Patent ID: 7328774

Claim:
A lift drive comprising: a plastic spiral drive element having an axis of rotation; a single plastic rack having a base and a plurality of teeth extending from said base, wherein each tooth has a thrust surface sized and shaped to be engaged by said spiral drive element, said base having a reinforcing element, and said rack having a longitudinal axis parallel to said axis of rotation; a motor coupled to said spiral drive element for rotating said spiral drive element; a movable carriage having wheels, said motor being mounted onto said carriage, wherein said rack is comprised of a plurality of sections, each of said sections comprising a plastic molded body having a base and a plurality of teeth extending from said base, each tooth including a thrust surface sized and shaped to have sliding contact with a thread from a worm gear, said body further including a reinforcing element, and wherein said reinforcing element for said section is a metal reinforcing element and provides dimensional stability to said plastic molded body under load, and wherein said section is molded with a void and said reinforcing element is sized and shaped to fit into said void, and wherein upon said spiral drive element rotating, one of said spiral drive element and said rack moves relative to the other along said longitudinal axis in a lift direction or a lower direction.