Method of manufacturing reinforced flexible pvc hose

The present invention relates to a method for manufacturing a flexible hose made of PVC, which has a tubular blade made of fabric. This hose can be used in the field of irrigation or in the field of transporting pressurized fluid by open or closed circuits.

Conventional types of flexible hoses generally consist of a first tubular inner layer made of plastic or rubber, on which a tubular fabric is wrapped to improve the pressure resistance of the flexible hose, reduce deformation and. It is designed to improve performance.

One of the most popular and most suitable conventional hoses is the so-called "mesh reinforced" type. In this type of hose, tubular reinforced fabric is layered along parallel and evenly spaced columns with a series of threads spirally wound around the flexible hose in parallel and evenly spaced rows. It consists of the same number of threads in the transverse direction. These threads are arranged symmetrically with respect to the axis of the hose to form a mesh with diamond-shaped cells. The fabric surrounding the outer surface of the plastic inner layer is then coated with an additional outer layer made of plastic or rubber. This outer layer does not necessarily have to be transparent, but is usually transparent to secure the mesh fabric to the flexible hose and protect the hose. For this type of blade, the flexible hose is better suited to withstand high pressures than a hose without blades and is suitable for reducing hose deformation. This is because the weaving method is a non-stretchable type, so that the inner layer is prevented from being deformed.

The drawback of the mesh reinforced hose is that it is relatively inflexible. That is, the bending radius that can be achieved with this hose is considerably larger than that of the knit hose.

Another conventional flexible hose is made by knitting, rather than weaving, a blade that surrounds the outer portion of the hose.

EP-A-0 527 512 by the same applicant as this case discloses a hose with a unique knit reinforcement. In this reinforcement, each stitch is shaped into a trapezoidal loop by the filaments that are woven into the corners. This type of knit reinforcement has the advantage of strengthening the hose more than similar knit flexible hoses.

As is known, the knitted fabric is a special weaving. The knitted fabric is obtained by one or more threads interconnected by more or less complex turns (also called loops or basic stitches). This turn gives the knitted fabric a great deal of elasticity.

So-called chain knitting consists of a series of parallel threads. These threads are fed by multiple spools and are curved to form an equal number of rows of stitches that are intertwined in both the lateral and chain directions. The braiding of these threads forms a series of horizontal rows of stitches and a series of vertical columns of stitches or ridges.

One of the most common commercially available flexible hoses is a tricot chain type knitting method. The tricot chain type means a knitting method in which a stitch is formed by knitting one or more threads on the right side and one or more threads on the left side for each thread.

As is well known, the tricot knitted fabric yields when the hose diameter increases due to the increase in pressure, so that the flexible hose provided with this knitted fabric has great flexibility. However, the drawback of knitted fabrics, especially tricot knitted fabrics, is that as pressure increases, the hose is exposed to the twisting effect of the fluid flowing under pressure in the hose. This is due to the spiral arrangement of the stitch lines. This arrangement produces a disproportionate reaction, especially torque, to the hose, unlike the substantially vertical row arrangement.

EP-A-0 623 776 by the same applicant as this case discloses a hose, which is a plastic or rubber inner layer, chain-knitted part with an outer surface from the inside to the outside. It has a row and column of stitches, has a tubular shape, and has a chain knitting part, an outer stitch protection layer, which is wound in a single layer around the outer surface of the inner layer, and has a row of stitches and columns. The rows are tilted in opposite directions with respect to the longitudinal axis of the hose by substantially the same tilt angle to eliminate the effect of torque caused by the pressure load in the hose.

This prior patent does not provide a relationship between various parameters of knit reinforced parts, such as pitch, tilt angle, and number of threads per unit length, nor does it provide a relationship between these and the dimensional parameters of the inner layer. Not. Therefore, due to the large number of parameters involved and the large number of possible combinations of these, those skilled in the art will need to ensure that the intended results are achieved, or at least to optimize the anti-torque effect of the hose. You haven't got everything.

<p>An object of the present invention is to eliminate the above-mentioned drawbacks.</p><p>Another object of the present invention is, for example, between various parameters of the blade and inner layer to eliminate the torque generated in the knitted fabric by the pressure of the fluid without compromising flexibility and reducing pressure resistance. Is to give a relationship.</p>

<p>This object and the other objects described below are achieved by the method of manufacturing flexible hoses according to the present invention. The method for manufacturing a flexible hose of the present invention is a method for manufacturing a series of reinforced flexible PVC hoses according to the content of claim 1, and for each of the series of hoses, a) outside the range of 12.5 mm to 37 mm. Diameter (φ_{o o}) And at least one PVC tubular inner layer (2) with a longitudinal axis (Y), b) a chain knit type consisting of tricot chain type stitches on the outer surface of at least one tubular inner layer (2). A tubular single layer of the reinforcing material (3) is formed coaxially with the inner layer, and the chain knitting type reinforcing material (3) has the number of stitches (N) per unit length in the vertical direction._m) And a row of substantially parallel stitches (4) and the number of stitches per unit length in the vertical direction (N)_r) With a row of substantially parallel stitches (5) and c) an outer layer of PVC (6) overlaid on the reinforcement layer (3) to protect the reinforcement layer, step The row of stitches (4) and the column of stitches (5) consist of their respective longitudinal pitches (P)._m, P_r) And inclination angles (α, β), these inclination angles are relative to each other with respect to the longitudinal axis (Y), and for each of the series of hoses, based on the following equation: , Vertical pitch (P) of the row (5) of the stitch_r) Is the outer diameter (φ) of the inner layer (2)._{o o}) Is substantially proportional to: P_r= K (φ_{o o})²Here, K is 0.35 to 0.50 mm^-1The rows (4) and columns (5) of the substantially spiral stitches have different tilt angles (α, β) and the outer diameter of the inner layer (2) (2). φ_{o o}For all values of), the sum of these tilt angles is substantially constant, equal to or slightly less than 90 °, such that the forces generated by the columns and rows of the stitches are balanced and offset. In a method that eliminates the torque generated by the internal pressure of the hose, for each of the series of hoses, the vertical pitch (P) of the stitch line (4)._m) Is substantially constant, and the outer diameter (φ) of the inner layer (2) is substantially constant._{o o}) Is irrelevant, and for each of the series of hoses, the number of stitches (N) in the row of stitches (5)._r) Is the outer diameter (φ) of the inner layer (2)._{o o}) Is substantially directly proportional to).</p><p>A surprising finding here is that in order to eliminate the torque induced by the internal pressure of the fluid, the pitch of the rows of stitches must increase with increasing inner diameter, but of the coil of spiral threads of the stitches. In order to effectively counter the rotation induced by the thawing, it must be increased by the square relation, not the linear relation.</p><p>At the same time, the longitudinal pitch of the stitch rows can be kept substantially constant and can be independent of the outer diameter of the inner layer.</p><p>Preferably, the number of rows of stitches per unit length of hose is directly proportional to the outer diameter of the inner layer.</p><p>Further features and advantages of the invention will become apparent by the following description of preferred embodiments of the invention, shown in the accompanying drawings as merely non-limiting examples.</p>

In the accompanying drawings, the entire flexible hose according to the present invention is shown by reference numeral 1. This flexible hose consists of an inner layer 2 made of PVC. Inner layer 2 is substantially tubular. The inner layer 2 has a vertical axis Y and an inner diameter φ that coincide with the axis of the flexible hose._iInner surface, and diameter φ_{o o}Has an outer surface of.

The chain knitting part, which is shown as a whole with reference number 3, is knitted so as to cover the inner layer 2. This part 3 consists of a row 4 of substantially spiral stitches and a row 5 of substantially spiral stitches. Each of the rows 4 of the stitches is parallel to each other and has an inclination angle α with respect to the axis Y of the hose 10 in FIG. Column 5 of the stitch has an inclination angle β with respect to the axis Y, but the direction of inclination is opposite to that of row 4.

The rows and columns mentioned above have their respective vertical pitches P._mAnd P_rHave. In addition, the number of rows or columns per unit length (100 mm) of stitches (linear count or number) is N, respectively._mAnd N_rIs.

As is already known, the outer diameter φ of the inner layer 2 around which the blade 3 is wound._{o o}When is increased, it is necessary to increase the pitch of the row in order to be able to suppress the torque. However, until now, the exact relationship between these parameters has not been clarified. Tests and experiments have surprisingly confirmed that the relationship between these parameters is not linear, but squared.

That is, this relationship can be expressed by the following general formula. P_r= Kφ² (1) In this equation, the parameter K depends on the material and the units of measure used. In the case of PVC, if all parameters are expressed in mm, the constant K in Eq. (1) is generally 0.35 to 0.50 mm.^-1It is in the range of, preferably about 0.45 mm.^-1be equivalent to.

Note that the hose knit reinforcement in Figure 1 consists of a tricot type chain stitch. These stitches can be formed directly on the hose by a so-called knitting machine. This knitting machine is commercially available, and the method of forming stitches by this knitting machine is well known.

This configuration, which is tilted and intersected with respect to the axis Y of the hose, cancels out the torque generated on the hose, for example in the case of a normal chain stitch with substantially vertical rows. On the other hand, by arranging the columns in the transverse direction instead of the vertical direction, the rotational force component generated by the coil winding of the spiral row 4 is canceled out.

This type of knitted fabric balances and offsets the forces generated by the rows and rows of stitches. Therefore, the hose 1 becomes considerably insensitive to the torque induced by the pressure of the fluid in the hose.

On the other hand, the vertical pitch P of the stitch line_mCan be kept substantially constant, and the outer diameter of the inner layer φ_{o o}Note that it is irrelevant to. In addition, the number of rows of stitches per unit length of hose N_rIs practically directly outer diameter φ_{o o}Is proportional to.

The angles α and β are generally different, but the sum of these angles is the outer diameter φ of the inner layer 2._{o o}The value of is generally constant, equal to or slightly less than 90 °.

In particular, according to the observation results, the inclination angle β of the row 5 of the stitch is substantially the outer diameter φ of the inner layer 2._{o o}Is proportional to the square root of.

Outer diameter φ_{o o}The value of is 12 to 37 mm, inner diameter φ_iWhen 10 to 32 mm is used as the value of, according to the observation result, the number of rows per unit length N_mIs substantially constant, in the range of 30-40 lines per 100 mm, with an average value of 35 lines per 100 mm.

Under the same conditions, the number of columns per unit length N_rIs substantially the outer diameter φ of the inner layer 2._{o o}In proportion to, it is in the range of 10 to 16 lines per 100 mm.

The parameters of the examples of the present invention are summarized in Table I below. Most of these parameters are also shown in the graph of FIG.<tables num="1"><img file="JP2013166375A_D0001.tif" /></tables>

Finally, the PVC outer layer 6 secures the chain knitted fabric formed on the hose surface as described above, as is done with all other known flexible hose structures.

The column and row tilt angles of the stitches may be slightly higher than the above values, depending on the hose material, hose diameter, knitted fabric type, number of spools, row and column pitch, and thread type and / or count. It is important to note that it can be changed to.

<figref num="1">It is a partial view of the flexible hose manufactured by the method according to this invention.</figref><figref num="2">It is sectional drawing of the hose of FIG.</figref><figref num="3">It is a graph which shows the main parameter of the chain knitting of the reinforced blade of this invention with respect to the outer diameter of the inner layer.</figref>