管内濃度を自動調節しうる吸込装置を用いた厚層砂層の採取に関する模型実験

海底砂鉱採取機に関する基礎的研究 (第4報)

抄録

This paper propounds a new suction dredge. The points knowing this suction dredge from regular suction dredges are in a special suction-head attached to the forward end of a suction pipe joined to a sand pump, in a venturi-type detector of concentration in the suction pipe, and in the mechanism of automatic control for concentration.
The structure of the special suction-head may be mentioned as follows. A body finding a shape in which circumferences of two circular cones (or convex surfaces) stick together mutually is fixed in the inside of a conical suction pipe, with keepingth e suitable space between the body and the conical suction pipe, and a mouth is at the center of the convex bottom surface of the body.
In the suction-head, the convex bottom comes in contact with sand bed. When pressurized water is poured through the mouth into the sand bed, the sand bed of some thickness under the suction-head causes phenomenon of quick sand, and the suction-head may suck up sand of quick sand state. As a result, the suction-head goes down due to its own weight, and may suck up sand falling down about circumference of the suctionhead.
When flow of the pressurized water stops in the suction, the suction-head also stops going down into the sand bed, and sucking up sand.
The automatic control for concentration in pipe in pumping up sand-water mixture from the sand bed is done by on-off operation of the flow of the pressurized water, and upward and downward movements of the suction-head in a vertical line, which are controlled by signal of concentration in pipe being out-put of concentration meter.
This paper discusses theory of operation, static characteristics, and dynamic characteristics of the dredging of loose and thick sand bed by means of the suction dredge.
The tests of the laboratory model of the suction dredge built as a trial showed that automatic control for concentration in pipe is done successfully.