Foldable Knife Handle With Internal Spare Blade Retention

Resolve Bottlenecks,
Find Innovative Solutions
Generate Solutions

Solution Overview

Problem

Existing knives lack a convenient and secure mechanism for storing and replacing worn or broken blades without the need for external tools.

Innovation Solution

A foldable knife design with a blade holder that pivots between extended and folded positions, incorporating a liner with a spring arm to restrain replacement blades within the handle cavity, allowing easy replacement and removal of blades using a supplemental tool.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a knife includes a storage location for replacement blades, then blade replacement convenience is improved, but device complexity increases

Engineering Contradiction:
Improveblade replacement convenienceVSAvoidstructure complexity
Core Design Contradiction:
Ease of operationVSDevice complexity

Solution Approach 1:

The replacement blade is nested within the handle cavity, stored inside a liner that is itself within the handle. This nesting arrangement allows the knife to carry spare blades without adding external complexity, resolving the contradiction between convenience and structural simplicity

Inventive Principle:
Principle #7Nested doll (Nesting)

Solution Approach 2:

The spring arm automatically engages with the replacement blade's tab when inserted, and the blade holder's tab engages with the liner's opening. These self-engaging mechanisms eliminate the need for tools or complex operations to secure the replacement blade, improving ease of operation while maintaining simple structure

Inventive Principle:
Principle #25Self-service

2Reliability

If a spring arm mechanism is used to restrain replacement blades, then blade security is improved, but device complexity increases

Engineering Contradiction:
Improveblade securityVSAvoidmechanism complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The spring arm is biased to automatically engage with the replacement blade's tab upon insertion. The blade secures itself by simply being inserted into the liner, with the spring arm providing automatic retention. This self-securing mechanism improves reliability without requiring complex locking systems

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The spring arm acts as an intermediary between the liner and the replacement blade, providing a simple yet effective retention mechanism. The spring arm's tab engagement with the blade's tab creates a reliable connection without requiring complex fastening systems

Inventive Principle:
Principle #24Intermediary (Mediator)

3Ease of operation

If the blade holder pivots between extended and folded positions, then ease of operation is improved, but reliability may worsen due to moving parts

Engineering Contradiction:
Improveblade deployment convenienceVSAvoidmechanism stability
Core Design Contradiction:
Ease of operationVSReliability

Solution Approach 1:

The knife is divided into distinct functional segments: the handle, the liner, the spring arm, and the blade holder. This segmentation allows each component to perform its specific function independently, with the blade holder pivoting smoothly between positions without compromising the stability of other components

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The blade holder is designed to be dynamic, pivoting between extended and folded positions as needed. This dynamic capability provides ease of operation while the overall handle structure remains stable and reliable, resolving the contradiction between movability and stability

Inventive Principle:
Principle #15Dynamics

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

Enables quick and tool-free blade replacement, enhancing convenience and security during use.

Implementation Method 1

a spring arm to restrain the replacement blade

Methodology Applied
Scientific EffectElasticity: Elasticity

Data Source

PatentEP4114626B1Knife with blade storage
Publication Date: 2026.01.28 MILWAUKEE ELECTRIC TOOL CORP
  • EP4114626B1 patent drawingFigure 1~2
  • EP4114626B1 patent drawingFigure 3~4
  • EP4114626B1 patent drawingFigure 5~7

AI summary

A knife (10) with a replacement blade (26) stored within the knife (10) is provided. The knife (10) allows the replacement blade (26) to be easily and quickly accessible. An arm (42) is movable between a locked and unlocked position. In the locked position the arm (42) interfaces with the replacement blade (26) to restrain the replacement blade (26) from being removed.