Crossbow Spanning Device Reduces Effort via Linkage Mechanism
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Solution Overview
Problem
Conventional crossbows require significant effort to span the string, and if not successfully pulled to the cocked position, the string can bounce back and potentially harm the user.
Innovation Solution
A spanning device for a crossbow that utilizes a slideable action unit with a pull rod, pivotal rod, and link mechanism to leverage the force required for spanning, allowing the string to be easily pulled with reduced effort, featuring a hook member, safety member, and trigger system to manage the string's tension and release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the string is pulled backward to a cocked position manually, then the crossbow can be spanned, but significant effort is required and the string may bounce back and hurt the user if not successfully positioned
Solution Approach 1:
A spanning device is introduced as an intermediary mechanism between the user and the string. The spanning device includes a hook member that engages with the string and a spanning member that applies force to pull the string backward. This intermediary mechanism reduces the direct force requirement on the user and provides controlled spanning motion.
Solution Approach 2:
The spanning operation is divided into distinct functional components: a hook member for engaging the string, a spanning member for applying pulling force, and a connection mechanism linking them. This segmentation allows each component to be optimized for its specific function, improving overall spanning efficiency and safety.
2Reliability
If the string is pulled backward manually, then the crossbow can be spanned, but the string may bounce back and potentially harm the user
Solution Approach 1:
The hook member is designed to engage with the string before the spanning process begins. This preliminary engagement ensures that the string is securely held during the spanning operation, preventing unintended movement or recoil that could harm the user.
Solution Approach 2:
The spanning device acts as a controlled intermediary between the user and the high-tension string. By using the spanning member to gradually apply force through the hook member, the system provides controlled spanning motion and prevents sudden string recoil, thereby improving safety.
3Device complexity
If a simple manual pulling method is used, then the spanning mechanism is simple, but the force required is too high for comfortable operation
Solution Approach 1:
The spanning mechanism is segmented into functional components (hook member, spanning member, connection mechanism) that work together to reduce force requirements. This segmentation allows for a relatively simple overall structure while achieving mechanical advantage through the coordinated action of its parts.
Solution Approach 2:
The spanning device serves as an intermediary mechanism that provides mechanical advantage. The hook member engages the string while the spanning member applies force, creating a leveraged system that reduces the effort needed compared to direct manual pulling, without requiring complex mechanisms.
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
Enables the string to be efficiently spanned with less effort, ensuring safe operation by reducing the risk of string recoil and facilitating easier arrow shooting.
Implementation Method 1
A resilient member is located between the slide and the restriction member so as to bias the restriction member to press the push portion of the safety member
Implementation Method 2
A recovery spring is located between the action rod and the operation member. The recovery spring is biased between the hook member and the slide. The recovery spring provides a force to return the hook member.
Implementation Method 3
A compression spring is biased between the recess and the pawl to return the pawl.
Data Source
AI summary
A spanning device of a crossbow includes a barrel, an action unit and an spanning unit. A space is defined in the barrel. A limb is connected close to the front end of the barrel. A string is connected between two ends of the limb. The action unit slidably located in the space and has a portion exposed from the space. The action unit has a slide, a restriction member, a safety member, a hook member and a trigger. The restriction member, the safety member, the hook member and the trigger are connected to the slide which is slidably engaged with the space. The spanning unit has a pull rod, a pivotal rod and a first link. The spanning unit drives the action unit to move in the space, so that when the hook member hooks the string, the string is easily pulled with less effort.