The invention provides an automatic spanner for use on sleeve nut of sealed piping. The invented spanner is of an open type, with the jaws at the opening designed of an open cylindrical gear. There is a set of driving gear to match with the jaw gear with the matching distance longer than the jaw opening. The spanner handle is a hollow casing, inside which there is a mechanism for resetting of the jaw position composed of a crank-connecting rod device. The spanner can be withdrawn radially from the sealed piping. For manufal operation, it is provided with a lockable driving or driven gear with a two-way pawl. There is also a series of jaws of various sizes for replacement. The invention provides a novel multi-purpose automatic tool. |