Compound Bow Cam Assemblies for Multi-Cycle Energy Storage
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Solution Overview
Problem
The maximum energy stored in the limbs of compound bows is limited by draw weight and draw length, which restricts the effectiveness of the weapon.
Innovation Solution
A cam assembly for compound bows that includes a draw cam and a limb cam, configured to rotate independently and interact through a gear system, allowing for energy storage beyond the limits of a single draw cycle, with the ability to maintain stored energy independent of bowstring tension and selectively apply it upon release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If traditional single draw cycle is used, then device complexity is low, but energy storage is limited by draw weight and draw length
Solution Approach 1:
The cam assembly is divided into two independently rotatable cams: a draw cam that rotates during the draw cycle and a limb cam that rotates independently to store energy in the limbs. This segmentation allows the system to decouple the draw weight limitation from the energy storage capacity, enabling multiple draw cycles to be stored without increasing the apparent draw weight.
Solution Approach 2:
The limb cam is rotated in advance during the draw cycle to store energy in the limbs before the actual shooting moment. This preliminary energy storage action allows the archer to perform multiple draw cycles (e.g., two full draw cycles) and store their energy in the limbs, then release it all at once when needed, effectively multiplying the energy available without requiring proportionally higher draw weight.
2Use of energy by moving object
If multiple draw cycles are stored in limbs, then energy storage increases, but maintaining stored energy requires additional mechanical components
Solution Approach 1:
The draw cam and limb cam are merged into a single cam assembly that rotates together during the draw cycle, then can be decoupled to allow independent rotation of the limb cam for energy storage. This merging and subsequent decoupling enables the system to achieve multiple draw cycles of energy storage using a compact integrated mechanism rather than separate complex systems.
Solution Approach 2:
The cam assembly employs dynamic rotation and decoupling mechanisms that allow the draw cam and limb cam to rotate together during drawing, then independently during energy storage and release phases. This dynamic behavior enables the system to adapt its mechanical state based on operational requirements, storing energy in the limbs while maintaining a relatively simple overall mechanical structure.
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 propulsion of arrows with increased force by multiplying the energy stored in the limbs, improving projectile speed, accuracy, and impact force beyond what is achievable with traditional single draw cycles.
Implementation Method 1
The elastic member generally comprises a pair of elastic limbs joined by and extending from a central attachment piece referred to as a riser. Distal ends of the limbs are connected by the bowstring, in which tension is created by elastic deformation induced in the limbs by the bowstring.
Implementation Method 2
Compound bows address this issue by using a system of pulleys (commonly referred to as cams) to bend the limbs. This grants the archer a mechanical advantage that allows for stiffer limbs, which are capable of promoting accuracy.
Data Source
AI summary
Cam assemblies and methods of propelling an arrow with a compound bow having a pair of limbs, a bowstring, a cable, a draw cam coupled to the bowstring, and a limb cam coupled to the cable. Such a method includes drawing the bowstring a first time to rotate the draw cam and the limb cam in a first direction, releasing the bowstring to rotate the draw cam in an opposite direction to the first direction while the limb cam remains substantially stationary and then drawing the bowstring at least a second time to rotate the draw cam and the limb cam in the first direction and thereby multiply energy stored in the limbs beyond the energy stored by the limbs during the first draw.