Pressure applied between symmetrical pistons forces them apart against spring forces so that toothed extensions turn shaft through 180 degrees

摘要

The drive (1) is secured to and operates a shut-off valve (6). A symmetrical set of springs (19,20) acts on pistons (12,13). Extensions (14,15) have teeth (16,17) that engage a toothed wheel (18). Fluid pressure applied between the pistons forces them apart to turn the toothed wheel. When pressure is released, the springs push the pistons back, turning the wheel through 180 degrees.