GB2223778A - Screening particulate material in a dredging operation - Google Patents

Abstract

Particulate material from a dredging operation is screened by apparatus comprising a pivotable upper screen grid, a lower screen grid (42) below the upper grid, and a rotary scraper (45) adapted to move over the upper surface of the lower grid (42). The apparatus receives material dredged from e.g. the seabed, by a backhoe, and larger pieces of unwanted material are retained on the upper grid after earth and sand with smaller pieces of unwanted material have fallen through parallel bars of the upper grid on to the lower grid. The upper grid is pivoted to dump the larger pieces. The lower grid comprises an upper set of parallel rods (43a, 43b) across which the scraper (45) moves, and a lower set of parallel wires (44a) transverse to the upper set. The wires are resiliently supported (44a). A method of dredging is disclosed wherein particulate material scooped up from a sea-bed or sea-shore is transferred to a hopper (3) via the aforesaid screening apparatus, mixed in the hopper to form a slurry and pumped to a place of reclamation via associated onboard, marine and land tubes. <IMAGE>

Description

A method of dredging using pumping transportation and apparatus The present invention relates to method and apparatus for dredging and transporting earth and sand from a dredge vehicle such as a boat equipped with a backhoe to 2 place of reclamation.

In convent i ona I dreds i ns operat i ons us i ns a d redse bott equipped with a backhoe, the backhoe scoops earth and sand from a seabed or from a steep face of a seashore, and then a transportation boat is loaded with the earth and sand to transPort the same near a Place of reclamation. The earth and sand which is unloaded from the transportation boat, is conveyed to the place of reclamation by dump trucks, conveyers and other transporting means.

In such dredging operation using a dredge boat equipped with a backhoe, the scraper is driven forward to scoop earth and sand for instance from a seabed. The backhoe has its bucket with the mouth opening towards the machine, and in use the machine puts its bucket away from the machine, and then pulls its bucket towards the machine to scoop and load earth and sand.

Such conventional dredging operation requires transportation boats, dump cars, heavy machines for loadins and unloading earth and sand from transPorting means. This and labor wases raise the dredging and reclaimins cost. The earth and sand is liable to fall down from the bucket under around the bow of the dredge boat1 and the earth and sand lie in heaPs there. This reduces the efficiency with which the dredging oPeratiOn is carried out.

One object of the present invention is to provide a dredging method eliminating the necessity of transportation boats, dum; cars and other transportation means and requirins no Icadia and unloadins labor.

Another object of the Present invention is to Provide a dredsins method preventing the formation of heaPs of earth and sand under the bow of the dredge boat, and accordingly imorovins the dredging efficiency. To attain these objects a dredging method according to the present invention uses a dredge boat equipped with a backhoe, and it comprises the steps of: scooping earth and sand from the bottom of a sea, river or the steep face of a shore; throw earth and sandintoan inboard hopper which is equipped with obstacle eliminating means and a cutter; mixing obstacle-free earth and sand by the cutter in the hopper; and driving the resultant slurry into an associated suction tuce by a slurrv pump and transporting the same to a Place of reclamation via associated inboard, marine and land tubes, which are desisned to be connected together.A bucket is fixed to an operation ar with its open mouth ahead of the backhoe in the form of "faceshovel", and the bucket is pushed forward to scooP, and pulled back to brins earth and sand into the dredse boat, thereby preventins the formation of heaps of earth and sand under the cow of the boat,aswould be otherwise caused as a result of falling of earth and sand from the steep face of the seashore and from tre backet if it were fixed to an operating arm with its open mouth towards the backhoe.

An apparatus for removing Pieces of obstacle from earth and sand, is used in adredsins operation accordins to the present invention. It essentially comprises a rotatable primary selection grid and a secondary selection srid. These primary and secondary selection srids are arransed at upper and lower levels above the hopper located within the dredge boat. The secondary selection grid comprises an overlying screen which is composed of a plurality of parallel bars, and an underlying screen which Is comPosed of a plurality of wires resiliently stretched DerPen- e r p e n - dicu lar to the overlying parallel bars.A rotary scraper is adapted to move on the upper surface of the rod screen to remove pieces of obstacle, such as Pieces of wood or rock th :his arransement pieces of obstacle whose size is larser than the mesh of the selection grids, are removed from earth and sand before being thrown in the hopper. In operation earth and sand is thrown on the PrimarY selection slid, allowins Pieces of obstacle of smal- ler size than the mesh or parallel space of the rod grid to fall on the underlying secondary selection grid, leaving larser Pieces of obstacle on the primary selection grid. Then1 the primary selection srid is turned to throw away the remainins Pieces of obstacle.On the other hand the pieces of obstacle remaining on the secondarY net are taken off by the rotarY scraper. Fcr instance, elonsated Pieces of wood will be pushed down by the rotating scraper blades while the resiliently stretched wires yieldingly withdraw. Then, the elonsated pieces of obstacle will rise from the meshes and will be Put in horizontal position in which the Pieces of obstacle are easily caught and removed by the rotatins scraper blades. Thus, whether or not pieces of obstacle are causht in the meshes of the secondary net, all remaining pieces of obstacle will be removed from the secondary selection grid. Finally, obstacle-free earth and sand is thrown in the hoPPer .

Other objects and advantases of the present invention will be better understood from the followins descriPtion of a Preferred embodiment of the Present invention, which is shown in the accom panting drawinss: Fis.l is a plan view of a dredge boat equipped wi th a bockhoe; Fix.2 is a side view of the dredge boat; Fis.3 shows one mode of dredging oPeration with the backhoe:: Fig .4 shows another mode of dredging operation; Fig .5 is a sectional view of the dredse boat taken alons the line V-V in Fis.l; Fig.6 is an enlarged perspective view of the secondary selec tion srid of an obstacle eliminating device; and Fis.7 shows how the secondarY selection srid works tosetner with an associated scraper in removing pieces of obstacle.

As best shown in Fig. 1 and 2, a dredse boat 1 has a backhoe type hydraulic power shovel 2 at its bow. It should be noted that the backhoe 2 can have its bucket 21 a with the mouth open towards the machine as shown in Fig.3, or can have its bucket 21b with the mouth open ahead of the mach i ne in the form cf "faceshovel" as shown in Fis.4. The backhoe can selelctively take either form, depending on the desree of hardness of the ground of bav or river floor and other dredging conditions.

Specifically, the backhoe in the form of "faceshovel" can be advantageously used in scraping soft ground, for instance a deposit of sand, mud, etc. Then, the backet 21b is pushed forward to scoop earth and sand from the deposit. Then1 less amount of earth and sand falls from the backet and from the steep face of deposit to lie in heaps around under the bow of the boat1 compared with the backhoe dredging mode, in which a relatively larse amount of earth and sand is liable to fall from the bucket 21a when pulled and drassed on the seabed towards the machine and fall from the steep fece of deposit to lie in heaPs around under the bow of the boat, thus reducins the dredging efficiency.

A hoPPer 3 has an openable bottom. It is located behind the backhoe 2. When the hoPPer 3 is opened1 its bottom opens to the sea. The hoPPer 3 has an obstacle eliminating arrangement 4, which is shown in Figs. 5 to 7.

The obstacle eliminating arransement 4 comprises a rotatable primary selection grid 41 and secondary selection grid 42 a r ranged at upper and lower levels. above the hoPPer 3. The primary selection srid 41 is rotatably attached to the frame at its one end, and a hYdraulic motor or the like is used to raise the c.ner end of the primary selection srid 41 to turn about its other end pivot.The secondary selection grid 42 comprises an overlying screen 43 which is composed of a plurality of Parallel bars 43a, and an underlyins screen 44 which is composed of a plurality of wires 44b resiliently stretched (by sprinss 44a) perpendicular to the overlying parallel bars 43a, and a rotary scraper 45 which is adaPted to move on the upper surface of the rod screen 43 in the longitudinal direction of rods to remove pieces of obstacle.

The rotary scraper 45 has a plurality of radiant blades 45b on its shaft 45a, the shaft 45a is engaged with a chain drive (not shown).

A suction tube 5 has a cutter 6 at its front end, and the front end of the suction tube 5 is put in the hopper 3 The rotation of the cutter 6 in the hopper 3 will change the earth and sand to slurry. A slurry pump 7 is connected to tne rear end of the suction tube 5, and the slurry pump 7 is connected at Its outPut to marine and land tubes (not shown) via and associated inboard tube.

In operation first, the bucket of the backhoe throws earth and sand on the primary and secondary selection srids 41 and 42.

Pieces of obstacle whose size is larser than the mesh of the sel e lotion grids 41 and 42, are removed from earth and sand before falling in the hoPPer 3. Specifically, earth and sand is thrown on the Per many selection grid 41, allowing pieces of obstacle of smaller size than the mesh or parallel space of the rod srid to fall on the underlying secondarY selection srid 4, leaving larder pieces of obstacle on the primary selection grid 41. Then, the primary selection grid 41 is raised and tilted by the hydraulic motor to throw away the remaining feces of obstacle. Some pieces of obstacle 13 may be caught In Selected meshes of the secondary selection srid.These Pieces of obstacle still remainins on the secondary selection grid can be taken off by the rotarY scraper 45. For instance, elongated Pieces of wood 13 will be pushed down bv the rotating scraper blades 45b,while the resiliently stretched wires 44b yield ingly withdraw, as seen from Fig.7. Then, the elongated pieces of obstacle 13 will rise from the meshs under resilient counterforce, and will be put in horizontal position in which the pieces of obstacle 13 are easily caught and removed by the rotating scraper blades 45b. Thus, whether or not pieces of obstacle are causht in the meshes of the secondarY selection net, all remainins Pieces of obstacle will be removed. Finally, obstacle-free earth and sand is thrown in the hopper 3, where the earth and sand is mixed with a liquid bv the cutter 6. The resultant slurry will be PumPed to a Place of reclamation via associated inboard, marine and land tubes smoothly without such a trouble that the pump and/or tubes are blocked with pieces of obstacle.

Claims (8)

CLAIMS:

1. An apparatus for removing unwanted obstacles from particulate material such as earth and sand in a dredging operation, comprising a pivotable primary selection grid and a secondary selection grid comprising a plurality of parallel bars overlying a plurality of wiresvresiliently stretched perpendicular to the overlying parallel bars, and a rotary scraper adapted to move over the upper surface of the grid to remove obstacles.

2. An apparatus as claimed in Claim 1,wherein the primary selection grid is located above and has a larger mesh size than the secondary selection grid.

3. A method of dredging using a dredge vehicle equipped with a backhoe, comprising scooping particulate material such as earth and sand;transferring the scooped material to a hopper which is equipped with obstacle eliminating means and a cutter; mixing obstacle-free earth and sand with the cutter in the hopper; driving the resultant slurry into a suction tube with a pump and transporting the same to a place of reclamation.

4. A method as claimed in Claim 3, wherein the slurry is transported from the hopper to a place of reclamation via associated onboard, marine and land tubes.

5. A method as claimed in Claim 3 or 4,wherein the backhoe comprises a bucket fixed on the end of an operating arm with its mouth opening facing away from the dredge vehicle, and the scooping step comprises pushing the bucket forward, away from the boat,on a sea-bed or sea-shore to scoop earth and sand.

6. A method as claimed in Claim 3,4 or 5, wherein the obstacle eliminating means comprises an apparatus as claimed in Claim 1 or 2, and wherein an obstacle retained on the primary selection grid is removed by pivoting the grid upwards about one side and an obstacle retained on the secondary selection grid is removed by the rotary scraper as it moves across the upper surface of the grid.

7. An apparatus for removing unwanted obstacles from earth and sand substantially as hereinbefore described with reference to Figs. 5 to 7.

8. A method of dredging substantially as hereinbefore described with reference to Figs. 1 to 7.