Abstract:
A vehicle suspension system that is especially useful for truck trailer suspensions includes an adjustable support that stabilizes the vehicle when desired. The adjustable support preferably is hydraulic having a housing and a movable shaft. One end of the movable shaft preferably engages a receiver portion on a suspension beam to either adjust a position of the suspension beam relative to an underside of a truck trailer or to effectively lock the suspension beam into a desired position.

Description:
BACKGROUND OF THE INVENTION 
     This invention generally relates to vehicle suspension systems. More particularly, this invention relates to a system for stabilizing a suspension system under selected conditions. 
     A variety of suspension systems are available for passenger and heavy duty vehicles. One type of suspension provided for heavy duty vehicles is air-based and includes the ability to adjust the position of an axle on a truck trailer. These suspensions are particularly useful for truck trailers that are optionally made into trains and transported by railway. When such a truck trailer is utilized for driving along the highway, for example, the suspension is adjusted into a first position where the wheels are spaced from the underside of the trailer a sufficient distance for driving along the road. When the trailer is to be transported by train, however, the suspension is adjusted so that the wheels are in a relatively retracted position, closer to the underside of the trailer. Since the wheels need to be adjusted into the two different positions, the suspension system must be adjustable to accommodate movement of the wheel axle between the two positions. 
     While such systems have proven useful and advantageous, they are not without shortcomings and drawbacks. For example, since the suspension system must accommodate movement of the axle between two relatively extreme positions, there is a requirement for a large amount of resiliency in the suspension system. This resiliency can pose problems under certain conditions. 
     For example, when loading a trailer, it is common to drive a lift truck onto the trailer bed. Because the lift truck is typically very heavy, a large load is rapidly imposed on the suspension system, which cannot react quick enough to avoid having the trailer bed drop suddenly as a result of the weight of the lift truck. This poses at least two problems. First, this provides undesirable wear on the trailer suspension components. Second, when the trailer is at a docking station, for example, it is necessary to maintain the truck bed at a height that enables a worker to easily move between the truck bed and the loading dock. When the truck bed drops because the air-based suspension system cannot accommodate the weight of a lift truck, for example, it may not be possible to drive the lift truck off of the trailer bed back onto the loading dock. In some instances, the air-based suspension system is not capable of being adjusted sufficient to raise the trailer bed back to a height consistent with the loading dock. 
     Additionally, when a lift truck is driven off of a trailer bed, the trailer bed often bounces upward in response to the force that is provided by the air-based suspension system, which has been under high pressure in an attempt to counteract the weight of the lift truck. Since the suspension system is provided with enough air to support the weight of the lift truck, when the lift truck leaves the trailer bed, the system is not able to adjust quickly enough to avoid the trailer bed being bounced upward. This undesirably increases the wear on the suspension components and can pose problems to the cargo that is loaded onto the trailer bed. 
     Therefore, there is a need for an improved suspension system that can be stabilized to avoid the shortcomings and drawbacks discussed above while still permitting the suspension system to be adjusted into the positions necessary to accommodate driving along a highway or being transported by railway. This invention addresses those needs by providing an improved suspension system. 
     SUMMARY OF THE INVENTION 
     In general terms, this invention is a vehicle suspension system that is selectively adjustable to provide stability during loading or unloading operations and to allow the suspension to be adjustable to accommodate different transportation scenarios. 
     A system designed according to this invention includes several basic components. An axle is provided to support wheels for the vehicle in a conventional manner. A suspension beam is associated with the axle and has at least one end that is moveable relative to the body of the vehicle so that the position of the axle relative to the body of the vehicle is adjustable. An adjustable support has a first end supported adjacent the body of the vehicle. A second end of the adjustable support is selectively moveable relative to the first end. The second end of the support preferably is received by a receiver portion on the suspension beam. The adjustable support controls a distance between the moveable end of the suspension beam and the vehicle body so that the distance between the vehicle body and the wheels is controlled. The adjustable support is selectively locked to maintain a fixed distance between the moveable end of the suspension beam and the vehicle body. 
     In the preferred embodiment, the adjustable support is hydraulic. A hydraulic version of the adjustable support preferably includes a housing at the first end of the support and a moveable shaft at the second end. The hydraulic support is adjusted so that the moveable shaft moves relative to the housing to adjust a distance between the first and second ends of the support. The receiver portion on the suspension beam preferably receives a terminal portion of the moveable shaft when the moveable shaft is moved appropriately. 
     The adjustable support can be used to stabilize a trailer bed during loading or unloading operations and provides the additional advantage of assisting an air-based suspension system to lift a trailer bed to a desired height. 
     Further details and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 diagrammatically illustrates a vehicle that includes a suspension system designed according to this invention. 
     FIG. 2 diagrammatically illustrates selected portions of the suspension system designed according to this invention. 
     FIG. 3 diagrammatically illustrates other selected portions of the suspension system from a side view. 
     FIG. 4 illustrates the portions of FIG. 3 from a top view. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 illustrates a truck  20  including a cab portion  22  that includes the engine compartment and driver compartment. The cab portion  22  preferably supports a controller  24  and an operator interface module  26 . The cab portion  22  includes three wheel axles  28 ,  30  and  32 , which operate in a conventional manner. 
     The truck  20  also includes a trailer portion  40 . The illustrated embodiment includes two trailer wheel axles  42  and  44 . Each of the trailer axles includes an adjustable support  46  that is schematically illustrated in FIG.  1 . The adjustable support  46  provides stability to the suspensions associated with the axles  42  and  44  when necessary. 
     As shown in FIG. 2, the suspension  50  associated with the axle  44  is adjustable to accommodate different transportation requirements. The axle  44  is illustrated and the axle  42  preferably includes the same structural arrangement. The underside of the trailer  40  preferably includes a mounting structure  52  that supports a suspension beam  54 . Preferably, a first end  56  of the suspension beam  54  is pivotally supported on the mounting structure  52  near a suspension beam pivot axis  58 . A second end  59  of the suspension beam  54  is moveable relative to the trailer  40  so that the distance between the axle  44  and the underside of the trailer  40  can be adjusted as needed. FIG. 2 illustrates the suspension beam  54  in a first position that is commonly referred to as a “rail position” that is utilized when the trailer  40  is placed on a rail bogie for transportation by railway. The suspension beam  54  is also illustrated in FIG. 3 to illustrate a “ride height position” that is used when the trailer  40  is connected to a cab portion  22  to be driven along a highway, for example. 
     The suspension  50  is adjusted between the rail position and the ride height position primarily through an air-based suspension module that is diagrammatically, partially represented at  62 . By selectively controlling the amount of air in the air-based suspension module in a conventional manner, the distance between the second end  59  of the suspension beam  54  and the underside of the trailer  40  can be controlled. Since air is compressible, the air suspension module not only biases the suspension beam  54  away from the underside of the trailer  40 , but also provides cushion while in transit. 
     Since the suspension beam  54  needs to be adjustable between the two positions illustrated in FIG. 2, there must be a relatively wide range of movement available when desired. If only the air-based suspension module  62  were relied upon to provide the support necessary to maintain a desired distance between the suspension beam  54  and the underside of the trailer  40 , there would be difficulties under certain loading or unloading conditions as described above. Therefore, this invention includes an adjustable support  46  to provide stability and adjustability features to the suspension  50 . 
     FIG. 3 diagrammatically illustrates a preferred embodiment of an adjustable support  46 . The adjustable support  46  preferably is hydraulic and includes a housing  70 . A first end  72  of the support  46  preferably is supported on the underside of the trailer  40  so that the support  46  can pivot about a support pivot axis  74 . In the illustrated example, the pivot axis  74  is coincident with a mounting pin  74  that cooperates with a mounting structure  75  on the underside of the trailer  40  to securely mount the support  46  (as can be appreciated from FIG. 4, for example). The support  46  also includes a moveable member  76 , which preferably is a shaft that is at least partially received within the housing  70 . The shaft  76  has a terminal end that engages a receiver portion  78  on the suspension beam  54 . 
     The receiver portion  78  preferably is a pocket that is a part of the suspension beam  54 . The receiver portion  78  can be integrally formed as part of a suspension beam or can be made as a separate component that is rigidly secured to the suspension beam. As shown in FIG. 3, the receiver portion  78  preferably includes a generally curved receiving surface and the moveable shaft  76  preferably includes a rounded terminal end. The rounded surfaces on the receiver portion  78  and the shaft  76  accommodate maintaining contact between the support  46  and the suspension beam  54  as the suspension beam  54  pivots about the beam pivot axis  58 . The pivotal mounting of the support  46  on the underside of the trailer further facilitates a stable contact between the shaft  76  and the receiver portion  78 . 
     The suspension  50  preferably is used in the following general manner. Under most driving conditions, the air-based suspension module  62  is utilized to bias the suspension beam  54  away from the underside of the trailer  40 . Under all driving conditions, the adjustable support  46  is adjusted so that the moveable shaft  76  is retracted into the housing  70  and does not contact the receiver portion  78  on the suspension beam  54 . 
     Under certain conditions, such as when loading or unloading the trailer  40  at a loading dock, the adjustable support  46  preferably is utilized to stabilize the trailer bed. The support  46  is adjusted so that the moveable shaft  76  moves outward relative to the housing  70  and engages the receiver portion  78  on the suspension beam  54 . When the suspension beam  54  is in a desired position relative to the underside of the trailer  40 , the moveable shaft  76  preferably is locked in place. This can be accomplished, for example, by closing the valves in the hydraulic supply system (not illustrated) that is utilized to adjust the position of the shaft  76 . Since hydraulic fluid is not compressible, the adjustable support  46  prevents the trailer bed from undesirably dropping toward the suspension beam  54  as would have occurred under some circumstances where only the air-based suspension module  62  was utilized. Whenever a loading operation, for example, is completed, the moveable shaft  76  can be retracted back into the housing  70  and the vehicle can be used as desired. 
     When the suspension system is utilized as described in the previous paragraph, it is most preferred that the controller  24  controls the operation of the adjustable support  46 . Once the adjustable support  46  is moved into a desired position and locked, the air-based suspension module  62  can be automatically vented if needed. Once the trailer  40  is fully loaded or unloaded, the controller  24  preferably adjusts the bias provided by the air-based suspension module  62  to accommodate the desired spacing between the suspension beam  54  and the underside of the trailer  40  before the adjustable support  46  is disengaged. 
     An additional use for the adjustable support  46  of this invention is to assist the air-based suspension module  62  in adjusting the trailer height as shown in phantom in FIG. 2 for connecting the trailer  40  to a rail bogie, for example, where the trailer is loaded too heavy for the air-based system to make a needed adjustment on its own. 
     An operator input device  26  preferably is provided in the cab portion  22  to allow a vehicle operator to selectively activate or deactivate the adjustable support  46  and the air-based suspension module  62 . The controller  24  responds to operator input and controls the suspension accordingly. Alternatively, a controller can be provided on a separate device that allows an operator to interface with the adjustable support  46  and the air-based suspension module  62  to make adjustments when a trailer  40  is placed at a loading dock, for example. Given this description, those skilled in the art will be able to utilize commercially available microprocessors or computers and to program them to perform the functions of the controller  24 . 
     Although this invention has been described in relation to a truck trailer suspension, it is not limited in use to that particular application. Additionally, although the adjustable support  46  preferably is hydraulic, other adjustable mechanisms may be utilized. Given this description, those skilled in the art will be able to determine what kind of adjustment mechanism best suits the needs of a particular situation. 
     The description given above is exemplary rather than limiting in nature. Variations and modifications to the disclosed example may become apparent to those skilled in the art that do not necessarily depart from the basis of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims.