DESCRIPTION

Field of the invention

The present invention relates to the art of hose manufacturing, and particularly relates to a method, production line and working station for continuously manufacturing reinforced flexible hoses.

Moreover, the present invention relates to a hose manufactured by means of the above method, production line and/or working station.

Background of the invention

It is known that flexible hoses, such as garden hoses, are manufactured by a production line which basically includes a starting extruding station to extrude an inner layer, a braiding or knitting station to braid or knit a textile reinforcing layer onto the outer surface of the inner layer to form a semifinished hose and a final extruding station to extrude a cover layer.

The documents PL178431B1, PL397958A1, PL65373Y1, US4175992, GB1202094 and CA1054535 show hoses manufactured in this manner.

Generally, both the extruding stations, and in particular the final one, include an extruding die ED, as shown in FIG. 1, having male and female members MM, FM reciprocally faced to define a conical peripheral channel PC susceptible to convey and extrude the thermoplastic polymer material to form the cover layer.

In order to improve the adhesion between the semifinished hose and the cover layer, it is known to put the extruding die ED under vacuum by a pump VP.

In this manner, in the final extruding station the thermoplastic polymer material is extruded in the form of a relatively thick annular member that is drawn towards the semifinished hose to fill all the gaps thereon. As a result, as shown in FIG. 2, the cover layer CL of the hose H has a tubular shape, i.e. the radius RY, RUP of the hose H is the same in correspondence of both the yarns Y of the textile reinforcing layer RL and the portions UP of the outer surface of the inner layer IL which are not covered thereby.

This known method has the drawback that a very high vacuum is needed to effectively draw the annular member towards the semifinished hose, i.e. in the order of 70 - 80 mmHg or less. Another drawback of this known method is that many material of the cover layer is used to fill the gaps in correspondence of the uncovered portions UP of the outer surface of the inner layer IL.

Moreover, the hose may be improved in terms of aesthetical appeal.

Summary of the invention

The object of the present invention is to overcome the above drawbacks, by providing a method for manufacturing hoses that is highly efficient and relatively cost- effective.

A particular object is to provide a method for manufacturing hoses which is simple and cheap to be exploited.

Another object is to provide a cost-effective hose.

A further object is to provide a hose having an high aesthetical appeal.

These and other objects, as better explained hereafter, are fulfilled by the method according to which it is herein described and/or claimed and/or shown in the annexed figures.

In a further aspect, the invention provides a hose according to which it is herein described and/or claimed and/or shown in the annexed figures.

In a further aspect, the invention provides a production line according to which it is herein described and/or claimed and/or shown in the annexed figures.

In a further aspect, the invention provides an extruding station according to which it is herein described and/or claimed and/or shown in the annexed figures.

Advantageous embodiments of the invention are defined in accordance to the dependent claims.

Brief description of the figures Further features and advantages of the invention will become more apparent from 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 an axial section of an extruding die according to the prior art, some enlarged particulars thereof being shown in FIG. la;

FIG. 2 is a radial section of a hose according to the prior art;

FIG. 3 is an axial section of an extruding die 31, some enlarged particulars thereof being shown in FIG. 3a;

FIG. 4 is a radial section of a first embodiment of a hose 100;

FIG. 5 is a schematic view of a first embodiment of a production line 1;

FIG. 6 is a side view of the embodiment of the hose 100 of FIG. 4;

FIG. 7 is a radial section of a second embodiment of a hose 100.

FIG. 8 is a schematic view of a second embodiment of a production line 1.

Detailed description of a preferred embodiment

The production line 1 is suitable for manufacturing a reinforced flexible hose 100, in particular a garden hose.

In particular, the production line 1 shown in FIG. 5 is suitable to manufacture the garden hose 100 shown in the FIGs 4 and 6.

The production line 1 essentially includes a starting extruding station 10, a braiding or knitting station 20 and a final extruding station 30 which are subsequently placed each other along a forwarding axis X.

The starting extruding station 10 may include a starting extruder 11 suitable to extrude in a known manner an inner layer 110, which may be the load-bearing one of the hose 100.

To this aim, a first thermoplastic material may be used, e.g. a plasticized PVC compound having a K value according to DIN53726 of 70 and having a Shore A hardness of 75 to 90. In a further embodiment, shown in FIG. 7, the first thermoplastic material may be a polypropylene/SEBS-based TPE-S having a Shore A hardness of 25 to 50. For example, the polypropylene/SEBS-based TPE-S may be the one disclosed in the European Patent EP2032352.

The braiding or knitting station 20 may include a braiding or knitting machine 21 suitable to braid or knit in a known manner a reinforcing textile layer 120 onto the outer surface of the inner layer 110, so as to form a semifinished hose 125. The yarns 121 used for braiding or knitting the reinforcing textile layer 120 may be made of polyester, for example of 280, 550, 1100, 1670 or 2200 dtex.

The braiding or knitting machine 21 braids or knits the yarns 121 each other in such a manner to leave portions 111 of the outer surface of the inner layer 110 uncovered.

The starting extruding station 10 and the braiding or knitting station 20 may define a supplying apparatus suitable to continuously supply the semifinished hose 125 to a final extruding station 30.

The above arrangement is shown for illustration purpose only. It is understood that, for example, the starting extruding station 10 and the braiding or knitting station 20 may be equivalently replaced by a reel from which the semifinished hose 125 is continuously unwound to supply the final extruding station 30.

On the other hand, at the inner side of the inner layer 110 one or more layers may be coupled. Moreover, more than one reinforcing textile layer 120 may be provided.

The final extruding station 30 extrudes a second thermoplastic material to form a thin tubular film defining a cover layer 130 which covers the semifinished hose 125.

The second thermoplastic material may be a plasticized PVC compound having a K value according to DIN53726 of 70 and a Shore A hardness of 65 to 75. In a further embodiment, shown in FIG. 7, the second thermoplastic material may be the above mentioned TPE-S.

In order to extrude the thin tubular film, the final extruding station 30 may include an extruder with an extruding die 31 which includes an outer female member 32 and an inner male member 33, each having a passing-through hole defining a central bore 34 for housing the forwarding semifinished hose 125.

The female and male members 32, 33 may be telescopically coupled each other to define a peripheral channel 35 having an inlet 36 for the second thermoplastic polymer material to be extruded and an outlet 37 encompassing the central bore 34 to allow the deposition of the second thermoplastic polymer material onto the semifinished hose 125 forwarding along the axis X to form the cover layer 130.

Advantageously, the extruding station 30 may further include a vacuum pump 50 to put the central bore 34 under vacuum, in such a manner to draw the cover layer 130 in close contact with the semifinished hose 125.

The female and male members 32, 33 of the extruding die 31 may have a fustoconical portion 38', 39' and a tubular portion 38", 39", which may be reciprocally consecutive.

The fustoconical portions 38', 39' may have a respective slanted inner and outer surface 40', 4 faced each other to define a slanted portion 42' of the peripheral channel 35, while the tubular portions 38", 39" may have a respective substantially horizontal inner and outer surface 40", 41" faced each other to define a substantially horizontal portion 42" of the peripheral channel 35. Suitably, the slanted portion 42' the peripheral channel 35 may be convergent to convey the second thermoplastic polymer material towards the substantially horizontal portion 42". Moreover, the latter may have a length I sufficient to shape the second thermoplastic polymer material into a tubular film.

To this end, in case of the hose made of plasticized-PVC the length I may be not less than 1,5 mm, and preferably of 1,8 mm to 2,5 mm. On the other hand, in case of the hose made of the above mentioned TPE-S the length I may be of 0,5 mm to 30 mm.

In order to adjust the length I of the substantially horizontal portion 42" of the peripheral channel 35, the male member 33 may be movable with respect to the female member 32 along the forwarding axis X.

The distance d between the substantially horizontal inner and outer surfaces 40", 41" of the tubular portions 38", 39" of the extruding die 31 may be sufficient to impart a thickness T of 0,05 mm to 0,35 mm to the tubular film which defines the cover layer 130 to be drawn onto the semifinished hose 125 by the vacuum imparted by the vacuum pump 50.

Preferably, the thickness T of the tubular film may be of 0,08 mm to 0,25 mm, and even more preferably of 0,1 mm to 0,2 mm.

It is understood that the cover layer consists of the tubular film extruded by the extruding die 31. Therefore, in the present document the number 130 is used to equivalently indentify both the cover layer and the tubular film.

This configuration allows the continuous extrusion of the tubular film 130 without damages while uniformly covering both the yarns 121 of the reinforcing layer 120 and the uncovered portions 111 of the outer surface of the inner layer 110.

In fact, as shown below, if the thickness T of the tubular film 130 is less than Oji 0,05 mm possible damages may occur during the production process, while if thickness is greater than 0,35 mm it is not possible to provide a uniformly thick cover layer both in correspondence of the yarns 121 of the reinforcing layer 120 and of the uncovered portions 111 of the outer surface of the inner layer 110.

It is understood that the maximum thickness T of the tubular film 130 depends on the inner diameter of the hose. The higher is the inner diameter of the hose, the greater is the thickness T of the tubular film 130.

As a matter of fact, in case of thickness greater than the above value the polymer material tends to accumulate in correspondence of the uncovered portions 111, as for the solutions of the state of the art shown e.g. in FIG 2.

By contrast, as shown e.g. in FIG. 4, the hose 100 manufactured according to the above method has a cover layer 130 which thickness T is uniform all around the hose, while having an outer radius Rl in correspondence of the yarns 121 which is greater than the outer radius R2 in correspondence of the uncovered portions 111.

This is a dramatic improvement with respect to the state of the art, since no material is wasted to fill the gaps in correspondence of the uncovered portions 111.

Due to the very low thickness of the cover layer 130, the negative pressure reached by the vacuum pump 50 must not be too low.

Suitably, the absolute pressure in the central bore 34 may be no lower than 250 mmHg, in order to avoid breakage of the tubular film 130 during extrusion.

Preferably, the absolute pressure in the central bore 34 is of 300 mmHg to 650 mmHg, and more preferably of 300 mmHg to 500 mmHg.

In this manner, it is possible to avoid breakage of the tubular film 130 during extrusion while allowing a uniform deposition thereof to both the yarns 121 of the reinforcing layer 120 and the uncovered portions 111 of the outer surface of the inner layer 110.

Thanks to the above method, very high linear forwarding speeds can be reached, higher than the ones reached by the solutions of the state of the art.

Preferably, the linear forwarding speed of the semifinished hose 125 through the central bore 34 of the extruding die 31 may be of 25 m/min to 45 m/min, and more preferably of 30 m/min to 40 m/min, if the reinforcing layer 120 is a braided layer. On the other hand, the linear forwarding speed of the semifinished hose 125 through the central bore 34 of the extruding die 31 may be of 1 m/min to 8 m/min if the reinforcing layer 120 is a knitted one.

In a particularly preferred embodiment of the invention, no other steps are provided to cover the cover layer 130. In other words, the latter is the outermost layer of the hose 100, which therefore has a single cover layer.

In this manner, thanks to the unique very low thickness thereof, a user can feel by touching both the yarns 121 of the reinforcing layer 120 and the uncovered portions 111 of the outer surface of the inner layer 110, which improves the aesthetic appeal of the hose 100. Suitably, the cover layer 130 may be optically transparent, so that a user can see from outside both the yarns 121 and the uncovered portions 111 of the outer surface of the inner layer 110.

In a further particularly preferred embodiment of the invention, the weight of the inner layer may be of 75% to 95% of the sum of the weights of the inner and the cover layers of the hose, while the weight of the cover layer may be of 25% to 5% of the sum of the weights of the inner and the cover layers of the hose.

Preferably, the weight of the inner layer may be of 80% to 95% of the sum of the weights of the inner and the cover layer of the hose, while the weight of the cover layer may be of 20% to 5% of the sum of the weights of the inner and the cover layers of the hose.

Thanks to this configuration, the hose 100 manufactured according to the above method is lighter and cost-effective with respect to the hose of the state of the art, e.g. the one shown in FIG. 2, using the same materials and having the same burst pressure.

In fact, the burst pressure resistance is substantially imparted by the reinforcing layer 120.

By way of comparison, in the prior art hoses about 60% of the sum of the weights of the inner and the cover layers is due to the inner layer and about 40% thereof is due to the cover layer.

In both cases, i.e. in the hose of the present invention and in the ones of the prior art, the weight of the reinforcing layer being about 3% - 5% of the whole weight of the hose.

In a further aspect, the cover layer 130 may be made of virgin PVC, while the inner layer 110 may consist of regenerated PVC. In this manner, it is possible to obtain a very high cost-effective hose while maintaining a greatly pleasant aesthetic appeal.

The invention will be better shown by the following examples, which are provided for illustration purpose only and are not limitative of the invention.

Example 1

In order to investigate the influence of the thickness of the cover layer on the hose manufacturing, the Applicant prepared 6 samples of a three-layered hose by using a production line according to the above description, e.g. the one shown in FIG. 5.

The various samples, having a length of 10 meters, consisted of an inner load-bearing layer made of a plasticized PVC compound having a K value according to DIN53726 of 70 and a Shore A hardness of 80, a reinforcing braided layer and an outer cover layer made of a plasticized PVC compound having a K value according to DI N53726 of 70 and a Shore A hardness of 70.

The formulation of the PVC inner layer is:

- PVC K 70, suspension type 44 % by weight;

- Plasticizier (DI NP) 24 % by weight;

- Calcium carbonate 30 % by weight;

- Ca-Zn Stabilizer 0,5 % by weight;

- Epoxidized soybean oil 1,3 % by weight;

- Pigment 0,2 % by weight;

The formulation of the PVC cover layer is:

- PVC K 70, suspension type 58 % by weight;

- Plasticizier (DI NP) 39 % by weight;

- Ca-Zn Stabilizer 0,5 % by weight;

- Epoxidized soybean oil 2 % by weight;

- Pigment 0,5 % by weight;

The inner layer has been manufactured in a known manner by an extruding station having a conical extruding die.

The reinforcing layer has been manufactured by a braiding station having a braiding machine configured to braid each other 6+6 spools of polyester yarns of 1100 dtex. In this manner, the semifinished hose at the outlet of the braiding machine has uncovered portions having a generally diamond shape.

The outer cover layer has been manufactured by the above described extruding station having a specially extruding die as shown in FIG. 3 put under vacuum by a suitable vacuum pump, of the per se known type.

The linear forwarding speed of the production line was of 35 meters/minute. The vacuum pump was set to a pressure of 500 mmHg.

The extruders of the inner and the cover layers were put at a flow rate compatible with the above forwarding speed.

The inner diameter of all the samples was of 12,7 mm (1/2"), while the thickness of the inner layer thereof was of 1,27 mm.

The 6 samples had different thickness of the cover layer, from 0,05 mm to 0,5 mm. The % by weight of the reinforcing layer is of 2,5 % to 3,5 % with respect to the whole weight of the hose.

All the samples have the same burst pressure, namely 24 bars.

The following table 1 shows the data of the various samples.

Table 1

From the manufacturing point of view, the cover layer of the sample 1 had several rents and damages.

The samples 2 to 4 provided a hose in which the cover layer uniformly covered both the yarns of the reinforcing layer and the diamond-shaped uncovered portions of the outer surface of the inner layer, as shown e.g. in FIG 2.

By contrast, in the samples 5 and 6 the cover layer did not uniformly cover the reinforcing layer and the inner one. In particular, the PVC compound of the cover layer accumulated in correspondence of the diamond-shaped uncovered portions of the outer surface of the inner layer. Apparently, the samples 5 and 6 fall outside the scope of the appended claims, and therefore cannot be considered as part of the present invention.

Example 2

In order to investigate the influence of the inner diameter on the thickness of the outer cover layer, four samples (A to D) have been manufactured having different inner diameters, i.e. 12,7 mm (1/2"), 15,9 mm (5/8"), 19 mm (3/4") and 25,4 mm (1")

The following table 2 shows the data of the various samples. Table 2

In all samples the cover layer uniformly covered both the yarns of the reinforcing layer and the diamond-shaped uncovered portions of the outer surface of the inner layer, as shown e.g. in FIG 2.

Example 3

In order to investigate the influence of the pressure of the vacuum pump on the hose manufacturing, the Applicant prepared the above sample 3 by setting the vacuum pump to different pressures of 200 mmHg, 300 mmHg, 350 mmHg, 400 mmHg, 450 mmHg, 600 mmHg and 700 mmHg.

The sample prepared with the vacuum pump at pressure of 200 mmHg had the cover layer damaged.

The samples prepared with the vacuum pump at pressures of 300 mmHg to 600 mmHg had no difference with respect to the samples 2 to 4 of the above example 1, which were manufactured at 500 mmHg.

The sample prepared with the vacuum pump at pressure of 700 mmHg had the cover layer which did not cover the diamond-shaped uncovered portions of the outer surface of the inner layer in a uniform manner. In particular, in some points the cover layer did not adhere to the uncovered portions of the inner layer.

Example 4

In order to investigate the influence of the forwarding linear speed on the hose manufacturing, the Applicant prepared the samples 1, 3 and 5 of the above example 1 at different forwarding linear speed of 25 m/min and 45 m/min.

No difference was noticed on the hose configuration with respect to the samples of the example 1, which was manufactured at 35 m/min.

Example 5

In order to investigate the influence of the shape of the extruding die on the hose manufacturing, the Applicant compared the samples 2 to 4 of the above example 1 with samples having the same features, but manufactured with a final extruding station including a conical extruding die according to the prior art, as shown in FIG. 1.

The male and female members was put at a minimum distance of 0,1 mm, 0,2 mm and 0,3 mm, equivalent to the distance between the tubular portions of the male and female members of the extruding die of the present invention needed to extrude the cover layer of the above samples 2 to 4.

The samples thus manufactured had a not uniform cover layer. In particular, the PVC compound of the cover layer accumulated in correspondence of the diamond-shaped uncovered portions of the outer surface of the inner layer. Moreover, the cover layer had several damages on all samples.

Example 6

The Applicant manufactured another example of a garden hose 100 according to the present invention, which is shown in FIG. 7.

The hose includes, from the outer to the inner side, a cover layer 130, a double spirally-wrapped textile reinforcing layer 120, a first thermoplastic inner layer 110, a braided textile reinforcing layer 122, a second load-bearing thermoplastic inner layer 112 and a third thermoplastic inner layer 113, which is susceptible to contact the liquid to be transported, e.g. water.

The first thermoplastic inner layer 110, the second load-bearing thermoplastic inner layer 112 and the third thermoplastic inner layer 113 are made of Nilflex SH ^® (Taro Plast SpA), a polypropylene/SEBS-based TPE-S having a Shore A hardness of 40.

On the other hand, the double spirally-wrapped textile reinforcing layer 120 and the braided textile reinforcing layer 122 are respectively made of 2 and 6+6 yarns Brilen GLE ^® (Brilen Tech SA) of 550 dtex.

The inner diameter of the hose is 7,9 mm, while the maximum outer diameter, i.e. the one in correspondence of the yarn 121 is 12,7 mm.

As schematically shown in FIG. 8, the hose is manufactured by provided a first semifinished hose 126 including the third thermoplastic inner layer 113, the second load- bearing thermoplastic inner layer 112 and the braided textile reinforcing layer 122 to an extruding station 30' including an extruding die 31' suitable to manufacture the first thermoplastic inner layer 110.

The extruding die 3 is put under vacuum at about 300 mmHg to manufacture a tubular film which is in close contact with the underlying layers, as described above.

The second semifinished hose 127 is fed to a spiral wrapping machine 2 to obtain the third semifinished hose 125.

The latter is fed to an extruding station 30 including an extruding die 31 put under vacuum at about 300 mmHg to obtain the tubular film-cover layer 130.

In both the extruding dies 3 and 31, the slanted portion 42' has a length I of 1 mm.

The thicknesses (mm) and weights (gr/mt) of the various layers are:

cover layer 130: 0,1 mm thickness, 3,5 gr/mt weight;

spirally-wrapped textile reinforcing layer 120: 0,1 mm thickness, 3,5 gr/mt weight; first thermoplastic inner layer 110: 0,1 mm thickness, 3,5 gr/mt weight; braided textile reinforcing layer 122: 0,1 mm thickness, 3,5 gr/mt weight; second thermoplastic inner layer 112: 1,7 mm thickness, 49 gr/mt weight;

third thermoplastic inner layer 113: 0,3 mm thickness, 7 gr/mt weight. Therefore, the weight of the cover layer 130 is about 5,55% of the sum of the weights of the thermoplastic layers 113, 112, 110 and 130.