Trucks (including transport and garbage trucks) often contain load cells which are used for weighing the loads within the truck. It is important to weigh loads in trucks in general both to ensure regulatory compliance, and also to ensure that the loads are balanced within the trucks. It is also important to weigh loads in garbage trucks in particular since garbage truck operators often bill in terms of the weight they haul.
Over time, the weight readings given by these load cells will tend to become inaccurate due to “creep” within the metal of the load cell block. IE: after prolonged loading of a load cell, the loads will tend to produce a slightly greater distortion in the load cell over time (due to metal fatigue). Moreover, the amount of such “creep” distortions may be different at different loads.
A further problem with load cells is that the measured “force vs. deflection” relationship of the load cell is different when: (a) the loads are being progressively added to the load cell, and when (b) the loads are being progressively removed from the load cell. As a result, the same force applied to a load cell with result in a first deflection if weight had been previously added to the load cell; and a second deflection if weight had been previously removed from to the load cell.
A problem with existing truck load cells is that they are typically calibrated with only a single “force vs. deflection” relationship. Most typically, this “force vs. deflection” relationship is calibrated under conditions of increasing load. Thus, as weight is progressively added to the truck, the load cells will accurately indicate the addition of this load. However, as weight is removed from the load cell, the load cell will tend to show somewhat inaccurate results. This has proved to be particularly problematic for truck operators. Specifically, the portions of the total loads they are hauling are frequently added and/or removed during normal operations, resulting in somewhat inaccurate load cell readings.
Lastly, temperature variations of the load cells will tend to skew their weight readings.
What is instead desired is a load cell weighing system that provides accurate readings both as weight is added or removed from the load cell, thereby compensating for hysteresis in the load cell. Ideally, as well, such a system would also compensate for metal fatigue or “creep” as well. Lastly, as well, such a system would also compensate for temperature changes in the load cell.
USPTO Backgrounds
USPTO Backgrounds