having protective means, e.g. shields, for preventing or impeding entry of loose material into the working space or support

Full Title

Mine roof supports for step- by- step movement, e.g. in combination with provisions for shifting of conveyors, mining machines, or guides therefor ( shifting of mine conveyors at the working face E21F13/08) > having protective means, e.g. shields, for preventing or impeding entry of loose material into the working space or support