PURPOSE: To provide a novel stacking machine apparatus without requiring removing rollers in replacing a broken belt.

CONSTITUTION: In a stacker apparatus for forming an aligned stack of signatures from incoming streams of partially overlapping signatures in shingled form, the streams of the partially overlapping signatures in shingled form are received at an inlet end to pass a compression conveyor. The compression conveyor comprises two conveyor belts 18, 20 in mutually compressed opposition to each other which follow an upward arcuate path along a series of idler rollers. When the conveyor belt 18 is broken, an inner framework 44 is quickly released from an outer framework, a new belt is wound around the inner framework 44, and the inner framework 44 is re-mounted. A drive shaft pulley assembly 50 is rotatably mounted on the outer framework by a two-bolt flanged bearing provided with a quick release bearing.