A conveyor assembly includes a conveyor module including first and second roller bodies and a conveyor belt; a chassis; and a tensioning system. The tensioning system is operable to adjust the tension of the conveyor belt and includes a tensioning device selectively shiftably mounted to the chassis such that shifting of the tensioning system in the fore-aft direction along the chassis results in corresponding fore-aft shifting of the first roller body relative to the second roller body, thereby facilitating adjustment of the tension of the conveyor belt. The chassis includes a pair of side rails and a slider bed. A stiffening assembly includes a bracket spaced vertically below the slider bed such that a vertical gap is formed between the slider bed and the bracket. The stiffening assembly further includes an insert disposed on the bracket and extending upward across at least a portion of the gap.

An article transport vehicle includes a travel unit; an article holder; two lift mechanisms each including a roller chain and configured to raise and lower the article holder; and a guide mechanism configured to guide the article holder in a lifting direction. The guide mechanism includes a guide rail held by the travel unit and extending along an up-down direction; a plurality of rollers configured to roll in contact with the guide rail; a roller support supporting the plurality of rollers, and a joint mechanism joining the roller support to the article holder. The plurality of rollers are disposed in such a manner as to restrict movement of the roller support in a first direction and a second direction while allowing the roller support to move in the up-down direction relative to the guide rail.