Weighing scales – Structural installation – Vehicle
Reexamination Certificate
1998-11-06
2001-05-01
Gibson, Randy W. (Department: 2859)
Weighing scales
Structural installation
Vehicle
C177S141000, C701S050000
Reexamination Certificate
active
06225574
ABSTRACT:
BACKGROUND OF THE INVENTION
The field of the invention is heavy equipment used for collecting and moving a load from one place to another, and for measuring the weight of the load while it is being moved.
More particularly, the field of the invention is heavy equipment for surface mining loading operations such as power shovels, drag lines, and the like, and more particularly, systems used on such equipment to measure the net weight of material in each load.
In large scale surface mining operations, equipment of immense proportions is used to load and transport material. Loading is usually performed by power shovels with a dipper capacity of about 100 tons per scoop. Equally mammoth trucks are loaded with the material and haul it to a processing location. The largest trucks have a capacity of about 360 tons.
Overloading the trucks can lead to premature fatigue and failure causing excessive maintenance costs. Without a measurement of the actual weight of material in the truck, the power shovel operator can only guess the weight based on an extremely rough estimate of the volume of material in the truck. Therefore, to prevent chronic overloading, the trucks are routinely underloaded. But such underloading can cause significant loss of production.
Measurement systems have been developed to indicate the net weight of material in the power shovel dipper as it is transferred to the truck. The prior measurement systems function by first sensing the electrical load of the power shovel drive motors, then computing the motor dynamics based on that electrical load, and finally computing an estimate of the net weight based on the motor dynamics, the known power shovel geometry, and the known tare weights. Examples of such known systems include Radomilovich U.S. Pat. No. 4,677,599 and Blair et al. U.S. Pat. No. 4,809,794, which averages stored weight determinations calculate an actual material weight.
Although such measurement systems have been constructed and used, they have been ineffective due to large inaccuracies in the measurements on the order of ±20% or more. These errors stem from the fact that the existing measurement systems do not effectively account for the complex dynamic operation of such enormous equipment, or for all the environmental effects on the equipment, such as the level of the mine surface where the shovel is located. Therefore, measurements are not only in error, but are erratic and unpredictable. In order to be effective, a measurement system has to be capable of accurately and repeatedly performing measurements to within a small error, say ±2% for example. Otherwise, the problems of overloading and underloading would persist. Although the above noted measurement systems have attempted to account for dynamic factors affecting the load weighing process, such systems have been either too complex or incomplete.
SUMMARY OF THE INVENTION
The invention provides a method of measuring the quantity of material delivered per cycle by large mining and hoisting machinery, such as a shovel loader and a crane, the machinery having a device to hold the material to be delivered, the device being movable between loaded and unloading positions, the device being supported from a structure during movement between the positions, the method comprising determining the position of the device in respect to a selected location on the structure in the form of a processable position signal at a plurality of intervals during the movement of the device between the loaded and unloading positions, determining the load at a selected location within the structure where the load is related to the weight and position of the device and device contents in the form of a processable load signal at each the interval, processing the position and load signals for a plurality of interval determinations to provide a number of weight determinations of the device and device contents from the interval determinations made during the movement, selecting a sample of less than all of the weight determinations based upon the dynamic influences on the machinery when the signals are processed, and averaging the selected sample of weight determinations to provide a final determination of the weight of the device and device contents.
The invention further provides a hoisting machine including a device supported from a structure, the device holding the material to be lifted, the structure being movable to locate the device in respective loaded and unloading positions, and apparatus for measuring the quantity of material delivered by the device, the apparatus comprising means to determine the position of the device with respect to a selected location in the structure at a plurality of intervals during the movement of the device, means to provide a processable position signal indicative of the determined position of the device, means to determine the load at a selected location within the structure where the load is related to the weight of the device and device contents at the intervals during the movement of the device, means to produce a processable load signal indicative of the determined load at the location, and processing means to receive the position and load signals for a plurality of interval determinations and calculate therefrom a number of weight determinations of the device and device contents from the interval determinations made during the movement, to select a sample of less than all of the weight determinations based upon the dynamic influences on the machine when the signals are processed, and to average the sample of selected weight determinations to provide a final weight determination of the device and device contents.
In one embodiment, the structure includes a platform, and an upwardly extending boom connected at the lower end to the platform, and the device is suspended from the boom.
The invention also provides means to determine the position of the device with respect to a selected location in the structure at a plurality of intervals during the movement of the device including means for determining the angle of the boom relative to the direction of the force of gravity. In one embodiment, the boom angle determining means is an inclinometer mounted on the boom.
In one embodiment, the structure further includes a sheave at the top of the boom, and a hoist rope trained over the sheave and attached to the device to suspend the device from the boom, and wherein the means to determine the position of the device with respect to a selected location in the structure at a plurality of intervals during the movement of the device considers the sheave diameter and the angle the hoist rope leaves the sheave.
It is an advantage of the present invention to provide an improved system for measuring the load weight of large mining and lifting machinery, which system eliminates the need to try to compute dynamic force effects on the machine in order to get an accurate weight measurement.
It is still another advantage of this invention to provide a measuring system of the foregoing type which can determine such calculations in a dynamic state and with an accuracy of within ±2%.
It is yet another advantage of the present invention to provide a measuring system of the foregoing type which takes into account that the lifting machinery may be located on uneven ground.
It is yet another advantage of the present invention to provide a measuring system of the foregoing type which is adaptable for use with a wide variety of mining and lifting machinery.
REFERENCES:
patent: 4677579 (1987-06-01), Radomilovich
patent: 4691792 (1987-09-01), Shintani
patent: 4809794 (1989-03-01), Blair et al.
patent: 4919222 (1990-04-01), Kyrtsos et al.
patent: 5070953 (1991-12-01), Kyrtsos et al.
patent: 5105896 (1992-04-01), Kyrtsos
patent: 5717167 (1998-02-01), Filing et al.
Burant John S.
Chang Shu-Chieh
Chen Demeng
Phillips Paul G.
Rikkola Michael J.
Earl Lowe, Jr. James
Gibson Randy W.
Harnischfeger Technology, Inc.
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