WO2022123473A1

WO2022123473A1 - Parametric dynamic damper with an auto-powered sensor function

Info

Publication number: WO2022123473A1
Application number: PCT/IB2021/061485
Authority: WO
Inventors: Elvio Bonisoli; Domenico LISITANO; Luca DIMAURO
Original assignee: Politecnico di Torino
Current assignee: Politecnico di Torino
Priority date: 2020-12-09
Filing date: 2021-12-09
Publication date: 2022-06-16
Anticipated expiration: 2023-06-09

Abstract

A passive dynamic damper comprises a magnetic seismic mass (3) movable along a direction of oscillation; at least a first magnet (8) disposed along said direction so as to apply magnetic repulsion on the seismic mass; optionally a second magnet (8), and/or another type of spring element in series or in parallel, disposed along said direction on opposite sides of the first magnet with respect to the seismic mass and configured to apply a repulsion on the seismic mass opposed to the repulsion applied by the first magnet, and a first device for adjusting the relative distance (7) between the preload magnet (s) and the seismic mass to vary the repulsive forces applied thereon, so as to modify at least one dynamic parameter of the damper; a second device for adjusting the relative distance (4) between the eddy current or eddy current elements to vary the damping and/or energy recovery effect of the dynamic damper.

Description

"Parametric dynamic damper with an auto-powered sensor function"

DESCRIPTION

TECHNICAL FIELD

The present invention belongs to the technical field of vibration reduction and refers to a parametric and adj ustable dynamic vibration damper .

BACKGROUND

Unwanted vibrations are present in almost all machines , plants or structures . They are the cause of numerous negative ef fects , such as noise pollution, disturbance in the operation of equipment , reduction in the accuracy of instruments and machines , and cause damages to equipment and building structures . It is easy to perceive how these unwanted ef fects can become problematic also for safety reasons . Various methods are known in the state of the art to reduce the problems caused by vibrations , including vibration isolation, vibration absorption, vibration damping .

There are basically three large families of systems capable of responding to external dynamic stresses : passive systems , active systems and hybrid systems .

Passive systems do not require an external energy source to function and generate control forces that oppose external stresses . The main obj ective of this family of systems is to dissipate energy . Friction dampers , viscoelastic dampers , viscous dampers , mass dampers ( discussed more widely below) and liquid dampers belong to this family . Active systems , unlike the previous ones , require an external energy source to generate the control forces ( for example through actuators ) on the basis of information coming from the measurement of the external stress . Control forces can oppose or accommodate external stresses . For example , belongs to this family the active mass damper that operates in a s imilar way to the above , but through the action of controlled actuators .

Finally, hybrid systems require much less external energy to operate than active systems and are able to generate control forces whose intensity can be varied thanks to the external energy source . As with active systems , the control forces are generated on the basis of information from the measurement of external stress e . g . a periodic force . Variable friction dampers , semi-active viscous dampers and fluid controllable semi-active dampers belong to this family .

Taking into consideration the family of passive systems known in the state of the art , the reduction of vibrations is often obtained through solutions that include the use of dynamic dampers according to appropriate variants related to the speci fic system under consideration .

The dynamic or mass damper, known in the literature as Tuned-Mass-Damper ( TMD) , is a device that allows to reduce the vibration amplitude of an arbitrary degree o f freedom in a structure subj ected to dynamic periodic forces , i . e . variables over time . A dynamic damper generally comprises an element or inertial mass connected to an elastic element , which varies the degree of freedom of the system whose amplitude of oscillation is to be reduced . In other words the additional elastic element increases the degrees of freedom of the system to which the damper is applied, resulting in a reduction in the vibrations of the overall system . In principle , the TMD depends on some parameters such as the ratio between the mass of the TMD with respect to the mass of the original system, the damping coef ficient , the sti f fness and the ratio between the natural frequency of the TMD and the natural frequency of the original system . The dynamic damper is calibrated to resonate at the same frequency of the oscillations of the original system that are to be minimi zed, by appropriately choosing the value of the additional inertia and the sti f fness constant of the elastic element . The physical principle consists in the di f ferent energy distribution in the system with and without dynamic damper . The energy, which in the original system excites the degree of freedom under consideration, is redistributed between the system and the dynamic damper, through the use of the latter which is added to the original structure .

Therefore , the overall system, arranged with the original system and the dynamic damper, has an additional resonance , due to the degree of freedom introduced by the dynamic damper and quantitatively close to the frequency of interest . The advantage deriving from the use of a dynamic damper consists in the fact that the vibration ampl itude of the two resonances is smaller than the vibration amplitude of the resonance of the original system alone . The system can reduce the amplitude of the vibrations with an ef fectiveness that is much greater as much the stress frequency is closer to the natural frequency of the system for which the TMD device was designed . The dynamic damper concept was subsequently optimi zed with the addition of a dissipative element positioned in parallel with respect to the elastic element ; an appropriate calibration of the latter allows to minimi ze the oscillation amplitude of the two resonances at the same time .

However, the dynamic damper has its main disadvantage in the manufacturing ef fort , since it must be designed for a speci fic vibration situation, and consequently in manufacturing costs due to its extremely customi zed nature in solving the problems present in a speci fic vibrational application . Therefore these devices for individual applications , involving high costs , are often used only for systems of a certain relevance . Another known problem is the so called "detuning" phenomenon which occurs when the reference frequency of the original system varies over time , moving away from the frequency used as a reference for the TMD conf iguration . In this case , the greater the deviation of the frequency over time with respect to the reference frequency used to configure the damper, the less the ef fectivenes s of the damper itsel f will be , up to the cases wherein it is necessary to replace it with another one whose characteristics respond to changed conditions . In general , the solutions present in the state of the art allow the adj ustment of the working frequency in relatively extended frequency intervals , by modi fying the dynamic damper in its components . The adj ustment can be performed by changing the mass of the damper or the relative position of the mass with respect to a f ixed point . Some solutions provide the poss ibility of varying the sti f fness through the use of replaceable rubber elements with di f ferent elastic characteristics among them . With regard to the damping, in the solutions present in the state o f the art this is generally fixed or with the possibility of discrete adj ustments .

For example , referring to the adj ustment of the damping, sti f fness and frequency characteristics , the patent application CN-A1- 103615488A describes a dynamic damper with the elastic element formed by a circular spring and an electromagnet that allows to adj ust the working frequency . This solution does not provide any damping adj ustment and furthermore the frequency adj ustment is performed actively by acting on the current supplied to the electromagnet . Patent application DE-A1- 102014006193 describes a multiple dynamic damper formed by inertial elements with plates and connecting springs . The sti f fness is adj usted by changing the constraints between the plates and the damping is ensured by very viscous elements interposed between the plates . This solution allows the regulation of the sti f fness by changing the constraints between the plates which there fore occurs for discrete values .

SCOPE AND SUMMARY OF THE INVENTION

The scope of the present invention is to at least partially solve the disadvantages related to the reali zation of passive dampers as an ad hoc solution of a particular system . The present invention allows to adj ust in a simple and continuous way , by acting on the device in place without disassembly of components , the sti f fness and/or the damping of the dynamic damper, for an optimal calibration of the device according to the frequency of the vibration source even after installation . Such feature solves the problem of the variability of the dynamic properties of nominally equal systems in series production, allowing to optimi ze the invention functioning on each individual system . Furthermore , the present invention allows to adapt the working frequency to the source frequency even when these vary over time , for example due to wear of the machine , through fine adj ustments of the optimal working frequency . The invention therefore solves the problem of the loss of optimal operating conditions of the dynamic damper when the dynamic characteristics of the source change over time , thus avoiding the integral replacement of the dynamic absorber .

The present invention also allows a double adj ustment of the sti f fness through the adj ustment of the working frequency of the device and of the damping independently from each other .

The invention comprises an oscillating cylindrical magnet , which de fines the inertial element of the damper, inside an external casing, preferably cylindrical in shape , further containing inside it a preload magnet arranged at one end of an oscillation path of the seismic mass . The magnetic interaction of the inertial magnet with a preload magnet generates magnetic forces that represent the elastic element of the dynamic damper, o f magnetic type and with non-linear behavior .

There is also a magnetic element of dynamic damper selected from one of a further elastic element of preload opposed to the preload magnet with respect to the seismic mass along the direction of osci llation of the latter or a damping element with eddy currents or induced, in parallel with respect to the seismic mass , so as to concatenate the magnetic field o f the latter during the oscillations . The eddy current element is for example a block of diamagnetic or paramagnetic electrical conducting material and the generation of these currents applies a damping to the oscillation of the seismic mass . Through the appropriate positioning of the eddy current element along the stroke of the oscillating magnet it is possible to impact on the amount of energy dissipated by the dynamic damper . For example , it is possible that the seismic mass oscillates in presence of a single preload magnet having an action opposed to the acceleration of gravity or centripetal acceleration . In such case , the adj ustment of the position of the eddy current element along the oscillation stroke of the seismic mas s allows a modi fication of the dynamic damper performance .

Alternatively or in combination, by adj usting the preload applied by the elastic abutment elements , not necessarily both magnetic, a resonance frequency of the dynamic damper is changed . For example , it is also possible to combine the preload magnet with a linear opposing spring . In this way a non-linear spring and a linear spring are coupled, obtaining dynamic ef fects which further expand the application possibilities of the dynamic damper obj ect of the present invention .

In particular, the distance adj ustment device can be ma manually operated e . g . using a hand tool . It can be a discrete device , to adj ust the position or the distance in steps , or continuous . In the latter case it is possible to use a screwdriver and " screw-type" couplings between the threaded components to allow the adj ustment of the relative position between the preload magnet and said dynamic damper magnetic element in order to modi fy the dynamic damper performance . This feature allows to calibrate the system with respect to the particular application under consideration and to obtain, on board a single device , a variation of the lineari zed natural frequency of the damper of approximately 2 orders of magnitude .

According to a preferred embodiment , the passive dynamic damper comprises an extendable tubular element , e . g . telescopic, and housing the seismic mass and having at least one end portion connected to the distance adj ustment device .

In this way, the seismic mass is guided as it oscillates and impacts with the static components of the damper are avoided .

According to an alternative embodiment , the seismic mass can comprise two magnets with opposite magneti zation with an interposed ferromagnetic element , to achieve a greater magnetic field variation . According to an alternative embodiment , the seismic mass has a shape converging along the direction of oscillation to provide an aerodynamic damping, preferably asymmetrical between a first stroke towards the preload magnet and a second stroke away from the preload magnet .

According to an alternative embodiment , the first and second magnets can be of di f ferent si zes or of di f ferent materials so as to generate respective magnetic field intensities di f ferent from each other to obtain an asymmetric balance point of the seismic mass with respect to the midpoint of the stroke .

In this way, it is possible to extend the range of adj ustments of the dynamic damper .

According to a preferred embodiment , the damping element is concentric and diamagnetic, so as to provide a sel f centering action on the seismic mass .

In this way, the mechanical guides , e . g . the extendable tubular element , are less stressed by frictional forces during oscillation .

According to a preferred embodiment , the passive dynamic damper comprises the other between the magnetic dynamic damper elements and a second distance adj ustment device configured to adj ust the relative distance between the repulsion magnet and the other between the magnetic elements of dynamic damper .

Thus , both the position of the eddy current or induced current damper and the reciprocal position between the preload magnet ( s ) and the seismic mass can be adj usted independently .

According to a preferred embodiment , the second distance adj ustment device is concentric with the first distance adj ustment device .

In this way the passive dynamic damper has a compact configuration .

According to a preferred embodiment , the second distance adj ustment device carries the first distance adj ustment device so that an adj ustment of the second distance adj ustment device causes rigid movement of the first distance adj ustment device ; and a relative movement between the first and second distance adj ustment device causes a relative displacement between the damping element and the first and second magnet .

In this way it is possible to independently adj ust the position of the magnets and the damping element to eddy or induced currents .

According to an alternative embodiment , the passive dynamic damper comprises an electronic board having an electric current accumulation element connected to the eddy current damping element and programmed to perform an ' energy harvesting ' or hybrid dynamic damper function while the mass seismic oscillates .

In this way, the device can al so accumulate and/or recover, and/or manage in a hybrid way the electric energy coming from the conversion of the kinetic energy of the seismic mass .

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows the general scheme through a plane a ) and axonometric b ) cross-sectional view with of fset planes of the dynamic damper of the present invention . Figure 2 shows the respective adjustment positions of the damper of Figure 1, i.e. at reduced stroke a) and at maximum stroke b) .

Figure 3 shows sections of the dynamic damper in respective configurations of use related to the adjustment of an elasticity parameter.

Figure 4 shows sections of the dynamic damper in respective configurations of use related to the adjustment of a damping parameter to induced or eddy currents .

Figure 5 shows different types of paramagnetic or diamagnetic inserts for the adjustment of the dissipative effect of the dynamic damper of the present invention.

Figure 6 shows sections of the dynamic damper in respective independent adjustments between the elastic parameter and the damping parameter.

Figure 7 shows the continuous variation of the linearized working frequency of the dynamic damper of the present invention in relation to the adjustment of the stroke available for the oscillating magnet.

Figure 8 shows the dynamic damper in the configuration of a self powered sensor through 'energy harvesting' .

Figure 9 shows damper sections with respective form factors being examples of scalability. DETAILED DESCRIPTION OF THE INVENTION

According to an example of the preferred embodiment ( Figs . 1-4 ) the invention comprises an oscillating cylindrical magnet 3 , which defines the inertial element of the damper, connected to the external casing 1 , through the magnetic forces generated by the interaction of the oscillating cylindrical magnet 3 with two preload magnets 8 , preferably cylindrical in shape . The forces due to the magnetic interaction represent the elastic element of the dynamic damper, of the magnetic type and with non-linear behavior .

The cylindrical oscillating magnet 3 slides inside a thin plastic guide 2 formed by a central body and by two telescopic ends 9 which allow the extension of the guide 2 during the adj ustment phases . The guide 2 engages , by means of a plastic flange orthogonal to the axis of the guide , in a seat performed on the internal side of the cylindrical casing 1 , and is therefore rigidly fixed with the casing itsel f . The flange of the guide 2 is suitably lightened to facilitate the insertion inside the component 1 . The end portions 9 are instead rigidly fixed with the adj ustment elements described below, by gluing between the outer cylindrical surface of the end portions 9 and the cylindrical surface of spacers 5 , positioned one on each side . The internal diameter of the guide 2 is approprately increased with respect to the diameter of the cylindrical oscillating magnet 3 to allow the air leakages when the cylindrical oscil lating magnet 3 oscillates . The form ratio between the height of the cylindrical oscillating magnet 3 and the diameter of the magnet is usually limited to below about 0.5, to avoid jamming of the cylindrical oscillating magnet 3 inside the guide 2. The fittings or bevels present in the cylindrical oscillating magnet 3 allow to avoid possible jammings with respect to the discontinuity between the guide 2 and the telescopic ends 9 which form the guide when the device is in maximum extension.

The preload magnets 8 can be present in single quantity only at one end, in order to balance the weight force of the oscillating magnetic mass 3 with respect to gravity in vertical configuration, and/or the centrifugal force in rotor applications. In a version not shown and wherein the oscillation cycle of the magnet 3 is obtained through the acceleration of gravity, e.g. positioning the guide 2 in a substantially vertical direction. In such case, the adjustment comprises the appropriate spacing from the preload magnet 8 of a dissipative element, as it will be better specified below. Alternatively, two preload magnets 8, the same or different from each other (e.g. fig. 3) , e.g. configured to have different magnetic field intensities, can be arranged at the ends. For simplicity of representation in Fig. 1 the preload magnets are the same, but this solution does not complete all the possible configurations. Each of the preload magnets 8 is rigidly fixed with a position adjustment element e.g. a screw 7 or an element with discrete axial positioning configured to lock the working position by means of a bayonet rotation, which can also be of a commercial type, for example ISO 7435, or of similar geometry or specially manufactured. In the dynamic damper of the present invention there are two screws 7, one at each end. Each of the screws 7 engages in the threaded hole of the position adjustment device 4, also this one for each end in the dynamic damper of the present invention. The device 4 can be of the commercial type ISO 7436 or an element with discrete axial positioning configured to lock the working position by means of a bayonet rotation, of similar geometry or appropriately modified. The screw-type coupling between the adjustment device 7 and the adjustment device 4 allows to adjust the intensity of the magnetic interaction between the preload magnets 8 and the cylindrical oscillating magnet 3, and consequently to vary the stiffness of the magneto-elastic connection of the damper. This feature allows to calibrate the system with respect to a particular application.

The dissipative element of the dynamic damper is obtained by exploiting the effect of eddy currents generated by a time-varying magnetic flux concatenated to paramagnetic or diamagnetic elements and electrical conductors. The position of one of such diamagnetic or paramagnetic elements from the single preload magnet 8 is adjusted to vary the dynamic damping characteristics as indicated above. Furthermore, the rings 6, e.g. one for longitudinal part as illustrated in the figures, in paramagnetic material, for example aluminum, or diamagnetic material, for example copper, are concentric with respect to the guide 2 and to the external casing 1. The two damping rings 6 can generally be different, in external diameter and height, or can be the same as in the example in Fig. 1. Each of the damper rings 6 is rigidly connected to a spacer 5, in turn rigidly fixed with the adjustment device 4. The adjustment device 4 is connected to the external casing 1 with a coupling of the threaded type, which allows the adjustment of the axial position of the damper rings e.g. with respect to the preload magnet (s) 8, independently of the preload magnets themselves. The axial position of the damping rings 6 allows to adjust the damping coefficient, both in absolute value and with respect to the stroke of the magnet 3. For example, when the adjustment device 4 is in maximum extension, the damping rings 6 introduce the damping only at the stroke end of the cylindrical oscillating magnet 3 to avoid impacts with the preload magnets. Alternatively, when the adjustment device 4 is in minimum extension, the damping is introduced for small amplitudes of vibration of the oscillating cylindrical magnet 3. The adjustment of the damping value can be obtained by adjusting the axial position of the rings 6, or by changing the insert damping ring 6 (Figures 5 and 6) with a different form ratio, in length, thickness and/or of different material.

Using diamagnetic materials such as copper, the damping rings 6 also give the self-centering property of the oscillating cylindrical magnet 3 during its oscillatory motion inside the guide 2, thus allowing to limit the sliding between the cylindrical oscillating magnet 3 and guide 2 itself.

The external casing 1 must be mounted rigidly fixed with respect to the degree of f reedom/system to be damped, e.g. screwed or by means of brackets that appropriately orient the monoaxial direction of action to the machinery whose vibrations are intended to be attenuated. According to the invention, by keeping constant the damping characteristic, in particular high damping at the stroke end to avoid impacts between the oscillating magnet and the preload magnets , it is possible to adj ust the working frequency of the TMD in a continuous range . In Fig . 7 is shown a graph depicting the frequency and sti f fness values valid for the dynamic damper represented in Fig . l as the stroke varies . The interval covers with continuity the values from about 25 Hz to about 600 Hz . Points a, b, c, d are the corresponding values obtained with the configurations shown in Fig . 6 .

By bringing narrower the preload magnets 8 , the stroke available for the magnet is reduced by increasing the lineari zed working frequency, but this is compatible with the dynamic characteristics of classical mechanical systems , which involve even smaller oscillation amplitudes as the oscillation frequency increases .

By keeping valid the physical principles as the basis of the present invention, it is possible to provide the dynamic damper with modular si zes according to the needs of the application . This of fers the advantage of being able to choose the most appropriate si ze to the needs in addition to the possibility of adj usting for a determined si ze as described above . In Fig . 9 , by way of non-limiting example three possible si zes of the dynamic damper of the present invention are shown . For example , it is possible to ef fectively provide the invention when a ratio between the maximum oscillation stroke of the oscillating magnet 3 and its maximum transverse dimension, e . g . the diameter, is between 1 and 5 . A further advantage present in the solution proposed by the present invention concerns the recovery of the dissipated energy . The invention allows to exploit the dissipated energy to power low-power sensors , thus combining the function of a damper with that of a sel f- powered sensor . Alternatively, energy recovery can be used for hybrid logics in intelligent dynamic dampers .

This technology is known in the literature as energy harvesting . The concept of energy harvesting consists in recovering unused energy from a system, which would otherwise be dispersed in the environment . Fig . 8 shows the dynamic damper in sel f-powered sensor configuration obtained from the previously described dynamic damper . With respect to the dynamic damper shown in Fig . 1 , one or both of the damper rings 6 of Fig . 1 are replaced with windings of wire , for example of copper .

In this way the variation o f the magnetic flux concatenated with each coil of the solenoid produces currents inside the solenoid and therefore a potential di f ference acros s it, which can be used to power a low power sensor, with communication protocol , by way of example and that does not exhaust other communication solutions , low power Bluetooth or wireless . Unlike the solution in Figure 1 which dissipates heat , the eddy currents generated by the conductive material with which the solenoids 6 of Fig . 8 are made , convert the energy subtracted from the system into electrical energy, to power sensors and / or transmit signals .

Always referring to what is shown in Fig . 8 , the two solenoids are connected to each other in counter-series , the ends of the solenoids pass through two additional holes obtained in the adjustment device 4, and are connected to two electrical terminals and, rigidly fixed always to the adjustment device 4. The voltage across the solenoids is used to power an electronic board 11 which allows the transfer of the energy contained in a mounted casing 10, by way of example, and which does not limit further mounting or integration possibilities, for example rigidly joint on the pins. The system maintains all the adjustability properties, in terms of stroke, stiffness, damping and linearized working frequency, previously described. The electronics enclosed within the casing 10 is connected to the electrical terminals only after adjusting the device to optimize performance according to the specific application because the casing obstructs the access to the adjustment tool .

Finally, it is clear that it is possible to make changes or variants to the dynamic damper of the present invention without thereby getting out of the scope of protection as specified in the claims.

According to an example not illustrated, it is possible to provide the elastic component of the dynamic damper in a magneto-elastic hybrid way: a linear contact spring can in fact be opposed to a preload magnet, e.g. a helix spring, or a combination of mechanical and magnetic elements (helix spring and magnetic ring or magnet inside a spring) .

Furthermore, a lateral surface of the oscillating magnet 3 can be tapered towards the direction of oscillation to obtain an aerodynamic damping e.g. also asymmetrical between a stroke of approaching to the preload magnet 8 and a stroke away from the latter. For example, this is possible through the arrangement of opposing and different tapered surfaces or a single tapered surface converging towards or diverging from the preload magnet.

Claims

1. A passive dynamic damper comprising a magnetic seismic mass (3) movable along a direction of oscillation; a first magnet (8) arranged along said direction so as to apply a magnetic repulsion on the seismic mass; a dynamic damper element selected from one of an elastic element (8) disposed along said direction on the opposite side of the first magnet with respect to the seismic mass and configured to apply a repulsion on the seismic mass opposite to the repulsion applied by the first magnet; or of an eddy current or induced current damper (6) placed side by side to the seismic mass so as to concatenate a magnetic field of said mass, and a device for adjusting the relative distance (7) between the first magnet and the dynamic damper element ( 8, 6) to adjust an action applied to the seismic mass so as to modify at least one dynamic parameter of the damper such as the linearized resonance frequency and / or a quantity of dissipated energy.

2. Passive dynamic damper according to claim 1, comprising an extendable tubular element (2) housing the seismic mass and having at least one end portion connected to the device for adjusting the distance

3. Passive dynamic damper according to one of claims 1 or 2, wherein the adjusting device (7) is threaded in order to bring closer the preload magnet (8) and said dynamic damper element (8, 6) to increase said repulsion forces in the case of a further elastic preloading element or changing the dissipated energy in the case of the current damper element (6) ; or move the first preload magnet and said magnetic element of dynamic damper (8, 6) apart from each other to reduce said repulsion forces in the case of the further elastic preload element (8) or change the dissipated energy in the case of current damper element (6) during adjustment.

4. Passive dynamic damper according to any one of the preceding claims, further comprising the further elastic preload element, wherein the further elastic element is a further permanent preload magnet and wherein the preload magnets (8) have different dimensions one another and / or are configured to have a different magnetic field strength, to obtain an asymmetric point of balance of the seismic mass with respect to the midpoint of the stroke.

5. Passive dynamic damper according to any one of the preceding claims, wherein the seismic mass (3) has a converging shape along the direction of oscillation to provide aerodynamic damping, preferably asymmetrical between a first stroke towards the preload magnet and a second stroke away from the preload magnet.

6. Dynamic passive damper according to any of the previous claims, wherein the damping element (6) is concentric and diamagnetic, so as to provide a selfcentering action on the seismic, or paramagnetic mass.

7. Passive dynamic damper according to claim 1, wherein both the further elastic preload element and the damping element are present; the device for adjusting the distance (7) is configured to adjust the distance between the elastic preload elements; and also comprising a further distance adjustment device (4) configured to adjust the relative distance between the damping element and at least one of the elastic preload elements.

8. Passive dynamic damper according to claim 7, wherein the further distance adjustment device (4) is concentric to the distance adjustment device (7) .

9. Damper according to one of claims 7 or 8, wherein the further distance adjustment device (4) carries the distance adjustment device (7) so that an adjustment of the further distance adjustment device (4) causes rigid movement of the distance adjuster (7) ; and a relative movement between the distance adjustment devices (7, 4) causes a relative displacement between the damping element (6) and the elastic preload elements (8) .

10. Passive dynamic damper according to any of claims 6 to 9, wherein the further distance adjustment device (4) is threaded .

11. Damper according to any one of the preceding claims, comprising said damping element (6) and an electronic board (11) having an electric current storage element connected to the damping element (6) and programmed to perform an energy function harvesting while the seismic mass oscillates .

12. Damper according to claim 1, wherein the elastic repulsion element is a linear contact spring.