Excavating – Beneath a body of water – Suction
Reexamination Certificate
1999-04-29
2001-02-20
Pezzuto, Robert E. (Department: 3671)
Excavating
Beneath a body of water
Suction
C037S195000
Reexamination Certificate
active
06189243
ABSTRACT:
FIELD OF TECHNOLOGY
The present invention relates to a method of dredging and a dredging apparatus which can efficiently dredge large quantities of sand and gravels, deposited on the bottom of dams, rivers, harbours, etc.
BACKGROUND TECHNOLOGY
Recently, 80% or more of the capacities of some dams are filled with sand and gravels, thereby reducing dam operability and effectiveness.
To recover their function, an effective dredging method and an effective dredging apparatus are required.
Conventionally, sand and gravel deposites are removed by methods employing a dipper, a crab, a bucket, a pump or a siphon, which are selected according to the deposit condition of the sand and gravels.
TECHNICAL PROBLEMS
The conventional dredging methods have the following problems.
In the conventional methods not employing a siphon, a great power is required, so the dredging apparatus must be large and heavy. Further a large amount of turbid water, which is generated when the sand and gravels are dredged, remains untreated.
In the conventional methods employing a sand pump and the siphon, there is a problem of conveying a mingled fluid (a fluid including sand, gravels and a liquid). Namely, fluid resistance of the mingled fluid in a pipe is great, so energy consumption is also great. Thus, size of gravels conveyed is usually limited to about 5 mm, and it is therefore difficult to dredge gravels larger in size.
In the conventional method employing the siphon, a large amount of water (about 80% of capacity) is drained, so that the turbid water is also drained without treatment. In the case of employing the siphon, attention must be paid to the percentage of sand and gravels in water. If a suction pipe is set too close to the bottom of a boy of water, said percentage is rapidly increased, fluid speed is reduced, and the suction pipe is filled with the sand and gravels. On the other hand, if a suction pipe is set too far from the bottom of the water, the siphon sucks the water only, dredging efficiency is lowered lower, and a large amount of turbid water is generated. Therefore, in the case of employing the siphon, a distance between an inlet of the suction pipe and the bottom of the water should be fixed, but it has been a technical problem.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a dredging method and a dredging apparatus which can efficiently suck large quantities of sand and gravel deposited on the bottom of water, convey them while conserving as much energy as possible and can prevent diffusion of turbid water.
Namely, the method of dredging sand and gravels in a dredging apparatus includes: a case being laid down into water in communication with the atmosphere; a suction pipe having a suction portion at the lower end thereof, the suction pipe being connected to the case; and a drain pump for draining water in the case, and the method comprises the steps of: draining water in the case so as to form a space therein and to form a level difference between the water level in the case and the external water level; and sucking the sand and gravels from the suction pipe by the water current caused by the level difference.
In the method, sand and gravels can be properly dredged by: sucking them into the case via the suction pipe; and conveying the sand and gravels deposited in the case to the outside by a belt conveyor.
Further, in the method, sand and gravels can be properly dredged by sucking them into a container, which is removably disposed at an intermediate portion of the suction pipe.
The dredging apparatus of the present invention comprises: a case being laid down into the water in communication with the atmosphere; a suction pipe having a suction portion at the lower end thereof, the suction pipe being connected to the case; and a drain pump for draining water in the case and forming a level difference between the water level in the case and the external water level.
Preferably, the apparatus has a belt conveyor extending into the case so as to convey the sand and gravels deposited in the case.
Preferably, the case has a pocket portion at a lower part thereof, the suction pipe is connected to the pocket portion, and a guide plate, which is capable of guiding the sand and gravels sucked through the suction pipe sideward, is provided in the pocket portion.
Preferably, an upper end of the pipe is pivotably attached to a dredging boat, a first float communicating with the atmosphere is provided to the case, and the dredging apparatus further comprises a first pump for supplying water into and draining water from the first float so as to adjust buoyant forces of the first float.
Further preferably, a second float communicating with the atmosphere is provided to the suction pipe, and the dredging apparatus further comprises a second pump for supplying water into and draining water from the second float so as to adjust buoyant forces of the second float.
In the apparatus, a container, into which sand and gravels are introduced via the suction pipe, may be removably disposed at an intermediate portion of the suction pipe.
Preferably, in this case, a third float communicating with the atmosphere is provided to the container, and the dredging apparatus further comprises a third pump for supplying water into and draining water from the third float so as to adjust buoyant forces of the third float.
In the apparatus, a dome-shaped cover may be provided to the lower end of the suction pipe so as to cover over the suction portion thereof.
The apparatus may further comprise a contact plate having a suction hole and being provided to the suction pipe so as to cover over a lower part of the suction portion.
In this case, the contact plate preferably has a pile-shaped projection capable of piercing the bottom of the water.
Further, in this case, a vibrator for vibrating the contact plate is preferably provided.
In the dredging apparatus, the contact plate may be rotated, about an axis of the suction pipe, by a motor.
Further, the dredging apparatus may further comprise a precipitation tank in which turbid water drained from the case by the drain pump is reservoired.
In this case, the dredging apparatus may further comprise a circulation pump for spouting the water reservoired in the precipitation tank into the dome-shaped cover.
REFERENCES:
patent: 3815267 (1974-06-01), Laarman
patent: 4030216 (1977-06-01), Willums
patent: 4253255 (1981-03-01), Durell
patent: 4307525 (1981-12-01), Maloblocki
patent: 4353174 (1982-10-01), Maloblocki
patent: 4391468 (1983-07-01), Funk
patent: 62-284831 (1987-12-01), None
patent: 1207535 (1989-08-01), None
patent: 3151421 (1991-06-01), None
Moburon Design Office Co., Ltd.
Pezzuto Robert E.
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