Abstract:
With high speed machine tools, there is a desire to dampen vibrations and to retain the damper mass in proper position. The present invention relates to a tuned damped absorber support providing simultaneous energy dissipation in both horizontal and vertical directions which also provides for proper mass position retention. The tuned damped absorber assembly is attached directly or indirectly to a machine component requiring damping. Both single damper mass and double damper mass configurations are shown. With a double damper mass, the system can be tuned to two different frequencies. Therefore, the double damper mass provides for optimization in both a vertical and a horizontal direction.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field of the Invention 
     With high speed machine tools, there is a desire to damp vibrations resulting from, for example, acceleration and deceleration of machine components along the machine&#39;s axes of motion or from chatter vibrations inherent in the cutting process. One known method of damping such vibrations includes attaching a damper mass assembly to the machine component to be damped, and tuning the frequency of the response of the damper so that it is close to the frequency of the unwanted vibration of the machine component. 
     In some cases, it is desired to provide damper tuning on the component at more than one vibration frequency, or in more than one principal direction. In such cases, there is a desire to retain the attached damper mass in proper position and to provide flexibility in the damper&#39;s ability to act in the proper direction(s). The present invention relates to a tuned damped absorber support providing simultaneous energy dissipation in both horizontal and vertical directions which also provides for proper mass position retention. 
     2. Brief Description of the Related Art 
     Prior art vibration damping systems that are used to address more than one vibration frequency or more than one principal direction have generally utilized either multiple damper mass assemblies applied independently or damping elements applied in preselected, fixed orientations on a single damper mass to act in both shear and compression. Rods are found in the prior art to hang a damping mass that is required to have a vertical shear plane. This rod hanging application freely allows damping action in the horizontal direction along the shear plane, but renders any damping action in the vertical direction ineffective. 
     The following U.S. patent references are cited: U.S. Pat. No. 5,871,315, Burt et al., issued Feb. 16, 1999, for a tombstone fixture; U.S. Pat. No. 5,058,261, Kitamura, issued Oct. 22, 1991, for a machine tool; U.S. Pat. No. 5,033,340, Siefring, issued Jul. 23, 1991, for an apparatus and method for tool vibration damping; U.S. Pat. No. 4,921,378, Kytola, issued May 1, 1990, for a rotary-pallet system; U.S. Pat. No. 4,669,227, Treppner, issued Jun. 2, 1987, for an angle plate apparatus with precisely adjustable workpiece holder; U.S. Pat. No. 4,630,811, Rudisill, issued Dec. 23, 1986, for a model fixturing apparatus; U.S. Pat. No. 4,512,068, Piotrowski, issued Apr. 23, 1985, for a pallet receiver with compliant pin and socket registration; U.S. Pat. No. 4,468,019, Staudenmaier, issued Aug. 28, 1984, for a pallet clamping system for machine tools; U.S. Pat. No. 4,438,599, Kamman et al., issued Mar. 27, 1984, for a vibration damper for machine-carried workpiece; U.S. Pat. No. 3,790,153, Seidenfaden, issued Feb. 5, 1974, for equipment for holding workpieces; U.S. Pat. No. 3,522,864, Richter, issued Aug. 4, 1970, for a tuned damper assembly for machine tools; U.S. Pat. No. 3,447,402, Ray, issued Jun. 3, 1969, for a damped tuned boring bar; and, U.S. Pat. No. 2,714,823, Dall et al., issued Aug. 9, 1955, for a vibration damper. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a tuned damped absorber support assembly for machine tools providing simultaneous energy dissipation in at least two directions of motion to attenuate vibrations of the machine tool resulting from machine operation. The tuned damped absorber assembly of the present invention, oftentimes referred-to herein as an “attachment assembly”, is attached directly or indirectly to a machine component requiring damping. Both single damper mass and double damper mass configurations are shown. With a double damper mass, the system can easily be tuned to two different frequencies by independent adjustment of the damping elements. The single damper mass is typically applied for tuning of a single frequency, but could also be tuned for two different frequencies by providing a support rod with non-symmetric cross section. 
     Even more particularly, the preferred embodiment of the present invention is an attachment assembly to be attached to a machine component to accomplish energy dissipation simultaneously in both a horizontal direction and a vertical direction, where the attachment assembly comprises a damper mass having a rod bore therethrough from a bushing face to a component face, the rod bore having a threaded bushing receiving portion extending from the bushing face toward the component face and a rod receiving portion extending from the component face toward the bushing face; the damper mass having at least one preload bore therethrough from the bushing face to the component face; at least one damping element preload assembly including a cap screw having a threaded end, a spring retainer, a preload spring, and a damping element, the cap screw having the spring retainer and the preload spring inserted thereon, the cap screw received by the at least one preload bore with the threaded end extending therefrom on the component face, the cap screw having the damping element inserted thereover to abut the component/plate face; a bushing having a throughbore and a threaded outer portion; a rod having a threaded component end and an opposed lock nut end, the lock nut end having a threaded portion and an adjacent bushing receiving shaft portion, the bushing receiving shaft portion having an adjacent enlarged bushing stop portion toward the component end; the rod received by the rod bore in the damper, the component end of the rod bore extending therefrom on the component face, the bushing received over the lock nut end of the rod to abut the enlarged bushing stop portion with the bushing threaded outer portion threadably received by the threaded bushing receiving portion of the rod bore. This assembly can be attached directly or indirectly to the machine component. 
     According to one aspect of the present invention, an attachment assembly for dissipating energy of a moving machine component is provided, wherein the attachment assembly dissipates energy of the moving machine member in at least two directions of motion. 
     According to another aspect of the present invention, an attachment assembly for attenuating vibrations of a machine component is provided, comprising means for dissipating energy of the machine component in at least two directions. 
     According to yet another aspect of the present invention, an attachment assembly for dissipating energy of a moving machine component is provided, comprising at least one damper mass, at least one first preload assembly, each of the first preload assemblies having a first end coupled to the damper mass by a biasing element and a second end coupled to the machine component, at least one rod for mounting the at least one damper mass to the machine component and for applying a preload to the at least one first preload assembly, and at least one first damping element. 
     According to one embodiment of the present invention, an attachment assembly for dissipating energy of a moving machine component is provided, comprising at least a first damper mass and at least a second damper mass. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A better understanding of the present invention will be had upon reference to the following description in conjunction with the accompanying drawings in which like numerals refer to like parts, and wherein: 
     FIG. 1 shows the preferred embodiment, a representation of a damper mass connected to a machine component using an intermediate damper mounting plate; 
     FIG. 2 shows a cross-section view of the preferred embodiment of FIG. 1 along the section line  2 — 2 ; 
     FIG. 3 shows a side view of the rod of the preferred embodiment; 
     FIG. 4 shows an end view of the rod of FIG. 3 along the lines  4 — 4  of FIG. 3; 
     FIG. 5 shows a side view of the bushing of the preferred embodiment; 
     FIG. 6 shows a representation of the various bores and openings in the damper mounting plate; 
     FIG. 7 shows a side view of the damper mounting plate of the mass face; 
     FIG. 8 shows representation of the various bores and openings in the damper mass; 
     FIG. 9 shows a side view of the damper mass of the bushing face; 
     FIG. 10 shows the first alternative embodiment, a representation of a dual damper mass connected to a machine component using an intermediate damper mounting plate; 
     FIG. 11 shows a cross-section view of the first alternative embodiment of FIG. 10 along the section line  11 — 11 ; 
     FIG. 12 shows the second alternative embodiment, a representation of a damper mass connected to a machine component using a pair of flexure plates; 
     FIG. 13 shows a cross-section view of the second alternative embodiment of FIG. 12 along the section line  13 — 13 ; and, 
     FIG. 14 shows a cross-section view of a rod having an asymmetrical cross-section which may be used in any of the embodiments hereof. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiment is shown in FIGS. 1-9, a first alternative embodiment is shown in FIGS. 10-11, and a second alternative embodiment is shown in FIGS. 12-13. The following list provides a cross-reference of the reference numerals used in FIGS. 1-13 to represent exemplary components of the several embodiments of the instant invention. 
       1  machine component 
       6  viscoelastic damping element 
       7  preload spring 
       8  spring retainer 
       9  cap screw 
       20  damper mounting plate 
       22  component mounting bores 
       24  countersunk head opening 
       26  thread opening 
       28  preload threaded bore 
       30  damping element receptacle 
       32  threaded rod bore 
       34  component face 
       36  mass face 
       40  damper mass 
       42  preload countersunk bore 
       43  spring seat 
       44  spring receiving portion 
       46  retainer bore 
       47  damping element groove 
       48  rod bore 
       50  bushing receiving portion 
       52  rod receiving portion 
       54  bushing face 
       56  component face (depending on whether damper mass attaches to plate  20  or component  1 ) 
       58  lock nut 
       60  rod 
       62  component end 
       64  lock nut end 
       66  enlarged bushing stop portion 
       68  bushing receiving shaft portion 
       70  bushing 
       72  through bore 
       74  threaded portion 
       140  damper mass 
       142  rod bore 
       150  damper mass 
       160  threaded rod 
       162  rod nut 
       170  flexure plate 
       172  bolt 
       180  flexure plate 
       182  bolt 
     With reference to FIGS. 1-9, the preferred embodiment of the instant invention is shown. FIGS. 1 and 2 show a general representation, while FIGS. 3,  5 ,  7 , and  9  provide relative detail for one example, respectively showing rod  60 , bushing  70 , damper mounting plate  20 , and damper mass  40 . FIGS. 4,  6 , and  8  provide additional views. The specific measurements provided with respect to FIGS. 3,  5 ,  7 , and  9  are not limitations, but are given to explain how the related components may be sized so that those skilled in the art may resize the various components of the attachment assembly of the instant invention depending on the desired machine component application. 
     With reference to FIGS. 3 and 4, rod  60  is shown having a length of 309 mm. Rod  60  includes a lock nut end  64  and an opposed component end  62 . From right to left, as shown in FIG. 3, rod  60  includes a 32 mm long-20 mm diameter threaded portion, a 13 mm long-28 mm diameter portion, a 165 mm long-20 mm diameter portion, a 13 mm long-28 mm diameter enlarged bushing stop portion  66 , and a bushing receiving shaft portion  68  which includes a 34 mm long-20 mm diameter portion, a 40 mm long-20 mm diameter threaded portion, and a 12 mm long reduced portion. As seen in FIG. 4, this 12 mm long reduced portion at the lock nut end  64  has two flat sides. This permits the use of a wrench when threading component end  62  into its respective receiving threaded bore, for example, threaded rod bore  32  in damper mounting plate  20 , shown in FIG.  7 . 
     FIG. 5 shows the bushing  70 , which is 70 mm in length and includes a 22 mm diameter throughbore  72 . From right to left, as shown in FIG. 5, bushing  70  includes a 51 mm long threaded portion  74 . Once bushing  70  is placed onto the lock nut end  64  of the rod  60 , it abuts the enlarged bushing stop portion  66 . As seen in FIG.  2  and explained in more detail hereinafter, bushing  70  is threaded into damper mass  40  and is used to couple the lock nut end  64  of the rod  60  to the damper mass  40 . As shown in FIG. 5, opposed small bore holes (unnumbered) are provided in bushing  70  toward one side thereof. These holes permit a tool to be inserted thereinto to aid in threading the bushing  70  into damper mass  40 . 
     FIGS. 6 and 7 relate to a damper mounting plate  20 . As will be explained in the discussion of FIGS. 1 and 2, machine component  1  may have the damper mass  40  attached directly to it, if component  1  is of sufficient size, or it may have the damper mass  40  attached to it indirectly by using an intermediate damper mounting plate  20 . FIG. 7 shows a mass face surface  36  of the damper mounting plate  20 . FIG. 6 is a representation showing the relative thickness of the plate  20  so that the depth of the openings or bores therein can be seen in relation thereto. 
     Damper mounting plate  20  is about 38 mm thick. As shown in FIG. 7, damper mounting plate  20  is provided with six component mounting bores  22 , three such component mounting bores  22  shown near the left-hand side of FIG.  7  and three such component mounting bores  22  shown on the right-hand side of FIG.  7 . Each bore  22  includes a countersunk or enlarged head opening  24 , which preferably is about 20 mm in diameter and about 18 mm deep, and a thread opening  26 , which preferably is about 14 mm in diameter and about 20 mm deep. As seen in FIG. 6, each bore  22  passes completely through the mounting plate  20  and connects each head opening  24 , provided in the mass face  36  of the mounting plate  20 , with its respective thread opening  26 , provided in the component face  34 . Appropriate bolts(not shown) will be received by respective threaded bores (not shown) in machine component  1  to attach plate  20  to machine component  1 . Because the head openings  24  are countersunk, the bolt heads situated therein will not interfere with the attachment of the damper mass  40  to the plate  20 , as described in greater detail below. 
     As seen in FIG. 7, four preload threaded bores  28  are provided in the plate  20 . As seen in FIG. 6, each of these bores  28  preferably has a diameter of about 12 mm and is about 32 mm deep and extends into the plate  20  from the mass face  36  towards the component face  34 . A recessed damping element receptacle  30  is provided in the mass face  36  of the plate  20  surrounding each bore  36 . Receptacles  30  are rounded and preferably have a maximum depth of about 4 mm for seating a damping element therein, as will be described in greater detail below. 
     As seen at the top center of FIG. 7, plate  20  preferably includes a 20 mm diameter threaded rod bore  32 , which may be a throughbore. Rod bore  32  will receive the 32 mm long threaded portion of rod  60  at the component end  62  thereof and the adjacent 28 mm diameter portion of rod  60  will then abut mass face  36 . Where rod bore  32  is threaded, the 32 mm long threaded portion of rod  60  may be threaded thereonto; where rod bore  32  is a throughbore, a nut (not shown) or other attachment device may be used to couple the rod bore  32  to the plate  20 . 
     FIGS. 8 and 9 relate to a damper mass  40 . As will be explained in the discussion of FIGS. 1 and 2, machine component  1  may have the damper mass  40  attached directly to it, if component  1  is of sufficient size, or it may have the damper mass  40  attached indirectly to it by using the previously explained intermediate damper mounting plate  20 . FIG. 9 shows a bushing face surface  54  of the damper mass  40 . FIG. 8 is a representation showing the relative thickness of the mass  40  so that the depth of the openings or bores therein can be seen in relation thereto. 
     Damper mass  40  preferably is about 203 mm thick. As shown in FIG. 9, damper mass  40  includes at least one preload bores  42 , and preferably four preload bores  42  including two such preload bores  42  shown near the left-hand side of FIG.  9  and two such preload bores  42  shown near the right-hand side of FIG.  9 . Each bore  42  includes a countersunk or enlarged spring receiving portion  44 , which preferably is about 66 mm in diameter and about 180 mm deep, and a retainer bore portion  46 , which preferably is about 31 mm in diameter. As seen in FIG. 8, spring receiving portion  44  extends inwardly from the bushing face  54  of the damper mass  40  and retainer bore portion  46  extends inwardly from the component face  56  of the damper mass  40  and communicates with the spring receiving portion  44  such that each bore  42  passes completely through the damper mass  40 . A spring seat  43  may be provided in a radial step defined at the junction of the larger spring receiving portion  44  and the smaller retainer bore portion  46  to seat one end of the spring  7  thereon. The seat  43 , if provided, will inhibit radial movement of the spring  7  within the spring receiving portion  44  of the bore  42  and will prevent any portion of the preload assembly from contacting an inner surface of the bore  42 . 
     As seen at the top center of FIG. 9, damper mass  40  includes a rod bore  48  therethrough. With reference to FIG. 8, rod bore  48  includes a threaded bushing receiving portion  50  extending inwardly from the bushing face  54 . Portion  50  preferably is about 39 mm in diameter and about 51 mm deep. Rod bore  48  also includes a rod receiving portion  52  extending inwardly from the component face  56  and communicating with the bushing receiving portion  50  such that bore  48  passes completely through the damper mass  40 . Rod receiving portion  52  preferably is about 36 mm in diameter. 
     As shown in FIGS. 6 and 8, a small threaded hole (unnumbered) may be provided in the top center of both plate  20  and damper mass  40  so that a threaded eye-bolt or hook-like member can be temporarily threaded into either hole and used to help maneuver plate  20  or mass  40  into position on machine component  1 . 
     With these relative dimensions of rod  60  (FIGS.  3  &amp;  4 ), bushing  70  (FIG.  5 ), damper mounting plate  20  (FIGS.  6  &amp;  7 ), and damper mass  40  (FIGS.  8  &amp;  9 ), the connectivity is shown in FIGS. 1 and 2. Damper mounting plate  20  is attached to machine component  1 , as was explained by the use of appropriate bolts received by the six component mounting bores  22  of plate  20  and threaded into appropriately aligned and sized threaded bores in machine component  1 . If the surface of component  1  is of an adequate size, the damper mass  40  may attached directly to the component  1 , rather than indirectly by mounting the damper mass  40  to the mounting plate  20  and thereafter mounting the mounting plate  20  to the machine component  1 . Whether directly or indirectly attached, this damping mass  40  acts to deflect vibrations in both horizontal and vertical directions and to dissipate energy due to machine vibration thereby. 
     At least one, and preferably four, first identical damping element preload assemblies are used in the preferred embodiment. For each, a cap screw  9  passing through a retainer  8  (positioned near a cap end  9   a  of the cap screw  9 , said cap end  9   a  defining a first end of the preload assembly) and having a biasing element such as a spring  7  thereon is inserted into spring receiving portion  44  of one bore  42  provided in damper mass  40 . The spring  7  is stopped at the end of portion  44  adjacent smaller diameter retainer bore  46 . Cap screw  9  passes through bore  46 , exiting mass  40  and passes through a doughnut-shaped viscoelastic damping element  6  placed between mass  40  and plate  20 , element  6  being partway received by damping element receptacle  30 , receptacle  30  being shaped to help retain doughnut-shaped element  6  in proper position. A groove  47  at least partway encircles each retainer bore  46  in the component face  56  of the damper mass  40  and is sized and dimensioned to cooperate with corresponding receptacles  30  in the plate  20  so as to sandwich damping element  6  therebetween to prevent the damping element  6  from shifting out of position. A threaded end  9   b  of cap screw  9  opposite the cap end defines a second end of the preload assembly and is received by a preload threaded bore  28  in the mounting plate  20 . 
     Damping element preload assembly combinations consisting of element  6 , spring  7 , retainer  8 , and cap screw  9 , are typical, and are used typically to attach a mass atop a component so that the weight of the mass rests atop elements  6 . That is, in conventional uses, a preload assembly is mounted typically in a vertical orientation whereby a mass attached thereto urges the preload assembly under the influence of gravity against the bias of the spring  7 , either in compression (such as where the preload assembly is positioned vertically below the mass) or in tension such as where the preload assembly is positioned vertically above the mass. However, in the instant invention, the mass  40  is mounted to the side of plate  20  or machine component  1 . That is, a preload assembly of the present invention is mounted in a horizontal orientation. Employing only the multiple damping element preload assembly combinations of element  6 , spring  7 , retainer  8 , and cap screw  9 , for such a “side-hanging” orientation of the mass  40  would not adequately permit mass  40  to operate effectively. 
     Therefore at first rod  60  and bushing  70  are provided to support mass  40  and to be attached thereto at the bushing face  54  of mass  40 . Rod  60  is dimensioned to provide flexibility along both a horizontal axis (“H” in FIG. 1) and along a vertical axis (“V” in FIG. 1) and to have the same order of magnitude as the damping elements  6 . Referring for the moment to FIG. 14, rod  60  may be dimensioned with a non-symmetric cross-section to provide different stiffnesses along different axes. For example, the cross-section of the rod  60  may be elliptical whereby a major axis of the ellipse along a first direction or axis “D 1 ” provides a greater stiffness than a minor axis thereof along a second direction or axis “D 2 ”. Axes “D 1 ” and “D 2 ” may or may not be orthogonal. Alternatively, different stiffnesses of a symmetric rod  60  may be provided such as through the judicious selection of an anisotropic material. This would allow the damper assembly to be tuned for slightly different frequencies by influence of the different stiffness of the rod for example in the horizontal and vertical directions. Bushing  70  provides moment stiffness to the lock nut end  64  of the rod  60 , permitting “S-shape” motion of the rod  60  along most of its length, rather than pure bending, thereby reducing lateral stress. 
     With the four damping element preload assemblies (comprising element  6 , spring  7 , retainer  8 , and cap screw  9 ) being installed to attach mass  40  to the plate  20 , the rod  60  can be passed through the rod bore  48  of the mass  40  and have the threaded portion at the component end  62  thereof threaded into plate  20  threaded rod bore  32 ; for example, by using a wrench on the opposed flat sides of the smaller 12 mm portion of rod  60  at its lock nut end  64  (see, FIGS.  3  &amp;  4 ). Then, bushing  70  is placed over lock nut end  64  of rod  60  and threaded portion  74  of bushing  70  is threaded into threaded bushing receiving portion  50  of rod bore  48  of mass  40 ; for example, by inserting a tool through two of the small bores seen on the left side of bushing  70  in FIG.  5  and turning the tool. This allows preloading with the springs  7  first so that subsequent positioning of the bushing  70  in the correct location does not detract from the springs  7  applied preload. Bushing  70  is threaded further so that it passes over bushing receiving shaft portion  68  of rod  60  to engage or abut enlarged bushing stop portion  66  of rod  60 . Then, lock nut  58  can be threaded onto lock nut end  64  of rod  60 . 
     It is noted that the rod  60  preferably has a much.higher axial stiffness than radial or lateral stiffness. This prevents the mass  40  from rocking off the damper elements  6  during high acceleration or deceleration moves of the machine component  1 . 
     A first alternative embodiment is shown in FIGS. 10 and 11. In this embodiment a first damper mass  150  and a second damper mass  140  are employed with machine component  1 . Second damping element preload assemblies, identical in construction to first damping element preload assemblies described above and particularly comprising element  6 , spring  7 , retainer  8 , and cap screw  9 , are used to attach first damper mass  150  to the second damper mass  140 . Second damper mass  140  is attached to the machine component  1  and at least one second damping element  6  is positioned between the first damper mass  150  and the second damper mass  140 . A mounting plate  120  is attached to machine component  1  using bolts  122 . A rod  160  with a threaded end passes vertically downwardly through plate  120  and through a rod bore  142  of the second mass  140 . A rod nut  162  is threaded onto the threaded end of rod  160  to suspend the second mass  140  and to adjust the positioning of the first damping element preload assemblies between the second mass  140  and the machine component  1 . This mass  140  arrangement closest to the machine component  1  allows damping of horizontal motion, but not vertical motion to any significant degree. The second mass  140  is attached to the machine component  1 , as above, using first damping element preload assemblies, again comprising element  6 , spring  7 , retainer  8 , and cap screw  9 , and a pair of flexure plates  170 . Plates  170  are attached to the top and bottom of masses  140  and  150  using bolts  172 . Plates  170  are dimensioned to permit vertical motion by plate flexing. The plate  170  width is sized to prevent horizontal motion, thus adding to the effective mass in the horizontal plane. The first mass  150  and plates  170  are tuned specifically to damp vertical modes of vibration, while the sum of masses  140  and  150  are tuned to damp horizontal modes of vibration. 
     A second alternative embodiment is shown in FIGS. 12 and 13. Here, masses  140  and  150  are attached and flexure plates  170  are employed as with the first alternative embodiment shown in FIGS. 10 and 11. However, mounting plate  120  and rod  160  are not used to attach mass  140  to machine component  1 . Instead, a pair of flexure plates  180  are attached on the sides of mass  140  and machine component  1  using bolts  182 . As with the first alternative embodiment of FIGS. 10 and 11, top and bottom attached flexure plates  170  of FIGS. 12 and 13 are dimensioned to permit vertical motion by plate flexing, with the plate  170  width being sized to prevent horizontal motion. In contrast, side attached flexure plates  180  are dimensioned to permit horizontal motion by plate flexing, with the plate  180  width being sized to prevent vertical motion. 
     The preferred embodiment of FIGS. 1-9, the first alternative embodiment of FIGS. 10-11, and the second alternative embodiment of FIGS. 12-13, are all drawn to a vibration damper which provides means for damping in two separate axes of motion. The embodiments employ either a single mass  40  or dual masses  140 ,  150  and all employ damping element preload assemblies comprising element  6 , spring  7 , retainer  8 , and cap screw  9 , to directly or indirectly attach the respective mass  40  or  140  to the machine component  1  and to dissipate energy thereby. With FIGS. 1-9, the single mass  40  is attached to the side of machine component  1  indirectly employing a damper mounting plate  20 . With the embodiment of FIGS. 10-11, the mass  140  is attached directly to the side of machine component  1  using damping element preload assemblies comprising element  6 , spring  7 , retainer  8 , and cap screw  9 , with an additional vertical threaded rod  160  passing downward through a horizontal plate  120  and a bore  142  in mass  140  to support mass  140  and to assist in retaining it in proper alignment with machine component  1 . With the embodiment of FIGS. 12-13, the mass  140  is attached directly to the side of machine component  1  using damping element preload assemblies comprising element  6 , spring  7 , retainer  8 , and cap screw  9 , with a pair of side flexure plates  180  attaching the sides of mass  140  and machine component  1 . In both embodiments of FIGS. 10-11 and  12 - 13 , mass  140  and mass  150  are attached using damping element preload assemblies comprising element  6 , spring  7 , retainer  8 , and cap screw  9 , with a pair of top and bottom flexure plates  170  attached to both the top and bottom of masses  140  and  150 . 
     The foregoing detailed description is given primarily for clearness of understanding and no unnecessary limitations are to be understood therefrom for modifications can be made by those skilled in the art upon reading this disclosure and may be made without departing from the spirit of the invention and scope of the appended claims.