Abstract: A method of manufacturing plates, such as chipboards, fibre boards and the like boards, where the raw material in form of biomass particles, such as wood chips, wood fibres and the like applied with a thermosetting binder is spread onto a preforming band into an endless mat, and where this mat (B) is pre-compressed in a continuously operating prepress (C ) and then completely pressed in a continuously operating hot press, whereby the mat (B) is compressed into the desired thickness of the finished plate and the thermosetting binder is hardened. According to the invention, the mat (B) is pretreated by means of steam immediately before the introduction into the hot press (E) by means of a device (F) so as to obtain predetermined gradients of moisture content and temperature across the thickness of the mat. As a result the capacity of the apparatus can be increased at the same time as the energy consumption can be reduced.

Abstract: A method of determining the density profile of a plate-shaped material M, the density of which varies discretely or continuously across the plate thickness, whereas the density at a specific depth of the plate M is preferably assumed to be constant. The inventive method employs X-rays or .gamma.-rays from a source K. The latter source K is placed on one side of the plate M, whereas at least two detectors T, F are arranged on the opposite side of the endless plate being advanced during the measuring in the longitudinal direction. A first detector T is preferably placed in the radiating direction of the source and measures the transmittent radiation through the plate M, and the second detector F is placed outside the radiating direction of the source K and measures the scattered radiation on partial volumes along the radiating direction of the source. Based on the signals measured by the detectors it is possible to measure the density in each individual partial volume.

Abstract: A method of non-destructively, on-line determining the density profile in a plate-shaped material with a density which varies discretely or continuously over the plate thickness, while the density at a specific depth of the plate is assumed to be constant, such as for instance plates based on wood, by means of X-rays or gamma rays from a source placed on one side of the plate. Two detectors are placed on the other side of the plate, one detector measuring in the emitting direction of the source and the other detector measuring in the other direction and being movable relative to the plate. The counting number of the second detector is adjusted by means of the counting number of the first detector. By a suitable choice of emitting direction and detecting direction it is possible to provide a measurement of the density in a specific measuring volume merely by dividing the counting number of the second detector by the counting number of the first detector.