Hollow Stop Pin Shear Mechanism for Actuator Protection

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Solution Overview

Problem

Rotary or angularly adjustable valve arrangements in subsea or other environments risk damage when a control system failure causes continued torque application after the valve reaches its fully open or closed position, potentially damaging the actuator.

Innovation Solution

A hollow, substantially cylindrical stop pin with a blind bore and an annular groove of reduced wall thickness is used, designed to shear if excessive torque is applied, allowing the valve to continue rotating and preventing further damage to the actuator.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a stop pin is provided to limit the rotation angle of the valve member, then the valve arrangement achieves reliable positioning at fully open and fully closed positions, but the actuator may be damaged if torque is continued after the stop is engaged due to control system failure

Engineering Contradiction:

Improvevalve positioning reliabilityVSAvoidactuator damage risk

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The stop pin is designed as a sacrificial component that may be sheared off under excessive torque conditions. The pin includes a reduced wall thickness region that acts as a predetermined failure point, allowing the pin to break rather than damage the expensive actuator. This disposable approach protects the valuable actuator from damage while maintaining reliable valve positioning during normal operation.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The stop pin is designed with a predetermined weak point (reduced wall thickness region) that acts as a safety mechanism before damage occurs to the actuator. This beforehand cushioning ensures that if excessive torque is applied, the pin will fail in a controlled manner, preventing transmission of damaging forces to the actuator.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Strength

If the stop pin is designed with high strength to ensure reliable engagement, then the valve positioning is secure, but the stop pin may cause damage to the actuator in case of control system failure

Engineering Contradiction:

Improvestop pin engagement strengthVSAvoidactuator damage from excessive torque

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The stop pin exhibits different mechanical properties at different locations. The majority of the pin has full wall thickness for strong engagement, while a specific region (the reduced wall thickness region) has deliberately weakened structure. This local quality differentiation allows the pin to be strong where needed for positioning while being vulnerable where needed for protection.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The stop pin is segmented into two functional regions: a strong engagement region with full wall thickness that provides reliable positioning, and a weak sacrificial region with reduced wall thickness that fails under excessive torque. This segmentation allows the pin to simultaneously provide strong engagement and actuator protection.

Inventive Principle:

Principle #1Segmentation

3Reliability

If the stop pin is made solid and strong, then it provides reliable stopping action, but it cannot accommodate torque variations and may cause damage

Engineering Contradiction:

Improvestop engagement reliabilityVSAvoidtorque level accommodation

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The stop pin's wall thickness parameter is varied along its length to create different mechanical properties. The reduced wall thickness region creates a predetermined torque level at which the pin will fail, allowing the system to accommodate torque variations up to that level while providing protection beyond it. This parameter change enables both reliable engagement and torque level adaptation.

Inventive Principle:

Principle #35Parameter changes

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 stop pin's shearing mechanism reduces the risk of actuator damage by allowing the valve to maintain operation without interference from the remaining stop pin parts, ensuring free movement and preventing further torque application.

Implementation Method 1

the stop pin being designed to shear in the event that a torque greater than a predetermined level is applied to the rotatable part

Methodology Applied

Scientific EffectShear stress: Shear Stress

Data Source

PatentEP3227590B1Valve arrangement

Publication Date: 2019.05.22 LB BENTLEY

Figure 1~2
Figure 3

AI summary

A valve arrangement comprises a rotatable part 32 rotatable relative to a stationary part 12, wherein one of the rotatable part 32 and the stationary part 12 includes an abutment surface 36a, 36b engageable with a stop associated with the other of the rotatable part 32 and the stationary part12, wherein the stop comprises a stop pin40 of hollow, substantially cylindrical form.