Pin holder drive for music box movement - uses loose fit spring on drive shaft to form one way clutch between holder and driving gear

摘要

The music box movement comprises a pin holder (1) fixed (4) to a driving shaft (3, 5). As this rotates, the pins strike the reeds to produce the tune. A helical spring (6) is a loose sliding fit over the shaft. One end (7) is extended parallel to the shaft and is fixed to the inner bore of the gear (2) driving the movement. This spring forms a clutch. When the gear rotates in the correct direction, the spring tightens around the shaft and drives the pin holder. If the gear is operated in the reverse direction, the coils open and slip over the surface without driving.