a lifting and stabilizing mechanism for an apparatus such as a bag elevator assembly for an automated filling machine having a stationary frame and a generally horizontal carriage mounted for vertical movement relative to the frame . the carriage is carried on a plurality of geared belts which each criss - cross the frame in an opposing &# 34 ; z &# 34 ; configuration , and are alternately wrapped over and under opposed drive wheels and tensioning wheels rotatably mounted on the carriage . the opposing belts maintain the carriage in its horizontal orientation , and the drive wheels are rotated to provide the lift force for controllably raising and lowering the carriage . the drive belts are attached to and extend along vertical brace members of the frame using one of various clamping assemblies , and the vertical alignment of the carriage is augmented by a pin and channel guide assembly . exact vertical linear registration or displacement of the carriage is accomplished by monitoring the revolutions of the drive wheels , drive axle , or drive motor , and comparing those revolutions to a predetermined chart or formula relating revolutions to linear displacement .