Hand Cutting Tool Handle Lock Assembly Mechanism

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Solution Overview

Problem

Hand cutting tools, such as tin snips or aviation snips, often have spring-biased handles that tend to open when not in use, necessitating a mechanism to lock the handles in a closed position to prevent accidental opening.

Innovation Solution

A handle lock assembly is introduced, comprising a latch and a pin that can be manually moved between engaged and released positions, allowing the user to lock the handles in a closed position, preventing the blades from opening unintentionally.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If spring bias is used to return handles to open position, then ease of operation is improved, but reliability deteriorates due to accidental opening

Engineering Contradiction:

Improveease of operationVSAvoidreliability

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The handle lock assembly applies preliminary anti-action by engaging the latch and pin to prevent the spring-biased handles from opening accidentally. The latch engages with the pin to create a mechanical constraint that counteracts the spring force, preventing unintended handle opening while maintaining the spring bias for operational return

Inventive Principle:

Principle #9Preliminary anti-action

2Reliability

If a handle lock assembly is added, then reliability is improved by preventing accidental opening, but device complexity increases

Engineering Contradiction:

ImprovereliabilityVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The handle lock assembly merges multiple functions into a compact mechanism where the latch, pin, and spring work together as an integrated system. The latch is pivotally coupled to one handle while the pin is movably coupled to the other handle, creating a unified locking mechanism that prevents accidental opening without requiring separate complex components

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The handle lock assembly employs a nested structure where the latch pivots within the handle assembly and the pin moves within its own pathway, with both components nested within the overall handle structure. This nesting allows the locking mechanism to be compact and integrated into the existing handle geometry, minimizing added complexity

Inventive Principle:

Principle #7Nested doll (Nesting)

Data Source

PatentUS8713805B2Hand cutting tool

Publication Date: 2014.05.06 MILWAUKEE ELECTRIC TOOL CORP

AI summary

A hand cutting tool includes a handle lock assembly configured to retain handles of the cutting tool in a closed position. The handle lock assembly includes a latch that pivots with respect to a first handle about a latch axis from a locked position to an unlocked position and a pin manually movable with respect to a second handle between an engaged position and a released position. In a latched position of the handle lock assembly, the latch is in the locked position and engages the pin in the engaged position to retain the second handle in the closed position, and in an unlatched position of the handle lock assembly, the latch is in the unlocked position and is disengaged from the pin in response to the pin being manually moved to the released position to allow the second handle to move toward the open position.