Quick-Release Strut Mechanism for Secure Telescopic Adjustment
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Solution Overview
Problem
Existing telescopic struts for external fixators lack a reliable mechanism to quickly and accurately switch between rapid and gradual length adjustment modes, risking unintentional transitions under load and being costly to manufacture.
Innovation Solution
A telescopic strut design with a dual-tube structure featuring texturized surfaces and adjustment knobs that allow for secure locking and unlocking, utilizing a quick-release pin and spring mechanism to prevent unintentional mode transitions, and incorporating a biased detent system for stable adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a quick-release mechanism is added to enable rapid length adjustment, then the speed of length change is improved, but the reliability of preventing unintentional mode transitions deteriorates
Solution Approach 1:
A detent mechanism serves as an intermediary between the adjustment knob and the inner tube. The detent engages with the adjustment knob to prevent rotation, thereby controlling the mode transition. This intermediary component ensures that the quick-release mechanism can rapidly change length when intended, while preventing unintentional mode transitions during the correction phase by requiring deliberate action to disengage the detent.
Solution Approach 2:
The texturized surfaces on the inner tube and corresponding surfaces on the adjustment knob provide tactile feedback to indicate the current mode (locked or unlocked). This feedback mechanism helps the user understand the current state and prevents unintentional activation of rapid adjustment during the correction phase, while still allowing quick switching when intended.
2Reliability
If texturized surfaces are added to the inner tube and adjustment knob, then the reliability of engagement is improved, but the manufacturing complexity increases
Solution Approach 1:
Instead of treating the entire surface of the inner tube and adjustment knob, the texturized surfaces are applied locally only at the engagement areas where the detent interacts with the adjustment knob. This localized approach provides the necessary engagement reliability while minimizing the added complexity and cost of surface treatment compared to treating the entire component surfaces.
3Reliability
If a detent mechanism is implemented to prevent unintentional activation, then the reliability of mode control is improved, but the ease of operation deteriorates
Solution Approach 1:
The detent mechanism is designed to automatically engage and disengage based on the rotation of the adjustment knob. When the knob is rotated, the detent automatically engages with the corresponding surface to lock the mode, and automatically disengages when the knob is rotated in the opposite direction or when force is applied to override. This self-service behavior provides reliable mode control while maintaining ease of operation through automatic rather than manual intervention.
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 design provides a stable and cost-effective mechanism for telescopic struts to reliably switch between rapid and gradual length adjustments, minimizing the risk of unintentional mode changes under load, while maintaining structural integrity and patient safety.
Implementation Method 1
a spring configured to bias the quick-release pin between the first detent and the second detent
Implementation Method 2
the plurality of texturized surfaces of the inner tube engages the plurality of texturized surfaces of the interior surface of the first adjustment knob to prevent translation of the inner tube relative to the outer tube
Data Source
AI summary
An adjustable length strut for use in an external fixation system may include an outer tube, an inner tube within the outer tube, and a first adjustment knob. A plurality of texturized surfaces may extend in the length direction of the inner tube, each of the plurality of texturized surfaces of the inner tube being spaced apart from each other in the circumferential direction of the inner tube. Each circumferentially adjacent pair of texturized surfaces of the inner tube is separated by a non-texturized surface. The first adjustment knob may also include texturized surfaces separated by non-texturized surfaces, and may be rotatable relative to the outer tube and the inner tube between a locked condition and an unlocked condition. In the locked condition, the texturized surfaces engage each other, to prevent translation of the inner tube relative to the outer tube.