Variable Cross-Section Handle for Cramped Manual Tightening
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Solution Overview
Problem
Existing manual tightening tools, such as flat keys and combination keys, are not ergonomic enough for use in cramped environments like motor vehicle engines, leading to long and repetitive recovery phases of fasteners.
Innovation Solution
A one-piece manual tightening tool with a handle design that varies in cross-sectional dimensions along its length, featuring a progressive increase in the large dimension and a corresponding decrease in the small dimension, allowing for angular maneuvers and reduced pressure on the user's hand, while maintaining mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the handle has a constant cross-sectional dimension, then the manufacturing is simple, but the ergonomics and ease of operation in cramped environments deteriorate
Solution Approach 1:
The handle cross-section varies along its length, with the large dimension A increasing progressively from the connecting parts to the median plane, while the small dimension B decreases. This local variation in geometry optimizes ergonomics and maneuverability in confined spaces without requiring complete redesign of the entire tool structure.
Solution Approach 2:
The invention introduces variation in two cross-sectional dimensions (A and B) along the handle length, rather than maintaining a constant square or rectangular section. This dimensional variation allows the tool to adapt to different spatial constraints while maintaining structural integrity.
2Ease of operation
If the handle cross-section varies significantly, then the ergonomics improve, but the mechanical strength may deteriorate
Solution Approach 1:
The handle dimensions are optimized within specific ranges: the large dimension A varies between 15-30mm and the small dimension B between 8-15mm. The maximum widening/maximum narrowing ratio is controlled to be greater than 1 and less than or equal to 1.8, preventing excessive thinning that would compromise strength while still achieving ergonomic benefits.
Solution Approach 2:
The progressive increase in the large dimension A towards the median plane provides gradual reinforcement of the handle structure, cushioning against potential strength deficiencies that could arise from the variable cross-section design. This progressive thickening ensures adequate mechanical strength is maintained throughout the handle length.
3Ease of operation
If the handle has a larger cross-sectional dimension, then the user comfort improves, but the tool size increases making it harder to use in confined spaces
Solution Approach 1:
The handle cross-section is divided into two distinct dimensions (A and B) that serve different functions: dimension A (parallel to the general plane) provides user comfort and grip surface area, while dimension B (perpendicular to the general plane) is minimized to reduce the tool's profile and enable maneuverability in confined spaces. This segmentation allows independent optimization of comfort and compactness.
Data Source
Figure 1~6
Figure 7~11
Figure 12~15
AI summary
This tool extends substantially in an overall plane (XY) and comprises:- at least one working head (12, 13) intended to engage with the fastener; - a handle (14) formed as an integral part of the or each working head; the handle extending along a longitudinal axis (X-X) and comprising a main portion (15) and at least one connecting portion (16, 17) connecting the or each working head to the main portion, the main portion of the handle having a cross section in relation to the longitudinal axis (X-X) that has a relatively large transverse dimension substantially parallel to the overall plane (XY) of the tool and perpendicular to the longitudinal axis (X-X) and a relatively small dimension perpendicular to the overall plane (XY) of the tool. The large dimension and the small dimension of the said cross section evolve along the longitudinal axis. Application to open-ended spanners, combination spanners and box spanners.