WO2011138734A1

WO2011138734A1 - Apparatus, method and line for manufacturing knitted hoses

Info

Publication number: WO2011138734A1
Application number: PCT/IB2011/051946
Authority: WO
Inventors: Alessandro Mezzalira
Original assignee: Fitt S.P.A.
Priority date: 2010-05-04
Filing date: 2011-05-03
Publication date: 2011-11-10

Abstract

A flexible irrigation hose. The hose (1 ) comprises an inner layer (2) in a first thermoplastic polymer material, an outer layer (3) in a second thermoplastic polymer material, a first textile reinforcement layer (4) and a second textile reinforcement layer (5) in overlapped reciprocal relation. The first and second textile reinforcement layers (4, 5) are knitted together with chain stitches (6, 6') of the tricot type having rows (7, 7') and courses (8, 8'). The courses (8, 8') of said first and second textile layer (4, 5) have inclinations (α, β) opposite to one another with respect to the longitudinal axis (X) of the hose, and in that the rows (7, 7') of at least one between said first and said second textile layers (4, 5) are substantially parallel to said longitudinal axis (X). A method of manufacturing such hose, a line (10) for the production thereof and a knitting machine (20) for manufacturing such hose.

Description

APPARATUS, METHOD AND LINE FOR MANUFACTURING KNITTED HOSES

DESCRIPTION

Field of the invention

The present invention is generally applicable in the technical field of flexible hoses, and particularly relates to an apparatus and a method for the manufacturing of a knitted flexible hose, in particular of the irrigation type.

In particular, the hose manufactureable by means of the method and machine according to the invention has two or more overlapped layers knitted with tricot stitches.

The invention further concerns a production line of such hose, and a hose obtainable by the above method.

Background of the invention

Flexible hoses with a single textile layer are known in the art, and they comprise an inner layer susceptible to come into contact with the transported liquid, an outer layer susceptible to be grasped by a user and, interposed between these layers, a textile layer with tricot type stitches.

From the European patent EP-B1 -0623776, in the name of the same Applicant, an exemplary embodiment of this hose is known, wherein the rows of stitches and the courses of stitches of the textile layer have inclinations opposed to each other with respect to the axis of the hose.

This hose has good antitorsion properties and relatively high burst strength, and results also quick and simple to produce. An example of machine suitable for manufacturing this hose is known from the Italian patent IT1270776.

Flexible hoses with double knitted textile layer are also known, which comprise a pair of textile layers with tricot type stitches, in overlapped relation with each other, and interposed between the inner and outer layer. An example of these hoses is known from EP-B1 -1 156252, wherein the rows of stitches and the courses of stitches of both the textile layers have inclinations opposed to each other with respect to the axis of the hose. An example of machine suitable for manufacturing a hose of this type is known from FR2793866.

This prior art hose, although it has good antitorsion properties and bursting pressure greater than the hose with single textile layer, has the drawback of a particular difficult manufacturing and a relatively low production speed.

In the technical field of the manufacture of flexible hoses there is the need of an apparatus and/or of a method for the manufacturing of flexible hoses with double knitted layer which allow to producing the hose in a relatively quick and simple way.

In particular, the manufacturing of a hose with double knitted layer is particularly difficult due to the fact that the hose, continuously forwarding in the knitting heads, tends to rotate on its axis, with the consequent deviation from the initial position and/or inclination of the rows of stitches of the textile layers.

This causes an inhomogeneous distribution of the textile layers on the hose, to obviate which it is necessary to often stop the machine to manually correct the position of the hose or of the stitches, with consequent productivity loss for the whole production line.

This drawback is particularly damaging because the manufacture of the textile layers is usually the most time-consuming part of the production process of a hose, so that delays in this step seriously influence the whole production line.

Moreover, an inhomogeneous distribution of the courses and rows of stitches involves the danger of local breaking of the hose when subjected to inner pressure.

Summary of the invention

A main object of this invention is to overcome, at least in part, the above drawbacks, by providing a machine and/or a method for the manufacturing of a hose with a double knitted textile layer having high efficiency and relatively low costs.

Another object of the invention is to provide a machine and/or a method which allow the manufacture of a hose having two overlapped knitted textile layers which are homogeneously distributed.

Another object of the invention is to provide a machine and/or a method which allow the manufacture of a hose having a double knitted textile layer continuously knitted without interruptions.

Another object of the invention is to provide a machine and/or a method which allow the manufacture of a hose having a double textile layer knitted in a quick and simple way.

These and other objects, as better explained hereafter, are fulfilled by the knitting apparatus, the method, the hose and the production line according to the independent claims.

Advantageous embodiments of the invention are defined according to the dependent claims.

Brief description of the drawings Further features and advantages of the invention will appear more evident upon reading the detailed description of some preferred, non-exclusive embodiments of the invention, which are described as non- limiting examples with the help of the annexed drawings, in which:

FIG. 1 is a sectional view of the hose according to the invention;

FIG. 2 is a schematic view of a first embodiment of the hose according to the invention with the skin 3 partially removed, with in FIG. 2a some enlarged details;

FIG. 2b is a schematic view of a first embodiment of a production line of the hose according to the invention, by means of which the hose of FIGS. 2 and 2a is obtainable;

FIG. 3 is a schematic view of a second embodiment of the hose according to the invention with the skin 3 partially removed, with in FIG. 3a some enlarged details;

FIG. 4 is a schematic view of a second embodiment of a production line of the hose according to the invention, by means of which the hose of FIGG. 3 and 3a is obtainable;

FIG. 5 is a schematic view of a first embodiment of the knitting apparatus for the manufacturing of the hose according to the invention, by means of which it is possible to obtain, for example, the hose of FIG. 3 and 3a;

FIG. 6 is a schematic view of a second embodiment of the knitting apparatus for the manufacturing of the hose according to the invention, by means of which it is possible to obtain, for example, the hose of FIG. 2 and 2a;

FIG. 7 is an enlarged exploded view of some details of the knitting apparatus of FIG. 5;

FIG. 8 is a schematic view of some details of the knitting apparatus of FIG. 5 during operation, with an enlargement of the hose during the production;

FIG. 9 is a schematic view of some details of a preferred but non exclusive embodiment of the knitting apparatus of FIG. 5 during operation;

FIG. 10 is a schematic view of some details of a further preferred but non exclusive embodiment of the knitting apparatus of FIG. 5 during operation;

FIG. 11 is a schematic view of some details of a further preferred but non exclusive embodiment of the knitting apparatus of FIG. 5 during operation, with an enlargement of the hose during the production;

FIG. 12 is a schematic view of some details of a preferred but non exclusive embodiment of the knitting apparatus of FIG. 6 during operation, with an enlargement of the hose during the production.

Detailed description of a preferred embodiment

Referring to the above figures, the flexible hose according to the invention, globally indicated with the reference number 1 , may be particularly used as irrigation hose for domestic use, for example as so-called "garden" hose.

Essentially, as visible in FIG. 1 , the hose 1 is composed by an inner tubular layer or substrate 2, which may be manufactured in plasticized PVC, which is designed to come into contact with the transported liquid, an outer polymer layer or skin 3, which may be in plasticized PVC too, designed to be grasped by a user and, interposed between these layers, by a first and second textile layer 4, 5, in overlapped reciprocal relation, which may consist of polyester yarns.

Between the different layers other additional textile as well as polymer layers may also be provided, without departing from the scope of the invention expressed by the annexed claims.

The textile layers 4, 5 are of the knitted type with tricot chain stitches, indicated with 6 for the first textile layer 4 and with 6' for the second textile layer 5. Both textile layers 4, 5 may have rows of stitches, indicated with 7 for the first textile layer 4 and with T for the second textile layer 5, and courses of stitches, respectively indicated with 8, 8'.

The courses of stitches 8 of the first textile layer 4 are all substantially parallel to each other, as well as the courses of stitches 8' of the second textile layer 5.

The courses of stitches 8, 8' have inclinations α, β opposed to each other with respect to the axis X of the hose, and preferably equal.

The rows of stitches 7, T of the textile layers 4, 5 are substantially parallel to each other, independently from their inclination with respect to the axis X of the hose 1.

In a preferred, non-exclusive embodiment, the rows of stitches 7 are substantially parallel to this axis.

Advantageously, the rows of stitches 7 of the first textile layer 4 may have between them a circumferential pitch or predetermined distance D_{1 ;} whereas the rows of stitches T of the second textile layer 5 may have a distance D₂ from the rows of stitches 7 of the first layer 4 equal to substantially half of the distance D-i . Tanks to this feature, the rows of stitches 7, T result uniformly spaced along the periphery of the substrate 2, so as to remarkably increase the burst strength of the hose 1. In an alternative embodiment, the rows of stitches 7, 7' may also be placed side by side to each other, with the rows of stitches 7 of the first layer 4 adjacent to the rows of stitches T of the second layer, or in overlapped reciprocal relation.

The hose according to the invention results extremely simple, cheap and quick to produce, although it keeps good antitorsion and burst strength properties.

In practice, the hose according to the invention has antitorsion and burst strength properties comparable to one of the prior art knitted double layer hoses, with production speed comparable to that of the prior art knitted single layer hoses.

As used herein, the sentence "textile layer" or equivalents thereof is intended to indicate a layer consisting of at least two yarns or groups of yarns placed on the load-bearing layer.

As used herein, the sentence "textile layer knitted with chain stitches of the tricot type" or equivalents thereof is intended to indicate a layer consisting of at least two yarns or groups of yarns placed on the load-bearing layer and knitted with each other to form a plurality of "tricot type" chain stitches.

As used herein, the sentence "chain stitches of the tricot type" or equivalents thereof is intended to indicate the portion of yarn (or assembly of yarns grouped in a single yarn) which is knitted with the adjacent yarns to form a loop having generally ring shape.

In the enlargements of the FIGS 2a and 3a, some "tricot type chain stitches" are highlighted with a dashed hatch. Generally, "tricot type chain stitches" are also called in the art chains or chain stitches.

As used herein, the sentence "rows of stitches" of a textile layer knitted with chain stitches of the tricot type or equivalents thereof is intended to indicate the line defined by the "tricot chain stitches" connected to each other.

As used herein, the sentence "courses of stitches" of a textile layer knitted with chain stitches of the tricot type or equivalents thereof is intended to indicate the portion of yarn (or assembly of yarns grouped in a single yarn) which connects to each other two consecutive "tricot chain stitches" along the same yarn. In the enlargements of FIGS. 2a and 3a, some "courses of stitches" are highlighted with a solid hatch.

The rows of stitches of both the knitted textile layers may be substantially parallel to the axis, so as to make simple, cheap and quick to the utmost the production of the hose. Advantageously, the first and the second polymer material may be of the plasticized or elastomeric type.

The first and the second polymer material may be different from each other or equal. Advantageously, the first and the second polymer material may be compatible with each other.

As used herein, the sentence "compatible materials" or equivalents thereof is intended to indicate materials which have chemical and/or physical compatibility with each other, that is to say materials which, once coupled to form a substantially unitary body, originate a junction suitable to bear the transfer of tensile or shear stresses through the contact surface. As a consequence, the maximum compatibility is reached between identical materials or anyway materials having the matrix with the same base.

As used herein, the sentence "matrix" of a polymer or equivalents thereof is intended to indicate a polymer material capable to provide the molecular structure of the finished product.

Appropriately, the first and second polymer material may have a plasticized PVC (polyvinyl chloride)-based matrix. The first as well as the second polymer material may have Shore hardness A comprised between 40 and 100, preferably 60 and 90.

As used herein, the sentence "based matrix" preceded by the denomination of a given polymer material or equivalents thereof is intended to indicate a polymer material capable to provide the finished product with the molecular structure of the given polymer material, the denomination of which precedes the expression "based matrix".

The hose 1 may be manufactured by means of the production lines 10 shown in FIGS 2b and 4. In particular, by means of the line of FIG. 2b, which comprises the knitting apparatus 20 of FIG. 6, it is possible to obtain the hose of the FIGS. 2 and 2a, whereas by means of the line of FIG. 4, which comprises the knitting apparatus 20 of FIG. 5, it is possible to obtain the hose of FIGS 3 and 3a.

At first, the substrate 2, which is intended to act as bearing layer, is extruded in a per se known manner, by introducing plasticized PVC into a first extruder 11.

Therefore, the bearing layer is introduced into a knitting station 12, suitable for manufacturing onto the substrate 2 the first and the second textile layers 4, 5.

Finally, the semifinished product 13 so obtained is introduced into a second extruder 14, which is loaded from above with plasticized PVC, so as to extrude in a per se known manner the skin 3 onto the upper surface of the semifinished product 13, thus obtaining the finished hose 1.

For the purpose of the manufacture of the textile layers 4, 5 the knitting station 12 may comprise the knitting apparatus 20, schematically shown in FIGS. 5 and 6.

The apparatus 20 substantially comprises an inlet 21 for the load-bearing substrate 2 outgoing from the first extruder 11 , a first and a second sequentially placed knitting sections 22, 23 and an outlet 24 for the semifinished product 13, which is directed into the second extruder 14.

The dashed line in FIGS. 5 and 6 indicates the forwarding line of the bearing layer 2 through the apparatus 20, and further defines a longitudinal axis which coincides with the axis X of the hose. Externally to the apparatus 20 means 25 may be provided to pull the hose along the forwarding line X.

Each one of the knitting sections 22, 23 has a series of needles 26, 27, fixed to a respective needle-bearing cage 28, 29, which are operatively connected to respective yarn distributors 38, 39 and, by means of tensioning and transmission means, generally indicated as 30, 31 , to respective series of reels 32, 33 of yarn 34, 35, mounted on reel supporting plates 36, 37.

The reels and the needles may be provided in any quantity. The two sections 22, 23 may have an equal number of needles and of corresponding reels, for example eight for each series. In a preferred but non exclusive embodiment, to each reel may correspond a needle, and to the number of needles may correspond the number of rows of stitches 7, T which are manufactured onto the substrate 2.

During operation, the needles 26, 27 draw the respective yarn 34, 35 from the corresponding reel 32, 33 to knit it with the adjacent yarns and to form tricot stitches. The needles 26, 27 and the reels 32, 33 are mounted on the respective needle- bearing supports 28, 29 and reel-bearing supports 36, 37 peripherally around the axis X, so as to form on the outer surface of the forwarding substrate 2 at first the textile layer 4 and then the textile layer 5, which results to be in overlapped reciprocal relation with the former.

The reel supporting plates 36, 37 are mounted on the apparatus 20 free to rotate around the axis X, and are connected, by means of cam elements, to the needles 26, 27 so that the rotation of the reel supporting plates 36, 37 and of the reels 32, 33 connected thereto corresponds to the alternative movement of the needles 26, 27 along the direction defined by the axis X.

FIGS. 5 and 6 illustrate two embodiments of the knitting apparatus 20, which essentially differ for the position of the two series of needles 26 and 27, and of the corresponding needle-bearing cages 28, 29.

In the embodiment shown in FIG. 5, the needles 26, 27 fixed to the needle- bearing cages 28, 29 face each other and work in an opposite way, whereas in the embodiment shown in FIG. 6 the needles 26, 27 are placed in the same sense, so that they work in the same sense.

In other words, in the apparatus according to the first embodiment shown in FIG. 5, the alternative movements of the needles of the first series 26 and those of the second series 27 take place in opposite senses, so that the forwarding towards a reference central plane of a needle of the first series 26 corresponds to the forwarding towards the same reference central plane of the corresponding needle of the second series 27.

On the contrary, in the apparatus according to the second embodiment of FIG.

6 the senses of these movements are concordant, so that the forwarding towards a reference central plane of a needle of the first series 26 substantially corresponds to the moving away from the same reference central plane of the corresponding needle of the second series 27.

In both embodiments, in a per se known manner, the cam means are appropriately dimensioned and/or configured to obtain the above described effect.

FIGS. 2 and 3 show, respectively, a first embodiment of the hose 1 , which can be obtained by means of the second embodiment of the knitting apparatus 20 shown in FIG. 6, and a second embodiment of the hose 1 , which can be obtained by means of the first embodiment of the knitting apparatus 20 shown in FIG. 5.

These two embodiments of the hose 1 substantially differ from each other for the sense of the rows of stitches 7, 7'of the two textile layers 4, 5.

With the apparatus according to the second embodiment of FIG. 6, wherein the corresponding needles of the two series 26, 27 move in a concordant sense between each other and with the working sense W, the rows of stitches 7, 7' of both textile layers 4, 5 will be plain.

With the apparatus according to the first embodiment of FIG. 5, wherein the corresponding needles of the two series 26, 27 move in opposite senses, the rows of stitches 7 of the first lower layer 4 will be plain, whereas the rows of stitches 7' of the second upper layer 5 will be purl. In this embodiment the needles 26 work in a sense concordant to the working sense W, whereas the needles 27 work in a sense opposite to the working sense W.

Advantageously, the reel bearing plates 36, 37, unitary with the respective yarn distributors 38, 39, may rotate with opposite senses, for example one counterclockwise V₂ and the other one clockwise V-i .

In this way, the first knitting section 22 knits the first textile layer 4 with courses of stitches 8 inclined in a sense with respect to the axis X, whereas the second knitting section 23 knits, onto the first layer 4, the second textile layer 5 with courses of stitches 8' inclined in an opposite sense, as visible in FIGS. 2 e 3.

The inclination of the courses of stitches 8, 8', is adjusted by the rotation speed of the reel supporting plates 36, 37. In a preferred embodiment, the rotation speeds of the two plates may be equal, so that the inclinations of the courses of stitches 8, 8' will be accordingly equal.

FIG. 7 shows the working head group of the first embodiment of the knitting apparatus 20 of FIG. 5, in an exploded configuration. Each one of the heads 41 , 42, respectively belonging to the first and second knitting unit 22, 23, comprises a respective needle-bearing cage 28, 29 (for greater convenience, the needles are not shown) and a respective yarn distributor 38, 39, rotating unitarily with the respective reel supporting plate 36, 37 and suitable to distribute the yarns 34, 35 to the needles 26, 27.

In a per se known manner, the skilled person coordinates the alternative movement along the axis X of the needles 26, 27 with the rotational movement of the two yarn distributors 38. 39, which rotate around the axis X with opposite senses V₂, V-i and preferably with equal speeds. A central sleeve 40 is also provided for supporting and guiding the needles 26, 27 during their alternative movement.

FIG. 8 shows the working head group of the first embodiment of the knitting apparatus 20 of FIG. 5, in an exploded configuration and during operation. The working head 41 rotates around the axis X counterclockwise, whereas the head 42 rotates clockwise. The working sense by which the substrate 2 advances along X is indicated with the arrow W. The same FIG. 8 shows, in the bottom part, an enlargement of the substrate 2 during operation, which until the point A is uncovered, whereas after that point and until point B is covered by the first textile layer 4, and from this point is covered also by the second textile layer 5, which therefore results to be overlapped to the first layer. Points A and B are therefore the points where, respectively, the needles 26 and 27, once they have worked respectively the yarns 34 and 35, release the so formed stitches 6, 6' which thus fall down onto the substrate 2 forwarding along X to form the rows of stitches 7 and 7'.

This figure apparently shows that the first knitting head 41 knits the first textile layer 4 with rows of plain stitches 7, whereas the second knitting head 42 knits the second overlapping textile layer 5 with rows of purl stitches 7'. The working sense of the needles 26 of the first knitting head 41 , in fact, is concordant with the forwarding sense W of the substrate 2 along X, whereas the working sense of the needles 27 of the second knitting head 42 is opposite thereto. The stitches 6' knitted by the needles 27, therefore, falling on the substrate 2 at the point B are overturned, thus resulting purl with respect to the stitches 6 knitted by the needles 26.

The distance between the points A and B has to be as short as possible, possibly between 3 and 30 cm, preferably between 3 and 10 cm.

FIGS. 9, 10 and 1 1 show some particularly preferred, non exclusive embodiments of the knitting apparatus 20 according to the invention, which allow to correct possible deviations from the desired position and/or inclination of the rows of stitches 7, T during the working due to torsions of the substrate 2 forwarding along X.

Even if FIGS 9 and 10 illustrate only the first embodiment of FIG. 5 of the apparatus 20, the same is clearly valid also for the second embodiment of FIG. 6 of the apparatus 20, without departing from the scope of the invention expressed by the annexed claims.

According to this preferred, non exclusive embodiment, the knitting apparatus 20 may comprise means for the control of the reciprocal angular position of the first and of the second series of needles 26, 27.

These control means allow the selective adjusting of this position in response to the detecting of a variation of the inclination and/or of the position of at least one of the rows of stitches 7, 7', so as to correct this deviation and to allow an homogeneous distribution of the textile layers 4, 5 onto the substrate 2.

This will speed up to the utmost the knitting of the textile layers and the whole production process of the hose, by at the same time reducing to the minimum the danger of local breaking of the hose if subjected to inner pressure.

Advantageously, the control means may comprise driving means operatively connected to the needles 26 and/or 27 and actionable by the user to drive the reciprocal rotation thereof in response to the detecting of the variation.

Even if in the embodiments of FIGS. 9, 10 and 1 1 control means operatively connected to the second series of needles 27 are shown, whereas the first series of needles 26 is rotatably blocked, it is understood that the control means may be also connected to the first series of needles 26, whereas the second series of needles is rotatably blocked, or the control means may be connected to both series of needles 26 and 27, without departing from the scope of the invention expressed by the annexed claims.

In their simplest embodiment, shown in FIG. 9, the driving means may comprise an adjusting element 50 to be held by the user to allow a manual adjusting once the deviation has been detected.

In another embodiment, shown in FIG. 10, the control means include motor means 51 , operatively connected by means of the belt 52 to the second series of needles 27 for rotating thereof around the axis X, whereas the first series of needles is rotatably blocked.

In this embodiment, the driving means may include a control panel 53 drivable by the user and interacting with the motor means 51 for rotating the second series of needles 27 around the axis X and for adjusting the angular position thereof with respect to the first series 26, once the deviation has been detected by the user.

In another embodiment, shown in FIGS. 1 1 and 12, the control means include motor means 51 , operatively connected by means of the belt 52 to the second series of needles 27 for automatically rotating thereof around the axis X, whereas the first series of needles 26 is rotatably blocked. This embodiment further comprises means for the automatic detecting of the deviation of reciprocal inclination and/or position of at least one of the rows of stitches 7, 7'.

The two embodiments of the FIGS. 1 1 and 12 differ because in FIG. 1 1 the control means are applied to a knitting apparatus according to the first embodiment shown in FIG. 5, whereas in FIG. 12 the control means are applied to a knitting apparatus according to the second embodiment shown in FIG. 6.

The automatic detecting means, which may comprise a camera 54 for the optical detecting of the variations of the rows of stitches 7, T from the desired inclination and/or position, may be operatively connected to the motor means 51 for the automatic adjustment of the reciprocal angular position of the needles 26, 27.

The camera 54 may be configured to detect at predetermined time intervals the inclination and/or the position of at least one of the rows of stitches 7, 7'.

The control means may further comprise a logical control unit 55, which may be set wit a reference inclination and/or position V_R|_F and operatively connected to the camera 54 and to the motor means 51 .

The logical unit 55 may be configured to elaborate the data detected by the camera 54 and to determine a value V_R|_L, and to compare at predetermined time intervals the detected value V_R|_L with the reference inclination and/or position V_R|_F. In case the two values do not coincide, the logical unit 55 may send a signal 56 to the motor means 51 , so as to activate them.

The logical unit 55 may furthermore be susceptible to incorporate in the signal 56 an information V_A concerning the variation of the reciprocal angular position of the needles 26, 27 necessary to compensate the deviation between the values V_R!L and VR,_F.

Thanks to this configuration, the knitting apparatus 20 automatically detects and corrects the deviations of the rows of stitches 7, 7' , so that the textile layers 4, 5 result to be distributed as homogeneously as possible.

Advantageously, the camera 54 may be interposed between the first and the second series of needles 26, 27. This way, it detects the deviations of the rows of stitches 7 of the first layer 4 before the knitting of the following chain stitches 6' of the rows of stitches T of said second textile layer 5.

This allows the motor means 51 to adjust the reciprocal angular position of the needles 26, 27 before the substrate 2 arrives to point B, so that the following chain stitches 6' of the rows of stitches T has already correct reciprocal inclination and/or position.

In this case, the distance between the points A and B has to be calculated according to the accuracy of the detecting means 54, of the logical unit 55 and of the motor means 51 . In practice, such distance has to allow the system to make an effective rotation of the needles 27 with respect to the needles 26 before the substrate 2 reaches the point B.

The above description clearly shows that the invention fulfils the intended objects.

The knitting apparatus, the method and the production line of the hose 1 according to the invention are susceptible of a number of changes and variants, within the inventive concept disclosed in the appended claims. All the details thereof may be replaced by other technically equivalent parts, and the materials may vary depending on different needs, without departing from the scope of the invention.

Claims

1 . A knitting apparatus for the manufacturing of a flexible hose with two overlapped layers knitted with tricot stitches, comprising :

- an inlet (21 ) for an inner tubular layer (2) made of a first polymer material ; a first and a second knitting unit (22, 23) for forming on said inner layer (2) respectively a first textile layer (4, 5) knitted with chain stitches (6, 6') of the tricot type having courses (8, 8') and rows (7, 7') substantially parallel to each other so as to manufacture a semifinished product (13) defining a longitudinal axis (X) ; and an outlet (24) for said semifinished product (13);

- each one of said first and second knitting unit (22, 23) comprising a respective first and second yarn distributor (38, 39) operatively connected to a respective first and second series of reels (32, 33) of yarns (34, 35) and with a respective first and second series of needles (26, 27), said first and second distributor (38, 39) being susceptible to rotate in opposite senses (V₂, V-i) around said axis (X) ;

- each one of said first and second knitting unit (22, 23) further comprising respective cam means for the mutual operative connection of the respective series of needles (26, 27) and of the distributors (38, 39) so that to the rotation of the last ones (38, 39) corresponds to an alternative movement of the formers (26, 27) along a direction substantially parallel to said longitudinal axis (X), so that the courses of stitches (8, 8') of the textile layers (4, 5) have inclinations (α, β) opposed to each other with respect to said axis (X) and the rows of stitches (7, 7') of the corresponding textile layer (4, 5) have both a predetermined inclination with respect to said axis (X) and a predetermined reciprocal position.

2. Apparatus according to claim 1 , comprising means (50, 51 , 53, 54, 55) for controlling the reciprocal angular position of said first and second series of needles (26, 27) to allow the selective adjusting thereof in response to the detecting of a variation of the inclination and/or of the position of at least one of said rows of stitches (7, T).

3. Apparatus according to claim 2, wherein said control means comprise driving means (50, 53) operatively connected to said needles (26, 27) and actionable by the user for driving the reciprocal rotation of the last ones in response to the detection of said variation of the inclination and/or of the position of at least one of said rows of stitches (7, 7').

4. Apparatus according to claim 2, wherein said control means comprise motor means (51 ) operatively connected to at least one of said first and second series of needles (26, 27) for the reciprocal rotating thereof around said axis (X).

5. Apparatus according to claims 2 and 3, wherein said driving means (50, 53) include a control panel (53) operateable by the user, said motor means (51 ) being operatively connected to said control panel (53).

6. Apparatus according to claim 2, wherein said control means comprise means (54) for automatically detecting said variation of the inclination and/or of the reciprocal position of at least one of said rows of stitches (7, 7') operatively connected to said motor means (51 ) for the automatic adjustment of the reciprocal angular position of said first and second series of needles (26, 27).

7. Apparatus according to claim 6, wherein said detecting means comprise a camera (54) for the optical detection of said variation of the inclination and/or of the reciprocal position of at least one of said rows of stitches (7, 7').

8. Apparatus according to claim 6 or 7, wherein said detecting means (54) are interposed between said first and second series of needles (26, 27), so as to detect the deviations of the inclination and/or of the position of the rows of stitches (7) of said first textile layer (4) before the knitting of the following chain stitch (6') of the rows of stitches (7') of said second textile layer (5).

9. Apparatus according to claim 8, wherein said first series of needles (26) by which the first textile layer is manufactured (4) is rotatably blocked, said motor means (51 ) being operatively connected to said second series of needles (27) for rotating thereof around said axis (X) in response to the detection of deviations of the inclination and/or of the position of the rows of stitches (7) of said first textile layer (4) by said detection means.

10. Apparatus according to any of claims 6 to 9, wherein said detecting means (54) are configured to detect at predetermined times the inclination and/or the position of at least one of said rows of stitches (7, 7'), said control means comprising a logical control unit (55) settable with a reference inclination and/or position (V_R|_F) and operatively connected to said detection means (54) and to said motor means (51 ).

1 1 . Apparatus according to claim 10, wherein said logical control unit (55) is configured to compare at predetermined times the inclination and/or position detected (V_R|_L) by said detecting means (54) with the reference inclination and/or position (V_R|_F) and to send a signal (56) to said motor means (51 ) if the two values do not coincide, said logical unit (55) being further susceptible to incorporate in said signal (56) an information (V_A) relative to the variation of reciprocal angular position of said first and second series of needles (26, 27) necessary to compensate the deviation between the detected inclination (V_R|_L) and/or position and the reference inclination and/or position (V_R|_F).

12. A method for manufacturing a flexible hose with two overlapped layers knitted with tricot type stitches, comprising in sequence the steps of:

a) extrusion of a first polymer material to obtain a tubular load-bearing layer

(2);

b) manufacturing on said load-bearing layer (2) a first textile layer (4) knitted with chain stitches (6) of the tricot type to obtain a first semifinished product,

c) manufacturing on said first semifinished product a second textile layer (5) with stitches (6') of the tricot type to obtain a second semifinished product (13),

d) manufacturing of an outer layer (3) on said second semifinished product (13) to obtain the finished hose (1 ),

wherein both said first and second textile layers (4, 5) comprise rows of stitches (7, 7') and courses of stitches (8, 8') substantially parallel to each other and are manufactured with courses of stitches (8, 8') having inclinations (α, β) opposed to each other with respect to the axis of the hose (X),

wherein said textile layers (4, 5) are manufactured by means of the knitting apparatus according to one or more of the preceding claims.

13. A flexible hose with two overlapped layers knitted with tricot type stitches obtainable by means of the method according to the preceding claim, comprising at least one inner tubular load-bearing layer (2) made of a first thermoplastic polymer material, at least one outer layer (3) made of a second thermoplastic polymer material and at least one first (4) and one second (5) reinforcement textile layers in overlapped reciprocal relation and interposed between said inner (2) and outer layer (3), said first and second textile layers (4, 5) being knitted with chain stitches (6, 6') of the tricot type,

wherein both said first and second textile layers (4, 5) comprise rows of stitches (7, 7') and courses of stitches (8, 8') substantially parallel to each other, said first and second textile layers (4, 5) having courses of stitches (8, 8') with inclinations (α, β) opposed to each other with respect to the axis of the hose (X),

wherein the stitches (6) of the rows of stitches (7) of one between said first and second textile layer (4) are plain, the stitches (6') of the rows of stitches (7') of the other between said first and second textile layer (5) are purl.

14. A production line of a flexible hose with two ovelapping layers knitted with stitches of the tricot type, comprising in sequence:

a) an extrusion station (11 ) of a first polymer material to obtain a load-bearing tubular layer (2);

b) at least one knitting station (12) to manufacture on said load-bearing layer (2) a first and a second knitted textile layer (4, 5) with chain stitches (6, 6') of the tricot type, in overlapped reciprocal relation,

c) an extrusion station (14) of a second polymer material on the semifinished product (13) outgoing from the preceding station to obtain an outer layer (3), so as to manufacture the finished hose,

wherein said first and second knitted textile layers (4, 5) both comprise rows of stitches (7, 7') and courses of stitches (8, 8') substantially parallel to each other, said first and second textile layers (4, 5) being manufactured with courses of stitches (8, 8') having inclinations (α, β) opposed to each other with respect to the axis of the hose (X),

wherein said at least one knitting station comprises an apparatus according to any of the claims 1 to 1 1 .