Folding Rule Latch Mechanism for Wear Reduction
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Solution Overview
Problem
Folding rules with existing locking mechanisms face issues of reduced friction and self-retention when angled, leading to difficult handling and wear-induced loss of locking effectiveness, and increased manufacturing costs due to complex designs.
Innovation Solution
The design features elongated latching depressions and complementary elevations with ramping flanks, strategically positioned detent recesses and bodies, and a semicircular locking surface, which provide consistent pivoting resistance and secure locking without the need for additional gluing, reducing wear and manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the detent bodies and detent recesses are arranged at a large longitudinal distance from the joint bore to achieve good locking effect in parallel positions, then the locking effect in parallel positions is improved, but the friction between scale members in intermediate areas decreases and self-retaining effect is not guaranteed when angled
Solution Approach 1:
The locking mechanism is divided into multiple functional zones: detent bodies/recesses for parallel position locking and braking surfaces for angled position friction. This segmentation allows each zone to perform its specific function optimally without interfering with the other.
Solution Approach 2:
Braking surfaces are introduced as intermediary elements between the detent bodies/recesses and the scale members. These braking surfaces provide the necessary friction in intermediate angled positions while allowing the detent mechanism to maintain its locking effect in parallel positions.
2Reliability
If spherical cap-shaped locking bodies are used to achieve elastic pretension and locking, then secure locking is achieved, but punctiform pressure forces imprint full-circular and part-circular tracks in the adjacent ruler wood, causing gradual wear and loss of locking forces
Solution Approach 1:
The braking surfaces provide a homogeneous distribution of pressure forces across a larger contact area, replacing the concentrated punctiform pressure from spherical caps. This homogeneous pressure distribution prevents localized wood deformation and track imprinting.
Solution Approach 2:
The contact geometry is changed from punctiform (spherical cap) to planar (braking surface). This parameter change in contact area and pressure distribution eliminates the wood imprinting issue while maintaining locking effectiveness.
3Reliability
If spherical cap-shaped locking bodies are used with elastic pretension, then locking effect is achieved, but the ends of elements bend suddenly when detent bodies hit neighboring ruler elements during pivoting, making handling difficult
Solution Approach 1:
The braking surfaces act as cushioning elements that engage before the detent bodies reach their final locked position. This beforehand cushioning provides gradual resistance during pivoting, preventing sudden bending and making handling easier.
Solution Approach 2:
The braking mechanism provides dynamic friction that adapts to the pivoting motion, offering continuous resistance throughout the movement range. This dynamic interaction smooths the pivoting process compared to the abrupt engagement of spherical caps.
4Ease of operation
If multiple pairs of detent recesses and detent bodies are used to provide constant pivoting resistance throughout the pivoting range, then consistent friction is achieved, but manufacturing and assembly costs increase
Solution Approach 1:
The braking surfaces serve multiple functions: providing friction in intermediate positions, cushioning during pivoting, and supporting the detent mechanism. This multi-functionality allows a single component design to achieve constant pivoting resistance without requiring multiple separate locking pairs.
Solution Approach 2:
The braking function and locking function are merged into a unified mechanism where braking surfaces and detent bodies/recesses work together. This merging reduces the total number of components needed compared to using multiple independent locking pairs.
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
This configuration ensures consistent pivoting resistance and secure locking throughout the folding rule's range, maintaining effectiveness even after prolonged use and reducing handling difficulties, while minimizing manufacturing expenses.
Implementation Method 1
the latching mechanism of each articulated pair of links having two latching depressions arranged in the longitudinal direction on opposite sides at a distance from the joint bore and on the other ruler element having at least one complementary latching elevation which preferably latches into the parallel position under elastic pretension
Implementation Method 2
the latching depressions have ramping flanks which are inclined transversely to their longitudinal extent
Data Source
Figure 1~2
Figure 3~6
Figure 4a~4d
AI summary
The folding ruler has multiple longitudinally extending ruler members (14) pivoting against each other at the hinges. The members are locked in pairs over a latch mechanism, particularly made of wood, where the hinges grip through aligned articulated boreholes in adjacent ruler members. The detent recesses are formed in the ruler wood as longitudinal recesses running in a longitudinal direction of the ruler member. The limiting edges of the ruler member has a gap from the articulated boreholes.