Screw Head Design for Secure Tool Retention
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Solution Overview
Problem
Existing screw and tool systems with shaped recesses in screw heads often suffer from weak engagement due to the recess extending too far, leading to potential screw head weakening and failure to securely retain the screw during one-handed or robotic operations.
Innovation Solution
A screw head design featuring a hexalobular slot with a sloping transition surface and a further recess containing protrusions, such as ribs or flat elements, to enhance frictional engagement with a tool, ensuring the screw remains securely attached during driving.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the shaped slot extends too far downwardly into the screw head, then the engagement between tool and screw head is improved, but the screw head is weakened due to the slot approaching the undersurface
Solution Approach 1:
The slot is divided into multiple segments: an upper shaped portion for tool engagement, a transition portion with sloping surfaces, and a lower portion with protrusions. This segmentation allows the slot to extend deeper into the screw head for better tool retention while maintaining head strength through the distributed structure that prevents continuous material removal.
Solution Approach 2:
Different regions of the slot have different geometric properties optimized for their specific functions. The upper portion has a shape optimized for tool engagement, the transition portion has sloping surfaces for stress distribution, and the lower portion has protrusions for enhanced retention. This local optimization allows deep slot extension without compromising overall screw head strength.
2Reliability
If the recess extends deeper into the screw head to improve retention, then the screw is held more securely on the tool, but the screw head structure is compromised
Solution Approach 1:
The slot structure is nested within the screw head with multiple levels: the upper shaped recess, the transition zone, and the lower portion with protrusions nested within the head structure. This nested arrangement allows deep engagement for secure retention while maintaining the outer structural integrity of the screw head.
Solution Approach 2:
The slot structure combines different geometric features (shaped recess, sloping transition surfaces, and protrusions) to create a composite engagement system that provides both deep retention and structural strength, analogous to using composite materials to achieve multiple properties simultaneously.
3Reliability
If protrusions are added to the inside wall of the further recess to increase frictional engagement, then the stick fit between tool and screw is improved, but the manufacturing complexity increases
Solution Approach 1:
The protrusions within the slot structure serve dual purposes: they provide the frictional engagement needed for secure stick fit, and they are formed as integral parts of the slot during the same manufacturing process. This self-service approach enhances retention without requiring separate manufacturing steps or additional components.
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 screw head design provides a secure stick fit with the tool, reducing the risk of the screw falling off and improving engagement accuracy, especially in one-handed and robotic applications by increasing contact pressures and allowing excess coating displacement.
Implementation Method 1
there is a stick fit due to friction between the protrusion on the inside wall of the further recess and the lower engagement section of the tool
Data Source
AI summary
The invention provides a screw in which the screw head (1) has a slot (2) in the upper surface of the screw head, an upper peripheral wall (9) of regular planform extending down from the rim of the slot into the screwhead, the upper peripheral wall (9) being generally aligned with the axis of the screw to form a recess (3), a sloping transition surface (15), extending downwardly and inwardly with respect to the lower edge of the upper peripheral wall (9), and a further recess (11) extending downwardly from the lower edge of the sloping transition surface (15), in which the dimensions of the screw head are such that when the screwhead is engaged by a tool (6) having upper (16) and lower (17) engagement sections, and in which the upper engagement section (16) extends downwardly with respect to the axis of the screw to which the tool is to engage and the lower engagement section (17) extends further downwardly, and in which there is at least one protrusion (or rib) (21) on the inside wall (12) of the further recess (11), so that there is a ‘stick fit’ between the protrusion (21) on the inside wall (12) of the further recess (11) and the lower engagement section (17) of the tool (6).