Abstract: A slitter machine of the type where tab lock cases of varying height, width, and length are advanced therethrough in a product flow direction on a machine bed by a main drive motor, is presented. The slitter machine includes a frame, a centerline, a leading flap lifter and a trailing flap lifter. The leading flap lifter and trailing flap lifter are mounted are mounted to the frame on opposite sides of the centerline, and extend at an incline relative to the machine bed. Each flap lifter includes a tear drop assembly attached to a drive chain and actuated by a pair of cams to rotate the leading flap and the trailing flap toward a closed position. A chain track is disposed in each of the flap lifting assemblies, with the drive chains disposed therein. Each chain track has a first section having a first distance between the drive chains and a second section having a second distance between the drive chains. The second distance is greater than the first distance.