PURPOSE: To make the ice-breaking ability of a ship improvable ever so high while bringing the output down to some extent, by forming a screw drum diameter into a taper by degrees as going toward the end part.
CONSTITUTION: Screws 1 are situated higher than a water lever 8 each in their front parts, while both screws 1 are disposed each in parallel wth a hull center line 7 but slant to the water level 8 and supported by each of bearings 10 and 11. The screws are driven independently at both gunwales by each of prime movers 12, cut into an ince floe 13 as self-propelling on the ice field, ride on the ice floe 13 and performs ice-breaking running on the ice floe 13. Ice breaking takes place with a cylindrical intermediate part 4 but its diameter is constant throughout the length unlike taper forms in both front and rear parts 5 and 6 so that stability in the hull at ice breaking is excellent, thus ice-breaking operation in constant trimness is now possible to be achieved.
MIKAWA KATSUHIKO
SATOU SHIGEMI
MATSUO TADASHI
