Self-Drilling Screw Fastener for Flush Soffit Fixing
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Solution Overview
Problem
Current screw fasteners used for securing soffit linings in steel framed buildings cause material loss and mushrooming due to the need for countersinking, resulting in a weaker connection and additional installation steps.
Innovation Solution
A screw fastener design with a self-drilling or piercing point and a drive section that minimizes the need for countersinking, allowing the fastener head to be flush or slightly above the surface, reducing material loss and preventing mushrooming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a large frustoconical head with ribs is used to ream out the lining material and create a countersunk bore, then the screw fastener can be driven flush or below the surface of the lining panel, but material is forced out from the bore causing mushrooming that requires additional sanding steps
Solution Approach 1:
The invention extracts the harmful function of material displacement by removing the frustoconical reaming surface and ribs from the fastener head. Instead of forcing material out to create a countersunk bore, the head is designed with a lateral diameter substantially equal to the maximum external diameter of the screw thread, allowing it to sit flush with the lining surface without displacing material and causing mushrooming.
Solution Approach 2:
The invention changes the critical parameter of head lateral diameter from being larger than the screw thread diameter (frustoconical shape) to being substantially equal to the screw thread diameter. This parameter change eliminates the need for material removal and countersinking while maintaining surface flushness, thereby preventing mushrooming and eliminating additional sanding steps.
2Shape
If a large frustoconical head is used to ream out the lining material, then the screw fastener can be driven into the panel, but the head has a longitudinal depth of around 3 mm leaving very little supporting material around the fastener
Solution Approach 1:
The invention extracts the reaming function from the fastener head design. By removing the frustoconical shape and ribs that were used to ream out material, the design preserves the surrounding lining material as supporting material around the fastener, thereby maintaining connection strength while still achieving surface flushness through the dimensioned head design.
3Ease of manufacture
If material is forced out from the bore during driving, then the screw fastener can be installed in the lining panel, but an annular mound of fibre cement material is left surrounding the head requiring sanding down
Solution Approach 1:
The invention extracts the material displacement effect by eliminating the frustoconical reaming surface. The head is dimensioned with a lateral diameter substantially equal to the maximum external diameter of the screw thread, allowing installation without forcing material out and creating mushrooming that would require additional sanding time and labor.
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 solution maintains the strength of the connection by minimizing material loss and eliminating the need for additional installation steps, preventing mushrooming and ensuring a smooth surface for painting.
Implementation Method 1
a self-drilling or piercing point at an opposing end thereof for forming a bore in said one or more material layers
Implementation Method 2
an elongate shank having a screw thread extending along at least a substantial portion of the shank
Implementation Method 3
a drive section located at one end of the shank for allowing the screw fastener to be rotatably driven into one or more material layers
Data Source
AI summary
A screw fastener comprising: an elongate shank (3) having a screw thread (9) extending along at least a substantial portion of the shank; a drive section (7) located at one end of the shank for allowing the screw fastener to be rotatably driven into one or more material layers; and a self-drilling or piercing point (5) at an opposing end thereof for forming a bore in said one or more material layers; wherein the drive section is shaped to minimise or avoid the need for countersinking of the formed bore.