Method for operation to excavate underdrain in the field ground and a device for operation to excavate underdrain

A method of operation to effectively excavate an underdrain in the field ground having a long service life and ensuring that the underdrain will not be closed after a long period of time and a device for such operation. The method includes attaching a plurality of buckets to an endless chain, driving the endless chain to excavate a slit in the field ground, reforming inner side walls of the slit by a reformer, pressing soil from both sides of the slit later ally inwardly by a pressing member attached to the reformer to form a block to separate the slit into an upper space and a Iover space, and charging the upper space with discarded dirt.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a method for operation to excavate an 
underdrain and a device for such operation to excavate an underdrain. More 
particularly, the invention relates to a method for operation to excavate 
an underdrain with or without filling materials being used and a device 
for such operation. 
2. Description of the Prior Art 
For a conversion from rice paddy into a field cultivation, it is essential 
to improve water permeability and drainage in the field. For this purpose, 
open drainage and underdrainage have been recommended in the field while 
it is known that the under drain is more efficient in watery areas; that 
is, the acceleration of vertical permeation of surplus water is practiced 
as essential means. Many of conventional underdrainage excavating devices 
are of the type in which the plow section of a subsoiler is attached with 
a shell-shaped follower member or a so-called cannonball which is pulled 
by the tractor deep through the ground to form an underground space which 
is called a "shell" underdrain. 
Particularly, the underdrain is not only suited to the conversion from the 
rice paddy cultivation to the field cultivation but also is most effective 
to the soil improvement of both the rice paddy and the field. 
Conventionally, a known underdrain was made by forming a space in the field 
ground such that residual surface water or excess moisture within the 
ground was vertically permeated to build an aquatic environment suited to 
the field or rice paddies as well as improving the quality of the 
wet-fields. In this case, a care must be taken to prevent the underground 
space from being filled up with the passage of time. Actually, however, 
the surface soil in the field falls through an upper opening of the slit 
formed by the plow of the subsoiler into the slit space with the result 
that said slit space has been filled up as time goes on, thus frustrating 
the original objective. 
In a peat bog, the field surface is made of clay which tends to close or 
fix an open slit due to plasticity and resiliency of the soil forming the 
underground space, thus failing the function expected as the underdrain. 
It is also proposed to bury unglazed ceramic pipes in position for 
collecting the vertically permeating water but such pipes are merely 
connected in series. Therefore, the pipes can be disconnected as a result 
of aging to such a degree that sufficient drainage was not effected, thus 
making the service life of the underdrain short. 
SUMMARY OF THE INVENTION 
In order to solve the problems discussed in the foregoing, there is 
provided in the present invention a method of operation to excavate an 
underdrain comprising the steps of attaching a plurality of buckets for 
continuous movement in a vertical plane, moving said buckets horizontally 
by means of a tractor to form a slit in the field ground, setting out the 
sides of said slit by a reformer, pressing earth from both sides of said 
slit at an intermediate portion thereof to define an upper space and a 
lower space, charging said upper space with dirt excavated and discarded 
by said buckets to make said lower space independent after said lower 
space being worked on by rotors attached to a sprocket of the chain to 
form an underdrain having a substantially circular cross section to 
function as a drainage pipe and a device for such operation. 
While the soil removed by the lit reformer in the lower space is pressed, 
the upper space is charged with dirt discarded by the buckets from the 
transitional position of the ascending move and the descending move to 
cover the slit, thus preventing unnecessary fall of the dirt or earth from 
outside such that the closure of the underdrain is made.

DESCRIPTION OF THE EMBODIMENTS 
Now, a method for operation according to the present invention and a device 
suited for such operation will be described with reference to the attached 
drawings including FIG. 1 through FIG. 15. Referring to FIG. 1, TR 
generally denotes a tractor which is of a well-known crawler type. Said 
tractor TR is attached with an underdrain excavator 10 including four 
hydraulic cylinders 1 and 2 and support members 3 supported by said 
cylinders 2 and is adapted to travel in the arrow-marked direction D1. 
Said underdrain excavator 10 comprises a digging section 20 having on frame 
21 supported by said support members 3, a reformer knife member 30 
arranged rearwardly of said digging section 20, and a pressing member 40 
attached to said reformer knife member 30. 
Said digging section 20 supported by the support member 3 includes a 
support plate 21 provided in a vertical plane, said support plate being 
attached with a pair of sprockets 22X and 22Y by way of axles 22A and 22B 
at respective upper and lower ends thereof. An endless chain 23 is passed 
around said sprocket 22X and said sprocket 22Y attached to the support 
plate 21. Of the two sprockets, the sprocket 22X plays a part of a drive 
element to drive the chain 23 which in turn drives the sprocket 22Y. 
Actually, however, there is a transmission chain 4 passed around a 
receiving sprocket (not shown) coaxial to said sprocket 22X. Said 
transmission chain 4 is driven by a PTO axle (not shown) of the tractor 
TR. Said support plate 21 has a function to maintain the spacing of the 
tight end and the loose end of said chain 23. 
As better shown in FIG. 2, said endless chain 23 has a plurality of 
excavating buckets 24 arranged at regular intervals with the ascending run 
thereof being on the tractor side and the descending run being disposed 
rearwardly thereof to be driven to make a circuit. Each bucket 24 performs 
an excavating action at the beginning of the ascending run while it may 
discard the dirt scooped therein rearwardly during the transition from the 
ascending run to the descending run through a dirt discard guide 50 as 
will be explained later on. 
As shown in FIGS. 2 through 6, rotors 25 are provided at the support axles 
22B on both sides of the sprocket 22Y. Said rotors 25 are forced to rotate 
in the direction D.sub.2 when the sprocket 22Y is driven. As best shown in 
FIG. 4 and FIG. 6, each rotor 25 has an intermediate portion thereof 
widest and end portions thereof which gradually become narrower such that 
the locus thereof is a substantial circle as viewed in the direction of 
travel of the device, permitting an underdrain to be formed and perform a 
function of a drain pipe. 
It may be easily understood that the driven endless chain 23 causes the 
buckets attached thereto to work on the ground. As a result of this 
action, a slit S is excavated in the ground as shown in FIGS. 11 and 12. 
The reformer knife member 30 shown in detail in FIGS. 7 and 8 in the shape 
of a knife is provided in a plane including said slit S so as to set out 
the sides of said slit S. As best shown in FIG. 1, said reformer knife 30 
is attached through pins P to the framework forming the device 10 such 
that the depth of the digging work through the ground is selected by 
adjusting the pin positions. While the width of the reformer 30 is sized 
slightly larger than the slit width or the width of each bucket 24, the 
vertical size thereof is set to the lowest reach of each bucket 24 such 
that the lower end of the bucket protrudes downwardly of the reformer 
knife member 30. 
Further, said reformer knife member 30 is formed with a pair of 
semi-circular enlargements 31 extending in the direction of the width of 
the reformer knife member 30 at the lower portion thereof such that the 
inside walls of a circular space formed by the rotors 25 may be set or 
reformed. Furthermore, the lower end of the reformer knife member 30 is in 
the form of a chisel which sets out the floor portion of the bucket locus. 
Furthermore, the reformer knife member 30 is attached at a vertically 
intermediate portion thereof with a pressing member 40, which is formed 
with a pair of brackets 41 for attachment onto the reformer knife member 
30. Integrally with said brackets 41, a base plate 42 extends into the 
opposite direction of travel. Downwardly front both side edges of the base 
plate 42 extends a pair of pressing side plates 42 such that the distance 
therebetween converges rearwardly while the lateral cross section thereof 
is channel-shaped. Further, the bracket side of the side walls are allowed 
to define openings 43A to introduce the dirt into a space defined by the 
base plate 42 and the side walls 43 during the operation. 
Thus, the dirt collected from the walls of the slit S and pressed by and 
between the pressing side walls 43 of the pressing member 40 is centrally 
forced inwardly to close the slit S in the course of the operation to form 
a closing block H as seen in FIGS. 11 and 12. Said closing block H 
separates the slit S into upper and lower spaces. While the upper space is 
allowed to receive discarded dirt and be charged therewith as will be 
explained later on, the lower space remains as a space in the form of a 
guiding passage for introducing permeating water to the underdrain A 
formed at the lowest level. 
Further, the excavating device 20 has a dirt discard guide section 50 at an 
upper portion thereof to cover a transitional area of the buckets 24 from 
the ascending move to the descending move. Said dirt discard guide section 
50 is open rearwardly and attached with a closure plate 52 attached 
thereto by way of hinges such that said closure plate 52 is driven to 
close said dirt discard guide section 50 by the contraction of the 
hydraulic cylinder 51 shown in FIG. 1. When the closure plate 52 is shut, 
the dirt impinges on the shut closure plate to be deflected laterally. 
When the plate 52 is opened, the dirt is discarded rearwardly instead of 
impinging on the plate 51 to fill the upper space of the slit S. 
The operation and the work by use of the device according to the present 
invention will be explained in more detail hereinafter. First of all, the 
device 10 is attached to the tractor TR such that the device is driven by 
the power source which the tractor carries. 
Then, there is a need to lower the device 10 such that the digging section 
20 reaches the level desired to form the underdrain A. For this purpose, 
the hydraulic cylinders 2 are contracted and the cylinders 1 are extended 
until the digging section 20 is lowered as shown in FIG. 10. In this 
state, the operation is started from an open drain M through a ridge Z (in 
the arrow-indicated direction D1 of the operation). 
While the digging section 20 is driven by the transmission chains 4, and 
the sprockets 22X and 22Y, the tractor is also needed to run for 
operation. When the excavation is performed with the tractor being driver 
to run, the clay layer Cl, the pan of plow bottom Pn, and peat deposits Pd 
are cut through as shown in FIG. 12 and FIG. 13. In the meantime, the dirt 
excavated by the ascending action of each bucket 24 is discarded 
rearwardly when the bucket changes the course at the top of the ascending 
run of the chain 23. During this movement, a slit S is formed in the 
ground. While the rotors 25 rotate to form the underdrain A of circular 
cross section at the bottom portion of the slit S, the reformer 30 
following the digging section 20 set out the sides of the slit S to reform 
the slit walls. Thus, water W is allowed to flow through said underdrain A 
as shown in FIG. 14. It is also possible to form an underdrain A of a 
suitable shape by selecting the shape of the rotors 25. Further, since the 
pressing member 40 attached to the reformer knife member 30 is adapted to 
introduce the side walls of the slit S through the openings 43A formed 
between the pressing plates 43 whereas the space defined by the base plate 
42 is formed to converge in the opposite direction of travel, the dirt 
scraped off from the side walls of the slit S is tightly pressed to such 
an extent that the closing block H is formed at a vertically intermediate 
portion of the slit. Therefore, the slit space is divided into two by the 
closing block H after the passage of the digging section 20 to make the 
underdrain A a closed space. 
Further, the dirt excavated by each bucket 24 of the digging section 20 is 
discarded by a centrifugal force rearwardly through the dirt discard guide 
50 at the top of the transitional area of the bucket from the ascending 
love to the descending move, in other words, at the time of bucket 
reversion along the sprocket 22X and the thus discarded dirt falls onto 
the upper space of the slit S to be charged therein to. 
As shown in FIG. 13, in case a filling materials such as rice husks Rh are 
to be charged in the space of the slit S, the closing plate 51 of the dirt 
discard guide 50 is closed. In other words, the hydraulic cylinder 52 is 
extended to direct the plate 51 laterally of the direction of travel. 
Therefore, the dirt will not be charged into the slit S, which is left 
open. In such an instance, a water permeable pipe P1 of unglazed material 
is buried at the bottom of the slit S and the pipe P1 may be covered by 
reed, hay and etc. FIG. 15 shows that water W is allowed to flow through 
said water permeable pipe P1. 
Further, since the enlargement 31 provided at the lower end of the reformer 
knife member 30 has a contour similar to the underdrain A formed by rotors 
25, the space or the underdrain A is reformed thereby to prevent the 
deformation thereof. 
As explained in the foregoing, the method of operation to excavate an 
underdrain and a device for such operation of the present invention reside 
in that a slit space is formed by buckets acting as excavating pawls, said 
slit is formed with a closing block at a vertical intermediate portion 
thereof to separate the space into two, the upper space is charged with 
the discarded dirt from the buckets to cover the slit, the lower space 
blocked by the block formed as a result of pressing of the dirt in the 
slit acts as an independent underdrain from the field surface to prevent 
an external dirt entry thereinto, thus forming a perfect underdrain having 
a long service age. 
Since the discarded dirt is charged in the vertical intermediate portion of 
the slit while forming the closing block thereat simultaneously with the 
operation, the slit will not be destroyed during such operation to assure 
that the underdrain is firmly formed. 
Further, since the pressing member is adapted to press the soil from both 
sides of the slit laterally centrally to form a closing block, the 
operation is performed continuously and since the slit is firmly set at 
both side walls by the reformer, it is most suited for the operation at 
peat bog fields. 
Moreover, the driven sprockets and the rotated rotors assure the formation 
of the internal surfaces of the underdrain while the enlargements set the 
internal faces.