Abstract: A springless impact device including a piston-cylinder mechanism having at least one preselected coacting port and passageway operatively connected to a valve pressurized fluid control apparatus which selectively feeds and exhausts pressurized fluid to and from the device in a predetermined manner. There is an area differential between the top and bottom ends of the piston head. The device includes an inverted "U"-shaped seal ring on the piston head which functions as a one-way check valve to effect piston reciprocation in coaction with the area differential on the piston head.

Abstract: The vibratory screener presented is of a design to convert rotary vibration directly to an unsupported portion of a wire mesh or perforated plate screening surface, while imparting no vibratory energy to the screen's main supporting framework.