WO1997035123A1

WO1997035123A1 - Voided bushing for vehicle suspensions

Info

Publication number: WO1997035123A1
Application number: PCT/US1997/004356
Authority: WO
Inventors: Scott Allen Dilling
Original assignee: Boler Co
Current assignee: Boler Co
Priority date: 1996-03-21
Filing date: 1997-03-06
Publication date: 1997-09-25
Anticipated expiration: 1998-09-21
Also published as: AU2333797A

Abstract

A voided bushing (50) which is useful in the trailing arm suspensions of tractor-trailers. The bushing (50) includes an elastic, generally cylindrical-shaped body (51) formed with a central opening (52) which passes completely through the body (51) about its longitudinal axis. A rigid metal sleeve (53) is friction fitted in the central opening (52) and is adhesively bonded to the body (51) at the peripheral surface (52) of the sleeve. An improved void (54) is formed in each of the top and bottom portions of each side of the body (51). Each void (54) is generally radially inwardly curving, elongated rectangular-shaped having increased size bulbous or tear-drop shaped ends. The voids (54) can also be described as radially inwardly curving, elongated dog-bone shaped. Preferably at least about forty percent of the total area of each void (54), corresponding generally to the increased size bulbous ends, extends beyond a pair of spaced imaginary vertical lines which are tangential to the front and rear outer surfaces of the sleeve (53). The improved voided bushing (50) achieves the required load and deflection ratios or static rates of varying levels in different directions for semi-trailer suspension applications, and also eliminates premature bushing failure by providing long service life under severe loading conditions.

Description

VOIDED BUSHING FOR VEHICLE SUSPENSIONS

BACKGROUND OF THE INVENTION

TECHNICAL FIELD

The invention relates to bushings and in partic¬ ular to bushings for vehicle suspensions. More particu¬ larly, the invention is directed to bushings formed with generally curved dog-bone shaped voids to provide the required load and deflection characteristics found in prior art voided bushings, but which additionally provides optimized durability characteristics which are necessary for bushings used in the suspensions typically found on tractor-trailers.

BACKGROUND ART

Prior art voided bushings have been utilized on the suspensions of wheeled vehicles, and in particular on the trailing arm suspensions of tractor-trailers or semi- trailers, for many years. Prior art voided bushings were commonly referred to as trifunctional because they provid¬ ed the necessary load and deflection ratios, or static rates, of varying amounts in different directions for semi-trailer suspension applications. More specifically, the bushing static rate typically is required to be stiff in the horizontal radial direction, so that the axle supported by the tractor-trailer suspension remains substantially perpendicular to the direction of movement of the vehicle despite horizontal loading which may be placed on the axle and bushing. Conversely, the bushing rate typically needs to be relatively soft in the vertical radial direction, to enable the suspension and bushing to absorb vertical loading shocks and provide a smooth ride for the vehicle occupants and any cargo carried by the vehicle. The bushing voids make possible the soft verti¬ cal radial static rate, and in combination with the large size of the bushing enable the bushing and suspension to absorb angular loading or deflections placed on the vehicle axles and bushings to prevent the vehicle from rolling over under such uneven loads.

Although the prior art voided bushing provided the required static rates for semi-trailer trailing arm suspension applications, it was never optimized for durability requirements. Yet, due to the large size of the bushing needed to satisfy tractor-trailer suspension roll characteristics, the prior art voided bushing provid- ed excellent durability in most situations. However, in recent years tractor-trailer manufacturers have been requiring longer warranties on suspensions and in turn their components including bushings, while at the same time requiring suspensions and bushings to withstand increased loads. Under such severe loading conditions, prior art voided bushings have been found to wear out sooner than their expected life under less severe loading conditions. Thus, a long-standing need in the art for a new bushing design has been identified, in order to satisfy the new dual requirements of longer life under increased loading conditions, while still meeting the desired static rate characteristics.

More specifically, when placed under severe loading conditions, cracks form in the prior art voided bushing adjacent to certain areas of each void as well as other areas of the bushing remote from the voids. Such cracking shortens the useful life of the prior art voided bushing, and makes it an impractical bushing choice for semi-trailer suspensions in view of the new requirements of longer suspension/bushing life under severe loading conditions.

The present invention solves the problem of cracking of the bushing under severe loading conditions, generally by changing the shape of the voids. As a result, the voided bushing of the present invention has a life expectancy under severe loading conditions of from about 3 to about 4 times longer than prior art voided bushings placed under similar loads, and still achieves the required static rates for tractor-trailer suspension applications.

SUMMARY OF THE INVENTION Objectives of the present invention include providing a voided bushing for semi-trailer suspensions which provides required load and deflection ratios or static rates under severe loading conditions, yet which lasts from about 3 to about 4 times longer than prior art voided bushings subjected to similar loads.

Another objective of the present invention is to provide such a voided bushing for semi-trailer suspensions which can be manufactured for generally the same cost as prior art voided bushings. These objectives and advantages are obtained by the bushing for a vehicle suspension of the present inven¬ tion, the general nature of which may be stated as includ¬ ing a bushing for a vehicle suspension, the bushing including an elastic, generally cylindrical-shaped body having a pair of spaced-apart sides and being formed with a central opening which passes completely through the body and each of the sides about the longitudinal axis of the body, a rigid sleeve immovably mounted in the central opening, the rigid sleeve outside diameter being generally equal to the central opening diameter, the sleeve extend¬ ing substantially the entire longitudinal length of the central opening to facilitate mounting of the bushing on a vehicle suspension, a pair of spaced-apart voids formed in each of the elastic body sides, the pair of voids being formed in each of the sides above and below the central opening, and an imaginary vertical center of each void being disposed about 90° from an imaginary horizontal plane passing transversely through the body when the bushing is mounted on a vehicle suspension, the voids each being generally radially inwardly curving, elongated rectangu¬ lar-shaped and having an increased size bulbous shape at each of its ends, wherein substantially the entire in¬ creased size of the bulbous shape portions of each of the voids extend beyond an area bounded by a pair of spaced imaginary vertical lines located tangential to an outer surface of the sleeve, so that the bushing provides satisfactory static rates and durability when the vehicle suspension is subjected to severe loading conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred embodiments of the invention, illustrative of the best mode in which applicant has contemplated applying the principles, is set forth in the following description and is shown in the drawings and is particularly and distinctly pointed out and set forth in the appended claims.

FIG. 1 is a fragmentary elevational view of a tractor-trailer suspension system of the type currently in use and incorporating a prior art voided bushing, with hidden parts represented by broken lines;

FIG. 2 is a perspective view of a prior art voided bushing; FIG. 3 is a top view of the prior art voided bushing of FIG. 2;

FIG. 4 is a front view of the prior art voided bushing of FIGS. 2 and 3;

FIG. 5 is a side view of the prior art voided bushing of FIGS. 2 through 4;

FIG. 6 is a sectional view taken along line 6-6 Of FIG. 5;

FIG. 7 is a side view of the prior art voided bushing of FIGS. 2-6, showing common sites of cracking- type failure caused in the bushing after it is subjected to severe loading conditions,-

FIG. 8 is a perspective view of the voided bushing of the present invention;

FIG. 9 is a top view of the voided bushing of FIG. 8;

FIG. 10 is a front view of the voided bushing of FIGS. 8-9,-

FIG. 11 is a side view of the voided bushing of FIGS. 8-10;

FIG. 12 is a sectional view taken along line 12- 12 of FIG. 11; and

FIG. 13 is a side view of a second embodiment of the voided bushing of the present invention.

Similar numerals refer to similar parts through¬ out the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A prior art voided bushing is indicated general¬ ly at 20 and is shown in FIG. 1 in a common type of environment in which it is used. More specifically, such an environment can be found on a conventional vehicle such as a truck or a tractor-trailer (not shown) . This envi- ronment is a trailing arm suspension which is indicated generally at 21 and is representative of one type of suspension in use today on tractor-trailers. Suspension 21 is mounted on and depends from a longitudinally extend¬ ing frame member 22 of the vehicle by any suitable means such as welding or mechanical fastening.

Although prior art voided bushing 20 can be advantageously employed in a trailing arm suspension of the type indicated at 21 in FIG. 1, trailing arm suspen¬ sion 21 does not form an integral part of prior art voided bushing 20 or the voided bushing of the present invention which is described in detail hereinbelow. Thus, only the major components of suspension 21 will be cited for aiding in the description of one type of environment in which prior art voided bushing 20 and the voided bushing of the present invention can be utilized. A bracket 23 is securely mounted on and depends from vehicle frame 22. Bushing 20 is press fitted into a cylindrical sleeve 24, and the bushing is pivotally mounted on bracket 23 by any suitable means. The front end of a trailing arm or beam 25 in turn is rigidly attached to sleeve 24, preferably by welding. Other components of trailing arm suspension 21, mentioned herein only for the sake of relative complete¬ ness, include an air spring 31 which is securely mounted on and extends between the upper surface of the rear end of suspension beam 25 and vehicle frame 22. A shock absorber 32 extends between and is mounted on suspension beam 25 and frame 22 in a usual manner. A height control valve 33 extends between and is suitably mounted on bracket 23 and beam 25. An axle 34 is captured in beam 25 by a U-bolt 35 which is securely fastened to the beam by nuts 36.

Prior art voided bushing 20 of the type hereto- fore utilized in trailing arm suspension 21 and other suspension applications for trucks and tractor-trailers and the like, is now described. As shown in FIGS. 2-6, prior art voided bushing 20 includes an elastic, generally cylindrical-shaped body 41 formed with a central opening 42 which passes completely through the body about its longitudinal axis. A rigid metal sleeve 43 is friction fitted in opening 42 of body 41, and is bonded to the body at the peripheral surface of the sleeve by any suitable adhesive as is well-known to the art and literature. Sleeve 41 extends slightly outwardly from both ends of opening 42 to provide means for pivotally attaching bushing 20 to suspension bracket 23, as briefly described hereinabove. Elastic body 41, when used in tractor- trailer suspensions having a GAWR of from about 18,000 lbs. to about 25,000 lbs., preferably is formed of natural rubber having a durometer of from about 50 to about 75, and is available from the Goodyear Tire and Rubber Company of Akron, Ohio. Metal sleeve 43 can be made of any suitable hard metal such as steel. A horizontal nub 45 is formed on the front portion of each side of body 41, and aids in properly locating bushing 20 when pivotally mounting the bushing on bracket 23, as shown in FIG. 1. A pair of spaced-apart voids 44 is formed in each side of elastic body 41 of bushing 20. More specifically, a generally radially inwardly curving, rectangular-shaped void 44 is formed in each of the top and bottom portions of each side of body 41, with the vertical center of each void being positioned 90° from locator nub 45. Further- more, it has been determined that the total area of each void 44 is about 2.34 square inches. As shown in FIG. 5, it is important to note that the total area of each void 44 which extends frontwardly and rearwardly beyond a pair of spaced imaginary vertical lines T_f and T_r, respectively, which are tangential to the front and rear outer surfaces of sleeve 43, is about 0.26 square inches or only about 11 percent of the total area of each void 44.

Voids 44 enable prior art bushing 20 to achieve what has been commonly referred to as trifunctional characteristics. More specifically, the trifunctional characteristics include required load and deflection ratios, or static rates, of varying levels in different directions for semi-trailer suspension applications. The bushing static rate is stiff in the horizontal radial direction, so that axle 34 supported by tractor-trailer suspension 21 remains substantially perpendicular to the direction of movement of the vehicle despite horizontal loading which may be placed on the axle and bushing 20 (FIG. 1) . Conversely, the bushing rate is relatively soft in the vertical radial direction, to enable suspension 21 and bushing 20 to absorb vertical loading shocks and provide a smooth ride for the vehicle occupants and any cargo carried by the vehicle. Bushing voids 44 make possible the soft vertical radial static rate, and in combination with the large size of bushing 20 enable the bushing and suspension 21 to absorb angular loading or deflections placed on vehicle axle 34 and the bushing to prevent the vehicle from rolling over under such uneven loads.

Although prior art voided bushing 20 provides adequate static rates, it fails to optimize durability characteristics. Still, the large size of bushing 20 needed to satisfy tractor-trailer suspension roll charac- teristics also provides excellent durability in most loading situations. However, recent industry requirements for longer suspension service life, coupled with increased loading demands, has caused prior art bushing 20 to wear out sooner than is acceptable in view of the new require¬ ments.

More specifically, prior art voided bushing 20 has been found to usually fail prematurely in four primary locations, as shown at F_t, F_m, R_t, and R_ in FIG. 7, when the bushing is subjected to severe loading conditions. All four failure locations are caused by voids 44. Cracks R_t and F_t are caused by a localized buckling or puckering effect when the rubber surrounding top void 44 iε com- pressed under dynamic severe loading. Each cracks R_^ and F_m typically can be traced to the interface between the innermost portion of elastic body 41 and metal sleeve 43, which is represented approximately by phantom lines at X in FIG. 7. More specifically, it is believed that each crack H_ and F„ develops due to a large strain gradient located at its respective local interface X. This strain change is due to the location of nearly 90 percent of the area of voids 44 directly above and below sleeve 43 and between tangential lines T_£ and T_r (FIG. 6) . Under severe loading, a very soft section of elastic body 41 is created between sleeve 43 and each void 44, and a very stiff section of the elastic body is created in the areas of cracks F_m and R,.. Thus, most of the loading applied to bushing 20 is being supported by the area of bushing body 41 where cracks F_m and R,. occur, rather than being dis¬ tributed over the entire cross section of the elastic body. Therefore, it can be appreciated that while prior art voided bushing 20 has heretofore provided an excellent performing and durable bushing for most semi-trailer suspension applications, under severe loading situations the accelerated failure of the bushing is unacceptable.

Voided bushing 50 of the present invention is substantially similar to prior art voided bushing 20 in construction and materials, except that the size and shape of voids 54 of bushing 50 of the present invention differ from voids 44 of prior art bushing 20. More specifically, as shown in FIGS. 8-12, voided bushing 50 of the present invention includes an elastic, generally cylindrical- shaped body 51 formed with a central opening 52 which passes completely through the body about its longitudinal axis. A rigid metal sleeve 53 is friction fitted in opening 52 of body 51, and is bonded to the body at the peripheral surface of the sleeve by any suitable adhesive as is well-known to the art and literature. Sleeve 51 extends slightly outwardly from both ends of opening 52 to provide means for pivotally attaching bushing 50 to the suspension bracket of a tractor-trailer such as bracket 23 shown in FIG. 1. Elastic body 51, when used in tractor- trailer suspensions having a GA R of from about 18,000 lbs. to about 25,000 lbs., preferably is formed of natural rubber having a durometer of from about 50 to about 75, and is available from the Goodyear Tire & Rubber Company of Akron, Ohio. Metal sleeve 43 can be made of any suitable hard metal such as steel. A horizontal nub 55 is formed on the front portion of each side of body 51, and aids in properly locating bushing 50 when pivotally mounting the bushing on a suspension bracket. A pair of spaced-apart voids 54 is formed in each side of elastic body 51 of bushing 50. More specifically, a void is formed in each of the top and bottom portions of each side of body 51, with the vertical center of each void being positioned 90° from locator nub 55. However, rather than the generally radially inwardly curving rectangular shape of voids 44 of prior art bushing 20, voids 54 of bushing 50 of the present invention are generally radially inward¬ ly curving, elongated dog-bone shaped. Void 54 can be described as generally radially inwardly curving, elongat- ed rectangular-shaped and having a tear-drop or bulbous shape at each of its ends. Another difference that has been determined between bushing voids 54 of the present invention and prior art bushing voids 44, is that the total area of each void 54 is about 2.83 square inches, which is greater than the 2.34 square inches of area of each void 44. Although present invention bushing void 54 has a greater area than prior art bushing void 44, it can be appreciated by comparing FIGS. 12 and 6, as well as FIGS. 11 and 5, that the height of void 54 is less than the height of void 44, except at the bulbous ends of void 54, but void 54 is more elongated than void 44. Thus, it is important to note that the total area of each void 54 which extends frontwardly and rearwardly beyond a pair of spaced imaginary vertical lines T'_f and T'_r, respectively, which are tangential to the front and rear outer surfaces of sleeve 53, is about 1.48 square inches or about 52 percent of the total area of each void 54. This is to be compared to the relatively small 0.26 square inches or only about 11 percent of the total area of each void 44 which extends beyond similar tangential lines as shown in FIG. 5.

The above-described change in shape and size of voids 54 over voids 44 enables bushing 50 of the present invention to not only achieve the trifunctional character¬ istics of prior art bushing 20, but also improves the life of present invention bushing 50 to from about 3 to about 4 times over prior art bushing 20 when both bushings are subjected to severe loading situations. Thus, bushing 50 of the present invention meets or exceeds recent industry requirements for longer service life while being capable of handling greater loading demands. It is believed that by elongating voids 54, strain gradients are reduced in bushing body 51, wherein such strain gradients were described hereinabove and were believed to be the culprit for forming cracks R_» and F_m as shown in FIG. 7 for prior art bushing 20. Moreover, the tear-drop or bulbous shape at the ends of each void 54 eliminates the premature failure at crack sites R_t and F_t observed in prior art bushing 20 (FIG. 7) , by reducing localized buckling or puckering at those locations under severe loading.

An alternative or second embodiment of the present invention is indicated generally at 60 and is shown in FIG. 13. Voided bushing 60 is substantially similar to voided bushing 50, but displays slight differ¬ ences. More specifically, the size and shape of voids 64 of bushing 60 of the present invention differ slightly from the size and shape of voids 54 of bushing 50 of the present invention. Voided bushing 60 of the second embodiment of the present invention includes an elastic, generally cylindrical-shaped body 61 formed with a central opening 62 which passes completely through the body about its longitudinal axis. A rigid metal sleeve 63 is fric¬ tion-fitted in opening 62 of body 61, and is bonded to the body at the peripheral surface of the sleeve by any suitable adhesive as is well-known to the art and litera- ture. Sleeve 61 extends slightly outwardly from both ends of opening 62 to provide means for pivotally attaching bushing 60 to a semi-trailer suspension bracket, such as the one indicated at 23 in FIG. 1. Elastic body 61, when used in tractor-trailer suspensions having a GA R of from about 18,000 lbs. to about 25,000 lbs., preferably is formed of natural rubber having a durometer of from about 50 to about 75, and is available from the Goodyear Tire & Rubber Co. of Akron, OH. Metal sleeve 63 can be made of any suitable hard metal such as steel. A horizontal nub 65 is formed on the front portion of each side of body 61, and aids in properly locating bushing 60 when pivotally mounting the bushing on a suspension bracket. A pair of spaced-apart voids 64 is formed in each side of elastic body 61 of bushing 60. More specifically, a void is formed in each of the top and bottom portions of each side of body 61, with the vertical center of each void being positioned 90° from locator nub 65. Again, rather than the generally radially inwardly curving rectangular shape of voids 44 of prior art bushing 20, voids 64 of bushing 60 of the alternative embodiment of the present invention are generally radially inwardly curving, elongated dog-bone shaped. Void 64 also can be described as generally radially inwardly curving, elongated rectangular-shaped and having a tear-drop or bulbous shape at each of its ends. The total area of each void 64 is about 2.66 square inches, which also is greater than the 2.34 square inches of area of each prior art void 44. Also, the total area of each void 64 which extends frontwardly and rearwardly beyond a pair of spaced imaginary vertical lines T''_f and T' ' _ , respectively, which are tangential to the front and rear outer surfaces of sleeve 63, is about 1.09 square inches or about 41 percent of the total area of each void 64. As with first embodiment bushing 50 of the present invention, this is to be compared to and contrasted with the relatively small 0.26 square inches or only about 11 percent of the total area of each void 44 which extends beyond similar tangential lines as shown in FIG. 5. Thus, voids 64 of alternative embodiment bushing 60 of the present invention also achieve the trifunctional charac¬ teristics of prior art bushing 20, yet also displays a service life improvement of from about 3 to about 4 times over prior art bushing 20 when both bushings are tested under comparable severe loading conditions. Thus, bushing 60 of the present invention also meets or exceeds recent industry requirements for longer service life under severe loading conditions. More particularly, bushing 60 also displays improved performance at the heretofore premature cracking sites shown for prior art bushing 20 in FIG. 7. As with first embodiment bushing 50 of the present inven¬ tion, second embodiment bushing 60, through elongation of voids 64, reduces the strain gradients in bushing body 61, which is believed to be the cause of the cracking indicat- ed by R_^ and F_m in prior art bushing 20 as shown in FIG. 7. Moreover, the tear-drop or bulbous shape at the ends of each void 64 also reduces the puckering or buckling condition under severe loading which caused cracks R_t and F_t in prior art bushing 20, as also shown in FIG. 7. Thus, it can be appreciated that bushings 50, 60 of the present invention provide the required static rate performance under severe loading conditions in semi¬ trailer suspension applications, yet display a service life of from about 3 to about 4 times longer than prior art voided bushings subjected to similar loads. Also, bushings 50, 60 can be manufactured for generally the same cost as prior art voided bushings.

It is understood that the present invention contemplates a voided bushing which can be utilized in truck and tractor-trailer trailing arm suspensions, but also in other vehicle suspension applications. It is further understood that such a bushing may be useful in applications wholly unrelated to vehicles or suspensions. Accordingly, the improved voided bushing for vehicle suspensions is simplified, provides an effective, safe, inexpensive, and efficient article which achieves all the enumerated objectives, provides for eliminating difficulties encountered with prior voided bushings, and solves problems and obtains new results in the art.

In the foregoing description, certain terms have been used for brevity, clearness and understanding,- but no unnecessary limitations are to be implied therefrom beyond the requirements of the prior art, because such terms are used for descriptive purposes and are intended to be broadly construed.

Moreover, the description and illustration of the invention is by way of example, and the scope of the invention is not limited to the exact details shown or described.

Having now described the features, discoveries and principles of the invention, the manner in which the improved voided bushing is constructed, arranged and used, the characteristics of the construction and arrangement, and the advantageous, new and useful results obtained; the new and useful structures, devices, elements, arrange¬ ments, parts and combinations are set forth in the append¬ ed claims.

Claims

1. A bushing for a vehicle suspension, said bushing including: a) an elastic, generally cylindrical-shaped body having a pair of spaced-apart sides and being formed with a central opening which passes completely through said body and each of said sides about the longitudinal axis of the body; b) a rigid sleeve immovably mounted in said central opening, said rigid sleeve outside diameter being generally equal to the central opening diameter, the sleeve extending substantially the entire longitudinal length of said central opening to facilitate mounting of said bushing on a vehicle suspension,- c) a pair of spaced-apart voids formed in each of said elastic body sides, said pair of voids being formed in each of the sides above and below the central opening, and an imaginary vertical center of each void being disposed about 90° from an imaginary horizontal plane passing transversely through the body when said bushing iε mounted on a vehicle suspension, said voids each being generally radially inwardly curving, elongated rectangu¬ lar-shaped and having an increased size bulbous shape at each of its ends, wherein substantially the entire in- creased size of said bulbous shape portions of each of said voids extend beyond an area bounded by a pair of spaced imaginary vertical lines located tangential to an outer surface of said sleeve, so that said bushing pro¬ vides satisfactory static rates and durability when said vehicle suspension is subjected to severe loading condi¬ tions .

2. The bushing of Claim 1, in which the area of each of said voids is from about 2.34 square inches to about 3.15 square inches.

3. The bushing of Claim 1, in which the area of each of said voids is from about 2.50 square inches to about 2.99 square inches.

4. The bushing of Claim 1, in which the area of each of said voids is from about 2.65 square inches to about 2.84 square inches .

5. The bushing of Claim 1, in which said bushing body is formed of natural rubber having a dur¬ ometer of from about 50 to about 75.

6. The bushing of Claim 1, in which said rigid sleeve is formed of a hard metal; in which the sleeve extends slightly outwardly from bushing body sides for pivotally attaching the bushing to a vehicle suspension,- and in which said metal sleeve is adhesively bonded to said bushing body.

7. The bushing of Claim 6, in which said bushing is mounted on a trailing arm suspension of a tractor-trailer.

8. A bushing for a vehicle suspension, said bushing including: a) an elastic, generally cylindrical-shaped body having a pair of spaced-apart sides and being formed with a central opening which passes completely through said body and each of said sides about the longitudinal axis of the body,- b) a rigid sleeve immovably mounted in said central opening, said rigid sleeve outside diameter being generally equal to the central opening diameter, the sleeve extending substantially the entire longitudinal length of said central opening to facilitate mounting of said bushing on a vehicle suspension; c) a pair of spaced-apart voids formed in each of said elastic body sides, said pair of voids being formed in each of the sides above and below the central opening, and an imaginary vertical center of each void being disposed about 90° from an imaginary horizontal plane passing transversely through the body when said bushing is mounted on a vehicle suspension, said voids each being generally radially inwardly curving, elongated rectangu- lar-shaped and having an increased size bulbous shape at each of its ends, wherein from about 11 percent to about 80 percent of the total area of each of said voids extend beyond an area bounded by a pair of spaced imaginary vertical lines located tangential to an outer surface of said sleeve, so that said bushing provides satisfactory static rates and durability when said vehicle suspension is subjected to severe loading conditions.

9. The bushing of Claim 8, wherein from about 25 percent to about 70 percent of the total area of each of said voids extends beyond said area bounded by said pair of imaginary vertical lines.

10. The bushing of Claim 8, wherein from about 35 percent to about 60 percent of the total area of each of said voids extends beyond said area bounded by said pair of imaginary vertical lines.

11. The bushing of Claim 8, in which said bushing body is formed of natural rubber having a dur¬ ometer of from about 50 to about 75.

12. The bushing of Claim 11, in which said rigid sleeve is formed of a hard metal; in which the sleeve extends slightly outwardly from bushing body sides for pivotally attaching the bushing to a vehicle suspen¬ sion; and in which said metal sleeve is adhesively bonded to said bushing body.

13. The bushing of Claim 12, in which said bushing is mounted on a trailing arm suspension of a tractor-trailer.