Patent ID: 7896133

Claim:
A scaffolding assembly comprising: a vertical mast tower, the mast tower having a plurality of openings vertically spaced along the length of the mast tower, each of the mast tower openings is defined by a horizontal bottom edge and an arcuate upper edge connected to the horizontal bottom edge; a generally horizontal platform shiftably suspended from the mast tower for vertical movement along the mast tower; and lift means with support members connected to a generally horizontal sub-frame element on the generally horizontal platform carried by the platform for moving the platform along the mast tower, the lift means includes a pinion wheel in direct mating engagement with the mast tower where rotation of the pinion wheel, a motor for rotating a drive gear meshed to a pinion gear on the pinion wheel to move the platform vertically along the mast tower, the pinion wheel having a first radius and the pinion wheel having a plurality of radially spaced circular cogs placed on the first radius of the pinion wheel, each circular cog configured to extend into one of the mast tower openings and having an outer edge which bears against the bottom edge of one of the mast tower openings when one of the circular cogs is inserted into the one of the mast tower openings, and wherein the pinion wheel has a first center axis and the first radius and wherein the cogs have a second radius and a second center axis distant from the first center axis, and wherein the distance between the second center axis and the first center axis is greater than the first radius, wherein the pinion wheel includes a pair of shoes mounted to both side of each of the circular cogs, the shoes also having a contact edge which bears against the bottom edge of one of the mast tower openings when one of the circular cogs is inserted into the one of the mast tower openings, and wherein the contact edge of the shoes abuts and extends around the outer edge of the circular cogs, and wherein the cogs are configured such that two adjacent cogs contact the mast tower along its contact edge 85 percent of the time as the pinion wheel rotates.