Crusher

A heavy industrial crusher at Ashio Copper Mine sits on one of the upper levels of the processing plant, the steel frame anchored to a deep concrete pad, the working jaws of the crusher visible at the top opening. The frame is a riveted-steel cage around the working mechanism, with the drive motor and flywheel mounted on a separate platform alongside. The jaws are the standard alternating crushing surfaces of an industrial jaw crusher, the steel hard-faced and worn at the centre. A receiving chute drops ore into the open jaws from above. Below the crusher, a discharge chute carries the crushed product on to the conveyor that fed the milling area downstream.

The crusher is the first major processing stage in a mineral plant. Ore arrives from the mine in chunks too big for the mills and goes through the crusher to reduce it to a size the milling circuit can handle. At Ashio the crusher ran continuously through the working shifts under the Furukawa modernisation that began in 1877. The Excavation Department closed in 1973. The crusher stopped at the same time and has not run since. The wear-faces on the jaws are the last set of liners that were fitted before closure; the receiving chute holds the last batch of ore that did not make it into the jaws.