Device for connecting a draining and/or insulating screen within a trench

A sliding box for placing a film of insulating or draining material within a trench has a front section for receiving a roll of film and a rear section for delivery of the film into the trench. Between the front section (2) and the rear section (13), the box has a connecting chamber (4) provided at each end with a pair of rollers (5-6, 7-8) mounted within said chamber by means for varying the lateral spacing of the rollers of one and the same pair between an active position in which the two rollers grip the film (3) and a position of relative withdrawal in which the film passes freely between the rollers.

The invention relates to the operation which consists in placing filtering 
or insulating material in the form of a thin film within a trench dug in 
the ground and more particularly to the problem of connection between two 
successive films when the reel from which the film is unwound into the 
trench is located within the trench itself. 
In French patent No. 2,000,531, there is described a method of placing a 
film of this type within a trench by means of a vertical drum which 
carries the roll of film introduced in the trench at the rear of the 
excavating machine which is digging the trench, the film being directly 
unwound at its service location as the excavator moves forward. 
In Dutch patent No. 82.04737, there is described a "cassette" containing 
the roll of film and constituting a box which is displaced in sliding 
motion at the rear of the excavating machine. The box has the double 
function of guiding the film as it is being unwound and of maintaining the 
opening of the trench while the unwinding operation is in progress. 
A problem presented by this type of technique is the connection between two 
successive films and in particular the maintenance of water-tightness in 
the zone of junction between two successive films. 
This problem is solved in accordance with the invention by the fact that 
the sliding box which contains the roll of film has an extension in the 
form of a connecting chamber provided at the ends thereof with two pairs 
of rollers synchronized in pairs and mounted on devices which are capable 
of varying the lateral spacing between two rollers of any one pair between 
two positions, namely a position of maximum spacing in which the film 
passes freely and a gripping position in which the film is driven by the 
two rollers of one and the same pair. 
Thus at the time of laying of a roll of film as the excavating machine is 
traveling forward and pulling the film-laying box which is displaced in 
sliding motion within the trench, the film can pass freely from the 
magazine to the exit zone of the box through the connecting chamber. 
When the film supply magazine is empty, the machine is stopped, a fresh 
reel is placed within the magazine whilst the pair of rollers located near 
the exit of the box within the connecting chamber has gripped and 
immobilized the end of the previous film and the pair of rollers located 
near the magazine draws the starting portion of the following film towards 
the end of the previous film. A special connecting member is then 
introduced into the connecting chamber and securely joins the two film 
ends together. 
After this operation, both pairs of rollers of the connecting chamber can 
be withdrawn so as to allow the film to pass freely and thus to permit 
continuation of the film-laying operation as the excavating machine 
travels forward. 
By making use of simple means, the invention accordingly makes it possible 
to work practically continuously and essentially to carry out film repairs 
during a laying operation in the event of any damage to the film. 
This possibility of carrying out repairs or other work on the film within 
the trench permits the use of the method in trenches of substantial depth 
(over six meters), which had been out of the question up to the present 
time.

Machines for digging trenches and laying a draining or insulating screen 
are well known. They usually consist of a caterpilllar designed to carry 
an orientable excavating chain or of a tractor which draws a trenching 
wheel, the entire assembly being followed by a box which is intended to 
slide within a trench in order to lay an insulating or draining film or a 
perforated pipe forming a drain at the bottom of a building pit and to 
discharge draining materials such as sand-gravel mixture, porous concrete 
or bentonite. 
Machines of this type are well known and will therefore not be described in 
greater detail or illustrated in the accompanying drawings. The present 
description will be essentially concerned with the structure of the 
sliding box, whether the box is hitched or not to the rear of the 
excavating machine. 
In accordance with the invention, the sliding box has a structure made up 
of three sections: a front section constituting a loading magazine for the 
film to be unwound, an intermediate section or so-called connecting 
chamber and a rear section constituting the zone of delivery of the film 
into the trench. 
FIGS. 1 to 8 illustrate diagrammatically one example of execution of a 
connecting operation by means of a box in accordance with the invention. 
In this example, the front section 2 of the box 1 constitutes a receiving 
chamber for a roll 3 of film mounted vertically within the box. The roll 
of film 3 is for example mounted to rotate freely on a mandrel carried by 
bearings, one bearing being located at the bottom of the box and the other 
bearing being located at the top. The top bearing is preferably removable 
so as to permit introduction and withdrawal of the rolls. Advantageously, 
when the roll of film 3 is in position within the magazine 2, the magazine 
is closed by a centering frame which ensures uniform and rectilinear 
unwinding of the roll of film. 
At the exit of the magazine 2, the side walls of the box 1 become narrower 
and constitute a connecting chamber 4. At the entrance of said chamber 4, 
two vertical rollers 5 and 6 which can be motor-driven are mounted in 
bearings so as to be capable of lateral displacement towards each other, 
for example under the action of jacks (not shown), while at the same time 
rotating about their own axes. If they are motor-driven, the two rollers 5 
and 6 are contrarotating and synchronized so that, when they are applied 
against the film 3, their respective movements do not produce any 
undesirable tension on said film but only a uniformly rectilinear traction 
in the direction of the exit of the box. 
At the rear end of the chamber 4, a second pair of rollers 7 and 8 which is 
identical with the first and mounted in the same manner also serves to 
impart motion to the film 3. 
In FIG. 2, the rollers 5-6 and 7-8 are illustrated in the form of a set of 
rollers juxtaposed on a common shaft with interposition of bearings 
between the rollers of one and the same shaft. 
By way of alternative, the rollers of any one shaft can be separated by 
collars which are placed around the shaft and serve to mount the shaft on 
jacks rigidly fixed to the wall of the box. 
It is understood that, when they are in the withdrawn position close to the 
box wall which carries them, the rollers 5 and 6 are inactive and allow 
the film 3 as well as any overthickness which may technically be necessary 
to pass freely between them. 
When they are applied against each other on each side of the film 3, said 
rollers have the function of guiding and/or displacing the film in the 
direction of the box exit. 
A servocontrol system permits either joint or separate operation of the two 
pairs of vertical rollers 5-6 and 7-8. The rollers 5, 6, 7, 8 are normally 
vertical in the work position. It may prove useful, however, to allow them 
to assume an oblique position, especially when it proves necessary to 
compensate for differences in stretching of the film between its top 
portion and its bottom portion within the trench. 
To this end, in accordance with an advantageous alternative embodiment of 
the invention, the rollers 5, 6, 7, 8 are each mounted on a beam which is 
in turn pivotally mounted on a horizontal shaft located at the bottom of 
the box and means are provided for locking each beam individually in a 
plurality of different positions according to the work site requirements. 
In FIG. 2, there is shown in chain-dotted lines an oblique position of the 
roller 5 and the arrows show the directions of possible pivotal 
displacements of the rollers 5-6 and 7-8 on each side of the vertical. 
The exit of the chamber is closed by a transverse partition-wall 9 provided 
with a vertical slot 10 of sufficient width to provide a free passageway 
for the film 3 and for connecting means employed for joining two 
successive films together as will be described hereinafter. 
The two edges of the slot 10 are provided with flexible lips 11 and 12 
which ensure that the connecting chamber 4 is sealed, especially against 
penetration of water or mud which may be present within the trench. 
At the rear of the connecting chamber 4, the box 1 has an exit zone 13 
advantageously comprising a deflecting flap 14 pivotally mounted on a pin 
15 located on either of the two side walls of the box. This deflector 
ensures that the film 3 is correctly applied on the edge of the trench. 
The exit zone 13 can advantageously be fitted with a guide 16 for downward 
transfer of a drainage header-pipe and with a hopper 17 for discharging 
bulk material into the trench. 
The sliding box in accordance with this first example of construction 
operates as follows: 
When a fresh roll has been placed vertically on its bearings within the 
magazine 2, the starting end of the film 3 is passed between the first 
pair of rollers 5-6. These rollers are placed in contact with the film 
which is then transferred towards the exit zone. The film 3 then passes 
between the second pair of rollers 7-8. These rollers are in turn placed 
in contact with the film and cooperate with the first pair so as to ensure 
correct unwinding of the film by very uniform and rectilinear guiding 
and/or driving action. 
When the end of a film is reached, the movement of the film as the end 
portion passes between the first pair of rollers 5-6 is detected for 
example by means of a warning band which is integral with the end portion 
of the film. By way of example, the warning band can consist of a metallic 
strip which is intended to pass in front of a light or sound alarm system 
and to actuate the system. More simply, it can be a colored band which 
gives a visual indication of the end of a film. 
The machine is then stopped and the first pair of rollers 5-6 is caused to 
separate in order to permit positioning of a new reel within the magazine 
2. 
The starting end of said reel is passed between the first pair of rollers 
5-6 and said rollers 5-6 are drawn together in order to grip and displace 
the starting portion of the new film to the vicinity of the end portion of 
the previous film. This end portion has been maintained in readiness 
within the chamber 4 by the second pair of rollers 7-8 which had been 
immobilized at the time of detection of the end-of-reel signal. 
Connection between the two end portions of the film 3 is carried out by 
means of special connecting members inserted vertically within the 
connecting chamber 4. 
In the example illustrated in FIGS. 1 to 8, each end portion of the film 3 
is provided with a vertical rod 18 or with a beaded edge which forms a 
bearing element for the connecting member 19. 
Said vertical rod can be molded in one piece with the edge of the film or 
mounted separately within a gusset formed by folding the film around the 
rod and bonding the pleat as shown in FIG. 9. 
The connecting member 19 shown in cross-section in FIG. 10 is a sectional 
member of molded or injected material having two oblong cavities 20 and 21 
which open at their opposite ends into a slot 22, 23 through which the 
film 3 is intended to pass. The cavities 20 and 21 have a sufficient depth 
to permit easy engagement of the connecting member 19 over the two end 
rods 18 of the two successive films. 
Once this operation has been completed, the two films are put in tension by 
driving the two pairs of rollers 5-6 and 7-8 in opposite directions. The 
empty space of each cavity may be filled if necessary by injection of a 
sealing product such as bentonite or fast-setting polymer. 
As an advantageous feature, the vertical sectional member has a central 
cavity 24 located between the two cavities 20 and 21 and provided over its 
entire length with radial ducts which open into the cavities 20 and 21. 
Said central cavity is intended to be used for injection of the sealing 
product. 
When the sealing product has completely set, the pair of rollers 7-8 which 
is close to the rear zone of the box is separated in order to allow the 
connecting member 19 to pass through, whereupon the rollers are re-applied 
against the film 3 and the film-unwinding operation is resumed. 
In an alternative embodiment of the invention as shown in FIGS. 11 to 14, 
the film is not provided with any terminal rod or beaded edge, or else the 
connection is made as a result of rupture of the film 3. 
In this case, when driving of the pair of rollers 7-8 has stopped, the two 
end portions of film 3 are superposed with a substantial overlap. 
Two male-female members 25-26 having concordant sets of teeth along their 
plane of contact and provided with a central recess 27 which forms a 
housing for a key 28 are positioned on each side of the film 3 and 
maintained applied against each other, for example by means of claws 
provided within the connecting chamber 4. A cutting tool is lowered into 
the central recess 27 in order to cut the overlapping portion of the 
screen 3. A key 28 having a shape corresponding to that of the recess 27 
is placed in position and serves to lock the two members 27 and 26 
together and to grip the two ends of the film 3. 
By way of alternative, the key 28 has a central recess for the injection of 
a sealing product. 
As in the preceding embodiment, the rollers 7-8 are drawn apart in order to 
allow the connecting member 25-26 to pass through them, then again placed 
in contact for further unwinding of the film. 
As will be readily apparent, the invention is not limited to the 
film-connecting means which have been described with reference to FIGS. 5 
to 12. The connecting chamber in accordance with the invention permits the 
use of any type of means for fastening two ends of films together within a 
trench. 
By means of its motor-driven rollers 5-6, 7-8 which are capable of rotating 
in two opposite directions, said connecting chamber makes it possible to 
ensure good stabilization of the two film ends, thus facilitating all 
subsequent film-fastening operations. For example, instead of the male and 
female members 25 and 26 of the example of construction shown in FIGS. 9 
to 12, it is possible to make use of two jaws which apply a compressive 
force on the two film ends in their zone of overlap. While maintaining 
this compressive force, an ultrasonic bonding tool or any other known 
chemical or thermal means can be lowered along the film through an opening 
provided in the plane of contact of one of the compression jaws in order 
to form a bond between the two films over the entire distance from the 
bottom to the top of the trench. 
A diagrammatic example of a device of this type is illustrated in FIG. 15, 
in which are shown the two jaws 39 and 40 with their smooth bearing faces, 
the opening 41 for the insertion of the bonding tool 42 within the jaw 39 
and the two overlapping films 3a, 3b which are clamped between the jaws 39 
and 40. 
In FIGS. 16 to 18 are shown alternative forms of construction of a sliding 
box provided with a connecting chamber in accordance with the invention. 
There is shown in FIG. 16 a variant of the film-supply magazine 2 in which 
the film is wound on two reels 29-30 located at a distance from each 
other. The two reels are surrounded by an unwinding band 31 forming a belt 
in order to guard against the phenomenon of self-tightening of the film 3 
while it is being unwound. 
This arrangement permits a high film storage capacity within a relatively 
small space. 
FIG. 17 illustrates a magazine 2 in which the film 3 is stored in the form 
of accordion pleats 32. In this case, a pressure plate associated with a 
spring ensures progression of the film accordion within the magazine while 
it is being delivered. 
By way of alternative, and as shown in FIG. 17, the magazine is fitted with 
an inflatable membrane 33 which ensures that a uniform pressure is exerted 
on the accordion during its delivery. This arrangement facilitates 
reloading of the magazine 2 after deflation of the membrane 33. 
FIG. 18 illustrates another alternative mode of realization of the film 
supply. In this case, the front section 2 of the box is not strictly a 
magazine for the vertically-stored film but a section for receiving and 
guiding the film as it is being unwound from a reel located outside the 
trench. 
In this case, the film 3 is folded-back around three stationary and 
substantially vertical guides carried by the box. This special film 
receiving and guiding arrangement is disclosed in a co-pending patent 
Application filed on the same day as the present Application. 
FIG. 19 illustrates an alternative design of the exit zone 13 of the box in 
the event of delivery of two films at the same time, each film being 
intended to be applied against one wall of the trench. 
In this case, the exit zone 13 carries a stationary central beam 34 having 
two vertical distribution rollers 35 and 36 mounted on the rear face of 
said beam and associated with two pairs of anti-return scraping seals 37 
and 38. In this case, the films 3 and 3' pass directly from the rear pair 
of rollers 7-8 of the connecting chamber 4 onto the distribution rollers 
35 and 36. In this embodiment, the partition-wall 9, the flexible seals 
11-12 and the deflecting flap 14 of the previous examples of construction 
are dispensed with. 
It can readily be understood that, when it is necessary to feed two 
separate films, the receiving chamber 2 must be equipped with a double 
bearing system for supporting two juxtaposed rolls of film. 
The invention is not limited to the examples of construction which have 
been described in the foregoing. Other variants and details of 
construction may be employed without thereby departing from the scope of 
the invention. 
For example, the rollers of the connecting chamber are covered with 
slightly compressible material such as rubber in order to be applied in 
intimate contact with the film over its entire width in the vertical 
plane, thus ensuring that the film is transferred without slippage. 
The box can be equipped with light projectors in order to visualize the 
operations which take place within the box. 
The box can be equipped with cameras which serve to transmit images of the 
interior of the box to a display screen located in the control station, 
thus permitting remote surveillance of the progress of operations. 
The box can be equipped with a pump for sucking any mud-laden water which 
might seep-in despite the presence of the seals at the exit of the 
connecting chamber. 
The bottom of the box can be fitted with a removable drawer for receiving 
and discharging mud and the like. 
In order to limit frictional contact between the front section 2 which 
forms a magazine for rolls of film against the walls of the trench, said 
front section of the box can be of circular cross-section.