Abstract:
The invention is directed to vehicle suspension systems and components thereof including attachment devices for mounting an axle alignment and/or load reacting mechanism to an axle. Disclosed herein are axle towers used for connecting a torque box to an axle. The axle tower of the present invention can include one or more features to absorb and disperse loads to the axle. The axle tower has a more contoured or curved edge on the side plate that experiences a compressive force than a similar edge on the side plate that experiences a tensile force. Furthermore, the axle tower has appendages that extend out from the side plates providing a large footprint on the axle housing. At least one of the appendages extending from the side plate experiencing a compressive force has a curved or radiused corner. Also, the axle towers include an inner plate having an off-centered slot where the troque box connects. The off-centered slot provides additional material to absorb the compressive force experienced on one side of the inner plate.

Description:
This application claims the benefit of U.S. Provisional Application Ser. No. 60/662,233, filed Mar. 16, 2005. 

   BACKGROUND OF THE INVENTION 
   The present invention is directed to devices for attaching a suspension system component such as an axle alignment device and/or a load reacting mechanism to the axle housing. In particular, the present invention is directed to axle towers which attach a multifunctional axle aligning and/or load reacting device such as a torque box to the axle housing. 
   The suspension system of a vehicle provides a comfortable ride for the passenger(s) of the vehicle and protects cargo that the vehicle may be carrying from excessive vibration. Equally, if not more importantly, the suspension system also provides stability to the vehicle by controlling various forces acting on the axle which would otherwise cause an unwanted change in the position of the axle relative to the vehicle frame. Specifically, such forces operate to alter the vertical, lateral, and/or longitudinal position of the axle in relation to the vehicle frame and also can cause axle movement such as roll, yaw, and wind-up. Each of the components of the suspension system reacts and controls one or more of the forces. In order to reduce the complexity and weight of the suspension system, components of the suspension system are being designed to control multiple forces. 
   A torque box assembly is one such multifunctional component. It reacts to vertical air spring loads, resists braking/acceleration loads, acts as the core roll resisting feature, resists cornering or lateral loading and maintains axle location in relation to the frame rails and also helps to prevent undue yaw and axle wind-up. 
   In general, the torque box assembly typically comprises a welded steel rectangular box structure. The front and rear ends are welded to round steel tubes. Upon assembly, bonded rubber bushes are inserted into these tubes and round metal rods are placed in the bushings. On one end of the torque box, the rod is connected to a cross member which spans between the frame rails of the vehicle frame. On the opposite end of the torque box, each end of the inner round metal rod is in turn attached to an axle tower linking the torque box to the axle through the axle housing. Further details of a torque box assembly are disclosed in U.S. Pat. No. 6,527,286. The disclosure of U.S. Pat. No. 6,527,286 is incorporated herein by reference. 
   Clearly, the load path between the axle housing and the torque box is of major import. Attachment devices or axle towers as referred to herein are intended to provide a means of transferring these loads onto the axle housing. These axle towers transfer longitudinal, roll input, lateral and vertical loads. Preferably, the axle towers are capable of this load transfer without overloading and/or fracturing the axle housing. 
   Asymmetrical axles are the standard in North America. Asymmetrical refers to the fact that the differential housing is offset from the centerline of the axle. Asymmetrical axles present challenges in designing attachment devices that attach axle alignment devices and/or load reacting devices such as torque boxes to the axle housing. The torque box or other device is typically centered between the frame rails of a vehicle and accordingly centered between the opposite ends of the axle. In order to center the torque box or other device, the attachment devices such as axle towers are spaced apart an equal distance from the centerline of the axle. Consequently, since the differential housing is not centered on the axle, the axle towers are typically mounted to the differential housing at different distances from the either side of the centerline of the differential housing. In other words the axle towers are mounted at asymmetric points about the centerline of the differential housing such that a chord connecting the attachment points is not horizontal. 
   As such, axle towers are typically designed differently from each other to accommodate their asymmetric positioning about the differential housing. Besides having different base configurations due to accommodate the mounting position on the differential housing, the axle towers are also of differing heights in order to maintain the transverse extent of the torque box parallel to the axle at rest. In other words, since one axle tower may be placed at a more elevated position on the differential housing than the other axle tower, that elevated axle tower will shorter than the other axle tower otherwise the torque box will be skewed relative to the axle at rest. 
   The axle towers have to being able to withstand the stress forces exerted by the torque box or other such devices, the axle towers have to be able to absorb and/or disperse the forces along the axle housing in order to prevent possible failure of the axle and/or differential housings. 
   Other attachment devices known in the art are perhaps longitudinal and transverse torque rod towers encountered on most on highway suspensions or the tower which connects a “vee rod” to the top of the axle housing. However, these devices are not intended to be multifunctional in nature as is the case with the axle towers of the present invention. The axle towers of the present invention are unique in that they are multifaceted, multifunctional structural components, i.e. structures that react to loads on multiple axes, whereas existing devices are one dimensional in their function, i.e. structures that react to loads on a single axis. In order to provide the functions listed above, several features which are improvements over prior art structures can be included in the axle towers of the present invention. 
   As will be explained in more detail below, the torque box is in tension and reacts by pulling on the axle towers when a vertical load is applied to the air springs. Due to this cantilevered load into the axle towers, there is a compression side (closest to the torque box) and a tension side (furthest from the torque box) on the axle towers. These two sides of the axle towers therefore can be designed differently to provide an efficient design capable of carrying the loads. 
   In one embodiment of the axle towers of the present invention, the axle towers can include several features. While these features will be discussed in greater detail below, they are summarized as follows. One feature that may be included is that the compression side of the axle tower differs in shape from tension side of tower. The differing shapes affect the stiffness of each side of the tower and improve the stress distribution and reduce the stress load on the axle housing One difference in the shape in the tower sides is that the side of axle tower that experiences higher compression forces is scalloped or contoured to a greater extent than the other side or tension side of the axle tower. 
   Another feature that may be included is that slot of the internal connecting plate is asymmetrically shaped. The asymmetry addresses the concentration of stress on one side of the slot through the concentration of material to offset the higher stress level. In other words, there is more material on the side that experiences greater stress forces. 
   A further feature that can be included is an asymmetrical foot print attaching the axle towers to axle housing. The compression side of the axle tower or the side with the greater degree of cutout or curvature has at least one radiused or rounded corner. The rounded or radiused foot print radius on the compression side of the axle tower attenuates the effects of a sharp corner on the axle housing by distributing the stress load. In addition, the foot print has a sizable extent along the axle housing. This helps to disperse the stress along a larger area of the axle and differential housing. 
   Yet another feature that may be included is that the scalloping or contouring of the axle tower on the compression side allows it to flex and comply as the axle deforms under load without overloading attaching welds. A structure having no scalloping or contouring would be stiffer and would not flex as the axle distorts which could overload the welds 
   Yet another feature may be weldment of the axle towers. Weldment is lighter, more cost efficient and may be preferable over common steel casting. In addition, weldment does not require subsequent machining as a casting would. However, the axle tower could be manufactured in casting form versus the fabrication described herein without departing from the scope of the invention. The axle towers of the present invention could also be altered to serve as torque rod attachments. 
   SUMMARY OF THE INVENTION 
   In one aspect of the present invention an axle tower is provided for attaching a vehicle suspension component to a vehicle axle having a centerline. The axle tower comprises a compression side plate disposed generally parallel to a tension side plate with each of the compression and tension side plates having upper and lower portions. Each of the upper and lower portions of the compression and tension side plates has a proximate edge positioned closer to the centerline than a distal edge. First and second appendages extend from the distal edges of the lower portions of the compression and tension side plates, respectively and third and fourth appendages extend from the proximate edges of the lower portions of the compression and tension side plates, respectively. The proximate and distal edges of the lower portions of the compression and tension side plates have an arcuate portion. An inner plate joins and is positioned perpendicular to the compression and tension side plates. The inner plate has upper and lower portions and the upper portion of the inner plate has a slot for attaching the axle tower to the vehicle suspension component. 
   In another aspect of the present invention, a mounting assembly is provided for mounting a suspension component to an asymmetrical axle that includes a differential housing having a centerline. The mounting assembly comprises first and second axle towers mounted to the asymmetrical axle on opposite sides of the centerline, respectively. The first and second axle towers each comprises compression and tension side plates disposed parallel to each other and each of the compression and tension side plates has upper and lower portions. Each of the upper and lower portions includes a proximate edge facing towards the centerline and a distal edge facing away from the centerline. First and second appendages extend from the distal edges of the lower portions of the compression and tension side plates, respectively, and third and fourth appendages extend from the proximate edges of the lower portions of the compression and tension side plates, respectively. An inner plate joins the compression and tension side plates and is positioned perpendicular to the compression and tension side plates. Each of the inner plates has a slot for attaching the first and second axle towers to the vehicle suspension component and each of the slots is spaced an equal distance from a center of the axle. 
   In yet another aspect of the invention, a suspension system for supporting a vehicle chassis that includes transversely spaced longitudinally extending first and second frame rails over a transversely extending axle that includes a centerline is provided. The suspension system comprises a cross member extending transversely between and connected to the first and second frame rails; and a multifunctional suspension component connected at one end to the cross member and connected at another end to first and second axle towers. The first and second axle towers are transversely spaced apart and fixed to the axle at opposite sides of the centerline. The first and second axle towers each comprises compression and tension side plates longitudinally spaced from and parallel to each other. Each of the compression and tension side plates has upper and lower portions and each of the upper and lower portions has a proximate edge facing towards the centerline and a distal edge facing away from the centerline. First and second appendages extend from the distal edges of the lower portions of the compression and tension side plates, respectively and third and fourth appendages extend from the proximate edges of the lower portions of the compression and tension side plates, respectively. An inner plate joins the compression and tension side plates and is positioned perpendicular to the compression and tension side plates. Each of the inner plates has a slot for attaching the first and second axle tower to the multifunctional suspension component. The slots of the first and second axle towers are equally spaced from the centerline. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a suspension system of the present invention mounting a vehicle frame over a tandem axle. 
       FIG. 2A  is an elevation view of the leading arm asymmetrical axle of the tandem axle shown in  FIG. 1  having two axle towers of the present invention mounted thereon. 
       FIG. 2B  is an elevation view of the trailing arm asymmetrical axle of the tandem axle shown in  FIG. 1  having two axle towers of the present invention mounted thereon. 
       FIG. 3  is a side elevation view of the leading arm axle shown in  FIG. 2A . 
       FIG. 4A  is a perspective view of one embodiment of an axle tower of the present invention. 
       FIG. 4B  is a perspective view of another embodiment of an axle tower of the present invention. 
       FIG. 5A  is an elevation view of the axle tower shown in  FIG. 4A . 
       FIG. 5B  is an elevation view of the axle tower shown in  FIG. 4B . 
       FIG. 6  is a cross-sectional view taken at line  6 - 6  of  FIG. 5A . 
       FIG. 7  is a cross-sectional view taken at line  7 - 7  of  FIG. 5B . 
       FIG. 8A  is an elevation view of the side plate of the axle tower shown in  5 A that experiences tension. 
       FIG. 8B  is an elevation view of the side plate of the axle tower shown in  5 A that experiences compression and having an unbent appendage. 
       FIG. 9A  is an elevation view of the side plate of the axle tower shown in  5 B that experiences tension. 
       FIG. 9B  is an elevation view of the side plate of the axle tower shown in  5 B that experiences compression and having an unbent appendage. 
       FIG. 10A  is an elevation side view of an inner plate of the axle tower shown in  5 A 
       FIG. 10B  is an elevation view of the inner plate shown in  FIG. 10A  rotated 90°. 
       FIG. 11  is an elevation view of an inner plate of the axle tower shown in  FIG. 5B . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Before describing the embodiments of the axle tower of the present invention a general description of a suspension system, vehicle axle and frame will be provided. The axle towers of the present invention can be used with other suspension systems, vehicle axles and frames without affecting the overall concept of the present invention. 
   A tandem axle, vehicle suspension system and vehicle frame indicated generally at  10  is shown in  FIG. 1 . Each axle incorporates the axle towers of the present invention. Axle and suspension system  12  is a leading arm axle type and  14  is a trailing arm type. Each axle and suspension system  12 ,  14  is shown mounted on a frame  16  which includes longitudinally extending frame rails  18 ,  20 . Frame rails  18 ,  20  are rigidly connected by a pair of longitudinally spaced apart, transversely extending and parallel cross members  21 ,  23 . The cross members  21 ,  23  can be connected by any suitable means to each frame rail  18 ,  20  and typically with mounting brackets. 
   Leading arm suspension system  22  and trailing arm suspension system  24  support frame  16  on axles  26 ,  28 , respectively. Only the main components of the trailing arm suspension system  24  and which are duplicated on the leading arm suspension system  22  are briefly discussed. Air springs  30  are mounted on frame rails  18 ,  20  at their top ends and are connected at their bottom ends to pads  32  of axle seats  34 . Axle seats  34  are attached to each end of axles  26 ,  28 . On the end of each axle seat  34  opposite the pad  32 , torque rods  36  are pivotally connected using a pin and bushing arrangement. The other end of the torque rods  36  is also pivotally connected with a pin and bushing arrangement to a V-shaped hanger  38  that is mounted to the frame rails  18 ,  20 . 
   Shock absorbers  40  are attached at one end to the frame rail  18  through a bracket and pivotally connected at another end to torque rod  36 . Torque box  42  is attached at one end to the frame rails  18 ,  20  via pivotal connections at both ends of the transversely extending rod (not shown) to the cross member  23 . At the other end of the torque box  42 , one end of the transversely extending rod  44  is connected to axle tower  46  and the other end of rod  44  is connected to axle tower  48 . The rod  44  is sandwiched between clamp ends  50  and held in place with bolts. The rod may be connected to the axle tower by other means. 
   Axles  26 ,  28  shown in  FIGS. 2A and 2B  are nearly identical asymmetrical axles which are rotated 180° depending on their whether the axle is in a leading or trailing arm configuration. The axles are referred to as asymmetrical due to the fact that the differential housing portion  52  of each axle  26 ,  28  is offset from the centerline A of each axle  26 ,  28 . Since the differential housing is offset from the centerline of the axle and since the alignment devices and/or load reacting devices are typically centered in relation to the axle, the axle towers  46 ,  48  are fixed to the axle housing  54  at asymmetric positions along the differential housing  52 . In other words, axle tower  46  which is spaced further from the centerline D of the differential housing and has less of its footprint in contact with and is positioned lower on the differential housing  52  than axle tower  48  which is spaced closer to the centerline D and has more of its footprint in contact with and positioned higher on the differential housing  52 . Due to this asymmetric positioning along the differential housing  52 , axle towers  46 ,  48  as illustrated in  FIGS. 4A and 4B  may have different design configurations (besides the footprint or area contacting the housing) and heights in order to maintain the torque box mounting points horizontally aligned. However, it is not required that the axle towers have a different configuration especially if they are fixed to the axle housing without contacting the differential housing or if they are contacting the differential housing at symmetrical positions. Indeed, for symmetrical axles two axle towers could be utilized that are mirror images of each other; in particular axle tower  46  and a mirror image of axle tower  46  could be used to connect the torque box to a symmetrical axle. 
     FIG. 3  illustrates some of the forces/loads acting on the axle  26  and axle tower  46 . Arrows AL represents the load applied by the air spring (not shown), SL represents the load applied by the spindle  56 , TR represents the load applied by the torque rod (not shown), and TB represents the load applied by torque box (not shown). As illustrated in  FIG. 3 , the torque box (not shown) is in tension and applies a load in the direction of arrow TB. Accordingly, this load places the side plate  58  of axle tower  46 , which is closer to the torque box, in compression and places side plate  60  of axle tower, which is further from the toque box, in tension. 
   Axle tower  46  includes a compression side plate  58  and tension side plate  60  and axle tower  48  includes compression side plate  62  and tension side plate  64  as shown in  FIGS. 4A ,  4 B,  5 A and  5 B. Each side plate  58 ,  60 ,  62 ,  64  can have two appendages  66 ,  68 ,  70 ,  72 ,  74 ,  76 ,  78 ,  80 , respectively and upper and lower portions  82 ,  84 ,  86 ,  88 ,  90 ,  92 ,  94 ,  96 , respectively. Alternatively, instead of two appendages  66  and  70  intergrally formed with side plates  58 ,  60 , a single appendage incorporating  66  and  70  could be welded to side plates  58 ,  60 . This alternative construction can also be applied to appendages  74 ,  78  and  76 ,  80  and side plates  62 ,  64 . 
   Side plates  58 ,  60  each have two openings  89 ,  91 ,  93 ,  95 , respectively. Openings  89 ,  91  are concentric with openings  93 ,  95  respectively and used for attaching the rod  44  of torque box  42  to the axle tower  46 . Side plates  62 ,  64  also have a pair of openings  97 ,  99 ,  101 ,  103  respectively and are arranged in the same manner for the same purpose. 
   The side plates  58 ,  60 ,  62 ,  64  may be connected by inner plate  98 ,  100 , respectively. The inner plates  98 ,  100  also have upper and lower portions  102 ,  104 ,  106 ,  108 , respectively. The side plates  58 ,  60 ,  62 ,  64  and inner plates  98 ,  100  may be constructed of a hardened and high strength material such as steel and can be welded together, this includes the welding of appendage  66  to appendage  70  and the welding of appendage  74  to  78 . Alternatively, the entire axle tower structure could also be formed as a casting. 
   Lower portions  84 ,  88 ,  92 ,  96  have edges  110 ,  112 ,  114 ,  116 , respectively that face away from the centerline A or towards the nearest spindle. As discussed above, side plates  58 ,  62  experience compressive forces applied by the torque box or other load reacting/axle alignment device while side plates  60 ,  64  experience tensile forces. In order to adequately absorb and disperse this compressive force, edges  110  and  114  may be contoured, or scalloped. Edges  112 ,  116  can also be contoured or have a curvature. It is also desirable that edges  110 ,  114  have a greater contour or scallop than edges  112 ,  116 , respectively. In other words, edges  110 ,  114  are spaced closer to edges  138 ,  146  respectively, than are edges  112 ,  116  to edges  142 ,  150 , respectively as shown in  FIGS. 8A ,  8 B,  9 A, and  9 B. 
   Appendages  66  and  76  which extend from edges  110 ,  114 , respectively, may curve toward side plates  60 ,  64 , respectively and have radiused corners. As side plates  58 ,  62  experience compressive forces, these radiused corners reduce or spread the load on the axle and differential housings which would otherwise be concentrated with sharper corners. In addition, the radiused corners reduce the stress concentration to the welds attaching the axle towers to the axle housing. 
   As shown more clearly in  FIGS. 6 and 7 , appendages  66 ,  76  bend at about a 90° angle. In other words, first sections  118 ,  120  are oriented at about 90° to third sections  122 ,  124 , respectively with curved second sections  126 ,  128  joining first sections  118 ,  120  and third sections  122 ,  124 , respectively. The appendages  66 ,  76  can be long enough to meet and be welded to respective appendages  70 ,  80 . Also, third sections  122 ,  124  may meet at about a 90° angle to appendage  70 ,  80  and that first sections  118 ,  120  extend parallel to appendages  70 ,  80 . Indeed, appendages  66 ,  74  and  76  are shown in  FIGS. 8B and 9B  prior to applying the bend or curve. 
   Appendage  74  may also curve toward and have a length sufficient to meet be welded to appendage  78  since axle tower  48  is positioned higher on the differential housing and typically experiences higher stress in the area of appendages  74 ,  78 . Appendage  74  also bends at about a 90° angle such that first section  130  is at about 90° to third section  132  with curved second section  134  joining the first and third sections  130 ,  132 . Third section  132  may also meet appendage  78  at about a 90° angle and that first section  130  extends parallel to appendage  78 . In addition, appendages  68  and  72  may extend parallel to each other as shown in  FIG. 4A  or can be connected to each other as described with the other pairs of appendages. 
   Upper and lower portions  82 ,  84 ,  86 ,  88  also have edges  136 ,  138 ,  140 ,  142  that face toward the centerline A as best shown in  FIGS. 8A and 8B . Likewise, upper and lower portions  90 ,  92 ,  94 ,  96  have edges  144 ,  146 ,  148 ,  150  that face toward the centerline A. Edges  136 ,  140 ,  144 ,  148  may be substantially linear while edges  138 ,  142 ,  146 ,  150  have some curvature. The curvature or radius of curvature of edge  138  may be substantially the same as that of edge  142  and the curvature or radius of curvature of edge  146  may be substantially the same as that of edge  150 . 
   Inner plate  98  of axle tower  46  shown in  FIGS. 10A and 10B  has upper and lower portions  102 ,  104 , respectively. The inner plate  100  of axle tower  48  also has upper and lower portions  106 ,  108  as shown in  FIG. 11 . The upper and lower portions  102 ,  104  may be inclined relative to each other and may be at an angle of from about 160° to about 170° In the embodiment shown in  FIGS. 10A and 10B  upper and lower portions meet a about a 165° angle. This helps to stiffen the area of side plates  58 ,  62  from the lower portion  104  of inner plate  98  to the end of appendages  68 ,  72  shown in  FIG. 5A . Upper and lower portions  106 ,  108  can be linearly arranged as shown in  FIG. 5B  especially since the area of side plates  62 ,  64  from lower portion  174  of the inner plate  100  to the end of appendages  74 ,  78 . 
   In order to connect the torque box  42  to axle towers  46 ,  48 , inner plates  98 ,  100  may include slots  160 ,  162  (see  FIGS. 10 and 11 ) for accepting the rod  44  as shown in  FIGS. 1 and 3 . It is understood that a load reacting mechanism/axle alignment device may be connected to the axle towers in other ways known in the art without departing from the scope of the invention. 
   The forked configuration of upper portions  102 ,  106  creates slots  160 ,  162  that are V-shaped and have open ends  164 ,  166  and closed ends  168 ,  170 . The closed ends  168 ,  170  of the V-shaped slots  160 ,  162  may be offset. This creates an area of increased material  172 ,  174 . The inner plates  98 ,  100  are connected to the side plates  58 ,  60 ,  62 ,  64 , respectively so that the increased material is closest to side plates  60 ,  64  to provided added strength to the side of the inner plate that is under compressive force as shown in  FIG. 3 . Also, the slots  160 ,  162  may be the same size and shape so that when the torque box  42  is attached to axle towers  46 ,  48  the transverse extent of the torque box is maintained in parallel relation to the ground or the axle at rest. 
   Upper portion  102  of inner plate  98  is attached to the upper portions  82 ,  86  adjacent edges  136 ,  140 , and the inner plate  98  extends to the base  172  of the axle tower  46 . Likewise, upper portion  106  of inner plate  100  is attached to upper portions  90 ,  94  adjacent edges  144 ,  148 , and the inner plate  100  extends to the base  174  as shown in  FIGS. 4A ,  4 B,  5 A and  5 B. Due to the placement of axle tower  46  lower on the differential housing  52  and axle tower  48  higher on the differential housing  52 , inner plate  98  is longer or taller than inner plate  100 . In addition, inner plate  98  is also longer due to the inclined relation of upper portion  102  to lower portion  104 . In order to center the torque box over the axle (and between the frame rails) the upper portion of the inner plates, particularly the slots should be equally spaced from the axle centerline. 
   The axle towers  46 ,  48  may be welded to each axle housing of axles  26 ,  28 . Welds are made along the bases of each side plates, appendages and inner plates. Since axle towers  46 ,  48  may be welded to the axle housing and appendages  66 ,  76  may be weld to appendages  70 ,  80 , respectively, the axle housing and axle tower forms a closed volume that can collect water. Accordingly, as shown in  FIGS. 4A and 4B  notches  175 ,  177  may be included in appendages  66 ,  76 , respectively to assist in draining away excess water. In addition, as shown in  FIGS. 10B and 11  inner plates  104 ,  108  may include holes  179 ,  181 , respectively to assist with the drainage of any excess water. 
   While the present invention has been described in detail with reference to the foregoing embodiments, other changes and modifications may still be made without departing from the spirit or scope of the present invention. It is understood that the present invention is not to be limited by the embodiments described herein. Indeed, the true measure of the scope of the present invention is defined by the appended claims including the full range of equivalents given to each element of each claim.