Abstract:
A suspension system for a multi-axle transport vehicle for moving heavy loads includes two fluid activated cylinders and two spaced apart arms for each wheel and axle set which allow the transport vehicle to be raised and lowered with respect to the roadway. The suspension system mechanically stabilizes the axles with respect to the transport vehicle thereby reducing axle yaw and allowing higher transport speeds.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application is a continuation of patent application having Ser. No. 10/443,550 filed on May 22, 2003, now U.S. Pat. No. 6,942,232 issued on Sep. 13, 2005, and claims priority therefrom which in turn claims priority from U.S. Provisional Application No. 60/383,554, filed May 24, 2002, each of which are included herein by reference. 

   TECHNICAL FIELD 
   The present invention pertains generally to multi-axle transport vehicles for moving heavy loads, and more particularly to a suspension system for such vehicles. 
   BACKGROUND OF THE INVENTION 
   Heavy hauling vehicles for moving transformers, cranes, boats, industrial equipment, and other heavy objects are well known in the art. An example of such a vehicle is given in U.S. Pat. No. 4,943,078 which discloses a heavy load hauler for traveling on conventional roadways for moving heavy construction equipment such as cranes or the like from one work site to another. The hauler includes a front tractor drawn carriage, a rear carriage, and a load unit disposed between and carried by the carriages. The front carriage is supported upon a multiplicity of independent wheel and axle units. There is a first fifth wheel coupling at the leading end of the front carriage for connecting to the fifth wheel coupling of a tractor. A second fifth wheel coupling is spaced rearwardly. The load carrying rear carriage is also supported upon a multiplicity of independent wheel and axle units. There is a fifth wheel coupling intermediate the leading and trailing ends of the carriage. The load unit has forwardly and rearwardly projecting goosenecks. Each gooseneck has a fifth wheel coupling. The one on the forwardly projecting gooseneck connects to the fifth wheel coupling on the front carriage. The one on the rearwardly projecting gooseneck connects to the fifth wheel coupling on the rear carriage. The load unit may be either the crane itself or a flatbed upon which the crane is carried. At least some of the independent wheel and axle units are steerably mounted on their carriages. Each wheel and axle unit has its wheels supported by a hydraulic suspension. Hydraulic circuitry interconnects all of the suspensions so as to equally distribute the load among all of the wheel units. Steering of the independent wheel and axle units is interphased for the front and rear carriages by a pair of operatively associated interrelated inline valve cylinder units.  FIG. 12A  shows a valve  718  used in a power steering system which is coupled to a connecting link  703 . 
   Other heavy hauling vehicles are sold by Goldhofer Fahrzeugwerk G.m.b.H. of Memmingen, Germany; Nicolas of Champs Sur Yonne, France; and Talbert of Rensselaer, Ind. 
   Improved systems having automatic steering at all speeds and suspension systems that respond rapidly to the varying road conditions imposed by higher speeds would greatly reduce the time and effort required to move the vehicle to the load, move the load, and return the vehicle to storage. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to a suspension system for a heavy load transport vehicles which tends to resist axle yaw. The body of the suspension system is connected to the axle by an axle linkage member which is connected to the body at four different pivotal locations. This four-point connection stabilizes the axle linkage member and substantially reduces any tendency to yaw when exposed to road induced forces. The suspension system employs two fluid activated cylinders rather than the conventional one cylinder. This feature allows the use of smaller diameter cylinders for a given system pressure. The cylinders are mounted on the outside of the suspension system for ease of maintenance. 
   In accordance with a preferred embodiment of the invention, a suspension system for a transport vehicle includes a body which is pivotable about a first axis, the body has a first attachment station separate and spaced apart from a second attachment station. An axle is disposable along a second axis which is perpendicular to the first axis. An axle linkage member has a third attachment station which is spaced apart from a fourth attachment station, the third attachment station of the axle linkage member is pivotally connected to the first attachment station of the body, and the fourth attachment station of the axle linkage member is pivotally connected to the second attachment station of the body. The axle linkage member is pivotable about a third axis which is parallel to the second axis. The axle is pivotally connected to the axle linkage member; the axle is pivotable about a fourth axis perpendicular to the first, second and third axes. Two separate and spaced apart fluid activated cylinders are pivotally connected between the body and the axle linkage member, wherein the two fluid activated cylinders are disposed outside of the first, second, third, and fourth attachment stations. When the two fluid activated cylinders are extended, the axle linkage member pivots away from the body. When the two fluid activated cylinders are retracted, the axle linkage member pivots toward the body. 
   In accordance with an aspect of the invention, when the transport vehicle is traveling on a road, the connection of the first attachment station to the third attachment station, the connection of the second attachment station to the fourth attachment station, and the connection of the two fluid activated cylinders between the body and the axle linkage member combine to reduce yaw of the axle. 
   Other aspects of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side elevation view of a prior art multi-axle transport vehicle for moving heavy loads; 
       FIG. 2  is a top plan view of the vehicle of  FIG. 1 ; 
       FIG. 3  a front elevation view of a prior art axle suspension system; 
       FIG. 4  is a side elevation view of the prior art suspension system; 
       FIG. 5  is a front elevation view of a suspension system in accordance with the present invention; 
       FIG. 6  is a side elevation view of the suspension system; 
       FIG. 7  is a rear elevation view of the suspension system; 
       FIG. 8  is a front elevation view of the suspension system with an axle rotated in a clockwise direction; 
       FIG. 9  is a front elevation view of the suspension system with the axle rotated in a counterclockwise direction; 
       FIG. 10  is a side elevation view of the suspension system in a fully retracted position; 
       FIG. 11  is a side elevation view of the suspension system in a mid-stroke position; 
       FIG. 12  is a side elevation view of the suspension system in a fully extended position; 
       FIG. 13  is a side elevation view of the suspension system when the tires encounter a pothole; 
       FIG. 14  is a side elevation view of the suspension system when the tires encounter a bump; 
       FIG. 15  is a simplified bottom plan view of a prior art axle linkage member; and, 
       FIG. 16  is a simplified bottom plan view of the axle linkage member of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 and 2  illustrate side elevation and top plan views, respectively, of a prior art multi-axle transport vehicle  500  for moving heavy loads. The vehicle  500  has a front dolly  502  and a pair of rear dollies  504  upon which a load  506  rests. The front dolly  502  and rear dollies  504  each have two axles  505  with four tires  507 . Axles  505  are rotatable about a vertical pivot axis  509  thereby allowing the axles  505  and tires  507  to turn to the right or left. The axles  507  are connected to the frames of the dollies  502 ,  504  by a suspension system which controls the vertical movement of the axles  505 . A towing vehicle  508  such as a tractor pulls transport vehicle  500  using a tow bar  510 . 
     FIGS. 3 and 4  illustrate front elevation and side elevation views, respectively, of a prior art axle suspension system  600 . Suspension system  600  includes an upper body  602  which is pivotally connected to an axle linkage member  604  at point  605 . Body  602  is connected to the underside of a dolly and pivots about vertical axis  606  thereby permitting suspension system  600  to turn. An axle  608  and associated tires  610  are connected to axle linkage member  604  thereby permitting axle  608  to roll in response to the road environment (also refer to  FIGS. 8 and 9 ). A single fluid activated cylinder  612  is pivotally connected between body  602  and axle linkage member  604 . Fluid activated cylinder  612  usually operates using a combined hydraulic and nitrogen gas system which is well known in the art. When cylinder  612  is extended, axle linkage member  604  pivots away from body  602  raising the top of the dolly further off of the ground (refer to  FIG. 12 ). When cylinder  612  is retracted, axle linkage member  604  pivots toward body  602  lowering the top of the dolly closer to the ground (refer to  FIG. 10 ). In typical operation when the transport vehicle is traveling down a highway, the height of suspension system  600  is set to a mid position by appropriately activating cylinder  612 . When the transport vehicle goes over an obstacle such as a large bump or the crest of a hill, suspension system  600  is extended to raise the transport vehicle and thereby prevent possible dragging. Conversely when the transport vehicle goes under an obstruction such as an overpass, suspension system  600  is retracted to lower the transport vehicle and thereby prevent possible collision with the overpass. 
   Because axle linkage member  604  is connected to body  602  at only one point  605 , the stresses encountered during travel can cause axle linkage member  604  and therefore axle  608  to yaw (refer also to  FIG. 15  and the discussion pertaining thereto). 
   Suspension system  600  is typically designed as a split system so that dollies on the right side of the transport vehicle can be raised and lowered independently from dollies on the left side of the vehicle. 
     FIGS. 5–7  illustrate front, side, and rear elevation views, respectively, of a suspension system for a transport vehicle in accordance with the present invention, generally designated as  20 . Suspension system  20  includes a body  22  which is pivotable about a first nominally vertical axis  24 . Body  22  further includes a first attachment station  26  spaced apart from a second attachment station  28 . In the shown embodiment, body  22  includes first arm  30  and second arm  32  having distal ends upon which the first attachment station  26  and second attachment station  28  are respectively disposed. 
   An axle  34  is disposable along a second axis  36  which is perpendicular to first axis  24 . Axle  34  is nominally aligned with second axis  36 . However, axle  34  can pivot or roll with respect to second axis  36  as a function of the road surface (also refer to  FIGS. 8 and 9 ). Axle  34  has tires  35  disposed at its two ends. 
   An axle linkage member  38  has a third attachment station  40  spaced apart from a fourth attachment station  42 . Third attachment station  40  of axle linkage member  38  is pivotally connected to first attachment station  26  of body  22 , and fourth attachment station  42  of axle linkage member  38  is pivotally connected to second attachment station  28  of body  22 . Axle linkage member  38  is pivotable about a third axis  44  which is parallel to second axis  36 . 
   Axle  34  is pivotally connected to axle linkage member  38  and is pivotable about a fourth axis  46  which is perpendicular to first axis  24 , second axis  36 , and third axis  44  (refer also to  FIGS. 8 and 9 ). 
   At least one fluid activated cylinder  48  is pivotally connected between body  22  and axle linkage member  38 . Preferably, two spaced apart fluid activated cylinders  48  are pivotally connected between body  22  and axle linkage member  38 . The two fluid cylinders  48  are disposed outside of first, second, third, and fourth attachment stations  26 ,  28 ,  40 , and  42 . As defined herein, outside means that cylinders  48  reside closer to tires  35  than the four attachment stations  26 ,  28 ,  40 , and  42 , and that the two cylinders  48  are therefore spaced wider apart than the two pairs of attachment stations. 
     FIG. 8  is a front elevation view of suspension system  20  with axle  34  rotated about axis  46  in a clockwise direction.  FIG. 9  is a front elevation view of suspension system  20  with axle  34  rotated about axis  46  in a counterclockwise direction. Such positions would result from traveling upon an inclined or crowned road surface. 
     FIGS. 10–12  are side elevation views of suspension system  20  in fully retracted, mid-stroke, and fully extended positions, respectively. In  FIG. 10 , the two fluid activated cylinders  48  are retracted causing axle linkage member  38  to pivot toward body  22  thereby lowering the transport vehicle. In  FIG. 11 , the two fluid activated cylinders  48  are in a mid-stroke position such as would be useful in traveling down a road under nominal conditions. In  FIG. 12 , the two fluid activated cylinders  48  are extended causing axle linkage member  38  to pivot away from body  22  thereby raising the transport vehicle. 
     FIG. 13  is a side elevation view of suspension system  20  traveling along a road. When the tires  35  encounter a pothole  700 , suspension system  20  automatically extends from a mid-stroke position on the left side to an extended position in the middle, and returns to a mid-stroke position on the right side thereby cushioning the ride of the transport vehicle. 
     FIG. 14  is another side elevation view of suspension system  20  traveling along a road. When the tires  35  encounter a bump  800 , suspension system  20  again automatically cushions the ride of the transport vehicle. In this case, the suspension retracts from a mid-stroke position on the left to a retracted position in the middle and returns to the mid-stroke position on the right. 
     FIG. 15  is a simplified bottom plan view of the prior art axle linkage member  604  of  FIGS. 3 and 4  which is pivotally connected to axle  608 . Since axle linkage member  604  is only connected to body  602  at one point  605 , forces experienced during driving such as by turning, driving on an incline, going over bumps, going over potholes, etc. can cause axle linkage member  604  and axle  608  to yaw or rotate horizontally as indicated by the dotted lines so that the axle  608  is no longer perpendicular to the direction of travel. This condition can cause unwanted mechanical stresses and/or vibration particularly at higher speeds. 
     FIG. 16  is a simplified bottom plan view of axle linkage member  38  of the present invention. In suspension system  20 , axle linkage member  38  is not just connected to body  22  at one point (see  FIGS. 5–7 ). Rather, axle linkage member  38  has four attachment points to body  22 : left cylinder  48 , attachment stations  28 / 42 , attachment stations  26 / 40 , and right cylinder  48 . As a result of the four attachment points, axle linkage member  38  is rigidly locked in place with respect to body  22  and will therefore resist the tendency to yaw. Axle  34  is therefore always substantially perpendicular to the direction of travel. In other words, when the transport vehicle is traveling on a road, connection of first attachment station  26  to third attachment station  40 , connection of second attachment station  28  to fourth attachment station  42 , and connection of two fluid activated cylinders  48  between body  22  and axle linkage member  38  combine to reduce the yaw of axle  34 . 
   The preferred embodiments of the invention described herein are exemplary and numerous modifications, variations, and rearrangements can be readily envisioned to achieve an equivalent result, all of which are intended to be embraced within the scope of the appended claims.