upper shield against the land of caving powered support, especially for use in underground, in the coal mines

摘要

A mine roof frame with a roof girder to which a goaf screen or fender is pivotably suspended. A bracket assembly composed of a series of parallel shaped webs welded between two plates is attached to the roof girder. The lowermost plate carries a guide piece having a bore therein slidably receiving a spigot inclined in relation to the vertical and horizontal. The spigot has a support shoe which engages the fender to retain the latter in a working position. A shear pin extends through the guide piece and the spigot and the pin is designed to fracture when the fender is subjected to excessive loading to cause the spigot to slide inwardly of the guide piece to thereby allow the fender to pivot inwards to a near vertical position.