Excavating – Ditcher – Having endless digger
Reexamination Certificate
1998-04-03
2001-04-24
Lillis, Eileen D. (Department: 3673)
Excavating
Ditcher
Having endless digger
C037S352000, C037S462000, C037S195000, C299S073000, C299S076000
Reexamination Certificate
active
06219945
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an excavating method for excavating an underground continuous ditch to construct an underground continuous wall to be used, for example, for water sealing or for foundation.
2. Description of the Prior Art
Heretofore, as an apparatus for excavating an underground continuous ditch, there has been known such an apparatus as shown in
FIG. 6
, in which a chain type cutter
4
is attached vertically to a traveling carrier car
1
through a main frame
2
and a leader
3
, and with the cutter
4
positioned underground, the cutter is rotated while being allowed to move horizontally (traversing), to excavate a ditch G of a constant width continuously (see, for example, Japanese Patent Laid Open Nos. 280043/93,280044/93 and 173835/95).
The chain type cutter
4
comprises an endless chain
8
and a large number of excavating edges
9
formed on the outer periphery of the chain
8
to excavate the ditch G. The endless chain
8
is stretched between a driving wheel (sprocket)
6
disposed at the upper end of a cutter post
5
which is a vertically long, box-shaped frame and a floating wheel (pulley)
7
disposed at the lower end of the cutter post.
The cutter
4
is supported vertically movably with respect to the leader
3
. It is moved vertically to adjust the depth by means of a lift cylinder (a hydraulic cylinder)
10
disposed between the leader
3
and the cutter
4
or by such a lift means as a winch (not shown).
The cutter
4
is also supported so as to be movable (traversing) in the horizontal transverse direction together with the leader
3
with respect to the main frame
2
. The cutter
4
is pressed against a ground A (the thick arrow in
FIG. 6
represents this pressing force) by means of upper and lower traversing cylinders (hydraulic cylinders)
11
,
12
disposed between the main frame
2
and the leader
3
.
The traversing force of the cutter
4
is created and imparted to the cutter mainly by the lower traversing cylinder
12
. The upper traversing cylinder
11
functions to bear a pressing reaction force.
When the traversing cylinders
11
and
12
assume the state of maximum extension, both cylinders are contracted and at the same time the carrier car
1
advances in the excavating direction. By repeating this operation the ditch G is excavated continuously.
According to such a conventional method for excavating an underground continuous ditch, there arises the following problem because there is performed only the traversing excavation in which the ground A is excavated in reliance on the traversing force imparted to the cutter
4
by the traversing cylinders
11
and
12
.
Generally, as the depth increases, the ground A tends to become harder and the frictional force between the cutter
4
and the wall of the excavated ditch G tends to increase.
On the other hand, with an increase of the depth, the traversing force (pressing force) capable of being exerted on the ground A by the cutter
4
becomes smaller, and when the depth exceeds a certain limit, the traversing force required for excavation is no longer imparted to the lower portion of the cutter.
Consequently, the movement of the lower portion of the cutter becomes slower than the upper portion thereof, so that the cutter as a whole is inclined or deflected forward. In this state, the lower portion of the ground A is left unexcavated, which eventually becomes a portion incapable of being excavated.
Thus, according to the conventional excavating method, an excavatable depth limit depth in excavation) is small.
SUMMARY OF THE INVENTION
According to the present invention, in view of the above-mentioned point, there is provided a method for excavating an underground continuous ditch which can make up for the deficiency in traversing excavation and thereby increase the limit depth in excavation.
To be more specific, according to the present invention, in an underground continuous ditch excavating method involving, with a chain type cutter positioned underground, rotating the cutter while pressing the cutter horizontally against the ground, the cutter comprising a cutter post and an endless chain having excavating edges and stretched vertically on the cutter post, there is performed a vertical excavation in which the ground is excavated while the chain type cutter is moved vertically.
According to this method, when it is likely that a portion of the ground will be left unexcavated at the lower portion of the cutter due to insufficient traversing force, or when there actually occurs an unexcavated portion due to tilting or deflection of the cutter, the cutter is raised to decrease the stress acting on the lower portion of the cutter, and thereafter the said ground portion is excavated while the cutter is moved downward, whereby the ground portion left unexcavated can be excavated.
Further, according to the present invention, in an underground continuous ditch excavating method involving, with a chain type cutter positioned underground, rotating the cutter while pressing the cutter horizontally against the ground, the cutter comprising a cutter post and an endless chain having excavating edges and stretched vertically on the cutter post, there is performed a reverse excavation at an appropriate timing in which the rotating direction of the chain type cutter is reversed to reverse the operating direction of the excavating edges against the ground.
According to this method, since the rotating direction of the cutter is reversed, the bite of the excavating edges into the ground A is improved and it is possible to enhance the excavation efficiency to a higher extent than before the reversal of the rotating direction.
Further, according to the present invention, in an underground continuous ditch excavating method involving, with a chain type cutter positioned underground, rotating the cutter while pressing the cutter horizontally against the ground, the cutter comprising a cutter post and an endless chain having excavating edges and stretched vertically on the cutter post, there are simultaneously performed at an appropriate timing both a reverse excavation in which the rotating direction of the chain type cutter is reversed to reverse the operating direction of the excavating edges against the ground and a vertical excavation in which the ground is excavated while the cutter is moved vertically.
According to this method as a combination of both vertical excavating method and reverse excavating method, the excavation efficiency is improved to a remarkable extent by virtue of a synergistic effect of the combination in comparison with only the vertical excavation or only the reverse excavation, and the ground portion left unexcavated can surely be excavated.
Further, according to the present invention, in any of the above methods, during normal excavation, the chain type cutter is rotated in a rake-up direction in which the excavating edges of the cutter come into upward contact with the ground, while during reverse excavation, the cutter is rotated in a rake-down direction in which the excavating edges come into downward contact with the ground.
Particularly, by changing from the rake-up rotation to the rake-down rotation during normal excavation, the bite of the excavating edges into a ground portion A
1
left unexcavated at the lower portion of the cutter due to tilting or deflection of the cutter is improved and it becomes easier to excavate the unexcavated ground portion A
1
.
Further, according to the present invention, in any of the above methods, one or both of the vertical excavation and the reverse excavation are performed when the chain type cutter is tilted or deflected forward in the excavating direction.
Further, according to the present invention, in any of the above methods, one or both of the vertical excavation and the reverse excavation are performed while applying a depressing force separate from the own weight of the chain type cutter to the cutter.
According to this method, when there is adopted a construction method
Heishi Mituo
Mizutani Motohiko
Hartmann Gary S.
Kabushiki Kaisha Kobe Seiko Sho
Lillis Eileen D.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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