Description

The present invention relates to a method for introducing fibres into the ground using a device, comprising the following steps:

A providing a thread-like fibre,

B positioning the fibre under a fibre-inserting pin of the device by means of positioning means of the device,

C moving the fibre-inserting pin down and up in which case the fibre is pushed into the ground during the downward part of the movement,

D moving the fibre-inserting pin parallel to and above the ground over a step length in a direction of motion,

E repeating steps A to D.

It is known to introduce plastic fibres into the ground for the purpose of producing so-called hybrid turf pitches, in particular sports fields, in which the fibres are used in combination with natural grass. For the introduction of fibres, relatively large mobile machines are used which move in steps and along parallel strips over the zone where the hybrid field has to be produced. The machines have a row of for example at least 60 pins, which row has a length, for example, of at least 1 .2 metres. This length determines the width of the abovementioned strips. The machine has rotatable spools around which long lengths of fibres are wound, for example of 5000 metres. The number of spools usually corresponds with the number of pins. In use, the fibres are unwound from the spools and taken to a position under the pins. The pins move down and up. During the downward movement, a short length of fibre, which has at that point been separated from the fibre on the roll, for example by a cutting operation, is pushed into the ground by the corresponding pin. The Dutch publications NL 20141 189 and NL 1014978 give examples of devices by means of which fibres such as those described above can be introduced into the ground. Typically, the surface area of hybrid fields is a few thousand square metres, for example approximately 7500 square metres. With such dimensions, the use of known mobile machines is still economically viable. However, with decreasing surface areas, the use of the known machines is less cost-effective and even not economically viable.

The invention is based on the insight that there is a latent need for introducing fibres into the ground in an economically viable way over relatively small surfaces of for example less than 100 square metres or even less than 10 square metres. In this case, consideration may be given, for example, to repair work to heavily worn parts of a hybrid turf pitch, such as the penalty area of a football field, to the area extending directly along the periphery of an existing hybrid turf pitch, to lawns in gardens, whether private or not, to public playing fields in residential areas, to footpaths or to dykes. In particular with repair work, it is known per se to prick the ground and introduce fibres individually by hand. This is very time-consuming and consequently expensive. Also, the use of known devices mentioned above is not economically viable with this type of relatively small-scale application. It is an object of the invention to satisfy this demand and to this end, the invention provides a method according to the preamble in which the fibre, according to step A, forms part of a collection of thread-like fibres, in which the fibres in the collection of fibres are positioned with respect to each other by a band-shaped substrate member to which the fibres are connected and of which collection of fibres one fibre is positioned under the fibre-inserting pin during step B before each step E, and in that the fibre is separated from the substrate member during the execution of step C due to the force which the fibre-inserting pin exerts on the fibre during the downward part of the movement.

For a better understanding of the invention, it should be noted that the term "fibre" in the present text is understood to refer to an individual fibre with a length of at most 50 cm. Thus, a fibre should be distinguished from a fibre string, which is wound around a spool in lengths of many hundreds of metres. Lengths of at most 50 cm are cut from such a fibre string, resulting in fibres. The fibres are thus threadlike. At least until now, the fibres often comprise filaments which are connected to each other by, for example, being twisted or are bound together by means of a binding yarn. During step C, the fibres are typically pushed into the ground to a depth of at most 20 cm. The abovementioned length of at most 50 cm allows for a limited length of the fibre which remains above the ground after the fibre has been pushed into the ground and the possibility of the fibre-inserting pin gripping a fibre in the middle, as a result of which the fibre is folded in two. The minimum length of an individual fibre is 10 cm. The invention uses a collection of fibres which have already been cut to a desired length prior to the work of introducing fibres into the ground in a surface area of ground. By no longer using a number of spools around which fibre strings are wound and by not cutting the fibres to a desired length on location, but directly providing the fibres at the desired length on location, the possibility arises of making the equipment used to introduce the fibres into the ground simpler than the existing machines. After all, the invention makes it possible to omit provisions for accommodating spools, for unwinding the fibre strings from the spools and for cutting the fibres to length comprised in prior-art machines. This also has a positive effect on the safety with which the method according to the invention can be carried out. The substrate member may help to correctly position the fibres under a fibre-inserting pin during step B, in which case the band-shaped character of the substrate member helps to facilitate transportation of the fibres for the purpose of step B inside the device. In this case, the substrate member may be presented to the device as a roll. Generally, the substrate member will be made from a different material than the material of the fibres as the requirements which the material of the substrate member and the material of the fibres have to meet in practice are different. The connection between the fibres and the substrate member has been effected via a connecting step and has to be such that this connection can be severed again while performing step C. Separating the fibre from the substrate member while performing step C means that the connection between the substrate member and the fibres is severed.

It may be advantageous if the length direction of the fibre-inserting pin during step C encloses an angle with a direction parallel to the direction of motion according to step D. Thus, for example starting from a fixed length of the fibre, it is possible to limit the depth of the layer of ground into which the fibre is pushed, which may be of interest, for example, if heating ducts are provided at a certain depth in the ground. In addition, the force which is required to pull a fibre out of the ground at a tensile force which is oriented at right angles to the ground may be increased. In addition, natural grass roots can thus more readily become entangled with a number of fibres, as a result of which the anchoring of the natural grass roots improves.

The size of the angle may be between 0 degrees and 60 degrees, more preferably between 15 degrees and 50 degrees. The invention may be used advantageously if the ground is an incline with an angle of inclination, with the direction of motion according to step D extending parallel to the incline. Such an incline may, for example, form part of a slope or a dyke.

In case an incline is used, the length direction of the fibre-inserting pin may advantageously extend in a vertical direction during step C.

The measures related to previous embodiments in which the length direction of the fibre-inserting pin encloses an angle during step C with a direction parallel to the direction of motion according to step D may also advantageously be used with a method according to the prior art. Therefore, the present invention also relates to a method for introducing fibres into the ground using a device and comprising the following steps:

A providing a fibre,

B positioning the fibre under a fibre-inserting pin of the device by means of positioning means of the device,

C moving the fibre-inserting pin down and up in which case the fibre is pushed into the ground during the downward part of the movement,

D moving the fibre-inserting pin parallel to and above the ground over a step length in a direction of motion,

E repeating steps A to D,

in which the length direction of the fibre-inserting pin during step C encloses an angle with a direction parallel to the direction of motion according to step D.

According to a further embodiment, during step C, the resistance which the fibre-inserting pin encounters due to the movement in the ground is determined, and in that the speed with which the fibre-inserting pin moves in the ground during step C depends on the determined resistance. Said resistance depends on the type of ground and on other conditions, such as the moisture content in the ground. Furthermore, it generally holds good that the resistance is greater as the fibre- inserting pin is pushed deeper into the ground. The mechanical loadability of the fibre- inserting pin is limited. By making the speed at which the fibre-inserting pin moves in the ground during step C dependent on the determined resistance which the fibre- inserting pin encounters, the loadability of the fibre-inserting pin can be used to the maximum in order thus to shorten the cycle time of the movement according to step C. The aforementioned dependency between the determined resistance and the speed of the fibre-inserting pin can also be used advantageously with a prior- art method. Therefore, the present invention also relates to a method for introducing fibres into the ground using a device, comprising the following steps:

A providing a number of fibres,

B positioning the fibres under the fibre-inserting pins of a row of fibre- inserting pins of the device by means of positioning means of the device,

C moving the fibre-inserting pins down and up in which case the fibres are pushed into the ground during the downward part of the movement,

D moving the fibre-inserting pins parallel to and above the ground over a step length in a direction of motion,

E repeating steps A to D,

in which, during step C, the resistance which the fibre-inserting pin encounters due to the movement in the ground is determined, and in that the speed with which the fibre- inserting pin moves in the ground during step C depends on the determined resistance. In order to increase the capacity, a number of fibre-inserting pins arranged in a row may be moved down and up during step C in order to push an equally large number of fibres into the ground, preferably simultaneously to shorten the cycle time.

In this case, it is possible for the fibre-inserting pins arranged in a row to move synchronously, as a result of which the device may be of a relatively simple design.

In order to limit the total resistance which the fibre-inserting pins may encounter while the fibre-inserting pins are being pushed into the ground, as a result of which, for example, there may be a risk that the device which is used to carry out the method is pushed upward, it may be preferable a first portion of the number of fibre-inserting pins and a second portion of the number of fibre-inserting pins for to move asynchronously during step C. Thus, it is possible already to move the first portion of the number of fibre-inserting pins upward, for example during the last part of the downward movement of the second portion of the number of fibre-inserting pins, during which part of the downward movement the resistance encountered by the respective fibre-inserting pins is greatest, in which case the reaction forces between the ground and the first portion of the number of fibre-inserting pins and the second portion of the number of fibre-inserting pins act in opposite directions and thus cancel each other to a certain degree. A good compromise between, on the one hand, the desire for a short cycle time and, on the other hand, the desire for limiting the resistance which the fibre- inserting pins encounter during the downward movement because of the ground, may be achieved if the time period between the starts of the downward movements of the first portion of the number of fibre-inserting pins and of the second portion of the number of fibre-inserting pins is shorter than 25 %, preferably shorter than 15 %, of the time period between the start of the downward movement and the end of the upward movement of the first portion of the number of fibre-inserting pins.

In case the resistance which the fibre-inserting pins encounter due to the movement in the ground is determined during step C, it is also possible for the time period between the starts of the downward movements of the first portion of the number of fibre-inserting pins and of the second portion of the number of fibre-inserting pins to depend on the determined resistance. Thus, it is for example conceivable for said time period to be shorter with soft ground, into which the fibre-inserting pins can be inserted relatively easily, than with harder ground. This principle can also be applied with a prior-art method. In that case, this is a method for introducing fibres into the ground using a device, comprising the following steps:

A providing a number of fibres,

B positioning the fibres under the fibre-inserting pins of a row of fibre- inserting pins of the device by means of positioning means of the device,

C moving the fibre-inserting pins down and up in which case the fibres are pushed into the ground during the downward part of the movement,

D moving the fibre-inserting pins parallel to and above the ground over a step length in a direction of motion,

E repeating steps A to D,

characterized in that, during step C, the resistance which the fibre-inserting pin encounters due to the movement in the ground is determined and the time period between the starts of the downward movements of the first portion of the number of fibre-inserting pins and of the second portion of the number of fibre-inserting pins depends on the determined resistance.

According to a possible embodiment, the time period between the start of the downward movement and the end of the upward movement of the first portion of the number of fibre-inserting pins equals the time period between the start of the downward movement and the end of the upward movement of the second portion of the number of fibre-inserting pins. Such an embodiment of the method is with a relatively simple device, in the sense that it may only have a single drive member for driving both the first portion and the second portion of the number of fibre-inserting pins.

Alternatively, it may also be possible for the time period between the start of the downward movement and the end of the upward movement of the first portion of the number of fibre-inserting pins to be longer than the time period between the start of the downward movement and the end of the upward movement of the second portion of the number of fibre-inserting pins. Thus, due to the upward movement of the first portion of the number of fibre-inserting pins, the downward reaction force can be used to enable the movement of the second portion of the number of fibre-inserting pins to take place more quickly than the movement of the first portion of the number of fibre-inserting pins. In a specific embodiment, the upward movements of the first portion and the second portion of the fibre-inserting pins end simultaneously, or at least substantially simultaneously.

In order to simplify the device by means of which the method according to the invention can be carried out, it may be advantageous if at least some of the fibre-inserting pins of the first number of fibre-inserting pins, preferably all fibre- inserting pins of the first number of fibre-inserting pins, are situated directly next to each other and/or that at least some of the fibre-inserting pins of the second number of fibre-inserting pins, preferably all fibre-inserting pins of the second number of fibre- inserting pins, are situated directly next to each other.

Alternatively, it is also possible for the fibre-inserting pins of the first portion of the number of fibre-inserting pins and the fibre-inserting pins of the second portion of the number of fibre-inserting pins to be arranged in a staggered fashion. Thus, the tendency for lateral tilting is reduced compared to the previous embodiment.

If the fibre-inserting pins of the first portion of the number of fibre- inserting pins are driven independently from the fibre-inserting pins of the second portion of the number of fibre-inserting pins, there are more possibilities to shorten the cycle time or the time required for step C.

Alternatively, it is also possible for the fibre-inserting pins of the first portion of the number of fibre-inserting pins to be driven in dependence on the fibre- inserting pins of the second portion of the number of fibre-inserting pins. In this way, the method may be carried out by means of a relatively simple device. The above-described measures in which a first portion of the number of fibre-inserting pins and a second portion of the number of fibre-inserting pins move asynchronously during step C, may also be used advantageously with a prior-art method. Therefore, the invention also relates to a method for introducing fibres into the ground using a device, comprising the following steps:

A providing a number of fibres,

B positioning the fibres under the fibre-inserting pins of a row of fibre- inserting pins of the device by means of positioning means of the device,

C moving the fibre-inserting pins down and up in which case the fibres are pushed into the ground during the downward part of the movement,

D moving the fibre-inserting pins parallel to and above the ground over a step length in a direction of motion,

E repeating steps A to D,

characterized in that a first portion of the number of fibre-inserting pins and a second portion of the number of fibre-inserting pins move asynchronously during step C.

The number of fibre-inserting pins is preferably at most 35, more preferably at most 25, and/or the length of the row is preferably at most 70 cm, more preferably at most 50 cm. The device by means of which the method is carried out can thus be relatively lightweight and be readily manually operable, in this case, for example, supported by one or a number of relatively lightweight (electric) motors, for example servomotors, with a (combined) power of, for example, between approximately 1 kW and 10 kW, as a result of which the method is particularly suitable for relatively small-scale projects.

Such an embodiment offers the possibility for the substrate member to be unwound from an unwinding spool upstream from the fibre-inserting pin or, optionally, a row of fibre-inserting pins while the method is being carried out. The fibres which are situated in the length of the unwound part of the band-shaped substrate member can in this case be pushed into the ground by the fibre-inserting pins during step C.

Also, a band-shaped substrate member offers the possibility for the substrate member to be wound onto a winding spool downstream while the method is being carried out. This facilitates disposal and possible re-use of the substrate member. When using a substrate member, it may be advantageous if the positioning means engage with the substrate member in order to position the fibre under a fibre-inserting pin according to step B. To this end, the substrate member may, for example, be provided with engagement elements, such as holes, in which teeth of the positioning means engage.

If a substrate member is being used and if, during step C, a number of fibre-inserting pins arranged in a row are simultaneously moved down and up in order to push an equally large number of fibres into the ground, as has been discussed above, it may be advantageous if the substrate member supports the fibres in neighbouring rows, in which rows the fibres extend parallel to each other and to the direction of motion, with the distance between the respective fibres in a row being equal to the distance between the fibre-inserting pins of the device, and with the positioning means moving the substrate member over a pitch length in the direction of motion for each step E. In this case, the pitch length corresponds with the distance between neighbouring fibres of neighbouring rows as supported by the substrate and which fibres are successively being pushed into the ground by the same fibre-inserting pin during successive steps C.

Alternatively, it is also possible in this case for the substrate member to support the fibres in a single row, in which row the fibres extend parallel to each other and to the direction of motion, with the distance between the respective fibres in the row being equal to the distance between the fibre-inserting pins of the device, and with the positioning means moving the substrate member over a pitch length in a horizontal direction at right angles to the direction of motion for each step E. If the device by means of which the method is being carried out comprises a row of fibre- inserting pins, the pitch length corresponds with the distance between the outermost fibres of a number of neighbouring fibres, which number corresponds with the number of fibre-inserting pins of the row of fibre-inserting pins plus one.

The connection between the fibres and the band-shaped substrate member may be an adhesive connection which is easy to bring about.

Alternatively, or in combination with another form of connection, such as an adhesive connection, as mentioned above, the connection between the fibres and the band-shaped substrate member may be a form-fitted connection. In that case, a practical embodiment may be achieved if the fibres are each retained, along part of their length, between the substrate member and at least one elongate retaining member which extends at right angles to the fibres and is connected with the substrate member at positions between the fibres, or more specifically if each of the fibres is retained between the substrate member and two elongate retaining members extending parallel to each other. In case the connection also relates to an adhesive connection, it may furthermore be advantageous if the at least one elongate retaining member is provided with a layer of adhesive on the side facing the substrate member.

It is possible to obtain a highly practical embodiment if the substrate member comprises a passage for each fibre, in which case each of the fibres extends through a passage, if desired. In this case, the passage may ensure a form-fitted connection.

Alternatively, each of the fibres may also intersect the corresponding passage.

If, as described above, two retaining members per fibre are used, it may be advantageous if each passage is provided between the two retaining members.

If the fibre-inserting pin moves through the passage during step C, the passage may form a guide for the fibre.

The reliability of the process of pushing the fibres into the ground by the fibre-inserting pin may be influenced in a positive manner if the substrate member is clamped by clamping members of the device, at least during part of the downward part of step C, which clamping is discontinued before step B is subsequently performed.

According to a possible embodiment, the substrate member is configured as a packaging comprising compartments for the fibres. In this case, consideration may for example be given to a substrate member which is configured as a blister pack.

An advantageous embodiment of the method is characterized by the fact that the fibres have a thickened part. The thickened part may thus serve as a point of engagement for a fibre-inserting pin, so that a fibre may be pushed into the ground during step C with increased reliability. In addition, in practice, the thickened part may serve as an anchor for the fibre in the ground following step C.

Advantageously, filaments of the fibre are connected to each other at the location of the thickened part. Thus, it is possible to prevent, or at least greatly reduce the risk of, the filaments of the fibres moving with respect to each other in their length direction during or after the fibres have been pushed into the ground.

If the fibres are engaged in the traditional manner in the middle of its length by the fibre-inserting pin, it is preferred that the thickened part is situated in the centre of the length of the fibre.

However, the use of a thickened part also offers the possibility of engaging the fibres outside the centre. There is thus no need to push the fibres into the ground folded in half. Thus, the thickened part may also be situated outside the centre of the length of the fibre and may preferably be situated at one end of the fibre.

According to a possible embodiment, the thickened part is formed by a knot in the fibre. This knot may have been tied in a single fibre, but may also be tied between two fibres, so that the two fibres are connected to each other.

According to an alternative, the thickened part is formed by an annular member or binding yarn which extends around the fibre. The use of an annular member offers more freedom regarding the design and dimensions of the thickened part.

One very practical embodiment, at least in terms of production engineering, may be obtained if the thickened part is formed by cured adhesive or if the fibre comprises a thermoplastic material and the thickened part is formed by solidified melt of the thermoplastic material.

The advantages of using a thickened part in each fibre are in particular relevant if, during the downward part of the movement of the fibre-inserting pin, the fibre-inserting pin engages on the thickened part or on a part of the fibre which directly adjoins the latter.

When using fibres with thickened parts and a passage in the substrate member for each fibre, as discussed above, it may be advantageous if the thickened part of the fibre is situated on that side of the passage facing away from the fibre- inserting pin during step B and the largest part of the length of the fibre is situated on that side of the passage which faces the fibre-inserting pin, in which case the fibre- inserting pin more preferably moves through the passage during step C.

In particular, but not only, if the substrate is made from non-elastic material, it may furthermore be advantageous if, during step B or C, the thickened part of the fibre is moved by a moving member of the device from a retaining zone of the passage behind at least a part of the peripheral edge of which the thickened part hooks, in the direction of a releasing zone of the passage, which releasing zone is connected with the retaining zone and in which the periphery of the thickened part fits inside the periphery of the passage in the releasing zone. To this end, the passage may, at least substantially, have the shape of a keyhole.

The substrate member may be both of the disposable type and of the re-usable type. The first case may be advantageous for ease of use, whereas the second case may be advantageous from an environmental point of view.

The invention furthermore relates to a combination of a substrate member and a collection of thread-like fibres for use in a method according to the invention as discussed above, which fibres are positioned with respect to each other by the substrate member to which the fibres are connected. The advantages which may be achieved by such a combination have already been explained by means of the explanation of the method of the invention in the various possible embodiments thereof.

In particular, it is pointed out that the fibres may be positioned in parallel rows, that the substrate member is band-shaped and/or that the substrate member for each fibre comprises an optionally non-round passage. In the last embodiment, each fibre may extend through a passage.

Further advantageous embodiments may be obtained if each fibre has a thickened part which is situated on one side of the passage and that the largest part of the length of the fibre is situated on the opposite side of the passage.

A form-fitted connection between the fibres and the substrate member may be obtained if each fibre extends through a passage in such a way that the thickened part of the fibre hooks behind at least a part of the peripheral edge of the passage in a retaining zone of the passage. The thickened part can thus be positioned accurately, which promotes reliable engagement of the fibre by a fibre-inserting pin during step C.

In order to permit, on the one hand, an accurate mutual positioning of the fibres, more specifically of the thickened parts thereof, and, on the other hand, prevent damage/deformation of the substrate member during step C, it is possible to configure the combination in such a way that the passage has a releasing zone which is connected to the retaining zone, with the periphery of the thickened part fitting inside the periphery of the passage in the releasing zone.

The substrate in the combination may furthermore be provided with engagement elements which are arranged in a regular pattern for engagement by engagement members of positioning means in order to move the substrate and thus position the fibres under fibre-inserting pins of a device in accordance with step B.

In this case, a relatively simple embodiment may be obtained if the engagement elements are formed by holes which are engageable by teeth of positioning means.

The combination preferably also comprises an axle body around which the substrate is wound. In this case, it is further preferred if the weight of the combination is at most 20 kg, preferably at most 15 kg, so that the combination, i.e. including the axle body, can be handled by one single individual. A highly suitable weight of the respective combination would be, for example, approximately 10 kg.

More preferably, the ratio of the weight of the fibres and the weight of the substrate member is at least 1 : 12, preferably at least 1 :6. As the ratio increases, it will be possible to introduce fibres in a larger ground surface area using a single combination, starting from a constant weight of the combination. The optimum ratio will also depend on whether the substrate is of the re-usable type or not.

The invention also relates to a device for introducing thread-like fibres into the ground, comprising a frame which can travel over the ground in a direction of motion, one fibre-inserting pin, moving means for moving the fibre-inserting pin down and up with respect to the frame, positioning means for positioning a fibre under the fibre-inserting pin, in which, as a characteristic feature of the invention, the device is furthermore provided with unwinding means for unwinding a roll of a band-shaped substrate which carries a collection of fibres and/or winding means for winding the band-shaped substrate to form a roll.

For the abovementioned reasons, it may be advantageous if the fibre- inserting pin encloses an angle with a direction parallel to the direction of motion when pushing a fibre into the ground. If this is desirable, the device preferably comprises adjustment means for adjusting the angle which the length direction of the fibre- inserting pin encloses with a direction parallel to the direction of motion. Use of a such a measure may also be advantageous with a prior-art device. Therefore, the invention also relates to a device for introducing fibres into the ground comprising a frame which can travel over the ground in a direction of motion, one fibre-inserting pin, moving means for moving the fibre-inserting pin down and up with respect to the frame, positioning means for positioning a fibre under the fibre-inserting pin, in which the device comprises adjustment means for adjusting the angle which the length direction of the fibre-inserting pin encloses with a direction parallel to the direction of motion.

Furthermore, it may be advantageous for the abovementioned reasons if the device has control means for controlling the speed with which the fibre- inserting pin moves down and/or up, based on the resistance encountered by the fibre- inserting pin due to contact with ground during the movement of the fibre-inserting pin. Use of such a measure may also be advantageous with a prior-art device. Therefore, the invention also relates to a device for introducing fibres into the ground comprising a frame which can travel over the ground in a direction of motion, a number of fibre- inserting pins which are arranged in a row extending at right angles to the direction of motion, moving means for moving the fibre-inserting pins down and up with respect to the frame, positioning means for positioning fibres under the fibre-inserting pin, in which the device has control means for controlling the speed with which the fibre- inserting pin moves down and/or up, based on the resistance encountered by the fibre- inserting pin due to contact with ground during the movement of the fibre-inserting pin.

The device may comprise a number of fibre-inserting pins which are arranged in a row extending at right angles to the direction of motion, in which the moving means are configured for moving the fibre-inserting pins down and up, preferably together and thus simultaneously, with respect to the frame.

The unwinding means and/or the winding means may be configured for rotating the corresponding roll about a rotation axis, which rotation axis extends in a direction parallel to the direction of motion or in a horizontal direction exactly at right angles to the direction of motion.

The moving means may be configured for synchronously moving the fibre-inserting pins arranged in a row.

According to a further embodiment, a first portion of the number of fibre-inserting pins are connected to each other via a first subframe and a second portion of the number of fibre-inserting pins are connected to each other via a second subframe, with the moving means being configured for asynchronously moving the first portion of the number of fibre-inserting pins via the first subframe and moving the second portion of the number of fibre-inserting pins via the second subframe.

In this case, it is possible for the moving means to have a first drive member for driving the first subframe and to have a second drive member for driving the second subframe or for the moving means to have a single drive member for driving both the first subframe and the second subframe.

Use of the above-described measure in connection with asynchronously moving the first portion of the number of fibre-inserting pins via the first subframe and moving the second portion of the number of fibre-inserting pins via the second subframe may also be advantageous with a prior-art device. Therefore, the invention also relates to a device for introducing fibres into the ground comprising a frame which can travel over the ground in a direction of motion, a number of fibre- inserting pins which are arranged in a row extending at right angles to the direction of motion, moving means for moving the fibre-inserting pins down and up with respect to the frame, positioning means for positioning fibres under the fibre-inserting pin, in which a first portion of the number of fibre-inserting pins are connected to each other via a first subframe and in that a second portion of the number of fibre-inserting pins are connected to each other via a second subframe, with the moving means being configured for asynchronously moving the first portion of the number of fibre-inserting pins via the first subframe and moving the second portion of the number of fibre- inserting pins via the second subframe.

When using a first portion of the number of fibre-inserting pins which are connected to each other via a first subframe and a second portion of the number of fibre-inserting pins which are connected to each other via a second subframe, in with moving means being configured for asynchronously moving the first portion of the number of fibre-inserting pins via the first subframe and moving the second portion of the number of fibre-inserting pins via the second subframe, it may furthermore be advantageous if the device has control means for controlling the time period between the starts of the downward movements of the first portion of the number of fibre- inserting pins and of the second portion of the number of fibre-inserting pins, based on the resistance which the fibre-inserting pins encounter due to contact with ground during the movement of the fibre-inserting pins. Use of such a measure may also be advantageous with a prior-art device. Therefore, the invention also relates to a device for introducing fibres into the ground comprising a frame which can travel over the ground in a direction of motion, one fibre-inserting pin, moving means for moving the fibre-inserting pin down and up with respect to the frame, positioning means for positioning a fibre under the fibre-inserting pin, in which the device furthermore has control means for controlling the time period between the starts of the downward movements of the first portion of the number of fibre-inserting pins and of the second portion of the number of fibre-inserting pins based on the resistance encountered by the fibre-inserting pins due to contact with ground during the movement of the fibre- inserting pins.

The advantages associated with the device according to the invention as explained above, optionally in possible embodiments thereof, will be clear to the reader after the above explanation of the method according to the invention.

The invention will be explained in more detail below with reference to the following figures, in which:

Fig. 1 shows an isometric view of a device according to the invention for introducing fibres into the ground;

Fig. 2 shows a cross section of Fig. 1 ;

Fig. 3 shows an unwinding roll and a winding roll for a substrate as used in the device from Fig. 1 ;

Fig. 4 shows the substrate from Fig. 3 in greater detail;

Fig. 5a and Fig. 6 show the inserting mechanism which forms part of the device from Fig. 1 in a top position and in a bottom position, respectively;

Fig. 5b and Fig. 5c show a part of Fig. 5a in greater detail in side view and in isometric view, respectively;

Fig. 7 shows a first alternative embodiment of a band-shaped substrate;

Fig. 8 shows a detail of Fig. 7;

Fig. 9 shows a second alternative embodiment of a band-shaped substrate;

Fig. 10 shows a detail of Fig. 9;

Fig. 1 1 shows a third alternative embodiment of a band-shaped substrate;

Fig. 12 shows a detail of Fig. 1 1 ;

Figs. 13a to 13d show four successive moments during use of the invention with a fourth alternative embodiment of a band-shaped substrate, in which a side view and, below the latter, a plan view are shown for each figure;

Figs. 14a and 14b show in detail a plan view of the band-shaped substrate from Figs. 13a and 13b, respectively; Fig. 14c show the band-shaped substrate without fibre in detail;

Figs. 15a and 15b show two isometric views of a further device according to the invention;

Fig. 16 shows an isometric view of an injecting unit as used with the device according to Figs. 15a and 15b;

Figs. 17a and 17b show two isometric views of an alternative embodiment for an injecting unit;

Figs. 18a to 18f show a perpendicular view of six successive positions of the injecting unit in operation.

Figs. 1 and 2 show a device configured as a trolley 1 for introducing thread-like fibres into the ground. The trolley 1 is configured with a single front wheel 2 and two rear wheels 3. The trolley 1 furthermore comprises a roller 9 behind the rear wheels 3. The front wheel 2 is of the steerable type. Trolley 1 is furthermore provided with driving means which comprise an electric motor for driving the rear wheels 3. Trolley 1 furthermore comprises a housing 4. A handle 5 is provided on the rear side of housing 4 by means of which the front wheel 2 can be steered and directed in a desired direction.

A band-shaped substrate 7 is provided inside housing 4 (see also Figs. 3 and 4). The substrate 7 may be, for example, made of paper or plastic, such as polyvinyl chloride. At one end, this substrate 7 is wound up to form a roll 6 and, at the opposite end, substrate 7 is wound up to form a roll 12. Roll 6 is supported by an axle body (not shown in more detail) which extends inside the central passage 8 of roll 6. The axis of the axle body extends parallel to the direction 10 of motion of trolley 1 . Roll 6 is rotatable about axis in the direction of rotation 1 1 , as a result of which the band-shaped substrate 7 is unwound from roll 6. It can be seen in Figs. 2, 3, 5a and 6a that the band-shaped substrate 7 is then wound up again to form roll 12. Roll 6 will be referred to as unwinding roll 6 below whereas roll 12 will be referred to as winding roll 12. Winding roll 12 is also supported by an axle body (not shown in more detail) whose axis extends parallel to the direction of 10 motion for trolley 1 . In this case, winding roll 12 is rotatable about this axis. The axle body is accommodated in the central passage 14 of winding roll 12 in a clamping manner, so that the respective axle body and the winding roll 12 can only rotate together. Trolley 1 comprises driving means, at least comprising an electric motor, by means of which the axle body associated with winding roll 12 and thus winding roll 12 itself can be rotated in the direction of rotation 15. Excitation of the electric motor will result in the band-shaped substrate 7 being unwound from unwinding roll 6 and being wound onto winding roll 12. On the side of unwinding roll 6, trolley 1 is provided with a guide roller 16a which is freely rotatable about its axis and which extends parallel to the direction 10 of motion. On the side of winding roll 12, trolley 1 is provided with a guide roller 16b which is also freely rotatable about its axis and extends parallel to direction 10 of motion. The band-shaped substrate 7 is passed around the guide rollers 16a, 16b between unwinding roll 6 and winding roll 12, so that the band-shaped substrate 7 extends in a straight line and horizontally between them and moves in the direction of motion 18, which extends at right angles to the direction 10 of motion, during the unwinding from unwinding roll 6 and the winding onto winding roll 12. As an aside, it should be noted that Fig. 3 does not show the guide rollers 16a and 16b, as a result of which the band-shaped substrate 7 runs in a straight line between the unwinding roll 6 and the winding roll 12. Trolley 1 is provided with a pair of gear wheels 17 between the guide rollers 16a and 16b. The axes of these gear wheels 17 are aligned with each other and extend parallel to the direction 10 of motion.

On its two opposite longitudinal sides, the band-shaped substrate 7 is provided with round holes 19 which are situated a regular distance 20 apart. In operation, the teeth of the two gear wheels 17 engage in the holes 19. It is also conceivable to provide one or both guide rollers 16a, 16b with teeth which would engage in holes 19. At least one of the gear wheels 17 is coupled with a sensor which records the magnitude of the angular displacement of gear wheel(s) 17 and thus also the number of rotations of gear wheel(s) 17. This sensor is coupled with an electronic control unit which actuates the electric motor associated with winding roll 12.

Trolley 1 furthermore comprises a flat guide panel 21 , whose width is equal to the width of the band-shaped substrate 7. Guide panel 21 extends directly underneath the band-shaped substrate 7 in the area between the unwinding roll 6 and the winding roll 12 and, in use, provides guidance and support for the band-shaped substrate 7. In order to provide space to the teeth of gear wheels 17 and to any teeth of guide roller 16a and/or 16b, recesses can be provided in the respective positions of guide panel 21 . On the side which faces away from the guide panel 21 , the band- shaped substrate 7 is provided with thread-like fibres 31 which extend parallel to each other in the direction 10 of transport. The fibres may be made of plastic, but may also be made of a natural material, such as bamboo, flax or coconut. The fibres may in this case consist of a number of filaments, for example six or eight, which are, for example, twisted together. Typically, the length of the fibre is, for example, 43 cm. The mutual distance between the aforementioned holes 19 in the band-shaped substrate 7 is chosen such that each of the holes extends exactly between two fibres 31. In the present example, five fibres are provided between neighbouring holes 19. The width of the band-shaped substrate 7 is adapted to this length of the fibres 31 and is at least substantially equal thereto. The fibres 31 are equidistant from one another and are connected to the band-shaped substrate 7 by means of two adhesive strips 32 which are provided with respective layers of adhesive. The adhesive strips 32 extend parallel to each other in the length direction of the band-shaped substrate and bond to the band-shaped substrate 7 between the fibres 31 . The fibres 31 are retained between the adhesive strips 31 on the one hand and the band-shaped substrate 7 on the other hand. The adhesive strips 32 are provided close to the centre of the length of the fibres 31 . The respective distance between the centre of the length of the fibres 31 and the adhesive strips 32 is denoted in Fig. 4 by reference numeral 33. A round hole 34 is provided in substrate 7 under each fibre 31 exactly in the centre of the length of fibres 31 , i.e. exactly between the two parallel adhesive strips 32.

Trolley 1 is furthermore provided with a row of fibre-inserting pins 41 , more specifically in this example with a row of twenty pins 41 . The pins 41 extend downward from beam 42 which is connected to the top ends of the pins 41 . The respective connection is detachable, so that a pin 41 can readily be dismounted and possibly replaced if necessary. The row of pins 41 extends parallel to the length direction of the band-shaped substrate 7. The intermediate distance between the pins 41 equals the intermediate distance between the fibres 31. The pins 41 are provided with an inverted V-shaped groove 43 at their bottom ends.

Trolley 1 furthermore comprises two actuators 44, such as pneumatic cylinders by means of which beam 42 can be moved down and up between the top position from Fig. 5a and the bottom position from Fig. 6a. Just above the bottom ends of pins 41 , trolley 1 is provided with a guide beam 45 in which a guide hole 46 is provided for each pin 41 . At two opposite ends of the guide beam 45, two upright guide rods 47 are provided which are in line with the row of pins 41 . The top ends of the guide rods 47 extend through guide holes (not shown in more detail) in the beam 42. The guide beam 45 is provided with pressure-exerting elements 49 at positions between the pins 41 . Guide holes (not shown in more detail in the figures) are also provided for each pin 41 directly under the guide holes 46 in the guide beam 45 in guide panels 21 .

Trolley 1 functions as follows. Trolley 1 is placed on ground in such a way that there is a strip of ground at the front of the trolley 1 into which fibres 31 have to be introduced. Subsequently, actuators 44 are actuated to cause a downward and upward movement, so that the fibres 31 which are situated directly under the pins 41 are inserted into the ground. During the downward stroke, the inverted V-shaped bottom ends 43 help to ensure that the respective fibres 31 are engaged in a satisfactory manner by the pins 41 . During the downward movement, the bottom end 43 of each pin 41 successively moves through the corresponding hole 34 in substrate 7, into the guide hole in the guide panel 21 situated directly underneath and finally into the ground. The fibre 31 is thus also forced through said holes and folded in half in the process. In this case, the downward movement ends at a position in which the two ends of the fibre 31 still protrude a few centimetres, for example 2 cm, above the ground. During the first part of the downward movement, guide beam 45 also moves downward until the pressure-exerting elements 49 bear against the top sides of the adhesive strips 32 and clamp the substrate 7 against the guide panel 21 due to the action of the aforementioned pressure springs. Due to this clamping action, the substrate 7 remains taut while the fibres 31 are being pushed into the ground. During the upward movement of the pins 41 , the fibres 31 remain behind in the ground. At the end of the upward movement, the guide beam 45 moves upward again and the pressure-exerting elements 49 are released from the substrate 7. The downward and upward movement of the guide beam 45 with pressure-exerting elements 49 may be achieved, for example, by means of separate actuators and/or spring members.

Subsequently, the control unit of trolley 1 ensures, on the one hand, that the trolley 1 moves over the ground in the direction of motion 10 over a pitch distance, which is typically equal to the distance between neighbouring fibres 31 . On the other hand, the electric motor associated with winding roll 12 is excited so that the band-shaped substrate 7 is wound further onto winding roll 12 and a new part of band- shaped substrate 7 is unwound from unwinding roll 6 in such a manner that the next twenty fibres on substrate 7 are again positioned under the twenty pins 41 . The respective electric motor is excited until the sensor associated with gear wheels 17 determines that the required length of band-shaped substrate has been wound onto winding roll 12 and unwound from unwinding roll 6. The above process is repeated for the entire strip of ground into which fibres 31 are to be introduced. Subsequently, fibres may be introduced in a similar way in one or a number of neighbouring strips of ground. It will be clear that the band-shaped substrate 7, insofar as it forms part of the unwinding roll 6, is provided with fibres 31 and, insofar as it forms part of winding roll 12, is no longer provided with fibres 31. It is conceivable for substrate 7 to be re-used after use by again providing it with fibres 31.

It is also possible to introduce fibres 31 into a strip of ground which is narrower than the length of a row of twenty pins 41 . To this end, some of the pins 41 of the beam 42 may be dismounted, so that the length of the row of pins 41 corresponds to the desired width of the strip of ground. Subsequently, the electric motor associated with the winding roll is excited in such a way that every time only a length corresponding to the smaller number of pins 41 of the substrate 7 is wound onto winding roll 12 and logically unwound from unwinding roll 6.

Figs. 7 and 8 relate to an alternative embodiment of a band-shaped substrate 51 with thread-like fibres 52, as could also be used with the invention. The longitudinal edges of the band-shaped substrate 51 are provided with holes 19, just like band-shaped substrate 7. An important difference is the fact that the fibres 52 extend with their length direction parallel to the length direction of the band-shaped substrate 51 and are provided in groups in successive rows of a number of, in this example 21 , fibres 52, which number corresponds to the number of fibre-inserting pins of the device by means of which the fibres 52 can be introduced into the ground. The respective device can again be configured as a trolley. The fibre-inserting pins of this trolley are arranged in a row of twenty-one pins, the length direction of which extends at right angles to the direction of motion of the trolley, as is the case with trolley 1 . However, the axes and thus the rotation axes of the axle bodies which support an unwinding roll and a winding roll for the band-shaped substrate 51 are not oriented parallel to the direction of motion of the trolley, as is the case with trolley 1 , but rather at right angles thereto, with the respective unwinding roll and winding roll being situated on opposite sides of the row of fibre-inserting pins, i.e. in the direction of motion of the trolley on the front side and on the rear side of the row of pins. As is illustrated, in particular in Fig. 8, each of the fibres 52 of a row of fibres 52 is connected to the band-shaped substrate 51 via two adhesive strips 53, 54. The adhesive strips 53, 54 are provided slightly out of the centre of the length of each of the fibres 52. A round hole 55, similar to hole 34 in band-shaped substrate 7, is provided between the two adhesive strips 53, 54 for each fibre 52 in the band- shaped substrate 51.

In use, the band-shaped substrate 51 is positioned under the row of fibre-inserting pins in such a way that each of the holes 55 is aligned with one of the fibre-inserting pins, so that, during the downward movement of the fibre-inserting pins, these first engage a fibre 52 with their bottom end and then move through the holes 55 and the guide holes situated underneath the latter in the guide panel, similarly to guide panel 21 , and then into the ground beneath them.

The thread-like fibres 62 associated with the band-shaped substrate 61 according to Figs. 9 and 10 may be introduced into the ground using the same device as is used with the band-shaped substrate 51 from Figs. 7 and 8. In contrast to fibres 52 which run in a straight line, fibres 62 on the substrate 51 are shaped to form a U shape. In this case, each of the fibres 62 has two leg portions 62a, 62b, whose length almost corresponds with half the total length of the fibre 62, and a relatively short body part 62c which extends at right angles to the leg portions 62a, 62b and connects the latter to each other.

A U-shaped recess 63 is provided for each of the fibres 62 in the band-shaped substrate 61 with leg portions 63a and 63b, as well as body part 63c. Due to the U-shaped recess 63, the band-shaped substrate 61 comprises a lip 64 for each of the fibres 62. A round hole 65 is provided in each of the lips 64. On opposite sides of the hole 65, indentations 66a, 66b are provided on the outer sides of the leg portions 63a and 63b. The leg portions 62a and 62b of fibres 62 extend parallel to the leg portions 63a, 63b of the U-shaped recess 63 on the top side of the band-shaped substrate 61 . The body part 62c of fibre 62 extends on the bottom side of lip 64, more specifically directly under the hole 65 of the respective lip 64. In the transition areas between leg portion 62a and body part 62c, and between leg portion 62b and body part 62c of fibre 62, fibre 62 extends through the indentations 66a, 66b. The material of the band-shaped substrate 61 has a stiffness which is such that lip 64 is in line with the rest of the band-shaped substrate 61 . As a result thereof, lip 64 presses on the body part 62c of fibre 62, on the bottom side of band-shaped substrate 61. The fibres 62 may be introduced into the ground in a way which is similar to the way in which fibres 52 may be introduced into the ground.

The band-shaped substrate 71 from Figs. 1 1 and 12 could be seen as an elongate blister-like packaging for thread-like fibres 72. For each of the fibres 72, a blister 73 is provided. Just like the fibres 52 in Figs. 7 and 8, the fibres 72 extend in groups, parallel to each other and to the length direction of the band-shaped substrate 71 . At the location of the centre of the length of each fibre 72, a round passage 74 is provided in each blister 73, through which a fibre-inserting pin can move downward in use and engage the fibre 72 situated in the respective blister 73 in order to then push it into the ground as the downward movement of the fibre-inserting pin continues.

In the band-shaped substrate 81 from Figs. 13a to 13d, keyhole- shaped holes 83 are provided. More specifically, this keyhole shape comprises a circular part 83a and a narrowed part 83b which adjoin each other and in which the diameter of the circular part 83a is greater, for example three times greater, than the width of the narrowed part 83b. The holes 83 are arranged in rows, which rows extend at right angles to the direction of motion of the trolley by means of which the fibres 82 can be introduced into the ground.

In Figs. 13a to 13d, only one hole 83 is shown in the respective plan views for the sake of clarity.

The thread-like fibres 82 are of a different type from those described above. The reason for this is that fibres 82 comprise a thickened part 82a, whose diameter is smaller than that of the circular part 83a, but larger than the width of the narrowed part 83b. The thickened part may for example be formed by making a knot in the fibre 82, by a cured adhesive which connects the filaments of the fibre 82 with each other or an annular clamping part which connects the filaments. In the initial position in Figs. 13a and 14a, the thickened part 82a extends on the bottom side of the band-shaped substrate 81 , more specifically at the location of the narrowed part 83b of an associated hole 83. The remaining part of the fibre 82 extends from the thickened part 82a through the narrowed part 83b to the top side of the substrate 81 .

In use, the holes 83 are positioned under the corresponding fibre- inserting pin 41 in such a way that the circular parts 83a thereof are aligned with the fibre-inserting pin 41. Thereafter, the thickened part 82a is pushed from the narrowed part 83b to the circular part 83a by a pressure-exerting body 85, as is illustrated in Fig. 13b. As a result thereof, the thickened part 82a is aligned with the fibre-inserting pin 41 which can then push the fibre 82 into the ground by means of a downward movement, as is illustrated in Figs. 13c and 13d. While the pressure-exerting body is moving the thickened part 82a, roller 84 pushes the fibre 82 lightly against the substrate 82 in order to fix the position of fibre 82, also if the thickened part 82a is positioned at the circular part 83a of hole 83. In this way, the reliability with which pin 41 engages with the fibre 82 is increased.

Figs. 15a and 15b show at least the internal parts of a device configured as a trolley 101 for introducing fibres into the ground. Trolley 101 has an injecting unit 102 (Fig. 16c) which extends between unwinding roll 6 and winding roll 12. Injecting unit 102 comprises two beams 103, 104 which, at least in the highest position of these beams 103, 104, are situated in line with one another. Injecting unit 102 furthermore comprises a row of twenty parallel fibre-inserting pins 105. The top ends of one half of directly adjacent fibre-inserting pins 105 are rigidly connected to beam 103. The top ends of the other half of the fibre-inserting pins 105 are rigidly connected to the other beam 104. The band-shaped substrate 7 which, in use, is unwound from unwinding roll 6 and wound onto winding roll 12 is passed under the bottom ends of the fibre-inserting pins 105, at least if these are in their highest position. In the centre of the length, on those sides of the beams 103, 104 facing away from the fibre-inserting pins 105, each of the beams 103, 104 is connected with a piston rod 106, 107 of a cylinder which is operated by respective servomotors 108, 109. In order to guide this movement, the injecting unit also comprises a guide beam 1 10 which is provided with guide holes for each of the fibre-inserting pins 105. By means of the two servomotors 108, 109, the beams 103, 104 and fibre-inserting pins 105 connected thereto can be moved down and up independently from each other in the length direction of the piston rods 106, 107 and of the fibre-inserting pins 105. The independent control by means of the two servomotors 108, 109 makes it possible, for example, to move the beams 103, 104 down and up with an identical speed profile, but with a specific phase difference or to move beams 103, 104 down and up with a different speed profile. Furthermore, it is possible to determine the mechanical resistance which the fibre-inserting pins due to the contact with the ground encounters or at least deduce it from the power which the servomotors 108, 109 require. Depending on the determination, it is then possible, for example, to adjust the speed profile of the beams 103, 104 and/or to adjust the phase difference between the beams 103, 104. If the ground into which the fibre-inserting pins 105 are pushed is relatively soft, the downward speed may, for example, be greater and/or the phase difference may be smaller.

The injecting unit 102 is arranged so as to be tiltable with respect to the chassis of the trolley 101 about a virtual tilting axis which coincides with the row which is formed by the points where the fibre-inserting pins stick into the ground when in use. In order to fix a tilting position, trolley 101 comprises on opposite sides of the trolley 101 a fixing plate 121 with holes 122, 123, each of which are arranged in an arcuate shape. The heart of the arcuate shapes coincides with the virtual tilting axis. Fig. 15a shows a position in which the fibre-inserting pins 105 are oriented at right angles to the surface over which the trolley 101 is driving. In Fig. 15b, the injecting unit is tilted, as a result of which the fibre-inserting pins 105 are not pushed into the ground at right angles and consequently the fibres are not pushed into the ground at right angles either.

Figs. 17a and 17b relate to an alternative injecting unit 151 such as may form part of a device configured as a trolley according to the invention, for example as alternative, for injecting unit 102 according to Fig. 16. Injecting unit 151 comprises two parallel beams 152, 153. The beams 152, 153 are provided with teeth 154, 155 on sides facing each other. The teeth 154, 155 secure the top ends of fibre- inserting pins 156, 157. Viewed in a direction parallel to the length direction of the fibre-inserting pins 156, 157, the teeth 154, 155 are arranged in a staggered fashion in such a way that the fibre-inserting pins 156, 157 are also provided in a staggered fashion in a row.

At the opposite ends of the row of fibre-inserting pins 156, 157, two guide rods 158, 159 and 160, 161 are provided for each beam which extend through guide holes on the opposite ends of the beams 152, 153. A guide panel 162 is rigidly connected to the bottom ends of the guide rods 158 to 161. Guide holes are provided in the guide panel 162 for each of the fibre-inserting pins 156, 157. The guide rods 158 to 161 are rigidly connected to the chassis of the trolley.

In order to move the fibre-inserting pins 156, 157 down and up, the injecting unit comprises a double crank mechanism 163. The mechanism 163 comprises a crank 164, 165 and a connecting rod 166, 167 for each of the beams 152, 153 with corresponding fibre-inserting pins 156, 157. Crank 164 and connecting rod 166 are connected to each other via hinge 168. Crank 165 and connecting rod 167 are connected to each other via hinge 169. At the end situated opposite hinge 168, connecting rod 166 is connected to the centre of beam 152 via hinge 170. At the end situated opposite hinge 169, connecting rod 168 is connected to the centre of beam 153 via hinge 171 . The cranks 164, 165 are rigidly connected to each other via continuous transmission 172. For the purpose of the rigid connection, the cranks 164, 165 may also be connected to each other at a distance from transmission 172, for example by means of a strip which extends between hinges 168 and 169. The cranks 164, 165 enclose an angle with each other. The size of the angle determines the phase difference between the downward and upward movement of the beams 152, 153 and thus of the fibre-inserting pins 156, 157. The injecting unit 151 comprises a drive member 173 for driving the crank mechanism 163, such as a servomotor which is coupled to the crank mechanism 163 via the transmission 172.

Starting from the situation according to Fig. 17a, in which the fibre- inserting pins 156, 157 are in their highest position, excitation of the servomotor 173 results in the fibre-inserting pins 156, 157 moving down and up, with there being a phase difference between the fibre-inserting pins 156 on the one hand and fibre- inserting pins 157 on the other hand which corresponds to the angle between the cranks 164, 165. Consequently, the fibre-inserting pins 156 will be pushed into the ground first, followed by the fibre-inserting pins 157. Logically, the fibre-inserting pins 156 will also start the reversal from the downward movement to the upward movement sooner and the fibre-inserting pins 156 will re-emerge from the ground sooner.