EP1762312B1 - Method and apparatus for crimping of fittings in a pipe joint - Google Patents

Description

The invention relates to a device for pressing connectors as part of a pipe joint according to the preamble of patent claim 1 and a method for pressing connectors as part of a pipe joint using such a device according to the preamble of claim 16.

There are a variety of references to the same applicant, in which the function of a connector is shown as part of a sealing pipe connection.

Only by way of example is on the PCT / EP2004 / 001886 referenced, in which the function of such a connector is shown.

The same applies to the US 5,855,399 or the PCT / WO2005 / 047751 A1 ,

The subject of the prior art pipe joints is that a sealing plug connection is made between a plug and a socket.

The problem with such connectors is the connection of a hose to be connected to the plug. In the above-mentioned documents, it is provided that the plug forms an annular receiving space in which engages the front end of the hose, wherein the inner part of the plug is deformed with an attached from inside to the inner wall of the plug expansion tool such that a radially outwardly directed, ring encircling Verpressnut results, which reduces the hose diameter-reducing over the entire circumference in the annulus of the plug. In this way, the hose is sealingly and firmly received by said press connection in the annular space of the plug.

However, difficulties have arisen in the production of this grout. The problem here is that the hose does not always have a constant diameter and in particular the wall thickness varies.

If you were to form the Verpressnut always with the same Verpresstiefe, then it may happen that in hoses with a smaller wall thickness, the connection is not secure enough. Likewise, the tightness of this connection could be impaired.

The invention is therefore based on the object of developing a method and a device for pressing elastomeric tubes into plugs as part of a pipe connection in such a way that a secure and operative press connection between the plug and the elastomeric hose is produced, which is independent of wall thickness differences of the plug, the hose and the like.

The term "hose" is used broadly in the context of the present invention. It is understood not only an elastomeric hose, but also a tube, which also does not necessarily have to be elastomeric. It may therefore also be conventional plastic pipes in which it is also possible due to the material properties to deform the material such that a radially outward press bead engages in the inner part of the plug into the material of the tube.

With the publication EP 0 637 473 A1 For example, there is disclosed a generic apparatus for crimping a metallic ring into a cylindrical body and its use for securing a flexible tube to an automotive vehicle engine, the apparatus comprising a probe which detects a force and displacement for monitoring the crimping operation.
This document has the disadvantage that the crimping process disclosed here also ensures a reliable connection with different material thicknesses.

With the publication NL 8300123 A there is disclosed insertion of a plastic tube length into inner annular grooves of a metal shell by expanding a metal bushing to a predetermined deformation, wherein deformation is measured and terminated by means of a deformation sensor connected to a computer when the measured deformation reaches a predetermined value.

This document has the disadvantage that a compression of a plastic tube with different thicknesses of these is not apparent.

With the publication DE 298 718 U1 a radial press is disclosed, wherein the pressing operation is automatically monitored and controlled by means of an end stop due to measurement of the displacement of a displaceable pressing piece.
This document does not show that the implementation of different pressing operations by a reliable monitoring of the actual deformation force at different thicknesses is feasible.

With the publication DE 26 13 240 A1 discloses a device for pressing fittings on hose ends, wherein a plunger is guided by a further piston which forms a stop for the plunger and thus limits the pressure chamber of the plunger, and the plunger to a hydraulic pressure source and the other piston to a pneumatically connected pressure source. The plunger is connected to an adjustable stop ram of a switching valve and forms an automatic termination of the pressing operation.
This document has the disadvantage that a secure pressing of, for example, an elastomeric hose with different wall thicknesses in a pipe joint is not disclosed.

To achieve the object, the invention proposes a device and a method having the features of claims 1 and 16.

With the given technical teaching, a completely new device or a completely new method is described, which are directed to a direct detection of the deformation forces during the compression of hoses, pipes and the like.

Thus, a direct measuring system for an automatic assembly machine for the production of said pressings is realized, whereby at the same time a tool breakage monitoring of the spreading tool is given.

The technical teaching according to the invention also provides tightening torque monitoring of fastening screws, which fastening screws represent the connection between the actual expansion tool and the slanting sliders that attach to the expansion tool.

A significant advantage of a development of the invention lies in the fact that the Verpressnut is attached directed from the inner circumference of the plug to the outside. This results in the advantage that the spreading forces can be measured from radially inward to radially outward, which is a significant advantage over the prior art, in which the spreading forces could be detected (indirectly) only in the radial outer region of the plug.

The technical teaching according to the invention also provides the advantage that crack formation during the pressing process is avoided, as a result of which the press connection produced in this way is free of cracks and therefore operates reliably.

It can be detected and compensated with the method according to the invention even small differences in wall thickness both in the hose and in the plug.

In known systems, the compression pressure is detected only via the measurement of the path or the pressure, but not via a force measurement. Thus, wall thickness variations of the injection materials (plug and tube or hose) can not be monitored accurately enough. It is also known to detect the forces indirectly on the outer diameter of the plug, but this is prone to failure, because only an indirect measurement takes place and thereby the measurement accuracy is impaired.

• direktes Messen der auftretenden Umformkraft auf kleinstem Raum
• Überwachung eines Werkzeugbruches
• Überwachung des Anzugsmomentes der Werkzeugbefestigungsschrauben
• Bruchüberwachung der Werkzeugbefestigungsschrauben
• Erkennung und Überwachung geringer Wandstärkenunterschiede des Schlauches, des Rohres und des Steckteils
• Risserkennung der Steckteile, Rohre und Schläuche
• Toleranzminimierung bzgl. Konzentrizität
• kostengünstig, weniger störanfällig
• extreme Krümmungen vom Schlauch, Rohr, ... möglich, da die Aufnahme von innen gemacht wird

Advantage of the invention are therefore the following points:

• Direct measurement of the occurring forming force in the smallest space
• Monitoring a tool breakage
• Monitoring the tightening torque of the tool fastening screws
• Breakage monitoring of the tool fixing screws
• Detection and monitoring of small wall thickness differences of the hose, the pipe and the male part
• Crack detection of the plug-in parts, pipes and hoses
• Tolerance minimization regarding concentricity
• inexpensive, less prone to failure
• extreme bends of the hose, pipe, ... possible, since the recording is made from the inside

With the invention, therefore, a path-dependent force control of the compression between hose, tube and the like media and a deformable plug is realized that regardless of the wall thicknesses of the hose, the tube, the plug always pressed to the desired - depending on the way / wall thickness, set Verpressgrad becomes.

In a preferred embodiment, the plug is therefore made of a deformable metal material, such. As a steel sheet, an aluminum material, stainless steel and the like deformable solid materials more.

By optimizing the pressing function, the desired degree of pressing (variable) is thus always achieved independently of wall thickness, both from the hose and from the plug.

Here, according to the invention, at least one sensor is used, but preferably a plurality of sensors, which are installed in the so-called inclined slides, which oblique slides are each connected with their front free ends with a spreading jaw. The expansion jaws engage in the interior of the plug to be deformed and lead with a correspondingly radially outward directed Spreizschulter the Verpressnut on the inside of the plug (directed radially outward).

In this case, it is preferred if the sensors which measure deformation are arranged in the inclined slides.

In another embodiment of the invention, however, it may also be provided that these sensors are integrated directly into the expanding jaws themselves.

According to the invention, the spreading mechanism consists essentially of a rotationally driven spindle on which a spindle nut moves, which converts its axial movement into a corresponding, radial spreading movement of the expanding jaws. For this purpose, a wedge slide is attached to the spindle nut, and the wedge slide also performs an axial movement with the spindle nut. According to a preferred embodiment, the spindle nut acts on an inclined slide, which is forced to a radial movement and which consequently drives the expanding jaws in the radial direction.

In a second embodiment of the invention, it is therefore envisaged that the aforementioned wedge slide part of a tube, which is displaced as a whole and thus entrains the aforementioned oblique slide, which then perform the aforementioned spreading in the same way. This makes it clear that the drive principle for the spreading device can be varied in various ways.

The subject of the present invention results not only from the subject matter of the individual claims, but also from the combination of the individual claims with each other.

In the following the invention will be explained in more detail with reference to drawings showing only one embodiment. Here are the drawings and their description further advantageous features and advantages of the invention.

Show it:

FIG. 1:

schematically shows in perspective view the representation of a plug with a hose secured by a Verpressnut;

FIG. 2:

a section through a spreading device according to the invention;

FIG. 3:

a perspective, partially sectioned view of the device according to FIG. 2 ;

FIG. 4:

the perspective view of the spreading device in side view;

FIG. 5:

a further partial section through the rear portion of the spreading device in a perspective view;

FIG. 6:

the sectional view of the spreading tool in the idle state;

FIG. 7:

the spreading tool when performing the spreading process;

FIG. 8:

an enlarged sectional view through the attachment of a sensor in the inclined slide;

FIG. 9:

a schematic representation of the path-dependent force control.

In FIG. 1 It is shown that a preferably made of a metal material plug 10 forms an annular space 17, in which the front end face of a tube 11 is inserted and fixed there with an inwardly directed Verpressnut 15.

The plug 10 consists of an inner and an outer part, which together form the annular space 17 at the free rear end. The inner and outer parts are materially connected to each other.

It can of course also be provided to bind the two parts (inner and outer part) by a flanging or other fastening with each other.

For the sake of completeness, it is still shown that in the insertion direction of the annular space 17, a receptacle 29 connects to a sealing ring 18, which then results in a sealing connection, not shown, with the pipe joint. The nozzle is then inserted into the interior of the plug 10 and fixed there.

The determination is made with a detent spring 14, so that this connector is easily detachable.

Subsequently, a spreading device and a method for operating the spreading device will now be explained, with which the Verpressnut 15 introduced in the direction of arrow 22 is made.

The FIGS. 2 to 7 show the same parts of the device in different representations. For the same parts, the same reference numerals have been used, so that - even if certain reference numerals are not indicated - the same parts are always present in the drawings in the same place.

The rotational movement 20 generated by an electric motor 1 is converted into an axial movement 21 by a roller screw drive consisting of a spindle 2 and a spindle nut 3. At the spindle nut 3 is the Keilschieber 4 fixed on the nut mounting 5. By this fixation and by a keyway connection between the spindle 2 and wedge slide 4 of the wedge slide 4 also performs an axial movement, since this 7 can perform only axial movement 21 through the guide columns 6 and the linear ball bushings. Due to the axial movement of the wedge slide are inclined by 8 degrees guide window in the wedge slide 4, the oblique slides 8 to a radial movement 22, since they can perform 26 no axial movement through the fixed radial guides. Due to the positive connection between the inclined slide 8 and spreading jaws 9, these also move in the radial direction. By this generated movement 22 of the spreading jaws 9, the material of the plug 10 is deformed and thus pressed onto the tube 11. The sensors 13 located in the inclined slides 8 measure the forces transmitted by the spreading jaws 9, which are required for the deformation of the plug.

Out FIG. 2 and especially from FIGS. 4 . 6 and 7 It can be seen that a total of 8 evenly distributed on the circumference spreading jaws 9 are present, each spreader 9 is associated with associated mounting screws 27 with the front, free ends of the respective associated inclined slide 8.

The expanding jaws 9 are taken in a tool holder 19 in which an axial and radial guide 23 for the plug positioning of the plug 10 is present.

The plug is plugged onto the front of the spreader jaws 9 and secured against rotation by a groove.

It is not shown in the drawing, that in the front region of the spreading jaws 9, a guide member is present, which engages in a radially outwardly open groove of the plug 10 and thus centered on the spreading jaws 9.

In the FIGS. 6 and 7 only an axial stop for the rear end of the plug 10 is shown on the expanding jaws 9.

Out FIG. 2 and 5 It follows, moreover, that a support plate 24 is present, on which the radial guides 26 are fastened, which serve for the radial guidance of the oblique slides 8.

In FIGS. 6 and 7 is still the radial expansion shoulder 16 shown, wherein in FIG. 6 the spreading tool in rest position and in FIG. 7 in working position. It can be seen that thus the wedge slide 4, 4a have migrated in the axial direction forward in the direction of the spreading jaws 9 and at the same time the spreader jaws 9 were displaced outward in the radial direction, so that the Spreizschulter 16 at the front free ends of the spreader 9th the material of the plug from the inside in the direction of arrow 22 (see also FIG. 1 ) radially outwardly directed plastically deformed.

It can be seen, moreover, that the entire spreading device is flanged to the electric motor 1 via a fastening plate 25.

FIG. 3 shows, moreover, that the wedge slide is formed in two parts and consists of two spaced-apart wedge slides 4, 4a, which are screwed together by means of screw 28.

However, the invention is not limited thereto. It has already been pointed out in the general part that the wedge slide 4, 4a can also be designed as a tube and this tube can be moved in a certain way by a linear drive.

Likewise, it is provided in another embodiment that the wedge slide 4, 4a form a material integral, coherent part.

In the preparation of the compression, a gap 30 is formed according to FIG. 7 between the evenly distributed on the circumference arranged spreading jaws. 9

Important now is the technical teaching that in each case a sensor 13 is arranged in the region of the spreading tool, preferably in the region of the oblique slide.

It is preferred in this case if each slanted slide 8 is assigned its own sensor 13.

However, it can also be provided in another embodiment that only every second or every third inclined slide 8 is equipped with a corresponding sensor.

It is important that perpendicular to the longitudinal extent of the respective inclined slide 8, a bore 31 is introduced into the material of the inclined slide, which passes through the entire inclined slide 8. This is for example in FIG. 4 recognizable.

In FIG. 7 the deformation force 35 is drawn with an arrow which acts on the outside of the oblique slide 8, perpendicular to the bore center axis of the respective bore 31 for receiving the sensor thirteenth

Out FIG. 8 further details of the construction of the bore 31 show.

It can be seen that the bore 31 in the middle forms two opposite webs 33, between which a receiving bore 34 is formed.

In this receiving bore engages approximately knob-shaped sensor 13 with its collar of reduced diameter and is recorded there in a form-fitting manner in the receiving bore 34.

It follows that the ring-running webs 33 also act on the collar of the sensor 13 over the entire circumference and thus uniformly detect all forces acting on the circumference in the direction of the deformation force 35.

The sensor 13 is fixed in the receiving bore 34 in such a way that it has a head of increased diameter, and is welded to the web of the smaller diameter with the web 33 so as to hold the sensor in the receiving bore 34 in a non-displaceable and positive manner.

• Durch die Abstimmung eines Schlauches, Rohres,...werden die Parameter des Verpressprogrammes definiert definiert. Dazu werden drei verschiedene Schlauchdurchmesser auf den gewünschten Verpressgrad (variabel) verpresst. Wir erhalten dadurch die drei Eckpunkte der Verpressfunktion.
  • Fmax / smin
  • Fwp/swp
  • Fmin / smax

Based on FIG. 9 Now, the control of the force measurement for the above assembly machine will be described in more detail. The result is the following sequence:

• By tuning a hose, pipe, ... the parameters of the grouting program are defined defined. For this purpose, three different tube diameters are pressed to the desired degree of compression (variable). This gives us the three key points of the injection function.
  • Fmax / smin
  • Fwp / swp
  • Fmin / smax

These three points are used by the database to calculate the two slopes k1 and k2 and transfer them to the controller. The controller positions the press until smin, where it is checked if Fist <Fmax. At this point, the path-dependent force control begins. The controller must constantly calculate Fsoll (variable curve), which changes with increasing sist.

The controller must position until Fsoll = Fist brake tolerance has been reached, ie when the actual curve - the brake tolerance with the setpoint curve intersects the compression is completed.

The advantage of the control is that regardless of the wall thicknesses of the hose, the pipe, the Teckers always on the desired - depending on the path / wall thickness, set - pressing degree is pressed.

Basic pressing procedure:

• drive to minimal Verpressweg
• check actual force <Fmax
• continue until the end force is reached, Fsoll must be calculated continuously
• stop when Fsoll = Fist - Brake tolerance is reached
• Check if we are within the limits of the individual forces
• constant monitoring of the stop criteria

Definition of compression: o shortcut:

• smax MaxPressing distance (mm) • swp Waypoint (mm) • smin Min. Travel (mm) • Fmax MaxEndkraft (N) • Fwp Force Turn Point (N) • Fmin MinEndkraft (N) • min./max single-F Single force tolerance (%) • F tolerance in% Final force tolerance (%) • F-crack Crack detection (?) • k1 Gradient 1 • k2 Slope 2 • Tk1 Tempfaktor k1 • Tk2 Tempfaktor k2 • Tswp TempfaktorWegWP • v fast v fast (mm / s) • slow v slow (mm / s) • v slowly off the path v slowly off the way (mm) • Pre-pressing single force Prepressing force (N) • Downtime Downtime (ms)

In FIG. 9 on the ordinate the deformation force is shown, while on the abscissa the path of the deformation is shown. More precisely, it is the path which the expansion shoulders 16 of the expanding jaws 9 execute in the radial direction.

Starting from the position 36, the entangling process now begins, and initially there is a quasi-linear deformation on the straight line 37. It is defined a Verpresskurve 38, which represents the relationship between the pressing force and Verpressgrad.

From a turning point 39, the injection curve can also take a different form. This is shown with the Verpresskurve 40.

At position 41 and continuously in the process on the straight line 37 in the direction of arrow 42, for example, the desired force is determined at position 41, which is necessary for the compression and which represents the final force. In this case, the maximum force F _max should not be exceeded.

Consequently, several consecutive positions 41 on the straight line 37 are traversed and an actual force is always compared with a desired force until such time as the actual force corresponds to the desired force at position 43, whereby a certain tolerance is still taken into account got to.

In this point (position 43), the compression is now completed.

The representation in FIG. 9 shows with the straight line 45 in total the tube wall thickness between a minimum and a maximum value.

If, for example, the hose wall thickness is defined for a thick hose at position 44, then it can be seen in the diagram that a relatively high pressing force is required.

However, if a relatively small tube wall thickness is pressed at position 46, then it can be seen that the compression force is only slight. This results in each case at the intersection on the straight line 40 (Verpresskurve).

This has the advantage that now for the first time directly the deformation forces can be measured on the expanding jaws 9 and thus a path-dependent force control is proposed for the compression, whereby the grouting function is optimized and independent of the wall thickness of the grout, so that always reaches the desired Verpressgrad becomes.

drawing Legend

1

electric motor

2

spindle

3

spindle nut

4

Cotter pin 4a

5

nut fixing

6

guide column

7

Linear ball bushing

8th

lifters

9

expanding jaw

10

plug

11

tube

13

sensor

14

detent spring

15

Verpressnut

16

Spreizschulter

17

Annular space (plug 10)

18

seal

19

tool holder

20

rotational motion

21

Move

22

radial movement

23

Guide (axial and radial)

24

support plate

25

mounting plate

26

radial guide

27

fixing screw

28

screw

29

Receptacle (for sealing ring 18)

30

gap

31

drilling

32

attachment point

33

web

34

location hole

35

deforming force

36

position

37

Straight line (actual curve)

38

Verpresskurve

39

turning point

40

Verpresskurve

41

position

42

arrow

43

position

44

position

45

Just

46

position

Claims (22)

1. Device for moulding plug-in connectors as part of a pipe connection, which pipe connection comprises a sealing plug-in connection with a connector and a plug (10) which can be fitted with the connector, and the plug (10) comprises an outer part and inner part integrally joined to one another and forms an annular gap (17) at the rear free end, with an expander tool acting in the radial direction in order to form a moulded indentation (15) in the material of the plug (10) which extends into the material of the pipe or hose (11), and a sensor (13) subjected to at least a radial deformation is disposed on at least one point of the expander jaw (9) which detects the radial deformation work of the expander jaw (9) and regulates the expanding drive of the expander tool thereby, characterised in that the expander drive has an electric motor (1) constituting an expander tool which is able to convert a rotating movement (20) of a spindle (20) and a spindle nut (3) into an axial movement, and guide posts (6) extend through a wedge-type slide (4) attached to the spindle nut (3) so that the latter is able to effect an axial movement (21).
2. Device as claimed in claim 1, characterised in that the wedge-type slide comprises two wedge-type slides (4, 4a) spaced at a distance apart from one another, which are fixedly connected to one another by means of screws (28).
3. Device as claimed in claim 1 or 2, characterised in that the wedge-type slide (4) has inclined guide windows through which oblique slides (8) extend and effect a radial movement (22) by means of fixed radial guides (26), and the oblique slides (8) are positively connected to the expander jaws (9) by means of co-operating fixing screws (27) on the front free ends of the respective co-operating oblique slides (8).
4. Device as claimed in claims 1 to 3, characterised in that the expander jaws (9) are retained in a tool holder (19) which has a radial and axial guide (23) for plug positioning and centring the plug (10).
5. Device as claimed in claims 1 to 4, characterised in that the expander tool forms a moulded indentation (15) directed outwards from the inner circumference of the plug (10) and the sensor (13) detects resultant expansion forces directed radially outwards from radially inside constituting a distance-dependent force control system.
6. Device as claimed in claims 1 to 5, characterised in that the sensor (13) for detecting the deformation work is preferably disposed in the oblique slide (8) and/or in the expander jaw (9) of the expander tool used to produce the indentations.
7. Device as claimed in claims 1 to 6, characterised in that the expander jaw (9) which extends into the interior of the plug (10) to be deformed has an expander shoulder (16) directed radially outwards and makes a moulded indentation (15) by pressing against the internal face of the plug (10).
8. Device as claimed in claims 1 to 7, characterised in that the expanding mechanism effected by means of the expander jaws (9) can be adjusted.
9. Device as claimed in claims 1 to 8, characterised in that the wedge-type slides (4, 4a) secured on the spindle nut (3) are designed as part of a pipe and/or as an integral piece.
10. Device as claimed in claims 1 to 9, characterised in that the sensor (13) is disposed in a bore (31) disposed perpendicular to the longitudinal extension of the respective oblique slide (8) and the bore (31) extends through the entire oblique slide (8).
11. Device as claimed in claims 1 to 10, characterised in that the bore (31) has two oppositely lying, annular webs (33) in the middle with a receiving bore (34) for the sensor (13) disposed in between.
12. Device as claimed in claims 1 to 11, characterised in that the sensor (13) has a head with an enlarged diameter which is welded to the cylindrical surface of the smaller diameter (32) by means of the webs (33) so that the sensor (13) is positively retained in the receiving bore without being able to move.
13. Device as claimed in claims 1 to 12, characterised in that the expander device has a support plate (24) which is designed for mounting the radial guides (26).
14. Device as claimed in claims 1 to 13, characterised in that the entire expander device is mounted on the electric motor (1) by means of a mounting plate (25).
15. Device as claimed in claims 1 to 14, characterised in that the indentation forms a gap (30) between the expander jaws (9) distributed uniformly around the circumference.
16. Method of moulding plugs as part of a pipe connection using a device as claimed in claims 1 to 15, whereby the pipe connection forms a sealing plug-in connection with a connector and a plug (10) which can be locked onto the connector, and the plug (10) has an outer and inner part integrally joined to one another and forms an annular gap (17) at the rear free end, and hoses (11) and/or pipes or similar and a plug (10) with differing wall thicknesses are moulded as a function of directly detected deformation forces (35) at the expander jaws (9) of the expander tool during moulding in such a way that the deformation forces (35) at the expander jaws (9) are directly detected, thereby resulting in a distance-dependent force control system for the moulding operation so that the degree of moulding is always constant, and the method comprises the following method steps:

    - directly measuring the moulding force which occurs;

    - monitoring tool breakage of the expander tool;

    - monitoring the tightening torque of the tool fixing screws (27);

    - monitoring breakage of the tool fixing screws;

    - detection and monitoring of slight differences in the wall thickness of the hose (11), pipe and plug (10);

    - detection of tearing in the plug parts (10), pipes and hoses (11);

    - tolerance minimisation with respect to concentricity;

    - moulding between hose (11), pipe and similar and a deformable plug (10) with differing wall thicknesses by means of a distance-dependent force control.
17. Method as claimed in claim 16, characterised in that the distance-dependent force control involves the following steps:

    - moving until a minimum moulding distance has been reached,

    - checking actual force < Fmax ,

    - continuing movement until ultimate force is reached, Fdesired is calculated continuously,

    - stopping if Fdesired = Factual - braking tolerance,

    - checking whether force values lie within the limits of the individual forces,

    - constant monitoring of the stop criteria.
18. Method as claimed in claim 16 or 17, characterised in that the method defines points by means of coordinates and two gradients which indicate the moulding parameters are calculated by means of at least three points.
19. Method as claimed in claims 16 to 18, characterised in that the deformation force (35) is a function of the distance travelled by the expander shoulders (16) or the expander jaws (9) in the radial direction.
20. Method as claimed in claims 16 to 19, characterised in that the expansion process results in a quasi-linear deformation, and a deformation curve is defined which represents the correlation between the moulding force and the degree of moulding.
21. Method as claimed in claims 16 to 20, characterised in that the method determines the desired force needed for moulding which constitutes the ultimate force by comparing the measured actual force with the desired force until the actual force = desired force, and the maximum force F_max is not exceeded.
22. Method as claimed in claims 16 to 21, characterised in that the plug (10) is preferably made from a deformable metal material, such as sheet steel, aluminium, stainless steel or materials with similar properties, for example, into which the front terminal end of a hose (11) is inserted and secured by means of a moulded indentation (15) directed outwards from the inside.

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