Optics: measuring and testing – By polarized light examination – With light attenuation
Patent
1992-07-06
1993-11-30
Evans, F. L.
Optics: measuring and testing
By polarized light examination
With light attenuation
356385, G01B 1100
Patent
active
052670180
DESCRIPTION:
BRIEF SUMMARY
The object of the invention is a stacking method and equipment, especially for the measurement of the timber volume and other dimensions of a stack of timber, in which method measurements are made of the external dimensions of the stack, and the average diameter and length of the logs, from which the timber volume is calculated. When connected to the measurement of the total weight the invention is also concerned with the measurement of the specific gravity of the stack.
In the manufacture of cellulose in particular it is advantageous to know the moisture content of the timber being used as raw material. Raw timber comes to the cellulose mill as stacks of logs, and the moisture content in these can vary considerably. When the moisture content of the raw timber being fed into the process can be measured more accurately than previously, savings are made in the chemicals used in cooking, because they can be more accurately portioned.
On the other hand, the size of the logs contained in the log stacks is of particular significance in the manufacture of mechanical pulp, in which it is not advantageous to mix logs of different size with one another. In practice the smaller logs are partly lost among the large ones. Often the variation in the diameters of the logs in a stack is not great, but different stacks vary greatly in this. By ascertaining the average diameter of the logs in a stack it is possible to roughly sort the logs into size grades.
A stack measuring method, in which the ends of the stack are filmed with a video camera and the outlines of the ends of the logs are recognized and their location is measured, is known from the international application publication WO 89/7749. The filming and measurements are carried out from both ends, in which case it is possible to measure the total volume of the logs of the stack very accurately. This kind of method is, however, so slow that it cannot be applied to the measurement of each stack of logs arriving at the mill.
A measurement method, in which the relation between the dark and light areas is measured from a video picture of the end of the stack, from which the so-called side density can be calculated, is known from the Swedish publication print 391580.
No known method of measurement makes it possible to measure the desired dimensions quickly from the stack and without separating the stack from the transportation device. By means of this invention a method and equipment is created by means of which the desired dimensions can be measured directly from the load. In particular it is wished to create a so-called drive-through measurement line, in which the measurements are made by driving the load past the measurement point. The main principle of the invention is to recognize the forms of the outer logs and those projecting from the ends of the stack, by means of which the average dimensions can be calculated. The recognition of the forms of the logs to be measured is based on the analysis of the curves appearing in the video picture, the curves arising when the stack is illuminated by a beam of light from the side.
In what follows the invention is illustrated with the aid of the accompanying figures, which show one form of application of the invention.
FIG. 1 shows the stack measuring equipment as seen from above.
FIG. 2 shows the equipment seen from the side.
FIG. 3 shows the equipment seem from the direction of arrival of the stacks.
FIG. 4 shows logs located on the side of an example stack.
FIG. 5 shows a cross-section of the logs furthest to the side in a stack.
FIG. 6 shows the image information of a pair of cameras.
The equipment in accordance with FIGS. 1-3 is installed in hall 1, through which a log truck can drive. Hall 1 is so long that a log truck with a full trailer can fit entirely inside it. When the measuring equipment is ready, the truck driver is shown a green light by means of traffic light 2, when he can drive the truck with its load slowly through hall 1.
The displacement of the vehicle and the stacks of logs with it is measured with the ai
REFERENCES:
patent: 3593632 (1971-07-01), Woodruff
patent: 4913551 (1990-04-01), Davis
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