Classifying – separating – and assorting solids – Sifting
Reexamination Certificate
1999-10-29
2001-02-13
Walsh, Donald P. (Department: 3653)
Classifying, separating, and assorting solids
Sifting
C209S240000
Reexamination Certificate
active
06186336
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to dredges, and, more particularly, to grizzlies for such a dredge which separate recoverable material from material to be discharged or waste material.
Water-based and floating dredges typically include one or more bucket or clamshell-types grabs which are lowered into a waterway to collect sand, clay, gravel or the like from the bottom of the waterway. The grab typically deposits the collected material onto a grizzly which often includes a sieve having a plurality of generally parallel bars. The dredged material often contains components whose value justifies recovering them such as sand and gravel. Other components, such as clay, are not desirable for recovery and are simply collected for removal and disposal. Separating the recoverable material from the material to be discharged, however, in the past has been an inefficient and often time consuming process. Frequently, the dredged material includes a wide variety of materials. In other words, rarely does the dredged material include entirely recoverable material or entirely waste material to be discarded.
The time and expense involved in recovering useful material through a water-based dredging operation are very significant. Therefore, it is important to effectively and efficiently retain all of the available recoverable material from a given load. Currently, one common method for dredging is to deposit or dump the load of dredged material in the grab onto a primary grizzly for further processing. Once the dredged material is deposited onto the grizzly, smaller materials, such as sand and gravel, pass through the bars of the grizzly for recovery and further processing. The material remaining atop the grizzly is then discharged therefrom.
One manner of discharging the material remaining atop the grizzly is disclosed in U.S. Pat. No. 5,588,536 issued to the present inventor and hereby incorporated by reference in its entirety. In that patent, the dredge includes a bi-directional grizzly which includes a rake structure that can be operated in either of two opposite directions. If the material remaining atop the grizzly includes sufficient recoverable material for further processing, the rake is operated in a first direction to discharge that material directly into in a crusher or the like. However, if the material remaining atop the grizzly is not worthy of recovery, the rake is operated in a second opposite direction for discharge of the material down an inclined chute and onto a refuse barge, conveyor or the like.
However, the material remaining atop the primary grizzly often includes a mixed variety of components. For example, the remaining material may include larger rocks, gravel or the like which are too large to pass between the spaced bars of the primary grizzly but are still worthy of recovery for further processing. Nevertheless, the material remaining atop the primary grizzle often includes clay and/or other waste along with the recoverable components. The operator of the dredge then must decide whether to discard the entire contents of the material atop the primary grizzly or further process the waste material included therein in an effort to retain the available recoverable material. This dilemma often results in the discharge of a significant quantity of worthwhile recoverable material or processing of clay and other undesirable elements resulting in an inefficient and ineffective dredging operation.
SUMMARY OF THE INVENTION
A primary objective of this invention has been to provide an improved dredge and associated method which allows for the efficient and effective recovery of a larger percentage of the worthwhile recoverable material from a load of dredged material without the processing of waste material such as clay and the like. These and other objectives of the invention have been attained by a dredging station which includes a primary grizzly, as previously discussed in the background of this invention, for separating a load of material collected by the grab into a first recoverable portion which falls through the sieve of the primary grizzly and a first discharge portion which remains atop the sieve of the primary grizzly.
The primary or first grizzly includes a discharge mechanism for removing the discharge portion of the material remaining atop that sieve. In one embodiment, the discharge mechanism of the primary grizzly is a tipping grizzly in which one longitudinal end of the grizzly elevates relative to the opposite end so that the first discharge portion slides off of the grizzly and onto an inclined chute. One example of such a tipping grizzly is shown in U.S. Pat. No. 5,427,251, which is hereby incorporated by reference in its entirety. Alternatively, the discharge mechanism may comprise a rake or other arrangement as disclosed in U.S. Pat. No. 5,588,536.
The chute is inclined so that an upstream end is elevated relative to a downstream end. As the first discharge portion of material flows or falls down the chute, it encounters a second or auxiliary grizzly having a sieve which includes a number of generally parallel spaced bars for straining the first discharge portion of the material into a second recoverable portion of material and a second discharge portion. The second discharge portion of material remains atop the second grizzly on the chute and subsequently flows toward the downstream end of the chute and onto a barge, conveyor or the like for ultimate disposal. Advantageously, a crusher is positioned below the chute and in communication with the second grizzly for processing of the second recoverable portion of material which passes through the second grizzly and into a funnel connected to the crusher.
A movable gate is included on the chute for selectively opening and closing the second grizzly to permit or inhibit, respectively, access to the second grizzly as required depending upon the make-up of the first discharge portion of material discharged from the primary grizzly. Additionally, the sieve of the second grizzly includes a plurality of spaced bars which, in a present embodiment, are removable to provide for convenient access to the funnel and crusher therebelow for dislodging jams or other accumulations that may inhibit the flow of material.
As a result of this invention, material recovered from a waterway or the like can be more effectively and efficiently processed so that a higher percentage of recoverable material is retained and waste material such as clay or the like is ultimately discharged for disposal without being processed.
REFERENCES:
patent: 784584 (1905-03-01), Myers
patent: 1263829 (1918-04-01), Wintersgill
patent: 4116326 (1978-09-01), Tuman
patent: 4287064 (1981-09-01), Ando et al.
patent: 4731180 (1988-03-01), Huff
patent: 4792394 (1988-12-01), Rudzinski
patent: 5072991 (1991-12-01), Rohr
patent: 5427251 (1995-06-01), Landmann et al.
patent: 5449072 (1995-09-01), Braun et al.
patent: 5588536 (1996-12-01), Rohr
patent: 6059120 (2000-05-01), Rohr et al.
Beauchaine Mark J.
Walsh Donald P.
Wood Herron & Evans L.L.P.
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