Patent Publication Number: US-2006017254-A1

Title: Vehicle-towed trailer with independent suspension

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims priority to U.S. provisional application 60/584,053 filed on Jun. 30, 2004, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to vehicle-towed trailers and more particularly to vehicle-towed trailers having an independent suspension system.  
      2. Description of the Related Art  
      Vehicle-towed trailers typically include a rigid axle on which a pair of wheels are rotatably supported. The body of the trailer is supported above the axle by leaf springs. Trailers that include more than one rigid axle generally support the axles using a common set of leaf springs. Since each wheel shares an axle with another wheel, and since two or more axles generally share a common set of leaf springs, movement of any one wheel is not truly independent of the other wheels on the trailer. Accordingly, many trailers including the aforementioned suspension structure are limited to “on-road” operation or other operating conditions that do not require independent movement of each wheel. The present invention overcomes the limitations of prior art vehicle-towed trailers that do not permit independent movement of each wheel.  
     SUMMARY OF THE INVENTION  
      A vehicle-towed trailer is provided that includes a trailer frame, at least two wheels, and an independent suspension system securing each wheel to the frame. The independent suspension system includes a rotatable suspension rod supported by the frame and a trailing arm secured to the suspension rod. The trailing arm is adapted to pivot relative to the vehicle frame as the suspension rod rotates. The trailing arm includes a hub adapted to support one of the wheels. A bellcrank is secured to the suspension rod and adapted to pivot relative to the vehicle frame as the suspension rod rotates. The bellcrank is spaced angularly relative to the trailing arm about the axis of the suspension rod. A spring member is pivotably secured on one end to the frame and on the other end to the bellcrank. The spring member is adapted to be compressed and extended as the bellcrank pivots relative to the vehicle frame. Other aspects of the invention will be apparent to those skilled in the art after review of the drawings and detailed description provided below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, wherein:  
       FIG. 1  is a side view of a vehicle-towed trailer according to an embodiment of the present invention;  
       FIG. 2  is a side view of the trailer of  FIG. 1  with the wheels removed to expose an independent suspension system in a compressed state;  
       FIG. 3  is a side view of the trailer of  FIG. 1  with the wheels removed to expose the independent suspension system in an extended state;  
       FIG. 4  is a perspective view of the trailer shown in  FIGS. 1-3  with a frame rail from one side of the trailer removed to further expose the independent suspension system;  
       FIG. 5  is a perspective view of an independent suspension system according to an embodiment of the present invention;  
       FIG. 6  is a detailed view of  FIG. 2 , showing the independent suspension system in a compressed state;  
       FIG. 7  is a perspective view of the independent suspension system shown in  FIG. 6 ;  
       FIG. 8  is a detailed view of the trailer of  FIG. 3 , showing the independent suspension system in an extended state; and  
       FIG. 9  is a perspective view of the independent suspension system shown in  FIG. 8 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Referring to  FIGS. 1-4 , a vehicle-towed trailer  20  according to an embodiment of the present invention is shown. Trailer  20  includes a frame  22  having a pair of longitudinally extending frame rails  24 . Frame rails  24  are interconnected by at least one transversely mounted cross-member  26  upon which a load floor  28  is supported (see, e.g.,  FIG. 4 ). A connecting member  29  is secured to frame  22  and functions to connect trailer  20  to the towing vehicle (not shown). Trailer  20  also includes at least one wheel  30  positioned outwardly of each frame rail  24  and supported on frame  22  by an independent suspension system  32 . It will be appreciated after further description of independent suspension system  32  that frame  22  and connecting member  29  are not limited to the configurations illustrated in  FIGS. 1-4 , and that other frame and connecting member configurations that support the use and operation of independent suspension system  32  are within the scope of the present invention.  
      Referring to  FIGS. 5-9 , an embodiment of independent suspension system  32  is shown in detail. As a preliminary matter, suspension system  32  permits movement of its supported wheel  30  in a manner that is completely independent of the movement of the other wheel(s). To facilitate this operation, an embodiment of suspension system  32  includes a rotatable suspension rod  34  that is supported proximate one of its ends by frame rail  24  and proximate its other end by a support flange  36  secured to and positioned generally orthogonal to load floor  28 . A portion of suspension rod  34  extends through frame rail  24  and is secured to a trailing arm  38  that pivots about a longitudinal axis A-A (see  FIGS. 5 and 7 ) of suspension rod  34  as suspension rod  34  rotates. Trailing arm  38  extends generally perpendicular to suspension rod  34  and supports a rotatable wheel hub  40  at some distance removed from suspension rod  34 . A bearing (not shown) may be provided between wheel hub  40  and trailing arm  38  to facilitate rotation of wheel hub  40 .  
      With further reference to  FIGS. 5-9 , suspension system  32  also includes a bellcrank  42  secured to suspension rod  34 . As shown in  FIG. 5 , bellcrank  42  extends through an elongated opening  43  in the generally C-shaped frame rail  24  between support flange  36  and trailing arm  38 . In an embodiment, a cap  44  is attached to bellcrank  42  using a pair of fasteners, such as threaded bolts, to sandwich suspension rod  34  therebetween. When properly secured to suspension rod  34 , bellcrank  42  pivots about the axis A-A of suspension rod  34  as suspension rod  34  rotates.  
      As shown in  FIGS. 6 and 8 , bellcrank  42  is positioned on suspension rod  34  such that an angle θ exists between trailing arm  38  and bellcrank  42  about the axis A-A of suspension rod  34  (see  FIG. 6 ). In the illustrated embodiment, θ is about 90°; however, θ may be between about 80° and 110° depending on the desired ground clearance and the diameter of the wheel  30  attached to hub  40 .  
      To permit movement of wheel  30  about suspension rod  34  and to dampen this movement, independent suspension system  32  may include a spring member  46  and a damper member  48 , respectively. In a particular configuration, spring member  32  includes a compression spring and damper member  34  includes a gas or oil-filled damper.  
      In an embodiment, spring member  46  and damper member  48  are combined into a shock absorber  50  that is fixed on one end to frame rail  24  (or other structural component of trailer  20 ) and on the other end to bellcrank  42 . In a particular configuration, shock absorber  50  is pivotably attached on one end to an extension arm  52  that is secured to bellcrank  42 , and on the other end to an anchor member  54  that is fixed to frame rail  24  (or other structural component of trailer  20 ). In this manner, shock absorber  50  is free to pivot between anchor member  54  and bellcrank  42  as it is extended and compressed. Trailer  20  may also include a bump-stop  56  proximate each bellcrank  42  to limit the amount of travel of bellcrank  42  and, accordingly, the extension of shock absorber  50 .  
      It will be appreciated that in some “light-duty” applications a damper member  48  may not be needed. However, in other applications, if suspension system  32  were equipped with just spring member  46 , wheel  30  may bounce up and down several times after each bump. When compressed by a bump, damper member  48  dissipates the energy that is stored in spring member  46  and prevents the suspension from bouncing out of control.  
      It will also be appreciated the spring member  46  and damper member  48  may not necessarily be incorporated into a shock absorber  50 . Alternatively, spring member  46  and damper member  48  may be separately attached to bellcrank  42  and frame rail  24  (or other structural component of trailer  20 ). Additionally, while spring member  46  and damper member  48  are shown as being mounted above frame rail  24 , spring member  46  and damper member  48  may also be mounted below frame rail  24 , provided the trailer wheels  30  are sized to allow the necessary ground clearance for operation of the suspension system.  
      The present invention has been particularly shown and described with reference to the foregoing embodiments, which are merely illustrative of the best modes for carrying out the invention. It should be understood by those skilled in the art that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention without departing from the spirit and scope of the invention as defined in the following claims. It is intended that the following claims define the scope of the invention and that the method and apparatus within the scope of these claims and their equivalents be covered thereby. This description of the invention should be understood to include all novel and non-obvious combinations of elements described herein, and claims may be presented in this or a later application to any novel and non-obvious combination of these elements. Moreover, the foregoing embodiments are illustrative, and no single feature or element is essential to all possible combinations that may be claimed in this or a later application.