| 摘要 |
A mine roof support has a main roof engaging member 10 which is provided with an extensible roof engaging member 11. The extensible roof engaging member 11 is operable to apply a constant load to the mine roof, irrespective of its degree of extension from the main roof engaging member. This may be done by providing the extensible roof engaging member 11 with a free end 25 arranged to engage with the mine roof to apply a load thereto, the extensible roof engaging member also having a pivot point 22 and a force application point 23, at which force can be applied from the mine roof support to tilt the extensible roof engaging member, the distance of the free end 25 and the pivot point 22 from the force application point 23 being fixed. <IMAGE> |
