Countersunk Screw 100° Taper Flush Mount
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Solution Overview
Problem
Current screws used for fixing accessories to thin metal walls face challenges such as insufficient screwing resistance due to fine thread pitch, excessive tightening time, and risk of thread damage, as well as the screw head protruding from pre-drilled holes, especially in window systems with tilt-and-turn fittings.
Innovation Solution
A countersunk screw with a 100° conical underhead and thread extending to the junction of the underhead, featuring a self-drilling end and a pitch of 1 mm, which ensures engagement in thin metal walls and accommodates a screwing tool recess without protrusion, utilizing an intermediate cone with a 40° conicity to enhance thread engagement and resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a standard countersunk screw with conical underhead is used, then the head can be received in the countersunk pilot hole, but the screw head protrudes from the surface because the pre-drilling does not leave enough space in height
Solution Approach 1:
The patent changes the geometric parameters of the underhead by specifying a 100° taper angle and reducing the height of the conical portion. This allows the screw head to sit flush with or below the surface of the workpiece while still accommodating the necessary recess for tool engagement, directly resolving the protrusion issue
2Ease of manufacture
If a metric pitch screw is used, then the screw can be manufactured with standard dimensions, but the thread pitch is too fine requiring several turns for tightening which results in excessive tightening time
Solution Approach 1:
The patent modifies the thread pitch parameter from standard fine metric pitch to a coarser pitch specifically suited for thin metal walls. This reduction in the number of threads per unit length allows for faster tightening while maintaining adequate engagement in the thin substrate, directly addressing the productivity issue
3Ease of manufacture
If a standard metric pitch screw is used, then the screw can be manufactured with standard dimensions, but the difference between external diameter and diameter at bottom of thread is too small which does not allow good attachment between thread and hole
Solution Approach 1:
The patent changes the thread geometry parameters including the pitch and the relationship between major and minor diameters. The coarser pitch creates a larger difference between external and internal thread diameters, providing better mechanical interlocking and attachment strength in thin metal walls
4Ease of operation
If standard screwing torque is applied, then the screw can be tightened adequately, but the resistance to overtorsion is too low so that the thread risks being destroyed by excessive rotation
Solution Approach 1:
The patent modifies the thread parameters including pitch and diameter relationships to increase the structural strength of the thread. The coarser pitch and optimized diameter differences create a more robust thread form that can withstand higher torsional loads without destruction, improving reliability during screwing operations
5Ease of operation
If the screw pitch is large and greater than the thickness of the metal support, then the screw can be installed easily, but the attachment does not take place sufficiently between the thread of the screw and the wall of the hole
Solution Approach 1:
The patent optimizes the pitch parameter to be appropriate for thin metal walls - not too fine like standard metric pitch (which requires excessive turns), but not too large (which would prevent sufficient engagement). The specific pitch value is chosen to balance installation ease with adequate thread engagement strength
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The screw (200) has a countersunk-head (210) including a conical sub-head (212) connected to a screw shank (220) provided with a thread (221). A curved top (211) of the countersunk-head has a cavity (214) for receiving a screwing tool. The sub-head of the head is provided with a cone having conicity of 100 degrees. The thread of the shank is raised till to a junction between the sub-head and the shank. An intermediate cone (215) has another thread (216) that is raised on a surface of the intermediate cone till to another junction between the intermediate cone and the cone of the sub-head.