Fluid is delivered by pump 2 at constant pressure from tank 1 to directional valve 3 and along pipeline a to the middle space of cylinder 4 (between pistons 5 and 6). By the action of the fluid, pistons 5 and 6 are moved upward and downward, and, by means of levers 7 and 8, the stock is clamped by vertical an horizontal jaws 9 and 10. Fluid, forced out of the top and bottom ends of cylinder 4, drains back to tank 1 through pipelines b, channel c and pipeline d. When the spool of valve 3 is shifted to the left, fluid is delivered through pipelines b to the top and bottom ends of cylinder 4. This moves pistons 5 and 6 toward each other and jaws 9 and 10 release the stock. Fluid, forced out of the middle space of cylinder 4, drains back to tank 1 through pipdeline a, groove e, channel f and pipeline g. When pistons 5 an 6 approach each other, fluid delivered by the pump drains to tank 1 through pipeline h. Relief valve 11 allows surplus fluid to drain back to the tank.
$3886$LHP,GC$