Patent Description:
The invention also relates to a method for producing such a cylinder.

Various types of high-pressure cylinders are known that are obtained from an internal core in metal or plastic material, on which a nozzle in metal material is formed or applied, normally provided with a thread suitable for clamping a tap or a sealing valve. The core is then covered with one or more layers of reinforcing threads which also wrap around the external base of the nozzle.

A critical aspect of these cylinders is represented by the coupling between the neck of the core and the nozzle, especially in the case of a core in plastic material. In fact, at the interface between the plastic material of the core and the surface of the nozzle the pressurised gas tends to produce a delamination with consequent possible leaking.

Various solutions have been proposed to try to limit this problem, none of which has proved completely satisfactory.

<CIT> discloses a boss for use with a vessel. The boss includes a first component adapted to be formed in an opening of the vessel, wherein the first component includes a first coupling element, and a second component including a second coupling element, wherein the second coupling element engages the first coupling element to secure the second component to the first component, and wherein a liner of the vessel is disposed therebetween.

It is, therefore, the object of the present invention to eliminate the disadvantages encountered in the solutions of the prior art.

More particularly, it is an object of the invention to provide a high-pressure cylinder with a core in plastic material and a surface covering in composite material, wherein the nozzle ensures an excellent seal over time under all conditions of use.

A further object of the invention is to provide such a cylinder in which the nozzle can be quickly and safely applied.

Yet another object of the invention is to provide such a cylinder in which a nozzle element suitable for receiving accessories is shaped so as to be removable for possible maintenance work.

These and other objects are achieved by the cylinder according to the invention that has the features of the appended independent claim <NUM>.

Advantageous embodiments of the invention are disclosed in the dependent claims.

Substantially, the high-pressure cylinder according to the invention has an internal core or liner in plastic material and a surface covering constituted by one or more layers of composite material, partially incorporating a nozzle applied to the upper end part of the neck of the core shaped to receive at least one accessory, such as a tap, valve, or other, said nozzle comprising an internal metal element and an external metal element which can be screwed together to tighten on said neck of the core, wherein said core neck has a slight narrowing in diameter starting from its mouth, such as to determine an internal conical surface suitable for coupling with a corresponding external conical surface of the internal element of the nozzle, and an external conical surface suitable for coupling with a corresponding internal conical surface of a modular ring in plastic or elastomeric material placed between said neck and said external element of the nozzle, and wherein said nozzle likewise comprises an annular protective element in plastic or elastomeric material, acting as a bearing, which is interposed between a widened base of the nozzle and the upper part of the core of the container.

The invention also relates to a method of producing the cylinder according to the invention, having the features of claim <NUM>.

Further features of the invention will be made clearer by the following detailed description, referring to a purely illustrative, and therefore non-limiting embodiment thereof, illustrated in the accompanying drawings, wherein:.

In <FIG> the high-pressure cylinder, for containing gases and fluids in general according to the invention, has been denoted by reference numeral <NUM> and comprises a core or liner <NUM> made of plastic material, externally covered with a plurality of reinforcing layers in composite material <NUM>, such as, by way of non-limiting example, carbon or Kevlar or mixed fibre threads embedded in synthetic resins partially incorporating a nozzle <NUM> with parts in metal and plastic material, applied to the end portion/upper orifice of the neck <NUM> of the core <NUM>.

More particularly, the nozzle <NUM> is made up of four coaxial annular elements:.

The internal element <NUM> has a head <NUM> suitably shaped, for example of a hexagonal type, as shown in the example of <FIG>, or of another shape, for the engaging of a tightening key, and an annular protrusion <NUM> that abuts against the upper edge of the external element <NUM>.

In a manner in itself known, a thread <NUM> is provided on the upper internal part of the internal element <NUM> for mounting/locking a valve or tap, or any other accessory, suitable for dispensing the fluid contained in the cylinder <NUM>. Optionally, on the lower internal part of the internal element <NUM> a second thread <NUM> can be provided, for mounting other accessories, such as for example an EFV (Excess Flow Valve).

On the lower external part of the internal element <NUM> there is instead provided at least one annular seat <NUM> (two in the embodiments shown in the drawings) suitable for accommodating a respective sealing gasket <NUM>, for example in particular an O-ring, which comes into contact with the internal surface of the neck <NUM> of the core <NUM> of the cylinder <NUM>.

The neck <NUM> of the core <NUM> has an annular edge <NUM> and a slight narrowing of diameter starting from its mouth, such as to determine an inclined or conical internal surface <NUM> suitable for coupling with a corresponding external conical surface <NUM> of the internal element <NUM> of the nozzle <NUM>, and a conical external surface <NUM> suitable for coupling with a corresponding conical internal surface <NUM> of the elastomeric or plastic ring <NUM> placed between the neck <NUM> and the external element <NUM> of the nozzle <NUM>.

The provision of the ring <NUM> becomes necessary in that a possible conicity formed directly on the internal surface of the external element <NUM> would make mounting thereof impossible on the neck <NUM> which would be presented as undercut.

In fact the ring <NUM>, in order to be able to be fitted around the neck <NUM>, is formed in two separate parts <NUM>, <NUM>, which can be seen more clearly in the axonometric view of <FIG>.

In the example given, the two parts <NUM>, <NUM> of the ring <NUM> are perfectly identical one to the other and provided, at the respective ends, with complementary slotting means <NUM>, <NUM>, made up of tapers of the wall of the ring, obtained by removing material, respectively, from the exterior and from the interior of the wall itself. Obviously other slotting means could be provided, or these means could be completely absent.

The external surface of the ring <NUM>, which can be cylindrical or slightly conical, couples with a corresponding cylindrical or slightly conical internal surface <NUM> of the external element <NUM> of the nozzle, placed below the thread <NUM>.

Between said internal surface <NUM> and said thread <NUM> of the external element <NUM> an internal annular relief <NUM> is provided, which abuts against the edge <NUM> of the neck <NUM> of the core <NUM>, closing the ring <NUM> above. Above said edge <NUM> of the neck <NUM> an external shoulder <NUM> of the internal element <NUM> of the nozzle <NUM> abuts.

The double conicity of the neck <NUM> of the core <NUM>, together with the conicity of the internal element <NUM> of the nozzle and of the ring <NUM> below the external element <NUM>, makes it possible to obtain an excellent mechanical coupling between core and nozzle, since the inclined surfaces increase the adhesion and the resistance to stresses in the axial direction.

The external element <NUM> of the nozzle <NUM> has a radial protrusion <NUM>, preferably of hexagonal, octagonal or decagonal shape, for a better grip of the external surface covering <NUM> and to avoid possible rotations that could occur, when tightening the internal element <NUM> on the external element <NUM>, and a widened base <NUM> that goes to rest on the upper part of the core <NUM> of the container <NUM>.

In order to avoid a biting effect between the metallic material of the external element <NUM> of the nozzle <NUM> and the plastic material of the core <NUM>, between this external element <NUM> and the core <NUM> said annular protective element in plastic or elastomeric material <NUM> is interposed, which acts as a bearing, shown axonometrically in <FIG>.

On the opposite side to the nozzle <NUM>, in the lower part of the core <NUM>, a bottom <NUM> in metal or also plastic material is applied, with the interposition of a bearing ring <NUM> in plastic or elastomeric material. This bottom <NUM> is used to allow the winding of carbon fibre threads to make the external surface covering <NUM> of the cylinder.

Referring to <FIG>, <FIG> a description is now given of how the cylinder <NUM> is formed with the nozzle <NUM>.

The core <NUM> is formed from a preform <NUM> shown in <FIG>, in a view and section respectively.

The preform <NUM> is stretch-blow moulded to form the core <NUM> of the cylinder <NUM>, as shown partially in <FIG>.

Before the stretch-blow moulding the preform is subjected to a heat treatment during which the neck <NUM> of the preform, with said internal <NUM> and external <NUM> conicities, undergoes a phase change that determines a crystallization thereof allowing, after a resumption of mechanical processing, a perfect coupling with the elements of the nozzle <NUM>.

After the stretch-blow moulding of the preform the protective bearing <NUM> is mounted, which has a central hole <NUM> (<FIG>) sufficiently large to house the neck <NUM> of the core <NUM>, as shown in <FIG>.

The two parts <NUM>, <NUM> of the ring <NUM> are then mounted around the neck <NUM>, as shown in sequence by <FIG> and <FIG>.

Subsequently the external element <NUM> of the nozzle is mounted, as shown in <FIG>. At this point, after application of the bottom <NUM> on the core <NUM>, carbon fibre threads can be wound in order to realize the external surface covering <NUM> of the cylinder which partially incorporates the external element <NUM> of the nozzle <NUM>.

Finally, the internal element <NUM> of the nozzle is screwed, bringing its shoulder <NUM> in abutment above the annular edge <NUM> of the neck <NUM>.

Naturally, alternatively, the internal element <NUM> can be mounted prior to the winding of the surface covering <NUM> in composite material. In any case, the internal element <NUM> can be removed if necessary for reasons of maintenance or to carry out replacement of the gasket(s).

The cylinder <NUM> shown in the drawings has a "barrel" shape, i.e. a cylindrical shape tapered above and below, but it is clear that it can be of any desired shape, for example cylindrical with a circular section, square section, rectangular, elliptical, etc..

<FIG> shows a slightly different embodiment, in which said annular internal relief <NUM> of the external element <NUM> of the nozzle is threaded and screws onto a corresponding thread provided on the annular edge <NUM> of the neck <NUM> of the core <NUM>, so as to ensure a firm coupling between these elements.

From what is disclosed, the advantages of the high-pressure cylinder according to the invention and of the relative manufacturing process, which enables a perfect sealed coupling of the nozzle <NUM> to be obtained, thanks to the double conicity of the neck <NUM> of the core <NUM>, appear clear.

Claim 1:
High-pressure cylinder (<NUM>) having an internal core or liner (<NUM>) in plastic material and a surface covering (<NUM>) consisting of one or more layers of composite material, partially incorporating a nozzle (<NUM>) applied to the upper end portion of neck (<NUM>) of the core (<NUM>) shaped to receive at least one accessory, such as a tap, a valve, or other, said nozzle (<NUM>) comprising an internal metal element (<NUM>) and an external metal element (<NUM>) which can be screwed one to the other to tighten on said neck (<NUM>) of the core (<NUM>),
characterised in that said neck (<NUM>) of the core (<NUM>) has a slight narrowing of diameter starting from its mouth, such as to determine an internal conical surface (<NUM>) suitable for coupling with a corresponding external conical surface (<NUM>) of the internal element (<NUM>) of the nozzle (<NUM>), and an external conical surface (<NUM>) suitable for coupling with a corresponding internal conical surface (<NUM>) of a modular ring in plastic or elastomeric material (<NUM>) placed between said neck (<NUM>) and said external element (<NUM>) of the nozzle, and in that said nozzle (<NUM>) also comprises an annular protective element in plastic or elastomeric material (<NUM>), acting as a bearing, which is interposed between a widened enlarged base (<NUM>) of the nozzle (<NUM>) and the upper part of the core (<NUM>) of the cylinder (<NUM>).