Detent Fitting Pawl Layout for Tolerance-Robust Pull-Out Locking
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Solution Overview
Problem
Existing locking fittings are prone to incorrect actuation due to manufacturing tolerances and installation position changes, and lubrication can compromise functional reliability, particularly in regions where the switching element is not positively guided.
Innovation Solution
A locking fitting with a unidirectional pawl on each branch of a switching cam, ensuring the switching element can only move in one direction, preventing incorrect actuation and maintaining functionality regardless of installation conditions, with a resilient design that minimizes user-perceptible force and a central pawl projection for secure closure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a switching element is guided along a curved guide without unidirectional pawls, then the device structure remains simple, but incorrect actuation occurs when the switching element is moved in the wrong direction, particularly in junction regions where positive guidance is lost
Solution Approach 1:
The patent applies local quality by providing unidirectional pawls specifically at critical junction regions of the switching curve where positive guidance is lost. These pawls are strategically positioned only where needed to prevent incorrect actuation, rather than throughout the entire switching path, thus maintaining simplicity while ensuring reliability at critical points.
Solution Approach 2:
The unidirectional pawls embody asymmetry by allowing movement in one direction while blocking movement in the opposite direction. This asymmetric design ensures that the switching element can pass through the junction in the correct direction but is prevented from moving in the wrong direction, eliminating incorrect actuation while maintaining a relatively simple structure.
2Ease of operation
If lubricant is provided for smooth movement of the switching element, then movement becomes smoother, but functional reliability is compromised due to potential slippage or loss of positive engagement
Solution Approach 1:
The patent applies local quality by differentiating between regions requiring smooth movement and regions requiring positive engagement. Lubrication is applied to regions where smooth movement is needed, while unidirectional pawls are positioned at junction regions where positive engagement is critical, thus maintaining both smoothness and reliability in their respective zones without compromising overall functional reliability.
3Reliability
If manufacturing tolerances and installation position variations are not accounted for, then production costs remain lower, but incorrect actuation occurs due to misalignment in the switching curve
Solution Approach 1:
The unidirectional pawls serve as a protective measure against manufacturing tolerances and installation position variations. By providing mechanical guidance and constraint at critical junction points, the pawls compensate for potential misalignments before they can cause incorrect actuation, thus ensuring functional reliability without requiring extremely tight manufacturing tolerances.
Solution Approach 2:
Instead of trying to achieve perfect alignment through tight tolerances, the patent inverts the approach by using unidirectional pawls to enforce correct movement direction regardless of alignment variations. This ensures that even with manufacturing tolerances and installation position variations, the switching element cannot move in the wrong direction, maintaining reliability without demanding high manufacturing precision.
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 solution reliably prevents incorrect actuation and maintains functional reliability across various installation situations and manufacturing tolerances, ensuring secure closure with minimal user effort and no issues from lubrication, while being compact and suitable for ejection devices.
Implementation Method 1
The pawl is resilient and in its initial position it only allows the switching element to pass in one direction
Data Source
Figure 1~2
Figure 3
Figure 4A~4D
AI summary
The detent fitting has a switching element (10) which is moveable along a switching curve (20). The switching element is latched in a closed position on the switching curve and is prestressed in the latched position by a spring. A junction is provided on the switching curve for the switching element and a one-side working pawl (40) is arranged on the junction. An independent claim is also included for a pull-out guide with a guide rail.