Foamed Polymer Screen Door Heat Welded Joints
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Solution Overview
Problem
Foamed polymer screen doors face durability issues with joints made from dowels, which can rot, and screen securement using rubber splines that can deform and loosen over time due to normal forces.
Innovation Solution
The joints are strengthened by heat-welding the foamed polymer interior of the stiles to the rails, and the screen is secured using a flat spline in a specially shaped groove, which is wider internally than at the entrance, providing enhanced resistance to normal forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If dowels are used to join stiles and rails, then the joint can be assembled, but the joint strength is insufficient and dowels can rot over time
Solution Approach 1:
The patent replaces the mechanical dowel joint system with a heat welding system. The foamed polymer interior is heated to melt and fuse the stile and rail together, creating a monolithic joint that eliminates the weaknesses of mechanical fasteners including rot, loosening, and insufficient strength.
Solution Approach 2:
The patent changes the physical state of the foamed polymer from solid to molten through heating, then allows it to cool and solidify, creating a permanent bond. This phase change enables the formation of a joint that is integral to the frame members themselves.
2Ease of operation
If rubber spline is used to secure the screen, then the screen can be held in place, but the spline deforms and loosens under repeated pressure
Solution Approach 1:
The patent removes the rubber spline component entirely from the system. Instead of using a separate resilient element to hold the screen, the groove itself is designed with a shape that mechanically locks the screen in place through its geometry alone.
Solution Approach 2:
The patent transitions from a circular cross-section spline to a rectangular groove with varying width. The groove is wider at the bottom than at the entrance, creating a dimensional change that prevents the screen from being pulled out while still allowing easy installation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The heat-welded joints are over ten times stronger than dowel joints and the flat spline securement resists normal forces significantly better, ensuring the screen door's durability and stability, with tests showing it can withstand up to 1000 pounds of force without loosening.
Implementation Method 1
Then that exposed portion is heat-welded to the cut end of a rail.
Implementation Method 2
exposed portion is heat-welded to the cut end of a rail
Data Source
AI summary
A screen door made of foamed polymer with heat welded joins between rails and stiles and a flat spline groove. The rails and stiles are extruded with the flat spline groove. Prior to joining the rails and stiles, a thin notch is made to remove the smooth skin of the extruded stiles before being joined to the cut ends of the rails. The heat welded joint between the notched stile and cut end of the rail is ten times stronger than conventional polymer door joints. A flat spline is used to insert the marginal portion of the screen into the flat spline groove, which is wider in the interior than at its entrance and resists the pull from normal forces on the screen much more effectively than a round spline in a rectangular groove.