Welding apparatus and method for joining roofing materials

Abstract

Pressure roller and heating element combination for a welding apparatus and a method designed to weld a first thermoplastic sheet laid on the deck of a roof structure and secured to the deck by a line of fastening means, and an overlapping second thermoplastic sheet disposed over the line of the fastening means. The pressure roller includes a distal end, a proximal end, and a center portion which defines a groove. The groove is provided with an elastomeric cushion to smoothly ride over the line of fastening means and expel air from between welds produced on both sides of the fastening means when the apparatus is advanced in tandem with a heating element longitudinally along the overlapping portions of the thermoplastic sheets.

What is claimed is:  
     
         1 . A pressure roller in combination with a heating element for a welding apparatus for running longitudinally along an area of overlapment between an underlying first thermoplastic sheet having an upper surface and being supported by a deck of a roof structure, said first thermoplastic sheet being secured to said deck by a line of fastening means adjacent to and parallel with an edge thereof, and an overlapping second thermoplastic sheet having a lower surface which is disposed over said line of fastening means and in an overlapping registry with a portion of said first thermoplastic sheet, said pressure roller being integral with an axle designed to be connected to a driving means at one end thereof and comprising at the other end of said axle: a distal end, a proximal end and a center portion which defines a groove between the distal and proximal ends, said groove carrying an elastomeric cushion designed to ride over said line of fastening means; 
 said heating element positioned between the upper surface of said first thermoplastic sheet and the lower surface of said second thermoplastic sheet and above said line of fastening means having a blower therein and a nozzle having an outlet therein with three portions, two of which are large openings to allow delivery of the major portion of heated air produced by the heating element, and a restricted portion therebetween which allows delivery of sufficient amount of the heated air to soften the overlapping portions of said thermoplastic sheets under and over said fastening means;    wherein as said welding apparatus is advanced longitudinally along the overlapping portions of said thermoplastic sheets while being heated by said heating element softens to plasticity the upper surface of said first thermoplastic sheet and the lower surface of said second thermoplastic sheet and said pressure roller produces a weld on both sides of said line of fastening means.    
     
     
         2 . The pressure roller in combination with a heating element according to  claim 1  wherein said elastomeric cushion material is selected from the group consisting of: 
 natural rubber;  
 acrylate-butadiene rubber;  
 cis-polybutadiene;  
 chlorobutyl rubber;  
 chlorinated polyethylene elastomers;  
 polyalkylene oxide polymers;  
 ethylene vinyl acetate;  
 fluorosilicone rubbers;  
 hexafluoropropylene-vinylidene fluoride-tetrafluoroethylene terpolymers;  
 butyl rubbers;  
 polyisobutene;  
 synthetic polyisoprene rubber;  
 silicone rubbers;  
 styrene-butadiene rubbers;  
 tetrafluoroethylene propylene copolymers; and  
 thermoplastic-copolyesters.  
 
     
     
         3 . The pressure roller in combination with a heating element according to  claim 2  wherein the durometer of said elastomeric material is from about 25 to 80 Shore A.  
     
     
         4 . The pressure roller in combination with a heating element according to  claim 2  wherein said elastomeric material is foam rubber.  
     
     
         5 . The pressure roller in combination with a heating element according to  claim 1  wherein said fastening means comprises a plurality of stress plates or a batten bar.  
     
     
         6 . The pressure roller in combination with a heating element according to  claim 1  wherein said fastening means secure said fist thermoplastic sheet to said deck of a roof structure with nails, screws or bolts through openings in said fastening means.  
     
     
         7 . The pressure roller in combination with a heating element according to  claim 1  wherein said fastening means have a circular configuration and a diameter of from about 0.5 to 2 inches.  
     
     
         8 . The pressure roller in combination with a heating element according to  claim 1  wherein the distance between the center of one fastening means to the center of the adjacent fastening means is about 4 to 12 inches.  
     
     
         9 . The pressure roller in combination with a heating element according to  claim 7  wherein said circular fastening means are spaced from each other at a distance of from 0.1 to 1 inch.  
     
     
         10 . The pressure roller in combination with a heating element according to  claim 1  wherein said roller has a width of 5.5 inches, 2 inches of which are covered by foam rubber at the center thereof and said heating element having a 5.25 inches nozzle opening.  
     
     
         11 . The pressure roller in combination with a heating element according to  claim 10  capable of producing a 5-inch weld.  
     
     
         12 . A process of joining two thermoplastic sheets together by welding comprising the steps of: 
 placing a first thermoplastic sheet having an upper surface on a supportive deck of a roof structure;    securing said first thermoplastic sheet adjacent to and parallel with an edge thereof onto said deck by a line of fastening mean;    placing a second thermoplastic sheet having a lower surface over said line of fastening means and in overlapping registry with a portion of said first thermoplastic sheet;    placing a nozzle of a heating element between the upper surface of said first thermoplastic sheet and the lower surface of said second thermoplastic sheet and over said line of fastening means;    heating said thermoplastic sheets to plasticity with said heating element;    pressing said overlapping portions of said first and second thermoplastic sheets with a pressure roller, said pressure roller comprising: 
 a distal end,  
 a proximal end, and  
 a center portion which defines a groove between the distal and proximal ends of said pressure roller, wherein said groove is covered by an elastomeric cushion designed to ride over said line of fastening means;  
   advancing said heating element and said pressure roller in tandem longitudinally along the overlapping portions of said thermoplastic sheets and thereby simultaneously producing a weld on both sides of said line of fastening means.    
     
     
         13 . The process of  claim 12  wherein a weld is produced on both sides of said line of fastening means and over said fastening means between the first and second thermoplastic sheets.  
     
     
         14 . The process of  claim 12  wherein said heating element and said pressure roller are advanced in tandem manually along the overlapping portions of said thermoplastic sheets.  
     
     
         15 . The process of  claim 12  wherein said heating element and said pressure roller are advanced in tandem by a welding apparatus along the overlapping portions of said thermoplastic sheets.  
     
     
         16 . The process of  claim 12  wherein said elastomeric cushion material is selected form the group consisting of: 
 natural rubber;  
 acrylate-butadiene rubber;  
 cis-polybutadiene;  
 chlorobutyl rubber;  
 chlorinated polyethylene elastomers;  
 polyalkylene oxide polymers;  
 ethylene vinyl acetate;  
 fluorosilicone rubbers;  
 hexafluoropropylene-vinylidene fluoride-tetrafluoroethylene terpolymers;  
 butyl rubbers;  
 polyisobutene;  
 synthetic polyisoprene rubber;  
 silicone rubbers;  
 styrene-butadiene rubbers;  
 tetrafluoroethylene propylene copolymers; and  
 thermoplastic-copolyesters.  
 
     
     
         17 . The process of  claim 16  wherein the durometer of said elastomeric material is from about 25 to 80 Shore A.