Patent Description:
In the industry field, the need to move abrasive materials, such as coal, glass powder, metals and waste of various forces and sizes, is known.

In the prior art, said abrasive materials are moved by means of plastic or elastomeric tubes which are fluidly connected to suction or delivery systems.

The inner walls of said plastic or elastomeric tubes are inevitably subject to early wear, due to the fact that the bodies moved therein tend to significantly abrade the inner walls of the tubes through which they are conveyed. For this reason, the tubes undergo very rapid deterioration which makes frequent replacement necessary, in the worst scenario, even once a week. As a result, the maintenance and downtime costs of the system significantly increase.

Several solutions aimed at solving the aforesaid technical problems exist in the art.

For example, it is known to provide plastic or rubber tubes equipped, at the inner side walls thereof, with protective elements such as spheres made of a highly hard material, as in case of ceramic materials, which are at least partially embedded in the main rubber structure forming the thickness of the conveying tube. It is apparent that embedding spheres inside the polymer matrix of the tube creates a solid, long-lasting fastening of the spheres with respect to the inner side walls of the tube itself.

However, such a solution is not free of some technical drawbacks. In particular, the spherical bodies have ends that interfere with and limit the passage lumen of the hollow tube: on the one hand, such ends reduce the effective flow rate of the tube, and on the other hand, they tend to be damaged and removed over time because of the continuous and violent impacts to which they are subjected by the bodies passing inside the tube. Therefore, even if such solutions require longer maintenance intervals as compared to the mentioned solutions of the prior art, they still imply non-negligible maintenance costs. It has been seen, for example, that by virtue of such spheres made of ceramic material it is possible to increase the maintenance intervals up to two or at the most three weeks.

Such maintenance intervals, although improved compared to some solutions of the prior art, are however not considered acceptable, as they result in significant increases in cost.

Moreover, it has been noted that such ceramic spheres significantly limit the curvature which can be given to the conveying tube, in particular at the intrados of the tube, since said curvature is limited indeed when adjacent spheres come into mutual contact at the already curved parts of the tube (typically at the intrados).

The curvature limits can be unacceptable drawbacks in some specific applications in which the available spaces impose particularly small radii of curvature, which are not practicable due to the reasons set out above. Solutions according to prior art are disclosed by <CIT>, <CIT> and <CIT>.

Therefore, the need is felt to solve the drawbacks and limitations mentioned with reference to the prior art.

Such a need is met by a tube for conveying abrasive materials according to claim <NUM> and a method for making a flexible tube according to claim <NUM>.

Further features and advantages of the present invention will be more comprehensible from the description given below of preferred, non-limiting embodiments thereof, in which:.

The elements or parts of elements common to the embodiments described below will be indicated by the same reference numerals.

With reference to the aforesaid figures, reference numeral <NUM> indicates an overall view of a flexible tube for conveying abrasive materials.

A 'flexible' tube means a tube that can be easily laid and reversibly bent along a predetermined path without the aid of any bending tools; flexibility does not necessarily imply compressibility, i.e., modification of the geometry of the inner passage lumen of the tube, which remains substantially unvaried, typically with a circular section, throughout the laying and operating conditions of the flexible conveying tube.

Abrasive materials mean any type of material that is substantially hard and/or cutting and/or sharp, such as production waste, scraps.

The flexible tube <NUM> comprises a tubular body <NUM> extending along a main extension axis Z-Z.

Obviously, since the tube <NUM> is flexible, the main extension axis can be rectilinear but also curvilinear according to the final configuration of the tube: in this latter case, the main extension axis Z-Z will be assimilated to the segment tangential to the corresponding curvilinear abscissa. Below and in the figures in general, reference will be made to rectilinear segments of tube, without losing in generality.

The tubular body <NUM> has a thickness <NUM> extending from an inner side wall <NUM>, which delimits an inner cavity <NUM> used for transporting abrasive material, to an outer side wall <NUM>, opposite to said inner side wall <NUM> along a radial direction R-R, perpendicular and incident to said main extension axis Z-Z.

The tubular body <NUM> comprises a covering layer <NUM> made of synthetic rubber at the outer side wall <NUM>. For example, said covering layer <NUM> made of synthetic rubber is made of an NR/BR mixture and/or SBR, EPDM, CR mixtures.

An advantage of the invention is that said tubular body <NUM> comprises an elastomeric matrix <NUM>, in which there are at least partially embedded circular disks <NUM> having a diameter D and flat faces, made of ceramic material.

Said circular disks <NUM> act as a partial anti-abrasive coating of the inner side wall <NUM>. In other words, the circular disks <NUM> increase the resistance of the inner side wall <NUM> when an abrasive material passes inside the cavity <NUM>.

Said circular disks <NUM> have a first flat face <NUM> directly facing said inner cavity <NUM> so as to at least partially form the inner side wall <NUM> and a second flat face <NUM> embedded in the elastomeric matrix <NUM>.

According to the invention, with respect to a diametric projection plane passing through the main extension axis Z-Z, the circular disks <NUM> are arranged on rows parallel to a first laying direction X-X with a first constant pitch p1, and on rows parallel to a second laying direction Y-Y, with a second constant pitch p2, said laying directions X-X, Y-Y being perpendicular to each other.

According to a possible embodiment, the first pitch p1 and the diameter D of the circular disks <NUM> are linked by the following relationship: <NUM>≤p1/D≤<NUM>.

According to a possible embodiment, the second pitch p2 and the diameter D of the circular disks <NUM> are linked by the following relationship: <NUM>≤p2/D≤<NUM>.

According to a possible embodiment, the circular disks <NUM> are arranged so that <NUM>°≤α≤<NUM>°, α being the angle identified between the first laying direction X-X and said main extension axis Z-Z of the tube <NUM>.

According to a possible embodiment, the circular disks <NUM> are arranged so that <NUM>≤f≤ p1/<NUM>, f being equal to the distance, measured parallel to said first laying direction X-X, between the centres of two disks <NUM> arranged on rows adjacent to each other and parallel to the second laying direction Y-Y.

The circular disks <NUM> can have several dimensions; preferably the circular disks <NUM> have a diameter D between <NUM> and <NUM>.

Preferably, said circular disks <NUM> have a thickness S between <NUM> and <NUM>, the thickness S being equal to the distance between the first flat face <NUM> and the second flat face <NUM>.

Preferably, the circular disks <NUM> are made of at least <NUM>% Al2O3 sintered alumina; preferably said circular disks <NUM> have a Rockwell hardness (HRA) equal to at least <NUM>.

According to a possible embodiment, said circular disks <NUM> are treated in advance with a solution cycle in order to improve the adhesion with said elastomeric matrix <NUM>.

Said elastomeric matrix <NUM> comprises a portion of anti-abrasive rubber <NUM> directly facing the inner cavity <NUM>. The inner side wall <NUM> is thus delimited by the first flat faces <NUM> of the circular disks <NUM> and by the portion of anti-abrasive rubber <NUM> filling the gaps between the first flat faces <NUM> of the circular disks <NUM> adjacent to one another.

Said elastomeric matrix <NUM> can comprise an NR/BR SBR and/or EPDM mixture.

According to a possible embodiment, at least one reinforcement layer <NUM> is embedded inside the elastomeric matrix <NUM>, comprising synthetic fabrics embedded in SBR, NR/BR and/or EPDM mixture.

For example, said synthetic fabrics comprise cellulose and/or polyester and/or aramid and/or polyvinyl alcohol and/or polyamide, with titres between <NUM> dtex and <NUM> dtex.

According to a possible embodiment, said reinforcement layer <NUM> comprises a steel spiral <NUM> of a diameter between <NUM> and <NUM>.

According to a possible embodiment, at least one copper braid <NUM> is embedded inside the elastomeric matrix <NUM>, for the dissipation of the electrostatic charges; for example, the copper braid consists of <NUM>-<NUM> tinned copper wires of diameter <NUM>.

According to a possible embodiment, at said outer side wall <NUM>, the flexible tube <NUM> has a corrugated outer profile <NUM> and, at at least one axial end <NUM> of the flexible tube <NUM>, at least one flange <NUM> having a corrugated inner profile <NUM> corresponding to said outer profile of the flexible tube is applied, so as to obtain a shape coupling with the latter.

For example, said flange <NUM> comprises a pair of mirrored half-shells <NUM> clamped to each other on the outer side wall <NUM> of the flexible tube <NUM> and at least one lip seal <NUM> at said axial end of the tube <NUM>.

Preferably, said lip seal <NUM> is at least partially interposed between the half-shells <NUM> and the outer side wall <NUM> of the tube <NUM>.

The method for making and mounting a flexible tube according to the present invention will now be described.

In particular, the method for making a flexible tube <NUM> according to the invention comprises the steps of arranging and constraining, on a plastic film <NUM>, a plurality of circular disks <NUM> according to the pattern described above (<FIG>). It is to be specified that, following the use of the tube, with the passage of the abrasive material, such a plastic film <NUM> is removed; therefore, the purpose of said plastic film <NUM> consists in allowing/facilitating the correct arrangement of the circular disks <NUM> in the inner side wall <NUM> of the flexible tube <NUM>.

Therefore, a solution step is carried out on the second flat faces <NUM> of the circular disks <NUM> intended to be embedded in an elastomeric matrix <NUM> (<FIG>).

This is followed by the step of rolling said plastic film <NUM> (carrying the aforesaid circular disks <NUM>) onto a cylindrical core intended to positively reproduce the inner cavity delimited by the flexible tube <NUM>.

A first layer of elastomeric matrix <NUM> is spread onto the previously rolled plastic film <NUM>, so as to embed the circular disks <NUM> on the side of the second flat faces <NUM> of the circular disks themselves.

Then, at least a second layer of elastomeric matrix <NUM> is spread, so as to completely incorporate the circular disks <NUM> and reinforce the overall structure of the tube <NUM>.

Moreover, possible reinforcement layers <NUM> are applied, comprising synthetic fabrics made of SBR, NR/BR and/or EPDM mixture, and/or a steel spiral <NUM> and/or a copper braid <NUM> for the dissipation of the electrostatic charges.

Finally, a covering layer <NUM> of NR/BR or SBR or EPDM or CR mixture is applied.

As can be appreciated from the description above, the present invention allows overcoming the drawbacks of the prior art.

In particular, the flexible conveying tube according to the present invention is capable of transporting abrasive materials moved by suction or delivery without undergoing deterioration due to abrasion.

The solution according to the present invention has significantly longer maintenance intervals compared to the above mentioned solutions of the prior art.

Moreover, the present invention allows transporting products that require the absolute absence of electric charges, due to the provision of copper braids that can dissipate said electrostatic charges.

In addition, the solution according to the present invention allows making great tube curvatures, because the ceramic disks do not protrude into the passage lumen of the tube itself. Moreover, the particular geometry and arrangement of such reinforcement disks ensures excellent flexibility for the tube itself.

In order to meet specific contingent needs, those skilled in the art may make several changes and variations to the solutions described above.

Claim 1:
Flexible tube (<NUM>) for conveying abrasive materials, comprising
- a tubular body (<NUM>) extending along a main extension axis (Z-Z), the tubular body (<NUM>) having a thickness (<NUM>) extending from an inner side wall (<NUM>), which delimits an inner cavity (<NUM>) to be used for transporting abrasive material, to an outer side wall (<NUM>), opposite said inner side wall (<NUM>) along a radial direction (R-R), perpendicular and incident with said main extension axis (Z-Z),
- wherein said tubular body (<NUM>) comprises a covering layer (<NUM>) at the outer side wall (<NUM>),
- wherein said tubular body (<NUM>) comprises an elastomeric matrix (<NUM>), inside which are at least partially embedded circular disks (<NUM>) having a diameter (D) and flat faces,
in ceramic material, having a first flat face (<NUM>) directly facing said inner cavity (<NUM>), so as to at least partially constitute the inner side wall (<NUM>) and a second flat face (<NUM>) embedded in the elastomeric matrix (<NUM>),
characterized in that, with respect to a diametric projection plane, passing through the main extension axis (Z-Z), the circular disks (<NUM>) are arranged on rows parallel to a first laying direction (X-X) with a first constant pitch (p1), and on rows parallel to a second laying direction (Y-Y), with a second constant pitch (p2), said laying directions (X-X,Y-Y) being perpendicular to each other.