Patent Publication Number: US-7588391-B2

Title: Drainage element

Description:
This is a Continuation-in-Part of U.S. Ser. No. 12/001,703, filed Dec. 12, 2007, which is a Continuation-in-Part of U.S. Ser. No. 11/637,534, filed Dec. 12, 2006 no U.S. Pat. No. 7,475,477 which is a Continuation-in-Part of U.S. Ser. No. 11/591,420, filed Nov. 2, 2006, the specifications of which are incorporated by reference herein. 

   This invention relates to a drainage element. More particularly, this invention relates to a drainage elements having a discrete aggregate encased in a water permeable filter material. 
   As previously described, a drainage element can be made with a mass of discrete aggregate within a sleeve of water-permeable filter material wherein the sleeve has a longitudinally extending pattern of slits in a peripheral portion thereof. 
   It is an object of this invention to improve the techniques for making a preassembled drainage element with a membrane material with slits in a peripheral potion. 
   It is another object of the invention to provide an improved drainage element. 
   Briefly, the invention is directed to a drainage element comprised of a mass of discrete aggregate defining passageways for a flow of fluid therethrough, a sleeve of water-permeable filter material encasing the mass of discrete aggregate and an optional perforated pipe embedded and extending through the aggregate. 
   The water-permeable filter material typically has a plurality of interstices characterized in being of a size for the passage of water therethrough and the filtering of fine particles of solid material from water passing through said membrane. When in place in a trench or the like, soil particles and the like are blocked from entering into the drainage element while water and other fluids may pass through the membrane sleeve and aggregate into the drain pipe embedded therein. 
   The slits are located in a peripheral portion of the sleeve that is to form the bottom of the drainage element when in place and constitute less than 50% of the total periphery of the sleeve. The slits are arranged in parallel rows coaxially of the axis of the drainage element so that the slits may be readily formed in the membrane material before or during fabrication of the drainage element. Alternatively, the slits may be formed in parallel rows transverse to the axis of the drainage element, i.e. circumferentially of the drainage element. Also, the slits may be formed in longitudinally spaced apart sections of the sleeve. 
   The drainage element is made in a manner as described in the parent application Ser. No. 12/001,703. After manufacture, the drainage element is allowed to cure in an ambient atmosphere as described in copending patent application Ser. No. 11/248,753, filed Oct. 12, 2005 (US 2007/0080573) so that the synthetic aggregate, i.e. foamed polystyrene, expands causing the portion of the membrane sleeve containing the slits to expand radially. 
   Where the slits are formed in longitudinally spaced apart sections, only those sections expand radially thereby giving the drainage element a lumpy appearance. 
   The expansion of the slit portions of the membrane material also opens the slits to a wider degree. This, in turn, allows a greater outlet area for the outflow of water or other liquid passing downwardly out of the drainage element. 

   
     These and other objects and advantages of the invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings wherein: 
       FIG. 1  illustrates a perspective view of a drainage element in accordance with the invention; 
       FIG. 2  illustrates a sectional view of a membrane used to make a sleeve for a drainage element with a pattern of slits in accordance with the invention; and 
       FIG. 3  illustrates a perspective view of a drainage element in accordance with the invention after curing of the aggregate and opening of the slits. 
   

   Referring to  FIG. 1 , the drainage element  10  is comprised of a tubular sleeve  11  and a mass of aggregate  12  made of an expanded thermoplastic material within the sleeve  11 . The aggregate  12  is made of discrete elements of a size to define passageways for a flow of fluid therethrough. 
   The tubular sleeve  11  encases the mass of discrete aggregate  12  and is made from a web that is formed into the tubular sleeve  11 , seamed longitudinally and gathered together at each end with tie means  13 , for example in the form of ties, closing around each gathered end of the sleeve  11  to retain the aggregate  12  therein. 
   The drainage element  10  may have a pipe extending completely therethrough, may have a pipe extending from one end only or no pipe at all. 
   The tubular sleeve  11  is made of a water-permeable membrane that is tear resistant and water-permeable with a plurality of interstices characterized in being of a size for the passage of water therethrough and the filtering of fine particles of solid material from the water passing through the membrane  11 . The membrane  11  is made from a web of spun bonded polyester material as described in the above-noted parent applications. 
   The drainage element  10  is made on apparatus as described in copending application, U.S. Ser. No. 12/001,703 that includes a supply station having means to support a roll of the membrane  11  for delivery of a web of the membrane  11  to a tube disposed on a horizontal axis. 
   Referring to  FIG. 2 , the web of membrane  11  may be previously fabricated with slits  14  or the slits  14  may be formed in the web of membrane during the manufacture of a drainage unit prior to the web being formed into a tubular sleeve. The slits  14  are arranged in parallel rows coaxially of the axis of the web of membrane or in parallel rows transversely of the web. The slits  14  may also be arranged in an even pattern, as shown, or in a staggered pattern. Also, the slits  14  may be formed in longitudinally spaced apart sections of the web of membrane  11 . 
   The longitudinally extending pattern of rows of slits  14  is formed in a portion of the web that is to form the bottom of the drainage element  10  when in place, particularly in a septic system, and that constitutes less than 50% of the total periphery of the resultant sleeve  11 . These slits  14  are formed in any suitable manner, for example, by a plurality of pins that have a chisel-like tip or a knife. For the purpose of clarity, the slits  14  are illustrated in each of  FIGS. 1 and 2  as narrow rectangular shaped openings. 
   For example, each slit  14  may have a length of one inch and may be laterally spaced from an adjacent slit  14  a distance of one inch and longitudinally spaced from an adjacent slit  14  a distance of one inch relative to the axis of the sleeve  11 . The slits  14  may be of any length, for example, of from 1/16 inch to one inch or more, so long as the pieces of aggregate  12  are retained in place. 
   The apparatus for making the drainage element  10  also has a forming means, for example, in the form of a plurality of longitudinally spaced pairs of guide plates can be angularly disposed about the tube in a progressive pattern. Each pair of guide plates serves to guide the delivered web about the tube in order to progressively bring the longitudinal edges of the web into overlapping relation. Alternatively, a forming collar can be used as the forming means to form the delivered web into a tube with overlapping longitudinal edges. 
   The apparatus also includes a securing means for securing the overlapped edges of the membrane  11  together to form the sleeve  11  about the tube. This securing means includes a valve for expelling a glue or adhesive between the overlapped edges as well as a nozzle for applying a stream of air under pressure onto the overlapped edges and glue to press the glue into each of the longitudinal edges to secure the overlapped edges of the membrane  11  together to form a strong seam. 
   The remainder of the apparatus is as described in above-noted copending parent patent application that is incorporated by reference herein. 
   The drainage element  10  is to be arranged in a trench, ditch, or the like so that the slit portion of the membrane  11  is at the bottom of the element  10 . In this arrangement, soil will not infiltrate into the drainage element  10  from above. On the other hand, water may pass through the membrane material. Further, in the event that larger particles do pass into the drainage element  10 , for example, in a septic field, these particles may easily flow through the slits  14  in the material  11  at the bottom. 
   The slits  14  in the sleeve of membrane material  11  being placed at the bottom of a drainage element  10  allows soil, stones and the like that infiltrate into the drainage element to be passed through the bottom of the drainage element without accumulating within the drainage element. This avoids clogging of the drainage element in use over time, particularly with septic effluent when used in a septic system. The size of the slits  14  are made to accommodate the passage of infiltrating debris, such as dirt and stones while, retaining the aggregate in place. 
   The mass of aggregate  12  within the sleeve  11  is, preferably, made of expanded polystyrene elements characterized in having been expanded from an initial state to an expanded state after filling of the sleeve  11  therewith and in imparting a degree of rigidity to the drainage element  10  in the expanded state sufficient to maintain an expanded three dimensional shape of the sleeve  11 . That is to say, the aggregate  12  is post-expandable, as described in copending application, U.S. Ser. No. 11/248,753. As a result, the expansion of the aggregate imposes a radially expanding force on the sleeve (membrane)  11  that, in turn, causes the slits  14  to open to an oblong shape as shown in  FIG. 3  and the adjacent parts of the membrane  11  to bulge radially. Thus, the finished drainage element  10  is characterized in having slits  14  that are of oblong shape and in having the peripheral portion of membrane (sleeve)  11  radially outwardly bulged. 
   The pattern of slits  14  extends along the longitudinal length of the sleeve  11 , and preferably along at least one-eighth of the length of the sleeve  11 . Further, the pattern of slits  14  may be formed of a plurality of longitudinally spaced apart sections of slits  14  with the slits  14  in each said section being disposed in parallel. The slits  14  in each section may be transverse to or coaxial of the longitudinal axis of the sleeve  11 . 
   The expansion of the slit portions of the membrane  11  material also opens the slits  14  to a wider degree. The opening up of the slits  14 , for example, to a width of 1/32 inch or more at the center, allows a greater outlet area for the outflow of water or other liquid passing downwardly out of the drainage element  10 . The size of the opening created by the expansion of a slit  14  depends on the length of the slit  14 , i.e. the longer the slit, the greater the width of the slit at the center, and the amount of post-expansion (curing) of the aggregate  12 , i.e. the more the aggregate  12  post-expands, the greater the width of the slit at the center. 
   The drainage element may also be made as described in U.S. Ser. No. 11/637,534 wherein the sleeve encasing the aggregate is with a part-peripheral portion of net material with large openings and a part-peripheral portion of water-permeable filter material. In this embodiment, the slits would be formed in the water-permeable filter material as above. 
   The drainage element  10  may include a perforated pipe that passes through the aggregate  12  in known manner. In this regard, the drainage element may be used in a septic system wherein effluent passes through the perforated pipe, into and through the aggregate  12 , through the sleeve  11  and into the ground. Also, the drainage element may be used for drainage wherein water enters through the sleeve  11  and passes into the perforated pipe to be drawn off. In this latter case, the bottom half of the perforated pipe would be placed only in the upper half of the pipe. Any fine particles that pass into the drainage element are allowed to migrate downwardly and through the slits  14  rather than accumulating and clogging the aggregate  12 . 
   The invention thus provides a drainage element that is not only able to filter fine particles of solid material from effluent entering into the element but also avoids clogging of the discrete aggregate when in use. Further, the invention provides a drainage element that is able to pass large particles out of the bottom of the element that might otherwise be prevented from passing through the membrane.