Flexible Latch Reduces Crossbow Trigger Pull Weight
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Solution Overview
Problem
Crossbows with higher draw weights require significant trigger pull weight, leading to decreased accuracy due to variations in pull weight, especially in crossbows with adjustable draw weights.
Innovation Solution
A flexible latch with a flexure design in the trigger device that reduces pull weight by altering the angle of engagement with the sear, utilizing a flexible leg and channel configuration to minimize the moment arm of the latch force, and optionally using stopper pins to limit flexure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the draw weight of the crossbow is increased, then the holding weight capability is improved, but the pull weight required to fire the crossbow increases
Solution Approach 1:
The latch is designed with a flexible leg that dynamically changes its engagement angle with the sear in response to varying holding weights. As the holding weight increases, the flexible leg flexes to alter the moment arm geometry, thereby dynamically adjusting the mechanical advantage to maintain consistent pull weight across different draw weight configurations.
Solution Approach 2:
The flexible leg changes the geometric parameters of the latch-sear engagement in response to applied load. The flexure modifies the moment arm length and engagement angle as parameters, transforming the relationship between holding weight and pull weight to achieve reduced trigger effort while maintaining high holding capacity.
2Use of energy by moving object
If the draw weight is increased to provide higher power, then the energy storage is improved, but the accuracy decreases due to variations in pull weight
Solution Approach 1:
The flexible latch creates a dynamic adaptation mechanism that responds to different energy storage levels (draw weights) by adjusting its geometric configuration. This dynamic adjustment compensates for the variations in pull weight that would otherwise occur with different draw weights, thereby maintaining consistent trigger actuation force and improving shot accuracy.
3Reliability
If a rigid latch is used to maintain structural strength, then the reliability is improved, but the pull weight increases due to fixed moment arm geometry
Solution Approach 1:
The latch incorporates a flexible leg that acts as a compliant structural element. This flexible component maintains the necessary structural strength to handle high holding weights while allowing geometric adjustment to optimize the moment arm configuration, thereby reducing the pull weight required compared to a rigid latch with fixed geometry.
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 flexible latch design reduces the required pull weight to fire the crossbow, maintaining accuracy by compensating for increased draw weights, thereby improving shot consistency.
Implementation Method 1
the flexible latch having a flexure design configured to flex in response to a holding weight applied by the bowstring
Data Source
AI summary
A trigger device is described comprising a string hook, a trigger, a sear, and a flexible latch. The string hook is configured to retain a bowstring. The sear is coupled to the trigger and configured to release the string hook in response to actuation of the trigger. A flexible latch is coupled between the string hook and the sear. The flexible latch has a flexure design configured to flex in response to a holding weight applied by the bowstring, wherein flexure of the flexible latch reduces a pull weight of the trigger.