Apparatus for driving pipes through the ground

In an apparatus for driving open-ended pipes through the ground, a hollow intermediate piece having a truncated conical transition portion with outlet openings for the removal of soil, which is forced into the pipe during driving, is disposed between the rearward end of the pipe and a pneumatic rammer for driving the pipe.

This invention relates to apparatus for driving open-ended pipes, such as 
protective ducts or pipelines through the ground. 
BACKGROUND OF THE INVENTION 
The driving of steel pipes through the ground, for example with the help of 
a pneumatic rammer which has a part-conical driving nose engaging directly 
or via a driving cap into the rearward end of the pipe, which is guided on 
bearing blocks and has a driving shoe fitting over both the inside and the 
outside of the forward end, has become increasingly common. Since the 
driven pipe is open at its forward end, that is at the driving shoe, the 
soil through which the pipe is driven penetrates during driving further 
and further into the interior of the pipe, while the driving shoe compacts 
the soil surrounding the pipe. Because the driving shoe has a larger 
external diameter than that of the pipe, it creates a channel in the soil, 
through which the driven pipe moves forwards under the impact of the 
rammer with comparatively low wall friction. 
As the interior of the pipe becomes increasingly filled with soil as 
driving advances, the soil friction against the inner face of the pipe 
also increases. This occurs particularly when the soil inside the pipe 
becomes more and more compacted under the influence of the driving impacts 
and of the soil being forced into the pipe from its forward end. 
Furthermore, the soil inside the pipe has to be accelerated with the 
forward movement of the pipe. Because of this an additional consumption of 
total energy by the rammer results. Moreover, the soil must from time to 
time be removed from the driven pipe. A number of techniques for removing 
the soil from the interior of the pipe are known. Thus, for example, the 
soil can be removed from the pipe interior by means of a screw conveyor 
within the pipe. This, however, like the flushing out of the soil with 
high-pressure water, requires the expense of additional equipment and is 
accompanied by considerable interruptions in driving. In another technique 
for removing the soil from the pipe interior, after driving has been 
terminated a thrust disc which bears sealingly against the inner face of 
the wall of the pipe is fitted into the forward end of the pipe and the 
interior of the pipe in front of the disc is subjected to compressed air, 
in order to force the soil counter to the direction of driving out of the 
pipe by movement of the thrust disc along the pipe under the air pressure. 
This technique is also complicated and expensive and moreover can only be 
used for short pipe lengths and with low frictional resistance, on account 
of the friction of the soil against the inner face of the wall of the 
pipe. 
OBJECT OF THE INVENTION 
The main object of the present invention is to provide an apparatus for 
driving a pipe through the ground, the apparatus, with low expenditure on 
equipment, making possible continuous driving and continuous removal of 
the soil from the interior of the pipe. 
SUMMARY OF THE INVENTION 
To this end, according to this invention, apparatus for driving an 
open-ended pipe through the ground comprises a driving member, means for 
applying a driving force to the member, and an intermediate piece 
disposable between the rearward end of the pipe and the driving member, 
the intermediate piece having at least one outlet opening for soil passing 
through the pipe and having an external conical face for engaging in the 
pipe end and a truncated conical transition portion tapering from the 
external diameter of the pipe towards the external diameter of the driving 
member, the outlet opening or openings being disposed in the truncated 
conical transition portion. 
Preferably, the external diameter of the transition portion decreases from 
approximately the external diameter of the pipe to approximately the 
external diameter of the driving member. In this way a space is created 
behind the end of the pipe, into which the soil can emerge from the pipe. 
The intermediate piece may be a hollow member, which is closed at its rear 
adjacent the driving member and which is seated on the rear end of the 
pipe and against the rear of which the driving member is fitted. 
The soil can emerge through the outlet opening or openings disposed in the 
truncated conical transition portion, so that continuous driving and 
continuous removal of the soil from the interior of the pipe are assured. 
The truncated conical transition portion constitutes a guide device acting 
outwardly and in the direction towards the outlet openings. Moreover, for 
a pipe of large diameter, a driving member of smaller diameter may be 
used, without requiring special adapter pieces. An intermediate piece 
having an external conical face engaging in the pipe end, an internal 
conical surface serving as seating for a driving member on a striking nose 
on a pneumatic rammer and the truncated conical portion connecting the two 
conical faces together, has proved especially successful. With the 
external conical face engaging in the pipe end, the driving force of the 
rammer is transmitted to the pipe without damage to the pipe end, and 
variations in the internal diameter of the pipe are compensated by the 
varying depth of penetration of the external conical face into the pipe. 
The striking nose of the rammer engaging into the internal conical face 
serves as the closure of the rear end of the intermediate piece, so that 
the guiding of the soil by the truncated conical portion in the 
intermediate piece towards the outlet openings is assured.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
In horizontal driving, a pneumatic driving ram 2, which is guided on a 
bearing block 1, has a striking nose 3 which engages via an intermediate 
piece 4 into the rearward end of a pipe 7. The pipe 7 is guided on bearing 
blocks 5 and is provided at its forward end with a driving shoe 6. The 
intermediate piece 4 is, as shown in FIG. 2, of tubular construction and 
has at its forward end an external cone 8, which engages in the rearward 
end of the pipe, and also an internal cone 9 for receiving the striking 
nose 3. Between the external cone 8 and the internal cone 9, there is a 
truncated conical transition portion 11, the diameter of which decreases 
from approximately the internal diameter of the pipe to approximately the 
diameter of the driving nose of the ram 2. In the transition portion 11, 
there are outlet openings 10. The soil which is forced into the interior 
of the pipe during driving is guided by the truncated conical transition 
portion 11, acting as guide device, to outlet openings 10 and emerges from 
these openings backwards out of the intermediate piece 4 into space behind 
the external cone 8, without interfering with the forward driving of the 
pipe 7. 
A pipe, not shown, for the supply of lubricant may lead to the driving shoe 
6, this lubricating pipe being connected to outlet ducts in the driving 
shoe. A lubricating liquid conveys the soil, which is rendered low in 
friction by the lubricant, outwards out of the pipe interior. By means of 
the supply of lubricating liquid, the consistency of the soil and thus the 
soil friction inside the pipe can be reduced virtually as much as desired 
and simultaneously the removal of the soil through the pipe interior and 
the outlet openings 10 in the intermediate piece 4 can be considerably 
facilitated. Depending upon the local circumstances, the soil penetrating 
into the interior of the pipe can be converted into a pasty or even a 
liquid state. This is mainly a question of the ratio of the quantity of 
liquid supplied to the quantity of soil in each individual case.