Crossbow Cam Alignment via Multi-Cord Force Balancing

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Solution Overview

Problem

Crossbows face reliability, weight, cost, maintenance, efficiency, and safety issues due to 'cam lean', which occurs when cams are out of alignment with the operational plane due to force imbalances.

Innovation Solution

A crossbow design featuring a bow with two cam sets, each comprising a shaft, power cord cams, and a bowstring cam, where power cords are engaged between the cams to minimize cam lean, ensuring alignment and balanced force distribution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional cam designs are used in crossbows, then the structure is simple and cost-effective, but cam lean occurs due to force imbalances causing reliability and safety issues

Engineering Contradiction:

Improvecam alignment reliabilityVSAvoidcam set structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The cam system is divided into multiple independent cam components (first cam, second cam, third cam) that can be individually designed and positioned. Each cam handles specific force transmission paths, allowing independent optimization of each component to achieve overall force balance and eliminate cam lean while maintaining manufacturing simplicity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different cam surfaces and contact points are designed with locally optimized geometries to handle specific force vectors. The cam profiles are customized at each location to ensure proper force distribution, and the mounting positions of cams are strategically selected to create balanced force moments, eliminating cam lean without requiring complex overall structure.

Inventive Principle:

Principle #3Local quality

2Reliability

If additional cam sets are added to reduce cam lean, then reliability improves, but weight and cost increase

Engineering Contradiction:

Improvepower cord engagement reliabilityVSAvoidcrossbow weight

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

Multiple cam functions are merged into integrated cam assemblies where the first, second, and third cams work together as a unified system. The cams are positioned and configured to share the load and balance forces collectively, achieving reliable power cord engagement without requiring separate independent cam mechanisms for each function, thereby minimizing weight increase.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The cam set is designed as a multi-functional system where each cam serves multiple purposes: the first cam handles primary power cord engagement, the second cam manages secondary engagement, and the third cam provides additional support and balance. This universal design allows a single integrated cam assembly to perform multiple functions that would otherwise require separate mechanisms, reducing overall weight.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS10502516B2Crossbow cam

Publication Date: 2019.12.10 HUNTERS MFG CO INC

AI summary

Provided is a crossbow comprising a bow having: a riser having a first riser side and a second riser side; a first cam set having a first shaft, a first power cord cam of the first cam set, a bowstring cam, and a second power cord cam of the first cam set; a second cam set having a second shaft, a first power cord cam of the second cam set, a bowstring cam, and a second power cord cam of the second cam set; a first power cord engaged with the first power cord cam of the first cam set and the first riser side; a second power cord engaged with the first power cord cam of the second cam set and the second riser side; and a third power cord engaged between the second power cord cams.