Electric Lopper Drive Shaft Layout for Lightweight Tubes

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Solution Overview

Problem

Existing electrically powered loppers face issues with weight distribution and handling due to the placement of the drive components, leading to difficulty in precision and ease of use, especially when extended, and require sturdy, heavy tubes that are cumbersome.

Innovation Solution

The lopper design places the electric motor and gearbox at the handle portion and the mechanism for translating rotating motion into linear motion at the cutting portion, with a rotatable drive shaft extending through the tube, distributing weight and subjecting the tube to torsional loads, allowing for a lighter, more slender design.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If the electric motor and leadscrew are arranged at the handle portion, then the linear force can be transmitted through the tube, but the tube must be dimensioned to withstand high compressive loads which makes it heavy and cumbersome

Engineering Contradiction:

Improvecutting forceVSAvoidtube weight

Core Design Contradiction:

PowerVSWeight of moving object

Solution Approach 1:

The patent replaces the traditional leadscrew mechanism with a cable-driven system. The cable transmits tensile force from the motor at the handle to the shears at the cutting portion, eliminating the need for a heavy tube that must withstand compressive loads. The tube only needs to provide structural support and guide the cable, significantly reducing its weight and complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

Instead of transmitting force through compression (leadscrew pushing against the tube), the invention inverts the approach by using tension (cable pulling on the shears). Cables are inherently stronger in tension and can be much lighter than rod structures designed for compression, thus reducing the overall weight of the moving parts.

Inventive Principle:

Principle #13The other way round (Inversion)

2Device complexity

If the entire shears driving mechanism including the electric motor is arranged at the shears in the cutting portion, then the cutting mechanism is compact, but the cutting portion becomes heavy and bulky which makes it difficult to control with precision and reach certain twigs or branches

Engineering Contradiction:

Improvecutting mechanism compactnessVSAvoidhandling precision

Core Design Contradiction:

Device complexityVSEase of operation

Solution Approach 1:

The patent segments the driving mechanism into two separate parts: the power source (electric motor) remains at the handle portion where it provides stable control, while only the cable anchoring and shears are positioned at the cutting portion. This segmentation allows the cutting portion to remain lightweight and maneuverable while still achieving compact integration of the essential cutting elements.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The heavy electric motor and gear train are extracted from the cutting portion and relocated to the handle portion. Only the essential cable attachment point and shears remain at the cutting portion, dramatically reducing its weight and bulk while maintaining the ability to perform compact cutting operations.

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If a sturdy tube is used to support compressive loads from the handle to the shears, then the structure is reliable, but the tube becomes heavy and makes handling cumbersome especially when long

Engineering Contradiction:

Improvestructural stabilityVSAvoidoverall lopper weight

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The patent replaces the compression-based mechanical system (leadscrew in tube) with a tension-based cable system. The tube transitions from being a load-bearing compression member to a lightweight structural support and cable guide, significantly reducing its required thickness and weight while maintaining reliability through the cable-tensioned connection.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

This configuration enables easier handling and precise control, with a lighter and more versatile lopper that can reach further distances and navigate dense foliage, while reducing the need for heavy, bulky components.

Implementation Method 1

the tube portion is mainly subjected to torsional load, which can be supported by a more slender and lighter tube portion

Methodology Applied

Scientific EffectTorsional load: Torque

Data Source

PatentEP4326048B1lopper

Publication Date: 2025.10.29 HUSQVARNA AB

Figure 1a~1b
Figure 1c~1g
Figure 2~3b

AI summary

The disclosure concerns a lopper (2) for cutting branches comprising a handle portion (4), a cutting portion (6) comprising a pair of shears, a tube portion (8) interconnecting the handle portion (4) with the cutting portion (6), and an electrically powered drive arrangement (12) for actuation of at least one of the shears. The drive arrangement (12) comprises an electric 5 motor (14), a gearbox (16), and a mechanism (18) for translating rotating motion into linear motion, the electric motor (14) and gearbox (16) being arranged in or at the handle portion (4) and the mechanism (18) for translating rotating motion into linear motion being arranged in or at the cutting portion (6). The drive arrangement (12) further comprises a rotatable drive shaft (20) extending through the tube portion (8) and being connected to the gearbox (16) 10 and to the mechanism (18) for translating rotating motion into linear motion.