Multi-layer hose

Abstract

Provided is a multi-layer hose capable of achieving both pressure resistance and swing durability. The multi-layer hose (1) comprises a plurality of reinforcement layers (12) stacked on a hose body (11), and the reinforcement layers (12) include reinforcement yarns (13). The yarn density ρ of the plurality of reinforcement layers (12) is at least 90 and less than 96.

Description

Technical Field

[0001] The present invention relates to a multi-layer hose. Background Art

[0002] Multilayer hoses include, for example, high-pressure hoses having a reinforcement layer formed of spirally wound reinforcing yarns (see, for example, PTL 1 and PTL 2). High-pressure hoses include multiple reinforcing layers stacked on an inner rubber layer. Such high-pressure hoses require densely wound reinforcing yarns in each reinforcing layer to ensure pressure resistance and durability.

[0003] Reference List

[0004] Patent Literature

[0005] PTL 1:2013-151994A

[0006] PTL 2: H9-26062A Summary of the Invention

[0007] Problems to be solved by the invention

[0008] However, increasing the density of the reinforcing filaments will reduce the flexibility of the multilayer hose. Consequently, the increased density of the reinforcing filaments can actually reduce the durability of the multilayer hose. For example, the durability of a multilayer hose includes so-called oscillating durability. Oscillating durability refers to the durability of a multilayer hose when subjected to internal pressure while repeatedly bent. If the flexibility of the multilayer hose is reduced due to the increased density of the reinforcing filaments, the oscillating durability may also be reduced.

[0009] Based on this, lower reinforcement density can be considered. However, lower reinforcement density may result in lower pressure resistance. Furthermore, when the density of the reinforcement is reduced, uniform alignment of the reinforcements becomes difficult during manufacturing. Therefore, by improving the swing durability while maintaining pressure resistance, there is room for improvement in achieving both pressure resistance and swing durability in conventional multilayer hoses.

[0010] The object of the present invention is to provide a multi-layer hose that can achieve both pressure resistance and swing durability.

[0011] Solutions for solving problems

[0012] The multilayer hose according to the present invention comprises a hose body and a plurality of reinforcement layers laminated on the outer circumference of the hose body, wherein each of the plurality of reinforcement layers comprises reinforcement filaments, and wherein the filament density of all the plurality of reinforcement layers is 90% or more and less than 96%. The multilayer hose according to the present invention achieves both pressure resistance and swing durability.

[0013] The multilayer hose according to the present invention comprises a hose body and a plurality of reinforcement layers laminated on the outer circumference of the hose body, wherein each of the plurality of reinforcement layers comprises reinforcing filaments, and wherein the filament density of all the plurality of reinforcement layers is 90% or more and less than 95%. The multilayer hose according to the present invention achieves both pressure resistance and swing durability.

[0014] In the multilayer hose according to the present invention, preferably, the filament density of each of the plurality of reinforcing layers decreases from the innermost reinforcing layer closest to the hose body to the outermost reinforcing layer furthest from the hose body. In this case, both pressure resistance and swing durability can be effectively achieved.

[0015] In the multilayer hose according to the present invention, the winding angle of the reinforcement filaments in each of the plurality of reinforcement layers is preferably 40° to 70°, and in this case, 50° to 60° is particularly preferred.

[0016] In the multilayer hose according to the present invention, preferably, when the multilayer hose is bent at a bending radius determined by the specifications of the multilayer hose, the filament density of each of the plurality of reinforcing layers does not exceed 100%. In this case, the swing durability can be further improved.

[0017] In the multilayer hose according to the present invention, it is preferable that the multilayer hose is a spiral hose including the reinforcing wire wound in a spiral shape. In this case, the multilayer hose can be easily manufactured.

[0018] Effects of the Invention

[0019] According to the present invention, a multi-layer hose can be provided that can achieve both pressure resistance and swing durability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In the attached figure:

[0021] Figure 1 A partial perspective view schematically showing the internal structure of a multi-layer hose according to a first embodiment of the present invention;

[0022] Figure 2 Schematically shown Figure 1 A portion of a reinforcement layer of the multi-layer hose shown;

[0023] Figure 3 Schematically shows the winding state of the reinforcing wire to include Figure 2 As an example, a portion of the reinforcing wire in the reinforcing layer; and

[0024] Figure 4Schematically shows that Figure 1 The bending state of the multi-layer hose when it is bent with a bending radius Rb. DETAILED DESCRIPTION

[0025] A multi-layer hose according to various embodiments of the present invention will be described below with reference to the accompanying drawings.

[0026] Figure 1 FIG2 is a partial perspective view schematically showing the internal structure of a multilayer hose according to a first embodiment of the present invention. Figure 1 As shown, the multi-layer hose 1 includes a hose main body 11 and a plurality of reinforcement layers 12 stacked on the outer peripheral side of the hose main body 11 , and each of the plurality of reinforcement layers 12 includes a reinforcement filament 13 .

[0027] In this embodiment, the multilayer hose 1 is composed of a plurality of cylindrical layers stacked concentrically. The multilayer hose 1 serves as a flow path for distributing fluids and can also be used, for example, as a hydraulic hose. Specifically, the multilayer hose 1 is used as a high-pressure hose for distributing hydraulic oil from a pump in hydraulically operated devices.

[0028] The following is a more detailed description of the multi-layer hose 1 .

[0029] exist Figure 1 In the figure, reference numeral 11 refers to the hose body as described above. Hose body 11 is the innermost layer of the cylindrical layers that make up the multilayer hose 1. In this embodiment, hose body 11 is an inner rubber layer comprising rubber, i.e., a rubber member. In this embodiment, the interior of hose body 11 is filled with high-pressure hydraulic oil, i.e., a liquid. Hydraulic fluid can, for example, transmit supply pressure from a hydraulic pump to a device operated by the hydraulic fluid pressure, such as construction equipment, and operate the device.

[0030] Reference numeral 12 designates a reinforcement layer 12. The reinforcement layer 12 is an intermediate layer between the inner and outer layers of the multilayer hose 1, one of the cylindrical layers comprising the multilayer hose 1. The reinforcement layer 12 includes reinforcement filaments 13. In this embodiment, the reinforcement filaments 13 are composed of steel wires wound in a spiral or helical shape, i.e., wire ropes. The reinforcement layer 12 improves the pressure resistance of the multilayer hose 1.

[0031] In this embodiment, the multilayer hose 1 is provided with a plurality of reinforcement layers 12 to further improve its pressure resistance. This allows the multilayer hose 1 to cope with high pressures, for example, above 80 MPa. In this embodiment, the multilayer hose 1 includes four reinforcement layers 12. Figure 1As shown, the winding direction of the reinforcing filaments 13 of each of the four reinforcing layers 12 is opposite to the winding direction of the reinforcing filaments 13 of the adjacent reinforcing layers 12 in the hose thickness direction, i.e., the hose radial direction. This allows the multilayer hose 1 to handle high pressures of, for example, 112 MPa to 168 MPa.

[0032] In this embodiment, the four reinforcing layers 12 are a first reinforcing layer 12a, a second reinforcing layer 12b, a third reinforcing layer 12c, and a fourth reinforcing layer 12d. The first reinforcing layer 12a is the innermost reinforcing layer closest to the hose body 11. The second reinforcing layer 12b is an intermediate reinforcing layer further away from the hose body 11 than the first reinforcing layer 12a. The third reinforcing layer 12c is an intermediate reinforcing layer further away from the hose body 11 than the second reinforcing layer 12b. The fourth reinforcing layer 12d is the outermost reinforcing layer further away from the hose body 11 than the third reinforcing layer 12c. In this embodiment, the fourth reinforcing layer 12d is the reinforcing layer farthest from the hose body 11.

[0033] Reference numeral 10 denotes an outer sheath layer. The outer sheath layer 10 is an outermost layer disposed on the outermost side of the cylindrical layers that comprise the multilayer hose 1. In this embodiment, the outer sheath layer 10 is a rubber layer containing rubber, i.e., a rubber member. The outer sheath layer 10 is integrally formed with the hose body 11 via a reinforcing layer 12 and an intermediate rubber layer 13.

[0034] The multi-layer hose 1 may further include six reinforcement layers 12. In this case, the multi-layer hose 1 can cope with a high pressure of, for example, 112 MPa to 168 MPa.

[0035] When there are six reinforcement layers 12, these six reinforcement layers 12 are the first reinforcement layer 12a, the second reinforcement layer 12b, the third reinforcement layer 12c, the fourth reinforcement layer 12d, the fifth reinforcement layer 12e (not shown), and the sixth reinforcement layer 12f (not shown). The first reinforcement layer 12a is the innermost reinforcement layer closest to the hose body 11. The second reinforcement layer 12b is an intermediate reinforcement layer further from the hose body 11 than the first reinforcement layer 12a. The third reinforcement layer 12c is an intermediate reinforcement layer further from the hose body 11 than the second reinforcement layer 12b. The fourth reinforcement layer 12d is an intermediate reinforcement layer further from the hose body 11 than the third reinforcement layer 12c. The fifth reinforcement layer 12e is an intermediate reinforcement layer further from the hose body 11 than the fourth reinforcement layer 12d. The sixth reinforcement layer 12f is the outermost reinforcement layer further from the hose body 11 than the fifth reinforcement layer 12e. In this embodiment, the sixth reinforcement layer 12 f is the reinforcement layer farthest from the hose main body 11 .

[0036] Reference numeral 14 designates an intermediate rubber layer. Similar to the reinforcement layer 12, the intermediate rubber layer 14 is an intermediate layer between the inner and outer layers of the multilayer hose 1, among the cylindrical layers constituting the multilayer hose 1. In this embodiment, the intermediate rubber layer 14 is a rubber member containing rubber. In this embodiment, the intermediate rubber layer 14 includes four intermediate rubber layers 14. The four intermediate rubber layers 14 are respectively arranged between the hose body 11 and the first reinforcement layer 12a, between the first reinforcement layer 12a and the second reinforcement layer 12b, between the second reinforcement layer 12b and the third reinforcement layer 12c, and between the third reinforcement layer 12c and the fourth reinforcement layer 12d.

[0037] In the multilayer hose 1 provided with a plurality of laminated reinforcement layers 12 , increasing the wire density ρ of the reinforcement layers 12 can ensure the pressure resistance of the multilayer hose 1 , but may also reduce its swing durability.

[0038] Based on this, if the filament density of all the multiple reinforcement layers 12 in the multilayer hose 1 is 90% or greater and less than 96%, it is possible to improve sway resistance while maintaining the filament density p to ensure pressure resistance. Therefore, the multilayer hose 1 can achieve both pressure resistance and sway resistance. This allows the multilayer hose 1 to achieve both pressure resistance and sway resistance. Furthermore, when the density p is reduced in conventional constructions, uniform alignment of the reinforcement filaments during manufacturing tends to be difficult. In contrast, in the multilayer hose 1, the filament density p of each reinforcement layer 12 is increased to a certain level, which facilitates uniform alignment of the reinforcement filaments 13 during manufacturing. Consequently, the quality of the multilayer hose 1 becomes uniform.

[0039] Furthermore, if the filament density of all the multiple reinforcing layers 12 in the multilayer hose 1 is 90% or greater and less than 95%, the filament density p can be maintained to ensure pressure resistance while also improving sway resistance. Therefore, the multilayer hose 1 can maintain pressure resistance while also improving sway resistance. This allows the multilayer hose 1 to achieve both pressure resistance and sway resistance. Furthermore, the multilayer hose 1 having the above filament density p facilitates uniform alignment of the reinforcing filaments 13 during manufacturing. Consequently, the quality of the multilayer hose 1 becomes uniform.

[0040] The filament density ρ of the reinforcing layer 12 is the ratio (%) of the area Sw of the reinforcing filaments 13 per unit area S12 of the reinforcing layer 12. The unit area S12 of the reinforcing layer 12 can be expressed as any area of ​​the reinforcing layer 12 when the multilayer hose 1 is viewed on a flat surface. Alternatively, the unit area S12 of the reinforcing layer 12 can be expressed as any area of ​​the reinforcing layer 12 when the reinforcing layer 12 is unfolded.

[0041] Figure 2 A portion of a reinforcement layer 12 of a multilayer hose 1 is schematically shown. Figure 2Although a plan view of the reinforcing layer 12 is shown, a developed view of the reinforcing layer 12 also has a similar composition. As a specific example, the unit area S12 can be determined by multiplying a length Ls along the extension direction d1 of the multilayer hose 1 by the diameter D12 of the reinforcing layer 12 (Ls*D12) when the multilayer hose 1 extends linearly.

[0042] However, the calculation method of the unit area S12 of the reinforcing layer 12 is not limited to this specific example. For example, the filament density ρ of the reinforcing layer 12 can be calculated using four parameters: (1) the winding diameter Dw of the reinforcing filaments 13, (2) the wire diameter (diameter) D13 of the reinforcing filaments 13, (3) the number of reinforcing filaments N13, and (4) the winding angle A13 of the reinforcing filaments 13.

[0043] An exemplary calculation formula for the filament density ρ of the reinforcing layer 12 is as follows.

[0044] ρ=dK / {π*(WOD-d)*cosθ}*100(%)

[0045] ρ: yarn density, d: wire diameter (mm), K: number of strikes (pcs), WOD: braided outer diameter (mm), θ: braiding angle

[0046] Furthermore, in the multilayer hose 1, it is preferred that the filament density ρ of each of the multiple reinforcement layers 12 decreases from the innermost reinforcement layer 12a closest to the hose body 11 to the outermost reinforcement layer 12d furthest from the hose body 11. In this case, pressure resistance can be effectively improved by increasing the filament density ρ on the inner side of the multilayer hose 1, which is susceptible to pressure. Meanwhile, by suppressing the increase in filament density ρ on the outer side of the multilayer hose 1, flexibility can be effectively improved. Therefore, the multilayer hose 1 effectively achieves both pressure resistance and sway resistance.

[0047] In the multilayer hose 1, the filament density p of each of the four reinforcing layers 12 is set to decrease from the first reinforcing layer 12a to the fourth reinforcing layer 12d. In the multilayer hose 1, the filament density p1 of the first reinforcing layer 12a is the highest among the four reinforcing layers 12. The filament density p2 of the second reinforcing layer 12b is lower than the filament density p1 of the first reinforcing layer 12a. The filament density p3 of the third reinforcing layer 12c is lower than the filament density p2 of the second reinforcing layer 12b. The filament density p4 of the fourth reinforcing layer 12d is lower than the filament density p3 of the third reinforcing layer 12c. Therefore, in this embodiment, the filament density p4 of the fourth reinforcing layer 12d is the lowest among the four reinforcing layers 12.

[0048] Furthermore, in the multilayer hose 1, it is preferable that the winding angle A of the reinforcement filaments 13 of each of the plurality of reinforcement layers 12 is between 40° and 70°. In this case, it is particularly suitable to be between 50° and 60°.

[0049] Figure 3 The winding state of the reinforcing wire 13 is schematically shown to include Figure 2 For example, a portion of the reinforcing yarn 13 in the reinforcing layer 12 in the multilayer hose 1 is set so that the winding angle A13 of the reinforcing yarn 13 is greater than or equal to 50 degrees and less than or equal to 60 degrees. Figure 3 As shown, a specific example of the winding angle A13 of the reinforcing filament 13 is an acute angle formed by the center line L13 of the reinforcing filament 13 relative to the extension direction d1 of the multilayer hose 1. However, the winding angle A13 of the reinforcing filament 13 is not limited to this example. The winding angle A13 of the reinforcing filament 13 may be, for example, an obtuse angle formed relative to the extension direction d1 of the multilayer hose 1. The winding angle A13 of the reinforcing filament 13 may also be an obtuse angle or an acute angle formed relative to the direction d2 perpendicular to the extension direction d1 of the multilayer hose 1 (the radial direction of the multilayer hose 1) in a plan view of the multilayer hose 1.

[0050] Furthermore, in the multilayer hose 1, it is preferred that the filament density p of each of the plurality of reinforcing layers 12 does not exceed 100% when the multilayer hose 1 is bent within a bending radius determined by the specifications of the multilayer hose 1. In this case, when the multilayer hose 1 is bent, the reinforcing filaments 13 in the reinforcing layers 12 are less likely to interfere with each other. Therefore, the multilayer hose 1 can further improve its swing durability.

[0051] Figure 4 The diagram schematically illustrates the bending state of the multilayer hose 1 when it is bent at a bending radius Rb. The wire bending density ρb is the wire density ρ of the associated reinforcing layer 12 when the multilayer hose 1 is bent at a bending radius Rb determined by the specifications of the multilayer hose 1. Specifically, the wire density ρ of the reinforcing layer 12 is the wire density ρ of the reinforcing layer 12 when the multilayer hose 1 is bent and viewed from the inner circumference to the outer circumference in the radial direction of the bend. The bending radius Rb, also known as the allowable bending radius, is the limit of the bending radius that the hose can withstand for use as a multilayer hose. The bending radius Rb is the radius of curvature produced at the innermost circumference of the multilayer hose 1 in the bending radius direction when the multilayer hose 1 is bent. The specifications of the multilayer hose 1 include, for example, standards that are individually required each time the multilayer hose is used, or standards predetermined by each hose manufacturer.

[0052] The multilayer hose 1 is configured so that the filament bending density ρb of each of the four reinforcing layers 12 does not exceed 100% when the multilayer hose 1 is bent at a bending radius Rb determined by the specifications of the multilayer hose 1. In the multilayer hose 1, each of the four reinforcing layers 12 is configured so that the filament bending density ρb of all four reinforcing layers 12 is substantially 100%.

[0053] Here, "substantially 100%" means including an error of "-0.5" relative to 100%. Suitably, the error is "-0.3" relative to 100%, and more suitably, "-0.2" relative to 100%. That is, in the multilayer hose 1, when the multilayer hose 1 is bent at a bending radius Rb, the filament bending density ρb of all four reinforcing layers 12 is between 99.5% and 100%, suitably between 99.7% and 100%, and more suitably between 99.8% and 100%.

[0054] Furthermore, in the multilayer hose 1, it is preferable that the multilayer hose 1 is a spiral hose having the reinforcing filaments 13 wound in a spiral. In this case, the reinforcing filaments 13 in the reinforcing layer 12 can be arranged by winding them in a spiral. Therefore, the multilayer hose 1 can be easily manufactured.

[0055] The multilayer hose 1 is a spiral hose. In the multilayer hose 1, the reinforcement layer 12 is a spiral layer comprising at least one reinforcing filament 13 wound in a spiral. In this embodiment, the reinforcing filament 13 in a reinforcing layer 12 is wound in a direction opposite to that of the reinforcing filament 13 in an adjacent reinforcing layer 12.

[0056] Example

[0057] Table 1 below shows Example 1 and Comparative Example 1.

[0058] (Table 1)

[0059] Example 1 Comparative Example 1 Hose inner diameter [mm] 25 25 Wire density ρ1[%] 93.4 96.2 Wire density ρ2[%] 92.7 97.6 Wire density ρ3[%] 92.1 98.2 Wire density ρ4[%] 91.7 96.8 Wire bending density ρb1[%] 99.9 102.9 Wire bending density ρb2[%] 99.8 105.1 Wire bending density ρb3[%] 99.8 106.4 Wire bending density ρb4[%] 99.9 105.5 Calculated burst pressure [MPa] 159.0 169.0 Swing pulse times [10,000 times] 66.2 18.0

[0060] Example 1 is a multilayer hose having four reinforcement layers 12. Comparative Example 1 is a multilayer hose having four reinforcement layers.

[0061] In Table 1, the hose inner diameter is the inner diameter of the hose body 11, that is, the inside diameter. The unit is mm.

[0062] In Table 1, the yarn densities ρ1 to ρ4 are the yarn density ρ of the first reinforcing layer 12a, the yarn density ρ of the second reinforcing layer 12b, the yarn density ρ of the third reinforcing layer 12c, and the yarn density ρ of the fourth reinforcing layer 12d, respectively.

[0063] The filament bending densities ρb1 to ρb4 are the filament bending densities ρb of the first reinforcing layer 12a, the filament bending density ρb of the second reinforcing layer 12b, the filament bending density ρb of the third reinforcing layer 12c, and the filament bending density ρb of the fourth reinforcing layer 12d, respectively. The filament densities ρ and ρb are expressed in percentages (%).

[0064] In Table 1, the calculated burst pressure is the ultimate pressure at which the multilayer hose 1 will rupture when a high-pressure liquid is pumped through it. The unit is MPa. The calculated burst pressure is an indicator used to evaluate the pressure resistance of the multilayer hose 1. The higher the calculated burst pressure, the better the pressure resistance. In Example 1, the calculated burst pressures were all above 80 MPa.

[0065] The swing pulse count is the number of times the multilayer hose 1 is bent at the bend radius Rb. The unit is 10,000. The swing pulse count is an indicator used to evaluate the swing durability of the multilayer hose 1. The higher the swing pulse count, the better the swing durability. The bend radius Rb in Example 1 is 140 mm. The bend radius Rb in Comparative Example 1 is 620 mm. The swing pulse count in Example 1 is 600,000 or more.

[0066] In Example 1, the filament density ρ of the reinforcing layer 12 is 90% or more and less than 96% in all four reinforcing layers 12. Similarly, in Example 1, the filament density ρ of the reinforcing layer 12 is 90% or more and less than 95% in all four reinforcing layers 12.

[0067] Referring to Table 1, it can be seen that Example 1 improves the swing durability performance while ensuring the pressure resistance performance. Therefore, it can be clearly seen from Table 1 that Example 1 can achieve both the pressure resistance performance and the swing durability performance.

[0068] Referring to Example 1, the four reinforcing layers 12 are constructed so that the fiber density ρ of the reinforcing layers 12 decreases from the first reinforcing layer 12 a to the fourth reinforcing layer 12 d .

[0069] Referring to Example 1, the multilayer hose 1 has the reinforcing layers 12 such that the filament bending density ρb1 of the first reinforcing layer 12a to the filament bending density ρb4 of the fourth reinforcing layer 12d are all substantially 100%.

[0070] Referring to Table 1, in Example 1, the filament bending density ρ of the fourth reinforcing layer 12d is substantially 100%.

[0071] The exemplary embodiments of the present invention are described above, and various changes can be made without departing from the scope of the claims. The various configurations adopted in each of the above-described embodiments can be appropriately replaced with each other.

[0072] Description of Reference Numerals

[0073] 1 Multi-layer hose

[0074] 10 outer layer

[0075] 11 Hose body

[0076] 12 Enhancement Layer

[0077] 12a First reinforcement layer (innermost reinforcement layer)

[0078] 12b Enhancement Layer 2

[0079] 12c Enhancement Layer 3

[0080] 12d 4th reinforcement layer (outermost reinforcement layer)

[0081] 12e Enhancement Layer 5

[0082] 12f 6th reinforcement layer (outermost reinforcement layer)

[0083] S12 Unit area of ​​reinforcing layer 12

[0084] 13 Reinforced filament

[0085] A13 Reinforcement yarn winding angle

[0086] 14 Middle rubber layer

[0087] Rb bending radius

[0088] ρ filament density

[0089] ρb wire bending density

Claims

1. A multi-layer hose comprising a hose body and a plurality of reinforcement layers stacked on the outer peripheral side of the hose body, wherein each of the plurality of reinforcement layers comprises a reinforcement filament, wherein The fiber density of all the reinforcing layers of the plurality of reinforcing layers is greater than or equal to 90% and less than 96%. When the multi-layer hose is bent at a bending radius determined by the specifications of the multi-layer hose, the filament density of each of the plurality of reinforcement layers does not exceed 100%.

2. A multilayer hose comprising a hose body and a plurality of reinforcing layers stacked on an outer peripheral side of the hose body, wherein each of the plurality of reinforcing layers comprises reinforcing filaments, wherein the filament density of all the reinforcing layers is 90% or more and less than 95%, When the multi-layer hose is bent at a bending radius determined by the specifications of the multi-layer hose, the filament density of each of the plurality of reinforcement layers does not exceed 100%.

3. A multi-layer hose comprising a hose body and a plurality of reinforcing layers stacked on an outer peripheral side of the hose body, wherein each of the plurality of reinforcing layers comprises reinforcing filaments, wherein the filament density of all the reinforcing layers is 90% or more and less than 95%, The filament density of each of the plurality of reinforcement layers decreases from an innermost reinforcement layer closest to the hose body to an outermost reinforcement layer farthest from the hose body. 4 . The multilayer hose according to claim 1 , wherein a winding angle of the reinforcement filaments of each of the plurality of reinforcement layers is 40° or more and 70° or less.

5. The multi-layer hose according to claim 3, wherein when the multi-layer hose is bent at a bending radius determined by the specifications of the multi-layer hose, the filament density of each of the plurality of reinforcement layers does not exceed 100%. 6 . The multi-layer hose according to claim 1 , wherein the multi-layer hose is a wire spiral hose comprising the reinforcing wire wound in a spiral shape.

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