Apparatus for driving pipes through the ground
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. 
    
    
     SHORT DESCRIPTION OF THE DRAWINGS 
     An example of an apparatus in accordance with the invention is illustrated in the accompanying drawings, in which: 
     FIG. 1 is a side view of the apparatus and of a pipe being driven by the apparatus; and, 
     FIG. 2 is a sectional side view to a larger scale of part of the apparatus and of the rear end of the pipe. 
    
    
     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.