DE9208519U1 - Pipe connection - Google Patents

Description

"Pipe connection"

Description

The invention relates to a pipe connection or plug connection for pipes, in particular plastic pipes with a connection housing with a support sleeve arranged therein.

Such pipe connection or plug connections are used, for example, to connect pressure lines to pressure vessels or valve housings. These well-known plug connections must be strictly distinguished from the equally well-known screw connections. While the plug connection with a support sleeve arranged in it is screwed to a connection and the pipe is then inserted into the connection housing, screw connections are connected to the connection in a different way. In this case, the connection housing and a cutting or clamping ring must first be pushed onto the pipe and the support sleeve inserted into it. The connection housing is then screwed to the connection together with the inserted pipe.

DE-OS 33 25 350 discloses a plug connection for plastic pipes which has a connection housing for a connection. The connection housing is designed as a screw and has an external thread. Accordingly, such a plug connection can only be used with connections with an internal thread. Direct use with a connection that has an external thread and standardized bore shapes (e.g. DIN 3861, 3862, 3863) and in accordance with international standards (e.g. JIC, SAE, PTT)

and special user standards is excluded. The use of this known plug connection with a standardized connection with an external thread is only possible if the plug connection is connected to a special connecting part, which in turn can be connected to the connection.

The object of the invention is to provide a pipe connection of the type mentioned at the beginning, which avoids the disadvantages of the prior art, whereby functional reliability, interchangeability and simplicity as well as the use of conventional standardized connection pieces should be possible.

This object is essentially achieved according to the invention in that the connection housing has an internal thread for connection to a connection piece with a corresponding external thread and that the support sleeve or a sealing and holding element arranged in the connection housing is supported on the bore contour or a shoulder on the bore base or on the front face of the connection piece, whereby the thread preload required when screwing is applied to the support sleeve and/or the sealing and holding element.

Such a plug connection offers several advantages. Firstly, the plug connection can be screwed onto any connection with an external thread. Since the invention connects the plug connection directly to the standardized connection piece, no connecting or intermediate piece is required. Another advantage is that no circumferential collar or stop is required on the outside of the connection piece in order to apply the appropriate thread preload for screwing or tightening the connection. Usually, such a collar or edge is required as a counter bearing for the connection housing screwed onto an external thread in order to screw it tight. However, with the Ei f iiiduny, this is not necessary.

such a collar or the like, since the support sleeve or the sealing and holding element is supported on the bore contour or a step on the bore base or on the front face of the connecting piece. It goes without saying that the sealing and holding element also performs a supporting function. In contrast to known plug connections with an external so-called installation space limitation, in the invention the installation space is limited internally, i.e. in or on the bore or on the front face of the connecting piece.

In a preferred embodiment of the invention, the sealing on the connection piece can be achieved via the sealing and holding element and/or the support sleeve, which rests on the front surface of the connection piece. This would then result in a metallic seal.

In an alternative embodiment of the invention, in which the connection housing also has an internal thread for connection to a connection piece with a corresponding external thread, instead of the metal seal between the sealing and holding element and the front face of the connection piece, an internal seal made of an elastomer is arranged on the front face of the connection piece. The seal made of an elastomer material always ensures a leak-free seal and is also very cost-effective. Since the pre-tensioning in the present case is applied via the support sleeve or the sealing and holding element and not via the internal seal, it is ensured that the internal seal is not damaged when the plug connection is screwed on and thus does not leak. In addition, this embodiment offers all of the advantages already mentioned.

In a further development of this inventive concept, the inner seal is accommodated in a chamber that is formed by the nozzle face, a surface of the connection housing and the sealing and holding element and/or the support sleeve. Such a chamber secures the seal against over-assembly.

The following features relate to both embodiments of the invention.

In order to hold the pipe securely inserted into the plug connection, it is intended that the support sleeve on its side facing the connection and/or the sealing and holding element is adapted to the bore contour of the connection piece in a form-fitting manner. In a further development of this idea, the support sleeve can be moved towards the connection piece and out of the connection housing when the plug connection is not installed. This ensures that the support sleeve can be easily replaced if necessary. The invention ensures that if the bore contour of the connection piece changes, only the support sleeve needs to be replaced, which is easily possible due to the mobility in the connection housing. All other parts arranged in the connection housing can be adopted identically. For the respective application site, this means that only a very small number of connection housings are required and if the bore shapes change, only the support sleeve needs to be replaced. Overall, this contributes to a significant reduction in the number of parts that need to be kept in stock.

In order to ensure that the inserted pipe is not pulled out of the plug connection under tensile stress, the invention further provides that the support sleeve is, if necessary, secured via the sealing and retaining element.

element transfers tensile forces to the connection housing when the pipe is subjected to tensile stress. In this way, in addition to the usual cutting ring retaining slats, a possibility is created to transfer part of the tensile force to the connection piece.

In a further development of this inventive concept, the support sleeve, the sealing and holding element or another element against which the support sleeve or the sealing or holding element rests (in the pulling direction of the pipe) strikes a shoulder in the connection housing. This allows the tensile force from the pipe to be easily transferred via the frictional connection between the support sleeve and the pipe to the support sleeve and from the latter either itself or via the aforementioned parts to the shoulder of the connection housing. Since the connection housing is in turn screwed to the connection piece, the transferred tensile force is transferred to the connection piece. In this way, the tensile load capacity of a pipe inserted into the plug connection according to the invention is considerably increased.

In a further embodiment of the invention, the sealing and holding element is screwed and/or pressed into the thread of the connection housing. This offers the enormous advantage that the elements in the connection housing, such as seals, cutting rings and any holding elements, are held in the connection housing when the pipe is not inserted, so that the pipe connection according to the invention represents an easily replaceable unit in which the above-mentioned parts are not only held captive by the sealing and holding element, but are also fixed in the connection housing.

In order to further improve the tensile force absorption in the invention, it is further provided that retaining teeth pointing towards the pipe are provided on the support sleeve.

whose clear diameter is larger than the inner diameter of the pipe.

If the support sleeve is designed as a reducing sleeve, pipes with a smaller inner diameter can also be used without any problems with an identical connection housing. As already explained above, this does not cause any problems as the support sleeve is easily replaceable. Furthermore, the housing can also be designed as a reducing housing if a pipe with a smaller diameter is to be connected to a connection piece with a large diameter. No special connecting parts are required here as the connection is made directly.

In a further advantageous inventive concept, a marking or the like is provided on the connection housing, which is roughly aligned with the lower end face or the groove base of the support sleeve, against which the pipe hits when plugged together. This makes it easier for the fitter to check whether the pipe is properly plugged into the plug connection.

Further features, advantages and possible applications of the present invention will become apparent from the description of embodiments and from the drawing itself.

Show it:

Fig. 1 a view of the pipe connection according to the invention with the pipe inserted in a partially sectioned representation,

Fig. 2 a pipe connection in the non-inserted state of the pipe with the associated pipe connection piece,

Fig. 3 a view of a section of a pipe connection joint and an associated pipe connection piece,

Fig. 4 another embodiment of connection joint and pipe connection piece in a partial cross-sectional view,

Fig. 5 is a cross-sectional view of a tandem seal according to the invention,

Fig. 6 is a cross-sectional view of a quad ring seal according to the invention,

Fig. 7 shows another embodiment of the pipe connection device according to the invention in a partially sectioned view,

Fig. 8 shows a further embodiment of the pipe connection according to the invention in a partial cross-sectional view,

Fig. 9 another pipe connection as a reduction without pipe in cross-sectional view,

Fig. 10 is a cross-sectional view of another embodiment of the pipe connection according to the invention with a two-part support sleeve,

Fig. 11 shows another embodiment of the present invention in cross-sectional view,

Fig. 12 a cross section through a reducing support sleeve and

Fig. 13 a view of a pipe connection according to the invention with determination shown

the pipe insertion length.

Fig. 1 shows the pipe connection or plug connection 1 according to the invention, which is screwed onto a pipe connection piece 2. The pipe connection piece 2 has an external thread 3 and an inwardly tapered bore 4.

The plug connection 1 itself has a connection housing 5, which is provided with an upper housing part 6, which has an approximately cylindrical outer surface 7. The connection housing 5 also has a lower housing part 8, which is designed as a hexagon. The connection housing 5 is provided with an internal thread, which is screwed onto the external thread 3 of the connection piece 2. The internal thread 9 is screwed into a hole 10, which ends at a shoulder and merges into a smaller hole 12, which in turn ends at a shoulder 13. On its upper end face, the connection housing 5 has a through hole 14, the diameter of which corresponds to the external diameter of the pipe 20.

In the connection housing 5 there is a support sleeve 15 which has a sleeve part 16 and a conical pin 17. The support sleeve 15 is loosely arranged in the connection housing 5 and is therefore easy to replace. If the pipe is not installed or not yet screwed to the port connection piece, the support sleeve 15 would fall out of the connection housing 5, although the support sleeve 15 is to be regarded as part of the connection housing. The sleeve part 16 and pin 17 are designed as one piece, but can also be made up of several parts. The outer surface of the pin 17 is adapted to the contour of the bore 4, so that the pin 17 and the bore 4 lie closely against one another. The pin 17 has a projection 18, so that between the projection 18 and the sleeve part 16 a groove 19 is formed, into which the tube 29 is inserted. The groove base is approximately

the shoulder formed by the hexagon at the transition to the housing part 6. Furthermore, in this embodiment, the connection housing contains a sealing and holding element 21, a cutting ring 22, a holding element 23, a seal designed as a tandem seal 24 and a support ring 25. However, not all of the elements mentioned are absolutely necessary for the implementation of the invention.

The sealing and holding element 21 is designed here as an annular cone, which is screwed or pressed into the internal thread 9 and rests with its connection-side surface 26 on the front surface 27 of the pipe connection socket 2. The element 21 is metallic and creates a seal on the socket 2. The holding element 23 is located in the bore 10 of the connection housing 5 and is limited at its connection-side end by the pipe-side surface 28 of the sealing and holding element 21. At its pipe-side end, the holding element 23 abuts the shoulder 11. The sealing and holding element screwed or pressed into the internal thread 9 fixes the holding element 23 firmly in the bore 10. The holding element 23 is designed as an inner cone, while the cutting ring 22 is designed as an outer cone, so that the cutting ring 22 and the holding element 23 can interact at their bevels 29, which means that the cutting ring 22 can be moved along the bevels 29 of the holding element 23. The cutting ring 22 has holding teeth 30, the inner diameter of the cutting ring being smaller than the outer diameter of the pipe 20.

The conical holding element 23, i.e. its rear pipe-side face 31, forms a chamber 32 in the bore 12 in which the tandem seal 24 is arranged. The support ring 25 is located between the two sealing elements of the tandem seal 24. The tandem seal 24 seals on the

Pipe jacket surface 33. Instead of the two sealing elements of the tandem seal 24, a single sealing element can also be provided.

In an alternative embodiment, the element 23 is formed integrally with the connection housing 5.

In Fig. 1, the pipe connection joint 1 according to the invention is shown in the inserted and pressurized state. After the pipe connection joint has been mounted on the pipe connection piece 2, the support sleeve 5 is held and centered between the sealing and holding element 21 and the pipe connection piece 2, i.e. its bore 4.

In Fig. 2, the pipe connection 1 is shown without the pipe 20 inserted. A holding element 34 is inserted into the through hole 14, which has an annular body 35 that is located between the tandem seal 24 or the connection housing 5 and the sleeve part 16 of the support sleeve 15. The thickness of the annular body 35 is selected such that a frictional connection with the annular body is formed between the tandem seal 24 and the connection housing 5 on the one hand and the sleeve part 16 on the other. This frictional connection means that, on the one hand, the support sleeve 15 cannot fall out of the connection housing 5 and, on the other hand, that the holding element 34 can also fall out of the connection housing 5 when the pipe is not installed or inserted. The annular body 35 is adjoined by a collar 36 that projects approximately perpendicularly from it. This collar 36 projects with its outer end beyond the connection housing 5.

In the example shown, the bore 4 of the pipe connection piece 2 has an inner cone 37 inclined at 24°, while the pin 17 has a correspondingly inclined at 24°.

sloping outer cone 38. In the example in Fig. 3, the inner cone 37 and outer cone 38 are inclined by 60° and also fit together accordingly. In Fig. 3 it is also shown that an assembly space 39 is formed behind the sealing and holding element 21.

To form the pipe connection 1 according to the invention as an assembled unit, the tandem seal 24 with support ring 25 is first inserted into the bore 12. To limit the tandem seal 24, the holding element 23 is then inserted into the bore 10 together with the cutting ring 22. Then the sealing and holding element 21 is screwed or pressed in, which prevents the aforementioned parts from falling out of the connection housing 5 and at the same time fixes the holding element 23. Then the support sleeve 15 is inserted from the connection side, which abuts with its pin on the connection-side surface 26 of the sealing and holding element 21. The holding element 34 is then pushed into the through hole 14 from the pipe side of the connection housing 5, which holds the support sleeve 15 in a frictional manner and thus prevents the support sleeve 15 from falling out of the connection housing 5. The connection housing 5 thus forms a structural unit with the parts accommodated therein.

To insert the pipe into the described assembly, the pipe connection 1 is screwed onto the pipe connection piece 2 so that the support sleeve 15 can no longer fall out of the connection housing 5 after the holding element 34 has been removed. The holding element 34 is then pushed out of the connection housing 5, whereby the pipe is pushed onto the sleeve part 16 of the support sleeve 15. The pushing in continues until the pipe 20 hits the front surface of the groove 19 or the groove base. During the pushing in process, the cutting ring 22

due to its smaller internal diameter, it is moved into the assembly space 39 along the slope 29. After the pipe 20 is subjected to tension and/or pressure, it moves slightly away from the pipe connection piece 2, so that the cutting ring 2 resting on the pipe surface slides along the slope 29 in the direction of movement of the pipe 20 and cuts into the pipe. At the same time, due to the frictional connection between the support sleeve and the pipe, a certain proportion of the tensile force is transferred to the support sleeve. This force is transferred via the pin 17 of the support sleeve 15 to the sealing and holding element 21 and from there via the holding element 23 to the shoulder 11, and thus to the connection housing 5. Since the connection housing 5 is in turn connected to the connection piece 2, the connection piece takes over the tensile force acting on the support sleeve. In this way, the pipe connection 1 is firmly connected to the pipe 20.

In Fig. 4, the receiving bore 4 of the pipe connection piece 2 is cylindrical and therefore has a flat surface 40 or bore contour. Accordingly, the pin 17 of the support sleeve 15 is provided with a corresponding surface 41 such that the surfaces 40 and 41 lie closely against one another in the assembled state. In Fig. 4, the pin 17 has a peripheral edge 42 at its end, which is received in a corresponding recess 43 of the sealing and holding element 21 and rests against it. In this embodiment, both the edge 42 of the support sleeve 15 and a part of the sealing and holding element 21 lie on the end face of the connection piece 2 in the assembled state.

In an embodiment not shown, the edge 42 rests completely on the front surface of the connection piece 2. A sealing and holding element 21 is not absolutely necessary if the support sleeve strikes against a shoulder in the connection housing.

Fig. 5 shows the tandem seal 24 from Fig. 1, but without a support ring.

Fig. 6 shows a square seal 44 instead of the tandem seal 24, which has a lip 45 on the pipe side and a lip 46 on the connection side. The lip 45 serves as a dirt seal, while the lip 46 serves as a medium seal.

Another embodiment of the invention is shown in Figs. 7 and 8. The support sleeve 15 is provided with its own toothing 54, which is located at the transition between the sleeve part 16 and the pin 17. The toothing 54 consists of slightly conical teeth pointing in the direction of the pipe socket 2. Another difference from the embodiment shown in Fig. 1 is that the sealing and holding element has a sleeve part 55, which is adapted on its outside to the inner bevel 37 of the bore 4. The groove 19 described in Fig. 1 is formed in the present case of Fig. 7 by the sleeve part 55, the end wall of the pin 17 and the sleeve part 16 of the support sleeve 15. Another difference to the embodiment shown in Fig. 1 is that the support sleeve is centered in the bore 4, but is axially movable in it. When the tube 20 is inserted, it hits the front surface of the groove 19 of the pin 17 and presses the support sleeve 15 into the bore 4 until it hits the front surface 56. This insertion process is shown in Fig. 8 in dashed lines and designated 57. At the same time as the support sleeve 15 is inserted into the

The cutting ring is moved into the assembly space 39 through the bore 4 until it abuts the sealing and holding element 21. This is also shown in dashed lines in Fig. 8. When pushed in, the upper part of the pipe 20 is slightly expanded at the toothing 54. When tension and/or pressure are subsequently applied, the pipe 20 and the cutting ring are moved away from the nozzle 2, with the cutting ring 22 sliding along the slope 29. The teeth of the cutting ring 22 engage in the pipe wall. At the same time, the teeth of the toothing 54 dig into the inside of the pipe. When tension and/or pressure are applied, the support sleeve 15 also moves back into the position shown in Fig. 8. In this case, in the pressurized state, there is a gap between the front face 56 of the pipe connection piece 2 and the front face 58 of the support sleeve 15 (from left, Fig. 7). As already described above, the pressure is transferred from the support sleeve to the sleeve part 55 of the element 21 and finally to the connection piece 2.

Fig. 9 shows a further embodiment of the invention, in which the pipe connection 1 is designed as a pipe reduction. In the embodiment shown, the bore 4 of the pipe connection socket 2 has a pipe diameter of D1. The outside diameter of the pipe is D2, whereby D1 is larger than D2. The pipe is not shown in the present case. The pipe reduction from D1 to D2 is achieved by selecting the height H on the front side of the pin 17 accordingly and adjusting it to D2. A further change is that the entire inner contour of the connection housing 5 with bores 10 and 12 has been adapted to the changed smaller diameter D2 of the pipe 20. In this case, this results in the advantage that the fitter can easily connect the pipe with the smaller diameter D2 to the socket 2 with the large diameter D1 at the assembly point.

Fig. 10 shows a further embodiment of the pipe connection 1 according to the invention. The pipe connection 1 is shown in the assembled state, i.e. screwed onto the connection piece 2, but without a pipe. The structure of the connection housing 5 corresponds to the structure of the connection housing in Figs. 1 to 4. In the case shown here, the support sleeve 15 consists of the sleeve part 16 and a collar 65, which adjoins the sleeve part 16 and rests on the front surface of the bore 4 of the pipe connection piece 2. The pin part of the support sleeve from Figs. 1 to 4 is formed in the present case from the sealing and holding element 21. This pin part is designated 66 in Fig. 10. The front end 67 of the pin part 66 rests on the collar 65. The support sleeve tensile force is transmitted via the collar 65 and the front end 67 of the pin part 66 of the sealing and holding element 21. The support sleeve 15 can be a cost-saving sheet metal part. In this example, the sealing can be carried out via the front surfaces 68 and 69, for example, using metal. Alternatively, the support sleeve 15 can also be formed in one piece with the sealing and holding element 21, which is not shown, however.

pipe connection connection 1 according to the invention. The difference from the embodiment according to Fig. 10 is that the thread sealing in this embodiment is carried out via a soft seal 70. This soft seal can be a seal made of an elastomeric material. The seal 70 is arranged in a chamber 71 which is formed between pipe socket 2, connection housing 5 and support and sealing elements 21. The soft seal 70 is held in a turn or undercut 72 of the connection housing 5, which adjoins the internal thread 9. Due to this undercut 72, a

The soft seal 70 is prevented from falling out. The soft seal 70 also ensures that the support and holding element 21 or the support sleeve 15 in the one-piece design with support and holding element is held in the connection housing 5, since a projection 73 of the support and holding element 21 engages behind the seal 70. The inner seal 70, designed here as a round cord ring, lies tightly in the assembled state according to Fig. 11 at least on the pipe socket face, the undercut surface and the in this embodiment conical outer surface of the support and holding element 21. The friction of the seal 70 on the outer surface of the support and holding element 21 and the projection 73 prevent the support and holding element 21 from falling out of the connection housing 5. The chamber 71 is accessible on the nozzle side through an annular gap whose diameter is smaller than the diameter of the seal 70. This results in the seal 70 being captive in the chamber 71.

In the unscrewed state without a pipe, it is expedient in this embodiment and also in that according to Fig. 10 to provide a holding element 34 as described in Fig. 2 to prevent the support sleeve 15 from falling out of the connection housing 5.

The support sleeve of the figures described above can also be designed as a reducing sleeve, as shown in Fig. The contour 74 of the support sleeve is designed so that the diameter 75 in the area of the sealing and holding element according to Fig. 10 and for the smallest possible pipe wall and the diameter 76 is variable over the pipe insertion length.

Finally, Fig. 13 shows the possibility of determining the pipe insertion length 77. The connection housing with its union nut or hexagon 8 is turned over in its outer surface 7 to the insertion length of the pipe 20 in the pipe connection 1. The pipe 20 is brought into contact with the hexagon 8 on the outside before assembly. Instead of the hexagon, another form of marking (e.g. a notch) can also be provided. The rear face 78 of the connection housing 5 points to a point on the pipe marking 79, which can be, for example, a label on the pipe 20. The fitter can also mark this point in some way. This point on the pipe marking 79 must be flush with the face 78 of the connection housing 5 after assembly. In this position, the pipe is properly inserted into the connection 1, as the hexagon or the marking is approximately aligned with the base of the groove, where the pipe hits after it has been properly inserted.

List of reference symbols:

1 Pipe connection 2 Pipe connection socket 3 External thread 4 drilling 5 Connection housing 6 upper housing part 7 Shell surface 8th lower housing part, hexagon 9 inner thread 10 drilling 11 shoulder 12 drilling 13 shoulder 14 Through hole 15 Support sleeve 16 Sleeve part 17 cone 18 Got over 19 Groove 20 Pipe 21 Sealing and retaining element 22 Cutting ring 23 Holding element 24 Tandem seal 25 Support ring 26 connection side surface 27 Frontal area 28 pipe-side surface 29 Slope 30 Retaining teeth 31 Frontal area 32 chamber 33 Pipe surface area 34 Holding element

35 ring-shaped body 36 Federation 37 Inner cone 38 Outer cone 39 Assembly room 40 Area 41 Area 42 edge 43 Recess 44 Quadring seal 45 lip 46 lip 54 Gearing 55 Sleeve part 56 Frontal area 57 Insertion process 58 Frontal area 65 collar 66 Tenon part 67 front end 68 Frontal area 69 Frontal area 70 Soft seal 71 chamber 72 Undercut 73 Got over 74 contour 75 diameter 76 diameter 77 Pipe insertion length determination 78 Frontal area 79 Pipe marking Dl diameter D2 Pipe diameter H Height

Claims (12)

Protection claims 1. Pipe connection or plug connection (1) for pipes (20), in particular plastic pipes, with a connection housing (5) with a support sleeve (15) arranged in the connection housing (5), characterized in that the connection housing (5) has an internal thread (9) for connection to a connection piece (2) with a corresponding external thread (3), wherein the support sleeve (15) is supported on the bore contour or a shoulder on the bore base or on the front surface (27) of the connection piece (2) via a corresponding peripheral edge (42) and/or a sealing and holding element (21) arranged in the connection housing (5), where the thread preload required when screwing is applied via the support sleeve (15) and/or the sealing and holding element (21). 2. Pipe connection or plug connection according to claim 1, characterized in that the sealing and holding element (21) and/or the support sleeve (15) on the end face (27) of the connection piece (2) seals/seals. 3. Pipe connection or plug connection according to the preamble of claim 1, characterized in that the support sleeve (15) and/or a sealing and holding element (21) is supported on the bore contour or a shoulder on the bore base of the connecting piece, whereby the thread preload required during screwing is applied via the support sleeve and/or the sealing and holding element (21) is applied, and that an inner seal (70) consisting of an elastomer is provided on the end face (27) of the connecting piece (2). 4. Plug connection according to claim 3, characterized in that the inner seal (70) is accommodated in a chamber (71) which is formed by the nozzle end face, a surface of the connection housing (5) and the sealing and holding element (21) and/or the support sleeve (15). 5. Plug connection according to one or more of the preceding claims, characterized in that the support sleeve (15) on its side facing the connecting piece (2) and/or the sealing and holding element (21), insofar as it projects into the bore of the connecting piece, is/are adapted in a form-fitting manner to the bore contour of the connecting piece (2). 6. Plug connection according to one or more of the preceding claims, characterized in that the support sleeve (15) in the non-installed state is movable in the direction of the connection piece (2) and can be moved out of the connection housing (5). 7. Plug connection according to one or more of the preceding claims, characterized in that the support sleeve (15) transmits tensile forces to the connection housing (5) if necessary via the sealing and holding element (21) when the pipe is subjected to tensile loading. 8. Plug connection according to claim 6, characterized in that the support sleeve (15), the sealing and holding element (21) which is in the pulling direction of the pipe rests on the support sleeve, or another element (23) which rests on the support sleeve (15) or the sealing and holding element (21) in the pulling direction of the pipe, strikes a shoulder (11) in the connection housing (5). 9. Plug connection according to one or more of the preceding claims, characterized in that the sealing and holding element (21) is screwed and/or pressed into the internal thread (9) of the connection housing (5). 10. Plug connection according to one or more of the preceding claims, characterized in that retaining teeth (54) pointing in the direction of the tube (20) are formed on the support sleeve (15), the inside diameter of which is larger than the inside diameter of the tube (20). 11. Plug connection according to one or more of the preceding claims, characterized in that the support sleeve (15) is designed as a reducing sleeve and/or that the connection housing (5) is designed as a reduction to the connection piece (2). 12. Plug connection according to one or more of the preceding claims, characterized in that a marking such as a shoulder or notch is provided on the connection housing (2), which is aligned with the lower end face (groove base) of the support sleeve (15) or the sealing and holding element (21), against which the pipe abuts in the plugged-together state.