Crossbow Cocking Device Multi-Stage Link Mechanism
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Solution Overview
Problem
Cocking a crossbow requires significant force, and existing assistance devices can lead to user injury if the string is not properly positioned, as it may bounce back unexpectedly.
Innovation Solution
A cocking device with a barrel, handle, bow, arrow track, and a link unit that includes a restriction member with a serrated slot, where a rod and springs engage to facilitate multiple-stage cocking, allowing users to take breaks and reducing the risk of injury by distributing the force over multiple actions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a rope cocking device is used to assist cocking, then the force required to cock the crossbow is reduced, but the device complexity increases
Solution Approach 1:
The cocking device divides the cocking process into multiple stages using a multi-link mechanism (first link, second link, third link) with distinct functional segments. Each link performs a specific motion function, allowing the system to reduce required force through mechanical advantage while maintaining manageable complexity through modular design
Solution Approach 2:
The device employs dynamic motion paths for each link, where the first link rotates about a first pivot, the second link rotates about a second pivot, and the third link rotates about a third pivot. This dynamic multi-stage rotation system transforms the cocking force application, reducing the instantaneous force requirement while the retractable nature of the mechanism allows automatic reconfiguration
2Productivity
If the string is pulled quickly to cock the crossbow, then the cocking action is completed faster, but the risk of injury increases if the string is not properly positioned
Solution Approach 1:
The mechanism performs preliminary positioning actions through its multi-stage motion sequence. The first link's rotation about the first pivot initially engages the string, followed by the second link's rotation about the second pivot to advance the string further, and finally the third link's rotation about the third pivot to complete positioning. This staged preliminary action sequence ensures proper string engagement before full cocking force is applied
Solution Approach 2:
The mechanism provides inherent feedback through its mechanical geometry and pivot points. As each link rotates through its designated arc, the physical constraints of the pivot locations and link lengths provide natural feedback on the string's position and tension state, allowing the user to sense when proper engagement has occurred before completing the cocking motion
3Ease of operation
If a single forceful action is used to cock the crossbow, then the cocking is completed in one motion, but users without sufficient force cannot successfully cock it
Solution Approach 1:
The cocking operation is segmented into three distinct rotational phases, each requiring less force than the total single-action requirement. The first phase involves rotating the first link about the first pivot, the second phase involves rotating the second link about the second pivot, and the third phase involves rotating the third link about the third pivot. This segmentation distributes the power requirement across multiple lower-force actions
Solution Approach 2:
The mechanism dynamically adapts the force application through its multi-link rotational system. Each link's rotation creates a different mechanical advantage ratio at different stages of the cocking process, allowing users with limited strength to complete the cocking action by applying force progressively through the staged motion sequence rather than requiring peak force in a single action
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 easier and safer cocking of crossbows by allowing users to engage and disengage the rod from the serrated portion using springs, reducing the need for a single, forceful action and preventing the string from bouncing back.
Implementation Method 1
A positioning unit includes a rod and multiple springs, wherein the rod extends through the elongate hole and the slot. The springs each have the first end thereof connected to the tubular part, and respective second ends of the springs are respectively connected to the two ends of the rod.
Data Source
AI summary
A crossbow includes a barrel, a retention unit, a link unit and a positioning unit. When the second link pivots toward the restriction member, the rod is moved with the slot of the restriction member, and the restriction member is pivoted relative to the second link. The pivotal action of the first link drives the retention unit to move in the arrow track and toward the bow. On the contrary, when the retention unit is connected to the bow, the second link is moved to its initial position, and the rod is engaged with the serrated portion to form a stand-by status. When the second link continuously pivots to disengage the rod from the serrated portion, the second link is engaged with the handle to form a completion status. During the cocking action, the users may have multiple stages of action to cock the crossbow.