Abstract: A roof support employs an hydraulic piston and cylinder unit as an adjustment device between the goaf shield and the roof-engaging structure. The cylinder unit is mounted to the shield with the aid of a bearing body defining a cup receiving a spherical end of the cylinder. The body also has recesses accessible via offset openings in which journals projecting from the cylinder are located. Locking pieces detachably fitted to the shield block the openings to retain the journals therein yet permit easy assembly and dismantling of the unit.

Abstract: A roof support unit for a walking frame roof support assembly is provided with a two part goaf shield. One the goaf shield parts is connected, by means of a link, to the roof cap of the unit; the other goaf shield part being connected, by means of a link, to the floor sill of the unit; and the two parts being hinged to one another. At least one of the links is such as to permit the roof cap to be retracted by an amount sufficient to permit the advance of the unit while preventing the hinged connection between the two goaf shield parts moving towards the goaf side of the mine working.