Crossbow Bowstring and Power Cable Assembly
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Solution Overview
Problem
Crossbows require significant force to cock, making it difficult for elderly, disabled, and young users to operate without assistance, as the draw weight often exceeds one hundred pounds, and existing mechanical aids are bulky and inconvenient.
Innovation Solution
A crossbow design featuring a reciprocating linear rack and a bow assembly with a traveler, cocking pawl, and locking pawls, along with a hand lever to facilitate a cocking cycle, allowing for easier and more efficient cocking by moving the reciprocating linear rack through its advancing and releasing portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If manual cocking is used, then the crossbow can be operated, but it requires excessive force that exceeds one hundred pounds, making it difficult for elderly, disabled, and young users
Solution Approach 1:
A cable system acts as an intermediary between the user's manual input and the bowstring. The cable runs from the handle through a series of pulleys and idler wheels to the bowstring, allowing the user to apply force at a convenient location rather than directly pulling the heavy bowstring. This mechanical intermediary multiplies the user's effort and changes the direction of force application.
Solution Approach 2:
The cable system redirects the cocking force from a direct linear pull on the bowstring to a different spatial path through pulleys and idler wheels. By changing the dimensionality of the force application path, the system allows the user to apply force in a more ergonomic direction while still achieving the necessary bowstring displacement.
2Ease of operation
If external mechanical aids are used to assist cocking, then the force required is reduced, but the devices become bulky and inconvenient to carry
Solution Approach 1:
The cable system serves multiple functions: it assists with cocking the bow, provides a mechanical advantage system, and integrates with the crossbow's existing structure. The same cable mechanism that aids cocking also serves as part of the trigger and release system, eliminating the need for separate bulky cocking devices.
Solution Approach 2:
The cable system is nested within the existing crossbow structure, utilizing the stock, limbs, and existing mechanical components. The cable runs through channels and attaches to existing parts of the crossbow, rather than requiring a separate external apparatus. This nesting approach minimizes additional volume while maintaining the mechanical advantage function.
3Ease of operation
If cranks or levers are used to draw the bowstring, then cocking assistance is provided, but the mechanisms are cumbersome and awkward to employ
Solution Approach 1:
The complex crank and lever mechanisms have been extracted and replaced with a simpler cable-pulley system. The essential function of mechanical advantage is retained, but the complicated rotating and pivoting components are removed in favor of a more straightforward linear cable system that integrates with the crossbow's existing geometry.
Solution Approach 2:
The cable system is designed to be self-contained, with the cable itself serving as both the force transmission medium and the structural element. The system uses the crossbow's own components (stock, limbs, pulleys) to provide the mechanical advantage, rather than requiring separate external mechanisms. The user simply pulls the cable handle, and the system automatically routes the force through the appropriate path.
Data Source
AI summary
A crossbow is provided with a reciprocating linear rack and a locking linear rack, wherein a traveler having a pawl for each linear rack is engaged by the reciprocating linear rack to move rearward relative to the locking rack, thereby moving the traveler to a drawn position. A cocking lever is hand operated by the user though a plurality of cycles to move the traveler, and captured bowstring to a fully drawn configuration. A trigger mechanism engage the traveler in the drawn configuration and selectively releases the bowstring from the traveler. A bow assembly is provided, wherein the bowstring wraps about a front edge of opposing rotatable members, to be longitudinally located in front of a portion of power cables. The bow assembly includes a power cable on each side of the stock, and thus the power cables do not cross a longitudinal axis of the crossbow.