Reduced-Length Crossbow with Helical Reverse-Draw Cable Routing

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Solution Overview

Problem

Conventional bows and crossbows are limited by a power stroke of about 270 degrees due to the contact of power cables with power cable take-up journals, restricting the rotation of string guides and preventing further extension of the power stroke without increasing the size of pulleys, which results in a larger and less usable bow.

Innovation Solution

The implementation of a reverse draw configuration with helical power cable take-up journals that allow the power cables to be wrapped around the string guides, enabling rotation beyond 360 degrees, thereby increasing the power stroke by at least 25% without enlarging the string guides, and incorporating a string carrier system for enhanced accuracy and repeatability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the power cables contact the power cable take-up journals in conventional bows, then the structure is simple, but the power stroke is limited to about 270 degrees

Engineering Contradiction:

Improvestructure simplicityVSAvoidpower stroke

Core Design Contradiction:

Device complexityVSLength of moving object

Solution Approach 1:

The patent inverts the conventional power cable routing by having the power cables wrap around the string guides instead of being taken up by journals on the same component. This reverse configuration allows the power cables to follow a longer path around the string guides, enabling rotation beyond 360 degrees and extending the power stroke while maintaining structural simplicity

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The invention adds a dimensional aspect to the power cable path by wrapping it around the string guides in a helical or multi-turn configuration. This transforms the power cable's linear path into a three-dimensional wrapping pattern, effectively increasing the power stroke length without proportionally increasing the size of individual components

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Length of moving object

If the diameter of the pulleys is increased to increase the power stroke, then the power stroke length increases, but the bow becomes larger and less usable

Engineering Contradiction:

Improvepower strokeVSAvoidbow size

Core Design Contradiction:

Length of moving objectVSVolume of moving object

Solution Approach 1:

The invention segments the power transmission function across multiple components: the string guides are separated from the power cable take-up journals, allowing each to be optimized independently. The string guides can remain compact while the power cables wrap around them multiple times, achieving extended power stroke without increasing the diameter of the string guides themselves

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The power cables are nested around the string guides in a wrapping configuration, similar to a nested doll structure. This allows the power cables to utilize the space around the string guides efficiently, creating a longer power stroke path within a compact overall structure, thereby avoiding the need for larger pulleys

Inventive Principle:

Principle #7Nested doll (Nesting)

Data Source

PatentUS20250264294A1Reduced length crossbow

Publication Date: 2025.08.21 RAVIN CROSSBOWS LLC

AI summary

A crossbow including a center rail including a bottom portion, a proximal end, and a distal end positioned opposite the proximal end, the center rail at least partially defining a crossbow length and a midpoint plane intersecting a horizontal midpoint of the crossbow, a riser extending horizontally from the distal end, one or more limbs coupled to the riser, and a trigger extending from the bottom portion of the center rail and positioned within ten percent of the crossbow length from the midpoint plane.