Nested Planetary Transmission for Compact Multi-Speed Power Tools

Solution Overview

Problem

Multi-speed power tools are often bulky due to the arrangement of transmission components, making them difficult to operate in confined spaces, and there is a need for a more compact design that enhances utility and functionality.

Innovation Solution

A multi-speed power tool with a compact planetary transmission mechanism that includes multiple subsections with planet gears and ring gears, a carrier assembly, and a speed selector that allows for different output speeds by grounding specific ring gears to the housing, enabling a more compact and efficient operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If traditional multi-speed transmission components are arranged in a conventional configuration, then the tool can achieve multiple speed settings, but the tool becomes relatively large and difficult to operate in confined spaces

Engineering Contradiction:

Improvemulti-speed capabilityVSAvoidtool size

Core Design Contradiction:

Adaptability or versatilityVSVolume of moving object

Solution Approach 1:

The patent implements a nested planetary transmission system where multiple planetary gear sets are arranged concentrically around a common sun gear. The first planetary gear set includes planet gears meshing with the sun gear and a first ring gear, while the second planetary gear set includes planet gears meshing with the sun gear and a second ring gear. This nested configuration allows multiple speed reduction stages to be compactly integrated within a single transmission housing, achieving multiple speed settings without increasing overall tool volume.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The patent transitions from conventional linear or sequential transmission arrangements to a radial/concentric dimensional arrangement. By organizing planetary gear sets around a central sun gear axis, the transmission utilizes radial space efficiently, packing multiple gear stages into a compact axial footprint. This dimensional reorganization reduces the tool's overall size while maintaining multi-speed functionality.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Adaptability or versatility

If transmission components are arranged to achieve multiple speed settings, then the tool can accommodate different tasks, but the arrangement renders the tool relatively large

Engineering Contradiction:

Improvetask accommodation capabilityVSAvoidaxial length

Core Design Contradiction:

Adaptability or versatilityVSLength of stationary object

Solution Approach 1:

The patent implements a nested planetary transmission system where multiple planetary gear sets are arranged concentrically around a common sun gear. The first planetary gear set includes planet gears meshing with the sun gear and a first ring gear, while the second planetary gear set includes planet gears meshing with the sun gear and a second ring gear. This nested configuration allows multiple speed reduction stages to be compactly integrated within a single transmission housing, achieving multiple speed settings without increasing overall tool volume.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The patent combines multiple planetary gear sets into a single integrated transmission unit sharing a common sun gear and housing. The first and second planetary gear sets are merged spatially and structurally, with their planet gears radially offset but both engaging the same sun gear. This consolidation reduces the axial length compared to separate transmission units, achieving compact multi-speed operation.

Inventive Principle:

Principle #5Merging (Combining)

3Volume of moving object

If a compact transmission design is implemented, then the tool's axial length is reduced for better usability in confined spaces, but the complexity of arranging multiple planetary gear sets increases

Engineering Contradiction:

Improvetool compactnessVSAvoidtransmission component arrangement

Core Design Contradiction:

Volume of moving objectVSDevice complexity

Solution Approach 1:

The patent segments the transmission into distinct modular components: a sun gear, a first planetary gear set with its own planet gears and ring gear, and a second planetary gear set with its own planet gears and ring gear. Each planetary gear set is further segmented into planet gears carried by separate carrier assemblies. This segmentation allows for standardized manufacturing of individual modules and simplifies the assembly process, reducing the practical complexity despite the compact integrated design.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The sun gear serves multiple functions simultaneously: it is the central gear for the first planetary gear set and the central gear for the second planetary gear set. The common sun gear eliminates the need for separate sun gears for each planetary stage, reducing the total component count and simplifying the overall arrangement while maintaining compact dimensions.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentEP3919231B1Power tool with multispeed transmission

Publication Date: 2023.05.03 BLACK & DECKER CORP

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AI summary

A multi-speed power tool having a transmission comprising a multi-piece planet carrier with radially offset planets. A multi-speed power tool having a transmission comprising a multi-piece carrier with compound planets. A multi-speed power tool having a shutter on a speed selector switch. A multi-speed power tool having a compliant speed shifter.