EP3402927B1

EP3402927B1 - Device and method for inserting fibres into sod-covered ground

Info

Publication number: EP3402927B1
Application number: EP17702965.9A
Authority: EP
Inventors: Johannes Thomas GOOIKER
Original assignee: Desso Sports BV
Current assignee: Desso Sports BV
Priority date: 2016-01-11
Filing date: 2017-01-09
Publication date: 2020-04-22
Anticipated expiration: 2037-01-09
Also published as: WO2017123084A1; EP3402927A1

Description

The invention in the first place relates to a device for inserting fibres into sod-covered ground, each sod comprising a layer of earth and a layer of grass on top thereof, the device being according to the preamble of claim 1.
Such a device is known from publication EP-A-1 387 817 . Known devices are not different from devices that are used for inserting fibres directly into the ground, i.e. without sods present thereon. By combining natural grass with fibres that are inserted into the natural grass, the natural grass lawn is reinforced. In that case the term hybrid grass or fibre-reinforced grass is used. Sods are typically used for sports fields if little time is available for installing a natural grass lawn, as can for example be the case with sports field in stadiums that are used for important sports competitions. To reinforce the grass, a possible option in the case of pressure of time is to inject the fibres into the natural grass and the ground relatively shortly after the sods have been laid on the ground. At that stage the sods have not yet grown together much with the ground via the roots of the grass of the sods. This entails the risk that upon injection of the fibres, when the fibres are inserted into the sods and the ground by pins, more specifically during the retracting movement of the pins, the sods are moved up along with the pins and come loose from the ground. This has an adverse effect on the quality of the hybrid grass, for example because parts of the fibres can be folded flat between the ground and the sods. To solve this problem, the sods are weighted by spraying water thereon and/or by spreading earth thereover. In the former case, the sods become spongy, which has an adverse effect on the flatness of the hybrid grass. In the latter case the grass is "buried" as it were, which is also undesirable. The object of the invention is to provide an improved solution to the above problems. In order to achieve that object, the device comprises the features defined in claim 1. The retaining element thus prevents, in a very reliable manner, the sods from moving up along with the fibre insertion pins without there being a need to weight the sods with water or earth. The use of the second moving means makes it possible to ensure that the retaining element will be free from contact with the sods while the device moves over the ground, as is necessary when fibres are to be inserted into the ground in an entire field or at least a larger area, so that the sods cannot be damaged by the retaining element.
To achieve the latter advantage, it is furthermore preferable that the second moving means are configured to move the retaining element up and down between the operative position and the non-operative position for every up-and-down movement of the fibre insertion pins, and/or that the second moving means are configured to keep the retaining element in the non-operative position while the device moves over the ground.
In order to be able to guarantee that the retaining element will be operative from the start of the retracting upward stroke of the fibre insertion pins, it is advantageous if the second moving means are configured to keep the retaining element in the operative position at least during the last part of the movement of the fibre insertion pins from the high position to the low position as effected by the first moving means.
According to a possible embodiment, the device comprises sensor means for measuring the distance in the vertical direction between the layer of earth and the frame, wherein the device further comprises control means configured for determining the low operative position of the retaining element on the basis of the measurements by the sensor means. This makes it possible to achieve that the retaining element will be positioned a relatively short distance, for example 1 mm, above the layer of earth in the operative position, so that the retaining element will not press on the sods, which might cause damage to the sods.
In particular, but not exclusively, if no use is made of the aforesaid sensor means it may be advantageous that the second moving means are configured to have the retaining element press on the layer of earth in the operative position.
The at least one retaining element preferably comprises passages through which, in use, the first moving means move the fibre insertion pins during the up-and-down movement of the fibre insertion pins between the high position and the low position. The passages in question can also serve as guides for the fibre insertion pins.
If the passages are provided in an elevated part of the retaining element, the direct surroundings of the location where the fibre insertion pins are inserted into the layer of earth by means of the retaining element need not be retained in place.
It may furthermore be advantageous if the at least one retaining element further comprises passages in front of and behind the positions where, in use, the fibres are inserted into the sods and the ground. This makes it possible to reduce the mass of the retaining element, whilst in addition the further passages provide space for the sod grass and any fibres that have already been inserted into the sods and the ground to extend therethrough.
The invention can in particular be used effectively if the at least one retaining element is configured to be operative within a distance of at most 50 cm, preferably at most 35, seen in the direction of movement, and/or if the at least one retaining element has a symmetrical configuration in relation to the fibre insertion pins.
The present invention further relates to a method for inserting fibres into sod-covered ground, each sod comprising a layer of earth and layer of grass on top thereof. The method according to the invention comprises the repetitive steps defined in claim 12.
The invention will now be explained in more detail by means of a description of two possible embodiments, not to be interpreted as limiting the invention, of a device according to the invention and of a possible embodiment, likewise not to be interpreted as limiting the invention, of the method according to the invention, in which reference is made to the following figures:

Figures 1a-1e schematically show in vertical cross-section five successive steps during the insertion of fibres into sod-covered ground in accordance with the invention;
Figure 2 schematically shows figure 1d in more detail;
Figure 3 schematically shows figures 1d and 2 in perspective view.

Figures 1a-1e schematically show a ground surface 1 for a hybrid lawn to be installed thereon, on which sods 2 have been laid. Each sod has a layer of earth 2a and a layer of grass 2b on top thereof (see also figures 2, 3 4). The term "layer of grass 2b" is understood to mean the layer on top of the layer of earth 2a, within which extends the grass whose roots extend into the layer of earth 2a.
To inject fibres into the sods 2 and the ground 1, a vehicle equipped with a device configured for injecting fibres as mentioned before is used. In use, the vehicle moves in a direction of movement from the bottom left to the top right in figure 3. In the figures, only those parts of the device that are relevant to the present invention are shown. A detailed description of all the parts of the injection device is unnecessary in this case, because such devices are already known to the skilled person, for example from Dutch publication NL 1014978 .
Figure 1a shows a fibre 3 made to length, which extends horizontally, directly below a pin 4. The pin, which forms part of a row of pins (see also figure 3, can be moved vertically up and down relative to the frame of the vehicle by moving means (not shown) between a high position as shown in figure 1a and a low position as shown in figures 1c-1e. During the downward movement, the pin first moves against the fibre 3, midway the length thereof, and subsequently through a guide 5 with a reduced passage, so that the fibre 3 is folded double, as it were, about the point of the pin 4. To obtain an improved guidance, the guide for itself is also movable between a high position (figures 1a and 1e) and a low position (figures 1b-1d).
During its downward movement, the pin 4 first penetrates the sod 2 (figure 1b) and subsequently the ground (figure 1c), for example to a depth of 20 cm. The pin 4 is then moved back up to the high position (figures 1d and 1e) by the moving means. During this retracting movement the fibre 3 remains behind in the ground. The length of the fibre and the stroke length of the pins 4 are such that once the pins 4 have been retracted, the two free ends of the fibres 3 extend above the layer of earth 2a, but still below the tops of the grass in the layer of grass 2b.
There is a risk that a sod 2 will be pulled up briefly upon retraction of the pins 4. This may have an adverse effect on the flatness of the final hybrid lawn. In addition, in some cases folds are formed in one or both fibre halves of the fibres 3, which folds are clamped between the ground 1 and the sod 2 once the latter falls back again. To prevent such problems, the injection device comprises a retaining element 7. This retaining element can be moved between a high, non-operative position (figures 1a and 1e) and a low, operative position (figures 1b-1d) by moving means (not shown). The retaining element 7 is profile-shaped and is for example made of steel or plastic material. The retaining element 7 has a symmetrical configuration in relation to the pins 4 and comprises two contact surfaces 8a, 8b, which are connected via a central, elevated bridge portion 9. On the outer sides of the contact surfaces 8a, 8b, the retaining element further comprises inclined surfaces 10a, 10b and upright edges 11a, 11b.
The distance between the longitudinal edges facing away from each other of the two contact surfaces 8a, 8b, or in other words, between the edges where the contact surfaces 8a, 8b and the inclined surfaces 10a, 10b join one another, is about 22 cm. This distance determines the width (seen in the direction of movement) of the area are within which the retaining element 7 is operative, as will become apparent hereinafter. The length of the area in question is determined by the length of the row of pins 4. In the central, elevated bridge portion 9, a passage 12 is provided for each pin 4, the diameter of which passage is so small that the passages 12 can perform a guiding function for the associated pins 4, for example in the case that a pin strikes a hard object in the ground 1. Significantly larger passages 13 are furthermore provided in the contact surfaces 8a, 8b.
The retaining element 7 functions as follows: During the downward movement of the pins 4, the retaining element 7 also moves from the high, non-operative position to the low, operative position (figure 1b). Ideally, the low, operative position is such that the retaining element, more specifically the contact surfaces 8a, 8b thereof, are positioned a short distance, for example 1 mm, above the layer of earth 2a. Because the thickness of the layer of earth 2a can vary, it is also possible within the scope of the invention to make use of a sensor, for example a mechanical tactile sensor or an optical sensor, which determines the vertical distance between the frame and the layer of earth. Control means may in that case be configured to control the moving means for the retaining element such that the low, operative position is determined on the basis of the measurement by the sensor. Alternatively it is also conceivable, for safety's sake, to use a low, operative position of the retaining element a small distance, for example 1 or 2 mm, below the theoretically ideal operative position. In practice, the retaining element will thus apply a certain pressure to the layer of earth in the operative position thereof. In both cases the grass in the layer of grass 2b as well as the fibres that already extend from the layer of earth 2a into the layer of grass 2b are flattened to a certain degree, except at the positions of the passages 13. This is clearly shown in figures 2 and 3. This is one of the advantages of the passages 13. Another advantage of the passages 13 is that they reduce the weight of the retaining element 7, which is in any case advantageous from the viewpoint of mass inertia effects.
In a variant of the retaining element 7, no elevated bridge portion 9 is provided, but the contact surfaces 8a, 8b join one another directly, so that a single contact surface comprising the passages 12 and (optionally also) the passages 13 is provided.

Claims

A device for inserting fibres (3) into sod-covered ground (1), each sod (2) comprising a layer of earth (2a) and a layer of grass (2b) on top thereof, the device comprising a frame that can be moved in a direction of movement over the ground, a plurality of fibre insertion pins (4) which can move up and down, into and out of the sods (2) and the ground (1), between a high position and a low position relative to the frame, first moving means for moving the fibre insertion pins (4) between the high position and the low position, supply means for carrying fibre (3) to a position under the fibre insertion pins (4) while the fibre insertion pins (4) are in the high position, wherein, in use, the fibre (3) is inserted into the sods (2) and the ground (1) while the fibre insertion pins (4) are subsequently moved from the high position to the low position by the first moving means, wherein the device comprises at least one retaining element (7) for holding the sods (2) in place on the ground, at least while the fibre insertion pins (4) are moved from their low position out of the ground and the sods (2) in the direction of the high position by the first moving means, characterized in that the device comprises second moving means for moving the retaining element (7) up and down between a low, operative position and a high, non-operative position, in which operative position the at least one retaining element (7) retains the sods (2) vertically in place.
A device according to claim 1, wherein the second moving means are configured to move the retaining element (7) up and down between the operative position and the non-operative position for every up-and-down movement of the fibre insertion pins.
A device according to claim 1 or 2, wherein the second moving means are configured to keep the retaining element (7) in the non-operative position while the device moves over the ground.
A device according to claim 1, 2 or 3, wherein the second moving means are configured to keep the retaining element (7) in the operative position at least during the last part of the movement of the fibre insertion pins (4) from the high position to the low position as effected by the first moving means.
A device according to any one of claims 1, 2, 3 or 4, wherein the device comprises sensor means for measuring the distance in the vertical direction between the layer of earth and the frame, wherein the device further comprises control means configured for determining the low operative position of the retaining element (7) on the basis of the measurements by the sensor means.
A device according to any one of claims 1 - 5, wherein the second moving means are configured to have the retaining element (7) press on the layer of earth in the operative position.
A device according to any one of the preceding claims, wherein the at least one retaining element comprises passages (12) through which, in use, the first moving means move the fibre insertion pins during the up-and-down movement of the fibre insertion pins between the high position and the low position.
A device according to claim 7, wherein the passages are provided in an elevated part (9) of the retaining element.
A device according to any one of the preceding claims, wherein the at least one retaining element further comprises passages (13) in front of and behind the positions where, in use, the fibres are inserted into the sods and the ground.
A device according to any one of the preceding claims, wherein the at least one retaining element (7) is configured to be operative within a distance of at most 50 cm, preferably at most 35, seen in the direction of movement.
A device according to any one of the preceding claims, wherein the at least one retaining element has a symmetrical configuration in relation to the fibre insertion pins.
A method for inserting fibres (3) into sod-covered ground (1), each sod (2) comprising a layer of earth (2a) and a layer of grass (2b) on top thereof, comprising the repetitive steps of
A first moving means moving a plurality of fibre insertion pins (4) to a high position, in which a lower end of each fibre insertion pin (4) is spaced above the sods (2),

B supply means carrying fibres to a position under the respective lower ends of the fibre insertion pins (4),

C the first moving means moving the fibre insertion pins (4) downward from the high position to a low position, during which movement the fibres (3) are inserted into the sods (2) and the ground (1) by the fibre insertion pins (4),

D the first moving means moving the fibre insertion pins (4) from the low position in the direction of the high position until the lower end is positioned above the sods (2), or at least above the layer of earth (2a),

E horizontally moving the fibre insertion pins (4) by a stroke length in a direction of movement over the ground,
wherein the sods (2) are vertically retained in place on the ground by a retaining element (7) at least during step D, wherein second moving means keep the retaining element (7) in a low, operative position during step D, and wherein, during two successive steps D, the second moving means move the retaining element (7) from the low, operative position to a non-operative, high position prior to step E and move the retaining element (7) from the non-operative, high position to the low, operative position after step E.