Load-Limiting Line Grab With Automatic 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 incorrect installation, inefficiency, and degradation of the host line due to friction and overload, particularly during slip events, and lack automatic re-grabbing capabilities.
Innovation Solution
A load-limiting line grab device with a spring, unlevered cam, and tail, featuring a V-shaped groove that increases friction and rotates with increased load, automatically slipping and re-grabbing the line at predetermined thresholds to prevent degradation and overload, allowing for single-handed operation.
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, and degrades the host line during slip events due to friction
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 and lever arm to create a mechanical gripping action on the line, eliminating the need for friction-dependent knotting. This substitution provides a more controlled and less damaging gripping mechanism that doesn't degrade the host line during slip events.
Solution Approach 2:
The patent introduces a cam as an intermediary mechanical element between the user's force application and the line gripping. The cam surface acts as a mediator that converts rotational or linear motion into a controlled gripping force, providing a more reliable and less harmful interaction with the host line compared to direct knot friction.
2Reliability
If a levered camming device with sharp teeth is used, then it prevents slip between the rope and cam in overload situations, but it causes degradation to the host rope due to the sharp teeth
Solution Approach 1:
The patent applies local quality by using duller teeth with a larger toothing angle specifically at the cam surface that contacts the line. This localized modification reduces the harmful effect of tooth sharpness on the rope while maintaining the overall gripping function. The duller teeth distribute pressure more evenly, preventing concentrated stress points that would degrade the host rope.
Solution Approach 2:
The patent changes the geometric parameters of the cam teeth, specifically increasing the toothing angle and reducing tooth sharpness. This parameter modification allows the cam to maintain its gripping and slip-prevention functionality while reducing the mechanical damage inflicted on the host rope during operation.
3Object-affected harmful factors
If an automatic release device is used during overload, then it releases the line to prevent degradation, but it cannot automatically re-grab the line
Solution Approach 1:
The patent implements self-service by designing the cam mechanism to automatically perform both release and re-grabbing functions. The spring-loaded cam system automatically releases the line when overload occurs and then automatically re-engages or re-grabs the line when the load decreases, without requiring user intervention. This eliminates the need for separate manual operations to reset the device.
Solution Approach 2:
The patent incorporates feedback through the spring mechanism that senses load changes. When the load exceeds the threshold, the cam releases; when the load decreases, the spring automatically drives the cam to re-engage the line. This feedback loop enables automatic adaptation to load conditions, providing both protection during overload and automatic recovery afterward.
4Force
If a cam with acute toothing angle is used, then it provides strong gripping force, but it requires greater force on the host line to grab it and causes more degradation
Solution Approach 1:
The patent changes the geometric parameter of the cam teeth by increasing the toothing angle from acute to a larger, more obtuse angle. This parameter change reduces the stress concentration on the line while maintaining adequate gripping force through the increased surface area and distributed contact points of the broader teeth.
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 provides predictable slipping and grabbing without user input, reducing line degradation and overload risks, with faster and more reliable setup compared to traditional rope knots and cam devices.
Implementation Method 1
A load-limiting line grab device with a spring, unlevered cam, and tail
Implementation Method 2
featuring a V-shaped groove that increases friction
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 allow a user to actuate a side plate and a cam independently of one another.