Abstract:
An elastomeric isolator has an elastomeric body which defines a void extending into the elastomeric body from one side and a void extending into the elastomeric body from the opposite side. One member for attaching the elastomeric body to a component is located inside of the two voids and another member for attaching the elastomeric body to a component is located outside of the two voids. The two voids overlap a specified distance to determine the stresses and stiffness for the isolator.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an automotive exhaust system isolator. More particularly, the present invention relates to an isolator which is configured to provide a very soft on-center rate but yet have the ability to endure spike durability loads. 
     BACKGROUND OF THE INVENTION 
     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 prior art exhaust mounts or isolators have included rubber isolators which are 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. The metal stud is provided with an enlarged head that can be forced through the aperture in the isolator, but it cannot be readily removed from the isolator. The opposite end of the stud 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 of a spoke design where spokes are loaded in tension and compression and a shear leg design that include a leg that is subjected to shearing in the primary loading direction. Most elastomers which are utilized for exhaust isolators exhibit poor tensile fatigue properties stemming from low tear strength properties. The preferred method to load the elastomeric material is in compression or shear. 
     The prior art puck design is the simplest design, and as discussed above, two pins are inserted at opposite ends of the elastomer and the loads inflict pure 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 or rigid bands are typically designed inside or around the outside of the elastomeric puck. The advantage of this design is its ability to swivel about one hanger hole to accommodate large positional tolerances for the hanger. 
     The prior art 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 positioned within the deflection zone. 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. 
     The prior art shear leg design has 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 shear style loading. In addition, this 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. 
     SUMMARY OF THE INVENTION 
     The present invention provides the art with an elastomeric bushing which uses radial loading to avoid the tension stress loading of the bushing. The radial loading cause shear stresses of the elastomeric bushing regardless of the direction of the loading. Tuning for rate and deflection in specific directions can be independent from other directions by altering voids in the elastomeric bushings. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of an elastomeric isolator in accordance with the present invention; 
         FIG. 2  is a cross-sectional view of the elastomeric isolator illustrated in  FIG. 1 ; 
         FIG. 3  is a perspective view partially in cross-section illustrating the inner metal of the elastomeric isolator illustrated in  FIG. 1 ; 
         FIG. 4  is a perspective view partially in cross-section illustrating the directions of isolation for the elastomeric isolator illustrated in  FIG. 1 ; 
         FIG. 5  is a perspective view of an elastomeric isolator in accordance with another embodiment of the present invention; 
         FIG. 6  is a cross-sectional view of the elastomeric isolator illustrated in  FIG. 5 ; 
         FIG. 7  is a perspective view of an elastomeric isolator in accordance with another embodiment of the present invention; 
         FIG. 8  is a cross-sectional view of the elastomeric isolator illustrated in  FIG. 7 ; 
         FIG. 9  is a perspective view of an elastomeric isolator in accordance with another embodiment of the present invention; 
         FIG. 10  is a cross-sectional view of the elastomeric isolator illustrated in  FIG. 9 ; 
         FIG. 11  is a perspective view of an elastomeric isolator in accordance with another embodiment of the present invention; 
         FIG. 12  is a cross-sectional view of the elastomeric isolator illustrated in  FIG. 11 ; 
         FIG. 13  is a cross-sectional view of the elastomeric isolator illustrated in  FIG. 11  taken 90 degrees from the cross-section illustrated in  FIG. 12 ; 
         FIG. 14  is a side view of an elastomeric isolator in accordance with another embodiment of the present invention; 
         FIG. 15  is a cross-sectional view of the elastomeric isolator illustrated in  FIG. 14 ; 
         FIG. 16  is a cross-sectional view of the elastomeric isolator illustrated in  FIG. 14  taken 90 degrees from the cross-section illustrated in  FIG. 15 ; 
         FIG. 17  is a side view of an elastomeric isolator in accordance with another embodiment of the present invention; 
         FIG. 18  is a cross-sectional view of the elastomeric isolator illustrated in  FIG. 17 ; 
         FIG. 19  is a perspective view of an elastomeric isolator in accordance with another embodiment of the present invention; 
         FIG. 20  is a cross-sectional view of the elastomeric isolator illustrated in  FIG. 19 ; 
         FIG. 21  is a side view of an elastomeric isolator in accordance with another embodiment of the present invention; 
         FIG. 22  is a cross-sectional view of the elastomeric isolator illustrated in  FIG. 21 ; and 
         FIG. 23  is a perspective view of an exhaust system which incorporates the unique exhaust isolators in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     Referring now to the drawings, there is shown in  FIG. 23  an exhaust system which includes the exhaust system isolators in accordance with the present invention and which is designated generally by the reference numeral  10 . 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 an intermediate pipe  12 , a muffler  14 , a tailpipe  16  and a plurality of isolator assemblies of various designs. Intermediate pipe  12  is typically connected to the engine or to a catalytic converter (not shown) which is then attached to an exhaust pipe which extends between the engine and the catalytic converter. The catalytic converter 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. Also, intermediate pipe  12  can be attached to a plurality of catalytic converters which connect together prior to reaching muffler  14  using intermediate pipe  12  or the vehicle can have a plurality of exhaust pipes, a plurality of catalytic converters, a plurality of intermediate pipes  12  and a plurality of mufflers  14  which connect together using a single or multiple tailpipes  16 . In addition, the exhaust system isolator of the present invention is applicable to any type of exhaust system including but not limited to dual exhaust system which have two separate parallel exhaust systems 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 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 which mount exhaust system  10  to the vehicle while at the same time, isolate the movement of exhaust system  10  with respect to the vehicle. 
     Referring now to  FIGS. 1-4 , an exhaust system isolator  30  in accordance with the present invention is illustrated. Isolator  30  comprises an elastomeric body  32  within which a reinforcement inner metal  34  is molded. Isolator  30  is a two-hole shear hub design where elastomeric body  32  defines a pair of holes  36  and  38  which are designed to accept a pair of inner tubes or hanger pins  40  and  42 . One of hanger pins  40  or  42  is secured to the frame or the mounting structure of the vehicle and the other hanger pin  40  or  42  is secured to exhaust system  10 . Thus, exhaust system  10  is secured to the vehicle through isolator  30 . 
     Elastomeric body  32  defines an outer circumferential void  44  and an inner circumferential void  46 . While voids  44  and  46  are illustrated as asymmetrical with respect to the center of hole  38 , it is within the scope of the present invention to have voids  44  and  46  symmetrical with respect to hole  38  if desired. The design of the voids, specifically their thickness, will determine the amount of travel until the rate of the bushing spikes up due at the closing of the voids. Until the closing of the voids, the radial loads cause pure shear regardless of the loading direction. As illustrated in  FIG. 4 , the loading direction can be in any one of the three axial directions. Tuning for rate and deflection in selective directions can be accomplished independently from other directions by altering voids  44  and  46  in the required sectors. As can be seen in  FIG. 2 , void  44  overlaps with void  46 . The larger the overlap between voids  44  and  46 , the lower the stresses and stiffness for isolator  30 . The peak loads bottom out voids  44  and  46  and start to impart compressive stress to elastomeric body  32  from hanger pins  40  and/or  42  and inner metal  34  by sandwiching. As illustrated in  FIG. 3 , inner metal  34  extends around the periphery of elastomeric body  32 . The bottoming out of voids  44  and  46  and subsequent compression of elastomeric body  32  makes the stress spread out to all of the material between hanger pins  40  and  42  and inner metal  34  rather than having the stress concentrated in a spoke or leg cross-section as in the prior art. This permits the stress magnitude to decrease as well as changing the stress loading to a more favorable type. 
     Thus, exhaust system isolator  30  provides a very soft on-center rate which is desirable with the ability to endure spike durability loads after closing of the voids. 
     Referring now to  FIGS. 5 and 6 , an exhaust system isolator  60  in accordance with another embodiment of the present invention is illustrated. Isolator  60  comprises an elastomeric body  62  within which an inner reinforcement  64  and an outer reinforcement  66  are molded. Isolator  60  is a single hole shear hub design where elastomeric body  62  defines a hole  68  which is designed to accept an inner tube or hanger pin  70 . Hanger pin  70  is secured to exhaust system  10  and isolator  60  is secured to the frame or the mounting structure of the vehicle using outer reinforcement  66 . Thus, exhaust system  10  is secured to the vehicle through isolator  60 . 
     Elastomeric bushing  62  defines an outer circumferential void  74  and an inner circumferential void  76 . While voids  74  and  76  are illustrated as symmetrical with respect to the center of hole  68 , it is within the scope of the present invention to have voids  74  and  76  asymmetrical with respect to hole  68  if desired. The design of the voids, specifically their thickness, will determine the amount of travel until the rate of the bushing spikes up at the closing of the voids. Until the closing of the voids, the radial loads cause pure shear regardless of the loading direction. Similar to that discussed above for isolator  30 , isolator  60  can be loaded in any of the three axial directions illustrated in  FIG. 4 . Tuning for rate and deflection in selective directions can be accomplished independently from other directions by altering voids  74  and  76  in the required sectors. As can be seen in  FIG. 6 , void  74  overlaps with void  76 . The larger the overlap between voids  74  and  76 , the lower the stresses and stiffness for isolator  60 . Voids  74  and  76  are located between inner reinforcement  64  and outer reinforcement  66  such the peak loads bottom out voids  74  and  76  and start to impart compressive stress to elastomeric body  62  from inner reinforcement  64  and outer reinforcement  66  by sandwiching. As illustrated in  FIGS. 5 and 6 , outer reinforcement  66  comprises a generally U-shaped bracket  80  which is adapted to be secured to the frame or the mounting structure of the vehicle and a generally straight bracket  82  which extends between the two legs or U-shaped bracket  80  and is secured to each leg of U-shaped bracket  80  by crimping or by any other means known in the art. Thus, the bottoming out of voids  74  and  76  and subsequent compression of elastomeric body  62  makes the stress spread out to all of the material between inner reinforcement  64  and outer reinforcement  66  as well as between hanger pin  70  and inner reinforcement  64  rather than having the stress concentrated in a spoke or leg cross-section as in the prior art. This permits the stress magnitude to decrease as well as changing the stress loading to a more favorable type. 
     Thus, exhaust system isolator  60 , similar to isolator  30 , provides a very soft on-center rate which is desirable with the ability to endure spike durability loads after closing of the voids. 
     Referring now to  FIGS. 7 and 8 , an exhaust system isolator  90  in accordance with another embodiment of the present invention is illustrated. Isolator  90  comprises an elastomeric body  92  within which an inner reinforcement  94  and an outer reinforcement  96  are molded. Isolator  90  is a three-hole shear hub design where elastomeric body  92  defines a centrally located hole  98  which is designed to accept a single hanger pin  42  which is secured to exhaust system  10  and a pair of holes  100  which are each designed to accept a hanger pin  40 . Each hanger pin  40  is secured to the frame or mounting structure of the vehicle. Thus, exhaust system  10  is secured to the vehicle through isolator  90 . By using two hanger pins  40 , anti-rotation is provided to isolator  90  to support the three degrees of freedom or motion of hanger pin  42  as illustrated in  FIG. 4  for isolator  30 . 
     Elastomeric body  92  defines an outer circumferential void  104  and an inner circumferential void  106 . While voids  104  and  106  are illustrated as symmetrical with respect to the center of hole  98 , it is within the scope of the present invention to have voids  104  and  106  asymmetrical with respect to hole  98  if desired. The design of the voids, specifically their thickness, will determine the amount of travel until the rate of the bushing spikes up due at the closing of the voids. Until the closing of the voids, the radial loads cause pure shear regardless of the loading direction. As illustrated in  FIG. 4 , the loading direction can be in any one of the three axial directions. Tuning for rate and deflection in selective directions can be accomplished independently from other directions by altering the voids in the required sectors. As can be seen in  FIG. 8 , void  104  overlaps with void  106 . The larger the overlap between voids  104  and  106 , the lower the stresses and stiffness for isolator  90 . The peak loads bottom out voids  104  and  106  and start to impart compressive stress to elastomeric body  92  from voids  104  and  106  are located between inner reinforcement  94  and outer reinforcement  96  such that peak loads bottom out voids  104  and  106  and start to impart compressive stress to elastomeric body  92  from inner reinforcement  94  and outer reinforcement  96  by sandwiching. As illustrated in  FIGS. 7 and 8 , inner reinforcement  94  extends around hole  98  and outer reinforcement  96  extends around the periphery of elastomeric body  92 . Thus, the bottoming out of voids  104  and  106  and subsequent compression of elastomeric body  92  makes the stress spread out to all of the material between inner reinforcement  94  and outer reinforcement  96  as well as between hanger pin  42  and inner reinforcement  94  and outer reinforcement  96  and hanger pins  42 . This is preferred over the stress concentrated in a spoke or leg cross-section as in the prior art. This permits the stress magnitude to decrease as well as changing the stress loading to a more favorable type. 
     Thus, exhaust system isolator  90 , similar to isolator  30 , provides a very soft on-center rate which is desirable with the ability to endure spike durability loads after closing of the voids. 
     Referring now to  FIGS. 9 and 10 , an exhaust system isolator  120  in accordance with another embodiment of the present invention is illustrated. Isolator  120  comprises an elastomeric body  122  within which an inner reinforcement  124  and an outer reinforcement  126  are molded. Isolator  120  is a hole shear hub design where elastomeric body  122  defines a hole  128  which is designed to accept an inner tube or hanger pin  42 . Hanger pin  42  is secured to exhaust system  10  and isolator  120  is secured to the frame or the mounting structure of the vehicle using outer reinforcement  126 . Thus, exhaust system  10  is secured to the vehicle through isolator  120 . 
     Elastomeric bushing  122  defines an outer circumferential void  134  and an inner circumferential void  136 . While voids  134  and  136  are illustrated as symmetrical with respect to center of hole  128 , it is within the scope of the present invention to have voids  134  and  136  asymmetrical with respect to hole  128  if desired. The design of the voids, specifically their thickness will determine the amount of travel until the rate of the bushing spikes up at the closing of voids  134  and  136 . Until the closing of voids  134  and  136 , the radial loads cause pure shear regardless of the loading direction. Similar to that discussed above for isolator  30 , isolator  120  can be loaded in any of the three axial directions as shown in  FIG. 4 . Tuning for rate and deflection in selective directions can be accomplished independently from other directions by altering voids  134  and  136  in the required sectors. As can be seen in  FIG. 10 , void  134  overlaps with void  136 . The larger the overlap between voids  134  and  136 , the lower the stresses and stiffness for isolator  60 . Voids  134  and  136  are located between inner reinforcement  124  and outer reinforcement  126  such the peak loads bottom out voids  134  and  136  and start to impart compressive stress to elastomeric body  132  from inner reinforcement  134  and outer reinforcement  136  by sandwiching. As illustrated in  FIGS. 9 and 10 , outer reinforcement  126  comprises a generally U-shaped bracket  140  which is adapted to be secured to the frame or the mounting structure of the vehicle and a bracket  142  which extends between the two legs or U-shaped bracket  140  and is secured to each leg of U-shaped bracket  140  by crimping or by any other means known in the art. Thus, the bottoming out of voids  134  and  136  and subsequent compression of elastomeric body  122  makes the stress spread out to all of the material between inner reinforcement  124  and outer reinforcement  126  as well as between hanger pin  42  and inner reinforcement  124  rather than having the stress concentrated in a spoke or leg cross-section as in the prior art. This permits the stress magnitude to decrease as well as changing the stress loading to a more favorable type. 
     Thus, exhaust system isolator  120 , similar to isolator  30 , provides a very soft on-center rate which is desirable with the ability to endure spike durability loads after closing of the voids. 
     Referring now to  FIGS. 11-13 , an exhaust system isolator  150  in accordance with another embodiment of the present invention is illustrated. Isolator  150  comprises an elastomeric body  152  within which an inner reinforcement  154  and an outer reinforcement  156  are molded. Isolator  150  is a single hole shear hub design where elastomeric body  152  defines a hole  158  which is designed to accept an inner tube or hanger pin  42 . Hanger pin  42  is secured to exhaust system  10  and isolator  150  is secured to the frame or the mounting structure of the vehicle using outer reinforcement  156 . Thus, exhaust system  10  is secured to the vehicle through isolator  150 . 
     Elastomeric bushing  152  defines an outer circumferential void  164  and an inner circumferential void  166 . While voids  164  and  166  are illustrated as asymmetrical with respect to the center of hole  158 , it is within the scope of the present invention to have voids  164  and  166  symmetrical with respect to hole  158  if desired. The design of the voids, specifically their thickness, will determine the amount of travel until the rate of the bushing spikes up at the closing of the voids. Until the closing of the voids, the radial loads cause pure shear regardless of the loading direction. Similar to that discussed above for isolator  30 , isolator  150  can be loaded in any of the three axial directions as illustrated in  FIG. 4 . Tuning for rate and deflection in selective directions can be accomplished independently from other directions by altering the voids in the required sectors. As can be seen in  FIG. 12 , void  164  overlaps with void  166 . The larger the overlap between voids  164  and  166 , the lower the stresses and stiffness for isolator  60 . Voids  164  and  166  are located between inner reinforcement  154  and outer reinforcement  156  such the peak loads bottom out voids  164  and  166  and start to impart compressive stress to elastomeric body  162  from inner reinforcement  164  and outer reinforcement  166  by sandwiching. As illustrated in  FIGS. 11-13 , outer reinforcement  156  comprises a generally U-shaped bracket  170  which is adapted to be secured to the frame or the mounting structure of the vehicle and a bracket  172  which extends between the two legs or U-shaped bracket  170  and is secured to each leg of U-shaped bracket  170  by crimping or by an other means known in the art. Thus, the bottoming out of voids  164  and  166  and subsequent compression of elastomeric body  152  makes the stress spread out to all of the material between inner reinforcement  154  and outer reinforcement  156  as well as between hanger pin  160  and inner reinforcement  154  rather than having the stress concentrated in a spoke or leg cross-section as in the prior art. This permits the stress magnitude to decrease as well as changing the stress loading to a more favorable type. 
     Thus, exhaust system isolator  150 , similar to isolator  30 , provides a very soft on-center rate which is desirable with the ability to endure spike durability loads after closing of the voids. 
     Referring now to  FIGS. 14-16 , an exhaust system isolator  180  in accordance with another embodiment of the present invention is illustrated. Isolator  180  comprises an elastomeric body  182  within which an outer reinforcement  186  is molded. Isolator  180  is a double hole shear hub design where elastomeric body  182  defines a pair of holes  188  each of which are designed to accept an inner tube or hanger pin  42 . Hanger pins  42  are secured to exhaust system  10  and isolator  180  is secured to the frame or the mounting structure of the vehicle using outer reinforcement  186 . Thus, exhaust system  10  is secured to the vehicle through isolator  180 . 
     Elastomeric bushing  182  defines an outer circumferential void  194  and an inner circumferential void  196 . While voids  194  and  196  are illustrated as symmetrical with respect to the center of isolator  180 , it is within the scope of the present invention to have voids  194  and  196  asymmetrical with respect to isolator  180  if desired. The design of the voids, specifically their thickness, will determine the amount of travel until the rate of the bushing spikes up at the closing of the voids. Until the closing of the voids, the radial loads cause pure shear regardless of the loading direction. Similar to that discussed above for isolator  30 , isolator  180  can be loaded in any of the three axial directions as illustrated in  FIG. 4 . Tuning for rate and deflection in selective directions can be accomplished independently from other directions by altering the voids in the required sectors. As can be seen in  FIG. 16 , void  194  overlaps with void  196 . The larger the overlap between voids  194  and  196 , the lower the stresses and stiffness for isolator  60 . Voids  194  and  196  are located within outer reinforcement  186  such the peak loads bottom out voids  194  and  196  and start to impart compressive stress to elastomeric body  192  from hanger pins  42  and outer reinforcement  196  by sandwiching. As illustrated in  FIGS. 14-16 , outer reinforcement  186  comprises a generally U-shaped bracket  200  which is adapted to be secured to the frame or the mounting structure of the vehicle and a bracket  202  which extends between the two legs or U-shaped bracket  200  and is secured to each leg of U-shaped bracket  200  by crimping or by an other means known in the art. Thus, the bottoming out of voids  194  and  196  and subsequent compression of elastomeric body  182  makes the stress spread out to all of the material between hanger pins  42  and outer reinforcement  186  rather than having the stress concentrated in a spoke or leg cross-section as in the prior art. This permits the stress magnitude to decrease as well as changing the stress loading to a more favorable type. 
     Thus, exhaust system isolator  180 , similar to isolator  30 , provides a very soft on-center rate which is desirable with the ability to endure spike durability loads after closing of the voids. 
     Referring now to  FIGS. 17 and 18 , an exhaust system isolator  210  in accordance with another embodiment of the present invention is illustrated. Isolator  210  comprises an elastomeric body  212  within which an inner reinforcement  214  and an outer reinforcement  216  are molded. Isolator  210  is a single hole shear hub design where elastomeric body  212  defines a hole  218  which is designed to accept an inner tube or hanger pin  42 . Hanger pin  42  is secured to exhaust system  10  and isolator  210  is secured to the frame or the mounting structure of the vehicle using outer reinforcement  216 . Thus, exhaust system  10  is secured to the vehicle through isolator  210 . 
     Elastomeric bushing  212  defines an outer circumferential void  224  and an inner circumferential void  226 . While voids  224  and  226  are illustrated as asymmetrical with respect to the center of hole  218 , it is within the scope of the present invention to have voids  224  and  226  symmetrical with respect to hole  218  if desired. The design of the voids, specifically their thickness, will determine the amount of travel until the rate of the bushing spikes up at the closing of the voids. Until the closing of the voids, the radial loads cause pure shear regardless of the loading direction. Similar to that discussed above for isolator  30 , isolator  210  can be loaded in any of the three axial directions as illustrated in  FIG. 4 . Tuning for rate and deflection in selective directions can be accomplished independently from other directions by altering the voids in the required sectors. As can be seen in  FIG. 18 , void  224  overlaps with void  226 . The larger the overlap between voids  224  and  226 , the lower the stresses and stiffness for isolator  60 . Voids  224  and  226  are located between inner reinforcement  214  and outer reinforcement  216  such the peak loads bottom out voids  224  and  226  and start to impart compressive stress to elastomeric body  222  from inner reinforcement  224  and outer reinforcement  226  by sandwiching. As illustrated in  FIGS. 17 and 18 , outer reinforcement  216  comprises a generally U-shaped bracket  230  which is adapted to be secured to the frame or the mounting structure of the vehicle and a bracket  232  which is disposed within a bore defined by U-shaped bracket  230  and is secured to U-shaped bracket  230  by a press fitting or by an other means known in the art. Thus, the bottoming out of voids  224  and  226  and subsequent compression of elastomeric body  212  makes the stress spread out to all of the material between inner reinforcement  214  and outer reinforcement  216  as well as between hanger pin  42  and inner reinforcement  214  rather than having the stress concentrated in a spoke or leg cross-section as in the prior art. This permits the stress magnitude to decrease as well as changing the stress loading to a more favorable type. 
     Thus, exhaust system isolator  210 , similar to isolator  30 , provides a very soft on-center rate which is desirable with the ability to endure spike durability loads after closing of the voids. 
     Referring now to  FIGS. 19 and 20 , an exhaust system isolator  240  in accordance with another embodiment of the present invention is illustrated. Isolator  240  comprises an elastomeric body  242  within which an inner reinforcement  244  and an outer reinforcement  246  are molded. Isolator  240  is a single hole shear hub design where elastomeric body  242  defines a hole  248  which is designed to accept an inner tube or hanger pin  42 . Hanger pin  42  is secured to exhaust system  10  and isolator  240  is secured to the frame or the mounting structure of the vehicle using outer reinforcement  246 . Thus, exhaust system  10  is secured to the vehicle through isolator  240 . 
     Elastomeric bushing  242  defines an outer circumferential void  254  and an inner circumferential void  256 . While voids  254  and  256  are illustrated as symmetrical with respect to the center of hole  248 , it is within the scope of the present invention to have voids  254  and  256  asymmetrical with respect to hole  248  if desired. The design of the voids, specifically their thickness, will determine the amount of travel until the rate of the bushing spikes up at the closing of the voids. Until the closing of the voids, the radial loads cause pure shear regardless of the loading direction. Similar to that discussed above for isolator  30 , isolator  240  can be loaded in any of the three axial directions. Tuning for rate and deflection in selective directions can be accomplished independently from other directions by altering the voids in the required sectors. As can be seen in  FIG. 20 , void  254  overlaps with void  256 . The larger the overlap between voids  254  and  256 , the lower the stresses and stiffness for isolator  60 . Voids  254  and  256  are located between inner reinforcement  244  and outer reinforcement  246  such the peak loads bottom out voids  254  and  256  and start to impart compressive stress to elastomeric body  252  from inner reinforcement  254  and outer reinforcement  256  by sandwiching. As illustrated in  FIGS. 19 and 20 , outer reinforcement  246  comprises a generally rectangular shaped bracket  260  which is adapted to be secured to the frame or the mounting structure of the vehicle and a bracket  262  which extends around the periphery of elastomeric body  252 . Thus, the bottoming out of voids  254  and  256  and subsequent compression of elastomeric body  242  makes the stress spread out to all of the material between inner reinforcement  244  and outer reinforcement  246  as well as between hanger pin  42  and inner reinforcement  244  rather than having the stress concentrated in a spoke or leg cross-section as in the prior art. This permits the stress magnitude to decrease as well as changing the stress loading to a more favorable type. 
     Thus, exhaust system isolator  240 , similar to isolator  30 , provides a very soft on-center rate which is desirable with the ability to endure spike durability loads after closing of the voids. 
     Referring now to  FIGS. 21 and 22 , an exhaust system isolator  270  in accordance with another embodiment of the present invention is illustrated. Isolator  270  comprises an elastomeric body  272  within which an inner reinforcement  274  and an outer reinforcement  276  are molded. Isolator  270  is a single hole shear hub design where elastomeric body  272  defines a hole  278  which is designed to accept an inner tube or hanger pin  42 . Hanger pin  42  is secured to exhaust system  10  and isolator  270  is secured to the frame or the mounting structure of the vehicle using outer reinforcement  276 . Thus, exhaust system  10  is secured to the vehicle through isolator  270 . 
     Elastomeric bushing  272  defines an outer circumferential void  284  and an inner circumferential void  286 . While voids  284  and  286  are illustrated as symmetrical with respect to the center of hole  278 , it is within the scope of the present invention to have voids  284  and  286  asymmetrical with respect to hole  278  if desired. The design of the voids, specifically their thickness, will determine the amount of travel until the rate of the bushing spikes up at the closing of the voids. Until the closing of the voids, the radial loads cause pure shear regardless of the loading direction. Similar to that discussed above for isolator  30 , isolator  270  can be loaded in any of the three axial directions. Tuning for rate and deflection in selective directions can be accomplished independently from other directions by altering the voids in the required sectors. As can be seen in  FIG. 22 , void  284  overlaps with void  286 . The larger the overlap between voids  284  and  286 , the lower the stresses and stiffness for isolator  60 . Voids  284  and  286  are located between inner reinforcement  274  and outer reinforcement  276  such the peak loads bottom out voids  284  and  286  and start to impart compressive stress to elastomeric body  282  from inner reinforcement  274  and outer reinforcement  276  by sandwiching. As illustrated in  FIGS. 21 and 22 , outer reinforcement  276  comprises a bracket  290  which is adapted to be secured to the frame or the mounting structure of the vehicle and a bracket  292  which is disposed within a bore defined by bracket  290  and is secured to bracket  290  by press fitting or by an other means known in the art. Thus, the bottoming out of voids  284  and  286  and subsequent compression of elastomeric body  272  makes the stress spread out to all of the material between inner reinforcement  274  and outer reinforcement  276  as well as between hanger pin  42  and inner reinforcement  274  rather than having the stress concentrated in a spoke or leg cross-section as in the prior art. This permits the stress magnitude to decrease as well as changing the stress loading to a more favorable type. 
     Thus, exhaust system isolator  270 , similar to isolator  30 , provides a very soft on-center rate which is desirable with the ability to endure spike durability loads after closing of the voids. 
     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.