Device for introducing into a soil an elongate, flexible element, such as a drainage element.

BACKGROUND OF THE INVENTION

The invention relates to a device and process for introducing into a soil body an elongate flexible element, such as a drainage element, in particular a drainage ribbon.

Such devices are for instance employed for consolidating a slack, water-bearing soil by stimulated or forced drainage. There drainage ribbons, vertically introduced into the soil, of water transporting construction/composition are being used, through which the water is more rapidly drained upward from the soil and this soil will consolidate more rapidly, and the bearing strength of that soil increases . It is common use to introduce drainage ribbons into the soil by means of a hollow lance that is kept upright by a king post and - at least substantially - vertically driven into and out of the soil body while leaving behind the ribbon that initially extends through the lance to a supply. The king post is carried by a machine that is displaceable along the ground or water. The assembly is furthermore provided with a holder for a supply reel of drainage ribbon. Examples of it are shown in the Dutch patent application 85.03390 and the International patent application WO 02/29164.

The drainage ribbon extends from the supply reel via the upper end of the king post through the hollow lance to its lower end. In many cases the drainage ribbon at the lower end of the lance is provided with an anchor, that also closes the lower end of the lance against penetrating soil material. When the lower end of the drainage ribbon has been introduced to the required depth, the lance is lifted again, wherein the anchor in the soil ensures that the drainage ribbon remains in the soil. Instead of an anchor attached at the lower end of the drainage ribbon the lower end of the lance may be provided with a pivotal valve for closing the lance during its downward movement against penetration of soil. In the lance is also included a push bar, around the lower end of which the ribbon is folded, also with the aid of the valve in closed position.

When moving the lance back the valve will open by itself. The push bar is held at the same depth a while longer. The soil material may, at least at one side of the ribbon, exert a retaining force on it. When the push bar is lifted again the drainage ribbon is left behind, without the use of an anchor. Alternatively it is also possible that after having reached the required depth for the lance the push bar is forced downward with respect to the lance, wherein the valve is opened and the drainage ribbon is forced further into the soil. After that the lance and push bar are lifted.

Just as when using an anchor the ribbon that is retained by the soil will be pulled through the lance passage during the upward movement of the lance and push bar. When the lower end of the push bar and lance at the end of the upward stroke has returned to the initial

position again, the ribbon is cut and the cycle can be repeated at a new location.

An example of such a device is known from the European patent application 0.233.312 and the Japanese patent application 59-195915.

During the installation process of the drainage ribbon various different forces are exerted on the ribbon because of which the installation in the soil body may fail. It is an object of the invention to provide a device with which an elongate, flexible element, such as a drainage element, can be placed in a soil in a reliable manner.

It is an object of the invention to provide a device with which disturbance of the depth position of the flexible, elongate element during lifting of a lance assembly is not or hardly disturbed.

SUMMARY OF THE INVENTION

From one aspect the invention provides a device for introducing into a soil an elongate, flexible element, such as a drainage element, in particular a drainage ribbon, comprising a lance and a lance drive for the lance to drive same into the soil and lift same out of it again, a holder for a supply of elongate element, wherein the lance forms a first accommodation space for the elongate element to shield same during introduction into the soil with the lance of a length thereof, wherein the device furthermore comprises a push bar that is displaceable relative to the lance and that is parallel thereto, with which the lower end of the elongate element after introduction thereof into the soil is held during a

lifting movement of the lance, wherein the push bar is located in a space that, along a longitudinal section extending in or along the lance, preferably along the major longitudinal section of the first accommodation space, preferably along the major longitudinal section of the lance, is kept separate from the first accommodation space by separating members on the lance. The major longitudinal section is defined here as more than half the respective total length. By the effective separation of the displacement space for the ribbon and the displacement space of the push bar a relative deflection or buckling of the push bar within the lance as a consequence of the forces which are exerted on the lance and push bar, will not or hardly result in a clamping force exerted by the push bar on the ribbon, against the lance . Then the ribbon could no longer move freely with respect to the lance and/or push bar and during the upward stroke of lance and push bar it would be subjected to an undesirable extent to an upward pulling force, resulting in the lower end of the ribbon being pulled up, away from the required depth. With the invention a smooth lifting of the lance with the push bar while leaving the ribbon behind at the intended depth is enhanced. In an embodiment the separating members are situated at least in a central area of the longitudinal section of the push bar that extends in or along the lance, because in the central area the relative deflection or buckling could lead to the largest displacement. in an embodiment the separating members are uninterrupted in lance direction, so that they form a perforated or unperforated continuous wall or the like. In another embodiment the separating members are spaced apart

in longitudinal direction, preferably substantially equally distributed. They may for instance be formed by a series of spaced apart bars, partitions, plates etc., with which weight may be saved. In order to stimulate a relative movement, if intended, between the elongate element and lance/push bar the separating members may be provided with guide planes for the elongate element and/or with guide planes for the push bar.

In an embodiment the lance comprises a second accommodation space, situated adjacent to the first accommodation space, that forms the said space for the push bar. There the lance may be tubular, wherein the first and second accommodation spaces are located within the tube. Then the push bar and the drainage ribbon are both shielded from the soil material during introduction into the soil. The tube may have a polygonal (for instance rectangular) or bent (for instance circular) cross- section.

In an embodiment the space for the push bar is located at the exterior of the lance. The inner space of the - in particular tubular - lance may then be used entirely for the elongate element, that may consequently have a relatively large cross-section, optionally folded, folded in two, etc. Preferably the lance is provided at the exterior with guides for the push bar.

In a further development of the device according to the invention it is furthermore provided with a push bar drive for the push bar to force same into the soil relative to the lance. The push bar drive may also be equipped for lifting the push bar.

In an embodiment the push bar drive at a distance from the lower end engages onto the push bar, preferably

onto the upper end thereof that is located opposite the lower end. The lower end penetrates the soil, and thereby it is accessible to for instance penetrating water and abrasive sand or clay depositions. The push bar drive at a distance from the lower end may remain unaffected, which can enhance the continuity of the drive.

When the push bar drive engages onto the lance and is positioned relative to the lance so as to be situated entirely above the soil in the position of the lance when introduced into the soil, then the push bar drive may remain unaffected by water and abrasive sand or clay depositions which penetrate from the soil, which can enhance the continuity of the drive. In this embodiment the lower end of the lance may contain elements which are only powered from a distance, wherein more vulnerable, active drive components, such as for instance also the lance drive itself, are at a distance from it.

At the lower end the lance may then be provided with a closure member for it, wherein the closure member is movable between a closed position in which the lower end of the lance is closed and the elongate element is being clamped between the closure member and the lance and an open position in which the lower end of the lance is open and the push bar with elongate element can move through it. During the introduction of the lance with elongate element an entrainment of the elongate element is ensured by the closure member provided on the lance itself and cooperating with it .

In an embodiment the closure member can be actuated by the push bar. Then the closure member may form a valve, that is rotatably connected to a first side of the lance, wherein the first accommodation space is located between the second accommodation space and the first side of the

lance, because of which the moment to be exerted by the push bar can be large.

From a further aspect the invention provides a process for introducing into a soil a flexible drainage element, such as a drainage ribbon, with the aid of a lance in which a length of the elongate element is accommodated that near the lower end of the lance is retained by a lance bottom valve in cooperation with the lower end of the lance, wherein the lance is introduced into the soil at a required depth, after which a push bar while entraining the lower end of the elongate element forces the valve to open and is driven further into the soil, and after that the push bar is lifted while leaving the lower end of the elongate element in the soil. During the introduction of the lance with the elongate element an entrainment of the elongate element is ensured by the closure member provided on the lance itself and cooperating with it, after which the push bar will start to perform its function. In order to enhance the entrainment of the elongate element by the push bar the lower end of the elongate element during introduction into the soil with the lance, may at least be partially folded around the lower end of the push bar. This is enhanced further when the lower end of the push bar is provided with a retainer for fixing the elongate element relative to the push bar, such as a hook or puncture pin that penetrates the elongate element.

In an embodiment the push bar is lifted again to within the lower end of the lance and the lance and the push bar - optionally accommodated therein - are lifted.

A further problem may arise as a consequence of forces which develop when the drainage ribbon during the downward stroke of the lance is pulled from the supply

reel. Because of the mass inertia of the supply reel and the resistance in the guide track of the ribbon the ribbon may come loose from the lower end of the lance . Then the lance has to be lifted again and the ribbon has to be pulled through it again. Because of this the operation is delayed.

From a further aspect the invention provides a device for introducing along a required dispension length into a soil an elongate, flexible element, such as a drainage element, in particular a drainage ribbon, comprising a lance assembly and a drive for the lance assembly to drive same into the soil and lift same out of it again, and a holder for a supply of elongate element, wherein the lance assembly comprises a lance and the lance forms an accommodation space for the elongate element to shield same during introduction into the soil with the lance of a length thereof, while retaining the lower end of the elongate element, wherein the device furthermore comprises a buffer device for the elongate element to form a buffer length of elongate element that substantially corresponds to the dispension length, during lifting of the lance assembly.

The formed buffer length may be used in the next introduction stroke. The necessary length of elongate element is already available then, because of which the supply reel does not have to be unwound. Thus it can be achieved that the elongate element in the downward stroke of the lance is entrained in a substantially low tension manner, because of which an undesired coming loose can be prevented to a high extent.

The buffer capacity of the tube can be equal to the maximal installation depth of a single elongate element.

In an embodiment the buffer device comprises a return pulley for the elongate element, that is displaceable between a first position in which the required buffer length is formed and a second position in which the buffer length is being utilized, wherein the return pulley is arranged to be forced by the introduction movement of the lance assembly from the first position to the second position, preferably in a simultaneous movement. The device may then furthermore be provided with a return pulley carrier, that is connected to the lance assembly by means of a connection, in particular a pull connection, such as a cable, to follow the movement thereof, at least during the introduction movement . During the downward stroke of the push bar the return pulley carrier is moved upward by the cable and then it supports the return pulley, because of which the elongate element is entrained by the lance assembly at the same speed, thus almost without force .

The lance assembly may comprise a push bar, that is incorporated in the lance and engages onto the lower end of the elongate element so as to introduce same into the soil and leave it there, wherein the return pulley carrier is connected to the push bar. Also when using a push bar the dispensing length is attuned to the maximal introduction depth.

The buffer device may operate in a vertical plane, matching a common king post along which the lance assembly is moved. Then the return pulley may be vertically movable between the first and the second position. At the upper end of the king post or buffer device a self activating clamp may be arranged that allows the elongate element to pass only in longitudinal direction. This clamp prevents the elongate element from being pulled

back from the soil or lance, so that a new buffer dispension length comes exclusively from the supply reel by displacing the return pulley back into the buffer device, from the second to the first position. From a further aspect, or alternatively phrased, the invention provides a device for introducing along a required dispension length into a soil an elongate, flexible element, such as a drainage element, in particular a drainage ribbon, comprising a lance assembly and a drive for the lance assembly to drive same into the soil and lift same out of it again, a holder for a supply of elongate element, wherein the lance assembly comprises a lance and the lance forms an accommodation space for the elongate element to shield same during introduction into the soil with the lance of a length thereof, and for a retainer to keep the lower end of the elongate element at the lower end of the lance during introduction into the soil of the lance assembly, provided with one or more of the measures as described above as such. From a further aspect the invention provides a device for introducing into a soil an elongate, flexible element, such as a drainage element, in particular a drainage ribbon, comprising a lance and a lance drive for the lance to drive same into the soil and lift same out of it again, a holder for a supply of elongate element, wherein the lance forms a first accommodation space for the elongate element to shield same during introduction into the soil with the lance of a length thereof, wherein the device furthermore comprises a push bar that is displaceable relative to the lance and that is parallel thereto, with which the lower end of the elongate element after introduction thereof into the soil is retained during a lifting movement of the lance, wherein the push bar is

located in a space that is located at the exterior of the lance, wherein the lance is provided with guides for guiding a movement of the push bar along the lance .

In an embodiment of it the guides form surfaces which engage guidingly onto the push bar at a side that faces away from the lance .

In an embodiment the push bar and a wall of the lance are provided with cooperating guide slots and guide pins .

In an embodiment the lance is provided at the exterior with lock in members which at least partially surround the space for the push bar.

From a further aspect the invention provides a device for introducing into a soil an elongate, flexible element, such as a drainage element, in particular a drainage ribbon, comprising a lance and a lance drive for the lance to drive same into the soil and lift same out of it again, a holder for a supply of elongate element, wherein the lance forms a first accommodation space for the elongate element to shield same during introduction into the soil with the lance of a length thereof, wherein the lance is provided with a second accommodation space for a push bar with which the lower end of the elongate element after its introduction into the soil is held during a lifting movement of the lance, wherein the first and the second accommodation space form separate first and second longitudinal passages in the lance which extend along a longitudinal section of the push bar that extends in or along the lance, preferably along the major longitudinal section of the first accommodation space, preferably along the major longitudinal section of the lance.

The lance may be tubular, wherein the first and second accommodation spaces are located within the tube .

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The first and second longitudinal passages may at least locally be separated from each other by one or more separating members .

The aspects and features as described in this description and claims of the application and/or shown in the drawings of this application can when possible also be applied individually. Those individual aspects, such as the separation of (accommodation) spaces for the elongate element and push bar, clamping the lower end of the elongate element, the introduction process and buffering of the elongate element, the push bar that is located at the exterior of the push bar and other aspects can be the subject of divisional patent applications directed thereto. This holds true in particular for the features and aspects that are described as such in the sub claims.

SHORT DESCRIPTION OF THE DRAWINGS

The invention will by way of example be elucidated on the basis of an exemplary embodiment that is shown in the attached drawings, in which: figure 1 is a schematic view of an example of an arrangement according to the invention; figure IA is a schematic side view at the arrangement of figure 1; figure 2 is a detail of the arrangement according to figure 1, according to view II, in starting position; figures 2A, 2B, 2C, respectively, show two details of ribbon clamps and a cross-section through a lance in the arrangement of figure 2; figure 3 is a view that corresponds with figure 2, in a next process step;

figure 4 is a view that corresponds with figures 2 and 3, in a next process step; figure 5 is a detail in cross-section of a lance for use in the arrangement of figure 1 and figure 5A is a cross-section through the lance of figure 5; figure 6 is the lance of figure 5, during a next process step, and figure 6A is a view inclined to the situation of figure 6; figures 7A-C are a side view, partially (upper section) in cross-section, a longitudinal cross-section transverse thereto and a cross-section through an alternative embodiment of a lance, respectively, in an arrangement according to the invention,- and figures 8A-C are a number of alternative embodiments of the assembly of lance and push bar.

DETAILED DESCRIPTION OF THE DRAWINGS

The arrangement/device 1 of figure 1 and further comprises a displaceable hydraulic machine 2, that is placed on ground level 100 of a soil 101, in which a soil layer 102 to be consolidated is present.

To the extreme end 5 of the arm 3 of the machine 2 a bracket 4 has been fastened, onto which a retainer 6 for a king post 7 has been fastened. On the king post 7 a bracket 51 has been fastened for a winch 50 for a drive cable 41, which (vide figure 2) travels around return pulleys 12 and 13 which have been fastened to the king post 7. The cable 41 with ends 41a and 41b has been fastened to a slide 15, that has been fixedly fastened to a tubular lance 9. The lance 9 is upwardly and downwardly displaceably guided with respect to the king post 7 within the vertical profile 80, that is connected to the

remaining part of the king post 7 by means of transverse plates 14. At the top of the profile 80 a number of return pulleys has been fastened, namely return pulley 17 for a drainage ribbon 40 and return pulleys 18 and 19 for a cable 42, that has been fastened with the end 42b to the upper end 20b of a push bar 20 that is accommodated in the lance 9. At the upper end of the push bar 20 by means of the cross bar 95 (vide figure 2C) the extreme end of the piston rod 91 of a cylinder 90 has been fastened, that extends downward and is connected to the slide 15 with the sleeve 92. By activating the cylinder 90 the push bar 20 can be displaced with respect to the lance 9.

To the king post 7 on a bracket 11 a supply reel 10 of ribbon 40 has been fastened. Above it a buffer tube 8 has been fastened to the king post 7. At the upper end of the buffer tube 8 the other extreme end 42a of the cable 42 has been fixed to the cable 42. From there the cable 42 extends downward into the buffer tube 8, and at the bottom it is guided around return pulley 32 that has been fastened to a lifting table 33, that can move up and down in a guided manner within the buffer tube 8. Subsequently the cable 42 travels upward, to the above-mentioned return pulleys 19 and 18.

The drainage ribbon 40 travels via a pulley 36 and a return pulley 30 at the top of the buffer tube 8 to within the buffer tube 8, with a downward length 40c, and then it travels around return pulley 31 that is accommodated in a table 35, which table 35 can be supported on the table 33.

The ribbon 40 travels upward from there (within the tube 40 with length 4Od) to the return pulley 17 at the top of the king post 7, and than it extends downward through the lance 9, to the lower end thereof.

As depicted in figures 5 and 5A the lance 9 forms an accommodation space 70. At regular intervals cross-bars 73 have been fastened in the lance 9, dividing the accommodation space 70 in accommodation spaces 71 and 72. The push bar 20 extends through the accommodation space 71, and the ribbon 40 extends through the accommodation space 72.

At the lower end the lance 9 is provided with a tube section 21 with two oppositely located walls 22a and 22b. At its exterior the outer wall 22b is provided with a boss 23 with an abutment edge 23a and at the lower end via hinge 24 it is provided with a valve 25. The valve 25 comprises an abutment edge 25b that can abut against the abutment edge 23a, so that the valve 25 cannot move through the vertical and thus it will not open too much and when hitting the soil and penetrating it, it will close. As depicted in figure 5 the valve 25 can clamp the extreme end 4Oa of the drainage ribbon 40 against the lower edge 22a of the wall 22 with a (not shown) inner peripheral plane 25a that is provided with teeth which extend transverse to the hinge pin 24 and are separated from each other by grooves. The push bar 20 is situated in the accommodation space 71 that is more remote from the hinge 25 than the accommodation space 72 for the drainage ribbon 40. The teeth/grooves at the inner peripheral plane 25a ensure that at least a part of the ribbon 40 remains intact when the ribbon 40 unexpectedly becomes jammed between the push bar 20 and the valve 25. One of the grooves may also provide space for a mandrel or puncture pin for the ribbon at the lower end 20a of the push bar 20.

In figures 2A and 2B two exemplary embodiments are shown of a mechanism for holding the drainage ribbon 40

back from a return movement. In the embodiment of figure 2A at the upper end of the lance 9 a spring-biased ribbon clamp 16 has been arranged, that permits downward movement of the drainage ribbon 40, but not a return movement. In figure 2B a spring-biased ribbon clamp 60 is depicted, that has the configuration of a lever with arms 61 and 62, which have been rotatably fastened to the exterior of the upper end of the buffer tube 8 at the location of hinge 63. By means of the spring load the arm 62 with the extreme end 65 is forced against the drainage ribbon 40, that is clamped then against a profile 8a, provided in the buffer tube, and that at an upward movement of the lance 9, so that the drainage ribbon 40 that is situated above the clamping location is kept free from the weight of the table 35 and winding the drainage ribbon off the roll 10 is enhanced. In case anchoring the ribbon in the soil fails and the ribbon is pulled along with the lifted lance the action of the ribbon clamp 60 can be released with the aid of a cylinder 61 that acts upon the arm 61. Then the ribbon 40 can travel back into the buffer tube 8 and/or a length of it can be accommodated again on the supply reel 10 that is spring-biased in winding direction, usually to keep the ribbon firm.

For introducing a length of drainage ribbon 40 into the layer 102 to be consolidated the king post is arranged vertically at the correct location by means of the hydraulic machine 2. Then the winch 50 is actuated, because of which the cable 41 is forced in a direction A (figure 2) and via slide 15 the lance 9 in the direction B is forced downward into the soil 101, guided by the king post 7 between the profile 80 and transverse plates 14. By the impact of the soil the valve 25 is forced to close, wherein the lower end 40a is clamped between the inner

peripheral plane 25a of the valve 25 and the lower edge 22a of the wall 22 at the lower end of the lance 9. Then the ribbon 40 can be forced by the valve 25 onto the mandrel at the lower end of the push bar 20. For the clamping action it is not necessary that the push bar 20 also presses on the ribbon 40.

With the downward movement of the lance 9 and the push bar 20 that is accommodated therein a pulling force will be exerted on the cable 42. Because of this the return pulley 32 is moved upward within the buffer tube 8 in the direction H (figure 2) , wherein also the lifting table 33 and thereby the table 35 with return pulley 31 is entrained, in the same movement. The downward, upward lengths 40c, 4Od, respectively, of the drainage ribbon 40, initially present in the buffer tube 8, are released then in order to move along with the lance 9 into the soil 101, 102. As a consequence the supply reel 10 does not have to be wound off. As a consequence the drainage ribbon 40 does not experience any resistance during introduction into the soil as a consequence of winding off the supply reel, and during travel of the drainage ribbon 40 along the pulleys 36 and 30.

The altitude of the return pulleys 31 and 32 within the buffer tube 8 has been adjusted to the required penetration depth of the drainage ribbon 40. Also when the lance 9 has arrived at the required depth (figure 3) , the cylinder 90 is above the soil 101, 102. Subsequently the lance 9 can be lifted again, while keeping the push bar 20 in its place with respect the soil, while activating the winch 50 (the cable 41 moves in direction C, figure 4) and the cylinder 90. Because of this the valve 25 will open by itself as it were, as a consequence of the presence of the lower end 20a (that is kept stationary) of the push bar 20

in the direction F (figure 6) . A for instance mandrel-like or puncture pin-like provision at the lower end of 20a of the lance 20 prevents here, by puncturing the ribbon, that the extreme end 40a of the drainage ribbon 40 is pulled along by the valve 25. Shortly after this the push bar 20 is pulled up as well, while leaving the lower end 40a of the drainage ribbon 40 in the soil. Because of the soil load that is exerted on both sides on the lower section of the drainage ribbon 40, the ribbon 40 will be able to remain in the soil at the required depth, and not be pulled back by the upward movement of the lance and/or push bar.

In the described case of the first pulling back of the lance and shortly after that of the push bar there could be question of disturbed soil around the drainage ribbon. Under circumstances, dependent upon the type of soil, it may occur that the soil load that is exerted on the drainage ribbon 40, has to be increased. This can be achieved by keeping the lance itself stationary in the lowermost position of the lance 9, and by activating the cylinder 90 forcing the push bar 20 itself further in the direction E (figure 5) . The lower end 20a of the push bar 20 then forces the valve 25 to open, in fact in accordance with figure 6. It is then however the push bar 20 that moves downward in an absolute sense. With the aid of the above-mentioned mandrel or comparable means the extreme end 40a remains at the lower end 20a of the push bar 20, and is forced deeper into the layer 102. Here the extra length, relative to the lance depth 9, of the drainage ribbon 40 may also be provided by the buffer length 40c, d in the buffer tube 8, because the cable 42 has been fastened to the upper end of the push bar 20.

After the lower end 40a of the drainage ribbon 40 has been brought at the required depth, the push bar 20 can be lifted again, while leaving the lower end 40a at that required depth. The one side of the drainage ribbon 40, during introducing the drainage ribbon 40 deeper, has come in direct contact with the soil material. At the opposite side the soil material will come almost directly in contact with the drainage ribbon because of the narrow design of the push bar 20 in comparison with the tube of the lance 9. when being lifted the lance 9 and the push bar 20 displace with respect to the drainage ribbon 40. By the separation bars 73 the push bar 20 is kept at a distance from the drainage ribbon 40, so that the movement of the push 20 can have no influence on it, in particular when by forces which are exerted on it, the push bar 20 is inclined or becomes bent within the lance 9, or the lance 9 becomes inclined. The accommodation space 72 provides sufficient space with respect to the drainage ribbon 40 to keep frictional forces, exerted on the drainage ribbon 40 by the lance 9, as low as possible. The design of the cross-section of the separation rods 73 is attuned to this.

During the return movement of the push bar 20 the weight of the lifting table 33 ensures that the cable 42 follows the movement. The table 35 with return pulley 31 will be able to follow the downward movement of the lifting table 33 with delay (direction J, figure 4) . The weight of the return pulley 31, which otherwise has no obstructing influence on the dispense of the drainage ribbon, because of its entrainment by the lifting table 33, ensures the provision of buffer lengths 40c, 4Od by unwinding the supply reel 10. The advantage of it is that

the supply reel 11 need not follow the downward speed of the lifting table 33. This is beneficial because the supply reel will have a velocity of circulation that changes along with the progress of the process, according to the decrease of the supply on the reel. By the action of the ribbon clamp 60 the section of the ribbon 40 that extends above the buffer tube 8, is then not loaded by the table 35.

After the starting position has been reached the ribbon 40 can be cut above ground level. At the next downward movement of the lance 9 the soil will force the valve 25 to close and then place the lower end 40a around the lower edge 22a and possibly pin it onto the mandrel, so that the lower end 40a is clamped tight. In figures 7A-C another possible embodiment of a lance 109 has been shown, wherein the lance 109 has a round cross-section, the interior 170 of which has been divided by cross spindles 173 into a passage 172 for the ribbon and a passage 171 for the push bar 120. The push bar 120 has been provided with a stiffening rib 120b that is transverse thereto, that is guided between a number of pairs of pins 174 that extend inward from the wall of the lance. The lower end 109a of the lance 109 forms a transition from the round cross-section to a planar cross- section, directed in conformity with the cross-section of the ribbon 140. The stiffening rib 120b is absent along the push bar length 120 that has to be able to extend downward from the lance.

In figure 8A the tubular lance 209 forms a passage 270 for a drainage element, in particular a drainage ribbon, that is not shown. Here the wall 273 of the tubular lance 209 forms a separation between the space 371 where the push bar 220 is situated, and the passage 270.

The push bar 220 is held at/on the lance 209 by means of a longitudinal series of pins 201, provided with widened heads, which pins have been fastened in, threaded, holes 292 in the wall 273. The push bar 220 has been provided with a series of longitudinal slots 290, through which the pins 291 extend. The length of the longitudinal slots determines the maximal displacement of the push bar 220 along the lance 209.

In figure 8B two angle irons or series of angle irons 391 are welded to the edges of the wall 373 of the tubular lance 309. With the wall 373 they determine a passage 371 for the push bar 320. Then the push bar 320 is held at the wall 373 by the two angle irons, but can be displaced all the same in longitudinal direction with respect to the lance 309.

The embodiment of figure 8C resembles that of figure 8B, but here the angle irons 491 have been provided with longer legs with which they are welded to the tubular lance 409. The above description is included to illustrate the operation of preferred embodiments of the invention and not to limit the scope of the invention. Starting from the above explanation many variations that fall within the spirit and scope of the present invention will be evident to an expert.