Abstract: Poorly conducting substances, such as chips of cellulose material containing a heat hardenable binder, are heated by passing them between the plates of an operational capacitor supplied with energy from a high frequency generator. An adjustable auxiliary capacitor is connected in parallel with the operational capacitor and is adjusted to match the capacity of the output circuit to the generator with changing conditions of the poorly conducting substances. Coarse initial control is effected by adjusting the separation of the plates of the operational capacitor. The apparatus is especially useful for making chip boards and the like in which a precompressed mass of chips is passed between the plates of the operational capacitor sandwiched between two endless belts.

Abstract: Particleboard made from particles in the form of chips or fibers or the like is made by distributing a mass of chip material onto an endless belt conveyer system. The mass of material is subsequently passed to a precompressor, a high frequency preheating device, a further press and a finishing press. The unheated further press serves to reduce the thickness of the material to substantially that of the finished board prior to its consolidation by temperature and pressure in the finishing press. A further endless belt contacts the surface of the material and runs through the precompressor, the high frequency heating device and the further press and serves to counteract any tendency of the chip material to expand after leaving the precompressor. This endless belt additionally yields a number of other significant advantages, in particular a reduction of loss of heat from the material prior to reaching the finishing press.

Abstract: A high frequency industrial generator, especially suitable for supplying power to a device for heating an electric poorly conducting substance such as a fleece of a cellulose material, comprises two hollow concentrically disposed conductors each of square section and supporting respective electrode plates of an associated capacitor. All the plates are vertically disposed and lie at right angles to the walls of the respective conductors. In the middle of the electric plates there is situated a triode electron tube electrically connected to the plates to form an oscillating circuit. The anode potential and cooling water supply for the electron tube is located within a field free space inside the internal conductor. One set of electrode plates can be adjusted relative to the other to adjust the frequency and the arrangement ensures only low electrical losses are incurred.