Printer Drive Train Ribbon Tension Control
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Solution Overview
Problem
Printers face challenges in maintaining optimal ribbon tension both during and between printing cycles, leading to issues like creases, thermal distortion, and print defects, especially when reversing the ribbon direction, due to backlash in the gear train and the need for additional tensioning elements in the ribbon cartridge.
Innovation Solution
A drive train system that includes a slip-overdrive assembly to maintain tension downstream of the drive roller and a drag-overrun assembly to resist unwinding upstream, ensuring proper ribbon tension in both directions without internal tensioning elements in the ribbon cartridge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a complex series of gears is used to move the ribbon and print media, then the ribbon can be transported upstream and downstream of the print head, but improper tension in the ribbon causes slack both upstream and downstream of the print head
Solution Approach 1:
The drive train pre-tensions the ribbon upstream of the print head before the printing cycle begins. This preliminary action ensures that the ribbon is properly tensioned before printing, preventing slack, creases, and wrinkles that would degrade print quality.
Solution Approach 2:
The system dynamically adjusts ribbon tension during operation. The drive train maintains optimal tension both upstream and downstream of the print head during the printing cycle, adapting to the changing mechanical conditions as the ribbon moves through the printer.
2Reliability
If internal tensioning elements are incorporated within the ribbon cartridge, then freewheeling of the supply spool and take-up spool is prevented, but the added costs are incurred in the ultimately disposable ribbon cartridge
Solution Approach 1:
The tensioning function is extracted from the disposable ribbon cartridge and relocated to the reusable drive train mechanism. The drive train incorporates tensioning elements that maintain proper ribbon tension without requiring additional components in the ribbon cartridge itself, thereby reducing cartridge costs.
Solution Approach 2:
The drive train serves multiple functions: it transports the ribbon, maintains tension upstream and downstream of the print head, and prevents spool freewheeling. This multi-functional approach eliminates the need for separate tensioning elements in the ribbon cartridge.
3Adaptability or versatility
If the direction the ribbon cartridge is being driven is reversed, then the ribbon can be fed in both directions, but maintaining ribbon tension becomes more difficult due to backlash in the gear train
Solution Approach 1:
The drive train pre-tensions the ribbon before direction changes occur. This preliminary action compensates for potential backlash in the gear train, ensuring that the ribbon remains properly tensioned when the printing direction is reversed.
Solution Approach 2:
The system dynamically maintains ribbon tension during direction reversals. The drive train adjusts its operation to keep the ribbon taut both upstream and downstream of the print head regardless of the printing direction, overcoming the effects of gear train backlash.
Data Source
AI summary
A drive train for a printer is disclosed that provides and maintains a desired tension in the ribbon during transfer of the ribbon between a supply spool and a take-up spool. The drive train is configured to pre-tension the ribbon proximate the driven spool prior to driving the drive roller. During operation, the drive train provides and maintains the requisite tension in the ribbon proximate the driven spool with use of a slip-overdrive assembly. Additionally, the drive train induces a drag on the spool from which ribbon is being unwound with the use of a drag-overrun assembly.