Rotating Limb Pocket Crossbow Mechanism for Low Poundage Cocking
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Solution Overview
Problem
High poundage crossbows are difficult to cock due to their high mechanical resistance, making them cumbersome for operation and transportation, and existing designs do not allow for easy adjustment between cocking and shooting states.
Innovation Solution
A crossbow with rotating limb pockets and a crank mechanism that adjusts the limb position to reduce cocking effort, allowing the crossbow to be easily cocked at a low poundage and quickly transitioned to a high poundage state for shooting, eliminating the need for a stirrup and enabling a longer power stroke.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the crossbow uses fixed limb pockets with high poundage limbs, then the crossbow achieves high power and shooting capability, but it becomes extremely difficult to cock and requires a stirrup for assistance
Solution Approach 1:
The patent applies dynamics by making the limb pockets rotatable rather than fixed. The limb pockets can rotate between a retracted position (for high poundage shooting) and an extended position (for low poundage cocking). This dynamic adjustment allows the crossbow to transition between high power state and easy-to-cock state, resolving the contradiction between power and ease of operation.
Solution Approach 2:
The patent changes the geometric parameter of the limb pockets by rotating them to different angular positions. When the limb pockets are extended outwardly, the effective lever arm changes, reducing the poundage to approximately 20 pounds for easy hand-cocking. When retracted, the full 200+ pounds of power is available for shooting. This parameter change resolves the contradiction between high power and ease of cocking.
2Adaptability or versatility
If the crossbow uses fixed limb pockets, then the structure is simple and compact, but the crossbow cannot be easily adjusted between cocking and shooting states
Solution Approach 1:
The patent introduces a rotatable limb pocket mechanism that can dynamically adjust between extended and retracted positions. This dynamic feature provides adaptability between cocking and shooting states while adding only moderate complexity through the use of pivot pins, links, and a crank mechanism.
Solution Approach 2:
The limb pockets serve multiple functions: they support the limbs during shooting (high poundage state), facilitate easy cocking when extended (low poundage state), and enable compact storage when retracted. This multi-functionality increases adaptability while the modular design keeps the added complexity manageable.
3Ease of operation
If the crossbow has a stirrup for cocking assistance, then it is easier to cock high poundage limbs, but the overall length increases and compactness for transportation is reduced
Solution Approach 1:
The patent extracts and eliminates the stirrup component entirely by using a different mechanism - rotatable limb pockets that reduce the effective poundage during cocking. This allows the crossbow to be easily cocked by hand without requiring the additional length and structure of a stirrup, thus maintaining compactness for transportation while achieving ease of operation.
4Ease of operation
If the limb pockets are extended outwardly for low poundage cocking, then the crossbow becomes less compact, but it enables easy hand-cocking without stirrup
Solution Approach 1:
The limb pockets are designed to be dynamically positionable - extended outwardly during the cocking phase to reduce poundage and enable easy hand operation, then retracted inwardly after cocking to achieve a compact configuration for transportation and storage. This dynamic repositioning resolves the contradiction between ease of hand-cocking and compactness.
Solution Approach 2:
The limb pockets undergo periodic motion - extended outwardly during cocking operations and retracted inwardly during transportation. This periodic action allows the crossbow to alternate between an operational state (easy hand-cocking) and a storage state (compact), resolving the contradiction between ease of operation and compactness.
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 a crossbow with a poundage rating well over 200 pounds to be easily cocked and uncocked by hand, maintaining compactness for transportation and providing a simple mechanism for power stroke extension, facilitating safe and efficient operation.
Implementation Method 1
controlled by a crank mechanism. Extending the actuator rotates the limb pockets outwardly and the limb cams inwardly to a low poundage state
Implementation Method 2
Rotating limb pockets are pivotally and rearwardly secured to the arch support pivot pins. Extending the actuator rotates the limb pockets outwardly and the limb cams inwardly
Data Source
AI summary
A crossbow with rotating limb pockets has a rifle-like frame with forward, outward limb arch supports which support pivot pins at their distal ends. Rotating limb pockets are pivotally and rearwardly secured to the arch support pivot pins. Limbs with distal cams supporting cables and bow string are suitably fixed to the limb pockets such as by screws. Forwardly the limb pockets are pivotally secured to links which are pivotally joined to a forward and rearward moving actuator controlled by a crank mechanism. Extending the actuator rotates the limb pockets outwardly and the limb cams inwardly to a low poundage state for easy cocking of the string and loading a bolt or arrow. Retracting the actuator rotates the limb pockets inwardly and the limb cams outwardly to a high poundage state ready for shooting.