Line Trimmer Telescoping Lock and Pivoting Head Assembly

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Solution Overview

Problem

Current line trimmers with telescoping mechanisms are difficult to assemble, especially for users with small hands or arthritis, and the existing mechanisms for converting trimmers into edging tools are complicated and unsafe.

Innovation Solution

A lockable, telescoping tube with a snap-fit closure system and a pressure latch that allows for easy assembly and use, combined with a snap-fit fastener for attaching a tool guard and a releasably-lockable rotational and pivoting mechanism for safe conversion into an edging tool.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a screw-type mechanism is used to lock the telescoping tubes, then the cutting head can be held in place, but the mechanism becomes difficult to assemble and operate for users with small hands or arthritis

Engineering Contradiction:
Improvelocking reliabilityVSAvoidease of assembly
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The patent replaces the screw-type mechanical fastening system with a snap-fit closure system. The closure member engages with protrusions on the tube members through elastic deformation, eliminating the need for threading and manual tightening. This substitution maintains secure locking while dramatically improving ease of operation for users with limited hand strength or dexterity.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The snap-fit closure mechanism is designed to be self-locking through elastic engagement. Once the tubes are inserted, the closure member automatically secures them in place without requiring additional tightening actions. The friction fit and elastic deformation provide automatic stabilization, eliminating the need for users to continuously adjust or tighten the connection.

Inventive Principle:
Principle #25Self-service

2Reliability

If multiple screws and parts are used in the telescoping mechanism, then the cutting head can be securely held, but the assembly becomes complicated and time-consuming

Engineering Contradiction:
Improvesecuring reliabilityVSAvoidmechanism complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines multiple separate components (screws, washers, locking nuts, and adjustment mechanisms) into a single integrated snap-fit closure member. This unified component performs all securing functions simultaneously through elastic engagement with the tube members, dramatically reducing part count and assembly complexity while maintaining secure attachment.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The closure member is designed with segmented functional zones: an elastic body portion for engagement, protrusions for interlocking with tube features, and a user interface portion for operation. This segmentation allows each zone to perform its specific function efficiently while contributing to the overall simplicity of the integrated component.

Inventive Principle:
Principle #1Segmentation

3Object-affected harmful factors

If the tool guard is permanently affixed to the motor housing, then user protection is ensured, but manufacturing becomes complicated and maintenance becomes difficult

Engineering Contradiction:
Improvedebris protectionVSAvoidmanufacturing simplicity
Core Design Contradiction:
Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The tool guard is pre-assembled with the handle assembly using snap-fit closures before final assembly with the trimmer head. This preliminary assembly allows the guard to be pre-positioned and secured in the correct orientation, simplifying the final assembly process and ensuring proper protection without requiring complex permanent attachment methods.

Inventive Principle:
Principle #10Preliminary action

4Adaptability or versatility

If the cutting head is made to pivot for edging, then edging capability is added, but the mechanism becomes complicated and confusing to use

Engineering Contradiction:
Improveedging capabilityVSAvoidmechanism complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The trimmer head assembly is designed with a pivot mechanism that allows the same head to perform both trimming and edging functions. The head can rotate to different orientations and be secured in multiple positions, enabling the user to switch between cutting modes without requiring separate tools or complex adjustment mechanisms. This universal design adds edging capability while keeping the mechanism relatively simple.

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

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

The solution simplifies the assembly and use of telescoping mechanisms, enhances safety by preventing accidental movement of the cutting head, and allows for easy conversion of trimmers into edging tools, making the device more user-friendly and safer.

Implementation Method 1

The friction block is releasably-pressable against the inner tube. When the pressure latch is closed it physically presses the friction block against the inner tube so as to restrict movement of the inner tube.

Methodology Applied
Scientific EffectFriction: Friction

Data Source

PatentEP3525570B1Line trimmer
Publication Date: 2022.04.27 TECHTRONIC OUTDOOR PRODS TECH
  • EP3525570B1 patent drawingFigure 1
  • EP3525570B1 patent drawingFigure 2~3
  • EP3525570B1 patent drawingFigure 4~5

AI summary

A trimming tool (70) may have a variety of features such as a lockable telescoping tube (10), a tool guard (96) having a snap-fit fastener, an adjustment mechanism comprising a rotational mechanism (112) and a pivoting mechanism (114), or any combination of these features. A method of attaching a tool guard to a trimming tool is also provided.