Image Number 2 for United States Patent #4529482.
A diffusion washer and/or thickener assembly is provided that is greatly simplified. A number of withdrawal screens and fluid introducing structures are provided supported by spider arms which comprise conduits for introduction of liquid into and withdrawal of liquid from an elongated upright hollow vessel in which the assembly is disposed. The conduit means, with attached screen structures, is reciprocated up and down by a single linear actuator located preferably above the vessel and within the cross-sectional area thereof so that the wall of the vessel need not be penetrated by the conduits. The screens and fluid introducing structures remain stationary with respect to each other during reciprocation. A number of wiper blades, which may be operated by a single linear actuator, are provided at the top of the vessel for moving upwardly flowing pulp into withdrawal conduits surrounding the vessel periphery.