EP2799189B1 - Arrest mechanism for a telescopic handle - Google Patents

Description

The invention relates to a locking mechanism for an inner tube and an outer tube having telescopic handle, in particular for a telescopic handle for household or garden tools, with an outer part, an inner part and at least one clamping part, wherein the outer part and the inner part relative to each other in the axial direction in a clamping direction K and in one of the clamping direction K opposite release direction L are displaceable, being pressed by a displacement in the clamping direction K, the clamping member against the telescopic handle to determine the inner tube and the outer tube against each other via a clamping force, and wherein by a shift in the release direction L, the clamping is solved to produce a displacement and / or rotation of the inner tube and the outer tube to each other.

Such a locking mechanism or a telescopic handle with such a locking mechanism is from the EP 2 255 712 A1 known. In this case, a displaceable relative to an inner sleeve in the axial direction outer sleeve is displaced in a clamping direction relative to the inner sleeve, whereby a clamping portion of the inner sleeve is made against the telescopic handle to set the two tubes of the telescopic handle against each other.

The Indian EP 2 255 712 However, locking mechanism shown is still in need of improvement, because when the outer sleeve relative to the inner sleeve is moved in the release direction to produce the mobility of the telescopic handle tubes to each other, there is the problem that the jaw pair, so to speak, only by its own power, in particular due to the inherent material elasticity of the inner tube , that it was previously hired, removed. But this is only possible be ensured insufficient, so that - especially after prolonged use of the telescopic handle, after which the material of the jaw pair has "used" to the clamping position - the danger that despite the displacement of the outer sleeve in the release position, the jaw pair still - if even slightly - rests against the inner tube and the inner tube along a relative movement of the inner tube relative to the pair of clamping jaws along the pair of clamping jaws along and also optionally braked rotational movements of the inner tube are braked. Because of this effect is also to be considered that the material of the jaw pair can not be a material such as soft plastic, which has a particularly high coefficient of friction, since such a material would further hinder the movement of the inner tube on the jaw pair past or even sticking of the jaw pair on the inner tube possible would be, for example, after prolonged disuse of the telescopic handle.

An initially mentioned telescopic handle also discloses the publication DE 36 25 287 A1 , Here, the displacement of the outer tube and inner tube is prevented by the fact that provided on the inner part against the inner tube tongue are provided with inwardly directed projections which cooperate with depressions in the inner tube, so that in a displacement of outer part to inner part in the release direction no free Displaceability of the inner and outer tube is made.

In the European patent application with the application number EP 12 163 819.1 Among other things, to eliminate the existing in the above prior art disadvantages a telescopic handle is described with the aforementioned locking mechanism, wherein two jaws are pivotally mounted on a hinge on the outer part of the locking mechanism and also a spreading member is provided to move away the jaws from the stem when outer part and inner part are displaced relative to each other in the release direction. In this embodiment, it has been found to be disadvantageous that when braking the rotational movement of the drill stem, the forces in the Braking in the circumferential direction act on the clamping part, are unfavorably transmitted to the hinge attachment, so that in cases of heavier load can lead to failure of this hinge attachment. Furthermore, it has been found that the hinge attachment in cases in which one presses the clamping force by further narrowing of the clamping point for clamping, by means of which the clamping jaws are pressed onto the pipe to be determined or braked increases (useful, for example, to increase the clamping force. or braking force), the hinge attachment as a result of the further narrowing increased, acting on the hinge attachment tensile force can also fail. Clamping mechanisms of the type mentioned are also in the publications US 4,277,197 . US 2011/02774481 A1 . US 5,983,455 . US 2012/0155950 A1 and US 4,524,484 disclosed. However, the clamping parts are here each designed as clamping cheeks material integral with the inner part, so that even in these embodiments, the disadvantages described above.

The object of the invention is therefore to provide a locking mechanism of the type described above, which allows an improved clamping or braking action, in particular an increased clamping or braking force, while minimizing the risk of failure of the locking mechanism. Furthermore, the locking mechanism should ensure the complete release of the clamping in order to ensure a possible unhindered movement of the telescopic handle tubes against each other.

This object is achieved according to the invention in that on the locking mechanism acting in the circumferential direction on the clamping part support is provided which is capable of supporting a force acting in the circumferential direction on the clamping part load, and / or that the locking mechanism acting in the axial direction on the clamping part support is provided, which is able to support a force acting in the axial direction on the clamping part load.

Due to the fact that the at least one clamping part additionally receives support in the circumferential direction and / or in the axial direction, forces acting on the clamping part can be intercepted much better and more reliably and introduced into the adjacent components. The support of the braking forces on adjacent components is no longer via a hinge or a similar failure-prone attachment or at least not alone on this, but directly on the Housing structure of the component that forms the support.

The support acting in the circumferential direction is arranged in the axial direction in an advantageous manner in the amount of acting on the (inner or outer) tube of the telescopic handle clamping surface of the clamping member and thus holds a possibly axially offset from the clamping surface arranged additional attachment of the clamping part Braking a rotating tube of the telescopic handle free of bending moments.

The described type of additional support is particularly important for a clamping part of meaning that is a separate component from the inner and outer part and so cooperates with the inner part or outer part, that it can be free in the radial direction of the outer or inner tube, if the locking mechanism is in the release position without the radially directed away from the telescopic handle tube movement associated with a deflection of the inner part or the outer part. In this case, the clamping part is not supported by the inner or the outer part not already in the circumferential direction and / or in the axial direction, because it is for example an integral part of the inner or outer part.

Preferably, the support via the inner part, which in turn rotatably preferably on the (outer or inner) tube of the telescopic handle is supported. The support can also be done via the outer part.

It can further be provided that the at least one clamping part is received in a recess of the locking mechanism, in particular in a shaft-like recess in the inner part of the locking mechanism or an inside, groove-like recess in the outer part, wherein the body edges or surface areas of the recess adjacent to the clamping part in the circumferential direction Form support, which are able to support the clamping part in the circumferential direction. To realize a support acting in the axial direction can be provided that the body edges adjacent in the axial direction to the clamping part or Surface regions of the recess form the support.

Preferably, the clamping part is loosely inserted as a loose part in the recess. More preferably, the recess forms a shaft in the inner part of the clamping mechanism, in which the recess surrounds the clamping part completely. Alternatively, the clamping member with an inside, that is on the side facing the tube to a telescopic handle side of the outer part, cooperate with the outer part, for example, in which a survey on the clamping part or the clamping member as a whole engages in a groove-like depression on the outer part or in the a radially inwardly projecting extension acts on the clamping part.

But it can also be provided that the at least one clamping part via an additional attachment, in particular via a hinge or hinge, on the locking mechanism, in particular on the inner part or on the outer part, is articulated. In this embodiment, it may still not come to the problems described above, as is relieved by the additional support and thus enabling self-supporting the clamping part on the body edges or surface areas of the recess, the additional attachment. Also in this case, the clamping part can be regarded as a separate component from the inner part and outer part, since the clamping part also move independently of the inner part or outer part in the radial direction, albeit in a directed around the rotary joint or hinge axis movement, the free mobility in the radial direction but limited for the application described here to a negligible extent.

The result of this embodiment is that the at least one clamping part during braking of a rotating part of the telescopic handle no longer has to support braking torque alone on a rather failure-susceptible mounting, but the braking or pulling forces acting on the clamping part when transferring the locking mechanism in the clamping position, can be intercepted directly via the support on the inner or outer part. A support which also acts in the axial direction, for example a surrounding recess which surrounds the clamping part, is possible such a favorable introduction of force from the clamping part on the support forming adjacent component, that the pressure of the at least one clamping member on the tube of the telescopic handle on which the clamping member acts, by narrowing the bottleneck responsible for the clamping force despite the concomitant to the clamping part acting tensile force can be interpreted very high, without causing the high tensile forces in a displacement of the inner part relative to the outer part in the clamping direction to a failure of the locking mechanism.

It may also be provided a the clamping part of the (outer or inner) tube of the telescopic handle wegdrängendes expansion member, so as to ensure that the clamping member, when the outer and inner parts are moved in the release direction against each other, is actively moved away from the telescopic handle. Such a spreading member exerts an expanding force on the clamping part, which actively ensures that the clamping surface of the clamping part lying in clamping position against the surface of the telescopic handle is urged away from the telescopic handle surface in the radial direction. This reliably ensures that in the release position, the clamping surface of the clamping part and the surface of the telescopic handle are spaced apart and also - as long as the release position is maintained - be maintained. The risk that the clamping member during a movement, for example, of the inner tube relative to the clamping member along this grinding, is excluded. In particular, the inner tube can be rotated and displaced so freely and unaffected by the clamping part relative to the clamping part. In addition, since the spreading members active, ie by exerting an expanding force on the clamping part, move away from the telescopic handle, a material is used on the inside of the clamping member, a material ensures that ensures a very high coefficient of friction. In particular, a soft plastic may be provided on the inside of the clamping part, while on the outside of the clamping part, over which, as will be explained below, the sliding part of the locking mechanism slides away, a harder plastic with a low friction value can be used than on the inside.

The spreading members are preferably designed as bending springs, such as wire or leaf springs, which act on the clamping part and are supported on the outer or inner part. They are biased so that they then move the clamping part, when the locking mechanism is in the release position, from the telescopic tube.

But it can also be provided spreading members, which move in the axial direction on the clamping part, when inner part and outer part are moved in the release direction relative to each other. In this case, the spreading members can either push under the clamping part and this by an inclined plane radially outward, ie away from the surface of the telescopic handle, lift. Or they can penetrate into one or more axially or circumferentially extending gaps and thus actively move away the at least one clamping part from the pipe surface in the radial direction.

Preferably, the inner part is firmly and immovably connected to the telescopic handle and the outer part can move largely free of play on the inner part. For this purpose, the outer part may be formed as a tubular outer sleeve and the inner part as an integral with the telescopic handle inner sleeve, wherein the inner diameter of the outer sleeve is adapted to the outer diameter of the inner sleeve, that the outer sleeve can be easily, but largely free of play over the inner sleeve.

In order to move the inner part and outer part relative to each other, a locking mechanism mounted on the actuating member is provided, via the actuation of the inner part and the outer part can be moved relative to each other. For this purpose, the actuator may be pivotable about a pivot axis fixedly defined in its spatial position either to the inner part or to the outer part. About a eccentric to the pivot axis mounted cam, which acts upon pivoting of the actuator to the other part to move this, the outer part and inner part are then moved relative to each other in the axial direction of the telescopic handle. The pivot axis is v orthogonal to the axially extending Aligned center axis of the telescopic handle. As actuator advantageously a pivot lever is provided.

It may further be provided a locking mechanism holding the locking mechanism in releasable detent connection, which counteracts a transfer of the locking mechanism from the clamping position into the release position, ie a movement in the release direction. For this purpose, the actuating member may have a first (male or female) detent member which cooperates with a second detent member (female or male) corresponding to the first detent member to hold the actuator in the clamping position. As a result, the probability that the locking mechanism is transferred by accidental operation unintentionally from the clamping position to the release position, minimized.

Further advantages of the invention will become apparent from the dependent claims and from the following description of preferred embodiments with reference to the drawings.

Fig. 1

einen Teleskopstiel mit einem Feststellmechanismus in einer Gesamtansicht,

Fig. 2a

eine Außenansicht des Feststellmechanismus in Klemmstellung,

Fig. 2b

eine Außenansicht des Feststellmechanismus in Lösestellung,

Fig. 3a

den inneren Aufbau des in Klemmstellung befindlichen Feststellmechanismus in einer ersten Ansicht mit teilweise zeichnerisch freigeschnittenen Klemmteil,

Fig. 3b

den inneren Aufbau des in Lösestellung befindlichen Feststellmechanismus in einer zweiten Ansicht mit teilweise zeichnerisch freigeschnittenen Klemmteil,

Fig. 4a

eine alternative Ausgestaltung einer auf ein Betätigungsglied wirkenden Rastverbindung bei in Lösestellung befindlichen Feststellmechanismus, und

Fig. 4b

die Ausgestaltung aus Figur 4a bei in Klemmstellung befindlichen Feststellmechanismus.

In the drawings shows:

Fig. 1

a telescopic handle with a locking mechanism in an overall view,

Fig. 2a

an external view of the locking mechanism in clamping position,

Fig. 2b

an external view of the locking mechanism in the release position,

Fig. 3a

the inner structure of the clamping mechanism located in the clamping position in a first view with partially diagrammatically cut free clamping part,

Fig. 3b

the inner structure of the locking mechanism located in the release position in a second view with partially graphically cut free clamping part,

Fig. 4a

an alternative embodiment of a force acting on an actuator latching connection located in the release position locking mechanism, and

Fig. 4b

the embodiment FIG. 4a when located in clamping position locking mechanism.

In FIG. 1 a telescopic handle 1 is shown in an overall view. The telescopic handle 1 is constructed in several parts and, in addition to an upper outer tube 2, a lower inner tube 3, which can slide into the outer tube 3 in order to vary the length of the telescopic handle 1. At the lower end of the inner tube 3, a holder 4 is provided for a work attachment, not shown. Such a work attachment may in particular be formed by a mop head, a dust catcher, a broom, a window wiper or similar work attachments that can be used in the home or garden.

Outer tube 2 and inner tube 3 can optionally be braced against each other to prevent relative mobility with respect to the other part, or be detached from each other to produce the relative mobility (displacement and / or rotation). For this purpose, a locking device is provided with a locking mechanism 5.

The in FIG. 1 shown telescopic handle 1 also has an optional feature an internal drive unit 6, which ensures that after loosening the locking device and when sliding in the inner tube 3 in the outer tube 2, the inner tube 3 is rotated relative to the outer tube 2 in rotation, which, for example, the ejection of a can serve on the holder 4 mounted wiping head of a wiper device. Of course, the locking mechanism according to the invention can also be used with telescopic handles without such a drive unit.

As far as above and below the telescopic handle 1 is always described by way of example in connection with an upper outer tube 2 and a lower inner tube 3, it should be noted that, of course, the outer tube below and the inner tube can be arranged above. Any components of a drive unit 6 or the locking device 5 and the position of the components would be adapted in this case to the other structure.

Figure 2a and 2b show the locking device in a schematized external view, wherein in FIG. 2a the locking device 5 is shown in clamping position, in the inner tube 3 and outer tube 2 are not movable relative to each other, and in FIG. 2b the locking device 5 is shown in the release position, in which the clamping mechanism is released and inner tube 3 and outer tube 2 are movable relative to each other. In order to change between the clamping position and the release position, an actuating member in the form of a pivot lever 7 is provided. The pivot lever 7 is defined via a pivot axis S against an inner part 8 pivotally defined. To form the defined pivot axis S, the rocker lever 7 engages with two bearing journals in the inner part 8. At the same time an outwardly directed sliding cam 10 is provided on the pivoting lever 7, which is arranged eccentrically to the pivot axis S and which is engaged by engagement in a provided in an outer part 11 of the locking device 5 groove 12 with the outer part 11 in operative connection.

Like the juxtaposition of FIG. 2a and the FIG. 2b show, the position of the sliding cam 10 relative to the pivot axis S is changed by the pivoting of the pivot lever 7. Due to the fact that the pivot lever 10 is in engagement both with the inner part 8 and with the outer part 11, upon pivoting of the pivot lever 7 inner part 8 and outer part 11 are displaced against each other in the axial direction, without a rotation of the outer part 11 opposite the inner part 8 would have to, which is necessarily the case with solutions in which outer part and inner part mesh via a thread, necessarily. This is a particular advantage of the embodiment described here, as this significantly increases handling comfort. When opening the pivot lever 7, ie the transition from the in FIG. 2a shown clamping position to the in FIG. 2b shown release position, the outer part 11 moves relative to the inner part 8 in the release direction L. When closing the clamping lever, so when it is transferred from the release position ( FIG. 2b ) in the clamping position ( FIG. 2a ), the outer part 11 moves relative to the inner part 8 in the clamping direction K.

On an end face of the outer part of a cover sleeve 13 is placed and connected to it in such a way that the cover sleeve 13 engages over the inner part in the axial direction and covers optically.

In the Figure 2a and 2b shown embodiments are in Figure 3a and 3b in a slightly modified version, but with largely identical and on the in Figure 2a and 2b embodiment shown shown transferable functionality with further details of the partially graphically cut free inner life.

There are clamping parts provided, which is formed from here by way of example of two radially opposite and evenly distributed over the circumference jaws 15 (from the figures, only one jaw is visible, which is also shown in the drawing in section). Of course, not necessarily exactly two clamping parts must be provided. In certain cases, a single clamping part may be sufficient or more than two clamping parts may be used.

The clamping parts 15 are in the form of loose parts in a recess 9 provided in a component of the locking mechanism (here, for example, in a shaft-like recess provided in the inner part 8) and are peripherally surrounded in their entirety by this recess 9. The clamping parts can move independently of the inner part and outer part in the radial direction freely. The lateral body edges or surface areas of the recess 9, which are adjacent to the clamping parts 15, form a support on which forces acting on the clamping parts 15 are supported by the inner tube 3 of the telescopic handle and intercepted by the inner part 8.

As in Figure 3a and 3b recognizable, the inner part 8 is fully closed at its downwardly facing end face. The web 22, which is therefore located in the axial direction below the clamping part 15, securely supports the clamping part 15 or forces acting thereon in the axial direction in the clamping operation described below. In the same way supports the web 22 in the axial direction opposite edge 22 'of the recess 9 at a force acting on the clamping member 15 load in the opposite direction. The forces acting on the clamping part in the circumferential direction are supported by the lateral edges 23 recess 9.

Figure 3a and 3b also illustrate the clamping function. In FIG. 3b It can be seen that the inner diameter of the outer part 11 in the area in which the clamping parts 15 are located, starting from the end-face, the lower end of a first diameter section 16 with the diameter d ₁ to a second diameter section 17 with the diameter d ₂ tapered (d ₁ > d ₂ ). For this purpose, a clamping cone 24 is provided on the outer part on the inside. In the in FIG. 3a shown clamping position are the clamping members 15 with its outermost extending contact point 18, which is formed by a circumferentially extending survey on the outside of the clamping member 15, in the second diameter portion 17. Here, the outer part 11 is close to its inner wall Clamping part 15, so that the pointing to the telescopic handle clamping surface of the clamping member 15 is made on the resulting clamping force against the telescopic handle tube and the desired clamping effect occurs.

FIG. 3b shows the locking mechanism in release position. The contact point 18 is now in the first diameter region 16 with the diameter d ₁ , so that the inner wall of the outer part 11 is radially spaced from the contact point 18 and from the circumferentially extending elevation on the outside of the clamping member and the jaws, without a counterforce would occur, can remove the suspension of the clamping effect to the outside of the inner tube surface.

On the one hand to achieve a large clamping force, but on the other hand to ensure low operating forces (which also has the advantage that the components have to absorb low forces and therefore can be constructed inexpensively with little material), the clamping member 15 is formed such that it at the the telescopic handle surface facing inside has a soft plastic, which ensures a high friction value. On the outside, in particular in the region of the contact point 18, and also on the area of the clamping jaws coming into contact with the spreading members, on the other hand, a material is advantageous which ensures a low coefficient of friction. Thus, the individual components during the transfer of the clamping position in the release position and vice versa slide well on each other and thus produce only small, the respective relative movements opposite forces. For this purpose, the jaws can be produced in particular by two-component injection molding.

At the in Figure 3a and 3b as in FIG. 1 As shown, the inner part 8 is fixedly arranged on the outer tube 2 of the telescopic handle. The inner tube 3 of the telescopic handle is guided within the outer tube 2 and thus also within the inner part 8.

As far as the invention has been described to the effect that the pivot lever 10 engages in the inner part 8 to form a defined pivot axis S and the eccentric sliding cam 10 with a groove 12 in the outer part 11 is engaged, it should be noted that such an arrangement is not mandatory , Depending on the structural conditions and requirements of the case, other constellations may be useful in which, for example, the outer part is firmly connected to the telescopic handle and the inner part is moved. It is also conceivable that the pivot lever engages in the outer part to form a defined pivot axis and the sliding cam or a comparable component acts on the inner part. Also, the clamping part is not necessarily embed the inner part, but can - depending on the structural requirements of the case - be articulated on the outer part. Of course, the number of clamping pieces or jaws can of course be varied and is not limited to the above-mentioned number of a single clamping part or of only two jaws.

In Figure 2a and 2b It can also be seen that in the exemplary sleeve-like outer part 11, a receptacle 19 is provided, into which the actuating member forming pivot lever 7 in the clamping position so flush dives that outer part 11 and actuator form a substantially flush outer surface. Actuator us outer part form in particular an outside largely smooth cylinder.

On the other hand clarify Figure 3a and 3b an alternative embodiment in which the example designed as a pivot lever 7 actuator projecting the outer part 11 in the axial direction beyond the upper end face 20 of the outer part. This has the advantage that the actuator can be particularly easily grasped.

Further show Figure 3a and 3b respectively. Figure 4a and Figure 4b acting between the actuator 7 and another component of the locking mechanism, releasable by hand latching connection 21 which holds the actuator in the clamping position and counteracts an accidental adjustment of the locking mechanism in the release direction L by a manually bridged locking resistor.

At the in Figure 3a and 3b 1, a male detent member 21 'is provided on the outer member 11 and a female detent member 21 "is provided on the actuating member 7. The female detent member 21" is formed by an edge-side recess on the actuating member 7 formed as a pivoting lever into which the male corresponding to the outer member 8 is inserted Detent member 21 'engages when the pivot lever 7 is in the clamping position.

As an alternative to the in Figure 3a and 3b illustrated embodiment illustrate Figure 4a and Figure 4b an embodiment in which the latching connection 21 is provided via a male locking member 21 'on the actuating member 7 and a female locking member 21 "on the inner part 8. The male locking member 21' extends in the clamping position of the inside of the pivot lever 7 in radial direction on the inner part 8, penetrates the female locking member 21 "and engages behind with a locking projection, the inner part. 8

The design of the locking mechanism with a latching connection is considered as a further advantage over the prior art and as an independent invention.

LIST OF REFERENCE NUMBERS

1

telescopic handle

2

outer tube

3

inner tube

4

bracket

5

Locking device

6

drive unit

7

pivoting lever

8th

inner part

9

recess

10

pushers

11

outer part

12

groove

13

off the barrel

14

Spreading elements, expanding wedges

15

Clamping part, jaw

16

first diameter range

17

second diameter range

18

contact point

19

admission

20

upper end of the outer part

21

locking connection

21 ', 21 "

male detent member, female detent member

22

lower end of the inner part with support bar

22 '

upper support edge of the recess

23

lateral supporting edges of the recess

24

clamping cone

K

clamping direction

L

release direction

S

swivel axis

A

axial direction

R

radial direction

U

circumferential direction

Claims (9)

1. Fastening mechanism (5) for a telescopic handle (1) comprising an internal tube (3) and an external tube (2), with an outer part (11), an inner part (8) and at least one clamping part (15), wherein the outer part (11) and the inner part (8) can be displaced relative to one another in a clamping direction K and in a loosening direction L opposite to the clamping direction K, wherein, through a displacement in clamping direction K, the clamping part (15) is pressed against the telescopic handle (1) in order to fasten the internal tube (3) and the external tube (2) against one another via a clamping force, and wherein, through a displacement in loosening direction L, the clamping is released in order to allow a displaceability and/or rotatability of the internal tube (3) and of the external tube (2), wherein a support acting on the clamping part (15) in peripheral direction U, which can support a load acting on the clamping part (15) in peripheral direction U, is provided on the fastening mechanism (5), and/or that a support acting on the clamping part (15) in axial direction A, which can support a load acting on the clamping part (15) in axial direction A, is provided on the fastening mechanism (5), characterised in that, a recess (9) is provided in the inner part (8) or in the outer part (11), in which the clamping part is retained, and the support is formed via the sides of the recess adjoining the clamping part (15).
2. Fastening mechanism according to claim 1, characterised in that, viewed in axial direction A, the support acting in peripheral direction is arranged at the level of the clamping surface of the clamping part (15) acting on the telescopic handle (1).
3. Fastening mechanism according to any one of the preceding claims, characterised in that the clamping part (15) is a separate component from the inner part (8) and outer part (11), which is freely movable relative to the telescopic handle in radial direction R, independently of the inner part (8) or outer part (11).
4. Fastening mechanism according to any one of the preceding claims, characterised in that the at least one clamping part (15) is inserted in a recess (9) in the inner part (8) or in the outer part (11).
5. Fastening mechanism according to any one of the preceding claims, characterised in that the clamping part (15) is inserted loosely into the recess (9).
6. Fastening mechanism according to any one of the preceding claims, characterised in that a recess (9) is constituted in a component of the clamping mechanism (5) as an insertion shaft for the clamping part (15).
7. Fastening mechanism according to any one of the preceding claims, characterised in that the recess (9) surrounds the full periphery of the clamping part (15).
8. Fastening mechanism according to any one of the preceding claims, characterised in that an expansion element forcing the clamping part away from the external tube (2) or from the internal tube (3) is provided, which acts on the at least one clamping part (15) in order to move the clamping part (15) away from the external tube (2) or from the internal tube (3) when outer part (11) and internal part (8) are displaced relative to one another loosening direction L.
9. Fastening mechanism according to any one of the preceding claims, characterised in that a snap-in connection (21) is provided, which holds the fastening mechanism (5) in the clamping position and counteracts a displacement in loosening direction L through a snap-in resistance.

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