Patent Publication Number: US-8522933-B2

Title: Adjustable run height lift axle suspension system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a division of prior application Ser. No. 11/039,051 filed on Jan. 20, 2005. The entire disclosure of this prior application is incorporated herein by this reference. 
    
    
     BACKGROUND 
     The present invention relates generally to vehicle suspension systems and, in an embodiment described herein, more particularly provides an adjustable run height lift axle suspension system. 
     It is at times desirable to be able to change the run height of a suspension system. For example, a run height which would be appropriate for one application may not be acceptable when the suspension system is used in another application. 
     Unfortunately, typical suspension systems do not permit convenient adjustment of their run heights. In most cases, weldments which determine the run height of the suspension system would have to be reconfigured at great expense of time and money. 
     This problem is particularly troublesome in lift axle suspension systems. This is due to the added complexity of the lift mechanism, a geometry of which changes when the run height is changed. 
     Therefore, it may be seen that it would be desirable to be able to provide an adjustable run height lift axle suspension system. 
     SUMMARY 
     In carrying out the principles of the present invention, an adjustable run height lift axle suspension system is provided which solves at least one problem in the art. One example is described below in which the suspension system permits convenient, efficient and economical adjustment of run height. 
     In one aspect of the invention, an adjustable run height lift axle suspension system is provided which includes an axle assembly, an air spring for suspending a vehicle frame above the axle assembly and a lift actuator operable to lift the axle assembly relative to the vehicle frame. A device is releasably attached to the axle assembly and connected to each of the air spring and the lift actuator. The device spaces the air spring away from the axle assembly. 
     In another aspect of the invention, an adjustable run height lift axle suspension system includes an axle assembly, an air spring for suspending a vehicle frame above the axle assembly, a lift actuator operable to lift the axle assembly relative to the vehicle frame, and a selected one of first and second devices. The suspension system has one run height when the first device is releasably attached to the axle assembly and connected to each of the air spring and the lift actuator, and the suspension system has a different run height when the second device is releasably attached to the axle assembly and is connected to each of the air spring and the lift actuator. 
     In a further aspect of the invention, an adjustable run height lift axle suspension system includes an axle assembly, an air spring for suspending a vehicle frame above the axle assembly and a lift actuator operable to lift the axle assembly relative to the vehicle frame. The suspension system has multiple run heights, the air spring having approximately the same operational height when the suspension system is at different run heights. 
     These and other features, advantages, benefits and objects of the present invention will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of a representative embodiment of the invention hereinbelow and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric exploded view of a suspension system embodying principles of the present invention; 
         FIG. 2  is a side view of the suspension system of  FIG. 1  configured to have a first run height; and 
         FIG. 3  is a side view of the suspension system of  FIG. 1  configured to have a second run height. 
     
    
    
     DETAILED DESCRIPTION 
     Representatively illustrated in  FIG. 1  is an adjustable run height lift axle suspension system  10  which embodies principles of the present invention. In the following description of the suspension system  10  and other apparatus and methods described herein, directional terms, such as “above”, “below”, “upper”, “lower”, etc., are used for convenience in referring to the accompanying drawings. Additionally, it is to be understood that the various embodiments of the present invention described herein may be utilized in various orientations, such as inclined, inverted, horizontal, vertical, etc., and in various configurations, without departing from the principles of the present invention. The embodiments are described merely as examples of useful applications of the principles of the invention, which is not limited to any specific details of these embodiments. 
     As depicted in  FIG. 1 , the suspension system  10  includes an axle assembly  12  which is connected to a hanger bracket  14  by upper and lower trailing arms  16 ,  18 . Each of the upper and lower trailing arms  16 ,  18  is pivotably connected to the axle assembly  12  and to the hanger bracket  14 , thereby forming a parallelogram, or modified parallelogram, type of suspension system. It will be appreciated by those skilled in the art that two of the hanger brackets  14  and two each of the upper and lower trailing arms  16 ,  18  are provided in the suspension system  10 , one of each on each lateral side of the suspension system, although for clarity of illustration only one of each is shown in  FIG. 1 . 
     The axle assembly  12  includes a spindle  20  pivotably mounted at each end of the axle assembly by a steering knuckle  22 . Thus, the suspension system  10  is also a steerable type of suspension system. However, it should be understood that it is not necessary for the suspension system  10  to be steerable, or for the suspension system to be a parallelogram or modified parallelogram suspension system, in keeping with the principles of the invention. 
     The suspension system  10  is also liftable. A lift actuator  24  is connected between the lower trailing arm  18  and a run height adjustment device  26  in a unique manner described in further detail below. The actuator  24  is preferably a pneumatic actuator. As the actuator  24  is elongated by applying pressure thereto, the axle assembly  12  is raised relative to a vehicle frame  46  (see  FIGS. 2  &amp;  3 ) to thereby disengage wheel assemblies (not shown) connected to the spindles  20  from a road surface. Other types of actuators (such as, electric, hydraulic, etc.) may be used for the lift actuator  24  if desired. 
     The lower arm  18  is pivotably connected to the axle assembly  12  at a pivot connection  28 . The pivot connection  28  is formed at a bracket  30  rigidly attached (such as by welding) to an axle  32  of the axle assembly  12 . Note that the device  26  is also releasably attached to the bracket  30  by means of a conveniently detachable fastener  34 . 
     The lift actuator  24  is pivotably connected to a forwardly projecting portion  36  of the device  26  using another conveniently detachable fastener  38 . Thus, it will be appreciated that the device  26  may be readily detached from both the lift actuator  24  and the bracket  30  when desired. When the lift actuator  24  elongates, it applies an upwardly directed force to the portion  36  of the device  26  and a downwardly directed force to the lower arm  18 , thereby pivoting the lower arm downward about the pivot connection  28 , and lifting the axle assembly  12 . 
     Note that the lower arm  18  at each of its ends is positioned laterally inward relative to the upper arm  16 . This positioning permits convenient locating of the lift actuator  24 , bracket  30  and device  26  as depicted in  FIG. 1 . However, other relative positions between the upper and lower arms  16 ,  18  may be used in keeping with the principles of the invention. 
     An air spring  40  is mounted to an upper platform  42  of the device  26  using conveniently detachable fasteners  44 . The air spring  40  suspends the vehicle frame  46  above the axle assembly  12 . Air pressure is exhausted from the air spring  40  when the lift actuator  24  is elongated, thereby permitting the axle assembly  12  to be lifted toward the frame  46 . 
     The device  26  is also releasably attached to the axle  32  using a conveniently detachable fastener  48 . Thus, it will be appreciated that the device  26  may be readily detached from both the air spring  40  and the axle  32 . In addition, note that the bracket  30  efficiently and economically provides an attachment for each of the lower arm  18 , the device  26  and thereby the air spring  40  and lift actuator  24  to the axle  32 , which also desirably reduces a weight of the suspension system  10  as compared to the use of multiple brackets or other attachments for these components. 
     The device  26  spaces the air spring  40  vertically away from the axle  32 . In one important feature of the suspension system  10 , the vertical distance by which the device  26  spaces the air spring  40  away from the axle  32  may be conveniently changed to thereby conveniently adjust a run height of the suspension system. As used herein, the term “run height” is used to indicate a vertical distance between a center of the spindle  20  and the vehicle frame  46 . 
     Referring additionally now to  FIGS. 2&amp;3 , the suspension system  10  is depicted in two alternate configurations. Note that in  FIG. 2  the suspension system  10  has a run height RHa, and that in  FIG. 3  the suspension system has an increased run height RHb. Additional configurations are possible and are conveniently provided for using the principles of the invention, as described in further detail below. 
     In another important feature of the suspension system  10 , the run heights RHa, RHb differ without changing, or without substantially changing, an operational height of the air spring  40 . Thus, the same air spring  40  may be used for each configuration of the suspension system  10 , thereby eliminating the cost of maintaining multiple different air springs in inventory for the different configurations. The operational height of the air spring  40  is the height of the air spring when the suspension system  10  is at its designed run height RHa or RHb. 
     In  FIG. 2 , the device  26   a  spaces the air spring  40  away from the axle  32  a vertical distance Da, thereby producing the run height RHa. In  FIG. 3 , the device  26   b  spaces the air spring  40  away from the axle  32  an increased vertical distance Db, thereby producing the increased run height RHb. In yet another important feature of the suspension system  10 , the device  26   a  may be conveniently substituted for the device  26   b  (or vice versa), or for another device which spaces the air spring  40  away from the axle  32  a different vertical distance, due in part to the manner in which the device is releasably connected to the air spring, axle, bracket  30  and lift actuator  24 . 
     In still another important feature of the suspension system  10 , the pivotable connection between the lift actuator  24  and the devices  26   a ,  26   b  allows the change in geometry between the  FIGS. 2&amp;3  configurations to be accommodated without requiring use of a different lift actuator. Thus, the same lift actuator  24  may be used for each configuration of the suspension system  10 , thereby eliminating the cost of maintaining multiple different lift actuators in inventory for the different configurations. 
     Of course, a person skilled in the art would, upon a careful consideration of the above description of representative embodiments of the invention, readily appreciate that many modifications, additions, substitutions, deletions, and other changes may be made to these specific embodiments, and such changes are within the scope of the principles of the present invention. Accordingly, the foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims and their equivalents.