Method for the coating of sewer pipes including apparatus for carrying out the method

A method as well as a respective apparatus for lining pipes and ducts are suggested, wherein a flexible tube is introduced in turning up manner into a pipe having respective openings at the pipe access end and the pipe terminal end. Here, prior to the turning up operation, a traction means is led through the flexible tube and the pipe and is secured to the flexible tube access end, wherein the flexible tube with the terminal end of the flexible tube is joined to the pipe access end and the traction means is automatically or distance-controlled pulled from the pipe access end by means of a motor winch. Here, the pipe by using turning up the flexible tube is lined therewith. The method is particularly suited for lining pipes and ducts having a plurality of pipe bends or angles.

The present invention relates to a method for lining pipes and ducts, 
wherein a flexible tube is introduced in turning inside out manner into a 
pipe having respective openings at the pipe access end and pipe terminal 
end as well as an apparatus for carrying out the same. 
With well known methods which are carried out with apparatuses according to 
the prior art, here, before turning up operation a traction means is led 
through the flexible tube and the pipe and is secured to the flexible tube 
access end, the flexible tube having a flexible tube terminal end is 
joined to the pipe access end and the traction means is pulled from the 
pipe terminal end with a manually operated winch by an operator, wherein 
the pipe using the turning up operation of said flexible tube is lined 
therewith. 
A disadvantage of the prior art is the high personnel effort, since in the 
regular case in addition to the personnel being situated at the pipe 
access end and, for example, watching a drum for the introduction of the 
flexible tube, personnel for pulling the traction means is required at the 
pipe terminal end as well. In addition, it is a problem to communicate 
between the personnel at the pipe access end and pipe terminal end, which 
has to be ensured by shout or walkie-talkies. Poor coordination between 
the personnel for pulling the traction means at the pipe terminal end and 
the personnel for controlled ceasing down and pressing in the flexible 
tube at the pipe access end can result in an impairement of installation 
safety of the flexible tube within the pipe. In particular, the 
installation safety could be limited with a highly wound and buckled pipe 
course, since particularly in these cases, high controlled pulling the 
traction means, which is adapted to the respective pipe curvature in order 
to enable a perfectly lining the pipe with flexible tube, without 
resulting for example a damage and a fracture of the traction means. 
Starting from this prior art, it is the object of the present invention to 
provide a method for lining pipes and ducts and an apparatus for carrying 
out the same, which ensures a high installation safety of the flexible 
tube with low personnel effort and thus reduced cost. 
This object is achieved with respect to the method by claims 1 and 2 as 
well as with respect to the apparatus by claims 13 and 14. 
By respective automatic and distance-controlled pulling the flexible tube 
from the pipe terminal end, at this pipe terminal end personnel is 
absolutely not required. Having an automatic motor winch at the pipe 
terminal end such motor winch, for example, may operate with a 
characteristic curve (for the tension force or tractive speed) matched for 
the requirements of the pipe to be lined. Here, lining the pipe may take 
place based on a previously determined characteristic curve matched for 
pipe relations. Moreover, the automatic motor winch may be additionally 
equipped with measuring devices for the tractive force and tractive speed, 
respectively, and in accordance with these measurement results the 
automatic motor winch may pull said traction means with a respective 
tractive speed and tractive force, respectively. Here, for example with 
passing the pipe contractions and pipe bends, respectively, the tractive 
force is correspondingly, increased by the "turning up front" of the 
flexible tube to be lined. 
With a remote controlled motor winch, said motor winch can be controlled 
for example from the region of the pipe access end by a single person that 
observes flexible tube ceasing down into the pipe access end such that 
matching problem introductorily described are avoided. 
The winch according to the invention is not only limited to the application 
in pipes having circular cross-section but is also possible in ducts 
having a different cross-section such as an ellipsoidal cross-section. In 
addition, application is not limited to the pressurized turning up method 
explained above, automatic and remote controlled pulling a flexible tube 
is also enabled with such a motor winch. 
Advantageous aspects of the present invention are described in the 
dependent claims. 
A basic modification of the present invention provides for the flexible 
tube to be filled inside with adhesive such as epoxy resin prior to the 
turning up operation, the traction means to be led through the flexible 
tube and said pipe and to be secured to the flexible tube access end, the 
flexible tube having the flexible tube terminal end to be annularly and 
gastight joined to the pipe access end and a pressure medium to be led 
from the interior of the pipe upon the annularly fixed position of the 
flexible tube and the traction means to be automatically or 
distance-controlled pulled from the pipe terminal end. Here, introducing 
under pressure the flexible tube can advantageously be applied from a 
travelling pressure container in which interior the folded flexible tube 
is wound on a drum. With pulling the traction means according to the 
invention such as a flexible tube or a rope, the pressure for the turning 
up advance of the flexible tube inside the pipe can significantly reduced. 
This leads to a significant increase of the installation safety according 
to the invention. 
A particularly advantageous aspect of the present invention provides a 
retaining means such as in form of a rope or belt extending in the 
opposite direction of the traction means to be existed at the flexible 
tube access end, wherein the other end of the retaining means is 
controlled maintained under tension and eased down in the surroundings of 
the pipe access end by a retainer, which for example is within said 
pressure container mentioned above, for controlling the speed of the 
lining operation. With this modification of the invention, a complete 
control of the flexible tube within the pipe is enabled, since both from 
the pipe access end and from the pipe terminal end the advance of the 
flexible tube can be controlled by means of the elongated pulling and 
retaining means, respectively. 
Another advantageous aspect provides the traction means pulled out of the 
pipe terminal end to be wound on an exchangeable throw-away drum secured 
to the motor winch. During filling the flexible tube with adhesive prior 
to turning up a complete coverage of the traction means with adhesive 
results. Thus the wound traction means is also encompassed with adhesive. 
In order to save a lavish and expensive cleaning of the motor winch, it is 
hence advantageous to construct the drum of the motor winch as a 
throw-away winch to be simply joined (such as with a plug-type connection 
to be joined without any tool), which can be easily disposed after winding 
the traction means. Here, it is also advantageous for an excess adhesive 
to be stripped of the traction means and to be collected within drain off 
means provided thereto such as a collecting basin or outlet. Another 
advantageous development of the invention provides that a shaft-shaped 
deflection device is provided between the pipe terminal end and the 
winding means such as the throw-away drum, upon which the traction means 
slides down under deflection. It is ensured with it, having narrowed space 
relations in the region of the pipe terminal end, the traction means being 
led out of the pipe terminal end, is firstly deflected such that the motor 
winch has not to be mounted directly aligning toward the pipe terminal 
end. In addition, thus a particularly suitable position of the shaft of 
the take-up drum such as horizontally to the ground surface can always be 
realized. 
A further particularly advantageous development of the invention provides 
the control of the motor winch to be achieved from the region of the pipe 
access end. This may occur such as by means of an operator control panel 
having displays of the tractive speed and tractive force of the motor 
winch, an accompanying monitoring of said motor winch is enabled such as 
by means of a video camera arranged in the region of the motor winch, 
wherein a monitor connected to said video camera is mounted in the region 
of the pipe access end for monitoring the motor winch. With occurring 
difficulties such as a slowing-down of the lining operation, the tractive 
force of the motor winch, for example, can be increased and lowered again 
with a defined characteristic curve by means of a switch inside the 
operator control panel. 
Further advantageous developments of the present invention will be given in 
the remaining dependent claims.

FIG. 1 shows the flexible tube 2 having a flexible tube access end 2a and a 
flexible tube terminal end 2b as well as the pipe 1 being partly bent with 
a pipe access end 1a and a pipe terminal end 1b. The traction means 3 such 
as a rope or a belt, is led through the flexible tube 2 and being fixedly 
located to the flexible tube terminal end 2a. The traction means 3 can be 
constructed as a belt and may be formed of similiar material as the 
flexible tube 2, since it should be flat collapsibel along with the 
flexible tube 2 and is allowed to be rolled up upon a spool and drum 15, 
respectively (see FIG. 2a). 
The traction belt 3 can be arranged such as with a projectile shaped needle 
into the flexible tube 2, with the rear portion of the needle has a 
slightly reduced cross-section and is connected to said traction belt. 
Then the needle is introduced inside the traction belt, wherein said 
traction belt is Compressed from outside at the rear portion of the needle 
by means of a pair of nip rollers and the needle within the traction belt 
is forwardly forced by transferring said nip rollers in the respective 
rotational movement. An adhesive may be deposited upon the inner surface 
of the traction belt such as by means of inclusion a great amount of 
adhesive at the one end of the lining and by squeezing between the nip 
rollers. The traction belt 3 is pressure sealed clamped at the flexible 
tube access end 2a such as by means of a suitable clamp, wherein the 
flexible tube access end 2a is pressure sealed strapped together. 
A retaining means 8 such as a belt or rope as the traction means 3 is also 
clamped at the flexible tube access end 2a (traction means and retaining 
means may be configured from the same material and throughout). For 
example, the retaining means 8 and the flexible tube 2 starting with the 
retaining means 8 are rolled up upon the drum 15 (see FIG. 2a). The 
portion of the traction belt 3 protruding from the flexible tube 2 is at 
least as long as the whole pipe length from the pipe access end 1a to to 
the pipe terminal end 1b. This portion of the traction belt 3 may be blown 
such as by means of compressed air from the pipe access end 1a towards the 
pipe terminal end 1b and may be put there on the motor winch 4. 
FIG. 2a shows an arrangement according to the invention at the begin of a 
lining operation. As previously described above, prior to the turning up 
operation, the turned up flexible tube is filled inside with adhesive, a 
traction belt is led through the flexible tube and the pipe and is secured 
to the flexible tube access end. In addition, a retaining belt 8 is 
arranged at the flexible tube access end, and the other end of the 
retaining belt is secured to the shaft of the rotary drum 15 and 
subsequently the retaining means 8 and flexible tube 2 are rolled up on 
the shaft of the drum 15. By means of a pressure sealed clamping device 29 
the flexible tube terminal end 2b is secured pressure sealed to the pipe 
access end 1a. With this, the end of the flexible tube, which annularly 
embraces the pipe access end 1a, is plonked on the pipe access end 1a and 
a reducer, respectively, connected to the pipe access end. The drum 15 is 
located in the interior of a pressure sealed container 16, in which a 
pressure medium 6 can be introduced. By introducing a pressure medium 6 
into the pressure container 16 pressure is applied on the annularly fixed 
position 7 of the flexible tube such that the flexible tube 2 turns inside 
out starting in the region of the clamping piece 29 and proceeds inside 
the pipe as shown in FIG. 2b. 
The advance of the flexible tube 2 and its turning up front 30, 
respectively, substantially occurs by introducing the pressure medium 6 
into the pressure container and the inner space of the flexible tube 
gastight connected thereto (the flexible tube access end 2a is pressure 
sealed clamped), and is preferably supported with running through the pipe 
bends by the tractive force of the motor winch 4. The motor winch 4 is 
substantially stationary arranged within the region of the pipe terminal 
end 1b and comprises a control means 11 for automatic or 
distance-controlled controlling of the motor winch 4. In FIGS. 3 and 5 it 
will be gone into more detail of the motor winch, which winds the pulled 
traction belt 3 upon a drum. The control means 11 include a device for 
detecting the speed of the traction belt 3 in the region of the pipe 
terminal end 1b. Detection of speed can be carried out, here, with the 
rotational speed of the winding drum of the motor winch 4 or in other ways 
such as in an optical manner (using application of indicia on the traction 
belt 3). In addition, the control means and control device 11, 
respectively, comprises a device for detecting the tractive force F, by 
which the motor winch 4 pulls the traction belt out of the pipe terminal 
end 1b. Controllling the motor winch 4 can take place in various ways 
either automatically or distance-controlled. With an automatic control of 
the motor winch, characteristic curves previously determined, for example, 
can be set in advance by the control device 11, which depend on the pipe 
parameters determined prior to the lining operation. For example, thus the 
tractive force of the motor winch can be pre-determined on the traction 
belt 3 protruding from the pipe terminal end such that the tractive force 
decreases with an increasing proceeding of the turning up front 30 towards 
the pipe terminal end 1b. At the beginning of the lining operation, for 
example, the tractive force can amount to 200 N and merely 50 N at the end 
thereof. This decrease of the tractive force is the result of the traction 
belt to comprise friction with the pipe wall at more positions at the 
beginning of the lining operation than at the end thereof. 
Friction is particularly increased in the region of curvatures 31, that is 
in interfaces 32 between the pipe wall and the traction belt 3. Obviously, 
it is also possible to pre-determine a characteristic curve of the speed 
set in advance. Thus, for example, a winding speed and tractive speed of 4 
to 12 meters per minute can be set in advance by the control device 11. 
This corresponds to a speed of the turning up front 30 of 2 to 6 meters 
per minute. This proceeding speed of the turning up front 30 is only half 
as high as the winding speed of the traction belt 3, since the flexible 
tube access end has merely to pass the pipe length in the same time 
interval, whereas the traction belt has to travel a double length (length 
of the flexible tube plus length of the pipe). 
Besides fixed guidelines for the tractive force or tractive speed of the 
motor winch 4 the automatic control thereof by said control device 11 can 
also take place based on the values measured during the lining operation. 
Thus, for example the speed of the traction belt can be constantly 
measured, and with remaining under a limit speed, the tractive force of 
the motor winch can be continuously increased such that a pre-determined 
value for the speed adjusts. On the contrary, it is possible for the 
tractive force within the traction belt, for example, to be determined by 
a control device associated with a force measuring device and the speed of 
the traction belt 3 and the rotational speed respectively, of a take-up 
drum of said motor winch 2 is regulated in a manner, that a pre-determined 
characteristic curve of the tractive force is maintained. 
With this automatic control, playing together of the traction belt 3 and 
retaining means 8 is substantially as well. The shaft of the rotary drum 
15 provides a not shown drive as well as a not shown brake for controlling 
the rotational speed of the drum 15. This brake and drive are controlled 
by a retainer 9, which is regulated through an operator control panel 
received in the region of the pipe access end 1a. 
The retainer of the drum 15 is connected to a control device of the motor 
winch 4. Here, the retainer controls the brake and drive of the drum such 
that the retaining means 8 is continuously under tension during the lining 
operation. As a result of connecting the retainer as well as the control 
means 11 to each other by means of lines for data transfer, the continuous 
control of the position of the flexible tube access end 2a is always 
enabled. This connection also permits, that both the retaining means and 
the traction belt are allowed to be maintained under tension and be eased 
and pulled in continuously controlled manner. With regular proceeding of 
the turning up front 30, hence ceasing the retaining means is always as 
much as the traction belt 3 is pulled by the motor winch 4. This 
comprehensive control appears for example such that with the relieve of 
tension within the traction belt 3, which is detected by the control 
device 11, either the rotational speed of the winch is increased or a 
respective signal is transmitted to the retainer, which is to increase the 
tension within the retaining means by actuating the brake of the shaft of 
the rotary drum 15 such that the tension within the traction belt 3 
accordingly increases. 
In place of the above described automatic control of the motor winch 4 and 
rotary drum 15, respectively, a manual control is also possible in 
accordance with display instruments. Control device 11 comprises an 
operator control panel 27 connected to cable 28. The operator control 
panel 27 which is considered in more detail further below comprises a 
display of the tractive force in the traction belt 3 as well as a display 
of the speed of the traction belt 3 and rotational speed of a take-up 
drum. Displaying the tractive force takes place in accordance with a 
tractive force measuring instrument disposed on the motor winch 4 and 
displaying the rotational speed takes place in accordance with a 
rotational speed measuring instrument of a driving motor disposed on the 
motor winch 4. 
In an alternative aspect the operator control panel 27 is allowed to be 
connected to other members of the control device via radio link (in place 
of the cable 28). Thus, for example, operating the motor winch from the 
region of pipe access end 1a can continuously take place by means of the 
operator control panel 27. Hence, this operator control panel is 
constructed as a single-hand control such that the retainer 9 can be 
operated with another hand of an operator. In addition, camera 25 being 
directed upon the motor winch 4 is connected via cable to a monitor 26, 
which is received in the region of the pipe access end 1a. With this, 
complete monitoring the motor winch 4 beyond the monitoring by tractive 
force and speed displays of the operator control panel 27 is enabled. 
FIG. 3 shows a detailed view of the motor winch 4. Motor winch 4 comprises 
a mounting plate 33, which is connected to the ground by supports being 
not shown. The height of the mounting plate 33 should be in the same 
height as the pipe terminal end 1b such that the traction belt 3 is 
allowed to run horizontally. With this, two sustainers being not shown, 
which can be clamped, are allowed to be raised from the mounting plate 33 
to the mine floor. For greater heights telescopically extendible supports 
are to be provided. 
A plastic spool 10 is disposed on the over-mounted shaft 34 of the motor 
winch. Prior to the lining operation, firstly a slot is sawn into the 
plastic spool 10 representing a take-up drum, traction belt is pulled 
through the slot and knotted up such that a tensile support of the 
traction belt on the plastic spool 10 is ensured. Preferably, the used 
traction belt has a width of approximately 1/3 to 2/3 of the diameter of 
the flexible tube and a height of 1 mm (this is also intended for the 
retaining belt). The over-mounted shaft 34 is connected to a gearing 18. 
This gearing comprises a forward running and an oppositely reverse motion, 
wherein with forward running the motor winch pulls the traction belt 3 out 
of the pipe 1. Gearing 18 is self-locking and connected to a direct 
current electric motor 17, which comprises a voltage supply 17'. The 
electric motor 17 is controlled by a control device 11 as previously 
mentioned above, which also includes an operator control panel 27. The 
traction belt pulled from the pipe terminal end 1b is pulled through a 
rectangular guide window 19a being in the plane perpendicularly to the 
longitudinal shaft of the traction belt, which is connected to the 
mounting plate 33 via a guide rod 19b. In front of the guide window 19a 
adjacent to the respective flat sides of the traction belt 3 rubber lips 
are disposed, which strip a part of the adhesive from the traction belt 
and allow to drain it off into a container not shown, which is disposed 
below. The guide 19 as well as the stripping device not shown serve to the 
adhesive poor and purposeful winding the traction belt 3 on the plastic 
spool 10. 
The traction belt and the retaining belt are preferably formed of a smooth 
material, e.g. polyester and polyester silk, respectively, having 
thermally surface treatment. To minimize friction, the belt is 
particularly narrow braided and coated in case. 
The use of a high slidable belt is particularly advantageous for some 
reasons with lining pipe bends. By virtue of a smooth belt surface, 
firstly friction between the belt and the pipe (such as at the interfaces 
32) is minimized. In addition, "slitting" into the flexible tube material 
with a flexible tube damage resulting therefrom, such as it occurs with 
the use of ropes with lining of curvature regions, is prevented. 
The plastic spool 10 is merely pinned up on the over-mounted shaft 34. The 
plastic spool 10 is pinned up to a stop member 34 of the over-mounted 
shaft 34 and is secured by means of a cotter pin. After lining the pipe, 
the traction belt 3 is cut through and the attachment of the traction belt 
at the flexible tube access end 1a is released, respectively, and the 
plastic spool 10, which has received the entire traction belt is pulled 
off from the over-mounted shaft 34 by releasing the cotter pin 35, and is 
disposed. Obviously, another fastening methods for the spool 10 are 
possible according to the prior art (such as snap-in connections), it is 
merely important for the plastic spool 10 to be easily exchangeable. 
The mounting plate 33 is also connected to a pipe clip via telescopic arms 
23. The pipe clip 21 is matched for the diameter of the pipe 1 to be lined 
and is pinned up thereon. Axial attachment takes place via screw handles 
22 radially arranged, which are rotatable in the threaded through holes 
disposed in the circumferential direction of the pipe clip. With rotating 
the screw handles pressure is exerted upon the pipe terminal end 1b such 
that the pipe clip 21 is axially fixed on the pipe. 
With the embodiment shown in FIG. 3, a pulser is disposed on the 
over-mounted supported shaft 34 which is associated with the control 
device 11 and measures the rotational speed as well as the rotational 
direction of the over-mounted supported shaft. Thus, with a known spool 
diameter the absolute speed of the traction belt 3 can be easily 
determined, as well. Alternatively, a direct determination of the 
translational speed of the traction belt 3 pulled from the pipe terminal 
end 1b such as by means of optical methods is enabled. The tractive force, 
by which the traction belt 3 is pulled out of the pipe 1 can be measured 
by means of force transducers determining the bar tension inside the 
supports 23. Alternatively, it is possible to determine the tractive force 
by the load of motor 17. 
FIG. 5 shows a section from a further embodiment of a motor winch 4 
according to the invention. Here, parts not shown are identical with the 
device from FIG. 3. 
The traction belt 3 pulled out of the pipe terminal end 1b is led here via 
a shaft-shaped deflection device 20, wherein the 
traction belt is rectangularly deflected. The traction belt then travels 
two rubber lips 14 adjacent to the traction belt, which strip adhesive 
from the traction belt 3 and allow to drain it off into collecting basins 
and outlets, respectively. Past the stripping device the traction belt 3 
travels a guide 19', which comprises two by two respective rectangularly 
disposed rolls, wherein the axes of the four rolls are perpendicularly 
disposed with respect to the longitudinal direction of the traction belt. 
Thereafter, the traction belt 3 is rolled up on a cardboard sleeve 10', 
which is disposed on an over-mounted shaft 34 being perpendicularly with 
respect to the earth's surface. To avoid pollutions of the drive unit 
(electric motor 17, gearing 18) disposed below the cardboard sleeve 10', a 
plate-like paper rest 10' is arranged. 
The motor winch is configured such that the length of the traction belt to 
be wound is 60 m on average (however, significantly greater lengths of the 
traction belt are also possible). During the winding operation, the winch 
pulls at the traction belt with an adjustable force of mostly 50 to 300 N 
(on the average 100 N). At the beginning of lining hence the winch has to 
operate with a higher tractive force, in order to overcome the increased 
friction by the contact of the traction belt with the inner pipe wall, 
which particularly increasingly occurs inside the pipe bends. When the 
turning up front 30 of the flexible tube 2 reaches a pipe bend, the 
tractive force of the winch has to be momentarily increased up to 500 to 
1000N, in order to overcome the increased friction and turning up forces, 
respectively. However, it is to be considered, that these high tractive 
forces are only applied momentarily and with a defined increase as well as 
a defined decrease since the rapture limit of the traction belt is indeed 
significantly above 1000N, however the tension strength can be influenced 
by chafing the traction belt inside the pipe bends. 
FIG. 6 shows a graph for momentarily increasing the tractive force as can 
be manually triggered by a circuit breaker on the operator control panel 
27. Within one second, hence the tractive force of the motor winch 4 is 
constantly increased from 100N to 1000N, and is reduced within another 
second from 1000N to 100N. Gradually increasing and decreasing the 
tractive force, on the one hand, ensures a careful treatment of the 
traction belt and, on the other hand, safe travelling of the turning up 
front 30 through the pipe bends. 
In addition, the flexible tube access end 2a can get jammed at the reducing 
fitting and the pipe access end 1a (i.e. in the region of the "inversion 
head"). When approximately half of the flexible tube 2 is travelled inside 
the pipe 1 to be redeveloped the connection position of the flexible tube 
2 and traction belt 3 leaves the pressure container. With this, a 
standstill of the flexible tube may result at the narrow location. In such 
a case, momentary manual increasing the tractive force is to be performed 
according to FIG. 6. 
Another interfering possibility is in that the traction belt 3 get jammed 
by the flexible tube, that is, passing between the flexible tube and pipe 
wall. This particularly happens when the traction speed of the motor winch 
4 is too low. Such a jamming is apparent in that the motor winch does not 
rotate although the flexible tube 2 still further penetrates into the pipe 
(this is apparent with rotating of the drum 15). In this case, the 
rotational direction of the drum 15 is to be inverted by means of the 
retainer 9 such that the flexible tube is partly pulled back into the 
pressure container 16. with releasing the jammed traction belt an increase 
of the tractive force of the traction belt 3 results towards the pipe 
access end 1a. This tractive force increase is detected by a sensor 
associated with the control device 11 and displayed to the operator on the 
operator control panel 27. Subsequently, the drum 15 is automatically and 
manually stopped, respectively, by the operator and the normal lining 
operation can be continued as described above. 
A completion of the lining operation takes place with a switch off device 
which is not illustrated in more detail. This includes a switch off sensor 
disposed within the region of the pipe terminal end, which detects the 
flexible tube escaping from the pipe terminal end. This switch off sensor 
may be constructed as a light barrier or mechanical switch (during pipe 
escaping the flexible tube pushes against the mechanical switch). The 
switch off sensor gives a signal to the retainer which stops the drum 15. 
Alternatively to the automatic completion an alert on the operator control 
panel 27 is possible for a later manual completion. 
FIG. 4 shows a detailed view of the operator control panel 27 for 
controlling and monitoring the operations as described above. This 
comprises a circuit closer and circuit breaker 37, lamps for displaying 
the present operation mode (Ready, Belt loose, Error, Belt end), a switch 
"Forward" 38 for pulling the traction belt out of the pipe terminal end 
1b, a switch "Rearward" 39 for ceasing the traction belt 3 into the pipe, 
a switch "STOP" 40 for stopping the operation of the motor winch 4 as well 
as a switch "Forward fast" 12 for momentary manual increase the tractive 
force as shown in FIG. 6. The operator control panel further comprises a 
rotary potentiometer 44 for adjusting the tractive force of the traction 
belt 3 (range of tractive force from 50 to 1000N). A respective tractive 
force display, which displays tractive forces of 50N to 1000N in a 
logarithmic manner by means of different coloured light emitting diodes, 
is indicated with numeral 41. A corresponding luminuous band composed of 
LED-diodes is provided for the rotational speed as well (reference numeral 
42), wherein the left four LED-diodes indicate rearward oriented 
rotational speeds. In addition, the operator control panel 27 comprises an 
"Emergency Off Switch" 43. It turned out, that the display of the tractive 
force and speed, respectively (rotational speed of the traction belt 3) 
preferably takes place by means of these luminuous bands, since they 
permit a faster detection of the importance of measured values by the 
operating personnel than alphanumeric displays enable.