Crossbow Cam Cocking Mechanism for Lower Draw Force
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Solution Overview
Problem
Existing crossbow cocking mechanisms require excessive force, often exceeding one hundred pounds, and existing assistive devices are bulky, expensive, and add weight to the bow.
Innovation Solution
A crossbow design with first and second limbs pivotally coupled to a frame, featuring first and second cams and a cocking mechanism that slides on a center rail to engage and move the draw string between released and drawn configurations, utilizing a rotary crank, lever, or motor to facilitate cocking, with synchronization and limb relief mechanisms to reduce the required force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a traditional cocking mechanism is used, then the crossbow can be cocked, but excessive force exceeding one hundred pounds is required
Solution Approach 1:
A cam mechanism acts as an intermediary between the drawstring and the limbs, transforming the cocking motion and reducing the force required. The cam converts rotational motion into linear motion while providing mechanical advantage, allowing the user to cock the crossbow with significantly less than one hundred pounds of force.
Solution Approach 2:
The cam mechanism dynamically changes the mechanical advantage throughout the cocking stroke. As the cam rotates, its profile varies the leverage applied to the drawstring, optimizing the force requirements at different stages of the cocking process and making the operation feasible for average users.
2Force
If motorized or hand cranked cocking devices are used, then the force requirement is reduced, but the device becomes bulky, expensive, and adds weight
Solution Approach 1:
The cam mechanism is passively operated by the user's manual input, eliminating the need for motors, batteries, or complex cranking mechanisms. The system uses the user's own force applied through the cam's mechanical advantage to cock the crossbow, avoiding additional weight from motorized components while still reducing the effective force requirement through mechanical design.
3Force
If complex assistive cocking devices are used, then the force requirement is reduced, but the device becomes expensive and complicated
Solution Approach 1:
The cocking mechanism is segmented into simple, discrete components: the cam, the drawstring, and the trigger assembly. This segmentation allows each component to perform a specific function with simple geometry, avoiding the need for complex mechanisms while achieving the force reduction goal through the clever design of the cam profile and its interaction with the drawstring.
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 design significantly reduces the force needed to cock the crossbow, providing a more efficient and user-friendly cocking mechanism that is compact and lightweight compared to existing systems.
Implementation Method 1
cams that increase the mechanical advantage associated with the draw of the bowstring
Implementation Method 2
First and second cams are attached to the first and second limbs at locations between the distal portion and the proximal portions
Implementation Method 3
Sufficient force must be exerted to bend the limbs of the bow which carry the string
Data Source
AI summary
The present disclosure is directed to a crossbow having first and second limbs with distal portions pivotally coupled to the frame at distal limb mounts and proximal portions pivotally coupled to the frame at proximal limb mounts. First and second cams are attached to the first and second limbs at locations between the distal portion and the proximal portions. A cocking mechanism slides on the center rail to engage with a draw string in the released configuration and slides to a retracted position to move the draw string to the drawn configuration and to engage with a trigger assembly.