HOLLOW PIVOTABLE COUPLING

Abstract: A hollow pivotable coupling which includes a first pipe section (6), a first pipe section bulbous end (16) including a first part-spherical external surface (20), a second pipe section (12), a second pipe section bulbous end (18) including a second part-spherical internal (22) and a second part-spherical external (24) surface, the said first external surface (20) being sized as a sliding fit within the said second internal surface (22) characterised by an annular pressure ring (26) slidably engageable with the second pipe section external surface (24), said ring being located about the first pipe section (6), and further characterised by resilient spring means (30) urging the pressure ring (26) into engagement with the said second external surface (24), and urging the first (6) and second (12) pipe sections apart and further characterised by the said first external surface (20), the said second internal surface (22) and the said second external surface (24) being concentric.

Description: HOLLOW PIVOTABLE COUPLING This invention relates to a hollow pivotable coupling, and in particular to a hollow pivotable coupling for use in an engine exhaust * system. It is conventional practice, in a vehicle powered by an internal combustion engine, firstly to mount the engine on flexible supports to permit it some vibration and lunge during vehicle movement, and secondly to mount a major part of the exhaust system rigidly on the vehicle chassis. It is therefore usual to include a flexible joint between the engine and the exhaust system, to inhibit fracture of the exhaust system from the stresses arising from the relative (motion-induced) movements of engine and exhaust, and also to alleviate acoustical drumming. Various embodiments of a suitable joint are shown in my U.S. Patent 4,856,822; the joint comprises three universally pivotable couplings. Each of the disclosed couplings includes a first pipe section having a bulbous end through which the hot exhaust gases exit, and a second pipe section to receive the exhaust gases; the • second pipe section also has a bulbous end and this is of a size to mate slidingly and pivotably around the bulbous end of the first pipe section; the respective sliding surfaces are urged sealingly together by resilient means carried by the bulbous member of the second (downstream) pipe section. An advantage of the arrangements disclosed in my US Patent 4,856,822 is that the spring pressure provided by the resilient means remains substantially symmetrically disposed irrespective of the pivoting angle between the first and second pipe sections. However, I have now realised that I can simplify the construction, and possibly the cost of manufacture of such a coupling, without loss of the desirable coupling gas sealing function, by a modified spring mounting and locating arrangement. I have further realised that in common with earlier arrangements, the spring pressure of my π Patent 4,856,822 arrangements acts in the "compression" direction tending to shorten the distance between the pipe sections; I extended the (inner) bulbous end of the first pipe section within the bulbous end of the second pipe section to form one of the sealing surfaces, with the spring pressure urging this surface against the adjacent surface of the bulbous end of the second pipe section. There can however be created a gap between these two sealing sufaces when the engine moves upwardly under motion-induced vibration i.e. in the "tension" direction between the pipe ends. I now prefer to mount the resilient means so as to co-act with the tension force i.e. with the first pipe section being urged relative to the second pipe section in the "tension" direction, and with therefore the bulbous ends being resilently urged in a direction to increase the distance between the pipe sections, and so with the pipe sections being urged apart. Thus according to one feature of my invention I propose a hollow pivotable coupling which includes a first pipe section, a first pipe section bulbous end including a first part-spherical external surface, a second pipe section, a second pipe section bulbous end including a second part-spherical internal and a second part-spherical external surface, the said first external surface being sized as a sliding fit within the said second internal surface characterised by an annular pressure ring slidably engagable with the second pipe section external surface, said ring being located about the first pipe section, and further characterised by resilient spring means urging the pressure ring into engagement with the said second external surface, and urging the first and second pipe sections apart and further characterised by the said first external surface, the said second internal surface and the said second external surface being concentric. It will be understood that the "first" surface is on the first bulbous end, and that the "second" surfaces are on the second bulbous end. Preferably the spring means is an annular coil spring having one end located in or on an abutment, conveniently formed as a flange or cup rigidly fixed to the first pipe section, but alternatively as an outwardly protruding pipe formation; in an alternative embodiment the cup can be adjustably fixed to the first pipe section, to permit a variable spring loading. In an engine exhaust system, usually at least one such coupling will be mounted vertical or substantially vertical, with exhaust gas flowing downwardly; although I prefer the exhaust gas to flow from the first pipe section into the second pipe section, with my modified arrangement of spring means this can be reversed. Furthermore I can provide means to avoid direct impingement of the exhaust gas on the sealing surfaces, and also if desired a buffer zone adjacent the sealing surfaces with cool exhaust gas . I also propose a method of forming a hollow pivotable coupling having a first pipe section terminating in a bulbous end with a sealing surface, and a second pipe section terminating in a bulbous end with a sealing surface, the sealing surfaces being part-spherical and concentric, part of the first bulbous end being within and in sliding engagement with the second bulbous end at said sealing surfaces, and with resilient means to urge the sealing surfaces together, the coupling in use being subjected to tension forces acting in a direction to separate the pipe sections and compression forces acting in a direction to press the pipe sections together characterised by arranging the resilient means to co-act with the tension forces. The invention will be further described by way of example with reference to the accompanying drawings in which:- Fig.1 is a schematic end view of an engine which is transversely and flexibly mounted on the chassis of a vehicle, including part of an exhaust system comprising a composite hollow universally-articulating pipe joint comprising three hollow pivotable couplings made according to the invention; Fig.2 is an enlarged schematic sectional view of one hollow pivotable coupling according to the invention, with the sealing surfaces shown spaced apart for clarity; and Fig.3 is a schematic sectional view of an alternative embodiment of hollow pivotable coupling incorporating a separately fabricated coupling unit, again with the sealing surfaces shown spaced apart for clarity. As seen in Fig.1, the vehicle engine 2 is transversly mounted, on chassis attachment points 13. Interposed flexible mountings 3 enable the engine 2 and consequently the exhaust manifold 4 to vibrate and lurch relative to exhaust pipe section 8, which is rigidly connected to the vehicle chassis 1. A typical engine movement, about the centre of twist C, during vehicle motion is shown by arrow C1. Exhaust silencer box 15 is rigidly connected to chassis 1 by arms 17, and thus moves therewith; there may be sonant dampers between silencer box 15 and the chassis attachment points. Exhaust manifold 4 has its egress directed generally downwards, and has bolted thereto a first pipe section 6 having a bulbous end 16 (Fig.2). It is partly surrounded by a second bulbous end 18 of larger diameter, forming part of second pipe section 12. The bulbous ends 16, 18 are elements of a pivotable coupling 11a; additional pivotable pipe couplings 11b and 11c are located downstream of coupling 11a, and in a substantially horizontally disposed exhaust run. In the embodiment disclosed, the first bulbous end of coupling 11b is carried by the end of pipe 12 remote from bulbous end 18; similarly, pipe section 14 carries at its inlet end the second bulbous end for coupling 11b, as well as the first bulbous end for coupling 11c. Each of the couplings 11a,11b,11c has a limited range universal articulation. Thus interposed between in the exhaust pipe line is a pipe length with three couplings i.e between engine 2 and pipe is an articulated joint 10, comprising couplings 11a,11b,11c, with in this embodiment the couplings being identical in structure and operation, but in an alternative embodiment one or both of the downstream couplings being in accordance with the disclosure of my US Patent 4,856,222. In this embodiment pipe section 8 is connected to inlet pipe 9 of silencer box 15. In an alternative embodiment, silencer inlet pipe 9 is formed with the second bulbous end for coupling 11c. As more clearly seen in Fig.2, shown with the joint 11a in its rest position with pipe sections 6,12 co-axial, the first bulbous end 16 has a part-spherical (mating) surface 20 concentric with pipe diameter 6 and is located within the downstream second part-spherical bulbous end 18, which has respective internal and external concentric part-spherical (mating) surfaces 22, 24. Surfaces 20,22 are sized to mate to permit relative rotation, including pivoting and swivelling, of the bulbous ends. Such pivoting and swivelling is of restricted range, for instance until the terminal portion 23 of the second bulbous end 18 abuts pipe section 6, whereupon any additional pivoting which may temporarily be required in response to vehicle-induced movements is effected at one or both of the other couplings. It is a feature of my invention that I provide an annular pressure-ring 26 having an internal (mating) part-spherical surface 28 shaped complementarily to outer surface 24 of bulbous end 18. During pivoting movement of bulbous end 18, pressure-ring 26 can slide relative to bulbous end 18, with surface 28 in engagement with surface 24. When the vehicle is travelling over uneven surfaces, engine 2 will rise and fall relative to chassis 1. When the engine rises (as viewed in Fig.1) the sealing surfaces 20,22 engage more closely; when it falls there is a tendency for a gap to be created between surfaces 20, 22, perhaps to allow the escape of exhaust gas. Compression spring 30 is fitted between an abutment 32 formed as a flange or cup on pipe section 6 and a location surface 33 of pressure ring 26. In this embodiment flange 32 is rigidly secured, as by welding, to pipe section 6; In an alternative embodiment the abutment is an outwardly flared annulus on pipe section 6. Location section 33 is formed between an annular face 34 and a shoulder 35 of pressure ring 26, annular face 34 being a sliding fit around pipe section 6; in an alternative embodiment, annular face 34 is extended (upwardly as viewed in Fig.2) as a bore to inhibit gas transfer along the annulus between pressure ring 26 and pipe section 6. Spring 30 is selected to be of a strength both to retain surfaces 20, 22 in sealing engagement when the first and second bulbous ends are in the position shown schematically in Fig.2 i.e. with no externally induced separating force; and also to load pressure ring 26 to resist forces on the adjacent pipe sections in the "compression" direction, so that surfaces 24,28 are urged to remain in gas sealing engagement. Thus pressure ring 26 sits upon surface 24 and urges pipe section 6 upwardly, as viewed in Fig.2. Surfaces 24,28 can be mating sealing surfaces, to provide yet further sealing restriction to gas escape, not only when pipe section 12 has pivoted relative to pipe section 6 to take up a new relative angular position, but also when pipe section 12 may have lifted (as viewed in Fig.2) relative to pipe section 6 to allow a temporary gap between surfaces 20, 22. Since spring 30 is mounted on and is abutted against pipe section 6, the spring rate and loading upon pressure ring 26 remains symmetrical and is unaffected by pivoting of pipe section 6 relative to pipe section 12; effectively, spring 30 does not pivot relative to pipe section 6, nor does pressure ring 26. It will be understood that the lifting of bulbous end 18 relative to bulbous end 16 by vehicle-induced movements is inhibited by spring 30, which becomes more compressed the greater the relative lift. It will be further understood that spring 30 permits the continuous take-up of wear between the mating surfaces. In an alternative embodiment, encircling spring 30 is replaced by three equi-spaced small diameter compression springs. The cup or abutment flange 32 can be perforated or finned, to inhibit heat transfer to the spring(s). In a further alternative embodiment, cup 32 is adjustably mounted on pipe section 6, whereby to vary the spring rate and loading from spring 30 upon pressure ring 26. Usefully the end faces of spring 30 are ground substantially parallel to provide symmetrical pressure to surfaces 28,24, and to surfaces 22,20. In a further alternative embodiment, the first bulbous end 16 of pipe section 6 can be extended (downwardly as viewed in Fig. 2) so that relative upward movement of pipe section 12 is also restrained by engagement of its second bulbous end 18 with such extension. In a further alternative embodiment pipe section 6 can be extended within the bulbous ends and towards pipe section 12 with a tube of diameter preferably similar to that of the pipe sections, to inhibit direct impingement of the exhaust gases with the sealing surfaces 20,22 and 24,28; if the (lower) extremity of that tube is outwardly flared, use of the coupling to accommodate exhaust gas flow in the opposite direction is made more possible, since direct gas impingement on the sealing surfaces is again made less likely. In the alternative embodiment of Fig.3, pipe section 6 is fabricated from a first tubular portion 6a, a second tubular portion 6b rigidly connected thereto (as by welding) and a third tubular but bulbous portion 16c rigidly connected (again as by welding) to section 6b but upstream of its exit end. Portion 16c is shaped for surface to surface mechanical inter-engagement with bulbous end 12b to limit inward (compression) movement of the bulbous ends. Section 6b encourages non-turbulent flow of the gas from pipe section 6 to pipe section 12, further inhibiting counter flow back between surfaces 20,22. Pipe 6b extends towards the downstream extremity of bulbous end 16a to prevent direct impingement of hot exhaust gases onto the mating surfaces, but terminates short of a position within the allowed relative pivoting of the bulbous, part-spherical ends. Pipe section 12 includes a tubular section 1 a and a bulbous end portion 12b. Bulbous end 12b comprises connected parts 18a and 18b, with part 18b including a spring cup 42 having a face abutting shoulder 44 on part 18a. In this embodiment, spring cup 32a is made of larger diameter, and provides a base not only for spring 30, but also for auxiliary spring 40 the other end of which locates in spring cup 42. Spring 40 is of less compressive capability than spring 30, and helps to return the coupling to the rest position shown in Fig.3 i.e. wherein the pipe sections 6 and 12 are in-line. Flange 44 facilitates seam welding of the fabricated bulbous end parts 18a,18b. An advantage of my coupling is that the sealing surfaces resist separation of the bulbous ends under tension forces up to their destruction limit. A further advantage is that exhaust gas sealing can be maintained even when the coupling is subjected to compressive loading. A yet further advantage is that I can use pressure ring 26 to provide secondary sealing for those occasions when primary sealing surfaces 20,22 separate under compression forces.

Claims: CLAIMS 1. A hollow pivotable coupling which includes a first pipe section (-6), a first pipe section bulbous end (16) including a first part-spherical external surface (20), a second pipe section (12), a second pipe section bulbous end (18) including a second part-spherical internal (22) and a second part-spherical external (24) surface, the said first external surface (20) being sized as a sliding fit within the said second internal surface (22) characterised by an annular pressure ring (26) slidably engagable with the second pipe section external surface (24), said ring being located about the first pipe section (6), and further characterised by resilient spring means (30) urging the pressure ring (26) into engagement with the said second external surface (24), and urging the first (6) and second (12) pipe sections apart and further characterised by the said first external surface (20), the said second internal surface (22) and the said second external surface (24) being concentric. 2. A hollow pivotable coupling according to claim 1 characterised in that the resilient spring means is an annular compression spring (30) located around the first pipe section (6) and positioned between the pressure ring (26) and an abutment (32) carried by the first pipe section. 3. A hollow pivotable coupling according to claim 2 characterised by means to adjust the position of the abutment on the first pipe section (6). 4. A hollow pivotable coupling according to claim 1 characterised in that the first bulbous end (16c) extends within the second bulbous end (18a,18b) a distance such that separation between the bulbous ends in any direction is inhibited by mechanical inter-engagement between surfaces of the bulbous ends and such that the maximum compression of the resilient spring means (30) is pre-determined. 5. A hollow pivotable coupling according to claim 1 characterised by auxiliary spring means (40) positioned between the first pipe section (6) and the second bulbous end (18a,18b) and biasing the first (6) and second (12) pipe sections towards their rest positions. 6. An exhaust joint (10) for a vehicle having a chassis (1) to which is flexibly mounted an engine (2) having an exhaust manifold (4) and to which is rigidly mounted an exhaust silencer box (15) characterised by an exhaust pipe length adapted to connect the manifold and the silencer box, the exhaust pipe length (6,12, 14, 8) including at least one hollow pivotable coupling (11a) according to claim 1. 7. A vehicle characterised by a hollow pivotablel coupling as claimed in claim 1. 8. A vehicle characterised by an exhaust joint as claimed in claim 6. 9. A method of constructing a hollow pivotable coupling (11a) having a first pipe section (6) terminating in a bulbous end (16) with a sealing surface (20), and a second pipe section (12) terminating in a bulbous end (18) with a sealing surface (22), the sealing surfaces (20,22) being part-spherical and concentric, part of the first bulbous end being within and in sliding engagement with the second bulbous end at said sealing surfaces (20,22), and with resilient means (30) to urge the sealing surfaces together, the coupling in use being subjected to tension forces acting in a direction to separate the pipe sections (5,12) and compression forces acting in a direction to press the pipe sections (6,12) together characterised by arranging the resilient means to co-act with the tension forces. 10. A method of constructing a hollow pivotable coupling according to Claim 9 characterised in that the resilient means urges the sealing surfaces together by way of an annular pressure ring (26), the pressure ring being a sliding fit around the first pipe section (6) and a sealing fit upon the bulbous end (18; 18b) of the second pipe section (12 12b), whereby the coupling can remain effectively gas-tight even when subjected to compression force between the pipe sections (6,12) sufficient to separate the sealing surfaces (20,22).

Inventors: BIRCH FRED PARKER, BIRCH, FRED, PARKER
Applicants: BIRCH FRED PARKER, BIRCH, FRED, PARKER
Application year: 1990
Main classification: F16L27
IPC codes: F01N7, F16L27