Reciprocating Scissors Cam Shaft Inertia Balance

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Solution Overview

Problem

Existing reciprocating power tools experience significant vibration due to imbalance, leading to discomfort for users during prolonged use, thereby hindering efficient landscaping operations.

Innovation Solution

The reciprocating power tool design incorporates a cam shaft with rotationally offset cam lobes, an inner shaft assembly with a first link and first blade, and an outer shaft assembly with a second link and second blade, where the centers of mass of these components are aligned within 1 centimeter of a center of mass axis, minimizing vibrational loads.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If reciprocating power tools operate at high speed to improve productivity, then cutting efficiency increases, but vibration and imbalance worsen causing user discomfort

Engineering Contradiction:

Improvecutting efficiencyVSAvoidvibration

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent applies counterbalancing mechanisms by positioning the second blade assembly opposite the first blade assembly and configuring the cam lobes to reciprocate both blades simultaneously. This creates opposing forces that cancel out vibrational imbalances, reducing the net vibration transmitted to the user while maintaining high-speed operation for improved productivity.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

2Productivity

If multiple blades are used to improve cutting performance, then productivity increases, but device complexity increases

Engineering Contradiction:

Improvecutting performanceVSAvoidshaft assembly complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent combines multiple blade assemblies into a single integrated unit where the first and second blades are mounted on shared shaft assemblies. The cam-driven mechanism reciprocates both blades simultaneously through a unified drive system, merging multiple cutting functions into one coordinated assembly that improves productivity without proportionally increasing complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The shaft assemblies serve multiple functions: they support both the first and second blades, provide reciprocating motion through cam engagement, and act as structural connectors between the blade assemblies and the housing. This multi-functionality reduces the need for separate components, maintaining simplicity while achieving enhanced cutting performance.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS20250048961A1Reciprocating scissors

Publication Date: 2025.02.13 MILWAUKEE ELECTRIC TOOL CORP

AI summary

A reciprocating power tool comprising a first blade and a second blade, wherein the first blade is driven by a first shaft assembly, wherein the second blade is driven by a second shaft assembly, wherein the first and second blade assemblies are reciprocally driven by a cam shaft, wherein the first shaft assembly defines a first moment of inertia, wherein the second shaft assembly defines a second moment of inertia, and wherein the first and second moments of inertia are within 5% of one another.