GB2068489A

GB2068489A - Pipe connections

Info

Publication number: GB2068489A
Application number: GB8037940A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-01-30
Filing date: 1980-11-26
Publication date: 1981-08-12
Also published as: DE3003236C2; DE3003236A1; JPS56109977A; FR2474637A1

Abstract

The invention relates to a pipe connection, which is capable of rotary movement, between a housing (4, 5) and a socket (6) which enters the housing approximately coaxially. The socket carries within the housing a flange-like part (7) with a spherical rear surface (8). This surface is supported on an identically spherical sealing surface (8) of a sealing ring (14) in a ceramic material. The sealing ring bears, with its supporting surface (16) that is directed away from the sealing surface, against a supporting surface (21) which is connected to the housing, the supporting surfaces (21, 21) being substantially conical. <IMAGE>

Description

SPECIFICATION Pipe connections The invention relates to a pipe connection between a housing and a socket entering the housing approximately coaxially, which connection is capable of rotary movement and has, on the socket within the housing, a flange-like part which, with its spherical rear surface, is supported on an identically spherical sealing surface of a sealing ring which is made of a ceramic material and whose supporting surface that is directed away from the sealing surface bears against a supporting surface which is connected to the housing.

In pipe connections which are capable of rotary movement and which are subjected to high stresses by pressure and/or temperature, there are used as sealing elements ceramic sealing rings which consist, for example, of carbon ceramic material. They co-operate through a spherical sealing surface with a mating sealing surface which is of a corresponding oppositely spherical design. The spherical construction of the sealing surface is necessary so as to prevent leakages in the event of misalignments, which arise not only on angularly moveable pipe connections but are also unavoidable on coaxially extending pipe connections. For, in contrast to sealing rings made of elastic or plastic materials, sealing rings consisting of ceramic material cannot yield to such alignment errors while maintaining the tightness.

In known sealing arrangements of the kind mentioned at the beginning, the sealing pressure is produced by an axially acting spring and, additionally, by the medium pressure acting on the sealing arrangement. The sealing force acting on the sealing surface of the sealing ring is transmitted from its rear, which is designed as a supporting surface, to the supporting surface of a supporting part which is generally formed by the housing. In the known pipe connections, the supporting surface of the sealing ring and the supporting surface of the supporting part lie in a radially extending plane.In a first constructional form, the sealing ring is free on its circumference so that the arrrangement is capable of transmitting only axial forces, while for the absorption of the radial forces there is provided a special bearing which makes the pipe connection complicated, more expensive and larger. In a second constructional form, the sealing ring is retained not only in the axial direction, but on its circumference, also in the radial direction so that it is also capable of transmitting radial forces. To ensure that it is reliable held in the radial direction even at high temperatures and despite the lower thermal expansion of ceramic material as compared to metals, it has to be very carefully shrunk into the surrounding housing parts in this second constructional form.Because this impairs the accuracy of shape of its spherical sealing surface, it is necessary for the sealing ring and the mating sealing surface co-operating therewith to be ground in during the assembly (and also during the exchange of a worn sealing ring). Compared to the first constructional form, this second constructional form has indeed the advantage of a greater simplicity and smaller dimensions; however, these advantages are wholly or partly cancelled out by the increased assembly expenditure, more especially during the exchange of a sealing ring.

The task underlying the invention therefore is to provide a pipe connection of the kind mentioned at the beginning which combines the advantages of the two constructions.

The solution according to the invention consists in that the supporting surfaces are substantially conical.

The invention is based on the realisation that in connection with the arrangement presupposed in the gernic term, it is not necessary for the transmission of radial forces to fix the sealing ring precisely by a cylindrical circumferential surface.

On the contrary, a conical surface is sufficient as long as the radial forces multiplied by the tangent of the cone angle are not greater than the axial forces, the cone angle being the angle formed between an element of the cone and the axial direction. This condition can be easily fulfilled with sufficient reliability by the suitable choice of the cone angle.

One thus obtains an arrangement in which the sealing ring can be easily fitted without any complicated adaptation work and is nevertheless capable of transmitting radial forces. It has also turned out that the re-grinding-in of the sealing ring and the spherical cup co-operating therewith is not necesary during the installation or replacement of the sealing ring.

With a view to a low material consumption for the sealing ring and a good stability thereof, it is expedient if that part of the sealing ring rear surface that is involved in the formation of the supporting surface extends approximately parallel to its spherical sealing surface. In fact, measured transversely to the sealing surrace and the supporting surface, the sealing ring is then everywhere substantially equally tight. Without basically departing from this teaching, it may in some cases be expedient if the central cone angle of the supporting surface is somewhat smaller than that of the spherical sealing surface.By this means, there comes about between the mentioned surfaces a wedge-shaped widening towards the interior, by means of which there is exerted on the sealing ring a rdailly inwardly directed force which subjects it to compressive stress in the circumferential direction. This can sometimes be expedient with respect to other stresses. However, in those cases in which the pressure of the medium acts on the sealing ring from the outside radially to the inside, it may be more desirable that the inclination ratio of the mentioned surfaces should exert on the sealing ring a radially outwardly acting force, in other words a force which counteracts the mentioned medium pressure. In these surfaces, the central cone angle of the supporting surface is made somewhat larger than that of the spherical sealing surface.

Since it is the function of the conical supporting surface to fix the sealing ring not only axially but also radially, it is obviously not of importance that the conical surface is formed by rectilinear generatrices. Such a construction is indeed generally preferred; however, the term 'substantially conical' is also meant to cover constructions in which the conical surface is approximated by a spherical surface. In any case, it is expedient if the radius of curvature of the supporting surface is somewhat larger than that of the sealing surface.

Since cermaic materials are sensitive relative to tensile stresses (and therefore also to bending strain), ceramic sealing rings are in general carefully rigidly supported. According to a special feature of the invention, a departure is made from this principle in favour of a limited resilient support of the sealing ring. Put more precisely, the supporting part is meant to allow the sealing ring to carry out a slight torsion about its circumferential axis for a better adaptation of the sealing surface to the mating sealing surface in the event of machining tolereances or uneven wear. In this regard, the invention is based on the realisation that with adequately careful machining, these deformations can be kept within the stress limits of the ceramic material.Incidentally, the above-mentioned additional feature to the effect that by appropriate ratios of inclination on the sealing surface and the supporting surface of the sealing ring, this latter is subjected to compressive pre-stressing may be desirable in this context.

In this context, it is furthermore advantageous if the supporting part is designed as a ring in order to enable it also to perform a torsional movement about its circumferential axis so that the sealing ring does not lose its support over the entire surface by the supportirig ring. Finally, it is advantageous in this context if not only the sealing ring but also the supporting ring has in a radial section a main extension that is approximately parallel to its supporting surface which cooperates with the supporting surface of the sealing ring.

In order to keep the stress to which the sealing ring material is subjected in such a deformation as low as possible, it is expedient to make provision for the support of the supporting ring to be narrow and approximayely central relative to its configruration as shown in a radial section. The narrowness of the support facilitates the torsion of the supporting ring about its circumferential axis, while the central arrangement of the support results in that the deformation on both sides of the support is approximately equal in opposite directions, while the neutral line of the deformation extends in the centre of the supporting surface. The supporting ring then behaves (viewed in a radial section) like a weigh beam which is capable of yielding to any inaccuracies that may exist by turning in one direction or the other.

Expediently, the supporting part is provided at the housing end and the sealing surface of the sealing ring (as well as the supporting surface between the sealing ring and the supporting part) is concave. However, the reverse application of the teaching of the invention is obviously also ible.

possible.

Finally, it is a feature of the invention that radially inside the supporting ring, in other words in the gap between the supporting ring and a socket brought out from the pipe connection, there is provided a filling ring which, in the event of the sealing ring being damaged, prevents parts of the sealing ring from being hurled to the outside under the action of the medium which wants to emerge.

The invention will hereinafter be exaplained in more detail with reference to the drawing which illustrates two exemplfied embodiments on either side of the central line of a longitudinal section.

Let it be assumed that the socket 2, which is connected to the flange 1, is weleded together with a fixed pipe line not shown. The flange 1 is screwed together with a stationary component 3 which carries the entire arrangement.

To the flange 1 there is flanged the pipe connection housing which is composed of the two parts 4 and 5. Into the housing 4, 5 there projects, coaxially with the socket 2 and from the opposite side, a socket 6 which, let it be assumed, is connected to a rotating component which is not shown in the drawing. In connection with the invention, the term rotation also refers to a rotating reciprocating movement. Within the housing 4, 5, the socket 6 is integrally connected to a flange-like part 7, whose surface that points towards the socket 6 is designed as a convex spherical surface with a centre of curvature at 9.

The other side forms a seat for a sliding ring 10, which consists of a slidable material, for example artificial carbon, and the flange 11, which is supported on the sliding ring 10, of a spring guide bush 12. A compression spring 13, which is preloaded, lies between the flange 11 and the housing part 4. The spherical surface 8 of the flange-like part 7 co-operates with an identical spherical surface, the sealing surface of the sealing ring 14. The sealing ring 14 is (indirectly) supported on a radially inwardly drawn flange 1 fez of the housing part 5. Up to this point, the arrangement can be regarded as being known.

If one now initially considers the representation at the top of the Figure, one will find that, at its side that is opposite to the sealing surface 8, the sealing ring 14 is bounded by a likewise spherical rear surface 1 6. The centre of curvature 1 7 of the rear surface 16 may be somewhat axially offset with respect to the centre of curvature 9 of the sealing surface 8, in order to produce a definite position or the difference in inclination between these two surfaces, which has been discussed in more detail above. The offset of the centres of curvature also has a favourable effect on the positioning of the sealing ring 14 which, for the rest, can be roughly ensured with ample clearance by the co-operation of the circumferential surface 18 with the housing internal surface or by any collar surfaces provided on the sealing ring.

Behind the sealing ring 14, there is located a supporting ring 19 which has been firmly fitted into the housing part 5 and therefore acts as a rigid support for the sealing ring 14. Its entire front surface that is directed towards the sealing ring 14 is of as spherical a design as the rear surface 16 of the sealing ring. To the extent that the rear surface of the sealing ring and the front surface of the supporting ring 1 9 coincide, they form the socalled supporting surfaces, the conicity of which is of importance according to the invention. Of course, there is no need for the rear surface of the sealing ring 14 and the front surface of the supporting ring 19 to be conical in their entirety, but this is only necessary to the extent that they form the supporting surfaces.

The conicity approximated in the above example by a spherical surface 16 not only allows axially extending forces to be absorbed but also causes the sealing ring 14 to be definitely fixed in the radial direction, so that it is also possible to transmit radial forces. The installation of the sealing ring 14 is obviously without any problems whatsoever because an exact fitting of the sealing ring 14 into housing parts is not necessary.

The construction shown at the bottom of the Figure has the same adavantages, in which construction the supporting surface 21, which is jointly formed by the sealing ring 14 and the supporting ring 20, extends conically with the cone angle 22, while the spherical sealing surface 8 has a central cone angle 23. One discerns that the angle 22 is a little smaller than the angle 23, so that the wedge being formed between them exerts an inwardly acting bias on the sealing ring 14.

In contrast to the construction shown at the top, the supporting ring 20 is not rigidly fixed in the housing; on the contrary, it co-operates with the housing only through the narrow circumferential surface 24 and an elastic sealing ring 25 which lies between two front surfaces. The ring element shown in a radial section in the drawing can therefore obviously be rotated around a swivel point, whose position one can approximately indicate with the tip of the arrow 26. This arrow passes from the centre of curvature 9 approximately through the central zone of the supporting surface 21.The pivot point for the ring element shown is thus approximately concentric with this supporting surface, so that the outwardly located parts of the supporting surface approach the sealing ring or move away from it to the same extent during a rotation, so that there comes about a balanced deformation with the smallest possible stress concentrations. Should the radii of curvature of the spherical surfaces of the parts 7 and 14 not be completely identical, there therefore comes about, under the pressure exerted by the spring 13 as well as the medium pressure, a torsion of the supporting ring 20 in one direction of rotation or the other about that axis, extending parallel to the circumference, which passes through the drawing plane approximately at the tip of the arrow 26.

Radially inside the supporting ring 20 there is provided a filling ring 27, the object of which is to prevent the emergence of parts of the sealing ring 1 4 in the event of the destruction thereof. In the construction shown at the top of the Figure, this function is fulfilled by the supporting ring 19. In the construction shown at the bottom, one has, by contrast, preferred not to lengthen the supporting ring 20 to such an extent towards the socket 6, in order not to disturb the equivalency of the wings located on either side of the pivot point. Instead, the filling ring 27 has been inserted, which does not hinder the setting movement of the supporting ring 20.

Claims

1. A pipe connection between a housing (4, 5) and a socket (6) which enters the housing approximately coaxially, which connection is capable of rotary movement and which has, on the socket inside the housing, a flange-like part (7) which, with its spherical rear surface (8), is #supported on an identically spherical sealing surface (8) of a sealing ring (14) which is made of a ceramic material and whose supporting surface (16, 21) that is directed away from the sealing surface bears against a supporting surface (16, 21) which is connnected to the housing, characterised in that the supporting surfaces (16, 21) are substantially conical.

2. A pipe connection as claimed in Claim 1, characterised in that the supporting surface (16, 21) of the sealing ring (1 4) extends approximately parallel to the sealing surface (8) thereof.

3. A pipe connection as claimed in Claim 2, characterised in that the central cone angle (22) of the supporting surface (1 6, 21) is somewhat smaller than that (23) of the sealing surface (8).

4. A pipe connection as claimed in Claim 1 or 2, characterised in that the central cone angle of the supporting surface is somewhat larger than that of the sealing surface.

4. A pipe connection as claimed in Claim 1 or 2, characterised in that the central cone angle (22) of the supporting surface (16,21) is somewhatlarger than that (23) of the sealing surface (8).

5. A pipe connection as claimed in one of Claims 1 to 4, characterised in that the supporting surface (21) is conical with rectilinear generatrices.

6. A pipe connection as claimed in one of Claims 1 to 4, characterised in that the supporting surface (16) is spherical.

7. A pipe connection as claimed in Claim 6, characterised in that the radius of curvature of the supporting surface (1 6, 21) is larger than- that of the sealing surface (8).

8. A pipe connection as claimed in one of Claims 1 to 7, characterised in that the supporting surface (21) which is connected to the housing is formed by a supporting part (20) of limited resilience.

9. A pipe connection as claimed in Claim 8, characterised in that the supporting part (20) is designed as a ring which is supported on the housing.

10. A pipe connection as claimed in Claim 9, characterised in that the main extension of the supporting ring (20), as viewed in a radial section, is approximately parallel to its supporting surface (21).

11. A pipe connection as claimed in one of Claims 8 to 10, characterised in that the support (24, 25) of the supporting ring (20) is provided so as to be narrow and approximately central in relation to its configuration as shown in a radial section.

12. A pipe connection as claimed in one of Claims 1 to 11, characterised in that a filling ring (27) is provided radially within the supporting ring (20).

13. A pipe connection substantially as hereinbefore described with reference to and as illustrated in the single figure in the accompanying drawing.

New claims or amendments to claims filed on 13th April, 1981.

Superseded claims 1 to 4 New or amended claims:

1. A pipe connection between a housing and a socket arranged approximately coaxially therewith, the said connection being capable of rotary movement and comprising, on the socket and inside the housing, a flange-like part having a spherical rear surface bearing on an indentically spherical sealing surface of a ceramic sealing ring, a surface of the sealing ring remote from the said sealing surface bearing against and being located by a radially fixed supporting surface connected the housing, the said supporting surface being substantially conical.

2. A pipe connection as claimed in Claim 1 characterised in that the supporting surface of the sealing ring extends approximately parallel to the sealing surface thereof.

3. A pipe connection as claimed in Claim 2, characterised in that the central cone angle of the supporting surface is somewhat smaller than that of the sealing surface.