Sandwich design of four bag suspension for bus and coach rear drive axles

[0001] Suspension assemblies for bus and coach rear drive axles typically comprise four air springs, also known as bags, spaced at four separate locations to support the frame of the bus or coach on the axle. Such assemblies usually have two lateral tubes that connect the air springs from side-to-side and two fabricated I-beams, which connect the axle to these lateral tubes. The lateral tubes are welded to the I-beams. Welds are placed either on the top and/or bottom of the tubes at the intersection of the tubes and the I-beams.

[0002] The intersection of the I-beams and the tubes is subject to significant stress as part of the vehicle suspension. Consequently, the welds in these areas are also subject to significant stress. Due to the difference in geometry between the tubes and the I-beam, welds at the top and/or bottom surfaces of the lateral tubes serve as stress risers. Moreover, heat from the welding process may change the material properties at the location of the weld, weakening the strength of the material. This combination of stress and weakened material may shorten part life.

[0003] A need therefore exists for a suspension assembly that avoids the weld problems that occur at the intersection of the tubes and the I-beam.

[0004] Like existing suspension assemblies, the inventive suspension assembly has four springs spaced at four different locations. However, rather than employ separate tubes and I-beams to support each spring, a unitary plate is used. This plate is sized to support each spring at each location as well as to support a vehicle axle. In this way, the inventive suspension assembly eliminates the need for lateral tubes and I-beams and avoids unreceptive weld geometry. The inventive assembly accordingly leads to longer part life.

[0005] The suspension assembly may have additional bracing. A second plate may be spaced from the first plate and serve to also support each spring at each location, like the first plate. Webbing may attach the first plate to the second plate and may extend across these plates. Webbing may be doubled to provide greater strength to areas that require such support.

[0006] Accordingly, the suspension assembly may comprise four springs spaced at four different locations with a generally horizontal upper plate extending to support each spring at each location. Another generally horizontal plate may be spaced from the first plate by a vertical support to provide further strength to the assembly. The axle may be connected to the first plate.

[0007] The inventive suspension assembly may be manufactured by spacing four springs at four different locations. A first and second plate may be sized to extend to each of the four different locations of the springs. The first plate is spaced from the second plate and mounted to the second plate. An axle may be attached to one of the plates. A support, such as webbing, may be sandwiched between these plates.

[0008] The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows:

[0009] FIG. 1 illustrates the inventive suspension assembly, showing springs, first plate, second plate and axle.

[0010] FIG. 2 illustrates an overhead view of the inventive suspension assembly of FIG. 1.

[0011] FIG. 3 illustrates an exploded view of the inventive suspension assembly of FIGS. 1 and 2.

[0012] FIG. 1 illustrates inventive suspension assembly 10. Suspension assembly 10 comprises four springs, such as air springs, spaced at locations A, B, C and D. Springs 10, 18, 22 and 26, such as air springs, are mounted as known to first plate 30, which is sized to extend to support each spring at locations A, B, C and D. Preferably, plate 30 is of unibody or unitary construction so that stress may be distributed across first plate 30 without the weak points associated with joined pieces. Spaced from first plate 30 is second plate 38, which may mirror the size and shape of first plate 30 so as to provide additional support to springs 10, 18, 22 and 26 at locations A, B, C and D, respectively. Second plate 38 is also preferably of unibody or unitary form. First plate 30 is mounted to second plate 38 by support 42, which is sandwiched between each plate 30, 38. Axle 34 is attached to first plate 30 by known techniques.

[0013] FIG. 2 illustrates a plan view of suspension assembly 10. As shown in this figure, first plate 30 extends to each location A, B, C and D without the welding seams that are typically found at locations E, F, G and H when lateral tubes and I-beams are employed in known designs. Hence, rather than use two lateral tubes and two I-beams to support the four springs at locations A, B, C and D, a single plate 30 may be cut to extend to each of these locations. First plate 30 may comprise first lateral portion 45 that extends from location A to location C and second lateral portion 43 that extends from location B to location D. Interconnecting these lateral portions 43, 45 to each other are first transverse portion 47 and second transverse portion 40. Portions 40, 43, 45 and 47 preferably form a single plate.

[0014] FIG. 3 illustrates an exploded view of the suspension assembly of FIGS. 1 and 2. First plate 30 is spaced from second plate 38. Between first plate 30 and second plate 38 is support 42, which serves to mount first plate 30 to second plate 38 in a sandwich-like manner. Support 42 may comprise webs that extend between first plate 30 and second plate 38. As shown, web 46 extends along the length of first lateral portion 45 from location A to location C. Web 60 may extend along the length of second lateral portion 43 from location B to location D. Spaced from web 60 is web 64, which serves as a rear brace that provides additional support to assembly 10.

[0015] In addition, web 50 may extend along the length of transverse portion 40 while web 54 may extend along the length of transverse portion 47. Webs 46, 50, 54, 60 and 64 may comprise a single piece or multiple pieces that are welded together as known. Further, support 42 is attached to first plate 30 and second plate 38 by welding. It is preferable that the welds be located inside of plates 30 and 38 and the oriented parallel to the bending axis of the anticipated load on assembly 10 instead of against it. In this way, welds are not placed at potential locations of cracking.

[0016] The aforementioned description is exemplary rather that limiting. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed. However, one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. Hence, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For this reason the following claims should be studied to determine the true scope and content of this invention.