Excavation-roof support

A roof support for use in underground excavations of different roof heights, comprising a base having one side facing towards and another side facing away from a face of the excavation;

• a shield having a first end portion spaced from and another end portion adjacent said other side, and extending upwardly of said base;
• a roof support cap mounted on said first end portion of said shield;
• means for connecting said second end portion of said shield to said base, including at least one guide member and at least one support member each having a first portion remote from and a second portion at said base, a pivot shaft mounted on said first portions of said members and articulating the same to one another, and means for mounting said second portions of said members on said base for pivoting about spaced axes, and at least one of said second portions for selective displacement relative to said base to thereby change the position of said pivot shaft with respect to said base, said second end portion of said shield being supported on said pivot shaft so that said displacement of the latter results in commensurate displacement of the former, and for pivoting about said pivot shaft;
• means for pivoting said shield about said pivot shaft and including a pit prop extending between and engaging said base and said shield;
• and means for selectively infinitely displacing said pivot shaft with respect to said base in dependence on the instantaneous roof height so as to maintain said cap in engagement with the roof close to the face of the excavation for each instantaneous roof height.