Compressed air from the mains is admitted by a directional device through port 1 into the annular cylinder formed by pipes 3 and 4. At this, annular piston 2 moves to the right and liquid from the annular cylinder passes through ports 5 and 6 into the right end of the inner cylinder. Piston 7 moves to the left because port 8 is connected to the atmosphere. With this motion of piston 7, piston rod 9 is extended. To provide for the required velocity of motion of piston 7 a regulating valve, not shown, is mounted in the pipeline between ports 5 and 6. If the required velocity of motion of piston 7 is constant and the same for the forward and reverse strokes, the regulating valve may be a simple flow-control valve. In the reverse stroke, port 1 is connected to the atmosphere and compressed air is admitted into port 8. Piston 7 moves to the right, and the liquid from the right end of the inner cylinder is forced through ports 6 and 5 into the right end of the annular cylinder, moving annular piston 2 to the left.
$3754$SHP,Dr$