Abstract:
An air suspension system for a multi-axle vehicle having air bags ( 4,5; 6,7; 8,9; 10,11; 44  to  49 ) supporting either side of the axles ( 2,3; 41  to  43 ), including separate air lines ( 18  to  25; 50  to  55 ) respectively connecting each air bag to a level control valve ( 16,17; 56,57 ) via manifolds ( 26,27 ; M) and air lines ( 28,29; 54,55 ) to independently control air supply to the bags on either side, the separate air lines being of the same size and length to ensure that substantially the same volume of air is supplied to each bag to improve the responsiveness and stability of the system.

Description:
[0001]    This application is a divisional of U.S. Ser. No. 11/993,235 filed Dec. 20, 2007, which is a 35 U.S.C. 371 National Phase Entry Application from PCT/AU2005/000925 filed Jun. 24, 2005, the disclosures of which are incorporated herein in its entirety by reference. 
     
    
     FIELD 
       [0002]    This invention relates to improvements in air suspension systems for load carrying prime mover and trailer vehicles having multiple axles supported by air bags on either side of each axle. 
       BACKGROUND 
       [0003]    Air suspension systems for load carrying prime mover vehicles can include as many as eight air suspension bags supporting the two driven axles in pairs on either side of each axle. In one well-known prime mover, the pairs of air bags are connected by a common large diameter air lines extending between correspondingly positioned air bags on adjacent axles. 
         [0004]    The common air lines are each connected by an air line to a control valve which controls the air supply to the common air lines to adjust the inflation of the air bags to ensure that the prime mover is kept level as it is driven over variable road conditions. 
         [0005]    In other air suspension systems, such as the Hendrickson HAS Series suspension, each axle is supported at either side by a single large air bag mounted on a frame hanger to which the axle is connected. 
         [0006]    While the known air suspension systems may be adequate for slowly changing road conditions, they are not sufficiently responsive to rapidly changing conditions such as are experienced in cornering and on rough sections of road. As a result the vehicle becomes unstable, reducing driver control, increasing driver fatigue, causing increased tyre wear and potential damage to the freight. 
       SUMMARY 
       [0007]    It is an object to provide an improved air suspension system which is more responsive under changing driving conditions. 
         [0008]    The invention provides an air suspension system for a multi-axle vehicle having at least one air bag supporting each side of each axle, a level controlling valve for separately controlling air flow to the air bags on each side respectively, separate air lines connecting each valve and each of the air bags on either side respectively, said separate air lines being such that substantially the same volume of air is supplied to each air bag to maintain stability under changing driving conditions. 
         [0009]    The invention further provides an air suspension system for a multi-axle vehicle having at least one air bag supporting each side of each axle, a level controlling valve for separately controlling air flow to the air bags on each side respectively, a separate air line connected between each valve and a distribution manifold, separate air lines connected between each manifold and each of the air bags on either side respectively, the first mentioned air lines being of substantially the same size and length, and the second mentioned airlines between the respective manifolds and the respective air bags being of the same size and length whereby substantially the same volume of air is supplied to each air bag to maintain stability under changing driving conditions. 
         [0010]    In comparison with the known air suspension systems, in which the air lines to each air bag are of variable length, a system embodying the invention will allow the air bags to respond to the changing road conditions maintaining stability and enabling the vehicle to be more easily controlled. 
         [0011]    In one form, each axle has a pair of air suspension bags supporting each side of the axle and separate air lines extend from the valve controlling each side to the separate air bags. 
         [0012]    In one such arrangement, the air bags on each side are interconnected by common air lines extending between air bags in similar positions on adjacent axles, the separate air lines being connected to the common air lines adjacent the respective air bags. 
         [0013]    In another form, each axle is supported by a single air bag at each side of the axle. 
         [0014]    The vehicle may take the form of a prime mover having driven axles, or a trailer having passive axles. 
         [0015]    To further improve responsiveness, each level controlling valve has a separate air feed line from the air supply tank of the prime mover. The size and length of the separate feed lines is preferably the same. 
         [0016]    The level controlling valves are preferably actuated by control means extending to a common rigid bar fixed to the means attaching the air bags on either side to one axle. 
         [0017]    In another form the invention provides an air suspension system for a multi-axle vehicle having at least one air bag supporting each side of each axle, a level controlling valve for separately controlling air flow to the air bags on each side respectively, separate air lines connecting each valve and each of the air bags on either side respectively, each level controlling valve having a separate air feed line from an air supply tank of the vehicle to improve the responsiveness of the system. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    In the drawings: 
           [0019]      FIG. 1  is a schematic fragmentary plan view of a prime mover chassis having an air suspension system embodying the invention; 
           [0020]      FIG. 2  is a similar plan view of a prime mover chassis having a modified air suspension embodying the invention; 
           [0021]      FIG. 3  is a schematic fragmentary plan view of a trailer chassis having an air suspension system embodying the invention; 
           [0022]      FIG. 4  is a schematic fragmentary plan view of a prime mover having another modified air suspension system embodying the invention, and 
           [0023]      FIG. 5  is a schematic plan view of a further modified suspension system embodying the invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0024]    Referring first to  FIG. 1 , the prime mover chassis  1  has front and rear driven wheeled axles  2  and  3 , which are supported in a known manner on the chassis  1  by pairs of air suspension bags  4  and  5 ,  6  and  7 ,  8  and  9  and  10  and  11 , positioned as illustrated on either side of the axles  2  and  3 . 
         [0025]    The air bags  4  and  8 ,  5  and  9 ,  6  and  10  and  7  and  11  are connected in a known manner by common large capacity air lines  12  to  15  respectively, which are usually about 5 cm (2 inches) in diameter. The air suspension system so far described is typical of a Kenworth Airglide 200 as found on a Kenworth T 904 prime mover. 
         [0026]    Under normal circumstances, the common lines  12  to  15  on either side of the axles are connected by an air line (not shown) to suitable ride height or level controlling valves  16  and  17 , such as Hadley valves, but in the present embodiment they are supplied with air, at the air line connector fittings of each air bag, by separate air lines  18  to  21  respectively on one side and  22  to  25  on the other side, connected to junction fittings  26  and  27  which are supplied with air by lines  28  and  29  extending from the level control valves  16  and  17 . To ensure an adequate supply of air to each valve  16  and  17 , separate air lines  30  and  31  are connected to an air supply tank (not shown) mounted on the prime mover in the usual manner. The length and size of these lines are also the same. 
         [0027]    To ensure a balanced supply air of substantially the same volume and pressure to each air bag, the separate air lines  18  to  21  and  22  to  25  are of substantially the same size or internal diameter and length. For similar reasons, the air lines  28  and  29  between the valves  16  and  17  are of substantially the same size and length. 
         [0028]    The lines to the front air bags  4  and  6  are connected, in the usual manner, as indicated by the arrows, to the gauges and dump switch (not shown) in the cabin of the prime mover. Since this aspect does not from part of the invention it will not be further described. 
         [0029]    The provision of the separate air lines  18  to  21  and  22  to  25 , and the connection of these lines to the separately supplied level control valves  16  and  17 , ensure that an equal volume of air is rapidly supplied to each of the air bags so that they respond appropriately to changes in road conditions relayed to the valves  16  and  17  by their control rods  32  and  33  via a rigid bar  34  mounted under the bags  9  and  11  as illustrated. The air lines  18  to  21  and  22  to  25  suitably have a bore diameter of about 12 mm (½ inch). 
         [0030]    In the embodiment of  FIG. 2 , the common air lines  12  to  15  have been omitted. Otherwise the system is as described in relation to  FIG. 1  and the same reference numerals identify similar components. In this embodiment, the feed lines  28  and  29  from the level valves  16  and  17  are connected to branch lines which are connected by manifolds  26  and  27  to the lines  18  to  25  as illustrated. It will be noted that the manifolds  26 ,  27  are positioned centrally in the branch lines, and the connections of the branch line to the similarly sized lines  18  to  24  are centralised so that the air lines  18  to  25  are of equal length. It will be appreciated that a line arrangement similar to that shown in  FIG. 1 , absent the common lines  12  to  15 , could also be used. 
         [0031]      FIG. 3  schematically illustrates a trailer chassis  40  having three wheeled axles  41 ,  42  and  43 , supported on each side by air suspension bags  44  to  49 . The bags are fed with air by separate air lines  50  to  55 , of equal size and length, respectively extending from distribution manifolds M fed on either side air supply lines  54  and  55  connected to level control valves  56  and  57  supplied with air from supply tank  58  by air feed lines  58  and  59  of equal size and length. The control valves are operated similarly to the above arrangements by control rods  59  and  60  attached to the rear axle  43 . Again it is important that the air lines  50  to  55  are of substantially the same size and length and that the supply lines  58   a  and  58   b  are of substantially the same size and length. This arrangement operates similarly to the prime mover system to provide stable control of the trailer to further improve the controllability of the prime mover and trailer combination. 
         [0032]    In the embodiment of  FIG. 4 , the pairs of air suspension bags  4 , 5 ; 6 , 7 ; 8 , 9  and  10 , 11  are connected to each other by common air lines  12   a  to  15   a , similar to common air lines  12  to  15  in  FIG. 1 . As in the embodiment of  FIG. 1 , air is supplied to the air line connector fittings of each air bag  4  to  11  by separate air lines  18  to  25  connected to distribution manifolds  27  and  28  supplied with air by air lines  28  and  29  from level control valves  16  and  17 . This arrangement operates in the same way as the embodiment of  FIG. 1  and again the separate air lines  18  to  25  are of substantially the same size and length as are the air lines  28  and  29 . 
         [0033]    In the embodiment of  FIG. 5 , which is a schematic representation of a Hendrickson HAS suspension, the axles  2 , 3  are supported by larger air bags  60  to  63 , in a known manner. As in the earlier embodiments, ride height adjusting valves  64 ,  65  are separately supplied with air from the air tank (not shown) by air lines  66 , 67  of equal size and length. Air supply lines  68 , 69  of equal size and length extend from the valves  64 , 65  to distribution manifolds  70 , 71 , and air lines of equal size and length extend from the manifolds to each air bag  60  to  63 . This embodiment operates in the same manner as the earlier embodiments. 
         [0034]    In each of the embodiments the separate air lines suitably have a bore diameter of 12 mm. Other sizes may be used with similar results provided the size and length of the air lines in each set or group (eg  18  to  25 ,  28  and  29 ,  30  and  31  etc) are the same. 
         [0035]    While embodiments of the invention have been described in connection with an air suspension typical of Kenworth prime movers, such as the Airglide 200 on the T 904 prime mover, it will be appreciated that the invention is equally applicable to other Kenworth suspensions, such as the Airglide or AG 400, AG 460 or the AG 690. Similar comments apply to the schematically illustrated Hendrickson HAS suspension. The invention is equally applicable to any air bag suspension system having one or more air bags supporting each driven axle.