Abstract:
The suspension system of the present invention broadly comprises a method of retrofitting an existing torsion axle suspension carried by a frame with an air spring comprising the steps of removing an original torsion axle that was fixed to a frame from the frame and mounting the torsion axle to at least one rotatable arm such that rotation of the arm causes vertical translation of the original torsion axle. The suspension system also comprises a retrofit kit for use with a torsion axle suspension system having a torsion axle and a spindle comprising a hanger bracket adapted to be attachable to the frame, a pivot arm for mounting to the hanger bracket and adapted for rotatably supporting the existing torsion axle, an air spring, a support assembly secured to the pivot arm for supporting the air spring, and an attachment for securing the pivot arm to the support assembly.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from U.S. Provisional Patent application Ser. No. 61/171,618 filed Apr. 22, 2009; the disclosure of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Technical Field 
         [0003]    The invention relates generally to an improved vehicle suspension system for vehicles, such as trailers and trucks. More particularly, the invention relates to a retrofit kit for a torsion arm suspension. Specifically, the invention relates to a retrofit kit which can easily be installed on a torsion arm suspension so that the system provides both spring and torsion arm dampening without the additional expense of replacing the torsion arm suspension. 
         [0004]    2. Background Information 
         [0005]    Torsion axles have been known for many years, such as shown in U.S. Pat. No. 2,998,981. Torsion axles have proven to be extremely popular because if one wheel hits a bump or rut, it can react independently of the other wheel, which may not hit a bump or rut at the same time. This torsion axle concept operates to keep a trailer moving as straight as possible behind a towing vehicle and absorbs some of the shock of the road over which it is passing with an independent rut or is slowed down for any reason while the other wheel of the trailer does not have the same experience at the same time, the trailer would tend to turn somewhat to allow the wheel that is on the flat part of the road to move forward while the wheel that is in the rut is restrained, therefore causing the axle not to be perpendicular with the direction of towing of the vehicle itself. 
         [0006]    Most torsion axles are constructed of a square axle in cross section with elongated rubber members disposed in-between the square axle and a larger outer tube. U.S. Pat. Nos. 5,161,814 and 5,820,156 discloses such a construction. One common torsion axle is a TorFlex® rubber torsion suspension system distributed by Dexter Axle. This type of torsion axle has independent and separate stub axles or stub shafts on each end which are part of spaced suspension assemblies mounting each of the wheels on the trailer frame to enhance the independent aspect of such an axle. 
         [0007]    Torsion axles can also be constructed as in U.S. Pat. No. 5,163,701 which uses a plurality of elongated bars which can twist and bend but return to their original position after such bending. It is also known to use air bags, commonly referred to as air springs, for straight, non-torsion axles, such as shown in U.S. Pat. Nos. 3,784,221 and 5,427,404. While it is true that both the torsion axle technology and the air spring technology has been quite successful independently in making a smoother ride and enhanced the handling performances of vehicles having such suspension systems, these suspension systems still have their shortcomings and there is a need for improvement thereto. 
         [0008]    The vehicle suspension system of U.S. Pat. No. 6,340,165 combines the advantage of both the torsion axle and air spring into a single suspension assembly and has provided a more efficient and better performing suspension system than that believed provided by the systems using only a torsion axle or only an air spring. Nevertheless, the combination system requires great expense and a significant amount of space. Further, the consumer is forced to decide at the outset whether to spend the extra money and purchase the combination suspension or purchase only one of the two suspensions. 
         [0009]    Therefore, a need exists for a compact, cost-efficient, and simple retrofit kit for a suspension which allows the consumer to purchase components that can easily be connected to the existing suspension without modification. 
       SUMMARY OF THE INVENTION 
       [0010]    The suspension system of the present invention broadly comprises a method of retrofitting an existing torsion axle suspension carried by a frame with an air spring comprising the steps of removing an original torsion axle that was fixed to a frame from the frame and mounting the torsion axle to at least one rotatable arm such that rotation of the arm causes vertical translation of the original torsion axle. 
         [0011]    The present invention also broadly comprises a retrofit kit for use with a torsion axle suspension system having a torsion axle and a spindle comprising a hanger bracket adapted to be attachable to the frame, a pivot arm for mounting to the hanger bracket and adapted for rotatably supporting the existing torsion axle, an air spring, a support assembly secured to the pivot arm for supporting the air spring, and an attachment for securing the pivot arm to the support assembly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The preferred embodiment of the invention, illustrative of the best mode in which Applicant has contemplated applying the principles of the invention, is set forth in the following description and is shown in the drawings. 
           [0013]      FIG. 1  is a left elevation view of a truck towing a trailer having a preferred embodiment suspension system retrofit kit; 
           [0014]      FIG. 2  is a rear elevation view of a retrofit suspension system of the preferred embodiment with a vehicle body attached to the frame and shown in dot-dash lines; 
           [0015]      FIG. 3  is an exploded perspective view of the mounting hardware of the driver side of a preferred embodiment suspension system retrofit kit being assembled on a torsion arm suspension; 
           [0016]      FIG. 4  is an exploded perspective view of a driver side of a preferred embodiment suspension system retrofit kit being assembled on a torsion arm suspension; 
           [0017]      FIG. 5  is a perspective view of the driver side of a preferred embodiment suspension system retrofit kit assembled; 
           [0018]      FIG. 6  is a bottom view of the driver side of a preferred embodiment suspension system retrofit kit installed; 
           [0019]      FIG. 7  is an enlarged rear view of the driver side of a preferred embodiment suspension system retrofit kit installed; 
           [0020]      FIG. 8  is an enlarged front view of the driver side of a preferred embodiment suspension system retrofit kit installed; 
           [0021]      FIG. 9  is a cross-sectional view of the driver side of the preferred embodiment suspension system in  FIG. 7  taken generally along line  9 - 9 ; 
           [0022]      FIG. 10  is a left elevation view of the driver side of a preferred embodiment suspension system retrofit kit installed and in the design position; 
           [0023]      FIG. 11  is a left elevation view of the driver side of a preferred embodiment suspension system retrofit kit installed and in the rebound position; and, 
           [0024]      FIG. 12  is a left elevation view of the driver side of a preferred embodiment suspension system retrofit kit installed and in the jounce position. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0025]    At the outset, it should be appreciated that like drawing numbers on different drawing views identify identical, or functionally similar, structural elements of the invention. While the present invention is described with respect to what is presently considered to be the preferred embodiment, it is to be understood that the invention as claimed is not limited to the disclosed aspects. 
         [0026]    Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs. Although any methods, devices or materials similar or equivalent to those described herein can be used in the practice or testing of the invention, the preferred methods, devices, and materials are now described. 
         [0027]    The vehicle suspension of the present invention is indicated generally at  14 , as is particularly shown in  FIGS. 1 through 12  mounted on a vehicle  16 , such as a trailer of the type being towed by a truck  18 . As seen in  FIG. 2 , trailer  16  is supported on a pair of frame rails  20  extending longitudinally along the length of the trailer. A pair of the retrofit kit suspension assemblies, each indicated generally at  22 , are mounted on a respective frame rail  20 , each generally adjacent a tire-wheel assembly  24 . 
         [0028]    Averting to  FIGS. 3 and 4 , one of the retrofit suspension assemblies is shown in exploded views. Initially, a torsion axle  26  is provided and attached to the trailer frame. It is to be understood that the retrofit kit is installed around the trailing beam, or any other suitable suspension system that is provided by the trailer manufacturer and that virtually no modification is necessary for the retrofit kit installation. 
         [0029]    Torsion axle  26  typically includes an axle  28 , a mounting bracket  30  on each side, and a torsion arm  32  on each end of axle  28 . Each mounting bracket  30  is located at least partially around the axle and proximate torsion arm  32 . The torsion arm includes a first end  34  and a second end  36  opposite the first end. The first end includes an aperture  38  adapted to receive a torsion bar  40 , while the second end includes a spindle  42  extending perpendicular from torsion arm  32  in a direction away from axle  28 . Torsion bar  40  extends concentrically and longitudinally through axle  28  and preferably terminates flush with an outer side  44  of each torsion arm  32 . In an alternative embodiment, torsion bar  40  may be split into two bars so that each wheel operates independent of the other. 
         [0030]    Further, torsion bar  40  is surrounded by rubber cords  46  longitudinally running the length of axle  28  as particularly seen in  FIG. 9 . In a preferred embodiment, four rubber cords are used and each is arranged along a flat side of torsion bar  40 . Torsion bar  40  is preferably arranged asymmetrical to axle  28 , so that flat sides of the torsion bar are directed at corners of the axle and corners of the torsion bar are directed at flat sides of the axle. 
         [0031]    In a preferred embodiment, mounting bracket  30  includes vertical wall  48  and horizontal wall  50 . Frame rails  20  are attached to horizontal wall  50 , while vertical wall  48  includes through holes  52 ,  54 , and  56  for attachment of the retrofit suspension. If through holes  52 ,  54 , and  56  are not included in the mounting bracket from the trailer manufacturer, they will need to be drilled by the retrofit kit consumer before installation. 
         [0032]    In accordance with one of the main features of the present invention, suspension retrofit kit  22  includes a pivot arm  58 , a support assembly  60 , a hanger bracket  62 , and a spring  64 . Pivot arm  58  includes a front end  66  and a back end  68 . In a preferred embodiment, the pivot arm includes two parallel walls  70  and  72  connected to one another with mounting tab  74  via welding at the front end. A guide sleeve  76  is welded near the back end and a bushing mount  78  is attached at the back end with a through bore  80  via welding. Although welding is the preferred method of attachment, any suitable attachment means known in the art may be utilized. At the front end, both parallel walls  70  and  72  include through holes  82  which are arranged coaxially with one another. The guide sleeve includes a through hole arranged coaxially with through holes  84  in the parallel walls. Parallel walls  70  and  72  each also include U-shaped channels  86  between through holes  82  and  84  which are complimentary sized and shaped to fit around axle  28 . 
         [0033]    Support assembly  60  includes a mounting surface  88  with through holes  90 , an outer arm  92 , and an inner arm  94 . Mounting surface  88  preferably extends between the inner and outer arms, as well as locates the bottom side of spring  64 . Outer arm  92  preferably extends upwardly and outwardly away from mounting surface  88  such that the mounting surface is spaced apart from a back end  96  of the outer arm. Further, outer arm  92  includes a pair of through holes  98  spaced apart and arranged to be concentric with through holes  54  and  56  of mounting bracket  30 . 
         [0034]    Inner arm  94  is arranged similar to outer arm  92  in that the inner arm also extends upwardly and outwardly away from the mounting surface in the same direction as the outer arm. However, inner arm  94  terminates in a cradle  100 . The cradle is shaped complimentary to one-half of axle  28 , so that the cradle fits securely around the axle. Cradle  100  also includes a plurality of mounting holes  102  disposed around the perimeter. On the opposite side of axle  28  is bracket  104 . Bracket  104  is also shaped complimentary to axle  28  and also includes a plurality of mounting holes  106 . Advantageously, when cradle  100  and bracket  104  are each located around axle  28 , mounting holes  102  and  106  are aligned and arranged to receive bolts  108  with nuts  109  to secure the cradle and the bracket together around the axle. 
         [0035]    In order to secure pivot arm  58  to mounting bracket  30 , through holes  84  of the pivot arm are aligned with through holes  52  and  54  of the mounting bracket. Next, support assembly  60  is located so that through holes  98  are aligned with through holes  54  and  56 . Accordingly, bolts  110  are inserted through the respective through holes and nuts  112  are threaded thereon ( FIG. 8 ). Further, as discussed above, cradle  100  and bracket  104  are secured together around axle  28 . Thus, the pivot arm and support assembly are secured both to each other and to torsion axle  26  at both mounting bracket  30  and axle  28 . 
         [0036]    As is particularly seen in  FIG. 4 , hanger bracket  62  and spring  64  are preferably installed next. Initially, through bore  80  of bushing mount  78  is arranged to receive a bushing  114 , which is preferably a split-bushing where one-half of the bushing is inserted into each end of the through bore. 
         [0037]    As particularly seen in  FIGS. 4 and 6 , hanger bracket  62  includes a front end  116  that is slightly wider than guide sleeve  78  so that the front end can fit around the guide sleeve. Further, the front end has a pair of downwardly extending side walls  118  each having an opening  120  proximate the bottom of the side wall. The hanger bracket extends rearward from the front end and terminates at rear end  122 . Rear end  122  includes apertures  124  to provides access to air lines and other components as necessary. A bottom side of the rear end is adapted to abut plate assembly  126  which is secured to the top of spring  64  with bolts or screws  128 . Thus, movement of spring  64  translates into movement of rear end  122  of hanger bracket  62 . 
         [0038]    After the pivot arm and support assembly are secured, split bushing  114  is inserted into through bore  80 . In the alternative, split bushing  114  could be factory installed and not require this step at this time. Next, hanger bracket  62  is installed around bushing mount  78  so that openings  120  are concentric with and on each side of through bore  80 . A bolt  130  is then inserted through opening  120  and split bushing  114  and secured in place by threading a nut  132  onto the bolt. Thus, hanger bracket  62  can pivot about the connection at bushing  114 . Next, spring  64 , which is an air spring in the preferred embodiment, is located on mounting surface  88  of support assembly  60  and secured with bolts or screws  134 . At the top of the air spring, bolts or screws  136  are preferably used to secure the plate assembly to spring  64 . Thus, pivot arm  58  pivots at hanger bracket  62  the support assembly is moved upward or downward by spring  64 . Further, this movement occurs because support assembly  60  is fixed in relation to mounting bracket  30  and pivot arm  58 . Although in the preferred embodiment spring  64  is installed after hanger bracket  62 , it is within the spirit and scope of the present invention as claimed to install the spring before the hanger bracket. 
         [0039]      FIG. 5  illustrates the torsion axle suspension with the retrofit kit assembly installed and connected to frame rail  20 . As can be seen, frame rail  20  only contacts the retrofit kit assembly at hanger bracket  62 . 
         [0040]    In accordance with another main feature of the invention, and particularly shown in  FIG. 7 , mounting bracket  30  is no longer directly connected to frame rail  20  after hanger bracket  62  is installed. Specifically, mounting bracket  30  is supported by support assembly  60  and pivot arm  58 . Thus, mounting bracket  30  also moves with support assembly  60  and the torsion axle. 
         [0041]    Having described the structure of the present invention, a preferred method of operation will be described in detail and should be read in light of  FIGS. 1 through 12  and specifically  FIGS. 10 through 12 . The following preferred embodiment description utilizes a Dexter 8000 rubber torsion axle with a standard frame bracket, a 22.5 degree up swing arm angle, and the through bore  80  of pivot arm  58  located approximately 2.5 inches from the trailer frame, but is not limited to such and is only representative of potential system dimensions, which are limited only by the Claims. 
         [0042]      FIG. 10  illustrates the vehicle suspension system in the design position and also represents the state of the suspension when traveling down a smooth road without undulations. The trailer will ride slightly higher with the retrofit suspension assembly when spring  64  is at the design position and the torsion axle is at full load. In a preferred embodiment, the ride height is approximately 3.11 inches and allows for approximately 3.78 inches of spindle jounce travel. However, the present invention is not limited to any particular ride height or spindle jounce travel as various size tire/wheel assemblies and desired suspension arrangements will require or allow for significantly different parameters. 
         [0043]      FIG. 11  illustrates the vehicle suspension system in the rebound position and occurs as spindle  42  travels in the direction associated with arrow  138 . Here, the total spindle travel available with the torsion axle at full load and spring  64  fully exhausted is approximately 6.96 inches in the preferred embodiment. 
         [0044]      FIG. 12  illustrates the vehicle suspension system with no air in spring  64  and in the jounce position which occurs as spindle  42  travels in the direction associated with arrow  140 . In this arrangement, the spindle jounce travel available with the torsion axle from full load to shock load is approximately 0.67 inches, while the total spindle travel from no load to shock load is approximately 1.95 inches. Thus it is seen that the retrofit suspension kit provides the additional dampening and suspension of an air spring or axial spring suspension system without the high up-front costs of a factory installation or the removal and replacement of the original torsion axle. 
         [0045]    In summary, vehicle suspension system  14  includes an easily installed retrofit kit  22  that is installed around a trailing beam axle. The retrofit kit includes pivot arm  58  for pivotal connection with hanger bracket  62 . Hanger bracket  62  is connected to support assembly  60  through spring  64 . Thus, when spring  64  is expanded or contracted, support assembly  60  is pivoted at the pivotal connection between the hanger bracket, the pivot arm, and the support assembly. Further, installation of the retrofit kit assembly is accomplished by initially securing the pivot arm and support assembly to mounting bracket  30 . Next, spring  64  is mounted to support assembly  60  and hanger bracket  62  is rotated downwards into contact with the top of spring  64 . 
         [0046]    Accordingly, the suspension system retrofit kit is an effective, safe, inexpensive, and efficient device that achieves all the enumerated objectives of the invention, provides for eliminating difficulties encountered with prior art devices, systems, and methods, and solves problems and obtains new results in the art. 
         [0047]    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 requirement of the prior art, because such terms are used for descriptive purposes and are intended to be broadly construed. 
         [0048]    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. 
         [0049]    Having now described the features, discoveries, and principles of the invention, the manner in which the suspension system retrofit kit is constructed and used, the characteristics of the construction, and the advantageous new and useful results obtained; the new and useful structures, devices, elements, arrangement, parts, and combinations are set forth in the appended claims.