Pliable air duct with dust and condensation repellency

Abstract

A fabric air duct with main discharge openings includes additional, much smaller openings that help ventilate the surface of the duct. Ventilating the surface of the duct with a slight yet even amount of airflow helps inhibit the accumulation of condensate and dust on the surface of the duct. In some embodiments, the duct includes a pliable sheet consisting of a rather porous fabric base material. To achieve an appropriately low level of airflow, a coating on the fabric reduces, but does not eliminate the fabric's porosity. A calendering process then reduces the porosity even further. In some embodiments, the calendering process occurs before the coating process. In other embodiments, the pliable sheet is substantially air impermeable, except for its main discharge openings. The sheet is then perforated with numerous smaller openings to achieve the desired amount of surface ventilation. In yet other embodiments, an emorizing or sueding process is used to abrade or nap the surface of a porous or non-porous base material to create a pliable sheet having a desired amount of porosity. From any of these processes, air ducts of various shapes may be formed, including air ducts that are circular, ½ round, and ¼ round in shape, as well as air ducts having a non-uniform cross-sectional shape across their lengths.

1 . An air duct, comprising a pliable sheet configured to convey air, wherein the pliable sheet includes a fabric base material that is porous and a coating on the fabric base material that reduces the porosity of the fabric base material yet leaves the pliable sheet porous, wherein the pliable sheet is formed into a tubular shape and wherein the air duct defines a plurality of discharge openings that provide a first open area and the porosity of the pliable sheet provides a second open area with the first open area being greater than the second open area.  
     
     
         2 . The air duct of  claim 1 , wherein the first open area is at least twice as great as the second open area.  
     
     
         3 . The air duct of  claim 1 , wherein the fabric base material consists essentially of polyester.  
     
     
         4 . The air duct of  claim 1 , wherein the coating consists essentially of acrylic.  
     
     
         5 . The air duct of  claim 1 , wherein the coating consists essentially of polyurethane.  
     
     
         6 . The air duct of  claim 1 , wherein the pliable sheet is anti-microbial.  
     
     
         7 . The air duct of  claim 1 , wherein the pliable sheet is at least flame retardant.  
     
     
         8 . The air duct of  claim 1 , wherein the porosity of the pliable sheet is adapted to convey air therethrough at a rate of one to four CFM/ft.sup.2 when a 0.02 psia pressure differential exists across the pliable sheet.  
     
     
         9 . A method of creating an air duct, comprising: 
 applying a coating on a fabric base material to create a pliable sheet that is air permeable;    applying pressure to the pliable sheet to reduce its air permeability; and    configuring the pliable sheet to convey air.    
     
     
         10 . The method of  claim 9 , further comprising forming the pliable sheet into a tubular shape.  
     
     
         11 . The method of  claim 9 , further comprising heating the pliable sheet while applying pressure to the pliable sheet.  
     
     
         12 . The method of  claim 11 , wherein heating the pliable sheet involves heating one side of the pliable sheet more than an opposite side of the pliable sheet.  
     
     
         13 . The method of  claim 9 , wherein applying pressure to the pliable sheet involves calendering.  
     
     
         14 . The method of  claim 9 , wherein the air permeability of the pliable sheet is such that the pliable sheet is able to convey air therethrough at a rate of one to four CFM/ft.sup.2 when a 0.02 psia pressure differential exists across the pliable sheet.  
     
     
         15 . The method of  claim 9 , wherein the fabric base material consists essentially of polyester.  
     
     
         16 . The method of  claim 9 , wherein the coating consists essentially of acrylic.  
     
     
         17 . The method of  claim 9 , wherein the coating consists essentially of polyurethane.  
     
     
         18 . The method of  claim 9 , wherein the pliable sheet is anti-microbial.  
     
     
         19 . The method of  claim 9 , wherein the pliable sheet is at least flame retardant.  
     
     
         20 . A method of creating an air duct, comprising: 
 applying a coating on a fabric base material to create a pliable sheet;    perforating the pliable sheet to create a plurality of perforations having a first open area; and    forming the pliable sheet to help create a tube that defines a plurality of discharge openings having a second open area that is greater than the first open area.    
     
     
         21 . The method of  claim 20 , wherein upon perforating the pliable sheet, the plurality of perforations are created more by displacing material within the pliable sheet than by removing material from the pliable sheet.  
     
     
         22 . The method of  claim 20 , wherein the second open area is at least twice as great as the first open area.  
     
     
         23 . The method of  claim 20 , wherein the fabric base material consists essentially of polyester.  
     
     
         24 . The method of  claim 20 , wherein the coating consists essentially of acrylic.  
     
     
         25 . The method of  claim 20 , wherein the coating consists essentially of polyurethane.  
     
     
         26 . The method of  claim 20 , wherein the pliable sheet is anti-microbial.  
     
     
         27 . The method of  claim 20 , wherein the pliable sheet is at least flame retardant.  
     
     
         28 . The method of  claim 20 , wherein the plurality of perforations allow the pliable sheet to convey air therethrough at a rate of one to four CFM/ft.sup.2 when a 0.02 psia pressure differential exists across the pliable sheet.  
     
     
         29 . The method of  claim 20 , wherein the tubular shape has a circumference and the plurality of perforations are distributed over most of the circumference.  
     
     
         30 . The method of  claim 20 , wherein the plurality of discharge openings is able to pass more than twenty times as much air as the plurality of perforations.  
     
     
         31 . The method of  claim 20 , wherein the plurality of perforations have a distribution of between 100 and 2000 perforations per square-inch.  
     
     
         32 . The method of  claim 20 , wherein each perforation of the plurality of perforations has an effective diameter that is less than a material thickness of the pliable sheet.