Crossbow Trigger Nock Sensor Dry Fire Prevention

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Solution Overview

Problem

Existing crossbow trigger systems lack effective mechanisms to prevent dry firing and ensure the bowstring is released only when a nock of an arrow is properly engaged, leading to potential misfires and safety concerns.

Innovation Solution

A crossbow trigger system incorporating a nock sensor with a wheel portion and a dry fire prevention assembly, including a bypass block, release switch, and lockout pawl, which prevents the bowstring from being released unless a nock is properly aligned and engaged, and allows controlled deactivation of the nock sensor to facilitate safe string retraction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a nock sensor mechanism is added to prevent dry firing, then safety and reliability are improved, but device complexity increases

Engineering Contradiction:

Improveprevention of dry firingVSAvoidtrigger system structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The nock sensor wheel is nested within the existing trigger guard structure, with the wheel portion positioned inside the gap between hook portions. The nock sensor pivot pin is accommodated within the nock pivot bore of the trigger guard, integrating the sensing mechanism into the existing framework rather than adding separate external components.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The nock sensor wheel acts as an intermediary element between the nock and the trigger mechanism. When the nock engages the wheel, it rotates the wheel which then interacts with the sear to enable or disable trigger actuation, providing a mechanical mediation that prevents dry firing without requiring complex electronic systems.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If a bypass mechanism is added to allow controlled deactivation of the nock sensor, then ease of operation is improved, but device complexity increases

Engineering Contradiction:

Improvestring retractionVSAvoidtrigger system structure

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The bypass block is pre-positioned in the trigger system, with the bypass key initially engaged with the nock sensor wheel. The lockout pawl is pre-configured in the locked position, preventing bypass activation until the string is properly positioned. This allows the operator to simply pull the trigger to activate the bypass function without requiring separate manual steps.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The bypass mechanism is self-regulating through the lockout pawl and spring system. When the string is properly positioned near the catch, the hook portions automatically interact with the lockout pawl to enable bypass activation. The spring automatically returns the bypass block to its original position after use, eliminating the need for manual resetting.

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS10866055B1Crossbow trigger system

Publication Date: 2020.12.15 BARNETT OUTDOORS LLC

AI summary

A crossbow trigger assembly with a nock sensor enabling the catch to release the crossbow string only when a nock of an arrow is properly engaging the crossbow string. The trigger assembly also contains a bypass feature for deactivating the nock sensor to cause release of the crossbow string from the catch when a user activates a release switch. The bypass feature can only be activated when retractable hooks are positioned to receive the crossbow string near the catch, thereby preventing a dry fire of the crossbow string.