Abstract: A hollow cylinder is fitted with a piston, whose hollow rod or shank protrudes downward from the cylinder to apply lifting suction to print media. The upper end of the cylinder communicates with a suction system. In the cylinder side walls, main passageways and reapportioning passageways apply suction to the underside of the piston when the piston is less than fully extended, drawing the piston down to extend the shank. When the shank is fully extended the piston blocks the reapportioning passageways--reallocating more of the available suction to other feet, in the same system, that remain unextended.

Abstract: This suction foot or "sheet sucker" has a cylinder and a hollow piston fitted in the cylinder. The piston has a piston rod whose tip protrudes downwardly from the cylinder to apply suction to the top sheet of stock in a small press. The cylinder is supported from and moved by a hollow support rod that is connected with the suction system of the press. The piston and rod are spring-loaded upward relative to the cylinder. The hole in the support rod communicates with a point in the cylinder cavity below the piston. Applied suction consequently draws the cylinder and rod downward, against the spring action, in effect telescoping the suction foot tip outwardly toward the stock. When a sheet of stock closes the bottom end of the hollow piston and rod, pressure on the cylinder is equalized and the suction foot tip retracts, raising the stock for travel into the press. The necessary air communication is effected by several fine air passageways in the cylinder side wall and top wall.