Laser Welded Trowel Handle Connection

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Solution Overview

Problem

Existing smoothing trowels face challenges with durable and reliable connections between the handle and the smoothing blade, which can weaken over time due to mechanical stress and exposure to chemicals like mortar and plaster.

Innovation Solution

The solution involves a smoothing trowel design where bolts are led through recesses in the smoothing blade and welded to it, providing a firm and permanent connection. This design includes using laser welding for connecting the bolts to the smoothing plate, made of chrome-molybdenum steel, and ensuring the bolts are evenly distributed for stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If traditional mechanical connections (screws, clips, or adhesive bonds) are used to attach the handle to the smoothing blade, then the manufacturing process is simple, but the connection strength and durability are insufficient under mechanical stress and chemical exposure

Engineering Contradiction:
Improveconnection strengthVSAvoidmanufacturing complexity
Core Design Contradiction:
StrengthVSEase of manufacture

Solution Approach 1:

The patent replaces traditional mechanical connection systems (screws, clips, adhesive bonds) with a laser welding process to join the handle support to the smoothing blade. This substitution provides superior connection strength and durability while maintaining manufacturing efficiency through automated laser welding technology.

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

Solution Approach 2:

The patent utilizes laser welding parameters (energy density, pulse duration, focal point) to create a strong metallurgical bond between the handle support and smoothing blade. By controlling these parameters, the process achieves high-strength connections without requiring complex mechanical fastening systems.

Inventive Principle:
Principle #35Parameter changes

2Strength

If soldered joints are used to connect the handle to the blade, then connection strength is improved, but design freedom and material selection are limited

Engineering Contradiction:
Improveconnection strengthVSAvoiddesign freedom
Core Design Contradiction:
StrengthVSAdaptability or versatility

Solution Approach 1:

The patent replaces soldering with laser welding, which provides comparable or superior connection strength while offering greater material compatibility. Laser welding can join dissimilar metals and materials without the chemical constraints of soldering, thereby expanding design freedom and material selection options.

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

3Duration of action of stationary object

If a curved tubing tang is used to connect the handle behind the blade, then connection durability is achieved, but the design is not suitable for other trowel shapes with handles located above the blade center

Engineering Contradiction:
Improveservice lifeVSAvoiddesign adaptability
Core Design Contradiction:
Duration of action of stationary objectVSAdaptability or versatility

Solution Approach 1:

The patent creates a universal connection system where the handle support can be positioned at various locations on the smoothing blade through laser welding. This universal approach allows the same joining technology to accommodate different trowel designs, handle positions, and blade shapes, making the system adaptable to multiple applications.

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

Solution Approach 2:

By replacing the fixed curved tubing tang design with laser welding, the patent enables flexible positioning of the handle support. The laser welding process can accommodate various geometries and positions, providing durability across different design configurations without being constrained by a single structural form.

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

4Reliability

If multiple bolts are used to connect the handle holder to the smoothing blade, then connection reliability is improved, but manufacturing time and complexity increase

Engineering Contradiction:
Improveconnection reliabilityVSAvoidmanufacturing efficiency
Core Design Contradiction:
ReliabilityVSProductivity

Solution Approach 1:

The patent replaces multiple mechanical fasteners (bolts, screws, or clips) with a laser welding process that joins the handle support directly to the smoothing blade. This substitution eliminates the need for multiple fastening components and assembly steps, thereby improving manufacturing efficiency while maintaining or enhancing connection reliability through a unified metallurgical bond.

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 approach results in a long-lasting and robust smoothing trowel with a secure handle attachment, capable of withstanding high mechanical and chemical stresses over an extended service life, while also being cost-effective and suitable for mass production.

Implementation Method 1

using laser welding for connecting the bolts to the smoothing plate

Methodology Applied
Scientific EffectLaser welding: Laser Beam Welding

Data Source

PatentEP4359623B1Long-life trowel
Publication Date: 2025.04.23 NELA
  • EP4359623B1 patent drawingFigure 1
  • EP4359623B1 patent drawingFigure 2
  • EP4359623B1 patent drawingFigure 3

AI summary

The present invention relates to a tool which can be used to spread and smooth building materials, especially plaster and mortar. The present invention relates in particular to a smoothing trowel (10) which comprises a smoothing board (20) and a handle (30) and in which a grip holder (40) connects the handle (30) to the smoothing board (20), the grip holder (40) being connected to the smoothing board (20) by means of a large number of bolts (50), characterised in that holes (60) are provided in the smoothing board (20) and the bolts (50) are introduced into these holes (60).