Abstract: A filter includes a lower filter plate mounted to a frame, an upper filter plate movably mounted above the lower filter plate and filter paper between the two plates. A number of shafts are mounted to the frame below the lower filter plate and extend past opposite sides of the filter. Elongate crank arms and eccentrically positioned tie rod connection pins are secured to the ends of the shafts. The upper ends of the tie rods are mounted to opposite sides of the upper filter plate. The tie rods' lower ends are pivotally mounted to the tie rod connections for eccentric movement about the axes of the shafts. A pneumatic ram is used to rotate one of the shafts through an actuator arm keyed to the shaft. The outer ends of the crank arms on each side are coupled together by connecting bars so the crank arms move in unison. A locking arm is mounted to one of the shafts and is positioned to engage locking recesses in upper and lower locking dogs when the upper filter plate is fully opened and fully closed.