Line Grab Device With Cam And Tail For Load Limiting
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Solution Overview
Problem
Existing line grab devices, such as the Prusik knot and levered camming devices, face issues with incorrect installation, inefficiency due to friction, difficulty in resetting after heavy loads or slip events, and degradation of the host line during overload conditions.
Innovation Solution
A load limiting line grab device configured to slip at or above a threshold load, featuring a spring, an unlevered cam with a V-shaped groove, and a tail that contacts the line to block further cam rotation, preventing degradation of the host line and allowing for automatic re-grabbing once the load decreases below the threshold.
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 inefficient when sliding along the host line 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 controlled mechanical interaction between the cam surface and the host line to achieve grabbing and slipping functions, eliminating the inefficiencies of friction-based sliding while maintaining simplicity of configuration.
2Device complexity
If a Prusik knot is used, then it is simple to configure, but it is difficult to reset to a desired position after being heavily loaded or following a slip event
Solution Approach 1:
The cam-based device automatically resets to its functional position after a slip event or heavy load. The cam mechanism self-adjusts through the controlled interaction with the host line, eliminating the need for manual resetting that plagues Prusik knots after they have been heavily loaded.
3Ease of manufacture
If a Prusik knot is used, then it is inexpensive, but during slip events the knot may degrade the host line and/or 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 system that controls line interaction through precise geometric surfaces. This substitution prevents the line degradation and welding issues that occur with Prusik knots during slip events, while the cam device can be manufactured at comparable cost.
4Reliability
If levered camming devices are used, then they may prevent slip between the rope and the cam in overload situations, but they may not be configured to automatically re-grab the line after releasing
Solution Approach 1:
The cam device automatically re-grabs the line after releasing during overload. The cam mechanism's geometric design and interaction with the host line enable it to self-reset and re-engage without manual intervention, providing both overload protection and automatic re-grabbing functionality.
5Ease of operation
If a cam with slots engaged with protrusions is used, then operation can be simplified for a user such as allowing single-handed operation, but the device complexity increases
Solution Approach 1:
The patent integrates multiple functions into the cam component itself. The cam combines the gripping surface, the slot mechanism for controlled movement, and the interaction with host line protrusions into a single integrated component. This merging reduces the number of separate parts needed, enabling simplified single-handed operation while keeping overall device complexity manageable.
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 ensures predictable slipping and grabbing of the line without degrading it, provides faster and more reliable setup compared to rope knots, and maintains line integrity by limiting overload forces.
Implementation Method 1
The device includes a spring, an unlevered cam with a V-shaped groove, and a tail that contacts the line to block further cam rotation
Implementation Method 2
The line grabbing device may be a device configured to block and allow slipping of a line at a pre-determined load
Data Source
Figure 1~2
Figure 3A~3B
Figure 4A~4E
AI summary
A device configured to couple to a line, comprising a cam arranged between a side plate and a chassis, and a retaining system including at least one protrusion positioned to slide within at least one slot. Further, line grab devices are disclosed which are embodiments of the device.