Actuator Stem and Rod End Bearing Coupling via Threaded Stud

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing control valve connections between rod end bearings and actuator stems are weak due to machining away high-strength material from the outer surface of bar stock, leading to potential twist off or fracture under torsional loads during assembly or disassembly, especially due to over-torquing.

Innovation Solution

An externally threaded stud couples a rod end bearing with an actuator stem, both featuring internally threaded bores, providing a stronger connection and using a tapered surface for self-locking, eliminating the need for machining external threads and enhancing resistance to torsional loads.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If external threads are machined on rod end bearing or actuator stem, then connection can be formed, but high-strength material is machined away reducing connection strength

Engineering Contradiction:

Improveconnection formationVSAvoidconnection strength

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

Instead of machining external threads on the rod end bearing or actuator stem (which removes high-strength material), the patent inverts the approach by providing internally threaded bores in both components and using an externally threaded stud as a separate fastening element. This preserves the high-strength material in the main components while achieving the required connection.

Inventive Principle:

Principle #13The other way round (Inversion)

2Ease of manufacture

If externally threaded end is formed from core material, then manufacturing is simplified, but connection strength is reduced

Engineering Contradiction:

Improvethread formationVSAvoidresistance to torsional loads

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent reverses the conventional approach by placing external threads on a separate stud component rather than on the rod end bearing or actuator stem themselves. This allows the main components to maintain their full structural integrity and resistance to torsional loads while still enabling threaded connection through the stud.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The externally threaded stud acts as an intermediary component that facilitates the connection between the rod end bearing and actuator stem without requiring the main components to have external threads. This mediator preserves the strength of the primary components while achieving the required connectability.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of operation

If conventional threaded connection is used, then assembly is simple, but twist off or fracture occurs under over-torquing

Engineering Contradiction:

Improveassembly simplicityVSAvoidresistance to over-torquing

Core Design Contradiction:

Ease of operationVSStrength

Solution Approach 1:

The externally threaded stud serves as a sacrificial intermediary that can absorb over-torquing forces without compromising the integrity of the rod end bearing or actuator stem. This maintains assembly simplicity while significantly improving resistance to over-torquing and fracture.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentEP2286122B1Apparatus and methods to couple actuator stems and rod end bearings

Publication Date: 2012.07.25 FISHER CONTROLS INT LLC

Figure 1
Figure 2
Figure 3

AI summary

Methods and apparatus to couple actuator steins and rod end bearings are described. An example apparatus includes a bearing (208) having a body and a portion extending from the body in which the portion includes an internally threaded bore. An actuator stem (202) has a first end that includes an internally threaded bore. An externally threaded stud (216) threadably engages the bores of the rod end bearing and the actuator stem to couple the rod end bearing and the actuator stem.