Title:
Actuating means able to be activated by fluid action
Kind Code:
A1


Abstract:
An actuating means adapted for fluid activation has a contractile hose terminally secured by clamping on at least one head piece. The contractile hose fits into an annular clamping gap or nip, whose wall bears saw tooth serrations, the saw tooth serrated areas being so arranged that their teeth are radially opposite each other and arranged in pairs each at the same level. The outer saw tooth serrated area is located on a compression sleeve, which is radially pressed to join it with the hose end section surrounded by it.



Inventors:
Schantze, Achim (Sulz a.N., DE)
Müller, Alexander (Altbach, DE)
Lorenz, Bernd (Baltmannsweiler, DE)
Application Number:
11/124737
Publication Date:
12/01/2005
Filing Date:
05/09/2005
Assignee:
Festo AG & Co.
Primary Class:
Other Classes:
417/474
International Classes:
F04B43/08; F04B43/12; F15B15/10; F15B15/14; (IPC1-7): F04B43/08; F04B43/12
View Patent Images:
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Primary Examiner:
RIPLEY, JAY R
Attorney, Agent or Firm:
Hoffmann & Baron LLP (Syosset, NY, US)
Claims:
1. An actuating means able to be activated by fluid action comprising a contractile hose, extending between two head pieces and adapted, under fluid action in the space within it, to undergo radial expansion while simultaneously exerting axial tension forces on the head pieces involving a tendency to draw same together, the contractile hose having a hose body of a material with rubber elastic properties and a strand structure embedded in the wall of the hose body with a coaxial arrangement, said contractile hose being secured to at least one head piece by having an end section thereof clamped in an annular clamping gap, which is defined by the outer periphery of an inner head piece part extending axially into the contractile hose and the inner periphery of an outer head piece part coaxially surrounding the contractile hose at the level of the inner head piece part, wherein the outer periphery of the inner head piece part and the inner periphery of the outer head piece part have saw tooth serrated areas, whose direction of serration is in the axial direction, the flat tooth flanks facing the clamping gap opening with the contractile hose extending through it, the two saw tooth serrated areas are so arranged that their teeth, lying at the same axial level, are respectively radially opposite each other in pairs and the outer head piece part is designed in the form of a compression sleeve radially compressed, with radial deformation, with the hose end section surrounded by it.

2. The actuating means as set forth in claim 1, wherein prior to such radial pressing the compression sleeve is able to be slipped from the front side opposite to the axial clamping gap opening coaxially onto the inner head piece part and owing to mutually engaging abutment faces provided on the one hand on the compression sleeve and on the other hand on the inner head piece part an axial slipping on position of the compression sleeve is set, in which the teeth of the two saw tooth serrated areas are opposite to each other in pairs at the same axial level.

3. The actuating means as set forth in claim 2, wherein abutment faces provided for setting the slipping on position possess an annular configuration.

4. The actuating means as set forth in claim 1, wherein the compression sleeve possesses a radially inwardly protruding annular projection, which during radial pressing fits into a radially open locating groove in the inner head piece part.

5. The actuating means as set forth in claim 4, wherein prior to such radial pressing the compression sleeve is able to be slipped from the front side opposite to the axial clamping gap opening coaxially onto the inner head piece part and owing to mutually engaging abutment faces provided on the one hand on the compression sleeve and on the other hand on the inner head piece part an axial slipping on position of the compression sleeve is set, in which the teeth of the two saw tooth serrated areas are opposite to each other in pairs at the same axial level and wherein the abutment faces are constituted by respectively one flank of the annular projection and the locating groove.

6. The actuating means as set forth in claim 1, wherein at the front side axially opposite to the axial clamping gap opening the clamping gap merges with an annular gap extending in a radially outward direction and defined between the inner head piece part and the compression sleeve, into which gap hose body material may be displaced during pressing.

7. The actuating means as set forth in claim 1, wherein the resulting envelope lines running in the longitudinal direction and radially opposite to each other, of the two saw tooth serrated areas extend in parallelism to each other.

8. The actuating means as set forth in claim 1, wherein the two saw tooth serrated areas widen conically toward the axial clamping gap opening, which has the contractile hose extending through it.

9. The actuating means as set forth in claim 1, wherein the radial distance apart between the envelope faces defined by the tooth tips of the two saw tooth serrated areas is equal to at least the radial dimensions of the strand structure embedded in the wall of the hose body.

10. The actuating means as set forth in claim 1, wherein the rear end section, directly adjoining the axial clamping gap opening, of the clamping gap is free of teeth and has a smooth surface.

11. The actuating means as set forth in claim 1, wherein the height of the teeth of the saw tooth serrated areas is approximately equal to one quarter of the wall thickness of the hose body.

12. The actuating means as set forth in claim 1, wherein one tooth is provided per millimeter length of the saw tooth serrated areas.

13. The actuating means as set forth in claim 1, wherein the strand structure comprises strands arranged in a cross over pattern.

14. The actuating means as set forth in claim 1, wherein the strand structure comprises two strand groups arranged in a cross over configuration with flexurally bending strands extending alongside each other and with the same longitudinal orientation within a strand group, such strand groups being constantly held at a radial distance apart from each other by the material of the hose body.

15. The actuating means as set forth in claim 1, wherein the contractile hose is secured at both ends as set forth in claim 1 at a head piece.

Description:

BACKGROUND OF THE INVENTION.

The invention relates to an actuating means able to be activated by fluid action comprising a contractile hose, extending between two head pieces and adapted, under fluid action in the space within it, to undergo radial expansion while simultaneously exerting axial tension forces on the head pieces involving a tendency to draw same together, the contractile hose having a hose body of a material with rubber elastic properties and a strand structure embedded in the wall of the hose body with a coaxial arrangement, said contractile hose being secured to at least one head piece by having an end section thereof clamped in an annular clamping gap, which is defined by the outer periphery of an inner head piece part extending axially into the contractile hose and the inner periphery of an outer head piece part coaxially surrounding the contractile hose at the level of the inner head piece part.

THE PRIOR ART.

In the case of an actuating means of this type disclosed in the patent publication WO 00/61952 A1 a contractile hose, composed of a rubber elastic hose body and a strand structure embedded in the hose body has both its hose end sections secured in a respective head piece. The head pieces comprise an inner head piece part extending into the contractile hose and an outer head piece part surrounding the associated hose end section, such outer head piece part being designed like a union nut and being screwed onto the inner head piece part. Between the two parts an annular clamping gap is defined, in which the associated hose end section is clamped by compression. The pressing operation occurs because there is the axial screwing of the two parts of the head piece and a conical shape of the clamping gap or nip.

For the activation of the actuating means the inner space of the contractile hose is filled with a pressure medium under a certain actuating pressure. This causes a radial expansion of the contractile hose resulting in a tendency to axially contract so that tension forces are applied to the head pieces, whose action on the head pieces involves moving same together. It is in this manner that external structures or, respectively, components, which are fixed to the head pieces, may be braced together and/or shifted in relation to one another.

The clamping connection between the contractile hose and the head pieces has turned out to be problematical more especially on the occurrence of substantial tension forces. Although the clamping face of one of the clamping units is provided with several projections, which are able to bite into the material of the contractile hose, there is danger of the contractile hose's being pulled out of the clamping gap.

In order to meet this problem there has already been a proposal in the German patent publication 10,034,389 C2 to design the portions, which lie against the hose end sections, of the inner head piece part and of the outer head piece part so that same may be moved in relation to each other axially to a limited extent so that on activation of the actuating means there is an entraining effect which results in a reduction in the width of the clamping gap and therefore an increase in the surface pressure. In order to optimize the entraining effect the faces engaging the hose body may have a finely divided surface structure, as for example a groove structure, or also have a finely divided structure with punctuate mounds and pits. This design does however involve increased design complexity, something which renders manufacture more costly.

SHORT SUMMARY OF THE INVENTION

One object of the invention is to create an actuating means which despite a simple structure ensures a reliable connection between the contractile hose and the head piece even on the occurrence of high tensile forces.

In order to achieve these and/or other objects appearing from the present specification, claims and drawings, in the present invention the outer periphery of the inner head piece part and the inner periphery of the outer head piece part have saw tooth serrated areas, whose direction of serration is in the axial direction, the flat tooth flanks facing the clamping gap opening with the contractile hose extending through it, the two saw tooth serrated areas are so arranged that their teeth, lying at the same axial level, are respectively radially opposite each other in pairs with their tips opposite each other and the outer head piece part is designed in the form of a compression sleeve radially compressed, with radial deformation, with the hose end section surrounded by it.

Owing to the saw tooth serrated areas it is possible for both the inner head piece part and also the outer head piece part to bite into the elastic material of the hose body so that there is a powerful interlocking effect, so that even in the case of a high tension load a drawing of the contractile hose out of the respective head piece is prevented. Since the teeth of the saw tooth serrated areas lie at the same axial level, the strand structure embedded in the hose body is essentially only subjected to transverse compression and not to flexure so that despite substantial compression a straight longitudinal alignment of the strand structure may be ensured. Accordingly slipping of the contractile hose out of the clamping gap is opposed. Furthermore the danger of damage to the strand structure at the teeth tips is minimized in this way. Damage to the material is furthermore prevented by the preferably strictly radial pressing of the two parts of the head piece so that during assembly axial relative movement between the saw tooth serrated areas are prevented, which could otherwise lead to damage of the elastic material of the hose body.

Further advantageous developments of the invention are defined in the claims.

The compression sleeve is preferably able to be slipped from the opposite front side (opposite to the axial clamping gap opening) coaxially on the inner head piece part prior to radial pressing until owing to mutually cooperating abutment faces, an axial relative position is reached in which the paired radial alignment of teeth of the saw tooth serrated areas on the two sides is attained. This renders possible high speed production without involved adjustment operations.

It is an advantage if the compression sleeve has an annular, radially inwardly extending positioning projection, which during radial pressing fits into an annular, radially outwardly open securing groove in the inner head piece part and in this manner sets the desired axial relative position of the two parts of the head piece.

At the front side axially opposite to the axial clamping gap opening the clamping gap can merge with an annular gap extending radially outward and defined between the inner part of head piece and the compression sleeve, such gap rendering possible a displacement without damage of the pressed hose body material.

The saw tooth serrated areas are preferably so arranged that their envelope lines defined by the teeth tips extend in parallelism to each other. This means that there is an even pressing along the entire length of the clamped hose end section avoiding local overloading.

A further advantage results from there being a form of the two saw tooth serrated areas, and therefore of the clamping gap, widening toward the axial clamping gap opening, through which the contractile hose extends. The slope in relation to the longitudinal axis of the head piece is of the order of 2 degrees. As has been found this slope of the clamping gap, which is opposite to the design of the said patent publication 00/61952 A1, leads to substantially improved attachment conditions. This is more especially the case when the diameter of the clamping gap at the axial clamping gap opening is somewhat larger than the diameter of the contractile hose in the middle section between the two head pieces in the deactivated condition.

When the radial distance between the two envelope faces, defined by the teeth tips, of the two saw tooth serrated areas is at least as large as the radial dimensions of the strand structure embedded in the wall of the hose body and is preferably even somewhat larger, a particularly secure clamping of the contractile hose without damage of the strand structure is possible.

The load on the contractile hose at the axial clamping gap opening may be substantially reduced if the rear end section located here, of the clamping gap, is free of teeth and smooth. The saw tooth serrated area the comes to an end before reaching the clamping gap opening.

It has been found to be particularly advantageous if the height of the teeth of the saw tooth serrated areas is so selected that it is approximately equal to ¼ of the wall thickness of the hose body.

Further advantageous developments and convenient forms of the invention will be understood from the following detailed descriptive disclosure of an embodiment thereof in conjunction with the accompanying drawings.

LIST OF THE SEVERAL VIEWS OF THE FIGURES

FIG. 1 shows a preferred working example of the actuating means in accordance with the invention, partly in longitudinal section and in the pressed state of the compression sleeve.

FIG. 2 shows part of the end section, illustrated in the top figure half of FIG. 1, of the actuating means on a larger scale.

FIG. 3 represents the end section, illustrated in the top half of FIG. 1, of the actuating means prior to pressing of the compression sleeve, the compression sleeve being indicated in chained lines prior to coaxial placement on the inner part of head piece provided with the contractile hose.

DETAILED ACCOUNT OF WORKING EMBODIMENT OF THE INVENTION

The actuating means 1 illustrated in the drawings by way of example comprises two first and second head pieces 2 and 3 arranged at an axial distance apart, which are permanently connected together by way of a linearly extending contractile hose 4. At least in the deactivated state of the actuating means 1 the contractile hose 4 preferably has an essentially tubular form.

As regards details the contractile hose 3 of the working example possesses an elongated hose body 5 consisting of a material with rubber elastic properties. As a material more particularly rubber itself or another elastomeric material is employed. In the wall of the hose body 5 a strand structure 6 is embedded, which is for the sake of simplicity only indicated in chained lines, which is completely surrounded by the material of the hose body 5 and is coaxial to the body.

Preferably the structural design of the contractile hose 4 is the same as that described in the said patent publication WO 00/61952 A1. In the following explanations about the strand structure 6 there is accordingly a limitation the principal features. As regards further details attention is called to the content of the above mentioned specification.

The strand structure 6 comprises strands 7a and 7b arranged to cross over one another and having a high tensile strength. These strands are collected in two strand groups including on the one hand the strands 7a and on the other hand the strands 7b, the strands 7a and 7b extending within a respective strand group having the same longitudinal orientation. The two strand groups themselves are arranged in a crossed over configuration as is illustrated in FIG. 1 in the enlarged part thereof, showing the strand structure looking radially in relation to longitudinal axis 9 of the actuating means 1.

Preferably there is no physical contact between the two strand groups. The material of the hose body 5 holds the strand groups constantly at a radial distance apart in relation to each other. Direct contact between the strand groups 7a and 7b, which would cause increased friction may thus be excluded.

The contractile hose 4 has its two axial end sections 10—in the drawing only illustrated in connection with the sectioned left hand head piece 2—so secured to the respectively associated head piece 2 and 3 that on the one hand there is a fluid-tight connection between the hose body 5 and the respective head piece 2 and 3 and on the other hand tension forces are able to be transmitted to the respective head piece 2 and 3.

In its interior the contractile hose delimits an interior space 13 which at the end is terminated at the ends by the two head pieces 2 and 3. Into the interior space 13 there opens at least one fluid duct 14, which in the working example extends through the first head piece 2 outside the plane of the drawing. The outer end of the fluid duct 14 is so designed that a fluid line, not illustrated in detail, is able to be attached with which the connection with a pressure source may be produced. By the use of an intermediately placed control valve arrangement, not illustrated in detail, there is accordingly the possibility of supplying fluid pressure medium, for example compressed air, through the fluid duct 14 for the purpose of activating the actuating means, into the interior of the hose, or for the purpose of deactivating the actuating means by letting off fluid from the interior space 13 of the hose.

Preferably the actuating means 1 is operated with a gaseous medium and more particularly compressed air. It is however suitable for operation with a hydraulic fluid, for instance oil or water too.

Each head piece 2 and 3 is provided at an externally accessible point with force output connection means 17. In the working embodiment same are constituted by a threaded sections. They render possible the attachment of the respective head piece 2 and 3 to a component, not illustrated. For instance it would be possible to secure the first head piece 2 at its force output means 17 stationarily on a holding structure and to the connect the other head piece 3 with a machine part moving in relation to the holding structure. The output means 17 are as a rule connected with such components, which in the case of need must be drawn together with a certain force.

The operating pressure building up in the interior space 13 of the hose during activation of the actuating means causes an actuation of the contractile hose 4 such that there is a radial expansion. The consequence of this is that the contractile hose 4 simultaneously undergoes an axial contraction, the axial tension forces then resulting acting to produce a mutual movement together of the head pieces 2 and 3. It is in this manner that components secured to the two head pieces 2 and 3 may be shifted in relation to each other.

The drop in pressure taking place on deactivation in the interior space 13 in the hose means that the contractile hose 4 returns to the original condition of extent. In case of need this return movement may however be aided with additional means, as for example spring means.

The particular movement and deformation characteristics of the contractile hose 4 result from the above mentioned integrated strand structure 6. Owing to the crossed over configuration, which in the working example results from an opposite helical course of the two strand groups in relation to the longitudinal axis 9, there are rhombic grid areas. Owing to the internal pressure actuation of the contractile hose 4 a change of the angles of the rhombs is caused, something which ultimately causes the effects described.

In order to transmit the tension forces to the head pieces 2 and 3 the contractile hose 4 has its end sections 10 firmly clamped in an annular clamping gap or nip 18 in the respectively associated head piece 2 and 3.

The clamping gap 18 is located radially between the outer periphery of an inner head piece part 22 and the outer head piece part 23 coaxially surrounding the outer head piece part 23. In this case the clamping gap 18 is provided with an axially orientated annular clamping gap opening 24 facing the respectively other head piece 2 and 3 and through which the contractile hose 4 extends into the clamping gap 18.

The inner head piece part 22 is preferably that respective component of the head piece 2 and 3, which is provided with the force output means 17. Its first attachment section 25, which in the example is stud-like, 25 extends from the end some distance into the contractile hose 4, the outer periphery of such attachment section 25 being provided with a first saw tooth serrated area 27. At the same axial level as the first attachment section 25 the inner head piece part 22 is surrounded, with the hose end section 10 is axially in between, by a sleeve-like attachment section 26 of the outer head piece part 23, whose inner periphery is provided with a second saw tooth serrated area 28.

The individual teeth 32 and 33 of the saw tooth serrated areas 27 and 28 are annularly shaped and with a form concentric to the longitudinal axis 9, the teeth being arranged in sequence in the direction of the longitudinal axis 9, that is to say axially, this resulting in a saw tooth serrated form in the axial direction.

As more particularly clearly depicted in FIG. 2 the saw tooth serrated areas 27 and 28 are so designed that their flat tooth flanks 34 face the clamping gap opening 24 and accordingly the respectively opposite other head piece. On the other hand the steep tooth flanks 35 face forward toward the front end, opposite to the contractile hose 4, of the respective head piece 2 and 3.

FIG. 2 furthermore clearly shows that the two saw tooth serrated areas 27 and 28 are so arranged that their teeth are respectively arranged in pairs at the same level so that in the axial direction, that is to say in the direction of the longitudinal axis 9 there is a plurality of pairs of teeth, one respective tooth 32 of the first saw tooth serrated area 27 and a tooth 33 of the second saw tooth serrated area 28 being radially opposite each other. Several such radial “tooth planes” are indicated in chained lines in FIG. 2.

The outer head piece part 23 constitutes a compression sleeve 37 and is radially pressed with radial deformation together with the hose end section 10 surrounded by it, the hose end section 10 being supported in a radially inward direction by the first attachment section 25 gripping it of the inner head piece part 22. Owing to such pressed connection the teeth 32 and 33 are forced into the wall of the hose body 5, while the hose material then displaced is received in the intermediate spaces 38 between teeth. It is in this manner that the entire clamping gap 18 with the saw tooth serrations is filled up with the material of the hose body 5. In conjunction with the strong pressing effect the resulting interlocking and hooking hold lead to a firm engagement with the hose end section 10 and prevent its dropping out even under extremely high tension forces.

The compression sleeve 17 bears against the inner head piece part 22 axially to resist the acting tension forces. For this purpose the inner head piece part 22 possesses an axially projecting first abutment face 42 in the working example, which is orientated axially to the fore, that is to say away from the contractile hose 4. This first abutment face 42 preferably has an annular form and is located on a radially projecting annular collar 44 (delimiting the clamping gap 18 on the front side opposite to the clamping gap opening) on the inner head piece part 22. The annular collar 44 thus extends radially past the first saw tooth serrated area 27.

A second abutment face 43 provided on the compression sleeve 37 and preferably also annular, faces the first abutment face 42 and is axially opposite to it. It is located on an annular projection 45 axially to the fore of the second attachment section 26, such projection 45 extending inward and hooking about the annular collar 44 at the the front axial side opposite to the clamping gap 18.

The two abutment faces 42 and 43 serve not only for the transmission of force but also for positioning the compression sleeve 37 during assembly.

Prior to assembly the compression sleeve 37 is so radially expanded in accordance with FIG. 3 that the radial distance between the first and second envelope faces of the two saw tooth serrated areas, defined by the tips of the teeth 32 and 33, of the two saw tooth serrated areas 27 and 28 is the same as the wall thickness of the contractile hose 4 or is slightly larger. The inner diameter of the annular projection 45 is at the same time somewhat smaller than the outer diameter of the annular collar 44 so that there is a radial overlap. In this condition, after the hose end section 10 to be secured has been slipped over the first saw tooth serrated area 27 of the inner head piece part 22, the compression sleeve 37 is indicated by the arrow slipped from the front side coaxially onto the inner head piece part 22 until the annular projection 45 engages the annular collar 44 and accordingly the desired axial slipping-on position of the compression sleeve 37 is reached, the teeth 32 and 33 lying in pairs at the same axial level.

After this using a pressing tool, not illustrated in detail, a deforming force radially orientated in relation to the longitudinal axis 9 is exerted on the compression sleeve 37 as indicated by the arrows 53 so that the there is

a radial deformation of the compression sleeve 37 in connection with a reduction in diameter of the second envelope face 47 and of the annular projection 45. In this case the contractile hose 4 is firmly radially pressed between the two saw tooth serrated areas 27 and 28.

In order to ensure that the contractile hose 4 can be reliably shifted into the desired slip on position during assembly the annular collar 44 also functions as an abutment for slipping on the contractile hose. The contractile hose 4 is slipped on so far from the rear side onto the inner head piece part 22 that its end face 54 engages the annular collar 44.

In order to ensure during the following compression that material of the hose body 5, which is prevented from axially deforming, is able to move out of the way and is not crushed by excessive compression, there is an outwardly extending result gap 55 adjoining the front end of the clamping gap 18, hose body material displaced during compression being able to flow off through such gap.

In the working embodiment the annular gap 55 extends into that portion which is located radially between the annular collar 44 and the section, which surrounds it, of the compression sleeve 37. On pressing the compression sleeve 37 the radial height of the annular gap 55 is reduced as can be readily seen from a comparison of the FIGS. 3 and 2.

Circumferential grooves 53 extending in the outer periphery of the compression sleeve 37 facilitate holding in the pressing tool, not illustrated.

In the working embodiment the first abutment face 42 constitutes the flank of an annular groove termed a locating groove 57, which is axially to the fore of the annular collar 44 and whose second flank is located on a further annular collar 58, which is located at a distance in front of the annular collar 44. The outer diameter of the further annular collar 58 is smaller than that of the annular collar 44 serving for setting the slipping on position and is slightly smaller than the inner diameter of the undeformed annular projection 45. Accordingly the annular projection 45 can, during assembly by slipping on, slide over the further annular collar 58. During the following radial pressing it moves into the locating groove 57 so that the compression sleeve 37 is also reliably prevented from moving forward in relation to the inner head piece part 22.

As has been found a particularly satisfactory interlocking effect is obtained if the two saw tooth serrated areas 27 and 28 widen conically toward the axial clamping gap opening 24, through which the contractile hose 4 extends. In other words the two envelope faces 46 and 47 have a conical shape tapering toward the front side of the respective head piece 2 and 3. The apex angle is however relatively small and preferably is of the order of approximately 4 degrees. This results in an oblique slope between a respective envelope face 46 and 47 and the longitudinal axis 9 of approximately 2 degrees.

The envelope lines, defined by the two envelope faces 46 and 47, of the two saw tooth serrated areas 27 and 28 are preferably parallel to each other. Furthermore the individual teeth 32 and 33 are preferably identically designed. Accordingly there is a constant surface pressure along the entire clamping zone covered by the saw tooth serrated areas 27 and 28.

It has been found to be advantageous to have one tooth per millimeter length of a respective saw tooth serrated area 27 and 28. It has furthermore turned out to be advantageous to design the teeth so as to have a height equal to one quarter of the wall thickness of the hose body 5 to be secured. In the case of typical applications the contractile hose 4 in the deactivated home position has an outer diameter of 10, 20 or 40 mm, a number of teeth equal to 12, 18 and, respectively, 29 being satisfactory and convenient. The height of the teeth is more particularly the same in all these design sizes.

In the mounted state the contractile hose 4 preferably has a somewhat larger diameter than in the non-mounted state. This is more particularly because of the conically tapering form of clamping gap in the slip-on direction of the contractile hose 4. The contractile hose 4 is in this case caused to slightly bulge outward in the clamping gap opening 24 and in the rear end section 62, directly following same in the axial direction, of the clamping gap 18.

Along the above mentioned rear end section 62 the clamping gap is preferably unserrated and has a smooth surface. Accordingly the load on the contractile hose 4 in the transition zone merging with the clamping gap 18 is minimized.

Finally it is also an advantage if the radial distance apart between the two envelope faces 46 and 47 of the two saw tooth serrated areas 27 and 28 in the completely assembled state of the compression sleeve 37 is at least equal to the radial dimensions of the strand structure 6 embedded in the wall of the hose body and preferably is slightly larger than it. Such a configuration is depicted in FIG. 2. Accordingly it is possible to ensure that the strand structure is not damaged by the teeth 32 and 33 pressed into the hose body 5.

As further shown in FIG. 2 the strand structure 6 maintains an at least essentially linear form along the length of the contractile hose 4 even in the completely assembled state of the respective head piece 2 and 3. If the saw tooth serrated areas 27 and 28 were axially offset in relation to each other, one respective tooth of the one saw tooth serrated area on the contractile hose could be pressed into the radially opposite tooth gap so that there might be a corrugated deformation of the strand structure 6 and resulting longitudinal stretch zones, which could impair strength. Owing to the particular tooth arrangement this disadvantage is countered.