Abstract:
A suspension system for use with a vehicle comprising a control arm having an upper rear arm and a spring mounting plate integrally formed as a single member, a spindle extending outwardly from the upper rear arm, an air spring adapted to be mounted intermediate the spring plate and the vehicle, and a pivot assembly for pivotally mounting the control arm to the vehicle whereby the pivot assembly has a fist axis of rotation.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority from U.S. Provisional Patent Application Ser. No. 61/171,637 filed Apr. 22, 2009; the disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The invention relates generally to an improved vehicle suspension system for vehicles, such as trailers and trucks. More particularly, the invention relates to an air spring suspension system with a single piece trailing beam for land vehicles. Specifically, the invention relates to a trailing beam air suspension system which provides the advantages of independent wheel suspension with integrated components and a more compact arrangement. 
     2. Background Information 
     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 suspension. This is contrasted with a straight axle where if one wheel drops into a 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. 
     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. 
     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. 
     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. 
     The suspension assembly of the present invention improves on the prior art by providing a more rugged, compact, lighter weight suspension by providing a completely independent trailing arm style suspension that still provides superior lateral stability. This also allows the traditional torsion axle to be completely removed and enable lower design heights to be achieved. This also requires only a single integrated moving part at each wheel to provide a superior ride quality. 
     Therefore, a need exists for a trailing arm suspension which is a fully independent wheel suspension and incorporates air springs to improve ride quality. 
     SUMMARY OF THE INVENTION 
     The suspension system of the present invention broadly comprises a suspension system for use with a vehicle comprising a control arm having an upper rear arm and a spring mounting plate integrally formed as a single member, a spindle extending outwardly from the upper rear arm, an air spring adapted to be mounted intermediate the spring plate and the vehicle, and a pivot assembly for pivotally mounting the control arm to the vehicle whereby the pivot assembly has a fist axis of rotation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The preferred embodiments of the invention, illustrative of the best modes in which Applicant has contemplated applying the principles of the invention, are set forth in the following description and are shown in the drawings. 
         FIG. 1  is a side view of a truck towing a trailer having a preferred embodiment suspension system; 
         FIG. 2  is a front view of a suspension system of the preferred embodiment with a vehicle body attached to the frame and shown in dot-dash lines; 
         FIG. 3  is a perspective view of the driver side of a preferred embodiment suspension system; 
         FIG. 4  is an exploded perspective view of the driver side of a preferred embodiment suspension system; 
         FIG. 5  is a bottom view of the driver side of a preferred embodiment suspension system; 
         FIG. 6  is a cross-sectional view of the driver side of a preferred embodiment suspension system taken generally along line  6 - 6  in  FIG. 3 ; 
         FIG. 7  is a cross-sectional view of the driver side of a preferred embodiment suspension system taken generally along line  7 - 7  in  FIG. 3 ; 
         FIG. 8  is a side view of the driver side of a preferred embodiment suspension system in the design position; 
         FIG. 9  is a side view of the driver side of a preferred embodiment suspension system in the rebound position; and, 
         FIG. 10  is a side view of the driver side of a preferred embodiment suspension system in the jounce position. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     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. 
     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. 
     The vehicle suspension system of the present invention is indicated generally at  12 , as is particularly shown in  FIGS. 1 through 10  mounted on a vehicle  14 , such as a trailer of the type being towed by a truck  16 . Averting to  FIG. 2 , trailer  14  is supported on a pair of frame rails  18  extending longitudinally along the length of the trailer. A pair of the improved suspension assemblies, each indicated generally at  20 , are mounted on a respective frame rail  18  each generally adjacent a tire-wheel assembly  22 . 
     Referring to  FIG. 4 , suspension assembly  20  includes a frame mounting bracket  24  which is secured to frame rail  18  by a plurality of bolts, by welding, or another type of attachment known in the art. Bracket  24  preferably has a U-shaped channel with sidewalls  26  and  28  perpendicular to and on each side of a center wall  30 . Sidewalls  26  and  28  decrease in height from a front end  32  to a back end  34  and include a circular shaped opening  36  proximate front end  32 . Opening  36  is arranged to receive and secure an axle tube  62  discussed below. 
     In accordance with one of the main features of the present invention, control arm  38  is generally arcuate in shape and includes a central body  40  with a cavity  42  extending through the front portion of the central body. The control arm also includes an upper rear portion  43  with a spindle  44  protruding from an outer surface  46  and arranged to support tire-wheel assembly  22 . A rear surface  47 , proximate and below upper rear portion  43 , is preferably concave in shape with the bowl-shaped opening directed rearward. The generally concave shape of rear surface  47  is partially defined at the top by upper rear portion  43  and at the bottom by bottom rear portion  57  (described infra). Cavity  42  receives and supports a complimentary shaped cross tube assembly  48 . Control arm  38  pivots at cavity  42  due to spindle  44  and cavity  42  being offset from one another. 
     In particular, cross tube assembly  48  has a first end  50  and a second end  52  with an overall length of approximately 19.75 inches in a preferred embodiment. First end  50  is fully inserted within cavity  42  such that the outer portion of first end  50  is generally flush with outer surface  46 . A plug  54  is inserted at least partially into first end  50  and protects the inner diameter of cross tube assembly  48  as well the bearings and connections between control arm  38  and cross tube assembly  48 . 
     Control arm  38  also includes a lower spring support  56  extending from a bottom rear portion  57  of the control arm. The lower spring support is preferably welded to the control arm at bottom rear portion  57 . However, the lower spring support may also be arranged to be bolted to the control arm without departing from the spirit and scope of the invention. Lower spring support  56  has a spring mounting surface  58 . Advantageously, an air spring  60  is located on an axis rearward of the cross tube assembly  48  and permits full functional use of the air spring. In particular, the distance between the center of control arm cavity  42  and the center axis of air spring  60  is approximately 10 inches in a preferred embodiment, while the distance between the center of control arm cavity  42  and the center axis of spindle  44  is approximately 7.36 inches. Thus, the control arm is a compact component that locates the spindle axis very close to the air spring axis to provide superior isolation by using virtually the full range of motion of air spring  60 . 
     An axle tube  62  extends from the driver side to the passenger side and is preferably a hollow tube that includes a first end  64  with a bearing surface  66 . Axle tube  62  is intermediate the pair of cross tube assemblies  48  and arranged to accept second end  52  of the cross tube assembly. Cross tube  48  is coupled to axle tube  62  by welding  69  through weld windows  68  after the cross tube is fully seated within the axle tube, as particularly seen in  FIG. 7 . 
     While axle tube  62  is described as connecting the driver side and passenger side suspensions, the axle tube need not connect the driver side and passenger side suspensions. In particular, each suspension can be connected to a separate axle tube, which is in turn connected to the frame or other structurally sound component. While only one end of axle tube  62  has been described in detail, the second end is identical to first end  64  with respect to suspension system  20  of the passenger side, as should be apparent to one of ordinary skill in the art. 
     Averting to  FIGS. 5 and 6 , suspension system  20  is shown as a single integrated unit and separated from axle tube  62 . Further, first end  50  of cross tube assembly  48  is shown press fit and welded within cavity  42  of control arm  38 . Although press fitting is the preferred fastening method, cross tube assembly  48  may also be welded or bolted to control arm  38 , which is within the spirit and scope of the invention as claimed. 
     Air spring  60  is located between the bottom side of frame mounting bracket  24  and spring mounting surface  58  of control arm  38 . Preferably, the bottom of air spring  60  is bolted to mounting surface  58  with bolts  59  and the top of air spring  60  is bolted to plate  61  with another set of bolts  59 . A plate  61  may be integral to frame mounting bracket  24 , welded to bracket  24 , or be secured with additional fasteners at slots  63  ( FIG. 3 ). Air Spring  60  is preferably a heavy-duty unit, such as Goodyear Model 2B9-251 or similar air spring, although any suitable isolation mechanism may be incorporated as should be immediately apparent to one of ordinary skill in the art. 
     In accordance with another main feature of the present invention and referring to  FIG. 7 , cross tube assembly  48  includes an inner member  72  which is concentric with axle tube  62  when the cross tube assembly is installed within the axle tube. The cross tubes each have an inner bushing  74  proximate second end  52  and an outer bushing  76  proximate first end  50 . Outer bushing  76  has a larger outer diameter than inner bushing  74  and outer bushing  76  is seated within a bushing surface  66  of axle tube  62  when cross tube assembly  48  is fully inserted within the axle tube. Inner bushing  74  has an outside diameter approximately equal to the inside diameter of axle tube  62  is generally located in a space  78  formed by the gap between axle tube  62  and inner member  72 . Further, it is within the spirit and scope of the present invention to replace inner bushing  74  and outer bushing  76  with a pair of bearings. 
     A retainer assembly  80  includes an insert  82  which is welded to a first end  81  of inner member  72  indicated at  83 . Next, an inner axle retainer  88  is slid onto the outer surface of the insert and located proximate first end  81 . The inner axle retainer includes clearances  85  and  87 . Clearance  85  is provided to allow room for weld  83 , while clearance  87  is provided to allow rotation of inner member  72  and insert  82 . After the inner axle retainer is located on insert  82 , a stop  84  is slid onto the outer surface of the insert. The stop is then welded to the outer surface of the insert at  86  and prevents movement of the axle in the direction associated with arrow A. Insert  82  preferably has an outside diameter of approximately 3″, but may be any appropriate size to slide within the inside diameter of inner member  72  and is arranged to assist in preventing axial movement of the inner member relative to axle tube  62 . 
     Inner axle retainer  88  is then welded into place through weld window  68  at weld  69 . Inner axle retainer  88  is thus axially and rotationally secured after being welded and thereby prevents axial movement of retainer assembly  80  due to the welding of the inner member and insert  82 . Accordingly, retainer assembly  80  prevents axial movement of inner member  72  and control arm  38  in the directions indicated by arrow A while still permitting free rotational movement at bushings  74  and  76 . 
     Axle tube  62  is axially spaced apart from control arm  38  by a washer  90  and connected to the control arm at a weld  89 . Washer  90  is preferably a heavy-duty washer with an inside diameter slightly larger than the outside diameter of inner member  72  and an outside diameter approximately equal to the outside diameter of axle tube  62 . Advantageously, washer  90  properly spaces axle tube  62  and outer bushing  76  axially apart from control arm  38  to allow inner member  72  and control arm  38  to spin freely with little resistance. While the preferred embodiment is described with an axle tube, it is within the spirit and scope of the present invention to provide a pair of control arms  38  spaced apart from and parallel to one another and mounted to frame rail  18 . 
     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 10 . 
       FIG. 8  is a side view of suspension assembly  20  in the design position and also represents the state of the suspension when traveling down a smooth road without undulations. In a preferred embodiment, distance D is approximately 9.60 inches, while angle α is approximately 22.9°.  FIG. 9  is a side view of suspension assembly  20  with air spring  60  fully extended in the rebound position when the suspension is fully decompressed. The rebound position occurs as spindle  44  travels vertically downward after encountering an undulation in the road surface or upon entering a pothole and spring mounting surface  58  moves downward in the direction of arrow C. In the full rebound position, distance R is approximately 12.70 inches, while angle β is approximately 43.0°.  FIG. 10  is a side view of suspension assembly  20  in the jounce position when the suspension is fully compressed. The jounce position occurs when spindle  44  moves vertically upward upon contacting an undulation in the road and the bottom of air spring  60  is forced upward by spring mounting surface  58  due to the rotational movement of control arm  38  in the direction of arrow E. In the jounce position, distance J is approximately 5.11 inches, while angle {circle around (-)} is equal to approximately zero degrees. Advantageously, spindle  44  of suspension system  20  has a jounce travel H approximately equal to 2.62 inches and a rebound travel K approximately equal to 2.72 inches. Thus the total travel of spindle  44  is 5.34 inches and 43° in a preferred embodiment. 
     Averting to  FIG. 8 , when spindle  44  is moved vertically in the directions associated with arrows M and N due to movement of the tire-assembly (not shown), control arm  38  is rotated at the pivot connection of cross tube assembly  48  and axle tube  62  due to the vertical spindle movement. Thus, when spindle  44  is moved in the direction of arrow N, a clockwise rotation is imparted on control arm  38 . Further, when spindle  44  is moved in the direction of arrow M, a counter-clockwise rotation is imparted on control arm  38 . Air spring  60  acts to isolate and reduce the effects of any rotational movement of control arm  38  and is particularly effective since the spindle  44  is very close to the air spring  60 . In addition, the “C” shape of control arm  38  means that spring mounting surface  58  is horizontally spaced about the same distance from the pivot connection of cross tube assembly  48  and axle tube  62  as the air spring mounting position on frame mounting bracket  24 . Therefore, air spring  60  is generally compressed about its vertical axis to improve the air spring life and efficiency. 
     In summary, suspension system  12  provides a trailing beam style suspension with fully independent wheel action and all the advantages known in the art, while still providing a suspension that is light weight and compact when fully assembled. Each suspension assembly  20  operates such that as tire-wheel assemblies  22  encounter road contours and obstructions, each control arm  38  pivots independently from the opposing control arm. Thus, the need for a heavy torque arm, u-bolt frame connections, rubber strips, and rubber bushings, which add significant weight and unwanted compliance, have been eliminated, as well as the associated variations in tow and camber. Further, since suspension assembly  20  is a one-piece structure and bearings or bushings are located at the pivot points, hysteresis is virtually eliminated and allows frame rails  18  to be located closer to the ground while dramatically improving ride quality. 
     Accordingly, the suspension system 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. 
     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. 
     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 suspension system 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.