An endless conveyor includes plural load bearing plates mounted for continual horizontal movement by two endless chains which run in spaced and parallel vertical planes. Each plate has at diagonally opposite corners thereof a pivotally connected main support which is driven by one of the chains. Each plate also has pivotally connected thereto, at only one of the other corners thereof, an auxiliary support which is not driven by a chain but which is laterally aligned with and rotationally connected with a laterally opposite main support. The remaining corner of each plate is unsupported. All of the three supports have rollers which are guided in endless guide rails, such that the plates maintain a constant horizontal alignment.