FIELD OF THE INVENTION

The present invention concerns a tubular body made of composite material, for example a jacket of a linear actuator, a pipe, a pressurized container or suchlike, which can be applied on mechanical equipment such as, by way of example, articulated arms of pumps transported on trucks, or lifting means. In particular, the tubular body according to the present invention is used for applications which need mechanical components with a weight that can be a critical design parameter.

The present invention also concerns the corresponding method for manufacturing the tubular body.

BACKGROUND OF THE INVENTION

Tubular bodies are known, for example the jackets of hydraulic or pneumatic actuators made of metal material, such as for example steel or cast iron, which during use are subjected to high working pressures of the work fluid.

Here and hereafter in the description, where not specifically indicated, we shall refer to the particular application of a jacket for a hydraulic actuator although, obviously, similar considerations can be made for different applications such as for pipes for transferring concrete, pressurized tanks, containers for fluids or similar applications.

Usually a plurality of said actuators or pipes are installed on mechanical equipment, such as for example articulated arms, and are very large in size, due both to the type of installation required and also to the loads and stresses they have to support.

One disadvantage of these known actuators and/or pipes, made completely of metal material, is that they are particularly heavy. This disadvantage is even more accentuated when a plurality of actuators and/or pipes are installed on the mechanical equipment described above, and are decisive with regard to the overall weight of the equipment and possibly of the vehicle on which they are installed.

It is also known that, in order to reduce the energy consumption of said vehicles on which the articulated arms are installed, and to optimize their performance both in terms of weight and in terms of efficiency, efforts have been made to reduce the weight of their components, such as for example the segments of the articulated arm, the actuators, pipes or possible mechanical components that are mounted on the vehicle.

Tubular bodies are also known, such as jackets for actuators or pipes, that comprise a central tubular element and two sleeves that are solidly associated in correspondence with the opposite ends of the tubular element and in correspondence with its internal surface.

The tubular element is usually made of composite material such as carbon fibers drowned in binding resins such as epoxy, polyester and polyamide resins, while the two sleeves are usually made of metal material to confer on this part a greater resistance to mechanical stresses.

In fact, usually connection flanges are associated with the two sleeves, for example to define the connection with another tubular body, or closing lids such as for example a head and a bottom, to define the closed chamber of an actuator.

The sleeves are integrated into the central tubular element already during the manufacture of the latter.

A solution is also known which provides to make the tubular element for example by filament winding techniques.

These techniques provide to wind a plurality of fibers around a male mold having the shape and size of the tubular element in negative, in order to define the geometry and sizes of the latter. Subsequently, the fibers are drowned in a binding resin which in turn is subjected to a polymerization process to confer mechanical resistance to the tubular element.

During the step of winding the fibers, the technique provides to wind them not only on the male mold but also on the external circumferential surface of the sleeves, to integrate them inside it.

The sleeves have a particular conformation of their external surface which prevents them from detaching or dis-inserting from the tubular element because of the stresses to which they are subjected during use. The sleeves can have for example suitable conical geometries, circumferential cavities in which the fibers are wound, or possibly surface irregularities. One disadvantage of known tubular bodies made of composite material is that they are extremely complex to make. In fact, during their manufacture it is necessary to determine a very precise reciprocal positioning of the tubular element and sleeves so as to prevent subsequent disadvantages due to an axial misalignment thereof. Furthermore, to prevent the problems of dis-inserting as described above, the sleeves must have suitably studied geometries that are complex to achieve.

Given these production complexities, the tubular body is very expensive.

DE-B-1188880 describes a tubular body, closed at the ends by two flanges. The perimeter edge of the flanges couples conically with the ends of the tubular body, except for a last cylindrical segment with a centering function. The coupling is made solid by gluing. This solution has the problem that any excess glue cannot be discharged into a free space, nor can it be removed because, once the coupling of the tubular body and flanges has been made, the glued zone is no longer accessible from the outside in any way. Furthermore, the external edge of the flanges, once coupled with the tubular body, is not flush with the external wall of the tubular body, and this can be a limit to its usability in some applications.

Document US-A-6.196.1 12 describes a coupling between the ends of a cylindrical body and corresponding closing flanges, in which the coupling is obtained by a mixed system of threading and gluing.

Documents FR-A5-2.109.232, FR- A- 1.463.952 and GB-2.219.057 also describe solutions for coupling conical surfaces of tubular bodies, but these do not solve the problem of removing possible excess adhesive after the two bodies to be connected have been made solid by gluing them.

One purpose of the present invention is to obtain a tubular body that is light and simple to make, while still keeping mechanical performances comparable to those of tubular bodies made of metal material.

Another purpose of the present invention is to obtain a tubular body that has high mechanical characteristics of resistance to stresses, even variable and pulsing stresses.

Another purpose of the present invention is to obtain a tubular body that is economical to make. Another purpose of the present invention is to perfect a method for making a tubular body of the type described above which is simple and economical.

The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.

SUMMARY OF THE INVENTION

The present invention is set forth and characterized in the independent claims, while the dependent claims describe other characteristics of the invention or variants to the main inventive idea.

In accordance with the above purposes, a tubular body made of composite material such as a jacket for an actuator, a pipe or suchlike, comprises a tubular element made of composite material and at least one sleeve which is associated to at least one of the ends of the tubular element.

The composite material that the tubular element is made of can be for example the molded type or the stratified type.

The use of composite material to make the tubular element allows to reduce its weight considerably compared to similar applications made of metal material.

According to one feature of the present invention, at least one of the ends of the tubular element is provided on its external surface with a first conical surface with a taper that narrows axially toward the outside. On the contrary, the at least one sleeve is provided with a second conical surface, internal, mating in shape with the first conical surface, to allow the reciprocal coupling with the tubular element so that, when coupling is completed, the external surface of the sleeve is disposed substantially flush with the external surface of the tubular element. A layer of glue is also provided between the first conical surface and the second conical surface, to make the tubular element and the sleeve solid with each other.

In this way it is possible to determine the reciprocal connection of the tubular element and sleeve solely by means of the layer of glue, which is suitable to support the mechanical stresses to which the tubular body is subjected during use. In the case of an application of the tubular body to a jacket of an actuator, two lids, respectively bottom and head, are associated with the sleeves, and the layer of glue is able to support the actions of pressure and traction to which the tubular body and the sleeve or sleeves are subjected. In the case of an application to a pipe, the sleeves allow to achieve the reciprocal connection with other pipes or other components.

The taper of the two conical surfaces of the tubular element and the sleeve allows to guarantee the reciprocal adhesion with the layer of glue and to obtain an axial alignment thereof. It is therefore possible to obtain the tubular element separately, with the at least one conical surface, to obtain the sleeves with the second conical surface, and then proceed to connect them reciprocally solely with the layer of glue and pressing the sleeve against the tubular element.

It is thus possible to obtain a method for manufacturing the tubular body that is extremely simple, quick and economical compared with state-of-the-art solutions.

The first conical surface of the tubular element has an angle of amplitude comprised between 2° and 10°, preferably between 3° and 8°, even more preferably between 4° and 6°. These amplitudes of the angles allow to obtain rather large conical surfaces, which allow good resistance to the mechanical stresses to which the tubular body is subjected during use.

According to one form of embodiment of the present invention, the layer of glue is uniformly distributed between the first conical surface and the second conical surface so as to join the sleeve and the tubular element solidly.

According to the present invention, on the internal surface of the sleeve, in a position adjacent to the second conical surface, a circumferential discharge throat is made, for the layer of glue. In fact, during the gluing of the sleeve to the tubular element, the excess glue that is disposed on the conical surfaces is discharged into the discharge throat, and because the discharge throat is accessible from the outside, even after the sleeve and tubular element have been made solid with each other, it can be easily removed by the operator also to limit the problems of triggering a possible detachment of the sleeve and the tubular element.

According to one form of embodiment, the sleeve is provided on its internal surface with a threaded portion that allows to screw onto it a closing element, such as for example a head and a bottom of an actuator, or connection flanges for pipes.

According to a variant, at least one of either the first or second conical surface is provided with cavities inside which the layer of glue is disposed and which connects the sleeve and the tubular element.

According to another variant, the tubular body according to the present invention comprises a connection element glued onto the external surface of the sleeve and of the tubular element, which at least partly surrounds them. This entails a further increase in the resistance of the connection.

In other forms of embodiment, the tubular body can also comprise hydraulic sealing means which prevent the work fluid from reaching unsuitable zones, to prevent infiltrations which would compromise the correct functioning of the tubular body.

The present invention also concerns an actuator comprising a tubular body as described above and the corresponding method for manufacturing the tubular body.

DESCRIPTION OF THE DRAWINGS

These and other characteristics of the present invention will become apparent from the following description of one form of embodiment, given as a non- restrictive example with reference to the attached drawings wherein:

- fig. 1 is a lateral view of an articulated arm comprising a plurality of hydraulic linear actuators to which the present invention is applied;

- fig. 2 is a section view of a hydraulic actuator which comprises a tubular body made of composite material according to the present invention;

- fig. 3 is an enlarged detail of fig. 2;

- fig. 4 is a variant of fig. 2;

- fig. 5 is another variant of fig. 2;

- fig. 6 shows a variant of a tubular body according to the present invention.

To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one form of embodiment can conveniently be incorporated into other forms of embodiment without further clarifications.

DETAILED DESCRIPTION OF SOME FORMS OF EMBODIMENT

With reference to fig. 1, a plurality of actuators 11, in this case six hydraulic actuators, are installed on an articulated arm 12 to articulate with respect to each other a plurality of segments 14 provided to support a pipe for transferring concrete.

The articulated arm 12 is in turn mounted on a vehicle 15, for example a truck. The articulated arm 12 is suitable to assume at least a transport condition, in which the segments are substantially folded back over each other in order to reduce their overall bulk, and a work condition, in which the segments are disposed so as to reach a determinate work zone which may even be some tens of meters distant from the truck, in order to cast the concrete.

In this latter operating condition, the stresses to which the articulated arm 12 is subjected are due substantially to its own weight and the weight of the concrete that is transferred through the pipes, as well as to the dynamic pulsations caused by pumping the concrete and by the movement of the segments.

The actuators 11 comprise a cylindrical tubular body 10 (fig. 2) according to the present invention, inside which a plunger 17 and a rod 18 can slide, in a known manner.

The plunger 17 defines two separate work chambers 16 into each of which the work fluid is pumped or discharged.

The tubular body 10 comprises a tubular element 20 with a substantially cylindrical shape, hollow inside, and having a first end 23 and an opposite second end 24.

The tubular element 20 is made of composite material, consequently making the individual actuator 11 lighter overall. This advantage is even more accentuated if we consider the application of the tubular body 10 to the plurality of actuators 1 1 associated with the articulated arm 12. All in all it is possible to considerably reduce the weight of the articulated arm 12 and hence of the vehicle 15 on which it is mounted.

The composite material that the tubular element 20 is made of comprises fibers that are wound in a binding polymer resin. The fibers are chosen from a group comprising carbon fibers, glass fibers or aramidic fibers. The binding polymer resin is chosen from a group comprising poly amid resins, epoxy or polyester resins.

The first end 23 and the second end 24 of the tubular element 20 have tapers that narrow axially toward the outside. In particular, the first 23 and second end 24 each have a conical external surface 26 inclined by an angle a (fig. 3) with an amplitude comprised between 2° and 10°, preferably between 3° and 8°, even more preferably between 4° and 6°.

The tubular element 20 also comprises on its internal surface a cylindrical lining element 27 made of ceramic material, or metal material such as aluminum, or steel or polymer material such as for example resins. The lining element 27 therefore allows to define the circumferential surface of the two chambers 16 and the sliding of the plunger 17 without any problems of seizing up.

A sleeve 29 respectively 30 is associated both to the first end 23 and to the second end 24.

Each of the sleeves 29, 30 is substantially cylindrical in shape, hollow inside, and is provided with a conical internal surface 35 that opens axially toward the outside with a substantially mating angle of amplitude and with shape and size equal to those of the conical external surface 26 of the tubular element 20.

This allows, during the step when the tubular body 10 is assembled, to couple the sleeves 29, 30 and the tubular element 20 respectively with their conical external surface 26 and conical internal surface 35, thus maintaining, when coupling is complete, the respective external surfaces substantially flush with respect to each other.

Between the conical external surface 26 and the conical internal surface 35 a layer of glue 37 (fig. 3) is uniformly distributed, which provides to join the sleeves 29, 30 and the tubular element 20 together solidly.

The extension of the conical external surface 26 and the conical internal surface 35, and hence the amplitude of the angle a is determined as a function of the mechanical resistance to traction that the actuator 11 has to support during use.

The smaller the amplitude of the angle a, the greater the surface extension of the conical external surface 26 and the conical internal surface 35, and hence the greater the resistant surface of the connection.

The glue used to determine the coupling of the sleeves 29, 30 and the tubular element 20 is chosen from a group comprising glues of the bicomponent type and/or structural glues. In the internal part of both sleeves 29, 30, and immediately downstream of its conical internal surface 35, substantially in the transition zone between the cylindrical part and conical part of the sleeve 29, 30, a discharge throat 40 is made, which extends circumferentially.

During the step when the sleeves 29, 30 are glued to the tubular element 20, the glue is deposited on the respective conical surfaces 26, 35. The action of pressing the sleeves 29, 30 against the tubular element 20 allows to discharge the excess glue into the discharge throat 40 and, since the discharge throat 40 is accessible from the outside even after the coupling of the tubular element 20 and sleeves 29, 30 has been consolidated, the operator can easily proceed to remove it. Indeed, it is indispensable to remove the glue in this zone because it limits the triggering of a possible detachment of the sleeves 29, 30 and tubular element 20.

A threaded portion 39 is made in the internal surface of both sleeves 29, 30 and at the opposite end with respect to which there is the conical internal surface 35.

In the specific case of the application of the tubular body 10 to an actuator 11, respective closing lids 31, 32 are screwed into the threaded portion 39 of the sleeves 29, 30, so as to define respectively a head 21 and a bottom 22.

In proximity to the end which in use is disposed inside the chambers 16, both the lids 31, 32 are provided with a circumferential groove into which a first sealing element 44 is inserted.

The function of the first sealing element 44 is to prevent the pressurized work fluid inside the two chambers 16 from also affecting the discharge throat 40, causing an irreversible damage to the tubular element 20, due to shearing actions that would occur on the end fibers of the tubular element 20.

The discharge throat 40, during use, is therefore in a condition of atmospheric pressure.

The sleeve 29, associated with the head 21 of the tubular body 10, is provided with a through hole 45 made through its thickness.

The corresponding lid 3 1 of the head 21 is provided with a channel 46 to introduce the fluid, defined by a first hole 47 made radially in the lid 31 , a second hole 48 made in an axial direction, and a circumferential cavity 49 made on the external surface of the lid 31 and which is fluidically connected with the first hole 47, the second hole 48 and the chamber 16.

The circumferential cavity 49 is disposed during use substantially aligned with the through hole 45 so as to allow the work fluid, such as for example water or oil, to be introduced or expelled.

Second sealing elements 50 mounted on the external surface of the lid 31 at the sides of the circumferential cavity 49 are provided to prevent infiltrations of the work fluid.

An attachment element 52 is associated with the lid 32 of the bottom 22 and allows to connect the actuator 1 1 for example to the segments 14 of the articulated arm 12.

According to a variant (fig. 4), the sleeve 29 associated with the head 21 is provided on its conical internal surface 35 with a plurality of gluing cavities 57, inside which the layer of glue 37 is disposed, to join the sleeve 29 with the tubular element 20. In this way the glue stays inside the gluing cavities 57, without disposing itself on a large part of the conical surfaces 26, 35.

According to another variant (fig. 5), the connection between the sleeve 29 and the tubular element 20 is also defined by a connection element 59 which characterizes a bridge connection. The connection element 59 winds around the sleeve 29 and the tubular element 20 and a layer of glue is disposed between them, or gluing cavities 60 are provided, made in the sleeve 29, in which the glue is disposed. The connection element 59 therefore provides to reinforce the join between the sleeves 29, 30 and tubular element 20, increasing the safety thereof.

With reference to fig. 6, a tubular body is denoted in its entirety by the reference number 110 and is applied in this case to make a pipe, advantageously but not only for transferring concrete, and the type applicable on the articulated arm 12 (fig. 1).

The tubular body 1 10 is provided, similar to what was described with reference to figs. 2 and 3, with a first 23 and a second end 24 having a conical external surface 26 inclined by the angle a.

Two sleeves 129, 130 are associated, at the respective ends and using the gluing techniques as described above, with the tubular body 1 10, and are also provided with the conical internal surface 35 having shape and sizes and angle mating with those of the conical external surface 26 of the tubular body 110. The sleeves 129, 130 also have a respective circumferential throat 40, suitable to be accessible from the outside even after the solid connection of the sleeves 129 and 130 with the tubular element 20, so as to remove the excess glue after coupling.

The sleeves 129, 130 are provided, in their end which is most external during use, with a collar 160 which allows to connect with another tubular body 1 10 of the above type, for example by means of flanges.

It is quite obvious that other connection elements can be provided, such as flanges associable with the sleeves 129, 130, to allow connection with other tubular bodies 1 10.

The lining element 27 disposed in the internal surface of the tubular element 20 can be made of anti-wear material to limit the effects of abrasion due to the concrete that is made to pass through it.

Also for the particular application of the tubular body 110 to a pipe for transferring fluid, as well as obtaining a considerable reduction in the overall weight with respect to a similar pipe made of metal material, the manufacturing method is simplified and the coupling between tubular element 20 and sleeves 129, 130 is guaranteed.

The method for manufacturing the tubular body 10 according to the present invention provides at least a first step of making the tubular element 20, a second step of making the sleeves 29, 30 and a third step of reciprocal connection of the tubular element 20 and the sleeves 29, 30.

The first step of making the tubular element 20 provides to wind fibers, possibly pre- impregnated with the binding resin, onto the lining element 27.

The first step of making the tubular element 20 can be carried out using the filament winding technique or mandrel wrapping or tape winding.

During the first step the geometry of the tubular element 20 is therefore already defined, that is, the conical external surfaces 26 of the first 23 and second end 24 are defined.

The fibers are therefore immersed in a binding resin with vacuum techniques to obtain a homogeneous distribution thereof in the fibers. A subsequent operation is then provided to polymerize the resin to confer structural resistance on the tubular element 20.

The second step of making the sleeves 29, 30 provides at least a substep during which the conical internal surfaces 35 are defined in each of the sleeves 29, 30, with an angle of amplitude mating with the angle a of the conical external surfaces 26.

The third step provides to deposit the layer of glue on one or both the conical surfaces 26, 35 or, with reference to fig. 4, in the gluing cavities 57, to define the reciprocal connection between the sleeves 29, 30 and the tubular element 20. Finally, another step may provide to remove the excess glue from the circumferential throat 40 made so as to be accessible from the outside even after the solid coupling of the tubular element 20 with the respective sleeves 29, 30 or 129, 130.

It is clear that modifications and/or additions of parts may be made to the tubular body 10 and the method for manufacturing the tubular body 10 as described heretofore, without departing from the field and scope of the present invention.

It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art shall certainly be able to achieve many other equivalent forms of tubular body 10, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby. ,