Patent Publication Number: US-2007116521-A1

Title: Surface structure for athletic fields

Description:
TECHNICAL FIELD  
      The present invention relates, in general, to a surface structure for athletic fields and, more particularly, to a surface structure for athletic fields capable of performing a drainage function and a shock-absorbing function at the same time.  
     BACKGROUND ART  
      In recent years, participation in social sports has increased due to, for example, the recent trend of reduction in labor-time, causing an increase in the number of athletic fields for a variety of sports, such as soccer, baseball, tennis, volleyball, Jokgu, etc.  
      The athletic fields for sports must be equipped with surfaces which can drain water, such as rainwater or irrigation water, and absorb shock, thereby protecting players on the fields from injury. Furthermore, in response to an increase in the use of artificial grass which is an all-weather surface material for athletic fields, surfaces with enhanced drainage and shock-absorbing functions are required.  
       FIG. 1  shows a conventional surface structure for athletic fields.  
      As shown in  FIG. 1 , the conventional surface structure for athletic fields comprises an underdrain  10  to drain groundwater and surface water to a sewer, a freezing prevention layer  20  to prevent the athletic field from freezing during the winter season, and a pebbled subsurface layer  30  spread on the freezing prevention layer  20  to support thereon a permeable layer  40  and an elastic layer  50 . The permeable layer  40  of permeable concrete or permeable ascon (asphalt concrete) is spread on the subsurface layer  30  to allow surface water that has penetrated the surface structure to move downwards, while the elastic layer  50  of rubber chips is spread on the permeable layer  40  to protect players from shock.  
      In the conventional surface structure for athletic fields, in which permeable concrete or permeable ascon is spread to form the permeable layer for drainage, and rubber chips are spread on the permeable layer to form the elastic layer, water is contained in pores of the elastic layer made of rubber chips. The water in the pores of the elastic layer freezes during the winter season, thus prominently reducing the shock-absorbing ability of the elastic layer.  
      Furthermore, when water contained in pores of the permeable layer of permeable concrete or permeable ascon freezes during the winter season, the volume of the permeable layer increases to cause freezing damage resulting in a reduction in the durability of the permeable layer.  
      In addition, as time goes by, the pores of both the elastic layer and the permeable layer become blocked by impurities, such as dust, introduced into the pores along with water, so that the drainage abilities of the elastic layer and the permeable layer are reduced.  
      Particularly, the conventional surface structure for athletic fields incurs excessive construction costs and requires and unduly lengthy construction period.  
     DISCLOSURE OF THE INVENTION  
      Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a surface structure for athletic fields which performs a drainage function and a shock-absorbing function at the same time.  
      In order to accomplish the above object, the present invention provides a surface structure for athletic fields, comprising an underdrain to drain groundwater and penetrating water to a sewer, a freezing prevention layer to prevent the athletic field from freezing during the winter season, and a pebbled subsurface layer spread on the upper surface of the freezing prevention layer, further comprising: a shock-absorbing and drainage layer placed on the upper surface of the subsurface layer to drain rainwater and irrigation water and perform a shock-absorbing function to protect players.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:  
       FIG. 1  is a sectional view illustrating the construction of a conventional surface structure for athletic fields;  
       FIG. 2  is a sectional view illustrating the construction of a surface structure for athletic fields according to the present invention;  
       FIG. 3  is an exploded perspective view of a shock-absorbing and drainage layer included in the surface structure of  FIG. 2 ;  
       FIG. 4A  is a sectional view of the shock-absorbing and drainage layer of  FIG. 3  before an upper plate is assembled with a lower plate; and  
       FIG. 4B  is a sectional view of the shock-absorbing and drainage layer of  FIG. 3  after the upper plate is assembled with the lower plate. 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION  
      Herein below, a surface structure for athletic fields according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings.  
       FIG. 2  is a sectional view illustrating the construction of a surface structure for athletic fields according to the present invention.  
      As shown in  FIG. 2 , the surface structure for athletic fields according to the present invention comprises an underdrain  100  to drain groundwater and penetrating water to a sewer, a freezing prevention layer  200  to prevent the athletic field from freezing during the winter season, and a pebbled subsurface layer  300  which is spread on the upper surface of the freezing prevention layer  200 . The surface structure further comprises a shock-absorbing and drainage layer  400  which is placed on the upper surface of the pebbled subsurface layer  300  to drain rainwater and irrigation water and perform a shock-absorbing function to protect players.  
      In the surface structure for athletic fields according to the present invention, the shock-absorbing and drainage layer  400  comprises a lower plate  400 - 1  which is placed on the upper surface of the subsurface layer  300  to drain rainwater and irrigation water as shown in  FIG. 3 . A plurality of lower support columns  400 - 5  is provided on the upper surface of the lower plate  400 - 1  while being spaced out at regular intervals, with a bore  400 - 3  having a predetermined length formed through a center of each of the lower support columns  400 - 5  to contain a shock-absorbing member  400 - 7  therein. The shock-absorbing member  400 - 7  which is contained in the bore  400 - 3  of each of the lower support columns  400 - 5  performs the shock-absorbing function to protect the players from injury when the players apply pressure to an upper plate  400 - 11 . A plurality of longitudinal lower reinforcing ribs  400 - 9  having a predetermined length protrudes upwards on the upper surface of the lower plate  400 - 1  at positions between the lower support columns  400 - 5 , thus supporting the lower plate  400 - 1  and guiding water drained from a plurality of drainage holes  400 - 15  of the upper plate  400 - 11  so as to drain the water. The upper plate  400 - 11  is placed above the upper surface of the lower plate  400 - 1  to drain rainwater and irrigation water. A plurality of water guide grooves  400 - 13  having a predetermined length is formed on the upper surface of the upper plate  400 - 11  to define a lattice pattern, thus guiding the rainwater and the irrigation water to the drainage holes  400 - 15  to allow the water to drain smoothly. The drainage holes  400 - 15  are formed through the upper plate  400 - 11  at positions along the water guide grooves  400 - 13  while being spaced out at regular intervals, thus draining the water guided by the water guide grooves  400 - 13  to the lower plate  400 - 1 . A plurality of upper support columns  400 - 17  is provided on the lower surface of the upper plate  400 - 11  while being spaced out at regular intervals, with a bore  400 - 21  (see  FIG. 4A ) having a predetermined length formed through a center of each of the upper support columns  400 - 17  to receive therein each of the lower support columns  400 - 5  containing the shock-absorbing member  400 - 7 . The shock-absorbing and drainage layer  400  further comprises a plurality of longitudinal upper reinforcing ribs  400 - 19  having a predetermined length and protruding downwards on the lower surface of the upper plate  400 - 11  at positions between the upper support columns  400 - 17 , thus supporting the upper plate  400 - 11 .  
      In the surface structure, the shock-absorbing members  400 - 7  contained in the bores  400 - 3  of the lower support columns  400 - 5  have different heights.  
      Furthermore, the bore  400 - 21  of each of the upper support columns  400 - 17  has an inner diameter larger than an outer diameter of each of the lower support columns  400 - 5 , so that the lower support columns  400 - 5  are smoothly inserted into the bores  400 - 21  of the upper support columns  400 - 17 .  
      The lower plate  400 - 1  and the upper plate  400 - 11  are preferably made of plastic materials.  
      The surface structure for athletic fields having the above-mentioned construction according to the present invention is built on an athletic field as follows.  
      First, a plurality of underdrains  100  is formed in the ground at positions spaced out at regular intervals, and thereafter, the freezing prevention layer  200  is spread on the ground.  
      Thereafter, the pebbled subsurface layer  300  is spread on the upper surface of the freezing prevention layer  200 .  
      After the spreading of the pebbled subsurface layer  300 , the shock-absorbing and drainage layer  400  to drain rainwater and irrigation water and perform a shock-absorbing function to protect players is placed on the upper surface of the pebbled subsurface layer  300 .  
      Particularly, the process of placing the shock-absorbing and drainage layer  400  on the pebbled subsurface layer  300  will be described in detail herein below.  
      First, the lower plate  400 - 1  of the shock-absorbing and drainage layer  400  having the lower support columns  400 - 5  is placed on the upper surface of the subsurface layer  300  which acts as a junction material.  
      Thereafter, the shock-absorbing members  400 - 7  are inserted into the bores  400 - 3  of the lower support columns  400 - 5 .  
      In that case, the shock-absorbing members  400 - 7  comprise two types of members with different heights, which are alternately arranged on the lower plate  400 - 1  while being contained in the bores  400 - 3 .  
      Thereafter, the upper plate  400 - 11  is placed on the lower plate  400 - 1 .  
      In that case, as shown in  FIG. 4A , the upper support columns  400 - 17  formed on the lower surface of the upper plate  400 - 11  are aligned with the lower support columns  400 - 5  formed on the upper surface of the lower plate  400 - 1 .  
      When the upper plate  400 - 11  is pressed downwards, the lower support columns  400 - 5  having the shock-absorbing members  400 - 7  are inserted into the bores  400 - 21  of the upper support columns  400 - 17  as shown in  FIG. 4B .  
      In the present invention, the outer diameter of each of the lower support columns  400 - 5  is designed to be slightly smaller than the inner diameter of the bore  400 - 21  of each of the upper support columns  400 - 17 . Thus, the lower support columns  400 - 5  are smoothly inserted into the bores  400 - 21  of the upper support columns  400 - 17  and the assembled state of the lower and upper support columns  400 - 5  and  400 - 17  is maintained regardless of thermal expansion and contraction of the columns  400 - 5  and  400 - 17  according to variation in atmospheric temperature.  
      Thus, the shock-absorbing members  400 - 7  having the higher height are in contact with the lower surface of the upper plate  400 - 11 , while the shock-absorbing members  400 - 7  having the lower height are not in contact with the lower surface of the upper plate  400 - 11 .  
      The operational effect of the shock-absorbing and drainage layer placed on the pebbled subsurface layer will be described herein below.  
      When rainwater or irrigation water drops onto the upper plate  400 - 11 , the water flows to the drainage holes  400 - 15  through the water guide grooves  400 - 13 .  
      In that case, because the water guide grooves  400 - 13  are formed to define a lattice pattern, the drainage effect of the shock-absorbing and drainage layer  400  is enhanced.  
      The drainage holes  400 - 15  drain water to the lower plate  400 - 1 .  
      The water drained to the lower plate  400 - 1  flows along the longitudinal lower reinforcing ribs  400 - 9  to the subsurface layer  300  and the freezing prevention layer  200  which are sequentially placed under the lower plate  400 - 1 . Thereafter, the water drains to a sewer through the underdrains  100 .  
      In the meantime, when a player carelessly falls on the upper plate  400 - 11  while playing on the athletic field, the upper plate  400 - 11  applies pressure to the lower plate  400 - 1 .  
      Thus, the lower support columns  400 - 5  of the lower plate  400 - 1  having the shock-absorbing members  400 - 7  are further inserted into the bores  400 - 21  of the upper support columns  400 - 17  of the upper plate  400 - 11  while compressing the shock-absorbing members  400 - 7 .  
      Therefore, impact which may be applied from the shock-absorbing and drainage layer  400  to the player can be distributed and absorbed by the shock-absorbing members  400 - 7 .  
      Furthermore, because the shock-absorbing members  400 - 7  with different heights are alternately arranged in the bores  400 - 3  on the lower plate  400 - 1 , the shock-absorbing members  400 - 7  absorb the impact in a stepwise manner.  
     INDUSTRIAL APPLICABILITY  
      As described above, the present invention provides a surface structure for athletic fields, which has desired elasticity and permeability, thus performing a shock-absorbing function and a drainage function at the same time.  
      Furthermore, the shock-absorbing operation of the surface structure for athletic fields is executed in a stepwise manner, so that the surface structure protects players from injury.  
      In addition, as the shock-absorbing and drainage layer is made of hard plastic materials, thus having desired durability and desired load support ability.  
      Although the preferred embodiment of the present invention has been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.