Abstract: An apparatus for controlling the operation of a package filling device, comprises a cylinder which has inlet and outlet means for the intake and discharge of a filling material into a package to be filled. A clamp piece is secured to a piston rod which is connected to the piston and a slider is movable along said piston rod below the clamp piece. A drive mechanism connected to the slider moves it upwardly and downwardly along said piston rod through a path to cause the slider to contact the clamp piece and to raise it along with the piston rod and the piston to deliver material from the cylinder. The rod is movable downwardly when the slide is caused to move downwardly by the drive mechanism and this causes the piston to draw in an additional charge of filling material.