Drainage element and method and machine for making same

Abstract

A strip of membrane material is laminated to a wider strip of netting and then the longitudinal edges of the strip of netting are seamed together into a sleeve for receiving aggregate to form an elongated tubular drainage element. The laminated peripheral portion of the resultant sleeve is used as the top of the drainage element to preclude fine material from entering the drainage element. Where a membrane is used to form the sleeve, holes or slits are placed in the peripheral portion of the sleeve that is to form the bottom of the drainage element. The seaming of the overlapped longitudinal edges of the membrane is effected using glue and a nozzle that blows air under pressure onto the seam to force the edges and glue to bond together.

1 . A drainage element comprising 
 a mass of discrete aggregate defining passageways for a flow of fluid therethrough; and    a sleeve encasing said mass of discrete aggregate, said sleeve including a first peripheral portion including a membrane material and a net material laminated together to form an integral two-ply layer and a second peripheral portion of net material having openings for retaining said aggregate and allowing the passage of water.    
   
   
       2 . A drainage element as set forth in  claim 1  wherein said membrane is a water-permeable filter material having 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.  
   
   
       3 . A drainage element as set forth in  claim 1  wherein said membrane is a web of paper.  
   
   
       4 . A drainage element as set forth in  claim 1  wherein said membrane is a web of plastic film.  
   
   
       5 . A drainage element as set forth in  claim 1  wherein said second peripheral portion of net material has a pair of longitudinal edges secured together in overlapping relation.  
   
   
       6 . A drainage element as set forth in  claim 5  further comprising at least one strip of netting of finer mesh than said netting disposed in overlapping relation to said pair of longitudinal edges and an adhesive bonding said strip of netting and said pair of longitudinal edges together to form a seam.  
   
   
       7 . A drainage element as set forth in  claim 1  wherein said second peripheral portion of net material has a pair of longitudinal edges secured together in parallel upstanding relation relative to the remainder of the drainage element.  
   
   
       8 . A drainage element as set forth in  claim 1  wherein said second peripheral portion of laminated membrane material and a net material extends longitudinally and over at least 45% of the periphery of the drainage element.  
   
   
       9 . A drainage element comprising 
 a mass of discrete aggregate defining passageways for a flow of fluid therethrough; and    a sleeve of water-permeable filter material encasing said mass of discrete aggregate, said sleeve having a longitudinally extending pattern of holes in a peripheral portion thereof, said peripheral portion constituting less than 50% of the total periphery of said sleeve.    
   
   
       10 . A drainage element as set forth in  claim 9  wherein said pattern of holes constitute less than 45% of the total periphery of said sleeve and are disposed on a spacing of one inch on centers.  
   
   
       11 . A drainage element comprising 
 a mass of discrete aggregate defining passageways for a flow of fluid therethrough; and    a sleeve of water-permeable filter material encasing said mass of discrete aggregate, said sleeve having a longitudinally extending pattern of slits in a peripheral portion thereof, said peripheral portion constituting less than 50% of the total periphery of said sleeve.    
   
   
       12 . In a method of making a drainage element, the steps of 
 overlapping a longitudinal edge of a travelling web of material with a longitudinal edge of the travelling web of material;    applying a glue between said overlapped longitudinal edges at a predetermined station; and    applying a stream of air under pressure onto said overlapped edges and glue to press said glue into each of said longitudinal edges to form a seam.    
   
   
       13 . In a method as set forth in  claim 12  wherein said step of overlapping said edges includes shaping of said traveling web about a tube to define a tubular sleeve about the tube.  
   
   
       14 . In a method as set forth in  claim 13  further comprising the steps of closing one end of the sleeve at a point spaced from the tube and thereafter feeding a light weight aggregate through the tube and into said sleeve while moving said sleeve in a direction away from the tube.  
   
   
       15 . In a method as set forth in  claim 12  the further step of placing at least one strip of netting in overlapping relation to the overlapped longitudinal edges of the web of material prior to said step of applying a glue between said overlapped longitudinal edges.  
   
   
       16 . In a method of making a drainage element, the steps of 
 overlapping a longitudinal edge of a first travelling web of material with a longitudinal edge of second travelling web of material;    applying a glue between said overlapped longitudinal edges at a predetermined station; and    applying a stream of air under pressure onto said overlapped edges and glue to press said glue into each of said longitudinal edges to form a seam.    
   
   
       17 . In a method as set forth in  claim 16  wherein said first travelling web of material is a membrane of a water-permeable filter material.  
   
   
       18 . In a method as set forth in  claim 17  the further step of placing a strip of netting between the overlapped edges of material prior to said step of applying a glue between said overlapped longitudinal edges.  
   
   
       19 . An apparatus for making a drainage element comprising 
 a tube for passing a flow of aggregate therethrough;    means for shaping a continuously supplied strip of material having a pair of longitudinal edges into a sleeve about said tube with the longitudinal edges thereof in overlapping relation to receive a flow of aggregate therein;    at least one valve for expelling glue between said overlapped edges; and    a nozzle for applying a stream of air under pressure onto said overlapped edges and glue to press said glue into each of said longitudinal edges to secure the overlapped edges of the strip together.