Method for drawing cables into a pipe

A method for inserting cables within a pipe characterized by closing one end of the pipe with a cap having an opening or port for introducing a flow of an agent and having a plurality of closed entry channels, opening one of said entry channels and inserting a cable through said opened entry channel while applying a flow through the opening or port so that the flowing agent creates a turbulence within the pipe for engaging the surfaces of the cable inserted through the opened entry channel to carry said cable along the length of said pipe.

BACKGROUND OF THE INVENTION 
The present invention is directed to a method for introducing or pulling 
cables into a pipe by utilizing a flowing agent that will transport the 
cable as it is introduced at one end with the agent flowing out of the 
remote end. 
European Patent Application A 0 186 753 discloses introducing a cable into 
a channel by utilizing a flow of air or gas. As disclosed, a plurality of 
longitudinal channels are kept relatively small in the cross section and 
are provided in a larger pipe cross section. One or more light waveguide 
leads are capable of being individually introduced into these longitudinal 
channels. Due to the small size of the cross section of these individual 
longitudinal channels, special measures are not required in the region of 
the pressure connection for the flowing agent. 
In many cases, however, it is desirable to either draw cables into existing 
pipes having a relatively large diameter, for example 10 cm, or to lay 
simple and universally employable pipes that, due to the prescribed, small 
cross sectional area of the longitudinal channels, only allows a drawing 
in of a very specific number of light waveguide leads or of extremely thin 
cables. In addition to the disadvantages that only light waveguide leads 
having a relatively small cross section can be blown into the thin 
channels, the problem also occurs that the range of such systems are 
limited, even given high pressures. 
SUMMARY OF THE INVENTION 
The object of the present invention is to provide a specific method wherein 
light waveguide cables can be shot into pipes intended for the drawing-in 
at any time, either subsequently or simultaneously, without great outlay. 
This object is achieved with an improvement in a method for drawing cables 
into a pipe with a flowing agent that transports the cables, said flowing 
agent being introduced at a near end of the pipe and flowing out of the 
remote end. The improvements are that the near end of the pipe is closed 
by a pressure-tight pressure cap having a plurality of closable entry 
channels for the individual cables and preferably a port for introducing 
the flowing agent, opening one of the individual channels and introducing 
a cable through said open channel, introducing a flowing agent into the 
near end of the pipe, said flowing agent creating a turbulence and 
transporting the cable along the interior of the pipe as the agent flows 
out the far or remote end thereof. 
In the method of the invention, no special demands are made on the pipe in 
and of themselves because a pressure cap can be attached at any time, as 
needed. The available free cross section of the interior of the pipe, 
moreover, can be filled to a greater or lesser degree, dependent on the 
demands, and can also be filled at different times and, potentially, with 
different types of cables. The cables, that were previously shot in or 
cables that are already connected, do not impede the introduction of 
additional cables, as long as the pipe cross section is not significantly 
diminished by the cables already present. For example, about 30 cables 
having an outside diameter on the order of magnitude of 6 mm and each 
having about six light waveguides can still be reliably drawn into the 
pipe having an inside clearance of 10 cm so that the maximum of about 180 
light waveguides are available overall for light transmission. Overall, 
the pipe cross section should be maximally filled with introduced cables 
to less than 20% of its total cross sectional area and preferably between 
10% and 15% of this area. The remote end of the pipe will remain open 
during the step of insertion and is expediently protected against the 
entry of water after the introduction, for example by employing a cut-out 
cover and a sealing compound or the like. 
Optical cables are preferably introduced by the method of the present 
invention, since these are especially light weight and relatively 
flexible. Insofar as has already been done in due time, the cable jackets 
are to be differently identified during the introduction event in order to 
facilitate the identification of individual cables at the remote end of 
the pipe. If there is a risk that the pipe may be destroyed from an 
outside force anywhere along the length of the pipe, an identification 
over the entire length of each of the cables is expedient in order to 
facilitate the identification during any repair work. Such a continuous 
marking can be undertaken during the introduction event, for example with 
a simple foil printer. 
It is expedient to employ 10 foil optical cables whereby the outside 
diameter of these correspondingly flexible cables should lie in a range of 
between 4 mm and 10 mm. The clearance of the pipe provided for the 
acceptance of the optical cable expediently lies between 5 cm and 10 cm 
and must be adapted to the diameter and to the plurality of cables to be 
introduced therein. 
Given employment of armored optical cables, for example with inserted 
aramide yarns, a normal draw-in process over the straight path can be 
combined with a blow-in process of the invention over highly curved 
sub-paths. Extremely long cable sections can be drawn-in and blown-in in 
this fashion. For example, cables can be drawn-in over a length of 500 m, 
then blown-in over an additional 500 m with the use of an auxiliary cable 
feeder device, such as a track-like device positioned before the pressure 
connection. Subsequently, further drawing-in can occur over another 
additional 500 m. 
Other advantages and features of the invention will be readily apparent 
from the following description of the preferred embodiments, the drawings 
and claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The principles of the present invention are particularly useful for feeding 
optical cables, such as a cable CA2, into a pipe RO, which is preferably 
composed of a plastic material. 
As illustrated in FIG. 1, the pipe RO has one end closed by a 
pressure-tight pressure cap PC, which is secured to the end of the pipe 
with a clip or band BD. The pressure cap PC has a port or connection VS 
through which a flowing agent SM is delivered from a pressure source PS 
(see FIG. 3). The flowing agent can be either a liquid or gas and is 
preferably air. 
The pressure cap PC, in addition to the opening or connection VS, is 
provided with a plurality of entrance channels EC1-ECn which extend 
parallel to each other and are preferably along a longitudinal axis of the 
pipe RO. Each of these entrance channels has a through-opening, such as an 
opening D03 for the channel EC3. Normally, each of these entrance channels 
EC1-ECn is closed with a plug, such as a plug ST3 for the channel EC3, in 
a pressure-tight manner. For example, they can be closed with a plug and 
an appropriate hose clamp, or the plug can have threads and is screwed 
into internal threads of the channel. The total number of entrance 
openings EC1-ECn, which are provided in the cap PC, corresponds to the 
maximum number of optical cables which are to be inserted into the pipe 
RO. 
As illustrated, a cable CA2 is being inserted through the entrance opening 
EC2. How an optical cable CA2 is drawn into this entrance channel is shown 
in the present example. To this end, a simple thrusting means (TM), for 
example a caterpillar or belted cable engager, can be provided on the 
right side of the entrance channel EC2 of the cap PC, as illustrated in 
FIG. 1. This thrusting means will exert a longitudinal force on the 
optical cable CA2 and convey it into the interior of the pipe RO. The 
actual forward motion, even given a curved course of the pipe, however, is 
created by a highly turbulent flowing agent SM that will engage the 
optical cable, for example CA2, to be respectively drawn-in and to form 
this cable in a wave-like manner or into a serpentine shape so that it 
will move in a longitudinal direction along the axis of the pipe RO. What 
is, thus, involved is a thrusting process, i.e., an attack of the flowing 
agent at every wave crest of the wave-like or serpentine structure of the 
cable. 
The employment of a piston or the like at a remote cable end is not 
necessary with the present method. Such a draw-in aid of a piston or an 
enlarged end would also involve the disadvantage that it could easily 
become blocked, for example at narrow locations, which is not the case 
given a remote cable end that is simply cut smooth and is not thickened, 
as in the present invention. A simple protective cap that prevents an 
impaling or unsplicing of the cable is adequate at the remote cable end. 
This shoot-in event is not significantly impeded or influenced by the 
cables that are already drawn-in or shot-in. It is expedient to shoot-in 
optimally uniform cables. The cables should also be adequately flexible so 
that the turbulent flowing agent can bring them into the wave shape and 
can, thus, move them forward. A longitudinal pull, for example with a 
piston at the start of the cable, would stretch the cable and, thereby, 
eliminate the wave shape and prevent a "quantized feed" by the attack or 
engagement of the turbulent flow on the wave crest. 
After the draw-in process, the entry location of the respective entry 
cable, for example the channel EC2, can be additionally sealed. This will 
prevent the penetration of water into the laid cable pipe. In this case, 
it is also expedient to seal a remote pipe end FE of FIG. 3 of the pipe 
line path ROS in a corresponding fashion, for example with an appropriate 
sealing compound of bitumen. By contrast, the remote pipe end FE (see FIG. 
1) is maintained open during the actual drawing-in process whereby the 
near pipe end NE is closed by the pressure cap PC. 
After the draw-in of the plurality of cables CA1-CAn and after the 
conclusion of the drawing-in process, an overall structure similar to the 
illustrations of FIG. 2 will occur. The optical cables CA1-CAn lie on the 
floor of the pipe RO. In order to improve the clarity of the illustration, 
that region of the optical cables CA1-CAn is omitted, however, the 
respective ends would proceed through the given entry channels to the 
illustrated position of the optical cable CA1-CAn with a slight bending 
arc (see cable CA2 of FIG. 1 as an example). 
Although various minor modifications may be suggested by those versed in 
the art, it should be understood that I wish to embody within the scope of 
the patent granted hereon all such modifications as reasonably and 
properly come within the scope of my contribution to the art.