Striking mechanism unit for a repeater striking mechanism, including a drive plate with a pipe pivoting about an axis and carrying a hook provided with a beak, a detent ratchet pivoting about the axis carrying a pin which is in abutment, through a hole in the plate, on the hook against a spring for the operation thereof when the detent ratchet is pivoting, and depending on the position thereof, the beak allows or prevents the pivoting of a pipe ratchet of a downstream stage which pivots integrally with a first hour ratchet. The downstream stage includes a second hour ratchet which pivots about the axis and whose toothing is inclined in the same direction as that of the first hour ratchet.