1. Field of the invention The present invention relates to an arrangement for adjustment of a friction force

on a rotatable shaft or an axially displaceable rod. Such an arrangement can be

used for different fields of use, preferably for the attenuation of movements in the

automotive field and fulfil the function of hinges, joints or pneumatic springs.

2. Prior art In the prior art various possibilities are known to attenuate mechanical move¬ ments, preferably pivoting or axial movements. So, for example the movements of engine hoods or deck lids are supported by gas springs and simultaneously their opening and closing movement is attenuated. In the interior of a motor vehicle for example pivoting movements of fold away handholds or the opening movements of lids of glove boxes or compartments or mechanically attenuated.

In other industries, for example in the electronic industry such attenuated joints are also used. So, for example the US 5,771,539 shows a spring hinge for a dis- play of a notebook computer, wherein a helical spring is wrapped around a shaft and generates a torque and a friction force. In this arrangement a first end of the helical spring is connected to the lower part of the notebook computer and the other end of the helical spring to the pivotable display, such that the opening movement is supported by the spring effect and simultaneously the friction force is increased during the opening. The document US 2002/0042971 Al shows a friction hinge for an electronic de¬ vice, for example a notebook computer or a PDA, which comprises a sleeve shaped friction element between a rotatable pin and a support body. The friction element is pressed into the support body, wherein the rotatable pin receives a fric- tion force.

The described solutions show possibilities to attenuate pivoting movements by means of friction to a certain amount, but these possibilities are not sufficient for particular mechanical applications. The change of the friction force depending on the pivoting position could for example be undesired.

At conventional pressed in sleeve shaped friction elements during the lifetime also the friction force will decrease due to material fatigue and abrasion effects, such that the attenuation will decrease over time. Further, the friction and thereby the attenuation of previously known joints is not adjustable or readjustable after the assembly but fixed. Further, the described joints are suitable only for one kind of movement, either rotational or translational.

It is therefore desirable to be able to exactly dose the attenuation effect of an ar- rangement and to keep it constant along the complete movement range. Further it is desirable to ensure a free rotation of the shaft and not only to allow a pivoting movement of less than 360°. Further it is desirable to provide an arrangement by means of which a rotational as well as translational movements or both kinds si¬ multaneously can be attenuated with one single arrangement. The arrangement should also be as technically uncomplicated and simple as possible to increase the lifetime of the arrangement and to keep the production costs as low as possible. Also, the desired attenuation effect should be adjustable as easy as possible.

3. Summary of the invention The present problems are solved by an arrangement for adjusting a friction force

according to patent claims 1 or 4. In particular they are solved by an arrangement for adjusting a friction force, comprising a shaft, a support for supporting the

shaft, wherein the shaft is rotatable with respect to the support, and a helical tor¬

sion spring, which is wrapped around the shaft, to exert an adjustable friction

force to the shaft, wherein the torsion spring is adjustably fixed with respect to the

support.

By such an arrangement the rotational movement of the shaft is independent from the adjustment of the torsion spring, such that the movement of the shaft does not influence the adjustment of the torsion spring. The friction effect and thereby the attenuation can be adjusted as desired, and also be later adapted or changed. By the use of a helical torsion spring the adjustment furthermore is done continu¬ ously, from fairly small attenuation to strong attenuation. Also, the claimed ar¬ rangement is very simple in construction, such that it comprises a high security to failure and is low-cost in production.

In a preferred embodiment, the shaft can freely rotate with respect to the support. Thereby free pivoting or rotational movements of more than 360° are possible without problems. Arbitrary rotational movements of a shaft can adjustably be decelerated or attenuated.

In a further preferred embodiment the shaft is additionally axially displaceable with respect to the support. Therefore, the shaft can perform a rotational move¬ ment as well as also an axial displacement with respect to the support. The ar¬ rangement provides the possibility to simultaneously attenuate rotational move- ments as well as also linear movements with only one single arrangement. This provides various possibilities for the attenuation of mechanical movements, pref¬ erably in the automotive field. So, for example the movements of the lid of a glove box or the pivoting movements of a handhold can be attenuated by me- - A -

chanically simple means. Further it is possible to use this arrangement where until now substantially more expensive pneumatic springs are used.

Furthermore, these problems are solved by an arrangement for adjusting a friction force, comprising a rod, a support for supporting the rod, wherein the rod is axi- ally displaceable with respect to the support, and a helical torsion spring, which is wrapped around the rod, to exert an adjustable friction force to the rod, wherein the torsion spring is adjustably fixed with respect to the support. With such an arrangement it is also possible to attenuate pure axial movements of a rod by means of an adjustable friction force.

Preferably the rod is additionally rotatable with respect to the support. As ex¬ plained above, also a combination of rotational and translational movements can simultaneously be attenuated.

In a further preferred embodiment the support is fixed and the shaft or rod is ro¬ tatable and/or axially displaceable. In this arrangement the support is fixed and the shaft or rod can move therein.

In another preferred embodiment the shaft or rod is fixed and the support is ro¬ tatable and/or axially displaceable. In this embodiment the shaft or rod is fixed and the support moves together with the friction adjustment.

In a further preferred embodiment for adjusting the friction force on the shaft or the rod two ends of the torsion spring are turned against each other, such that the torsion spring expands or contracts in its diameter. Thereby the adjustment of the friction force is done by means of a simple turning of the ends of the torsion spring which presses against the shaft or rod with a variable normal force, such that during a movement of the shaft or rod a friction force is generated. In a further preferred embodiment the support comprises at least two support bod¬ ies, which are arranged in or at a housing. Preferably the arrangement further comprises at least one, preferably two adjustment elements, which engage the ends of the torsion spring and which are rotatably arranged for adjusting the tor- sion spring. The adjustment elements therefore act to turn the ends of the torsion spring against each other, whereby the friction force on the shaft or rod can be varied.

In a further preferred embodiment the adjustment elements are connected with the support bodies or are integrally formed with them. Therefore the adjustment ele¬ ments form a unit with the support bodies, such that the torsion spring can be ad¬ justed by a turning of the combination of support bodies and adjustment elements against each other. This can for example be done by a manual turning of the sup¬ port bodies, such that the adjustment of the attenuation can be done fast and easy and without tools.

In a further preferred embodiment of the arrangement at least one bearing shell is arranged between the torsion spring and the shaft or the rod. This bearing shell on the one hand serves for an equal distribution of the normal force of the torsion spring to the shaft or rod and on the other hand for the definition of the generated friction forces. The bearing shell preferably consists of a material having a low friction coefficient, such that the movement of the shaft or rod can be performed without jerk and smoothly.

In a further preferred embodiment the bearing shell extends also between at least one of the support bodies and the shaft or the rod. In this arrangement, the bearing shell also serves for an improvement of the slide bearing of the shaft or the rod within the support body. Furthermore, the support body does not have to be made of a material having good slide properties, whereby material costs can be saved. In a further preferred embodiment a torsion spring consists of a wire having a square or rectangular section. Therefore, the threads of the torsion spring form a quasi continuos cylindrical inner face, which exerts a normal force particularly uniform to the shaft or the rod. Thereby a wear-off of the torsion spring as well as of the shaft or of the rod is avoided. Furthermore, the friction force can be defined very exactly, since the complete inner surface of the torsion spring particularly uniformly presses against the shaft or the rod.

In a further preferred embodiment the rod comprises a square, preferably quad- ratic or hexagonal or octagonal section. The rod cannot only have a round section, but if desired and for example no rotational movement is planned, have a square section. Depending on the section of the rod the bearing shells are correspond¬ ingly formed.

Further preferred embodiments result from the subclaims.

4. Short description of the drawings In the following further preferred embodiments of the invention are explained by

means of the drawings. It shows:

Fig. 1 a three-dimensional view of a preferred embodiment of an ar¬ rangement according to the invention for adjusting a friction force in assembled condition;

Fig. 2 a three-dimensional explosionary view of an arrangement of Fig. 1 and a housing including Hd;

Fig. 3 a three-dimensional view of a shaft or a rod together with two bear¬ ing shells according to a first embodiment; Fig. 4 a three-dimensional view of a further embodiment of a shaft or rod with square section together with two suitable bearing shells;

Fig. 5 a three-dimensional view of a support body and an inter-connected adjustment element;

Fig. 6 a three-dimensional view of a torsion spring;

Fig. 7 a three-dimensional view of a cylindrical housing; and

Fig. 8 a disk-shaped lid, for closing the housing of Fig. 7.

5. Description of preferred embodiments Figure 1 shows an arrangement 1, which can be used for adjustment of a friction force on a shaft 10 or a rod 20. The arrangement 1 comprises a shaft 10 or a rod 20, a first support body 30, a second support body 32, a first adjustment element 60, a second adjustment element 62, a torsion spring 40 as well as two bearing shells 70 and 72.

The support bodies 30, 32 serve for supporting or bearing the shaft 10 or the rod 20, which is here shown as a shaft 10 or rod 20 having a round section. In this embodiment the shaft 10 or rod 20 can rotate within the support bodies 30, 32, as it is indicated by arrow 80, as well as also be axially displaced, as it is indicated by arrow 85.

The torsion spring 40, which is also shown in Fig. 6, has an inner diameter, which can be varied by turning the ends 42, 44 against each other. The torsion spring 40 quasi contracts or expands.

The first end 42 of torsion spring 40 is engaged by an axially extending fork 64 of first adjustment element 60. In the same way the second end 42 of torsion spring 40 is engaged by a fork 64 (not shown in Fig. 1) of the second adjustment element 62. The adjustment elements 60, 62 thereby can turn the ends 42, 44 of torsion spring 40 against each other, whereby the diameter of the torsion spring 40 is ad¬ justed. The adjustment elements 60, 62 themselves can for example be moved by hand or by mechanical, electrical, pneumatic, hydraulic or other suitable means (not shown).

In Fig. 1 further two bearing shells 70, 72 arc shown, which are arranged between torsion spring 40 and shaft 10 or rod 20. They are preferably made of a material with appropriate friction properties. Suitable materials are for example thermo¬ plastic materials (PA, POM, PEEK, PI, PBT), which if desired may comprise a glass fiber part for increasing the strength or a part of PTFE or SO2 for improving the slide properties. The bearing shells however can also be made of a metal mate¬ rial, for example copper, steel or bronze, which can be provided with a PTFE coating if desired.

As shown in Fig. 3 the bearing shells 70, 72 preferably comprise at one end a col¬ lar 74 respectively 75, which prevents an axial displacement of the bearing shells 70, 72. It is also possible that the bearing shells 70, 72 comprise a collar 74, 75 at both ends.

Figure 3 shows a shaft 10 or rod 20 having a circular section, whereby the shaft 10 or rod 20 is axially displaceable as well as also rotatably supported.

In Fig. 4 a further preferred embodiment is shown, in which shaft 10' or rod 20' comprise a quadratic section, such that they are not able to rotate with respect to the therefore adapted bearing shells 70', 72' but can axially be displaced. How¬ ever, a rotational movement could also be made possible with a shaft 10' or rod 20' with quadratic section, if the bearing shells 70', 72' in turn are rotatably sup- ported within the support bodies 30, 32. If the bearing shells 70', 72' are held ro- tatably fixed with respect to the support bodies 30, 32, the shaft 10' or rod 20' can only be axially displaced in a attenuated manner.

The bearing shells 70, 72 are pressed to the surface of the shaft 10 or rod 20 by the torsion spring 40. Consequently, a normal force, i.e. a force perpendicular to the desired movement direction of shaft 10 or rod 20, is generated.

During a desired movement of the shaft 10 respectively rod 20, this normal force generates a friction force, which is directed against this movement, with an amount, which is proportional to the exerted normal force (FR = μ x FN). Thereby, a rotational movement of shaft 10 as well as also a translational movement of rod 20 can be attenuated.

The attenuation is adjustable by changing the normal force. The normal force is changed by a diameter variation of torsion spring 40, wherein simply the ends 42, 44 of torsion spring 40 are turned against each other or to each other. In this case, the torsion spring 40 acts equally over all threads onto the shaft 10, rod 20, re¬ spectively the bearing shells 70, 72.

In fig. 5 it is shown that the support bodies 30, 32 are preferably connected with the adjustment elements 60, 62 or are integrally formed with them. The support bodies are cylindrically shaped elements having a suitable opening for receiving the shaft 10 or rod 20. Preferably they are rotatably arranged in a housing 70 or an arbitrary other housing. Then, the torsion spring 40 is adjustable in its diameter by a turning of the support bodies 30, 32 to change the friction force on the shaft 10 or the rod 20 in this manner. After this adjustment, the support bodies 30, 32 are fixed appropriately, for example by screwing a second housing half or a housing lid onto the housing, which prevents an undesired turning of the support bodies 30, 32. Further, the adjustment elements 60, 62 serve for fixing the torsion spring 40 such that the generated friction force can be introduced into the support bodies 30, 32 and therefore into the housing 50.

An exemplary housing 50 as well as a suitable housing Hd 52 are shown in figs. 6

and 7. The housing 50 preferably comprises a cylindrical shape, having a cylindri¬

cal inner opening 55 into which an arrangement 1 according to fig. 1 can axially

be inserted. The diameter of the opening 55 is preferably formed such that the

support bodies 30, 32 cannot turn against each other in an undesired way. This can

for example be achieved in that a slight press fit of the support bodies 30, 32 is

provided within opening 55, or for example in that the support bodies 30, 32 com¬

prise a toothing at their outer side (not shown) which corresponds with a toothing

(not shown) at the inner side of opening 55.

For assembly of the arrangement according to fig. 1 in the housing 50, first the first support body 30 is inserted into opening 55, then the second support body 32 is turned with respect to housing 50 until the desired friction effect is achieved and then the second support body 32 is inserted into opening 55. After that, the housing 50 is closed by a Hd 52 according to fig. 7. To this end, preferably screws or similar mounting means are screwed into the openings 56 and 57. Other mount¬ ing possibilities as clips etc. to fix the Hd 52 at housing 50 are of course possible.

For mounting of housing 50 at the desired element it can be provided with mount¬ ing flaps 54. The Hd 52 preferably comprises a suitable passage 58, through which the shaft 10 or the rod 20 can extend. Further, mounting elements 59 at the Hd 52 can be provided for mounting the housing 50 including Hd 52 at the desired ele¬ ment. An arrangement 1 according to the invention can be used to brake down or to at¬ tenuate any kind of rotational movements or axial movements of two elements to each other by means of an adjustable friction force. So, for example, the bearing bodies 30, 32 could be mounted at the dash board of a motor vehicle and the rod 20 at the lid of a glove box. With such an arrangement, the glove box does not immediately open, but with an attenuated slow motion such that injuries are avoided.

The arrangement 1 could also be integrated into any other kind of joints, to gener- ate such an attenuated motion. This could for example be the rotational joints of a parking brake lever or of pedals and also the rotational joints of fold-away hand¬ holds or sun visors. The attenuation of a linear motion by means of arrangement 1 could be used for the height adjustment of headrests in a motor vehicle seat. Fur¬ ther, the lids of armrests or other compartments can be opened or closed in an attenuated manner. .

By the unlimited possibility to rotate or possibility to translate the shaft 10 or rod 20 of course further applications in the automotive field or in other fields of use may arise.

List of reference signs 1 arrangement 10 shaft 20 rod 30 first support body 32 second support body 40 torsion spring 42 first end 44 second end 50 housing 52 housing lid 54 flap 55 opening 56 hole 57 hole 58 passage 59 mounting element 60 first adjusting element 62 second adjusting element 64 fork 70 first bearing shell 72 second bearing shell 74, 75 collar 80, 85 arrow