EP4288226A1

EP4288226A1 - Manufacturing process of spherical components by hydroforming, hydroforming machine for carrying out the method and spherical component

Info

Publication number: EP4288226A1
Application number: EP22700686.3A
Authority: EP
Inventors: Pietro Marino; Andrea MORVILLE
Original assignee: Unifer Srl
Current assignee: Unifer Srl
Priority date: 2021-02-02
Filing date: 2022-01-21
Publication date: 2023-12-13
Also published as: WO2022167888A1; IT202100002219A1

Abstract

A manufacturing process of components (12, 13, 13') with spherical and hollow shape and defining at least one radially inner recess (12b, 13b) with respect to an outer surface (12a, 13a) of said spherical shape is described; the process comprising the steps of i) arranging an initial component (10) inside a first hydroforming mould (3); ii) performing a hydroforming operation of the initial component (10) inside the first mould (3) in order to obtain a first intermediate component (11); iii) performing a work-hardening reduction heat treatment of the first intermediate component (11) obtained in step ii); iv) arranging the first intermediate component (11) heat-treated in step iii) inside a second hydroforming mould (4); v) performing a further hydroforming process of the first intermediate component (11) inside the second mould (4) in order to obtain the spherical shaped component (12, 13, 13') provided with the recess (12b, 13b); wherein the maximum value of pressure of said hydraulic fluid during said further hydroforming operation is greater than the maximum value of pressure of said hydraulic fluid during said hydroforming process.

Description

MANUFACTURING PROCESS OF SPHERICAL COMPONENTS BY HYDROFORMING, HYDROFORMING MACHINE FOR CARRYING OUT THE METHOD AND SPHERICAL COMPONENT

CROSS-REFERENCE TO RELATED APPLICATIONS

5 This Patent Application claims priority from Italian Patent Application No . 102021000002219 filed on February 2 , 2021 , the entire disclosure of which is incorporated herein by reference

TECHNICAL SECTOR

10 The present invention relates to a process for manufacturing elements with a spherical and hollow shape provided with at least one radially inner recess with respect to the outer surface of said spherical shape . In particular, the invention relates to the production of spherical shutters

15 for taps or ball valves having a recess capable of being coupled to a control member of the spherical shutters themselves .

In addition, the present invention relates to a spherical component for use as a shutter .

20 BACKGROUND OF THE INVENTION

Production processes are known for manufacturing spherically shaped shutters provided with one or more recesses with respect to the outer surface of the spherical shape . These processes involve the machining by chip removal

25 of a semi- finished metal product , e . g . made of brass or stainless steel .

However, the Applicant has repeatedly observed the collapse of the shutters obtained by such known processes .

From the analyses carried out , it has been deduced that

30 the origin of these collapses is to be found primarily in the thermal stresses acting on the shutter during its use and in the residual stresses due to machining by chip removal .

In particular, it was observed that the notch ef fect due to the recess profoundly alters the tensional state of the shutter, resulting in overstressing of the component in proximity to such recess .

There is therefore a need for a manufacturing process that enables the production of shutters with mechanical strength characteristics that prevent them from collapsing during use .

In addition, it should be noted that spherical shutters obtained by the known chip removal machining processes are made from solid material and therefore involve the loss of a large amount of material in the form of chips and the waste of a large amount of energy .

Therefore , a need is also felt for a manufacturing process that enables the waste of material and energy to be reduced .

US-A-5097689 discloses a process for producing hollow one-piece elements having a highly curved lateral wall from metal , in particular copper or copper alloy, pipes . A cylindrical pipe is widened via permanent deformation between two appropriately shaped dies , by simultaneously applying hydraulic pressure directly inside the pipe and axial pressure on the opposite ends of the pipe ; the required finished shape being achieved in successive stages , by inserting inside the dies molds having a predetermined profile and of gradually increasing si ze .

JP-A-2005081432 discloses a valve housing manufacturing method and CN-C- 100574969 discloses a ball valve core hydraulic expansion method . The aim of the present invention is to meet the above requirements .

SUMMARY OF THE INVENTION

The aforementioned aim is achieved by a manufacturing process as claimed in the accompanying claims .

The present invention also relates to a hydroforming machine , a manufacturing system for carrying out said manufacturing process and a spherical component .

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment is described below for a better understanding of the present invention, provided by way of non-limiting example with reference to the accompanying drawings , wherein :

• figure 1 schematically illustrates a machine for performing the hydroforming steps of the manufacturing process according to the present invention;

• figures 2 to 6 il lustrate some of the steps of the manufacturing process according to the present invention;

• figure 7 illustrates the starting component of the manufacturing process according to the present invention;

• figure 8 illustrates a component obtained following a first hydroforming step of the component in figure 7 ;

• figure 9 illustrates a component obtained following a second hydroforming step of the component in figure 8 ;

• figure 10 illustrates a component obtained by the manufacturing process according to the present invention; • figure 11 shows a detail of the machine of figure 1 during the second hydroforming step of the manufacturing process according to the present invention; and

• figures 12 and 13 show an example of a ball valve in two respective operating positions and comprising the component in figure 10 ;

• figures 14 , 15 and 16 illustrate respective further steps of the manufacturing process according to a first embodiment of the present invention;

• figures 17 , 18 and 19 illustrate respective further steps of the manufacturing process according to a second embodiment of the present invention ;

• figure 20 shows a longitudinal cross section of a component obtained following the steps illustrated in figures 14 , 15 and 16 or 17 , 18 and 19 ; and

• figures 21 and 22 are perspective views of alternative forms of the component of figure 20 . DETAILED DESCRIPTION OF THE INVENTION

Figure 1 illustrates a hydroforming machine 1 for performing the process of manufacturing components 13 , 13 ' having a spherical outer surface portion 13a and at least one recess 13b at said spherical outer surface portion 13a according to the present invention . These components 13 , 13 ' are used, for example , as shutters for taps or ball valves and are known in the industry as "balls" . In particular, the recess 13b is adapted to be coupled to a control member for manual or automatic actuation of the tap or ball valve ( as illustrated in figures 12 and 13 ) .

The hydroforming machine 1 comprises a press 2 inside which a mould 3 , 4 is housed, a hydraulic system 5 for supplying a pressuri zed hydraulic fluid ( e . g . water ) inside the mould 3 , 4 and a control unit 6 configured to control the press 2 and the hydraulic system 5 .

In particular, the press 2 is provided with a f ixed portion 2a and a movable portion 2b to which a first hal fmould 3a, 4a and a second hal f-mould 3b, 4b of the mould 3 , 4 are fixed, respectively . Further, the press 2 is movable between an open position ( illustrated in figure 1 ) , wherein the fixed portion 2a and the movable portion 2b are spaced apart from each other along a direction Z , and a closed position, wherein the fixed portion 2a and the movable portion 2b are close to each other along a direction Z and define a cavity 7 . In particular, the fixed and movable portions 2a, 2b exert on the mould 3 , 4 a clamping force directed along the Z direction and/or along a Y direction, transverse to the Z direction . Such clamping force is proportional to the pressure of the hydraulic fluid supplied by the hydraulic system 5 .

Please note that the representation of the hydraulic system 5 and the control unit 6 in figure 1 should be understood as purely schematic . Therefore , the hydraulic system 5 and the control unit 6 can be placed at di f ferent heights or at the same height as the press 2 along the Z direction .

The press 2 alternatively houses a first mould 3 for performing a first hydroforming step (which may be intended as a roughing hydroforming step ) and a second mould 4 for performing a second hydroforming step (which may be intended as a finishing hydroforming step ) . In detail , in order to operate with the first mould 3 or the second mould 4 , the press 2 may be equipped with di f ferent implements . Alternatively, the first mould 3 and the second mould 4 can be mounted on di f ferent presses 2 .

In addition, the first mould 3 and the second mould 4 may include one or more removable elements . In this way, the worn profiles of the moulds 3 , 4 can be restored by replacing only these removable elements and not the moulds 3 , 4 as a whole .

Essentially, following the first hydroforming step of an initial component 10 a first intermediate component 11 is obtained and following the second hydroforming step of the first intermediate component 11 a second intermediate component 12 is obtained . In other words , the first intermediate component 11 is obtained by plastic deformation starting from the initial component 10 and the second intermediate component 12 is obtained by plastic deformation starting from the first intermediate component 11 .

The first mould 3 is adapted to house the initial component 10 and its cavity 7 has a shape corresponding to the first intermediate component 11 ; the second mould 4 is adapted to house the first intermediate component 11 obtained at the end of the first hydroforming step of the initial component 10 and its cavity 7 has a shape corresponding to the second intermediate component 12 .

In particular, the initial component 10 and the first intermediate component 11 are each provided with a respective internal cavity into which the pressuri zed hydraulic fluid is inj ected during the first and second hydroforming steps , respectively .

Furthermore , the workpiece 10 , 11 undergoes a workhardening phenomenon due to the plastic deformation obtained during the first and second hydroforming steps , respectively .

In the embodiment illustrated, the initial component 10 is a cylindrical tubular element having an axis A ( figures 2 , 3 and 7 ) . In particular, the initial component 10 is a tube obtained by die forging starting from a piece of bar stock .

On the other hand, the first intermediate component 11 comprises two curved portions I la and a cylindrical portion 11b having axis A as axis of the cylindrical portion, which is interposed between the two curved portions I la along the axis A ( figure 8 ) . The intermediate component 11 also comprises two portions of cylindrical tubular shape 11c having axis A as axis of the cylindrical tubular shape , which are arranged at two opposite axial ends of the curved portions I la along the axis A.

In particular, the two curved portions I la define a concave curvature with respect to the axis A. More preferably and as illustrated in figure 8 , each curved portion I la is equal to the other and symmetrical thereto with respect to the cylindrical portion 11b . Further, as illustrated, each curved portion I la defines a radially increasing profile with respect to the axis A between a minimum extension at the cylindrical tubular shape 11c and a maximum extension at the cylindrical portion 11b .

The first intermediate component 11 undergoes heat treatment to reduce the work-hardening obtained at the end of the first hydroforming step, before being placed in the second mould 4 .

For example , the heat treatment may be a solubili zation treatment , comprising a step of heating and keeping the first intermediate component 11 at a high temperature (preferably around 1042 ° C ) and in a controlled atmosphere ( e . g . hydrogen) and a subsequent cooling step in free air .

In particular, it is possible to define a manufacturing system for carrying out the process according to the present invention comprising the hydroforming machine 1 and a device for carrying out said heat treatment . Such a device is known and not illustrated and can be , for example , a conveyor belt oven .

Further, the second intermediate component 12 comprises a portion 12a having a spherical or substantially spherical surface , a recess 12b and two cylindrical tubular shaped portions 12c having an axis A as axis of the cylindrical tubular shaped portions arranged at two opposite axial ends of the spherical portion 12a along the axis A ( figure 9 ) .

The recess 12b extends radially from the outer surface of the spherical portion 12a towards axis A. Advantageously, the recess 12b has a slotted shape , i . e . it is axially delimited by a pair of walls along the axis A and is delimited along a direction, which is transversal to axis A. In particular, this direction is parallel to the Z direction of the mould 4 .

More preferably and as illustrated, the inner radial surface of the recess 12b is curved, such that the extension of the recess 12b itsel f along said transverse direction varies from a maximum at the central portion of the recess 12b to a minimum, in particular equal to a null extension, at the transverse ends of the recess 12b . In detail , such internal radial surface is circular in a plane orthogonal to axis A.

It is also possible to define an inner radial surface 12d of second intermediate component 12 . In detail , inner radial surface 12d is the radially innermost surface of second intermediate component 12 . In further detail , inner radial surface 12d and the outer surface of the spherical portion 12a are radially spaced by the thickness of second intermediate component 12 .

It is important to stress that the inner radial surface of recess 12b is radially spaced from the inner radial surface 12d . In detail , inner radial surface 12d and the inner radial surface of the recess 12b are radially spaced by the thickness of second intermediate component 12 .

Furthermore , inner radial surface 12d defines a radially inner volume 23 of second intermediate component 12 .

Since , during the first and second hydroforming steps , the workpiece 10 , 11 expands radially with respect to the axis A and contracts axially, the cylindrical tubular shaped portions 11c have a greater extension than the cylindrical tubular shaped portions 12c along the axis A. In contrast , the radial extension of the cylindrical tubular shaped portions 11c and 12c with respect to the axis A is identical or substantially identical to the radial extension of the initial component 10 .

Starting from the second intermediate component 12 it is possible to obtain the said component 13 , hereinafter referred to as the finished component 13 . In particular, the finished component 13 is obtained from the second intermediate component 12 following machining by chip removal .

The finished component 13 comprises the spherical or substantially spherical outer surface portion 13a and the recess 13b, which extends from the outer surface of the spherical portion 13a radially with respect to the axis A ( figure 10 ) . The finished component 13 further comprises a radially inner portion 13d, which is radially inner with respect to the outer surface 13a and recess 13b relative to the axis A ( figure 10 ) .

In particular, the spherical portion 13a , recess 13b and radially inner portion 13d are identical or substantially identical respectively to the spherical portion 12a, the recess 12b and radially inner portion 12d of the second intermediate component 12 .

The finished component 13 di f fers from the second intermediate component 12 in that it does not comprise cylindrical tubular portions ( figure 10 ) .

Alternatively, the finished component 13 could comprise two cylindrical tubular portions placed at two opposite axial ends of the spherical portion 13a with respect to the axis A. In particular, such cylindrical tubular portions of the finished component 13 could have an extension along the axis A smaller than the extension of the cylindrical tubular portions 12c and equal to the design length .

Furthermore , the second intermediate component 12 could be designed in such a way that the cylindrical tubular portions 12c have the design dimensions envisaged for the cylindrical tubular portions of the finished component 13 . In this case the second intermediate component 12 would coincide with the finished component 13 .

Preferably, the finished component 13 also undergoes a polishing treatment in order to improve its outer surface quality .

The initial component 10 , the finished component 13 and the intermediate components 11 and 12 are made of metal material, e.g. stainless steel.

The hydroforming machine 1 further comprises two punches 8, 9 movable along an X direction transverse to the Y and Z directions and through which pressurized hydraulic fluid is injected into the cavities 7 of the moulds 3 and 4. The punches 8, 9 are also used to clamp the workpiece 10, 11 inside the mould 3, 4 along the X direction, exerting a clamping force on it parallel to the X direction. In the embodiment shown, the punches 8 and 9 are cylindrical in shape and are adapted to engage the workpiece 10, 11 coaxially with the axis A (figures 3 to 6) .

In particular, the punches 8 and 9 are adapted to engage the initial component 10 each at a respective axial end of the initial component 10 along the axis A (figure 3) ; furthermore, the punches 8 and 9 are suitable to engage the first intermediate component 11 each at a respective cylindrical tubular portion 11c (figures 4 and 5) .

Moreover, the punches 8, 9 are adapted to push the workpiece 10, 11 at the respective axial ends thereof, to compensate for the fact that workpiece 10, 11 expands radially and contracts axially during the first and second hydroforming steps.

Furthermore, the displacement of punches 8, 9 along direction X is controlled on the basis of the value of pressure of the hydraulic fluid. In detail, a variation of the pressure of the hydraulic fluid is correlated to a displacement of punches 8, 9 along direction X according to a specific law of motion. In further detail, the motion of punches 8, 9 is started when the pressure of the hydraulic fluid is greater than a pressure threshold.

Preferably, a sealing element 15 (illustrated in figures 2 to 6 ) is interposed between each punch 8 , 9 and the workpiece 10 , 11 to prevent leakage of pressuri zed hydraulic fluid during the first and second hydroforming steps .

The second mould 4 further comprises a movable element 14 , which enables the recess 12b to be formed by plastic deformation during the second hydroforming step ( figures 5 , 6 and 11 ) . In detail , the movable element 14 has a shape corresponding to the recess 12b and is movable radially with respect to the axis A.

Alternatively, the second mould 4 could be shaped to allow the recess 12b to be made during the second hydroforming step even without the movable element 14 . The manufacturing process according to the present invention is described below .

First of all , the initial component 10 is positioned in the first mould 3 mounted on the hydroforming machine 1 in such a way that the axis A is parallel to the X direction ( figure 2 ) . Subsequently, the control unit 6 brings the hydroforming machine 1 into the closed position . In this condition, the fixed portion 2a and the movable portion 2b are close to each other along the Z direction and the first and second hal f-moulds 3a, 3b define the cavity 7 .

The punches 8 , 9 are then moved in the direction X so as to approach the initial component 10 placed inside the first mould 3 . Each punch 8 , 9 then engages coaxially with the axis A at a respective axial end of the initial component 10 ( figure 3 ) .

In particular, in this condition, the initial component

10 is completely clamped along the Z and Y directions between the first and the second hal f-mould 3a, 3b thanks to the clamping force exerted by the fixed and movable parts 2a, 2b of the machine 1 and between the two punches 8 , 9 along the X direction thanks to the clamping force exerted by the punches themselves .

At this point , the hydraulic system 5 starts to inj ect pressuri zed hydraulic fluid into the internal cavity of the initial component 10 placed inside the first mould 3 , in order to carry out the first hydroforming step . In detail , the pressure of the inj ected pressuri zed hydraulic fluid is increased from a minimum value ( e . g . a null value ) to a maximum value according to a ramp .

The pressure exerted by the hydraulic fluid against the walls of the internal cavity of the initial component 10 causes the plastic deformation thereof . As a result , the initial component 10 expands radially with respect to the axis A, until it corresponds to the shape of the internal walls of the cavity 7 of the mould 3 ( figure 4 ) .

At the same time , as the initial component 10 expands radially, its extension parallel to the axis A is reduced . As the initial component 10 contracts along the axi s A, the punches 8 , 9 move along the axis A towards each other, following the contraction of the initial component 10 and continuing to exert the clamping force ( figure 4 ) .

When the punches 8 , 9 finish their stroke parallel to the X direction, the first hydroforming is complete and the first intermediate component 11 is obtained ( figure 4 ) .

At this point , the supply of pressuri zed hydraulic fluid is interrupted, the hydroforming machine 1 is moved to the open position and the first intermediate component 11 is removed from the first mould 3 .

The first intermediate component 11 thus obtained is then subj ected to thermal solubili zation treatment , during which it is heated and maintained at a high temperature in a controlled atmosphere and then cooled in free air .

At the end of the solubili zation treatment , the first intermediate component 11 undergoes the second hydroforming step . Similarly to the first hydro forming step, the initial component 10 is positioned in the second mould 4 in such a way that the axis A is parallel to the X direction . Subsequently, the control unit 6 brings the hydroforming machine 1 into the closed position .

The punches 8 , 9 are then moved parallel to the X direction, so as to approach the f irst intermediate component 11 placed inside the second mould 4 . Each punch 8 , 9 is then engaged coaxially to the axis A at the respective cylindrical tubular portion 11c of the first intermediate component 11 ( figure 5 ) . Therefore , in this condition, the first intermediate component 11 is completely clamped in the Z and Y directions between the first and second hal f-moulds 4a, 4b and between the two punches 8 , 9 in the X direction due to the clamping force exerted by the punches 8 , 9 themselves .

At this point , the hydraulic system 5 starts to inj ect pressuri zed hydraulic fluid into the internal cavity of the first intermediate component 11 placed inside the second mould 4 .

It is to be noted that during the second hydroforming step the hydraulic fluid is at a higher pressure than during the first hydroforming step . In particular, the maximum value of the hydraulic fluid during the second hydroforming step is greater than the maximum value of the hydraulic fluid during the first hydroforming step . For example , the maximum pressure value of the hydraulic fluid during the second hydroforming step may be a multiple (preferably with a multiplication factor of 5 ) of the maximum pressure value of the hydraulic fluid during the first hydroforming step .

In the embodiment shown, the maximum pressure value of the hydraulic fluid during the f irst hydroforming step is approx . 500 bar and the maximum pressure value of the hydraulic fluid during the second hydroforming is approx . 2500 bar .

In detail , since the maximum pressure value of the hydraulic fluid during the second hydroforming step is greater than the maximum value of the hydraulic fluid during the first hydroforming step, the geometrical details of second intermediate component 12 - and in particular, recess 12b - can be obtained with great accuracy .

The pressure exerted by the hydraulic fluid against the walls of the internal cavity of the first intermediate component 11 causes the plastic deformation thereof . Consequently, the first intermediate component 11 expands radially with respect to the axis A and contracts parallel to the axis A, until it corresponds to the shape of the internal walls of the cavity 7 of the mould 4 .

In addition, the punches 8 , 9 move along the axi s A, supporting this contraction of the first intermediate component 11 .

Moreover, the law of motion that correlates displacement of punches 8 , 9 along direction X with the value of pressure of the hydraulic fluid in the first hydroforming step may be di f ferent from the law of motion that correlates displacement of punches 8 , 9 along direction X with the value of pressure of the hydraulic fluid in the second hydroforming step . In addition, during the second hydroforming step, the movable element 14 moves radially with respect to the axis A, in order to create the recess 12b .

Once the plastic deformation of the first intermediate component 11 has been completed, the supply of pressurized hydraulic fluid is interrupted, the hydroforming machine 1 is brought into the open position and the second intermediate component 12 thus obtained is removed from the second mould 4 .

The second intermediate component 12 is substantially identical to the finished component 13 , except that the finished component 13 does not comprise cylindrical tubular portions placed at two axially opposite ends of the spherical portion 13a, or that it comprises cylindrical tubular portions having a length shorter than the length of the cylindrical tubular portions 12c along the axis A.

The cylindrical tubular portions 12c are then subj ected to a trimming operation, which allows cylindrical tubular portions to be obtained of the desired length, poss ibly zero .

The finished component 13 can then be subj ected to a polishing treatment in order to improve the surface quality thereof .

It should be noted that through the manufacturing process described, it is possible to obtain a component 13 of various si zes , depending on the si ze of the valve or tap in which it is to operate and the particular application .

The manufacturing process according to the present invention may comprise a further step of adding a portion of material 20 , which comprises a through cylindrical hole 21 , to finished component 13 on the side of radially inner surface 13d . The resulting component 13' is suitable be used as a shutter and comprises (figure 20) :

- the finished component 13, the spherical portion 13a of which comprises the radially outermost surface of component 13' with respect to longitudinal axis A; and

- the portion 20, which is radially inner relative to finished component 13.

In addition, through cylindrical hole 21 defines an axis B parallel to longitudinal axis A (figure 20) .

Therefore, finished component 13 and portion 20 respectively constitute a sleeve portion and an inner portion of component 13' . In addition, in other words, component 13' is a concave spherical component having a cylindrical inner volume .

In detail, portion 20 is fixed to finished component 13. Therefore, portion 20 cannot move relative to finished component 13. Preferably, portion 20 is directly in contact with radially inner surface 13d.

Furthermore, cylindrical hole 21 has a circular shape in a plane orthogonal to axis B (figures 21 and 22) . According to not-shown variants, cylindrical hole 21 may have a polygonal shape in a plane orthogonal to axis B. By way of example, cylindrical hole 21 may have a rectangular shape, an oval shape, a triangular shape or a hexagonal shape .

More specifically, cylindrical hole 21 is coaxial to longitudinal axis A. In other words, axis B and longitudinal axis A coincide.

Preferably, spherical portion 13a and portion 20 have respective extensions el, e2 parallel to longitudinal axis A that are equal or substantially equal to each other. Therefore , each axial end of spherical portion 13a is aligned to a respective axial end of portion 20 ( figure 20 ) .

Furthermore , the material of portion 20 may be a metal or a polymer . In detail , the material of portion 20 may be the same metal as finished component 13 .

With reference to the embodiment shown in figures 14 to 16 , the addition of the portion of material 20 to finished component 13 and the manufacturing of through hole 21 is obtained by introducing a material in radially inner volume 23 ( figure 14 ) and by subsequently forming through hole 21 by removing part of the material introduced in radially inner volume 23 ( figure 15 ) .

Preferably, the material is introduced in radially inner volume 23 so as to completely fill radially inner volume 23 .

In particular, the material is introduced in radially inner volume 23 in a liquid or pasty state . Therefore , the material may be inj ected or poured into radially inner volume 23 . In addition, through hole 21 may be obtained by drilling, milling or other technologies known in the art , such as electrical discharge machining (EDM) or water j et cutting .

As shown in the exemplary embodiment shown in figures 15 and 16 , a drilling tool 24 may be moved along axis A while spinning about an axis of its own so as to drill through hole 21 at portion 20 . Once the through hole 21 is formed, drilling tool 24 is disengaged from through hole 21 ( figure 16 ) . Nevertheless , more than one drilling tools may be used or more than one drilling steps may be performed to drill through hole 21 , as is well known to a person skilled in the art .

With reference to the embodiment shown in figures 17 to 19 , the addition of the portion of material 20 to finished component 13 is obtained by engaging radially inner volume 23 with a core 22 having a shape substantially corresponding to the shape of cylindrical through hole 21 and by subsequently introducing a material in radially inner volume 23 while core 22 is kept engaged in radially inner volume 23 . Subsequently, core 22 is disengaged from radial ly inner volume 23 , thereby forming through hole 21 .

In detail , core 22 - which is shown as sectioned in figures 17 , 18 and 19 - is an elongated body having a cylindrical external surface 25 . In further detail , cylindrical external surface 25 ( at least the portion thereof engaging with inner volume 23 ) has a shape and dimensions corresponding or substantially corresponding to the shape of through hole 21 .

In addition, the material may be inj ected or poured into radially inner volume 23 so as to fill radially inner volume 23 . In further detail , the material is introduced in a portion of radially inner volume 23 defined by radially inner portion 13d and cylindrical external surface 25 .

According to the preferred embodiment shown in figures 17 to 19 , core 22 is also an inj ection tool adapted to inj ect the material into radially inner volume 23 . In detail , core 22 comprises one or more inj ection openings 22a, through which the material is inj ected into radially inner volume 23 , and a plurality of channels 22b, which fluidly connect a source of the material to be inj ected to inj ection openings 22a . In further detail , inj ection openings 22a are formed at cylindrical external surface 25 .

Preferably, during the inj ection, an axial end 22c of core 22 axially protrudes with respect to spherical portion 13a ( figure 18 ) .

In addition, during the inj ection of the material of portion 20 , finished component 13 axially abuts against an abutment element 26 . In the embodiment shown in figures 17 to 19 , abutment element 26 is a cylindrical element fitted about core 22 and abutting against an axial end of spherical portion 13a arranged on the side of axial end 22 c ( figure 18 ) . Alternatively or in addition, during the inj ection of the material of portion 20 , finished component 13 may be placed in a mould .

In other words , the portion 20 obtained following the manufacturing steps illustrated in figures 14 , 15 , 16 or 17 , 18 , 19 is overmoulded on finished component 13 on the side of radially inner portion 13d .

The manufacturing steps illustrated in figures 14 , 15 , 15 or 17 , 18 , 19 may be also applied to second intermediate component 12 . The resulting component is identical to component 13 ' , except that the resulting component comprises cylindrical tubular portions , like second intermediate component 12 .

Alternatively or in addition to what stated above , the polishing treatment may be carried out after the step of adding portion of material 20 to finished component 13 is completed .

In use , second intermediate component 12 , finished component 13 or component 13 ' is arranged in a valve body to be used as a shutter .

In the exemplary embodiment shown in figures 12 and 13 , the valve body comprises an inlet and an outlet and component 12 , 13 or 13 ' may be rotated between a first position, in which it allows the passage of a fluid from the inlet to the outlet ( figure 12 ) , and a second position, in which it denies the passage of the fluid from the inlet to the outlet ( figure 13 ) .

In detail , when component 12 , 13 or 13 ' is in the first position, the fluid crosses the valve through the radially inner volume 23 .

In addition, the rotation of component 12 , 13 or 13 ' between the first and the second position is obtained by means of the control member coupled to recess 12b, 13b .

From the above , the advantages of the invention are clear .

Since the finished component 13 , comprising the recess 13b on its external spherical surface portion 13a, is obtained by means of two separate hydroforming steps , the mechanical behaviour of the component 13 is improved with respect to that of identically shaped components obtained by the known processes discussed in the introductory part of the present description .

Indeed, since hydroforming is a cold plastic deformation process , it has been observed that the particular arrangement of the crystalline grains obtained makes it possible to contain the notching ef fect due to the 13b recess . Furthermore, the finished component 13 obtained by the claimed manufacturing proces s is not subj ect to the residual stresses acting on the components obtained by known processes . Indeed, the recess 13b is also obtained by plastic deformation and not by chip removal .

Consequently, despite the thermal stresses af fecting the finished component 13 during the process , the risk of such stresses causing the collapse of the finished component 13 is signi ficantly reduced . In addition, the claimed manufacturing process signi ficantly reduces material waste , as the finished component 13 is obtained by plastic deformation by hydroforming and chip removal is limited to the trimming operation only .

The claimed manufacturing process has also been observed to require a lower amount of energy to be carried out with respect to the machining processes discussed in the introductory portion of the present description . In detail , the amount of energy necessary to manufacture the component by means of the claimed manufacturing process has been observed to be 30 % lower than the amount of energy necessary to manufacture the component by a chip removal machining process . Furthermore , since the claimed manufacturing process includes a solubili zation treatment after the first hydroforming step and before the second hydroforming step, the material of the workpiece 10 , 11 may undergo even very high elongation, around 50% and more . This makes it possible to obtain spherical or substantially spherical components with a high level of precision . In fact , the solubi li zation treatment allows the work-hardening state of the first intermediate component 11 at the end of the first hydroforming step to be eliminated or at least reduced and the residual tensions to be relaxed, so as to restore its machinability before the second hydroforming step . The solubili zation treatment also maximises the oxidation and corrosion resistance , which is of outmost importance for mechanical components such as the finished component 13 , which is used as a shutter in taps and ball valves .

Since , at the same time , at the end of the second hydroforming step the second intermediate component 12 is work-hardened and the finished component 13 does not undergo any further heat treatment prior to installation, the mechanical strength of the finished component 13 is maximised .

Furthermore , component 13 ' comprises portion 20 having cylindrical through hole 21 that is coaxial to axis A. This signi ficantly improves the conditions of the flow of the fluid through the valve in which component 13 ' is arranged as a shutter .

In particular, the shape and dimensions of through hole 21 may be chosen to be equal or substantially equal to the shape and dimensions of the ducts of a fluid circuit at which the valve is arranged . By way of example , i f the ducts have a circular cross section and a speci fic diameter, the valve may be chosen to comprise a component 13 ' having a through hole 21 with a circular cross section and the same diameter as the ducts . The conditions of the flow crossing the valve are considerably improved because , when the valve allows the passage of the fluid from the inlet to the outlet , the fluid does not experience abrupt changes in cross section . This allows the turbulence in the flow crossing the valve and the pressure drops to be limited .

Finally, it is clear that modi fications and variations can be made to the process , the hydroforming machine , the manufacturing system and the spherical component according to the present invention which, however, do not depart from the scope of protection defined by the claims .

In particular, more than one first hydroforming step and/or more than one second hydroforming step may be envisaged, carried out by means of as many moulds 3 , 4 . These multiple hydroforming steps could be interspersed with as many heat treatments to reduce the work-hardening of the workpiece 10 , 11 .

Furthermore , the step of adding portion of material 20 to finished component 13 might be carried out by sintering powders of the material , or by additive manufacturing .

Moreover, component 13 ' may be obtained by adding portion 20 to a finished component 13 that is obtained by means of a manufacturing process other than hydroforming . In detail , finished component 13 may be made of a material other than metal . In further detail , finished component 13 may be made of a polymer .

Claims

1.- Manufacturing process of spherical components (12, 13, 13' ) for use as shutters having hollow shape and defining at least one radially inner recess (12b, 13b) with respect to an outer surface (12a, 13a) of said spherical shape; said process comprising the steps of: i) arranging an initial component (10) inside a first hydroforming mould (3) ; ii) performing a hydroforming process of said initial component (10) inside said first mould (3) in order to obtain a first intermediate component (11) ; iii) performing a work-hardening reduction heat treatment of said first intermediate component (11) obtained in step ii ) ; iv) arranging the first intermediate component (11) heat-treated in step iii) inside a second hydroforming mould (4) ; v) performing a further hydroforming process of said first intermediate component (11) inside said second mould (4) in order to obtain said component (12, 13, 13' ) with said recess (12b, 13b) ; wherein said step ii) comprises the step vi) of injecting a pressurized hydraulic fluid in a cavity of said initial component (10) in order to cause plastic deformation thereof; said step v) comprising the step vii) of injecting said pressurized hydraulic fluid in a cavity of said first intermediate component (11) in order to cause plastic deformation thereof; the maximum value of pressure of said hydraulic fluid during said step vii) being greater than the maximum value

25 of pressure of said hydraulic fluid during said step vi) .

2.- Manufacturing process according to claim 1, wherein said step v) comprises the step viii) of moving a movable element (14) of said second mould (4) radially with respect to the outer surface of said first intermediate component (11) , in order to obtain said recess (12b, 13b) .

3.- Manufacturing process according to claim 1 or 2, wherein said initial component (10) is a cylindrical tubular element defining a longitudinal axis (A) ; and said first intermediate component (11) obtained from said initial component (10) through said steps i) and ii) comprises two curved portions (Ila) and a first cylindrical portion (11b) having said longitudinal axis (A) and interposed between said two curved portions (Ila) along said longitudinal axis (A) .

4.- Manufacturing process according to any one of the foregoing claims, wherein the heat treatment carried out in said step iii) is a solubilisation heat treatment.

5.- Manufacturing process according to any one of the foregoing claims comprising a further step ix) of trimming the axial ends (12c) of a second intermediate component (12) obtained in said step v) in order to obtain said component (13, 13' ) ; said second intermediate component (12) defining a longitudinal axis (A) with respect to which said axial ends (12c) are defined.

6.- Manufacturing process according to any one of the foregoing claims, further comprising a step x) of polishing said component (13, 13' ) .

7.- Manufacturing process according to any one of the foregoing claims, further comprising a step xi) of adding a portion of material (20) defining a cylindrical through hole (21) on the side of an inner surface (12d, 13d) of said spherical shape, which is radially inner relative to said external surface (12a, 13a) .

8.- Manufacturing process according to claim 7, wherein said step xi) comprises the steps of: xii) introducing a material in a radially inner volume (23) defined by said inner surface (12d, 13d) ; and xiii) making said cylindrical through hole (21) by removing part of said material from said portion of material (20) .

9.- Manufacturing process according to claim 7, wherein said step xi) comprises the steps of: xiv) engaging a radially inner volume (23) defined by said inner surface (12d, 13d) with a core (22) having a shape substantially corresponding to the shape of said cylindrical through hole (21) ; xv) introducing a material in said radially inner volume (23) while said core (22) is engaged in said radially inner volume (23) ; and xvi) disengaging said core (22) from said radially inner volume (23) .

10.- A spherical component (13' ) for use as a shutter, comprising :

- a sleeve portion (13) defining a longitudinal axis (A) and comprising a spherical surface (12a, 13a) , which is the radially outermost surface of said spherical component ( 13 ’ ) with respect to said longitudinal axis (A) ; said sleeve portion (13) being made of a first material; and an inner portion (20) , which is radially inner relative to said sleeve portion (13) with respect to said longitudinal axis (A) ; said inner portion (20) being made of a second material; wherein said inner portion (20) comprises a through cylindrical hole (21) , which defines an axis (B) parallel to said longitudinal axis (A) .

11.- The spherical component according to claim 10, wherein said spherical surface (12a, 13a) has a first extension (el) parallel to said longitudinal axis (A) and said inner portion (20) has a second extension (e2) parallel to said longitudinal axis (A) that is equal or substantially equal to said first extension (el) .

12.- The spherical component according to claim 10 or 11, wherein said first material is a metal and said second material is a polymer.

13.- The spherical component according to claim 10 or 11, wherein said first material is a first metal and said second material is a second metal; said first and second metals being equal to each other or different from each other .

14.- The spherical component according to any one of claims 10 to 13, wherein said through cylindrical hole (21) has a circular or polygonal shape in a plane orthogonal to said axis (B) .

15.- The spherical component according to any one of claims 10 to 14, wherein said through cylindrical hole (21) is coaxial with said longitudinal axis (A) .

16.- Hydroforming machine for carrying out the hydroforming steps of the manufacturing process according to any one of claims 1 to 9; said hydroforming machine (1) comprising :

- a press (2) adapted to alternately housing a first hydroforming mould (3) and a second hydroforming mould (4) ;

28 - a hydraulic system (5) adapted to supply a pressurized fluid inside said first mould (3) and said second mould (4) ;

- a control unit (6) configured to control said press (2) and said hydraulic system (5) .

17.- Manufacturing system for carrying out the manufacturing process according to any one of claims 1 to 9; said system comprising:

- a hydroforming machine (1) according to claim 16; and

- a device for carrying out a work-hardening reduction heat treatment according to said step iii) .

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