This invention is directed to an apparatus for continuous hydraulic dredging. Customarily, a hydraulic dredge is swung from side-to-side in an arc during dredging operations and after digging through an arc, or through several arcs if the depth of the digging is greater than that removed by the cut of a single arc, the hydraulic dredge is moved forward using a digging spud and a walking spud which are located on opposite sides of the dredge stern. The movement from side-to-side during digging has been controlled by swing cables attached to swing anchors with the cables wound and unwound on winch drums. If the dredging is done in open water, the swing anchors are carried by boats to their positions and dropped into the water. If the dredging in done in a narrow channel, the swing anchors are located on land on opposite sides of the channel area being dredged.
In open water, the present method of moving the swing anchors requires the use of one or more anchor barges. When the dredge has completed digging in its arc, the anchor barge lifts one anchor and moves it forward the required distance which can possibly be 60, 70 or 80 feet. It then drops the anchor to the bottom of the cut. While this movement of the anchor is going on, the dredge has lowered its cutting ladder to the cut bottom so that it will hold itself in position while the setting of the anchor is tested. If the anchor which has been moved sets properly, then the anchor on the other side of the dredge must be moved to keep both anchors abreast of the dredge. If shore or land anchors are used, these must also be moved in the same manner. Under best dredging conditions, about 12% of available dredge time is spent in moving anchors. Under poor conditions, as much as 25% of the available dredge time can be spent relocating the anchors.
Another obstacle to continuous dredging is the necessity to move the dredge forward along its cutting path. With present types of dredges which use a walking spud and a digging spud, considerable time is wasted in lowering and lifting the walking and digging spuds when it is necessary to move the dredge to a new digging position.
Thus, an object of this invention is an apparatus for more efficiently conducting shallow dredging where the cutter head is moved through only a single cutting arc to reach its maximum digging depth.
Another object of this invention is an apparatus for advancing a hydraulic dredge without wasting any digging movements of the cutter head.
Another object of this invention is a dredging apparatus that does not require swing anchors.
Another object of this invention is a dredging apparatus that can dig efficiently in confined quarters.
Additional objects may be found in the following specification, claims and drawings.