Continuous board-making press including press plate deformation safety

Abstract

A press for making pressed board has a plurality of longitudinally spaced rigid frames, a lower press plate extending longitudinally through and secured to the frames, and a normally planar upper press plate extending longitudinally above the lower plate through the frames and defining with the lower press plate a longitudinally throughgoing press gap. A plurality of vertically effective double-acting hydraulic cylinders carried on the frames above the upper plate each have a back compartment and a front compartment, are connected to the upper plate, and support the upper plate on the frames. Respective upper and lower endless belts have respective lower and upper stretches extending through the gap immediately below and above the respective upper and lower plates and respective upper and lower rollers advance the stretches longitudinally through the frames. Sensors connected to the lower plate produce an output corresponding to the size of the gap. A safety unit connected to the upper plate produces an output when the upper plate is deformed to a predetermined extent from a planar shape. A hydraulic valve system connected to the compartments of the double-acting cylinders pressurizes and depressurizes same. A controller connected to the safety unit and valve system pressurizes the front compartments of the cylinders when the safety unit generates its output and thereby hydraulically blocks downward movement of the upper plate.