EP0680399B1 - Vibration isolator for hand-held vibrating devices - Google Patents

Description

Cross-Reference to Related Applications
• The present application is a continuation-in-part of application Serial No.08/009,695 filed by James T. Gwinn on January 27, 1993, and owned by theassignee of the present invention.
Field of the Invention
• This invention relates to the area of vibration isolators. Specifically,the invention relates to the area of elastomer-containing vibration isolatorsfor isolation of a user from mechanical vibrations of hand-held vibratingdevices.
Background of the Invention
• One of the problems facing users of hand-held vibrating equipmentis exposure to elevated mechanical vibration levels. Long term exposurehas produced symptoms of vascular, nervous system and bone/muscledeterioration such as hand-arm vibration syndrome and white hand.Many have attempted to solve the problem of excessive vibration transmittedto the users of hand-held tools by incorporating elastomer elements betweenthe user and the vibrating device. Approaches have attempted to isolateand/or damp the mechanical vibration of the device.
• One such isolating approach is taught in US Patent 3,968,843 toShotwell, which is hereby incorporated by reference, and provides apneumatic air hammer with a shock and vibration-absorbing insert orcushion member 30 between the body of thetool 10 and thehandle 19. Theisolator used is a plain compression-type sandwich isolator. Its theory ofoperation is to place a soft spring between the user and the vibrating device,thus isolating the user from mechanical vibration. However, compression-typeisolators have one serious drawback. They experience an inherentstiffening effect when the operator exerts an increased force on the tool.This is due to the inherent strain sensitivity of elastomer in compression.Because of this, as the force increases, the level of vibration felt by the user is worsened. In other words, the harder the operator pushes the moreineffective the isolator becomes.
• In addition, in order to maintain control of the tool, the cocking andtorsional motions of the tool must be restrained. US Patent 2,500,036 toHorvath uses dual resilient members 80 and 81 to allow limited axialmovement and restrain cocking. It also uses a plurality of lockingsegments 85 to restrain torsional rotation of the handle member 13 relativeto thebarrel 10.
• In US Patent 5,054,562 to Honsa et al., an isolator which was toprovide axial vibration isolation as well as cocking/torsional control bysurrounding the workingcup 20 with laminar layers of elastomer isdescribed. Although this makes for a convenient package, this has thesame inherent problem of compression strain stiffening as the Shotwell'843 approach.
• As taught in US Patent 4,401,167 to Sekizawa et al., others haveattempted to place the elastomer elements 6a and 6b between thetool body 1and the handle 2. Although placing the elastomer in shear substantiallyeliminates the strain stiffening effects, it cannot provide low enoughstiffness for optimum control and still maintain control of the tool.
• Further attempts to improve the vibration isolation characteristicsof hand-held tools have included the addition of fluid damping to theisolator. By adding damping, over and above what is available from anelastomeric device alone, the vibrations emanating from the tool can befurther reduced. US Patent 4,667,749 to Keller, which is herebyincorporated by reference, describes such an isolator which adds fluiddamping to an isolator and which is suitable for mounting a handle to avibrating tool body.
• Further, US Patent 4,236,607 to Hawles et al. describes a vibrationsuppression system wherein the fluid passes through the inner member ofthe mounting to provide amplified counter inertial forces. The commonlyassigned US Patent 4,969,632 issued to Hodgson et al. and US Patent4,733,758 issued to Duclos et al., which are both hereby incorporated byreference, describe other tunable mountings.
• EP-A-2046212 describes an anti-vibration device fora power operated hand tool and includes an anti-vibrationelement between the handle and the tool. The deviceincludes a collapsible element for absorbing vibration.
• EP-A-6020734 describes a similar device wherein thecollapsible section includes outer and inner sleeves, theouter sleeve being flexible to absorb vibration.
• US-A-3072955 reveals a hand grip for use with toolsand the like which comprises an internally splined splitelastomeric cylinder. The grip is designed to protectthe user's hand from heat or friction.
Summary of the Invention
• The present invention has been designed to providean improved vibration isolator for reducing themechanical vibration level transmitted to the user inorder to overcome the features and shortcomings of theavailable mountings for vibrating hand-held devices andtools and consists in an isolator as defined inClaim 1.
• More particularly, the present invention provides anisolator for use in a hand-held vibrating device whichexhivits a spring rate characteristic for the mountingwhich softens by about a factor in the range of 2 to 20with increased application of force by the operator thusimproving the vibration isolation.
• The isolator may provide a means for allowing axialvibration isolation of a tool body relative to a toolhandle with means incorporated for restraining torsionalrotational and cocking of the tool body relative to thetool handle essential for control of the vibratingdevice.
• The elastomer isolator may include a means forsnubbing to prevent unwanted excess motions.
• The isolator may include means for providing radialvibration isolation to the user by incorporating multipleradial buckling elements.
• The isolator may provide vibration isolation of theuser at a discreet operating frequency by incorporatinginertial fluid forces within the elastomeric and fluidisolator.
• The isolator may include metal buckling elements forproviding vibration isolation of the user.It is an additional feature to provide an elastomericvibration isolator for use on a hand-held vibratingdevice which reduces the radial mechanical vibrationimparted to the user, comprising a body of elastomer forbeing grasped by said users hand, said body of elastomerdisposed about
• Thecharacteristics of the present invention will become apparent from theaccompanying descriptions of the preferred embodiment and attacheddrawings.
Brief Description of the Drawings
• The accompanying drawings which form a part of the specification,illustrate several embodiments of the present invention. The drawings anddescription together, serve to fully explain the invention. In the drawings,
• Fig. 1A is a partially sectioned side view showing the installation of anembodiment of the buckling isolator and an embodiment of the grip isolator ona hand-held vibrating device;
• Fig. 1B is a partially sectioned side view showing a second embodiment of thegrip isolator;
• Fig. 2A is a sectioned side view illustrating an embodiment of a grip isolatorfor a hand-held vibrating device as seen alongline 2A-2A inFig. 2B;
• Fig. 2B is an end view illustrating an embodiment of the grip isolator andillustrating the multiple buckling sections;
• Fig. 2C is an enlarged partial isometric view illustrating one of thebuckling sections of the grip isolator;
• Fig. 2D is an end view illustrating another embodiment of the grip isolatorand shows the multiple buckling sections;
• Fig. 2E is a sectioned side view illustrating an embodiment of a grip isolatorfor a vibrating device as seen alonglines 2E-2E inFig. 2D;
• Fig. 2F is an enlarged end view with a portion broken away illustrating themeans for restraining torsional motion for the vibrating device;
• Fig. 2G is a partial end view illustrating one buckling section of the gripisolator in the buckled state;
• Fig. 2H is an enlarged partial end view illustrating the dimensions of thebuckling section of the grip isolator;
• Fig. 3A is a top view of a first embodiment of the buckling isolator;
• Fig. 3B is a sectioned side view of the buckling isolator as seen alongline3B-3B inFig. 3A;
• Fig. 3C is a side view of the first embodiment of the buckling isolator shownin the buckled state;
• Fig. 3D is a partially sectioned side view of another embodiment of thebuckling isolator for use in a hand-held vibrating device;
• Fig. 3E is an enlarged partially sectioned side view of the secondembodiment of the buckling isolator;
• Fig. 4A is a sectioned side view of an embodiment of a fluid and elastomerisolator installed within a hand-held vibrating device;
• Fig. 4B is a sectioned side view of a second embodiment of a fluid andelastomer isolator;
• Fig. 5A is a graph illustrating the spring rate characteristics exhibited bythe buckling isolator within the hand-held vibrating device;
• Fig. 5B is a graph illustrating the spring rate characteristics exhibited bythe fluid and elastomeric isolator within the hand-held vibrating device;
• Fig. 6A is a sectioned side view of a third embodiment of an isolator for usein hand tools employing a tuned vibration absorber;
• Fig. 6B is a sectioned side view of a fourth embodiment of an isolator for usein hand tools which uses a hybrid absorber/buckling column isolator;
• Fig. 6C is a graph illustrating the intended performance characteristics ofthe third embodiment of isolator within the hand-held vibrating device;
• Fig. 6D is a graph illustrating the actual performance characteristicsexhibited by the third embodiment of isolator within the hand-held vibratingdevice;
• Fig. 7A is a perspective view of a fifth embodiment of the isolator of thepresent invention depicting the use of metallic bucking springs;
• Fig. 7A' is an enlarged cross-sectional side view of an individual springelement of the isolator of Fig. 7A with the buckled position shown in dottedline;
• Fig. 7B is a perspective view of a sixth embodiment of the isolator of thepresent invention depicting a second form of metallic buckling spring;
• Fig. 7B' is an enlarged cross-sectional side view of an individual springelement of the isolator of Fig. 7B with the buckled position shown in dottedline;
• Fig 7C is a perspective view of a seventh embodiment of the isolator of thepresent invention depicting a third form of metallic buckling spring; and
• Fig 7C' is an enlarged cross-sectional side view of an individual springelement of the isolator of Fig. 7C with the buckled position ghosted in.
Detailed Description of the Invention
• InFig. 1A, an embodiment of a bucklingisolator20A and a separateembodiment of agrip isolator30A are shown installed in the environmentof the hand-held vibratingdevice10. The vibratingdevice10 that is used toillustrate the present invention is a pneumatic air hammer, but thebucklingisolator20A andgrip isolator30A are equally effective, whenproperly situated, for any type of hand-held vibrating equipment or device.The pneumatic air hammer or vibratingdevice10 in the present inventionincludes a tool bit32 (Fig. 1B) which is preferably steel and which contactsthe work piece (not shown). The vibratingdevice10 also includes ahandle34 which is grasped by a first rear hand of the user. Further, the handleattaches to asleeve36 that is preferably cylindrically shaped. However, asleeve integrated into a handle may be envisioned, as well. One end of thebucklingisolator20A attaches to thehandle34 by way of bolts or otherfastening means37. The other end of bucklingisolator20A is attached tothetool body38 by bolts or other fastening means37. The bucklingisolator20A attaches between thetool body38 and thehandle34 and allows thetoolbody38 to deflect axially and thus acts as an isolator spring between thetoolbody38 and handle34. The axial motion is limited by asnubber48. Thesnubber consists of acollar47 which is part of or attached to thetool body38 and a series ofshoulders49A and49B which alternativelycontact the ends of thecollar47 at the excursion limits. By way of exampleand not by limitation, thesnubber48 constrains the movement in the axialdirection to 1 cm (0.4 inch (in.)) maximum compression deflection and 0.25 cm (0.1 inch(in.)) tensile deflection.
• In order to maintain control of the vibratingdevice10, it isimportant to keep the torsional and cocking stiffness of the vibratingdevice10 as high as possible. Contrarily, in order to isolate the user fromvibration, it is desirable to keep the axial stiffness as low as possible. Theseare competing criteria and usually both are not obtainable because, as theaxial stiffness is reduced, by reductions in elastomer thickness and/ormodulus, the cocking and torsional stiffnesses are also reduced. Lowcocking and torsional stiffnesses make for poor tool control.
• In the present invention, thetool body38 is restrained from cockingrelative to thesleeve36 and, thus also, thehandle34 by way of slidingsurfaces40A and40B which are axially spaced and which lightly contacttheouter periphery42 of thetool body38. The slidingsurfaces40A and40Band/orouter peripheries42 are coated with Teflon® or other suitable meansfor reducing friction. This allows thetool body38 to slide telescopicallywithin thesleeve36 and compress axially theelastomeric buckling section44A of the bucklingisolator20A, thus reducing the spring rate in the axialdirection within a working thrust load range to be described later.
• As shown inFig. 2F, in order to restrain torsional motion, splinesorkeys50 which are added on thetool body38 are received withingrooves52formed in thesleeve36. Together, the splines orkeys50 andgrooves52comprise the means for restrainingtorsional movement56, while allowingunrestricted axial motion. Other means of restraining torsional movementsuch as flats and non-round shapes are also acceptable. Again, referringtoFig. 1A, the slidingsurfaces40A and40B together with theouterperiphery42 of thetool body38 act as the means for restraining cockingmotion while allowing relatively unrestricted axial motion.
• The cocking and torsional modes are restrained, but axialdisplacement of thetool body38 relative to thehandle34 can occur bycompressing the bucklingisolator20A. The bucklingisolator20A achieves a much lower axial spring rate than prior art devices. When the userprovides an axial force to thehandle34 along the axial axis, that force willcompress the bucklingisolator20A and cause theelastomeric section44Ato undergo buckling. Theelastomeric section44A will experience a highstatic stiffness initially, yet as more force is applied and theelastomericsection44A starts to buckle, the force needed to maintain the section inbuckling falls off dramatically. After reaching this fall off point, or what isknown as the "knee" in the spring rate curve, an operating zone (orworking thrust load range) is reached where the spring rate is very low.Normally, within this zone the spring rate is in the range of 2 to 30 timeslower than the initial static spring rate. It can even drop off more withproper sizing of theelastomeric section44A. Within this operating range,maximum vibration isolation is achieved. A full description of bucklingelastomer sections can be found in US Pat. Nos. 3,798,916 to Schwemmer,3,948,501 to Schwemmer, 3,280,970 to Henshaw, and Re 27,318 toGensheimer which are all hereby incorporated by reference herein.
• By way of example and not by limitation, the initial staticspring rate of the buckling isolator is 664 N·cm^-1 375 lbf/in at 22.5 N (5 lbf load) and at theoperating load of 180 N (40 lbf) the spring rate is 26.6 N·cm^-1 (15 lbf/in). The bucklingisolator20Aprovides axial vibration isolation superior to the prior art compression-typeisolators and fluid damped mounts for vibrating hand-held devices.However, in some instances, radial vibration can impart severe vibration tothe user, in spite of theisolator20A as a result of the key50 hammering inkeyway52.
• InFigs. 2A and2B, a first embodiment of agrip isolator30A isshown. The grip isolator30A functions both as a grip for the user to graspthe vibratingdevice10 and also as a radial and axial isolator to isolate theuser from radial and axial mechanical vibration emanating therefrom.Thegrip isolator30A can be installed on the vibratingdevice10 at an pointwhich is convenient, such as tool body38 (Fig. 1A). Alternatively, thegripisolator30B could encircle the tool32 (Fig. 1B). In some instances, thislatter embodiment will be preferred as many operators desire to grip thehammer10 as far forward as possible for improved balance.
• The grip isolator30A includes a body ofelastomer46B, a multiplenumber of bucklingsections44B extending radially inward from the body ofelastomer46B toward a central axisA. As shown inFig. 2C these bucklingsections44B have a lengthL (in.), a widthW (in.), a thicknesst (in.), andare molded of elastomer with a shear modulusG (psi). The parametersL,W,t, andG can be chosen to provide the optimum buckling for the vibratingdevice10 (Fig. 1A). The buckling sections are formed by substantiallyparallel slots45 extending into said body ofelastomer46B. As fully set forthin the two Schwemmer patents and the patents to Henshaw andGensheimer, in order to exhibit buckling, the sections must have a lengthto thickness ratioL/t ≥ 2.
• Prior art grips have included foam rubber construction whichhas excellent vibration isolation characteristics; however, these gripsquickly deteriorate due to abrasion, are of poor overall strength, and aresubject to being contaminated with oil. Prior art natural rubber grips weremore rugged than foam grips, but failed to properly isolate the user's hand.The presentinvention grip isolator30A or30B is slid over the member to beisolated32 or38, such that in its static form, the bucklingsections44B arebuckled and the user is optimally isolated from the vibration (See Fig. 2G).The present invention provides a rugged grip that is capable of isolating theuser from vibration.
• A second embodiment ofgrip isolator30B is illustrated inFig. 2Dand2E. This embodiment is comprised of a body ofelastomer46C, but thebucklingsections44C are formed by a series of substantially parallel coresor bores58 extending into the body ofelastomer46C. Thelarge bore60, asinstalled, has an interference fit with the member to be isolated, such as atool bit32 (Fig. 1B) or tool body38 (Fig. 1A). An intermediate wall59 (Fig.2E) of elastomer provides radial stability to bores58 while permitting axialsoftness of theisolator30B. By pressing thegrip isolator30B over themember to be isolated, the bucklingsections44C (Fig. 2D) are buckled andas a result the radial spring rate is lowered substantially.
• In this embodiment, the bucklingsections44C have lowcombined axial stiffness to provide isolation from axial vibrations. Thisconfiguration is preferred for usage in theFig. 1B environment where theaxial vibration will be pronounced. The soft elastomer which is usedpreferably has a hardness in the range of 30 to 100 durometer. Ideally, soft natural rubber with a shear modulus of approximately 75 psi should beused for thegrip isolator30A and30B.
• Fig. 2H illustrates the bucklingsections44C having a lengthL,a widthW, a thicknesst, and which are molded of elastomer with a shearmodulusG. The parametersL,W,t, are chosen to make the bucklingsection44C buckle properly for the application. Other shapes of bored out orcored out sections can be envisioned which will allow buckling, such asrectangular, triangular, and sections which direct the buckling direction.
• A view of a first embodiment of bucklingisolator20A is illustratedinFig. 3A and3B. Theisolator20A is comprised of afirst end member62, asecond end member64, and a body ofelastomer46A integrally bonded to themembers62 and64. The body ofelastomer46A includes a bucklingsection44A which buckles outwardly under the application of load as shown inFig.3C.
• Figs. 3D and3E illustrate another type of bucklingisolator20B foruse in a hand-held vibratingdevice10. This bucklingisolator20B has aslight taper from eitherend member62 and64 on the outside surface of thebody ofelastomer46D such that the center most portion is thinnest. This isto promote inward directional buckling of the W-shaped bucklingsection44D. When the extended throw available with theFig. 1A embodiment isunnecessary, this second embodiment offers a more compact envelope.
• InFig. 4A a fluid-and-elastomer version of the bucklingisolator20C is shown. The bucklingisolator20C includes a first variablevolumefluid chamber68, a second variablevolume fluid chamber70 and afluidpassageway72 which allows for fluid communication between thechambers68 and70.Fluid74 substantially fills, and is contained within,thechambers68 and70 and thefluid passageway72. The theory ofoperation of the fluid and elastomer isolator is simple. As the air pulsesenter thedevice10 through an air passage orair supply tube80A and excitethetool body38, thetool body38 oscillates correspondingly. The dynamicoscillation of thetool body38 relative to thehandle34 will cause the bucklingsection44E to flex dynamically. This will pump fluid74 from onechamber68 to the other70. Because of the differential in area between thefluidpassageway72 and thefluid chambers68 and70, and the transmissibility at resonance of the fluid74, the fluid74 can be accelerated to very largevelocities as it flows through thepassageway72 and can generatesignificant phased counter inertial forces. As a result, with proper tuning,these inertial forces can be tuned to provide a dynamic stiffness notch at apredominant operating frequency. This will substantially reduce thevibration transmitted to the user.
• In this embodiment, a firstflexible element76 which defines aportion of the first variablevolume fluid chamber68 is a fabric reinforceddiaphragm. The diaphragm accommodates temperature expansion andallows static displacement of fluid from one chamber to another. A secondflexible element78 which defines a portion of the second variablevolumefluid chamber70 includes the bucklingsection44E. Theair passage80A isa flexible bellows such as a steel spring bellows and passes through thesecond variablevolume fluid chamber70.
• InFig. 4B a second embodiment of a fluid and elastomer version ofthe bucklingisolator20C is shown. The only difference between theembodiment shown inFig. 4A and this one is in the construction of theairpassage80B. In this embodiment, theair passage80B slides telescopicallywithin atube82 attached to the tool body. A pair ofseals84 prevents fluid74from escaping from thechamber68 and air from entering thechamber68.
• InFig. 5A a performance curve of the bucklingisolators20A,20B,and20C are shown. The performance curve plots axial load in poundsforce (lbf.) on the vertical axis versus deflection in inches (in.) on thehorizontal axis and is split into five different sections labeled 1 to 5.Section1 of the curve illustrates the initial-low-strain spring rate, prior to theoccurrence of any buckling. Section 2 illustrates the onset of bucklingwhere the spring rate begins to fall off.Section 3 illustrates the optimumoperating point where the tangent spring rate is the lowest.Section 4 iswhere the buckling section is so buckled that it begins to behave as acompression element and substantially stiffens.Section 5 is where thebuckling section is bottomed out and begins to snub.
• InFig. 5B a performance curve of a fluid and elastomer version of thebucklingisolator20C is shown. The curve section labeled 1 is the lowfrequency dynamic stiffness which is essentially the contribution due to the elastomer stiffness. Section 2 is the notch section. The notch is tuned tocoincide with the fundamental frequency of input vibration by varying thefunctional characteristics of the fluid portion, e.g., the length of the inertiatrack, density of the fluid, etc.Section 3 is the peak dynamic stiffness andcoincides closely with the fluid natural frequency.Section 4 is the highfrequency stiffness after the fluid dynamically locks up and no longer flowsthrough the fluid passageway.
• InFig. 6A is described another embodiment ofisolator20F. Thisisolator20F is useful for reducing the vibration transmitted to a user from ahand-held device and the like. In this embodiment, like numerals denotelike elements as compared to the previous embodiments. The device iscomprised of ahandle34F, asleeve36F attached to saidhandle34F, and atool body38F similar to the previous embodiments. The main difference isthat the reduction in spring rate within an operating range of frequency isaccomplished by incorporating a first andsecond elastomer84 and85 and asuspended, tunedmass86.
• Thefirst elastomer element84 is a pure shear element, i.e., underaxial loading along axis Y-Y, thefirst elastomer section84 is placed in pureshear. Thesecond elastomer section85 is preferably also a pure shearsection, but either could be a compression loaded section as well. Thefirstelastomer section84 is integrally and chemically bonded to thefirst endmember62F and thesecond end member64F. The first end memberincludes asleeve portion87 and an attachedplate portion89 which issecured to thehandle34F. Thesecond end member64F is comprised of asleeve portion87' and an attached plate portion89' which, in turn, attachesto thetool body38F. Thefirst elastomer section84 provides a flexibleconnection between, and acts to isolate, thehandle34F from thetool body38F by allowing relative axial motion therebetween.Snubber48 limits theaxial motion in a similar manner as the previous embodiments. Themass86 is also integrally attached to and chemically bonded to thefirst endmember62F.
• Mass86 andsecond elastomer element85 are tuned such that themass86 resonates at a frequency just above the frequency of interest, i.e.,the motor frequency or air hammer frequency. The tuned frequency ornatural frequencyfn in Hz of the mass86 can be approximated by the relationshipfn = 1/2π (K/M)1/2, whereK is the shear stiffness (lb/in) inpounds per inch of thesecond elastomer element85, andM is the mass ofthemass86. By way of example and not by limitation, the shear stiffnessK= 100 pounds per inch (lb/in), massM = 1 lb mass in pound seconds perinch squared (lb sec/in²), and the resonant frequency is about 31 Hz. Bytuning the natural frequency at 31 Hz and including thismass86 on atypical chipper hammer, the operating range, for example, will be betweenabout 28 and 31 Hz. Normally, the input vibration for a air hammer isabout 30 Hz. This provides a reduction in the transmission of mechanicalvibration to the user within the frequency range.Fasteners37F and37F'secure thefirst end member62F andsecond end members64F to thehandle34F andtool body38F respectively.
• Fig. 6B is another embodiment ofisolator20G. This embodiment issimilar to the embodiment inFig. 6A except thefirst elastomer element84Gis a buckling section. Buckling sections are described in the art in US Pat.Nos. 3,948,501, 3,798,916, 3,280,970, and Re 27,318. Theelement84G bucklesradially inward (as shown in dotted lines) upon application of axial load.Themass86 andsecond elastomer element85 function as a tuned absorberas in the previous embodiment. In this case, the buckling section ispreferably integrally and chemically bonded between the cup-shapedfirstend member62F' and plate-likesecond end member64F'. Upon buckling,the spring rate of the buckling section will drop off dramatically (by asmuch as 30 times or more) and provide a low spring rate for isolation of theuser within a deflection range. The tuned absorber is comprised ofmass86andelastomer element85, which can further reduce the vibration impartedto the user.
• Fig. 6C is an illustration of the intended or analytical performance ofthe tuned absorber embodiment ofisolator20F ofFig. 6A. Thesolid line88indicates the analytical performance of the system without a tuned absorberand including a shear type first elastomer element84 (Fig. 6A). Theresonance at about 9 Hz is the system resonance. The curve indicated at90is for a system including a very small mass for the tuned mass86 (Fig. 6A).Thecurve92 illustrates a mass86 (Fig. 6A) used it the experiment of about1 (lb) pound in weight. Theoretically, for this example, a range of improved isolation can be seen between about 28-31 Hz where the peak accelerationsare reduced.
• Fig. 6D is an illustration of the actual experimental performance ofthe tuned absorber embodiment ofisolator20F ofFig. 6A. Thesolid line94indicates the performance in peak acceleration in inches per secondsquared (in/s²) as a function of frequency (Hz). As expected, the peakaccelerations are substantially reduced within the operating range of about28-31 Hz.
• Fig. 7A is an illustration of another embodiment of bucklingisolator20H. Theisolator20H buckles radially outward under application of loadsuch that the spring rate is reduced within a deflection range in a similarmanner as the aforementioned elastomer embodiments. Theisolator20His comprised of a series of bucklingelements95H extending betweenendportions96H and97H.End portions96H and97H attach to tool handle34Handtool body38H, respectively. Preferably the bucklingelements95H havea curvature formed thereon for biasing the buckling in one direction. Thebucklingelements95H are preferably metal and are formed from astamped and bent sheet and are preferably made of spring-type steel or aremade into spring-type steel through an appropriate heat treatmentoperation. As shown inFig. 7A', upon application of axial load, thebucklingelement95H will buckle radially outward as shown in dotted lines.Upon buckling, the spring rate of the isolator drops off dramatically.
• Fig. 7B is an illustration of another embodiment of bucklingisolator20J. This embodiment is functionally similar to theFig. 7A embodimentexcept that the bucklingelements95J are not part of a stamped plate. Theelements95J are individual and preferably metal members of wire shapewith a curvature formed thereon. The preferable cross section is rounded.The wire-type buckling elements95J are fitted in recesses inend portions96J and97J. Again, preferably the bucklingmembers95J are made fromspring steel or the like. Upon buckling, the axial spring rate issubstantially reduced.
• Fig. 7C is an yet another illustration of an embodiment of bucklingisolator20K. In this embodiment, the bucklingelements95K are stripmembers with coiled or wrapped ends for acceptingpins99K. Themembers95K preferably have a curvature along their length to initiate orbias buckling in the proper direction. The members95 are connected toclevises98K or the like such that a pin joint is formed bypins99Kinteracting with coiled ends at the interface withend portions96K and97K.Fig. 7C' illustrates the bucklingelement95K in its buckled form. Uponbuckling, the axial spring rate is substantially reduced.
• In summary, the present invention relates to a vibration isolator foruse on a hand-held vibrating device for reducing the mechanical vibrationimparted to the user. One embodiment of isolator attaches between the toolbody and the handle reduce the mechanical vibration within a range offrequency or deflection range. Embodiments are drawn to bucklingelastomer type and buckling metal type isolators, tuned fluid isolators, andtuned mass isolators for reducing the spring rate within a range. In thebuckling isolator embodiments, the buckling means attaches between ahandle for being grasped by said user and a tool body and the initial springrate is reduced within an operating range upon application of load. In thefluid isolator, a tuned fluid is used to generate counter inertial fluid forcesfor reducing the transmitted forces within a frequency range, while in thetuned absorber embodiment, the tuned mass and second spring are tunedto provide the vibration reduction within a frequency range. The gripisolator embodiment comprises multiple buckling means extendingradially inward toward a central axis of said hand-held vibrating device forexhibiting an installed radial spring rate in a buckled condition which islower than a spring rate in a non-installed condition. All of these isolatorsare intended to reduce the mechanical vibration imparted to the user andreduce or eliminate the incidence of "white hand" or other phsiologicaldeterioration.
• While several embodiments of the present invention have beendescribed in detail, various modifications, alterations, changes andadaptations to the aforementioned may be made without departing from thespirit and scope of the present invention defined in the appended claims. Itis intended that all such modifications, alterations and changes beconsidered part of the present invention.

Claims (18)

1. A vibration isolator (20 etc) for use on a hand-held vibrating device (10 etc) forreducing the mechanical vibration imparted to the user, said vibrating device including a handle(34 etc) for grasping by the user and a tool body (38 etc), said vibration isolator comprising:

   a first end member (62 etc) mounted to the handle,

   a second end member (64 etc) mounted to the tool body,

   a collapsible element attached between and extending in a longitudinal directionbetween said handle and said tool body and secured to said end members, said elementhaving an initial spring rate and including a buckling section (44, 95 etc) which bucklesin a direction transverse to said longitudinal direction about a radial periphery of saidbucking section under application of load resulting in a reduction of 2 to 30 times saidspring rate and a corresponding force to displace said handle relative to said tool bodywithin an operating range as compared to said initial spring rate and to an initialdisplacement force and, thus, reducing said mechanical vibration imparted to said userwithin said operating range.
2. A vibration isolator (20 etc) in accordance with Claim 1 wherein said section (44,95 etc) is further comprised of a metal buckling element (95H etc).
3. A vibration isolator (20 etc) in accordance with Claim 1 wherein said bucklingsection (44, 95 etc) is elastomeric and said hand-held device includes means for restrainingcocking movement and means for restraining torsional movement, yet allows translation andcompression of said buckling means along an axial direction.
4. A vibration isolator (20 etc) in accordance with Claim 1 including a snubber[with] (48 etc) including a projection (47 etc) and a shoulder (48A etc) wherein movement ofsaid handle (34 etc) relative to said tool body (38 etc) in the axial direction is constrained by saidprojection contacting said shoulder.
5. An elastomeric vibration isolator (30 etc) for use on a hand-held vibrating device(10 etc) for reducing the radial and axial mechanical vibration imparted to the user, comprising:

   (a) a body of elastomer (46B etc) for being grasped by a hand of a prospectiveuser, said body of elastomer disposed about a central axis of said hand-held vibratingdevice (10 etc.); and

   (b) multiple buckling sections (44B etc) extending radially inward toward saidcentral axis, each said buckling section including a length dimension (L) extendingtoward said central axis and a thickness dimension (t) extending in a direction transverseto said length dimension, a ratio of said length dimension (L) to said thickness dimension(t) being greater than or equal to two, said buckling sections buckling under applicationof load and exhibiting

   i) an installed radial spring rate in a buckled condition, and

   ii) a resistance to movement of said hand-held vibrating device relative to saiduser's hand,

   which are each, respectively, lower than an initial spring rate in a non-installed, unbuckledcondition and a corresponding initial resistance to movement of said hand-held vibrating devicerelative to said user's hand whereby the amount of radial and axial vibration transmitted to saidhand is significantly reduced.
6. An elastomeric vibration isolator (30 etc) in accordance with Claim 5 wherein saidmultiple buckling sections (44B etc) each exhibit a low axial stiffness such that the combinedaxial stiffness is low enough to isolate axial vibration of said device from said grasping hand.
7. An elastomeric vibration isolator (30 etc) in accordance with Claim 5 wherein saidmultiple buckling sections (44B etc) extending radially inward toward said central axis areformed by a series of substantially parallel slots axially extending radially outwardly from saidcentral axis into said body of elastomer (46B etc).
8. An elastomeric vibration isolator (30 etc) in accordance with Claim 5 wherein saidmultiple buckling sections (44B etc) extending radially inward toward said central axis areformed by a series of substantially parallel cores (58 etc) axially extending radially outward fromsaid central axis into said body of elastomer (46B etc).
9. An elastomeric vibration isolator (30 etc) in accordance with Claim 5 wherein saidbuckling sections (44B etc) and said body of elastomer (46B etc) are formed of a soft elastomerhaving a hardness in the range of between 30 and 100 durometer.
10. An elastomeric vibration isolator (30 etc) in accordance with Claim 5 whichencircles and isolates said hand of said user from said radial and axial mechanical vibrations ofa member selected from the group consisting of a tool (32 etc) and a tool body (38 etc).
11. A hand-held vibrating device (10 etc) which reduces the mechanical vibrationimparted to a user, comprising:

    (a) a handle (34 etc.) for being grasped by said user;

    (b) a tool body (38 etc);

    (c) a tool bit (32 etc) attached to said tool body;

    (d) buckling means (20 etc) attached between said handle and said tool bodysaid buckling means including

    a first end member (62 etc) mounted to the handle,

    a second end member (64 etc) mounted to the tool body,

    a collapsible element attached between and extending in a longitudinal directionbetween said handle and said tool body and secured to said end members, said collapsibleelement including a buckling section which buckles in a direction transverse to saidlongitudinal direction about a radial periphery of said bucking section, said collapsibleelement having an initial spring rate which decreases under application of load, thusreducing said spring rate by 2 to 30 times within a working thrust load range and amagnitude of thrust needed to move said handle relative to said tool body therebyimproving axial vibration isolation;

    (e) a grip isolator (30 etc) further including a body of elastomer (48B etc) for beinggrasped by the user's hand, said body of elastomer disposed about a central axis andsurrounding one element selected from the group consisting of said tool bit and said toolbody, multiple buckling sections extending radially inward toward said central axis, eachsaid buckling section including a length dimension (L) extending toward said central axisand a thickness dimension (t) extending in a direction transverse to said lengthdimension, a ratio of said length dimension (L) to said thickness dimension (t) beinggreater than or equal to two, said buckling sections reducing said spring rate and amagnitude of thrust needed to move said selected element relative to said user's handthereby improving radial vibration isolation thereof.
12. A hand-held vibrating device (10 etc) in accordance with Claim 11 furtherincluding a tuned mass (86 etc) suspended on a spring element (85 etc).
13. A hand-held vibrating device (10 etc) in accordance with Claim 11 furtherincluding axially spaced sliding surface means (40A etc) for contacting an outer periphery of saidtool body (38 etc) to constrain relative cocking motion between said tool body (38 etc) and saidhandle (34 etc) and spine means (50 etc) received in grooves (52 etc) in said tool body forrestraining said handle from torsional movement.
14. A hand-held vibrating device (10 etc) in accordance with Claim 11 furtherincluding a projection (47 etc) and a shoulder (49A etc), wherein said tool body (38 etc) and saidhandle (34 etc) are constrained from relative axial movement by said projection contacting saidshoulder.
15. A hand-held vibrating device (10 etc) in accordance with Claim 11 wherein saidgrip isolator (30 etc) includes buckling means for reducing said spring rate formed by bores (58etc) extending into said body of elastomer (46C etc).
16. A vibration isolator (20 etc) in accordance with Claim 1 further comprising:

    (a) a first (68 etc) and second (70 etc) variable volume chambers;

    (c) first (76 etc) and second (78 etc) flexible elements defining at least aportion of said first and second variable volume chambers, respectively, wherein oneof said flexible elements includes said buckling section (44E etc);

    (d) a fluid passageway (72 etc) between said variable volume chambers;

    (e) a fluid (74 etc) contained within, and substantially filling, said variablevolume chambers, and said passageway wherein relative vibratory movement betweensaid handle (34 etc) and said tool body (38 etc) causes said fluid to flow to and fromsaid variable volume chambers through said fluid passageway thereby creating counterinertial forces which reduce vibration forces transmitted to the user.
17. A vibration isolator (20 etc) in accordance with Claim 16 wherein an air supplytube (80A etc) is surrounded by at least one of said variable volume chambers (76 etc).
18. A vibration isolator (20 etc) in accordance with Claim 1 further comprising tunedabsorber means comprising a second spring (85 etc) and a attached mass (86 etc.) for providinga tuned inertia effect substantially coinciding with said operating frequency of said vibratingdevice (10 etc).

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