Hydraulic and earth engineering – Underground passageway – e.g. – tunnel – Vertical
Reexamination Certificate
2000-03-22
2001-10-16
Will, Thomas B. (Department: 3673)
Hydraulic and earth engineering
Underground passageway, e.g., tunnel
Vertical
C405S133000, C405S102000
Reexamination Certificate
active
06302622
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
This invention concerns improvements made to tamping rammers for tamping the ground, and mile particularly to the structure of a tamping plate of a tamping rammer.
A conventional tamping rammer shown in
FIG. 6
comprises a tamping foot
32
comprising an inner spring cylinder
34
and an outer guide cylinder
33
which are inserted slidably to each other below a power transmission system
31
which changes rotational movements of an engine
30
to vertical movements, and a tamping plate
35
at the lower end of the tamping foot
32
. As vertical movements of the transmission system
31
are transmitted to a coil spring
37
positioned inside the spring cylinder
34
via a piston rod
36
, the vertical movements of the spring cylinder
34
generated by compression of the coil spring
37
are transmitted to the tamping plate
35
. This structure is widely known, for instance, from Japanese UM Kokai Heil-84307.
The above mentioned rammer generally requires a coil spring
37
with a large spring constant in order to efficiently perform tamping of the ground C with a strong impact force by increasing the amount of jumping of the tamping plate
35
.
In this type of rammer, the centerline A of the machine body along the longitudinal direction of the guide cylinder
33
and the spring cylinder
34
comprising the tamping foot
32
is tilted frontward in respect of the bottom face of the tamping plate
35
contacting the ground so that the machine automatically advances repeating jumps of the tamping plate
35
. Generally, there is provided a sleigh-shaped component with the front end or the front and rear ends standing upright from the bottom face of the tamping plate
35
for securely supporting the machine body, and the entire bottom face contacting the ground is flat and parallel to the ground.
In some rammers, the bottom face of the tamping plate is shaped like a hill when looked from the side as disclosed in Japanese UM Kokai Sho62-196209, or has a spherical surface as disclosed in Japanese UM Kokai Sho58-165005.
On the other hand, a conventional rammer, of which tamping plate
35
has a flat ground-contacting face at the bottom which is entirely parallel to the ground as shown in
FIG. 6
, is used for tamping the soft ground or the relatively hard ground paved with asphalt depending on the purpose of work. In this case, increasing the amount of jumping of the tamping plate
35
by the coil spring
37
with a large spring constant as discussed above achieves effective tamping and presents no problems even if the ground is soft.
However, it the rammer provided with a coil spring having a large spring constant is used to tamp the relatively hard ground surface paved with asphalt, etc., impact resilience between the ground and the tamping plate
35
becomes high, making jumping behavior of the rammer unstable and causing it “to dance”, creating problems for the operator.
The rammer on such an occasion jumps swaying lengthwise and crosswise, and the tamping plate cannot carry out strokes parallel to the ground.
The inventor of this invention studied causes for such unstable jumping behavior when a conventional rammer is used for tamping the hard ground, and found out that the tamping plate of a conventional rammer has a bottom face that is completely parallel to the ground except for a tilted surface standing upright at the front end of the plate.
As shown in
FIG. 6
, the centerline A of the tamping foot
32
of the rammer is tilted forward in respect of the ground-contacting face of the tamping plate
35
in order that the machine automatically advances while repeating jumps. Thus, the machine jumps in the direction along the centerline A.
On the other hand, the center of gravity G of the machine is positioned at the rear of the centerline A at the middle of the machine height so that the machine is stably supported instead of falling forward when the bottom face of the tamping plate
35
contacts the ground C. However, as the tamping foot
32
is tilted forward as mentioned above, the point E on the bottom face of the tamping plate
35
that receives the perpendicular line B from the center of gravity G is in the front of the point D on the bottom face of the tamping plate
35
where the centerline A passes.
As shown in
FIG. 7
, when the rammer jumps to a certain height and then falls, the tamping plate
35
hits the ground C and the center of gravity G moves forward by a large margin beyond the point D on the bottom face of the tamping plate
35
where the centerline A passes. The tamping foot
32
assumes a frontward tilting posture so that the angle &thgr;
2
between the centerline A and the ground C becomes larger than the angle &thgr;
1
shown in FIG.
6
.
As the center of gravity G leans forward beyond the point D where the centerline A passes at the moment when the tamping plate
35
hits the ground C, the centerline A assumes the frontward tilting posture with the angle &thgr;
2
. Since the bottom face of the tamping plate
35
is entirely flat, it momentarily becomes unstable with its rear end floating up and creating a void between the ground C and the point M, which is ahead of the point E supporting the center of gravity G.
When the machine jumps and the tamping plate
35
rises at the next moment, the machine is unstably supported at the point M, which is in front of the point E receiving the center of gravity G. As shown in
FIG. 8
, the machine then jumps bending backward (to the right) and the tilting angle &thgr;
3
of the centerline A becomes smaller than the original angle &thgr;
1
shown in
FIG. 6
, causing the tamping plate
35
to hit the ground from the point N at its rear end, thus creating unstable conditions again.
Movements mentioned above were described in respect of the lengthwise direction of the machine. In practice, such movements occur also in respect of crosswise direction because of a similar reason or because of the irregular ground surface. Thus, tamping the hard ground with a rammer creates extremely unstable jumping behavior of the machine, forcing the operator to work with extreme difficulty.
In order to prevent unstable jumping behavior of the machine when tamping the hard ground, the stroke length of the tamping plate may be shortened or the spring constant of the coil spring may be minimized. However, such measures are not enough to achieve sufficient and effective tamping effects even though the work may be performed perfunctorily.
SUMMARY OF THE INVENTION
The present invention aims to obviate the above mentioned problems of conventional tamping rammers and to offer a tamping rammer which can perform adequate tamping of the ground at all times with stable jumping behavior without deteriorating the tamping performance even when tamping the hard ground.
According to this invention, in a rammer of which body is tilted forward in respect of the tamping plate, there are provided on the bottom face of the tamping plate contacting the ground parallel thereto a flat area for validly supporting the machine body having the range R and the radius r corresponding to the distance between the perpendicular line B drawn from the center of gravity G of the machine body to the ground and the centerline A of the machine body drawn in inclined fashion along the longitudinal direction of the tamping foot, and inclined surfaces around the supporting area standing upright toward the outer edge of the tamping plate on the outer periphery of the free-supporting area of the machine.
According to a preferred embodiment of the present invention, the area for validly supporting the machine body is provided on the bottom face of the tamping plate and has a circular range R having the radius r that corresponds to the distance between the perpendicular line B drawn from the machine center of gravity G to the ground and the centerline A inclining toward the ground along the longitudinal direction of the tamping foot.
According to another preferred embodiment of the present invention, the area for validly support
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Mikasa Sangyo Co., Ltd.
Pechhold Alexandra K.
Will Thomas B.
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