抄録
(1) Reaction forces at the bottom (or landside plate) of plow with vertical suction are considered as two supporting points in two dimensional problem.
(2) When a plow with suction is set at the same condition as a plow without suction in balancing state of external forces, reactions at bottom are not necessarily same, but in case of former moment of force originates.
(3) This moment is inclined to set down the front point of bottom, so the suction is useful in deep plowing.
(4) The value of the moment is determined with arm length l, and l is increasing function of suction angle at front point α, but decreasing function of suction angle at rear point β.
In order to be effective the suction, α must be rather larger and α must be rather smaller, and real plows are observed to be manufactured to satisfy this conditions.
