| 摘要 |
The invention is for a mine roof support comprising a roof engaging structure or canopy mounted on hydraulic prop means and having an extension bar which can be advanced and set to the roof, following the passage of a mineral mining machine along the mineral face, so as to provide immediate roof support over the face conveyor and/or adjacent the coal face. A hydraulic ram for advancing the extension bar is connected to said bar by a lever device having a part which engages an abutment on the roof engaging member or canopy, at a predetermined amount of extension of the extension bar, so as automatically to cause the extension bar to tilt or move upwardly and be set against the roof by said advancing ram.
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