the invention is particularly useful for accumulation conveyors . an assembly located beneath its corresponding zone of item transporting rollers activates the item transporting rollers by lifting the accumulator &# 39 ; s narrow belt to engage the underneath side of the item transporting rollers . electric actuation rather than the traditional pneumatic actuation activates the assembly &# 39 ; s vertical movement toward its corresponding zone of item transporting rollers . whether activated or not , the assembly &# 39 ; s rack journals a plurality of pressure rollers that remain contiguous with the narrow belt . centering of the sideways movement of the narrow belt as the belt travels about the rack is associated with either a pivoting tracking roller journaled in the rack or a flanged pressure roller or rollers channel in the rack . a constant force takeup can be supplied to the belt .