Line Grab Cam Mechanism for Controlled Slip and Re-Grabbing
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Solution Overview
Problem
Existing line grab devices, such as the Prusik knot and camming devices, face issues with inefficiency, degradation of the host line, and difficulty in configuring for varying slip events, particularly under overload conditions, as they either slip or degrade the line without automatically re-grabbing it.
Innovation Solution
A line grab device featuring a cam with an increasing camming angle as it rotates, which slips at loads above or equal to a threshold and re-grabs the line when the load decreases below the threshold, utilizing a spring and a V-shaped groove to manage friction and prevent overloading, allowing for automatic slipping and grabbing without user input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a Prusik knot is used as a line grab device, then it is relatively inexpensive and simple to configure, but it is vulnerable to incorrect installation, troublesome to set-up, inefficient when sliding along the host line due to friction, and difficult to reset after being heavily loaded
Solution Approach 1:
The patent replaces the friction-based Prusik knot mechanism with a cam-based mechanical system. The cam device uses a cam surface that converts rotational motion into linear motion to grip and release the line, eliminating the inefficiencies of friction-based sliding while maintaining simple configuration. The cam mechanism provides controlled engagement and disengagement without the installation troubles of knot-tying systems.
2Reliability
If a Prusik knot is used, then it can grab the line, but during slip events it may degrade the host line and the lines may weld together and become difficult to separate
Solution Approach 1:
The patent replaces the Prusik knot's friction-based gripping mechanism with a cam-based mechanical system. The cam surface provides controlled contact with the line through a defined engagement geometry, preventing the excessive friction and heat generation that cause line degradation and welding in Prusik knots. The cam mechanism allows for clean engagement and disengagement without damaging the host line.
3Strength
If levered camming devices are used, then they can handle higher loads with duller teeth and larger toothing angle, but they may not slip under overload conditions and degrade the host line
Solution Approach 1:
The patent employs a cam surface with specifically engineered geometry parameters including a defined camming angle and surface profile. The camming angle is optimized to provide sufficient mechanical advantage for high load handling while ensuring that the contact pressure distribution prevents line degradation. The cam surface geometry is designed to allow controlled slipping at overload conditions, unlike levered camming devices with aggressive teeth that may not slip and instead damage the line.
4Object-affected harmful factors
If automatic release devices are used during overload scenarios, then they can prevent line degradation, but they may not be configured to automatically re-grab the line
Solution Approach 1:
The patent designs the cam mechanism to be self-actuating based on load conditions. When the line load exceeds the threshold, the cam automatically rotates to a position where it releases the line. When the load decreases below the threshold, the cam automatically rotates back to its gripping position and re-engages the line without requiring user intervention. This self-service mechanism combines automatic release with automatic re-grabbing in a single integrated system.
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 device effectively prevents line degradation by slipping predictably at high loads and re-grabbing when loads decrease, ensuring reliable operation and reducing the risk of complete load release, thus maintaining line integrity and efficiency.
Implementation Method 1
a cam configured to increase a camming angle as rotation of the cam increases
Implementation Method 2
The cam may grab the line at a low cam angles and continue to grab the line as the load and cam rotation increases
Implementation Method 3
utilizing a spring and a V-shaped groove to manage friction and prevent overloading
Implementation Method 4
The groove may be configured with a V-shape and increase in width away from a pivot point of the cam
Data Source
AI summary
Methods and systems are provided for a device. In one example, the device is configured to automatically grab and slip a line. The device is further configured to decrease degradation to the line by limiting a rotation of the device via contact with the line.