Nut Locking Sleeve With Pivoting Arms for Tamper-Proof Retention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing tamper-proof devices for securing nuts are either easy to release or difficult to assemble, lacking a balance between security and ease of installation.
Innovation Solution
The design features an inner sleeve with articulated locking arms that tilt over a collar on an outer sleeve, engaging the bolt thread, and a configuration where the outer sleeve is longer than the inner sleeve, with locking arms positioned around the axis to prevent removal, and a hollow truncated cone collar for assembly, ensuring the device is difficult to disassemble without tools.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single locking connection is used (as in DE 101 56 876 A1), then the device is easy to assemble, but it can be easily removed by lifting the cap off the nut
Solution Approach 1:
The locking mechanism is divided into multiple independent locking arms (at least two, preferably three or four) distributed around the inner sleeve. Each locking arm independently engages with the nut, creating multiple locking points. This segmentation transforms a single weak locking connection into multiple reinforced connections, preventing the cap from being lifted off while maintaining ease of assembly through the modular structure of the locking arms that can be independently formed or attached.
Solution Approach 2:
The locking arms are designed to extend radially outward from the inner sleeve in a direction perpendicular to the axial direction of assembly. This dimensional change from axial to radial locking provides mechanical advantage, making removal require significant radial force rather than simple axial lifting. The locking arms can be deflected during assembly but lock firmly in the radial direction, securing the cap to the nut.
2Reliability
If multiple locking arms are added to improve security, then removal becomes difficult, but the device complexity increases
Solution Approach 1:
The locking arms are integrated with the inner sleeve to form a single monolithic component, eliminating the need for separate assembly of locking arms and inner sleeve. This merging reduces structural complexity while maintaining the security benefits of multiple locking arms. The locking arms are formed as extensions or integrals of the inner sleeve body, simplifying manufacturing and reducing part count while providing robust multi-point locking.
Solution Approach 2:
The inner sleeve serves multiple functions: it provides the central structural element, supports the locking arms, engages with the nut threads, and maintains the geometric relationship between all locking arms. This multi-functionality reduces the need for additional components, simplifying the overall device structure while achieving reliable multi-point locking security.
3Reliability
If the locking arms are positioned to engage the bolt thread, then the device becomes difficult to release, but it may obstruct the rotation of the outer sleeve
Solution Approach 1:
The locking arms are positioned to engage only the protruding portion of the bolt beyond the nut, leaving the main body of the bolt and nut free for rotation. The engagement is localized to specific regions where locking is needed, while other regions maintain operational freedom. The outer sleeve can still rotate freely because the locking arms are contained within the inner sleeve structure and do not extend outward to interfere with outer sleeve rotation.
Data Source
Figure 1~2
Figure 3~5
AI summary
A tamper-evident device for permanently securing nuts (6) screwed onto a bolt (14) up to a flat stop consists of an inner sleeve (1) and a coaxially arranged outer sleeve (2) that is freely rotatable relative to the inner sleeve (1) and has a collar (11). The inner sleeve (1) is placed onto the nut (6) together with the outer sleeve (2). Locking arms (7), which are pivotally connected to the inner sleeve (1), are pushed outwards by the bolt (14) so that the locking arms (7) are tilted and lie above the collar (11), with their inner surfaces engaging the bolt (14). Thus, neither the outer sleeve (2) can be pulled off the inner sleeve (1), nor the inner sleeve (1) can be pulled off the nut (6).