Internal dismounting tool and method for packing box of piston rod of marine low-speed diesel engine

The invention discloses an internal dismounting tool and method for a packing box of a piston rod of a marine low-speed diesel engine. The internal dismounting tool comprises a pair of copper liner plates which are assembled together, a pair of half clamping hoops which are assembled together, and a pair of half trays which are assembled together. The copper liner plates are fixed to the inner circles of the half clamping hoops. The half clamping hoops and ribbed plates at the outer ends of radial rods are fixed to the lower side faces of the half trays. The pair of half clamping hoops is clamped and fixed to the piston rod through clamping bolt and nut sets at the two ends of a radial clamping plate. The internal dismounting method comprises the steps that (1) the clamping hoops are primarily clamped and fixed to the piston rod; (2) the clamping hoops are lifted to be close to the lower side faces of a connecting flange and the packing box; (3) the packing box, the connecting flange and connecting bolts of t