WO1998026847A1 - Method of maintaining turf - Google Patents

Abstract

A method of maintaining turf in a stadium which includes having the turf in the form of slabs on a prepared surface which gives the required drainage and, on a regular or needs basis, moving the slabs of turf so that over a period, they all spend a sufficient time in a good growing position to enable the health of the turf overall to be maintained to thereby maximise the overall usage of the stadium. The invention also provides means whereby the stadium can be provided with line numbering which is completely removed when the purpose for which the stadium is used is changed and also means whereby a logo or the like can be located on and removed from the stadium when the use is to be changed.

Description

METHOD OF MAINTAINING TURF

This invention relates to a method of maintaining turf and is particularly applicable for use with turf in stadia and even more specifically, for use with turf in stadia which are at least partially enclosed.

In order to maintain the economic viability of stadia, it is essential that they be available for a degree of use which was unthought of some years ago and, whilst artificial turf can take the wear that can develop from this, natural turf can be badly damaged. The concept of the invention virtually removes usage limitation for stadia.

We have already proposed the use of a system whereby slabs of pre-established turf modules can be used to replace turf which is badly worn and which can enable the stadium surface to be used immediately. To illustrate this some such slabs were used, for example, during a finals match during a soccer series in the 1996 Atlanta Olympic Games and in this case the slabs were actually replaced during the half time interval and the surface was playable in the second half.

Both 4' x 4' and 8' x 8' slabs are regularly used on the Melbourne Cricket Ground.

There has been a tendency over the last years to produce stadia which provide all weather comfort for patrons and such stadia normally have substantial areas of their roof slidable, so that provided the weather is clement, the roof can be opened and the patrons obtain the benefit of an outdoor stadium but when the weather is inclement, the roof can be closed to protect the patrons, the surface and the sportsmen or any other event which is occurring on the stadium surface.

Also, stadiums historically tended to be tiered so that the dimensions at the top of the stadium were very much greater than those at the bottom of the stadium. To obtain maximum usage it is often now that at the top of the stadium, there are corporate boxes or the like which extend inwardly over the outer general seating so that the effective area at the top of the stadium is less than would have been the case previously.

Other stadia are fully enclosed by a dome or the like and where stadia are fully enclosed, it has effectively not been possible to use natural turf as a long terms thing and such stadia normally have an artificial surface. It has been proposed, and used, to grow turf in containers which can be shipped into and out of the stadium normally on railway lines or the like. Such an arrangement is extremely expensive and while it might be justified in very unusual circumstances, it is certainly not satisfactory for normal operations.

Where the stadium is enclosed or semi-enclosed it has not been feasible to use natural turf as it simply does not get the contact necessary with the sun and air to maintain a healthy growth.

It will be appreciated that if the stadium is to be used regularly, the health of the turf is critical.

It is the object of the present invention to provide a method of maintaining a turf surface and is particularly applicable to maintaining a surface for enclosed or semi enclosed stadia.

The invention includes a method of maintaining turf in a stadium which includes having the turf in the form of slabs on a prepared surface which gives the required drainage and, on a regular or needs basis, moving the slabs of turf so that over a period, they all spend a sufficient time in a good growing position to enable the health of the turf overall to be maintained to thereby maximise the overall usage of the stadium.

The invention also includes a method of providing line marking in a stadium maintained as set out above including the steps of marking the line position and then cutting along the line with a pair of blades spaced to encompass the required width of line to the depth of the slab, removing the strip of turf cut thereby and inserting an equivalent length and width of material having line marking thereon.

Still further, the invention includes a method of providing an alternative area in a stadium maintained as set out above including the steps of marking the position required for the area and removing the slabs from the area, if necessary cutting along the edge of the position if it is not at a slab edge and introducing the alternative area into the stadium in one or a small number of pieces and locating it in the area exposed by the removed slabs.

Preferably, the turf from the areas which receive the least sun or greatest usage, and this will depend upon the actual form of stadium and the type of sport played, are moved into areas where a greater amount of sun is received. It may also be that some of the slabs are moved out of the stadium to recuperate either when weakened by the lack of sun or air or usage wear.

Further, all sports fields have areas of high and low usage. Exchange of modules between these areas will permit increased usage with little additional expense

The invention may also include means whereby a sufficient and satisfactory airflow is maintained over the surface.

In order that the invention may be more readily understood, we shall describe one specific embodiment in a stadium with reference to the accompanying drawings; in which:

Fig 1 is a highly schematic view of a stadium providing an indication of the impact of the sun on the surface thereof under different conditions; Fig 2 shows the general arrangement of the formation of the surface of the stadium; Fig 3 shows the location of a removeable line in the stadium; Fig 4 provides an indication of the use of an alternative surface over a substantial part of the stadium; and Fig 5 shows a form of tray which can be used to hold and permit ready movement of slabs.

For the purpose of the exercise we shall assume the stadium as being one which has a movable roof. If the stadium is of a sufficient size to play, for example, Australian Rules Football, that is a stadium in which there can be an oval playing area of the order of 150 metres to 200 metres long and 100 metres to 150 metres wide then the roof will normally only expose the centre portion of the stadium and it will be appreciated that there will be infrastructure necessary to support and control the roof movement.

Depending on the direction of location of the stadium and the positioning of the roof, so it will be appreciated that even with the roof open, the movement of the sun, particularly during the Winter months, when the sun, in the Southern Hemisphere, moves around a Northern arc, and in the Northern Hemisphere a Southern arc, there will be large areas of the stadium which receive only a minimal amount of direct sunlight and possibly no sunlight at all. This is indicated generally in Fig 1 where, when the sun is low in the sky (ray a), as during winter months at a relatively high latitude, a substantial part of the stadium in the direction of the sun will get little or no sun. Even during the summer months, there can be an area (ray b) which gets only relatively little sun. These are, of course, when the roof is open, if it is closed for use in inclement weather, none of the surface gets sun.

Generally, the turf in the centre of the stadium and often that on the southern side in the Southern Hemisphere and the northern side in the Northern Hemisphere, depending on the roof construction, will tend to receive sunlight but, again during Winter, possibly only for a short time each day.

The period will be sufficient to maintain healthy growth in the turf upon which it impinges but the turf which is not in this area can well suffer from lack of sunlight and become very weak, particularly during usage.

In the invention, illustrated schematically in Fig 2, the surface 20 of the stadium is formed with a base formation 21 to give a desired final profile but normally will include drainage channels 22 with gravel or other material 23 with relatively widely spaced interstices and, normally, a layer 24 of gravel or other material thereabove. In or adjacent the drainage channels, there can be sensing devices 25 so that moisture and nutrient levels can be monitored. Above the drainage system a growing medium 26 of 100 mm to 200 mm in depth is normally installed. This lower growing medium is levelled to the required tolerance and contour and then covered with a perforated plastic sheet 27 which has sufficient round or rectangular holes 28 therethrough to permit the necessary drainage of the surface 100 mm to 150 mm surface reinforced layer 29.

The plastic sheet 27 may be either a light weight building sheet in which case it will be replaced each time the slabs are lifted and moved. Alternatively, it may be 3 mm to 5 mm in thickness in which case care will be taken so that it is not damaged when the slabs are cut up for the first time after the construction of the field. Once the slabs have been cut and lifted for the first time they will be wrapped with light netting or plastic 30 and thereafter only the surface turf 31 will have knitted across the joint and thus required to be cut.

The surface layer 29 is of sand, a sand/loam mixture or a loam, and the reinforcing may be plastic elements 32 such as those sold under the trade mark Netlon mesh elements, it may be fibres or it could be other material. In each case the sand, or other soil, 29, the reinforcing elements 32 and the roots 33 of the turf 31 provide a structural rigidity to the slab.

If the turf is initially grown on the surface of the stadium, it can, once established, be cut as mentioned before and wrapped about the edges to enable ready replacement later.

Alternatively, slabs which have been grown remotely can have their edges wrapped in plastic sheet and/or netting can be located on the surface of the stadium.

In either case, the slabs may be of any required size but normally would be of a minimum of 4' x 4' but could be 8' x 8', or even larger.

As the turf grows on the top of the slab there is interaction between the roots of the turf and the elements which gives the total slab stability and further, the reinforcing elements 32 maintain a degree of openness in growing medium of the slab to permit good water transmission therethrough.

Whether the slabs are independently grown or grown on the surface, there is the plastic layer 27 therebeneath and this stimulates horizontal root growth which aids in the stability of the slab It is preferred that each slab has a plastic layer on its underside and this may be achieved by cutting the layer already on the surface, when the slabs are initially formed or may be in addition to the layer over the surface.

In such an arrangement, deep rooting, that is rooting into the sand layer of the basic profile 26 can occur only through the drainage holes 28 and this can readily be broken away when a slab is being lifted.

It is also preferred that when the slabs are first positioned or formed, the perimeter wrapped with a light netting and/or light plastic material and corner fittings 35 may provided to prevent damage to the corners. Where wrapping is used, this will prevent or substantially restrict horizontal movement of roots from one slab to the next adjacent slab to co-join these.

When slabs have been in position from some time, the surface turf rhizomes will move across the surface of the join and may need to be cut prior to lifting of the slab.

In a alternative arrangement, we can use a system as shown in Fig 5 wherein instead of having a plastic layer at the underside of the slab, we have a tray 50 which has a base 51 and a peripheral skirt 52 which receives the slab 53 and extends up the sides thereof. The base of the tray 50 has apertures therein which serve two purposes, the first being to provide drainage for the slab and the second to permit interconnection with a grab 54 whereby the slab can be readily moved. This is particularly useful where slabs are likely to be very worn when removed.

In order to locate the joint and to facilitate cutting, detector tape or some metal implant may be secured to the corner fittings. Alternatively, we could provide a passive or active electronic member which can be detected by a transmitter/receiver to permit accurate location of the detector.

In the present invention, the various areas of the stadium are monitored and any which are suffering from a lack of exposure to the sun or from usage wear can be uplifted from their position and replace slabs from an area where there has been optimum growth or could be moved out of the stadium and replaced by slabs grown and maintained under desirable conditions.

In very broad terms, this would mean that generally, slabs from the wings of the area which are most shaded, as mentioned above, possibly from the North wing in a Southern Hemisphere, tend to be moved relatively regularly whilst, say, the slabs from the southern wing may need to be moved less often.

By good husbandry, control of fertilisation and watering the whole stadium surface can be maintained in a healthy and desirable condition.

Slabs sold under the trade mark SquAyrs were originally introduced into stadia, in part, to enable areas of high wear to be maintained, generally by the introduction of new slabs grown away from the stadia and it thought that by the use of the present invention, the necessity to make changes for this reason will be minimised simply because the slabs generally are moved around the stadium.

It will be appreciated that if any of the slabs be damaged or their growth become too weak for ready rejuvenation, it is to be appreciated that these can still be removed from the stadium and replaced by a healthy slab from elsewhere.

A major feature of the present invention, is that the number of slabs which will have to be so replaced will effectively be minimal as it can be appreciated that each slab is heavy and movement and replacement where the slab has to be taken some distance can be quite time consuming and expensive. If this is kept to a minimum, then the maintenance for the stadium will also be minimised.

Where a stadium is to be used for multipurpose use, there will be different line markings used for different games and it is critical that markings remaining from previous line positions be completely removed as such old markings can be detrimental in television broadcasting, where they appear to be enhanced, and for spectators and players who may have difficulties is separating the new markings from the old.

In order to provide the lines we initially mark the line position, and if, for example, the area to be marked is circular, we can provide a bar or the like extending from the central position and generally we provide a unit having two circular blades which are, say, 100 mm to 300 mm apart.

This unit may be a ride on unit or may be a hand operated unit and is moved along the required line position so that the material of the slab is cut to its full depth, conventionally 100 mm to 150 mm.

These portions can then be removed and can be replaced with line portions 50 which are of the same width and which are provided with the necessary line 51 whether in the form of a painted line, which is conventional in normal stadia or a plastic strip or the like.

After the initial material is removed, the material having the line is placed in its stead. Whilst, particularly in sports which play up to or over lines, it is desired that the line be formed on turf, it is possible to provide the material which forms the line of another material, such as a synthetic plastics material.

Alternatively, the line and the non-line section of the same size can be moved and shifted to suite the various sporting codes. Additional line sections could be stored on the periphery of the stadium where they could be easily removed and replaced when required.

If the lines are straight lines, it may well be that when a different form of sport has been played, the existing lines can be uplifted and located directly into cut out portions from other slabs, with the material removed from these other slabs being directly replaced into the slabs from which the lines have come. When not being used, lined portions could be located in slabs on the edge of the arena, provided there is no confusion with the game being played or external to the arena.

If the lines are curved lines, it is possible to establish either on the periphery of the stadium or, more likely external to the stadium, an area of slabs into which portions of the curved lines, or portions of the material removed to incorporate the lines effectively for storage purposes.

That is to say that as the portions of the lines are taken out to be located in the stadium, the material removed to receive the lines can be placed in the same position, which will have the correct shape.

Alternatively, short lengths of 'curved' lines can be made up of straight components.

The actual way of cutting the material can be by means of a circular saw unit which may have two blades say, 100 mm to 300 mm apart and have a small engine and, as mentioned above, this can be a ride on or a walk behind unit.

The invention can also be applied to provide relatively large logos or the like for location in the stadium for a particular sport.

A logo could be 10 metres to 12 metres along each side, or even larger.

We can shift slabs of this size by providing spiral members which can be screwed into the surface and screw these in lines so that the individual members along the line can each be connected to a lifting member, possibly by providing eyelets on the top of the screwed members and a steel bar or the like passing through these, connecting the various lifting members to a yoke or the like attached to a prime mover and then simply lifting and handling the piece of turf in one piece and locating it in an area from which slabs have been removed. Fig 4 is a purely schematic illustration of an area which occupies the spaces of a number of slabs and which is adapted to receive a logo or the like.

A similar arrangement can be used with a tennis court, which could be put into two pieces which could be of the order of 12 metres long by 11 metres wide with the connection being along the net line. There can be constructed using either a sand/loam mixture or, alternatively, the heavy black clay preferred for top class tennis can be utilised.

These court members could be grown exteriorly of the stadium and simply located when required.

In some cases they would be used as tennis courts close to synthetic court and then simply lifted into place. This would avoid over-width transport problems.

Should it not be require to place them on a synthetic court they could be placed on a carefully levelled area of sand or loam with an appropriate drainage system in place.

When they are used over an impervious surface a shallow plastic type drainage concept can be utilised.

A similar method could be used into relation to cricket pitches which could be grown independently using a soil with mesh elements rather than sand alone to give the required hardness when rolled.

It may be desirable into the invention to provide means whereby air can be directed onto the surface.

It will be appreciated that, for optimum growth, turf needs not only sunlight and certain nutrients, but also a good airflow to enable the planted material to obtain the required amounts of oxygen and carbon dioxide as and when required. We may blow air through the layers from above or below to maintain oxygen to the root zone. One way of effecting this is to suck air out of the drainage modules or to blow air though these. In the first case air is drawn through the turf from above and in the second blown through it from beneath.

Alternatively, we may provide an installation, possibly one which is mobile which directs air downwardly onto or across the surface of the turf to ensure that the required amount of air is provided to the turf.

It may be desirable into the invention to provide travelling light banks similar to irrigation boom sprays to supply artificial light to provide extra light periods and intensity. These travelling light units would be of a size that allows for either travelling on a consistent track direction or a variable track direction and are arranged to minimise damage to the grass. Such travelling light banks would aid in increasing the growth and strength of grass.

There have been objections by various sports people playing games on synthetic turf as these can cause substantial injuries and into particular into football codes synthetic codes are considered to be most undesirable.

The concept of the invention could readily be used into many applications as a direct replacement for a synthetic turf surface into a stadium.

Whilst we have described herein one particular form of the invention, it will be appreciated that variations and modifications can be made into this without departing from the spirit and scope of the invention.

Claims

We claim:

1. A method of maintaining turf in a stadium which includes having the turf in the form of slabs on a prepared surface which gives the required drainage and, on a regular or needs basis, moving the slabs of turf so that over a period, they all spend a sufficient time in a good growing position to enable the health of the turf overall to be maintained to thereby maximise the overall usage of the stadium.

2. A method as claimed in Claim 1 wherein the turf from the areas which receive the least sun or greatest usage are moved into areas where a greater amount of sun is received.

3. A method as claimed in any preceding claim wherein the surface of the stadium is formed with a base formation to give a desired final profile and includes drainage channels, the drainage channels being filled with gravel or other material with relatively widely spaced interstices and having a sand layer thereabove.

4. A method as claimed in claim 3 wherein there is a gravel or other layer over the surface and below the sand layer.

5. A method as claimed in any preceding claim wherein there are sensing devices in or adjacent the gravel or other layer by means of which moisture and nutrient levels can be monitored and watering and fertilizing can be controlled.

6. A method as claimed in any one of claims 1 to 4 wherein a first growing medium layer is installed above the drainage system.

7. A method as claimed in claim 6 wherein the first lower growing medium layer is levelled to the required tolerance and contour and then covered with a perforated sheet which has sufficient apertures therethrough permit the necessary drainage of the slabs of turf which are located thereabove.

8. A method as claimed in claim 7 wherein the perforated sheet is a light weight plastic building sheet which is replaced each time the slabs are lifted and moved.

9. A method as claimed in claim 7 wherein the perforated sheet is a plastic sheet of sufficient thickness to remain in position whilst slabs are removed therefrom and replaced thereover.

10. A method as claimed in any preceding claim wherein the slabs are wrapped with light netting and/or plastic sheet so that lateral movement of the root system is restricted and when the slab is to be replaced only the surface turf can have moved onto the adjacent slab and may have to be cut.

11. A method as claimed in any one of claims 1 to 9 wherein the slabs are located in trays which have a base which is perforated and side walls to restrain the slab, the base having apertures therein the permit drainage therethrough and to accept a grab whereby the slab can be lifted.

12. A method as claimed in claim 10 or claim 11 where the slabs may be provided with corner fittings so that the edge of each slab remains defined.

13. A method as claimed in claim 10 or claim 11 wherein the corner fittings are provided with means whereby they can be located to assist in removing the slab.

14. A method as claimed in claim 13 wherein there is an active or a passive electronic device associated with the corner fittings which can be detected by a transmitter receiver device whereby the bounds of the slab can accurately be determined.

15. A method as claimed in any preceding claim wherein means are provided to ensure an airflow which is sufficient and satisfactory to maintain the health of the turf is maintained over the surface.

16. A method as claimed in claim 15 wherein air is sucked from or blown into the drainage channels to cause is to be drwn through or blown from the surface of the slabs.

17. A method as claimed in any preceding claim wherein when slabs are weakened by the lack of sun or air or usage wear they are moved out of the stadium to recuperate and are replaced by healthy slabs.

18. A method of providing line marking in a stadium maintained in accordance with any one of claims 1 to 17 including the steps of marking the line position and then cutting along the line with a pair of blades spaced to encompass the required width of line to the depth of the slab, removing the strip of turf cut thereby and inserting an equivalent length and width of material having line marking thereon.

19. A method as claimed in claim 18 wherein the material with line marking thereon is turf and wherein the necessary line is in the form of a painted line.

20. A method as claimed in claim 18 wherein the material with line marking thereon is turf and wherein the necessary line is in the form of a strip of material located thereon.

21. A method as claimed in claim 18 wherein the material with line marking thereon is a synthetic material and wherein the necessary line is in the form of a painted line.

22. A method as claimed in claim 18 wherein the material with line marking thereon is a synthetic material and wherein the necessary line is in the form of a strip of material located thereon.

23. A method as claimed in any one of claims 18 to 22 wherein the turf removed to provide the position for the line is stored to be replaced when the line is to br removed.

24. A method as claimed in claim 23 wherein the turf removed is stored in a corresponding cut-out portion in a slab separate from the stadium surface.

25. A method as claimed in claim 24 wherein before storing, the turf removed is wrapped in a plastic sheet or mesh to that its roods do not move laterally into the adjacent area.

26. A method as claimed in any one of claims 18 to 25 wherein the way of cutting the material can be by means of a circular saw unit which has two blades the required distance apart and which are driven by an engine or motor.

27. A method of providing an alternative area in a stadium maintained in accordance with any one of claims 1 to 26 including the steps of marking the position required for the area and removing the slabs from the area, if necessary cutting along the edge of the position if it is not at a slab edge and introducing the alternative area into the stadium in one or a small number of pieces and locating it in the area exposed by the removed slabs.

28. A method as claimed in claim 27 wherein the alternative area is a logo.

29. A method as claimed in claim 27 wherein the alternative area is an alternative surface for use on the arena.

30. A method as claimed in any one of claims 27 to 29 wherein the alternative area is provided with means whereby it can be handled and located where desired.

31. A method as claimed in any one of claims 27 to 29 wherein when the alternative area is no longer required, it is removed and replaced by slabs.