Method for manufacturing a pressure-resistant hose having a reinforcing layer and a pressure-resistant hose

Abstract

Provided are a pressure-resistant hose structure and a manufacturing method thereof, which is formed by extrusion molding, has a reinforcing layer of hard resin or rubber, has flexibility in the bending direction, kink resistance, and pressure resistance, does not require processes such as braiding threads or winding woven fabrics, and is made entirely of the same type of synthetic resin or synthetic rubber. [Solution] The pressure-resistant hose (1) has a multi-layer structure with a reinforcing layer (3) made of hard resin between an outer layer (2) and an inner layer (4) made of soft resin, and a spiral groove (5) is formed on the outer surface of the reinforcing layer (3) using a groove-forming blade attached to a rotating body, creating unevenness on the outer surface of the reinforcing layer (3) consisting of spirally continuous convex and concave portions with square cross-sections.

Description

[Technical Field]

[0001] The present invention relates to a pressure-resistant hose that is required to have high pressure resistance, such as an intake and exhaust piping hose for pneumatic equipment or an intake and exhaust piping hose in an engine compartment of a vehicle. [Background technology]

[0002] Generally, hoses with improved pressure resistance have been proposed, such as wound hoses made of rubber, resin, or the like, with a reinforcing layer of braided thread, fabric-wrapped hoses with a woven fabric reinforcing layer (see, for example, Patent Documents 1 and 2), and hoses in which a string-like hard resin is wrapped around the hose as a reinforcing material (see, for example, Patent Document 3).

[0003] Also proposed is a hose that has spiral grooves in its inner layer to improve the flame resistance and breakage prevention of the hose (see, for example, Patent Document 4). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Unexamined Patent Publication No. 167991 / 1983 [Patent Document 2] Special Publication No. 2015-522765 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-158038 [Patent Document 4] Special Publication No. 2019-512649 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the prior art disclosed in Patent Documents 1 and 2, the equipment used to braid the yarn during the manufacturing process is complex, limiting the speed at which the yarn can be braided. In addition, the hose is manufactured while operating the equipment that winds the braided yarn or woven fabric around the inside of the hose, so the production speed is limited by these devices.

[0006] Furthermore, when a bobbin that supplies yarn or woven fabric on a production line becomes empty, production must be stopped and the bobbin must be replaced, which is also a factor that reduces production efficiency.

[0007] Furthermore, in the conventional technologies disclosed in Patent Documents 1 and 2, although the braided thread reinforcing layer or woven fabric reinforcing layer improves resistance to expansion due to internal pressure, there is a problem in that it is difficult to improve kink resistance against crushing that occurs when the hose is bent.

[0008] Furthermore, in the conventional technologies disclosed in Patent Documents 1 and 2, it is difficult to separate the reinforcing layer made of yarn or woven fabric from the inner and outer coating layers made of synthetic rubber or synthetic resin during recycling, which significantly reduces recycling performance.

[0009] Furthermore, in the method proposed in Patent Document 3 in which string-like hard resin is wound around the material, the winding device is complex, and the upper limit of the production speed of the product is determined by the operating speed of the device.

[0010] Furthermore, when the bobbin that supplies the string-like hard resin becomes empty, production must be stopped to replace the bobbin, and this work also reduces production efficiency.

[0011] Furthermore, in the hose proposed in Patent Document 4, in which a spiral groove is provided on the outer periphery of the inner layer, the spiral groove is limited to the outer periphery of the inner layer, and in a molded product with such varying thickness, so-called sink marks occur, making it difficult to mold the smooth inner periphery of the hose, which is the flow surface. Furthermore, Patent Document 4 does not disclose a method for forming the spiral groove, and the cross-sectional structure of the spiral groove is a curved shape such as a sine wave.

[0012] The present invention has been made to solve the above problems, and provides a pressure-resistant hose with a resin-reinforced layer that does not require the steps of braiding threads or winding braided threads or woven fabric inside the hose when manufacturing the hose, has pressure resistance against expansion, flexibility when bending, improves the kink resistance of the pressure-resistant hose against crushing when bent, improves recyclability, and further does not require complex production equipment or the replacement of empty bobbins. [Means for solving the problem]

[0013] In order to solve the above problems, the method for manufacturing a pressure hose according to the present invention includes the steps of: extruding an extrusion molded product (40) of a pressure hose in which a reinforcing layer (3) made of a hard resin is provided on the outside of an inner layer (4) made of a soft resin; and rotating a groove forming blade (23) on the outside of the extruded extrusion molded product (40) of the pressure hose to cut the outer circumferential surface of the reinforcing layer (3) of the extrusion molded product (40) to form a spiral groove (5) extending in the longitudinal direction, thereby forming spirally continuous convex portions (5a) and concave portions (5b) with a square cross section on the outer circumferential surface of the reinforcing layer (3). A process of providing an outer layer (2) made of a soft resin on the outside of an extrusion-molded pressure hose (40) having a reinforcing layer (3) on its outer circumferential surface with a convex portion (5a) and a concave portion (5b) having a square cross section formed by a spiral groove (5). and The method for manufacturing a pressure-resistant hose according to the present invention is characterized by comprising the steps of: extruding an extrusion-molded product (40) of a pressure-resistant hose having a reinforcing layer (3) made of a hard resin; rotating a groove-forming blade (23a) on the outside of the extruded extrusion-molded product (40) of the pressure-resistant hose to cut the outer surface of the reinforcing layer (3) of the extrusion-molded product (40) and form a spiral groove (5) extending in the longitudinal direction, thereby forming convex portions (5a) and concave portions (5b) with a square cross section that are continuous in a spiral pattern on the outer surface of the reinforcing layer (3); and providing an outer layer (2) made of a soft resin on the outside of the extrusion-molded product (40) of the pressure-resistant hose having the convex portions (5a) and concave portions (5b) with a square cross section formed by the spiral groove (5) on the outer surface of the reinforcing layer (3). Furthermore, the method for manufacturing a pressure-resistant hose according to the present invention is characterized in that in the step of cutting the outer peripheral surface of the reinforcing layer (3) of the extrusion-molded product (40) with a rotating groove-forming blade (23a) to form convex portions (5a) and concave portions (5b) with square cross sections formed by spiral grooves (5) on the outer peripheral surface, the spacing of the spiral grooves (5) can be changed by changing the rotation speed of the groove-forming blade (23a). Further, the pressure resistant hose according to the present invention is The reinforcing layer (3) is made of a hard resin, has a smooth inner peripheral surface, and has a spiral groove (5) on the outer peripheral surface, the spiral groove having a square cross section of convex portions (5a) and concave portions (5b) that are spirally continuous, and has an outer layer (2) made of a soft resin and provided with a smooth outer peripheral surface on the outside of the reinforcing layer (3). It is characterized by: The pressure resistant hose according to the present invention is also characterized in that an inner layer (4) made of a soft resin is further provided inside the reinforcing layer (3). [Effects of the Invention]

[0014] Therefore, in the present invention, the spiral grooves (3) extending in the longitudinal direction of the outer peripheral surface of the reinforcing layer (3) of the pressure-resistant hose form continuous spiral convex portions (5a) and concave portions (5b) with a square cross section on the outer peripheral surface of the reinforcing layer (3), which eliminates the need for a process of braiding threads or winding braided threads or woven fabric around the inside of the hose when manufacturing the hose, thereby improving pressure resistance against expansion and flexibility in bending. Furthermore, since the continuous spiral convex portions (5a) and concave portions (5b) with a square cross section are formed on the outer peripheral surface of the reinforcing layer (3) of the pressure-resistant hose and the inner peripheral surface of the reinforcing layer (3) is smooth, the kink resistance of the pressure-resistant hose against crushing when bent is improved, improving recyclability, and further, a pressure-resistant hose with a resin reinforcing layer can be provided that does not require complex production equipment or replacement of empty bobbins. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a cross-sectional perspective view of a pressure-resistant hose having a three-layer structure of an inner layer, a reinforcing layer, and an outer layer according to an embodiment of the present invention. [Figure 2] 1 is a cutaway view showing an inner layer, an outer layer, and a reinforcing layer of a pressure hose having a three-layer structure according to an embodiment of the present invention. FIG. [Figure 3] 1 is an explanatory diagram showing, in a simplified form, the entire manufacturing process of a method for manufacturing a pressure-resistant hose according to an embodiment of the present invention. FIG. [Figure 4]4 is a diagram showing an example of the configuration of the groove forming blade and groove forming mechanism in FIG. 3, showing a state in which a spiral groove is formed by the groove forming blade on the outer peripheral surface of an extruded molded product. FIG. [Figure 5] FIG. 2 is an enlarged perspective view showing irregularities caused by spiral grooves formed in a reinforcing layer. [Figure 6] (a) to (c) are a side view and a front view showing an example of a two-layer pressure-resistant hose in which spiral grooves with varying groove spacing are formed on the outer surface of the reinforcing layer by changing the rotation speed of the rotor, and an explanatory diagram illustrating the different ways in which the pressure-resistant hose bends. [Figure 7] 1(a) to 1(d) are diagrams showing examples of groove forming blades attached to a rotating body used in the method for manufacturing a pressure hose of the present embodiment. [Figure 8] 1 is a cross-sectional perspective view of a pressure-resistant hose according to an embodiment of the present invention, which is a pressure-resistant hose having a two-layer structure of an inner layer and a reinforcing layer. [Figure 9] 1 is a cross-sectional perspective view of a pressure-resistant hose according to an embodiment of the present invention, which is a pressure-resistant hose having a two-layer structure of an outer layer and a reinforcing layer. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the method for manufacturing a pressure-resistant hose having a reinforcing layer and the pressure-resistant hose according to the present invention will be described in detail with reference to the accompanying drawings. Note that the embodiments described below are merely examples of the present invention, and are not limited to the embodiments of the present invention, and can be modified as appropriate within the scope of the technical concept of the present invention.

[0017] The pressure-resistant hose (1) of the embodiment of the present invention relates to a piping hose, and relates to a hose that requires pressure resistance, such as an intake and exhaust piping hose for pneumatic equipment and an intake and exhaust piping hose in the engine compartment of a vehicle.

[0018] <Configuration of the pressure-resistant hose (1) according to the embodiment> FIG. 1 is a cross-sectional view of a pressure resistant hose 1 according to an embodiment of the present invention. The pressure-resistant hose (1) of this embodiment has a three-layer structure consisting of an inner layer (4) made of synthetic resin with a Shore A hardness of 30 to 70, a reinforcing layer (3) made of synthetic resin with a Shore D hardness of 10 to 50, and an outer layer (2) made of synthetic resin with a Shore A hardness of 30 to 70. The same hardness will be obtained when synthetic rubber is used instead of synthetic resin.

[0019] The outer layer (2), inner layer (4), and reinforcing layer (3) that make up the pressure-resistant hose (1) are all made of the same olefin-based resin, making it possible to recycle the hose without separating the layers.

[0020] FIG. 2 is a cutaway view showing a spiral groove (5) formed in a spiral shape in a reinforcing layer (3) provided between an inner layer (4) and an outer layer (2) of a pressure hose (1).

[0021] The pressure-resistant hose (1) is constructed of layers in the following order from the inside: inner layer (4), reinforcing layer (3), and outer layer (2). According to a manufacturing method of the pressure-resistant hose (1) of an embodiment described later, unevenness consisting of spirally continuous convex portions (5a) and concave portions (5b) with a square cross section is formed only on the outer peripheral surface of the reinforcing layer (3) by a groove-forming blade (23a) attached to a rotating body (23). The inner peripheral surface, outer peripheral surface, and inner peripheral surface of the reinforcing layer (3) are smooth surfaces without any unevenness with a square cross section.

[0022] <Method for manufacturing pressure-resistant hose (1) according to the embodiment> Next, a method for manufacturing the pressure-resistant hose 1 of the embodiment configured as described above will be described with reference to explanatory diagrams showing simplified devices for each step.

[0023] FIG. 3 is an explanatory diagram showing in simplified form each device used in the manufacturing method for manufacturing the pressure-resistant hose 1 of the present invention.

[0024] As shown in FIG. 3, in the manufacturing method of the pressure-resistant hose (1) of the embodiment, a first extruder (20) is filled with a synthetic resin having a Shore D hardness of 10 to 50 for molding the reinforcing layer (3), while a second extruder (21) is filled with a synthetic resin having a Shore A hardness of 30 to 70 for molding the inner layer (4). In a first mold die (22), the synthetic resin for molding the reinforcing layer (3) injected from the first extruder (20) and the synthetic resin for molding the inner layer (4) injected from the second extruder (21) are used to mold and extrude an extrusion-molded product (40) having a two-layer structure of the inner layer (4) and the reinforcing layer (3).

[0025] The two-layer extrusion molded product (40) consisting of the inner layer (4) and the reinforcing layer (3) extruded from the first mold die (22) passes through a central cavity (23b) of a ring-shaped rotor (23) rotated by a motor (26) via gears, a V-belt, etc., and is then formed into a spiral groove (5) with a desired depth (d), groove width (w), and groove spacing (p) on the outer surface of the reinforcing layer (3) by one or more groove-forming blades (23a) attached to the rotor (23), forming a spiral groove (5) with a desired depth (d), groove width (w), and groove spacing (p) on the outer surface of the reinforcing layer (3), forming a spiral of continuous convex portions (5a) and concave portions (5b) with a square cross section. The groove spacing (p) of the spiral groove (5) can be changed by changing the rotation speed of the rotor (23), as shown in Figure 6, which will be described later.

[0026] FIG. 4 is a schematic perspective view showing the configuration of a groove forming blade (23a) that forms a spiral groove (5) on the outer periphery of a two-layer extrusion molded product (40) extruded by the first mold die (22) and the first extruder (20).

[0027] The two-layer extrusion molded product (40) extruded from the first mold die (22) passes through one or more groove forming blades (23a) provided on the rotating rotor (23), and the desired spiral groove (5) is formed.

[0028] In this embodiment, as shown in FIG. 5, the depth (d) of the spiral groove (5) formed by the groove forming blade (23a), i.e., the height of the convex portion (5a), is in the range of 60% to 95% of the thickness (t) of the reinforcing layer (3).

[0029] The groove width (w) of the spiral groove (5), that is, the width of the convex portion (5a), is set in the range of 0.1% to 30% of the outer diameter (Di) of the reinforcing layer (3).

[0030] Furthermore, the groove spacing (p) of the spiral groove (5), that is, the width of the recess (5b), is set in the range of 10% to 200% of the outer diameter (Di) of the reinforcing layer (3).

[0031] Therefore, in the pressure-resistant hose (1) of this embodiment, a spiral groove (5) is formed only on the outer peripheral surface of the reinforcing layer (3) using a groove-forming blade (23a) attached to the rotor (23), thereby providing irregularities consisting of convex portions (5a) and concave portions (5b) with a square cross section having the above-mentioned characteristics. As a result, a pressure-resistant hose (1) can be manufactured that has improved flexibility in the bending direction and kink resistance, similar to a corrugated tube, etc.

[0032] Furthermore, due to the characteristics of the reinforcing layer (3), the pressure-resistant hose (1) of the embodiment according to the present invention has flexibility in the bending direction, improving kink resistance against crushing when bent, and also improving resistance to expansion of the hose due to internal pressure.

[0033] Returning to the explanation of the manufacturing method shown in Figure 3, the two-layer extrusion molded product (40) in which the spiral groove (5) is formed in the reinforcing layer (3) passes through a cooling tank (24) and then through a first take-up machine (27) where water is removed from the outer periphery of the reinforcing layer (3) by water-removing air (28), and the surface of the reinforcing layer (3) is heated by a heating device (29) such as infrared radiation or hot air.

[0034] Thereafter, the two-layer extrusion-molded product (40), the surface of which has been heated by the heating device (29), enters the second mold die (30), and the outer layer (2) is molded around the outer periphery of the two-layer extrusion-molded product (40) using soft resin injected from a third extrusion molding machine (31), which is filled with soft resin for molding the outer layer (2) having a synthetic resin Shore A hardness of 30 to 70, to form a three-layer extrusion-molded product (41). The extrusion-molded product is cooled in a second cooling tank (32), passes through a second take-up machine (33), and is cut to a desired length by a cutter (34) to form a pressure-resistant hose (1).

[0035] The above-described manufacturing method is an example for manufacturing a pressure-resistant hose (1) having a three-layer structure. To manufacture a pressure-resistant hose (1) having a two-layer structure as shown in FIGS. 8 and 9 described later, the extruders (21, 31) that handle unnecessary materials in the above-described equipment can be omitted to manufacture the pressure-resistant hose (1) having a two-layer structure.

[0036] Figures 6(a) and (b) are a side view and a front view showing an example of a two-layer pressure-resistant hose (1) in which spiral grooves (5) with varying groove spacing (p) are formed on the outer surface of the reinforcing layer (3) by changing the rotation speed of the rotor (23), and Figure 6(c) is a schematic diagram illustrating the different bending patterns of a two-layer pressure-resistant hose (1) having spiral grooves (5) with varying groove spacing (p).

[0037] By controlling the rotation speed of the rotor (23) rotated by the motor (26) depending on the intended use of the pressure-resistant hose (1), it is possible to change and form the groove spacing (p) of the spiral groove (5) as shown in Figures 6(a) and (b). By changing the groove spacing (p) of the spiral groove (5), it is possible to change the degree of bending so that the spiral groove (5) bends more sharply at locations where the groove spacing (p) of the spiral groove (5) is small, and bends more sharply at locations where the groove spacing (p) of the spiral groove (5) is large, as shown in Figure 6(c).

[0038] 7(a) to 7(d) are diagrams showing examples of groove forming blades (23a) attached to a rotor (23) used in the manufacturing method of the pressure resistant hose (1) of this embodiment.

[0039] The ring-shaped rotating body (23) is provided with three groove forming blades (23a) that are trapezoidal when viewed from the front, as shown in Figure 7(a), two groove forming blades (23a) that are approximately crescent-shaped when viewed from the front, as shown in Figure 7(b), two groove forming blades (23a) that are approximately crescent-shaped with semicircular tips when viewed from the front, as shown in Figure 7(c), or two groove forming blades (23a) that are triangular-shaped when viewed from the front, as shown in Figure 7(d).The optimum groove forming blades (23a) are used depending on the material of the reinforcing layer (3).

[0040] <Summary of the manufacturing method of the pressure-resistant hose (1) according to the embodiment> As described above, in the manufacturing method of the pressure-resistant hose (1) according to the embodiment of the present invention, a multilayer structure is formed in which a reinforcing layer (3) made of a hard resin is provided between an outer layer (2) and an inner layer (4) made of a soft resin, and a spiral groove (5) is formed on the outer peripheral surface of the reinforcing layer (3) by a groove forming blade (23a) attached to a rotor (23), thereby providing irregularities on the outer peripheral surface of the reinforcing layer (3) consisting of convex portions (5a) and concave portions (5b) with a square cross section that are spirally continuous.

[0041] Therefore, according to the manufacturing method of the pressure-resistant hose (1) of the embodiment of the present invention, the spiral groove (3) extending in the longitudinal direction on the outer peripheral surface of the reinforcing layer (3) of the pressure-resistant hose (1) forms irregularities consisting of convex portions (5a) and concave portions (5b) with a square cross section that are spirally continuous on the outer peripheral surface of the reinforcing layer (3). Therefore, when manufacturing the pressure-resistant hose (1), it is not necessary to perform a process of braiding thread or winding braided thread or woven fabric inside the hose, and it is possible to improve the pressure resistance against expansion and flexibility against bending.

[0042] Furthermore, in the manufacturing method of the pressure-resistant hose (1) of the embodiment according to the present invention, the groove-forming blade (23a) attached to the rotor (23) forms irregularities on the outer peripheral surface of the reinforcing layer (3) consisting of convex portions (5a) and concave portions (5b) with a square cross section that are continuous in a spiral pattern. This improves the kink resistance of the pressure-resistant hose (1) against crushing when bent, improves recyclability, and makes it possible to provide a pressure-resistant hose with a resin reinforcing layer that does not require complex production equipment or replacement of empty bobbins.

[0043] Furthermore, by forming all layers of the pressure resistant hose (1) having a resin reinforcement layer according to the present invention from the same synthetic resin, recycling is easy without separating the layers.

[0044] Furthermore, the pressure-resistant hose (1) having a resin reinforcing layer according to the present invention has a three-layer structure consisting of an outer layer (2) and an inner layer (4) made of soft resin, and a reinforcing layer (3) having a spiral groove (5) made of hard resin between them. This reduces the expansion of the hose due to internal pressure, and the reinforcing layer (3) has a spiral groove on its outer periphery, which has the effect of allowing the hose to bend flexibly without being crushed.

[0045] Furthermore, in the pressure-resistant hose (1) having a resin reinforcement layer according to the present invention, a spiral groove (5) is formed on the outer peripheral surface of the reinforcement layer (3) using a groove forming blade (23a) attached to a rotor (23). This eliminates the need for processes such as weaving thread or winding fiber, which are common reinforcing materials, and thus improves molding efficiency and molding speed.

[0046] Furthermore, in the manufacturing method of the pressure-resistant hose (1) having a resin reinforcing layer according to the present invention, the pressure-resistant hose (1) having the reinforcing layer (3) is manufactured in a series of extrusion molding lines, and does not require bobbins for supplying yarn or woven fabric, so there is no need to temporarily stop the production line to replace empty bobbins.

[0047] In addition, in the manufacturing method of the pressure-resistant hose (1) having a resin-reinforced layer according to the present invention, the groove spacing (p) of the spiral grooves (5) can be freely changed simply by changing the rotation speed of the groove-forming blades (23a), which has the advantage of allowing the degree of bending of the pressure-resistant hose (1) to be freely changed without the need for new equipment or facilities. Furthermore, by controlling the rotation of the rotor (23) provided with the groove-forming blades (23a) using a servo motor, it is possible to form spiral grooves (5) with partially uneven spacing, which has the advantage of allowing specifications in which the groove spacing (p) is partially changed within a single product depending on the application.

[0048] Furthermore, depending on the application, the linear expansion of the pressure hose (1) in the longitudinal direction can be reduced by using a hard resin in which at least one non-shrinking element made of talc, glass fiber, or wollastonite is contained in the hard resin of the reinforcing layer (3).

[0049] In the above embodiment, the pressure resistant hose (1) has been described as having a three-layer structure consisting of an outer layer (2), a reinforcing layer (3), and an inner layer (4) as shown in FIG. 1. However, the present invention is not limited to this. For example, as shown in FIG. 3, by stopping the operation of the third extruder (31) filled with synthetic resin for molding the outer layer (3), a pressure resistant hose (1') having a two-layer structure consisting of an inner layer (4) and a reinforcing layer (3) can be manufactured, as shown in FIG. 8. Furthermore, by stopping the operation of the second extruder (21) filled with synthetic resin for molding the inner layer (4) as shown in FIG. 3, a pressure resistant hose (1") having a two-layer structure consisting of an outer layer (2) and a reinforcing layer (3) can be manufactured, as shown in FIG. 9. In this way, the outer layer (2) or the inner layer (4) can be omitted depending on the application to reduce product costs. [Explanation of symbols]

[0050] 1,1',1" pressure hose 2 Outer layer 3 Reinforcement layer 4 Inner layer 5 Spiral groove 5a Convex part 5b Recess 20 First Extruder 21 Second Extrusion Molding Machine 22 First mold die 23 Rotating body 23a Groove forming blade 23b Cavity 24 1st cooling tank 26 motor 27 First Pick-up Machine 28 Water draining air 29 Heating device 30 Second mold die 31 Third Extrusion Molding Machine 32 Second cooling tank 33 Second collection machine 34 Cutter 40 Two-layer extrusion molding 41 Three-layer extrusion molding d Groove depth w Groove width Di: Outer diameter of the reinforcing layer (1) p Groove spacing t is the thickness of the reinforcing layer (1)

Claims

1. a step of extruding an extrusion-molded pressure hose (40) having an inner layer (4) made of a soft resin and a reinforcing layer (3) made of a hard resin provided on the outside of the inner layer (4) made of a soft resin; a step of rotating a groove forming blade (23a) on the outside of the extruded pressure-resistant hose extrusion molded product (40) to cut the outer peripheral surface of the reinforcing layer (3) of the extrusion molded product (40) and provide a spiral groove (5) extending in the longitudinal direction, thereby providing spirally continuous convex portions (5a) and concave portions (5b) with a square cross section on the outer peripheral surface of the reinforcing layer (3); a step of providing an outer layer (2) made of a soft resin on the outside of an extrusion-molded pressure hose (40) having a reinforcing layer (3) on its outer peripheral surface with a convex portion (5a) and a concave portion (5b) having a square cross section formed by a spiral groove (5); A method for manufacturing a pressure hose, comprising:

2. A step of extruding an extrusion molded pressure hose (40) having a reinforcing layer (3) made of a hard resin; a step of rotating a groove forming blade (23a) on the outside of the extruded pressure-resistant hose extrusion molded product (40) to cut the outer peripheral surface of the reinforcing layer (3) of the extrusion molded product (40) and provide a spiral groove (5) extending in the longitudinal direction, thereby providing spirally continuous convex portions (5a) and concave portions (5b) with a square cross section on the outer peripheral surface of the reinforcing layer (3); a step of providing an outer layer (2) made of a soft resin on the outside of an extrusion-molded pressure hose (40) having a reinforcing layer (3) on its outer peripheral surface with a convex portion (5a) and a concave portion (5b) having a square cross section formed by a spiral groove (5); A method for manufacturing a pressure hose, comprising:

3. The method for manufacturing a pressure hose according to claim 1 or 2, In the step of cutting the outer peripheral surface of the reinforcing layer (3) of the extrusion-molded product (40) with a rotating groove-forming blade (23a) to form a convex portion (5a) and a concave portion (5b) having a square cross section on the outer peripheral surface by a spiral groove (5), A method for manufacturing a pressure-resistant hose, characterized in that the intervals of the spiral grooves (5) are changed by changing the rotation speed of the groove-forming blade (23a).

4. A reinforcing layer (3) made of hard resin, the inner peripheral surface of which is smooth, while the outer peripheral surface is provided with a spiral groove (5) having a convex portion (5a) and a concave portion (5b) with a square cross section that are spirally continuous; The pressure hose is characterized by having an outer layer (2) made of a soft resin and having a smooth outer surface on the outside of the reinforcing layer (3).

5. The pressure-resistant hose according to claim 4, The pressure-resistant hose further comprises an inner layer (4) made of a soft resin provided inside the reinforcing layer (3).

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