阅读说明：本技术 波纹管及其制造方法 (Corrugated pipe and manufacturing method thereof ) 是由 中平雄人 山崎元气 于 2019-03-06 设计创作，主要内容包括：本发明提供一种能提高管或快速连接器的压入工作操作性能的波纹管及其制造方法。波纹管(10)包括由第一波纹管部(15)和第二波纹管部(16)构成的挠性部(11)和分别在所述挠性部(11)的两端设置为一体的直管部(12、13)。设置在直管部(12)和第一波纹管部(15)之间的第二波纹管部(16)的山部(23)的间距(P2)是通过使在轴心方向上的谷部(24)的长度大于第一波纹管部(15)的谷部(22)的长度来使该间距(P2)大于第一波纹管部(15)的山部(21)的间距(P1)的。(The present invention provides a corrugated pipe capable of improving press-in operation performance of a pipe or a quick connector and a manufacturing method thereof. The corrugated tube (10) comprises a flexible portion (11) composed of a first corrugated tube portion (15) and a second corrugated tube portion (16), and straight tube portions (12, 13) provided integrally at both ends of the flexible portion (11). A pitch (P2) of the ridges (23) of the second bellows portion (16) provided between the straight tube portion (12) and the first bellows portion (15) is such that the length of the trough portion (24) in the axial direction is greater than the length of the trough portion (22) of the first bellows portion (15), and the pitch (P2) is greater than the pitch (P1) of the ridges (21) of the first bellows portion (15).)

1. A corrugated tube in which a flexible portion and a straight tube portion in a straight tube shape at one end of the flexible portion are provided,

the flexible portion includes:

a corrugated first bellows portion in which a plurality of mountain portions are formed at a first pitch;

a corrugated second bellows portion provided between the first bellows portion and the straight tube portion, wherein a plurality of mountain portions are formed at a second pitch larger than the first pitch,

in the second bellows portion, the length of the peak portion in the axial direction is the same as the length of the first bellows portion in the axial direction, and the length of the valley portion in the axial direction is larger than the length of the valley portion of the first bellows portion in the axial direction.

2. The bellows of claim 1,

the wall thickness of the second bellows portion is the same as or greater than the wall thickness of the first bellows portion.

3. The bellows according to claim 1 or 2,

the straight tube portions are formed at both end portions of the flexible portion respectively,

the second bellows portion is provided between the straight tube portion and the first bellows portion at least one end portion.

4. A method of manufacturing a corrugated pipe, comprising:

a feeding step of feeding a tubular molding material vertically downward at a constant feeding amount per unit time;

and a forming step of forming while placing the forming material in a mold and moving the mold vertically downward at a constant speed, wherein a straight tube portion forming surface for forming a straight tube portion in a straight tube shape, a first bellows portion forming surface for forming a first bellows portion in a bellows shape in which a plurality of mountain portions are arranged at a first pitch, and a second bellows portion forming surface for forming a second bellows portion in a bellows shape in which a plurality of mountain portions are arranged at a second pitch larger than the first pitch are formed in this order along a moving direction in the order of the straight tube portion forming surface, the second bellows portion forming surface, and the first bellows portion forming surface.

Technical Field

The invention relates to a corrugated pipe and a manufacturing method thereof.

Background

There is known a corrugated resin pipe which can be bent freely so as to be able to form a pipe in a desired path and shape. The corrugated tube is used for protection of wiring, a filler tube, and the like. For example, as a bellows used as a filler pipe, there is a bellows including a flexible portion that can be bent freely and straight pipe-shaped straight pipe portions that are formed at both ends of the flexible portion and are hardly bent. The flexible portion is formed in a bellows shape by alternately arranging convex ridges and concave valleys which are annular in the circumferential direction, and is freely bendable. Further, a fuel tank or a fuel filler pipe is connected to the straight pipe portion. In this connection, a pipe or a quick connector connected to the pipe is usually press-fitted into the straight pipe portion (for example, see patent document 1).

Disclosure of Invention

Problems to be solved by the invention

However, when a pipe or a quick connector is press-fitted into the straight pipe portion of the corrugated pipe, a force is required to be applied to the corrugated pipe in the axial direction thereof. In this case, when the flexible portion is gripped and pushed in due to a restriction in an operation space or the like, if the direction of the applied force is deviated from the axial center direction, the flexible portion may be bent and the pushing may not be performed. Further, since the force required for press-fitting is large, the flexible portion may be bent and broken. On the other hand, if a sufficiently large force is not applied, the pipe or the quick connector is not completely pushed in, which causes leakage or separation.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a corrugated tube capable of improving the press-in working workability of a tube or a quick connector, and a method for manufacturing the same.

Means for solving the problems

The corrugated tube of the present invention is a corrugated tube provided with a flexible portion and a straight tube portion in a straight tube shape at one end of the flexible portion, the flexible portion including: a corrugated first bellows portion in which a plurality of mountain portions are formed at a first pitch; and a corrugated second bellows portion provided between the first bellows portion and the straight tube portion, wherein a plurality of mountain portions are formed at a second pitch larger than the first pitch, and in the second bellows portion, a length of the mountain portions in an axial direction is equal to a length of the mountain portions in the axial direction of the first bellows portion, and a length of the valley portions in the axial direction is larger than a length of the valley portions in the axial direction of the first bellows portion.

The method for manufacturing the corrugated pipe comprises the following steps: a feeding step of feeding a tubular molding material vertically downward at a constant feeding amount per unit time; and a forming step of forming the material by placing the material in a mold and moving the mold vertically downward at a constant speed, wherein a straight pipe portion forming surface for forming a straight pipe portion in a straight pipe shape, a first bellows portion forming surface for forming a first bellows portion in a bellows shape in which a plurality of mountain portions are arranged at a first pitch, and a second bellows portion forming surface for forming a second bellows portion in a bellows shape in which a plurality of mountain portions are arranged at a second pitch larger than the first pitch are formed in this order along a moving direction of the straight pipe portion forming surface, the second bellows portion forming surface, and the first bellows portion forming surface.

Effects of the invention

According to the present invention, by providing the second bellows portion having the larger pitch of the mountain portions than the first bellows portion between the first bellows portion and the straight tube portion, the second bellows portion having high bending rigidity can be used in addition to the straight tube portion when the pipe or the quick connector is press-fitted into the straight tube portion. This improves workability when the pipe or the quick connector is pressed into the straight pipe portion. Further, since the second bellows portion has flexibility, the bellows can be arranged in a desired path and shape.

Drawings

Fig. 1 is a plan view showing a bellows according to the present embodiment.

Fig. 2 is a sectional view showing a section of the bellows.

Fig. 3 is an explanatory view schematically showing a structure of a corrugator.

Fig. 4 is a plan view showing a corrugated pipe having a second corrugated pipe portion in which mountain portions are formed at different pitches.

Fig. 5 is a graph showing the relationship between the average wall thickness ratio and the average failure pressure ratio of the straight tube portion.

Detailed Description

In fig. 1, a corrugated tube 10, for example, used as a filling tube, includes: the flexible pipe has a flexible portion 11 and straight pipe portions 12 and 13 integrally formed at both ends of the flexible portion 11. The flexible portion 11 is constituted by a first bellows portion 15 and a second bellows portion 16. A second bellows portion 16 is integrally provided at one end of the first bellows portion 15, and a straight tube portion 13 is integrally provided at the other end of the first bellows portion 15. Further, a straight tube portion 12 is integrally provided at one end of the second bellows portion 16 on the opposite side to the first bellows portion 15. Therefore, the second bellows portion 16 is provided between the first bellows portion 15 and the straight tube portion 12.

In the corrugated tube 10 of this example, it is assumed that a quick connector or a tube is press-fitted into the straight tube portion 12, and the second corrugated tube portion 16 is provided only on the straight tube portion 12 side of the flexible portion 11. Further, a second bellows part 16 may be provided between the first bellows part 15 and the straight tube part 13.

The first bellows portion 15 is formed in a bellows shape in which convex peak portions 21 formed in a ring shape along the circumferential direction of the bellows 10 and concave valley portions 22 also formed in a ring shape are alternately and continuously provided in the axial direction (arrow X direction) of the bellows 10. The second bellows portion 16 is formed in a bellows shape, in which convex ridges 23 and concave valleys 24 formed in a ring shape are alternately and continuously provided in the axial direction of the bellows 10, as in the first bellows portion 15. The peak portions 21 and 23 of the first bellows portion 15 and the second bellows portion 16 have the same outer diameter and the same shape. Further, the outer diameters of the trough portions 22 of the first bellows portion 15 and the trough portions 24 of the second bellows portion 16 are the same.

The mountain portions 21 of the first bellows portion 15 are formed at a pitch P1 (first pitch). The mountain portions 23 of the second bellows portion 16 are formed at a pitch P2 (second pitch) that is greater than the pitch P1 in order to be harder to bend than the first bellows portion 15. In this example, the length in the axial direction of the trough portion 24 of the second bellows portion 16 is made larger than the trough portion 22 of the first bellows portion 15, and the pitch P2 in the second bellows portion 16 is made larger than the pitch P1 in the first bellows portion 15. For example, in the first bellows portion 15, the trough portions 22 each have a substantially U-shaped cross section, a flat bottom length of 0mm and a pitch P1 of the ridge portions 21 of 3mm, whereas in the second bellows portion 16, the trough portions 24 each have a flat bottom length of 2mm and a pitch P2 of the ridge portions 23 of 5 mm.

The straight tube portions 12 and 13 are straight tube-shaped and have no mountain portions or valley portions formed therein. Therefore, the straight tube portions 12 and 13 are portions that are hardly bent. Further, in the straight tube portions 12 and 13, flanges 12b and 13b are integrally formed at the ends of straight tube main bodies 12a and 13a, respectively. In this example, the outer diameters of the straight pipe main bodies 12a and 13a are smaller than the outer diameters of the peak portions 21 and 23 and larger than the outer diameters of the valley portions 22 and 24.

In the bellows 10 configured as described above, the length in the axial direction of the trough portions 24 of the second bellows portion 16 is large, and thus the pitch P2 of the peak portions 23 is made larger than the pitch P1 of the peak portions 21 of the first bellows portion 15. Therefore, the second bellows portion 16 has a greater bending rigidity than the first bellows portion 15.

Since the second bellows portion 16 has appropriate bending rigidity in the bellows 10, for example, when the quick connector (or pipe) is connected to the straight tube portion 12, it is possible to apply a force of pressing the quick connector into the straight tube portion 12 by gripping the second bellows portion 16, instead of applying the force by gripping the straight tube portion 12. Even if the same connecting operation is performed by gripping the first bellows portion 15 or the straight tube portion 13, the second bellows portion 16 is provided so that the portion having a large bending rigidity together with the straight tube portion 12 is formed long, and therefore the force applied is hard to escape in the direction in which the flexible portion 11 is bent. Thus, the operation of pressing the bellows 10 into the quick connector is facilitated, and the operability is improved. Further, since the second bellows portion 16 has appropriate flexibility, the bellows 10 can be arranged in a desired path and shape.

The high bending rigidity of the second bellows portion 16 is also caused by the fact that the wall thickness (wall thickness) of the second bellows portion 16 is greater than the wall thickness of the first bellows portion 15. This point will be explained below. As shown in fig. 2, the thickness of the peak portion 21 of the first bellows portion 15 is t1a, the thickness of the valley portion 22 is t1b, the thickness of the peak portion 23 of the second bellows portion 16 is t2a, and the thickness of the valley portion 24 is t2 b. The thicknesses t1a, t2a are thicknesses of tops of the peaks 21, 23, and the thicknesses t1b, t2b are thicknesses of bottoms (portions having the smallest outer diameters) of the valleys 22, 24.

When the corrugated tube 10 is manufactured by a corrugator described later, the larger the pitch of the peaks 21 and 23, the smaller the surface area per unit length, and in particular, the greater the wall thicknesses t1b and t2b of the valleys 22 and 24 tend to be. As described above, since the pitch P2 of the second bellows portion 16 is larger than the pitch P1 of the first bellows portion 15, the wall thickness t2b of the trough portion 24 of the second bellows portion 16 is larger than the wall thickness t1b of the trough portion 22 of the first bellows portion 15. Thus, the second bellows portion 16 has greater bending rigidity than the first bellows portion 15. The thicknesses t1a and t2a of the ridges 21 and 23 are not so different from each other due to the difference in pitch.

When comparing the sizes of the thicknesses t1b, t2b of the trough portions 22, 24, the thickness t1b is preferably the thickness of the trough portion 22 adjacent to the second bellows portion 16, and the thickness t2b is preferably the thickness of the trough portion 24 adjacent to the first bellows portion 15. In the case where the trough portions extend in the axial direction of the bellows 10 as in the second bellows portion 16, for example, it is preferable to use a thickness at the center of the trough portions that is not affected by the mountain portions on both sides.

A corrugator 30 for making corrugated pipe 10 is schematically shown in fig. 3. The corrugator 30 is composed of an extruder 31, a forming section 32, and the like. The extruder 31 feeds a molding material 33 to the molding section 32. The molding material 33 is a thermoplastic resin, and is heated and softened by the extruder 31 and extruded in a tubular shape. The feeding speed of the molding material 33 fed from the extruder 31 is constant, that is, the feeding amount of the molding material 33 per unit time is constant.

The forming section 32 includes a pair of mold assemblies 35A, 35B and a vacuum suction mechanism 36. The die unit 35A includes a pair of pulleys 38, a seamless belt 39 wound around the pair of pulleys 38, a plurality of divided dies 41 constituting the dies, a motor (not shown) for moving the seamless belt 39 in the direction of the arrow in the drawing via the pulleys 38, and the like. On the outer peripheral surface of the seamless belt 39, a split die 41 is continuously attached along the traveling direction thereof. The die unit 35B is also configured similarly to the die unit 35A, and includes a pair of pulleys 38, a seamless belt 39, a plurality of split dies 41, a motor (not shown) for moving the seamless belt 39, and the like, and split dies 42 are continuously attached to the outer peripheral surface of the seamless belt 39.

The die assemblies 35A and 35B are driven so that the split dies 41 and 42 are cyclically moved in different directions from each other. Thus, the split dies 41 and 42 are aligned with the split dies corresponding to each other at the junction portion near the extruder 31, move downstream (right side in fig. 3) in the aligned state, are opened at the flow dividing portion, and then move toward the junction portion. The mold units 35A and 35B are driven so that the split molds 41 and 42 move at the same speed while maintaining a constant speed.

A molding surface (not shown) corresponding to the outer peripheral surface shape of the corrugated tube 10 is formed on the outer peripheral side surface of each of the split molds 41 and 42. The outer peripheral surface shape of the corrugated tube 10 is divided into a plurality of molding surfaces along the axial direction thereof in each of the divided molds 41 and 42. Therefore, the split molds 41 and 42 include a molding surface (straight pipe portion molding surface) corresponding to the shape of the straight pipe portion 12, a molding surface (second bellows portion molding surface) corresponding to the second bellows portion 16, a molding surface (first bellows portion molding surface) corresponding to the first bellows portion 15, and a molding surface corresponding to the shape of the straight pipe portion 13. In the corrugating machine 30, the split molds 41 and 42 are arranged so that the straight tube portion 12, the second bellows portion 16, the first bellows portion 15, and the straight tube portion 13 are formed in this order for one bellows 10.

A semi-annular concave portion corresponding to the peak portion 21 is formed at a pitch P1 on the molding surface corresponding to the first bellows portion 15, and a semi-annular concave portion corresponding to the peak portion 23 is formed at a pitch P2 on the molding surface corresponding to the second bellows portion 16. The molding surfaces corresponding to the first bellows portion 15 and the second bellows portion 16 include semi-annular convex portions corresponding to the trough portions 22, 24, but the convex portions corresponding to the trough portions 24 are longer than the convex portions corresponding to the trough portions 22 in the axial direction of the bellows 10 (the moving direction of the split molds 41, 42).

As described above, the hollow portion surrounded by the molding surface for molding the corrugated tube 10 is formed inside the aligned split molds 41 and 42. When aligned as described above, the split dies 41 and 42 take the molding material 33 from the extruder 31 into the hollow portion and move it downstream. When the split molds 41 and 42 that take the molding material 33 into the hollow portion are moved to the position of the vacuum suction mechanism 36, suction by the vacuum suction mechanism 36 is performed from suction ports (not shown) provided in the split molds 41 and 42. Thereby, the tubular molding material 33 is brought into close contact with the molding surfaces of the split molds 41 and 42, and a tubular shape corresponding to the molding surfaces is molded. After the molding material 33 is cured, the split molds 41 and 42 are opened at the split portions, and the molded portions are taken out from the insides thereof.

The manufacturing is continuously performed from the time when the molding material 33 is taken into the hollow portions of the split molds 41 and 42 to the time when the molded portions are taken out, and the split molds 41 and 42 are circulated and manufactured continuously in a state where the end portions of the plurality of corrugated tubes 10 are connected to each other. The plurality of corrugated tubes 10 are cut at respective ends to be separated into the respective corrugated tubes 10.

As described above, when the supply amount per unit time of the molding material 33 is constant for the die assemblies 35A, 35B in which the moving speeds of the split dies 41, 42 are constant, the supply amount per unit length of the molding material 33 of the corrugated tube 10 to be manufactured is constant. The unit length is the axial length of the bellows 10. Therefore, the wall thicknesses t1b, t2b of the trough portions 22 of the first bellows portion 15 and the trough portions 24 of the second bellows portion 16 in the axial direction of the bellows 10 manufactured by the corrugator 30 become larger as the surface areas per unit length of the corresponding first bellows portion 15, second bellows portion 16 become smaller. The surface area per unit length decreases as the distance between the mountain portions 21, 23 increases. Therefore, as described above, the surface area per unit length of the second bellows portion 16 is smaller than that of the first bellows portion 15 by increasing the pitch P2 of the ridges 23 of the second bellows portion 16 relative to the pitch P1 of the ridges 21 of the first bellows portion 15. As a result, the thickness t2b of the trough portion 24 of the second bellows portion 16 is greater than the thickness t1b of the trough portion 22 of the first bellows portion 15.

As described above, the bellows 10 provided with the second bellows portion 16 also has an effect of suppressing a decrease in pressure resistance due to thinning of the flexible portion caused by sagging of resin occurring during the manufacturing process. Hereinafter, the effect of suppressing the decrease in pressure resistance will be described.

The thinning of the flexible portion due to the sagging of the resin of the corrugated tube 10 is a phenomenon that occurs when a vertical corrugating machine is used. In a vertical corrugating machine, an extruder feeds a molding material downward (vertically downward), and performs molding while moving downward in a state in which corresponding split molds are aligned with each other. The structure of the other vertical corrugating machine is the same as that of the corrugating machine 30 shown in fig. 3, and therefore, illustration thereof will be omitted.

In the production of the corrugated tube 10 in the vertical corrugator, any of the straight tube portions, for example, the straight tube portion 12 is formed before the flexible portion 11, and the straight tube portion 12 is positioned below the flexible portion 11. The molded material 33 sags downward by gravity while it is completely solidified. In the straight tube portion 12 having no irregularities on the inner peripheral surface, the amount of sagging of the molding material 33 on the inner peripheral surface is larger than that on the inner peripheral surface of the flexible portion 11. As a result, the uncured portion of the molding material 33 on the inner peripheral surface of the straight tube portion 12 hangs down, and the portion of the molding material 33 on the inner peripheral surface of the flexible portion 11 moves downward, thereby reducing the thickness of the portion. In this way, the flexible portion 11 is thinned due to the sagging of the resin.

When the corrugated tube 10 is manufactured by a vertical corrugator, the thickness t2b of the trough portion 24 of the second bellows portion 16 is thicker than the thickness t1b of the trough portion 22 of the first bellows portion 15, and the difference in the distance does not occur much with respect to the thicknesses t1a and t2a of the peak portions 21 and 23. The second bellows portion 16 also tends to have a smaller thickness t2a, t2b as it approaches the straight tube portion 12.

In the conventional corrugated tube, the flexible portion is thinned due to the sagging of the resin, and the thickness of the flexible portion in the vicinity of the straight tube portion is thinner than that of the other portions of the flexible portion, so that the pressure resistance of the portion is lowered. In such a conventional bellows, the pressure resistance of the bellows is determined by the pressure resistance of the flexible portion that is thinned due to sagging of the resin.

In contrast, in the bellows 10 of this example, the thickness of the second bellows portion 16 is reduced by the downward movement of the partial molding material 33 on the inner peripheral surface of the second bellows portion 16 due to the sagging of the resin. However, by appropriately adjusting the pitch P2 of the peak portions 23, even if the resin droops as described above, the thickness of the second bellows portion 16 can be made the same as or thicker than the thickness of the first bellows portion 15. More specifically, the wall thickness t2b of the trough portion 24 of the second bellows portion 16 may be equal to or greater than the wall thickness t1b of the trough portion 22 of the first bellows portion 15.

Therefore, when the pitch of the ridges of the conventional bellows is the same as the pitch P1 of the ridges 21 of the first bellows portion 15, the thickness t2b of the trough portions 24 of the second bellows portion 16 is thicker than the thickness of the trough portions that are thinned by sagging of resin in the conventional bellows. Further, since the thickness t1b of the trough portion 22 of the first bellows portion 15 is not thinned due to sagging of the resin, the thickness is thicker than that of the thin trough portion thinned due to sagging of the resin in the conventional bellows. As a result, the pressure resistance of the flexible portion 11 including the second bellows portion 16, which is thinned due to sagging of the resin, of the bellows 10 is improved compared to the pressure resistance of the conventional bellows.

Further, of the peak portions 21 and 23 and the trough portions 22 and 24, a broken portion when an internal pressure is applied to the bellows 10 manufactured by the vertical corrugating machine in which the thickness t2a of the peak portion 23 is smallest and broken is the first bellows portion 15. It is considered that the increased wall thickness of the trough portions 24 of the second bellows portion 16 contributes to an improvement in pressure resistance.

The shape of the bellows, the number of the peak portions of each bellows portion, the pitch, and the like are examples, and are not limited thereto. The second bellows portion 16A of the bellows 10 shown in fig. 4 is shorter in length than that shown in fig. 1, and the first bellows portion 15 is lengthened by a component thereof so that the entire length of the bellows 10 is the same as that in fig. 1. The number of the peak portions 23 of the second bellows portion 16A is 3 (the peak portions including the boundary with the first bellows portion 15 and the boundary with the straight tube portion 12), and the pitch P3 (second pitch) of the peak portions 23 is, for example, 4.7 mm. Then, the pitch P3 of the ridges 23 of the second bellows portion 16A is increased relative to the pitch P1 of the ridges 21 of the first bellows portion 15, whereby the thickness t2b of the trough portion 24 of the second bellows portion 16A is made equal to or thicker than the thickness t1b of the trough portion 22 of the first bellows portion 15.