| 摘要 |
A mine roof support unit includes a pair of generally parallel floor girders, and an advance mechanism positioned between the floor girders. The advance mechanism comprises a hydraulic advance ram and a guide rod system. The advance ram is pivotally connected between the guide rod system and a cross member which interconnects the floor girders. The guide rod system is attachable to a longwall conveyor positioned adjacent to a work face. The cross member is engageable with the floor girders in such a manner that the floor girders are relatively displaceable in a vertical direction. Each of the floor girders is provided with a respective hydraulic lifting ram, the arrangement being such that the lifting rams can be operated to lift one of the floor girders relative to the other floor girder.
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