Patent Publication Number: US-9845720-B2

Title: Micro shear hub dual ring isolator

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 62/203,659, filed on Aug. 11, 2015. The entire disclosure of the above application is incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates general to an automotive exhaust system isolator. More particularly, the present disclosure relates to an isolator which is configured to provide a very soft on-center rate but yet have even the ability to endure spike durability loads. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     Typically, automotive vehicles including cars and trucks have an internal combustion engine which is coupled to at least a transmission and a differential for providing power to the drive wheels of the vehicle. An engine exhaust system which typically includes an exhaust pipe, a catalytic converter and a muffler is attached to the engine to quiet the combustion process, to clean the exhaust gases and to route the products of combustion away from the engine to a desired position typically at the rear of the vehicle. The exhaust system is supported by exhaust mounts which are positioned between the exhaust system and the frame or some other supporting structure of the vehicle body. In order to prevent engine vibrations from being transmitted to the car body, the exhaust mounts incorporate flexible members or elastic suspension members to isolate the vehicle&#39;s exhaust system from the vehicle&#39;s body. In order to effectively isolate the vehicle&#39;s exhaust system from the vehicle&#39;s body, it is preferred that the isolator include a soft on-center rate of deflection. 
     The common prior art exhaust mounts or isolators have included two-hole pendulum rubber isolators which include a solid rubber component or a puck that is at least three-quarters of an inch thick and which is provided with at least one pair of apertures extending therethrough. The apertures each receive an elongated metal stud hanger. The metal stud hanger is often provided with an enlarged tapered head that can be forced through the aperture in the isolator, but which cannot be readily removed from the isolator. The opposite end of the hanger is welded to or otherwise secured to either a support point in the vehicle or to one of the components of the exhaust system. 
     Other designs for isolators include elastomeric moldings having a 1-hole spoke design wherein spokes are loaded in tension and compression, elastomeric moldings having a 1-hole shear leg design that include a pair of molded legs subjected to shearing in the primary loading direction, and elastomeric moldings having a bell-shaped design. 
     Most high temp elastomers utilized in exhaust isolator assemblies exhibit poor tensile fatigue properties stemming from low tear strength properties. It is therefore preferred to load the elastomeric material in compression or shear. For example, the puck design, as discussed above, provides for two pins to be inserted at opposite ends of the elastomeric element which allows loading in tension on the elastomer cords connecting both ends. While this is typically the lowest cost design, it is also the most abusive to the material. In order to offset the failure risk, flexible and/or rigid bands are typically designed inside or around the outside of the elastomeric puck. 
     Spoke design isolators load the elastomeric material in compression and tension. The tensile loading makes the design vulnerable to fractures in overloaded conditions. The stress magnitude is directly proportional to the load divided by the minimum spoke cross-sectional area. An additional requirement of the spoke design is that the mating component or hanger pin be centered within the deflection zone while statically preloaded by the weight of the exhaust. If it is not, the voids designed into the isolator will be bottomed out or positioned in a groundout condition. This results in the soft on-center rate not being employed, thus defeating the purpose of the isolator. 
     Shear leg design isolators have a primary loading direction which is typically vertical and a secondary loading direction which is typically lateral. When the shear leg design is loaded in its primary loading direction, the loading method is the preferred shear style loading. Shear style loading is able to be designed desirably soft. However, the secondary loading direction inflicts tensile compressive stresses which are unfavorable for durability. In addition, the secondary loading direction has a rate that is two to three times stiffer than the primary rate which is also an unfavorable condition. 
     The continued development of elastomeric mounts has been directed to elastomeric mounts which include a soft on-center rate while avoiding the undesirable tension loading of the elastomeric bushing and which avoid the vulnerable stress concentrations. While this has been achieved in the prior art shear-hub designs, stress concentrations at the ends of the voids continues to be an issue. 
     SUMMARY OF THE INVENTION 
     In one aspect the present disclosure relates to an isolator assembly for supporting an exhaust component from a structural portion of a vehicle. The isolator assembly may comprise a mounting bracket having a pair of spaced apart rings defining a mounting bore. An elastomer shear hub component may be disposed within the mounting bracket. The elastomer shear hub component may include an outer diameter (OD) shear hub extending between the pair of spaced apart rings, and an inner diameter (ID) shear hub disposed within the OD shear hub. The ID shear hub may define a central mounting bore adapted to receive an external hanger component. 
     In another aspect the present disclosure relates to an isolator assembly for supporting an exhaust component from a structural portion of a vehicle. The isolator assembly may comprise a mounting bracket having a pair of spaced apart circumferential rings defining a circular mounting bore. An elastomer shear hub component may be included which is disposed within the mounting bracket. The elastomer shear hub component may include an outer diameter (OD) shear hub extending between the pair of spaced apart rings, and an inner diameter (ID) shear hub disposed within the OD shear hub and connected to the OD shear hub via a transition portion. The ID shear hub may include a pair of ID shear hub portions extending in generally opposite directions that define a common, central mounting bore adapted to receive an external hanger component. 
     In still another aspect the present disclosure relates to an isolator assembly for supporting an exhaust component from a structural portion of a vehicle. The isolator assembly may comprise a mounting bracket having a pair of spaced apart circumferential rings defining a circular mounting bore, and a bottom wall having an aperture. An elastomer shear hub component may be disposed within the mounting bracket. The elastomer shear hub component may include an outer diameter (OD) shear hub extending between the pair of spaced apart circumferential rings, and an inner diameter (ID) shear hub disposed within the OD shear hub and connected to the OD shear hub via a transition portion. The ID shear hub may include a pair of mirror image ID shear hub portions extending in generally opposite directions that define a co-linear central mounting bore adapted to receive an external hanger component. The mirror image pair of ID shear hub portions may be coupled at an approximate midpoint along an axial length thereof to an approximate midpoint of the OD shear hub by the transition portion. 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of a vehicle exhaust system; 
         FIG. 2  includes a front view and a side view of a shear hub isolator in accordance with a first embodiment of the present invention; 
         FIG. 3  is a cross-sectional view of the shear hub isolator of  FIG. 2 ; 
         FIG. 4  is a semi-transparent, isometric view of the shear hub isolator of  FIG. 2 ; 
         FIG. 5  includes two isometric views of a shear hub isolator in accordance with a second embodiment of the present invention; 
         FIG. 6  is a cross sectional plan view of a portion of another embodiment of the isolator mounting bracket showing a plurality of staking ribs which are used to engage a fastener, and to relieve stress on the bracket from its press-fit fastener; 
         FIG. 7  is a perspective view of another embodiment of the present disclosure that incorporates a dual ring mounting bracket with an outer diameter (“OD”) shear hub and a mirror image pair of inner diameter (“ID”) shear hubs; 
         FIG. 8  is a cross-sectional view taken in accordance with section line  8 - 8  in  FIG. 7  better showing the mirror image pair of ID shear hubs; 
         FIG. 9  is a perspective view of just the dual ring mounting bracket and the embedded fastener; 
         FIG. 10  is a front view of another embodiment of the present disclosure showing a dual ring mounting bracket with an OD shear hub and a mirror image pair of ID shear hubs, but where a compression bumper of the shear hubs extends a full axial length of the pair of ID shear hubs; 
         FIG. 11  is a perspective view of the assembly of  FIG. 10 ; 
         FIG. 12  is a quarter sectional view of a portion of the assembly of  FIG. 11  taken in accordance with section line  12 - 12  in  FIG. 11 ; 
         FIG. 13  is a front elevational view of another embodiment of a dual ring isolator assembly in accordance with the present disclosure in which a clamp face of a dual ring mounting bracket has a bore extending therethrough parallel to a bottom face of the mounting bracket, to provide a through-bolt bracket configuration; 
         FIG. 14  is a perspective view of the isolator assembly of  FIG. 13 ; and 
         FIG. 15  is another embodiment of an isolator assembly in accordance with the present disclosure in which no void is formed between the OD shear hub and the ID shear hubs to decouple rubber tension to the bolt head. 
     
    
    
     DETAILED DESCRIPTION 
     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the disclosure, its application, or uses. 
     Referring now to the drawings, there is shown in  FIG. 1  a vehicle exhaust system  10  which includes the exhaust system isolators  100  in accordance with the present invention and which is designated generally by the reference numeral  100 . A typical vehicle comprises an internal combustion engine (not shown), a body (not shown), a suspension system (not shown) and exhaust system  10  which is attached to the internal combustion engine and which is supported typically beneath the vehicle. The internal combustion engine is designed to power one or more drive wheels of the vehicle and the exhaust system routes the products of combustion to a desired exhaust location around the outside of the vehicle. 
     Exhaust system  10  comprises a muffler  14 , an intermediate pipe  12 , a catalytic converter  15 , an exhaust hanger pin  16 , a tailpipe  18  and a plurality of isolator assemblies  100  of various designs. Intermediate pipe  12  is typically connected to the engine or to a catalytic converter  15  which is then attached to an exhaust pipe which extends between the engine and the catalytic converter. The catalytic converter  15  may be attached to a single exhaust pipe which leads to a single exhaust manifold or the catalytic converter can be attached to a branched exhaust pipe which leads to a plurality of exhaust pipes which lead to a plurality of exhaust manifolds. In one alternative embodiment, intermediate pipe  12  can be attached to a plurality of catalytic converters which join together upstream of the muffler  14 . In another alternative, the vehicle can have a plurality of exhaust pipes, a plurality of catalytic converters, a plurality of intermediate pipes and a plurality of mufflers which join together. It is further understood that an exhaust system may include a single tailpipe or multiple tailpipes. It should be further appreciated that, the exhaust system isolator of the present invention may be applied to any type of exhaust system including but not limited to dual exhaust systems having two parallel exhaust paths extending from the internal combustion system. 
     Exhaust system  10  is utilized to route the exhaust gases from the engine to a desired location around the outside of the vehicle. While traveling through the exhaust system, the catalytic converter  15  cleans the exhaust gases and muffler  14  quiets the noise created during the combustion process in the engine. The present invention is directed toward the exhaust system isolators  100  which mount exhaust system  10  to the vehicle while at the same time, isolate and damp the movement of exhaust system  10  with respect to the vehicle. 
     Referring now to  FIGS. 2-4 , an exhaust system isolator assembly  100  comprises a mounting bracket  102  and an elastomeric body  104  positioned within the mounting bracket. The mounting bracket  102  is a metal or plastic component which defines a bracket mounting bore  112  for elastomeric body  104 . Within the bracket mounting bore  112 , a fastener  108  (best seen in  FIG. 3  as a T-bolt) is provided for securing exhaust system isolator assembly  100  to a vehicle frame or another structural component of the vehicle. While  FIG. 2  illustrates bracket mounting face  106  being generally perpendicular to a front face  102   a  of the bracket  102 , it is within the scope of the present disclosure to arrange bracket mounting face  106  in any orientation which is required to have bracket  102  properly interface with the mounting structure of the vehicle. 
     Referring now to  FIG. 3 , isolator bracket  102  includes in inner circumferential surface defining a bracket mounting bore  112  that is bonded to the elastomeric body  104 . The bracket mounting bore  112  includes a bolt-head pocket  116  ( FIG. 4 ) which is cut out of the isolator bracket  102 , or otherwise formed in the isolator bracket, to provide a space for a bolt-head  118   a  of the fastener  108 . The bracket mounting bore  112  includes a leading edge  114  adjacent the bolt-head pocket  116  that provides for a constant ground out rate in all directions including the direction of the bolt head pocket  116 . The general shape of the bolt head pocket  116  may be square or any other shape to prevent rotation of the fastener  108  during assembly. An aperture  118  is further provided between the bolt head pocket  116  and the bracket mounting face  106 . The tight fit between a shoulder (not shown) of the fastener  108  and the aperture  118 , as well as the bolt head  118   a  to bolt head pocket  116  contact  119 , acts to seal the aperture  118  from leakage during the molding of the elastomeric body  104 . Encapsulating a bolt head  120  of the fastener  108  within the isolator assembly  100  provides a more compact design. 
     The elastomeric body  104  further comprises an OD shear hub  124 , an ID shear hub  122 , and a ground-out hub  126 . The elastomeric body  104  defines a central mounting bore  110  which is designed to accept an inner tube, a bolt, or a hanger pin  16 . Hanger pin  16  can further include a head and collar that act as hanger slide limiters. Hanger pin  16  is attached to a component of exhaust system  10 . While bracket  102  is disclosed as being attached to a structural component of the vehicle and elastomeric body  104  is disclosed as being attached to a component of exhaust system  10 , using hanger pin  16 , it is within the scope of the present disclosure to have bracket  102  attached to exhaust system  10  and exhaust system isolator assembly  100  attached to a structural component of the vehicle using hanger pin  16 . Thus, exhaust system  10  is secured to the vehicle through one or more exhaust system isolator assemblies  100 . 
     Elastomeric body  104  includes a chamfer  130  located at one end of mounting bore  110 . Chamfer  130  interfaces with the hanger pin  16 . In at least one preferred embodiment, the chamfer  130  is tunable, typically ending flush to a leading edge of the isolator bracket  102 . In at least one embodiment, the diameter of the chamfer is tuned such that the wall thickness of the OD shear hub  124  is equal to the wall thickness of the ID shear hub  122 . Elastomeric body  104  defines a circumferential annular void  128 . While annular void  128  is illustrated as being asymmetrical with respect to bracket mounting bore  112 , it is within the scope of the present disclosure to have annular void  128  symmetrical with bracket mounting bore  112 . The asymmetrical design for annular void  128  permits central mounting bore  110  to become disposed at or near the centerline of the bracket mounting bore  112  during the assembled or statically loaded condition of exhaust system isolator assembly  100 . This is accomplished by molding mounting bore  110  vertically offset. 
     The design of both void  128  and chamfer  130 , particularly the radial dimension of void  128  and the radial thickness of chamfer  130 , will determine the distance a hanger pin disposed within the mounting bore  110  may radially translate with respect to the bracket mounting bore  112 . Until the closing of void  128  and/or chamfer  130 , the radial movements of central mounting bore  110  cause pure shear in elastomeric body  104  regardless of the loading direction. This shear loading occurs in the portion of elastomeric body  104  disposed between structural bracket mounting face  106  and hanger pin  16  as discussed below. Tuning for rate and deflection in selected directions can be accomplished independently from other directions by altering void  128  and chamfer  130  in the selected direction or by adding voids at specific circumferential positions of elastomeric body  104 . 
     As can be seen in the figures, void  128  extends beyond bracket  102  and overlaps chamfer  130  in the axial direction to define the ID shear hub  122 . The ID shear hub  122  which undergoes the shear loading due to the deflection of elastomeric body  104 . During larger loading of exhaust system isolator assembly  100 , void  128  and chamfer  130  will close and compressive stresses are imparted to elastomeric body  104  by the sandwiching of the ground-out hub  126  of the elastomeric body  104  between hanger pin  16  and bracket mounting bore  112 . This contact between hanger pin  16 , ground-out hub  126  and bracket mounting bore  112  eliminates the compression and thus the compression stresses on the OD shear hub  124  and the ID shear hub  122  when isolator assembly  100  experiences high ground-out loads. This improves both the performance and the reliability of exhaust system isolator assembly  100 . 
     Exhaust system isolator assembly  100  avoids tension stress loading in the elastomeric body  104  during radial loading. The shear style loading in all directions enables exhaust system isolator assembly  100  to achieve a lower and more stable rate of deflection. This is because the shear modulus (shear loading) is lower than the elasticity modulus (tensile loading). Also, the spring rate of elastomeric materials in shear is more consistent than in tension. The rates and deflections are capable of being symmetrical about the center axis or they can be tuned using annular void  128  and chamfer  130  or by otherwise altering the size or shape of elastomeric body  104  or the rigid structures. An additional advantage is that the rate of deflection for ID shear hub  122  is linear throughout the deflection (until void  128  closes), which adds robustness to the design in regards to the position. This means that any pre-load from positional tolerances will not spike the rates of deflection and make the Noise, Vibration and Harshness (NVH) of the vehicle change with the exhaust geometry tolerances. 
       FIG. 5  illustrates an alternative embodiment of an exhaust isolator assembly  200 . This assembly  200  includes a hanger bracket  202 , an elastomeric body  208 , and a fastener  206 . A “pocket”  226  is formed in the hanger bracket  202  to prevent rotation of the fastener  206  during assembly to the vehicle. The elastomeric body  208  includes a central mounting bore  210  to accommodate a rod hanger (not shown). In other respects, the isolator assembly  200  resembles the isolator assembly  100 . While not shown, it is understood that isolator assembly  200  includes ID and OD shear hubs, as well as a ground out hub, an annular void, and a chamfer as shown on isolator assembly  100 . 
     Referring to  FIG. 6 , another embodiment of a hanger bracket  102 ′ is shown. Hanger bracket  102 ′ is the otherwise identical to hanger bracket  102  with the exception that a bracket mounting face  106 ′ includes a clearance fit opening  118 ′ instead of the press fit aperture  118 , and the opening  118 ′ includes a plurality of spaced apart, interference fit staking ribs  118   a ′. The opening  118 ′ helps to alleviate any excessive hoop stress on the bracket hole, while the staking ribs  118   a ′ fixture the fastener head until rubber overmolding. 
     Referring now to  FIGS. 7-9 , a dual ring isolator assembly  300  (herein simply “isolator”  300 ) is shown in accordance with another embodiment of the present disclosure. The isolator  300  provides the compact size of the isolator assembly  100  but with essentially double the amount of elastomer material being incorporated to even better spread the load across a greater portion of elastomer material of the isolator, and thus enabling even lower stress on the elastomer material when the elastomer is at the full travel strain. This permits even higher stiffness for preload capacity, but with lower stress at the full travel strain. 
     The isolator  300  includes a mounting bracket  302  having a circular mounting bore  302   a  made up of axially aligned bores  302   a   1  and  302   a   2 , and an elastomer shear hub component  304  which may be insert molded onto the mounting bracket  302 . The mounting bracket  302  may be made from aluminum or any other suitably strong material which is resistant to the elements. In this embodiment the mounting bracket  302  has a unique configuration which includes dual, spaced apart circumferential rings  306  that help to form the mounting bore  302   a . The rings  306  extend from sidewall portions  308  and merge into end walls  310 . A bottom wall  312  of the mounting bracket  302  includes an aperture  314  through which a threaded shaft  318  of a fastener  316  is positioned. The fastener  316  enables the isolator  300  to be secured to an external mounting element associated with either an exhaust component or a structural portion of a vehicle. The fastener  316  also includes a head portion  320  which is shaped and of dimensions so that it resides in a pocket  322  of the mounting bracket  302 , as best seen in  FIG. 9 . The pocket  322  may be formed by spaced apart, parallel upstanding shoulder portions or ribs  322   a  (only one being visible in  FIG. 9 ) that project upwardly from an inside surface of the bottom wall  312 . Alternatively, the pocket  322  may effectively be formed by using just one wall or shoulder portion that prevents rotation of a bolt head positioned therein. In either implementation, the pocket  322  prevents the fastener  316  from turning when a threaded nut is being tightened onto the threaded shaft  318 . The fastener  316  may be over-molded (i.e., captured) within the pocket  322  during molding of the elastomer shear hub component  304 . Optionally, adhesives may be used to help secure the head portion  320  to a portion of the elastomer material that lays over the head portion. 
     With further reference to  FIGS. 7 and 8 , the elastomer shear hub component  304  includes a unique mirror image, tandem outer diameter (“OD”) and inner diameter (“ID”) shear hub configuration. This configuration is facilitated by an OD shear hub  324  which is extends between the two circumferential rings  306 , and a pair of ID shear hubs  326  (or “ID shear hub portions”  326 ), formed by voids  328 , which are coupled to the OD shear hub  324  by a transition portion  325 . In this example the ID shear hubs  326  and the voids  328  are mirror images of one another, although in practice they do not necessarily have to have precise, mirror image configurations. Likewise, while the transition portion  325  is shown in  FIGS. 7 and 8  being disposed at an axial midpoint of the OD shear hub  324 , the transition portion could be offset from the axial center of the OD shear hub if desired. 
     It will also be appreciated that while the rings  306  are shown in  FIGS. 7-9  as forming a complete circle, such a configuration could be modified. For example, the rings  306  could form a pair of parallel arches. Still further, the rings  306  need not be circular in shape, but could be modified to be non-circular, and thus take virtually any other shape, to even better meet the needs of a specific application. 
     The OD shear hub  324  and both of the ID shear hubs  326  are located between the end walls  310  of the mounting bracket  302  and thus do not extend axially outwardly from the end walls  310 , as with the isolator  100 . However, the OD shear hub  324  and the ID shear hub  326  could alternatively be formed such that one, or both, extend axially outwardly from the end walls  310  to further restrict sliding. The ID shear hubs  326  are further radially offset from a radial center of the mounting bore  302   a . A central mounting bore  330  extends co-linearly through the ID shear hubs  326  to allow a portion of an external hanger to be received therein. The central mounting bore  330  is thus also radially offset from the radial center of the mounting bore  302   a  in order to provide a vertical offset for preload sag. 
     With further reference to  FIG. 8 , a compression bumper portion  332  of the ID shear hubs  326  projects toward the bottom wall  312 . A partial circumferential void  334 , visible in  FIGS. 7 and 8 , is formed by the removal of a portion of material forming the transition portion  325  adjacent the bottom wall  312 . This decouples tension stress for travel away from the bottom wall  312 . 
     Referring to  FIGS. 10-12 , an isolator assembly  400  in accordance with another embodiment of the present disclosure is shown. Isolator assembly  400  is similar in some respects to isolator  300  and incorporates a dual ring mounting bracket  402  which in this example is identical to mounting bracket  302  except for a large blend  411  to end wall  410  and removal of ribs  322   a . An elastomer shear hub component  404  is included which is similar to elastomer shear hub component  304  in that it includes an OD shear hub portion  424  and a mirror image pair of ID shear hub portions  426 . A central mounting bore  430  extends through the ID shear hub portions  426 . A fastener  416  is over-molded within the mounting bracket  402  in a manner identical to fastener  316 . In this embodiment, however, a compression bumper portion  432  is included, formed in part by void  434 , which extends along a full axial length of the ID shear hub portions  426 . The radius of curvature of the compression bumper portion  432  in this example is the same as the radius of curvature of a lower wall portion  404   a  of the elastomer shear hub component  404 , although the two surfaces need not necessarily be perfectly identical in radius of curvature. The increased surface area and elastomer material provided by the full axial length compression bumper portion  432  even further helps to reduce compressive stress when a ground out condition occurs. The void  434  preferably also incorporates increased radius stress relief portions  434   a  at its opposite ends. The width of void  434 , as well as its circumferential length, may vary significantly. However, in most instances the width of the void  434  may be between about 2 mm and the full thickness of the elastomer shear hub component  404 . The void  434  enables the decoupling of tension elements to adjacent side portions of the elastomer shear hub component  404 . 
     An additional benefit of the isolator  400  of  FIGS. 10-12  results from an added amount of material at an outer end of one of the ID shear hubs  426  which forms a small ridge  430   a . The ridge  430   a  acts as an interference section on an inner diameter of the ID shear hub  426 , as shown in  FIG. 12 . The ridge  426   a  even further helps the isolator assembly  400  to avoid any possible noise and/or contamination issues resulting from a less than perfect coupling with an end portion of an external hanger positioned in the central mounting bore  430 . 
     Referring to  FIGS. 13 and 14 , an isolator assembly  500  is shown in accordance with another embodiment of the present disclosure. The isolator assembly  500  is similar to the isolator assembly  400  and includes a mounting bracket  502  which houses an elastomeric isolator component  504 . The elastomeric isolator component  504  is identical to the component  404  shown in  FIGS. 10-12  with the exception that the mounting bracket  502  is formed with a through bore  514  through which a threaded fastener  516  is inserted. A clamp face  540  may be a conventional flat surface with an anti-rotation feature. Alternatively, the clamp face  540  may be an extruded arch joint, as shown in  FIGS. 13 and 14 , or possibly may even have a V-block configuration. This permits a clamping attachment of the mounting bracket  502  to an optimized small face with precise clocking (i.e., precise angular orientation). 
     Referring to  FIG. 15 , an isolator assembly  600  is shown in accordance with another embodiment of the present disclosure. The isolator assembly  600  is similar to the isolator  300  and includes a mounting bracket  602  within which an elastomer shear hub component  604  is molded, and which encapsulates a head portion of a threaded fastener  616 . The elastomer shear hub component  604  includes an OD shear hub  624 , an ID shear hub  626 , and a bore  630  extending through ID shear hub. The isolator assembly  600  differs, however, in that no void is included in the elastomer shear hub component  604 . The lack of a void  334  or  434  provides an even higher ground out rating for the isolator assembly  600 . In addition, the mounting bracket  602  has bracket ribs  602   a  which are removed , and the end walls  610  are of reduced height as well. These modifications even further reduce the stress on the elastomer material. Still another embodiment could have the isolator assembly  600  with an even taller overall height as a result of making the OD shear hub  624  section, which lays above the bolt head of the fastener, even thicker. 
     While various embodiments have been described, those skilled in the art will recognize modifications or variations which might be made without departing from the present disclosure. The examples illustrate the various embodiments and are not intended to limit the present disclosure. Therefore, the description and claims should be interpreted liberally with only such limitation as is necessary in view of the pertinent prior art.