Frangible Locking Pin for Fluid Strut
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Solution Overview
Problem
Existing fluid strut systems, such as gas springs, lack a mechanism to prevent accidental closure of heavy closure members without risking damage when a predetermined force is applied, as they either fail to lock the strut in an extended position or cause damage if the lock is not removed before slamming the cover.
Innovation Solution
A frangible locking mechanism with a spring-loaded plunger-type lock that can be moved between operative and inoperative positions, featuring a reduced-diameter locking pin that shears when a predetermined force is applied, allowing the strut to collapse and prevent damage to the closure member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spring-loaded plunger lock is employed to automatically lock the gas strut rod when in an extended position, then the safety feature of preventing inadvertent closure is improved, but the risk of serious damage occurs if the user fails to remove the lock and slams the cover downwardly against the locking pressure
Solution Approach 1:
The locking mechanism uses a frangible locking element with specific material properties that allow it to maintain locking force under normal conditions but fail safely when subjected to excessive force. The element's shear strength is deliberately designed to be lower than the force required to damage the closure member, transforming the locking parameter from purely rigid to conditionally flexible.
Solution Approach 2:
The potential harmful effect of the locking mechanism is converted into a beneficial safety feature. Instead of the lock being a source of damage when accidentally engaged, the frangible nature of the locking element causes it to fail in a controlled manner under excessive force, preventing damage to the closure member while still providing reliable locking during normal operation.
2Reliability
If a locking mechanism is added to prevent accidental closure, then the safety and stability of the open position is improved, but the device complexity increases
Solution Approach 1:
The locking mechanism is merged with the existing gas strut structure. The frangible locking element is integrated into the rod assembly, and the spring-loaded plunger is incorporated into the housing, combining the locking function with the existing support mechanism rather than adding a completely separate system.
Solution Approach 2:
The locking mechanism operates automatically without requiring user intervention. The spring-loaded plunger automatically engages the frangible locking element when the strut is in the extended position, and the locking state is maintained self-servingly until a deliberate closing action occurs, eliminating the need for manual locking or unlocking operations.
3Adaptability or versatility
If a frangible locking element with reduced diameter is used, then the ability to allow purposeful closure without damage is improved, but the locking strength under normal conditions must be carefully balanced
Solution Approach 1:
The locking element exhibits different mechanical properties at different locations. The reduced-diameter portion is specifically designed with lower shear strength to fail under excessive force, while the rest of the locking mechanism maintains sufficient strength for normal operation. This local variation in geometric properties creates the desired differential response to different loading conditions.
Solution Approach 2:
The locking mechanism transitions from a static rigid lock to a dynamic system that responds differently to different force levels. Under normal conditions, the lock provides rigid restraint, but when subjected to excessive force beyond the shear strength of the frangible element, the system dynamically transitions to an unlocked state, allowing the rod to be retracted without damage.
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
Enables the strut to remain locked in an open position until a purposeful closing force is applied, preventing accidental closure and minimizing damage to the closure member by shearing the locking pin under excessive force.
Implementation Method 1
a spring-loaded plunger lock on a housing concentric with a gas cylinder
Implementation Method 2
the locking pin can shear, allowing the rod to be retracted within the cylinder
Data Source
AI summary
A fluid strut includes a frangible locking member including a generally cylindrical locking pin mounted to an outer cylindrical housing of the strut and extending radially inwardly toward a gas spring cylinder. The locking pin is movable between operative and inoperative positions. In the operative position, the spring-loaded frangible locking pin extends into engagement with the gas cylinder and can advance radially to a locking position once the outer housing extends beyond the location of the gas cylinder. In an inoperative position, the locking pin is held in a retracted position. The end of the locking pin has a reduced diameter, such that, if a purposeful force is placed upon the strut when in a locked position, the pin can shear, allowing the rod to be retracted within the cylinder and the closure member to be closed without damage.