Crossbow Draw-String Mechanism With Pulley Force Amplification
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Solution Overview
Problem
Traditional crossbow draw-string mechanisms are labor-consuming and can cause finger damage, as they require direct hand operation to draw back the bowstring.
Innovation Solution
A draw-string mechanism featuring a carriage with a hook-string board, pull-cord device, and reset device, utilizing pulley blocks and a coilspring wheel to amplify drawing force, allowing the carriage to slide back and forth within the crossbow limb, reducing operator effort and eliminating finger risk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If direct hand operation is used to draw back the bowstring, then the structure is simple, but it causes finger damage and is labor-consuming
Solution Approach 1:
The patent introduces a carriage as an intermediary device between the operator and the bowstring. The carriage carries draw-string hooks that engage with the bowstring ends, allowing the operator to pull the carriage back along the slideway rather than directly pulling the bowstring. This intermediary mechanism protects fingers from damage and reduces operator effort while maintaining operational effectiveness
Solution Approach 2:
The drawing mechanism is segmented into distinct functional components: the carriage that moves along the slideway, the draw-string hooks that engage the bowstring, and the pull-cord device with pulley blocks that provides mechanical advantage. This segmentation allows each component to perform its specific function efficiently, resolving the contradiction between operational ease and structural complexity
2Ease of operation
If a basic draw-string device with sliding rods is used, then finger damage is avoided, but it remains labor-consuming
Solution Approach 1:
The patent employs dynamic pulley systems where the pulley blocks are mounted on movable carriages rather than fixed positions. As the carriage moves back and forth along the slideway, the pulleys dynamically change their position and mechanical advantage ratio. This dynamic configuration allows the system to provide 2-4 times drawing force multiplication while maintaining operational flexibility
Solution Approach 2:
The patent transforms the one-dimensional linear pulling motion into a multi-dimensional system by incorporating pulley blocks that redirect forces in multiple directions. The pull cords wrap around pulleys mounted at different positions and orientations on the carriage, creating a complex force vector system that multiplies the operator's input force into 2-4 times drawing force on the bowstring
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 mechanism significantly reduces operator effort by generating 2-4 times the drawing force, making it easier and safer to operate the crossbow, while avoiding finger damage.
Implementation Method 1
pull-cord device used to drive the carriage to slide back on the slideway of the crossbow limb... generate 2-4 fold drawing force to draw string via force-increasing effect of pull-cord pulley blocks
Implementation Method 2
reset device to draw the carriage to slide forward to its initial position... comprises a coilspring wheel and a coil spring
Data Source
AI summary
The invention relates to the technical field of the athletic equipment, specifically relating to a draw-string mechanism for crossbows comprising a carriage mounted inside the slideway of the crossbow limb, a hook-string board mounted on the carriage, a pull-cord device used to drive the carriage to slide back on the slideway of the crossbow limb and a reset device to draw the carriage to slide forward to its initial position; said pull-cord device includes two pull cords, a pull handle, and pull-cord pulley blocks wherein two pull cords respectively has a corresponding pull-cord pulley block and passes around the pull-cord pulley block with its end fixed inside pull handles. The invention can not only avoid hurting fingers of crossbow operators, but also generate 2-4 fold drawing force to draw string via force-increasing effect of pull-cord pulley blocks, which is very easy to operate and more labor-saving.