Abstract:
An automated auxiliary axle deployment control system for a load-hauling vehicle having a time-variable payload and one or more fluid-operated auxiliary support axles comprising one or more load sensing devices for determining the payload distribution of the vehicle in real-time. One or more automatically operable pressure modulation valves adjusts the pressure applied to the one or more auxiliary axles to adjust the load carrying capacity thereof based on payload distribution. A signal processing system receives input signals from the one or more load sensing devices and produces output control signals for operating the pressure modulation valve(s).

Description:
BACKGROUND OF THE INVENTION 
     I. Field of the Invention 
     The present invention is directed generally to controlling auxiliary pusher or trailer load support axles for utility or load hauling vehicles such as dump trucks, over-the-road tractors and trailers, transit concrete mixing trucks or refuse collecting vehicles. The auxiliary pusher or trailer axle systems are used to selectively deploy auxiliary wheels in a ground-engaging, load-supporting position or to retract them to an elevated or stowed position. The systems are normally operated by forces generated by hydraulic cylinders or pneumatic springs and the amount of load support may be varied by varying cylinder pressure. The present invention more particularly relates to the automatic control of the relative amount of shared support, in keeping with the vehicle loading weight so that the axle loading of the vehicle is compensated accordingly to optimize load distribution. 
     II. Related Art 
     Transit concrete mixers are typical among those commercial vehicles that are called upon to haul a variety of load weights at different times. Such vehicles further typically include a single set of forward steering wheels and a plurality of rear, load-supporting drive axles carrying dual wheel arrangements, all mounted on an elongated continuous chassis. The chassis length or distance between certain sets of dual wheel arrangements may further be adjustable in some models. For additional support, particularly in transit when loading exceeds a minimum amount, vehicles of the class typically are provided with one or more pivotally mounted, hydraulically or pneumatically operated, auxiliary axles able to operate between a raised or stowed position carried by the truck and in a load-bearing or deployed position wherein the auxiliary axle and its wheels share the load of the truck with the permanent steering and drive wheel system. Auxiliary axles mounted forward of the drive wheels of a vehicle are typically referred to as pusher axles and those mounted aft of the drive wheels are known as trailer or tag axles. Each auxiliary axle system includes two or more wheels and possibly a plurality of dual wheel axles in such systems, the wheels may be connected by one or more through or common shafts or be independently mounted on stub axles. 
     Not only does an auxiliary pusher or trailer axle system assist in balancing the load carried by the truck adding safety and convenience, it also enables the truck to carry a higher total payload than would otherwise be permitted by adding one or more additional load bearing axles to which a portion of the load may be distributed to meet legal load per-axle limitations. Because the load often varies, with time however, it is often desirable to adjust the pressure in the system deploying the auxiliary axle so that the axle loading and thus the distribution of weight to the various axles of the truck is maintained at an optimum to compensate for the total loading of the vehicle. 
     Examples of prior auxiliary axle systems utilized with transit concrete mixing vehicles include U.S. Pat. No. 4,195,856 to Larson et al, U.S. Pat. No. 4,705,133 to Christenson et al; U.S. Pat. No. 5,498,021 to Christenson and U.S. Pat. No. 5,549,322 to Hauri. Additional tag axle systems as applied to load hauling vehicles of the refuse collecting class can be found in U.S. Pat. No. 5,090,495 to Christenson; U.S. Pat. No. 5,597,174 to Christenson et al; and U.S. Pat. No. 5,713,42,4, also to Christenson. 
     While these and similar embodiments have been relatively successful over the years, prior pusher and tag or trailer axles have either had no provision for adjusting the pressure applied to the deployed axle or have had only manually operable systems for adjusting the pressure applied to the axle to adjust road force in response to estimated truck payload weights. Charts for adjusting such systems manually based on estimated data may be provided for drivers to follow. One such chart is shown in Table I below. The ability to adjust the hydraulic or pneumatic pressure utilized to lower and apply force to pusher and trailer axles over a rather wide bed range not only allows a transit mixer, for example, to carry a larger legal load of concrete while complying with the required state highway weight laws, but it also allows the system to properly balance a variety of different sized loads. For example, if a driver hauls a ten-yard load of concrete (generally given as 40,000 pounds) on one load and only five yards (20,000 pounds) on another load, clearly the downward force or load carried by an auxiliary pusher or trailer axle should be readjusted downward (lowered) to maintain proper shared load balance coordination among the axles. Likewise, when the driver gets to the jobsite and the load is discharged, the pressure to the trailer axle should be reduced to a minimum or the axle prestowed by manual adjustment. 
     Manual systems, however, have drawbacks. In certain cases, if the driver fails to readjust the pressure for individual loads, the mixer truck may not comply with state axle weight limitations and, moreover, if the pressure is not properly reduced, the lift exerted by the pusher or trailer axle may reduce traction in the rear drive wheels of the truck. In addition, the estimated payload weights may not be as close to the actual values as desired. 
     Of course, the same type of load variation and estimation problems arise with respect to the collection of refuse, with large dump trucks, log-hauling vehicles or in other load hauling situations in which the weight of the payload can vary over a fairly wide range with respect to the use of the vehicle. In view of the present state of the art, there remains a need for an auto-responsive control system to modulate the application of force by auxiliary axle systems by automatically adjusting applied 
     
       
         
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE I 
               
               
                   
               
               
                   
                 Tag 
                 Tag 
                 Pusher 
                 Tag 
                 Pusher 
                 Front 
                 Tandem 
                   
               
               
                 Yardage 
                 Pressure 
                 Axle 
                 Axle 
                 Weight 
                 Weight 
                 Axle 
                 Axle 
                 GVW 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 4.00 
                 1,200.00 
                 Tag Down 
                 Pusher Up 
                  5,989.39 
                    0.00 
                 15,513.13 
                 25,188.08 
                 46,690.60 
               
               
                 5.00 
                 1,200.00 
                 Tag Down 
                 Pusher Up 
                  5,989.39 
                    0.00 
                 15,822.23 
                 28,878.99 
                 50,690.60 
               
               
                 6.00 
                 1,400.00 
                 Tag Down 
                 Pusher Up 
                  6,705.95 
                    0.00 
                 16,544.91 
                 31,439.74 
                 54,690.60 
               
               
                 7.00 
                 1,800.00 
                 Tag Down 
                 Pusher Up 
                  8,139.08 
                    0.00 
                 17,681.19 
                 32,870.33 
                 58,690.60 
               
               
                 8.00 
                 2,400.00 
                 Tag Down 
                 Pusher Up 
                 10,288.77 
                    0.00 
                 19,231.05 
                 33,170.78 
                 62,690.60 
               
               
                 9.00 
                 2,500.00 
                 Tag Down 
                 Pusher Down 
                 10,647.06 
                 5,000.00 
                 17,947.34 
                 33,096.20 
                 66,690.60 
               
               
                 10.00 
                 3,100.00 
                 Tag Down 
                 Pusher Down 
                 12,796.75 
                 5,000.00 
                 19,304.82 
                 33,589.03 
                 70,690.60 
               
               
                 11.00 
                 3,100.00 
                 Tag Down 
                 Pusher Down 
                 12,796.75 
                 5,000.00 
                 19,036.76 
                 37,857.09 
                 74,690.60 
               
               
                   
               
             
          
         
       
     
     hydraulic or pneumatic pressure applied to the system. This would improve both the versatility and the safety of the vehicles. 
     Accordingly, it is a primary object of the present invention to provide an automated control system for auxiliary axles that is responsive to changes in vehicle payload weight. 
     It is a further object of the present invention to provide an automated system for controlling the deployment pressure to auxiliary axles including each pusher or trailer axle of a vehicle based on the then-present measured payload weight. 
     It is a still further object of the present invention to provide an automated deployment control system for auxiliary axles which further indicates present auxiliary axle state and whether the axle should be deployed or stowed. 
     Yet another object of the present invention is to provide an automated auxiliary axle deployment pressure control system that utilizes real-time payload weight distribution. 
     Another object of the present invention is to provide an automated auxiliary axle control system that coordinates real-time, payload weight distribution with data from a permanent stored record of unloaded vehicle parameters to provide desired real-time axle/weight distribution. 
     Other objects or advantages will become apparent to those skilled in the art upon familiarization with the specification, claims and drawings contained herein. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method and apparatus for automated auxiliary pusher (forward) or trailer (rearward deployed) axle pressure control. The invention supplies the ability to automatically adjust road support force applied by pusher or trailer wheels in each set of such wheels and is very useful in a vehicle subject to time-variable loading. The invention applies equally to hydraulically or pneumatically operated pusher and/or trailer wheels and the wheels of each axle or set can be controlled in accordance with the invention. The system can also be using auxiliary support wheels mounted and configured to operate separately on stub axles or in unison on single or multiple through axles. The control system is particularly suitable for use with a class of vehicles including any heavy-duty hauling truck or trailer accustomed to payload variations, examples including transit concrete mixers, dump trucks, log haulers and refuse collecting vehicles. Generally, not only does the total load change but the distribution of the load among vehicle axles may also vary greatly. 
     The control system of the invention includes one or more integral devices or frame scales which enable accurate weight measurement of amount and distribution the carried payload such as the weight of a load of concrete in a mixing drum. The measurements may be sensed continually, i.e., metered on a real-time basis and may include measurements of the weight carried by each axle or axle group. These measurements then, in turn, are used in the control of the hydraulic or pneumatic pressure applied to one or more deployed sets of pusher and/or trailer wheels, and/or other aspects of a vehicle suspension system thereby compensating for light loads, intermediate and maximum loads and load distribution. In the case of concrete, for example, the direct accurate weight measurement, of course, has the added value over volume based measurements in that it further compensates for the difference in the weight per yard (density) of various mixes not taken into consideration by previous manual systems that predicted adjustment based on yardage (volume) alone. 
     Because every axle or axle set can be metered and the system can have the ability to modulate pressure to individual auxiliary wheel sets and possibly individual auxiliary wheels on either side of the vehicle as well, this allows the invention to function as an auto leveling system or to compliment such a system by adjusting relative load distribution among support axles and possibly individual wheels. 
     Of course, the system of the invention also recognizes the lightly loaded or unloaded truck or trailer condition which can be utilized to reduce the pressure to a minimum or prompt the driver to stow the pusher or trailer wheels completely. Thus, when the drum of a mixing vehicle or load compartment of another vehicle is empty, the pressure is reduced to a minimum setting, i.e., 900-1000 psi typically for a hydraulic system and 0-120 psi for a pneumatic spring bellows system or the axle raised and stowed. Conversely, the system may prompt the driver to lower raised auxiliary or trailer axles when the load weight reaches a certain given minimum amount, depending on the vehicle involved. The control system itself can also be configured to automatically raise and lower the pusher or trailer axles if desired. 
     Any conventional vehicle-mounted weighing system, including strain gauges, leverage devices and beam type scales or load cells, etc., can be used and, in one embodiment, the system includes a chassis/axle balanced beam differential system which measures chassis/axle gap variations at several points and yields an electrical output signal which can be utilized as an input to a control system used to control a pneumatic or hydraulic pressure modulating valve automatically. Onboard frame scale systems including embodiments that may be leaf-spring mounted, air spring or axle mounted are available, for example, from Weigh-Right of Hutchinson, Kansas and other manufacturers of such systems. If deployment/storage is not automatic, audio and/or visual signals may be utilized to alert the driver of the vehicle, as necessary, to deploy or stow trailer and/or pusher axles as needed. 
     The control system itself contains an amount of pre-programmed computer data relating to final sizes and weight parameters of the unloaded vehicle typically stored on a computer card located in an enclosure and which is integral to the hydraulic system. The card is programmed for the particular vehicle as manufactured and contains all the necessary fixed parameters and data to utilize real-time weight signals to accomplish the correct control utilizing pressure modulation. 
     Of course, the system is also configured so that if it experiences a malfunction, the auxiliary wheels may be deployed and adjusted using standard manual operating system as a back up or another alternate system can also be used. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings where like numerals like parts throughout the same: 
     FIG. 1 shows a side view of a transit concrete mixer of the stretch variety suitable for use with the axle pressure control system of the present invention illustrating a retracted pusher auxiliary axle system and a trailer auxiliary axle systems depicted in the deployed or ground-engaging position; 
     FIG. 2 is a fragmentary view of the rear portion of a truck similar to that shown in FIG. 1; 
     FIG. 3 is a fragmentary schematic view of an onboard front axle scale system; 
     FIG. 4 is a fragmentary schematic view illustrating a possible configuration of a spring mounted onboard scale system for dual axles; 
     FIG. 5 shows a further fragmentary schematic view of an air scale system usable in accordance with the invention; 
     FIG. 6 is a schematic drawing showing common locations of frame scales; 
     FIG. 7 is a simplified hydraulic schematic drawing illustrating an embodiment of the invention; 
     FIG. 8 is a simplified hydraulic schematic drawing illustrating and trailer cylinder control system; and 
     FIG. 9 is a schematic drawing of a pressure control system in accordance with the invention. 
    
    
     DETAILED DESCRIPTION 
     The present invention contemplates improved axle loading control with respect to vehicles equipped with auxiliary pusher or trailer load support axles, particularly for utility or load-hauling vehicles, including dump trucks, transit concrete mixing trucks refuse collecting vehicles or the like. The additional control contemplates not only indicating to the driver whether or not the trailer or pusher wheels should be deployed and warning of improper condition but also contemplates total load and load balance control in a manner which can be used to maximize allowable load and optimize load distribution. Although the detailed embodiment described below, describes a stretch-type concrete transit mixing vehicle this is meant by way of example only with no limitation intended with respect to the scope of the invention. 
     FIGS. 1 and 2 depict a transit concrete mixing truck of the stretch variety, generally at  10  that includes a forward cab  12  and a rotatable mixing drum of  14  mounted on a truck chassis  16  and spaced behind the cab. The mixing drum is provided with a loading hopper  18  that facilitates the loading of cement, water, fly ash, chemicals and aggregate into the drum through an access opening in the upper rear of the drum  14 . Mixed concrete is also discharged through the rearward opening by reversing the rotation of the drum thereby reversing the movement of the concrete caused by the flights of the mixing fins, the concrete placement being guided by a compound cylinder-operated chute system at  20 , an access ladder  22  is provided to assist the operator in inspecting and cleaning the drum. The drum rotating mechanism is shown generally by  24  and an inspection hatch cover is depicted at  26 . 
     As indicated, the cab  12  and the mixing drum  14  are supported by the chassis  16  which is, in turn, carried by a plurality of axle mounted wheels including a front or forward steering axle  28  having a pair of wheels one of which is shown at  30  and a set of dual drive axles carrying sets of dual wheels  32  a forward dual tandem pusher axle set which may be similar to those shown in FIGS. 2 and 3 includes tires two of which are shown at  34 . In FIG. 1 the pusher system is shown in the raised or stowed position. The truck chassis or frame further includes a pair of spaced heavy longitudinal structural members, normally channel shapes such as those depicted at  36  in FIG.  1  and FIG.  5 . 
     The trailer axle system of the invention is depicted generally by the reference numeral  40  and pivots generally vertically as depicted by the arrow  41 . The trailer axle system  40  also includes space tag wheels  42  and  42   a  generally mounted on a stub axles, one of which is shown at  43 . The frame of the trailer axle system  40  also includes a pair of spaced trailer axle arms  44  and  44   a , each connected at one end to an outer frame member (not shown) and near the other end by an inner transverse frame member  46 , normally a heavy tubular member. A trailer axle cylinder mounting lever shown at  50  is fixed to the member  46  with a trailer axle cylinder pivot mount shown at  54  and the entire trailer axle is pivoted about a pair of joints, which attach the trailer wheel assembly to the members  36 , one of which is shown at  56 , by a double-acting fluid cylinder shown partially at  57 . The deployment cylinder/cylinders operate the lever  50  through pivot joint  54 . Extending the cylinder  57  deploys the trailer axle with a downward force commensurate with applied fluid pressure and retracting the cylinder raises and stows the trailer assembly. A trailer axle fender is depicted at  58  and a moveable discharge chute at  59 . 
     The construction and operation of both the dual pusher axle system and trailer axle system  40  are well known to those skilled in the art and, it is believed, need no further detailed description here. The degree of support offered, of course, is related to the pressure in the hydraulic or the pneumatic system which is utilized for the deployment for such auxiliary axles. If more details are required, such are available, for example, in U.S. Pat. Nos. 4,684,142, 5,090,495 and 4,416,135 (pneumatic or dual systems) and U.S. Pat. Nos. 5,498,021, 4,684,142, 4,195,856, 5,597,174 and other patents for hydraulic and dual operable examples. These references are deemed incorporated by reference herein for any purpose. 
     FIGS. 3-6 illustrate the various onboard weighing or frame scale systems usable with the control system of the present invention. FIG. 6 depicts a general schematic view of typical frame scale locations. A truck body  61  with body frame  63  is supported by a plurality of frame scales some of which are shown at  65  between the body frame  63  and the truck frame or chassis  67 . 
     FIG. 3 pneumatically depicts an air scale system which employs a plurality of air bags  60 , one associated with each wheel of a four-wheel set mounted on a two through axles  62  and  64 . This system further includes a leveling valve  66  and a pressure measuring air sensor  68 , which taps into the air line between the air bag  60  and the leveling valve  66  to monitor the pressure in the system. This produces an output  70  carried by a conductor cable indicative of the weight on the entire suspension group and which can be used for monitoring and control of group deployment pressure. 
     FIG. 4 depicts a fragmentary schematic view showing of a spring scale system and a leaf-spring mounted version. This system is mounted on a single through axle  80  and carries a pair of heavy walking beams  82  and  82   a  each designed to carry a pair of dual-wheel stub axles  84  and  84   a . A pair of leaf springs  86  and  86   a  are provided which carry on respective mounting pads  88  and  88   a , a rugged but sensitive balance beam type scale system, including an averaging beam  90  with axle bed mount  92  and transducer carrier  94  which produces an output carried on a three wire cable as at  96 . 
     A front axle scale system is shown at FIG. 5 mounted between a frame rail  36  and front axle  28 . That system includes a pressure transducer carrier  100  connected to an output utilization system by a multiple wire 12-volt cable system  102 . 
     It should be noted that the outputs from the onboard scale system illustrated at  70 ,  96 , and  102  can also be connected to alarms, analog or digital meters and even printers. Signals may be conditioned and processed in any well known manner to be utilized in the control of the associated auxiliary axles of the vehicle and the readings from all axles of the vehicle. Systems of this class can be readily retro-fit on present vehicles or installed on newly manufactured models. As illustrated in the figures it can be seen that the onboard weighing systems illustrated can either be used with pneumatic or hydraulic control systems and can be used to meter the weight distributed on either deployable or fixed axle systems. 
     FIG. 7 depicts a simplified schematic of a possible hydraulic system utilized to control the deployment pressure to a pusher or tag axle system in accordance with the invention. This system includes a fluid reservoir  110  which is connected by a hydraulic line  112  with pump  114 . The high pressure pump output line  116  is connected to a cylinder control valve  118  which, in turn, is connected to a valve module  120  via line  122 . A further high pressure line  124  connects valve module  120  with manifold  126  which, in turn, is connected to the blind end of cylinders of  128  and  130  via lines  132  and  134  and to an accumulator  136 . A pair of rod end lines are shown at  138  and  140 , respectively, connecting the rod end ports of cylinders  128  and  130  with a second manifold  142  which, in turn, is connected to the valve module  120  via line  144 . The reservoir return line  146  connects back through control valve  118  and drain line  148  to the reservoir  110 . A bypass return line is provided at  150 . 
     A variable pressure controller device  152  is shown connected to manifold  126  and a similar device  154  is shown connected to the manifold  142 . These are pressure control devices that are connected to receive respective control signals on line  156  and  158  emanating from control module  160  shown in FIG. 9 to control the operation of cylinder  128  and  130 . In FIG. 9, the control module is generally shown connected to various weight scale inputs that may be represented by  162 ,  164 , and  166  and include an audio alarm or other output  168  and possibly a visual output or warning device  170 . The output signals  156  and  158  may be used to modulate the hydraulic pressure to the blind end and rod end of the cylinders  128  and  130  as required to control pusher or tag axle deployment and are to deploy or retract the pusher or tag wheels automatically or to indicate to the driver or operator that this should be done. 
     Manufacturer&#39;s specifications and other relevant redetermined data related to the vehicle involved that may be contained on a data card is shown at  172  connected via  174  with a CPU  176  shown connected to Module  160  via cable  178 . CPU  176  is normally an integral part of control module  160 . 
     Another typical hydraulic system for manually or automatically raising and lowering the trailer wheel system of a transit mixer or the like is schematically represented in FIG.  8 . That system includes a pump  200  with associated reservoir  201 , filter  202 , associated central control manifold  204  with directional valve  206  and pressure reducing valve  208 . An accumulator is as shown at  210  and a chute lift cylinder at  212 . A trailer axle deployment cylinder is depicted at  214 . In this embodiment the pressure reducing valve  208  is adjusted to regulate the pressure in the trailer cylinder  214   
     Shown at  172 , in FIG. 9, readouts of weight distribution on all axles or axle systems can also be available at a on-going basis using the received data and, responsive to such data, the hydraulic system of FIGS. 5 or  8  can be utilized to automatically modulate the pressure and the cylinders to thereby modulate the force exerted by tag or pusher axle system required to achieve the optimum load balancing and maintain a legal axle load deployment for the entire vehicle. This can be achieved by modulating the system on an on-going basis. 
     This invention has been described herein in considerable detail in order to comply with the Patent Statutes and to provide those skilled in the art with the information needed to apply the novel principles and to construct and use such specialized components as are required. However, it is to be understood that the invention can be carried out by specifically different equipment and devices, and that various modifications, both as to the equipment details and operating procedures, can be accomplished without departing from the scope of the invention itself.