WO2017058009A1

WO2017058009A1 - Sand injection device

Info

Publication number: WO2017058009A1
Application number: PCT/NL2016/050662
Authority: WO
Inventors: Arend Willem VERSCHOOR
Original assignee: Awv Beheer B.V.
Priority date: 2015-09-29
Filing date: 2016-09-27
Publication date: 2017-04-06
Also published as: NL2015526B1

Abstract

The present invention relates to a mobile sand injector for injecting sand into the ground, the device comprising: a base frame configured to be moved over a pitch, a liquid supply connector for connection to a source of pressurized liquid, at least one storage compartment for sand, a plurality of mixing chambers for mixing the sand with the liquid, a plurality of injector nozzles for injecting the mixture of sand and liquid into soil under the pitch, wherein each injector nozzle is associated with a mixing chamber, a plurality of liquid supply conduits, wherein each mixing chamber is connected to at least one liquid supply conduit, wherein the liquid supply conduit supplies pressurized liquid from the source of pressurized liquid to the mixing chamber, a plurality of sand supply tubes, wherein each mixing chamber is connected to at least one sand supply tube, wherein the sand supply tubes are configured for supplying sand to the respective mixing chambers, a control system and at least one operable valve configured for providing a volume of pressurized liquid in pulse form through the liquid supply conduits and into each mixing chamber, wherein the volume of liquid mixes with a quantity of sand in each mixing chamber and wherein the mixture is ejected into the ground, wherein the device comprises a vibration device configured to vibrate the sand supply tubes in order to feed the sand through the sand supply tubes into the mixing chambers.

Description

Title: Sand injection device Field of the invention

The present invention relates to a sand injection device. The sand injection device is used for injecting sand in a grass pitch. The method further relates to a method of injecting sand in a grass pitch. Devices for injecting sand in a grass pitch are known. Background of the invention

Golf courses need to have a grass pitch (fairway and green) which is in excellent shape. The quality of the grass pitch plays a critical role in the business success of the golf course. The grass pitch needs to be even to let the ball roll properly and also needs to have an aesthetically attractive appearance. Other requirements also play a role.

In order to achieve a high quality of the green, the soil beneath the grass needs to have a certain set of properties. Many aspects play a role in the quality of the soil, such as: average grain size, grain size distribution, porosity in combination with hydraulic conductivity (or permeability), water content, aeration, drainage, cohesion, strength, chemical composition, availability of nutrients and fertilizers, presence of pesticides, soil temperature and other factors. Some of these factors are interrelated or mutually conflicting.

For most other sports which are played on a grass pitch, the condition of the grass pitch and the soil on which the grass grows is also very important. The desired

characteristics of the grass pitch may be somewhat different than for a golf course, but a shared requirement is that the grass should be healthy and strong. This also applies for lawns in public parks, lawns in privately owned gardens and other grass pitches.

Often, over the course of time the soil settles and becomes more compact. As a result, the permeability and aeration decreases. This results in slower growth of the grass, the grass roots, slower germination and a decrease in the overall quality of the pitch.

Furthermore, over time it may become clear that the average grain size or grain size distribution of the soil is not optimal. This may be become clear because the grass grows slower than expected or sustains easier damage as a result of usage than expected, or because there are problems with drainage, resulting in pools after rain. The discussed problems may also occur in public or private parks or gardens.

These problems may require corrective action in order to improve the soil underneath the grass pitch. Devices have been developed to improve the soil by injecting material, in particular sand into the soil. The injected sand may have a specific grain size and grain size distribution. One such device has been developed by the company Dryject (www.dryiect.inc) and is published in WO2015/1 12965A1.

In the device according to WO2015/112965A1 , the sand is stored in a hopper and drawn into the nozzle 114 by means of vacuum. Although the device according to

WO2015/1 12965A1 works, it was recognized in the present invention that this device has a disadvantage in that dry sand is required to make it work. The device does not work with relatively wet or humid sand because the moisture between the sand grains results in a certain cohesiveness of the sand. The vacuum force generally is not able to overcome this.

One disadvantage of this phenomenon is that the sand which is generally readily available on a golf course cannot be used because it is too wet. The wetness results from the fact that often the sand is located outdoors and is stored as a pile of sand under the open sky. As a result, the sand will get wet when it rains. The sand can then no longer be used until it is completely dry or almost completely dry. This requires an extra drying operation which often is difficult and takes a lot of time. This is in particular a problem in areas which have a lot of rain.

If it is not possible to provide dry sand from the location of the golf course, sand has to be transported from another location. Apart from the fact that this brings along extra costs, the sand from another location may be different from the sand of the golf course in terms of average grain size, grain size distribution and other properties, and be qualified as "strange sand". It may be undesirable to inject "strange sand" into a golf course. Generally, it is preferable to use sand from the golf course itself or from the direct vicinity of the gold course because this sand is the same as the sand of the existing golf course.

A basic requirement for sand injection is further that the grass pitch should sustain only minimal damage as a result of the treatment. It should further be possible to carry out the treatment in a relatively short period of time in order to prevent excessive down time of the golf course. An earlier device of Dryject has been published as US7581684. This device also only works with dry sand, for the same reasons.

Object of the invention

It is an object of the present invention to provide a method and device for injecting moist or wet sand into the soil underneath a grass pitch.

It is a further object of the present invention to provide an alternative to the prior art.

Summary of the invention

In order to achieve at least one object, the present invention provides a mobile sand injector for injecting sand into the ground, the device comprising:

- a base frame configured to be moved over a pitch,

a liquid supply connector for connection to a source of pressurized liquid, at least one storage compartment for sand,

a plurality of mixing chambers for mixing the sand with the liquid, a plurality of injector nozzles for injecting the mixture of sand and liquid into soil under the pitch, wherein each injector nozzle is associated with a mixing chamber,

a plurality of liquid supply conduits, wherein each mixing chamber is connected to at least one liquid supply conduit, wherein the liquid supply conduit supplies pressurized liquid from the source of pressurized liquid to the mixing chamber, - a plurality of sand supply tubes, wherein each mixing chamber is connected to at least one sand supply tube, wherein the sand supply tubes are configured for supplying sand from the storage compartment to the respective mixing chambers,

a control system and at least one operable valve configured for providing a volume of pressurized liquid in pulse form through the liquid supply conduits and into each mixing chamber, wherein the volume of liquid mixes with a quantity of sand in each mixing chamber and wherein the mixture is ejected as a pulse jet into the ground through the associated nozzle,

wherein the device further comprises at least one vibration device configured to vibrate the sand supply tubes in order to feed the sand through the sand supply tubes into the mixing chambers. The invention has a benefit that wet sand can be injected into the soil.

Although the present invention is focused on improving the injection of wet sand, it will be understood that together with the sand, other substances may be injected such as earth, calcined clay, seeds, insecticides, herbicides, fungicides, root stimulants, fertilizers, and other substances.

In an embodiment, the mobile sand injector comprises or more sand trays positioned downstream from the sand storage compartment, wherein the sand storage compartment is configured to discharge the sand onto the one or more sand trays, wherein upper ends of the sand supply tubes are connected to an underside of the one or more sand tray, wherein the at least one vibration device is configured to vibrate the one or more sand trays. It was advantageously found that the vibrating sand tray ensures a sufficient supply of sand to the mixing chambers. The sand storage compartment does not need to vibrate and is configured to discharge the sand onto the sand tray.

In an embodiment, the sand storage compartment comprises an outflow opening, a ridge, a chute and a sand moving device constructed for moving the sand from the sand storage compartment over the ridge, through the outflow opening and down the chute onto the sand tray. This configuration provides a reliable flow of sand from the sand storage compartment to the sand tray.

In an embodiment, the vibration device is configured to vibrate the sand supply tubes via the vibration of the sand tray. In this way, a single vibration device may vibrate both the sand tray and the sand supply tubes.

In an embodiment, the at least one sand tray is mounted to the frame via at least one flexible member. This effectively ensures a relative freedom of movement of the sand tray to the base frame. In an embodiment, a plurality of sand supply tubes share a single vibration device. In an embodiment this can advantageously be achieved via the sand tray.

In an embodiment, the mobile sand injector comprises a plurality of funnels are defined at a bottom of each sand tray for guiding the sand into the sand supply tubes each bottom end of a funnel has a sand supply tube connected to it. The funnels are arranged in a row and achieve an effective and substantially equal distribution of the sand. In an embodiment, each sand tray comprises a sieve. This allows the use of uncleaned sand which is generally available.

In an embodiment, the mobile sand injector comprises, the mobile sand injector comprises a pump and an accumulator and is configured to raise the pressure of the liquid which enters through the liquid supply connector to a pressure of at least 200 bar. This effectively makes a penetration depth of at least 15 cm possible. The device can be adjusted in order to vary the penetration depth between 5 and 25 cm. The adjustment is performed by adjusting the water volume per pulse, the pulse time or the pressure, or by varying a combination of these.

In an embodiment, the vibration device is configured to vibrate the sand tray in a substantially horizontal plane. This movement advantageously guides the sand into the funnels and into the san supply tubes. In an embodiment, the vibration device is configured to vibrate the sand tray in a substantially circular motion for creating vortices of sand in the sand tray, wherein each sand vortex empties out in a sand supply tube. The vortices prevent blocking of the funnels.

In an embodiment, the sand supply tubes are flexible conduits. This ensures a proper vibration of the sand supply tubes.

In an embodiment, the mobile sand injector comprises, the mobile sand injector comprises one or more wheels, rollers or tracks, and/or a connector for connecting the mobile device to a vehicle such as a tractor.

The present invention further relates to a method of injecting sand into the soil, the method comprising:

positioning a mobile sand injector according to any of the preceding claims on a pitch, in particular a grass pitch,

- supplying sand and volumes of pressurized liquid into the mixing chambers, wherein the vibration device vibrates the sand supply tubes to feed the sand into the mixing chamber.

The method provides the same advantages as the device according to the invention. The sand which is fed into the mixing chambers may be moist or wet. In an embodiment, the method comprises one or more sand trays positioned downstream from the sand storage compartment, wherein the at least one vibration device vibrates the one or more sand trays.

In an embodiment of the method, the vibration device vibrates the sand supply tubes via the vibration of the sand tray.

In an embodiment of the method, the vibration device vibrates the sand tray in a horizontal plane, in particular in a substantially circular motion, and creates vortices of sand in the sand tray, wherein each sand vortex empties out in a sand supply tube.

The penetration depth of the sand may be up to 25 cm. The sand particles spread out as they enter the soil. The sand particles are distributed substantially in the form of an inverted trumpet shape or an inverted cone. In an embodiment, the method comprises varying a penetration depth of the mobile sand injector by adjusting:

a water volume per pulse, or

the pulse time or

the pressure,

or by varying a combination of these parameters.

In an embodiment, the method comprises operating the mobile sand injector at a pressure of at least 200 bar, more in particular 260 - 280 bar. These and other aspects of the invention will be more readily appreciated as the same becomes better understood by reference to the following detailed description and considered in connection with the accompanying drawings in which like reference symbols designate like parts. List of figures

Figure 1 shows a general isometric view of the device according to the invention. Figure 2 shows a side view of the device according to the invention.

Figure 3 shows a top view of the device according to the invention.

Figure 4 shows a rear view of the device according to the invention.

Figure 5 shows an isometric view of the injection carriages. Figure 6 shows a sectional side view of the sand storage compartment and the sand tray.

Figure 7 discloses a sectional side view of a mixing chamber and the associated nozzle.

Detailed description of the drawings

Turning to figures 1 , 2, 3 and 4, the mobile sand injector 10 for injecting sand into the ground comprises a base frame 12 configured to be moved over a pitch. The mobile sand injector comprises a first roller 14 and a second roller 15 for rolling along the pitch. The mobile sand injector may as an alternative have one or more wheels or tracks. A sensor 19 is provided on one of the rollers to measure the travel distance of the mobile sand device

The mobile sand injector further comprises at least one connector 18 for connecting the mobile device to a vehicle such as a tractor. In this case, three connectors 18 are provided. The mobile sand injector further has a power take-off 20 with which power can be taken from the tractor.

The mobile sand injector further comprises a liquid supply connector 22 for connecting to a source of pressurized liquid. The source may be a water tap on the golf course. A water hose extends between the water tap and the connector . The mobile sand injector comprises a support 23 for supporting the water hose in such a way that it cannot come underneath the mobile sand injector.

At least one storage compartment 24 is provided for storing sand. The storage compartment 24 is a hopper having a broad upper part which gradually narrows to a narrow lower part.

The mobile sand injector further comprises legs 28 with which it can stand on the ground independently from the tractor.

The mobile sand injector further comprises an accumulator 29 and a pump 30. The pump 30 is powered with the power take-off 20. The pump and the accumulator raise the pressure of the incoming water to above 200 bar, in particular to a pressure of 250 - 350 bar, more in particular 300 bar. The mobile sand injector further comprises a water filter 31 for filtering the incoming water. The incoming water is filtered with the water filter to prevent blocking of any of the conduits, mixing chambers or nozzles. The mobile sand injector further comprises an additive reservoir 38 for holding additives which can be mixed with the water. The additives may be nutrients, pesticides, herbicides, seeds, and other additives.

The mobile sand injector further comprises a vibration device 50, which will be explained further below.

Turning to figures 2 and 5, each manifold 27A, 27B is provided on an injection carriage 32A, 32B which further comprises a forward roller and a rear roller. Each injection carriage 32A, 32B is pivotably connected to the base frame via an arm 33 and a pivot 34 and is capable of pivoting about two axes, i.e. a first axis 35 which extends horizontally in the transport direction 36 and a second pivot axis 37 which extends horizontally transverse to the transport direction. The injection carriages may pivot independently from one another up to about 5 degrees about both pivot axes 35, 37.

Turning to figure 2 and 6, the mobile sand injector 10 comprises one or more sand trays 40 positioned downstream from the sand storage compartment (when viewed in the flow direction of the sand). Sand supply tubes 52 extend between the sand tray 40 and the manifolds 27A, 27B. There are twenty sand supply tubes 52. The sand supply tubes 52 are flexible tubes and made from a synthetic material. The sand supply tubes 52 have a length (L1) and a main axis.

Upper ends 53 of the sand supply tubes are connected to an underside 54 of the sand tray 30. The vibration device 50 is configured to vibrate the one or more sand trays 40.

In this case there is a single sand tray 40, but in an alternative variant there may be two separate sand trays 40, each sand tray being provided with a vibration device 50.

The vibration does not extend to the manifolds, because the sand supply tubes are flexible. The vibration device 50 is mounted to the underside of the sand tray 40 and comprises an electric motor and an eccenter weight 55. The motor is configured to let the eccenter weight rotate about a substantially vertical axis 56. The vibration device 50 is configured to vibrate the sand tray 40 and the supply tubes 52 in order to feed the sand through the sand supply tubes into the mixing chambers. The vibration device 50 is configured to vibrate the sand tray 40 in a substantially horizontal plane. The vibration device 50 is configured to vibrate the sand supply tubes 52 via the vibration of the sand tray 40. In other words, the vibration device is not connected directly to the sand supply tubes. In this way, multiple sand supply tubes 52 share a single vibration device 50. Turning to figure 6, the sand storage compartment 24 comprises an outflow opening

42, a ridge 43, a chute 44 and a sand moving device 45. The sand moving device 45 is driven by a motor and is a rotary device configured to rotate in direction 47. The sand moving device 45 rotates about a horizontal axis and comprises pusher elements 46 constructed for moving the sand from the sand storage compartment over the ridge, through the outflow opening and down the chute onto the sand tray 40. The arrows 48 indicate the path of the sand.

A separation plate 41 is provided above the opening 42 to separate excess sand and let the excess sand stay in the sand storage compartment. The separation plate is positioned above the outflow opening 42.

Multiple funnels 60 are defined at a bottom of each sand tray for guiding the sand into the sand supply tubes. The sand tray comprises a sieve 64 for removing large objects from the sand. The sieve has a zig-zag shape and distributes the sand over the funnels.

Inclined partition walls 62 separate the funnels 60 from one another. There are twenty funnels. The vibration device 50 is configured to vibrate the sand tray in a substantially circular motion for creating vortices of sand in the funnels of the sand tray, wherein each sand vortex empties out in a sand supply tube 52.

The sand tray 40 comprises a sieve 64. In use, the sand falls through the chute 44 and onto the sieve 64, passes the sieve 64 and falls into the funnels.

The sand tray is mounted to the frame via arms 58. The arms 58 extend forward from the sand tray and are connected to the base frame 12 via flexible members 90, to allow some freedom of movement of the sand tray relative to the base frame. The flexible members 90 are provided between the arms 58 and beams 91 , 92 of the base frame 12 and are shown in fig. 6. The flexible members 90 may be of rubber or another resilient material.

Turning to figure 7, the mobile sand injector comprises a plurality of mixing chambers 25 for mixing the sand with the liquid. The mixing chambers are provided in a first manifold 27A and a second manifold 27B, shown in figure 5. Each manifold comprises ten mixing chambers, but a different number is also possible.

The mobile sand injector further comprises a plurality of injector nozzles 70 for injecting the mixture of sand and liquid into soil under the pitch. Each injector nozzle 70 is associated with a mixing chamber 25. The injector nozzles 70 are positioned vertically underneath the mixing chambers and have a vertical outflow direction of the mixture of water and sand. The mixing chambers 25 are formed in the manifold 27A, 27B.

Each mixing chamber 25 is connected to at least one liquid supply conduit 72, wherein the liquid supply conduit supplies pressurized liquid from the source of pressurized liquid to the mixing chamber. The liquid supply conduits are also formed in the manifold.

A Venturi nozzle 85 is positioned directly above the mixing chamber. The water flow enters the mixing chamber through the Venturi nozzle and creates under pressure which provides some assistance in sucking the sand into the mixing chamber.

Each mixing chamber 25 is further connected to at least one sand supply tube 52. The sand supply tubes are configured for supplying sand from the sand tray 40 to the respective mixing chambers 25. Each mixing chamber has a sand entry 88 where the sand enters the mixing chamber. The diameter of the sand entry is about 1 cm.

The mobile sand injector further comprises a control system 80 and at least one operable valve 82 configured for providing a volume of pressurized liquid in pulse form through the liquid supply conduits 72 and into each mixing chamber 25. The volume of liquid mixes with a quantity of sand in each mixing chamber 25 and the mixture is ejected as a pulse jet into the ground through the associated nozzle 70.

The valve 82 is operable with a solenoid. The valve 82 is positioned upstream of a division point where the liquid supply conduit branches into multiple smaller liquid supply conduits. Therefore, a single valve 82 is used to control the supply of water to all mixing chambers 25 of a manifold. A bottom plate 83 is provided to prevent spats from spatting too much. The bottom plate hovers at a small distance above the ground. Holes are provided in the bottom plate for the nozzles 70.

The mobile sand injector is modular. The tray 40 may be removed and exchanged for dry sand tray if required.

Operation

In operation, the mobile sand injector 10 is positioned on a pitch, in particular a grass pitch. The sand storage compartment is filled with sand and the liquid supply connector is connected to a water tap on the golf course.

The rotary sand moving device 45 starts to rotate and the vibration device 50 starts to vibrate the sand tray. The vibration device may rotate at between 1000 and 3000 rpm, in particular at 2000 rpm. The tray may vibrate with an amplitude of 0.5 cm - 3 cm.

The sand is moved through the opening 42, over the ridge 43 , down the chute 44, through the sieve 64 and into the sand tray 40. The sand is distributed over the funnels 60. The vibration device 50 vibrates the sand tray 40 and the sand supply tubes 52 creates vortices of sand in the funnels, and as a result the sand moves down the funnels 60 and through the sand supply tubes into the mixing chambers 25.

The pump and the accumulator increase the pressure up to 250 bar. The mobile sand injector 10 uses about 2500 liter per hour.

Next the mobile sand injector is moved forward. At intervals, the valve 82 opens for a controlled time period to provide pulses of water into the mixing chambers 25. In the mixing chamber 25, the water mixes with the sand and the mixture is ejected through the nozzles 70 as a pulse jet. The pulse jets may also be referred to as blasts.

The sand which is fed into the mixing chambers can be moist or wet, which is a substantial benefit over the device according to the prior art. The liquid is generally water. The nozzles fire at certain time intervals. The intervals may be pre-set or be linked to the speed of the mobile sand injector and be set as a function of the travelled distance by a control unit 100 and a sensor which measures the speed of the mobile sand injector. The control unit 100 may be a hand held device or be connected to the base frame

12.

The valves 82 are opened during a time period of 10 - 200 milliseconds, in particular during a time period of 30-80 milliseconds. This time period also defines the duration of the pulse jets.

As long as there is sand in the sand storage compartment, it is guaranteed that there will be sufficient sand supply to the mixing chambers. The tray 40 will be completely filed with sand

The sand is held in suspension by the water for the short period of time in which the mixture exists. As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting, but rather, to provide an understandable description of the invention.

The terms "a" or "an", as used herein, are defined as one or more than one. The term plurality, as used herein, is defined as two or more than two. The term another, as used herein, is defined as at least a second or more. The terms including and/or having, as used herein, are defined as comprising (i.e., open language, not excluding other elements or steps). Any reference signs in the claims should not be construed as limiting the scope of the claims or the invention. It will be recognized that a specific embodiment as claimed may not achieve all of the stated objects.

The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

1. Mobile sand injector (10) for injecting sand into the ground, the device

comprising:

- a base frame (12) configured to be moved over a pitch,

a liquid supply connector (22) for connection to a source of pressurized liquid, at least one storage compartment (24) for sand,

a plurality of mixing chambers (25) for mixing the sand with the liquid, a plurality of injector nozzles (70) for injecting the mixture of sand and liquid into soil under the pitch, wherein each injector nozzle is associated with a mixing chamber,

a plurality of liquid supply conduits (72), wherein each mixing chamber is connected to at least one liquid supply conduit, wherein the liquid supply conduit supplies pressurized liquid from the source of pressurized liquid to the mixing chamber,

a plurality of sand supply tubes (52), wherein each mixing chamber is connected to at least one sand supply tube, wherein the sand supply tubes are configured for supplying sand from the storage compartment to the respective mixing chambers,

- a control system (100) and at least one operable valve (82) configured for providing a volume of pressurized liquid in pulse form through the liquid supply conduits and into each mixing chamber, wherein the volume of liquid mixes with a quantity of sand in each mixing chamber and wherein the mixture is ejected as a pulse jet into the ground through the associated nozzle,

wherein the device further comprises at least one vibration device (50) configured to vibrate the sand supply tubes in order to feed the sand through the sand supply tubes into the mixing chambers.

Mobile sand injector according to claim 1 , comprising one or more sand trays (40) positioned downstream from the sand storage compartment, wherein the sand storage compartment is configured to discharge the sand onto the one or more sand trays, wherein upper ends (53) of the sand supply tubes are connected to an underside (54) of the one or more sand trays, wherein the at least one vibration device is configured to vibrate the one or more sand trays.

3. Mobile sand injector according to claim 2, wherein the sand storage compartment comprises an outflow opening (42), a ridge (43), a chute (44) and a sand moving device (45) constructed for moving the sand from the sand storage compartment over the ridge, through the outflow opening and down the chute onto the sand tray.

4. Mobile sand injector according to any of claims 2 - 3, wherein the vibration device is configured to vibrate the sand supply tubes via the vibration of the sand tray.

5. Mobile sand injector according to any of claims 2 - 4, wherein the at least one sand tray is mounted to the frame via at least one flexible member (90).

6. Mobile sand injector according to any of the preceding claims, wherein a plurality of sand supply tubes share a single vibration device. 7. Mobile sand injector according to any of claims 2 - 7, wherein a plurality of funnels (60) are defined at a bottom of each sand tray for guiding the sand into the sand supply tubes, wherein each bottom end of a funnel has a sand supply tube connected to it. 8. Mobile sand injector according to any of the preceding claims, wherein each sand tray comprises a sieve (64).

9. Mobile sand injector according to any of the preceding claims, comprising a pump (30) and an accumulator (29) configured to raise the pressure of the liquid which enters through the liquid supply connector (22) to a pressure of at least 200 bar.

10. Mobile sand injector according to any of claims 2 - 9, wherein the vibration device is configured to vibrate the sand tray in a substantially horizontal plane. 1 1. Mobile sand injector according to the preceding claim, wherein the vibration device is configured to vibrate the sand tray in a substantially circular motion for creating vortices of sand in the sand tray, wherein each sand vortex empties out in a sand supply tube.

Mobile sand injector according to any of the preceding claims, wherein the sand supply tubes are flexible conduits.

13. Mobile sand injector according to any of the preceding claims, comprising one or more wheels, rollers (14, 15) or tracks, and/or a connector (16) for connecting the mobile device to a vehicle such as a tractor.

14. Method of injecting sand into the soil, the method comprising:

positioning a mobile sand injector (10) according to any of the preceding claims on a pitch, in particular a grass pitch,

supplying sand and volumes of pressurized liquid into the mixing chambers (25),

wherein the vibration device (50) vibrates the sand supply tubes to feed the sand into the mixing chambers.

15. Method according to the preceding method claim, wherein the sand which is fed into the mixing chambers is moist or wet.

16. Method according to any of the preceding method claims, comprising one or more sand trays (40) positioned downstream from the sand storage compartment, wherein the at least one vibration device (50) vibrates the one or more sand trays.

17. Method according to any of the preceding method claims, wherein the vibration

device vibrates the sand supply tubes via the vibration of the sand tray.

18. Method according to any of the preceding method claims, wherein the vibration

device vibrates the sand tray in a horizontal plane, in particular in a substantially circular motion, and creates vortices of sand in the sand tray, wherein each sand vortex empties out in a sand supply tube.

19. Method according to any of the preceding method claims, comprising varying a

penetration depth of the mobile sand injector by adjusting:

a water volume per pulse, or

the pulse time or

the pressure,

or by varying a combination of these parameters.

20. Method according to any of the preceding method claims, comprising operating the mobile sand injector at a pressure of at least 200 bar, more in particular 260 - 280 bar.