This invention relates to pipe seals, especially pipe seals for un pressurised joints for pipes having a preformed groove for the seal. The invention further refers to a pipe assembly comprising a pipe having a groove and the pipe seal arranged in the groove.

Pipe assemblies are known for comprising a ring-shaped elastomer seal that is located in a groove in a first pipe or pipe fitting that is to be connected with a second pipe or pipe fitting, with the seal located circumferentially between the two pipes. Generally, a pipe seal must be made within specific tolerances to fit a particular size of a pipe and a groove.

For achieving a good sealing performance, it is necessary that the seal is correctly positioned within the groove. In this case, the sealing portions of the seal properly contact both the groove of the first pipe and the outer surface of the second pipe. However, during the insertion of the second pipe into the first pipe, there is the risk that the seal is dislocated within the groove such that the sealing performance is deteriorated or completely destroyed.

Hence, it is an object of the invention to provide a pipe seal and a pipe assembly having an improved sealing performance.

The above object is solved by the pipe seal according to claim 1 and the pipe assembly according to claim 12. The dependent claims describe preferred embodiments of the invention.

A pipe seal for fitting in a groove of a first pipe to engage with a second pipe inserted in the first pipe comprises an annular carrier member and an annular sealing member attached to the carrier member. The carrier member is resiliently deformable such that the seal can be inserted into the groove preformed in the first pipe. The carrier member takes up an area in a cross- sectional view of the seal more than 20 % of the area of the seal in a cross- sectional view of the seal. A pipe seal assembly comprises a seal as described above and a pipe having an annular groove to receive the seal.

An advantage of the seal and the seal assembly is that the volume of the carrier member is increased such that the rigidity of the carrier member and, thus, of the seal is increased. Due to the increased rigidity of the seal, an unwanted dislodgement of the seal in the groove during the insertion of a second pipe into the (first) pipe can be avoided such that the seal is properly positioned within the groove. The correct positioning of the seal in the groove ensures a consistent sealing performance of the seal. In particular, leakage due to an improper insertion of the second pipe in the first pipe can be avoided.

The first pipe and the second pipe may be concentric to each other. The first pipe may be regarded as a female pipe, a pipe fitting, or a pipe having a bell end. The second pipe may be constituted by a male pipe, a pipe fitting, or spigot end. The two concentric pipes may be plastic pipes, such as PVC pipes.

However, other materials, for example ductile iron pipes can be contemplated.

The groove in the first pipe is preformed. The groove is arranged in the pipe wall of the first pipe; in particular the groove is formed by a contour of the pipe wall. For example, the pipe wall has an outer exterior surface having a shape similar to the groove, i.e. an inner surface of the pipe follows the contour of the outer surface providing a constant thickness of the pipe even at the location of the groove.

The groove may have a rectangular or triangular shape in a cross-sectional view of the groove. For example, the groove has a base wall preferably extending in the axial direction, a first side wall, and a second side wall which may extend parallel to the radial direction or inclined to the radial direction. The groove is open to an inside of the first pipe such that the seal can contact the second pipe if the second pipe is inserted into the first pipe. The seal seals an inner surface of the first pipe to an outer surface of the second pipe. The seal is an annular or ring-shaped seal; preferably the seal is uninterrupted. The seal may be called a gasket. The seal is resiliently deformable for inserting the seal into the groove. To this end, the seal is resiliently deformed, for example, by pressing diametrically opposing portions of the seal together and this deformed seal is placed below the groove. By releasing the seal, the seal returns to its original shape and is placed within the groove. The seal is held in the groove by its resilient nature; i.e. the seal needs not be otherwise fixed to the groove.

The seal may have a diameter which is adapted to the diameter of the pipe and the groove, respectively. Hence, various seals having different diameter can be employed for different pipes.

The carrier member is intended for providing the rigidity of the seal. The carrier member is, for example, made of a non-elastomeric, substantially non-flexible, or rigid material, such as plastic. In particular, the elastic modulus, the IHRD hardness, or the shore A hardness of the carrier member is greater than the corresponding hardness of the sealing member. For example, the shore A hardness of the carrier member is at least 90 or at least 100, whereas the shore A hardness of the sealing member is between 40 and 80, more preferably between 50 and 70 and most preferably about 55. The carrier member may be made of thermoplastic materials which include polyolefins, such as polyethylene or polypropylene (polyvinylchloride PVC) and like materials. Furthermore, the reinforcing member may be made from polyamide.

The sealing member is intended to provide the sealing capability of the sealing. To this end, the sealing member has a lower hardness than the carrier member, such that the sealing member can better adapt its contour to the shape of the groove. The sealing member is preferably made of an incompressible material. The sealing member may include elastomers, natural and synthetic rubbers, including, for example, SPR, EPDM, NBR, nitrile rubber, fluoroelastomers, such as perfluoroelastomers, tetrafluoroethylene-propylene rubbers (FEPM) or an elastomer sold under the name of Viton ^® . Furthermore, the sealing member may be made from thermoplastic elastomers (TPE) or thermoplastic

vulcanizates (TPV or TPE-V).

The sealing member is attached to the carrier member by various means, for example, by vulcanization, by adhesion, or by lock-fitting. The sealing member and the carrier member may be made using a 2-component moulding process. Generally, the carrier member and the sealing member can be manufactured by co-extrusion. The sealing member may be made from the same material as the carrier member, however, the rigidity differs.

A radial direction of the seal extends in a direction of the diameter the seal. A circumferential direction is perpendicular to the radial direction and extends along the circumference of the seal. An axial direction is perpendicular to both the radial direction and the circumferential direction.

The area the carrier member takes up in a cross-sectional view is preferably judged when cutting the seal along the axial direction and looking onto the seal in the circumferential direction. The carrier member takes up more than 20 %, preferably more than 30 %, further preferably more than 40 %, 50 % or 60 %, in a cross-sectional view of seal compared to the area of the seal in a cross- sectional view.

In a preferred embodiment, the radial thickness of the carrier member is between 70 % and 100 %, preferably between 70 % and 85 %, of the radial depth of the groove and/or an axial length of the carrier member is at least 30 %, preferably more than 40 %, further preferably more than 50 % or 60 %, of the axial length of the seal. The radial thickness of the carrier member is preferably measured along the radial direction. The radial thickness of the seal is preferably larger than the radial thickness of the carrier member, i.e. the sealing member has a radial thickness that is greater than the radial thickness of the carrier member. This provides a compression of the sealing member when the second pipe is inserted into the first pipe as the sealing member is compressed in the radial direction. The compression of the sealing member in the radial direction may increase the compression of the sealing member in the axial direction against an adjacent sidewall of the groove due to the rubber-like nature of the sealing member.

The axial length is preferably measured along the axial length of the seal or of the groove. For example, the carrier member and the sealing member are adjacent to each other in the axial direction. Hence, the carrier member is arranged on one side in the axial direction whereas the sealing member is arranged on the other side in the axial direction. This means that the seal has an axial length that is longer than both the axial length of the sealing member and of the carrier member.

By providing a radial thickness of the carrier member between 70 % and 100 %, the carrier member basically acts as a sidewall for the sealing member since the sealing member is hindered from expanding in a space between the groove and the carrier member. The carrier member basically restricts the axial length of the groove. Hence, the space in which the sealing member can be pressed is reduced such that the resilient force of the sealing in the radial direction generated by pressing the sealing member in the space between the groove and the carrier member is increased. The sealing member is pressed stronger against the groove which increases the area of contact between the sealing member and the groove and, thus, the sealing performance.

By providing the axial length of the carrier member of at least 30 %, the space for the sealing member limited by the carrier member and the groove is further reduced. This in turn increases the amount of which the sealing member is compressed increasing the force of which the sealing member is pressed to the groove. This also enhances the sealing performance of the seal.

In a preferred embodiment, the carrier is free from recesses that preferably extend in a circumferential direction of the seal.

The carrier member may only comprise protrusions, but no recesses. In particular, the carrier member only comprises projections that extend in a circumferential direction of the seal or, put in other words, the carrier member is free from recesses that extend in a circumferential direction of the seal. This can also be worded in that the carrier member has a surface whose second derivative on the surface does not change its sign; i.e. the curvature of the carrier member points always in the same direction. The carrier member preferably is a solid element without cavities.

The omission of recesses in the carrier member increases the rigidity of the carrier member which in turn increases the rigidity of the seal. As discussed above, the increased rigidity of the seal facilitates the correct positioning of the seal in a groove.

In a preferred embodiment, the sealing member comprises a first arm portion preferably extending in an axial direction of the seal and a second arm portion preferably being inclined to the first arm portion, wherein, further preferably, a distance between an inner exterior surface of the first arm portion adjacent to the second arm portion and an outer exterior surface of the second arm portion adjacent to the first arm portion linearly increases along the axial direction in an unmounted state of the seal.

Preferably, the sealing member mainly consists of the first arm portion and the second arm portion. The first arm portion generally extends in the axial direction, while the second arm portion is inclined to the first arm portion and/or the axial direction. In particular, the second arm portion projects radially inwards. The inner exterior surface of the first arm portion as well as the outer exterior surface of the second arm portion may extend along the complete

circumferential direction. The inner exterior surface of the first arm portion and the outer exterior surface of the second arm portion may be separated by a gap whose cross-section as seen along the circumferential direction has a triangular shape. In particular, the value of the distance measured at a first axial position between the inner exterior surface of the first arm portion and the outer exterior surface of the second arm portion divided by the value of the distance measured at a second axial direction equals a constant value irrespective of the exact position of the first and second distance.

This can be constituted by that the inner exterior surface of the first arm portion as well as the outer exterior surface of the second arm portion are not bent along the axial direction, but solely in the circumferential direction for providing the annual shape of the sealing member. For example, the inner exterior surface of the first arm portion as well as the outer exterior surface of the second arm portion may both be straight along their extension in the axial direction.

The configuration of the inner exterior surface of the first arm portion and the outer exterior surface of the second arm portion as described above has the effect that, when the second arm portion is pressed against the first arm portion due to the insertion of the second pipe into the first pipe, both the first arm portion and the second arm portion are compressed not only at certain axial position of the sealing member, but roughly all along the axial direction.

Furthermore, the compression in the radial direction is approximately constant along the axial direction. Such a constant compression along the axial direction cannot be achieved with sealing lips known from the prior art, in which the first and/or the second arm portion taper towards their free end, respectively. The provision of a roughly constant compression along the axial direction thus provides a better overall compression of the sealing member which, in turn, presses the sealing member better against the groove increasing the sealing performance. In a preferred embodiment, the second arm portion further comprises an inner exterior surface, wherein preferably, in a non-compressed state of the seal, the inner and outer exterior surfaces of the second arm portion are substantially parallel to each other.

Hence, in this embodiment, the seal as described therein differs from sealing lips of the prior art in which the seal tapers towards its free end. Here, the thickness of the second arm portion is approximately constant, which

contributes to the approximately constant compression of the sealing member, in particular the first arm portion, along the axial direction. The thickness of the second arm portion is preferably constant both along the circumferential direction and the direction of its extension.

Optionally, the first arm portion further comprises an outer exterior surface, wherein preferably the inner and outer exterior surfaces of the first arm portion are substantially parallel to each other.

In a preferred embodiment, the first arm portion and the second arm portion, in a non-compressed state of the seal, each have a radial thickness, wherein preferably the sum of the radial thickness of the first and the second arm portion is higher than the radial thickness of the carrier member. In particular, the sum of the radial thicknesses of the first and second arm portion is higher than a radial depth of the groove. This facilitates that both the first arm portion and the second arm portion are compressed in a radial direction if the second pipe is inserted into the first pipe. This compression in a radial direction may increase - due to the incompressible nature of the sealing member - the compression of the sealing member along the axial direction such that a better adaption of the sealing member against the contour of the groove can be achieved increasing the sealing performance.

The non-compressed state of the seal is a state in which the seal is not radially compressed for example by inserting the second pipe into the first pipe. The non-compressed state for example a state in which the seal has not yet been mounted to the groove or the seal is places within the groove. The latter may be called an unmounted state since the second pipe has not been inserted into the first pipe.

In a preferred embodiment, in a non-compressed state of the seal, the first arm portion juts out above the second arm portion in the axial direction.

In other words, the first arm portion is longer than the second arm portion when viewed along the radial direction. When the second arm portion is pressed against the first arm portion, the second arm portion may still be longer than the second arm portion, however, it is also possible that in this state, the first arm portion and the second arm portion have the same axial length. In the former case, only the first arm portion contacts a sidewall of the groove in a

compressed state of the sealing member, i.e. in mounted state of the seal. In the latter, both the first arm portion and the second arm portion contact the sidewall of the groove in a mounted state of the seal.

It is preferred that the second arm portion is shorter than the first arm portion such that a compensation gap between the second arm portion and the side wall of the groove is present in the compressed state of the seal. In this case, the axial and radial compression of the second arm is unlikely to press parts of the second arm portion in the gap between the first pipe and the second pipe such that the insertion of second pipe into the first pipe is not blocked by the second arm portion. Furthermore, the compensation gap provides space for the first arm portion if the first arm portion is severely compressed. In this case, due to the incompressible nature of the first arm portion, there is space for the first arm portion to evade which reduces the risk that severe compressions of the first arm portion lead to deformations of the sealing member and/ or the pipe causing leakages.

In a preferred embodiment, the first arm portion comprises at least two sealing protrusions extending in the axial direction for contacting an adjacent side wall of the groove. The two sealing protrusions preferably extend along the circumferential direction and may be spaced apart in the radial direction. The two sealing protrusions may be constituted by a circumferentially extending sealing recess on an axial side of the first arm portion. In a state, in which the seal is located in the groove, but the second pipe has not been inserted into the first pipe, only the sealing protrusions of the first arm portion may contact the sidewall of the groove. After the insertion of the second pipe into the first pipe, the area over which the sealing protrusions contact the sidewall of the groove may be increased. In particular, there may be no longer a free space between the two protrusions and the sidewall of the groove, i.e. the sealing recess between the sealing protrusions is no longer present.

Furthermore, the provision of the sealing protrusions help to position the seal within the groove since the at least two sealing protrusions can be easily bent to accommodate the seal within the groove. Furthermore, the at least two sealing protrusions provide a seat of the seal against the sidewall of the groove; in particular, a rotation of the seal can be suppressed during the insertion of the second pipe into the first pipe.

In a preferred embodiment, the first arm portion further comprises a bulge on an outer exterior surface, wherein preferably the bulge projects from the carrier member in the radial direction.

The bulge ensures that a good sealing performance is achieved between a radially outer exterior surface of the seal and a base wall of the groove. Since the bulge of the sealing member projects from the carrier member in the radial direction, it is ensured that the sealing member contacts the groove in the radial direction, in particular, it is avoided that the carrier member is the main contact between the seal and a base wall of the grove. In this unwanted situation, the radial compression would be at least partly absorbed by the carrier member. This is avoided by the provision of the bulge, such that the compression of the seal in the radial direction is mainly absorbed by the sealing member increasing pressure in the sealing members and, thus, the sealing performance. In a preferred embodiment, the seal has an axial length greater than an axial length of the groove.

In this configuration, the seal can be easily pre-positioned in the groove before the second pipe is inserted into the first pipe. Since the axial length of the seal is greater than the axial length of the groove, the seal is axially compressed when inserting the seal into the groove. This facilitates the positioning of the seal into the groove. Furthermore, the axial compression prevents the seal from dislodging during the insertion of the second pipe into the first pipe.

The carrier member preferably has a carrier protrusion for contacting a sidewall of the groove. This carrier protrusion may extend over the complete

circumferential direction or the carrier protrusion partially extends along the circumferential direction. It is preferred that the carrier member has only one carrier protrusion that contacts the adjacent. This means that the carrier member provides one point of contact for a compression of the seal in the axial direction. The provision of only one carrier protrusion simplifies the pre- positioning of the seal in the groove.

The radial thickness of the carrier member is less than 100 % of the radial thickness of the grove, while preferably the radial thickness of the sealing member is more than 100 % of the radial thickness of the groove in an unmounted state. This ensures that, when the seal is compressed by inserting the second pipe into the first pipe, the compression is solely absorbed by the sealing member, while the carrier member does not interact with the pipes in a radial direction.

In a preferred embodiment, the carrier member comprises at least a flat portion at its radial inner surface which preferably has a constant radial diameter along the axial direction, wherein further preferably a carrier projection protrudes from the flat portion and the sealing member is attached to the flat portion up to the carrier projection. The carrier projection preferably is the part of the carrier member which projects the furthest inwards in the radial direction. The carrier projection and the flat portion may form a step. The sealing member is attached to the flat portion of the carrier member, and, preferably, to a side of the carrier projection. This increases the area over which the sealing member is attached to the carrier member such that the attachment of the sealing member to the carrier member is reinforced. In particular, the sealing member protrudes from the carrier projection inwards in the radial direction.

The invention will now be described by way of example with reference to the accompanying drawings.

Fig. 1 shows one half of a cross-sectional view of a pipe assembly in an

unmounted state;

Fig. 2 shows an enlarged portion of the pipe assembly of Fig. 1 , however, in a mounted state of the seal;

Fig. 3a shows a view of the seal of the pipe assembly according to Figs. 1 and

2 in a view along the axial direction;

Fig. 3b shows a cross-sectional view of the seal of Fig. 3a along the line A-A;

and

Fig. 3c shows an enlarged cross-sectional view of the seal as indicated in Fig.

3b.

A pipe assembly 10 comprises a first pipe 12, a second pipe 14 and a seal 16. The first pipe 12 and the second pipe 14 may be plastic pipes, for example, made from PVC. The first pipe 12 may be a bell end of a female pipe. The first pipe 12 comprises a groove 18 which has an approximately rectangular cross- section as viewed along a circumferential direction CD, i.e. a direction along the seal 16 and the groove 18, respectively. However, the groove 18 may have a triangular shape in a cross-sectional view. The groove 18 is constituted by a pipe wall of the first pipe 12 and is preformed in the first pipe 12. The circumferential direction CD is perpendicular to a radial direction RD and an axial direction AD, both with reference to the first pipe 12, the second pipe 14 and the seal 16, respectively.

The groove 18 has a base wall 20, a first sidewall 22 and a second sidewall 24. The groove 18 has a groove depth GD along the radial direction RD. The groove depth GD is smaller than a radial thickness RT of the seal 16 in a non- compressed state of the seal 16, i.e. a state in which the second pipe 14 has not been inserted into the first pipe 12, as shown in Fig. 1 . The compressed state of the seal 16 is shown in Fig. 2.

The second pipe 14 may be a male pipe or spigot that can be inserted into the first pipe 12. This means the second pipe 14 has an outer diameter that is smaller than an inner diameter of the first pipe 12.

As also seen in Figs. 3a to 3c, the seal 16 has a carrier member 26 and a sealing member 28. The carrier member 26 has a higher rigidity compared to the sealing member 28. The carrier member 26 is resiliently deformable and may be made form a thermoplastic material, such as PVC. The carrier member 26 takes up an area of the seal 16 in a cross-sectional view of the seal 16, for example, along the circumferential direction CD, as seen in Figs. 1 and 2, that is more than 30 % of the area of the seal 16 in a cross-sectional view of the seal 16. Furthermore, the carrier member 26 has a radial thickness RT between 70 % and 100 % of the groove depth GD. Furthermore, an axial length AL of the seal 16 is longer than an axial length AL of the groove 18. The axial length AL of the carrier member 26 is at least 30 % of the axial length AL of the seal 16.

The carrier member 26 comprises one circumferentially extending carrier protrusion 30 for contacting the first sidewall 22 of the groove 18. Furthermore, the carrier member 26 comprises a flat portion 32 from which a carrier projection 34 protrudes radially inwards. The sealing member 28 contacts the carrier member 26 along the flat portion 32 up to the carrier projection 38. Both the flat portion 32 and the carrier projection 34 extend along the circumferential direction CD. The sealing member 28 is made of an incompressible material, such as rubber, and comprises a first arm portion 36 that extends along the axial direction AD and a second arm portion 38 that is inclined to the first arm portion 36. The first arm portion 36 comprises two sealing protrusions 40 that contact the second sidewall 24 of the groove 18. The sealing protrusions 40 completely extend along the circumferential direction CD. The sealing protrusions 40 are formed by a circumferentially extending recess in a sidewall of the first arm portion 36.

The first arm portion 36 may further comprises a bulge 42 which projects from the carrier member 26 in the radial direction RD outwards such that the bulge 42 contacts the base wall 20 of the groove 18.

The first arm portion 36 has an outer exterior surface 44 and an inner exterior surface 46. The outer exterior surface 44 and the inner exterior surface 46 of the first arm portion 36 are at least partially parallel to each other. This means that the thickness of the first arm portion 36 is approximately constant except for the bulge 42.

The second arm portion 38 also has an outer exterior surface 48 and an inner exterior surface 50. The outer exterior surface 48 and the inner exterior surface 50 of the second arm portion 38 are also approximately parallel to each other.

The distance between the inner exterior surface 46 of the first arm portion 36 and the outer exterior surface 48 of the second arm portion 38 linearly increases along the axial direction AD in a non-compressed state of the seal 16 (see Fig. 1 ). The sum of the radial thicknesses RT of the first arm portion 36 and the second arm portion 38 is higher than a radial thickness RT of the carrier member 26 and in particular higher than the groove depth GD of the groove 18.

As seen from Figs. 1 and 2, the first arm portion 36 is longer in the axial direction AD than the second arm portion 38 providing a compensation gap 39 between the second arm portion 38 and the second side wall 24 of the groove 18 in the compressed state of the seal 16. In this case, the axial and radial compression of the second arm 38 is unlikely to press parts of the second arm portion 38 in the gap between the first pipe 12 and the second pipe 14 such that the insertion of second pipe 14 into the first pipe 12 is not jammed.

Furthermore, the compensation gap 39 provides space for the first arm portion 36 if the first arm portion 36 is severely compressed. In this case, due to the incompressible nature of the first arm portion 36, there is space for the first arm portion 36 to evade which reduces the risk that severe compressions of the first arm portion 36 lead to deformations of the sealing member 28 and/ or the pipe 12, 14 causing leakages.

The functioning of the seal 16 is as follows:

The seal 16 is bent such that the seal 16 can be inserted into the first pipe 12. Under the groove 18, the bending force is released such that the seal 16 is located in the groove 18 due to the resilient force of the carrier member 26. Since the axial length AL of the seal 16 is greater than the axial length AL of the groove 18, the seal 16 is axially compressed. This ensures that the seal 16 can be pre-positioned within the groove 18, i.e. the seal 16 is less likely to move once it is located within the groove 18. For the pre-positioning of the seal 16, the provision of only one carrier protrusion 30 and two sealing projections 40 help to achieve a good pre-positioning of the seal 16 within the groove 18.

Furthermore, since the volume of the carrier member 26 compared to the volume of the seal 16 is relatively high, the rigidity of the carrier member 26 is increased. This also helps to pre-position the seal 16 within the groove 18.

After the pre-positioning of the seal 16 within the groove 18, the second pipe 14 is inserted into the first pipe 12. Since the seal 16 has a greater radial thickness RT than the groove 18, the seal 16 is compressed in the radial direction RD. In particular, due to the configuration of the sealing member 28, only the sealing member 28 is radially compressed; in particular, the bulge 42, the first arm portion 36, and the second arm portion 38 are radially compressed. This increases the compression force within the sealing member 28.

Furthermore, due to the configuration of the first arm portion 36 and the second arm portion 38, the radial compression is roughly constant along the axial direction AD of the sealing member 38. Due to the large volume of the carrier member 26 compared to the overall volume of the seal 16, the space for the sealing member 28 within the groove 18 is reduced. Hence, the sealing member 28 is further compressed. All these aspects contribute that the sealing member 28 is strongly pressed against the base wall 20 and - due to the incompressible nature of the sealing member 28 - the second sidewall 24 of the groove 18 resulting in a good sealing performance.

Furthermore, due to the high rigidity of the carrier member 26, the likelihood of a dislodgement of the seal 16 during the insertion of the second pipe 14 into the first pipe 12 is reduced.

List of reference signs

10 pipe assembly

12 first pipe

14 second pipe

16 seal

18 groove

20 base wall

22 first sidewall

24 second sidewall

26 carrier member

28 sealing member

30 carrier protrusion

32 flat portion

34 carrier projection

36 first arm portion

38 second arm portion

39 compensation gap

40 sealing protrusion

42 bulge

44 outer exterior surface (of the first arm portion)

46 inner exterior surface (of the first arm portion)

48 outer exterior surface (of the second arm portion)

50 inner exterior surface (of the second arm portion)

AD axial direction

AL axial length

CD circumferential direction

GD groove depth

RD radial direction

RT radial thickness