Helical dredge cutter head with scoop-in plates

A dreging helical cutter suited for use, for example, with a dredger is equipped according to the present invention with scoop-in plates. Earth and sand is transported by helical vanes to a send-out end portion of the helical cutter. The scoop-in plates transport the earth and sand to an opening of an earth/sand suction tube. The opening of the suction tube is provided in a portion of the helical cutter for receiving a rotary shaft. All of the earth and sand excavated by the helical cutter can therefore be sucked into the suction tube and the efficiency of the dredging operation can be greatly increased by a simple structure.

BACKGROUND OF THE INVENTION 
This invention relates to a dredging helical cutter and a method for more 
efficiently dredging an underwater area. In the past, dredgers have had 
the general configuration shown in FIGS. 4 and 5, wherein on one end 
section of a hull 8, the base end portion of a rudder 9, which is swung 
vertically depending upon the depth of the bottom of the water, is 
attached to a transverse shaft 10. A suspension rope 11, suspended from a 
winch provided on the hull 8, is coupled to the point portion of the 
rudder 9 through a pulley provided on the point of a boom 12 fixed on the 
hull 8. The point portion of the rudder 9 is equipped with a cutter 13 
which is rotated by a driving device. In the other end section of the hull 
8, a first spud 14 and second spud 15 are provided. The first and second 
spuds 14 and 15, are elevatably movable and mutually spaced in the 
widthwise direction of the ship. 
When the ground at the bottom of the water is to be excavated using this 
dredger, the first spud 14 is fixed to the ground 16. The first step of 
excavation is performed using the cutter 13, which is spaced R meters from 
the first spud 14, while turning the hull 8 and rudder 9 laterally in 
either direction. For example, after the rudder 9 is rotated downward a 
given angle (i.e., the angle corresponding to the distance through which 
the cutter 13 moves down, which is about one-half of the diameter of the 
cutter), the hull 8 and rudder 9 are moved laterally clockwise about the 
first spud 14. The second step of the excavation is performed while 
turning the hull 8 and rudder 9 counterclockwise. After the rudder 9 is 
rotated downward a given angle, the third step of the excavation is 
performed while again turning the hull 8 and rudder 9 clockwise. 
After the repetitive turning excavation described above has reached a given 
depth, the cutter 13 is kept at the final right turn position, the rudder 
9 is rotated upward, the second spud 15 is put through the ground 16, the 
first spud 14 is pulled out, the hull 8 and rudder 9 are turned 
counterclockwise about the second spud 15 up to the final left turn 
position, the first spud 14 is put through the ground 16 at position 14A, 
the second spud 16 is pulled out (through the foregoing series of 
operations, the hull 8 has moved and advanced in the forward direction of 
excavation), and a second repetitive turning excavation similar to the 
first one is performed. Then, a series of operations similar to that 
described above is repeated, and successively, the repetitive turning 
excavations are performed. 
Conventional cutters used in the foregoing dredger are of the helical type, 
as shown in FIG. 6. Helical vanes 3 are fixed on a rotary body 2, which is 
fitted and secured to a driving shaft 1. A number of excavating picks 4 
are attached to the periphery of each helical vane 3, and an inlet port 6 
of an earth/sand suction tube 5 supported by a bearing 22 fitted on the 
driving shaft 1, is disposed opposite to the lower portion of the send-out 
end portion (i.e., the end portion of the vanes of the helical cutter 
toward which sand and dirt to be excavated is moved) of the helical vanes 
3. 
When the foregoing conventional helical cutter is used to dredge, earth and 
sand and the like, excavated by the picks 4, are conveyed by the helical 
vanes 3 toward the inlet port 6 while being guided along an excavated 
plane 18. However, a greater part of earth and sand flows out along a 
previously excavated, formed, inclined plane 19 after reaching the 
inlet-port side end portion, i.e., the terminated portion, of the 
excavated plane 18, thereby causing inefficiency in the suction of earth 
and sand by the earth/sand suction tube 5. 
SUMMARY OF THE INVENTION 
This invention was developed in view of the foregoing background and to 
overcome the foregoing drawbacks. 
It is accordingly an object of the present invention to provide a helical 
cutter with scoop-in plates to ease suction of earth and sand into a 
suction tube, thereby enhancing the efficiency of suction of earth and 
sand into the suction tube. 
It is a further object of the invention to provide a method for dredging 
which includes a step of transporting earth and sand from a send-out end 
portion of a helical cutter to a suction tube. 
To achieve the foregoing object, the present invention provides a helical 
cutter of the type wherein helical vanes are fixed on a rotary body which 
is secured to a driving shaft. A number of excavating picks are attached 
to the periphery of each helical vane, and an inlet portion of an 
earth/sand suction tube is disposed opposite to a send-out end portion of 
the helical vanes. Scoop-in plates are attached in the vicinity of the 
periphery of the send-out end portion of the helical vanes. 
According to the helical cutter of the present invention, the scoop-in 
plates attached to the send-out end portion of the helical vanes function 
so that earth and sand are excavated and conveyed toward the inlet port of 
the suction tube and guided along an excavated plane by means of the 
helical vanes and, when the earth and sand reach a location close to the 
end portion of the excavated plane, the earth and sand are scooped in by 
means of the scoop-in plates and led toward the inlet port. Thus, little 
of the earth and sand excavated flows out from the terminated portion of 
the excavated plane. Instead, the earth and sand are led toward the inlet 
port with the water. As a result, the efficiency of suction of earth and 
sand achieved by the earth/sand suction tube is enhanced. This invention, 
therefore, provides a simple and economical method and means to increase 
the efficiency of suction during a dredging operation.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIGS. 1 through 3 show a helical cutter with scoop-in plates of the dredger 
according to an embodiment of the present invention. A rotary body 2 is 
secured to the point portion of a driving shaft 1 which is rotated by a 
driving device. A number of pick boxes 20 are fixed, preferably by 
welding, on the outer periphery of each helical vane 3 provided on the 
rotary body 2. Excavating picks 4 are fixed in these pick boxes 20. The 
helix direction of the helical vanes is set in a right-handed mode when 
the driving shaft 1 is rotated to the right. The vanes are set in a 
left-handed mode when the driving shaft 1 is rotated to the left. Thus, 
the helical vanes 3 illustrated are in the right-handed mode because the 
driving shaft 1 illustrated is rotating to the right. 
The driving shaft rotates the helical vanes 3. The excavating picks 4 free 
the sand and gravel and the vanes convey the sand and gravel toward the 
send-out end portion of the helical vanes 3. The send-out end portion of 
the helical vanes 3 is the end of the helical vanes 3 toward which sand 
and gravel is conveyed. 
The driving shaft 1 is fitted rotatably in a bearing 22 equipped with a 
disc 21 disposed concentrically with the driving shaft 1. A suspension 
rope coupling member 23 is formed integrally with the upper portion of the 
bearing 22. The upper end portion of each helical vane 3 is fixed, 
preferably by welding, to a circular ring 24 which surrounds the disc 21. 
In one embodiment of the invention, the circular ring 24 is provided 
within a plane which is perpendicular to the driving shaft 1. The disc 
extends perpendicularly to the lengthwise direction of the driving shaft 
1. A space is provided between disc 21 and circular ring 24. An inlet port 
6 of an earth/sand suction tube 5, supported by the lower portion of the 
disc 21 is disposed opposite to the lower portion of the send-out end 
portion of the helical vanes 3. A plurality of arc-like scoop-in plates 7 
concentric with the axis of shaft 1 are coupled between the vicinity of 
the periphery of the end portion of each helical vane 3 and the ring 24. 
The scoop-in plates 7 are fixed through welding to the helical vanes 3 and 
ring 24, and the width L of a wider end portion of each scoop-in plate 7 
is set to be larger than the gap 1 between the ring 24 and an inclined 
plane 19 formed through excavation. 
When the ground 16 of the bottom of water is to be excavated using the 
helical cutter 25 with scoop-in plates configured as above, the helical 
cutter 25 with scoop-in plates is, as shown in FIG. 3, rotated clockwise 
and moved toward the left while turning. As a result, earth and sand 26 
excavated by the excavating picks 4 are conveyed toward the inlet port 6 
while being gathered to the left by the helical vanes 3 and guided along 
an excavated plane 18. Upon reaching the vicinity of the end portion of 
the excavated plane 18, the earth and sand are scooped in by means of the 
scoop-in plates 7. Thus, little of the earth and sand 26 flows out from 
the terminated portion of the excavated plane 18, and most of the earth 
and sand is sucked into the earth/sand suction tube 5 through the inlet 
port 6 with the water. 
The disc 21 does not rotate with the helical vanes 3. Therefore, the 
suction tube 5 and coupling member 23 also do not rotate with the helical 
vanes 3. 
While the present invention has been described in its preferred 
embodiments, it is to be be understood that the invention is not limited 
thereto, and may be otherwise embodied within the scope of the following 
claims.