Patent Application
20180236839
The present invention is in the field of load distributing add-on-axle trailers, for adding at least one axle to a load carrying trailer, and distributing the trailer load between the trailer axle or axles and the add-on-axle. The term “load carrying trailer” or “trailer” is intended to encompass any type of load carrying trailer, including without limitation semi-trailers, lowboy trailers, flatbed trailers, freight trailers, tanker trailers, step deck trailers, removable gooseneck trailers, dry vans, extendable double drop trailers, refrigerated trailers, Conestoga trailers, heavy haul trailers, etc. The term “add-on-axle” refers to the axle of the “add-on-axle trailer.” The combination of a truck, load carrying trailer and add-on-axle trailer is referred to herein as a “rig.”
By regulation, heavy duty load carrying trailers typically have a per-axle load limit on what they carry, usually 25,000 pounds per axle. Add-on-axle trailers have double acting hydraulic lifter cylinders which extend to lift the trailer load off the load carrying trailer axles, thereby distributing the weight of the load between the trailer axles and the axle of the add-on-axle trailer. Thus, a two axle semi-trailer can carry a 75,000-pound load by attaching the add-on-axle trailer, and using the lifter cylinders to distribute the load such that each of the three axles is carrying 25,000 pounds.
A mechanical gauge on the add-on trailer measures the pressure in the ride height air bag, located between the axle and the add-on trailer frame. This provides the user with a point of reference, but the air pressure reading is not used to set the load to be transferred to the add-on-axle trailer. That determination is made based on a hydraulic pressure gauge on the hydraulic system of the add-on-axle trailer. The relationship between hydraulic pressure in the add-on-axle trailer hydraulic system and the load on the add-on trailer axle has been empirically determined and is presented on a chart associated with the add-on axle trailer. To transfer the required load to the add-on axle, the operator starts the hydraulic pump, which is typically gasoline powered, and opens a valve to pump fluid to the cylinders to extend them. When the mechanical gauge shows a hydraulic pressure corresponding to the desired load on the add-on axle, as indicated by the chart, the operator closes the valve and turns off the hydraulic pump. The entire process is manually accomplished, and is performed only before travel begins.
Both the trailer axles and the add-on-axle have associated pressurized airbags between the wheel axles and their respective frames, whereby the ride heights of the trailer and the add-on axle trailer are maintained during travel of the rig. Height adjustment is automatically maintained via ride height valves associated with each axle on the trailer and add-on trailer, which are operated by mechanical linkage between the frame and axle. If the trailer frame or add-on trailer frame is too low, the linkage opens the ride height valve to allow air to flow into the air bags to raise the frame height. On the other hand, if the frame is riding too high, the linkage opens the ride height valve to release air from the airbags and lower the frame. When the trailer air system is first coupled to the truck air compressor via a quick disconnect coupling, air flows into the trailer air bags to initially establish the intended ride height. The ride height valves continue to operate the flow of air to and from the air bags during the travel of the rig, thereby tending to maintain the trailer and add-on trailer at the proper level though-out the travel of the rig.
In the present invention, the add-on trailer is provided with a computer control system for automatically or semi-automatically monitoring and controlling the load equalizing function and preferably other functions of the add-on trailer. Preferably, display and control software is loaded into a portable computer such as a tablet or personal digital assistant (PDA), with wireless connection to the computer control system in the add-on trailer, such that the computer control system can be operated remotely.
Prior artisans have failed to appreciate that while ride height of the trailer and add-on trailer tend to remain constant throughout the travel of the rig, the load distribution on the axles does not. The present invention facilitates a dynamic load distribution system for automatically initially setting at the time of loading the load trailer, and then maintaining throughout its trip, a generally uniform load on each of the load carrying trailer axles and the-add-on axle. The system continues to operate to equalize the axle loads as the rig corners or travels up or down grades, or encounters other travel variations. These and other objects, advantages and features of the invention will be more fully understood and appreciated by reference to the drawings and description of the preferred embodiments of the invention.
In the following description of the preferred embodiments of the invention, the following numbered parts are referred to:
The load carrying trailer 10 used to illustrate the preferred embodiment is a “lowboy” carrier which includes a frame 11 pinned at its goose neck front 11a to a truck and as shown here, includes two rear axles carrying two wheels 12 on each side, for eight wheels total (
Air conduit 18b provides pass through compressed air from its junction with line 18 to trailer port T2. (
Attachment brackets 16 on the back of frame 11 facilitate the attachment of add-on-axle trailer 20 to load carrying trailer 10 (
Add-on-axle trailer 20 comprises a frame 24 with wheels 25 mounted on axles 26, located at the rear thereof (
Air brake tank 27 at wheels 25 is fed by add-on air-line 27a (
Air conduit line 27b on add-on trailer 20 feeds air from trailer port T1 to a pressure monitoring transducer 44 mounted on add-on-trailer 20 (
Air conduit line 27c connects to trailer port T3, and feeds control air to add-on-trailer brakes 29 (
The add-on-axle trailer lifting system 30 includes double acting lifting cylinders 31 pivotally connected at their cylinder end to frame 24, while their cylinder rods 31a are pivotally connected at their ends to the upper portion of hinge frame 24a, via pins 31b (
The lifting cylinders 31 are fed hydraulic fluid via hydraulic pump 32 from a hydraulic fluid tank 34, located on the interior of front hinge frame 24a (
Hydraulic fluid is also pumped to an accumulator tank 35, which acts as a shock absorber for add-on-axle trailer 20 (
In operation, cornering and travelling up and down hills, over rough roads and the like will cause imbalanced load problems. The present dynamic load distribution system in its various embodiments automatically maintains a generally uniform load on each of the load carrying trailer axles and the-add-on axle as the rig corners or traverses other travel variations. At the time the trailer is loaded with freight, it also automatically equalizes the per-axle load carried by each axle of the load trailer 10 and the add-on-axle 26.
In the preferred embodiments, three different monitoring and control systems are contemplated. In both control systems 1 and 2, the per axle loads between the load trailer and the add on trailer are automatically equalized by activating the add-on trailer hydraulic system to extend or retract the hydraulic cylinders of the add-on trailer as a function of the air pressure in the load trailer air bags. However, the algorithm for the function differs for the two control systems. Both systems employ a load comparator module which compares the per axle load on the load trailer axles as a function of said load trailer air bag pressure to the load on the add-on trailer axle as a function of either the add-on axle air bag pressure (System 1) or the add-on trailer hydraulic pressure (System 2). When we say the comparator is comparing loads “as a function of,” we are not comparing the respective loads per se. In System 1, we are literally comparing the load trailer air bag pressure to the “area adjusted” add-on axle air bag pressure, each measurement serving as a measure of the load on their respective axles. Thus, the respective loads are compared as a function of the respective air bag pressures. In System 2, the load trailer air bag pressure is converted to “load,” and the add-on trailer hydraulic pressure is converted to load. Thus, the comparator is comparing the load trailer axle load to the add-on trailer axle load, where the loads are determined as a function of the load trailer air bag pressure and the add-on trailer hydraulic pressure.
In control system 1 disclosed herein, the system continually monitors the pressure in the load carrying trailer airbag system at transducer 44, and in the add-on-axle trailer airbag system at transducer 43 (
In control system 2, the system continually monitors the load trailer air bag pressure at transducer 44, and the hydraulic pressure at transducer 37 (
Each mode of operation includes an automatic mode, requiring minimal operation by a human operator, and a semi-automatic mode which facilitates more hands-on control. Automatic operation and semi-automatic operation can be initiated and controlled at a control panel on the add-on trailer, but is preferably initiated and controlled from the software loaded tablet or PDA 150, which includes a wireless connection (represented by dashed lines) to the add-on trailer computer system (
In the first option embodiment, initial set up and continual ride adjustment is achieved by monitoring and continually adjusting as required the air pressure in the load carrying trailer airbags as compared to pressure in the add-on-axle trailer airbags, using the add-on-axle trailer airbag control system 40 (
Because in this embodiment, hydraulic pump 32 is air driven by truck compressed air, rather than being electrical or gasoline powered, a hydraulic pump air control system 50 is required (
The preferred embodiment computer control system 1 for operation of the dynamic load distribution system is illustrated in the flow diagram of
Module 105A determines via locking pin indicator 23d whether locking pin 23a is engaged in aperture 23b in locking tongue 24d. If it is engaged, module 105b instructs pilot valve 57a to activate the cylinder of locking pin 23a, to withdraw it from aperture 23b in locking tongue 24d. This allows add-on-trailer to pivot from side to side as the rig corners.
Control system 1 then asks at module 106, via hydraulic pressure transducer 37, whether the hydraulic pressure in the system is above a predetermined value. If it is, module 107 opens valve 33 to tank 34 to release the hydraulic pressure to a lower level. Valve 33 is then closed at 108.
Preferred embodiment control system 1 includes an optional cornering feature at steps 109 and 110. Software module 109 asks whether a cornering indicator switch 23c indicates that the rig is cornering. If it is, valve 33 is opened to tank 34 to release the hydraulic pressure level to a lower level, e.g. 2000 psi, as indicated by transducer 37. This keeps add-on-axle trailer 20 from lifting trailer 10 to an unsafe height as the rig corners. This is an optional additional feature, in that even without this feature, the rest of the monitoring system and adjustment method should automatically accomplish this result, as will be discussed below. However, it does provide a more direct control of cornering control.
Module 111 then asks whether the air pressure at pressure switch 51 is above a level sufficient to ensure that the air brakes will have sufficient pressure to operate, for example above 80 psi. If so, pilot valve 53 is instructed to open valve 52 by module 112, and air flows to air tank 54. Various approaches can be used to ensure that the flow of air to tank 54 does not bleed off too much pressure from the rest of the system. Thus, if the pressure falls below 80 psi during the process, valve 52 can be closed until the pressure rises again. Alternatively, valve 52 can be opened only at short intervals, with a delay there between to give the system time to recover from any drop-in pressure.
Step/module 113 also proceeds if the pressure at pressure switch 51 is above 80 psi, thus opening the electrically powered hydraulic accumulator valve 36. This allows hydraulic fluid to flow into the shock absorbing accumulator tank 35.
At module 114, the software is continually reading the load trailer airbag pressure as indicated by transducer 44. The pressure is averaged over an interval, such as 30 seconds. Alternatively, trending software is used, as opposed to averaging software. Since the load trailer air bags are identical, the pressure reading at transducer 44 is representative of the per axle load on each load trailer axle. If the add-on trailer air bags were the same configuration as the load trailer air bags, one could insure equal per axle distribution of the load simply by making the airbag pressure of the load trailer airbags equal to the add-on axle air bag pressure. However, the add-on trailer air bags are typically smaller, having a smaller area than the load trailer air bags. Thus, to provide equal load distribution by equating load trailer air bag pressure to add-on axle air bag pressure, the add-on airbag pressure reading must be “area adjusted.”
Module 114a reads the average add-on-axle trailer airbag pressure as indicated by transducer 43, and averages or trends it as is done above for the load trailer airbag pressure. Software module 114C then makes an area adjustment so that the area adjusted air pressure readings for the add-on trailer air bags are the same as they would be if the add-on trailer air bags had the same configuration as the load trailer air bags. The airbag working area for different load carrying trailers will vary from trailer to trailer, and the airbags used on the add-on-axle trailer will typically be smaller in working area than those on the load carrying trailer. Thus, in determining whether the load trailer airbags with a psi of X and the smaller add-on airbags with a psi of Y are carrying the same load, area adjustment module 114C must divide the working area of the per axle load trailer airbags by the working area of the per axle add-on-axle trailer airbags to determine a ratio Z, and then compare Y/Z to X and determine whether those numbers are comparable. By “comparable,” we mean the values are equal or are within some variation from equal which those operating the system would regard as reasonable. We have used a variation of 5% for purposes of exemplification herein, but recognize that greater or lesser variations would be acceptable to experienced rig operators. The Y/Z value is referred to as the “area adjusted pressure” for the add-on-axle trailer airbags.
For example, in a system having a trailer air bag with an upper working circular surface which is 2 ft. in diameter over each wheel, and an add-on airbag which has a working surface which is 1 ft. in diameter over each wheel, the working area of each trailer air bag would be 4 times the working area of each add-on-axle trailer airbag (3.14/0.785=4). Assuming a pressure of 60 psi on the trailer airbags, the “area adjusted pressure in each of the add-on airbags would have to be 240 psi to lift the same load. Thus, the system would compare 60 psi to 240 psi/4, and conclude that at 60 psi and 240 psi, respectively, the trailer axles and the add-on-axle axles are carrying the same load.
Module 115 asks whether the load trailer air bag pressure matches the “area adjusted add-on trailer air bag pressure, preferably within a predetermined acceptable limit, for example 5%. If they do, the system monitors the pressures again for the predetermined time interval, to determine whether they still match to within the limit. If the pressures do not match within 5%, module 116 asks whether the add-on airbag pressure is lower than the trailer airbag pressure. If it is not, module 116a opens hydraulic control valve 33 to tank to drain fluid back into tank 34 and thereby reduce the pressure in cylinders 31, until the area adjusted pressure equals the load carrying trailer pressure at transducer 44. Module 118 then closes valve 33. If the add-on airbag area adjusted pressure is lower than the trailer airbag pressure, module 117a starts hydraulic pump 32 and opens valve 33 to cylinders 31, to extend cylinder rods 31a and thereby increase pressure on add-on airbags 28, and reduce the pressure on trailer airbags 15. When they are equalized or reach a targeted value, Module 119 then closes valve 33 and turns off pump 32. Because pump 32 is air driven, there is another step in the process at module 117. Module 117 asks whether the pressure at air tank transducer 54a is above a predetermined pressure, e.g. 100 psi. If it is not, the system recycles until the 120-psi source from the truck is able to build it up to at least the predetermined level. This is a safety measure, to make sure the operation of the air driven pump 32 does not bleed off so much air pressure that the air brakes will not work. If pump 32 were electric or gasoline powered, module 117 would not be necessary.
The control system 1 operates automatically to equalize the per axle load between the trailer and the add-on trailer when trailer 10 is first loaded, and during the continuing travel of the rig from start to finish.
In the second option, control system 2, each trailer or type of trailer is calibrated to determine load per axle which the trailer will be carrying at a given air bag pressure. This calibration is performed once for each trailer, and the information stored in the control software. To accomplish the calibration, the weight of the load carrying trailer empty is measured, and the air pressure on the trailer axles is noted. A load is then added to the load carrying trailer, its weight determined, and the air bag pressures on its axles noted. We have found that the relationship between trailer load and air bag pressure is linear, such that the correlation between air bag pressure and load for each axle can be determined from these two preliminary measurements, and of course the number of axles for the trailer.
The relationship between the hydraulic pressure in the add-on-trailer and the load on the add-on-trailer axle is also calibrated (usually provided by the manufacturer) and stored in the computer control software.
The computer software (hardware) control system employing option 2 is illustrated in
Software module 120 reads the load trailer airbag pressure via transducer 44. Converter module 122 converts this pressure reading to the load per trailer axle, using the “pressure to load” calibration for the load carrying trailer being used. In module 121, the add-on-trailer hydraulic pressure is determined from transducer 37. At converter module 124, the hydraulic pressure is converted to the load on the add-on axle. This conversion information is typically provided by the manufacturer, but can be calibrated by the operator.
In module 125, the average per axle trailer load is compared to the average add-on axle load over a predetermined interval of time (e.g. 15-30 seconds). If they are comparable, e.g. within a predetermined percentage of one another, e.g. 5% (determination by module 126), the system recycles through these operations until a divergence greater than 5% occurs. If so, interrogator module 127 inquires whether the add-on axle load is lower than the load trailer axle load. If it is, software module 128 automatically starts hydraulic pump 32 and opens valve 33 to pump fluid to cylinders 31, until the loads match. Module 129 then closes valve 33 and turns off pump 32. If the load on the add-on axle is not lower than the load per trailer axle, it is of course higher, and module 130 automatically opens valve 33 to release hydraulic fluid to tank 34, until the loads match. Module 131 then closes valve 33
As above, the control system 2 operates automatically to equalize the per axle load between the trailer and the add-on trailer when trailer 10 is first loaded, and during the continuing travel of the rig from start to finish. An option 3 system dynamically monitoring both air bag pressures and cylinder pressures would have to blend both algorithms.
The operator can monitor system operation remotely on his or her tablet computer 150. The display section 160 on the computer screen may include:
The “controls 170, which are preferably touch screen activated from the display 160 of tablet 150, may include (as shown in
The controls and display software for tablet 150 can of course be varied. In a preferred simplification, a “load axle” control 175 could be added which would control both pump 32 and valve 33 by activating software module 117a (option 1 system) or module 128 (option 2 system) (
There are certain functions which can be performed semi-automatically, and one which must be. To perform functions semi-automatically, the user turns on the semi auto mode 171, on tablet 150, or at the add-on trailer control panel (
One optional semi-automatic operation would be the initial load distribution between the load trailer axles and the add-on trailer axle. When the trailer is loaded, the operator can monitor the per axle load on the load trailer axel load display 162 remotely on his or her tablet or PDA 150, or at the add-on axle trailer display. When the loading is completed, the operator can activate the hydraulic fluid pump 32 at pump control 173, and the hydraulic fluid valve using valve control 174 (
Other features can be programmed into the system. For example, tablet 150 can be provided with a backup camera display.
Of course, it is understood that the forgoing are preferred embodiments of the invention, and that various changes and alterations could be made without departing from the spirit and broader aspects of the invention, as set forth in the appended claims.
This application claims priority to U.S. Provisional Application Ser. No. 62/462,044 filed Feb. 22, 2017, and entitled DYNAMIC LOAD DISTRIBUTION SYSTEM FOR ADD-ON-AXLE TRAILERS.
| Number | Date | Country | |
|---|---|---|---|
| 62462044 | Feb 2017 | US |
