| Abstract |
A mine roof support is provided comprisi~g a base roof engaging canopy, jack means acting between the base and canopy, and auxiliary jack means connected to the base for use in lifting or lowering at least part of the base when the support advances, for eXaml)l.e if it meets an obstruction, the connection, ,'between the base and .the auxiliary jack means including lost motion means. The lost motion means may increase the ability of the base a~d canopy to move towards one another, thus' assisting vertical compaction of the support for transportation or storage. The lost motion means may be used to prolong the contact between the auxiliary jack means and suppmrt advancing means over a greater-distance than would be available solely from the auxil~ryjack means. |