DK180415B1

DK180415B1 - A union for connecting pipes

Info

Publication number: DK180415B1
Application number: DKPA201870233A
Authority: DK
Inventors: Henriksen Jørgen
Original assignee: Jh Consulting V/Joergen Henriksen
Priority date: 2018-04-18
Filing date: 2018-04-18
Publication date: 2021-04-22
Also published as: DK201870233A1

Abstract

The present invention relates to a type of union mainly used for joining stainless steel pipes. The union is preferably designed in such a way that it has no horizontal surfaces or cavities having a horizontal opening whether it is installed in a vertical or horizontal pipeline. This design ensures that no water remains on the surface after cleaning has taken place

Description

DK 180415 B1 1

A UNION FOR CONNECTING PIPES

FIELD OF THE INVENTION The present invention relates to a type of union mainly used for joining stainless steel pipes. The union is preferably designed in such a way that it has no horizontal surfaces or cavities having a horizontal opening whether it is installed in a vertical or horizontal pipeline. This design ensures that no water remains on the surface after cleaning has taken place

BACKGROUND OF THE INVENTION Ever since welding of stainless steel became possible the design of unions for joining the stainless steel pipes has followed the same trend. A welding liner placed against a welding male part pressed together by an external female nut.

WO2014152139A1 discloses another fitting in the form of a sanitary fitting for biopharmaceutical equipment. The disclosed sanitary fitting includes an elongate tubular insert having a main tubular section, which is cylindrical and terminates at an annular flange or annulus which seats at a bottom of a socket in an equipment housing. The bottom face of the annulus includes a groove, which receives a gasket that is compressed between the annulus and bottom face of the socket to prevent entry of fluids into this space. A threaded section of the socket is spaced outwardly of the smooth surfaced fitting so as to receive a threaded nut within such space. A threaded nut is slid down the fitting and engaged with the socket threads wherein the nut drives the socket into and retains the fitting tightly within the socket. Common for all the standards is that the units are suitable for installation in horizontal pipelines, but if installed in vertical pipelines some water will remain in the cavities e.g. between the nut and the welding liner/welding male part after cleaning. Thus, although great care is taken to clean the units, experience has shown that the known units are prone to accumulate dirt wherein bacteria can grow, often resulting in contamination in dairy installations where for instance milk and other components are dosed in open containers prior to sealing such containers.

DK 180415 B1 2 In most up to date food factories processing takes place in ultra clean rooms, and in such rooms it is not acceptable to have water or dirt remaining on part of the equipment thus creating a source for bacteria growth.

Hence, an improved union would be advantageous, and in particular a more efficient and/or reliable union would be advantageous.

OBJECT OF THE INVENTION An object of the present invention is to provide an alternative to the prior art. In particular, it may be seen as a further object of the present invention to provide a unioin that solves the above mentioned problems of the prior art with respect to water and/or dirt accumulation.

SUMMARY OF THE INVENTION Thus, the above described object and several other objects are intended to be obtained in a first aspect of the invention by providing a union according to claim

1. By "measured outside the flange” is typically meant the part of the flange 11 extending axially away from the flange and to which the pipe is to be welded (e.g. as illustrated in fig. 1). Further embodiments and aspects of the invention are presented in the following as well as in the accompanying claims.

BRIEF DESCRIPTION OF THE FIGURES The figures show ways of implementing the present invention and are not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set. The dimensions indicated in the figures are not to be construed as limiting the scope of the invention.

DK 180415 B1 3 Fig. 1 is a schematical illustration of a union useful in connection with the invention, and Fig. 2 is a schematical illustration of a union useful in connection with the invention.

Fig. 3 is a schematical illustration of a union useful in connection with the invention.

Fig. 4 is a schematical illustration of a device useful in connection with the invention. Fig. 5 is a schematical illustration of a dovetail groove, which is a preferred shape of the longitudinally extending grooves.

Fig. 6 is an illustration of of a female part useful in connection with the invention which has a protrusion on an inner end surface. Fig. 7 is an illustration of a male part useful in connection with the invention which has a protrusion on a inner surface of the male part, which clamps the end tubular seal, when the male part is screwed into the female part. Fig. 8 is an illustration of a welding liner useful in connection with the invention which has a protrusion on the outwardly protruding flange.

Figs. 9-11 illustrates the features disclosed in figs. 6-8. Fig. 12 is an illustration of a male part useful in connection with the invention which has a protrusion on a inner surface of the male part and where the inner end surface has a mechanical stop having an abutment surface. Figs. 13 and 14 is an illustration of an inner end surface useful in connection with the invention which has a mechanical stop having an abutment surface.

DK 180415 B1 4 Fig. 15 is an illustration of a male part useful in connection with the invention which has a mechanical stop having an abutment surface allowing the flange to abut against the mechanical stop. Fig. 16 is an illustration of an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS A first union useful in connection with the invention can be seen in fig. 1, where 1 is the welding liner, 2 is the female part and 3 is the male part pressing 1 and 2 together when the male part 3 is screwed into the female part 2. In fig. 1 and 2, the numbers 4, 5 and 6 denote rubber gaskets as will be elucidated below.

Fig. 1 shows in detail, a union useful in connection with the invention; it is noted thatthe upper part of fig. 1 (as well as in fig. 2 and 3) illustrates the union with a cutaway to reveal the interior of the union illustrated by cross-hatching. The following description covers both the unions shown in fig. 1 and 2 if not otherwise stated.

The union in fig. 1 comprises a female part 2 in the form of a tubular element having an inner diameter D1. The outer end 18 of the female part 2 is for being welded to a pipe to be united with the union. By “a pipe to be united with the union” is typically meant that the pipe is to be united with another pipe by use of the union. The female part 2 has an annular outer end surface 7 (distant to the outer end 18), an annular inner end surface 9 and an inner recessed section 8 extending from the outer end surface 7 to the inner end surface 9. As will be disclosed below, the inner end surface 9 is designed to form a sealing surface. The female part 2 further comprises an internal thread 10 provided in at least a part the wall of the inner recessed section 8.

The union also comprises a tubular welding liner 1 being a separate part of the union and is for being welded to another pipe to be united the union. The welding liner has an inner diameter being at least substantially equal to the inner diameter D1 of the female part 2 and comprises at one end an outwardly protruding flange 11, preferably having a constant outer diameter, extending through-out the

DK 180415 B1 circumference of the welding liner 1. This flange 11 cooperates with the inner end surface to form a seal (with a seal clamped in between as disclosed below). The outer geometry of the flange 11 mate the internal geometry of the recess at 5 the inner end surface 9 so as to provide for the tubular welding liner 1 to be accommodated in a snug-fit in the inner recessed section 8 with a centre axis of the tubular welding liner 1 aligned with a centre axis of the female part 2. By snug-fit is preferably meant that the flange 11 may be introduced into the female part 2 without the need for altering mechanically the flange 11 while at the same time being kept in a fixed position relatively to the female part 2 to align the centre axes of the female part 2 and the welding liner 1.

To provide a fluid tight seal, the union has an inner tubular seal 4, being a separate part, having an inner diameter being at least substantially equal to the inner diameter D1 of the female part 2, and an outer geometry allowing arrangement of the inner tubular seal 4 to abut said inner end surface 9 of the female part 2 and an end surface of the welding liner 1. The seal 4 is preferably made from a resilient material, such as rubber.

The union further comprises a male part 3, being a separate part, having an internal diameter being larger than an outer diameter, measured outside the flange 11, of the welding liner 1 to allow the pipe to be welded to the welding liner 1 to extend within the male part 3. By “measure outside the flange 11” is typically meant the part of the flange 11 extending axially away from the flange and to which the pipe is to be welded (as illustrated in fig. 1). The male part 3 has an external thread 23 provided along a section of the male part 3. The external thread 23 is configured to cooperate with the internal thread 10 on the female part 2 to screw the male part 3 into the female part 2 and to clamp the flange 11 of the welding liner 1 and the inner tubular seal 4 in-between the inner end surface 9 of the female part 2 and an end surface of the male part 3.

As can be seen from figs. 1 and 2, water will drain from the surface of the assembled unions, whether the union is installed in a vertical or horizontal pipeline.

DK 180415 B1 6 A further advantage by the design shown is that by using the male part for fastening instead of the female nut, the outer dimensions of the union can be reduced considerably compared to the dimensions of the conventional unions. This naturally reduces material cost as well as manufacturing cost.

In the dairy industry sterile products are becoming more and more popular, the union according to the invention is well suited for aseptic production as the inner surface of the rubber gasket (seal) item 4 in figs. 1, 2 and 3 is provided to be flush with the inner dimension of the pipeline.

Herein, the term “flush” is typically used to mean that two or more surface are dimensioned or arranged so that the presence of cavities is aimed at being avoided - ideally - providing a seamless connection between two or more parts. Ideally refers to the production accuracy often setting a limit for when something is categorized as seamless.

Herein, the term "during use” is used frequently and is typically intended to mean the situation where the union is assembled to unite two pipes.

The male part 3 may preferably have a ring shaped section 12 defining an annular surface 13 facing, during use, the annular end surface 7 of the female part 2. This, ring shaped section 12, may advantageously be occupied by an outer tubular seal 6 being clamped, during use, in-between the annular surface 13 of the male part 3 and the outer end surface 7 of the female part 2. Also this seal 6 may preferably be made from a resilient material, such as rubber. The seal 6 is preferably shaped so that the transition between the male part and female part is flush.

A section of the female part 2 extending from the outer end surface 7 and the ring shaped section of the male part 3 both have an outer cylindrical shape with at least substantially the same diameter, and the outer diameter of the outer tubular seal 6 is at least substantially equal to the diameter of said outer cylindrical shape, typically measured when the outer tubular seal 6 is being clamped. This is intended to provide a seamless transition between the female and male parts 2, 3 ofthe union as seen from the outside of the union.

DK 180415 B1 7 To prevent liquid — or in general dirt — from entering into the union along the pipe being welded to the welding line 1, the union may further comprise an end tubular seal 5 arranged to create a seal between an outer surface of a pipe extending inside the male part 3 and an inner surface of the male part 3. Such an end tubular seal 5 is typically configured by its shape to provide a flush transition between the male part 3 and the outer surface of the pipe. The seal 5 may preferably be made from a resilient material, such as rubber.

Reference is now made specifically to fig. 1 illustrating the end tubular seal 5 which has an L-shaped cross section. The male part 3 comprises an inner groove 14 configured for receiving a section of the end tubular seal 5 - as illustrated the inner groove 14 receives the outwardly protruding part of the tubular seal 5.

Reference is now made specifically to fig. 2 illustrating the end tubular seal 5 cylindrically extending internally in the male part 3, during use, from an end surface 15 of the male part 3. The opening in the male part distant from the threaded section may be tapered (with the least diameter at the outer most position of the opening) to producing a clamping action to clamp the tubular seal 5 in-between the male part 3 and the pipe welded to the welding liner 1.

To allow a tool to grip on the male part 3 to ease assembly, the male part 3 comprises longitudinally extending grooves 16.

While such longitudinally extending grooves 16 may accumulate water and/or dirt depending on the orientation in which the union is installed, the male part 3 may be provided with a circular extending groove 17, preferably being arranged so that each of the longitudinal extending grooves 16 opens into the circular extending groove 17, preferably the depth of the circular extending groove 17 is bigger than or equal to the depth of the longitudinal extending grooves 16. As illustrated, such a circular extending groove 17 is typically wedge-shaped which further reduces the risk that water and/or dirt accumulates on the union.

Grooves like 16 and 17 may also be provided to the female part 2.

DK 180415 B1 8 With reference to figs. 12, 13 and 14, the inner end surface 9 may preferably comprise a mechanical stop 25 comprising an abutment surface allowing the flange 11 to abut against the mechanical stop 25. When the union is assembled, an abutment surface of the mechanical stop 25 and the flange 11 are pressed together, creating a space between part of the flange 11 and part of the inner end surface 9. The space created between part of the flange 11 and part of the inner end surface 9, ensures that the inner tubular seal 4 cannot be compressed to such a degree that its ability to function as a seal is compromised. A third union useful in connection with the invention can be seen in fig. 3, where 1 is the welding liner, 2 the female part and 3 is the male part. The female part press 1 and 3 together when the female part 2 is screwed on to the male part 3.

In fig. 3 the numbers 4, 5 and 6 denote rubber gaskets as will be further elaborated below. Fig. 3 shows in details a union useful in connection with the invention. As in fig. 1 and 2, the upper part of fig. 3 illustrates the union with a cutaway to reveal the interior of the union illustrated by cross-hatching. The union in fig. 3 comprises a female part 2 in the form of a tubular element having an annular outer end surface 7, which is designed to form a sealing surface as will be disclosed below. The female part 2 also has an annular inner end surface 9 and an inner recessed section 8, which extends from the outer end surface 7 to the inner end surface 9. Further, the female part 2 has an internal thread 10 provided in at least a part of the wall of the inner recessed section 8. The union also comprises a tubular welding liner 1 with an inner diameter D1. The tubular welding liner 1 is a separate part of the union and is meant to be welded to a pipe to be united by use of the union. The tubular welding liner 1 has at one end an outwardly protruding flange 11, preferably having a constant outer diameter, extending through-out the circumference of the welding liner 1.

DK 180415 B1 9 The outer geometry of the flange 11 mate the internal geometry of the recess at the inner end surface 9 such that the tubular welding liner 1 can be accommodated in a snug-fit in the inner recessed section 8 with a centre axis of the tubular welding liner 1 aligned with a centre axis of the female part 2. By snug-fit is preferably meant that the flange 11 may be introduced into the female part without the need for altering mechanically the flange 11 while at the same time being kept in a fixed position relatively to the female part 2 to align the centre axes of the female part 2 and the welding liner 1.

To provide a fluid tight seal, the union has an inner tubular seal 4 with an inner diameter that is at least substantially equal to the inner diameter D1 of the welding liner 1, and an outer geometry allowing arrangement of the inner tubular seal 4 to abut said flange 11. The seal 4 is preferably made from a resilient material, such as rubber.

The union further comprises a male part 3, being a separate part, having an internal diameter at least substantially equal to the inner diameter D1 of the welding liner 1. The outer end 22 of the male part 3 is meant to be welded to a pipe that is to be united with another pipe by use of the union. The male part 3 has an external thread 23 provided along a section of the male part 3, which external thread 23 is configured to cooperate with the internal thread 10 on the female part to screw the male part into the female part and to clamp the flange 11 of the welding liner 1 and the inner tubular seal 4 in-between the inner end surface 9 of the female part and an end surface of the male part 3.

The male part 3 may preferably have a ring shaped section 12 defining an annular surface 13 facing, during use, the annular end surface 7 of the female part 2. This ring shaped section 12 may advantageously be occupied by an outer tubular seal 6 being clamped, during use, in-between the annular surface 13 of the male part 3 and the outer end surface 7 of the female part 2. The seal 6 may preferably be made from a resilient material, such as rubber, and is preferably shaped so that the transition between the male part 3 and female part 2 is flush.

A section of the female part 2 extending from the outer end surface 7 and the ring shaped section of the male part 3 both have an outer cylindrical shape with at

DK 180415 B1 10 least substantially the same diameter, and the outer diameter of the outer tubular seal 6 is at least substantially equal to the diameter of said outer cylindrical shape, typically measured when the outer tubular seal 6 being clamped. This is intended to provide a seamless transition between the female and male parts 2, 3 ofthe union as seen from the outside of the union.

To prevent liquid — or in general dirt — from entering into the union along the pipe being welded to the welding line 1, the union may further comprise an end tubular seal 5 arranged to seal between an outer surface of the welding liner 1 extending inside the female part 2 and an inner surface of the female part 2. Such an end tubular seal 5 is typically configured to provide a flush transition between the female part 2 and the outer surface of the pipe. The end tubular seal 5 may preferably have an L-shaped cross section and the welding liner 1 may preferably comprise an inner groove 14 configured for receiving a section of the end tubular seal 5 - as illustrated in fig. 3 the inner groove 14 receives the outwardly protruding part of the tubular seal 5. The seal 5 may preferably be made from a resilient material, such as rubber.

To allow a tool to grip on the female part to ease assembly, the female part 2 comprises longitudinally extending grooves 16. While such longitudinally extending grooves 16 may accumulate water and/or dirt depending on the orientation in which the union is installed, the female part 2 may be provided with a circular extending groove 17, preferably being arranged so that each of the longitudinal extending grooves 16 opens into the circular extending groove 17, preferably the depth of the circular extending groove 17 is bigger than or equal to the depth of the longitudinal extending grooves 16. As illustrated, such a circular extending groove 17 is typically wedge-shaped which further reduces the risk that water and/or dirt accumulates on the union. Grooves like 16 and 17 may also be provided to the male part 3. The longitudinally extending grooves 16 of a union according to the present invention may preferably be dovetail grooves as shown in fig. 5. Dovetail grooves

DK 180415 B1 11 have a trapezoidal cross section with the bottom of the groove being wider than the top of the groove. The dovetail groove has the advantage that the groove can be made with less depth than the square grooves, as the fastening tool gets a better grip. Thus, the outer diameter of the union can be reduced which reduces the production cost.

Advantageously, the bottom of the longitudinal groove of a union according to the present invention can have a slight angle with respect to the centre axis of the union. This allows for proper draining after cleaning.

A union as illustrated in fig. 3 has the advantage that upon unscrewing the female part 2 and moving the female part away from the flange 11, the pipe welded to the tubular welding liner 1 may be moved vertically (with reference to the orientation of fig 3) without the need for a horizontal movememt (again with reference orientation of fig. 3). This is particular advantageous in relation to what is shown in fig. 4, which is disclosed below. With reference to fig. 15, the male part 3 may preferably comprise a mechanical stop 25 comprising an abutment surface allowing the flange 11 to abut against the mechanical stop 25. When the union is assembled, an abutment surface of the mechanical stop 25 and the flange 11 are pressed together, creating a space between part of the flange 11 and part of the male part 3. The space created between part of the flange 11 and part of the male part 3, ensures that the inner tubular seal 4 cannot be compressed to such a degree that its ability to function as a seal is compromised. A union according to the present invention is typically rotationally symmetric along a longitudinal direction except for the longitudinally extending grooves 16 and the pitch of the threads, thereby providing a union with at least internal circular cross sections (perpendicular to the longitudinal direction defined by the pipes united).

DK 180415 B1 12 A union according to the present invention is typically made from stainless steel and is typically produced by a turning process, and if considered necessary, followed by a polishing process.

The unions according to the present invention can be used in a device for transferring fluid, such as liquid in a dairy production facility, as shown in fig. 4. The device comprises a first fluid connection 19, a connection pipe 21 and a plurality of second fluid connections 20. The second fluid connections 20 are arranged along a perimeter of a circle having its centre coinciding with the centre ofthe first fluid connection. A fluid connection is a pipe, which can transport fluid and which is to be connected to a union by welding.

The connection pipe 21 is connected at one end to the first fluid connection and at the other end to one of the second fluid connections by use of unions.

In such a device one can advantageously connect one end of the connection pipe 21 to a first fluid connection 19 by use of a union according to the union shown in fig. 1 or 2 and the other end of the connection pipe to one of the second fluid connections 20 by a union shown in fig. 3.

By loosening the male nut 3 at the first fluid connection A and unscrewing the female nut 2 at the second fluid connection the connection pipe 21 is free to rotate to another second fluid connection, e.g. from B to C in fig. 4.

As mentioned above, in situations where unions as disclosed in fig. 4 are used to connect the connection pipe 21 at position e.g. A, B and C in fig. 4, where male parts 3 are arragned at the various positions and female parts 2 are arranged on the connection pipe 21. To change the position of the connection pipe, the female part 2 can be loosened at connection A and unscrewed at position B. Then the pipe 21 can be rotated to position C (while the male and female parts 2, 3 remains threaded) at which position the female part 2 is screwed onto a male part 3 at position C, and the female part 2 at position A is fastened. Thereby, the connection pipe 21 can be positioned in the new position by a substantial rotational movement only. It is noted that the male parts 3 remain in their positions.

DK 180415 B1 13 Reference is made to fig. 16 illustrating an embodiment a union according to the present invention. The dimensions indicated in the figures are not to be construed as limiting the invention to such dimensions and a give for illustrating an example.

The reference numerals used in the preceding figures are repeated for similar elements in fig. 16. In the embodiment of figure 16, the inner tubular seal is in cross section torus shaped with an inward facing protrusion. The dimensioning of the invarding facing protrusion 4a is of a size so that at e.g. room temperature (20°C) the protrusion is below the inner surface by a distance A which may be in the order of 1-2 tenth of milimeter. The distance is chosen so that once the union is at a pre-determined operating temperature, the inwarding facing surface of the protrusion 4a forms a flush transition between neigbouring surface due to thermal expansion.

The female part 2 and the male part 3 are mutually dimensions to the the inner tubular seal 4 is compressed with the end of the male part 3 abuts an end in the female part as shown in fig. 16.

Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms “comprising” or “comprises” do not exclude other possible elements or steps. Also, the mentioning of references such as “a” or “an” etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.

LIST OF REFERENCE SYMBOLS USED 1 Tubular welding liner 2 Female part 3 Male part

DK 180415 B1 14 4 Inner tubular seal End tubular seal 6 Outer tubular seal 7 Outer end surface 5 8 Inner recessed section

9 Inner end surface Internal thread 11 Outwardly protruding flange 12 Ring shaped section

10 13 Annular surface of male part 14 Inner groove End surface of the male part 16 Longitudinal extending groove 17 Circular extending groove

15 18 Outer end of female part 19 First fluid connection Second fluid connection 21 Connection pipe 22 Outer end of male part

20 23 External thread 24 Protrusion Mechanical stop

Claims

DK 180415 B1 1 PATENTKRAV

A union comprising - a female coupling (2) in the form of a tubular element with an inner diameter (D1) and comprising an annular outer end face (7), an annular inner end face (9) and an inner recessed portion (8) extending from the outer end face (7) to the inner end face (9), the female coupling (2) further comprising an inner thread (10) provided in at least a part of the wall of the inner recessed portion (8); a tubular welding insert (1) having an inner diameter at least substantially equal to the inner diameter (D1) of the female coupling (2) and comprising at one end an externally projecting flange (11) extending over the entire circumference of the welding insert (1) , the outer geometry of the flange connects (GB: mate) the inner geometry of the countersunk portion at the inner end face (9) to provide the tubular welding insert (1) to be received in a snug fit in the inner countersunk portion ( 8) with a central axis of the tubular welding insert (1) in line with a central axis of the female coupling (2); - an inner, tubular seal (4) with an outer geometry which allows arrangement of the inner, tubular seal (4) to abut against the inner end face (9), the inner, tubular seal being annular in cross section; - a male coupling (3) with an inner diameter greater than an outer diameter, measured outside the flange (11), of the welding insert (1), the male coupling (3) having an outer thread (23) provided along a part of the male coupling (3) , which outer thread (23) is configured to cooperate with the inner thread (10) of the female coupling to screw the male coupling into the female coupling and to clamp the flange (11) and the inner tubular seal (4) between the inner end face ( 9) of the female coupling and an end face of the male coupling (3); characterized in that - the inner tubular seal (4) has an inner diameter which is at least substantially equal to the inner diameter (D1) of the female coupling (2) and has an inwardly facing projection (4a).

DK 180415 B1 2

A union according to claim 1, wherein the male coupling (3) comprises an annular part (12) defining an annular surface (13) facing, in use, the annular end face (7) of the female coupling (2).

The union of claim 2, further comprising an outer tubular seal (6) clamped, in use, between the annular surface (13) of the male coupling (3) and the outer end face (7) of the female coupling (2).

A union according to claim 3, wherein a part of the female coupling (2) extends from the outer end face (7) and the annular part of the male coupling (3) both have an outer cylindrical shape with at least substantially the same diameter, and the outer diameter of the outer tubular seal (6) is at least substantially equal to the diameter of the outer cylindrical shape, typically measured when the outer tubular seal (6) is clamped.

A union according to any one of the preceding claims, further comprising an end, tubular seal (5) adapted to seal between the outer surface of a pipe extending inside the male coupling and an inner surface of the male coupling (3), which end, tubular seal (5) is configured to provide a flush transition between the male coupling (3) and the outer surface of the tube.

The union of claim 5, wherein the end tubular seal (5) has an L-shaped cross section and the male coupling (3) comprises an inner groove (14) configured to receive a portion of the end tubular seal (5). .

Union according to claim 5, wherein the end, tubular seal (5) is cylindrically extending inside the male coupling (3), in use, from an end face (15) of the male coupling (3).

A union according to any one of the preceding claims, wherein the male coupling (3) comprises longitudinal extending grooves (16).

Union according to claim 8, wherein the male coupling (3) comprises a circular extending groove (17), preferably arranged so that each of the longitudinal extending grooves (16) opens into the annular extending groove (17), preferably with the depth of the

DK 180415 B1 3 circularly extending groove (17) is greater than or equal to the depth of the longitudinal extending groove (16).

A union according to claim 8 or 9, wherein the bottom of the longitudinal extending grooves (16) is at an angle relative to the central axis of the union.

Union according to claims 8, 9 or 10, wherein the longitudinal extending grooves (16) have a trapezoidal cross-sectional part, with the bottom of the groove being wider than the top of the groove.

A union according to any one of the preceding claims, wherein one or more of the surfaces which come into contact with a seal when the male coupling (3) is screwed into the female coupling (2) has a projection (24).

A union according to claim 12, wherein the surface which comes into contact with a seal when the male coupling (3) is screwed into the female coupling (2) is the inner end face (9) of the female coupling (2) and the seal is the inner tubular seal (4).

A union according to claim 12, wherein the surface which comes into contact with a seal when the male coupling (3) is screwed into the female coupling (2) is a surface of the outer projecting flange (11), and the seal is the inner, tubular seal (4).

A union according to claim 5, wherein the inner surface of the male coupling (3), which clamps the end, tubular seal (5) when the male coupling (3) is screwed into the female coupling (2), has a projection (24).

A union according to claims 12-15, wherein the projection (24) extends over the entire circumferential surface defined by the surface which comes into contact with a seal.

A union according to any one of the preceding claims, wherein the inner end face (9) comprises a mechanical stop (25), which comprises an abutment surface which allows the flange (11) to abut against the mechanical stop (25).