Retrofittable Locking Apparatus for Screw-Threaded Nuts
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Solution Overview
Problem
Existing locking mechanisms for screw-threaded nuts in machinery often require additional secondary locking solutions that are not easily retrofittable or desirable by default, especially in safety-critical applications where machine vibration can cause loosening.
Innovation Solution
A locking apparatus comprising an annular tab washer and arcuate tab plates that provide both primary and secondary locking functions, with radially inner and outer tabs for engagement with the nut and housing, allowing for orthogonal bending and secure fixation, along with equispaced threaded holes for additional fastening, enabling a secondary lock that can be retrofitted if needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tab washer is used as a primary mechanical lock, then reliability is improved, but device complexity increases when a secondary lock is added
Solution Approach 1:
The patent combines the primary lock (tab washer) and secondary lock (tab plate) into a single integrated locking apparatus. The tab plate is positioned adjacent to the tab washer and works in conjunction with it, merging two separate locking functions into one unified structure that reduces overall complexity while maintaining dual-locking reliability.
Solution Approach 2:
The tab plate serves multiple functions: it provides a secondary locking mechanism through its own tab engagement, simultaneously engages with both the nut and the element to create a rigid triangular arrangement, and can be selectively fitted only when a secondary lock is desirable. This multi-functionality allows a single component to address multiple locking requirements without proportionally increasing complexity.
2Reliability
If a secondary mechanical lock is added to the nut, then reliability is improved, but ease of operation deteriorates due to additional fitting steps
Solution Approach 1:
The tab plate is designed to be pre-positioned adjacent to the tab washer before the nut is fully tightened. The radially outer tab of the tab washer engages the nut during the tightening process itself, establishing the secondary lock's position in advance. This preliminary positioning allows the secondary lock to be established as part of the normal tightening sequence rather than requiring separate fitting operations afterward.
Solution Approach 2:
The tab plate incorporates an arcuate slot that allows it to flex and adapt during the tightening process. The slot enables the tab plate to move dynamically as the nut is tightened, facilitating easy installation without requiring precise pre-alignment, while still achieving the rigid fixed position needed for reliable locking once tightened.
3Adaptability or versatility
If a secondary lock is made retrofittable, then adaptability is improved, but reliability may be compromised if the secondary lock is not initially fitted
Solution Approach 1:
The locking apparatus is segmented into distinct functional components: the tab washer providing primary locking, and the tab plate providing secondary locking. This segmentation allows the tab plate to be selectively fitted or omitted based on whether a secondary lock is required, while maintaining the integrity and reliability of the primary lock regardless of the secondary lock's presence.
Solution Approach 2:
The radially outer tab of the tab washer acts as an intermediary element that connects both the nut and the tab plate. During installation, this tab engages the nut first, establishing the primary locking position, and then provides a reference point for positioning the tab plate. This intermediary engagement ensures proper alignment and facilitates retrofittability while maintaining reliable locking geometry.
Data Source
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AI summary
A lock nut (16) includes a conventional lock tab washer (20) for fixing thereof. One or more tab plates (30) are provided for fixing to a flank face (25) of the nut. The tab plates have a radially inner tab (31) to prevent relative rotation thereof, and provide a secondary locking function. Bolts (27) attach the tab plates, and have individual lock washers (28).