GB2052661A

GB2052661A - Pipe Sealing Device

Info

Publication number: GB2052661A
Application number: GB7922347A
Authority: GB
Original assignee: Forsheda Gummifabrik AB
Current assignee: Forsheda Gummifabrik AB
Priority date: 1979-06-27
Filing date: 1979-06-27
Publication date: 1981-01-28
Also published as: GB2052661B

Abstract

A resiliently deformable sealing ring in an annular groove in an outer pipe 6 has a sealing portion 14 for engaging an inner pipe 7. A semi-rigid or rigid plastics or metal retainer ring 10 cooperates with a projection 11 of the ring in order to retain the ring in position during insertion of the inner pipe 7. <IMAGE>

Description

SPECIFICATION Pipe Sealing Device The present invention relates to a sealing device comprising a sealing ring consisting of an elastic material and also comprising means for retaining the sealing ring in a groove in a pipe especially during the mounting of the pipe joint.

In joining different types of pipes and especially pipes consisting of plastics material and adapted to constitute water pipes, which must be able to stand substantial internal overpressures but also lower external pressures, it is preferred to position the sealing rings for sealing the pipe joints in the grooves for retaining the sealing ring already during manufacturing of the pipes. However, it has been difficult to provide for secure retention of the pre-mounted sealing rings during the transport and handling of the pipes with the sealing rings mounted therein. The problem of retaining the sealing rings during the jointing of the pipes is further emphasised in the case where the grooves have a bottom surface which is at least partly of a rounded shape.Radially directed forces can create substantial twisting forces within the sealing rings, which thereby can be placed in a position wherein they are not able to satisfy the intended sealing function.

As the type of pipe for which the present sealing device is especially intended are often used for outdoor water pipes it has also been a problem to maintain the end portion of the pipe which is to be introduced in a sealing ring clean from dirt and foreign matter, especially as the mounting work must often take place outdoors under adverse conditions. This has meant that foreign matter is introduced into the inner pipe and into the sealing ring, which has often caused leakage at the joint.

The present invention provides a sealing device comprising a sealing ring consisting of an elastic material and adapted to be positioned in an annular groove in an outer pipe and having a sealing portion adapted sealingly to engage an inner pipe introduced into the outer pipe and the sealing ring, said sealing ring having in addition to said sealing portion an inwards directed annular projection, and comprising a retainer ring which is adapted to cooperate with said projection in order to retain said sealing ring in a correct position in the groove especially during the introduction of the end portion of the inner pipe into the sealing ring.

In order to obstruct twisting of the sealing ring in the groove in the outer pipe when the inner pipe is introduced in and deforms the sealing portion of the sealing ring, it is preferred that the said projection is positioned immediately in front of the retainer ring in the direction of the movement of the inner pipe when providing the joint the sealing portion being positioned behind the retainer ring.

In a preferred embodiment of the invention the said projection has an entry surface converging in the direction of introduction of the inner pipe and a surface positioned in a radial plane facing the retainer ring so that the projection is folded over the retainer ring and presses the ring radially outwards when the projection is subjected to the action of the end portion of the inner pipe.

The invention is described in the following, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a section through a sealing device; Figure 2 is a section through the device positioned in an internal groove in an outer pipe before the mounting of a pipe joint; Figure 3 is a section corresponding to Figure 2 during mounting; and Figure 4 is a section corresponding to Figures 2 and 3 after the mounting of the joint.

The sealing device is especially intended to be used in connection with water pipes manufactured from plastics and formed with standardized internal grooves for receiving sealing rings. Pipes of this type can for example have a diameter of 1 50 mm and be subjected to an inner pressure of up to 10 kp/cm2 (1 MPa). Pipes of this type are often placed outdoors, for which reason the jointing of the pipes often provides problems with regard to pollution of the joint areas and the sealing rings thereof. Additionally the standardization of the pipes and the grooves therein provide that the shape and dimensions of the grooves are predetermined and cannot be changed.

The type of groove which is used for receiving sealing rings (of rubber or other resiliently deformable material) for pipes of the above type has a bottom surface whose cross-section is defined by a substantially arcuate portion and a substantially straight portion which faces the adjacent opening of the pipe. Thus, the groove has a portion widening from the opening of the pipe, the said portion being connected with a substantially cylindrical bottom portion in turn terminating in a relatively obtuse conical converging portion. This shape of the groove provides that a sealing ring adapted to be mounted therein must have an outer surface whose cross-section is defined by a straight portion 1 which is inclined in relation to the axis of the pipe, an arcuate portion 2, and a further, inclined portion 3 connected therewith.These surface portions 1, 2, and 3 define, between themselves and radially inwardly therefrom, the main portion 4 of the sealing ring, the body portion 4 being received in a groove in an outer pipe 6, the inner surface of the pipe being designated by means of line 5 in Figure 1 and the axis being defined by means of line 8 in all the Figures.

As appears from Figure 1, there is a substantially U-shaped groove 9 in the main portion 4 of the sealing ring. The groove 9 receives a retainer ring 10 which is manufactured from a semi-rigid or rigid plastics material or metal and can be provided with an axially extending slot (not shown). As appears from the drawings, the retainer ring 10 is positioned radially outside the inner surface 5 of the outer pipe 6, which provides that the retainer ring does not have any influence on the possibility of introducing an end portion of an inner pipe 7 in the sealing ring. The retaining ring 10 has the object of firmly retaining the sealing ring in the groove in the outer pipe 6 from the time of mounting of the sealing ring until the pipe shall be jointed at the place where it is to be used.

Besides, the retainer ring 10 has the object of making sure that the sealing ring is retained in the intended position in the groove by cooperating with other portions of the sealing ring. A radially inwardly directed projection 1 1 is provided on the main portion of the sealing ring for cooperation with the retainer ring 10 during mounting. The projection is defined by a radially extending annular surface 12 which defines the projection 1 1 in the direction of the retainer ring 10. In the opposite direction the projection 11 is defined by a substantially conical entry surface, which is convergent in the direction of introduction of the inner pipe 7.

When designing sealing rings of this type it is important that the deformation length is as long as possible for the portion of the sealing ring that is deformed for engaging the inner pipe and sealing thereagainst For this reason the sealing ring has a sealing portion 6which in the axial direction of the sealing ring is provided within the area where the main portion 4 of the sealing ring has as great a radial dimension as possible. This means that the sealing portion 14 is positioned at the inner portion of the sealing ring, where the main portion 4 is outwardly restricted by the inclined surface portion 3 and the arcuate surface portion 2.In the embodiment shown in the drawings the sealing portion 14 is a combination of a sealing lip and a compression portion, which provides that the sealing portion 14, during the mounting of the joint is deformed in such a way that a substantial sealing pressure is created by the deformation but also in such a way that an inner overpressure in the jointed pipes 6, 7 additionally increases the sealing pressure. Thus, the sealing portion 14 has, like the projection 1 1, a substantially conical surface 15 converging in the direction of the introduction of the inner pipe 7 and a substantially radially directed surface 16.

The design of the sealing portion 14 as described above guarantees very effective and (in all positions) sufficient sealing against the inner pipe 7. In order to provide for additional security against leakage from the interior of the pipes to the environment through a gap between the bottom of the groove in the outer pipe 6 and the main portion 4 of the sealing ring, the main portion 4 is provided with an additional sealing projection 17 which, during the existence of an overpressure, works as a lip seal and seals against a surface portion of the groove corresponding to the inclined surface portion 3 of the main portion of the sealing ring.

However, the above-mentioned position of the sealing portion 14 with regard to the desired, long radial compression is not quite without problems.

When the inner pipe 7 is introduced through the sealing ring 14, deformation of the sealing ring 14 will of course take place, a great radial component force being exerted on the sealing ring. As this component force will be transferred substantially to the portion of the groove, which is defined by surfaces corresponding to the inclined portion 3 of the main portion of the sealing ring these radial forces will provide a great twisting moment on the sealing ring in the counterclockwise direction as the sealing ring is shown in Figure 1.

If this twisting moment is not counter-acted the right end of the sealing ring as viewed in Figure 1 is raised from the groove, so that the sealing ring does not take the intended position after the introduction of the inner pipe 7. This problem is obviated as follows. Figures 2-4 schematically show the jointing procedure of a pipe joint.Figure 2 is a section through the sealing ring, the outer pipe 6 and the inner pipe 7, the axis of the outer pipe 6 being schematically shown by means of the dot and dash line 8 and the direction of introduction of the inner pipe being schematically shown by means of the arrow 18. In Figure 3 the inner pipe 7 has been introduced into the sealing ring and the outer pipe 6 so far that the projection 1 1 has been deformed so that substantially the whole of its annular surface 12 (Figure 1) engages the inner surface of the retainer ring 10.This action has taken place during centering of the inner pipe 7 because of the conical shape of the entry surface 13 of the projection 11, whereby also dirt or pollution on the outer surface of the inner pipe 7 has been wiped off by the projection 11 , so that such foreign matter cannot enter the sealing ring itself.

As appears from the drawings the radial dimension of the projection 11 as well as of the part of the main portion 4 of the sealing ring adjacent to the projection is relatively small, in turn providing that the contact between the projection 1 1 and the inner pipe 7 is relatively rigid. This means that the part of the main portion 4 which is outwards restricted by the inclined surface portion 1 is firmly pressed against the corresponding surface portion of the groove for receiving the sealing ring, whereby the whole sealing ring is securely maintained in the correct position when the phase of the mounting procedure requiring the exertion of a substantial force takes place. The relative dimensioning of the projection 11 in the radial direction and the differences between the diameters of the pipes 6 and 7 is chosen in such a way that the radial force created by the deformation of the projection 1 1 in relation to the inclination angle of the inclined surface portion 1 does not provide the sealing ring with any clockwise directed twisting moment which has to be considered in this connection.

Furthermore, the axial displacement of the projection 1 1 to engagement with the retainer ring 10 provides that the radial force is also transferred to the retainer ring, whereby the ring is securely maintained in its correct position.

When the introduction of the inner pipe 7 is continued its end 20 will engage the conical surface 15 of the sealing portion 14, the sealing portion 14 being thereby deformed from the position according to Figures 2 and 3 to the position according to Figure 4, wherein the sealing portion 14 is substantially deformed.

Thereby the sealing portion 14 will be folded inwards in the direction of the arrow 18 and the sealing portion 14 will also be compressed so that the space 1 9 between the radial surface 16 of the sealing portion 14 and the additional sealing lip 17 will be quite or partly filled. It appears from the drawings, that the deformation of the sealing portion 14 thereby taking place is substantial, in turn providing that the above mentioned radial forces against the inclined surface portion of the groove corresponding to the inclined surface portion 3 of the main portion 4 can be substantial.

However, this does not include any twisting risk and thereby no displacement risk, as the main portion 4 is securely fixed in the correct position because of the relatively rigid engagement between the projection 1 1 and the inner pipe 7.

The invention can be modified within the scope of the following claims. Thus, it is possible that the annular substantially radially directed surface 1 2 of the projection 1 1 might instead be more or less parallel with the entry surface 13 of the projection 1 1, so that the projection can already before the introduction of the end portion 1 7 of the inner pipe 7 extend across the retainer ring 10. A corresponding modification of the design of the sealing portion 14 is of course also possible, the sealing portion 14 thereby being more or less a lip seal.

Of course, it is possible to apply the invention to other types of sealing rings having an outer surface which is not predetermined by the design of a standardized groove in the pipe, where the sealing ring is to be placed.

Claims

1. A pipe sealing device comprising a sealing ring manufactured from resiliently deformable material and positioned in an annular groove in an outer pipe and having a sealing portion adapted sealingly to engage an inner pipe introduced therein, and further comprising a retainer ring manufactured from a semi-rigid or rigid material and adapted to cooperate with a radially inwardly extending projection of the sealing ring for retaining the ring in position in the groove during the introduction of the end portion of the inner pipe into the sealing ring to an engaging position wherein the end portion deforms the sealing portion.

2. A device as claimed in claim 1, wherein the projection is positioned immediately in front of the retainer ring in the direction of introduction of the inner pipe and the sealing ring is positioned behind the retainer ring.

3. A device as claimed in claim 1 or 2, wherein the projection has an entry surface turned away from the retainer ring and converging in the direction of introduction of the inner pipe and a surface positioned substantially in a radial plane and facing the retainer ring, so that the projection is folded over the retainer ring and presses the ring radially outwards when the projection is acted on by the end portion of the inner pipe.

4. A pipe sealing device substantially as described with reference to, and as shown in, the accompanying drawings.