The Tonjes et al patent also describes a mechanism for reciprocating a sieve shaker
unit vertically depending from a base frame wherein a stack of alternate sieve shaker screens or trays and spacers is held firmly together in the sieve shaker unit by means of a pair of long pull-type clamp rods and a pair of hydraulic cylinders which are controlled by a manually hand operated hydraulic pump and valve assembly unit on top of the apparatus.