Crossbow Trigger Assembly With Nock Sensor to Prevent Dry Firing

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Solution Overview

Problem

Crossbows are prone to accidental trigger activation and dry firing, which can lead to reduced lifespan and potential human injury, due to safety mechanisms that are not robust enough to prevent unintended firing without an arrow in place.

Innovation Solution

A crossbow trigger device incorporating a housing, trigger lever, linkage, sear, safety lock lever, safety actuating lever, safety, catch, nock sensor, and sensor lock lever, with various torsion springs and convex shafts, ensuring the trigger cannot be activated without an arrow properly positioned.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the safety protrudes out to both sides of the trigger to facilitate switching on/off, then the ease of operation is improved, but the reliability deteriorates due to high likelihood of accidental switching on

Engineering Contradiction:

Improveease of switching safety on/offVSAvoidlikelihood of accidental switching on

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The safety mechanism is segmented into multiple independent components: safety lever (5), safety lock lever (9), and sensor lock lever (11). Each component performs a specific function in the safety sequence, preventing accidental activation while maintaining ease of intentional operation. The segmentation allows the system to require deliberate multi-step action rather than simple single-motion switching.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system performs preliminary actions before allowing trigger activation: the safety lever must first be moved to the on position, which then enables the safety lock lever to move to its second position, which finally allows the trigger to be pulled. This preliminary sequence of actions ensures intentional operation while preventing accidental firing.

Inventive Principle:

Principle #10Preliminary action

2Ease of operation

If the trigger device allows easy switching on/off, then the ease of operation is improved, but the reliability deteriorates due to inability to prevent dry fire

Engineering Contradiction:

Improveease of trigger operationVSAvoidprevention of dry fire

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The nock sensor (10) performs a preliminary check to detect whether an arrow is properly loaded before allowing the trigger to be pulled. The sensor lock lever (11) remains in a position that blocks trigger activation until the nock sensor detects the arrow's presence, preventing dry fire while maintaining ease of operation when properly loaded.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The nock sensor (10) acts as an intermediary between the arrow loading state and the trigger activation. It translates the physical presence of an arrow into a mechanical state that either permits or prevents trigger operation, eliminating the need for complex user judgment while preventing dry fire.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If the trigger device incorporates multiple safety mechanisms and sensors, then the reliability is improved, but the device complexity increases

Engineering Contradiction:

Improvesafety and prevention of accidental firingVSAvoidnumber of components in trigger device

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Multiple safety functions are merged into a single integrated trigger device assembly. The safety lever (5), safety lock lever (9), sensor lock lever (11), and nock sensor (10) are combined into one cohesive unit that performs multiple safety checks simultaneously, rather than as separate distributed systems. This reduces overall system complexity while maintaining high reliability.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The trigger device is designed as a multi-functional universal component that simultaneously provides: accidental activation prevention, dry fire prevention, arrow presence detection, and controlled firing capability. This consolidation of multiple functions into a single device reduces the need for separate safety systems and lowers overall complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

Prevents accidental trigger activation and dry firing by ensuring the trigger can only be engaged when an arrow is correctly inserted, thereby extending the crossbow's lifespan and enhancing safety.