Utility Knife Handle Blade Storage With Spring-Arm Retention

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Solution Overview

Problem

Existing knives lack a convenient and secure mechanism for storing and replacing worn or broken blades, necessitating separate storage and retrieval of replacement blades, which can be cumbersome and inefficient.

Innovation Solution

A folding knife design with a liner and spring arm mechanism that allows for secure storage of replacement blades within the handle cavity, enabling easy replacement by transitioning the spring arm to an unlocked position for removal and attachment of new blades using a supplemental hand tool.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a separate storage mechanism for replacement blades is added to the knife, then blade storage and replacement convenience is improved, but device complexity increases

Engineering Contradiction:
Improveblade replacement convenienceVSAvoidknife structure complexity
Core Design Contradiction:
Ease of operationVSDevice complexity

Solution Approach 1:

The replacement blade is stored within the handle cavity of the knife, nesting the storage function inside the existing handle structure. The liner with spring arm mechanism is integrated into the handle, creating a compact nested arrangement that provides blade storage without adding external components.

Inventive Principle:
Principle #7Nested doll (Nesting)

Solution Approach 2:

The liner serves multiple functions: it acts as a structural component of the handle, a storage mechanism for the replacement blade, and a release mechanism through its spring arm. This multi-functionality reduces the need for separate dedicated components for each function.

Inventive Principle:
Principle #6Universality (Multi-functionality)

2Reliability

If a secure restraint mechanism is implemented for the replacement blade, then blade storage security is improved, but ease of blade removal deteriorates

Engineering Contradiction:
Improveblade storage securityVSAvoidblade removal ease
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The spring arm transitions between different states (engaged and disengaged) to provide secure restraint during normal storage and easy release when needed. The dynamic nature of the spring arm allows it to maintain constant pressure for security while enabling quick release through user activation.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The spring arm acts as an intermediary between the user's manual input and the blade restraint mechanism. By pressing the spring arm, the user mediates the transition from a securely restrained state to a easily removable state, providing controlled access to blade replacement.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Volume of moving object

If blade storage is integrated within the handle cavity, then device portability and compactness are improved, but manufacturing complexity increases

Engineering Contradiction:
Improveknife overall volumeVSAvoidhandle assembly complexity
Core Design Contradiction:
Volume of moving objectVSEase of manufacture

Solution Approach 1:

The handle is divided into functional zones: the handle members form the outer structure, the liner creates the internal storage compartment, and the spring arm provides the restraint mechanism. This segmentation allows each component to be manufactured separately and assembled into the final integrated structure.

Inventive Principle:
Principle #1Segmentation

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

Facilitates quick and secure replacement of blades within the knife handle, enhancing user convenience and efficiency by integrating blade storage and replacement directly within the knife structure.

Implementation Method 1

The liner includes a spring arm that is movable between a locked position and an unlocked position. The spring arm stores mechanical energy when deformed and releases it to either restrain the second blade in the locked position or allow removal in the unlocked position.

Methodology Applied
Scientific EffectElasticity: Elasticity

Data Source

PatentEP4678340A2Knife with blade storage
Publication Date: 2026.01.14 MILWAUKEE ELECTRIC TOOL CORP
  • EP4678340A2 patent drawingFigure 1~2
  • EP4678340A2 patent drawingFigure 3~4
  • EP4678340A2 patent drawingFigure 5~7

AI summary

A utility knife (10) comprising: a handle (60) having an interior surface (62) defining a handle cavity (32); a liner (40) coupled to the handle (60), the liner (40) disposed at least partially within the handle cavity (32); a first blade (18) comprising a cutting edge (19); a blade holder (16) coupled to the first blade (18), the blade holder (16) pivotable with respect to the handle (60) between an extended position where the cutting edge (19) of the first blade is exposed and configured to cut a work-piece and a folded position where the cutting edge (19) of the first blade (18) is within the handle cavity (32); and a second blade (26) comprising a first notch (28) that interfaces with the liner (40), wherein the interface between the liner (40) and the first notch (28) restrains the second blade (26) from being removed from the handle cavity (32).