Doctor blade supply system with intelligent viscosity logic

摘要

A supply system for a chambered doctor blade assembly makes possible the sequential use of water-based and non-water-based liquid inks through automated functions programmed in a PLC that controls the system. A pair of pneumatically driven diaphragm pumps serve as supply pump and return pump between the doctor blade chamber and an ink reservoir A PLC controls the pulse rate of pneumatic pressure to the pumps to control the rate of flow of the liquid into, and out of the doctor blade chamber. A capacitive sensor detects a high liquid level in the ink reservoir. The PLC is programmed to modify the pulse rate of the supply pump and return pump to maintain the liquid level in the reservoir above the drain thereof and below the maximum level.