Self-Centering Screw with Diametrically Opposed Support Elements
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Solution Overview
Problem
Screws designed for hard materials like concrete often tilt during insertion, leading to failure and damage, especially when encountering hard aggregates or reinforcements, due to inadequate support and centering, resulting in unusable screws and holes.
Innovation Solution
A self-centering screw with support elements arranged diametrically opposite cutting elements on the core, which act as a centering aid, preventing tilting and ensuring secure guidance during screwing by transmitting torque effectively, and featuring a helical arrangement of support elements to maintain reduced turning resistance and preserve load-bearing capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a screw is inserted into a drilled hole in hard material, then the screw can be fastened, but the screw may tilt about the central longitudinal axis when the external thread comes into contact with the inner wall, causing the screwing process to fail
Solution Approach 1:
The support elements are arranged on the core before the screwing process to provide preliminary centering and support. These elements prevent tilting by contacting the hole wall before the external thread engages, ensuring the screw remains centered throughout the screwing-in process.
Solution Approach 2:
The support elements act as intermediary components between the screw core and the hole wall. They provide a mediating contact that distributes forces and prevents direct engagement between the external thread and hole wall that would cause tilting, thereby facilitating smooth screwing-in.
2Device complexity
If the screw is designed without support elements, then the structure is simpler, but the screw tilts and spins during insertion, damaging both the screw and the drill hole
Solution Approach 1:
The screw is segmented into functional zones: the external thread for fastening, the support elements for centering and support, and the core for structural integrity. This segmentation allows each component to perform its specific function, preventing tilting while maintaining overall structural efficiency.
Solution Approach 2:
Support elements are strategically positioned at specific locations on the core where they provide maximum centering effect. The local addition of these elements provides the necessary centering function without requiring complex modifications to the entire screw structure.
3Adaptability or versatility
If support elements are arranged along a helix, then the screw is supported along a larger screw-in angle range, but the turning resistance may increase with screwing depth
Solution Approach 1:
The helical support elements are designed to provide support over a sufficient but not excessive angular range. The helix angle and extent are optimized to cover the necessary screw-in angles while limiting the contact area to prevent excessive turning resistance and force requirements.
Data Source
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AI summary
A self-centring screw for screwing into a drilled hole in a hard material, in particular concrete, wherein the screw (1) comprises a cylindrical core (2) with an insertion end (3), an outer end (4) which lies opposite the latter, a core diameter (DK), a screw-in direction (5) and a centre longitudinal axis (7) which is parallel to the latter; an external thread (8) which is configured integrally with the core (2) and extends along a thread section (AG) for screwing it into the material with a thread diameter (DG), a thread start (16) which is arranged at the insertion end (3) and at least one cutting element (9) for cutting the external thread (8) into the material; a torque transmission means which is arranged on the core (2) for transmitting a screw-in torque from a screw-in tool (26) to the core (2) for screwing it into the material; and at least one supporting element (17) for supporting the screw (1) in the drilled hole (24) during the screwing-in operation, wherein the at least one supporting element (17) is arranged on the core (2) in the region of the thread start (16) and lying diametrically opposite the at least one cutting element (9) in relation to the centre longitudinal axis (7).