Patent Application
20080217874
The present invention relates generally to suspensions for motorized vehicles and trailers. More specifically, the present invention relates to active suspensions for vehicles and trailers for transporting fluids in a mobile tank, where the suspension components are actively controlled to respond to motions of the transported fluid.
Rollover is unfortunately a common problem with mobile tankers, due to the height and narrow width. The reasons for rollover have been studied, one example of such a study is set forth in Winkler, C. Rollover of Heavy Commercial Vehicles, UMTRI research Review, pages 1-20, October-December 2000, which is incorporated by reference herein in its entirety. The traditional approaches to reducing rollover include sway-bars, and sensor monitoring of pitch, with a display presented to the driver or electronic control to limit acceleration of the vehicle. Where a liquid containing tank is present on a trailer, the problems may become more pronounced.
Mobile tanks are often fastened to a frame, such as a trailer or a railroad car, for use in transporting liquids. During transportation, the liquids in a mobile tank are always moving. As the liquid moves it causes the center of gravity of the load to change and results in instability, which can lead to a tip-over or to dangerous loss of control over the transported tank. In theory, a mobile tank could even tip over traveling in a straight line on flat ground, if the there are bumps at the right locations to cause a buildup of side-to-side wave action.
There are generally two stability problems in transporting a fluid in a mobile tank. Although there is overlap between the two general categories. The first is the formation of“waves” in the transported fluid and the other is the sloping of the fluid due to inertia during movement of the tank.
Traditionally, these problems have been dealt with by placing baffles in a tank. One example of a mobile tank for transporting liquids that contains a baffle is that disclosed in U.S. patent application Ser. No. 10/690,764, filed Oct. 22, 2003 and entitled Methods of Tank Construction, which is incorporated herein by reference in its entirety. Basically, a baffle works by restricting movement of the liquid in a tank to individual sections of the tank and/or by dispersing a wave or slope by physically blocking its generation or movement. While baffles reduce the effects of motion on the transported liquid, the reduction may not be sufficient to avoid additional stress on the tank or trailer. Baffles also reduce the holding capacity of a tank and are not capable of adjusting to interact in the best possible way with different fluids that may be carried at different times in the same tank.
Thus, apparatus, systems and methods that provide ways of actively reducing the effects from the motion of liquids in a mobile tank would be an improvement in the art.
The present invention provides apparatus, systems and methods for the stabilization of a mobile liquid tank during transportation of a liquid. Sensors feed information regarding the status and position of a liquid retained therein to a control unit, which may be an on-board computer. Other information, including acceleration/deceleration, travel speed, steering, centrifugal force from turns, slope, GPS, and radar to sense the topography of the terrain not yet traveled may be similarly be monitored and input. The control unit calculates the expected movement of the liquid, and controls a set of pneumatic valves to adjust airsprings of a pneumatic suspension as to minimize undesirable movement of the liquid. In an emergency the airsprings may be deflated, lowering the entire tank to lower the center of gravity reduce the likelihood of the tank tipping over.
It will be appreciated by those of ordinary skill in the art that the elements depicted in the various drawings are for exemplary purposes only. The nature of the present invention, including the best mode, as well as other embodiments of the present invention, may be more clearly understood by reference to the following detailed description of the invention, to the appended claims, and to the several drawings.
The present invention relates to systems and methods for stabilizing a mobile tank for transporting liquids during transport with the tank. It will be appreciated by those skilled in the art that the embodiments herein described, while illustrating certain embodiments, are not intended to so limit the invention or the scope of the appended claims. Those skilled in the art will also understand that various combinations or modifications of the embodiments presented herein can be made without departing from the scope of the invention. All such alternate embodiments are within the scope of the present invention. Similarly, while the drawings depict illustrative embodiments of devices and components in accordance with the present invention and illustrate the principles upon which the depicted device or component is based, they are only illustrative and any modification of the invented features presented herein are to be considered within the scope of this invention.
Movement of liquids in a tank may be predicted mathematically. For example, the sloshing behavior in a liquid cargo tank has been studied with respect to tanker ships for marine transport of liquids, such as oil and gas. One paper addressing such simulations is Mikelis, N. E. et al., Experimental and Numerical Simulations of Sloshing Behaviour in Liquid Cargo Tanks and its effects on Ship Motions, National Conference on Numerical Methods for Transient and Coupled Problems, 9-13 Jul. 1984, Venice, Italy, Report 0661-P, 1984 Delft University of Technology, the disclosure of which is incorporated by reference herein. As set forth therein, numerical modeling using the “marker and cell” technique (where Navier-Stokes equations are solved for each “cell” of a computational mesh corresponding to a partially filled tank) allows for transient fluid flow problems to be addressed. Comparison of the predicted sloshing movements of the liquid and the effect on the tank containing the liquid were compared to actual data obtained by experimental measurement, and were found to show good agreement. Other suitable techniques for predicting the movement of liquid in a tank are known to those of skill in the art and may be used in systems in accordance with the present invention.
Turning to
Disposed in the tank T are a number of sensors 120. The number of sensors 120 used may vary based on the size and shape of tank T, so long as sufficient sensors 120 are used to allow for monitoring and prediction of movement of liquid retained in the tank T. The sensors 120 may be pressure sensors, motion sensors, or other types of sensors useful for sensing the presence, the pressure, and/or the motion of a liquid retained in the tank T. The specific type of sensor used may vary based on the liquids intended for placement in the tank T. Combinations of different sensor types may also be used.
The placement of the sensors 120 may vary based upon the shape of the tank T, in order to allow for accurate prediction. For example, sensors 120A and 120B may be placed at opposite ends of the tank T to detect pressure differences and motion therebetween (
Using the sensors 120, the condition and motion of liquid L retained in the tank may be detected. The information obtained by the sensors 120 is provided to a control unit, represented by box 122. Control unit 122 may be a computer or a microprocessor onboard the trailer 110 or in a prime mover for operating the trailer 110. Where the sensors 120 include electronic sensors, the detected information may be directly provided to the control unit 122 over an electrically communicative connection therebetween, as by an electrically conductive cable. Alternatively, the electronic sensors could provide the information using an appropriate wireless transmission protocol, such as WAP, Bluetooth, etc.
The control unit 122 may be a computer which runs a program, typically by executing lines of code contained in software loaded therein. The control unit 122 predicts the behavior of liquid retained in the tank T, by analyzing data provided to it by the sensors 120 and numerically predicting the expected motion of the liquid based on such data. This monitoring and prediction will occur on a continuous basis when the system is in use.
In addition to sensor 120 disposed within the tank, additional sensors 124 may be placed on the trailer or a prime mover at various locations to detect the motion and position of the trailer 110, or the future motion of the trailer 110. Such sensors 124 may include cameras, motion sensors, inclinometers, ground scanning radar, GPS receivers, etc, for monitoring the conditions around the trailer and predicting motion thereof, or other such sensors as known in the art, as for example those described in the Winkler paper previously cited herein. Additionally, where the prime mover attached to the trailer 110 has an onboard computer system, such as a semi tractor with an onboard computer for controlling electronic engine or other components, information from the onboard computer regarding speed, acceleration, deceleration, turning, etc. may be provided to the control unit 122 over a communicative connection. Using such sensors 124, acceleration/deceleration, travel speed, steering, centrifugal force from turns, slope, GPS, and the topography of the terrain not yet traveled may be provided.
As the control unit 122 predicts movement of liquid inside the tank T, it controls a series of valves, represented by box 150, to inflate and deflate pneumatic airsprings 104 in a suspension system, in order to counter the predicted motion of the liquid. It will be appreciated that valves 150 may be any suitable valves for controlling the inflation or exhaust (deflation) of an airspring 104 with an electronic control unit and that a single valve may be used for control of each individual airspring 104. As depicted in
Airsprings 104 may be airbags designed for used as springs in automotive, train, tractor-trailer, and other vehicular suspension systems. As depicted in
It will be appreciated that where each airspring 104 may be considered a pneumatic spring configured as a column of gas (air) confined within a container. The pressure of the confined gas, and not the structure of the container, acts as the force medium of the spring. A wide variety of sizes and configurations of airsprings are available, including sleeve-type airsprings, bellows-type airsprings, convoluted-type airsprings, rolling lobe airsprings, etc. Such airsprings commonly are used in both vehicular and industrial applications. Airsprings, regardless of their size and configuration, share many common elements. In general, an airspring includes a flexible, sleeve-like member made of fabric-reinforced rubber that defines the sidewall of an inflatable container. Each end of the flexible member is closed by an enclosure element, such as a bead plate that is attached to the flexible member by crimping. The uppermost enclosure element typically also includes air supply components and mounting elements (e.g., studs, blind nuts, brackets, pins, etc.) to couple the airspring to the vehicle structure. The lowermost enclosure element also typically includes mounting elements to couple the airspring to the vehicle axle. Examples of airsprings are set forth and discussed in U.S. Pat. No. 6,957,806, the disclosure of which is incorporated by reference herein.
As best depicted in
The air hose 322 is attached to a gas source 430 (
Where the tank T is located on a truck (such as a “straight-truck”), or on an earth moving apparatus that is self-propelled implement, an air compressor located thereon and powered by an onboard engine may provide the gas to the airbag 104.
As depicted in
As depicted in
The suspension system 20 includes at least one airsprings 204 disposed between the tank T and the trailer 210. It is presently preferred that multiple airsprings 204 be used. In one illustrative embodiment, at least four airsprings 204 are used. Each airspring 204 may be positioned such that its inflation will elevate a section of the tank, such as a corner or a quarter of the tank, where four airsprings 204 are used.
As the control unit 122 predicts movement of liquid L inside the tank T, it controls a series of valves 150 to inflate and deflate pneumatic airsprings in a suspension system, in order to counter the predicted motion of the liquid L. Where the control unit 122 predicts that movement of the liquid L is forming a “side slope” in the tank, the control unit 122 will activate the appropriate valves 150 to move the tank by lowering the “uphill” side, and raising the “downhill” side relative to one another, making the tank more stable. Where the control unit 122 predicts the formation of waves in the tank, whether “side-to-side,” “front-to rear” or a combination thereof, the control unit 122 will activate the appropriate valves 150 to adjust the tank in a manner to dampen the waves. Where the control unit 122 predicts movement of the liquid L from cornering of the tank in motion, the control unit 122 may activate the appropriate valves 150 to lower the side of the tank T on the inside of the turn and raise (or firm) the outside of the tank T, relative to one another, thus tipping the top of the tank T inward and resulting in better stability through the turn.
It will be appreciated that the active suspension systems 10 of the present invention may be continually monitoring and responding to the motion and predicted motion of liquid in the tank T during transportation of the tank.
One or more sensors 120 and 124 may be disposed on the tank T and trailer or vehicle on which the tank T is mounted. These sensors may be motion sensors, pressure sensors or other sensors as previously discussed herein. Such sensors may provide output in the form of electrical signal that may be digitally read by a computer to determine a parameter regarding the motion of the tank T or the movement of liquid L retained in the tank T. During use, a control unit 122, such as an onboard computer system, monitors the conditions reported by the sensor(s) 120 and/or 124. As movement of liquid L inside the tank T is predicted, a series of valves 150 are actuated to inflate and deflate pneumatic airsprings in a suspension system, in order to counter the predicted motion of the liquid L, as discussed previously herein.
In this way, the effect of “sloshing” liquid in the tank T can be reduced. It will be appreciated that the control system 122 may be further configured to deflate all the airsprings 104, upon the sensors 122 reporting conditions that may signal potential rollover danger for the trailer or vehicle o which the tank T is mounted. This may lower the entire tank T and reduce the center of gravity for the mass, reducing the tendency of the tank T to rollover.
While this invention has been described in certain illustrative embodiments, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
