Roof support shield structure for use in an excavation

A shield support structure for use in a mine having a floor, a working face with a rear portion and a roof portion including a part with broken down rock, comprising a sill beam adapted to be supported on the floor, a supporting shield disposed against the working face having one end pivoted to said sill beam and an opposite end, a roof cap comprising a lever having a roof engagement portion pivoted at a first point adjacent its one end to said opposite end of said support shield and having an arm portion extending outwardly from said pivot in a direction toward said sill beam, a first hydraulic piston and cylinder system pivotally connected between said shield at a location intermediate its length and said one arm of said roof cap, a second hydraulic piston and cylinder system pivotally connected to and bearing against said sill beam and to said roof cap for bracing said roof cap against the roof and the broken down rock, said said second piston and cylinder system bearing against said sill comprising a power prop which in a position perpendicular to said working face or inclined toward said working face is pivotally applied against said roof cap at a second point intermediate to the first point and free end of said roof cap.