Tool Handle Radial Flexibility via Intermediate Layer
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Solution Overview
Problem
Existing tool handles, particularly screwdriver handles, face challenges in balancing manufacturing costs, adaptability to different hand sizes, and effective transmission of torsional moments without causing user discomfort or injury due to issues like 'walking' of soft plastic handle casings on hard cores.
Innovation Solution
A handle design featuring a hard plastic core with a circumferential jacket layer and an intermediate layer of varying stiffness, allowing radial flexibility while maintaining torsional rigidity, and a ribbed structure for enhanced connection and stress distribution, which adapts to user hands and ensures efficient torque transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a soft plastic handle cover is mounted on a hard plastic handle core, then the grip comfort is improved, but the handle cover lifts off and forms wrinkles under heavy loads
Solution Approach 1:
The handle is divided into three distinct layers: a hard plastic handle core, a soft plastic handle cover, and an intermediate layer between them. This segmentation allows each layer to perform its specific function - the core provides structural support, the cover provides grip comfort, and the intermediate layer prevents relative movement between the two, solving the walking problem through functional division.
Solution Approach 2:
An intermediate layer is introduced between the hard plastic handle core and the soft plastic handle cover. This intermediate layer acts as a mediator that bonds the two materials together, preventing the handle cover from lifting off or forming wrinkles under heavy loads while maintaining the grip comfort benefits of the soft outer layer.
2Ease of operation
If a soft plastic handle cover is used, then grip comfort is improved, but manufacturing costs increase
Solution Approach 1:
The thickness of the soft plastic handle cover is optimized to provide sufficient grip comfort while minimizing material usage and manufacturing complexity. By carefully controlling the parameter of cover thickness, the design achieves the desired ergonomic performance without excessive cost, balancing comfort and manufacturability.
3Reliability
If the handle core and handle casing are materially bonded, then the handle cover walking is prevented, but the adaptability to different hand sizes is reduced
Solution Approach 1:
The intermediate layer is not uniformly distributed but is arranged in specific patterns or locations where bonding is most critical. This local quality approach provides sufficient stability to prevent walking in key areas while leaving other areas more compliant to adapt to different hand sizes and grip styles, achieving a balance between reliability and adaptability.
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 design achieves a compromise between low manufacturing costs, long service life, and adaptability to various hand sizes, reducing the risk of user injury while effectively transmitting forces and moments, with improved ergonomics and radial flexibility.
Implementation Method 1
an intermediate layer (11) arranged between the handle core (4) and the jacket layer (8), which is formed with a plastic with a second rigidity, wherein the second rigidity is smaller than the first rigidity and the third rigidity
Implementation Method 2
a hard plastic core with a circumferential jacket layer and an intermediate layer of varying stiffness, allowing radial flexibility while maintaining torsional rigidity
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
Tool handle has a core (4) in which the tool shaft is embedded. This is surrounded by a peripheral outer layer (8) which is separated from it by an intermediate layer (11) which is less rigid than either the core or outer layer. Two diametrically spaced ribs (14, 15) connect the core to the outer layer.