Screw Head Tapered Recess Interference Fit
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Solution Overview
Problem
Existing screw driving systems with hexalobular slots and tapered recesses often experience 'stick fit' issues due to inadequate engagement between the tool's tapered sections and the screw's sloping transition surface, leading to inefficient torque transfer and potential screw detachment during use.
Innovation Solution
A screw head design featuring a hexalobular slot with a sloping transition surface and a tapered recess, paired with a tool having upper and lower engagement sections that create an interference fit between the tapered recess and the lower engagement section, while avoiding contact with the sloping transition surface, ensuring secure engagement and reduced angular movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the tool engages with the sloping transition surface, then angular movement is reduced, but torque transfer efficiency deteriorates due to stick fit issues
Solution Approach 1:
The tool is divided into two distinct engagement sections: an upper engagement section that interfaces with the hexalobular slot and a lower engagement section that interfaces with the tapered recess. This segmentation allows each section to perform its specific function optimally without interference from the other, resolving the stick fit problem while maintaining engagement stability.
Solution Approach 2:
The tapered recess acts as an intermediary element between the tool's lower engagement section and the screw head's main body. This intermediate tapered interface provides a smooth transition zone that eliminates the stick fit issue while ensuring reliable torque transfer through the lower engagement section.
2Reliability
If the tool is designed with tapered sections, then engagement stability is improved, but manufacturing complexity increases
Solution Approach 1:
The upper and lower engagement sections are merged into a single integrated tool body, with the transition between them occurring through the tapered recess. This merging approach maintains engagement stability while avoiding the complexity of separate components, as the entire structure can be manufactured as one piece using conventional machining processes.
3Productivity
If the upper engagement section fits within the hexalobular slot, then torque transfer is enhanced, but angular movement between tool and screw head occurs
Solution Approach 1:
Different sections of the tool are given different geometric properties: the upper engagement section has a hexalobular shape that matches the slot for torque transfer, while the lower engagement section has a tapered shape that matches the tapered recess for angular stability. This local differentiation of geometric properties allows each function to be optimized independently.
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 provides a secure 'stick fit' between the tool and screw head, enhancing torque transfer and preventing screw detachment, particularly beneficial for one-handed and robotic tools by maintaining frictional engagement without excess coating obstruction.
Implementation Method 1
there is an interference fit between the surface of the tapered recess and the external surface of the lower engagement section
Data Source
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Figure 3
Figure 4~5
AI summary
A screw, tool and a system for driving a screw, comprising a screw and a corresponding tool, wherein the screw includes a screw head comprising a slot in the upper surface of the screw head, a tapered recess disposed downwardly of the slot in the screw, and wherein the tool comprises an upper engagement section which fits within the slot, and further being characterized by a lower engagement section shaped to extend into the tapered recess with a contact surface (30) of an external surface of the lower engagement section in an interference fit with the tapered recess when the upper engagement section is disposed within the slot, the contact surface having a shape which substantially matches any of a plurality of angular inclinations the surface of the tapered recess may have at the interference fit.