Patents
A device for measuring convergence of the roof in a mine, quickly and accurately. A device for measuring convergence of the roof in a mine, quickly and accurately, which comprises in combination a plurality of vertically placed coaxial tubes (2,4,5) movably fixed by means (3,6), characterised in that a top tube (2) being provided with a sucker (1) attached at the top-end, the bottom-end of the said top tube (2) being co-axially connected by means (3) to the top-end of a middle tube (4) having measuring scale marked on its surface, the bottom-end of the said middle tube (4) being co-axially inserted into the top-end of a bottom tube (5) and held in position by means (6).