Pre-tightening Locking Device for Shaft Retention

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Solution Overview

Problem

Existing hydraulic nut systems for pre-tightening cemented carbide rolls are prone to failure due to aging of polymer sealing members under environmental influences, leading to unstable fastening and high maintenance costs, and are not suitable for repeated use.

Innovation Solution

A pre-tightening locking device comprising a backing ring, a pre-tightening nut, and a hydraulic nut with a filling member that maintains pre-tightening force without continuous hydraulic pressure, allowing the hydraulic nut to be removed from the hostile environment, thus extending its service life and reducing costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the hydraulic nut is used to generate large axial pre-tightening force, then the fastening stability is improved, but the sealing member ages under environmental influences leading to reduced reliability

Engineering Contradiction:

Improvefastening stabilityVSAvoidservice life of hydraulic nut

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The hydraulic nut is extracted from the permanent installation and used only temporarily during the pre-tightening process. After the filling member is installed to maintain the pre-tightening force, the hydraulic nut is removed from the shaft assembly, preventing prolonged exposure to hostile environmental conditions that cause sealing member aging.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The hydraulic nut performs the pre-tightening action in advance during assembly, generating the required axial pre-tightening force to ensure stable fastening. The filling member is then installed to maintain this pre-tightening force without requiring the hydraulic nut to remain in place, allowing the hydraulic nut to be removed after completing its preliminary function.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If the hydraulic nut remains in place to maintain pre-tightening force, then the fastening stability is improved, but the sealing member is exposed to hostile environment reducing its service life

Engineering Contradiction:

Improvefastening stabilityVSAvoidenvironmental influences on sealing member

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The filling member acts as an intermediary that takes over the function of maintaining pre-tightening force after the hydraulic nut has completed its tightening action. This intermediary component allows the hydraulic nut to be removed, thereby protecting the sealing member from prolonged environmental exposure while maintaining fastening stability.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of manufacture

If polymer sealing members are used in the hydraulic nut, then the manufacturing cost is reduced, but the sealing members age quickly under temperature and oil influences

Engineering Contradiction:

Improvemanufacturing costVSAvoidservice life of sealing member

Core Design Contradiction:

Ease of manufactureVSDuration of action of stationary object

Solution Approach 1:

The hydraulic nut with its polymer sealing members is extracted from permanent service and used only temporarily during assembly. After the pre-tightening force is established and the filling member is installed, the hydraulic nut is removed, preventing the polymer sealing members from prolonged exposure to temperature and oil that would cause aging, while maintaining the cost advantage of using polymer materials.

Inventive Principle:

Principle #2Taking out (Extraction)

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 provides reliable pre-tightening and extended service life of the hydraulic nut, reducing costs by 30% and increasing the sealing member's service life by over 5 times, while maintaining stable fastening without the need for continuous hydraulic pressure.

Implementation Method 1

an annular piston of the hydraulic nut is capable of exerting an acting force on the backing ring under fluid pressure so as to form an interval between the backing ring and the pre-tightening nut

Methodology Applied

Scientific EffectFluid pressure: Pressure Increase

Data Source

PatentEP2711099B1Pre-tightening locking device for retaining parts on shaft

Publication Date: 2017.05.24 ZHUZHOU HARD ALLOY GRP CO LTD

Figure 1~2
Figure 3~4
Figure 5~6

AI summary

The present disclosure discloses a pre-tightening locking device (100) for retaining a component on a shaft, comprising: a backing ring (1) having a first end face (11) and an opposite second end face (12), wherein the backing ring is mounted on the shaft with the first end face (11) thereof closely engaging with the component to be retained; a pre-tightening nut (3) threadedly coupled on the shaft, wherein one end of the pre-tightening nut engages with the second end face (12) of the backing ring (1); a hydraulic nut (4) arranged outside of the pre-tightening nut (3) through threads, wherein an annular piston (5) of the hydraulic nut (4) is capable of exerting an acting force on the backing ring (1) under fluid pressure so as to form an interval between the backing ring (1) and the pre-tightening nut (3); and a filling member for filling the interval. A filling member is provided for filling the interval so that a pre-tightening force can be maintained, which ensures that the component on the shaft is closely retained. Under this condition, the hydraulic nut can be removed, whereby the cost is significantly reduced.