Integrated Bobbin Gear Design for Thermal Transfer Printers

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Solution Overview

Problem

Thermal transfer printers face increased production costs and operational complexities due to separate driving flanges in bobbins, which can cause scratching on touch rollers during ribbon winding.

Innovation Solution

A bobbin design with a cylindrical body featuring a gear with parallelogram-shaped teeth on one end, chamfered corners, and a smooth surface, eliminating the need for separate flanges and reducing component count, and incorporating an engagement groove for mounting a flange part.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a separate driving flange is mounted on the bobbin body, then the bobbin can engage with the drive mechanism, but the number of components increases and production cost increases

Engineering Contradiction:

Improveengagement capabilityVSAvoidnumber of components

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The gear is formed integrally with the bobbin body as a single piece, eliminating the need for a separate driving flange. The gear teeth are directly molded or machined onto the bobbin body's outer surface, creating a unified component that maintains engagement capability while reducing part count and assembly complexity.

Inventive Principle:

Principle #5Merging (Combining)

2Reliability

If driving irregularities are formed on the bobbin body surface, then engagement with drive mechanism is enabled, but the touch roll comes into contact with irregularities causing scratches

Engineering Contradiction:

Improveengagement capabilityVSAvoidscratching on touch roll

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The gear teeth are localized to specific regions on the bobbin body's outer surface, allowing engagement functionality to be concentrated in discrete tooth structures rather than distributed across the entire surface. This leaves the majority of the bobbin surface smooth and free of irregularities, preventing contact with the touch roll while maintaining drive engagement capability through the localized gear teeth.

Inventive Principle:

Principle #3Local quality

3Reliability

If driving irregularities are formed on the bobbin body, then the drive mechanism can engage, but production cost increases due to additional processing

Engineering Contradiction:

Improveengagement capabilityVSAvoidproduction cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The gear structure is integrated into the bobbin body as a single molded or machined component, eliminating the need for separate driving flange parts and their associated assembly operations. This integration simplifies the manufacturing process by reducing the number of machining operations, part handling steps, and quality inspection points, thereby lowering production costs while maintaining reliable drive engagement.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentEP3357848B1Bobbin for thermal transfer sheet or image receiving sheet, combined body of bobbin and sheet, and thermal transfer printer

Publication Date: 2020.11.18 DAI NIPPON PRINTING CO LTD

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AI summary

The present invention makes it possible to reduce the number of constituent components, and to provide a bobbin body having a smooth surface. A bobbin for a thermal transfer sheet or an image-receiving sheet includes a cylindrical bobbin body 11, wherein a a gear 12 including a plurality of teeth 13 is formed on one side end of the bobbin body 11. Each tooth 13 of the gear 12 has a parallelogram shape as a whole, when viewed from a lateral side.