HU200961B - Pressure hose - Google Patents

Abstract

A pressure hose (10) comprises a tubing body (1), a plurality of reinforcing layers each containing a plurality of reinforcing cords (2) each made of mutually twisted strands, and a covering layer (3). The twisting direction of at least the outermost strands in the reinforcing cord arranged in at least the innermost layer among the reinforcing layers is opposite to the winding direction of this reinforcing cord. <IMAGE>

Description

BACKGROUND OF THE INVENTION The present invention relates to a pressure hose for conveying a high pressure fluid.

Known pressure hoses have a hose body made of rubber or rubber-like material, reinforcing layers disposed on the outer circumference of the hose body, and an outer casing layer surrounding the reinforcing layers. The reinforcing layers and the outer casing layer make the pressure hose resistant to a defined fluid pressure.

In the prior art, reinforcing layers are formed, for example, by cords consisting of twisted wires or twisted fibers. When such cords are used, the stranding direction is the same as the winding of the string itself onto the hose body. Equivalent twisting and winding serves to prevent the twisted fibers from breaking down.

The disadvantage of this solution is that the pressure hose can be damaged in a relatively short period of time as the hydraulic system advances, as a result of increasing the operating fluid pressure. This problem occurs especially when the compressive hose is subjected to repetitive compression. In this case, the reinforcing cords are subjected to repetitive spiral torsion action, resulting in increased friction and premature fatigue of the twisted strands forming the cords, in extreme cases breaking the cord.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pressure hose which is repetitive, resistant to high pressures, reliable in operation and sufficiently durable.

SUMMARY OF THE INVENTION In accordance with the present invention, the present invention has been accomplished by providing a pressure hose having a rubber or rubber elastomeric hose body, reinforcing layers arranged around the hose body and outer wrapping layers arranged around the reinforcing layers, the reinforcing layers being formed from organic or inorganic fibers. that at least the twisted strand of at least the innermost reinforcing layer has a twist direction opposite to the winding direction of said twisted strand.

Preferably, the twisted strand of the reinforced layer has an inner core formed of internal fibers, around which the outer fibers are arranged such that the twisting direction of the outer fibers is opposite to that of the winding of the cord.

DETAILED DESCRIPTION OF THE INVENTION The invention will be described in detail with reference to the drawing. In the drawing it is

Figure 1 is a view of an exemplary embodiment of a hose body of a pressure hose according to the invention in a detail view of a reinforced layer; the

2a. and 2b. FIGS. 4A to 5B are schematic views of the hose body and innermost reinforcing layer of a pressure hose according to the invention, showing the winding direction of the twisting cords forming the reinforcing layer; the

2c. FIG. 4 is a schematic cross-sectional view of the strand forming the reinforcing layer; FIG. the

Figure 3 is a vector diagram illustrating the forces acting at a given point in the twisted cord of Figure 1; the

Figure 4 is a sectional view (detail) of an exemplary embodiment of a pressure hose according to the invention.

As shown in Figure 1, the outer cylindrical surface 2 of the hose body 1 of the pressure hose 10 of the present invention is wound on a helical thread 2. The hose body 1 is formed of rubber or rubber-like material. Preferably, the pressure hose 10 has two or four reinforcing layers of twisted cord 2, which are shown in FIG. 1 for greater clarity and are not shown in FIG. 1 for greater clarity. The pressure hose 10 further has an outer casing layer 3, not shown in Figure 1 (Figure 4). The strand 2 shown in Fig. 1 forms the innermost reinforcing layer of the pressure hose 10.

The stranded strand 2 is formed as a strand of a plurality of inorganic or organic fibers, possibly metallic fibers. The

In the exemplary embodiment of Figure 1, the stranded strand 2 is a steel strand, which is a Z-strand stranded steel strand. The twisted cord 2 is wound helically on the outer cylindrical surface S of the hose body 1 in the horizontal direction. Such a winding direction is shown in Figure 2a. In this case, the twisting direction of the strands forming the twisted cord 2 is opposite to the direction of winding the twisted string 2 onto the hose body 1.

In Fig. 2b, twisted color meters 2 made of twisted strands S are wound helically on the outer surface of the hose body 1 in a striking direction Z.

The twisted cord 2 is already prone to deformation due to the helical winding. The amount of torsion per turn in the 2 stranded wire (steel wire) can be determined as follows:

1, t is the tangential unit vector, n is the theoretical normal unit vector, and b is the binormal unit vector for the curvature line described by the twisted cord 2. The variation of the binary binary binary vector between two points ds apart, that is, the torsion of the twisted cord 2 (steel cord) can be determined from Figure 3 by the following equation:

όψ db i | dB | - = -, where Δψ = f ι —Ids ds dsj ° fds | where 1 is the considered curvature length.

From the above equation, Δψι torsion per 2 turns of twisted cord:

Δψι = 2 Irish cos Θ where Θ is the angle enclosed by the twisted cord 2 and the longitudinal axis of the hose body 1. The angle Θ is optionally 54.7 °, which is generally the so-called resting friction angle for pressure hoses.

Thus, as shown above, the twisted cord 2 is subjected to a torsion Δψι of 207.9 ° per turn, which is equivalent to the winding direction. It follows that the twisted strands forming the twisted cord 2 are subject to an additional thread 207.9 ° in each pass resulting from the winding of the twisted cord 2 on the outer surface of the hose body 1.

In the embodiment of the invention, where the steel strands forming the twisted cord 2 are, for example, twisted in the laying direction Z and the twisted strand 2 is wound in the opposite direction, they are not subjected to further torsion as a result of the winding, moreover, the helical winding of the twisted cord 2 acts in the direction of breaking the strand of the steel fibers. As a result, even the pressurized steel fibers forming the twisted cord 2 are not subjected to intense abrasion even under the pressure of the fluid within the hose body 1. In this way, the pressure resistance of the pressure hose 10 is increased.

In the opposite case (Fig. 2b), where the steel strands forming the twisted cord 2 are wound together in the laying direction S and the twisted cord 2 is wound on the outer cylindrical surface of the hose body 1 in the opposite direction Z, the effect according to the invention .

Fig. 2c is a sectional view of an exemplary embodiment of the twisted cord 2, wherein the seven coaxially arranged inner steel strands form the inner core of the twisted strap 2 and the twelve steel strands forming the outer layer of the twisted strap coaxially around the inner core. Again, the advantageous effect of the invention is obtained if only the twisting direction of the twelve steel fibers forming the outer layer is opposite to the winding direction of the twisted cord 2. In this case, the tearing of the stranded cord depends on the degree of friction between the steel strands forming the outer layer of the strand and the steel strands forming the inner core of the strand, and the additional friction of the stranded strand strand can be eliminated.

During operation of the pressure hose, the transported high pressure fluid exerts pressure on the inner wall of the hose body 1, thereby indirectly tensioning the strands forming the reinforcing layer 2. By twisting the strands in the opposite direction to the outer cylindrical surface of the hose body 1, the twisted string 2 is more resistant to deformation due to the tension caused by the high pressure fluid, and the friction between the strands is reduced. In the embodiment shown in Fig. 4, four reinforcing layers are formed from the twisted cord 2 around the hose body. The outer wrapping layer 3 of the pressure hose 10 is arranged around twisted cords 2 arranged in a screw-like manner. The direction of winding of the twisted cord R1 of the innermost reinforcing layer around the hose body 1 is opposite to that of the forming fibers (steel fibers). The twisted cords R1 of the innermost reinforcing layer are subjected to an increased tensile action of the high pressure fluid transported inside the hose body 1, but the torsion effect on the strands constituting the twisted cords R1 can be significantly reduced by the winding or twisting directions chosen according to the invention.

During the examination of the pressure hose according to the invention, a comparison was made with conventional pressure hoses. The results of the comparative studies are summarized in Table I below.

Table I

the pressure hose according to the invention traditional pressure hose direction of winding of the twisted cords S S Z of the stranded strand direction of strand twisting S direction of tear of the cords 25-35 80-95

The test was performed on pressure hoses made of a three inch (7.62 cm) inner diameter, oil resistant synthetic rubber hose body and six reinforcing layers made of steel cord. The steel wires have the structure shown in Figure 2c. The outer casing of the tested pressure hoses is a heat-resistant synthetic rubber layer. The test pressure hoses were subjected to fluid pressures of 0 to 350 kgf / cm ² ((£ -34.3 MPa)) during the test.

As shown in Table I, the operating reliability of the pressure hoses according to the invention is significantly higher than that of conventional pressure hoses.

In some conventional hoses, the hose body punctures during the test after about 320,000 repetitive pressures due to rupture of the reinforcing twisted cords. These experiences also show that the pressure hoses according to the invention are significantly more durable than conventional pressure hoses.

Claims (2)

PATENT CLAIMS A pressure hose having a rubber or rubber elastomeric hose body, an even number of reinforcing layers and an outer casing layer disposed on the outermost reinforcing layer, each of the reinforcing layers consisting of at least one of organic or inorganic twisted strands, characterized in that: at least the direction of twisting of the outermost strands in the twisted strand (2) of the reinforcing layer is opposite to the winding direction of said strand (2). A pressure hose according to claim 1, characterized in that the twisted cord (2) has an -3EN 200961 Β has an inner core of its own, surrounded by outer strands, where the strands of the outer strands are opposite to the winding direction of the cord.