Hose manufacturing method

Abstract

To reduce a pressure loss of a hose.SOLUTION: A hose according to one embodiment includes: a tubular inner layer; a tubular outer layer enclosing the inner layer; and an intermediate layer provided between the inner layer and the outer layer. The intermediate layer includes: a reinforcement material having multiple wires; and a foam filling gaps between the wires.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a hose of It relates to a manufacturing method. [Background technology]

[0002] Conventionally, hoses having a multilayer structure including a jacket and rubber layers attached to the inner and outer surfaces of the jacket have been used in various fields. From the viewpoint of reducing the pressure loss of the fluid flowing inside, it is preferable that the inner surface of such a hose is smooth. However, there are cases where it is difficult to make the inner surface of the hose smooth.

[0003] For example, in a hose such as a suction tube connected to a pump, the inside becomes negative pressure when in use. Therefore, a spiral metal wire is used as the weft of the jacket so that the hose can maintain its shape even under negative pressure. In such a configuration, the wire can cause unevenness on the inner surface of the hose. It is possible to reduce the unevenness by increasing the thickness of the rubber layer near the jacket, but in this case the weight of the hose increases. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-211075 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a hose capable of reducing pressure loss and a method for manufacturing the same. [Means for solving the problem]

[0006] A hose according to one embodiment includes a tubular inner layer, a tubular outer layer surrounding the inner layer, and a middle layer provided between the inner layer and the outer layer, the middle layer including a reinforcing material having a plurality of wires and a foam filling gaps between the plurality of wires.

[0007] The plurality of wires may include a wire surrounding the inner layer. The foam may be made of foam rubber. In this case, the foam may be in close contact with each of the inner layer and the outer layer. The inner layer and the outer layer are formed of, for example, rubber. The average irregularity of the inner surface of the inner layer is preferably 0.2 mm or less.

[0008] A method for manufacturing a hose according to one embodiment includes a tube forming step of forming a tube having a tubular inner layer, a tubular outer layer surrounding the inner layer, a reinforcing material provided between the inner layer and the outer layer, and a foam layer containing a foaming agent provided between the inner layer and the reinforcing material, and a heating step of heating the tube while applying pressure to the inside of the inner layer, thereby foaming the foam layer.

[0009] For example, the foam layer foamed in the heating step fills gaps between the plurality of wires of the reinforcing material. The foamed layer foamed in the heating step may be in close contact with both the inner layer and the outer layer. For example, the outer layer of the tube formed in the tube forming step is made of unvulcanized rubber, and in this case, the outer layer may be vulcanized in the heating step. For example, the inner layer of the tube formed in the tube forming step is made of vulcanized rubber. For example, the foam layer is a rubber composition in which the foaming agent is added to unvulcanized rubber. In this case, the rubber of the foam layer may be vulcanized in the heating step. Effect of the Invention

[0010] According to the present invention, it is possible to provide a hose capable of reducing pressure loss and a method for manufacturing the same. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic perspective view of a hose according to one embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view along an axial direction of a hose according to one embodiment. [Diagram 3] FIG. 3 is a schematic cross-sectional view illustrating an example of a method for manufacturing a hose according to an embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view showing a manufacturing process of a hose according to a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 is a schematic perspective view showing a part of a hose 1 according to this embodiment. The hose 1 is, for example, a suction pipe whose shape is maintained so that it can be used even when the inside of the hose 1 is under negative pressure.

[0013] That is, in a cross section perpendicular to the axis AX of the hose 1, the shape of the inner surface 11 and the outer surface 12 of the hose 1 is approximately circular. The inner diameter D of the hose 1 is, for example, 40 to 200 mm, and in one example, 65 mm or 75 mm. In the following description, the direction along the axis AX is referred to as the axial direction X.

[0014] 2 is a schematic cross-sectional view along the axial direction X of a portion of the hose 1. The hose 1 includes an inner layer 2, an outer layer 3, and an intermediate layer 4 between the inner layer 2 and the outer layer 3. The above-mentioned inner surface 11 corresponds to the surface of the inner layer 2, and the above-mentioned outer surface 12 corresponds to the surface of the outer layer 3. In addition to the inner layer 2, the outer layer 3, and the intermediate layer 4, the hose 1 may further include other layers.

[0015] In this embodiment, both the inner layer 2 and the outer layer 3 are made of rubber. The type of rubber is not particularly limited, but ethylene propylene diene rubber may be used as an example. The inner layer 2 and the outer layer 3 may be made of different materials. At least one of the inner layer 2 and the outer layer 3 may be made of a material other than rubber.

[0016] The intermediate layer 4 includes a reinforcing material 5 and a foam 6. The reinforcing material 5 is, for example, a cylindrical jacket, and has a metal wire 51 wound in a spiral shape so as to surround the inner layer 2, and a plurality of warp threads 52 woven together with the wire 51. The wire 51 and the warp threads 52 are an example of a wire material constituting the reinforcing material 5. The warp threads 52 are formed to be sufficiently thinner than the wire 51.

[0017] The wire 51 is, for example, a steel wire having a circular cross-sectional shape. In the example of Fig. 2, the diameter of the wire 51 is larger than the thicknesses of the inner layer 2 and the outer layer 3. In one example, the wire diameter (diameter) of the wire 51 is 1.8 mm, and the thicknesses of the inner layer 2 and the outer layer 3 are 1.2 mm. Note that the relationship between the wire diameter of the wire 51, the thickness of the inner layer 2, and the thickness of the outer layer 3 is not limited to that exemplified here.

[0018] The foam 6 fills the gaps between the multiple wires that make up the reinforcing material 5. Specifically, the foam 6 fills the gaps between the various portions of the wires 51 aligned in the axial direction X, the gaps between the multiple warp threads 52, and the gaps between the wires 51 and the warp threads 52. In this embodiment, the foam 6 is in close contact (or bonded) with each of the inner layer 2 and the outer layer 3.

[0019] The foam 6 has a base material 61 and a foaming agent 62 dispersed in various places in the base material 61. In this embodiment, the foam 6 is a foamed rubber in which the base material 61 is made of rubber. The type of rubber is not particularly limited, but in one example, ethylene propylene diene rubber can be used, as in the inner layer 2 and the outer layer 3. The foaming agent 62 is a thermally expandable microcapsule in which a gas such as a hydrocarbon is covered with a gas-barrier outer shell polymer. However, the foam 6 may include air bubbles that are not covered with such an outer shell polymer.

[0020] The foam 6 has a thickness between adjacent wires 51 that is equal to or greater than the wire diameter of the wires 51. This ensures that the wires 51 do not cause unevenness on the inner surface 11.

[0021] Next, an example of a method for manufacturing the hose 1 will be described. Fig. 3 is a schematic cross-sectional view showing an example of a manufacturing method for the hose 1. In manufacturing the hose 1, a tube 1b shown in Fig. 3(a) is formed (tube forming step). The tube 1b includes a tubular inner layer 2, a tubular outer layer 3a surrounding the inner layer 2, a reinforcing material 5 provided between the inner layer 2 and the outer layer 3a, and a foam layer 6a provided between the inner layer 2 and the reinforcing material 5. In the example of Fig. 3(a), the outer surface of the outer layer 3a is covered with a covering material 8 such as a fabric material.

[0022] The inner layer 2 is made of, for example, vulcanized rubber. The outer layer 3a is a base layer for the outer layer 3 and is made of, for example, unvulcanized rubber. The foam layer 6a is a base layer for the foam 6 and is, for example, a rubber composition in which a powdered unexpanded foaming agent 62a is added to a base material 61a, which is, for example, unvulcanized rubber.

[0023] After the tube forming step, the tube 1b is heated (heating step) while the inside of the inner layer 2 is pressurized with air. For heating the tube 1b, a heating device such as a steam kettle can be used.

[0024] 3(a), the foam layer 6a is located between the inner layer 2 and the reinforcing material 5. The inside of the inner layer 2 is pressurized, and the outer layer 3a is pressed by the covering material 8, so that the foam layer 6a is pressed against the reinforcing material 5. The foam layer 6a contains a base material 61a, which is unvulcanized rubber, and an unexpanded foaming agent 62a.

[0025] As the heating progresses, as shown in Fig. 3(b), the softened foam layer 6a penetrates into the gaps between the multiple wires (wires 51 and warp threads 52) that make up the reinforcing material 5. Eventually, as shown in Fig. 3(c), the foam layer 6a penetrates the entire reinforcing material 5 and adheres to the outer layer 3a. The foam layer 6a also adheres to the inner layer 2.

[0026] In the heating step, the outer layer 3a is vulcanized, thereby forming the outer layer 3. The matrix 61a of the foamed layer 6a is also vulcanized, thereby forming the matrix 61. Furthermore, the foaming agent 62a expands due to heat, and the volume of the foamed layer 6a increases. As a result, the foam 6 is formed.

[0027] The heating time, heating temperature, and pressure inside the inner layer 2 in the heating step are appropriately set according to the material and thickness of the outer layer 3a and the base material 61a of the foam layer 6a, the type of foaming agent 62a, etc. In one example, when ethylene propylene diene rubber is used for the outer layer 3a and the base material 61a of the foam layer 6a and thermally expandable microcapsules are used as the foaming agent 62a, the heating time can be set to 30 to 50 minutes, the heating temperature to 125 to 150°C, and the internal pressure to 0.3 to 0.5 MPa.

[0028] Here, an example of the effect achieved by this embodiment will be described. Fig. 4 is a schematic cross-sectional view showing the manufacturing process of a hose according to a comparative example of the present embodiment. As shown in Fig. 4(a), a tube 1x that is the base of the hose in the comparative example includes an inner layer 2, an outer layer 3a, and a reinforcing material 5, similar to the tube 1b. Furthermore, the tube 1x includes a rubber layer 6x disposed between the inner layer 2 and the reinforcing material 5. The rubber layer 6x is formed of the same rubber as the base material of the foam layer 6a, but does not include a foaming agent.

[0029] When such a tube 1x is heated with the inside of the inner layer 2 being pressurized, as shown in Fig. 4(b), the softened rubber layer 6x permeates into the gaps between the multiple wires (wires 51 and warp threads 52) that make up the reinforcing material 5. Eventually, as shown in Fig. 4(c), the rubber layer 6x permeates the entire reinforcing material 5 and adheres to the outer layer 3a.

[0030] In this comparative example, since the rubber layer 6x does not contain a foaming agent, the volume of the rubber layer 6x hardly changes before and after heating. Therefore, the inner surface of the rubber layer 6x may deform according to the shape of the reinforcing material 5. Furthermore, the inner layer 2 also deforms according to the shape of the inner surface of the rubber layer 6x. This causes unevenness on the inner surface 11. In particular, when the reinforcing material 5 includes the wire 51, unevenness according to the shape of the wire 51 is likely to appear on the inner surface 11.

[0031] These irregularities create pressure losses when liquids, such as water, flow through the hose, reducing the flow rate through the hose or requiring a higher pump output to achieve a given flow rate.

[0032] The unevenness in the comparative example can be reduced by, for example, increasing the thickness of the rubber layer 6x, but increasing the thickness of the rubber layer 6x also increases the weight of the finished hose.

[0033] In contrast, in this embodiment, the foam layer 6a foams in the heating step, forming a foam 6 having a larger volume than the foam layer 6a. Furthermore, when the foaming agent 62a foams, a force that repels the internal pressure of the tube 1b is generated in the foam layer 6a. As a result, in the configuration of this embodiment, the base of the inner layer 2 becomes relatively flat. As a result, it is possible to suppress unevenness of the inner surface 11 while suppressing an increase in the weight of the hose.

[0034] For example, in the above comparative example, when the wire diameter of the wire 51 is about 1.8 mm and the rubber layer 6x is about 1.5 mm, regular irregularities of about 0.2 to 0.3 mm on average may occur on the inner surface 11 in the axial direction X. When the hose 1 is manufactured under similar conditions by the manufacturing method according to the present embodiment, the average value of the irregularities on the inner surface 11 in the axial direction X can be suppressed to 0.2 mm or less, or even 0.1 mm or less. With such irregularities, it is possible to sufficiently reduce pressure loss during use of the hose 1. The numerical values ​​of the irregularities exemplified here correspond to the radial distance between the bottom of the valley and the top of the mountain on the inner surface 11, centered on the axis AX.

[0035] The present invention is not limited to the configurations disclosed in the above-described embodiments, and the elements disclosed in the embodiments can be modified in various ways to be realized.

[0036] For example, in the above embodiment, a suction tube that is capable of retaining its shape so that it can be used even when the inside of the hose is under negative pressure is shown as an example of a hose. In addition to such a suction tube, the configuration of the present invention can be applied to various hoses that may have unevenness on their inner surfaces.

[0037] The reinforcement 5 does not necessarily have to be a jacket. For example, the reinforcement 5 may include wires 51 and no warp threads 52. [Explanation of symbols]

[0038] 1... hose, 1b... tube, 2... inner layer, 3... outer layer, 4... middle layer, 5... reinforcing material, 51... wire, 52... warp thread, 6... foam, 61... base material, 62... foaming agent, 8... covering material.

Claims

1. a tube forming process for forming a tube comprising a tubular inner layer, a tubular outer layer surrounding the inner layer, a reinforcing material provided between the inner layer and the outer layer, and a foam layer containing a foaming agent provided between the inner layer and the reinforcing material, the outer surface of the outer layer being covered with a coating material; a heating step of heating the tube while the inside of the inner layer is pressurized to foam the foam layer; Including, a hose manufacturing method in which, in the heating step, the inside of the inner layer is pressurized and the outer layer is pressed by the covering material, thereby pressing the foam layer against the reinforcing material, and the softened foam layer penetrates into gaps between a plurality of wires that constitute the reinforcing material and adheres to the inner layer and the outer layer.

2. The plurality of wires includes a metal wire wound in a spiral shape so as to surround the inner layer, and a plurality of warp threads braided together with the metal wire, In the heating step, the foam layer fills gaps between the wires arranged in the axial direction of the hose, gaps between the warp threads, and gaps between the wires and the warp threads. A method for manufacturing the hose according to claim 1.

3. the diameter of the wire is greater than the thickness of each of the inner layer and the outer layer after the heating step; A method for manufacturing the hose according to claim 2.

4. the outer layer of the tube formed in the tube forming step is made of unvulcanized rubber, the inner layer of the tube formed in the tube forming step is made of vulcanized rubber, In the heating step, the outer layer is vulcanized. A method for manufacturing the hose according to claim 1.

5. The foam layer is a rubber composition in which the foaming agent is added to unvulcanized rubber, In the heating step, the rubber of the foam layer is vulcanized. A method for manufacturing the hose according to claim 1.

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