JPH04347086A - Reinforced rubber hose - Google Patents

Abstract

PURPOSE:To improve a pressure-resistance holding ratio after repetitive deformation in a reinforced rubber hose for dredging or the like by arranging a fiber code reinforced layer between inner and outer rubbers, and providing rigid members around which a rubber layer having specified compressive forces at specified compressions is arranged. CONSTITUTION:A reinforced rubber hose is prepared by arranging a reinforcing layer 23 including fiber codes such as rayon codes between an inner face rubber 21 and an outer face rubber 22, and embedding spiral or circular rigid members 24 thereinto. A rubber layer 25 is arranged around the rigid members 24, which layer 25 is made of rubber having a compressive force of 6.0kg/cm<2> or higher at the time of 10% compression and/or a compressive force of 20.0kg/cm<2> or higher at the time of 30% compression.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is used for dredging hoses, fluid transport hoses, high pressure air hoses, etc.
This invention relates to a reinforced rubber hose in which a reinforcing layer containing a fiber cord is provided between an inner rubber surface and an outer rubber surface, and a spiral or ring-shaped rigid material is embedded therein.

0002

[Prior Art] Conventionally, reinforced rubber hoses have been used in which a reinforcing layer of chemical fiber cord is provided between an inner rubber surface and an outer rubber surface, and a spiral or ring-shaped rigid material is embedded to prevent collapse. It is being The reinforcing layer is mainly made of chemical fiber cord at 35°00' to 35°00' with respect to the axial direction of the hose.
The layers are stacked to form an angle of 54°44', and function as a pressure-resistant layer. Further, the spiral or ring-shaped rigid material is embedded in order to improve the buckling resistance against crushing or bending of the rubber hose due to external force. A rubber layer is arranged between the rigid materials. This rubber layer is generally made of rubber having a compression force of 5.0 kg/cm 2 or less when compressed by 10% and 16.0 kg/cm 2 or less when compressed by 30%.

[0003] Such reinforced rubber hoses are often used in places where flexibility is required, and the hose must maintain the required pressure resistance even when subjected to repeated bending deformation. is important.

0004

A rubber elastic body reinforced with fiber cords, such as the above-mentioned reinforced rubber hose, has a characteristic in that it has a large stress in response to a tensile force, but a stress in response to a compressive force is not so large. For example, in a rubber elastic body reinforced with fiber cords, the relationship between stress and strain in the longitudinal direction of the fiber cords is shown in Figure 6.
“Non-Linear Cord-Rubber C
Composite”: S. K. Clark and R
．． N. Donge:SAE Technical P
aper Series 892339,Septem
ber 25-28, 1989). That is, the stress σL increases rapidly with respect to tensile strain (εL >0), and its absolute value does not increase much with compressive strain (εL <0). From this, it is understood that in the rubber elastic body reinforced with fiber cords, the tensile elastic modulus is much larger than the compressive elastic modulus.

Generally, when a rubber hose is bent, the portion on the outside of the radius of curvature undergoes tensile deformation, and the portion on the inside of the radius of curvature undergoes compressive deformation. If the tensile elastic modulus and the compressive elastic modulus are equal, the strain amount ΔE on the tension side and the strain amount ΔC on the compression side of the rubber hose 1 will be equal, as shown in FIG. However, in the rubber elastic body reinforced with fiber cords as described above, the tensile elastic modulus is larger than the compressive elastic modulus, so in the conventional reinforced rubber hose, the strain amount ΔE on the tensile side is larger than the tensile elastic modulus, as shown in FIG. The amount of distortion ΔC on the compression side becomes larger. In tests conducted by the present inventors, when a conventional reinforced rubber hose is bent and deformed, the amount of strain on the tensile side when the curvature (1/bending radius) is 5.0 x 10-4 (1/mm), for example. ΔE was 6.5%, and the amount of strain ΔC on the compression side was 17.5%. Note that in FIGS. 7 and 8, curves a1 and a2 indicate positions where the amount of distortion is zero.

On the other hand, it can be said that the retention rate of the pressure resistance performance of a reinforced rubber hose after being repeatedly deformed depends almost on the durability of the fiber cord. However, since this fiber cord has a structure made of extremely thin threads (filaments) twisted together, the cord has good durability against tensile strain because the force acts on the cord in the direction where the twists are tightly fastened. On the other hand, in response to compressive strain, a force is applied to the cord in the direction of untwisting it, resulting in poor durability. Figure 9 is a diagram showing the results of a durability test by applying a tensile strain of 6% to the fiber cord, and the results of a durability test by applying compressive strains of 3%, 6%, 10%, and 15%. It is. In Fig. 9, the change in tension retention rate with respect to the number of times strain is applied is shown in relative units with the initial tension retention rate being 100%, and curve L (+6) shows the change in tension retention rate with respect to the number of times strain is applied. Corresponding to the case, the curves L(-3), L(-6), L(-
10), L(-15) is 3%, 6%, 10%, respectively.
This corresponds to the case where a compressive strain of 15% is applied. curve L
(+6) and the residual curve, the tension retention rate of the fiber cord does not decrease even when tensile strain is applied, but when compressive strain is applied, it decreases as the compressive strain increases, and durability deteriorates. It is understood that In addition, FIG. 9 shows ""
Large Bore Flexible Hose
Lifetime Prediction”:A. P.
D. Cox, Dunlop Ltd Offshore
Technology Conference 19
This is a quote from ``86''.

[0007] In a reinforced rubber hose using a fiber cord having poor durability against compressive strain, if the strain on the compression side during bending deformation is large, the retention rate of pressure resistance performance after repeated deformation will be poor. However, as described above, in conventional reinforced rubber hoses, the tensile modulus is greater than the compressive modulus, so there has been a problem that the retention rate of pressure resistance performance after repeated deformation is poor.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a reinforced rubber hose that solves the above-mentioned technical problems and improves the retention rate of pressure resistance performance after repeated deformation.

[0009]

[Means for Solving the Problems] FIG. 2 is a partially cutaway perspective view showing the entire structure of the reinforced rubber hose of the present invention, and FIG. 1 is a longitudinal cross-sectional view showing an enlarged partial structure. be. This reinforced rubber hose has an inner rubber 21 and an outer rubber 22.
A reinforcing layer 23 containing fiber cords is provided between the two, and a spiral or ring-shaped rigid material 24 is embedded therein. A rubber layer 25 is arranged between the rigid materials 24. 26 is a cap for connection to other rubber hoses, etc. The fiber cord of the reinforcing layer 23 may be a chemical fiber cord or a natural fiber cord.

The rubber layer 25 has a compression force of 6 when compressed by 10%.
．． It is made of rubber with a compression force of 0 kg/cm2 or more and/or 20.0 kg/cm2 or more at 30% compression. The rubber layer 25 is preferably made of rubber having a compression force of 7.0 kg/cm 2 or more when compressed by 10%, and a compression force of 25.0 kg/cm 2 or more when compressed by 30%. Here, the compressive force is defined as "JIS K
6301-1975 Vulcanized Rubber Physical Test Method (Compression Test).

[0011]

[Operation] Figure 3 is a diagram showing the relationship between the amount of strain εL and the stress σL of a rubber elastic body reinforced with a single rubber or a fiber cord. Curve L1 corresponds to the rubber alone, and curve L2 corresponds to the rubber elastic body reinforced with a fiber cord. Compatible with rubber elastic bodies. Curve L1
, L2, it is understood that in a rubber elastic body reinforced with fiber cords, the tensile elastic modulus is larger than the compressive elastic modulus, whereas in the case of rubber alone, the compressive elastic modulus is larger than the tensile elastic modulus. . That is, in the reinforced rubber hose, the contribution of the reinforcing layer 23 including the fiber cord is dominant in terms of the tensile modulus, whereas the contribution from the rubber layer 25 disposed between the rigid materials 24 is the dominant contribution in terms of the compressive modulus. It is understood that the contribution is also large.

In the present invention, the rubber layer 25 contains 10%
The compression force during compression is 6.0 kg/cm2 or more and/or the compression force at 30% compression is 20.0 kg/cm2 or more (
Preferably, the compression force at 10% compression is 7.0 kg/cm2.
The compression force at 30% compression is 25.0 kg/c
m2 or more) is used. That is, conventionally, as mentioned above, the compression force when compressed by 10 to 30% is 5.
Whereas rubber with a relatively small stress when compressed, such as 0 to 16.0 kg/cm2 or less, was applied to the rubber layer 2, in the present invention, a rubber with a large stress when compressed is used in the rubber layer 2.
5 has been applied. This improves the compressive elastic modulus of the entire reinforced rubber hose. As a result, the amount of compressive strain on the inner side of the radius of curvature when the hose is bent is reduced, so the amount of compressive strain in the reinforcing layer 23 including the fiber cords can be reduced and the durability of the reinforced rubber hose can be improved. can. That is, even after the reinforced rubber hose is repeatedly bent and deformed, its pressure resistance is maintained well.

[0013] The compression force of the rubber layer when compressed by 10% is 6
．． When applying a rubber material with a compression force of less than 0 kg/cm2 and a compression force of less than 20.0 kg/cm2 at 50% compression, the compressive strain during bending deformation may become large enough to deteriorate the durability of the fiber cord. There is.

[0014]

[Example 1]

The rubber layer 25 disposed between the rigid materials 24 was made of rubber having a compression force of 7.5 kg/cm 2 when compressed by 10% and a compression force of 26.5 kg/cm 2 when compressed by 30%. A rayon cord was applied to the fiber cord of the reinforcing layer 23.

This reinforced rubber hose was bent to measure the amount of strain on the inner side of the radius of curvature (ie, the compression side) and on the outer side of the radius of curvature (ie, the tension side). FIG. 4 is a diagram showing the measurement results, and the change in the amount of strain on the compression side with respect to the curvature of the hose in this example is shown by a curve L (C1),
The change in the amount of strain on the tension side with respect to the curvature of the hose is shown by the curve L (
E1). Also, in this FIG. 4, the compression ratio 1
Compression force at 0-30% is 4.7-15.6kg/cm2
The amounts of strain on the compression side and tension side of a conventional reinforced rubber hose in which the following rubber is applied to the rubber layer between rigid materials are shown by curves L (CP) and L (EP), respectively.

From FIG. 4, it can be seen that in the reinforced rubber hose of this example, the amount of strain on the tension side is greater than that of the conventional reinforced rubber hose, while the amount of strain on the compression side is significantly smaller than that of the conventional reinforced rubber hose. That is understood. As a result of the reduction in the amount of strain on the compression side, the compression strain of the reinforcing layer 23 made of rayon cord is reduced. Thereby, the durability life of the reinforcing layer 23 is extended, and even after the reinforced rubber hose is repeatedly bent and deformed, the pressure resistance performance of the hose can be maintained well. As mentioned above, since the fiber cord has good durability against tensile strain, a slight increase in the amount of tensile strain during bending deformation does not affect the durability of the reinforcing layer 23 at all.

FIG. 5 shows the results of a hydraulic fracture test conducted on the reinforced rubber hose of this embodiment and the conventional reinforced rubber hose after a durability test against bending deformation under the same conditions. In the durability test against bending deformation, a hose with an inner diameter of 305 mmφ and a length of 4 m was repeatedly tested 100 times until the curvature (1/bending radius) was 5.0 x 10-4 (1/mm).
I tried to bend it ten thousand times. The bending speed was 200 times per hour.

From FIG. 5, it can be seen that in the conventional reinforced rubber hose, if the pressure at break before the durability test was 1.0, the pressure at break after the durability test was reduced to 0.7, whereas in this example For this hose, if the pressure at break before the durability test was 1.0, the pressure at break after the durability test was 0.85. From this result, it is understood that the reinforced rubber hose of this example maintains good pressure resistance even when subjected to repeated bending deformation.

[Example 2] When the rubber layer 25 disposed between the rigid materials 24 is compressed by 10%, the compression force is 15.2 kg.
/cm2, and the compression force at 30% compression is 40.5kg.
/cm2 of rubber. Bending deformation was applied to this reinforced rubber hose, and the amount of strain on the compression side and the amount of strain on the tension side were measured. The measurement results are simultaneously shown in FIG. 4 above, where the curve L (C2) corresponds to the compression side and the curve L (E2) corresponds to the tension side. curve L
Comparison of (C1) and L(C2) and curve L(E1)
From the comparison between be understood.

[0020] In this way, by applying a rubber having a large stress when compressed to the rubber layer 25, the durability against tensile force of the reinforcing layer 23 made of rayon cord can be effectively utilized, while the strength of this reinforcing layer is Since distortion in the compression direction is suppressed, the durability of the reinforcing rubber hose is further improved. Thereby, even after repeated bending deformation, pressure resistance performance can be maintained favorably.

It should be noted that the present invention is not limited to the above-described embodiments, and various design changes can be made without changing the gist of the present invention. Further, the reinforced rubber hose of the present invention is applicable not only to dredging hoses, fluid transport hoses, high-pressure air hoses, etc., but also to hoses for any purpose that are subjected to repeated deformation.

[0022]

As described above, according to the reinforced rubber hose of the present invention, since the rubber layer disposed between the rigid materials is made of rubber that has a large stress when compressed, the compressive strain during bending deformation can be reduced. Can be suppressed. As a result, the compressive strain of the reinforcing layer containing the fiber cord can be reduced, thereby suppressing fatigue of the fiber cord, and in turn, significantly improving the retention rate of pressure resistance performance of the reinforced rubber hose after repeated deformation. become.

[Brief explanation of the drawing]

FIG. 1 is a partial longitudinal sectional view showing the basic structure of a reinforced rubber hose of the present invention.

FIG. 2 is a partially cutaway perspective view of the overall configuration.

FIG. 3 is a diagram showing the relationship between each stress of a rubber elastic body including a fiber cord or a rubber element and the amount of strain.

FIG. 4 is a graph showing the measurement results of the amount of strain on the compression side and the amount of strain on the tensile side when the reinforced rubber hose of the example of the present invention is bent and deformed.

FIG. 5 is a diagram showing the results of a hydraulic fracture test after a durability test.

FIG. 6 is a diagram showing changes in stress with respect to the amount of strain in a rubber elastic body reinforced with fiber cords.

FIG. 7 is a diagram schematically showing the amount of strain on the compression side and the amount of strain on the tensile side when a reinforced rubber hose whose tensile elastic modulus is equal to the compressive elastic modulus is bent and deformed.

FIG. 8 is a diagram schematically showing the amount of strain on the compression side and the amount of strain on the tensile side when a conventional reinforced rubber hose is bent and deformed.

FIG. 9 is a graph showing the results of a durability test against tensile strain or compressive strain on a rubber elastic body including a fiber cord.

[Explanation of symbols]

21 Inner rubber 22 External rubber 23 Reinforcement layer containing fiber cords 24 Rigid material 25 Rubber layer

Claims (1)

[Claims] Claim 1: A reinforced rubber hose in which a reinforcing layer containing fiber cords is provided between an inner rubber surface and an outer rubber surface, and a spiral or ring-shaped rigid material is embedded between the rigid materials. The compression force at 10% compression is 6.0k.
A reinforced rubber hose comprising a rubber layer made of rubber having a compression force of 20.0 kg/cm 2 or more at 30% compression.