MASS DAMPER DEVICE, WORKING TOOL AND WORKING TOOL HOLDER COMPRISING A MASS DAMPER DEVICE

Abstract

Mass damper device comprising a tubular housing having a first and a second longitudinal end; at least one damping mass which is received in the tubular housing with a circumferential clearance; a first resilient element and a second resilient element. At least one end closure is arranged at the first or second longitudinal end. The housing and the end closure have cooperating mounting surfaces which define a longitudinal mounting position of the first and second end closures. The mounting surfaces are arranged such that the first and second resilient elements are compressed between the damping mass and the end closure, when the first and second end closures have been mounted, at the longitudinal mounting position, to the housing.

Claims

1. A mass damper device comprising: a tubular housing having a first and a second longitudinal end; at least one damping mass which is received in the tubular housing with a circumferential clearance and which exhibits a central bore; a first resilient element and a second resilient element, at least one end closure arranged at the first or second longitudinal end and exhibiting a respective central through opening, a coolant media tube which extends with a radial clearance through the central bore and is received in the central through opening of the at least one end closure, wherein the housing and the end closure have cooperating mounting surfaces which define a longitudinal mounting position of the end closure; and wherein the mounting surfaces are arranged such that the first and second resilient elements are compressed to a predetermined compression rate between the damping mass and the end closure, to thereby achieve a correct tuning to a desired nominal Eigen frequency of the damping mass, by mounting the end closure, at the longitudinal mounting position, to the housing.

2. The mass damper device according to claim 1, wherein the predetermined compression rate ranges between 5% and 50%.

3. The mass damper device according to claim 1, wherein the mounting surfaces are mutually parallel and arranged such that each resilient element is evenly compressed over its surfaces facing the damping mass and the end closure.

4. The mass damper device according to claim 1, wherein the cooperating mounting surfaces comprise at least one first contact surface arranged at or in proximity to a longitudinal end of the housing and at least one second contact surface arranged at the first and/or a second end closure, which first and second contact surfaces are in mutual contact when the respective end closure is in the longitudinal mounting position.

5. The mass damper device according to claim 1, wherein the cooperating mounting surfaces comprise a least one first alignment surface arranged at or in proximity to a longitudinal end of the housing and at least one second alignment surface arranged at the first and/or a second end closure, which first and second alignment surfaces are arranged in the same cross sectional plane of the housing when the respective end closure is in the longitudinal mounting position.

6. The mass damper device according to claim 1, wherein the first and/or second resilient elements comprise a material having a frequency depending Young's modulus.

7. The mass damper device according to claim 6, wherein the first and/or second resilient elements comprise a material at which, after mounting the end closure at the longitudinal mounting position, the Young's modulus increases by at least 20% when the vibration frequency of the damping mass increase by 100%, over the frequency range from 100 Hz to 2000 Hz.

8. The mass damper device according to claim 6, wherein said material comprises a nanostructure material with a structural size of 100 nm or less in at least one dimension.

9. The mass damper device according to claim 1, wherein the housing, the damping mass, the first and a second resilient elements and the at least one end closure form an integral module which is arranged to be inserted into and extracted from a working tool or a working tool holder.

10. The mass damper device according to claim 1, further comprising at least one sealing arranged between the housing and the first and/or second end closure.

11. The mass damper device according to claim 1, wherein the damping mass is provided with at least one distancing member arranged to prevent the damping mass from contacting the interior longitudinal wall of the housing.

12. The mass damper device according to claim 11, wherein the at least one distancing member comprises an annular member which encircles the damping mass.

13. The mass damper device according to claim 11, wherein the distancing member comprises a plurality of elongate members which extend radially out from the envelope surface of the damping mass and which are arranged to bend or buckle when making contact with the inner wall of the housing.

14. The mass damper device according to claim 11, wherein the distancing member comprises a plurality of stud shaped members which extend radially out from the envelope surface of the damping mass and which are arranged to be axially compressed when making contact with the inner wall of the housing.

15. The mass damper device according to claim 11, wherein the at least one distancing member comprises a pin shaped member which extends longitudinally from the damping mass to one of the first and second end closures.

16. The mass damper device according to claim 1, comprising a first end closure arranged at the first longitudinal end and a second end closure, arranged at the second longitudinal end.

17. The mass damper device according to claim 1, wherein the predetermined compression rate ranges between 20% and 30%.

18. A working tool comprising the mass damper device according to claim 1.

19. A working tool holder comprising the mass damper device according to claim 1.

20. A working tool comprising a shank arranged to be fixed to a tool holder and a tool portion, wherein the shank exhibits an outwardly open, central and axial bore; and wherein a mass damper device is detachably fixed in the bore, said mass damper device comprising a tubular housing having a first and a second longitudinal end; at least one end closure arranged at the first or second longitudinal end; and at least one damping mass which is received in the tubular housing with a circumferential clearance and supported by a first and a second resilient element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Further details, advantages and aspects of the present disclosure will become apparent from the following embodiments taken in conjunction with the drawings, wherein:

[0076] FIG. 1a is a longitudinal partly exploded section through a mass damper device according to a first embodiment of the invention. FIG. 1b shows an exploded portion on enlarged scale and FIG. 1c shows a detail thereof in further enlarged scale and when mounted.

[0077] FIG. 2a is a longitudinal section through a mass damper according to a second embodiment and FIG. 2b shows a portion thereof in an exploded view.

[0078] FIG. 3 is a longitudinal exploded section of a mass damper according to a third embodiment.

[0079] FIG. 4 is a longitudinal section of a mass damper device according to fourth embodiment.

[0080] FIG. 5 is a longitudinal section of a mass damper device according to a fifth embodiment.

[0081] FIG. 6 is a schematic perspective view illustrating a damping mass with distancing members.

[0082] FIG. 7 is a schematic perspective view illustrating alternative distancing members.

[0083] FIG. 8a is a schematic perspective view illustrating further alternative distancing members. FIG. 8b is a longitudinal section of FIG. 8a and FIG. 8c shows a portion of FIG. 8b in enlarged scale.

[0084] FIG. 9a is a side view, partly in section of a working tool holder provided with a mass damping device as shown in FIGS. 1a-c. FIGS. 9b and 9c show details thereof in enlarged scale.

[0085] FIG. 10 is a diagram illustrating the increased damping efficiency of the present mass damping device in comparison with previously known mass damping devices.

[0086] FIG. 11a is a perspective view of another working tool holder provided with a milling tool and FIG. 11b is a perspective view in enlarged scale illustrating the milling tool shown in FIG. 11a.

[0087] FIG. 12a is a longitudinal section of the milling tool shown in FIG. 11b and illustrates further a mass damper device inserted into the milling tool,

[0088] FIG. 12b is a longitudinal section in enlarged scale of the mass damper device shown in FIG. 12a.

[0089] FIG. 13 is a schematic diagram illustrating the general principle of a damping mas according to the prior art.

DETAILED DESCRIPTION

[0090] The invention will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout the description.

[0091] FIG. 1 illustrates a first exemplifying embodiment of a mass damper device. The mass damper is formed as a module which may be directly inserted in a conventional working tool or working tool holder having a standardized cavity for receiving various previously known mass damper arrangements.

[0092] The mass damper comprises a cylindrical tubular housing 10. The housing has a first 11 and a second 12 longitudinal end, each end defining a cross sectional plane which is perpendicular to the longitudinal axis of the housing.

[0093] A first end closure 13 is secured to the first longitudinal end 11 and a second end closure 14 is secured to the second longitudinal end 12 of the housing 10. A damping mass 30 is received in the housing 10 and arranged between the end closures 12, 13. The damping mass 30 is formed generally as annular cylindrical body having a constant cross section with and outer diameter D1 and an inner bore 33. The damping mass 30 exhibits a first longitudinal end 31 and a second longitudinal end 32. In the shown example, the damping mass 30 exhibits an outer circumferential grove 34 which is arranged centrally between the first 31 and second 32 longitudinal ends.

[0094] A coolant media tube 40 extends with a radial clearance through the central bore 33 and is received in central through openings 15, 16 in the first 13 and second 14 end closures respectively.

[0095] The mass damper further comprises a first 51 and a second 52 resilient element. The resilient elements 51, 52 are arranged for holding the damping mass 30 in the housing 10. The first resilient element 51 is clamped between the inside of the first end closure 13 and the end surface of the damping mass' first end 31. The second resilient element 52 is correspondingly clamped between the inside of the second end closure 14 and the end surface of the damping mass' second end 14. At this embodiment the resilient elements 51, 52 are purely held by friction between on the one hand the resilient element and on the other hand the damping mass 30 and the respective end closure 51, 52. Such friction depends on the compression rate of the resilient members, which compression rate is achieved as described below.

[0096] The resilient elements 51, 52 are constituted of a material having a frequency dependent stiffness. In the shown embodiment the resilient elements 51, 52 are formed of 3M® 110, 112, 130 or 242NR01 which are nanostructure polymeric materials.

[0097] The resilient elements 51, 52 are identical and are each formed as an annular ring having a nominal uncompressed thickness t.sub.1 in the longitudinal direction of the mass damper device, as best seen in FIG. 1b.

[0098] Although the resilient elements 51 and 52 are identical in this embodiment, they do not need to be identical in other embodiments. For example, the elements 51 and 52 can be made of different materials, and the elements 51 and 52 can have different dimension. For example, elements 51 and 52 can have different thickness.

[0099] With such resilient elements having a frequency dependent stiffness, it is possible to decide the nominal frequency range by compressing the resilient elements to a corresponding compression rate. In this disclosure the compression rate CR is defined as:

CR=(t1−t2)/t1

[0100] Where t1 is the material thickness before compression and t2 is the material thickness after compression.

[0101] The desired compression rate of the resilient elements is achieved by longitudinally compressing the first 41 and second 42 resilient elements equally between the end surfaces 31, 32 of the damping mass 40 and the corresponding end closure 13, 14.

[0102] Although the resilient elements 51 and 52 are compressed equally in this embodiment, they can also be compressed into different ratios in other embodiments. For example, when the two elements 51 and 52 have different elastic modulus while the dimensions are identical, the compression ratio of the two elements 51 and 52 are not identical as the element with lower elastic modulus will be compressed more than the other.

[0103] The compression of the two resilient elements 51 and 52 is achieved by mounting the end closures 13, 14 at predetermined longitudinal mounting positions such that the distance between the inner surfaces of the end closures 13, 14 and the respective end surface 31, 32 of the damping mass 30 equals the desired thickness t2 after compression of the resilient elements 41, 42.

[0104] In the embodiment shown in FIGS. 1a-1b and as best seen in FIG. 1b, this is here achieved by arranging first contact surfaces 11a, 12a at the first 11 and second 12 ends of the housing 10 and corresponding second contact surfaces 13a, 14a at the respective end closure 13, 14. In this embodiment the second contact surfaces 13a, 14a form stop surfaces which are constituted by the inner walls of the end closures 13, 14 and are thus arranged in the same radial plane as the support surface for the resilient element 41, 42 at each respective end closure 12, 14. At this embodiment the distance between the first contact surfaces 11a, 12a are thus selected as the length of the damping mass 30 plus the desired thickness of both resilient elements 41, 42 after compression. The first contact surfaces 11a, 12a are further arranged as bottom surfaces of inner cylindrical widened portions or end bores 11b, 12b at the end portions of the housing 10. The bores 11b, 12b thus extend axially from the end surface of the housing 10 to the respective first stop surface 11a, 12a. The inner diameter of the bores 11b, 12b corresponds to the outer diameter of the end closures 13, 14, such that each end closure 13, 14 may be received in the respective bore 11b, 12b with a tight fit.

[0105] As understood, it is important that the second contact surfaces 13a, 14a are securely held against the respective first stop surface 11a, 12a for maintaining the desired compression rate and the nominal frequency range of the mass damper unit comprising the damping mass 30 and the resilient elements 51, 52 during operation. In the embodiment shown in FIGS. 1a-c, the end closures 13, 14 are axially held in position by the aid of the coolant tube 40. At the first end of the mass damper, the coolant tube 40 exhibits an externally threaded portion 41 which extends axially out beyond the first end closure 13. The second end of the coolant tube 40 also exhibits an externally threaded portion 42 which is threadedly engaged with an internal thread of the second end closure's 14 bore 16.

[0106] The first 13 and second 14 end closures are held in position and pressed against the first stop surfaces 11a, 12a by an internally threaded securing nut 60 which is threaded engaged with the threaded portion 41 and the nut is secured by screwing until the second contact surfaces of the first 13 and second 14 end closures make contact with their corresponding first contact surfaces 11a, 12a.

[0107] In the exemplifying embodiment, there are two end closures in the mass damper device. In another embodiment, the mass damper device can have a number of end closures other than two. For example, one of the end closures and the housing 10 can be formed as a single component, and there will be only one end closure component to assemble in the assembly process. As an example, the housing 10 and one end closure can be extruded, rolling formed or casted as a single component.

[0108] For preventing dust and other contaminations from entering into the housing 10, a seal 61 in the form of a rubber o-ring 61 is arranged on the coolant tube 60, between the first end closure 13 and an internal recess in the nut 60.

[0109] For the same purpose rubber o-rings 62 are also arranged between the end closures 13 and the housing. These o-rings 62 are received in outer circumferential grooves in the first 13 and second 14 end closure and arranged in sealing contact with inner surfaces of the housing 10.

[0110] Although the disclosed embodiments have only the described components, the embodiments can be extended by adding additional components. For example, a plastic disc (example thickness of 1 mm) having an outer diameter close to the outer diameter of the mass 30, and an inner diameter close to the outer diameter of the coolant tube 40, can be disposed between the resilient element 51 or 52 and their respective end closures 13 or 14. By adding such intermediate plastic discs, it is easier to assemble the parts together and the plastic discs can also function as thermal barriers to protect the resilient elements 51 and 52 from heat in the operational environment. The intermediate plastic discs can also be replaced by parts made of other type of materials and having other dimensions and/or geometries.

[0111] FIGS. 2a and 2b illustrate an embodiment where the mounting surfaces are arranged as contact surfaces in an alternative manner. Here the first contact surfaces 111a, 112a coincide with the end planes of the housing. Corresponding second contact surfaces 113a, 114a, are arranged on peripheral radially protruding flanges of the end closures 113, 114. Each end closure 113, 114 is inserted into the housing from a respective end until the flanges and the second contact surfaces 113a, 114a come into contact with and are pressed against the respective first contact surface 111a, 112a of the housing.

[0112] FIG. 3 illustrates another embodiment. At this embodiment the housing 210 and the end closures 213, 214 are provided with mounting surfaces formed as contact surfaces 211a, 212a, 213a, 214a as shown in the same manner as the contact surfaces 11a, 12a, 13a, 14a shown in FIGS. 1a-c. This embodiment differs from the previously described mass damper units in that the damping mass 230 exhibits annular recesses 231a, 231b formed in each end surface 231, 232. An annular resilient element 252, 252 is received in each recess 231a, 232a and is compressed to the predetermined compression rate against the inner wall of the respective end closure 213, 214 when the end closures 213, 214 have been mounted to the mounting position and the pairs of contact surfaces 211a, 212a, 213a, 214a are in contact.

[0113] FIG. 4 illustrates a further embodiment where the mounting positions for the end closures 313, 314 are defined by contact surfaces 311a, 312a, 313a, 314a arranged at the housing 310 and the end closures 313, 314. Here, the resilient elements 351, 352 formed as annular elements which are supported by annular, chamfered or beveled edge portions 331a, 32a formed in the end surfaces 331, 332 of the end closures 313, 314. When the end closures 313, 314 have been mounted to the mounting positions, the resilient elements are compressed to the desired compression rate between these edge portions 331a, 332a on the one hand and, on the other hand, the peripheral portions of the end closures' 313, 314 inner walls and end portions of the housings 310 inner wall.

[0114] FIG. 5 illustrates a further alternative embodiment. In this embodiment the mounting surfaces are formed of first 411a, 412a and second 413a, 414a alignment surfaces instead of the contact surfaces as described above. The first alignment surfaces 411a, 412a are formed of the cross sectional end surfaces of the cylindrical housing 410. The second alignment surfaces 413a, 414a are formed of the outer planar end surfaces of the first 413 and second 414 end closure. The length of the housing 410, the length of the damping mass 430, the axial thickness of the resilient elements 451, 452 and the thickness of the end closures 413, 414 are chosen such as to achieve the desired predetermined compression rate of the resilient elements 451, 452 when both end closures has been inserted into the housing 410 at the mounting position where the first alignment surfaces 4111a, 412a are aligned with the respective second alignment surface 413a, 414a. At this embodiment, the resilient elements 451, 452 are fixed to the damping mass 430 by means of adhesion. Such adhesion may be accomplished by an adhesive which is applied between the resilient element on the one hand and the damping mass and the respective end closure on the other hand. Alternatively, the adhesion may be self-adhesion of the materials forming the resilient elements, the damping mass and the end closure. When adhesion is used for fixation of the resilient elements the compression rate may normally be lower than the compression rate required for achieving a secure fixation purely by means of friction. It is also possible to use a combination for friction and adhesion for fixation of the resilient elements.

[0115] In practice, when assembling the mass damping device, the damping mass 430 is inserted into the housing 410 and the first 451 and second 452 resilient elements are place at the respective end of the damping mass 430. Thereafter, the enclosures 412, 414 are inserted into the housing 410 from the respective end. The end closures 413, 414 are inserted until the second alignment surfaces 413a, 414a are aligned with the first alignment surfaces 411a, 412a, i.e. when the end closures 413, 414c are flush with the first 411 and second 412 end surface of the housing 410.

[0116] The end closures 413, 414 may be press fitted into the housing 410. At such occasions the end closures 413, 414 may be pressed into the housing 410 by means of a tool (not shown) which has a pressing surface larger than the cross-sectional area of the end closures 413, 414. When the end closures have been inserted to the degree that the pressing surface makes contact with the end surface of the housing 410 it is ascertained that the first 411a, 412a and the second 413a, 414a alignment surfaces are aligned and that the resilient elements 451, 452 have been compressed to the desired predetermined compression rate.

[0117] At an alternative not shown embodiment the end closures may have external threads and the housings first and second end may be provided with corresponding internal threads. In such cases the end closures may be mounted to the housing by screwing until the outer end surfaces of the end closures are flush with the end surfaces of the housing, i.e. until the first and second alignment surfaces are aligned.

[0118] As understood these embodiments at assembly automatically results in a very precise positioning of the end closures relative to the housing and thereby a correct compression rate, with low tolerances, of the resilient elements which in turn assure secure fixation of the resilient elements. The mass damper device also allows easy assembling and further ascertains that the resilient elements may be automatically tuned for achieving the correct nominal Eigen frequency range of the mass damper device.

[0119] FIGS. 1, 6 and 7, illustrate schematically different means for preventing the damping mass from making contact with the circumferential wall of the housing. At some applications there may be a tendency of the material of resilient elements to creep over time. Under the influence of gravity and/or the vibrational forces acting on the damping mass, such creeping may cause the damping mass to be displaced off-center, which reduces the damping efficiency. Creeping may also result in that the damping mass hits the circumferential wall of the housing. Naturally such contact between the damping mass and the housing is most unwanted since it impairs the vibration damping effect of the mass damper and since it may even lead to damage or failure of the mass damping device. The specific means illustrated in FIGS. 6-8 efficiently prevent such creeping and hinder the damping mass from contacting the interior wall of the housing.

[0120] At the embodiment shown in FIG. 6, the damping mass 530 is provide with a number of recesses 535 which are distributed in the longitudinal and circumferential envelope surface of the damping mass 530. Each recess 535 receives a radially protruding distancing member 536 in the form of a stud shaped elastic material, such as rubber or the like. The distancing members 436 may be press fitted and/or fixed by adhesives in the respective recesses 435.

[0121] It is preferred that the distancing members protrude radially from the damping mass a distance which is smaller than the distance between the damping mass' envelop surface and the inner wall of the housing. By this means the distancing members will not come into contact with the inner wall during normal use without creeping. Such contact would otherwise negatively affect the damping characteristics of the mass damper unit. Typically, the distancing members protrude from the envelope surface of the damping mass a distance which is equal to or less than half of the radial distance between the damping mass and the inner wall of the housing. Thus, in case creeping occurs in the resilient element (not shown in FIG. 6) the distancing member will make contact with the interior wall of the housing, thereby supporting the damping mass 530 and preventing further creeping. For avoiding the just above described problem, the distancing members are preferably made of a material having low stiffness such that in cases where the distancing members 535, during operational vibration, make contact with the interior wall, the Eigen frequency of the damping mass will not be influenced to any significant degree.

[0122] At the embodiment shown in FIG. 1, the damping mass is also provided with corresponding means for preventing creeping and hinder the damping mass 30 from making contact with the housing 10. At this embodiment these means comprise a ring 35 of a low stiffness material, such as rubber. The ring 35 is received in a circumferential groove 34 arranged in the envelope surface of the damping mass 30, and arranged such that it protrudes into the gap formed between the damping mass 30 and the cylindrical inner wall of the housing 10.

[0123] At a further not shown embodiment the damping mass may be provided with several such grooves and rings distributed one after the other in the longitudinal direction of the damping mass.

[0124] FIG. 7 schematically illustrates another means for preventing creeping of the resilient elements and hindering contact between the damping mass and the housing. Here the distancing member 635 comprise an annular base 635a which is received in a circumferential grove 634 formed in the envelope surface of the damping mass 630. A plurality of comparatively thin and elongate pin members 635b extend radially outwards from the base 635a. The pin members 635b are formed of a material which, in combination with their elongate shape may sustain axial forces up to a certain threshold. When the axial force exceeds the threshold the pin members 635b collapse by bending or buckling. In the shown example the base 635a and the pin members 635b are made of nylon bristles. However other suitable materials are thermal plastic, metallic wires, fibers and etc. If creeping occurs in the resilient elements (not shown in FIG. 7) the free end of the pin member 635b will contact the interior wall of the housing (not shown in FIG. 7). The initial comparatively high stiffness of the pin member will prevent further creeping of the resilient elements. However, during operational vibration of the damping mass 530 the axial force threshold will be exceeded and the pin member will collapse such that its stiffness is reduced considerably. Thereby the pin members 635b will not, during operational vibration, influence the Eigen frequency of the damping mass to any significant degree.

[0125] FIGS. 8a-c illustrates yet another means for preventing creeping of the resilient elements and for hindering the damping mass from contacting the housing. At this embodiment, the end closure 713 exhibits two through holes 713b and the corresponding end surface 731 of the damping mass 730 exhibits two corresponding axial bores 734. A distancing member in the form of a flexible pin 735 is inserted through and fixed in each through hole 713b. The flexible pins 735 extend through a respective through hole in the resilient element 751 and into the each bore 734.

[0126] In case of creeping of the resilient elements 751, the flexible pin 735 will bend but still, by engaging the walls of the bore 734, prevent the damping mass 730 from being displaced radially in the housing. Thereby creeping of the resilient element is limited and the damping mass 730 is, during operational vibration prevented from contacting the interior wall of the housing (not shown in FIGS. 8a-c). As an example, the pin 735 is made of Teflon materials, silicon rubbers, fluOro rubber and other materials that have a low creep profile and low elastic modulus.

[0127] FIG. 9a-c illustrate how the mass damping device shown in FIG. 1 has been implemented in a conventional and standardized tool holder 80. The tool holder 80 comprises cylindrical stem 81 and a head 82 where a cutting tool 83 is removably mounted. A cylindrical interior cavity 84 extends from approximately the mid portion of the stem 81 to the head 82 and is accessible from the end of the stem when the head 82 has been removed. As best seen in FIG. 8b the interior cavity 84 has a central extension 85 with reduced diameter which extends from the bottom of the interior cavity in the direction away from the head 82.

[0128] Although the embodiment shown in FIG. 9a-9c has the mass damping device inserted in a tool holder cavity 84, the mass damping device can also be connecting to the tool holder via other means. For example, the mass damping device can connect to a tool holder via glue, threads, welded or brazed onto the tool holder. As an example, the mass damping device can have two ends, whereas one end is connected to the tool body and the other end is connected to the cutter head, instead of inserted into a tool holder cavity. In those cases, the mass damping device is affecting the overall stiffness of the cutter head by functioning as an important element on the stiffness chain.

[0129] The mass damping device shown in FIG. 1 is received in the cavity 84 with a circumferential play of approx. 1 mm between the interior wall of the cavity and the outer cylindrical wall of the housing 10 and the securing nut 60 is received in the cavity extension 85. The securing nut 60 is received in the extension 85 with a tight fit, such that the mass damping device is positioned centered with respect to the longitudinal center line of the stem 81. The mass damping device is further suspended in the cavity 84 by means of a first 86 and a second 87 O-rings. The first O-ring 86 is clamped between a chamfered mouth of the extension 85 into the cavity 84 on the one hand and outer surfaces of the first end closure 13 and the securing nut on the other hand. The second O-ring 87 is compressed between the outer wall of the second end closure 14 and an inner wall of the removable head 82. Central fixation of the mass damping device is thus achieved by first inserting the mass damping device in the cavity 84 and thereafter mounting the head 82 to the stem 81 of the tool holder.

[0130] As understood, the use of a pre-assembled mass damping module, which has already been tuned to the correct nominal frequency range and which may easily be mounted to a standardized tool holder greatly facilitates the process of preventing vibrations at any machine tool.

[0131] At the example shown in FIGS. 9a-c, the radial play between the housing 10 and the interior wall of the tool holder's cavity 84 as well as the O-rings 86, 87 forms a thermal insulations which reduces the heat transmission from the tool 83 to the mass damping device, thereby reducing the risk of the resilient elements 51, 52 to be heated such that their stiffness and thereby the frequency range of the mass damping device is influenced. At the shown example, the gap between the housing 10 and the interior wall of the cavity 84 is filled with air. However, in other not shown embodiments this gap may be filled with other heat insulating materials, such as rubber or other polymer materials. In a further not shown example the housing may be received in the cavity by a tight fit or by press fitting. In such cases the housing may or may not be coated by a thermally insulating coating.

[0132] FIG. 10 is a diagram illustrating the relationship between compression rate or ratio of resilient elements (nominal dimension before compression t1 and after compression t2), nominal stiffness of resilient elements and a mass dampers' damping efficiency. In the diagram, the damping efficiency of the mass damping device according to the invention (using dimension-controlled compression of resilient elements), is compared with previously known mass damping devices (using torque controlled compression of resilient elements).

[0133] The diagram shows the nominal stiffness of the resilient elements in mass damping devices and the efficiency of the mass damper device as a function of the compression rate of the resilient element. In an example where the optimal compression rate of the resilient elements (thickness 0.7 mm) is 30%, the optimized thickness t2 of the resilient elements after compression is 0.49 mm. Using torque-controlled compression rate, the torque wrench has an error range of ±20%, and the resilient elements after compression may have a thickness between 0.35 mm and 0.63 mm (compression ratio between 50% and 90%). Using dimension-controlled compression rate according to the invention instead, the fine finished components will allow a dimension error range of ±100 μm in assembly (over a linear length of 70 mm), and the dimension error is divided by two when there are two resilient elements compressed. Thus, the dimension error range for each of the two resilient elements is ±50 μm, and the compression ratio of the resilient elements is between 63% and 77% (t2 range between 0.45 mm and 0.54 mm), which is narrower and the mass damper's damping efficiency is kept close to the optimum situation.

[0134] With the damping mass device according to the present disclosure it has proven that the device may be applied not only to working tool holders but also directly to the working tool. At some applications this constitutes an important advantage since the mass damper device is then positioned closer to the area where the vibrations to be damped are generated.

[0135] In FIGS. 11a-12b it is illustrated how a damping mass device according to the present disclosure may be applied to such a working tool.

[0136] FIG. 11a shows a working tool holder 901 having a first end provided with an end piece 902 which is arranged to be fixed to a rotatable support such as a spindle (not shown), An elongate and tapering main body 903 extends axially from the end piece 902. The main body 903 exhibits, at its free end which is opposite to the end piece 902, a working tool fixation opening 904 for fixedly receiving a working tool 905. In the shown example the working tool constitutes a milling tool. As best seen in FIG. 11b the working tool comprises a mounting portion or shank 906 which, in use, is fixedly received in the fixation opening 904. The working tool further comprises a tool portion 907 which exhibits a number of spiral teeth and intermediate flutes.

[0137] In the shown example the working tool 905 is formed of a carbide material such as tungsten carbide and titanium carbide. Other suitable materials are high speed steel and ceramics.

[0138] In FIG. 12a it is illustrated how a mass damper device is applied directly to the working tool 905, As best seen in FIG. 12b the damping mass device according to this embodiment is similar to the damping mas device shown in FIGS. 1a-c. It comprises a cylindrical tubular housing 910 with a first 911 and a second 912 longitudinal end. A first contact surface 911a, 912a is arranged in proximity to each longitudinal end. A first end closure 913 is inserted into the first end such that a second contact surface 913a of the first end closure comes into contact with the first contact surface 911a at the first longitudinal end 911. Correspondingly, a second end closure 914 is inserted into the second end 912 such that a second contact surface 914a of the first end closure 914 comes into contact with the first contact surface 912a at the first longitudinal end 912.

[0139] The mass damper device further comprises a damping mass 930 which is received in the housing 910 and arranged between the end closures 912, 913. The damping mass 930 is formed generally as annular cylindrical body having a constant cross section with an outer diameter and an inner bore 933. The damping mass 30 exhibits a first longitudinal end 931 and a second longitudinal end 932. In the shown example, the damping mass 930 exhibits an outer circumferential outer grove 934 which is arranged centrally between the first 931 and second 932 longitudinal ends and which receives a distancing member 935.

[0140] A coolant media tube 940 extends with a radial clearance through the central bore 933 and is received in central through openings 915, 916 in the first 913 and second 914 end closures respectively.

[0141] The mass damper further comprises a first 951 and a second 952 resilient element. The resilient elements 951, 952 are arranged for holding the damping mass 30 in the housing 10. So far, the embodiment shown in FIG. 12b fully corresponds to the mass damper device shown in FIGS. 1a-c.

[0142] The mass damper device shown in FIG. 12b however differ from the previous embodiments in that it comprises a first heat insulating disk 961 which is arranged between the first end closure 913 and the first resilient element 951. Correspondingly a second heat insulating disk 962 is arranged between the second end closure 915 and the second resilient element 952. In the shown embodiment, the heat insulating plates are circular having a diameter which is essentially equal to the outer diameter of the damping mass 930. However, the geometry and dimension of the heat insulating disk may be different such that they may have e.g. a polygonal cross section. In the shown example, the heat insulating disks 961, 962 are made of PC polycarbonate. Alternatively, the heat insulating disks can be made of steel or aluminum, with or without surface coatings.

[0143] Hence, at this embodiment the first resilient element 951 is clamped between the inside of the first heat insulating disk 961 and the end surface of the damping mass' first end 931. The second resilient element 952 is correspondingly clamped between the inside of the second heat insulating disk 962 and the end surface of the damping mass' second end 914.

[0144] As in the mass damper device shown in FIGS. 1a-c, the first contact surfaces 911a, 912a and the second contact surfaces 913a, 914a are arranged such that the first 951 and second 952 resilient elements are compressed to the predetermined compression rate, via the heat insulating plates 961, 962 when the end closures 613, 914 have been inserted to the respective longitudinal mounting position, where the second contact surfaces 913a, 914a make contact with the first contact surfaces 911a, 912a.

[0145] Just as in the previous embodiments, the resilient elements 951, 952 are constituted of a material having a frequency dependent stiffness.

[0146] The damping mass device shown in FIG. 12b thus forms an integral modular unit which may readily be inserted into and extracted from a working tool or a working toll holder.

[0147] FIG. 12a illustrates how the damping mass device shown in FIG. 12b has been inserted into and fixed in the working tool 905. The working tool 905 exhibits a cavity or bore 908 which extends from the free end of the shank 906 centrally in the axial direction towards the tool portion 907 of the working tool 905a. The bore 908 exhibits a cylindrical portion 908a arranged proximal to the free end of the shank 906 and is open at the free end of the shank 906. At the end of the bore 908 arranged proximal to the tool portion 907 the inner diameter tapers towards the tool portion 907 such that the bore exhibits a bottom portion 908b where the transition between the bottom surface arranged in a radial plane and the cylindrical wall of the bore 908 is rounded. This rounded bottom portion 908b reduces stress concentrations in the working tool when in use. The inner diameter of the cylindrical portion 908a is essentially equal to the outer diameter of the mass damper devices housing 910. Additionally, the axial length of the cylindrical portion 908a is essentially equal to or somewhat longer than the axial length of housing 910.

[0148] The mass damper device may thus readily be inserted into the cylindrical portion 908a of the bore 908 and securely fixed therein by press fitting. When an already inserted mass damper device is to be exchanged in the working tool 905, it suffices to detach the working tool 905 from the working tool holder 901, extract the old mass damper device from the bore 908, insert a new mass damper device into the bore 908 ant reattach the working tool 905 to the working tool holder 901.

[0149] The mass damper device may alternatively be fixed in the bore 908 by other means than press fitting. Examples of such other means are by adhesives, threads, shrink fit (cooling down or heating up) and external means of fixing, such as by a plug inserted into the bore externally of the mass damper device.

[0150] Above exemplifying embodiments of the invention have been described. The invention is however not limited to these examples but may be varied within scope of the appended claims. For example, the different means for preventing creeping of the resilient elements and contact between the damping mass and the housing may freely be combined with the different arrangements of the mounting surfaces described above.