Abstract: Crusher has a housing with a cylindrical crushing chamber defined by a tubular wall. Opposed side plates are secured to respective ends of the wall. A drive shaft rotates impact tools within the chamber. An intake aperture and a discharge aperture are in communication with the chamber. An inlet door, having an inner face with a curvature of similar radius to the cylindrical chamber, may be pivoted over the intake aperture such that the inner face is flush with the inner surface of the chamber, whereby impact tools strike and remove material adhering to the inner face. An arcuately shaped screen, having a curvature of similar radius to the cylindrical chamber, may be pivoted over the discharge aperture such that the screen is flush with the inner surface of the chamber. The screen may be pivoted away from the discharge aperture for the service thereof.

Abstract: A laser transmitter is suspended from spads set in the ceiling of the mining tunnel to establish a visible light beam aligned with the desired directional heading of the tunnel. In a first embodiment, the laser transmitter is attached to a bar suspended by means of cables from the spads. In a second embodiment, the laser transmitter assembly is suspended by means of adjustable ball chains, and includes a slide plate for moving the housing in directions transverse to the light beam. The method and apparatus is usable with existing tunnel operations having spads already in place.