CA2409637A1 - Base structure of artificial turf - Google Patents
Base structure of artificial turf Download PDFInfo
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- CA2409637A1 CA2409637A1 CA 2409637 CA2409637A CA2409637A1 CA 2409637 A1 CA2409637 A1 CA 2409637A1 CA 2409637 CA2409637 CA 2409637 CA 2409637 A CA2409637 A CA 2409637A CA 2409637 A1 CA2409637 A1 CA 2409637A1
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- layer
- flexible
- base structure
- sand particles
- resilient
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
- E01C13/00—Pavings or foundations specially adapted for playgrounds or sports grounds; Drainage, irrigation or heating of sports grounds
- E01C13/08—Surfaces simulating grass ; Grass-grown sports grounds
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
- E01C13/00—Pavings or foundations specially adapted for playgrounds or sports grounds; Drainage, irrigation or heating of sports grounds
- E01C13/02—Foundations, e.g. with drainage or heating arrangements
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- Engineering & Computer Science (AREA)
- Architecture (AREA)
- Civil Engineering (AREA)
- Structural Engineering (AREA)
- Road Paving Structures (AREA)
Abstract
A playing surface, such as a synthetic grass turf includes a base structure having a layer of fine particulates, preferably a layer of sand stabilized by fibers for supporting the playing surface lying thereupon. A method of providing an adequate resiliency property for impact absorption to the base structure comprises a step of embedding a plurality of flexible and resilient granules into the layer of fine particulates.
The flexible and resilient granules are spaced-apart clusters in the layer of the fine particulates. This method is advantageously applicable to various types of playing fields in both new construction and retrofitting tasks.
The flexible and resilient granules are spaced-apart clusters in the layer of the fine particulates. This method is advantageously applicable to various types of playing fields in both new construction and retrofitting tasks.
Description
BASE STRUCTURE OF ARTIFICIAL TURF
TECHNICAL FIELD
This invention generally relates to a base structure of a ground playing surface, and more particularly to a synthetic grass turf base which provides an adequate resiliency property beneath the synthetic grass turf for better impact absorption, without making the playing surface too resilient or too soft for the requirements of a specific use.
BACKGROUND OF THE INVENTION
Synthetic grass sports surfaces are well known. They are used to replace natural grass surfaces which do not stand up well to wear and which require a great deal of maintenance. Some synthetic grass surfaces comprise rows of strips or ribbons made of a synthetic material, extending vertically and upwardly from a backing mat with particulate material in-filled between the ribbons on the mat. The ribbons of synthetic material usually extend a short distance above the layer of particulate material and represent blades of grass. The in-filled particulates in a properly designed synthetic grass surface are specially selected to provide adequate resiliency and softness to the playing surface in accordance with various requirements of different sports.
Synthetic grass sports surfaces are usually built on crushed stone bases which have water permeable characteristics such that the backing mat of the synthetic grass surface allows the water to flow through the permeable base structure to a specific drainage system designed for the sports playing ground.
The crushed stone base for a synthetic grass sports surface should be compacted to a compaction rate of between 90°s and 97% standard proctor. This is relatively hard and inflexible, and does not add any safety factor to the playing surface. The installation of a crushed stone base is also relatively expensive because heavy equipment is required to install the crushed stone base and the cost of crushed stone is becoming more expensive in many areas.
Efforts have been made in the industry to provide alternative base structures for synthetic grass sports surfaces. One of the alternative base structures is built with a layer of ground rubber installed to form an elastic base structure on which the synthetic grass sports surface lies. However, the cushion under the synthetic grass sports surface provided by such an elastic layer can add an excessive amount of resiliency to the playing surface of the synthetic grass turf. This added resiliency can be the cause of additional injuries because of the additional energy required to run on such surfaces. Such an elastic layer also deteriorates over time and eventually falls apart or hardens.
It is also well known that the properties of a natural soil can be improved by being mixed with fibers .
The fibers reinforce the soil and provide better load bearing capabilities as well as related engineering properties, thereby benefiting foundations and column supports. Examples of fiber reinforced soil and the methods for building same are described by Freed in his United States Patents 4,790,691 on December 13, 1988, 4,867,614 on September 19, 1989 and 5,326,192 on July 5, 1994 .
Nevertheless, efforts continue in the industry to develop new technologies for building better base structures for a synthetic grass turf with improved stability, impact absorption and drainage characteristics.
TECHNICAL FIELD
This invention generally relates to a base structure of a ground playing surface, and more particularly to a synthetic grass turf base which provides an adequate resiliency property beneath the synthetic grass turf for better impact absorption, without making the playing surface too resilient or too soft for the requirements of a specific use.
BACKGROUND OF THE INVENTION
Synthetic grass sports surfaces are well known. They are used to replace natural grass surfaces which do not stand up well to wear and which require a great deal of maintenance. Some synthetic grass surfaces comprise rows of strips or ribbons made of a synthetic material, extending vertically and upwardly from a backing mat with particulate material in-filled between the ribbons on the mat. The ribbons of synthetic material usually extend a short distance above the layer of particulate material and represent blades of grass. The in-filled particulates in a properly designed synthetic grass surface are specially selected to provide adequate resiliency and softness to the playing surface in accordance with various requirements of different sports.
Synthetic grass sports surfaces are usually built on crushed stone bases which have water permeable characteristics such that the backing mat of the synthetic grass surface allows the water to flow through the permeable base structure to a specific drainage system designed for the sports playing ground.
The crushed stone base for a synthetic grass sports surface should be compacted to a compaction rate of between 90°s and 97% standard proctor. This is relatively hard and inflexible, and does not add any safety factor to the playing surface. The installation of a crushed stone base is also relatively expensive because heavy equipment is required to install the crushed stone base and the cost of crushed stone is becoming more expensive in many areas.
Efforts have been made in the industry to provide alternative base structures for synthetic grass sports surfaces. One of the alternative base structures is built with a layer of ground rubber installed to form an elastic base structure on which the synthetic grass sports surface lies. However, the cushion under the synthetic grass sports surface provided by such an elastic layer can add an excessive amount of resiliency to the playing surface of the synthetic grass turf. This added resiliency can be the cause of additional injuries because of the additional energy required to run on such surfaces. Such an elastic layer also deteriorates over time and eventually falls apart or hardens.
It is also well known that the properties of a natural soil can be improved by being mixed with fibers .
The fibers reinforce the soil and provide better load bearing capabilities as well as related engineering properties, thereby benefiting foundations and column supports. Examples of fiber reinforced soil and the methods for building same are described by Freed in his United States Patents 4,790,691 on December 13, 1988, 4,867,614 on September 19, 1989 and 5,326,192 on July 5, 1994 .
Nevertheless, efforts continue in the industry to develop new technologies for building better base structures for a synthetic grass turf with improved stability, impact absorption and drainage characteristics.
SLTi~IARY OF THE INVENTION
It is one object of the present invention to provide a method of providing adequate resiliency properties to a base structure of a ground playing surface for better impact absorption, without making the playing surface too resilient or too soft.
Another object of the present invention is to provide a base structure beneath a ground playing surface providing stability, adequate impact absorption and drainage characteristics.
In accordance with one aspect of the present invention there is a method of providing adequate resiliency properties for impact absorption to a base structure of a playing surface, the base structure substantially including a layer of fine particles for supporting the playing surface lying thereupon. The method comprises embedding a flexible and resilient material into the layer of fine particulates, the flexible and resilient material being distributed in a substantially spaced-apart pattern within the layer of fine particulates.
It is one object of the present invention to provide a method of providing adequate resiliency properties to a base structure of a ground playing surface for better impact absorption, without making the playing surface too resilient or too soft.
Another object of the present invention is to provide a base structure beneath a ground playing surface providing stability, adequate impact absorption and drainage characteristics.
In accordance with one aspect of the present invention there is a method of providing adequate resiliency properties for impact absorption to a base structure of a playing surface, the base structure substantially including a layer of fine particles for supporting the playing surface lying thereupon. The method comprises embedding a flexible and resilient material into the layer of fine particulates, the flexible and resilient material being distributed in a substantially spaced-apart pattern within the layer of fine particulates.
The depth and spacing of the embedment of the flexible and resilient granules within the layer of fine particulates, are determined preferably in accordance with a required resiliency property of the base structure.
In accordance with another aspect of the present invention there is method of providing a ground playing surface with a base structure having stability, impact absorption and drainage characteristics. The method comprises: (a) forming the base structure by positioning a layer of sand particles over a compacted base substrate; (b) adding a plurality of granules of a flexible and resilient material into the layer of sand particles in order to provide an impact absorption property to the base structure, the flexible and resilient granules being distributed in spaced-apart clusters; and (c) placing the ground playing surface onto the layer of sand particles imbedded with the flexible and resilient granules.
In one embodiment of the present invention the step (a) of the method further comprises mixing a plurality of fibers with the sand particles, such that the fibers are positioned randomly or uniformly in the layer of sand particles and are in a substantially inter-contacting condition.
In another embodiment of the present invention the step (a) of the method further comprises installing at least one piece of mesh into the layer of sand particles.
In accordance with a further aspect of the present invention a base structure is provided beneath a ground playing surface. The base structure has stability, impact absorption and drainage characteristics, and comprises a compacted substrate adapted to drain water away therefrom, and a layer of sand particles placed over the compacted substrate and adapted to support the ground playing surface lying thereupon. A plurality of fibers are mixed into the layer of sand particles for stabilizing the sand particles. A plurality of granules made of a flexible and resilient material are embedded in the layer of sand particles mixed with fibers, and are distributed in spaced-apart clusters in order to provide impact absorption properties to the base structure according to the requirements of the field activity.
Sand is generally less expensive than crushed stone and the installation of a sand base beneath a ground playing surface is relatively easier and less expensive than the installation of a crushed stone base. The layer of sand particles also provides relative softness to the base structure for impact absorption in contrast to the compacted crushed stone base. The fibers or mesh mixed with the sand particles stabilize the layer of sand particles and reduce displacement of the sand particles under dynamic loads transferred from the playing surface lying thereupon. The embedded flexible and resilient granules distributed in spaced-apart clusters within the layer of sand particles mixed with fibers, advantageously provides the base structure with adequate resiliency properties for impact absorption, while not making the playing surface too resilient or too soft. Adjustment of the size of flexible and resilient granules, the depth and spacing of the clusters of flexible and resilient granules within the base structure, and other relevant parameters, can change the resiliency properties of the base structure. This makes it possible to calibrate the resiliency properties of a synthetic grass turf base and improve the impact absorption characteristics of the synthetic grass turf in accordance with various requirements of different uses.
The method of providing resiliency properties for impact absorption to a base structure of a playing surface according to the present invention, is advantageously applicable to various types of playing ground base structures, provided that those structures substantially include a layer of fine particles for supporting a playing surface lying thereupon, such as sand particles, fine particles of ground stones, fine organic particles, soil and mixtures thereof. This method can also be applied either in building a new playing field or in retrofitting an existing playing field, in order to improve the impact absorption characteristics thereof.
Other features and advantages of the present invention will be better understood with reference to preferred embodiments described hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
Having thus generally described the nature of the present invention, reference will now be made to the accompanying drawings, showing by way of illustration the preferred embodiments thereof, in which:
_ g _ Fig. 1 is a cross-sectional view of an installed synthetic grass turf assembly having a base structure, according to a preferred embodiment of the present invention;
Fig. 2 is a cross-sectional view of the base structure of the embodiment of Fig. 1, showing as an example, one step of the installation of the base structure;
Fig. 3 is a cross-sectional view similar to that of Fig. 2, showing a further step of the exemplary installation of the base structure of Fig. 1;
Fig. 4 is a top plan view of Fig. 3, showing one spacing pattern of the spaced-apart clusters of the flexible and resilient granules;
Fig. 5 is a cross-sectional view similar to Fig. 3, showing a similar step as in Fig. 3, according to another embodiment of the present invention; and Fig. 6 is a cross-sectional view similar to Fig. 3, showing a similar step as in Fig. 3, according to a further embodiment of the present invention, but with a full cavity and a different pattern of perforation into the fine particulate.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference to Fig. l, a synthetic grass turf assembly generally indicated at numeral 10 includes a base structure 12 and is installed on a supporting soil substrate 13 in order to provide a ground playing surface 28 which can be a sports playing surface for human beings or a playing surface for animals, such as for dog racing or horse riding. The supporting soil substrate 13 is formed, for example, by removing turf, loam, etc., and by grading and compacting the soil.
Excavation is necessary to establish a proper grade of the supporting substrate 13, to a tolerance of about 1 inch per 10 feet. The slope of the supporting soil substrate 13 is preferably 0.5% to about 1.0% from the field center line downwards to the opposed edges of the field, in order to facilitate drainage, and the supporting soil substrate 13 is compacted to about 95%
proctor density, if possible, in order to form a firm and stable surface.
The synthetic grass turf assembly 10 is positioned over the entire graded supporting soil substrate 13. The ground playing surface 28 includes a pile fabric including a flexible, porous sheet backing 14, that, in the embodiment shown, is a one or more ply open weave fabric. It can also be made of a non-stretch fabric.
However, more backings may be used. Extending upwardly from an upper surface of the backing 14, are a large number of upright synthetic ribbons 16. The ribbons 16 are of a length L and are tufted through the backing 14, in rows spaced apart by a distance W. The length of the ribbons 16 is selected depending upon the depth of an infill layer 18 and the desired resilience of the completed synthetic grass turf assembly 10.
The ribbons 16 may include a mixture of multiple fibers and individual ribbons may be fibrillated on site or left in their original state. The onsite fibrillation can be achieved by passing over the ground playing surface 15 with a wire brush for example, or by other brushing means, after installation of the infill 18.
Thin fibers cannot be top-dressed on site easily because they are more fragile and tend to collapse more easily than thicker fibers, especially in high heat environments. The mixture of thick and thin fibers in the ribbons 16 can affect the roll and bounce of a sports ball in a manner that could be adjustable for the specific sport or intended use in a more predictable manner, depending on the resistance of the fibers to the moving ball. Modification of the ribbon width and density in the turf assembly 10 will also affect the ball rolling and bouncing characteristics.
The ribbons 16 are made from suitable synthetic plastic material which is extruded in a strip that is relatively wide and thin. Narrower ribbon films can also be used. Details of the synthetic ribbons 16 and the porous sheet backing 14 as well as the method for attaching the ribbons 16 to the sheet backing 14 are described in Canadian Patent Application No. 2,218,314 , which was filed on October 16, 1997 and published on September 10, 1998, and is assigned to the assignee of this application.
Deposited interstitially between the upstanding ribbons 16 upon the upper surface of the backing 14, is the infill layer 18 of particulate matter. The particulate matter may be selected from any number of commonly available hard granules such as sand, small rocks, or other graded particulate matter, and selected from resilient granules such as crumbed rubber.
The infill layer 18 is made up of a base course 20, a middle course 22 and a top course 24. The base course 20 is substantially composed of ,hard sand granules disposed immediately upon the top surface of the backing 14. The middle course 22 consists of intermixed hard sand granules and resilient rubber granules. The composition of the mixture is selected on the basis of a weight ratio greater than 2:1 of hard and resilient granules, respectively. The top course 24 is substantially composed of resilient rubber granules.
Other particulate combinations can be all rubber, sand or a hard particulate on the bottom of the infill layer with an all rubber infill on top, having a homogeneous mixture of particulate material with an all rubber layer on top.
An upper portion 26 of the synthetic ribbons 16 extends upwardly from a top surface of the top course 24 which forms the ground playing surface 28. The resulting artificial turf surface can be adapted for several indoor and outdoor uses, such as athletic playing fields, horse racing and recreational areas. The detailed characteristics of the infill layer 18 and the selection in particular of the particulate sizes and unit weights of the respective courses, are described in United States Patent 5,958,527 which issued to Prevost on September 28, 1999, and was assigned to the assignee of this application.
The base structure 12 generally includes a layer of sand particles 30 placed over the compacted supporting soil substrate 13 to support the synthetic grass turf assembly 10 thereupon. The water permeable property of the infill layer 18, the woven sheet backing 14 and the layer of sand particles 30 allow water to drain downwardly from the playing surface 28 and flow away along the graded compacted supporting soil substrate 13.
In this embodiment, the layer of sand particles 30 is mixed with a plurality of fibers 32 which are positioned randomly or uniformly and in a substantially inter-contacting condition. The fibers 32 embedded in the layer of sand particles 30 stabilize the base structure 12 by way of restraining the displacement of sand particles 32 caused by dynamic loads transferred from the playing surface 28 of the synthetic grass turf assembly 10. In contrast to a compacted crushed stone base, the sand base is relatively soft and better for impact absorption, while still having good drainage properties. The sand base is however, generally not as stable as the compacted crushed stone base.
Nevertheless, this disadvantage of the sand base is overcome by mixing the fibers 32 into the layer of sand particles 30 in order to form a stabilized sand base.
Methods of making the layer of sand particles 30 embedded with the stabilizing fibers 32 are generally described by Freed in his United States Patents 4,790,691 and 4,867,614, and therefore, will not be further described herein.
It should be noted that the stabilizing fibers can be made in the form of a mesh. Therefore the layer of sand particles 30 stabilized by fibers 32 can be built by installing one or more pieces of mesh into the layer of sand particles 30.
It should further be noted that the stabilizing fibers can be replaced by synthetic grass. In an alternative embodiment of the present invention, synthetic grass is laid on a soil base which has been prepared by means of laser grading and compacting. Sand particles are used to infill the synthetic grass. The synthetic grass is fibrillated when infilling and therefore the ribbons of the synthetic grass open and act in the same manner that Freed's patent fibers do, such that the synthetic grass stabilizes the sand by creating the matrix of ribbons in the sand layer.
The layer of sand particles 30 mixed with the stabilizing fibers is further embedded with a plurality of granules 34 made of a flexible and resilient material, preferably selected from the group of ambient ground rubber, cryogenically ground rubber, ground tires, shredded tires, recycled carpet fluff, recycled sneaker uppers, SBR rubbers, ground SBR rubbers, plastic pellets, synthetic rubbers, and other synthetic pellets. The flexible and resilient granules 34 are embedded in the layer of sand particles 30 and are distributed in spaced-apart clusters, as is more clearly shown in Fig. 4, such that a portion of a dynamic load acting on the playing surface 28 is transferred to the individual flexible and resilient granules 34 which absorb the energy thereof, and the remaining portion of the dynamic load acting on the playing surface 28 is generally supported on the sand particles 30 which are stabilized by the fibers 32. The spacing of the flexible and resilient granules 34 depends on what type of use for which the synthetic grass assembly 10 is intended. For example, when the synthetic grass turf assembly 10 is used for most human sports games, the flexible and resilient granules 34 are preferably distributed in spaced-apart clusters so as to take a percentage of the dynamic load generated by the foot pressure applied to the playing surface 28, and the remaining portion of the dynamic load is directly supported by the sand particles 30.
The object of the flexible and resilient granules 34 in the spaced-apart pattern is also to prevent head injuries. In a head injury test, a G-max testing unit which is designed to simulate the player' s head size, is dropped on a field surface where it touches a certain amount of square inches. Therefore, according to the test results the spacing of the flexible and resilient granules 34 must be predetermined to absorb the impact of a head on the surface when a player falls in a sports environment. For other uses, the requirement may be different. For use in children's playgrounds, more flexible and resilient granules 34 would be better to make the surface thereof softer, without adversely affecting the child's play thereon. However, this does improve the safety when the child drops from a higher point than an athlete might, The average depth D of each cluster of flexible and resilient granules 34 as measured from the top surface of the layer of the sand particles 30, is another factor which affects the transfer of a dynamic load to this particular flexible and resilient granule 34 and thereby affects the impact absorption capability of the local area of the base structure 12 immediately surrounding this particular flexible and resilient granule 34.
Therefore, it is desirable to position the clusters of flexible and resilient granules 34 substantially in a plane which is indicated by line 35 in Fig. 1. This plane 35 is generally parallel to the playing surface 28 such that the flexible and resilient granules 34 are embedded within the layer of stabilized sand particles 30, to a substantially consistent depth, thereby providing evenly distributed impact absorption characteristics to the base structure 12. For the same purpose, the clusters of flexible and resilient granules 34 should be distributed substantially evenly throughout the layer of stabilized sand particles 30, and the amount of the flexible and resilient granules 34 in the clusters should not be significantly different. It is also preferred that the size differential of the individual flexible and resilient granules 34 is not significant.
However, in order to meet various resiliency and impact absorption requirements in different applications, the average size of the flexible and resilient granules 34 can be selected from a range between 4 and 40 mesh.
A method of embedding the flexible and resilient granules 34 into the stabilized layer of sand particles 30 is described below as an example with reference to Figs. 1-3.
l0 Once the stabilized layer of sand particles 30 which is mixed with the fibers 32 is installed upon the compacted supporting soil substrate 13 and a top surface 36 is achieved, a roller (not shown) equipped with special spikes spaced apart in a predetermined pattern is used to produce a plurality of holes 38 in a spaced-apart pattern corresponding to the predetermined pattern of the spikes of the roller. The pre-selected flexible and resilient granules 34 are deposited on the surface by means for example, of a standard spreader (not shown).
The flexible and resilient granules 34 deposited on the top surface 36 of the layer of sand particles 30 are lightly and evenly brushed into those holes 38. After the flexible and resilient granules 34 are brushed into the holes 38, additional sand particles 30 can be used to in-fill the holes 38 and then a roller (not shown) without the spikes can be used to roll the top surface 36 of the layer of sand particles 30 again in order to properly compact the in-filled sand particles into the holes 38. Any extra sand particles protruding from the top surface 36 can then be swept off by means (not shown) for example, of sweepers, blowers or other equipment designed for such use. The base structure 12 is now properly installed and ready for placement of the grass turf over the top surface 36 of the layer of sand particles 30.
It is optional to apply water to the top surface 36 of the layer of sand particles 30 in order to dampen the same before the holes 38 are produced. The wet sand particles 30 are better for maintaining the shape of the holes 38 when the holes 38 are being produced, as well during the further steps prior to the in-filling of the holes 38.
In another example of embedding the flexible and resilient granules 34, after the flexible and resilient granules 34 deposited on the top surface 36 of the layer of sand particles 30 are lightly and evenly brushed into the holes 38, no additional sand particles 30 are refilled into the holes 38. Alternatively, the top surface 36 of the layer of sand particles 30 is lightly rolled again and is then covered by the sheet backing 14 when the synthetic grass turf is installed thereupon.
Because there is no refilling in the holes 38, the sand particles 30 surrounding the holes 38 will collapse into the hole 38 under the pressure of the roller and later from the weight of the synthetic grass turf placed over the base structure 12. Thus, the sand particles 30 in the regions immediately surrounding the individual holes 38, illustrated by broken lines 40, move towards and fall into the individual holes 38, and eventually fill up the individual holes 38 and bury the flexible and resilient granules 34 therebeneath. The base structure 12 built using such a method will have a lower density in a plurality of regions 40, around the individual flexible and resilient granules 34 (see Fig. 1), than the density of the layer in the remaining regions thereof, thereby having an effect on the overall impact absorption properties of the base structure 12. The degree of the lower density and the size of the lower density regions are determined by the diameter and depth of the individual holes 38, as well as by the size of the individual flexible and resilient granules 34. Thus, the resiliency properties and the impact absorption characteristics of the base structure 12 can be calibrated by adjusting the parameters of the diameter, depth and spacing of the holes 38.
In a further example, the flexible and resilient granules 34 are placed into holes 38 which are made simultaneously when the granules 34 are placed. There is an apparatus (not shown) having a spike roller, the hollow spikes of which each include push rods reciprocating therein, such that the holes 38 are made simultaneously with the flexible and resilient granules 34 being fed through the hollow spikes into the holes.
In a still further example, the flexible and resilient granules 34 are evenly disposed by means of a calibrated spreader (not shown) upon the top surface 36 of the layer of sand particles 30 in which there are no pre-produced holes. The evenly disposed flexible and resilient granules 34 on the top surface 36 are then embedded into the layer of sand particles 30 as shown in Fig. 5, by means of either vibration or a miniature sheep's-foot type of apparatus (not shown). This method is applicable for building a base structure in which it is required that the flexible and resilient granules 34 are only slightly embedded into the top surface 36 thereof. Another means of imbedding the resilient granules is by means of injecting them into the prepared sand base.
In order to embed the flexible and resilient granules 34 into the base structure 12 to a predetermined depth, an alternative method can be used without making l0 pre-produced holes in the base structure 12. In this method, a fast binding liquid slurry with the flexible and resilient granules 34 is injected under pressure into the layer of sand particles 30 to a predetermined depth thereof.
In a still further example of the installation of the base structure 12, instead of preparing the flexible and resilient granules 34 and embedding the same into the base structure 12, the embedment of the flexible and resilient material 34 in the base structure 12 is achieved by injecting a liquid rubberized mixture directly into the holes 38 pre-produced or simultaneously produced in the base structure 12, or directly into the layer of sand particles 30 without the need to produce the holes in the base structure, as shown in Fig. 6, in which numeral 34 indicates the flexible and resilient solids resulting from the liquid rubberized mixture. A
special injecting spike roller (not shown) can be used to implant the mixture. For example, in the golf industry, there are means of injecting water and/or sand into the ground in order to create drainage channels for the water to drain through. Such equipment can be used to inject a predetermined amount of liquid rubber into the base structure 12 to the selected spacing and depth. By modifying the nozzle size, the pressure and frequency of injection of these high pressure injecting apparatuses, the rubber size and quantity can be adjusted to provide the predetermined level of resiliency. This method eliminates the need to roll or compact the top surface 36 of the layer of sand particles 30 additional times. More particularly, the direct injection method without making pre-produced holes, advantageously enables in a retrofitting task to embed the flexible and resilient granules 34 into a base structure 12 beneath a ground playing surface 28 without removal of the playing surface 28. The jet of water and/or air can be calibrated to perforate the carpet backing, thereby forcing the resilient particulate through the grass pile and through the underside of the grass. The resilient particulate could be adjusted to inject more or less material depending on the resiliency required for the application.
In a yet further example, the embedment of the flexible and resilient granules 34 can be completed simultaneously with the installation of the layer of sand particles 30 mixed with the fibers 32. In this method, the fibers 32, sand particles 30 and the flexible and resilient granules 34 are premixed in a blender (not shown) to create a homogeneous mixture which is calibrated to give a predetermined resiliency property.
The mixture of sand particles 30, fibers 32 and flexible and resilient granules 34 is installed upon the compacted supporting soil substrate 13 to a predetermined thickness by paving equipment (not shown). The thickness of the premixed material on the compacted supporting soil substrate 13 can be selected from a range between 0.5 inches and 10 inches depending on the desired resiliency properties in order to provide adequate impact absorption for each particular use.
The fiber stabilized sand base with embedded flexible and resilient granules can be applied to any kind of synthetic grass turf assembly in both new construction and retrofitting tasks. For example, the flexible and resilient granules 34 can be directly injected through a synthetic grass turf into the base structure beneath the synthetic grass turf without need for removing the synthetic grass turf . This can be done either by using apparatus having a roller equipped with hollow spikes and push rods, or by using pressurized injection The method of providing adequate resiliency properties to a base structure of a playing surface however, can be more extensively applied to any ground base without necessarily relating to a synthetic grass turf assembly. The base structure may not necessarily be built with fiber stabilized sand particles but can be other types of fine particles. For example, the flexible arid resilient granules can be embedded into a base structure comprising relatively fine gravels of crushed stone or fine particulates of organic materials, soil, or a mixture thereof. The fibers mixed into the base structure stabilizes the fine particles and reinforces the base structure, but need not necessarily be used together with the flexible and resilient granules when the objective is to adjust the resiliency properties of the base structure.
Furthermore, the method of the present invention can be applied to a natural grass field. The flexible and resilient granules can be embedded, either through the grass turf into a soil base beneath the grass turf without removing the grass turf, or embedded into the soil base after the top grass turf is removed. Tn the latter, the top grass turf is placed back on the soil base after the embedding process is completed.
Modifications and improvements to the above described embodiments of the present invention may become apparent to those skilled in the art. The foregoing description is intended to be exemplary rather than limiting. The scope of the invention is therefore intended to be limited solely by the scope of the appended claims.
In accordance with another aspect of the present invention there is method of providing a ground playing surface with a base structure having stability, impact absorption and drainage characteristics. The method comprises: (a) forming the base structure by positioning a layer of sand particles over a compacted base substrate; (b) adding a plurality of granules of a flexible and resilient material into the layer of sand particles in order to provide an impact absorption property to the base structure, the flexible and resilient granules being distributed in spaced-apart clusters; and (c) placing the ground playing surface onto the layer of sand particles imbedded with the flexible and resilient granules.
In one embodiment of the present invention the step (a) of the method further comprises mixing a plurality of fibers with the sand particles, such that the fibers are positioned randomly or uniformly in the layer of sand particles and are in a substantially inter-contacting condition.
In another embodiment of the present invention the step (a) of the method further comprises installing at least one piece of mesh into the layer of sand particles.
In accordance with a further aspect of the present invention a base structure is provided beneath a ground playing surface. The base structure has stability, impact absorption and drainage characteristics, and comprises a compacted substrate adapted to drain water away therefrom, and a layer of sand particles placed over the compacted substrate and adapted to support the ground playing surface lying thereupon. A plurality of fibers are mixed into the layer of sand particles for stabilizing the sand particles. A plurality of granules made of a flexible and resilient material are embedded in the layer of sand particles mixed with fibers, and are distributed in spaced-apart clusters in order to provide impact absorption properties to the base structure according to the requirements of the field activity.
Sand is generally less expensive than crushed stone and the installation of a sand base beneath a ground playing surface is relatively easier and less expensive than the installation of a crushed stone base. The layer of sand particles also provides relative softness to the base structure for impact absorption in contrast to the compacted crushed stone base. The fibers or mesh mixed with the sand particles stabilize the layer of sand particles and reduce displacement of the sand particles under dynamic loads transferred from the playing surface lying thereupon. The embedded flexible and resilient granules distributed in spaced-apart clusters within the layer of sand particles mixed with fibers, advantageously provides the base structure with adequate resiliency properties for impact absorption, while not making the playing surface too resilient or too soft. Adjustment of the size of flexible and resilient granules, the depth and spacing of the clusters of flexible and resilient granules within the base structure, and other relevant parameters, can change the resiliency properties of the base structure. This makes it possible to calibrate the resiliency properties of a synthetic grass turf base and improve the impact absorption characteristics of the synthetic grass turf in accordance with various requirements of different uses.
The method of providing resiliency properties for impact absorption to a base structure of a playing surface according to the present invention, is advantageously applicable to various types of playing ground base structures, provided that those structures substantially include a layer of fine particles for supporting a playing surface lying thereupon, such as sand particles, fine particles of ground stones, fine organic particles, soil and mixtures thereof. This method can also be applied either in building a new playing field or in retrofitting an existing playing field, in order to improve the impact absorption characteristics thereof.
Other features and advantages of the present invention will be better understood with reference to preferred embodiments described hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
Having thus generally described the nature of the present invention, reference will now be made to the accompanying drawings, showing by way of illustration the preferred embodiments thereof, in which:
_ g _ Fig. 1 is a cross-sectional view of an installed synthetic grass turf assembly having a base structure, according to a preferred embodiment of the present invention;
Fig. 2 is a cross-sectional view of the base structure of the embodiment of Fig. 1, showing as an example, one step of the installation of the base structure;
Fig. 3 is a cross-sectional view similar to that of Fig. 2, showing a further step of the exemplary installation of the base structure of Fig. 1;
Fig. 4 is a top plan view of Fig. 3, showing one spacing pattern of the spaced-apart clusters of the flexible and resilient granules;
Fig. 5 is a cross-sectional view similar to Fig. 3, showing a similar step as in Fig. 3, according to another embodiment of the present invention; and Fig. 6 is a cross-sectional view similar to Fig. 3, showing a similar step as in Fig. 3, according to a further embodiment of the present invention, but with a full cavity and a different pattern of perforation into the fine particulate.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference to Fig. l, a synthetic grass turf assembly generally indicated at numeral 10 includes a base structure 12 and is installed on a supporting soil substrate 13 in order to provide a ground playing surface 28 which can be a sports playing surface for human beings or a playing surface for animals, such as for dog racing or horse riding. The supporting soil substrate 13 is formed, for example, by removing turf, loam, etc., and by grading and compacting the soil.
Excavation is necessary to establish a proper grade of the supporting substrate 13, to a tolerance of about 1 inch per 10 feet. The slope of the supporting soil substrate 13 is preferably 0.5% to about 1.0% from the field center line downwards to the opposed edges of the field, in order to facilitate drainage, and the supporting soil substrate 13 is compacted to about 95%
proctor density, if possible, in order to form a firm and stable surface.
The synthetic grass turf assembly 10 is positioned over the entire graded supporting soil substrate 13. The ground playing surface 28 includes a pile fabric including a flexible, porous sheet backing 14, that, in the embodiment shown, is a one or more ply open weave fabric. It can also be made of a non-stretch fabric.
However, more backings may be used. Extending upwardly from an upper surface of the backing 14, are a large number of upright synthetic ribbons 16. The ribbons 16 are of a length L and are tufted through the backing 14, in rows spaced apart by a distance W. The length of the ribbons 16 is selected depending upon the depth of an infill layer 18 and the desired resilience of the completed synthetic grass turf assembly 10.
The ribbons 16 may include a mixture of multiple fibers and individual ribbons may be fibrillated on site or left in their original state. The onsite fibrillation can be achieved by passing over the ground playing surface 15 with a wire brush for example, or by other brushing means, after installation of the infill 18.
Thin fibers cannot be top-dressed on site easily because they are more fragile and tend to collapse more easily than thicker fibers, especially in high heat environments. The mixture of thick and thin fibers in the ribbons 16 can affect the roll and bounce of a sports ball in a manner that could be adjustable for the specific sport or intended use in a more predictable manner, depending on the resistance of the fibers to the moving ball. Modification of the ribbon width and density in the turf assembly 10 will also affect the ball rolling and bouncing characteristics.
The ribbons 16 are made from suitable synthetic plastic material which is extruded in a strip that is relatively wide and thin. Narrower ribbon films can also be used. Details of the synthetic ribbons 16 and the porous sheet backing 14 as well as the method for attaching the ribbons 16 to the sheet backing 14 are described in Canadian Patent Application No. 2,218,314 , which was filed on October 16, 1997 and published on September 10, 1998, and is assigned to the assignee of this application.
Deposited interstitially between the upstanding ribbons 16 upon the upper surface of the backing 14, is the infill layer 18 of particulate matter. The particulate matter may be selected from any number of commonly available hard granules such as sand, small rocks, or other graded particulate matter, and selected from resilient granules such as crumbed rubber.
The infill layer 18 is made up of a base course 20, a middle course 22 and a top course 24. The base course 20 is substantially composed of ,hard sand granules disposed immediately upon the top surface of the backing 14. The middle course 22 consists of intermixed hard sand granules and resilient rubber granules. The composition of the mixture is selected on the basis of a weight ratio greater than 2:1 of hard and resilient granules, respectively. The top course 24 is substantially composed of resilient rubber granules.
Other particulate combinations can be all rubber, sand or a hard particulate on the bottom of the infill layer with an all rubber infill on top, having a homogeneous mixture of particulate material with an all rubber layer on top.
An upper portion 26 of the synthetic ribbons 16 extends upwardly from a top surface of the top course 24 which forms the ground playing surface 28. The resulting artificial turf surface can be adapted for several indoor and outdoor uses, such as athletic playing fields, horse racing and recreational areas. The detailed characteristics of the infill layer 18 and the selection in particular of the particulate sizes and unit weights of the respective courses, are described in United States Patent 5,958,527 which issued to Prevost on September 28, 1999, and was assigned to the assignee of this application.
The base structure 12 generally includes a layer of sand particles 30 placed over the compacted supporting soil substrate 13 to support the synthetic grass turf assembly 10 thereupon. The water permeable property of the infill layer 18, the woven sheet backing 14 and the layer of sand particles 30 allow water to drain downwardly from the playing surface 28 and flow away along the graded compacted supporting soil substrate 13.
In this embodiment, the layer of sand particles 30 is mixed with a plurality of fibers 32 which are positioned randomly or uniformly and in a substantially inter-contacting condition. The fibers 32 embedded in the layer of sand particles 30 stabilize the base structure 12 by way of restraining the displacement of sand particles 32 caused by dynamic loads transferred from the playing surface 28 of the synthetic grass turf assembly 10. In contrast to a compacted crushed stone base, the sand base is relatively soft and better for impact absorption, while still having good drainage properties. The sand base is however, generally not as stable as the compacted crushed stone base.
Nevertheless, this disadvantage of the sand base is overcome by mixing the fibers 32 into the layer of sand particles 30 in order to form a stabilized sand base.
Methods of making the layer of sand particles 30 embedded with the stabilizing fibers 32 are generally described by Freed in his United States Patents 4,790,691 and 4,867,614, and therefore, will not be further described herein.
It should be noted that the stabilizing fibers can be made in the form of a mesh. Therefore the layer of sand particles 30 stabilized by fibers 32 can be built by installing one or more pieces of mesh into the layer of sand particles 30.
It should further be noted that the stabilizing fibers can be replaced by synthetic grass. In an alternative embodiment of the present invention, synthetic grass is laid on a soil base which has been prepared by means of laser grading and compacting. Sand particles are used to infill the synthetic grass. The synthetic grass is fibrillated when infilling and therefore the ribbons of the synthetic grass open and act in the same manner that Freed's patent fibers do, such that the synthetic grass stabilizes the sand by creating the matrix of ribbons in the sand layer.
The layer of sand particles 30 mixed with the stabilizing fibers is further embedded with a plurality of granules 34 made of a flexible and resilient material, preferably selected from the group of ambient ground rubber, cryogenically ground rubber, ground tires, shredded tires, recycled carpet fluff, recycled sneaker uppers, SBR rubbers, ground SBR rubbers, plastic pellets, synthetic rubbers, and other synthetic pellets. The flexible and resilient granules 34 are embedded in the layer of sand particles 30 and are distributed in spaced-apart clusters, as is more clearly shown in Fig. 4, such that a portion of a dynamic load acting on the playing surface 28 is transferred to the individual flexible and resilient granules 34 which absorb the energy thereof, and the remaining portion of the dynamic load acting on the playing surface 28 is generally supported on the sand particles 30 which are stabilized by the fibers 32. The spacing of the flexible and resilient granules 34 depends on what type of use for which the synthetic grass assembly 10 is intended. For example, when the synthetic grass turf assembly 10 is used for most human sports games, the flexible and resilient granules 34 are preferably distributed in spaced-apart clusters so as to take a percentage of the dynamic load generated by the foot pressure applied to the playing surface 28, and the remaining portion of the dynamic load is directly supported by the sand particles 30.
The object of the flexible and resilient granules 34 in the spaced-apart pattern is also to prevent head injuries. In a head injury test, a G-max testing unit which is designed to simulate the player' s head size, is dropped on a field surface where it touches a certain amount of square inches. Therefore, according to the test results the spacing of the flexible and resilient granules 34 must be predetermined to absorb the impact of a head on the surface when a player falls in a sports environment. For other uses, the requirement may be different. For use in children's playgrounds, more flexible and resilient granules 34 would be better to make the surface thereof softer, without adversely affecting the child's play thereon. However, this does improve the safety when the child drops from a higher point than an athlete might, The average depth D of each cluster of flexible and resilient granules 34 as measured from the top surface of the layer of the sand particles 30, is another factor which affects the transfer of a dynamic load to this particular flexible and resilient granule 34 and thereby affects the impact absorption capability of the local area of the base structure 12 immediately surrounding this particular flexible and resilient granule 34.
Therefore, it is desirable to position the clusters of flexible and resilient granules 34 substantially in a plane which is indicated by line 35 in Fig. 1. This plane 35 is generally parallel to the playing surface 28 such that the flexible and resilient granules 34 are embedded within the layer of stabilized sand particles 30, to a substantially consistent depth, thereby providing evenly distributed impact absorption characteristics to the base structure 12. For the same purpose, the clusters of flexible and resilient granules 34 should be distributed substantially evenly throughout the layer of stabilized sand particles 30, and the amount of the flexible and resilient granules 34 in the clusters should not be significantly different. It is also preferred that the size differential of the individual flexible and resilient granules 34 is not significant.
However, in order to meet various resiliency and impact absorption requirements in different applications, the average size of the flexible and resilient granules 34 can be selected from a range between 4 and 40 mesh.
A method of embedding the flexible and resilient granules 34 into the stabilized layer of sand particles 30 is described below as an example with reference to Figs. 1-3.
l0 Once the stabilized layer of sand particles 30 which is mixed with the fibers 32 is installed upon the compacted supporting soil substrate 13 and a top surface 36 is achieved, a roller (not shown) equipped with special spikes spaced apart in a predetermined pattern is used to produce a plurality of holes 38 in a spaced-apart pattern corresponding to the predetermined pattern of the spikes of the roller. The pre-selected flexible and resilient granules 34 are deposited on the surface by means for example, of a standard spreader (not shown).
The flexible and resilient granules 34 deposited on the top surface 36 of the layer of sand particles 30 are lightly and evenly brushed into those holes 38. After the flexible and resilient granules 34 are brushed into the holes 38, additional sand particles 30 can be used to in-fill the holes 38 and then a roller (not shown) without the spikes can be used to roll the top surface 36 of the layer of sand particles 30 again in order to properly compact the in-filled sand particles into the holes 38. Any extra sand particles protruding from the top surface 36 can then be swept off by means (not shown) for example, of sweepers, blowers or other equipment designed for such use. The base structure 12 is now properly installed and ready for placement of the grass turf over the top surface 36 of the layer of sand particles 30.
It is optional to apply water to the top surface 36 of the layer of sand particles 30 in order to dampen the same before the holes 38 are produced. The wet sand particles 30 are better for maintaining the shape of the holes 38 when the holes 38 are being produced, as well during the further steps prior to the in-filling of the holes 38.
In another example of embedding the flexible and resilient granules 34, after the flexible and resilient granules 34 deposited on the top surface 36 of the layer of sand particles 30 are lightly and evenly brushed into the holes 38, no additional sand particles 30 are refilled into the holes 38. Alternatively, the top surface 36 of the layer of sand particles 30 is lightly rolled again and is then covered by the sheet backing 14 when the synthetic grass turf is installed thereupon.
Because there is no refilling in the holes 38, the sand particles 30 surrounding the holes 38 will collapse into the hole 38 under the pressure of the roller and later from the weight of the synthetic grass turf placed over the base structure 12. Thus, the sand particles 30 in the regions immediately surrounding the individual holes 38, illustrated by broken lines 40, move towards and fall into the individual holes 38, and eventually fill up the individual holes 38 and bury the flexible and resilient granules 34 therebeneath. The base structure 12 built using such a method will have a lower density in a plurality of regions 40, around the individual flexible and resilient granules 34 (see Fig. 1), than the density of the layer in the remaining regions thereof, thereby having an effect on the overall impact absorption properties of the base structure 12. The degree of the lower density and the size of the lower density regions are determined by the diameter and depth of the individual holes 38, as well as by the size of the individual flexible and resilient granules 34. Thus, the resiliency properties and the impact absorption characteristics of the base structure 12 can be calibrated by adjusting the parameters of the diameter, depth and spacing of the holes 38.
In a further example, the flexible and resilient granules 34 are placed into holes 38 which are made simultaneously when the granules 34 are placed. There is an apparatus (not shown) having a spike roller, the hollow spikes of which each include push rods reciprocating therein, such that the holes 38 are made simultaneously with the flexible and resilient granules 34 being fed through the hollow spikes into the holes.
In a still further example, the flexible and resilient granules 34 are evenly disposed by means of a calibrated spreader (not shown) upon the top surface 36 of the layer of sand particles 30 in which there are no pre-produced holes. The evenly disposed flexible and resilient granules 34 on the top surface 36 are then embedded into the layer of sand particles 30 as shown in Fig. 5, by means of either vibration or a miniature sheep's-foot type of apparatus (not shown). This method is applicable for building a base structure in which it is required that the flexible and resilient granules 34 are only slightly embedded into the top surface 36 thereof. Another means of imbedding the resilient granules is by means of injecting them into the prepared sand base.
In order to embed the flexible and resilient granules 34 into the base structure 12 to a predetermined depth, an alternative method can be used without making l0 pre-produced holes in the base structure 12. In this method, a fast binding liquid slurry with the flexible and resilient granules 34 is injected under pressure into the layer of sand particles 30 to a predetermined depth thereof.
In a still further example of the installation of the base structure 12, instead of preparing the flexible and resilient granules 34 and embedding the same into the base structure 12, the embedment of the flexible and resilient material 34 in the base structure 12 is achieved by injecting a liquid rubberized mixture directly into the holes 38 pre-produced or simultaneously produced in the base structure 12, or directly into the layer of sand particles 30 without the need to produce the holes in the base structure, as shown in Fig. 6, in which numeral 34 indicates the flexible and resilient solids resulting from the liquid rubberized mixture. A
special injecting spike roller (not shown) can be used to implant the mixture. For example, in the golf industry, there are means of injecting water and/or sand into the ground in order to create drainage channels for the water to drain through. Such equipment can be used to inject a predetermined amount of liquid rubber into the base structure 12 to the selected spacing and depth. By modifying the nozzle size, the pressure and frequency of injection of these high pressure injecting apparatuses, the rubber size and quantity can be adjusted to provide the predetermined level of resiliency. This method eliminates the need to roll or compact the top surface 36 of the layer of sand particles 30 additional times. More particularly, the direct injection method without making pre-produced holes, advantageously enables in a retrofitting task to embed the flexible and resilient granules 34 into a base structure 12 beneath a ground playing surface 28 without removal of the playing surface 28. The jet of water and/or air can be calibrated to perforate the carpet backing, thereby forcing the resilient particulate through the grass pile and through the underside of the grass. The resilient particulate could be adjusted to inject more or less material depending on the resiliency required for the application.
In a yet further example, the embedment of the flexible and resilient granules 34 can be completed simultaneously with the installation of the layer of sand particles 30 mixed with the fibers 32. In this method, the fibers 32, sand particles 30 and the flexible and resilient granules 34 are premixed in a blender (not shown) to create a homogeneous mixture which is calibrated to give a predetermined resiliency property.
The mixture of sand particles 30, fibers 32 and flexible and resilient granules 34 is installed upon the compacted supporting soil substrate 13 to a predetermined thickness by paving equipment (not shown). The thickness of the premixed material on the compacted supporting soil substrate 13 can be selected from a range between 0.5 inches and 10 inches depending on the desired resiliency properties in order to provide adequate impact absorption for each particular use.
The fiber stabilized sand base with embedded flexible and resilient granules can be applied to any kind of synthetic grass turf assembly in both new construction and retrofitting tasks. For example, the flexible and resilient granules 34 can be directly injected through a synthetic grass turf into the base structure beneath the synthetic grass turf without need for removing the synthetic grass turf . This can be done either by using apparatus having a roller equipped with hollow spikes and push rods, or by using pressurized injection The method of providing adequate resiliency properties to a base structure of a playing surface however, can be more extensively applied to any ground base without necessarily relating to a synthetic grass turf assembly. The base structure may not necessarily be built with fiber stabilized sand particles but can be other types of fine particles. For example, the flexible arid resilient granules can be embedded into a base structure comprising relatively fine gravels of crushed stone or fine particulates of organic materials, soil, or a mixture thereof. The fibers mixed into the base structure stabilizes the fine particles and reinforces the base structure, but need not necessarily be used together with the flexible and resilient granules when the objective is to adjust the resiliency properties of the base structure.
Furthermore, the method of the present invention can be applied to a natural grass field. The flexible and resilient granules can be embedded, either through the grass turf into a soil base beneath the grass turf without removing the grass turf, or embedded into the soil base after the top grass turf is removed. Tn the latter, the top grass turf is placed back on the soil base after the embedding process is completed.
Modifications and improvements to the above described embodiments of the present invention may become apparent to those skilled in the art. The foregoing description is intended to be exemplary rather than limiting. The scope of the invention is therefore intended to be limited solely by the scope of the appended claims.
Claims (18)
1. A method of providing an adequate resiliency property for impact absorption to a base structure of a ground playing surface, the base structure substantially including a layer of fine particulates for supporting the ground playing surface lying thereupon, the method comprising a step of embedding a flexible and resilient material into the layer of fine particulates, the flexible and resilient material being distributed in a substantially spaced-apart pattern within the layer of the fine particulates.
2. A method as claimed in claim 1 wherein the flexible and resilient material comprises a plurality of granules which are embedded in the layer of fine particulates and are distributed in spaced-apart clusters.
3. A method as claimed in claim 2 further comprising steps of determining a depth and spacing of the clusters of flexible and resilient granules embedded in the layer of fine particulates, in accordance with a required resiliency property of the base structure.
4. A method as claimed in claim 1 wherein the embedding of the flexible and resilient granules into the layer of fine particulates is conducted by means of pressurized injection.
5. A method as claimed in claim 1 wherein the flexible and resilient material is injected into the base structure through a synthetic grass turf which lies upon the base structure.
6. A method of providing a ground playing surface with a base structure having stability, impact absorption and drainage characteristics, comprising:
a) forming the base structure by positioning a layer of sand particles over a compacted base substrate;
b) adding a plurality of granules of a flexible and resilient material into the layer of sand particles in order to provide an impact absorption property to the base structure, the flexible and resilient granules being distributed in spaced-apart clusters; and c) placing the ground playing surface onto the layer of sand particles embedded with the flexible and resilient granules.
a) forming the base structure by positioning a layer of sand particles over a compacted base substrate;
b) adding a plurality of granules of a flexible and resilient material into the layer of sand particles in order to provide an impact absorption property to the base structure, the flexible and resilient granules being distributed in spaced-apart clusters; and c) placing the ground playing surface onto the layer of sand particles embedded with the flexible and resilient granules.
7. A method as claimed in claim 6 further comprising a step prior to step (a), of preparing the compacted base substrate.
8. A method as claimed in claim 6 wherein the step (a) further comprises mixing a plurality of fibers with the sand particles such that the fibers are positioned randomly or uniformly and precisely in the layer of sand particles and are in a substantially inter-contacting condition.
9. A method as claimed in claim 6 wherein the step (a) further comprises installing at least one piece of mesh into the layer of sand particles.
10. A method as claimed in claim 6 wherein step (b) further comprises sub-steps of providing a plurality of holes in a spaced-apart pattern in the layer of sand particles and adding the flexible and resilient granules into the individual holes.
11. A method as claimed in claim 10 further comprising determining a diameter and a depth of the individual holes, the spacing of the holes, and a size of the flexible and resilient granules in accordance with a desired impact absorption property of the base structure.
12. A method as claimed in claim 10 further comprising steps prior to step (b), of compacting and dampening the layer of the sand particles.
13. A base structure beneath a ground playing surface, the base structure having stability, adequate impact absorption and drainage characteristics, and comprising:
a compacted substrate adapted to drain water away therefrom;
a layer of sand particles placed over the compacted substrate and adapted to support the ground playing surface lying thereupon;
a plurality of fibers mixed into at least a portion of the layer of sand particles for stabilizing the sand particles; and a plurality of granules made of a flexible and resilient material, embedded in the layer of mixed sand particles and fibers and distributed in spaced-apart clusters in order to provide an adequate impact absorption property to the base structure.
a compacted substrate adapted to drain water away therefrom;
a layer of sand particles placed over the compacted substrate and adapted to support the ground playing surface lying thereupon;
a plurality of fibers mixed into at least a portion of the layer of sand particles for stabilizing the sand particles; and a plurality of granules made of a flexible and resilient material, embedded in the layer of mixed sand particles and fibers and distributed in spaced-apart clusters in order to provide an adequate impact absorption property to the base structure.
14. A base structure as claimed in claim 13 wherein the compacted substrate is graded for better drainage.
-31 ~-
-31 ~-
15. A base structure as claimed in claim 13 wherein the fibers are positioned randomly or uniformly and in a substantially inter-contacting condition.
16. A base structure as claimed in claim 13 wherein at least a number of fibers are interlocked, thereby forming a mesh embedded in the layer of sand particles.
17. A base structure as claimed in claim 13 wherein the flexible and resilient granules are made from a material selected from a group of materials consisting of ambient ground rubber, cryogenically ground rubber, ground tires, shredded tires, synthetic rubber, and plastic pellets.
18. A method of providing an adequate resiliency property for impact absorption to a soil base of a natural grass field, comprising a step of embedding a plurality of flexible and resilient granules into the soil base, the flexible and resilient granules being distributed spaced-apart clusters in the soil base under the natural grass field.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2409637 CA2409637A1 (en) | 2002-10-24 | 2002-10-24 | Base structure of artificial turf |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2409637 CA2409637A1 (en) | 2002-10-24 | 2002-10-24 | Base structure of artificial turf |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2409637A1 true CA2409637A1 (en) | 2004-04-24 |
Family
ID=32399795
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2409637 Abandoned CA2409637A1 (en) | 2002-10-24 | 2002-10-24 | Base structure of artificial turf |
Country Status (1)
| Country | Link |
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| CA (1) | CA2409637A1 (en) |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7189445B2 (en) | 2003-12-12 | 2007-03-13 | Generalsports Turf, Llc | Synthetic sports turf having improved playability and wearability |
| AU2005248917B2 (en) * | 2005-01-10 | 2007-05-17 | Maddocks Sports Pty Ltd | Playing Surface and Method Thereof |
| US8329265B2 (en) | 2004-06-16 | 2012-12-11 | Astroturf, Llc | Transition synthetic sports turf |
| GB2521873A (en) * | 2014-01-07 | 2015-07-08 | Traffipave Ltd | Surface dressing of ground |
| CN106414851A (en) * | 2014-03-12 | 2017-02-15 | 博尔玛沃尔德有限公司 | Sports field structure and method for forming the same |
| EP3252231A1 (en) * | 2016-06-01 | 2017-12-06 | Regesports | Substrate for outdoor floor covering |
| US10208434B2 (en) | 2014-03-12 | 2019-02-19 | Permavoid Limited | Sports field structure and method for forming the same |
| US10400398B2 (en) | 2015-05-12 | 2019-09-03 | Enplast Technology LLC | Pads |
| CN113914358A (en) * | 2021-10-26 | 2022-01-11 | 中国长江三峡集团有限公司 | Intelligent bionic scouring protection structure for cylindrical foundation and application method of intelligent bionic scouring protection structure |
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2002
- 2002-10-24 CA CA 2409637 patent/CA2409637A1/en not_active Abandoned
Cited By (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7189445B2 (en) | 2003-12-12 | 2007-03-13 | Generalsports Turf, Llc | Synthetic sports turf having improved playability and wearability |
| US8329265B2 (en) | 2004-06-16 | 2012-12-11 | Astroturf, Llc | Transition synthetic sports turf |
| AU2005248917B2 (en) * | 2005-01-10 | 2007-05-17 | Maddocks Sports Pty Ltd | Playing Surface and Method Thereof |
| GB2521873A (en) * | 2014-01-07 | 2015-07-08 | Traffipave Ltd | Surface dressing of ground |
| GB2521873B (en) * | 2014-01-07 | 2017-11-29 | Traffipave Ltd | Surface dressing of ground |
| CN106414851B (en) * | 2014-03-12 | 2020-07-10 | 博尔玛沃尔德有限公司 | Playground structure and method of forming the same |
| CN106414851A (en) * | 2014-03-12 | 2017-02-15 | 博尔玛沃尔德有限公司 | Sports field structure and method for forming the same |
| US11505901B2 (en) | 2014-03-12 | 2022-11-22 | Permavoid Limited | Sports field structure and method for forming the same |
| US10844552B2 (en) | 2014-03-12 | 2020-11-24 | Permavoid Limited | Sports field structure and method for forming the same |
| US10208434B2 (en) | 2014-03-12 | 2019-02-19 | Permavoid Limited | Sports field structure and method for forming the same |
| US10400398B2 (en) | 2015-05-12 | 2019-09-03 | Enplast Technology LLC | Pads |
| FR3052172A1 (en) * | 2016-06-01 | 2017-12-08 | Regesports | SUBSTRATE FOR EXTERIOR SOIL COATING |
| EP3252231A1 (en) * | 2016-06-01 | 2017-12-06 | Regesports | Substrate for outdoor floor covering |
| CN113914358A (en) * | 2021-10-26 | 2022-01-11 | 中国长江三峡集团有限公司 | Intelligent bionic scouring protection structure for cylindrical foundation and application method of intelligent bionic scouring protection structure |
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