Abstract: The specification describes a linear fluidic actuator comprising a plurality of expansible tubes or tubular envelopes closed at opposite ends and coupled in a chain and arranged to have one end of the chain anchored while the other end is adapted to move and exert a tensile force upon inflation of one or more of the tubes, as by compressed air, into a circular diameter, in accordance with the degree of contraction of the chain of tubes. A variation of the actuator utilizes the contracting force of the chain of tubes to effect compression of one or more caged springs, the compressive force of which is illustratively shown and described as actuating a floating member to operate a valve device of the gate or plug type. Also disclosed are modifications utilizing a plurality of parallel-related chains of tubes and tubes expansible to different diameters for utilizing different inflating pressures.