AUXILIARY DAMPER FOR RUBBER SUSPENSION MOUNTINGS

Abstract: An auxiliary damper (12) is provided for a passenger cab (13) on heavy equipment or the like, the damper (12) being contained within the confines of the primary suspension system (11) and being secured to a first one of a supported element and a support to provide surface effect damping as needed to damp high-amplitude, low-frequency vibration in the region of the resonant frequency of the primary suspension (11). An elastomeric sleeve (16) is bonded to a rigid sleeve member (14) which surrounds the securement bolt (17) for the primary mount. A spool member (18) with internal protrusions (26) engagingly surrounds the elastomeric sleeve (16). The spool (18) has upper and lower flanges (22, 24) which overlie and underlie, respectively, in non-engaged relationship, the second of a supported element and a support. When there is low-amplitude, high frequency motion of the support, this non-engaged relationship allows the supported element to be isolated from such motion. When the amplitude of the vibration becomes large enough as, for example, near resonance, the spool (18) of the auxiliary damper (12) engages its supported element or support and dissipates the vibrational energy as heat to effectively damp the large amplitude motion and maintain a comfortable ride.

Description: AUXILIARY DAMPER FOR RUBBER SUSPENSION MOUNTINGS Background and Summary of the Invention The present invention is directed to an auxiliary damper for use with rubber or other spring suspension mountings. More particularly, the present invention is directed to an auxiliary surface- effect damper that can be confined within the existing space envelope occupied by the primary suspension mounting. Laminated rubber and metal mounts have been around for some time. In addition, the focalization of elastomeric mounts h a s been employed to decouple the translational and rotational vibrational modes in order to greatly simplify the required mou ntin g system needed to provide the necessary damping and isolation. The present invention proposes to add auxiliary damping to a system to reduce movement at or near the system's resonance frequency. The system may employ an elastomeric spring mount o r other type of spring mount in the primary suspension, a n d preferably will include focalization. An elastomeric sleeve bonded t o a rigid collar that surrounds a support bolt for a pair of pri mary mounts provides a workable surface element for surface-effect (frictional and hysteretic, combined) damping. The bolt secures th e primary suspension mountings and auxiliary damper to a first one of a supported element and a support. A metallic sleeve which has a C- shaped cross section and an internal peripheral surface which h a s cylindrical protrusions formed thereon surrounds the elastomeric sleeve and the protrusions work the elastomer to dissipate energy by hysteresis. The upper flange of the C-shaped sleeve overlies and th e lower flange underlies the other of the supported element and t h e support. Most preferably, the distance between the flanges exceeds the maximum thickness of that other member and the outer diameter of the central portion of the C-shaped member is smaller than th e diameter of the opening in the support. This clearance between th e sleeve and its received member permit vibrations of low amplitude, high frequency to be isolated (i.e., not transmitted) from the support vis-a-vis the supported element. When the vibration of the s upport exceeds this minimally permitted magnitude as, for example, w h e n the disturbance frequency approaches the natural, or resonant, frequency of the system, the auxiliary damper will dissipate th e objectionable motion-inducing energy and restore controlled movement between the supported element and the support. Various features, advantages and characteristics of t h e present invention will become apparent after a reading of th e following specification. Brief Description of the Drawings This section describes the drawings. FIG. 1 is isometric schematic depiction of the application of the auxiliary damper of the present invention in a cab mountin g system ; FIG. 2 is a cross-sectional side view of the auxiliary d amper of the present invention shown installed within the pri mary suspension system; FIG. 3 A is an end view of the cylindrical spool of th e auxiliary damper of the present invention; Fig. 3 B is a cross-sectional side view of the cylindrical spool as seen along line 3B-3B in Fig. 3A; Fig. 4 is a cross-sectional side view of an alternative application of the auxiliary damper of the present invention; and Fig. 5 is a side view of the auxiliary damper of the pre sen t invention in the application of Fig. 1. Detailed Description of the Preferred Embodiments The auxiliary damper 12 of the present invention is shown i n Fig. 1 as a part of a mounting system 20 which includes a pri mary suspension member 11. As depicted in Fig. 1, four focalized primary suspension members 1 1 are used to support a cab 13 relative to a support or frame 15 (Fig. 2). In practice, a minimum of three members 1 1 are required to achieve focalization, which results i n decoupling of the rotational and translational modes of vibration. Focalization is well known in the industry and has been aptly described in commonly assigned US pat. no. 2,685,425, which i s hereby incorporated by reference. As best seen in Figs. 2 and 5 , auxiliary damper 1 2 of t h e present invention is received within a pair of aligned pri m ary suspension members 11 which are held in alignment by su spension bolt 17. Bolt 1 1 secures inner sleeve 1 4 to supported element 1 9 which is, in this utilization, a floor portion of cab 13. Cab 1 3 may, for example, be the passenger compartment of a tractor, combine, o r other farm or industrial equipment. Primary suspension m em bers 1 1 are preferably elastomeric mounts of laminated metal - and - elastomer construction having upper (21 ) and lower (23 ) plates laminated to the respective upper most and lowermost elastomeric surface layers. These mounts 1 1 function as both spring members (storing and releasing energy) and dampers (dissipating energy as heat). Lower plates 23 are positioned on either side of a support 25 which, in this application, may comprise a portion of the vehicular frame. Lower plates 23 are clamped against a pair of split-ring members 2 9 which facilitate assembly of the suspension system 20 with s upport 25. Support 25 has an opening formed therein with an i n nermost periphery 3 1 having a diameter Di. Split-ring members 2 9 eac h have a flange 33 which has a height of one-half the thickness of support 25 and a width extending from a maximum diameter whic h is generally equal to Di and a minimum diameter D 2 . An elastomeric sleeve 16 having an outer diameter D 3 is bonded to an external peripheral portion of inner sleeve 1 4 which is preferably of a metallic or plastic material. Metallic spacer washers 27 are employed to preload the elastomer of primary suspension members 11 by an amount permitted by the combined length of washers 27 and sleeve 14. A cylindrical spool 1 8 (see Figs. 3 A -B ) has an inner diameter D 4 which is less than the outer diameter D 3 of elastomeric sleeve 1 6 to create an interference fit between the two. Upper flange 22 overlies split-rings 33 and lower flange 2 4 underlies said rings. The spacing between flanges 2 2 and 2 4 exceeds the combined thickness of rings 33 and, in its centered, a t rest position, spool 18 will not engage rings 33. The inner perip hery of spool 18 has a plurality of protrusions 26 thereon which provide hysteresis damping when spool 18 is moved relative to elastomeric sleeve 16. Minimum outer diameter D 5 of spool 1 8 is less than th e maximum diameter D 2 of flanges 33 on split-rings 29. In assembling the suspension system 20 , bolt 17 is i n serted through a hole in supported element 1 9 and plate 21 . Washers 2 7 may be internally threaded to afford the possibility of partial preassembly. Four equally space centering pins 37 (two s h own) extending through support 25 may be utilized to assist in positioning the two suspension members 1 1 on opposite sides of support 2 5 (Fig. 5). Sleeve 14 is slid over bolt 1 7 with spool 18 pre assembled thereon and second washer 27 threaded onto bolt 17 . The cab 1 3 with its four partially assembled suspension members 1 1 are positioned relative to frame 25. Split-rings 33 , which are halv ed along a diameter, are installed with flanges 33 capturing th e peripheral edge 3 1 of the opening in support 25. Most preferably, the two diametrical seams in split-rings 33 will be offset at right angles so as not to form a break line. Lower suspension member 1 1 is positioned and nut 3 5 tightened to bring each of upper plates 2 1 into engagement with its respective spacer washer 27 to provide the designed preload of th e elastomer in members 11 . The weight of cab 1 3 can be taken into account to equalize the loading on upper and lower members 1 1 b y varying the unloaded thickness of the mounts and/or their respective static spring rates. In operation, the paired primary suspension members 11 will isolate the cab 13 from low amplitude, generally high frequency, vibrations through the "spring action" of the elastomeric layers, th e lower of the paired members 11 preventing rebound motion. Should the support be subject to a large amplitude, typically, low frequenc y vibration, the flanges 33 of split-rings 2 9 will engage the overlying (22 ) and underlying (24 ) flanges successively causing spool 18 t o translate relative to elastomeric sleeve 16. This translational motion will induce surface-effect damping (i.e., damping having both frictional and hysteresis components), causing this high amplitude vibrational energy to be dissipated as heat. This is particularl y important for frequencies in the 15-20 Hz range which tend to be the natural frequency of the suspension system. Without the interaction of the auxiliary damper 12 of the present invention, the vibrational input from support 25 would be amplified as it was transmitted t o the passenger compartment 13. Not only would this produce significant discomfort for the equipment operator, it might c au se her/him to lose control of the vehicle resulting in significant dan ger to herself/himself and others. The auxiliary damper 1 2 maintains a smooth ride through any transition through the resonant frequency occurring during low speed operation of the vehicle. The smaller diameter D 5 vis-a-vis the inner diameter D 2 of rings 29 permits some relative lateral an d torsional movement of support 25 relative to cabin 13 with ou t engaging the damper 12. It will be understood that while t h e auxiliary damper 12 provides a necessary and beneficial function of damping out excess motion, its engagement will result in some c ab movement and, therefore, some transmission of vibration to t h e passenger compartment; hence, the preference for the isolation of spool 1 8 from engagement with support 25 when damping is n o t needed. . As seen in Fig. 5 , each of the suspension members 1 1 an d associated auxiliary dampers 12 are canted from vertical some 21.5 ° to provide the desired focalization of the system 20 . This will provide a center of restraining elastic force which coincides with th e center of gravity of cab 13. A second embodiment of the present invention is depicted i n Fig. 4 generally at 12a . While for most applications the spring member of the primary suspension member will most preferably b e an elastomeric mount of laminated construction, for s ome applications it may be desirable to utilize a coil spring I l a . The principles of operation of the auxiliary damper 1 2 a remains unchanged in this embodiment. The restorative and damping forces of the primary suspension are simply provided by a pair of coil springs I la depicted in Fig. 4 as conically coiled. The present invention of an auxiliary surface-effect d a mper which is entirely contained within the existing suspension m ou n t provides an easy, inexpensive solution to what is potentially a complex problem of what to do about damping large ampl i tude vibration associated with the resonant frequency of the primary suspension mount. Various changes, alternatives and modifications will b e apparent to a person of ordinary skill in the art following a read in g of the foregoing application. It is intended that all such changes, alternatives and modifications as fall within the scope of t h e appended claims be considered part of the present invention.

Claims: C l a i m s What is claimed is: 1 . An auxiliary damper for controlling undesired vi bratory motion of a supported element relative to a support in connection with a primary suspension member, said auxiliary damper including: a ) an elastomeric sleeve at least partially s urroundin g a support bolt, said sleeve being attached to one of said supported element and said support; b ) a cylindrical spool surrounding said sleeve, a n d having protruding surface portions on an internal surface for engaging said elastomeric sleeve and deforming it to create frictional and hysteretic damping upon relative m ov emen t between said sleeve and said spool, said spool adapted t o engage another of said supported element and said s upport and to move generally in conjunction therewith during large amplitude movements thereof; said auxiliary damper being substantially entirely contained within said primary suspension member so as not to require additional space. 2. The auxiliary damper of Claim 1 wherein said cylindrical spool is C-shaped in axial cross section, having an upper flange overlying said support and a lower flange underlying said support. 3. The auxiliary damper of Claim 2 further comprising tw o ring inserts overlying and underlying an inner peripheral surface of said support to facilitate installation. 4. The auxiliary damper of Claim 3 wherein said u pper flange and said lower flange are spaced by a distance greater than a n accommodated thickness of said support and said overlying a n d underlying ring inserts. 5. The auxiliary damper of Claim 4 wherein said spool has a minimum diameter which is less than said minimum diameter of said ring inserts whereby said spool is free to move relative to said support without creating damping in any of three pri mary directional axes such that low amplitude high frequency vibrations in said support are isolated from said one element. 6. The auxiliary damper of Claim 1 wherein said pri mary suspension element comprises a pair of spring dampers positioned on either side of said support. 7. The auxiliary damper of Claim 6 wherein said spring dampers comprise elastomeric spring dampers, each said elastomeric spring damper being of laminated el astomer-and -steel- spacer-plate construction. 8. The auxiliary damper of Claim 7 wherein said s upport bolt extends through said pair of elastomeric spring d ampers, attaches said supported element to said support and precompresses said pair of elastomeric spring dampers. 9. The auxiliary damper of Claim 8 further comprising a rigid sleeve made from a material selected from a list consisting of steel, aluminum, and plastic, said sleeve surrounding said s u pport bolt and having said elastomeric sleeve bonded thereto. 10. The auxiliary damper of Claim 9 wherein said pair of elastomeric spring dampers with said support bolt and auxiliary damper form a first unit of at least three such units in a focalized mounting system. 1 1 . The auxiliary damper of Claim 1 wherein said pri m ary suspension element comprises a pair of metallic conical springs positioned on either side of said support and said auxiliary damper i s received in the center thereof. AMENDED CLAIMS [received by the International Bureau on 10 January 1997 (10.01.97); original claims 1-6 and 11 amended; remaining claims unchanged (3 pages)] 1 . An auxiliary damper for controlling undesired vibratory motion of a supported element relative to a support i n connection with a fluidless primary suspension member, said auxiliary damper including: a) an elastomeric sleeve at least partially surrounding a support bolt and fixed against axial movement relative thereto, said sleeve being attached to one of said supported element and said support; b ) a spool-shaped member surrounding said elastomeric sleeve, and having protruding surface portions on an internal surface for engaging said elastomeric sleeve and deforming it to create frictional and hysteretic damping upon relative movement between said sleeve an d said spool, said spool-shaped member being engagable with another of said supported element and said support and to move generally in conjunction therewith during large amplitude movements thereof; said auxiliary damper being substantially entirely con tained within said primary suspension member so as not to req uire additional space. 2. The auxiliary damper of Claim 1 wherein said spool - shaped member is C-shaped in axial cross section, having a n upper flange overlying said another of said supported element and said support and a lower flange underlying said another of said supported element and said support. 3. The auxiliary damper of Claim 2 further comprising two ring inserts overlying and underlying an inner peripheral surface of said another of said supported element and said support to facilitate installation. 4. The auxiliary damper of Claim 3 wherein said upper flange and said lower flange are spaced by a distance greater th an an accommodated thickness of said another of said supported element and said support and said overlying and underlying rin g inserts . 5. The auxiliary damper of Claim 4 wherein said spool - shaped member has a minimum diameter which is less than said minimum diameter of said ring inserts whereby said spool-shaped member is free to move relative to said another of said s upported element and said support without creating damping in any of three primary directional axes such that low amplitude high frequency vibrations in said support are isolated from said supported element. 6. The auxiliary damper of Claim 1 wherein said primary suspension element comprises a pair of spring dampers posi tioned on either side of said another of said supported element and said support. 7. The auxiliary damper of Claim 6 wherein said spring dampers comprise elastomeric spring dampers, each said elastomeric spring damper being of laminated elastomer-and - steel-spacer-plate construction. 8. The auxiliary damper of Claim 7 wherein said support bolt extends through said pair of elastomeric spring dampers, attaches said supported element to said support a n d precompresses said pair of elastomeric spring dampers. 9. The auxiliary damper of Claim 8 further comprising a rigid sleeve made from a material selected from a list consisting of steel, aluminum, and plastic, said sleeve surrounding said s u pport bolt and having said elastomeric sleeve bonded thereto. 10. The auxiliary damper of Claim 9 wherein said pair of elastomeric spring dampers with said support bolt and auxiliary damper form a first unit of at least three such units in a focalized mounting system. 1 1 . The auxiliary damper of Claim 1 wherein said primary suspension element comprises a pair of metallic conical sprin gs positioned on either side of said another of said s upported element and said support and said auxiliary damper is received i n the center thereof. 11 AIVIENDED SHEET (ARTICLE 19)

Inventors: GWINN JAMES T, GWINN, JAMES, T.
Applicants: LORD CORP, LORD CORPORATION
Application year: 1996
Main classification: B60G11
IPC codes: B60G13, B60G25, B62D33, F16F1, F16F7