Excavating – Clamshell bucket
Reexamination Certificate
2002-07-08
2004-11-30
Novosad, Christopher J. (Department: 3671)
Excavating
Clamshell bucket
C037S195000, C294S068230, C701S050000
Reexamination Certificate
active
06823616
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable
REFERENCE TO A “MICROFICHE APPENDIX”
Not applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method of excavating a layer of soil by using an excavator comprising a grab with two bucket halves.
2. General Background of the Invention
Excavating methods using a grab are very well-known for excavating soil layers on land or under water.
Soil layers may have to be excavated for various reasons. One reason is that the depth of a water course must be increased. Another, more recent reason is that the soil layer contains contaminated material. In that case care has to be taken that the material of the soil layer is disturbed to a minimal extent, in order to prevent diffusion of the contaminated material into the surrounding water. Usually, contaminated soil layers are relatively thin layers.
In addition, which is true for both land and under-water operation, the amount of removed material must be kept as small as possible.
Furthermore, the excavating process should be as efficient as possible, in order to ensure that the capacity of each excavating cycle is optimal and the required number of movements is kept to a minimum.
Thus, there is a need for an excavating method by which contaminated soil layers can be excavated in a controlled manner.
In addition, there is a need for an efficient excavating method.
Moreover, there is a need for an accurate excavating method for excavating layers of soil material, in particular thin layers of (contaminated or not) material.
Incorporated herein by reference are European Patent No. 067747, its published patent application no. 95200709.4, published on 18 Oct. 1995, and Dutch patent application no. NL 9500450, filed 22 Mar 1994.
SUMMARY OF THE INVENTION
According to one aspect, the invention provides a method of excavating a surface layer of soil by using an excavator comprising a grab having two bucket halves with cutting edges, comprising the steps of:
a) in a first excavating position the grab is held in a first orientation as seen in projection on a horizontal plane and inserted into the layer of soil in an open position of the bucket halves until their cutting edges reach a first predetermined level while maintaining said first orientation,
b) while maintaining that level and first orientation, the bucket halves are moved to a closed position during which movement their cutting edges move towards each other through a substantially straight path so as to excavate a first rectangular portion of the layer of soil,
c) the grab is lifted and moved to a discharge position horizontally spaced from the excavating position and emptied there to make further transport of the excavated soil possible,
d) the grab is moved towards a second excavating position and held in said first orientation and inserted into the layer of soil in an open position of the bucket halves until their cutting edges reach a second predetermined level,
e) while maintaining that level and said first orientation, the bucket halves are moved to a closed position during which movement their cutting edges move towards each other through a substantially straight path so as to excavate a second rectangular portion of the layer of soil, said second portion being adjoining to said first portion before excavation,
f) the grab is lifted and moved to a discharge position horizontally spaced from the first and second excavating positions and emptied there to make further transport of the excavated soil possible;
whereafter steps d, e and f are repeated in a corresponding manner for excavating subsequent third, fourth, etcetera rectangular portions until the layer of soil is excavated.
Thus it is ensured that a repeated excavating movement on the same spot is avoided to a large extent and any possible overlap can be known and can be kept as small as possible. The grab can be filled with a portion of the layer of soil, the location and orientation of which is known and thus filled to an optimal capacity. The straight closing movement of the cutting edges and the stable holding of the grab during closing and excavating, minimize the risk of spreading soil particles.
Preferably, the excavation is carried out according to a pattern comprised of adjoining, parallel rectangular portions of the layer of soil, wherein said first and second predetermined levels are on a same level or horizontal plane. In this way a horizontal layer or part of such a layer can be removed by moving the grab one pattern step after each excavating cycle.
In an advantageous further development according to the invention, the excavation is carried out according to a pattern comprised of superposed, in projection in a horizontal plane, coinciding rectangular portions of the layer of soil, wherein said first and second levels are different. In this way a vertical column of two or more excavating portions can be removed.
The cutting edges may be moved through a substantially horizontal path during the closing of the bucket halves, so that a horizontal cutting surface is left after an excavating cycle, which permits a reliable estimate of the actual bottom level and of the quantity of soil which is yet to be excavated.
According to a further development, the angle of the grab with respect to the vertical is measured during insertion of the grab into the layer of soil by means of an inclinometer.
In yet a further development of the method according to the invention, a projection of the area to be excavated is entered into a control and monitoring system for the excavating device in the form of a horizontal template of rectangles corresponding to the rectangular portions to be removed by the grab in an excavating step and determining the location of the grab required for each subsequent excavating step. The prosecution of the excavating process can thus be controlled in a positive and therefore reliable manner.
The orientation of said horizontal template may be selected depending on main profiles in the original surface of the layer of soil, such as a bank of a river or canal, or a harbour.
Advantageously, the rectangles are selected to have a length and a width slightly smaller than the span and the width of the grab, so as to enable a slight and known overlap of the area enclosed by the grab and the rectangles of the horizontal template.
In a further development according to the invention the original location and course of the surface of the layer of soil as well as of the desired location and course of the surface to be obtained by excavation of the layer of soil, are entered into said control and monitoring system for the excavating device in respective digital terrain models—such models are known per se in the art—and combined with said horizontal template, the control and monitoring system dividing the area to be excavated into equidistant or parallel and adjacent subareas, each rectangle of the template comprising a plurality of such subareas, and attributing a thickness value to each subarea, said thickness value corresponding to the difference in the levels of the actual surface and the desired surface for that subarea.
Preferably, the control and monitoring system matches a vertical template on the area between the original surface and the desired surface, the vertical template having horizontal grid lines.
According to a further development of the process of the invention the distance between the horizontal grid lines of the vertical template is selected in relation to the volume of the grab divided by the footprint of the grab. The footprint of the grab is the largest surface area of the grab for excavating purposes.
According to a further development of the process of the invention, the control and monitoring system updates the actual level of the surface layer after each excavating cycle by adjusting the level and thickness values for the subareas located in the rectangle concerned in the horizontal template.
According to a further development of the process of the invention, the control and moni
Gutter Arnold
Korf Dick
Boskalis Westminister Inc.
Garvey, Jr. Charles C.
Garvey, Smith, Nehrbass & Doody, L.L.C.
Nehrbass Seth M.
Novosad Christopher J.
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