Abstract:
A four point vehicular suspension system for a vehicle having left and right side frame members and spaced apart front and rear axles, comprising a plurality of lever beams having proximal and distal ends, a pair of which are each pivotally attached at their proximal ends, in spaced apart relationship, to each of the left and right frame members and attached at their distal ends to the front and rear axles, an expandable force-producing pneumatic bag disposed between each of the lever beams and the respective frame member to which the lever beam is pivotally attached, each bag being positioned between the proximal end and the distal end of each of the respective lever beams, and a source of air pressure and a valving system that is responsive to an unlevel position of the vehicle frame to selectively expand or contract the pneumatic bags to level the vehicle frame.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to a suspension and leveling system for wheeled vehicles, especially cargo carrying vehicles, such as pick-up trucks.  
         BACKGROUND OF THE INVENTION  
         [0002]    Pneumatic devices that replace the traditional leaf, coil or torsion bar springs in vehicular suspension systems have been used in a variety of different configurations and are the subject of considerable prior art. While some of these prior systems could be constituted for a smaller vehicle such as a pick-up truck, most of the prior art involves complex systems that are designed for large load carrying vehicles, buses and recreational vehicles. The U.S. Patent to Heider et al., U.S. Pat. No. 4,923,210, is exemplary of a complex electrically controlled pneumatic suspension system that is unnecessarily complex for use on a smaller vehicle, either as original equipment or as an after-market retrofit.  
           [0003]    The primary object of the present invention is to provide a simple pneumatic vehicular suspension system that can be retrofitted into the standard leaf, coil or torsion spring-shock absorber type of suspension system in most small-load carrying vehicles.  
           [0004]    A second object of the invention is to provide a suspension system for vehicles that will be instantly responsive to changes in forces acting on the vehicle so as to make the necessary adjustments in the suspension system to level the vehicle and prevent tilting or pitching as a function of load distribution, acceleration, deceleration or turning of the vehicle.  
           [0005]    Other and further objects, features and advantages of the present invention will become apparent as the description of the invention proceeds.  
         SUMMARY OF INVENTION  
         [0006]    The vehicular suspension system of the present invention is intended to replace the traditional leaf, coil or torsion bar spring suspension system, either as original equipment or as a retrofit of the original structure of the vehicle. Vehicles intended for application of the present invention are those having a pair of spaced apart, longitudinally extending and laterally interconnected vehicular frame members and front and rear wheel axles variably spaced apart from the frame members and generally perpendicular thereto.  
           [0007]    In the combination of the present invention, the left and right vehicle frame members and the front and rear axles are each pivotally interconnected with third class lever beams. In contact with a point intermediate the fulcrum of each lever beam and the distal location on the lever beam to which the axle is attached is one side of an expandable pneumatic bag that provides a force component to the lever. The other side of each expandable pneumatic bag is in contact with the vehicle frame. A source of air pressure acts through an air intake valve to inflate the pneumatic bag to increase the distance between the vehicle axle and the vehicle frame when such increase is required to level the vehicle body. A vehicle body-position sensor controls the air intake valve. The vehicle posture sensor also actuates an air exhaust valve to allow deflation of a respective one of the pneumatic bags when decreasing the force between the vehicle frame and the lever beam is necessary to level the vehicle body.  
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a diagrammatic side view of the suspension system of the present invention for both the left and right sides of the vehicle frame.  
         [0009]    [0009]FIG. 2 is a diagrammatic bottom view of a typical vehicle frame, with front and rear wheel axles, that incorporates the suspension system of the present invention.  
         [0010]    [0010]FIG. 3 is a diagrammatic front view of the front axle of a vehicle incorporating the suspension system of the present invention with the left and right frame members shown in cross section.  
         [0011]    [0011]FIG. 4 is a diagrammatic rear view of the rear axle of a vehicle incorporating the suspension system of the present invention with the left and right frame members shown in cross section. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0012]    Referring first to FIG. 1, a typical pick-up truck frame comprising left and right side members  2  and  3  is diagrammatically shown. Spaced apart rear and front wheel mounting axles  8  and  10  are positioned perpendicularly to the left and right frame members. The axles are disposed below the frame members and spaced therefrom, as seen in the side views shown in FIG. 1. The vehicle whose frame is depicted in FIGS. 1 and 2 does not include the traditional leaf springs that traditionally interconnect the vehicle frame with the wheel axles to form a suspension system. Shock absorbers are intended to be included in the suspension system of the present invention but are not shown on the drawings.  
         [0013]    In the suspension system of the present invention the left and right side frame members  2  and  3  of the vehicle are connected to the vehicle&#39;s rear axle  8  by a pair  4 L and  4 R of rigid lever beams. Another pair  6 L and  6 R of rigid lever beams connects the respective left and right vehicle side frame members to the vehicle&#39;s front axle  10 . The exact layout of the lever beams with respect to the vehicle frame will depend on the particular vehicle frame structure, however for a frame design similar to the one shown in FIG. 1, the lever beam arrangement shown in FIG. 1 is preferable. The rear lever beams  4 L and  4 R are connected at their respective fulcrum-forming ends  5  with a pivotal connection  15  to the central portion of a cross frame member  11 . The rearmost distal ends  7  of the rear lever beams  4 L and  4 R are spread from their points of connections to the frame member  11  to form a “V,” with their distal ends  7  extending respectively over the left and right end portions of the rear axle  8 . The distal end  7  of each lever beam  4  is attached to the axle  8  with a “U” clamp  9 .  
         [0014]    The lower side of an expandable pneumatic bag  12  is in contact with the lever beam  4 R at a point intermediate the beam&#39;s pivotal connection  15 , at its fulcrum end, and the point at which the lever beam is attached to the axle with the clamp  9 . The opposing upper side of the expandable pneumatic bag  12  is disposed against the underside of the side frame member  3 , as shown in FIG. 1, in order to provide an expansion force to separate the frame member and the lever beam between which the bag is located. The fact that the force element, the pneumatic bag, is intermediate the fulcrum  15  and the load (axle), the each lever beam becomes a third class lever.  
         [0015]    The rear portion of the left side frame member  2  is assembled with an expandable pneumatic bag  17  and left lever beam  4 L, similarly to the described right rear lever beam  4 R and the right rear portion of the frame member  3 .  
         [0016]    The pneumatic bags act in some manner as shock absorbers but are primarily intended to provide the force that spreads the side frame members  2  and  3  from their respective lever beams  4 L and  4 R to effect a leveling of the vehicle. The pneumatic bags are arranged to allow them to deflate in order to remove the expansion forces and thereby allow the spaces between the frame members and the lever beams to contract, as will be subsequently explained.  
         [0017]    While functionally similar to the rear axle-frame interconnections, the front axle is suspended from the front portion of the right and left side frame members  3  and  2  by pivotal lever beams  6 R and  6 L that are mutually parallel, as seen best in FIG. 2. Each of the front lever beams are pivotally interconnected to their respective frame members  2  and  3  by connections  16 . The front lever beams  6 R and  6 L are respectively attached to the right and left ends of the front axle  10  by U clamps  13 . Expandable pneumatic bags  14  and  18  are disposed between the right and left lever beams  6 R and  6 L and the right and left side frame members  3  and  2  in the same manner as with the rear pneumatic bags  12  and  17 .  
         [0018]    The pneumatic bags  12 ,  17 ,  14  and  18  are supplied with pressurized air through air lines  23  connected to a compressed air tank  25  and an associated air pump  27  that is driven by the vehicle&#39;s engine  28 . Air pressure is maintained at an appropriate level in the tank  25  by conventional means (not shown in the drawings) of pressure sensing and associated switching to turn the air pump on and off.  
         [0019]    Prior to an explanation of the valve system that regulates air pressure in the pneumatic bags it is helpful to understand the function of the air bags vis-à-vis the invention&#39;s objective to maintain a level vehicle posture notwithstanding the loading, vehicle acceleration, deceleration or turning forces acting on the vehicle. A heavy load in the bed of a pick-up truck tends to lower the rear end and elevate the front end of the vehicle. Turning forces tend to tilt the body and frame. Acceleration tends to raise the front end while deceleration forces the front end down. Because the truck handles and responds to control better with a level body, it is desirable to maintain it in that position. But, expanding the pneumatic bags to spread the specified frame and lever beams and by allowing specified pneumatic bags to exhaust air and deflate, the vehicle frame can be kept in the desired level position. The valving system of the present invention is intended to implement the expansion and accommodate the contraction of the pneumatic bag or bags to execute the leveling operation. If a load exhibits greater weight on one side of the truck than the other, or in a turn, the truck body tends to tilt, or rotate about its longitudinal axis, the sensors for the valving system operate to actuate a specific valve to either allow a bag to be inflated or deflated so for example, the low side of the vehicle will be raised and the high side will be allowed to descend.  
         [0020]    The front of the vehicle is not as susceptible to load induced posture variations as the rear, however the front of the vehicle is inclined to dip on deceleration and raise on acceleration. The reverse is true of the rear end. Accordingly, a combined valve arrangement is provided for the two front pneumatic bags  14  and  18 . However, each of the front bags could easily be connected to their own individual valves, as do the rear pneumatic bags.  
         [0021]    Because each of the pneumatic valves must admit air pressure to expand or pump up the bag, an intake valve is necessary to admit pressurized air through the air lines  23  from the compressed air tank  25 . Similarly, when the leveling of the vehicle requires compression of one or more of the pneumatic bags, an exhaust valve is necessary to allow pressurized air to escape from the bag.  
         [0022]    In the preferred embodiment of the invention, as illustrated in the drawings, each of the rear bags  12  and  17  have their own individual intake and exhaust valves. The intake and exhaust valves may be housed in one valve body but for illustrative purposes they are shown in FIG. 1 as two separate valves  31  and  32 . In the preferred form, only one set of intake and exhaust valves  34  and  36  is shown for controlling the air in the front pneumatic bags  14  and  18 . The mechanical actuation lever  38  for the left rear intake and exhaust valves  31  and  32  is similar to the same lever for both the right rear valve set  31  and  32  and to the front valve set  34  and  36 . The explanation for one set of valves will serve as an explanation of all three sets that are shown in FIG. 1.  
         [0023]    Exemplary of all valve sets is the set of valves that controls the inflation of the left rear pneumatic bag  17 . In the preferred embodiment the center portion of the lever  38  is connected by mechanical attachment  39  to the intake and exhaust valves  31  and  32 . When the frame member  2  is depressed by a cargo load in the bed of the truck the center portion of the lever  38  is rotated, moving the attachment  39  to open the intake valve  31  and admit additional pressurized air to expand the bag  17  and raise the rear portion of the left frame member  2 . Simultaneously, when the left side is initially depressed the right rear side of the frame  3  tends to rise. This lifting the right side  3  of the vehicle frame causes the center portion of the right rear lever  38  to rotate in a direction opposite to the rotation explained for the center portion of the left rear sensing lever  38 , causing the exhaust valve  32  to open and allow pressurized air in the pneumatic bag  12  to escape, letting the right rear frame of the vehicle to be lowered. A level truck body position would represent a neutral position of the mechanical sensor  38 .  
         [0024]    The pneumatic bags  14  and  18  in the front of the vehicle are simultaneously pumped up and exhausted, utilizing the single sensor lever  41  to control the linkage  40  that activates the intake and exhaust valves  31  and  32  for the front end of the vehicle. The sensor lever  41  operates in a similar fashion to the sensor levers  38  in the rear of the vehicle, that is sensing the elevation or dipping of the front end and admitting additional air pressure to pump up the left and right front pneumatic bags or allowing the bags to simultaneously deflate and lower the front end of the vehicle.  
         [0025]    In order to maintain lateral stability of the vehicle body with respect to the front and rear axles, stabilizers are provided in the form of rigid tracking arms  42  and  52 . The rear tracking arm  42  is pivotally attached at one of its ends  44  with a bracket  43  to the rear axle  10 . The other end  45  of the arm  42  is pivotally attached to the frame member  2 . The front tracking arm  52  is pivotally attached at one of its ends  54  to the front axle  8 . The other end  55  of the arm  52  is pivotally attached to the frame member  3 . The pivotal connections allow the front and rear axles to move vertically with respect to the frame members  2  and  3  but the tracking bars  42  and  52  maintain lateral stability between the vehicle frame and the front and rear axles.