WO2011161524A1

WO2011161524A1 - Decoupling joint for exhaust pipings of endothermic engines

Info

Publication number: WO2011161524A1
Application number: PCT/IB2011/001416
Authority: WO
Inventors: Gian Luca Spada
Original assignee: Flexider S.R.L.
Priority date: 2010-06-21
Filing date: 2011-06-21
Publication date: 2011-12-29
Also published as: IT1400861B1; ITTO20100533A1

Abstract

A decoupling joint (1) comprising: a first flexible metal sleeve (2), constructed as a fluid tight bellows, presenting a plurality of first annular corrugations (5) and a pair of opposed cylindrical terminal ends (9, 10), free of corrugations, and opposed heads (3, 4) each being coaxially and fluid-tightly secured to a cylindrical end (9, 10) of the first bellows (2); in which a second flexible metal sleeve, fluid-tightly constructed in the shape of a bellows (12) is arranged within the first one, radially spaced from the first corrugations (5) and with its respective opposed cylindrical ends (13,14) free of corrugations radially coupled in contact with the cylindrical ends (9,10) of the first bellows (2); the second bellows (12) having second annular corrugations (15) which are smaller and larger in number than the first, axially squeezed at the base, in correspondence to their respective depressions (20) directed radially towards the outside to create towards a symmetry axis (A) of the second bellows (12) a substantially continuous flow-guide surface (21) which hydraulically shields towards the axis the ridges (16) of the second corrugations (15).

Description

DECOUPLING JOINT FOR EXHAUST PIPINGS OF ENDOTHERMIC ENGINES"

TECHNICAL FIELD

The present invention relates to a decoupling joint for exhaust pipings of endothermic engines, made in a particularly- simple, inexpensive, and highly efficient way.

BACKGROUND ART

It is known that the exhaust systems of thermic engines of modern vehicles are equipped with one or more flexible sleeves described here and in the following description with the general term of "decoupling joints", placed between the engine and the final part of the exhaust piping, with the task of compensating for misalignments/positioning errors of the different sections of the exhaust piping and/or reducing/eliminating vibration transmitted from the engine to the exhaust system in general and to some of the more sensitive components thereof, such as catalytic purifiers (the so-called "catalytic muffles"), in particular. According to what described, for example in EP 0 657 683, these decoupling joints are formed by a flexible metal sleeve in the shape of a bellows and fluid tightly constructed, provided in turn with one or more non-fluid tight reinforcing flexible metal sleeves, in particular of a tubular flow-guide element or "liner", disposed concentrically inside the flexible sleeve in the shape of a bellows and made of a metal crimped band, helix coiled to form a tube, and damping elements interposed between the bellows and at least one of the reinforcement sleeves; decoupling joints are, in use, arranged at least along the section of the piping comprised between the engine and the catalytic purifier, in an area, therefore, relatively inaccessible and in which the available space is reduced. The known decoupling joints, although relatively efficient, in particular according to EP 0 657 683, have the disadvantage of requiring numerous component elements, which increases the cost of production, bulk and weight.

A simplified joint is known from US6220023B1, where the bellows sleeve is simply covered with a single sleeve made of woven wire mesh tightly bound against the corrugations of the bellows. In this type of solution, however, the wire mesh sleeve, to be effective, must be locked directly on the annular heads that delimit the ends of the joint; therefore, the ends of the woven wire mesh sleeve are interested in use by the welding bead required to connect the heads to pipings sections to be joined, making the welding procedure difficult and producing an unreliable welding bead. JP58042483U does not solve the problems pointed out.

DISCLOSURE OF INVENTION

The aim of the invention is therefore to solve these problems by means of a decoupling joint that present reduced dimensions and weight along with a low manufacturing cost and high operation efficiency, both in terms of duration, dampening of vibrations and noise, and does not pose any problem during the welding procedure of the heads.

According to the invention a decoupling joint is thus provided for exhaust pipings of thermic engines as defined in claim 1.

In particular, the decoupling joint comprises: a first flexible metal sleeve, fluid tightly constructed in the shape of a bellows and, in turn, comprising a plurality of first annular corrugations and a pair of opposed cylindrical terminal ends, free of corrugations; and a pair of opposed heads, each being coaxially and fluid-tightly secured to a respective cylindrical end of the first bellows-like sleeve and intended, in use, to be connected to the exhaust piping. According to the main feature of the invention, the joint also comprises a second flexible metal sleeve, fluid tightly constructed also in the shape of a bellows, which is arranged within the first sleeve, radially spaced from the first corrugations and with its own respective opposed cylindrical ends free of corrugations radially jointed in contact with the corresponding cylindrical ends of the first bellows-like sleeve .

The second bellows-like sleeve has second annular corrugations smaller and larger in number than the first corrugations of the first sleeve, outward radially defining a plurality of ridges and respective depressions alternating between one another. These second corrugations, according to an aspect of the invention, have been axially squeezed at the base, in correspondence to the respective depressions, so as to create towards a symmetry axis of the second bellows, a flow-guiding substantially continuous surface that hydraulically shields the ridges of the second corrugations towards the axis.

In particular, the second corrugations result substantially closed towards the axis of the second bellows-like sleeve, so that their internal space defined by the internal annular volume of the second bellows-like sleeve enclosed, for each second corrugation, between the ridge of the latter and two depressions which are immediately adjacent from opposite sides of the same ridge, is substantially inaccessible for the exhaust gas flow of the engine which, in use, passes through the joint; apart from a possible leakage between the adjacent edges in contact with each other of opposite radially inner sides of each second corrugation, laterally delimiting on the outside of the second sleeve the depressions adjacent to the corrugation itself, such leakage, however, only representing a negligible fraction of the flow of exhaust gases.

In this way, a decoupling joint of extremely simple and lightweight structure is achieved, made for the essential parts of only the heads and two elements coupled to each other composed of two coupled bellows-like sleeves, also only hereinafter referred to as "bellows".

Surprisingly, however, such a joint has been proven highly efficient and reliable in dampening vibrations and noise; in fact, the second bellows on one hand absorbs some of the stress to which the joint is subjected, thus making further reinforcement elements unnecessary for the first outer bellows. On the other hand, the second bellows, which clearly has its own frequencies different than those of the first bellows, interacts dynamically with the latter, effectively dampening vibrations even in the absence of a conventional dampener element, such as a bearing or padding-sleeve made of wire-mesh (compressed wire mesh pad) .

For this purpose, the second corrugations present in the radial direction, a height equal to or less than about half the height, measured in the same radial direction, of the first corrugations, and are present in a number at least double the number of the first corrugations. Furthermore, the first bellows-like sleeve is produced as a double-wall sleeve, while the second bellows sleeve is designed as a single wall sleeve . In addition, the axial "squeezing" at the base of the second corrugations, which in use prevents most of the exhaust gas through the joint to penetrate into the second corrugations creating turbulence, noise and excessive pressure drops, allows the second sleeve, on the one hand, to effectively exert a flow-guide function, similar to a traditional liner of crimped metal band, although of course its inner surface is not smooth but defined by a sequence of adjacent convexity corresponding to the bottom of each depression present between two adjacent corrugations, and on the other hand, to present a limited flexibility so that it can effectively support the first sleeve. Finally, due to the absence of a dampener element consisting of awire mesh sleeve or pad, the area of the heads destined to receive the welding results free of extraneous elements, thus ensuring easy and rapid achievement of high reliable welding beads .

BRIEF DESCRIPTION OF THE DRAWINGS

Additional features and advantages of the invention will appear clear from the following description of a non- restrictive embodiment thereof, made only by way of example, with reference to the attached drawing, in which:

- Figure 1 shows a longitudinal view in elevation, partially in radial section of a decoupling joint made according to the invention; and

- Figure 2 shows on an enlarged scale a detail of the construction joint of Figure 1.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to Figures 1 and 2, with 1 is indicated as a whole a decoupling joint (or decoupler joint) for exhaust pipes of thermic engines (known and not shown for simplicity) , insertable in use, in a known way, in series along an exhaust piping of an endothermic engine, also known and not shown for simplicity. The decoupling joint 1 is symmetrical with respect to a longitudinal axis A, and comprises a first flexible metal sleeve 2, fluid-tightly constructed in the shape of a bellows and a pair of opposed heads 3, 4 intended in use to be connected in a known way, by welding, to the exhaust piping. The bellows sleeve or just bellow 2 in turn comprises a plurality of first annular corrugations 5 and a pair of opposed cylindrical terminal ends 9, 10, free of corrugations, coaxially bound and fluid-tightly constructed, each at a respective head, 3 and 4 respectively. According to a known configuration, some of the corrugations 5 closest to the cylindrical terminal ends 9, 10, indicated with 5b, present in the radial direction, i.e. perpendicular to the axis A, a height less than that of the remaining corrugations 5, each having a substantially identical shape and size. According to the main aspect of the invention, the joint 1 also comprises, instead of a traditional metal crimped band liner, a second flexible metal sleeve 12, fluid tightly constructed, being also in the shape of a bellows, indicated below for simplicity also only as "bellows 12", which is arranged within the first bellows-like sleeve 2 or, simply bellow 2, radially spaced from the first corrugations 5 and with its own respective opposed cylindrical ends 13, 14 free of corrugations radially jointed in contact with the corresponding cylindrical ends 9, 10 of the bellows 2.

In addition, the second bellows-like sleeve 12 has second annular corrugations 15 smaller and larger in number than the corrugations 5, defining radially outwardly the sleeve 12 and, therefore, towards the bellows 5 a plurality of ridges 16 and respective depressions 20 alternating between one another. According to the invention, in contrast with the corrugations 5, which present a profile in radial section, generally omega- shaped and define respective annular loops open both towards the outside of the bellows 2, and towards the axis A, with respect to which the bellows 2 is symmetrical, the second corrugations 15 also have a profile in radial section, generally omega-shaped, but have been axially squeezed at the base, in correspondence to the respective depressions 20, so as to create towards a symmetry axis A which is also the symmetry axis of the second bellows 12, a flow-guide substantially continuous surface 21 that hydraulically shields the ridges 16 towards the axis A.

In other words, the second corrugations 15 are substantially closed towards the axis of the second bellows-like sleeve 12, so that their interior space, defined by the enclosed annular volume inside the bellows 12, for each corrugations 15, between the crest 16 of the latter and two depressions 20 immediately adjacent to opposite sides of the ridge 16, is substantially inaccessible to the flow F of exhaust gases from the engine that, in use, passes through the joint 1, schematically indicated with an arrow in Figures 1 and 2.

The only part of the exhaust gas that can eventually reach the interior of the ridges 16 is represented by the possible leakage between adjacent respective edges 22 and in reciprocal contact of the opposite radially interior sides of each corrugation 15, laterally delimitating on the outside of the sleeve 12 the depressions 20 adjacent to the corrugation 15 itself; in fact, the squeezing effect by the corrugations 15 at their base, so as to bring in reciprocate contact the opposed terminal edges 22 of the same, is anyway not such as to ensure the complete fluid-tightness; it has been experimentally found, however, that such leaks represent only a negligible fraction of the flow F of exhaust gases, therefore the shielding defined by the surface 21 formed by the adjacent edges 22 of the various corrugations 15 and by segments of the bottom wall of the depressions 20 defined between the ridges 16 is effective and allows the surface 21 to form an effective flow-guiding element for the flow F.

According to one aspect of the invention, the corrugations 15 have, in the radial direction, a height equal to or less than about half the height, measured in the same radial direction, of the corrugations 5, and are present in a number at least double the number of the corrugations 5.

In addition, the thickness, measured in the radial direction, of the side wall of the bellows-like sleeve 2 is approximately twice that of the side wall of the second bellows-like sleeve 12. In particular, according to a further aspect of the invention, the bellows-like sleeve 2 is made, in a known way, as a double-wall sleeve, defined by concentrically coupling in close contact the two sleeves 32 and 42 (Figure 2), each having a single side wall, through the plastic deformation by which the corrugations 5 were formed; however, the bellows- like sleeve 15 is made, as known, as a single wall sleeve. Therefore, the sleeves 32 and 42 defining the bellows 2 and the sleeve defining the bellows 12 have substantially the same radial thickness.

At least one of the corrugations 15, indicated with 15b, closer to each cylindrical end 13, 14, therefore two corrugations 15b, one on each side, is not completely closed at the base towards the symmetry axis A and is shorter in height .

In addition, the heads 3 and 4, each comprises, an annular element 50, radially arranged on the outside with respect to the bellows-like sleeve 2 and mechanically coupled in contact with a respective cylindrical end free of corrugations 9 and 10, respectively, which is radially sandwiched between the corresponding annular element 50 and the corresponding cylindrical end 13, 14 free of corrugations of the second bellows-like sleeve 15.

Finally, each cylindrical end 9, 10 free of corrugations of the first bellows-like sleeve 2 has a cylindrical portion 60 of larger diameter from the part facing the corrugations 5, against which a respective flanged end 61 of the annular element 50 of the head 3 or 4 axially abuts, and within which at least one, not fully closed terminal corrugation 15b of the second sleeve element 15 extends. Experimental tests on prototypes and computer simulations have shown that the described joint 1, despite its utter simplicity, which guarantees a low manufacturing cost, low weight and high ease of assembly, is particularly effective as a decoupling element reaching performance equal to or only slightly lower than joints of more complex shape having much higher cost and weight. All with a fluid dynamics efficiency sufficiently adapt for the purpose.

Claims

1. A decoupling joint (1) insertable in series along an exhaust piping of an endothermic engine, comprising: a first flexible metal sleeve (2), fluid tightly constructed in the shape of a bellows and, in turn, comprising a plurality of first annular corrugations (5) and a pair of opposed cylindrical terminal ends (9, 10), free of corrugations; and a pair of opposed heads (3, 4), each being coaxially and fluid- tightly secured to a respective cylindrical end (9, 10) of the first bellows-like sleeve (2) and intended, in use, to be connected to the exhaust piping; it further comprising a second flexible metal sleeve (12), fluid tightly constructed in the shape of a bellows, which is arranged within the first sleeve (2), radially spaced from the first corrugations (5) and with its own respective opposite cylindrical ends (13, 14) free of corrugations radially jointed in contact with the corresponding cylindrical ends (9, 10) of the first bellows- like sleeve; the second bellows-like sleeve (12) having second annular corrugations (15) which are smaller and larger in number than the first (5) , radially defining a plurality of ridges (16) and respective depressions (20) alternating between one another, outwards from the second sleeve (12); characterized in that the second corrugations (15) have been axially squeezed at the base, at the respective depressions (20) , so as to create a substantially continuous flow-guide surface (21) towards a symmetry axis ( A) of the second bellows, which surface hydraulically shields the ridges (16) of the second corrugations (15) towards the axis ( A) , said second corrugations (15) being substantially closed towards the axis ( A) of the second bellows-like sleeve (12) , so that their internal space defined by the internal annular volume of the second bellows-like sleeve enclosed, for each second corrugation (15), between the ridge (16) of the latter and two depressions (20) which are immediately adjacent from opposite sides of the ridge (16), is substantially inaccessible for the exhaust gas flow (F) of the engine which, in use, passes through the joint.

2. A joint according to claim 1, characterized in that in the radial direction, said second corrugations (15) have a height which is equal to or shorter than around half the height of the first corrugations (5), measured in the same radial direction, and are at least double in number with respect to the first corrugations .

3. A joint according to one of the preceding claims, characterized in that the thickness of the side wall of the first bellows-like sleeve (2), measured in the radial direction, is about twice the thickness of the side wall of the second bellows sleeve (12) .

4. A joint according to claim 3, characterized in that said first bellows-like sleeve (2) is constructed as a double-wall sleeve, defined by concentrically coupling two sleeves (32, 42) in close contact, each having a single side wall, through the plastic deformation of which the first corrugations (5) were formed; while said second bellows-like sleeve (12) is constructed as a single-wall sleeve.

5. A joint according to one of the preceding claims, characterized in that at least one (15b) of the second corrugations (15) which is closer to said cylindrical ends (13, 14) free of corrugations of the second bellows-like sleeve is not completely closed at the base towards said symmetry axis (A) of the second bellows-like sleeve and is shorter in height .

6. A joint according to one of the preceding claims characterized in that said heads (3, 4) each comprise an annular element (50) , radially arranged outside said first bellows-like sleeve (2) and mechanically coupled in contact with a respective cylindrical end (9, 10) free of corrugations of the first bellows-like sleeve (2), which is radially sandwiched between said annular element (50) and the corresponding cylindrical end (13, 14) free of corrugations of the second bellows-like sleeve (12) .

7. A joint according to claim 6, characterized in that each said cylindrical end (9, 10) free of corrugations of the first bellows-like sleeve (2) has a cylindrical portion (60) of larger diameter from the part facing the first corrugations (5) , against which a respective flanged end (61) of the annular head element (50) axially abuts, and within which at least a second, not fully closed terminal corrugation (15b) of the second sleeve element (12) extends.