WO2009040610A1

WO2009040610A1 - High flexibility hose structure for high pressure apparatus, and method for making same

Info

Publication number: WO2009040610A1
Application number: PCT/IB2007/053910
Authority: WO
Inventors: Gianmaria Mezzalira
Original assignee: Fitt S.P.A.
Priority date: 2007-09-26
Filing date: 2007-09-26
Publication date: 2009-04-02

Abstract

A hose structure, particularly for high pressure applications, comprises an inner layer (2) of a first thermoplastic polymeric material, an outer layer (3) of a second thermoplastic polymeric material (4) and an intermediate layer (4) interposed therebetween. The intermediate layer (4) comprises a braided fiber fabric (5, 5', 5') radially but not longitudinally held between said at least one inner layer (4) and said at least one outer layer (3) to allow free mutual sliding of the various layers when the hose is subjected to bending stresses. A method for making such structure.

Description

HIGH FLEXIBILITY HOSE STRUCTURE FOR HIGH PRESSURE APPARATUS, AND METHOD FOR MAKING SAME

Field of the invention

The present invention finds application in the field of flexible hoses, and particularly relates to a high flexibility hose structure, particularly for high pressure applications.

The invention further relates to a method for making such high flexibility hose.

Background of the invention

Flexible hoses in general, and particularly hoses designed for high pressure devices, e.g. exposed to a pressure from 100 to 200 bar, are subjected in operation to torsional and/or bending stresses, which tend to create bulges, i.e. bends with a small radius of curvature, commonly known as kinking. This problem particularly arises in pressure washers, in which a drum device is typically used, in operation, to wind the hose in concentric more or less adjacent turns.

Flexible hoses, particularly for use in pressure washers, generally have an inner layer and an outer layer, both formed of a thermoplastic material, with an intermediate layer of braided-fiber fabric therebetween. The latter is usually fixed to the inner layer, generally bonded and glued thereto. Examples of these prior art structures are disclosed in US-A-4380252 and US-A-5964409.

One drawback of the above structures is that, due to kinking, hoses tend to become plastically and permanently deformed at the bending area, and hence to choke. As a result, a structurally weakened area is generated in the hose wall, which can lead to straining and ruptures, as well as considerable pressure drops in fluid flow. As a consequence, such prior art hoses may be not suitable for proper winding in concentric turns on the winding device as described above, as well as for common use.

Summary of the invention

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

A particular object is to provide a high flexibility hose for high pressure applications that limits kinking.

Another object of the invention is to provide a high pressure-resistant, durable hose.

These and other objects, as better explained hereinafter, are fulfilled by a hose structure as defined in claim 1 , which comprises at least one inner layer, at least one outer layer, at least one intermediate layer interposed therebetween, characterized in that said at least one intermediate layer is substantially in contact and uniformly coupled with said at least one inner layer and said at least one outer layer, so as to be radially constrained therebetween, though allowing mutual longitudinal sliding thereof.

In another aspect, the invention relates to a method for making the above flexible hose in accordance with claim 20, characterized in that said at least one intermediate layer is laid in such a manner as to be substantially in contact and informally coupled with both said at least one inner layer and to said at least one outer layer, to be radially constrained therebetween though allowing mutual longitudinal sliding between the layers.

In another aspect, the invention relates to a high pressure apparatus, such as a pressure washer or a similar apparatus as defined in claim 26, comprising the above described and claimed hose structure.

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

Brief description of drawings

Further features and advantages of the invention will be more apparent upon reading the detailed description of a preferred, non-exclusive embodiment of a flexible hose according to the invention, which is described as a non-limiting example with the help of the annexed drawings, in which: FIG. 1 is a sectional view of the hose of the invention; FIG. 2 is an enlarged view of certain details of the hose of the invention; FIGS. 3 to 5 show various steps of the method for making the flexible hose of the invention;

FIG. 6 is another sectional view of the hose of the invention, as taken along a plane Vl-Vl.

Detailed description of a preferred embodiment

Referring to the above figures, the hose structure of the invention, generally designated by numeral 1 , may be advantageously used for high pressure apparatus, such as pressure washers or similar devices, for delivering a working fluid, such as water and/or steam, using special means such as a tube, a nozzle or the like for delivering it onto a surface to be treated.

As shown in Figures 1 and 2, the hose structure 1 may be composed of an inner layer 2, which may be formed of a first thermoplastic polymeric material, an outer layer 3, which may be composed of a second thermoplastic polymeric material, and an intermediate layer 4 located therebetween.

It shall be understood that multiple respective inner, outer and intermediate layers, in the same relative positions as described above may be provided instead of single layers, without departure from the scope of the invention.

Both the first polymeric material of the inner layer 2 and the second polymeric material of the outer layer 3 may be independently selected from the group comprising PVC (polyvinyl chloride), TPU (thermoplastic polyurethane), TPE (thermoplastic elastomer), TPE-V (vulcanized thermoplastic elastomer) or mixtures of these materials. Also, they may be either identical or different from each other and have various colors depending on the needs of the final user.

Advantageously, one of the above thermoplastic polymeric materials, and preferably the first, may have a Shore A hardness of less than 90, as measured according to the ISO 868 standard.

Conveniently, the above thermoplastic polymeric materials are selected with Shore A hardness values in the range from 60 to 90, preferably from 74 to 80, and more preferably of about 78.

The material used for the intermediate layer 4 may be a braided-fiber fabric, as shown in Figure 4, i.e. composed of intermeshing fibers 5, 5', 5".

In a possible embodiment, the fibers 5, 5', 5" may be grouped into sets of substantially parallel adjacent fibers 7, T, 7", which are intermeshed with other sets 7, 7', 7" transverse to the former, as schematically shown in Figure 4. Other intermeshing arrangements may be possibly used for the same purposes and with the same functions.

The fibers may be of a synthetic nature and may be selected from aramid, polyester, polyamide fibers or a mixture thereof. In a preferred embodiment, the fibers may be of polyester type.

In a preferred embodiment, the intermediate layer 4 may cover the whole outer surface of the inner layer 2, to impart high pressure resistance to the whole structure 1.

The yarn count of the fibers 5, 5', 5" depends on the operating pressure of the hose structure 1. Thus, the yarn count of the braided fibers 5, 5', 5" may be in a range from 2200 dtex to 13200 dtex, and preferably from 6600 dtex to 8800 dtex.

Experimental tests have shown that fibers of such size allow a hose structure capable to withstand operating pressures in a range from 100 to 200 bar, and at least to 140 bar.

A peculiar feature of the invention is that the intermediate layer 4 is substantially in contact and coupled both to the inner layer 2 and to the outer layer 3, in such a manner as to be constrained therebetween radially, i.e. along a direction Y perpendicular to the axis X of the hose, while being allowed to slide longitudinally, i.e. along the direction coincident with the axis X of the hose. In other words, both the inner layer 2 and the outer layer 3 are directly in contact with the intermediate layer 4, i.e. without any clearance with its fibers 5, 5', 5", so that they can oppose the radial forces generated by the pressurized fluid, while allowing their relative sliding motion.

This can occur both due to the lack of glues and adhesives between the intermediate layer 4 and the inner 2 and outer layer 3, and thanks to the sliding properties of the materials being used.

Thanks to this configuration, the hose structure of the invention is subjected to minimal kinking. As the hose is subjected to a bending stress that causes the formation of bulges, the intermerdiate layer 4 will be longitudinally unrestrained, thereby allowing free mutual sliding of the fibers 5, 5', 5" between the lower and upper layers 2, 3, which are in turn free to elastically recover their original shape.

The contact fit between the intermediate layer 4 and the inner and outer layers 2, 3 will further allow optimal operation of the above mechanism, as the layers 2, 3 above and below the intermediate layer 4 will act as a "guide" for this latter, preventing any overlapping of the fibers 5, 5\ 5" during their sliding motion.

In a preferred non exclusive embodiment of the invention, the fibers 5, 5\ 5" of the layer 4 are braided on the inner layer 2, but not permanently coupled to the inner layer 2 and to the outer layer 2. This means that the intermediate layer is neither glued, nor heat sealed, nor permanently joined in any manner to the inner and outer layers 2, 3.

Advantageously, the materials that constitute the inner layer 2, the outer layer 3 and the intermediate layer 4 will be selected amongst high flowability materials, to allow easy sliding thereof. If the dynamic friction factor f_d is used as a flowability parameter, materials may be selected in which such factor of 0.2 to 0.5, preferably of 0.25 to 0.45 and more preferably of 0.3 to 0.4.

The use of materials having such function factor f_d will further enhance relative longitudinal sliding of the various layers, thereby imparting greater flexibility to the structure as a whole.

In a variant embodiment, the structure 1 may include lubricating means, such as a layer of materials such as talc, graphite or the like, interposed between the intermediate layer 4 and the inner layer 2 and/or the outer layer 3.

The method for making the hose structure of the invention may include the following steps, as shown with reference to Figures 3 to 6.

In the first step, an inner tubular layer 2 is formed with the cross section as shown in Fig. 3, preferably by extruding a first thermoplastic polymeric material in a traditional manner.

The rough semifinished product so obtained may be subjected to a first inflation step, such as by blowing compressed air therein at a pressure of 2 to 8 bar so that it can be slightly expanded until its inside diameter reaches a first predetermined value D₁. This inflation step will add flexibility to the structure, and further increase resistance to inward pressure exerted by the subsequent step of deposition of the intermediate layer 4.

By way of mere example, using an inner layer 2 as thick as 1 mm to 1.5 mm, for instance of about 1 mm, the inside diameter D₁ will be in a range from 4 mm to 10 mm, preferably of about 6 mm.

The next step will consist in laying the intermediate layer 4 on the inflated inner layer 2, by braiding the fibers 5, 5', 5" to obtain a semifinished product 6 as shown in Figure 4. During such step, the fibers 5, 5', 5" will be laid in direct contact with the outer surface of the inner layer 2, without exerting an excessive stress, to facilitate sliding of contacting layers. The fibers and their yarn count will be selected in such a manner that the thickness of the intermediate layer 4 is in a range from 0.5 mm to 1.5 mm and preferably of about 0.9 mm.

To compensate for any reduction of the diameter of the inner layer 2, caused by the fiber braiding step, a second step of inflation with compressed air may be provided, as shown in Figure 5, in which the semifinished product 6, formed of the inner layer 2 with the intermediate layer 4 braided thereon, is expanded to a second inside diameter D₂, which will be substantially coincident with the inside diameter of the finished product, and very close to the first inside diameter D₁.

This is followed by a step in which a layer of a second polymeric material, identical or different from the former, is extruded to a thickness of 0.8 mm to 1.2 mm, and preferably of about 1 mm, possibly of different color from the former. The layer will be laid on the semifinished product 6, to form the outer layer, thereby obtaining the finished hose structure 1 as shown in Figure 6, operating in the same manner as with the intermediate layer, i.e. taking care that a clearance-free longitudinally sliding contact is practically obtained. From the foregoing description, it is apparent that the hose structure of the invention fulfills the intended objects and particularly meets the requirement of providing a flexible hose subjected to minimal kinking.

Indeed, due to the contact fit of the intermediate layer 4 between the inner and outer layers 2, 3 which hold it in the radial direction and not longitudinally, as the hose 1 is subjected to tensile, bending or torsional stresses, the various layers will be substantially free to slide relative to each other, for enhanced elastic deformation thereof and easy recovery of the initial configuration.

The hose structure of the invention is 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 departure from the scope of the invention.

While the hose structure has been described with particular reference to the accompanying figures, the numerals referred to in the disclosure and claims are only used for the sake of a better intelligibility of the invention and shall not be intended to limit the claimed scope in any manner.

Claims

1. A high flexibility hose structure, particularly for high pressure apparatus, comprising: - at least one inner layer (2);

- at least one outer layer (3);

- at least one intermediate layer (4) interposed between said at least one inner layer (2) and said at least one another layer (3); characterized in that said at least one intermediate layer (4) is substantially in contact and uniformly coupled both to said at least one inner layer (2) and to said at least one outer layer (3), to be radially constrained therebetween, though allowing mutual longitudinal sliding between the same layers (2, 3).

2. Hose structure as claimed in claim 1 , wherein said at least one inner layer (2) is formed of a first thermoplastic polymeric material and said at least one outer layer (3) is formed of a second thermoplastic polymeric material.

3. Hose structure as claimed in claim 2, wherein said first and said second thermoplastic polymeric materials are the same.

4. Hose structure as claimed in any one of claims 1 to 3, wherein said first and said second thermoplastic polymeric materials are selected from the group comprising PVC, TPU, TPE, TPE-V or mixtures thereof.

5. Hose structure as claimed in claim 4, wherein at least one of said first and second thermoplastic polymeric materials has a Shore A hardness of less than 90, as measured under the ISO 868 standard.

6. Hose structure as claimed in one or more of the preceding claims, wherein at least one of said first and second thermoplastic polymeric materials has a Shore A hardness in a range from 60 to 90.

7. Hose structure as claimed in one or more of the preceding claims, wherein said first thermoplastic polymeric material has a Shore A hardness in a range from 74 to 80 and preferably of about 78.

8. Hose structure as claimed in one or more of the preceding claims, wherein said intermediate layer (4) is formed of a fabric composed of braided fibers (5, 5', 5^").

9. Hose structure as claimed in the preceding claim, wherein said fibers (5, 5', 5") comprise synthetic fibers.

10. Hose structure as claimed in claim 9, wherein said synthetic fibers (5, 5', 5") are selected from the group comprising aramid, polyester, polyamide fibers or mixtures thereof.

11. Hose structure as claimed in one or more of the preceding claims, wherein said intermediate layer (4) covers the whole outer surface of said inner layer (2).

12. Hose structure as claimed in one or more of the preceding claims, wherein the yarn count of said braided fibers (5, 5', 5") is in a range from 2200 dtex to

13200 dtex, and preferably from 6600 dtex to 8800 dtex.

13. Hose structure as claimed in one or more of the preceding claims, wherein the inside diameter of said inner layer (2) is of 4 mm to 10 mm, and preferably of about 6 mm.

14. Hose structure as claimed in one or more of the preceding claims, wherein the thickness of said inner layer is of 1 mm to 1.5 mm, and preferably of about 1 mm.

15. Hose structure as claimed in one or more of the preceding claims, wherein the thickness of said intermediate layer (4) is of 0.5 mm to 1.5 mm, and preferably of about 0.9 mm.

16. Hose structure as claimed in one or more of the preceding claims, wherein the thickness of said outer layer (3) is of 0.8 mm to 1.2 mm, and preferably of about 1 mm.

17. Hose structure as claimed in claim 1 , wherein the dynamic friction factor (f_d) between said inner (2) and outer layers (3) and said intermediate layer (4) is of 0.2 to 0.5 and preferably of 0.25 to 0.45.

18. Hose structure as claimed in one or more of the preceding claims, wherein lubricating means are interposed between said intermediate layer (4) and said inner layer (2) and/or said outer layer (3).

19. Hose structure as claimed in the preceding claim, wherein said lubricating means include a layer of talc or similar material.

20. A method for making a high flexibility hose structure as claimed in one or more of the preceding claims comprising the following steps of: - forming at least one inner tubular layer (2) of a first polymeric material;

- laying at least one intermediate layer (4) of fibrous material on said inner tubular layer (2);

- forming at least one outer tubular layer (3) of a second polymeric material on said intermediate layer (4); characterized in that said at least one intermediate layer (4) is laid in such a manner as to be substantially in contact and uniformly coupled both to said at least one inner layer (2) and to said at least one outer layer (3), to be radially constrained therebetween, although allowing mutual longitudinal sliding of the same layers (2, 3).

21. Method as claimed in claim 20, wherein said step of forming said at least one inner layer (2) comprises a first internal inflation step to expand the inside diameter of said layer (2) to a first predetermined value (Di).

22. Method as claimed in claim 21 , wherein said intermediate layer (4) is laid on said inner layer (2) to form a semifinished product (6) whish is subjected to a second internal inflation step to expand the inside diameter of said inner layer (2) to a second predetermined value (D₂).

23. Method as claimed in claim 21 or 22, wherein said first inflation step and/or said second inflation step are carried out at a pressure of 2 to 8 bar.

24. Method as claimed in claims 21 to 23, wherein said at least one outer layer (3) is formed by extrusion of said second polymeric material on said semifinished product (6).

25. Method as claimed in claim 21 , wherein said intermediate layer (4) is a fabric formed by braiding fibers (5, 5', 5") on the outer surface of said inner layer (2).

26. A high pressure apparatus, such as a pressure washer or a similar machine, comprising a hose structure as claimed in one or more of claims 1 to 20.