X-ray or gamma ray systems or devices – Specific application – Absorption
Patent
1994-08-22
1996-08-20
Church, Craig E.
X-ray or gamma ray systems or devices
Specific application
Absorption
378 51, G01B 1502
Patent
active
055486266
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an apparatus for establishing a density profile through the thickness of a panel-like workpiece of non-homogeneous material, for example a particle board panel or fibre board panel bonded with glue or minerals, comprising: an emitter of a measuring device, whose radiation is arranged to pass through the workpiece, thereby being attenuated by absorption in dependence upon the local density of the workpiece, and is directed to a detector of the measuring device, wherein the detector produces an electrical signal corresponding to the output intensity of the attenuated radiation, and wherein the detector is electrically connected to means for establishing the density profile.
The invention also relates to a method of establishing a density profile through the thickness of a panel-like workpiece of non-homogeneous material, for example a particle board panel or fibre board panel, comprising the following steps: device, according to step B) in dependence upon the local density of the workpiece to a detector of the measuring device, output intensity of the attenuated radiation, and establish the density profile.
In one known apparatus of this type (R Thompson et al: "Design and Construction of a Profile Density Measurement System for the Composite Wood Products Industry" in: IEEE Proceedings--1989 Southeastcon, Session 12D2, pages 1366 to 1371) a specimen cut from a particle board panel or fibre board panel is moved through a gamma radiation beam of a measuring device (see page 1367, FIG. 2). The gamma radiation travels perpendicular to a narrow face of the specimen. One is talking here about a laboratory apparatus. The specimens are taken from the running panel production line and are analysed. It is disadvantageous however that the panels have to be destroyed in order to remove the specimens and that there is a long period until the density profile is produced. The production process can therefore only be controlled with a corresponding delay.
An apparatus of the type first mentioned above is also known from C. Boehme: "The significance of the density profile for MDF" in: Holz als Roh- und Werkstoff 50 (1992), pages 18 to 24. As shown in FIG. 10, a vertical radiation beam is transmitted through a front shutter, then through the length of a perpendicularly arranged test body of 50.times.50.times.thickness mm.sup.3, then through a rear shutter and finally to a detector (scintillation counter). The test body is moved in steps of 1/10 mm transversely to the direction of the radiation by means of a stepping motor. The measuring period is 2 seconds for each step. The disadvantages mentioned above apply likewise to this apparatus.
From DE 34 29 135 C2 it is known per se to obtain a continuous thickness measurement of rolled material, and in particular steel sheet of 1.5 to 30 mm thickness, and among other things to display or print-out the transverse profile of the rolled product. For this, the upper surface of the rolled product is irradiated from above by a fan-shaped beam from at least one very strong gamma radiator 5, 6 in a measuring plane which is perpendicular to the direction of rolling. Detector beams 7, 8 with rows of ionization chambers 18, 19 are arranged below the rolled product at right-angles to the direction of rolling. The fan-shaped form of the gamma radiation has the result that the radiation paths in the rolled product are longer the more the direction of the radiation departs from the vertical. Consequently, the analogue values of the measurement currents relating to the different measurement paths must be corrected.
It is the object of the invention to establish the density profile of the workpiece more rapidly.
This object is achieved by an apparatus having the features of claim 1. The workpieces can consist for example of particles or fibres of wood or fibres from one year old plants such as flax or bamboo. A mineral binder can be used such as gypsum or cement for example. Gamma radiation or highly penetrative X-ray radiation can be used in particular as suitable radiat
REFERENCES:
patent: 4720808 (1988-01-01), Repsch
R. Thompson et al.: "Design and Construction of a Profile Density Measuring System for the Composite Wood Products Industry" in: IEEE Proceedings-1989 Southeastcon, Session 1202, pp. 1366-1371.
C. Boehme: "The significance of the density profile for MDF" in: Holz als Ron--und Werkstoff 50 (1992), pp. 18-24 (Die Bedeutung des Rohdichteprofils fur MDF).
Church Craig E.
Fagus-GreCon Greten GmbH & Co. KG
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