WO2013164243A1

WO2013164243A1 - Tie rod head

Info

Publication number: WO2013164243A1
Application number: PCT/EP2013/058600
Authority: WO
Inventors: Matthias Müller
Original assignee: Jet Aviation Ag
Priority date: 2012-05-02
Filing date: 2013-04-25
Publication date: 2013-11-07
Also published as: EP2844885A1

Abstract

The invention is directed to a tie rod head (5) comprising a shaft element (6) with an external thread (9), which in a mounted position interacts with an internal thread (14) arranged in an opening (13) of a sleeve (12). The shaft element (6) comprises at least one keyway (10) extending in axial direction. The keyway (10) is interconnected to a ratchet mechanism (11) preventing unwanted rotation of the shaft element (6) with respect to the sleeve (12).

Description

TIE ROD HEAD

RELD OFTHE INVENTION

The present invention relates to a tie rod head according to the preamble of patent claims.

BACKGROUND OFTHE INVENTION FR460408A was published on 02.1 2.1 91 3 on behalf of Emile Henri Chambon . It describes a complicated self- locking turnbuckle that can be used to induce tension in metal cables, which were widely used in early airplanes. The disclosed self- locking mechanism is implemented by using a pair of notched faces, which are similar to crown gears and are pressed together by a spring . The corresponding notches of the two faces only allow rela- tive rotations in one direction . Such rotations cause a shortening of the turnbuckle and subsequently a tensioning of an attached cable. In order to disengage the self- locking turnbuckle a bushing can be pulled back, thereby releasing the spring load acting on the pair of notched faces. The bushing can be secured in a rear position by a bayonet mount.

GB52471 7A was published on 1 3.08.1 940 on behalf of Francis William Kennedy. It describes a ratchet mechanism for turnbuckles, which is located within the turnbuckle. A ratchet mechanism includes a first ratchet disc with crown ratchet teeth . Throug h a projection , the first ratchet disc is connected to a longitudinal keyway and thus locked against relative rotations with respect to one coupling of the turnbuckle. By a spring element, the first ratchet disc is pressed against a second ratchet disc that is connected to the second coupling of the turnbuckle, inducing a predefined constant rotation resistance between the two ratchet discs.

US281 0595 was published on 22.1 0.1 957 on behalf of George W. Purdy. It describes a turnbuckle that can be used to apply tension on wires or guys. For that purpose, the threaded rod-shaped parts of two couplings have to be screwed into the centerpiece of the turnbuckle. Disk-shaped means are mounted slidably in axial direction on these rods and are restraint against rotation by longitudinal flat unthreaded sections. The means include a notched face which can be brought into contact with a notched face on an end of the centerpiece, whereby the shape of the notches only allows relative rotations be- tween the centerpiece and means in one direction. In order to bring the two notched faces of the means and the centerpiece into contact, some sort of hollow covers are connected to the ends of the centerpiece. The connection is implemented with a bayonet mount, whereby a mounted hollow cover strains a spring, which subsequently presses the notched mean to the notched face of the centerpiece. In order to induce a relative rotation in the normally blocked direction, the bayonet mounts must first be disconnected on both sides of the center piece and the notched means have to be moved manually away from the notched face of the centerpiece. The described system therefore only allows two different types of rotation restraints. As first type, no rotation restraint in both directions is present, when the hollow cover is not connected to the centerpiece. As sec- ond type, a full locking in one rotation direction and a predefined restraint in the other is present.

EEP1588975B1 was published on 1 1 .04.201 2 on behalf of SACS GmbH. It describes a tie rod with a complicated internal axial ratchet mechanism that should prevent changes in tie rod length after it has been adjusted to the correct length. The ratchet mechanism consists of two corresponding crown wheels, the first wheel being attached to a coupling of the tie rod, the second crown wheel being mounted on polygonal shank. This shank is mounted axially movable but rotationally restrained in a guide sleeve, which itself is fully restrained with respect to the tie rod centerpiece. A spring element between the guide sleeve and the second crown wheel presses the latter against the second wheel, causing a rotation resistance between the two ratchet discs. The deg ree of resistance increases with increasing penetration depth of the coupling in the centerpiece.

DE20201 1 051 1 35U1 was published on 29.1 2.201 1 on behalf of RO- RA Produktions GmbH. It describes a tie rod, which has at least one snap- in locking device in order to prevent unintended changes in length after the installation of the tie rod. This sort of locking device consists of some sort of ratchet teeth, which in a first embodiment are aligned annularly on the inner side of the centerpiece and in a second embodiment on the outer side of a coupling that is anchored inside of the centerpiece. A counter piece, in the first embodiment attached to the coupling and in the second embodiment attached to the centerpiece, is pressed by a spring element in radial direction to the ratchet teeth and thus induces a predefined constant rotation resistance between the centerpiece and the coupling. The ratchet mechanism is spatially separated from the threads which are used in order to anchor the coupling in the tie rod centerpiece. One draw back is the relatively limited range of adjustability. DE20201 0008858U1 ( resp. W01 1 057627A1 ) was published on 1 6.1 2.201 0 on behalf of RO- RA Produktions GmbH. It describes a tie rod with a ratchet mechanism that uses a two discs with crown ratchet teeth ( ratchet discs) . One ratchet disc is mounted slidably but restricted against rotations on the rod of the tie rod coupling. By means of a spring it is pressed against a notched counter piece that is connected to the centerpiece of the tie rod. By this, relative rotations between the connecting ports and the centerpiece are only possible after applying a predefined moment. In one embodiment, the ratchet mechanism is arranged inside the rod and not visible/ controllable from the outside. In another embodiment, the force is increasing with decreasing deg rees of extension . The described system does neither allow varying the rotation resistance for a given tie rod extension nor locking of the mechanism in a predefined position.

WO06042750 was published on 27.04.2006 on behalf of GMT Gummi Metall Technik GmbH. It describes a tie rod with at least one coupling element that can be used to adjust the tie rod length during installation , even when spatial accessibility is limited . At least one of the two coupling elements is connected to the centerpiece by a thread so that the tie rod length can be changed by screwing the coupling element in or out. In add ition , an apparatus is described which can be used to fix the coupling agent in order to prevent further relative rotations between coupling element and centerpiece and thus also changes in tie rod length . This fixation device consists of a clamp that is mounted on the coupling element using a bolt and which embraces like a collar a part of the centerpiece that is shaped like a gearwheel. By form closure relative rotations are inhibited . Only a limited range of a tie rod extension can be locked by this method, depending on the size of the clamp. The described tie rod also includes a spring element, which is used to preload the thread in order to reduce vibration/ noise when in service. The presence of this spring element also limits how much the length of the tie rod can be changed.

DE202004004407U was published on 22.07.2004 on behalf of Trigum Engineering GmbH and claims a tie rod, which in many details conforms to the one presented in WO06042750. A restraint element on the coupling element prevents the threaded coupling element from being screwed out too much. In contrast to WO06042750 , the pre- sented tie rod does not include any spring element. The clamping element used to prevent rotations is mounted using the same bolt that will be used to connect the tie rod to the aircraft.

SUMMARY OFTHEINVBMTION One object of the present invention is to provide a head for a tie rod, which offers a simple, robust and light-weight design and an extensive adjustability compared to the heads for tie rods known from the prior art. A further object of the invention is a tie rod comprising a head according to the present invention . A further object of the invention is a tie rod kit system comprising a head according to the present invention . Tie rods are an important component used in aircraft construction. Serving as connectors between built- in components and structural components of the aircraft's hull, they are especially in the field of VI P aircraft completion commonly used for the installation of cabin compartments and other modules. As each aircraft is custom built, tie rods having a fixed length are often inadequate as only minor changes in the design or the position of a built- in component results in the necessity to remake the tie rods. As indicated above, tie rods with tie rod heads offering certain adjustability of their length are obtainable from multiple manufacturers. However, the products known from the prior art allow only for a slight adjustment of the length or have a complicated and therefore heavy set- up.

In an embodiment an adjustable tie rod head according to the invention comprises a shaft element with an external thread which in a mounted position interacts with an internal thread arranged in an opening of a sleeve. The shaft element comprises at its free end an adapter by which the tie rod head can be interconnected to another structure. The shaft element comprises along an outer cylindrical surface at least one keyway extending in axial direction. The keyway is interconnected to a ratchet mechanism preventing unwanted rotation of the shaft element with respect to the sleeve. The shaft element preferably has a hollow design with an inner diameter with a large diameter to reduce the weight of the tie rod head without having negative influence on the load carrying capacity. The external thread preferably is of a fine- pitch thread. The axial length of the inner diameter normally is at least as long as the length of the external thread of the shaft element. The at least one keyway may intersperse at least partially with the external thread of the shaft element. Thereby the adjustable length of the tie rod head can be increased significantly.

In an embodiment the tie rod head preferably comprises at least one ratchet element which is spring loaded by a spring in a radial direction with respect to the shaft element. The at least one ratchet element is pressed against the outer surface of the shaft element where it interacts with the at least one keyway. The keyway preferably has a U- or V- shaped cross-section which provides a ramp like interaction with the ratchet element.

In a further embodiment the ratchet mechanism comprises a ratchet element which is arranged axially displaceable along the shaft element. The ratchet element comprises first teeth which in a locked position interact with second teeth of a counter element thereby preventing unwanted rotation of the shaft element with respect to the counter element. The second teeth can e.g. be incorporated in the sleeve mentioned above.

In an embodiment the first teeth and the second teeth are arranged in a radial direction. The first teeth of the ratchet element may be pressed by a spring, e.g. a helical spring, against the second teeth . The helical spring may be supported by a threaded bush which is in a mounted position interconnected to the counter element. The threaded bush may be interconnected to the counter element by a screw fastening or in another suitable manner. The threaded bush may be designed to adjust the load executed by the helical spring onto the ratchet element. The threaded bush may comprise a shoulder which in a locking position interacts with the ratchet element whereby the first teeth of the ratchet element are pressed against the second teeth of the counter element thereby locking the sleeve element with respect to the counter element.

In a further embodiment the first teeth and the second teeth are arranged in an axial direction. In this case the ratchet element may have a bell-shaped design whereby the first teeth are arranged along an inner surface of the ratchet element and the second teeth are arranged along a corresponding outer ( cylindrical) surface of the counter element. The rotation of the sleeve element with respect to the counter element can prevented in that the ratchet element is put in axial direction over the counter element such that the fist and the second teeth interlock with each other. Alternatively or in add ition the first teeth of the ratchet element can be spring loaded in a radial direction. Advantages of the described embodiments are that if required they can be designed such that they can be operated in a single handed manner.

The ratchet element is preferably made of metal alloy, e.g. steel, titanium or aluminum, or a plastic, e.g. PEEK.

Along the shaft of the tie rod head there may be at least one scale, which preferably is located in a keyway. The scale can include calibrated lines and numbers to indicate the distance between a specific point of the tie rod's head load application means and a specific point on the centerpiece of the rod or even the corresponding second load applica- tion means. By this the total distance between the two points connected by the tie rod can easily be determined by adding indicated numbers or is even indicated directly.

In another embodiment, the scale may consist of a color bar that indicates special ranges of extension by specified colors. A range colored in red could for example indicate an extension of the tie rod head that is too high for a nominal maximal (compression) force. In that case, the current tie rod may be replaced by another type of tie rod. A range colored in green may indicate a tie rod extension that allows maximal nominal axial compression of the tie rod. A range colored in yellow/ blue may indicate an very short extension that would even allow a specified higher maximal axial compression if needed or - alternatively - replacing the current tie rod by a shorter tie rod which would lead to a economically significant decrease in weight and costs.

BRIEF D CRIPTI ON OFTHE DRAWINGS

The herein described invention will be more fully understood from the detailed description given herein below and the accompanying drawings, which should not be consid- ered limiting to the invention described in the appended claims. The drawings are showing :

Fig. 1 a rod end with a first embodiment of a tie rod head in a perspective manner partially cut;

Fig. 2 the inside of the tie rod head according to Fig . 1 ; Fig. 3 a top view of the rod end with the tie rod head according to Fig . 1 ; Fig. 4 a section view along section line DD of Fig. 3 ;

Fig. 5 a rod end with a second embodiment of a tie rod head in a perspective manner partially cut;

Fig. 6 the inside of the tie rod head according to Fig . 5 ;

Fig. 7 a top view of the rod end with the tie rod head according to Fig . 5 ;

Fig. 8 a section view along section line EEof Fig . 7 ;

Fig. 9 a third embodiment of a tie rod head in a perspective manner partially cut.

DESCRIPTION OFTHE EMBODIMENTS

The foregoing summary as well as the following detailed description of the preferred embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention , embodiments that are presently preferred, in which like numerals represent similar parts throughout the several views of the drawings, are subseguently explained . It being understood, however, that the invention is not limited to the specific methods and instrumentalities disclosed .

Rgure 1 shows a first embodiment of a rod 1 with a tie rod head 5 according to the present invention . Portions of the rod 1 and the tie rod head 5 are shown in a cut manner such that the inside becomes visible. Rgure 2 shows the tie rod head 5 in a disassembled manner in a perspective view. Rgure 3 shows the rod 1 with the tie rod head 5 in a top view and Figure 4 shows a section view of the (staggered) section line DD according to Figure 3.

Figure 5 shows a second embodiment of a rod 1 with a tie rod head 5 according to the present invention . Portions of the rod 1 and the tie rod head 5 are shown in a cut manner such that the inside becomes visible. Figure 6 shows the tie rod head 5 in a disassembled manner ( exploded view) in a perspective view. Figure 7 shows the rod 1 with the tie rod head 2 in a top view and Figure 8 shows a section view of section line EE according to Figure 7.

In the shown embodiments the rod 1 is only partially visible, i.e. the opposite end of the rod 1 is not visible. The rod 1 comprises a flange 2 with an opening 3 to which the tie rod head 5 as shown in Figures 1 -4 is attached via a first internal thread 4. If required, it is possible to attach the tie rod head 5 in another manner.

The tie rod head 5 comprises a shaft element 6 with a lug 7 at one end. The shaft element 6 comprises along at least part of an outer surface 8 a first external thread 9 , which is at least partially interspersed with at least one keyway ( notch) 1 0. The thread 9 is preferably designed as fine pitch thread according to ISO- standard. The advantages are the possibility of fine adjustment of length and low gauge, which offers the possibility to reduce the weight of the tie rod head 5 in that an inner diameterl 9 (see Rgs. 4 and 8) of the shaft element 6 can be maximized in diameter and length without taking negative influence on the load carrying capacity of the tie rod head 5. The inner diameter 1 9 preferably has a circular shape with a constant diameter or a diameter which decreases in the direction of the lug 7. The diameter may decrease in a constant or in a staggered manner. If appropriate, the inner diameter 1 9 has a non-circular cross-section. It may comprise one or more struts ( not shown in detail) , which increase the load carrying capacity. One advantage of the shown tie rod heads 5 is an extensive adjustability, low weight compared to the tie rod heads known from the prior art and a simple and robust setup. The keyway 1 0 normally extends in longitudinal direction of the shaft element 6 and serves as interconnection means for a ratchet mechanism 1 1 . The ratchet mechanism 1 1 provides a mechanical interconnection between the shaft element 6 and a sleeve 1 2 as described subsequently. The sleeve 1 2 comprises an opening 1 3 with an internal thread 1 4, which in a mounted position interacts with the external thread 9 of the shaft element 6.

The ratchet mechanism 1 1 of the first embodiment as shown in Rgures 1 -4 consists of two ratchet elements 1 5 arranged opposite to each other in coaxial bores 1 6 of the sleeve 1 2. The ratchet elements 1 5, which in the shown embodiment are spherical, are pressed inwardly against the external thread 9 of the shaft element 6 by a here cramp- like spring 1 7, which is arranged in a here circumferential slot 1 8 of the sleeve 1 2. The thread 9 is interspersed by several keyways 1 0 , which are arranged in longitudinal direction (z-axis) . The keyways 1 0 are shaped such that the ratchet elements 1 5 may fall into them in defined positions when the shaft element 6 is rotated relative to the sleeve 1 2. In that the at least one keyway 1 0 is arranged in ( interspersing with) the external thread 9 , the external thread 9 and thereby the adjustability range can be made very long compared to the prior art.

If the number of keyways 1 0 shall be kept low, it is possible to increase the number of ratchet elements 1 5 instead and arrange them in a circumferential manner with respect to the rotation axis (z-axis) of the shaft element. Eg. it is possible to provide only one axial keyway 1 0 , which interacts with several ratchet elements 1 5 ( not shown in detail) .

By screwing the shaft element 6 in or out of the sleeve 1 2 , the length of the rod 1 can be adjusted . The ratchet mechanism 1 1 avoids unwanted displacement of the shaft element 6 with respect to the sleeve 1 2 in that the ratchet elements 1 5 are pressed by a spring 1 7 into keyways 1 0. The shape ( cross-section) of the keyways can be U- or V-shaped . The edges of the at least one keyway 1 0 is preferably shaped as a ramp for the ratchet elements 1 5 in at least one circumferential direction. The ratchet elements 1 5 may be shaped corresponding to the shape of the thread 9 , thereby avoiding unwanted wear of the interacting parts. Instead of spherical the ratchet elements 1 5 can be tooth-shaped or V- or U-shaped in circumferential direction . The shape may at least partially correspond to the shape of the cross-section of the keyways 1 0. At the lower end the axial keyways 1 0 may finish into a circumferential keyway ( not shown in detail) which acts as a stop element. When the shaft element 6 reaches its final outer position the ratchet elements 1 5 fall into the circumferential direction keyway. The circumferential keyway has a cross- section which prevents by interaction with the ratchet element 1 5 that the shaft element 6 can be screwed further out thereby acting as a stop element. The cross-section of the circumferential keyway is shaped such that it only works in one direction and does not prevent that the shaft element 6 is from its most outer position screwed back in again. In this case a stop element 20 as described subsequently can be avoided.

The ratchet mechanism 1 1 may be designed such that it can be sealed, respectively locked, e.g. by a sealing wax. The sealing wax may be applied to the ratchet mechanism reliably indicating modification of the tie rod head 5. Alternatively or in addition , the spring 1 7 may have a design which allows locking of the ratchet mechanism 1 1 e.g. by moving the spring 1 7 into a locking position .

The maximum outer position of the shaft element 6 with respect to the sleeve 1 2 is in the shown embodiment defined by the stop element 20 which is arranged inside the inner diameter 1 9 of the shaft element 6. The stop element 20 reaches above the outer surface

8 of the shaft element 6 and interacts with the read end of the sleeve 1 2. The stop element 20 may be designed to interact alternatively or in add ition with the external thread

9 of the shaft element, e.g. in that it has a ring like shape and is attached to the thread 9. Lock washers, e.g. snap rings, are normally arranged in circumferential grooves. As such circumferential grooves must have a diameter, which is significantly less then the inner diameter of the external thread 9 , such stop elements cause the draw back that the inner diameter 1 9 is significantly reduced, which results in negative increasing of the weight of the tie rod head 5. The stop elements can e.g. be made out of plastic material .

In the shown embodiment the ratchet elements 1 5 are secured by securing elements 21 here in the form of snap rings 21 , which are attached to the rear end of the bores 1 6. Other securing elements, e.g. in the form of screws are possible. Alternatively or in add ition to the spring 1 7, a spring, e.g. a coil spring , may be arranged between the securing element 21 and the ratchet element 1 5 to press the ratchet element 1 5 into the axial keyways 1 0 of the shaft element 6. In the second embodiment shown in Figures 5-8, the shaft element 6 comprises only one keyway 1 0 , which interacts with a first ratchet element 22. The first ratchet element 22 comprises a guide bushing 23 , which extends along the shaft element 6. The guide bushing 23 comprises an axial opening 24 in which the shaft element 6 is arranged. In the axial opening 24 the first ratchet element 22 comprises a pin 25 , which interacts with the at least one keyway 1 0 and provides a coupling between the first ratchet element 22 and the shaft element 6 in circumferential (torsional) direction . The first ratchet element 22 is arranged movable in axial direction along the shaft element 6. As best visible in Fig- ure 6 the first ratchet element 22 comprises a disc 26, which expands at the lower end of the guide bushing 23. The disc comprises several first teeth 27, which in a mounted position interact with second teeth 28 of a counter element ( herein sleeve 1 2) . In the shown embodiment the second teeth are incorporated into an end face 29 of the sleeve 1 2. If required, the second teeth 28 can be incorporated in a separate part. In a mounted position , the first teeth 27 of the first ratchet element 22 are pressed by a helical spring 30 against the second teeth 28 of the end face 29 of the sleeve 1 2. Thereby, unwanted rotation of the shaft element 6 with respect to the sleeve 1 2 is prevented . The teeth 27 , 28 preferably have a ramp- like cross section such that when a certain torsional moment is applied to the shaft the first teeth 27 are deflected in axial direc- tion against the force of the helical spring 30 and skip from one position into a next circumferential position . The rear end of the helical spring 30 is supported by a threaded bush 31 , which is attached to the sleeve 1 2 by a screw fastening 32. The force of the helical spring 30 can be adjusted by the screw fastening 32. When the threaded bush 31 is attracted more firmly, the helical spring 30 is compressed and thereby the force by which the first ratchet element 22 is pressed against the end face 29 of the sleeve 1 2 increases. Thereby, the torsional moment for rotating the shaft element with respect to the sleeve 1 2 can be adjusted . When the threaded bush 31 is further attracted , a shoulder 33 of the threaded bush 31 presses against the rear end of the guide bush 23 and thereby locks the ratchet mechanism 1 1 completely such that the length of the tie rod head 5 can not be adjusted anymore. When the shaft element 6 is screwed outward ly and it reaches its most outer position , the pin 25 reaches a lower end 34 of the keyway 1 0 , which in the shown embodiment is not continuous. Thereby, it can be prevented that the shaft element 6 is screwed out to far.

Figure 9 is showing a third embodiment of a tie rod head 5 according to the present in- vention. With respect to the general explanations it is referred to the description of the previous drawings. The ratchet mechanism 1 1 comprises a ratchet element 22 which has a bell-shaped design . The first teeth 27 ( partially visible through an opening) are arranged along an inner surface of the ratchet element 22. The second teeth 28 are arranged along an outer cylindrical surface of the counter element (sleeve) 1 2. The rotation of the sleeve element 6 with respect to the sleeve 1 2 is prevented in that the ratchet element 22 is put over the sleeve 1 2 such that the first and the second teeth 27 , 28 interlock with each other. To rotate the shaft element 6 with respect to the sleeve 1 2 and thereby adjust the length of the tie rod head 5, the ratchet element 22 is d isengaged by moving it in axial direction along the shaft element 6. Then the ratchet element 22 can be used as handle to easily move the shaft element 6 without the need for an add itional tool. To improve grip the outer surface of the ratchet element 22 comprises notches. The ratchet element 22 can be designed that it is put in an opening of the counter element 1 2 and interacts at least partially from the inside with the counter element 1 2. Eg. in the shown embodiment the ratchet element 22 can be designed that it can be at least par- tially inserted in a recess 36 of the counter element 1 2. In this case the recess 36 preferably has a cross section which is non circular and which interacts with an outer shape of the ratchet element 22 thereby avoiding unwanted rotation of the ratchet element 22 with respect to the counter element. Alternatively or in addition the ratchet element 22 can be secured with respect to the counter element 1 2 by other securing means such as a bolt and/ or a locking wire and/ or seal and/ or an anti-tamper seal. The securing means is preferably designed such that it prevents and/ or indicates unwanted movement of the ratchet element 22 with respect to the counter element 1 2.

Advantages of the shown embodiment are the simple and light weight design, the possibility to control the status of the ratchet mechanism from outside and a comparably large adjustability of the length.

LIST OF DESIGNATIONS

1 Rod 1 9 Inner diameter (axial bore in

2 Range shaft element)

3 Opening 20 Stop element

4 Internal thread ( rod) 21 Snap ring

5 Tie rod head 25 22 Ratchet element

6 Shaft element 23 Guide bushing

7 Lug (adapter / load application 24 Opening (of first ratchet element means) 22)

8 Outer surface 25 Pin

9 External thread (of shaft element) 30 26 Disc

1 0 Keyway ( Notch) 27 First teeth

1 1 Ratchet mechanism 28 Second teeth

1 2 Sleeve / Counter element 29 End face

1 3 Opening (of sleeve) 30 Helical spring

1 4 Internal thread (of sleeve) 35 31 Threaded bush

1 5 Ratchet element (sphere) 32 Screw fastening

1 6 Bore (for ratchet element 1 5) 33 Shoulder (of threaded bush 31 )

1 7 Spring 34 Lower end (of keyway 1 0)

1 8 Slot (for spring) 35 Notches

40 36 Recess

Claims

PATBMT CLAIMS

1. Tie rod head (5) comprising a shaft element (6) with an external thread (9), which in a mounted position interacts with an internal thread ( 14) arranged in an opening (13) of a sleeve (12), whereby a shaft element (6) comprises at least one keyway (10) extending in axial direction, said keyway being interconnected to a ratchet mechanism (11) preventing unwanted rotation of the shaft element (6) with respect to the sleeve (12).

2. Tie rod head (5) according to claim 1 , wherein the shaft element (6) has an inner diameter (19).

3. Tie rod head (5) according to claim 2, wherein the axial length of the inner diameter (19) is at least as long as the length of the external thread (9) of the shaft element.

4. Tie rod head (5) according to one of the previous claims, wherein the at least one keyway ( 10) intersperses at least partially with the external thread (9) of the shaft element (6).

5. Tie rod head (5) according to one of the previous claims, wherein the ratchet mechanism (11) comprises at least one ratchet element (15), which is spring loaded by a spring (17) in a radial direction with respect to the shaft element (6) .

6. Tie rod head (5) according to claim 5, wherein the at least one ratchet element (15) is pressed against the outer surface of the shaft element (6), where it interacts with the at least one keyway (10).

7. Tie rod head (5) according to claim 5, wherein the keyway (10) has a U- or V- shaped cross- section.

8. Tie rod head (5) according to one of the previous claims, wherein the ratchet mechanism (11) comprises a ratchet element (22), which is arranged axially dis- placeable along the shaft element (6), said ratchet element (22) comprising first teeth (27), which in a locked position interact with second teeth (28) of a counter element (12) preventing unwanted rotation of the shaft element (6) with respect to the counter element (12).

9. Tie rod head (5) according to claim 8, wherein the second teeth (28) are incorporated in the sleeve (12).

10. Tie rod head (5) according to claim 8 or 9, wherein the first teeth (27) and the second teeth (28) are arranged in a radial direction.

11. Tie rod head (5) according to claim 10, wherein the first teeth (27) of the ratchet element (22) are pressed by a spring (30) against the second teeth (28).

12. Tie rod head (5) according to claim 11 , wherein the spring (30) is supported by a threaded bush (31 ), which is in a mounted position interconnected to the counter element (12).

13. Tie rod head (5) according to claim 1 2, wherein the threaded bush (31 ) is interconnected to the counter element ( 1 2) by a screw fastening (32) .

14. Tie rod head (5) according to claim 1 3, wherein the threaded bush (31 ) suits to adjust the load executed by the helical spring (30) onto the ratchet element (22) .

15. Tie rod head (5) according to one of the claims 1 2 through 1 4, wherein threaded bush (31 ) comprises a shoulder (33) by which in a locking position the first teeth (27) of the ratchet element (22) are pressed against the second teeth (28) of the counter element ( 1 2) , thereby locking the sleeve element (6) with respect to the counter element ( 1 2) .

1 6. Tie rod head (5) according to claim 8 or 9, wherein the first teeth (27) and the second teeth (28) are arranged in an axial direction.

17. Tie rod head (5) according to claim 1 6, wherein the ratchet element (22) has a bell-shaped design and the first teeth (27) are arranged along an inner surface of the ratchet element (22) and the second teeth (28) are arranged along an outer cylindrical surface of the counter element ( 1 2) , whereby the rotation of the sleeve element (6) with respect to the counter element ( 1 2) is prevented in that the ratchet element (22) is put over the counter element ( 1 2) such that the first and the second teeth (27, 28) interlock.