WO2004033143A1

WO2004033143A1 - Method to make mechanical components for fluid-dynamic devices, compressors or motors operating at high pressure, and mechanical components thus achieved

Info

Publication number: WO2004033143A1
Application number: PCT/IB2003/004099
Authority: WO
Inventors: Enzo Scaglia
Original assignee: Scaglia Spa
Priority date: 2002-10-08
Filing date: 2003-09-22
Publication date: 2004-04-22
Also published as: AU2003263463A1

Abstract

A method to make mechanical components for fluid-dynamic devices, compressors or motors operating at high pressure, wherein each component comprises at least a first metal part (15) and a second metal part (16, 30) able to be joined permanently together by means of friction welding. The two metal parts (15; 16, 30) are finished by means of mechanical treatments before being permanently joined together and the welding flash (21, 41, 52) that is formed during the friction welding is mechanically removed only in the case wherein it is outside the component, or is easily accessible from the outside if it is inside a cavity of the component.

Description

"METHOD TO MAKE MECHANICAL COMPONENTS FOR FLUID-DYNAMIC DEVICES, COMPRESSORS OR MOTORS OPERATING AT HIGH PRESSURE, AND MECHANICAL COMPONENTS THUS ACHIEVED"

^•k Λ" " ~k ^■&^• FIELD OF THE INVENTION

The present invention concerns a method to make, by friction welding, mechanical components such as pistons and hollow cylinders, for fluid-dynamic, pneumatic, hydraulic, oil-dynamic devices or otherwise, and also for compressors or motors, able to be used at very high pressures, even in the range of tens of millions of Pascal (Mpa) .

BACKGROUND OF THE INVENTION It is known that the mechanical components, such as pistons or hollow cylinders, of fluid-dynamic devices, compressors or motors, wherein very high pressures develop, even more than 16 Mpa, are made employing very resistant materials and using particular mechanical treatments in order to obtain precision products that must be very reliable and durable. Sometimes, when two or more parts that form a particular mechanical component, whether it is a hollow cylinder, a piston or otherwise, have to be joined together, in the state of the art until now traditional welding methods have been used. These have the disadvantage, however, that they leave a welding bead of the weld material, and the component thus requires a subsequent mechanical treatment, very accurate, such as lapping, grinding or suchlike, in order to totally or partly remove the welding bead. However, this treatment reduces the resistance of the component.

With regard to limiting production costs, this subsequent mechanical treatment, which can also be very difficult to perform, especially inside cylinders having long, narrow cavities, is sometimes unacceptable because it is too expensive.

Applicant has devised and perfected the method according to the present invention in order to overcome this shortcoming, to increase the resistance of the components and hence reduce the production costs of the mechanical components .

SUMMARY OF THE INVENTION

The method according to the present invention to make mechanical components for fluid-dynamic devices, compressors or motors working at high pressure, and the mechanical components thus made, are set forth and characterized in the main claims, while the dependent claims describe other innovative characteristics of the present invention.

One purpose of the present invention is to perfect a production method that will allow to produce mechanical components, such as pistons and hollow cylinders, for fluid-dynamic devices, compressors or motors working at high pressure, that is to say, in the range of several tens of Mpa, wherein it is possible to join together the different metal parts of each mechanical component by welding, without needing to make subsequent mechanical treatments on the components, or limiting such treatments to the minimum indispensable and in any case to zones of the component that are easily accessible to tools, and at the same time increasing the resistance of the welding.

In accordance with this purpose, the method according to the present invention provides that the different parts that make up each mechanical component are welded together by friction.

Friction welding, as is known, is a welding performed under pressure, wherein one of the two parts to be welded is made to rotate rapidly with respect to the other part which does not rotate; then, the part that does not rotate is first brought into contact with the rotating part, with a slight pressure, so that the two parts are heated through friction, until the two ends to be joined become incandescent; subsequently, the rotating part is stopped and the other part is further advanced so as to obtain heading and pressure welding. However, heading creates a typical curl of material, called flash, on the edges of the joined ends.

In accordance with a characteristic feature of the present invention, this welding flash is removed, by means of a mechanical treatment, only in the event that it is outside the component or, if it is inside a cavity, if it is easily accessible from outside. On the contrary, when it is in a position that is difficult to access from outside, such as for example on the bottom of a long, narrow inner cavity, closed at one end, of a hollow cylinder, then the welding flash is enclosed in a suitable annular sealed seating.

When the mechanical component to be made comprises at least a first substantially tubular metal part, and a second closing metal part, before the friction welding step, on the second metal part a coupling part is made axially, of a size mating with that of the first metal part, so that the coupling part cooperates with a circular surface of the first metal part, so as to prevent the formation of a welding flash during the friction welding step. The aforesaid coupling part has one circular surface completely smooth, that is, without hollows or seatings in which to accommodate the welding bead.

In this way, we obtain the advantage that we prevent the formation of the welding flash, without needing to make a specific seating on the coupling part of the second metal part to accommodate the welding bead.

BRIEF DESCRIPTION OF THE DRAWINGS These and other characteristics of the present invention will be apparent from the following description of some preferential forms of embodiment, given as a non- restrictive example, with reference to the attached drawings wherein : - fig. 1 is a longitudinal section of a fluid-dynamic device that uses a cylinder and a piston made with the method according to the present invention;

- fig. 2 is a first enlarged detail of the device in fig. 1 in an intermediate working step; - fig. 3 is a schematic view of a variant of the working step in fig. 2 ;

- fig. 4 is a second enlarged detail of the device in fig. 1;

- fig. 5 is a third enlarged detail of the device in fig. 1;

- fig. 6 is a right side view of the detail in fig. 5 ;

- fig. 7 is a side view, partly in section, of a first variant of the detail in fig. 5;

- fig. 8 shows a second variant of the detail in fig. 5 ; - fig. 9 is a right side view of the detail in fig. 8;

- fig. 10 is a sectioned side view of a detail of a cylinder made according to a variant of the present invention;

- fig. 11 is a sectioned side view of another detail of the cylinder in fig. 10;

- fig. 12 is a sectioned side view of two parts of a cylinder, ready to be friction welded in accordance with a second form of embodiment of the present invention; - fig. 13 is a sectioned side view of the two parts shown in fig. 12 after they have been friction welded;

- fig. 14 is an enlarged detail of fig. 13;

- fig. 15 is a side view of an unworked detail of fig. 1; - fig. 16 is a side view of the detail in fig. 1 after a first working step;

- fig. 17 is a side view of the detail in fig. 1 after a second working step;

- fig. 18 is a side view of a variant of the detail in fig. 16;

- fig. 19 is a side view of a variant of the detail in fig. 17.

DETAILED DESCRIPTION OF A PREFERENTIAL FORM OF EMBODIMENT

OF THE INVENTION Fig. 1 shows, in a longitudinal section, a fluid- dynamic device 10 that comprises essentially a cylinder 11, hollow inside, and a piston 12 arranged inside it, both made with a method according to the present invention. The cylinder 11 has a length that can vary between a few decimeters and several meters, and an inner diameter in the range of centimeters .

To be more exact, to make the cylinder 11 a metal tubular element 15, for example made of steel, whose inner and outer surfaces are advantageously already finished, is friction welded with a bottom element 16, also made of steel, previously prepared.

In a first form of embodiment, shown in figs. 1, 2 and 3, the bottom element 16 comprises an outer part 17 shaped like a disk with the same outer diameter as the metal tubular element 15, and an inner part 19 that defines a circular seating 20 and that, at rest, is slightly flared towards the inside of the tubular element 15. The diameter of the inner part 19 is initially less than the inner diameter of the cylinder 11, but is able to become equal to the inner diameter of the tubular element 15 when the flare is eliminated, as will be described in detail hereafter.

Once the tubular element 15 and the bottom element 16 have been friction welded together, the welding flashes 21 that form outside (shown by dashes in figs. 1, 2 and 3) are mechanically removed, for example by turning, while the inner welding flash 22 is left in the circular seating 20, because it would be very laborious and difficult to remove it mechanically.

The inner part 19 is then widened and flattened, by means of a punch 25 (fig. 2), which is thrust axially with force by any known means, so that the inner part 19 itself goes into contact with the inner surface of the tubular element 15. The purpose of this is to prevent possible impurities or parts of the inner flash 22 from becoming dispersed, during use, inside the cylinder 11, damaging the surfaces thereof, and thus compromising the functioning of the whole device 10. According to a variant, shown in fig. 3, the punch 25 is provided with wheels 26 mounted rotatable on its substantially inclined appendices 27 that encourage the deformation of the inner part 19. In this case the punch 25 is not only thrust axially against the inner part 19, but also is made to rotate around its central axis X.

In a second form of embodiment, shown in figs. 12, 13 and 14, the inner part 19, which defines the circular seating 20, has a diameter slightly greater than the inner diameter of the tubular element 15 but, at rest (fig. 12), is slightly flared towards the outer part 17 of the bottom element 16, so that it is slight distant (e.g. few tenths of millimeter) from the inner surface of the tubular element 15 and does not interfere with the latter. In this way, when friction welding occurs, the inner flash 22, penetrating the circular seating 20, thrusts the inner part 19 towards the inside of the tubular element 15, until the inner part 19 stops against the inner surface of the latter, possibly interfering therewith. At the end of welding (fig. 13), the inner part 19 is substantially perpendicular to the axis of the tubular element 15.

In this way a perfect sealed closure is obtained of the circular seating 20, even without the aid of the punch 25 or other tools.

From the various trials carried out, it has been seen that, when the inner part 19, at rest, is slightly flared towards the outer part 17 of the tubular element 15, during the friction welding the flash 22, curling on itself, is preferably formed in the opposite direction to that which is formed when the inner part 19, on the contrary, is flared towards the inside of the tubular element 15. This further encourages the deformation of the inner part 19 itself towards the inner surface of the tubular element 15. The head 30 (figs. 1 and 4) of the cylinder 11 comprises a metal flange 31, also made of steel for example, which is friction welded to the tubular element

15, on the opposite side with respect to the bottom element

16, and a closing disk 32 screwed onto the flange 31 by means of screws 33. Sealing rings 34 are arranged between the flange 31 and the closing disk 32.

To be more exact, the flange 31 comprises a part 35 having the form of a holed disk, with the inner diameter equal to that of the tubular element 15, and a second part 36 that defines a circular seating 37.

Once the tubular element 15 and the flange 31 have been friction welded together, the welding flashes 41 that form inside (shown by dashes in figs. 1 and 4) are mechanically removed, for example by turning, while the outer welding flash 42 is left in the circular seating 37. The removal of the inner flashes 41 is performed without any difficulty, inasmuch as they are near the holed end of the flange 31 and this operation is performed before the closing disk 32 is mounted.

The piston 12 comprises a cylindrical head 45, provided with sealing rings 46, to slide inside the metal tubular element 15, and solid with a cylindrical rod 47. The latter is able to slide axially in a hole 49 of the closing disk 32, provided with sealing rings 50.

The end of the rod 47 outside the cylinder 11 is friction welded to a holed sleeve 51, substantially cylindrical in shape (figs. 1, 5 and 6) . The welding flash 52 that is formed is removed mechanically, for example by turning.

According to a variant, shown in fig. 7, a circular seating 53 can be provided to totally or partly accommodate the welding flash 52. According to another variant, shown in figs. 8 and 9, the holed sleeve 51, instead of having a cylindrical shape, can comprise a plane surface 55 on which the friction welding is performed.

Fig. 10 shows a detail of a mechanical component 100, for example a cylinder, made according to another form of embodiment of the present invention. In this case too, the mechanical component 100 consists of a first metal part 115, substantially tubular, permanently associated with a second closing metal part 116. In this embodiment it can be seen however that the central part 119 has the outer circular surface 118 without seatings or hollows, so as to be completely smooth in order to cooperate with the inner circular surface of the first metal part 115 to prevent the formation of the inner flash during the friction welding step.

In this way, the times taken to make the second metal part 116 are reduced, since it is not necessary to make the annular seating 20, which instead is provided in the corresponding bottom element 16.

Fig. 11 shows another detail of the mechanical component 100, provided with a lateral part 131 having an inner circular surface 134 without seatings or hollows, thus to prevent the formation of the outer flash during friction welding.

According to another characteristic feature of the present invention, on the unworked holed sleeve 51 (fig. 15), at least some plane reference surfaces 60 (fig. 16) are made, by means of mechanical treatment; such reference surfaces 60 can be parallel or orthogonal to each other, or angularly offset with respect to each other at predetermined angles (fig. 18) . Finally, on the holed sleeve 51 also the front surfaces 62 (fig. 6), parallel to each other, the circular surface of the holes 61 (fig. 17 and 19) and the transversal surface 63, able to be permanently joined to the rod 47, are also finished by means of further mechanical treatment. The purpose of these mechanical treatments is to define reference surfaces for the subsequent other treatments using machine tools and so as to correctly center and assemble the different pieces.

It is clear, however, that some steps of the method as described heretofore can be modified or inverted, or other steps can be added, 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 be able to perfect many other equivalent methods, all of which shall come within the field and scope of the present invention. Moreover, the components that can be made with the production method according to the present invention can be of many different types, and not only include cylinders and pistons for fluid-dynamic devices, but also other components for motors, compressors and any other type of machine .

Claims

CLAIMS 1. Method to make mechanical components for fluid-dynamic devices, compressors or motors operating at high pressure, wherein each of said components comprises at least a first metal part (15) and a second metal part (16, 30) able to be joined permanently together by means of friction welding, characterized in that said first and second metal parts (15; 16, 30) are finished by means of mechanical treatments before being permanently joined together and that the welding flash (21, 41, 52) which is formed during said friction welding is mechanically removed only in the case wherein it is outside the component, or is easily accessible from the outside if it is inside a cavity of the component .

2. Method as in claim 1, characterized in that said welding flash (22, 42) is enclosed in a sealed annular seating (20) when it is in a position that is difficult to access from outside.

3. Method as in claim 1 or 2 , characterized in that, in the event that said component is a cylinder (11) , hollow inside, said metal parts comprise a metal tubular element (15) , a bottom element (16) , which is friction welded to a first end of said metal tubular element (15), and a head element (30) which is friction welded to a second end of said metal tubular element (15) .

4. Method as in claim 3, characterized in that said bottom element (16) comprises an outer part (17) in the form of a cylindrical disk with an outer diameter substantially equal to the outer diameter of said metal tubular element (15), and an inner part (19) which defines a circular seating

(20) inside which the inner welding flash (22) which is not removed is arranged.

5. Method as in claim 4, characterized in that the diameter of said inner part (19) is initially less than the inner diameter of said metal tubular element (15) and in that, once the friction welding has been completed of said metal tubular element (15) with said bottom element (16) , said inner part (19) of said bottom element (16) is widened until it touches the inner surface of said metal tubular element (15), by means of a thrust means (25) arranged inside said metal tubular element (15) and thrust axially against said inner part (19) with a force sufficient to deform it.

6. Method as in claim 5, characterized in that said thrust means comprises a punch (25) provided with wheels (26) mounted rotatable on its inclined appendices (27) which encourage the deformation of said inner part (19) and in that said punch (25) is not only thrust axially against said inner part (19) but is also made to rotate around its central axis (X) .

7. Method as in claim 4, characterized in that, initially and at rest, said inner part (19) has an outer diameter slightly greater than the inner diameter of said metal tubular element (15) and is slightly flared towards said outer part (17) so that, at the start of the friction welding step, said inner part (19) does not interfere with the inner surface of said metal tubular element (15), and in that, when friction welding occurs, said inner welding flash (22), penetrating into said circular seating (20), thrusts said inner part (19) towards the inside of said metal tubular element (15) until the inner part (19) itself stops against the inner surface of said metal tubular element (15) , possibly interfering therewith.

8. Method as in any claim from 3 to 7 inclusive, characterized in that said head element (30) comprises a metal flange (31) , welded directly to said metal tubular element (15), and a closing disk (32) screwed onto said flange (31) .

9. Method as in claim 8, characterized in that said flange (31) comprises a first part (35) substantially having the form of a holed disk, with the inner diameter equal to the inner diameter of said metal tubular element (15), and a second part (36) which defines a circular seating (37) inside which the welding flash (22) which is not removed is arranged.

10. Method as in claim 9, characterized in that said closing disk (32) is screwed onto said flange (31) by means of screws (33) passing through said circular seating (37).

11. Method as in claim 1 or 2 , characterized in that, in the event that said component is a piston (12), said parts comprise a cylindrical head (45) and a cylindrical rod (47) solid with said cylindrical head (45) and having one end friction welded to a sleeve (51), and in that the flash (52) which is formed during the welding step is mechanically removed.

12. Method as in claim 11, characterized in that a circular seating (53) is arranged in said sleeve (51), able to totally or partly accommodate said welding flash (52) .

13. Method as in claim 11 or 12, characterized in that, on said sleeve (51) in its unworked state, at least some plane reference surfaces (60) are made by means of mechanical treatment, which can be parallel or orthogonal to each other, or angularly offset to each other by pre-determined angles .

14. Method as in claim 13, characterized in that on said sleeve (51) the circular surfaces of the inner holes (61) , and the front surfaces (62) which are parallel to each other, are then finished.

15. Method to make mechanical components for fluid-dynamic devices, compressors or motors operating at high pressure, wherein each of said components comprises a metal tubular element (15) and a bottom element (16) able to be joined permanently together by means of friction welding, wherein said bottom element (16) comprises an outer part (17) in the form of a cylindrical disk with an outer diameter substantially equal to the outer diameter of said metal tubular element (15) , and an inner part (19) which defines a circular seating (20) inside which an inner welding flash (22) is able to be arranged, characterized in that, initially and at rest, said inner part (19) has an outer diameter slightly greater than the inner diameter of said metal tubular element (15) and is slightly flared towards said outer part (17) so that, at the start of the friction welding step, said inner part (19) is slightly distant from the inner surface of said metal tubular element (15), and in that, when friction welding occurs, said inner welding flash (22), penetrating into said circular seating (20), thrusts said inner part (19) towards the inside of said metal tubular element (15) until the inner part (19) itself stops against the inner surface of said metal tubular element (15), possibly interfering therewith.

16. Method to make mechanical components for fluid-dynamic devices, compressors or motors operating at high pressure, wherein each of said components is made by joining permanently together, by means of a friction welding step, at least a first metal part (115) , substantially tubular, and a second closing metal part (116), characterized in that, before said friction welding step, a coupling part (119, 131) is made axially on said second metal part (116) , of a size mating with that of said first metal part (115), so that said coupling part (119, 131) cooperates with a circular surface of said first metal part (115) and thus prevents the formation of a welding flash during said friction welding step.

17. Method as in claim 16, characterized in that said coupling part (119, 131) is made in such a manner that a circular surface (118, 134) thereof is completely smooth.

18. Mechanical component for fluid-dynamic devices, compressors or motors operating at high pressure, comprising at least a first metal part (15, 115) and a second metal part (16, 30, 116) joined permanently together by means of friction welding, characterized in that the corresponding welding flash (22, 42) produced by said friction welding is at least partly enclosed in a sealed annular seating (20, 37) made in at least one of said metal parts (16, 30) .

19. Mechanical component as in claim 18, characterized in that said second metal part (116) comprises a coupling part (119, 131) which extends axially, has dimensions mating with said first metal part (115) and is able to cooperate with a circular surface of said first metal part (115) in order to prevent the formation of a welding flash.

20. Mechanical component as in claim 19, characterized in that a circular surface (118, 134) of said coupling part (119, 131) is smooth.

21. Mechanical component for fluid-dynamic devices, compressors or motors operating at high pressure made using the method according to any one of the claims from 1 to 17 inclusive.