip side housing contacts the inner peripheral surface for joining, and the outer peripheral surface of the rear end portion of the tip side housing is on the rear side corresponding to the inner peripheral surface for joining. It has a reverse taper shape that decreases in diameter. And when the outer peripheral surface of the tip side housing is coated, the coating film may reach the outer peripheral surface of the rear end. In such a case, when the inner peripheral surface of the end portion having an inverse taper shape with a taper ratio larger than that of the inner peripheral surface for joining is formed at the opening end portion of the base-side housing, the two bodies are joined together. Therefore, it is possible to prevent the coating film of the tip side casing from being peeled off.

  Conversely, when the outer peripheral surface of the tip side housing is not painted, the opening end portion is provided with an end inner peripheral surface having a taper ratio different from that of the joining inner peripheral surface, and the end inner peripheral surface is: It is a reverse taper shape that expands toward the front side with a taper rate smaller than the inner peripheral surface for joining, a straight shape with a substantially constant diameter, or a forward taper that shrinks toward the front side The shape is preferred. When the outer peripheral surface of the heel side casing is not painted, there is no need to worry about peeling of the coating film, so by conversely reducing the taper ratio of the inner peripheral surface of the end portion, etc. The joined state can be secured. Moreover, the ingress of water from the seamed portion can be suppressed.

  As described above, by forming a step portion between the inner peripheral surface for joining and the main inner peripheral surface, post-processing such as reaming is unnecessary, and it can be easily manufactured with a single mandrel. Since the section where the mandrel is forcibly pulled out can be shortened, the accuracy of the joining portion is also ensured.

BRIEF DESCRIPTION OF THE DRAWINGS It is principal part sectional drawing of the parallel splicing rod in one Embodiment of this invention, Comprising: (a) shows the state before a casing is joined, (b) shows the state where a casing was spliced together. Show. Sectional drawing of the principal part of the base side housing | casing of the parallel splice in the same embodiment. The front view which shows the mandrel for manufacturing the same coffin former side housing. (A) And (b) is principal part sectional drawing which shows the heel side side housing | casing of the side-by-side spear in other embodiment of this invention. (A) And (b) is principal part sectional drawing which shows the heel side side housing | casing of the side-by-side spear in other embodiment of this invention. (A) And (b) is principal part sectional drawing which shows the heel side side housing | casing of the side-by-side spear in other embodiment of this invention.

  Hereinafter, a spliced kite and a casing thereof according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a spliced portion of side-by-side ridges according to the present embodiment, and FIG. 1 (a) shows a state in which the heel-side housing 1 and the heel-side housing 2 are separated from each other, and FIG. b) is a state in which the heel side housing 1 and the heel side housing 2 are joined together. The side-by-side rod is configured by joining a plurality of rods, but the number of rods is arbitrary, and may be two or three or more.

  The rear end portion of the heel side housing 1 is inserted and joined to the inside of the front end portion of the heel side housing 2, and the rear end portion of the heel side housing 1 is connected to the rear side. The outer peripheral surface 10 for joining of the reverse taper shape which is diameter-reduced toward is formed. The tip side casing 1 may be tubular, that is, hollow or solid, and is tubular as a whole, but a core material is inserted and fixed at the rear end thereof. The structure by which the outer peripheral surface 10 for joining was formed in the core material may be sufficient.

  The heel side housing 2 occupies most or the main part of the joint inner peripheral surface 20 with which the joint outer peripheral surface 10 of the heel side housing 1 abuts and the inner peripheral surface of the heel side housing 2. An inner peripheral surface 21 is provided, and a step portion 22 is formed between the joint inner peripheral surface 20 and the main inner peripheral surface 21. Specifically, the joining inner peripheral surface 20 is located at the front end of the heel side housing 2 and is formed from the front opening end 23 to a position behind a predetermined length. The inner peripheral surface 20 for joining is a reverse taper shape which reduces in diameter toward the rear side, and the shape corresponds to the outer peripheral surface 10 for joining of the tip side housing 1, and the outer peripheral surface 10 for joining. And the taper rate of the joint inner peripheral surface 20 are substantially equal to each other. The place where the inner diameter is the largest in the inner peripheral surface 20 for joining is the front end 20a of the inner peripheral surface 20 for joining. Therefore, the maximum inner diameter in the region in front of the step portion 22 is the inner diameter at the front end 20a of the inner peripheral surface 20 for joining. And the opening diameter at the opening end 23. The maximum inner diameter will be referred to as d1.

  A step portion 22 is formed at the rear end 20 b of the joining inner peripheral surface 20. The step portion 22 has any shape as long as the inner diameter on the rear side is larger than the inner diameter on the front side and the inner diameter on the rear side is larger than the inner diameter on the front side. Then, the surface is orthogonal to the axis 24 of the heel side housing 2. Therefore, the inner peripheral surface of the heel-side housing 2 has a diameter that is substantially perpendicular to the rear end 20b of the joining inner peripheral surface 20.

  A main inner peripheral surface 21 is formed on the rear side of the step portion 22. The rear end 20b of the joining inner peripheral surface 20 is the inner edge of the stepped portion 22, and the front end 21a of the main inner peripheral surface 21 is the outer edge of the stepped portion 22, and the inner diameter of the rear end 20b of the joining inner peripheral surface 20 is larger. Also, the inner diameter of the front end 21a of the main inner peripheral surface 21 is larger. Therefore, the step portion 22 is formed so as to connect the rear end 20 b of the joining inner peripheral surface 20 and the front end 21 a of the main inner peripheral surface 21. The main inner peripheral surface 21 has a straight shape with a substantially constant diameter or a forward tapered shape that expands toward the rear side. In any case, the inner diameter of the main inner peripheral surface 21 is at the front end 21a. Minimal. Therefore, the minimum inner diameter in the region on the rear side of the step portion 22 is the inner diameter of the front end 21 a of the main inner peripheral surface 21. If the minimum inner diameter in the region on the rear side of the step portion 22 is referred to as d2, it is preferable that d1 ≦ d2. That is, in the present embodiment, it is preferable that the maximum inner diameter of the main inner peripheral surface 21 is equal to or greater than the maximum inner diameter of the joining inner peripheral surface 20.

  As shown in FIG. 2, the heel side housing 2 is formed with the joining inner layer 25 only in the range from the opening end 23 to the stepped portion 22 in the entire length, and the inner circumferential surface of the joining inner layer 25 An inner circumferential surface 20 for joining is configured. And the thickness of the inner layer 25 for joining becomes thick gradually toward a rear side, and becomes the largest thickness in the level | step-difference part 22. FIG. However, the joining inner layer 25 may be provided so as to cross the stepped portion 22 to the rear side such that the inner layer 25 for joining protrudes from the stepped portion 22 to the rear side by a predetermined length. In addition, one or a plurality of fiber reinforced resin layers are formed on the outer side of the joining inner layer 25, and the number of layers and the layer configuration may be various. For example, the tape-shaped prepreg has a full length. An inner layer formed by being spirally wound and a sheet-like prepreg formed on the outer side of the inner layer, for example, in which reinforcing fibers are aligned in the direction of the axis 24 of the heel side housing 2 The formed intermediate layer and an outer layer formed on the outside of the intermediate layer and formed by winding a tape-like prepreg spirally over the entire length can be provided. Further, a reinforcing layer may be formed on the front end portion that is the outer portion of the outer layer and is a spliced portion. Although various reinforcing fibers such as carbon fibers can be used as the reinforcing fibers, it is preferable to use glass fibers for the inner layer 25 for joining. The glass fibers of the joining inner layer 25 may be aligned in the direction of the axis 24, may be aligned in the circumferential direction, and are inclined with respect to the direction of the axis 24 and intersect each other. It may be aligned in the direction.

  The inner peripheral surface of the heel side casing 2 formed as described above is a molding surface formed by molding, and not only the main inner peripheral surface 21 but also the inner peripheral surface 20 for joining are post-processed such as reamer processing. This is not a processed surface formed by the above process, but a molded surface. The heel-side housing 2 is formed by winding various prepregs around a mandrel 3 shown in FIG. Therefore, the shape of the outer peripheral surface of the mandrel 3 matches the shape of the inner peripheral surface of the heel side housing 2.

  The mandrel 3 extends to the rear side of the joining front part 30 via the step part 31 and the joining front part 30 having an outer peripheral face corresponding to the joining inner peripheral face 20, and corresponds to the main inner peripheral face 21. And a main portion 32 having an outer peripheral surface. The joining front portion 30 has a reverse tapered shape that decreases in diameter toward the rear side, and the main portion 32 has a straight shape with a substantially constant diameter or a forward tapered shape that increases in diameter toward the rear side. is there. The maximum diameter of the joining front portion 30 is the outer diameter at the front end 30a of the joining front portion 30 and is D1. The minimum diameter of the main portion 32 is the outer diameter at the front end 32a of the main portion 32, and it is preferable that D1 ≦ D2 when D2 is the minimum diameter.

  The prepreg is wound around the mandrel 3. The joining prepreg is placed on the innermost side in order to fill the stepped portion 31 of the mandrel 3 and level the outer peripheral surface of the mandrel 3. It is preferable to wind the prepreg, and the prepreg wound on the outer side can be wound neatly. The joining inner layer 25 is formed by the prepreg for filling. It is preferable that the prepreg for supplementation uses glass fiber. Thus, after winding various prepregs and heating and baking, the mandrel 3 is pulled out to the back side. At this time, since the joining front portion 30 has a reverse taper shape, the front end 30a of the joining front portion 30 is the rear end 20b of the joining inner peripheral surface 20, that is, the step portion 22 on the inner peripheral surface of the heel side housing 2. Until it passes, the inner circumferential surface 20 for joining is pushed out radially outward by the joining front part 30 and the inner circumferential surface 20 for joining is elastically deformed radially outward. When the joint inner layer 25 is formed and glass fiber is used for it, the joint inner layer 25 can be elastically deformed smoothly when the mandrel 3 is pulled out. Thus, it is preferable to use glass fiber for the reinforcing fiber of the layer constituting the inner peripheral surface 20 for joining.

  And since the inner diameter of the heel side housing 2 has expanded rapidly at the stepped portion 22, when the front end 30 a of the joining front portion 30 of the mandrel 3 passes the joining inner peripheral surface 20 to the rear side, The mandrel 3 can be pulled out without greatly elastically deforming the main inner peripheral surface 21 radially outward. In particular, when d1 ≦ d2 in the heel side housing 2 and D1 ≦ D2 in the mandrel 3, the front end 30a of the joining front portion 30 of the mandrel 3 is connected to the heel side housing 2. After passing through the step portion 22, the main inner peripheral surface 21 is not pushed outward in the radial direction, and the mandrel 3 can be pulled out more smoothly. That is, the section where the mandrel 3 is forcibly pulled out while elastically deforming the base side casing 2 radially outward is only the section of the inner circumferential surface 20 for joining. By forming the step portion 22 on the inner peripheral surface of the heel side housing 2 in this manner, the section in which the mandrel 3 is forcibly pulled out can be shortened as compared to the conventional case, and in particular, d1 ≦ d2 (D1 ≦ If the relationship D2) is established, the area where the mandrel 3 is forcibly pulled out may be only the area in front of the step portion 22. Therefore, the shape of the heel side housing 2 can be accurately formed according to the design value, and in particular, the shape of the joint portion can be formed with high accuracy. In addition, since it is not necessary to form the joint inner peripheral surface 20 by reamer processing or the like, it is possible to reduce the number of manufacturing steps and to reduce the cost, and to secure a high coaxiality with respect to the joint inner peripheral surface 20. Therefore, the seam-free joining state is maintained over a long period of time. Further, since the mandrel 3 also has a one-piece configuration, it is easier to manufacture than the conventional two-piece configuration, and the mandrel 3 can be manufactured with high precision. High accuracy can be secured for the degree of coaxiality with the peripheral surface 20.

  In addition, you may form the edge part inner peripheral surface 26 of the shape different from the inner peripheral surface 20 for joining in the opening edge part of the front side of the collar side housing 2. For example, as shown in FIG. 4 (a), an end inner peripheral surface 26 having a reverse taper shape whose diameter is increased toward the front side at a taper rate larger than the inner peripheral surface 20 for joining is formed at the opening end. Also good. In this way, when the end inner peripheral surface 26 having a taper ratio larger than the taper ratio of the joint inner peripheral surface 20 is formed at the opening end, it is effective when the outer peripheral surface of the tip side housing 1 is painted. . That is, when the outer peripheral surface of the tip side casing 1 is painted, the coating film may reach the joint outer peripheral surface 10. In such a case, an end inner peripheral surface 26 having a reverse taper shape with a taper ratio larger than that of the inner peripheral surface 20 for joining is formed at the opening end portion of the base-side casing 2, thereby providing a casing. It can prevent that the coating film of the heel side casing 1 peels off by joining together. In the case of FIG. 4A, the maximum inner diameter d1 in the region in front of the step portion 22 is the opening diameter at the opening end 23 and the inner diameter at the front end of the end inner peripheral surface 26.

  Conversely, as shown in FIG. 4B, a forward tapered end inner peripheral surface 26 that decreases in diameter toward the front side may be formed at the opening end. When the outer peripheral surface of the tip side housing 1 is not painted, there is no need to worry about peeling of the coating film. The joined state can be secured. In the case of FIG. 4B, the maximum inner diameter d1 in the region in front of the step portion 22 is the inner diameter at the rear end of the end inner peripheral surface 26, that is, the front end 20a of the connecting inner peripheral surface 20. The end inner peripheral surface 26 may have a straight shape with a substantially constant diameter. Further, the end inner peripheral surface 26 may have a reverse taper shape like the joint inner peripheral surface 20, but in that case, the taper rate of the end inner peripheral surface 26 is determined from the taper rate of the joint inner peripheral surface 20. By reducing the length, it is possible to secure a more stable seamed state.

  Various changes can be made to the configuration of the region in front of the step portion 22, for example, the diameter between the inner peripheral surface 20 for joining and the step portion 22 is substantially constant as shown in FIG. A straight intermediate intermediate surface 27 may be provided, or a forward taper that increases in diameter toward the rear side between the joint inner peripheral surface 20 and the stepped portion 22 as shown in FIG. A shaped intermediate inner peripheral surface 27 may be provided. Further, the intermediate inner peripheral surface 27 may have a reverse taper shape in which the diameter decreases toward the rear side with a taper rate smaller than the taper rate of the joint inner peripheral surface 20, and is a combination of a plurality of shapes. May be. As described above, the shape of the region in front of the step portion 22 can be changed as appropriate.

  Furthermore, the shape of the stepped portion 22 may be various shapes, and the stepped portion 22 is constituted by a single surface orthogonal to the axis 24 of the heel side housing 2 as described above. As shown in FIG. 6A, there is a step from a surface 22a orthogonal to the axis 24 of the heel side housing 2 and an inclined surface 22b inclined at an inclination angle of less than 90 degrees with respect to the axis 24 of the heel side housing 2. The part 22 may be configured. That is, you may comprise a part of level | step-difference part 22 from the inclined surface 22b. Conversely, the inclined surface 22b may be positioned inside the surface 22a perpendicular to the axis 24 of the heel side housing 2. In the case of FIG. 6A, a chamfered portion is formed on the outer peripheral portion of the stepped portion 22 of the mandrel 3 shown in FIG. 3, and an inclined surface 22b in the stepped portion 22 of the base side housing 2 is formed by the chamfered portion. can do. The inclined surface 22b may be a flat surface as shown in FIG. 6A or a curved surface. Further, as shown in FIG. 6B, the entire stepped portion 22 may be configured by an inclined surface 22 b inclined at an inclination angle of less than 90 degrees with respect to the axis 24 of the heel side housing 2. In this case as well, the inclined surface 22b may be a curved surface. As described above, the shape of the stepped portion 22 of the heel side housing 2 may be various.

DESCRIPTION OF SYMBOLS 1 Tip side housing 2 Base side housing 3 Mandrel 10 Outer peripheral surface 20 Joint inner peripheral surface 20a Front end 20b Rear end 21 Main inner peripheral surface 21a Front end 22 Stepped portion 22a Orthogonal surface 22b Inclined surface 23 Open end 24 Axis 25 Inner layer for joining 26 End inner peripheral surface 27 Intermediate inner peripheral surface 30 Front part for joining 30a Front end 31 Step part 32 Main part 32a Front end

Claims (2)

Inside of the front end of the tubular rod root side rod body a parallel joint rod the rear end is spliced in Saosaki side rod body,
The outer peripheral surface of the rear end of the tip side housing is painted,
The inner peripheral surface of the heel side housing is a molding surface formed by molding, the heel side housing is located at the front end, and the outer peripheral surface of the rear end portion of the heel side housing contacts, Positioned on the back inner side of the joint with a reverse taper shape that increases in diameter toward the front side and on the rear side of the inner peripheral surface for connection, the diameter increases toward a straight shape with a substantially constant diameter or the rear side. a main inner peripheral surface of the forward tapered shape, between the joint coupling for the peripheral surface Omonai peripheral surface is stepped portion is formed inside diameter of the rear side is larger than the front of the inner diameter,
When the maximum inner diameter in the region on the front side from the step portion is d1, and the minimum inner diameter in the region on the rear side from the step portion is d2, the relationship is d1 ≦ d2.
The base side housing is provided with a reverse tapered end inner peripheral surface at the opening end portion, which has a taper ratio larger than that of the joining inner peripheral surface and increases toward the front side. Seam . A side-by-side spear where the rear end of the tip side casing is joined to the inside of the front end of the tubular base side casing,
The outer peripheral surface of the rear end of the tip side housing is unpainted,
The inner peripheral surface of the heel side housing is a molding surface formed by molding, the heel side housing is located at the front end, and the outer peripheral surface of the rear end portion of the heel side housing contacts, Positioned on the back inner side of the joint with a reverse taper shape that increases in diameter toward the front side and on the rear side of the inner peripheral surface for connection, the diameter increases toward a straight shape with a substantially constant diameter or the rear side. A forward taper-shaped main inner peripheral surface is provided, and between the inner peripheral surface for joining and the main inner peripheral surface, there is formed a step portion in which the inner diameter on the rear side is larger than the inner diameter on the front side,
When the maximum inner diameter in the region on the front side from the step portion is d1, and the minimum inner diameter in the region on the rear side from the step portion is d2, the relationship is d1 ≦ d2.
The flange-side housing has an end inner peripheral surface with a taper ratio different from the inner peripheral surface for joining at the opening end, and the end inner peripheral surface is at the front side with a smaller taper ratio than the inner peripheral surface for joining. A parallel spear that has a reverse tapered shape that increases in diameter toward the front, a straight shape that has a substantially constant diameter, or a forward tapered shape that decreases in diameter toward the front side.

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