Modification of Coupling System of Extrac tor of Φ177 mm PQF Pipe Mill

Analyzed in the paper are the three shortcomings of the extractor link rod coupling system of the Φ177mm PQF pipemill as originated from the design thereof.Accordingly，countermeasures as follows are proposed. Taking out the existing drum gear structure；getting the connecting axel and inner gear bush integrated into one structure，and getting the external gear axel and the gear coupling integrated into a one-piece type external gear bush；replacing the connecting bolt within the coupling with a through-hole bolt which links the above said two entirety structures.As a result，the strength of the coupling as a whole is increased，and so is the service span of it.