Patent Description:
In detail, the present invention relates to a tubing or pipe of the corrugated type, i.e., shaped to define a plurality of shoulders and dips arranged in an alternating manner, i.e., wherein between each pair of consecutive shoulders, there is a dip connecting said consecutive shoulders.

Even more in detail, the present invention relates to a corrugated type tubing comprising an external reinforcing spiral.

The use of flexible tubings or pipes for the easy and reliable connection of components of hydraulic and/or hydrodynamic systems is well known and widespread in the prior art, to allow the transport of fluids, in particular but not exclusively under pressure, between said components.

In particular, the tubings according to the prior art are often made of polymeric material, thermoplastic materials, and vulcanized rubbers, according to the applications for which they are intended, and so that the tubings comply with various requirements including no leakage points (the tubing must be tight), resistance to the pressures applied by the transported fluid, resistance to the temperatures of the transported fluid and more generally of the working environment, resistance to the collapse of the tubing when bent to follow and define tight bending radii. Furthermore, for applications in the heating and plumbing sector, for example, the requirements for contact with drinking water often have to be added to the requirements mentioned above.

The need to meet the aforesaid requirements led to the development of several solutions which can be summarized as:.

The first group comprises tubings made of vulcanized rubber monolayer or multilayer, typically in EPDM (Ethylene-Propylene Diene Monomer), used in various fields, from the hydraulic sector (connections under the sink) to the automotive sector or the hydrodynamic sector.

The second group comprises, for example, soft PVC water inlet tubings for household appliances, such as washing machines and dishwashers, or even conventional "garden hoses".

The third group comprises the tubings of the heating and plumbing sector for applications in which tight bending radii without tubing collapse are required. The corrugated tubing can also be made of thermoplastic materials which meet even more stringent requirements in terms of suitability for contact with drinking water, thus overcoming the intrinsic limits of vulcanized rubber tubings.

In particular, the need to create tubings capable of withstanding the operating pressures and/or temperatures has led to the idea of applying a mechanical reinforcement consisting of a braid or a double spiral externally to the tubing and sometimes even in an "integrated" manner in the structure of the tubing.

The braiding technique (application/formation of the braid) consists in braiding on the tubing a series of metallic filaments (stainless steel, galvanized, etc) or textile filaments (polyester, nylon, Kevlar, etc) which compose a real fabric enclosed on the tubing itself, allowing the achievement of very high bursting pressures. This production method is the best performing from a mechanical point of view because the braid filaments are kept in position on the tubing by the structure of the braid itself, which is a real fabric made up of various threads. Tubings with this type of reinforcement can reach burst pressures comprised between <NUM> and <NUM> bar as a function of (depending on) the nature of the reinforcing fiber (metallic rather than textile) and the diameter of the tubing.

The double spiral technique, on the other hand, consists of depositing two spirals of n threads on the tubing at the same time (an example of configuration is with <NUM> threads) in an opposite direction - clockwise and counterclockwise - which together create a lattice which contributes to increasing the bursting resistance of the tubing. Since the double helix is not a fabric, i.e. a structure in which each thread is held in place by the other threads, these filaments must be "embedded" in the thermoplastic matrix which makes up the tubing, so that the filaments do not move as a result of bending of the tubing or as a result of internal pressures; indeed, if this were not the case, a weak point would be created in the tubing in which the reinforcing element is not present, and the tubing would fail prematurely. It is common to find on these tubings also filaments arranged longitudinally whose purpose is to counteract the elongation of the tubing when subjected to internal pressure. The reinforcing fibers used are mainly textile, typically polyester but sometimes also nylon, Kevlar, etc. The spiraling process consists of a first step during which the filaments are laid on the surface of the tubing to be reinforced, and a successive step of the cohesive coating of the tubing with a material compatible with the material of which the tubing is made, thus maintaining the reinforcement fibers in a fixed position.

Tubings with this type of reinforcement can withstand pressures of up to <NUM>-<NUM> bar as a function of the diameter of the tubing and the type of fiber used.

The main advantage offered by spiraling compared to braiding lies in the high production speed, which can reach up to <NUM>-<NUM>/min.

The smooth, corrugated tubing of the known type briefly described above, while appreciable for the aforesaid advantages, nevertheless has disadvantages and/or drawbacks which the owner of the present patent application intends to overcome with the tubing according to the present invention.

A first drawback of the smooth tubings reinforced by means of a braid is given by the high cost generated by the number of filaments deposited on the tubing and especially by the manufacturing speed of the braid which is <NUM>-<NUM>/min as a function of the diameter of the tubing to be coated.

Concerning corrugated tubings, the main drawback is the fact that they are not suitable to be subjected to the spiral process.

Indeed, the regular arrangement of the spiral fibers is optimal only when it is deposited on a smooth tubing on which to lay the filaments because as the thread is not self-supporting as would be in the case of braiding, maintaining the position of the reinforcing fiber on the tubing is problematic; in particular, even the pressure applied by the molten material during the step of over-extruding (external tubing coating) would be able to displace the fibers, where a poor positioning of the fibers results in a loss of mechanical strength.

It is thus the main object of the present invention to overcome or at least minimize the drawbacks outlined above and affecting the prior art.

In particular, it is a first object of the present invention to make available a corrugated type tubing reinforced with an external spiral.

It is a second, not secondary object of the present invention to make available a tubing of the aforesaid type which offers both the typical advantages of corrugated tubing and those provided by the external spiral.

A non-secondary purpose of the present invention is to provide a tubing which:.

The present invention is based on a novel concept of applying a reinforcing spiral to a corrugated core.

As explained below, the general concept described above requires the corrugated core to be made adapted to receive the spiraling by prior application of a smooth coating, in particular one which simulates a smooth tubing.

In view of the above, as well as of the problems and/or drawbacks encountered in the flexible tubing according to the prior art, the present invention provides a flexible tubing according to claim <NUM>. Further embodiments of the tubing are defined by the dependent claims.

The flexible tubing, for hydraulic and/or hydrodynamic use, comprises a main flexible tubular body made of thermoplastic material which extends about a longitudinal extension axis, the sections of said main tubular body being substantially circular on planes perpendicular to said longitudinal extension axis, said main tubular body being of a corrugated type and thus conformed to define a first plurality of ridges or shoulders arranged in succession and a second plurality of dips or valleys arranged in succession to connect each of two consecutive ridges or shoulders; wherein said main tubular body is housed within a first coating made of thermoplastic elastomer, and wherein said tubing comprises a spiraling constituted by a plurality of filaments each spirally wound on said first coating made of thermoplastic elastomer.

According to the described embodiment, the diameter of each of the coils defined by said filaments is either equal to or greater than the maximum outer diameter of said main tubular body, wherein said filaments are thus arranged outside said valleys of said main tubular body.

According to the invention, said tubing comprises a second outer thermoplastic elastomer coating, wherein said filaments of said spiraling are embedded in said second outer thermoplastic elastomer coating.

According to a described embodiment, said spiraling comprises a first plurality of filaments each spirally wound on said first coating according to a first winding direction, and a second plurality of filaments each spirally wound on said first coating according to a second winding direction opposite to said first winding direction, wherein said filaments of said first plurality and second plurality are mutually arranged to define a lattice.

According to a described embodiment, said filaments of said spiraling are made of a textile material such as polyester, nylon, Kevlar, or similar material.

According to a described embodiment, said second outer coating is internally substantially cylindrical and of smooth tubular type, wherein the minimum inner diameter of said second outer coating is either equal to or greater than the maximum outer diameter of said main tubular body and said first coating, wherein said second outer coating does not follow the corrugation of said main tubular body and/or said first coating.

According to a described embodiment, said second outer coating is made by over-extrusion on said spiraling wound on said first coating in which said main tubular body is housed.

According to the described embodiment, said first external outer coating is substantially cylindrical inside and of smooth tubular type, wherein the minimum inner diameter of said first coating is either equal to or greater than the maximum outer diameter of said main tubular body, wherein said first outer coating does not follow the corrugation of said main tubular body.

According to a described embodiment, said first outer coating is made by over-extrusion on said main tubular body.

According to a described embodiment, said main tubular body is of a two-layer type, wherein said main tubular body comprises a main inner layer and an outer layer, and thus wherein said first coating comprises the outer layer of said main tubular body.

According to a described embodiment, said tubular body is made by simultaneous co-extrusion of said main inner layer and outer layer.

According to a described embodiment, said main tubular body is of the square wave and narrow valley type, wherein each of said shoulders is bounded externally by a substantially cylindrical surface.

According to a described embodiment, the longitudinal extent of said substantially cylindrical surface of each of said shoulders is either equal to or greater than twice the longitudinal pitch of said coils of said spiraling.

According to a described embodiment, the longitudinal extent of said substantially cylindrical surface of each of said shoulders is either equal to or greater than twice the maximum longitudinal distance between two consecutive shoulders. According to any one of the described embodiments, the thickness of said main tubular body is between <NUM> and <NUM> and/or an inner diameter is comprised between <NUM> and <NUM>.

According to a described embodiment, said first coating has an average thickness comprised between <NUM> and <NUM>.

According to a described embodiment, said second outer coating has a thickness comprised between <NUM> and <NUM>.

Hereafter, the present invention will be further clarified by means of the following detailed description of the possible embodiments depicted in the drawings, in which corresponding or equivalent features and/or component parts of the present invention are identified by the same reference numerals. It must be noted that the present invention is not limited to the embodiments described hereafter and depicted on the accompanying drawings; on the contrary, all the variants and/or changes to the embodiments described below and shown on the accompanying drawings which will appear obvious and immediate to a person skilled in the art are comprised in the scope of the present invention.

The present invention is particularly applied in the field of dispensing and transmission systems of water or liquid in general, in particular for mutually connecting components, e.g. such as the components of household appliances, this being the reason for which the present invention is described hereafter with particular reference to its applications in the field of components for household appliances.

However, it is worth specifying that the possible applications of the present invention are not limited to those described hereafter. On the contrary, the present invention is conveniently applied in all cases in which it is necessary to hydraulically connect components of any type, e.g. hydrodynamic systems.

According to the embodiment as depicted in <FIG> and <FIG>, the tubing shown therein, identified by reference numeral <NUM> and hereafter referred to simply as tubing or tube for the sake of briefness, comprises, from the inside out, a corrugated tubing (a main tubular body of the corrugated type) <NUM>, a smooth coating <NUM> which surrounds and encloses within itself the main tubular body <NUM>, a plurality of filaments <NUM> each wound spirally over the coating <NUM> to define a spiral <NUM>, and finally an outer layer or coating <NUM> which surrounds and encloses within itself the spiral <NUM> and thereby also the inner coating <NUM> and the main tubular body of corrugated type <NUM>.

The main body <NUM> is developed, as shown, along an extension direction X-X and, being of a corrugated type, comprises, as usual, a plurality of shoulders or protrusions (also called ridges) <NUM> arranged in succession along the direction X-X, and a plurality of valleys or dips <NUM> also arranged in succession along the direction X-X, wherein the shoulders <NUM> and the valleys <NUM> are mutually alternated along the direction X-X, and wherein, therefore, each valley <NUM> connects two consecutive shoulders <NUM> (and likewise each shoulder <NUM> connects two consecutive valleys <NUM>). For the purposes of the present invention, in particular according to the embodiment shown in <FIG> and <FIG>, the shoulders <NUM> and the valleys <NUM> may have any conformation (e.g., one conformation among those according to the prior art), wherein a detailed description thereof is omitted for the sake of brevity.

The materials may be those as a function of the applications of the tubing <NUM>, wherein by way of non-limiting example, the main tubular body <NUM> may be made of thermoplastic material (e.g., with an average wall thickness of about <NUM>, and an inner diameter between <NUM> to <NUM>), the inner liner <NUM> may be made of thermoplastic elastomer compatible with the material of the main body <NUM> (e.g., with an average thickness of <NUM>-<NUM>), the filaments <NUM> may be either metallic or textile type (e.g., polyester but also nylon, Kevlar, and similar materials).

By way of non-limiting example, the tubing <NUM> shown in <FIG> and <FIG> may be constructed by the following procedure.

Forming on the main body <NUM> of the smooth inner liner <NUM> by means of the over-extrusion technique on the corrugated tubing <NUM>;.

According to alternative embodiments, the outer coating <NUM> can also be omitted. Thus, it is apparent that the purpose of the inner coating <NUM> is to make the main body <NUM> resemble a tubular body externally not corrugated but substantially smooth. Indeed, the inner coating <NUM>, made in the form of a tubular sheath, allows the formation of the spiral <NUM> as in the case of a smooth tubing and thus to avoid the risk of the filaments <NUM> moving accidentally (already during the step of spiraling and/or during the over-extrusion of the outer coating <NUM>).

As anticipated, the coating <NUM> may be constructed as a tubular sheath and thus either to leave the valleys <NUM> of the main body <NUM> substantially empty or to substantially fill said valleys <NUM>.

The embodiment depicted in <FIG> differs from that shown in <FIG> and <FIG> in that the main tubular body <NUM> is of the double layer type and thus comprises a main inner layer <NUM> (e.g., PP) and an outer layer <NUM> (e.g., TPE-S) made, for example (but not necessarily), by the simultaneous co-extrusion technique. According to this embodiment, the outer layer <NUM> replaces the inner coating <NUM> of the embodiment in <FIG> and <FIG> by performing substantially the same functions. Therefore, the outer layer <NUM> has the main function of allowing the formation of the spiraling by preventing the accidental displacement of the filaments <NUM>, in particular by preventing the spirals from being deposited predominantly in the valleys <NUM> by virtue of at least in part but not solely to the high friction coefficient of the thermoplastic rubber surface of the layer <NUM>.

Furthermore, for this purpose (and as shown), the corrugated conformation may be chosen so that the shoulders <NUM> define a preferred bearing surface for the filaments <NUM>. In particular, the main tubular body <NUM> may be of the "square wave and narrow valley" type, wherein that is, each shoulder <NUM> is bounded externally by a substantially cylindrical surface <NUM> which serves as a support for the filaments <NUM>. Eventually, the longitudinal extent (along the X-X axis) of the surfaces <NUM> may be chosen as a function of the pitch of the coils defined by the filaments <NUM>, and that is, as a function of the longitudinal distance (along the X-X axis) between two successive coils, e.g. so that the longitudinal extent of each surface <NUM> is greater than or at least equal to twice the pitch of the coils of the spiral <NUM>.

In this case, the method for making the tubing <NUM> may comprise:.

It has thus demonstrated by means of the detailed description given above of the embodiments shown in the drawings that the present invention makes it possible to achieve the desired objects and to overcome or at least limit the drawbacks affecting the prior art.

In particular, the present invention makes available a tubing <NUM> which:.

Although the present invention is explained above by means of a detailed description of the embodiments thereof shown in the drawings the present invention is obviously not limited to the embodiments described above and shown on the drawings; on the contrary, all the variants and/or changes to the embodiments described and shown on the accompanying drawings are comprised in the object of the present invention and will be apparent and immediate to a person skilled in the art. For example, the corrugated main body <NUM> may be made of polyolefin resin, and the coating layers <NUM> and <NUM> of TPE-V or TPE-S.

Claim 1:
A flexible tubing (<NUM>) for hydraulic and/or hydrodynamic use, said tubing (<NUM>) comprising a main flexible tubular body (<NUM>) made of thermoplastic material which extends along an axis of longitudinal extension, the sections of said main tubular body (<NUM>) being substantially circular on planes perpendicular to said longitudinal extension axis, said main tubular body (<NUM>) being of a corrugated type and thus conformed to define a first plurality of ridges or shoulders (<NUM>) arranged in succession and a second plurality of dips or valleys (<NUM>) arranged in succession to connect each of two consecutive ridges or shoulders (<NUM>); wherein said main tubular body (<NUM>) is housed within a first coating (<NUM>) made of thermoplastic elastomer, wherein
said tubing comprises a spiraling (<NUM>) constituted by a plurality of non-braided filaments (<NUM>), each spirally wound on said first coating (<NUM>) made of thermoplastic elastomer,
wherein said tubing (<NUM>) comprises a second outer coating (<NUM>) made of thermoplastic elastomer, wherein
said filaments (<NUM>) of said spiraling (<NUM>) are embedded in said second outer coating (<NUM>) made of thermoplastic elastomer.